WO2015125435A1 - High-strength hot-dip galvanized steel plate and method for producing same - Google Patents
High-strength hot-dip galvanized steel plate and method for producing same Download PDFInfo
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- WO2015125435A1 WO2015125435A1 PCT/JP2015/000544 JP2015000544W WO2015125435A1 WO 2015125435 A1 WO2015125435 A1 WO 2015125435A1 JP 2015000544 W JP2015000544 W JP 2015000544W WO 2015125435 A1 WO2015125435 A1 WO 2015125435A1
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- steel sheet
- annealing
- steel plate
- plating
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- 229910001335 Galvanized steel Inorganic materials 0.000 title claims abstract description 50
- 239000008397 galvanized steel Substances 0.000 title claims abstract description 50
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 132
- 239000010959 steel Substances 0.000 claims abstract description 132
- 238000007747 plating Methods 0.000 claims abstract description 111
- 238000000137 annealing Methods 0.000 claims abstract description 72
- 238000010438 heat treatment Methods 0.000 claims abstract description 32
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 26
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 25
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 18
- 239000001257 hydrogen Substances 0.000 claims abstract description 18
- 238000000034 method Methods 0.000 claims description 32
- 238000005275 alloying Methods 0.000 claims description 16
- 229910052787 antimony Inorganic materials 0.000 claims description 13
- 229910052758 niobium Inorganic materials 0.000 claims description 12
- 229910052718 tin Inorganic materials 0.000 claims description 12
- 229910052802 copper Inorganic materials 0.000 claims description 11
- 239000012535 impurity Substances 0.000 claims description 11
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 229910052750 molybdenum Inorganic materials 0.000 claims description 11
- 229910052719 titanium Inorganic materials 0.000 claims description 11
- 229910052721 tungsten Inorganic materials 0.000 claims description 11
- 229910052720 vanadium Inorganic materials 0.000 claims description 11
- 229910052782 aluminium Inorganic materials 0.000 claims description 10
- 238000005246 galvanizing Methods 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 10
- 229910052804 chromium Inorganic materials 0.000 claims description 9
- 229910052715 tantalum Inorganic materials 0.000 claims description 9
- 229910052796 boron Inorganic materials 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims 1
- 238000012545 processing Methods 0.000 abstract description 39
- 238000005260 corrosion Methods 0.000 abstract description 33
- 230000007797 corrosion Effects 0.000 abstract description 33
- 239000010953 base metal Substances 0.000 abstract description 3
- 230000032798 delamination Effects 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 35
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 33
- 230000003647 oxidation Effects 0.000 description 32
- 238000007254 oxidation reaction Methods 0.000 description 32
- 239000010410 layer Substances 0.000 description 19
- 229910052760 oxygen Inorganic materials 0.000 description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 14
- 239000000463 material Substances 0.000 description 14
- 239000001301 oxygen Substances 0.000 description 14
- 239000007789 gas Substances 0.000 description 13
- 239000002344 surface layer Substances 0.000 description 12
- 230000015572 biosynthetic process Effects 0.000 description 8
- 230000006866 deterioration Effects 0.000 description 7
- 229920006395 saturated elastomer Polymers 0.000 description 7
- 238000002791 soaking Methods 0.000 description 7
- 201000006705 Congenital generalized lipodystrophy Diseases 0.000 description 6
- 238000005097 cold rolling Methods 0.000 description 6
- 238000005098 hot rolling Methods 0.000 description 5
- 230000001737 promoting effect Effects 0.000 description 5
- 230000009467 reduction Effects 0.000 description 5
- 238000005096 rolling process Methods 0.000 description 5
- 230000001590 oxidative effect Effects 0.000 description 4
- 229920000298 Cellophane Polymers 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 230000001771 impaired effect Effects 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 238000005121 nitriding Methods 0.000 description 3
- 238000001953 recrystallisation Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 241000316887 Saissetia oleae Species 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 230000001154 acute effect Effects 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 102100040160 Rabankyrin-5 Human genes 0.000 description 1
- 101710086049 Rabankyrin-5 Proteins 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000005255 carburizing Methods 0.000 description 1
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 239000013077 target material Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
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- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
-
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
-
- 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
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
-
- 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
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
-
- 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
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
-
- 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
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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
- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
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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
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- 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
- C21D2211/005—Ferrite
Definitions
- the present invention relates to a high-strength hot-dip galvanized steel sheet excellent in plating appearance, corrosion resistance, plating peeling resistance during high processing and workability during high processing, and a high-strength steel plate containing Si and Mn. It relates to a manufacturing method.
- a steel plate that is a base material of a hot dip galvanized steel plate is a thin steel plate obtained by hot rolling or cold rolling a slab.
- a high-strength hot-dip galvanized steel sheet is manufactured by performing recrystallization annealing in a continuous hot-dip galvanizing line (hereinafter referred to as CGL) annealing furnace and hot-dip galvanizing treatment in a plating apparatus.
- CGL continuous hot-dip galvanizing line
- an alloyed hot-dip galvanized steel sheet it is manufactured after further hot-dip galvanizing treatment.
- the heating furnace type of the CGL annealing furnace there are a DFF type (direct flame type), a NOF type (non-oxidation type), an all radiant tube type, and the like.
- DFF type direct flame type
- NOF type non-oxidation type
- the all radiant tube type heating furnace does not have an oxidation step immediately before annealing. For this reason, when processing the steel plate containing oxidizable elements, such as Si and Mn, using the equipment which has this heating furnace, it is disadvantageous at the point of ensuring plating nature.
- Patent Document 1 discloses a technique of annealing and plating at a recrystallization temperature of 900 ° C.
- Patent Document 2 discloses a technique of annealing and plating at 750 to 900 ° C.
- Patent Document 3 discloses a technique of annealing and plating at 800 to 850 ° C.
- Patent Document 4 and Patent Document 5 disclose a technique for internally oxidizing the surface layer of the ground iron by defining the heating temperature in the reduction furnace by an expression represented by a water vapor partial pressure and increasing the dew point.
- the area where the dew point is controlled is the entire inside of the furnace, it is difficult to control the dew point and stable operation is difficult.
- variations in the distribution of internal oxides formed on the steel sheet are recognized. As a result of this variation, there is a concern that defects such as plating wettability and uneven alloying may occur in the longitudinal direction and width direction of the steel sheet.
- Patent Document 6 not only the oxidizing gases H 2 O and O 2, but also the CO 2 concentration is simultaneously defined, so that the surface layer immediately before plating is internally oxidized to suppress external oxidation and plating.
- a technique for improving the appearance is disclosed.
- cracks are likely to occur during processing due to the presence of the internal oxide, and the plating peel resistance deteriorates.
- deterioration of corrosion resistance is also recognized.
- CO 2 may cause problems such as furnace contamination and carburizing on the surface of the steel sheet, resulting in changes in mechanical properties.
- the present invention has been made in view of such circumstances. It is intended to provide a high-strength hot-dip galvanized steel sheet with a steel plate containing Si and Mn as a base material and excellent in plating appearance, corrosion resistance, anti-plating resistance during high processing and workability during high processing, and a method for producing the same. Objective.
- the heating rate is 7 ° C./s or more.
- the maximum steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower.
- the steel plate passage time in the temperature range of 600 ° C. or more and 750 ° C. or less is set to 30 seconds or more and 10 minutes or less, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
- the present invention is based on the above findings, and features are as follows.
- A any value selected from 500 ⁇ A
- the rate of temperature rise is 7 ° C./s or more
- the maximum temperature of the steel sheet is 600 in the annealing.
- the steel plate temperature in the annealing is not less than 750 ° C. and not more than 750 ° C.
- a high-strength hot-dip galvanized steel sheet in which a steel sheet passage time in a temperature range of 00 ° C. or higher and 750 ° C. or lower is set to 30 seconds or more and 10 minutes or less, a hydrogen concentration in the atmosphere is set to 20 vol% or higher, Production method.
- the steel sheet has a component composition in mass%, and B: 0.001 to 0.005%, Nb: 0.005 to 0.050%, Ti: 0.005 to 0.050%, Cr: 0.001 to 1.000%, Mo: 0.05 to 1.00%, Cu: 0.05 to 1.00%, Ni: 0.05 to 1.00%, Sn: 0.001 to 0.20%, Sb: 0.001 to 0.20%, Ta: 0.001 to 0.10%, W: 0.001 to 0.10%, V: 0.001 to 0.10%
- the steel sheet is further heated to a temperature of 450 ° C. or more and 600 ° C. or less to be alloyed, so that the Fe content of the plating layer is in the range of 8 to 14% by mass (1) Or the manufacturing method of the high intensity
- a high-strength hot-dip galvanized steel sheet produced by the method for producing a high-strength hot-dip galvanized steel sheet according to any one of (1) to (3), A steel plate and a galvanized layer formed on the steel plate, wherein the steel plate has the component composition described in (1) or (2), and the ground directly under the galvanized layer.
- high strength means a tensile strength (TS) of 980 MPa or more.
- a high-strength hot-dip galvanized steel sheet excellent in plating appearance, corrosion resistance, plating peeling resistance during high processing, and workability during high processing can be obtained.
- (Condition 1) In the annealing heating process, in the temperature range of annealing furnace temperature: 450 ° C. to A ° C. (however, A: any value selected from 500 ⁇ A), the rate of temperature increase: 7 ° C./s That's it.
- the maximum steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower.
- the steel plate passage time in the temperature range of 600 ° C. or more and 750 ° C. or less is set to 30 seconds or more and 10 minutes or less, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
- the oxygen potential at the interface between the steel sheet and the atmosphere can be lowered.
- internal oxidation can be suppressed, and selective surface diffusion and surface concentration of Si, Mn, etc. can be suppressed.
- a high-strength hot-dip galvanized steel sheet that has no unplating or the like, is excellent in appearance, has excellent workability, has higher corrosion resistance, and good plating peeling resistance during high processing can be obtained.
- the manufacturing method of a steel plate is not specifically limited.
- a method of producing a hot-rolled sheet by hot rolling steel a method of producing a cold-rolled sheet by cold rolling after hot rolling the steel, hot rolling the steel, pickling, A method of manufacturing a cold-rolled sheet by cold rolling can be employed.
- the hot-rolled sheet and the cold-rolled sheet thus obtained can be used as an object to be annealed.
- the thickness of the hot rolled sheet or cold rolled sheet is not particularly limited, but is preferably 0.3 to 5.0 mm.
- the conditions for hot rolling and pickling at the time of manufacturing the steel sheet are not particularly limited, and may be set as appropriate.
- the cold rolling is preferably performed at a rolling reduction of 40% or more and 80% or less. If the rolling reduction is less than 40%, the recrystallization temperature is lowered, and the mechanical characteristics are likely to deteriorate. On the other hand, when the rolling reduction exceeds 80%, the steel sheet is a high-strength steel plate, so that not only the rolling cost is increased, but also the surface concentration during annealing is increased and the plating property may be deteriorated.
- the annealing can be performed using a general continuous hot dip galvanizing facility.
- An annealing furnace included in a general continuous hot dip galvanizing facility has a heating zone in the front stage and a soaking zone in the rear stage.
- the steel sheet is heated to a predetermined temperature in the preceding heating zone, and the steel sheet is held under conditions of a predetermined temperature and a predetermined time in the latter-stage soaking zone.
- thermometer a multiple reflection thermometer, a radiation thermometer, etc. can be illustrated, and the system of a thermometer is not specifically limited.
- the temperature range for controlling the heating rate is set to 450 ° C. or higher is as follows. In the temperature range below 450 ° C., surface enrichment and internal oxidation to such an extent that non-plating occurs, corrosion resistance deteriorates, plating peel resistance deteriorates, etc. do not occur. Therefore, the temperature range for controlling the rate of temperature rise is set to 450 ° C. or more, which is the temperature range where the effects of the present invention are manifested.
- the reason why the temperature range for controlling the rate of temperature rise is A ° C. or lower (A: any value selected from 500 ⁇ A) is as follows. First, when the upper limit of the temperature range for controlling the temperature increase rate is below 500 ° C., the time for controlling the temperature increase rate to 7 ° C./s or more is short, and the effect of the present invention cannot be sufficiently obtained. For this reason, A shall be 500 degreeC or more.
- the upper limit of the temperature range for controlling the rate of temperature rise exceeds 600 ° C., there is no problem with the effect of the present invention, but it is disadvantageous from the viewpoint of cost increase (equipment of induction heaters, etc.) required for the equipment in the annealing furnace. It becomes. Therefore, 600 ° C. or lower is preferable.
- the heating rate in the above temperature range is 7 ° C./s or more is as follows. It is at a temperature increase rate of 7 ° C./s or more that the effect of suppressing surface concentration begins to be recognized. Although there is no particular upper limit for the rate of temperature increase, the effect is saturated at 500 ° C./s or more, which is disadvantageous in terms of cost. For this reason, the heating rate is desirably 500 ° C./s or less. Note that it is possible to set the rate of temperature rise to 7 ° C./s or more, for example, by placing an induction heater in an annealing furnace in which the steel plate temperature is 450 ° C. or more and A ° C. or less. In the present invention, “s” in the unit of temperature increase rate means second.
- the highest temperature reached in the steel sheet is 600 ° C. or higher and 750 ° C. or lower in annealing.
- the steel plate maximum temperature is a temperature that is further increased by heating from the maximum temperature A ° C. in the heating in the heating process, except when A ° C. is the same as the steel plate maximum temperature.
- the maximum steel plate temperature refers to the maximum value during annealing when measured by the same method as the method for measuring the steel plate temperature.
- the reason why the maximum steel sheet temperature in the annealing furnace is 600 ° C. or higher and 750 ° C. or lower is as follows. When the maximum temperature reached by the steel sheet is below 600 ° C., surface enrichment and internal oxidation to the extent that non-plating occurs, corrosion resistance deterioration, plating peel resistance deterioration, etc., will not occur, but the effect of the present invention is sufficient. I can't get it. In addition, when the maximum temperature reached by the steel sheet is below 600 ° C., a good material cannot be obtained. Therefore, in this invention, the said steel plate highest reached temperature shall be 600 degreeC or more.
- the maximum temperature of the steel sheet exceeds 750 ° C.
- the surface concentration becomes remarkable, and the occurrence of non-plating, deterioration of corrosion resistance, deterioration of plating peeling resistance, and the like becomes severe.
- the maximum steel sheet temperature exceeds 750 ° C. in both strength (TS) and ductility (El)
- the effect of balance between strength and ductility is saturated. From the above, the maximum temperature reached by the steel sheet is set to 600 ° C. or higher and 750 ° C. or lower.
- the steel plate temperature in the temperature range of 600 ° C. to 750 ° C. is set to 30 seconds to 10 minutes, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
- the target material (TS, El) cannot be obtained.
- the steel plate passage time exceeds 10 minutes, the effect of balance between strength and ductility is saturated.
- the hydrogen concentration in the atmosphere where the steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower is 20 vol% or higher, the effect of suppressing surface concentration is recognized.
- the upper limit of the hydrogen concentration is not particularly set, but even if the hydrogen concentration exceeds 50 vol%, the effect is saturated, which is disadvantageous in terms of cost. For this reason, the hydrogen concentration is desirably 50 vol% or less.
- Components other than hydrogen gas contained in the atmosphere in the above temperature range are not particularly limited as long as the effects of the present invention are not impaired, and the gas in the atmosphere is usually composed of hydrogen gas, nitrogen gas, and inevitable impurity gas. .
- other gases may be included as long as the effects of the present invention are not impaired.
- the hydrogen concentration outside the temperature range where the hydrogen concentration is controlled is not particularly limited, and the hydrogen concentration is preferably 1 vol% or more and 50 vol% or less. If the hydrogen concentration is less than 1 vol%, the activation effect due to reduction cannot be obtained, and the plating peel resistance may deteriorate. On the other hand, if it exceeds 50 vol%, the cost increases and the effect is saturated.
- the atmospheric gas in the above temperature range the atmospheric gas in other temperature ranges is composed of hydrogen gas, nitrogen gas, and inevitable impurity gas. In addition, other gases may be included as long as the effects of the present invention are not impaired.
- the conditions of the soaking temperature and soaking time in the soaking zone are not particularly limited, and may be set as appropriate.
- the soaking temperature may be the above-mentioned maximum steel plate temperature, or may be a temperature lower than the above-mentioned maximum steel plate temperature.
- the dew point of the atmosphere in the annealing is not particularly limited, and may be in the range of ⁇ 10 to ⁇ 40 ° C., for example.
- ⁇ Plating is performed on the surface of the steel sheet after the annealing. Plating is also performed in a continuous hot dip galvanizing facility.
- the conditions for the plating treatment are not particularly limited except for the conditions for the amount of plating, and may be set as appropriate.
- the plating adhesion amount per side is 20 to 120 g / m 2 .
- the plating adhesion amount is less than 20 g / m 2 , it becomes difficult to ensure corrosion resistance.
- the plating adhesion amount exceeds 120 g / m 2 , the plating peel resistance deteriorates.
- the alloying process may be performed following the plating process.
- the steel plate after the plating treatment is heated to 450 ° C. or more and 600 ° C. or less. At this time, heating is preferably performed so that the Fe content of the plating layer is 8 to 14% by mass. If the Fe content is less than 8%, unevenness in alloying and flaking properties deteriorate. On the other hand, if the Fe content exceeds 14%, the plating peel resistance deteriorates.
- the high-strength hot-dip galvanized steel sheet manufactured by the method of the present invention includes both high-strength hot-dip galvanized steel sheets that have not been alloyed and alloyed high-strength hot-dip galvanized steel sheets that have been alloyed. including.
- the present invention is characterized by the annealing conditions of the steel sheet. Then, the steel plate used as the object of annealing is demonstrated.
- “%” means “mass%”.
- C 0.03-0.35%
- C improves workability by forming martensite or the like in the steel structure.
