0001]The present disclosure relates to a plated steel.
BACKGROUND
[0002]For example, in the field of civil engineering and building materials, Sakumizo, corrugated pipes, drainage ditch lid, Hisuna prevention plate, bolts, wire mesh, guardrail, as the steel material of various shapes such as a cut-off wall, Zn-plated steel is used there. Zn-based plating layer of Zn-plated steel, other protective effect of rust base steel (the steel) from corrosion, are exposed to severe corrosive environments. Therefore, the Zn-based plating layer, other corrosion, flying objects, impact resistance and abrasion resistance to protect the base steel from gravel or the like is required.
[0003]
　For such performance requirements, for example, Patent Document 1, Patent Document 2, Patent Document 3 and the like, Zn-Al-Mg-based immersion plating steel is proposed. By including a small amount of Mg in Zn-Al alloy plating layer, achieving high corrosion resistance of long-term anticorrosive effect is obtained. Also, generally Zn-Al-based plating layer is, in the Al content is less than 20 wt%, since the principal plating layer is soft Zn phase and Al phase, scratches, susceptible to impact or the like, subject to wear . On the other hand, Zn-Mg-Al-based alloy plated layer containing Mg, in order to harden, it is advantageous for impact resistance and abrasion resistance.
[0004]
　Patent Document 4, the Zn-Al-Mg-based immersion plating steel, increasing the thickness of the intermediate layer (Al-Fe alloy layer), have also been developed techniques to increase the life of the plating steel. Intermediate layer (Al-Fe alloy layer), because it is hard, because the overall thickness of the immersion plating layer is increased, the impact resistance and abrasion resistance is high, in terms of protecting the base steel (steel) is It becomes more advantageous to.
[0005]
　On the other hand, Patent Document 5, Zn-Mg-Al alloy hot dipping steel containing a large amount of Mg in Zn-Mg-Al-based alloy plated layer is also proposed. The hot dipping steel, since it contains Mg in a large amount, a number of intermetallic compounds contained in the plating layer hardens, high corrosion resistance, and wear resistance.
[0006]
Patent Document 1: Japanese Patent Laid-Open 9-256134 discloses
Patent Document 2: Japanese Patent Laid-Open 11-117052 discloses
Patent Document 3: Japanese Patent 2010-70810 JP
Patent Document 4: Japanese Patent 2015-40334 JP
Patent Document 5: Japanese Patent 5785336 JP
Summary of the Invention
Problems that the Invention is to Solve
[0007]
　Here, as described above, the plating layer of the plated steel material, flying objects, impact resistance and abrasion resistance to protect the base steel from gravel or the like is required.
[0008]
　However, the immersion plating steel described in Patent Documents 1-3, when forming a Zn-Al-Mg-based alloy plating layer containing a large amount of Mg, reduce the activity of Fe. Further exacerbates the wettability and reactivity with the immersion plating bath base iron (steel). As a result, the growth of the intermediate layer (Al-Fe alloy layer) is poor, and, it may not be sufficiently reduced reactivity is changed base steel (the steel) with a flux, a good appearance Zn formation of -al-Mg-based alloy plating layer (the production of dip Zn-Al-Mg-based alloy plated steel good appearance) has been difficult. That is, in the immersion plating using Zn-Al-Mg-based alloy plating bath containing a large amount of Mg, were not able to secure a thickness and structure of Zn-Al-Mg-based alloy plating layer.
　Therefore, the range (specifically with limited Mg density component adversely affecting the immersion plating resistance is not implemented only immersion plating in (range limits the Mg content of 5 wt% or less). Further, the intermediate layer even without, to ensure the thickness and adhesion sufficient plating layer, two-step plating method is used.
[0009]
　Therefore, immersion plating steel described in Patent Documents 1 to 3 is a sufficient corrosion resistance, current situation is the impact resistance and abrasion resistance is not obtained.
[0010]
　Immersion plating steel described in Patent Document 4, since the thickness of the intermediate layer (Al-Fe alloy layer), the intermediate layer (Al-Fe alloy layer) is corroded, punctate Elution Fe component red rust now stand out, corrosion resistance is the current situation is not enough.
[0011]
　Hot dipping steel described in Patent Document 5, the corrosion resistance, although a high abrasion resistance, since Mg is contained in a large amount, the plating layer formation, because of low reactivity with the base steel (steel), the intermediate layer (Al-Fe alloy layer) is not formed, or the intermediate layer (Al-Fe alloy layer) is hard to be thickened. Therefore, the thickness of the plating layer is small, tends low impact resistance, plating layer reaches the cracks as soon steel (base steel) is easily peeled off the plating layer by the impact. Furthermore, flying objects, by gravel or the like, once the scratches or cracks in the plating layer occurs, corrosion is likely to progress, at present, the corrosion resistance is lowered.
[0012]
　Accordingly, one aspect of the present disclosure has been made in view of the background described above, corrosion resistance, impact resistance and abrasion resistance is high, and the high corrosion resistance after the wound or crack occurs in the plating layer plated steel it is an object of the present invention to provide.
Means for Solving the Problems
[0013]
　The present disclosure has been made based on the above background, including the following aspects.
[0014]
<1>
　and steel,
　coated on the surface of the steel material, by mass%, Mg: 8 ~ 50% , Al: 2.5 ~ 70.0%, Ca: 0.30 ~ 5.00%, Y: 0 ~ 3.50%, La: 0 ~ 3.50%, Ce: 0 ~ 3.50%, Si: 0 ~ 0.50%, Ti: 0 ~ 0.50%, Cr: 0 ~ 0.50% , Co: 0 ~ 0.50%, Ni: 0 ~ 0.50%, V: 0 ~ 0.50%, Nb: 0 ~ 0.50%, Cu: 0 ~ 0.50%, Sn: 0 ~ 0.50%, Mn: 0 ~ 0.20 %, Sr: 0 ~ 0.50%, Sb: 0 ~ 0.50%, Cd: 0 ~ 0.50%, Pb: 0 ~ 0.50%, and B: comprises 0 to 0.50%, the balance being Zn and impurities, and a plating layer which satisfies the following formulas (a) and the following formula (B),
　interposed between the steel and the plating layer an intermediate layer, Al- a sea consisting of e alloy phase, and the island portion Mg content containing 8 mass% or more Zn-Mg-Al alloy phase, in have constructed sea-Kaifu comprising the Al-Fe alloy phase an intermediate layer area fraction of 55 to 90%
　plating steel with a.
- formula (A): Si + Ti + Cr + Co + Ni + V + Nb + Cu + Sn + Mn + Sr + Sb + Cd + Pb + B ≦ 0.50%
, formula (B): Ca + Y + La + Ce ≦ 5.00%
　formula (A) and formula (B), the chemical symbol shows the content of each element in mass% .
<2>
　The thickness of the intermediate layer, plating steel according to a 5 ~ 500 [mu] m <1>.
<3>
　The sea part, Al as the Al-Fe alloy phase 5 Fe 2 consists phase,
　said island portion, the Zn-Mg-Al alloy phase as a quasicrystal phase and MgZn 2 or consisting of phase, or the Zn- quasicrystalline phase as mg-Al alloy phase, MgZn 2 plated steel according to phase, and consisting of mg-phase <1> or <2>.
<4>
　The thickness ratio of the intermediate layer to the thickness of the plating layer, the plating steel according to any one of claims 1 to 3 from 0.2 to 4 times.
<5>
　Mg content of the plating layer is at least 15 mass%, and Mg content of the Zn-Mg-Al alloy phase is 15 mass% or more <1> to any one of <4> plated steel material as claimed in.
<6>
　the plating layer is immersion plating layer <1> - plated steel material according to any one of <5>.
The invention's effect
[0015]
　According to one aspect of the present disclosure, corrosion, impact resistance and abrasion resistance is high, and can provide high corrosion resistance after the wound or crack occurs in the plating layer plated steel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
Is a photograph showing a cross section of an example of plating steel according to the embodiment of FIG. 1 the present disclosure.
Is a photograph showing a cross section of another example of plating steel according to the embodiment of FIG. 2 present disclosure.
A reflection electron image of SEM showing an example of an intermediate layer in the plating steel according to the embodiment of FIG. 3 present disclosure.
Is an electron diffraction image of TEM of FIG. 4 quasicrystalline phase.
In the plating steel according to the embodiment of FIG. 5 the present disclosure, is a schematic diagram for explaining an estimation mechanism that intermediate layer is formed to have a sea-island structure.
DESCRIPTION OF THE INVENTION
[0017]
　The following describes the plating steel and a manufacturing method thereof according to an example embodiment of the present disclosure.
　In the present specification, the numerical range expressed using "to" means a range including numerical values described before and after "to" as the lower and upper limits.
　In this specification, "%" indicating the content of the composition (elemental) means "% by mass".
[0018]
(Steel Plated)
　plating steel according to the embodiment includes a steel, a plated layer coated on the surface of the steel material, and a middle layer interposed between the steel and the plating layer (see FIGS. 1 and 2) .
　Plating layer, by mass%, Mg: 8 ~ 50% , Al: 2.5 ~ 70.0%, Ca: includes 0.30 to 5.00%, the balance being Zn and impurities. On the other hand, the intermediate layer has a sea consisting of Al-Fe alloy phase, and the island portion Mg content containing 8% or more Zn-Mg-Al alloy phase, in the constructed sea-island structure, Al-Fe area fraction of sea made of an alloy phase of 55 to 90%.
[0019]
　Here, in FIGS. 1-2, 1-plated layer, 2 the intermediate layer, 3 is steel, 4 denotes a plating steel.　　　
[0020]
　Plated steel material according to the embodiment, the above-described configuration, corrosion, impact resistance and abrasion resistance is high and, corrosion resistance after wound or a crack occurs in the plating layer higher. Plated steel material according to the embodiment was found based on the knowledge described below.
