A heat treatment method for improving wear resistance of 9310 carburized steel

Abstract

The application discloses a heat treatment method for improving wear resistance of 9310 carburized steel, and mainly comprises the following steps: normalizing raw materials, carburizing, reheating and quenching, deep cryogenic treatment and tempering treatment; according to the action characteristics of Ni, Cr and other alloy elements in the 9310 steel, the carbon concentration of the carburized layer is controlled through carbon potential regulation to avoid the precipitation of net-shaped carbide; meanwhile, a low-temperature tempering process is adopted to form an adaptation with the martensite structure after carburizing, so that the internal stress is eliminated, secondary strengthening is realized through the dispersion precipitation of alloy elements, and the wear resistance is improved. The carbon concentration distribution of the carburized layer of the 9310 steel is controlled through the regulation of the carburizing carbon potential, the generation of the surface net-shaped carbide is avoided, the depth of the carburized layer can reach 1.5 mm, and the uniformity of the structure is significantly improved; and the wear resistance is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for metallic materials, and in particular to a heat treatment method for improving the wear resistance of 9310 carburized steel. Background Technology

[0002] 9310 steel is a high-quality alloy structural steel with high strength, high toughness, and good hardenability, and is widely used in aerospace, automotive manufacturing, and engineering machinery. These components often endure complex conditions such as reciprocating friction and impact loads during service, and wear failure is one of their main failure modes. Therefore, improving the wear resistance of 9310 steel is of great significance for extending the service life of components and reducing maintenance costs.

[0003] In the field of mechanical manufacturing, wear and tear of parts is one of the main reasons for equipment downtime and increased maintenance costs. To improve the wear resistance of parts, carburizing heat treatment is a commonly used surface strengthening technology. It involves infiltrating carbon atoms into the surface layer of the part in a high-temperature carburizing atmosphere to form a carburized layer of a certain depth, followed by quenching and tempering to obtain a microstructure with "hard exterior and tough interior". Summary of the Invention

[0004] The purpose of this invention is to provide a heat treatment method for improving the wear performance of 9310 carburized steel, so as to solve the problem that the existing treatment process does not improve the wear performance sufficiently.

[0005] The technical solution of the present invention: a heat treatment method for improving the wear resistance of 9310 carburized steel, comprising the following steps:

[0006] S1. Hold 9310 steel at 950°C for 30 minutes, then cool it to room temperature. Remove the surface oxide scale by first polishing the sample surface with 60-grit sandpaper and then sandblasting the sample.

[0007] S2, Place the workpiece processed in step S1 into a carburizing furnace, heat it to 600°C and hold it for 10 minutes, then heat it to 925°C.

[0008] S3, the workpiece processed in step S2 is kept at 925°C for a 180-minute carburizing and strong carburizing stage. Pulse carburizing is used. First, carburizing gas is introduced to bring the pressure to 15 kPa and maintain this pressure for 20 seconds. Finally, a vacuum is drawn. This process is repeated continuously. During the repeated process of the strong carburizing stage, the vacuum time is continuously increased.

[0009] S4. The workpiece treated in step S3 is further subjected to a carburizing diffusion stage at 925°C for 360 min. After diffusion, the temperature is reduced to 840°C at a rate of 10°C / min and held for 30 min. Finally, the sample is cooled to room temperature.

[0010] S5, perform a first quenching on the workpiece processed in step S4.

[0011] S6, Perform deep cryogenic treatment on the workpiece processed in step S5.

[0012] S7. Perform low-temperature tempering on the workpiece processed in step S6.

[0013] S8. Perform a friction and wear test on the workpiece processed in step S7.

[0014] Furthermore, in step S3, the vacuuming time increases from 40s to 20min, and the vacuuming time and the carburizing time are cycled until the carburizing and strong carburizing stage is completed in 180min.

[0015] Furthermore, the cooling method in step S1 is air cooling.

[0016] Furthermore, the heating rate in step S2 is 10℃ / min.