- the C content needs to be 0.03% or more.
- the C content is 0.03% or more and 0.35% or less.
- Si 0.01 to 0.50% Si is an effective element for strengthening steel and obtaining a good material.
- Si is an easily oxidizable element, it is disadvantageous for plating properties. From this point of view, it is an element that should be avoided as much as possible.
- the lower limit of the Si content is 0.01%.
- the Si amount is set to 0.01% or more and 0.50% or less.
- Mn 3.6 to 8.0% Mn is an element effective for increasing the strength of steel. In order to ensure mechanical properties and strength, the Mn content needs to be 3.6% or more. On the other hand, if the Mn content exceeds 8.0%, it becomes difficult to ensure weldability and plating adhesion, and to ensure a balance between strength and ductility. Therefore, the Mn content is 3.6% or more and 8.0% or less.
- Al 0.001 to 1.000% Al is added for the purpose of deoxidizing molten steel. If the Al content is less than 0.001%, the object is not achieved. The effect of deoxidation of molten steel can be obtained by making the Al content 0.001% or more. On the other hand, if the Al content exceeds 1.000%, the cost increases. Therefore, the Al amount is set to 0.001% or more and 1.000% or less.
- P 0.10% or less P is one of the elements inevitably contained.
- the steel sheet may not contain P.
- the P content is preferably 0.005% or more.
- P exceeds 0.10%, weldability deteriorates.
- the surface quality deteriorates.
- the plating adhesion deteriorates during non-alloying treatment, and the desired degree of alloying cannot be achieved unless the alloying treatment temperature is increased during alloying treatment.
- the ductility deteriorates and at the same time the adhesion of the alloyed plating film deteriorates.
- the content of P exceeds 0.10%, a desired degree of alloying, good ductility, and an alloyed plating film cannot be achieved. Therefore, the P content is preferably 0.10% or less, and the lower limit is preferably 0.005% or more.
- S 0.010% or less S is one of elements inevitably contained, and S may not be contained. Although the lower limit of the S content is not specified, the weldability deteriorates when the S content increases. For this reason, content of S shall be 0.010% or less.
- the steel plate to be annealed is B: 0.001 to 0.005%, Nb: 0.00. 005 to 0.050%, Ti: 0.005 to 0.050%, Cr: 0.001 to 1.000%, Mo: 0.05 to 1.00%, Cu: 0.05 to 1.00% , Ni: 0.05 to 1.00%, Sn: 0.001 to 0.20%, Sb: 0.001 to 0.20%, Ta: 0.001 to 0.10%, W: 0.001
- One or more elements selected from -0.10% and V: 0.001-0.10% may be included as required. The reason for limiting the proper content in the case of containing these elements is as follows.
- B 0.001 to 0.005%
- the content of B is less than 0.001%, it is difficult to obtain the quenching promoting effect.
- the B content exceeds 0.005%, the plating adhesion may deteriorate. Therefore, when it contains B, it is preferable to make B amount into 0.001% or more and 0.005% or less.
- Nb 0.005 to 0.050%
- the content of Nb is less than 0.005%, it is difficult to obtain the effect of improving the adhesion of plating at the time of strength adjustment or composite addition with Mo.
- the Nb content exceeds 0.050%, the cost increases. Therefore, when Nb is contained, the Nb content is 0.005% or more and 0.050% or less.
- Ti 0.005 to 0.050% If the Ti content is less than 0.005%, the effect of adjusting the strength is difficult to obtain. On the other hand, if the Ti content exceeds 0.050%, the plating adhesion may be deteriorated. Therefore, when Ti is contained, the Ti content is preferably 0.005% or more and 0.050% or less.
- Cr 0.001 to 1.000%
- Cr content is less than 0.001%, it is difficult to obtain a hardenability effect.
- the Cr content exceeds 1.000%, the surface of Cr is concentrated, so that the plating adhesion and weldability deteriorate. Therefore, when it contains Cr, it is preferable that Cr amount shall be 0.001% or more and 1.000% or less.
- Mo 0.05-1.00%
- Mo content is less than 0.05%, it is difficult to obtain the effect of adjusting the strength and the effect of improving the plating adhesion at the time of composite addition with Nb, Ni or Cu.
- Mo content exceeds 1.00%, the cost increases. Therefore, when it contains Mo, it is preferable to make Mo amount into 0.05% or more and 1.00% or less.
- the amount of Cu is preferably 0.05% or more and 1.00% or less.
- Ni 0.05-1.00%
- the amount of Ni is preferably 0.05% or more and 1.00% or less.
- Sn and Sb can be contained from the viewpoint of suppressing decarburization in the region of several tens of microns from the steel sheet surface caused by nitriding, oxidation, or oxidation of the steel sheet surface.
- Sn or Sb is contained, each content is preferably 0.001% or more. Further, if each content exceeds 0.20%, the toughness is deteriorated, so the Sn and Sb contents are preferably 0.20% or less.
- Ta 0.001 to 0.10% Ta, like Nb and Ti, contributes to increasing the strength by forming carbides and carbonitrides with C and N. Furthermore, Ta contributes to a high yield ratio (high YR). From such a viewpoint, by containing Ta, a high seizure hardening amount (BH amount) can be obtained due to an increase in the amount of C segregation to the grain boundary accompanying an increase in the grain boundary area. From such a viewpoint, 0.001% or more of Ta can be contained. On the other hand, when the content of Ta exceeds 0.10%, not only the raw material cost is increased, but similarly to Nb and Ti, the formation of martensite in the cooling process after annealing may be hindered. Furthermore, TaC precipitated in the hot-rolled sheet increases the deformation resistance during cold rolling, which may make it difficult to manufacture a stable actual machine. For this reason, when it contains Ta, it is preferable to make the content into 0.10% or less.
- W 0.001 to 0.10%
- V 0.001 to 0.10%
- Fe and unavoidable impurities The balance other than the above components is Fe and unavoidable impurities.
- the unavoidable impurity is, for example, O.
- O is a typical inevitable impurity inevitably mixed.
- the content of inevitable impurities is not particularly limited, and the allowable content of inevitable impurities depends on the type of inevitable impurities, but in the case of O, there is a problem if the content is 0.005% or less. No.
- the high-strength hot-dip galvanized steel sheet produced by the above method will be described.
- the high-strength hot-dip galvanized steel sheet of the present invention is characterized by the structure of the surface layer of the steel sheet directly below the plating layer.
- Fe, Si, Mn, Al, P, B, Nb which are present in a region within 100 ⁇ m from the surface of the steel sheet directly under the galvanized layer.
- the total amount of oxides of one or more selected from Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V is 0.010 g / side. less than m 2 .
- Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, V oxides are formed in total (except for Fe only) It is good also as less than 0.010 g / m ⁇ 2 > per single side
- the amount of oxide is measured by the method described in the examples described later.
- the oxygen potential is lowered during annealing in order to ensure plating properties.
- the internal oxidation formed in the surface layer part of the iron core is also suppressed by the annealing conditions, and the corrosion resistance and the workability at the time of high processing are improved.
- the total oxide formation amount hereinafter referred to as internal oxidation amount
- internal oxidation amount is 0.010 g / m 2 or more, corrosion resistance and workability deteriorate.
- the lower limit of the internal oxidation amount is preferably 0.0001 g / m 2 or more.
- the base iron structure on which the Si and Mn based composite oxide grows is preferably a soft and rich workability ferrite phase.
- a hot-rolled steel sheet having a steel composition shown in Table 1 was pickled, and after removing the black scale, it was cold-rolled to obtain a cold-rolled steel sheet having a thickness of 1.0 mm.
- a part of the hot-rolled steel sheet (thickness: 2.0 mm) after removing the black scale was used without performing cold rolling.
- the cold-rolled steel plate and hot-rolled steel plate obtained above were charged into CGL equipped with an all-radiant tube type heating furnace in an annealing furnace.
- CGL as shown in Tables 2 and 3, the heating rate in a predetermined temperature range in the annealing furnace, the hydrogen concentration, the steel plate passage time, and the maximum temperature reached by the steel plate are controlled, heated in the heating zone, and uniform. Maintained soaking in the tropics and annealed.
- the hydrogen concentration in the region where the hydrogen concentration in the atmosphere was not controlled was adjusted to 5 vol%. Furthermore, the dew point in the furnace was controlled at -35 ° C.
- the control of the dew point of the atmosphere in the annealing, H 2 and N 2 gas flows pipe water tank humidified by heating which is installed in a space N 2 gas is filled is connected to the annealing furnace, the N 2 gas humidified
- the dew point of the atmosphere was controlled by introducing and mixing the gas and introducing it into the furnace.
- hot dip galvanization was performed in an Al-containing Zn bath at 460 ° C.
- a 0.14 mass% Al-containing Zn bath is used for the production of GA (alloyed high-strength hot-dip galvanized steel sheet), and 0.18 mass% Al is used for the production of GI (high-strength hot-dip galvanized steel sheet).
- a containing Zn bath was used.
- the amount of adhesion was adjusted by gas wiping so that a galvanized layer having a plating adhesion amount of 20 to 120 g / m 2 per side was formed.
- the alloying treatment temperatures were as shown in Tables 2 and 3, and the alloying temperature and time were adjusted so that the Fe content in the plating layer became the values shown in Tables 2 and 3.
- the hot-dip galvanized steel sheets (GA and GI) obtained as described above were examined for appearance (plating appearance), corrosion resistance, plating peeling resistance during high processing, and workability during high processing. Moreover, the formation amount (internal oxidation amount) of the oxide which exists in the area
- ⁇ Plating resistance> In GA high-strength hot-dip galvanized steel sheets, it is required to suppress plating peeling at bent portions when bent at an acute angle exceeding 90 °.
- the cellophane tape (registered trademark) was pressed against the processed portion bent by 120 ° to transfer the peeled material to the cellophane tape (registered trademark), and the amount of the peeled material on the cellophane tape (registered trademark) was expressed as the Zn count. Obtained by line method.
- the mask diameter is 30 mm
- the fluorescent X-ray acceleration voltage is 50 kV
- the acceleration current is 50 mA
- the measurement time is 20 seconds.
- Fluorescent X-ray Zn count number Rank 0 to less than 500: 1 (good) 500 or more and less than 1000: 2 ⁇ 1000 or more and less than 2000: 3 ⁇ 2000 or more and less than ⁇ 3000: 4 ⁇ 3000 or more: 5 (poor) ⁇
- the GI high-strength hot-dip galvanized steel sheet is required to have anti-plating resistance during an impact test. A ball impact test was performed, the processed part was peeled off with tape, and the presence or absence of peeling of the plating layer was visually determined. Ball impact conditions are a ball weight of 1000 g and a drop height of 100 cm.
- Plating layer is not peeled
- Plating layer is peeled ⁇ Corrosion resistance>
- a hot-dip galvanized steel sheet (GA and GI) having a size of 70 mm ⁇ 150 mm was subjected to a salt spray test based on JISZ 2371 (2000) for 3 days, and then chromic acid (concentration 200 g / L, in order to remove corrosion products) (80 ° C.) for 1 minute, and the plating corrosion weight loss (g / m 2 ⁇ day) before and after the test per one side was measured by a weight method and evaluated according to the following criteria.
- the amount of internal oxidation is measured by “impulse furnace melting-infrared absorption method”.
- the oxygen concentration in the steel is measured at a position polished by 100 ⁇ m or more from both sides of the high-strength steel plate after annealing.
- the measured value was defined as the amount of oxygen OH contained in the material.
- board thickness direction of the high strength steel plate surface after annealing was measured, and the measured value was made into oxygen amount OI after internal oxidation.
- GI and GA invention examples produced by the method of the present invention contain a large amount of oxidizable elements such as Si and Mn, and are high-strength steel sheets. Nevertheless, the corrosion resistance, the workability at the time of high processing, the plating peeling resistance at the time of high processing and the plating appearance are also good. On the other hand, in the comparative example, any one or more of plating appearance, corrosion resistance, workability at high processing, and plating peeling resistance at high processing is inferior.
- the high-strength hot-dip galvanized steel sheet according to the present invention is excellent in plating appearance, corrosion resistance, workability, and anti-plating resistance during high processing, and is used as a surface-treated steel sheet for reducing the weight and strength of an automobile body. be able to.
- the steel sheet can be applied in a wide range of fields such as home appliances and building materials as a surface-treated steel sheet provided with rust prevention properties.
Abstract
Provided are: a high-strength hot-dip galvanized steel plate having a steel plate containing Si and Mn as a base metal and having superior plating appearance, corrosion resistance, plating delamination resistance during high processing, and processing properties during high processing; and a method for producing same. In a heating process for annealing, the following conditions (1)-(3) are adopted: (condition 1) in the heating process for annealing, the rate of temperature rise is at least 7°C/s in the temperature region of an annealing furnace temperature of 450-A°C inclusive (where any given value is selected such that 500≤A); (condition 2) the maximum achieved temperature of the steel plate during annealing is 600-750°C inclusive; (condition 3) the transit time of the steel plate in the temperature region at which the steel plate temperature is 600-750°C inclusive during annealing is at least 30 seconds and no greater than 10 minutes, and the hydrogen concentration of the ambient is at least 20 vol%.
Description
本発明は、ＳｉおよびＭｎを含有する高強度鋼板を母材とする、めっき外観、耐食性、高加工時の耐めっき剥離性および高加工時の加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法に関するものである。
The present invention relates to a high-strength hot-dip galvanized steel sheet excellent in plating appearance, corrosion resistance, plating peeling resistance during high processing and workability during high processing, and a high-strength steel plate containing Si and Mn. It relates to a manufacturing method.
近年、自動車、家電、建材等の分野に用いられる部品等の素材として、防錆性を付与した表面処理鋼板、中でも溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板が広範に使用されている。また、自動車の燃費向上および自動車の衝突安全性向上の観点から、車体材料の高強度化によって薄肉化を図り、車体そのものを軽量化しかつ高強度化する要望が高まっている。そのために高強度鋼板の自動車への適用が促進されている。
In recent years, surface-treated steel sheets imparted with rust resistance, particularly hot-dip galvanized steel sheets and galvannealed steel sheets have been widely used as materials for parts used in the fields of automobiles, home appliances, building materials and the like. In addition, from the viewpoint of improving the fuel efficiency of automobiles and improving the collision safety of automobiles, there is an increasing demand for reducing the thickness of the vehicle body by increasing the strength of the vehicle body material and reducing the weight of the vehicle body. Therefore, application of high-strength steel sheets to automobiles is being promoted.
一般的に、溶融亜鉛めっき鋼板の母材となる鋼板は、スラブを熱間圧延や冷間圧延した薄鋼板である。また、高強度溶融亜鉛めっき鋼板は、連続式溶融亜鉛めっきライン（以下、ＣＧＬと称す）の焼鈍炉にて再結晶焼鈍およびめっき装置にて溶融亜鉛めっき処理を行い製造される。合金化溶融亜鉛めっき鋼板の場合は、溶融亜鉛めっき処理の後、さらに合金化処理を行い製造される。
Generally, a steel plate that is a base material of a hot dip galvanized steel plate is a thin steel plate obtained by hot rolling or cold rolling a slab. A high-strength hot-dip galvanized steel sheet is manufactured by performing recrystallization annealing in a continuous hot-dip galvanizing line (hereinafter referred to as CGL) annealing furnace and hot-dip galvanizing treatment in a plating apparatus. In the case of an alloyed hot-dip galvanized steel sheet, it is manufactured after further hot-dip galvanizing treatment.
ここで、ＣＧＬの焼鈍炉の加熱炉タイプとしては、ＤＦＦ型（直火型）、ＮＯＦ型（無酸化型）、オールラジアントチューブ型等がある。近年では、操業のし易さやピックアップが発生しにくい等により低コストで高品質なめっき鋼板を製造できるなどの理由からオールラジアントチューブ型の加熱炉を備えるＣＧＬの建設が増加している。しかしながら、ＤＦＦ型（直火型）、ＮＯＦ型（無酸化型）と異なり、オールラジアントチューブ型の加熱炉は焼鈍直前に酸化工程がない。このため、この加熱炉を有する設備を用いて、Ｓｉ、Ｍｎ等の易酸化性元素を含有する鋼板を処理する場合、めっき性確保の点で不利である。
Here, as the heating furnace type of the CGL annealing furnace, there are a DFF type (direct flame type), a NOF type (non-oxidation type), an all radiant tube type, and the like. In recent years, there has been an increase in the construction of CGLs equipped with an all-radiant tube-type heating furnace because, for example, it is possible to produce high-quality plated steel sheets at low cost due to ease of operation and difficulty in picking up. However, unlike the DFF type (direct flame type) and the NOF type (non-oxidation type), the all radiant tube type heating furnace does not have an oxidation step immediately before annealing. For this reason, when processing the steel plate containing oxidizable elements, such as Si and Mn, using the equipment which has this heating furnace, it is disadvantageous at the point of ensuring plating nature.
Ｓｉ、Ｍｎを多量に含む高強度鋼板を母材とした溶融亜鉛めっき鋼板の製造方法として、特許文献１には、再結晶温度～９００℃で焼鈍し、めっきする技術が開示されている。特許文献２には、７５０～９００℃で焼鈍し、めっきする技術が開示されている。特許文献３には、８００～８５０℃で焼鈍し、めっきする技術が開示されている。しかしながら、Ｓｉ、Ｍｎを多量に含む高強度鋼板の場合、７５０℃を超える高い温度で焼鈍をすると、鋼中Ｓｉ、Ｍｎが選択酸化し、鋼板表面に酸化物を形成するため、めっき密着性を劣化させ、不めっき等の欠陥が発生する懸念がある。
As a method for producing a hot-dip galvanized steel sheet using a high-strength steel sheet containing a large amount of Si and Mn as a base material, Patent Document 1 discloses a technique of annealing and plating at a recrystallization temperature of 900 ° C. Patent Document 2 discloses a technique of annealing and plating at 750 to 900 ° C. Patent Document 3 discloses a technique of annealing and plating at 800 to 850 ° C. However, in the case of a high-strength steel sheet containing a large amount of Si and Mn, if annealing is performed at a high temperature exceeding 750 ° C., Si and Mn in the steel selectively oxidize and form an oxide on the steel sheet surface. There is a concern that defects such as non-plating may occur due to deterioration.
