CN116837287A - Hot galvanizing low-alloy high-strength steel for automobile structure and production method thereof - Google Patents
Hot galvanizing low-alloy high-strength steel for automobile structure and production method thereof Download PDFInfo
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- CN116837287A CN116837287A CN202310758547.7A CN202310758547A CN116837287A CN 116837287 A CN116837287 A CN 116837287A CN 202310758547 A CN202310758547 A CN 202310758547A CN 116837287 A CN116837287 A CN 116837287A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 103
- 239000010959 steel Substances 0.000 title claims abstract description 103
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 33
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 23
- 239000000956 alloy Substances 0.000 title claims abstract description 23
- 238000005246 galvanizing Methods 0.000 title claims description 23
- 239000000126 substance Substances 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 238000005096 rolling process Methods 0.000 claims description 68
- 238000001816 cooling Methods 0.000 claims description 50
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 46
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 32
- 229910052725 zinc Inorganic materials 0.000 claims description 32
- 239000011701 zinc Substances 0.000 claims description 32
- 238000010438 heat treatment Methods 0.000 claims description 31
- 238000007670 refining Methods 0.000 claims description 29
- 238000000034 method Methods 0.000 claims description 27
- 229910052742 iron Inorganic materials 0.000 claims description 22
- 238000005266 casting Methods 0.000 claims description 20
- 238000010583 slow cooling Methods 0.000 claims description 20
- 230000008569 process Effects 0.000 claims description 19
- 238000003723 Smelting Methods 0.000 claims description 17
- 238000000137 annealing Methods 0.000 claims description 16
- 230000009467 reduction Effects 0.000 claims description 16
- 238000002791 soaking Methods 0.000 claims description 16
- 238000005097 cold rolling Methods 0.000 claims description 14
- 238000009749 continuous casting Methods 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 239000002253 acid Substances 0.000 claims description 11
- 238000006477 desulfuration reaction Methods 0.000 claims description 9
- 230000023556 desulfurization Effects 0.000 claims description 9
- 239000006185 dispersion Substances 0.000 claims description 8
- 238000010791 quenching Methods 0.000 claims description 8
- 230000000171 quenching effect Effects 0.000 claims description 8
- 238000010079 rubber tapping Methods 0.000 claims description 8
- 229910000859 α-Fe Inorganic materials 0.000 claims description 7
- 238000005098 hot rolling Methods 0.000 claims description 6
- 229910001567 cementite Inorganic materials 0.000 claims description 5
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 claims description 5
- 238000005554 pickling Methods 0.000 claims description 4
- 238000010276 construction Methods 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 238000009489 vacuum treatment Methods 0.000 claims description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000007689 inspection Methods 0.000 description 7
- 229910052786 argon Inorganic materials 0.000 description 6
- 238000007664 blowing Methods 0.000 description 6
- 238000009529 body temperature measurement Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 6
- 238000011065 in-situ storage Methods 0.000 description 6
- 238000012423 maintenance Methods 0.000 description 6
- 229910000922 High-strength low-alloy steel Inorganic materials 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 5
- 238000001035 drying Methods 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 229910000885 Dual-phase steel Inorganic materials 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 238000012356 Product development Methods 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- 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
- C21D1/26—Methods of annealing
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- 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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—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
- C21D2211/003—Cementite
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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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Coating With Molten Metal (AREA)
Abstract
The invention discloses hot dip galvanized low alloy high strength steel for an automobile structure and a production method thereof, wherein the provided hot dip galvanized low alloy high strength steel for the automobile structure comprises the following chemical components in percentage by mass: c: 0.06-0.08%, si: 0.02-0.04%, mn:0.40 to 0.65 percent, P is less than or equal to 0.020 percent, S is less than or equal to 0.008 percent, nb:0.025 to 0.040 percent, ti:0.010 to 0.020%, alt: 0.020-0.050%, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities. The mechanical property of the hot dip galvanized low alloy high strength steel for the automobile structure provided by the invention meets the requirement that the yield strength is 357-396 MPa, the tensile strength is 446-490 MPa, and the elongation is more than or equal to 25%.
Description
Technical Field
The invention belongs to the technical field of metallurgical plate production, and particularly relates to hot dip galvanized low-alloy high-strength steel for an automobile structure and a production method thereof.
