W-series high-temperature bearing steel bar and preparation method thereof

Abstract

The invention discloses a W-series high-temperature bearing steel bar and a preparation method thereof. The W-series high-temperature bearing steel bar comprises the following chemical components in percentage by mass: 0.60-0.90% of C, 4.0-5.0% of Cr, 16.0-25.0% of W, 0.5-1.5% of V, 0.01-0.5% of Nb, less than or equal to 0.0045% of S, less than or equal to 0.0080% of P, less than or equal to 0.0030% of Ti, less than or equal to 0.0050% of N and the balance of Fe and inevitable impurities. By designing alloy components and optimizing process parameters, the problems of segregation, poor carbide homogeneity and the like of the W-series high-temperature bearing steel are solved, the eutectic carbide size of the bar is smaller than or equal to 20 microns, homogeneous dispersion distribution is achieved, and the W-series high-temperature bearing steel bar has the advantages of being excellent in high-temperature hardness, high in abrasion resistance, high in fatigue strength and the like; and the cable is suitable for serving in high-temperature, high-speed and heavy-load environments.

Description

Technical Field

[0001] The present invention relates to the technical field of bearing steel, and more specifically, to a W-series high-temperature bearing steel bar and a preparation method thereof. Background Art

[0002] Bearings are very crucial basic components in modern equipment manufacturing, and are widely used in various fields such as automobiles, high-speed rails, wind power, precision machine tools, and aerospace. Bearings are the "joints" of the main engine transmission system, and their performance, service life, and reliability have become one of the main factors restricting the improvement of the main engine's service life. And bearing steel plays a crucial role in the quality, service life, and reliable performance of bearing products.

[0003] The working temperature of the traditional bearing steel GCr15 is below 150°C. After exceeding this temperature, the hardness drops sharply to below HRC58, and it cannot meet the use requirements under working conditions such as high speed, high temperature, and heavy load in the aerospace field. For this reason, W-series, W-Mo series, and Mo series high-temperature bearing steels developed from many high-speed steels have been widely used in the aviation field. Their service temperature can reach 315°C, and they have sufficiently high high-temperature hardness, high-temperature wear resistance, and fatigue strength. In the actual use process, the main factors affecting the service performance of high-temperature bearing steel are inclusions and large-sized carbides. Usually, large particles of inclusions and second phases such as carbides will become the fatigue crack sources. For nearly a century, with the improvement of smelting technology, especially high-temperature bearing steel is generally smelted by vacuum induction plus electroslag remelting, the fatigue failure problem caused by inclusions has been controlled. However, with the development of aviation technology and the harsh service environment of bearings, the homogeneity problem of bearing steel has become increasingly prominent. In particular, the role of large-sized primary carbides existing in the steel in the bearing failure process is becoming more and more obvious, and has become an important factor affecting the service life of bearing steel. Therefore, the technology for refining and homogenizing large-sized primary carbides is the key to further improving the fatigue life of high-temperature bearing steel.

[0004] Chinese Patent Application No. 202210435316.8 introduces a preparation method of M50 bearing steel bars, which adopts a double-vacuum method for smelting (vacuum induction plus vacuum consumable). By electroslag remelting, high-temperature diffusion, and deformation control, the equivalent diameter of primary carbides is less than 25 μm; the alloying elements of M50 are mainly Mo, and the primary carbides are mainly M2C and MC, and M2C is the main one; among them, M2C is a metastable primary carbide, and through high-temperature diffusion treatment, it can decompose to form M6C and MC, so as to improve its size and quantity. The M50 alloy is mainly composed of Mo carbides, and its carbide control mechanism is different from that of W-series carbides.

[0005] Chinese Patent Application No. 202110603335.2 introduces a high-temperature bearing steel with long service life, high reliability and large-atom alloying. The chemical composition in weight percentage is as follows: C: 0.75 - 0.85%, Cr: 3.75 - 4.25%, Mo: 4.0 - 4.5%, V: 0.90 - 1.10%, Si: ≤0.35%, Mn: ≤0.35%, P: ≤0.015%, S: ≤0.0080%, Cu: ≤0.20%, Ni: ≤0.25%, Co: ≤0.25%, W: ≤0.25%, Nb: ≤0.20%, Zr: ≤0.20%, Ce: ≤0.05%, La: ≤0.05%. The alloying elements Nb and Zr are added jointly, and the total alloy content is limited within the range of 0.05 ≤ Ce + La + Nb + Zr ≤ 0.30%. This technology adopts the design of adding rare earth elements. The ingot is treated at a high temperature of 1200 - 1250°C and by hot deformation and other technologies to refine the carbides. The invention is mainly based on the carbides of Mo, and it is mainly improved through high-temperature diffusion, and its control mechanism is different from that of W-based carbides.

[0006] Chinese Patent Application No. 202010489419.3 provides a high-carbon bearing steel. The chemical composition in weight percentage is as follows: C: 0.80 - 1.20%, Cr: 0.40 - 2.0%, Mn: 0.15 - 0.15%, Si: 0.15 - 0.75%, Nb: 0 - 0.20%, Mo: 0 - 0.20%, V: 0 - 0.20%. This technology adds micro-alloying elements Nb, Mo and V to the high-carbon bearing steel, and cooperates with other element components to refine the matrix structure of the bearing steel and the carbides in the bearing steel, and promote the precipitation of a large number of nano-carbides. The carbide type of this invention is different from that of W-based bearing steel, and the control mechanism is also different.

[0007] In view of the above situation, it is urgent to develop a W-based high-temperature bearing steel bar and its preparation method, which can solve the problems such as segregation and poor carbide homogeneity of W-based high-temperature bearing steel. Summary of the Invention

[0008] Aiming at the above defects existing in the prior art, the purpose of the present invention is to provide a W-based high-temperature bearing steel bar and its preparation method. By designing the alloy composition and optimizing the process parameters, problems such as segregation and poor carbide homogeneity of W-based high-temperature bearing steel are solved, so that the eutectic carbide size of the bar is ≤20μm, and it is evenly and dispersedly distributed. The W-based high-temperature bearing steel bar has excellent high-temperature hardness, high wear resistance and high fatigue strength and other characteristics, and is suitable for serving in high-temperature, high-speed and heavy-load environments.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions:

[0010] The first aspect of the present invention provides a W-series high-temperature bearing steel bar, which comprises the following chemical components by mass percentage: C: 0.60 - 0.90%, Cr: 4.0 - 5.0%, W: 16.0 - 25.0%, V: 0.5 - 1.5%, Nb: 0.01 - 0.50%, S ≤ 0.0045%, P ≤ 0.0080%, Ti ≤ 0.0030%, N ≤ 0.0050%, O ≤ 0.0015%, and the balance is Fe and inevitable impurities; wherein, the chemical components W, V, and Nb satisfy: 18% ≤ W + V + Nb ≤ 25%, where W, V, and Nb respectively refer to the mass percentages of the corresponding chemical components.

[0011] Preferably, the eutectic carbide size of the W-series high-temperature bearing steel bar is ≤ 20 μm;

[0012] The carbide non-uniformity is ≤ 2.0 grade, and the bar specification is The carbide non-uniformity is ≤ 3.0 grade, and the bar specification is The carbide non-uniformity is ≤ 3.5 grade.

