A precision cold rolling process for bearing ring traps

Abstract

This invention belongs to the technical field of alloy products. This invention provides a precision cold rolling process for bearing rings, comprising the following steps: S1, adding 95-95.5 parts by weight of pure iron, 1.48-1.51 parts by weight of chromium strip and 0.49-0.52 parts by weight into a vacuum induction furnace, evacuating to a pressure ≤1 Pa, purging with argon gas, and melting; S2, after melting and clearing, adding another 0.48-0.51 parts by weight of graphite into the vacuum induction furnace, evacuating again, performing carbon deoxidation, controlling the vacuum degree at 12-17 Pa, carbon deoxidation time at 30-35 min, and purging with argon gas again. S3. Add 0.23-0.26 parts of silicon blocks and 0.31-0.35 parts of manganese flakes sequentially to the vacuum induction furnace. Adjust the power to reach a temperature of 1540-1600℃. Then add 0.95-1 parts of ferrovanadium, 0.45-0.48 parts of ferroboron powder, and 0.27-0.3 parts of niobium-nitrogen composite sequentially. After holding at this temperature for 4-5 minutes, cast the mixture. Then, proceed with forging and bainitic isothermal treatment to obtain a bearing steel ring blank. S4. Perform a cold rolling forming process on the bearing steel ring blank to obtain the final product. This invention improves the impact toughness of high-carbon chromium bearing steel by adding vanadium (V), a strong carbide-forming element, while further enhancing its surface wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of alloy product technology, and in particular relates to a precision cold rolling process for bearing rings. Background Technology

[0002] Bearings, arguably the most fundamental and crucial core component of modern industrial systems, are often referred to as the "joints of high-end equipment," their importance permeating the entire industrial chain. They are widely used in both major equipment (such as machine tools and automobiles) and emerging industries (such as wind power generation and high-speed trains). Bearing rings are annular parts of radial rolling bearings with one or more raceways; high-carbon chromium bearing steel is generally used in the production of bearing rings.

[0003] In the preparation of high-carbon chromium bearing steel, the addition of vanadium (V), a strong carbide-forming element, can eliminate quenching microcracks that occur during quenching and tempering, thereby improving performance (such as impact toughness). Furthermore, the addition of vanadium (V) can also reduce the content of residual austenite after heat treatment, thereby improving the dimensional stability of the workpiece.

[0004] However, at the same time, the addition of vanadium (V) reduces the nucleation sites of bainite, resulting in insufficient bainite and an excess of martensite / retained austenite. Although martensite has high hardness, it is also brittle and is prone to brittle spalling during friction, forming hard abrasive grains and aggravating wear. Meanwhile, retained austenite has low hardness and is prone to plastic deformation under contact stress, resulting in a decrease in surface wear resistance / wear resistance. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a precision cold rolling process for bearing rings. By adding vanadium (V), a strong carbide-forming element, the impact toughness of the high-carbon chromium bearing steel is improved, while its surface wear resistance is further enhanced.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A precision cold rolling process for bearing rings includes the following steps: S1. By weight, add 95-95.5 parts of pure iron, 1.48-1.51 parts of chromium strip and 0.49-0.52 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside the furnace is ≤1Pa. Turn on the power and purge 50KPa argon gas into the furnace to begin the melting stage. S2. After melting and cleaning, add 0.48-0.51 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 12-17 Pa, and the carbon deoxidation time is 30-35 min. Argon gas is then introduced again.

[0007] S3. Add 0.23-0.26 parts of silicon block and 0.31-0.35 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. Adjust the power to make the temperature reach 1540-1600℃. Then add 0.95-1 parts of ferrovanadium, 0.45-0.48 parts of ferroboron powder and 0.27-0.3 parts of niobium-nitrogen composite in sequence. After the addition is completed, keep it at the temperature for 4-5 minutes, and then cast it. Then, it goes through forging and bainitic isothermal treatment in sequence to obtain the bearing steel ring blank. S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0008] Furthermore, the preparation method of the niobium-nitrogen composite is as follows: niobium powder is cold-pressed into a porous blank, heated and sintered under a nitrogen atmosphere to carry out a nitriding reaction, cooled and crushed in the furnace to obtain the niobium-nitrogen composite.

