Method for improving purity of molten steel at low cost based on LF-VD production route

Abstract

The invention provides a low-cost molten steel purity improving method based on an LF-VD production route, and relates to the technical field of steelmaking, the low-cost molten steel purity improving method comprises the following steps: obtaining to-be-refined molten steel with a first set aluminum content so as to facilitate removal and floating of inclusions in the subsequent refining process; the molten steel to be refined is heated, a deoxidizing agent is added into the heated molten steel to be refined for refining, the aluminum content of the molten steel to be refined is controlled, refined molten steel with the second set aluminum content is obtained, the purity of the refined molten steel is guaranteed, and aluminum product consumption is reduced; and the refined molten steel is subjected to degassing treatment, the aluminum content of the refined molten steel is controlled, and degassed molten steel with the third set aluminum content is obtained, so that it is guaranteed that the degassed molten steel is free of oxidability, the follow-up casting requirement can be met, and meanwhile the purity of the molten steel is improved as much as possible. The degassed molten steel prepared through the method is high in purity, the oxidability meets the follow-up casting requirement, and consumption of aluminum products is greatly reduced through the whole method.

Description

Technical Field

[0001] The present application relates to the technical field of steelmaking, and in particular to a method for improving the purity of molten steel at low cost based on a LF-VD production route. Background Art

[0002] At present, when LF-VD is used to produce steel in China, the VD furnace produces ordinary carbon steel by using the LF furnace excess deoxidation method to produce white slag. At the end of LF furnace refining, the aluminum content reaches 0.07% to 0.08%, exceeding the national standard range of aluminum content of steel grades of 0.02% to 0.06%. The VD furnace is high-aluminum entering the station, and no aluminum alloy is added during the deep vacuum period of the VD furnace. After the VD is broken, a part of the aluminum alloy is added according to the actual aluminum content. This process method makes the consumption of aluminum products in the whole process extremely high, and the consumption of pure aluminum per ton of steel reaches 3.5kg. In addition, if more deoxidizer is added to the VD furnace during the preparation process, more calcium aluminate will be generated in the VD furnace; if less deoxidizer is added, it needs to be added after breaking the air, which will cause the molten steel to contact with air and deteriorate the purity of the molten steel. Summary of the invention

[0003] The present application provides a method for improving the purity of molten steel at low cost based on the LF-VD production route to solve the following technical problem: how to improve the purity of molten steel at low cost.

[0004] The present application embodiment provides a method for improving the purity of molten steel at low cost based on the LF-VD production route, comprising the following steps:

[0005] Obtaining molten steel to be refined with a first set aluminum content to facilitate the removal and floating of inclusions in a subsequent refining process;

[0006] Heating the temperature of the molten steel to be refined, adding a deoxidizer to the heated molten steel to be refined, and controlling the aluminum content of the molten steel to be refined to obtain a refined molten steel with a second set aluminum content;

[0007] The refined molten steel is degassed and the aluminum content of the refined molten steel is controlled to obtain degassed molten steel with a third set aluminum content.

[0008] Optionally, the first set aluminum content is 0.02% to 0.05%; and / or,

[0009] The second set aluminum content is 0.025% to 0.04%; and / or,

[0010] The third set aluminum content is 0.03% to 0.04%.

[0011] Optionally, the degassing the refined molten steel and controlling the aluminum content of the refined molten steel to obtain degassed molten steel with a third set aluminum content specifically includes: sending the refined molten steel into a degassing device for degassing, controlling the deep vacuum time and vacuum degree of the degassing device, adding a deoxidizer before the degassing device is degassed, and controlling the aluminum content of the refined molten steel to obtain degassed molten steel with a third set aluminum content.

[0012] Optionally, adding a deoxidizer before the degassing device breaks air specifically includes: adding a deoxidizer 1 min to 3 min before the degassing device breaks air.

[0013] Optionally, the amount of deoxidizer added during degassing meets the following conditions:

[0014] The second setting is that the aluminum content is <0.035%, and 60kg to 90kg of deoxidizer is added;

[0015] When the second setting aluminum content is ≥ 0.035%, 50kg to 60kg of deoxidizer is added.