[0017] Furthermore, in step S3, the carburizing gas includes acetylene and nitrogen with a total flow rate of 8 L / min, and the ratio of acetylene to nitrogen is 1.2:1.

[0018] Furthermore, in step S4, the cooling medium is oil.

[0019] Furthermore, the first quenching in step S5 involves heating the workpiece to 860°C at a rate of 10°C / min in a vacuum environment, holding it at that temperature for 30 minutes, and finally oil quenching the workpiece to room temperature.

[0020] Furthermore, in step S6, the cryogenic treatment involves placing the workpiece at a temperature of -80°C, holding it at that temperature for 3 hours, and finally removing the sample and cooling it to room temperature.

[0021] Furthermore, the low-temperature tempering in step S7 involves heating to 180°C at a rate of 10°C / min, holding at that temperature for 120 min, and finally removing the sample and cooling it to room temperature.

[0022] Furthermore, the friction and wear test step S8 is as follows:

[0023] S8.1, Grind the workpiece before the test using sandpaper with grits of 120, 400, 600, 800, 1000, 1200, 1500 and 2000.

[0024] S8.2 Wear test: Dry sliding wear test was performed on a wear testing machine. The friction pair - WC, rotation speed: 300 r / min, load: 50 N, wear diameter: 6 mm, wear time: 60 min.

[0025] The beneficial effects of this invention compared to existing technologies are as follows: Targeting the characteristics of alloying elements such as Ni and Cr in 9310 steel, the carbon concentration of the carburized layer is controlled through carbon potential regulation, preventing the precipitation of network carbides. Simultaneously, a low-temperature tempering process is employed, which adapts to the martensitic structure after carburizing. This eliminates internal stress while achieving secondary strengthening through the dispersed precipitation of alloying elements, thereby improving wear resistance. By regulating the carburizing carbon potential, the carbon concentration distribution of the carburized layer in 9310 steel is controlled, preventing the formation of surface network carbides. The carburized layer depth can reach 1.5 mm, significantly improving the uniformity of the microstructure and wear resistance. 9310 steel treated with this process exhibits significantly improved wear resistance in dry sliding wear tests on a wear testing machine. The carbon potential and tempering parameters can be flexibly adjusted according to different carburized layer depth requirements, making it suitable for the heat treatment of various low-alloy structural steel parts, especially for the manufacture of critical wear parts such as gears and bearings. Attached Figure Description

[0026] Figure 1 This is a flowchart of the heat treatment process of the present invention;

[0027] Figure 2 Images of the diffusion layer structure in the heat treatment processes of the present invention where the carbon potential is acetylene:nitrogen in ratios of 1:1 and 1.2:1;

[0028] Figure 3 This is a hardness gradient curve for the heat treatment process of the present invention where the carbon potential is acetylene:nitrogen in ratios of 1:1 and 1.2:1;

[0029] Figure 4 The curves showing the changes in friction coefficient and wear performance in the heat treatment processes of the present invention with carbon potential of acetylene:nitrogen ratios of 1:1 and 1.2:1 are shown.

[0030] Figure 5 This is a SEM image of the worn surface in the heat treatment process of the present invention where the carbon potential is acetylene:nitrogen in ratios of 1:1 and 1.2:1. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0032] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0033] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0034] See Figure 1-5 The present invention discloses a heat treatment method for improving the wear resistance of 9310 carburized steel, comprising the following steps:

[0035] S1. Hold 9310 steel at 950°C for 30 minutes, then cool it to room temperature. Remove the surface oxide scale by first polishing the sample surface with 60-grit sandpaper and then sandblasting the sample.

[0036] In some embodiments of the present invention, the heat treatment method is normalizing, which eliminates the microscopic inhomogeneity of chemical composition and structure, and the cooling method is air cooling.

[0037] S2, Place the workpiece processed in step S1 into a carburizing furnace, heat it to 600°C and hold it for 10 minutes, then heat it to 925°C at a rate of 10°C / min.

