Technical field
[0001]The present disclosure relates to a plated steel.
BACKGROUND
[0002]Galvanized steel, construction, widely used from the viewpoint of improving corrosion resistance of structural members in the fields of automobiles. Conventionally, for improving corrosion resistance of the civil engineering structures, welding the non-plated steel, then immersed in a zinc bath, to adhere the plated steel material and the weld surface, it not is used a method of ensuring the corrosion resistance of the entire structure It was.
　However, in this method, because it is plated after welding, the productivity is poor, equipment such as a plating bath is required, it had become a cause of increasing the manufacturing cost.
　To avoid this, a method of manufacturing a structure by welding a galvanized steel material previously plated (e.g. galvanized steel) has come to be applied.
　Also, recently, in order to further improve the corrosion resistance of the structural member, as compared with the conventional general galvanized steel, further zinc alloy coated with enhanced corrosion resistance (Zn-Al-Mg-Si-based alloy plating, Al- Zn-Si-based alloy plating, etc.) by welding a zinc-based alloy plated steel material subjected to a surface (e.g., a zinc-based alloy plated steel sheet) has become to produce a welded structure (e.g., see Patent documents 1-7 .).
[0003]
　If by welding galvanized steel or zinc alloy coated steel to produce a welded structure, a specific problem, the weld metal and the liquid metal embrittlement cracks due to hot dipping in a heat-affected zone of the base material (hereinafter, " also referred to as LME. "), decrease in bonding strength due to the formation of blowholes due to Zn evaporation, and welds around and weld back surface due to the Zn evaporation (hereinafter, the welds around and weld back surface" weld heat affected parts "that there is a corrosion resistance of the deterioration of the also referred to).
[0004]
　For example, LME may be galvanized components remaining in the molten state on the surface of the base metal heat affected zone that is present in the vicinity of the weld penetrates into the grain boundaries of the welded parts is believed to be the major cause . Incidentally, Al, plating layer that contains a metal such as Mg in the plating layer, it is known that LME becomes more pronounced.
[0005]
　Welding for these problems, for example, in welding a plated steel Zn-Al-Mg-based alloy plated, after applying or placing the solidified flux welding planned site, to the welding planned site method of applying a (Patent Document 8) have been proposed.
　Further, by using the flux-cored wire, a method of detoxifying during welding to slag the elements of Al and Mg (Patent Document 9) it has been proposed.
　Further, a method of using a stainless steel-based welding wire (Patent Document 10) have been proposed.
　Furthermore, plated steel sheet suitable for weldability as a product (Non-Patent Documents 1 and 2) have also been proposed.
[0006]
Patent Document 1: Japanese Patent 2000-064061 JP
Patent Document 2: WO 2013/002358
Patent Document 3: Japanese Patent 2006-193791 JP
Patent Document 4: Japanese Patent 2002-332555 JP
Patent Document 5: WO 2010/082678
Patent Document 6: Japanese Patent 2015-214747 JP
Patent Document 7: WO 2014/059474
Patent Document 8: Japanese Patent 2007-313535 JP
Patent literature 9: Japanese Patent 2005-230912 JP
Patent Document 10: Japanese Patent 2006-35293 JP
[0007]
Non-Patent Document 1: Technical Report No. Nisshin 92 (2011) p. 39-47
Non-Patent Document 2: NSSC Technical Report No. 398 (2014) p. 79-82
Summary of the Invention
Problems that the Invention is to Solve
[0008]
　However, even taking these measures, LME, blowholes formed due to Zn evaporation, and Zn difficult here to suppress evaporation both the corrosion resistance degradation of weld heat affected zone due to.
[0009]
　An object of one aspect of the present disclosure is to provide is to provide a plating steel to suppress the LME and blow hole formation, and corrosion resistance of the weld heat affected zone is improved.
Means for Solving the Problems
[0010]
　It means for solving the problems include the following aspects.
[0011]
<1>
　and steel, is disposed on the surface of the steel, a plated steel material with a plated layer containing Zn-Al-Mg alloy layer,
　in the cross section of the Zn-Al-Mg alloy layer, MgZn 2 phase area fraction of 45 to 75%, MgZn 2 phase and the total area fraction of the Al phase is 70% or more, and Zn-Al-MgZn 2 ternary eutectic structure area fraction of a 0-5% ,
　the plating layer is, in mass%,
　Zn: less than 44.90% super ~
　79.90%, Al: less than 15% super ~
　35%, Mg: less than 5% ultra 20%
　~, Ca: 0.1% less than 3.0%
　~,
　Si:
　0% ~ 1.0%, B: 0% ~ 0.5%,
　Y: 0% ~ 0.5%, La: 0% ~
　0.5%, Ce: 0
　~ 0.5%%,
　Cr: 0%
　~ 0.25%, Ti: 0% ~ 0.25%, Ni:
　0% ~ 0.25%, Co: 0% ~ 0.25 ,
　V:
　0 Pasento ～ 0.25 Pasento, Nb: 0 Pasento ～ 0.25 Pasento,

