CN112593146A - 450 MPa-grade steel for automobile structure and production method thereof - Google Patents
450 MPa-grade steel for automobile structure and production method thereof Download PDFInfo
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- 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
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention relates to 450 MPa-grade steel for an automobile structure and a production method thereof, wherein the steel for the structure comprises the following chemical components in percentage by mass: c: 0.065% -0.075%, Si: 0.09% -0.25%, Mn: 0.90% -1.40%, Al: 0.025 to 0.050%, Nb: 0.030-0.045%, Ti: 0.020-0.038%, Cr: 0.11-0.27%, rare earth Ce: 0.002% -0.012%, Cu: 0.60% -0.80%, Sb: 0.054% -0.11%, Bi: 0.015-0.045%, P less than or equal to 0.015%, S less than or equal to 0.006%, and the balance of Fe and inevitable impurities. The advantages are that: the invention has excellent mechanical property and corrosion resistance, and is used for steel for automobile structures.
Description
Technical Field
The invention belongs to the field of production of steel for automobile structures, and particularly relates to 450 MPa-grade steel for automobile structures and a production method thereof.
Background
With the rapid development of the automobile industry and the transportation industry in China, the demand of large-tonnage trucks is particularly increased continuously, the purposes of reducing the weight of automobile structural parts to reduce the self weight, saving energy, reducing environmental pollution and improving carrying efficiency are achieved, and the application of high-performance and high-surface-quality hot-rolled automobile steel plates is promoted. The modern automobile industry generally adopts the protection measures for the corrosion of the steel plate to plate zinc on the surface of the steel plate or brush coating anti-corrosion paint, and the automobile steel plate does not have the anti-corrosion performance. Once the anticorrosive coating falls off, the steel plate can be corroded rapidly, so that the steel plate is invalid in use, and the anticorrosive coating can pollute the environment and destroy the ecological environment. Therefore, the hot-rolled steel for automobile structure, which has high corrosion resistance and high surface quality, has improved service life and can occupy the domestic market of steel for automobile structure, has been developed.
The steel plate with the yield strength of more than or equal to 450MPa, the tensile strength of more than or equal to 560MPa and the transverse elongation A of more than or equal to 30 percent is applied more frequently. In the prior art, Chinese patent application with publication number CN 107641760A discloses a 460 MPa-grade hot-rolled automobile structural steel plate with good fatigue performance and a manufacturing method thereof, a hot-rolled steel plate produced by adding a certain amount of Nb and Ti is designed by utilizing a common C-Mn component system, S, N in steel is fixed by utilizing trace Ti, and the fine grain function of Nb and Ti is fully exerted. But the elongation of the steel plate is up to 22 percent, which does not meet the requirement of high-forming automobile parts and has no corrosion resistance.
The Chinese patent application with publication number CN 107723607A discloses a 420 MPa-grade hot-rolled automobile structural steel plate with excellent cold-forming performance and a manufacturing method thereof, a hot-rolled steel plate produced by adding a certain amount of Nb and Ti is designed by utilizing a common C-Mn component system, S, N in steel is fixed by utilizing trace Ti, the fine grain function of Nb is fully exerted, but the elongation of the steel plate is up to 25 percent, the steel plate does not meet the requirement of high-forming automobile parts, and the steel plate has no corrosion resistance.
Chinese patent application with publication number CN 105369134B discloses a 400 MPa-grade acid-washing-free hot rolled steel plate for an automobile structure and a production method thereof, the hot rolled steel plate is designed by a common C-Mn component system, the strength is improved by solid solution strengthening of carbon and manganese elements, but the yield strength of the steel plate is 311MPa at most, the steel plate does not meet the requirement of high-strength formed automobile parts, and the steel plate has no corrosion resistance.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide 450 MPa-grade steel for automobile structures and a production method thereof, the steel plate has the yield strength of more than or equal to 450MPa, the tensile strength of more than or equal to 560MPa and the transverse elongation A of more than or equal to 30 percent, has the corrosion resistance, and meets the production requirement of high-strength formed automobile parts.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the 450 MPa-grade steel for the automobile structure comprises the following chemical components in percentage by mass:
c: 0.065% -0.075%, Si: 0.09% -0.25%, Mn: 0.90% -1.40%, Al: 0.025 to 0.050%, Nb: 0.030-0.045%, Ti: 0.020-0.038%, Cr: 0.11-0.27%, rare earth Ce: 0.002% -0.012%, Cu: 0.60% -0.80%, Sb: 0.054% -0.11%, Bi: 0.015-0.045%, P is less than or equal to 0.015%, S is less than or equal to 0.006%, and the balance is Fe and inevitable impurities; 25 to 35 percent of ferrite, 55 to 65 percent of pearlite and 7 to 10 percent of bainite by volume percent.
