A heat treatment process for nitrided stainless steel bearing and nitrided stainless steel bearing

Abstract

The application relates to the technical field of bearing steel heat treatment, and discloses a heat treatment process of nitriding stainless steel bearing and the nitriding stainless steel bearing. The heat treatment process of the nitriding stainless steel bearing comprises the following steps: nitriding treatment, heat treatment and tempering of the stainless steel bearing; the heat treatment is composed of first-stage heat treatment, second-stage heat treatment and third-stage heat treatment; in the first-stage heat treatment, the temperature is raised to 830-860 DEG C at a temperature rising speed of 20-40 DEG C / h, and the temperature is kept; in the second-stage heat treatment, the temperature is raised to 1020-1040 DEG C from 830-860 DEG C at a temperature rising speed of 20-40 DEG C / h, and the temperature is kept; and in the third-stage heat treatment, the temperature is lowered to 940-960 DEG C from 1020-1040 DEG C at a cooling speed of 10-15 DEG C / h, and the temperature is kept. Through the technical scheme, the problem of poor wear resistance of the stainless steel bearing in the related art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bearing steel heat treatment, in particular to a heat treatment process of nitriding stainless steel bearing and the nitriding stainless steel bearing. BACKGROUND

[0002] Stainless steel bearings are widely used in aerospace, marine engineering and other fields due to their high hardness, high fatigue life and other excellent properties.

[0003] However, the wear resistance of stainless steel bearings is often insufficient when working at high speed, high load or in harsh environments, reducing the service life and reliability. In order to improve the wear resistance of stainless steel bearings, nitriding treatment has become an effective surface strengthening technology. Nitriding treatment is to place the stainless steel bearing workpiece in a certain temperature range of nitriding process, so that the nitrogen atoms in the medium penetrate into the surface layer of the workpiece and diffuse a certain distance inward, thereby forming a certain thickness of nitriding layer in the surface layer area to improve the surface hardness of the workpiece and thus improve its wear resistance.

[0004] The heat treatment link after nitriding plays an important role in the stability of the final nitriding effect, and the heat treatment, cooling and tempering treatment can optimize the internal organization of the bearing steel and facilitate the stability of the nitriding layer. However, the current heat treatment process after nitriding has the problem of insufficient process parameter matching, which not only leads to coarse grains and incomplete stress relief of the internal organization of the stainless steel bearing, but also causes the formation of large size carbides due to the segregation and precipitation of Cr, V and other alloy elements and carbon elements at the grain boundary during the heat treatment stage (especially when the heating and cooling speed is not properly controlled), resulting in unsatisfactory final nitriding stability effect and limiting the improvement of the wear resistance of the nitriding stainless steel bearing. SUMMARY

[0005] The present application provides a heat treatment process of nitriding stainless steel bearing and the nitriding stainless steel bearing, which solves the problem of poor wear resistance of stainless steel bearings in the related art.

[0006] The technical scheme of the present application is as follows:

[0007] The present application provides a heat treatment process of nitriding stainless steel bearing, comprising the following steps: nitriding treatment, heat treatment and tempering of the stainless steel bearing.

[0008] The heat treatment consists of first, second and third heat treatments.

[0009] In the first heat treatment, the temperature is raised to 830-860℃ at a rate of 20-40℃ / h, and the temperature is maintained for 0.5-1.5h.

[0010] During the second stage of heat treatment, the temperature is increased from 830~860℃ to 1020~1040℃ at a heating rate of 20~40℃ / h, and held at that temperature for 0.5~1.5h.

[0011] During the third stage of heat treatment, the temperature is reduced from 1020-1040℃ to 940-960℃ at a cooling rate of 10-15℃ / h, and held for 20-30 minutes.

[0012] As a further technical solution, the heating rate of the first heat treatment stage is greater than the heating rate of the second heat treatment stage.

[0013] In this invention, during the heat treatment process, the heating rate of the first heat treatment stage is adjusted to be greater than that of the second heat treatment stage. The heating is first carried out at a relatively fast rate to suppress abnormal grain coarsening, and then at a relatively slow rate to release internal stress. This helps to further improve the uniformity of the stainless steel bearing structure and can further improve the wear resistance of the nitrided stainless steel bearing.

[0014] As a further technical solution, after the heat treatment, the stainless steel bearing is subjected to oil quenching and deep cryogenic treatment.

