A smelting method of 25MnV steel

Abstract

The present application relates to the technical field of metallurgical process, and particularly relates to a smelting method of 25MnV steel grade. The present application realizes deep degassing and inclusion floating of molten steel by optimizing the matching of parameters of each process and with the help of VD refining, further realizes accurate control of 25MnV steel composition, efficient utilization of vanadium resources, and double promotion of cleanliness and purity of molten steel, and simultaneously reduces the defect rate of continuous casting billet. The smelting method of the present application can adapt to the core demand of high strength, high toughness and low gas content of 25MnV steel in the fields of mechanical manufacturing, automobile industry, high-pressure container and the like, and takes into account production efficiency and cost control, and has remarkable practicability and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of metallurgical process technology, and more particularly to a smelting method for 25MnV steel. Background Technology

[0002] 25MnV steel, as a medium-carbon alloy structural steel, is widely used in machinery manufacturing, automotive industry, energy equipment and other fields due to its high strength, good toughness and processing performance. Its smelting process mainly uses electric furnace melting as the core, combined with refining and continuous casting processes to complete the forming.

[0003] The existing smelting methods mainly have the following three technical paths: (1) Traditional electric furnace smelting + simple refining + continuous casting: conventional electric furnace smelting is used, and after tapping, simple deoxidation and alloying are carried out before entering the continuous casting process. This method is simple and low-cost, but the composition control accuracy is poor, the vanadium element recovery rate is only 80%-88%, the S and P impurities in the molten steel are difficult to reduce to a low level, and no degassing process is set up, the gas (H, N) content in the molten steel is too high, and the continuous casting billet is prone to defects such as subcutaneous cracks, central porosity, and gas holes, resulting in a low product qualification rate. (2) Electric furnace + LF refining + continuous casting: The LF furnace refining process is added on the basis of the traditional process, focusing on composition adjustment and deoxidation, but the synergistic matching between the various processes is not achieved, and a deep degassing process is lacking. The connection between the electric furnace tapping temperature, composition and refining process is not smooth. Vanadium is easily oxidized and lost during the refining process. The gas content of molten steel cannot be effectively controlled. The cooling parameters of the continuous casting process do not match the composition and temperature of molten steel. There are still problems such as high incidence of crack defects, composition fluctuation exceeding internal control requirements, and molten steel porosity defects. (3) Electric furnace + VD refining + continuous casting (or electric furnace + LF refining + simple degassing + continuous casting): Some processes have tried to add a degassing link, but the synergistic matching of LF and VD has not been achieved. Either the process of precise composition fine-tuning of LF furnace and enhanced absorption of vanadium is lacking, or the VD refining parameters are not compatible with the state of molten steel, resulting in poor degassing effect and large fluctuation of vanadium recovery rate. It is difficult to balance the accuracy of composition and the purity of molten steel.

[0004] Based on existing production practices, it is known that 25MnV steel has high requirements for compositional uniformity, molten steel purity, and gas content. In particular, vanadium, as a key strengthening element, directly affects the mechanical properties of the steel due to the stability of its yield. In existing technologies, improper timing of ferrovanadium addition and insufficient matching of the refining slag system lead to large fluctuations in vanadium yield, increasing alloy consumption and production costs. Simultaneously, improper control of slag quantity and temperature during electric furnace tapping increases the load on the refining process, making it difficult to achieve deep removal of harmful impurities. Furthermore, the lack of a professional deep degassing process or incomplete degassing allows hydrogen and nitrogen gases in the molten steel to easily cause defects such as porosity and white spots in continuously cast billets, further affecting product quality and subsequent processing performance.