[0009] Furthermore, the niobium powder is passed through a 100-200 mesh sieve.

[0010] Furthermore, the pressure of the nitrogen atmosphere is 0.1-0.15 MPa.

[0011] Furthermore, the sintering temperature is 900-1150℃, and the nitriding reaction time is 1.5-2h.

[0012] Furthermore, the particle size of the niobium-nitrogen composite is 0.5-1 mm.

[0013] Furthermore, the boron content of the ferroboron powder is 20-25 wt%.

[0014] Furthermore, the particle size of the ferroboron powder is 80 mesh.

[0015] Furthermore, in S3, the initial forging temperature is 1170-1230℃, and the final forging temperature is 840-860℃.

[0016] Furthermore, in S3, the specific operation of the bainitic isothermal treatment is as follows: heating temperature 850-870℃, holding at that temperature for 30-35 minutes, then rapidly cooling to 235-245℃, isothermal for 4-4.2 hours, and then air cooling.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention introduces a niobium-nitrogen composite. On one hand, the niobium-nitrogen composite can form nanoscale Nb(C,N) particles, dispersed within the austenite grains and grain boundaries. These highly coherent precipitates provide a large number of heterogeneous nucleation sites for bainitic ferrite, increasing the nucleation rate and weakening / counteracting the inhibition mechanism of V on nucleation. Simultaneously, Nb in the multiphase matrix, as a metallic phase, possesses good toughness, buffering stress concentration between the hard phase and the matrix, preventing brittle fracture. Meanwhile, NbN and Nb2N in the multiphase matrix, as hard phases, are dispersed in the tough matrix, achieving a balance between wear resistance and impact resistance. On the other hand, the niobium-nitrogen composite can also form (Nb,V)(C,N) nanocomposite carbides with V, exhibiting extremely high hardness. Their dispersed distribution hinders dislocation movement, refines abrasive grains (fine-grain strengthening), and resists abrasive wear; thereby improving the impact toughness and surface wear resistance of the resulting bearing steel.

[0018] This invention also introduces ferroboron powder, which allows Nb and B to form the NbB phase. This eliminates the poisoning effect of B on bainite while enabling B to improve hardenability and stabilize the microstructure. The composite precipitation strengthening (Nb(C,N)+VC+NbB phase compound) forms multi-scale nano-hard particles (wear-resistant microstructure), ultimately synergistically improving the surface wear resistance of the obtained bearing steel. Attached Figure Description

[0019] Figure 1 This is a comparative trend chart of impact energy test data of bearing steel ring blanks prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention. Figure 2 This is a comparative trend chart of wear loss weight test data of bearing steel ring blanks prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention. Figure 3 This is a flowchart of the cold rolling forming process of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0022] The preparation method of the niobium-nitrogen complex involved in the following examples and comparative examples includes the following steps: Step 1: Pass niobium powder through a 100-mesh sieve to remove large agglomerated particles, add 2.8 wt% anhydrous ethanol, wet mix for 1 hour to improve formability, and dry at 75°C for 2 hours to remove ethanol.

[0023] Step 2: The treated niobium powder is loaded into a steel mold and cold-pressed at 240MPa to obtain a porous niobium billet; the size is 50×50×20mm and the relative density is 58% (the porosity is retained to facilitate nitriding). Step 3: Place the porous niobium billet in a corundum boat, put it into a tube furnace, evacuate to 10 Pa, heat to 300℃ at a rate of 10℃ / min, hold for 30 min to degas; continue heating at a rate of 10℃ / min to 600℃, introduce high-purity N2, and maintain the furnace pressure at 0.11 MPa (slight positive pressure); continue heating at a rate of 10℃ / min to 920℃, hold for 1.2 h (nitriding); continue heating at a rate of 10℃ / min to 1120℃, hold for 0.7 h (nitriding); continue N2 protection, cool with the furnace to 200℃, turn off the nitrogen, remove the sample and air-cool to room temperature, mechanically crush to 0.5-1 mm to obtain the niobium-nitrogen composite.

[0024] The resulting niobium-nitrogen complex is not a single phase of niobium nitride, but a multiphase complex of Nb2N, NbN and metallic Nb.

