Steelmaking method capable of controlling inclusions in steel and steel prepared through steelmaking method

Abstract

The invention discloses a steelmaking method for controlling inclusions in steel and steel prepared through the steelmaking method, and relates to the technical field of ferrous metallurgy. According to the steelmaking method, low-carbon ferrosilicon with the low Ca content is used in the converter tapping alloying process, it is avoided that large-size calcium aluminate inclusions are generated due to the fact that the Ca element is introduced into molten steel, the Al2O3 inclusions are fully removed in cooperation with control over LF refining final slag alkalinity and refining time, and the smelting quality is improved. Meanwhile, in the LF refining process, a rare earth alloy micro-treatment mode is adopted to replace a traditional calcium treatment technology, on one hand, the oxygen content in molten steel is lower, and on the other hand, rare earth elements can form high-melting-point inclusions which are removed through a tundish with a reasonable weir and dam structure. The metallographic grade of various inclusions in the obtained steel is below 0.5 grade, the proportion of the inclusions existing in a tensile test break is as low as 21% or below, and the lowest proportion can reach 0.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and in particular to a steelmaking method for controlling inclusions in steel and a steel material prepared therefrom. Background Art

[0002] Except for some steel grades with special requirements, non-metallic inclusions in steel have adverse effects on various properties of steel. These inclusions will become stress concentration points when the steel is subjected to external forces, and then become cracking sources. It is the constant pursuit of steelmaking to control the number, size and composition of non-metallic inclusions in steel by adjusting the process to minimize their impact on steel. The most common inclusion in commonly used aluminum deoxidized alloy steel is Al2O3, and the LF-RH duplex refining process is the most commonly used process route for controlling inclusions in aluminum deoxidized alloy steel. For steel grades that have been treated with duplex refining, the conventional metallographic rating of inclusions in continuous casting billets or hot-rolled coils is generally below grade 1.0, which meets the requirements of most steel grades. However, even for steel grades whose metallographic rating of inclusions meets the requirements, larger inclusions will be found on some tensile fractures. In particular, in order to reduce the amount of Al2O3 inclusions that are more harmful to steel and improve the castability of molten steel, the existing steelmaking process usually uses calcium treatment to modify Al2O3 into calcium aluminate and calcium aluminate. The calcium aluminate and its salt inclusions obtained after modification have less impact on the properties of steel than solid Al2O3, but their melting point is lower, and they are easily drawn into the molten steel again in the subsequent process, resulting in large-sized CaO-Al2O3 inclusions remaining in the finished steel. In aluminum-deoxidized alloy steel produced by the conventional LF-RH double refining process, the maximum size of some calcium aluminate inclusions can even reach 50μm. The presence of such inclusions is bound to affect the mechanical properties of the finished steel in all aspects.

[0003] Chinese patent CN 110257589 A discloses a production method for reducing calcium aluminate inclusions in aluminum-killed steel. In this method, aluminum blocks are added to the molten steel for primary deoxidation during the converter smelting and steel tapping. Subsequently, in the LF refining process, the molten steel is subjected to Al-Ca alloy composite deoxidation after the molten steel is made into white slag. Finally, calcium wire is fed into the ladle before casting to perform Ca treatment on the molten steel, thereby achieving the removal of large-size calcium aluminate. However, the metallographic rating of Class D inclusions in the steel obtained by this method is still relatively high. Summary of the invention

[0004] In order to solve the problem that the removal rate of large-size calcium aluminates in the existing process is insufficient, resulting in a high metallographic grade of inclusions in the steel section, the present invention provides a steelmaking method for controlling inclusions in steel, by controlling the final slag basicity and refining time in the LF refining process, and using rare earth alloys for micro-treatment in the middle and late stages of refining, thereby avoiding the residual calcium element in the molten steel from denaturing Al2O3 inclusions into calcium aluminates, and also achieving sufficient removal of Al2O3, and the metallographic grades of various inclusions in the obtained steel are all below grade 0.5.

[0005] Another object of the present invention is to provide a steel material prepared by the above steelmaking method.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A steelmaking method for controlling inclusions in steel comprises the following steps:

[0008] S1. Converter smelting: molten iron and scrap steel are passed into a converter for smelting, and molten steel is obtained after tapping and slag making;

[0009] S2.LF refining: the molten steel is passed into the LF furnace for heating and refining, the molten steel is slag-formed, and then soft argon blowing is performed; the LF refining time is ≤45min, and the binary basicity of the final refined slag is ≤4.0; the mass ratio of the rare earth alloy added to the molten steel is 0.05-0.15kg:1t;

[0010] S3.RH refining, refining time is controlled at more than 20min;

[0011] S4.Continuous casting.

