A method for improving castability of molten steel

Abstract

The present invention relates to a method for improving the castability of molten steel, and the method for improving the castability of molten steel includes: adding aluminum-containing refined slag when tapping steel from a converter, and then performing LF refining and VD vacuum in sequence; wherein, the LF refining includes a first lower electrode and a second lower electrode performed in sequence; the first lower electrode is to add a first deoxidizer after being energized, and then the mass percentage of aluminum element in the molten steel is controlled to be 0.05-0.06%, and a first alloying is performed; the second lower electrode is to perform a second alloying and desulfurization in sequence, and then a slag regulating agent is used for slag regulation, and finally a second deoxidizer is added for deoxidation. The method for improving the castability of molten steel provided by the present invention can avoid the problem of interruption of continuous casting of the tundish due to blockage of the water inlet between the tundish and the crystallizer, significantly improves the castability of molten steel, and can achieve the purpose of multi-furnace casting of sulfur-controlled and aluminum-controlled steel in one tundish.

Description

Technical Field

[0001] The present invention relates to the field of steelmaking, and in particular to a method for improving the castability of molten steel. Background Art

[0002] At present, the main purpose of continuous casting round billets with a diameter of more than φ700mm is forging and processing key components of wind power or large-scale mechanical slewing supports. High purity of steel is required, so the deoxidizing element aluminum in the steel needs to be controlled within a certain range to ensure low oxygen content in the steel. However, in order to ensure the mechanical processing performance of the steel, the sulfur content in the steel cannot be controlled too low and needs to be controlled within a certain range. Therefore, this type of steel belongs to the type that requires sulfur and aluminum element control.

[0003] For example, CN101147961A discloses a continuous casting process for producing extra-large round billets on an arc-shaped continuous casting machine with a radius of R12-14m: the molten steel from the steelmaking furnace is poured into a ladle, which is then hoisted onto the ladle turret of the arc-shaped continuous casting machine with a radius of 12-14m. The molten steel is then poured into a tundish, where the superheat of the molten steel is 10-25°C. The molten steel flows into a crystallizer and gradually condenses into a steel shell along the periphery of the crystallizer. An electromagnetic stirring device is used outside the crystallizer for stirring, and the pulling is started. The straightening machine and the crystallizer vibration device allow the round billet with the liquid center to enter the arc-shaped guide section, and 3-5 straightening machines are used for 3-5 point straightening. The 3-5 straightening machines are used to implement light reduction at the end of the solidification of the round billet, with a total reduction of 10-20mm. After the round billet is straightened and completely solidified, it is cut into fixed-length round billets and hoisted to the slow cooling pit for slow cooling for more than 24 hours. On the existing R12-14m arc continuous casting machine, it is possible to produce extra-large round billets of φ500-φ700mm.

[0004] However, in the prior art, inclusions formed by sulfur and aluminum elements may block the nozzle, resulting in a reduction in the number of continuous casting furnaces in the continuous casting process, a decrease in production efficiency, and an increase in production costs. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for improving the castability of molten steel to solve the problem that inclusions block the water nozzle during continuous casting, resulting in a reduction in the number of continuous casting furnaces in the continuous casting process and a decrease in production efficiency.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for improving the castability of molten steel, the method for improving the castability of molten steel comprising:

[0008] Aluminum-containing refined slag is added when tapping the converter, followed by LF refining and VD vacuuming;

[0009] Wherein, the LF refining includes the first lower electrode and the second lower electrode performed sequentially;

[0010] The first lower electrode is energized and then a first deoxidizer is added, and then the mass percentage of aluminum in the molten steel is controlled to be 0.05-0.06%, and a first alloying is performed;

[0011] The second lower electrode is subjected to second alloying and desulfurization in sequence, followed by slag conditioning using a slag conditioning agent, and finally deoxidation by adding a second deoxidizing agent.

[0012] The method for improving the castability of molten steel provided by the present invention can avoid the problem of blockage of the water inlet between the ladle and the crystallizer, which causes the interruption of continuous casting of the ladle, significantly improves the castability of molten steel, and can achieve the purpose of controlling sulfur and aluminum steel in multiple furnaces with one tundish.

[0013] As a preferred technical solution of the present invention, the amount of aluminum refining slag added is determined based on the endpoint sulfur when tapping the converter;

[0014] Preferably, the endpoint sulfur content of the converter steel is greater than 0.08% by mass, and the amount of the aluminum-containing refined slag added is 12-13 kg / t molten steel.

