WO2018131171A1 - めっき鋼材 - Google Patents
めっき鋼材 Download PDFInfo
- Publication number
- WO2018131171A1 WO2018131171A1 PCT/JP2017/001286 JP2017001286W WO2018131171A1 WO 2018131171 A1 WO2018131171 A1 WO 2018131171A1 JP 2017001286 W JP2017001286 W JP 2017001286W WO 2018131171 A1 WO2018131171 A1 WO 2018131171A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- phase
- plating
- steel material
- layer
- intermediate layer
- Prior art date
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
-
- 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
- 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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/10—Alloys based on aluminium with zinc as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/02—Alloys based on magnesium with aluminium as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/04—Alloys based on magnesium with zinc or cadmium as the next major constituent
-
- 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
- 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
-
- 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
- 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
- C23C2/12—Aluminium or alloys based thereon
-
- 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
- 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
-
- 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
- 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
- C23C28/027—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 matrix material comprising a mixture of at least two metals or metal phases or metal matrix composites, e.g. metal matrix with embedded inorganic hard particles, CERMET, MMC.
-
- 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
- C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
-
- 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
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/24—Nitriding
- C23C8/26—Nitriding of ferrous surfaces
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C2200/00—Crystalline structure
- C22C2200/06—Quasicrystalline
Definitions
- This disclosure relates to plated steel materials.
- Zn-based plated steel materials are used as steel materials of various shapes such as fences, corrugated pipes, drainage groove covers, flying sand prevention plates, bolts, wire mesh, guardrails, water barriers, etc. Yes.
- the Zn-based plated layer of the Zn-based plated steel material is exposed to a severe corrosive environment in addition to the protective action of preventing the rust (steel material) from corrosion. Therefore, in addition to corrosion resistance, the Zn-based plating layer is required to have impact resistance and wear resistance for protecting the ground iron from flying objects, earth and sand, and the like.
- Patent Document 1 Patent Document 2, Patent Document 3 and the like have proposed Zn—Al—Mg based immersion plated steel materials. Inclusion of a small amount of Mg in the Zn—Al-based alloy plating layer increases the corrosion resistance and provides a long-term antirust effect. In general, when the Al content is less than 20% by mass, the Zn—Al-based plating layer is weak against scratches, impacts, etc. and easily wears because the main component of the plating layer is a soft Zn phase or Al phase. . On the other hand, the Zn—Mg—Al-based alloy plating layer containing Mg is hardened, so that it is advantageous in terms of impact resistance and wear resistance.
- Patent Document 4 a technique for extending the life of the plated steel material by increasing the thickness of the intermediate layer (Al—Fe alloy layer) in the Zn—Al—Mg-based immersion plated steel material has also been developed. Since the intermediate layer (Al—Fe alloy layer) is hard, the total thickness of the immersion plating layer is increased, so that the impact resistance and wear resistance are high, and in terms of protecting the base iron (steel material). It becomes even more advantageous.
- Patent Document 5 also proposes a Zn—Mg—Al alloy hot dipped steel material containing a large amount of Mg in the Zn—Mg—Al alloy plating layer. Since this hot-dip plated steel material contains a large amount of Mg, the plating layer contains many intermetallic compounds and is hardened, and has high corrosion resistance and wear resistance.
- Patent Document 1 Japanese Patent Application Laid-Open No. 9-256134 Patent Document 2: Japanese Patent Application Laid-Open No. 11-117052 Patent Document 3: Japanese Patent Application Laid-Open No. 2010-70810 Patent Document 4: Japanese Patent Application Laid-Open No. 2015-40334 Patent Document 5: Japanese Patent No. 5785336
- the plated layer of the plated steel material is required to have impact resistance and wear resistance for protecting the base iron from flying objects, earth and sand, and the like.
- the thickness and structure of the Zn—Al—Mg alloy plating layer could not be ensured. Therefore, only immersion plating is performed in a range in which the Mg concentration component that adversely affects immersion plating properties is limited (specifically, a range in which the Mg content is limited to 5% by mass or less). In order to ensure sufficient plating layer thickness and adhesion, a two-step plating method is used.
- the current conditions are that the immersion-plated steel materials described in Patent Documents 1 to 3 do not have sufficient corrosion resistance, impact resistance, and wear resistance.
- the hot dip plated steel material described in Patent Document 5 has high corrosion resistance and wear resistance, it contains a large amount of Mg, and therefore has a low reactivity with the base iron (steel material) when forming the plating layer. (Al—Fe alloy layer) is not formed, or the intermediate layer (Al—Fe alloy layer) is difficult to be thickened. Therefore, the thickness of the plating layer tends to be small and the impact resistance tends to be low. When a crack occurs in the plating layer due to the impact, it immediately reaches the steel (base metal) and the plating layer easily peels off. In addition, once scratches or cracks occur in the plating layer due to flying objects, earth and sand, etc., the corrosion is likely to proceed and the corrosion resistance is reduced at present.
- one aspect of the present disclosure has been made in view of the above-described background, and a plated steel material having high corrosion resistance, impact resistance, and wear resistance, and having high corrosion resistance after scratches or cracks are generated in the plating layer.
- the issue is to provide.
- the element symbol indicates the content of each element in mass%.
- the sea part is composed of an Al 5 Fe 2 phase as the Al—Fe alloy phase
- the island part is composed of a quasicrystalline phase and MgZn 2 phase as the Zn—Mg—Al alloy phase, or is composed of a quasicrystalline phase, MgZn 2 phase and Mg phase as the Zn—Mg—Al alloy phase.
- ⁇ 4> The plated steel material according to any one of claims 1 to 3, wherein a ratio of the thickness of the intermediate layer to the thickness of the plating layer is 0.2 to 4 times.
- the Mg content of the plating layer is 15% by mass or more, and the Mg content of the Zn—Mg—Al alloy phase is 15% by mass or more.
- ⁇ 1> to ⁇ 4> Plated steel.
- ⁇ 6> The plated steel material according to any one of ⁇ 1> to ⁇ 5>, wherein the plating layer is an immersion plating layer.
- a plated steel material that has high corrosion resistance, impact resistance, and wear resistance, and also has high corrosion resistance after scratches or cracks occur in the plating layer.
- 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.
- “%” indicating the content of the composition (element) means “% by mass”.
- the plated steel material according to the embodiment includes a steel material, a plated layer coated on the surface of the steel material, and an intermediate layer interposed between the steel material and the plated layer (see FIGS. 1 and 2).
- the plating layer contains, by mass%, Mg: 8 to 50%, Al: 2.5 to 70.0%, Ca: 0.30 to 5.00%, with the balance being Zn and impurities.
- the intermediate layer has a sea-island structure composed of a sea part composed of an Al—Fe alloy phase and an island part containing a Zn—Mg—Al alloy phase with an Mg content of 8% or more, and Al—Fe The area fraction of the sea part composed of the alloy phase is 55 to 90%.
- 1 is a plating layer
- 2 is an intermediate layer
- 3 is a steel material
- 4 is a plating steel material
- the plated steel material according to the embodiment has high corrosion resistance, impact resistance, and wear resistance due to the above configuration, and also has high corrosion resistance after scratches or cracks are generated in the plating layer.
- the plated steel material which concerns on embodiment was discovered based on the knowledge shown below.
- the inventors have made a Zn—Mg—Al alloy plating bath (hereinafter referred to as “high high”) containing Mg at a high concentration of 8% or more.
- high high Zn—Mg—Al alloy plating bath
- An example of immersion plating using “concentration Mg plating bath” was studied.
- the plating layer formed by immersion plating using a high concentration Mg plating bath contains Mg at a high concentration of 8% or more. Therefore, the corrosion resistance of the plating layer is increased. In addition, since the plating layer itself is hard, the impact resistance and wear resistance of the plating layer are also increased. However, at the time of immersion plating, the alloying reactivity of Al and Fe (that is, the reactivity of the plating component Al and the iron base (steel) component Fe: hereinafter, this reaction is also referred to as “Al-Fe reaction”). ) Tends to be suppressed, and it is difficult to increase the thickness of the intermediate layer. Therefore, the impact resistance of the plating layer is low, and the plating layer is easily peeled off by impact.
- the Al—Fe alloy phase is formed so as to surround a part of the plating component containing Zn, Mg and Al.
- the alloy phase including at least the Zn—Mg—Al alloy phase is scattered in an island shape in the Al—Fe alloy phase.
- the alloy phases scattered in the form of islands are formed from a high concentration Mg plating bath.
- an intermediate layer having a sea-island structure composed of a sea part composed of an Al—Fe alloy phase and an island part containing a Zn—Mg—Al alloy phase having an Mg content of 8% or more is composed of a base iron (steel) And a plating layer.
- an intermediate layer having the above-described sea-island structure and having an area fraction of the sea part composed of an Al—Fe alloy phase having the area ratio of 55 to 90% has the following characteristics.
- the plated steel material according to the embodiment has high corrosion resistance, impact resistance, and wear resistance, and also has high corrosion resistance after scratches or cracks occur in the plating layer.
- 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 molded into home appliance members (such as casings of outdoor units of air conditioners) and automobile parts (such as underbody members).
- home appliance members such as casings of outdoor units of air conditioners
- automobile parts such as underbody members
- 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 manufacturing method and a steel plate manufacturing method (hot rolling method, pickling method, cold rolling method, etc.).
- the crystal grain size of the surface of the steel material is preferably less than 5 ⁇ m, and more preferably less than 1 ⁇ m.
- the “Al-Fe reaction” is promoted during immersion plating, and the intermediate layer having the sea-island structure is easily formed.
- a smaller crystal grain size on the surface of the steel material is more preferable, but a practical lower limit value that can be minimized is about 0.1 ⁇ m. It is not dominant point in the reaction with the plated layer due to crystal grains is large.
- the crystal grain size of the surface of the steel material is an average value of the crystal grain sizes of the ferrite phase included in the range of 100 ⁇ m in the depth direction from the surface.
- the crystal grain size is measured by the steel-crystal grain size microscope test method specified in JIS G0551.
- the steel material may be increased in dislocation density on its surface (surface on which the plating layer and intermediate layer are formed) by processing.
- dislocation density on the surface of the steel material By increasing the dislocation density on the surface of the steel material, the “Al—Fe reaction” is promoted during immersion plating, and the intermediate layer having the sea-island structure is easily formed.
- the steel material may be a steel material plated with Cu-Sn substitution plating steel material, Ni substitution plating steel material, Zn plating steel material (plating steel material having a Zn deposition amount of 40 g / m 2 or less) or the like.
- the “Al-Fe reaction” is promoted during immersion plating, and the intermediate layer having the sea-island structure is easily formed.
- a Cu—Sn concentrated layer, a Ni concentrated layer, a Zn—Al—Fe alloy layer, etc. are used as the steel material between the steel material and an intermediate layer described later. It may be formed corresponding to the original plating thickness.
- the intermediate layer When forming the plating layer, the intermediate layer takes in the plating component together with the formation of the Al—Fe alloy phase by the reaction between Al of the plating component and Fe of the steel material (base iron), and between the plating layer and the steel material. It is a layer to be formed. Therefore, the composition of the intermediate layer includes Zn, Mg, Al, Ca, and Fe, and the balance is made of impurities (however, Ca may not be included). Specifically, the composition of the intermediate layer is as follows: Zn: 3.0-30.0%, Mg: 0.5-25.0%, Al: 30.0-55.0%, Ca: 0-3. It is preferable that it contains 0% and Fe: 24.0 to 40.0%, with the balance being impurities.
- a region containing 24.0 to 40.0% Fe in the layer covering the steel material is defined as an “intermediate layer”.
- the intermediate layer may contain “Zn, Mg, Al, Ca and elements other than impurities (Y, La, Ce, Si, etc.)” that may be included in the plating layer.
- elements (including impurities) other than Zn, Mg, Al, and Ca in the intermediate layer are always less than 0.5% and are handled as impurities.
- the composition of the intermediate layer (content of each element) is measured by the following method.
- a reflected electron image of an SEM (scanning microscope) with an EPMA (electron beam microanalyzer) is obtained for a cross section of an arbitrary intermediate layer (cross section cut in the thickness direction of the intermediate layer).
- a rectangular region is selected from the inside of the intermediate layer from the obtained SEM reflected electron image.
- the size and arrangement of the rectangular area are set so as to be located inside the intermediate layer. Specifically, in the rectangular region, the upper side and the bottom side are sides substantially parallel to the steel material surface, and the length of one side is 10 ⁇ m. These two sides are both positioned in the intermediate layer, and their positions are set so that the distance between them is maximized.
- the rectangular region is a region containing both a sea part and an island part to be described later. Further, the location of the rectangular area is set so that the area fraction of the sea area of the rectangular area is within ⁇ 5% of the area fraction of the sea area of the entire intermediate layer. Then, 20 or more rectangular regions that meet these conditions are selected. Then, each rectangular region is quantitatively analyzed by EPMA, and the average value of each obtained element is defined as the content of each element in the intermediate layer. In addition, the thickness of the intermediate layer, the area fraction of the sea part of the intermediate layer, and the area fraction of the sea part of the rectangular region are measured by the method described later.
