Technical field
[0001]The present disclosure relates to a plated steel sheet.
BACKGROUND
[0002]In recent years, automobile structural members, in view of rust prevention, plated steel sheets are used, which are mainly in the domestic market are applied galvannealed steel sheet. Galvannealed steel sheet, heat-treated alloy after performing molten zinc plating steel sheet was by diffusing Fe from the steel sheet (substrate steel sheet) in the plating layer improves the weldability and corrosion resistance after painting plating it is a steel plate. For example, plated steel sheet disclosed in Patent Document 1 is used typically as an automotive coated steel sheet in Japan.
[0003]
　Usually, the plated steel sheet for automobiles, because they are used in a state of being molded of a plate into complex shapes, often are subjected to press forming. For galvannealed steel sheet, the plating layer becomes hard by diffusion of Fe from the substrate steel sheet. Therefore, easy plating layer is peeled off, such as powdering or flaking, plating layer is also present unique problems not found in hot-dip galvanized steel sheet softer.
[0004]
　Furthermore, plated steel sheet with a plating layer of rigid, easily plated layer is damaged by external pressure, once the cracks, the crack propagates to the interface between the plated layer and the base steel (steel plate). Therefore, the plating layer is peeled off starting from the interface with the base steel (steel plate), it tends to generate a dropout is a problem.
　For example, when using the galvannealed steel sheet outer panel of an automobile, the pebble collisions stone recoil vehicle (chipping), and coated with the plating layer is peeled off at the same time, the base steel (steel plate) is exposed Prone. Therefore, there is the corrosion becomes severe than plated steel sheet having a plating layer of soft without alloying.
　Further, from the viewpoint of rust prevention, galvannealed steel sheet contains Fe in the plating layer. Therefore, when such a chipping occurs due to corrosion of the plating layer immediately rust it is likely to occur in the red-brown, cause problems on car appearance.
[0005]
　The resolution of these problems, the plating layer has a toughness, and the application of plated steel sheet containing no Fe is effective. For example, an automotive coated steel sheet in a plating layer not containing Fe, North America, in Europe, etc. are mainly galvanized steel sheet is used. However, galvanized steel sheets have not been processed alloying hardly occurs and chipping. In addition, hardly occurs even corrosion initial red rust for the plating layer containing no Fe as galvannealed steel sheet. However, in the state where painted easily corrosion plated layer under the coating film, the coating film is raised (swelling). Therefore, galvanized steel sheet can not be said that never suitable as plated steel sheet for automobiles.
[0006]
　The molten Zn-based plating as a method for high corrosion resistance of, and a method of incorporating the Al to Zn plating layer. In building materials as high corrosion resistance coated steel sheet, molten Al-Zn alloy coated steel sheet as disclosed in Patent Document 2 has been widely put into practical use. Plated layer of such a molten Al-Zn-based plated steel sheet is comprised of first crystallized out dendritic alpha-Al phase (dendrite structure), Zn phase and Al phase formed in the gap dendritic structure from a molten state It is formed from the tissue (inter dendrite structure). Dendritic structure is passivated, and, inter dendritic structure has a high Zn concentration compared with the dendritic structure. Therefore, corrosion is concentrated on the inter dendritic structure.
　As a result, the corrosion proceeds inter dendritic tissue vermicular, corrosion travel path becomes complicated. Therefore, less likely to reach the corrosion easily base steel (steel plate).
　Thus, molten Al-Zn-based plating steel sheet, when the coating is used as a bare material not made, resistant to corrosion that the thickness of the plating layer was superior to the same hot-dip galvanized steel sheet.
[0007]
　When using such a molten Al-Zn-based plated steel sheet as automotive exterior panels, the plated steel sheet is subjected to an automobile manufacturer or the like in a state that has been subjected to plating in a continuous hot-dip plating equipment. Therefore, the plated steel sheet after being processed in the panel component shape, chemical conversion treatment, electrodeposition coating, it is common to total paint for automobiles containing intermediate coating and top coating is applied.
[0008]
　For the purpose of improving corrosion resistance is also considered that the inclusion of Mg to Zn-Al-based plating layer. For example, Patent Document 3, the plating layer during MgZn 2 Zn / Al / MgZn containing a Mg compound such as 2 to form a ternary eutectic structure, the molten Zn-Al-Mg plated steel sheet with improved corrosion resistance It has been disclosed. The content of Mg, the sacrificial corrosion resistance of the plating layer is improved, anticorrosion effect of the base steel is considered to be improved.
[0009]
　Further, in Patent Document 4, by containing Sn or In, to destroy the passivation dendrite structure, the molten Al-Zn alloy coated steel sheet having improved corrosion resistance after painting is disclosed.
[0010]
　Further, Patent Document 5 and 6, Mg is a Sn description molten Al-Zn alloy coated steel sheet which contains the composite.
In Patent Documents 5 and 6, the molten Al-Zn alloy coated steel sheet corrosion resistance after painting It is described as excellent and / or processability.
[0011]
Patent Document 1: Japanese Patent 2003-253416 JP
Patent Document 2: Japanese Patent Publication 46-7161 discloses
Patent Document 3: Japanese Patent 2001-329383 JP
Patent Document 4: Japanese WO 2014 / 155944 Patent
Patent Document 5: Japanese Patent 2015-214747 JP
Patent Document 6: Japanese Patent 2002-180225 JP
Summary of the Invention
Problems that the Invention is to Solve
[0012]
　However, the outer panel with molten Al-Zn-based plated steel sheet described in Patent Document 2, (when exposed base steel) damage to the coating and the plating layer was when occurred, above-mentioned dendrite structure and inter due to the phase structure of the unique plating layer consisting of two organizations with dendritic structure, Zn preferentially dissolves in the wound portion in origin (preferential corrosion of inter dendritic structure) is at the interface between the coating and the plating layer Occur. This is progress towards deep in the paint healthy part, cause blistering large coating film. As a result, it is known that there is a problem that not enough corrosion resistance (corrosion resistance after painting).
　Moreover, inter-dendritic structure, compared to the dendritic structure, low hardness. Therefore, due to the hardness difference between the inter dendritic structure and dendritic tissue, during pressing, deformation is concentrated on the inter dendritic structure. As a result, it is known to crack reaching the base steel to the plating layer. Since the base steel corrosion is accelerated in the crack vicinity portion exposed, corrosion resistance after painting of the working portion has not been satisfied.
[0013]
　Further, MgZn contained in the plating layer of the hot-dip Zn-Al-Mg plated steel sheet described in Patent Document 3 2 -phase is brittle. Therefore, when subjected to this plating steel sheet machining, Zn / Al / MgZn 2 there is a possibility that results in a number of cracks starting from the ternary eutectic structure. Since the cracking base steel is exposed, there is still a problem that securing Dekii corrosion resistance after painting of the processing unit.
[0014]
　Further, the molten Al-Zn-based plated steel sheet described in Patent Document 4, the plating layer Mg is not contained in, is not any consideration attempts to reduce the corrosion rate of the plating layer itself. Therefore, the corrosion resistance after painting is considered not intended satisfactory as plated steel sheet for automobiles.
[0015]
　Further, MgZn as a melt in the Al-Zn alloy coated steel sheet, not been sufficient study for controlling the plating tissue, brittle Mg intermetallic compound thus plating layer described in Patent Documents 5 and 6 2 it is estimated that the phase is formed.
　In this case, the molten Al-Zn alloy coated steel sheet obtained has poor processability, resulting in cracks in the plating layer during press working. Therefore, the processing unit considered corrosion starting from the crack progresses.
　These molten Al-Zn alloy coated steel sheet is inferred that does not have a satisfactory workability after painting corrosion resistance as a plated steel sheet for automobiles.
[0016]
　Therefore, conventionally, plated steel sheet having both workability and corrosion resistance after coating has not been developed, were not especially exist plated steel sheet suitable as automotive applications.
[0017]
　Challenges One aspect of the present disclosure is to provide is to provide a superior plated steel sheet in workability and corrosion resistance after coating.
Means for Solving the Problems
[0018]
　The means for solving the above problems includes the following aspects.
[0019]
<1>
　A plated steel sheet having a steel sheet, and a plated layer provided on at least part of the surface of the steel sheet,
　the plating layer is, in
　mass%, Al: 15%
　~ 60% Mg: 0.