[0038] S3. The workpiece processed in step S2 is kept at 925°C for 180 minutes of strong carburizing stage. Pulse carburizing is used. First, carburizing gas is introduced to bring the pressure up to 15 kPa and maintain this pressure for 20 seconds. Finally, a vacuum is drawn. This process is repeated continuously.

[0039] The cyclic process involves introducing carburizing gas at 15 kPa and maintaining this pressure for 20 seconds during intense carburizing, followed by vacuuming, constituting one pulse cycle. This process is repeated, with the total vacuuming and carburizing times combined, until 180 minutes have elapsed, completing the intense carburizing stage. For example, the vacuuming time in the first cycle is 40 seconds, and in the next cycle, it is set to 45 seconds. The vacuuming time varies with each cycle, gradually increasing from 40 seconds to 20 minutes. Pulse carburizing not only cleans the surface of the parts but also creates a uniform carburized layer in deep recesses and small-diameter blind holes. The carburizing gas consists of acetylene and nitrogen with a total flow rate of 8 L / min, and the acetylene to nitrogen ratio is 1.2:1.

[0040] S4. The workpiece treated in step S3 is further subjected to a carburizing diffusion stage at 925°C for 360 minutes. After diffusion, the temperature is reduced to 840°C at a rate of 10°C / min and held for 30 minutes. Finally, the sample is cooled to room temperature. The diffusion stage is to allow excess carbon atoms accumulated on the surface to continue to migrate deeper into the part, and at the same time, it will make the carbon concentration distribution on the surface more gradual.

[0041] S5. The workpiece processed in step S4 is quenched once. Under vacuum, the temperature is raised to 860℃ at a rate of 10℃ / min and held for 30min. Finally, the workpiece is oil quenched to room temperature. The purpose of quenching once is to partially dissolve the fine carbides and make the overall carbon distribution more uniform.

[0042] S6. The workpiece processed in step S5 is subjected to cryogenic treatment. The workpiece is placed in a container at -80℃ and held for 3 hours. Finally, the sample is removed and cooled to room temperature. Cryogenic treatment is intended to promote the transformation of unstable retained austenite into harder and more stable martensite.

[0043] S7. The workpiece processed in step S6 is subjected to low-temperature tempering. The temperature is increased to 180°C at a rate of 10°C / min and held for 120 min. Finally, the sample is taken out and cooled to room temperature. Low-temperature tempering is to promote the transformation of unstable structure into stable structure in advance.

[0044] S8. Perform a friction and wear test on the workpiece processed in step S7. The friction and wear test steps in step S8 are as follows:

[0045] S8.1, Grind the workpiece before the test using sandpaper with grits of 120, 400, 600, 800, 1000, 1200, 1500 and 2000.

[0046] S8.2 Wear Test: Dry sliding wear test was conducted on a wear testing machine. The friction pair - WC, rotational speed: 300 r / min, load: 50 N, wear diameter: 6 mm, wear time: 60 min. The wear test was conducted to analyze the tribological performance of various processes under high load (50 N).

[0047] In this step, the heat treatment process is performed when the carbon potential is acetylene:nitrogen in a 1:1 ratio.

[0048] 1.1 Hold 9310 steel at 950℃ for 30 minutes, then cool it to room temperature, and then remove the surface oxide scale;

[0049] 1.2. Place the processed workpiece into a carburizing furnace, heat it to 600℃ at 10℃ / min and hold it for 10min, then heat it to 925℃.

[0050] 1.3. The workpiece is kept at 925℃ for 180 minutes for a strong carburizing stage. An acetylene:nitrogen gas with a ratio of 1:1 is introduced at a total flow rate of 8L / min to bring the pressure to 1.5kPa. The pressure is then maintained for 20 seconds, and finally a vacuum is drawn. This process is repeated continuously.

[0051] 1.4. Continue the carburizing diffusion stage at 925℃ for 360 minutes. After diffusion, cool down to 840℃ at 10℃ / min and hold for 30 minutes. Finally, quench the sample in oil to room temperature.

