WO2018139620A1 - めっき鋼材 - Google Patents
めっき鋼材 Download PDFInfo
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- WO2018139620A1 WO2018139620A1 PCT/JP2018/002596 JP2018002596W WO2018139620A1 WO 2018139620 A1 WO2018139620 A1 WO 2018139620A1 JP 2018002596 W JP2018002596 W JP 2018002596W WO 2018139620 A1 WO2018139620 A1 WO 2018139620A1
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- alloy layer
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- intermetallic compound
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Classifications
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C18/00—Alloys based on zinc
- C22C18/04—Alloys based on zinc with aluminium as the next major constituent
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C—CHEMISTRY; METALLURGY
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
- C23C2/261—After-treatment in a gas atmosphere, e.g. inert or reducing atmosphere
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
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- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/021—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material including at least one metal alloy layer
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- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
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- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
- C23C28/025—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only with at least one zinc-based layer
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
- C23C22/08—Orthophosphates
- C23C22/12—Orthophosphates containing zinc cations
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- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/38—Chromatising
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- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D13/00—Electrophoretic coating characterised by the process
- C25D13/22—Servicing or operating apparatus or multistep processes
Definitions
- This disclosure relates to plated steel materials.
- Galvanized steel materials are widely used from the viewpoint of improving the corrosion resistance of structural members in fields such as architecture and automobiles.
- a method has been used in which non-plated steel is welded and then immersed in a zinc bath so that plating is attached to the surface of the steel and the welded portion to ensure the corrosion resistance of the entire structure. It was.
- productivity is inferior and facilities such as a plating bath are required, which increases the manufacturing cost.
- a method of manufacturing a structure by welding a galvanized steel material (for example, a galvanized steel plate) that has been plated in advance has been applied.
- zinc alloy plating Zn-Al-Mg-Si alloy plating, Al-- A welded structure has been manufactured by welding a zinc-based alloy-plated steel material (for example, a zinc-based alloy-plated steel plate) having a surface coated with Zn—Si-based alloy plating (see, for example, Patent Documents 1 to 7). .)
- LME liquid metal embrittlement cracks
- LME is considered to be mainly caused by the zinc plating component remaining in the molten state on the surface of the base metal heat-affected zone existing in the vicinity of the welded portion invades the crystal grain boundary of the welded portion.
- LME will become more remarkable in the plating layer in which metals, such as Al and Mg, are contained in a plating layer.
- Patent Document 8 when welding a plated steel material plated with Zn—Al—Mg based alloy, a solidified flux is applied or placed on the planned welding site, and then welded to the planned welding site.
- Patent Document 9 a method
- Patent Document 10 a flux-cored wire is used to slag the elements of Al and Mg to make them harmless during welding.
- the method (patent document 10) using a stainless steel type welding wire is proposed.
- a plated steel sheet suitable for weldability as a product Non-Patent Documents 1 and 2 has also been proposed.
- Patent Document 1 Japanese Patent Application Laid-Open No. 2000-064061
- Patent Document 2 International Publication No. 2013/002358
- Patent Document 3 Japanese Patent Application Laid-Open No. 2006-193791
- Patent Document 4 Japanese Patent Application Laid-Open No. 2002-332555
- Patent Document 5 International Publication No. 2010/082678
- Patent Document 6 Japanese Unexamined Patent Publication No. 2015-214747
- Patent Reference 7 International Publication No. 2014/059474
- Patent Reference 8 Japanese Unexamined Patent Publication No. 2007-313535 9: Japanese Patent Application Laid-Open No. 2005-230912
- Patent Document 10 Japanese Patent Application Laid-Open No. 2006-35293
- Non-Patent Document 1 Nisshin Steel Technical Report No. 92 (2011) p. 39-47
- Non-Patent Document 2 Nippon Steel & Sumitomo Metal Technical Report No. 398 (2014) p. 79-82
- a problem to be solved by one aspect of the present disclosure is to provide a plated steel material in which the formation of LME and blowholes is suppressed and the corrosion resistance of the weld heat affected zone is improved.
- the means for solving the problem includes the following aspects.
- a plated steel material comprising: a steel material; and a plating layer disposed on a surface of the steel material and including a Zn—Al—Mg alloy layer, In the cross section of the Zn—Al—Mg alloy layer, the area fraction of MgZn 2 phase is 45 to 75%, the total area fraction of MgZn 2 phase and Al phase is 70% or more, and Zn—Al—MgZn 2 three The area fraction of the original eutectic structure is 0-5%, The plating layer is mass%, Zn: more than 44.90% to less than 79.90%, Al: more than 15% to less than 35%, Mg: more than 5% to less than 20%, Ca: 0.1% to less than 3.0%, Si: 0% to 1.0%, B: 0% to 0.5% Y: 0% to 0.5%, La: 0% to 0.5% Ce: 0% to 0.5% Cr: 0% to 0.25% Ti: 0% to 0.25%, Ni: 0% to 0.25%, Co:
- the Zn—Al—Mg alloy layer is selected from the group consisting of Mg 2 Si phase, Ca 2 Si phase, CaSi phase, Ca—Zn—Al intermetallic compound phase, and Ca—Zn—Al—Si intermetallic compound phase.
- the plated steel material according to ⁇ 1> which contains at least one intermetallic compound phase.
- the Al content is more than 22% to less than 35%
- the Mg content is more than 10% to less than 20%
- the Ca content is 0.3% to less than 3.0%.
- ⁇ 4> The plated steel material according to ⁇ 1> or ⁇ 2>, wherein the Al content is more than 15% to 22%.
- ⁇ 5> When the plating layer contains B, the content of B is 0.05% to 0.5% by mass%, When the plating layer contains an element selected from the element group A, the total content of elements selected from the element group A is 0.05% to 0.5% by mass%, When the plating layer contains an element selected from the element group B, the total content of elements selected from the element group B is 0.05% to 0.25% by mass%, When the plating layer contains an element selected from the element group C, the total content of the elements selected from the element group C is 0.05% to 0.5% by mass% ⁇ 1> to ⁇ The plated steel material according to any one of 3>.
- the Zn-Al-Mg alloy layer, Al 2 CaB 5 phase, and, Ca-Al some atomic positions of the Al 2 CaB 5 phase is selected from the group consisting of compound phase substituted with Zn and Mg
- the plating layer contains an element selected from the element group D
- the total content of elements selected from the element group D is 0.05% to 20% by mass%
- the Zn—Al—Mg alloy layer contains at least one intermetallic compound phase selected from the group consisting of Mg 2 Sn phase, Mg 3 Bi 2 phase and Mg 3 In phase ⁇ 1> to ⁇ 6>
- the plated steel material according to any one of the above.
- ⁇ 8> The plated steel material according to any one of ⁇ 1> to ⁇ 7>, wherein the plated layer has an Al—Fe alloy layer between the steel material and the Zn—Al—Mg alloy layer.
- % display of content of each element of chemical composition means “mass%”.
- a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
- a numerical range in which “exceeding” or “less than” is added to the numerical values described before and after “to” means a range not including these numerical values as the lower limit value or the upper limit value.
- the element content of the component composition may be expressed as an element amount (for example, Zn amount, Mg amount, etc.) or an element concentration (for example, Zn concentration, Mg concentration, etc.).
- Process is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes.
- Plane refers to the surface of the steel plate other than the weld heat affected zone of the steel material, and “around the weld zone” refers to the heat affected zone of the steel material during welding other than the welded portion (welded metal portion).
- Yielding part back surface shows the back surface of the steel material facing the welding part formed in the surface side of steel materials.
- the plated steel material of the present disclosure is a hot-dip plated steel sheet having a steel material and a plated layer that is disposed on the surface of the steel material and includes a Zn—Al—Mg alloy layer, and in a cross section of the Zn—Al—Mg alloy layer,
- the area fraction of the MgZn 2 phase is 45 to 75%
- the total area fraction of the MgZn 2 phase and the Al phase is 70% or more
- the area fraction of the Zn—Al—MgZn 2 ternary eutectic structure is 0 to 5 %
- the plating layer has a predetermined chemical composition.
- the plated steel material of the present disclosure is a hot-dip plated steel material that suppresses LME and blowhole formation and has improved corrosion resistance at the weld heat affected zone (around the weld zone and the back of the weld zone).
- the plated steel material of this indication was discovered by the following knowledge.
- the present inventors use a general-purpose product or a general-purpose stainless wire as the welding means and the weld metal, and specify a component of the plating layer itself of the plated steel material to provide a plating structure suitable for weldability.
- a general-purpose product or a general-purpose stainless wire as the welding means and the weld metal, and specify a component of the plating layer itself of the plated steel material to provide a plating structure suitable for weldability.
- Worked on development Conventionally, there is almost no knowledge about the structure of a new plating layer suitable for weldability, and the fact is that only the plated steel materials used for products have been investigated for weldability.
- the present inventors discovered the following.
- the composition of Al and Mg components in the plating layer is carefully selected and the structure is further controlled to increase the MgZn 2 phase and the Al phase in the plating layer, while Zn—Al—MgZn. 2 ternary eutectic structure and Zn phases can be suppressed as much as possible.
- LME can be suppressed even in a plating layer in which a metal such as Al or Mg is contained in the plating layer.
- the amount of Zn evaporated is suppressed, and the corrosion resistance of the weld heat affected zone is improved while suppressing the formation of blowholes.
- the plated steel material of the present disclosure becomes a hot-dip plated steel material that suppresses the formation of LME and blowholes and improves the corrosion resistance of the weld heat affected zone.
- Steel materials include steel plates, steel pipes, civil engineering and construction materials (fence fences, corrugated pipes, drainage groove covers, flying sand prevention plates, bolts, wire mesh, guardrails, water barriers, etc.) , Steel materials that have been formed and processed, such as home appliance members (such as housings of air conditioner outdoor units) and automobile parts (such as suspension members).
- home appliance members such as housings of air conditioner outdoor units
- automobile parts such as suspension members.
- various plastic working methods such as press working, roll forming, and bending can be used.
- Steel materials include, for example, general steel, Ni pre-plated steel, Al killed steel, ultra-low carbon steel, high carbon steel, various high-tensile steels, some high alloy steels (strengthening element-containing steels such as Ni and Cr, etc.), etc.
- Various steel materials can be applied.
- the steel material is not particularly limited with respect to conditions such as a steel material production method, a steel plate production method (hot rolling method, pickling method, cold rolling method, etc.).
- the steel material may be a pre-plated pre-plated steel material.
- the plating layer includes a Zn—Al—Mg alloy layer.
- the plating layer may include an Al—Fe alloy layer in addition to the Zn—Al—Mg alloy layer.
- the Al—Fe alloy layer exists between the steel material and the Zn—Al—Mg alloy layer.
- the plating layer may have a single-layer structure of a Zn—Al—Mg alloy layer or a laminated structure including a Zn—Al—Mg alloy layer and an Al—Fe alloy layer.
- the Zn—Al—Mg alloy layer is preferably a layer constituting the surface of the plating layer.
- an oxide film of a plating layer constituent element is formed on the surface of the plating layer by about 50 nm, it is considered that the thickness of the plating layer is small with respect to the entire thickness of the plating layer and does not constitute the main body of the plating layer.
- the thickness of the Zn—Al—Mg alloy layer is, for example, 2 ⁇ m to 95 ⁇ m (preferably 5 ⁇ m to 75 ⁇ m).
- the thickness of the entire plating layer is, for example, about 100 ⁇ m or less. Since the thickness of the entire plating layer depends on the plating conditions, the upper limit and the lower limit of the thickness of the entire plating layer are not particularly limited. For example, the thickness of the entire plating layer is related to the viscosity and specific gravity of the plating bath in a normal hot dipping method. Further, the basis weight is adjusted by the drawing speed of the steel plate (plating original plate) and the strength of wiping. Therefore, it may be considered that the lower limit of the thickness of the entire plating layer is about 2 ⁇ m.
- the thickness of the plating layer that can be produced by the hot dipping method is approximately 95 ⁇ m due to the weight and uniformity of the plated metal. Since the thickness of the plating layer can be made freely depending on the drawing speed from the plating bath and the wiping conditions, the formation of the plating layer having a thickness of 2 to 95 ⁇ m is not particularly difficult to manufacture.
- Al-Fe alloy layer (specifically, between the steel and the Zn-Al-Mg alloy layer) the surface of the steel material is formed on, Al 5 Fe phase is a layer of the main phase as a tissue.
- the Al—Fe alloy layer is formed by mutual atomic diffusion of the base iron (steel material) and the plating bath.
- the hot dipping method is used as a manufacturing method, an Al—Fe alloy layer is easily formed in a plating layer containing an Al element. This is because Al of a certain concentration or more is contained in the plating bath.
- the most Al 5 Fe phase is formed. However, atomic diffusion takes time, and there is a portion where the Fe concentration is high in a portion close to the ground iron.
- the Al—Fe alloy layer may partially contain a small amount of an AlFe phase, an Al 3 Fe phase, an Al 5 Fe 2 phase, or the like.
- the Al—Fe alloy layer contains a small amount of Zn.
- corrosion resistance refers to corrosion resistance at a portion not affected by welding.
- the thickness of the Al-Fe alloy layer in the plating layer is small, and the corrosion resistance is low compared to the Zn-Al-Mg alloy layer, so the overall corrosion resistance is very different even if the ratio of these phases is changed. There is no.
- Si when Si is contained in the plating layer, Si is particularly likely to be taken into the Al—Fe alloy layer and may become an Al—Fe—Si compound phase.
- the compound to be identified includes an AlFeSi phase, and isomers include ⁇ , ⁇ , q1, q2-AlFeSi phase and the like. Therefore, the Al—Fe alloy layer may detect these AlFeSi phases.
- These Al—Fe alloy layers containing the AlFeSi phase and the like are also referred to as Al—Fe—Si alloy layers. Note that since the thickness of the Al—Fe—Si alloy layer is smaller than that of the Zn—Al—Mg alloy layer, the influence on the corrosion resistance of the entire plating layer is small.
- the structure of the Al—Fe alloy layer may change depending on the amount of pre-plating.
- an intermetallic compound phase in which the constituent components of the Zn—Al—Mg alloy layer and the pre-plating component are combined forms an alloy layer
- Al—Fe alloy layer in which some Al atoms and Fe atoms are substituted, or some Al atoms, Fe atoms, and Si atoms are substituted.
- an Al—Fe—Si alloy layer is formed.
- these alloy layers have a smaller thickness than the Zn—Al—Mg alloy layer, the influence on the corrosion resistance of the entire plating layer is small.
- the Al—Fe alloy layer is a layer that includes the alloy layers of the various aspects described above in addition to the alloy layer mainly composed of the Al 5 Fe phase.
- the thickness of the Al—Fe alloy layer is, for example, from 0 ⁇ m to 5 ⁇ m (usually from 100 nm to 5 ⁇ m). That is, the Al—Fe alloy layer may not be formed. However, usually, when a plating layer is formed by a hot dipping method with a plating composition defined in the present disclosure, an Al—Fe alloy layer of 100 nm or more is formed between the steel material and the Zn—Al—Mg alloy layer.
- the lower limit of the thickness of the Al—Fe alloy layer is not particularly limited, and it has been found that an Al—Fe alloy layer is inevitably formed when forming a hot-dip plated layer containing Al. Yes.
- the thickness around 100 nm is the thickness when the formation of the Al—Fe alloy layer is most suppressed, and the thickness sufficiently secures the adhesion between the plating layer and the ground iron (steel material). Since the Al concentration is high unless special measures are taken, it is difficult to form an Al—Fe alloy layer thinner than 100 nm by the hot dipping method. However, even if the thickness of the Al—Fe alloy layer is less than 100 nm, and even if the Al—Fe alloy layer is not formed, it is presumed that the plating performance is not greatly affected.
- the thickness of the Al—Fe alloy layer is 5 ⁇ m or more, the Al component of the Zn—Al—Mg alloy layer formed on the Al—Fe alloy layer is insufficient, and the adhesion and workability of the plating layer are further reduced. Tend to be extremely worse. Therefore, the thickness of the Al—Fe alloy layer is limited to 5 ⁇ m or less. Note that a welded structure is generally suitable for the structure using the plated steel material of the present disclosure as a form after processing, and it is not always necessary to ensure the workability of the plating layer.
- the plated steel material of the present disclosure can be a plated steel material that has better weldability than existing Zn—Al—Mg-based alloy plated steel materials and hot-dip Zn plated steel materials, if the application is limited.
- the workability of the plating layer is obtained, it is possible to process the plated steel material into various shapes, such as circular and curved, and use the plated steel material after processing as a welding material. It is preferable that the property is obtained.
- the workability of the plating layer may be evaluated by cold-working a plated steel sheet having good plating properties in a V-bending press test and evaluating the powdering amount of the plating layer at the V-curved portion.
- the chemical composition of the Al—Fe alloy layer is as follows: Fe: 25 to 35%, Al: 65 to 75%, Zn: 5% or less, And the balance: a composition containing impurities can be exemplified.
- the thickness of the Zn—Al—Mg alloy layer is usually larger than that of the Al—Fe alloy layer, the contribution of the Al—Fe alloy layer to the corrosion resistance of the planar portion as the plated steel sheet is Zn— Small compared to the Al—Mg alloy layer.
- the Al—Fe alloy layer contains a certain concentration or more of Al and Zn, which are corrosion resistant elements, as estimated from the component analysis results. Therefore, the Al—Fe alloy layer has a certain degree of sacrificial anticorrosive ability and corrosion barrier effect with respect to the ground iron (steel material).
- the Zn-Al-Mg alloy layer on the Al-Fe alloy layer is precisely removed by cutting from the surface of the plating layer by end milling, etc.
