Preparation method of wheel steel and wheel steel

Abstract

The invention discloses a preparation method of steel for a wheel and the steel for the wheel. The preparation method comprises the steps that when LF furnace refining is finished, first-stage magnesium treatment is conducted on LF furnace refined molten steel, so that the mass percent of MgO of inclusions in the refined molten steel reaches 30%-60%, and the magnesium adding amount of the first-stage magnesium treatment is 0.1-0.2 kg per ton of steel; performing RH vacuum treatment on the refined molten steel to obtain RH refined molten steel; wherein second-stage magnesium treatment is carried out after the RH vacuum treatment is finished, so that the mass percent of MgO of inclusions in molten steel reaches 61%-100%, and the magnesium adding amount of the second-stage magnesium treatment is 0.35-0.5 kg per ton of steel; wherein the RH vacuum treatment comprises the step of carrying out soft stirring at the flow rate of 100-300L / min after the second-stage magnesium treatment, and the soft stirring time is 5-10 minutes. According to the preparation method disclosed by the invention, the steel for the wheel, which is less in inclusion and good in mechanical property and fatigue property, is prepared.

Description

Technical Field

[0001] The present application belongs to the technical field of steel smelting, and specifically relates to a method for preparing wheel steel, wheel steel and steel products. Background Art

[0002] Wheel steel has extremely high requirements for material strength, toughness and cleanliness due to its key application in automobile manufacturing. The presence of inclusions will seriously affect the performance of wheel steel, especially its fatigue life. Controlling the type, size and distribution of inclusions is the key to improving the performance of wheel steel.

[0003] Therefore, a new process is urgently needed to improve it. Summary of the invention

[0004] In view of this, the present application provides a method for preparing wheel steel, wheel steel and steel products, aiming to provide a wheel steel with good cleanliness and good mechanical properties and fatigue properties.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing wheel steel, comprising:

[0006] When the LF furnace refining is finished, the refined molten steel in the LF furnace is subjected to the first stage of magnesium treatment, so that the mass percentage of MgO in the refined molten steel reaches 30% to 60%, wherein the amount of magnesium added in the first stage of magnesium treatment is 0.1-0.2kg / ton of steel;

[0007] The refined molten steel is subjected to RH vacuum treatment to obtain RH refined molten steel; wherein, at the end of the RH vacuum treatment, a second stage of magnesium treatment is performed to make the mass percentage of MgO in the inclusions in the RH molten steel reach 61% to 100%, wherein the amount of magnesium added in the second stage of magnesium treatment is 0.35-0.5kg / ton of steel;

[0008] The RH vacuum treatment includes soft stirring at a flow rate of 100-300 L / min after the second stage of magnesium treatment, and the soft stirring time is 5-10 minutes.

[0009] According to an embodiment of one aspect of the present application, when the LF furnace refining is completed, before the refined molten steel in the LF furnace is subjected to the first stage of magnesium treatment, the method further comprises:

[0010] The molten steel is subjected to LF refining to obtain refined molten steel; wherein the LF refining comprises: adjusting the slag composition so that the mass percentage of Fe in the ladle refining slag at the end of LF furnace refining is less than 0.5%, the C / A ratio of the refining slag is 1.4-1.8, S in the molten steel is ≤0.0015%, and the C / A ratio represents the mass ratio of calcium oxide to aluminum oxide.

[0011] According to an embodiment of one aspect of the present application, the adjustment of the slag composition includes: adding lime, top slag modifier and low silicon pre-melted refined slag, wherein the composition of the top slag modifier is as follows by mass percentage: Al: 32-47%, CaO: 18-25%, Al2O3: 17-28%, SiO2: 3-8%, and the composition of the low silicon pre-melted refined slag is as follows by mass percentage: CaO: 40-55%, Al2O3: 35-45%, SiO2: 2-7%, MgO: 3-7%, so that the initial composition of the slag is transformed into the final composition of the slag.

[0012] According to an embodiment of one aspect of the present application, the composition of the refined slag at the end of the LF refining includes, in mass percentage, the following: CaO: 48% to 54%, SiO2: 4.4% to 6%, P2O5: 0.02% to 0.03%, Al2O3: 31% to 35%, MgO: 6.0% to 6.9%, MnO: 0 to 0.15%, FeTOT: 0.15% to 0.5%, and unavoidable impurities, and the mass ratio of CaO / SiO2 is 8.5 to 12.

