A method for precisely controlling the content of dissolved carbon in BH steel

Abstract

The present invention relates to a method for precisely controlling the content of dissolved carbon in BH steel, belonging to the field of metallurgical materials. Specifically, it includes steps of pre-treatment confirmation, RH decarburization, alloying and net circulation. The present invention adopts the scheme of ultra-low C+Nb, dynamically controls the matching of C content and Nb content during the RH refining process, can more precisely control the content of dissolved C in the finished product, and the BH value is more stable. It solves the problems of high cost and large fluctuation of BH value in the prior art for producing BH steel by controlling the content of dissolved C through the annealing process of the cold rolling continuous annealing process.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical materials, and particularly relates to a method for precisely controlling the content of dissolved carbon in BH steel. Background Art

[0002] Entering the 21st century, China's automotive industry has developed rapidly and has now become the world's largest producer and seller of automobiles. With the development of the automotive industry, the automotive materials are gradually changing. Due to the excellent formability and good dent resistance of bake hardening (BH) steel, it is beneficial to realize the thinning of automotive panels, and it has now become the main material for modern automotive panels.

[0003] The bake hardening characteristic of bake hardening steel is due to the presence of a certain amount of dissolved C atoms in the steel. After painting and baking, the dissolved C atoms are enriched around the dislocations and pin the dislocations, thereby increasing the strength. At present, BH steel adopts a special annealing process (high-temperature annealing, rapid cooling) in the cold rolling continuous annealing process to ensure a certain amount of dissolved C in the finished product, but this method has a high production cost. In addition, automotive panel products are mostly thin and wide products, which makes it difficult to carry out high-temperature annealing production in the continuous annealing furnace, difficult to guarantee the surface quality, and difficult to precisely control the content of dissolved C, resulting in large fluctuations in the BH value. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for dynamically controlling the content of dissolved C in steel during the RH refining process in the steelmaking process, solving the problems of high cost and large fluctuations in controlling dissolved C by the annealing process in the cold rolling continuous annealing process for producing BH steel in the prior art. Using this method can more precisely control the content of dissolved C in the finished product and make the BH value of BH steel more stable.

[0005] The BH steel composition design involved in the present invention adopts a scheme of ultra-low C + Nb, and dynamically controls the matching of C content and Nb content during the RH refining process to ensure that the content of dissolved C in the continuous casting billet finished product is within 0.0007% - 0.0015%.

[0006] The specific content of the invention is as follows:

[0007] A method for precisely controlling the content of dissolved carbon in BH steel, comprising the following steps:

[0008] S1. Confirmation before treatment, specifically, measuring temperature, determining oxygen, measuring slag thickness, measuring free space, confirming that the conditions meet the production conditions of the target steel grade, lifting the ladle to ensure that the nozzle inserts into the liquid surface ≥ 400 mm.

[0009] S2. Open the main vacuum valve and start the vacuum treatment module. Manually lift and compensate by about 100 mm according to the liquid level condition, and pay attention to the change of the lifting height. Select the lifting gas flow rate of 90 - 120 Nl / min according to the treatment mode; the minimum vacuum degree ≤ 100 Pa; the decarburization time is 15 - 25 minutes. During the process, according to the RH decarburization reaction equilibrium coefficient: Adjust the oxygen value in real time to promote the RH decarburization reaction to proceed to the right, ensuring that RH quickly decarburizes the carbon in the steel to the lowest level. According to the designed decarburization conditions of the RH equipment, adjust the carbon to 0.0020 - 0.0030%, the end point oxygen value is 250 - 400 ppm. Add aluminum for deoxidation and calmness. After 2 - 3 minutes of aluminum deoxidation alloying, conduct oxygen determination to ensure alloying under the premise of ensuring the aluminum content in the molten steel. Take three samples during the RH treatment process. Take sample A at 8 - 12 minutes of RH decarburization, analyze the spectral and infrared carbon components, and set the RH end point carbon at the maximum and minimum values according to the designed decarburization capacity of the RH equipment. Before production, predict the decarburization end point oxygen in combination with the conditions before RH, and dynamically adjust the oxygen supplement amount to create the initial conditions for RH production. The theoretical expected final value of the decarburization oxygen = initial [O] - (initial [C] - target [C]) * 16 / 12; when the actual oxygen value reaches the theoretical expected final value of the decarburization oxygen, take sample B and analyze the infrared carbon component. If the carbon content is on the high side, appropriately extend the RH refining time; if the carbon content is on the low side, conduct carbon addition according to the target carbon. For every 1 ppm increase in C, add 15 - 20 g / ton of high-carbon ferromanganese. Before weighing the high-carbon ferromanganese, electrolytic manganese must be used as a cushion.