さらに、特許文献４および特許文献５には、還元炉における加熱温度を水蒸気分圧で表される式で規定し露点を上げることで、地鉄表層を内部酸化させる技術が開示されている。しかしながら、上記技術では、露点を制御するエリアが炉内全体であるため、露点の制御が困難であり安定操業が困難である。また、不安定な露点制御のもとでの合金化溶融亜鉛めっき鋼板の製造は、地鉄鋼板に形成される内部酸化物の分布状態にバラツキが認められる。このバラツキの結果、鋼板の長手方向や幅方向でめっき濡れ性や合金化ムラなどの欠陥が発生する懸念がある。
Furthermore, Patent Document 4 and Patent Document 5 disclose a technique for internally oxidizing the surface layer of the ground iron by defining the heating temperature in the reduction furnace by an expression represented by a water vapor partial pressure and increasing the dew point. However, in the above technique, since the area where the dew point is controlled is the entire inside of the furnace, it is difficult to control the dew point and stable operation is difficult. Further, in the production of an alloyed hot-dip galvanized steel sheet under unstable dew point control, variations in the distribution of internal oxides formed on the steel sheet are recognized. As a result of this variation, there is a concern that defects such as plating wettability and uneven alloying may occur in the longitudinal direction and width direction of the steel sheet.
また、特許文献６には、酸化性ガスであるＨ２ＯやＯ２だけでなく、ＣＯ２濃度も同時に規定することで、めっき直前の地鉄表層を内部酸化させ外部酸化を抑制してめっき外観を改善する技術が開示されている。しかしながら、特許文献６では、内部酸化物の存在により加工時に割れが発生しやすくなり、耐めっき剥離性が劣化する。また、特許文献６の技術では、耐食性の劣化も認められる。さらにＣＯ２は炉内汚染や鋼板表面への浸炭などが起こり、機械特性が変化するなどの問題が懸念される。
In Patent Document 6, not only the oxidizing gases H 2 O and O 2, but also the CO 2 concentration is simultaneously defined, so that the surface layer immediately before plating is internally oxidized to suppress external oxidation and plating. A technique for improving the appearance is disclosed. However, in Patent Document 6, cracks are likely to occur during processing due to the presence of the internal oxide, and the plating peel resistance deteriorates. Moreover, in the technique of patent document 6, deterioration of corrosion resistance is also recognized. Furthermore, there is a concern that CO 2 may cause problems such as furnace contamination and carburizing on the surface of the steel sheet, resulting in changes in mechanical properties.
さらに、最近では、加工の厳しい箇所への高強度溶融亜鉛めっき鋼板、高強度合金化溶融亜鉛めっき鋼板の適用が進んでおり、高加工時の耐めっき剥離特性が重要視されるようになっている。具体的にはめっき鋼板に９０°超えの曲げ加工を行い、より鋭角に曲げたときや衝撃が加わり鋼板が加工を受けた場合の、加工部のめっき剥離の抑制が要求される。
Furthermore, recently, the application of high-strength hot-dip galvanized steel sheets and high-strength alloyed hot-dip galvanized steel sheets to places where machining is severe has progressed, and the anti-plating resistance characteristics at the time of high processing have become important. Yes. Specifically, when the plated steel sheet is bent over 90 ° and bent at an acute angle, or when the steel sheet is subjected to processing by applying an impact, suppression of plating peeling at the processed portion is required.
以上のような特性を満たすためには、鋼中に多量にＳｉを添加し所望の鋼板組織を確保するだけでなく、高加工時の割れなどの起点になる可能性があるめっき層直下の地鉄表層の組織、構造のより高度な制御が求められる。しかしながら従来技術ではそのような制御は困難である。つまり、従来技術では、焼鈍炉にオールラジアントチューブ型の加熱炉を備えるＣＧＬでＳｉ含有高強度鋼板を母材として高加工時の耐めっき剥離特性に優れた溶融亜鉛めっき鋼板を製造することはできない。
In order to satisfy the above characteristics, not only a large amount of Si is added to the steel to secure the desired steel sheet structure, but also the ground directly under the plating layer, which may become a starting point for cracks during high processing. More advanced control of the structure and structure of the iron surface layer is required. However, such control is difficult with the prior art. In other words, in the prior art, a hot-dip galvanized steel sheet with excellent anti-plating resistance at the time of high processing cannot be manufactured using CGL with an all-radiant tube-type heating furnace in the annealing furnace and using a Si-containing high-strength steel sheet as a base material. .
本発明は、かかる事情に鑑みてなされたものである。Ｓｉ、Ｍｎを含有する鋼板を母材とし、めっき外観、耐食性、高加工時の耐めっき剥離性および高加工時の加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法を提供することを目的とする。
The present invention has been made in view of such circumstances. It is intended to provide a high-strength hot-dip galvanized steel sheet with a steel plate containing Si and Mn as a base material and excellent in plating appearance, corrosion resistance, anti-plating resistance during high processing and workability during high processing, and a method for producing the same. Objective.
従来は、めっき性を改善する目的で積極的にＦｅを酸化させたり、内部酸化させたりしていた。しかし、この方法では、めっき性は改善するものの、耐食性や加工性が劣化する。
Conventionally, Fe has been actively oxidized or internally oxidized for the purpose of improving plating properties. However, with this method, although the plating property is improved, the corrosion resistance and workability are deteriorated.
そこで、本発明者らは、従来の考えにとらわれない新たな方法で課題を解決する方法を検討した。その結果、鋼板を焼鈍する際の雰囲気と温度を適切に制御して、めっき層直下の地鉄表層部における内部酸化の形成を抑制することで、優れためっき外観と、より高い耐食性、高加工時の優れた加工性、高加工時の良好な耐めっき剥離性が得られることを知見した。具体的には、焼鈍の加熱過程において、以下の（条件１）～（条件３）を採用する。
（条件１）焼鈍の加熱過程において、焼鈍炉内温度：４５０℃以上Ａ℃以下（但し、５００≦Ａから選択される任意の値）の温度域では、昇温速度：７℃/s以上とする。
（条件２）焼鈍において鋼板最高到達温度を６００℃以上７５０℃以下とする。
（条件３）焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の鋼板通過時間を３０秒以上１０分以内、雰囲気の水素濃度を２０ｖｏｌ％以上とする。 Therefore, the present inventors have studied a method for solving the problem by a new method not confined to the conventional idea. As a result, by properly controlling the atmosphere and temperature when annealing the steel sheet, and suppressing the formation of internal oxidation in the surface layer of the base metal directly under the plating layer, excellent plating appearance, higher corrosion resistance, high processing It has been found that excellent workability at the time and good plating peel resistance at the time of high processing can be obtained. Specifically, the following (Condition 1) to (Condition 3) are employed in the annealing heating process.
(Condition 1) In the annealing heating process, in the annealing furnace temperature: 450 ° C. or more and A ° C. or less (however, an arbitrary value selected from 500 ≦ A), the heating rate is 7 ° C./s or more. To do.
(Condition 2) In annealing, the maximum steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower.
(Condition 3) In annealing, the steel plate passage time in the temperature range of 600 ° C. or more and 750 ° C. or less is set to 30 seconds or more and 10 minutes or less, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
（条件１）焼鈍の加熱過程において、焼鈍炉内温度：４５０℃以上Ａ℃以下（但し、５００≦Ａから選択される任意の値）の温度域では、昇温速度：７℃/s以上とする。
（条件２）焼鈍において鋼板最高到達温度を６００℃以上７５０℃以下とする。
（条件３）焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の鋼板通過時間を３０秒以上１０分以内、雰囲気の水素濃度を２０ｖｏｌ％以上とする。 Therefore, the present inventors have studied a method for solving the problem by a new method not confined to the conventional idea. As a result, by properly controlling the atmosphere and temperature when annealing the steel sheet, and suppressing the formation of internal oxidation in the surface layer of the base metal directly under the plating layer, excellent plating appearance, higher corrosion resistance, high processing It has been found that excellent workability at the time and good plating peel resistance at the time of high processing can be obtained. Specifically, the following (Condition 1) to (Condition 3) are employed in the annealing heating process.
(Condition 1) In the annealing heating process, in the annealing furnace temperature: 450 ° C. or more and A ° C. or less (however, an arbitrary value selected from 500 ≦ A), the heating rate is 7 ° C./s or more. To do.
(Condition 2) In annealing, the maximum steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower.
(Condition 3) In annealing, the steel plate passage time in the temperature range of 600 ° C. or more and 750 ° C. or less is set to 30 seconds or more and 10 minutes or less, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
上記の（条件１）～（条件３）を採用することで、鋼板と雰囲気の界面の酸素ポテンシャルを低下させ、内部酸化を極力生じさせずに、Ｓｉ、Ｍｎなどの選択的表面拡散および酸化（以後、表面濃化と呼ぶ）を抑制する。
By adopting the above (Condition 1) to (Condition 3), the oxygen potential at the interface between the steel sheet and the atmosphere is lowered, and selective surface diffusion and oxidation of Si, Mn, etc. are performed without causing internal oxidation as much as possible ( Hereinafter referred to as surface thickening).
このように昇温速度、焼鈍温度や雰囲気の水素濃度を制御することにより、内部酸化を抑制するとともに、表面濃化を極力抑制する。その結果、めっき外観、耐食性、高加工時の加工性および高加工時の耐めっき剥離性に優れる高強度溶融亜鉛めっき鋼板が得られることになる。なお、めっき外観に優れるとは、不めっきや合金化ムラが認められない外観を有することをいう。
In this way, by controlling the heating rate, annealing temperature and hydrogen concentration in the atmosphere, internal oxidation is suppressed and surface concentration is suppressed as much as possible. As a result, a high-strength hot-dip galvanized steel sheet excellent in plating appearance, corrosion resistance, workability during high processing, and plating peel resistance during high processing can be obtained. In addition, being excellent in plating appearance means having an appearance in which non-plating and alloying unevenness are not recognized.
そして、以上の方法により得られる高強度溶融亜鉛めっき鋼板では、亜鉛めっき層の直下の、地鉄鋼板表面から１００μｍ以内の領域において、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉ、Ｓｎ、Ｓｂ、Ｔａ、Ｗ、Ｖのうちから選ばれる１種以上（Ｆｅのみの場合を除く）の酸化物の形成が抑制される。その形成量は合計で片面あたり０．０１０ｇ／ｍ２未満である。これにより、めっき外観に優れ、耐食性が著しく向上し、地鉄表層における曲げ加工時の割れ防止を実現させ、高加工時の耐めっき剥離性に優れる効果が得られる。
And in the high-strength hot-dip galvanized steel sheet obtained by the above method, Fe, Si, Mn, Al, P, B, Nb, Ti, in a region within 100 μm from the surface of the steel sheet directly under the galvanized layer, Formation of one or more oxides selected from Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V (except for Fe alone) is suppressed. The total amount formed is less than 0.010 g / m 2 per side. As a result, the plating appearance is excellent, the corrosion resistance is remarkably improved, the crack prevention at the bending process in the surface layer of the base metal is realized, and the effect of being excellent in the plating peeling resistance at the high processing is obtained.
本発明は上記知見に基づくものであり、特徴は以下の通りである。
The present invention is based on the above findings, and features are as follows.
（１）質量％で、Ｃ：０．０３～０．３５％、Ｓｉ：０．０１～０．５０％、Ｍｎ：３．６～８．０％、Ａｌ：０．００１～１．０００％、Ｐ：０．１０％以下、Ｓ：０．０１０％以下を含有し、残部がＦｅおよび不可避的不純物からなる鋼板に焼鈍を施し、該焼鈍後の鋼板の表面に、片面あたりのめっき付着量が２０～１２０ｇ／ｍ２の亜鉛めっき層を有する高強度溶融亜鉛めっき鋼板を製造する方法であって、鋼板を連続式溶融亜鉛めっき設備において焼鈍を施すに際し、前記焼鈍の加熱過程において、焼鈍炉内温度：４５０℃以上Ａ℃以下（但し、Ａ：５００≦Ａから選択される任意の値）の温度域では、昇温速度：７℃/s以上とし、前記焼鈍において鋼板最高到達温度を６００℃以上７５０℃以下とし、前記焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の鋼板通過時間を３０秒以上１０分以内、雰囲気の水素濃度を２０ｖｏｌ％以上とし、前記焼鈍後の鋼板に溶融亜鉛めっき処理を施す高強度溶融亜鉛めっき鋼板の製造方法。
(1) By mass%, C: 0.03 to 0.35%, Si: 0.01 to 0.50%, Mn: 3.6 to 8.0%, Al: 0.001 to 1.000% , P: 0.10% or less, S: 0.010% or less, with the balance being annealed to a steel plate made of Fe and inevitable impurities, and the amount of plating deposited on one side on the surface of the steel plate after the annealing Is a method for producing a high-strength hot-dip galvanized steel sheet having a galvanized layer of 20 to 120 g / m 2 , and when annealing the steel sheet in a continuous hot-dip galvanizing facility, In the temperature range of the inner temperature: 450 ° C. or more and A ° C. or less (where A: any value selected from 500 ≦ A), the rate of temperature rise is 7 ° C./s or more, and the maximum temperature of the steel sheet is 600 in the annealing. And the steel plate temperature in the annealing is not less than 750 ° C. and not more than 750 ° C. A high-strength hot-dip galvanized steel sheet in which a steel sheet passage time in a temperature range of 00 ° C. or higher and 750 ° C. or lower is set to 30 seconds or more and 10 minutes or less, a hydrogen concentration in the atmosphere is set to 20 vol% or higher, Production method.
（２）前記鋼板は、成分組成として、質量％で、さらに、Ｂ：０．００１～０．００５％、Ｎｂ：０．００５～０．０５０％、Ｔｉ：０．００５～０．０５０％、Ｃｒ：０．００１～１．０００％、Ｍｏ：０．０５～１．００％、Ｃｕ：０．０５～１．００％、Ｎｉ：０．０５～１．００％、Ｓｎ：０．００１～０．２０％、Ｓｂ：０．００１～０．２０％、Ｔａ：０．００１～０．１０％、Ｗ：０．００１～０．１０％、Ｖ：０．００１～０．１０％の中から選ばれる１種以上の元素を含有する（１）に記載の高強度溶融亜鉛めっき鋼板の製造方法。
(2) The steel sheet has a component composition in mass%, and B: 0.001 to 0.005%, Nb: 0.005 to 0.050%, Ti: 0.005 to 0.050%, Cr: 0.001 to 1.000%, Mo: 0.05 to 1.00%, Cu: 0.05 to 1.00%, Ni: 0.05 to 1.00%, Sn: 0.001 to 0.20%, Sb: 0.001 to 0.20%, Ta: 0.001 to 0.10%, W: 0.001 to 0.10%, V: 0.001 to 0.10% The manufacturing method of the high intensity | strength hot-dip galvanized steel plate as described in (1) containing 1 or more types of elements chosen from.
（３）溶融亜鉛めっき処理後、さらに、４５０℃以上６００℃以下の温度に鋼板を加熱して合金化処理を施し、めっき層のＦｅ含有量を８～１４質量％の範囲にする（１）または（２）に記載の高強度溶融亜鉛めっき鋼板の製造方法。
(3) After the hot dip galvanizing treatment, the steel sheet is further heated to a temperature of 450 ° C. or more and 600 ° C. or less to be alloyed, so that the Fe content of the plating layer is in the range of 8 to 14% by mass (1) Or the manufacturing method of the high intensity | strength hot-dip galvanized steel plate as described in (2).
（４）（１）～（３）のいずれかに記載の高強度溶融亜鉛めっき鋼板の製造方法により製造した高強度溶融亜鉛めっき鋼板であって、
地鉄鋼板と、地鉄鋼板上に形成された亜鉛めっき層とを備え、前記地鉄鋼板は、（１）又は（２）に記載の成分組成を有し、前記亜鉛めっき層直下の前記地鉄鋼板表面から１００μｍ以内の領域に存在する、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉ、Ｓｎ、Ｓｂ、Ｔａ、Ｗ、Ｖのうちから選ばれる１種以上（Ｆｅのみの場合を除く）の酸化物の形成量が合計で片面あたり０．０１０ｇ／ｍ2未満である高強度溶融亜鉛めっき鋼板。
なお、本発明において高強度とは引張り強度（ＴＳ）980MPa以上を意味する。 (4) A high-strength hot-dip galvanized steel sheet produced by the method for producing a high-strength hot-dip galvanized steel sheet according to any one of (1) to (3),
A steel plate and a galvanized layer formed on the steel plate, wherein the steel plate has the component composition described in (1) or (2), and the ground directly under the galvanized layer. Selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V existing in a region within 100 μm from the steel plate surface A high-strength hot-dip galvanized steel sheet in which the total amount of oxides of one or more (excluding the case of Fe only) is less than 0.010 g / m 2 per side.
In the present invention, high strength means a tensile strength (TS) of 980 MPa or more.
地鉄鋼板と、地鉄鋼板上に形成された亜鉛めっき層とを備え、前記地鉄鋼板は、（１）又は（２）に記載の成分組成を有し、前記亜鉛めっき層直下の前記地鉄鋼板表面から１００μｍ以内の領域に存在する、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉ、Ｓｎ、Ｓｂ、Ｔａ、Ｗ、Ｖのうちから選ばれる１種以上（Ｆｅのみの場合を除く）の酸化物の形成量が合計で片面あたり０．０１０ｇ／ｍ2未満である高強度溶融亜鉛めっき鋼板。
なお、本発明において高強度とは引張り強度（ＴＳ）980MPa以上を意味する。 (4) A high-strength hot-dip galvanized steel sheet produced by the method for producing a high-strength hot-dip galvanized steel sheet according to any one of (1) to (3),
A steel plate and a galvanized layer formed on the steel plate, wherein the steel plate has the component composition described in (1) or (2), and the ground directly under the galvanized layer. Selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V existing in a region within 100 μm from the steel plate surface A high-strength hot-dip galvanized steel sheet in which the total amount of oxides of one or more (excluding the case of Fe only) is less than 0.010 g / m 2 per side.