[0005] To address the shortcomings of the existing technologies, there is an urgent need for a smelting method that can achieve full-process coordinated control of 25MnV steel, precise and stable composition, efficient utilization of vanadium, high purity of molten steel, low gas content, and low defect rate of continuously cast billets. Summary of the Invention

[0006] To address the technical challenges in existing 25MnV steel smelting processes, such as large compositional fluctuations, low vanadium recovery, insufficient steel purity, high gas content, and frequent cracking defects in continuously cast billets, this invention provides a smelting method with coordinated control across the entire process from electric arc furnace (EAF) refining to vacuum distillation (VD) refining and continuous casting. By optimizing the matching of parameters in each process and leveraging VD refining to achieve deep degassing and inclusion flotation in the molten steel, this method further achieves precise control of the 25MnV steel composition, efficient utilization of vanadium resources, and a dual improvement in the cleanliness and purity of the molten steel, while simultaneously reducing the defect rate of continuously cast billets. This method is suitable for the core requirements of high strength, high toughness, and low gas content in 25MnV steel in industries such as machinery manufacturing, automotive, and high-pressure vessels, balancing production efficiency and cost control, and possesses significant practicality and economic benefits.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] This invention provides a method for smelting 25MnV steel, the smelting method comprising the following steps: (1) Raw materials: Scrap steel is used as raw material; the P content in the scrap steel is ≤0.025%, the S content is ≤0.020%, and the moisture content is <1%; (2) Electric furnace smelting: Add slag-forming agent, turn on the power to raise the temperature, first dephosphorize, control the final steel P content ≤0.015%, then add graphite recarburizer, control the final steel C content 0.22%-0.25%; (3) LF furnace refining: After the ladle is put into the furnace, refining slag is added and the furnace is heated by electricity. The LF furnace refining is controlled in three stages: the first stage controls the argon blowing stirring flow rate to 300-400 NL / min, adds aluminum particles for deoxidation, controls the oxygen content of the molten steel to ≤20ppm, adds ferromanganese for alloying, and the refining time is 10-15min; the second stage controls the argon blowing stirring flow rate to 100-200 NL / min, and does not include 100 NL / min, adds ferrovanadium for alloying, and the refining time is 10-15min; the third stage controls the argon blowing stirring flow rate to 50-100 NL / min, finely adjusts the composition according to the target value of the molten steel, and the refining time is 8-15min; the total LF furnace refining time is 35-45min, the white slag refining time is ≥35min, the final temperature is 1590-1630℃, and after the LF furnace refining is completed, it is kept warm and transferred to the VD furnace; (4) VD furnace refining: The temperature of molten steel entering the VD furnace is 1580-1620℃; segmented vacuum degassing is adopted: the first stage is evacuated to a vacuum degree of 100-200Pa, the argon flow rate is 150-200NL / min, and it is maintained for 5-10min; the second stage is evacuated to a vacuum degree of ≤67Pa, the argon flow rate is 80-120NL / min, and does not include 80NL / min, and it is maintained for 15-20min; the third stage is evacuated to a vacuum degree of ≤67Pa, the argon flow rate is 50-80NL / min, and it is maintained for 5-8min; the total refining time of the VD furnace is 25-40min, the final temperature is 1570-1590℃, the final steel H content is ≤1.5ppm, N content is ≤65ppm, oxide inclusions are ≤1.0 grade, and sulfide inclusions are ≤0.5 grade; after the vacuum is broken, the steel is transferred to the continuous casting machine under argon protection. (5) Continuous casting: The steel casting temperature is 1550-1575℃, and the casting speed is 1.0-1.2m / min; the cooling is carried out in three stages in the second cooling zone, and the cooling intensity gradually decreases; protective slag is added, and the continuous casting billet is slowly cooled after exiting the billet, and then the surface is ground.

[0009] In the above technical solution, further, in step (1), the size of the scrap steel block is controlled at 100-500mm.

