Method for improving impact wear resistance of steel through retained austenite and application

Abstract

The invention relates to the technical field of steel smelting, in particular to a method for improving the impact wear resistance of steel through retained austenite and application. The method comprises the following steps: carrying out desulfurization treatment on molten iron to obtain molten iron with the sulfur content of less than 0.02%, carrying out converter blowing, LF refining, RH refining and continuous casting to obtain a continuous casting billet, and sequentially carrying out austenitizing, quenching and partitioning to obtain steel, the content of retained austenite in the steel is 5-10%, the steel shows good impact wear resistance, the retained austenite exists in the form of thin films and thin sheets, and the content of the residual austenite in the form of thin films and thin sheets is 5-10%. By means of partitioning, the steel has good mechanical stability, under stress strain, most retained austenite is subjected to phase change or only partially transformed, strain energy can be absorbed, cracks are branched or passivated, crack propagation resistance is increased, and the wear resistance of the steel is improved.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a method and application of improving the impact and wear resistance of steel by using residual austenite. Background Art

[0002] With the continuous progress of science and technology and society, the service conditions of mechanical parts are becoming more and more severe. They must not only have high wear resistance, but also be able to withstand impact and high stress strain to extend the service life of the equipment.

[0003] However, at present, domestic steel mills have insufficient wear resistance of wear-resistant steel due to narrow composition, difficulty in composition, uneven organization control, etc., which affects the use of materials, especially in high-strength wear-resistant engineering machinery steel.

[0004] China is developing microalloyed and refined wear-resistant steel to improve the quality and performance of steel materials. This technology enhances wear resistance by refining grains and adding trace alloying elements. However, the application of this technology in wear-resistant materials is still relatively lagging and requires further research and development. ([1] Lu Jing, Ouyang Hang, Li Yong, et al. Research and development status of wear-resistant materials and technologies at home and abroad [J]. Materials Science, 2018, 8(9): 11.)

[0005] The performance of ultra-high strength and toughness steel is affected by many factors such as chemical composition, processing process, and internal microstructural characteristics. At present, domestic production technology and quality control are unstable, and there are problems such as non-metallic inclusions and internal cracks, which limit its use (Luo Haiwen, Shen Guohui, Haiwen LUO, et al. Research progress and prospects of ultra-high strength and high toughness steel [J]. Acta Metallurgica Sinica, 2020, 56(4): 19.) Summary of the invention

[0006] In order to solve the above problems, the present invention provides a method and application for improving the impact wear resistance of steel by using retained austenite. The method provided by the present invention improves the impact wear resistance of steel.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for improving the impact wear resistance of steel by using retained austenite, comprising the following steps:

[0009] 1) desulfurizing the molten iron to obtain molten iron with a sulfur content of less than 0.02%;

[0010] 2) blowing the molten iron with a sulfur content of less than 0.02% obtained in step 1) through a converter to obtain molten steel, wherein the sulfur content of the molten steel is less than 0.008%, the nitrogen content is less than 0.005%, and the amount of slag discharged during the converter tapping process is not more than 3.5 kg / t;

[0011] 3) subjecting the molten steel obtained in step 2) to LF refining, RH refining and continuous casting in sequence to obtain a continuously cast billet;

[0012] During the LF refining process, the content of ferrous oxide in the top slag is controlled to be less than 1%;

[0013] During the RH refining process, the vacuum time is controlled to be no less than 8 minutes;

[0014] During the continuous casting process, the molten steel level in the crystallizer is kept stable, and the fluctuation of the liquid level is within ±2.0 mm;

[0015] 4) subjecting the continuous casting material obtained in step 3) to austenitization, quenching and partitioning in sequence to obtain a steel material, wherein the steel material has a C content of 0.3% to 0.4%, a Mn content of 1.0% to 1.2%, a Si content of 0.6% to 1.0%, a Ti content of 0.2% to 0.4%, and a retained austenite content of 5% to 10%;

[0016] The austenitizing temperature is 900-920°C and the time is not less than 30 minutes;

[0017] The quenching temperature is 200-250°C and the time is 1-5 minutes;

[0018] The temperature of the partitioning is 280-350°C and the time is 30-60 minutes;

[0019] All the above are mass percentages.

[0020] Preferably, the conditions for the desulfurization treatment in step 1) include: using KR desulfurization treatment, adding no less than 10 kg of desulfurizer per ton of iron, and a stirring rate of 90 to 120 rpm.