[0013] Preferably, after the W-series high-temperature bearing steel bar is subjected to high-temperature quenching treatment at 1200 - 1260 °C for 30 min, its grain size is ≥ 8 grade;

[0014] After the W-series high-temperature bearing steel bar is subjected to high-temperature quenching treatment at 1200 - 1260 °C for 30 min and tempering treatment at 560 ± 10 °C for 2 h, its quenched and tempered hardness HRC ≥ 62.

[0015] The second aspect of the present invention provides a preparation method of a W-series high-temperature bearing steel bar as described in the first aspect of the present invention, comprising the following steps:

[0016] S1, vacuum induction melting, adding raw materials into a vacuum induction furnace for melting, controlling the tapping temperature at 1500 - 1560 °C, and after casting with electricity, the obtained electrode bar is cooled in a mold in a vacuum chamber and then demolded;

[0017] S2, annealing and finishing of the electrode bar, after the electrode bar is kept at 500 - 650 °C for more than 2 h, it is continuously heated to 820 - 880 °C and kept for 4 - 12 h, then cooled in the furnace to below 430 °C and taken out of the furnace, and then the scale on its surface is removed through finishing;

[0018] S3, electroslag remelting, the annealed and finished electrode bar is subjected to electroslag remelting treatment in a mold to obtain an electroslag ingot;

[0019] S4, annealing of the electroslag ingot, after the electroslag ingot is kept at 500 - 650 °C for more than 2 h, it is continuously heated to 820 - 880 °C and kept for 4 - 12 h, then cooled in the furnace to below 430 °C and taken out of the furnace;

[0020] S5, Forging and cogging: Heat the electroslag ingot to 1130 - 1220 °C and hold for more than 2 h, then obtain the forged blank after multi-pass upsetting and drawing deformation.

[0021] S6, Annealing of the forged blank: After holding the forged blank at 600 - 650 °C for more than 1 h, continue to heat it to 800 - 880 °C and hold for 2 - 12 h, then cool it in the furnace to below 430 °C and take it out of the furnace.

[0022] S7, Hot rolling: Heat the annealed forged blank in a heating furnace, and then perform rolling to obtain a hot-rolled bar.

[0023] S8, Annealing of the hot-rolled bar: After holding the hot-rolled bar at 600 - 650 °C for more than 1 h, continue to heat it to 820 - 880 °C and hold for 2 - 5 h, cool it in the furnace to 720 - 760 °C and hold for 3 - 8 h, then continue to cool it in the furnace to below 430 °C and take it out of the furnace. After finishing and ultrasonic flaw detection of the bar, obtain the W-series high-temperature bearing steel bar.

[0024] Preferably, in step S1, after the electrode bar is cooled in the mold in the vacuum chamber for 1 - 10 h, it is demolded.

[0025] Preferably, during the annealing processes in steps S2, S4, S6, and S8, the heating rate for continued heating ≤ 100 °C / h;

[0026] During the annealing processes in steps S2 and S4, the cooling rate for furnace cooling ≤ 50 °C / h.

[0027] Preferably, during the annealing processes in steps S2, S4, S6, and S8, the heating rate for continued heating ≤ 80 °C / h;

[0028] During the annealing processes in steps S2 and S4, the cooling rate for furnace cooling ≤ 40 °C / h.

[0029] Preferably, in step S3:

[0030] Before the electroslag remelting, clean the mold; the electroslag remelting process includes an arc starting stage, a stable stage, and a capping and feeding stage; in the arc starting stage, power control is adopted, and the power is set to 50 - 300 KW, in the stable stage, melting rate control is adopted, and the melting rate is set to 4.0 - 2.0 kg / min, in the capping and feeding stage, power control is adopted, and the power is set to 10 - 100 KW;

[0031] After the electroslag remelting is completed, cool it in the mold for 60 - 120 min and then demold.

[0032] Preferably, in step S5, during the forging and cogging process:

[0033] The heating rate of the electroslag ingot is ≤100°C / h;

[0034] For the forging and cogging, the cogging temperature is ≥1100°C, the finishing temperature is ≥950°C, and the total deformation ratio of forging is ≥9.

[0035] Preferably, in step S7, during the heating of the annealed forging billet in the heating furnace, the preheating temperature of the forging billet is ≤800°C, the heating temperature is 1150 - 1200°C, the soaking temperature is 1150 - 1200°C, the temperature difference between the positive and negative sides of the forging billet is ≤30°C, and the total heating time is ≥2.5 h

[0036] The design principle of the chemical composition of the W-series high-temperature bearing steel bar of the present invention is as follows:

[0037] Carbon: C, as the most commonly used strengthening element in steel materials, can form carbides such as M 23 C6 and MX, effectively pinning the lath boundaries and maintaining the properties of the material for a long time. However, too high a C content will lead to poor hardenability, affecting mechanical properties such as hardness, and serious segregation in industrial production. Therefore, the C content range of the steel of the present invention is controlled at 0.60 - 0.90%.

[0038] Chromium: From the perspective of improving oxidation resistance, it is often desirable to have a higher Cr content. However, when the Cr content is too high, δ-ferrite will appear in the material, reducing the strength and toughness of the material. Therefore, the Cr content range selected for the steel of the present invention is 4.0 - 5.0%.

[0039] Tungsten: The W element mainly exists in the form of carbide precipitation phase, playing a role in precipitation strengthening. When the W content is less than 15%, it is not sufficient to ensure the high-temperature hardness of the alloy. However, when the W content is too high, it will significantly reduce the tissue stability during the long-term service of the alloy, resulting in a decrease in the strength of the alloy. At the same time, W is an element with serious positive segregation in steel. Especially when large-sized steel ingots are used in industrial production, the solidification segregation is more serious and difficult to completely eliminate. Therefore, to reasonably control the W content, the W content selected for the steel of the present invention is 16.0 - 25.0%.

[0040] Vanadium and niobium: V and Nb mainly form MC phases with C element, which are important strengthening phases in steel. Relevant research shows that the composite addition of V and Nb can significantly improve the fatigue strength of the steel. Therefore, the V content selected for the steel of the present invention is 0.5 - 1.5%, and the Nb content is 0.01 - 0.50%.

[0041] W, V, and Nb satisfy: 18% ≤ W + V + Nb ≤ 25%. W exists in the form of carbide precipitation phase, playing a role in precipitation strengthening; V and Nb mainly form MC phases with C element, which are also important strengthening phases in steel. Considering factors such as carbide control and mechanical properties, the total content of W, V, and Nb is limited between 18% and 25%.

[0042] The present invention has the following beneficial effects:

[0043] 1. Aiming at the problems of serious segregation and poor carbide homogeneity in W-series high-temperature bearing steel in industrial-scale production, the present invention makes the eutectic carbide size of the bar ≤20 μm and uniformly dispersed by compounding chemical components such as W, V, and Nb, optimizing the vacuum induction casting temperature, demoulding time, stress relief process of the electrode bar (i.e., electrode bar annealing), strengthening the cooling effect of the mold, optimizing the electroslag remelting parameters, and deformation process (i.e., forging and blooming), etc.; after the W-series high-temperature bearing steel bar is heat-treated by quenching at 1200-1260 °C, its grain size is finer than grade 8; after the W-series high-temperature bearing steel bar is heat-treated by quenching at 1200-1260 °C and tempering at 560±10 °C, its tempered hardness HRC≥62;

[0044] 2. The W-series high-temperature bearing steel bar of the present invention has the characteristics of excellent high-temperature hardness, high wear resistance and high fatigue strength, and is suitable for serving in high-temperature, high-speed and heavy-load environments. Specific embodiments

[0045] In order to better understand the above technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with embodiments.