[0015] The oil quenching time is 30-35 minutes;

[0016] During the cryogenic treatment, the temperature is -80 to -70°C and the time is 85 to 95 minutes.

[0017] As a further technical solution, during the tempering process, the temperature is increased to 300-400℃ at a heating rate of 30-40℃ / min, held for 1.5-2 hours, and then increased to 500-550℃ at a heating rate of 10-20℃ / min, held for 1.5-2 hours, and then cooled to room temperature.

[0018] As a further technical solution, the nitriding treatment is gas nitriding, and the gas is ammonia.

[0019] The nitriding process is divided into a first-stage nitriding and a second-stage nitriding.

[0020] During the first stage of nitriding, the nitriding temperature is 480~510℃ and the nitriding time is 10~12h;

[0021] During the second stage of nitriding, the nitriding temperature is 530~540℃ and the nitriding time is 10~12h.

[0022] In this invention, a segmented nitriding process is adopted, in which nitrogen atoms are first adsorbed and diffused at a relatively low temperature of 480~510℃, and then further diffused at a temperature of 530~540℃. The segmented nitriding process can accelerate the diffusion of nitrogen atoms and shorten the process cycle.

[0023] As a further technical solution, the nitriding voltage of the first stage and the nitriding of the second stage are each independently 550~600V, and the nitriding gas pressure is each independently 300~350Pa.

[0024] As a further technical solution, the stainless steel bearing, before nitriding treatment, consists of the following components by weight percentage:

[0025] C 1.0%~1.15%, Si≤0.55%, Mn≤0.6%, Cr 13.5%~14.8%, Mo 3.83%~4.20%, V 0.10%~0.20%, S≤0.03%, P≤0.03%, balance Fe and its unavoidable impurities.

[0026] The nitrided stainless steel bearing proposed in this invention is obtained by impregnating the stainless steel bearing, which has undergone heat treatment, with an impregnation solution.

[0027] As a further technical solution, the impregnation treatment specifically includes the following steps:

[0028] After tempering, the stainless steel bearing is immersed in an impregnation solution, removed, dried, ultrasonically treated in a silane coupling agent solution, washed, and dried.

[0029] As a further technical solution, before the impregnation treatment, the tempered stainless steel bearing is first impregnated in a tannic acid solution for 6-8 minutes; the mass fraction of the tannic acid solution is 2%-3%.

[0030] In this invention, after tempering, the stainless steel bearing is first impregnated with a tannic acid solution. The chelating effect of tannic acid can be used to improve the surface affinity of the stainless steel bearing, which is beneficial to enhance the interaction between the stainless steel bearing and the components in the subsequent impregnation solution and improve the impregnation effect.

[0031] As a further technical solution, the impregnation process is carried out at a temperature of 40~50℃ for 5~8 hours.

[0032] As a further technical solution, during the ultrasound, the ultrasound frequency is 10~12kHz and the duration is 2~3h.

[0033] As a further technical solution, the impregnation solution comprises the following components in parts by weight:

[0034] Citric acid 3-5 parts, iminodisuccinic acid 4-14 parts, polyacrylamide 2-10 parts, nano zinc oxide 4-6 parts, water 100 parts.

[0035] In this invention, when the impregnation solution includes iminodisuccinic acid and polyacrylamide, an organic coating with a certain bonding effect can be formed on the surface of the nitrided stainless steel bearing through the chelating effect of iminodisuccinic acid and the interaction between iminodisuccinic acid and polyacrylamide. This provides adsorption sites for nano zinc oxide, which helps nano zinc oxide to deposit on the surface of the organic coating. After treatment with a silane coupling agent, the hydrophobic effect of the nitrided stainless steel bearing surface can be improved, thereby improving its corrosion resistance.

[0036] As a further technical solution, the weight ratio of iminodisuccinic acid to polyacrylamide is 1~3:1.

[0037] In this invention, the corrosion resistance of nitrided stainless steel bearings is further improved by adjusting the content ratio of iminodisuccinic acid and polyacrylamide. When the weight ratio of iminodisuccinic acid to polyacrylamide is 1~3:1, the time for corrosion to appear on the nitrided stainless steel bearing after a neutral salt spray test can be extended to more than 208 hours. However, when the weight ratio of iminodisuccinic acid to polyacrylamide is outside the range of 1~3:1, the time for corrosion to appear is earlier.