[0015] Preferably, the endpoint sulfur content of the converter steel is 0.05-0.08% by mass, and the amount of the aluminum-containing refined slag added is 10-10.5 kg / t molten steel.

[0016] Preferably, the endpoint sulfur content of the converter steel is less than 0.05% by mass, and the amount of the aluminum-containing refined slag added is 9.6-10 kg / t molten steel.

[0017] As a preferred technical solution of the present invention, the mass percentage of aluminum in the aluminum-containing refined slag calculated as alumina is 38-41%.

[0018] As a preferred technical solution of the present invention, the first deoxidizer includes aluminum material and silicon carbide material.

[0019] Preferably, the addition amount of the aluminum material is 0.25-0.38 kg / t molten steel.

[0020] Preferably, the addition amount of the silicon carbide material is 0.37-0.5 kg / t molten steel.

[0021] As a preferred technical solution of the present invention, the desulfurizing agent used in the desulfurization includes lime.

[0022] Preferably, the amount of desulfurizer added in the desulfurization is ≤1.25kg / t molten steel.

[0023] As a preferred technical solution of the present invention, the sulfur content in the LF steel melt after desulfurization is 0.025-0.03% by mass.

[0024] As a preferred technical solution of the present invention, the slag conditioning agent includes silica.

[0025] Preferably, the addition amount of the slag conditioning agent is 0.12-0.25 kg / t molten steel.

[0026] As a preferred technical solution of the present invention, the second deoxidizer includes silicon carbide material.

[0027] Preferably, the addition amount of the second deoxidizer is 0.12-0.25 kg / t molten steel.

[0028] As a preferred technical solution of the present invention, the content of oxygen in the molten steel after deoxidation is ≤15ppm.

[0029] As a preferred technical solution of the present invention, the calcium content of the molten steel in the VD vacuum is controlled to be 0.0007-0.001% by mass.

[0030] Compared with the existing technical solutions, the present invention has the following beneficial effects:

[0031] The method provided by the present invention can effectively control the generation of inclusions, that is, reduce the Al2O3 inclusions and CaS inclusions that will be formed during the refining process and the refining to continuous casting process, and thus prevent the inclusions from adhering to the inner surface of the nozzle and clogging the nozzle during the pouring of molten steel. DETAILED DESCRIPTION

[0032] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0033] This embodiment provides a method for improving the castability of molten steel, the method for improving the castability of molten steel comprising:

[0034] Aluminum-containing refined slag is added when tapping the converter, followed by LF refining and VD vacuuming;

[0035] Wherein, the LF refining includes the first lower electrode and the second lower electrode performed sequentially;

[0036] The first lower electrode is energized and then a first deoxidizer is added, and then the mass percentage of aluminum in the molten steel is controlled to be 0.05-0.06%, and a first alloying is performed;

[0037] The second lower electrode is subjected to second alloying and desulfurization in sequence, followed by slag conditioning using a slag conditioning agent, and finally deoxidation by adding a second deoxidizing agent.

[0038] In the present invention, the molten steel targeted is capable of producing a steel with a diameter of The above molten steel for continuous casting round billets, such as C45 steel, C60 steel or 20Mn2, etc.

[0039] Among them, the first deoxidizer is added to the first lower electrode after power is applied, and then the mass percentage of aluminum element in the molten steel is controlled to be 0.05-0.06%, for example, it can be 0.05%, 0.052%, 0.054%, 0.056%, 0.058% or 0.06%, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0040] Specifically, the amount of the aluminum refining slag added is determined based on the endpoint sulfur when the converter is tapping.

[0041] The endpoint sulfur content of the converter steel is greater than 0.08% by mass, and the amount of the aluminum-containing refined slag added is 12-13 kg / t of molten steel, for example, 12 kg / t of molten steel, 12.2 kg / t of molten steel, 12.4 kg / t of molten steel, 12.6 kg / t of molten steel, 12.8 kg / t of molten steel, or 13 kg / t of molten steel, but is not limited to the listed values. Other values not listed within this range are also applicable.

[0042] The endpoint sulfur content of the converter steel is 0.05-0.08% by mass, for example, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075% or 0.08%, and the amount of the aluminum-containing refined slag added is 10-10.5 kg / t of molten steel, for example, 10 kg / t of molten steel, 10.1 kg / t of molten steel, 10.2 kg / t of molten steel, 10.3 kg / t of molten steel, 10.4 kg / t of molten steel or 10.5 kg / t of molten steel, but is not limited to the listed values, and other values not listed within this range are equally applicable.