[0046] A W-series high-temperature bearing steel bar of the present invention comprises the following chemical components by mass percentage: C: 0.60-0.90%, Cr: 4.0-5.0%, W: 16.0-25.0%, V: 0.5-1.5%, Nb: 0.01-0.50%, S≤0.0045%, P≤0.0080%, Ti≤0.0030%, N≤0.0050%, O≤0.0015%, and the balance is Fe and inevitable impurities.

[0047] Among them, in the W-series high-temperature bearing steel bar, W, V, and Nb satisfy: 18%≤W+V+Nb≤25% (where W, V, and Nb in the formula refer to the mass percentages of the corresponding chemical components).

[0048] Among them, the eutectic carbide size of the W-series high-temperature bearing steel bar ≤20 μm, uniformly dispersed, and the carbide inhomogeneity ≤3.5 levels. In specific embodiments, the carbide inhomogeneity ≤2.0 levels, and the bar specification is the carbide inhomogeneity ≤3.0 levels, and the bar specification is the carbide inhomogeneity ≤3.5 levels.

[0049] After the above-mentioned W-series high-temperature bearing steel bars are subjected to high-temperature quenching treatment at 1200 - 1260°C for 30 minutes, their grain size ≥ grade 8, that is, the grain size is finer than grade 8. After the W-series high-temperature bearing steel bars are subjected to high-temperature quenching treatment at 1200 - 1260°C for 30 minutes and tempering treatment at 560 ± 10°C for 2 hours, their quenched and tempered hardness HRC ≥ 62.

[0050] The preparation method of the above-mentioned W-series high-temperature bearing steel bars has the process of vacuum induction melting → electrode bar annealing and finishing → electroslag remelting → electroslag ingot annealing → forging and blooming → forged billet annealing → hot rolling → hot rolled bars, specifically including the following steps:

[0051] S1, vacuum induction melting, adding raw materials into a vacuum induction furnace for melting, controlling the tapping temperature at 1500 - 1560°C, and after casting with electricity, the obtained electrode bar is cooled in the mold in the vacuum chamber and then demolded.

[0052] Specifically, high-quality raw material steel is selected as the basic raw material, alloy elements are incorporated with metal Cr, W, ferrovanadium (V-Fe), etc. Among them, metal Cr, W, ferrovanadium, etc. must undergo baking treatment, be rust-free, oil-free, and dry; the raw materials are configured according to the composition requirements of the W-series high-temperature bearing steel bars, specifically including the following chemical components by mass percentage: C: 0.60 - 0.90%, Cr: 4.0 - 5.0%, W: 16.0 - 20.0%, V: 0.5 - 1.5%, Nb: 0.01 - 0.5%, S ≤ 0.0045%, P ≤ 0.0080%, Ti ≤ 0.0030%, N ≤ 0.0050%, and the balance is Fe and inevitable impurities. Then the above raw materials are melted in a vacuum induction furnace, the tapping temperature is controlled at 1500 - 1560°C, casting is carried out with electricity and poured as close as possible to the lower limit temperature, and the obtained electrode bar has a specification of . After casting is completed, the electrode bar is cooled in the mold in the vacuum chamber for 1 - 10 hours and then demolded.

[0053] S2, electrode bar annealing and finishing, after the electrode bar is held at 500 - 650°C for more than 2 hours, it is continuously heated to 820 - 880°C and held for 4 - 12 hours, and then cooled in the furnace to below 430°C and taken out of the furnace, and then the scale on its surface is removed through finishing.

[0054] Specifically, the above-mentioned manufactured electrode bar is held at 500 - 650°C for ≥ 2 hours, and then continuously heated to 820 - 880°C at a heating rate of ≤ 100°C / h and held for 4 - 12 hours, and then cooled in the furnace to below 430°C at a cooling rate of ≤ 50°C / h and taken out of the furnace. Then the electrode bar is finished (such as surface grinding) to clean the scale on its surface.

[0055] In a specific embodiment, during the annealing process of the electrode bar, the heating rate for continuous heating can specifically be within ranges such as ≤80 °C / h, ≤60 °C / h, or 60 - 100 °C / h; the cooling rate during furnace cooling can specifically be within ranges such as 30 - 50 °C / h, ≤40 °C / h, or ≤30 °C / h; in this step, by controlling the heating rate and the cooling rate, the temperature and structure of the entire material are made uniform to improve the thermal stress and structure stress caused during the heating and cooling processes.

[0056] S3. Electro-slag remelting: The annealed and finished electrode bar undergoes electro-slag remelting treatment in a mold to obtain an electro-slag ingot.

[0057] Specifically, a mold (the size of which can be ) is used for electro-slag remelting, and a dummy bar of the same steel type is used. Before electro-slag remelting, the mold is cleaned to confirm the cooling effect; the annealed and finished electrode bar is subjected to electro-slag remelting in the mold. The electro-slag remelting process is controlled in three stages, specifically including the arc starting stage, the stable stage, and the capping and feeding stage; in the arc starting stage, power control is used, and the power is set to 50 - 300 KW; in the stable stage, melting rate control is used, and the melting rate is set to 4.0 - 2.0 kg / min; in the capping and feeding stage, power control is used, and the power is set to 10 - 100 KW. After the electro-slag remelting is completed, it is cooled in the mold for 60 - 120 min and then demolded.

[0058] S4. Annealing of the electro-slag ingot: After the electro-slag ingot is held at 500 - 650 °C for more than 2 h, it is continuously heated to 820 - 880 °C and held for 4 - 12 h, and then cooled in the furnace to below 430 °C and then taken out of the furnace.

[0059] Specifically, after the electro-slag ingot is held at 500 - 650 °C for ≥2 h, it is continuously heated to 820 - 880 °C at a heating rate of ≤100 °C / h and held for 4 - 12 h, and then cooled in the furnace at a cooling rate of ≤30 °C / h to below 430 °C and then taken out of the furnace.

[0060] In a specific embodiment, during the annealing of the electro-slag ingot, the heating rate for continuous heating can specifically be within ranges such as ≤80 °C / h, ≤60 °C / h, or 60 - 100 °C / h; the cooling rate during furnace cooling can specifically be within ranges such as 30 - 50 °C / h, ≤40 °C / h, or ≤30 °C / h; in this step, by controlling the heating rate and the cooling rate during annealing, the temperature and structure of the entire material are made uniform to improve the thermal stress and structure stress caused during the heating and cooling processes.

[0061] S5. Forging and blooming: The electro-slag ingot is heated to 1130 - 1220 °C and held for more than 2 h, and then a forged billet is obtained after multi-pass upsetting and drawing deformation.

[0062] Specifically, first heat the electroslag ingot to 1130 - 1220°C at a heating rate of 60 - 100°C / h and hold for ≥2 h, and then obtain a forging blank after multi-pass upsetting and drawing deformation; during the process of forging and blooming, the starting forging temperature ≥1100°C, the finishing forging temperature ≥950°C, and the total forging deformation ratio ≥9.

[0063] S6. Anneal the forging blank. After holding the forging blank at 600 - 650°C for more than 1 h, continue to heat it to 800 - 880°C and hold for 2 - 12 h, and then cool it in the furnace to below 430°C and then take it out of the furnace;

[0064] Specifically, hold the forging blank at 600 - 650°C for ≥1 h, and then continue to heat it to 800 - 880°C at a heating rate of ≤100°C / h and hold for 2 - 12 h, and then cool it in the furnace to below 430°C and then take it out of the furnace.

