Method for smelting high-strength cold-formed steel for automobile structural parts from vanadium-containing molten iron

Abstract

The invention relates to a method for smelting high-strength cold-formed steel for an automobile structure from vanadium-containing molten iron. The method comprises the following steps of desulfurization, vanadium extraction and steelmaking, converter steelmaking, LF refining, RH refining furnace refining and continuous casting. The alloy comprises the following smelting components in percentage by mass: 0.05 to 0.08 percent of C, 0.10 to 0.20 percent of Si, 1.75 to 1.90 percent of Mn, less than or equal to 0.012 percent of P, less than or equal to 0.006 percent of S, 0.050 to 0.060 percent of Nb, 0.090 to 0.110 percent of Ti, less than or equal to 0.30 percent of Cu, less than or equal to 0.30 percent of Cr, less than or equal to 0.30 percent of Ni, 0.010 to 0.020 percent of Mo, 0.020 to 0.050 percent of ALs, less than or equal to 0.0035 percent of [N] and the balance of iron and inevitable elements. According to the invention, the product with high precision, high quality and good surface quality can be manufactured, and the product has high plasticity and toughness.

Description

Technical Field

[0001] The patented technology of the present invention relates to a steel smelting method and process, specifically to a method for smelting high-strength cold-formed automobile structural steel with vanadium-containing molten iron. Background Art

[0002] As the global environment and energy crisis intensifies, energy conservation and emission reduction have become major issues facing the automotive industry. Automotive lightweight technology has become the development trend of the current automotive industry and has received widespread attention. High-strength steel has significant effects in reducing the weight of automobiles and improving safety, and is increasingly used in car body manufacturing. In the entire automobile manufacturing process, 60-70% of metal parts need to be stamped and formed. Authoritative research shows that if the weight of the entire vehicle is reduced by 10%, the fuel efficiency can be improved by 6%-8%; for every 100kg reduction in the curb weight of the vehicle, the fuel consumption per 100 kilometers can be reduced by 0.3-0.6 liters; if the weight of the vehicle is reduced by 1%, the fuel consumption can be reduced by 0.7%. It can be seen that stamping parts play a pivotal role in automobile manufacturing. With the development of automobile lightweight, energy-saving, high reliability and high quality requirements, a broad prospect has been shown. This has driven the automobile industry to adopt high-strength steel plates and some high-strength lightweight materials. The development and production of high-strength steel has become a very competitive automobile lightweight material. It has great advantages over other materials in terms of collision resistance, processing technology and cost, and can manufacture high-precision, high-quality and good surface quality products. Summary of the invention

[0003] The purpose of the present invention is to provide a method for smelting high-strength cold-formed automobile structural steel with molten vanadium iron. The steel provided by the present invention has high strength and light weight, and can be used to manufacture products with high precision, high quality and good surface quality.

[0004] The technical solution to the above problems is:

[0005] A method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron, characterized in that it comprises the following steps: desulfurization - vanadium extraction and steelmaking - converter steelmaking - LF refining - RH refining furnace - continuous casting process;

[0006] The smelting composition and mass percentage are: C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.75-1.90%, P≤0.012%, S≤0.006%, Nb: 0.050-0.060%, Ti: 0.090-0.110%, Cu≤0.30%, Cr≤0.30%, Ni≤0.30%, Mo: 0.010-0.020%, Als: 0.020-0.050%, [N]≤0.0035%, and the balance is iron and unavoidable elements.

[0007] Preferably, the desulfurization process: adopts composite injection, multiple slag removal or pre-slag removal according to the sulfur content and slag amount of the molten iron entering the station, the granular magnesium injection amount is 0.57-1.15kg / t, the lime injection amount is 1.71-3.42kg / t, the nitrogen pressure is 4.5-5.0bar, so that the sulfur content of the molten iron meets the process requirements: S mass content ≤0.003%.