[0043] The endpoint sulfur content of the converter steel is less than 0.05% by mass, and the amount of the aluminum-containing refined slag added is 9.6-10 kg / t molten steel.

[0044] Specifically, the mass percentage of aluminum in the aluminum-containing refined slag as alumina is 38-41%, for example, it can be 38%, 38.5%, 39%, 39.5%, 40%, 40.5% or 41%, etc., but is not limited to the listed values, and other unlisted values within this range are also applicable.

[0045] Illustratively, the aluminum-containing refined slag includes, by mass percentage, FeO 0.6-1%, CaO 42-45%, MgO 6-6.7%, SiO2 7-7.8%, Al2O3 38-41%, MnO 0.25-0.37%, V2O5 0.06-0.08%, and S 1.1-1.6%.

[0046] Specifically, the first deoxidizer includes aluminum material and silicon carbide material.

[0047] In the present invention, the aluminum material can be deoxidized aluminum materials in the art such as aluminum particles.

[0048] Among them, the addition amount of the aluminum material is 0.25-0.38kg / t molten steel, for example, it can be 0.25kg / t molten steel, 0.26kg / t molten steel, 0.28kg / t molten steel, 0.3kg / t molten steel, 0.32kg / t molten steel, 0.34kg / t molten steel, 0.36kg / t molten steel or 0.38kg / t molten steel, etc., but is not limited to the listed values, and other values not listed within the range are also applicable.

[0049] Among them, the addition amount of the silicon carbide material is 0.37-0.5kg / t molten steel, for example, it can be 0.37kg / t molten steel, 0.38kg / t molten steel, 0.4kg / t molten steel, 0.42kg / t molten steel, 0.44kg / t molten steel, 0.46kg / t molten steel, 0.48kg / t molten steel or 0.5kg / t molten steel, etc., but is not limited to the listed values, and other values not listed within the range are also applicable.

[0050] Specifically, the desulfurization agent used in the desulfurization includes lime.

[0051] In the present invention, the content of calcium oxide in the lime used is ≥80% by mass.

[0052] The amount of the desulfurizer added in the desulfurization is ≤1.25 kg / t molten steel, for example, it can be 1.25 kg / t molten steel, 1.2 kg / t molten steel, 1 kg / t molten steel, 0.8 kg / t molten steel, 0.6 kg / t molten steel, 0.4 kg / t molten steel, 0.2 kg / t molten steel or 0.1 kg / t molten steel, but is not limited to the listed values, and other values not listed within the range are also applicable.

[0053] Specifically, the sulfur content in the LF steel melt after desulfurization is 0.025-0.03% by mass, for example, it can be 0.025%, 0.026%, 0.027%, 0.028%, 0.029% or 0.03%, etc., but is not limited to the listed values, and other unlisted values within this range are also applicable.

[0054] Specifically, the slag conditioning agent includes silica.

[0055] Specifically, the addition amount of the slag conditioning agent is 0.12-0.25 kg / t molten steel, for example, it can be 0.12 kg / t molten steel, 0.14 kg / t molten steel, 0.16 kg / t molten steel, 0.18 kg / t molten steel, 0.2 kg / t molten steel, 0.22 kg / t molten steel, 0.24 kg / t molten steel or 0.25 kg / t molten steel, etc., but is not limited to the listed values, and other values not listed within the range are also applicable.

[0056] Specifically, the second deoxidizer includes silicon carbide material.

[0057] Specifically, the addition amount of the second deoxidizer is 0.12-0.25 kg / t molten steel, for example, it can be 0.12 kg / t molten steel, 0.14 kg / t molten steel, 0.16 kg / t molten steel, 0.18 kg / t molten steel, 0.2 kg / t molten steel, 0.22 kg / t molten steel, 0.24 kg / t molten steel or 0.25 kg / t molten steel, but is not limited to the listed values, and other values not listed within the range are also applicable.

[0058] Specifically, the content of oxygen in the molten steel after deoxidation is ≤15ppm, for example, it can be 15ppm, 14ppm, 13ppm, 12ppm, 11ppm, 10ppm, 9ppm, 8ppm, 7ppm, 6ppm, 5ppm, 4ppm, 3ppm, 2ppm or 1ppm, etc., but is not limited to the listed values, and other unlisted values within the range are also applicable.

