Method for improving welding performance of 380mpa grade automobile wheel rim steel

Abstract

The application discloses a preparation method of 380MPa-grade automobile wheel rim steel with excellent welding performance, and comprises the following steps: converter smelting, refining process, continuous casting process, continuous casting blank heating, rolling, cooling and coiling; the chemical components of the 380MPa-grade automobile wheel rim steel are as follows: 0.05-0.07% of C, 0.03-0.10% of Si, 0.80-1.00% of Mn, less than or equal to 0.018% of P, less than or equal to 0.005% of S, 0.020-0.040% of Alt, 0.010-0.020% of Ti, 0.0030-0.0070% of N, 0.0010-0.0030% of Ca, and the rest is iron elements and inevitable impurities. The application aims to improve the uniformity of the circumferential welding performance of the wheel rim and greatly improve the welding deformation and cracking problem of the product.

Description

Technical Field

[0001] This invention belongs to the field of hot-rolled automotive steel preparation technology, and particularly relates to a method for improving the welding performance of 380MPa grade automotive wheel rim steel. Background Technology

[0002] Steel wheels are primarily used in commercial trucks and are a crucial component of the driving system. Currently, 380CL remains one of the most widely used materials for processing wheel rims on small trucks. The production process for 380CL wheel rims is as follows: steel plate → strip cutting → hemming → rolling → flattening → welding → slag removal → roll weld seam → head cutting → rounding → flaring → first roll forming → second roll forming → third roll forming → flaring finishing → valve hole punching → inspection. Welding often employs flash butt welding, which offers advantages such as high thermal efficiency, no need for additional welding materials, and good weld quality. However, flash butt welding frequently results in weld seam or heat-affected zone deformation and cracking, increasing the quality and cost of wheel rim production. If small cracks are not detected promptly, they can lead to slow tire leaks after tire installation, affecting the wheel's lifespan and safety.

[0003] Chinese patent application CN 112662855 A discloses a method for improving the low-temperature impact toughness of 380MPa grade hot-rolled wheel steel. This patent improves the stability of low-temperature impact toughness by increasing the deformation of the core material and optimizing the deformation uniformity of the intermediate billet in the thickness direction. While this patent does not mention the weldability of the product, weldability is one of the important technical indicators for wheel steel, especially rim steel. In contrast, this patent further refines the composition design to achieve superior weldability.

[0004] Chinese patent application CN 105088070 A discloses a method for producing 380MPa grade wheel steel, composed of the following components by weight percentage: 0.06–0.10% C, ≤0.10% Si, 0.70–1.10% Mn, ≤0.020% P, ≤0.010% S, 0.015–0.050% Als, 0.010–0.030% Ti, with the balance being Fe and unavoidable impurities. This patented method successfully developed 380MPa grade wheel steel with good weldability by adding Ti to a C-Mn strengthening system. The mechanism by which Ti improves weldability is through the reaction with N to form a TiN second phase of suitable size, inhibiting grain coarsening in the weld and heat-affected zone. The N content has a significant impact on the size and quantity of TiN. However, the method described in this patent does not address controlling the N content of the steel, resulting in an unsatisfactory improvement in weldability. Compared to this patent, which further limits the N element and proposes to control the Ti / N ratio, the effect of Ti element in improving welding performance can be maximized.