　Cu:
　0% ~ 0.25%, Mn: 0% ~
　0.25%, Sr: 0% ~ 0.5%, Sb:
　0% ~ 0.5%, Pb: 0% ~ 0.5%,
　sn:
　0% ~
　20.00%, Bi: 0% ~ 2.0%, an In:
　0% ~ 2.0%, Fe: 0% ~ 5.0%, and
　consists of the impurity,
　the element group a Y when La and Ce, the element group B were Cr, Ti, Ni, Co, V, Nb, Cu and Mn, the element group C Sr, Sb and Pb, and the element group D Sn, and Bi and In,
　wherein the sum is 0% to 0.5% the content of the element selected from the group consisting
　a, the total content of the element selected from Ca and the element group a is less than 0.1% to 3.0% , and the
　said total content of element selected from the group B is 0% to 0.25%
　the 0% content of total element selected from the group consisting C-0.5 , And the
　plating steel having a chemical composition the total content of element selected from the element group D is 0% to 20.00%.
<2>
　the Zn-Al-Mg alloy layer, Mg 2 Si phase, Ca 2Si phase, according to the CaSi phase, Ca-Zn-Al intermetallic compound phase, and contains at least one intermetallic phase selected from the group consisting of Ca-Zn-Al-Si intermetallic compound phase <1> plated steel.
<3>
　the a content of less than 22% super to 35% Al, the content of the Mg is less than 10% ultra -20%, the content of the Ca is 0.3% ~ 3.0% less than a, the content of the Si is 0.1% to 1.0% <1> or plating steel according to <2>.
<4>
　plated steel according to the content of the Al is 15% ultra-22% <1> or <2>.
<5>
　If the plating layer contains the B, the content of the B is 0.05% to 0.5% in mass%,
　containing an element which the plating layer is selected from the element group A If total content of element selected from the element group a is 0.05% to 0.5% in mass%,
　when containing the element the plating layer is selected from the element group B, the element the total content of element selected from the group B is 0.05% to 0.25% in mass%,
　when containing the element the plating layer is selected from the element group C, selected from the element group C element total content is 0.05% to 0.5% in mass% <1> - plated steel material according to any one of <3> of that.
<6>
　The Zn-Al-Mg alloy layer, Al 2 CaB 5Phase, and the Al 2 CaB 5 part of atomic positions in the phase a Ca-Al-B intermetallic compound phase selected from the group consisting of compound phase substituted with Zn and Mg, B is atomic% in containing 40% or more of Ca-Al-B intermetallic compound phase <1> - plated steel material according to any one of <5>.
<7>
　If the plating layer contains an element selected from the element group D, the total content of element selected from the element group D is 0.05% to 20% in mass%,
　the Zn- al-Mg alloy layer, Mg 2 Sn phase, Mg 3 Bi 2 phase and Mg 3 contains at least one intermetallic phase selected from the group consisting of in-phase <1> - or <6> plated steel according to item 1.
<8>
　the plating layer, the plating steel according to any one of <1> to <7> having the Al-Fe alloy layer between the steel and the Zn-Al-Mg alloy layer.
The invention's effect
[0012]
　According to the present disclosure, it is possible to provide a plating steel to suppress the LME and blow hole formation, and corrosion resistance of the weld heat affected zone is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
FIG. 1 is a conventional Zn-Al-Mg plated layer (Zn-11% Al-3 % Mg-0.2% Si) SEM reflection electron image showing.
[2] is a SEM reflection electron image of an example (plating layer No.18A in Example A) of the plating layer of the present disclosure.
Shown FIG 3] Zn-Al phase diagram of (mass% indication).
Is a SEM reflection electron image showing another example of FIG. 4 plating layer of the present disclosure (plating layer No.8A in Example A).
Is a [FIG 5] SEM reflection electron image of a cross section of the plating layer for the purpose of describing particular method of Al phase (alpha phase and β-phase).
Is an enlarged image of the SEM reflected electron image of FIG. 6.
[Figure 7] Zn-Al-MgZn 2 is a SEM reflection electron image of a cross section of the plating layer for explaining a method of measuring the determination and the area fraction of the ternary eutectic structure.
DESCRIPTION OF THE INVENTION
[0014]
　Hereinafter, an example of the present disclosure.
　In the present disclosure, the content of each element in the chemical composition shown in the "%" means "% by mass".
　Further, the numerical range expressed using "to" means a range including numerical values described before and after "to" as the lower and upper limits.
　Further, numerical ranges when the numerical values set forth are "super" or "less than" are assigned before and after "to" means a range that does not include the lower limit or the upper limit value of these values.
　The content of elements in chemical composition, element content (e.g., Zn amount, Mg content, etc.) or elemental concentrations (e.g., Zn concentration, Mg concentration, etc.) may be referred to.
　Also, the term "process" not only separate steps, even if that can not be clearly distinguished from other processes intended purpose of the process if it is achieved, are included in this term.
　In addition, the "planar portion", shows the surface of the steel plate other than the weld heat affected zone of the steel, the term "weld around", other than the weld (weld metal portion), the heat-affected zone of the steel during welding shown, the "weld back surface" refers to a rear surface of the steel facing the weld formed on the surface side of the steel material.
[0015]
　Plated steel of the present disclosure, a steel, is disposed on the surface of the steel material, a hot dip plated steel sheet having a plating layer containing Zn-Al-Mg alloy layer, in the cross section of the Zn-Al-Mg alloy layer, MgZn 2 phase area fraction of 45 ~ 75%, MgZn 2 total area fraction of the phase and Al phase is 70% or more, and Zn-Al-MgZn 2 ternary eutectic structure area fraction of 0-5 a%, the plating layer has a predetermined chemical composition.
[0016]
　Plated steel of the present disclosure, the above configuration suppresses LME and blow hole formation, and the molten plating steel with improved corrosion resistance of the weld heat affected zone (weld around and weld back surface). Plated steel of the present disclosure has been found by the following findings.
[0017]
　First, conventionally, what has been studied in order to improve the weldability and corrosion resistance of the plated steel material is mainly a welding means, also it was to improve the weld metal itself.
[0018]
　In contrast, the present inventors have welding means, weld metal in terms of using general-purpose products, or general-purpose stainless steel wire, a plated structure suitable for weldability by defining the ingredients of the plating layer itself plating steel It worked on the development. Conventionally, the structure of the new plated layer suitable for weldability, little knowledge, weldability not been investigated only plated steel used in the product is in reality.
[0019]
　Then, the present inventors have found out the following things. In the molten zinc-based alloy plated steel, Al in the plating layer, carefully selected Mg component composition, by further tissue control, the plating layer, MgZn 2 while increasing phase and Al phase, Zn-Al-MgZn 2 ternary eutectic structure and Zn phases can be suppressed as much as possible. And, thereby, Al in the plating layer, even with a plating layer that contains a metal such as Mg, LME can be suppressed. Additionally, the evaporation amount of Zn is suppressed, while suppressing the blow hole formation, improves the corrosion resistance of the weld heat affected zone.
[0020]
　From the above, the plating steel of the present disclosure inhibit LME and blow hole formation, and corrosion resistance of the weld heat affected zone to be a hot-dipping steel having improved were found.
[0021]
　The following is a detailed explanation of the plating steel of the present disclosure.
[0022]
　For steel to be plated will be described.
　The shape of the steel is not particularly limited, steel, other steel plate, steel pipe, civil engineering materials (Sakumizo, corrugated pipes, drainage ditch lid, Hisuna prevention plate, bolts, wire mesh, guardrail, cut-off wall, etc.) , household members (housing of the air conditioner outdoor unit, etc.), automobile parts (suspension member or the like), and a molded processed steel. Molding, for example, pressing, roll forming, various plastic working techniques such as bending can be utilized.
[0023]
　The material of the steel is not particularly limited. Steel, for example, generally steel, Ni pre-plating steel, Al-killed steel, very low carbon steel, high carbon steel, various high strength steels, a part of high-alloy steels (Ni, strengthening such as Cr element-containing steel) such as various steel is applicable.
　Steel, the method of manufacturing the steel, the production method of the steel sheet (hot rolling process, pickling process, cold-rolled process, etc.) for also conditions such as, but is not particularly limited.
　Steel may be a pre-plated steel which is pre-plated.
[0024]
　Next, a description will be given of a plating layer.
　Plating layer comprises a Zn-Al-Mg alloy layer. Plating layer, in addition to the Zn-Al-Mg alloy layer may include Al-Fe alloy layer. Al-Fe alloy layer is present between the steel and the Zn-Al-Mg alloy layer.
[0025]
　That is, the plating layer may be a single-layer structure of Zn-Al-Mg alloy layer may have a laminated structure including a Zn-Al-Mg alloy layer and the Al-Fe alloy layer. For the laminated structure, Zn-Al-Mg alloy layer may be a layer constituting the surface of the plating layer.
　However, regarded as but the oxide film of the plated layer constituent elements on the surface of the plating layer is formed to a thickness of about 50 nm, it does not constitute a subject of small thickness and the plating layer the thickness of the entire plating layer.
[0026]
　The thickness of the Zn-Al-Mg alloy layer is, for example, 2μm or more 95μm or less (preferably 5μm or 75μm or less).
[0027]
　On the other hand, the thickness of the entire plating layer is, for example, lower than about 100 [mu] m. Since the plating layer total thickness depends on plating conditions, there is no particular limitation on the upper limit and the lower limit of the plating layer total thickness. For example, the thickness of the entire plating layer is in the conventional melt plating related viscosity and specific gravity of the plating bath. Furthermore the drawing speed and the wiping of the strength of the steel sheet (plating original plate), the plating amount is basis weight adjusted. Therefore, the lower limit of the plating layer total thickness can be considered to be about 2 [mu] m.
　On the other hand, by the weight and uniformity of the plated metal can be manufactured by hot dipping, the thickness of the plating layer is about 95 .mu.m.
　By drawing speed and the wiping condition from the plating bath, since the thickness of the plating layer can be freely, forming a plating layer having a thickness of 2 ~ 95 .mu.m is not particularly difficult to manufacture.
[0028]
　It will now be described Al-Fe alloy layer.
[0029]
　Al-Fe alloy layer (specifically, between the steel and the Zn-Al-Mg alloy layer) the surface of the steel material is formed on, Al as a tissue 5 Fe phase is a layer of the main phase. Al-Fe alloy layer, the base steel (steel), is formed by the mutual atomic diffusion of the plating bath. When using the hot-dip plating method as method, a plating layer containing Al element, easy to Al-Fe alloy layer is formed. Certain concentration or more Al in the plating bath because it is contained. Al 5 Fe phase are most often formed. However, the atomic diffusion takes time, and in a portion near the base steel, there is also a portion where the Fe concentration is high. Therefore, AlFe alloy layer, in part, AlFe phase, Al 3 Fe phase, Al 5 Fe 2 in some cases and phase contains minor amounts. Furthermore, since the Zn also included a constant concentration in the plating bath, the Al-Fe alloy layer, Zn also contain minor amounts.
[0030]
　In the corrosion resistance, Al 5 Fe phase, Al 3 Fe phase, AlFe phase, and Al 5 Fe 2 is not much different be any phase of phase. The corrosion resistance referred to herein is a corrosion resistance in a portion not affected by the welding. Occupied plating layer, the thickness of the Al-Fe alloy layer is small, and because low corrosion resistance compared to Zn-Al-Mg alloy layer, the corrosion resistance in the whole, much difference between the proportion of these phases is replaced there is no.
[0031]
　Here, if containing Si in the plating layer, Si is particularly easily incorporated into Al-Fe alloy layer, it may become Al-Fe-Si compound phase. The identified compounds, there are AlFeSi phase, isomers, alpha, beta, q1, q2-AlFeSi equality exists. Therefore, Al-Fe alloy layer is sometimes they AlFeSi equality is detected. The Al-Fe alloy layer containing these AlFeSi equality also referred to as Al-Fe-Si alloy layer.
　Incidentally, with respect to Al-Fe-Si alloy layer also Zn-Al-Mg alloy layer, since the thickness is small, the effect in the corrosion resistance in the entire plating layer small.
[0032]
　Further, when using various pre-plated steel material raw material of plating steel, the amount of deposition of the pre-plating, may change the structure of the Al-Fe alloy layer. Specifically, around Al-Fe alloy layer, if pure metal layer used for the pre-plating remains, Zn-Al-Mg alloy layer component intermetallic compound phase preplating component is bonded (e.g., Al 3 If Ni equality) to form an alloy layer, if Al-Fe alloy layer partially substituted Al atoms and Fe atoms form, or, Al atoms, a part of Fe atoms and Si atoms were replaced and the like when forming the al-Fe-Si alloy layer. In any case, for these alloy layers also Zn-Al-Mg alloy layer, since the thickness is small, a small influence in the corrosion resistance in the entire plating layer.
[0033]
　In other words, the Al-Fe alloy layer, Al 5 besides the alloy layer composed mainly of Fe phase, a layer comprising an alloy layer of the various embodiments.
[0034]
　The thickness of the Al-Fe alloy layer is, for example, more than 0 .mu.m 5 [mu] m or less (typically, 100 nm or 5 [mu] m or less).
　That, Al-Fe alloy layer may not be formed. However, usually, by hot dipping in a plating composition defined in the present disclosure, when a plating layer is formed, between the steel and the Zn-Al-Mg alloy layer, 100 nm or more Al-Fe alloy layer is formed. The lower limit of the thickness of the Al-Fe alloy layer is not intended to particularly limit, in forming the molten plating layer containing Al is found to inevitably Al-Fe alloy layer is formed there. Then, a thickness of the case of forming the empirically 100nm before and after the most Al-Fe alloy layer is suppressed, and is determined to a thickness to sufficiently secure adhesion between the plated layer and the base steel (steel). Since there is Al concentration is high unless taken special means, in the hot dipping method, it is difficult to form a thin Al-Fe alloy layer than 100 nm. However, urban thickness of Al-Fe alloy layer is less than 100nm are also, Al-Fe alloy layer is not necessarily formed, great influence is presumed to not give the plating performance.
[0035]
　On the other hand, when the thickness of the Al-Fe alloy layer is greater than or equal to 5 [mu] m, Al component is insufficient for Zn-Al-Mg alloy layer formed on the Al-Fe alloy layer further adhesion of the plating layer, workability there is a tendency that is extremely deteriorated. Therefore, the thickness of the Al-Fe alloy layer is limited to 5μm or less.
　Incidentally, the structure utilizing the plating steel of the present disclosure is generally welded structure is suitable as the form after processing, it is not always necessary to ensure the workability of the plating layer. Therefore, the plating steel of the present disclosure, if limited applications, can be a good plating steel weldability than conventional Zn-Al-Mg-based alloy plated steel and hot-dip Zn plated steel material.
　However, the workability of the plating layer is obtained, the processing is circular, Kyokugata etc., for processing a plated steel material in various shapes, it may be possible to use a plated steel material after processing as welding material, as a plated steel sheet it is preferable that sex was obtained. Workability of the plating layer may plated steel sheets plated properties to cold working with V press bending test, it is preferable to evaluate the powdering amount of the plating layer of V Magaritani portion.
[0036]
　Al-Fe alloy layer is Al 5 because often Fe phase is the main structure, the chemical composition of the Al-Fe alloy layer, Fe: 25 ~ 35%, Al: 65 ~ 75%, Zn: 5% or less, and balance: composition containing impurities can be exemplified.
[0037]
　Usually, contribution since it towards the thickness of the Zn-Al-Mg alloy layer than Al-Fe alloy layer is thick is normally, to the plane portion corrosion resistance of a plated steel sheet Al-Fe alloy layer, Zn- small compared to the al-Mg alloy layer. However, the Al-Fe alloy layer contains Al and Zn is a corrosion resistant element to be inferred from component analysis results certain concentration or more. Therefore, Al-Fe alloy layer has a corrosion barrier effect and some sacrificial capacity for the base steel (steel).
[0038]
　Here, it is difficult to verify the sole corrosion resistance contribution of small thickness Al-Fe alloy layer in a quantitative measurement. However, for example, when there is a sufficient thickness to Al-Fe alloy layer, a Zn-Al-Mg alloy layer on the Al-Fe alloy layer precisely removed by cutting from the surface of the plating layer in end milling or the like, corrosion test by applying, evaluating a single corrosion resistance of Al-Fe alloy layer it is possible. Al-Fe alloy layer, because it contains Al component and a small amount of Zn component, if having a Al-Fe alloy layer, red rust occurred in dots, not have the Al-Fe alloy layer, the base steel ( as at the time of steel) bare, not over the entire surface rust.
[0039]
　Also, during the corrosion test, when carried observing a section of the plating layer that led up to red rust immediately before the base steel (steel), Al-Fe alloy layer be an upper layer of Zn-Al-Mg alloy layer is eluted and Sabika only There remains, it can be confirmed that by corrosion of the base iron (steel). This electrochemically, but Al-Fe alloy layer is more noble than Zn-Al-Mg layer, in order to position the negative than the base steel (steel). For these reasons, also Al-Fe alloy layer can be determined to have a certain corrosion resistance.
[0040]
　From the viewpoint of corrosion, Al-Fe alloy layer has the effect of delayed thicker preferably red rust time if thicker. However, a thick Al-Fe alloy layer because causes significantly degrade the plating workability, the thickness is preferably less than a certain thickness.
[0041]
　Plated steel sheet of the present disclosure, sometimes variously processed before (i.e. before welding) to the welding structure. Therefore, in order to ensure the workability, it is still preferable to the thickness of the Al-Fe alloy layer below a certain level. From the viewpoint of workability and suitable thickness is found, Al-Fe alloy layer is preferably 5μm or less, V bending cracks generated starting from the plating Al-Fe alloy layer generated in the test or the like, powdering amount There is reduced. Still more preferably 2μm or less.
[0042]
　Al-Fe alloy layer is different from the Zn-Al-Mg alloy layer, Al is in principal constituent, a small thickness, has high melting point, it is maintained without being evaporated at the time of arc welding. Therefore, formation of blow holes, not related to LME. Further, in the weld heat affected zone before and after welding, it takes in Al component from Zn-Al-Mg alloy layer, there is a case where the thickness of the Al-Fe alloy layer grows. In particular, the heat input is intense portion by welding (welded portion back surface, etc.) may be Al-Fe alloy layer only. In this case, Al-Fe alloy layer, leaving the crystalline structure of the Al-Fe intermetallic compound phase is maintained, other Al, sometimes slightly containing Zn, the plating layer configuration elements such as Si. In the case where Zn-Al-Mg alloy layer is remaining, Al-Fe alloy layer with the growth of the layer thickness, spheronized Al-Fe intermetallic compound phase Zn-Al-Mg alloy layer in some cases to be confirmed.
[0043]
　As described above, Al-Fe alloy layer to have a certain corrosion resistance, in order to ensure the corrosion resistance of the surrounding weld, the selection of Zn-Al-Mg layer can be left Al-Fe alloy layer is important is there. However, since it is sufficient to grow the Al-Fe alloy layer by heat input welding, it is not necessary to grow thicker in advance Al-Fe alloy layer.
[0044]
　Next, a description will be given chemical composition of the plating layer.
　Composition of Zn-Al-Mg alloy layer contained in the plating layer, the component composition ratio of the plating bath is substantially maintained also in Zn-Al-Mg alloy layer. In the melt plating, Al-Fe for the formation of the alloy layer to react in the plating bath has been completed, Al component of the Zn-Al-Mg alloy layer by Al-Fe alloy layer formed, reduction in Zn ingredient is usually rare.
[0045]
　Then, LME and suppression of the blow hole formation, and to realize the improvement of the corrosion resistance of the weld heat affected zone, if the chemical composition of the plating layer (plating layer has a single-layer structure of Zn-Al-Mg alloy layer, Zn-Al the chemical composition of -Mg alloy layer, if the plating layer has a stacked structure of Al-Fe alloy layer and Zn-Al-Mg alloy layer, the sum of the chemical composition of the Al-Fe alloy layer and Zn-Al-Mg alloy layer) , it is as follows.
[0046]
　In other words, the chemical composition of the plating layer, by
　mass%, Zn: less than 44.90% super ~
　79.90%, Al: less than 15% super ~
　35%, Mg: less than 5% ultra ~
　20%, Ca: 0 less than% ~ 3.0
　.1%,
　Si: 0% ~
　1.0%, B: 0% ~ 0.5%, Y:
　0% ~ 0.5%, La: 0% ~ 0.5%, 　ce:
　0% ~ 0.5%, Cr: 　0% ~ 0.25%, Ti: 0% ~ 0.25%, 　Ni: 0% ~ 0.25%, Co: 0% ~ 0.25%, 　V: 　0% ~ 0.25%, Nb: 0% 　~ 0.25%, Cu: 0% ~ 0.25%, Mn: 　0% ~ 0.25%, Sr: 0% ~ 0.5%, 　sb: 　0% ~ 0.5%, Pb: 0% ~ 　0.5%, Sn: 0% ~ 20.00%, Bi: 　0% ~ 2.0%, an In: 0% ~ 2.0%, 　Fe: 0% ~ 5.0%, and

