JP6065884B2 - Steel sheet excellent in corrosion resistance of cut end face and manufacturing method thereof - Google Patents
Steel sheet excellent in corrosion resistance of cut end face and manufacturing method thereof Download PDFInfo
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- JP6065884B2 JP6065884B2 JP2014144714A JP2014144714A JP6065884B2 JP 6065884 B2 JP6065884 B2 JP 6065884B2 JP 2014144714 A JP2014144714 A JP 2014144714A JP 2014144714 A JP2014144714 A JP 2014144714A JP 6065884 B2 JP6065884 B2 JP 6065884B2
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- 229910000831 Steel Inorganic materials 0.000 title claims description 184
- 239000010959 steel Substances 0.000 title claims description 184
- 238000005260 corrosion Methods 0.000 title claims description 66
- 230000007797 corrosion Effects 0.000 title claims description 64
- 238000004519 manufacturing process Methods 0.000 title claims description 19
- 239000002244 precipitate Substances 0.000 claims description 62
- 239000011247 coating layer Substances 0.000 claims description 57
- 238000007747 plating Methods 0.000 claims description 55
- 239000011701 zinc Substances 0.000 claims description 40
- 238000000137 annealing Methods 0.000 claims description 38
- 229910052725 zinc Inorganic materials 0.000 claims description 36
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 35
- 238000000576 coating method Methods 0.000 claims description 32
- 238000005096 rolling process Methods 0.000 claims description 31
- 239000010410 layer Substances 0.000 claims description 29
- 239000011248 coating agent Substances 0.000 claims description 28
- 239000000049 pigment Substances 0.000 claims description 26
- 239000002335 surface treatment layer Substances 0.000 claims description 19
- 238000004381 surface treatment Methods 0.000 claims description 17
- 239000012535 impurity Substances 0.000 claims description 15
- 239000002131 composite material Substances 0.000 claims description 14
- 239000003973 paint Substances 0.000 claims description 14
- 238000005097 cold rolling Methods 0.000 claims description 10
- 238000005098 hot rolling Methods 0.000 claims description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims description 10
- 230000009466 transformation Effects 0.000 claims description 8
- 238000004804 winding Methods 0.000 claims description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 28
- 238000000034 method Methods 0.000 description 24
- 239000000047 product Substances 0.000 description 15
- 238000003303 reheating Methods 0.000 description 15
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 13
- 230000009471 action Effects 0.000 description 11
- 239000000203 mixture Substances 0.000 description 11
- 239000000463 material Substances 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 238000005520 cutting process Methods 0.000 description 7
- 150000003568 thioethers Chemical class 0.000 description 7
- 238000009749 continuous casting Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 3
- 229910019142 PO4 Inorganic materials 0.000 description 3
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 3
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 239000010452 phosphate Substances 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 238000010008 shearing Methods 0.000 description 3
- 229910000077 silane Inorganic materials 0.000 description 3
- 229910018134 Al-Mg Inorganic materials 0.000 description 2
- 229910018467 Al—Mg Inorganic materials 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 2
- 229910001335 Galvanized steel Inorganic materials 0.000 description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 229910007570 Zn-Al Inorganic materials 0.000 description 2
- 229910007567 Zn-Ni Inorganic materials 0.000 description 2
- 229910007614 Zn—Ni Inorganic materials 0.000 description 2
- YRKCREAYFQTBPV-UHFFFAOYSA-N acetylacetone Chemical compound CC(=O)CC(C)=O YRKCREAYFQTBPV-UHFFFAOYSA-N 0.000 description 2
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910021538 borax Inorganic materials 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000009713 electroplating Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000008397 galvanized steel Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000010422 painting Methods 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 235000010339 sodium tetraborate Nutrition 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 241000221535 Pucciniales Species 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229920006026 co-polymeric resin Polymers 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- UQGFMSUEHSUPRD-UHFFFAOYSA-N disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane Chemical compound [Na+].[Na+].O1B([O-])OB2OB([O-])OB1O2 UQGFMSUEHSUPRD-UHFFFAOYSA-N 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- -1 for example Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000006166 lysate Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920001225 polyester resin Polymers 0.000 description 1
- 239000004645 polyester resin Substances 0.000 description 1
- 229920005672 polyolefin resin Polymers 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000009966 trimming Methods 0.000 description 1
- BSVBQGMMJUBVOD-UHFFFAOYSA-N trisodium borate Chemical compound [Na+].[Na+].[Na+].[O-]B([O-])[O-] BSVBQGMMJUBVOD-UHFFFAOYSA-N 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
- B32B15/012—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of an iron alloy or steel, another layer being formed of aluminium or an aluminium alloy
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
- B32B15/013—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/54—Furnaces for treating strips or wire
- C21D9/56—Continuous furnaces for strip or wire
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
Description
本発明は、主として表面に亜鉛系めっき層等の表面処理層を形成して使用され、室内の電気製品、事務機器などの素材として好適な鋼板に関し、鋼板のせん断端面、打ち抜き面など、亜鉛等の犠牲防食作用が及ばない切断端面の耐食性に優れた鋼板、およびその製造方法に関する。 The present invention is mainly used by forming a surface treatment layer such as a zinc-based plating layer on the surface, and relates to a steel plate suitable as a material for indoor electrical products, office equipment, etc. The present invention relates to a steel plate excellent in corrosion resistance of a cut end face that does not have the sacrificial anticorrosive action, and a method for producing the same.
亜鉛系めっき等を施した表面処理鋼板は、優れた耐食性を有することから、家電、事務機器などの製品部材として広く使用されている。これらの製品部材は、その生産工程で鋼板の片面または両面に亜鉛系めっき等の表面処理層を、或いは更にその上に塗装を施してなる表面処理鋼板に、せん断加工、打ち抜き加工、穴あけ、トリミングなど何らかの機械的切断加工したものを所望の形に成形して製造される。 A surface-treated steel sheet to which zinc-based plating or the like has been applied is widely used as a product member for home appliances, office equipment and the like because of its excellent corrosion resistance. These product members are sheared, punched, drilled, trimmed into a surface-treated steel sheet with a zinc-plated surface treatment layer on one or both surfaces of the steel sheet in the production process, or further coated thereon. It is manufactured by molding a product that has been mechanically cut into a desired shape.
従来、これらの製品部材として使用された後の表面処理鋼板は、製品と共に廃却されるのが一般的であった。しかしながら、平成１３年より施行された家電リサイクル法により、これらの部材が再利用（リユース）されるようになった。しかるに、製品を回収して部材を再度同様の製品の部材として利用しようとすると、部材製造時において機械的切断加工により形成された表面処理鋼板の切断面（せん断面、打ち抜き面、トリミング面など）、すなわち亜鉛系めっき等が付着していない面に赤錆が発錆して、再利用に適合し難いという問題が露呈した。錆は、電気伝導性などを有し、錆の剥落による電気回路の損傷などが懸念されるためである。 Conventionally, the surface-treated steel sheet after being used as a product member has been generally discarded together with the product. However, due to the Home Appliance Recycling Law that came into effect in 2001, these members have been reused. However, if the product is recovered and the member is used again as a member of the same product, the cut surface (shear surface, punched surface, trimming surface, etc.) of the surface-treated steel sheet formed by mechanical cutting during the manufacture of the member That is, the problem that red rust rusts on the surface to which zinc-based plating or the like is not attached and is difficult to adapt to reuse. This is because rust has electrical conductivity and the like, and there is a concern about damage to the electric circuit due to rust peeling.
亜鉛系めっき鋼板などは、切断端面を除く大部分の面積が十分に防食されている。そのため、従来、亜鉛系めっき鋼板などを家電製品分野で使用する際、切断端面にも亜鉛の犠牲防食効果が及ぶものと考えられており、切断端面の耐食性について十分な検討がなされていなかった。 Most of the zinc-plated steel sheet and the like are sufficiently anticorrosive except for the cut end face. For this reason, conventionally, when zinc-based plated steel sheets and the like are used in the field of home appliances, it has been considered that the sacrificial anticorrosive effect of zinc is also exerted on the cut end face, and sufficient investigation has not been made on the corrosion resistance of the cut end face.
亜鉛系めっき鋼板などの切断端面にみられる耐食性不足の問題を根本的に解決するには、母材となる鋼板の耐食性を向上させる必要があると考えられる。亜鉛系めっき鋼板の切断端面耐食性向上を図る技術に関し、例えば、特許文献１には、母材となる鋼板を、質量％で、C：0.001〜0.1％、Si：0.1％以下、Mn：0.05〜0.15％、P：0.02％以下、S：0.001〜0.010％、Al：0.003〜0.03％、Ti：0.03〜0.2％、Zr：0.001〜0.1％を含有し、かつZr/Ti≧0.03を満たす鋼板とする技術が提案されている。また、特許文献１には、鋼中に含まれる不純物の量を制限するとともに、Mn系析出物、S系析出物を減少させることにより、良好な切断端面の耐食性が得られると記載されている。 In order to fundamentally solve the problem of insufficient corrosion resistance seen on the cut end face of galvanized steel sheets, it is considered necessary to improve the corrosion resistance of the steel sheet as the base material. Regarding the technology for improving the corrosion resistance of the cut end surface of a galvanized steel sheet, for example, Patent Document 1 discloses that a steel sheet as a base material is in mass%, C: 0.001 to 0.1%, Si: 0.1% or less, Mn: 0.05 to A steel plate containing 0.15%, P: 0.02% or less, S: 0.001-0.010%, Al: 0.003-0.03%, Ti: 0.03-0.2%, Zr: 0.001-0.1% and satisfying Zr / Ti ≧ 0.03 Techniques to do this have been proposed. Patent Document 1 describes that, by limiting the amount of impurities contained in the steel, reducing the Mn-based precipitates and the S-based precipitates, it is possible to obtain good cut end surface corrosion resistance. .
一方、家電、事務機器などの製品部材として使用される鋼板は、所望の強度を有することも要求される。従来、家電、事業機器などの製品部材には、主に引張強さ（TS）270MPa級の軟質鋼板が多く用いられていた。しかし、近年、製品の軽量化や運送費の低減を目的として鋼板の薄肉化が要求されている。このような理由により、家電、事務機器用素材として、板厚が薄くても強度を保持できる引張強さ（TS）440MPa超えの高張力鋼板の需要が高まりつつある。 On the other hand, a steel plate used as a product member for home appliances, office equipment, etc. is also required to have a desired strength. Conventionally, soft steel sheets with a tensile strength (TS) of 270 MPa have been mainly used for product members such as home appliances and business equipment. However, in recent years, thinning of steel sheets has been demanded for the purpose of reducing product weight and reducing transportation costs. For these reasons, there is an increasing demand for high-tensile steel plates with a tensile strength (TS) exceeding 440 MPa that can maintain strength even when the plate thickness is thin, as materials for home appliances and office equipment.