Background
At present, most of the parts used in domestic automobiles are formed by stamping, and according to statistics, about 700 stamping parts are assembled from a body panel such as a cover plate, a door and the like to internal components such as a beam, a supporting plate and the like, namely, a plurality of parts are formed in a combined mode, so that the requirements on the formability of the steel plate are higher for improving the safety and the overall performance of the automobiles. On the premise of meeting the requirements of reducing the vehicle weight, reducing the oil consumption, reducing the emission and stabilizing the manufacturing cost, the utilization of high-strength low-alloy steel to replace common carbon steel is a necessary choice under the condition of energy shortage and serious environmental pollution at present. The high-strength low-alloy steel has better comprehensive performance by using lower alloy elements, and the yield strength is about 3 times that of common carbon steel, so that the high-strength low-alloy steel can greatly save steel consumption and reduce the pressure on resources, energy sources and environment.
The galvanized low-alloy high-strength steel product for the automobile structure not only has higher strength, good welding performance and cold stamping forming performance, but also can effectively improve the corrosion resistance of the automobile body, is mainly applied to manufacturing automobile structural members, reinforcing members, supporting members and the like, has lower cost compared with the dual-phase steel because the strength grade of the galvanized low-alloy high-strength steel product is between carbon structural steel and the dual-phase steel, and gradually increases the market demand of the galvanized low-alloy high-strength steel along with the vigorous development of the automobile industry in China and the continuous promotion of energy conservation and emission reduction work.
Patent publication No. CN 107739993A discloses a production method of an electro-galvanized high-strength low-alloy steel plate H340 LA+ZE for automobiles, which mainly comprises the following production processes: smelting molten steel and casting into a plate blank, hot continuous rolling, cold continuous rolling, continuous annealing, leveling and electrogalvanizing. The main production process of the invention comprises hot rolling, acid rolling, continuous annealing, hot galvanizing, finishing, withdrawal and straightening, passivation, coiling and finished product production. The invention adopts electrogalvanizing, which only coats zinc on the surface of the metal original piece through electrolysis, so that the metal original piece is easy to fall off; the zinc layer of the electrogalvanized film has a thickness of less than 35 mu m and has poor corrosion resistance.
Patent publication No. CN 103469065A discloses 340MPa grade HSLA steel for automobile structure and a production method thereof, and the main production process is as follows: steelmaking, continuous casting, hot rolling, pickling, continuous rolling, hood annealing and leveling. Patent publication No. CN 104250703A discloses 340MPa grade cold-rolled low-alloy high-strength steel and a manufacturing method thereof, and the main production process is as follows: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, LF molten steel refining treatment, CSP sheet billet continuous casting and rolling, pickling and cold continuous rolling, bell-type furnace annealing, leveling, inspection, packaging and warehousing. Both adopt the cover annealing process, which is only limited to the production of soft steel plates, and has the advantages of long production period, low efficiency, unstable performance, easy generation of quality defects such as adhesion, flanging and the like, and is only suitable for small-batch production; the other two are cold-rolled products, and the corrosion resistance is poor.
Disclosure of Invention
Aiming at one or more problems in the prior art, one aspect of the invention provides hot dip galvanized low alloy high strength steel for an automobile structure, which comprises the following chemical components in percentage by mass: c: 0.06-0.08%, si: 0.02-0.04%, mn:0.40 to 0.65 percent, P is less than or equal to 0.020 percent, S is less than or equal to 0.008 percent, nb:0.025 to 0.040 percent, ti:0.010 to 0.020%, alt: 0.020-0.050%, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities.
In some embodiments, the microstructure of the hot dip galvanized low alloy high strength steel for automobile structure is mainly composed of ferrite and free cementite, wherein ferrite grains are equiaxed grains, the free cementite is dispersed in the ferrite grains or at grain boundaries in a granular form, and the mechanical properties are as follows: the yield strength is 357-396 MPa, the tensile strength is 446-490 MPa, and the elongation is more than or equal to 25%.