[0010] In the above technical solution, further, in step (2), the slag-forming agent is composed of 50%-70% lime, 25%-45% lightly calcined dolomite, and 5%-10% fluorite by mass percentage; the amount of slag-forming agent added is 1.5%-2.0% of the mass of molten steel; In the above technical solution, further, in step (2), the steel is tapped with slag blocked, the amount of slag tapped is ≤5kg / t steel, the tapping temperature is 1610-1670℃, the temperature fluctuation of the tapping is controlled to be ≤±15℃, a pre-deoxidizer is added during the tapping process, the pre-deoxidizer is Si-Al-Ba alloy, the amount added is 0.7-0.9kg / t steel, and argon gas protection is used at the same time, the argon gas flow rate is 350-500NL / min.

[0011] In the above technical solution, further, in step (3), by mass percentage, the refining slag is composed of 45%-65% lime, 32%-43% bauxite, and 3%-8% fluorite, and the basicity of the refining slag is 3.0-3.5; the amount of refining slag added is 1.0%-1.5% of the mass of molten steel; the amount of aluminum particles added is 0.3-0.5 kg / t steel; after fine-tuning the composition, the mixture is gently stirred for 3-5 min, and the argon flow rate is controlled at 50-80 NL / min; the temperature fluctuation at the end of the refining process in the LF furnace is controlled at ≤±10℃; and the transfer time to the VD furnace is controlled at ≤10 min.

[0012] In the above technical solution, step (3) further includes a drying process for ferrovanadium and ferromanganese, with a drying temperature of 150-200℃ and a drying time of 2-3h, and the dried ferrovanadium is crushed to 50-100mm.

[0013] In the above technical solution, further, in step (4), the vacuum breaking time is ≥5min; the transfer time to the continuous casting machine is controlled to be ≤8min.

[0014] In the above technical solution, further, in step (5), the cooling intensity of the three sections of the second cooling zone is as follows: the first section is the lower foot roller section of the crystallizer and the No. 0 fan-shaped section, with a cooling intensity of 1.0-1.2L / kg, excluding 1.0L / kg; the second section is the No. 1-2 arc-shaped main fan-shaped section, with a cooling intensity of 0.8-1.0L / kg, excluding 0.8L / kg; and the third section is the No. 3 fan-shaped section to the straightening section and the end of the horizontal section, with a cooling intensity of 0.5-0.8L / kg.

[0015] In the above technical solution, further, in step (5), the amount of protective slag added is 0.3-0.5 kg / t steel; the casting speed fluctuation is ≤ ±0.1 m / min; and the casting temperature fluctuation is ≤ ±10℃.

[0016] The beneficial effects of this invention are as follows: 1. In the smelting method of the present invention, a specific refining slag is added to the LF furnace to form a high-basicity, low-viscosity reducing slag, which can achieve deep desulfurization, inhibit the oxidation of vanadium, and adsorb oxide inclusions in molten steel. At the same time, the low-viscosity slag system can avoid hindering gas overflow during VD refining and improve the degassing effect.

[0017] 2. The LF furnace refining method of this invention does not adopt the traditional late addition method of ferrovanadium. Instead, it adopts a staged alloying strategy to ensure accurate composition and improve vanadium yield, while avoiding gas intake caused by alloy addition.

[0018] 3. This invention adopts a vacuum degassing mode, which precisely controls the vacuum level and time to ensure the degassing effect, while avoiding secondary oxidation of molten steel and loss of vanadium.

[0019] 4. The continuous casting stage cooling of this invention adopts segmented cooling and gradient temperature reduction. The secondary cooling zone is divided into three sections, and the cooling intensity gradually decreases. Combined with the toughness advantage of ultra-low gas molten steel, the cooling parameters are optimized to reduce thermal stress cracks.