[0025] Example 1: A precision cold rolling process for bearing rings, comprising the following steps: S1. By weight, add 95.16 parts of pure iron, 1.5 parts of chromium strip and 0.52 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside is 1 Pa. Turn on the power and purge 50 kPa argon gas into the furnace to begin the melting stage.

[0026] The details of the main components (wt%) of pure iron are shown in Table 1.

[0027] Table 1. Main components of pure iron (wt%)

[0028] S2. After melting and cleaning, add 0.5 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 15 Pa, the carbon deoxidation time is 33 min, and then argon gas is introduced again at 10 kPa.

[0029] S3. Add 0.25 parts of silicon block and 0.33 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. After 4 minutes, measure the temperature and adjust the power to reach 1580℃. Then add 0.99 parts of ferrovanadium, 0.47 parts of ferroboron powder and 0.28 parts of niobium-nitrogen composite in sequence. After the addition is completed, keep it at the temperature for 4.5 minutes, and then cast it. Then, it goes through forging and bainitic isothermal treatment in sequence to obtain the bearing steel ring blank.

[0030] The vanadium content of the ferrovanadium is 50 wt%, and it was purchased from Zhengzhou Xingyan Mining Co., Ltd. The boron content of the ferroboron powder is 24.3 wt%, and the particle size is 80 mesh; it was purchased from Hebei Jincan Metal New Materials Co., Ltd.

[0031] The specific forging operation is as follows: the steel ingot obtained by casting is heated to 850°C along with the furnace temperature, maintained for 2 hours, then heated to 1200°C, and maintained for another 2 hours; then it is taken out of the furnace and forged directly, with a final forging temperature of 850°C; it is water-cooled in room temperature water to about 570°C, and then air-cooled at room temperature.

[0032] The specific procedure for isothermal treatment of bainite is as follows: heat to 860℃, hold for 32 minutes, then rapidly cool to 240℃ and remain isothermal for 4 hours.

[0033] S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0034] The cold rolling forming process is an existing technology, and its specific operation is as follows: Figure 3 The process is as follows: The bearing ring blanks are fed into the feeding machine, which automatically feeds them sequentially into the cold rolling mill. After 10 seconds of operation, the cold-rolled bearing rings are formed and transported through the material channel to the cold-rolled bearing ring storage area. When a certain quantity of cold-rolled bearing rings accumulates in the storage area, they are boxed and enter the stress-relief annealing furnace through the inlet. After the stress-relief annealing cycle, they are produced from the outlet and enter the annealed bearing ring storage area. The annealed bearing rings are fed back into the feeding machine, which sequentially feeds them into the first-stage CNC lathe for machining one side and the inner hole of the bearing ring. The machined bearing rings are then removed by a gantry robot and transferred to the second-stage CNC lathe for machining the other side and the outer diameter. The machined bearing rings are then removed by the gantry robot and transferred to the finished bearing ring storage area for storage. This processing cycle is repeated continuously.

[0035] Example 2: The difference between this example and Example 1 is that a precision cold rolling process for bearing rings includes the following steps: S1. By weight, add 95.21 parts of pure iron, 1.51 parts of chromium strip and 0.51 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside is 1 Pa. Turn on the power and purge 50 kPa argon gas into the furnace to begin the melting stage.

[0036] S2. After melting and cleaning, add 0.48 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 15 Pa, the carbon deoxidation time is 33 min, and then argon gas is introduced again at 10 kPa.

[0037] S3. Add 0.23 parts of silicon block and 0.31 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. After 4 minutes, measure the temperature and adjust the power to reach 1580℃. Then add 1 part of ferrovanadium, 0.48 parts of ferroboron powder and 0.27 parts of niobium-nitrogen composite in sequence. After the addition is completed, keep it at the temperature for 4.5 minutes, and then cast it. Then, it goes through forging and bainitic isothermal treatment in sequence to obtain the bearing steel ring blank.

[0038] S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0039] Example 3: The difference between this example and Example 1 is that a precision cold rolling process for bearing rings includes the following steps: S1. By weight, add 95.23 parts of pure iron, 1.48 parts of chromium strip and 0.5 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside the furnace is 1 Pa. Turn on the power and purge 50 kPa argon gas into the furnace to begin the melting stage.

