A method of machining a bearing ring

Abstract

The application relates to a bearing ring machining method and belongs to the technical field of bearing machining. The bearing ring machining method is characterized in that the raceway of a bearing ring blank is sequentially subjected to first induction heating and second induction heating. After the first induction heating, sufficient time and heat can be provided to make the heating position of the part uniform in temperature. When the second induction heating is started, the part to be heated has a high starting heating temperature, which can greatly reduce the temperature difference from the surface to the center of the heating position of the part during the second heating, and can further reduce the temperature of the second heating. The combined action of the two can greatly reduce the thermal stress generated during the heating process, and avoid cracks generated due to too large thermal stress during quenching.

Description

Technical Field

[0001] This invention relates to a method for processing bearing rings, belonging to the field of bearing processing technology. Background Technology

[0002] In recent years, with the rapid development of the wind power industry, high-power wind turbine yaw and pitch bearings have been widely used. Currently, the materials used for the bearing rings of yaw and pitch bearings for wind turbines below 7MW in China are mainly bearing steel composed of elements such as Cr, Mo, and Fe. The heat treatment process of the bearing rings has a significant impact on the machinability of the bearings.

[0003] In existing technologies, the heat treatment process for bearing rings mainly employs medium-frequency quenching. The medium-frequency quenching process primarily includes the following methods: 1. Using a single quenching inductor to continuously quench each bearing ring individually. This method results in significant deformation of the ring after quenching. 2. Using two quenching inductors positioned 180° apart (i.e., the distance between the two inductors equals the diameter of the bearing ring) to continuously quench the tooth surfaces of the bearing ring individually. This method can reduce the deformation of the ring to some extent, but it still affects the normal use of the bearing. 3. Using a cross-symmetrical quenching method. After two quenching inductors positioned 180° apart have quenched the tooth surfaces of two bearing rings, the ring is rotated a certain angle before quenching again. This method can further reduce the deformation of the ring. For example, Chinese patent document CN101629235A discloses a method for quenching the raceways of a double-raceway pitch bearing. This method involves quenching each raceway of the annular double-raceway pitch bearing individually. The annular double-raceway rings of the pitch bearing rotate at a constant speed on a vertical quenching machine, while the quenching inductor for medium-frequency quenching remains relatively fixed, achieving uniform quenching of the rotating annular double-raceway pitch bearing raceways. Each raceway is quenched individually. The quenching inductor employs a dual-power structure with two inductor heads, one for auxiliary heating and the other for quenching heating. After the uniformly rotating raceways undergo sequential heating, a synthetic quenching agent is sprayed on them for quenching and cooling. Chinese patent document CN101660025A discloses a medium-frequency quenching process for ultra-large diameter bearing cast steel parts, including the following steps: the bearing cast steel parts are sequentially subjected to a first heating, air cooling, a second heating, and water cooling. The first heating is medium-frequency induction heating at a temperature of 750–800℃, and the second heating is medium-frequency induction heating at a temperature of 880–920℃. The first heating is preheating, and the second heating is quenching heating. Although the above method can improve the hardness of the raceway surface, the quenching depth, and reduce the deformation of the bearing rings, cracks are prone to appear on the processed raceway surface, affecting its use. Summary of the Invention

[0004] The purpose of this invention is to provide a method for processing bearing raceways that can solve the problem that cracks easily appear on the raceways of yaw and pitch bearing raceways when they are subjected to medium-frequency quenching.

[0005] To achieve the above objectives, the technical solution adopted in the bearing ring processing method of the present invention is as follows:

[0006] A method for processing bearing raceways includes the following steps: sequentially subjecting the raceway of the bearing raceway blank to a first induction heating, a second induction heating, and a cooling process; the time interval between the first and second induction heating is 15-20 minutes, the temperature of the first induction heating is 890-920°C, the temperature of the second induction heating is 860-890°C, and the temperature of the first induction heating is higher than the temperature of the second induction heating.

[0007] The bearing ring processing method of the present invention involves sequentially performing a first induction heating and a second induction heating on the raceway of the bearing ring blank. After the first induction heating, there is sufficient time and heat to homogenize the temperature of the heated part. When the second induction heating is started, the part to be heated already has a high initial heating temperature, which can greatly reduce the temperature difference from the surface to the core of the heated part during the second heating. At the same time, it can further reduce the temperature of the second heating. The combined effect of these two factors can significantly reduce the thermal stress generated during the heating process and avoid cracks caused by excessive thermal stress during quenching.