[0038] As a further technical solution, the silane coupling agent solution is an ethanol solution of silane coupling agent, wherein the weight ratio of silane coupling agent to ethanol in the ethanol solution of silane coupling agent is 3~5:100.

[0039] In this invention, the silane coupling agent can be any conventional coupling agent in the art, such as γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, preferably γ-aminopropyltriethoxysilane.

[0040] The working principle and beneficial effects of this invention are as follows:

[0041] In this invention, the stainless steel bearing undergoes nitriding, heat treatment, and tempering sequentially. The heat treatment is a segmented process. In the first stage, the temperature is increased to 830-860℃ at a rate of 20-40℃ / h. This relatively rapid heating reduces the dwell time in the lower temperature range, thus preventing abnormal grain growth to some extent. Then, the temperature is increased to 1020-1040℃ at a rate of 20-40℃ / h and held for 0.5-1.5h. This stable heating rate of 20-40℃ / h helps to further adjust the internal structure of the stainless steel bearing, allowing for more complete diffusion of alloying elements and forming a more uniform and fine grain structure. Afterward, the temperature is reduced from 1020-1040℃ to 940-960℃ at a cooling rate of 10-15℃ / h and held for 20-30min. This 10-15℃ / h cooling rate avoids the defect caused by excessively rapid cooling, which leads to the segregation and precipitation of alloying elements such as Cr and V with carbon at the grain boundaries, forming coarse carbides. Through the proper combination of the first, second, and third heat treatment stages, the internal structure of the stainless steel bearing becomes more uniform, and the nitrided layer becomes more stable, thus giving the nitrided stainless steel bearing excellent wear resistance. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] In the following examples and comparative examples, the average particle size of the nano zinc oxide was 30 nm.

[0044] Example 1

[0045] S1. The stainless steel bearing was ultrasonically cleaned in ethanol for 5 minutes, dried, and then nitrided at 480°C for 12 hours under an ammonia atmosphere of 300 Pa and a nitriding voltage of 550 V. After that, it was nitrided at 530°C for 12 hours under an ammonia atmosphere of 300 Pa and a nitriding voltage of 550 V. Finally, it was cooled to room temperature to complete the nitriding process.

[0046] S2. The nitrided stainless steel bearing is heated to 830℃ at a heating rate of 20℃ / h and held for 1.5h. Then, it is heated from 830℃ to 1020℃ at a heating rate of 20℃ / h and held for 1.5h. After that, it is cooled from 1020℃ to 940℃ at a cooling rate of 10℃ / h and held for 30min. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30min. Finally, it is cryogenically treated at -80℃ for 85min to obtain the cooled stainless steel bearing.

[0047] S3. The cooled stainless steel bearing is heated to 300℃ at a heating rate of 30℃ / min, held for 1.5h, then heated to 500℃ at a heating rate of 10℃ / min, held for 1.5h, and then cooled to room temperature in the furnace to obtain the nitrided stainless steel bearing.

[0048] The stainless steel bearings, before nitriding treatment, consist of the following components by weight percentage:

[0049] C 1.0%, Si 0.18%, Mn 0.30%, Cr 13.5%, Mo 3.83%, V 0.10%, S 0.01%, P 0.01%, balance Fe and its unavoidable impurities.

[0050] Example 2

[0051] S1. The stainless steel bearing was ultrasonically cleaned in ethanol for 5 minutes, dried, and then nitrided at 490°C for 11 hours under an ammonia atmosphere of 340 Pa and a nitriding voltage of 580 V. The bearing was then nitrided at 535°C for 11 hours under an ammonia atmosphere of 340 Pa and a nitriding voltage of 580 V. The bearing was then cooled to room temperature to complete the nitriding process.

[0052] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 30℃ / h and held for 1 hour. Then, it is heated from 850℃ to 1030℃ at a heating rate of 30℃ / h and held for 1 hour. After that, it is cooled from 1030℃ to 950℃ at a cooling rate of 15℃ / h and held for 25 minutes. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes. Finally, it is cryogenically treated at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0053] S3. The cooled stainless steel bearing is heated to 350°C at a heating rate of 35°C / min, held for 2 hours, and then heated to 530°C at a heating rate of 15°C / min, held for 2 hours, and then cooled to room temperature in the furnace to obtain the nitrided stainless steel bearing.