[0016] Optionally, the molten steel to be refined is heated, and a deoxidizer is added to the heated molten steel to be refined for refining, specifically comprising: heating the molten steel to be refined, and adding a deoxidizer to the molten steel to be refined after the temperature is increased for a set time for refining;

[0017] The setting time is 3 minutes to 6 minutes.

[0018] Optionally, the amount of deoxidizer added during refining is 250kg to 320kg; and / or,

[0019] The content of iron oxide and manganese oxide in the slag produced after refining is less than 1.0%.

[0020] Optionally, the step of obtaining the molten steel to be refined having the first set aluminum content specifically includes:

[0021] Obtaining molten steel to be converted into a converter;

[0022] Adding a deoxidizer to the molten steel to be refined for deoxidation to obtain the molten steel with a first set aluminum content;

[0023] and / or,

[0024] The amount of the deoxidizer added is 300kg to 500kg per batch of molten steel to be used as the converter.

[0025] Optionally, the horizontal number density of inclusions in the degassed molten steel is less than 0.55 inclusions / mm2.

[0026] Optionally, the deoxidizer includes at least one of the following: steel grit aluminum, aluminum particles and aluminum slag balls.

[0027] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0028] The embodiment of the present application provides a method for improving the purity of molten steel at low cost based on the LF-VD production route, comprising the following steps: obtaining molten steel to be refined with a first set aluminum content to facilitate the removal and floating of inclusions in the subsequent refining process; heating the molten steel to be refined, adding a deoxidizer to the heated molten steel to be refined for refining, and controlling the aluminum content of the molten steel to be refined to obtain refined molten steel with a second set aluminum content, thereby ensuring the purity of the refined molten steel and reducing the consumption of aluminum products; degassing the refined molten steel, and controlling the aluminum content of the refined molten steel to obtain degassed molten steel with a third set aluminum content, thereby ensuring that the degassed molten steel is non-oxidizing and can meet the needs of subsequent casting, while improving the purity of the molten steel as much as possible.

[0029] The degassed molten steel prepared by the method has high purity, and its oxidizability meets the subsequent casting requirements, and the whole method greatly reduces the consumption of aluminum products. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1 The present invention is a flow chart of a method for improving the purity of molten steel at low cost based on the LF-VD production route according to some embodiments of the present application. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0034] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0035] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions, refers to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0037] Figure 1 A schematic flow chart of a method for improving the purity of molten steel at low cost based on the LF-VD production route according to some embodiments of the present application;

[0038] like Figure 1 As shown, the embodiment of the present application provides a method for improving the purity of molten steel at low cost based on the LF-VD production route, comprising the following steps:

[0039] Obtaining molten steel to be refined with a first set aluminum content to facilitate the removal and floating of inclusions in a subsequent refining process;

[0040] Heating the temperature of the molten steel to be refined, adding a deoxidizer to the heated molten steel to be refined, and controlling the aluminum content of the molten steel to be refined to obtain a refined molten steel with a second set aluminum content;

[0041] The refined molten steel is degassed and the aluminum content of the refined molten steel is controlled to obtain degassed molten steel with a third set aluminum content.

[0042] In the above-mentioned embodiment, firstly, molten steel to be refined with a first set aluminum content is obtained to facilitate the removal and floating of inclusions in the subsequent refining process; the molten steel to be refined is heated, a deoxidizer is added to the heated molten steel to be refined for refining, and the aluminum content of the molten steel to be refined is controlled to obtain refined molten steel with a second set aluminum content, thereby ensuring the purity of the refined molten steel and reducing the consumption of aluminum products; the refined molten steel is degassed, and the aluminum content of the refined molten steel is controlled to obtain degassed molten steel with a third set aluminum content, thereby ensuring that the degassed molten steel is non-oxidizing and can meet the needs of subsequent casting, while increasing the purity of the molten steel as much as possible.

[0043] The degassed molten steel prepared by the method has high purity, and its oxidizability meets the subsequent casting requirements, and the whole method greatly reduces the consumption of aluminum products.

