CN113755746B - Method for improving band-shaped structure of hot-forming steel plate - Google Patents
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- 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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Abstract
The invention relates to a method for improving a band-shaped structure of a hot forming steel plate, which comprises the steps of adjusting the chemical components of the plate and optimizing the production process of the plate; wherein, the adjustment of the chemical composition of the plate is to add rare earth element RE into the plate. In addition, the generation probability of the band-shaped structure defects of the hot forming steel products is further reduced by controlling the content of harmful element components, the purity of molten steel, a controlled rolling and controlled cooling process, a cold rolling and annealing process. By adopting the technical scheme provided by the invention, the purity of the molten steel can be improved, the steel plate structure can be refined, the generation of the strip structure defects of the product can be reduced, and the requirements of high-quality steel grades can be met without adding additional equipment and treatment means.
Description
Technical Field
The invention relates to a method for improving a band-shaped structure of a hot forming steel plate, belonging to the technical field of ferrous metallurgy and rolling.
Background
The steel for hot forming means a steel sheet or a steel strip for direct and indirect hot press forming. The original structure is ferrite and pearlite, and the martensite structure is formed by rapid stamping after heat treatment. The material is used on the automobile body, under the condition that the weight of the automobile body is almost not changed greatly, the bearing capacity is improved by 30 percent, the rigidity strength of the automobile reaches a brand new level, and the material is widely applied to anti-collision safety parts such as automobile B columns, doorsills and the like, and the collision safety of the automobile is improved.
Due to dendrite segregation inherent to the cast slab, a band-shaped distribution in which ferrite and pearlite are alternately overlapped is formed in the rolling direction during rolling, and this is called a band-shaped structure. The band-shaped structure reduces the plasticity, toughness and reduction of area of the steel. Since steel for hot press forming is often subjected to heat treatment processes such as heating and quenching during use, the content of alloying elements such as carbon, manganese, and chromium is required to a certain extent. The addition of high carbon, manganese and other alloy elements inevitably causes a certain level of strip-shaped structure to be generated in the microstructure of the steel, and the structure can also cause the nonuniformity of the structure after heat treatment, thereby causing the nonuniformity of the hardness distribution of the steel plate and the deterioration of the bending performance and the like.
At present, no systematic study on the steel for hot stamping forming of a band-shaped structure exists in China, and therefore, no optimal solution for generating the band-shaped structure in the hot forming steel exists.
Disclosure of Invention
The invention aims to provide a method for improving a band-shaped structure of a hot forming steel plate, thereby improving the application performance of the hot stamping forming steel.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a method for improving the banded structure of a hot-formed steel plate comprises the steps of adjusting the chemical components of the plate and optimizing the production process of the plate; wherein, the adjustment of the chemical composition of the plate is to add rare earth element RE into the plate.
Preferably, the content of the rare earth element RE in the invention is not more than 0.1% by mass.
Preferably, the plate comprises the following chemical components in percentage by weight: c: 0.20 to 0.45%, Mn: 1.0 to 1.50%, Si: 0.15-0.35%, S is less than or equal to 0.005%, P is less than or equal to 0.022%, Al: 0.030-0.050%, RE is less than or equal to 0.1%, Ti: 0.01-0.06%, Cr: 0.10-0.50%, B: 0.001 to 0.005% and the balance of iron and inevitable impurities.
The production process of the plate comprises molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing.
Preferably, the molten iron desulphurization pretreatment process of the invention comprises the following steps: the outbound S is less than or equal to 0.010 percent.
Preferably, the converter molten steel smelting process of the present invention: the sedation time is more than or equal to 140 s; the tapping of the converter adopts the slag discharge detection and sliding plate slag stopping technology, and the slag discharge of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are sequentially added for alloying and deoxidation.
Preferably, the molten steel refining treatment process of the LF furnace comprises the following steps: white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is more than 4.0; stirring the refined molten steel by bottom blowing argon weakly stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a steel ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is required to be 30-80 m 3 The static blowing time is more than or equal to 8min between the hour and the hour.
Preferably, the continuous casting process of the present invention: superheat degree of molten steel: 25-35 ℃; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; when the width of the plate blank is less than or equal to 1150mm, the pulling speed is controlled to be 1.30-1.40 m/min; when the width of the plate blank is larger than 1150mm, the pulling speed is controlled to be 1.20-1.30 m/min; and feeding RE wires into the crystallizer, and adjusting the wire feeding speed according to the throwing speed and the addition amount of rare earth per ton of steel.