[0012] The steelmaking method for controlling inclusions in steel provided by the present invention generally follows the traditional BOF (converter smelting)-LF-RH-CC (continuous casting) steelmaking dual process route, but rare earth alloy is added to the steel before the last process (soft argon blowing) of LF refining in step S2, and the traditional calcium treatment process is replaced by rare earth alloy micro-treatment, which can not only prevent the residual calcium element in the molten steel from transforming Al2O3 inclusions into calcium aluminates (such inclusions are likely to remain in the steel and transform into large particles), but also the introduction of rare earth elements can improve the dispersibility of Al2O3 inclusions in the steel and reduce the particle size thereof. In combination with the subsequent RH refining process with a refining time of ≥20min, the present invention can fully remove small-particle Al2O3 inclusions in the steel, the proportion of inclusions existing in the tensile fracture is as low as less than 21%, and the metallographic ratings of various inclusions in the steel are also all below level 0.5. The time of the refining of step S2 LF is controlled to be ≤45min, and the binary basicity of the final refined slag is ≤4.0, in order to prevent the small amount of calcium in the molten steel raw material from denaturing the Al2O3 inclusions into low-melting calcium aluminates. In addition, the addition of rare earth alloys can further reduce the residual oxygen content in the steel, avoid the formation of new Al2O3 inclusions and CaO-Al2O3 inclusions, and the rare earth inclusions formed after the introduction of rare earth alloys are high-melting solid inclusions, which can be easily removed in subsequent processes.

[0013] In a specific embodiment of the present invention, the converter smelting described in step S1 includes the following steps: passing molten iron and scrap steel into a converter for smelting, adding a deoxidizer to the steel for deoxidation during tapping, and adding 3-4 kg of lime per ton of molten steel for slag making according to conventional operations after tapping.

[0014] In a specific embodiment of the present invention, the RH refining process in step S3 of the present invention is carried out in a conventional manner in the art.

[0015] In a specific embodiment of the present invention, the continuous casting process in step S4 of the present invention is carried out in a conventional manner in the art.

[0016] In a specific embodiment of the present invention, the rare earth alloy in step S2 is a lanthanum-cerium alloy.

[0017] More specifically, the lanthanum-cerium alloy used in step S2 of the present invention is a lanthanum-cerium alloy that complies with the industry standard "T / BTXT 0002-2016 Lanthanum-Ceium Alloy", wherein (La+Ce) / RE (mass ratio) is not less than 99.5%, and the rest are inevitable impurities in the alloy.

[0018] Preferably, the mass ratio of the added amount of the rare earth alloy in step S2 to the molten steel is 0.08-0.12 kg: 1 t.

[0019] Preferably, the binary basicity of the refined final slag in step S2 is 3.5±0.5.

[0020] Preferably, during the steel tapping in step S1, aluminum and low-carbon ferrosilicon are added to the steel for deoxidation.

[0021] In the conventional converter smelting process, aluminum and ferrosilicon are usually added as deoxidizers to deoxidize the molten steel when tapping. In the present invention, in order to avoid the introduction of calcium and thus prevent the Al2O3 inclusions in the steel from being denatured into calcium aluminates, low-carbon ferrosilicon with a lower calcium content can be used to replace ordinary ferrosilicon in the converter smelting process, so that the steel obtained has a lower inclusion content in the tensile section. It should be noted that the low-carbon ferrosilicon used in the present invention complies with the provisions of the metallurgical industry standard "YBT4114-2003 Low-carbon Ferrosilicon", wherein the content of calcium is not higher than 0.1%.

[0022] In a specific embodiment of the present invention, the specific operation of adding aluminum and low-carbon ferrosilicon to the steel for deoxidation during steel tapping in step S1 is: when 1 / 4-3 / 4 of the steel is tapped from the converter, an aluminum block is added to the steel; after adding the aluminum block and before the end of steel tapping, low-carbon ferrosilicon is added to the steel for alloying.

