CN107641761B - 500 MPa-grade hot-rolled automobile structure steel plate with good welding performance and manufacturing method thereof - Google Patents

500 MPa-grade hot-rolled automobile structure steel plate with good welding performance and manufacturing method thereof Download PDF

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CN107641761B
CN107641761B CN201710881208.2A CN201710881208A CN107641761B CN 107641761 B CN107641761 B CN 107641761B CN 201710881208 A CN201710881208 A CN 201710881208A CN 107641761 B CN107641761 B CN 107641761B
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CN107641761A (en
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魏兵
毛新平
张超
刘永前
孔君华
汪水泽
朱万军
刘斌
郑海涛
黄海娥
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Wuhan Iron and Steel Co Ltd
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Abstract

The invention discloses a 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance and a manufacturing method thereof, wherein the hot-rolled automobile structural steel plate comprises 0.03-0.06% of carbon, 1.0-1.3% of manganese, 0.035-0.045% of niobium, 0.035-0.045% of titanium, less than 0.10% of silicon, less than or equal to 0.005% of sulfur, less than or equal to 0.015% of phosphorus, less than or equal to 40ppm of nitrogen, 0.025-0.050% of acid-soluble aluminum, and the balance of iron and inevitable impurities. The Nb-Ti microalloying technology is adopted in a short process, the design of low-carbon components is adopted, the carbon equivalent in the steel is reduced, meanwhile, S, N (S is less than or equal to 0.005 percent and N is less than or equal to 40ppm) in the steel is fixed by using trace Ti, the fine grain function and precipitation strengthening function of Nb and Ti are fully exerted, a fine F + P structure and a fine precipitate of niobium and titanium are obtained, the welding performance of the steel is improved while higher strength is obtained.

Description

500 MPa-grade hot-rolled automobile structure steel plate with good welding performance and manufacturing method thereof
Technical Field
The invention belongs to the technical field of steel hot-rolled plate strip production, and particularly relates to a 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance and a manufacturing method thereof.
Background
In recent years, the automobile industry in China continues to develop at a high speed, and great influence is brought to social energy supply and environmental protection. With the increase of environmental protection pressure, a series of compendial documents are issued in China, and the transformation pace that the manufacturing industry in China should accelerate green manufacturing and ecological development is clearly pointed out. The existing research shows that the weight reduction is the most effective measure for realizing the energy conservation and emission reduction of the automobile, and the high reinforcement of the steel material is an important technical path for realizing the weight reduction of the automobile. The green and high-performance steel materials for automobiles are developed.
The traditional steel for automobile structures, particularly the steel with the thickness of less than 2.0mm, adopts a hot rolling and cold rolling manufacturing process, has long manufacturing flow, complex working procedures and high energy consumption, and faces the challenges of green manufacturing and cost from the automobile industry. Therefore, how to develop a new steel for automobile structure with green color, low cost and thin specification becomes a new topic in the steel industry.