The invention also provides a production method of the hot dip galvanized low alloy high strength steel for the automobile structure, which comprises the following process steps: smelting, continuous casting, hot rolling, acid rolling, continuous annealing, hot galvanizing, finishing and straightening; wherein:
the smelting-continuous casting process comprises the following steps: KR desulfurization, converter, LF refining, RH vacuum treatment, slab continuous casting and slow cooling; wherein the molten steel composition of the casting machine comprises C: 0.06-0.08%, si: 0.02-0.04%, mn: 0.40-0.65%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, nb:0.025 to 0.040 percent, ti:0.010 to 0.020%, alt: 0.020-0.050%, ca:0.0008 to 0.0020 percent;
the hot rolling process comprises the following steps: heating a casting blank, rough rolling, finish rolling, cooling and coiling; wherein the tapping temperature of the casting blank is 1215+/-20 ℃, the rough rolling is performed by adopting a 3+3 mode 2-frame rolling mill, the finish rolling is performed by adopting a 7-frame continuous variable convexity rolling mill, and the thickness of an intermediate blank is 40-45mm; the initial rolling temperature of the finish rolling is 1030+/-20 ℃, the final rolling temperature of the finish rolling is 870+/-20 ℃, and the thickness of the hot rolled steel strip is 2.3-5.0mm; the cooling adopts laminar flow cooling equipment and a front dispersion cooling mode, the cooling speed is 20+/-5 ℃/s, and the coiling temperature is 570+/-15 ℃;
the acid rolling process specifically comprises the following steps: pickling the hot rolled steel strip, removing surface iron scales, and then cold-rolling the hot rolled steel strip by a 5-frame cold rolling mill until the cold rolling reduction is 58-76%, wherein the cold rolling reduction is 0.6-1.8 mm, thereby obtaining cold-rolled hard coil steel;
the hot galvanizing process specifically comprises the following steps: continuously annealing and hot dip galvanizing the cold and hard coil steel by heating after uncoiling, wherein the heating temperature and the soaking temperature are 780+/-15 ℃, the heating time is 80-120s, the soaking time is 80-120s, the slow cooling temperature is 630+/-15 ℃, the slow cooling speed is 5 ℃/s, the fast cooling temperature is 465+/-10 ℃, the fast cooling speed is 25-30 ℃/s, the temperature of the cold and hard coil steel is 460+/-10 ℃ when entering a zinc pot, the cold and hot dip galvanizing are carried out after the cold and hot dip galvanizing is carried out, the cold and hot dip galvanizing is carried out after the cold and hot dip galvanizing is carried out, the heating time is 80-120s, the slow cooling temperature is 630+/-15 ℃, the slow cooling speed is 5 ℃/s, the fast cooling speed is 25+/-30 ℃/s, the zinc pot temperature is 460+/-10 ℃, the zinc pot is cooled to below 240 ℃ after the cold and the cold dip galvanized and the cold coil steel is dried to the room temperature by water quenching;
the finishing and withdrawal straightening process specifically comprises the following steps: the finishing elongation is 0.8-1.5%, and the withdrawal elongation is 0.2-0.4%.
According to the hot dip galvanized low alloy high strength steel for the automobile structure, which is provided by the technical scheme, on the basis of low carbon steel, microalloy elements Nb and Ti are added, and the product has good toughness, cold forming performance and welding performance in the modes of fine grain strengthening, precipitation strengthening and the like. The mechanical property meets the requirement, the yield strength is 357-396 MPa, the tensile strength is 446-490 MPa, the elongation is more than or equal to 25%, and meanwhile, the hot dip galvanized product produced by the invention has the advantages of excellent surface quality, strong corrosion resistance, low production cost and simple preparation method, and is suitable for industrial production. In addition, the production process is continuous annealing, can produce soft steel plates and high-strength steel plates with higher grades, has obvious product development advantages, continuous production, short production period, high efficiency, good product quality, flat and straight plate shape, smooth surface, uniform performance, high yield and diversified varieties, and is suitable for mass production.
Drawings
FIG. 1 is a microstructure of a hot dip galvanized low alloy high strength steel for automobile construction produced in example 1.
Detailed Description
The invention aims to provide hot dip galvanized low alloy high strength steel for an automobile structure and a production method thereof.
The following describes the invention in detail by way of specific examples, which are intended to aid in understanding the invention and are not intended to limit the invention.
Example 1
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at a temperature of 1653 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1565 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 26 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. And heating the plate blank at 1208 ℃ for 235min, and removing phosphorus from the heated plate blank by high-pressure water. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1030 ℃, the finish rolling finishing temperature is 875 ℃, and the thickness of the finished product is 2.5mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel belt is reduced to 575 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 76%, and the rolling reduction rate is 0.6mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 85m/min, the heating temperature and the soaking temperature are 768 ℃, the heating time is 85-120 s, and the soaking time is 85-120 s; the slow cooling temperature is 640 ℃, the slow cooling speed is 5 ℃/s, and the time is 13-15 s; the rapid cooling temperature is 465 ℃, the rapid cooling speed is 22 ℃/s, and the time is 8-12 s; the zinc is put into a zinc pot at 460 ℃ for 25 to 30 seconds, cooled to below 240 ℃ at 16 ℃/s after being taken out of the zinc pot, and then dried to room temperature through water quenching; the finishing elongation was 0.8% and the withdrawal elongation was 0.2%, and finally the product properties were examined as shown in Table 2 below. As shown in fig. 1, a microstructure of the hot-dip galvanized low alloy high strength steel for automobile construction obtained in this example is shown, and it can be seen that the microstructure is ferrite and free cementite.