[0023] More preferably, during the steel tapping step S1, the mass ratio of aluminum added to the steel to the mass ratio of molten steel is 1.0-2.0 kg: 1 t.

[0024] More preferably, the final oxygen content of the molten steel obtained in step S1 is 400-850 ppm.

[0025] The preferred amount of aluminum blocks added and the oxygen content at the converter end point are to allow the residual oxygen in the molten steel obtained after the converter to fully react with aluminum to form Al2O3 inclusions, avoiding the formation of other forms of oxygen-containing aluminum inclusions that are difficult to remove during subsequent rare earth treatment.

[0026] Preferably, step S1 further includes a step of performing KR desulfurization pretreatment on the molten iron before the converter smelting, and the sulfur content in the molten iron obtained after the KR desulfurization pretreatment is ≤10ppm.

[0027] Preferably, the sulfur content of the molten steel obtained by converter smelting in step S1 is 0.003% to 0.006%.

[0028] Through the KR desulfurization process, the S content of the molten iron entering the converter can be controlled below 10ppm, and the sulfur content of the molten steel obtained by converter smelting can be reduced to 0.003%~0.006%, which significantly reduces the desulfurization task of the LF refining process. In the subsequent LF refining process, only how to fully remove Al2O3 inclusions needs to be considered.

[0029] Preferably, in the continuous casting process of step S4, a tundish with a slag retaining weir and / or a guide dam structure is used for continuous casting.

[0030] Using a tundish with a slag weir and / or diversion dam structure for continuous casting can allow the molten steel to stay in the tundish for a longer time, ensuring that inclusions in the steel have time to float up and be removed, and the resulting steel has less inclusions at the tensile end.

[0031] In a specific embodiment of the present invention, 5t of steel is retained in the ladle during continuous casting in step S4.

[0032] During continuous casting, 5t of steel is retained in the ladle to ensure that the slag from the ladle cannot flow into the tundish and remain in the steel.

[0033] The present invention also protects a steel material prepared by the steelmaking method for controlling inclusions in steel.

[0034] In a specific embodiment of the present invention, the steel material comprises the following chemical components calculated by mass percentage:

[0035] C: 0.06%-0.40%, Si: 0.20%-0.60%, Mn: 0.5%-1.5%, P: ≤0.015%, S: ≤0.002%, Al: 0.02%-0.06%, alloying elements: 0.20%-1.50%, the balance is Fe and unavoidable impurities;

[0036] The alloying element is at least one of Nb, V, Ti, Ni, Cr and Mo.

[0037] The above components are typical components of aluminum deoxidized alloy steel. The steelmaking method of the present invention can be used to prepare aluminum deoxidized alloy steel with the same components as those produced by the ordinary duplex refining process, but the content of inclusions inside the steel is lower.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The steelmaking method provided by the present invention adopts rare earth micro-treatment to replace the traditional calcium treatment in the LF refining process, thereby avoiding the introduction of calcium into the steel, which leads to the generation of large-particle calcium aluminate inclusions. In the steel smelted by the steelmaking method provided by the present invention, the metallographic rating of various inclusions is below 0.5 level, and the proportion of inclusions in the fracture in the tensile test is as low as below 21%, and the lowest reaches 0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The fracture inclusions and energy spectrum of the tensile specimen of the steel obtained in Comparative Example 1 of the present invention.

[0041] Figure 2This is the microstructure of the hot-rolled coil of the steel obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0043] Example 1

[0044] A steelmaking method for controlling inclusions in steel comprises the following steps:

[0045] S1. Converter smelting: 170t of molten iron is desulfurized in the KR process, and the sulfur content of the molten iron is 8ppm; the molten iron and 50t of scrap steel are passed into the converter for smelting and tapping. When 1 / 4-3 / 4 of the steel is tapped, 250kg of aluminum blocks are added to the steel (1.22kg per ton of molten steel); after adding the aluminum blocks and before the end of tapping, 1200kg of low-carbon ferrosilicon is added to the steel for alloying; after tapping, 700kg of lime is added to slag to obtain 205t of molten steel, with an end point oxygen content of 620ppm and a sulfur content of 50ppm;

[0046] S2.LF refining: the molten steel is passed into the LF furnace for heating and refining, the molten steel is slag-formed, 20 kg of lanthanum-cerium alloy is added to the steel (~0.1 kg per ton of molten steel), and then soft argon is blown for 6 minutes; the LF refining time is 40 minutes, and the binary basicity of the refined final slag is 3.52;

[0047] S3.RH refining, refining time is 22min;

[0048] S4. Continuous casting, using a tundish with a slag weir and diversion dam structure for pouring, leaving 5t of steel in the ladle during continuous casting.