[0013] According to an embodiment of one aspect of the present application, before the first stage magnesium treatment is performed on the refined molten steel in the LF furnace, the method further includes: performing soft stirring at a flow rate of 200-400 L / min, and the soft stirring time is 8-12 min.

[0014] According to an embodiment of one aspect of the present application, the RH vacuum treatment includes: the vacuum degree of the RH furnace is 5-7KPa, the vacuum treatment time is 15-20min, the flow rate of the lifting gas is 80-100Nm 3 / h.

[0015] According to an embodiment of one aspect of the present application, the chemical composition of the RH molten steel includes, in mass percentage, 0.2wt%≤C≤0.4wt%, 0.1wt%≤Si≤0.4wt%, 0.4wt%≤Mn≤2.0wt%, S≤0.0015wt%, 0.01wt%≤Ti≤0.04wt%, 0.001wt%≤B≤0.005wt%, N≤0.005wt%, and the rest is iron and other inevitable impurities.

[0016] In a second aspect, an embodiment of the present application provides a wheel steel, which is prepared by the preparation method of the first aspect.

[0017] According to an embodiment of one aspect of the present application, the inclusions of the wheel steel are classified according to GB / T10561-2023, with Class B inclusions ≤ Grade 1.0 and Class Ds inclusions ≤ Grade 0.5; the mechanical properties of the wheel steel meet the following requirements: yield strength ≥ 1000MPa, tensile strength ≥ 1400MPa, and elongation ≥ 7%; the fatigue resistance of the wheel steel meets the following requirements: bending fatigue life ≥ 500,000 times and radial fatigue life ≥ 900,000 times.

[0018] This application has at least the following beneficial effects:

[0019] The method provided in the present application performs a first stage magnesium treatment and a second stage magnesium treatment at the end of LF furnace refining and at the end of RH vacuum cycle, respectively, so as to transform liquid spherical calcium-aluminate inclusions in the molten steel into solid inclusions, thereby improving the efficiency of flotation removal of inclusions, especially large-sized inclusions, and further refining the inclusions in the molten steel, so that the B-type inclusions in the wheel steel or its rolled products are ≤1.0 level, and the Ds-type inclusions are ≤0.5 level, thereby improving the mechanical properties and fatigue resistance of the wheel steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the implementation regulations of this application, the following is a brief introduction to the drawings required for use in the embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 A micrograph of the morphology of non-metallic inclusions used in a wheel according to an embodiment of the present application is shown.

[0022] Figure 2 A micrograph of the morphology of non-metallic inclusions used in a wheel of a comparative example of the present application is shown.

[0023] Figure 3 A schematic diagram of the morphology of Mg-Al inclusions and Mn / CaS composite inclusions of Example 1 of the present application is shown.

[0024] Figure 4 The energy spectrum analysis diagram of the peripheral Mn / CaS sulfide in Example 1 of the present application is shown.

[0025] Figure 5 The energy spectrum analysis diagram of the core Mg-Al inclusions in Example 1 of the present application is shown.

[0026] Figure 6 A schematic diagram of the morphology of pure MgO inclusions in Example 1 of the present application is shown.

[0027] Figure 7 The energy spectrum analysis diagram of pure MgO inclusions in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0028] In order to make the application purpose, technical solution and beneficial technical effect of this application clearer, the application is further described in detail below in conjunction with the embodiments. It should be understood that the implementation regulations described in this specification are only for explaining this application, not for limiting this application.

[0029] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0030] In the description of the present application, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number, and the “multiple” in “one or more” means two or more than two.

[0031] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided through a series of embodiments, and these implementation regulations can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0032] Method for preparing steel for wheel

[0033] In a first aspect, an embodiment of the present application provides a method for preparing wheel steel, comprising:

[0034] When the LF furnace refining is finished, the refined molten steel in the LF furnace is subjected to the first stage of magnesium treatment, so that the mass percentage of MgO in the refined molten steel reaches 30% to 60%, wherein the amount of magnesium added in the first stage of magnesium treatment is 0.1-0.2kg / ton of steel;

[0035] The refined molten steel is subjected to RH vacuum treatment to obtain RH refined molten steel; wherein, at the end of the RH vacuum treatment, a second stage of magnesium treatment is performed to make the mass percentage of MgO in the inclusions in the RH molten steel reach 61% to 100%, wherein the amount of magnesium added in the second stage of magnesium treatment is 0.35-0.5kg / ton of steel;

[0036] The RH vacuum treatment includes soft stirring at a flow rate of 100-300 L / min after the second stage of magnesium treatment, and the soft stirring time is 5-10 minutes.