[0065] In a specific embodiment, when annealing the forging blank, the heating rate of continuous heating can specifically be in the range of ≤80°C / h, ≤60°C / h, or 60 - 100°C / h, etc.; in this step, by controlling the heating rate during annealing, the temperature and structure of the whole billet are made uniform to improve the thermal stress and structure stress caused by the heating process.

[0066] S7. Hot rolling. Heat the annealed forging blank in a heating furnace and then perform rolling to obtain a hot-rolled bar;

[0067] Specifically, heat the annealed forging blank in a heating furnace and then perform rolling. Among them, the preheating temperature of the forging blank ≤800°C, the heating temperature is 1150 - 1200°C, the soaking temperature is 1150 - 1200°C, the temperature difference between the front and back sides of the forging blank ≤30°C, the total heating time ≥2.5 h. After completing hot rolling, a hot-rolled bar is obtained, and its dimensional tolerance meets the requirements of Group 1 of GB / T702 - 2017.

[0068] S8. Anneal the hot-rolled bar. After holding the hot-rolled bar at 600 - 650°C for more than 1 h, continue to heat it to 820 - 880°C and hold for 2 - 5 h, cool it in the furnace to 720 - 760°C and hold for 3 - 8 h, and then continue to cool it in the furnace to below 430°C and then take it out of the furnace. After finishing and ultrasonic flaw detection of the bar, a W-series high-temperature bearing steel bar is obtained.

[0069] Specifically, hold the above-prepared hot-rolled bar at 600 - 650°C for ≥1 h, and then continue to heat it to 820 - 880°C at a heating rate of ≤100°C / h and hold for 2 - 5 h, and then cool it in the furnace to 720 - 760°C and hold for 3 - 8 h, and then continue to cool it in the furnace to below 430°C and then take it out of the furnace. After finishing and ultrasonic flaw detection of the bar, a W-series high-temperature bearing steel bar is obtained; among them, finishing can be carried out by surface grinding; ultrasonic flaw detection is carried out according to Grade A standard of GB / T 4162.

[0070] In a specific embodiment, when annealing the hot-rolled bar, the heating rate for continuous heating can specifically be within a range such as ≤80 °C / h, ≤60 °C / h, or 60 - 100 °C / h, etc.; in this step, by controlling the heating rate during annealing, the temperature and structure of the entire material are homogenized to improve the thermal stress and structure stress caused by the heating process.

[0071] Samples of the W-series high-temperature bearing steel bars prepared above are taken for inspection. After sampling from the W-series high-temperature bearing steel bars, the specimens are subjected to quenching treatment and tempering treatment. The quenching treatment regime is to hold at 1200 - 1260 ± 10 °C for 30 min and then air-cool, and the tempering treatment regime is to hold at 560 ± 10 °C for 2 h and then air-cool. The grain size is detected in the quenched state. After the W-series high-temperature bearing steel bars are subjected to high-temperature quenching treatment, their grain size ≥ 8 grades; the hardness HRC, carbide non-uniformity, and carbide size are detected in the quenched and tempered state. After the W-series high-temperature bearing steel bars are subjected to high-temperature quenching treatment and tempering treatment, their quenched and tempered hardness HRC ≥ 62.

[0072] The following further introduces the W-series high-temperature bearing steel bars and their preparation method of the present invention in combination with specific examples.

[0073] Example 1

[0074] The preparation method of the W-series high-temperature bearing steel bars in this example specifically includes the following steps:

[0075] 1) Vacuum induction melting. High-quality raw steel is selected as the basic raw material, and alloying elements are incorporated in the form of metallic Cr, metallic W, ferrovanadium, etc. Metallic Cr and V-Fe are baked, rust-free, oil-free, and dry. After preparing the raw materials according to the composition ratio of the W-series high-temperature bearing steel bars, vacuum induction melting is carried out, and the tapping temperature is 1500 °C. After the charged casting is completed, an electrode bar with the composition shown in Table 1 is obtained, and its specification is The electrode bar is kept in the vacuum chamber for 2 h and then demolded.

[0076] 2) Annealing and finishing of the electrode bar. The electrode bar is held at 500 °C for ≥2 h, heated to 820 °C at 80 °C / h and held for 5 h, and then cooled to 430 °C at ≤30 °C / h and taken out of the furnace. The surface of the electrode bar is ground to remove the scale completely.

[0077] 3) Electro-slag remelting. The size of the mold The dummy bar is made of the same steel grade as the ingot. The mold is cleaned before electro-slag remelting. The remelting process is controlled in three stages. In the arc starting stage, power control is mainly used, and the power is set to 50 - 250 KW; in the stable stage, melting rate control is used, and the melting rate is set to 3.5 kg / min; in the capping and feeding stage, power control is mainly used, and the power is set to 10 - 50 KW. After electro-slag remelting is completed, it is cooled in the mold for 60 min and then demolded.

[0078] 4) Electroslag ingot annealing. Keep it at 500 °C for ≥2 h, heat it to 820 °C at ≤100 °C / h and keep it for 6 h, then reduce the temperature to 430 °C at ≤30 °C / h and take it out of the furnace.

[0079] 5) Forging and cogging. Heat the electroslag ingot to 1180 °C at ≤100 °C / h and keep it for ≥2 h, perform upsetting and drawing deformation in multiple passes. The starting forging temperature is 1120 °C, the final forging temperature is 950 °C, and the total deformation ratio is ≥9.

[0080] 6) Forged billet annealing. Keep the forged billet at 600 °C for ≥1 h, heat it to 820 °C at ≤80 °C / h and keep it for 6 h, then cool it in the furnace to 430 °C and take it out of the furnace.

[0081] 7) Hot-rolled bar. The preheating temperature of the forged billet is 800 °C, the heating temperature is 1200 °C, the soaking temperature is 1200 °C, the temperature difference between the positive and negative sides is 20 °C, the total heating time is ≥2.5 h, and finally a hot-rolled bar with the following specifications is obtained of the hot-rolled bar.

[0082] 8) Annealing, finishing and flaw detection of hot-rolled bar. Keep the hot-rolled bar at 600 °C for ≥1 h, heat it to 820 °C at ≤80 °C / h and keep it for 2 h, then cool it in the furnace to 730 °C and keep it for 4 h, and then cool it in the furnace to 430 °C and take it out of the furnace. Polish the surface of the bar, and perform ultrasonic flaw detection according to Grade A of GB / T 4162 to obtain a W-series high-temperature bearing steel bar.

[0083] 9) Sampling and inspection. Take samples from the W-series high-temperature bearing steel bar, and perform quenching and tempering treatments on the samples. The quenching regime is to keep it at 1250 ± 10 °C for 30 min / air cooling, and the tempering regime is to keep it at 560 ± 10 °C for 2 h / air cooling. Detect the grain size in the quenched state, and detect the hardness HRC, carbide non-uniformity and carbide size in the quenched and tempered state. Among them, the grain size rating is carried out according to GB / T6394, and the carbide non-uniformity rating is carried out according to the first rating diagram of GB / T 14979-1994. The specific results are shown in Tables 2, 3 and 4.