[0049] The steel material smelted by the steelmaking method provided in Example 1 includes the following chemical components calculated by mass percentage:

[0050] C: 0.22%, Si: 0.45%, Mn: 0.58%, P: ≤0.015%, S: ≤0.002%, Al: 0.043%, alloying elements: 1.25%, the balance is Fe and unavoidable impurities, of which the residual Ca element content is 0.0001%;

[0051] The alloying elements are Nb, V, Ti, Ni, Cr and Mo.

[0052] Example 2

[0053] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0054] Step S2: Add 24.6 kg of lanthanum-cerium alloy to the steel (0.12 kg per ton of molten steel).

[0055] The steel smelted by the steelmaking method provided in Example 2 has substantially the same chemical composition as the steel in Example 1.

[0056] Example 3

[0057] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0058] Step S2: Add 16.4 kg of lanthanum-cerium alloy to the steel (0.08 kg per ton of molten steel).

[0059] The steel smelted by the steelmaking method provided in Example 3 has substantially the same chemical composition as the steel in Example 1.

[0060] Example 4

[0061] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0062] Step S2: Add 10.25 kg of lanthanum-cerium alloy to the steel (0.05 kg per ton of molten steel).

[0063] The steel smelted by the steelmaking method provided in Example 4 has substantially the same chemical composition as the steel in Example 1.

[0064] Example 5

[0065] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0066] Step S2: Add 30.75 kg of lanthanum-cerium alloy into the steel (0.15 kg per ton of molten steel).

[0067] The steel smelted by the steelmaking method provided in Example 5 has a chemical composition that is substantially the same as that of the steel in Example 1.

[0068] Example 6

[0069] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0070] The binary basicity of the final slag from LF refining in step S2 is 4.0.

[0071] The steel smelted by the steelmaking method provided in Example 6 has a chemical composition that is substantially the same as that of the steel in Example 1.

[0072] Example 7

[0073] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0074] The LF refining time in step S2 is 45 min.

[0075] The steel smelted by the steelmaking method provided in Example 7 has a chemical composition that is substantially the same as that of the steel in Example 1.

[0076] Example 8

[0077] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0078] After adding the aluminum block in step S1 and before the steel is tapped, 1200 kg of ordinary ferrosilicon is added to the steel for alloying.

[0079] The steel smelted by the steelmaking method provided in Example 8 has substantially the same chemical composition as the steel in Example 1, except that the Ca content in the steel reaches 0.0015%.

[0080] Example 9

[0081] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0082] In step S4, a tundish without a slag retaining weir and a diversion dam structure is used for pouring.

[0083] The steel smelted by the steelmaking method provided in Example 9 has a chemical composition substantially the same as that of the steel in Example 1.

[0084] Comparative Example 1

[0085] A LF-RH dual process steelmaking method comprises the following steps:

[0086] S1. Converter smelting: 170t of molten iron and 50t of scrap steel are passed into the converter for smelting and tapping. When 1 / 4-3 / 4 of the steel is tapped, 100kg of aluminum blocks are added to the steel (0.5kg is added per ton of molten steel); after adding the aluminum blocks and before the end of tapping, 1200kg of ordinary ferrosilicon is added to the steel for alloying; after tapping, 700kg of lime is added to slag to obtain 205t of molten steel. The terminal oxygen content of the molten steel obtained by converter smelting is 620ppm;

[0087] S2.LF refining: the molten steel is passed into the LF furnace for heating and refining, the molten steel is slag-formed, 20 kg of lanthanum-cerium alloy is added to the steel, and then soft argon is blown for 6 minutes; the LF refining time is 85 minutes, and the binary basicity of the refined final slag is 8.38;

[0088] S3.RH refining, refining time is 22min;

[0089] S4. Continuous casting, using a tundish without a slag weir and diversion dam structure for pouring.

[0090] The steel smelted by the steelmaking method provided in Comparative Example 1 has substantially the same chemical composition as the steel in Example 1.

[0091] Comparative Example 2

[0092] A LF-RH dual process steelmaking method, which is different from Example 8 only in that:

[0093] In step S4, a tundish without a slag retaining weir and a diversion dam structure is used for pouring.