[0021]
　First, we, corrosion resistance, in order to form a good plating layer in impact resistance and abrasion resistance, Zn-Mg-Al alloy plating bath containing a high concentration of 8% or more of Mg (hereinafter "high the immersion plating using also referred) and Mg-plating bath "discussed examples. Moreover, even after the wound or crack occurs in the plating layer, in order to increase the corrosion resistance of the plated steel material were investigated to increase the corrosion resistance of the intermediate layer formed by the alloying reaction of Al and Fe. More specifically, it is as follows.
[0022]
　Plating layer formed by immersion plating using a highly Mg-plating bath, Mg is contained at a high concentration of more than 8%. Therefore, it increased corrosion resistance of the plating layer. In addition, since the plating layer itself becomes hard, increasing impact resistance and wear resistance of the plating layer. However, at the time of immersion plating, alloying reactivity between Al and Fe (i.e., reactivity with the Fe of Al and base iron (steel) component of the plating components: hereinafter this reaction is referred to as "Al-Fe inter-reaction" ) tends to be suppressed, it is difficult to increase the intermediate layer. Therefore, low impact resistance of the plating layer, the plating layer is easily peeled off by the impact.
[0023]
　The inventors have found that in immersion plating using a highly Mg-plating bath, it was studied to promote alloying reaction of Al and Fe. Although details will be described later, as a result, the inventors have obtained the following findings. In immersion plating, to promote alloying reaction of Al and Fe, Al-Fe alloy phase, Zn, it is formed to surround a portion of the plating components containing Mg and Al. Then, an alloy phase containing at least a Zn-Mg-Al alloy phase, a form of scattered islands in the Al-Fe alloy phase. Alloy phase that dot the island shape, and is formed from the highly Mg-plating bath. That is, the intermediate layer having a sea consisting of Al-Fe alloy phase, and the island portion Mg content containing 8% or more Zn-Mg-Al alloy phase, in the configured sea-island structure is, base steel (steel) It is formed to be interposed between the plated layer.
[0024]
　Then, we have the sea-island structure, the intermediate layer was 55 to 90 percent area fraction of sea consisting of Al-Fe alloy phase was found that has the following characteristics.
[0025]
　By 1) sea-island structure, it progress of corrosion of the intermediate layer (path) complex path, the corrosion resistance of the intermediate layer itself is increased (i.e., wound or a crack occurs in the plating layer, even if the intermediate layer reaches the corrosion stage, corrosion is less likely to progress).
　2) Mg in the intermediate layer, since the high content of corrosion elements such as Zn, acts sacrificial anticorrosion effect of corrosion elements, the corrosion resistance of the intermediate layer itself is increased (i.e., wound or a crack occurs in the plating layer, the intermediate layer even reach the corrosion stage, red rust is less likely to occur).
　By 3) sea-island structure, the distribution of the hardness occurs in the intermediate layer, the crack propagation behavior is complicated, flying object, also plated layer by gravel or the like is subjected to impact, peeling of the plating layer is less likely to occur.
[0026]
　By the above findings, the plating steel according to the embodiment, corrosion, impact resistance and abrasion resistance is high and, scratches or cracks were found to be higher corrosion resistance after generated in the plating layer.
[0027]
　The following is a detailed description of plating steel according to the embodiment.
[0028]
　Steel 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.), automotive parts (suspension member and the like) and the molded processed steel and the like. Molding, for example, pressing, roll forming, various plastic working techniques such as bending can be utilized.
[0029]
　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, steelmaking method of 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.
[0030]
　However, the crystal grain size of the surface of the steel (surface plated layer and the intermediate layer is formed) is preferably less than 5 [mu] m, more preferably less than 1 [mu] m. By reducing the crystal grain size of the surface of the steel, "Al-Fe inter-reaction" is promoted during immersion plating, the intermediate layer is easily formed with the sea-island structure. Crystal grain size of the surface of the steel it is more preferred small, practical lower limit that can be the minimization of the order of 0.1 [mu] m. Incidentally, there is no dominant terms in the reactivity of the plating layer due to crystal grains is large.
　Here, the crystal grain size of the surface of the steel from the surface, the average value of the grain size of the ferrite phase contained in the range of 100μm in the depth direction. The method of measuring the crystal grain size of steel specified in JIS G0551 - measured in the grain size microscopic examination method.
[0031]
　Steel, the dislocation density of the surface (surface on which the plated layer and the intermediate layer is formed) may be enhanced by the processing. By increasing the dislocation density of the surface of the steel material, "Al-Fe inter-reaction" is promoted during immersion plating, the intermediate layer is easily formed with the sea-island structure.
[0032]
　Moreover, steel, Cu-Sn substitution plating steel, Ni substituted plating steel, Zn-plated steel (Zn adhered amount 40 g / m 2 may be a steel plating is made of such less plating steel). These plated steel by applying a steel, "Al-Fe inter-reaction" is promoted during immersion plating, the intermediate layer is easily formed with the sea-island structure. In the case of using a plated steel material as described above as steel, between the intermediate layer described later with steel, Cu-Sn concentrated layer, Ni-enriched layer, Zn-Al-Fe alloy layer or the like, used as a steel material may be formed on the original plate thickness corresponds to the. These layers are usually immersed at the same time, there may not be observed for spreading the plating bath, for some reason, it reacts with the surface of the plating steel with components of the immersion plating bath, the Al-Fe alloy phase captured, remains between the steel and the intermediate layer is a layer formed.
[0033]
　The intermediate layer will be described.
　Intermediate layer, when forming the plating layer, by reaction with Fe in the Al and steel plated component (base steel), while capture the plating components with generation of Al-Fe alloy phase, between the plating layer and steel a layer to be formed. Therefore, the composition of the intermediate layer comprises Zn, Mg, Al, Ca and Fe, the balance being impurities (although, in some cases Ca is not included). Specifically, the composition of the intermediate layer, Zn: 3.0 ~ 30.0%, Mg: 0.5 ~ 25.0%, Al: 30.0 ~ 55.0%, Ca: 0 ~ 3. 0%, and Fe: comprises 24.0 to 40.0%, it is preferable that the balance being impurities. In the present embodiment, among the layers covering the steel, a region containing the Fe 24.0 ~ 40.0% is defined as "intermediate layer".
　The intermediate layer may contain "Zn, Mg, Al, Ca and elements other than impurities (Y, La, Ce, Si, etc.)" which may be included in the plating layer. However, the element (including impurities) other than Zn, Mg, Al and Ca in the intermediate layer is always less than 0.5%, treated as an impurity.
[0034]
　Composition of the intermediate layer (content of each element) is measured by the following method. The cross section of any of the intermediate layer (cross section cut in the intermediate layer thickness direction), to obtain a reflection electron image of the EPMA (electron probe microanalyzer) with SEM (scanning electron microscope). From the reflected electron image of the resulting SEM, selecting a rectangular area from the inside of the intermediate layer. This rectangular area is to be located inside the intermediate layer, to set the position and its size. Specifically within rectangular region, the top and bottom and substantially parallel sides in the steel surface, the is 1 side length and 10 [mu] m. These both two sides is located in the intermediate layer, and, as the distance therebetween is maximum and set its position. Further, the rectangular region is a region containing both the sea portion and the island portion to be described later. The area fraction of the sea portion of the rectangular area so that the difference within 5% ± relative area fraction of the sea portion of the entire intermediate layer, to set the position of the rectangular region. Then, select the rectangular area meeting these criteria 20 or more points. Then, each rectangular region was quantitatively analyzed at each EPMA, the average value of each element are respectively determined, and defined as the content of each element in the intermediate layer.
　The thickness of the intermediate layer, the area fraction of the sea portion of the intermediate layer, the area fraction of the sea portion of the rectangular region is determined by the method described later.
[0035]
　Organization of the intermediate layer has a sea consisting of Al-Fe alloy phase, and the island portion includes a Zn-Mg-Al alloy phase, in the configured sea-island structure. Specifically, tissue of the intermediate layer, when observing a cross section cut in the intermediate layer thickness direction, "phase containing Zn-Mg-Al alloy phase" (islands surrounded by Al-Fe alloy phase (sea) the portion) has a plurality having structure (see FIG. 3).
[0036]
　Ama is a region consisting of Al-Fe alloy phase. Al-Fe alloy phase Al 5 Fe 2 made of phase. Incidentally, Al 5 Fe 2 during the reaction phase is formed (Al and steel plated component (reaction with Fe in the base steel)), Zn in the plating components Al 5 Fe 2 embodiment to replace the Al position in the phase there is to be taken up in. Thus, Zn may be interspersed with partially sea portion.
[0037]
　In the present embodiment, a region other than the sea part in the intermediate layer in the "island". Island portion has, for example, Zn-Mg-Al alloy phase, Zn-Mg alloy phase, and a metal phase of Mg equality. These alloy phase and the metal phase is a quasi-crystal phase or equilibrium phase.
　The Zn-Mg-Al alloy phase, for example, quasi-crystalline phase "Mg 32 (Zn, Al) 49" "can be mentioned. A part of the Zn-Mg-Al Zn alloy phase may be substituted by Al.
　The Zn-Mg alloy phase, for example, MgZn 2 include equality.
　Island portion is preferably a region consisting of two or three phases. Specifically, the island portion, quasicrystalline phase, and MgZn 2 region consisting phase, or quasi-crystalline phase, MgZn 2 is preferably a region consisting of phase, and Mg phase.
[0038]
　Incidentally, the quasi-crystal phase "Mg 32 (Zn, Al) 49 ' is, Mg, Zn, other Al, may contain Ca. Further, MgZn a Zn-Mg alloy phase 2 phase addition of Mg and Zn, may contain at least one of Ca and Al. Mg phase is a metallic phase, other Mg, may contain Zn. Moreover, each phase constituting the island part, Fe, may contain impurities.
[0039]
　Islands, in addition to the alloy phase and a metal phase which is quasi-crystalline phase or equilibrium phase, the remaining structure may be included more than 10% in area fraction in the intermediate layer is a non-equilibrium phase. The remaining structure, e.g., MgZn phases, Mg 2 Zn 3 phase, Mg 51 Zn 20 unstable MgZn alloy phase equality and the like. If 10% or less in content area fraction of the remaining structure, is not the characteristics of the intermediate layer is greatly impaired.
