Heat treatment process method for high-speed precise single-row angular contact ball bearing

Abstract

A heat treatment process method for a high-speed precise single-row angular contact ball bearing belongs to the field of heat treatment processing of bearing parts, and comprises the following steps: 1, cleaning and drying before a ring is sleeved, then quenching and heating, immersing into molten nitrate for rapid quenching and cooling, and then air-cooling; 2, manually measuring elliptical deformation after cleaning and rust prevention of the ferrules, performing high-temperature tempering on qualified ferrules, manually smashing unqualified ferrules, marking and distinguishing the qualified ferrules, independently performing high-temperature tempering, and degrading for use; and detecting after high-temperature tempering, and finishing after the product is qualified. According to the invention, the appearance color of the quenched ferrule is ensured to be uniform and consistent; the product rejection rate is greatly reduced, and the production efficiency is high. High-temperature tempering is adopted to replace cold treatment, all procedures are completed in a heat treatment furnace production line, the production procedures are reduced, the production efficiency is improved, and the production cost is reduced. And the retained austenite content, the hardness and the metallographic structure of the ferrule subjected to high-temperature tempering are similar to those of the original process, and all meet the standard requirements.

Description

Technical Field

[0001] The invention belongs to the field of heat treatment processing of bearing parts, and specifically relates to a heat treatment process method for a high-speed precision single-row angular contact ball bearing. Background Art

[0002] The outer diameter of high-speed precision single-row angular contact ball bearings is less than 250mm, and the rotation accuracy grade of the bearings is P4 or P2. They are mainly used in high-speed rotation occasions with light loads, requiring high precision, high speed, low temperature rise and low vibration of the bearings, such as machine tool spindles, high-speed electric spindles, high-frequency motors and various precision electromechanical equipment.

[0003] In order to ensure that the rotation accuracy of the bearing reaches P4 or P2 level, the heat treatment production process is: placing and loading - pre-cleaning and drying - quenching heating - quenching cooling - air cooling - primary cleaning and rust prevention - elliptical deformation measurement (tapping shaping) - cold treatment - secondary cleaning and rust prevention - low temperature tempering.

[0004] During the heat treatment process, a cold treatment process is added to reduce the residual austenite content of the ring after quenching to less than 5%. However, the cold treatment process is not in the heat treatment production line and needs to be cold treated in a cold treatment box. The ring after cold treatment needs to be cleaned and rust-proofed twice, which has low production efficiency and high production cost. Moreover, if the elliptical deformation does not meet the standard requirements, it needs to be manually shaped. During the subsequent grinding process, some rings that have passed the manual shaping will be ground and deformed, resulting in waste and production waste. Summary of the invention

[0005] The purpose of the present invention is to solve the above-mentioned technical problems and to provide a heat treatment process method for a high-speed precision single-row angular contact ball bearing.

[0006] A high-speed precision single-row angular contact ball bearing heat treatment process method is implemented according to the following steps:

[0007] 1. After the high-speed precision single-row angular contact ball bearing rings are placed and loaded, they are pre-cleaned and dried, and then placed in a heating furnace for quenching and heating. After quenching and heating, the rings are immersed in molten nitrate through a transfer mechanism for rapid quenching and cooling, and then enter the air cooling zone to reduce the ring temperature to below 40°C;

[0008] The quenching heating: introducing a protective atmosphere, controlling the carbon potential in the furnace to be 0.6-0.9CP%, the pressure in the furnace to be 150-200Pa, the temperature of the first heating zone to be 780-820°C, the temperature of the other heating zones to be 835-855°C, and the heating time to be 40-65min;

[0009] The molten nitrate salt is rapidly quenched and cooled: the temperature of the nitrate salt is 140-200°C, the water content of the nitrate salt is 0-0.6%, the speed of the salt tank stirring motor is 50-200rpm, the speed of the salt tank moving up and down is 150-300mm / s, and the cooling time is 3-6min;

[0010] 2. After the air-cooled rings are cleaned and rust-proofed, the elliptical deformation is manually measured. The qualified rings are placed in an air tempering furnace for high-temperature tempering, and then the rings are inspected. When the test results meet the standards, the heat treatment process of the high-speed precision single-row angular contact ball bearing is completed.

[0011] Furthermore, the material placement described in step 1 is as follows: the rings are placed in one layer on the tooling, with a gap of 5 to 10 mm between the rings.