[0008] As can be understood, induction heating involves placing a metal part inside an induction coil. An alternating current is passed through the coil, generating an alternating electromagnetic field, which induces an alternating current within the metal part. Due to the skin effect, the current concentrates primarily on the surface of the metal part, resulting in the highest surface temperature. After induction heating, the metal part is cooled. Because heating and cooling are mainly concentrated on the surface, surface modification is significant, while internal modification is minimal, achieving very specific heat treatment effects. Induction heating and cooling constitute a complete surface hardening process. Induction heating equipment includes a power supply and an inductor. Appropriate power and frequency (power frequency, intermediate frequency, and high frequency) can be selected based on the size of the workpiece and the depth of the hardened layer. The shape and size of the inductor mainly depend on the workpiece's shape and the requirements of the hardening process.

[0009] Preferably, the time difference between the end of the second induction heating and the start of the cooling is 50–100 s. Controlling this time difference to 50–100 s makes the heating temperature during quenching more uniform, further reducing the temperature difference from the surface to the core of the part, thus reducing internal stress during quenching. Experimental results show that when the time difference between the end of the second induction heating and the start of the cooling is <50 s, the rapid cooling increases the risk of crack formation; when the time difference is >100 s, the slow cooling leads to the formation of some bainite and pearlite, resulting in a shallow hardened layer depth in the quenched area of ​​the part.

[0010] To improve the heating rate and reduce defects on the bearing raceway surface, preferably, the induction hardening frequencies of the first and second induction heating are independently 2–5 kHz. For example, the induction hardening frequencies of the first and second induction heating are independently 3 kHz.

[0011] To ensure continuous industrial production and improve processing efficiency, it is preferable that the first and second induction heating are performed using a hardening machine tool. Before heat treatment of the raceway of the bearing ring blank, the bearing ring blank is first fixed on the hardening machine tool, and then the surface of the bearing ring blank to be treated is sequentially subjected to the first and second induction heating using the inductor on the hardening machine tool.

[0012] To improve processing efficiency, preferably, two inductors are used to perform a first induction heating and a second induction heating on the raceway of the bearing ring blank in sequence. During the heating process, the bearing ring blank is controlled to rotate at a constant speed, while the two inductors are kept stationary.

[0013] Preferably, the cooling treatment method is method A, method B, or method C; method A involves air cooling the raceway after the second induction heating; method B involves cooling the raceway after the second induction heating with compressed air; method C involves sequentially performing a first cooling treatment and a second cooling treatment on the raceway after the second induction heating, with a time interval of 10-15 seconds between the first and second cooling treatments, and a total time of 45-75 seconds for both treatments. In this invention, using air cooling or compressed air cooling on the part after the second induction heating can significantly reduce the quenching crack sensitivity of the parts, completely solve the quenching crack problem, and also significantly reduce production costs and protect the environment; or, sequentially performing a first cooling treatment and a second cooling treatment on the part after the second induction heating, controlling the total time of the first and second cooling treatments to 45-75 seconds and the time interval to 10-15 seconds, can improve the cooling rate while ensuring that no cracks occur on the metal surface.

[0014] Preferably, the pressure of the compressed air is 1.5–2 MPa. High-speed ejected cold air rapidly removes heat from the quenched areas of the part, causing the treated surface to cool down quickly. This cooling method can significantly reduce the quenching crack sensitivity of the part while ensuring that the quenching hardness and hardened layer depth requirements are met (raceway surface hardness ≥ 58 HRC, hardened layer depth ≥ 8 mm), completely solving the quenching crack problem. It can also significantly reduce production costs and protect the environment.

[0015] Preferably, when the cooling method is method B, the rotational speed of the bearing ring blank is 150–210 mm / min. If the rotational speed of the bearing ring blank is too low, the quenching time will be long and the production efficiency will be low. If the rotational speed of the bearing ring blank is too high, the heated raceway surface will not cool sufficiently, resulting in low raceway surface hardness.

[0016] To improve processing efficiency and increase the surface hardness of the raceway, preferably, when the cooling method is method C, the first cooling treatment time is 15–25 s, and the cooling rate of the first cooling treatment is 16–26 °C / s. Preferably, the flow rate of the coolant used in the first cooling treatment is 24–28 L / min. Controlling the flow rate of the coolant used in the first cooling treatment to 24–28 L / min makes it difficult for a vapor film to form on the surface of the workpiece during quenching, increasing the surface cooling rate and achieving high surface hardness. Simultaneously, the shorter first cooling treatment time avoids excessive martensite transformation during this stage.