- the Al—Fe alloy layer contains an Al component and a small amount of Zn component, when the Al—Fe alloy layer is included, red rust is generated in the form of dots, without the Al—Fe alloy layer, Steel) It does not have red rust on the entire surface as it was exposed.
- the thicker the Al—Fe alloy layer the more preferably the red rust occurrence time is delayed.
- the thickness is preferably equal to or less than a certain thickness.
- the plated steel sheet of the present disclosure may be variously processed before forming a welded structure (that is, before welding). Therefore, for the purpose of ensuring workability, it is preferable to keep the thickness of the Al—Fe alloy layer below a certain level. Appropriate thickness is known from the viewpoint of workability, and the Al—Fe alloy layer is preferably 5 ⁇ m or less, and the amount of cracks and powdering generated from the plated Al—Fe alloy layer generated in the V-bending test or the like Decrease. More preferably, it is 2 ⁇ m or less.
- the Al—Fe alloy layer is maintained without being evaporated during arc welding because Al is a main constituent material, has a thin thickness, and has a high melting point as compared with the Zn—Al—Mg alloy layer. Therefore, it is not related to the formation amount of blowholes and LME.
- an Al component may be taken from the Zn—Al—Mg alloy layer, and the thickness of the Al—Fe alloy layer may grow. In particular, a portion where the heat input by welding is intense (such as the back of the weld) may be only the Al—Fe alloy layer.
- the Al—Fe alloy layer may slightly contain plating layer constituent elements such as Zn and Si in addition to Al while maintaining the crystal structure of the Al—Fe intermetallic compound phase.
- the Zn—Al—Mg alloy layer remains, the Al—Fe alloy layer grows with the thickness of the layer, and the spheroidized Al—Fe intermetallic compound phase is present in the Zn—Al—Mg alloy layer. May be confirmed.
- the Al—Fe alloy layer has a certain corrosion resistance, it is important to select a Zn—Al—Mg layer that can leave the Al—Fe alloy layer in order to ensure the corrosion resistance around the weld. is there. However, since it is sufficient to grow the Al—Fe alloy layer by heat input of welding, it is not necessary to grow the Al—Fe alloy layer thick beforehand.
- the chemical composition of the plating layer will be described.
- the component composition of the Zn—Al—Mg alloy layer contained in the plating layer the component composition ratio of the plating bath is almost maintained even in the Zn—Al—Mg alloy layer.
- the hot dipping method since the formation of the Al—Fe alloy layer is completed in the plating bath, the reduction of the Al component and Zn component of the Zn—Al—Mg alloy layer by the formation of the Al—Fe alloy layer is usually rare.
- the chemical composition of the plating layer in the case where the plating layer is a single layer structure of a Zn—Al—Mg alloy layer, Zn—Al
- the chemical composition of the Mg alloy layer and the total chemical composition of the Al-Fe alloy layer and the Zn-Al-Mg alloy layer when the plating layer is a laminated structure of an Al-Fe alloy layer and a Zn-Al-Mg alloy layer The following is assumed.
- the chemical composition of the plating layer is mass%, Zn: more than 44.90% to less than 79.90%, Al: more than 15% to less than 35%, Mg: more than 5% to less than 20%, Ca: 0.1% to less than 3.0%, Si: 0% to 1.0%, B: 0% to 0.5% Y: 0% to 0.5% La: 0% to 0.5% Ce: 0% to 0.5% Cr: 0% to 0.25% Ti: 0% to 0.25%, Ni: 0% to 0.25%, Co: 0% to 0.25% V: 0% to 0.25% Nb: 0% to 0.25% Cu: 0% to 0.25%, Mn: 0% to 0.25% Sr: 0% to 0.5%, Sb: 0% to 0.5%, Pb: 0% to 0.5%, Sn: 0% to 20.00%, Bi: 0% to 2.0% In: 0% to 2.0% Fe: A chemical composition comprising 0% to 5.0% and impurities.
- element group A is Y, La and Ce
- element group B is Cr
- Ti Ni, Co, V, Nb, Cu and Mn
- element group C is Sr, Sb and Pb
- the total content of elements selected from element group A is 0% to 0.5%;
- the total content of Ca and an element selected from the element group A is 0.1% to less than 3.0%,
- the total content of elements selected from element group B is 0% to 0.25%,
- the total content of elements selected from element group C is 0% to 0.5%.
- the total content of elements selected from element group D is 0% to 20%.
- Si, B, Y, La, Ce, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, Sn, Bi, In, and Fe are optional. It is an ingredient. That is, these elements may not be included in the plating layer. When these optional components are included, the content of the optional elements is preferably in the range described below.
- Zn is an element necessary for constituting the main phase of the Zn—Al—Mg alloy layer.
- Zn is above a certain level in order to ensure the corrosion resistance of the flat portion and the corrosion resistance of the heat affected zone (corrosion resistance after welding). It needs to be contained.
- the Zn concentration that is, the Zn phase in the Zn—Al—Mg alloy layer is closely related to the amount of LME and the amount of blow holes formed.
- the plating layer evaporates due to heat input during welding, and a plating-less region is formed. This region is preferably reduced as much as possible by suppressing evaporation of the plating layer.
- a method for suppressing the evaporation of the plating layer a method in which the element that changes the Zn phase into another intermetallic compound phase that has high sacrificial corrosion resistance and is difficult to evaporate is added to the plating layer in advance (for example, (Corrosion prevention method using elements with high sacrificial anticorrosive properties such as Mg and Ca), a method of anticorrosion by mixing corrosion-resistant elements into the oxide formed during evaporation, and a metal with high corrosion resistance using the heat input of welding
- an intermetallic compound phase such as a phase in which an Fe element and a plating layer component are combined.
- the lower limit value of the Zn concentration is set to exceed 44.90%. More preferably, the lower limit of the amount of Zn is more than 65.00%.
- the Zn concentration is 74.90% or more
- the Zn phase tends to increase, LME and blowholes are vigorously generated, and the weldability tends to deteriorate.
- the Zn concentration is in the range of 74.90% to 79.90%
- the Ca—Zn—Al intermetallic compound phase and the Ca—Zn—Al—Si are included in the plating layer as described later.
- the upper limit value of the Zn concentration is set to less than 79.90%.
- Al is also an element necessary for constituting the main phase of the Zn-Al-Mg alloy layer, and contains more than a certain amount to ensure the corrosion resistance of the flat part and the corrosion resistance of the heat affected zone (corrosion resistance after welding) as a plated steel sheet. Need to be done. Al increases the amount of Al phase in the Zn—Al—Mg alloy layer and decreases the amount of Zn phase. Therefore, the weldability tends to improve as the Al concentration increases.
- the effect of Al is to suppress the evaporation of the plating layer due to heat input during welding, and the components of the base iron (steel material) and the Al—Fe intermetallic compound phase (Al 5 Fe phase, AlFe phase, Al 2 Fe phase, Al 3 Fe phase, etc.) is formed to improve the corrosion resistance around the weld.
- the Al concentration is preferably over 20%.
- the heat input during welding causes a large amount of solid solution to dissolve in the Fe phase of the steel, and the Al-Fe intermetallic compound layer on the back of the weld becomes thinner, improving the corrosion resistance around the weld. May not be expected.
- the Ca-Zn-Al intermetallic compound phase and the Ca-Zn-Al-Si compound phase are also included in the Zn-Al-Mg alloy layer, as will be described later.
- the lower limit of the Al concentration is set to more than 15%. Further, in order to ensure the corrosion resistance on the back surface of the welded portion, which is superior to the existing Zn—Al—Mg based plated steel material, it is preferable to use the Ca-containing effect described later together.
- the upper limit value of the Al concentration is set to less than 35%.
- the upper limit value of the Al concentration be further less than 30%.
- Mg is also an element necessary for constituting the main phase of the Zn-Al-Mg alloy layer, and contains more than a certain amount to ensure the corrosion resistance of the flat part and the corrosion resistance of the heat affected zone (corrosion resistance after welding) as a plated steel sheet. Need to be done.
- Mg is contained in the plating layer, it exhibits an effect similar to that of Zn. Improvement of sacrificial anticorrosive property can be expected by containing Mg.
- LME becomes prominent because Mg is a metal having a low vapor pressure like Zn.
- various flux wires have been developed because weldability deteriorates.
- the deterioration of LME is suppressed by selecting the Mg concentration.
- the Mg concentration is in the range of 0 to 5%, the LME is surely deteriorated.
- the Mg concentration exceeds 5%, the LME is improved over the ordinary Zn-plated steel material.
- production is also suppressed and it becomes a preferable form as a plating layer.
- the Mg concentration ranges from 0 to 3%, the melting point of the plating layer decreases and the liquid phase becomes more stable.
- the Mg concentration ranges from 3 to 5%, the plating melting point rises. If it exceeds 5%, the rate of increase in melting point becomes high, and the plating layer becomes difficult to become liquid phase.
- the plating layer is less likely to evaporate. Therefore, when the Mg concentration is in the range of more than 5% to less than 20%, the proportion of the MgZn 2 phase, which has better weldability than the Zn phase, increases, so that weldability is improved. That is, the formation of LME and blow holes is suppressed.
- the Mg concentration is more than 10% because it takes advantage of the property of easily forming an oxide by heat input during welding, and there is a large amount of MgO on the back surface of the welded portion, thereby improving the corrosion resistance.
- the Mg concentration is 20% or more, the viscosity of the plating bath increases and the formation of the plating layer itself becomes difficult. Moreover, the plating properties are poor and the plating layer is easy to peel off. Therefore, the upper limit of Mg concentration is set to less than 20%.
- ⁇ Ca 0.1% to less than 3.0%>
- the amount of dross formed during the plating operation decreases with increasing Mg concentration, and the plating productivity is improved.
- the Mg concentration is high, the plating operability is generally poor. Therefore, when the Mg concentration exceeds 7%, the formula: 0.15 + 1/20 Mg ⁇ Ca (where the element symbol is mass%) It is preferable to adjust the Ca concentration so as to satisfy the content of each element.
- Ca when Ca is contained in the plating layer, it forms an intermetallic compound phase with Al and Zn. Furthermore, when Si is contained in the plating layer together with Ca, Ca forms an intermetallic compound phase with Si. Since these intermetallic compound phases have a high melting point and a stable structure, the inclusion of Ca has the effect of suppressing Zn evaporation during welding. The effect is seen when the Ca concentration is 0.1% or more, and the effect of reducing the amount of LME and blowhole is observed. Moreover, the remaining amount of the plating layer around the welded portion increases. When Ca is not contained, the weldability tends to be extremely deteriorated. That is, the formation of LME and blowhole tends to be remarkable. Therefore, the lower limit value of the Ca concentration is set to 0.1% or more.
- the intermetallic compound phase containing Ca becomes Ca oxide because Ca is most easily oxidized among the constituent elements of the plating layer during welding.
- the oxide layer containing Ca oxide remains on the Al—Fe alloy layer on the back surface of the welded portion with sufficient adhesion, and improves the corrosion resistance on the back surface of the welded portion.
- oxide (fume traces) and the like formed on the back surface of the welded portion hardly peel off and remain on the Al—Fe alloy layer when wiped with a waste cloth or the like.
- the oxide layer becomes difficult to peel off, and the oxide layer remains on the Al—Fe alloy layer in a dense state.
- the oxide layer containing Ca oxide is relatively insoluble in neutral and alkaline aqueous solutions.
- the oxide layer remaining on the Al—Fe alloy layer contains elements such as Zn and Mg in addition to Ca, and may contain a small amount of Si. It exists as an oxide compound phase.
- the Ca—Zn—Al intermetallic compound phase and the Ca—Zn—Al—Si intermetallic compound phase must be formed in the Zn—Al—Mg alloy layer.
- Ca needs to be contained in the plating layer at a concentration of 0.1% or more. As the Ca concentration increases, the Ca oxide concentration contained in the oxide layer also increases. Ca oxide has an effect on the adhesion of the oxide layer, but the effect on the corrosion resistance of the oxide layer itself is not so great.
- a Ca—Zn—Al—Si intermetallic compound phase incorporating Si may be formed in addition to the Ca—Zn—Al intermetallic compound phase, thereby improving corrosion resistance.
- a Ca—Zn—Al—Si intermetallic compound phase incorporating Si may be formed in addition to the Ca—Zn—Al intermetallic compound phase, thereby improving corrosion resistance.
- the corrosion resistance itself of the flat part of the plating layer tends to deteriorate, and the corrosion resistance around the welded part is also reduced. to degrade.
- concentration shall be less than 3.0%.
- a Ca—Zn—Al—Si intermetallic compound phase is formed in a plating layer containing a large amount of Al and Zn.
- specific intermetallic compounds are not known, and details are unknown.
- Si does not have a clear crystal structure and may be mixed in a Ca—Zn—Al intermetallic compound such as Al 2 CaZn 2 in an interstitial solid solution state.
- the effect of the Ca—Zn—Al—Si intermetallic compound phase, that is, the combined use effect of Ca and Si is that the corrosion resistance of the weld back surface is improved. These effects are difficult to obtain with the Mg 2 Si phase and the MgAlSi phase.
- the lower limit value of the Si concentration is preferably 0.1% or more.
- an increase in the Mg 2 Si, MgAlSi, and Ca—Zn—Al—Si intermetallic phase accompanying the Si content in the plating bath is not preferable because of an increase in the viscosity of the plating bath.
- a large amount of Ca 2 Si, CaSi, or Ca—Zn—Al—Si intermetallic compound phase is formed by the bond between Si atoms and Ca, and improvement in operability due to the Ca content cannot be expected. Therefore, it is difficult to obtain good plating properties. Therefore, the upper limit value of the Si concentration is set to 1.0% or less.
- ⁇ B 0.05% to 0.5%>
- B When B is contained in the plating layer, it has an effect of improving LME.
- the content When the content is 0.05% or more, it is estimated that various intermetallic compound phases are formed by combining with Zn, Al, Mg, and Ca elements in the plating layer. In particular, it has a strong binding property with Ca and tends to form a Ca—Al—B intermetallic compound phase (eg, Al 2 CaB 5 phase) (see FIG. 4).
- the formation of the Ca—Al—B intermetallic compound phase is considered to have an effect of improving LME. Therefore, the lower limit of the B concentration is preferably 0.05% or more.
- JCPDS intermetallic compound data
- X-ray diffraction image from the surface of the “plating layer” using a Cu target 31.0 °, 33.5 °, 35.2 °
- B is an intermetallic compound of 40% or more in atomic%.
- Zn and Mg are also detected in the spectrum of EDS.
- a Ca—Al—B intermetallic compound in which some atomic positions are substituted with Zn and Mg for example, a part of Ca is one of Mg and Al.
- the inclusion of B has an effect of improving LME by moving B from the plating layer to the ground iron and changing the LME sensitivity of the steel itself by grain boundary strengthening.
- the inclusion of B is considered to act on the suppression of liquid phase formation, evaporation, and the like of the Zn phase because the melting point of the formed intermetallic compound is extremely high.
- the inclusion of B in the plating bath causes a rapid increase in the melting point of plating, and the plating operability is deteriorated, so that a plated steel material with good plating properties cannot be produced. Therefore, the upper limit value of the B concentration is set to 0.5% or less.
- Y, La, Ce 0.05% to 0.5%>
- Y, La, and Ce as the element group A are elements that have almost the same role as Ca. This is because the mutual atomic radii are close to the atomic radius of Ca. When it is contained in the plating layer, it is substituted at the Ca position and can be detected at the same position as Ca by EDS. Even when oxides are formed after welding, these oxides are detected at the same position as CaO. When these elements are contained in a total of 0.05% or more, the corrosion resistance on the back of the weld zone is improved. This indicates that these oxides have higher corrosion resistance than CaO. Therefore, the content of each element selected from the element group A is preferably 0.05% or more. The total content of elements selected from the element group A is also preferably 0.05% or more.
- the content of each element selected from the element group A is 0.5% or less.
- the total content of elements selected from element group A is also 0.5% or less.
- the total concentration of the element group A needs to be lower than the Ca concentration. Therefore, the total content of Ca and an element selected from element group A is set to 0.1% to less than 3.0%.
- element group B (Cr, Ti, Ni, Co, V, Nb, Cu, Mn): 0.05% to 0.25%>
- element group B is contained in the plating layer in a total amount of 0.05% or more, it is taken into the Al—Fe alloy layer during welding.
- the Al—Fe alloy layer contains the element group B, the corrosion resistance of the back surface of the welded portion is improved.
- the element group B is taken in, it is considered that the insulating property of the Al—Fe alloy layer is improved. Therefore, the content of each element selected from the element group B is preferably 0.05% or more. Further, the total content of elements selected from the element group B is also preferably 0.05% or more.
- the content of each element selected from the element group B is 0.25% or less.
- the total content of elements selected from element group B is also 0.25% or less.
- Cd is also an element included in the element group C, and may be detected in a small amount (less than 0.1%) as an impurity of Zn and Pb. The effect in etc. has not been confirmed.
- any intermetallic compound phase has a high melting point, it remains as an intermetallic compound phase without being evaporated after welding.
- Mg which is easily oxidized by welding heat and forms MgO, is not oxidized by forming Sn, Bi, In and an intermetallic compound phase, and it remains as an intermetallic compound phase and remains as a plating layer after welding. Become. When these elements are present, the corrosion resistance sacrificial corrosion resistance is improved, and the corrosion resistance around the weld is improved.
- MgZn 2 is also the same Mg-based compound, but these intermetallic compounds have a higher sacrificial anticorrosive effect.
- the content of each element selected from the element group D is preferably 0.05% or more. Further, the total content of elements selected from the element group D is also preferably 0.05% or more.
