Preparation method of hot-rolled round steel for high-temperature bearing

Abstract

The invention discloses a preparation method of hot-rolled round steel for a high-temperature bearing. The preparation method comprises the steps of converter smelting, LF refining, VD vacuum degassing, continuous casting, heating of a casting blank heating furnace, round steel rolling and heat treatment. The heat treatment system is that the temperature is kept at 1190 + / -20 DEG C for 4.5-5.5 hours, and air cooling is performed; the round steel comprises the following chemical components in percentage by mass: 0.70%-0.80% of C, less than or equal to 0.40% of Si, less than or equal to 0.40% of Mn, less than or equal to 0.025% of P, less than or equal to 0.015% of S, 3.80%-4.40% of Cr, 0.20%-0.80% of Mo, 1.30%-1.70% of V, 8.5%-10.0% of W and the balance of Fe and impurities. The W, Cr, V and Mo composite alloying principle is utilized, the performance of the hot-rolled round steel is remarkably improved, the hot-rolled round steel for the high-temperature bearing is produced, the overall service life of the bearing for the high-temperature environment is remarkably prolonged, and the safety of the bearing for the high-temperature environment is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, rolling and heat treatment, and in particular relates to a method for preparing hot-rolled round steel for high-temperature bearings. Background Art

[0002] As the requirements for equipment efficiency and reliability in the industrial field continue to increase, the demand for high-temperature bearings is increasing. Especially under high-temperature operating conditions, the use of high-temperature bearing steel can significantly improve equipment performance and service life. With the growing demand for high-performance vehicles, high-temperature bearings are increasingly used in turbochargers, engines and transmission systems. High-temperature bearing steel can improve vehicle performance and reduce energy consumption and emissions. Industrial machinery and equipment operating in high-temperature environments, such as steel smelting equipment, mining machinery, etc., also require high-temperature bearings to ensure the stability and durability of the equipment. High-temperature bearing steel needs to have excellent high-temperature strength, oxidation resistance, wear resistance and thermal stability. This usually requires innovations in material composition design, smelting process and heat treatment process to meet these demanding performance requirements. The development of high-temperature bearing steel has high feasibility and broad application prospects. Through technological innovation and process optimization, steel mills can enter the high-value-added material market, provide high-performance high-temperature bearing solutions for various industries, and promote industry technological progress and economic development.

[0003] Publication No. CN 114990428 A introduces the research and development of Cr-Mo-Co-W high-temperature bearing steel, focusing on its alloy composition and manufacturing process to improve tolerance and bearing application performance at high temperatures. This patent introduces a production method for GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings, emphasizing the improvement of the mechanical properties of the material and the extension of the service life of the bearing by adding specific alloying elements (W, Cr, V, Mo) and process control. This patent uses converter smelting instead of electric furnaces, and combines LF refining and VD vacuum degassing technology to reduce the impurity content and inclusions in production, making the material cleaner and significantly reducing production costs.

[0004] Publication No. CN 117821839 A introduces a large-size fine-grained high-temperature bearing steel bar and its manufacturing method, aiming to improve the comprehensive performance at high temperatures by optimizing the composition and process. This patent describes a method for preparing GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings, focusing on improving the performance of steel under high temperature conditions through the composite application of alloying elements such as W, Cr, V, Mo and simplified processes. The advantage of this patent is that it reduces production costs and improves the high-temperature strength and cleanliness of the material through simplified smelting processes and optimized alloy composition design.

[0005] Publication No. CN 106893947 A describes a method for preparing bearing steel that can withstand temperatures of 400°C, with the focus on improving the high-temperature tolerance of steel by optimizing alloy composition and heat treatment process. This patent introduces a method for preparing GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings, emphasizing the improvement of steel strength and performance at high temperatures through composite alloying of W, Cr, V, and Mo elements and simplified processes. This patent uses a simplified smelting process to significantly reduce production costs, and at the same time significantly improves the strength and cleanliness of the material through a more optimized alloy composition design. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing hot-rolled round steel for high-temperature bearings, which utilizes the composite alloying principle of W, Cr, V and Mo to significantly improve the performance of hot-rolled round steel, thereby producing GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings, thereby significantly improving the overall life and safety of bearings for high-temperature environments.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing hot-rolled round steel for high-temperature bearings, comprising: converter smelting, LF refining, VD vacuum degassing, continuous casting, heating in a casting furnace, round steel rolling, and heat treatment; wherein:

