Deep groove ball bearing raceway production line and its production process

Abstract

The application discloses a deep groove ball bearing raceway production line, which comprises a bearing ring blank, an automatic feeding device, a numerical control cold rolling machine, an automatic conveying device, a high-frequency induction stress relief annealing device, an automatic discharging device and a control system. The application also discloses a production process, which comprises the following steps: S1, feeding and positioning; S2, cold rolling processing; S3, automatic transfer; S4, high-frequency induction stress relief annealing treatment; and S5, automatic discharging circulation. The application solves the technical problems of the separation of the cold rolling forming and the stress relief annealing process of the existing deep groove ball bearing ring, the long time consumption and high energy consumption of the traditional furnace annealing heating, the serious workpiece oxidation, the large annealing deformation, the easy aging recovery of the residual stress and the low production efficiency.

Description

Technical Field

[0001] This invention relates to the field of bearing processing equipment and technology, specifically to a deep groove ball bearing raceway production line and its production process. Background Technology

[0002] Deep groove ball bearings are the most widely used type of bearing in the machinery field. The machining quality and dimensional stability of their raceways directly affect the bearing's service life and reliability. GCr15 high-carbon chromium bearing steel is the main material for manufacturing deep groove ball bearing raceways. It has a carbon content of about 1% and features high strength, high hardness, good wear resistance, and good tempering stability.

[0003] Traditional deep groove ball bearing raceway machining typically involves hot forging, spheroidizing annealing, turning, quenching and tempering, and precision grinding. In recent years, however, cold rolling technology has been increasingly applied to bearing raceway manufacturing. Cold rolling involves plastically shaping the raceway blank at room temperature using rolling rollers and mandrels, causing the raceway to deform and enlarge during rotation to reach the target dimensions. This process offers advantages such as high material utilization, high precision, good surface quality, and continuous metal flow lines. During cold rolling, the raceway undergoes plastic deformation under rolling pressure, inevitably generating significant residual stress. Research indicates that cold rolling and quenching are two critical steps in the cold rolling process of bearing rings, and the resulting residual stress can significantly impact the geometric accuracy and microstructure of the bearing rings, requiring effective treatment.

[0004] Currently, stress-relief annealing after cold rolling typically involves prolonged annealing in a mesh belt furnace or box furnace. Taking GCr15 material as an example, the conventional stress-relief annealing process involves heating to 600-700℃ and holding for several hours, followed by furnace cooling or air cooling. While this method can eliminate some residual stress, it has the following significant drawbacks: (i) Long heating time and high energy consumption: Traditional furnace annealing requires heating the entire furnace to the process temperature and holding it at that temperature for a long time, resulting in low thermal efficiency and serious energy waste.

[0005] (ii) Severe surface oxidation: Some dimensions of the cold-rolled rings are already finished product dimensions, and oxidation is not allowed. However, in traditional furnace annealing without a protective atmosphere, oxide scale inevitably forms on the surface of the workpiece, which requires subsequent shot blasting or pickling processes to remove.

[0006] (iii) Large annealing deformation: Due to overall heating and long-term heat preservation, the ring is prone to thermal deformation and stress relaxation deformation, which affects the accuracy of subsequent quenching and fine grinding.

[0007] (iv) Discontinuous production process: The cold rolling process and the stress-relieving annealing process are separated, and the workpieces need to be transferred, loaded into the furnace and unloaded between processes, resulting in long production cycle, high labor intensity and low efficiency.

[0008] To address the aforementioned issues, some existing technologies attempt to apply induction heating to the field of bearing heat treatment. For example, one patent discloses an annealing device for the set screw hole of a bearing inner ring, which uses a high-frequency induction heater for localized annealing. However, this only targets the set screw hole area and is a single-piece, non-continuous operation. Another patent discloses a rapid localized annealing device for bearing rings, which uses a high-frequency induction heater in conjunction with an intermittent rotation mechanism to achieve single-piece annealing. However, this is still an independent localized annealing process and does not achieve integrated production of cold rolling and annealing.