　%
　~ 8.0 5% Sn:
　0.5% ~ 20.0% Si: 0.05% ~ 1.50%
　Bi: 0% ~ 5.0%, an In: 0% ~
　2.0%, Ca :
　0%
　~ 3.0%,
　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%, B : 0% to 0.5%,
　Contains, has a chemical composition and the balance being Zn and impurities,
　and the plating layer, the area fraction 5-65% particulate Mg 2 and Sn phase containing tissue, the tissue including a solid solution of Zn and Al has,
　the granular Mg 2 Sn phase containing tissue, Zn phase and granular Mg less than the crystal grain size 1μm dispersed in the Zn phase 2 is the Sn phase, consisting of tissue, plated steel sheet.
<2>
　in weight%, the content of 0.5% to 3.0% of the Mg, plated steel sheet according to the above content of Sn is 1.0% to 7.5% <1>.
<3>
　in mass%, the content of Al is 20% to 60%, the content of Mg is 1.0% to 2.0%, the content of the Sn 1.0% to 5.0% plated steel sheet according to <1> or <2>, and the content of the Si is 0.05% to 1.0%.
<4>
　The content of the content and the Mg of the Sn is plated steel sheet according to any one of the satisfying the following formula (1) <1> to <3>.
　Mg ≦ Sn ≦ 2.5 × Mg ··· Equation (1)
　In the formula (1), each element symbol represents the content of each element in weight percent.
<5>
　the granular Mg 2Area fraction of Sn phase containing tissue, plated steel sheet according to any one of the 20% to 60% <1> to <4>.
<6>
　The particulate Mg 2 plated steel sheet of the area fraction of the Sn phase containing tissue, according to any one of the 30% and 60% <1> to <5>.
<7>
　plated steel sheet according to any one of the area fraction of the tissue, including a solid solution of the Zn and Al, the 35% -95% <1> to <6>.
<8>
　the plating layer is equivalent circle diameter 1μm or more bulk MgZn 2 -plated steel sheet according to any one of the having 0% to 20% phase area fraction <1> to <7>.
<9>
　the plating layer is equivalent circle diameter 1μm or more bulk MgZn 2 -plated steel sheet according to any one of the having 0% to 5% phase area fraction <1> to <8>.
<10>
　the plating layer is plated steel sheet according to any one of <1> to <9> having 0% to 20% equivalent circular diameter 2μm or more bulk Zn phase in area fraction.
<11>
　plated steel sheet according to any one of the plating layer, wherein with 0% to 10% equivalent circular diameter 2μm or more bulk Zn phase in area fraction <1> to <10>.
<12>
　Between the plated layer and the steel sheet plated according to any one of the, further comprising an interfacial alloy layer consisting of Al-Fe intermetallic compound having a thickness of 100nm ~ 1.5μm <1> ~ <11> steel sheet.
The invention's effect
[0020]
　In one aspect of the present disclosure can provide an excellent plated steel sheet in workability and corrosion resistance after coating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021]
It is a [1] reflection electron image of the photographed SEM an example of the plating layer of the plated steel sheet according to the present disclosure (No.29 Example) 2000-fold (BSE images).
It is an enlarged view of region A of FIG. 2 in FIG.
No. [Figure 3] Example The plating layer of the plated steel sheet according to 31 is a reflection electron image of the photographed SEM at 2000 times (BSE images).
No. [Figure 4] Example The plating layer of the plated steel sheet according to 32 as a reflected electron image of the photographed SEM at 2000 times (BSE images).
[FIG 5] Zn / Al / MgZn 2 is a ternary eutectic structure determination and reflected electron image of SEM of a cross section of the plating layer to the area fraction explaining a method of measuring (BSE images).
DESCRIPTION OF THE INVENTION
[0022]
　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".
　Numerical ranges expressed using "to" means a range including numerical values described before and after "to" as the lower and upper limits.
　Numerical range when "super" or "less than" are assigned to the numerical values described before and after "to" means a range that does not include the lower limit or the upper limit value of these values.
　Content of the element of 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.
　The "corrosion resistance after painting", indicating the corrosion hardly nature of the plating layer itself.
　The "sacrificial corrosion resistance", the base steel bare portion (cut end surface of example plated steel sheet, plating layer cracking unit during processing, and the peeling of the plating layer, portions of the base steel is exposed) the property of inhibiting corrosion of show.
　The "equivalent circle diameter", when observing a plating layer cross-section (taken along the cross section in the thickness direction of the plated layer), when the area defined by the contour of the phases, was considered a circle having the same area the diameter of a circle.
　The "C direction" indicates a direction perpendicular to the rolling direction of the steel sheet.
　The "L direction" indicates a direction parallel to the rolling direction of the steel sheet.
[0023]
　Plated steel sheet of the present disclosure includes a steel sheet, a plated layer provided on at least part of the surface of the steel sheet, a.
　Plating layer has a predetermined chemical composition. Also, the plating layer, the area fraction 5-65% particulate Mg 2 has a Sn phase containing tissue, tissue containing a solid solution of Zn and Al (hereinafter, for convenience, referred to as a "dendritic structure") and the.
　Then, the granular Mg 2 Sn phase containing tissue, and Zn phases, the Zn phase particulate Mg less than dispersed grain size 1μm to in 2 and Sn phase, a tissue consisting of.
[0024]
　Plated steel sheet of the present disclosure, the above-described configuration, an excellent plated steel sheet in workability and corrosion resistance after coating. Plated steel sheet of the present disclosure were found based on the following findings.
[0025]
Inventors, automotive applications, suitable for coated steel sheet such as building materials, were studied workability corrosion resistance after painting of the plating layer. As a result, we obtained the following findings.
　Mg intermetallic compounds, although a brittle phase, Mg 2 Sn phase MgZn 2 has a plastic deformability than the phase. The Mg 2 Sn, phase, by a tissue micro-dispersed Zn phase having a plastic deformability, express plastic deformability organization as a whole, contributes to the improvement of workability. In addition, Mg 2 Sn phase becomes a source of Mg ions in a corrosive environment, for Mg ions to the insulating coating of the corrosion products, coatings corrosion under the painting state is suppressed.
[0026]
　Therefore, Zn phase and granular Mg less than the crystal grain size 1μm dispersed in Zn phase 2 Sn phase and particulate Mg consisting 2 by the presence predetermined amount of Sn phase containing tissue area fraction, corrosion resistance after painting and the workability and increases both. Specifically, the granular Mg 2 when the area fraction of the Sn phase containing tissue is 5% or more, than the commercial plated steel sheet, the higher the workability and corrosion resistance after coating.
[0027]
　By the above findings, the plated steel sheet of the present disclosure has been found to be a good plated steel sheet in workability and corrosion resistance after coating.
[0028]
　Furthermore, plated steel sheet of the present disclosure, since the granular layer dispersion tissue expressing plastic deformability is present in the plating layer, excellent in chipping resistance, can be realized longer life of the plated steel sheet after painting.
　Plated steel sheet of the present disclosure includes a predetermined amount of Al in the plating layer has a dendritic structure to increase the melting point of the plating layer. Therefore, excellent galling resistance can be suppressed adhesion to the press die of the plating layer during press molding. In other words, plated steel sheet of the present disclosure, it is possible to achieve both excellent corrosion resistance after painting and press formability.
[0029]
　In particular, in the plated steel sheet automotive applications, the period until the coating film swelling and red rust from processability and cutting wounds is important. Therefore, excellent plated steel sheet corrosion resistance after painting and workability of the plating layer is suitable for automotive applications.
[0030]
　It will be described in detail below plated steel sheet of the present disclosure.
[0031]
　First, a description will be given of steel plate.
　Steel plate becomes be plated is not particularly limited, Al-killed steel, very low carbon steel, high carbon steel, various high strength steels, Ni, various steel sheets such as Cr-containing steel can be used. Steelmaking process, the strength of the steel, hot rolling method, the pickling method, there is no special restriction on the pretreatment process of the steel sheet cold-rolled process, or the like.
[0032]
　Chemical composition of the steel sheet (C, Si, etc.) are not particularly limited. Ni contained in the steel sheet, Mn, Cr, Mo, Ti, elements such as B it is, has not been confirmed to affect the plating layer.
[0033]
　Next, a description will be given of a plating layer.
　First described the chemical composition of the plating layer.
　The chemical composition of the plated steel sheet comprises Al, Mg, Sn, and Si as essential elements, the balance being Zn and impurities. The chemical composition of the plated steel sheet, Bi, In, Ca, Y , La, Ce, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, as optional elements at least one of Pb and B it may contain. In other words, any element may not contain.
　The content of each element of the plating layer means the average content of each element contained in the entire plating layer.