Preferably, the hot continuous rolling process of the present invention: heating temperature of the plate blank: 1250-1310 ℃; finish rolling inlet temperature: 1050-1100 ℃; the finishing temperature is as follows: 830-860 ℃; coiling temperature: 580 to 620 ℃.
Preferably, the pickling cold continuous rolling process of the invention comprises the following steps: the control of a large reduction rate is adopted, and the total reduction rate is more than or equal to 50 percent;
preferably, the continuous annealing process of the present invention: the annealing temperature is 780-820 ℃, the thickness range of the produced product is 0.6-2.5 mm, the process speed is 80-140 m/min, and the process speed is adjusted according to the thickness of the product, so that the qualified performance and the uniform structure of the steel strip are ensured.
The method provided by the invention has the following mechanism: on one hand, the rare earth elements are added to purify molten steel, the solidification structure of the steel is refined, the property, the form and the distribution of inclusions are changed, and segregation is reduced. In low alloy steel, C, Mn and Cr are easy segregation elements, and along with segregation of Mn and Cr and segregation of C, the toughness of a casting is reduced and the mechanical property is uneven. Dendrite segregation causes the austenite transformation characteristics between dendrite trunk and dendrite to be different, resulting in differences in microstructure, strength, hardness and plasticity, and at the same time, stress is generated between the structures, causing cracking. The rare earth has good effect on improving dendrite segregation, and researches show that secondary dendrite arms are refined by rare earth element cables. As the secondary dendrite arm spacing decreases, the solute distribution is more dispersed and uniform, thereby mitigating dendrite segregation. In addition, the rare earth elements delay the peritectic reaction, reduce the peritectic temperature and lead the distribution coefficient K of the alloy elements 0 The values increase, both of which mitigate dendrite segregation. On the other hand, the generation probability of the band-shaped structure defects of the hot forming steel products is further reduced by controlling the content of harmful element components, the purity of molten steel, a controlled rolling and controlled cooling process, a cold rolling and annealing process.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:
1. the method can reduce the generation probability of the band-shaped structure defects of the hot forming steel product without adding extra equipment and treatment means, and meet the requirements of high-quality steel grades.
2. By adding rare earth elements, molten steel is purified and the solidification structure of the steel is refined, so that not only can the banded structure be improved, but also the impact toughness, anisotropy, fatigue, welding performance and other performances of the steel are improved.
Drawings
FIG. 1 is a typical strip morphology (hot rolled 200X) for hot formed steel.
FIG. 2 shows the metallographic structure (hot rolled 200X) of the hot formed steel prepared in example 1.
FIG. 3 shows the metallographic structure (hot rolled 200X) of the hot formed steel prepared in example 2.
FIG. 4 shows the metallographic structure (hot rolled 200X) of the hot formed steel prepared in example 3.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the examples and the accompanying drawings. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
The hot forming steel generally contains high alloy elements such as carbon and manganese, so that a certain level of strip-shaped structure is often generated in the microstructure, and as shown in fig. 1, the structure causes uneven distribution of hardness of the steel sheet after heat treatment, and the properties such as bending of the steel sheet are deteriorated.
According to the invention, by adding rare earth elements and controlling the content of harmful element components, the purity of molten steel, the controlled rolling and controlled cooling process, the cold rolling and annealing process and the like, the generation probability of band-shaped tissue defects of the hot forming steel product is effectively reduced.
Example 1:
the hot stamping steel of the embodiment comprises the following chemical components in percentage by mass: c: 0.20%, Mn: 1.5%, Si: 0.15%, S: 0.005%, P: 0.022%, Al: 0.030%, RE: 0.1%, Ti: 0.03%, Cr: 0.40%, B: 0.005%, and the balance of iron and inevitable impurities.
The production process of the hot stamping forming steel comprises the working procedures of molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing. Wherein:
(1) molten iron desulphurization pretreatment: the outbound S content was 0.008%.
(2) Smelting molten steel in a converter: sedation time 150 s; the tapping of the converter adopts the slag discharge detection and sliding plate slag stopping technology, and the slag discharge of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are sequentially added for alloying and deoxidation.
(3) Refining treatment of molten steel in an LF (ladle furnace): white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is 4.2; stirring the refined molten steel by bottom blowing argon weakly stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is 80m 3 And/h, and the static blowing time is 10 min.
(4) Continuous casting: the superheat degree of the molten steel is 25 ℃; electromagnetic stirring is adopted; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; the width of the plate blank is 1270mm, and the pulling speed is controlled at 1.20 m/min; feeding RE wire into crystallizer at speed V RE ：80-90m/min。
(5) Hot continuous rolling: heating temperature of the plate blank: 1280 deg.C; finish rolling inlet temperature: 1080 ℃; the finishing temperature is as follows: 850 ℃; coiling temperature: at 600 ℃.