[0059] Specifically, the calcium element in the molten steel in the VD vacuum is controlled to have a mass percentage of 0.0007-0.001%, for example, it can be 0.0007%, 0.00075%, 0.0008%, 0.00085%, 0.0009%, 0.00095% or 0.001%, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0060] In order to further illustrate the effect of the method for improving the castability of molten steel provided by the present invention on improving the castability of molten steel, the following practical examples are specifically provided:

[0061] The following Examples 1-2 are castability verification processes for φ700 continuous casting round billets of C45 steel, and Examples 3-4 are castability verification processes for φ700 continuous casting round billets of C60. The main components of the C45 used are shown in Table 1 below in terms of mass percentage.

[0062] Table 1

[0063]

[0064] The main components of the C60 used are shown in Table 2 below in terms of mass percentage.

[0065] Table 2

[0066] element C Si Mn P S Al Require / % 0.57-0.65 ≤0.45 0.55-0.90 ≤0.025 0.020-0.035 0.020-0.045 Example requirements / % 0.61 0.25 0.73 0.010 0.025 0.022

[0067] Example 1

[0068] This embodiment provides a method for improving the castability of molten steel, specifically C45 steel, and the method for improving the castability of molten steel includes:

[0069] Aluminum-containing refined slag is added when tapping the converter, followed by LF refining and VD vacuuming;

[0070] Wherein, the LF refining includes the first lower electrode and the second lower electrode performed sequentially;

[0071] The first lower electrode is energized and then a first deoxidizer is added, and then the mass percentage of aluminum in the molten steel is controlled to be 0.053%, and a first alloying is performed;

[0072] The second lower electrode is subjected to second alloying and desulfurization in sequence, followed by slag conditioning using a slag conditioning agent, and finally deoxidation by adding a second deoxidizing agent.

[0073] The amount of aluminum refined slag added is determined based on the endpoint sulfur content at the time of converter tapping; the endpoint sulfur content of converter tapping is 0.09% by mass, and the amount of aluminum-containing refined slag added is 12 kg / t of molten steel; the aluminum content of the aluminum-containing refined slag, calculated as alumina, is 39% by mass.

[0074] The first deoxidizer is aluminum material and silicon carbide material; the addition amount of the aluminum material is 0.34 kg / t molten steel; the addition amount of the silicon carbide material is 0.4 kg / t molten steel;

[0075] The desulfurizer used in the desulfurization is lime; the amount of the desulfurizer added in the desulfurization is 1.25 kg / t molten steel; the sulfur content in the molten steel leaving the LF station after the desulfurization is 0.028% by mass;

[0076] The slag conditioning agent is silica; the addition amount of the slag conditioning agent is 0.18 kg / t molten steel;

[0077] The second deoxidizer is silicon carbide; the addition amount of the second deoxidizer is 0.17 kg / t molten steel;

[0078] The oxygen content in the deoxidized molten steel is 15 ppm; the calcium content in the molten steel is controlled to be 0.0008% by mass in the VD vacuum.

[0079] Example 2

[0080] This embodiment provides a method for improving the castability of molten steel, specifically C45 steel, and the method for improving the castability of molten steel includes:

[0081] Aluminum-containing refined slag is added when tapping the converter, followed by LF refining and VD vacuuming;

[0082] Wherein, the LF refining includes the first lower electrode and the second lower electrode performed sequentially;

[0083] The first lower electrode is energized and then a first deoxidizer is added, and then the mass percentage of aluminum in the molten steel is controlled to be 0.056%, and a first alloying is performed;

[0084] The second lower electrode is subjected to second alloying and desulfurization in sequence, followed by slag conditioning using a slag conditioning agent, and finally deoxidation by adding a second deoxidizing agent.

[0085] The amount of aluminum refined slag added is determined based on the endpoint sulfur content at the time of converter tapping; the endpoint sulfur content of converter tapping is 0.1% by mass, and the amount of aluminum-containing refined slag added is 13 kg / t of molten steel; the aluminum content of the aluminum-containing refined slag, calculated as alumina, is 40% by mass.

[0086] The first deoxidizer includes aluminum material and silicon carbide material; the addition amount of the aluminum material is 0.3 kg / t molten steel; the addition amount of the silicon carbide material is 0.45 kg / t molten steel;

[0087] The desulfurizer used in the desulfurization includes lime; the amount of the desulfurizer added in the desulfurization is 1 kg / t molten steel; the sulfur content in the molten steel leaving the LF station after the desulfurization is 0.026% by mass;

[0088] The slag conditioning agent includes silica; the addition amount of the slag conditioning agent is 0.22 kg / t molten steel;

[0089] The second deoxidizer includes silicon carbide material; the addition amount of the second deoxidizer is 0.2 kg / t molten steel;

[0090] The oxygen content in the deoxidized molten steel is 13 ppm; the calcium content in the molten steel is controlled to be 0.0009% by mass in the VD vacuum.

