High-strength F + P type non-quenched and tempered steel 25MnV5 for automobile steering knuckle flange and production method of high-strength F + P type non-quenched and tempered steel 25MnV5

Abstract

The invention provides high-strength F + P type non-quenched and tempered steel 25MnV5 for an automobile steering knuckle flange and a production method of the high-strength F + P type non-quenched and tempered steel 25MnV5. Comprising the following chemical components in percentage by weight: 0.21 to 0.26 percent of C, 0.10 to 0.40 percent of Si, 1.30 to 1.60 percent of Mn, less than or equal to 0.03 percent of P, 0.015 to 0.035 percent of S, 0.10 to 0.30 percent of Cr, 0.10 to 0.20 percent of Ni, less than or equal to 0.10 percent of Mo, 0.13 to 0.16 percent of V, 0.020 to 0.040 percent of Nb, less than or equal to 0.20 percent of Cu, 0.005 to 0.050 percent of Al and 0.010 to 0.020 percent of N. The invention further relates to a production method of the high-strength F + P type non-quenched and tempered steel 25MnV5 for the automobile steering knuckle flange. Through chemical component microalloying design, after the steel is forged into the steering knuckle flange, the high-strength F + P type non-quenched and tempered steel for the automobile steering knuckle flange is produced without quenching and tempering treatment and other processes, the indexes such as the mechanical property, the obdurability and the like of the steel can reach the standard requirement level, the traditional quenching and tempering process is omitted in the production process, and the production cost is reduced. The method has good economic and social benefits and prominent environmental protection contribution.

Description

Technical Field

[0001] This invention belongs to the field of new materials; in particular, it relates to a high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges and its production method. Background Technology

[0002] The steering knuckle flange is a key component of the steering system. Located at the end of the steering knuckle, it typically includes bolt holes, bearing housings, and the steering arm connection point. It is fixed to the wheel hub with bolts, supporting the wheel and transmitting steering force. During operation, it withstands the reverse torque during braking, ensuring braking stability. Its design, material selection, and manufacturing process directly affect the vehicle's safety and functionality; therefore, the material must possess high fatigue strength while also exhibiting a good balance of strength and toughness. Microalloyed non-quenched and tempered steel is a high-efficiency and energy-saving steel developed in response to international energy shortages. It makes significant contributions to environmental protection by integrating rolling (or forging) with heat treatment processes, thus replacing the quenching and tempering process. Because it reduces losses caused by quenching deformation and cracking of parts, it features energy saving, environmental protection, and reduced production costs. Therefore, it is widely used in the automotive, construction machinery, agricultural machinery, standard parts, and petroleum industries. The application of non-quenched and tempered steel can save 30% to 40% of energy consumption in parts manufacturing and reduce costs by 20%. It also reduces deformation and cracking caused by quenching during the tempering process, resulting in significant economic and social benefits. Due to factors such as research foundation, technological level, and production equipment, my country lags behind foreign countries in the quantity and variety of non-quenched and tempered steel applications, and some high-performance non-quenched and tempered steels still rely on imports. With the increase in automobile production and ownership, the pressure for energy conservation and emission reduction is rapidly increasing, and the variety, quality, application scope, and quantity of non-quenched and tempered steel for automobiles will inevitably continue to expand and develop.

[0003] Therefore, to address the above issues, it is essential to develop a high-strength "F+P" type non-quenched and tempered steel for automotive steering knuckle flanges. This steel utilizes a high Mn content and adds appropriate amounts of microalloying elements V, Ni, and Nb to improve its strength and toughness, resulting in excellent strength and toughness, as well as superior fatigue performance. A high-strength "F+P" type non-quenched and tempered steel, 25MnV5, for automotive steering knuckle flanges, achieves a uniform and fine F+P microstructure through microalloying chemical composition design and controlled rolling and cooling processes, eliminating the need for heat treatment. Furthermore, the use of V, Ni, and Nb for microalloying further refines the steel's microstructure, significantly improving its comprehensive mechanical properties and meeting the lightweight and special performance requirements of automotive components. Therefore, the development of high-strength "F+P" type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges has a significant existing and potential market and is of great importance to improving the technological level of non-quenched and tempered steel for automotive steering knuckle flanges in my country. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges and its production method.

