Heat treatment method of low-alloy 9310 carburized gear steel

Abstract

The invention relates to the technical field of heat treatment of novel gear steel, in particular to a heat treatment method of low-alloy 9310 carburized gear steel. The heat treatment method of the low-alloy 9310 carburizing gear steel comprises the following steps that S1, a low-alloy 9310 carburizing gear steel component to be treated is cleaned; s2, carburizing is carried out; s3, carbonitriding is carried out; s4, performing high-temperature annealing; s5, quenching is conducted; s6, performing cold treatment; and S7, low-temperature tempering is conducted. On the basis of a carburizing process, nitrogen atoms are introduced into a carburizing layer, so that the hardness of the carburizing layer of the low-alloy carburizing gear steel is further improved while a fine dispersed structure of the carburizing layer is guaranteed, other treatment processes are matched, the surface hardness of a treated component is relatively high, and on the premise that the cost is not remarkably increased, the surface hardness of the component is greatly improved. And the anti-gluing, anti-fatigue and anti-wear capabilities of the low-alloy carburized gear steel member are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment of novel gear steel, and in particular to a heat treatment method of low-alloy 9310 carburized gear steel. Background Art

[0002] Aviation gears are crucial components of helicopter and engine transmission systems, characterized by high speeds, heavy loads, and high power density. These gears must withstand a variety of extreme operating conditions, placing extremely high demands on their resistance to scuffing, fatigue, and wear. 9310 steel, due to its excellent strength and toughness, good process adaptability, and low cost, is currently the most widely used gear steel material in aviation gears.

[0003] As the power density of helicopter transmission systems continues to increase, the insufficient load-bearing capacity of low-alloy carburized gear steel is becoming increasingly prominent. This is primarily due to the generally low-alloy carburized gear steel's surface hardness after carburizing heat treatment, which is between 58 and 60 HRC, and no longer meets the increasingly demanding load-bearing requirements of components under increasingly demanding service conditions. The new generation of high-alloy, ultra-high-strength carburized gear steel can achieve a surface hardness of 64 to 68 HRC after carburizing. However, the heat treatment process for high-alloy, ultra-high-strength carburized gear steel is complex, and the material cost is high, often 6 to 7 times that of low-alloy carburized gear steel. This high cost is a significant constraint on its widespread application. Further improving the carburized layer hardness of low-alloy carburized gear steel while maintaining a fine, dispersed carburized layer structure would be of great significance for improving the performance and reducing the cost of aviation gear components. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a heat treatment method for low alloy 9310 carburized gear steel, which can improve the surface hardness of low alloy 9310 carburized gear steel components.

[0005] The present invention provides a heat treatment method for low-alloy 9310 carburized gear steel, comprising the following steps:

[0006] S1. Clean the low alloy 9310 carburized gear steel components to be processed;

[0007] S2. After the component treated in step S1 is kept at 910-930°C, it is carburized with the carbon potential controlled at 1.25±0.05C% for 350-410 minutes. After that, the carbon potential is adjusted to 1.0±0.05C%, and the component is cooled to 860-880°C.

[0008] S3, mixing the component treated in step S2 with ammonia, and performing carbonitriding at 860-880°C, with the ammonia flow rate controlled at 5±1m 3 / h, the carbon potential is controlled at 1.0±0.05C%, and the carbonitriding time is 220-260min, followed by oil quenching;

[0009] S4, performing high temperature annealing on the oil-quenched component;

[0010] S5. Heat the component treated in step S4 to 815±5°C, mix it with ammonia and carburizing medium, and control the ammonia flow rate at 5±1m 3 / h, carbon potential controlled at 0.9±0.05C%, heat preservation for 60~120min, oil quenching;

[0011] S6, cold-treating the component after the treatment in step S5;

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

[0013] Preferably, in step S2, the carburizing medium is propane gas;

[0014] The insulation time is 20 to 30 minutes.

[0015] Preferably, in step S3, in the carbonitriding, the carburizing medium is propane gas.

[0016] Preferably, in step S3, the temperature of the oil quenching is 70±2° C., and the stirring frequency is 48-52 Hz.

[0017] Preferably, in step S4, the high temperature annealing is:

[0018] The oil-quenched component is heated to 700-730° C., kept at this temperature for 180-240 minutes, and then cooled to room temperature.

[0019] Preferably, the method of cooling to room temperature is:

[0020] After the furnace temperature drops to 645-655°C, it is cooled by nitrogen filling until the temperature drops below 100°C, and then taken out of the furnace and air-cooled to room temperature.

[0021] Preferably, in step S5, the carburizing medium is propane gas;

[0022] The temperature of the oil quenching is 50±2°C.

[0023] Preferably, in step S6, the cold treatment is:

[0024] The component treated in step S5 is cooled to -70 to -90°C, kept warm for 120 to 180 minutes, taken out, and returned to room temperature in air.

[0025] Preferably, in step S7, the low-temperature tempering is:

[0026] Heat the component to 150±10℃, keep it warm for 180~300min, and air cool it to room temperature.