亜鉛系めっき鋼板の高張力化を図る技術に関しては、例えば、特許文献２に、母材となる鋼板を、質量％で、C：0.0010〜0.0080％、Si：0.4％以下、Mn：0.1〜1.0％、P：0.08％以下、S：0.05％以下、Al：0.05％以下、N：0.0060〜0.0200％を含み、かつNとAlを、N含有量とAl含有量との比、N/Alが0.2以上となるように含有し、さらに固溶Nを0.0040％以上含み、残部Feおよび不可避的不純物からなる組成を有する鋼板とする技術が提案されている。 Regarding the technology for increasing the tensile strength of a zinc-based plated steel sheet, for example, in Patent Document 2, the steel sheet used as a base material is, in mass%, C: 0.0010 to 0.0080%, Si: 0.4% or less, Mn: 0.1 to 1.0. %, P: 0.08% or less, S: 0.05% or less, Al: 0.05% or less, N: 0.0060 to 0.0200%, and N and Al, ratio of N content to Al content, N / Al There has been proposed a technique for forming a steel sheet containing 0.2 or more, further containing 0.0040% or more of solute N, and having a composition composed of the remaining Fe and inevitable impurities.
しかしながら、特許文献１に提案された技術では、Mn系析出物やS系析出物（MnS）を減少させる目的で、鋼板のMn含有量を質量％で0.15％以下に制限している。このように、鋼の強度向上に寄与するMnの含有量を0.15％以下に制限した場合、引張強さ（TS）440MPa超えの高張力鋼板は得られない。 However, in the technique proposed in Patent Document 1, the Mn content of the steel sheet is limited to 0.15% or less by mass for the purpose of reducing Mn-based precipitates and S-based precipitates (MnS). Thus, when the content of Mn that contributes to improving the strength of steel is limited to 0.15% or less, a high-tensile steel plate with a tensile strength (TS) exceeding 440 MPa cannot be obtained.
一方、特許文献２に提案されているように、高張力鋼板では多くの場合、Mn含有量を質量％で0.1％以上とすることにより鋼板の高張力化を図っている。しかしながら、Mn含有量が高くなるにつれて、鋼板中のMnS析出量が増加する。MnSを主とする析出物は、化学的に活性で水に溶解し易いことから、MnS析出量が増加すると該析出物を起点とした発錆が問題となる。したがって、例えばMn含有量が質量％で0.15％を超えると、特に鋼板の切断端面での発錆を抑制することができない。 On the other hand, as proposed in Patent Document 2, in many high-strength steel sheets, the tensile strength of the steel sheet is increased by setting the Mn content to 0.1% or more by mass%. However, as the Mn content increases, the amount of MnS precipitation in the steel sheet increases. Since precipitates mainly composed of MnS are chemically active and easily dissolved in water, when the amount of MnS deposited increases, rusting starting from the precipitates becomes a problem. Therefore, for example, when the Mn content exceeds 0.15% by mass%, it is not possible to suppress rusting particularly at the cut end face of the steel sheet.
以上のように、従来では、鋼板の高張力化と耐食性の両立は極めて困難であった。このような状況下、Mnを高濃度で含有する鋼板においても、切断端面の耐食性に優れた鋼板が強く求められている。 As described above, conventionally, it has been extremely difficult to achieve both high tensile strength and corrosion resistance of the steel sheet. Under such circumstances, a steel sheet excellent in corrosion resistance of the cut end face is strongly demanded even in a steel sheet containing Mn at a high concentration.
本発明は、かかる事情に鑑みてなされたものであって、Mn含有量が質量％で0.15％超えであり且つ切断端面の耐食性に優れた鋼板およびその製造方法を提案することを目的とする。なお、ここでいう「切断端面」とは、鋼板等に、せん断、打ち抜き等の機械的切断加工を施すことにより生じた鋼板端面を意味する。 This invention is made | formed in view of this situation, Comprising: It aims at proposing the steel plate which Mn content exceeds 0.15% by mass%, and was excellent in the corrosion resistance of a cut end surface, and its manufacturing method. The “cut end face” as used herein means a steel plate end face produced by subjecting a steel sheet or the like to mechanical cutting such as shearing or punching.
本発明者らは、上記課題を解決すべく、質量％で0.15％を超えるMnを含有する鋼板、具体的には質量％で0.16％以上のMnを含有する鋼板の耐食性に影響を及ぼす各種要因について鋭意検討した。 In order to solve the above problems, the present inventors have various factors that affect the corrosion resistance of steel sheets containing Mn exceeding 0.15% by mass, specifically, steel sheets containing Mn of 0.16% or more by mass%. We studied earnestly.
先述のとおり、鋼板中の析出物、特にMnを含有する析出物は、発錆の起点となるため、鋼板の耐食性に悪影響を及ぼす。それゆえ、鋼板の耐食性向上を図るうえでは、Mnを含有する析出物の析出量を極力低減することが好ましい。しかしながら、質量％で0.16％以上のMnを含む鋼板の場合、Mnを含有する析出物、例えばMnSをはじめとするMn系硫化物の析出を抑制することが極めて困難である。 As described above, precipitates in the steel sheet, in particular, precipitates containing Mn serve as a starting point for rusting, and thus adversely affect the corrosion resistance of the steel sheet. Therefore, in order to improve the corrosion resistance of the steel sheet, it is preferable to reduce the precipitation amount of the precipitate containing Mn as much as possible. However, in the case of a steel plate containing 0.16% or more of Mn by mass%, it is extremely difficult to suppress precipitation of Mn-containing precipitates, for example, Mn-based sulfides including MnS.
そこで、本発明者らは、大気中、特に屋内使用環境下での鋼板の腐食について考究し、Mnを含有する析出物の形態を最適化することで鋼板の耐食性を改善することを試みた。その結果、鋼板に存在するMnを含有する析出物のうち、直径0.5μm超えの析出物が、特に発錆の起点になり易く、鋼板の耐食性に悪影響を及ぼすという知見を得た。 Therefore, the present inventors have studied the corrosion of the steel sheet in the atmosphere, particularly in an indoor use environment, and tried to improve the corrosion resistance of the steel sheet by optimizing the form of the precipitate containing Mn. As a result, it was found that among the precipitates containing Mn present in the steel sheet, precipitates having a diameter of more than 0.5 μm are particularly likely to be the starting point of rusting and adversely affect the corrosion resistance of the steel sheet.
また、Mnを含有する析出物のうち、直径0.5μm超えの析出物が鋼板に存在する場合であっても、直径0.5μm超えの析出物に含まれるMn量を100質量ppm以下に抑制すれば、鋼板の耐食性を大幅に改善できるという知見を得た。具体的には、鋼板の質量をWtとし、直径0.5μm超えの析出物に含まれるMnの合計質量をWpとした場合に、Wp/Wt×100≦0.01を満足すれば、鋼板の耐食性が大幅に改善され、切断端面の耐食性に優れた鋼板が得られるという知見を得た。そして、Mn含有量を質量％で0.16％以上とし、直径0.5μm超えの析出物に含まれるMn量を100質量ppm以下に抑制することにより、鋼板の高張力化を図りつつ耐食性を飛躍的に改善することができ、室内環境下において切断端面での発錆を大幅に抑制できるという知見を得た。 Further, among the precipitates containing Mn, even if a precipitate having a diameter exceeding 0.5 μm is present in the steel sheet, the amount of Mn contained in the precipitate having a diameter exceeding 0.5 μm is suppressed to 100 mass ppm or less. The knowledge that the corrosion resistance of the steel sheet can be greatly improved was obtained. Specifically, when the mass of the steel sheet is Wt and the total mass of Mn contained in the precipitate having a diameter exceeding 0.5 μm is Wp, if Wp / Wt × 100 ≦ 0.01 is satisfied, the corrosion resistance of the steel sheet is greatly increased. It was found that a steel sheet with improved corrosion resistance at the cut end face can be obtained. And by making Mn content 0.16% or more by mass% and suppressing Mn content contained in precipitates with a diameter exceeding 0.5 μm to 100 mass ppm or less, the corrosion resistance is drastically improved while increasing the tensile strength of the steel sheet. It was possible to improve, and the knowledge that rusting at the cut end face can be greatly suppressed under the indoor environment.
更に、本発明者らは、質量％で0.16％以上のMnを含む鋼板について、上記の如く直径0.5μm超えの析出物に含まれるMn量を100質量ppm以下に抑制する手段について検討した。 Furthermore, the present inventors examined a means for suppressing the amount of Mn contained in precipitates having a diameter exceeding 0.5 μm as described above to a steel plate containing 0.16% or more of Mn by mass% as described above.
家電製品や事務機器などの製品部材として使用される鋼板は、一般的に、鋳片を、再加熱し、熱間圧延を施して熱延板とし、該熱延板を酸洗後、冷間圧延を施して冷延板とし、該冷延板に連続焼鈍処理を施し、必要に応じて調質圧延を施すことにより製造される。ここで、鋳片には、通常、Mn系硫化物が析出している。そして、鋳片の再加熱温度が低いと、再加熱時にMn系硫化物を溶解することができず、鋳片に析出していたMn系硫化物が連続焼鈍後の鋼板に残存する。一方、鋳片の再加熱温度が十分に高い場合、再加熱時にMn系硫化物は溶解するが、後工程である連続焼鈍時にMn系硫化物が再析出する。 Steel sheets used as product members for home appliances and office equipment are generally reheated slabs, hot rolled to form hot rolled sheets, pickled hot rolled sheets, It is manufactured by rolling to obtain a cold-rolled sheet, subjecting the cold-rolled sheet to a continuous annealing treatment, and subjecting it to temper rolling as necessary. Here, Mn-based sulfide is usually deposited on the slab. If the reheating temperature of the slab is low, the Mn sulfide cannot be dissolved at the time of reheating, and the Mn sulfide deposited on the slab remains in the steel sheet after the continuous annealing. On the other hand, when the reheating temperature of the slab is sufficiently high, the Mn sulfide is dissolved at the time of reheating, but the Mn sulfide is reprecipitated at the time of continuous annealing, which is a subsequent process.
本発明者らは、鋳片に析出していたMn系硫化物が残存した鋼板と、連続焼鈍時にMn系硫化物が再析出した鋼板について、直径0.5μm超えの析出物に含まれるMn量を比較した。その結果、連続焼鈍時にMn系硫化物が再析出した鋼板よりも、鋳片に析出していたMn系硫化物が残存した鋼板のほうが、直径0.5μm超えの析出物に含まれるMn量が低くなる傾向にあることを突き止めた。 The present inventors have determined the Mn content contained in precipitates having a diameter of more than 0.5 μm for steel sheets in which Mn-based sulfides remaining in the slab remain and steel sheets in which Mn-based sulfides re-deposited during continuous annealing. Compared. As a result, the amount of Mn contained in precipitates with a diameter exceeding 0.5 μm is lower in steel sheets with Mn-based sulfides remaining in the slab than in steel sheets in which Mn-based sulfides re-deposited during continuous annealing. I found out that it tends to be.