[0009] Furthermore, CN107228121A discloses a cold-rolled deep groove ball bearing, whose main processing steps include hot forging, spheroidizing annealing, semi-finish turning and cold rolling of the blank, cold rolling, heat treatment, finish machining of the outer diameter of the end face, and assembly. However, the heat treatment still uses the traditional furnace method. In another process method for directly precision grinding forgings after cold rolling, the process flow does not involve any improvement to the stress-relieving annealing step.

[0010] In summary, there is currently no solution in the existing technology that integrates cold rolling raceway forming with high-frequency induction stress-relief annealing in a single production line. This is especially true in the manufacturing of deep groove ball bearing GCr15 rings, where there is an urgent need for a new stress-relief annealing process and supporting production line that is efficient, energy-saving, oxidation-free, and produces minimal deformation. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a deep groove ball bearing raceway production line and its manufacturing process, which solves the problems of existing deep groove ball bearing ring cold rolling forming and stress-relieving annealing processes being separated, traditional furnace annealing heating being time-consuming and energy-intensive, severe workpiece oxidation, large annealing deformation, easy recovery of residual stress over time, and low production efficiency.

[0012] To achieve the above objectives, the present invention provides a deep groove ball bearing raceway production line, comprising a bearing ring blank, an automatic feeding device, a CNC cold rolling mill, an automatic conveying device, a high-frequency induction stress-relieving annealing device, an automatic unloading device, and a control system. The automatic feeding device is linked to the CNC cold rolling mill to convey the bearing ring blank to the CNC cold rolling mill. The CNC cold rolling mill includes a machine tool, rolling rollers, a core roller, and a roundness adjustment mechanism. The CNC cold rolling mill is used to perform cold rolling plastic processing on the bearing ring blank at room temperature. The automatic conveying device is used to unload the cold-rolled plastic processed bearing ring blank. The bearing ring blank is conveyed to the high-frequency induction stress-relief annealing device for annealing. The high-frequency induction stress-relief annealing device includes a high-frequency induction heating power supply, a ring induction heating coil, a workpiece rotation drive mechanism, and an infrared thermometer. The automatic unloading device is linked with the high-frequency induction stress-relief annealing device to unload and transfer the annealed bearing ring blank. The control system is communicatively connected to the automatic feeding device, the CNC cold rolling machine, the automatic conveying device, the high-frequency induction stress-relief annealing device, and the automatic unloading device.

[0013] The present invention further comprises: the inner diameter of the annular induction heating coil is adapted to the raceway diameter of the bearing ring blank so that the annular induction heating coil is oriented to the raceway area to achieve local induction heating; and a magnetic conductor is embedded inside the annular induction heating coil to improve the induction heating efficiency of the raceway area of ​​the bearing ring blank.

[0014] The present invention further includes: both the discharge side of the CNC cold rolling mill and the discharge side of the high-frequency induction stress-relieving annealing device are equipped with online dimensional measuring instruments for collecting data on the outer diameter, raceway roundness, and wall thickness difference of the bearing ring blank. The online dimensional measuring instruments are communicatively connected to the control system to transmit the data on the outer diameter, raceway roundness, and wall thickness difference of the bearing ring blank to the control system.

[0015] The present invention further includes: the high-frequency induction stress-relieving annealing device is equipped with a sealed atmosphere protective cover for linkage with an external gas supply device to continuously supply inert protective gas to the heating area of ​​the annular induction heating coil.

[0016] The advantages of adopting the above technical solution are: the above technology integrates feeding, cold rolling, transfer, induction annealing and unloading into a complete production line, and relies on the control system to uniformly schedule the operation sequence of each piece of equipment, eliminating the steps of manual transfer, stacking and secondary clamping between two processes in the traditional process; the rings that have been cold rolled can be quickly sent to the annealing station, avoiding the residual stress generated by cold rolling from aging recovery due to long-term placement, the entire production line runs smoothly, the production cycle is greatly shortened, manual operation is reduced, and the workshop space occupied is reduced. Compared to the traditional furnace-based method of heating the entire bearing raceway blank for an extended period, this invention employs a ring-shaped induction coil adapted to the raceway profile, with a magnetic conductor added inside the coil. This allows for targeted heating only in the raceway region where plastic deformation occurs, directly applying electrical energy to the bearing raceway blank. This results in higher heat utilization efficiency, eliminating the need for continuous high-temperature insulation in a large furnace. This significantly reduces the energy consumption of heat treatment for a single bearing raceway blank, achieving energy-saving production. Furthermore, the induction heating process is very short, limiting the heating time of the bearing raceway blank and reducing oxide scale formation at its source. On the other hand, the annealing station is equipped with a sealed atmosphere protection hood, which allows the introduction of inert protective gas to isolate the air, further preventing oxidation of the raceway surface. The processed raceway retains its original metal surface condition, eliminating the need for additional auxiliary processes such as shot blasting and pickling to remove the oxide layer. This simplifies the process and reduces the cost of auxiliary materials and supporting equipment.

