A method for controlling the plasticity of inclusions in high-strength spring steel

Abstract

This invention discloses a method for controlling the plasticity of inclusions in high-carbon steel wire rod, comprising: 1: tapping steel from a converter or electric furnace, using metallic manganese and carbon powder for deoxidation, without adding slag-forming materials; 2: after tapping, using silicon carbide to deoxidize and protect the slag surface; 3: then transporting the steel to an LF refining plant, where all alloy components are fully incorporated before adding synthetic slag, controlling the bottom blowing flow rate, reducing slag-metal reaction, and reducing CaO entering the molten steel; 4: controlling the alumina and metallic aluminum content in the refractory materials and alloys, reducing the alumina and magnesium oxide content in the inclusions, and obtaining ultra-low melting point inclusions with Al2O3≤15%, CaO≤20%, SiO2≥45%, and MnO≥20%; 5: only heating in the LF process, then transporting the steel to an RH process, increasing the vacuum chamber pressure and reducing the flow rate of the lifting gas when adding ferrosilicon alloys, reducing the circulation of molten steel, and reducing the reduction of MnO by Si, and obtaining ultra-low melting point inclusions with high SiO2 and MnO content.

Description

Technical Field

[0001] This invention relates to a method for controlling the plasticity of inclusions in high-strength spring steel, belonging to the technical field of steelmaking. Background Technology

[0002] High-strength spring steel has extremely high technical requirements regarding impurity element content, inclusions, segregation, microstructure, decarburization, and surface quality, directly affecting the fatigue life of springs. To obtain high-strength, high-performance spring steel, it is necessary to improve the control level of impurity elements and inclusions during its production process; solve the problems of uneven billet composition and internal and surface quality during continuous casting; and control decarburization, microstructure uniformity, and surface quality during rolling. The influence of inclusions in steel has become one of the most significant causes of failure in high-strength spring steel. Improving the fatigue performance of high-strength spring steel requires controlling non-metallic inclusions. There are many types of inclusions in steel, and it is difficult to simultaneously reduce multiple types of inclusions in production. Coupled with extremely high production requirements, this not only results in high losses during production but also leads to a low finished product qualification rate and serious production waste.

[0003] Patent CN 104056871 B discloses a production process for spring steel wire rod with controlled inclusions. It discloses a Si / Mn deoxidation smelting process to control the Al and Ca content in the steel and increase the MgO content in the inclusions, resulting in low-melting-point CaO·SiO2·Al2O3 inclusions. During the smelting process, through deoxidation control and secondary refining, the target control range for inclusions is SiO2: 40-70%, Al2O3: 10-25%, CaO: 20-50%, with a CaO to SiO2 ratio of 0.2-1.0. Under these conditions, the size of most inclusions can be controlled below 5μm. While this method controls the size of inclusions, controlling the MgO and Al2O3 content to obtain low-melting-point inclusions leads to uncontrollable Al2O3 and magnesium-aluminum spinel-type brittle inclusions, which still have a fatal impact on the fatigue fracture resistance of the spring steel wire rod.

[0004] Patent announcement number CN 106191652 B, entitled "A Smelting Method for Reducing Inclusions in Spring Steel," discloses the following steps: 1) smelting using a high-coalloy process, 2) argon blowing treatment, 3) LF furnace refining, 4) vacuum treatment, 5) LF soft blowing, and 6) rolling spring steel. Specifically, the high-coalloy process employs aluminum-free deoxidation, and the LF furnace refining uses a low-basicity slag process. By controlling the deoxidation depth during smelting, the oxide content is reduced. The low-basicity slag process facilitates the plasticization of inclusions, which are then easily aggregated and grown. The secondary refining soft blowing process facilitates flotation and removal, thereby achieving the goal of controlling the level of non-metallic inclusions in spring steel. This completely solves the problem of re-judgment due to excessive inclusions and significantly reduces production costs. However, this process mainly relies on the polymerization and growth of plastic inclusions, which are then removed. However, it does not control impurities such as Al and Ti brought in by molten steel or iron. Furthermore, it does not allow for further control of refractory materials and auxiliary materials, making it impossible to completely obtain plastic inclusions. It also does not inhibit or reduce the content of brittle inclusions, and does not fundamentally solve the problem of harmful inclusion content. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a method for controlling the plasticity of inclusions in high-strength spring steel, the specific technical solution of which is as follows:

[0006] A method for controlling the plasticity of inclusions in high-strength spring steel, produced according to the KR desulfurization—smelting—LF refining—RH vacuum—continuous casting process, characterized in that the composition of the high-strength spring steel wire, by mass percentage, is: C: 0.50-0.60%, Si: 1.35-1.55%, Mn: 0.60-0.80%, Cr: 0.55-0.75%, V: 0.1-0.2%, P≤0.012%, S≤0.005%, TO≤0.0015%, N≤0.0035%, H≤0.0002%, Alt≤0.0015%, Ti≤0.0008%, with the remainder being Fe and other unavoidable impurities; the specific operating steps are as follows:

[0007] Step 1: KR molten iron pretreatment. After KR molten iron pretreatment, molten iron with S content ≤0.0020% is obtained and added to the converter for smelting.

[0008] Step 2: Smelting in a converter or electric furnace. After smelting, tap the steel. When 15% of the steel has been tapped, add 1.5-2.5 kg / t of silicon carbide, metallic manganese, low-carbon ferrochrome, and ferrovanadium for deoxidation and alloying. When more than 85% of the steel has been tapped, add carbon powder. After tapping, add silicon carbide and calcium silicate to the surface of the ladle to deoxidize and form slag. Then, transport it to the LF treatment.

[0009] Step 3: LF refining, heating with electricity, and adjusting the C, Mn, Cr and V elements in the molten steel to achieve the target composition, and adding silicon carbide to diffuse deoxidize the slag. After the molten steel temperature reaches the standard, lime is evenly spread on the slag surface of the ladle, and then transported to RH vacuum treatment.

[0010] Step 4: RH vacuum treatment. After the molten steel reaches the treatment position, three water ring pumps and four steam pumps are turned on in sequence to create a vacuum, increasing the gas flow rate to 120-150 Nm. 3 / h, vacuum degree ≤1mbar, circulation processing time ≥10min, then turn off the three steam pumps and increase the gas flow rate to 80-100Nm 3 / h, low titanium and low aluminum silicon iron alloying, after addition, the circulation time is ≥8min, the steel is broken out and transported to continuous casting for pouring;

[0011] Step 5: Continuous casting. Molten steel is transported to the continuous casting station and allowed to settle for more than 10 minutes before casting begins. The entire casting process is protected.

[0012] Furthermore, in step 2, the final temperature of the converter smelting is 1620-1660℃, C is 0.04-0.08% by mass, and O is 0.035-0.065% by mass.

[0013] Furthermore, in step 2, during the converter tapping process, 6.5-7.5 kg / t of metallic manganese, 9-11 kg / t of low-carbon ferrochrome, 2.5-3.5 kg / t of ferrovanadium, and 5-6 kg / t of carbon powder are added. During the tapping process, the maximum bottom blowing flow rate of the double-permeable brick ladle is 800-1000 NL / min, and the minimum permeable brick flow rate is 30-50% of the maximum flow rate. After tapping, 1.0-1.5 kg / t of silicon carbide and 10-15 kg / t of calcium silicate synthesis slag are added, and the bottom blowing flow rate of the double-permeable brick ladle is 300-500 NL / min, which is kept consistent.

[0014] Furthermore, the content of Mn element in metallic manganese is ≥99%, Ti content is ≤0.003%, Al content is ≤0.005%, P content is ≤0.007%, S content is ≤0.003%, and the remainder is iron and unavoidable impurity elements;

[0015] Silicon carbide contains ≥98% SiC and other unavoidable impurity elements;

[0016] Low-carbon ferrochrome contains 55-60% Cr, ≤1.8% C, ≤0.006% S, and ≤0.013% P, with the remainder being iron and unavoidable impurity elements.

[0017] Ferrovanadium contains 45-50% V, ≤1.6% C, ≤0.008% S, and ≤0.015% P, with the remainder being iron and unavoidable impurity elements.

[0018] Furthermore, the composition of the synthetic slag added after the converter tapping process includes: CaO: 35-45%, SiO2: 40-50%, CaF2: 1-3%, MnO: 1-3%, MgO≤3%, Al2O3≤1.5%, and other unavoidable impurity components. The basicity is CaO / SiO2=0.65-0.85, and the proportion of monocalcium silicate in the phase is 80-90%, with the remainder being SiO2, CaO, CaF2, MnO, and unavoidable phases.