[0027] Preferably, in step S1, the cleaning method is washing and drying;

[0028] The surface roughness of the component after cleaning is Ra≤0.4 μm.

[0029] The present invention proposes a heat treatment method for low-alloy 9310 carburized gear steel. By introducing nitrogen atoms into the carburized layer on the basis of the carburizing process, the hardness of the carburized layer of the low-alloy carburized gear steel is further improved while ensuring a fine dispersed structure of the carburized layer. Combined with other treatment processes, the surface hardness of the component after treatment is relatively high. Without significantly increasing the cost, the anti-adhesion, anti-fatigue and anti-wear capabilities of the low-alloy carburized gear steel component are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 Schematic diagram of the microstructure of the carburized layer of the low alloy 9310 carburized gear steel component after treatment in Example 1 (metallographic diagram);

[0032] Figure 2 Schematic diagram of the microstructure of the core of the 9310 steel low alloy carburized gear component after treatment in Example 1 (metallographic diagram);

[0033] Figure 3 Schematic diagram of the Vickers hardness gradient of the 9310 steel low alloy carburized gear component after treatment in Example 1 and Comparative Example 1 respectively. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The present invention provides a heat treatment method for low-alloy 9310 carburized gear steel, comprising the following steps:

[0036] S1. Clean the low alloy 9310 carburized gear steel components to be processed;

[0037] S2. After the component treated in step S1 is kept at 910-930°C, it is carburized with the carbon potential controlled at 1.25±0.05C% for 350-410 minutes. After that, the carbon potential is adjusted to 1.0±0.05C%, and the component is cooled to 860-880°C.

[0038] S3, the component treated in step S2 is mixed with ammonia (NH3), and carbonitriding is performed at 860-880°C, and the ammonia flow rate is controlled at 5±1m 3 / h, the carbon potential is controlled at 1.0±0.05C%, and the carbonitriding time is 220-260min, followed by oil quenching;

[0039] S4, performing high temperature annealing on the oil-quenched component;

[0040] S5. Heat the component treated in step S4 to 815±5°C, introduce ammonia and carburizing medium, and control the ammonia flow rate at 5±1m 3 / h, carbon potential controlled at 0.9±0.05C%, heat preservation for 60~120min, oil quenching;

[0041] S6, cold-treating the component after the treatment in step S5;

[0042] S7. Perform low-temperature tempering on the component processed in step S6.

[0043] Regarding step S1:

[0044] Clean the low alloy 9310 carburized gear steel components to be processed.

[0045] In some embodiments of the present invention, the cleaning method is washing and drying to ensure that the surface of the component is clean.

[0046] In some embodiments of the present invention, the surface roughness of the component after cleaning is Ra≤0.4 μm, specifically, Ra=0.4 μm.

[0047] Regarding step S2:

[0048] Carburizing: After the component treated in step S1 is kept at 910-930°C, it is carburized again, with the carbon potential controlled at 1.25±0.05C%, and the carburizing time is 350-410min. Thereafter, the carbon potential is adjusted to 1.0±0.05C%, and the component is cooled to 860-880°C in the furnace.

[0049] In some embodiments of the present invention, the carburizing medium is propane gas.

[0050] In some embodiments of the present invention, the insulation temperature is 930° C. and the insulation time is 20 to 30 minutes, such as 30 minutes.

[0051] In some embodiments of the present invention, the carbon potential is controlled at 1.25C%; the carburizing time is 390 minutes; thereafter the carbon potential is adjusted to 1.0C%; and the component is furnace cooled to 860°C.

[0052] In some embodiments of the present invention, the carburizing is performed in a gas carburizing furnace.

[0053] In some embodiments of the present invention, the cooling is furnace cooling.

[0054] Regarding step S3:

[0055] Carbonitriding: Mix the components treated in step S2 with ammonia and perform carbonitriding at 860-880℃. The ammonia flow rate is controlled at 5±1m 3 / h, the carbon potential is controlled at 1.0±0.05C%, and the carbonitriding time is 220-260min, followed by oil quenching.

[0056] In some embodiments of the present invention, in the carbonitriding, the carburizing medium is propane gas.

[0057] In some embodiments of the present invention, the carbonitriding temperature is 860°C.

[0058] In some embodiments of the present invention, the ammonia flow rate is controlled at 5m 3 / h; carbon potential is controlled at 1.0C%; carbonitriding time is 240min.

[0059] In some embodiments of the present invention, the temperature of the oil quenching is 70±2° C., such as 70° C.; and the stirring frequency is 48-52 Hz, such as 50 Hz.

[0060] Regarding step S4:

[0061] The oil-quenched component is subjected to high-temperature annealing.

[0062] In some embodiments of the present invention, the high temperature annealing is:

[0063] The oil-quenched component is heated to 700-730° C., kept at this temperature for 180-240 minutes, and then cooled to room temperature.

[0064] Specifically, the oil-quenched component is heated to 730° C. and kept warm for 180 minutes.

[0065] In some embodiments of the present invention, the method of cooling to room temperature is:

[0066] After the furnace temperature drops to 645-655°C, it is cooled by nitrogen filling until the temperature drops below 100°C, and then taken out of the furnace and air-cooled to room temperature.