The yield strength of the steel for the structure is more than or equal to 450MPa, the tensile strength is more than or equal to 560MPa, and the transverse elongation A is more than or equal to 30%.
Wherein, the main functions of the chemical components are as follows:
c: carbon is the most important solid solution strengthening element in steel and guarantees the strength of the steel. In view of excellent cold press formability and weldability and dimensional stability after cold pressing, the carbon content cannot be excessively high, and too low a carbon content does not exert a solid solution strengthening effect, and therefore, the carbon content is selected in the range of 0.065% to 0.075%.
Si: silicon is a solid-solution strengthening element and can contribute to the strength of the steel sheet. However, too high a silicon in the steel affects the hot rolled surface quality. Therefore, the content of silicon is 0.09% to 0.25%.
Mn: manganese can form a substitutional solid solution in steel, so that a strong solid solution strengthening effect is achieved, the yield strength and the tensile strength are linearly increased, the steel strength is increased within a certain range, the plasticity and the toughness of the steel are hardly reduced, and the carbon equivalent of the steel can be increased due to the excessively high manganese content. Therefore, the manganese content is selected to be 0.90-1.40%.
Al: al is a common deoxidizer in steel, a small amount of Al is added into the steel, AlN can be formed to be precipitated, a certain grain refining effect is achieved, the Al also has oxidation resistance and corrosion resistance, the combination of the Al, Cr and Si can obviously improve the high-temperature non-peeling performance of the steel and the surface quality of a steel plate, and the Al is too high and is easy to form oxide inclusions, so that the content of the Al is limited to 0.025-0.050%.
P: phosphorus increases the temperature at which the alpha phase is formed, and expands the temperature range over which the alpha phase is formed. However, the content of phosphorus is too high, which deteriorates the workability of the steel sheet, and is limited to 0.015% for obtaining a high elongation.
S: since sulfur forms sulfide inclusions such as MnS and becomes a starting point of cracks to deteriorate workability, the content is preferably as small as 0.006%.
Nb: niobium can effectively delay recrystallization of deformed austenite, prevent austenite grains from growing, increase austenite recrystallization temperature, refine grains, and improve strength and toughness of steel, and is a strong carbon and nitride forming element which can be combined with carbon and nitrogen to form stable and fine carbon and nitride to play a significant role in precipitation strengthening, and the addition of Nb increases recrystallization termination temperature, so that the finish rolling temperature can be carried out at a higher temperature, and the load of a rolling mill is reduced, therefore, the optimal range of the niobium content is between 0.030% and 0.045%.
Ti: is a strong carbide forming element, and adds a trace amount of Ti into the steel, the formed TiC can prevent austenite grains from excessively growing when the steel billet is heated, thereby achieving the purpose of refining the original austenite grains. Ti can also exist in the form of second phase particles in the steel to play a role in precipitation strengthening, so that the addition amount of Ti is 0.020-0.038%.
Cr: is a carbide forming element, can delay pearlite transformation and improve the hardenability of the steel. Thereby being beneficial to the formation of bainite structure, refining the structure and playing a role in strengthening. If the chromium content is too high, the workability and formability of the material will be deteriorated. The chromium content is selected in such a way that the formation of bainite is promoted, and therefore, the chromium content is selected to be 0.11% to 0.27%.
Rare earth Ce: the steel plate has strong deoxidation and desulfurization capability, and the formed spherical sulfide or oxysulfide replaces long-strip manganese sulfide inclusions, so that the plasticity and anisotropy of the steel plate can be improved. The rare earth Ce has strong affinity with other impurity elements in the steel, can reduce the contents of elements such as sulfur, oxygen, phosphorus, hydrogen and the like in the steel, and eliminates the harmful effect of the elements. Meanwhile, rare earth Ce can also delay austenite transformation. Therefore, the content of the rare earth Ce is selected to be 0.002% -0.012%.