[0017] To ensure more thorough and less drastic cooling, the second cooling process preferably lasts 30–50 seconds, with a cooling rate of 6–10 °C / s. Preferably, the coolant flow rate used in the second cooling process is 15–20 L / min. The longer duration of the second cooling process and the controlled coolant flow rate of 15–20 L / min ensure more thorough and less drastic cooling during this stage.

[0018] Both the first and second cooling treatments are performed by spraying coolant from the coolant tanks on the quenching machine. Specifically, two coolant tanks are installed on the quenching machine. The time interval between the first and second cooling treatments can be adjusted by changing the rotation speed of the bearing rings and the distance between the two coolant tanks. The duration of either the first or second cooling treatment can be adjusted by changing the size of the coolant tanks and the rotation speed of the bearing rings.

[0019] The coolant used for medium-frequency quenching of bearing rings is applicable to this invention.

[0020] To reduce the risk of quenching cracks and effectively improve the material's hardness, hardened layer depth, and reduce defects on the raceway surface, the bearing ring blank is preferably made of bearing steel, which comprises the following elements by mass fraction: carbon 0.45–0.55%, silicon 0.17–0.37%, manganese 0.80–1.10%, chromium 1.00–1.20%, molybdenum 0.20–0.35%, vanadium 0.02–0.09%, nickel ≤0.25%, aluminum 0.015–0.035%, copper ≤0.20%, phosphorus ≤0.02%, sulfur ≤0.02%, titanium ≤0.003%, hydrogen ≤0.0002%, and oxygen ≤0.002%. Experimental results show that, compared to other types of alloy steel, the bearing steel described above has higher hardenability, and when used to process bearing rings, higher surface hardness and hardened layer depth can be obtained.

[0021] To reduce internal and surface defects in bearing ring blanks and improve their surface hardness, the bearing ring blanks are preferably manufactured using a method comprising the following steps: heat-treating a metal blank, then forging it to obtain a ring forging, and finally cooling the ring forging and subjecting it to quenching and tempering heat treatment to obtain the bearing ring blank. By subjecting the metal blank to heat treatment, forging, and quenching and tempering heat treatment, the resulting bearing ring blank exhibits lower stress. Furthermore, applying the aforementioned surface heat treatment method for metal parts to heat-treat the raceway can further reduce the thermal stress on the bearing rings and the risk of cracking.

[0022] To simultaneously improve processing efficiency and reduce defects in bearing ring blanks, the heat treatment preferably includes a first-stage heat treatment, a second-stage heat treatment, and a third-stage heat treatment performed sequentially. The temperature of the first-stage heat treatment is 600–650°C, and the duration is 0.5–1 hour. The temperature of the second-stage heat treatment is 830–860°C, and the duration is 1–2 hours. The temperature of the third-stage heat treatment is 1150–1200°C, and the duration is 3–4 hours. Preferably, the temperature of the first-stage heat treatment is T1, the temperature of the second-stage heat treatment is T2, and the temperature of the third-stage heat treatment is T3. The heating rate from room temperature to T1 is no greater than 100°C / hour, and the heating rate from T1 to T2 is no greater than 120°C / hour. Preferably, the heating rate from T2 to T3 is 350–400°C / hour. By adopting a staged heating method and controlling the heating rates of the first and second stages within the aforementioned range, the thermal stress generated during the heating process can be reduced, preventing excessive thermal stress from causing internal cracks. Controlling the temperature of the third stage heating within the aforementioned temperature range can improve production efficiency while reducing the degree of oxidation and decarburization.

[0023] To improve processing efficiency and reduce defects in bearing ring blanks, the forging process preferably includes upsetting, punching, and rolling in sequence, with an initial forging temperature of 1150–1200°C and a final forging temperature of 800–900°C.

[0024] Preferably, the quenching and tempering heat treatment includes sequential quenching and tempering. The quenching method includes the following steps: heating the ring forging to 830–850°C, holding it at that temperature for 3–4 hours, then cooling it to 150–180°C at a cooling rate of 30–40°C / min, and finally air-cooling it to room temperature. The tempering method includes the following steps: heating the quenched ring forging to 620–640°C, holding it at that temperature for 6–8 hours, then furnace-cooling it to 290–310°C, and finally air-cooling it to room temperature. Using the above quenching and tempering heat treatment method can improve the hardness and hardenability of the ring forging, and also reduce the formation of internal cracks in the ring forging.