また、本発明者らが更に検討を進めた結果、不純物成分をはじめとする鋳片成分の含有量を制限し、鋳片の再加熱温度を1000℃以上1100℃以下と通常よりも低めに設定し、鋳片の再加熱時にMn系硫化物を溶解させずに残存させ、熱延板の巻取り温度や冷延板の焼鈍温度を最適化することにより、直径0.5μm超えの析出物に含まれるMn量が100質量ppm以下に抑制された鋼板が得られるという知見を得た。 In addition, as a result of further investigation by the inventors, the content of slab components including impurity components is limited, and the reheating temperature of the slab is set to 1000 ° C. or higher and 1100 ° C. or lower and lower than usual. In addition, Mn-based sulfides remain undissolved during reheating of the slab, and by optimizing the coiling temperature of the hot-rolled sheet and the annealing temperature of the cold-rolled sheet, it is included in precipitates exceeding 0.5 μm in diameter. It was found that a steel sheet in which the amount of Mn produced was suppressed to 100 mass ppm or less was obtained.
なお、鋳片のMn系硫化物を残存させることにより鋼板の耐食性が大幅に改善される理由は定かではない。しかし、本発明者らは、以下の理由によるものと推測している。 The reason why the corrosion resistance of the steel sheet is greatly improved by leaving the Mn-based sulfide in the slab is not clear. However, the present inventors presume that this is due to the following reason.
鋳片に存在するMn系硫化物の多くは、多少ともFeSを含んでおり、(Mn・Fe)Sなる組成を有する。一方、鋳片の再加熱時にこの(Mn・Fe)Sが溶解すると、後工程の連続焼鈍でMnSが再析出する。すなわち、連続焼鈍時に再析出するMn系硫化物は、FeSを含まず、主にMnSなる組成を有する。 Many of the Mn-based sulfides present in the slab contain FeS somewhat, and have a composition of (Mn · Fe) S. On the other hand, when this (Mn · Fe) S is dissolved during reheating of the slab, MnS is reprecipitated by continuous annealing in the subsequent process. That is, the Mn sulfide that re-deposits during continuous annealing does not contain FeS and has a composition that is mainly MnS.
ここで、MnSは、アノード欠陥を増大するため、発錆起点となり得る。また、MnSは水に溶け易く、MnS＋2H2O→Mn(OH)2＋H2Sの反応で生成するH2Sがアノード部のpHを下げて、鉄の溶解を促進すると推定される。一方、MnSにFeが固溶した(Mn・Fe)Sは、Feが固溶している分、MnSと比較して化学的に不活性であり、水に溶け難い。以上の理由により、鋳片に存在するMn系硫化物（(Mn・Fe)S）よりも、連続焼鈍時に再析出するMn系硫化物（MnS）のほうが発錆の起点となり易くなるものと推測される。 Here, since MnS increases anode defects, it can be a starting point for rusting. MnS is easily dissolved in water, and it is estimated that H 2 S produced by the reaction of MnS + 2H 2 O → Mn (OH) 2 + H 2 S lowers the pH of the anode part and promotes dissolution of iron. On the other hand, (Mn · Fe) S in which Fe is dissolved in MnS is chemically inactive as compared with MnS and hardly dissolves in water because Fe is dissolved. For the above reasons, Mn sulfide (MnS) reprecipitated during continuous annealing is more likely to be the starting point of rusting than Mn sulfide ((Mn · Fe) S) present in the slab. Is done.
また、鋼中のSが、MnSの形態で析出するよりも、(Mn・Fe)Sの形態で析出するほうが、鋼中のSを固定するために必要となるMn量が少なくなる。そのため、連続焼鈍時にMn系硫化物（MnS）が再析出した鋼板よりも、鋳片に析出していたMn系硫化物（(Mn・Fe)S）が残存した鋼板のほうが、直径0.5μm超えの析出物に含まれるMn量が低くなるものと推測される。 In addition, the amount of Mn required to fix S in the steel is smaller when S in the steel is precipitated in the form of (Mn · Fe) S than in the form of MnS. Therefore, the steel plate with Mn sulfide ((Mn · Fe) S) remaining in the slab is larger than the diameter of 0.5μm than the steel plate with Mn sulfide (MnS) reprecipitated during continuous annealing. It is presumed that the amount of Mn contained in the precipitate is reduced.
更に、鋳片の再加熱時にMn系硫化物（(Mn・Fe)S）を溶解せずに残存させると、後工程の冷間圧延により得られる冷延板の固溶S量や固溶Mn量を低減することができる。したがって、冷延板の連続焼鈍時に再析出するMn系硫化物（MnS）が抑制され、鋼板の耐食性が改善するものと推測される。また、直径0.5μm超えの析出物に含まれるMn量が上記した範囲に抑制されていれば、Si含有量を4.0％まで増加させても、鋼板の耐食性の著しい低下は認められないことも知見した。 Furthermore, if Mn sulfide ((Mn · Fe) S) is left undissolved during reheating of the slab, the amount of solute S and solute Mn of the cold-rolled sheet obtained by cold rolling in the subsequent process The amount can be reduced. Therefore, it is presumed that the Mn-based sulfide (MnS) reprecipitated during the continuous annealing of the cold rolled sheet is suppressed, and the corrosion resistance of the steel sheet is improved. In addition, if the amount of Mn contained in precipitates with a diameter exceeding 0.5 μm is suppressed within the above range, it is also found that even if the Si content is increased to 4.0%, no significant decrease in the corrosion resistance of the steel sheet is observed. did.
本発明は、かかる知見に基づき、更に検討を重ねた末に完成されたものである。すなわち、本発明の要旨構成は次のとおりである。
［１］質量％で、C：0.001％以上0.1％以下、Si：4.0％以下（但し、0.01％以下を除く）、Mn：0.16％以上1.0％以下、P：0.03％以下、S：0.02％以下、Al：0.003％以上0.06％以下を含有し、残部がFeおよび不可避的不純物からなる組成を有し、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下であることを特徴とする引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板。
［２］鋼板の片面または両面に、表面処理層として亜鉛系めっき層を備える鋼板であって、該鋼板が質量％で、C：0.001％以上0.1％以下、Si：0.5％以下（但し、0.01％以下を除く）、Mn：0.16％以上1.0％以下、P：0.03％以下、S：0.02％以下、Al：0.003％以上0.06％以下を含有し、残部がFeおよび不可避的不純物からなる組成を有し、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下であることを特徴とする引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板。
［３］前記［２］において、前記亜鉛系めっき層が、片面当たりのめっき付着量が5g/m2以上の亜鉛系めっき層であることを特徴とする鋼板。
［４］前記［３］において、前記亜鉛系めっき層の表面にさらに、無機被覆層、有機被覆層、無機有機複合被覆層のいずれか１種以上の被覆層を備えることを特徴とする鋼板。
［５］鋼板の片面または両面に、表面処理層として犠牲防食顔料を含む塗膜を有する鋼板であって、該鋼板が質量％で、C：0.001％以上0.1％以下、Si：0.5％超え4.0％以下、Mn：0.16％以上1.0％以下、P：0.03％以下、S：0.02％以下、Al：0.003％以上0.06％以下を含有し、残部がFeおよび不可避的不純物からなる組成を有し、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下であることを特徴とする引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板。
［６］前記［５］において、前記犠牲防食顔料を含む塗膜が、片面当たりの付着量で10g/m2以上の塗膜であることを特徴とする鋼板。
［７］前記［５］または［６］において、前記犠牲防食顔料が、Znおよび／またはAlを含むことを特徴とする鋼板。
［８］前記［５］ないし［７］のいずれかにおいて、前記塗膜の表面にさらに、無機被覆層、有機被覆層、無機有機複合被覆層のいずれか１種以上の被覆層を備えることを特徴とする鋼板。
［９］質量％で、
C ：0.001％以上0.1％以下、 Si：4.0％以下（但し、0.01％以下を除く）、
Mn：0.16％以上1.0％以下、 P ：0.03％以下、
S ：0.02％以下、 Al：0.003％以上0.06％以下
を含有し、残部がFeおよび不可避的不純物からなる組成を有する鋳片を、再加熱して1000℃以上1100℃以下の温度域に均熱保持した後、仕上げ圧延終了温度をAr3変態点以上とする熱間圧延を施し、650℃以上680℃以下の巻取り温度で巻取ることにより熱延板とし、該熱延板を酸洗した後、60％以上90％以下の圧延率で冷間圧延を施して冷延板とし、該冷延板に、700℃以上850℃以下の焼鈍温度で連続焼鈍を施すことを特徴とする請求項１に記載の引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板の製造方法。
［１０］前記［９］において、前記連続焼鈍を施したのちに、表面処理を施し、鋼板の片面または両面に表面処理層を形成するに当たり、前記鋳片のSi含有量が質量％で0.5％以下である場合には、前記表面処理を亜鉛系めっき処理として前記表面処理層を亜鉛系めっき層とし、前記鋳片のSi含有量が質量％で0.5％超えである場合には、前記表面処理を犠牲防食顔料を含む塗料による塗装処理とし、前記表面処理層を犠牲防食顔料を含む塗膜とする、ことを特徴とする鋼板の製造方法。
［１１］前記［１０］において、前記亜鉛系めっき処理が、片面当たりのめっき付着量を5g/m2以上とするめっき処理であり、前記犠牲防食顔料を含む塗料による塗装処理が、片面当たりの付着量を10g/m2以上とする塗装処理であることを特徴とする鋼板の製造方法。
［１２］前記［１０］または［１１］において、前記表面処理層の表面にさらに、無機被覆層、有機被覆層、無機有機複合被覆層のいずれか１種以上の被覆層を形成することを特徴とする鋼板の製造方法。
The present invention has been completed after further studies based on such findings. That is, the gist configuration of the present invention is as follows.
[1] By mass%, C: 0.001% to 0.1%, Si: 4.0% or less (excluding 0.01% or less), Mn: 0.16% to 1.0%, P: 0.03% or less, S: 0.02% hereinafter, Al: 0.003% to 0.06% or less, the balance has a set formed of Fe and unavoidable impurities, Mn-content in the precipitates exceeds 0.5μm diameter is less than 100 mass ppm A steel sheet with a tensile strength exceeding 440 MPa and excellent corrosion resistance on the cut end face.
[2] A steel plate provided with a zinc-based plating layer as a surface treatment layer on one or both surfaces of the steel plate, the steel plate being in mass%, C: 0.001% to 0.1%, Si: 0.5% or less (provided that 0.01 % except for the following), Mn: 0.16% to 1.0% or less, P: 0.03% or less, S: 0.02% or less, Al: 0.003% or more 0.06% or less, the set formed the balance being Fe and unavoidable impurities the a, has a strength of greater than the tensile strength of 440MPa, wherein the Mn content in the precipitates exceeds 0.5μm diameter is less than 100 mass ppm, steel sheet excellent in corrosion resistance of the cutting edge.
[3] The steel sheet according to [2], wherein the zinc-based plating layer is a zinc-based plating layer having a plating adhesion amount per side of 5 g / m 2 or more.
[4] The steel sheet according to [3], further comprising one or more coating layers of an inorganic coating layer, an organic coating layer, and an inorganic-organic composite coating layer on the surface of the zinc-based plating layer.
[5] A steel sheet having a coating film containing a sacrificial anticorrosive pigment as a surface treatment layer on one or both sides of the steel sheet, the steel sheet being in mass%, C: 0.001% to 0.1%, Si: 0.5% to 4.0 %, Mn: 0.16% or more, 1.0% or less, P: 0.03% or less, S: 0.02% or less, Al: 0.003% or more and 0.06% or less, with the balance being composed of Fe and inevitable impurities, A steel sheet having a tensile strength exceeding 440 MPa and excellent corrosion resistance at the cut end face, wherein the amount of Mn contained in precipitates having a diameter exceeding 0.5 μm is 100 ppm by mass or less.