[0019] Furthermore, in step 3, the bottom blowing flow rate of the double permeable bricks in the ladle during the LF refining process remains consistent. The bottom blowing flow rate for power-on heating is 250-350 NL / min, the bottom blowing flow rate for adjusting alloy composition is 300-400 NL / min, and the bottom blowing flow rate for slag deoxidation and composition adjustment is 150-250 NL / min.

[0020] Furthermore, in step 3, 1.0-1.5 kg / t of silicon carbide is added to the deoxidizing LF refining slag, and 4-6 kg / t of lime is added during tapping. The lime contains ≥95% CaO, as well as other unavoidable components. The slag basicity CaO / SiO2 = 1.0-1.5 during tapping, the MnO content in the slag is 3-6%, and the molten steel temperature is 1570-1590℃.

[0021] Furthermore, in step 4, after shutting down the three steam pumps during RH vacuum treatment, the vacuum chamber pressure rises to over 30 mbar, the amount of low-titanium, low-aluminum ferrosilicon added is 16.5-18.5 kg / t, and the RH tapping temperature is 1510-1540℃.

[0022] Furthermore, the low-titanium, low-aluminum ferrosilicon contains 75-80% Si by mass, ≤0.004% Al by mass, ≤0.002% Ti by mass, ≤0.01% P by mass, and ≤0.005% S by mass, with the remainder being iron and unavoidable impurity elements.

[0023] Furthermore, the magnesium coating used in the continuous casting process for the inner wall of the tundish comprises MgO ≥ 80%, Al2O3 ≤ 3%, SiO2 1-3%, and other unavoidable components; the stopper rod and submerged entry nozzle are made of magnesium carbon, and the stopper rod head composition, by mass percentage, comprises MgO 70-80%, ZrO2 5-10%, C ≤ 10%, Al2O3 ≤ 1.5%, SiC 1-3%, and other unavoidable components; the inner wall thickness of the submerged entry nozzle is 5-7 mm, and its composition, by mass percentage, comprises MgO 75-80%, C 6-10%, SiC 3-5%, Al2O3 ≤ 1.5%, and other unavoidable components.

[0024] Furthermore, the inclusions in the molten steel obtained by the above production method are mainly low-melting-point silicate inclusions. The average mass percentage of inclusions larger than 1 μm is as follows: Al2O3 ≤ 15%, CaO ≤ 20%, SiO2 ≥ 45%, MnO ≥ 20%, and a small amount of other components. More than 98% of the inclusions have a melting point below 1400℃ and a size ≤ 25 μm. The number of brittle inclusions such as alumina and magnesium aluminum spinel is ≤ 0.003 per mm. 2 Size ≤ 5μm.

[0025] The principle of the smelting process of this invention is as follows:

[0026] First, silicon carbide and metallic manganese are added as the main deoxidizing elements during converter tapping to deoxidize the molten steel. The C and Si elements in silicon carbide simultaneously deoxidize the steel, reducing Si oxidation. By controlling the amount of silicon carbide added, and with sufficient metallic manganese, low-melting-point inclusions of SiO2-MnO are mainly formed in the molten steel. Simultaneously, no synthetic slag is added during tapping to avoid slag entrapment caused by steel mixing and to reduce the entry of CaO from the slag into the molten steel, thus preventing inclusion formation. Furthermore, calcium silicate synthetic slag is added at the end of tapping, with a controlled bottom blowing flow rate to promote the flotation and removal of deoxidation products, while also preventing slag entrapment and controlling the CaO content in inclusions.

[0027] Secondly, silicon carbide is used for diffusion deoxidation of the slag during converter tapping and LF refining processes, while small-to-medium bottom blowing is employed in the refining process to reduce slag reactions. The silicon carbide deoxidation process produces SiO2, further reducing slag basicity and thus reducing the transport of CaO from the slag to the molten steel. Furthermore, since the calcium silicate in the synthetic slag is a calcium silicate-silica phase, it is very stable and does not easily enter the molten steel, thus modifying ferrosilicon-manganese inclusions. Simultaneously, high-quality materials are selected for alloys, ladles, and continuous casting refractories, reducing the ingress of alumina and titanium oxide into the molten steel and significantly improving the erosion resistance of the refractories, which is extremely beneficial for controlling foreign brittle inclusions.

