Process method for solving denitrification after heat treatment of high-nitrogen stainless steel bearing part

Abstract

A process method for solving denitrification of a high-nitrogen stainless steel bearing part after heat treatment belongs to the field of bearing part heat treatment and processing, and comprises the following steps: adding 0.30 mm grinding allowance to the high-nitrogen stainless steel bearing part before vacuum heat treatment, and grinding to remove 0.30 mm thickness in a grinding process after vacuum heat treatment. According to the method, the depth of the denitrification layer is measured through the process test, the turning grinding allowance of the bearing part is increased according to the depth of the denitrification layer, it is guaranteed that the denitrification layer generated during vacuum heat treatment can be removed during grinding, and the product quality is guaranteed. In order to guarantee the quality of the bearing parts, detection of surface denitrification items of the bearing parts is increased, the influence of vacuum heating denitrification on the product quality is eliminated by increasing the grinding allowance of the bearing parts, and the device is suitable for vacuum heating gas cooling and vacuum heating oil cooling, wide in application range, free of denitrification on the surfaces of the products and qualified in product quality.

Description

Technical Field

[0001] The invention belongs to the field of heat treatment processing of bearing parts, and particularly relates to a process method for denitrification of high-nitrogen stainless steel bearing parts after heat treatment. Background Art

[0002] In some special corrosion-resistant environments, high-nitrogen stainless steel is used as the raw material for making bearing parts. Bearing parts include: bearing outer ring, bearing inner ring, and rolling elements. There are two types of high-nitrogen stainless steel, namely X30CrMoN15-1 (Cronidur30) and X40CrMoVN16-2 (40Cr15Mo2VN); after vacuum heat treatment, high-nitrogen stainless steel is cold-treated and low-temperature tempered to obtain a hardness of ≥58HRC, with high wear resistance and high corrosion resistance. As this type of steel is increasingly used in the bearing field, a new problem has been discovered during vacuum heat treatment. During vacuum heating, the nitrogen partial pressure is very low, and the nitrogen on the surface of high-nitrogen stainless steel bearing parts can easily evaporate, resulting in denitrification. Denitrification on the surface of bearing parts will cause the surface hardness to be lower than 58HRC, and the wear resistance and corrosion resistance will be reduced. If the denitrification layer cannot be removed during the grinding process, the bearing parts will be scrapped. Summary of the Invention

[0003] The purpose of the present invention is to solve the above-mentioned technical problems and to provide a process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment.

[0004] A process method for solving the problem of denitrification of high-nitrogen stainless steel bearing parts after heat treatment. The process increases the grinding allowance of the high-nitrogen stainless steel bearing parts by 0.30 mm before vacuum heat treatment, and then grinds away the thickness by 0.30 mm in a grinding process after vacuum heat treatment, thereby completing the process of solving the problem of denitrification of high-nitrogen stainless steel bearing parts after heat treatment.

[0005] Furthermore, the specific process of the process is as follows:

[0006] 1. Preparation of high nitrogen stainless steel samples:

[0007] Ten high-nitrogen stainless steel bearing parts to be heat-treated were randomly selected and processed into the following dimensions: length × width × thickness = 20 mm × 10 mm × 10 mm. These were used as specimens to measure the depth of the denitrification layer during vacuum heat treatment.

[0008] 2. Denitrification layer depth detection:

[0009] The above 10 samples were subjected to vacuum heat treatment, and then the depth of the denitrification layer was detected using an inverted metallographic microscope;

[0010] 3. Confirm the amount of wear:

[0011] The 10 samples after the above test were ground to remove 0.30mm of thickness, and then the hardness and structure tests were carried out. If the test results met the standards, it was confirmed that the remaining grinding amount was 0.30mm;

[0012] 4. For the remaining high nitrogen stainless steel bearing parts to be heat treated except the sample blocks, a grinding allowance of 0.30mm is added on the basis of the original turning allowance, and then the high nitrogen stainless steel bearing parts to be heat treated are turned and then vacuum heat treated. The high nitrogen stainless steel bearing parts after vacuum heat treatment are ground, and the 0.30mm grinding allowance is removed during the grinding process. Hardness and structure tests are carried out. When the test results meet the standards, the process of solving the denitrification of high nitrogen stainless steel bearing parts after heat treatment is completed.

[0013] Furthermore, the results of the denitrification layer depth detection in step 2 are as follows: the denitrification layer depth of the sample block that has been vacuum-cooled by air quenching during the vacuum heat treatment process is 0.12 to 0.20 mm; the denitrification layer depth of the sample block that has been vacuum-cooled by oil quenching during the vacuum heat treatment process is 0.15 to 0.25 mm.