[6] The steel sheet according to [5], wherein the coating film containing the sacrificial anticorrosive pigment is a coating film having an adhesion amount per side of 10 g / m 2 or more.
[7] The steel sheet according to [5] or [6], wherein the sacrificial anticorrosive pigment contains Zn and / or Al.
[8] In any one of the above [5] to [7], the surface of the coating film may further include one or more coating layers of an inorganic coating layer, an organic coating layer, and an inorganic / organic composite coating layer. Characteristic steel sheet.
[9] In mass%,
C: 0.001% to 0.1%, Si: 4.0% or less (excluding 0.01% or less),
Mn: 0.16% to 1.0%, P: 0.03% or less,
S: 0.02% or less, Al: 0.003% to 0.06% or less, the slab the balance has a set formed of Fe and unavoidable impurities, reheated to 1000 ° C. or higher 1100 ° C. equalizing the temperature range below After heat holding, hot rolling is performed with the finish rolling finish temperature being the Ar 3 transformation point or higher, and the hot rolled sheet is wound at a winding temperature of 650 ° C. or higher and 680 ° C. or lower, and the hot rolled sheet is pickled. after, claims subjected to cold rolling and cold-rolled sheet, the cold rolled sheet, and characterized by applying continuous annealing in the following annealing temperature 700 ° C. or higher 850 ° C. at a rolling ratio of 60% to 90% Item 2. A method for producing a steel sheet having a tensile strength exceeding 440 MPa and excellent corrosion resistance at a cut end face.
[10] In the above [9], when the surface treatment is performed after the continuous annealing and the surface treatment layer is formed on one surface or both surfaces of the steel plate, the Si content of the slab is 0.5% by mass. If the following, the surface treatment is a zinc-based plating treatment, the surface treatment layer is a zinc-based plating layer, and if the Si content of the slab exceeds 0.5% by mass, the surface treatment A coating method containing a sacrificial anticorrosive pigment, and the surface treatment layer is a coating film containing a sacrificial anticorrosive pigment.
[11] In the above [10], the zinc-based plating treatment is a plating treatment in which a plating adhesion amount per side is 5 g / m 2 or more, and the coating treatment with the paint containing the sacrificial anticorrosive pigment is performed per side A method for producing a steel sheet, characterized by being a coating treatment with an adhesion amount of 10 g / m 2 or more.
[12] In the above [10] or [11], one or more coating layers of an inorganic coating layer, an organic coating layer, and an inorganic-organic composite coating layer are further formed on the surface of the surface treatment layer. A method for manufacturing a steel sheet.
本発明によれば、高張力鋼板に亜鉛系めっき等の表面処理を施したのち機械的な切断加工を施した場合であっても、せん断端面、打ち抜き面など、亜鉛系めっき等の表面処理層の犠牲防食作用が及ばない切断端面の耐食性を十分に確保することができる。それゆえ、本発明によると、高張力鋼板を再利用する際に問題視されていた切断端面の発錆を抑制することができる。したがって、本発明を、主として室内で使用される電気製品、事務機器などに適用することにより、製品部材の高強度化を図ることに加えて、製品部材を容易に再利用（リユース）することが可能となる。 According to the present invention, a surface treatment layer such as a zinc-based plating, such as a shear end face, a punched surface, etc., even when a high-strength steel sheet is subjected to a surface treatment such as zinc-based plating and then subjected to mechanical cutting. It is possible to sufficiently secure the corrosion resistance of the cut end face that does not have the sacrificial anticorrosive action. Therefore, according to the present invention, it is possible to suppress rusting of the cut end face, which has been regarded as a problem when reusing high-tensile steel plates. Accordingly, by applying the present invention mainly to electrical products and office equipment used indoors, in addition to increasing the strength of product members, product members can be easily reused. It becomes possible.
以下、本発明について具体的に説明する。 Hereinafter, the present invention will be specifically described.
まず、本発明鋼板の成分組成および析出物の限定理由について説明する。本発明で規定された鋼成分の元素は、鋼板の切断端面における耐食性の低下因子ともなり得る。なお、以下の成分組成を表す％は、特に断らない限り質量％を意味するものとする。 First, the component composition of this invention steel plate and the reason for limitation of a precipitate are demonstrated. The element of the steel component specified in the present invention can be a factor for reducing the corrosion resistance on the cut end face of the steel sheet. In addition,% showing the following component composition shall mean the mass% unless there is particular notice.
C ：0.001％以上0.1％以下
C含有量が0.1％を超えると、鋼板の硬質化や延性の劣化が問題となる。一方、C含有量が0.001％未満になると、鋼板が軟化し過ぎて切断時にバリなどの不具合が発生し易くなる。したがって、C含有量は0.001％以上0.1％以下とする。好ましくは0.001％以上0.05％以下である。
C: 0.001% to 0.1%
If the C content exceeds 0.1%, hardening of the steel sheet and deterioration of ductility become problems. On the other hand, if the C content is less than 0.001%, the steel sheet becomes too soft and defects such as burrs are likely to occur during cutting. Therefore, the C content is 0.001% or more and 0.1% or less. Preferably it is 0.001% or more and 0.05% or less.
Si：4.0％以下
Siは、固溶強化元素であり、鋼板の高強度化に寄与する。しかし、4.0％を超える多量の含有は、腐食起点となるSiO2に代表される析出物が増加して耐食性を著しく低下させる。このため、Si含有量は4.0％以下とする。下限は、不可避的不純物レベル（0.01％程度）とすることが望ましい。なお、めっき性の観点からは、0.5％以下に制限することが好ましく、より好ましくは耐食性の観点から0.1％以下、さらに好ましくは0.05％以下である。
Si: 4.0% or less
Si is a solid solution strengthening element and contributes to increasing the strength of the steel sheet. However, if the content exceeds 4.0%, the amount of precipitates typified by SiO 2 that becomes the starting point of corrosion increases and the corrosion resistance is remarkably lowered. For this reason, Si content shall be 4.0% or less. The lower limit is desirably an inevitable impurity level (about 0.01%). From the viewpoint of plating properties, it is preferably limited to 0.5% or less, more preferably from 0.1% or less, and even more preferably from 0.05% or less from the viewpoint of corrosion resistance.
Mn：0.16％以上1.0％以下
Mnは、鋳片の熱間圧延時、Sによる赤熱脆性の抑制に有効な元素である。また、Mnは、固溶強化元素であり、鋼板の高強度化に有効な元素である。引張強さ（TS）440MPa超えの鋼板強度を得るためには、Mn含有量を0.16％以上とする必要がある。一方、Mn含有量が1.0％を超えると、鋼の連続鋳造中にMnSが析出して熱間脆性を促進し、鋳片割れを招く。また、Mn含有量が1.0％を超えると、鋼板の耐食性が劣化する。したがって、Mn含有量は0.16％以上1.0％以下とする。好ましくは0.16％以上0.5％以下である。
Mn: 0.16% to 1.0%
Mn is an element effective for suppressing red heat brittleness due to S during hot rolling of a slab. Mn is a solid solution strengthening element and is an element effective for increasing the strength of a steel sheet. In order to obtain a steel plate strength exceeding the tensile strength (TS) of 440 MPa, the Mn content needs to be 0.16% or more. On the other hand, if the Mn content exceeds 1.0%, MnS precipitates during continuous casting of steel and promotes hot brittleness, which causes slab cracking. Moreover, when Mn content exceeds 1.0%, the corrosion resistance of a steel plate will deteriorate. Therefore, the Mn content is 0.16% or more and 1.0% or less. Preferably it is 0.16% or more and 0.5% or less.
P ：0.03％以下
Pは、不可避的に含有される元素であり、その含有量が増加するにつれて鋼板の耐食性が劣化する。したがって、P含有量は0.03％以下とする。
P: 0.03% or less
P is an element inevitably contained, and the corrosion resistance of the steel sheet deteriorates as its content increases. Therefore, the P content is 0.03% or less.
S ：0.02％以下
Sは、不可避的に含有される元素であり、鋳片の熱間圧延時に赤熱脆性を招く有害な元素である。また、Sは、鋼の連続鋳造中にMnSとして析出して熱間脆性を促進し、鋳片割れを招く。したがって、S含有量は、極力低減することが好ましく、0.02％以下とする。好ましくは0.01％以下である。
S: 0.02% or less
S is an element inevitably contained, and is a harmful element that causes red brittleness during hot rolling of the slab. Further, S precipitates as MnS during continuous casting of steel, promotes hot brittleness, and causes slab cracking. Accordingly, the S content is preferably reduced as much as possible, and is 0.02% or less. Preferably it is 0.01% or less.
Al：0.003％以上0.06％以下
Alは、製鋼の脱酸に必要な元素であり、その含有量を0.003％以上とする。一方、Al含有量が過剰に高くなると、介在物が増加して鋼板の表面欠陥が発生し易くなる。したがって、Al含有量は0.06％以下とする。
Al: 0.003% to 0.06%
Al is an element necessary for deoxidation of steel making, and its content is set to 0.003% or more. On the other hand, when the Al content is excessively high, inclusions increase and surface defects of the steel sheet are likely to occur. Therefore, the Al content is 0.06% or less.
以上が本発明鋼板の基本成分である。なお、本発明の鋼板は、例えば加工性の向上等を目的として、必要に応じて選択元素としてNb、Ti、B、V等を含有してもよい。 The above are the basic components of the steel sheet of the present invention. In addition, the steel plate of the present invention may contain Nb, Ti, B, V, and the like as selective elements as needed for the purpose of improving workability, for example.
本発明において、上記以外の成分（残部）は、Feおよび不可避的不純物である。不可避的不純物としてはSn、Sb、Ca、Zr等が挙げられ、これらの含有量は合計で2％以下であれば許容できる。 In the present invention, components other than the above (remainder) are Fe and inevitable impurities. Inevitable impurities include Sn, Sb, Ca, Zr, etc., and these contents are acceptable if the total content is 2% or less.
本発明鋼板は、上記した組成を有し、さらに鋼板中に存在する析出物のうち、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下である鋼板である。 The steel sheet of the present invention is a steel sheet having the above-described composition and having a Mn content of 100 mass ppm or less contained in precipitates having a diameter exceeding 0.5 μm among the precipitates present in the steel sheet.
直径が0.5μm超えの析出物に含まれるMn量：100質量ppm以下
先述のとおり、鋼板中に存在する析出物のうち、直径が0.5μm超えの析出物に含まれるMn量が100質量ppmを超えると、鋼板の耐食性が著しく低下する。したがって、直径が0.5μm超えの析出物に含まれるMn量を100質量ppm以下とする。好ましくは90質量ppm以下である。なお、本発明の鋼板に存在する析出物のうち、Mnを含有する析出物は主に(Mn・Fe)Sなる組成を有するが、MnSが多少混在する場合もある。
Mn content contained in precipitates with a diameter exceeding 0.5 μm: 100 ppm by mass or less As described above, among the precipitates present in the steel sheet, the amount of Mn contained in precipitates with a diameter exceeding 0.5 μm is 100 mass ppm. When it exceeds, the corrosion resistance of a steel plate will fall remarkably. Therefore, the amount of Mn contained in the precipitate having a diameter exceeding 0.5 μm is set to 100 mass ppm or less. Preferably it is 90 mass ppm or less. Of the precipitates present in the steel sheet of the present invention, the precipitate containing Mn mainly has a composition of (Mn · Fe) S, but MnS may be mixed somewhat.
