Preparation method of high-cleanliness GW18Cr5V hot-rolled round steel for high-temperature bearing

Abstract

The invention discloses a preparation method of high-cleanliness GW18Cr5V hot-rolled round steel for a high-temperature bearing, which comprises the steps of converter smelting, LF (ladle furnace) refining, VD (vacuum degassing), continuous casting, heating of a casting blank heating furnace, round steel rolling and heat treatment, and the GW18Cr5V hot-rolled round steel comprises the following chemical components in percentage by mass: 0.70-0.80% of C, 0.15-0.35% of Si, less than or equal to 0.40% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 4.00-5.00% of Cr, 1.00-1.50% of V, 17.5-19.0% of W and the balance of Fe and impurities. The W, Cr and V composite alloying principle is utilized, the performance of the hot-rolled round steel is remarkably improved, the size of steel type inclusions is controlled through low P and S, and then the overall service life of the bearing used in the high-temperature environment is remarkably prolonged, and the safety of the bearing used in the high-temperature environment is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of smelting, rolling and heat treatment, and in particular relates to a preparation method of GW18Cr5V hot-rolled round steel for high-cleanliness and 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 invented a Cr-Mo-Co-W high-temperature bearing steel and its preparation method, introduced its raw material composition and the role of each element, and described in detail the preparation process including smelting, forging, pretreatment and quenching and tempering heat treatment and the process parameters of each stage. This patent introduces a GW18Cr5V brand high-cleanliness hot-rolled round steel for high-temperature bearings and its preparation method, introduced its chemical composition and the role of each element, and described in detail the preparation process including converter smelting, LF refining, VD vacuum degassing, continuous casting, billet heating furnace heating, round steel rolling, heat treatment and the process parameters of each stage. The GW18Cr5V composition design and corresponding preparation process of the steel introduced in this patent are unique, and may have better performance in improving steel cleanliness, refining carbides and controlling inclusions, so as to meet the high performance requirements of high-temperature bearing steel.

[0004] Publication No. CN 117821839 A introduces a large-size fine-grained high-temperature bearing steel bar and its manufacturing method, and introduces its composition, performance characteristics, and manufacturing steps including smelting, homogenization treatment, hot processing forming, annealing heat treatment, and quenching and tempering treatment. This patent introduces a preparation method for GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings, involving composition, process and effect, and preparing hot-rolled round steel that meets the requirements by controlling the process. This patent has more detailed control over the process in the preparation method, and clearly explains the composition and effect, which is conducive to better realizing the preparation of high-temperature bearing steel with specific performance.

[0005] Publication No. CN 113564317 A introduces a heat treatment method for controlling the structure and properties of high-temperature bearing steel (8Cr4Mo4V steel), including spheroidizing annealing, vacuum isothermal quenching (two methods) and three tempering treatments, which can improve the comprehensive properties of the steel such as impact toughness, Rockwell hardness, and tensile strength. This patent introduces a preparation method for GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings, including converter smelting, LF refining, VD vacuum degassing and other processes, and improves the performance of the round steel by controlling the composition and process. This patent proposes a new composition design and preparation method for high-temperature bearing steel, and the preparation process involves fine control of multiple links, providing different ideas and methods for improving the performance of high-temperature bearing steel. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation method of GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings, which utilizes the composite alloying principle of W, Cr and V to significantly improve the performance of the hot-rolled round steel, and utilizes low P and S to control the size of steel inclusions, thereby producing high-cleanliness high-temperature bearing hot-rolled round steel with a grade of GW18Cr5V, thereby significantly improving the overall life and safety of bearings used in high-temperature environments.

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

[0008] The present invention discloses a method for preparing GW18Cr5V hot-rolled round steel for high-cleanliness 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] < 0.008%, [S] < 0.030%; 3.8-4.2 kg (preferably 4.0 kg) of AlMnFe deoxidizer and various high-purity alloys are added per ton of steel for pre-deoxidation and initial adjustment of W, V, and Cr components, and slag retention is used to prevent P from returning; 2.5-4 kg of binary synthetic slag is added per ton of steel 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 1120~1170℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1050~1100℃, prevent overheating, overburning and decarburization, heat up slowly, ensure the billet heating temperature is uniform, and reduce the temperature difference; the final rolling temperature is 850~950℃;

[0014] The heat treatment system is 1250℃ for 1h and oil cooling;

[0015] The mass percentage of the chemical composition of the GW18Cr5V hot-rolled round steel includes: C 0.70%-0.80%, Si 0.15-0.35%, Mn≤0.40%, P≤0.010%, S≤0.005%, Cr 4.00-5.00%, V 1.00-1.50%, W 17.5-19.0%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0016] Furthermore, the specification of the rolled product is φ120mm.

