Reductive dephosphorizing agent for base steel smelting, cored wire and method

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a reductive dephosphorizing agent for base steel smelting, a cored wire and a method. The steel generally adopts a converter + LF + RH + continuous casting process, the phosphorus requirement is extremely low, but LF desulfurization is needed. In the LF desulfurization process, rephosphorization is inevitably caused by strong reducibility during desulfurization, phosphorus of a finished product is extremely easy to be qualified, and the production difficulty is extremely high. According to the method, after molten iron converter tapping, aluminum is added in an LF for deep desulfurization, then RH treatment is carried out, a cored wire of a reductive dephosphorization agent is fed into the molten steel in the treatment process, phosphorus in the steel is reduced to a product required range through a reduction reaction, and resulfurization is avoided. The operation is simple, and the refining rate is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a reducing dephosphorizing agent, a cored wire and a method for smelting base steel. Background Art

[0002] An ultra-low phosphorus high-purity base steel, mainly used in aviation and military fields such as high-temperature resistant materials for military engines, requiring C 0.50-0.80%, P≤0.0018%, S≤0.0010%. This type of steel is generally produced using converter + LF + RH + continuous casting process, but due to the extremely low P requirement and the excessive increase in P during the LF desulfurization process, it is not easy to produce.

[0003] In the existing steelmaking technology, the traditional dephosphorization method is oxidation dephosphorization, which has limited dephosphorization, especially for molten steel with a carbon content of less than 2%, the effect of oxidation dephosphorization is very poor. CN 114032355 B discloses an ultra-low phosphorus continuous casting billet and its production method and application, the production method includes molten iron pretreatment, converter double dephosphorization and decarburization process, LF refining, RH vacuum refining and continuous casting, wherein the converter double dephosphorization and decarburization process includes dephosphorization converter smelting and decarburization converter smelting, and defines the gun position, oxygen supply, bottom blowing flow, slag, basicity and other parameters in the dephosphorization converter smelting and decarburization converter smelting process. The content of impurities such as phosphorus, sulfur, nitrogen, and hydrogen in the continuous casting billet obtained by this method is extremely low, but the P content of the billet is still around 0.005%. CN116656913A discloses a smelting method for producing low-phosphorus steel based on BOF converter, wherein the double slag retention steelmaking technology is used in the converter smelting process to obtain a dephosphorization rate of more than 95%, and then the argon blowing station oxidizing slag stirring dephosphorization technology is used to make the dephosphorization rate of the argon blowing station reach more than 50%, and obtain ultra-low phosphorus molten steel with a phosphorus content of 20-50 ppm. It can be seen that these two smelting methods are not applicable to the aforementioned ultra-low phosphorus high-purity base steel, and the phosphorus content still needs to be further reduced.

[0004] CN 119120823 A discloses a low-phosphorus steel and a smelting method thereof. The smelting method comprises the following steps: tapping the steel after smelting in a steelmaking furnace, adding a slag-making agent during the tapping process to make an oxidizing slag with a basicity of 4 to 10 (CaO: 45-55%, SiO 2 :5.5-12.0%, FeO: 17-35%, MgO: 6-10%, MnO: 1.5-5.0%, Al 2 O 3:1.5-3.0%, the rest are inevitable impurities), to obtain primary molten steel; vacuum refine the primary molten steel by VD to obtain refined molten steel; LF refine the refined molten steel after slagging treatment to obtain low-phosphorus molten steel, the mass fraction of phosphorus is 8-20 ppm, and the dephosphorization effect is good. However, this smelting method is not suitable for the existing converter + LF + RH + continuous casting process, and the ultra-low phosphorus high-purity base steel also has certain requirements on the sulfur content, and the LF desulfurization process is prone to rephosphorization.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a reducing dephosphorizing agent, a cored wire and a method for base steel smelting to overcome the problem of excessive phosphorus content after smelting. The present invention performs RH treatment after steel is tapped from a converter and deep desulfurized by adding aluminum to LF. During the RH treatment, the cored wire of the reducing dephosphorizing agent is fed into the molten steel to reduce phosphorus in the steel to the required range of the product. The operation is simple and the smelting rate is effectively improved.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, a reductive dephosphorizing agent for base steel smelting is provided, wherein the reductive dephosphorizing agent comprises calcium aluminate and CaC 2 , the calcium aluminate content is ≥40wt%, the CaC 2 Content ≥20wt%.