[0005] Chinese patent application CN 109112401 A discloses a 380MPa grade titanium-containing steel strip for wheel rims and its production method. The strip is composed of the following components by weight percentage: 0.06–0.10% C, 0.05–0.15% Si, 0.70–0.90% Mn, ≤0.020% P, ≤0.010% S, 0.020–0.050% Als, 0.010–0.030% Ti, ≤0.0060% N, with the balance being Fe and unavoidable impurities. The patent describes a composition design with low C and low Mn content, and the addition of small amounts of alloying elements Si and Ti. The layer cooling section employs a water-cooling + air-cooling + water-cooling process to obtain a 380MPa grade steel strip for wheel rims. This patent utilizes Ti to achieve grain refinement, improve strength and toughness, and enhance weldability, while controlling the N content to ≤0.0060%. Compared to other patents, this patent not only further effectively limits the Ti and N elements in steel, but also proposes Ti / N parameters that have a significant impact on the size of TiN, and provides a control range, which can better leverage the effect of Ti element in improving welding performance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the welding performance of 380MPa grade automotive wheel rim steel. This method employs a low-C+Mn+Ti composition design route and effectively controls the N element content and Ti / N ratio in the steel. The mechanical properties of the product are mainly achieved through Mn element solid solution strengthening and controlled rolling and cooling processes. The Ti element content is limited to 0.01-0.02%, and the N element content is controlled at 30-70ppm, resulting in a Ti / N ratio range of 2.0-6.0. Ti in the steel does not play a strengthening role. After the Ti and N element contents meet the above control requirements, TiN with a size of approximately 4-16nm will precipitate during heating. This size of TiN can first inhibit high-temperature austenite coarsening, refine the grain size, and promote improved plastic deformation capacity. More importantly, TiN has high-temperature thermal stability. During wheel rim welding, this size of TiN can maximize its role in inhibiting grain coarsening in the weld and heat-affected zone, preventing performance deterioration in this area, thereby improving the uniformity of the circumferential post-weld performance of the wheel rim and greatly improving the problem of welding deformation and cracking.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention discloses a method for improving the welding performance of 380MPa grade automotive wheel rim steel, specifically comprising the following steps:

[0009] Step 1: To ensure low sulfur content control in molten iron, KR desulfurization treatment adopts deep desulfurization operation. At the end of desulfurization, the sulfur content in molten iron should be ≤0.0010%, and the slag removal ratio on the surface of the molten iron ladle should be ≥95%.

[0010] Step 2: To improve the cleanliness of molten steel, the carbon content of the final component in the converter smelting process must be controlled at 0.04% to 0.06%. The target component must be achieved in one go at the converter's final stage. Point blowing operation is prohibited at the converter's final stage. The converter tapping temperature is controlled at 1620℃ to 1660℃. Sliding plate slag blocking operation is used at the beginning and end of the converter tapping process to prevent converter slag from falling into the ladle.

[0011] Step 3: Slag formation, deoxidation and desulfurization in the LF furnace, and the addition of aluminum ferromanganese, ferrosilicon and ferroniobium alloys to adjust the composition to the target range. In order to reduce the amount of nitrogen added to the molten steel and control the cleanliness of the molten steel during the LF refining process, the speed of the dust removal fan needs to be adjusted during the LF heating process to ensure that the pressure inside the fume hood is at a slightly positive pressure during the LF refining heating process, so as to prevent outside air from entering the fume hood and contacting the molten steel.

[0012] Step 5: Argon gas is used for protection throughout the casting process. The slag detection equipment is turned on during the ladle pouring process, and slag from the ladle is prevented from flowing into the tundish at the end of the ladle pouring. Constant casting speed control is used during the casting process, and the casting speed is set in the range of 1.1m / min to 1.6m / min according to different casting sections. The superheat of the tundish is controlled between 20℃ and 35℃.

[0013] Step 6: The heating process includes furnace time and furnace exit temperature. The furnace time is controlled at 180-240 min, the soaking temperature is controlled at 20-50 min, and the furnace exit temperature is controlled at 1170-1240℃.

[0014] Step 7: Rolling includes roughing and finishing. Roughing is done on a 2-stand mill, and finishing is done on a 7-stand continuous variable crown mill. The first pass reduction in roughing is ≥35mm, the intermediate billet thickness is 35-40mm, the initial rolling temperature of intermediate finishing is controlled at ≤1000℃, and the final rolling temperature of finishing is controlled at 840-880℃.

[0015] Step 7: Cooling adopts laminar flow continuous cooling equipment, with the upper and lower cooling nozzles opening alternately, the cooling rate is 30-45℃ / s, and the winding temperature is 560-600℃;

[0016] The chemical composition of the 380MPa grade automotive wheel rim steel by mass percentage is as follows: 0.05-0.07% C, 0.03-0.10% Si, 0.80-1.00% Mn, less than or equal to 0.018% P, less than or equal to 0.005% S, 0.020-0.040% Alt, 0.010-0.020% Ti, 0.0030-0.0070% N, 0.0010-0.0030% Ca, with the remainder being iron and unavoidable impurities.

[0017] Furthermore, the chemical composition and mass percentage content of the 380MPa grade automotive wheel rim steel are as follows: C: 0.06%, Si: 0.05%, Mn: 0.90%, P: 0.012%, S: 0.002%, Alt: 0.041%, Ti: 0.013%, N: 0.0056%, with the balance being Fe and unavoidable impurities.

