CN112831717A - 690 MPa-grade low-yield-ratio thin-specification weather-resistant bridge steel and manufacturing method thereof - Google Patents
690 MPa-grade low-yield-ratio thin-specification weather-resistant bridge steel and manufacturing method thereof Download PDFInfo
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- 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
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Abstract
The invention discloses a thin-specification weather-resistant bridge steel with a yield strength of 690MPa grade and a low yield ratio and a manufacturing method thereof, wherein the bridge steel comprises the following components in percentage by mass: c: 0.05-0.09%, Si: 0.21 to 0.50%, Mn: 1.30-1.70%, P: less than or equal to 0.010 percent, S: less than or equal to 0.002%, Nb: 0.041-0.070%, Ti: 0.010 to 0.020%, Cu: 0.15 to 0.40%, Ni: 0.40-0.80%, Cr: 0.40 to 0.70%, Mo: 0.15-0.35%, Alt: 0.02-0.04%, and the balance of Fe and inevitable impurities. According to the invention, the thin-specification weather-resistant bridge steel with the thickness of 6-32 mm and the yield strength of 690MPa is produced by an economical component design and a matched manufacturing method of controlled rolling and controlled cooling, offline quenching and offline tempering, so that the bridge steel has the characteristics of low yield ratio, high low-temperature toughness, high ductility and good plate shape.
Description
Technical Field
The invention relates to weathering resistant steel, in particular to thin-specification weathering resistant bridge steel with 690 MPa-grade yield strength and a low yield ratio and a manufacturing method thereof.
Background
Along with the development of large-scale steel structure bridge towards large-span, heavy load, all welded structure direction, the requirement on the fail safe nature of bridge structures is more and more strict. The steel plate has high strength to meet the requirement of light weight, and has excellent plasticity, low temperature toughness, weldability, corrosion resistance, etc. to meet the conditions of great bridge span and heavy load. The application of the high-strength high-toughness high-plasticity high-weather-resistance bridge steel can reduce the dead weight of a bridge structure, reduce the difficulty of bridge engineering design, manufacture and construction and the like, and can prolong the service life.
However, as the strength of the steel increases, the yield ratio of the steel generally increases, and may even reach 0.93 or more. Due to the high yield ratio, once the component is overloaded, such as in earthquake, the ultimate strength of the steel grade can be quickly reached, and accidents are caused. Therefore, the application of high-strength structural steel in bridge engineering is limited due to the high yield ratio. The frequent occurrence of earthquakes and the catastrophic consequences caused by the earthquakes cause high concern on bridge earthquake resistance at home and abroad, and relevant regulations are made in some structural design specifications. Therefore, the bridge steel with low yield ratio, high strength, high toughness, high plasticity and high weather resistance is a development trend of bridge construction.
In the high-strength weather-resistant bridge steel with the yield strength of 690MPa, the alloy addition amount is large, and the bainite structure obtained by a steel matrix structure has high tendency, so the control difficulty is mainly focused on the control of indexes such as plasticity, yield ratio and the like of the steel, particularly the control of the plate shape and the plasticity and yield ratio of a thin-specification steel plate in the production process, and the performance uniformity of the thin-specification steel plate in the length direction is poor, so the steel plate prepared by the traditional thermo-mechanical controlled rolling and tempering production process has physical level hindering the further engineering application.