[0017] Furthermore, the mass percentage of the chemical composition of the GW18Cr5V hot-rolled round steel includes: C 0.77%, Si 0.26%, Mn 0.25%, P 0.007%, S 0.003%, Cr 4.49%, V 1.28%, W 18.15%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0018] Furthermore, the mass percentage of the chemical composition of the GW18Cr5V hot-rolled round steel includes: C 0.78%, Si 0.27%, Mn 0.26%, P 0.008%, S 0.002%, Cr 4.48%, V 1.27%, W 18.17%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0019] Furthermore, the mass percentage of the chemical composition of the GW18Cr5V hot-rolled round steel includes: C 0.77%, Si 0.26%, Mn 0.25%, P 0.006%, S 0.003%, Cr 4.51%, V 1.28%, W 18.13%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0020] Furthermore, the longitudinal mechanical properties of the prepared hot-rolled round steel meet the following requirements: Rm≤950MPa, Brinell hardness HBW≤269 in the annealed state, depth of decarburization layer ≤2mm, meeting the standard requirements, and there are no cracks, scars, folds or inclusions on the steel surface.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] (1) By adding alloying elements such as Cr, V, and W, it is possible to ensure that the steel still has excellent performance under high load and complex stress conditions. Chromium, vanadium, and tungsten can work together to refine the organizational structure, reduce harmful inclusions and grain boundary embrittlement in the steel, and prevent brittle cracking or fatigue failure of the steel in a high temperature environment;

[0023] (2) By strictly controlling the content of P and S, the cleanliness of steel can be effectively improved and the impact of harmful inclusions on the microstructure and performance can be reduced, thereby ensuring that the steel has better performance. DETAILED DESCRIPTION

[0024] The preparation method of the hot-rolled round steel for high-cleanliness and high-temperature bearings of the present invention is further described in detail below.

[0025] The preparation method of the hot-rolled round steel for high-temperature bearings in this embodiment is a steel having a grade of GW18Cr5V, and the mass percentage of its chemical components includes: C 0.70% to 0.80%, Si 0.15 to 0.35%, Mn≤0.40%, P≤0.010%, S≤0.005%, Cr 4.00 to 5.00%, V 1.00 to 1.50%, W 17.5 to 19.0%, and the rest is Fe and unavoidable trace impurities, with a total mass fraction of 100%.

[0026] The preparation method of the 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.

[0027] Further: Combined blowing converter smelting ensures that the smelting materials are dry to prevent water vapor from entering the steel to produce white spots; [P] < 0.008%, [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, and Cr 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;

[0028] Further: deep steel stripping and alloying are carried out in the LF furnace, high basicity slag is made to strengthen S removal and inclusion removal, and stirring is adopted throughout the refining process;

[0029] Further: vacuum degree ≤ 67Pa, deep vacuum time 20min, after breaking the vacuum, feed 150m of silicon calcium wire, soft blowing time 20min, during which the molten steel shall not be exposed;

[0030] Further: 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;

[0031] Further: the billet heating temperature is 1120-1170℃, the temperature difference is allowed to be ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1050-1100℃, overheating, overburning and decarburization are prevented, the temperature is slowly increased to ensure uniform billet heating temperature and reduce temperature difference; the final rolling temperature is 850-950℃;

[0032] Further: 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 knocks on the surface of the rolled piece. The specification of the rolled product is φ120mm. The heat treatment system is 1250℃ for 1h and oil cooling.

[0033] The hot-rolled round steel for high-temperature bearings produced by the chemical composition and process flow of the present invention has longitudinal mechanical properties of Rm≤950MPa, Brinell hardness HBW≤269 in the annealed state, and a decarburization layer depth ≤2mm, which meets the standard requirements, and the steel surface has no cracks, scars, folds or inclusions.

[0034] Table 1 shows the chemical compositions of three embodiments and three comparative examples of the present invention, and Table 2 and Table 3 further illustrate the present invention.