[0091] Example 3

[0092] This embodiment provides a method for improving the castability of molten steel, specifically C60 steel, and the method for improving the castability of molten steel includes:

[0093] Aluminum-containing refined slag is added when tapping the converter, followed by LF refining and VD vacuuming;

[0094] Wherein, the LF refining includes the first lower electrode and the second lower electrode performed sequentially;

[0095] The first lower electrode is energized and then a first deoxidizer is added, and then the mass percentage of aluminum in the molten steel is controlled to be 0.05%, and a first alloying is performed;

[0096] The second lower electrode is subjected to second alloying and desulfurization in sequence, followed by slag conditioning using a slag conditioning agent, and finally deoxidation by adding a second deoxidizing agent.

[0097] The amount of aluminum refined slag added is determined based on the endpoint sulfur content at the time of converter tapping; the endpoint sulfur content of converter tapping is 0.05% by mass, the amount of aluminum-containing refined slag added is 10 kg / t molten steel; the aluminum content of the aluminum-containing refined slag as alumina is 41% by mass;

[0098] The first deoxidizer includes aluminum material and silicon carbide material; the addition amount of the aluminum material is 0.38 kg / t molten steel; the addition amount of the silicon carbide material is 0.37 kg / t molten steel;

[0099] The desulfurizer used in the desulfurization includes lime; the amount of the desulfurizer added in the desulfurization is 1.05 kg / t molten steel; the sulfur content in the LF molten steel after desulfurization is 0.025% by mass;

[0100] The slag conditioning agent includes silica; the addition amount of the slag conditioning agent is 0.12 kg / t molten steel;

[0101] The second deoxidizer includes silicon carbide material; the addition amount of the second deoxidizer is 0.25 kg / t molten steel;

[0102] The oxygen content in the deoxidized molten steel is 6 ppm; the calcium content in the molten steel in the VD vacuum is controlled to be 0.0007% by mass.

[0103] Example 4

[0104] This embodiment provides a method for improving the castability of molten steel, specifically C60 steel, and the method for improving the castability of molten steel includes:

[0105] Aluminum-containing refined slag is added when tapping the converter, followed by LF refining and VD vacuuming;

[0106] Wherein, the LF refining includes the first lower electrode and the second lower electrode performed sequentially;

[0107] The first lower electrode is energized and then a first deoxidizer is added, and then the mass percentage of aluminum in the molten steel is controlled to be 0.06%, and a first alloying is performed;

[0108] The second lower electrode is subjected to second alloying and desulfurization in sequence, followed by slag conditioning using a slag conditioning agent, and finally deoxidation by adding a second deoxidizing agent.

[0109] The amount of aluminum refined slag added is determined based on the endpoint sulfur content at the time of converter tapping; the endpoint sulfur content of converter tapping is 0.08% by mass, and the amount of aluminum-containing refined slag added is 10.5 kg / t molten steel; the aluminum content of the aluminum-containing refined slag, calculated as alumina, is 38% by mass.

[0110] The first deoxidizer is aluminum material and silicon carbide material; the addition amount of the aluminum material is 0.25 kg / t molten steel; the addition amount of the silicon carbide material is 0.5 kg / t molten steel;

[0111] The desulfurizer used in the desulfurization is lime; the amount of the desulfurizer added in the desulfurization is 0.95 kg / t molten steel; the sulfur content in the molten steel leaving the LF station after the desulfurization is 0.03% by mass;

[0112] The slag conditioning agent is silica; the addition amount of the slag conditioning agent is 0.25 kg / t molten steel;

[0113] The second deoxidizer is silicon carbide; the addition amount of the second deoxidizer is 0.12 kg / t molten steel;

[0114] The oxygen content in the deoxidized molten steel is less than or equal to 9 ppm; and the calcium content in the molten steel is controlled to be 0.001% by mass in the VD vacuum.

[0115] Example 5

[0116] The only difference from Example 1 is that no aluminum-containing refined slag is added when tapping the converter.

[0117] Example 6

[0118] The only difference from Example 1 is that no slag conditioning agent is used for slag conditioning.

[0119] Example 7

[0120] The only difference from Example 1 is that desulfurization is performed after slag adjustment.

[0121] Example 8

[0122] The only difference from Example 1 is that the aluminum material in the first deoxidizer is replaced by an equal amount of silicon carbide.