[0008] In a second aspect, a cored wire for base steel smelting is provided, wherein the cored wire uses the reducing dephosphorization agent described in the first aspect as a core material.

[0009] In a third aspect, a method for smelting base steel is provided, wherein the molten iron is subjected to RH treatment after being tapped from a converter and subjected to deep desulfurization by adding aluminum in LF, wherein the RH treatment comprises feeding a cored wire having the reducing dephosphorization agent described in the first aspect as a core material into the molten steel so that P in the steel is ≤0.0018wt%.

[0010] Furthermore, before the converter is tapped, low-phosphorus molten iron with a phosphorus content of 300-500 ppm is subjected to double slag oxidation decarburization. After the converter is tapped, the composition of the molten steel, measured by mass percentage, includes: C≤0.08%, Mn≤0.05%, Si≤0.03%, P≤0.0020%, S≤0.015%, and Al 0.01-0.10%.

[0011] Furthermore, the LF aluminum deep desulfurization step includes: based on the amount of molten steel, 3-6 kg of aluminum is added per ton of steel, and desulfurization is performed to S≤0.0008wt%.

[0012] Furthermore, in the RH treatment, the feeding time of the cored wire is ≥ 6 min; And / or, the feeding speed of the cored wire is 150-200 m / min; And / or, the outer diameter of the cored wire is 9-11 mm, and the thickness is 0.2-0.4 mm; And / or, the reductive dephosphorization agent is a powder with a particle size of ≤3 mm; And / or, in the reductive dephosphorization agent, the calcium aluminate salt is 12CaO·7Al 2 O 3 ; And / or, the impurity content in the reductive dephosphorization agent does not exceed 3%.

[0013] Furthermore, in the RH treatment, after the cored wire is fed, the recirculation time is ≥6 min, so that the molten steel C is 0.50-0.80wt%, P is ≤0.0018wt%, and S is ≤0.0008wt%.

[0014] Furthermore, the recirculation time is ≥8 min.

[0015] Furthermore, after the RH treatment, a steel billet is obtained by continuous casting.

[0016] Furthermore, in terms of mass percentage, the C content in the steel billet is 0.50-0.80%, the P content does not exceed 0.0018%, and the S content does not exceed 0.0010%.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention proposes a smelting method of ultra-low phosphorus high-purity base steel. After the steel is tapped from the converter, aluminum is added in LF for deep desulfurization, and then in the RH treatment process, a cored wire with a reducing dephosphorizing agent is fed into the molten steel to reduce the phosphorus in the steel to the required range of the product. The operation is simple and the smelting rate is effectively improved. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0019] An ultra-low phosphorus high-purity base steel, requiring C 0.50-0.80%, P≤0.0018%, S≤0.0010%. This type of steel generally adopts the converter → LF → RH → continuous casting process.

[0020] The composition range (%) of the finished steel billet is usually required to be as follows: This ultra-low phosphorus high-purity base steel is mainly used for high-temperature resistant materials in the aviation and military fields, such as military engines. It has extremely high purity requirements. In addition to the requirements for carbon, phosphorus and sulfur, the remainder is preferably all iron, and no other elements will be intentionally added to ensure its purity. Among them, since the P requirement is extremely low and the P will increase to an abnormal level during the LF desulfurization process, it is not easy to produce.

[0021] In order to solve the above problems, the first aspect of the present invention provides a reductive dephosphorization agent for base steel smelting, the reductive dephosphorization agent comprises calcium aluminate and CaC 2 , the calcium aluminate content is ≥40wt%, the CaC 2 Content ≥20wt%.

[0022] The dephosphorization agent of the present invention can reduce dephosphorization, which is essentially different from oxidative dephosphorization. 2 As the main reactant, it undergoes reduction reaction with P to generate calcium phosphide. When the sulfur content requirement is very low, its use can further reduce the phosphorus lower limit to below 0.002%, avoiding phosphorus exceeding the limit and avoiding sulfur reversion.