[0040]
　In the case where the island portion contains a plurality of phases, each island portion, be formed of a plurality of phases may be either be composed solely phase. Specifically, for example, quasi-crystalline phase "Mg 32 (Zn, Al) 49" , MgZn 2 phase, and the islands of Mg phase, and the island portion consisting of two phases among the three phases, 3 one of the island portion consisting of a single phase of the phase, may be mixed.
[0041]
　In islands, Zn-Mg-Al alloy phase (quasicrystal phase "Mg 32 (Zn, Al) 49" ) are, Mg content is 8% or more. By Mg content in the island portion comprises less than 8% of Zn-Mg-Al alloy phase, the corrosion resistance of the intermediate layer is improved. In this respect, Mg content of Zn-Mg-Al alloy phase is preferably 10% or more, more preferably 15% or more. On the other hand, from the viewpoint of maintaining adequate corrosion rate, the upper limit of the Mg content of Zn-Mg-Al alloy phase is preferably 50% or less.
　Then, it from the viewpoint of improving both the corrosion resistance of the intermediate layer and the plating layer, when Mg content of Zn-Mg-Al alloy phase is more than 15%, the Mg content of the plating layer is also 15% or more preferable.
[0042]
　From the viewpoint of the corrosion resistance of the intermediate layer is improved, other than Zn-Mg-Al alloy phase constituting the island phase (Mg-Zn alloy phase etc.) also, it is preferable that the Mg content is 8% or more, 10 more preferably at least%, more preferably at least 15%.
　Mg content of each phase can be calculated by TEM-EDX (Transmission Electron Microscope- EnergyDispersive X-ray Spectroscopy) quantitative analysis by, or EPMA quantitative analysis by (Electron Probe Micro-Analyzer) mapping. Specifically, in an arbitrary cross section of the measured intermediate layer (cross section cut in the intermediate layer thickness direction), the quantitative analysis of TEM-EDX or each phase of the Mg content by EPMA 3 points, the average value the the phase of the Mg content.
[0043]
　In the sea-island structure of the intermediate layer, the area fraction of the sea consisting of Al-Fe alloy phase (i.e. the area fraction of the Al-Fe alloy phase) is 55 to 90%. The area ratio of the Al-Fe alloy phase increases the area of the island portion is less than 55%, it becomes impossible maintain the sea-island structure as an intermediate layer. Therefore, the area fraction of Ama and 55% or more. By securing the area fraction of the "islands containing Zn-Mg-Al alloy phase" surrounded by sea unit, sea-island structure is maintained. Thereby, the progress of corrosion of the intermediate layer (path) is complicated route, increased corrosion resistance of the intermediate layer, it is possible to suppress the peeling of the plating layer. Further, Mg in the intermediate layer, by containing a large amount of corrosion elements such as Zn, increases the corrosion resistance of the intermediate layer itself.
　Mg, in order to contain a large amount of corrosion elements such as Zn in the intermediate layer, it is necessary to maintain Mg, the ratio of the island portion containing the corrosion resistance elements such as Zn constant or more. Therefore, the area fraction of Ama and 90% or less.
　From these viewpoints, the area fraction of the sea is preferably 65 to 85%, more preferably 70-80%.
[0044]
　The area fraction of the island portion is in a range obtained by subtracting the area fraction of sea part from 100%. Here, the phases constituting the island part, formation behavior of sea-island structure is complex, irregular or formed in any area fraction, a low correlation to a plating bath. Therefore, there is no particular limitation on the each phase area fraction constituting the island portion.
[0045]
　In the sea-island structure of the intermediate layer, the area fraction of the sea consisting of Al-Fe alloy phase (i.e. the area fraction of the Al-Fe alloy phase) is measured by the following method.
　Any cross-section which is a kind of (cut to the middle layer thickness direction cross-section) to the ion milling CP (cross session polisher) processing of the measured intermediate layer applied. After CP machining, reflected electron image (image with the three or more locations with a desired area of about 2000 .mu.m × 2000 .mu.m square in cross-section of the intermediate layer was observed at a magnification of 3,000 times the cross section of the intermediate layer SEM (scanning electron microscope) (approximately obtain a 30μm × 30μm)).
　Then, applying any cross-sectional FIB processed (section cut in the intermediate layer thickness direction) (focused ion beam) processing of the intermediate layer having the same measured. After FIB processing, obtain an electron diffraction image of the cross-sectional structure of the intermediate layer TEM (transmission electron microscope). Then, to identify the intermetallic compound contained in the intermediate layer.
　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 the intermediate layer. Note that in each phase of the identification with the intermediate layer, may be analyzed EDX point by EDX (energy dispersive X-ray spectrometer) with SEM, collates the identification results of the electron diffraction image of the results and TEM and EDX point analysis.
[0046]
　Next, it is determined in the reflection electron image of SEM, the gray scale indicated by the phase having the intermediate layer lightness, 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, the more the phase content of the atomic number is smaller Mg content is large, a black color, higher Zn content rich phase tends to exhibit white.
　Therefore, to match the reflection electron image of SEM, only the range of the three values indicated by the Al-Fe alloy phase, implementing the computer image processing, such as color change. This image processing, obtaining the area fraction of Al-Fe alloy phase occupying the reflection electron image of SEM.
　The area fraction of Al-Fe alloy phase is at least 3 in the above field, area fraction of Al-Fe alloy phase which was determined by the operation of an arbitrary cross section of the intermediate layer (cross section cut in the intermediate layer thickness direction) and the average value.
[0047]
　Incidentally, the same operation, each phase constituting the island portion (Zn-Mg-Al alloy phase, Zn-Mg alloy phase, metal phase etc.) can also be determined area fraction of.
[0048]
　Here, an example of a reflection electron image of the intermediate layer SEM in FIG. In the reflection electron image of the intermediate layer SEM shown in FIG. 3, the white portion is MgZn 2 phase (Fig. 3 in MgZn 2 hereinafter), light gray portions quasicrystalline phase "Mg 32 (Zn, Al) 49 phase" (FIG. 3 in Mg 32 (Zn, Al) 49 hereinafter), dark gray portion Al 5 Fe 2 phase (in Fig. 3 Al 5 Fe 2 denoted), the black portion indicates a Mg phase (denoted as in Figure 3 Mg) ing. Then, each phase having a chemical composition obtained by EDX with SEM is as follows.
- white portion = MgZn 2 phase: chemical composition = Mg: 13%, Al: 3%, Ca: 5%, Zn: 79%
, light gray portion = quasicrystalline phase Mg 32 (Zn, Al) 49 : Chemical composition = mg: 20.4%, Zn: 75.5%, Al: 3%, Ca: 1%
· dark gray portion = Al 5 Fe 2 phases: the chemical composition of Al =: ± 52.5%. 5%, of Fe: 44 is ±%. 5%, a Zn:% ± 3.5 of. 1%
· Black color = Mg phase portion: a chemical composition = Mg94%, Zn: 6%
[0049]
　The reflection electron image of the intermediate layer SEM shown in FIG. 3, the intermediate layer is, for example, quasi-crystalline phase as a Zn-Mg-Al alloy phase "Mg 32 (Zn, Al) 49" MgZn, as Zn-Mg alloy phase 2 phase, and the island portion consisting of Mg phase as the metal phase, Al as Al-Fe alloy phase 5 Fe 2 and it is shown to have a sea-island structure surrounded by a sea portion made of phase.
[0050]
　Thus, in the reflection electron image of SEM of the intermediate layer shown in FIG. 3, each phase can be identified by a gray scale. Then, as described above, only the range of the three values ​​indicated by the Al-Fe alloy phase, when carrying out the computer image processing, such as color change, phase occupying the reflected electron image of SEM (Al-Fe alloy phase, Zn -mg-Al alloy phase, Zn-Mg alloy phase, it is possible to obtain the area fraction of metal phase etc.).
[0051]
　Incidentally, each phase area fraction constituting the intermediate layer may also be calculated by the binarization processing of the reflected electron image of SEM. That is, in the reflection electron image of SEM, the indicated phase "lightness, three values ​​of hue and contrast values", among the phases, determining the area fraction of the two regions of black and white can be separated. Of each phase, changing the selection of the two regions of black and white can be separated to obtain the area fraction of the two regions of black and white. Then, repeating the above operations, by taking the difference between the obtained area fraction can also calculate the area fraction of phases of interest.
[0052]
　Specifically, for example, in the reflection electron image of SEM of the intermediate layer shown in FIG. 3, it is as follows.
　Black and Mg phase black portion, the other phases displayed in white, determine the area fraction of Mg phase.
　MgZn white portion 2 white the phase, the other phases are displayed in black, MgZn 2 area fraction of phases is determined.
　MgZn white portion 2 paracrystalline phase of phase and light gray portion white, the other phases are displayed in black, MgZn 2 obtains the total area fraction of the phase and the quasi-crystal phase. Then, MgZn 2 area fraction of the total phase and quasi-crystal phase and MgZn 2 By taking the difference between the phase area fraction of, determine the area fraction of quasicrystalline phase.
　MgZn white portion 2 phase, semi-crystalline phase of the light gray part, and from the difference of the total area fraction of the Mg phase, dark gray portion Al 5 Fe 2 obtains the area fraction of phases.
[0053]
　The thickness of the intermediate layer is preferably 5 ~ 500 [mu] m.
Corrosion resistance to form a sufficient plating layer, and to prevent plating defects non-coating or the like, it is at least the thickness of 5μm or more intermediate layers are present. Is less than the thickness of the intermediate layer is 5 [mu] m, hard plating layer with a thickness is formed, it may become the plating adhesion layer defects.
　On the other hand, the thickness of the intermediate layer, Al-Fe diffusion is involved. Therefore, for example, the case of forming a plating layer by immersion plating method, under normal operating conditions of immersion plating, the thickness of the formed can intermediate layer is 500μm or less are usually. The intermediate layer having a thickness of 500μm greater, since not reach the supply of Fe component from steel (base steel), formed is difficult.