[0010] S3. Alloy addition. Calculate the addition amount with reference to the alloy model. The actual addition amounts of Mn, Ti, B, Nb, and Al alloys are the calculated values ± 20 kg / ton of steel. Alloying is carried out in sequence according to the alloy addition order. Before adding the alloy, the belt is reversed to remove the residual alloy on the belt to ensure the accuracy of the added alloy amount. Among them, the addition amount of Nb is dynamically controlled according to the RH decarburization end point carbon in combination with the dissolved C in the steel.

[0011] S4. Net circulation. After adding the last batch of alloy materials, start the net circulation module. After the timer time meets the process requirements, click to repressurize, and the net circulation will end automatically. The net circulation time is 6 - 8 min.

[0012] S5. Close the main vacuum valve and start the repressurization module. Manually lower the ladle by less than 100 mm to prevent slag overflow. Only when the vacuum degree reaches 85 KPa can the ladle be officially lowered, so that the suction nozzle leaves the molten steel surface, and the ladle is lowered to the ground.

[0013] Preferably, the oxygen value before treatment in step S1 is 550 - 750 ppm; if the confirmed oxygen value before treatment is lower than 450 ppm, forced oxygen supplementation is carried out 3 minutes after opening the main vacuum valve; if the confirmed oxygen value before treatment is higher than 750 ppm, add metallic aluminum to reduce the oxygen.

[0014] Preferably, before processing the target steel, it also includes arranging to process more than 4 furnaces of extra-low carbon steel in advance.

[0015] Preferably, when adjusting the carbon to 0.0020 - 0.0030% in step S2, the carbon after high manganese alloying and the carbon increase amount of 2 - 5 ppm in the ladle should be comprehensively considered.

[0016] Preferably, the alloy addition sequence in step S3 is Mn → Ti → B → Nb → Al.

[0017] Preferably, the dynamic addition amount of Nb in step S3 = (RH end point [C] - Ex.C) × 7.75 × 180 × 0.98) × 1000 / 100, ensuring that the solid solution C content in the continuous casting billet finished product is within 0.0007% - 0.0015%.

[0018] Preferably, in step S3, sample C is taken two minutes after adding the alloy, and the alloy amount is adjusted according to the actual test results until the target value.

[0019] Preferably, the reporting time of the sample test result is 5 - 10 minutes.

[0020] The beneficial effects of the present invention are as follows:

[0021] ① During the RH refining process of the present invention, the post-argon carbon is calculated based on the end point carbon and high manganese alloy theory, and the production process uses the predicted calculation results to dynamically control the Nb alloying, which can more precisely control the solid solution C content in the finished product.

[0022] ② The BH value of the finished product prepared by the method of the present invention has a smaller fluctuation range and is stable. Its cold rolling annealing temperature is lower than that of the traditional process, and the energy consumption per ton of steel is reduced by about 100 yuan.

[0023] ③ The present invention uses high manganese alloy instead of metallic manganese, reducing the production cost. Specific embodiments

[0024] The following non-limiting embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0025] In the following embodiments, the test methods are all conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0026] One of the specific embodiments:

[0027] A method for precisely controlling the solid solution carbon content in BH steel:

[0028] 1. Before processing the target steel, arrange to process more than 4 heats of ultra-low carbon steel in advance, measure the temperature, determine the oxygen content, measure the slag thickness, and measure the freeboard, and confirm that the conditions meet the production conditions of the target steel grade. The oxygen value before processing is 550 - 750 ppm. If the oxygen value confirmed before processing is lower than 450 ppm, forcibly supply oxygen 3 minutes after opening the vacuum main valve; if the oxygen value confirmed before processing is higher than 750 ppm, add metallic aluminum to reduce the oxygen content. Lift the ladle to ensure that the nozzle inserts into the liquid surface by ≥400 mm.