- the element group D can contain up to 20.00% mainly of Sn. If the Sn concentration exceeds 20.00%, the Mg 2 Sn phase amount increases and the corrosion resistance after welding deteriorates rapidly. The same is true even if the total content of Sn, Bi and In exceeds 20.00%. This is because Zn, which originally existed as the MgZn 2 phase, has an adverse effect on LME and blowhole properties due to the presence of the Zn phase due to an increase in Mg 2 Sn. Therefore, the Sn content is 20.00% or less. Further, the total content of elements selected from the element group D is also set to 20.00% or less.
- the Bi content and the In content are each 2.0% or less.
- Fe 0% to 5.0%> Fe is mixed into the plating layer as an impurity when the plating layer is manufactured.
- it is often less than 1%.
- the Fe concentration gradually increases due to the passage of a plating raw material (plating raw plate or the like). For this reason, when it mixes with a plating bath with the supersaturation concentration of about 0.5% of Fe in a plating bath, the raise of the Fe concentration of a plating bath can be prevented.
- An impurity refers to a component contained in a raw material or a component mixed in a manufacturing process and not intentionally included.
- a component other than Fe may be mixed in the plating layer as impurities due to mutual atomic diffusion between the steel (base metal) and the plating bath.
- the Al content is more than 22% to less than 35%
- the Mg content is more than 10% to less than 20%
- the Ca content is 0.3% to 3.0%
- the Si content is preferably 0.1% to 1.0%.
- the Ca content is preferably at least twice the Si content.
- the Al content may be more than 15% to 22%, or more than 15% to 20%.
- the corrosion resistance after coating is improved.
- Many of the welded structures are painted after welding.
- red rust is likely to occur around the welded part at an early stage. Therefore, in order to ensure the corrosion resistance of the welded part, it is preferable to perform some kind of coating treatment.
- the behavior of red rust generated from the welded part is observed after electrodeposition coating is applied around the welded part, there is a correlation between the Al concentration and the corrosion resistance after painting. When the coating is applied, even after the Al concentration exceeds 22%, sufficient post-coating corrosion resistance can be obtained in the weld zone.
- the Al concentration is preferably 22% or less and more preferably 20% or less from the viewpoint of suppressing the occurrence of red rust from the periphery of the weld.
- adhesion to the metal part of the plating layer with the coating film is related, and it is estimated that the lower the Al concentration, the more effective the base treatment that affects the coating film adhesion.
- the Zn—Al—Mg alloy layer is a layer mainly composed of two phases of MgZn 2 phase and Al phase.
- the Zn—Al—Mg alloy layer does not contain or contains a trace amount of Zn—Al—MgZn 2 ternary eutectic structure.
- the Zn—Al—Mg alloy layer may contain a Zn phase, an intermetallic compound phase, or the like.
- the area fraction of the MgZn 2 phase is 45 to 75%
- the total area fraction of the MgZn 2 phase and the Al phase is 70% or more
- the area fraction of the —MgZn 2 ternary eutectic structure is 0 to 5%.
- the area fraction of the Zn phase is preferably less than 25% and more preferably less than 10%.
- the MgZn 2 phase will be described.
- the corrosion resistance of the Zn—Al—Mg alloy layer is improved. Since it is an intermetallic compound phase excellent in insulation, it has higher corrosion resistance than a Zn phase.
- Mg is contained as a constituent element, the corrosion potential is lower than that of the Zn phase, the sacrificial corrosion resistance is excellent, and the phase that improves the corrosion resistance around the welded portion is preferable.
- Mg elutes during the corrosion process it has the effect of densifying the formed corrosion product, and the red rust suppressing effect is higher than the corrosion product of the Zn phase alone, and white rust may be maintained for a long time.
- the MgZn 2 phase plays an important role. Zn atoms are likely to evaporate when present as a Zn phase, but are difficult to evaporate when present as an MgZn 2 phase.
- the MgZn 2 phase evaporates and forms a large amount of MgO and ZnO oxides. These intermetallic compounds are deposited on the Al—Fe alloy layer formed on the back surface of the welded portion via CaO, which is an oxide of Ca, and improve the corrosion resistance of the back surface of the welded portion.
- the MgZn 2 phase melts but can hardly be evaporated and remain.
- MgZn 2 phase remains even after welding is MgZn 2 phase was present as a pre-mass to a Zn-Al-Mg alloy layer.
- a MgZn 2 phase was also present in a Zn—Al—Mg alloy Zn—Al—Mg alloy layer.
- the Mg concentration is low, and the existence state of the MgZn 2 phase in the Zn—Al—Mg alloy layer exists as a Zn—Al—MgZn 2 ternary eutectic structure, and MgZn 2 present in a lump.
- the phase was an extremely small amount of less than 5% in an arbitrary cross-sectional structure of the Zn—Al—Mg alloy layer (see FIG. 1).
- the MgZn 2 phase remaining after welding is different from the fine MgZn 2 phase that precipitates as a Zn—Al—MgZn 2 ternary eutectic structure by a eutectic reaction.
- MgZn 2 phase which defines the area fraction MgZn 2 phase remaining after welding, Zn-Al-MgZn not as 2 ternary eutectic structure, MgZn 2 phase precipitated alone It is.
- the Zn—Al—MgZn 2 ternary eutectic structure easily evaporates during welding, and elements such as Mg and Zn cannot remain around the weld.
- the MgZn 2 phase existing in a lump shape can remain around the weld.
- FIG. 2 A SEM reflected electron image of a representative example of the plating layer of the present disclosure is shown in FIG. As shown in FIG. 2, it can be seen that a large number of massive MgZn 2 phases exist in the Zn—Al—Mg alloy layer and are connected to each other to form a coarse MgZn 2 phase. When it is desired to increase the residual amount after welding, it is preferable that the MgZn 2 phases are connected and coarse.
- the area fraction of the MgZn 2 phase is set to 45 to 75%, preferably 55 to 75%.
- the Al phase contains an ⁇ phase (ordinary ⁇ phase) in which about 0 to 3% of Zn is dissolved, and an excess of 70% to 85% Zn phase ( ⁇ phase).
- the normal ⁇ phase and Zn phase ( This corresponds to the ⁇ phase (normal ⁇ phase) finely separated from the ( ⁇ phase) (see FIGS. 2 and 5 to 6).
- FIG. 3 shows a Zn—Al phase diagram.
- the final solidification reaction of Zn—Al is an eutectoid separation by an eutectoid reaction between ⁇ phase containing 10% Zn at 275 ° C. and ⁇ phase (Zn phase) containing almost no Al.
- the plating solidification process generally has a high cooling rate, and a state that does not follow the phase diagram may occur.
- the eutectoid reaction does not occur completely, and an Al phase containing 0 to 85% of Zn, which is a high-temperature stable phase, often remains as a Zn supersaturated solid solution.
- the ⁇ phase is enlarged 10,000 times or more, it is composed of a fine Al phase and a fine Zn phase.
- the performance of the ⁇ phase and ⁇ phase such as corrosion resistance and sacrificial anticorrosion, shows the properties of the Al phase and is different from the properties of the Zn phase. Therefore, the Al phase of the present disclosure also corresponds to the ⁇ phase.
- region ((beta) phase) shown by 21 the area
- an Al-phase Zn supersaturated solid solution (an Al phase different from the normal ⁇ -phase and ⁇ -phase component concentrations) may be formed.
- Al phase different from the normal ⁇ -phase and ⁇ -phase component concentrations
- Zn supersaturated solid solution of the Al phase is a phase that does not finally exist at the time of slow cooling (when the ⁇ phase and the ⁇ phase are formed), and is an abnormal ⁇ phase and ⁇ phase.
- the ⁇ -phase Zn supersaturated solid solution is an Al phase in which Zn is supersaturated in a Zn concentration exceeding 3% to 70%, unlike the normal ⁇ -phase.
- the ⁇ phase of the Zn supersaturated solid solution is brittle and deteriorates workability.
- the ⁇ phase Zn supersaturated solid solution contains 70% to 85% Zn phase ( ⁇ phase), and ⁇ phase ( ⁇ phase Zn supersaturated solid solution in which Zn is supersaturated at a Zn concentration of 3% to 70%) ) And Zn phase ( ⁇ phase) are finely separated Al phases.
- the ⁇ phase of the ⁇ phase Zn supersaturated solid solution is also brittle and deteriorates workability because it contains the ⁇ phase Zn supersaturated solid solution.
- the Al phase of the Zn supersaturated solid solution is an Al phase different from the normal ⁇ phase and ⁇ phase component concentrations, and is a phase that deteriorates workability. Therefore, it does not correspond to the Al phase of the present disclosure.
- the identification method of the Al phase is as follows.
- the Al phase ( ⁇ phase and ⁇ phase) is specified by taking an SEM reflected electron image of the cross section of the plating layer (cut surface cut along the thickness direction of the plating layer) (see FIGS. 5 and 6).
- the cross section of the plating layer for measuring the area fraction of each phase (plating layer thickness direction)
- the same SEM backscattered electron image is used as the cut surface cut along the line.
- FIG. 5 and FIG. 6 an SEM reflected electron image of an inclined (4 °) polished cross section of the plated layer polished by 4 ° with respect to the cut surface cut along the plating layer thickness direction. Is shown.
- the ⁇ phase is specified by EDS or the like.
- each phase is deposited so that the central portion becomes the ⁇ phase and the ⁇ phase exists in the outer peripheral portion of the ⁇ phase.
- the Al phase starts from the crystallization of the Al phase, and the Al phase that can no longer contain Zn due to the decrease in the solid solubility limit due to solidification discharges the Zn component to the surrounding Al phase.
- the component analysis inside the Al phase is quantitatively analyzed in a certain area (for example, 1 ⁇ m ⁇ 1 ⁇ m) in an enlarged image (see FIG.
- the ⁇ phase (ordinary ⁇ phase) is specified. If the phase present on the outer periphery of the ⁇ phase (normal ⁇ phase) is an Al phase finely separated into a normal ⁇ phase and a Zn phase ( ⁇ phase), the phase is specified as a ⁇ phase (normal ⁇ phase). In addition, an Al phase in which Zn is over 3% to 70% supersaturated solid solution is specified as an ⁇ -phase Zn supersaturated solid solution. In addition, if the ⁇ phase Zn supersaturated solid solution and the Zn phase ( ⁇ phase) are finely separated Al phase, it is identified as the ⁇ phase Zn supersaturated solid solution.
- the element contained most in the plating layer is Zn, and Al is limited to more than 15% and less than 35%.
- the Al phase is in the Zn-Al-Mg alloy layer.
- the three-dimensional network structure is not formed and the main body is not formed, and the amount of MgZn 2 phase is the largest, and the structure is often the Al phase.
- the peritectic structure composed of the MgZn 2 phase around the Al phase that occupies most of the Zn—Al—Mg alloy layer forms a three-dimensional network structure. This is related to the blending ratio of Al concentration and Mg concentration in the plating layer.
- the concentration ratio Mg / Al when the concentration ratio Mg / Al is less than 1/10, the proportion of the Al phase in the Zn—Al—Mg alloy layer is larger than that of the MgZn 2 phase.
- the concentration ratio Mg / Al when the concentration ratio Mg / Al is in the range of 1/10 or more, the proportion of the MgZn 2 phase increases, and the Zn—Al—Mg alloy layer mainly composed of the Al phase cannot be obtained. For this reason, the corrosion resistance, sacrificial corrosion resistance, and other properties of the flat portion and the like that are not related to the welded part are closer to those of the Zn-based plated steel sheet than the Al-based plated steel sheet and the Al—Zn-based plated steel sheet.
- Al phase ( ⁇ phase, ⁇ phase) reacts with Fe of steel (steel) when welding heat is applied and exposed to 500 ° C or more, and between Al-Fe alloy layer, spherical or massive Al-Fe metal It becomes a compound phase.
- AlFe phase, Al 2 Fe phase, Al 3 Fe phase, Al 3.2 Fe phase, Al 5 Fe 2 phase, etc. were composed of almost the same constituent materials as the Al—Fe alloy layer described above, and were dissolved in the Al phase.
- An intermetallic compound phase in which Zn is substituted with a part of Al is formed. Further, as described above, these Al—Fe alloy layers and Al—Fe intermetallic compound phases have a certain corrosion resistance with respect to the base iron (steel material).
- Al becomes an Al—Fe alloy layer and improves the corrosion resistance of the back surface of the weld zone.
- the Al—Fe intermetallic compound phase does not form as much as a layer is formed, and often exhibits a spherical or massive form. The effect of these Al—Fe alloy layers and Al—Fe intermetallic compound phases on corrosion protection is small compared to the Zn—Al—Mg alloy layer, but has a certain contribution to corrosion resistance.
- the total area fraction of the MgZn 2 phase and Al phase is 70% or more, preferably 80% or more, more preferably 90% or more, most preferably 95 % Or more.
- the upper limit of the total area fraction of the MgZn 2 phase and the Al phase is preferably 98% or less, more preferably 100% or less. If MgZn 2 phase and Al phase are present at this area fraction, the Zn—Al—Mg alloy layer tends to remain in the heat affected zone of 500 to 1000 ° C., and the effect of improving the corrosion resistance around the weld is apparent. I can confirm. If it is less than 70%, much of the Zn—Al—Mg alloy layer evaporates, and the corrosion resistance around the welded portion is inferior.
- the ternary eutectic structure includes an Al phase, a Zn phase, and an MgZn phase. Since the shape of each phase changes depending on the component composition, the shape is indefinite. However, since the eutectic structure is an isothermal transformation and element movement during solidification is suppressed, each phase forms a complicated shape, and usually each phase precipitates finely (see FIG. 7). Normally, each phase has a large Zn phase and forms an island shape, and then the MgZn phase is large and fills the gap between the Zn phases, and the Al phase is dispersed in the form of spots between the MgZn 2 phases. There are many cases.
- the constituent phases do not change, but what precipitates in an island shape may be an MgZn 2 phase, an Al phase or an MgZn 2 phase, and the positional relationship is a component immediately before solidification. Depends on change. A method for specifying the ternary eutectic structure will be described later.
- the area fraction of the Zn—Al—MgZn 2 ternary eutectic structure is 0 to 5%, preferably 0 to 2%.
- the area fraction of the ternary eutectic structure is most preferably 0%.
- the Zn phase is preferably contained in the Zn—Al—Mg alloy layer from the viewpoint of corrosion resistance and sacrificial anticorrosion, but this is not preferable because it causes LME and blowhole formation during welding. Further, since the Zn layer easily evaporates, corrosion resistance at the weld heat affected zone can hardly be expected. Therefore, it is preferable to manage the content of the Zn phase. When the Zn concentration is high, a Zn phase is likely to be formed, but if the area fraction of the Zn phase is 10% or more in the Zn—Al—Mg alloy layer, the amount of LME and blowhole generation tends to deteriorate.
- the area fraction of the Zn phase may be less than 25%.
- the tendency that a smaller amount of Zn phase is preferable from the viewpoint of weldability does not change.
- the area fraction of the Zn phase is preferably less than 10%, more preferably 5% or less, and even more preferably 3% or less.
- the area fraction of the Zn phase is ideally 0%, but is preferably 2% or more from the viewpoint of manufacturing.
- the final solidified part (420 to 380 ° C.) of the plating layer is often the Zn phase.
- a single phase of the Zn phase Can be prevented from being precipitated as much as possible.
- a Ca—Zn—Al intermetallic compound phase may be formed in the Zn—Al—Mg alloy layer. This is because Ca originally tends to form an intermetallic compound phase (CaZn 2 phase, CaZn 5 phase, CaZn 11 phase, Al 4 Ca phase, etc.) with Al and Zn.
- Ca concentration is high, Ca is an element that is very easily segregated, and the intermetallic compound phase to be bonded is not defined as one of them.
- the Ca—Zn—Al intermetallic compound phase forms CaO oxide on the back of the weld and forms an oxide layer with high adhesion on the Al—Fe alloy layer. By forming the oxide layer, the corrosion resistance of the back surface of the welded portion is improved.
- the phase amount and size of the Ca—Zn—Al intermetallic compound phase depend on the weldability and the corrosion resistance of the weld heat affected zone.
- the crystal grain size is large, the Ca—Zn—Al intermetallic compound phase easily forms an oxide layer having high adhesion as the CaO oxide on the back surface of the welded portion. That is, the effect of improving the corrosion resistance on the back surface of the welded portion is enhanced.
- the crystal grain size of the Ca—Zn—Al intermetallic compound phase is large, the proportion of Zn bonded to the Ca—Zn—Al intermetallic compound phase tends to increase, suppressing evaporation of the Zn phase, The effect of improving LME and blowhole formation is enhanced.
- the plating layer with a low Zn phase content was treated to coarsen the Ca—Zn—Al intermetallic compound phase, the effect of improving LME and blowhole formation tends to be difficult to confirm. is there.
- the Ca—Zn—Al intermetallic compound phase usually has various shapes (cube, needle shape, rod shape, amorphous shape, etc.) in the Zn—Al—Mg alloy layer.
- the length of the longest line is the crystal grain size of the Ca—Zn—Al intermetallic compound phase.
- the equivalent circular diameter of the area is the crystal grain size of the Ca—Zn—Al intermetallic compound phase.
- the performance changes. It is not necessary for all the Ca—Zn—Al intermetallic compound phases to be confirmed to have a crystal grain size of 1 ⁇ m or more, but if a Ca—Zn—Al intermetallic compound phase having a crystal grain diameter of 1 ⁇ m or more cannot be confirmed, There is a tendency that the effect of improving the corrosion resistance is reduced. Moreover, there exists a tendency for the inhibitory effect of formation of LME and a blowhole to reduce.
- the upper limit value of the average crystal grain size of the Ca—Zn—Al intermetallic compound phase is not particularly limited, but is, for example, 100 ⁇ m or less.