[0009] Combined blowing converter smelting ensures that the smelting materials are dry to prevent water vapor from entering the steel to produce white spots; [P] < 0.012%, [S] < 0.030%; 4.0 kg of AlMnFe deoxidizer and various high-purity alloys are added per ton for pre-deoxidation and initial adjustment of W, V, Cr, and Mo components during steel tapping, and slag retention during steel tapping is used to prevent P from returning; 2.5-4 kg of binary synthetic slag is added per ton during steel tapping; slag is blocked during steel tapping, and argon is blown throughout the steel tapping process;

[0010] In the LF furnace, the molten steel is deeply stripped and alloyed, and high-basicity slag is made to strengthen the removal of sulfur and inclusions. The refining process adopts stirring throughout the whole process.

[0011] Vacuum degree ≤ 67Pa, deep vacuum time 20min, after breaking the vacuum, feed 150m of calcium silicon wire, soft blowing time 20min, during which the molten steel shall not be exposed;

[0012] Adopt continuous casting machine, use mold protection slag, work casting speed is 1.5-1.8m / min, implement full protection casting to produce continuous casting billet, the billet enters the slow cooling pit, the slow cooling time is ≥36 hours;

[0013] The billet heating temperature is 1080~1120℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1030~1050℃, prevent overheating, overburning and decarburization, and heat up slowly to ensure uniform billet heating temperature and reduce temperature difference;

[0014] The heat treatment system is 1190±20℃ for 4.5-5.5h, followed by air cooling;

[0015] The mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C 0.70%-0.80%, Si≤0.40%, Mn≤0.40%, P≤0.025%, S≤0.015%, Cr 3.80-4.40%, Mo 0.20-0.80%, V1.30-1.70%, W 8.5-10.0%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0016] Furthermore, pay attention to the condition of the rollers, steel turning machines, guide plates, roller tables and cover plates, and ensure that they are smooth and have no sharp edges to avoid scratches and bumps on the surface of the rolled product.

[0017] Furthermore, the specification of the rolled product is φ120mm.

[0018] Furthermore, the heat treatment system is 1190 °C for 5 h and air cooling.

[0019] Furthermore, the mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C 0.76%, Si 0.29%, Mn 0.35%, P 0.017%, S 0.003%, Cr 4.29%, Mo 0.64%, V 1.58%, W 9.15%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0020] Furthermore, the mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C0.77%, Si0.30%, Mn 0.36%, P 0.013%, S 0.004%, Cr 4.28%, Mo 0.65%, V 1.57%, W 9.17%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0021] Furthermore, the mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C 0.76%, Si 0.30%, Mn 0.35%, P 0.015%, S 0.005%, Cr 4.27%, Mo 0.64%, V 1.58%, W 9.13%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0022] The C element in high-temperature bearing steel can ensure that the material has sufficient hardenability, hardness and wear resistance; the V element is a strong carbide-forming element, and the generated MC carbide is excellent in stability and hardness, so it is mainly used to improve wear resistance in high-temperature bearing steel. The Cr element is a medium-strength carbide-forming element. When added to bearing steel together with Mo, V and other elements, it can effectively control various properties. The Mo element is the main additive element for high-temperature bearing steel, which can form a certain amount of insoluble primary carbides, allowing the bearing steel to withstand high-temperature quenching close to the melting point, while generating sufficient secondary carbides to provide secondary hardening and improve wear resistance.

[0023] The invention adds W as a high-temperature resistant element to the bearing steel. The addition of W can reduce the precipitation temperature of M2C to a certain extent, and reduce the number and size of undissolved primary carbides; at the same time, it can also promote the nucleation rate of M2C and increase the number of secondary precipitations. The addition of W causes the diffraction peak of the bearing steel to shift slightly to the left, and the lattice constant increases. Part of the W element can be dissolved in the martensite matrix to enhance the solid solution strengthening, thereby improving the high-temperature strength. As a medium-strength carbide-forming element, W can combine with C to form carbides, precipitate during high-temperature tempering, and improve the secondary hardening effect. Therefore, the operating temperature and high-temperature performance of the high-temperature bearing steel are improved, and the fatigue life is improved.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are:

[0025] (1) Through the composite alloying of elements such as W, Cr, V, and Mo, the GW9Cr4V2Mo hot-rolled round steel of the present invention exhibits excellent oxidation resistance, wear resistance, and high-temperature strength under high-temperature conditions, thereby extending the service life of the bearing in a high-temperature environment and effectively reducing the maintenance cost and downtime of the equipment;