[0025] Preferably, the time difference between the end of the quenching process and the start of the tempering process is no more than 4 hours. Controlling the time difference between the end of the quenching process and the start of the tempering process to no more than 4 hours can prevent the forging from cracking due to high quenching stress after quenching. Attached Figure Description

[0026] Figure 1 This is a schematic diagram showing the positions of the two induction heaters and two coolant boxes in Embodiment 1 of the present invention; the reference numerals are as follows: 1-first induction heater; 2-second induction heater; 3-first coolant box; 4-second coolant box. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0028] The bearing steel used in the processing methods of bearing rings in Examples 1-5 comprises the following elements by mass fraction: carbon 0.45-0.55%, silicon 0.17-0.37%, manganese 0.80-1.10%, chromium 1.00-1.20%, molybdenum 0.20-0.35%, vanadium 0.02-0.09%, nickel ≤0.25%, aluminum 0.015-0.035%, copper ≤0.20%, phosphorus ≤0.02%, sulfur ≤0.02%, titanium ≤0.003%, hydrogen ≤0.0002%, oxygen ≤0.002%, with the balance being iron.

[0029] Example 1

[0030] The bearing ring processing method of this embodiment specifically includes the following steps:

[0031] (1) The bearing steel is smelted into a continuous casting billet with a diameter φ of 800mm. The continuous casting billet is then heat-treated to obtain a heated part. The heated part is then forged and rolled into a ring to obtain a ring forging. The ring forging is then air-cooled to room temperature. Finally, the ring forging is subjected to quenching and tempering heat treatment to obtain a bearing ring blank. The heat treatment involves heating the continuous casting billet to 650℃ at a heating rate of 100℃ / h and holding it at that temperature for 0.5h. Then, it is heated to 860℃ at a heating rate of 120℃ / h and held at that temperature for 1h. Finally, it is heated to 1200℃ at a heating rate of 400℃ / h and held at that temperature for 3h. The forging involves upsetting, punching, and rolling the heated part in sequence. The initial forging temperature is 1200℃. The final forging temperature is 900℃. The quenching and tempering heat treatment method includes the following steps: the ring forging is placed in a heating furnace, then heated to 850℃ and held for 3 hours. The ring forging is then removed from the heating furnace and immersed in a cooling liquid at a cooling rate of 30℃ / min to 180℃. The ring forging is then removed from the cooling liquid and air-cooled to room temperature to complete the quenching treatment. The quenched ring forging is then placed in a heating furnace and heated to 640℃ and held for 6 hours. It is then cooled in the furnace to 310℃. The quenched ring forging is then removed from the heating furnace and air-cooled to room temperature to complete the tempering treatment. The time difference between the end of the quenching treatment and the beginning of the tempering treatment is no more than 4 hours.

[0032] (2) Fix the bearing ring blank on the quenching machine, and simultaneously make the raceway of the bearing ring blank pass through two induction heaters at a certain angle; the position diagram of the two induction heaters and the two coolant boxes is shown in the figure. Figure 1 As shown, Figure 1 The heater located on the left is the first induction heater 1, and the heater located on the right is the second induction heater 2. The lower end of the second induction heater 2 is respectively provided with a first coolant box 3 and a second coolant box 4.

[0033] (3) Turn on the quenching machine and make the bearing ring blank rotate at a constant speed. At the same time, turn on the first induction heater. During the uniform rotation of the bearing ring blank, the first induction heater performs the first induction heating on each part of the raceway of the bearing ring blank in sequence. When a part of the bearing ring blank passes the second induction heater after being induction heated for the first time, turn on the second induction heater. During the uniform rotation of the bearing ring blank, the second induction heater performs the second induction heating on each part of the raceway of the bearing ring blank. The time interval between the first and second induction heating on each part of the raceway of the bearing ring blank (i.e., the time difference between the end of the first induction heating and the start of the second induction heating) is 20 min. The temperature of the first induction heating is 900℃, the temperature of the second induction heating is 870℃, the time of the first induction heating is 70 s, the time of the second induction heating is 70 s, and the induction quenching frequency of the first and second induction heating is 3 kHz. After a part of the raceway of the bearing ring blank is induction heated for the second time, it passes the second induction heater. When the first coolant box is opened, the coolant in the first coolant box is sprayed out at a flow rate of 26 L / min to perform the first cooling treatment on the part after the second induction heating. The first cooling treatment time for each part of the bearing ring blank raceway is 20 s, and the cooling rate of the first cooling treatment is 26℃ / s. When a part of the bearing ring blank raceway passes through the second coolant box after the first cooling treatment, the second coolant box is opened, and the coolant in the second coolant box is sprayed out at a flow rate of 17 L / min to perform the second cooling treatment on the part after the first cooling treatment. The second cooling treatment time for each part of the bearing ring blank raceway is 40 s, and the cooling rate of the second cooling treatment is 10℃ / s. The time interval between the first and second cooling treatments for each part of the bearing ring blank raceway (i.e., the time difference between the end of the first cooling treatment and the start of the second cooling treatment) is 15 s. The time difference between the end of the second induction heating and the start of the first cooling treatment for each part of the bearing ring blank raceway is 80 s. In this embodiment, the mass fraction of the coolant in the first coolant box and the quenching agent in the second coolant box is 16%.