- the structure of the intermediate layer has a sea-island structure composed of a sea part composed of an Al—Fe alloy phase and an island part containing a Zn—Mg—Al alloy phase.
- the structure of the intermediate layer is a “phase containing Zn—Mg—Al alloy phase” (island) surrounded by an Al—Fe alloy phase (sea part) when observing a cross section cut in the thickness direction of the intermediate layer. Part) (see FIG. 3).
- the sea part is an area composed of an Al—Fe alloy phase.
- the Al—Fe alloy phase is composed of an Al 5 Fe 2 phase.
- Zn in the plating component is substituted at the Al position by the Al 5 Fe 2 phase. May be taken in. For this reason, Zn may be partially scattered in the sea.
- a region other than the sea portion in the intermediate layer is defined as an “island portion”.
- the island part has, for example, a metal phase such as a Zn—Mg—Al alloy phase, a Zn—Mg alloy phase, and an Mg phase. These alloy phases and metal phases are quasicrystalline or equilibrium phases. Examples of the Zn—Mg—Al alloy phase include a quasicrystalline phase “Mg 32 (Zn, Al) 49” ”. A part of Zn in the Zn—Mg—Al alloy phase may be replaced by Al. Examples of the Zn—Mg alloy phase include an MgZn 2 phase.
- the island is preferably a region composed of these two or three phases. Specifically, the island portion, quasicrystalline phase, and the region consisting of MgZn 2 phase, or quasi-crystal phase is preferably a region consisting of MgZn 2 phase and Mg phase.
- the quasicrystalline phase “Mg 32 (Zn, Al) 49” may contain Ca in addition to Mg, Zn, and Al. Further, the MgZn 2 phase that is a Zn—Mg alloy phase may contain at least one of Ca and Al in addition to Mg and Zn. The Mg phase that is a metal phase may contain Zn in addition to Mg. Moreover, each phase which comprises an island part may contain Fe, an impurity, etc.
- the remaining structure that is non-equilibrium phases may include 10% or less of the area fraction in the intermediate layer.
- the remaining structure include unstable Mg—Zn alloy phases such as an MgZn phase, an Mg 2 Zn 3 phase, and an Mg 51 Zn 20 phase. If the content of the remaining structure is 10% or less in terms of area fraction, the properties of the intermediate layer will not be greatly impaired.
- each island part may be comprised by the several phase, or may be comprised by the single phase.
- the island part which consists of a single phase of two phases may be mixed.
- the Zn—Mg—Al alloy phase (quasicrystalline phase “Mg 32 (Zn, Al) 49” ) has an Mg content of 8% or more.
- the corrosion resistance of the intermediate layer is improved.
- the Mg content of the Zn—Mg—Al alloy phase is preferably 10% or more, and more preferably 15% or more.
- the upper limit of the Mg content of the Zn—Mg—Al alloy phase is preferably 50% or less. From the viewpoint of improving the corrosion resistance of both the intermediate layer and the plating layer, when the Mg content of the Zn—Mg—Al alloy phase is 15% or more, the Mg content of the plating layer may be 15% or more. preferable.
- the phase other than the Zn—Mg—Al alloy phase (Mg—Zn alloy phase, etc.) constituting the island portion preferably has an Mg content of 8% or more. % Or more is more preferable, and 15% or more is more preferable.
- the Mg content of each phase can be calculated by quantitative analysis using TEM-EDX (Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy) or EPMA (Electron Probe Micro-Analyzer) mapping.
- any cross section of the intermediate layer to be measured (cross section cut in the thickness direction of the intermediate layer)
- quantitative analysis of the Mg content of each phase by TEM-EDX or EPMA is performed at three locations, and the average value is obtained. Is the Mg content of each phase.
- the area fraction of the sea part composed of the Al—Fe alloy phase (that is, the area fraction of the Al—Fe alloy phase) is 55 to 90%. This is because when the area ratio of the Al—Fe alloy phase is less than 55%, the area of the island portion becomes large and the sea-island structure as the intermediate layer cannot be maintained. Therefore, the area fraction of the sea part is 55% or more.
- the progress (path) of the corrosion of the intermediate layer becomes a complicated path, the corrosion resistance of the intermediate layer is increased, and the peeling of the plating layer can be suppressed.
- middle layer itself increases by containing many corrosion resistance elements, such as Mg and Zn, in an intermediate
- the area fraction of the sea part is 90% or less. From these viewpoints, the area fraction of the sea part is preferably 65 to 85%, more preferably 70 to 80%.
- the area fraction of the island is a range obtained by subtracting the area fraction of the sea from 100%.
- each phase constituting the island portion has a complicated formation behavior of the sea-island structure, and is irregular in what area fraction is formed, and has low correlation with the components of the plating bath. Therefore, there is no particular limitation on the area fraction of each phase constituting the island.
- the area fraction of the sea part composed of the Al—Fe alloy phase (that is, the area fraction of the Al—Fe alloy phase) is measured by the following method.
- An arbitrary cross section (cross section cut in the thickness direction of the intermediate layer) of the intermediate layer to be measured is subjected to CP (cross session polisher) processing which is a kind of ion milling method.
- CP cross session polisher
- SEM scanning electron microscope
- reflected electron image of the cross section of the intermediate layer image obtained by observing three or more locations in an arbitrary area of about 2000 ⁇ m ⁇ 2000 ⁇ m square in the cross section of the intermediate layer at a magnification of 3,000 times
- FIB processing focused ion beam processing is performed on an arbitrary cross section (cross section cut in the thickness direction of the intermediate layer) of the intermediate layer to be measured.
- a TEM (transmission electron microscope) electron diffraction image of the cross-sectional structure of the intermediate layer is obtained.
- middle layer is identified.
- the identification result of the SEM reflected electron image and the TEM electron diffraction image is compared, and each phase of the intermediate layer is identified in the SEM reflected electron image.
- identifying each phase in the intermediate layer it is preferable to perform EDX point analysis using an SEM with an EDX (energy dispersive X-ray spectrometer) and collate the result of the EDX point analysis with the identification result of the electron diffraction image of the TEM.
- EDX energy dispersive X-ray spectrometer
- the three values of gray scale brightness, hue, and contrast value indicated by each phase in the intermediate layer are determined. Since the three values of brightness, hue, and contrast value shown by each phase reflect the atomic number of the element contained in each phase, usually, the phase with a high content of Mg content with a small atomic number exhibits a black color, A phase with a high Zn content tends to exhibit white. Therefore, computer image processing is performed such that the color changes only in the above three-value range indicated by the Al—Fe alloy phase so as to match the reflected electron image of the SEM. By this image processing, the area fraction of the Al—Fe alloy phase in the SEM reflected electron image is obtained.
- the area fraction of the Al—Fe alloy phase is the area fraction of the Al—Fe alloy phase obtained by the above operation in at least three views of an arbitrary cross section of the intermediate layer (cross section cut in the thickness direction of the intermediate layer).
- the area fraction of each phase (Zn—Mg—Al alloy phase, Zn—Mg alloy phase, metal phase, etc.) constituting the island portion can also be obtained by the same operation.
- the white part is the MgZn 2 phase (indicated as MgZn 2 in FIG. 3), and the light gray part is the quasicrystalline phase “Mg 32 (Zn, Al) 49 phase” (FIG. 3).
- 3 represents Mg 32 (Zn, Al) 49 )
- the dark gray portion represents the Al 5 Fe 2 phase (denoted as Al 5 Fe 2 in FIG. 3)
- the black portion represents the Mg phase (denoted as Mg in FIG. 3).
- required by SEM with EDX is as follows.
- the intermediate layer has, for example, a quasicrystalline phase “Mg 32 (Zn, Al) 49” as a Zn—Mg—Al alloy phase and MgZn as a Zn—Mg alloy phase. It is shown that the island part composed of two phases and the Mg phase as the metal phase has a sea island structure surrounded by the sea part composed of the Al 5 Fe 2 phase as the Al—Fe alloy phase.
- each phase can be identified in gray scale. Then, as described above, when computer image processing is performed such that the color changes only in the above three-value range indicated by the Al—Fe alloy phase, each phase (Al—Fe alloy phase, Zn in the reflected electron image of the SEM) is obtained. -Mg-Al alloy phase, Zn-Mg alloy phase, metal phase, etc.) can be obtained.
- the area fraction of each phase constituting the intermediate layer can also be calculated by binarization processing of the SEM reflected electron image. That is, in the reflected electron image of the SEM, the area fraction of two regions of black and white that can be separated out of each phase is obtained from “three values of brightness, hue, and contrast value” indicated by each phase. Of each phase, the selection of two separable black and white regions is changed, and the area fraction of the two black and white regions is obtained. And the area fraction of the target phase can also be calculated by repeating the above operation and taking the difference of the obtained area fractions.
- the SEM reflected electron image of the intermediate layer shown in FIG. 3 is as follows.
- the black portion of the Mg phase is displayed in black, and the other phases are displayed in white, and the area fraction of the Mg phase is determined.
- the white portion of the MgZn 2 phase is displayed in white, and the other phases are displayed in black, and the area fraction of the MgZn 2 phase is determined.
- the white portion of the MgZn 2 phase and the light gray portion of the quasicrystalline phase are displayed in white, and the other phases are displayed in black, and the total area fraction of the MgZn 2 phase and the quasicrystalline phase is determined.
- the area fraction of the total of MgZn 2 phase and quasicrystal phase and MgZn 2 phase area fraction of determine the area fraction of quasicrystalline phase. From the difference in the total area fraction of the MgZn 2 phase in the white part, the quasicrystalline phase in the light gray part, and the Mg phase, the area fraction of the Al 5 Fe 2 phase in the dark gray part is determined.
- the thickness of the intermediate layer is preferably 5 to 500 ⁇ m.
- an intermediate layer having a thickness of at least 5 ⁇ m or more exists. If the thickness of the intermediate layer is less than 5 ⁇ m, it is difficult to form a thick plating layer, which may result in poor adhesion of the plating layer.
- the thickness of the intermediate layer is related to Al—Fe diffusion. Therefore, for example, when the plating layer is formed by the immersion plating method, the thickness of the intermediate layer that can be formed is usually 500 ⁇ m or less under the normal operation conditions of the immersion plating. In addition, since the supply of the Fe component from steel materials (base iron) cannot reach
- the thickness of the intermediate layer is more preferably 10 ⁇ m or more, and further preferably 100 ⁇ m or more.
- the thickness of the intermediate layer is preferably 200 ⁇ m or less.
- the thickness of the intermediate layer is 5 to 500 ⁇ m, if the intermediate layer does not have the sea-island structure, the sacrificial anticorrosive effect cannot be obtained, and red rust tends to occur in the intermediate layer at an early stage.
- the ratio of the thickness of the intermediate layer to the thickness of the plating layer is preferably 0.2 to 4 times, and more preferably 0.5 to 2 times. If the ratio of the thickness of the intermediate layer is too small or too large, cracks may propagate and peel at the interface between the plating layer and the intermediate layer due to impact. Therefore, it is preferable to make the ratio of the thickness of the intermediate layer 0.2 to 4 times. Even if the ratio of the thickness of the intermediate layer to the thickness of the plating layer is 0.2 to 4 times, if the intermediate layer does not have the sea-island structure, the interface between the plating layer and the intermediate layer is caused by impact. The crack propagates and becomes easy to peel off.
- the thickness of the intermediate layer is measured as follows. Cross-sectional observation of the intermediate layer (observation of a region corresponding to a length of 2.5 mm in the direction parallel to the intermediate layer in the cross-section cut in the thickness direction of the intermediate layer) is performed by SEM (scanning electron microscope). . For example, the thickness of the thickest part and the thinnest part of each intermediate layer observed in each of these three visual fields is about 100 times as shown in FIG. Observe the difference in thickness.
- the upper surface of the intermediate layer has a different wave shape depending on the location. Examples of the method for calculating the average thickness of the intermediate layer include the following methods. First, the area of the cross section of the intermediate layer is obtained by image processing.
- the bottom surface and the top surface of the intermediate layer cross section are each approximated by a straight line, and converted to a rectangle of the same area with the intermediate layer / ground iron (steel plate) interface as one side (bottom side). And let the length of the height direction of the rectangle be an average value of thickness.
- the average value of the values obtained from at least three views in this way is set as the average value of the thickness of the intermediate layer.
- the sample adjustment method for cross-sectional observation may be performed by a known resin embedding or cross-sectional polishing method.
- the plating layer contains Mg: 8 to 50%, Al: 2.5 to 70.0%, and Ca: 0.30 to 5.00%, with the balance being Zn and impurities.
- Mg 8-50%
- Mg is an element that improves the corrosion resistance of the plating layer. Further, it is an element that makes the plating layer hard and improves the impact resistance and wear resistance of the plating layer.