Cu: the copper element can enlarge an austenite phase region, improve the weather resistance of steel, improve the weldability of the steel and effectively improve the corrosion resistance of the steel, but causes hot brittleness when the Cu content is high, the surface performance of the steel plate is deteriorated, in addition, the copper element is beneficial to the strength and the hot workability of the steel plate under a certain Cu content, the hot rolling edge crack tendency of the steel plate is effectively reduced, and the surface quality of the steel plate is obviously improved. Cu also has the effect of reducing work hardening and improving the plasticity of the steel sheet. Therefore, the copper content is selected to be between 0.60% and 0.80%.
Sb: the antimony element is mainly distributed in the crystal boundary and the crystal grain in the steel, so that the strength of the steel plate is improved, the diffusion rate of elements such as carbon, oxygen and the like on the crystal boundary is reduced, the decarburization and the oxidation phenomena are reduced, the surface and the mechanical property of the steel plate are improved, and the addition of the antimony can promote the surface of a steel plate matrix to form a uniform and compact oxide film (rich in elements such as Sb, Cu, Cr and the like), so that the moisture and oxygen in the air can be effectively prevented from continuously entering the matrix to form a corrosive internal environment, the corrosion resistance of the matrix is improved, and the corrosion. The Sb content is too low, so that the passive film is not uniformly dispersed and the integral corrosion resistance effect cannot be achieved; when the content exceeds the upper design limit, the corrosion prevention effect is achieved, but the hot workability is obviously reduced, so that the Sb content is limited to 0.054-0.11%.
Bi: the bismuth is mainly distributed in the crystal boundary and the crystal grain in the steel, so that the strength of the steel plate is improved, the diffusion rate of elements such as carbon, oxygen and the like on the crystal boundary is reduced, the decarburization and the oxidation phenomena are reduced, and the surface and the mechanical property of the steel plate are improved. Therefore, the Bi content is limited to 0.015% to 0.045%.
A production method of 450 MPa-grade steel for automobile structures comprises smelting, heating and rolling processes, wherein the rolling process adopts 6 racks for finish rolling production, and the specific production method comprises the following steps:
1) a heating process: directly hot-charging (170) 230mm thick x (1550-1880) mm wide continuous casting slabs into a heating furnace for heating, wherein the hot charging temperature is more than 750 ℃, the preheating section is preheated at the furnace gas temperature of 800-1000 ℃, the preheating time is 25-30 min, the temperatures of the heating 1 section and the heating 2 section are respectively controlled at 1120-1200 ℃ and 1210-1240 ℃, the total soaking time of the heating 1 section and the heating 2 section is 15-20 min, the temperature of the heating 1 section is 1220-1240 ℃, the soaking time is 65-110 min, the furnace pressure is in a micro-positive pressure state, and the positive pressure value is controlled at 3-15 Pa;
2) the rolling process comprises the following steps: the rough rolling adopts 6-pass rolling and 3-pass descaling processes, the first rough rolling mill R1 descales 1, 3 and 5 passes, the upper row and the lower row of water spray headers of a descaling box are simultaneously opened, the pressure of a high-pressure water outlet is 21-30 MPa, the temperature of the rough rolling outlet is 1070-1100 ℃, the thickness of an intermediate blank is 30-40 mm, the width is 1550-1880 mm, the intermediate blank is subjected to heat preservation by a heat preservation cover before entering a hot rolling finishing mill set, the finish rolling is 6-stand continuous rolling, the high-pressure water descaling before the finish rolling, the temperature of a finish rolling inlet is not higher than 1060 ℃, the finish rolling temperature is 890 ℃, the finish rolling adopts finish rolling with large tension, meanwhile, the F5 and F6 stands adopt 21-30 MPa of high water pressure to descale, and cooling water between the rest; the convexity control precision of the steel plate is +/-13 mu m, the flatness is controlled within 25I, the thickness control precision is +/-25 mu m, and the thickness of a finished product is 3-10 mm.