[0034] Example 2

[0035] The bearing ring processing method of this embodiment specifically includes the following steps:

[0036] (1) The bearing steel is smelted into a continuous casting billet with a diameter of φ of 800mm. The continuous casting billet is then heat-treated sequentially to obtain a heated part. The heated part is then forged to obtain a ring forging. The ring forging is then air-cooled to room temperature. Finally, the ring forging is subjected to quenching and tempering heat treatment to obtain a bearing ring blank. The heat treatment involves heating the continuous casting billet to 600℃ at a heating rate of 100℃ / h and holding it for 1h. Then, it is heated to 830℃ at a heating rate of 120℃ / h and held for 2h. Then, it is heated to 1150℃ at a heating rate of 350℃ / h and held for 4h. The forging involves upsetting, punching, and rolling the heated part sequentially. The initial forging temperature is 1150℃, and the final forging temperature is 1150℃. The temperature is 800℃; the quenching and tempering heat treatment method includes the following steps: the ring forging is placed in a heating furnace, then heated to 830℃ and held for 4 hours. The ring forging is then removed from the heating furnace and immersed in a cooling liquid at a cooling rate of 40℃ / min to 150℃. The ring forging is then removed from the cooling liquid and air-cooled to room temperature to complete the quenching treatment. The quenched ring forging is then placed in a heating furnace and heated to 620℃ and held for 8 hours. It is then cooled in the furnace to 290℃. The quenched ring forging is then removed from the heating furnace and air-cooled to room temperature to complete the tempering treatment. The time difference between the end of the quenching treatment and the beginning of the tempering treatment is no more than 4 hours.

[0037] (2) This step is the same as step (2) in Example 1;

[0038] (3) Turn on the quenching machine and make the bearing ring blank rotate at a constant speed. At the same time, turn on the first induction heater. During the uniform rotation of the bearing ring blank, the first induction heater performs the first induction heating on each part of the raceway of the bearing ring blank in sequence. When a part of the bearing ring blank passes the second induction heater after being induction heated for the first time, turn on the second induction heater. During the uniform rotation of the bearing ring blank, the second induction heater performs the second induction heating on each part of the raceway of the bearing ring blank. The time interval between the first and second induction heating on each part of the raceway of the bearing ring blank (i.e., the time difference between the end of the first induction heating and the start of the second induction heating) is 15 min. The temperature of the first induction heating is 890℃, the temperature of the second induction heating is 860℃, the time of the first induction heating is 64 s, and the time of the second induction heating is 64 s. The induction quenching frequency of the first and second induction heating is 5 kHz. When a part of the raceway of the bearing ring blank is heated... After the second induction heating, when the bearing ring blank passes through the first coolant box, the first coolant box is opened, allowing the coolant in the first coolant box to spray out for the first cooling treatment of the part after the second induction heating. The first cooling treatment time for each part of the bearing ring blank raceway is 15s, and the cooling rate of the first cooling treatment is 21℃ / s. When a part of the bearing ring blank raceway passes through the second coolant box after the first cooling treatment, the second coolant box is opened, allowing the coolant in the second coolant box to spray out for the second cooling treatment of the part after the first cooling treatment. The second cooling treatment time for each part of the bearing ring blank raceway is 30s, and the cooling rate of the second cooling treatment is 8℃ / s. The time interval between the first and second cooling treatments for each part of the bearing ring blank raceway (i.e., the time difference between the end of the first cooling treatment and the start of the second cooling treatment) is 10s. The time difference between the end of the second induction heating and the start of the first cooling treatment for each part of the bearing ring blank raceway is 50s.