- Mg is also an element that generates an Mg phase that degrades the corrosion resistance of the plating layer. Therefore, the Mg content is 8 to 50%.
- the Mg content is preferably 8 to 50%, more preferably 10 to 45%, still more preferably 15 to 35%, and particularly preferably 15 to 25%.
- Mg is an element that promotes the formation of a quasicrystalline phase with high corrosion resistance in the plating layer. Therefore, when the Mg content is 8 to 50%, a quasicrystalline phase is easily generated in the plating layer.
- Al: 2.5-70.0% Al is an element that improves the corrosion resistance. It is also an element necessary for thickening the intermediate layer having an Al—Fe alloy phase. On the other hand, if the plating layer contains a large amount of Al, red rust is likely to occur. Therefore, the Al content is set to 2.5 to 70.0%. Al content is 3 to 60% is preferable, 5.0 to 50.0% is more preferable, and 5.0 to 15.0% is more preferable. A large amount of Al functions to suppress the formation of a quasicrystalline phase having high corrosion resistance in the plating layer. Therefore, when the Al content is 2.5 to 70.0%, a quasicrystalline phase is easily generated in the plating layer.
- Cg is an element that prevents oxidation of Mg.
- Mg content In order to form a plating layer having an Mg content of 8% or more, it is necessary to use a plating bath having the same Mg content.
- Mg black oxide is generated in a few minutes in the atmosphere.
- Ca itself is also easily oxidized, which adversely affects the corrosion resistance of the plating layer.
- a large amount of Ca tends to make it difficult for Zn as a corrosion-resistant element to be taken into the Al—Fe alloy phase of the intermediate layer. Therefore, the Ca content is set to 0.30 to 5.00%.
- the Ca content is preferably 0.50 to 3.00%.
- a large amount of Ca functions to suppress the formation of a quasicrystalline phase having high corrosion resistance in the plating layer. Therefore, when the Ca content is 0.30 to 5.00%, a quasicrystalline phase is easily generated in the plating layer.
- the remaining Zn is an element that improves the corrosion resistance.
- the remaining Zn is an element that has a certain degree of reactivity with steel (base metal) in a high Mg plating bath and promotes the reaction between Al and Fe.
- the balance Zn is an element necessary for suppressing the Al-Fe reaction at an appropriate rate when the Al concentration is high, and contributes to the adhesion between the plating layer and the steel (base metal). But there is. Therefore, the remaining Zn content is preferably 20% or more, and more preferably 30% or more.
- the plating layer contains a large amount of remaining Zn, the reaction between the plating layer and the ground iron between Al and Fe becomes active, and an intermediate layer having a sea-island structure may not be formed. Therefore, the remaining Zn content is preferably 70% or less, and more preferably 65% or less. Zn is an element that promotes the generation of a quasicrystalline phase with high corrosion resistance in the plating layer. Therefore, when the Zn content is 20 to 70%, a quasicrystalline phase is easily generated in the plating layer.
- the remaining impurity means a component contained in the raw material or a component mixed in the manufacturing process and not intentionally included.
- a maximum of about 2% of Fe may be mixed in the plating layer as an impurity due to mutual atomic diffusion between the steel (base metal) and the plating bath.
- the performance of the plating layer is not affected.
- the plating layer is Y: 0 to 3.50%, La: 0 to 3.50%, Ce: 0 to 3.50%, Si: 0 to 0.50%, Ti: 0 to 0.50. %, Cr: 0 to 0.50%, Co: 0 to 0.50%, Ni: 0 to 0.50%, V: 0 to 0.50%, Nb: 0 to 0.50%, Cu: 0 ⁇ 0.50%, Sn: 0 ⁇ 0.50%, Mn: 0 ⁇ 0.20%, Sr: 0 ⁇ 0.50%, Sb: 0 ⁇ 0.50%, Cd: 0 ⁇ 0.50% , Pb: 0 to 0.50%, and B: 0 to 0.50%.
- Formula (A) Si + Ti + Cr + Co + Ni + V + Nb + Cu + Sn + Mn + Sr + Sb + Cd + Pb + B ⁇ 0.50%
- the element symbol indicates the content of each element in mass%.
- Y, La, Ce, Si, Ti, Cr, Co, Ni, V, Nb, Cu, Sn, Mn, Sr, Sb, Cd, Pb and B satisfy the expressions (A) and (B). If it is in the range, it can be contained in the plating layer without affecting the performance of the plating layer. Of course, these elements may not be contained in the plating layer.
- Y, La and Ce are the same elements as Ca that prevent oxidation of Mg.
- Y, La and Ce themselves are also easily oxidized, which adversely affects the corrosion resistance of the plating layer. Therefore, as long as it is a range satisfying the formula (B), one or more of Y, La and Ce may be contained in the plating layer.
- Y, La, and Ce are also elements that promote the formation of a quasicrystalline phase having high corrosion resistance in the plating layer, similar to Ca. On the other hand, when the total content of Ca, Y, La, and Ce exceeds 5.0%, the quasicrystalline phase is not formed immediately.
- Si When Si is contained in the plating layer, it combines with other elements to form Mg 2 Si, Ca—Si compounds (CaSi, Ca 5 Si 3 , Ca 2 Si, etc.), and the like. It is an element that has a crystal structure that is more difficult to elute and improves corrosion resistance. However, in this embodiment, since the Si concentration and the Ca concentration are small and the area fraction occupied by these phases in the plating layer is less than 5%, the performance of the plating layer is hardly affected. On the other hand, it is an element that slows the growth of an intermediate layer having an Al—Fe alloy phase.
- the Si content is preferably 0 to 0.500%, more preferably 0 to 0.050%, still more preferably 0 to 0.005%. 0% (that is, not containing Si) is particularly preferable.
- Sn, Cr, and B are elements that function as a reaction aid for promoting the reaction between Al and Fe. Therefore, in order to obtain an intermediate layer having a thickness of 5 to 500 ⁇ m, one or two of Sn, Cr, and B are used in a range that does not adversely affect the performance of the plating layer, that is, in a range that satisfies the formula (B).
- the plating layer may contain the above.
- the composition of the plating layer is measured by high frequency glow discharge spectroscopy (GDS). Specifically, it is as follows. A sample having a plated layer forming surface of 30 mm square is collected from the plated steel material. This sample is used as a sample for high frequency glow discharge spectroscopy (GDS). Argon ion sputtering is performed from the plated layer and intermediate layer forming surface side of the sample, and an element strength plot in the depth direction is obtained. On the other hand, a standard sample such as a pure metal plate of each element to be measured is prepared, and an element strength plot is obtained in advance from the standard sample. By comparing these two element strength plots, the concentrations (contents) of the constituent elements of the plating layer and the intermediate layer are converted. The measurement conditions are an analysis area of ⁇ 4 mm or more and a sputtering rate in the range of about 0.04 to 0.1 ⁇ m / sec.
- the element strength plot of the surface layer 5 ⁇ m deep from the surface of the plating layer is ignored, and the average value of each element concentration obtained from the element strength plot of the region 5 ⁇ m to 10 ⁇ m deep from the surface of the plating layer is obtained. This is to eliminate the influence of the oxide layer formed on the surface layer of the plating layer.
- the said operation is performed in ten or more places, and the average value of each element concentration of the plating layer in each place (that is, the average value of the average value of each element concentration of the plating layer obtained by the above operation) The content of each element.
- the structure of the plating layer will be described.
- the structure of the plating layer is not particularly limited.
- main structures constituting the plating layer include a quasicrystalline phase, a MgZn2 phase, a Mg2Zn3 phase (the same material as Mg4Zn7), a Mg51Zn20 phase, a Mg phase, a MgZn phase, and an Al phase.
- the quasicrystalline phase exhibits physical properties that are extremely excellent in corrosion resistance. Further, when the quasicrystalline phase is corroded by a corrosion acceleration test or the like, a corrosion product having a high barrier effect is formed, and the steel material (base iron) is prevented from corrosion for a long period of time. Corrosion products having a high barrier effect are related to the proportion of Zn—Mg—Al component contained in the quasicrystalline phase. In the component composition of the plating layer, when the formula: Zn> (Mg + Al + Ca) (where the element symbol indicates the content of each element in mass%), the barrier effect of the corrosion product is high. Become.
- the MgZn 2 phase and the Mg 2 Zn 3 phase have a small corrosion resistance improvement effect compared to the quasicrystalline phase, but have a certain corrosion resistance. Further, the MgZn 2 phase and the Mg 2 Zn 3 phase contain a large amount of Mg and are excellent in alkali corrosion resistance.
- the quasicrystalline phase, MgZn 2 phase and Mg 2 Zn 3 phase coexist in the plating layer, the oxide film on the surface of the plating layer in a highly alkaline environment (pH 13 to 14) is stabilized, and particularly high alkali corrosion resistance is achieved. As shown.
- the plating layer contains a large amount of a quasicrystalline phase in terms of corrosion resistance.
- the quasicrystalline phase itself is a very hard phase, and a plating layer containing a large amount of the quasicrystalline phase may contain some cracks in the phase. Therefore, when there is a tightening part for bolted joints in the plated steel material, or when the plated steel material is exposed to various flying objects by being used in an outdoor environment, it is necessary to give the plated layer somewhat ductility. Is good.
- the plating layer preferably has the following structure (1) or (2).
- the remaining structure of the structure (1) include an Mg 51 Zn 20 phase, an MgZn phase, an Mg 2 Zn 3 phase, a Zn phase, and an Al phase.
- the area fraction of the quasicrystalline phase is preferably 3 to 70%, and more preferably 10 to 70%. From the same point of view, the total area fraction of the quasicrystalline phase, the MgZn2 phase, and the Mg2Zn3 phase is preferably 3 to 100%, and more preferably 90 to 100%.
- the total area fraction of the quasicrystalline phase, the MgZn2 phase, and the Mg2Zn3 phase increases, for example, even in a strong alkaline environment (in ammonia water, caustic soda, etc.), the amount of corrosion becomes almost zero, so that it shows excellent alkali corrosion resistance become.
- (2) A structure composed of a quasicrystalline phase, an Al phase, and a remaining structure.
- the organization of the remaining structure of (2) for example, MgZn2 phase, Mg2Zn3 phase, Mg 51 Zn 20 phase, MgZn phase, Mg 2 Zn 3 phase, Zn equality.
- the area fraction of the quasicrystalline phase is preferably 25 to 45%, more preferably 30 to 45%.
- the total area fraction of the quasicrystalline phase and the Al phase is preferably 75 to 100%, more preferably 90 to 100%.
- the plating layer having the structure (1) or (2) may include other intermetallic compound phases such as an Al4Ca phase, an Al2Zn2Ca phase, and an Al3ZnCa phase as the remaining structure.
- this other intermetallic compound is an intermetallic compound phase formed depending on the Ca concentration, and in this embodiment, the area fraction occupied in the plating layer is also less than 5%, which contributes to the performance of the plating layer. Has no major impact.
- the area fraction of each phase of the plating layer is the area fraction in the cross section of the plating layer (cross section cut in the thickness direction of the plating layer), and the area fraction of each phase of the plating layer is the intermediate layer
- the area fraction of each phase Al—Fe alloy phase, Zn—Mg—Al alloy phase, Zn—Mg alloy phase, metal phase
- the thickness of the plating layer is preferably 20 ⁇ m or more, and more preferably 50 ⁇ m or more. If the corrosion resistance of the plating layer and the intermediate layer is compared, the plating layer is excellent in corrosion resistance. Therefore, from the viewpoint of ensuring sufficient corrosion resistance for the plated steel material, the thickness of the plating layer is preferably 20 ⁇ m or more, and more preferably 50 ⁇ m or more. On the other hand, since an increase in the thickness of the plating layer may impair the appearance of the plating layer, the thickness of the plating layer is preferably 100 ⁇ m or less.
- the thickness of the plating layer is the same as the measurement of the thickness of the intermediate layer, and the cross-sectional observation of the plating layer by SEM (scanning electron microscope) (in the cross section cut in the thickness direction of the plating layer, parallel to the plating layer) The observation of the region corresponding to the length of 2.5 mm in a certain direction is measured with 3 visual fields).
- the plating layer may be an immersion plating layer formed by immersion plating as described later.
- the quasicrystalline phase is defined as a quasicrystalline phase in which Mg content, Zn content, and Al content in the quasicrystalline phase satisfy 0.5 ⁇ Mg / (Zn + Al) ⁇ 0.83 in atomic%. Is done. That is, Mg: (Zn + Al), which is the ratio of Mg atoms to the sum of Zn atoms and Al atoms, is defined as a quasicrystalline phase of 3: 6 to 5: 6. Roughly, Mg: (Zn + Al) is considered to be about 4: 6.