[0054]
　From the viewpoint of improving the corrosion resistance of the plated layer and the intermediate layer, the thickness of the intermediate layer is more preferably more than 10 [mu] m, and even more preferably 100 [mu] m. On the other hand, increase in the thickness of the intermediate layer, since it may impair the appearance of the plating layer, the thickness of the intermediate layer is preferably in the 200μm or less.
[0055]
　Even a thickness of 5 ~ 500 [mu] m of the intermediate layer, when the intermediate layer does not have the sea-island structure, not to obtain the effect of the sacrificial protection property, rust in the intermediate layer tends to occur at an early stage.
[0056]
　The thickness ratio of the intermediate layer to the thickness of the plating layer (thickness of the intermediate layer thickness / plating layer) is preferably from 0.2 to 4 times, more preferably 0.5 to 2 times.
　Even if the ratio of the thickness of the intermediate layer is too small, too large, the impact, sometimes cracks peeling propagates at the interface between the plated layer and the intermediate layer. Therefore, it is preferable that the ratio of the thickness of the intermediate layer to 0.2 to 4 times.
　Even 0.2 to 4 times the ratio of the thickness of the intermediate layer is to the thickness of the plating layer, when the intermediate layer does not have the sea-island structure, the shock, the interface between the plated layer and the intermediate layer in the crack is likely to be peeled off and propagation.
[0057]
　The thickness of the intermediate layer is measured as follows. The SEM (scanning electron microscope), (in which is cut in the cross section in the thickness direction of the intermediate layer, the observation of the region corresponding to 2.5mm length fraction in the intermediate layer in a direction parallel) cross-section observation of the intermediate layer performing the . The thickness of the thickest portion and the thinnest portion of each intermediate layer is observed, respectively, in the these three field for performing at least three field of view obtained by observing the same field of view, for example, magnification of about 100 times as shown in FIG. 2 in the observation, the thickness is different. Upper surface of the intermediate layer has a different wave shape depending on the location. As a method for calculating the average value of the thickness of the intermediate layer, the following method can be mentioned. First, the area of the intermediate layer section by image processing. Then, the bottom and upper surface of the intermediate layer section to each linear approximation, into a rectangle having the same area in which an intermediate layer / base steel (steel) surface to one side (bottom). Then, the length in the height direction of the rectangle and the average value of the thickness. The average value of the values obtained from at least three field of view in this manner, the average value of the thickness of the intermediate layer.
　Incidentally, sample preparation methods for cross-sectional observation may be carried out by known resin embedding or cross-section polishing method.
[0058]
　Next, a description will be given of a plating layer.
　Plating layer, Mg: 8 ~ 50%, Al: 2.5 ~ 70.0%, and Ca: includes 0.30 to 5.00%, the balance being Zn and impurities.
[0059]
　The composition of the plating layer will be described numerical limitation range and the reasons for limitation.
"Mg: 8 ~ 50%"
　Mg is an element for improving the corrosion resistance of the plating layer. The plating layer becomes hard, is an element that improves the impact resistance and wear resistance of the plating layer. On the other hand, Mg is also an element for generating a Mg phase degrading the corrosion resistance of the plating layer. Therefore, Mg content is 8 to 50%. Mg content is preferably 8 to 50%, more preferably from 10 to 45%, more preferably 15 to 35% and particularly preferably 15 to 25%.
　Incidentally, Mg is an element which promotes the formation of high corrosion resistance quasicrystalline phase in the plating layer. Therefore, when the Mg content of 8% to 50% more likely to generate the quasi-crystalline phase in the plating layer.
[0060]
"Al: 2.5 ~ 70.0%"
　Al is an element to improve the corrosion resistance. It is also a necessary element to a thick film the intermediate layer having Al-Fe alloy phase. On the other hand, if containing a large amount of Al in the plating layer, red rust is likely to occur. Therefore, Al content shall be 2.5 to 70.0%. Al content
is preferably from 3 to 60%, more preferably from 5.0 to 50.0%, more preferably from 5.0 to 15.0%.
　Incidentally, a large amount of Al serves to suppress the generation of high corrosion resistance quasicrystalline phase in the plating layer. Therefore, when the Al content to 2.5 to 70.0%, it becomes easy to generate the quasi-crystalline phase in the plating layer.
[0061]
"Ca: 0.30 ~ 5.00%"
　Cg is an element to prevent oxidation of Mg. The Mg content to form more than 8% of the plating layer, it is necessary to use a plating bath having the same Mg content. If Mg content is not contained Ca 8% or more of the plating bath, black oxide of Mg is generated in a few minutes in the atmosphere. On the other hand, Ca itself easily oxidized and adversely affects the corrosion resistance of the plating layer. A large amount of Ca is, tends to be difficult corrosion resistant element Zn is incorporated into Al-Fe alloy phases of the intermediate layer is increased. Therefore, Ca content, and 0.30 to 5.00%. Ca content is preferably 0.50 to 3.00%.
　Incidentally, a large amount of Ca serves to suppress the generation of high corrosion resistance quasicrystalline phase in the plating layer. Therefore, when the Ca content to 0.30 to 5.00 percent, likely to generate the quasi-crystalline phase in the plating layer.
[0062]
: "The balance Zn and impurities"
　Zn of the balance, is an element that improves the corrosion resistance. Also, the balance of Zn is in the high-Mg plating bath is an element which promotes a degree of steel (the base steel) reactivity imparted Al-Fe inter-reaction with. Furthermore, the balance of Zn, when the Al concentration is high, an element necessary for suppressing the inter-Al-Fe reaction in a suitable speed, contributes to the adhesion between the plating layer and steel (the base steel) elements But there is. Therefore, Zn content of the remainder is preferably 20% or more, preferably 30% or more.
　On the other hand, if containing a large amount of the remainder of Zn in the plating layer, it became popular is between Al-Fe of the plating layer and the base steel reaction, may become a state of not intermediate layer forms with a sea-island structure. Therefore, Zn content of the remainder is preferably 70% or less, preferably 65% or less.
　Incidentally, Zn is an element which promotes the formation of high corrosion resistance quasicrystalline phase in the plating layer. Therefore, when the Zn content of 20 to 70%, tends to generate quasi-crystal phase in the plating layer.
[0063]
　The remainder of the impurities, the 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 impurities, may be Fe is mixed up about 2%. Incidentally, also contain up to about 2% Fe in the plating layer, it does not give influence on the performance of the plating layer.
[0064]
　Here, the plating layer, Y: 0 ~ 3.50%, La: 0 ~ 3.50%, Ce: 0 ~ 3.50%, Si: 0 ~ 0.50%, Ti: 0 ~ 0.50 %, Cr: 0 ~ 0.50% , Co: 0 ~ 0.50%, Ni: 0 ~ 0.50%, V: 0 ~ 0.50%, Nb: 0 ~ 0.50%, Cu: 0 ~ 0.50%, Sn: 0 ~ 0.50%, Mn: 0 ~ 0.20%, Sr: 0 ~ 0.50%, Sb: 0 ~ 0.50%, Cd: 0 ~ 0.50% , Pb: 0 - 0.50%, and B: 0 to ~ 0.50% may contain one or two or more. However, to satisfy the following formulas (A) and the following formula (B).
- formula (A): Si + Ti + Cr + Co + Ni + V + Nb + Cu + Sn + Mn + Sr + Sb + Cd + Pb + B ≦ 0.50%
, formula (B): Ca + Y + La + Ce ≦ 5.00%
　formula (A) and formula (B), the chemical symbol shows the content of each element in mass% .
[0065]
　These, Y, La, Ce, Si, Ti, Cr, Co, Ni, V, Nb, Cu, Sn, Mn, Sr, Sb, Cd, Pb and B satisfy the formula (A) and (B) if range, without affecting the performance of the plating layer may contain the plating layer. Of course, these elements may not contain the plating layer.
[0066]
　Incidentally, Y, La and Ce are the same as Ca, an element to prevent oxidation of Mg. On the other hand, Y, La and Ce itself easily oxidized and adversely affects the corrosion resistance of the plating layer. Therefore, as long as it satisfies the formula (B), Y, may be contained in the plating layer of one or more of La and Ce.
　Also, Y, La and Ce are the same as Ca, is also an element to promote the formation of high corrosion resistance quasicrystalline phase in the plating layer. On the other hand, Ca, Y, the total content of La and Ce exceeds 5.0%, the quasi-crystal phase is not formed in the tin. Therefore, even when generating a quasi-crystal phase in the plating layer, as long as it satisfies the formula (B), Y, may be contained in the plating layer of one or more of La and Ce.
[0067]
　Si, when contained in the plating layer, Mg combined with another element 2 Si, CaSi compound (CaSi, Ca 5 Si 3 , Ca 2 Si or the like) or the like to form a, Mg, and Ca is , become more eluted hard crystal structure, an element which improves corrosion resistance. However, in the present embodiment, Si concentration and the Ca concentration is small, since the area fraction occupied by these phases is less than 5% in the plating layer has little effect on the performance of the plating layer. On the other hand, an element which slows down the growth of the intermediate layer having Al-Fe alloy phase. Therefore, in order to the intermediate layer having a thickness of 5 ~ 500 [mu] m, the Si content is preferably 0 to 0.500%, more preferably from 0 to 0.050%, more preferably from 0 to 0.005%, 0% (i.e. it does not contain Si) is particularly preferred.
[0068]
　Sn, Cr, and B is an element that functions as a reaction aid to promote inter-Al-Fe reaction. Therefore, in order to the intermediate layer having a thickness of 5 ~ 500 [mu] m, the range which does not adversely affect the performance of the plating layer, that is, in a range satisfying formula (B), Sn, Cr, and one or two B it may be contained in the plating layer higher.
[0069]
　The composition of the plating layer is measured by high-frequency glow discharge spectrometry (GDS). More specifically, it is as follows.