[0014] Furthermore, the vacuum heat treatment process described in steps 2 and 4 is the same: a bearing parts heat treatment process method of 40Cr15Mo2VN material is used, application date: 20240927, publication number: CN118957241A, a process pending patent application.

[0015] Furthermore, the results of the hardness and structure tests described in steps three and four meet the same standards: the hardness 0.30 mm from the surface is 59.5-60 HRC, and the hardness of the core is 59.5-60 HRC; the metallographic structure is composed of tempered martensite + a small amount of primary carbide + dispersed secondary carbide + a small amount of retained austenite.

[0016] Compared with the existing technology, the present invention has the following advantages:

[0017] 1. The present invention measures the depth of the denitrification layer through process tests, and increases the grinding allowance of the bearing parts according to the depth of the denitrification layer, thereby ensuring that the denitrification layer generated during vacuum heat treatment can be removed during grinding, thereby ensuring product quality.

[0018] 2. In order to ensure the quality of bearing parts, the present invention adds the detection of denitrification items on the surface of bearing parts. By increasing the wear retention of bearing parts, the influence of vacuum heating denitrification on product quality is eliminated. It is suitable for vacuum heating gas cooling and vacuum heating oil cooling, has a wide range of applications, the product surface is not denitrified, and the product quality is qualified.

[0019] The invention is suitable for solving the problem of denitrification of high-nitrogen stainless steel bearing parts after heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a 100x micrograph of the denitrified metallographic structure of the sample surface after vacuum oil quenching during the vacuum heat treatment process in the embodiment;

[0021] Figure 2 This is a 500x micrograph of the surface non-denitrified metallographic structure of a high-nitrogen stainless steel bearing part obtained by the process for solving the denitrification of a high-nitrogen stainless steel bearing part after heat treatment in the embodiment. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0023] Specific implementation method 1: This implementation method is a process method for solving the denitrification of high-nitrogen stainless steel bearing parts after heat treatment. It increases the grinding allowance of high-nitrogen stainless steel bearing parts by 0.30mm before vacuum heat treatment, and then grinds away the thickness of 0.30mm in the grinding process after vacuum heat treatment, thereby completing the process for solving the denitrification of high-nitrogen stainless steel bearing parts after heat treatment.

[0024] In this embodiment, the high nitrogen stainless steel bearing parts are increased by 0.30mm of grinding allowance before heat treatment, that is, the 0.30mm grinding allowance is increased on the basis of the original turning allowance of the high nitrogen stainless steel bearing parts, so as to ensure that the denitrification layer of the high nitrogen stainless steel bearing parts can be completely removed in the grinding process during the subsequent process after vacuum heat treatment, without affecting the size and performance of the high nitrogen stainless steel bearing parts.

[0025] Specific embodiment 2: This embodiment differs from the specific embodiment 1 in that the specific process of the process is as follows:

[0026] 1. Preparation of high nitrogen stainless steel samples:

[0027] Ten high-nitrogen stainless steel bearing parts to be heat-treated were randomly selected and processed into the following dimensions: length × width × thickness = 20 mm × 10 mm × 10 mm. These were used as specimens to measure the depth of the denitrification layer during vacuum heat treatment.

[0028] 2. Denitrification layer depth detection:

[0029] The above 10 samples were subjected to vacuum heat treatment, and then the depth of the denitrification layer was detected using an inverted metallographic microscope;

[0030] 3. Confirm the amount of wear:

[0031] The 10 samples after the above test were ground to remove 0.30mm of thickness, and then the hardness and structure tests were carried out. If the test results met the standards, it was confirmed that the remaining grinding amount was 0.30mm;

[0032] Fourth, for the remaining high-nitrogen stainless steel bearing parts to be heat treated, except for the sample blocks, a grinding allowance of 0.30 mm is added to the original turning allowance. The high-nitrogen stainless steel bearing parts to be heat treated are then turned and vacuum heat treated. The high-nitrogen stainless steel bearing parts after vacuum heat treatment are then ground, and the 0.30 mm grinding allowance is removed during the grinding process. Hardness and microstructure tests are then performed. If the test results meet the standards, the process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment is completed. Other aspects are the same as those in the first embodiment.

[0033] Specific embodiment 3: This embodiment differs from specific embodiment 2 in that the results of the denitrification layer depth test in step 2 show that the denitrification layer depth of the sample cooled by vacuum gas quenching during vacuum heat treatment is 0.12-0.20 mm; the denitrification layer depth of the sample cooled by vacuum oil quenching during vacuum heat treatment is 0.15-0.25 mm. The other steps and parameters are the same as those in specific embodiment 2.