- the chemical component of the quasicrystalline phase can be calculated by quantitative analysis using TEM-EDX (Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy) or EPMA (Electron Probe Micro-Analyzer) mapping. Note that it is not easy to define a quasicrystal with an accurate chemical formula like an intermetallic compound. This is because the quasicrystalline phase cannot define a repetitive lattice unit like a unit cell of a crystal, and furthermore, it is difficult to specify the atomic positions of Zn and Mg.
- the quasicrystalline phase is a crystal structure first discovered by Daniel Schuchmann in 1982 and has an icosahedral atomic arrangement.
- This crystal structure is a non-periodic crystal structure with a unique rotational symmetry that cannot be obtained with ordinary metals and alloys, for example, a 5-fold symmetry, and is equivalent to an aperiodic structure represented by a three-dimensional Penrose pattern.
- In order to identify this metal substance it is usually confirmed by obtaining a radial regular decagonal electron beam diffraction image resulting from the regular icosahedron structure by electron beam observation by TEM observation.
- the electron beam diffraction image of the TEM shown in FIG. 4 is obtained only from the quasicrystal, and is not obtained from any other crystal structure. Therefore, the quasicrystalline phase and the MgZn alloy phase such as MgZn 2 phase can be distinguished.
- the quasicrystalline phase is simply a diffraction peak that can be identified by the JCPDS card: PDF # 00-019-0029 or # 00-039-0951 by X-ray diffraction as the Mg 32 (Zn, Al) 49 phase. Show.
- the plated steel material according to the embodiment is preferably manufactured by immersion plating using an immersion plating bath having the same composition as the composition of the plating layer (a composition other than impurities). Further, the immersion plating is preferably performed by one-step plating.
- the Fe-Al reaction (alloying reaction between Al and Fe) is promoted by shortening the latent time, and an intermediate layer with an appropriate thickness can be formed. Once formed, a plating layer can be formed.
- the plating bath temperature is preferably 550 ° C. or higher, and more preferably 600 ° C. or higher.
- the plating bath temperature is preferably the melting point of the plating component + 50 ° C. or more, more preferably the melting point +50 to 100 ° C., from the viewpoint of ensuring the plating properties and the wettability between the steel material and the plating bath.
- the plating bath temperature is less than 550 ° C., even if immersion plating is performed, the incubation time is prolonged and the reaction between Al and Fe is difficult to start.
- the plating bath temperature is preferably 650 ° C. or lower.
- the immersion time is preferably 1 minute or longer, and more preferably 5 minutes or longer.
- the immersion time is less than 1 minute, even if immersion plating is performed at a plating bath temperature of 550 ° C. or higher, the plating bath does not get wet with the steel (base metal), and sufficient Fe—Al reaction does not proceed easily.
- the immersion time is too long, the intermediate layer grows too much and becomes brittle.
- internal stress acts due to the temperature difference, and cracks are likely to occur on the surface of the plating layer.
- the immersion time is preferably less than 30 minutes.
- the shortening of the latent time is not only an increase in the plating bath temperature, an increase in the Al concentration and the Zn concentration in the plating bath, and a decrease in the oxygen potential on the plating bath surface, It is preferable to use at least one of the methods shown in the following (1) to (9). By using these methods, the latent time can be further shortened.
- a method of heating a steel material before immersion plating The heating temperature is preferably 200 ° C. or higher, more preferably 400 ° C. or higher, in terms of the surface temperature of the steel material.
- the heating atmosphere is preferably an inert atmosphere.
- the steel material is preferably a low alloy steel.
- a method of vibrating and / or rotating a steel material in a plating bath (3) A method of stirring the plating bath in which the steel material is immersed.
- the crystal grain size is preferably less than 5 ⁇ m, more preferably less than 1 ⁇ m.
- the Sn content is preferably 0.50% or less, the Cr content is 0.50% or less, and the B content is 0.50% or less.
- the range satisfies the above formula (B).
- the intermediate surface having the above-mentioned sea-island structure along with the immersion plating layer on the surface of the steel material A layer is formed between the steel material and the immersion plating layer.
- the immersion plating bath begins to get wet on the surface of the steel material in a short time by shortening the incubation time.
- the Al—Fe reaction starts from a place where the interface energy such as the crystal grain boundary and the uneven portion is small on the surface of the steel material (see FIG. 5 (2)).
- Al—Fe alloy phase grows.
- Al-deficient plating liquid phase a liquid phase of the plating bath in which Al is deficient (low Al) is generated (see FIG. 5 (3)).
- the tip of the grown Al—Fe alloy phase reacts with the liquid phase of the plating bath rich in Al, and the Al—Fe alloy phase grows irregularly.
- Al atom diffusion from the offshore of the plating bath to the vicinity of the surface of the steel material is gradual.
- the temperature range where the plating bath temperature is 550 ° C. or higher once the Al—Fe reaction starts, elution of Fe occurs actively from the surface of the steel (base metal). Moreover, the elution rate of Fe from the surface of steel materials (base iron) becomes high. Fe easily reaches offshore. At the place where the reaction between Al and Fe occurs, the feed rate of Fe is higher than that of Al.
- the plating bath having an Mg content of 8% or more the reaction between Al—Fe and the generation of an Al-deficient liquid phase occur actively, and the growth of the Al—Fe alloy phase proceeds irregularly.
- the Al—Fe alloy phase does not grow irregularly but grows in layers.
- the Al—Fe alloy phase grows while partially surrounding the Al-deficient plating solution phase (see FIG. 5 (4)). That is, the Al-deficient plating solution phase is partially left in the Al—Fe alloy phase. Note that the plating component Zn may be slightly incorporated into the Al—Fe alloy phase.
- the “Al-deficient plating solution phase” surrounded by the Al—Fe alloy phase is solidified and transformed into an intermetallic compound having the closest component concentration.
- at least a Zn—Mg—Al alloy phase (quasicrystalline phase) is generated.
- phase transformation or phase separation may occur due to equilibrium solidification, and intermetallic compounds (Zn—Mg alloy phase, etc.), metal phases (Mg phase, etc.) may also be generated.
- Fe is dissolved in the Al-deficient plating solution phase, and an intermetallic compound containing a small amount of Fe is generated.
- an intermediate layer having a sea-island structure composed of “islands including a Zn—Mg—Al alloy phase” surrounded by a sea composed of an Al—Fe alloy phase is formed.
- a plating component solidifies and a plating layer is formed.
- 10 is a steel material
- 12 is a plating bath
- 12A is an Mg oxide film
- 12B is an Al-deficient plating solution phase
- 14 is an Al—Fe alloy phase.
- an alloy having a predetermined component composition prepared in a vacuum melting furnace or the like is used, and the steel material is immersed in a “plating bath” dissolved in the air. If there is no problem in the structure to be immersed, installing a lid or the like on the plating bath and substituting with nitrogen can lower the oxygen potential and shorten the latency time for the reaction between Al and Fe.
- the capacity of the plating bath for the steel material should be sufficiently increased. For example, with respect to a steel material having a length of 100 mm, a width of 50 mm, and a thickness of 2 mm, it is preferable that at least the capacity of the plating bath is 5 L or more.
- the steel material Before immersion in the plating bath, the steel material may be subjected to a surface cleaning process (for example, a surface cleaning process in which degreasing, pickling, water washing and drying are performed). Specifically, for example, by immersing a steel material in 10% hydrochloric acid for 10 minutes or more, a strong oxide film (black skin, scale) generated on the surface layer of the steel material is peeled off. Thereafter, the steel material is pickled and washed with water. Then, the moisture of the steel material is removed using a dryer, a drying furnace or the like.
- a surface cleaning process for example, a surface cleaning process in which degreasing, pickling, water washing and drying are performed.
- the steel after the oxide film removal by the above treatment is subjected to flux treatment, shot blasting, shot It is preferable to perform peening, pickling, brush grinding, or the like. And after these processes, it is preferable to use it as an immersion steel material as it is, or to use it as an immersion steel material by applying only a post-treatment that is stopped by a dry cleaning process or the like.
- the vibration and / or rotation of the steel material has a role of shortening the incubation period, and also has a role of suppressing appearance defects of the plated steel material.
- the flux chloride
- the flux reacts with the plating component to form Mg-based chloride on the surface of the steel, and the surface appearance is impaired. There is a case. Therefore, also from this viewpoint, the method of vibrating and / or rotating the steel material is effective.
- the steel material pulling speed is preferably 100 mm / s or less, and more preferably 50 mm / s or less.
- the pulling speed of the steel material is high, the thickness of the plating layer formed on the intermediate layer becomes excessively thick and may cause peeling of the plating layer.
- the steel After pulling up from the plating bath, the steel is cooled at a predetermined cooling rate from the temperature immediately after the pulling (plating bath temperature) to room temperature.
- This temperature is the surface temperature of the steel material.
- the steel material may be cooled by being immersed in water, or may be naturally cooled.
- the plated steel material may be cooled at the following cooling rate.
- the steel material is preferably cooled within 8 seconds in the temperature range from the temperature immediately after the pulling (plating bath temperature) to 500 ° C.
- Al rapidly moves toward the interface between the steel material and the plating layer to form an Al—Fe alloy phase (that is, an intermediate layer). Therefore, by cooling the steel material from the temperature immediately after the pulling up to 500 ° C. within 8 seconds, it is possible to suppress the incorporation of Al in the plating layer into the intermediate layer.
- the Al concentration inside the plated layer before solidification is optimized, and a state suitable for forming a quasicrystalline phase is obtained.
- the cooling device is preferably a cooling device that sprays an inert gas, a mist cooling device, or the like in order to prevent oxidation of the plating components.
- the steel material is preferably cooled at a cooling rate of 5 ° C./second or less in order to keep the steel material for 30 seconds or more.
- the cooling rate In the temperature range below 500 ° C. and 350 ° C. or higher, the growth of the Al—Fe alloy phase (that is, the intermediate layer) stops, while the most stable phase is the quasicrystalline phase. Therefore, in this temperature range, by setting the cooling rate to 5 ° C./second or less, a quasicrystalline phase is easily generated in the intermediate layer (the island portion of the sea-island structure) of the plated steel material and the plated layer. Note that if the cooling rate is higher than 5 ° C./second, the quasicrystalline phase is cooled before the precipitation, so that the ratio of the quasicrystalline phase may become extremely small or the quasicrystalline phase may not be contained.
- the steel material is preferably cooled at a cooling rate of 10 ° C./second or more.
- the temperature range of less than 350 ° C. and 250 ° C. or more enters the stable region of the intermetallic compound phase (Mg 2 Zn 3 phase, MgZn phase, etc.) and metal phase (Mg phase, etc.) rather than the quasicrystalline phase.
- the quasicrystalline phase may change into an intermetallic compound phase (Mg 2 Zn 3 phase, MgZn phase, etc.).
- the cooling rate is not particularly limited in the temperature range from 250 ° C. to room temperature after pulling up. This is because, in the temperature range of 250 ° C. or lower and room temperature or higher, the temperature is low, the atomic diffusion is low, and it is no longer below the temperature required for phase formation and decomposition.
- post-treatment may be performed after forming the plating layer.
- post-treatment include various treatments for treating the surface of the plated steel material, such as treatment for upper layer plating, glazing treatment, non-chromate treatment, phosphate treatment, lubricity improvement treatment, weldability improvement treatment, etc.
- resin-based paints for example, polyester resin-based, acrylic resin-based, fluororesin-based, vinyl chloride resin-based, urethane resin-based, epoxy resin-based, etc.
- roll coating spray coating, curtain flow coating, etc.
- a treatment for forming a paint film by coating by a method such as dip coating or a film laminating method for example, a film laminating method when laminating a resin film such as an acrylic resin film.
- the conditions in the examples are one condition example adopted to confirm the feasibility and effects of the present disclosure.
- the present disclosure is not limited to this one example condition.
- the present disclosure can adopt various conditions as long as the object of the present disclosure is achieved without departing from the gist of the present disclosure.
- plating baths A to K having a predetermined composition were prepared.
- the bath volume of the plating bath was 16L.
- the components of the plating bath were confirmed by ICP emission spectroscopic analysis of the solidified piece of the plating bath and acid-dissolving the chips.
- a general carbon steel plate JIS G 3101 (2010) regulation SS400 black skin material having a plate width of 70 mm, a plate length of 150 mm, and a plate thickness of 2.3 mm was used as a steel material to be subjected to immersion plating.
- the steel film was immersed in 10% hydrochloric acid for 10 minutes or more to peel off the oxide film formed on the surface layer of the steel material. Thereafter, the steel material was sufficiently drained and then dried. Then, the steel material surface was ground on the whole surface with a # 600 belt sander, and the ground grinding powder was blown off with a dryer.
- the steel material was fixed to a mounting jig of a lifting device for immersion.
- the lifting device can penetrate the steel material into the plating bath at a constant speed and pull it up.
- the lifting device can finely vibrate the steel material immersed in the plating bath by ultrasonic waves emitted from the mounting jig.