[0017] Furthermore, the aforementioned technology only heats the raceway locally for a short time, resulting in a low overall temperature rise of the bearing ring base and a much lower thermal deformation than traditional high-temperature long-term annealing. The accompanying workpiece rotation mechanism ensures uniform heating of the raceway circumferentially. At the same time, online dimensional measuring instruments are set at the cold rolling and annealing exit positions to collect the dimensional data of the bearing ring blanks in real time and feed it back to the control system. This allows for timely adjustments to the production process, resulting in smaller dimensional deformation of the annealed rings and better uniformity of roundness and wall thickness. This provides high-precision blanks for subsequent quenching and precision grinding processes, thereby reducing the scrap rate of bearing ring blanks.

[0018] Furthermore, the aforementioned technology incorporates an infrared thermometer linked with a high-frequency power supply to achieve closed-loop temperature control, which can stably maintain a suitable heating temperature range for stress relief. Uniform heating can fully release the residual stress caused by cold rolling plastic deformation. At the same time, this heating range will not damage the spheroidized annealed structure formed in the early stage of the bearing ring blank, which is conducive to obtaining a uniform matrix through subsequent quenching. This reduces the risk of deformation and grinding cracks in the subsequent processing of the bearing ring blank, and improves the dimensional stability and service life of the finished bearing.

[0019] Further, all the devices of the above-mentioned technology are in communication connection with the control system, and the whole process from the blank feeding to the finished product discharging is automatically transferred, so as to avoid the process parameters and the size fluctuation of the bearing ring blank caused by manual operation; the online size detection feeds back the size deviation in real time and adjusts the processing parameters in linkage, forming a closed-loop production control, so that the batch-produced bearing rings are highly unified in size, heat treatment organization and performance, and the product processing quality is stable and reliable.

[0020] The production process of the deep groove ball bearing raceway production line comprises the following steps: S1, the automatic feeding device sequentially feeds the bearing ring blank to the cold rolling station of the numerical control cold rolling machine for positioning; S2, the positioned bearing ring blank is sleeved on the core roller of the numerical control cold rolling machine, and the rolling pressure is applied to the bearing ring blank by the rolling roller at room temperature to implement cold rolling plastic forming, so that the raceway of the bearing ring blank is formed to a predetermined size and forms a continuous metal flow line along the contour thereof, the core roller feeding speed range is 0.4-1.2mm / s, the rolling pressure applied by the rolling roller is in the range of 70-135kN, and the rolling time range is 2-9s; S3, the bearing ring blank after cold rolling is moved to the working station of the high-frequency induction stress relief annealing device by the automatic conveying device and is fixed; S4, the annular induction heating coil is aligned with the raceway of the bearing ring blank, and the high-frequency induction heating is started, the heating frequency is 10-50kHz, the heating temperature is 550-650°C, the heating and holding time is 5-15s, the raceway temperature of the bearing ring blank is monitored in real time by an infrared temperature measuring instrument, and the temperature fluctuation is controlled within ±10°C of the set temperature in linkage with the high-frequency induction heating power supply, the workpiece rotating drive mechanism drives the bearing ring blank to rotate at a constant speed to ensure that the raceway of the bearing ring blank is uniformly heated in the circumferential direction, and the bearing ring blank after heating is cooled to room temperature by natural air cooling or auxiliary air cooling; S5, the bearing ring blank cooled to room temperature is discharged by the automatic discharging device.

[0021] Further, in the step S4, the atmosphere protection cover continuously introduces inert gas to inhibit the trace oxidation of the raceway surface of the bearing ring blank.