- the Ca—Zn—Al intermetallic compound phase is an intermetallic compound phase having a very high melting point, which is immediately formed immediately after solidification of the plating layer and is innumerable in the Zn—Al—Mg alloy layer.
- the Ca—Zn—Al metal that is finely precipitated by combining with the nearby Ca—Zn—Al intermetallic compound phase.
- a Ca—Zn—Al intermetallic phase grows while reducing the number of intermetallic phases.
- an Mg 2 Si phase may be formed in the Zn—Al—Mg alloy layer.
- the Ca concentration is high, it may contain a Ca 2 Si phase, a CaSi phase, and a Ca—Zn—Al—Si intermetallic compound phase.
- these compound phases are present in the Zn—Al—Mg alloy layer, the effect of improving the corrosion resistance of the weld heat affected zone is enhanced.
- the Ca—Zn—Al—Si intermetallic compound phase has the same effects as the Ca—Zn—Al intermetallic compound phase (the effect of improving the corrosion resistance of the weld back surface and the effect of improving the formation of LME and blowholes).
- the presence of the Ca-Zn-Al-Si intermetallic compound phase will contain Si in the oxide layer remaining on the Al-Fe alloy layer after welding. Increases effectiveness.
- the Ca—Zn—Al—Si intermetallic compound phase having an average crystal grain size of 1 ⁇ m or more (or 1 to 100 ⁇ m) is present in the Zn—Al—Mg alloy layer, the Ca—Zn—Al—Si intermetallic compound phase Similarly, the effect of improving the corrosion resistance on the back surface of the weld and the effect of suppressing the formation of LME and blowholes are enhanced.
- the Zn—Al—Mg alloy layer includes a group consisting of Mg 2 Si phase, Ca 2 Si phase, CaSi phase, Ca—Zn—Al intermetallic compound phase, and Ca—Zn—Al—Si intermetallic compound phase. It is preferable that at least 1 type of intermetallic compound phase chosen from these is included.
- the Zn—Al—Mg alloy layer is replaced with Al 2 CaB 5 phase and a compound in which some atomic positions of the Al 2 CaB 5 phase are substituted with Zn and Mg.
- a Ca—Al—B intermetallic compound phase selected from the group consisting of phases may form a Ca—Al—B intermetallic compound phase in which B is at least 40% by atomic%.
- the inclusion of this Ca—Al—B intermetallic compound phase in the Zn—Al—Mg alloy layer is preferable because LME improves.
- an element selected from the element group D is contained in the plating layer (specifically, when 0.05% to 20% in total is selected from the elements selected from the element group D), a Zn—Al—Mg alloy is obtained.
- at least one intermetallic compound phase selected from the group consisting of Mg 2 Sn phase, Mg 3 Bi 2 phase and Mg 3 In phase is formed in the layer.
- this intermetallic compound phase is contained in the Zn—Al—Mg alloy layer, the corrosion resistance around the welded portion is improved.
- the other characteristic of the plated layer is the hardness of the plated layer.
- the Zn—Al—Mg alloy layer contains a large amount of the MgZn 2 phase, which is a hard intermetallic compound, and in addition, the intermetallic compound formed by the additive element is also generally hard, so the plating layer Hardness shows 150Hv or more.
- the plated steel material of the present disclosure can be obtained by forming a plating layer on the surface (namely, one side or both sides) of a steel material (plating raw material such as a plating original plate) by a hot dipping method.
- the plating bath uses a pure metal or alloy having a predetermined component composition prepared in a vacuum melting furnace or the like, prepares a predetermined amount so as to have a target composition, and dissolves in the atmosphere.
- an operation temperature higher than the melting point is usually required.
- the steel material reduced with hydrogen at 800 ° C. in a non-oxidizing environment is immersed in the plating bath as it is. Although it affects the thickness of the Al—Fe alloy layer of the plating layer, the immersion time is usually sufficient as long as 0.5 seconds. After the immersion, the amount of adhesion is adjusted by spraying N 2 gas.
- the plating bath temperature melting point of the plating bath + 20 ° C.
- the holding time at 420 ° C. or higher is set.
- the amount of Zn phase remaining in the Zn—Al—Mg alloy layer increases, and the final solidified portion of the Zn—Al—Mg alloy layer is Zn—Al—MgZn 2 ternary eutectic.
- the amount of Al phase and MgZn 2 phase becomes tissue decreases, the plated layer weldability is deteriorated.
- the Zn-Al-Mg alloy layer contains a Zn supersaturated solid solution of the Al phase (normal ⁇ Al phase different from the component concentration of the phase and ⁇ phase) is formed, the MgZn 2 phase is decreased, the amount of Zn phase is abnormally increased, and the workability is deteriorated.
- MgZn 2 phase, Al phase, and Zn phase are precipitated.
- the cooling rate is large, so the liquid phase does not depend on the phase diagram. Is maintained at a low temperature, and a Zn—Al—MgZn 2 ternary eutectic structure is formed or a large amount of Zn phase is precipitated.
- the Zn supersaturated solid solution of Al phase occupies a large amount. As a result, undesirable tissue increases.
- the most suitable cooling conditions to provide a retention time Zn melting point 420 ° C. or more high temperature, can be sufficiently grow the MgZn 2 phase and Al phase.
- the area fraction occupied by the MgZn 2 phase and the Al phase in the plating layer can be maximized.
- the amount of Al—MgZn 2 phase is maximized, the amount of Zn phase can be minimized at the same time.
- the plating bath temperature (the melting point of the plating bath + 20 ° C.) is used, and after the plating treatment (after the steel material is pulled up from the plating bath).
- the holding time at 420 ° C. or higher is set to exceed 5 seconds. That is, by setting the holding time at 420 ° C. or more to more than 5 seconds, it is possible to sufficiently secure the precipitation time of the MgZn 2 phase and the Al phase, the Zn phase, the Zn—Al—MgZn 2 ternary eutectic structure, or the Al phase.
- the plating bath temperature melting point of the plating bath + 20 ° C.
- the cooling rate from the melting point of the plating bath to 420 ° C. is 5 ° C./second or less
- the holding time at 420 ° C. or higher is set to exceed 5 seconds.
- the melting point of the plating bath is 500 ° C. or higher
- the precipitation time of the MgZn 2 phase and the Al phase is sufficient even if the cooling rate from the melting point of the plating bath to 420 ° C.
- the temperature at which the liquid phase disappears in the Zn—Al—Mg alloy layer during solidification (about 350
- the crystal grain size of these intermetallic compounds can be increased by performing sufficient cooling to (° C.).
- the cooling rate from the melting point of the plating bath to 350 ° C. is set at 5 ° C. / Less than a second.
- the chemical composition of the plating layer containing a large amount of Mg is a composition that becomes a hard plating layer as described above and is disadvantageous in workability and plating adhesion.
- eutectic reaction from the Al phase to the Zn phase occurs at 275 ° C. described above at a temperature of 420 ° C. or higher. And this eutectic reaction is completed by 250 degreeC.
- the Zn supersaturated solid solution of Al phase (Al phase different from the normal ⁇ phase and ⁇ phase component concentrations) disappears, and the workability is also improved. This is a preferable condition.
- the Zn phase amounts precipitated by the eutectic reaction grow with each other, the Zn phase amount increases, and the weldability is slightly deteriorated.
- rapid cooling is not preferable from the viewpoint of workability because it keeps the Al-phase Zn supersaturated solid solution (Al phase different from the normal ⁇ phase and ⁇ phase component concentrations) as it is.
- the average cooling rate in this temperature range is preferably in the range of 10 to 20 ° C./second, which is the same as that in the normal plating process.
- the average cooling rate is less than 10 ° C./second, the amount of Zn phase tends to increase slightly, which is not preferable for weldability.
- the average cooling rate is 20 ° C./second or more
- the temperature treatment in which the average cooling rate in the temperature range from 420 ° C. to 250 ° C. is in the above range is an effective means particularly when the Al concentration is low and the Zn concentration is high.
- the melting point of the plating bath in addition to setting the holding time at 420 ° C. or higher to exceed 5 seconds, the melting point of the plating bath to 350 ° C. (or 250 ° C.)
- the cooling rate is less than 5 ° C./second.
- the chemical component of the plating layer is measured by the following method. First, an acid solution is obtained in which the plating layer is peeled and dissolved with an acid containing an inhibitor that suppresses corrosion of the base iron (steel material). Next, by measuring the obtained acid solution by ICP analysis, the chemical composition of the plating layer (in the case where the plating layer is a single layer structure of a Zn—Al—Mg alloy layer, the chemical composition of the Zn—Al—Mg alloy layer) In the case where the plating layer has a laminated structure of an Al—Fe alloy layer and a Zn—Al—Mg alloy layer, the total chemical composition of the Al—Fe alloy layer and the Zn—Al—Mg alloy layer can be obtained.
- the acid species is not particularly limited as long as it is an acid that can dissolve the plating layer.
- the chemical composition is measured as an average chemical composition.
- a calibration curve for quantitative analysis of each element is obtained by GDS (High Frequency Glow Discharge Spectroscopy). Then, it is good to measure the chemical component of the depth direction of the target plating layer. For example, several 30 mm squares are sampled from the prepared plated steel sheet sample and used as a GDS sample. Argon ion sputtering is performed from the surface layer of the plating layer, and an element strength plot in the depth direction is obtained. Furthermore, if a standard sample such as each element pure metal plate is prepared and an element intensity plot is obtained in advance, the concentration can be converted from the intensity plot. When GDS is used for the analysis of chemical composition, it is preferable to measure 10 times or more with an analysis area of ⁇ 4 mm or more, and adopt an average value of components at each location.
- the sputtering rate is preferably in the range of about 0.04 to 0.1 ⁇ m / second.
- the sputtering rate is preferably in the range of about 0.04 to 0.1 ⁇ m / second.
- the place where the Fe element strength is 95% or more of the total elemental analysis is determined by using the base iron (steel material) and the plating layer (that is, the Al—Fe alloy layer).
- the surface position of the plating layer from the interface position is the Al—Fe alloy layer.
- a method for confirming each phase in the Zn—Al—Mg alloy layer is as follows.
- Each phase of the Zn—Al—Mg alloy layer may be identified by X-ray diffraction from the surface of the Zn—Al—Mg alloy layer.
- the intensity of X-ray diffraction can be Cu, Co, or the like for the radiation source, but it is necessary to finally calculate and change the diffraction angle according to the Cu radiation source.
- the measurement range is preferably 5 ° to 90 °, and the step is preferably about 0.01 °.
- the cross section of the Zn—Al—Mg alloy layer was polished and the structure after the night etching was observed, and the Al—Fe alloy layer and the Zn—Al— The thickness of the Mg alloy layer can be measured. If CP processing is used, it is possible to observe the plating layer structure more precisely. FE-SEM is preferably used for observation of the Zn—Al—Mg alloy layer.
- the area fraction of each phase in the Zn—Al—Mg alloy layer (however, each phase excluding the Zn—Al—MgZn 2 ternary eutectic structure) is measured by the following method.
- FE-SEM and TEM equipped with EDS are used to measure the area fraction of each phase in the Zn—Al—Mg alloy layer. Note that an EPMA apparatus may be used for identification of each phase.
- CP cross session polisher processing
- an SEM reflected electron image of the cross section of the Zn—Al—Mg alloy layer is obtained.
- the SEM backscattered electron image is approximately 100 ⁇ m or more (thickness direction: selection of the field of view where the Zn—Al—Mg alloy layer can be accommodated) ⁇ 2000 ⁇ m (parallel to the surface of the steel material). This is an image (about Zn—Al—Mg alloy layer thickness ⁇ m ⁇ about 150 ⁇ m) observed at a magnification of 1000 times.
- FIB focused ion beam processing
- FIB processing is applied to an arbitrary cross section (cross section cut in the thickness direction of the Zn—Al—Mg alloy layer) of the Zn—Al—Mg alloy layer to be measured.
- a TEM transmission electron microscope
- each phase of the Zn—Al—Mg alloy layer is identified in the reflected electron image of the SEM.
- EDS point analysis may be performed, and the result of EDS point analysis and the result of identification of the electron diffraction image of the TEM may be collated.
- the three values of gray scale brightness, hue and contrast value indicated by each phase in the Zn—Al—Mg alloy layer are determined. Since the three values of brightness, hue, and contrast value indicated by each phase reflect the atomic number of the element contained in each phase, the amount of Al with a small atomic number, the phase with a large amount of Mg content, usually black The phase with a large amount of Zn tends to exhibit a white color.
- the area fraction of each phase of the Zn—Al—Mg alloy layer is at least at least three fields of view of an arbitrary cross section of the Zn—Al—Mg alloy layer (cross section cut in the thickness direction of the Zn—Al—Mg alloy layer).
- the average value of the area fraction of each phase determined by the above operation.
- the “MgZn 2 phase, Al phase and Zn phase” present in the Zn—Al—MgZn 2 ternary eutectic structure cannot be identified as a boundary / area fraction.
- the SEM images of the cross section of the Zn—Al—Mg alloy layer are all taken as a backscattered electron image, but usually the phases constituting the Zn—Al—Mg alloy layer. (Al phase, MgZn 2 phase, Zn phase, etc.) can be easily distinguished because the atomic number difference is clear.
- intermetallic compound phases may show a contrast close to that of the MgZn 2 phase, but have a unique shape. Therefore, these intermetallic compound phases can also be identified relatively easily.
- An intermetallic compound phase containing Si having a small atomic number such as a Ca—Zn—Al—Si intermetallic compound
- An intermetallic compound phase containing B with a small atomic number such as a Ca—Al—B intermetallic compound phase
- the average crystal grain sizes of the Ca—Zn—Al intermetallic compound phase and the Ca—Zn—Al—Si intermetallic compound phase are as follows. In the SEM observation when measuring the area fraction of each phase, the compound phases having the top five crystal grain sizes are selected from the confirmed compound phases. Then, this operation is performed for five visual fields, and the arithmetic average of a total of 25 crystal grain sizes is calculated as the average crystal grain size of each of the Ca—Zn—Al intermetallic compound phase and the Ca—Zn—Al—Si intermetallic compound phase. To do.
- Identification and area fraction of Zn-Al-MgZn 2 ternary eutectic structure of Zn-Al-Mg alloy layer is measured by the following method.
- the structure in which the three phases of the Al phase, Zn phase, and MgZn 2 phase are co-crystallized is identified in the SEM reflected electron image To do.
- a part of the tissue is observed in a rectangular field having a magnification of 30000 times and a size of 3 ⁇ m ⁇ 4 ⁇ m (diagonal line is 5 ⁇ m) (see FIG. 7).
- the diagonal line crosses the Zn phase 5 times or more per Mg, and the MgZn 2 phase or Al phase spreading around the Zn phase 5 times or more.
- the ternary eutectic structure is determined. This determination is based on a standard that “a structure in which each of the three phases is finely dispersed” peculiar to the ternary eutectic structure.
- the structure is in a 1 ⁇ m square lattice. When one or more of each phase is contained in the lattice, it is determined as a ternary eutectic structure.
- the same SEM reflected electron image (magnification 1000 times, size: about Zn—Al—Mg alloy layer thickness ⁇ m ⁇ about 150 ⁇ m), which is the same as the measurement of the area fraction of each phase in the Zn—Al—Mg alloy layer
- the above operation is repeated on the image), and the outline (region) of the ternary eutectic structure is grasped while confirming the continuity of the ternary eutectic structure.
- the area fraction of the ternary eutectic structure in the Zn—Al—Mg alloy layer in the grasped SEM reflected electron image is obtained.
- the area fraction of the ternary eutectic structure is obtained by the above operation in at least three fields of view of an arbitrary cross section of the Zn—Al—Mg alloy layer (cross section cut in the thickness direction of the Zn—Al—Mg alloy layer). It is set as the average value of the area fraction of each phase.
- the plating layer hardness may be determined by measuring the Vickers hardness with an indentation with a load of 10 gf from the surface of the plating layer. It is preferable to obtain the Vickers hardness from an average value of about 30 points.
- a film may be formed on the plating layer.
- the coating can form one layer or two or more layers.
- Examples of the type of film directly above the plating layer include a chromate film, a phosphate film, and a chromate-free film.
- the chromate treatment, phosphate treatment, and chromate-free treatment for forming these films can be performed by known methods.
- electrolytic chromate treatment which forms a chromate film by electrolysis, a film is formed by utilizing the reaction with the material, and then the reactive chromate treatment, in which excess treatment liquid is washed away, is applied to the substrate.
- a coating-type chromate treatment in which a film is formed by drying without washing with water. Any processing may be adopted.
- Electrolytic chromate treatment uses chromic acid, silica sol, resin (phosphoric acid, acrylic resin, vinyl ester resin, vinyl acetate acrylic emulsion, carboxylated styrene butadiene latex, diisopropanolamine-modified epoxy resin, etc.), and electrolysis using hard silica.
- a chromate treatment can be exemplified.
- Examples of the phosphate treatment include zinc phosphate treatment, zinc calcium phosphate treatment, and manganese phosphate treatment.
- Chromate-free treatment is particularly suitable without any environmental impact.
- electrolytic chromate-free treatment that forms a chromate-free coating by electrolysis
- reaction-type chromate-free treatment that removes excess treatment liquid
- treatment solution that forms a film using the reaction with the material.
- coating-type chromate-free treatment in which a film is formed by applying to an object and drying without washing with water. Any processing may be adopted.
- organic resin films may be provided on the film immediately above the plating layer.
- the organic resin is not limited to a specific type, and examples thereof include polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, and modified products of these resins.
- the modified product is obtained by reacting a reactive functional group contained in the structure of these resins with another compound (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the functional group in the structure. Refers to resin.