[0026] (2) The use of converter smelting combined with LF refining and VD vacuum degassing processes significantly reduces the content of impurities and inclusions in the steel and improves the cleanliness of the material, thereby greatly improving the strength, toughness, fatigue life and fracture resistance of the steel, ensuring the stable performance of the bearing under harsh conditions;

[0027] (3) By reasonably controlling the content of W element, the hot-rolled round steel of the present invention can significantly improve the secondary hardening effect during high-temperature tempering, ensure the durability and stability of the material during high-temperature operation, and further improve its reliability in use under high-stress and high-temperature environments;

[0028] (4) The present invention optimizes the preparation process, uses a converter instead of an electric furnace to reduce the preparation cost, and performs degassing and removal of inclusions to improve the cleanliness of the material, thereby significantly improving the strength and toughness of the steel and the life of the material. The preparation method is simple in process, low in energy consumption, and suitable for the preparation technology of the existing industrial equipment level. DETAILED DESCRIPTION

[0029] The preparation method of the GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings of the present invention is further described in detail below.

[0030] Embodiment: This embodiment is a preferred embodiment among various implementation modes of the present invention.

[0031] The preparation method of GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings of this embodiment comprises the following chemical components in percentage by weight: C 0.70% to 0.80%, Si≤0.40%, Mn≤0.40%, P≤0.025%, S≤0.015%, Cr 3.80 to 4.40%, Mo 0.20 to 0.80%, V 1.30 to 1.70%, W 8.5 to 10.0%, and the rest are Fe and unavoidable trace impurities, with a total mass fraction of 100%.

[0032] The preparation method of GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings in this embodiment is: converter smelting, LF refining, VD vacuum degassing, continuous casting, heating in a casting furnace, round steel rolling, and heat treatment.

[0033] Combined blowing converter smelting ensures that the smelting materials are dry to prevent water vapor from entering the steel to produce white spots; [P] < 0.012%, [S] < 0.030%; 4.0 kg of AlMnFe deoxidizer and various high-purity alloys are added per ton for pre-deoxidation and initial adjustment of W, V, Cr, and Mo components during steel tapping, and slag retention during steel tapping is used to prevent P from returning; 2.5-4 kg of binary synthetic slag is added per ton during steel tapping; slag is blocked during steel tapping, and argon is blown throughout the steel tapping process;

[0034] In the LF furnace, the molten steel is deeply stripped and alloyed, and high-basicity slag is made to strengthen the removal of sulfur and inclusions. The refining process adopts stirring throughout the whole process.

[0035] Vacuum degree ≤ 67Pa, deep vacuum time 20min, after breaking the vacuum, feed 150m of calcium silicon wire, soft blowing time 20min, during which the molten steel shall not be exposed;

[0036] Adopt continuous casting machine, use mold protection slag, work casting speed is 1.5-1.8m / min, implement full protection casting to produce continuous casting billet, the billet enters the slow cooling pit, the slow cooling time is ≥36 hours;

[0037] The billet heating temperature is 1080~1120℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1030~1050℃, prevent overheating, overburning and decarburization, and heat up slowly to ensure uniform billet heating temperature and reduce temperature difference;

[0038] Pay attention to the condition of the rolls, steel turning machine, guide plate, roller table and cover plate, and ensure that they are smooth without sharp edges and corners to avoid scratches and dents on the surface of the rolled piece. The specification of the rolled product is φ120mm. The heat treatment system is 1190℃ for 5h and air cooling.

[0039] The GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings produced by the chemical composition and process flow of the present invention can achieve Rm≤910MPa in the longitudinal mechanical properties, HBW≤260 in the annealed state, and a decarburization layer depth≤2mm, meeting the standard requirements, and there is no crack, scar, fold or inclusion on the steel surface.

[0040] Table 1 shows the chemical compositions of three embodiments and four comparative examples of the present invention, and Tables 2 and 3 further illustrate the present invention.