[0021] Preferably, the conditions for converter blowing in step 2) include: the temperature of molten iron entering the furnace is ≥1230°C, the material entering the furnace is clean and dry, the binary basicity of the converter final slag is controlled at 3.0-4.0, the amount of slag is strictly controlled during steel tapping, and the amount of slag is ≤3.5Kg / ton of steel, and the converter end point target is: C content is 0.08-0.14%, P content is ≤0.005%, S content is ≤0.005%, T=1580-1660°C, all are mass percentages.

[0022] Preferably, the conditions of LF refining in step 3) include: argon is blown from the bottom throughout the LF refining process, the argon pressure is 0.4-0.6 MPa when blowing is started, and drops to 0.2-0.3 MPa after blowing, aluminum particles or calcium carbide are added to the slag surface, the top slag is deoxidized, the mass percentage of ferrous oxide in the top slag is controlled to be less than 1%, the treatment cycle of the molten steel entering the LF furnace is not more than 50 minutes, the temperature shall not be greater than 80°C at one time, and the error of the hit rate of the temperature rise is ≤±10%.

[0023] Preferably, the conditions of RH refining in step 3) include: ensuring that the minimum vacuum degree of the RH furnace is ≤133pa before treatment, the vacuum tank and the immersion tube are hot and in good condition, the RH vacuum cycle time is 8 to 30 minutes, the circulation flow rate is opened to the maximum after 2 minutes of circulation, aluminum supplementation is prohibited during the RH treatment process, the RH cycle is >6 minutes after the last batch of materials is added, and the calming time of the molten steel after breaking the air is >15 minutes.

[0024] Preferably, the conditions for continuous casting in step 3) include: after normal pouring, stabilizing the liquid level of a drawing speed tundish according to the production situation: the molten steel level in the tundish is 1000±100mm, and the height of the remaining steel in the last tundish is >200mm when the pouring is stopped; using a double layer of pure steel covering agent (lower layer) and an acid covering agent (upper layer), and adding them reasonably to prevent the molten steel from being exposed; it is strictly forbidden to cast steel without long nozzle sealing argon, stopper rod argon, upper nozzle gas and inter-plate argon, and the back pressure of the long nozzle sealing argon and the inter-plate argon should be greater than 0Mpa; the pure steel covering agent is the lower layer, and the acid covering agent is the upper layer.

[0025] The present invention also provides application of the method described in the above technical solution in improving the impact and wear resistance of steel.

[0026] The present invention also provides application of the method described in the above technical solution in improving the yield strength and / or tensile strength of steel.

[0027] The present invention also provides application of the method described in the above technical solution in improving the impact energy and / or elongation of steel.

[0028] Beneficial effects of the present invention:

[0029] The present invention adopts a reasonable component design and Q&P process to obtain a martensitic matrix structure, and contains a certain amount of residual austenite, the residual austenite content is about 8% to 10%, and exhibits good impact wear resistance. The residual austenite in the form of thin films and flakes has good mechanical stability through partitioning. Under stress and strain, most of the residual austenite undergoes phase transformation or only part of the transformation, which can absorb strain energy and cause cracks to branch or passivate, increase crack propagation resistance, and improve its wear resistance. At the same time, the tensile strength of the wear-resistant steel is greater than 1500MPa, the strength-plasticity product is ≥25GPa﹪, and the impact energy is greater than 70J / cm2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0031] Figure 1 A heat treatment process diagram of an embodiment of the present invention;

[0032] Figure 2 This is the microstructure diagram of the steel prepared in Example 1, a is the IPF result; b is the phase distribution result, FCC represents the residual austenite structure, which accounts for about 5%, and can effectively improve the impact resistance of the material. DETAILED DESCRIPTION

[0033] The present invention provides a method for improving the impact wear resistance of steel by using retained austenite, comprising the following steps:

[0034] 1) desulfurizing the molten iron to obtain molten iron with a sulfur content of less than 0.02%;

[0035] 2) blowing the molten iron with a sulfur content of less than 0.02% obtained in step 1) through a converter to obtain molten steel, wherein the sulfur content of the molten steel is less than 0.008%, the nitrogen content is less than 0.005%, and the amount of slag discharged during the converter tapping process is not more than 3.5 kg / t;

[0036] 3) subjecting the molten steel obtained in step 2) to LF refining, RH refining and continuous casting in sequence to obtain a continuously cast billet;