- organic resin one or two or more organic resins (unmodified) may be mixed and used, or in the presence of at least one organic resin, at least one other One or two or more organic resins obtained by modifying the organic resin may be used.
- the organic resin film may contain an arbitrary colored pigment or rust preventive pigment. What was made water-based by melt
- Example A A plating bath was built in a vacuum melting furnace in the atmosphere using a predetermined amount of pure metal ingot so that a plating layer having the chemical composition shown in Tables 1-1 to 1-3 was obtained. A batch-type hot dipping apparatus was used for producing the plated steel sheet.
- No. as a comparative material for Nos. 102 and 103 commercially available Zn-Al-Mg-based plated steel sheets and hot-dip Zn-plated steel sheets were prepared. In any case, the thickness of the plating layer is 20 ⁇ m.
- the same reduction treatment method was applied to the plating original plate in the steps from the immersion in the plating bath to the pulling up. That is, the temperature of the plated steel sheet was raised from room temperature to 800 ° C. in an N 2 —H 2 (5%) (dew point ⁇ 40 ° or less, oxygen concentration less than 25 ppm) environment by heating and held for 60 seconds, and then N 2 It was cooled to the plating bath temperature + 10 ° C. by gas blowing and immediately immersed in the plating bath. In addition, all the plating original plates were immersed in the plating bath for 0.2 seconds. A plated steel sheet was prepared by adjusting the N 2 gas wiping pressure so that the plating thickness was 20 ⁇ m ( ⁇ 1 ⁇ m). From the immersion in the plating bath to the completion of wiping, the batch type plating apparatus was operated at a high speed and completed within 1 second. Immediately, N 2 gas was blown to lower the temperature to the plating melting point.
- N 2 gas was blown to lower the temperature to the plating melting point
- the plating process was carried out in the following six ways.
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating original plate from the plating bath, wiping was completed immediately above the plating melting point. A cooling process in which the average cooling rate from the melting point of the plating bath to 250 ° C. is 15 ( ⁇ 5) ° C./second, and the average cooling rate from 250 ° C. to 150 ° C. is 7.5 ( ⁇ 2.5) ° C./second. A plating layer was obtained. However, the cooling rate from the melting point of the plating bath to 420 ° C. is more than 5 ° C./second, and the holding time at 420 ° C. or more is less than 5 seconds.
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating original plate from the plating bath, wiping was completed immediately above the plating melting point.
- a plating layer was obtained by a cooling process (mist cooling) in which the average cooling rate from the melting point of the plating bath to 150 ° C. was 40 ( ⁇ 10) ° C./second). However, the cooling rate from the melting point of the plating bath to 420 ° C. is over 5 ° C./second, and the holding time at 420 ° C. or higher is less than 5 seconds.
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating base plate from the plating bath, wiping was completed immediately above the melting point of the plating bath.
- the average cooling rate from the melting point of the plating bath to 420 ° C. is 4 ( ⁇ 1) ° C./second (the retention time at 420 ° C. or higher is over 5 seconds), and the average cooling rate from 420 ° C. to 250 ° C. is 15 ( ⁇ 5).
- a plating layer was obtained by a cooling process of 0 ° C./second.
- Production method D The plating bath temperature was set to the melting point of the plating bath + 20 ° C. After lifting the plating base plate from the plating bath, wiping was completed immediately above the melting point of the plating bath.
- the average cooling rate from the melting point of the plating bath to 420 ° C. is 4 ( ⁇ 1) ° C./second (the holding time at 420 ° C. or higher is more than 5 seconds), and the average cooling rate from 420 ° C. to 250 ° C. is 30 ( ⁇ 5)
- a plating layer was obtained by a cooling process of ° C./second.
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating base plate from the plating bath, wiping was completed immediately above the melting point of the plating bath.
- the average cooling rate from the melting point of the plating bath to 420 ° C. is 8 ( ⁇ 2) ° C./second (the retention time at 420 ° C. or higher is more than 5 seconds), and the average cooling rate from 420 ° C. to 250 ° C. is 15 ( ⁇ 5 ) ° C./second) to obtain a plating layer by a cooling process.
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating base plate from the plating bath, wiping was completed immediately above the melting point of the plating bath.
- the average cooling rate from the melting point of the plating bath to 420 ° C. is 8 ( ⁇ 2) ° C./second (the holding time at 420 ° C. or higher is more than 5 seconds), and the average cooling rate from 420 ° C. to 250 ° C. is 30 ( ⁇ 5 )
- a plating layer was obtained with a cooling process at a temperature of C / sec.
- the arc weldability of the plating layer was evaluated as follows. Two 100 mm square samples were prepared, and a fillet weld sample was prepared using a CO 2 / MAG welding machine. Arc welding was carried out with an overlap of 10 mm on one end of the plated steel sheet, a stacking gap between the plated steel sheets of 0 mm, and a lower plate leg length of about 6 mm. The welding speed was 0.3 m / min, the welding wire was solid wire YGW14, ⁇ 12, CO 2 shield gas flow rate, 15 l / min, the welding current was 150 to 250 (A), the arc voltage was 20 to 24 V, and 2 pass. An X-ray transmission test was carried out on the weld bead from the upper side to determine the blowhole occupancy Bs (%).
- the blow hole occupancy rate Bs of Zn-Al-Mg based steel plate and Zn plated steel plate is about 40%, and the blow hole occupancy rate Bs is evaluated as "B" when 40% or more.
- the blow hole occupancy rate Bs is 20-40%. Was evaluated as “A”, and blow hole occupancy Bs of less than 20% was evaluated as “S”.
- the corrosion resistance of the back surface of the welded part was carried out as follows.
- a bead-on-plate specimen was obtained in the same manner as the LME evaluation.
- the back surface of this test piece was evaluated for red rust on the back surface of the bead in 90 to 180 cycles in a corrosion acceleration test (JASO M 609-91).
- JASO M 609-91 a corrosion acceleration test
- spot rust occurred on the back surface of the bead in 90 cycles.
- the entire surface of the Zn-plated steel sheet was red rust.
- a sample in which dotted red rust was confirmed on the back surface of the bead in 90 cycles was evaluated as “B”.
- a dot red rust confirmed on the back surface of the bead in 120 cycles was designated as “A”.
- a dot-like red rust confirmed on the back of the bead after 150 cycles was designated as “AA”.
- the evaluation of “AAA” was that in which dotted red rust was confirmed on the back surface of the bead in 180 cycles.
- a sample having no red rust on the back surface of the bead after 180 cycles was evaluated as “S”.
- the corrosion resistance around the welded part was carried out as follows.
- a bead-on-plate specimen was obtained in the same manner as the LME evaluation.
- the surface of this test piece was subjected to a salt spray test (JIS Z 2371) for 1000 to 1300 hours to confirm corrosion resistance.
- JIS Z 2371 JIS Z 2371
- red rust sagging was observed around the weld after 1000 hours.
- the entire surface of the Zn-plated steel sheet was red rust.
- the processability of the plated layer was evaluated as follows. A 10R-90 ° V bending press test was performed on the plated steel sheet, and a cellophane tape having a width of 24 mm was pressed against the V-bent valley and pulled apart, and powdering was judged visually.
- Example A is listed in Table 1-1 to Table 1-6.
- Example B In order to obtain a plating layer having the chemical composition shown in Table 2-1, a plating bath was built in a vacuum melting furnace in the atmosphere using a predetermined amount of pure metal ingot. A batch-type hot dipping apparatus was used for producing the plated steel sheet.
- the same reduction treatment method was applied to the plating original plate in the steps from the immersion in the plating bath to the pulling up. That is, the temperature of the plated steel sheet was raised from room temperature to 800 ° C. in an N 2 —H 2 (5%) (dew point ⁇ 40 ° or less, oxygen concentration less than 25 ppm) environment by heating and held for 60 seconds, and then N 2 It was cooled to the plating bath temperature + 10 ° C. by gas blowing and immediately immersed in the plating bath. In addition, all the plating original plates were immersed in the plating bath for 0.2 seconds. A plated steel sheet was prepared by adjusting the N 2 gas wiping pressure so that the plating thickness was 20 ⁇ m ( ⁇ 1 ⁇ m). From the plating bath immersion to the completion of wiping, the batch type plating apparatus was operated at a high speed and completed within 1 second. Immediately, N 2 gas was blown to lower the temperature to the melting point of the plating bath.
- N 2 gas was blown to lower the temperature to the melting point of
- the plating process was carried out in the following two ways.
- Production method C (same as Example A):
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating base plate from the plating bath, wiping was completed immediately above the melting point of the plating bath.
- the average cooling rate from the melting point of the plating bath to 420 ° C. is 4 ( ⁇ 1) ° C./second (the retention time at 420 ° C. or higher is more than 5 seconds), and the average cooling rate from 420 ° C. to 250 ° C. is 15 ( ⁇ 5)
- a plating layer was obtained by a cooling process of ° C./second.
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating base plate from the plating bath, wiping was completed immediately above the melting point of the plating bath.
- the average cooling rate from the melting point of the plating bath to 350 ° C. is 4 ( ⁇ 1) ° C./second (the retention time at 420 ° C. or higher is over 7 seconds), and the average cooling rate from 350 ° C. to 250 ° C. is 15 ( ⁇ 5 )
- a plating layer was obtained by a cooling process at a temperature of ° C / second.
- the plating bath temperature was the melting point of the plating bath + 20 ° C. After lifting the plating base plate from the plating bath, wiping was completed immediately above the melting point of the plating bath.
- a plating layer was obtained by a cooling process in which the average cooling rate from the melting point of the plating bath to 250 ° C. was 4 ( ⁇ 2) ° C./second (the retention time at 420 ° C. or higher was more than 10 seconds).
- Example A Using the obtained plated steel sheet, the area fraction of each phase and various performance evaluations were performed in the same manner as in Example A.
- the average crystal grain size of each compound phase was measured according to the method described above.
- the average crystal grain size is shown in the table.
- the unit of average crystal grain size is “ ⁇ m”.
- the corrosion resistance after coating was implemented as follows using the obtained plated steel plate.
- a bead-on-plate test piece was prepared in the same manner as in the evaluation of LME performed in Example A. With respect to this test piece, surface adjustment was performed at room temperature for 20 seconds using a surface conditioning agent (trade name: Preparen X) manufactured by Nippon Parkerizing Co., Ltd.
- phosphate treatment was performed using a zinc phosphate treatment solution (trade name: Palbond 3020) manufactured by Nippon Parkerizing Co., Ltd. Specifically, the temperature of the treatment liquid was 43 ° C., and the hot pressed steel was immersed in the treatment liquid for 120 seconds. Thereby, the phosphate film was formed on the steel material surface.
- the bead-on-plate test piece after the phosphoric acid treatment was subjected to electrodeposition coating with a cation-type electrodeposition paint manufactured by Nippon Paint Co., Ltd. with a slope voltage of 160 V, Furthermore, baking painting was performed at a baking temperature of 170 ° C. for 20 minutes. The average film thickness of the paint after electrodeposition coating was 15 ⁇ m for all samples.
- each test piece was subjected to a JASO test (M609-91) to confirm the occurrence of red rust around the bead after coating.
- the evaluation of “B” was that the spotted red rust was confirmed in the bead portion or the heat affected zone within 90 cycles.
- An evaluation of “A” was made in which dotted red rust was confirmed in the bead portion or the heat affected zone within 120 cycles.
- the “AA” evaluation was that in which dotted red rust was confirmed in the bead portion or the heat-affected zone within 150 cycles.
- the evaluation of “AAA” was that in which dotted red rust was confirmed in the bead portion or the heat-affected zone within 180 cycles.
- Example B is listed in Tables 2-1 and 2-2.
- a hot-dip galvanized steel sheet comprising a steel material and a plating layer including a Zn-Al-Mg alloy layer disposed on a surface of the steel material,
- the total area ratio of the MgZn 2 phase and the Al phase having an equivalent circular diameter and a crystal grain size of 1 ⁇ m or more is 70% or more, and the area ratio of the Zn phase is 10%.
- the Zn—Al—Mg alloy layer is at least one metal selected from the group consisting of Mg 2 Si phase, Ca 2 Si phase, CaSi phase, Ca—Zn—Al phase, and Ca—Zn—Al—Si phase.
- the plating layer is mass%, Zn: more than 44.9% to less than 74.9%, Al: more than 20% to less than 35%, Mg: more than 5% to less than 20%, Ca: 0.1% to less than 3.0%, Si: 0% to 1% B: 0% to 0.5% Y: 0% to 0.5% La: 0% to 0.5% Ce: 0% to 0.5% Cr: 0% to 0.25% Ti: 0% to 0.25%, Ni: 0% to 0.25%, Co: 0% to 0.25% V: 0% to 0.25% Nb: 0% to 0.25% Cu: 0% to 0.25%, Mn: 0% to 0.25% Sr: 0% to 0.5%, Sb: 0% to 0.5%, Pb: 0% to 0.5%, Sn: 0% to 20% Bi: 0% to 2% In: 0% to 2%, Fe: 0% to 5%, and impurities, element group A is Y, La and Ce, element group B is Cr, Ti, Ni,
- the Al is more than 22% to less than 35%, the Mg is more than 10% to less than 20%, the Ca is 0.3% to less than 3.0%, and the Si is 0.1% to The hot-dip galvanized steel sheet according to Supplementary Note 1, which is 1%.
- the plating layer is B, element group A (Y, La, Ce), element group B (Cr, Ti, Ni, Co, V, Nb, Cu, Mn), and element group C (Sr, Sb, Pb). Containing at least one selected from the group consisting of: When B is contained, B: 0.05% to 0.5%, When the element selected from the element group A is contained, the total content is 0.05% to 0.5%, When the element selected from the element group B is contained, the total content is 0.05% to 0.25%,
- the Zn-Al-Mg alloy layer is Al2CaB5, or a Ca-Al-B compound in which some atomic positions are substituted with Zn and Mg, and B is 40% or more in atomic percent.
- plating layer further includes an Al—Fe alloy layer, the Al—Fe alloy layer is formed on a surface of the steel material, and the Zn—Al—Mg alloy layer is formed on the Al—Fe alloy layer. 6.
- the hot-dip plated steel sheet according to any one of appendix 5.