[0034]
[Al: 15% ~
　60%] Al is an essential element for improving the seizure resistance after painting corrosion resistance of the plating layer. Most Al in the plating layer is present as Al phase in the interior of the dendritic structure.
　Dendritic structure to be described later is not passivated by the inclusion effect of Sn, in a state of not a factor to lower the corrosion resistance after coating. On the other hand, the metal in the plating layer is low melting point of the plating layer is baked stick that becomes a problem in the press die. However, as the Al concentration is high, the area fraction of the dendritic structure is a high melting point tissue is increased. Therefore, as a result suppressing the adhesion of the press die of the plating layer during press forming (i.e., improves the seizure resistance) becomes possible.
　Al concentration required to secure the area fraction of dendritic structure capable of expressing a sufficient seizure resistance is 15% or more. Therefore, the 15% lower limit of the Al concentration. Preferred Al concentration is 20% or more.
　On the other hand, when the Al concentration exceeds 60%, excessively grown is "interfacial alloy layer consisting of Al-Fe intermetallic compound" formed in the interface of the plating layer and the base steel to be described later, impairs workability. Therefore, the 60% upper limit of the Al concentration. Preferred Al concentration is 40% or less.
[0035]
[Mg: 0.5% ~
　8.0%] Mg is granular Mg 2 the Sn phase containing tissue is formed in the plating layer, is an essential element for imparting processability and corrosion resistance after painting the plating layer . Mg is present as Mg intermetallic compound in plating layer elutes corrosive environment as Mg ions in a corrosive environment. Mg ion, a Zn-based corrosion products and insulating coating of, for barrier coating of rust. Thereby suppressing the invasion of corrosive factors to the plating layer and the coating film under can contribute to corrosion resistance after painting improves. Most Mg granular Mg 2 contained in the Sn phase containing tissue. Granular Mg 2 by formation of Sn phase containing tissues, improves both the workability and the corrosion resistance after coating. Mg concentration required to improve the workability and the corrosion resistance after coating is 0.5%. Therefore, the 0.5% the lower limit of the Mg concentration. Preferred Mg concentration is 1.0% or more.
　On the other hand, if the Mg concentration exceeds 8.0%, the bulk MgZn below 2 phase is excessively formed, impairing workability. Therefore, the 8.0% upper limit of the Mg concentration. Massive MgZn impair the workability 2 from the viewpoint of suppressing the generation of phase, the preferred Mg concentration is set to 3.0% or less. More preferred Mg concentration is 2.0% or less.
[0036]
[Sn: 0.5% ~
　20.0%,] Sn is, Mg granular Mg with 2 to Sn phase containing tissue is formed in the plating layer, essential in order to impart processability and corrosion resistance after painting the plating layer it is an element. Further, Sn is, Zn / Al / MgZn 2 with ternary eutectic structure, bulk MgZn 2 is an element having also an effect of suppressing generation of phase.
　Therefore, Sn is also an element enhancing the workability and corrosion resistance after painting to the plating layer.
　When the Sn concentration is small, the granular Mg 2 While Sn phase containing tissue is not easily formed, Zn / Al / MgZn 2 ternary eutectic structure and bulk MgZn 2 generation amount of phase is increased, corrosion resistance after painting of the plating layer and processability tends to decrease. Therefore, the lower limit of the Sn concentration is 0.5%. Granular Mg 2 Sn phase containing tissue was sufficiently formed, Zn / Al / MgZn 2 ternary eutectic structure and bulk MgZn 2 from a sufficiently suppressing the generation of phase, the preferred Sn concentration is 0.1% or more . More preferred Sn concentration is 1.5% or more.
　On the other hand, when an excess of Sn concentration, Sn surplus crystallized out as a potentially noble Sn phase, it lowers the corrosion resistance after coating. Therefore, the upper limit of the Sn concentration is 20.0%. From the viewpoint of improving the corrosion resistance after painting, preferable Sn content is not more than 7.5%. More preferred Sn concentration is 5.0% or less.
[0037]
[Si: 0.05% ~
　1.50%] Si suppresses when contained in the plating bath, and Zn and Al contained in the plating bath, the reactivity of Fe element be plated elements it is. That, Si is plated layer and by controlling the reactivity of the steel matrix, affect the adhesiveness and workability of the plating layer composed of "Al-Fe intermetallic compound interface alloy layer (particularly, Fe 2 Al 5 is an essential element to control the formation behavior of the interfacial alloy layer) comprising or consisting of. minimum Si concentration required for inhibition of interfacial alloy layer is 0.05%.
　Si content If it is less than 0.05%, interfacial alloy layer is grown immediately after immersing be plated in the plating bath, the ductility imparting the plating layer is difficult, workability tends to decrease. Therefore, the lower limit of the Si concentration , 0.05%. the preferred Si concentration is 0.2% or more.
　on the other hand, when the Si concentration exceeds 1.50%, potentially noble Si phase remains to the plating layer, the corrosion acts as the cathode portion. as a result, the coating Leads to a decrease in Sogo corrosion resistance. Therefore, the upper limit of the Si concentration is 1.50%. The preferred Si concentration is 1.0% or less.
　In addition, Si is between metal and Mg in the plating layer Mg compounds 2 may exist as a Si phase, Mg 2 area fraction of Si phases is not more than 5%, no effect on performance.
[0038]
[Bi: 0% ~
　5.0%] Bi is an element which contributes to the improved processability. Therefore, the lower limit of the Bi concentration is 0% greater than (preferably 0.1% or more, more preferably 3.0 or higher) is good.
　On the other hand, when the Bi concentration is excessively increased, corrosion resistance after painting tends to deteriorate. Therefore, the upper limit of the Bi concentration is 5.0% or less (preferably 0.5% or less, more preferably 0.1% or less) and.
[0039]
[An In: 0% ~
　2.0%] an In is an element which contributes to the improved processability. Therefore, the lower limit of the In concentration is 0% greater than (preferably 0.1% or more, more preferably 3.0 or higher) is good.
　On the other hand, when the In concentration is increased, the tendency for corrosion resistance after coating is deteriorated. Therefore, the upper limit of the In concentration is 2.0% or less (preferably 0.3% or less).
[0040]
[Ca: 0% ~ 3.0%] Ca
　is an element which can adjust the optimal Mg elution amount to impart corrosion resistance after painting and sacrificial corrosion resistance. Therefore, the lower limit of the Ca concentration is 0% greater than (preferably more than 0.05%) is better.
　On the other hand, when the Ca concentration increases, tends to deteriorate corrosion resistance after painting and workability. Therefore, the upper limit of the Ca concentration is 3.00 or less (preferably 1.0% or less).
[0041]
[Y: 0% ~ 0.5%]
　Y is an element which contributes to the improved processability. Therefore, the lower limit of the Y concentration is 0% greater than (preferably 0.1% or more) is good.
　On the other hand, when the Y concentration increases, the tendency for corrosion resistance after coating is deteriorated. Therefore, the upper limit of the Y concentration is 0.5% or less (preferably 0.3% or less).
[0042]
[La and Ce: 0% ~
　0.5%] La and Ce is an element contributing to improving the workability. Therefore, the lower limit of the La concentration and Ce concentrations, respectively, 0% greater than (preferably 0.1% or more) is good.
　On the other hand, when the La concentration and Ce concentration increases, the tendency for corrosion resistance after coating is deteriorated. Therefore, the upper limit of the La concentration and Ce concentration, respectively, and 0.5% or less (preferably 0.3% or less).
[0043]
[Cr, Ti, Ni, Co , V, Nb, Cu , and
　Mn: 0% ~ 0.25%] Cr, Ti, Ni, Co, V, Nb, Cu and Mn is the element contributing to improving the workability is there. Therefore, Cr, Ti, Ni, Co , V, Nb, the lower limit of the concentration of Cu and Mn, respectively, Si concentration exceeding 0 (preferably 0.05% or more, more preferably 0.1% or more) good .
　Meanwhile, Cr, Ti, Ni, Co , V, Nb, when the concentration of Cu and Mn increases, the tendency for corrosion resistance after coating is deteriorated. Therefore, Cr, Ti, Ni, Co , V, Nb, the upper limit of the concentration of Cu and Mn, respectively, and 0.25% or less.
[0044]
[Sr, Sb, Pb and B: 0%
　~ 0.5%] Sr, Sb, Pb and B is an element contributing to improving the workability. Therefore, Sr, Sb, the lower limit of the concentration of Pb and B, respectively, Si concentration exceeding 0 (preferably 0.05% or more, more preferably 0.1% or more) is good.