In the present invention, high strength means a tensile strength (TS) of 980 MPa or more.
本発明によれば、めっき外観、耐食性、高加工時の耐めっき剥離性および高加工時の加工性に優れた高強度溶融亜鉛めっき鋼板が得られる。
According to the present invention, a high-strength hot-dip galvanized steel sheet excellent in plating appearance, corrosion resistance, plating peeling resistance during high processing, and workability during high processing can be obtained.
以下、本発明の実施形態について説明する。なお、本発明は以下の実施形態に限定されない。
Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.
鋼中に多量のＳｉおよびＭｎが添加された高強度溶融亜鉛めっき鋼板において、耐食性及び高加工時の耐めっき剥離性を満足させるためには、腐食や高加工時の割れなどの起点となる可能性があるめっき層直下の地鉄表層の内部酸化を極力少なくすることが求められる。
In high-strength hot-dip galvanized steel sheets with a large amount of Si and Mn added to the steel, in order to satisfy corrosion resistance and anti-plating resistance during high processing, it may be the starting point for corrosion and cracking during high processing. Therefore, it is required to minimize internal oxidation of the surface layer of the railway just below the plating layer.
Ｆｅを酸化させたり、ＳｉやＭｎの内部酸化を促進させたりすることによりめっき性を向上させることは可能ではある。しかし、この方法は、耐食性や加工性の劣化をもたらすことになってしまう。このため、Ｆｅを酸化させる方法、ＳｉやＭｎの内部酸化を促進させる方法以外で、良好なめっき性を維持しつつ、内部酸化を抑制して耐食性、加工性を向上させる必要がある。検討した結果、本発明では、めっき性を確保するために、鋼板の焼鈍において、酸素ポテンシャルを低下させ、易酸化性元素であるＳｉやＭｎ等の地鉄表層部における活量を低下させる。そして、これらの元素の外部酸化を抑制し、めっき性を改善する。そして、鋼板の焼鈍において、酸素ポテンシャルを低下させることで、地鉄表層部に形成する内部酸化も抑制され、耐食性及び加工性が改善することになる。
It is possible to improve the plating property by oxidizing Fe or promoting internal oxidation of Si or Mn. However, this method brings about deterioration of corrosion resistance and workability. For this reason, it is necessary to improve corrosion resistance and workability by suppressing internal oxidation while maintaining good plating properties other than a method of oxidizing Fe and a method of promoting internal oxidation of Si and Mn. As a result of the examination, in the present invention, in order to ensure the plateability, in the annealing of the steel sheet, the oxygen potential is lowered, and the activity in the surface layer portion of the iron ore such as Si or Mn which is an easily oxidizable element is lowered. And external oxidation of these elements is suppressed and plating nature is improved. And in annealing of a steel plate, by reducing the oxygen potential, internal oxidation formed in the surface layer portion of the iron base is also suppressed, and corrosion resistance and workability are improved.
具体的には、焼鈍の加熱過程において、以下の（条件１）～（条件３）を採用する。
（条件１）焼鈍の加熱過程において、焼鈍炉内温度：４５０℃以上Ａ℃以下（但し、Ａ：５００≦Ａから選択される任意の値）の温度域では、昇温速度：７℃/s以上とする。
（条件２）焼鈍において鋼板最高到達温度を６００℃以上７５０℃以下とする。
（条件３）焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の鋼板通過時間を３０秒以上１０分以内、雰囲気の水素濃度を２０ｖｏｌ％以上とする。 Specifically, the following (Condition 1) to (Condition 3) are employed in the annealing heating process.
(Condition 1) In the annealing heating process, in the temperature range of annealing furnace temperature: 450 ° C. to A ° C. (however, A: any value selected from 500 ≦ A), the rate of temperature increase: 7 ° C./s That's it.
(Condition 2) In annealing, the maximum steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower.
(Condition 3) In annealing, the steel plate passage time in the temperature range of 600 ° C. or more and 750 ° C. or less is set to 30 seconds or more and 10 minutes or less, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
（条件１）焼鈍の加熱過程において、焼鈍炉内温度：４５０℃以上Ａ℃以下（但し、Ａ：５００≦Ａから選択される任意の値）の温度域では、昇温速度：７℃/s以上とする。
（条件２）焼鈍において鋼板最高到達温度を６００℃以上７５０℃以下とする。
（条件３）焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の鋼板通過時間を３０秒以上１０分以内、雰囲気の水素濃度を２０ｖｏｌ％以上とする。 Specifically, the following (Condition 1) to (Condition 3) are employed in the annealing heating process.
(Condition 1) In the annealing heating process, in the temperature range of annealing furnace temperature: 450 ° C. to A ° C. (however, A: any value selected from 500 ≦ A), the rate of temperature increase: 7 ° C./s That's it.
(Condition 2) In annealing, the maximum steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower.
(Condition 3) In annealing, the steel plate passage time in the temperature range of 600 ° C. or more and 750 ° C. or less is set to 30 seconds or more and 10 minutes or less, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
このように焼鈍の条件を制御することにより、鋼板と雰囲気の界面の酸素ポテンシャルを低下させることができる。上記酸素ポテンシャルが低下することで、内部酸化を抑制するとともに、Ｓｉ、Ｍｎなどの選択的表面拡散、表面濃化を抑制することができる。その結果、不めっき等がなく外観に優れるとともに加工性に優れ、より高い耐食性と高加工時の良好な耐めっき剥離性を有する高強度溶融亜鉛めっき鋼板が得られることになる。
Thus, by controlling the annealing conditions, the oxygen potential at the interface between the steel sheet and the atmosphere can be lowered. By reducing the oxygen potential, internal oxidation can be suppressed, and selective surface diffusion and surface concentration of Si, Mn, etc. can be suppressed. As a result, a high-strength hot-dip galvanized steel sheet that has no unplating or the like, is excellent in appearance, has excellent workability, has higher corrosion resistance, and good plating peeling resistance during high processing can be obtained.
先ず、焼鈍の対象となる鋼板の製造方法について説明する。鋼板の製造方法は特に限定されない。例えば、鋼を熱間圧延して熱延板を製造する方法、鋼を熱間圧延した後、冷間圧延して冷延板を製造する方法、鋼を熱間圧延した後、酸洗し、冷間圧延して冷延板を製造する方法等を採用することができる。このようにして得られた熱延板や冷延板を焼鈍する対象として用いることができる。該熱延板や冷延板の板厚は特に限定されないが、０．３～５．０ｍｍが好ましい。
First, a method for manufacturing a steel sheet to be annealed will be described. The manufacturing method of a steel plate is not specifically limited. For example, a method of producing a hot-rolled sheet by hot rolling steel, a method of producing a cold-rolled sheet by cold rolling after hot rolling the steel, hot rolling the steel, pickling, A method of manufacturing a cold-rolled sheet by cold rolling can be employed. The hot-rolled sheet and the cold-rolled sheet thus obtained can be used as an object to be annealed. The thickness of the hot rolled sheet or cold rolled sheet is not particularly limited, but is preferably 0.3 to 5.0 mm.
なお、上記鋼板を製造する際の、熱間圧延の条件、酸洗の条件は特に限定されず、適宜設定すればよい。また、冷間圧延については、４０％以上８０％以下の圧下率で行うことが好ましい。圧下率が４０％未満では再結晶温度が低温化するため、機械特性が劣化しやすい。一方、圧下率が８０％超えでは、高強度鋼板であるため圧延コストがアップするだけでなく、焼鈍時の表面濃化が増加して、めっき性が劣化する場合がある。
In addition, the conditions for hot rolling and pickling at the time of manufacturing the steel sheet are not particularly limited, and may be set as appropriate. Further, the cold rolling is preferably performed at a rolling reduction of 40% or more and 80% or less. If the rolling reduction is less than 40%, the recrystallization temperature is lowered, and the mechanical characteristics are likely to deteriorate. On the other hand, when the rolling reduction exceeds 80%, the steel sheet is a high-strength steel plate, so that not only the rolling cost is increased, but also the surface concentration during annealing is increased and the plating property may be deteriorated.
続いて、鋼板を焼鈍する際の条件について説明する。焼鈍は一般的な連続式溶融亜鉛めっき設備を用いて行うことができる。一般的な連続式溶融亜鉛めっき設備が有する焼鈍炉は、前段に加熱帯、後段に均熱帯を有する。通常、前段の加熱帯で鋼板を所定温度まで加熱し、後段の均熱帯で所定温度、所定時間の条件で鋼板を保持する。
Subsequently, conditions for annealing the steel sheet will be described. The annealing can be performed using a general continuous hot dip galvanizing facility. An annealing furnace included in a general continuous hot dip galvanizing facility has a heating zone in the front stage and a soaking zone in the rear stage. Usually, the steel sheet is heated to a predetermined temperature in the preceding heating zone, and the steel sheet is held under conditions of a predetermined temperature and a predetermined time in the latter-stage soaking zone.
上記（条件１）の通り、焼鈍の加熱過程において、焼鈍炉内温度：４５０℃以上Ａ℃以下（但し、Ａ：５００≦Ａから選択される任意の値）の温度域では、昇温速度：７℃/s以上とする。この加熱は通常、加熱帯で行われる。なお、この温度域の温度は、焼鈍されている鋼板の温度（鋼板温度）を指す。鋼板温度は、焼鈍炉内の各パスのロール位置において、温度計を設置し、測温して得られた値を指す。温度計としては多重反射温度計及び放射温度計などを例示でき、温度計の方式は特に限定されない。
As described above (Condition 1), in the annealing heating process, in the annealing furnace temperature: 450 ° C. or more and A ° C. or less (however, A: any value selected from 500 ≦ A), the rate of temperature increase: 7 ° C / s or more. This heating is usually performed in a heating zone. In addition, the temperature of this temperature range points out the temperature (steel plate temperature) of the steel plate currently annealed. The steel sheet temperature is a value obtained by installing a thermometer and measuring the temperature at the roll position of each pass in the annealing furnace. As a thermometer, a multiple reflection thermometer, a radiation thermometer, etc. can be illustrated, and the system of a thermometer is not specifically limited.
昇温速度を制御する温度域を４５０℃以上とした理由は以下の通りである。４５０℃を下回る温度域では、不めっき発生、耐食性の劣化、耐めっき剥離性の劣化等が問題になる程度の表面濃化や内部酸化は起こらない。よって、昇温速度を制御する温度域は、本発明の効果が発現する温度域である４５０℃以上とする。
The reason why the temperature range for controlling the heating rate is set to 450 ° C. or higher is as follows. In the temperature range below 450 ° C., surface enrichment and internal oxidation to such an extent that non-plating occurs, corrosion resistance deteriorates, plating peel resistance deteriorates, etc. do not occur. Therefore, the temperature range for controlling the rate of temperature rise is set to 450 ° C. or more, which is the temperature range where the effects of the present invention are manifested.
また、昇温速度を制御する温度域をＡ℃以下（Ａ：５００≦Ａから選択される任意の値）とした理由は以下の通りである。先ず、昇温速度を制御する温度域の上限が５００℃を下回ると、昇温速度を７℃／ｓ以上に制御する時間が短く、本発明の効果が十分に得られない。このため、Ａは５００℃以上とする。また、昇温速度を制御する温度域の上限が６００℃超えの場合、本発明の効果に何ら問題はないが、焼鈍炉内設備にかかるコスト増大（インダクションヒーターの増設など）の観点から、不利となる。したがって、６００℃以下が好ましい。
Further, the reason why the temperature range for controlling the rate of temperature rise is A ° C. or lower (A: any value selected from 500 ≦ A) is as follows. First, when the upper limit of the temperature range for controlling the temperature increase rate is below 500 ° C., the time for controlling the temperature increase rate to 7 ° C./s or more is short, and the effect of the present invention cannot be sufficiently obtained. For this reason, A shall be 500 degreeC or more. In addition, when the upper limit of the temperature range for controlling the rate of temperature rise exceeds 600 ° C., there is no problem with the effect of the present invention, but it is disadvantageous from the viewpoint of cost increase (equipment of induction heaters, etc.) required for the equipment in the annealing furnace. It becomes. Therefore, 600 ° C. or lower is preferable.
上記温度域における昇温速度を７℃／ｓ以上とした理由は以下の通りである。表面濃化の抑制効果が認められはじめるのが、昇温速度７℃／ｓ以上である。昇温速度の上限は特に設けないが、５００℃／ｓ以上では効果は飽和し、コスト的に不利となる。このため昇温速度は５００℃／ｓ以下が望ましい。なお、昇温速度を７℃／ｓ以上とすることは、例えばインダクションヒーターを鋼板温度が４５０℃以上Ａ℃以下となる焼鈍炉内に配置することで可能である。なお、本発明において、昇温速度の単位における「ｓ」は秒を意味する。
The reason why the heating rate in the above temperature range is 7 ° C./s or more is as follows. It is at a temperature increase rate of 7 ° C./s or more that the effect of suppressing surface concentration begins to be recognized. Although there is no particular upper limit for the rate of temperature increase, the effect is saturated at 500 ° C./s or more, which is disadvantageous in terms of cost. For this reason, the heating rate is desirably 500 ° C./s or less. Note that it is possible to set the rate of temperature rise to 7 ° C./s or more, for example, by placing an induction heater in an annealing furnace in which the steel plate temperature is 450 ° C. or more and A ° C. or less. In the present invention, “s” in the unit of temperature increase rate means second.
上記（条件２）の通り、焼鈍において鋼板最高到達温度を６００℃以上７５０℃以下とする。上記鋼板最高到達温度は、Ａ℃が鋼板最高到達温度と同じ場合を除き、加熱過程での上記加熱における最高到達温度Ａ℃からさらに加熱して上昇させた温度である。ここで、鋼板最高到達温度とは、上記鋼板温度の測定方法と同様の方法で測定したときに、焼鈍中で最高となる値を指す。
As described above (Condition 2), the highest temperature reached in the steel sheet is 600 ° C. or higher and 750 ° C. or lower in annealing. The steel plate maximum temperature is a temperature that is further increased by heating from the maximum temperature A ° C. in the heating in the heating process, except when A ° C. is the same as the steel plate maximum temperature. Here, the maximum steel plate temperature refers to the maximum value during annealing when measured by the same method as the method for measuring the steel plate temperature.
焼鈍炉内での鋼板最高到達温度を６００℃以上７５０℃以下とした理由は以下の通りである。鋼板最高到達温度が６００℃を下回ると、不めっき発生、耐食性の劣化、耐めっき剥離性の劣化等が問題になる程度の表面濃化や内部酸化は起こらないが、本発明の効果が十分に得られない。また、鋼板最高到達温度が６００℃を下回ると良好な材質が得られない。よって、本発明では上記鋼板最高到達温度を６００℃以上とする。一方、鋼板最高到達温度が７５０℃を上回ると、表面濃化が顕著となり、不めっき発生、耐食性の劣化、耐めっき剥離性の劣化等が激しくなる。さらに、材質の観点では強度（ＴＳ）、延性（Ｅｌ）共に、鋼板最高到達温度が７５０℃を上回ると、強度と延性のバランスの効果が飽和する。以上のことから、鋼板最高到達温度は６００℃以上７５０℃以下とする。
The reason why the maximum steel sheet temperature in the annealing furnace is 600 ° C. or higher and 750 ° C. or lower is as follows. When the maximum temperature reached by the steel sheet is below 600 ° C., surface enrichment and internal oxidation to the extent that non-plating occurs, corrosion resistance deterioration, plating peel resistance deterioration, etc., will not occur, but the effect of the present invention is sufficient. I can't get it. In addition, when the maximum temperature reached by the steel sheet is below 600 ° C., a good material cannot be obtained. Therefore, in this invention, the said steel plate highest reached temperature shall be 600 degreeC or more. On the other hand, when the maximum temperature of the steel sheet exceeds 750 ° C., the surface concentration becomes remarkable, and the occurrence of non-plating, deterioration of corrosion resistance, deterioration of plating peeling resistance, and the like becomes severe. Furthermore, in terms of material, when the maximum steel sheet temperature exceeds 750 ° C. in both strength (TS) and ductility (El), the effect of balance between strength and ductility is saturated. From the above, the maximum temperature reached by the steel sheet is set to 600 ° C. or higher and 750 ° C. or lower.
上記（条件３）の通り、焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の鋼板通過時間を３０秒以上１０分以内、雰囲気の水素濃度を２０ｖｏｌ％以上とする。
As described above (condition 3), in the annealing, the steel plate temperature in the temperature range of 600 ° C. to 750 ° C. is set to 30 seconds to 10 minutes, and the hydrogen concentration in the atmosphere is set to 20 vol% or more.
上記鋼板通過時間が３０秒を下回れば目標とする材質（ＴＳ、Ｅｌ）が得られない。一方、上記鋼板通過時間が１０分を上回れば、強度と延性のバランスの効果が飽和する。
If the steel plate passage time is less than 30 seconds, the target material (TS, El) cannot be obtained. On the other hand, if the steel plate passage time exceeds 10 minutes, the effect of balance between strength and ductility is saturated.
焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の雰囲気の水素濃度を２０ｖｏｌ％以上とすると、表面濃化の抑制効果が認められる。水素濃度の上限は特に設けないが、水素濃度を５０ｖｏｌ％超えにしても効果が飽和し、コスト的に不利となる。このため、上記水素濃度は５０ｖｏｌ％以下が望ましい。
In the annealing, when the hydrogen concentration in the atmosphere where the steel sheet temperature is 600 ° C. or higher and 750 ° C. or lower is 20 vol% or higher, the effect of suppressing surface concentration is recognized. The upper limit of the hydrogen concentration is not particularly set, but even if the hydrogen concentration exceeds 50 vol%, the effect is saturated, which is disadvantageous in terms of cost. For this reason, the hydrogen concentration is desirably 50 vol% or less.
上記温度域の雰囲気に含まれる水素ガス以外の成分は、本発明の効果を害さない範囲で特に限定されず、通常、雰囲気のガスは、水素ガス、窒素ガスおよび不可避的不純物ガスから構成される。また、本発明の効果を害さない範囲であれば、これら以外のガスを含んでもよい。
Components other than hydrogen gas contained in the atmosphere in the above temperature range are not particularly limited as long as the effects of the present invention are not impaired, and the gas in the atmosphere is usually composed of hydrogen gas, nitrogen gas, and inevitable impurity gas. . In addition, other gases may be included as long as the effects of the present invention are not impaired.
なお、上記で水素濃度を制御する温度域以外の水素濃度は特に限定されず、好ましくは水素濃度が１ｖｏｌ％以上５０ｖｏｌ％以下である。水素濃度が１ｖｏｌ％未満では還元による活性化効果が得られず耐めっき剥離性が劣化する可能性がある。一方、５０ｖｏｌ％超えではコストアップし、かつ効果が飽和する。その他の温度域の雰囲気ガスも、上記温度域の雰囲気ガスと同様に、雰囲気のガスは、水素ガス、窒素ガスおよび不可避的不純物ガスから構成される。また、本発明の効果を害さない範囲であれば、これら以外のガスを含んでもよい。
It should be noted that the hydrogen concentration outside the temperature range where the hydrogen concentration is controlled is not particularly limited, and the hydrogen concentration is preferably 1 vol% or more and 50 vol% or less. If the hydrogen concentration is less than 1 vol%, the activation effect due to reduction cannot be obtained, and the plating peel resistance may deteriorate. On the other hand, if it exceeds 50 vol%, the cost increases and the effect is saturated. Similarly to the atmospheric gas in the above temperature range, the atmospheric gas in other temperature ranges is composed of hydrogen gas, nitrogen gas, and inevitable impurity gas. In addition, other gases may be included as long as the effects of the present invention are not impaired.
焼鈍において、上記（条件１）～（条件３）を採用することが、外観、耐食性、高加工時の耐めっき剥離性および高加工時の加工性に優れた高強度溶融亜鉛めっき鋼板を得るために重要である。上記必須条件以外の焼鈍における条件は以下の通りである。
In order to obtain a high-strength hot-dip galvanized steel sheet excellent in appearance, corrosion resistance, plating peeling resistance during high processing, and workability during high processing by adopting the above (Condition 1) to (Condition 3) in annealing Is important to. Conditions in annealing other than the above essential conditions are as follows.
本発明において、均熱帯における均熱温度、均熱時間の条件は特に限定されず適宜設定すればよい。なお、均熱温度は上記鋼板最高到達温度であってもよいし、上記鋼板到達最高温度よりも低い温度であってもよい。
In the present invention, the conditions of the soaking temperature and soaking time in the soaking zone are not particularly limited, and may be set as appropriate. In addition, the soaking temperature may be the above-mentioned maximum steel plate temperature, or may be a temperature lower than the above-mentioned maximum steel plate temperature.
上記焼鈍における、雰囲気の露点は特に限定されず、例えば、－１０～－４０℃の範囲であればよい。
The dew point of the atmosphere in the annealing is not particularly limited, and may be in the range of −10 to −40 ° C., for example.
上記焼鈍後の鋼板表面にめっき処理を施す。めっき処理も連続式溶融亜鉛めっき設備で行われる。めっき処理の条件はめっき付着量の条件を除いて特に限定されず、適宜設定すればよい。
¡Plating is performed on the surface of the steel sheet after the annealing. Plating is also performed in a continuous hot dip galvanizing facility. The conditions for the plating treatment are not particularly limited except for the conditions for the amount of plating, and may be set as appropriate.
本発明では、めっき処理において、片面あたりのめっき付着量が２０～１２０ｇ／ｍ２になる条件を採用する。めっき付着量が２０ｇ／ｍ２未満では耐食性の確保が困難になる。一方、めっき付着量が１２０ｇ／ｍ２を超えると耐めっき剥離性が劣化する。
In the present invention, in the plating process, a condition is adopted in which the plating adhesion amount per side is 20 to 120 g / m 2 . When the plating adhesion amount is less than 20 g / m 2 , it becomes difficult to ensure corrosion resistance. On the other hand, when the plating adhesion amount exceeds 120 g / m 2 , the plating peel resistance deteriorates.
上記めっき処理に続いて、合金化処理を行ってもよい。めっき処理に引き続き合金化処理を行うときは、めっき処理後の鋼板を、４５０℃以上６００℃以下に加熱する。このとき、めっき層のＦｅ含有量が質量％で８～１４％になるよう加熱を行うのが好ましい。上記Ｆｅ含有量が８％未満では合金化ムラ発生やフレーキング性が劣化する。一方、上記Ｆｅ含有量が１４％超えは耐めっき剥離性が劣化する。
The alloying process may be performed following the plating process. When the alloying treatment is performed subsequent to the plating treatment, the steel plate after the plating treatment is heated to 450 ° C. or more and 600 ° C. or less. At this time, heating is preferably performed so that the Fe content of the plating layer is 8 to 14% by mass. If the Fe content is less than 8%, unevenness in alloying and flaking properties deteriorate. On the other hand, if the Fe content exceeds 14%, the plating peel resistance deteriorates.
なお、本発明の方法で製造される高強度溶融亜鉛めっき鋼板には、合金化処理をしていない高強度溶融亜鉛めっき鋼板、合金化処理を施してなる合金化高強度溶融亜鉛めっき鋼板の両者を含む。
The high-strength hot-dip galvanized steel sheet manufactured by the method of the present invention includes both high-strength hot-dip galvanized steel sheets that have not been alloyed and alloyed high-strength hot-dip galvanized steel sheets that have been alloyed. including.
上記の通り、本発明は鋼板の焼鈍条件に特徴がある。続いて、焼鈍の対象となる鋼板について説明する。以下の成分組成の説明における「％」は「質量％」を意味する。
As described above, the present invention is characterized by the annealing conditions of the steel sheet. Then, the steel plate used as the object of annealing is demonstrated. In the following description of the component composition, “%” means “mass%”.
Ｃ：０．０３～０．３５％
Ｃは、鋼組織中にマルテンサイトなどを形成させることで加工性を向上させる。そのためには、Ｃの含有量を０．０３％以上にする必要がある。一方、Ｃの含有量が０．３５％を超えると溶接性が劣化する。したがって、Ｃ量は０．０３％以上０．３５％以下とする。 C: 0.03-0.35%
C improves workability by forming martensite or the like in the steel structure. For this purpose, the C content needs to be 0.03% or more. On the other hand, if the C content exceeds 0.35%, the weldability deteriorates. Therefore, the C content is 0.03% or more and 0.35% or less.
Ｃは、鋼組織中にマルテンサイトなどを形成させることで加工性を向上させる。そのためには、Ｃの含有量を０．０３％以上にする必要がある。一方、Ｃの含有量が０．３５％を超えると溶接性が劣化する。したがって、Ｃ量は０．０３％以上０．３５％以下とする。 C: 0.03-0.35%
C improves workability by forming martensite or the like in the steel structure. For this purpose, the C content needs to be 0.03% or more. On the other hand, if the C content exceeds 0.35%, the weldability deteriorates. Therefore, the C content is 0.03% or more and 0.35% or less.
Ｓｉ：０．０１～０．５０％
Ｓｉは鋼を強化して良好な材質を得るのに有効な元素ではある。しかし、Ｓｉは易酸化性元素であるため、めっき性には不利であり、この観点からは、極力添加することは避けるべき元素である。また、０．０１％程度のＳｉは不可避的に鋼中に含まれ、Ｓｉの含有量をこれ以下に低減するためにはコストが上昇してしまう。以上より、Ｓｉの含有量は０．０１％を下限とする。一方、Ｓｉの含有量が０．５０％を超えると高加工時の耐めっき剥離性の改善が困難となる。したがって、Ｓｉ量は０．０１％以上０．５０％以下とする。本発明は、Ｓｉの含有量が多い場合であっても、良好な性質を有する高強度溶融亜鉛めっき鋼板を得られることが特徴の１つである。 Si: 0.01 to 0.50%
Si is an effective element for strengthening steel and obtaining a good material. However, since Si is an easily oxidizable element, it is disadvantageous for plating properties. From this point of view, it is an element that should be avoided as much as possible. Moreover, about 0.01% Si is inevitably contained in the steel, and the cost increases in order to reduce the Si content below this. From the above, the lower limit of the Si content is 0.01%. On the other hand, if the Si content exceeds 0.50%, it is difficult to improve the plating peel resistance during high processing. Therefore, the Si amount is set to 0.01% or more and 0.50% or less. One feature of the present invention is that a high-strength hot-dip galvanized steel sheet having good properties can be obtained even when the Si content is high.
Ｓｉは鋼を強化して良好な材質を得るのに有効な元素ではある。しかし、Ｓｉは易酸化性元素であるため、めっき性には不利であり、この観点からは、極力添加することは避けるべき元素である。また、０．０１％程度のＳｉは不可避的に鋼中に含まれ、Ｓｉの含有量をこれ以下に低減するためにはコストが上昇してしまう。以上より、Ｓｉの含有量は０．０１％を下限とする。一方、Ｓｉの含有量が０．５０％を超えると高加工時の耐めっき剥離性の改善が困難となる。したがって、Ｓｉ量は０．０１％以上０．５０％以下とする。本発明は、Ｓｉの含有量が多い場合であっても、良好な性質を有する高強度溶融亜鉛めっき鋼板を得られることが特徴の１つである。 Si: 0.01 to 0.50%
Si is an effective element for strengthening steel and obtaining a good material. However, since Si is an easily oxidizable element, it is disadvantageous for plating properties. From this point of view, it is an element that should be avoided as much as possible. Moreover, about 0.01% Si is inevitably contained in the steel, and the cost increases in order to reduce the Si content below this. From the above, the lower limit of the Si content is 0.01%. On the other hand, if the Si content exceeds 0.50%, it is difficult to improve the plating peel resistance during high processing. Therefore, the Si amount is set to 0.01% or more and 0.50% or less. One feature of the present invention is that a high-strength hot-dip galvanized steel sheet having good properties can be obtained even when the Si content is high.
Ｍｎ：３．６～８．０％
Ｍｎは鋼の高強度化に有効な元素である。機械特性や強度を確保するためは、Ｍｎの含有量を３．６％以上にする必要がある。一方、Ｍｎの含有量が８．０％を超えると溶接性やめっき密着性の確保、強度と延性のバランスの確保が困難になる。したがって、Ｍｎ量は３．６％以上８．０％以下とする。 Mn: 3.6 to 8.0%
Mn is an element effective for increasing the strength of steel. In order to ensure mechanical properties and strength, the Mn content needs to be 3.6% or more. On the other hand, if the Mn content exceeds 8.0%, it becomes difficult to ensure weldability and plating adhesion, and to ensure a balance between strength and ductility. Therefore, the Mn content is 3.6% or more and 8.0% or less.
Ｍｎは鋼の高強度化に有効な元素である。機械特性や強度を確保するためは、Ｍｎの含有量を３．６％以上にする必要がある。一方、Ｍｎの含有量が８．０％を超えると溶接性やめっき密着性の確保、強度と延性のバランスの確保が困難になる。したがって、Ｍｎ量は３．６％以上８．０％以下とする。 Mn: 3.6 to 8.0%
Mn is an element effective for increasing the strength of steel. In order to ensure mechanical properties and strength, the Mn content needs to be 3.6% or more. On the other hand, if the Mn content exceeds 8.0%, it becomes difficult to ensure weldability and plating adhesion, and to ensure a balance between strength and ductility. Therefore, the Mn content is 3.6% or more and 8.0% or less.
Ａｌ：０．００１～１．０００％
Ａｌは溶鋼の脱酸を目的に添加される。Ａｌの含有量が０．００１％未満の場合、その目的が達成されない。溶鋼の脱酸の効果はＡｌの含有量を０．００１％以上にすることで得られる。一方、Ａｌの含有量が１．０００％を超えるとコストアップになる。したがって、Ａｌ量は０．００１％以上１．０００％以下とする。 Al: 0.001 to 1.000%
Al is added for the purpose of deoxidizing molten steel. If the Al content is less than 0.001%, the object is not achieved. The effect of deoxidation of molten steel can be obtained by making the Al content 0.001% or more. On the other hand, if the Al content exceeds 1.000%, the cost increases. Therefore, the Al amount is set to 0.001% or more and 1.000% or less.
Ａｌは溶鋼の脱酸を目的に添加される。Ａｌの含有量が０．００１％未満の場合、その目的が達成されない。溶鋼の脱酸の効果はＡｌの含有量を０．００１％以上にすることで得られる。一方、Ａｌの含有量が１．０００％を超えるとコストアップになる。したがって、Ａｌ量は０．００１％以上１．０００％以下とする。 Al: 0.001 to 1.000%
Al is added for the purpose of deoxidizing molten steel. If the Al content is less than 0.001%, the object is not achieved. The effect of deoxidation of molten steel can be obtained by making the Al content 0.001% or more. On the other hand, if the Al content exceeds 1.000%, the cost increases. Therefore, the Al amount is set to 0.001% or more and 1.000% or less.
Ｐ：０．１０％以下
Ｐは不可避的に含有される元素のひとつであり、本発明において鋼板はＰを含有しなくてもよい。Ｐの含有量を０．００５％未満にするためには、コストの増大が懸念されるため、Ｐの含有量は０．００５％以上が望ましい。一方、Ｐが０．１０％を超えて含有されると溶接性が劣化する。さらに、表面品質が劣化する。また、非合金化処理時にはめっき密着性が劣化し、合金化処理時には合金化処理温度を上昇しないと所望の合金化度とすることができない。また所望の合金化度とするために合金化処理温度を上昇させると延性が劣化すると同時に合金化めっき皮膜の密着性が劣化する。このため、Ｐの含有量が０．１０％を超えると、所望の合金化度、良好な延性、合金化めっき皮膜を両立させることができない。したがって、Ｐ量は０．１０％以下とし、下限としては０．００５％以上が望ましい。 P: 0.10% or less P is one of the elements inevitably contained. In the present invention, the steel sheet may not contain P. In order to reduce the P content to less than 0.005%, there is a concern about an increase in cost. Therefore, the P content is preferably 0.005% or more. On the other hand, if P exceeds 0.10%, weldability deteriorates. Furthermore, the surface quality deteriorates. Also, the plating adhesion deteriorates during non-alloying treatment, and the desired degree of alloying cannot be achieved unless the alloying treatment temperature is increased during alloying treatment. Further, when the alloying temperature is raised to obtain a desired degree of alloying, the ductility deteriorates and at the same time the adhesion of the alloyed plating film deteriorates. For this reason, when the content of P exceeds 0.10%, a desired degree of alloying, good ductility, and an alloyed plating film cannot be achieved. Therefore, the P content is preferably 0.10% or less, and the lower limit is preferably 0.005% or more.
Ｐは不可避的に含有される元素のひとつであり、本発明において鋼板はＰを含有しなくてもよい。Ｐの含有量を０．００５％未満にするためには、コストの増大が懸念されるため、Ｐの含有量は０．００５％以上が望ましい。一方、Ｐが０．１０％を超えて含有されると溶接性が劣化する。さらに、表面品質が劣化する。また、非合金化処理時にはめっき密着性が劣化し、合金化処理時には合金化処理温度を上昇しないと所望の合金化度とすることができない。また所望の合金化度とするために合金化処理温度を上昇させると延性が劣化すると同時に合金化めっき皮膜の密着性が劣化する。このため、Ｐの含有量が０．１０％を超えると、所望の合金化度、良好な延性、合金化めっき皮膜を両立させることができない。したがって、Ｐ量は０．１０％以下とし、下限としては０．００５％以上が望ましい。 P: 0.10% or less P is one of the elements inevitably contained. In the present invention, the steel sheet may not contain P. In order to reduce the P content to less than 0.005%, there is a concern about an increase in cost. Therefore, the P content is preferably 0.005% or more. On the other hand, if P exceeds 0.10%, weldability deteriorates. Furthermore, the surface quality deteriorates. Also, the plating adhesion deteriorates during non-alloying treatment, and the desired degree of alloying cannot be achieved unless the alloying treatment temperature is increased during alloying treatment. Further, when the alloying temperature is raised to obtain a desired degree of alloying, the ductility deteriorates and at the same time the adhesion of the alloyed plating film deteriorates. For this reason, when the content of P exceeds 0.10%, a desired degree of alloying, good ductility, and an alloyed plating film cannot be achieved. Therefore, the P content is preferably 0.10% or less, and the lower limit is preferably 0.005% or more.
Ｓ：０．０１０％以下
Ｓは不可避的に含有される元素のひとつであり、Ｓを含有しなくてもよい。Ｓの含有量の下限は規定しないが、Ｓの含有量が多量になると溶接性が劣化する。このため、Ｓの含有量は０．０１０％以下とする。 S: 0.010% or less S is one of elements inevitably contained, and S may not be contained. Although the lower limit of the S content is not specified, the weldability deteriorates when the S content increases. For this reason, content of S shall be 0.010% or less.