[0020] 5. The electric furnace smelting process of this invention achieves coarse control of P and C, the LF furnace process achieves precise fine adjustment of Si, Mn and V, the VD furnace process ensures no significant fluctuation in composition, and the continuous casting process ensures composition uniformity through protective slag and cooling optimization, ultimately achieving a composition fluctuation of ≤±0.01% for 25MnV steel. Detailed Implementation

[0021] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0022] Example 1 (1) The scrap steel raw materials used should have a P content of ≤0.025%, a S content of ≤0.020%, a moisture content of <1%, and a scrap steel block size of 100-500mm. Scrap steel with severe rust and excessive oil stains should be removed. (2) Electric furnace smelting: Add slag-forming agent, which consists of 62% lime, 33% light-burned dolomite and 5% fluorite. The amount of slag-forming agent added is 2.0% of the mass of molten steel. Heat up by electric current. Blow oxygen to remove phosphorus 25 minutes before smelting. The final P content of molten steel is 0.01%. Add graphite carbon raiser after 25 minutes of smelting. Control the C content of molten steel to 0.22% at the end. Slag is blocked and steel is tapped. The amount of slag tapped is ≤5kg / t steel. The tapping temperature is 1650℃. Add pre-deoxidizer during the tapping process. The pre-deoxidizer is Si-Al-Ba alloy. The amount added is 0.7kg / t steel. Argon gas protection is used at the same time. The argon gas flow rate is 390NL / min. (3) LF furnace refining: After the ladle is put into the furnace, refining slag is added. The refining slag consists of 56% lime, 40% bauxite, and 4% fluorite, and the basicity of the refining slag is 3.2. The amount of refining slag added is 1.5% of the mass of the molten steel. The LF furnace refining is controlled in three stages: the first stage controls the argon blowing stirring flow rate to 300NL / min, adds aluminum particles for deoxidation, the amount of aluminum particles added is 0.5kg / t steel, controls the oxygen content of the molten steel to ≤20ppm, adds ferromanganese for alloying, after alloying, the vanadium content of the molten steel is 0.14%, and the refining time is 15 minutes. The second stage involves controlling the argon gas blowing flow rate at 200 NL / min, adding ferrovanadium for alloying, and refining for 15 minutes. The third stage involves controlling the argon gas blowing flow rate at 100 NL / min, refining for 8 minutes, fine-tuning the composition according to the target value of the molten steel, and then gently stirring for 5 minutes while controlling the argon gas flow rate at 50 NL / min. The total refining time in the LF furnace is 38 minutes, with the white slag refining time ≥35 minutes and the final temperature at 1602℃. After the LF furnace refining is completed, the slag is kept warm and transferred to the VD furnace, with a transfer time ≤10 minutes. (4) VD furnace refining: The temperature of molten steel entering the VD furnace is 1590℃; segmented vacuum degassing is adopted. In the first stage, the vacuum degree is 100Pa and held for 6min with an argon flow rate of 200NL / min; in the second stage, the vacuum degree is ≤67Pa and held for 20min with an argon flow rate of 120NL / min; in the third stage, the vacuum degree is ≤67Pa and the argon flow rate is 80NL / min and held for 5min; the total refining time of the VD furnace is 31min, the final temperature is 1570℃, the final steel has H content of 1.3ppm, N content of 62ppm, oxide inclusions ≤1.0 grade, and sulfide inclusions ≤0.5 grade; after the vacuum is broken, the steel is transferred to the continuous casting machine under argon protection. The vacuum breaking time is ≥5min and the transfer time is ≤8min. (5) Continuous casting: The steel pouring temperature is 1565℃, and the pouring temperature fluctuation is controlled to be ≤±10℃. The casting speed is 1.0m / min, and the casting speed fluctuation is controlled to be ≤±0.1m / min. The two cooling zones are three-stage cooling: the first stage is 1.2L / kg for the lower foot roller section of the crystallizer and the No. 0 fan-shaped section; the second stage is 1.0L / kg for the No. 1-2 arc-shaped main fan-shaped section; and the third stage is 0.8L / kg for the No. 3 fan-shaped section to the straightening section and the end of the horizontal section. Protective slag is added, and the amount of protective slag added is 0.5kg / t. After the continuous casting billet is discharged, it is slowly cooled and then the surface is ground.