[0037] According to the embodiment of the present application, the first stage of magnesium treatment is carried out to transform the liquid calcium-aluminum-magnesium inclusions in the molten steel into solid inclusions, which is beneficial to the floating and removal of the solid inclusions in the subsequent refining process; the molten steel is subjected to RH vacuum treatment to promote the collision, growth, floating and removal of the solid inclusions; because magnesium is an active alkaline earth metal element and is easily volatilized during the RH furnace treatment, the second stage of magnesium treatment transforms all the inclusions in the molten steel into composite inclusions with a MgO content of 60-70% or pure MgO inclusions. Such inclusions are relatively small and can provide nucleation points for easily deformed inclusions such as MnS and TiN precipitated during the solidification process to form composite inclusions of Mg oxide, thereby reducing the formation of strip-shaped MnS or chain-shaped TiN inclusions in the rolled material, and improving the fatigue resistance of wheel steel while taking into account the mechanical properties of wheel steel.

[0038] In some optional embodiments, when the LF furnace refining is completed and before the refined molten steel in the LF furnace is subjected to the first stage of magnesium treatment, the method further comprises:

[0039] The molten steel is subjected to LF refining to obtain refined molten steel; wherein the LF refining includes: adjusting the slag composition so that the mass content of Fe in the ladle refining slag at the end of LF furnace refining is less than 0.5%, the C / A ratio of the refining slag is 1.4-1.8, S in the molten steel is ≤0.0015%, and the C / A ratio expresses the mass ratio of calcium oxide to aluminum oxide. The C / A ratio of the refining slag can be selected to be 1.5-1.7, etc.

[0040] According to the embodiment of the present application, the content of Fe in the refined slag is less than 0.5%, which means that the oxidizability of the refined slag is low, which helps to reduce the secondary generation of oxide inclusions (such as aluminum oxide and silicon oxide), improve the purity of molten steel, and further reduce the adverse effects of inclusions on steel performance; the C / A ratio is controlled within the range of 1.4 to 1.8, so that the ladle refined slag has good fluidity and stability at the steelmaking temperature, providing good kinetic conditions for the absorption of inclusions. In order to remove the S content in the molten steel to the above range, the slag basicity is relatively high, that is, the CaO content in the slag is increased, and as the CaO content increases, the slag and the molten steel are stirred and contacted to react, and calcium aluminate inclusions will be generated. This inclusion is liquid, and the wetting angle in the molten steel is small, which is difficult to remove. A small amount of magnesium is added for light magnesium treatment, which can be converted into solid MgO-Al2O3-CaO inclusions, which then collide and polymerize and grow in the vacuum cycle treatment of the RH furnace to achieve effective removal.

[0041] Sulfur will precipitate sulfide inclusions (such as MnS inclusions) during the pouring and solidification of molten steel, which will easily extend along the rolling direction after rolling to form long strips of MnS, which is extremely unfavorable to the transverse ductility and impact toughness of the product and will reduce the fatigue resistance of the steel. Therefore, the sulfur content is controlled within the above range.

[0042] In some optional embodiments, the LF refining includes: making the temperature of the refined molten steel 1520 to 1620°C.

[0043] In some optional embodiments, adjusting the slag composition includes: adding lime, top slag modifier and low-silicon pre-melted refined slag to transform the initial composition of the slag into the final composition of the slag.

[0044] In some optional embodiments, the composition of the refined slag at the end of LF refining includes, by mass percentage: CaO: 48% to 54%, SiO2: 4.4% to 6%, P2O5: 0.02% to 0.03%, Al2O3: 31% to 35%, MgO: 6.0% to 6.9%, MnO: 0 to 0.15%,

[0045] R2O: 5% to 12%, FeTOT: 0.15% to 0.5%, and unavoidable impurities, the mass ratio of CaO / SiO2 is 8.5 to 12.

[0046] According to the embodiment of the present application, the first stage of magnesium treatment is carried out to transform the liquid calcium-aluminum-magnesium inclusions in the molten steel into solid inclusions, which is beneficial to the floating and removal of the solid inclusions in the subsequent refining process.