なお、直径0.5μm超えの析出物に含まれるMn量は、次のような方法により算出することができる。 The amount of Mn contained in the precipitate having a diameter exceeding 0.5 μm can be calculated by the following method.
鋼板から採取した試料を非水溶媒系の電解液に浸漬し、定電流電解して試料を溶解する。そして得られた溶解液を、孔径0.5μmのフィルターでろ過し、フィルター上に残留した析出物（直径0.5μm超えの析出物）を採取する。採取した析出物を灰化し、炭酸ナトリウムと4ホウ酸ナトリウム（例えば2：1の質量比）を加え、混合して加熱してガラス状に溶融させる。さらに、溶融したものを、塩酸と水（例えば1：1の質量比）の混合液に溶解して溶液化し、ICP発光分析装置でMnの定量分析を行い、直径0.5μm超えの析出物に含まれるMn量（質量）を定量し、溶解した試料の質量に対する比率を算出し、0.5μm超えの析出物に含まれるMn量（質量％）とする。 A sample collected from a steel plate is immersed in a non-aqueous solvent electrolyte, and the sample is dissolved by constant current electrolysis. Then, the obtained solution is filtered through a filter having a pore size of 0.5 μm, and a precipitate remaining on the filter (a precipitate having a diameter exceeding 0.5 μm) is collected. The collected precipitate is incinerated, sodium carbonate and sodium tetraborate (for example, a mass ratio of 2: 1) are added, mixed, heated and melted into a glass. Furthermore, the melted material is dissolved in a mixed solution of hydrochloric acid and water (for example, a mass ratio of 1: 1) to form a solution, and quantitative analysis of Mn is performed using an ICP emission spectrometer, which is included in precipitates with a diameter exceeding 0.5 μm. The amount of Mn (mass) to be quantified is calculated, and the ratio to the mass of the dissolved sample is calculated to obtain the amount of Mn (mass%) contained in the precipitate exceeding 0.5 μm.
以上のように組成と析出物の形態を規定することで、高強度であり且つ耐食性に優れた鋼板が得られる。したがって、本発明によれば、高張力鋼板に亜鉛系めっき等の表面処理を施したのち機械的な切断加工を施した場合であっても、せん断端面、打ち抜き面など、亜鉛系めっき等の表面処理層の犠牲防食作用が及ばない切断端面の耐食性を十分に確保することができる。 By defining the composition and the form of precipitates as described above, a steel sheet having high strength and excellent corrosion resistance can be obtained. Therefore, according to the present invention, even when a high-strength steel sheet is subjected to a surface treatment such as zinc plating and then subjected to a mechanical cutting process, a surface such as a shear end face, a punched surface, etc. It is possible to sufficiently secure the corrosion resistance of the cut end face that does not have the sacrificial anticorrosive action of the treatment layer.
本発明鋼板の片面または両面には、耐食性向上のために、犠牲防食作用を有する表面処理を施すことが好ましい。犠牲防食作用を有する表面処理としては、鋼板のSi含有量が0.5％以下である場合には、亜鉛系めっき処理を施し亜鉛系めっき層を、鋼板のSi含有量が0.5％超えである場合には、犠牲防食作用を有する顔料（犠牲防食顔料）を含む塗料を塗布する塗装処理を施し犠牲防食作用を有する塗膜を、設けることが好ましいが、これに限定されないことは言うまでもない。 One or both surfaces of the steel plate of the present invention are preferably subjected to a surface treatment having a sacrificial anticorrosive action in order to improve corrosion resistance. As a surface treatment with sacrificial anticorrosive action, when the Si content of the steel sheet is 0.5% or less, a zinc-based plating treatment is applied to the zinc-based plating layer, when the Si content of the steel sheet exceeds 0.5%. Although it is preferable to provide a coating film having a sacrificial anticorrosive action by applying a coating treatment containing a paint having a sacrificial anticorrosive action (sacrificial anticorrosive pigment), it goes without saying that the present invention is not limited thereto.
本発明鋼板の片面または両面に亜鉛系めっき層を設ける場合には、亜鉛の犠牲防食性を十分に確保する観点から、亜鉛系めっき層の付着量を片面当たり5g/m2以上とすることが好ましい。より好ましくは10g/m2以上である。なお、上記付着量の上限は特に定める必要がなく、製造上の制約から適宜設定すればよい。また、めっきの種類は特に問わず、溶融めっき、電気めっき、蒸着めっき等、いずれも適用可能である。めっき金属は、亜鉛単一系のほか、Zn-Al系、Zn-Ni系、Zn-Cr系、Zn-Fe系、Zn-Al-Mg系などの多元系、合金めっき系でもよい。 When providing a zinc-based plating layer on one or both sides of the steel sheet of the present invention, from the viewpoint of sufficiently ensuring the sacrificial corrosion resistance of zinc, the adhesion amount of the zinc-based plating layer may be 5 g / m 2 or more per side. preferable. More preferably, it is 10 g / m 2 or more. Note that the upper limit of the adhesion amount is not particularly required, and may be set as appropriate due to manufacturing restrictions. Further, the type of plating is not particularly limited, and any of hot-dip plating, electroplating, vapor deposition plating and the like can be applied. The plating metal may be a zinc-based, multi-component system such as Zn-Al, Zn-Ni, Zn-Cr, Zn-Fe, Zn-Al-Mg, or alloy plating.
なお、上記しためっき層の表面に、例えばクロメート処理層、リン酸塩処理層、シラン処理層などを設けてもよい。これらの層は、鋼板を無塗装で使用する場合の鋼板平板部における赤錆対策（耐食性向上）や、鋼板に塗装などの被覆処理を行って使用する場合の塗装との密着性向上や鋼板平板部における耐食性向上に有効である。また、これらの層は、耐食性以外の特性、例えば耐指紋性などの向上を図るうえでも有効である。 For example, a chromate treatment layer, a phosphate treatment layer, a silane treatment layer, or the like may be provided on the surface of the plating layer. These layers are used to prevent red rust (improvement of corrosion resistance) in the steel plate flat part when using the steel plate without coating, and to improve the adhesion with the paint when the steel plate is coated and used for coating. It is effective in improving the corrosion resistance in These layers are also effective in improving properties other than corrosion resistance, such as fingerprint resistance.
また、亜鉛系めっき層に代えて、本発明鋼板の片面または両面に、犠牲防食顔料を含む塗膜を設ける場合には、犠牲防食性を十分に確保する観点から、犠牲防食顔料を含む塗膜の付着量は、片面当たり10g/m2以上とすることが好ましい。より好ましくは20g/m2以上である。なお、上記付着量の上限は特に定める必要がなく、製造上の制約から適宜設定すればよい。ここでいう「犠牲防食顔料を含む塗膜」とは、通常塗膜を形成するために使用する、例えばエポキシ系塗料、アクリル系塗料、フェノール系塗料に、鉄に対し犠牲防食作用を有するZn、Alのうちの１種以上を含む顔料（犠牲防食顔料）を加えた塗料を用いる塗装処理で形成された塗膜をいう。犠牲防食顔料としては、Zn粉末、Al粉末が挙げられる。なお、犠牲防食顔料の添加量は、塗膜全量に対する質量％で10〜80％とすることが好ましい。添加量が10％以上であれば、犠牲防食の効果が認められる。一方、80％以下であれば、犠牲防食顔料が塗料中で分散しやすく沈降しにくくなり、塗装が困難になることはない。 In addition, in the case where a coating film containing a sacrificial anticorrosion pigment is provided on one or both surfaces of the steel sheet of the present invention instead of the zinc-based plating layer, a coating film containing a sacrificial anticorrosion pigment from the viewpoint of sufficiently ensuring sacrificial anticorrosion properties The amount of adhering is preferably 10 g / m 2 or more per side. More preferably, it is 20 g / m 2 or more. Note that the upper limit of the adhesion amount is not particularly required, and may be set as appropriate due to manufacturing restrictions. "Coating film containing sacrificial anticorrosive pigment" as used herein is usually used to form a coating film, for example, epoxy paint, acrylic paint, phenol paint, Zn having sacrificial anticorrosive action on iron, The coating film formed by the coating process using the coating material which added the pigment (sacrificial anticorrosive pigment) containing 1 or more types of Al. Examples of the sacrificial anticorrosive pigment include Zn powder and Al powder. In addition, it is preferable that the addition amount of a sacrificial anticorrosive pigment shall be 10-80% in the mass% with respect to the coating-film whole quantity. If the addition amount is 10% or more, the effect of sacrificial corrosion protection is recognized. On the other hand, if it is 80% or less, the sacrificial anticorrosive pigment is easy to disperse in the paint and is difficult to settle, so that painting is not difficult.
本発明鋼板の片面または両面に、上記した表面処理層を設けたのちさらに、該表面処理層の表面に、無機被覆層、有機被覆層、無機有機複合被覆層のいずれか１種以上の被覆層を設けてもよい。無機被覆層としては、例えば、SiO2、TiN等が挙げられる。また、有機被覆層としては、例えばアクリル樹脂、エポキシ樹脂、ポリエステル樹脂、ポリオレフィン樹脂、フッ素樹脂、およびこれらの共重合体樹脂等を含む有機被覆層が挙げられる。無機有機複合被覆層は、有機被覆層を構成する樹脂成分と無機被覆層を構成する無機成分を複合して含有する被覆層である。無機被覆層、有機被覆層、無機有機複合被覆層のいずれか一つを形成してもよいし、例えば無機被覆層、有機被覆層の順に形成してもよい。これらの被覆層を形成することにより、鋼板の切断端面耐食性や鋼板平板部の耐食性がより一層向上する。また、これらの被覆層を形成すると、耐食性以外の特性、例えば耐指紋性などの向上効果も得られる。 After providing the above-mentioned surface treatment layer on one side or both sides of the steel sheet of the present invention, on the surface of the surface treatment layer, one or more coating layers of an inorganic coating layer, an organic coating layer, and an inorganic / organic composite coating layer are provided. May be provided. Examples of the inorganic coating layer include SiO 2 and TiN. Examples of the organic coating layer include organic coating layers containing an acrylic resin, an epoxy resin, a polyester resin, a polyolefin resin, a fluororesin, and a copolymer resin thereof. The inorganic / organic composite coating layer is a coating layer containing a composite of a resin component constituting the organic coating layer and an inorganic component constituting the inorganic coating layer. Any one of an inorganic coating layer, an organic coating layer, and an inorganic / organic composite coating layer may be formed, or for example, an inorganic coating layer and an organic coating layer may be formed in this order. By forming these coating layers, the cut end surface corrosion resistance of the steel plate and the corrosion resistance of the steel plate flat portion are further improved. In addition, when these coating layers are formed, it is possible to obtain an effect of improving characteristics other than corrosion resistance, such as fingerprint resistance.