[0028] Secondly, in the later stages of LF refining, an appropriate amount of fine lime powder is added to the slag surface to facilitate rapid melting into the slag and increase the slag basicity. Simultaneously, a small bottom-blowing agitation is used to prevent slag entrapment. A proper increase in slag basicity is highly beneficial for subsequent steel deoxidation and inclusion adsorption. In the RH vacuum treatment process, a large pumping capacity is first used to initiate deep vacuum circulation degassing and inclusion removal. Then, three steam pumps are shut down and the booster gas flow rate is reduced to decrease the steel circulation throughput and reduce erosion of the refractory materials. Simultaneously, low-titanium, low-aluminum ferrosilicon is added for alloying. The addition of silicon alloy at this stage shortens the reaction time with MnO and other inclusions, resulting in inclusions with high MnO content. This is highly beneficial for lowering the melting point of inclusions, ultimately yielding steel with low gas content, high purity, and ultra-low melting point inclusions.

[0029] Finally, during the continuous casting process, a calming treatment is first applied to promote the floating of large inclusions entangled in the molten steel during the RH breaking process. In addition, the continuous casting tundish and the three main components all use low-alumina, high-magnesium refractory materials to improve corrosion resistance and prevent the formation of foreign inclusions. Foreign inclusions that erode into the molten steel during the continuous casting process are difficult to float and remove; therefore, controlling the quality of the continuous casting refractory materials is particularly important for reducing brittle, high-melting-point inclusions.

[0030] The beneficial effects of this invention are:

[0031] This invention relates to a converter or electric furnace steelmaking process. Steel is deoxidized using metallic manganese and carbon powder, without the addition of slag-forming materials. After tapping, silicon carbide is used to deoxidize and protect the slag surface, and calcium silicate synthetic slag is added to stabilize the slag composition before transporting it to the LF refining plant. After the refining process ensures all alloy components are properly matched, an appropriate amount of lime is added to adjust the slag basicity, control the bottom blowing flow rate, reduce the slag-metal reaction, reduce CaO ingress into the molten steel, control the alumina and metallic aluminum content in the refractory materials and alloys, and reduce the alumina and magnesium oxide content in inclusions, resulting in ultra-low melting point SiO2-MnO inclusions with low alumina and calcium oxide content. Once the molten steel composition and temperature meet the standards, it is then transported to the RH treatment plant. When adding ferrosilicon alloys, the vacuum chamber pressure is increased, the booster gas flow rate is reduced, and the circulation of the molten steel is weakened to reduce Si reduction of MnO, thus obtaining ultra-low melting point SiO2-MnO inclusions.

[0032] This invention enables the formation of plastic inclusions during the steelmaking process, significantly reducing brittle inclusions, avoiding fatigue fracture problems in high-strength spring steel, and thus significantly improving the overall performance of high-strength spring steel. Attached Figure Description

[0033] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0034] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] Combined with appendix Figure 1As can be seen, this method for controlling the plasticity of inclusions in high-strength spring steel is carried out according to the KR desulfurization—smelting—LF refining—RH vacuum—continuous casting process. The composition of the high-strength spring steel wire rod, by mass percentage, is: C: 0.50-0.60%, Si: 1.35-1.55%, Mn: 0.60-0.80%, Cr: 0.55-0.75%, V: 0.1-0.2%, P≤0.012%, S≤0.005%, TO≤0.0015%, N≤0.0035%, H≤0.0002%, Alt≤0.0015%, Ti≤0.0008%, with the remainder being Fe and other unavoidable impurities. The specific operating steps are as follows:

[0036] Step 1: KR molten iron pretreatment. After KR molten iron pretreatment, molten iron with S content ≤0.0020% is obtained and added to the converter for smelting.

[0037] Step 2: Smelting in a converter or electric furnace. After smelting, tap the steel. When 15% of the steel has been tapped, add 1.5-2.5 kg / t of silicon carbide, metallic manganese, low-carbon ferrochrome, and ferrovanadium for deoxidation and alloying. When more than 85% of the steel has been tapped, add carbon powder. After tapping, add silicon carbide and calcium silicate composite slag to the surface of the ladle to deoxidize and form slag. Then, transport it to LF for treatment.

[0038] The final temperature of converter smelting is 1620-1660℃, C: 0.04-0.08% by mass, and O: 0.035-0.065% by mass.