Example 2
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1643 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1563 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 30 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1216 ℃, the heating time is 227min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The initial rolling temperature of the finish rolling is 1035 ℃, the final rolling temperature of the finish rolling is 886 ℃, and the thickness of the finished product is 2.7mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel strip is reduced to 572 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 70%, and the rolling reduction rate is 0.8mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 86m/min, the heating temperature and the soaking temperature are 786 ℃, the heating time is 85-120 s, and the soaking time is 85-120 s; the slow cooling temperature is 632 ℃, the slow cooling speed is 6 ℃/s, and the time is 13-15 s; the rapid cooling temperature is 463 ℃, the rapid cooling speed is 26 ℃/s, and the time is 8-10 s; feeding the zinc into a zinc pot at 462 ℃ for 25-30 s, cooling the zinc to below 240 ℃ at 16 ℃/s after the zinc is discharged from the zinc pot, and then carrying out water quenching and drying to room temperature; the finishing elongation was 0.8% and the withdrawal elongation was 0.2%, and finally the product properties were examined as shown in Table 2 below.
Example 3
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1645 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1564 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 28 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The slab is heated at 1222 ℃ for 225min, and the heated slab is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1038 ℃, the finish rolling temperature is 868 ℃, and the thickness of the finished product is 3.0mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel strip is reduced to 576 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 67%, and the rolling reduction rate is 1.0mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 90m/min, the heating temperature and the soaking temperature are 783 ℃, the heating time is 85-120 s, and the soaking time is 85-120 s; slow cooling temperature 635 ℃, slow cooling speed 6 ℃/s and time 13-15 s; the rapid cooling temperature is 462 ℃, the rapid cooling speed is 25 ℃/s, and the time is 8-10 s; putting the zinc into a zinc pot at 458 ℃ for 25-30 s, cooling the zinc to below 240 ℃ at 16 ℃/s after taking the zinc out of the zinc pot, and then carrying out water quenching and drying to room temperature; the finishing elongation was 0.9% and the withdrawal elongation was 0.3%, and finally the product properties were measured as shown in Table 2 below.
Example 4
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1646 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1562 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 27 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1228 ℃ and the heating time is 230min, and the heated plate blank is dephosphorized by high-pressure water. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1026 ℃, the finish rolling finishing temperature is 872 ℃, and the thickness of the finished product is 3.2mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel belt is reduced to 580 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 63%, and the rolling reduction rate is 1.2mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 82m/min, the heating temperature and the soaking temperature are 785 ℃, the heating time is 85-120 s, and the soaking time is 85-120 s; the slow cooling temperature is 630 ℃, the slow cooling speed is 6 ℃/s, and the time is 13-15 s; the rapid cooling temperature is 463 ℃, the rapid cooling speed is 28 ℃/s, and the time is 8-10 s; feeding the zinc into a zinc pot at 462 ℃ for 25-30 s, cooling the zinc to below 240 ℃ at 16 ℃/s after the zinc is discharged from the zinc pot, and then carrying out water quenching and drying to room temperature; the finishing elongation was 1.2% and the withdrawal elongation was 0.3%, and finally the product properties were examined as shown in Table 2 below.
Example 5
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at a temperature of 1652 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1563 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 30 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1230 ℃, the heating time is 223min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1027 ℃, the finish rolling temperature is 883 ℃ and the thickness of the finished product is 3.6mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel belt is reduced to 565 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 61%, and the rolling reduction rate is 1.4mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 80m/min, the heating temperature and soaking temperature are 782 ℃, the heating time is 85-120 s, and the soaking time is 85-120 s; slow cooling temperature 633 deg.c, slow cooling speed 6 deg.c/s and time 13-15 s; the rapid cooling temperature is 465 ℃, the rapid cooling speed is 25 ℃/s, and the time is 8-10 s; the zinc is put into a zinc pot at 460 ℃ for 25 to 30 seconds, cooled to below 240 ℃ at 16 ℃/s after being taken out of the zinc pot, and then dried to room temperature through water quenching; the finishing elongation was 1.3% and the withdrawal elongation was 0.3%, and finally the product properties were examined as shown in Table 2 below.