Currently, there are many patents on hot-rolled steel for automobile structures. Such as: the Chinese patent publication No. CN1641059A provides a low-alloy high-strength steel and a manufacturing method thereof, wherein three alloys of Nb, V and Ti are added, and the contents of the three alloys are 0.015-0.025% of Nb, 0.025-0.035% of V and 0.010-0.020% of Ti respectively; the Mn content is more than 1.3 percent, the yield strength is only required to be more than 325MPa, and the elongation is more than 22 percent. Chinese patent application publication No. CN1920081A provides a low-alloy high-strength steel, which not only has Mn content of 1.25 to 1.75%, but also is added with a relatively expensive Mo alloy. Chinese patent application publication No. CN101768699A provides a low alloy high strength steel strip and a method for producing the same, in which expensive Mo and Cr alloys are also added. The chinese patent publication No. CN102534368A, filed for, provides a low-alloy, high-strength wide thin steel sheet and a method for producing the same, wherein the Mn content is required to be 1.4 to 1.6%, and the V content is required to be 0.34 to 0.36%. The existing steel grade of low-alloy high-strength steel can add expensive alloy components in the actual production process, thereby causing high cost and low economic benefit. The Chinese patent with the application number of 201410036071.7, namely a low-alloy high-strength steel galvanized plate and a production method thereof, comprises the following chemical components in percentage by mass: c: 0.04-0.07%; si is less than or equal to 0.03 percent; mn0.3-0.4%, P is less than or equal to 0.015%, S is less than or equal to 0.012%, Als0.020-0.045%, N is less than or equal to 0.0050%, and the balance is Fe, through optimizing the component design, simultaneously correspondingly adjusting the technological parameters of hot rolling, cold rolling and galvanizing procedures, adding cheap Mn alloy with the content of only 0.3-0.4%, and producing the low-alloy high-strength galvanized sheet with the yield strength of 260-355 MPa under the condition of not adding any other alloy elements, wherein the elongation rate reaches more than 28%. The product produced by the above patents is produced by the following generally adopted production process: converter steelmaking, hot rolling, acid pickling and cold rolling, galvanizing and the like, the production flow is long, the cost is high, and the product has no strong competitiveness. Due to the characteristics of a production line of the short process, the thin hot-rolled automobile structural steel with the thickness of 1.0-3.0 mm and the yield strength of more than or equal to 500MPa can be produced, the subsequent cold rolling and annealing processes are reduced, the cost is reduced, and the product competitiveness is improved. Most structural parts in a white automobile body need to be welded, the weldability of high-strength steel is generally poor, and the application and popularization of materials are affected, so that the 500 MPa-level hot-rolled automobile structural steel plate with good welding performance is produced based on a short process and is one of the technical difficulties to be solved urgently in the field.
Disclosure of Invention
The invention aims to provide a 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance and a manufacturing method thereof, which can produce a thin-specification hot-rolled product with the yield strength of 500MPa, the carbon equivalent w of the steel is less than or equal to 0.25%, the steel has good welding performance, and meanwhile, the fluctuation ranges of the yield strength and the tensile strength are controlled within 60MPa, so that the standard requirements of cold-rolled products with the same strength grade can be met, and the steel plate has good cold forming performance.
In order to achieve the purpose, the invention adopts the technical scheme that: the 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance comprises the following chemical element components in percentage by weight: 0.03-0.06% of carbon, 1.0-1.3% of manganese, 0.035-0.045% of niobium, 0.035-0.045% of titanium, less than 0.10% of silicon, less than or equal to 0.005% of sulfur, less than or equal to 0.015% of phosphorus, less than or equal to 40ppm of nitrogen, 0.025-0.050% of acid-soluble aluminum, and the balance of iron and inevitable impurities.
In order to realize that the steel grade is 'hot instead of cold', meet the requirements of automobile parts, have strict requirements on inclusions and surface quality in steel, and redesign a component system by combining a short process and adopting a 'low-silicon and low-manganese' Nb-Ti microalloy component design idea.
The weight percentage of the carbon is 0.05-0.055%.
Si (silicon): has strong solid solution strengthening effect, but is oxidized into SiO under high temperature condition2Then SiO2React with FeO in the oxide layer to form fayalite phase (Fe)2SiO4) Easily enriched at the junction surface of the iron scale and the matrix, and once continuous Fe is formed between the iron scale and the matrix2SiO4The layer plays a role of 'pinning' on the scale, causes scale defects in the rolling process, deteriorates the surface quality of the hot rolled steel plate, increases the roughness of the scale and the substrate interface, so that the Si is strictly limited, and the content of the Si is limited to be<Within the range of 0.10%.
Mn (manganese): solid solution strengthening elements, oxides at high temperature similar to those of Fe, MnO, Mn3O4、Mn2O3And the like, and has high intersolubility with corresponding oxides of Fe. When the Mn content is too high, it is liable to form (FeMn)2SiO4The iron scale is easy to be enriched at the joint surface of the iron scale and the matrix, so that the interface between the iron scale and the matrix is rough, and the defects of iron scale are formed, so that the content of the iron scale is limited to 1.0-1.3%, and the preferred content is 1.05-1.15%.