[0054] The stainless steel bearings, before nitriding treatment, consist of the following components by weight percentage:

[0055] C 1.1%, Si 0.40%, Mn 0.45%, Cr 14.2%, Mo 4.0%, V 0.15%, S 0.03%, P 0.03%, balance Fe and its unavoidable impurities.

[0056] Example 3

[0057] S1. The stainless steel bearing is ultrasonically cleaned in ethanol for 5 minutes, dried, and then nitrided at 510°C for 10 hours under an ammonia atmosphere of 350 Pa and a nitriding voltage of 600 V. It is then nitrided at 540°C for 10 hours under an ammonia atmosphere of 350 Pa and a nitriding voltage of 600 V. After cooling to room temperature, the nitriding process is complete.

[0058] S2. The nitrided stainless steel bearing is heated to 860℃ at a heating rate of 40℃ / h and held for 0.5h. Then, it is heated from 860℃ to 1040℃ at a heating rate of 40℃ / h and held for 0.5h. After that, it is cooled from 1040℃ to 960℃ at a cooling rate of 15℃ / h and held for 20min. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 35min. Finally, it is cryogenically treated at -70℃ for 95min to obtain the cooled stainless steel bearing.

[0059] S3. The cooled stainless steel bearing is heated to 400℃ at a heating rate of 40℃ / min, held for 1.5h, then heated to 550℃ at a heating rate of 20℃ / min, held for 1.5h, and then cooled to room temperature in the furnace to obtain the nitrided stainless steel bearing.

[0060] The stainless steel bearings, before nitriding treatment, consist of the following components by weight percentage:

[0061] C 1.15%, Si 0.55%, Mn 0.6%, Cr 14.8%, Mo 4.20%, V 0.20%, S 0.03%, P 0.03%, balance Fe and its unavoidable impurities.

[0062] Example 4

[0063] The only difference between this embodiment and embodiment 2 is that step S2 is different in this embodiment, specifically:

[0064] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 20℃ / h and held for 1 hour. Then, it is heated from 850℃ to 1030℃ at a heating rate of 30℃ / h and held for 1 hour. After that, it is cooled from 1030℃ to 950℃ at a cooling rate of 15℃ / h and held for 25 minutes. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes. Finally, it is cryogenically treated at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0065] Example 5

[0066] The only difference between this embodiment and embodiment 2 is that step S2 is different in this embodiment, specifically:

[0067] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 30℃ / h and held for 1 hour. Then, it is heated from 850℃ to 1030℃ at a heating rate of 20℃ / h and held for 1 hour. After that, it is cooled from 1030℃ to 950℃ at a cooling rate of 15℃ / h and held for 25 minutes. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes. Finally, it is cryogenically treated at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0068] Example 6

[0069] S1. The stainless steel bearing was ultrasonically cleaned in ethanol for 5 minutes, dried, and then nitrided at 490°C for 11 hours under an ammonia atmosphere of 340 Pa and a nitriding voltage of 580 V. The bearing was then nitrided at 535°C for 11 hours under an ammonia atmosphere of 340 Pa and a nitriding voltage of 580 V. The bearing was then cooled to room temperature to complete the nitriding process.

[0070] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 30℃ / h and held for 1 hour. Then, it is heated from 850℃ to 1030℃ at a heating rate of 30℃ / h and held for 1 hour. After that, it is cooled from 1030℃ to 950℃ at a cooling rate of 15℃ / h and held for 25 minutes. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes. Finally, it is cryogenically treated at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0071] S3. The cooled stainless steel bearing is heated to 350°C at a heating rate of 35°C / min, held for 2 hours, and then heated to 530°C at a heating rate of 15°C / min, held for 2 hours, and then cooled to room temperature in the furnace to obtain the tempered stainless steel bearing.

[0072] S4. After tempering, the stainless steel bearing is immersed in a 3% tannic acid solution for 7 minutes, then immersed in the immersion solution and treated at 45°C for 7 hours. After removal and drying, it is ultrasonicated at 10kHz for 2.5 hours in an ethanol solution of γ-aminopropyltriethoxysilane (the weight ratio of γ-aminopropyltriethoxysilane to ethanol is 4:100). After washing and drying, the nitrided stainless steel bearing is obtained.

[0073] The stainless steel bearing, before nitriding treatment, consists of the following components by weight percentage:

[0074] C 1.1%, Si 0.40%, Mn 0.45%, Cr 14.2%, Mo 4.0%, V 0.15%, S 0.03%, P 0.03%, balance Fe and its unavoidable impurities;

[0075] The impregnation solution comprises the following components in parts by weight:

[0076] 3 parts citric acid, 4 parts iminodisuccinic acid, 10 parts polyacrylamide, 4 parts nano zinc oxide, 100 parts water.