The finish rolling in the step 2) adopts high-tension rolling:
the tension between the frames of the first frame finishing mill F1 and the second frame finishing mill F2 is controlled to be 7-14N/mm2The tension between the frames of the second finishing mill F2 and the third finishing mill F3 is controlled to be 13-22N/mm2The tension between the stands of the third finishing mill F3 and the fourth finishing mill F4 is controlled to be 13-20N/mm2The tension between the stands of the fourth finishing mill F4 and the fifth finishing mill F5 is controlled to be 8-18N/mm2The tension between the frames of the fifth finishing mill F5 and the sixth finishing mill F6 is controlled to be 6-12N/mm2。
The method also comprises a cooling process: and after the final rolling, adopting front-section rapid continuous laminar cooling, wherein the cooling rate is 22-45 ℃/s.
Further comprising a coiling temperature: the coiling temperature is 600-640 ℃.
Compared with the prior art, the invention has the beneficial effects that:
1. the addition of Nb increases the recrystallization termination temperature, so that the finish rolling temperature can be carried out at a higher temperature, and the load of a rolling mill is reduced;
2. rare earth Ce: the steel plate has strong deoxidation and desulfurization capacities, and the formed spherical sulfide or oxysulfide replaces long-strip manganese sulfide inclusions, so that the plasticity and anisotropy of the steel plate can be improved;
3. the addition of Cu expands an austenite phase region, improves the weather resistance of steel, improves the weldability of steel and can also effectively improve the corrosion resistance of steel;
4. the addition of Sb can reduce the diffusion rate of elements such as carbon, oxygen and the like on a crystal boundary, reduce the phenomena of decarburization and oxidation, improve the surface and the mechanical property of the steel plate, and promote the surface of a steel plate matrix to form a layer of uniform and compact oxide film (rich in elements such as Sb, Cu, Cr and the like) by the addition of Sb, so that air moisture and oxygen can be effectively prevented from continuously entering the matrix to form a corrosive internal environment, the corrosion resistance of the matrix is improved, and the corrosion resistance of the steel plate is enhanced;
5. bi: the bismuth is mainly distributed in the crystal boundary and the crystal grain in the steel, so that the strength of the steel plate is improved, the diffusion rate of elements such as carbon, oxygen and the like on the crystal boundary is reduced, the decarburization and the oxidation phenomena are reduced, and the surface and the mechanical property of the steel plate are improved.
6. And a front-section rapid continuous cooling process is adopted after rolling, so that the generation of a band-shaped structure in a steel plate is avoided.
7. The invention has excellent mechanical property and corrosion resistance, is used for steel for automobile structures, and has yield strength of more than or equal to 450MPa, tensile strength of more than or equal to 560MPa and transverse elongation A of more than or equal to 30 percent.
Detailed Description
The present invention is described in detail below, but it should be noted that the practice of the present invention is not limited to the following embodiments.
The 450 MPa-grade steel for the automobile structure comprises the following chemical components in percentage by mass:
c: 0.065% -0.075%, Si: 0.09% -0.25%, Mn: 0.90% -1.40%, Al: 0.025 to 0.050%, Nb: 0.030-0.045%, Ti: 0.020-0.038%, Cr: 0.11-0.27%, rare earth Ce: 0.002% -0.012%, Cu: 0.60% -0.80%, Sb: 0.054% -0.11%, Bi: 0.015-0.045%, P is less than or equal to 0.015%, S is less than or equal to 0.006%, and the balance is Fe and inevitable impurities; 25 to 35 percent of ferrite, 55 to 65 percent of pearlite and 7 to 10 percent of bainite by volume percent. The yield strength of the steel for the structure is more than or equal to 450MPa, the tensile strength is more than or equal to 560MPa, and the transverse elongation A is more than or equal to 30%.