Ｓは不可避的に含有される元素のひとつであり、Ｓを含有しなくてもよい。Ｓの含有量の下限は規定しないが、Ｓの含有量が多量になると溶接性が劣化する。このため、Ｓの含有量は０．０１０％以下とする。 S: 0.010% or less S is one of elements inevitably contained, and S may not be contained. Although the lower limit of the S content is not specified, the weldability deteriorates when the S content increases. For this reason, content of S shall be 0.010% or less.
また、本発明の製造方法で製造される高強度鋼板の強度と延性のバランスの改善を図るために、焼鈍が施される鋼板は、Ｂ：０．００１～０．００５％、Ｎｂ：０．００５～０．０５０％、Ｔｉ：０．００５～０．０５０％、Ｃｒ：０．００１～１．０００％、Ｍｏ：０．０５～１．００％、Ｃｕ：０．０５～１．００％、Ｎｉ：０．０５～１．００％、Ｓｎ：０．００１～０．２０％、Ｓｂ：０．００１～０．２０％、Ｔａ：０．００１～０．１０％、Ｗ：０．００１～０．１０％、Ｖ：０．００１～０．１０％の中から選ばれる１種以上の元素を必要に応じて含んでもよい。これらの元素を含有する場合における適正含有量の限定理由は以下の通りである。
Further, in order to improve the balance between strength and ductility of the high-strength steel plate produced by the production method of the present invention, the steel plate to be annealed is B: 0.001 to 0.005%, Nb: 0.00. 005 to 0.050%, Ti: 0.005 to 0.050%, Cr: 0.001 to 1.000%, Mo: 0.05 to 1.00%, Cu: 0.05 to 1.00% , Ni: 0.05 to 1.00%, Sn: 0.001 to 0.20%, Sb: 0.001 to 0.20%, Ta: 0.001 to 0.10%, W: 0.001 One or more elements selected from -0.10% and V: 0.001-0.10% may be included as required. The reason for limiting the proper content in the case of containing these elements is as follows.
Ｂ：０．００１～０．００５％
Ｂの含有量が０．００１％未満では焼き入れ促進効果が得られにくい。一方、Ｂの含有量が０．００５％超えではめっき密着性が劣化する場合がある。よって、Ｂを含有する場合、Ｂ量は０．００１％以上０．００５％以下とすることが好ましい。 B: 0.001 to 0.005%
When the content of B is less than 0.001%, it is difficult to obtain the quenching promoting effect. On the other hand, if the B content exceeds 0.005%, the plating adhesion may deteriorate. Therefore, when it contains B, it is preferable to make B amount into 0.001% or more and 0.005% or less.
Ｂの含有量が０．００１％未満では焼き入れ促進効果が得られにくい。一方、Ｂの含有量が０．００５％超えではめっき密着性が劣化する場合がある。よって、Ｂを含有する場合、Ｂ量は０．００１％以上０．００５％以下とすることが好ましい。 B: 0.001 to 0.005%
When the content of B is less than 0.001%, it is difficult to obtain the quenching promoting effect. On the other hand, if the B content exceeds 0.005%, the plating adhesion may deteriorate. Therefore, when it contains B, it is preferable to make B amount into 0.001% or more and 0.005% or less.
Ｎｂ：０．００５～０．０５０％
Ｎｂの含有量が０．００５％未満では強度調整やＭｏとの複合添加時におけるめっき密着性改善効果の効果が得られにくい。一方、Ｎｂの含有量が０．０５０％超えではコストアップを招く。よって、Ｎｂを含有する場合、Ｎｂ量は０．００５％以上０．０５０％以下とする。 Nb: 0.005 to 0.050%
When the content of Nb is less than 0.005%, it is difficult to obtain the effect of improving the adhesion of plating at the time of strength adjustment or composite addition with Mo. On the other hand, if the Nb content exceeds 0.050%, the cost increases. Therefore, when Nb is contained, the Nb content is 0.005% or more and 0.050% or less.
Ｎｂの含有量が０．００５％未満では強度調整やＭｏとの複合添加時におけるめっき密着性改善効果の効果が得られにくい。一方、Ｎｂの含有量が０．０５０％超えではコストアップを招く。よって、Ｎｂを含有する場合、Ｎｂ量は０．００５％以上０．０５０％以下とする。 Nb: 0.005 to 0.050%
When the content of Nb is less than 0.005%, it is difficult to obtain the effect of improving the adhesion of plating at the time of strength adjustment or composite addition with Mo. On the other hand, if the Nb content exceeds 0.050%, the cost increases. Therefore, when Nb is contained, the Nb content is 0.005% or more and 0.050% or less.
Ｔｉ：０．００５～０．０５０％
Ｔｉの含有量が０．００５％未満では強度調整の効果が得られにくい。一方、Ｔｉの含有量が０．０５０％超えではめっき密着性の劣化を招く場合がある。よって、Ｔｉを含有する場合、Ｔｉ量は０．００５％以上０．０５０％以下とすることが好ましい。 Ti: 0.005 to 0.050%
If the Ti content is less than 0.005%, the effect of adjusting the strength is difficult to obtain. On the other hand, if the Ti content exceeds 0.050%, the plating adhesion may be deteriorated. Therefore, when Ti is contained, the Ti content is preferably 0.005% or more and 0.050% or less.
Ｔｉの含有量が０．００５％未満では強度調整の効果が得られにくい。一方、Ｔｉの含有量が０．０５０％超えではめっき密着性の劣化を招く場合がある。よって、Ｔｉを含有する場合、Ｔｉ量は０．００５％以上０．０５０％以下とすることが好ましい。 Ti: 0.005 to 0.050%
If the Ti content is less than 0.005%, the effect of adjusting the strength is difficult to obtain. On the other hand, if the Ti content exceeds 0.050%, the plating adhesion may be deteriorated. Therefore, when Ti is contained, the Ti content is preferably 0.005% or more and 0.050% or less.
Ｃｒ：０．００１～１．０００％
Ｃｒの含有量が０．００１％未満では焼き入れ性効果が得られにくい。一方、Ｃｒの含有量が１．０００％超えではＣｒが表面濃化するため、めっき密着性や溶接性が劣化する。よって、Ｃｒを含有する場合、Ｃｒ量は０．００１％以上１．０００％以下とすることが好ましい。 Cr: 0.001 to 1.000%
When the Cr content is less than 0.001%, it is difficult to obtain a hardenability effect. On the other hand, if the Cr content exceeds 1.000%, the surface of Cr is concentrated, so that the plating adhesion and weldability deteriorate. Therefore, when it contains Cr, it is preferable that Cr amount shall be 0.001% or more and 1.000% or less.
Ｃｒの含有量が０．００１％未満では焼き入れ性効果が得られにくい。一方、Ｃｒの含有量が１．０００％超えではＣｒが表面濃化するため、めっき密着性や溶接性が劣化する。よって、Ｃｒを含有する場合、Ｃｒ量は０．００１％以上１．０００％以下とすることが好ましい。 Cr: 0.001 to 1.000%
When the Cr content is less than 0.001%, it is difficult to obtain a hardenability effect. On the other hand, if the Cr content exceeds 1.000%, the surface of Cr is concentrated, so that the plating adhesion and weldability deteriorate. Therefore, when it contains Cr, it is preferable that Cr amount shall be 0.001% or more and 1.000% or less.
Ｍｏ：０．０５～１．００％
Ｍｏの含有量が０．０５％未満では強度調整の効果やＮｂ、またはＮｉやＣｕとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、Ｍｏの含有量が１．００％超えではコストアップを招く。よって、Ｍｏを含有する場合、Ｍｏ量は０．０５％以上１．００％以下とすることが好ましい。 Mo: 0.05-1.00%
When the Mo content is less than 0.05%, it is difficult to obtain the effect of adjusting the strength and the effect of improving the plating adhesion at the time of composite addition with Nb, Ni or Cu. On the other hand, if the Mo content exceeds 1.00%, the cost increases. Therefore, when it contains Mo, it is preferable to make Mo amount into 0.05% or more and 1.00% or less.
Ｍｏの含有量が０．０５％未満では強度調整の効果やＮｂ、またはＮｉやＣｕとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、Ｍｏの含有量が１．００％超えではコストアップを招く。よって、Ｍｏを含有する場合、Ｍｏ量は０．０５％以上１．００％以下とすることが好ましい。 Mo: 0.05-1.00%
When the Mo content is less than 0.05%, it is difficult to obtain the effect of adjusting the strength and the effect of improving the plating adhesion at the time of composite addition with Nb, Ni or Cu. On the other hand, if the Mo content exceeds 1.00%, the cost increases. Therefore, when it contains Mo, it is preferable to make Mo amount into 0.05% or more and 1.00% or less.
Ｃｕ：０．０５～１．００％
Ｃｕの含有量が０．０５％未満では残留γ相形成促進効果やＮｉやＭｏとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、Ｃｕの含有量が１．００％超えではコストアップを招く。よって、Ｃｕを含有する場合、Ｃｕ量は０．０５％以上１．００％以下とすることが好ましい。 Cu: 0.05 to 1.00%
When the Cu content is less than 0.05%, it is difficult to obtain the effect of promoting the formation of the residual γ phase and the effect of improving the plating adhesion upon the combined addition with Ni or Mo. On the other hand, if the Cu content exceeds 1.00%, the cost increases. Therefore, when Cu is contained, the amount of Cu is preferably 0.05% or more and 1.00% or less.
Ｃｕの含有量が０．０５％未満では残留γ相形成促進効果やＮｉやＭｏとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、Ｃｕの含有量が１．００％超えではコストアップを招く。よって、Ｃｕを含有する場合、Ｃｕ量は０．０５％以上１．００％以下とすることが好ましい。 Cu: 0.05 to 1.00%
When the Cu content is less than 0.05%, it is difficult to obtain the effect of promoting the formation of the residual γ phase and the effect of improving the plating adhesion upon the combined addition with Ni or Mo. On the other hand, if the Cu content exceeds 1.00%, the cost increases. Therefore, when Cu is contained, the amount of Cu is preferably 0.05% or more and 1.00% or less.
Ｎｉ：０．０５～１．００％
Ｎｉの含有量が０．０５％未満では残留γ相形成促進効果やＣｕとＭｏとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、Ｎｉの含有量が１．００％超えではコストアップを招く。よって、Ｎｉを含有する場合、Ｎｉ量は０．０５％以上１．００％以下とすることが好ましい。 Ni: 0.05-1.00%
When the Ni content is less than 0.05%, it is difficult to obtain the effect of promoting the formation of the residual γ phase and the effect of improving the plating adhesion at the time of the combined addition of Cu and Mo. On the other hand, if the Ni content exceeds 1.00%, the cost increases. Therefore, when Ni is contained, the amount of Ni is preferably 0.05% or more and 1.00% or less.
Ｎｉの含有量が０．０５％未満では残留γ相形成促進効果やＣｕとＭｏとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、Ｎｉの含有量が１．００％超えではコストアップを招く。よって、Ｎｉを含有する場合、Ｎｉ量は０．０５％以上１．００％以下とすることが好ましい。 Ni: 0.05-1.00%
When the Ni content is less than 0.05%, it is difficult to obtain the effect of promoting the formation of the residual γ phase and the effect of improving the plating adhesion at the time of the combined addition of Cu and Mo. On the other hand, if the Ni content exceeds 1.00%, the cost increases. Therefore, when Ni is contained, the amount of Ni is preferably 0.05% or more and 1.00% or less.
Ｓｎ：０．００１～０．２０％、Ｓｂ：０．００１～０．２０％
ＳｎやＳｂは鋼板表面の窒化、酸化、あるいは酸化により生じる鋼板表面から数十ミクロン領域の脱炭を抑制する観点から含有することができる。窒化や酸化を抑制することで鋼板表面においてマルテンサイトの生成量が減少するのを防止し、得られる高強度鋼板の疲労特性や表面品質が改善する。窒化や酸化を抑制する観点から、ＳｎあるいはＳｂを含有する場合は、各々０．００１％以上とすることが好ましい。また、各々の含有量が０．２０％を超えると靭性の劣化を招くので、Ｓｎ、Ｓｂ含有量は０．２０％以下とすることが好ましい。 Sn: 0.001 to 0.20%, Sb: 0.001 to 0.20%
Sn and Sb can be contained from the viewpoint of suppressing decarburization in the region of several tens of microns from the steel sheet surface caused by nitriding, oxidation, or oxidation of the steel sheet surface. By suppressing nitriding and oxidation, the amount of martensite produced on the steel sheet surface is prevented from decreasing, and the fatigue properties and surface quality of the resulting high strength steel sheet are improved. From the viewpoint of suppressing nitriding and oxidation, when Sn or Sb is contained, each content is preferably 0.001% or more. Further, if each content exceeds 0.20%, the toughness is deteriorated, so the Sn and Sb contents are preferably 0.20% or less.
ＳｎやＳｂは鋼板表面の窒化、酸化、あるいは酸化により生じる鋼板表面から数十ミクロン領域の脱炭を抑制する観点から含有することができる。窒化や酸化を抑制することで鋼板表面においてマルテンサイトの生成量が減少するのを防止し、得られる高強度鋼板の疲労特性や表面品質が改善する。窒化や酸化を抑制する観点から、ＳｎあるいはＳｂを含有する場合は、各々０．００１％以上とすることが好ましい。また、各々の含有量が０．２０％を超えると靭性の劣化を招くので、Ｓｎ、Ｓｂ含有量は０．２０％以下とすることが好ましい。 Sn: 0.001 to 0.20%, Sb: 0.001 to 0.20%
Sn and Sb can be contained from the viewpoint of suppressing decarburization in the region of several tens of microns from the steel sheet surface caused by nitriding, oxidation, or oxidation of the steel sheet surface. By suppressing nitriding and oxidation, the amount of martensite produced on the steel sheet surface is prevented from decreasing, and the fatigue properties and surface quality of the resulting high strength steel sheet are improved. From the viewpoint of suppressing nitriding and oxidation, when Sn or Sb is contained, each content is preferably 0.001% or more. Further, if each content exceeds 0.20%, the toughness is deteriorated, so the Sn and Sb contents are preferably 0.20% or less.
Ｔａ：０．００１～０．１０％
ＴａはＮｂやＴｉと同様に、ＣやＮと炭化物や炭窒化物を形成することで高強度化に寄与する。さらに、Ｔａは高降伏比（高ＹＲ）化に寄与する。このような観点から、Ｔａを含有することにより、粒界面積の増大に伴う粒界へのＣ偏析量の増大により、高焼付き硬化量（ＢＨ量）を得ることができる。このような観点から、Ｔａを０．００１％以上含有することができる。一方、Ｔａの含有量が０．１０％を超えると、原料コストの増加を招くだけでなく、ＮｂやＴｉと同様に、焼鈍後の冷却過程におけるマルテンサイトの形成を妨げる可能性がある。さらに熱延板中に析出したＴａＣは、冷間圧延時の変形抵抗を高くし、安定した実機製造を困難にする場合がある。このため、Ｔａを含有する場合は、その含有量を０．１０％以下とすることが好ましい。 Ta: 0.001 to 0.10%
Ta, like Nb and Ti, contributes to increasing the strength by forming carbides and carbonitrides with C and N. Furthermore, Ta contributes to a high yield ratio (high YR). From such a viewpoint, by containing Ta, a high seizure hardening amount (BH amount) can be obtained due to an increase in the amount of C segregation to the grain boundary accompanying an increase in the grain boundary area. From such a viewpoint, 0.001% or more of Ta can be contained. On the other hand, when the content of Ta exceeds 0.10%, not only the raw material cost is increased, but similarly to Nb and Ti, the formation of martensite in the cooling process after annealing may be hindered. Furthermore, TaC precipitated in the hot-rolled sheet increases the deformation resistance during cold rolling, which may make it difficult to manufacture a stable actual machine. For this reason, when it contains Ta, it is preferable to make the content into 0.10% or less.
ＴａはＮｂやＴｉと同様に、ＣやＮと炭化物や炭窒化物を形成することで高強度化に寄与する。さらに、Ｔａは高降伏比（高ＹＲ）化に寄与する。このような観点から、Ｔａを含有することにより、粒界面積の増大に伴う粒界へのＣ偏析量の増大により、高焼付き硬化量（ＢＨ量）を得ることができる。このような観点から、Ｔａを０．００１％以上含有することができる。一方、Ｔａの含有量が０．１０％を超えると、原料コストの増加を招くだけでなく、ＮｂやＴｉと同様に、焼鈍後の冷却過程におけるマルテンサイトの形成を妨げる可能性がある。さらに熱延板中に析出したＴａＣは、冷間圧延時の変形抵抗を高くし、安定した実機製造を困難にする場合がある。このため、Ｔａを含有する場合は、その含有量を０．１０％以下とすることが好ましい。 Ta: 0.001 to 0.10%
Ta, like Nb and Ti, contributes to increasing the strength by forming carbides and carbonitrides with C and N. Furthermore, Ta contributes to a high yield ratio (high YR). From such a viewpoint, by containing Ta, a high seizure hardening amount (BH amount) can be obtained due to an increase in the amount of C segregation to the grain boundary accompanying an increase in the grain boundary area. From such a viewpoint, 0.001% or more of Ta can be contained. On the other hand, when the content of Ta exceeds 0.10%, not only the raw material cost is increased, but similarly to Nb and Ti, the formation of martensite in the cooling process after annealing may be hindered. Furthermore, TaC precipitated in the hot-rolled sheet increases the deformation resistance during cold rolling, which may make it difficult to manufacture a stable actual machine. For this reason, when it contains Ta, it is preferable to make the content into 0.10% or less.
Ｗ：０．００１～０．１０％、Ｖ：０．００１～０．１０％
ＷやＶを、Ｓｉ、Ｍｎと複合添加することにより、Γ相の生成を抑制し、めっきの密着性を向上させる効果がある。このような効果は、Ｗ、Ｖいずれの元素とも０．００１％以上含有して認められる。一方、いずれの元素共に０．１０％を超えて含有しても効果が飽和し、含有量に見合う効果を期待できず、経済的に不利となる。 W: 0.001 to 0.10%, V: 0.001 to 0.10%
By adding W and V together with Si and Mn, there is an effect of suppressing the formation of a Γ phase and improving the adhesion of plating. Such an effect is recognized by containing 0.001% or more of both W and V elements. On the other hand, if any element is contained in excess of 0.10%, the effect is saturated, an effect commensurate with the content cannot be expected, and this is economically disadvantageous.