[0084] Example 2

[0085] The preparation method of the W-series high-temperature bearing steel bar in this example specifically includes the following steps:

[0086] 1) Vacuum induction melting. Select high-quality raw steel as the basic raw material, and alloy elements are added in the form of metallic Cr, metallic W, ferrovanadium, etc. Metallic Cr and V-Fe are baked, rust-free, oil-free and dry. After preparing the raw materials according to the composition ratio of the W-series high-temperature bearing steel bar, carry out vacuum induction melting. The tapping temperature is 1510 °C. After the charged casting is completed, an electrode bar with the composition shown in Table 1 is obtained, and its specifications are The electrode bar is demoulded in the vacuum chamber after 5 h.

[0087] 2) Annealing and finishing of electrode bars. Keep the electrode bars at 530 °C for ≥ 2 h, heat them to 840 °C at 100 °C / h and hold for 5 h, then cool them to 430 °C at ≤ 40 °C / h and take them out of the furnace. Grind the surface of the electrode bars and clean off the scale.

[0088] 3) Electroslag remelting. The size of the mold Use an ingot guide plate of the same steel grade. Clean the mold before electroslag remelting. The electroslag remelting process is controlled in three stages. In the arc starting stage, power control is mainly adopted, and the power is set at 50 - 250 KW; in the stable stage, melting rate control is adopted, and the melting rate is set at 4.0 kg / min; in the capping and feeding stage, a process mainly based on power control is adopted, and the power is set at 10 - 50 KW. After electroslag remelting, carry out mold cooling for 60 min and then demold.

[0089] 4) Annealing of electroslag ingots. Keep at 550 °C for ≥ 2 h, heat to 840 °C at ≤ 80 °C / h and hold for 6 h, then cool to 430 °C at ≤ 30 °C / h and take them out of the furnace.

[0090] 5) Forging and cogging. Heat the electroslag ingots to 1200 °C at ≤ 100 °C / h and hold for ≥ 2 h, carry out upsetting and drawing out deformation in multiple heats. The starting forging temperature is 1150 °C, the final forging temperature is 950 °C, and the total deformation ratio ≥ 9.

[0091] 6) Annealing of forged billets. Keep the forged billets at 600 °C for ≥ 1 h, heat to 840 °C at ≤ 80 °C / h and hold for 6 h, then cool in the furnace to 430 °C and take them out of the furnace.

[0092] 7) Hot - rolled bars. The pre - heating temperature of the billet is 800 °C, the heating temperature is 1170 °C, the soaking temperature is 1170 °C, the temperature difference between the positive and negative sides is 10 °C, and the total heating time ≥ 2.5 h, to obtain hot - rolled bars with the following specifications

[0093] 8) Annealing, finishing and flaw detection of hot - rolled bars. Keep the hot - rolled bars at 600 °C for ≥ 1 h, heat to 840 °C at ≤ 80 °C / h and hold for 2 h, then cool in the furnace to 750 °C and hold for 4 h, and then cool in the furnace to 430 °C and take them out of the furnace. Polish the surface of the bars, and carry out ultrasonic flaw detection according to Grade A of GB / T 4162, finally obtaining W - series high - temperature bearing steel bars.

[0094] 9) Sampling inspection. Samples are taken from the W-series high-temperature bearing steel bars, and the specimens are quenched and tempered. The quenching regime is holding at 1200 - 1260 ± 10 °C for 30 min and then air-cooling, and the tempering regime is holding at 560 ± 10 °C for 2 h and then air-cooling. The grain size is detected in the quenched state, and the hardness HRC, carbide non-uniformity, and carbide size are detected in the quenched and tempered state. Among them, the grain size is rated according to GB / T6394, and the carbide non-uniformity is rated according to the first rating chart of GB / T 14979-1994. The specific results are shown in Tables 2, 3, and 4.

[0095] Example 3

[0096] The preparation method of the W-series high-temperature bearing steel bars in this example specifically includes the following steps:

[0097] 1) Vacuum induction melting. High-quality raw steel is selected as the basic raw material, and alloying elements are added in the form of metallic Cr, metallic W, ferrovanadium, etc. Metallic Cr and V-Fe are baked to be rust-free, oil-free, and dry. After preparing the raw materials according to the component ratio of the W-series high-temperature bearing steel bars, vacuum induction melting is carried out. The tapping temperature is 1520 °C, and an electrode bar with the composition shown in Table 1 is obtained after the charged casting is completed. Its specifications are The electrode bar is demolded after being kept in the vacuum chamber for 2 h.

[0098] 2) Annealing and finishing of the electrode bar. The electrode bar is held at 560 °C for ≥ 2 h, heated to 860 °C at 60 °C / h and held for 5 h, and then cooled to 430 °C at ≤ 50 °C / h and taken out of the furnace. The surface of the electrode bar is ground to remove the scale completely.

[0099] 3) Electro-slag remelting. The size of the mold The dummy bar is made of the same steel type as the ingot. The mold is cleaned before electro-slag remelting. The electro-slag remelting process is controlled in three stages. In the arc starting stage, power control is mainly adopted, and the power is set at 50 - 250 KW; in the stable stage, melting rate control is adopted, and the melting rate is set at 2.0 kg / min; in the capping and feeding stage, power control is mainly adopted, and the power is set at 20 - 80 KW. After electro-slag remelting, it is cooled in the mold for 60 min and then demolded.

[0100] 4) Annealing of the electro-slag ingot. It is held at 600 °C for ≥ 2 h, heated to 860 °C at ≤ 60 °C / h and held for 6 h, and then cooled to 430 °C at ≤ 30 °C / h and taken out of the furnace.

[0101] 5) Forging and blooming. The electro-slag ingot is heated to 1150 °C at ≤ 100 °C / h and held for ≥ 2 h, and is upset and drawn with multiple passes of deformation. The starting forging temperature is 1100 °C, the final forging temperature is 950 °C, and the total deformation ratio is ≥ 9.

[0102] 6) Annealing of forged billets. Keep the forged billets at 600 °C for ≥1 h, heat them to 860 °C at a rate of ≤80 °C / h and keep them at this temperature for 6 h, and then cool them in the furnace to 430 °C and take them out of the furnace.

[0103] 7) Hot-rolled bars. The preheating temperature of the billet is 800 °C, the heating temperature is 1150 °C, the soaking temperature is 1150 °C, the temperature difference between the positive and negative sides is 10 °C, and the total heating time is ≥2.5 h, obtaining hot-rolled bars with the following specifications of hot-rolled bars.

[0104] 8) Annealing, finishing and flaw detection of hot-rolled bars. Keep the hot-rolled bars at 600 °C for ≥1 h, heat them to 860 °C at a rate of ≤80 °C / h and keep them at this temperature for 2 h, then cool them in the furnace to 760 °C and keep them at this temperature for 4 h, and then cool them in the furnace to 430 °C and take them out of the furnace. Polish the surface of the bars, and perform ultrasonic flaw detection according to Grade A of GB / T4162, finally obtaining W-series high-temperature bearing steel bars.

[0105] 9) Sampling and inspection. Take samples from the W-series high-temperature bearing steel bars, and perform quenching and tempering treatments on the samples. The quenching regime is to keep them at 1250 ± 10 °C for 30 min and air-cool, and the tempering regime is to keep them at 560 ± 10 °C for 2 h and air-cool. Detect the grain size in the quenched state, and detect the hardness HRC, carbide non-uniformity and carbide size in the quenched and tempered state. Among them, the grain size is rated according to GB / T6394, and the carbide non-uniformity is rated according to the first rating diagram of GB / T 14979-1994. The specific results are shown in Tables 2, 3 and 4.