[0018] Furthermore, the chemical composition and mass percentage content of the 380MPa grade automotive wheel rim steel are as follows: C: 0.06%, Si: 0.03%, Mn: 0.90%, P: 0.010%, S: 0.004%, Alt: 0.040%, Ti: 0.014%, N: 0.0061%, with the balance being Fe and unavoidable impurities.

[0019] Furthermore, the chemical composition and mass percentage content of the 380MPa grade automotive wheel rim steel are as follows: C: 0.07%, Si: 0.03%, Mn: 0.95%, P: 0.012%, S: 0.003%, Alt: 0.038%, Ti: 0.012%, N: 0.0058%, with the balance being Fe and unavoidable impurities.

[0020] Furthermore, the specific steps of each process are as follows:

[0021] 1) Smelting and continuous casting process: The molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR molten iron leaving the station at 0.0009% and the iron temperature at 1324℃. A top-and-bottom blowing converter is used to decarburize and dephosphorize the molten iron to obtain steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1626℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel after converter smelting is then subjected to LF ladle refining at a refining temperature of 1528℃. LF slag formation and desulfurization are performed, and aluminum ferroalloys, ferrosilicon, ferromanganese, and ferrotitanium alloys are added according to the steel composition. After LF treatment, calcium treatment is performed, and the soft blowing time is ensured to be 9 minutes after wire feeding.

[0022] 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 520℃, the temperature at the end of the soaking zone is 1206℃, and the soaking time is 43min to ensure that the alloying elements are fully dissolved.

[0023] 3) Rolling process: The first pass reduction in roughing is 38mm, and the temperature of the last pass in roughing is 1020℃; the thickness of the intermediate billet is 38mm, and the temperature of entering the finishing mill is 940℃.

[0024] 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 33℃ / s and a winding temperature control of 594℃.

[0025] Furthermore, the specific steps of each process are as follows:

[0026] Smelting and continuous casting processes: Molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR molten iron leaving the station at 0.0009% and the iron temperature at 1326℃. A top-and-bottom blowing converter is used for smelting to decarburize and dephosphorize the molten iron, yielding steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1628℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel from the converter is then subjected to LF ladle refining at a temperature of 1525℃. LF slag formation and desulfurization are performed, and aluminum-iron, silicon-iron, manganese-iron, and titanium-iron alloys are added according to the steel composition. After LF treatment, calcium treatment is performed, and the soft blowing time is ensured to be 11 minutes after wire feeding.

[0027] 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 500℃, the temperature at the end of the soaking zone is 1197℃, and the soaking time is 44min to ensure that the alloying elements are fully dissolved.

[0028] 3) Rolling process: The first pass reduction in roughing is 37mm, and the temperature of the last pass in roughing is 1020℃; the thickness of the intermediate billet is 40mm, and the temperature of entering the finishing mill is 940℃.

[0029] 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 35℃ / s and a winding temperature control of 581℃.

[0030] Furthermore, the specific steps of each process are as follows:

[0031] Smelting and continuous casting processes: Molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR molten iron leaving the station at 0.0009% and the iron temperature at 1328℃. A top-and-bottom blowing converter is used for smelting to decarburize and dephosphorize the molten iron, yielding steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1630℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel from the converter is then subjected to LF ladle refining at a temperature of 1532℃. LF slag formation and desulfurization are performed, and aluminum-iron, silicon-iron, manganese-iron, and titanium-iron alloys are added according to the steel composition. After LF treatment, calcium treatment is performed, and soft blowing time is ensured to be 10 minutes after wire feeding.

[0032] 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 480℃, the temperature at the end of the soaking zone is 1190℃, and the soaking time is 48min to ensure that the alloying elements are fully dissolved.

[0033] 3) Rolling process: The first pass reduction in roughing is 36mm, and the temperature of the last pass in roughing is 1025℃; the thickness of the intermediate billet is 43mm, and the temperature of entering the finishing mill is 950℃;

[0034] 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 35℃ / s and a winding temperature control of 588℃.