[0037] During the LF refining process, the content of ferrous oxide in the top slag is controlled to be less than 1%;

[0038] During the RH refining process, the vacuum time is controlled to be no less than 8 minutes;

[0039] During the continuous casting process, the molten steel level in the crystallizer is kept stable, and the fluctuation of the liquid level is within ±2.0 mm;

[0040] 4) subjecting the continuous casting material obtained in step 3) to austenitization, quenching and partitioning in sequence to obtain a steel material, wherein the steel material has a C content of 0.3% to 0.4%, a Mn content of 1.0% to 1.2%, a Si content of 0.6% to 1.0%, a Ti content of 0.2% to 0.4%, and a retained austenite content of 5% to 10%;

[0041] The austenitizing temperature is 900-920°C and the time is not less than 30 minutes;

[0042] The quenching temperature is 200-250°C and the time is 1-5 minutes;

[0043] The temperature of the partitioning is 280-350°C and the time is 30-60 minutes;

[0044] All the above are mass percentages.

[0045] The present invention desulfurizes molten iron to obtain molten iron with a sulfur content of less than 0.02%, which is a mass percentage. The present invention does not specifically limit the conditions of the desulfurization treatment, and those skilled in the art can adopt conventional methods. For example, in the present invention, the conditions of the desulfurization treatment preferably include: using KR desulfurization treatment, adding no less than 10 kg of desulfurizer per ton of iron, and stirring at a rate of 90 to 120 rpm. The present invention does not specifically limit the type of the desulfurizer, and those skilled in the art can adopt conventional methods, such as lime and calcium fluoride, and the mass ratio of lime to calcium fluoride is 9:1. In the present invention, the temperature of the molten iron is preferably above 1310°C.

[0046] The present invention obtains molten iron with a sulfur content of less than 0.02% by blowing in a converter to obtain molten steel, wherein the sulfur content in the molten steel is less than 0.008%, the nitrogen content is less than 0.005%, and the amount of slag in the converter steel-making process is not more than 1.5kg / t, all of which are mass percentages. The present invention does not specifically limit the conditions for converter hammering, and those skilled in the art can adopt conventional methods. For example, in the present invention, the conditions for converter blowing preferably include: the temperature of the molten iron entering the furnace is ≥1230°C, the entering material is clean and dry, the binary basicity of the converter final slag is controlled at 3.0-4.0, the amount of slag is strictly controlled during steel-making, and the amount of slag is ≤3.5Kg / ton of steel, and the converter terminal target: C content is 0.08-0.14%, P content is ≤0.005%, S content is ≤0.005%, T=1580-1660°C, all of which are mass percentages.

[0047] The present invention sequentially subject the obtained molten steel to LF refining, RH refining and continuous casting to obtain a continuous casting billet; during the LF refining process, the content of ferrous oxide in the top slag is controlled to be less than 1%, which is a mass percentage content; during the RH refining process, the vacuum time is controlled to be not less than 8min; during the continuous casting process, the liquid level of the molten steel in the crystallizer is kept stable, and the liquid level fluctuation is within ±2.0mm. The present invention does not specifically limit the conditions of the LF refining, RH refining and continuous casting, and those skilled in the art can adopt conventional methods. For example, in the present invention, the conditions of the LF refining preferably include: argon is blown throughout the LF refining process, and the argon pressure is 0.4-0.6MPa when the blowing is started, and it is reduced to 0.2-0.3MPa after the blowing is started, aluminum particles or calcium carbide are added to the slag surface, and the top slag is deoxidized, and the mass percentage content of ferrous oxide in the top slag is controlled to be less than 1%, and the molten steel treatment cycle entering the LF furnace treatment is not more than 50min, and the temperature rise shall not be greater than 80°C at one time, and the error of the hit rate of the temperature rise is ≤±10%. In the present invention, the conditions for RH refining preferably include: ensuring that the minimum vacuum degree of the RH furnace is ≤133pa before treatment, the vacuum tank and the immersion tube are hot and in good condition, the RH vacuum cycle time is 8 to 30 minutes, the circulation flow rate is opened to the maximum after 2 minutes of circulation, aluminum supplementation is prohibited during the RH treatment process, the RH cycle is >6 minutes after the last batch of materials is added, and the calming time of the molten steel after breaking the air is >15 minutes. In the present invention, the conditions for continuous casting preferably include: after normal pouring, stabilize the liquid level of a drawing speed tundish according to the production situation: the liquid level of molten steel in the tundish is 1000±100mm, and the height of the remaining steel in the last tundish is>200mm when the pouring is stopped; double-layer covering with pure steel covering agent (lower layer) and acid covering agent (upper layer) is used, and reasonable addition is made to prevent the molten steel from being exposed; it is strictly forbidden to cast steel without long nozzle sealing argon, plug rod argon, upper nozzle gas and argon between plates, and the back pressure of long nozzle sealing argon and argon between plates should be greater than 0Mpa; the pure steel covering agent is the lower layer, and the acid covering agent is the upper layer. The present invention preferably prevents secondary oxidation of the tundish and the crystallizer, controls the light pressure at the end of continuous casting, and reduces the segregation of the slab.