[0005] This invention is achieved through the following technical solution:

[0006] This invention relates to a high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges, comprising the following chemical composition and weight percentage of each component: C 0.21-0.26%, Si 0.10-0.40%, Mn 1.30-1.60%, P≤0.03%, S 0.015-0.035%, Cr 0.10-0.30%, Ni 0.10-0.20%, Mo≤0.10%, V 0.13-0.16%, Nb 0.020-0.040%, Cu≤0.20%, Al 0.005-0.050%, N 0.010-0.020%.

[0007] This invention also relates to a method for producing the aforementioned high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges, comprising the following steps:

[0008] Consteel electric furnace smelting + LF ladle refining (with tellurium treatment) + VD vacuum degassing → continuous casting 250mm×280mm → rolling product (controlled rolling and controlled cooling) → rack cooling → pit cooling and heat preservation → finishing → flaw detection → inspection → check → packaging → delivery.

[0009] Preferably, the production method of the high-strength F+P type non-quenched and tempered steel 25MnV5 for the automotive steering knuckle flange includes the following specific steps:

[0010] Step 1: Smelting and casting of continuously cast billets

[0011] Consteel electric furnace smelting + LF ladle refining + VD vacuum degassing + 250×280mm Danieli three-strand billet continuous casting;

[0012] Step 2, rolling the product

[0013] The 250mm×280mm section is heated using a walking beam furnace. The first heating section has a temperature of 1050~1150℃, the second heating section has a temperature of 1160~1200℃, and the soaking section has a temperature of 1140~1180℃. The total heating time is controlled at 3.5~4.5h, and the high temperature diffusion time is ≥1.5h.

[0014] in,

[0015] Initial rolling temperature control: Initial rolling temperature control ≥1030℃, final rolling temperature ≥930℃;

[0016] Rolling process: The rolling process adopts the thermomechanical rolling technology of SMS Company, with 21 continuous rolling mills and the middle 3 mills using water ring quenching.

[0017] Step 3, rack cooling

[0018] After rolling, the material is collected using a rack cooling bed with an upper cooling bed temperature of 800–900℃.

[0019] Step 4, Insulate the pit

[0020] After the steel is cooled on the rack and pinion cooling bed, it is promptly placed into the pit for heat preservation, with the pit temperature at 300-400℃.

[0021] Step 5, finishing

[0022] The bending degree of the steel is ≤2.5mm / m, and the out-of-roundness is ≤65% of the diameter tolerance;

[0023] Step 6, Flaw Detection

[0024] Ultrasonic testing of steel meets the quality grade A of GB / T 4162 standard;

[0025] Step 7: Inspection → Check → Packaging → Submission.

[0026] Preferably, in step 1, the ingredients are molten iron and scrap steel, with the furnace charge controlled at 50-80t, of which the proportion of molten iron is controlled at 60-80% and the amount of scrap steel is controlled at 20-40%.

[0027] Preferably, in step 1, the Consteel electric furnace smelting is as follows: the final C content of the electric furnace is ≥0.08% and P is ≤0.015%. 500±50 kg of lime, 100±20 kg of composite deoxidizer, 180±20 kg of pre-melted slag, and 180±20 kg of low-silicon deoxidizing refining slag are added to the tapping slag, which is equivalent to 0.6-1.2 kg / t of pure aluminum. The tapping volume is 70±5 tons. The order of adding deoxidizer and alloy during the tapping process is: Al ingot or steel-core aluminum → composite deoxidizer, pre-melted slag → alloy → lime. After tapping, C powder is added to the ladle to increase carbon content based on the C content of the tapped steel and the amount of carbon added to the alloy.

[0028] Preferably, in step 1, the LF ladle refining process involves: molten steel entering the LF station at a temperature ≥1500℃, electrically heated for ≥20 minutes, and after the temperature is suitable and the slag turns white, a sample is taken for chemical composition analysis. Based on the analysis results, the composition is adjusted according to the internal control composition specifications. Argon gas control during the refining process is 100–400 NL / min. Al control during the refining process is as follows: target Al content of 0.010–0.025% upon entering the refining process. Slag conditioning during the process involves appropriately adding SiC, C powder, Al particles, and lime. The target composition of the refined slag is: CaO: 55–60%, SiO2: 5–10%, Al2O3: 22–28%, MgO: 3–8%. The white slag refining time is ≥35 minutes.

