Carburizing heat treatment method for high-strength super-tough cylindrical roller

Abstract

The invention discloses a carburizing heat treatment method for a high-strength super-tough cylindrical roller. The invention belongs to the field of bearing part machining and manufacturing, and particularly relates to a carburizing heat treatment method for a high-strength super-tough cylindrical roller. The invention aims to solve the problems that the whole surface carburizing layer is not uniform due to carburizing supporting contact in the carburizing process of the surface strengthening cylindrical roller, soft spots exist in a contact area during carburizing, and then the whole surface performance is not uniform. The method comprises the following steps: 1, processing a low-carbon carburizing bearing material into a to-be-carburized bearing for rolling; 2, a carburizing tool is designed according to actual requirements by taking a graphite material as a material; thirdly, the bearing rolling body to be carburized is installed in a carburizing tool and placed in a vacuum carburizing heat treatment furnace together for carburizing treatment, and the carburized bearing rolling body is obtained; fourthly, the auxiliary boss is removed through turning; and fifthly, the carburized bearing rolling body is placed on a tool frame to be subjected to heat treatment, and then carburizing heat treatment of the high-strength super-tough cylindrical roller is completed. The method is used for carburizing heat treatment of the high-strength super-tough cylindrical roller.

Description

Technical Field

[0001] The invention belongs to the field of bearing parts processing and manufacturing, and specifically relates to a high-strength and ultra-tough cylindrical roller carburizing heat treatment method. Background Art

[0002] In today's aerospace field, aircraft engine technology is experiencing rapid development, and the continuous improvement of its performance has put forward strict requirements on various key components. Among them, bearings, as one of the core components, play a pivotal role. With the gradual increase in engine performance indicators, such as higher thrust-to-weight ratio, better fuel economy and more reliable durability, the performance requirements for bearings are becoming more and more stringent. This is not only reflected in the need for bearings to have higher speed adaptability and stronger load-bearing capacity, but also requires them to be able to operate stably and reliably under complex, changeable and extreme working conditions.

[0003] In order to meet these growing performance requirements, the research and development of bearing materials is also constantly advancing, and the strength of the materials used is gradually increasing. Among cylindrical roller bearings, surface-hardened cylindrical rollers stand out compared to traditional fully hardened cylindrical rollers. After carburizing, this type of roller can achieve an ideal combination of high surface strength and high core toughness. The high strength of the surface gives the roller good wear and fatigue resistance, allowing it to maintain surface integrity when subjected to huge pressure and frequent friction, effectively extending the service life of the roller; while the high toughness of the core ensures that the roller is not prone to breakage when subjected to impact and complex stress, ensuring the reliability of the bearing operation.

[0004] However, surface-hardened cylindrical rollers face severe challenges during the carburizing process. Since the roller surface requires full surface strengthening, in the actual carburizing process, the carburized roller has the problem of uneven carburizing layer on the entire surface due to the contact between the carburizing support. During carburizing, the contact area between the roller and the support is difficult for the gas carburizing medium to diffuse fully and evenly to this area, resulting in poor carburizing effect in this area and the presence of soft spots. The appearance of these soft spots destroys the uniformity of the roller's full surface performance, greatly affecting the overall performance and reliability of the roller. Under the conditions of high-speed rotation and high-load operation of aircraft engines, the uneven surface performance of the roller may cause local stress concentration, leading to premature failure of the roller, which seriously threatens the safe operation of aircraft engines.

[0005] In summary, developing a carburizing heat treatment method for cylindrical rollers that can effectively solve the problem of uneven carburization layer on the surface of carburized rollers, achieve uniform performance on the entire surface of the roller, and at the same time have high-strength and super-toughness properties, is of extremely important practical significance for meeting the ever-increasing high-performance requirements of aircraft engines and improving my country's aerospace technology level. Summary of the invention

[0006] The present invention provides a high-strength and super-tough cylindrical roller carburizing heat treatment method to solve the problem that the carburizing layer of the surface-strengthened cylindrical roller is uneven due to the contact of the carburizing support during the carburizing process, and soft spots exist in the contact area during carburizing, which leads to uneven performance of the entire surface.