　Meanwhile, Sr, Sb, if the concentration of Pb and B increases, the tendency for corrosion resistance after coating is deteriorated. Therefore, the upper limit of the concentration of Sr, Sb, Pb and B, respectively, and 0.5% or less (preferably 0.1% or less).
[0045]
: [Balance Zn and impurities]
　balance of the chemical composition of the plating layer is a Zn and impurities.
　Zn, the sacrificial corrosion protection ability of the plated layer, corrosion resistance after painting, in order to properly secure a paint undercoating of a certain concentration or more, contained in the plated layer. These viewpoints, the chemical composition of the plating layer, the majority of Al and Zn.
　Impurities, 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 base steel (steel), as an impurity component such as Fe also be incorporated trace.
[0046]
　For example, by hot dipping, the case of forming a plating layer, the plating layer is sometimes contain certain Fe concentration as an impurity. Until Fe content of 3.0%, it has been confirmed no adverse effect on the performance included in the plating layer.
[0047]
[Chemical composition of the preferred plating layer]
　In the chemical composition of the plating layer, 0.5% to 3.0% content of Mg, it is preferable that the content of Sn is 1.0% 7.5% . When the Mg concentration and the Sn concentration in the above range, further improves corrosion resistance after painting and workability.
　In particular, in the chemical composition of the plating layer, the content of Al is 20% to 60%, the content of Mg is 1.0% to 2.0%, and the content of Sn is 1.0% to 5.0% and it is preferable that the content of Si is 0.05% to 1.0%. Al concentration, Mg concentration, when the above-mentioned range of the Sn concentration and Si concentration, thereby further improving corrosion resistance after painting and workability. In addition, further improved seizure resistance.
[0048]
: [Formula (1) Mg wt% ≦ Sn wt% ≦ 2.5 × Mg wt%]
　for corrosion resistance after painting and workability is further improved, the granular Mg 2 fully form Sn phase containing tissue, Zn / Al / MgZn 2 ternary eutectic structure and bulk MgZn 2 it is preferable to sufficiently suppress the formation of phases.
　Therefore, the content of the content and Mg of Sn is preferably satisfies the following formula (1), more preferably satisfies the following formula (2).
　Mg ≦ Sn ≦ 2.5 × Mg ··· Equation (1)
　1.5 × Mg ≦ Sn ≦ 2.0 × mg · · · formula (2)
　Equation (1) to formula (2), the element symbol shows the contents of the elements in% by weight
[0049]
　Sn concentration did not satisfy the formula (1), if Sn is insufficient with respect to Mg, bulk MgZn 2 phase is formed, corrosion resistance after coating tends to decrease with processability.
　On the other hand, Sn concentration did not satisfy the formula (1), if Sn is excessive relative to Mg, potentially out noble Sn phase crystallizes, after painting corrosion resistance tends to be low.
[0050]
　It will now be described metal structure of the plating layer.
　Plating layer, granular Mg 2 has a Sn phase containing tissues, dendritic tissue (tissue comprising the solid solution of Zn and Al), the.
　Then, the plating layer is granular Mg 2 as Sn phase containing tissue other than the tissue, or equivalent circular diameter 1μm massive MgZn 2 phase, equivalent circular diameter 2μm or more bulk Zn phase, Zn / Al / MgZn 2 ternary eutectic structure there is a case of having a like.
[0051]
　Here, in FIG. 1, the reflected electron image of SEM of an example of the plating layer of the plated steel sheet of the present disclosure taken at 2000 times (BSE images) shown.
　As shown in FIG. 1, plated steel sheets, for example, a plating layer 1, and the steel plate 2, during the plating layer 1 and the steel plate 2 has an interfacial alloy layer 3 made of Al-Fe intermetallic compound, the ing.
　Tissue plating layer 1 is mainly granular Mg 2 is composed of a Sn phase containing tissues 4 and dendrite structure 5. Further, as shown in FIG. 2 is an enlarged view of a region A in FIG. 1, the granular Mg 2 Sn phase containing tissue 4, the granular Mg less than the crystal grain size 1μm in Zn phase 7 2 Sn phase 8 is dispersed and it has become a organization.
　In Figure 1, dendritic tissue 5, together with the region shown in gray color, the area black indicated area surrounded corresponds. Color differences both regions, due to the difference of the Al concentration. Specifically, an area where dendrite structure 5 Al concentration is low is indicated by a gray color, an area dendrite structure 5 Al concentration was shown by high gray is shown in black.
　Note that in the plating layer 1, granular Mg 2 other than Sn phase containing tissue 4 and dendrite structure 5, bulk MgZn 2 phase 6 (see FIGS. 1 and 2), bulk Zn phase 10 (see FIG. 3), Zn / Al / MgZn 2 may have a ternary eutectic structure 9 (see FIG. 3).
[0052]
[Granular Mg 2 Sn phase containing tissues: the area fraction 5-65%]
　particulate Mg 2 Sn phase containing tissue, Zn phase and the Zn phase particulate Mg less than dispersed grain size 1μm to in 2 and Sn phase , consisting of. That is, in particulate Mg2Sn phase containing tissues, granular Mg 2 Sn phase is contained (i.e. encapsulated) in Zn phase.
　Incidentally, the granular Mg 2 crystal grain size of the Sn phase is equivalent circular diameter.
[0053]
　More specifically, the granular Mg 2 Sn phase containing tissue, granular Mg less than the crystal grain size 1μm to Zn phase 2 Sn phase number density of 1 to 25 / [mu] m 2 is dispersed organization.
　Granular Mg 2 if the grain size is less than 1μm of Sn phase, particulate Mg 2 can suppress the stress applied to the boundary of the Sn phase and Zn phase. Therefore granular Mg 2 while preventing the Sn phase is a starting point of cracking, granular Mg 2 the plastic deformability of the Sn phase can be maintained sufficiently. On the other hand, the granular Mg 2 the grain size of the Sn phase exceeds 1μm particulate Mg 2 particulate Mg is stress on the boundary of the Sn phase and Zn phase increased 2 preferably for Sn phase may become a starting point of cracking Absent.
　Granular Mg 2 average composition of the entire Sn phase containing tissue is not particularly limited, for example, Mg concentration of 1 to 10 mass%, Sn concentration of 1 to 25 mass%, Al concentration is 1 to 8 mass%, the balance There consisting Zn and about 2 wt% less impurities. Granular Mg 2The composition of the entire Sn phase containing tissue, which may also include the optional elements that may be included in the chemical composition of the plating layer.
[0054]
　In the present disclosure, the particulate phase of the intermetallic compound corresponding to the following (1) to (5), the granular Mg 2 regarded as Sn phase.
　(1) Mg was interstitial solid solution elements such as Si 2
　Sn (2) Mg 2 Sn phase Mg was transformed 9 Sn
　5 (3) Bi in a part of the Sn, In, Cr, Ti, Ni, Co, V, Nb, Cu, and at least one is substituted with substituted Mg of Mn 2 Sn and Mg 9 Sn 5 (Mg 2 Sn and Mg 9 Sn 5 of
　substituents) (4) Ca in a part of Mg, Y, La and substituted Mg for at least one Ce is substituted 2 Sn and Mg 9 Sn 5 (Mg 2 Sn and Mg 9 Sn 5 of
　substituents) (5) Ca in a part of Mg, Y, and at least one substitution of La and Ce, and Bi in a part of the Sn, In, Cr, Ti, Ni, Co, V, Nb, Cu, and substituted Mg for at least one is substituted for Mn 2 Sn and Mg 9 Sn 5 (Mg 2 Sn and Mg 9 Sn 5 substituted product)
[0055]
　Granular Mg 2 Sn phase containing tissue, as described above, Mg is a brittle Mg intermetallic compound 2 but containing Sn phase, Mg 2 Sn phase MgZn 2 has a plastic deformability than the phase. The Mg 2 Sn, phase, by a tissue micro-dispersed Zn phase having a plastic deformability, express plastic deformability organization as a whole, contributes to the improvement of workability. In addition, Mg 2 Sn phase becomes a source of Mg ions in a corrosive environment, for Mg ions to the insulating coating of the corrosion products, coatings corrosion under the painting state is suppressed.
　The particulate Mg 2 Sn phase containing tissue effect of improving corrosion resistance after painting and workability by the granular Mg present in the plating layer 2 increases the higher the Sn phase containing tissue area fraction of.