Abstract
Description
しかし、この方法では、溶接した後にめっき処理されるため、生産性が劣るとともに、めっき浴等の設備が必要となり、製造コストを増加させる原因になっていた。
これを回避するため、予めめっきが施された亜鉛めっき鋼材(例えば亜鉛めっき鋼板)を溶接することにより構造物を製造する方法が、適用されるようになってきた。
また、最近、構造部材の耐食性をより向上させるために、従来の一般的な亜鉛めっき鋼材に比べて、さらに耐食性を高めた亜鉛系合金めっき(Zn-Al-Mg-Si系合金めっき、Al-Zn-Si系合金めっきなど)を表面に施した亜鉛系合金めっき鋼材(例えば亜鉛系合金めっき鋼板)を溶接して溶接構造物を製造するようになってきた(例えば、特許文献1~7参照。)。
また、フラックス入りワイヤを使用して、AlおよびMgの元素をスラグ化して溶接時に無害化する方法(特許文献9)が提案されている。
また、ステンレス系溶接ワイヤを使用する方法(特許文献10)が提案されている。
また、製品として溶接性に適しためっき鋼板(非特許文献1~2)も提案されている。
特許文献2:国際公開第2013/002358号
特許文献3:日本国特開2006-193791号公報
特許文献4:日本国特開2002-332555号公報
特許文献5:国際公開第2010/082678号
特許文献6:日本国特開2015-214747号公報
特許文献7:国際公開第2014/059474号
特許文献8:日本国特開2007-313535号公報
特許文献9:日本国特開2005-230912号公報
特許文献10:日本国特開2006-35293号公報
非特許文献2:新日鐵住金技報 第398号(2014)p.79-82
鋼材と、前記鋼材の表面に配され、Zn-Al-Mg合金層を含むめっき層と、を有するめっき鋼材であって、
前記Zn-Al-Mg合金層の断面において、MgZn2相の面積分率が45~75%、MgZn2相およびAl相の合計の面積分率が70%以上、かつZn-Al-MgZn2三元共晶組織の面積分率が0~5%であり、
前記めっき層が、質量%で、
Zn:44.90%超~79.90%未満、
Al:15%超~35%未満、
Mg:5%超~20%未満、
Ca:0.1%~3.0%未満、
Si:0%~1.0%、
B :0%~0.5%、
Y :0%~0.5%、
La:0%~0.5%、
Ce:0%~0.5%、
Cr:0%~0.25%、
Ti:0%~0.25%、
Ni:0%~0.25%、
Co:0%~0.25%、
V :0%~0.25%、
Nb:0%~0.25%、
Cu:0%~0.25%、
Mn:0%~0.25%、
Sr:0%~0.5%、
Sb:0%~0.5%、
Pb:0%~0.5%、
Sn:0%~20.00%、
Bi:0%~2.0%、
In:0%~2.0%、
Fe:0%~5.0%、及び
不純物からなり、
元素群AをY、La及びCe、元素群BをCr、Ti、Ni、Co、V、Nb、Cu及びMn、元素群CをSr、Sb及びPb、並びに元素群DをSn、Bi及びInとした場合、
前記元素群Aから選ばれる元素の合計の含有量が0%~0.5%であり、
Caと前記元素群Aから選ばれる元素との合計の含有量が0.1%~3.0%未満であり、
前記元素群Bから選ばれる元素の合計の含有量が0%~0.25%であり、
前記元素群Cから選ばれる元素の合計の含有量が0%~0.5%であり、
前記元素群Dから選ばれる元素の合計の含有量が0%~20.00%である化学組成を有するめっき鋼材。
<2>
前記Zn-Al-Mg合金層が、Mg2Si相、Ca2Si相、CaSi相、Ca-Zn-Al金属間化合物相、及びCa-Zn-Al-Si金属間化合物相よりなる群から選ばれる少なくとも1種の金属間化合物相を含有する<1>に記載のめっき鋼材。
<3>
前記Alの含有量が22%超~35%未満であり、前記Mgの含有量が10%超~20%未満であり、前記Caの含有量が0.3%~3.0%未満であり、前記Siの含有量が0.1%~1.0%である<1>又は<2>に記載のめっき鋼材。
<4>
前記Alの含有量が15%超~22%である<1>又は<2>に記載のめっき鋼材。
<5>
前記めっき層が前記Bを含有する場合、前記Bの含有量は質量%で0.05%~0.5%であり、
前記めっき層が前記元素群Aから選ばれる元素を含有する場合、前記元素群Aから選ばれる元素の合計の含有量は質量%で0.05%~0.5%であり、
前記めっき層が前記元素群Bから選ばれる元素を含有する場合、前記元素群Bから選ばれる元素の合計の含有量は質量%で0.05%~0.25%であり、
前記めっき層が前記元素群Cから選ばれる元素を含有する場合、前記元素群Cから選ばれる元素の合計の含有量は質量%で0.05%~0.5%である<1>~<3>のいずれか1項に記載のめっき鋼材。
<6>
前記Zn-Al-Mg合金層が、Al2CaB5相、および、前記Al2CaB5相の一部の原子位置がZn及びMgで置換された化合物相よりなる群から選択されるCa-Al-B金属間化合物相であって、Bが原子%で40%以上のCa-Al-B金属間化合物相を含有する<1>~<5>のいずれか1項に記載のめっき鋼材。
<7>
前記めっき層が前記元素群Dから選ばれる元素を含有する場合、前記元素群Dから選ばれる元素の合計の含有量は質量%で0.05%~20%であり、
前記Zn-Al-Mg合金層が、Mg2Sn相、Mg3Bi2相及びMg3In相からなる群より選択される少なくとも1種の金属間化合物相を含有する<1>~<6>のいずれか1項に記載のめっき鋼材。
<8>
前記めっき層が、前記鋼材と前記Zn-Al-Mg合金層との間にAl-Fe合金層を有する<1>~<7>のいずれか1項に記載のめっき鋼材。
なお、本開示において、化学組成の各元素の含有量の「%」表示は、「質量%」を意味する。
また、「~」を用いて表される数値範囲は、「~」の前後に記載される数値を下限値及び上限値として含む範囲を意味する。
また、「~」の前後に記載される数値に「超」または「未満」が付されている場合の数値範囲は、これら数値を下限値または上限値として含まない範囲を意味する。
また、成分組成の元素の含有量は、元素量(例えば、Zn量、Mg量等)又は元素濃度(例えば、Zn濃度、Mg濃度等)と表記することがある。
また、「工程」との用語は、独立した工程だけではなく、他の工程と明確に区別できない場合であってもその工程の所期の目的が達成されれば、本用語に含まれる。
また、「平面部」とは、鋼材の溶接熱影響部以外の鋼板の表面を示し、「溶接部周囲」とは、溶接部(溶接金属部分)以外で、溶接時の鋼材の熱影響部を示し、「溶接部裏面」とは、鋼材の表面側に形成される溶接部に対向した鋼材の裏面を示す。
鋼材の形状には、特に制限はない、鋼材は、鋼板の他、鋼管、土木建築材(柵渠、コルゲートパイプ、排水溝蓋、飛砂防止板、ボルト、金網、ガードレール、止水壁等)、家電部材(エアコンの室外機の筐体等)、自動車部品(足回り部材等)など、成形加工された鋼材が挙げられる。成形加工は、例えば、プレス加工、ロールフォーミング、曲げ加工などの種々の塑性加工手法が利用できる。
鋼材は、鋼材の製造方法、鋼板の製造方法(熱間圧延方法、酸洗方法、冷延方法等)等の条件についても、特に制限されるものではない。
鋼材は、プレめっきされたプレめっき鋼材でもよい。
めっき層は、Zn-Al-Mg合金層を含む。めっき層は、Zn-Al-Mg合金層に加え、Al-Fe合金層を含んでもよい。Al-Fe合金層は、鋼材とZn-Al-Mg合金層との間に存在する。
ただし、めっき層の表面にめっき層構成元素の酸化被膜が50nm程度形成しているが、めっき層全体の厚みに対して厚みが薄くめっき層の主体を構成していないと見なす。
一方、めっき金属の自重および均一性により、溶融めっき法で作製できる、めっき層の厚みはおよそ95μmである。
めっき浴からの引抜速度とワイピング条件によって、めっき層の厚みは自在にできるため、厚さ2~95μmのめっき層の形成は特に製造が難しいものではない。
なお、Al-Fe-Si合金層もZn-Al-Mg合金層に対し、厚みは小さいため、めっき層全体における耐食性において与える影響は小さい。
つまり、Al-Fe合金層は、形成されていなくてもよい。ただし、通常、本開示で規定するめっき組成で溶融めっき法により、めっき層を形成すると、鋼材とZn-Al-Mg合金層との間に、100nm以上のAl-Fe合金層が形成される。Al-Fe合金層の厚さの下限値は特に制限するものでなく、Alを含有する溶融めっき層を形成する際には、必然的にAl-Fe合金層が形成されることが判明している。そして、経験的に100nm前後が最もAl-Fe合金層の形成が抑制された場合の厚みであり、めっき層と地鉄(鋼材)との密着性を十分確保する厚みと判断されている。特別な手段を講じない限りはAl濃度が高いため、溶融めっき法では、100nmよりも薄いAl-Fe合金層を形成することは困難である。しかし、Al-Fe合金層の厚さが100nm未満であってとしも、また、Al-Fe合金層が形成されていなくても、めっき性能に大きな影響は与えないと推測される。
なお、本開示のめっき鋼材を利用した構造物は、加工後の形態として一般的に溶接構造物が適しており、必ずしも、めっき層の加工性を確保する必要はない。したがって、本開示のめっき鋼材は、用途を限定すれば、既存のZn-Al-Mg系合金めっき鋼材及び溶融Znめっき鋼材よりも溶接性に優れためっき鋼材となりうる。
ただし、めっき層の加工性が得られると、円形、曲形等、様々な形状にめっき鋼材を加工し、加工後のめっき鋼材を溶接材料として使用できる可能性があるため、めっき鋼板としては加工性が得られた方が好ましい。めっき層の加工性は、めっき性状の良いめっき鋼板をV曲げプレス試験で冷間加工し、V曲谷部のめっき層のパウダリング量を評価するとよい。
めっき層に含まれるZn-Al-Mg合金層の成分組成は、めっき浴の成分組成比率がZn-Al-Mg合金層でもほぼ保たれる。溶融めっき法における、Al-Fe合金層の形成はめっき浴内で反応が完了しているため、Al-Fe合金層形成によるZn-Al-Mg合金層のAl成分、Zn成分の減少は通常、ほとんどない。
Zn:44.90%超~79.90%未満、
Al:15%超~35%未満、
Mg:5%超~20%未満、
Ca:0.1%~3.0%未満、
Si:0%~1.0%、
B:0%~0.5%、
Y:0%~0.5%、
La:0%~0.5%、
Ce:0%~0.5%、
Cr:0%~0.25%、
Ti:0%~0.25%、
Ni:0%~0.25%、
Co:0%~0.25%、
V:0%~0.25%、
Nb:0%~0.25%、
Cu:0%~0.25%、
Mn:0%~0.25%、
Sr:0%~0.5%、
Sb:0%~0.5%、
Pb:0%~0.5%、
Sn:0%~20.00%、
Bi:0%~2.0%、
In:0%~2.0%、
Fe:0%~5.0%、及び
不純物からなる化学組成とする。
元素群Aから選ばれる元素の合計の含有量が0%~0.5%であり、
Caと前記元素群Aから選ばれる元素との合計の含有量が0.1%~3.0%未満とし、
元素群Bから選ばれる元素の合計の含有量が0%~0.25%とし、
元素群Cから選ばれる元素の合計の含有量が0%~0.5%とし。
元素群Dから選ばれる元素の合計の含有量が0%~20%とする。
Znは、Zn-Al-Mg合金層の主相を構成するために必要な元素であり、めっき鋼材として平面部の耐食性、溶接熱影響部の耐食性(溶接後耐食性)を確保する上で一定以上含有される必要がある。一方、Zn濃度、すなわち、Zn-Al-Mg合金層中におけるZn相が、LME量、ブローホールの形成量に密接に関係する。
AlもZn-Al-Mg合金層の主相を構成するために必要な元素であり、めっき鋼板として平面部の耐食性、溶接熱影響部の耐食性(溶接後耐食性)を確保する上で一定以上含有される必要がある。Alは、Zn-Al-Mg合金層中のAl相量を増やし、Zn相量を減らす。そのため、Al濃度が増加すれば溶接性は良くなる傾向にある。Alの効果は、溶接時の入熱によりめっき層が蒸発するのを抑制し、地鉄(鋼材)の成分とAl-Fe金属間化合物相(Al5Fe相、AlFe相、Al2Fe相、Al3Fe相等)を形成して、溶接部周囲の耐食性を向上させる。特に、鋼材の厚みが薄い場合で、めっき層が完全蒸発する溶接部裏面の耐食性を確保するためには、Alはめっき層中に含有された方が好ましい成分である。そのため、Al濃度は、20%を超えるとすることがよい。Al濃度が20%以下では、溶接時の入熱により地鉄のFe相に多く固溶し、溶接部裏面のAl-Fe金属間化合物の合金層が薄くなり、溶接部周囲での耐食性向上効果が見込めないことがある。
MgもZn-Al-Mg合金層の主相を構成するために必要な元素であり、めっき鋼板として平面部の耐食性、溶接熱影響部の耐食性(溶接後耐食性)を確保する上で一定以上含有される必要がある。Mgはめっき層に含有されるとZnとよく似た効果を表す。Mgの含有により犠牲防食性の向上が見込める。
一方、従来、めっき層中へMgを含有させると、MgはZnと同じく蒸気圧の低い金属であることからLMEが顕著になると考えられている。また、溶接性が低下するため様々なフラックスワイヤが開発されてきていることは前述の通りである。
Caはめっき層中に含有されると、Mg濃度増加に伴う、めっき操業時におけるドロスの形成量が減少し、めっき製造性を向上させる。特にMgが高濃度の時は、一般的にめっき操業性が悪いため、Mg濃度が7%を超える場合は、式:0.15+1/20Mg<Ca(ただし、式中、元素記号は、質量%での各元素の含有量を示す。)を満たすように、Ca濃度を調整することが好ましい。
Siは、めっき層中に含有されると、Mgと金属間化合物相(例えばMg2Si相)を形成する。また、Caが含有されている場合は、Caとの結合力が強いため、Ca-Si金属間化合物相(Ca2Si相、CaSi相等)も作る。ただし、Ca濃度よりも多くのSiが含有されている場合には、Mg2Siがやはり形成する。また、少量ではあるが、Mg-Al-Si金属間化合物相が形成する場合もある。Ca、Siと併用される場合は、Si濃度の2倍以上の濃度でCaを含有した方が好ましい。Ca濃度が高い方が、Mg2Siの形成量が減少する。
Bは、めっき層中に含有させるとLMEを改善する効果がある。0.05%以上含有すると、めっき層中で、Zn、Al、Mg、Ca元素と化合し、様々な金属間化合物相をつくると推定される。特にCaとの結合性が強く、Ca-Al-B金属間化合物相(例えばAl2CaB5相)を作る傾向にある(図4参照)。そして、Ca-Al-B金属間化合物相の生成はLMEを改善する効果があると考えられる。よって、B濃度の下限値は0.05%以上が好ましい。
元素群AとするY、La、Ceは、Caとほぼ同等の役割を示す元素である。これは互いの原子半径がCaの原子半径と近いことに起因する。めっき層中に含有されるとCa位置に置換し、EDSでCaと同位置に検出することができる。溶接後、酸化物となった場合も、CaOと同じ位置でこれらの酸化物が検出される。これらの元素が合計で0.05%以上含有されると、溶接部裏面の耐食性が向上する。これは、CaOよりこれらの酸化物の耐食性が高いことを示す。よって、元素群Aから選ばれる各元素の含有量は、各々0.05%以上が好ましい。そして、元素群Aから選ばれる元素の合計の含有量も0.05%以上が好ましい。
元素群Bがめっき層中に合計量で0.05%以上含有されると、溶接時、Al-Fe合金層に取り込まれる。Al-Fe合金層が元素群Bを含有することによって、溶接部裏面の耐食性が向上する。元素群Bが取り込まれると、Al-Fe合金層の絶縁性が向上すると考えられる。よって、元素群Bから選ばれる各元素の含有量は、各々0.05%以上が好ましい。また、元素群Bから選ばれる元素の合計の含有量も、0.05%以上が好ましい。
一方、元素群Bは、過剰含有すると様々な金属間化合物相をつくり、粘性上昇を引き起こす。このため、単独又は元素群B群の合計で0.25%超の範囲では、めっき浴の建浴そのものが困難となることが多く、めっき性状が良好なめっき鋼板を製造できない。よって、元素群Bから選ばれる各元素の含有量は、各々0.25%以下とする。そして、元素群Bから選ばれる元素の合計の含有量も0.25%以下とする。
元素群Cがめっき層中に合計量で0.05%以上含有されると、めっき層の外観が変化し、スパングルが形成されて、金属光沢の向上が確認される。溶接性能における変化はない。よって、元素群Cから選ばれる各元素の含有量は、各々0.05%以上が好ましい。元素群Cから選ばれる元素の合計の含有量も0.05%以上が好ましい。
一方、元素群Cが0.5%超で含有すると、めっき浴中のドロス生成量が多くなり、めっき浴の建浴そのものが困難となることが多く、めっき性状が良好なめっき鋼材を製造できない。よって、元素群Cから選ばれる各元素の含有量は、各々0.5%以下とする。そして、元素群Cから選ばれる元素の合計の含有量も0.5%以下とする。
元素群Dは、めっき層中に合計量で0.05%以上含有すると、めっき層中に、新たな金属間化合物相としてMg2Sn相、Mg3Bi2相、Mg3In相等が形成し、検出されるようになる。元素群Dは、めっき層主体を構成する元素Zn、Alといずれとも金属間化合物相を形成することなく、Mgのみと金属間化合物相を形成する。新たな金属間化合物相が形成するため、めっき層の溶接性を大きく変化させる元素である。このうち、Snが低融点金属でめっき浴の性状を損なうことなく容易に含有させることができる。元素群Dの含有濃度が増えると、これらの金属間化合物相の形成量が増大する。
Feはめっき層を製造する際に、不純物としてめっき層に混入する。Al-Fe合金層の厚みが厚い程、Fe濃度が高くなる傾向にあり、最大5.0%程度まで含有されることがある。通常の溶融めっき法にて製造した際には、1%未満であることが多い。新規めっき浴を建浴した場合、めっき原材(めっき原板等)の通板によって、Fe濃度は徐々に上昇する。このため、めっき浴でのFeの過飽和濃度0.5%程度でめっき浴に混入させておくと、めっき浴のFe濃度の上昇を防ぐことができる。
不純物は、原材料に含まれる成分、または、製造の工程で混入する成分であって、意図的に含有させたものではない成分を指す。例えば、めっき層には、鋼材(地鉄)とめっき浴との相互の原子拡散によって、不純物として、Fe以外の成分も微量混入することがある。
めっき層の化学組成において、Alの含有量は22%超~35%未満であり、Mgの含有量は10%超~20%未満であり、Caの含有量は0.3%~3.0%未満であり、Siの含有量は0.1%~1.0%であることが好ましい。また、Caの含有量はSiの含有量の2倍以上であることが好ましい。Al、Mg、CaおよびSiの各元素濃度が上記範囲であると、上述した各種金属間化合物相が形成され易く、LEMおよびブローホール形成の抑制効果、並びに、溶接熱影響部の耐食性向上効果が高まる。