[0039] Example 3

[0040] The bearing ring processing method of this embodiment specifically includes the following steps:

[0041] (1) This step is the same as step (1) in Example 1;

[0042] (2) This step is the same as step (2) in Example 1;

[0043] (3) Turn on the quenching machine and rotate the bearing ring blank at a constant speed. At the same time, turn on the first induction heater. During the constant speed rotation of the bearing ring blank, the first induction heater performs the first induction heating on each part of the raceway of the bearing ring blank in sequence. When a certain part of the raceway on the bearing ring blank passes the second induction heater after being induction heated for the first time, turn on the second induction heater. During the constant speed rotation of the bearing ring blank, the second induction heater performs the second induction heating on each part of the raceway of the bearing ring blank. The time interval between the first and second induction heating on each part of the raceway of the bearing ring blank (i.e., the time difference between the end of the first induction heating and the start of the second induction heating) is 18 min. The temperature of the first induction heating is 920℃, the temperature of the second induction heating is 890℃, the time of the first induction heating is 78 s, the time of the second induction heating is 78 s, and the induction quenching frequency of the first and second induction heating is 2 kHz. When the bearing raceway part passes through the first coolant box after being induction heated for the second time, the first coolant box is opened, allowing the coolant in the first coolant box to spray out and perform the first cooling treatment on the part after the second induction heating. The first cooling treatment time for each part of the bearing raceway part is 25s, and the cooling rate of the first cooling treatment is 16℃ / s. When a part of the bearing raceway part passes through the second coolant box after the first cooling treatment, the second coolant box is opened, allowing the coolant in the second coolant box to spray out and perform the second cooling treatment on the part after the first cooling treatment. The second cooling treatment time for each part of the bearing raceway part is 50s, and the cooling rate of the second cooling treatment is 6℃ / s. The time interval between the first and second cooling treatments for each part of the bearing raceway part (i.e., the time difference between the end of the first cooling treatment and the start of the second cooling treatment) is 12s. The time difference between the end of the second induction heating and the start of the first cooling treatment for each part of the bearing raceway part is 100s.

[0044] Example 4

[0045] The bearing ring processing method of this embodiment specifically includes the following steps:

[0046] (1) This step is the same as step (1) in Example 1;

[0047] (2) Fix the bearing ring blank on the quenching machine tool, and at the same time make the raceway of the bearing ring blank pass through two induction heaters at a certain angle; the first induction heater is located on the left side, the second induction heater is located on the right side, and the lower end of the second induction heater is equipped with a compressed air cooling device.

[0048] (3) Turn on the quenching machine and make the bearing ring blank rotate at a constant speed. At the same time, turn on the first induction heater. During the uniform rotation of the bearing ring blank, the first induction heater performs the first induction heating on each part of the raceway of the bearing ring blank in sequence. When a certain part of the raceway on the bearing ring blank passes the second induction heater after being induction heated for the first time, turn on the second induction heater. During the uniform rotation of the bearing ring blank, the second induction heater performs the second induction heating on each part of the raceway of the bearing ring blank. The time interval between the first and second induction heating of each part of the raceway on the bearing ring blank (i.e., the time difference between the end of the first induction heating and the start of the second induction heating) is 15 minutes. The temperature of the first induction heating is 890℃, and the temperature of the second induction heating is 860℃. The duration of the first induction heating is 64s, and the duration of the second induction heating is 64s. The induction quenching frequency of both the first and second induction heating is 3kHz. After a certain raceway part of the bearing ring blank is induction heated for the second time, it passes through the compressed air cooling device. The compressed air cooling device is turned on, and compressed air at a pressure of 1.8MPa is sprayed out to cool the part after the second induction heating. The distance between the compressed air outlet of the compressed air cooling device and the quenching heating head of the second induction heater is 55mm. The time difference between the end of the second induction heating and the start of the compressed air cooling at each part of the raceway of the bearing ring blank is 22s.

[0049] Example 5

[0050] The bearing ring processing method of this embodiment specifically includes the following steps:

[0051] (1) This step is the same as step (1) in Example 3;

[0052] (2) Fix the bearing ring blank on the quenching machine tool, and at the same time make the raceway of the bearing ring blank pass through two induction heaters at a certain angle; the first induction heater is located on the left and the second induction heater is located on the right.

[0053] (3) Turn on the quenching machine and make the bearing ring blank rotate at a constant speed. At the same time, turn on the first induction heater. During the constant speed rotation of the bearing ring blank, the first induction heater performs the first induction heating on each part of the raceway of the bearing ring blank in sequence. When a certain part of the raceway on the bearing ring blank passes the second induction heater after being induction heated for the first time, turn on the second induction heater. During the constant speed rotation of the bearing ring blank, the second induction heater performs the second induction heating on each part of the raceway of the bearing ring blank. The time interval between the first induction heating and the second induction heating on each part of the raceway of the bearing ring blank (i.e., the time difference between the end of the first induction heating and the start of the second induction heating) is 18 min. The temperature of the first induction heating is 920℃ and the temperature of the second induction heating is 890℃. The time of the first induction heating is 78 s and the time of the second induction heating is 78 s. The induction quenching frequency of the first induction heating and the second induction heating is 3 kHz. Then, the part of the bearing ring blank that has been induction heated for the second time is air-cooled.