　From the plating steel, taking a sample of the plating layer forming surface is 30mm square. This sample is designated as Sample high frequency glow discharge spectrometry (GDS). From the plating layer and the intermediate layer formation side of the sample was performed with argon ions sputter obtain elemental intensity plot in the depth direction. On the other hand, standard samples were prepared of pure metal plate or the like of each element to be measured to obtain the advance element intensity plot from a standard sample. Comparison of the two elements intensity plots, converting the concentration (content) of the constituent elements of the plated layer and the intermediate layer. Measurement conditions, an analysis area φ4mm above, the range of the sputtering rate of about 0.04 ~ 0.1 [mu] m / sec.
[0070]
　The surface layer of the element intensity plot of depth 5 [mu] m from the surface of the plating layer is ignored and the average value of each element concentrations determined from elemental intensity plot area of ​​depth 5 [mu] m ~ 10 [mu] m from the surface of the plating layer. This is to eliminate the influence of the oxide layer formed on the surface of the plating layer.
[0071]
　Then, perform the above operation in more than 10 positions, the average value of each element concentration of the plating layer in each of the locations (i.e., the average value of the average value of each element concentration of the plating layer obtained by the above operation), the plating layer the content of each element.
[0072]
　Organization of the plating layer will be described.
　Organization of the plating layer is not particularly limited. For example, as the main structure constituting the plating layer, quasi-crystalline phase, MgZn2 phase, Mg2Zn3 phase (Mg4Zn7 the same material), Mg51Zn20 phase, Mg phase, MgZn phase, there is Al equality.
[0073]
　Here, the quasi-crystalline phase, shows the physical properties excellent in very corrosion resistance. Further, the quasi-crystalline phase, when corrosion accelerated corrosion test or the like, a high corrosion products form a barrier effect and anti-corrosion steel (base steel) over time. High corrosion products Accessible effect, Zn-Mg-Al component ratio contained in the quasi-crystal phase is concerned. In the component composition of the plating layer, wherein: Zn> (Mg + Al + Ca) (. Wherein, the atomic symbol, which indicates the content of each element in mass%) if has been established, a high barrier effect of the corrosion product Become.
[0074]
　On the other hand, MgZn 2 phase, and Mg 2 Zn 3 phase (Mg 4 Zn 7 of the same material) is corrosion resistance improving effect when compared with the quasi-crystal phase is small, has certain corrosion resistance. Further, MgZn 2 phase, and Mg 2 Zn 3 phase contains a large amount of Mg, excellent in alkali corrosion. In particular, the quasi-crystal phase and MgZn 2 phase and Mg 2 Zn 3 when coexist in phase Togamekki layer, a surface layer of oxide film of the plating layer in a highly alkaline environment (pH 13 ~ 14) is stabilized, a particularly high alkali corrosion resistance It is shown.
[0075]
　Further, in the plating steel without significant processing, in terms of corrosion resistance, is suitable for that containing a large amount of quasicrystalline phase in the plating layer. However, the quasi-crystal phase itself is a very rigid phase, the plating layer containing a large amount of quasicrystalline phase may include some cracks in the intra-phase. Therefore, if the clamping part for the bolt joined to the plating steel is present, or if the plating steel is exposed to a variety of flying objects that are used in an outdoor environment, somewhat, thereby imparting ductility to the plating layer good. Then, to grant ductility with corrosion resistance in the plating layer, together with the quasi-crystalline phase, it is possible to coexist the Al phase having a plastic deformability soft in the plating layer. Granting ductility plating layer of Al phase, increased impact resistance, delamination of the plating layer is decreased.
[0076]
　From the above, the plating layer, it is preferable to have a structure of the following (1) or (2).
　(1) semi-crystalline phase, MgZn2 phase, Mg2Zn3 phase, and tissue composed of the remaining structure.
　(1) The tissue remaining structure of, for example, Mg 51 Zn 20 phase, MgZn phase, Mg 2 Zn 3 phase, Zn phase and Al equality.
　In tissues (1), corrosion resistance, from the viewpoint of impact resistance and abrasion resistance, the area fraction of the quasi-crystal phase is preferably 3 to 70%, more preferably 10 to 70%. Further, from the same viewpoint, the quasi-crystal phase, MgZn2 phase and the total area fraction of the Mg2Zn3 phase is preferably 3 to 100%, more preferably from 90 to 100%.
　In particular, the quasi-crystalline phase, MgZn2 phase and the total area fraction of the Mg2Zn3 phase increases, for example, strongly alkaline environment (ammonia water, sodium hydroxide secondary) to exhibit excellent alkali corrosion resistance as any amount of corrosion is substantially 0 become.
[0077]
　(2) quasi-crystalline phase, Al phase, and tissue composed of the remaining structure.
　The organization of the remaining structure of (2), for example, MgZn2 phase, Mg2Zn3 phase, Mg 51 Zn 20 phase, MgZn phase, Mg 2 Zn 3 phase, Zn equality.
　In tissues (2), corrosion resistance, and in view of impact resistance, the area fraction of the quasi-crystal phase is preferably 25 to 45%, more preferably 30 to 45%. Further, from the same viewpoint, the total area fraction of the quasi-crystal phase and Al phase, preferably 75 to 100%, more preferably from 90 to 100%.
[0078]
　Incidentally, the plating layer having a structure of (1) or (2), as the remaining structure, Al4Ca phase, Al2Zn2Ca phase, also contain other intermetallic phases of Al3ZnCa equality. However, this other intermetallic compounds, intermetallic compound phase to form, depending on the Ca concentration, in the present embodiment, the area fraction occupied by the plating layer was less than 5%, the performance of the plating layer It does not have a significant impact.
[0079]
　Here, each phase area fraction of the plating layer is the area fraction in a cross section of the plating layer (a plating layer is cut in the thickness direction cross-section), then the phases of the area fraction of the plating layer, the intermediate layer of each phase (Al-Fe alloy phase, Zn-Mg-Al alloy phase, Zn-Mg alloy phase, metal phase) can be determined as the area fraction of.
[0080]
　The thickness of the plating layer is preferably at least 20 [mu] m, more preferably not less than 50 [mu] m. By comparing the corrosion resistance of the plating layer and the intermediate layer, the plating layer is excellent in corrosion resistance. Therefore, from the viewpoint of securing sufficient corrosion resistance to plating steel, it is preferable that the thickness of the plating layer and above 20 [mu] m, and more preferably to 50μm or more. On the other hand, the increase in thickness of the plating layer, since it may impair the appearance of the plating layer, the thickness of the plating layer is preferably in the 100μm or less.
　Parallel thickness of the plating layer, similarly to the thickness measurement of the intermediate layer, the SEM (scanning electron microscope) is cut in the thickness direction of the cross-sectional observation (plating layer of the plated layer by the cross-section, the plating layer measuring the observation of the region corresponding to 2.5mm length min with three fields of views) in a direction.
[0081]
　Plating layer may be a dip plated layer formed by immersion plating as described later.
[0082]
　Next, a description for the definition of quasicrystalline phases which are common to the plating layer and the intermediate layer.
　Quasicrystalline phase, Mg content in the quasicrystalline phase, Zn content and Al content, in atomic%, defined as a quasi-crystal phase satisfies 0.5 ≦ Mg / (Zn + Al ) ≦ 0.83 It is. That is, the Mg atoms, Mg is the ratio of the sum of Zn atoms and Al atoms: the (Zn + Al), 3: 6 ~ 5: is defined as 6 to become quasi-crystal phase. Approximate, Mg: (Zn + Al) is about 4: believed to be 6.
　Chemical components of the quasi-crystalline phase can be calculated by TEM-EDX (Transmission Electron Microscope- EnergyDispersive X-ray Spectroscopy) quantitative analysis by, or EPMA quantitative analysis by (Electron Probe Micro-Analyzer) mapping. Incidentally, it is not easy to define the quasi-crystals in the correct chemical formula as intermetallic compounds. Quasicrystalline phase can not be defined a grid unit of repeating such a unit cell of the crystal, and further, Zn, because also difficult to identify the atomic positions of Mg.
[0083]
　Quasicrystalline phase is the first discovered crystalline structure by Daniel Shuhitoman in 1982, and has an atomic arrangement in the icosahedron (icosahedron). The crystal structure, usually of metal, specific rotational symmetry which can not be obtained in the alloy, in a non-periodic crystal structure having, for example, 5-fold symmetry, aperiodic structure equivalent represented by 3-dimensional Penrose pattern It is known as Do not crystal structure. This in order to identify the metal material, typically by electron beam observation by TEM observation, the phase is confirmed by obtaining a radial positive decagonal electron beam diffraction image due to the icosahedral structure. For example, an electron beam diffraction image of TEM shown in FIG. 4, obtained only from the quasicrystals, not be obtained from any other crystal structure. Therefore, the quasi-crystal phase and MgZn 2 and equality MgZn alloy phase can be identified.
[0084]
　Quasicrystalline phase, the simple, Mg 32 (Zn, Al) 49 by X-ray diffraction as a phase, JCPDS card: PDF # 00-019-0029, or, the diffraction peaks that can be identified by # 00-039-0951 show.
[0085]
(Method of manufacturing a plated steel material)
　Next, an example of a method for manufacturing a plated steel material according to the embodiment.
　Plated steel material according to the embodiment may be produced by immersion plating using immersion plating bath having the same composition as the plating layer (composition other than impurities). Also, immersion plating may be carried out in one stage plating.
[0086]
　Here, usually, in the immersion plating, immersion plating bath containing a high concentration of 8% or more of Mg in (highly Mg plating bath) is between Al-Fe reaction is inactive. This is because, as described in paragraph 0007 of Patent Document 1, the immersion plating which is carried out under atmospheric environment, in immersion plating bath, other selective oxidation of Al, selective oxidation of Mg is generated, these oxides is to prevent contact between the plating bath components and steel. There also before immersion plating, when subjected to a flux treatment steel, is used as the flux reacts with Al "zinc chloride, ammonium chloride, chloride such as tin chloride", also because reducing flux effect . In particular, if the contained Mg in immersion plating bath, to react with Mg also chloride in addition to Al, the more chloride is reacted further reduces flux effect.