[0008] Preferably, the vanadium extraction process: optimize the vanadium extraction production organization according to the production rhythm and Si and Ti content of vanadium-containing molten iron, speed up the connection between iron connection and vanadium extraction process, effectively reduce the auxiliary time of vanadium extraction production, and ensure sufficient oxygen supply for vanadium extraction. Use oxygen and nitrogen vanadium extraction mode, and adjust the nitrogen flow rate to 11000-13000Nm 3 / min, oxygen flow rate is adjusted to 9000~11000Nm 3 / min, oxygen supply for 6-8min, ensure the full oxidation of vanadium and reduce the loss of vanadium. Effectively improve the cooling and stirring effect of the molten pool, promote the reduction of impurities brought in by cold materials, and effectively control the mass percentage of residual vanadium ≤ 0.0015%.

[0009] Preferably, the converter steelmaking process: the amount of lime is determined according to the type of steel and the semi-steel [P] content. When the mass content of semi-steel [P] is less than 0.15%, the lower limit of lime is taken; when the mass content of semi-steel [P] is greater than 0.15%, the upper limit of lime is taken. The added lime value range is 25 to 35 kg / t, raw dolomite is 20.57 to 21.80 kg / t, machine-burned ore is 10.28 to 10.90 kg / t, and dephosphorization agent is 0.51 to 0.55 kg / t.

[0010] Preferably, the converter steelmaking process: when there is residual steel or the slag in the converter is too thin to discharge the slag, 500-800 kg of lime is added per furnace to reduce the temperature and thicken it, and the slag condition in the furnace is confirmed by the front shaking furnace, 7-10 tons of scrap steel is added per furnace, and 165-170 tons of molten iron are added per furnace; the carbon mass content of semi-steel is less than 3.30% or the temperature is lower than 1330°C, 2-3 tons of scrap steel is added per furnace or no scrap steel is added, and the amount of slag-making material added is reduced while ensuring that the final phosphorus mass content is ≤0.010%.

[0011] Preferably, in the converter steelmaking process: the S mass content of the semi-steel entering the furnace is ≤0.003%, the end point temperature of the converter is ≥1650°C, the continuous pulling temperature is ≥1640°C, the oxygen lance position of the process smelting is controlled at 1.4-1.7 meters, the oxygen pressure is 0.7-0.9Mpa, and the oxygen flow rate is 24000-36000Nm 3 / h, within 2 to 3 minutes of blowing, the oxygen flow rate is 24000Nm 3 / h. According to the flame state and the sound in the furnace, determine the slag removal and blowing state, adjust the gun position and add cold material to control the blowing steadily, and control the oxygen supply time at 11-15min. After the blowing is completed, open the ladle bottom blowing before tapping, and control the flow rate at 50-100Nm 3 / min, to ensure liquid surface creep; optimal endpoint control mass percentage: C: 0.03-0.04%, P≤0.010%, S≤0.006%.

[0012] Preferably, the LF refining process: the argon gas flow rate is set to ≤1500NL / min for smelting treatment at the station, the slag shell is fully stirred to be broken, 0.85-1.71kg / t of ladle modifier and 0.85-1.71kg / t of submerged arc slag are added according to the ladle slag thickness and the oxygen content in the steel, the heating gear is reasonably selected after sufficient stirring and melting, long arc heating is adopted in the early stage of heating, the argon gas flow rate is adjusted to 150-300NL / min, and foam slag is made to ensure the submerged arc effect, improve the electrode thermal power, and reduce the carbon increase of the electrode; the slag material is reasonably matched, the deoxidation degree is determined according to the S content of the chemical sample and the sticky slag state and color, and the amount of deoxidizer aluminum particles and lime added is adjusted in time to make the sticky slag state thickness 1.5-3mm appropriate, and the slag fluidity is good; deep deoxidation forms white slag during the strong stirring of argon gas, Ensuring sufficient alkalinity of the slag is beneficial to desulfurization. Before heating, add 600-800 kg / furnace of small-grain lime. After adding, stir and melt thoroughly, and then heat it. In the early stage of electrode heating, long arc heating is used for 2-3 minutes to melt the slag, and in the later stage, short arc rapid heating is used for 5-8 minutes. The compensation temperature is 1630-1640°C for the first furnace temperature; 1610-1620°C for continuous furnaces. After heating, adjust argon gas at 300-500NL / min to uniform temperature and composition. Adjust argon gas for temperature measurement. Whether to perform secondary heating is determined by the measured temperature. If the first furnace temperature of 1630-1640°C is not met, the continuous furnace temperature of 1610-1620°C requires secondary heating. The temperature meets the process requirements for chemical sample composition compensation.