Ti (titanium): the grain is refined, a small amount of Ti is added to fix free N, S in molten steel and improve the welding performance of steel grades, so the content of the Ti is limited to 0.035-0.045%, and preferably 0.035-0.042%.
Nb (niobium): the grains are refined to play a role in fine grain strengthening, but Nb is used for improving austenite recrystallization, so that mixed crystal structure in steel is easily caused, and the content of Nb is limited to 0.035-0.045%, preferably 0.035-0.042%.
A method for manufacturing a hot-rolled automobile structural steel plate with good welding performance in the 500MPa level comprises the following steps:
1) smelting
Uniformly mixing the components in percentage by weight to form molten steel, and adopting a deep desulfurization pretreatment-converter steelmaking-LF-RH (or RH-free) process during smelting;
the molten iron desulphurization pretreatment requirement S is less than or equal to 0.005%, the converter molten steel smelting requirement C is more than or equal to 0.03%, and the tapping temperature is 1660-1690 ℃; deoxidizing and slagging in an LF furnace, wherein the leaving temperature is more than or equal to 1620 ℃; molten steel enters an RH furnace, decarburization and deoxidation are carried out, Nb-Ti alloy is added, after the alloy is added, circulation is carried out for more than or equal to 8min, then air breaking is carried out, and argon blowing is carried out for more than or equal to 5 min;
2) calcium treatment
Carrying out calcium treatment to improve slag property, controlling N to be less than or equal to 40ppm, controlling Als to be 0.025-0.050%, and controlling tapping temperature to be 1570-1590 ℃;
3) continuous casting
Continuously casting at a blank drawing speed of 4-6 m/min and a casting blank thickness of 50-150 mm to form a continuously cast thin slab; the casting blank adopts a weak edge cooling system in a secondary cooling water section, the cooling water quantity is controlled to ensure that the temperature of the continuous casting sheet blank entering a soaking furnace is 900-1000 ℃, and the edge cracks of the casting blank are reduced;
4) continuous casting thin slab soaking
After the continuous casting sheet billet is put into a soaking furnace, the furnace time is 20-40 min, and the tapping temperature is 1180-1230 ℃;
5) descaling
Carrying out high-pressure water descaling before the continuous casting sheet billet is discharged from the soaking pit furnace and enters the rolling mill, wherein the descaling header is more than or equal to 2 groups, and the descaling water pressure is controlled to be 280-320 bar;
6) rolling of
The temperature of the continuous casting sheet billet entering a rolling mill is 1120-1170 ℃, and the first pass reduction rate, the second pass reduction rate and the third pass reduction rate are controlled to be more than or equal to 50% in finish rolling; providing deformation conditions for sufficient recrystallization of austenite in the rolling process, eliminating mixed crystals in the structure, and controlling the final rolling temperature to be 820-880 ℃;
7) cooling down
The rolled steel coil adopts a front-stage rapid cooling process, the laminar flow intermediate temperature is 680-720 ℃, and the coiling temperature is controlled at 560-620 ℃;
8) leveling
And (4) flattening the steel coil, wherein the flattening force is 210-240 tons, and a yield platform is eliminated.