なお、亜鉛系めっき層の表面に、前記処理層（クロメート処理層、リン酸塩処理層、シラン処理層など）を設けたのちに、無機被覆層、有機被覆層、無機有機複合被覆層のいずれか１種以上の被覆層を設けてもよい。 In addition, after providing the treatment layer (chromate treatment layer, phosphate treatment layer, silane treatment layer, etc.) on the surface of the zinc-based plating layer, any of the inorganic coating layer, the organic coating layer, and the inorganic-organic composite coating layer Alternatively, one or more coating layers may be provided.
次に、本発明鋼板の製造方法について説明する。 Next, the manufacturing method of this invention steel plate is demonstrated.
本発明の鋼板の製造方法は、上記組成を有する鋳片を、好ましくは一旦300℃以下の温度域に冷却し、ついで、再加熱して1000℃以上1100℃以下の温度域に均熱保持した後、仕上げ圧延終了温度をAr3変態点以上とする熱間圧延を施し、680℃以下の巻取り温度で巻取ることにより熱延板とし、該熱延板を酸洗した後、60％以上90％以下の圧延率で冷間圧延を施して冷延板とし、該冷延板に、700℃以上850℃以下の焼鈍温度で連続焼鈍を施すことを特徴とする。 In the method for producing a steel sheet of the present invention, the slab having the above composition is preferably cooled once to a temperature range of 300 ° C. or less, and then reheated to keep the temperature so uniform in the temperature range of 1000 ° C. to 1100 ° C. Thereafter, hot rolling with a finish rolling finish temperature of Ar 3 transformation point or higher is performed, and a hot rolled sheet is formed by winding at a winding temperature of 680 ° C. or less, and after pickling the hot rolled sheet, 60% or more Cold rolling is performed at a rolling rate of 90% or less to obtain a cold rolled sheet, and the cold rolled sheet is subjected to continuous annealing at an annealing temperature of 700 ° C. or higher and 850 ° C. or lower.
鋳片の製造方法は特に限定する必要はなく、例えば、上記した組成を有する溶鋼を、転炉等で溶製し、連続鋳造等の鋳造方法で鋳片とする常用の方法がいずれも適用可能である。また、造塊―分塊方法や薄スラブ連続鋳造法を用いてもよい。 The method for producing the slab need not be particularly limited. For example, any conventional method can be used in which molten steel having the above composition is melted in a converter or the like and is cast by a casting method such as continuous casting. It is. Further, an ingot-bundling method or a thin slab continuous casting method may be used.
本発明では、鋳片を一旦、好ましくは300℃以下の温度域まで冷却したのち、再加熱する。鋳片を一旦冷却することにより、Mnを含む析出物が鋳片に析出する。なお、この析出物は、主に(Mn・Fe)Sなる組成を有する析出物である。 In the present invention, the slab is once cooled, preferably to a temperature range of 300 ° C. or lower, and then reheated. By cooling the slab once, a precipitate containing Mn is deposited on the slab. This precipitate is a precipitate mainly having a composition of (Mn · Fe) S.
鋳片の再加熱温度：1000℃以上1100℃以下
本発明においては、再加熱温度を、鋳片に存在する析出物（主に(Mn・Fe)S）が溶解しない温度域に設定する。鋳片の再加熱温度が1100℃超えると、鋳片中の析出物が溶解してしまう。その結果、後工程の連続焼鈍時に、MnSが析出してしまい、鋼板の耐食性が劣化する。一方、鋳片の再加熱温度が1000℃を下回ると、圧延性が著しく低下し、熱間圧延に支障をきたす。したがって、鋳片の再加熱温度は1000℃以上1100℃以下とする。
Reheating temperature of slab: 1000 ° C. or higher and 1100 ° C. or lower In the present invention, the reheating temperature is set to a temperature range in which precipitates (mainly (Mn · Fe) S) present in the slab are not dissolved. When the reheating temperature of the slab exceeds 1100 ° C., precipitates in the slab are dissolved. As a result, MnS precipitates during continuous annealing in the subsequent process, and the corrosion resistance of the steel sheet deteriorates. On the other hand, when the reheating temperature of the slab is lower than 1000 ° C., the rollability is remarkably lowered, and hot rolling is hindered. Therefore, the reheating temperature of the slab is set to 1000 ° C. or more and 1100 ° C. or less.
鋳片の再加熱、均熱保持に続き、鋳片に熱間圧延を施す。熱間圧延は通常、粗圧延と仕上げ圧延とからなるが、粗圧延条件については特に限定されない。また、例えば薄スラブ連鋳法によりスラブ（鋼素材）を鋳造する場合には、粗圧延を省略してもよい。仕上げ圧延は、以下の条件で実施する。 Following reheating of the slab and soaking, the slab is hot rolled. Hot rolling usually consists of rough rolling and finish rolling, but the rough rolling conditions are not particularly limited. For example, when casting a slab (steel material) by a thin slab continuous casting method, rough rolling may be omitted. Finish rolling is performed under the following conditions.
仕上げ圧延終了温度：Ar3変態点以上
仕上げ圧延終了温度がAr3変態点未満になると、圧延後の結晶粒径が不均一になり易くなる。鋼板の結晶粒径が不均一になると、鋼板を所定形状の部材にプレス成形する際、不均一変形やプレス表面の肌荒れ等の問題が生じる。したがって、仕上げ圧延終了温度はAr3変態点以上とする。好ましくは、Ar3変態点＋5℃以上である。但し、仕上げ圧延終了温度が過剰に高くなると、スケールによる表面性状の劣化や生産能率の低下が懸念されるため、Ar3変態点＋50℃以下とすることが好ましい。
Finish rolling end temperature: Ar 3 transformation point or higher If the finish rolling end temperature is lower than the Ar 3 transformation point, the grain size after rolling tends to be non-uniform. If the crystal grain size of the steel sheet is non-uniform, problems such as non-uniform deformation and rough surface of the press surface occur when the steel sheet is press-formed into a member having a predetermined shape. Therefore, the finish rolling finish temperature is set to the Ar 3 transformation point or higher. Preferably, Ar 3 transformation point + 5 ° C or higher. However, if the finish rolling finish temperature is excessively high, there is a concern about deterioration of surface properties due to scale and a decrease in production efficiency. Therefore, the Ar 3 transformation point is preferably set to + 50 ° C. or lower.
巻取り温度：680℃以下
巻取り温度が680℃を超えると、鋳片に存在していた析出物（主に(Mn・Fe)S）の溶解が促進される。その結果、後工程の連続焼鈍時にMnSが析出し、鋼板の耐食性が劣化する。したがって、巻取り温度は680℃以下とする。但し、巻取り温度が低くなり過ぎると、生産性の低下が懸念されるため、650℃以上とすることが好ましい。
Winding temperature: 680 ° C. or less When the winding temperature exceeds 680 ° C., dissolution of precipitates (mainly (Mn · Fe) S) present in the slab is promoted. As a result, MnS precipitates during the subsequent continuous annealing, and the corrosion resistance of the steel sheet deteriorates. Therefore, the coiling temperature is 680 ° C. or less. However, if the coiling temperature becomes too low, there is a concern that the productivity is lowered.
次いで、上記巻取り温度で巻き取ることで得られた熱延板を、酸洗したのち、冷間圧延を施し、冷延板とする。 Next, the hot-rolled sheet obtained by winding at the above-described winding temperature is pickled and then cold-rolled to obtain a cold-rolled sheet.
冷間圧延の圧延率：60％以上90％以下
冷間圧延の圧延率が60％を下回ると、後工程の連続焼鈍で結晶粒径が粗大となり、鋼板のプレス成形時に表面外観が劣化する。一方、冷間圧延の圧延率が90％を超えると、圧延負荷が大きくなるため、圧延が困難になる。したがって、冷間圧延の圧延率は60％以上90％以下とする。好ましくは70％以上90％以下である。
Rolling ratio of cold rolling: 60% or more and 90% or less If the rolling ratio of cold rolling is less than 60%, the crystal grain size becomes coarse by continuous annealing in the subsequent process, and the surface appearance deteriorates during press forming of the steel sheet. On the other hand, if the rolling rate of cold rolling exceeds 90%, rolling load becomes large, and rolling becomes difficult. Therefore, the rolling rate of cold rolling is 60% or more and 90% or less. Preferably they are 70% or more and 90% or less.
次いで、上記の冷間圧延により得られた冷延板を、連続焼鈍ラインに通板し、連続焼鈍に供する。 Next, the cold-rolled sheet obtained by the above cold rolling is passed through a continuous annealing line and subjected to continuous annealing.
連続焼鈍の焼鈍温度：700℃以上850℃以下
本発明では、鋼の再結晶温度以上の温度域で連続焼鈍を施し、加工組織を再結晶化させることで鋼板の加工性向上を図る。焼鈍温度が700℃未満になると、鋼の再結晶を促進することができない。その結果、鋼板に硬質な加工組織が残留してプレス成形性が劣化する。一方、焼鈍温度が850℃を超えると、エネルギー負荷が大きくなり、生産コストの高騰を招く。したがって、連続焼鈍の焼鈍温度は700℃以上850℃以下とする。好ましくは720℃以上830℃以下である。
Annealing temperature of continuous annealing: 700 ° C. or higher and 850 ° C. or lower In the present invention, continuous annealing is performed in a temperature range equal to or higher than the recrystallization temperature of steel, and the workability of the steel sheet is improved by recrystallizing the work structure. When the annealing temperature is less than 700 ° C., the recrystallization of steel cannot be promoted. As a result, a hard processed structure remains on the steel sheet and press formability deteriorates. On the other hand, if the annealing temperature exceeds 850 ° C., the energy load increases and the production cost increases. Therefore, the annealing temperature of continuous annealing is set to 700 ° C or higher and 850 ° C or lower. Preferably they are 720 degreeC or more and 830 degrees C or less.
なお、連続焼鈍を施す際、冷延板を700℃以上850℃以下の温度域に滞留する時間は300s以上2000s以下とすることが好ましい。上記温度域での滞留時間が300s以上であれば、鋼板組織に未再結晶部が残存することがなく、鋼板の加工性が劣位とならない。一方、上記温度域での滞留時間が2000s以下であれば、生産性が劣位とならない。 In addition, when performing continuous annealing, it is preferable that the time during which a cold-rolled sheet stays in a temperature range of 700 ° C. or higher and 850 ° C. or lower is 300 seconds or more and 2000 seconds or less. If the residence time in the temperature range is 300 s or longer, no non-recrystallized portion remains in the steel sheet structure, and the workability of the steel sheet does not deteriorate. On the other hand, if the residence time in the above temperature range is 2000 s or less, the productivity is not inferior.
連続焼鈍後、鋼板の形状や表面粗さを整える目的で、調質圧延を施してもよい。調質圧延の伸長率は特に規定しないが、通常、0.3％以上2.0％以下の範囲とすることが好ましい。 After continuous annealing, temper rolling may be performed for the purpose of adjusting the shape and surface roughness of the steel sheet. Although the elongation rate of temper rolling is not particularly specified, it is usually preferably in the range of 0.3% to 2.0%.