[0034] Specific embodiment 4: This embodiment differs from specific embodiment 2 in that the vacuum heat treatment process described in steps 2 and 4 is the same. Other steps and parameters are the same as those in specific embodiment 2.

[0035] The vacuum heat treatment described in this embodiment adopts a bearing parts heat treatment process method of 40Cr15Mo2VN material, application date: 20240927, publication number: CN118957241A, a process pending patent application.

[0036] Specific Embodiment 5: This embodiment differs from Specific Embodiment 2 in that the hardness and microstructure test results described in Steps 3 and 4 meet the same standards: the hardness at 0.30 mm from the surface is 59.5-60 HRC, and the core hardness is 59.5-60 HRC. The metallographic structure is composed of tempered martensite, a small amount of primary carbides, dispersed secondary carbides, and a small amount of retained austenite. Other steps and parameters are the same as Specific Embodiment 2.

[0037] The beneficial effects of the present invention are verified by the following examples:

[0038] Example:

[0039] A process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment, the specific process of the process is as follows:

[0040] 1. Preparation of high nitrogen stainless steel samples:

[0041] Ten high-nitrogen stainless steel bearing parts to be heat-treated were randomly selected and processed into the following dimensions: length × width × thickness = 20 mm × 10 mm × 10 mm. These were used as specimens to measure the depth of the denitrification layer during vacuum heat treatment.

[0042] 2. Denitrification layer depth detection:

[0043] The above 10 samples were vacuum heat treated, and then the depth of the denitrification layer was tested using a Zeiss inverted metallographic microscope. The test results showed that the depth of the denitrification layer of the sample that was vacuum oil quenched during the vacuum heat treatment was 0.25 mm; Figure 1 As shown;

[0044] 3. Confirm the amount of wear:

[0045] The 10 samples after the above test were ground to remove 0.30mm of thickness, and then the hardness and structure tests were carried out. If the test results met the standards, it was confirmed that the remaining grinding amount was 0.30mm;

[0046] 4. For the remaining high nitrogen stainless steel bearing parts to be heat treated except the sample blocks, a grinding allowance of 0.30mm is added on the basis of the original turning allowance, and then the high nitrogen stainless steel bearing parts to be heat treated are turned and then vacuum heat treated. The high nitrogen stainless steel bearing parts after vacuum heat treatment are ground, and the 0.30mm grinding allowance is removed during the grinding process. Hardness and structure tests are carried out. When the test results meet the standards, the process of solving the denitrification of high nitrogen stainless steel bearing parts after heat treatment is completed.

[0047] In this embodiment, the material of the high nitrogen stainless steel bearing part to be heat treated is X30CrMoN15-1 (Cronidur30).

[0048] The vacuum heat treatment process described in step 2 of this embodiment adopts a heat treatment process method for bearing parts made of 40Cr15Mo2VN material, application date: 20240927, publication number: CN118957241A, and patent pending process; the specific operations are as follows:

[0049] 1. Quenching heating and cooling:

[0050] Ten samples were pre-cleaned and then placed in a vacuum heating furnace. The vacuum was evacuated to 6 Pa and the temperature was raised from room temperature to 650°C at a rate of 3°C / min and kept at that temperature for 60 min. The temperature was then raised to 850°C at a rate of 5°C / min and kept at that temperature for 60 min. The temperature was then raised to 1060°C at a rate of 10°C / min and kept at that temperature for 70 min. The heated samples were then taken out of the furnace after cooling.

[0051] 2. Cold treatment and tempering:

[0052] The sample blocks after being taken out of the furnace are placed in a cold treatment device and cold treated at -90°C for 3 hours to complete the first cold treatment; after the sample blocks return to room temperature, they are kept at 170°C for 4 hours to complete the first tempering treatment; after the sample blocks cool to room temperature, they are placed in a cold treatment device and cold treated at -90°C for 3 hours to complete the second cold treatment; after the sample blocks return to room temperature, they are kept at 170°C for 4 hours to complete the second tempering treatment;

[0053] 3. Hardness and structure inspection:

[0054] After the second tempering treatment is completed, the hardness and metallographic structure of the sample are tested, and the test is completed if it passes the test;

[0055] Pre-cleaning: 10 specimens were placed on a workpiece according to process requirements and entered the pre-cleaning station, which was divided into cleaning agent cleaning and water cleaning. The cleaning agent temperature was 60°C, the cleaning time for each cleaning was 8 minutes, and the cleaning agent concentration was 2%. The cleaning agent was a water-based metal cleaning agent produced by Nanjing Kerun Industrial Media Co., Ltd., model: KR-F400H. The water cleaning temperature was 60°C, the cleaning time was 8 minutes. After cleaning, the samples were dried at 120°C and the drying time was 8 minutes.