　A chemical composition consisting of impurities.
[0047]
　However, in the above chemical composition, the element group A Y, La and Ce, the element group B Cr, Ti, Ni, Co , V, Nb, Cu and Mn, the element group C Sr, Sb and Pb, and element group when the D Sn, and Bi and in,
　the sum of 0% to 0.5% of the content of the element selected from the group consisting a,
　the total content of the element selected from Ca and the element group a There was less than 0.1% to 3.0%,
　the total content of element selected from the group B to 0% to 0.25%
　the total content of element selected from the group consisting C 0% and to 0.5%.
　The total content of element selected from group D is 0% to 20%.
[0048]
　In the chemical composition of the plating layer, Si, B, Y, La, Ce, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, Sn, Bi, In, and Fe, optionally it is a component. That is, these elements may not include the plating layer. When including these optional components, the content of the optional elements is preferably in the range described below.
[0049]
　The following describes each element of the plating layer.
[0050]
Zn is an element necessary for constituting the main phase of the Zn-Al-Mg alloy layer, the corrosion resistance of the flat portion as the plating steel, weld heat-affected It needs to be contained certain level in order to ensure the Department of corrosion resistance (welding and corrosion resistance after). On the other hand, Zn concentration, i.e., Zn phase in Zn-Al-Mg alloy layer is, LME amount closely related to the formation of blow holes.
[0051]
　Zn concentration is less than or equal to 44.9%, the corrosion resistance maintained around the weld becomes difficult as plated steel sheet. HAZ (weld around and weld back surface), the plating layer is evaporated by heat input during welding, it is the plating-free region. This region as much as possible is preferably reduced by suppressing the evaporation of the plating layer. As a method of suppressing the evaporation of the plating layer, the plating layer in advance sacrificial corrosion resistance is high and, imparting altering element Zn phase hard intermetallic phase of another evaporation (e.g., plating layer how to corrosion evaporation portion Mg, by sacrificial protection highly element Ca), a method of corrosion protection by mixing the corrosion resistance element in the oxide formed during evaporation, high corrosion resistance by using a heat input of weld metal during compound phase and a method of forming a (Fe element and the plating layer component phases such as bound). If the Zn concentration is less than 44.90%, the sacrificial corrosion resistance becomes inferior, rust around the weld becomes difficult. Therefore, the lower limit of the Zn concentration to 44.90% greater. More preferably, the lower limit of the Zn content is 65.00% greater.
[0052]
　On the other hand, Zn concentration is tends to increase Zn phase when it comes to 74.90% or more, LME and blowholes vigorously occurs, tends to weldability is deteriorated. However, Zn concentration, even if the range of 74.90% - 79.90%, as described later, in the plating layer, Ca-Zn-Al intermetallic phase, and Ca-Zn-Al-Si by changing the existing state of the intermetallic phase, it is possible to suppress the formation of LME and blowholes. Therefore, the upper limit of the Zn concentration is less than 79.90%.
[0053]
Al is also an element necessary for constituting the main phase of the Zn-Al-Mg alloy layer, the corrosion resistance of the flat portion as plated steel, heat affected zone corrosion resistance (welding It needs to be contained certain level in order to ensure a post-corrosion resistance). Al is increased Al Airyo of Zn-Al-Mg alloy layer, reducing Zn Airyo. Therefore, there is a tendency that Al concentration the better weldability An increase. The effect of Al is plated layer is prevented from being evaporated by heat input during welding, component and AlFe intermetallic phase of base iron (steel) (Al 5 Fe phase, AlFe phase, Al 2 Fe phase, al 3 Fe phase etc.) to form, improve the corrosion resistance of the surrounding weld. Particularly, in case the thickness of the steel material is thin, in order to secure the weld back surface of the corrosion-resistant plating layer is completely evaporated, Al is the preferred component is better to be contained in the plating layer. Therefore, Al concentration may be greater than 20%. The Al concentration is 20% or less, much dissolved in the Fe phase of the base steel by heat input during welding, the alloy layer becomes thin weld back surface of the Al-Fe intermetallic compounds, weld corrosion resistance improvement effect of ambient there is that is not expected.
[0054]
　However, the range of 20% or less than Al concentration of 15%, as described later, Zn-Al-Mg in the alloy layer, Ca-Zn-Al intermetallic phase, and Ca-Zn-Al-Si compound phase the by changing the existing state of the Zn-Al-Mg alloy layer, even when thin Al-Fe alloy layer, the corrosion resistance improvement effect in the weld back surface can be secured.
[0055]
　Therefore, the lower limit of the Al concentration is 15 percent. Further, in order to ensure the corrosion resistance in the weld back surface superior to existing Zn-Al-Mg plated steel, it is preferable that also in combination Ca-containing effect which will be described later.
[0056]
　　On the other hand, when the Al concentration increases, the corrosion resistance of the surrounding weld is extremely deteriorated. Therefore, the upper limit of the Al concentration is less than 35%. When importance is attached to corrosion resistance of the surrounding weld, it is preferable to even less than 30% the upper limit of the Al concentration.
[0057]
Mg is also an element necessary for constituting the main phase of the Zn-Al-Mg alloy layer, the corrosion resistance of the flat portion as plated steel, heat affected zone corrosion resistance (welding It needs to be contained certain level in order to ensure a post-corrosion resistance). Mg represents a similar effect when it is contained in the plating layer and Zn. Improvement of the sacrificial corrosion resistance by the inclusion of Mg can be expected.
　On the other hand, conventionally, the inclusion of Mg to the plating layer, Mg is LME considered is remarkable because it is also metal having a low vapor pressure and Zn. Further, it is described above that various flux wires for weldability decreases have been developed.
[0058]
　However, deterioration of the LME is suppressed by selecting the Mg concentration. Usually, Mg concentration in the range of 0-5%, but certainly LME is deteriorated, when the Mg concentration is 5%, the improved LME than normal Zn plating steel, further, the blow holes generation is suppressed becomes preferred embodiment as a plating layer. Mg concentration in the range of 0-3% decreases the melting point of the plating layer while the liquid phase is more stable, turned upward plating melting range Mg concentration of 3-5%, is still more Mg concentration 5% the melting point becomes high increase rate by more than, the plating layer is less likely to liquid phase. Furthermore, the plating layer is less likely to evaporate. Therefore, Mg concentration in the range of less than 5% ultra ~ 20%, MgZn excellent weldability than Zn phase 2 the ratio of the phase is increased, thereby improving the weldability. That is, formation of the LME and blowholes is suppressed.
[0059]
　In particular, in the range Mg concentration greater than 10%, taking advantage of the property of forming a readily oxide by heat input during welding, MgO contains a large amount of the weld back surface is preferred because the effect of improving the corrosion resistance. However, if the Mg concentration is 20% or more, the viscosity increases of the plating bath, the formation of the plating layer itself becomes difficult. In addition, the plating properties or worse, a plating layer is also easy to peel. Therefore, the upper limit of the Mg concentration is less than 20%.
[0060]
:
　If the Ca is contained in the plating layer, due to Mg concentration increases, the amount of the formed dross in the plating operation is reduced, thereby improving the plating manufacturability. Especially when Mg is high concentration, because of poor general plating operability, if the Mg concentration is more than 7%, the formula: 0.15 + 1 / 20Mg Si, when contained in the plating layer, Mg intermetallic compound phase (e.g. Mg 2 forming the Si phase). Further, if the Ca is contained, because strong binding force with Ca, CaSi intermetallic phase (Ca 2 Si phase, CaSi phase etc.) is also made. However, if the number of Si than the Ca concentration is contained in, Mg 2 Si is also formed. Also, albeit in small amounts, sometimes Mg-Al-Si intermetallic compound phase is formed. Ca, when used in combination with Si, who containing Ca at a concentration of at least 2 times the Si concentration is preferred. Write Ca concentration is high, Mg 2 formed of Si is reduced.
[0067]
　Further, in the plating layer containing a large amount of Al and Zn, it is estimated to make Ca-Zn-Al-Si intermetallic compound phase. However, in the conventional JCPDS database such, no specific intermetallic compound is known, details are unclear. Si takes no distinct crystalline structure, Al 2 CaZn 2 to CaZn-Al intermetallic compound such as possibly being incorporated in a solid solution state of interstitial. Ca-Zn-Al-Si intermetallic compound phase effects, namely, Ca, combined effect of Si is to improve weld back surface of the corrosion resistance. These effects, Mg 2 Si phase, difficult to obtain in MgAlSi phase. Then, in order to obtain this effect, the lower limit of the Si concentration is preferably 0.1% or more.
[0068]
　From the standpoint of operation, due to the Si-containing in the plating bath, Mg 2 Si, MgAlSi, increased Ca-Zn-Al-Si intermetallic compound phase is undesirable from an increase in viscosity of the plating bath. Further, Ca by binding of Si atoms and the Ca 2 Si or CaSi, or Ca-Zn-Al-Si intermetallic compound phase to cause a large amount to form, not expected even improve runnability by Ca-containing. Therefore, it becomes difficult favorable plating properties can be obtained. Therefore, the upper limit of the Si concentration is 1.0% or less.
[0069]

　B has the effect of improving the inclusion LME in the plating layer. When containing less than 0.05%, in the plating layer, Zn, Al, Mg, combine with Ca elements, is estimated to produce a variety of intermetallic phases. Particularly strong binding to Ca, Ca-Al-B intermetallic compound phase (e.g. Al 2 CaB 5 tends to make the phase) (see FIG. 4). The generation of Ca-Al-B intermetallic compound phase is considered to be effective to improve the LME. Therefore, the lower limit of the B concentration is preferably 0.05% or more.
[0070]
　Although not present as existing intermetallic compound data (JCPDS), the X-ray diffraction image from the surface of the "plating layer" using a Cu target, 31.0 °, 33.5 °, 35.2 ° due peaks of the intermetallic compound by containing B is observed. Examples of the intermetallic compound, CaAl (2 ~ 4) B (5 ~ 7) A intermetallic compound, when B is the intermetallic compound of 40% or more in atomic%, are determined from the analysis results there. Another aspect simultaneously since the Zn and Mg are also detected in the spectrum of the EDS, a portion of the atomic positions Ca-Al-B intermetallic compound substituted with Zn and Mg (for example, a part of Ca Mg, the Al parts are Ca-Al-B intermetallic compound substituted with Zn) and also conceivable. Besides Ca-AlB intermetallic phase, MgB 7 phase, MgB 4 phase, MgB 2 phase, Al 2 B 3 -phase, AlB 2 phases, AlB 12 phase, (Al, Mg) B 2 phase, AlMgB 14 etc. of Zn, it is also considered likely to be present in the form of Ca substituents.
[0071]
　The content of B is plated layer B is moved to the base steel from is believed that the effect of improving the LME by changing the LME sensitivity of the steel material itself by grain boundary strengthening. The content of B, in addition to the above effects, since the melting point of the formed intermetallic compound is very high, the liquid phase of the Zn phase is believed to be acting on the suppression of evaporation or the like.
[0072]
　The content of B of the plating bath causes a rapid rise in the plating melting point, plating steel can not be produced with good plating characteristics plating operability is deteriorated. Therefore, the upper limit of the B concentration is 0.5% or less.
[0073]

　Y and element group A, La, Ce is an element showing substantially the same role as Ca. This is because the mutual atomic radius close to the atomic radius of Ca. When contained in the plating layer was replaced with Ca positions, it is possible to detect the Ca same position EDS. After welding, even when it becomes an oxide, these oxides are detected at the same position as CaO. When these elements are contained more than 0.05% in total, it is improved weld back surface of the corrosion resistance. This indicates a higher corrosion resistance of these oxides than CaO. Thus, the content of each element selected from the group A, each 0.05% or more. Then, the total content of element selected from the group A is also preferably 0.05% or more.
[0074]
　On the other hand, the element group A causes viscosity increase of the plating bath to excessive content. Therefore, in the range element group A concentration greater than 0.5%, often vatting itself of the plating bath is difficult, can not produce a good plated steel plating properties. Thus, the content of each element selected from the group A, respectively 0.5% or less. Then, the total content of element selected from the group A is also 0.5% or less.
[0075]
　The group of elements A, because the role of the substitution element of Ca is mainly the sum of the concentration of the element group A is, it is necessary to lower than the Ca concentration. Therefore, the total content of element selected from Ca and the element group A is less than 0.1% to 3.0%.
[0076]

　group of elements B is 0.05% or more in a total amount in the plating layer If that, during welding, it is incorporated into the Al-Fe alloy layer. By Al-Fe alloy layer containing an element group B, and improved weld back surface of the corrosion resistance. When the group of elements B are captured is considered that an insulating Al-Fe alloy layer is improved. Thus, the content of each element selected from the group B, each 0.05% or more. Further, the total content of element selected from the group B is also preferably 0.05% or more.
　On the other hand, the element group B, when excessive content make various intermetallic phases causes a viscosity increase. Therefore, in the range of 0.25 percent in total alone or group of elements B group, often vatting itself of the plating bath is difficult, can not produce a good plated steel sheet plated properties. Thus, the content of each element selected from the group B, respectively and 0.25% or less. Then, the total content of element selected from the group B also 0.25% or less.
[0077]
　In the case where the element of the element group A and the group of elements B are combined, the effect of improving the weld back surface of the corrosion resistance, distinguish whether due to either group of elements is difficult.
[0078]
:
　If the element group C is 0.05% or more in a total amount in the plating layer, the appearance of the plating layer is changed , spangles are formed, improved metallic luster is confirmed. Changes in the welding performance is not. Thus, the content of each element selected from the group C, respectively 0.05% or more. The total content of element selected from the group C is also preferably 0.05% or more.
　On the other hand, when the element group C contains 0.5 percent, the number of dross generation amount in the plating bath often vatting itself of the plating bath is difficult, it can not produce a good plated steel plating properties . Thus, the content of each element selected from the group C are each 0.5% or less. Then, the total content of element selected from the group C also 0.5% or less.
[0079]
　Incidentally, naturally also Cd, an element included in the element group C, Zn, there is a case where the trace detected (less than 0.1%) as an impurity Pb, for this element, spangle formed by being contained effect has not been confirmed in the like.
[0080]

　element group D, when 0.05% or more in a total amount in the plating layer, the plating layer, Mg as a new intermetallic phase 2 Sn phase, Mg 3 Bi 2 phases, Mg 3 an in phase etc. is formed, the detection It comes to be. Element group D is an element Zn constituting the plating layer mainly without forming the Al and with any intermetallic phases, Mg only forms intermetallic phases. Since the new intermetallic compound phase is formed, is an element which greatly change the weldability of the plated layer. Among, Sn can be easily contained without compromising the properties of the plating bath at a low melting point metal. When the concentration of the element group D increases, forming amounts of these intermetallic phases is increased.
[0081]
　First, because of the high any intermetallic phases also melting, present as intermetallic phase without also after welding evaporates. Originally, Mg and easy form by oxidizing MgO by welding heat also Sn, Bi, not oxidized by forming as In intermetallic compound phase, while also intermetallic phase after welding, easily remains as the plating layer Become. Improved corrosion resistance sacrificial protection property when these elements are present, improves the corrosion resistance of the surrounding weld. MgZn 2 is also the same Mg-based compound, towards these intermetallic compounds, high sacrificial corrosion resistance effect.
[0082]
　Thus, the content of each element selected from the group D, respectively 0.05% or more. Further, the total content of element selected from group D is also preferably not less than 0.05%.
[0083]
　On the other hand, the element group D can contain up to 20.00% of Sn as a principal. When the Sn concentration exceeds 20.00% Mg 2 corrosion resistance after welding Sn Airyo increases abruptly becomes worse. Also, Sn, the total content of Bi and In is the same even if more than 20.00%. This is inherently MgZn 2 is Zn was present as phase, Mg 2 by increasing Sn, by present as Zn phase, in order to adversely affect the LME and blowholes properties. Thus, the content of Sn is less 20.00%. Further, the content of the element total selected from the following element group D also 20.00 percent.
[0084]
　Further, Bi, an In the brittle plating layer by excessive content, it easily peeled, plating property is poor. Further, the corrosion resistance after welding is rapidly deteriorated. Therefore, the content of Bi, the content of In, respectively, and 2.0% or less.
[0085]
Fe is in making the plating layer, is mixed into the plating layer as an impurity. The thicker the thickness of the Al-Fe alloy layer tends to Fe concentration increases, it may be contained up to a maximum of about 5.0%. When produced by the conventional melt plating is often less than 1%. If you vatting new plating bath, the strip passing plating raw material (be plated, etc.), Fe concentration gradually increases. Therefore, when the advance is mixed in the plating bath at a supersaturated concentration of about 0.5% Fe in the plating bath, it is possible to prevent an increase in the Fe content of the plating bath.
[0086]

　impurity components contained in the raw material, or a component mixed in the manufacturing process, refers to a do not have intentionally containing component. For example, the plating layer, by mutual atomic diffusion between the plating bath and the steel material (the base steel), as an impurity, components other than Fe may also be incorporated trace.
[0087]