[0012] Furthermore, the pre-cleaning and drying described in step one: the pre-cleaning station is divided into cleaning agent cleaning and clean water cleaning; the cleaning agent cleaning temperature is 50-80°C, and the cleaning time for each step is 3-6 minutes; the clean water cleaning temperature is 50-80°C, and the cleaning time is 3-6 minutes; after cleaning, drying is performed at 110-130°C for 3-6 minutes.

[0013] Furthermore, the protective atmosphere in step 1 is a mixed gas composed of nitrogen, propane gas and methanol cracking gas in any ratio.

[0014] Furthermore, the nitrate salt in step 1 is composed of 45% to 50% sodium nitrite and 50% to 55% potassium nitrate by weight.

[0015] Furthermore, the cleaning and rust prevention described in step 2: immersion cleaning and rust prevention are adopted, with a total of three stations:

[0016] ①. Ultrasonic cleaning, frequency 28KHZ, water temperature 45~55℃;

[0017] ②. Foaming cleaning, water temperature 45 ~ 55 ℃;

[0018] ③. Cold water cleaning, water temperature 6 ~ 10 ℃, the cold water station uses a 0.7% sodium nitrite aqueous solution for rust prevention; after cleaning, dry at 120 ~ 160 ℃ for 5 ~ 10 minutes.

[0019] Furthermore, in step 2, the elliptical deformation is manually measured, and the qualified rings can be used for precision bearings with a rotation accuracy of P4 or P2 after high-temperature tempering.

[0020] Furthermore, in step 2, the elliptical deformation is manually measured, and the unqualified rings are manually shaped. After the shaping, the elliptical deformation is manually measured again. After the qualified measurement, it is marked and distinguished from the qualified rings, and then high-temperature tempering is performed separately and downgraded for use, that is, it is not used for precision bearings with rotation accuracy P4 or P2.

[0021] Furthermore, the high temperature tempering in step 2 is: keeping warm at 200-250° C. for 210 min to 270 min.

[0022] Furthermore, the qualified standards for the inspection in step 2 are: the content of retained austenite in the ring is less than 5%; the surface hardness of the ring is 60-65HRC; the metallographic structure of the ring is level 2-4; the depth of the decarburized layer on the surface of the ring is less than 0.05mm.

[0023] Compared with the existing technology, the present invention has the following advantages:

[0024] 1. The rings of the present invention are arranged in one layer, because the rings of high-speed precision single-row angular contact ball bearings are all thin and light series. If the multi-layer arrangement method is adopted, during the high-temperature heating process, the rings are affected by gravity, which will cause some rings in the lower layer to be compressed and deformed, resulting in a high proportion of rings with elliptical deformation exceeding the standard requirements. In addition, the rings are arranged in a single layer with gaps between the rings, which can ensure that the appearance color of the rings after quenching is uniform.

[0025] 2. When the ferrule is heated in the present invention, the temperature of the heating zone is lowered, which can effectively prevent the release of ferrule stress when the surface temperature of the ferrule changes from room temperature to high temperature, resulting in elliptical deformation of part of the ferrule that does not meet the standard requirements.

[0026] 3. The present invention increases the temperature of other heating zones to the process upper limit and prolongs the heat preservation time, which can improve the hardness of the ferrule after quenching. The purpose of improving the hardness after quenching is: a high-temperature tempering process is subsequently adopted to ensure that the hardness of the ferrule after high-temperature tempering is within the standard range. Tests have shown that the process method of the present invention has a hardness of 64-66HRC after quenching, and the hardness of the original process after quenching is 63-65HRC.

[0027] 4. In the present invention, the ferrules that are unqualified in elliptical deformation and qualified after smashing are distinguished from the ferrules that are qualified in elliptical deformation. Because the ferrules that are qualified in smashing have internal stress, the stress will be slowly released during subsequent grinding, resulting in the ferrule size accuracy not meeting the requirements of precision products, the product being scrapped and affecting production efficiency.

[0028] 5. The present invention adopts high temperature tempering instead of cold treatment, and all processes are completed in the heat treatment furnace production line, which reduces the production process, improves production efficiency, and reduces production costs. Moreover, the residual austenite content, hardness, and metallographic structure of the ferrule after high temperature tempering are similar to those of the original process, and all meet the standard requirements.