[0054] Comparative Example 1

[0055] The difference between the bearing ring processing method of this comparative example and the bearing ring processing method of Example 1 is that in step (3) of the bearing ring processing method of this comparative example, the size of the first coolant box is adjusted so that the time for the first cooling treatment of each part of the raceway of the bearing ring blank is equal to the sum of the time for the first cooling treatment and the second cooling treatment of each part of the raceway of the bearing ring blank in Example 1, and the flow rate of the coolant in the second coolant box is adjusted to 0.

[0056] Comparative Example 2

[0057] The difference between the bearing ring processing method of this comparative example and the bearing ring processing method of Example 1 is that in step (3) of the bearing ring processing method of this comparative example, the size of the second coolant box is adjusted so that the time for the second cooling treatment of each part of the raceway of the bearing ring blank is equal to the sum of the time for the first cooling treatment and the second cooling treatment of each part of the raceway of the bearing ring blank in Example 1, and the flow rate of the coolant in the first coolant box is adjusted to 0.

[0058] Comparative Example 3

[0059] The only difference between the bearing ring processing method of this comparative example and the bearing ring processing method of Example 1 is that the first coolant box used in step (3) of the bearing ring processing method of this comparative example is the second coolant box in Example 1, and the second coolant box is the first coolant box in Example 1. At the same time, the cooling rate of the first cooling treatment in the bearing ring processing method of this comparative example is the same as the cooling rate of the second cooling treatment in Example 1. The time for the first cooling treatment of each part of the raceway of the bearing ring blank is equal to the time for the second cooling treatment of each part of the raceway of the bearing ring blank in Example 1. The cooling rate of the second cooling treatment is the same as the cooling rate of the first cooling treatment in Example 1. The time for the second cooling treatment of each part of the raceway of the bearing ring blank is equal to the time for the first cooling treatment of each part of the raceway of the bearing ring blank in Example 1.

[0060] Comparative Example 4

[0061] The difference between the bearing ring processing method of this comparative example and the bearing ring processing method of Example 1 is that the temperature of the first induction heating in step (3) of the bearing ring processing method of this comparative example is 870°C and the temperature of the second induction heating is 900°C.

[0062] Experimental Example 1

[0063] To evaluate the quality of bearing raceways processed by different methods, the surface Rockwell hardness and hardened layer depth of the bearing raceways processed in Examples 1-5 and Comparative Examples 1-4 were tested. Simultaneously, surface and near-surface defects of the bearing raceway were tested using magnetic particle testing equipment. The results are shown in Table 1. When testing the surface Rockwell hardness and hardened layer depth, five different locations were randomly selected on the bearing raceway surface for testing. The minimum and maximum values ​​of the test results were recorded, and the results are expressed as a numerical range.

[0064] Table 1 Rockwell hardness, hardened layer depth, and surface defects of bearing ring raceways processed by various methods.

[0065]

[0066]

[0067] Experiment Example 2

[0068] To investigate the effects of the heat treatment methods for continuously cast billets and the tempering heat treatment methods for ring forgings on the experimental results when machining bearing ring blanks, the bearing ring blanks were machined according to step (1) of the bearing ring machining method in Example 1. The difference was that the heat treatment method for continuously cast billets in Example 1 was adjusted to heat treatment method 1, heat treatment method 2, or heat treatment method 3, or the tempering heat treatment method for ring forgings was adjusted to tempering heat treatment method 1 or tempering heat treatment method 2. Then, the bearing ring blanks obtained after forging and tempering heat treatment after different heat treatment methods, as well as the bearing ring blanks obtained after different tempering heat treatments, were subjected to performance tests. The results are shown in Tables 2-3. In Table 3, the performance indicators of the bearing ring blanks are specified as follows: the surface hardness of the bearing ring blanks is 260~320HBW, the impact energy KV2 at -40℃ is ≥27J, and there should be no cracks.