[0094] The steel smelted by the steelmaking method provided in Comparative Example 2 has substantially the same chemical composition as the steel in Example 1.

[0095] Comparative Example 3

[0096] A LF-RH dual process steelmaking method, which is different from Example 1 only in that:

[0097] In step S2, 400 m of calcium wire (120 kg) is fed into the steel at the later stage of LF refining to perform calcium treatment on the molten steel.

[0098] The steel smelted by the steelmaking method provided in Comparative Example 3 has substantially the same chemical composition as the steel in Example 1, except that the Ca content in the steel reaches 0.0025%.

[0099] Comparative Example 4

[0100] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0101] The LF refining time in step S2 is 60 min.

[0102] The steel smelted by the steelmaking method provided in Comparative Example 4 has substantially the same chemical composition as the steel in Example 1.

[0103] Comparative Example 5

[0104] A steelmaking method for controlling inclusions in steel, wherein the difference from Example 1 is only that:

[0105] The binary basicity of the final slag from LF refining in step S2 is 5.0.

[0106] The steel smelted by the steelmaking method provided in Comparative Example 5 has substantially the same chemical composition as the steel in Example 1.

[0107] Performance Testing

[0108] Test on the proportion of inclusions in the tensile fracture of steel: The steels obtained in the examples and comparative examples were prepared into tensile specimens with a width of 25 mm and a length of 300 mm for tensile testing. After the specimens were broken, inclusions on the tensile fracture were detected by electron microscopy and energy dispersive spectrometer.

[0109] Metallographic rating of inclusions in steel: Rating of inclusions is carried out in accordance with the method of "GBT 10561-2005 Determination of non-metallic inclusions in steel".

[0110] The performance test data are shown in Tables 1 to 2. Figures 1-2 As shown:

[0111] Table 1. Data on the proportion of inclusions in the tensile fracture of steel obtained in the examples and comparative examples

[0112] Group Proportion of inclusions in tensile fracture Example 1 0％ Example 2 0％ Example 3 0％ Example 4 1.5％ Example 5 1.2％ Example 6 0.7％ Example 7 0.6％ Example 8 21％ Example 9 17％ Comparative Example 1 85％ Comparative Example 2 53％ Comparative Example 3 67％ Comparative Example 4 32％ Comparative Example 5 28％

[0113] Table 2. Metallographic rating of inclusions in steel obtained in Example 1 and Comparative Example 1

[0114] Group A B C D Ds Example 1 0 0.5 0 0.5 0.5 Comparative Example 1 0 2.5 0.5 2.0 2.0

[0115] It is clear from the data in Tables 1 to 2 that the metallographic ratings of various inclusions in the steel smelted by the steelmaking method provided by the present invention are all below 0.5, and the proportion of inclusions in the fracture during the tensile test is as low as below 21%. This shows that the method provided by the present invention can avoid the formation of calcium aluminate inclusions and can also fully remove aluminum oxide inclusions. Among them, according to the data of Examples 1 to 5, it can be seen that in step S2, 0.08 to 0.12 kg of rare earth alloy (Examples 1 to 3) is added to each ton of molten steel for micro-treatment, and the proportion of inclusions in the tensile fracture of the obtained steel is smaller. According to the data of Examples 1, 6-7 and Comparative Examples 4-5, it can be seen that the time of LF refining in step S2 and the binary basicity of the final slag have an important influence on the inclusions in the steel. When the LF refining time is greater than 45min (Comparative Example 4), or the basicity of the final slag of LF refining is greater than 4.0 (Comparative Example 5), more than 20% of inclusions are present in the tensile fracture of the obtained steel, indicating that in order to fully remove the inclusions in the steel, especially the large-particle calcium aluminate inclusions, it is necessary to control the LF refining time and the basicity of the final slag to avoid the small amount of calcium in the molten steel raw material from denaturing the Al2O3 inclusions into low-melting calcium aluminates. According to the data of Examples 1, 8-9, the addition of low-carbon ferrosilicon for alloying in step S1 of the present invention and the use of a tundish containing a "weir" or "dam" structure for casting in step S4 can further reduce the inclusion content in the steel. Comparative Example 1 uses ordinary ferrosilicon for alloying during the converter steel tapping process, and the refining time and final slag basicity are not controlled in LF refining, and the tundish containing "weir" and "dam" structures is not used for casting. The steel obtained has up to 85% inclusions in the tensile section, and the metallographic ratings of D and DS inclusions are both 2.0. Comparative Example 2 is a steel obtained by adding ordinary ferrosilicon for alloying during the converter steel tapping process, and using a tundish without "weir" and "dam" structures for casting during continuous casting. It can be seen from the data of Comparative Example 2 that adding ordinary ferrosilicon for alloying during the converter steel tapping process will still introduce a certain amount of calcium into the molten steel, and this part of calcium will form calcium aluminate inclusions. At the same time, rare earth element inclusions will be formed during LF refining. If the tundish containing weirs and dams is not used for casting the steel in the subsequent continuous casting, the inclusions will stay in the tundish for a longer time and then be fully removed, and the obtained steel will contain a large amount of inclusions. Comparative Example 3 is a process for calcium treatment of steel commonly used in the existing LF refining process. The data of Comparative Example 3 can confirm that more inclusions are likely to remain in the steel produced by the traditional calcium treatment process.