[0007] The present invention provides a high-strength and ultra-tough cylindrical roller carburizing heat treatment method comprising:

[0008] 1. Processing low-carbon carburized bearing materials into bearing rolling elements to be carburized;

[0009] 2. Design carburizing tooling based on actual needs using graphite material;

[0010] 3. Install the bearing rolling element to be carburized in the carburizing tooling and place them in a vacuum carburizing heat treatment furnace for carburizing treatment to obtain the carburized bearing rolling element;

[0011] 4. Turning to remove the auxiliary boss;

[0012] 5. Place the carburized bearing rolling elements on a fixture for heat treatment, thus completing the carburizing heat treatment of the high-strength and super-tough cylindrical rollers.

[0013] Beneficial effects of the present invention:

[0014] For carburized bearing rollers, it has high surface hardness and high toughness in the core, which improves the compression strength of the rollers. For fully hardened bearing rollers, the fracture toughness of the core is less than 20MPa·cm 1 / 2 The fracture toughness of the carburized bearing roller core can reach 40MPa·cm 1 / 2 For example, the core fracture toughness of 15Cr14Co12Mo5Ni2W carburized bearing rollers can reach over 70. Under high load conditions, carburized bearing rollers can effectively improve the impact resistance of the bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the carburizing tooling structure in the embodiment;

[0016] Figure 2 This is a physical picture of the bearing rolling element to be carburized after being installed in the carburizing tooling in the embodiment;

[0017] Figure 3 The microstructure diagram of the carburized bearing roller prepared in the embodiment at the cross section position 1 along the circumferential direction, wherein 0.5 mm, 0.3 mm, and 0.1 mm are the position marks from the cylindrical surface;

[0018] Figure 4The microstructure diagram of the carburized bearing roller prepared in the embodiment at the cross section position 2 along the circumferential direction, wherein 0.5 mm, 0.3 mm, and 0.1 mm are the position marks from the cylindrical surface;

[0019] Figure 5 It is the Vickers microhardness gradient at a depth of 2.5mm from the surface to the core at different positions of the carburized bearing roller after the cross section is cut along the circumferential direction. 1#, 2#, 3#, and 4# represent four points evenly distributed in the circumferential direction. DETAILED DESCRIPTION

[0020] Specific implementation method 1: A high-strength and super-tough cylindrical roller carburizing heat treatment method of this implementation method includes:

[0021] 1. Processing low-carbon carburized bearing materials into bearing rolling elements to be carburized;

[0022] 2. Design carburizing tooling based on actual needs using graphite material;

[0023] 3. Install the bearing rolling element to be carburized in the carburizing tooling and place them in a vacuum carburizing heat treatment furnace for carburizing treatment to obtain the carburized bearing rolling element;

[0024] 4. Turning to remove the auxiliary boss;

[0025] 5. Place the carburized bearing rolling elements on a fixture for heat treatment, thus completing the carburizing heat treatment of high-strength and super-tough cylindrical rollers.

[0026] The carburizing tooling of this embodiment uses a perforated graphite plate with holes of specific depth, spacing and aperture designed to provide stable and uniform support for the rollers and reduce the adverse effects of contact between the rollers and the tooling on carburizing. The auxiliary boss is machined on the end face of the bearing rolling element, which changes the contact point between the roller and the tooling, so that the gas carburizing medium can be more evenly diffused to the entire surface of the roller during carburizing, avoiding local uneven carburizing caused by traditional support contact methods and eliminating carburizing soft spots. After carburizing, the auxiliary boss is removed by lathing, which will not affect the final performance of the roller.

[0027] This embodiment uses a vacuum carburizing heat treatment furnace and sets a cycle period of 18-80 times and a total carburizing time of 24-130 hours. Through multiple cycles and longer carburizing times, carbon atoms can diffuse more fully and evenly to the roller surface and interior, effectively improving the uniformity of the carburized layer and achieving uniform performance across the entire surface.

[0028] This embodiment uses heat treatment processes such as quenching, cold treatment and tempering, which can further refine the structure, eliminate the residual stress generated during carburizing, and improve the size, morphology and distribution of carbides. For example, the appropriate quenching temperature and holding time can make the structure fully austenitized; cold treatment can further transform the residual austenite, improve the hardness and dimensional stability; tempering can eliminate internal stress and adjust the balance between hardness and toughness. By alternating and repeating cold treatment and tempering, the structure and performance can be precisely controlled to compensate for the slight unevenness that may exist during carburizing, ensuring that the final roller surface hardness and carburized layer depth are uniform and stable.