[0044] As an optional implementation, the first set aluminum content is 0.02% to 0.05%; and / or,

[0045] The second set aluminum content is 0.025% to 0.04%; and / or,

[0046] The third set aluminum content is 0.03% to 0.04%.

[0047] In the above embodiment, molten steel to be refined is first obtained from the steelmaking process as a raw material for refining, and the first set aluminum content is required to be 0.02% to 0.05% to meet the subsequent refining requirements; illustratively, the first set aluminum content can be 0.02%, 0.03%, 0.04% or 0.05%.

[0048] Then, the molten steel to be refined is sent to the LF furnace, and after the LF furnace is heated up, a deoxidizer is added for refining to remove impurities in the molten steel to obtain a refined molten steel with higher quality. At this time, the second set aluminum content in the refined molten steel is controlled to be 0.025% to 0.04%. For example, the second set aluminum content can be 0.025%, 0.030%, 0.035% or 0.04%.

[0049] Finally, the refined molten steel is sent to the VD furnace, and the pressure in the furnace is reduced so that the refined molten steel is effectively degassed in a vacuum environment, and vacuum degassing is performed to obtain degassed molten steel: the third set aluminum content in the degassed molten steel obtained is 0.03% to 0.04% to meet the subsequent casting requirements. Exemplarily, the third set aluminum content can be 0.03%, 0.035% or 0.04%.

[0050] As an optional embodiment, the degassing of the refined molten steel and controlling the aluminum content of the refined molten steel to obtain degassed molten steel with a third set aluminum content specifically includes: sending the refined molten steel into a degassing device for degassing, controlling the deep vacuum time and vacuum degree of the degassing device, adding a deoxidizer before the degassing device is degassed, and controlling the aluminum content of the refined molten steel to obtain degassed molten steel with a third set aluminum content.

[0051] In the above-mentioned embodiment, when the refined molten steel is degassed, controlling the deep vacuum time and vacuum degree of the VD furnace helps to create a good atmosphere for degassing the molten steel; adding a deoxidizer before the VD furnace is broken allows the refined molten steel to be degassed for a longer time in a vacuum environment, and the oxygen content is controlled to the maximum extent. Adding a deoxidizer at this time can not only effectively reduce the consumption of aluminum products, but also improve the cleanliness and quality of the molten steel.

[0052] As an optional implementation, the VD furnace meets at least one of the following conditions: the deep vacuum time is 17 min to 18 min; the vacuum degree is less than 67 Pa.

[0053] In the above embodiment, the deep vacuum time of the VD furnace is controlled to be 17min-18min, and the vacuum degree is less than 67Pa, in order to ensure that the molten steel is fully degassed and the quality of the molten steel is ensured. Exemplarily, the deep vacuum time of the VD furnace can be 17min-18min, and the vacuum degree is less than 67Pa.

[0054] As an optional implementation, adding a deoxidizer before the degassing device is broken specifically includes: adding a deoxidizer 1 min to 3 min before the degassing device is broken.

[0055] As an optional embodiment, the amount of deoxidizer added during the degassing process satisfies the following conditions:

[0056] The second setting is that the aluminum content is <0.035%, and 60kg to 90kg of deoxidizer is added;

[0057] When the second setting aluminum content is ≥ 0.035%, 50kg to 60kg of deoxidizer is added.

[0058] In the above embodiment, classified management is performed according to the different aluminum contents in the refined molten steel, which can save aluminum costs and improve the purity of the molten steel. Exemplarily, when the aluminum content in the refined molten steel is <0.035%, 60kg, 65kg, 70kg, 75kg, 80kg, 85kg or 90kg of deoxidizer can be added to the VD furnace. When the aluminum content in the refined molten steel is ≥0.035%, 50kg, 51kg, 52kg, 53kg, 54kg, 55kg, 56kg, 57kg, 58kg, 59kg or 60kg of deoxidizer can be added.

[0059] As an optional implementation, the molten steel to be refined is heated, and a deoxidizer is added to the heated molten steel to be refined for refining, specifically comprising: heating the molten steel to be refined, and adding a deoxidizer to the molten steel to be refined after the temperature is increased for a set time for refining;

[0060] The setting time is 3 minutes to 6 minutes.