Compared with the prior art, the invention has the following advantages:
1) the invention adopts Nb-Ti microalloying technology in a short process, adopts the design of low-carbon components, reduces the carbon equivalent of the steel grade, simultaneously fixes S, N (S is less than or equal to 0.005 percent and N is less than or equal to 40ppm) in the steel by utilizing trace Ti, fully exerts the fine grain function and precipitation strengthening function of Nb and Ti, obtains fine F + P structure and fine precipitates of niobium and titanium, and improves the welding performance of the steel grade while obtaining higher strength;
2) the method is characterized in that a brand-new component system is adopted in a short-flow production line to produce a thin hot-rolled automobile structural steel plate with the yield strength of 500MPa, the structure is fine ferrite and pearlite, the grain size is 12-13, no mixed crystal structure appears, the thickness is 1.0-3.0 mm, the yield strength of the steel is 500-620 MPa, the tensile strength is 530-690 MPa, the elongation A80 is more than or equal to 14%, the carbon equivalent w is less than or equal to 0.25%, the steel plate has excellent welding performance, meanwhile, the steel plate is qualified by a wide cold bending test at 180 ℃, and the bending diameter d is 0.5a (sample thickness);
3) the method is based on a short-process production line, has simple and efficient process, is energy-saving and environment-friendly, is suitable for producing the thin hot-rolled automobile structural steel plate with the thickness of 1.0-3.0 mm, can replace the traditional cold-rolled product, saves the complex cold rolling and annealing processes, greatly shortens the manufacturing process, reduces the manufacturing cost, reduces the energy consumption and water consumption and the discharge of various wastes, and meets the requirements of green manufacturing and low cost in the automobile industry;
4) the invention gives full play to the characteristic of uniform temperature in the short-process rolling process, can produce thin hot rolled products with the yield strength of 500MPa, has stable performance and small fluctuation, controls the fluctuation range of the yield strength and the tensile strength within 60MPa, can meet the standard requirements of cold rolled products with the same strength grade, and can replace the cold rolled products.
Drawings
FIG. 1 is a schematic drawing showing precipitates in a hot rolled automobile structural steel sheet having good weldability at 500MPa according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples to facilitate the clear understanding of the present invention, but the present invention is not limited thereto.
Example 1
In the embodiment, the 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance is produced by adopting a low-carbon, low-silicon and low-manganese Nb-Ti microalloy component system, and the mass percentages of chemical components of the elements are controlled as follows: c: 0.05%, Si: less than or equal to 0.07 percent, Mn: 1.05%, S: less than or equal to 0.005 percent, P: less than or equal to 0.015 percent, Nb: 0.036%, Ti: 0.035%, N: less than or equal to 40ppm, Als: 0.025 to 0.050%;
the manufacturing method comprises the following steps:
1) smelting
Uniformly mixing the components in percentage by weight to form molten steel, and adopting a deep desulfurization pretreatment-converter steelmaking-LF-RH process during smelting;
molten iron desulphurization pretreatment requirement S: not more than 0.005 percent, the smelting requirement C of converter molten steel is 0.05 percent, and the tapping temperature is 1690 ℃; deoxidizing and slagging in an LF furnace, wherein the leaving temperature is more than or equal to 1653 ℃; molten steel enters an RH furnace, decarburization and deoxidation are carried out, Nb-Ti alloy is added, after the alloy is added, circulation is carried out for more than or equal to 8min, then air breaking is carried out, and argon blowing is carried out for more than or equal to 5 min;
2) calcium treatment
Carrying out calcium treatment to improve slag property, controlling N to be less than or equal to 40ppm, controlling Als to be 0.025-0.050%, and controlling tapping temperature to be 1578 ℃;
3) continuous casting
Continuously casting at a speed of 4.3m/min and a thickness of 50mm to form a continuously cast sheet billet; the casting blank adopts a weak edge cooling system in a secondary cooling water section, the cooling water quantity is controlled to ensure that the temperature of the continuous casting sheet blank in the soaking furnace is 920 ℃, and the edge cracks of the casting blank are reduced;
4) continuous casting thin slab soaking
After the continuous casting sheet billet is put into a soaking furnace, the furnace time is 25min, and the tapping temperature is 1180 ℃;
5) descaling
Carrying out high-pressure water descaling before the continuous casting sheet billet is discharged from the soaking pit and enters the rolling mill, wherein the descaling header is more than or equal to 2 groups, and the descaling water pressure is controlled to be 300 bar;
6) rolling of
The temperature of the continuous casting sheet billet entering a rolling mill is 1140 ℃, and the first pass reduction rate, the second pass reduction rate and the third pass reduction rate are controlled to be 51 percent, 53 percent and 52 percent respectively in finish rolling; providing deformation conditions for sufficient recrystallization of austenite in the rolling process, eliminating mixed crystals in the structure, and controlling the final rolling temperature to be 820-880 ℃;
7) cooling down
The rolled steel coil adopts a front-stage rapid cooling process, the laminar flow intermediate temperature is 680-720 ℃, and the coiling temperature is controlled at 560-620 ℃;
8) leveling
And (4) flattening the steel coil, wherein the flattening force is 210-240 tons, and a yield platform is eliminated.