[0041] Table 1 Chemical composition of various examples of GW9Cr4V2Mo hot-rolled round steel for high temperature bearings (mass percentage / %)

[0042]

[0043]

[0044] Table 2 Mechanical properties of various examples of GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings

[0045]

[0046] Table 3 Non-metallic inclusions and austenite grain size of various examples of GW9Cr4V2Mo hot-rolled round steel for high-temperature bearings

[0047]

[0048]

[0049] It can be seen from Tables 1 to 3 that: (1) Compared with the embodiment, the strength and wear resistance of the material in Comparative Example 1 are significantly reduced, especially the creep resistance at high temperature is significantly reduced. This is because the lack of Mo greatly limits the hardening ability of the material under high temperature conditions. In addition, the low content of Cr leads to insufficient oxidation resistance; (2) The lack of V element in Comparative Example 2 will cause the material to be unable to form effective carbides, especially under high temperature conditions, the hardness and wear resistance are significantly reduced. Compared with the embodiment, the V element plays a key role in stability and high temperature strengthening, and its addition can significantly improve the comprehensive performance of the material under extreme conditions; (3) Compared with the embodiment, the hardness of Comparative Example 3 is improved, but the toughness is sharply reduced, and poor fatigue resistance is shown in fatigue tests. Under high temperature environment, due to the brittleness of the carbide phase, the material is more likely to crack and break, thereby affecting the service life of the bearing; (4) Comparative Example 4 The comparative example proves that the Mo element is crucial to improving the wear resistance and heat resistance at high temperature. Compared with the embodiment, the reduction of Mo causes the comprehensive mechanical properties of the material to decline, especially under high temperature working conditions, the performance is far inferior to the embodiment.

[0050] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing hot-rolled round steel for high-temperature bearings, characterized in that: include: Converter smelting, LF refining, VD vacuum degassing, continuous casting, billet heating furnace heating, round steel rolling, heat treatment; including: Combined blowing converter smelting ensures that the smelting materials are dry to prevent water vapor from entering the steel to produce white spots; [P] < 0.012%, [S] < 0.030%; 4.0 kg of AlMnFe deoxidizer and various high-purity alloys are added per ton for pre-deoxidation and initial adjustment of W, V, Cr, and Mo components during steel tapping, and slag retention during steel tapping is used to prevent P from returning; 2.5-4 kg of binary synthetic slag is added per ton during steel tapping; slag is blocked during steel tapping, and argon is blown throughout the steel tapping process; In the LF furnace, the molten steel is deeply stripped and alloyed, and high-basicity slag is made to strengthen the removal of sulfur and inclusions. The refining process adopts stirring throughout the whole process. Vacuum degree ≤ 67Pa, deep vacuum time 20min, after breaking the vacuum, feed 150m of calcium silicon wire, soft blowing time 20min, during which the molten steel shall not be exposed; Adopt continuous casting machine, use mold protection slag, work casting speed is 1.5-1.8m / min, implement full protection casting to produce continuous casting billet, the billet enters the slow cooling pit, the slow cooling time is ≥36 hours; The billet heating temperature is 1080~1120℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1030~1050℃, prevent overheating, overburning and decarburization, and heat up slowly to ensure uniform billet heating temperature and reduce temperature difference; The heat treatment system is 1190±20℃ for 4.5-5.5h, followed by air cooling; The mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C 0.70%-0.80%, Si≤0.40%, Mn≤0.40%, P≤0.025%, S≤0.015%, Cr 3.80-4.40%, Mo 0.20-0.80%, V1.30-1.70%, W 8.5-10.0%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

2. The method for preparing hot-rolled round steel for high-temperature bearings according to claim 1, characterized in that: Pay attention to the condition of the rollers, steel turning machines, guide plates, roller tables and cover plates, and ensure that they are smooth and have no sharp edges to avoid scratches and bumps on the surface of the rolled product.

3. The method for preparing hot-rolled round steel for high-temperature bearings according to claim 1, characterized in that: The specification of the rolled product is φ120mm.

4. The method for preparing hot-rolled round steel for high-temperature bearings according to claim 1, characterized in that: The heat treatment system is 1190℃ for 5h and air cooling.

5. The method for preparing hot-rolled round steel for high-temperature bearings according to claim 1, characterized in that: The mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C 0.76%, Si 0.29%, Mn 0.35%, P 0.017%, S0.003%, Cr 4.29%, Mo 0.64%, V 1.58%, W 9.15%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

6. The method for preparing hot-rolled round steel for high-temperature bearings according to claim 1, characterized in that: The mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C 0.77%, Si 0.30%, Mn 0.36%, P 0.013%, S0.004%, Cr 4.28%, Mo 0.65%, V 1.57%, W 9.17%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

7. The method for preparing hot-rolled round steel for high-temperature bearings according to claim 1, characterized in that: The mass percentage of the chemical composition of the hot-rolled round steel for high-temperature bearings includes: C 0.76%, Si 0.30%, Mn 0.35%, P 0.015%, S0.005%, Cr 4.27%, Mo 0.64%, V 1.58%, W 9.13%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

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