なお、鋼板の板厚は特に問わないが、例えば0.2〜2mmの範囲で鋼板の目的に応じて適宜選択することができる。 The plate thickness of the steel plate is not particularly limited, but can be appropriately selected depending on the purpose of the steel plate within a range of 0.2 to 2 mm, for example.
以上により、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下である高張力鋼板、すなわち、亜鉛系めっき処理等の表面処理を施したのち機械的な切断加工を施した場合であっても、せん断端面、打ち抜き面など、亜鉛系めっき等の犠牲防食作用が及ばない切断端面の耐食性を十分に確保し得る高張力鋼板が得られる。 As described above, high-strength steel sheets with a Mn content of 100 mass ppm or less contained in precipitates with a diameter exceeding 0.5 μm, that is, when mechanical cutting is performed after surface treatment such as zinc plating treatment Even so, it is possible to obtain a high-strength steel sheet that can sufficiently ensure the corrosion resistance of the cut end face, such as the shear end face and the punched face, which does not have the sacrificial anticorrosive action such as zinc plating.
鋼板にめっき処理を施す方法は特に問わず、溶融めっき処理、電気めっき処理、蒸着めっき処理等、いずれも適用可能である。また、鋼板の片面のみにめっき処理を施してもよく、鋼板の両面にめっき処理を施してもよい。鋼板に亜鉛系めっき処理を施す場合は、亜鉛系めっき層の片面当たりの付着量を5g/m2以上とすることが好ましい。めっき金属は、亜鉛単一系のほか、Zn-Al系、Zn-Ni系、Zn-Cr系、Zn-Fe系、Zn-Al-Mg系などの多元系、合金めっき系でもよい。 The method for plating the steel sheet is not particularly limited, and any of hot-dip plating, electroplating, vapor deposition and the like can be applied. Moreover, a plating process may be given only to one side of a steel plate, and a plating process may be given to both surfaces of a steel plate. When the zinc-based plating treatment is performed on the steel sheet, the amount of adhesion per one side of the zinc-based plating layer is preferably 5 g / m 2 or more. The plating metal may be a zinc-based, multi-component system such as Zn-Al, Zn-Ni, Zn-Cr, Zn-Fe, Zn-Al-Mg, or alloy plating.
また、鋼板に表面処理として、めっき処理に代えて、犠牲防食顔料を含む塗料による塗装処理を施す方法は、犠牲防食顔料を含む塗料を用いる以外は、常用の塗装処理がいずれも適用可能である。例えばエポキシ系塗料、アクリル系塗料、フェノール系塗料に、鉄に対し犠牲防食作用を有するZn、Alのうちの１種以上を含む顔料（犠牲防食顔料）を加え、ロールコート、フローコート等の塗布手段を用いて鋼板の片面あるいは両面に塗布する方法が例示できる。犠牲防食作用が十分に発揮できるように、片面当たりの付着量が10g/m2以上となるように調整することが好ましい。 In addition, as a surface treatment for the steel sheet, instead of plating, a method of performing a coating process using a paint containing a sacrificial anti-corrosion pigment can be applied to any conventional coating process except using a paint containing a sacrificial anti-corrosion pigment. . For example, a pigment (sacrificial anticorrosive pigment) containing at least one of Zn and Al, which has a sacrificial anticorrosive action against iron, is added to an epoxy paint, acrylic paint, phenolic paint, and coating such as roll coat and flow coat is applied. The method of apply | coating to the single side | surface or both surfaces of a steel plate using a means can be illustrated. It is preferable to adjust the adhesion amount per side to be 10 g / m 2 or more so that the sacrificial anticorrosive action can be sufficiently exhibited.
上記の如くめっき処理等の表面処理を施して鋼板表面にめっき層等の表面処理層を形成したのち、あるいはさらに、クロメート処理、リン酸塩処理、シラン処理等を施したのち、該めっき層等の表面処理層の表面に、無機被覆層、有機被覆層、無機有機複合被覆層のいずれか１種以上を形成してもよい。例えば、無機被覆層、有機被覆層、無機有機複合被覆層のいずれか一つを形成してもよいし、無機被覆層、有機被覆層の順に形成してもよい。無機被覆層の形成方法としては、例えば電着塗装、還元析出などを用いることができる。また、有機被覆層、無機有機複合被覆層の形成方法としては、例えば塗装、ラミネート（フィルム貼付け）などを用いることができる。 After forming a surface treatment layer such as a plating layer on the surface of the steel sheet by performing a surface treatment such as plating as described above, or after further applying a chromate treatment, a phosphate treatment, a silane treatment, etc. Any one or more of an inorganic coating layer, an organic coating layer, and an inorganic / organic composite coating layer may be formed on the surface treatment layer. For example, any one of an inorganic coating layer, an organic coating layer, and an inorganic / organic composite coating layer may be formed, or an inorganic coating layer and an organic coating layer may be formed in this order. As a method for forming the inorganic coating layer, for example, electrodeposition coating, reduction deposition and the like can be used. Moreover, as a formation method of an organic coating layer and an inorganic organic composite coating layer, for example, painting, laminating (film sticking), or the like can be used.
溶鋼を転炉で溶製し、連続鋳造法により鋳片とした。鋳片は、表１に示す化学成分を含有し、残部がFeおよび不可避的不純物からなる組成であった。室温まで冷却した鋳片を、再加熱して熱間圧延を施し、熱間圧延終了後、水冷し、巻取り、熱延板とした。次いで、熱延板を酸洗し、冷間圧延を施して冷延板とし、該冷延板に連続焼鈍を施し、更に調質圧延を施して鋼板とした。鋳片の再加熱温度、熱間圧延の仕上げ圧延終了温度、巻取り温度、冷間圧延の圧延率、連続焼鈍の焼鈍温度、焼鈍時間（焼鈍温度での冷延板の保持時間）、調質圧延の伸長率および調質圧延後の鋼板の板厚を、表２に示す。 Molten steel was melted in a converter and made into a slab by a continuous casting method. The slab contained the chemical components shown in Table 1, and the balance was composed of Fe and inevitable impurities. The slab cooled to room temperature was reheated and subjected to hot rolling, and after the hot rolling was completed, it was cooled with water, wound up, and formed into a hot rolled sheet. Next, the hot-rolled sheet was pickled, cold-rolled to obtain a cold-rolled sheet, the cold-rolled sheet was subjected to continuous annealing, and further subjected to temper rolling to obtain a steel sheet. Reheating temperature of slab, finish finish temperature of hot rolling, coiling temperature, rolling rate of cold rolling, annealing temperature of continuous annealing, annealing time (holding time of cold rolled sheet at annealing temperature), tempering Table 2 shows the elongation ratio of rolling and the thickness of the steel sheet after temper rolling.
上記により得られた各鋼板の板幅中央部から、長さ50mm×幅30mmの試料を採取し、非水溶媒系の10％アセチルアセトン電解液に浸漬し、20mA/cm2の電流値で定電流電解し、試料を溶解した。得られた溶解液を、孔径0.5μmのフィルターに通し、フィルター上に残留した直径0.5μm超えの析出物を採取した。採取した析出物を、灰化し、炭酸ナトリウム：4ホウ酸ナトリウム＝2：1（質量比）と混合して加熱し、ガラス状に溶融した。溶融後、更に、HCl：水＝1：1（質量比）の液に溶解して溶液化し、ICP発光分析装置にてMnの定量分析を行うことにより、直径0.5μm超えの析出物に含まれるMnの質量（Wp）を求めた。このようにして求めたMnの質量（Wp）と、溶解した試料の質量（Wt）から、直径0.5μm超えの析出物に含まれるMn量（Wp/Wt×106、単位：質量ppm）を算出した。これらの結果を、表２に示す。 From the center of the plate width of each steel plate obtained as described above, a sample of length 50 mm x width 30 mm was taken, immersed in a nonaqueous solvent-based 10% acetylacetone electrolyte, and a constant current at a current value of 20 mA / cm 2. Electrolysis was performed to dissolve the sample. The obtained lysate was passed through a filter having a pore size of 0.5 μm, and a precipitate having a diameter exceeding 0.5 μm remaining on the filter was collected. The collected precipitate was incinerated, mixed with sodium carbonate: 4 sodium borate = 2: 1 (mass ratio), heated, and melted into glass. After melting, it is dissolved in a solution of HCl: water = 1: 1 (mass ratio) to form a solution, and Mn is quantitatively analyzed with an ICP emission spectrometer, so that it is contained in precipitates with a diameter exceeding 0.5 μm. The mass (Wp) of Mn was determined. From the mass of Mn thus obtained (Wp) and the mass of the dissolved sample (Wt), the amount of Mn contained in the precipitate having a diameter exceeding 0.5 μm (Wp / Wt × 10 6 , unit: mass ppm) Calculated. These results are shown in Table 2.
また、上記により得られた各鋼板から、圧延方向に対して直角方向にJIS 5号引張試験片（JIS Z 2201(2009)）を採取し、JIS Z 2241(2011)の規定に準拠した引張試験を行い、引張強さ（TS）を測定した。これらの結果を、表２に示す。 In addition, JIS No. 5 tensile specimens (JIS Z 2201 (2009)) are taken from each steel plate obtained above in a direction perpendicular to the rolling direction, and a tensile test in accordance with the provisions of JIS Z 2241 (2011). And tensile strength (TS) was measured. These results are shown in Table 2.
更に、上記により得られた各鋼板の表面（両面）に、表面処理を施した。表面処理方法を、表３に示す。表面処理は、鋼板のSi含有量に応じて変更した。鋼板のSi含有量が0.5％以下の場合には、めっき処理を、鋼板のSi含有量が0.5％超えの場合には、塗装処理を、施した。なお、鋼板No.9は、Si含有量が0.5％超えであるが、めっき処理を施した。不めっきが生じたが、切断端面の腐食試験を実施した。 Furthermore, surface treatment was performed on the surface (both sides) of each steel plate obtained as described above. Table 3 shows the surface treatment method. The surface treatment was changed according to the Si content of the steel sheet. When the Si content of the steel sheet was 0.5% or less, a plating treatment was performed, and when the Si content of the steel sheet exceeded 0.5%, a coating treatment was performed. Steel plate No. 9 had a Si content exceeding 0.5%, but was plated. Although non-plating occurred, a corrosion test on the cut end face was performed.
得られた表面処理後の鋼板を、せん断機でせん断し、板幅中央部から長さ50mm×幅50mmの試料を採取した。このようにせん断加工により採取した切断端面（せん断端面）を有する試料を用い、乾湿繰返し試験を実施した。乾湿繰返し試験の試験条件は、湿潤試験機にて、試料を温度：32℃、相対湿度：60％で5分保持した後、試料を温度：20℃、相対湿度：35％で30分保持する処理を1サイクルとし、10サイクル繰返し実施する条件とした。 The obtained steel sheet after the surface treatment was sheared with a shearing machine, and a sample having a length of 50 mm and a width of 50 mm was collected from the center of the sheet width. Using the sample having the cut end face (shear end face) collected by the shearing process in this way, a wet and dry repeated test was performed. The test condition of the wet and dry test is that the sample is held at a temperature of 32 ° C and a relative humidity of 60% for 5 minutes on a wet testing machine, and then the sample is held at a temperature of 20 ° C and a relative humidity of 35% for 30 minutes. The treatment was set to 1 cycle, and the conditions were set to repeat 10 cycles.