(6) Acid pickling and cold continuous rolling: the control of large reduction rate is adopted, the thickness of the raw material is 3.0mm, the sheet with the thickness of 1.0mm is rolled, and the total reduction rate is about 67%.
(7) And (3) continuous annealing: the annealing temperature is 800 ℃, the thickness of the produced product is 1.0mm, and the process speed is 100 m/min.
The performance of the hot stamping steel product prepared by the embodiment meets the requirements of related standards such as EN10083-3, and a metallographic structure does not have a banded structure, which is shown in FIG. 2.
Example 2:
the hot stamping steel of the embodiment comprises the following chemical components in percentage by mass: c: 0.45%, Mn: 1.0%, Si: 0.35%, S: 0.004%, P: 0.015%, Al: 0.050%, RE: 0.05%, Ti: 0.01%, Cr: 0.50%, B: 0.001%, and the balance of iron and inevitable impurities.
The production process of the hot stamping forming steel comprises molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing. Wherein:
(1) molten iron desulphurization pretreatment: the outbound S content was 0.010%.
(2) Smelting molten steel in a converter: sedation time 140 s; the tapping of the converter adopts the slag discharge detection and sliding plate slag stopping technology, and the slag discharge of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are sequentially added for alloying and deoxidation.
(3) Refining treatment of molten steel in an LF (ladle furnace): white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is 4.0; stirring the refined molten steel by bottom blowing argon weakly stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is 30m 3 And/h, the static blowing time is 8 min.
(4) Continuous casting: the superheat degree of the molten steel is 30 ℃; electromagnetic stirring is adopted; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; the width of the plate blank is 1150mm, and the pulling speed is controlled at 1.40 m/min; feeding RE wire into crystallizer at speed V RE ：40-50m/min。
(5) Hot continuous rolling: heating temperature of the plate blank: 1250 ℃; finish rolling inlet temperature: 1050 ℃; the finishing temperature is as follows: 830 ℃; coiling temperature: 580 deg.C.
(6) Acid pickling and cold continuous rolling: the large reduction rate is adopted for control, the thickness of the raw material is 2.0mm, the sheet with the thickness of 0.6mm is rolled, and the total reduction rate is 70%;
(7) and (3) continuous annealing: the annealing temperature is 780 ℃, the thickness of the produced product is 0.6mm, and the process speed is 140 m/min.
The performance of the hot stamping steel product prepared by the embodiment meets the requirements of EN10083-3 and other relevant standards, and no banded structure appears in metallographic structure detection, which is shown in FIG. 3.
Example 3:
the hot stamping steel of the embodiment comprises the following chemical components in percentage by mass: c: 0.23%, Mn: 1.2%, Si: 0.25%, S: 0.003%, P: 0.017%, Al: 0.040%, RE: 0.01%, Ti: 0.06%, Cr: 0.40%, B: 0.003% and the balance iron and inevitable impurities.
The production process of the hot stamping forming steel comprises molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing. Wherein:
(1) molten iron desulphurization pretreatment: the outbound S content was 0.007%.
(2) Smelting molten steel in a converter: sedation time 160 s; the tapping of the converter adopts the slag discharge detection and sliding plate slag stopping technology, and the slag discharge of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are sequentially added for alloying and deoxidation.
(3) Refining treatment of molten steel in an LF (ladle furnace): white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is 4.5; stirring the refined molten steel by adopting bottom blowing argon weak stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a steel ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is 50m 3 And the static blowing time is 9min between the times of the reaction and the reaction.
(4) Continuous casting: the superheat degree of the molten steel is 35 ℃; electromagnetic stirring is adopted; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; when the width of the plate blank is 1120mm, the pulling speed is controlled to be 1.30 m/min; feeding RE wire into crystallizer at speed V RE ：5-15m/min。
(5) Hot continuous rolling: heating temperature of the plate blank: 1310 ℃; finish rolling inlet temperature: 1100 ℃; the finishing temperature is as follows: 860 ℃; coiling temperature: 620 ℃ is adopted.
(6) Acid pickling and cold continuous rolling: the large reduction rate is adopted for control, the thickness of the raw material is 5.0mm, the sheet with the thickness of 2.5mm is rolled, and the total reduction rate is 50 percent;
(7) and (3) continuous annealing: the annealing temperature is 820 ℃, the thickness of the produced product is 2.5mm, and the process speed is 80 m/min.