After retrieval:
the Chinese patent with the publication number of CN108531808A provides a low yield ratio weather-proof bridge structural steel with the yield strength more than or equal to 690MPa and a production method thereof, and the structural steel comprises the following components in percentage by weight: c: 0.04-0.10%, Si: 0.01 to 0.20%, Mn: 0.80-1.70%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cu: 0.20 to 0.55%, Ni: 0.40 to 1.50%, Mo: 0.20-0.80%, 0.35-0.70% of Cr, Nb: 0.030 to 0.090%, Ti: 0.008-0.030%, Als: 0.015 to 0.060%, N: less than or equal to 0.0080%, Ca: 0.0010-0.0050%, and the balance of Fe and inevitable impurities, wherein the weight ratio of C + Nb: 0.11-0.15%; the controlled rolling and cooling process is adopted: cooling to 100-350 ℃ at a cooling rate of 10-30 ℃/s; and a third stage: naturally cooling to room temperature; tempering is carried out, the tempering temperature is 180-380 ℃, the temperature is kept for 20-40 min, and the temperature keeping time is in positive correlation with the thickness of the finished product. The steel related by the document adopts a low-Si high-Ni and high-Mo component design on a component system, the temperature of the red returning is low, the shape of a rolled steel plate is extremely difficult to control when the temperature of the red returning is low, particularly a thin steel plate, the tempering temperature is 180-380 ℃, the low-temperature tempering is adopted, and generally, the tempering temperature of bridge steel can be above 400 ℃ to better eliminate stress.
The Chinese patent application with the publication number of CN110468349A provides an anti-seismic high-strength weather-resistant bridge steel plate Q690qENHZ35 and a production method thereof, and the anti-seismic high-strength weather-resistant bridge steel plate comprises the following components in percentage by weight: c: 0.05-0.12%, Si: 0.08-0.25%, Mn: 0.09-1.45%, P is less than or equal to 0.012%, S is less than or equal to 0.003%, Cu: 0.25 to 0.35%, Ni: 0.80-1.85%, Mo: 0.25-0.80%, Cr: 0.50-1.0%, V: 0.040-0.080%, Ti: 0.010-0.020%, B: 0.0008 to 0.00135 percent, and the balance of Fe and inevitable impurities; the pre-quenching treatment, the sub-temperature quenching treatment and the tempering treatment are adopted, but the pre-quenching treatment is added, so that the cost of the steel grade is obviously increased.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects of the prior art, the invention discloses 690 MPa-grade low-yield-ratio thin-specification weather-resistant bridge steel which has the characteristics of low yield ratio, high-low-temperature toughness and high ductility.
The invention also aims to provide a manufacturing method of the 690 MPa-grade low-yield-ratio thin-specification weather-proof bridge steel.
The technical scheme is as follows: the 690 MPa-grade low-yield-ratio thin-specification weather-resistant bridge steel disclosed by the invention comprises the following components in percentage by mass: 0.05-0.09%, Si: 0.21 to 0.50%, Mn: 1.30-1.70%, P: less than or equal to 0.010 percent, S: less than or equal to 0.002%, Nb: 0.041-0.070%, Ti: 0.010 to 0.020%, Cu: 0.15 to 0.40%, Ni: 0.40-0.80%, Cr: 0.40 to 0.70%, Mo: 0.15-0.35%, Alt: 0.02-0.04%, and the balance of Fe and inevitable impurities.
The determination of the component proportion is realized by changing the content of certain elements and adding alloy elements capable of strengthening and improving the mechanical property of the material, the method of controlled rolling and controlled cooling, offline quenching and offline tempering is adopted according to the principle of multiple elements and a small amount, the steel with the thickness specification of 6-32 mm and the yield ratio of less than or equal to 0.85 is obtained, and the delivery state is quenching and tempering treatment.
Particularly, the carbon content in the steel in the components of the invention is not suitable to be too high, and simultaneously, the sulfur content is reduced, the content of corrosion resistant element phosphorus is controlled, and the purity and the toughness of the steel are ensured. The invention realizes low yield ratio, high and low temperature toughness and high extensibility by taking tempered bainite as a main structure type and a small amount of ferrite, and the description of each component and content is as follows:
c is an indispensable element for improving the strength and the hardness of steel in steel, and has obvious influence on steel structure. C is dissolved in the matrix to form a gap solid solution, so that the solid solution strengthening effect is achieved, and the strength of the matrix is obviously improved. As the carbon content increases, the tensile strength and yield strength of the steel increase and the elongation and impact toughness decrease, and cold cracking is more likely to occur when the C content in the steel is high. Therefore, the percentage content of C in the invention is set to be 0.05-0.09%.