[0013] Preferably, LF refining process: the chemical composition of the samples after smelting meets the quality requirements, C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.80-1.90%, P≤0.010%, S≤0.003%, Nb: 0.050-0.060%, Mo: 0.10-0.20%, ALs: 0.020-0.030%.

[0014] Preferably, the RH refining furnace process: top gun baking operation is performed before smelting treatment, two furnaces of low-carbon steel are used for tank washing before smelting this steel grade, oxygen is controlled at 100-300ppm at the converter end point to wash the tank and clean the cold steel in the tank, reduce the alloy burning loss of RH treated steel liquid, and improve the alloy recovery rate, confirm that the vacuum tank immersion pipe circulation pipe is well permeable, the gun position is 6.0-4.5m, and the flow rate is 180-220Nm 3 / h, make the inner wall of the tank temperature>1000℃; adjust the circulating argon gas to 70~100Nm 3 / h, control the degassing for 15 to 20 minutes to carry out molten steel circulation treatment, and the molten steel circulation in the vacuum tank begins to be adjusted to the upper limit of the target ALs content by adding Taiwan aluminum according to the chemical sample steel of the previous process, and circulates for 3 to 6 minutes; perform the ALs content operation of the oxygen meter, and perform alloying fine-tuning when it meets the upper limit of the target ALs content.

[0015] Preferably, the RH refining furnace process: add 270-300 kg of ferrotitanium / furnace, adjust the alloy composition compensation at one time to achieve the process target C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.75-1.90%, P≤0.012%, S≤0.006%, Nb: 0.050-0.060%, Ti: 0.090-0.110%, Cu≤0.30%, Cr≤0.30%, Ni≤0.30%, Mo: 0.010-0.020%, Nb+V+Ti≤0.22%, ALs: 0.020-0.050%, [N]≤0.0035%, maintain the vacuum degree ≤100 Pa, the pure degassing time ≥8 min, and after the treatment, calcium treatment 200-400 m / furnace and stand for 15-20 min.

[0016] Preferably, the RH refining furnace process: the first furnace steel tapping temperature: 1590 ~ 1600 ° C, the continuous drawing temperature: 1570 ~ 1580 ° C.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention optimizes the vanadium extraction production organization according to the Si and Ti content of vanadium-containing molten iron in the production rhythm, accelerates the connection between the iron connection and vanadium extraction process, effectively reduces the auxiliary time of vanadium extraction production, ensures sufficient oxygen supply for vanadium extraction, and adopts the coarse oxygen (oxygen + nitrogen) vanadium extraction mode to ensure that the vanadium element is fully oxidized and reduce the loss of vanadium element. Effectively improve the cooling and stirring effect of the molten pool, promote the reduction of impurities brought in by cold materials, effectively control the residual vanadium ≤ 0.0015%, and the vanadium recovery rate reaches 75.67% and above.