[0056]
　Granular Mg 2 when the area fraction of the Sn phase containing tissue is below 5%, the effect of improving the corrosion resistance after painting and workability can not be obtained. Therefore, the granular Mg 2 the lower limit of the area fraction of Sn phase containing tissue is 5%. From the viewpoint of reliably improve both the corrosion resistance after painting and workability, granular Mg 2 area fraction of Sn phase containing tissue is preferably 20% or more, more preferably 30% or more.
　On the other hand, as described above, the granular Mg 2 higher is the area fraction of the Sn phase containing tissues, the effect of improving the corrosion resistance after painting and workability is increased. Without limitation to the upper limit of the performance surface, on manufacturing constraints, it can generate particulate Mg 2 area fraction of Sn phase containing tissue is 65% at maximum. Therefore, the granular Mg 2 upper limit of the area fraction of the Sn phase containing tissue is 65%. From the viewpoint of stable production, granular Mg 2 area fraction of Sn phase containing tissue is preferably 60% or less.
　In other words, the granular Mg 2 area fraction of Sn phase containing tissue is 5 to 65%. Then, the granular Mg 2 area fraction of Sn phase containing tissue, preferably is 20-60%, more preferably 30 to 60%.
[0057]
[Dendritic organization: an area fraction of 35% to 95%
　dendritic structure is a tissue containing the solid solution of Zn and Al. Specifically, dendritic structure is a Al phase and Zn phase and finely divided tissue, Al concentration from 15 to 85%, a tissue exhibiting Zn concentration 15 to 85%. Therefore, dendritic tissue has an essentially plastic deformation capability, an organization that can contribute to improving the workability of the plating layer. In addition, there is also a contributing organization to the seizure improvement.
[0058]
　To ensure good workability, the area fraction of the dendritic structure is preferably at least 35%. From the standpoint of imparting to the plating layer superior workability, the area fraction of the dendritic structure is more preferably 40% or more. On the other hand, from a manufacturing standpoint, the upper limit of the dendritic structure is preferably 95%. In view of the particulate phase dispersed phase by improving corrosion resistance after painting and workability, dendritic structure is preferably 80% or less, more preferably 70% or less.
　That is, the area fraction of the dendritic structure is preferably 35 to 95%, more preferably 35 or 40 to 80%, more preferably 35 or 40% to 70%.
[0059]
[Massive Zn phase: an area fraction of 0% to 20%
　bulk Zn phase is present in amorphous in the plating layer, a Zn phase of 2μm or more bulk at equivalent circular diameter. The upper limit of the equivalent circular diameter of the bulk Zn phase is not particularly limited, for example, is 10μm or less.
　The higher the area fraction of the massive Zn phase, seizure resistance and corrosion resistance tend to decrease. Therefore, from the viewpoint of securing seizure resistance and corrosion resistance, the area fraction of the bulk Zn phase is preferably 20% or less. From the viewpoint of securing sufficient seizure resistance and corrosion resistance, the area fraction of the bulk Zn phase is more preferably 10% or less. Area fraction of bulk Zn phase 0 percent (most preferably free namely bulk Zn phase.) The most preferred
　words, the area fraction of the bulk Zn phase is preferably 0-20%, more preferably 0 to 10%, more preferably 0%.
[0060]
[Massive MgZn 2 : phase area fraction of 0% to 20%
　bulk MgZn 2 is phase was present in amorphous in the plating layer, a Zn phase of 2μm or more bulk at equivalent circular diameter. Bulk MgZn 2 maximum equivalent circle diameter of the phase is not particularly limited, for example, is 10μm or less.
　Bulk MgZn 2 phase is a brittle phase, likely to become the starting point of cracking at the time of processing. Then, in the vicinity of the crack corrosion is accelerated, which may become a cause of lowering the corrosion resistance after painting of the processing unit. Bulk MgZn 2 higher area fraction of phases, corrosion resistance after painting and workability tends to decrease. Therefore, from the viewpoint of securing corrosion resistance after painting and workability, bulk MgZn 2 area fraction of phases is preferably 20% or less. From the viewpoint of ensuring sufficient corrosion resistance after painting and workability, bulk MgZn 2 area fraction of phases is more preferably 5% or less. Bulk MgZn 2 area fraction of phases 0% (ie bulk MgZn most preferably 2 and most preferably does not contain the phase.)
　In other words, bulk MgZn 2 area fraction of phases is preferably 0 to 20% more preferably 0-5%, more preferably 0%.
[0061]
[Zn / Al / MgZn 2 ternary eutectic structure: an area
　fraction% ~ 3 0%] Zn / Al / MgZn 2 ternary eutectic structure is an Al phase, texture comprising Zn phase and 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. 5).
　Normally, each phase is, Zn phase is large, to form an island-like, then large MgZn phases, filled the gap Zn phase, Al phase, MgZn 2 an arrangement for distributed spots during phase it is often to take. 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.
[0062]
　Zn / Al / MgZn 2 ternary eutectic structure is likely to progress of corrosion, brittle MgZn ternary eutectic structure in 2 tends phase becomes a starting point of cracking during processing. Then, in the vicinity of the crack corrosion is accelerated, which may become a cause of lowering the corrosion resistance after painting of the processing unit. Zn / Al / MgZn 2 as ternary eutectic structure area fraction of high corrosion resistance after painting and workability tends to decrease. Therefore, from the viewpoint of securing corrosion resistance after painting and workability, Zn / Al / MgZn 2 area fraction of the ternary eutectic structure is preferably 3% or less. From the viewpoint of ensuring sufficient corrosion resistance after painting and workability, Zn / Al / MgZn 2 area fraction of the ternary eutectic structure is most preferably 0% (i.e. Zn / Al / MgZn 2 contains ternary eutectic structure is most preferred.) that no
　other words, Zn / Al / MgZn 2 area fraction of the ternary eutectic structure is preferably 0-3%, most preferably 0%.
[0063]
　The thickness of the 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 is, for example, about 2 [mu] m. On the other hand, by the weight and uniformity of the plated metal can be fabricated by melt plating, the thickness of the plating layer is about 95 .mu.m.
　Therefore, the thickness of the plating layer may be a 2 ~ 95 .mu.m. -
[0064]
　Next, a description will be given interfacial alloy layer.
　Plated steel sheet of the present disclosure may further include an interface alloy layer consisting of Al-Fe intermetallic compound between steel and the plating layer. Usually, between the plating layer and steel sheet, generally interfacial alloy layer is formed consisting of the following Al-Fe intermetallic compound 3 [mu] m. However, depending on the formation conditions of the plating layer, interfacial alloy layer may not be formed.
　Interfacial alloy layer, in order to ensure adhesion of the plating layer and the base steel (steel plate) preferably has a thickness of at least 100 nm. On the other hand, Al-Fe-based intermetallic compound constituting the interfacial alloy layer are the brittle intermetallic compounds, there is a case where the thickness of the interfacial alloy layer reduces the chipping resistance exceeds 1.5 [mu] m.
　Therefore, if the plated steel sheet of the present disclosure having an interfacial alloy layer, it is preferable that the thickness of the interfacial alloy layer is 100 nm ~ 1.5 [mu] m.
　Incidentally, the interface alloy layer is in a state of solid solution Si, also has role in suppressing the alloying reaction of the plating layer and the base steel.
[0065]
　Here, the interface alloy layer consisting of Al-Fe intermetallic compound is, Al 5 Fe phase is a layer of the main phase. Al-Fe alloy layer is formed by mutual atomic diffusion base iron (steel) and the plating bath. However, interfacial alloy layer is partially, AlFe phase, Al 3 Fe phase, Al 5 Fe 2 in some cases, such as phase contains minor amounts.
[0066]
　Also, the interface alloy layer is a component of the plating layer, Zn, also including various elements such as Si. In particular, when Si is incorporated into the interfacial alloy layer to form a Al-Fe-Si intermetallic compound in the interface alloy layer.
　Further, interfacial alloy layer, when using various pre-plated steel sheet be plated may include a pre-plating components (e.g., Ni, etc.). When the pre-plating components (e.g., Ni, etc.) is taken into the interfacial alloy layer to form a Al-Fe-Ni intermetallic compound at the interface alloy layer.
[0067]
　In other words, interfacial alloy layer consisting of Al-Fe intermetallic compound is, Al 5 besides the alloy layer composed mainly of Fe phase, a layer comprising an alloy layer of the various embodiments.
[0068]
　Hereinafter, an example of a method for manufacturing a plated steel sheet of the present disclosure.