- a thermocouple was attached to the steel so that the temperature history of immersion plating could be monitored at all times. Lifting device with nitrogen gas blowing mechanism installed on, it allowed the N 2 gas blown immediately after pulling.
- the steel material was dipped at a dipping rate of 100 mm / sec by a lifting device. Immediately after the steel material was completely immersed in the plating bath, ultrasonic waves were generated, and the vibration of the steel material was continued during the immersion. The surface dross generated during immersion was scooped with a metal handle and immediately removed.
- the steel material was pulled up from the plating bath at the pulling rate shown in Table 1.
- the thickness of the plating layer was adjusted by this pulling speed.
- N 2 gas is blown and cooled at the cooling rate shown in Table 1, and immediately after reaching 350 ° C., the steel material is immediately immersed in 20 L of water. Was immersed and cooled.
- the amount of N 2 gas sprayed was adjusted and cooled to 250 ° C. at the cooling rate shown in Table 1.
- flux treatment was performed.
- a plated steel material was manufactured by immersion plating (denoted as “immersion zinc plating” in the table) using a zinc plating bath as a plating bath.
- a plated steel material was manufactured by two-stage immersion plating.
- No. 39C also produced a plated steel material by two-stage immersion plating.
- the first stage is immersion plating using a zinc plating bath as a plating bath
- the bath volume of the plating bath was 8L.
- a general carbon steel plate JIS G 3101 (2010) regulation SS400 black skinned steel plate pickled
- a plate width of 100 mm, a plate length of 150 mm, and a plate thickness of 2.3 mm was used as a steel material to be subjected to immersion plating.
- the steel material was heated from room temperature to 800 ° C. by electric heating and held for 60 seconds. Thereafter, the steel material was cooled to the plating bath temperature + 10 ° C. by N 2 gas spraying, and immediately immersed in a plating bath having the types and plating bath temperatures shown in Table 1. Then, the immersion time in the plating bath was set to 1 second, the steel material was drawn out from the plating bath, and then the steel material was subjected to N 2 gas wiping. The drawing speed and the N 2 gas wiping pressure were adjusted so that the thickness of the plating layer was 20 ⁇ m ( ⁇ 1 ⁇ m).
- the batch type plating apparatus was operated at high speed and completed within 1 second.
- N 2 gas wiping no. 40C, no. For 41C, steel in blowing N 2 gas and cooled to 250 ° C. at an average cooling rate of 15 ° C. / sec.
- N 2 gas was sprayed onto the steel material, and the plated steel sheet was cooled at the cooling rate shown in Table 1.
- the thickness of the intermediate layer was 1 ⁇ m or less as a result of cross-sectional observation of the intermediate layer and the plated layer, and the corrosion resistance of the intermediate layer was not evaluated.
- the corrosion resistance of the plating layer was evaluated as follows.
- the plated steel sheet was cut into 150 ⁇ 70 mm, the cut end face was sealed, and immersed in a 1 mol / L NaOH aqueous solution at 40 ° C. for 24 hours. After 24 hours, the plated steel sheet was taken out and the corrosion product formed on the surface of the plating layer was removed by immersion in 20% chromic acid at room temperature for 15 minutes, and the corrosion weight loss before and after the test was measured. Corrosion weight loss was converted to corrosion thickness reduction using the theoretical density of each plating alloy to evaluate the alkaline environment corrosion resistance. The evaluation criteria are as follows.
- Corrosion thickness is less than 1 ⁇ m ⁇ Very Good: Corrosion thickness is 1 ⁇ m or more and 2 ⁇ m or less ⁇ Good: Corrosion thickness is over 2 ⁇ m, 4 ⁇ m or less ⁇ Bad: Corrosion thickness is over 4 ⁇ m
- the impact resistance of the plating layer was evaluated using a gravel test for peeling of the plating layer after application of impact.
- a Gravelo tester manufactured by Suga Test Instruments Co., Ltd.
- the crushed stone crashed.
- an EPMA-Fe element mapping image of the evaluation surface of the plated steel material was taken, and the total area ratio of the exposed surface and exposed intermediate layer was calculated.
- the evaluation criteria are as follows.
- the wear resistance of the plating layer was evaluated as follows. Using a pin-on-disk friction and wear tester (FDR-2100) manufactured by Reska, ⁇ 3 / 16 inch-SUS304Ball, load 1000 gf, radius 20 mm, 1 rpm, 5 rotations clockwise, 25 ° C. Formed. The trace portion on the line was embedded and polished, and the maximum recess depth from the surface of the plating layer was measured. The evaluation criteria are as follows.
- the numerical values in the columns of “quasicrystalline phase”, “MgZn 2 phase” and “Mg phase” in the island portion indicate the area fraction of each phase in the island portion. And when a numerical value is described, it indicates that the corresponding phase exists and the intermediate layer has a sea-island structure. The notation “-” indicates that the corresponding phase does not exist. The numerical value “100” in the column of the sea part indicates that the intermediate layer does not have a sea-island structure. The notation “bal.” In the column of Al indicates that the Al content corresponds to the balance including impurities.
- the plated steel materials 1E to 34E have a sea-island structure in the intermediate layer, and the intermediate layer itself has high corrosion resistance. Thereby, it turns out that the corrosion resistance after a crack or a crack arises in a plating layer is also high. No. It can also be seen that the plated steel materials of 1E to 34E have high alkaline environmental corrosion resistance, impact resistance, and wear resistance.
- the plated steel materials of 35C to 45C do not have a sea-island structure in the intermediate layer, and the intermediate layer itself has low corrosion resistance. Thereby, it turns out that the corrosion resistance after a crack or a crack arises in a plating layer is also low.
- the plated steel materials of 40C to 45C have a thin intermediate layer and no sea-island structure, so that the corrosion resistance of the intermediate layer itself and the impact resistance of the plated layer are low.
Abstract
Description
特許文献2:日本国特開平11-117052号公報
特許文献3:日本国特開2010-70810号公報
特許文献4:日本国特開2015-40334号公報
特許文献5:日本国特許5785336号公報
そのため、浸漬めっき性に悪影響を与えるMg濃度成分を制限した範囲(具体的には(Mg含有量を5質量%以下に制限した範囲)での浸漬めっきしか実施されていない。また、中間層がなくとも、十分なめっき層の厚み及び密着性を確保するため、2段めっき法が利用されている。
鋼材と、
前記鋼材の表面に被覆され、質量%で、Mg:8~50%、Al:2.5~70.0%、Ca:0.30~5.00%、Y :0~3.50%、La:0~3.50%、Ce:0~3.50%、Si:0~0.50%、Ti:0~0.50%、Cr:0~0.50%、Co:0~0.50%、Ni:0~0.50%、V :0~0.50%、Nb:0~0.50%、Cu:0~0.50%、Sn:0~0.50%、Mn:0~0.20%、Sr:0~0.50%、Sb:0~0.50%、Cd:0~0.50%、Pb:0~0.50%、及びB :0~0.50%を含み、残部がZn及び不純物からなり、かつ下記式(A)及び下記式(B)を満たすめっき層と、
前記鋼材と前記めっき層との間に介在する中間層であって、Al-Fe合金相からなる海部と、Mg含有量が8質量%以上のZn-Mg-Al合金相を含む島部と、で構成された海島構造を有し、前記Al-Fe合金相からなる海部の面積分率が55~90%である中間層と、
を備えるめっき鋼材。
・式(A):Si+Ti+Cr+Co+Ni+V+Nb+Cu+Sn+Mn+Sr+Sb+Cd+Pb+B≦0.50%
・式(B):Ca+Y+La+Ce≦5.00%
式(A)及び式(B)中、元素記号は、質量%での各元素の含有量を示す。
<2>
前記中間層の厚さが、5~500μmである<1>に記載のめっき鋼材。
<3>
前記海部が、前記Al-Fe合金相としてAl5Fe2相からなり、
前記島部が、前記Zn-Mg-Al合金相として準結晶相、及びMgZn2相からなるか、又は、前記Zn-Mg-Al合金相として準結晶相、MgZn2相、及びMg相からなる<1>又は<2>に記載のめっき鋼材。