[0019] 2. The present invention can manufacture products with high precision, high quality and good surface quality, and has high plasticity and toughness, good cold bending performance, and no thermal cracks and internal stress will occur during the molding process, thereby increasing the added value of the product. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0021] Examples 1-6

[0022] The present invention relates to a method for smelting high-strength cold-formed automobile structural steel with vanadium-containing molten iron, comprising the following steps: desulfurization - vanadium extraction and steelmaking - converter steelmaking - LF refining - RH refining furnace - continuous casting process; specifically as follows: (1) desulfurization process: adopting composite blowing, multiple slag removal or pre-slag removal according to the sulfur content and slag amount of the molten iron entering the station, the granular magnesium blowing amount is 0.57-1.15 kg / t, the lime blowing amount is 1.71-3.42 kg / t, and the nitrogen pressure is 4.5-5.0 bar, so that the sulfur content of the molten iron meets the process requirements: S≤0.003%.

[0023] Table 1 Desulfurization process parameters of Examples 1-6

[0024] Example Granular magnesium injection amount / kg / t Lime spray / kg / t Nitrogen pressure / bar Sulfur content of hot metal / % 1 0.57 1.71 4.5 0.003 2 0.70 2.20 4.6 0.002 3 0.85 2.85 4.7 0.003 4 0.90 3.00 4.8 0.003 5 1.05 3.20 4.9 0.002 6 1.15 3.42 5.0 0.002

[0025] (2) Vanadium extraction and steelmaking process: Optimize the vanadium extraction production organization according to the production rhythm and Si and Ti content of vanadium-containing hot metal, speed up the connection between iron connection and vanadium extraction process, effectively reduce the auxiliary time of vanadium extraction production, and ensure sufficient oxygen supply for vanadium extraction. Use oxygen and nitrogen vanadium extraction mode, and adjust the nitrogen flow rate to 11000~13000Nm 3 / min, oxygen flow rate is adjusted to 9000~11000Nm 3 / min, oxygen supply for 6-8min, ensure the full oxidation of vanadium and reduce the loss of vanadium. Effectively improve the cooling and stirring effect of the molten pool, promote the reduction of impurities brought in by cold materials, and effectively control the mass percentage of residual vanadium ≤ 0.0015%.

[0026] Table 2 Parameters of vanadium extraction and steelmaking process in Examples 1-6

[0027]

[0028] (3) Converter steelmaking process: The amount of lime is determined according to the type of steel and the content of semi-steel [P]. When the mass content of semi-steel [P] is less than 0.15%, the lower limit of lime is taken; when the mass content of semi-steel [P] is greater than 0.15%, the upper limit of lime is taken. The range of lime added is 25-35 kg / t, raw dolomite is 20.57-21.80 kg / t, machine-burned ore is 10.28-10.90 kg / t, and dephosphorization agent is 0.51-0.55 kg / t.

[0029] When there is residual steel or the slag in the converter is too thin to discharge the slag, add 500-800kg of lime per furnace to reduce the temperature and thicken it, and confirm the slag condition in the furnace through the front shaker, add 7-10 tons of scrap steel and 165-170 tons of semi-steel per furnace; the carbon mass content of the semi-steel is less than 3.30% or the temperature is lower than 1330℃, add 2-3 tons of scrap steel per furnace or no scrap steel, and reduce the amount of slag-making material while ensuring that the final phosphorus is qualified P≤0.010%.

[0030] The sulfur content of the semi-steel entering the furnace is ≤0.003%, the end point temperature is ≥1650℃, the continuous pulling temperature is ≥1640℃, the oxygen lance position of the process smelting is controlled at 1.4~1.7 meters, the oxygen pressure is 0.7~0.9Mpa, and the oxygen flow rate is 24000~36000Nm 3 / h, within 2 to 3 minutes of blowing, the oxygen flow rate is 24000Nm 3 / h. According to the flame state and the sound in the furnace, determine the slag removal and blowing state, adjust the gun position and add cold material to control the blowing steadily, and control the oxygen supply time at 11-15min. After the blowing is completed, open the ladle bottom blowing before tapping, and control the flow rate at 50-100Nm 3 / min, to ensure liquid surface creep; optimal endpoint control mass percentage: C: 0.03-0.04%, P≤0.010%, S≤0.006%.