[0123] Example 9

[0124] The only difference from Example 1 is that the amount of aluminum material added in the first deoxidizer is 0.4 kg / t molten steel, and the amount of silicon carbide material added is 0.3 kg / t molten steel.

[0125] Example 10

[0126] The only difference from Example 1 is that the desulfurization is moved before the addition of the first deoxidizer, that is, the desulfurization is performed after the lower electrode is energized for the first time.

[0127] Example 11

[0128] The only difference from Example 1 is that the order of slag conditioning and desulfurization is exchanged.

[0129] The molten steel was treated and continuously cast using the process of the above embodiment. The steel obtained by continuous casting was tested for Class A inclusions and Class B inclusions in accordance with GB / T 10561-2005. The results are shown in Table 3.

[0130] Table 3

[0131]

[0132] From the results of the above embodiments, it can be seen that the method for improving the castability of molten steel provided by the present invention can avoid the blockage of the water inlet between the ladle and the crystallizer, which causes the interruption of continuous casting of the ladle, significantly improves the castability of the molten steel, and can achieve the purpose of controlling sulfur and aluminum steel in multiple furnaces with one ladle.

[0133] It should be noted that the present invention uses the above-described embodiments to illustrate the detailed structural features of the present invention. However, the present invention is not limited to these detailed structural features, and this does not mean that the present invention must rely on these detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

[0134] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0135] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0136] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for improving the castability of molten steel, characterized in that: The method for improving the castability of molten steel comprises: Aluminum-containing refined slag is added when tapping the converter, followed by LF refining and VD vacuuming; Wherein, the LF refining includes the first lower electrode and the second lower electrode performed sequentially; The first lower electrode is energized and then a first deoxidizer is added, and then the mass percentage of aluminum in the molten steel is controlled to be 0.05-0.06%, and a first alloying is performed; The second lower electrode is subjected to second alloying and desulfurization in sequence, followed by slag conditioning with a slag conditioning agent, and finally deoxidation by adding a second deoxidizing agent; The first deoxidizer includes aluminum material and silicon carbide material; the addition amount of the aluminum material is 0.25-0.38 kg / t molten steel; the addition amount of the silicon carbide material is 0.37-0.5 kg / t molten steel.

2. The method for improving the castability of molten steel according to claim 1, wherein: The amount of aluminum refining slag added is determined based on the end point sulfur when tapping the converter.

3. The method for improving the castability of molten steel according to claim 2, wherein: The endpoint sulfur content of the converter steel is greater than 0.08% by mass, and the amount of the aluminum-containing refined slag added is 12-13 kg / t molten steel.

4. The method for improving the castability of molten steel according to claim 2, wherein: The endpoint sulfur content of the converter steel is 0.05-0.08% by mass, and the amount of the aluminum-containing refined slag added is 10-10.5 kg / t molten steel.

5. The method for improving the castability of molten steel according to claim 2, wherein: The endpoint sulfur content of the converter steel is less than 0.05% by mass, and the amount of the aluminum-containing refined slag added is 9.6-10 kg / t molten steel.

6. The method for improving the castability of molten steel according to claim 1, wherein: The mass percentage of aluminum in the aluminum-containing refined slag calculated as alumina is 38-41%.

7. The method for improving the castability of molten steel according to claim 1, wherein: The desulfurizing agent used in the desulfurization includes lime.

8. The method for improving the castability of molten steel according to claim 1, wherein: The amount of desulfurizer added in the desulfurization is ≤1.25kg / t molten steel.

9. The method for improving the castability of molten steel according to claim 1, wherein: The sulfur content in the LF steel melt after desulfurization is 0.025-0.03% by mass.

10. The method for improving the castability of molten steel according to claim 1, wherein: The slag conditioning agent includes silica.

11. The method for improving the castability of molten steel according to claim 1, wherein: The addition amount of the slag conditioning agent is 0.12-0.25 kg / t molten steel.

12. The method for improving the castability of molten steel according to claim 1, wherein: The second deoxidizer includes silicon carbide.

13. The method for improving the castability of molten steel according to claim 1, wherein: The addition amount of the second deoxidizer is 0.12-0.25 kg / t molten steel.

14. The method for improving the castability of molten steel according to claim 1, wherein: After the second deoxidizer is added for deoxidation, the oxygen content in the molten steel is ≤15ppm.

15. The method for improving the castability of molten steel according to claim 1, wherein: The calcium content of the molten steel in the VD vacuum is controlled to be 0.0007-0.001% by mass.

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