Mn is a main element in steel, can improve the material strength, and is a main element for preventing hot brittleness in steel, but high-content Mn is easy to generate serious center segregation in steel and deteriorates the low-temperature toughness of the steel, so that the percentage content of Mn in the invention is set to be 1.30-1.70%.
Si element mainly improves the strength of steel in a strong solid solution strengthening mode in the steel, is also a necessary element for steel-making deoxidation, can improve the atmospheric corrosion resistance, obviously reduces the plasticity and toughness of the steel and obviously reduces the surface coating performance of the steel, so the percentage content of Si in the invention is set to be 0.21-0.50% by comprehensively considering the factors of strength, toughness, plasticity and the like.
P promotes the amorphous transformation of the rust layer, generally speaking, Cu and P are compounded to have the optimal weather-resistant effect, the corrosion-resistant element is relatively economic, the P content is generally limited in the weathering steel for important welding structures in consideration of low-temperature brittleness and crack sensitivity caused by P, and the P percentage content is controlled to be less than or equal to 0.010%.
When the S content is higher, the corrosion resistance, the low-temperature toughness and the Z-direction performance of the steel can be reduced, and the S content is controlled to be less than or equal to 0.002 percent.
Nb is a strong carbonitride forming element and increases the austenite recrystallization temperature of steel, and austenite can be rolled at a higher rolling temperature. In addition, the Nb has precipitation strengthening effect in the continuous cooling process of rolling control, and austenite grains can be fixed through strain-induced precipitation of Nb carbonitride, so that the austenite grains are refined, and the strength and the low-temperature toughness are improved. The percentage content of Nb in the invention is controlled to be 0.041-0.070%.
Ti can obviously improve the strength, play a role in refining crystal grains and also improve the toughness of steel, and a proper amount of Ti can form a second particle to improve the toughness of metal, wherein the percentage content of Ti in the invention is 0.010-0.020%.
Ni can improve hardenability, has a certain strengthening effect, can also obviously improve the low-temperature toughness of a base metal and welding HAZ, can effectively prevent the network fracture caused by the hot brittleness of Cu, and can also improve the atmospheric corrosion resistance of steel. The percentage content of Ni in the invention is controlled to be 0.40-0.80%.
The Cu element mainly plays a role in solid solution strengthening in steel, and a proper amount of copper can improve the strength without reducing the toughness and can also improve the corrosion resistance of the steel, wherein the percentage content of Cu in the invention is 0.15-0.40%.
The proper addition of Cr can improve the strength of the steel and obviously improve the weather resistance of the steel, and the percentage content of Cr in the invention is 0.40-0.70%.
Mo is a strong solid solution strengthening element, the hardenability is strongly improved, the hot hardness can be obviously improved, the tempering stability is improved, and the tempering brittleness is obviously reduced, wherein the percentage content of Mo in the invention is 0.15-0.35%.
Al is a main deoxidizing element in steel, can be used for preventing grains from growing, but when the content of Al is too high, oxide inclusions of Al are increased, the purity of the steel is reduced, and the toughness of the steel is not facilitated. The percentage content of Alt is 0.02-0.04%.
Furthermore, the atmospheric corrosion resistance index I of the steel is more than or equal to 6.0. Wherein, the weather resistance index I =26.01(% Cu) +3.88(% Ni) +1.20(% Cr) +1.49(% Si) +17.28(% P) -7.29(% Cu) (% Ni) -9.10(% Ni) (% P) -33.39(% Cu) 2.