[0029] Preferably, in step 1, the VD vacuum degassing is performed by entering the VD station after the temperature is ≥1620℃, maintaining the vacuum at 0.5 Torr for ≥15 minutes, and controlling the argon gas during the deoxygenation operation: rough vacuum >200 Torr, argon gas flow rate 50~150 NL / min, and extreme vacuum, argon gas flow rate 100~200 NL / min.

[0030] S-controlled operation: After VD degassing, add 80 kg of silica and feed 130 m of S-line;

[0031] Tellurium treatment procedure: After feeding in S-line for 1 minute, feed in 30m of tellurium wire and gently blow for 25 minutes;

[0032] Soft blowing time: The weak argon stirring operation time should be ≥25 minutes according to the temperature of the molten steel, and the slag surface fluctuation of the molten steel should be 150-300mm during the weak argon operation.

[0033] Small billet continuous casting: The ladle is heated in the LF furnace station. When the temperature of the molten steel is 1550-1575℃, the ladle is lifted into the continuous casting machine for continuous casting of billets. With appropriate electromagnetic stirring, cooling parameters and straightening machine parameters, high-quality semi-finished billets with high cleanliness and high uniformity are produced.

[0034] The design concept of the chemical composition of the high-strength F+P type non-quenched and tempered steel 25MnV5 involved in this invention is as follows:

[0035] Carbon (C) is the second most important element after iron, directly affecting the strength, plasticity, and toughness of steel. As carbon content increases, the strength and hardness of steel improve, while plasticity and toughness decrease. To ensure both high strength and high toughness, the C content is controlled between 0.21% and 0.26%. Si is an important deoxidizer and reducing agent in the steelmaking process. Si exists in solid solution in ferrite or austenite, possessing strong solid solution strengthening and cold work hardening capabilities, which can improve the strength and wear resistance of steel. The Si content is controlled between 0.10% and 0.40%. Mn can be infinitely dissolved in Fe, improving the strength of steel with minimal impact on plasticity. Mn can significantly improve the hardenability of steel and strongly reduce the bainite and martensite transformation temperatures. To promote bainite transformation at lower temperatures, which is beneficial for refining the microstructure and improving strength, the Mn content is controlled at 1.30%–1.60%. P is a harmful element in steel, especially reducing its impact toughness; therefore, it should be controlled to a minimum, ≤0.030%, based on actual production levels. Cr is one of the elements that improves hardenability, significantly increasing the hardness and wear resistance of steel; the Cr content is controlled at 0.10–0.30%. This product innovatively adopts a Ni, V, Nb composite design to refine grains and improve strength, enhance yield strength ratio and low-temperature performance, ensuring performance even at higher forging temperatures for steering knuckle flanges. Under conditions of uneven deformation, the grains are fine and uniform, and the various properties are stable. The Ni content is controlled at 0.10-0.20%, the V content at 0.13-0.16%, and the Nb content at 0.020-0.040%. Al, as the main deoxidizer, can also refine the grains. The Al content is controlled at 0.005%-0.050%. Increasing the nitrogen content in the steel can promote the precipitation of alloying elements such as V and enhance the precipitation strengthening effect of alloying elements such as V, thereby improving the mechanical properties of the steel. The N content is controlled at 0.010-0.020%. The chemical composition and weight percentage (wt%) are shown in Table 1.

[0036] Table 1

[0037]

[0038] The present invention has the following advantages:

[0039] (1) Through the micro-alloying design of chemical composition, this invention produces a high-strength F+P type non-quenched and tempered steel for automotive steering knuckle flanges after the steel is forged into a steering knuckle flange without tempering (quenching + tempering) treatment. The mechanical properties and toughness of this steel can not only meet the standard requirements, but the production process also eliminates the traditional tempering process, which has good economic and social benefits and outstanding environmental protection contributions.

[0040] (2) In the smelting and production process of this invention, tellurium treatment is used to control the morphology and distribution of sulfides, so that the sulfides of the high-strength F+P type non-quenched and tempered steel 25MnV5 rolled material used for automobile steering knuckle flange are finely and dispersedly distributed, ensuring the excellent mechanical properties and fatigue strength of the steel.