[0029] 2. Open the vacuum main valve and start the vacuum treatment module. Manually lift and compensate by about 100 mm according to the liquid surface condition, and pay attention to the change in the lifting height; select the lifting gas flow rate of 90 - 120 Nl / min according to the treatment mode; the minimum vacuum degree ≤100 Pa; the decarburization time is 15 - 25 minutes. During the process, according to the RH decarburization reaction equilibrium coefficient: Adjust the oxygen value in real time to promote the RH decarburization reaction to proceed to the right, and ensure that RH quickly decarburizes the carbon in the steel to the lowest level; according to the decarburization conditions designed for the RH equipment, adjust the carbon to 0.0020 - 0.0030%. At this time, the carbon after high manganese alloying and the carbon increase amount of 2 - 5 ppm in the ladle should be comprehensively considered. The end point oxygen value is 250 - 400 ppm. Add aluminum for deoxidation and alloying. After 2 - 3 minutes of aluminum deoxidation alloying, determine the oxygen content, and ensure alloying on the premise of ensuring that the molten steel contains aluminum. Take three samples during the RH treatment process. Take sample A 8 - 12 minutes after RH decarburization, analyze the spectral and infrared carbon components, and set the RH end point carbon at the maximum and minimum values according to the decarburization capacity designed for the RH equipment. Before production, predict the decarburization end point oxygen in combination with the conditions before RH, and dynamically adjust the oxygen supply amount to create the initial conditions for RH production. The theoretical expected final value of the decarburization oxygen = initial [O] - (initial [C] - target [C]) * 16 / 12; when the actual oxygen value reaches the theoretical expected final value of the decarburization oxygen, take sample B and analyze the infrared carbon component. If the carbon content is on the high side, appropriately extend the RH refining time; if the carbon content is on the low side, perform carbon addition according to the target carbon. For every 1 ppm increase in C, add 15 - 20 g / ton of high-carbon ferromanganese. Before weighing the high-carbon ferromanganese, electrolytic manganese must be used as a cushion.

[0030] 3. Alloy addition: Refer to the alloy model for calculating the addition amount. The actual addition amounts of Mn, Ti, B, Nb, and Al alloys are the calculated values ±20 kg / ton of steel. Alloying is carried out in sequence according to the order of alloy addition, specifically in the order of Mn → Ti → B → Nb → Al. Before adding the alloy, the belt is reversed to remove the residual alloy on the belt to ensure the accuracy of the added alloy amount. And take sample C two minutes after adding the alloy, and it is required to report the test result of the sample within 5 - 10 minutes. Adjust the alloy amount according to the actual test result until the target value. Among them, the dynamic addition amount of Nb = (RH end point [C] - Ex.C) × 7.75 × 180 × 0.98) × 1000 / 100, ensuring that the solid solution C content in the cast billet finished product is within 0.0007% - 0.0015%.

[0031] 4. Net circulation: After adding the last batch of alloy materials, start the net circulation module. Click on re-press after the timer time meets the process requirements, and the net circulation will end automatically. The net circulation time is 6 - 8 min.

[0032] 5. Close the main vacuum valve, start the re-press module, manually lower the ladle within 100 mm to prevent slag overflow. Only when the vacuum degree reaches 85 KPa can the ladle be officially lowered, so that the suction nozzle leaves the molten steel surface, and lower the ladle to the ground.

[0033] The above method for precisely controlling the solid solution carbon content in BH steel only limits the key parameters, and the conventional process steps are carried out in the manner disclosed in the prior art as long as they meet the process requirements.

[0034] Example 1

[0035] Prepare BH steel using the technical solution of this invention patent. The specific production steps are as follows:

[0036] 1. Before processing the target steel, arrange to process 4 furnaces of ultra-low carbon steel in advance, and measure the temperature, oxygen, slag thickness, and net space to confirm that the conditions meet the production conditions of the target steel grade. The oxygen value before processing is 588 ppm. Lift the ladle to ensure that the suction nozzle inserts into the liquid surface ≥ 400 mm.