[0031] Table 3 Parameters of converter steelmaking process in Examples 1-6

[0032]

[0033] Table 4 Supplementary parameters of converter steelmaking process in Example 1-6

[0034]

[0035]

[0036] (4) LF refining process: the argon gas flow rate is set to ≤1500NL / min for smelting treatment at the station, and the slag shell is fully stirred to break. According to the ladle slag thickness and the oxygen content in the steel, 0.85-1.71kg / t of ladle modifier and 0.85-1.71kg / t of submerged arc slag are added. The heating gear is properly selected for full stirring and melting. Long arc heating is adopted in the early stage of heating. The argon gas flow rate is adjusted to 150-300NL / min, and foam slag is produced to ensure the submerged arc effect, improve the electrode thermal power, and reduce the carbon increase of the electrode; the slag material is reasonably matched, and the deoxidation degree is determined according to the S content of the chemical sample and the sticky slag state and color. The amount of deoxidizer aluminum particles and lime added is adjusted in time to make the sticky slag thickness 1.5-3mm and the slag fluidity good. During the strong stirring process of argon gas, deep deoxidation forms white slag, and ensuring sufficient alkalinity of the slag is beneficial to desulfurization. Before heating, 600-800 kg / furnace of small-grain lime is added. After adding, it is fully stirred and melted, and then heated. In the early stage of electrode heating, long arc heating is used for 2-3 minutes to melt the slag, and in the later stage, short arc rapid heating is used for 5-8 minutes. The compensation temperature is 1630-1640°C for the first furnace temperature; the temperature of continuous furnaces is 1610-1620°C. After heating, adjust the argon gas at 300-500NL / min to uniform the temperature and composition, adjust the argon gas for temperature measurement, and perform chemical sample composition compensation based on whether the measured temperature is in line with the process requirements for secondary heating.

[0037] LF refining process: The chemical composition of the samples after smelting meets the quality requirements, C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.80-1.90%, P≤0.010%, S≤0.003%, Nb: 0.050-0.060%, Mo: 0.10-0.20%, ALs: 0.020-0.030%.

[0038] Table 5 LF refining process parameters for Examples 1-6

[0039]

[0040]

[0041] Table 6 Chemical composition and mass percentage of molten steel in Example 1-6LF

[0042]

[0043] (5) RH refining furnace process: Top gun baking operation is carried out before smelting treatment. Two furnaces of low-carbon steel are used for tank washing before smelting this steel grade. The oxygen at the converter end point is controlled at 100-300ppm to wash the tank and cool the steel in the clean tank to reduce the alloy burning loss of RH treated steel liquid and improve the alloy recovery rate. Confirm that the vacuum tank immersion pipe circulation pipe is well ventilated, the gun position is 6.0-4.5m, and the flow rate is 180-220Nm 3 / h, make the inner wall of the tank temperature>1000℃; adjust the circulating argon gas to 70~100Nm 3 / h, control the degassing for 15 to 20 minutes to carry out molten steel circulation treatment, and the molten steel circulation in the vacuum tank begins to be adjusted to the upper limit of the target ALs content by adding Taiwan aluminum according to the chemical sample steel of the previous process, and circulates for 3 to 6 minutes; perform the ALs content operation of the oxygen meter, and perform alloying fine-tuning when it meets the upper limit of the target ALs content. Add 270-300 kg of ferrotitanium per furnace, adjust the alloy composition compensation at one time to achieve the process target, C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.75-1.90%, P≤0.012%, S≤0.006%, Nb: 0.050-0.060%, Ti: 0.090-0.110%, Cu≤0.30%, Cr≤0.30%, Ni≤0.30%, Mo: 0.010-0.020%, Nb+V+Ti≤0.22%, ALs: 0.020-0.050%, [N]≤0.0035%; keep the vacuum degree ≤100 Pa, the pure degassing time ≥8 min, and after the treatment, calcium treatment is completed for 200-400 m / furnace and allowed to stand for 15-20 min. RH first furnace tapping temperature: 1590~1600℃, continuous pulling temperature: 1570~1580℃.