溶接構造物の多くは、溶接後、塗装される。溶接部が外部に晒される場合は、溶接部周囲に、早期に赤錆が発生しやすいため、溶接部の耐食性を確保するためには、何らかの塗装処理を施されることが好ましい。溶接部周囲に電着塗装等で塗装を施した後、溶接部からの赤錆発生挙動を観察すると、Al濃度と塗装後の耐食性に相関性がある。塗装を施した場合、Al濃度が22%超えでも、十分な塗装後耐食性が溶接部には得られる。しかし、溶接部周囲からの赤錆発生挙動を確認すると、溶接部周囲からの赤錆発生抑制の観点から、Al濃度は22%以下とすることが好ましく、20%以下とすることより好ましい。塗装後耐食性に関しては、塗膜とのめっき層の金属部分との密着性が関連しており、Al濃度が低い方が、塗膜密着性に影響を及ぼす下地処理が有効に働くためと推定される。
MgZn2相は、Zn-Al-Mg合金層中に含有されると、Zn-Al-Mg合金層の耐食性が向上する。絶縁性に優れた金属間化合物相であるため、Zn相と比較すると耐食性が高い。また、構成元素としてMgを含有することから、Zn相より腐食電位が低く、犠牲防食性に優れ、溶接部周囲の耐食性を向上させる相としては好ましい。また、Mgは腐食過程で溶出すると、形成する腐食生成物をち密化する作用があり、赤錆抑制効果もZn相単独の腐食生成物より高く、白錆が長期に維持されることがある。
Al相は、0~3%前後のZnを固溶するα相(通常のα相)と、70%超え~85%のZn相(η相)を含有し、通常のα相とZn相(η相)とが微細に分離したβ相(通常のβ相)が該当する(図2、図5~図6参照)。
しかし、めっき凝固プロセスは、一般的に冷却速度が速く、状態図に従わない状態が起こり得る。例えば、めっき凝固プロセスでは、上記共析反応が完全に起こらず、高温安定相であるZnを0~85%含有したAl相がそのままZn過飽和固溶体として残存することが多い。
なお、図6中、21で示される領域(β相)のうち、白色を呈する領域がZn相で、黒色を示す領域がAl相である。
Al相のZn過飽和固溶体は、本来徐冷時(α相とη相が形成する際)には、最終的に存在しない相で、異常な成分のα相およびβ相のことである。
具体的には、α相のZn過飽和固溶体は、通常のα相とは異なり、Zn濃度3%超え~70%でZnを過飽和に固溶するAl相である。Zn過飽和固溶体のα相は、脆く、加工性を悪化させる相である。
β相のZn過飽和固溶体は、70%超え~85%のZn相(η相)を含有し、Zn濃度3%超え~70%でZnを過飽和に固溶するα相(α相のZn過飽和固溶体)とZn相(η相)とが微細に分離したAl相である。β相のZn過飽和固溶体のβ相も、α相のZn過飽和固溶体を含むため、脆く、加工性を悪化させる相である。
このように、Zn過飽和固溶体のAl相は、通常のα相とβ相の成分濃度と異なるAl相で、加工性を悪化させる相である。よって、本開示のAl相には該当しない。
まず、Al相(α相およびβ相)の特定は、めっき層の断面(めっき層厚さ方向に沿って切断した切断面)のSEM反射電子像を撮像する(図5及び図6参照)。
なお、Zn-Al-Mg合金層の断面におけるAl相(α相およびβ相)の面積分率を測定するには、各相の面積分率を測定するめっき層の断面(めっき層厚さ方向に沿って切断した切断面)と同じSEM反射電子像を使用する。
ただし、例示のため、図5および図6では、めっき層厚さ方向に沿って切断した切断面に対して4°傾斜して研磨しためっき層の傾斜(4°)研磨断面のSEM反射電子像を示している。
具体的には、SEM反射電子像の1000倍程度の拡大像(図5参照)で、Al相内部の成分分析を一定の面積(たとえば、1μm×1μm)範囲で定量分析し、Znを0~3%固溶したAl相であればα相(通常のα相)であると特定する。α相(通常のα相)の外周部に存在する相が、通常のα相とZn相(η相)に微細に分離したAl相であればβ相(通常のβ相)と特定する。
なお、Znを3%超え~70%過飽和固溶したAl相であれば、α相のZn過飽和固溶体と特定する。また、α相のZn過飽和固溶体とZn相(η相)とが微細に分離したAl相であれば、β相のZn過飽和固溶体と特定する。
この面積分率でMgZn2相およびAl相が存在すると、溶接の熱影響部500~1000℃の部分でZn-Al-Mg合金層が残存しやすくなって明らかな溶接部周囲の耐食性向上効果が確認できる。70%未満では、Zn-Al-Mg合金層の多くが蒸発してしまい、溶接部周囲の耐食性は劣位となる。
三元共晶組織には、Al相、Zn相、MgZn相が含まれている。それぞれの相の形状は、成分組成によって大きさが変化するために、形状は不定形である。しかし、共晶組織は、定温変態で、凝固時の元素移動が抑制されることから、各々の相が入り組んだ形状を形成し、通常、各相は微細に析出する(図7参照)。
通常、それぞれの相は、Zn相が大きく、島状を形成し、次いで、MgZn相が大きく、Zn相の隙間を充たし、Al相は、MgZn2相の間に斑点状に分散する構成をとることが多い。なお、成分組成によっては、構成する相は、変化しないが、島状に析出するものが、MgZn2相になる場合、Al相またはMgZn2相になる場合もあり、位置関係が凝固直前の成分変化に依存する。
なお、三元共晶組織の特定方法については後述する。
Zn相は、Zn-Al-Mg合金層中に少量存在してもよい(図2参照)。Zn相は、耐食性、犠牲防食性の観点からはZn-Al-Mg合金層に含有されることが好ましいが、溶接時には、LME、ブローホール形成の要因となり好ましくない。また、Zn層は、容易に蒸発することから、溶接熱影響部での耐食性はほとんど期待できない。従って、Zn相の含有量も管理することがよい。Zn濃度が高い場合、Zn相が形成しやすいが、Zn-Al-Mg合金層中で、Zn相の面積分率が10%以上となるとLME、ブローホール発生量が悪化しやすくなる。
ただし、溶接性の観点より、Zn相量が少ない方が好ましい傾向は変化しない。
このため、Zn相の面積分率は、好ましくは10%未満とし、より好ましくは5%以下とし、さらに好ましくは3%以下とする。ただし、Zn相の面積分率は、0%が理想であるが、製造上の点から、2%以上とすることがよい。
なお、めっき層の最終凝固部(420~380℃)がZn相となることが多いが、Zn相を減らすための成分調整、添加元素、さらには凝固方法を適用することにより、Zn相単相を出来る限り析出させないようにすることができる。
めっき層中にCaが含有されると、Zn-Al-Mg合金層にCa-Zn-Al金属間化合物相が形成することがある。これは本来Caが、AlおよびZnと金属間化合物相(CaZn2相、CaZn5相、CaZn11相、Al4Ca相等)を形成しやすいためである。Ca濃度が高い場合は、Caが非常に偏析しやすい元素であるため、結合する金属間化合物相は、このうちの一種に定まらない。Ca-Zn-Al金属間化合物相は溶接時、溶接部裏面でCaO酸化物を形成し、Al-Fe合金層上で密着性の高い酸化物層を形成する。酸化物層の形成により、溶接部裏面の耐食性が向上する。
なお、もともと、Zn相の含有率の低いめっき層に、Ca-Zn-Al金属間化合物相を粗大化するような処理をした場合は、LMEおよびブローホール形成の改善効果は確認しづらい傾向にある。
つまり、平均結晶粒径1μm以上のCa-Zn-Al金属間化合物相がZn-Al-Mg合金層に存在すると、溶接部裏面の耐食性向上効果、並びに、LMEおよびブローホールの形成の抑制効果が高まる。なお、Ca-Zn-Al金属間化合物相の平均結晶粒径の上限値は、特に制限はないが、例えば、100μm以下である。
特に、Ca-Zn-Al-Si金属間化合物相は、Ca-Zn-Al金属間化合物相と同様の効果(溶接部裏面の耐食性向上効果、並びにLMEおよびブローホール形成の改善効果)がある。それに加え、Ca-Zn-Al-Si金属間化合物相が存在すると、溶接後、Al-Fe合金層上に残存する酸化物層中にSiが含まれることになるため、溶接部裏面の耐食性向上効果が高まる。
特に、平均結晶粒径1μm以上(又は1~100μm)のCa-Zn-Al-Si金属間化合物相がZn-Al-Mg合金層が存在すると、Ca-Zn-Al-Si金属間化合物相と同様に、溶接部裏面の耐食性向上効果、並びに、LMEおよびブローホールの形成の抑制効果が高まる。
Zn-Al-Mg合金層中に、このCa-Al-B金属間化合物相を含有すると、LMEが改善するため好ましい。
Zn-Al-Mg合金層中に、この金属間化合物相を含有すると、溶接部周囲の耐食性が向上する。
まず、めっき浴に浸漬した時、直ちにAl-Fe合金層が形成した後、冷却過程で凝固点を下回ると最初に、融点の高い金属間化合物(Mg2Si相、Ca2Si相、CaSi相、Ca-Zn-Al金属間化合物相、Ca-Al-B金属間化合物相等)が直ちに析出する。これらの相量は合計でも5%に満たない相量であるため、めっき浴の融点直下では、Zn-Al-Mg合金層の大半は液相状態にある。
液相からは、MgZn2相、Al相、Zn相が析出するが、ここで上記のような一般的なめっき凝固プロセスをとると、冷却速度が大きいため、状態図に依存せず、液相が低温度まで維持されて、Zn-Al-MgZn2三元共晶組織が形成するか、Zn相が多く析出することになる。急冷時には、Al相のZn過飽和固溶体(通常のα相とβ相の成分濃度と異なるAl相)が多くを占める。結果として、好ましくない組織が増える。
この温度範囲では、Al-MgZn2相の共晶反応(Al相の方がやや早く晶出するため包晶反応ともいえる)によって凝固する。また、Al-MgZn2相量が極大化すれば、同時にZn相量を極小値化できる。
よって、本開示のめっき層(つまりZn-Al-Mg合金層)の組織を実現するには、めっき浴温(めっき浴の融点+20℃)とし、めっき処理後(めっき浴から鋼材を引き上げ後)、420℃以上での保持時間を5秒超えとする。つまり、420℃以上での保持時間を5秒超えとすることで、MgZn2相およびAl相の析出時間を十分確保でき、Zn相、Zn-Al-MgZn2三元共晶組織、又はAl相のZn過飽和固溶体(通常のα相とβ相の成分濃度と異なるAl相)の析出が低減される。
具体的には、めっき浴温(めっき浴の融点+20℃)とし、めっき処理後(めっき浴から鋼材を引き上げ後)、めっき浴の融点から420℃までの冷却速度を5℃/秒以下とし、420℃以上での保持時間を5秒超えとする。ただし、めっき浴の融点が500℃以上の場合、めっき浴の融点から420℃までの冷却速度は10℃/秒以下であっても、MgZn2相およびAl相の析出時間が十分であり問題がない。
420℃以上での保持時間が5秒未満では、Zn相、Zn-Al-MgZn2三元共晶組織、又はAl相のZn過飽和固溶体の形成が増加する。
平均冷却速度が10℃/秒未満は、ややZn相量が増加する傾向にあり溶接性に好ましくない。一方、平均冷却速度が20℃/秒以上はAl相のZn過飽和固溶体が形成する傾向がある。
なお、420℃から250℃までの温度範囲)の平均冷却速度を上記範囲とする温度処理は、特に、Al濃度が低く、Zn濃度が高い場合に有効な手段である。
まず、地鉄(鋼材)の腐食を抑制するインヒビターを含有した酸でめっき層を剥離溶解した酸液を得る。次に、得られた酸液をICP分析で測定することで、めっき層の化学組成(めっき層がZn-Al-Mg合金層の単層構造の場合、Zn-Al-Mg合金層の化学組成、めっき層がAl-Fe合金層及びZn-Al-Mg合金層の積層構造の場合、Al-Fe合金層及びZn-Al-Mg合金層の合計の化学組成)を得ることができる。酸種は、めっき層を溶解できる酸であれば、特に制限はない。なお、化学組成は、平均化学組成として測定される。
Zn-Al-Mg合金層の表面からのX線回折によって、Zn-Al-Mg合金層の各相を同定すればよい。X線回折の強度は、線源には、Cu、Co等用いることが可能だが、最終的にはCu線源に合わせた回折角度に計算、変更する必要がある。測定範囲は、5°~90°、ステップは、0.01°程度が好ましい。特定の回折角度での強度(cps)を得るためには、前後±0.05°の平均値を得る。添加成分が微量な場合は、添加元素に関わる金属間化合物が検出できない場合があるため、Zn-Al-Mg合金層からTEMサンプルを作製し、微小金属間化合物を探して、電子回折像から同定を行うと良い。
なお、倍率1000倍のSEMの反射電子像では、Zn-Al-MgZn2三元共晶組織中に存在する「MgZn2相、Al相およびZn相」は境界・面積分率識別できない。つまり、ここで、求める「MgZn2相、Al相およびZn相の各面積分率」は、後述するZn-Al-MgZn2三元共晶組織中に存在する「MgZn2相、Al相およびZn相」を除く各面積分率である。
ただし、10000倍を程度の拡大像では、三元共晶組織であっても個別の面積分率を求めることができるため、下記、画像処理の条件に従って、三元共晶中の各相の割合を算出することが可能である。
原子番号の小さいSiを含む金属間化合物相(Ca-Zn-Al-Si金属間化合物等)も、コントラストで暗く、比較的容易に識別することができる。
原子番号が小さいBを含む金属間化合物相(Ca-Al-B金属間化合物相等)も、Siを含む金属間化合物相と同様に、コントラストで暗く、比較的容易に識別することができる。判別が難しい場合は、TEMによる電子線回折を実施する。
上記各相の面積分率を測定するときのSEM観察において、確認された各化合物相のうち、上位5個の結晶粒径を持つ各化合物相を選択する。そして、この操作を5視野分行い、計25個の結晶粒径の算術平均を、Ca-Zn-Al金属間化合物相およびCa-Zn-Al-Si金属間化合物相の各平均結晶粒径とする。
そして、三元共晶組織の面積分率は、Zn-Al-Mg合金層の任意の断面(Zn-Al-Mg合金層厚み方向に切断した断面)の少なくとも3視野以上において、上記操作により求めた各相の面積分率の平均値とする。
表1-1~1-3に示す化学組成のめっき層が得られるように、所定量の純金属インゴットを使用して、大気中、真空溶解炉でめっき浴を建浴した。めっき鋼板の作製には、バッチ式溶融めっき装置を使用した。
なお、いずれのめっき原板も、めっき浴への浸漬時間は0.2秒とした。N2ガスワイピング圧力を調整し、めっき厚みが20μm(±1μm)となるようにめっき鋼板を作製した。めっき浴浸漬から、ワイピング完了までは、バッチ式めっき装置を高速運転し、1秒以内に完了し、ただちにN2ガスを吹き付け、めっき融点まで温度を降下させた。
得られためっき鋼板から、めっき層の断面(めっき層の厚み方向に沿って切断した断面)を有する試料片を切り出した。そして、既述の方法にしたがって、Zn-Al-Mg合金層に存在する下記相の面積分率を測定した。
・MgZn2相の面積分率
・Al相の面積分率
・Zn相の面積分率
・Zn-Al-MgZn2三元共晶組織(表中「三元共晶組織」と表記)の面積分率
・Ca-Al-B金属間化合物相(表中「B化合物」と表記)の面積分率:Al2CaB5相、および、Al2CaB5相の一部の原子位置がZn及びMgで置換された化合物相の合計の面積分率
・MgとSn、Bi又はInとの金属間化合物相(表中「Sn化合物相」と表記):Mg2Sn相、Mg3Bi2相及びMg3In相の合計の面積分率
・その他の金属間化合物の面積分率:Mg2Si相、Ca2Si相、CaSi相、Ca-Zn-Al金属間化合物相(表中「CZA」と表記)、及びCa-Zn-Al-Si金属間化合物相(表中「CZAS」と表記)の合計の面積分率(ただし、各相の面積分率は示さず、存在が確認された相を「Ex」と表記した。)
得られためっき鋼板を用いて、めっき層のアーク溶接性の評価を次の通り実施した。
100mm角のサンプルを2枚用意し、CO2/MAG溶接機で重ねすみ肉溶接サンプルを作製した。めっき鋼板一端10mmを重ね幅、互いのめっき鋼板の重ね隙間は0mm、下板脚長6mm程度でアーク溶接を実施した。溶接速度、0.3m/min、溶接ワイヤーはソリッドワイヤーYGW14、φ12、CO2シールドガス流量、15l/min、溶接電流は150~250(A)、アーク電圧は20~24V、2passとした。溶接ビードかを上側からX線透過試験を実施してブローホールの占有率Bs(%)を求めた。
得られためっき鋼板を用いて、LMEの評価を次の通り実施した。
めっき鋼板70mm×150mm中央に、ステンレス鋼溶接ワイヤφ1.2mm(JIS Z3323 YF309LC)で上記溶接条件(ただし、1pass)に従い、75mm長、3~5mm幅のビードオンプレート溶接したビードオンプレート試験片を得た。その後、試験片に対して浸透探傷試験により割れの有無を確認した。
そこで、目視で確認できる5mm以上のLMEが確認された場合は「B」評価とした。
溶接部(溶接金属)にLMEはなく、溶接金属、溶接熱影響部(HAZ部)境界に周長5%未満の長さでマーカー跡が確認されたが、亀裂断面をEPMA観察した結果、亀裂周囲にZnは確認されなかった場合は「A」評価とした。
溶接部周囲(溶接金属の周囲)に亀裂がなく、マーカー跡がなかったものは「S」評価とした。
得られためっき鋼板を用いて、溶接部裏面の耐食性を次の通り実施した。
LMEの評価と同様にビードオンプレート試験片を得た。この試験片の裏面を腐食促進試験(JASO M 609-91)にて、90~180サイクルでビード裏面部の赤錆を評価した。Zn-Al-Mg系めっき鋼板では、90サイクルで、ビード裏面上に点錆が発生した。Znめっき鋼板では全面赤錆となった。
120サイクルでビード裏面部に点状の赤錆が確認されたものを「A」評価とした。
150サイクルでビード裏面部に点状の赤錆が確認されたものを「AA」評価とした。
180サイクルでビード裏面部に点状の赤錆が確認されたものを「AAA」評価とした。
180サイクルでビード裏面部に赤錆発生がなかったものは「S」評価とした。
得られためっき鋼板を用いて、溶接部周囲の耐食性を次の通り実施した。
LMEの評価と同様にビードオンプレート試験片を得た。この試験片の表面を塩水噴霧試験(JIS Z 2371)に1000~1300時間供して、耐食性を確認した。
Zn-Al-Mg系めっき鋼板では、1000時間経過時点で、溶接部周囲から赤錆垂れが確認された。Znめっき鋼板では全面赤錆となった。
1100時間経過時点で溶接部周囲に点状の赤錆が確認されたものを「A」評価とした。
1200時間経過時点で溶接部周囲に点状の赤錆が確認されたものを「AA」評価とした。
1300時間経過時点で溶接部周囲に点状の赤錆が確認されたものを「AAA」評価とした。
1300時間経過時点で溶接部周囲に赤錆が確認されなかったものを「S」評価とした。
得られためっき鋼板を用いて、めっき層の加工性の評価を次の通り実施した。
めっき鋼板に対して10R-90°V曲げプレス試験を実施し、V曲げ谷部に巾24mmのセロハンテープを押し当てて引き離し、目視でパウダリングを判断した。
パウダリング剥離しなかったものは「A」評価とした
表2-1に示す化学組成のめっき層が得られるように、所定量の純金属インゴットを使用して、大気中、真空溶解炉でめっき浴を建浴した。めっき鋼板の作製には、バッチ式溶融めっき装置を使用した。