The production method of the 450 MPa-grade steel for the automobile structure adopts the chemical components, and the steel is produced through smelting, heating and rolling processes, wherein the rolling process adopts 6 stands for finish rolling production, and the specific manufacturing method comprises the following steps:
(1) a heating process: directly hot-charging the (170) and 230mm thick x (1550-1880) mm wide continuous casting plate blank into a stepping heating furnace for heating, wherein the hot-charging temperature is more than 750 ℃, the preheating section is preheated at the furnace gas temperature of 800-1000 ℃, the preheating time is 25-30 min, the temperatures of the heating section 1 and the heating section 2 are respectively controlled at 1120-1200 ℃, 1210-1240 ℃, the heating time is 15-20 min, (the heating time of the heating section 1 and the heating section 2), the temperature of the soaking section is 1220-1240 ℃, the soaking time is 65-110 min, the furnace pressure is in a micro-positive pressure state (3-12 Pa), and the oxidation burning loss is reduced. The proper heating temperature and the proper heat preservation time enable alloy elements in the plate blank to be completely dissolved in solid solution and the plate blank components to be uniform, and the effects of controlling the size of original austenite grains, saving energy and the like are achieved.
(2) The rolling process comprises the following steps: the rough rolling adopts 6-pass rolling and 3-pass descaling processes, the first rough rolling mill R1 carries out 1, 3 and 5-pass descaling, an upper water spray header and a lower water spray header of a descaling box are simultaneously opened, the pressure of a high-pressure water outlet is 21-30 MPa, the temperature of the rough rolling outlet is 1070-1100 ℃, the thickness of an intermediate blank is 30-40 mm, the width of the intermediate blank is 1550-1880 mm, the intermediate blank is subjected to heat preservation by a heat preservation cover before entering a hot rolling finishing mill set, the temperature drop of the intermediate blank on a delay roller way and the temperature difference of the head, the tail and the plate width direction are reduced, the finish rolling is 6-stand continuous rolling, the high-pressure water descaling is carried out before finish rolling, the temperature of a finish rolling inlet is not higher than 1060 ℃, the finish rolling temperature is 840-890 ℃, the finish rolling adopts high-tension rolling, and the tension rolling is carried out between the first finish2The tension between the frames of the second finishing mill F2 and the third finishing mill F3 is controlled to be 13-22N/mm2The tension between the stands of the third finishing mill F3 and the fourth finishing mill F4 is controlled to be 13-20N/mm2The tension between the stands of the fourth finishing mill F4 and the fifth finishing mill F5 is controlled to be 8-18N/mm2The tension between the frames of the fifth finishing mill F5 and the sixth finishing mill F6 is controlled to be 6-12N/mm2Meanwhile, the F5 and F6 racks are descaled by adopting high water pressure of 21-30 MPa, and cooling water in the rest racks is completely opened; the convexity control precision of the steel plate is +/-13 mu m, the flatness is controlled within 25I, the thickness control precision is +/-25 mu m, and the thickness of a finished product is 3-10 mm.
(3) And (3) a cooling process: and after the final rolling, adopting front-section rapid continuous laminar cooling, wherein the cooling rate is 22-45 ℃/s. The continuous laminar cooling process makes bainite precipitate fast in great amount, and this can inhibit the growth of crystal grains and ensure the bainite content, so as to refine the bainite crystal grains.
(4) Coiling temperature: the coiling temperature is 600-640 ℃. The coiling temperature is too high, so that the strength of the steel plate is insufficient, the elongation is reduced due to too low coiling temperature, the second phase particles can be fully precipitated after the steel plate is coiled in a temperature range, and the plasticity is good.
Examples
The specific components, temperature system, finishing tension control parameters, properties of the steel sheet and the percentage of the structure volume of 6 examples of the invention are shown in tables 1 to 5.
TABLE 1 chemical composition of inventive examples (wt%)
TABLE 2 Hot Rolling temperature System of examples of the present invention
TABLE 3 examples finishing tension control parameters
TABLE 4 mechanical Property parameters of the examples of the invention
TABLE 5 percentage of tissue volume in the examples of the invention
| Numbering | Ferrite | Pearlite | Bainite for treating cancer |
| Example 1 | 33％ | 60％ | 7％ |
| Example 2 | 35％ | 55％ | 10％ |
| Example 3 | 30％ | 62％ | 8％ |
| Example 4 | 25％ | 65％ | 10％ |
| Example 5 | 31％ | 62％ | 7％ |
| Example 6 | 26％ | 65％ | 9％ |
。
Claims (6)
1. The steel for 450 MPa-grade automobile structures is characterized by comprising the following chemical components in percentage by mass:
c: 0.065% -0.075%, Si: 0.09% -0.25%, Mn: 0.90% -1.40%, Al: 0.025 to 0.050%, Nb: 0.030-0.045%, Ti: 0.020-0.038%, Cr: 0.11-0.27%, rare earth Ce: 0.002% -0.012%, Cu: 0.60% -0.80%, Sb: 0.054% -0.11%, Bi: 0.015-0.045%, P is less than or equal to 0.015%, S is less than or equal to 0.006%, and the balance is Fe and inevitable impurities; 25 to 35 percent of ferrite, 55 to 65 percent of pearlite and 7 to 10 percent of bainite by volume percent.