[0022] The above technical solution has the advantages that: the above technology relies on the production line automatic transfer structure, so that the bearing ring after cold rolling forming can be quickly transported to the annealing station to release the residual stress generated by cold rolling in time, thereby avoiding the long-term storage of the bearing ring to cause the aging recovery of the residual stress; the whole set of feeding, cold rolling, transfer, annealing and discharging process runs continuously and automatically, the time consumption of the whole set of forming and heat treatment process of a single bearing ring is greatly compressed, compared with the traditional offline segmented processing mode, the production rhythm is significantly accelerated, the manual transfer and clamping time is greatly reduced, and the bearing rings processed in large quantities have small differences in raceway size, metallographic structure and stress state, the product batch stability is strong, and the yield rate is stably guaranteed, so that the production capacity is significantly improved.

[0023] The above technology limits the matching parameter interval of the core roller feeding speed to 0.4-1.2 mm / s, the rolling pressure of the rolling roller to 70-135 kN, and the rolling time to 2-9 s, so that the stress of the whole normal temperature cold rolling process is stable, the raceway profile forming is regular, the dense metal flow line that fits the raceway shape can be continuously formed, the metal organization of the raceway area is more dense, the raceway size is accurately guaranteed to meet the standards, and the raceway structure strength is strengthened from the blank level, thereby reducing the probability of local defects in subsequent processing.

[0024] The above technology adopts a 10-50 kHz annular induction heating coil and only heats the local raceway, the heat preservation time is only 5-15 s, and the heating temperature is controlled at 550-650 DEG C. Unlike the traditional whole-circle hours high-temperature furnace annealing, the heat applied by the annular induction heating coil is only concentrated in the deformed raceway area, so that the heat energy utilization rate is greatly improved, and the energy consumption of single heat treatment can be significantly reduced. The overall heating amplitude of the bearing ring is small, and the bearing ring is uniformly rotated, so that the raceway is uniformly heated in the circumferential direction, and the temperature is controlled by infrared temperature measurement closed loop control, so that the temperature fluctuation is controlled within ±10 DEG C, the deformation caused by thermal stress is greatly weakened, the size deformation of the bearing ring after annealing is controlled in a very low range, and the semi-finished product size precision is excellent.

[0025] The above technology uniformly heats in a short time within the set temperature range, which can efficiently release the residual stress accumulated by the plastic deformation of the bearing ring during cold rolling, so that the stress relief effect is excellent; and the annealing temperature and time will not damage the spheroidizing annealing organization of the previous blank, so that the metallographic structure inside the bearing ring blank is stable, the subsequent quenching process can generate uniform and stable martensite organization, effectively avoiding quenching deformation, grinding cracking and other problems, and the final product bearing raceway has better fatigue resistance and significantly longer service life.

[0026] Furthermore, the heat treatment process parameters in step four are optimized as follows: For GCr15 material, the preferred heating temperature is 600~620℃, the holding time is 8~12 seconds, and the heating frequency is 20~30kHz. This temperature range can effectively eliminate the residual stress generated by cold rolling without significantly changing the spheroidized annealing microstructure of the material, which is beneficial for obtaining a uniform martensitic microstructure in subsequent quenching treatment. Attached Figure Description

[0027] Figure 1 This is a flowchart of the production process in this invention. Detailed Implementation

[0028] This invention provides a deep groove ball bearing raceway production line and its manufacturing process: Example 1 This embodiment takes the manufacturing of the outer ring of a 6204 type deep groove ball bearing as an example. The ring material is GCr15 bearing steel, and the blank before cold rolling is subjected to hot forging and spheroidizing annealing treatment.

[0029] (a) Setting of cold rolling expansion process parameters The cold rolling process uses CNC cold rolling equipment to cold roll the raceway of the GCr15 bearing ring blank. The core roller feed speed is set to 0.6 mm / s, the rolling pressure to 80 kN, and the rolling time to 7 s. After cold rolling, the outer diameter of the ring reaches Φ47.0±0.02 mm, the raceway is well formed, and the metal flow lines are continuous and distributed along the raceway contour.