[0077] Example 7

[0078] The only difference between this embodiment and Embodiment 6 is that, in this embodiment, the impregnation solution comprises the following components in parts by weight:

[0079] 5 parts citric acid, 14 parts iminodisuccinic acid, 2 parts polyacrylamide, 6 parts nano zinc oxide, 100 parts water.

[0080] Example 8

[0081] The only difference between this embodiment and Embodiment 7 is that, in this embodiment, 6 parts of iminodisuccinic acid and 10 parts of polyacrylamide are added to the impregnation solution.

[0082] Example 9

[0083] The only difference between this embodiment and Embodiment 7 is that, in this embodiment, 8 parts of iminodisuccinic acid and 8 parts of polyacrylamide are added to the impregnation solution.

[0084] Example 10

[0085] The only difference between this embodiment and Embodiment 7 is that, in this embodiment, 12 parts of iminodisuccinic acid and 4 parts of polyacrylamide are added to the impregnation solution.

[0086] Comparative Example 1

[0087] The only difference between this comparative example and Example 2 is that step S2 is different in this comparative example, specifically:

[0088] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 30℃ / h and held for 1 hour. Then, the temperature is increased from 850℃ to 1030℃ at a heating rate of 30℃ / h and held for 1 hour. After that, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes and then subjected to deep cryogenic treatment at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0089] Comparative Example 2

[0090] The only difference between this comparative example and Example 2 is that step S2 is different in this comparative example, specifically:

[0091] S2. The nitrided stainless steel bearing is heated from 850℃ to 1030℃ at a heating rate of 30℃ / h and held for 1 hour. Then, it is cooled from 1030℃ to 950℃ at a cooling rate of 15℃ / h and held for 25 minutes. After that, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes and then subjected to deep cryogenic treatment at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0092] Comparative Example 3

[0093] The only difference between this comparative example and Example 2 is that step S2 is different in this comparative example, specifically:

[0094] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 30℃ / h and held for 1 hour. Then, the temperature is increased from 850℃ to 950℃ at a heating rate of 30℃ / h and held for 25 minutes. After that, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes and then subjected to deep cryogenic treatment at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0095] Comparative Example 4

[0096] The only difference between this comparative example and Example 2 is that step S2 is different in this comparative example, specifically:

[0097] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 10℃ / h and held for 1 hour. Then, it is heated from 850℃ to 1030℃ at a heating rate of 10℃ / h and held for 1 hour. After that, it is cooled from 1030℃ to 950℃ at a cooling rate of 5℃ / h and held for 25 minutes. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes. Finally, it is cryogenically treated at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0098] Comparative Example 5

[0099] The only difference between this comparative example and Example 2 is that step S2 is different in this comparative example, specifically:

[0100] S2. The nitrided stainless steel bearing is heated to 850℃ at a heating rate of 45℃ / h and held for 1 hour. Then, it is heated from 850℃ to 1030℃ at a heating rate of 45℃ / h and held for 1 hour. After that, it is cooled from 1030℃ to 950℃ at a cooling rate of 20℃ / h and held for 25 minutes. Then, the heat-treated stainless steel bearing is quenched in quenching oil in an oil bath for 30 minutes. Finally, it is cryogenically treated at -75℃ for 90 minutes to obtain the cooled stainless steel bearing.

[0101] Experimental Example 1

[0102] The nitrided stainless steel bearing samples prepared in Examples 1-5 and Comparative Examples 1-5 were ultrasonically treated in anhydrous ethanol for 10 min, then removed, dried, and weighed to obtain the initial weight of the nitrided stainless steel bearing samples. The nitrided stainless steel bearing samples were then subjected to friction treatment for 1 h using a wear testing machine. After the test, the samples were cleaned and weighed, and the mass difference before and after wear was calculated as the mass wear amount. During the friction treatment, the vertical load was 1 kN, and the grinding body was made of WC material. The test results are shown in Table 1.