[0037] 2. Open the main vacuum valve and start the vacuum treatment module. Manually lift and compensate by about 100 mm according to the liquid level situation, and pay attention to the change in the lifting height. Select the lifting gas flow rate of 1 Nl / min according to the treatment mode; the minimum vacuum degree is 80 Pa; the decarburization time is 17 minutes. During the process, according to the RH decarburization reaction equilibrium coefficient, adjust the oxygen value in real time to promote the RH decarburization reaction to proceed to the right, ensuring that RH quickly decarburizes the carbon in the steel to the lowest level. According to the decarburization conditions designed for the RH equipment, adjust the carbon to 0.0017%. At this time, the carbon after high manganese alloying and the carbon increase amount of 2 - 5 ppm in the ladle should be comprehensively considered. The end point oxygen value is 358 ppm. Add aluminum for deoxidation and alloying. After 3 minutes of aluminum deoxidation alloying, determine the oxygen to ensure alloying under the premise of ensuring the aluminum content in the molten steel. Take three samples during the RH treatment process. The oxygen content before RH is 0.0588%. Take sample A 9 minutes after RH decarburization to analyze the spectral and infrared carbon components. The carbon content of sample A is 0.0258%. The target carbon content at the end point of RH decarburization is 0.0010%. After calculation, the oxygen content at the end point of RH decarburization is 0.0257%, and the actual value determined by the oxygen lance is 0.0299%. The carbon content at the end point of RH decarburization analyzed by sampling is 0.0017%. When the actual oxygen value reaches the theoretical expected final value of the decarburization oxygen, take sample B and analyze the infrared carbon component. If the carbon content is on the high side, appropriately extend the RH refining time; if the carbon content is on the low side, adjust the carbon according to the target carbon. For every 1 ppm increase in C, add 17 kg of high-carbon ferromanganese. Before weighing the high-carbon ferromanganese, electrolytic manganese must be used as a cushion.

[0038] 3. Alloy addition: Calculate the addition amount according to the alloy model. Actually add 466 Kg of electrolytic manganese and 15 Kg of ferroboron per ton of steel. Alloying is carried out in sequence according to the alloy addition order, and the specific order is Mn → Ti → B → Nb → Al. Before adding the alloy, the belt is reversed to remove the residual alloy on the belt to ensure the accuracy of the added alloy amount. And take sample C two minutes after adding the alloy, and require the test result to be reported within 7 minutes. Adjust the alloy amount according to the actual test result until the target value. Among them, the dynamic addition amount of Nb = (RH end point [C] - Ex.C) × 7.75 × 180 × 0.98) × 1000 / 100, ensuring that the solid solution C content in the continuous casting billet finished product is within 0.0007% - 0.0015%. Theoretically calculated, 13.67 - 27.32 kg needs to be added. Considering the metal yield, the actual addition amount of Nb is 30 kg.

[0039] 4. Net circulation: After adding the last batch of alloy materials, open the net circulation module. After the timer time meets the process requirements, click on recompression, and the net circulation will end automatically. The net circulation time is 7 min.

[0040] 5. Close the main vacuum valve and start the recompression module. Manually lower the ladle by less than 100 mm to prevent slag overflow. When the vacuum degree reaches 85 KPa, the ladle can be officially lowered, making the suction nozzle leave the molten steel surface, and lowering the ladle to the ground.

[0041]

[0042]

[0043] Example 2

[0044] Prepare BH steel by adopting the technical solution of this invention patent. The specific production steps are as follows:

[0045] 1. Before processing the target steel, arrange to process 4 furnaces of ultra-low carbon steel in advance, measure the temperature, determine the oxygen content, measure the slag thickness, and measure the freeboard, and confirm that the conditions meet the production conditions of the target steel grade. The oxygen value before processing is 664 ppm. Lift the ladle to ensure that the nozzle inserts into the liquid surface ≥ 400 mm.