ＷやＶを、Ｓｉ、Ｍｎと複合添加することにより、Γ相の生成を抑制し、めっきの密着性を向上させる効果がある。このような効果は、Ｗ、Ｖいずれの元素とも０．００１％以上含有して認められる。一方、いずれの元素共に０．１０％を超えて含有しても効果が飽和し、含有量に見合う効果を期待できず、経済的に不利となる。 W: 0.001 to 0.10%, V: 0.001 to 0.10%
By adding W and V together with Si and Mn, there is an effect of suppressing the formation of a Γ phase and improving the adhesion of plating. Such an effect is recognized by containing 0.001% or more of both W and V elements. On the other hand, if any element is contained in excess of 0.10%, the effect is saturated, an effect commensurate with the content cannot be expected, and this is economically disadvantageous.
Ｆｅおよび不可避的不純物
上記した成分以外の残部は、Ｆｅおよび不可避的不純物である。ここで不可避的不純物とは、例えばＯである。Ｏは不可避的に混入する代表的な不可避的不純物である。不可避的不純物の含有量は特に限定されず、許容される不可避的不純物の含有量は不可避的不純物の種類にもよるが、Ｏの場合には含有量が０．００５％以下であれば問題が無い。 Fe and unavoidable impurities The balance other than the above components is Fe and unavoidable impurities. Here, the unavoidable impurity is, for example, O. O is a typical inevitable impurity inevitably mixed. The content of inevitable impurities is not particularly limited, and the allowable content of inevitable impurities depends on the type of inevitable impurities, but in the case of O, there is a problem if the content is 0.005% or less. No.
上記した成分以外の残部は、Ｆｅおよび不可避的不純物である。ここで不可避的不純物とは、例えばＯである。Ｏは不可避的に混入する代表的な不可避的不純物である。不可避的不純物の含有量は特に限定されず、許容される不可避的不純物の含有量は不可避的不純物の種類にもよるが、Ｏの場合には含有量が０．００５％以下であれば問題が無い。 Fe and unavoidable impurities The balance other than the above components is Fe and unavoidable impurities. Here, the unavoidable impurity is, for example, O. O is a typical inevitable impurity inevitably mixed. The content of inevitable impurities is not particularly limited, and the allowable content of inevitable impurities depends on the type of inevitable impurities, but in the case of O, there is a problem if the content is 0.005% or less. No.
以上のような成分組成を有する鋼板の焼鈍の条件等を調整することで、外観、耐食性、高加工時の耐めっき剥離性および加工性に優れた高強度溶融亜鉛めっき鋼板が得られる。以下、この高強度溶融亜鉛めっき鋼板について説明する。
By adjusting the annealing conditions and the like of the steel sheet having the above component composition, a high-strength hot-dip galvanized steel sheet excellent in appearance, corrosion resistance, plating peeling resistance during high processing and workability can be obtained. Hereinafter, this high-strength hot-dip galvanized steel sheet will be described.
前述の方法で製造した高強度溶融亜鉛めっき鋼板について説明する。本発明の高強度溶融亜鉛めっき鋼板は、めっき層直下の地鉄鋼板表層の構造に特徴を有する。具体的には、本発明の高強度溶融亜鉛めっき鋼板では、亜鉛めっき層の直下の、地鉄鋼板表面から１００μｍ以内の領域に存在する、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉ、Ｓｎ、Ｓｂ、Ｔａ、Ｗ、Ｖのうちから選ばれる１種以上（Ｆｅのみの場合を除く）の酸化物の形成量が合計で片面あたり０．０１０ｇ／ｍ2未満である。Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉ、Ｓｎ、Ｓｂ、Ｔａ、Ｗ、Ｖの酸化物（Ｆｅのみの場合を除く）の形成量が合計で片面あたり０．０１０ｇ／ｍ2未満としてもよい。なお、本発明において、上記酸化物量は後述の実施例に記載した方法により測定する。
The high-strength hot-dip galvanized steel sheet produced by the above method will be described. The high-strength hot-dip galvanized steel sheet of the present invention is characterized by the structure of the surface layer of the steel sheet directly below the plating layer. Specifically, in the high-strength hot-dip galvanized steel sheet of the present invention, Fe, Si, Mn, Al, P, B, Nb, which are present in a region within 100 μm from the surface of the steel sheet directly under the galvanized layer, The total amount of oxides of one or more selected from Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V (except for Fe alone) is 0.010 g / side. less than m 2 . Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, V oxides are formed in total (except for Fe only) It is good also as less than 0.010 g / m < 2 > per single side | surface. In the present invention, the amount of oxide is measured by the method described in the examples described later.
鋼中にＳｉ及び多量のＭｎが添加された溶融亜鉛めっき鋼板において、耐食性および高加工時の耐めっき剥離性を満足させるためには、腐食や高加工時の割れなどの起点になる可能性があるめっき層直下の地鉄表層の内部酸化を極力少なくすることが求められる。そこで、本発明では、めっき性を確保するために、焼鈍において酸素ポテンシャルを低下させる。上記酸素ポテンシャルを低下させることで、易酸化性元素であるＳｉやＭｎ等の地鉄表層部における活量が低下する。上記活量低下により元素の外部酸化を抑制し、結果的にめっき性が改善する。さらに、上記焼鈍条件により、地鉄表層部に形成する内部酸化も抑制され、耐食性及び高加工時の加工性が改善することになる。このような効果は、地鉄鋼板表面から１００μｍ以内の領域に存在する、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉ、Ｓｎ、Ｓｂ、Ｔａ、Ｗ、Ｖのうちから選ばれる１種以上（Ｆｅのみの場合を除く）の酸化物の形成量を合計で片面あたり０．０１０ｇ／ｍ2未満に抑制することで認められる。酸化物形成量の合計（以下、内部酸化量と称す）が０．０１０ｇ／ｍ２以上では、耐食性及び加工性が劣化する。また、内部酸化量を０．０００１ｇ／ｍ２未満に抑制しても、耐食性及び高加工時の加工性向上効果は飽和する。このため、内部酸化量の下限は０．０００１ｇ／ｍ２以上が好ましい。
In hot-dip galvanized steel sheets with Si and a large amount of Mn added to the steel, in order to satisfy the corrosion resistance and anti-plating resistance during high processing, there is a possibility of starting from corrosion and cracking during high processing. It is required to minimize the internal oxidation of the surface layer of the ground metal directly below a certain plating layer. Therefore, in the present invention, the oxygen potential is lowered during annealing in order to ensure plating properties. By reducing the oxygen potential, the activity in the surface layer portion of the iron base such as Si or Mn, which is an easily oxidizable element, is reduced. By reducing the activity, external oxidation of the element is suppressed, and as a result, the plating property is improved. Furthermore, the internal oxidation formed in the surface layer part of the iron core is also suppressed by the annealing conditions, and the corrosion resistance and the workability at the time of high processing are improved. Such an effect exists in the region within 100 μm from the surface of the steel sheet, Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W , V is recognized by suppressing the total amount of oxides selected from V (excluding the case of Fe alone) to less than 0.010 g / m 2 per side. When the total oxide formation amount (hereinafter referred to as internal oxidation amount) is 0.010 g / m 2 or more, corrosion resistance and workability deteriorate. Moreover, even if it suppresses the amount of internal oxidation to less than 0.0001 g / m < 2 >, the corrosion resistance and the workability improvement effect at the time of high processing are saturated. For this reason, the lower limit of the internal oxidation amount is preferably 0.0001 g / m 2 or more.
さらに、上記に加え、本発明では、耐めっき剥離性を向上させるために、Ｓｉ、Ｍｎ系複合酸化物が成長する地鉄組織は軟質で加工性に富むフェライト相が好ましい。
Furthermore, in addition to the above, in the present invention, in order to improve the plating peeling resistance, the base iron structure on which the Si and Mn based composite oxide grows is preferably a soft and rich workability ferrite phase.
以下、本発明を、実施例に基いて具体的に説明する。
Hereinafter, the present invention will be specifically described based on examples.
表１に示す鋼組成からなる熱延鋼板を酸洗し、黒皮スケールを除去した後、冷間圧延し、厚さ１．０ｍｍの冷延鋼板を得た。なお、一部は冷間圧延を実施せず、黒皮スケール除去後の熱延鋼板（厚さ２．０ｍｍ）のまま使用した。
A hot-rolled steel sheet having a steel composition shown in Table 1 was pickled, and after removing the black scale, it was cold-rolled to obtain a cold-rolled steel sheet having a thickness of 1.0 mm. A part of the hot-rolled steel sheet (thickness: 2.0 mm) after removing the black scale was used without performing cold rolling.
次いで、上記で得た冷延鋼板および熱延鋼板を、焼鈍炉にオールラジアントチューブ型の加熱炉を備えるＣＧＬに装入した。ＣＧＬでは、表２、３に示す通り、焼鈍炉内の所定の温度域の加熱速度、水素濃度および、鋼板通過時間、鋼板最高到達温度を制御して通板し、加熱帯で加熱し、均熱帯で均熱保持し、焼鈍した。なお、雰囲気の水素濃度を制御しない領域の水素濃度は、５ｖｏｌ％に調整した。さらに、炉内の露点は－３５℃に制御した。焼鈍における雰囲気の露点の制御については、Ｎ２ガスが充満した空間に設置した水タンクを加熱して加湿したＮ２ガスが流れる配管を焼鈍炉に接続し、加湿したＮ２ガス中にＨ２ガスを導入して混合し、これを炉内に導入することで雰囲気の露点を制御した。
Subsequently, the cold-rolled steel plate and hot-rolled steel plate obtained above were charged into CGL equipped with an all-radiant tube type heating furnace in an annealing furnace. In CGL, as shown in Tables 2 and 3, the heating rate in a predetermined temperature range in the annealing furnace, the hydrogen concentration, the steel plate passage time, and the maximum temperature reached by the steel plate are controlled, heated in the heating zone, and uniform. Maintained soaking in the tropics and annealed. The hydrogen concentration in the region where the hydrogen concentration in the atmosphere was not controlled was adjusted to 5 vol%. Furthermore, the dew point in the furnace was controlled at -35 ° C. The control of the dew point of the atmosphere in the annealing, H 2 and N 2 gas flows pipe water tank humidified by heating which is installed in a space N 2 gas is filled is connected to the annealing furnace, the N 2 gas humidified The dew point of the atmosphere was controlled by introducing and mixing the gas and introducing it into the furnace.
焼鈍した後、４６０℃のＡｌ含有Ｚｎ浴にて溶融亜鉛めっき処理を施した。ＧＡ（合金化高強度溶融亜鉛めっき鋼板）の製造の際には０．１４質量％Ａｌ含有Ｚｎ浴を用い、ＧＩ（高強度溶融亜鉛めっき鋼板）の製造の際には０．１８質量％Ａｌ含有Ｚｎ浴を用いた。付着量は、片面あたりのめっき付着量が２０～１２０ｇ／ｍ２の亜鉛めっき層が形成されるように、ガスワイピングにより調節した。合金化処理温度は表２、３に示す通りであり、合金化温度と時間はめっき層中のＦｅ含有量が表２、３に示す値になるように調整した。
After annealing, hot dip galvanization was performed in an Al-containing Zn bath at 460 ° C. A 0.14 mass% Al-containing Zn bath is used for the production of GA (alloyed high-strength hot-dip galvanized steel sheet), and 0.18 mass% Al is used for the production of GI (high-strength hot-dip galvanized steel sheet). A containing Zn bath was used. The amount of adhesion was adjusted by gas wiping so that a galvanized layer having a plating adhesion amount of 20 to 120 g / m 2 per side was formed. The alloying treatment temperatures were as shown in Tables 2 and 3, and the alloying temperature and time were adjusted so that the Fe content in the plating layer became the values shown in Tables 2 and 3.
以上により得られた溶融亜鉛めっき鋼板（ＧＡおよびＧＩ）に対して、外観性（めっき外観）、耐食性、高加工時の耐めっき剥離性、高加工時の加工性を調査した。また、めっき層直下の地鉄鋼板表面から１００μｍまでの領域に存在する酸化物の形成量（内部酸化量）を測定した。測定方法および評価基準を下記に示す。
The hot-dip galvanized steel sheets (GA and GI) obtained as described above were examined for appearance (plating appearance), corrosion resistance, plating peeling resistance during high processing, and workability during high processing. Moreover, the formation amount (internal oxidation amount) of the oxide which exists in the area | region to 100 micrometers from the base steel plate surface directly under a plating layer was measured. The measurement method and evaluation criteria are shown below.
＜外観性（めっき外観）＞
外観性は目視にて評価した。不めっきや合金化ムラなどの外観不良が無い場合は外観良好（記号：○）、ある場合は外観不良（記号：×）と判定した。 <Appearance (plating appearance)>
Appearance was evaluated visually. When there was no appearance defect such as non-plating or alloying unevenness, it was judged that the appearance was good (symbol: ○), and when there was, the appearance was poor (symbol: x).
外観性は目視にて評価した。不めっきや合金化ムラなどの外観不良が無い場合は外観良好（記号：○）、ある場合は外観不良（記号：×）と判定した。 <Appearance (plating appearance)>
Appearance was evaluated visually. When there was no appearance defect such as non-plating or alloying unevenness, it was judged that the appearance was good (symbol: ○), and when there was, the appearance was poor (symbol: x).
＜耐めっき剥離性＞
ＧＡの高強度溶融亜鉛めっき鋼板では、９０°を超えて鋭角に曲げたときの曲げ加工部のめっき剥離の抑制が要求される。本実施例では１２０°曲げした加工部にセロハンテープ（登録商標）を押し付けて剥離物をセロハンテープ（登録商標）に転移させ、セロハンテープ（登録商標）上の剥離物量をＺｎカウント数として蛍光Ｘ線法で求めた。なお、この時のマスク径は３０ｍｍ、蛍光Ｘ線の加速電圧は５０ｋＶ、加速電流は５０ｍＡ、測定時間は２０秒である。下記の基準に照らして、ランク１、２、３、４のものを耐めっき剥離性が良好（記号：◎又は○）、５のものを耐めっき剥離性が不良（記号×）と評価した。◎、○は高加工時のめっき剥離性に全く問題ない性能である。×は通常の実用には適さない性能である。
蛍光Ｘ線Ｚｎカウント数 ランク
０－５００未満：１（良）◎
５００以上－１０００未満：２○
１０００以上－２０００未満：３○
２０００以上－３０００未満：４○
３０００以上：５（劣）×
ＧＩの高強度溶融亜鉛めっき鋼板では、衝撃試験時の耐めっき剥離性が要求される。ボールインパクト試験を行い、加工部をテープ剥離し、めっき層の剥離有無を目視判定した。ボールインパクト条件は、ボール重量１０００ｇ、落下高さ１００ｃｍである。
○：めっき層の剥離無し
×：めっき層が剥離
＜耐食性＞
寸法７０ｍｍ×１５０ｍｍの溶融亜鉛めっき鋼板（ＧＡおよびＧＩ）について、ＪＩＳＺ ２３７１（２０００年）に基づく塩水噴霧試験を３日間行い、その後、腐食生成物を除去するためにクロム酸（濃度２００ｇ／Ｌ、８０℃）を用いて１分間洗浄除去し、片面あたりの試験前後のめっき腐食減量（ｇ／ｍ２・日）を重量法にて測定し、下記基準で評価した。
○（良好）：２０ｇ／ｍ２・日未満
×（不良）：２０ｇ／ｍ２・日以上
＜加工性＞
加工性は、試料から圧延方向に対して９０°方向にＪＩＳ５号引張試験片を採取し、ＪＩＳ Ｚ ２２４１の規定に準拠してクロスヘッド速度１０ｍｍ／ｍｉｎ一定で引張試験を行い、引張り強度ＴＳ（ＭＰａ）と伸びＥｌ（％）を測定し、ＴＳ×Ｅｌ≧２４０００のものを良好、ＴＳ×Ｅｌ＜２４０００のものを不良とした。 <Plating resistance>
In GA high-strength hot-dip galvanized steel sheets, it is required to suppress plating peeling at bent portions when bent at an acute angle exceeding 90 °. In this example, the cellophane tape (registered trademark) was pressed against the processed portion bent by 120 ° to transfer the peeled material to the cellophane tape (registered trademark), and the amount of the peeled material on the cellophane tape (registered trademark) was expressed as the Zn count. Obtained by line method. At this time, the mask diameter is 30 mm, the fluorescent X-ray acceleration voltage is 50 kV, the acceleration current is 50 mA, and the measurement time is 20 seconds. In light of the following criteria, those with ranks 1, 2, 3, and 4 were evaluated as having good plating peel resistance (symbol: A or B), and those having rank 5 were evaluated as having poor plating peel resistance (symbol x). ◎ and ○ are performances that have no problem with the plating peelability during high processing. X is a performance not suitable for normal practical use.
Fluorescent X-ray Zn count number Rank 0 to less than 500: 1 (good)
500 or more and less than 1000: 2 ○
1000 or more and less than 2000: 3 ○
2000 or more and less than −3000: 4 ○
3000 or more: 5 (poor) ×
The GI high-strength hot-dip galvanized steel sheet is required to have anti-plating resistance during an impact test. A ball impact test was performed, the processed part was peeled off with tape, and the presence or absence of peeling of the plating layer was visually determined. Ball impact conditions are a ball weight of 1000 g and a drop height of 100 cm.