　Plated steel of the present disclosure, the surface of the plating original plate (i.e., one side or both sides) is obtained by forming a plating layer by a hot dipping method.
[0069]
　Method for producing a plated steel sheet of the present disclosure, Zenjimia method, the pre-plating method, etc. are applicable. In the case of using Ni as a kind of pre-plating, there is a case where Ni is contained in it may be generated during the heating of the plating layer "interfacial alloy layer consisting of Al-Fe intermetallic compound."
[0070]
　Bath, so that the range of the chemical composition of the plating layer, to prepare a pure metal or alloy, for vatting dissolved in 450 ~ 650 ° C..
　Then, a plating original plate surface is sufficiently reduced, denominated Yokugo, immersed in the plating bath kept at a predetermined bath temperature, after pulling, cooled to form a plating layer on the surface of the plated original plate (steel plate) be able to. In order to control the coating weight of the plating layer, for example, N immediately after pulling up the be plated from the plating bath 2 implementing wiping by the gas.
[0071]
　Here, immediately after pulling up the be plated from the plating bath (i.e. plating temperature) the cooling rate of the temperature range from to 320 ° C. and 10 ° C. / s or higher, 6 ° C. The cooling rate of the temperature range up 280 ° C. from 320 ° C. / s or less to be.
　Reflection electron image of the cross section of SEM of the plating layer of the present disclosure plated steel sheet shown in FIG. 1 (BSE images) until 280 ° C. The cooling rate of the temperature range from the plating bath temperature to 320 ° C. from 10 ℃ / s, 320 ℃ a reflection electron image of SEM of a cross section of the plating layer of the plated steel sheet to prepare a cooling rate of temperature range as 6 ° C. / s of (BSE images).
　As shown in FIG. 1, when the cooling conditions, the plating layer, the granular Mg 2 tissue can be formed with a Sn phase containing tissue 4 and dendrite structure 5.
[0072]
　On the other hand, the cooling rate of the temperature range immediately after pulling up the be plated from the plating bath from (i.e. plating temperature) to 320 ° C. and 10 ° C. or higher, the cooling rate of the temperature range up 280 ° C. from 320 ℃ 6 ℃ / s or less even when a, when the Sn concentration is not appropriate, granular Mg of a sufficient amount 2 may not be formed the Sn phase containing tissue 4. For example, as shown in FIG. 3, if not containing Sn, granular Mg in the plating layer 1 2 Sn phase containing tissue 4 is not formed, instead, dendritic tissue 5 with Zn / Al / MgZn 2 ternary eutectic structure 9 is formed.
[0073]
　Also, if you do not change the temperature region immediately after pulling up the be plated from the plating bath from (i.e. plating temperature) to 320 ° C., a temperature range of up to 280 ° C. from 320 ° C., the cooling rate between the above-mentioned range, sufficient such particulate Mg amount 2 Sn phase containing tissue 4 may not be formed.
　For example, as shown in FIG. 4, the cooling rate at a cooling rate condition is not changed in the above range, the particulate Mg in the plating layer 1 2 Sn phase containing tissue 4 is not formed, instead, the plate-like in Zn phase mg 2 tissue 11 Sn phase are mixed is formed.
　Although this detailed formation mechanism of the tissue 11 is not clear, the cooling rate A temperature range immediately after pulling up the be plated from the plating bath from (i.e. plating temperature) to 320 ° C. and 10 ° C. or higher, up to 280 ° C. from 320 ° C. If the cooling rate B of the temperature range was exceeded ° C. 6 / s, Mg 2 hardly sufficient time is obtained for Sn phase is spheroidized. And the cooling rate A lower than 10 ° C. / s, when the cooling rate B not more than 6 ° C. / s, the solidification behavior to proceed to the original non-equilibrium approach to equilibrium, Mg spheroidized 2 can nucleation Sn phase hard. As a result the plate-like Mg 2 believed Sn phase forms.
[0074]
　Hereinafter will be described a method for analyzing the chemical composition and metal structure of the plated steel sheet of the present disclosure.
[0075]
　Chemical composition of the plating layer is measured by the following method.
　First, obtain a calibration curve for quantitative analysis of each element in GDS (RF glow discharge spectroscopy). Then, to measure the depth direction of the chemical components of the plating layer of interest.
　Specifically, implement GDS (RF glow discharge spectroscopy) for a standard sample such as each element pure metal plate, obtaining a calibration curve showing the relationship between the advance element intensity plot and each element concentration.
　On the other hand, a 30mm square and several pieces taken from a sample of plated steel sheet to be measured, and GDS sample. From the surface of the plating layer was performed with argon ions sputter obtain elemental intensity plot in the depth direction. The calibration curve is converted into elemental concentrations from the resulting intensity plot.
　Analysis of chemical composition by the GDS, the analyzed area φ4mm above, the sputtering rate as the range of 0.04 ~ 0.1 [mu] m / sec, measuring more than 10 points. Each element concentration of chemical composition, the average value of the element concentration in each location.
　However, in each of the GDS analysis points, in order to remove the influence of the outermost layer of the oxide layer, ignoring the component plot of the surface layer 1μm depth, depth 1 to the average value of each element concentration of 10 [mu] m (5 [mu] m width) the adopted.
[0076]
　Organization of the plating layer (however, Zn / Al / MgZn 2 area fraction of the ternary eutectic structure is excluded) is measured by the following method.
　The measurement of the area fraction of the tissue of the plating layer, using the FE-SEM equipped with EDS (energy dispersive X-ray analyzer).
[0077]
　From plated steel sheet, cutting the sample piece having a C direction 25 mm × L direction 15mm cross section (cross section cut in the thickness direction of the plated layer). The obtained test pieces embedded in a resin, CP (cross session polisher) to the cross section of the plating layer to be measured is subjected to machining. After CP processing, to produce an element mapping images by the reflected electron image and EDS of SEM of the cross section of the plating layer. Elemental mapping images by the reflected electron image and EDS of the SEM, magnification 5000 times, of the visual field size: a longitudinal 50 [mu] m × horizontal 200 [mu] m.
　Based on the element mapping images by the reflected electron image and EDS of SEM, to identify regions of the tissue.
[0078]
　Next, it is determined in the reflection electron image of SEM, lightness of the gray scale indicated by each organization having the plating layer, the three values ​​of hue and contrast values. Lightness each tissue exhibits, three values ​​of hue and contrast value, since it reflects the atomic number of the elements contained in the tissue, usually atomic number is small Al content, the more the phase content of the Mg content is large, black the exhibits, as Zn amount is large phase, tend to exhibit a white color.
[0079]
　Only the range of the three values ​​indicated by each tissue included in the plating layer, to implement the computer image processing, such as color change (e.g., a particular tissue only, so as to display a white image, the area of ​​each tissue in the field of view calculating the (number of pixels) and the like). By performing the image processing in each phase, determine the area fraction of each tissue in the coating layer occupied in the backscattered electron image of SEM.
[0080]
　The area fraction of each tissue of the plating layer, in any five visual fields of the cross section (cross section cut in the plating layer thickness direction) of the plating layer, the average value of the area fraction of each tissue was determined by the operation .
[0081]
　Here, the granular Mg 2 area fraction of Sn phase containing tissue, the Zn phase region, the crystal grain size 1μm below the granular Mg 2 Sn phase number density of 1 to 25 / [mu] m 2 of Zn phase has been identified in there are, granular Mg 2 is the area fraction of Zn phase, including the Sn phase.
　Area fraction of dendritic organization, a solid solution of Zn and Al (Al concentration from 15 to 85%, Zn concentration 15 to 85% are shown tissue) is the area fraction of the area occupied by the.
　Bulk MgZn 2 area fraction of phases is equivalent circular diameter 1μm or more MgZn 2 is the area fraction of phases.
　Area fraction of bulk Zn phase is the area fraction of the equivalent circular diameter 2μm or more Zn phase.
[0082]
　Incidentally, the granular Mg 2 average crystal grain size of the Sn phase is measured as follows. Magnification 10000 times, to observe the reflected electron image of SEM of a cross section of the plating layer was a size 10 [mu] m × 10 [mu] m field of view, the crystal grain size 1μm of less than granular Mg to be identified in field 2 of the Sn phase Top 5 granular Mg that of having a crystal grain size 2 to select the Sn phase. Then, the operation was carried out five fields of view, the arithmetic mean of the total of 25 grain size, grain size 1μm below the granular Mg 2 the average crystal grain size of the Sn phase.