[0039] During the converter tapping process, 6.5-7.5 kg / t of metallic manganese, 9-11 kg / t of low-carbon ferrochrome, 2.5-3.5 kg / t of ferrovanadium, and 5-6 kg / t of carbon powder are added. During the tapping process, the maximum bottom blowing flow rate of the double-permeable brick ladle is 800-1000 NL / min, and the minimum permeable brick flow rate is 30-50% of the maximum flow rate. After tapping, 1.0-1.5 kg / t of silicon carbide and 10-15 kg / t of calcium silicate synthesis slag are added, and the bottom blowing flow rate of the double-permeable brick ladle is 300-500 NL / min, which is kept consistent.

[0040] Table 1 Main Parameters of Smelting

[0041]

[0042] The content of Mn in metallic manganese is ≥99%, Ti content is ≤0.003%, Al content is ≤0.005%, P content is ≤0.007%, S content is ≤0.003%, and the remainder is iron and unavoidable impurity elements;

[0043] Silicon carbide contains ≥98% SiC and other unavoidable impurity elements;

[0044] Low-carbon ferrochrome contains 55-60% Cr, ≤1.8% C, ≤0.006% S, and ≤0.013% P, with the remainder being iron and unavoidable impurity elements.

[0045] Ferrovanadium contains 45-50% V, ≤1.6% C, ≤0.008% S, and ≤0.015% P, with the remainder being iron and unavoidable impurity elements.

[0046] The composition of the synthetic slag added after the converter tapping process includes: CaO: 35-45%, SiO2: 40-50%, CaF2: 1-3%, MnO: 1-3%, MgO≤3%, Al2O3≤1.5%, and other unavoidable impurities. The basicity is CaO / SiO2=0.65-0.85. The monocalcium silicate accounts for 80-90% of the phase, with the remainder being SiO2, CaO, CaF2, MnO, and other unavoidable phases.

[0047] Step 3: LF refining, heating with electricity, and adjusting the C, Mn, Cr and V elements in the molten steel to achieve the target composition, and adding silicon carbide to diffuse deoxidize the slag. After the molten steel temperature reaches the standard, lime is evenly spread on the slag surface of the ladle, and then transported to RH vacuum treatment.

[0048] In the LF refining process, the bottom blowing flow rate of the double permeable bricks in the ladle remains consistent. The bottom blowing flow rate is 250-350 NL / min when the power is turned on for heating, 300-400 NL / min when the alloy composition is adjusted, and 150-250 NL / min when the slag is deoxidized and the composition is adjusted.

[0049] LF refining slag deoxidation involves adding 1.0-1.5 kg / t of silicon carbide, and 4-6 kg / t of lime is added during tapping. The lime contains ≥95% CaO, along with other unavoidable components. The slag basicity at tapping is CaO / SiO2=1.0-1.5, the slag contains 3-6% MnO, and the molten steel temperature is 1570-1590℃.

[0050] Table 2 Main parameters of the LF refining process

[0051]

[0052] Step 4: RH vacuum treatment. After the molten steel reaches the treatment position, three water ring pumps and four steam pumps are turned on in sequence to create a vacuum, increasing the gas flow rate to 120-150 Nm. 3 / h, vacuum degree ≤1mbar, circulation processing time ≥10min, then turn off the three steam pumps and increase the gas flow rate to 80-100Nm 3 / h, low titanium, low aluminum silicon iron alloying, after addition, the circulation time is ≥8min, the steel is broken out and transported to continuous casting for pouring.

[0053] After shutting down the three steam pumps during RH vacuum treatment, the vacuum chamber pressure rises to over 30 mbar. The amount of low-titanium, low-aluminum ferrosilicon added is 16.5-18.5 kg / t, and the RH tapping temperature is 1510-1540℃.

[0054] Low-titanium, low-aluminum ferrosilicon contains 75-80% Si by mass, ≤0.004% Al by mass, ≤0.002% Ti by mass, ≤0.01% P by mass, and ≤0.005% S by mass, with the remainder being iron and unavoidable impurity elements.

[0055] The ladle bricks are magnesia-carbon bricks, wherein Al2O3≤2.0%, C content≤3%, and the remainder are unavoidable impurity components;

[0056] The refractory material used in the impregnation tubes and bottom tank of the RH vacuum furnace is magnesia-chromium ultra-low carbon brick, with a C content of ≤2.0%, MgO: 80-90%, Cr2O3: 10-15%, magnesium aluminum spinel ≤3%, and other unavoidable components.