乾湿繰返し試験後、試料の切断端面（せん断端面）の外観を目視観察し、切断端面の耐食性を３段階評価法によって評価した。切断端面の発錆面積率が10％以下である場合を、「切断端面の耐食性：極めて良好（◎）」と評価した。切断端面の発錆面積率が10％超え40％以下である場合を、「切断端面の耐食性：良好（○）」と評価した。一方、切断端面の発錆面積率が40％超えである場合を、「切断端面の耐食性：不良（×）」と評価した。これらの結果を、表２に示す。 After the wet and dry repetition test, the appearance of the cut end face (shear end face) of the sample was visually observed, and the corrosion resistance of the cut end face was evaluated by a three-step evaluation method. The case where the rust area ratio of the cut end face was 10% or less was evaluated as “corrosion resistance of the cut end face: extremely good (（)”. The case where the rusting area ratio of the cut end face was 10% and 40% or less was evaluated as “corrosion resistance of the cut end face: good (◯)”. On the other hand, the case where the rusting area ratio of the cut end face was more than 40% was evaluated as “corrosion resistance of the cut end face: poor (×)”. These results are shown in Table 2.
表２のとおり、比較例の鋼板はいずれも、十分な切断端面耐食性が得られていない。一方、発明例の鋼板はいずれも、耐食性の低下を招くMnを0.16％以上含有し、引張強さ（TS）が440MPaを超える高張力鋼板であるにも拘わらず、良好な切断端面耐食性を示している。 As shown in Table 2, none of the comparative steel sheets has sufficient cut end surface corrosion resistance. On the other hand, the steel sheets of the invention examples all have 0.16% or more of Mn that causes a decrease in corrosion resistance, and exhibit high corrosion resistance at the cut end despite being tensile steel (TS) exceeding 440 MPa. ing.
以上のように、本発明によると、高張力化を目的としてMn含有量を0.16％以上とした場合であっても、切断端面の耐食性に優れた鋼板が得られる。したがって、本発明鋼板にめっき処理等の表面処理を施した鋼板（表面処理鋼板）が実際に家電製品、事務機器等の強度部材に適用されると、優れた切断端面耐食性を発揮し、部材の再利用が可能となる。 As described above, according to the present invention, a steel sheet having excellent corrosion resistance at the cut end face can be obtained even when the Mn content is 0.16% or more for the purpose of increasing the tension. Therefore, when a steel plate (surface-treated steel plate) obtained by subjecting the steel plate of the present invention to surface treatment such as plating treatment is actually applied to a strength member of home appliances, office equipment, etc., it exhibits excellent cut end surface corrosion resistance, Reusable.
Claims (12)
C ：0.001％以上0.1％以下、 Si：4.0％以下（但し、0.01％以下は除く）、
Mn：0.16％以上1.0％以下、 P ：0.03％以下、
S ：0.02％以下、 Al：0.003％以上0.06％以下
を含有し、残部がFeおよび不可避的不純物からなる組成を有し、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下であることを特徴とする引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板。 % By mass
C: 0.001% or more and 0.1% or less, Si: 4.0% or less (excluding 0.01% or less),
Mn: 0.16% to 1.0%, P: 0.03% or less,
S: 0.02% or less, Al: 0.003% to 0.06% or less, the balance has a set formed of Fe and unavoidable impurities, Mn amount is 100 ppm by mass in diameter contained in the precipitates exceeds 0.5μm A steel sheet having a tensile strength exceeding 440 MPa and excellent corrosion resistance at the cut end face, characterized by the following:
C ：0.001％以上0.1％以下、 Si：0.5％以下（但し、0.01％以下は除く）、
Mn：0.16％以上1.0％以下、 P ：0.03％以下、
S ：0.02％以下、 Al：0.003％以上0.06％以下
を含有し、残部がFeおよび不可避的不純物からなる組成を有し、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下であることを特徴とする引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板。 A steel plate provided with a zinc-based plating layer as a surface treatment layer on one or both surfaces of the steel plate, the steel plate being in mass%,
C: 0.001% to 0.1%, Si: 0.5% or less (excluding 0.01% or less),
Mn: 0.16% to 1.0%, P: 0.03% or less,
S: 0.02% or less, Al: 0.003% to 0.06% or less, the balance has a set formed of Fe and unavoidable impurities, Mn amount is 100 ppm by mass in diameter contained in the precipitates exceeds 0.5μm A steel sheet having a tensile strength exceeding 440 MPa and excellent corrosion resistance at the cut end face, characterized by the following:
C ：0.001％以上0.1％以下、 Si：0.5％超え4.0％以下、
Mn：0.16％以上1.0％以下、 P ：0.03％以下、
S ：0.02％以下、 Al：0.003％以上0.06％以下
を含有し、残部がFeおよび不可避的不純物からなる組成を有し、直径が0.5μm超えの析出物に含まれるMn量が100質量ppm以下であることを特徴とする引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板。 A steel sheet having a coating film containing a sacrificial anticorrosive pigment as a surface treatment layer on one or both surfaces of the steel sheet, the steel sheet being in mass%,
C: 0.001% or more and 0.1% or less, Si: more than 0.5% and 4.0% or less,
Mn: 0.16% to 1.0%, P: 0.03% or less,
S: 0.02% or less, Al: 0.003% or more and 0.06% or less, with the balance being composed of Fe and inevitable impurities, the amount of Mn contained in precipitates with a diameter exceeding 0.5 μm is 100 mass ppm or less A steel sheet with a tensile strength exceeding 440 MPa and excellent corrosion resistance at the cut end face.
C ：0.001％以上0.1％以下、 Si：4.0％以下（但し、0.01％以下は除く）、
Mn：0.16％以上1.0％以下、 P ：0.03％以下、
S ：0.02％以下、 Al：0.003％以上0.06％以下
を含有し、残部がFeおよび不可避的不純物からなる組成を有する鋳片を、再加熱して1000℃以上1100℃以下の温度域に均熱保持した後、仕上げ圧延終了温度をAr3変態点以上とする熱間圧延を施し、650℃以上680℃以下の巻取り温度で巻取ることにより熱延板とし、該熱延板を酸洗した後、60％以上90％以下の圧延率で冷間圧延を施して冷延板とし、該冷延板に、700℃以上850℃以下の焼鈍温度で連続焼鈍を施すことを特徴とする請求項１に記載の引張強さ440MPa超えの強度を有し、切断端面の耐食性に優れた鋼板の製造方法。 % By mass
C: 0.001% or more and 0.1% or less, Si: 4.0% or less (excluding 0.01% or less),
Mn: 0.16% to 1.0%, P: 0.03% or less,
S: 0.02% or less, Al: 0.003% to 0.06% or less, the slab the balance has a set formed of Fe and unavoidable impurities, reheated to 1000 ° C. or higher 1100 ° C. equalizing the temperature range below After heat holding, hot rolling is performed with the finish rolling finish temperature being the Ar 3 transformation point or higher, and the hot rolled sheet is wound at a winding temperature of 650 ° C. or higher and 680 ° C. or lower, and the hot rolled sheet is pickled. after, claims subjected to cold rolling and cold-rolled sheet, the cold rolled sheet, and characterized by applying continuous annealing in the following annealing temperature 700 ° C. or higher 850 ° C. at a rolling ratio of 60% to 90% Item 2. A method for producing a steel sheet having a tensile strength exceeding 440 MPa and excellent corrosion resistance at a cut end face.
前記鋳片のSi含有量が質量％で0.5％超えである場合には、前記表面処理を犠牲防食顔料を含む塗料による塗装とし、前記表面処理層を犠牲防食顔料を含む塗膜とする、
ことを特徴とする請求項９に記載の鋼板の製造方法。 When the surface treatment is performed after the continuous annealing and the surface treatment layer is formed on one or both surfaces of the steel sheet, the surface of the cast slab is 0.5% or less by mass%. The surface treatment layer is a zinc-based plating layer as a zinc-based plating treatment,
When the Si content of the slab is more than 0.5% by mass, the surface treatment is applied by a paint containing a sacrificial anticorrosive pigment, and the surface treatment layer is a coating film containing a sacrificial anticorrosive pigment.
The manufacturing method of the steel plate of Claim 9 characterized by the above-mentioned.
前記犠牲防食顔料を含む塗料による塗装処理が、片面当たりの付着量を10g/m2以上とする塗装処理である、
ことを特徴とする請求項１０に記載の鋼板の製造方法。 The zinc- based plating treatment is a plating treatment in which the plating adhesion amount per side is 5 g / m 2 or more,
The coating treatment with the paint containing the sacrificial anticorrosive pigment is a coating treatment with an adhesion amount per side of 10 g / m 2 or more.
The manufacturing method of the steel plate of Claim 10 characterized by the above-mentioned.
ことを特徴とする請求項１０または１１に記載の鋼板の製造方法。 Further, on the surface of the surface treatment layer, one or more coating layers of an inorganic coating layer, an organic coating layer, and an inorganic-organic composite coating layer are formed.
The manufacturing method of the steel plate of Claim 10 or 11 characterized by the above-mentioned.
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| JP4119832B2 (en) * | 2003-12-24 | 2008-07-16 | 新日本製鐵株式会社 | High strength steel plate for automobile fuel tank with excellent press formability, corrosion resistance and secondary workability, and method for producing the same |
| JP5390839B2 (en) * | 2008-11-27 | 2014-01-15 | 株式会社神戸製鋼所 | Chromate-free chemical conversion-treated galvanized steel sheet with excellent cutting end surface corrosion resistance |
| JP5549307B2 (en) * | 2009-04-13 | 2014-07-16 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet excellent in aging and bake hardenability and method for producing the same |
| JP5521520B2 (en) * | 2009-12-03 | 2014-06-18 | 新日鐵住金株式会社 | Alloyed hot-dip galvanized steel sheet and method for producing the same |
| JP5477002B2 (en) * | 2010-01-13 | 2014-04-23 | 新日鐵住金株式会社 | Cold rolled steel sheet |
| JP5397263B2 (en) | 2010-02-23 | 2014-01-22 | Ｊｆｅスチール株式会社 | High tensile cold-rolled steel sheet and method for producing the same |
| CN102782175B (en) * | 2010-05-31 | 2014-07-30 | 新日铁住金株式会社 | Hot dipped aluminum alloy coated steel material with excellent cut edge surface corrosion resistance and processed part corrosion resistance, and method for producing same |
| CN103074546B (en) * | 2011-10-25 | 2014-12-10 | 上海梅山钢铁股份有限公司 | Cold-rolled strip steel for condenser tube of refrigerator and manufacturing method thereof |
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| KR20160003098A (en) | 2016-01-08 |
| CN105452508B (en) | 2018-10-09 |
| CN105452508A (en) | 2016-03-30 |
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| KR101771337B1 (en) | 2017-08-24 |
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