[0029] The invention is suitable for heat treatment of high-speed precision single-row angular contact ball bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a 1000-fold metallographic structure diagram of the outer ring of the 7019AC high-speed precision angular contact ball bearing in the embodiment after heat treatment. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0032] Specific implementation method 1: This implementation method is a high-speed precision single-row angular contact ball bearing heat treatment process method, which is implemented according to the following steps:

[0033] 1. After the high-speed precision single-row angular contact ball bearing rings are placed and loaded, they are pre-cleaned and dried, and then placed in a heating furnace for quenching and heating. After quenching and heating, the rings are immersed in molten nitrate through a transfer mechanism for rapid quenching and cooling, and then enter the air cooling zone to reduce the ring temperature to below 40°C;

[0034] The quenching heating: introducing a protective atmosphere, controlling the carbon potential in the furnace to be 0.6-0.9CP%, the pressure in the furnace to be 150-200Pa, the temperature of the first heating zone to be 780-820°C, the temperature of the other heating zones to be 835-855°C, and the heating time to be 40-65min;

[0035] The molten nitrate salt is rapidly quenched and cooled: the temperature of the nitrate salt is 140-200°C, the water content of the nitrate salt is 0-0.6%, the speed of the salt tank stirring motor is 50-200rpm, the speed of the salt tank moving up and down is 150-300mm / s, and the cooling time is 3-6min;

[0036] 2. After the air-cooled rings are cleaned and rust-proofed, the elliptical deformation is manually measured. The qualified rings are placed in an air tempering furnace for high-temperature tempering, and then the rings are inspected. When the test results meet the standards, the heat treatment process of the high-speed precision single-row angular contact ball bearing is completed.

[0037] The purpose of the pre-cleaning in step 1 of this embodiment is to remove impurities such as cutting fluid, dust, oil, etc. remaining on the bearing surface to ensure that the appearance color of the bearing parts after quenching and tempering is consistent.

[0038] The purpose of introducing the protective atmosphere in step 1 of this embodiment is to prevent oxidation and decarburization of the ferrule during the high-temperature heating process.

[0039] In step 2 of this embodiment, the elliptical deformation is manually measured, and if 10-20% of the ferrule elliptical deformation exceeds the standard requirement, the test is unqualified.

[0040] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that, in step 1, the ferrules are placed in one layer on the tooling, with a gap of 5 to 10 mm between the ferrules. The other steps and parameters are the same as those in specific implementation method 1.

[0041] Specific implementation method three: This implementation method is different from specific implementation method one in that the pre-cleaning and drying described in step one: the pre-cleaning station is divided into cleaning agent cleaning and water cleaning; the cleaning agent cleaning temperature is 50-80°C, and each cleaning time is 3-6 minutes; the water cleaning temperature is 50-80°C, and the cleaning time is 3-6 minutes; after cleaning, drying is performed at 110-130°C for 3-6 minutes. Other steps and parameters are the same as those in specific implementation method one.

[0042] Specific embodiment 4: This embodiment differs from specific embodiment 1 in that the protective atmosphere in step 1 is a mixed gas composed of nitrogen, propane gas and methanol cracking gas in any ratio. Other steps and parameters are the same as those in specific embodiment 1.

[0043] Specific embodiment 5: This embodiment is different from specific embodiment 1 in that the nitrate salt in step 1 is composed of 45% to 50% sodium nitrite and 50% to 55% potassium nitrate by weight. Other steps and parameters are the same as those in specific embodiment 1.

[0044] Specific implementation method 6: This implementation method is different from the specific implementation method 1 in that the cleaning and rust prevention described in step 2 is to use immersion cleaning and rust prevention, with a total of three stations:

[0045] ①. Ultrasonic cleaning, frequency 28KHZ, water temperature 45~55℃;

[0046] ②. Foaming cleaning, water temperature 45 ~ 55 ℃;

[0047] ③. Cold water cleaning, water temperature 6-10℃, cold water station using 0.7% sodium nitrite aqueous solution for rust prevention; after cleaning, drying at 120-160℃ for 5-10 minutes. Other steps and parameters are the same as the first embodiment.

[0048] Specific implementation method 7: This implementation method is different from specific implementation method 1 in that the elliptical deformation is manually measured in step 2, and the qualified rings can be used for precision bearings with rotation accuracy P4 or P2 after high temperature tempering. The other steps and parameters are the same as those of specific implementation method 1.

[0049] Specific implementation eight: This implementation is different from specific implementation one in that the elliptical deformation is measured manually in step two, the rings that fail the measurement are manually shaped, and the elliptical deformation is measured manually again after the shaping, and the qualified rings are marked and distinguished from the qualified rings, and then high-temperature tempering is performed separately and downgraded, that is, it is not used for precision bearings with rotation accuracy P4 or P2. Other steps and parameters are the same as those in specific implementation one.

[0050] Specific embodiment 9: This embodiment is different from specific embodiment 1 in that the high temperature tempering in step 2 is carried out at 200-250° C. for 210-270 minutes. Other steps and parameters are the same as those in specific embodiment 1.