　In the chemical composition of the plating layer, the content of Al is less than 22% ultra-35%, the content of Mg is less than 10% ultra -20%, the content of Ca is 0.3 % ~ less than 3.0%, the Si content is preferably 0.1% to 1.0%. Further, it is preferable that the content of Ca is more than twice the amount of Si. Al, Mg, when the element concentration of Ca and Si in the above-mentioned range, easy various intermetallic phase as described above is formed, LEM and blow hole formation inhibitory effect, as well, the corrosion resistance improvement effect of weld heat affected zone increased.
[0088]
　The content of Al is 15% ultra-22%, or a 15% super -20%. Reducing the Al concentration, it improves corrosion resistance after painting.
　Many welded structure after welding, is painted. If the weld is exposed to the outside, around the weld, since the early red rust is likely to occur, in order to ensure the corrosion resistance of the weld, it is preferable to be subjected to any coating treatment. After applying the coating in the electrodeposition coating or the like around the weld, when observing the red rust behavior from the weld, there is a correlation corrosion resistance after painting the Al concentration. If painted, even beyond Al concentration of 22%, after sufficient painting corrosion resistance is obtained in the weld. However, to confirm the red rust behavior from the surrounding weld in terms of red rust inhibition from the surrounding weld, Al concentration is preferably set to 22% or less, preferably from be 20% or less. For the corrosion resistance after painting, and adhesion in relation to the metal portion of the plating layer of the coating film, it Al concentration is low, is estimated to be because the influence primed in coating film adhesion works effectively that.
[0089]
　Next, a description will be given phase constituting the Zn-Al-Mg alloy layer.
[0090]
　Zn-Al-Mg alloy layer, MgZn 2 is a layer mainly composed of two phases of phase and Al phase. Zn-Al-Mg alloy layer, Zn-Al-MgZn 2 does not include the ternary eutectic structure, or comprise also very small. Zn-Al-Mg alloy layer, other, Zn phase may contain an intermetallic compound phase or the like.
[0091]
　Specifically, in the cross section of the Zn-Al-Mg alloy layer, MgZn 2 area fraction of phases is 45 ~ 75%, MgZn 2 total area fraction of the phase and Al phase 70% or more, and Zn-Al -MgZn 2 area fraction of the ternary eutectic structure is 0 to 5%. The area fraction of Zn phase is preferably less than 25%, more preferably less than 10%.
[0092]
　The following describes the reason for defining the phases of the area fraction.
[0093]
　First, MgZn 2 described phase.
　MgZn 2 phase, when contained in the Zn-Al-Mg alloy layer, thereby improving the corrosion resistance of the Zn-Al-Mg alloy layer. Because an intermetallic compound phase having excellent insulating properties, high corrosion resistance when compared to Zn phase. Further, since the containing Mg as an element, a lower corrosion potential than the Zn phase, excellent sacrificing corrosion resistance, preferably a phase to improve corrosion resistance of the surrounding weld. Further, when Mg is eluted with corrosion process, has the effect that densification of the corrosion products which form red rust inhibiting effect higher than corrosion products Zn phase alone, may be white rust is maintained long term.
[0094]
　In weldability, MgZn 2 phase plays an important role. If Zn atoms is present as Zn phase, easily evaporated but, MgZn 2 when present as phase, hardly evaporated. First, in the region of more than 1000 ° C. (weld back surface, etc.), MgZn 2 phase is evaporated, MgO, a large amount of an oxide of ZnO. These intermetallic compounds, via the CaO is an oxide of Ca, weld deposited on the Al-Fe alloy layer formed on the back surface, to improve the corrosion resistance of the weld back surface. Also, in 1000 ° C. ~ 500 ° C. in the region (weld surrounding the like), MgZn 2 phase may but melts remained hardly evaporated.
[0095]
　Further, MgZn remains even after welding 2 phase, MgZn was present as a pre-mass to a Zn-Al-Mg alloy layer 2 is phase. Conventionally, MgZn also in Zn-Al-Mg-based alloy Zn-Al-Mg alloy layer 2 phases were present. However, both the Mg concentration is low, MgZn with Zn-Al-Mg alloy layer 2 existing state of the phase, Zn-Al-MgZn 2 is present as the ternary eutectic structure, MgZn present in lump 2 phases were those in any cross-sectional structure of the Zn-Al-Mg alloy layer, very small and less than 5% (see Figure 1).
[0096]
　That, MgZn remains even after welding 2 is phase, Zn-Al-MgZn 2 fine MgZn precipitated eutectic reaction ternary eutectic structure 2 is different from the phase. In other words, MgZn remains even after welding 2 (in this disclosure, MgZn defines the area fraction phase 2 phase), Zn-Al-MgZn 2 rather than as ternary eutectic structure, MgZn precipitated alone 2 phases it is.
[0097]
　Zn-Al-MgZn 2 ternary eutectic structure can cause readily evaporate during welding, around the weld Mg, it is impossible to leave an element such as Zn. On the other hand, MgZn present in bulk 2 phase can remain around the weld.
[0098]
　The SEM reflection electron image of a typical example of the plating layer of the present disclosure shown in FIG. As shown in FIG. 2, the Zn-Al-Mg alloy layer, MgZn massive 2 exist phase number, connected to each other, coarse MgZn 2 it can be seen that by forming the phase. If you want to increase the residual amount after welding, MgZn 2 it is preferred phase is coarse linked to each other.
[0099]
　MgZn massive 2 that phase is present, Zn is hard to evaporate, LME, generation of blowholes is also reduced. This is because there is also associated with Zn Airyo, details will be described later
[0100]
　Therefore, in order to suppress the LME and blowholes formed, MgZn 2 area fraction of phases was 45 to 75%, preferably 55 to 75%.
[0101]
　Next, a description will be given Al phase.
　Al phase, alpha-phase solid solution of Zn of about 0-3% and (normal alpha phase), containing 70% greater than to 85% of the Zn phase (eta phase), normal alpha phase and Zn phase ( η phase) and is β phase separated fine (normal β-phase) correspond (see FIG. 2, FIGS. 5-6).
[0102]
　Here, FIG. 3 shows a Zn-Al phase diagram. According to the state diagram shown in FIG. 3, Zn-Al in the final coagulation reaction hardly solid solution α phase and Al were solid solution Zn 10% at 275 ° C. eta phase (Zn phase) equilibrated separated by eutectoid reaction to.
　However, the plating coagulation process is generally cooling rate is high, may occur a state that does not follow the state diagram. For example, in the plating solidification process, the eutectoid reaction does not take place completely, often Zn and 0-85% containing the Al phase is a high temperature stable phase remains as Zn supersaturated solid solution as it is.
[0103]
　Specifically, for example, as shown in FIG. 6, by extension β phase even 10000 times, it proves to be composed of fine Al phase and a fine Zn phase. However, in general, the corrosion resistance of the α-phase and β-phase, the performance such sacrificial protection property indicates the character of the Al phase, different from the nature of the Zn phase. Therefore, Al phase of the present disclosure is also β phase applicable.
　In FIG. 6, in the region (beta phase) represented by 21, a region exhibiting white with Zn phase, region showing black is Al phase.
[0104]
　Further, for example, using a water-cooled or the like, if rapid cooling to form a plating layer may be Zn supersaturated solid solution of Al phase (normal α-phase and β-phase component concentration different from Al phase) forms. Incidentally, if quenched, in most cases the usual α-phase and β phase is produced.
　Zn supersaturated solid solution of Al phase, the original time of slow cooling (when α phase and η phase is formed), with eventually no phase is that of α phase and β phase of the abnormal component.
　Specifically, Zn supersaturated solid solution of α-phase, contrary to the usual α-phase, an Al phase which forms a solid solution supersaturated with Zn in Zn concentration of 3% greater than 70%. Α phase of Zn supersaturated solid solution is brittle, a phase deteriorating the workability.
　Zn supersaturated solid solution of β-phase, 70% greater than containing ~ 85% Zn phase (eta phase), alpha-phase solid solution supersaturated with Zn in Zn concentration of 3% greater than ~ 70% (alpha phase Zn supersaturated solid solution of ) and Zn phase (eta phase) and is Al phase separated finely. β phase of Zn supersaturated solid solution of β-phase also, to include Zn supersaturated solid solution of α-phase, brittle, a phase deteriorating the workability.
　Thus, Al phase Zn supersaturated solid solution of Al phase different from the component concentration of normal α-phase and β-phase, a phase deteriorating the workability. Therefore, it does not correspond to the Al phase of the present disclosure.
[0105]
　Here, a specific method of Al phase (alpha phase and β-phase) is as follows.
　First, specific Al phase (alpha phase and β-phase) captures an SEM reflection electron image of the cross section of the plating layer (cut surface taken along the plating layer thickness direction) (see FIGS. 5 and 6).
　Incidentally, Zn-Al-Mg alloy layer Al phase in the cross section of the measuring the area fraction of (alpha phase and β phase), the plating layer that measures each phase area fraction sectional (plating layer thickness direction using the same SEM reflection electron image and the cutting plane) taken along.
　However, for illustrative purposes, Figure in 5 and FIG. 6, 4 ° inclined to polished inclined plating layer (4 °) SEM reflection electron image of polished cross-section relative to the cutting plane taken along the plating layer thickness direction the shows.
[0106]
　Next, in the SEM reflection electron image captured (see FIG. 5), to identify the α phase by EDS and the like. The solidification process of molten plating layer, next to the central portion is α-phase, each phase as β-phase is present in the outer peripheral portion of the α-phase is precipitated. This, during the solidification of the plating layer, begins crystallisation of Al phase, Al phase became impossible Zn content in decreased solubility limit due to solidification is for discharging the Zn component into the surrounding Al phase.
　Specifically, in 1000 times the magnification of SEM reflection electron image (see FIG. 5), Al phase internal component analysis certain area (e.g., 1 [mu] m × 1 [mu] m) were quantitatively analyzed in the range, the Zn 0 ~ if 3% solid solution of Al phase specified as being α phase (normal α-phase). phases present in the outer peripheral portion of the α phase (normal α phase), to identify a normal α phase and Zn phase (eta phase) to finely separated Al phase is long if β-phase (normal β phase).
　Incidentally, if the Al phase solid solution of 3% greater than 70% supersaturation and Zn, identified as Zn supersaturated solid solution of α-phase. Further, Zn supersaturated solid solution and Zn phase of α-phase and (eta phase) if the Al phase separated finely, identified as Zn supersaturated solid solution of β-phase.
[0107]
　In the present disclosure, elements contained in the most plating layer is Zn, Al is limited to less than 15% super to 35%. Thus, typical Al-based plated steel sheet, also unlike the Al-Zn alloy coated steel sheet (so-called Al Galvalume steel sheet content 55%, mainly (R)), Al phase with Zn-Al-Mg alloy layer not constitute a formed mainly of a three-dimensional network structure, MgZn 2 Airyo the largest number, then become often organizational structure as the Al phase. Rather, Zn-Al-Mg ambient around the Al phase, which accounts for most of the alloy layer MgZn 2 composed of phase peritectic structure forms a 3-dimensional network structure. This compounding ratio of Al concentration and Mg concentration in the coating layer is involved.
[0108]
　In general, if it is less than the concentration ratio Mg / Al is 1/10, Zn-Al-Mg alloy layer, MgZn 2 compared to phase, the greater the proportion of Al phase. On the other hand, in a range concentration ratio Mg / Al is less than 1/10, MgZn 2 increases the proportion of phase, not a Zn-Al-Mg alloy layer of Al-predominant. Thus, other properties corrosion resistance, sacrificial protection property and the flat portion or the like, not matter weld than Al-based plated steel sheet and Al-Zn-based plated steel sheet, close to the Zn-plated steel sheet itself.
[0109]
　Al phase (alpha phase, beta-phase) when the welding heat is exposed to more incident heated 500 ° C., to react with Fe of the base steel (steel), Al-Fe alloy layer, a spherical or bulk Al-Fe intermetallic the compound phase. AlFe phase, Al 2 Fe phase, Al 3 Fe phase, Al 3.2 Fe phase, Al 5 Fe 2 consists equality, the same constituents as the AlFe alloy layer almost above, was dissolved in the Al phase Zn forms an intermetallic compound phase was replaced with a portion of Al. Further, as described above, these Al-Fe alloy layer and Al-Fe intermetallic compound phase has a constant corrosion resistance to the base steel (steel). Particularly in the weld back surface, most of the Zn and Mg becomes whether or oxide evaporates, Al improves the corrosion resistance of the weld back surface becomes Al-Fe alloy layer. In the weld surrounding the like, it is enough to form a layer without formation Al-Fe intermetallic compound phase, often exhibit the form of a spherical or bulk. Effect on corrosion of these Al-Fe alloy layer and Al-Fe intermetallic compound phase is small compared with the Zn-Al-Mg alloy layer, there is a certain contribution to the corrosion resistance.
[0110]
　Therefore, in order to improve the corrosion resistance of the weld heat affected zone, MgZn 2 total area fraction of the phase and Al phase is 70% or more, preferably 80% or more, more preferably 90% or more, most preferably 95 % or more to be. Incidentally, MgZn 2 upper limit of the total area fraction of the phase and Al phase is preferably 98% or less, more preferably 100% or less.
　MgZn In this area fraction 2 the phase and Al phase is present, the corrosion resistance improving effect of apparent weld surrounding Zn-Al-Mg alloy layer at the portion of the heat affected zone 500 ~ 1000 ° C. welding becomes likely to remain It can be confirmed. If it is less than 70%, many of Zn-Al-Mg alloy layer ends up evaporation, the corrosion resistance of the surrounding weld becomes inferior.
[0111]
　Next, Zn-Al-MgZn 2 described ternary eutectic structure.
　The ternary eutectic structure, Al phase, Zn phase includes a MgZn phases. The shape of each phase, in order to change the size by chemical composition, shape is irregular. However, eutectic structure is at a constant temperature transformation, since the element moving during solidification is suppressed, to form a labyrinth that each phase shape, usually, each phase precipitates finely (see FIG. 7).