[0087]
　Therefore, in the immersion plating using a highly Mg-plating bath, without getting wet immersion plating bath at all to the base steel (steel), (also referred to as the "latency") unresponsive time is present time. Further, in the conventional immersion plating conditions (e.g., conditions such as less than the plating bath temperature 550 ° C.), serves as an inactive element Mg is in the air environment, the interface between the plating bath and the base steel (steel), the base steel Mg oxide film which inhibits the wettability with (steel) and the plating bath is formed.
　Therefore, when carrying out the immersion plating using a highly Mg-plating bath, the incubation time is continued indefinitely, after forming an intermediate layer of suitable thickness, is thought to be difficult to form a plating layer It was.
[0088]
　However, even in immersion plating using a highly Mg-dip plating bath, to shorten the latency time, (alloying reaction of Al and Fe) Fe-Al inter-reaction is accelerated, the intermediate layer of suitable thickness after having formed, it is possible to form a plating layer.
[0089]
　More specifically, in order to shorten the latency time, the plating bath temperature is preferably at least 550 ° C., more preferably at least 600 ° C.. Plating temperature is plating properties, in order to ensure the wettability of the steel and the plating bath is preferably the melting point + 50 ℃ above plating components, mp + 50 ~ 100 ° C. being more preferred.
　When the plating bath temperature is lower than 550 ° C., it is carried out immersion plating, incubation time is prolonged, it is difficult to start the inter-Al-Fe reaction.
　On the other hand, when the plating bath is too high, rapidly oxidizes the steel on the bath surface, except that scale formed wettability is deteriorated surface of the steel material, which may adversely affect the quality of the steel material. Therefore, the plating bath temperature is preferably 650 ° C. or less.
[0090]
　Immersion time is preferably at least 1 minute, more preferably at least 5 minutes.
　If the immersion time is less than 1 minute, be carried out immersion plating in a plating bath temperature 550 ° C. or higher, not wet plating bath steel (the base steel), between sufficient Fe-Al reaction hardly proceeds.
　On the other hand, when the immersion time is too long, brittle and intermediate layer is overgrown, immediately pulling the steel material from the plating bath, working internal stress due to temperature difference, crack tends to occur in the plating layer surface. Further, when steel material is thin, it may be collapsed by steel (base steel). Therefore, the immersion time is preferably less than 30 minutes.
[0091]
　The method of manufacturing a plated steel material according to the embodiment, shortening of the latency time, the high temperature of the plating bath temperature, increasing the Al concentration and the Zn concentration of the plating bath, and in addition to the decrease in the oxygen potential on the plating bath surface, following (1) to be able to use at least one of the methods shown in (9). By using these methods, reduction of further incubation time can be realized.
[0092]
(1) Before immersion plating, a method of heating the steel material. The heating temperature is preferably 200 ° C. or higher at a surface temperature of the steel material, more preferably at least 400 ° C.. Heating atmosphere is an inert atmosphere is preferred. Steel, low alloy steel is preferred.
(2) in the plating bath, a method of vibrating and / or rotating steel.
(3) a method for stirring the plating bath soaked steel.
(4) Before immersion plating, fluxing, shotblasting, shot peening, and methods of using the steel which has been subjected to at least one treatment of pickling process.
(5) Surface method of using a small grain size steel (surface plated layer and the intermediate layer is formed). Crystal grain size, preferably less than 5 [mu] m, more preferably less than 1 [mu] m.
(6) Surface method of using a steel the dislocation density was increased by grinding (surface plated layer and the intermediate layer is formed).
(7) Cu-Sn substitution plating steel, Zn-plated steel (Zn adhered amount 40 g / m 2 method using the following plating steel).
(8) How to use a plating bath containing reaction auxiliary which promotes the Al-Fe inter-reaction. As the reaction aid, Sn, Cr, B and the like. These elements, instead of steel, must be added to the immersion plating bath. From the viewpoint of not adversely affect the immersion plating properties, Sn content 0.50% is less, Cr content 0.50% is less, B content is preferably 0.50% or less. However, the range satisfying the above formula (B).
(9) How to use a plating bath with a limited Si content slowing the Al-Fe inter-reaction. Preferably 0 to 0.500%, from 0 to 0.050%, more preferably, more preferably 0 to 0.005%, (that does not contain the words Si) 0 percent particularly preferred.
[0093]
　Described above, Mg content using more than 8% of the plating bath, the subjected to immersion plating to "shorten the latent time" steel, the surface of the steel material, the immersion plating layer, an intermediate having the sea-island structure layer is formed between the steel and the immersion plating layer. The mechanism is not clear, but is presumed as follows.
[0094]
　First, when the Mg content is dipped steel 8% or more of the plating bath, in the initial stage, Mg oxide film which inhibits the wettability of the plating bath to the steel (base steel) is formed on the surface of the steel material, the steel material a state of immersion plating bath is not wetted (Fig. 5 (1) refer).
[0095]
　Then, the shortening of the latency in a short time, begin to wet immersion plating bath to the surface of the steel material. If immersion plating bath steel begins wetting, first, the surface of the steel, the crystal grain boundary, is between Al-Fe reaction from the interface energy is small place of the uneven portion such as to start (see Fig. 5 (2)).
[0096]
　Then, between the Al-Fe reaction proceeds, Al-Fe alloy phase grows. Then, (see Fig. 5 (3)) around the grown Al-Fe alloy phase, which Al is insufficient (Al is small) (also referred to as the "Al insufficient plating liquid phase") liquid phase of the plating bath may occur. Meanwhile, in the offshore of the plating bath, and the liquid phase of the tip and the Al of the grown Al-Fe alloy phase dark plating bath reaction, irregularly Al-Fe alloy phase grows.
[0097]
　Specifically, Al atomic diffusion to near the surface of the steel material from offshore plating bath is gradual. On the other hand, in the temperature range above the plating bath temperature is 550 ° C., once the inter-Al-Fe reaction is initiated, elution Fe from the surface of the steel material (the base steel) occurs actively. Moreover, the dissolution rate of Fe from the surface of the steel material (the base steel) is increased. Fe reaches easily to offshore. In places where Al-Fe inter-reaction occurs, a large Fe feed rate than Al. Under these circumstances, Mg content is 8% or more of the plating bath, generation of Al-Fe inter-react with Al insufficient liquid phase occurs actively, growth of Al-Fe alloy phase proceeds irregularly. Incidentally, if the Mg content was applied plating bath of less than 8%, Al-Fe alloy phase is not irregularly growing, grown in layers.
[0098]
　Thus, while partially surrounding the Al insufficient plating liquid phase, Al-Fe alloy phase grows (see Fig. 5 (4)). That, Al insufficient plating liquid phase in Al-Fe alloy phase in the partially left behind. Note that the Al-Fe alloy phase, which may Zn plating component is taken slightly.
[0099]
　Thereafter, Al-Fe surrounded by alloy phase "Al insufficient plating liquid phase", solidified, transforms into intermetallic compounds closest in component concentration. Thereby, at least Zn-Mg-Al alloy phase (semi-crystalline phase) is generated. Zn-Mg-Al alloy phase other than (quasicrystalline phase) occurs phase transformation or phase separation by equilibrium solidification, intermetallic compounds (Zn-Mg alloy phase etc.) and may also generate metal phase (Mg phase etc.) and the like . Further, a solid solution of Fe to Al insufficient plating liquid phase, the intermetallic compounds containing a small amount of Fe is also generated.
[0100]
　In this way, it is considered an intermediate layer having a configured sea-island structure in being surrounded by water portion consisting of Al-Fe alloy phase "islands containing Zn-Mg-Al alloy phase" is formed. Then, the surface of the intermediate layer having the sea-island structure, the plating component is solidified, the plating layer is formed.
[0101]
　In FIG. 5, 10 denotes a steel material, 12 the plating bath, 12A oxide Mg film, 12B is Al insufficient plating liquid phase, 14 a Al-Fe alloy phase.
[0102]
　Hereinafter, the method for producing a plated steel material according to the embodiment, the preferred other conditions will be described.
[0103]
　Method for producing a plated steel material according to the embodiment, for example, using an alloy of a predetermined component composition prepared in vacuum melting furnace or the like, the "plating bath" dissolved in air, immersing the steel material. If there is no problem on the structure soaking, if nitrogen substitution was placed lids on the plating bath, lowering the oxygen potential, it can be shortened latencies Al-Fe inter-reaction.
　Capacity of the plating bath for steel may be sufficiently large. For example, the length 100 mm × width 50 mm × a thickness of 2mm steel, the capacity of at least the plating bath is preferably at least 5L.
[0104]
　Before immersion in the plating bath, steel, surface cleaning treatment (e.g., degreasing, pickling treatment, surface cleaning treatment for performing washing and drying process) may be subjected to. Specifically, for example, by immersing for 10 minutes or more steel in 10% hydrochloric acid, strong oxide film generated on the surface of the steel material (mill scale, scale) is peeled off. Thereafter, pickling the steel material and water washing. The dryer uses a drying oven or the like to remove moisture steel.
　Incidentally, for the incubation period shortened, the steel, when carrying out blasting, a process to increase the dislocation density, such as a brush grinding treatment, the steel material after the oxide film removal by the process, flux process, shot blasting, shot peening, pickling, or it is preferable to brush grinding or the like. After these treatments, or directly used as an immersion steel, it is preferably used as an immersion steel subjected only post-processing fastened to a dry cleaning process or the like.
[0105]
　During immersion in the plating bath, it is preferable to vibrate the steel and / or rotation. Vibration and / or rotation of the steel material, while there is a role of shortening of the incubation period, there is also a role in suppressing the appearance defect of plating steel. In particular, when the flux process using chloride was applied to the steel, flux and the (chloride) and plated component reaction to form a Mg-based chloride or the like on the surface of the steel material, the surface appearance deteriorates as flux If there is a. Therefore, also from this point of view, a method of vibrating the steel material and / or rotation is enabled.