Example 6
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1645 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1560 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 28 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1216 ℃, the heating time is 235min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1028 ℃, the finish rolling temperature is 866 ℃, and the thickness of the finished product is 4.3mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel strip is reduced to 578 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 58%, and the rolling thickness is 1.8mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 87m/min, the heating temperature and the soaking temperature are 780 ℃, the heating time is 85-120 s, and the soaking time is 85-120 s; slowly cooling at 636 ℃ at a speed of 6 ℃/s for 13-15 s; the rapid cooling temperature is 462 ℃, the rapid cooling speed is 26 ℃/s, and the time is 8-10 s; the zinc is put into a zinc pot at 460 ℃ for 25 to 30 seconds, cooled to below 240 ℃ at 16 ℃/s after being taken out of the zinc pot, and then dried to room temperature through water quenching; the finishing elongation was 1.5% and the withdrawal elongation was 0.4%, and finally the product properties were examined as shown in Table 2 below.
Comparative example 1
The production process was as described in example 1, except that the chemical composition for the casting machine for the external refining of LF furnace was different from that used in example 1, as shown in Table 1 below. Finally, product performance was tested as shown in table 2 below.
Comparative example 2
The production process was as described in example 6, except that the LF external refining was used for the caster chemistry different from that used in example 6, as shown in Table 1 below. Finally, product performance was tested as shown in table 2 below.
Table 1: chemical Components (wt%) of examples 1-6 and comparative examples 1-2 of the present invention
| Examples | C | Si | Mn | P | S | Nb | Ti | Alt | Ca |
| 1 | 0.060 | 0.02 | 0.65 | 0.015 | 0.003 | 0.030 | 0.010 | 0.030 | 0.0018 |
| 2 | 0.070 | 0.03 | 0.45 | 0.016 | 0.005 | 0.028 | 0.020 | 0.032 | 0.0020 |
| 3 | 0.078 | 0.04 | 0.58 | 0.017 | 0.002 | 0.035 | 0.015 | 0.035 | 0.0016 |
| 4 | 0.075 | 0.03 | 0.40 | 0.014 | 0.003 | 0.032 | 0.018 | 0.038 | 0.0014 |
| 5 | 0.066 | 0.02 | 0.46 | 0.016 | 0.002 | 0.027 | 0.013 | 0.037 | 0.0018 |
| 6 | 0.080 | 0.04 | 0.52 | 0.015 | 0.003 | 0.040 | 0.016 | 0.032 | 0.0015 |
| Comparative example 1 | 0.060 | 0.02 | 0.85 | 0.015 | 0.003 | 0.030 | 0.010 | 0.030 | 0.0018 |
| Comparative example 2 | 0.080 | 0.04 | 0.52 | 0.015 | 0.003 | 0 | 0 | 0.032 | 0.0015 |
Table 2: mechanical Properties of the Steel coil of examples 1 to 6 and comparative examples 1 to 2 of the present invention
| Examples | Yield strength R p0.2 (MPa) | Tensile strength R m (MPa) | Elongation A 80 (％) |
| Example 1 | 396 | 490 | 25 |
| Example 2 | 370 | 463 | 29 |
| Example 3 | 382 | 478 | 26 |
| Example 4 | 357 | 446 | 33 |
| Example 5 | 365 | 456 | 31 |
| Example 6 | 378 | 473 | 28 |
| Comparative example 1 | 436 | 540 | 19 |
| Comparative example 2 | 325 | 418 | 35 |
| EN 10346-2015 | 340～420 | 410～520 | ≥21 |
From the descriptions in tables 1 and 2, it is clear that the steel grade meets the requirements of high strength and excellent cold forming property of steel for automobile structures, and meanwhile, the hot dip galvanized product produced by the invention has the advantages of excellent surface quality, low production cost and simple preparation method, is suitable for industrial production, and meets the EN 10346-2015 standard requirements and the use requirements of users.