[0052] 1.5. Under vacuum conditions, heat the workpiece to 860℃ at a rate of 10℃ / min, hold for 30min, and finally oil quench the workpiece to room temperature.

[0053] 1.6 Place the workpiece in a container at -80℃ and keep it at that temperature for 3 hours. Finally, remove the sample and cool it to room temperature.

[0054] 1.7. Heat to 200℃ at a rate of 10℃ / min, hold for 240min and 480min, and finally remove the sample and air cool to room temperature.

[0055] 1.8. Conduct a friction and wear test on the workpiece.

[0056] In this step, the heat treatment process is performed when the carbon potential is acetylene:nitrogen ratio of 1.2:1.

[0057] 2.1 Hold 9310 steel at 950℃ for 30 minutes, then cool it to room temperature, and then remove the surface oxide scale;

[0058] 2.2. Place the processed workpiece into a carburizing furnace, heat it to 600℃ at a rate of 10℃ / min, hold it for 10min, and then heat it to 925℃.

[0059] 2.3. The workpiece is kept at 925℃ for 180 minutes for a strong carburizing stage. An acetylene:nitrogen gas with a ratio of 1.2:1 is introduced, with a total gas flow rate of 8L / min, so that the pressure reaches 1.5kPa and is maintained for 20 seconds. Finally, a vacuum is drawn. This process is repeated continuously.

[0060] 2.4. Continue the carburizing diffusion stage at 925℃ for 360 min. After diffusion, cool down to 840℃ at 10℃ / min and hold for 30 min. Finally, quench the sample in oil to room temperature.

[0061] 2.5. Under vacuum conditions, heat the workpiece to 860℃ at a rate of 10℃ / min, hold for 30min, and finally oil quench the workpiece to room temperature.

[0062] 2.6 Place the workpiece in a container at -80℃ and keep it at that temperature for 3 hours. Finally, remove the sample and cool it to room temperature.

[0063] 2.7. Increase the temperature to 180℃ at a rate of 10℃ / min, hold for 120min and 240min, and finally remove the sample and air cool to room temperature.

[0064] 2.8. Conduct a friction and wear test on the workpiece.

[0065] Depend on Figure 1 It can be seen that the main heat treatment process route is: raw material normalizing → carburizing process → reheating and quenching → cryogenic treatment → tempering treatment.

[0066] Figure 2 These are schematic diagrams of the deep microstructure and core microstructure of 9310 carburized steel treated in Examples 1 and 2. Figure 2 It can be seen that the surface microstructure of 9310 carburized steel mainly consists of acicular martensite, retained austenite, and a small amount of carbides. The core microstructure is typical lath martensite, which originates from the low-carbon martensite formed during quenching. Its laths are relatively large, providing good plasticity to the sample.

[0067] The hardness of the 9310 carburized steel treated in Examples 1 and 2 were tested respectively:

[0068] Figure 3 The hardness gradient curves of 9310 carburized steel after treatments in Examples 1 and 2 are shown. The testing equipment was an automatic Vickers hardness tester. Figure 3 It can be seen that the surface hardness of 9310 carburized steel decreases with increasing tempering temperature and tempering time.

[0069] from Figure 3 It can be seen that after treatment by the method of the present invention, the maximum surface hardness of 9310 carburized steel is 765.6 HV0.5, which is the same as that after tempering at 180℃ for 2 hours in Example 2. This is an increase of 50-110 HV compared to the hardness after treatment by the method in Example 1. The hardness curve shows that the hardness of the carburized layer gradually decreases with increasing surface distance. The depth at HV550 reaches 1.4 mm, and the hardness reverts to the matrix hardness when the distance from the surface is less than 2.5 mm.