[0051] Specific embodiment 10: This embodiment is different from specific embodiment 1 in that the qualified standard of the inspection in step 2 is: the content of retained austenite in the ring is less than 5%; the surface hardness of the ring is 60-65HRC; the metallographic structure of the ring is 2-4 grades; the depth of the decarburized layer on the surface of the ring is less than 0.05mm. The other steps and parameters are the same as those in specific embodiment 1.

[0052] The beneficial effects of the present invention are verified by the following examples:

[0053] Example:

[0054] A high-speed precision single-row angular contact ball bearing heat treatment process method is implemented according to the following steps:

[0055] 1. After the high-speed precision single-row angular contact ball bearing rings are placed and loaded, they are pre-cleaned and dried, and then placed in a heating furnace for quenching and heating. After quenching and heating, the rings are immersed in molten nitrate through a transfer mechanism for rapid quenching and cooling, and then enter the air cooling zone to reduce the ring temperature to below 40°C;

[0056] The quenching heating: a protective atmosphere is introduced, the carbon potential in the furnace is controlled to be 0.7CP%, the pressure in the furnace is 160Pa, the temperature of the first heating zone is 800°C, the temperature of the other heating zones is 835°C, and the heating time is 50min;

[0057] The molten nitrate salt is rapidly quenched and cooled: the temperature of the nitrate salt is 180°C, the water content of the nitrate salt is 0%, the speed of the salt tank stirring motor is 100rpm, the speed of the salt tank moving up and down is 150mm / s, and the cooling time is 4min;

[0058] 2. After the air-cooled rings are cleaned and rust-proofed, the elliptical deformation is manually measured. The qualified rings are placed in an air tempering furnace for high-temperature tempering, and then the rings are inspected. When the test results meet the standards, the heat treatment process of the high-speed precision single-row angular contact ball bearing is completed.

[0059] The material placement described in step 1 of this embodiment is as follows: the rings are placed in one layer on the tooling, with a gap of 8 mm between the rings.

[0060] The pre-cleaning and drying described in step 1 of this embodiment: the pre-cleaning station is divided into cleaning agent cleaning and clean water cleaning; the cleaning agent cleaning temperature is 60°C, and the cleaning time for each cleaning is 4 minutes; the clean water cleaning temperature is 60°C, and the cleaning time is 4 minutes; after cleaning, drying is performed at 120°C for 4 minutes.

[0061] The protective atmosphere in step 1 of this embodiment is a mixed gas composed of nitrogen, propane gas and methanol cracking gas in any ratio.

[0062] The nitrate salt in step 1 of this embodiment is composed of 50% sodium nitrite and 50% potassium nitrate by weight.

[0063] The cleaning and rust prevention described in step 2 of this embodiment: immersion cleaning and rust prevention are adopted, with a total of three stations:

[0064] ①. Ultrasonic cleaning, frequency 28KHZ, water temperature 45~55℃;

[0065] ②. Foaming cleaning, water temperature 45 ~ 55 ℃;

[0066] ③. Cold water cleaning, water temperature 6 ~ 10 ℃, the cold water station uses a 0.7% sodium nitrite aqueous solution for rust prevention; after cleaning, dry at 120 ~ 160 ℃ for 5 ~ 10 minutes.

[0067] In step 2 of this embodiment, the elliptical deformation is manually measured, and the qualified rings can be used for precision bearings with a rotation accuracy of P4 or P2 after high-temperature tempering.

[0068] In step 2 of this embodiment, the elliptical deformation is manually measured, and the rings that fail the measurement are manually shaped. After the shaping, the elliptical deformation is manually measured again. After the measurement is qualified, it is marked and distinguished from the rings that pass the measurement. Then, it is separately subjected to high-temperature tempering and downgraded for use, that is, it is not used for precision bearings with rotation accuracy P4 or P2.

[0069] The high temperature tempering described in step 2 of this embodiment is: keeping warm at 220° C. for 240 minutes.

[0070] The high-speed precision single-row angular contact ball bearing ring described in step 1 of this embodiment is the outer ring of a 7019AC high-speed precision angular contact ball bearing.

[0071] In this embodiment, the quenching heating and high temperature tempering are processed using Tangshan Yajie Salt Bath Martensitic Quenching-750 production line with a protective atmosphere roller hearth furnace.

[0072] The number of materials placed in step 1 of this embodiment is: 25 pieces.

[0073] In the manual measurement of elliptical deformation in step 2 of this embodiment, 12% of the ferrules have elliptical deformation exceeding the standard requirement, ie, the test fails.