[0046] 2. Open the main vacuum valve and start the vacuum treatment module. Manually lift and compensate about 100 mm according to the liquid surface condition, and pay attention to the change of the lifting height; select the lifting gas flow rate of 1 Nl / min according to the treatment mode; the lowest vacuum degree is 76 Pa; the decarburization time is 18 minutes. During the process, adjust the oxygen value in real time according to the RH decarburization reaction equilibrium coefficient to promote the RH decarburization reaction to proceed to the right, and ensure that RH quickly decarburizes the carbon in the steel to the lowest level; according to the decarburization conditions designed by the RH equipment, adjust the carbon to 0.0018%. At this time, the carbon after high manganese alloying and the carbon increase amount of the ladle of 2 - 5 ppm should be comprehensively considered. The end point oxygen value is 270 ppm. Add aluminum for deoxidation and alloying. After 3 minutes of aluminum deoxidation alloying, determine the oxygen content to ensure alloying under the premise of ensuring the aluminum content in the molten steel. Take three samples during the RH treatment process. The oxygen content before RH is 0.0664%. Take sample A 9 minutes after RH decarburization to analyze the spectral and infrared carbon components. The carbon content of sample A is 0.0365%. The target carbon content at the end point of RH decarburization is 0.0010%. After calculation, the oxygen content at the end point of RH decarburization is 0.0191%, and the oxygen value is on the low side. For the decarburization efficiency, supplement oxygen by 25 m 3 , use an oxygen lance to determine the actual oxygen value of 0.0270%, and sample and analyze the carbon content at the end point of RH decarburization of 0.0018%. When the actual oxygen value reaches the theoretical expected final value of the decarburization oxygen, take sample B and analyze the infrared carbon components. If the carbon content is on the high side, appropriately extend the RH refining time; if the carbon content is on the low side, carry out carbon addition according to the target carbon. For every 1 ppm increase in C, add 18 kg of high-carbon ferromanganese. Electrolytic manganese must be used as a bottom layer before weighing the high-carbon ferromanganese.

[0047] 3. Alloy addition: Calculate the addition amount according to the alloy model. Actually add 510 Kg of electrolytic manganese and 16 Kg of ferrosilicon boron per ton of steel. Alloying is carried out in sequence according to the alloy addition order, and the specific order is Mn → Ti → B → Nb → Al. Before adding the alloy, the belt is reversed to remove the residual alloy on the belt to ensure the accuracy of the added alloy amount. And take sample C two minutes after adding the alloy, and require the test result to be reported within 7 minutes. Adjust the alloy amount according to the actual test result until the target value. Among them, the dynamic addition amount of Nb = (RH end point [C] - Ex.C) × 7.75 × 180 × 0.98) × 1000 / 100, ensuring that the solid solution C content of the cast billet finished product is within 0.0007% - 0.0015%. Theoretically calculated, 13.04 - 41.01 kg needs to be added. Considering the metal yield, the actual addition amount of Nb is 36 kg.

[0048] 4. Net circulation: After adding the last batch of alloy materials, start the net circulation module. After the timer time meets the process requirements, click on recompression, and the net circulation will end automatically. The net circulation time is 7 min.

[0049] 5. Close the main vacuum valve, start the recompression module, manually lower the ladle by less than 100 mm to prevent slag overflow. When the vacuum degree reaches 85 KPa, the ladle can be officially lowered, making the suction nozzle leave the molten steel surface, and lower the ladle to the ground.

[0050]

[0051]

[0052] Example 3

[0053] Prepare BH steel by adopting the technical solution of this invention patent. The specific production steps are as follows:

[0054] 1. Before processing the target steel, arrange to process 4 furnaces of ultra-low carbon steel in advance, and measure the temperature, oxygen, slag thickness, and net space to confirm that the conditions meet the production conditions of the target steel grade. The oxygen value before processing is 614 ppm. Lift the ladle to ensure that the suction nozzle inserts into the liquid surface ≥ 400 mm.