[0048] The invention sequentially austenitizes, quenches and partitions the obtained continuous casting material to obtain a steel material, wherein the C content of the steel material is 0.3% to 0.4%, the Mn content is 1.0% to 1.2%, the Si content is 0.6% to 1.0%, the Ti content is 0.2% to 0.4%, and the residual austenite content is 5% to 10%; the austenitizing temperature is 900 to 920°C and the time is not less than 30 minutes; the quenching temperature is 200 to 250°C and the time is 1 to 5 minutes; the partitioning temperature is 280 to 350°C and the time is 30 to 60 minutes; all the above are mass percentages. In the present invention, the composition design purpose of the steel is as follows: the C content is between 0.3% and 0.4%, while considering the weldability of the wear-resistant steel and the stability of the retained austenite; in order to ensure the rust resistance of the steel and the stability of the retained austenite, the Mn content is controlled within 1.0% to 1.2%; in order to inhibit the precipitation of cementite and stabilize the austenite at room temperature, a certain amount of Si is added to the wear-resistant steel, and its content is controlled within 0.6% to 1.0%; in order to further improve the strength and wear resistance of the steel, a certain amount of microalloying element Ti is added during the refining process, and its content is controlled within 0.2% to 0.4%.

[0049] The present invention also provides application of the method described in the above technical solution in improving the impact and wear resistance of steel.

[0050] The present invention also provides application of the method described in the above technical solution in improving the yield strength and / or tensile strength of steel.

[0051] The present invention also provides application of the method described in the above technical solution in improving the impact energy and / or elongation of steel.

[0052] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] A method for improving the impact wear resistance of steel by using retained austenite, comprising the following steps:

[0055] (1) Steel composition design: C content 0.32%, Mn content 1.15%, Si content 0.65%, Ti content 0.28%.

[0056] Composition design purpose: C content is between 0.3% and 0.4%, taking into account the weldability of wear-resistant steel and the stability of retained austenite;

[0057] In order to ensure the rust resistance of steel and the stability of retained austenite, the Mn content is controlled at 1.0% to 1.2%;

[0058] In order to inhibit the precipitation of cementite and stabilize the austenite at room temperature, a certain amount of Si is added to the wear-resistant steel, and its content is controlled at 0.6% to 1.0%;

[0059] In order to further improve the strength and wear resistance of the steel, a certain amount of microalloying element Ti is added during the refining process, and its content is controlled at 0.2% to 0.4%.

[0060] (2) Smelting process: hot metal pretreatment → converter → LF → RH refining → continuous casting to obtain continuous casting billets. The smelting process adopts the crystalline steel smelting method, and prevents secondary oxidation during the continuous casting process to minimize the number and size of non-metallic inclusions in the steel. The inclusion rating in the steel is ≤1.0;

[0061] Smelting process: The molten iron is first treated with KR desulfurization to ensure that the sulfur content of the molten iron entering the converter is 0.018%, and the molten iron temperature is ≥1310℃. After the converter blowing, the sulfur content in the molten steel is required to be ≤0.008%, and the nitrogen content is ≤0.005%. The amount of slag is controlled during the converter tapping process, which is not more than 1.5kg / t. During the LF refining process, the (FeO) content in the top slag is controlled to be ≤1% to avoid excessive oxidation of the slag. During the RH refining process, the vacuum time is controlled to be not less than 8min to promote the floating of large-sized inclusions as much as possible. During the continuous casting process, the liquid level of the molten steel in the crystallizer is kept stable, and the liquid level fluctuation is within ±2.0mm. Do a good job of preventing secondary oxidation of the tundish and crystallizer. Control the light pressure at the end of continuous casting to reduce slab segregation.