[0023] In the dephosphorizing agent, the content of calcium aluminate is controlled to be ≥40wt%, and the main reducing reactant CaC 2 The amount of the dephosphorizing agent is ≥ 20wt%, and the total amount of the two is about 100wt%, that is, the dephosphorizing agent can be added to the molten steel to carry out a sufficient and appropriate reduction reaction under operational conditions. The reductive dephosphorizing agent may also contain inevitable impurities, generally SiO 2 , MgO and other oxides do not affect dephosphorization, and their content is generally within 1% and not more than 3%. Of course, the lower the impurity content, the better. Controlling the content of calcium aluminate to no less than 40wt% can ensure that CaC 2 CaC is added within the operational range if the feed rate can be controlled. 2 Sufficient reaction time for moderate reaction to achieve good dephosphorization effect. If the content of calcium aluminate is less than 40wt%, it means that CaC 2 If the amount of calcium aluminate is too large, too much reactant is fed per unit time, the reaction is too intense, the reaction time is shortened, the dephosphorization effect is poor, and there is waste. 2 O 3 This material has a low melting point, many pores, strong adsorption capacity and low price. It is mainly used as a solvent by utilizing its low melting point characteristics, and can also absorb non-metallic inclusions in the molten steel. When the dephosphorization agent of the present invention is added to the molten steel, calcium aluminate can be quickly dissolved, promoting CaC2 It disperses quickly to carry out reduction dephosphorization. At the same time, in a vacuum, its melting point is low, inclusions are easy to aggregate, and it is easy to float up and remove slag after collision.

[0024] As an optional embodiment of the reductive dephosphorization agent of the present invention, the reductive dephosphorization agent is composed of calcium aluminate, CaC 2 and inevitable impurities, the calcium aluminate content is ≥40wt% (such as 41wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 78wt%), the CaC 2 The content is ≥20wt% (such as 21wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 58wt%), and the impurity content is ≤3wt% (such as 2.8wt%, 2.5wt%, 2.2wt%, 1.9wt%, 1.6wt%, 1.4wt%, 1.1wt%, 0.8wt%, 0.5wt%, 0.3wt%, 0.1wt%), and the total of the three is 100wt%.

[0025] A second aspect of the present invention provides a cored wire for base steel smelting, wherein the cored wire uses the reducing dephosphorization agent described in the first aspect as a core material.

[0026] The sheath of the cored wire of the present invention can be made of conventional materials that do not affect the smelting of molten steel, and can be low-carbon steel with a certain strength (without impurities such as Cr). The core is the reductive dephosphorization agent described in the first aspect, preferably a powder with a particle size of ≤3 mm, which can be densely arranged in the wire and can also be well melted after entering the molten steel. Furthermore, the particle size is preferably not less than 1 mm. When the particle size is less than 1 mm, it is not easy to disperse when entering the molten steel, and the dephosphorization effect becomes poor. In addition, the reductive dephosphorization agent powder is obtained by mechanical uniform mixing, that is, a certain mass ratio of calcium aluminate salt powder and CaC 2 The powder is mixed evenly by mechanical means and used as a reductive dephosphorization agent powder for core material. Therefore, as an optional embodiment of the cored wire of the present invention, the reductive dephosphorization agent is a powder with a particle size of ≤3 mm, and further, the particle size of the powder is 1-3 mm, typically but not limited to 2.9 mm, 2.7 mm, 2.5 mm, 2.3 mm, 2.1 mm, 1.9 mm, 1.7 mm, 1.5 mm, 1.3 mm, 1.1 mm.

[0027] The third aspect of the present invention provides a base steel smelting method, in which the molten iron is subjected to RH treatment after the steps of tapping from a converter and deep desulfurization with aluminum in LF, and the RH treatment comprises feeding a cored wire having the reducing dephosphorization agent described in the first aspect as a core material into the molten steel so that P in the steel is ≤0.0018wt%.