Corresponding to the 690 MPa-grade low-yield-ratio thin-specification weather-resistant bridge steel, the manufacturing method provided by the invention is characterized in that the working procedures comprise smelting, continuous casting, soaking, rolling, cooling, off-line quenching and off-line tempering;
wherein the continuous casting billet is heated to the central temperature of 1160-1230 ℃ in the soaking process;
the rolling procedure is to carry out reciprocating rolling on the descaled continuous casting billet in a single-stand medium plate rolling mill, a steel plate with the thickness less than or equal to 12mm is produced by adopting a one-stage rolling mode, a steel plate with the thickness more than 12mm is produced by adopting two-stage rolling, namely, rolling in a recrystallization zone and rolling in a non-recrystallization zone, and the accumulated deformation of the rolling in the recrystallization zone is more than 50% of the thickness of the continuous casting billet;
rolling a steel plate with the thickness less than or equal to 12mm, and controlling the finish rolling temperature to be 810-850 ℃;
rolling a steel plate with the thickness of more than 12mm, keeping the temperature of the intermediate blank at 850-920 ℃, keeping the temperature to be more than 3 times of the thickness of a finished product, and rolling in a non-recrystallization area after the temperature is reached, wherein the final rolling temperature is controlled at 790-830 ℃;
the cooling process is that laminar cooling is carried out after the final rolling, and in order to ensure that the rolled plate shape of the thin-gauge steel plate is good, the temperature of the red returning is controlled to be 350-550 ℃, and then air cooling is carried out to the room temperature;
in the off-line quenching procedure, the quenching temperature is 740-840 ℃, the temperature is kept for 10-50 min at the temperature, the temperature keeping time is in direct proportion to the thickness of a finished product, and then the finished product is naturally cooled to the room temperature;
in the off-line tempering procedure, the tempering temperature is 380-450 ℃, the temperature is kept for 20-90 min at the temperature, the temperature keeping time is in direct proportion to the thickness of the finished product, and then the finished product is naturally cooled to the room temperature.
Preferably, the thickness of a continuous casting billet adopted for manufacturing a finished product with the thickness of 6-32 mm is 150-260 mm.
Preferably, the continuous casting billet in the continuous casting process is subjected to stack cooling for more than 24h, the stack cooling time is increased along with the increase of the thickness of the continuous casting billet, and the stack cooling time is more than 48h for a 260mm continuous casting billet.
Preferably, the temperature uniformity of the continuous casting billet in the soaking process is less than 15 ℃.
Preferably, in the soaking process, the heating time is more than or equal to the thickness of the continuous casting billet by 0.9 min/mm.
Has the advantages that: compared with the prior art, the invention obtains the 6-32 mm thick 690MPa low-yield-ratio thin-specification weather-resistant bridge steel with low yield ratio, high toughness and high ductility through scientific component design and a matched manufacturing method of controlled rolling and controlled cooling, offline quenching and offline tempering. The yield strength is more than 730MPa, the tensile strength is more than 860MPa, the yield ratio of the finished steel is less than or equal to 0.85, Akv at minus 40 ℃ is more than 200J, the fiber section rate is more than 80%, the elongation is more than or equal to 15%, the performance uniformity of the steel is good, the plate shape of the steel is excellent, the comprehensive production cost is low, and the steel is suitable for application of bridge structures.
Drawings
FIG. 1 is a 500-fold optical metallographic structure of the product of example 2. The microstructure type is 'tempered bainite' + 'ferrite' structure.
Detailed Description
The process of the present invention is described in further detail below with reference to specific examples.
Example 1
The thin-specification weather-resistant bridge steel with the yield strength of 690MPa grade and the low yield ratio comprises the following components in percentage by mass: c: 0.05%, Si: 0.38%, Mn: 1.70%, P: 0.010%, S: 0.0010%, Nb: 0.045%, Ti: 0.015%, Ni: 0.40%, Cu: 0.20%, Cr: 0.50%, Mo: 0.35%, Alt: 0.02% and the balance Fe and unavoidable impurities.