[0055] 2. Open the main vacuum valve and start the vacuum treatment module. Manually lift and compensate by approximately 100 mm according to the liquid level condition, and pay attention to the change in the lifting height. Select the lifting gas flow rate of 1 Nl / min according to the treatment mode; the minimum vacuum degree is 596 Pa; the decarburization time is 16 minutes. During the process, according to the RH decarburization reaction equilibrium coefficient, adjust the oxygen value in real time to promote the RH decarburization reaction to proceed to the right, ensuring that RH quickly reduces the carbon in the steel to the lowest level. According to the decarburization conditions designed for the RH equipment, adjust the carbon to 0.0021%. At this time, the carbon after high manganese alloying and the carbon increase in the ladle of 2 - 5 ppm should be comprehensively considered. The end-point oxygen value is 350 ppm. Add aluminum for deoxidation and perform oxygen determination 3 minutes after aluminum deoxidation alloying. Alloying is carried out on the premise of ensuring that the molten steel contains aluminum. Take three samples during the RH treatment process. The oxygen content before RH is 0.0614%. Take sample A 9 minutes after RH decarburization and analyze the spectral and infrared carbon components. The carbon content of sample A is 0.0409%. The target carbon content at the end of RH decarburization is 0.0010%. After calculation, the oxygen content at the end of RH decarburization is 0.0082%, and the oxygen value is on the low side. For the decarburization efficiency, supplement oxygen by 50 m 3 , and use the oxygen lance to determine the actual oxygen value of 0.0350%. Take sample B and analyze the infrared carbon component after the actual oxygen value reaches the theoretical expected final value of the decarburization oxygen. If the carbon content is on the high side, appropriately extend the RH refining time; if the carbon content is on the low side, perform carbon matching according to the target carbon. For every 1 ppm increase in C, add 30 kg of high-carbon ferromanganese. Before weighing the high-carbon ferromanganese, electrolytic manganese must be used as a cushion.

[0056] 3. Alloy addition: Calculate the addition amount according to the alloy model. Actually add 490 Kg of electrolytic manganese and 19 Kg of ferroboron per ton of steel. Alloying is carried out in sequence according to the alloy addition order, and the specific order is Mn → Ti → B → Nb → Al. Before adding the alloy, the belt is reversed to remove the residual alloy on the belt to ensure the accuracy of the added alloy amount. Take sample C two minutes after adding the alloy, and require the sample test result to be reported within 7 minutes. Adjust the alloy amount according to the actual test result until the target value. Among them, the dynamic addition amount of Nb = (RH end-point [C] - Ex.C) × 7.75 × 180 × 0.98) × 1000 / 100, ensuring that the solid solution C content in the billet finished product is within 0.0007% - 0.0015%. Theoretically calculated, 13.04 - 41.01 kg needs to be added. Considering the metal yield, the actual addition amount of Nb is 35 kg.

[0057] 4. Net circulation: After adding the last batch of alloy materials, open the net circulation module. Click to restore pressure after the timer time meets the process requirements, and the net circulation automatically ends. The net circulation time is 7 minutes.

[0058] 5. Close the main vacuum valve, start the pressure recovery module, manually lower the ladle by within 100 mm to prevent slag overflow. Only when the vacuum degree reaches 85 KPa can the ladle be officially lowered, so that the suction nozzle leaves the molten steel surface, and the ladle is lowered to the ground.

[0059]

[0060]

[0061]

[0062] Product inspection and performance testing

[0063] In order to highlight the effects and advantages of this patent, based on Examples 1 to 3, 10 furnaces were respectively smelted according to the method of this patent and the traditional process, and a comparative analysis was carried out. The details are shown in Table (1).

[0064] Table 1 Key element content and BH value of finished products

[0065]

[0066] As can be seen from the above table, the annealing temperature of cold-rolled production using the traditional process is 70 °C higher than that using the method of this patent, and the energy consumption per ton of steel increases by about 100 yuan. In addition, in the comparison of the fluctuation range of the key index BH value of BH steel, it can be seen that the BH steel prepared by the method of this patent has a smaller and more stable fluctuation range of the BH value.