[0030] (ii) Automated conveying An automatic conveying device (pneumatic gripper robot) is used to automatically transfer the cold-rolled outer ring to the high-frequency induction stress-relieving annealing station, with a conveying time of about 6 seconds.

[0031] (III) Setting of process parameters for high-frequency induction stress-relief annealing After the outer ring is transferred to the annealing station, it is placed on the worktable and fitted into the ring-shaped induction heating coil. The workpiece rotation mechanism is then started, rotating at a constant speed of 60 r / min. The parameters of the high-frequency induction heating equipment are set as follows: heating frequency of 25 kHz, heating power of 25 kW, target heating temperature of 610℃, and heating time of 10 seconds. An infrared thermometer monitors the surface temperature of the workpiece in real time. When the temperature reaches 610℃, the power is automatically adjusted to maintain temperature stability, and the power is automatically cut off after the set time. The workpiece is then allowed to air cool to room temperature.

[0032] (iv) Test results The treated rings are then inspected. —Surface oxidation condition: The raceway surface has a metallic color and no visible oxide scale, so it can be directly transferred to the subsequent process without pickling.

[0033] — Dimensions after annealing: outer diameter Φ47.00±0.01mm, roundness deviation ≤0.005mm, wall thickness difference ≤0.008mm, deformation is reduced by about 70% compared with traditional box furnace annealing.

[0034] —Residual stress test: The residual stress on the raceway surface was tested using X-ray diffraction. After treatment, the residual stress was reduced from the original approximately 200 MPa to approximately 35 MPa, with an elimination rate of approximately 82.5%.

[0035] —Energy consumption comparison: The energy consumption for processing a single ring is about 0.12 kWh, which is about 73% lower than the 0.45 kWh / piece of traditional box furnace annealing.

[0036] Example 2 This embodiment takes the manufacture of the inner ring of a 6204 type deep groove ball bearing as an example, and the material is GCr15 bearing steel.

[0037] Cold rolling process parameters: core roller feed speed 0.8mm / s, rolling pressure 90kN, rolling time 6s.

[0038] High-frequency induction stress-relieving annealing parameters: heating frequency 30kHz, heating power 22kW, heating temperature 600℃, heating time 8 seconds, workpiece rotation speed 70r / min.

[0039] Test results: No oxide scale on the raceway surface, outer diameter Φ25.00±0.008mm, roundness deviation ≤0.004mm, wall thickness difference ≤0.006mm, residual stress relief rate of about 84%, and energy consumption per unit of about 0.10kWh.

[0040] Example 3 Production data for continuous operation of the production line in this embodiment (taking the outer ring of the 6204 model as an example): In summary, this invention integrates cold rolling and stress-relief annealing into a single production line. An automated conveying device enables seamless transfer of workpieces between the two processes, eliminating the need for intermediate transfers and re-clamping, significantly shortening the production cycle and thus improving efficiency. High-frequency induction heating is used for stress-relief annealing, with a heating time of only 5-15 seconds, resulting in energy consumption far lower than the several hours required by traditional box furnaces or mesh belt furnaces. Energy consumption per unit product can be reduced by more than 60%. Furthermore, due to the extremely short induction heating time, the workpiece produces virtually no oxide scale during annealing, retaining its metallic color. This eliminates the need for shot blasting or pickling to remove the oxide layer, simplifying the process and reducing costs. Simultaneously, high-frequency induction heating can rapidly heat the raceway area to 550-650°C. Because the heating temperature is uniform and controllable, residual stress is fully released. Tests show that the residual stress elimination rate can reach over 80%, effectively reducing the risk of subsequent quenching deformation and grinding cracks.

[0041] The deep groove ball bearing raceway production line and its manufacturing process provided by this invention are applicable to the cold rolling and stress-relief annealing of various GCr15 material deep groove ball bearing rings, and can be widely used in automotive bearings, precision machine tool bearings, industrial motor bearings, and other fields. It significantly outperforms traditional processes in terms of production efficiency, energy consumption, surface quality, and dimensional accuracy, and has significant industrial application value and promising prospects for widespread adoption.