[0047] In some optional embodiments, before the first stage magnesium treatment is performed on the refined molten steel in the LF furnace, the method further comprises: soft stirring at a flow rate of 200-400 L / min for 8-12 min to polymerize and float the large inclusions in the molten steel for removal.

[0048] In some optional embodiments, the LF refining in the LF furnace includes: soft stirring with a protective gas, where the protective gas may be nitrogen, an inert gas, etc. The inert gas may be argon.

[0049] In some optional embodiments, the RH vacuum treatment includes: the vacuum degree of the RH furnace is 5-7KPa, the vacuum treatment time is 15-20min, and the flow rate of the lifting gas is 80-100Nm 3 / h.

[0050] According to the embodiment of the present application, the vacuum degree is 5-7KPa, and the extreme vacuum is not adopted, so as to reduce the turbulence intensity of the molten steel in the RH furnace, so as to reduce the entrapment of inclusions by the molten steel, which is conducive to the removal of inclusions after the inclusions float to the slag interface.

[0051] In some optional embodiments, the chemical composition of the RH molten steel includes, in mass percentage, 0.2wt%≤C≤0.4wt%, 0.1wt%≤Si≤0.4wt%, 0.4wt%≤Mn≤2.0wt%, S≤0.0015wt%, 0.01wt%≤Ti≤0.04wt%, 0.001wt%≤B≤0.005wt%, N≤0.005wt%, and the rest is iron and other unavoidable impurities.

[0052] According to the embodiment of the present application, the wheel steel with this chemical composition has extremely high requirements on the strength, toughness and cleanliness of the material. Therefore, controlling the chemical composition of the RH molten steel is conducive to controlling inclusions by adopting a suitable process to prepare a wheel steel with both mechanical properties and good fatigue resistance.

[0053] In a second aspect, an embodiment of the present application provides a wheel steel, which is prepared by the preparation method of the first aspect.

[0054] In some optional embodiments, the inclusions of the wheel steel are classified according to GB / T 10561-2023, with Class B inclusions ≤ Grade 1.0 and Class Ds inclusions ≤ Grade 0.5; the mechanical properties of the wheel steel meet the following requirements: yield strength ≥ 1000MPa, tensile strength ≥ 1400MPa, and elongation ≥ 7%; the fatigue resistance of the wheel steel meets the following requirements: bending fatigue life ≥ 500,000 times and radial fatigue life ≥ 900,000 times.

[0055] Example

[0056] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations may be made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0057] Example 1

[0058] This embodiment provides a method for preparing wheel steel, comprising the following steps:

[0059] During the LF furnace refining process, lime, top slag modifier and low silicon pre-melted refined slag are added to adjust the slag composition. The composition of the refined slag in the ladle at the end of LF refining is shown in the attached table 1 for heat 1.

[0060] The slag is in a glassy state and has good fluidity. The binary basicity of the refined slag is relatively high. After strong stirring and desulfurization, the S content in the steel is 0.0005wt%.

[0061] The magnesium wire is soft-blown for 8-12 minutes before feeding, and the molten steel is subjected to the first stage of magnesium treatment. The amount of magnesium fed is 0.12 kg / ton of steel, so that the mass percentage of MgO in the refined molten steel inclusions is 30% to 60%.

[0062] RH furnace vacuum treatment for 18 minutes, vacuum degree is 5.8KPa, lifting gas flow rate is 85Nm 3 / h. After the vacuum treatment is completed, the molten steel is subjected to a second stage of magnesium treatment, and the amount of magnesium fed is 0.45kg / ton of steel, so that the mass percentage of MgO in the inclusions in the RH molten steel is 75% to 100%. The RH vacuum treatment includes soft stirring at a flow rate of 200L / min after the second stage of magnesium treatment, and the soft stirring time is 8min. And the chemical composition of the RH molten steel includes, in mass percentage, 0.2wt%≤C≤0.4wt%, 0.1wt%≤Si≤0.4wt%, 0.4wt%≤Mn≤2.0wt%, S≤0.0015wt%, 0.01wt%≤Ti≤0.04wt%, 0.001wt%≤B≤0.005wt%, N≤0.005wt%, and the rest is iron and other inevitable impurities.