　Normally, each phase, Zn phase is large, to form an island-like, then large MgZn phases, fills the gap between the Zn phase, Al phase, MgZn 2 adopts a configuration for distributing the spots during the phase in many cases. Note that the chemical composition, phase constituting does not change, which precipitates in an island shape, MgZn 2 may become phase, Al phase or MgZn 2 might be a phase component of the immediately preceding coagulation positional relationship depending on the change.
　It will be described later particular method of ternary eutectic structure.
[0112]
　If such exists ternary eutectic structure composed of fine phases, during welding, Zn is liable to evaporate, LME, generation of blow holes increases.
[0113]
　Thus, Zn-Al-MgZn 2 area fraction of the ternary eutectic structure is an 0-5%, preferably 0-2%. Area fraction of the ternary eutectic structure is most preferably 0%.
[0114]
　Next, a description will be given of Zn phase.
　Zn phase may be present in small amounts in Zn-Al-Mg alloy layer (see FIG. 2). Zn phase corrosion, but it is preferably contained in the Zn-Al-Mg alloy layer from the viewpoint of sacrificial corrosion resistance, at the time of welding, LME, unfavorably cause blow hole formation. Further, Zn layer, since it evaporates easily, corrosion resistance in a weld heat affected zone can hardly be expected. Therefore, it is possible to manage the content of Zn phase. If the Zn concentration is high, although Zn phase is easily formed, in Zn-Al-Mg alloy layer, LME the area fraction of Zn phase becomes 10% or more, blowholes amount tends to deteriorate.
[0115]
　However, even if the area fraction of Zn phase becomes 10% or more, it will be described later, in the Zn-Al-Mg alloy layer, Ca-Zn-Al intermetallic phase, and Ca-Zn-Al-Si intermetallic by changing the existing state of the compound phase, it is possible to suppress LME, the formation of blow holes.
[0116]
　Therefore, the area fraction of Zn phase may be less than 25%.
　However, from the viewpoint of weldability, preferably a tendency towards Zn phase small amount does not change.
　Therefore, the area fraction of Zn phase, preferably less than 10%, more preferably 5% or less, more preferably 3% or less. However, the area fraction of Zn phase is 0% is ideal from the viewpoint of production, it is possible to 2% or more.
　Although the final solidified portion of the plating layer (420 ~ 380 ℃) is often a Zn phase, component adjustment to reduce the Zn phase, additive element, by further applying the coagulation method, Zn Aitansho it is possible to so as not to deposit as much as possible.
[0117]
　Next, a description will be given intermetallic phases.
　When Ca is contained in the plating layer, may be Ca-Zn-Al intermetallic compound phase Zn-Al-Mg alloy layer is formed. This Ca originally, Al and Zn intermetallic compound phase (CaZn 2 phase, CaZn 5 phase, CaZn 11 phase, Al 4 Ca phase etc.) in order to easily form a. If Ca concentration is high, since Ca is very easily segregated elements, intermetallic phase binding is not fixed to one of the. When Ca-Zn-Al intermetallic phase welding, weld the CaO oxide formed on the rear surface, forming a high adhesion oxide layer on the Al-Fe alloy layer. The formation of the oxide layer, thereby improving the weld back surface of the corrosion resistance.
[0118]
　Here, the phase amount and the magnitude of the Ca-Zn-Al intermetallic phase is dependent on the corrosion resistance of the weldability and HAZ. Ca-Zn-Al intermetallic phase, when the crystal grain size is large, as CaO oxide in the weld back surface, easily form a high oxide layer adhesion to the weld back surface. That increases the corrosion resistance improving effect of the weld back surface. Additionally, Ca-Zn-Al intermetallic compound phase, if the crystal grain size is large, there is a tendency that the proportion of Zn to bind to Ca-Zn-Al intermetallic compound phase increases, suppressing the vaporization of Zn phase, LME and the effect of improving the blow hole formation is increased.
　Incidentally, originally, the lower plating layer having the content of Zn phase, Ca-Zn-Al intermetallic If compound phase were processed as coarse is the difficult tendency confirmed improving effects of the LME and blow hole formation is there.
[0119]
　Ca-Zn-Al intermetallic compound phase, a Zn-Al-Mg alloy layer may typically have a variety of shapes (cubic, needle-like, rod-like, amorphous, etc.). If the formation of Ca-Zn-Al intermetallic compound phase is "square, needle, bar", the length of the longest line (diagonal line, etc.), and crystal grain size of the Ca-Zn-Al intermetallic phase. If the formation of Ca-Zn-Al intermetallic compound phase is "square, needle, amorphous non-stick", the equivalent circle diameter of the area, and the crystal grain size of the Ca-Zn-Al intermetallic phase. If the average crystal grain size of the Ca-Zn-Al intermetallic phase is greater than or equal to 1 [mu] m, the performance varies. If all of Ca-Zn-Al intermetallic phase is confirmed need not be crystal grain size 1μm or more, the Ca-Zn-Al intermetallic compound phase or crystal grain diameter 1μm can not be confirmed, the weld back surface corrosion resistance effect of improving tends to be reduced. Further, there is a tendency to reduce the effect of suppressing formation of LME and blowholes.
　That is, when Ca-Zn-Al intermetallic compound phase or an average crystal grain size of 1μm is present in Zn-Al-Mg alloy layer, weld back surface of the corrosion resistance improving effect, as well, the effect of suppressing the formation of LME and blowholes increased. The upper limit of the average crystal grain size of the Ca-Zn-Al intermetallic phase is not particularly limited, for example, is 100μm or less.
[0120]
　Ca-Zn-Al intermetallic phase is at a very high intermetallic phase of melting, after plating layer solidification, formed immediately, innumerable present in Zn-Al-Mg alloy layer. Further, in the plating layer solidification, if the liquid phase Zn-Al-Mg alloy layer is present, in combination with Ca-Zn-Al intermetallic compound phase in the vicinity, Ca-Zn-Al metal was finely precipitated while reducing the number between compound phases, Ca-Zn-Al intermetallic compound phase are grown. In the solidification process of the plating layer, when an ordinary plating method, or the case of using quenching grain size (less than 1 [mu] m) is small, Ca-Zn-Al intermetallic phase innumerable exists. On the other hand, when in the liquid phase present state (until melting point of ~ 350 ° C.), the slow cooling, reducing their number, particle size will become coarse, the grain size 1μm in Zn-Al-Mg alloy layer more Ca-Zn-Al intermetallic phase becomes precipitated. Crystal grain size of the Ca-Zn-Al intermetallic compound phase, Ca concentration, tends to increase when the Al concentration is high, it is possible to increase the crystal grain size by these concentrations also slow cooling is lower .
[0121]
　Further, when Si is contained in large amounts in the plating layer, Mg in Zn-Al-Mg alloy layer 2 may form a Si phase. If Ca concentration is high, Ca 2 Si phase, CaSi phase, sometimes containing Ca-Zn-Al-Si intermetallic compound phase. When these compound phase exists in the Zn-Al-Mg alloy layer increases the corrosion resistance improving effect of weld heat affected zone.
　In particular, Ca-Zn-Al-Si intermetallic compound phase, Ca-Zn-Al intermetallic phase and the same effect (weld back surface of the corrosion resistance improving effect, as well as LME and improvement of the blow hole formation) is. Additionally, when the Ca-Zn-Al-Si intermetallic compound phase present, post-weld, since that will contain the Si in the oxide layer remaining on the Al-Fe alloy layer, improving the corrosion resistance of the weld back surface effect is enhanced.
　In particular, the Ca-Zn-Al-Si intermetallic compound phase having an average crystal grain size of 1μm or more (or 1 ~ 100 [mu] m) is present Zn-Al-Mg alloy layer, a Ca-Zn-Al-Si intermetallic compound phase Similarly, the weld back surface of the corrosion resistance improving effect, and increases the effect of suppressing the formation of LME and blowholes.
[0122]
　Therefore, the Zn-Al-Mg alloy layer, Mg 2 Si phase, Ca 2 Si phase, CaSi phase, Ca-Zn-Al intermetallic compound phase, and Ca-Zn-Al-Si intermetallic group consisting compound phase preferably contains at least one intermetallic phase selected from.
[0123]
　Also, the plating layer, to include B, and Zn-Al-Mg alloy layer, Al 2 CaB 5 -phase, and the Al 2 CaB 5 compound in which a part of the atomic positions of the phase is replaced with Zn and Mg a Ca-Al-B intermetallic compound phase selected from a phase the group consisting sometimes B form a Ca-Al-B intermetallic compound phase of more than 40% by atomic percent.
　The Zn-Al-Mg alloy layer and containing the Ca-Al-B intermetallic compound phase is preferable because the LME is improved.
[0124]
　Also, the plating layer and containing an element selected from the element group D (specifically, 0.05% of an element selected from the element group D in total and 20% when the content), Zn-Al-Mg alloy the layer, Mg 2 Sn phase, Mg 3 Bi 2 phase and Mg 3 may form at least one intermetallic phase selected from the group consisting of in-phase.
　The Zn-Al-Mg alloy layer, when containing the intermetallic compound phase, thereby improving the corrosion resistance of the surrounding weld.
[0125]
　Incidentally, in the plating steel of the present disclosure, as other characteristics of the plating layer, there is the hardness of the plating layer. As described above, Zn-Al-Mg in the alloy layer MgZn a hard intermetallic compound 2 included in the large amount of phase, other plating layer since intermetallic compound formed by the addition elements also generally rigid hardness, show more than 150Hv.
[0126]
　Next, an example of a method for manufacturing a plated steel material of the present disclosure.
[0127]
　Plated steel of the present disclosure, the steel surface of the (plated raw material such as be plated) (that is, one surface or both surfaces) obtained by forming a plating layer by a hot dipping method.
[0128]
　Plating bath using pure metal or alloy having a predetermined component composition prepared in vacuum melting furnace or the like, a predetermined amount formulated to become target composition dissolves in air. To carry out the hot-dip plating method, usually it requires more operating temperature of the melting point.
[0129]
　In the production of plated steel, for example, after rolling by Zenjimia method, non-oxidizing environment, as it is immersed in a plating bath steel which is reduced with hydrogen at 800 ° C.. Although also affects the thickness of the Al-Fe alloy layer of the plating layer, the immersion time is usually sufficient even 0.5 seconds. After immersion, N 2 implementing deposition amount adjustment by blowing gas.
[0130]
　In the production method of a plated steel material of the present disclosure, for performing the tissue control, temperature control of the plating bath temperature and the solidification process is essential. If no temperature control can not be reduced deposition of Zn phase.
[0131]
　If the chemical composition of the plating layer and the composition of the present disclosure, for example, the plating temperature (melting point + 20 ° C. of the plating bath), after plating (after pulling the steel from the plating bath), the holding time at 420 ° C. or higher When producing a plated steel material at 5 seconds or less, Zn-Al-Mg Zn Airyo remaining alloy layer is increased, Zn-Al-Mg final solidification portion Zn-Al-MgZn alloy layer 2 ternary eutectic Al phase and MgZn become tissue 2 tends to phase the amount of phase decreases, the plated layer weldability is deteriorated.
[0132]
　Further, 1) When plating welded on top roll, 2) in order to prevent spangle defects in the middle solidification of the plating layer, to rapid cooling using mist cooling, or 3) the melting point of the plating bath temperature (plating bath +20 ° C.), after plating, even when cooling at a cooling rate from the melting point to 0.99 ° C. of the plating bath 30 ° C. / sec or more, Zn-Al-Mg alloy layer, Zn supersaturated solid solution of Al phase (usually α phase and β-phase component concentration different from Al phase) forms, MgZn 2 becomes less phase, abnormally with Zn Airyo increases, workability is plated layer to deteriorate.
[0133]
　When analyzing the solidification process of the plating layer having the chemical ingredients of the present disclosure in detail, as follows.
　First, when immersed in the plating bath immediately after forming the Al-Fe alloy layer, the first below the freezing point during the cooling process, high melting point intermetallic compound (Mg 2 Si phase, Ca 2 Si phase, CaSi phase, Ca-Zn-Al intermetallic phase, Ca-Al-B intermetallic compound phase, etc.) immediately precipitated. Since these Airyo are phase amount less than 5% in total, in just below the melting point of the plating bath, most of the Zn-Al-Mg alloy layer is in the liquid phase.
　From the liquid phase, MgZn 2 phase, Al phase and Zn phase is precipitated, wherein Taking a typical plating coagulation process as described above, since the cooling rate is large, does not depend on the phase diagram, the liquidus There is maintained to a low temperature, Zn-Al-MgZn 2 so that the or ternary eutectic structure is formed, Zn phase many precipitates. During quenching, (Al phase different from the component concentration of normal α-phase and β-phase) Zn supersaturated solid solution of Al phase occupies much. As a result, undesirable organization increases.
[0134]
　On the other hand, the most suitable cooling conditions, to provide a retention time Zn melting point 420 ° C. or more high temperature, MgZn 2 can be sufficiently grow the phase and Al phase. As a result, MgZn in the plating layer 2 can maximize the area fraction occupied by the phase and Al phase.
　This temperature range is, Al-MgZn 2 solidified by eutectic reaction phase (towards Al phase also say peritectic reaction to slightly faster crystallization). Also, Al-MgZn 2 If maximization is Airyo be the minimum value of the Zn Airyo simultaneously.
　Therefore, the plating layer of the present disclosure (i.e. Zn-Al-Mg alloy layer) to achieve the organization, the plating temperature (melting point + 20 ° C. of the plating bath), (after pulling the steel from the plating bath) after plating the holding time at 420 ° C. or higher and more than 5 seconds. That is, the holding time at 420 ° C. or higher With more than 5 seconds, MgZn 2 sufficiently ensured deposition time of phase and Al phase, Zn phase, Zn-Al-MgZn 2 ternary eutectic structure, or Al phase deposition of Zn supersaturated solid solution of (normal α-phase and β-phase component concentration different from Al phase) is reduced.
　Specifically, the plating temperature (melting point + 20 ° C. of the plating bath), (after pulling the steel from the plating bath) after plating, the cooling rate to 420 ° C. from the melting point of the plating bath and 5 ° C. / sec or less, the holding time at 420 ° C. or higher and more than 5 seconds. However, if the melting point of the plating bath is more than 500 ° C., the cooling rate from the melting point to 420 ° C. of the plating bath also has an at 10 ° C. / sec or less, MgZn 2 a deposition time of phase and Al phase is sufficiently problem Absent.