[0042] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A deep groove ball bearing raceway production line, characterized in that: The system includes a bearing ring blank, an automatic feeding device, a CNC cold rolling mill, an automatic conveying device, a high-frequency induction stress-relieving annealing device, an automatic unloading device, and a control system. The automatic feeding device is linked to the CNC cold rolling mill to transport the bearing ring blank to the CNC cold rolling mill. The CNC cold rolling mill includes a machine tool, rolling rollers, a mandrel, and a roundness adjustment mechanism. The CNC cold rolling mill is used to perform cold rolling plastic processing on the bearing ring blank at room temperature. The automatic conveying device is used to transport the cold-rolled bearing ring blank to the high-frequency induction stress-relieving annealing device. The stress-relief annealing device is used to anneal bearing ring blanks using a high-frequency induction stress-relief annealing device. The high-frequency induction stress-relief annealing device includes a high-frequency induction heating power supply, a ring induction heating coil, a workpiece rotation drive mechanism, and an infrared thermometer. The automatic unloading device is linked with the high-frequency induction stress-relief annealing device to unload and transfer the annealed bearing ring blanks. The control system is communicatively connected to the automatic feeding device, the CNC cold rolling machine, the automatic conveying device, the high-frequency induction stress-relief annealing device, and the automatic unloading device.

2. The deep groove ball bearing raceway production line according to claim 1, characterized in that: The inner diameter of the annular induction heating coil is adapted to the raceway diameter of the bearing ring blank so that the annular induction heating coil is oriented to the raceway area to achieve local induction heating. The annular induction heating coil is embedded with a magnetic conductor to improve the efficiency of induction heating of the raceway area of ​​the bearing ring blank.

3. The deep groove ball bearing raceway production line according to claim 1, characterized in that: Both the discharge side of the CNC cold rolling mill and the discharge side of the high-frequency induction stress-relieving annealing device are equipped with online dimensional measuring instruments for collecting data on the outer diameter, raceway roundness, and wall thickness difference of the bearing ring blank. The online dimensional measuring instruments are communicatively connected to the control system to transmit the data on the outer diameter, raceway roundness, and wall thickness difference of the bearing ring blank to the control system.

4. The deep groove ball bearing raceway production line according to claim 1, characterized in that: The high-frequency induction stress-relief annealing device is equipped with a sealed atmosphere protective cover for linkage with external gas supply equipment to continuously supply inert protective gas to the heating area of ​​the annular induction heating coil.

5. The production process of the deep groove ball bearing raceway production line according to any one of claims 1 to 4, characterized in that: Includes the following steps: S1. The automatic feeding device sequentially transports the bearing ring blanks to the cold rolling station of the CNC cold rolling machine to complete the positioning. S2. The positioned bearing ring blank is placed on the mandrel of a CNC cold rolling mill. At room temperature, the rolling pressure is applied to the bearing ring blank by the rolling roller to perform cold rolling expansion and plastic forming, so that the raceway of the bearing ring blank is formed to a predetermined size and forms a continuous metal flow line along its contour. The feed speed of the mandrel is in the range of 0.4-1.2mm / s, the rolling pressure applied by the rolling roller is in the range of 70-135kN, and the rolling time is in the range of 2-9s. S3. The cold-rolled bearing ring blank is transferred to the station of the high-frequency induction stress-relieving annealing device through an automatic conveying device and fixed. S4. Align the annular induction heating coil with the raceway of the bearing ring blank and start high-frequency induction heating. The heating frequency is 10-50kHz, the heating temperature is 550-650°C, and the heating and holding time is 5-15s. The raceway temperature of the bearing ring blank is monitored in real time by an infrared thermometer and the high-frequency induction heating power supply is linked to control the temperature fluctuation within ±10°C of the set temperature. The workpiece rotation drive mechanism drives the bearing ring blank to rotate at a uniform speed to ensure that the circumferential heating of the raceway of the bearing ring blank is uniform. The heated bearing ring blank is cooled to room temperature by natural air cooling or auxiliary air cooling. S5. The bearing ring blanks cooled to room temperature are unloaded and transferred using an automatic unloading device.

6. The production process according to claim 5, characterized in that: In step S4, an inert gas is continuously introduced into the atmosphere protection cover to suppress trace oxidation on the raceway surface of the bearing ring blank.

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