The performance of the hot stamping steel product prepared by the embodiment meets the requirements of related standards such as EN10083-3, and a metallographic structure detection shows that no banded structure appears, as shown in FIG. 4.
Example 4:
the hot stamping steel of the embodiment comprises the following chemical components in percentage by mass: c: 0.38%, Mn: 1.4%, Si: 0.21%, S: 0.004%, P: 0.019%, Al: 0.034%, RE: 0.06%, Ti: 0.05%, Cr: 0.10%, B: 0.004%, and the balance of iron and inevitable impurities.
The production process of the hot stamping forming steel comprises the working procedures of molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing. Wherein:
(1) molten iron desulphurization pretreatment: the outbound S content was 0.008%.
(2) Smelting molten steel in a converter: sedation time 155 s; the tapping of the converter adopts the slag tapping detection and sliding plate slag stopping technology, and the slag tapping of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are sequentially added for alloying and deoxidation.
(3) Refining treatment of molten steel in an LF (ladle furnace): white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is 4.6; stirring the refined molten steel by adopting bottom blowing argon weak stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a steel ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is 60m 3 H, and the static blowing time is 11 min.
(4) Continuous casting: the superheat degree of the molten steel is 28 ℃; electromagnetic stirring is adopted; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; the width of the plate blank is 1330mm, and the pulling speed is controlled to be 1.30 m/min; feeding RE wire into crystallizer at speed V RE ：20-30m/min。
(5) Hot continuous rolling: heating temperature of the plate blank: 1270 ℃; finish rolling inlet temperature: 1090 deg.C; the finishing temperature is as follows: 850 ℃; coiling temperature: 595 ℃.
(6) Acid pickling and cold continuous rolling: the large reduction rate is adopted for control, the thickness of the raw material is 3.0mm, the raw material is rolled into a sheet with the thickness of 1.5mm, and the total reduction rate is about 50%.
(7) And (3) continuous annealing: the annealing temperature is 790 ℃, the thickness of the produced product is 1.5m, and the process speed is 90 m/min.
The performance of the hot stamping steel product prepared by the embodiment meets the requirements of EN10083-3 and other relevant standards, and no banded structure appears in metallographic structure detection.
Example 5:
the hot stamping steel of the embodiment comprises the following chemical components in percentage by mass: c: 0.27%, Mn: 1.1%, Si: 0.28%, S: 0.005%, P: 0.020%, Al: 0.046%, RE: 0.03%, Ti: 0.02%, Cr: 0.30%, B: 0.005%, and the balance of iron and inevitable impurities.
The production process of the hot stamping forming steel comprises molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing. Wherein:
(1) molten iron desulphurization pretreatment: the outbound S content was 0.005%.
(2) Smelting molten steel in a converter: sedation time 170 s; the tapping of the converter adopts the slag discharge detection and sliding plate slag stopping technology, and the slag discharge of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are added in sequence for alloying and deoxidation.
(3) Refining treatment of molten steel in an LF (ladle furnace): white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is 5.2; stirring the refined molten steel by adopting bottom blowing argon weak stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a steel ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is 70m 3 And/h, and the static blowing time is 9 min.
(4) Continuous casting: the superheat degree of the molten steel is 34 ℃; electromagnetic stirring is adopted; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; the width of the plate blank is 1180mm, and the pulling speed is controlled at 1.20 m/min; feeding RE wire into crystallizer at speed V RE ：30-40m/min。
(5) Hot continuous rolling: heating temperature of the plate blank: 1300 ℃; finish rolling inlet temperature: 1060 deg.C; the finishing temperature is: 840 ℃; coiling temperature: and 610 ℃.
(6) Acid pickling and cold continuous rolling: the control of large reduction rate is adopted, the thickness of the raw material is 4.5mm, the sheet with the thickness of 2.0mm is rolled, and the total reduction rate is about 55.6 percent.
(7) And (3) continuous annealing: the annealing temperature is 815 ℃, the thickness of the produced product is 2.0m, and the process speed is 80 m/min.
The performance of the hot stamping steel product prepared by the embodiment meets the requirements of EN10083-3 and other relevant standards, and no banded structure appears in metallographic structure detection.
Example 6:
the hot stamping steel of the embodiment comprises the following chemical components in percentage by mass: c: 0.42%, Mn: 1.3%, Si: 0.32%, S: 0.002%, P: 0.014%, Al: 0.042%, RE: 0.08%, Ti: 0.04%, Cr: 0.20%, B: 0.002%, and the balance of iron and inevitable impurities.