　The retention time is less than 5 seconds at 420 ° C. or higher, Zn phase, Zn-Al-MgZn 2 ternary eutectic structure, or formation of Zn supersaturated solid solution of Al phase increases.
[0135]
　Further, Ca-Zn-Al intermetallic compounds, and to grow the Ca-Zn-Al-Si intermetallic compound, the solidification time, temperature liquid phase Zn-Al-Mg alloy layer disappears (approximately 350 ° C.) until by sufficient slow cooling, it is possible to increase the crystal grain size of these intermetallic compounds. In particular, in the range Al concentration of 15% Ultra 20%, since the Al concentration is low, it takes a time for the growth of these intermetallic compounds, cooling rate 5 ° C. from the melting point of the plating bath up to 350 ° C. / and less than a second.
[0136]
　Further, originally, the chemical composition of the plating layer containing a large amount of Mg, as described above, it is hard plating layer, whose composition processability and plating adhesion is disadvantageous. MgZn 2 phase, the majority of the Al phase has been completed solidification, the subsequent 420 ° C. temperature, eutectic reaction of the Zn phase is generated from the Al phase to 275 ° C. as described above. Then, the eutectic reaction is completed by 250 ° C.. In order to obtain the workability of the plating layer, if also held for a long time after 420 ° C., (Al phase different from the component concentration of normal α-phase and β-phase) Zn supersaturated solid solution of Al phase disappears and in workability the preferred conditions. However, Zn Airyo precipitated eutectic reaction will grow together, increasing Zn Airyo, weldability is considered that slightly worse. Meanwhile, rapid cooling is undesirable from the viewpoint of workability since the Zn supersaturated solid solution of Al phase (normal α-phase and β-phase component concentration different from Al phase) will retain it.
[0137]
　Therefore, considering these characteristics, the average cooling rate in this temperature range (temperature range from 420 ° C. to 250 ° C.), it is preferable that a normal plating process and the same range of 10 ~ 20 ° C. / sec. If cooled at the cooling rate, Al phase Zn supersaturated solid solution (normal α-phase and β-phase component concentration different from Al phase) is little, also without growing more than necessary Zn phase, Zn-Al- the Mg alloy layer can be formed.
　The average cooling rate is less than 10 ° C. / sec tends to slightly Zn Airyo increases undesirable weldability. On the other hand, the average cooling rate is 20 ° C. / sec or more will tend to form the Zn supersaturated solid solution of Al phase.
　The temperature treatment in the above range of the average cooling rate temperature range) to 250 ° C. from 420 ° C., especially, Al concentration is low, an effective means when Zn concentration is high.
[0138]
　In the production method of a plated steel material of the present disclosure, in particular, if the Al concentration is to form a plating layer in the range of 15% ultra -20%, since the Al concentration is low, it takes time to deposit the Al phase. Therefore, MgZn 2 to ensure total area fraction of the phase and Al phase, in addition to the holding time at 420 ° C. or higher and more than 5 seconds, to 350 ° C. from the melting point of the plating bath (or 250 ° C.) the cooling rate is less than 5 ° C. / sec.
[0139]
　Next, a description will be given various measuring methods for the characteristics of the plating layer.
[0140]
　Chemical composition of the plating layer is measured by the following method.
　First, to obtain an acid solution prepared by stripping dissolved plating layer corrosion acids containing suppresses inhibitor of base iron (steel). Next, solution resulting acid to measure by ICP analysis, if the chemical composition of the plating layer (plating layer has a single-layer structure of Zn-Al-Mg alloy layer, the chemical composition of the Zn-Al-Mg alloy layer , plated layer is the case of the laminated structure of the Al-Fe alloy layer and Zn-Al-Mg alloy layer, it is possible to obtain the sum of the chemical composition) of the Al-Fe alloy layer and Zn-Al-Mg alloy layer. Acid species, as long as it is an acid which can dissolve the plating layer is not particularly limited. The chemical composition is determined as an average chemical composition.
[0141]
　Further, when it is desired to obtain an individual chemical composition of the Al-Fe alloy layer and Zn-Al-Mg alloy layer to obtain a calibration curve for quantitative analysis of each element in GDS (RF glow discharge spectroscopy). Thereafter, it is preferable to measure the depth direction of the chemical components of the plating layer of interest. For example, a 30mm square and several pieces taken from a sample of the plated steel sheet was produced, and GDS sample. From the surface of the plating layer was performed with argon ions sputter obtain elemental intensity plot in the depth direction. Further to prepare a standard sample such as each element pure metal plate, if you get advance element intensity plot, it is possible to concentration converted from the intensity plot. When using the GDS to the analysis of chemical composition, the analytical area as above .phi.4 mm, measured over 10 times, it is preferable to employ an average value of the components in each location.
[0142]
　Incidentally, the sputtering rate in the range of about 0.04 ~ 0.1 [mu] m / sec are preferred. In each of the GDS analysis point, in the case of employing the component analysis value of the Zn-Al-Mg alloy layer portion, to eliminate the influence of the outermost layer of the oxide layer, ignoring the depth component plot of the surface layer 1 [mu] m, it is preferable to employ a component average value of the element concentration in the depth 1 ~ 10 [mu] m (5 [mu] m width).
[0143]
　Also, when measuring the chemical composition of the Al-Fe alloy layer, where the Fe element intensity is 95% or more of the total of elemental analysis, the base steel (steel) and the plating layer (i.e. Al-Fe alloy layer) the set with the interface position, the plating layer surface and Al-Fe alloy layer from the interface position. Separately, while matching the thickness of the Al-Fe alloy layer obtained by SEM observation or the like, employing a component average value of the element concentration in the width corresponding to the thickness width of the Al-Fe alloy layer.
[0144]
　Can also be obtained from the quantitative analysis value using EPMA, easily separate the chemical composition of the Al-Fe alloy layer and Zn-Al-Mg alloy layer.
[0145]
　Zn-Al-Mg phase in the alloy layer (wherein, Zn-Al-MgZn 2 ternary eutectic structure phase, excluding the) method to check are as follows.
　By X-ray diffraction from the surface of the Zn-Al-Mg alloy layer, it may be identified phases of Zn-Al-Mg alloy layer. The intensity of the X-ray diffraction, the radiation source, Cu, but can be used Co, etc., and finally calculate the diffraction angle matching the Cu radiation source, it is necessary to change. Measuring range, 5 ° ~ 90 °, step is preferably about 0.01 °. To obtain the intensity (cps) at a specific diffraction angle, obtain an average value of about ± 0.05 °. If the additional component is trace, since the intermetallic compound of the additive element may not be detected, to prepare a TEM sample from Zn-Al-Mg alloy layer, looking for small intermetallic compound, identified from an electron diffraction image it may perform.
[0146]
　To the tissue observation of the Zn-Al-Mg alloy layer, by observing the tissue after nital etching by polishing the Zn-Al-Mg alloy layer section, Al-Fe alloy layer, and Zn-Al- it is possible to measure the thickness of the Mg alloy layer. With the CP processing, it is possible to observe the plating layer tissue more finely. The Zn-Al-Mg alloy layer observation it is preferable to use a FE-SEM.
[0147]
　Zn-Al-Mg phase in the alloy layer (wherein, Zn-Al-MgZn 2 ternary eutectic structure phase, excluding the) area fraction of is measured by the following method.
[0148]
　To measure each phase area fraction of Zn-Al-Mg alloy layer is, FE-SEM equipped with EDS (energy dispersive X-ray analyzer), using a TEM. Incidentally, each phase of the identification may be used EPMA apparatus.
[0149]
　Any cross section (cross section cut in the thickness direction) CP (cross session polisher) processing the measured Zn-Al-Mg alloy layer is subjected. After CP processing, to obtain a reflection electron image of SEM of a cross section of Zn-Al-Mg alloy layer. Reflection electron image of SEM is about 100μm or more: from any region square of (the thickness direction Zn-Al-Mg alloy layer field selection fit is) × 2000 .mu.m (surface parallel to the direction of the steel material), three for area measurement and an image obtained by observing over Tokoro at magnification of 1000 (about Zn-Al-Mg alloy layer thickness [mu] m × about 150 [mu] m).
[0150]
　Next, subjected to any cross-section (Zn-Al-Mg alloy layer thickness was cut in a direction cross-section) to the FIB (focused ion beam) processing of Zn-Al-Mg alloy layer having the same measured. After FIB processing, obtain an electron diffraction image of a TEM (transmission electron microscope) of cross-sectional structure of the Zn-Al-Mg alloy layer. Then, to identify the metal or intermetallic compound contained in the Zn-Al-Mg alloy layer.
[0151]
　Then, comparing the identification result of the electron diffraction image of reflected electron image and TEM of SEM, in the reflection electron image of SEM, identifying each phase having a Zn-Al-Mg alloy layer. Note that in each phase of the identification with the Zn-Al-Mg alloy layer, and analyzed EDS point, when collating the identification results of the electron diffraction image of the results and the TEM EDS point analysis may.
[0152]
　Next, it is determined in the reflection electron image of SEM, lightness of the gray scale indicated by the phase having the Zn-Al-Mg alloy layer, the three values ​​of hue and contrast values. Brightness indicated phases, the three values ​​of hue and contrast values, since it reflects the atomic number of the elements contained in each phase, typically, atomic number is small Al content, the more the phase is large content of Mg content, black the exhibits, as Zn amount is large phase, tend to exhibit a white color.
[0153]
　From the verification result of the EDS, to match a reflection electron image of SEM, only the range of the three values ​​indicated by phase contained in Zn-Al-Mg alloy layer, carrying out the computer image processing, such as color change (e.g., only certain phases, so as to display a white image, calculates the like of each phase area in the field of view in pixels). This by image processing performed in the respective phases, obtains each phase area fraction of Zn-Al-Mg alloy layer occupying in the reflection electron image of SEM.
[0154]
　Then, each phase area fraction of Zn-Al-Mg alloy layer is in the Zn-Al-Mg alloy layer arbitrary cross section (Zn-Al-Mg alloy layer was cut into a cross-section in the thickness direction) of at least 3 or more visual fields of , the phase of the average of the area fraction was determined by the above operation.
　In the reflection electron image of a magnification 1000 times SEM, Zn-Al-MgZn 2 present in the ternary eutectic structure in "MgZn 2 phase, Al phase and Zn phase" can not identify the boundary-area fraction. That is, herein, obtains "MgZn 2 phase, Al phase and Zn phase each area fraction of" is, Zn-Al-MgZn described below 2 is present in the ternary eutectic tissue "MgZn 2 phase, Al phase and Zn it is each area fraction except for the phase ".
　However, the enlarged image of the extent to 10000 times, it is possible to determine the individual area fraction even ternary eutectic structure, the following, in accordance with the conditions of the image processing, phase ratio of in the ternary eutectic it is possible to calculate the.
[0155]
　Here, as shown in FIGS. 2 and 4, Zn-Al-Mg alloy layer sectional SEM image is something that both taken with the reflected electron image, but usually phase constituting the Zn-Al-Mg alloy layer (Al phase, MgZn 2 phase, Zn phase etc.), since atomic number difference is clear, it can be easily distinguished.
[0156]
　Other intermetallic phase (Ca-Zn-Al intermetallic compound, etc.), MgZn 2 but may exhibit phase and close contrast, the shape is unique. Therefore, it is possible to relatively easily identify these intermetallic phases.
　Intermetallic phase including the low Si atomic number (Ca-Zn-Al-Si intermetallic compounds, etc.) can also be dark contrast, relatively easily identified.
　Intermetallic phase including the atomic number is smaller B (Ca-Al-B intermetallic compound phase, etc.), like the intermetallic compound phase containing Si, may be darker in contrast, relatively easily identified. If the determination is difficult, to implement the electron beam diffraction by TEM.
[0157]
　Each average crystal grain size of the Ca-Zn-Al intermetallic phase and Ca-Zn-Al-Si intermetallic phase is carried out in the following street.
　In SEM observation of the time measuring the area fraction of the phase, among the compound phase was confirmed to select each compound phase having five grain size higher. Then, the operation was carried out five fields of view, the arithmetic mean of the total of 25 grain size, and the average crystal grain size of the Ca-Zn-Al intermetallic phase and Ca-Zn-Al-Si intermetallic compound phase to.
[0158]
　Zn-Al-MgZn of Zn-Al-Mg alloy layer 2 Identification and area fraction of the ternary eutectic structure is measured by the following method.
[0159]
　First, in the same manner as the measurement of each phase of the area fraction of Zn-Al-Mg alloy layer, a reflective electron image of SEM, Al phase, Zn phase and MgZn 2 identify tissue three phases of phase is eutectic to. A portion of the tissue, a magnification of 30,000, size 3 [mu] m × 4 [mu] m (diagonal, 5 [mu] m) is observed in a rectangular field of view (see FIG. 7). At this time, in the rectangular field of view, when minus diagonal two, one diagonal per Zn phase five times or more, and Zn phases extending around MgZn 2 phase and Al phase 5 times or more, if the diagonal crosses , determined to be a three-way eutectic structure. This judgment is the reference that the ternary eutectic structure unique is "each three phases finely dispersed tissue."
[0160]
　Incidentally, the possibility that the ternary eutectic structure is unevenly distributed, or ternary eutectic structure is formed hard composition, the ternary eutectic structure is, if it is not possible to the region of 3 [mu] m × 4 [mu] m, the 1μm square lattice pattern to the organization the separator, if each phase in the lattice is contained 1 or more, it is determined that the ternary eutectic structure.
[0161]