The texture, mechanical properties and work hardening rate of the products produced according to the component systems of this example are shown in Table 1.
Table 1 shows the structure, mechanical properties and work hardening rate of the steel sheet of example 1
As can be seen from Table 1 and FIG. 1, the thin hot-rolled automobile structural steel with 500MPa grade yield strength produced in the embodiment meets the standard requirements of cold-rolled products with the same strength grade, meanwhile, the carbon equivalent w of the steel grade is less than or equal to 0.25%, the work hardening rate n is greater than or equal to 0.15, and the steel is qualified for 180 degrees of cold bending when the bending diameter d is 0.5a, and has excellent welding performance and cold forming performance.
Example 2
In the embodiment, the 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance is produced by adopting a low-carbon, low-silicon and low-manganese Nb-Ti microalloy component system, and the mass percentages of chemical components of the elements are controlled as follows: c: 0.055%, Si: less than or equal to 0.08 percent, Mn: 1.10%, S: less than or equal to 0.004%, P: less than or equal to 0.015 percent, Nb: 0.036%, Ti: 0.037%, N: less than or equal to 40ppm, Als: 0.025 to 0.050%;
the manufacturing method comprises the following steps:
1) smelting
Uniformly mixing the components in percentage by weight to form molten steel, and adopting a deep desulfurization pretreatment-converter steelmaking-LF-RH process during smelting;
molten iron desulphurization pretreatment requirement S: less than or equal to 0.004 percent, the smelting requirement C of the converter molten steel is 0.055 percent, and the tapping temperature is 1674 ℃; deoxidizing and slagging in an LF furnace, wherein the leaving temperature is more than or equal to 1635 ℃; molten steel enters an RH furnace, decarburization and deoxidation are carried out, Nb-Ti alloy is added, after the alloy is added, circulation is carried out for more than or equal to 8min, then air breaking is carried out, and argon blowing is carried out for more than or equal to 5 min;
2) calcium treatment
Carrying out calcium treatment to improve slag property, controlling N to be less than or equal to 40ppm, controlling Als to be 0.025-0.050%, and controlling tapping temperature to be 1576 ℃;
3) continuous casting
Continuously casting at a blank drawing speed of 4.5m/min and a casting blank thickness of 55mm to form a continuous casting sheet blank; the casting blank adopts a weak edge cooling system in a secondary cooling water section, the cooling water quantity is controlled to ensure that the temperature of the continuous casting sheet blank entering a soaking furnace is 950 ℃, and the edge cracks of the casting blank are reduced;
4) continuous casting thin slab soaking
After the continuous casting sheet billet is put into a soaking furnace, the furnace time is 30min, and the tapping temperature is 1200 ℃;
5) descaling
Carrying out high-pressure water descaling before the continuous casting sheet billet is discharged from the soaking pit and enters the rolling mill, wherein the descaling header is more than or equal to 2 groups, and the descaling water pressure is controlled to be 320 bar;
6) rolling of
The temperature of the continuous casting sheet billet entering the rolling mill is 1160 ℃, and the first pass reduction rate, the second pass reduction rate and the third pass reduction rate are controlled to be 52 percent, 53 percent and 51 percent respectively in finish rolling; providing deformation conditions for sufficient recrystallization of austenite in the rolling process, eliminating mixed crystals in the structure, and controlling the final rolling temperature to be 820-880 ℃;
7) cooling down
The rolled steel coil adopts a front-stage rapid cooling process, the laminar flow intermediate temperature is 680-720 ℃, and the coiling temperature is controlled at 560-620 ℃;
8) leveling
And (4) flattening the steel coil, wherein the flattening force is 210-240 tons, and a yield platform is eliminated.