[0106] Example 4

[0107] The preparation method of the W-series high-temperature bearing steel bars in this example specifically includes the following steps:

[0108] 1) Vacuum induction melting. Select high-quality raw steel as the basic raw material, and add alloying elements such as metallic Cr, metallic W, ferrovanadium, etc. Metallic Cr and V-Fe are baked, rust-free, oil-free and dry. After preparing the raw materials according to the component ratio of the W-series high-temperature bearing steel bars, carry out vacuum induction melting. The tapping temperature is 1540 °C. After the charged casting is completed, an electrode bar with the composition shown in Table 1 is obtained, and its specifications are The electrode bar is demoulded in the vacuum chamber for 1 h.

[0109] 2) Annealing and finishing of the electrode bar. Keep the electrode bar at 600 °C for ≥2 h, heat it to 880 °C at a rate of ≤100 °C / h and keep it at this temperature for 5 h, and then reduce the temperature to 430 °C at a rate of ≤30 °C / h and take it out of the furnace. Grind the surface of the electrode bar and clean the scale completely.

[0110] 3) Electro-slag remelting. The size of the mold The dummy bar uses a dummy bar of the same steel grade. The mold is cleaned before electroslag remelting. The remelting process is controlled in three stages. In the arc starting stage, power control is mainly adopted, and the power is set at 50 - 300 KW; in the stable stage, melting rate control is adopted, and the melting rate is set at 2.5 kg / min; in the capping and feeding stage, a process mainly based on power control is adopted, and the power is set at 20 - 100 KW. After electroslag remelting, mold cooling is carried out for 120 min, and then demolding is performed.

[0111] 4) Annealing of electroslag ingot. Keep it at 650 °C for ≥2 h, heat it to 880 °C at ≤100 °C / h and keep it for 6 h, then reduce the temperature to 430 °C at ≤30 °C / h and take it out of the furnace.

[0112] 5) Forging and blooming. Heat the electroslag ingot to 1220 °C at ≤100 °C / h and keep it for ≥2 h. Perform upsetting and drawing deformation in multiple heats. The starting forging temperature is 1160 °C, the final forging temperature is 950 °C, and the total deformation ratio is ≥9.

[0113] 6) Annealing of forged billet. Keep the forged billet at 600 °C for ≥1 h, heat it to 880 °C at ≤80 °C / h and keep it for 6 h, then cool it in the furnace to 430 °C and take it out of the furnace.

[0114] 7) Hot rolling of bars. The preheating temperature of the billet is 800 °C, the heating temperature is 1160 °C, the soaking temperature is 1160 °C, the temperature difference between the positive and negative sides is 20 °C, and the total heating time is ≥2.5 h to obtain hot-rolled bars with the following specifications: of hot-rolled bars.

[0115] 8) Annealing, finishing and flaw detection of hot-rolled bars. Keep the hot-rolled bars at 600 °C for ≥1 h, heat it to 880 °C at ≤80 °C / h and keep it for 2 h, then cool it in the furnace to 720 °C and keep it for 4 h, and then cool it in the furnace to 430 °C and take it out of the furnace. Polish the surface of the bars, and perform ultrasonic flaw detection according to Grade A of GB / T 4162. Finally, obtain W-series high-temperature bearing steel bars.

[0116] 9) Sampling and inspection. Take samples from the W-series high-temperature bearing steel bars, and perform quenching and tempering treatments on the samples. The quenching regime is 1250 ± 10 °C for 30 min / air cooling, and the tempering regime is 560 ± 10 °C for 2 h / air cooling. Detect the grain size in the quenched state, and detect the hardness HRC, carbide non-uniformity and carbide size in the tempered state. Among them, the grain size rating is carried out according to GB / T6394, and the carbide non-uniformity rating is carried out according to the first rating diagram of GB / T 14979 - 1994. The specific results are shown in Tables 2, 3 and 4.

[0117] Example 5

[0118] The preparation method of the W-series high-temperature bearing steel bars in this example specifically includes the following steps:

[0119] 1) Vacuum induction melting. High-quality raw steel is selected as the basic raw material, and alloying elements are added in the form of metallic Cr, metallic W, ferrovanadium, etc. Metallic Cr and V-Fe are baked, rust-free, oil-free and dry. After preparing the raw materials according to the composition ratio of W-series high-temperature bearing steel bars, vacuum induction melting is carried out. The tapping temperature is 1560 °C. After the charged casting is completed, an electrode bar with the composition shown in Table 1 is obtained, and its specifications are The electrode bar is demoulded in the vacuum chamber after being kept for 2 h.

[0120] 2) Annealing and finishing of the electrode bar. The electrode bar is kept at 650 °C for ≥2 h, heated to 850 °C at ≤80 °C / h and kept for 5 h, and then cooled to 430 °C at ≤50 °C / h and taken out of the furnace. The surface of the electrode bar is ground to remove the scale completely.

[0121] 3) Electroslag remelting. The size of the mold The dummy bar is made of the same steel grade as the ingot. The mold is cleaned before electroslag remelting. The remelting process is controlled in three stages. In the arc starting stage, power control is mainly adopted, and the power is set at 50 - 300 KW; in the stable stage, melting rate control is adopted, and the melting rate is set at 3.0 kg / min; in the capping and feeding stage, power control is mainly adopted, and the power is set at 20 - 80 KW. After electroslag remelting, it is cooled in the mold for 60 min and then demoulded.

[0122] 4) Annealing of the electroslag ingot. It is kept at 600 °C for ≥2 h, heated to 860 °C at ≤100 °C / h and kept for 6 h, and then cooled to 430 °C at ≤30 °C / h and taken out of the furnace.

[0123] 5) Forging and cogging. The electroslag ingot is heated to 1130 °C at ≤100 °C / h and kept for ≥2 h, and is upset and drawn out in multiple passes. The forging starting temperature is 1100 °C, the final forging temperature is 950 °C, and the total deformation ratio is ≥9.

[0124] 6) Annealing of the forged billet. The forged billet is kept at 600 °C for ≥1 h, heated to 860 °C at ≤80 °C / h and kept for 6 h, and then cooled in the furnace to 430 °C and taken out of the furnace.

[0125] 7) Hot-rolled bars. The preheating temperature of the billet is 800 °C, the heating temperature is 1190 °C, the soaking temperature is 1190 °C, the temperature difference between the positive and negative sides is 20 °C, and the total heating time is ≥2.5 h. Finally, hot-rolled bars with the following specifications are obtained of hot-rolled bars.

[0126] 8) Annealing, finishing and flaw detection of the hot-rolled bars. The hot-rolled bars are kept at 600 °C for ≥1 h, heated to 850 °C at ≤80 °C / h and kept for 2 h, and then cooled in the furnace to 730 °C and kept for 4 h, and then cooled in the furnace to 430 °C and taken out of the furnace. The surface of the bars is polished, and ultrasonic flaw detection is carried out according to Grade A of GB / T 4162. Finally, W-series high-temperature bearing steel bars are obtained.

[0127] 9) Sampling inspection. Samples are taken from the W-series high-temperature bearing steel bars, and the specimens are quenched and tempered. The quenching regime is holding at 1250 ± 10 °C for 30 min and air cooling, and the tempering regime is holding at 560 ± 10 °C for 2 h and air cooling. The grain size is detected in the quenched state, and the hardness HRC, carbide non-uniformity, and carbide size are detected in the quenched and tempered state. Among them, the grain size rating is in accordance with GB / T 6394, and the carbide non-uniformity rating is in accordance with the first rating diagram of GB / T 14979-1994. The specific results are shown in Tables 2, 3, and 4.