[0041] (3) The present invention adopts the process system of Consteel electric furnace + LF + VD + CC + TMCP rolling to produce high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flange. This process has the characteristics of high production efficiency, stable product quality, and strong universality in the promotion and application of process technology. Attached Figure Description

[0042] Figure 1 This is a photograph of the microstructure of high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges, which is involved in this invention, at low magnification.

[0043] Figure 2 These are photographs of the rolled microstructure of the high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges at different magnifications, as described in this invention.

[0044] Figure 3 This is a comparison chart of sulfide distribution in steel before and after tellurium treatment. Detailed Implementation

[0045] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are merely further illustrations of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0046] Example

[0047] This embodiment relates to a production method of high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges. The specific steps are as follows:

[0048] I. Continuous casting billet smelting and casting

[0049] Consteel electric furnace + LF ladle refining + VD vacuum degassing + 250×280mm Danieli three-strand billet continuous casting.

[0050] Raw materials: Use molten iron and scrap steel, with a furnace charge of 50-80t, of which molten iron accounts for 60-80% and scrap steel accounts for 20-40%.

[0051] Consteel electric arc furnace smelting: Final carbon content at the electric arc furnace is ≥0.08%, phosphorus ≤0.015%. The tapping slag contains 500±50 kg of lime, 100±20 kg of composite deoxidizer, 180±20 kg of pre-melted slag, and 180±20 kg of low-silicon deoxidizing refining slag, equivalent to 0.6-1.2 kg / t of pure aluminum. The tapping yield is 70±5 tons. The order of adding deoxidizer and alloy during tapping is: Al ingot or steel-cored aluminum → composite deoxidizer, pre-melted slag → alloy → lime. After tapping, carbon powder is added to the ladle to increase carbon content based on the carbon content of the tapped steel and the amount of carbon added by the alloy.

[0052] LF ladle refining: The temperature of the molten steel entering the LF station is ≥1500℃. After electric heating for ≥20 minutes, once the temperature is suitable and the slag turns white, samples are taken for chemical composition analysis. Based on the analysis results, the composition is adjusted according to the internal control composition specifications. Argon gas control during refining: 100~400NL / min. Al control during refining: Target Al (0.010~0.025%) upon entering the refining process. Slag conditioning during the process: Appropriate additions such as SiC, C powder, Al granules, and lime can be used for slag conditioning. Target composition of refining slag: CaO: 55~60%, SiO2: 5~10%, Al2O3: 22~28%, MgO: 3~8%. White slag refining time ≥35 minutes.

[0053] VD vacuum degassing: After the temperature reaches ≥1620℃, vacuum degassing is performed at the VD station. The vacuum degree is 0.5 Torr and the holding time is ≥15 minutes. Argon control during deoxygenation operation: argon flow rate is 50~150NL / min under rough vacuum (>200 Torr) and 100~200NL / min under extreme vacuum.

[0054] S-controlled operation: After VD degassing, add 80 kg of silica, feed 130 m of S wire, feed 30 m of tellurium wire after 1 minute, and gently blow for 25 minutes.

[0055] Soft blowing time: The weak argon stirring operation time should be ≥25 minutes according to the temperature of the molten steel. During the weak argon operation, the slag surface of the molten steel should fluctuate by 150-300mm.

[0056] Small billet continuous casting: The ladle is heated in the LF furnace station. When the temperature of the molten steel is 1550-1575℃, the ladle is lifted into the continuous casting machine for continuous casting of billets. With appropriate electromagnetic stirring, cooling parameters and straightening machine parameters, high-quality semi-finished billets with high cleanliness and high uniformity are produced.

[0057] II. Rolled Products

[0058] The 250mm×280mm section is heated using a walking beam furnace. The first heating stage has a temperature of 1050~1150℃, the second heating stage has a temperature of 1160~1200℃, and the soaking stage has a temperature of 1140~1180℃. The total heating time is controlled at 3.5-4.5h, and the high-temperature diffusion time is ≥1.5h.

[0059] Initial rolling temperature control: Initial rolling temperature control ≥1030℃, final rolling temperature ≥930℃;

[0060] Rolling process: The rolling process adopts the thermomechanical rolling technology of SMS Company, with 21 continuous rolling mills, and the middle 3 rolling mills adopt water ring water piercing;

[0061] Cooling process: After rolling, the material is collected on a rack cooling bed with an upper cooling bed temperature of 800-900℃;

[0062] Insulation upon entering the pit: After the steel is cooled on the rack and pinion bed, it should be placed in the pit for insulation in a timely manner, with the pit temperature being 300-400℃.