○: Plating layer is not peeled ×: Plating layer is peeled <Corrosion resistance>
A hot-dip galvanized steel sheet (GA and GI) having a size of 70 mm × 150 mm was subjected to a salt spray test based on JISZ 2371 (2000) for 3 days, and then chromic acid (concentration 200 g / L, in order to remove corrosion products) (80 ° C.) for 1 minute, and the plating corrosion weight loss (g / m 2 · day) before and after the test per one side was measured by a weight method and evaluated according to the following criteria.
○ (Good): Less than 20 g / m 2 · day x (Bad): 20 g / m 2 · day or more <Workability>
For workability, a JIS No. 5 tensile test piece was sampled from the sample in a 90 ° direction with respect to the rolling direction, a tensile test was conducted at a constant crosshead speed of 10 mm / min in accordance with the provisions of JIS Z 2241, and the tensile strength TS ( (MPa) and elongation El (%) were measured, and those with TS × E1 ≧ 24000 were judged good and those with TS × El <24000 were judged as bad.
ＧＡの高強度溶融亜鉛めっき鋼板では、９０°を超えて鋭角に曲げたときの曲げ加工部のめっき剥離の抑制が要求される。本実施例では１２０°曲げした加工部にセロハンテープ（登録商標）を押し付けて剥離物をセロハンテープ（登録商標）に転移させ、セロハンテープ（登録商標）上の剥離物量をＺｎカウント数として蛍光Ｘ線法で求めた。なお、この時のマスク径は３０ｍｍ、蛍光Ｘ線の加速電圧は５０ｋＶ、加速電流は５０ｍＡ、測定時間は２０秒である。下記の基準に照らして、ランク１、２、３、４のものを耐めっき剥離性が良好（記号：◎又は○）、５のものを耐めっき剥離性が不良（記号×）と評価した。◎、○は高加工時のめっき剥離性に全く問題ない性能である。×は通常の実用には適さない性能である。
蛍光Ｘ線Ｚｎカウント数 ランク
０－５００未満：１（良）◎
５００以上－１０００未満：２○
１０００以上－２０００未満：３○
２０００以上－３０００未満：４○
３０００以上：５（劣）×
ＧＩの高強度溶融亜鉛めっき鋼板では、衝撃試験時の耐めっき剥離性が要求される。ボールインパクト試験を行い、加工部をテープ剥離し、めっき層の剥離有無を目視判定した。ボールインパクト条件は、ボール重量１０００ｇ、落下高さ１００ｃｍである。
○：めっき層の剥離無し
×：めっき層が剥離
＜耐食性＞
寸法７０ｍｍ×１５０ｍｍの溶融亜鉛めっき鋼板（ＧＡおよびＧＩ）について、ＪＩＳＺ ２３７１（２０００年）に基づく塩水噴霧試験を３日間行い、その後、腐食生成物を除去するためにクロム酸（濃度２００ｇ／Ｌ、８０℃）を用いて１分間洗浄除去し、片面あたりの試験前後のめっき腐食減量（ｇ／ｍ２・日）を重量法にて測定し、下記基準で評価した。
○（良好）：２０ｇ／ｍ２・日未満
×（不良）：２０ｇ／ｍ２・日以上
＜加工性＞
加工性は、試料から圧延方向に対して９０°方向にＪＩＳ５号引張試験片を採取し、ＪＩＳ Ｚ ２２４１の規定に準拠してクロスヘッド速度１０ｍｍ／ｍｉｎ一定で引張試験を行い、引張り強度ＴＳ（ＭＰａ）と伸びＥｌ（％）を測定し、ＴＳ×Ｅｌ≧２４０００のものを良好、ＴＳ×Ｅｌ＜２４０００のものを不良とした。 <Plating resistance>
In GA high-strength hot-dip galvanized steel sheets, it is required to suppress plating peeling at bent portions when bent at an acute angle exceeding 90 °. In this example, the cellophane tape (registered trademark) was pressed against the processed portion bent by 120 ° to transfer the peeled material to the cellophane tape (registered trademark), and the amount of the peeled material on the cellophane tape (registered trademark) was expressed as the Zn count. Obtained by line method. At this time, the mask diameter is 30 mm, the fluorescent X-ray acceleration voltage is 50 kV, the acceleration current is 50 mA, and the measurement time is 20 seconds. In light of the following criteria, those with ranks 1, 2, 3, and 4 were evaluated as having good plating peel resistance (symbol: A or B), and those having rank 5 were evaluated as having poor plating peel resistance (symbol x). ◎ and ○ are performances that have no problem with the plating peelability during high processing. X is a performance not suitable for normal practical use.
Fluorescent X-ray Zn count number Rank 0 to less than 500: 1 (good)
500 or more and less than 1000: 2 ○
1000 or more and less than 2000: 3 ○
2000 or more and less than −3000: 4 ○
3000 or more: 5 (poor) ×
The GI high-strength hot-dip galvanized steel sheet is required to have anti-plating resistance during an impact test. A ball impact test was performed, the processed part was peeled off with tape, and the presence or absence of peeling of the plating layer was visually determined. Ball impact conditions are a ball weight of 1000 g and a drop height of 100 cm.
○: Plating layer is not peeled ×: Plating layer is peeled <Corrosion resistance>
A hot-dip galvanized steel sheet (GA and GI) having a size of 70 mm × 150 mm was subjected to a salt spray test based on JISZ 2371 (2000) for 3 days, and then chromic acid (concentration 200 g / L, in order to remove corrosion products) (80 ° C.) for 1 minute, and the plating corrosion weight loss (g / m 2 · day) before and after the test per one side was measured by a weight method and evaluated according to the following criteria.
○ (Good): Less than 20 g / m 2 · day x (Bad): 20 g / m 2 · day or more <Workability>
For workability, a JIS No. 5 tensile test piece was sampled from the sample in a 90 ° direction with respect to the rolling direction, a tensile test was conducted at a constant crosshead speed of 10 mm / min in accordance with the provisions of JIS Z 2241, and the tensile strength TS ( (MPa) and elongation El (%) were measured, and those with TS × E1 ≧ 24000 were judged good and those with TS × El <24000 were judged as bad.
＜めっき層直下１００μｍまでの領域における内部酸化量＞
内部酸化量は、「インパルス炉溶融－赤外線吸収法」により測定する。ただし、素材（すなわち焼鈍を施す前の鋼板）に含まれる酸素量を差し引く必要があるので、本発明では、焼鈍後の高強度鋼板の両面から１００μｍ以上研磨した位置での鋼中酸素濃度を測定し、その測定値を素材に含まれる酸素量ＯＨとした。また、焼鈍後の高強度鋼板表面の板厚方向全体での鋼中酸素濃度を測定して、その測定値を内部酸化後の酸素量ＯＩとした。このようにして得られた高強度鋼板の内部酸化後の酸素量ＯＩと、素材に含まれる酸素量ＯＨとを用いて、ＯＩとＯＨの差（＝ＯＩ－ＯＨ）を算出し、さらに片面単位面積（すなわち１ｍ２）当たりの量に換算した値（ｇ／ｍ２）を内部酸化量とした。 <Internal oxidation amount in the region of 100 μm directly under the plating layer>
The amount of internal oxidation is measured by “impulse furnace melting-infrared absorption method”. However, since it is necessary to subtract the amount of oxygen contained in the material (ie, the steel plate before annealing), in the present invention, the oxygen concentration in the steel is measured at a position polished by 100 μm or more from both sides of the high-strength steel plate after annealing. The measured value was defined as the amount of oxygen OH contained in the material. Moreover, the oxygen concentration in steel in the whole plate | board thickness direction of the high strength steel plate surface after annealing was measured, and the measured value was made into oxygen amount OI after internal oxidation. The difference between OI and OH (= OI−OH) is calculated using the oxygen amount OI after internal oxidation of the high-strength steel plate thus obtained and the oxygen amount OH contained in the material, and further, single-sided unit area (i.e. 1 m 2) value converted into the amount per (g / m 2) as an internal oxide amount.
内部酸化量は、「インパルス炉溶融－赤外線吸収法」により測定する。ただし、素材（すなわち焼鈍を施す前の鋼板）に含まれる酸素量を差し引く必要があるので、本発明では、焼鈍後の高強度鋼板の両面から１００μｍ以上研磨した位置での鋼中酸素濃度を測定し、その測定値を素材に含まれる酸素量ＯＨとした。また、焼鈍後の高強度鋼板表面の板厚方向全体での鋼中酸素濃度を測定して、その測定値を内部酸化後の酸素量ＯＩとした。このようにして得られた高強度鋼板の内部酸化後の酸素量ＯＩと、素材に含まれる酸素量ＯＨとを用いて、ＯＩとＯＨの差（＝ＯＩ－ＯＨ）を算出し、さらに片面単位面積（すなわち１ｍ２）当たりの量に換算した値（ｇ／ｍ２）を内部酸化量とした。 <Internal oxidation amount in the region of 100 μm directly under the plating layer>
The amount of internal oxidation is measured by “impulse furnace melting-infrared absorption method”. However, since it is necessary to subtract the amount of oxygen contained in the material (ie, the steel plate before annealing), in the present invention, the oxygen concentration in the steel is measured at a position polished by 100 μm or more from both sides of the high-strength steel plate after annealing. The measured value was defined as the amount of oxygen OH contained in the material. Moreover, the oxygen concentration in steel in the whole plate | board thickness direction of the high strength steel plate surface after annealing was measured, and the measured value was made into oxygen amount OI after internal oxidation. The difference between OI and OH (= OI−OH) is calculated using the oxygen amount OI after internal oxidation of the high-strength steel plate thus obtained and the oxygen amount OH contained in the material, and further, single-sided unit area (i.e. 1 m 2) value converted into the amount per (g / m 2) as an internal oxide amount.
以上により得られた結果を製造条件と併せて表２、３に示す。
The results obtained above are shown in Tables 2 and 3 together with the manufacturing conditions.
表２、３から明らかなように、本発明法で製造されたＧＩ、ＧＡ（本発明例）は、Ｓｉ、Ｍｎ等の易酸化性元素を多量に含有する場合であり高強度鋼板であるにもかかわらず、耐食性、高加工時の加工性、高加工時の耐めっき剥離性およびめっき外観も良好である。一方、比較例では、めっき外観、耐食性、高加工時の加工性、高加工時の耐めっき剥離性のいずれか一つ以上が劣る。
As is apparent from Tables 2 and 3, GI and GA (invention examples) produced by the method of the present invention contain a large amount of oxidizable elements such as Si and Mn, and are high-strength steel sheets. Nevertheless, the corrosion resistance, the workability at the time of high processing, the plating peeling resistance at the time of high processing and the plating appearance are also good. On the other hand, in the comparative example, any one or more of plating appearance, corrosion resistance, workability at high processing, and plating peeling resistance at high processing is inferior.
本発明の高強度溶融亜鉛めっき鋼板は、めっき外観、耐食性、加工性および高加工時の耐めっき剥離性に優れ、自動車の車体そのものを軽量化かつ高強度化するための表面処理鋼板として利用することができる。また、自動車以外にも、素材鋼板に防錆性を付与した表面処理鋼板として、家電、建材の分野等、広範な分野で適用できる。
The high-strength hot-dip galvanized steel sheet according to the present invention is excellent in plating appearance, corrosion resistance, workability, and anti-plating resistance during high processing, and is used as a surface-treated steel sheet for reducing the weight and strength of an automobile body. be able to. In addition to automobiles, the steel sheet can be applied in a wide range of fields such as home appliances and building materials as a surface-treated steel sheet provided with rust prevention properties.
Claims (4)
- 質量％で、Ｃ：０．０３～０．３５％、Ｓｉ：０．０１～０．５０％、Ｍｎ：３．６～８．０％、Ａｌ：０．００１～１．０００％、Ｐ：０．１０％以下、Ｓ：０．０１０％以下を含有し、残部がＦｅおよび不可避的不純物からなる鋼板に焼鈍を施し、該焼鈍後の鋼板の表面に、片面あたりのめっき付着量が２０～１２０ｇ／ｍ２の亜鉛めっき層を有する高強度溶融亜鉛めっき鋼板を製造する方法であって、
鋼板を連続式溶融亜鉛めっき設備において焼鈍を施すに際し、
前記焼鈍の加熱過程において、焼鈍炉内温度：４５０℃以上Ａ℃以下（但し、５００≦Ａから選択される任意の値）の温度域では、昇温速度：７℃/s以上とし、
前記焼鈍において鋼板最高到達温度を６００℃以上７５０℃以下とし、
前記焼鈍において鋼板温度が６００℃以上７５０℃以下の温度域の鋼板通過時間を３０秒以上１０分以内、雰囲気の水素濃度を２０ｖｏｌ％以上とし、
前記焼鈍後の鋼板に溶融亜鉛めっき処理を施す高強度溶融亜鉛めっき鋼板の製造方法。 By mass%, C: 0.03 to 0.35%, Si: 0.01 to 0.50%, Mn: 3.6 to 8.0%, Al: 0.001 to 1.000%, P: A steel sheet containing 0.10% or less and S: 0.010% or less, the balance being Fe and inevitable impurities is annealed, and the amount of plating adhesion per side on the surface of the steel sheet after annealing is 20 to A method for producing a high-strength hot-dip galvanized steel sheet having a galvanized layer of 120 g / m 2 , comprising:
When annealing steel sheets in continuous galvanizing equipment,
In the heating process of the annealing, the temperature inside the annealing furnace: 450 ° C. or more and A ° C. or less (however, an arbitrary value selected from 500 ≦ A) is set to a temperature rising rate of 7 ° C./s or more,
In the annealing, the steel sheet maximum temperature reached 600 ° C. or more and 750 ° C. or less,
In the annealing, the steel plate temperature in the temperature range of 600 ° C. or more and 750 ° C. or less is 30 seconds or more and 10 minutes or less, the hydrogen concentration of the atmosphere is 20 vol% or more,
The manufacturing method of the high intensity | strength hot-dip galvanized steel plate which performs the hot dip galvanization process to the steel plate after the said annealing. - 前記鋼板は、成分組成として、質量％で、さらに、Ｂ：０．００１～０．００５％、Ｎｂ：０．００５～０．０５０％、Ｔｉ：０．００５～０．０５０％、Ｃｒ：０．００１～１．０００％、Ｍｏ：０．０５～１．００％、Ｃｕ：０．０５～１．００％、Ｎｉ：０．０５～１．００％、Ｓｎ：０．００１～０．２０％、Ｓｂ：０．００１～０．２０％、Ｔａ：０．００１～０．１０％、Ｗ：０．００１～０．１０％、Ｖ：０．００１～０．１０％の中から選ばれる１種以上の元素を含有する請求項１に記載の高強度溶融亜鉛めっき鋼板の製造方法。 The steel sheet has a component composition in mass%, and B: 0.001 to 0.005%, Nb: 0.005 to 0.050%, Ti: 0.005 to 0.050%, Cr: 0 0.001 to 1.000%, Mo: 0.05 to 1.00%, Cu: 0.05 to 1.00%, Ni: 0.05 to 1.00%, Sn: 0.001 to 0.20 %, Sb: 0.001 to 0.20%, Ta: 0.001 to 0.10%, W: 0.001 to 0.10%, V: 0.001 to 0.10% The manufacturing method of the high intensity | strength hot-dip galvanized steel plate of Claim 1 containing 1 or more types of elements.
- 溶融亜鉛めっき処理後、さらに、４５０℃以上６００℃以下の温度に鋼板を加熱して合金化処理を施し、めっき層のＦｅ含有量を８～１４質量％の範囲にする請求項１または２に記載の高強度溶融亜鉛めっき鋼板の製造方法。 3. The hot-dip galvanizing treatment is further performed by heating the steel sheet to a temperature of 450 ° C. or more and 600 ° C. or less to perform an alloying treatment so that the Fe content of the plating layer is in the range of 8 to 14% by mass. A method for producing the high-strength hot-dip galvanized steel sheet.
- 請求項１～３のいずれかに記載の高強度溶融亜鉛めっき鋼板の製造方法により製造した高強度溶融亜鉛めっき鋼板であって、
地鉄鋼板と、地鉄鋼板上に形成された亜鉛めっき層とを備え、
前記地鉄鋼板は、請求項１又は２に記載の成分組成を有し、
前記亜鉛めっき層直下の前記地鉄鋼板表面から１００μｍ以内の領域に存在する、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉ、Ｓｎ、Ｓｂ、Ｔａ、Ｗ、Ｖのうちから選ばれる１種以上（Ｆｅのみの場合を除く）の酸化物の形成量が合計で片面あたり０．０１０ｇ／ｍ2未満である高強度溶融亜鉛めっき鋼板。 A high-strength hot-dip galvanized steel sheet produced by the method for producing a high-strength hot-dip galvanized steel sheet according to any one of claims 1 to 3,
Comprising a steel plate and a galvanized layer formed on the steel plate;
The steel sheet has the component composition according to claim 1 or 2,
Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, existing in a region within 100 μm from the surface of the steel sheet just below the galvanized layer A high-strength hot-dip galvanized steel sheet in which the total amount of oxides of one or more selected from W and V (excluding the case of Fe alone) is less than 0.010 g / m 2 per side.
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| JP2012251239A (en) * | 2011-05-12 | 2012-12-20 | Jfe Steel Corp | Vehicle collision energy-absorbing member excellent in collision energy-absorbing power and method for producing the same |
| JP2013194270A (en) * | 2012-03-19 | 2013-09-30 | Jfe Steel Corp | Method of manufacturing hot dip galvanized steel sheet of high strength, and hot dip galvanized steel sheet of high strength |
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| JP2012251239A (en) * | 2011-05-12 | 2012-12-20 | Jfe Steel Corp | Vehicle collision energy-absorbing member excellent in collision energy-absorbing power and method for producing the same |
| JP2013194270A (en) * | 2012-03-19 | 2013-09-30 | Jfe Steel Corp | Method of manufacturing hot dip galvanized steel sheet of high strength, and hot dip galvanized steel sheet of high strength |
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