[0069] Among them, the method of heating the continuously cast billet to 1200℃ at a heating rate of 100℃ / h and holding it at that temperature for 4.5h is called heat treatment method 1; the method of heating the continuously cast billet to 1200℃ at a heating rate of 120℃ / h and holding it at that temperature for 4.5h is called heat treatment method 2; and the method of heating the continuously cast billet to 1200℃ at a heating rate of 350℃ / h and holding it at that temperature for 4.5h is called heat treatment method 3. The quenching and tempering heat treatment method 1 includes the following steps: placing the ring forging in a heating furnace, heating the ring forging to 850°C, holding it at that temperature for 3 hours, then removing the ring forging from the heating furnace and immersing it in a cooling liquid to cool it to 200°C at a cooling rate of 30°C / min, then removing the ring forging from the cooling liquid and air-cooling it to room temperature to complete the quenching treatment, then placing the quenched ring forging in a heating furnace and heating it to 640°C, holding it at that temperature for 6 hours, then cooling it in the furnace to 310°C, and finally removing the quenched ring forging from the heating furnace and air-cooling it to room temperature to complete the tempering treatment. The quenching and tempering heat treatment method 2 includes the following steps: placing the ring forging in a heating furnace, heating the ring forging to 850°C, holding it at that temperature for 3 hours, then removing the ring forging from the heating furnace and immersing it in a cooling liquid to cool it to 130°C at a cooling rate of 30°C / min, then removing the ring forging from the cooling liquid and air-cooling it to room temperature to complete the quenching treatment, then placing the quenched ring forging in a heating furnace and heating it to 640°C, holding it at that temperature for 6 hours, then cooling it in the furnace to 310°C, and finally removing the quenched ring forging from the heating furnace and air-cooling it to room temperature to complete the tempering treatment.

[0070] Table 2 Performance test results of bearing ring blanks for different heat treatment methods

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[0073] Table 3 Performance test results of bearing ring blanks corresponding to different quenching and tempering heat treatment methods

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Claims

1. A method for machining bearing rings, characterized in that, Includes the following steps: The raceway of the bearing ring blank is subjected to a first induction heating, a second induction heating, and a cooling process in sequence. The time interval between the first and second induction heating is 15-20 minutes. The temperature of the first induction heating is 890-920℃, and the temperature of the second induction heating is 860-890℃. The temperature of the first induction heating is higher than that of the second induction heating. The time difference between the end of the second induction heating and the start of the cooling process is 50-100 seconds. The cooling process involves sequentially performing a first cooling process and a second cooling process on the raceway after the second induction heating. The time interval between the first and second cooling processes is 10-15 seconds, and the total time for the first and second cooling processes is 45-75 seconds. The first cooling process lasts 15-25 seconds and has a cooling rate of 16-26℃ / s. The second cooling process lasts 30-50 seconds and has a cooling rate of 6-10℃ / s.

2. The method for processing bearing rings as described in claim 1, characterized in that, The bearing ring blank is prepared by a method including the following steps: heating the metal blank, then forging it to obtain a ring forging, and then cooling the ring forging and performing a tempering heat treatment to obtain the bearing ring blank.

3. The method for processing bearing rings as described in claim 2, characterized in that, The heat treatment includes a first stage heat treatment, a second stage heat treatment, and a third stage heat treatment performed sequentially. The temperature of the first stage heat treatment is 600~650℃ and the time of the first stage heat treatment is 0.5~1h. The temperature of the second stage heat treatment is 830~860℃ and the time of the second stage heat treatment is 1~2h. The temperature of the third stage heat treatment is 1150~1200℃ and the time of the third stage heat treatment is 3~4h.

4. The method for processing bearing rings as described in claim 3, characterized in that, The temperature of the first stage of heating treatment is T1, the temperature of the second stage of heating treatment is T2, and the temperature of the third stage of heating treatment is T3. The heating rate from room temperature to T1 is no more than 100℃ / h, the heating rate from T1 to T2 is no more than 120℃ / h, and the heating rate from T2 to T3 is 350~400℃ / h.

5. The method for processing bearing rings as described in claim 2, characterized in that, The forging process includes upsetting, punching, and ring rolling performed sequentially, with an initial forging temperature of 1150~1200℃ and a final forging temperature of 800~900℃.

6. The method for processing bearing rings as described in claim 2, characterized in that, The quenching and tempering heat treatment includes quenching and tempering processes performed sequentially.

7. The method for processing bearing rings as described in claim 6, characterized in that, The quenching treatment method includes the following steps: heating the ring forging to 830~850℃, holding it at that temperature for 3~4h, then cooling it to 150~180℃ at a cooling rate of 30~40℃ / min, and then air-cooling it to room temperature; the tempering treatment method includes the following steps: heating the quenched ring forging to 620~640℃, holding it at that temperature for 6~8h, then furnace-cooling it to 290~310℃ and then air-cooling it to room temperature.

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