Claims

1. A method for precisely controlling the content of dissolved carbon in BH steel, the calculation formula for the content of dissolved C in the steel: Ex.C = C - Nb / 7.75, characterized in that: It includes the following steps: S1. Confirmation before processing, specifically, measuring temperature, determining oxygen content, measuring slag thickness, measuring the clear height, confirming that the conditions meet the production conditions of the target steel grade, lifting the ladle, and ensuring that the nozzle is inserted into the liquid surface by ≥400 mm; S2. Open the main vacuum valve and start the vacuum treatment module. Manually lift and compensate by 100 mm according to the liquid level condition, and pay attention to the change of the lifting height. Select the lifting gas flow rate of 90 - 120 NL / min according to the treatment mode; the minimum vacuum degree ≤ 100 Pa; the decarburization time is 15 - 25 minutes. During the process, according to the RH decarburization reaction equilibrium coefficient: Adjust the oxygen value in real time to promote the RH decarburization reaction to proceed to the right, and ensure that RH quickly decarburizes the carbon in the steel to the lowest level. According to the decarburization conditions designed for the RH equipment, adjust the carbon to 0.0020 - 0.0030%, the end-point oxygen value is 250 - 400 ppm. Add aluminum for deoxidation and alloying. After 2 - 3 minutes of aluminum deoxidation alloying, conduct oxygen determination to ensure alloying under the premise of ensuring the aluminum content in the molten steel; take three samples during the RH treatment process. Take sample A at 8 - 12 minutes of RH decarburization, analyze the spectral and infrared carbon components, and set the RH end-point carbon at the maximum and minimum values according to the decarburization capacity designed for the RH equipment. Before production, predict the decarburization end-point oxygen in combination with the conditions before RH, and dynamically adjust the oxygen supplement amount to create the initial conditions for RH production. The theoretical expected final value of the decarburization oxygen = initial [O] - (initial [C] - target [C]) * 16 / 12; when the actual oxygen value reaches the theoretical expected final value of the decarburization oxygen, take sample B and analyze the infrared carbon component. If the carbon content is on the high side, appropriately extend the RH refining time; if the carbon content is on the low side, conduct carbon addition according to the target carbon. For every 1 ppm increase in C, add 15 - 20 g / ton of high-carbon ferromanganese. Electrolytic manganese must be used as a base before weighing the high-carbon ferromanganese. S3. Alloy addition, calculating the addition amount with reference to the alloy model. The actual addition amounts of Mn, Ti, B, Nb, and Al alloys are the calculated values ±20 kg / ton of steel. Alloying is carried out in sequence according to the alloy addition order. Before adding the alloy, the belt is reversed to remove the residual alloy on the belt to ensure the accuracy of the added alloy amount. Among them, the addition amount of Nb is dynamically controlled according to the carbon at the end of RH decarburization and the dissolved C in the steel; S4. Net circulation, after adding the last batch of alloy materials, start the net circulation module. After the timer time meets the process requirements, click on recompression, and the net circulation will end automatically. The net circulation time is 6 - 8 min; S5. Close the main vacuum valve, start the recompression module, manually lower the ladle by within 100 mm to prevent slag overflow. When the vacuum degree reaches 85 kPa, the ladle can be officially lowered to make the nozzle leave the molten steel surface, and lower the ladle to the ground; When adjusting the carbon to 0.0020 - 0.0030% in step S2, the carbon after high - manganese alloying and the carbon increase amount of 2 - 5 ppm in the ladle should be comprehensively considered; The alloy addition order described in step S3 is Mn → Ti → B → Nb → Al; The dynamically added amount of Nb described in step S3 = (RH end - point [C] - Ex.C) × 7.75 × 180 × 0.98) × 1000 / 100, ensuring that the dissolved C content in the cast billet finished product is within 0.0007% - 0.0015%; In step S3, take a sample of C two minutes after adding the alloy, and adjust the alloy amount according to the actual test results until the target value; 2. The method according to claim 1, wherein: The oxygen value before processing in step S1 is 550 - 750 ppm; if the oxygen value confirmed before processing is lower than 450 ppm, then force - supply oxygen 3 minutes after opening the main vacuum valve; if the oxygen value confirmed before processing is higher than 750 ppm, then add metallic aluminum to reduce the oxygen; 3. The method according to claim 1, characterized in that: Step S1 also includes arranging to process more than 4 furnaces of ultra - low - carbon steel in advance before processing the target steel; 4. The method according to claim 1, characterized in that: The reporting time of the test results of the sample is 5 - 10 minutes.

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