[0083]
　Further, the granular Mg 2 number density of the Sn phase, magnification 10000 times, to observe the reflected electron image of the cross section of the plating layer was size 12 [mu] m × 12 [mu] m field of view SEM, granular Mg any 12 [mu] m × 12 [mu] m 2 Sn phase grain size 1μm below the granular Mg present in tissues containing 2 counts the number of Sn phase, unit area ([mu] m 2 ) per granular Mg 2 calculates the number of Sn phase. Then, the granular Mg 2 number density of the Sn phase, will, in any five visual fields of the cross section (cross section cut in the plating layer thickness direction) of the plating layer, the granular Mg were determined by the operation 2 of the number density of the Sn phase an average value.
[0084]
Zn / Al / MgZn in the plating layer 2 Identification and area fraction of the ternary eutectic structure is measured by the following method.
[0085]
　First, in the same manner as the measurement of the area fraction of each tissue in the coating layer, a reflective electron image of SEM, Al phase, Zn phase and MgZn 2 three phases of phase to identify the tissue eutectic. 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. 5). 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 , it 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."
[0086]
　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.
[0087]
　Then, the reflected electron image (5000 magnification, field of view size: length 50 [mu] m × horizontal 200 [mu] m) of the same SEM and measurement of the area fraction of each organization in the coating layer with respect to, repeat the above operation, three-way while confirming the continuity of the eutectic structure, to grasp the ternary eutectic structure of the contour (area). Then, determine the area fraction of the ternary eutectic structure in the coating layer occupied in the backscattered electron image of SEM was grasped.
　The area fraction of the ternary eutectic structure is in any of at least five visual fields of the cross section (cross section cut in the plating layer thickness direction) of the plating layer, the area fraction of the ternary eutectic structure obtained by the above operation an average value.
[0088]
　Bulk MgZn 2 mean equivalent circular diameter of the phase, and bulk Zn phase is measured by the following method.
　When measuring the area fraction of the tissue, in the reflection electron image of SEM was identified organizations, among the identified phase, selects a phase with a top 5 equivalent circular diameter. Then, the operation was carried out five fields of view, the arithmetic mean of the total of 25 equivalent diameter, bulk MgZn 2 phase, and an average equivalent circular diameter of the bulk Zn phase.
[0089]
　The thickness of the interfacial alloy layer consisting of Al-Fe intermetallic compound is determined as follows.
　When measuring the area fraction of the tissue, the reflection electron image of SEM identified each tissue (5000 magnification, field of view size: length 50 [mu] m × horizontal 200 [mu] m, however, the field of view interfacial alloy layer is visually recognized. in), for any five points of the identified interface alloy layer, to measure the thickness. Then, the arithmetic mean of five positions to the thickness of the interfacial alloy layer.
[0090]
　The following describes the post-processing that can be applied to the plated steel sheet of the present disclosure.
　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.
[0091]
　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.
[0092]
　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.
[0093]
　The phosphate treatment, for example, zinc phosphate treatment, zinc phosphate calcium treatment, can be exemplified manganese phosphate treatment.
[0094]
　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.
[0095]
　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.
[0096]
　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
[0097]
　It is shown below as examples as an example of the present disclosure.
[0098]
　As the plating bath, the chemical composition of the plating layer has bath preparation the plating bath components adjusted so as to chemical composition shown in Table 1. Plating bath temperature depending on the composition, it was 465 ~ 593 ° C. as shown in Table 1. As it is plated, using a hot-rolled steel sheet having a thickness of 0.8 mm (carbon concentration of 0.2%). Original sheet, after cutting into 100 mm × 200 mm, plated with molten plating test apparatus-house batch. The sheet temperature was monitored using a thermocouple spot welded to be plated center. Further, in Table 1, a case satisfying the expression (1) is a composition balance of Mg and Sn disclosed disclosure OK, a case not satisfying described as NG.
[0099]
　Before plating bath immersion, N oxygen concentration in the following furnace 20 ppm 2 -5% H 2 gas, reducing the plated original plate surface of 800 ° C., N 2 in air and immersed plate temperature is bath temperature + 20 ° C. with gas reached
after was about 3 seconds immersed in the plating bath. After the plating bath immersion, it was pulled up by pulling speed 100mm / sec. During withdrawal, N 2 was coating weight adjustment by wiping gas.
[0100]
　After withdrawal of the steel plate from the plating bath, and cooled from the plating bath temperature of the plating layer under the conditions shown in Table 1 to room temperature to prepare a plated steel sheet.
　Incidentally, (No.103 in Table 1) Commercially available hot-dip galvanized steel sheet, (No.104 in Table 1) alloyed galvanized steel sheet, and (No.105 in Table 1) Electro-galvanized steel sheet was also prepared .
[0101]
[Table 1-1]

[0102]
[Table 1-2]

[0103]
[Table 1-3]

[0104]
[Table 1-4]

[0105]
[Table 1-5]

[0106]
[Table 1-6]

[0107]
[Table 1-7]

[0108]
[Table 1-8]

[0109]
　Conducted the following measurement and evaluation for the coated steel sheet produced in each example are shown in the list in the above Table 1.
[0110]
- the area fraction of the measurement of each tissue -
　the area fraction below the tissue of the plating layer of the obtained coated steel sheet was measured according to the method described above.
· Granular Mg 2 Sn phase containing tissue (in the table referred to as "particulate phase containing tissue")
- dendrite tissue
-Zn / Al / MgZn 2 ternary eutectic structure
, equivalent circular diameter 1μm or more bulk MgZn 2 phase
-equivalent circle more massive Zn phase diameter 2μm
plate-like Mg in · Zn phase 2 tissue (in the table, "Zn phase + plate of Mg Sn phase are mixed 2 Sn phase"
denoted) · Sn phase
· Si phase
· Mg 2 Si phase
-the tissue other than the intermetallic compound phase (in the table referred to as "other phase" ")
[0111]
- Measurement of Average equivalent circle diameter of each tissue -
　a mean equivalent circular diameter below the tissue of the plating layer of the obtained coated steel sheet was measured according to the method described above. However, in Table 1, the average equivalent circle diameter is referred to as "equivalent circular diameter".
- equivalent circular diameter 1μm or more bulk MgZn 2 phase
-equivalent circular diameter 2μm or more massive Zn phase
-Sn phase
, Si phase -Mg
2 Si phase
[0112]
- thickness measurements of interfacial alloy layer -
　the thickness of the interfacial alloy layer of the obtained coated steel sheet was measured according to the method described above.
[0113]
- granular Mg 2 crystal grain size and number density of the granular MgSn phase of Sn phase containing tissues -
　No. shown in Table 1 To give 29 of the reflected electron image of SEM and (BSE images). No. shown in Table 1 29 reflection electron image of SEM of the (BSE images) shown in FIGS. As apparent from FIG. 1, the plating layer 1 is mainly granular Mg 2 was composed of Sn phase containing tissue 4 and dendrite structure 5. Then, the granular Mg shown in FIG. 2 2 particulate Mg formed in Sn phase containing tissue 4 2 was examined an average crystal grain size and number density of the Sn phase 8.
　Similarly, for the other samples, the granular Mg 2 was examined an average crystal grain size and number density of the Sn phase. As a result, the granular Mg 2 particulate Mg formed in Sn phase containing tissue 2 average representative value of the crystal grain size and number density of the Sn phase was shown in the table below 2.
[0114]
[Table 2]

[0115]
- bending workability -
　Evaluation of bending workability of the plating layer was performed in the following street.
　From the obtained plated steel sheets were cut test piece C direction 30 mm × L direction 60 mm (L). The test pieces were 180 ° bend (1T bending) in the C direction, the top of the working portion of the plating layer observed by SEM were counted number of cracks present on the top portion (1.6 mm × 30 mm).
　Three sandwiched specimen test piece inside the DoitaAtsu, the inside five sandwiched specimen test pieces DoitaAtsu, and each 180 ° bend in the direction C (3T bending and 5T Bend), Similarly, it counted number of cracks.
　Then, each plated steel sheet at least 3 samples prepared, calculates the average value of existing cracks was evaluated bending workability. Write number of cracks average is small, excellent in plastic deformability, bending property can be evaluated as good.
　Evaluation criteria "A" if the average number of cracks is a Crackless 0 present present, the case where the average number of cracks of 1 to 20 present "B", the average number of cracks the case between 21 and 100 " C ", the average number of cracks was not less than 101 present a" D ".
[0116]
- Evaluation of corrosion resistance after painting -
　Evaluation of corrosion resistance after painting of the plating layer was performed in the following street.