The texture, mechanical properties and work hardening rate of the products produced according to the component systems of this example are shown in Table 2.
Table 2 shows the structure, mechanical properties and work hardening rate of the steel sheet of example 2
As can be seen from Table 2 and FIG. 1, the thin hot-rolled automobile structural steel with 500 MPa-grade yield strength produced by the method meets the standard requirements of cold-rolled products with the same strength grade in performance, meanwhile, the carbon equivalent w of the steel grade is less than or equal to 0.25%, the work hardening rate n is more than or equal to 0.15, and the steel is qualified for cold bending at 180 degrees when the bending diameter d is 0.5a, and has excellent welding performance and cold forming performance.
Example 3
In the embodiment, the 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance is produced by adopting a low-carbon, low-silicon and low-manganese Nb-Ti microalloy component system, and the mass percentages of chemical components of the elements are controlled as follows: c: 0.055%, Si: less than or equal to 0.07 percent, Mn: 1.15%, S: less than or equal to 0.003 percent, P: less than or equal to 0.015 percent, Nb: 0.036%, Ti: 0.038%, N: less than or equal to 40ppm, Als: 0.025 to 0.050%;
the manufacturing method comprises the following steps:
1) smelting
Uniformly mixing the components in percentage by weight to form molten steel, and adopting a deep desulfurization pretreatment-converter steelmaking-LF-RH process during smelting;
the molten iron desulphurization pretreatment requirement S is less than or equal to 0.003 percent, the converter molten steel smelting requirement C is 0.055 percent, and the tapping temperature is 1680 ℃; deoxidizing and slagging in an LF furnace, wherein the leaving temperature is more than or equal to 1645 ℃; molten steel enters an RH furnace, decarburization and deoxidation are carried out, Nb-Ti alloy is added, after the alloy is added, circulation is carried out for more than or equal to 8min, then air breaking is carried out, and argon blowing is carried out for more than or equal to 5 min;
2) calcium treatment
Carrying out calcium treatment to improve slag property, wherein N is controlled to be less than or equal to 40ppm, Als is controlled to be 0.025-0.050%, and the tapping temperature is 1577 ℃;
3) continuous casting
Continuously casting at a blank drawing speed of 5.0m/min and a casting blank thickness of 60mm to form a continuously cast thin slab; the casting blank adopts a weak edge cooling system in a secondary cooling water section, the cooling water quantity is controlled to ensure that the temperature of the continuous casting sheet blank entering a soaking furnace is 990 ℃, and the edge cracks of the casting blank are reduced;
4) continuous casting thin slab soaking
After the continuous casting sheet billet is put into a soaking furnace, the furnace time is 30min, and the tapping temperature is 1230 ℃;
5) descaling
Carrying out high-pressure water descaling before the continuous casting sheet billet is discharged from the soaking pit and enters the rolling mill, wherein the descaling header is more than or equal to 2 groups, and the descaling water pressure is controlled to be 320 bar;
6) rolling of
The temperature of the continuous casting sheet billet entering the rolling mill is 1170 ℃, and the first pass reduction rate, the second pass reduction rate and the third pass reduction rate are controlled to be 53 percent, 53 percent and 52 percent respectively in finish rolling; providing deformation conditions for sufficient recrystallization of austenite in the rolling process, eliminating mixed crystals in the structure, and controlling the final rolling temperature to be 820-880 ℃;
7) cooling down
The rolled steel coil adopts a front-stage rapid cooling process, the laminar flow intermediate temperature is 680-720 ℃, and the coiling temperature is controlled at 560-620 ℃;
8) leveling
And (4) flattening the steel coil, wherein the flattening force is 210-240 tons, and a yield platform is eliminated.