[0040] S2. After melting and cleaning, add 0.48 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 15 Pa, the carbon deoxidation time is 33 min, and then argon gas is introduced again at 10 kPa.

[0041] S3. Add 0.26 parts of silicon block and 0.35 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. After 4 minutes, measure the temperature and adjust the power to reach 1580℃. Then add 0.95 parts of ferrovanadium, 0.45 parts of ferroboron powder and 0.3 parts of niobium-nitrogen composite in sequence. After the addition is completed, keep it at the temperature for 4.5 minutes, and then cast it. Then, it goes through forging and bainitic isothermal treatment in sequence to obtain the bearing steel ring blank.

[0042] S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0043] Comparative Example 1: The difference between this comparative example and Example 1 is that ferrovanadium, ferroboron powder and niobium nitrogen complex were all replaced with pure iron; that is, ferrovanadium, ferroboron powder and niobium nitrogen complex were not added.

[0044] Specifically, a precision cold rolling process for bearing rings includes the following steps: S1. By weight, add 96.9 parts of pure iron, 1.5 parts of chromium strip and 0.52 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside is 1 Pa. Turn on the power and purge 50 kPa argon gas into the furnace to begin the melting stage.

[0045] S2. After melting and cleaning, add 0.5 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 15 Pa, the carbon deoxidation time is 33 min, and then argon gas is introduced again at 10 kPa.

[0046] S3. Add 0.25 parts of silicon block and 0.33 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. After 4 minutes, measure the temperature and adjust the power to reach 1580℃. Hold the temperature for another 4.5 minutes, then cast the blank. After forging and bainitic isothermal treatment, the bearing steel ring blank is obtained.

[0047] S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0048] Comparative Example 2: The difference between this comparative example and Example 1 is that both the ferroboron powder and the niobium nitrogen complex were replaced with pure iron; that is, no ferroboron powder and niobium nitrogen complex were added.

[0049] Specifically, a precision cold rolling process for bearing rings includes the following steps: S1. By weight, add 95.91 parts of pure iron, 1.5 parts of chromium strip and 0.52 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside is 1 Pa. Turn on the power and purge 50 kPa argon gas into the furnace to begin the melting stage.

[0050] S2. After melting and cleaning, add 0.5 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 15 Pa, the carbon deoxidation time is 33 min, and then argon gas is introduced again at 10 kPa.

[0051] S3. Add 0.25 parts of silicon block and 0.33 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. After 4 minutes, measure the temperature and adjust the power to reach 1580℃. Then add 0.99 parts of ferrovanadium. After the addition is completed, keep it at the temperature for 4.5 minutes. Then cast it. Then, it goes through forging and bainitic isothermal treatment in sequence to obtain the bearing steel ring blank.

[0052] S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0053] Comparative Example 3: The difference between this comparative example and Example 1 is that the niobium-nitrogen complex was replaced with pure iron; that is, no niobium-nitrogen complex was added.

[0054] Specifically, a precision cold rolling process for bearing rings includes the following steps: S1. By weight, add 95.44 parts of pure iron, 1.5 parts of chromium strip and 0.52 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside is 1 Pa. Turn on the power and purge 50 kPa argon gas into the vacuum induction furnace to begin the melting stage.

[0055] S2. After melting and cleaning, add 0.5 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 15 Pa, the carbon deoxidation time is 33 min, and then argon gas is introduced again at 10 kPa.

[0056] S3. Add 0.25 parts of silicon block and 0.33 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. After 4 minutes, measure the temperature and adjust the power to reach 1580℃. Then add 0.99 parts of ferrovanadium and 0.47 parts of ferroboron powder in sequence. After the addition is completed, keep it at the temperature for 4.5 minutes, and then cast it. Then, it goes through forging and bainitic isothermal treatment in sequence to obtain the bearing steel ring blank.

[0057] S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0058] Comparative Example 4: The difference between this comparative example and Example 1 is that the ferroboron powder was replaced with pure iron; that is, no ferroboron powder was added.