[0057] Table 3 Main process parameters of RH treatment

[0058]

[0059] Step 5: Continuous casting. Molten steel is transported to the continuous casting station and allowed to settle for more than 10 minutes before casting begins. The entire casting process is protected.

[0060] The magnesium coating used in the continuous casting process for the inner wall of the tundish includes MgO ≥ 80%, Al2O3 ≤ 3%, SiO2 1-3%, and other unavoidable components. The stopper rods and submerged entry nozzles are made of magnesium carbon. The stopper rod head composition, by mass percentage, is MgO 70-80%, ZrO2 5-10%, C ≤ 10%, Al2O3 ≤ 1.5%, SiC 1-3%, and other unavoidable components. The inner wall thickness of the submerged entry nozzle is 5-7 mm, and its composition, by mass percentage, includes MgO 75-80%, C 6-10%, SiC 3-5%, Al2O3 ≤ 1.5%, and other unavoidable components.

[0061] Table 4 Continuous Casting Restoration Time

[0062]

[0063] Through parameter selection and control in Examples 1-5 above, the obtained high-strength spring steel meets the expected performance requirements.

[0064] This invention also applies for protection that the inclusions in the molten steel obtained by the above-mentioned production method are mainly low-melting-point silicate inclusions, with an average component mass percentage of inclusions larger than 1 μm: Al2O3 ≤ 15%, CaO ≤ 20%, SiO2 ≥ 45%, MnO ≥ 20%, and a small amount of other components; more than 98% of the inclusions have a melting point below 1400℃ and a size ≤ 25 μm; the number of brittle inclusions such as alumina and magnesium aluminum spinel is ≤ 0.003 per mm. 2 Size ≤ 5μm.

[0065] The technical means disclosed in this invention are not limited to those disclosed above, but also include technical solutions composed of any combination of the above technical features.

[0066] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for controlling the plasticization of inclusions in a high-strength spring steel, produced according to a KR desulphurization-melting-LF refining-RH vacuum-continuous casting process, characterized in that, The high-strength spring steel wire rod has the following components in percentage by mass: C: 0.50-0.60%, Si: 1.35-1.55%, Mn: 0.60-0.80%, Cr: 0.55-0.75%, V: 0.1-0.2%, P≤0.012%, S≤0.005%, T.O≤0.0015%, N≤0.0035%, H≤0.0002%, Alt≤0.0015%, Ti≤0.0008%, and the rest is Fe and other inevitable impurities; the specific operation steps are as follows: Step 1: KR molten iron pretreatment, after KR molten iron pretreatment, molten iron with S content≤0.0020% is obtained and is charged into a converter for smelting; Step 2: converter or electric furnace smelting, at the end of smelting, molten steel is discharged, at 15% of the molten steel discharge, 1.5-2.5 kg / t of silicon carbide, metal manganese, low-carbon chromium iron, vanadium iron deoxidizing alloy are added, at more than 85% of the molten steel discharge, carbon powder is added, after the end of molten steel discharge, silicon carbide and calcium silicate synthetic slag are added to the surface of the ladle, the slag is deoxidized and slagging is performed, and then the molten steel is transported to LF treatment; The converter smelting end temperature is 1620-1660℃, the C content is 0.04-0.08% by mass, and the O content is 0.035-0.065% by mass; During the converter molten steel discharge process, 6.5-7.5 kg / t of metal manganese, 9-11 kg / t of low-carbon chromium iron, 2.5-3.5 kg / t of vanadium iron, and 5-6 kg / t of carbon powder are added, the maximum flux of the double flux nozzles of the ladle during the molten steel discharge process is 800-1000 NL / min, and the minimum flux of the double flux nozzles is 30-50% of the maximum flux; after the end of the molten steel discharge, 1.0-1.5 kg / t of silicon carbide and 10-15 kg / t of calcium silicate synthetic slag are added, the flux of the double flux nozzles of the ladle is 300-500 NL / min and is kept consistent; Step 3: LF refining, power is turned on to heat up, the C, Mn, Cr, and V elements in the molten steel are adjusted to reach the target components, silicon carbide is added to diffuse and deoxidize the slag, after the molten steel temperature reaches the standard, lime is uniformly spread on the slag surface of the ladle, and then the molten steel is transported to RH vacuum treatment; During the LF refining process, the flux of the double flux nozzles of the ladle is kept consistent, the flux during power heating is 250-350 NL / min, the flux during alloy component adjustment is 300-400 NL / min, and the flux during slag deoxidization and component adjustment is 150-250 NL / min; Step 4: RH vacuum treatment, after the molten steel reaches the treatment position, three water ring pumps and four steam pumps are sequentially opened for vacuum treatment, and the gas flow is increased to 120-150 Nm 3 / h, the vacuum degree is ≤1 mbar, the circulation treatment time is ≥10 min, then the three steam pumps are closed, the gas flow is reduced to 80-100 Nm 3 / h, the vacuum chamber pressure rises to above 30 mbar, the low-titanium low-aluminum ferrosilicon is added in an amount of 16.5-18.5 kg / t, the low-titanium low-aluminum ferrosilicon is alloyed, after the addition is completed, the circulation time is ≥8 min, the vacuum is broken, the steel is tapped, the RH tapping temperature is 1510-1540℃; it is transported to continuous casting for casting; Step 5: continuous casting, the molten steel is transported to the continuous casting for 10 min or more for static casting and then is poured for the whole process under protection.