[0063] Sampling, sample preparation and metallographic analysis are carried out in the rolled material, as shown in the attached Figure 1 , which is a morphology diagram of non-metallic inclusions in wheel steel rolled products provided in an embodiment of the present invention.

[0064] Example 2

[0065] The difference between this embodiment and embodiment 1 is that the S content in the steel is 0.0007 wt %. The composition of the refined slag in the ladle at the end of refining is shown in heat 2 in attached table 1.

[0066] Example 3

[0067] The difference between this embodiment and embodiment 1 is that the S content in the steel is 0.0010 wt%. The composition of the refined slag in the ladle at the end of refining is shown in heat 3 in attached table 1.

[0068] Table 1 Composition of refined slag in ladle at the end of LF refining (%)

[0069] Heat CaO <![CDATA[SiO2]]> <![CDATA[P2O5]]> <![CDATA[Al2O3]]> MgO MnO Fe TOT C / A <![CDATA[R(CaO / SiO2)]]> 1 53.62 4.51 0.03 34.34 6.88 0.06 0.29 1.56 11.9 2 57.46 5.04 0.02 31.87 6.46 0.00 0.19 1.80 11.4 3 49.67 5.79 0.03 34.56 6.09 0.15 0.49 1.44 8.6

[0070] Example 4

[0071] The difference between this embodiment and embodiment 1 is that the amount of magnesium added in the first stage of magnesium treatment is 0.1 kg / ton of steel; and the amount of magnesium added in the second stage of magnesium treatment is 0.5 kg / ton of steel.

[0072] Example 5

[0073] The difference between this embodiment and embodiment 1 is that the amount of magnesium added in the first stage of magnesium treatment is 0.2 kg / ton of steel; and the amount of magnesium added in the second stage of magnesium treatment is 0.35 kg / ton of steel.

[0074] Example 6

[0075] The difference between this embodiment and embodiment 1 is that the RH vacuum treatment includes soft stirring at a flow rate of 300 L / min after the second stage of magnesium treatment, and the soft stirring time is 5 minutes.

[0076] Example 7

[0077] The difference between this embodiment and embodiment 1 is that the RH vacuum treatment includes soft stirring at a flow rate of 100 L / min after the second stage of magnesium treatment, and the soft stirring time is 10 minutes.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is that the RH vacuum treatment includes soft stirring at a flow rate of 120 L / min after the second stage of magnesium treatment, and the soft stirring time is 1 minute.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that in the LF furnace refining process, the first stage magnesium treatment is not performed.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 1 is that in the RH vacuum treatment, the second stage magnesium treatment is not performed.

[0084] Test Section

[0085] The wheel steels prepared in the examples and comparative examples were tested for mechanical properties and fatigue resistance, and inclusions were detected using an optical microscope and a scanning electron microscope.

[0086] The fatigue resistance performance is tested using a fatigue testing machine;

[0087] Tensile strength and yield strength: refer to "Tensile test of metallic materials Part 1: Room temperature test method" GB / T228.1 for testing.

[0088] Elongation: Refer to "Metallic Materials Tensile Test Part 1: Room Temperature Test Method" GB / T228.1 for testing.

[0089] The measured results are shown in Table 2

[0090] Table 2 Test results of wheel steel for example and comparative example

[0091]

[0092]

[0093] The above measured performance parameters are taken as average values.

[0094] Figure 1 A micrograph of a wheel steel according to an example of the present application is shown. Figure 1 The B-type inclusions in the rolled material in the example are 0.5 level, Figure 2 A micrograph of a wheel of a comparative example of the present application is shown. Figure 2 Comparative Example 1: Class B inclusions in rolled material 2.0 level, from Figure 1 and Figure 2 It can be seen that Figure 1 The inclusions in Figure 2 There are fewer in the sample and the volume is smaller, which corresponds to the anti-fatigue performance in Example 1 and Comparative Example 1.

[0095] Figure 3 Schematic diagram of the morphology of Mg-Al inclusions and Mn / CaS composite inclusions according to Example 1 of the present invention, Figure 4 for Figure 3 Energy spectrum analysis diagram of the middle and outer Mn / CaS sulfides; Figure 5 for Figure 3 Energy spectrum analysis diagram of Mg-Al inclusions in the middle core; Figure 6 Schematic diagram of the morphology of pure MgO inclusions according to Example 1 of the present invention, Figure 7 for Figure 6 Energy spectrum analysis diagram of medium-pure MgO inclusions.