[0061] In the above embodiment, when LF furnace refining is performed, the LF furnace needs to be heated first, and no aluminum products are added in the early stage of heating and slag-forming to avoid waste of aluminum products; after heating for 3min to 6min, the deoxidizer is added after the temperature in the LF furnace meets the refining conditions. At this time, the deoxidizer can further remove impurities and deoxidize the molten steel, thereby improving the utilization rate of aluminum products.

[0062] As an optional embodiment, the amount of deoxidizer added during refining is 250kg to 320kg.

[0063] In the above embodiment, the amount of deoxidizer added during refining is controlled in order to ensure that the aluminum content of the obtained refined molten steel is within the optimal range.

[0064] As an optional embodiment, the content of iron oxide and manganese oxide in the slag produced after refining is less than 1.0%.

[0065] In the above embodiment, by controlling the contents of iron oxide and manganese oxide in the final slag of the LF furnace, it can be effectively ensured that the oxidizing property of the refined molten steel is relatively weak.

[0066] As an optional embodiment, the step of obtaining the molten steel to be refined having the first set aluminum content specifically includes:

[0067] Obtaining molten steel to be converted into a converter;

[0068] Adding a deoxidizer to the molten steel to be refined for deoxidation to obtain the molten steel with a first set aluminum content;

[0069] and / or,

[0070] The amount of the deoxidizer added is 300kg to 500kg per batch of molten steel to be used as the converter.

[0071] The reason for controlling the amount of deoxidizer added to the molten steel to be prepared in the converter to be 300kg to 500kg is that within this range, the quality of the molten steel to be refined can be guaranteed and the amount of deoxidizer used can be controlled. Exemplarily, the amount of deoxidizer added is 300kg, 320kg, 340kg, 350kg, 360kg, 380kg, 400kg, 420kg, 440kg, 450kg, 460kg, 480kg or 500kg of deoxidizer per furnace of molten steel.

[0072] As an optional embodiment, the horizontal number density of inclusions in the degassed molten steel is less than 0.55 inclusions / mm 2 .

[0073] In the above-mentioned embodiment, the method provided in the present application can effectively reduce impurities in molten steel and improve the purity of molten steel to exceed the purity requirement.

[0074] As an optional embodiment, the deoxidizer includes at least one of the following: steel grit aluminum, aluminum particles and aluminum slag balls.

[0075] In the above embodiment, all three deoxidizers can be used for deoxidation treatment of molten steel.

[0076] As an optional implementation, the deoxidizer is steel grit aluminum, and the aluminum content in the steel grit aluminum is 80%.

[0077] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards / industry standards; if there are no corresponding national standards / industry standards, they are measured in accordance with common international standards, conventional conditions or conditions recommended by the manufacturer.

[0078] Example 1

[0079] This embodiment provides a method for improving the purity of molten steel at low cost based on the LF-VD production route, comprising the following steps:

[0080] S1, obtaining molten steel to be used for converter, adding 370kg of steel sand aluminum to the molten steel for deoxidation, and obtaining molten steel to be refined; the aluminum content in the molten steel to be refined is 0.037%;

[0081] S2, the molten steel to be refined enters the LF furnace, and after the LF furnace is heated for 5 minutes, 270 kg of steel sand aluminum is added for refining to obtain refined molten steel;

[0082] The slag sample at the end of the LF furnace is white slag, the oxidizability (FeO+MnO) of the LF furnace final slag is 0.35%, and the aluminum content in the refined molten steel is 0.037%;

[0083] S3, the refined molten steel enters the VD furnace for degassing, the deep vacuum time of the VD furnace is controlled to be 17 minutes, and 60 kg of steel sand aluminum is added 2 minutes before the VD furnace is broken, to obtain degassed molten steel:

[0084] The aluminum content of the degassed molten steel is 0.035%, which meets the casting requirements of the casting machine. The original level number density of the molten steel purity at the end of VD is 0.55 pieces / mm 2 The horizontal number density of this furnace is 0.27 pieces / mm 2 , higher purity.