The texture, mechanical properties and work hardening rate of the products produced according to the component systems of this example are shown in Table 2.
Table 3 shows the structure, mechanical properties and work hardening rate of the steel sheet of example 3
As can be seen from Table 3 and FIG. 1, the yield strength 500MPa grade 1.0-3.0 mm thin hot rolled automobile structural steel produced by the method meets the standard requirements of cold rolled products with the same strength grade, meanwhile, the carbon equivalent w of the steel grade is less than or equal to 0.25%, the work hardening rate n is more than or equal to 0.15, and the steel is qualified by cold bending 180 degrees when the bending diameter d is 0.5a, and has excellent welding performance and cold forming performance.

Claims (2)

1. The utility model provides a 500MPa level has hot rolling car structure steel sheet of good welding performance which characterized in that: 0.05-0.055% of carbon, 1.05-1.15% of manganese, 0.035-0.042% of niobium, 0.035-0.042% of titanium, less than 0.10% of silicon, less than or equal to 0.005% of sulfur, less than or equal to 0.015% of phosphorus, less than or equal to 40ppm of nitrogen, 0.025-0.050% of acid-soluble aluminum, and the balance of iron and inevitable impurities;
the manufacturing method of the 500 MPa-grade hot-rolled automobile structural steel plate with good welding performance comprises the following steps:
1) smelting
Uniformly mixing the components in percentage by weight to form molten steel, and adopting a deep desulfurization pretreatment-converter steelmaking-LF-RH process during smelting;
2) calcium treatment
Carrying out calcium treatment to improve slag property, controlling N to be less than or equal to 40ppm, controlling Als to be 0.025-0.050%, and controlling tapping temperature to be 1570-1590 ℃;
3) continuous casting
Continuously casting at a blank drawing speed of 4-6 m/min and a casting blank thickness of 50-150 mm to form a continuously cast thin slab; the casting blank adopts a weak edge cooling system in a secondary cooling water section, and the cooling water quantity is controlled to ensure that the temperature of the continuous casting sheet blank entering a soaking furnace is 900-1000 ℃;
4) continuous casting thin slab soaking
After the continuous casting sheet billet is put into a soaking furnace, the furnace time is 20-40 min, and the tapping temperature is 1180-1230 ℃;
5) descaling
Carrying out high-pressure water descaling before the continuous casting sheet billet is discharged from the soaking pit furnace and enters the rolling mill, and controlling the pressure of the descaling water to be 280-320 bar;
6) rolling of
The temperature of the continuously cast sheet billet entering a rolling mill is 1120-1170 ℃, the first pass reduction rate, the second pass reduction rate and the third pass reduction rate are controlled to be more than or equal to 50% in finish rolling, and the final rolling temperature is controlled to be 820-880 ℃;
7) cooling down
The rolled steel coil adopts a front-stage rapid cooling process, the laminar flow intermediate temperature is 680-720 ℃, and the coiling temperature is controlled at 560-620 ℃;
8) leveling
And (4) flattening the steel coil, wherein the flattening force is 210-240 tons.
2. The 500MPa grade hot rolled automotive structural steel sheet with good weldability according to claim 1 characterised in that: in the step 1), the components and the weight percentage are uniformly mixed to form molten steel, and a deep desulfurization pretreatment-converter steelmaking-LF process is adopted during smelting.
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CN109023110B (en) * 2018-09-26 2020-06-19 武汉钢铁有限公司 500 MPa-level thin-specification hot-rolled automobile structural steel produced by adopting short process and method
CN109097699B (en) * 2018-09-26 2020-01-14 武汉钢铁有限公司 900 MPa-grade hot-rolled automobile girder steel and manufacturing method thereof
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