[0116] Figure 1 The inclusions and energy spectrum of the tensile specimen of comparative example 1 are shown in Figure 1. Figure 1The right picture confirms that the inclusions in the steel are calcium aluminates; the left picture confirms that the size of the calcium aluminate inclusions in the steel is almost 50μm, and such inclusions have a huge impact on the mechanical properties of the steel.

[0117] Figure 2 This is the hot rolled coil structure morphology of the steel obtained in Example 1 of the present invention. Figure 2 It can be seen that the steel provided by the present invention has a good consistency in its organizational morphology because alumina inclusions are fully removed.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A steelmaking method for controlling inclusions in steel, characterized in that: The steps include: S1. Converter smelting: molten iron and scrap steel are passed into a converter for smelting, and molten steel is obtained after tapping and slag making; S2.LF refining: the molten steel is passed into the LF furnace for heating and refining, the molten steel is slag-formed, a rare earth alloy is added to the steel, and then soft argon is blown; the LF refining time is ≤45min, and the binary basicity of the final refined slag is ≤4.0; the mass ratio of the rare earth alloy added to the molten steel is 0.05-0.15kg:1t; S3.RH refining, refining time is controlled at more than 20min; S4.Continuous casting.

2. The steelmaking method for controlling inclusions in steel according to claim 1, characterized in that: The rare earth alloy in step S2 is a lanthanum-cerium alloy.

3. The steelmaking method for controlling inclusions in steel as claimed in claim 2, characterized in that: The mass ratio of the added amount of the rare earth alloy to the molten steel in step S2 is 0.08-0.12 kg: 1 t.

4. The steelmaking method for controlling inclusions in steel according to any one of claims 1 to 3, characterized in that: The binary basicity of the refined final slag in step S2 is 3.5±0.

5.

5. The steelmaking method for controlling inclusions in steel as claimed in claim 1, characterized in that: When tapping the steel in step S1, aluminum and low-carbon ferrosilicon are added to the steel for deoxidation.

6. The steelmaking method for controlling inclusions in steel as claimed in claim 5, characterized in that: When tapping the steel in step S1, the mass ratio of aluminum added to the steel to the mass ratio of molten steel is 1.0-2.0 kg: 1 t.

7. The steelmaking method for controlling inclusions in steel as claimed in claim 6, characterized in that: The final oxygen content of the molten steel obtained in step S1 is 400-850 ppm.

8. The steelmaking method for controlling inclusions in steel as claimed in claim 1, characterized in that: Step S1 also includes the step of performing KR desulfurization pretreatment on the molten iron before converter smelting, and the sulfur content in the molten iron obtained after the KR desulfurization pretreatment is ≤10ppm.

9. Steel produced by the steelmaking method for controlling inclusions in steel as claimed in any one of claims 1 to 8.

10. The steel material according to claim 9, characterized in that: The chemical composition calculated by mass percentage is as follows: C: 0.06%-0.40%, Si: 0.20%-0.60%, Mn: 0.5%-1.5%, P: ≤0.015%, S: ≤0.002%, Al: 0.02%-0.06%, alloying elements: 0.20%-1.50%, the balance is Fe and unavoidable impurities; The alloying element is at least one of Nb, V, Ti, Ni, Cr and Mo.

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