[0023] Example 2 (1) The scrap steel raw materials used should have a P content of ≤0.025%, a S content of ≤0.020%, a moisture content of <1%, and a scrap steel block size of 100-500mm. Scrap steel with severe rust and excessive oil stains should be removed. (2) Electric furnace smelting: Add slag-forming agent, which consists of 58% lime, 34% light calcined dolomite and 8% fluorite. The amount of slag-forming agent added is 2.0% of the mass of molten steel. Heat up by electric current. Blow oxygen to remove phosphorus 25 minutes before smelting. The final P content of molten steel is 0.012%. Add graphite carbon raiser after 25 minutes of smelting. Control the final C content of molten steel to 0.21%. Slag is blocked and steel is tapped. The amount of slag tapped is ≤5kg / t steel. The tapping temperature is 1660℃. Add pre-deoxidizer during the tapping process. The pre-deoxidizer is Si-Al-Ba alloy. The amount added is 0.7kg / t steel. Argon gas protection is used at the same time. The argon gas flow rate is 370NL / min. (3) LF furnace refining: After the ladle is put into the furnace, refining slag is added. The refining slag consists of 60% lime, 35% bauxite, and 5% fluorite, and the basicity of the refining slag is 3.4. The amount of refining slag added is 1.5% of the mass of the molten steel. The LF furnace refining is controlled in three stages: the first stage controls the argon blowing stirring flow rate to 350NL / min, adds aluminum particles for deoxidation, the amount of aluminum particles added is 0.5kg / t steel, controls the oxygen content of the molten steel to ≤20ppm, adds ferromanganese for alloying, after alloying, the vanadium content of the molten steel is 0.15%, and the refining time is 13m. In the second stage, the argon gas stirring flow rate is controlled at 150 NL / min, ferrovanadium is added for alloying, and the refining time is 15 min; in the third stage, the argon gas stirring flow rate is controlled at 100 NL / min, the refining time is 10 min, the composition is finely adjusted according to the target value of the molten steel, and after fine-tuning the composition, soft stirring is carried out for 5 min, and the argon gas flow rate is controlled at 50 NL / min; the total refining time in the LF furnace is 38 min, the white slag refining time is ≥35 min, the final temperature is 1605℃, after the LF furnace refining is completed, it is kept warm and transferred to the VD furnace, and the transfer time is ≤10 min; (4) VD furnace refining: The temperature of molten steel entering the VD furnace is 1595℃; segmented vacuum degassing is adopted. In the first stage, the vacuum degree is 100Pa and held for 6min with an argon flow rate of 200NL / min; in the second stage, the vacuum degree is ≤67Pa and held for 20min with an argon flow rate of 120NL / min; in the third stage, the vacuum degree is ≤67Pa and the argon flow rate is 80NL / min and held for 5min; the total refining time of the VD furnace is 31min, the final temperature is 1570℃, the final steel has H content of 1.2ppm, N content of 63pm, oxide inclusions ≤1.0 grade, and sulfide inclusions ≤0.5 grade; after the vacuum is broken, the steel is transferred to the continuous casting machine under argon protection. The vacuum breaking time is ≥5min and the transfer time is ≤8min. (5) Continuous casting: The steel pouring temperature is 1570℃, and the pouring temperature fluctuation is controlled to be ≤±10℃. The casting speed is 1.0m / min, and the casting speed fluctuation is controlled to be ≤±0.1m / min. The two cooling zones are three-stage cooling: the first stage is 1.2L / kg for the lower foot roller section of the crystallizer and the No. 0 fan-shaped section, the second stage is 1.0L / kg for the No. 1-2 arc-shaped main fan-shaped section, and the third stage is 0.8L / kg for the No. 3 fan-shaped section to the straightening section and the end of the horizontal section. Protective slag is added, and the amount of protective slag added is 0.5kg / t. After the continuous casting billet is discharged, it is slowly cooled and then the surface is ground.