[0035] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0036] The steel strip for automobile wheel rims of this invention has a yield strength ≥235MPa, a tensile strength of 380~480MPa, and an elongation A ≥28%. All indicators meet the requirements of YB / T 4151-2015 and customer requirements.

[0037] This invention obtains TiN of suitable size by controlling the content of Ti and N elements in steel, which not only refines the grain size of the finished product, but also effectively suppresses the coarsening of the heat-affected structure of the weld, improves the uniformity of the performance distribution after the wheel rim is welded, and improves the problem of welding deformation and cracking of the wheel rim.

[0038] This invention improves the problem of welding deformation and cracking in 380MPa grade automotive wheel rim steel, effectively enhancing product quality and customer satisfaction, laying a solid quality foundation for expanding product market share, and achieving substantial economic benefits. Attached Figure Description

[0039] The present invention will be further described below with reference to the accompanying drawings.

[0040] Figure 1 The metallographic structure of the product is shown in the example. Detailed Implementation

[0041] The following examples are used to illustrate the content of the present invention. These examples are only general descriptions of the content of the present invention and do not limit the content of the present invention.

[0042] Example 1

[0043] In this embodiment, the thickness of the 380MPa grade automotive wheel rim steel is 4.0mm, and its chemical composition and mass percentage content are as follows: C: 0.06%, Si: 0.05%, Mn: 0.90%, P: 0.012%, S: 0.002%, Alt: 0.041%, Ti: 0.013%, N: 0.0056%, with the balance being Fe and unavoidable impurities.

[0044] Its production process includes smelting, slab heating, high-pressure water descaling, controlled rolling, controlled cooling, and coiling. The specific steps of each process are as follows:

[0045] Smelting and continuous casting processes: Molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR iron leaving the station at 0.0009% and the iron temperature at 1324℃. A top-and-bottom blown converter is used for smelting to decarburize and dephosphorize the molten iron to obtain steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1626℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel from the converter is then subjected to LF ladle refining at a temperature of 1528℃. LF slag formation and desulfurization are performed, and alloys such as ferroaluminum, ferrosilicon, ferromanganese, and ferrotitanium are added according to the steel composition. After LF treatment, calcium treatment is performed, and the soft blowing time is ensured to be 9 minutes after wire feeding.

[0046] 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 520℃, the temperature at the end of the soaking zone is 1206℃, and the soaking time is 43min to ensure that the alloying elements are fully dissolved.

[0047] 3) Rolling process: The first pass of roughing rolling has a reduction of 38mm, and the temperature of the last pass of roughing rolling is 1020℃; the thickness of the intermediate billet is 38mm, and the temperature of entering the finishing rolling is 940℃.

[0048] 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 33℃ / s and a winding temperature control of 594℃.

[0049] Example 2

[0050] This embodiment uses 380MPa grade automotive wheel rim steel with a thickness of 6.5mm. Its chemical composition and mass percentage content are as follows: C: 0.06%, Si: 0.03%, Mn: 0.90%, P: 0.010%, S: 0.004%, Alt: 0.040%, Ti: 0.014%, N: 0.0061%, with the balance being Fe and unavoidable impurities.

[0051] Its production process includes smelting, slab heating, high-pressure water descaling, controlled rolling, controlled cooling, and coiling. The specific steps of each process are as follows:

[0052] Smelting and continuous casting processes: Molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR iron leaving the station at 0.0009% and the iron temperature at 1326℃. A top-and-bottom blowing converter is used to decarburize and dephosphorize the molten iron to obtain steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1628℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel from the converter is then subjected to LF ladle refining at a temperature of 1525℃. LF slag formation and desulfurization are performed, and alloys such as ferroaluminum, ferrosilicon, ferromanganese, and ferrotitanium are added according to the steel composition. After LF treatment, calcium treatment is performed, and the soft blowing time is ensured to be 11 minutes after wire feeding.

[0053] 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 500℃, the temperature at the end of the soaking zone is 1197℃, and the soaking time is 44min to ensure that the alloying elements are fully dissolved.

[0054] 3) Rolling process: The first pass of roughing rolling has a reduction of 37mm, and the temperature of the last pass of roughing rolling is 1020℃; the thickness of the intermediate billet is 40mm, and the temperature of entering the finishing rolling is 940℃.

[0055] 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 35℃ / s and a winding temperature control of 581℃.