[0128] Comparative Example 1

[0129] The preparation method of the bearing steel bars in this comparative example specifically includes the following steps:

[0130] 1) Vacuum induction melting. High-quality raw steel is selected as the basic raw material, and alloying elements are added in the form of metallic Cr, metallic W, ferrovanadium, etc. The tapping temperature is 1580 °C, and after the charged casting is completed, an electrode bar with the composition shown in Table 1 is obtained, and its specifications are The electrode bar is demolded after being held in the vacuum chamber for 2 h.

[0131] 2) Annealing and finishing of the electrode bar. The electrode bar is held at 12600 °C for ≥ 2 h, heated to 750 °C at ≤ 100 °C / h and held for 5 h, and then cooled to 430 °C at ≤ 30 °C / h and taken out of the furnace. The surface of the electrode bar is ground to remove the scale completely.

[0132] 3) Electroslag remelting. The mold size The dummy bar is made of the same steel grade. The remelting process is controlled in three stages, and the melting rate in the stable stage is set at 4.2 kg / min. After the electroslag is completed, it is cooled in the mold for 60 min and then demolded.

[0133] 4) Annealing of the electroslag ingot. It is held at 650 °C for ≥ 2 h, heated to 860 °C at ≤ 100 °C / h and held for 6 h, and then cooled to 430 °C at ≤ 30 °C / h and taken out of the furnace.

[0134] 5) Forging and blooming. The electroslag ingot is heated to 1200 °C at ≤ 100 °C / h and held for ≥ 2 h, and is upset and drawn with multiple passes of deformation, and the total deformation ratio is 6.

[0135] 6) Annealing of the forged billet. The forged billet is held at 600 °C for ≥ 1 h, heated to 860 °C at ≤ 80 °C / h and held for 6 h, and then cooled in the furnace to 430 °C and taken out of the furnace.

[0136] 9) Hot-rolled bars. The preheating temperature of the billet is 800 °C, the heating temperature is 1170 °C, the soaking temperature is 1170 °C, the total heating time is ≥ 2.5 h, and the hot-rolled bar specifications

[0137] 10) Annealing, finishing, and flaw detection of the hot-rolled bars. The hot-rolled bars are kept at 600 °C for ≥1 h, heated to 850 °C at a rate of ≤80 °C / h and held for 2 h, then cooled in the furnace to 730 °C and held for 4 h, and finally cooled in the furnace to 430 °C and taken out of the furnace. The surface of the bars is polished, and ultrasonic flaw detection is carried out according to Grade A of GB / T 4162, and finally bearing steel bars are obtained.

[0138] 10) Sampling and inspection. Samples are taken from the bearing steel bars, and the specimens are quenched and tempered. The quenching regime is 1250 ± 10 °C for 30 min / air cooling, and the tempering regime is 560 ± 10 °C for 2 h / air cooling. The grain size is detected in the quenched state, and the hardness HRC, carbide non-uniformity, and carbide size are detected in the quenched and tempered state. Among them, the grain size rating is carried out according to GB / T6394, and the carbide non-uniformity rating is carried out according to the first rating diagram of GB / T 14979-1994. The specific results are shown in Tables 2, 3, and 4.

[0139] Comparative Example 2

[0140] The preparation method of the bearing steel bars in this comparative example specifically includes the following steps:

[0141] 1) Vacuum induction melting. High-quality raw steel is selected as the basic raw material, and alloying elements are added in the form of metallic Cr, metallic W, ferrovanadium, etc. Metallic Cr and V-Fe are baked, rust-free, oil-free, and dry. The tapping temperature is 1570 °C, and after the charged casting is completed, an electrode bar with the composition shown in Table 1 is obtained, and its specifications are The electrode bar is demolded in the vacuum chamber after 2 h.

[0142] 2) Annealing and finishing of the electrode bar. The electrode bar is kept at 600 °C for ≥2 h, heated to 780 °C at a rate of ≤100 °C / h and held for 5 h, and then cooled to 430 °C at a rate of ≤30 °C / h and taken out of the furnace. The surface of the electrode bar is ground to remove the scale completely.

[0143] 3) Electroslag remelting. The size of the mold The dummy bar is made of the same steel grade as the ingot. The remelting process is controlled in three stages. The voltage control is mainly used in the arc starting stage; the melting rate control is used in the stable stage, and the melting rate is set at 2.5 kg / min; the voltage control is mainly used in the capping and feeding stage. After the electroslag is completed, it is cooled in the mold for 60 min and then demolded.

[0144] 4) Annealing of the electroslag ingot. It is kept at 650 °C for ≥2 h, heated to 860 °C at a rate of ≤100 °C / h and held for 6 h, and then cooled to 430 °C at a rate of ≤30 °C / h and taken out of the furnace.

[0145] 5) Forging and cogging. The electroslag ingot is heated to 1230°C at a rate of ≤100°C / h and held for ≥2 h, and is upset and drawn with multiple passes to a total deformation ratio of 4.

[0146] 6) Annealing of the forged billet. The forged billet is held at 600°C for ≥1 h, heated to 860°C at a rate of ≤80°C / h and held for 6 h, and then cooled in the furnace to 430°C and taken out of the furnace.

[0147] 7) Hot-rolling of bars. The preheating temperature of the billet is 800°C, the heating temperature is 1120°C, the soaking temperature is 1120°C, the total heating time is ≥2.5 h, and the specifications of the hot-rolled bars

[0148] 8) Annealing, finishing and flaw detection of hot-rolled bars. The hot-rolled bars are held at 600°C for ≥1 h, heated to 850°C at a rate of ≤80°C / h and held for 2 h, then cooled in the furnace to 730°C and held for 4 h, and then cooled in the furnace to 430°C and taken out of the furnace. The surface of the bars is polished, and ultrasonic flaw detection is carried out according to Grade A of GB / T 4162, and finally bearing steel bars are obtained.

[0149] 9) Sampling and inspection of bars. Samples are taken from the bearing steel bars, and the specimens are quenched and tempered. The quenching regime is 1250±10°C for 30 min / air cooling, and the tempering regime is 560±10°C for 2 h / air cooling. The grain size is detected in the quenched state, and the hardness HRC, carbide non-uniformity and carbide size are detected in the quenched and tempered state. Among them, the grain size rating is carried out according to GB / T6394, and the carbide non-uniformity rating is carried out according to the first rating diagram of GB / T 14979-1994. The specific results are shown in Tables 2, 3 and 4.

[0150] Table 1 gives the chemical compositions of Examples 1 to 5 and Comparative Examples 1 to 2 of the present invention; trace Nb element is added in the examples, and Nb forms composite precipitation strengthening with W and V; in addition, the residual elements S / P / Ti / O are strictly controlled in the examples. Table 2 gives the grain size grades of the examples and comparative examples of the present invention. The grain size rating is carried out according to GB / T6394; the grains in the examples are more uniform and finer. Table 3 gives the carbide non-uniformity grades and the maximum size of eutectic carbides of the examples and comparative examples of the present invention; the carbide non-uniformity rating is carried out according to the first rating diagram of GB / T 14979-1994; the carbide non-uniformity rating in the examples is lower, that is, the carbides are more uniform and the carbide size is smaller, which are all helpful for improving the fatigue performance. Table 4 gives the quenched and tempered hardness HRC of the examples and comparative examples of the present invention.