[0063] III. Steel Testing

[0064] 1. Chemical composition

[0065] The chemical composition and weight percentage (wt%) of the steel are shown in Table 2.

[0066] Table 2

[0067]

[0068] 2. Low-magnification tissue

[0069] The steel underwent low-magnification microstructure inspection, and the central porosity, general porosity, and ingot segregation were all grade 1.0, with no punctate segregation. The low-magnification microstructure of the steel, according to GB / T1979, should conform to the requirements of Table 3. Low-magnification microstructure photographs are shown below. Figure 1 As shown.

[0070] Table 3

[0071]

[0072] 3. Metallographic structure

[0073] Samples were taken from the 1 / 2R section of the steel to examine its microstructure. After polishing and etching, the rolled microstructure was observed under an optical microscope at 200x and 500x magnification. The rolled microstructure was identified as F+P structure. The photographs of the rolled microstructure are shown below. Figure 2 As shown.

[0074] 4. Mechanical properties

[0075] According to GB / T 2975, samples were taken at 1 / 2 radius of the steel to determine the longitudinal mechanical properties of the steel. The test results are shown in Table 4.

[0076] Table 4

[0077] - Specifications (mm) Rm / MPa Rel / MPa A / ％ Z / ％ Indicator Requirements - 700～950 ≥500 ≥10 ≥24 Actual test 1 60 816 567 20 50 Actual test 2 60 852 593 17 44

[0078] 5. Non-metallic inclusions

[0079] According to GB / T 10561, non-metallic inclusions were tested on the steel. The test results are shown in Table 5. Comparison photos of the morphology and distribution of sulfides before and after tellurium treatment are shown below. Figure 3 As shown.

[0080] Table 5

[0081]

[0082] 6. Ultrasonic flaw detection

[0083] The steel is subjected to 100% ultrasonic testing after leaving the pit, and the quality level meets the GB / T4162 Class A level.

[0084] In summary, the steel produced using the method of this invention fully meets the material selection requirements for automotive steering knuckle flanges. It can replace traditional Cr and Cr-Mo type quenched and tempered steels in the manufacture of automotive parts such as steering knuckle flanges, which require higher strength and toughness. Through controlled rolling and controlled cooling, the microstructure of the steel is made into a uniform and fine F+P structure. Through microalloying design of chemical composition, the mechanical properties of the non-quenched and tempered steel 25MnV5 are significantly improved. The tellurium treatment method used in the smelting process improves the morphology and distribution of sulfides, changing the original aggregated elongated distribution of sulfides to a dispersed short and coarse distribution, thereby achieving the purpose of improving the mechanical properties and fatigue strength of the steel. The high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges, developed and produced using the Consteel electric furnace + LF + VD + CC + TMCP rolling process system, has high production efficiency, stable product quality, and strong versatility in process technology promotion and application.

[0085] The development and application of the high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges involved in this invention does not require quenching and tempering treatment, which is of great significance for environmental protection, energy conservation and carbon reduction, and has a huge potential market for application and promotion. It is of great significance for improving the technical level of non-quenched and tempered steel for automotive steering knuckle flanges in my country.

[0086] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges, characterized in that, The chemical composition and weight percentage of each component are as follows: C 0.21–0.26%, Si 0.10–0.40%, Mn 1.30–1.60%, P≤0.03%, S 0.015–0.035%, Cr 0.10–0.30%, Ni 0.10–0.20%, Mo≤0.10%, V 0.13–0.16%, Nb 0.020–0.040%, Cu≤0.20%, Al 0.005–0.050%, N 0.010–0.020%.

2. A method for producing high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges as described in claim 1, characterized in that, Includes the following steps: Consteel electric arc furnace smelting + LF ladle refining + VD vacuum degassing → continuous casting → rolling of finished products → rack cooling → pit cooling and insulation → finishing → flaw detection → inspection → check → packaging → delivery.