<4>
前記めっき層の厚さに対する前記中間層の厚さの比率が、0.2~4倍である請求項1~請求項3のいずれか1項に記載のめっき鋼材。
<5>
前記めっき層のMg含有量が15質量%以上であり、かつ前記Zn-Mg-Al合金相のMg含有量が15質量%以上である<1>~<4>のいずれか1項に記載のめっき鋼材。
<6>
前記めっき層が、浸漬めっき層である<1>~<5>のいずれか1項に記載のめっき鋼材。
なお、本明細書において、「~」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。
本明細書において、組成(元素)の含有量を示す「%」は、「質量%」を意味する。
実施形態に係るめっき鋼材は、鋼材と、鋼材の表面に被覆されためっき層と、鋼材とめっき層との間に介在する中間層と、を備える(図1及び図2参照)。
めっき層は、質量%で、Mg:8~50%、Al:2.5~70.0%、Ca:0.30~5.00%を含み、残部がZn及び不純物からなる。一方、中間層は、Al-Fe合金相からなる海部と、Mg含有量が8%以上のZn-Mg-Al合金相を含む島部と、で構成された海島構造を有し、Al-Fe合金相からなる海部の面積分率が55~90%である。
2)中間層にMg、Zn等の耐食性元素を多く含有することから、耐食性元素による犠牲防食作用が働き、中間層自体の耐食性が高まる(つまり、めっき層に傷又は割れが生じ、中間層が腐食段階に到達しても、赤錆が発生し難くなる)。
3)海島構造によって、中間層中に硬度の分布が発生し、亀裂伝播挙動が複雑となり、飛来物、土砂等によりめっき層が衝撃を受けても、めっき層の剥離が発生し難くなる。
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)などに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、鋼材の製鋼方法、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。
ここで、鋼材の表面の結晶粒径は、表面から、深さ方向に100μmの範囲に含まれるフェライト相の結晶粒径の平均値である。そして、結晶粒径の測定方法はJIS G0551にて規定する鋼-結晶粒度の顕微鏡試験方法で測定する。
中間層は、めっき層を形成するとき、めっき成分のAlと鋼材(地鉄)のFeとの反応によって、Al-Fe合金相の生成と共にめっき成分を取り込みつつ、めっき層と鋼材との間に形成される層である。そのため、中間層の組成は、Zn、Mg、Al、Ca及びFeを含み、残部が不純物からなる(ただし、Caは含まない場合がある)。具体的には、中間層の組成は、Zn:3.0~30.0%、Mg:0.5~25.0%、Al:30.0~55.0%、Ca:0~3.0%、及びFe:24.0~40.0%を含み、残部が不純物からなることが好ましい。本実施形態においては、鋼材を被覆する層のうち、Feを24.0~40.0%含む領域を「中間層」と定義する。
なお、中間層は、めっき層に含まれ得る「Zn、Mg、Al、Ca及び不純物以外の元素(Y、La、Ce、Si等)」を含有する場合がある。しかし、中間層におけるZn、Mg、Al及びCa以外の元素(不純物含む)は、常に0.5%未満であり、不純物として取り扱う。
なお、中間層の厚さ、中間層の海部の面積分率、長方形領域の海部の面積分率は、後述する方法によって測定する。
Zn-Mg-Al合金相としては、例えば、準結晶相「Mg32(Zn,Al)49」」が挙げられる。なお、Zn-Mg-Al合金相中のZnの一部は、Alによって置換されていてもよい。
Zn-Mg合金相としては、例えば、MgZn2相等が挙げられる。
島部は、これら2つ又は3つの相からなる領域であることが好ましい。具体的には、島部が、準結晶相、及びMgZn2相からなる領域、又は、準結晶相、MgZn2相、及びMg相からなる領域であることが好ましい。
そして、中間層及びめっき層の双方の耐食性を向上する観点から、Zn-Mg-Al合金相のMg含有量が15%以上であるとき、めっき層のMg含有量も15%以上であることが好ましい。
各相のMg含有量は、TEM-EDX(Transmission Electron Microscope―EnergyDispersive X-ray Spectroscopy)による定量分析、又はEPMA(Electron Probe Micro-Analyzer)マッピングによる定量分析で算出することができる。具体的には、測定対象となる中間層の任意の断面(中間層厚み方向に切断した断面)において、TEM-EDX又はEPMAによる各相のMg含有量の定量分析を3箇所行い、その平均値を各相のMg含有量とする。
中間層にMg、Zn等の耐食性元素を多く含有させるためには、Mg、Zn等の耐食性元素を含有する島部の比率を一定以上に保つ必要がある。そのため、海部の面積分率を90%以下とする。
これら観点から、海部の面積分率は、65~85%が好ましく、70~80%がより好ましい。
測定対象となる中間層の任意の断面(中間層厚み方向に切断した断面)にイオンミリング法の一種であるCP(クロスセッションポリッシャ)加工を施す。CP加工後、中間層の断面のSEM(走査電子顕微鏡)の反射電子像(中間層の断面における約2000μm×2000μm四方の任意の領域から3か所以上を倍率3千倍で観察した像(約30μm×30μm))を得る。
次に、同じ測定対象となる中間層の任意の断面(中間層厚み方向に切断した断面)にFIB加工(集束イオンビーム)加工を施す。FIB加工後、中間層の断面組織のTEM(透過型電子顕微鏡)の電子回折像を得る。そして、中間層に含まれる金属間化合物を同定する。
次に、SEMの反射電子像とTEMの電子回折像の同定結果とを比較し、SEMの反射電子像において、中間層に有する各相を同定する。なお、中間層に有する各相の同定において、EDX(エネルギー分散型X線分光器)付きSEMによりEDX点分析し、EDX点分析の結果とTEMの電子回折像の同定結果とを照合するとよい。
そのため、SEMの反射電子像と整合するように、Al-Fe合金相が示す上記3値の範囲のみ、色変わりするようなコンピューター画像処理を実施する。この画像処理により、SEMの反射電子像中に占めるAl-Fe合金相の面積分率を求める。
そして、Al-Fe合金相の面積分率は、中間層の任意の断面(中間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Al-Fe合金相の面積分率の平均値とする。
・白色部=MgZn2相: 化学組成=Mg:13%,Al:3%,Ca:5%、Zn:79%
・薄灰色部=準結晶相Mg32(Zn,Al)49: 化学組成=Mg:20.4%、Zn:75.5%、Al:3%、Ca:1%
・濃灰色部=Al5Fe2相: 化学組成=Al:52.5%±5%、Fe:44%±5%、Zn:3.5%±1%
・黒色部=Mg相: 化学組成=Mg94%,Zn:6%
黒色部のMg相を黒色、それ以外の相を白色に表示し、Mg相の面積分率を求める。
白色部のMgZn2相を白色、それ以外の相を黒色に表示し、MgZn2相の面積分率が求める。
白色部のMgZn2相及び薄灰色部の準結晶相を白色、それ以外の相を黒色に表示し、MgZn2相及び準結晶相の合計の面積分率を求める。そして、MgZn2相及び準結晶相の合計の面積分率とMgZn2相の面積分率との差分を取ることで、準結晶相の面積分率を求める。
白色部のMgZn2相、薄灰色部の準結晶相、及びMg相の合計の面積分率の差分から、濃灰色部がAl5Fe2相の面積分率を求める。
耐食性が十分なめっき層を形成し、かつ不めっき等のめっき欠陥を防止するためには、少なくとも厚さ5μm以上の中間層が存在することがよい。中間層の厚さが5μm未満では、厚みのあるめっき層が形成され難く、めっき層の密着性不良となることがある。
一方、中間層の厚さは、Al-Fe拡散が関係する。そのため、例えば、浸漬めっき法によりめっき層を形成する場合、浸漬めっきの通常の操業条件において、形成できる中間層の厚さは500μm以下であるのが通常である。なお、厚さ500μm超の中間層は、鋼材(地鉄)からのFe成分の供給が届かなくなるため、形成が困難である。
中間層の厚さの比率が小さすぎても、大きすぎても、衝撃により、めっき層と中間層との界面で亀裂が伝播して剥離することがある。そのため、中間層の厚さの比率を0.2~4倍にすることが好ましい。
なお、めっき層の厚さに対する中間層の厚さの比率が0.2~4倍であっても、中間層が上記海島構造を有さない場合、衝撃により、めっき層と中間層との界面で亀裂が伝播して剥離しやすくなる。
なお、断面観察のためのサンプル調整方法は公知の樹脂埋め込み又は断面研磨方法によって行えばよい。
めっき層は、Mg:8~50%、Al:2.5~70.0%、及びCa:0.30~5.00%を含み、残部がZn及び不純物からなる。
「Mg:8~50%」
Mgは、めっき層の耐食性を向上させる元素である。また、めっき層が硬質となり、めっき層の耐衝撃性及び耐摩耗性を向上させる元素である。一方で、Mgは、めっき層の耐食性を劣化させるMg相を生成する元素でもある。そのため、Mg含有量は、8~50%とする。Mg含有量は、8~50%が好ましく、10~45%がより好ましく、15~35%がさらに好ましく、15~25%が特に好ましい。
なお、Mgは、めっき層中に耐食性の高い準結晶相の生成を促進させる元素である。そのため、Mg含有量を8~50%にすると、めっき層に準結晶相が生成しやすくなる。
Alは、耐食性を向上させる元素である。また、Al-Fe合金相を有する中間層を厚膜化するために必要な元素でもある。一方で、めっき層にAlを多量に含むと、赤錆が発生しやすくなる。そのため、Al含有量は、2.5~70.0%とする。Al含有量は、
3~60%が好ましく、5.0~50.0%がより好ましく、5.0~15.0%がさらに好ましい。
なお、多量なAlは、めっき層中に耐食性の高い準結晶相の生成を抑える働きをする。そのため、Al含有量を2.5~70.0%にすると、めっき層に準結晶相が生成しやすくなる。
Cgは、Mgの酸化を防止する元素である。Mg含有量が8%以上のめっき層を形成するには、同じMg含有量のめっき浴を利用する必要がある。Mg含有量が8%以上のめっき浴にCaを含有させない場合、大気中では数分でMgの黒色酸化物が発生する。一方で、Ca自体も酸化し易く、めっき層の耐食性に悪影響を及ぼす。多量のCaは、中間層のAl-Fe合金相に耐食性元素であるZnが取り込まれにくくなる傾向が高くなる。そのため、Ca含有量は、0.30~5.00%とする。Ca含有量は、0.50~3.00%が好ましい。
なお、多量なCaは、めっき層中に耐食性の高い準結晶相の生成を抑える働きをする。そのため、Ca含有量を0.30~5.00%にすると、めっき層に準結晶相が生成しやすくなる。
残部のZnは、耐食性を向上させる元素である。また、残部のZnは、高Mgめっき浴ではある程度の鋼材(地鉄)との反応性をもたせAl-Fe間反応を促進する元素である。さらに、残部のZnは、Al濃度が高い場合には、Al-Fe間反応を適切な速度に抑制するために必要な元素であり、めっき層と鋼材(地鉄)の密着性に寄与する元素でもある。そのため、残部のZn含有量は、20%以上が好ましく、30%以上が好ましい。
一方、めっき層に残部のZnを多く含むと、めっき層と地鉄のAl-Fe間反応が盛んになり、海島構造を有する中間層が形成しない状態となることがある。そのため、残部のZn含有量は、70%以下が好ましく、65%以下が好ましい。
なお、Znは、めっき層中に耐食性の高い準結晶相の生成を促進させる元素である。そのため、Zn含有量を20~70%にすると、めっき層に準結晶相が生成しやすくなる。
・式(A):Si+Ti+Cr+Co+Ni+V+Nb+Cu+Sn+Mn+Sr+Sb+Cd+Pb+B≦0.50%
・式(B):Ca+Y+La+Ce≦5.00%
式(A)及び式(B)中、元素記号は、質量%での各元素の含有量を示す。
また、Y、La及びCeは、Caと同じ、めっき層中に耐食性の高い準結晶相の生成を促進させる元素でもある。一方で、Ca、Y、La及びCeの総含有量が5.0%を超えると、準結晶相が途端に形成しなくなる。そのため、めっき層に準結晶相を生成する場合も、式(B)を満たす範囲であれば、Y、La及びCeの1種又は2種以上をめっき層に含有させてもよい。
めっき鋼材から、めっき層形成面が30mm角となる試料を採取する。この試料を高周波グロー放電分光分析(GDS)用試料とする。試料のめっき層及び中間層形成面側から、アルゴンイオンスパッタを実施し、深さ方向の元素強度プロットを得る。一方で、測定対象の各元素の純金属板等の標準試料作製し、標準試料からあらかじめ元素強度プロットを得る。この二つの元素強度プロットの比較により、めっき層及び中間層の構成元素の濃度(含有量)を換算する。測定条件は、分析面積をφ4mm以上、スパッタ速度を約0.04~0.1μm/秒の範囲とする。
めっき層の組織は、特に限定はない。例えば、めっき層を構成する主な組織としては、準結晶相、MgZn2相、Mg2Zn3相(Mg4Zn7と同一物質)、Mg51Zn20相、Mg相、MgZn相、Al相等がある。
(1)準結晶相、MgZn2相、Mg2Zn3相、及び残部組織からなる組織。
(1)の組織の残部組織としては、例えば、Mg51Zn20相、MgZn相、Mg2Zn3相、Zn相、Al相等である。
(1)の組織において、耐食性、耐衝撃性及び耐摩耗性の観点から、準結晶相の面積分率は3~70%が好ましく、10~70%がより好ましい。また、同観点から、準結晶相、MgZn2相、及びMg2Zn3相の合計の面積分率は、3~100%が好ましく、90~100%がより好ましい。
特に、準結晶相、MgZn2相、及びMg2Zn3相の合計の面積分率が高くなると、例えば、強アルカリ環境中(アンモニア水中、苛性ソーダ中等)でも腐食量がほぼ0となるほど優れたアルカリ耐食性を示すようになる。
(2)の組織の残部組織としては、例えば、MgZn2相、Mg2Zn3相、Mg51Zn20相、MgZn相、Mg2Zn3相、Zn相等である。
(2)の組織において、耐食性、及び耐衝撃性の観点から、準結晶相の面積分率は25~45%が好ましく、30~45%がより好ましい。また、同観点から、準結晶相及びAl相の合計の面積分率は、75~100%が好ましく、90~100%がより好ましい。
めっき層の厚さは、中間層の厚さの測定と同様にして、SEM(走査型電子顕微鏡)によるめっき層の断面観察(めっき層の厚さ方向に切断された断面において、めっき層と平行な方向に2.5mm長さ分に相当する領域の観察を3視野)で測定する。
準結晶相は、準結晶相に含まれるMg含有量、Zn含有量、およびAl含有量が、原子%で、0.5≦Mg/(Zn+Al)≦0.83を満足する準結晶相として定義される。すなわち、Mg原子と、Zn原子及びAl原子の合計との比であるMg:(Zn+Al)が、3:6~5:6となる準結晶相として定義される。おおよそ、Mg:(Zn+Al)が約4:6であると考えられる。
準結晶相の化学成分は、TEM-EDX(Transmission Electron Microscope―EnergyDispersive X-ray Spectroscopy)による定量分析、又はEPMA(Electron Probe Micro-Analyzer)マッピングによる定量分析で算出することができる。なお、準結晶を金属間化合物のように正確な化学式で定義することは容易でない。準結晶相は、結晶の単位格子のように繰り返しの格子単位を定義することができず、さらには、Zn、Mgの原子位置を特定するのも困難なためである。
次に、実施形態に係るめっき鋼材の製造方法の一例について説明する。
実施形態に係るめっき鋼材は、めっき層の組成(不純物以外の組成)と同じ組成の浸漬めっき浴を利用した浸漬めっきにより製造することがよい。また、浸漬めっきは、1段めっきで実施することがよい。
そのため、高濃度Mgめっき浴を利用した浸漬めっきを実施した場合、潜伏時間が無限に続き、適切な厚みの中間層を形成した上で、めっき層を形成するのは困難であると考えられていた。
めっき浴温が550℃未満の場合、浸漬めっきを実施しても、潜伏時間が長期化し、Al-Fe間反応が開始し難い。
一方で、めっき浴が高すぎると、浴面上で鋼材を急激に酸化させ、鋼材表面にスケールが形成し濡れ性が悪化する他、鋼材の品質への悪影響を与えることがある。そのため、めっき浴温は、650℃以下が好ましい。
浸漬時間が1分未満の場合、めっき浴温550℃以上で浸漬めっきを実施しても、鋼材(地鉄)にめっき浴が濡れず、十分なFe-Al間反応が進行し難い。
一方で、浸漬時間が長すぎると、中間層が成長し過ぎて脆くなり、鋼材をめっき浴から引き上げ直後に、温度差によって内部応力が働いて、めっき層表面に亀裂が発生しやすくなる。また、鋼材等が薄い場合は、鋼材(地鉄)ごと崩落する場合がある。そのため、浸漬時間は30分未満が好ましい。
(2)めっき浴中で、鋼材を振動及び/又は回転する方法。