The mechanical properties of the hot dip galvanized low alloy high strength steel for the automobile structure provided by the invention can be as follows: the yield strength is 357-396 MPa, the tensile strength is 446-490 MPa, the elongation is more than or equal to 25%, the steel grade has higher strength, good formability, welding performance, corrosion resistance and other comprehensive properties, and meanwhile, the surface quality of the hot dip galvanized product produced by the invention is good, and the standard requirement and the user requirement are met. According to the results of comparative examples 1-2, when the content of the chemical components, particularly the content of the alloy elements, fails to meet the requirements of the predetermined mechanical properties, for example, the strength of the product obtained when the Mn content in comparative example 1 is out of range is higher than the required value and the elongation is lower than the required value, so that the product is easy to crack and fail in use; the strength of the product obtained without adding Nb and Ti in comparative example 2 did not meet the standard requirements.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or that equivalents may be substituted for part of the technical features thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. The hot dip galvanized low alloy high strength steel for the automobile structure comprises the following chemical components in percentage by mass: c: 0.06-0.08%, si: 0.02-0.04%, mn:0.40 to 0.65 percent, P is less than or equal to 0.020 percent, S is less than or equal to 0.008 percent, nb:0.025 to 0.040 percent, ti:0.010 to 0.020%, alt: 0.020-0.050%, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities.
2. The low alloy, high strength steel for hot dip galvanization for automotive construction according to claim 1, wherein the microstructure is mainly composed of ferrite and free cementite, wherein ferrite grains are equiaxed grains, the free cementite is dispersed in the ferrite grains or at grain boundaries in the form of grains, and the mechanical properties are as follows: the yield strength is 357-396 MPa, the tensile strength is 446-490 MPa, and the elongation is more than or equal to 25%.
3. The method for producing a hot dip galvanized low alloy high strength steel for automotive structures as claimed in claim 1 or 2, comprising the following process steps: smelting, continuous casting, hot rolling, acid rolling, continuous annealing, hot galvanizing, finishing and straightening; wherein:
the smelting-continuous casting process comprises the following steps: KR desulfurization, converter, LF refining, RH vacuum treatment, slab continuous casting and slow cooling; wherein the molten steel composition of the casting machine comprises C: 0.06-0.08%, si: 0.02-0.04%, mn: 0.40-0.65%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, nb:0.025 to 0.040 percent, ti:0.010 to 0.020%, alt: 0.020-0.050%, ca:0.0008 to 0.0020 percent;
the hot rolling process comprises the following steps: heating a casting blank, rough rolling, finish rolling, cooling and coiling; wherein the tapping temperature of the casting blank is 1215+/-20 ℃, the rough rolling is performed by adopting a 3+3 mode 2-frame rolling mill, the finish rolling is performed by adopting a 7-frame continuous variable convexity rolling mill, and the thickness of an intermediate blank is 40-45mm; the initial rolling temperature of the finish rolling is 1030+/-20 ℃, the final rolling temperature of the finish rolling is 870+/-20 ℃, and the thickness of the hot rolled steel strip is 2.3-5.0mm; the cooling adopts laminar flow cooling equipment and a front dispersion cooling mode, the cooling speed is 20+/-5 ℃/s, and the coiling temperature is 570+/-15 ℃;
the acid rolling process specifically comprises the following steps: pickling the hot rolled steel strip, removing surface iron scales, and then cold-rolling the hot rolled steel strip by a 5-frame cold rolling mill until the cold rolling reduction is 58-76%, wherein the cold rolling reduction is 0.6-1.8 mm, thereby obtaining cold-rolled hard coil steel;
the hot galvanizing process specifically comprises the following steps: continuously annealing and hot dip galvanizing the cold and hard coil steel by heating after uncoiling, wherein the heating temperature and the soaking temperature are 780+/-15 ℃, the heating time is 80-120s, the soaking time is 80-120s, the slow cooling temperature is 630+/-15 ℃, the slow cooling speed is 5 ℃/s, the fast cooling temperature is 465+/-10 ℃, the fast cooling speed is 25-30 ℃/s, the temperature of the cold and hard coil steel is 460+/-10 ℃ when entering a zinc pot, the cold and hot dip galvanizing are carried out after the cold and hot dip galvanizing is carried out, the cold and hot dip galvanizing is carried out after the cold and hot dip galvanizing is carried out, the heating time is 80-120s, the slow cooling temperature is 630+/-15 ℃, the slow cooling speed is 5 ℃/s, the fast cooling speed is 25+/-30 ℃/s, the zinc pot temperature is 460+/-10 ℃, the zinc pot is cooled to below 240 ℃ after the cold and the cold dip galvanized and the cold coil steel is dried to the room temperature by water quenching;
the finishing and withdrawal straightening process specifically comprises the following steps: the finishing elongation is 0.8-1.5%, and the withdrawal elongation is 0.2-0.4%.
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