[0103] Table 1. Test results of wear resistance of Examples 1-5 and Comparative Examples 1-5

[0104]

[0105] Compared with Comparative Examples 1-5, the nitrided stainless steel bearings prepared in Examples 1-5 showed a reduction in wear, indicating that dividing the heat treatment of stainless steel bearings after nitriding into three stages—first, second, and third—and adjusting the heating rate and temperature of the first and second stages, as well as the cooling rate and temperature of the third stage, allows the stainless steel bearings to undergo a suitable heat treatment process, thereby forming a uniform microstructure and effectively improving the wear resistance of nitrided stainless steel bearings.

[0106] Experiment Example 2

[0107] The nitrided stainless steel bearing samples prepared in Examples 5-10 were subjected to corrosion resistance tests according to the method in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The test was conducted using a neutral salt spray test with a sodium chloride mass fraction of 5%, a spray pressure of 70 kPa, and a test temperature of 35°C. The time when corrosion began to appear on the samples was recorded. The test results are shown in Table 2.

[0108] Table 2. Corrosion resistance test results of Examples 5-10

[0109]

[0110] Compared with Example 5, the nitrided stainless steel bearings prepared in Examples 6-10 showed a longer corrosion time after neutral salt spray testing, reaching more than 201 hours. This indicates that treating the tempered stainless steel bearings with an impregnation solution and adjusting the content ratio of iminodisuccinic acid and polyacrylamide in the impregnation solution can improve the corrosion resistance of the nitrided stainless steel bearings to a certain extent.

[0111] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat treatment process for nitrided stainless steel bearings, characterized in that, The process includes the following steps: nitriding, heat treatment, and tempering of the stainless steel bearing. The heat treatment consists of a first heat treatment stage, a second heat treatment stage, and a third heat treatment stage. During the first stage of heat treatment, the temperature is increased to 830-860℃ at a rate of 20-40℃ / h, and held for 0.5-1.5h. During the second stage of heat treatment, the temperature is increased from 830~860℃ to 1020~1040℃ at a heating rate of 20~40℃ / h, and held at that temperature for 0.5~1.5h. During the third stage of heat treatment, the temperature is reduced from 1020-1040℃ to 940-960℃ at a cooling rate of 10-15℃ / h, and held for 20-30 minutes. After the heat treatment, the stainless steel bearing is subjected to oil quenching and deep cryogenic treatment. The oil quenching time is 30-35 minutes; During the cryogenic treatment, the temperature is -80 to -70°C and the time is 85 to 95 minutes. The nitrided stainless steel bearings after tempering are then immersed in an impregnation solution. The impregnation solution comprises the following components in parts by weight: Citric acid 3-5 parts, iminodisuccinic acid 4-14 parts, polyacrylamide 2-10 parts, nano zinc oxide 4-6 parts, water 100 parts; The weight ratio of iminodisuccinic acid to polyacrylamide is 1~3:

1.

2. The heat treatment process for a nitrided stainless steel bearing according to claim 1, characterized in that, The heating rate of the first heat treatment stage is greater than the heating rate of the second heat treatment stage.

3. The heat treatment process for a nitrided stainless steel bearing according to claim 1, characterized in that, During the tempering process, the temperature is increased to 300-400℃ at a heating rate of 30-40℃ / min, held for 1.5-2 hours, then increased to 500-550℃ at a heating rate of 10-20℃ / min, held for 1.5-2 hours, and then cooled to room temperature.

4. The heat treatment process for a nitrided stainless steel bearing according to claim 1, characterized in that, The nitriding treatment is gas nitriding, and the gas is ammonia. The nitriding process is divided into a first-stage nitriding and a second-stage nitriding. During the first stage of nitriding, the nitriding temperature is 480~510℃ and the nitriding time is 10~12h; During the second stage of nitriding, the nitriding temperature is 530~540℃ and the nitriding time is 10~12h.

5. A nitrided stainless steel bearing, characterized in that, The stainless steel bearing that has undergone the heat treatment process of the nitrided stainless steel bearing according to any one of claims 1 to 4 is obtained by impregnation with an impregnation solution.

6. A nitrided stainless steel bearing according to claim 5, characterized in that, The impregnation process specifically includes the following steps: The tempered stainless steel bearing is immersed in an impregnation solution, removed, dried, ultrasonically treated in a silane coupling agent solution, washed, and dried.

7. The nitrided stainless steel bearing according to claim 6, characterized in that, The silane coupling agent solution is an ethanol solution of silane coupling agent, and the weight ratio of silane coupling agent to ethanol in the ethanol solution of silane coupling agent is 3~5:100.

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