[0029] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the outer diameter of the bearing rolling element to be carburized in step 1 is set to d (mm), and the auxiliary boss is processed on the end surface of the bearing rolling element, and the size is d-3 (mm). Other steps and parameters are the same as those in specific implementation method 1.

[0030] Specific implementation method 3: This implementation method is different from specific implementation method 1 in that the carburizing tool in step 2 is a graphite plate with holes. Other steps and parameters are the same as those in specific implementation method 1.

[0031] Specific embodiment 4: This embodiment is different from specific embodiments 2 and 3 in that: the thickness of the carburizing tool is greater than 8-15 mm; the carburizing tool evenly processes multiple mounting holes, the hole diameter is d-3 (mm), the clearance with the auxiliary boss is matched, the hole depth is greater than 3-12 mm, and the hole spacing is 3-15 mm. The other steps and parameters are the same as those of specific embodiments 2 and 3.

[0032] Specific implementation method 5: This implementation method is different from specific implementation method 4 in that: in step 3, the bearing rolling element to be carburized is installed in the carburizing tooling, which is to install several bearing rolling elements to be carburized in the installation hole, and ensure that the height of the auxiliary boss processed on the end surface of the bearing rolling element is more than 3mm greater than the hole depth. The other steps and parameters are the same as those of specific implementation method 4.

[0033] Specific embodiment 6: This embodiment is different from the specific embodiment 1 in that the cycle of the carburizing treatment in step 3 is 18 to 80 times, and the total carburizing time is 24 to 130 hours. The other steps and parameters are the same as those in the specific embodiment 1.

[0034] Specific implementation method 7: This implementation method is different from specific implementation method 6 in that the heat treatment in step 4 includes quenching, cold treatment and tempering. The other steps and parameters are the same as those in specific implementation method 6.

[0035] Specific embodiment eight: This embodiment differs from specific embodiment seven in that the quenching process parameters are: heating temperature of 1000-1090°C, holding time of 20-90 min, high pressure nitrogen atmosphere of 1-5 bar. Other steps and parameters are the same as those of specific embodiment seven.

[0036] Specific embodiment 9: This embodiment differs from specific embodiment 7 in that the process parameters of the cold treatment are: the cold treatment temperature is -70 to -192°C, and the holding time is 0.5 to 2 hours. Other steps and parameters are the same as those of specific embodiment 7.

[0037] Specific embodiment 10: This embodiment differs from specific embodiment 7 in that the tempering process parameters are: vacuum tempering temperature is 450-600°C, and the holding time is 2-3h. Other steps and parameters are the same as those of specific embodiment 7.

[0038] The beneficial effects of the present invention are verified by the following examples:

[0039] Embodiment 1: A high-strength and ultra-tough cylindrical roller carburizing heat treatment method comprises:

[0040] 1. Processing the low-carbon carburized bearing material into a bearing rolling element to be carburized; the size of the bearing rolling element to be carburized is Φ12mm×12mm, and the end surface of the bearing rolling element is processed with an auxiliary boss, and the boss size is Φ6mm×6mm; the low-carbon carburized bearing material is low-carbon high-alloy steel, and the mass fraction of C in the low-carbon high-alloy steel is 0.1-0.2%, Cr is 11.0-17.0%, and Mo is 3.0-6.0%;

[0041] 2. Design carburizing tooling with graphite material according to actual needs; the carburizing tooling structure is a graphite plate with holes; the length, width and height of the graphite plate are 300mm×180mm×12mm, the designed hole depth of the graphite plate is 3mm, the hole spacing is 3mm, and a total of 60 Φ6mm×3mm holes are processed, see Figure 1 ;

[0042] 3. Install the bearing rolling element to be carburized in the carburizing tooling and put it into the vacuum carburizing heat treatment furnace for carburizing treatment. The cycle is 18 to 80 times and the total carburizing time is 24 to 130 hours to obtain the carburized bearing rolling element.

[0043] 4. Turning to remove the auxiliary boss;

[0044] 5. Place the carburized bearing rolling elements on a fixture for heat treatment, thereby completing the carburizing heat treatment of high-strength and super-tough cylindrical rollers; the heat treatment includes quenching, cold treatment and tempering; after alternating and repeating cold treatment and tempering cycles, cold treatment or tempering can be repeated individually or alternately; the process parameters of the quenching are as follows: heating temperature of 1000-1090°C, holding time of 20-90min, and high-pressure nitrogen atmosphere of 1-5bar; the process parameters of the cold treatment are as follows: cold treatment temperature of -70--192°C, holding time of 0.5-2h; the process parameters of the tempering are as follows: vacuum tempering temperature of 450-600°C, and holding time of 2-3h.