(3)鋼材を浸漬しためっき浴を撹拌する方法。
(4)浸漬めっき前に、フラックス処理、ショットブラスト処理、ショットピーニング処理、及び酸洗処理の少なくとも一つの処理を施した鋼材を使用する方法。
(5)表面(めっき層及び中間層が形成される面)の結晶粒径が小さい鋼材を使用する方法。結晶粒径は、5μm未満が好ましく、1μm未満がより好ましい。
(6)表面(めっき層及び中間層が形成される面)の転位密度を研削加工により高めた鋼材を使用する方法。
(7)Cu-Sn置換めっき鋼材、Znめっき鋼材(Zn付着量40g/m2以下めっき鋼材)を使用する方法。
(8)Al-Fe間反応を促進する反応助剤を含むめっき浴を使用する方法。反応助剤としては、Sn、Cr、B等が挙げられる。これらの元素は、鋼材ではなく、浸漬めっき浴に添加されなければならない。浸漬めっき性状に悪影響を与えない観点から、Sn含有量は0.50%以下、Cr含有量は0.50%以下、B含有量は0.50%以下が好ましい。ただし、上記式(B)を満たす範囲とする。
(9)Al-Fe間反応を鈍化させるSi含有量を制限しためっき浴を使用する方法。0~0.500%が好ましく、0~0.050%がより好ましく、0~0.005%がさらに好ましく、0%(つまりSiを含有させないこと)が特に好ましい。
鋼材に対するめっき浴の容量は、十分に多くすることがよい。例えば、長さ100mm×幅50mm×厚さ2mmの鋼材に対して、少なくともめっき浴の容量は、5L以上であることが好ましい。
なお、潜伏期間短縮のために、鋼材に、ブラスト処理、ブラシ研削処理等の転位密度を高める処理を実施する場合は、上記処理による酸化被膜除去後の鋼材に、フラックス処理、ショットブラスト処理、ショットピーニング処理、酸洗処理、またはブラシ研削加工等することが好ましい。そして、これら処理後、そのまま浸漬鋼材として使用するか、乾式の洗浄処理等に留めた後処理のみ施して浸漬鋼材として使用することが好ましい。
めっき浴からの引き上げ後の冷却速度には、特に制限はない。例えば、めっき浴からの引き上げ直後に、鋼材を水中に浸漬して冷却してもよく、自然冷却してもよい。
一方で、めっき鋼材の中間層(その海島構造の島部)及びめっき層に、効率的に準結晶相を生成するためには、次の冷却速度で冷却してもよい。
後処理としては、めっき鋼材の表面を処理する各種の処理が挙げられ、上層めっきを施す処理、ク口メー卜処理、非クロメート処理、りん酸塩処理、潤滑性向上処理、溶接性向上処理等がある。また、後処理としては、樹脂系塗料(例えば、ポリエステル樹脂系、アクリル樹脂系、フッ素樹脂系、塩化ビニル樹脂系、ウレタン樹脂系、エポキシ樹脂系等)を、ロール塗装、スプレー塗装、カーテンフロー塗装、ディップ塗装、フィルムラミネート法(例えば、アクリル樹脂フィルム等の樹脂フィルムを積層する際のフィルムラミネート法)等の方法により塗工して、塗料膜を形成する処理もある。
表1に示す製造条件に従って、浸漬めっきによりめっき鋼材を製造した。具体的には、次の通りである。
また、浸漬めっきを施す鋼材には、板幅70mm×板長さ150mm×板厚2.3mmの一般炭素鋼板(JIS G 3101(2010)規定SS400 黒皮材)を使用した。
A:組成=Zn-50%Mg- 2.5%Al-5.00%Ca
B:組成=Zn-35%Mg- 5.0%Al-3.00%Ca
C:組成=Zn-25%Mg-10.0%Al-2.00%Ca
D:組成=Zn-15%Mg-15.0%Al-1.00%Ca
E:組成=Zn-10%Mg-55.0%Al-0.50%Ca
F:組成=Zn- 8%Mg-67.0%Al-0.50%Ca-0.05%Si
G:組成=Zn- 8%Mg-67.0%Al-0.30%Ca-0.05%Si
H:組成=Zn- 8%Mg-67.0%Al-0.30%Ca-0.50%Cr
I:組成=Zn- 8%Mg-67.0%Al-0.30%Ca-0.50%Sn
J:組成=Zn- 8%Mg-67.0%Al-0.15%Ca-0.05%Si
K:組成=Zn- 5%Mg-70.0%Al-0.50%Ca
次に、めっき浴A~Bを利用した浸漬めっきの場合、鋼材の引き上げ後、N2ガスを吹き付けて表1に示す冷却速度で冷却し、350℃に到達と同時に直ちに、20Lの水中に鋼材を浸漬し、冷却した。一方、めっき浴C~Kを利用した浸漬めっきの場合、鋼材の引き上げ後、N2ガスの吹き付け量を調整して表1に示す冷却速度で250℃まで冷却した。
表1に示す製造条件に従って、ゼンジマー法を利用した溶融めっきにより、めっき鋼材を製造した。溶融めっきは、レスカ社製バッチ式溶融めっき装置を使用した。具体的には、次の通りである。
また、浸漬めっきを施す鋼材には、板幅100mm×板長さ150mm×板厚2.3mmの一般炭素鋼板(JIS G 3101(2010)規定SS400 黒皮材を酸洗した鋼板)を使用した。
そして、めっき浴への浸漬時間を1秒とし、めっき浴から鋼材を引抜き、その後、鋼材にN2ガスワイピングを施した。引抜速度、及びN2ガスワイピング圧は、めっき層の厚みが20μm(±1μm)となるように調整した。
また、めっき浴浸漬からN2ガスワイピングまでは、バッチ式めっき装置を高速運転し、1秒以内に完了した。
N2ガスワイピング完了後、No.40C、No.41Cについては、鋼材にN2ガスを吹き付け、平均冷却速度15℃/秒で250℃まで冷却した。また、No.42C~45Cについては、鋼材にN2ガスを吹き付け、表1に示す冷却速度にて、めっき鋼板を冷却した。
No.40C、No.41Cについては、作製しためっき鋼板を大気炉中で再度500℃にめっき鋼板を加熱し、めっき層表面を再溶融させた後、表1に示す冷却速度にて、めっき鋼板を水冷する処理を行った。
得られためっき鋼材について、中間層及びめっき層の特性(組成、組織、厚さ)について、既述の方法に従って測定した。結果を表2~表3に示す。
なお、めっき層の組成について、不純物以外は、使用しためっき浴の組成とほぼ同じであることが確認されたので、省略する。
得られためっき鋼材について、次の評価を行った。結果を表3に示す。
中間層の耐食性を評価するため、めっき鋼材の評価面のめっき層を表面切削加工で完全に除去した。めっき層を除去し、中間層のみとなった鋼材に対して、SST試験を実施した。そして、3000時間後(JIS Z 2371)の耐食性を評価した。評価基準は以下の通りである。
・Excellent:評価面に赤錆なし
・Very Good: 評価面の赤錆面積率5%以下
・Good: 評価面の赤錆面積率10%以下
・Bad: 評価面の赤錆面積率10%越え以上
めっき層の耐食性は、次のように評価した。めっき鋼板を150×70mmに切断し、切断端面部をシーリングして40℃の1mol/LのNaOH水溶液中に24時間浸漬した。24時間後、めっき鋼板を取り出して、めっき層表面上に形成した腐食生成物を常温20%クロム酸に15分浸漬して除去し、試験前後の腐食減量を測定した。腐食減量からそれぞれのめっき合金の理論密度を用いて腐食減厚に換算し、アルカリ環境耐食性を評価した。評価基準は、次の通りである。
・Excellent: 腐食減厚が1μm未満
・Very Good: 腐食減厚が1μm以上2μm以下
・Good: 腐食減厚が2μm超、4μm以下
・Bad: 腐食減厚が4μm超
めっき層の耐衝撃性は、衝撃付与後のめっき層の剥離についてグラベロ試験を用いて評価した。まず、グラベロ試験機(スガ試験機社製)を用いて、常温環境、距離30cm、空気圧3.0kg/cm2、角度90°の条件で、めっき鋼材の評価面100×100mmに、合計100kgの7号砕石を衝突させた。その後、めっき鋼材の評価面のEPMA-Fe元素マッピング像を撮影し、地鉄露出面及び中間層露出面の合計面積率を算出した。評価基準は、以下の通りである。
・Excellent:鋼材(地鉄)露出面及び中間層露出面なし
・Very Good:鋼材(地鉄)露出面及び中間層露出の合計面積率5%以下
・Good:鋼材(地鉄)露出面及び中間層露出の合計面積率10%以下
・Bad:鋼材(地鉄)露出面及び中間層露出の合計面積率10%超
めっき層の耐摩耗性は、次のように評価した。レスカ社製ピンオンディスク型摩擦摩耗試験機(FDR-2100)を使用し、φ3/16inch-SUS304Ball、荷重1000gf、半径20mm、1rpm、5回転時計回り、25℃にてめっき鋼板上に線上痕を形成した。線上痕部分を埋め込み研磨し、めっき層表面部からの最大凹部深さを測定した。評価基準は、次の通りである。
・Excellent: 最大凹部深さ 5μm未満
・Very Good: 最大凹部深さ 5μm以上7.5μm以下
・Good: 最大凹部深さ 7.5μm超、10.0μm以下
・Bad: 最大凹部深さ 10μm超
また、海部の欄の数値が「100」は、中間層が海島構造を有してないことを示している。
また、Alの欄の「bal.」との表記は、Al含有量が不純物を含む残部に相当する量であることを示している。
また、No.1E~34Eのめっき鋼材は、アルカリ環境耐食性、耐衝撃性及び耐磨耗性が高いこともわかる。
特に、40C~45Cのめっき鋼材は、中間層が薄く、海島構造が形成されていないため、中間層自体の耐食性及びめっき層の耐衝撃性が低いことがわかる。
Claims (6)
- 鋼材と、
前記鋼材の表面に被覆され、質量%で、Mg:8~50%、Al:2.5~70.0%、Ca:0.30~5.00%、Y :0~3.50%、La:0~3.50%、Ce:0~3.50%、Si:0~0.50%、Ti:0~0.50%、Cr:0~0.50%、Co:0~0.50%、Ni:0~0.50%、V :0~0.50%、Nb:0~0.50%、Cu:0~0.50%、Sn:0~0.50%、Mn:0~0.20%、Sr:0~0.50%、Sb:0~0.50%、Cd:0~0.50%、Pb:0~0.50%、及びB :0~0.50%を含み、残部がZn及び不純物からなり、かつ下記式(A)及び下記式(B)を満たすめっき層と、
前記鋼材と前記めっき層との間に介在する中間層であって、Al-Fe合金相からなる海部と、Mg含有量が8質量%以上のZn-Mg-Al合金相を含む島部と、で構成された海島構造を有し、前記Al-Fe合金相からなる海部の面積分率が55~90%である中間層と、
を備えるめっき鋼材。
・式(A):Si+Ti+Cr+Co+Ni+V+Nb+Cu+Sn+Mn+Sr+Sb+Cd+Pb+B≦0.50%
・式(B):Ca+Y+La+Ce≦5.00%
式(A)及び式(B)中、元素記号は、質量%での各元素の含有量を示す。 - 前記中間層の厚さが、5~500μmである請求項1に記載のめっき鋼材。
- 前記海部が、前記Al-Fe合金相としてAl5Fe2相からなり、
前記島部が、前記Zn-Mg-Al合金相として準結晶相、及びMgZn2相からなるか、又は、前記Zn-Mg-Al合金相として準結晶相、MgZn2相、及びMg相からなる請求項1又は請求項2に記載のめっき鋼材。 - 前記めっき層の厚さに対する前記中間層の厚さの比率が、0.2~4倍である請求項1~請求項3のいずれか1項に記載のめっき鋼材。
- 前記めっき層のMg含有量が15質量%以上であり、かつ前記Zn-Mg-Al合金相のMg含有量が15質量%以上である請求項1~請求項4のいずれか1項に記載のめっき鋼材。
- 前記めっき層が、浸漬めっき層である請求項1~請求項5のいずれか1項に記載のめっき鋼材。
Priority Applications (11)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
MX2019008300A MX2019008300A (es) | 2017-01-16 | 2017-01-16 | Producto de acero recubierto. |
CN201780083484.2A CN110191973B (zh) | 2017-01-16 | 2017-01-16 | 镀覆钢材 |
SG11201906466XA SG11201906466XA (en) | 2017-01-16 | 2017-01-16 | Coated steel product |
PCT/JP2017/001286 WO2018131171A1 (ja) | 2017-01-16 | 2017-01-16 | めっき鋼材 |
US16/477,987 US11473174B2 (en) | 2017-01-16 | 2017-01-16 | Coated steel product |
JP2017511360A JP6176424B1 (ja) | 2017-01-16 | 2017-01-16 | めっき鋼材 |
BR112019014494-3A BR112019014494A2 (pt) | 2017-01-16 | 2017-01-16 | Produto de aço revestido |
AU2017392662A AU2017392662A1 (en) | 2017-01-16 | 2017-01-16 | Plated steel material |
EP17891856.1A EP3569729A1 (en) | 2017-01-16 | 2017-01-16 | Plated steel material |
KR1020197022267A KR102272166B1 (ko) | 2017-01-16 | 2017-01-16 | 도금 강재 |
PH12019501649A PH12019501649A1 (en) | 2017-01-16 | 2019-07-16 | Coated steel product |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/JP2017/001286 WO2018131171A1 (ja) | 2017-01-16 | 2017-01-16 | めっき鋼材 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2018131171A1 true WO2018131171A1 (ja) | 2018-07-19 |
Family
ID=59559206
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2017/001286 WO2018131171A1 (ja) | 2017-01-16 | 2017-01-16 | めっき鋼材 |
Country Status (11)
Country | Link |
---|---|
US (1) | US11473174B2 (ja) |
EP (1) | EP3569729A1 (ja) |
JP (1) | JP6176424B1 (ja) |
KR (1) | KR102272166B1 (ja) |
CN (1) | CN110191973B (ja) |
AU (1) | AU2017392662A1 (ja) |
BR (1) | BR112019014494A2 (ja) |
MX (1) | MX2019008300A (ja) |
PH (1) | PH12019501649A1 (ja) |
SG (1) | SG11201906466XA (ja) |
WO (1) | WO2018131171A1 (ja) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2021171519A1 (ja) * | 2020-02-27 | 2021-09-02 | 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 | ||
WO2021171514A1 (ja) * | 2020-02-27 | 2021-09-02 | 日本製鉄株式会社 | めっき鋼材 |
WO2021171515A1 (ja) * | 2020-02-27 | 2021-09-02 | 日本製鉄株式会社 | ホットスタンプ成形体 |
WO2024047883A1 (ja) * | 2022-08-31 | 2024-03-07 | 日本製鉄株式会社 | めっき鋼材及びめっき鋼材の製造方法 |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN107090571B (zh) * | 2017-06-18 | 2018-05-25 | 荆门宁杰机电技术服务有限公司 | 一种焊管的外镀锌装置 |
WO2019131385A1 (en) * | 2017-12-26 | 2019-07-04 | Nippon Steel Nisshin Co., Ltd. | Hot-dip aluminized steel sheet and method of producing the same |
CN109161728A (zh) * | 2018-09-06 | 2019-01-08 | 靖江新舟合金材料有限公司 | 一种含镍的锌铝合金锭及其制备方法 |