[0028] The smelting method of the present invention feeds a cored wire of a reducing dephosphorizing agent into the molten steel during the RH treatment after deep desulfurization with aluminum in LF, so that the phosphorus in the steel is reduced to the required range of the product. The dephosphorizing agent is added by feeding the wire, firstly, it can be fed deep into the molten steel to improve the utilization rate of the material; secondly, it can prevent the dephosphorizing agent powder from being vacuumed or gasified. The skin of the dephosphorizing agent cored wire can be made of conventional materials that do not affect the smelting of molten steel, which can be low-carbon steel with a certain strength (without impurities such as Cr), and the core is the reducing dephosphorizing agent described in the first aspect, preferably a powder with a particle size of ≤3 mm, which can be densely arranged in the wire and can also be well melted after entering the molten steel. Furthermore, the particle size is preferably not less than 1 mm. After the particle size is less than 1 mm, it is not easy to disperse into the molten steel, and the dephosphorization effect is poor. Therefore, as an optional implementation method of the smelting method of the present invention, the outer diameter of the cored wire is Φ9~11 mm (such as 9.5 mm, 10 mm, 10.5 mm), the wall thickness (skin thickness) is 0.2~0.4 mm (such as 0.25 mm, 0.3 mm, 0.35 mm); and / or the reducing dephosphorization agent is a powder with a particle size of ≤3 mm.

[0029] As an optional implementation of the smelting method of the present invention, the LF aluminum deep desulfurization step includes: based on the amount of molten steel, 3-6 kg of aluminum is added per ton of steel, and desulfurization is performed to S≤0.0008wt%.

[0030] In the above technical solution, adding aluminum to LF for desulfurization will lead to increased silicon, carbon or manganese, but as long as there is no over-reduction, the rebound of carbon and silicon can be coordinated. Therefore, 3-6 kg of aluminum is added per ton of steel to ensure sufficient desulfurization without excessive reduction. The amount of aluminum added per ton of steel can be selected as 3.5 kg, 4 kg, 4.5 kg, 5 kg, and 5.5 kg, typically but not limitedly. In addition, since the requirement for S content of ultra-low phosphorus and high-purity base steel (high-purity iron) cannot exceed 10ppm, the reducing environment of LF furnace desulfurization cannot be changed during the LF treatment process. The reducing atmosphere is sensitive to phosphorus regeneration, which can easily cause the P content to rise or even exceed the limit. Therefore, more precise control of phosphorus is required during the RH treatment process, and the lower limit is reduced by dephosphorization with a reducing agent, while avoiding sulfur regeneration.

[0031] As an optional implementation manner of the smelting method of the present invention, the feeding time of the cored wire is ≥6 min (such as 7 min, 9 min, 11 min, 13 min, 15 min), and / or the feeding speed of the cored wire is 150-200 m / min (such as 160 m / min, 170 m / min, 180 m / min, 190 m / min).

[0032] In the present invention, the cored wire is generally added after the RH furnace is circulated, that is, after vacuuming for a certain period of time, such as about 3 minutes. In order to ensure the dephosphorization effect, the wire feeding time shall not be less than 6 minutes. Under normal circumstances, for dephosphorization, the longer the wire feeding time, the more complete the reaction, but the dephosphorization effect has a limit, and although adding too much has little effect on the composition of the molten steel, it will cause a waste of resources. Moreover, the wire feeding cannot be added too much at once, which will cause the temperature to drop and affect the dephosphorization, and will also cause insufficient reaction time to affect the dephosphorization. Therefore, it is generally based on the specific working conditions and under the condition of ensuring a good dephosphorization effect, the wire feeding time and speed are matched with each other to control the amount of dephosphorizing agent added within a suitable range.

[0033] As an optional implementation manner of the smelting method of the present invention, after the cored wire is fed, the recirculation time is ≥6 min (such as 7 min, 9 min, 11 min, 13 min), so that the molten steel C 0.50-0.80wt%, P≤0.0018wt%, S≤0.0008wt%; further, the recirculation time of the cored wire after feeding is ≥8 min (such as 9 min, 10 min, 11 min, 12 min).

[0034] In the above technical scheme, the purpose of circulating for a certain period of time after wire feeding is to float the removed inclusions and ensure that the molten steel C is 0.50-0.80wt%, P≤0.0018wt%, and S≤0.0008wt%. The circulation time is generally not less than 6 minutes to avoid the reaction of inclusions that cannot float up completely, resulting in a high O content in the molten steel. Usually, the circulation time can be controlled at about 8 minutes to avoid excessive cooling due to a long time that affects subsequent preparation. Controlling the circulation time within 6-12 minutes is a more appropriate compromise.

[0035] As an optional implementation of the smelting method of the present invention, the steel billet is obtained by continuous casting after the RH treatment.