[0059] Specifically, a precision cold rolling process for bearing rings includes the following steps: S1. By weight, add 95.63 parts of pure iron, 1.5 parts of chromium strip and 0.52 parts of graphite into the vacuum induction furnace. Start the vacuum pump to evacuate the furnace until the pressure inside is 1 Pa. Turn on the power and purge 50 kPa argon gas into the furnace to begin the melting stage.

[0060] S2. After melting and cleaning, add 0.5 parts of graphite to the vacuum induction furnace again, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 15 Pa, the carbon deoxidation time is 33 min, and then argon gas is introduced again at 10 kPa.

[0061] S3. Add 0.25 parts of silicon block and 0.33 parts of manganese sheet to the vacuum induction furnace of S2 in sequence. After 4 minutes, measure the temperature and adjust the power to reach 1580℃. Then add 0.99 parts of ferrovanadium and 0.28 parts of niobium-nitrogen composite in sequence. After the addition is completed, keep it at the temperature for 4.5 minutes, and then cast it. Then, it goes through forging and bainitic isothermal treatment in sequence to obtain the bearing steel ring blank.

[0062] S4. The bearing steel ring blank obtained in S3 is subjected to a cold rolling forming process to obtain the bearing ring.

[0063] Experimental Example: The bearing steel ring blanks prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests: Impact toughness: The room temperature impact performance was tested on a pendulum impact testing machine; the specimens were processed into V-notch impact specimens according to the requirements of national standard GB / T 229-2007.

[0064] Surface abrasion resistance: A wear loss test was conducted on an abrasion testing machine. The smaller the wear loss (accurate to 0.0001g), the better the abrasion resistance. The rotation speed was set to 200 rpm, the load to 30 lbs, and the total number of wear cycles to 1000 rpm.

[0065] Experimental results: see Table 2.

[0066] Table 2. Test Data for Experimental Examples

[0067] Results Analysis: Combining the data in Table 2 and... Figure 1 , Figure 2 Analysis of Examples 1-3 shows that the impact energy test data of the bearing steel ring blank samples prepared by the present invention (Examples 1-3) is as high as 53.0 J / cm. 2 The above figures are also true, and the wear loss test data is as low as 0.2647g.

[0068] Combining the data in Table 2 and Figure 1 , Figure 2 Analysis was performed on Example 1 and Comparative Examples 1-4: Specifically, comparing Comparative Example 1 and Comparative Example 2, it can be seen that, compared to Comparative Example 1, Comparative Example 2 introduced vanadium (ferrovanadium), resulting in an impact energy test data of 48.3 J / cm for the prepared bearing steel ring blank sample. 2 (Comparative Example 1) Increased to 50.8 J / cm 2 (Comparative Example 2) The impact toughness was improved; however, at the same time, the wear loss increased from 0.2882g (Comparative Example 1) to 0.3054g (Comparative Example 2), and the surface wear resistance decreased. This indicates that the addition of vanadium, a strong carbide-forming element, can improve the impact toughness of the prepared bearing steel ring blank sample, but it also leads to a decrease in its surface wear resistance.

[0069] Specifically, comparing Comparative Example 2 and Comparative Example 3, it can be seen that, compared to Comparative Example 2 which already had vanadium added, Comparative Example 3 added boron (iron boron powder) separately. As a result, the impact energy test data of the bearing steel ring blank sample increased from 50.8 J / cm². 2 (Comparative Example 2) decreased to 49.7 J / cm 2(Comparative Example 3) The impact toughness decreased; and the wear loss increased from 0.3054g (Comparative Example 2) to 0.3137g (Comparative Example 3), and the surface wear resistance also decreased. This indicates that adding boron (ferroboron powder) alone here will actually lead to a decrease in both the impact toughness and surface wear resistance of the bearing steel ring blank sample.

[0070] This is mainly because, although the generally known core functions of boron include improving hardenability and protecting austenite grain boundaries and inhibiting high-temperature embrittlement, typically enhancing toughness and wear resistance, adding boron alone here, on top of the fact that vanadium has already reduced / inhibited bainite nucleation sites, will further reduce grain boundary bainite nucleation efficiency and delay bainite transformation due to its relatively excessive amount compared to conventional methods and the non-equilibrium segregation of boron at austenite grain boundaries. This will produce a superimposed inhibition effect, causing the bainite transformation window to become excessively narrow. Under non-optimal cooling rate conditions, this can easily lead to microstructure inhomogeneity and increased residual stress, ultimately impairing impact toughness and surface wear resistance.