3. The production method of high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges as described in claim 2, characterized in that, The specific steps are as follows: Step 1: Smelting and casting of continuously cast billets Consteel electric furnace smelting + LF ladle refining + VD vacuum degassing + 250×280mm Danieli three-strand billet continuous casting; Step 2, rolling the product The 250mm×280mm section is heated using a walking beam furnace. The first heating section has a temperature of 1050~1150℃, the second heating section has a temperature of 1160~1200℃, and the soaking section has a temperature of 1140~1180℃. The total heating time is controlled at 3.5~4.5h, and the high temperature diffusion time is ≥1.5h. in, Initial rolling temperature control: Initial rolling temperature control ≥1030℃, final rolling temperature ≥930℃; Rolling process: The rolling process adopts the thermomechanical rolling technology of SMS Company, with 21 continuous rolling mills and the middle 3 mills using water ring quenching. Step 3, rack cooling After rolling, the material is collected using a rack cooling bed with an upper cooling bed temperature of 800–900℃. Step 4, Insulate the pit After the steel is cooled on the rack and pinion cooling bed, it is promptly placed into the pit for heat preservation, with the pit temperature at 300-400℃. Step 5, finishing The bending degree of the steel is ≤2.5mm / m, and the out-of-roundness is ≤65% of the diameter tolerance; Step 6, Flaw Detection Ultrasonic testing of steel meets the quality grade A of GB / T 4162 standard; Step 7: Inspection → Check → Packaging → Submission.

4. The production method of high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges as described in claim 3, characterized in that, In step 1, the smelting materials consist of molten iron and scrap steel, with the furnace charge controlled at 50-80 tons. The proportion of molten iron is controlled at 60-80%, and the amount of scrap steel is controlled at 20-40%.

5. The production method of high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges as described in claim 3, characterized in that, In step 1, the Consteel electric furnace smelting process is as follows: the final C content of the electric furnace is ≥0.08% and P is ≤0.015%. 500±50 kg of lime, 100±20 kg of composite deoxidizer, 180±20 kg of pre-melted slag, and 180±20 kg of low-silicon deoxidizing refining slag are added to the tapping slag, which translates to 0.6-1.2 kg / t of pure aluminum. The tapping volume is 70±5 tons. The order of adding deoxidizer and alloy during the tapping process is: Al ingot or steel-core aluminum → composite deoxidizer, pre-melted slag → alloy → lime. After tapping, C powder is added to the ladle to increase carbon content based on the C content of the tapped steel and the amount of carbon added to the alloy.

6. The production method of high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges as described in claim 3, characterized in that, In step 1, the LF ladle refining process involves: molten steel entering the LF station at a temperature ≥1500℃, electrically heated for ≥20 minutes, and after the temperature is suitable and the slag turns white, a sample is taken for chemical composition analysis. Based on the analysis results, the composition is adjusted according to the internal control composition specifications. Argon gas control during the refining process is 100–400 NL / min. Al control during the refining process is as follows: target Al content of 0.010–0.025% upon entering the refining process. Slag conditioning during the process involves adding appropriate amounts of SiC, C powder, Al particles, and lime. The target composition of the refining slag is: CaO: 55–60%, SiO2: 5–10%, Al2O3: 22–28%, MgO: 3–8%. The white slag refining time is ≥35 minutes.

7. The production method of high-strength F+P type non-quenched and tempered steel 25MnV5 for automotive steering knuckle flanges as described in claim 3, characterized in that, In step 1, the VD vacuum degassing: after the temperature is ≥1620℃, it is put into the VD station for vacuum degassing. The vacuum degree is 0.5 Torr and the holding time is ≥15 minutes. The argon gas control during the deoxygenation operation is: rough vacuum >200 Torr, argon gas flow rate 50~150 NL / min, and extreme vacuum, argon gas flow rate 100~200 NL / min. S-controlled operation: After VD degassing, add 80 kg of silica and feed 130 m of S-line; Tellurium treatment procedure: After feeding in S-line for 1 minute, feed in 30m of tellurium wire and gently blow for 25 minutes; Among them, the soft blowing time is ≥25 minutes for weak argon stirring operation based on the temperature of the molten steel, and the slag surface of the molten steel fluctuates by 150-300 mm during the weak argon operation. Small billet continuous casting: The ladle is heated in the LF furnace station. When the temperature of the molten steel is 1550-1575℃, the ladle is lifted into the continuous casting machine for continuous casting of billets. With appropriate electromagnetic stirring, cooling parameters and straightening machine parameters, high-quality semi-finished billets with high cleanliness and high uniformity are produced.

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