　Then, the reflected electron image of the Zn-Al-Mg alloy layer in each phase area fraction measured as the same SEM (magnification 1000 times, size: about Zn-Al-Mg alloy layer thickness [mu] m × about 150μm observed against the image), by repeating the above operation, while confirming the continuity of the ternary eutectic structure, to grasp the ternary eutectic structure of the contour (area). Then, determine the area fraction of a ternary eutectic structure of Zn-Al-Mg alloy layer occupying in the reflection electron image of SEM was grasped.
　The area fraction of the ternary eutectic structure, at least three field of view of any cross-section of the Zn-Al-Mg alloy layer (Zn-Al-Mg alloy layer thickness was cut in a direction cross-section), determined by the operation and an average value of area fraction of each phase.
[0162]
　Plating layer hardness may be measured Vickers hardness at an indentation load 10gf from the plating layer surface. It is preferable to obtain the Vickers hardness from an average value of about 30 points.
[0163]
　Powdering amount after V bending test by pressing in order to assess the workability of the plating layer evaluation is preferred. The V bend valley, since the compressive stress acts, plated steel sheet poor plastic deformability, powdering occurs. To perform a more severe processability evaluation, performing tape peeling after having returned the V bending test piece again flat, it is preferable to evaluate the unbending test.
[0164]
　The following describes the post-processing that can be applied to the plated steel sheet of the present disclosure.
[0165]
　The plated steel sheet of the present disclosure, the film may be formed on the plating layer. Coating can form one or more layers. The type of film immediately above the plated layer, for example, chromate film, phosphate film include chromate-free coatings. Forming these films, chromate treatment, phosphate treatment, chromate-free treatment may be carried out by known methods.
[0166]
　The chromate treatment, electrolytic chromate treatment to form a chromate film by electrolysis, by using the reaction with the material to form a film, then washing out the excess treatment liquid reaction type chromate treatment was applied to the treatment liquid to the object to be coated there are dried coating type chromate treatment to form a film without washing with water. It may be adopted any of the processing.
[0167]
　The electrolytic chromate treatment, chromic acid, silica sol, resin (phosphoric acid, acrylic resin, vinyl ester resin, a vinyl acetate acrylic emulsion, carboxylated styrene butadiene latex, diisopropanolamine modified epoxy resin), and an electrolyte that uses a hard silica it can be exemplified chromate treatment.
[0168]
　The phosphate treatment, for example, zinc phosphate treatment, zinc phosphate calcium treatment, can be exemplified manganese phosphate treatment.
[0169]
　Chromate-free treatment is particularly suitable without impact on the environment. The chromate-free treatment, electrolytic chromate-free treatment to form a chromate-free coating by electrolysis, by using the reaction with the material to form a film, then, the reaction type chromate-free treatment to wash away the excess treatment liquid, the treatment liquid there are dried coating type chromate-free treatment to form a film without washing with water was applied to the object to be coated. It may be adopted any of the processing.
[0170]
　Further, on the film immediately above the plated layer may have an organic resin film one layer or two or more layers. As the organic resin is not limited to a specific type, for example, polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, or modified products thereof and the like resins. Here modified products and is a reactive functional group contained in the structure of these resins were reacted and other compounds containing a functional group in the structure capable of reacting with a functional group (such as a monomer or a crosslinking agent) It refers to the resin.
[0171]
　Examples of such an organic resin may be used by mixing one or more organic resins (those not denatured), in the presence of at least one organic resin, at least one other the organic resin obtained by modifying an organic resin may be used alone or in combination. And it may include any coloring pigments and anticorrosive pigments in the organic resin film. Those water reduction by dissolving or dispersing in water can also be used.
Example
[0172]
　Although there will be described embodiments of the present disclosure, the conditions in the examples is an example of conditions adopted for confirming the workability and effects of the present disclosure, the disclosure is limited to this single example of conditions not. The present disclosure without departing from the gist of the present disclosure, as long as they accomplish the purpose of the present disclosure, it is capable of adopting various conditions.
[0173]
(Example A)
　, as the plating layer of the chemical compositions shown in Tables 1-1 to 1-3 is obtained by using the pure metal ingot having a predetermined amount, the atmosphere was bath preparation the plating bath in a vacuum melting furnace . The production of plated steel sheet, using a batch type hot dip plating apparatus.
[0174]
　No. As a comparative material 102 and 103, commercially available Zn-Al-Mg plated steel sheet was prepared dip Zn plated steel sheet. Any thickness of the even plating layer is 20 [mu] m.
[0175]
　The plating original plate, generally material hot-rolled carbon steel 100 × 200 mm in 3.2mm (C = 0.15%, Si = 0.005%, Mn = 0.55%, P = 0.015%, S = 0 using the .005%), the plating step immediately before, were performed degreased, pickled.
[0176]
　In any of the sample produced, for be plated, steps up pulling after plating bath immersion was carried out equivalent reduction treatment method. That is, a plated steel plate N 2 -H 2 (5%) (dew point -40 ° or less, an oxygen concentration less than 25 ppm) environment, the temperature was raised in electrically heated to 800 ° C. from room temperature, after holding 60 sec, N 2 gas at spraying, is cooled to the plating bath temperature + 10 ° C., and immersed immediately in a plating bath.
　Incidentally, any be plated also immersion time in the plating bath was set to 0.2 seconds. N 2 by adjusting the gas wiping pressure, plating thickness were produced plated steel sheet so as to 20μm (± 1μm). From the plating bath immersion, until the wiping is completed, the batch plating device and high speed operation, and complete within one second and immediately N 2 was blown gas, dropping the temperature to plating the melting point.
[0177]
　Plating process was carried out six of the following.
[0178]
　Process A: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above plating melting point. The average cooling rate from the melting point to 250 ° C. of the plating bath and 15 (± 5) ℃ / sec, the average cooling rate from 250 ° C. to 0.99 ° C. and 7.5 (± 2.5) ℃ / sec cooling process in to obtain a plating layer. However, the melting point of the plating bath, cooling rate to 420 ° C. is 5 ° C. / sec greater than the holding time at 420 ° C. or more and less than 5 seconds.
[0179]
　Process B: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above plating melting point. To obtain a plated layer at an average cooling rate from the melting point to 0.99 ° C. of the plating bath 40 (± 10) ° C. / sec) and cooled process (mist cooling). However, the melting point of the plating bath, cooling rate to 420 ° C. is 5 ° C. / sec greater than the holding time at 420 ° C. or higher is less than 5 seconds.
[0180]
　Process C: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above the melting point of the plating bath. The average cooling rate from the melting point of the plating bath up to 420 ° C. 4 (± 1) ° C. / sec (420 retention time at ℃ or higher for 5 seconds greater), and the average cooling rate of 15 to 250 ° C. from 420 ° C. (± 5) to obtain a plated layer at ° C. / cooling process to seconds.
[0181]
　Process D: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above the melting point of the plating bath. The average cooling rate from the melting point to 420 ° C. of the plating bath 4 (± 1) ° C. / sec (holding time at 420 ° C. or higher for 5 seconds greater) and, 30 (± Average cooling rate to 250 ° C. from 420 ° C. 5) to obtain a plated layer in the cooling process that ° C. / sec.
[0182]
　Process E: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above the melting point of the plating bath. Plating bath at an average cooling rate from the melting point to 420 ° C. 8 (± 2) ° C. / sec and (420 retention time at ℃ or higher for 5 seconds greater), the average cooling rate of 15 to 250 ° C. from 420 ° C. (± 5 ) was obtained ° C. / sec) plating layer in the cooling process as a.
[0183]
　Process F: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above the melting point of the plating bath. Plating bath at an average cooling rate from the melting point to 420 ° C. 8 (± 2) ° C. / sec (420 retention time at ℃ or higher for 5 seconds greater), and the average of up to 250 ° C. from 420 ° C. cooling rate 30 (± 5 ) was obtained plating layer with cooling Puroseru which was ° C. / sec.
[0184]
- phase of the area fraction measured -
　from the obtained plated steel sheets were cut sample piece having a cross section of the plating layer (cross section cut along the thickness direction of the plated layer). Then, according to the method described above, it was measured area fraction below phase present in Zn-Al-Mg alloy layer.
· MgZn 2 phase area fraction
· Al phase area fraction
· Zn phase area fraction
· Zn-Al-MgZn 2 area fraction of the ternary eutectic structure (in the table referred to as "ternary eutectic structure") rate
area fraction of · Ca-Al-B intermetallic phase (in the table referred to as "compound B"): Al 2 CaB 5 phase, and, Al 2 CaB 5 part of atom positions in phase with Zn and Mg total area fraction of substituted compound phase
· Mg and Sn, Bi or intermetallic phases of the in (in the table referred to as "Sn compound phase"): Mg 2 Sn phase, Mg 3 Bi 2 phase and Mg 3 total area fraction of the in-phase
And other area fraction of the intermetallic compound: Mg 2 Si phase, Ca 2 Si phase, CaSi phase, Ca-Zn-Al intermetallic phase (in the table as "CZA" hereinafter), and Ca-Zn-Al- Si intermetallic phases total area fraction of (in the table referred to as "CZAS") (where each phase area fraction is not indicated, and the presence is confirmed phases denoted as "Ex.")
[0185]
- arc welding of the plated layer -
　using the obtained plated steel sheets were evaluated for arc welding of the plating layer was performed as follows.
　Samples of 100mm square are prepared two, CO 2 was produced lap fillet welded samples / MAG welding machine. Plated steel end 10mm lap width, overlapping gaps plated steel sheet each other 0 mm, it was performed arc welding in the lower plate leg 6mm about. Welding speed, 0.3 m / min, the welding wire is solid wire YGW14, .phi.12, CO 2 shielding gas flow rate, 15l / min, the welding current is 150 ~ 250 (A), the arc voltage was 20 ~ 24V, and 2pass. It was determined occupancy Bs of blowholes (%) or weld bead to implement an X-ray transmission test from above.
[0186]
　Zn-Al-Mg plated steel sheet, blowhole occupancy Bs of Zn-plated steel sheet is about 40%, blowhole occupancy Bs "B" rating 40% or more, blowhole occupancy Bs is 20 to 40% "a" rating, blow hole occupancy rate of Bs was less than 20%, the "S" rating.
[0187]
-LME Evaluation of -
　using the obtained plated steel sheets were performed as the evaluation of the LME follows.
　The plated steel sheet 70 mm × 150 mm central, stainless steel welding wire φ1.2mm (JIS Z3323 YF309LC) above welding conditions (however, 1pass) according, 75 mm length, a bead-on-plate welded bead-on-plate test piece of 3 ~ 5 mm width Obtained. Thereafter, to confirm the presence or absence of cracks by penetrant on specimens.
[0188]
　Zn-Al-Mg plated steel sheet, Zn-plated steel sheet 3mm or more LME that can be confirmed visually (that cracking) was plurality confirmed.
　Accordingly, if the LME than 5mm can be confirmed visually confirmed was evaluated as "B" rating.
　The weld (weld metal) LME not, the weld metal, the heat affected zone is the marker trace was confirmed by (HAZ portion) length of the circumferential length less than 5% in the boundary, the result of the cracking section and EPMA observations, crack If the Zn was not observed around the "a" rating.
　The weld around (around the weld metal) without cracking, things did not have marker marks was the "S" rating.
[0189]
- weld back surface of the corrosion resistance -
　using the obtained plated steel sheet, and the corrosion resistance of the weld back surface was carried out as follows.
　To obtain a bead-on-plate test piece in the same manner as in the evaluation of the LME. At accelerated corrosion test rear surface of the test piece (JASO M 609-91), it was evaluated red rust of the bead back surface at 90-180 cycles. The Zn-Al-Mg plated steel sheet, with 90 cycles, Tensabi occurs on the bead back surface. It became over the entire surface rust in the Zn-plated steel sheet.
[0190]
　What point-like red rust was observed at the bead back surface at 90 cycles was evaluated as "B" rating.
　The bead back surface at 120 cycles that point-like red rust was observed was evaluated as "A" rating.
　The bead back surface at 150 cycle what point-like red rust was confirmed was the "AA" rating.
　What point-like red rust was observed at the bead back surface 180 cycles was evaluated as "AAA" rating.
　180 things there was no red rust generated in the bead back part in the cycle is set to "S" rating.
[0191]
　- weld around the corrosion resistance -
　using the obtained plated steel sheet, and the corrosion resistance of the surrounding weld carried out as follows.
　To obtain a bead-on-plate test piece in the same manner as in the evaluation of the LME. The surface of the test piece was subjected 1000-1300 hours salt spray test (JIS Z 2371), and confirmed the corrosion resistance.
　The Zn-Al-Mg plated steel sheet, at 1000 hours lapse, red rust dripping was confirmed from the surrounding weld. It became over the entire surface rust in the Zn-plated steel sheet.
[0192]
　The weld around 1000 hours elapse what point-like red rust was observed was evaluated as "B" rating.
　The weld around at 1100 hours elapsed time what point-like red rust was observed was evaluated as "A" rating.
　The weld around at 1200 hours elapsed time what point-like red rust was confirmed was the "AA" rating.
　The weld around at 1300 hours elapsed time what point-like red rust was observed was evaluated as "AAA" rating.
　What red rust has not been confirmed around the weld at 1300 hours elapsed time was the "S" rating.
[0193]
- workability of the plating layer -
　using the obtained plated steel sheets were evaluated for workability of the plating layer was performed as follows.
　10R-90 ° V bending conducted pressing test on coated steel sheet, detached by pressing a cellophane tape V bending width 24mm in valleys, determines the powdering visually.
[0194]
　Tape powdering those ring peeling dust is adhered "B" rating,
　powder that did not ring peeling was evaluated as "A" rating
[0195]
　For example A, showing a list in Table 1-1 to Table 1-6.
[0196]
[Table 1-1]