2. A method of controlling the plasticization of inclusions in a high-strength spring steel according to claim 1, characterized by, The metal manganese has the following components: Mn content≥99%, Ti content≤0.003%, Al content≤0.005%, P content≤0.007%, S content≤0.003%, and the rest is iron and inevitable impurity elements; The silicon carbide has the following components: SiC content≥98% and other inevitable impurity elements; The low-carbon chromium iron has the following components: Cr content 55-60%, C content≤1.8%, S content≤0.006%, P content≤0.013%, and the rest is iron and inevitable impurity elements; Vanadium iron V content 45%~50%, C content ≤1.6%, S content ≤0.008%, P content ≤0.015%, the rest is iron and inevitable impurity elements.

3. The method of claim 1, wherein the method is characterized by: The synthetic slag component added at the end of the converter tapping includes: CaO: 35%~45%, SiO2: 40%~50%, CaF2: 1%~3%, MnO: 1%~3%, MgO ≤3%, Al2O3 ≤1.5%, and other inevitable impurity components, the basicity CaO / SiO2=0.65-0.85, the proportion of calcium silicate in the phase is 80%~90%, and the rest is SiO2, CaO, CaF2, MnO and inevitable phases; The LF refining furnace slag deoxidization adds 1.0-1.5kg / t of silicon carbide, and 4-6kg / t of lime is added at the time of tapping, the CaO content in the lime is ≥95%, and other inevitable components, the slag basicity CaO / SiO2=1.0-1.5 at the time of tapping, the MnO content in the slag is 3%~6%, and the molten steel temperature is 1570-1590℃.

4. The method of claim 1, wherein the method is characterized by: The low-titanium low-aluminum ferrosilicon contains 75%~80% of Si, ≤0.004% of Al, ≤0.002% of Ti, ≤0.01% of P, and ≤0.005% of S, and the rest is iron and inevitable impurity elements.

5. The method of claim 1, wherein the method is characterized by: The magnesium-based spray coating composition for the inner wall of the continuous casting tundish used in the continuous casting process includes MgO ≥80%, Al2O3 ≤3%, SiO2: 1%~3%, and other inevitable components; the stopper and submerged entry nozzle material is magnesium-carbonaceous, the stopper head composition includes, by mass percent, MgO content 70%~80%, ZrO2: 5%~10%, C ≤10%, Al2O3 content ≤1.5%, SiC content 1%~3%, and other inevitable components; the submerged entry nozzle inner wall thickness is 5~7mm, and the composition includes, by mass percent, MgO: 75%~80%, C: 6%~10%, SiC: 3%~5%, Al2O3 ≤1.5%, and other inevitable components.

6. A method of controlling the plasticization of inclusions in a high-strength spring steel according to claim 5, characterized in that, The intermediate ladle molten steel obtained by the control method is low-melting-point silicate inclusions, the average component mass percentage of inclusions above 1 μm is Al2O3≤15%, CaO≤20%, SiO2≥45%, MnO≥20%, and a small amount of other components, the melting point of 98% of the inclusions is below 1400℃, the size is ≤25 μm; the number of brittle inclusions of alumina and magnesium aluminate spinel is ≤0.003 per mm 2 , the size is ≤5 μm.

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