[0106]
　Before and after immersion in the plating bath, and, during immersion, dross to be formed on the plating bath is preferably removed. Dross by removing, it can suppress the appearance of the plated steel material poor.
[0107]
　After immersion in the plating bath, the pulling rate of the steel is preferably not more than 100 mm / s, more preferably at most 50 mm / s. If the pulling speed of the steel is high, the thickness of the plated layer formed on the intermediate layer becomes too thick, it may cause peeling of the plating layer.
[0108]
　After raising from the plating bath, the steel is cooled at a predetermined cooling rate from immediately after the pulling temperature (temperature plating bath) to room temperature. Note that this temperature is the surface temperature of the steel material.
　The cooling rate after raising from the plating bath is not particularly limited. For example, immediately after pulling from the plating bath, the steel may be cooled by immersion in water may be cooled naturally.
　On the other hand, and the plating layer (islands of the sea-island structure) intermediate layer of plating steel to produce efficiently quasicrystalline phase may be cooled in the next cooling rate.
[0109]
　The temperature range from immediately after the pulling temperature (temperature plating bath) to 500 ° C., preferably to cool the steel material within 8 seconds. The temperature range temperature above the following 500 ° C. immediately after pulling, Al moves towards the interface between rapidly steel and plating layer to form a Al-Fe alloy phase (i.e., the intermediate layer). Therefore, within 8 seconds, the steel that is cooled from a temperature immediately after pulling up 500 ° C., is inhibited from Al in the coating layer is taken into the intermediate layer. Thereby achieving optimization of the plating layer inside the Al concentration before coagulation, the state suitable for the formation of the quasi-crystal phase.
[0110]
　In order to achieve the cooling of the steel within 8 seconds above, it is preferable to provide a cooling apparatus immediately above the plating bath. Cooling device, in order to prevent oxidation of the plated component, spray applying cooler inert gas, mist cooling device, and the like are preferable.
[0111]
　After raising, the temperature range from 500 ° C. to 350 ° C., in order to retain the steel more than 30 seconds, it is preferable to cool the steel at a cooling rate 5 ° C. / sec or less. The 350 ° C. or more and less than 500 ° C. temperature range, Al-Fe alloy phase (i.e. an intermediate layer) while the growth stops, the most stable to phase quasicrystalline phase. Therefore, in this temperature range, by the cooling rate 5 ° C. / sec or less, the intermediate layer and the plating layer (islands of the sea-island structure) of a plating steel, easily generated quasicrystalline phase. Incidentally, when the cooling rate to 5 ° C. / sec greater, because it is cooled before the quasi-crystal phase is precipitated, the proportion of quasicrystalline phase becomes extremely small, or quasi-crystalline phase may no longer contained.
[0112]
　After raising, the temperature range from 350 ° C. to 250 ° C., it is preferable to cool the steel at a cooling rate 10 ° C. / sec or more. 350 temperature range of 250 ° C. or more but less than ° C., rather than semi-crystalline phase, the intermetallic compound phase (Mg 2 Zn 3 phase, MgZn equality), into the stable region of the metal phase (Mg phase etc.). And, in this temperature range, the quasi-crystalline phase, the intermetallic compound phase (Mg 2 Zn 3 is sometimes altered phase, MgZn equality) to. Therefore, in this temperature range, than to increase the cooling rate over 10 ° C. / sec, the intermediate layer (the island portion of the sea-island structure), and area fraction of quasicrystalline phases generated in the plating layer of the plated steel material is maintained It becomes easier.
[0113]
　After raising, the temperature range to room 250 ° C., the cooling rate is not particularly limited. The 250 ° C. or less above room temperature range, the temperature is low, atomic diffusion becomes weak, no longer is because below the temperature required for generation and degradation phases.
[0114]
　Here, in the preparation of the plating steel, it may be carried out post-treatment after the formation of the plating layer.
　The post-treatment, various processes can be mentioned to treat the surface of the plating steel, process for performing upper plating, click port mail Bok treatment, non-chromate treatment, phosphate treatment, lubricity-improving treatment, weldability improving treatment such as there is. As the post-treatment, resin paint (e.g., polyester resin, acrylic resin, fluororesin, vinyl chloride resin, urethane resin, epoxy resin, etc.), roll coating, spray coating, curtain flow coating , dip coating, film lamination method (for example, a film lamination method at the time of laminating a resin film such as an acrylic resin film) is then applied by a method such as is also the process for forming a coating film.
Example
[0115]
　It described in an exemplary example of the present disclosure. Conditions in Examples is an example of conditions adopted for confirming the workability and effects of the present disclosure. The present disclosure is not intended to be limited to this single example of conditions. 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.
[0116]
(Test No.1E ~ 34E, 35C ~ 39C)
　in accordance with production conditions shown in Table 1, were produced plated steel by immersion plating. More specifically, it is as follows.
[0117]
　Here, the plating bath was prepared 8 kinds of following A ~ K of predetermined composition. Bath amount of the plating bath was set to 16L. Component of the plating bath, the coagulation piece of the plating bath was taken, what was the acid dissolving the swarf was confirmed by ICP emission spectroscopy.
　Further, the steel subjected to immersion plating, using general carbon steel plate width 70 mm × Itacho of 150 mm × thickness 2.3mm (JIS G 3101 (2010) defined SS400 black surface material).
[0118]
- the type of plating bath (Note that in the following composition plating bath, the mass% of the numerical value each element described before each element symbol, mass% of Zn is the balance and so forth.) -
A: composition Zn-50 =% Mg- 2.5% Al-5.00% Ca
B: composition Zn-35 =% Mg- 5.0% Al-3.00% Ca
C: composition = Zn-25% Mg- % Al-10.0 2.00% Ca
D: composition Zn-15 =% Mg-15.0% Al-1.00% Ca
E: composition = Zn-10% Mg-55.0 % Al-0. 50% Ca
F: composition Zn- 8% = Mg-67.0% Al-0.50% Ca-0.05% Si
G: composition = Zn- 8% Mg-67.0% Al-0.30% -0.05% Ca Si
H: composition Zn- 8% = Mg-67.0% Al-0.30% Ca-0.50% Cr
I: set Zn- 8% = Mg-67.0% Al-0.30% Ca-0.50% Sn
J: Composition = Zn- 8% Mg-67.0% Al-0.15% Ca-0.05% Si
K: composition = Zn- 5% Mg-70.0% Al-0.50% Ca
[0119]
　First, by soaking for 10 minutes or more steel in 10% hydrochloric acid, it was peeled oxide film produced on the surface layer of the steel material. Then, enough steel, was drained, and dried. Thereafter, the steel material surface entirely ground with # 600 belt sander, it blew grinding powder surface dryer.
[0120]
　Next, the steel was fixed to the mounting jig of the lifting device for immersion. Lifting device, penetrate the plating bath steel at a constant speed, it is possible to increase. Lifting apparatus, the ultrasonic waves emanating from the mounting jig, was immersed in a plating bath steel it is possible to finely vibrate. Further, a thermocouple attached to the steel and to be able to constantly monitor the temperature history of the immersion plating. Lifting device with nitrogen gas blowing mechanism installed in, N immediately pulled 2 allowed the gas blowing.
[0121]
　Next, the type and the plating bath temperature of the plating bath shown in Table 1, after scraped off the dross in the plating bath surface manually, it was dipped steel immersion speed 100 mm / sec by the lifting device. After complete immersion of the steel in the plating bath, immediately generates ultrasonic waves in immersion, continued vibration of the steel. Surface dross generated during immersion rake with metal ladle and immediately removed.
[0122]
　Then, after a immersion time shown in Table 1, at a pulling rate shown in Table 1, raised steel from the plating bath. And adjusting the thickness of the plating layer by the pulling rate.
　Next, the case of the immersion plating using a plating bath A ~ B, after pulling of the steel, N 2 by blowing gas cooled at a cooling rate shown in Table 1, immediately at the same time reached 350 ° C., the steel to water 20L It was immersed and cooled. On the other hand, in the case of utilizing the immersion plating the plating bath C ~ K, after pulling of the steel, N 2 and cooled to 250 ° C. at a cooling rate shown in Table 1 by adjusting the blowing amount of the gas.
[0123]
　In addition, No. 4E, went 17E, 21E, in 27E, the flux treatment. Flux treatment was carried out in the next street. Pickling, before dipping into after the surface grinding plating bath, after steel was washed 80 ° C. hot water, flux "ZnCl 2 / NaCl / SnC l2 · H 2 O = 215/25/5 (g / L) It was immersed for 1 minute in "and dried at 0.99 ° C..
[0124]
　No. In 37C, a plating bath was prepared plated steel by immersion plating using a galvanizing bath (in the table referred to as "dip galvanizing").
[0125]
　No. In 38C, to produce a plated steel material by a two-stage immersion plating. First stage, as a plating bath, subjected to immersion plating using a galvanizing bath, the second stage was carried out immersion plating using a plating bath composition = Zn-6% Al-1% Mg.
[0126]
　No. 39C also was prepared plated steel with two-stage immersion plating. First stage, as a plating bath, subjected to immersion plating using a galvanizing bath, the second stage, immersion plating using a plating bath composition = Zn-11% Al-3% Mg-0.2% Si It was carried out.
[0127]
(Test No.40C ~ 45C)
　in accordance with production conditions shown in Table 1, the molten plating utilizing Sendzimir method to produce a plated steel material. Melt plating, it was used Rhesca Co. batch hot dip plating apparatus. More specifically, it is as follows.
[0128]
　Here, the plating bath was prepared six types of the A ~ F. Bath amount of the plating bath was 8L.
　Further, the steel subjected to immersion plating, using general carbon steel plate width 100 mm × Itacho of 150 mm × thickness 2.3mm (JIS G 3101 (2010) steel sheet pickled defined SS400 black surface material).