The raw materials are smelted, refined, alloyed and subjected to calcium treatment to obtain molten steel, the molten steel is continuously cast on a slab, the thickness of a casting blank is 150mm, and the atmospheric corrosion resistance index I is 6.1. And (3) performing heap cooling on the continuous casting billet for more than 24 hours, soaking the billet at 1230 ℃, wherein the temperature uniformity is less than 15 ℃, heating for 150min, then removing phosphorus, and then performing one-stage rolling to obtain a final product with the thickness of 6mm, wherein the final rolling is 830 ℃.
And carrying out laminar cooling after the final rolling, wherein the temperature of the red returning is 550 ℃, then carrying out air cooling to room temperature, then carrying out off-line quenching on the steel plate, wherein the quenching temperature is 740 ℃, and carrying out heat preservation for 10min at the temperature. Then off-line tempering is carried out, the tempering temperature is 450 ℃, and the temperature is kept for 20min at the temperature.
The metallographic structure of the sample after controlled rolling and controlled cooling, quenching and tempering is observed, the microstructure type is 'tempered bainite' + 'ferrite' structure, the yield strength of the material is 756MPa, the tensile strength is 900MPa, the yield ratio of the finished steel is 0.84, the Akv at minus 40 ℃ is 240J, the fiber section rate is 95 percent, and the elongation A is 15 percent.
Example 2
The thin-specification weather-resistant bridge steel with the yield strength of 690MPa grade and the low yield ratio comprises the following components in percentage by mass: c: 0.06%, Si: 0.30%, Mn: 1.56%, P: 0.010%, S: 0.0015%, Nb: 0.041%, Ti: 0.020%, Ni: 0.60%, Cu: 0.15%, Cr: 0.70%, Mo: 0.15%, Alt: 0.04%, and the balance of Fe and unavoidable impurities.
The raw materials are smelted, refined, alloyed and subjected to calcium treatment to obtain molten steel, the molten steel is continuously cast on a slab, the thickness of a casting blank is 260mm, and the atmospheric corrosion resistance index I is 6.2. And (3) performing pile cooling on the continuous casting blank for more than 48h, soaking the blank at 1200 ℃, wherein the temperature uniformity is less than 15 ℃, removing phosphorus after heating for 260min, and then performing two-stage rolling. The rolling temperature of the recrystallization zone is 1070 ℃, the total deformation is 78 percent, and the thickness of the intermediate billet is controlled to be 3.5 times of that of the finished product. The rolling start temperature of the non-recrystallization zone is 890 ℃, the thickness of the final product is 16mm, and the final rolling temperature is 820 ℃.
And carrying out laminar cooling after final rolling, wherein the temperature of red returning is 450 ℃, then carrying out air cooling to room temperature, then carrying out off-line quenching on the steel plate, wherein the quenching temperature is 760 ℃, and carrying out heat preservation for 30min at the temperature. Then off-line tempering is carried out, the tempering temperature is 430 ℃, and the temperature is kept for 50min at the temperature.
As shown in figure 1, the metallographic structure of the sample after controlled rolling and controlled cooling, quenching and tempering is observed, the microstructure type is 'tempered bainite' + 'ferrite' structure, the yield strength of the material is 748MPa, the tensile strength is 901MPa, the yield ratio of the finished steel is 0.83, Akv at minus 40 ℃ is 225J, the fiber section rate is 95 percent, and the elongation A is 15.5 percent.
Example 3
The thin-specification weather-resistant bridge steel with the yield strength of 690MPa grade and the low yield ratio comprises the following components in percentage by mass: c: 0.09%, Si: 0.21%, Mn: 1.30%, P: 0.0090%, S: 0.0020%, Nb: 0.050%, Ti: 0.018%, Ni: 0.80%, Cu: 0.40%, Cr: 0.55%, Mo: 0.25%, Alt: 0.02% and the balance Fe and unavoidable impurities.