[0036] As an optional implementation of the smelting method of the present invention, the C content in the steel billet is 0.50-0.80%, the P content does not exceed 0.0018%, and the S content does not exceed 0.0010%. Further, the composition of the steel billet includes, by mass percentage: C 0.50-0.80%, P≤0.0018%, S≤0.0010%, and the balance is Fe and other unavoidable impurities.

[0037] In the above technical solution, except for C, P and S elements which need to be specially controlled and limited, the other elements are not limited, because other elements will not affect the effects of dephosphorization, desulfurization and decarbonization.

[0038] As an optional embodiment of the smelting method of the present invention, the composition of the steel billet includes, by mass percentage: C 0.50-0.80%, P≤0.0018%, S≤0.0010%, Mn≤0.20%, Si≤0.30%, Al≤0.03%, and the balance is Fe. The ultra-low phosphorus and high-purity base steel of the present invention needs to ensure high purity. Except for the elements C, P and S, which need to be specially controlled, the other elements are not intentionally added. However, during reduction desulfurization, Mn and Si in the slag may return to the molten steel. Due to the control of the present invention, the residual Mn will not exceed 0.20%, and the residual Si will not exceed 0.30%. In addition, the Al added during reduction desulfurization will not exceed 0.03% after RH removal.

[0039] The process route of one embodiment of the present invention is: converter → LF → RH → continuous casting. The specific process steps are as follows: (1) In the converter, low-phosphorus hot metal with a phosphorus content of 300-500 ppm is slag-made by the double slag method (i.e., lime and other conventional slag-making materials are added at the beginning and end of the converter steelmaking process to make slag once), and carbon is oxidized and removed by slag-making and oxygen blowing and stirring. The composition range (wt%) of the steel tapped from the converter is as follows: (2) LF adds aluminum for deep desulfurization. Based on the amount of molten steel, 3-6 kg of aluminum is added per ton of steel to desulfurize to S≤0.0008wt%. Although desulfurization will increase silicon, carbon or manganese in the molten steel, and carbon will return due to heating of graphite electrode rods, the components of the molten steel will not be out of the ordinary. The range of the outgoing components (wt%) is as follows: (3) Entering the RH station, after the vacuum cycle, the cored wire of the reductive dephosphorization agent is fed into the steel. The reductive dephosphorization agent is a powder with a particle size of 1 to 3 mm, and its composition includes aluminate calcium salt content ≥40wt%, CaC 2 Content ≥20wt% and 0.1-3wt% inevitable impurities; outer diameter of cored wire Φ9~11 mm, wall thickness 0.2~0.4 mm; wire feeding speed 150-200 m / min, wire feeding time ≥6 min, recirculation after wire feeding ≥6 min, at this time the outbound composition range (wt%) is as follows: Continuous Casting Finished billet composition range (wt%) The technical solution of the present invention is further described in detail below with reference to specific embodiments and comparative examples. Example 1 Based on the converter output of 80t, the process route for producing this type of steel is: converter → LF → RH → continuous casting. Specifically, it includes the following steps: (1) In the converter, low-phosphorus hot metal with a phosphorus content of 300-500 ppm is slag-made by the double slag method (i.e., lime and other conventional slag-making materials are added at the beginning and end of the converter steelmaking process to make slag once), and carbon is oxidized and removed by slag-making and oxygen blowing and stirring. The steel is tapped from the converter, and the composition (wt%) of the steel is as follows: (2) LF deep desulfurization, based on the amount of molten steel, 4.188 kg of aluminum is added per ton of steel, and the outgoing composition (wt%) is as follows: (3) Enter the RH station, evacuate for 3 minutes, and feed the steel with a cored wire containing a reducing dephosphorizing agent (the reducing dephosphorizing agent is a powder with a particle size of 1 to 3 mm, and its composition includes 12CaO·7Al 2 O 3 48wt%, the rest is CaC 2 and 1-3wt% unavoidable impurities; the outer diameter of the cored wire is Φ10 mm, the wall thickness is 0.4 mm), the wire feeding speed is 165 m / min, the wire feeding time is 6 min, and then it is recycled for 12 min. The outgoing composition (wt%) is as follows: Continuous Casting Finished billet composition (wt%) Example 2 Based on the converter output of 200t, the process route for producing this type of steel is: converter → LF → RH → continuous casting. Specifically, it includes the following steps: (1) In the converter, low-phosphorus hot metal with a phosphorus content of 300-500 ppm is slag-made by the double slag method (i.e., lime and other conventional slag-making materials are added at the beginning and end of the converter steelmaking process to make slag once), and carbon is oxidized and removed by slag-making and oxygen blowing and stirring. The steel is tapped from the converter, and the composition (wt%) of the steel is as follows: (2) LF deep desulfurization, based on the amount of molten steel, 4.255 kg of aluminum is added per ton of steel, and the outgoing composition (wt%) is as follows: (3) Enter the RH station, evacuate for 3 minutes, and feed the steel with a cored wire containing a reducing dephosphorizing agent (the reducing dephosphorizing agent is a powder with a particle size of 1 to 3 mm, and its composition includes 12CaO·7Al 2 O 3 50wt%, the rest is CaC 2and 1-3wt% unavoidable impurities; the outer diameter of the cored wire is Φ10 mm, the wall thickness is 0.4 mm), the wire feeding speed is 170 m / min, the wire feeding time is 8 min, and then it is recycled for 10 min. The outgoing composition (%) is as follows: Continuous Casting Finished billet composition (wt%) Comparative Example 1 The only difference from Example 1 is that the dephosphorization agent in the cored wire contains only calcium carbide and no calcium aluminate salt.