[0085] In this embodiment, a total of 700 kg of steel grit aluminum is used, wherein the aluminum content of the steel grit aluminum is 80%, which is equivalent to 560 kg of pure aluminum.

[0086] Example 2

[0087] This embodiment provides a method for improving the purity of molten steel at low cost based on the LF-VD production route, comprising the following steps:

[0088] S1, obtaining molten steel to be used for converter, adding 360kg of steel sand aluminum to the molten steel for deoxidation, and obtaining molten steel to be refined; the aluminum content in the molten steel to be refined is 0.029%;

[0089] S2, the molten steel to be refined enters the LF furnace, and after the LF furnace is heated for 5 minutes, 310 kg of steel sand aluminum is added for refining to obtain refined molten steel;

[0090] The slag sample at the end of the LF furnace is white slag, the oxidizability (FeO+MnO) of the LF furnace final slag is 0.61%, and the aluminum content in the refined molten steel is 0.035%;

[0091] S3, the refined molten steel enters the VD furnace for degassing, the deep vacuum time of the VD furnace is controlled to be 17 minutes, and 60 kg of steel sand aluminum is added 2 minutes before the VD furnace is broken, to obtain degassed molten steel:

[0092] The aluminum content of the degassed molten steel is 0.031%, which meets the casting requirements of the casting machine. The original level number density of the molten steel purity at the end of VD is 0.55 pieces / mm 2 The horizontal number density of this furnace is 0.15 pieces / mm 2 , higher purity.

[0093] In this embodiment, a total of 730 kg of steel grit aluminum is used, wherein the aluminum content of the steel grit aluminum is 80%, which is equivalent to 584 kg of pure aluminum.

[0094] Comparative Example 1

[0095] This comparative example provides a method for improving the purity of molten steel at low cost based on the LF-VD production route, comprising the following steps:

[0096] S1, obtaining molten steel to be used for converter, adding 360kg of steel sand aluminum to the molten steel for deoxidation, and obtaining molten steel to be refined; the aluminum content in the molten steel to be refined is 0.029%;

[0097] S2, the molten steel to be refined enters the LF furnace, and 205 kg of pure aluminum is added 5 minutes before the LF furnace starts to heat up for deoxidation and desulfurization to obtain refined molten steel;

[0098] In the middle and late stages of heating, 217 kg of pure aluminum is added, and the slag sample at the end of the LF furnace is white slag, the oxidizability (FeO+MnO) of the LF furnace final slag is 0.61%, and the aluminum content in the refined molten steel is 0.075%;

[0099] S3. The refined molten steel enters a VD furnace for degassing. The deep vacuum time of the VD furnace is controlled to be 17 minutes. The aluminum content in the degassed molten steel is 0.031%, which meets the casting requirements of the casting machine.

[0100] At the end of VD, the number density of the original level of steel liquid purity is 0.55 pieces / mm 2 The horizontal number density of this furnace is 0.73 pieces / mm 2 .

[0101] In this embodiment, a total of about 710 kg of pure aluminum is used.

[0102] Comparative Example 2

[0103] This comparative example provides a method for improving the purity of molten steel at low cost based on the LF-VD production route, comprising the following steps:

[0104] S1, obtaining molten steel to be used for converter, adding 410kg of steel sand aluminum to the molten steel for deoxidation, and obtaining molten steel to be refined; the aluminum content in the molten steel to be refined is 0.065%;

[0105] S2, the molten steel to be refined enters the LF furnace, and 192 kg of pure aluminum is added 5 minutes before the LF furnace starts to heat up for deoxidation and desulfurization to obtain refined molten steel;

[0106] In the middle and late stages of heating, 240 kg of pure aluminum is added, and the slag sample at the end of the LF furnace is white slag, the oxidizability (FeO+MnO) of the LF furnace final slag is 0.21%, and the aluminum content in the refined molten steel is 0.08%;

[0107] S3. The refined molten steel enters a VD furnace for degassing. The deep vacuum time of the VD furnace is controlled to be 17 minutes. The aluminum content in the degassed molten steel is 0.047%, which meets the casting requirements of the casting machine.