The raw materials are smelted, refined, alloyed and subjected to calcium treatment to obtain molten steel, the molten steel is continuously cast on a slab, the thickness of a casting blank is 260mm, and the atmospheric corrosion resistance index I is 6.9. And (3) cooling the casting blank in a heap for more than 48h, soaking the blank at 1180 ℃, heating for 234min to remove phosphorus, and then rolling in two stages. The rolling temperature of the recrystallization zone is 1050 ℃, the total deformation of rough rolling is 72 percent, and the thickness of the intermediate blank is controlled to be 3.0 times of that of the finished product. The rolling start temperature of the non-recrystallization zone is 860 ℃, the thickness of the final product is 24mm, and the final rolling temperature is 810 ℃.
And carrying out laminar cooling after the final rolling, wherein the temperature of the red returning is 390 ℃, then carrying out air cooling to room temperature, then carrying out off-line quenching on the steel plate, wherein the quenching temperature is 800 ℃, and carrying out heat preservation for 40min at the temperature. Then off-line tempering is carried out, the tempering temperature is 400 ℃, and the temperature is kept for 75min at the temperature.
The metallographic structure of the sample after controlled rolling and controlled cooling, quenching and tempering is observed, the microstructure type is 'tempered bainite' + 'ferrite' structure, the yield strength of the material is 738MPa, the tensile strength is 879MPa, the yield ratio of the finished steel is 0.84, the Akv at minus 40 ℃ is 220J, the fiber section rate is 90 percent, and the elongation A is 16 percent.
Example 4
The thin-specification weather-resistant bridge steel with the yield strength of 690MPa grade and the low yield ratio comprises the following components in percentage by mass: c: 0.07%, Si: 0.50%, Mn: 1.65%, P: 0.010%, S: 0.0012%, Nb: 0.070%, Ti: 0.010%, Ni: 0.70%, Cu: 0.38%, Cr: 0.40%, Mo: 0.30%, Alt: 0.025%, and the balance of Fe and unavoidable impurities.
The raw materials are smelted, refined, alloyed and subjected to calcium treatment to obtain molten steel, the molten steel is continuously cast on a slab, the thickness of a casting blank is 260mm, and the atmospheric corrosion resistance index I is 7.2. And (3) cooling the casting blank in a heap for more than 48h, soaking the blank at 1160 ℃, heating for 234min to remove phosphorus, and then rolling in two stages. The rolling temperature of the recrystallization zone is 1030 ℃, the total deformation of rough rolling is 72 percent, and the thickness of the intermediate blank is controlled to be 3.0 times of that of the finished product. The rolling start temperature of the non-recrystallization zone is 840 ℃ to reach the thickness of a final product of 32mm, and the final rolling temperature is 790 ℃.
And carrying out laminar cooling after the final rolling, wherein the temperature of the red returning is 350 ℃, then carrying out air cooling to room temperature, then carrying out off-line quenching on the steel plate, wherein the quenching temperature is 840 ℃, and carrying out heat preservation for 50min at the temperature. Then off-line tempering is carried out, the tempering temperature is 380 ℃, and the temperature is kept for 90min at the temperature.
The metallographic structure of the sample after controlled rolling and controlled cooling, quenching and tempering is observed, the microstructure type is 'tempered bainite' + 'ferrite' structure, the yield strength of the material is 730MPa, the tensile strength is 890MPa, the yield ratio of the finished steel is 0.82, the Akv at minus 40 ℃ is 218J, the fiber section rate is 90 percent, and the elongation A is 17 percent.
From the above embodiments, the 690 MPa-grade weather-resistant bridge steel with low yield ratio produced by the heavy and medium plate mill is subjected to the manufacturing process of auxiliary controlled rolling and controlled cooling, offline quenching and offline tempering through the component design, so that the yield ratio of the thin-specification weather-resistant bridge steel is effectively reduced, and the yield ratio of the finished steel is less than or equal to 0.85.