[0045] The surface hardness of the bearing roller processed by this process can be controlled at 60-69HRC, the depth of the carbide layer can reach 0.3-3.0mm, and the size, morphology and distribution of the carbide are properly controlled.

[0046] After the carburized bearing roller prepared in this embodiment is cut along the circumferential direction, positions 1 and 2 on the cross section are randomly selected to conduct microscopic observation of the structures at different positions of the cross section; Figure 3 The microstructure diagram of the carburized bearing roller prepared in the embodiment at the cross section position 1 along the circumferential direction, wherein 0.5 mm, 0.3 mm, and 0.1 mm are the position marks from the cylindrical surface; Figure 4 This is the microstructure diagram of the carburized bearing roller prepared in the embodiment at section position 2 along the circumferential direction, where 0.5mm, 0.3mm, and 0.1mm are position marks from the cylindrical surface; positions 1 and 2 are the microstructures on randomly selected sections, with 0.5mm, 0.3mm, and 0.1mm position marks from the cylindrical surface. From the figure, it can be seen that carbides are dispersed in the form of points, short needles, and short columns at different distances from the surface, respectively. The carbide sizes at 0.1mm, 0.3mm, and 0.5mm from the cylindrical surface can be calculated according to the ruler in the lower right corner, and the maximum carbide size does not exceed 20μm.

[0047] Figure 5 The Vickers microhardness gradient at a depth of 2.5mm from the surface to the core at different positions of the carburized bearing roller after the cross section is cut along the circumferential direction. 1#, 2#, 3#, and 4# represent four points evenly distributed in the circumferential direction. It can be seen from the figure that the hardness gradient trend of the four points is consistent, and the hardness fluctuation at the same depth does not exceed 30HV1, indicating that the circumferential hardness distribution of the carburized cylindrical roller is uniform and the performance uniformity is good.

Claims

1. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method, characterized in that The method includes:

1. Processing low-carbon carburized bearing materials into bearing rolling elements to be carburized; 2. Design carburizing tooling based on actual needs using graphite material; 3. Install the bearing rolling element to be carburized in the carburizing tooling and place them in a vacuum carburizing heat treatment furnace for carburizing treatment to obtain the carburized bearing rolling element; 4. Place the carburized bearing rolling elements on a fixture for heat treatment, thus completing the carburizing heat treatment of the high-strength and super-tough cylindrical rollers.

2. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 1, characterized in that In step 1, the outer diameter of the bearing rolling element to be carburized is set to d (mm), and the end face of the bearing rolling element is processed with an auxiliary boss with a size of d-3 (mm).

3. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 1, characterized in that The carburizing tool in step 2 is a graphite plate with holes.

4. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claims 2 and 3, characterized in that The thickness of the carburizing tool is greater than 8 to 15 mm; the carburizing tool evenly processes a plurality of mounting holes, the hole diameter is d-3 (mm), the hole depth is greater than 3 to 12 mm, and the hole spacing is 3 to 15 mm.

5. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 4, characterized in that In step 3, the bearing rolling elements to be carburized are installed on the carburizing tooling, that is, a number of bearing rolling elements to be carburized are installed in the installation holes, and the height of the auxiliary boss processed on the end face of the bearing rolling element is ensured to be more than 3 mm greater than the hole depth.

6. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 1, characterized in that The cycle of the carburizing treatment in step 3 is 18 to 80 times, and the total carburizing time is 24 to 130 hours.

7. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 1, characterized in that The heat treatment in step 4 includes quenching, cold treatment and tempering.

8. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 7, characterized in that The quenching process parameters are: heating temperature of 1000-1090° C., holding time of 20-90 min, and high-pressure nitrogen atmosphere of 1-5 bar.

9. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 7, characterized in that The process parameters of the cold treatment are as follows: the cold treatment temperature is -70 to -192°C, and the insulation time is 0.5 to 2h.

10. A high-strength and ultra-tough cylindrical roller carburizing heat treatment method according to claim 7, characterized in that The tempering process parameters are as follows: vacuum tempering temperature is 450-600° C., and the heat preservation time is 2-3 hours.

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