[0074] In step 2 of this embodiment, the test results are as follows: the content of retained austenite in the ferrule is 2.5% when the Italian GNR-AREX L retained austenite analyzer is used; the hardness of the ferrule is 61.5HRC when the Beijing Times Peak-TIME6168 full Rockwell hardness tester is used; the metallographic structure of the ferrule is observed using the German Zeiss-Axio Observer 5m inverted metallographic microscope, and the rating is 3. Figure 1 As shown; using the German Zeiss-Axio Observer 5m inverted metallographic microscope to observe the decarburization layer depth on the surface of the ring is 0.02mm. The test results meet the standard requirements and pass the inspection.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A heat treatment process for high-speed precision single-row angular contact ball bearings, characterized in that It is implemented as follows:

1. After the high-speed precision single-row angular contact ball bearing rings are placed and loaded, they are pre-cleaned and dried, and then placed in a heating furnace for quenching and heating. After quenching and heating, the rings are immersed in molten nitrate through a transfer mechanism for rapid quenching and cooling, and then enter the air cooling zone to reduce the ring temperature to below 40°C; The quenching heating: introducing a protective atmosphere, controlling the carbon potential in the furnace to be 0.6-0.9CP%, the pressure in the furnace to be 150-200Pa, the temperature of the first heating zone to be 780-820°C, the temperature of the other heating zones to be 835-855°C, and the heating time to be 40-65min; The molten nitrate salt is rapidly quenched and cooled: the temperature of the nitrate salt is 140-200°C, the water content of the nitrate salt is 0-0.6%, the speed of the salt tank stirring motor is 50-200rpm, the speed of the salt tank moving up and down is 150-300mm / s, and the cooling time is 3-6min; 2. After the air-cooled rings are cleaned and rust-proofed, the elliptical deformation is manually measured. The qualified rings are placed in an air tempering furnace for high-temperature tempering, and then the rings are inspected. When the test results meet the standards, the heat treatment process of the high-speed precision single-row angular contact ball bearing is completed.

2. According to claim 1, a high-speed precision single-row angular contact ball bearing heat treatment process method is characterized in that Place the materials as described in step 1: Place the rings in one layer on the tooling, leaving a gap of 5 to 10 mm between the rings.

3. A heat treatment process for a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that Pre-cleaning and drying described in step 1: the pre-cleaning station is divided into cleaning agent cleaning and clean water cleaning; the cleaning agent cleaning temperature is 50-80°C, and the cleaning time for each step is 3-6 minutes; the clean water cleaning temperature is 50-80°C, and the cleaning time is 3-6 minutes; after cleaning, drying is performed at 110-130°C for 3-6 minutes.

4. A heat treatment process for a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that The protective atmosphere described in step 1 is a mixed gas composed of nitrogen, propane gas and methanol cracking gas in any ratio.

5. The heat treatment process of a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that The nitrate salt in step 1 is composed of 45% to 50% sodium nitrite and 50% to 55% potassium nitrate by weight.

6. A heat treatment process for a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that Cleaning and rust prevention as described in step 2: Use immersion cleaning and rust prevention, with a total of three stations: ①. Ultrasonic cleaning, frequency 28KHZ, water temperature 45~55℃; ②. Foaming cleaning, water temperature 45 ~ 55 ℃; ③. Cold water cleaning, water temperature 6 ~ 10 ℃, the cold water station uses a 0.7% sodium nitrite aqueous solution for rust prevention; after cleaning, dry at 120 ~ 160 ℃ for 5 ~ 10 minutes.

7. The heat treatment process of a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that In step 2, the elliptical deformation is manually measured, and the qualified rings can be used for precision bearings with a rotation accuracy of P4 or P2 after high-temperature tempering.

8. The heat treatment process of a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that In step 2, the elliptical deformation is measured manually, and the unqualified rings are manually shaped. After the shaping, the elliptical deformation is measured manually again. After the qualified measurement, it is marked and distinguished from the qualified rings. Then, it is separately subjected to high-temperature tempering and downgraded for use, that is, it is not used for precision bearings with rotation accuracy P4 or P2.

9. A heat treatment process for a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that The high temperature tempering in step 2 is: keeping warm at 200-250°C for 210-270 minutes.

10. A heat treatment process for a high-speed precision single-row angular contact ball bearing according to claim 1, characterized in that The qualified standards for the inspection in step 2 are: the content of retained austenite in the ring is less than 5%; the surface hardness of the ring is 60-65HRC; the metallographic structure of the ring is grade 2-4; the depth of the decarburized layer on the surface of the ring is less than 0.05mm.

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