[0024] Comparative Example 1 (1) The scrap steel raw materials used should have a P content of ≤0.025%, a S content of ≤0.020%, a moisture content of <1%, and a scrap steel block size of 100-500mm. Scrap steel with severe rust and excessive oil stains should be removed. (2) Electric furnace smelting: Add slag-forming agent, which is composed of lime: alumina: fluorite in a mass ratio of 5:4:1. The amount of slag-forming agent added is 1.5% of the mass of molten steel. Heat up by electric current. Blow oxygen to remove phosphorus 25 minutes before smelting. The final P content of molten steel is 0.013%. Add graphite carbon raiser 25 minutes after smelting. Control the final C content of molten steel to 0.2%. The tapping temperature is 1660℃. (3) LF furnace refining: After the ladle is put into the furnace, refining slag is added. The refining slag is composed of lime: alumina: silicon dioxide: fluorite in a mass ratio of 5.5: 2.5: 1.5: 0.5, and the basicity of the refining slag is 3.6. The amount of refining slag added is 1.5% of the mass of the molten steel. Electric heating is applied. Aluminum particles are added during the refining process for deoxidation. The oxygen content of the molten steel is controlled to be ≤20ppm. Argon gas is used for stirring at a flow rate of 150NL / min. Ferromanganese and ferrovanadium alloys are added for alloying. After alloying, the vanadium content of the molten steel is 0.1%. The composition is finely adjusted according to the target value of the molten steel in the later stage. The total refining time of the LF furnace is 40min, and the final temperature is 1610℃. After the refining of the LF furnace is completed, the steel is kept warm and transferred to the VD furnace. The transfer time is ≤10min. (4) VD furnace refining: The temperature of molten steel entering the VD furnace is 1601℃; the vacuum degree is ≤67Pa, the argon flow rate is 120NL / min; the total refining time of the VD furnace is 35min, the final temperature is 1580℃, the final molten steel has H content of 2.8ppm, N content of 79ppm, oxide inclusions ≤1.5 grade, sulfide inclusions ≤1.0 grade; after the vacuum is broken, the steel is transferred to the continuous casting machine under argon protection, the vacuum breaking time is ≥5min, and the transfer time is ≤8min; (5) Continuous casting: The steel casting temperature is 1575℃ and the casting speed is 1.0m / min; protective slag is added, and the amount of protective slag added is 1.0kg / t; after the continuous casting billet is removed, it is slowly cooled and then the surface is ground.

[0025] Table 1

[0026] The embodiments described are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for smelting 25MnV steel, characterized in that, The smelting method includes the following steps: (1) Raw materials: Scrap steel is used as raw material; the P content in the scrap steel is ≤0.025%, the S content is ≤0.020%, and the moisture content is <1%; (2) Electric furnace smelting: Add slag-forming agent, turn on the power to raise the temperature, first dephosphorize, control the final steel P content ≤0.015%, then add graphite recarburizer, control the final steel C content 0.22%-0.25%; (3) LF furnace refining: After the ladle is put into the furnace, refining slag is added and the furnace is heated by electricity. The LF furnace refining is controlled in three stages: the first stage controls the argon blowing stirring flow rate to 300-400 NL / min, adds aluminum particles for deoxidation, controls the oxygen content of the molten steel to ≤20ppm, adds ferromanganese for alloying, and the refining time is 10-15min; the second stage controls the argon blowing stirring flow rate to 100-200 NL / min, and does not include 100 NL / min, adds ferrovanadium for alloying, and the refining time is 10-15min; the third stage controls the argon blowing stirring flow rate to 50-100 NL / min, finely adjusts the composition according to the target value of the molten steel, and the refining time is 8-15min; the total LF furnace refining time is 35-45min, the white slag refining time is ≥35min, the final temperature is 1590-1630℃, and after the LF furnace refining is completed, it is kept warm and transferred to the VD furnace; (4) VD furnace refining: The temperature of molten steel entering the VD furnace is 1580-1620℃; segmented vacuum degassing is adopted: the first stage is evacuated to a vacuum degree of 100-200Pa, the argon flow rate is 150-200NL / min, and it is maintained for 5-10min; the second stage is evacuated to a vacuum degree of ≤67Pa, the argon flow rate is 80-120NL / min, and does not include 80NL / min, and it is maintained for 15-20min; the third stage is evacuated to a vacuum degree of ≤67Pa, the argon flow rate is 50-80NL / min, and it is maintained for 5-8min; the total refining time of the VD furnace is 25-40min, the final temperature is 1570-1590℃, the final steel H content is ≤1.5ppm, N content is ≤65ppm, oxide inclusions are ≤1.0 grade, and sulfide inclusions are ≤0.5 grade; after the vacuum is broken, the steel is transferred to the continuous casting machine under argon protection. (5) Continuous casting: The steel casting temperature is 1550-1575℃, and the casting speed is 1.0-1.2m / min; the cooling is carried out in three stages in the second cooling zone, and the cooling intensity gradually decreases; protective slag is added, and the continuous casting billet is slowly cooled after exiting the billet, and then the surface is ground.