[0129]
First, N 2 -H 2 (5%) (dew point -40 ° or less, an oxygen concentration less than 25 ppm) environment, the steel was raised by electric heating to 800 ° C. from room temperature, and held for 60 seconds. Then, N 2 by spraying gas, the steel is cooled to the plating bath temperature + 10 ° C., were immediately immersed in a plating bath of the type and the plating bath temperature shown in Table 1.
　Then, the immersion time in the plating bath as a 1 second, pull the steel from the plating bath, then, N in steel 2 was subjected to gas wiping. Pulling rate, and N 2 gas wiping pressure, the thickness of the plating layer was adjusted to be 20μm (± 1μm).
　Further, from the plating bath immersion N 2 until gas wiping, a batch-type plating apparatus and high-speed operation was completed within one second.
　N 2 after the gas wiping completion, No. 40C, No. For 41C, steel in N 2 blowing gas and cooled to 250 ° C. at an average cooling rate of 15 ° C. / sec. In addition, No. For 42C ~ 45C, N in steel 2 blowing gas at cooling rates shown in Table 1, and the plated steel sheet is cooled.
　No. 40C, No. For 41C, performed after the plated steel sheet was produced by heating a plated steel sheet again 500 ° C. in an air furnace and allowed to re-melt the plating layer surface at a cooling rate shown in Table 1, the process of water-cooling the plated steel sheet It was.
[0130]
(Various Measurement)
　The obtained plating steel, characteristics of the intermediate layer and the plating layer (composition, structure, thickness) for, was measured according to the method described above. The results are shown in Tables 2 and 3.
　Note that the composition of the plating layer, other than impurities, so that the composition of the plating bath used is substantially the same has been confirmed, it is omitted.
[0131]
(Various evaluation)
　The obtained plating steel was evaluated as follows. The results are shown in Table 3.
[0132]
- corrosion resistance of the intermediate layer -
　To evaluate the corrosion resistance of the intermediate layer, to completely remove the plating layer of the evaluation level of the plating steel surface cutting. The plating layer is removed, with respect to the steel became only the intermediate layer was performed SST tests. And to evaluate the corrosion resistance after 3000 hours (JIS Z 2371). The evaluation criteria are as follows.
· Excellent: No red rust evaluation surface
· Very Good: evaluation surface of red rust area ratio of 5% or less
· Good: Red rust area ratio of 10% or less of the evaluation plane
· Bad: evaluation surface rust area ratio of 10% over more than
[0133]
　In addition, No. 40 ~ No. The 43-plated steel, the cross-sectional observation of the intermediate layer and the plating layer, the thickness of the intermediate layer has a 1μm or less, the corrosion resistance of the intermediate layer was not evaluated.
[0134]
(Alkaline environment corrosion resistance of the plating layer)
　corrosion resistance of the plating layer was evaluated as follows. The plated steel sheet was cut into 0.99 × 70 mm, was immersed for 24 hours in NaOH aqueous solution of by sealing the cut end face 40 ° C. of 1 mol / L. After 24 hours, remove the plated steel sheet, the corrosion products formed on the plating layer on the surface was immersed for 15 minutes in room temperature 20% chromic acid was removed to measure the corrosion weight loss before and after the test. Theoretical density of each of the plating alloy from corrosion weight loss in terms of corrosion decrease thickness was used to evaluate the alkali environment corrosion. The evaluation criteria are as follows.
· Excellent: Corrosion decrease thickness 1μm below
· Very Good: corrosion decrease thickness of 1μm or more 2μm or less
· Good: decrease corrosion thickness is 2μm greater, 4 [mu] m or less
· Bad: decrease corrosion thickness is 4 [mu] m greater
[0135]
(Impact resistance of the plating layer)
　impact resistance of the plating layer was evaluated using the Gurabero tested for peeling of the plating layer after the impact application. First, using Gurabero tester (manufactured by Suga Test Instruments Co., Ltd.), normal temperature, distance 30 cm, air pressure 3.0 kg / cm @ 2, under the conditions of an angle 90 °, the evaluation surface 100 × 100 mm of plating steel, a total of 100 kg 7 the No. crushed stone was collision. Then, taking the EPMA-Fe element mapping images of the evaluation level of the plating steel was calculated base steel exposed surface and the total area ratio of the intermediate layer exposed surface. The evaluation criteria are as follows.
· Excellent: steel (the base steel) without an exposure surface and the intermediate layer exposed surface
· Very Good: steel (the base steel) exposed surface and the total area ratio of 5% or less of the intermediate layer exposed
· Good: steel (the base steel) exposed surface and the intermediate total area ratio of 10% or less of the layer exposed
· Bad: steel (the base steel) exposed surface and the total area ratio of 10% of the intermediate layer exposed
[0136]
(Wear resistance of the plating layer)
　wear resistance of the plating layer was evaluated as follows. Use Rhesca Co. pin-on-disk type friction and abrasion tester (FDR-2100), φ3 / 16inch-SUS304Ball, load 1000 gf, radius 20 mm, 1 rpm, 5 around the rotation clockwise, the line marks on the plated steel sheet at 25 ° C. the formed. Polished embedded line mark portion was measured maximum recess depth from the plating layer surface portion. The evaluation criteria are as follows.
· Excellent: maximum recess depth 5μm below
· Very Good: maximum recess depth 5μm or 7.5μm or less
· Good: maximum recess depth 7.5μm greater, 10.0 [mu] m or less
· Bad: maximum recess depth 10μm greater
[0137]
[Table 1]

[0138]
[Table 2]

[0139]
[table 3]

[0140]
[Table 4]

[0141]
　Here, in Table 3, "quasicrystalline phase", "MgZn of islands 2 numerical column phase" and "Mg phase" indicates a phase of the area fraction of the island portion. Then, if the value is denoted, it indicates that the corresponding phase is present, the intermediate layer has a sea-island structure. Incidentally, "-" notation indicates that the corresponding phase does not exist.
　Further, "100" number is the column of sea indicates that intermediate layer does not have a sea-island structure.
　Further, notation and "bal." In the column of Al shows that the Al content is an amount corresponding to the remainder containing impurities.
[0142]
　From the above results, No. Plated steel 1E ~ 34E are the intermediate layer has a sea-island structure, it can be seen that the corrosion resistance of the intermediate layer itself is high. Thus, it can be seen that high corrosion resistance after the wound or cracks occurred in plating layer.
　In addition, No. Plated steel 1E ~ 34E are alkaline environment corrosion resistance, it can also be seen that high impact resistance and wear resistance.
[0143]
　On the other hand, No. Plated steel 35C ~ 45C has no sea-island structure in the intermediate layer, it can be seen that the corrosion resistance of the intermediate layer itself is low. Thus, it can be seen that even low corrosion resistance after wound or a crack occurs in the plating layer.
　In particular, plating steel 40C ~ 45C are thin intermediate layer, since the sea-island structure is not formed, it can be seen that the impact resistance of the corrosion resistance and the plating layer of the intermediate layer itself is low.
[0144]
　It should be noted that the test No. In 15E, the plating bath, Y, La, Ce, Si, Ti, Cr, Co, Ni, V, Nb, Cu, Sn, Mn, Sr, Sb, Cd, Pb, and at least one B formula ( When the test was carried out by adding in the range satisfying a) and formula (B), test No. 15E and evaluation similar results that were obtained were confirmed.

WE CLAIM

[Requested item 1]
　And steel,
　coated on the surface of the steel material, by mass%, Mg: 8 ~ 50% , Al: 2.5 ~ 70.0%, Ca: 0.30 ~ 5.00%, Y: 0 ~ 3. 50%, La: 0 ~ 3.50 %, Ce: 0 ~ 3.50%, Si: 0 ~ 0.50%, Ti: 0 ~ 0.50%, Cr: 0 ~ 0.50%, Co: 0 ~ 0.50%, Ni: 0 ~ 0.50%, V: 0 ~ 0.50%, Nb: 0 ~ 0.50%, Cu: 0 ~ 0.50%, Sn: 0 ~ 0.50 %, Mn: 0 ~ 0.20% , Sr: 0 ~ 0.50%, Sb: 0 ~ 0.50%, Cd: 0 ~ 0.50%, Pb: 0 ~ 0.50%, and B: 0 ~ comprises 0.50%, the balance being Zn and impurities, and a plating layer which satisfies the following formulas (a) and the following formula (B),
　an intermediate layer interposed between the steel and the plating layer there is, Al-Fe case A sea of phase, and the island portion Mg content containing 8 mass% or more Zn-Mg-Al alloy phase, in have constructed sea-island structure, the area of the sea component composed of the Al-Fe alloy phase and the intermediate layer rate is 55 to 90%,
　plating steel with a.
- formula (A): Si + Ti + Cr + Co + Ni + V + Nb + Cu + Sn + Mn + Sr + Sb + Cd + Pb + B ≦ 0.50%
, formula (B): Ca + Y + La + Ce ≦ 5.00%
　formula (A) and formula (B), the chemical symbol shows the content of each element in mass% .
[Requested item 2]
　The thickness of the intermediate layer is plated steel according to claim 1 which is 5 ~ 500 [mu] m.
[Requested item 3]
　The sea part, Al as the Al-Fe alloy phase 5 Fe 2 consists phase,
　said island portion, the Zn-Mg-Al alloy phase as a quasicrystal phase and MgZn 2 or consisting of phase, or the Zn- quasicrystalline phase as mg-Al alloy phase, MgZn 2 phase, and plating steel according to claim 1 or claim 2 consisting of mg phase.
[Requested item 4]
　The thickness ratio of the intermediate layer to the thickness of the plating layer, the plating steel according to any one of claims 1 to 3 is from 0.2 to 4 times.
[Requested item 5]
　The Mg content of the plating layer is at least 15% by weight and the Zn-Mg-Al Mg content of the alloy phase of any one of 15 mass% or more in a claims 1 to 4 plated steel.
[Requested item 6]
　The plating layer is immersion plating layer claims 1 to plated steel material according to any one of claims 5.