2. The steel for 450MPa grade automobile structure according to claim 1, characterized in that the steel for structure has a hot-rolled plate with yield strength of 450MPa or more, tensile strength of 560MPa or more, and transverse elongation A of 30% or more.
3. The production method of the steel for 450MPa grade automobile structure according to claim 1 or 2, characterized by comprising the steps of smelting, heating and rolling, wherein the rolling step adopts 6 stands for finish rolling production, and the specific production method comprises the following steps:
1) a heating process: directly hot-charging (170) 230mm thick x (1550-1880) mm wide continuous casting slabs into a heating furnace for heating, wherein the hot charging temperature is more than 750 ℃, the preheating section is preheated at the furnace gas temperature of 800-1000 ℃, the preheating time is 25-30 min, the temperatures of the heating 1 section and the heating 2 section are respectively controlled at 1120-1200 ℃ and 1210-1240 ℃, the total soaking time of the heating 1 section and the heating 2 section is 15-20 min, the temperature of the heating 1 section is 1220-1240 ℃, the soaking time is 65-110 min, the furnace pressure is in a micro-positive pressure state, and the positive pressure value is controlled at 3-15 Pa;
2) the rolling process comprises the following steps: the rough rolling adopts 6-pass rolling and 3-pass descaling processes, the first rough rolling mill R1 descales 1, 3 and 5 passes, the upper row and the lower row of water spray headers of a descaling box are simultaneously opened, the pressure of a high-pressure water outlet is 21-30 MPa, the temperature of the rough rolling outlet is 1070-1100 ℃, the thickness of an intermediate blank is 30-40 mm, the width is 1550-1880 mm, the intermediate blank is subjected to heat preservation by a heat preservation cover before entering a hot rolling finishing mill set, the finish rolling is 6-stand continuous rolling, the high-pressure water descaling before the finish rolling, the temperature of a finish rolling inlet is not higher than 1060 ℃, the finish rolling temperature is 890 ℃, the finish rolling adopts finish rolling with large tension, meanwhile, the F5 and F6 stands adopt 21-30 MPa of high water pressure to descale, and cooling water between the rest; the convexity control precision of the steel plate is +/-13 mu m, the flatness is controlled within 25I, the thickness control precision is +/-25 mu m, and the thickness of a finished product is 3-10 mm.
4. The production method of the steel for 450MPa grade automobile structure according to claim 3, wherein the finish rolling in the step 2) is performed by high tension rolling:
the tension between the frames of the first frame finishing mill F1 and the second frame finishing mill F2 is controlled to be 7-14N/mm2The tension between the frames of the second finishing mill F2 and the third finishing mill F3 is controlled to be 13-22N/mm2The tension between the stands of the third finishing mill F3 and the fourth finishing mill F4 is controlled to be 13-20N/mm2The tension between the stands of the fourth finishing mill F4 and the fifth finishing mill F5 is controlled to be 8-18N/mm2The tension between the frames of the fifth finishing mill F5 and the sixth finishing mill F6 is controlled to be 6-12N/mm2。
5. The production method of the steel for 450MPa grade automobile structure according to claim 3, characterized by further comprising a cooling process: and after the final rolling, adopting front-section rapid continuous laminar cooling, wherein the cooling rate is 22-45 ℃/s.
6. The production method of the steel for 450MPa grade automobile structure according to claim 3, characterized by further comprising the following coiling temperature: the coiling temperature is 600-640 ℃.
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| CN114807777A (en) * | 2022-04-27 | 2022-07-29 | 鞍钢股份有限公司 | 500 MPa-grade automobile axle housing steel for hot stamping and production method thereof |
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