[0071] Specifically, comparing Comparative Example 2 and Comparative Example 4, it can be seen that, compared to Comparative Example 2 which already had vanadium added, Comparative Example 4 further added niobium-nitrogen composite material. As a result, the impact energy test data of the prepared bearing steel ring blank sample increased from 50.8 J / cm². 2 (Comparative Example 2) Increased to 52.7 J / cm 2 (Comparative Example 4) The impact toughness was improved; and the wear loss decreased from 0.3054g (Comparative Example 2) to 0.2688g (Comparative Example 4), indicating improved surface wear resistance. This shows that the addition of niobium-nitrogen compound alone can improve the impact toughness and surface wear resistance of the prepared bearing steel ring blank sample.

[0072] In comparison with Example 1, it can be seen that, with vanadium already added, the simultaneous addition of boron (ferroborone powder) and niobium-nitrogen composite can produce a synergistic effect, synergistically improving the impact toughness and surface wear resistance of the prepared bearing steel ring blank sample.

[0073] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A precision cold rolling process for bearing rings, characterized in that, Includes the following steps: S1. By weight, add 95-95.5 parts of pure iron, 1.48-1.51 parts of chromium strip and 0.49-0.52 parts of graphite into a vacuum induction furnace, evacuate to a pressure ≤1Pa, introduce argon gas, and begin the melting stage. S2. After melting and cleaning, add 0.48-0.51 parts of graphite to the vacuum induction furnace, evacuate the vacuum furnace, and perform carbon deoxidation. The vacuum degree is controlled at 12-17 Pa. After carbon deoxidation time of 30-35 min, argon gas is introduced again. S3. Add 0.23-0.26 parts of silicon blocks and 0.31-0.35 parts of manganese sheets to the vacuum induction furnace in sequence. When the temperature reaches 1540-1600℃, add 0.95-1 parts of ferrovanadium, 0.45-0.48 parts of ferroboron powder and 0.27-0.3 parts of niobium-nitrogen composite in sequence. After holding at the temperature for 4-5 minutes, cast the mixture. Then, after forging and bainitic isothermal treatment, the bearing steel ring blank is obtained. S4. The bearing steel ring blank is subjected to a cold rolling forming process to obtain the bearing ring.

2. The precision cold rolling process for bearing rings according to claim 1, characterized in that, The preparation method of the niobium-nitrogen composite is as follows: niobium powder is cold-pressed into a porous blank, heated and sintered in a nitrogen atmosphere to carry out a nitriding reaction, cooled and crushed in the furnace to obtain the niobium-nitrogen composite.

3. The precision cold rolling process for bearing rings according to claim 2, characterized in that, The niobium powder is passed through a 100-200 mesh sieve.

4. The precision cold rolling process for bearing rings according to claim 2, characterized in that, The pressure of the nitrogen atmosphere is 0.1-0.15 MPa.

5. The precision cold rolling process for bearing rings according to claim 2, characterized in that, The sintering temperature is 900-1150℃, and the nitriding reaction time is 1.5-2h.

6. The precision cold rolling process for bearing rings according to claim 2, characterized in that, The particle size of the niobium-nitrogen composite is 0.5-1 mm.

7. The precision cold rolling process for bearing rings according to claim 1, characterized in that, The boron content of the ferroboron powder is 20-25 wt%.

8. The precision cold rolling process for bearing rings according to claim 1 or 7, characterized in that, The boron-iron powder has a particle size of 80 mesh.

9. The precision cold rolling process for bearing rings according to claim 1, characterized in that, In S3, the initial forging temperature is 1170-1230℃, and the final forging temperature is 840-860℃.

10. The precision cold rolling process for bearing rings according to claim 1, characterized in that, In S3, the specific operation of the bainitic isothermal treatment is as follows: heating temperature 850-870℃, holding temperature for 30-35 minutes, then rapidly cooling to 235-245℃, isothermal for 4-4.2 hours, and then air cooling.

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