[0056] Example 3

[0057] In this embodiment, the steel used for 380MPa grade automotive wheel rims has a thickness of 8.0mm, and its chemical composition and mass percentage content are as follows: C: 0.07%, Si: 0.03%, Mn: 0.95%, P: 0.012%, S: 0.003%, Alt: 0.038%, Ti: 0.012%, N: 0.0058%, with the balance being Fe and unavoidable impurities.

[0058] Its production process includes smelting, slab heating, high-pressure water descaling, controlled rolling, controlled cooling, and coiling. The specific steps of each process are as follows:

[0059] Smelting and continuous casting processes: Molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR iron leaving the station at 0.0009% and the iron temperature at 1328℃. A top-and-bottom blowing converter is used for smelting to decarburize and dephosphorize the molten iron to obtain steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1630℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel from the converter is then subjected to LF ladle refining at a temperature of 1532℃. LF slag formation and desulfurization are performed, and alloys such as ferroaluminum, ferrosilicon, ferromanganese, and ferrotitanium are added according to the steel composition. After LF treatment, calcium treatment is performed, and the soft blowing time is ensured to be 10 minutes after wire feeding.

[0060] 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 480℃, the temperature at the end of the soaking zone is 1190℃, and the soaking time is 48min to ensure that the alloying elements are fully dissolved.

[0061] 3) Rolling process: The first pass of roughing rolling has a reduction of 36mm, and the temperature of the last pass of roughing rolling is 1025℃; the thickness of the intermediate billet is 43mm, and the temperature of entering the finishing rolling is 950℃.

[0062] 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 35℃ / s and a winding temperature control of 588℃.

[0063] The mechanical properties of the example are shown in Table 1. All mechanical properties of the product meet the requirements of YB / T 4151-2015.

[0064] Table 1 Mechanical properties of 380MPa grade steel for automotive wheel rims of different thicknesses

[0065]

[0066] Metallographic structure of the example is shown below Figure 1 The product's microstructure consists of ferrite with a small amount of pearlite. The ferrite is polygonal, with fine and uniform grains, and a grain size rating of 11.

[0067] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for improving the welding performance of 380MPa grade automotive wheel rim steel, characterized in that, The specific steps include the following: Step 1: To ensure low sulfur content control in molten iron, KR desulfurization treatment adopts deep desulfurization operation. At the end of desulfurization, the sulfur content in the molten iron should be ≤0.0010%, and the slag removal ratio on the surface of the molten iron ladle should be ≥95%. Step 2: To improve the cleanliness of molten steel, the carbon content of the final component in the converter smelting process is controlled at 0.04% to 0.06%. The target component must be hit in one go at the converter's final stage. Point blowing operation is prohibited at the converter's final stage. The converter tapping temperature is controlled at 1620℃ to 1660℃. Sliding plate slag blocking operation is used at the beginning and end of the converter tapping process to prevent converter slag from falling into the ladle. Step 3: Slag formation, deoxidation and desulfurization in the LF furnace, and the addition of aluminum ferromanganese, ferrosilicon and titanium ferroalloys to adjust the composition to the target range. In order to reduce the amount of nitrogen added to the molten steel and control the cleanliness of the molten steel during the LF refining process, the speed of the dust removal fan needs to be adjusted during the LF heating process to ensure that the pressure inside the fume hood is at a slightly positive pressure during the LF refining heating process, so as to prevent outside air from entering the fume hood and contacting the molten steel. Step 4: Argon gas is used for protection throughout the casting process. The slag detection equipment is turned on during the ladle pouring process, and slag from the ladle is prevented from flowing into the tundish at the end of the ladle pouring. Constant casting speed control is used during the casting process, and the casting speed is set in the range of 1.1m / min to 1.6m / min according to different casting sections. The superheat of the tundish is controlled between 20℃ and 35℃. Step 5: The heating process includes furnace time and furnace exit temperature; the furnace time is controlled at 180-240 min, the soaking time is controlled at 20-50 min, and the furnace exit temperature is controlled at 1170-1240℃. Step 6: Rolling includes roughing and finishing. Roughing is done on a 2-stand mill, and finishing is done on a 7-stand continuous variable crown mill. The first pass reduction in roughing is ≥35mm, the intermediate billet thickness is 35-40mm, the initial rolling temperature in finishing is controlled at ≤1000℃, and the final rolling temperature is controlled at 840-880℃. Step 7: Employ centralized front-end cooling, with the upper and lower cooling nozzles operating alternately, achieving a cooling rate of 30-45℃ / s and a winding temperature of 560-600℃; The chemical composition of the 380MPa grade automotive wheel rim steel by mass percentage is as follows: 0.05-0.07%C, 0.03-0.10%Si, 0.80-1.00%Mn, less than or equal to 0.018%P, less than or equal to 0.005%S, 0.020-0.040%Al, 0.012-0.014%Ti, 0.0056-0.0061%N, 0.0010-0.0030%Ca, with the remainder being iron and unavoidable impurities.