[0151] Table 1 Chemical compositions of bearing steel bars in examples and comparative examples (wt.%)

[0152]

[0153] Table 2 Grain size grades of bearing steel bars in examples and comparative examples

[0154] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 1 Specification / mm Φ55 Φ75 Φ35 Φ45 Φ20 Φ55 Φ35 Grain size / grade 9.0 9.0 9.0 8.5 9.0 7.0～3.0 7.5～4.0

[0155] Table 3 Carbide non-uniformity level and maximum size in the bearing steel bars of the examples and comparative examples

[0156]

[0157] Table 4 Tempering hardness HRC of the examples and comparative examples

[0158] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 1 Specification / mm Φ55 Φ75 Φ35 Φ45 Φ20 Φ55 Φ35 HRC 64.0 63.5 64.0 64.0 64.5 62.0 61.5

[0159] In summary, as shown in Table 1, Table 2, Table 3 and Table 4, by compound adding chemical elements such as W, V, Nb, etc., and optimizing parameters such as vacuum induction casting temperature, electrode bar annealing process, electroslag remelting parameters, forging deformation ratio, etc., the eutectic carbide size of the present invention is ≤20 μm, and the eutectic carbides are evenly and dispersedly distributed; the carbide non-uniformity of the bar is ≤2.0 level, the carbide non-uniformity of the bar is ≤3.0 level, the carbide non-uniformity of the bar is ≤3.5 level. After the bar is subjected to high-temperature quenching at 1200 - 1260 ± 10 °C for 30 min, its grain size is finer than grade 8; after being quenched at 1200 - 1260 °C for 30 min and tempered at 560 ± 10 °C, its tempering hardness HRC ≥ 62.

[0160] Those of ordinary skill in the art in this embodiment should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention. As long as within the scope of the essential spirit of the present invention, changes and modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A W-series high-temperature bearing steel bar, characterized in that, It includes the following chemical components by mass percentage: C: 0.60 - 0.90%, Cr: 4.0 - 5.0%, W: 16.0 - 25.0%, V: 0.5 - 1.5%, Nb: 0.01 - 0.50%, S ≤ 0.0045%, P ≤ 0.0080%, Ti ≤ 0.0030%, N ≤ 0.0050%, O ≤ 0.0015%, and the balance is Fe and inevitable impurities; among them, the chemical components W, V, and Nb satisfy: 18% ≤ W + V + Nb ≤ 25%, where W, V, and Nb respectively refer to the mass percentages of the corresponding chemical components.

2. The W-series high-temperature bearing steel bar according to claim 1, characterized in that, The eutectic carbide size of the W series high-temperature bearing steel bar ≤ 20 μm; Bar stock specifications has carbide non-uniformity ≤ grade 2.0, and the bar stock specifications are has carbide non-uniformity ≤ grade 3.0, and the bar stock specifications are has carbide non-uniformity ≤ grade 3.

5.

3. The W-series high-temperature bearing steel bar according to claim 2, characterized in that, After the W series high-temperature bearing steel bar is subjected to high-temperature quenching treatment at 1200 - 1260 ± 10 °C for 30 min, its grain size ≥ 8 levels; After the W series high-temperature bearing steel bar is subjected to high-temperature quenching treatment at 1200 - 260 °C for 30 min and tempering treatment at 560 ± 10 °C for 2 h, its quenched and tempered hardness HRC ≥ 62.

4. A preparation method of the W-series high-temperature bearing steel bar according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1, Vacuum induction melting, adding raw materials into a vacuum induction furnace for melting, controlling the tapping temperature at 1500 - 1560 °C, and after casting with electricity, the obtained electrode bar is demolded after being cooled in a mold in a vacuum chamber; S2, Electrode bar annealing and finishing, after the electrode bar is kept at 500 - 650 °C for more than 2 h, it is continuously heated to 820 - 880 °C and kept for 4 - 12 h, then cooled in the furnace to below 430 °C and taken out of the furnace, and then the scale on its surface is removed through finishing; S3, Electroslag remelting, the annealed and finished electrode bar is subjected to electroslag remelting treatment in a mold to obtain an electroslag ingot; S4, Electroslag ingot annealing, after the electroslag ingot is kept at 500 - 650 °C for more than 2 h, it is continuously heated to 820 - 880 °C and kept for 4 - 12 h, then cooled in the furnace to below 430 °C and taken out of the furnace; S5, Forging and cogging, heating the electroslag ingot to 1130 - 1220 °C and keeping it for more than 2 h, and then obtaining a forged blank after multi-pass upsetting and drawing deformation; S6, Forged blank annealing, after the forged blank is kept at 600 - 650 °C for more than 1 h, it is continuously heated to 800 - 880 °C and kept for 2 - 12 h, then cooled in the furnace to below 430 °C and taken out of the furnace; S7, Hot rolling, heating the annealed forged blank in a heating furnace, and then rolling to obtain a hot-rolled bar; S8, Hot-rolled bar annealing, after the hot-rolled bar is kept at 600 - 650 °C for more than 1 h, it is continuously heated to 820 - 880 °C and kept for 2 - 5 h, cooled in the furnace to 720 - 760 °C and kept for 3 - 8 h, then continuously cooled in the furnace to below 430 °C and taken out of the furnace, and after the bar is finished and ultrasonically inspected, the W series high-temperature bearing steel bar is obtained.

5. The preparation method of the W-series high-temperature bearing steel bar according to claim 4, characterized in that, In the step S1, the electrode bar is demolded after being cooled in a mold in a vacuum chamber for 1 - 10 h.

6. The preparation method of the W-series high-temperature bearing steel bar according to claim 4, characterized in that, During the annealing processes in the steps S2, S4, S6, and S8, the heating rate of continuous heating ≤ 100 °C / h; During the annealing processes in the steps S2 and S4, the cooling rate of furnace cooling ≤ 50 °C / h.

7. The preparation method of the W-series high-temperature bearing steel bar according to claim 6, characterized in that, During the annealing process in steps S2, S4, S6, and S8, the heating rate for continuous heating is ≤ 80 °C / h; During the annealing process in steps S2 and S4, the cooling rate for furnace cooling is ≤ 40 °C / h.

8. The preparation method of the W-series high-temperature bearing steel bar according to claim 4, characterized in that, In step S3: Clean the mold before electroslag remelting; the electroslag remelting process includes an arc starting stage, a stable stage, and a capping and feeding stage; the arc starting stage uses power control with the power set to 50 - 300 KW, the stable stage uses melting rate control with the melting rate set to 4.0 - 2.0 kg / min, and the capping and feeding stage uses power control with the power set to 10 - 100 WK; After the electroslag remelting is completed, perform mold cooling for 60 - 120 min and then demold.

9. The preparation method of the W-series high-temperature bearing steel bar according to claim 4, characterized in that, In step S5, during the forging and blooming process: The heating rate of the electroslag ingot is ≤ 100 °C / h; the forging and blooming starting forging temperature is ≥ 1100 °C, the final forging temperature is ≥ 950 °C, and the total forging reduction ratio is ≥ 9.

10. The preparation method of the W-series high-temperature bearing steel bar according to claim 4, characterized in that, In step S7, during the heating of the annealed forging billet in the heating furnace, the preheating temperature of the forging billet is ≤ 800 °C, the heating temperature is 1150 - 1200 °C, the soaking temperature is 1150 - 1200 °C, the temperature difference between the front and back sides of the forging billet is ≤ 30 °C, and the total heating time is ≥ 2.5 h.

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