[0035] Table 1 Chemical composition of various examples of hot-rolled round steel for high-cleanliness and high-temperature bearings (mass percentage / %)

[0036] Example C Si Mn P S Cr V W Example 1 0.77 0.26 0.25 0.007 0.003 4.49 1.28 18.15 Example 2 0.78 0.27 0.26 0.008 0.002 4.48 1.27 18.17 Example 3 0.77 0.26 0.25 0.006 0.003 4.51 1.28 18.13 Comparative Example 1 0.78 0.24 0.24 0.014 0.006 4.45 1.24 18.16 Comparative Example 2 0.76 0.27 0.26 0.016 0.007 4.55 1.26 18.13 Comparative Example 3 0.79 0.28 0.27 0.018 0.006 4.50 1.28 18.17

[0037] Table 2 Mechanical properties of hot-rolled round steel for high-cleanliness and high-temperature bearings

[0038]

[0039] Table 3 Non-metallic inclusions and austenite grain size of various examples of hot-rolled round steel for high-cleanliness and high-temperature bearings

[0040]

[0041] It can be seen from Tables 1 to 3 that, compared with the comparative examples, each embodiment has the following advantages:

[0042] (1) The carbide particles in the steel have been effectively refined. Carbides are an important factor affecting the hardness and wear resistance of steel. The finer carbides are evenly distributed, which helps to improve the strength and wear resistance of steel, while reducing the tendency of the material to crack under high stress environments;

[0043] (2) Non-metallic inclusions are smaller in size. Smaller non-metallic inclusions make the internal structure of the steel more uniform, reducing the adverse effects of inclusions on mechanical properties, especially under high stress conditions, effectively improving the impact resistance and toughness of the material. In contrast, larger inclusions in the comparative example are more likely to become crack sources, resulting in a decrease in material performance.

[0044] (3) The unqualified flaw detection of the comparative example indicates that there are larger or more defects inside it, which may cause the material to fail during use, especially under high stress or dynamic load environment, which is very likely to cause fracture or fatigue failure. The qualified flaw detection of the example ensures the safety and long life of the product in application.

[0045] (4) The grain size in the embodiment is finer. The fine grain structure can also improve the plasticity of the material, making it better able to resist the initiation and expansion of cracks under long-term use or repeated loads. In contrast, the grain size in the comparative example is coarser, which easily leads to reduced performance of the steel.

[0046] 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 GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings, characterized in that: Including converter smelting, LF refining, VD vacuum degassing, continuous casting, billet heating furnace heating, round steel rolling, heat treatment; among which: Combined blowing converter smelting ensures that the smelting materials are dry to prevent water vapor from entering the steel to produce white spots; [P] < 0.008%, [S] < 0.030%; 3.8-4.2 kg of AlMnFe deoxidizer and various high-purity alloys are added per ton for pre-deoxidation and initial adjustment of W, V, and Cr 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 1120~1170℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1050~1100℃, prevent overheating, overburning and decarburization, heat up slowly, ensure the billet heating temperature is uniform, and reduce the temperature difference; the final rolling temperature is 850~950℃; The heat treatment system is 1250℃ for 1h and oil cooling; The mass percentage of the chemical composition of the GW18Cr5V hot-rolled round steel includes: C 0.70%-0.80%, Si 0.15-0.35%, Mn≤0.40%, P≤0.010%, S≤0.005%, Cr 4.00-5.00%, V 1.00-1.50%, W 17.5-19.0%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

2. The method for preparing GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings according to claim 1, characterized in that: The specification of the rolled product is φ120mm.

3. The method for preparing GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings according to claim 1, characterized in that: The chemical composition of the GW18Cr5V hot-rolled round steel includes by weight percentage: C 0.77%, Si 0.26%, Mn 0.25%, P 0.007%, S 0.003%, Cr 4.49%, V 1.28%, W 18.15%, and the rest is Fe and inevitable trace impurities, with a total weight fraction of 100%.

4. The method for preparing GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings according to claim 1, characterized in that: The mass percentage of the chemical composition of the GW18Cr5V hot-rolled round steel includes: C 0.78%, Si 0.27%, Mn 0.26%, P 0.008%, S 0.002%, Cr 4.48%, V 1.27%, W 18.17%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

5. The method for preparing GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings according to claim 1, characterized in that: The mass percentage of the chemical composition of the GW18Cr5V hot-rolled round steel includes: C 0.77%, Si 0.26%, Mn 0.25%, P 0.006%, S 0.003%, Cr 4.51%, V 1.28%, W 18.13%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

6. The method for preparing GW18Cr5V hot-rolled round steel for high-cleanliness high-temperature bearings according to claim 1, characterized in that: The longitudinal mechanical properties of the prepared hot-rolled round steel meet the following requirements: Rm≤950MPa, Brinell hardness HBW≤269 in the annealed state, depth of decarburized layer≤2mm, meeting the standard requirements, and no cracks, scars, folds or inclusions on the steel surface.

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