2. The method for improving the welding performance of 380MPa grade automotive wheel rim steel according to claim 1, characterized in that, The chemical composition and mass percentage of the 380MPa grade automotive wheel rim steel are as follows: C: 0.06%, Si: 0.03%, Mn: 0.90%, P: 0.010%, S: 0.004%, Alt: 0.040%, Ti: 0.014%, N: 0.0061%, Ca: 0.0010-0.0030%, balance Fe and unavoidable impurities.

3. The method for improving the welding performance of 380MPa grade automotive wheel rim steel according to claim 1, characterized in that, The chemical composition and mass percentage of the 380MPa grade automotive wheel rim steel are as follows: C: 0.07%, Si: 0.03%, Mn: 0.95%, P: 0.012%, S: 0.003%, Alt: 0.038%, Ti: 0.012%, N: 0.0058%, Ca: 0.0010-0.0030%, balance being Fe and unavoidable impurities.

4. The method for improving the welding performance of 380MPa grade automotive wheel rim steel according to claim 1, characterized in that, The specific steps for each process are as follows: 1) Smelting and continuous casting process: The molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR molten iron leaving the station at 0.0009% and the iron temperature at 1324℃. A top-and-bottom blowing converter is used to decarburize and dephosphorize the molten iron to obtain steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1626℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel after converter smelting is then subjected to LF ladle refining at a refining temperature of 1528℃. LF slag formation and desulfurization are performed, and aluminum ferroalloys, ferrosilicon, ferromanganese, and ferrotitanium alloys are added according to the steel composition. After LF treatment, calcium treatment is performed, and the soft blowing time is ensured to be 9 minutes after wire feeding. 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 520℃, the temperature at the end of the soaking zone is 1206℃, and the soaking time is 43min to ensure that the alloying elements are fully dissolved. 3) Rolling process: The first pass reduction in roughing is 38mm, and the temperature of the last pass in roughing is 1020℃; the thickness of the intermediate billet is 38mm, and the temperature of entering the finishing mill is 940℃. 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 33℃ / s and a winding temperature control of 594℃.

5. The method for improving the welding performance of 380MPa grade automotive wheel rim steel according to claim 2, characterized in that, The specific steps for each process are as follows: Smelting and continuous casting processes: Molten iron undergoes desulfurization pretreatment, with the sulfur content of the desulfurized KR molten iron leaving the station at 0.0009% and the iron temperature at 1326℃. A top-and-bottom blowing converter is used for smelting to decarburize and dephosphorize the molten iron, yielding steel. The entire converter smelting process is bottom-blown, with a tapping temperature of 1628℃ and a carbon content of 0.05%. Deoxidation and alloying treatment is performed during tapping, and slag-blocking is used. The molten steel from the converter is then subjected to LF ladle refining at a temperature of 1525℃. LF slag formation and desulfurization are performed, and aluminum-iron, silicon-iron, manganese-iron, and titanium-iron alloys are added according to the steel composition. After LF treatment, calcium treatment is performed, and the soft blowing time is ensured to be 11 minutes after wire feeding. 2) Heating process: Hot charging process is used. The temperature of the slab entering the furnace is 500℃, the temperature at the end of the soaking zone is 1197℃, and the soaking time is 44min to ensure that the alloying elements are fully dissolved. 3) Rolling process: The first pass reduction in roughing is 37mm, and the temperature of the last pass in roughing is 1020℃; the thickness of the intermediate billet is 40mm, and the temperature of entering the finishing mill is 940℃. 4) Cooling process: Centralized front-end cooling is adopted, with a cooling rate of 35℃ / s and a winding temperature control of 581℃.

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