[0096] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto, and any familiarity with the present technology or replacement should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing wheel steel, characterized in that: include: At the end of LF furnace refining, the refined molten steel in the LF furnace is subjected to the first stage of magnesium treatment, so that the mass percentage of MgO in the inclusions in the refined molten steel reaches 30% to 60%, wherein the amount of magnesium added in the first stage of magnesium treatment is 0.1-0.2kg / ton of steel; The refined molten steel is subjected to RH vacuum treatment to obtain RH refined molten steel; wherein, at the end of the RH vacuum treatment, a second stage of magnesium treatment is performed to make the mass percentage of MgO in the inclusions in the RH refined molten steel reach 61% to 100%, wherein the amount of magnesium added in the second stage of magnesium treatment is 0.35-0.5kg / ton of steel; The RH vacuum treatment includes soft stirring at a flow rate of 100-300 L / min after the second stage of magnesium treatment, and the soft stirring time is 5-10 minutes.

2. The preparation method according to claim 1, characterized in that: When the LF furnace refining is completed and before the refined molten steel in the LF furnace is subjected to the first stage of magnesium treatment, the method further comprises: The molten steel is subjected to LF refining to obtain refined molten steel; wherein the LF refining comprises: adjusting the slag composition so that the mass percentage of Fe in the ladle refining slag at the end of LF furnace refining is less than 0.5%, the C / A ratio of the refining slag is 1.4-1.8, S in the molten steel is ≤0.0015%, and the C / A ratio represents the mass ratio of calcium oxide to aluminum oxide.

3. The preparation method according to claim 2, characterized in that: The adjusting of slag composition comprises: adding lime, top slag modifier and low silicon pre-melted refined slag, wherein the composition of the top slag modifier is as follows by mass percentage: Al: 32-47%, CaO: 18-25%, Al2O3: 17-28%, SiO2: 3-8%, and the composition of the low silicon pre-melted refined slag is as follows by mass percentage: CaO: 40-55%, Al2O3: 35-45%, SiO2: 2-7%, MgO: 3-7%.

4. The preparation method according to claim 3, characterized in that: The components of the refined slag at the end of the LF refining include, by mass percentage, CaO: 48% to 54%, SiO2: 4.4% to 6%, P2O5: 0.02% to 0.03%, Al2O3: 31% to 35%, MgO: 6.0% to 6.9%, MnO: 0~0.15%, FeTOT: 0.15%~0.5%, and unavoidable impurities, the mass ratio of CaO / SiO2 is 8.5~12.

5. The preparation method according to claim 1, characterized in that: Before the first stage magnesium treatment is performed on the refined molten steel in the LF furnace, the method further comprises: performing soft stirring at a flow rate of 200-400 L / min for 8-12 minutes.

6. The preparation method according to claim 1, characterized in that: The RH vacuum treatment includes: the vacuum degree of the RH furnace is 5-7KPa, the vacuum treatment time is 15-20min, and the flow rate of the lifting gas is 80-100Nm 3 / h.

7. The preparation method according to claim 1, characterized in that: The chemical composition of the RH molten steel includes, by mass percentage, 0.2wt%≤C≤0.4wt%, 0.1wt%≤Si≤0.4wt%, 0.4wt%≤Mn≤2.0wt%, S≤0.0015wt%, 0.01wt%≤Ti≤0.04wt%, 0.001wt%≤B≤0.005wt%, N≤0.005wt%, and the rest is iron and other inevitable impurities.

8. The manufacturing method according to any one of claims 1 to 7, characterized in that: The RH refined molten steel is sequentially subjected to continuous casting, heating in a heating furnace, rough rolling, finish rolling and heat treatment to obtain a heat-treated steel plate.

9. A wheel steel, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. The wheel steel according to claim 9, characterized in that: The inclusions of the wheel steel are classified according to GB / T10561-2023, with Class B inclusions ≤ Grade 1.0 and Class Ds inclusions ≤ Grade 0.5; the mechanical properties of the wheel steel meet the following requirements: yield strength ≥ 1000MPa, tensile strength ≥ 1400MPa, and elongation ≥ 7%; the fatigue resistance of the wheel steel meets the following requirements: bending fatigue life ≥ 500,000 times and radial fatigue life ≥ 900,000 times.

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