CN113025935B (zh) * | 2020-07-06 | 2022-10-21 | 宝钢集团南通线材制品有限公司 | 一种桥梁缆索用热镀锌铝镁合金镀层钢丝及其制备方法 |
JP7063431B1 (ja) * | 2020-10-21 | 2022-05-09 | 日本製鉄株式会社 | めっき鋼材 |
CN112626374A (zh) * | 2020-12-16 | 2021-04-09 | 无锡华精新材股份有限公司 | 一种锌合金镀层中含镁锶钛的钢板带的制备方法 |
CN117583220A (zh) * | 2023-11-16 | 2024-02-23 | 天河(保定)环境工程有限公司 | 一种用于平板式脱硝催化剂金属网的制备方法 |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH01117052A (ja) | 1987-10-29 | 1989-05-09 | Mitsubishi Electric Corp | Icリードフレーム |
JPH09256134A (ja) | 1996-03-15 | 1997-09-30 | Tanaka Aen Mekki Kk | 高耐食性溶融Zn−Al合金めっき鋼材の製造方法 |
JP2000104154A (ja) * | 1998-07-02 | 2000-04-11 | Nippon Steel Corp | 耐食性に優れためっき鋼板と塗装鋼板及びその製造方法 |
JP2010070810A (ja) | 2008-09-18 | 2010-04-02 | Nippon Steel Corp | 高耐食性を有し加工性に優れためっき鋼材およびその製造方法 |
JP2011144429A (ja) * | 2010-01-15 | 2011-07-28 | Nippon Steel Corp | 高耐食性溶融亜鉛めっき鋼板 |
JP2015040334A (ja) | 2013-08-22 | 2015-03-02 | 新日鐵住金株式会社 | 耐食性に優れた溶融めっき鋼材及びその製造方法 |
JP5785336B1 (ja) | 2014-03-28 | 2015-09-30 | 新日鐵住金株式会社 | 準結晶含有めっき鋼板 |
JP2016514202A (ja) * | 2013-02-06 | 2016-05-19 | アルセロールミタル | 特定の微細構造を有するZnAlMgコーティングの金属シート、および対応する生産方法 |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2924894B2 (ja) | 1997-08-12 | 1999-07-26 | 田中亜鉛鍍金株式会社 | 鋼材の溶融亜鉛−アルミニウム合金めっき方法 |
US6465114B1 (en) * | 1999-05-24 | 2002-10-15 | Nippon Steel Corporation | -Zn coated steel material, ZN coated steel sheet and painted steel sheet excellent in corrosion resistance, and method of producing the same |
JP2001316791A (ja) * | 2000-04-28 | 2001-11-16 | Nippon Steel Corp | 耐食性、外観に優れた溶融亜鉛−アルミ系めっき鋼板 |
JP2002060978A (ja) * | 2000-08-17 | 2002-02-28 | Nippon Steel Corp | 金属被覆を有する耐食性に優れる鋼 |
US8911879B2 (en) * | 2009-01-16 | 2014-12-16 | Nippon Steel & Sumitomo Metal Corporation | Hot-dip Zn—Al—Mg—Si—Cr alloy-coated steel material with excellent corrosion resistance |
JP5593836B2 (ja) * | 2009-05-29 | 2014-09-24 | Jfeスチール株式会社 | 溶融Al−Zn系めっき鋼板 |
EP2821520B1 (de) * | 2013-07-03 | 2020-11-11 | ThyssenKrupp Steel Europe AG | Verfahren zum beschichten von stahlflachprodukten mit einer metallischen schutzschicht |
EP3369838B1 (en) * | 2015-10-26 | 2019-08-21 | Posco | Zinc alloy plated steel sheet having excellent bending workability and manufacturing method therefor |
WO2017203314A1 (en) * | 2016-05-24 | 2017-11-30 | Arcelormittal | Twip steel sheet having an austenitic matrix |
-
2017
- 2017-01-16 US US16/477,987 patent/US11473174B2/en active Active
- 2017-01-16 KR KR1020197022267A patent/KR102272166B1/ko active IP Right Grant
- 2017-01-16 MX MX2019008300A patent/MX2019008300A/es unknown
- 2017-01-16 WO PCT/JP2017/001286 patent/WO2018131171A1/ja active Application Filing
- 2017-01-16 EP EP17891856.1A patent/EP3569729A1/en not_active Withdrawn
- 2017-01-16 CN CN201780083484.2A patent/CN110191973B/zh active Active
- 2017-01-16 AU AU2017392662A patent/AU2017392662A1/en not_active Abandoned
- 2017-01-16 JP JP2017511360A patent/JP6176424B1/ja active Active
- 2017-01-16 SG SG11201906466XA patent/SG11201906466XA/en unknown
- 2017-01-16 BR BR112019014494-3A patent/BR112019014494A2/pt not_active IP Right Cessation
-
2019
- 2019-07-16 PH PH12019501649A patent/PH12019501649A1/en unknown
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH01117052A (ja) | 1987-10-29 | 1989-05-09 | Mitsubishi Electric Corp | Icリードフレーム |
JPH09256134A (ja) | 1996-03-15 | 1997-09-30 | Tanaka Aen Mekki Kk | 高耐食性溶融Zn−Al合金めっき鋼材の製造方法 |
JP2000104154A (ja) * | 1998-07-02 | 2000-04-11 | Nippon Steel Corp | 耐食性に優れためっき鋼板と塗装鋼板及びその製造方法 |
JP2010070810A (ja) | 2008-09-18 | 2010-04-02 | Nippon Steel Corp | 高耐食性を有し加工性に優れためっき鋼材およびその製造方法 |
JP2011144429A (ja) * | 2010-01-15 | 2011-07-28 | Nippon Steel Corp | 高耐食性溶融亜鉛めっき鋼板 |
JP2016514202A (ja) * | 2013-02-06 | 2016-05-19 | アルセロールミタル | 特定の微細構造を有するZnAlMgコーティングの金属シート、および対応する生産方法 |
JP2015040334A (ja) | 2013-08-22 | 2015-03-02 | 新日鐵住金株式会社 | 耐食性に優れた溶融めっき鋼材及びその製造方法 |
JP5785336B1 (ja) | 2014-03-28 | 2015-09-30 | 新日鐵住金株式会社 | 準結晶含有めっき鋼板 |
WO2015145721A1 (ja) * | 2014-03-28 | 2015-10-01 | 新日鐵住金株式会社 | 準結晶含有めっき鋼板 |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2021171519A1 (ja) * | 2020-02-27 | 2021-09-02 | 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 | ||
WO2021171514A1 (ja) * | 2020-02-27 | 2021-09-02 | 日本製鉄株式会社 | めっき鋼材 |
JPWO2021171514A1 (ja) * | 2020-02-27 | 2021-09-02 | ||
JPWO2021171519A1 (ja) * | 2020-02-27 | 2021-09-02 | ||
WO2021171515A1 (ja) * | 2020-02-27 | 2021-09-02 | 日本製鉄株式会社 | ホットスタンプ成形体 |
WO2021171517A1 (ja) * | 2020-02-27 | 2021-09-02 | 日本製鉄株式会社 | ホットスタンプ成形体 |
JPWO2021171515A1 (ja) * | 2020-02-27 | 2021-09-02 | ||
JP7226642B2 (ja) | 2020-02-27 | 2023-02-21 | 日本製鉄株式会社 | めっき鋼材 |
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 |
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 |
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 |
WO2024047883A1 (ja) * | 2022-08-31 | 2024-03-07 | 日本製鉄株式会社 | めっき鋼材及びめっき鋼材の製造方法 |
Also Published As
Publication number | Publication date |
---|---|
JP6176424B1 (ja) | 2017-08-09 |
KR102272166B1 (ko) | 2021-07-05 |
SG11201906466XA (en) | 2019-08-27 |
US11473174B2 (en) | 2022-10-18 |
CN110191973B (zh) | 2021-04-20 |
AU2017392662A1 (en) | 2019-08-15 |
PH12019501649A1 (en) | 2020-03-09 |
JPWO2018131171A1 (ja) | 2019-01-17 |
CN110191973A (zh) | 2019-08-30 |
KR20190102239A (ko) | 2019-09-03 |
BR112019014494A2 (pt) | 2020-02-11 |
US20190368007A1 (en) | 2019-12-05 |
EP3569729A1 (en) | 2019-11-20 |
MX2019008300A (es) | 2019-09-11 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP6176424B1 (ja) | めっき鋼材 | |
JP6428974B1 (ja) | めっき鋼材 | |
KR102240878B1 (ko) | 도금 강재 | |
JP6394843B1 (ja) | めっき鋼板 | |
JP6528627B2 (ja) | めっき鋼材 | |
KR101302291B1 (ko) | 내식성과 피로 특성이 우수한 교량용 고강도 Zn―Al 도금 강선 및 그 제조 방법 | |
JP6787002B2 (ja) | Al−Mg系溶融めっき鋼材 | |
EP1997927A1 (en) | Highly corrosion-resistant hot dip galvanized steel stock | |
CN110431249B (zh) | 镀覆钢板 | |
US10508330B2 (en) | Quasicrystal-containing plated steel sheet and method for producing quasicrystal-containing plated steel sheet | |
JP7136351B2 (ja) | めっき鋼材 | |
KR20200051723A (ko) | 도장 후 내식성이 우수한 용융 Zn계 도금 강판 | |
WO2020213688A1 (ja) | めっき鋼板 | |
KR20180039107A (ko) | Mg 함유 Zn 합금 피복 강재 | |
WO2011001640A1 (ja) | Zn-Alめっき鉄線及びその製造方法 | |
JP7031787B2 (ja) | めっき鋼材 | |
WO2020213680A1 (ja) | めっき鋼材 | |
CN115867693A (zh) | 镀覆钢材 | |
JP6880238B2 (ja) | 溶融めっき鋼線およびその製造方法 | |
CN117280069A (zh) | 热浸镀钢材 | |
WO2023191027A1 (ja) | めっき鋼線 | |
JP6848939B2 (ja) | 溶融めっき熱延鋼板の製造方法及び溶融めっき熱延鋼板、並びに溶融めっき処理用熱延鋼板の製造方法及び溶融めっき処理用熱延鋼板 | |
JP2020059888A (ja) | 溶融めっき線およびその製造方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
ENP | Entry into the national phase |
Ref document number: 2017511360 Country of ref document: JP Kind code of ref document: A |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 17891856 Country of ref document: EP Kind code of ref document: A1 |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
REG | Reference to national code |
Ref country code: BR Ref legal event code: B01A Ref document number: 112019014494 Country of ref document: BR |
|
ENP | Entry into the national phase |
Ref document number: 20197022267 Country of ref document: KR Kind code of ref document: A |
|
ENP | Entry into the national phase |
Ref document number: 2017392662 Country of ref document: AU Date of ref document: 20170116 Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2017891856 Country of ref document: EP |
|
ENP | Entry into the national phase |
Ref document number: 112019014494 Country of ref document: BR Kind code of ref document: A2 Effective date: 20190712 |