[0108] At the end of VD, the number density of the original level of steel liquid purity is 0.55 pieces / mm 2 The horizontal number density of this furnace is 0.69 pieces / mm 2 .

[0109] In this embodiment, a total of about 760 kg of pure aluminum is used.

[0110] In summary, the method for improving the purity of molten steel at low cost based on the LF-VD production route provided in some embodiments of the present application can reduce the cost of aluminum products, reduce the consumption of pure aluminum by about 0.9kg / t per ton of steel (the original aluminum consumption per ton of steel was 3.5kg, and the aluminum consumption per ton of steel after improvement was 2.6kg), and reduce the cost of aluminum products by about 16.2 yuan / ton of steel. The method is used to improve the purity of molten steel and reduce alumina inclusions. The inclusion level (diameter ≥5um) is reduced from 0.55 / mm 2 Reduced to 0.27 pieces / mm 2 .

[0111] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown in the present application, but will conform to the widest range consistent with the principles and novel features applied for by the present application.

Claims

1. A method for improving the purity of molten steel at low cost based on the LF-VD production route, characterized in that: The following steps are involved: Obtaining molten steel to be refined with a first set aluminum content to facilitate the removal and floating of inclusions in a subsequent refining process; Heating the temperature of the molten steel to be refined, adding a deoxidizer to the heated molten steel to be refined, and controlling the aluminum content of the molten steel to be refined to obtain a refined molten steel with a second set aluminum content; The refined molten steel is degassed and the aluminum content of the refined molten steel is controlled to obtain degassed molten steel with a third set aluminum content.

2. The method according to claim 1, characterized in that The first set aluminum content is 0.02% to 0.05%; and / or, The second set aluminum content is 0.025% to 0.04%; and / or, The third set aluminum content is 0.03% to 0.04%.

3. The method according to claim 1, characterized in that The degassing of the refined molten steel and controlling the aluminum content of the refined molten steel to obtain degassed molten steel with a third set aluminum content specifically includes: sending the refined molten steel into a degassing device for degassing, controlling the deep vacuum time and vacuum degree of the degassing device, adding a deoxidizer before the degassing device is degassed, and controlling the aluminum content of the refined molten steel to obtain degassed molten steel with a third set aluminum content.

4. The method according to claim 3, characterized in that Adding the deoxidizer before the degassing device breaks air specifically includes: adding the deoxidizer 1 min to 3 min before the degassing device breaks air.

5. The method according to claim 3 or 4, characterized in that: The amount of deoxidizer added during degassing treatment meets the following conditions: The second setting is that the aluminum content is <0.035%, and 60kg to 90kg of deoxidizer is added; When the second setting aluminum content is ≥ 0.035%, 50kg to 60kg of deoxidizer is added.

6. The method according to claim 1, characterized in that Heating the temperature of the molten steel to be refined, and adding a deoxidizer to the heated molten steel for refining, specifically comprising: heating the molten steel to be refined, and adding a deoxidizer to the molten steel to be refined after the temperature is increased for a set time for refining; The setting time is 3 minutes to 6 minutes.

7. The method according to claim 1 or 6, characterized in that: The amount of deoxidizer added during refining is 250kg to 320kg; and / or, The content of iron oxide and manganese oxide in the slag produced after refining is less than 1.0%.

8. The method according to claim 1, characterized in that The step of obtaining the molten steel to be refined with the first set aluminum content specifically comprises: Obtain molten steel to be converted into a converter; Adding a deoxidizer to the molten steel to be refined for deoxidation to obtain the molten steel with a first set aluminum content; and / or, The amount of the deoxidizer added is 300kg to 500kg per batch of molten steel to be used as the converter.

9. The method according to claim 1, wherein the horizontal number density of inclusions in the degassed molten steel is less than 0.55 inclusions / mm 2 .

10. The method according to claim 1, characterized in that The deoxidizer includes at least one of the following: steel sand aluminum, aluminum particles and aluminum slag balls.

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