The production process of the hot stamping forming steel comprises molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing. Wherein:
(1) molten iron desulphurization pretreatment: the outbound S content was 0.006%.
(2) Smelting molten steel in a converter: sedation time 165 s; the tapping of the converter adopts the slag discharge detection and sliding plate slag stopping technology, and the slag discharge of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are sequentially added for alloying and deoxidation.
(3) Refining treatment of molten steel in an LF (ladle furnace): white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is 4.9; stirring the refined molten steel by bottom blowing argon weakly stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is 40m 3 And the static blowing time is 10min between the times of the reaction and the reaction.
(4) Continuous casting: the superheat degree of the molten steel is 32 ℃; electromagnetic stirring is adopted; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; the width of the plate blank is 1135mm, and the pulling speed is controlled to be 1.30 m/min; feeding RE wire into crystallizer at speed V RE ：15-25m/min。
(5) Hot continuous rolling: heating temperature of the plate blank: 1260 ℃; finish rolling inlet temperature: 1070 ℃; the finishing temperature is as follows: 840 ℃; coiling temperature: at 600 ℃.
(6) Acid pickling and cold continuous rolling: the control of large reduction rate is adopted, the thickness of the raw material is 4.5mm, the sheet with the thickness of 2.2mm is rolled, and the total reduction rate is about 51.1 percent.
(7) And (3) continuous annealing: the annealing temperature is 810 ℃, the thickness of the produced product is 2.2m, and the process speed is 85 m/min.
The performance of the hot stamping steel product prepared by the embodiment meets the requirements of EN10083-3 and other relevant standards, and no band-shaped structure appears in metallographic structure detection.
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and it is intended to cover in the claims the invention as defined in the appended claims.
Claims (1)
1. A method for improving a banded structure of a hot forming steel plate is characterized by comprising the steps of adjusting the chemical composition of the plate and optimizing the production process of the plate; wherein, the step of adjusting the chemical components of the plate is to add rare earth element RE into the plate;
the plate comprises the following chemical components in percentage by weight: c: 0.20 to 0.45%, Mn: 1.0 to 1.50%, Si: 0.15-0.35%, S is less than or equal to 0.005%, P is less than or equal to 0.022%, Al: 0.030-0.050%, RE is more than or equal to 0.03% and less than or equal to 0.1%, Ti: 0.01-0.06%, Cr: 0.10-0.50%, B: 0.001-0.005% and the balance of iron and inevitable impurities;
the production process of the plate comprises molten iron desulphurization pretreatment, converter molten steel smelting, LF furnace molten steel refining treatment, continuous casting, hot continuous rolling, acid pickling cold continuous rolling and continuous annealing; wherein:
the converter molten steel smelting process comprises the following steps: the sedation time is more than or equal to 140 s; the tapping of the converter adopts the slag discharge detection and sliding plate slag stopping technology, and the slag discharge of the molten steel of the converter is controlled to be less than 2 kg/t; after one third of the steel is tapped, ferromanganese, ferrosilicon and aluminum are sequentially added for alloying and deoxidation;
the molten iron desulphurization pretreatment process comprises the following steps: s is less than or equal to 0.010 percent when the product is out of the station;
the LF furnace molten steel refining treatment process comprises the following steps: white slag produced by an LF furnace is deoxidized and desulfurized, and the alkalinity of refining slag is more than 4.0; stirring the refined molten steel by bottom blowing argon weakly stirring, wherein the amount of the bottom blowing argon is based on the principle that the slag surface in a steel ladle slightly shakes but the molten steel is not exposed, the composition is finely adjusted, and the flow of the bottom blowing argon is required to be 30-80 m 3 The static blowing time is more than or equal to 8min between/h
The continuous casting process comprises the following steps: the superheat degree of the molten steel is 25-35 ℃; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-5 mm; when the width of the plate blank is less than or equal to 1150mm, the pulling speed is controlled to be 1.30-1.40 m/min; when the width of the plate blank is larger than 1150mm, the pulling speed is controlled to be 1.20-1.30 m/min;
the hot continuous rolling process comprises the following steps: heating temperature of the plate blank: 1250-1310 ℃; finish rolling inlet temperature: 1050-1100 ℃; the finishing temperature is as follows: 830-860 ℃; coiling temperature: 580-620 ℃;
the pickling cold continuous rolling process comprises the following steps: the control of a large reduction rate is adopted, and the total reduction rate is more than or equal to 50 percent;
the continuous annealing process comprises the following steps: the annealing temperature is 780-820 ℃, the product thickness is 0.6-2.5 mm, and the process speed is 80-140 m/min.
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