[0040] The dephosphorization agent and feeding operation cannot be carried out in actual production. First, the feeding line speed cannot be too low, and if the feeding line speed is too low, the dephosphorization agent will not be able to penetrate deep into the molten steel; second, if the dephosphorization agent contains only calcium carbide, it will react with the molten steel in a short time after being added to the molten steel, which is too rapid and prone to explosion and waste, so it cannot be produced.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reductive dephosphorization agent for base steel smelting, characterized in that: The reductive dephosphorization agent comprises calcium aluminate and CaC2, wherein the content of the calcium aluminate is ≥40wt%, and the content of the CaC2 is ≥20wt%.

2. A cored wire for base steel smelting, characterized in that: The cored wire uses the reducing dephosphorization agent according to claim 1 as the core material.

3. A method for smelting base steel, characterized in that: The molten iron is subjected to RH treatment after the steps of tapping from a converter and deep desulfurization by adding aluminum to LF. The RH treatment comprises feeding a cored wire with the reducing dephosphorization agent as claimed in claim 1 as the core material into the molten steel so that P in the steel is ≤ 0.0018wt%.

4. The smelting method according to claim 3, characterized in that: Before the converter is tapped, low-phosphorus molten iron with a phosphorus content of 300-500 ppm is subjected to double slag oxidation decarburization. After the converter is tapped, the composition of the molten steel, measured by mass percentage, includes: C≤0.08%, Mn≤0.05%, Si≤0.03%, P≤0.0020%, S≤0.015%, and Al 0.01-0.10%.

5. The smelting method according to claim 3, characterized in that: The LF aluminum deep desulfurization step comprises: adding 3-6 kg aluminum per ton of steel based on the amount of molten steel, and desulfurizing to S≤0.0008wt%.

6. The smelting method according to claim 3, characterized in that: In the RH treatment, the feeding time of the cored wire is ≥ 6 min; And / or, the feeding speed of the cored wire is 150-200 m / min; And / or, the outer diameter of the cored wire is 9-11 mm, and the thickness is 0.2-0.4 mm; And / or, the reductive dephosphorization agent is a powder with a particle size of ≤3 mm; And / or, in the reductive dephosphorization agent, the calcium aluminate salt is 12CaO·7Al2O3; And / or, the impurity content in the reductive dephosphorization agent does not exceed 3%.

7. The smelting method according to claim 3, characterized in that: In the RH treatment, after the cored wire is fed, the recirculation time is ≥6 min, so that the molten steel C is 0.50-0.80wt%, P is ≤0.0018wt%, and S is ≤0.0008wt%.

8. The smelting method according to claim 7, characterized in that: The recirculation time is ≥8 min.

9. The smelting method according to claim 3, characterized in that: After the RH treatment, a steel billet is obtained by continuous casting.

10. The smelting method according to claim 9, characterized in that: Calculated by mass percentage, the C content in the steel billet is 0.50-0.80%, the P content does not exceed 0.0018%, and the S content does not exceed 0.0010%.

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