[0056] The cooling in step 1 is vacuum oil quenching; the vacuum oil quenching: after heating, the bearing parts are immersed in vacuum quenching oil for sufficient cooling, the oil temperature is 80 ° C, and the cooling time is 10 minutes; in this embodiment, the quenching oil is selected from Nanjing Kerun KR468G bearing special quenching oil;

[0057] After vacuum oil quenching, it is transported to the cleaning machine for immersion cleaning. There are three stations in total:

[0058] 1. Ultrasonic cleaning, frequency 28KHZ, water temperature 50℃;

[0059] 2. Foaming cleaning, water temperature 50℃;

[0060] 3. Alkaline water cleaning, water temperature 50 ℃, 0.6% sodium nitrite aqueous solution is used for rust prevention at the alkaline water station; after cleaning, dry at 150 ℃ for 8 minutes;

[0061] Vacuum heating furnace: Beijing Zhongfu Yueda JVTF966;

[0062] Cold treatment equipment: LC297 cold treatment equipment produced by Shenzhen Dejieli Metal Technology Co., Ltd.; the equipment used for primary cold treatment and secondary cold treatment is the same;

[0063] The first tempering treatment and the second tempering treatment use the same equipment, both of which are RHW-100-800 mesh belt low temperature tempering furnaces produced by Hangzhou Jinzhou Technology Co., Ltd.

[0064] The vacuum heat treatment in step 4 of this embodiment has the same process and parameters as those in step 2 above.

[0065] The results of the hardness and structure tests described in steps three and four of this embodiment meet the same standards: the hardness 0.30 mm from the surface is 59.5 HRC, and the hardness of the core is 59.5 HRC; the metallographic structure is composed of tempered martensite + a small amount of primary carbide + dispersed secondary carbide + a small amount of retained austenite.

[0066] In step 4 of this embodiment, the process of denitrification of high nitrogen stainless steel bearing parts after heat treatment is completed, and the metallographic structure of the obtained high nitrogen stainless steel bearing parts is as follows: Figure 2 The surface shown is not denitrified.

[0067] 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, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment, characterized in that It increases the grinding allowance of high nitrogen stainless steel bearing parts by 0.30mm before vacuum heat treatment, and then grinds away 0.30mm thickness in the grinding process after vacuum heat treatment, thus completing the process of denitrification of high nitrogen stainless steel bearing parts after heat treatment.

2. According to claim 2, a process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment, characterized in that The specific process of the process is as follows:

1. Preparation of high nitrogen stainless steel samples: 10 high nitrogen stainless steel bearing parts to be heat treated are randomly selected and processed into the size of length × width × thickness = 20 mm × 10 mm × 10 mm as samples for measuring the depth of denitrification layer during vacuum heat treatment; 2. Denitrification layer depth detection: The above 10 samples were subjected to vacuum heat treatment, and then the depth of the denitrification layer was detected using an inverted metallographic microscope; 3. Confirm the amount of wear: The 10 samples after the above test were ground to remove 0.30mm thickness, and then hardness and structure tests were carried out. After the test results met the standards, it was confirmed that the remaining grinding amount was 0.30mm; 4. For the remaining high nitrogen stainless steel bearing parts to be heat treated except the sample blocks, a grinding allowance of 0.30 mm is added to the original turning allowance, and then the high nitrogen stainless steel bearing parts to be heat treated are turned and then vacuum heat treated. The high nitrogen stainless steel bearing parts after vacuum heat treatment are ground, and 0.30 mm of grinding allowance is removed during the grinding process. Hardness and structure inspections are carried out. When the inspection results meet the standards, the process of denitrification of high nitrogen stainless steel bearing parts after heat treatment is completed.

3. According to claim 2, a process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment, characterized in that The results of the denitrification layer depth detection in step 2: the denitrification layer depth of the sample block that has been vacuum quenched and cooled during the vacuum heat treatment process is 0.12-0.20 mm; the denitrification layer depth of the sample block that has been vacuum oil quenched and cooled during the vacuum heat treatment process is 0.15-0.25 mm.

4. According to claim 2, a process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment, characterized in that The vacuum heat treatment process described in steps 2 and 4 is the same.

5. According to claim 2, a process for denitrification of high-nitrogen stainless steel bearing parts after heat treatment, characterized in that The results of the hardness and structure tests described in steps three and four meet the same standards: the hardness 0.30mm from the surface is 59.5~60HRC, and the hardness of the core is 59.5~60HRC; metallographic structure: composed of tempered martensite + a small amount of primary carbide + dispersed secondary carbide + a small amount of residual austenite.

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