なお、いずれのめっき原板も、めっき浴への浸漬時間は0.2秒とした。N2ガスワイピング圧力を調整し、めっき厚みが20μm(±1μm)となるようにめっき鋼板を作製した。めっき浴浸漬から、ワイピング完了までは、バッチ式めっき装置を高速運転し、1秒以内に完了し、ただちにN2ガスを吹き付け、めっき浴の融点まで温度を降下させた。
めっき浴温はめっき浴の融点+20℃とした。めっき原板をめっき浴から引き上げ後、めっき浴の融点直上でワイピングを完了した。めっき浴の融点から420℃までの平均冷却速度を4(±1)℃/秒(420℃以上での保持時間は5秒超)とし、420℃から250℃までの平均冷却速度を15(±5)℃/秒とする冷却プロセスでめっき層を得た。
実施例Aで実施したLMEの評価と同様にビードオンプレート試験片を作製した。この試験片に対して、日本パーカライジング株式会社製の表面調整処理剤(商品名:プレパレンX)を用いて、表面調整を室温で20秒間行った。
次に、日本パーカライジング株式会社製のりん酸亜鉛処理液(商品名:パルボンド3020)を用いて、りん酸塩処理を行った。具体的には、処理液の温度を43℃とし、熱間プレス鋼材を処理液に120秒間浸漬した。これにより、鋼材表面にりん酸塩被膜が形成された。
次に、リン酸塩処理を実施した後、りん酸処理後のビードオンプレート試験片に対して、日本ペイント株式会社製のカチオン型電着塗料を、電圧160Vのスロープ通電で電着塗装し、更に、焼き付け温度170℃で20分間焼き付け塗装した。電着塗装後の塗料の膜厚の平均は、いずれの試料についても15μmとした。
次に、おの試験片をJASO試験(M609-91)に供して、塗装後のビード部周囲の赤錆発生状況を確認した。
120サイクル以内でビード部もしくは熱影響部に点状の赤錆が確認されたものを「A」評価とした。
150サイクル以内でビード部もしくは熱影響部に点状の赤錆が確認されたものを「AA」評価とした。
180サイクル以内でビード部もしくは熱影響部に点状の赤錆が確認されたものを「AAA」評価とした。
1 :Al相(微細Zn相を含む。)
2 :MgZn2相(塊状)
3 :Zn-Al-MgZn2三元共晶組織
4 :MgZn2相(塊状)
5 :Al相(α相)
6 :Al相(β相)
7 :Zn相
8 :Ca-Al-B金属間化合物相B化合物(Al2CaB5相:原子比率はEDS定量分析による推定)
9 :Zn-Al-MgZn2三元共晶組織のZn相
10:Zn-Al-MgZn2三元共晶組織のMgZn2相
11:Zn-Al-MgZn2三元共晶組織のAl相
20:α相(通常のα相)
21:β相(通常のβ相)
100 :めっき層
100A:めっき層
101 :Zn-Al-Mg合金層
101A:Zn-Al-Mg合金層
102 :Al-Fe合金層
102A:Al-Fe合金層
(付記1)
鋼材と、前記鋼材の表面に配されたZn-Al-Mg合金層を含むめっき層とを備えた溶融めっき鋼板であって、
前記Zn-Al-Mg合金層の任意の断面組織において、相当円直径で結晶粒径1μm以上のMgZn2相とAl相の合計の面積率が70%以上であり、Zn相の面積率が10%未満であり、
前記Zn-Al-Mg合金層が、Mg2Si相、Ca2Si相、CaSi相、Ca-Zn-Al相、及びCa-Zn-Al-Si相からなる群より選ばれる少なくとも1種の金属間化合物相を含有し、
前記めっき層が、質量%で、
Zn:44.9%超~74.9%未満、
Al:20%超~35%未満、
Mg:5%超~20%未満、
Ca:0.1%~3.0%未満、
Si:0%~1%、
B:0%~0.5%、
Y:0%~0.5%、
La:0%~0.5%、
Ce:0%~0.5%、
Cr:0%~0.25%、
Ti:0%~0.25%、
Ni:0%~0.25%、
Co:0%~0.25%、
V:0%~0.25%、
Nb:0%~0.25%、
Cu:0%~0.25%、
Mn:0%~0.25%、
Sr:0%~0.5%、
Sb:0%~0.5%、
Pb:0%~0.5%、
Sn:0%~20%、
Bi:0%~2%、
In:0%~2%、
Fe:0%~5%、及び
不純物からなり、元素群AをY、La及びCe、元素群BをCr、Ti、Ni、Co、V、Nb、Cu及びMn、元素群CをSr、Sb及びPb、並びに元素群DをSn、Bi及びInとした場合、元素群Aから選ばれる元素の合計の含有量が0.5%以下、Caと元素群Aから選ばれる元素との合計の含有量が3.0%未満、元素群Bから選ばれる元素の合計の含有量が0.25%以下、元素群Cから選ばれる元素の合計の含有量が0.5%以下、元素群Dから選ばれる元素の合計の含有量が20%以下である溶融めっき鋼板。
前記Alが22%超~35%未満であり、前記Mgが10%超~20%未満であり、前記Caが0.3%~3.0%未満であり、前記Siが0.1%~1%である付記1に記載の溶融めっき鋼板。
前記めっき層が、B、元素群A(Y、La、Ce)、元素群B(Cr、Ti、Ni、Co、V、Nb、Cu、Mn)、及び元素群C(Sr、Sb、Pb)からなる群より選ばれる少なくとも1種を含有し、前記めっき層が、質量%で、
Bを含有する場合は、B:0.05%~0.5%、
元素群Aから選ばれる元素を含有する場合は、その合計の含有量が0.05%~0.5%、
元素群Bから選ばれる元素を含有する場合は、その合計の含有量が0.05%~0.25%、
元素群Cから選ばれる元素を含有する場合は、その合計の含有量が0.05%~0.5%を満たす付記1又は付記2に記載の溶融めっき鋼板。
前記Zn-Al-Mg合金層が、Al2CaB5、又は一部の原子位置がZn及びMgで置換されたCa-Al-B化合物であってBが原子%で40%以上のCa-Al-B化合物を含有する付記1~付記3のいずれか1項に記載の溶融めっき鋼板。
前記めっき層が、元素群D(Sn、Bi、In)から選ばれる少なくとも1種の元素を含有し、前記めっき層が、質量%で、
Sn+Bi+In=0.05%~20%
を満たし、前記めっき層が、Mg2Sn、Mg3Bi2及びMg3Inからなる群より選択される少なくとも1種の金属間化合物をさらに含有する付記1~付記4のいずれか1項に記載の溶融めっき鋼板。
前記めっき層がAl-Fe合金層をさらに含み、前記Al-Fe合金層が前記鋼材の表面に形成され、前記Zn-Al-Mg合金層が前記Al-Fe合金層上に形成された付記1~付記5のいずれか1項に記載の溶融めっき鋼板。
本明細書に記載された全ての文献、特許出願、および技術規格は、個々の文献、特許出願、および技術規格が参照により取り込まれることが具体的かつ個々に記された場合と同程度に、本明細書中に参照により取り込まれる。
Claims (8)
- 鋼材と、前記鋼材の表面に配され、Zn-Al-Mg合金層を含むめっき層と、を有するめっき鋼材であって、
前記Zn-Al-Mg合金層の断面において、MgZn2相の面積分率が45~75%、MgZn2相およびAl相の合計の面積分率が70%以上、かつZn-Al-MgZn2三元共晶組織の面積分率が0~5%であり、
前記めっき層が、質量%で、
Zn:44.90%超~79.90%未満、
Al:15%超~35%未満、
Mg:5%超~20%未満、
Ca:0.1%~3.0%未満、
Si:0%~1.0%、
B :0%~0.5%、
Y :0%~0.5%、
La:0%~0.5%、
Ce:0%~0.5%、
Cr:0%~0.25%、
Ti:0%~0.25%、
Ni:0%~0.25%、
Co:0%~0.25%、
V :0%~0.25%、
Nb:0%~0.25%、
Cu:0%~0.25%、
Mn:0%~0.25%、
Sr:0%~0.5%、
Sb:0%~0.5%、
Pb:0%~0.5%、
Sn:0%~20.00%、
Bi:0%~2.0%、
In:0%~2.0%、
Fe:0%~5.0%、及び
不純物からなり、
元素群AをY、La及びCe、元素群BをCr、Ti、Ni、Co、V、Nb、Cu及びMn、元素群CをSr、Sb及びPb、並びに元素群DをSn、Bi及びInとした場合、
前記元素群Aから選ばれる元素の合計の含有量が0%~0.5%であり、
Caと前記元素群Aから選ばれる元素との合計の含有量が0.1%~3.0%未満であり、
前記元素群Bから選ばれる元素の合計の含有量が0%~0.25%であり、
前記元素群Cから選ばれる元素の合計の含有量が0%~0.5%であり、
前記元素群Dから選ばれる元素の合計の含有量が0%~20.00%である化学組成を有するめっき鋼材。 - 前記Zn-Al-Mg合金層が、Mg2Si相、Ca2Si相、CaSi相、Ca-Zn-Al金属間化合物相、及びCa-Zn-Al-Si金属間化合物相よりなる群から選ばれる少なくとも1種の金属間化合物相を含有する請求項1に記載のめっき鋼材。
- 前記Alの含有量が22%超~35%未満であり、前記Mgの含有量が10%超~20%未満であり、前記Caの含有量が0.3%~3.0%未満であり、前記Siの含有量が0.1%~1.0%である請求項1又は請求項2に記載のめっき鋼材。
- 前記Alの含有量が15%超~22%である請求項1又は請求項2に記載のめっき鋼材。
- 前記めっき層が前記Bを含有する場合、前記Bの含有量は質量%で0.05%~0.5%であり、
前記めっき層が前記元素群Aから選ばれる元素を含有する場合、前記元素群Aから選ばれる元素の合計の含有量は質量%で0.05%~0.5%であり、
前記めっき層が前記元素群Bから選ばれる元素を含有する場合、前記元素群Bから選ばれる元素の合計の含有量は質量%で0.05%~0.25%であり、
前記めっき層が前記元素群Cから選ばれる元素を含有する場合、前記元素群Cから選ばれる元素の合計の含有量は質量%で0.05%~0.5%である請求項1~請求項3のいずれか1項に記載のめっき鋼材。 - 前記Zn-Al-Mg合金層が、Al2CaB5相、および、前記Al2CaB5相の一部の原子位置がZn及びMgで置換された化合物相よりなる群から選択されるCa-Al-B金属間化合物相であって、Bが原子%で40%以上のCa-Al-B金属間化合物相を含有する請求項1~請求項5のいずれか1項に記載のめっき鋼材。
- 前記めっき層が前記元素群Dから選ばれる元素を含有する場合、前記元素群Dから選ばれる元素の合計の含有量は質量%で0.05%~20%であり、
前記Zn-Al-Mg合金層が、Mg2Sn相、Mg3Bi2相及びMg3In相からなる群より選択される少なくとも1種の金属間化合物相を含有する請求項1~請求項6のいずれか1項に記載のめっき鋼材。 - 前記めっき層が、前記鋼材と前記Zn-Al-Mg合金層との間にAl-Fe合金層を有する請求項1~請求項7のいずれか1項に記載のめっき鋼材。
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NZ756382A NZ756382B2 (en) | 2017-01-27 | 2018-01-26 | Plated steel |
PL18744355.1T PL3575434T3 (pl) | 2017-01-27 | 2018-01-26 | Wyrób stalowy z powłoką metaliczną |
BR112019015349-7A BR112019015349B1 (pt) | 2017-01-27 | 2018-01-26 | Produto de aço revestido metálico |
US16/480,976 US11555235B2 (en) | 2017-01-27 | 2018-01-26 | Metallic coated steel product |
SG11201906851UA SG11201906851UA (en) | 2017-01-27 | 2018-01-26 | Metalic coated steel product |
JP2018522695A JP6365807B1 (ja) | 2017-01-27 | 2018-01-26 | めっき鋼材 |
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MX2019008677A MX2019008677A (es) | 2017-01-27 | 2018-01-26 | Producto de acero con recubrimiento metalico. |
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MYPI2019004275A MY194750A (en) | 2017-01-27 | 2018-01-26 | Metallic coated steel product |
PH12019501700A PH12019501700A1 (en) | 2017-01-27 | 2019-07-24 | Metallic coated steel product |
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EP4023787A4 (en) * | 2019-08-29 | 2022-10-12 | Nippon Steel Corporation | HOT STAMPING MOLDED BODY |
JPWO2021039973A1 (ja) * | 2019-08-29 | 2021-03-04 | ||
JP7248930B2 (ja) | 2019-08-29 | 2023-03-30 | 日本製鉄株式会社 | ホットスタンプ成形体 |
WO2021039973A1 (ja) * | 2019-08-29 | 2021-03-04 | 日本製鉄株式会社 | ホットスタンプ成形体 |
JPWO2021171519A1 (ja) * | 2020-02-27 | 2021-09-02 | ||
KR20220127890A (ko) | 2020-02-27 | 2022-09-20 | 닛폰세이테츠 가부시키가이샤 | 도금 강재 |
JP7277857B2 (ja) | 2020-02-27 | 2023-05-19 | 日本製鉄株式会社 | ホットスタンプ成形体 |
JPWO2021171517A1 (ja) * | 2020-02-27 | 2021-09-02 | ||
US11692249B2 (en) | 2020-02-27 | 2023-07-04 | Nippon Steel Corporation | Hot stamped body |
JPWO2021171515A1 (ja) * | 2020-02-27 | 2021-09-02 | ||
JP7277858B2 (ja) | 2020-02-27 | 2023-05-19 | 日本製鉄株式会社 | ホットスタンプ成形体 |
KR20220142517A (ko) | 2020-02-27 | 2022-10-21 | 닛폰세이테츠 가부시키가이샤 | 핫 스탬프 성형체 |
KR20220142518A (ko) | 2020-02-27 | 2022-10-21 | 닛폰세이테츠 가부시키가이샤 | 핫 스탬프 성형체 |
KR20220143744A (ko) | 2020-02-27 | 2022-10-25 | 닛폰세이테츠 가부시키가이샤 | 핫 스탬프 성형체 |
JP7277856B2 (ja) | 2020-02-27 | 2023-05-19 | 日本製鉄株式会社 | ホットスタンプ成形体 |
US11807940B2 (en) | 2020-02-27 | 2023-11-07 | Nippon Steel Corporation | Plated steel material |
JP7464849B2 (ja) | 2020-10-21 | 2024-04-10 | 日本製鉄株式会社 | めっき鋼材、およびめっき鋼材の製造方法 |
US11814732B2 (en) | 2021-09-07 | 2023-11-14 | Nippon Steel Corporation | Hot-dip plated steel |
JP7056811B1 (ja) * | 2021-09-07 | 2022-04-19 | 日本製鉄株式会社 | 溶融めっき鋼材 |
WO2023037396A1 (ja) * | 2021-09-07 | 2023-03-16 | 日本製鉄株式会社 | 溶融めっき鋼材 |
JP7328611B1 (ja) | 2021-10-26 | 2023-08-17 | 日本製鉄株式会社 | めっき鋼板 |
WO2023074088A1 (ja) * | 2021-10-26 | 2023-05-04 | 日本製鉄株式会社 | めっき鋼板 |
JP7328607B1 (ja) | 2022-01-31 | 2023-08-17 | 日本製鉄株式会社 | 溶接継手 |
WO2023145823A1 (ja) * | 2022-01-31 | 2023-08-03 | 日本製鉄株式会社 | 溶接継手 |
WO2023145822A1 (ja) * | 2022-01-31 | 2023-08-03 | 日本製鉄株式会社 | めっき鋼板 |
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PH12019501700A1 (en) | 2020-06-15 |
MX2019008677A (es) | 2019-11-08 |
EP3575434B1 (en) | 2022-11-30 |
EP3575434A4 (en) | 2020-07-01 |
TWI664315B (zh) | 2019-07-01 |
NZ756382A (en) | 2021-01-29 |
US11555235B2 (en) | 2023-01-17 |
MY194750A (en) | 2022-12-15 |
TW201835359A (zh) | 2018-10-01 |
JP6365807B1 (ja) | 2018-08-01 |
ES2936660T3 (es) | 2023-03-21 |
JPWO2018139620A1 (ja) | 2019-01-31 |
PT3575434T (pt) | 2023-01-10 |
EP3575434A1 (en) | 2019-12-04 |
KR102240878B1 (ko) | 2021-04-15 |
CN110234780A (zh) | 2019-09-13 |
AU2018211811A1 (en) | 2019-08-22 |
KR20190104619A (ko) | 2019-09-10 |
BR112019015349B1 (pt) | 2023-03-14 |
US20200002798A1 (en) | 2020-01-02 |
SG11201906851UA (en) | 2019-08-27 |
CN110234780B (zh) | 2021-09-07 |
BR112019015349A2 (pt) | 2020-03-10 |
AU2018211811B2 (en) | 2021-03-11 |
PL3575434T3 (pl) | 2023-02-27 |
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