2. The smelting method according to claim 1, characterized in that, In step (1), the size of the scrap steel block is controlled between 100-500mm.

3. The smelting method according to claim 1, characterized in that, In step (2), the slag-forming agent is composed of 50%-70% lime, 25%-45% lightly calcined dolomite and 5%-10% fluorite by mass percentage; the amount of slag-forming agent added is 1.5%-2.0% of the mass of molten steel.

4. The smelting method according to claim 1, characterized in that, In step (2), the steel is tapped with slag blocked, the amount of slag tapped is ≤5kg / t steel, the tapping temperature is 1610-1670℃, the temperature fluctuation is controlled to be ≤±15℃, a pre-deoxidizer is added during the tapping process, the pre-deoxidizer is Si-Al-Ba alloy, the amount added is 0.7-0.9kg / t steel, and argon gas protection is used at the same time, the argon gas flow rate is 350-500NL / min.

5. The smelting method according to claim 1, characterized in that, In step (3), the refining slag is composed of 45%-65% lime, 32%-43% bauxite, and 3%-8% fluorite by mass percentage, and the basicity of the refining slag is 3.0-3.5; the amount of refining slag added is 1.0%-1.5% of the mass of molten steel. The amount of aluminum granules added is 0.3-0.5 kg / t steel; After fine-tuning the composition, gently stir for 3-5 minutes, controlling the argon flow rate at 50-80 NL / min; Control the temperature fluctuation at the final refining point of the LF furnace to ≤±10℃; The transfer time to the VD furnace should be controlled to be ≤10min.

6. The smelting method according to claim 1, characterized in that, Step (3) also includes a drying process for ferrovanadium and ferromanganese, with a drying temperature of 150-200℃ and a drying time of 2-3 hours, and the dried ferrovanadium is crushed to 50-100mm.

7. The smelting method according to claim 1, characterized in that, In step (4), the vacuum breaking time is ≥5 min; the transfer time to the continuous casting machine is controlled to be ≤8 min.

8. The method according to claim 1, characterized in that, In step (5), the cooling intensities of the three sections of the second cooling zone are as follows: the first section is the lower foot roller section of the crystallizer and the No. 0 fan-shaped section, with a cooling intensity of 1.0-1.2L / kg, excluding 1.0L / kg; the second section is the No. 1-2 arc-shaped main fan-shaped section, with a cooling intensity of 0.8-1.0L / kg, excluding 0.8L / kg; and the third section is from the No. 3 fan-shaped section to the end of the straightening section and the horizontal section, with a cooling intensity of 0.5-0.8L / kg.

9. The method according to claim 1, characterized in that, In step (5), the amount of protective slag added is 0.3-0.5 kg / t steel; Pulling speed fluctuation ≤ ±0.1m / min; The casting temperature fluctuation is ≤ ±10℃.

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