[0062] The conditions for desulfurization treatment are: KR desulfurization treatment is used, the amount of desulfurizer (lime and calcium fluoride, mass ratio is 9:1) added per ton of iron is 15kg, and the stirring rate is 90-120rpm;

[0063] The conditions for converter blowing are: the temperature of the molten iron entering the furnace is 1250°C, the materials entering the furnace are clean and dry, the binary basicity of the converter final slag is controlled at 3.5, the amount of slag is strictly controlled during steel tapping, and the amount of slag is 2.5Kg / ton of steel, the converter end target: C content is 0.11%, P content is 0.004%, S content is 0.003%, T=1610°C, all are mass percentages;

[0064] The conditions of LF refining are as follows: argon is blown from the bottom throughout the LF refining process. The argon pressure is 0.5MPa when blowing is started and drops to 0.25MPa after blowing. Aluminum particles or calcium carbide are added to the slag surface to deoxidize the top slag. The mass percentage of ferrous oxide in the top slag is controlled to be 0.85%. The treatment cycle of the molten steel entering the LF furnace is 46 minutes, and the temperature shall not be higher than 80°C at one time.

[0065] The conditions for RH refining are: before treatment, the minimum vacuum degree of the RH furnace is ensured to be 100pa, the vacuum tank and the immersion tube are hot and in good condition, the RH vacuum cycle time is 15min, the circulation flow rate is opened to the maximum after 2min of circulation, aluminum is prohibited during the RH treatment process, the RH cycle is broken for 8min after the last batch of materials is added, and the calming time of the molten steel after breaking the vacuum is 20min;

[0066] The continuous casting conditions are as follows: after pouring is started normally, stabilize the tundish liquid level according to the production situation: the tundish steel liquid level is 980mm, and the final tundish residual steel height is 250mm when pouring is stopped; use double-layer covering of pure steel covering agent (lower layer) and acid covering agent (upper layer) to prevent molten steel from being exposed; it is strictly forbidden to cast steel without argon gas sealing in the long nozzle, argon gas in the plug rod, gas in the upper nozzle and argon gas between the plates, and the back pressure of argon gas sealing in the long nozzle and argon gas between the plates are both 0.1Mpa;

[0067] (3) Heat treatment process: The continuous casting billet obtained in step (2) is subjected to a quenching and partitioning process (Q&P), which is as follows: the austenitizing temperature (AT) is 920°C for a time of not less than 30 min, the quenching temperature (QT) is controlled at 240°C for a time of 3 min, and the partitioning temperature (PT) is controlled at 320°C for a time of 50 min. After the Q&P treatment, the content of retained austenite in the steel is 5.15%.

[0068] (4) Through the above process, the mechanical properties of the product can reach: hardness of 600HBW, tensile strength of 1520MPa, strength-plasticity product ≥25GPa﹪, impact energy of 72.3J / cm 2 , the elongation is 21.5%.

[0069] Hardness test: The national standard is GB / T 24523-2009 "Metallic Materials Rapid Indentation (Brinell) Hardness Test Method";

[0070] Tensile strength test and elongation: The national standard is GB / T 228.1-2021 "Tensile test of metallic materials Part 1: Room temperature test method";

[0071] Strength-plasticity product: Calculate the strength-plasticity product based on tensile strength and elongation: Strength-plasticity product = tensile strength × elongation;

[0072] Impact energy: The national standard is GB / T 229-2020 "Charpy Pendulum Impact Test Method for Metallic Materials".

[0073] Comparative Example 1

[0074] Please provide detailed comparative examples. Heat treatment process: quenching temperature 920℃, tempering temperature 300℃.

[0075] Table 1 Comparison of steel properties between Example 1 and Comparative Example 1

[0076] Yield strength / MPa Tensile strength / MPa Elongation, % <![CDATA[Impact energy / J / cm 2 > Example 1 1270 1520 21.5 72.3 Comparative Example 1 1222 1418 13.6 51.5

[0077] Table 2 Comparison of steel composition between Example 1 and Comparative Example 1

[0078] element C，％ Si, % Mn, % Ti, % Nb, % Example 1 0.32 0.65 1.15 0.28 — Comparative Example 1 0.25 0.30 0.95 0.02 0.04