[0197]
[Table 1-2]

[0198]
[Table 1-3]

[0199]
[Table 1-4]

[0200]
[Table 1-5]

[0201]
[Table 1-6]

[0202]
(Example B)
　as a plating layer of the chemical composition shown in Table 2-1 can be obtained using a pure metal ingot having a predetermined amount, the atmosphere was bath preparation the plating bath in a vacuum melting furnace. The production of plated steel sheet, using a batch type hot dip plating apparatus.
[0203]
　The plating original plate, generally material hot-rolled carbon steel 100 × 200 mm in 3.2mm (C = 0.15%, Si = 0.005%, Mn = 0.55%, P = 0.015, S = 0. use 005%), the plating step immediately before, were performed degreased, pickled.
[0204]
　In any of the sample produced, for be plated, steps up pulling after plating bath immersion was carried out equivalent reduction treatment method. That is, a plated steel plate N 2 -H 2 (5%) (dew point -40 ° or less, an oxygen concentration less than 25 ppm) environment, the temperature was raised in electrically heated to 800 ° C. from room temperature, after holding 60 sec, N 2 gas at spraying, is cooled to the plating bath temperature + 10 ° C., and immersed immediately in a plating bath.
　Incidentally, any be plated also immersion time in the plating bath was set to 0.2 seconds. N 2 by adjusting the gas wiping pressure, plating thickness were produced plated steel sheet so as to 20μm (± 1μm). From the plating bath immersion, until the wiping is completed, the batch plating device and high speed operation, and complete within one second and immediately N 2 was blown gas, to lower the temperature to the melting point of the plating bath.
[0205]
　Plating step was performed two ways below.
[0206]
　Process C (Example A similar):
temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above the melting point of the plating bath. The average cooling rate from the melting point to 420 ° C. of the plating bath 4 (± 1) ° C. / sec (holding time at 420 ° C. or higher for 5 seconds greater), and the average cooling rate to 250 ° C. from 420 ° C. 15 (± 5) to obtain a plated layer in the cooling process that ° C. / sec.
[0207]
　Process G: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above the melting point of the plating bath. The average cooling rate from the melting point of the plating bath up to 350 ℃ 4 (± 1) ℃ / sec (420 ° C. The holding time at least 7 seconds greater), and the average cooling rate from 350 ° C. to 250 ℃ 15 (± 5 ) was obtained plating layer in the cooling process was ° C. / sec.
[0208]
　Process H: temperature plating bath was mp + 20 ° C. of the plating bath. After pulling up the be plated from the plating bath, completing the wiping just above the melting point of the plating bath. The average cooling rate 4 from the melting point of the plating bath to 250 ° C. (± 2) ° C. / sec (holding time at 420 ° C. or higher than 10 seconds) to obtain a plated layer in the cooling process that.
[0209]
　Using the obtained coated steel sheet, in the same manner as in Example A, each phase area fraction was implemented various performance evaluation.
[0210]
　However, when the presence of Ca-Zn-Al intermetallic phase and Ca-Zn-Al intermetallic phase is confirmed, it was measured the average crystal grain size of the compound phase according to the method described above. Then, it shows the average crystal grain size in the table. The unit of the average grain size is "μm".
[0211]
　Further, by using the plated steel sheet obtained was the corrosion resistance after painting was carried out as follows.
　To prepare a bead-on-plate test piece in the same manner as in the evaluation of the LME was conducted in Example A. For this specimen, Nippon Parkerizing Co., Ltd. of surface conditioning treatment agent (trade name: Prepalene X) with the surface conditioning was performed at room temperature for 20 seconds.
　Then, Japan Parkerizing zinc phosphate treatment solution Co., Ltd. (trade name: PALBOND 3020) was performed using a phosphoric acid salt treatment. Specifically, the temperature of the processing solution and 43 ° C., was immersed for 120 seconds hot pressing steel in the process liquid. Thus, Phosphate coated surface of the steel material is formed.
　Then, after performing the phosphating, against phosphate treatment bead-on-plate test piece after the cationic electrodeposition paint made by Nippon Paint Co., and electrodeposition coating in the slope energizing voltage 160 V, Furthermore, and baking for 20 minutes at the baking temperature 170 ° C.. The average thickness of the paint after electrodeposition coating was a 15μm for any of the samples.
　Then subjected to contact of the specimen with JASO test (M609-91), confirmed the red rust occurrence condition of the bead portion around after painting.
[0212]
　What point-like red rust has been confirmed in the bead portion or the heat-affected zone within 90 cycle was a "B" rating.
　What point-like red rust has been confirmed in the bead portion or the heat-affected zone within 120 cycles was evaluated as "A" rating.
　What point-like red rust has been confirmed in the bead portion or the heat-affected zone within 150 cycles was evaluated as "AA" rating.
　What point-like red rust has been confirmed in the bead portion or the heat-affected zone within 180 cycle was a "AAA" rating.
[0213]
　For example B, submitted in the list in Table 2-1 to Table 2-2.
[0214]
[table 2-1]

[0215]
[Table 2-2]

[0216]
　Having described in detail preferred embodiments of the present disclosure with reference to the accompanying drawings, the present disclosure is not limited to such an example. It would be appreciated by those ordinarily skilled in the art that belongs present disclosure, within the scope of the technical idea described in the claims, it is intended to cover various changes in form , also such modifications are intended to fall within the technical scope of the present disclosure.
[0217]
　In FIG 1 to FIG 5, the target indicated by each reference numeral are as follows.
　1: Al phase (containing fine Zn
　phase.) 2: MgZn 2 phase
　(bulk) 3: Zn-Al-MgZn 2 ternary eutectic structure
　4: MgZn 2 phase
　(bulk) 5: Al phase (alpha
　phase) 6 : Al phase (beta
　phase) 7: Zn phase
　8: Ca-Al-B intermetallic phase B compound (Al 2 CaB 5 phases: atomic ratio estimated by EDS quantitative
　analysis) 9: Zn-Al-MgZn 2 ternary Zn phase eutectic structure
　10: Zn-Al-MgZn 2 ternary eutectic structure of MgZn 2 phase
　11: Zn-Al-MgZn 2 ternary eutectic structure of Al phase
　20: alpha phase (normal alpha
　phase) 21 : β-phase (normal β-phase)
100: plated layer
100A: plating layer
101: Zn-Al-Mg alloy layer
101A: Zn-Al-Mg alloy layer
102: Al-Fe alloy layer
102A: Al-Fe alloy layer
[0218]
　In this disclosure, the following additional statements are further disclosed.
(Supplementary Note 1)
　A hot dip plated steel sheet and a plating layer comprising a steel, a Zn-Al-Mg alloy layer disposed on the surface of the steel material,
　any cross-sectional structure of the Zn-Al-Mg alloy layer in, equivalent grain size 1μm or more MgZn in diameter 2 is a total area ratio of the phase and Al phase is 70% or more, the area ratio of the Zn phase is less than 10%,
　the Zn-Al-Mg alloy layer There, Mg 2 Si phase, Ca 2 Si phase, containing CaSi phase, Ca-Zn-Al phase, and at least one intermetallic phase selected from the group consisting of Ca-Zn-Al-Si phase,
　the plated layer, by
　mass%, Zn: less than 44.9% ultra ~
　74.9%, Al: less than 20% super ~
　35%, Mg: less than 5% ultra 20%
　~, Ca: 0.1% ~ 3 less than%
　.0,
　Si: 0% ~ 1%, B: 0% ~
　0.5%, Y: 0% ~
　% .5,
　La:
　0% ~ 0.5%, Ce: 0% ~ 0.5%,
　Cr: 0% ~ 0.25%, Ti: 0% ~ 0.25%,

　Ni:
　0% ~ 0.25%, Co:
　0% ~ 0.25%, V: 0% ~ 0.25%,
　Nb: 0% ~ 0.25%, Cu: 0% ~ 0.25%, 　Mn:
　0% ~ 0.25%, Sr: 　0% ~ 0.5%, Sb: 0% ~ 0.5%, 　Pb: 0% ~ 0.5%, Sn: 0% ~ 20%, 　Bi: 　0% ~ 2%, an In: 　0% ~ 2%, Fe: 0% ~ 5%, and 　consists of the impurity, the element group a Y, La and Ce, the element group B Cr, Ti, Ni, Co , V , Nb, Cu and Mn, the element group C Sr, Sb and Pb, and when the element group D Sn, and Bi and in, the total content of element selected from the group a of 0.5% or less, Ca and total content of element selected from the group a is less than 3.0%, the total content of element selected from the group B of 0.25% or less, based on selected from the following element group C Dip plated steel sheet total content of 0.5% or less, the total content of element selected from group D is 20% or less.

[0219]
(Supplementary Note 2)
　The Al is less than 22% ultra-35%, the Mg is less than 10% ultra -20%, the Ca is less than 0.3% to 3.0% the Si is 0 dip plated steel sheet according to note 1 is .1% to 1%.
[0220]
(Supplementary Note 3)
　The plated layer is, B, element group A (Y, La, Ce) , the element group B (Cr, Ti, Ni, Co, V, Nb, Cu, Mn), and the element group C (Sr, sb, contains at least one selected from the group consisting of Pb), the plating layer is, in mass%,　
　if containing B is, B: 0.05% ~ 0.5%,
　selected from the following element group a when containing the element is from 0.05 to 0.5% the content of the sum,
　when it contains an element selected from the group of elements B is ~ 0.05% content of the total 0. 25%,
　when it contains an element selected from the element group C is hot dip plated steel sheet according to Supplementary note 1 or 2 content of the sum satisfies 0.05% to 0.5%.
[0221]
(Supplementary Note 4)
　The Zn-Al-Mg alloy layer, Al2CaB5, or a portion of the atomic positions is a Ca-Al-B compound substituted with Zn and Mg B in atomic percent of 40% or more Ca- dip plated steel sheet according to any one of appendices 1 to Supplementary note 3 containing al-B compound.
[0222]
(Supplementary Note 5)
　The plating layer contains at least one element selected from the element group D (Sn, Bi, an In), the plating layer is, in
　　mass%, Sn + Bi + an In = 0.05% ~ 20%
of filled, the plating layer is melted plated steel sheet according to item 1 any one of Appendixes 1 to Supplementary note 4, further comprising at least one intermetallic compound selected from the group consisting of Mg2Sn, Mg3Bi2 and Mg3In.
[0223]
(Supplementary Note 6)
　comprises said plating layer further Al-Fe alloy layer, the Al-Fe alloy layer is formed on the surface of the steel, forming the Zn-Al-Mg alloy layer on the Al-Fe alloy layer dip plated steel sheet according to any one of appendices 1 to Appendix 5 which is.
[0224]
　Japanese disclosure of patent application 2017-013259 its entirety is incorporated herein by reference.
　All documents described herein, patent applications, and technical standards, each individual publication, patent application, and that the technical specification is incorporated by reference to the same extent as if marked specifically and individually, It incorporated by reference herein.

The scope of the claims
[Requested item 1]
　And steel, is disposed on the surface of the steel, a plated steel material with a plated layer containing Zn-Al-Mg alloy layer,
　in the cross section of the Zn-Al-Mg alloy layer, MgZn 2 area of the phases rate is 45 ~ 75% MgZn 2 phase and the total area fraction of the Al phase is 70% or more, and Zn-Al-MgZn 2 ternary eutectic structure area fraction of 0-5%
　the plating layers, in
　mass%, Zn: less than 44.90% super ~ 79.90%,
　Al: less than 15% super ~
　35%, Mg: less than 5% ultra 20%
　~, Ca: 0.1% ~ 3. less than%
　0,
　Si:
　0% ~ 1.0%, B: 0% ~
　0.5%, Y: 0% ~ 0.5%, La: 0% ~
　0.5%, Ce: 0% ~ 0
　% .5,
　Cr:
　0% ~ 0.25%, Ti: 0% ~ 0.25%,
　Ni: 0% ~ 0.25%, Co: 0% ~
　0.25%, V :
　0 Pasento ～ 0.25 Pasento, Nb: 0 Pasento ～ 0.25 Pasento,

　Cu:
　0% ~ 0.25%, Mn: 0% ~
　0.25%, Sr: 0% ~ 0.5%, Sb:
　0% ~ 0.5%, Pb: 0% ~ 0.5%,
　sn:
　0% ~
　20.00%, Bi: 0% ~ 2.0%, an In:
　0% ~ 2.0%, Fe: 0% ~ 5.0%, and
　consists of the impurity,
　the element group a Y when La and Ce, the element group B were Cr, Ti, Ni, Co, V, Nb, Cu and Mn, the element group C Sr, Sb and Pb, and the element group D Sn, and Bi and In,
　wherein the sum is 0% to 0.5% the content of the element selected from the group consisting
　a, the total content of the element selected from Ca and the element group a is less than 0.1% to 3.0% , and the
　said total content of element selected from the group B is 0% to 0.25%
　the 0% content of total element selected from the group consisting C-0.5 , And the
　plating steel having a chemical composition the total content of element selected from the element group D is 0% to 20.00%.
[Requested item 2]
　The Zn-Al-Mg alloy layer, Mg 2 Si phase, Ca 2 selected Si phase, from CaSi phase, Ca-Zn-Al intermetallic compound phase, and Ca-Zn-Al-Si intermetallic group consisting compound phase plated steel according to claim 1 which contains at least one intermetallic phase being.
[Requested item 3]
　Wherein Al is a content of less than 22% super to 35 percent, the is less than 10% ultra -20% content of Mg, the content of the Ca is located less than 0.3% 3.0% , plated steel according to claim 1 or claim 2 content of the Si is 0.1% to 1.0%.
[Requested item 4]
　Plated steel according to claim 1 or claim 2 content of the Al is 15% ultra to 22%.
[Requested item 5]
　If the plating layer contains the B, the content of the B is 0.05% to 0.5% in mass%,
　When containing the element the plating layer is selected from the element group A, wherein the total content of element selected from the group a is 0.05% to 0.5% in mass%,
　when containing the element the plating layer is selected from the element group B, from the element group B the total content of chosen elements is 0.05% to 0.25% in mass%,
　when containing the element the plating layer is selected from the element group C, an element selected from the element group C plated steel according to any one of the total claims 1 to 3 content is 0.05% to 0.5% by weight percent.
[Requested item 6]
　The Zn-Al-Mg alloy layer, Al 2 CaB 5 -phase, and the Al 2 CaB 5 Ca-Al some atomic position of phase is selected from the group consisting of compound phase substituted with Zn and Mg a -B intermetallic phase, plating steel according to any one of claims 1 to 5 B contains 40% or more of Ca-Al-B intermetallic compound phase in atomic%.
[Requested item 7]
　When containing the element the plating layer is selected from the element group D, the total content of element selected from the element group D is 0.05% to 20% in mass%,
　the Zn-Al-Mg alloy layer, Mg 2 Sn phase, Mg 3 Bi 2 phase and Mg 3 to any one of claims 1 to 6 which contains at least one intermetallic phase selected from the group consisting of in-phase plated steel described.
[Requested item 8]
The plating layer is plated steel according to any one of claims 1 to 7 having an Al-Fe alloy layer between the steel Zn-Al-Mg alloy layer.