[0044] Table 7 Example 1-6RH refining furnace process parameters

[0045]

[0046] Table 8 Chemical composition and mass percentage of molten steel in Example 1-6 (%)

[0047]

[0048]

[0049] Note: In Table 8, the remainder is Fe and unavoidable impurities.

[0050] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments with equivalent changes without departing from the scope of the technical solution of the present invention.

Claims

1. A method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron, characterized in that: The following steps are involved: Desulfurization - vanadium extraction steelmaking - converter steelmaking - LF refining - RH refining furnace - continuous casting process; The smelting composition and mass percentage are: C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.75-1.90%, P≤0.012%, S≤0.006%, Nb: 0.050-0.060%, Ti: 0.090-0.110%, Cu≤0.30%, Cr≤0.30%, Ni≤0.30%, Mo: 0.010-0.020%, Als: 0.020-0.050%, [N]≤0.0035%, and the balance is iron and unavoidable elements.

2. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 1, characterized in that: Desulfurization process: composite injection is adopted, and slag is removed multiple times or pre-slag is removed according to the sulfur content and slag amount of the molten iron entering the station. The granular magnesium injection amount is 0.57-1.15 kg / t, the lime injection amount is 1.71-3.42 kg / t, and the nitrogen pressure is 4.5-5.0 bar, so that the sulfur content of the molten iron meets the process requirements: S mass content ≤ 0.003%.

3. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 1, characterized in that: Vanadium extraction and steelmaking process: Oxygen and nitrogen are used to extract vanadium, and the nitrogen flow rate is adjusted to 11000-13000Nm 3 / min, oxygen flow rate is adjusted to 9000~11000Nm 3 / min, supply oxygen for 6 to 8 minutes to control the mass percentage of residual vanadium to ≤0.0015%.

4. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 1, characterized in that: Converter steelmaking process: determine the amount of lime according to the type of steel and semi-steel [P] content. When the mass content of semi-steel [P] is less than 0.15%, take the lower limit of lime; when the mass content of semi-steel [P] is greater than 0.15%, take the upper limit of lime. The range of added lime is 25-35 kg / t, raw dolomite is 20.57-21.80 kg / t, machine-burned ore is 10.28-10.90 kg / t, and dephosphorization agent is 0.51-0.55 kg / t.

5. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 4, characterized in that: Converter steelmaking process: when there is residual steel or the slag in the converter is too thin to be discharged, add 500-800kg of lime / furnace to cool and thicken it, and confirm the slag condition in the furnace by shaking the furnace, add 7-10 tons of scrap steel / furnace, and 165-170 tons of molten iron / furnace; when the carbon content of semi-steel is less than 3.30% or the temperature is lower than 1330℃, add 2-3 tons of scrap steel / furnace or no scrap steel, and reduce the amount of slag-making material added while ensuring that the final phosphorus content is ≤0.010%; The sulfur content of the semi-steel entering the furnace is ≤0.003%, the end point temperature is ≥1650℃, the continuous pulling temperature is ≥1640℃, the oxygen lance position of the process smelting is controlled at 1.4~1.7 meters, the oxygen pressure is 0.7~0.9Mpa, and the oxygen flow rate is 24000~36000Nm 3 / h, within 2 to 3 minutes of blowing, the oxygen flow rate is 24000Nm 3 / h. According to the flame state and the sound in the furnace, determine the slag removal and blowing state, adjust the gun position and add cold material to control the blowing steadily, and control the oxygen supply time at 11-15min. After the blowing is completed, open the ladle bottom blowing before tapping, and control the flow rate at 50-100Nm 3 / min, to ensure liquid surface creep; optimal endpoint control mass percentage: C: 0.03-0.04%, P≤0.010%, S≤0.006%.

6. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 1, characterized in that: LF refining process: the argon gas flow rate is set to ≤1500NL / min for smelting treatment at the station, and the slag shell is fully stirred and broken. According to the ladle slag thickness and oxygen content in the steel, 0.85-1.71kg / t of ladle modifier and 0.85-1.71kg / t of submerged arc slag are added. Long arc heating is used in the early stage of heating, and the argon gas flow rate is adjusted to 150-300NL / min, and foam slag is made. The deoxidation degree is determined according to the S content of the chemical sample and the sticky slag state and color. The amount of deoxidizer aluminum particles and lime added is adjusted in time to make the sticky slag thickness 1.5-3mm and the slag fluidity good; During the strong stirring process of argon, deep deoxidation forms white slag to ensure sufficient alkalinity of the slag. Before heating, 600-800 kg / furnace of small-grain lime is added. After adding, it is fully stirred and melted for heating treatment. In the early stage of electrode heating, long arc heating is used for 2-3 minutes to melt the slag, and short arc rapid heating is used for 5-8 minutes in the later stage. The compensation temperature is 1630-1640°C for the first furnace temperature; the continuous furnace temperature is 1610-1620°C. After heating, adjust the argon gas at 300-500NL / min to uniform the temperature and composition. Adjust the argon gas for temperature measurement. Whether to perform secondary heating is determined according to the measured temperature. If the first furnace temperature of 1630-1640°C is not met, the continuous furnace temperature of 1610-1620°C must be heated for a second time. The temperature meets the process requirements for chemical sample composition compensation.

7. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 6, characterized in that: LF refining process: The chemical composition of the samples after smelting meets the quality requirements, C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.80-1.90%, P≤0.010%, S≤0.003%, Nb: 0.050-0.060%, Mo: 0.10-0.20%, ALs: 0.020-0.030%.

8. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 1, characterized in that: RH refining furnace process: top gun baking operation is carried out before smelting treatment. Two furnaces of low-carbon steel are used for tank washing before smelting this steel grade. The oxygen at the converter end point is controlled at 100-300ppm to wash the tank and cool the steel in the clean tank. The gun position is 6.0-4.5m, and the flow rate is 180-220Nm 3 / h, make the inner wall of the tank temperature>1000℃; adjust the circulating argon gas to 70~100Nm 3 / h, control the degassing for 15 to 20 minutes to carry out molten steel circulation treatment, and the molten steel circulation in the vacuum tank begins to be adjusted to the upper limit of the target ALs content by adding Taiwan aluminum according to the chemical sample steel of the previous process, and circulates for 3 to 6 minutes; perform the ALs content operation of the oxygen meter, and perform alloying fine-tuning when it meets the upper limit of the target ALs content.

9. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 8, characterized in that: RH refining furnace process: add 270-300kg / furnace of ferrotitanium, adjust the alloy composition compensation at one time to achieve the process target C: 0.05-0.08%, Si: 0.10-0.20%, Mn: 1.75-1.90%, P≤0.012%, S≤0.006%, Nb: 0.050-0.060%, Ti: 0.090-0.110%, Cu≤0.30%, Cr≤0.30%, Ni≤0.30%, Mo: 0.010-0.020%, Nb+V+Ti≤0.22%, ALs: 0.020-0.050%, [N]≤0.0035%; keep the vacuum degree ≤100Pa, the pure degassing time ≥8min, and after the treatment, calcium treatment 200-400m / furnace, let it stand for 15-20min.

10. The method for smelting high-strength cold-formed automobile structural steel from vanadium-containing molten iron according to claim 9, characterized in that: RH refining furnace process: first furnace steel tapping temperature: 1590 ~ 1600 ℃, continuous pulling temperature: 1570 ~ 1580 ℃.

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