Claims (9)
1. The 690 MPa-grade low-yield-ratio thin-specification weather-resistant bridge steel is characterized by comprising the following components in percentage by mass: c: 0.05-0.09%, Si: 0.21 to 0.50%, Mn: 1.30-1.70%, P: less than or equal to 0.010 percent, S: less than or equal to 0.002%, Nb: 0.041-0.070%, Ti: 0.010 to 0.020%, Cu: 0.15 to 0.40%, Ni: 0.40-0.80%, Cr: 0.40 to 0.70%, Mo: 0.15-0.35%, Alt: 0.02-0.04%, and the balance of Fe and inevitable impurities.
2. The 690MPa grade, low yield ratio, thin gauge, weather resistant bridge steel of claim 1, wherein the metallographic structure is tempered bainite + a small amount of ferrite.
3. The 690MPa grade low yield ratio thin gauge weather resistant bridge steel according to claim 1, wherein the yield ratio of the steel plate with the thickness of 6-32 mm is less than or equal to 0.85.
4. The 690MPa grade, low yield ratio, thin gauge, weather resistant bridge steel of claim 1, wherein the atmospheric corrosion resistance index I is greater than or equal to 6.0.
5. The method for manufacturing the 690MPa grade low yield ratio thin specification weather-proof bridge steel according to any one of claims 1 to 4, wherein the process comprises smelting, continuous casting, soaking, rolling, cooling, off-line quenching and off-line tempering;
wherein the continuous casting billet is heated to the central temperature of 1160-1230 ℃ in the soaking process;
the rolling procedure is to carry out reciprocating rolling on the descaled continuous casting billet in a single-stand medium plate rolling mill, a steel plate with the thickness less than or equal to 12mm is produced by adopting a one-stage rolling mode, a steel plate with the thickness more than 12mm is produced by adopting two-stage rolling, namely, rolling in a recrystallization zone and rolling in a non-recrystallization zone, and the accumulated deformation of the rolling in the recrystallization zone is more than 50% of the thickness of the continuous casting billet;
rolling a steel plate with the thickness less than or equal to 12mm, and controlling the finish rolling temperature to be 810-850 ℃;
rolling a steel plate with the thickness of more than 12mm, keeping the temperature of the intermediate blank at 850-920 ℃, keeping the temperature to be more than 3 times of the thickness of a finished product, and rolling in a non-recrystallization area after the temperature is reached, wherein the final rolling temperature is controlled at 790-830 ℃;
the cooling procedure is that laminar cooling is carried out after the final rolling, the temperature of the red returning is controlled to be 350-550 ℃, and then air cooling is carried out to the room temperature;
in the off-line quenching procedure, the quenching temperature is 740-840 ℃, the temperature is kept for 10-50 min at the temperature, the temperature keeping time is in direct proportion to the thickness of a finished product, and then the finished product is naturally cooled to the room temperature;
in the off-line tempering procedure, the tempering temperature is 380-450 ℃, the temperature is kept for 20-90 min at the temperature, the temperature keeping time is in direct proportion to the thickness of the finished product, and then the finished product is naturally cooled to the room temperature.
6. The manufacturing method according to claim 5, wherein the thickness of the continuous casting billet used for manufacturing the finished product with the thickness of 6-32 mm is 150-260 mm.
7. The manufacturing method according to claim 5, wherein the slab is subjected to the continuous casting process for a stack cooling time of 24 hours or more, and the stack cooling time is increased as the thickness of the slab increases, and the stack cooling time is 48 hours or more for a slab of 260 mm.
8. The manufacturing method according to claim 5, wherein the temperature uniformity of the slab in the soaking step is less than 15 ℃.
9. The manufacturing method according to claim 5, wherein in the soaking step, the heating time is not less than 0.9min/mm for the thickness of the continuous cast slab.
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