[0079] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for improving the impact wear resistance of steel by using retained austenite, characterized in that: The following steps are involved: 1) desulfurizing the molten iron to obtain molten iron having a sulfur content of less than 0.02%; 2) blowing the molten iron with a sulfur content of less than 0.02% obtained in step 1) through a converter to obtain molten steel, wherein the sulfur content of the molten steel is less than 0.008%, the nitrogen content is less than 0.005%, and the amount of slag discharged during the converter tapping process is not more than 3.5 kg / t; 3) subjecting the molten steel obtained in step 2) to LF refining, RH refining and continuous casting in sequence to obtain a continuously cast billet; In the LF refining process, the content of ferrous oxide in the top slag is controlled to be less than 1%; During the RH refining process, the vacuum time is controlled to be no less than 8 minutes; During the continuous casting process, the molten steel level in the crystallizer is kept stable, and the fluctuation of the liquid level is within ±2.0 mm; 4) subjecting the continuous casting material obtained in step 3) to austenitization, quenching and partitioning in sequence to obtain a steel material, wherein the steel material has a C content of 0.3% to 0.4%, a Mn content of 1.0% to 1.2%, a Si content of 0.6% to 1.0%, a Ti content of 0.2% to 0.4%, and a retained austenite content of 5% to 10%; The austenitizing temperature is 900-920°C and the time is not less than 30 minutes; The quenching temperature is 200-250°C and the time is 1-5 minutes; The temperature of the partitioning is 280-350°C and the time is 30-60 minutes; All the above are mass percentages.

2. The method according to claim 1, characterized in that The conditions of the desulfurization treatment in step 1) include: using KR desulfurization treatment, adding a desulfurizer in an amount of not less than 10 kg per ton of iron, and a stirring rate of 90 to 120 rpm.

3. The method according to claim 1, characterized in that The conditions for converter blowing in step 2) include: the temperature of molten iron entering the furnace is ≥1230°C, the material entering the furnace is clean and dry, the binary basicity of the converter final slag is controlled at 3.0-4.0, the amount of slag is strictly controlled during steel tapping, and the amount of slag is ≤3.5Kg / ton of steel, and the converter end point target is: C content is 0.08-0.14%, P content is ≤0.005%, S content is ≤0.005%, T=1580-1660°C, all of which are mass percentages.

4. The method according to claim 1, characterized in that The conditions of LF refining in step 3) include: blowing argon from the bottom throughout the LF refining process, the argon pressure when blowing is started is: 0.4-0.6MPa, and it drops to 0.2-0.3MPa after blowing, adding aluminum particles or calcium carbide on the slag surface, deoxidizing the top slag, controlling the mass percentage of ferrous oxide in the top slag to be less than 1%, the treatment cycle of the molten steel entering the LF furnace is not more than 50min, the temperature shall not be higher than 80°C at one time, and the error of the hit rate of the temperature increase is ≤±10%.

5. The method according to claim 1, characterized in that: The conditions of RH refining in step 3) include: ensuring that the minimum vacuum degree of the RH furnace is ≤133pa before treatment, the vacuum tank and the immersion tube are hot and in good condition, the RH vacuum cycle time is 8 to 30 minutes, the circulation flow rate is opened to the maximum after 2 minutes of circulation, aluminum supplementation is prohibited during the RH treatment process, the RH cycle is >6 minutes after the last batch of materials is added, and the calming time of the molten steel after breaking the air is >15 minutes.

6. The method according to claim 1, characterized in that The conditions of step 3) continuous casting include: after normal pouring, stabilizing the liquid level of the tundish according to the production situation: the liquid level of the molten steel in the tundish is 1000±100mm, and the height of the remaining steel in the last tundish is>200mm when the pouring is stopped; using a double layer of pure steel covering agent and an acidic covering agent, and adding them reasonably to prevent the molten steel from being exposed; it is strictly forbidden to cast steel without argon gas sealed by a long water inlet, argon gas sealed by a stopper rod, gas on the upper water inlet, and argon gas between plates, and the back pressure of the argon gas sealed by the long water inlet and the argon gas between plates should be greater than 0Mpa; the pure steel covering agent is the lower layer, and the acidic covering agent is the upper layer.

7. Use of the method according to any one of claims 1 to 6 in improving the impact and wear resistance of steel.

8. Use of the method according to any one of claims 1 to 6 in improving the yield strength and / or tensile strength of steel.

9. Use of the method according to any one of claims 1 to 6 in improving the impact energy and / or elongation of steel.

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