　From the obtained plated steel sheets were taken test piece C direction 50 mm × L direction 100 mm. The plating layer surface of the test piece, Zn phosphate treatment: subjected to (SD5350 system Nippon Paint Industrial coding manufactured by standard).
　Then, the plating layer surface of Zn phosphate treated test piece, electrodeposition coating -: by (PN110 POWERNICS gray Nippon Paint Industrial coding Inc. standard), to form a coating film having a thickness of 20 [mu] m, the baking temperature 150 ° C., subjected to baking of the coating at 20 minutes to form a electrodeposition coating film.
　Next, put the base steel crosscut scratches reaching the (steel) (40 × √2 2 pieces) with respect to electrodeposition coating film of the test piece.
　The obtained test pieces were subjected to combined cycle corrosion test in accordance with JASO (M609-91). Then, measure the maximum swelling width of the cross-cut around eight after each lapse of 30,60,90,150 cycle, the average value was determined.
　It was to evaluate the corrosion resistance after painting by this blistering width. The evaluation criteria, at the time of the number of cycles of 30,60,90,150 cycle JASO (M609-91), "A" if the blister width from the cross cut scratches of 1mm or less, in the case of the following 1mm beyond ~ 2mm was "B", in the case of less than 2mm beyond ~ 4mm "C", if the red rust occurs "D".
[0117]
- chipping resistance evaluation -
　chipping resistance of the plating layer was performed in the following street.
　In the same manner as in the evaluation of the corrosion resistance after coating, were prepared test pieces subjected to electrodeposition coating in the plated layer surface. The electrodeposition coating film surface of the test piece, further intermediate coating was performed topcoat, a clear paint, the film thickness as a whole to form each coating film so as to be 40 [mu] m.
　Using Gurabero tester (manufactured by Suga Test Instruments Co., Ltd.), 3.0 kg / cm No. 7 crushed stone 100g from a distance of 30 cm 2 at an air pressure of an angle of 90 degrees to the coating film of the cooled specimen -20 ° C. in was a collision. Then, by using the adhesive tape to expose the peeling of the plating layer at a collision portion, the diameter of the peeled portion was measured, and the average value was defined as an average peel diameter to choose five from the largest of the peeling diameter.
　The average peel diameter, was evaluated chipping resistance. Higher average peel diameter is smaller, the better the chipping resistance.
　Evaluation criteria average when peeling diameter is less than 1.0mm "A", the case where the average peel diameter of less than 1.5mm or 1.0mm "B", less than the average peel diameter 1.5mm to 3.0 "C" in the case of an average peeling diameter was equal to or larger than 3.0mm and "D".
[0118]
- seizure resistance evaluation -
　seizing resistance of the plating layer was performed in the following street.
　From the obtained plated steel sheets were taken test piece C direction 80 mm × L direction 350mm by two, respectively. Subjected to drawbead processed using jig which imitates a die and a bead on the two test pieces was generated length 150mm or more sliding between the plating layer forming surface and the die shoulder and the bead portion of the test piece . Incidentally, the respective stations radii of the die shoulder and the bead portion of the jig used in the test 2mmR and 5MmR, pressing pressure of the die 60KNm 2 , drawing speed of drawbead processing was 2m / min. Further, at the time of the test, the lubricating oil on the surface of the test piece: 10 mg / m on both sides of (550S Nippon Parkerizing Co., Ltd.) 2 was applied.
[0119]
　Then, Width: 80 mm × length: the primary test piece 350mm were taken every two respectively, this applies drawbead processed using jig which imitates a die and a bead, surface-treated surface of the steel sheet and the die shoulder and the bead It raises the length 150mm or more sliding between the parts, to evaluate the seizure resistance. Incidentally, the respective stations radii of the die shoulder and the bead portion of the jig used in the test 2mmR and 5MmR, pressing pressure of the die is 60 kN / m 2 , the drawing speed of the drawbead processing was 2m / min. Further, at the time of the test, the lubricating oil on the specimen surface: 0.5 g / m on both sides of (550S Nippon Parkerizing Co., Ltd.) 2 was applied.
　Evaluation criteria "B" if the case minor but "A" if the plating layer to the die and the bead is not seizure in visually plating layer die and a bead in the visual is seizure, die in visual and bead plated layer has a case seizure is marked as "D".
[0120]
　In the figure, the object indicated by each reference numeral are as follows.
　1 plated layer
　2 steel
　3 interfacial alloy layer
　4 particulate Mg2Sn phase containing tissue
　5 tissue comprising a solid solution of Zn and Al (dendrite
　structure) 6 bulk MgZn 2 phase
　7 Zn phase
　8 granular Mg 2 Sn phase
　9 Zn / Al / MgZn 2 ternary eutectic structure
　10 bulk Zn phase
　plate-like Mg in 11 Zn phase 2 tissue Sn phase are mixed
　20: Zn / Al / MgZn 2 ternary eutectic structure of Zn phase
　21: Zn / Al / MgZn 2 ternary eutectic structure of MgZn 2 -phase
　22: Zn / Al / MgZn 2 Al phase of the ternary eutectic structure
[0121]
　Japanese disclosure of patent application 2017-053150 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 the steel sheet, a plated steel sheet having a plating layer provided on at least part of the surface of the steel sheet,
　the plating layer is, in
　mass%, Al:
　15% ~ 60% Mg: 0.5% ~
　% 8.0
　Sn:
　0.5% ~ 20.0% Si: 0.05% ~ 1.50%
　Bi: 0% ~ 5.0%, an In: 0% ~
　2.0%, Ca: 0%
　3.0% ~,

　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%
~,
　0% ~ 0.25%, Sr: 0% ~ 0.5%,
　Sb: 0% ~ 0.5%, Pb: 0% ~
　0.5%, B: 0% to 0.5 percent,
　Contains, has a chemical composition and the balance being Zn and impurities,
　and the plating layer, the area fraction 5-65% particulate Mg 2 and Sn phase containing tissue, the tissue including a solid solution of Zn and Al has,
　the granular Mg 2 Sn phase containing tissue, Zn phase and granular Mg less than the crystal grain size 1μm dispersed in the Zn phase 2 is the Sn phase, consisting of tissue, plated steel sheet.
[Requested item 2]
　By mass%, plated steel sheet according to claim 1, wherein the content of said Mg is from 0.5% to 3.0%, the content of the Sn is 1.0% to 7.5%.
[Requested item 3]
　In mass%, the content of 20% to 60% of Al, the content is 1.0% to 2.0% of Mg, the content of 1.0% to 5.0% of the Sn, and the plated steel sheet according to claim 1 or claim 2 content of Si is 0.05% to 1.0%.
[Requested item 4]
　Plated steel sheet according content of content and the Mg of the Sn is in any one of claims 1 to 3 satisfying the following formula (1).
　Mg ≦ Sn ≦ 2.5 × Mg ··· Equation (1)
　In the formula (1), each element symbol represents the content of each element in weight percent.
[Requested item 5]
　The particulate Mg 2 plated steel sheet according to the area fraction of the Sn phase containing tissue, any one of claims 1 to 4 is 20% to 60%.
[Requested item 6]
　The particulate Mg 2 plated steel sheet according to the area fraction of the Sn phase containing tissue, any one of claims 1 to 5 is 30% to 60%.
[Requested item 7]
　Plated steel sheet according to the area fraction of the tissue, including a solid solution of Zn and Al, any one of claims 1 to 6 is 35% to 95%.
[Requested item 8]
　The plating layer is equivalent circle diameter 1μm or more bulk MgZn 2 -plated steel sheet according to any one of claims 1 to 7 having 0% to 20% phase area fraction.
[Requested item 9]
　The plating layer is equivalent circle diameter 1μm or more bulk MgZn 2 -plated steel sheet according to any one of claims 1 to 8 having 0% to 5% phase area fraction.
[Requested item 10]
　Plated steel sheet according to any one of claims 1 to 9 wherein the plating layer is, having 0-20% equivalent circular diameter 2μm or more bulk Zn phase in area fraction.
[Requested item 11]
　Plated steel sheet according to any one of the plating layer, claims 1 to 10 having from 0% to 10% equivalent circular diameter 2μm or more bulk Zn phase in area fraction.
[Requested item 12]
　Between the plated layer and the steel sheet, plated steel sheet according to any one of claims 1 to 11, further comprising an interfacial alloy layer consisting of Al-Fe intermetallic compound having a thickness of 100 nm ~ 1.5 [mu] m .