[0070] Figure 4 The graphs show the changes in friction coefficient and wear performance of 9310 carburized steel treated in Examples 1 and 2. The friction coefficient and wear performance change with variations in carbon potential, tempering temperature, and time. Compared to the workpiece treated by the method in Example 1, the workpiece treated by the method in Example 2 exhibits a lower friction coefficient and better wear performance. Furthermore, as shown in Example 2, wear performance decreases with increasing tempering time.

[0071] Figure 5 Surface wear morphology of 9310 carburized steel treated in Examples 1 and 2. Figure 5 It is known that the main mechanisms of wear are oxidative wear and adhesive wear. The wear process can be described as follows: stable oxide film formation → effective prevention of adhesion → oxide film rupture and peeling under WC plowing and cyclic stress → fresh metal surface exposure → local adhesion with WC → material shearing and transfer → rapid oxidation of the new surface → formation of a new oxide film.

[0072] In addition to the preferred embodiments described above, the present invention has other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection claimed by the present invention.

Claims

1. A heat treatment method for improving the wear resistance of 9310 carburized steel, characterized in that, Includes the following steps: S1. Hold 9310 steel at 950°C for 30 minutes, then cool it to room temperature. Remove the surface oxide scale by first polishing the sample surface with 60-grit sandpaper and then sandblasting the sample. S2, Place the workpiece processed in step S1 into a carburizing furnace, heat it to 600°C and hold it for 10 minutes, then heat it to 925°C. S3, the workpiece processed in step S2 is kept at 925°C for a 180-minute carburizing and strong carburizing stage. Pulse carburizing is used. First, carburizing gas is introduced to bring the pressure to 15 kPa and maintain this pressure for 20 seconds. Finally, a vacuum is drawn. This process is repeated continuously. During the repeated process of the strong carburizing stage, the vacuum time is continuously increased. S4. The workpiece treated in step S3 is further subjected to a carburizing diffusion stage at 925°C for 360 min. After diffusion, the temperature is reduced to 840°C at a rate of 10°C / min and held for 30 min. Finally, the sample is cooled to room temperature. S5, perform a first quenching on the workpiece processed in step S4. S6, Perform deep cryogenic treatment on the workpiece processed in step S5. S7. Perform low-temperature tempering on the workpiece processed in step S6. S8. Perform a friction and wear test on the workpiece processed in step S7.

2. The heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 1, characterized in that, In step S3, the vacuuming time increases from 40s to 20min, and the vacuuming time and the carburizing time are cycled until 180min is completed to complete the strong carburizing stage.

3. The heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 1, characterized in that, The cooling method in step S1 is air cooling.

4. A heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 1 or 2, characterized in that, The heating rate in step S2 is 10℃ / min.

5. A heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 2, characterized in that, In step S3, the carburizing gas includes acetylene and nitrogen, with a total flow rate of 8 L / min and an acetylene to nitrogen ratio of 1.2:

1.

6. A heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 2, characterized in that, In step S4, the cooling medium is oil.

7. A heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 5, characterized in that, The first quenching in step S5 involves heating the workpiece to 860°C at a rate of 10°C / min in a vacuum environment, holding it at that temperature for 30 minutes, and finally oil quenching the workpiece to room temperature.

8. A heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 1, characterized in that, The cryogenic treatment in step S6 involves placing the workpiece in at a temperature of -80°C, holding it at that temperature for 3 hours, and finally removing the sample and cooling it to room temperature.

9. A heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 1, characterized in that, The low-temperature tempering in step S7 involves heating to 180°C at a rate of 10°C / min, holding at that temperature for 120 min, and finally removing the sample and cooling it to room temperature.

10. A heat treatment method for improving the wear resistance of 9310 carburized steel according to claim 1, characterized in that, The friction and wear test steps in step S8 are as follows: S8.1, Grind the workpiece before the test using sandpaper with grits of 120, 400, 600, 800, 1000, 1200, 1500 and 2000. S8.2 Wear test: Dry sliding wear test was performed on a wear testing machine. The friction pair - WC, rotation speed: 300 r / min, load: 50 N, wear diameter: 6 mm, wear time: 60 min.

Images