[0067] Specifically, after the furnace temperature is lowered to 650° C., nitrogen is filled for cooling.

[0068] Specifically, the temperature is lowered to 100° C., and then taken out of the furnace and air-cooled to room temperature.

[0069] Regarding step S5:

[0070] Quenching: Heat the component after step S4 to 815±5℃, mix it with ammonia and carburizing medium, and control the ammonia flow rate at 5±1m 3 / h, carbon potential controlled at 0.9±0.05C%, heat preservation for 60~120min, oil quenching.

[0071] In some embodiments of the present invention, the component after the treatment in step S4 is heated to 815°C.

[0072] In some embodiments of the present invention, the carburizing medium is propane gas.

[0073] In some embodiments of the present invention, the ammonia flow rate is controlled at 5m 3 / h; carbon potential controlled at 0.9C%; heat preservation for 120min.

[0074] In some embodiments of the present invention, the temperature of the oil quenching is 50±2°C, such as 50°C.

[0075] Regarding step S6:

[0076] The component processed in step S5 is subjected to cold treatment.

[0077] In some embodiments of the present invention, the cold treatment is:

[0078] The component treated in step S5 is cooled to -70 to -90°C, kept warm for 120 to 180 minutes, taken out, and returned to room temperature in air.

[0079] In some embodiments of the present invention, the temperature after cooling is -70°C and the insulation time is 120 minutes.

[0080] Regarding step S7:

[0081] The component processed in step S6 is subjected to low-temperature tempering.

[0082] In some embodiments of the present invention, the low temperature tempering is:

[0083] Heat the component to 150±10℃, keep it warm for 180~300min, and air cool it to room temperature.

[0084] Specifically, the component is heated to 150° C. and kept warm for 180 minutes.

[0085] The present invention proposes a heat treatment method for low-alloy 9310 carburized gear steel. By introducing nitrogen atoms into the carburized layer on the basis of the carburizing process, the hardness of the carburized layer of the low-alloy carburized gear steel is further improved while ensuring a fine dispersed structure of the carburized layer. Combined with other treatment processes, the surface hardness of the component after treatment is relatively high. Without significantly increasing the cost, the anti-adhesion, anti-fatigue and anti-wear capabilities of the low-alloy carburized gear steel component are improved.

[0086] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention.

[0087] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are provided to provide a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be implemented without requiring some of these specific details. The following description of the embodiments is intended only to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is in no way limited to any specific arrangement and method set forth below. In the accompanying drawings and the following description, well-known structures and techniques are not shown to avoid unnecessary ambiguity in the present invention.

[0088] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0089] Example 1

[0090] Heat treatment of low alloy 9310 carburized gear steel:

[0091] 1.1. Clean and dry the low alloy 9310 carburized gear steel component to be processed, wherein the surface roughness of the component after cleaning is Ra=0.4 μm;

[0092] 1.2. Place the component in a gas carburizing furnace and keep it at 930℃ for 30 minutes. Then, introduce propane gas for carburizing. The carbon potential is controlled at 1.25C%. The carburizing time is 390 minutes. After that, the carbon potential is adjusted to 1.0C%. At the same time, the component is cooled to 860℃ in the furnace.

[0093] 1.3. NH3 and carburizing medium propane gas are introduced into the heat treatment furnace and carbonitriding is carried out at 860℃. The NH3 flow rate is controlled at 5m 3 / h, the carbon potential was controlled at 1.0C%, the carbonitriding time was 240min, after which the component was oil quenched, the temperature was controlled at 70°C, and the stirring frequency was 50Hz;

[0094] 1.4. Heat the component to 730℃ and keep it warm for 180min. After the end of the heat preservation, cool it down to 650℃ with the furnace, fill it with nitrogen and cool it down to 100℃. Then take it out of the furnace and air cool it to room temperature.

[0095] 1.5. Heat the component to 815℃, introduce NH3 and carburizing medium propane gas into the furnace, and control the NH3 flow rate at 5m 3 / h, carbon potential controlled at 0.9C%, heat preservation for 120min, oil quenching (oil temperature 50℃);

[0096] 1.6. Cool the component to -70℃, keep it warm for 120min, take it out, and return it to room temperature in air;

[0097] 1.7. Heat the component to 150℃, keep it warm for 180 minutes, and air cool it to room temperature.

[0098] Comparative Example 1

[0099] Traditional methods:

[0100] 1.1. Clean and dry the low alloy 9310 carburized gear steel component to be processed, wherein the surface roughness of the component after cleaning is Ra=0.4 μm;

[0101] 1.2. Place the component in a gas carburizing furnace and keep it at 930℃ for 30 minutes. Then, introduce propane gas for carburizing. The carbon potential is controlled at 1.25C%. The carburizing time is 390 minutes. Then, the component is oil quenched at 70℃ and the stirring frequency is 50Hz.

[0102] 1.3. Heat the component to 650℃ and keep it warm for 180min. After the end of the heat preservation, fill it with nitrogen and cool it down to 100℃. Then take it out of the furnace and air cool it to room temperature.

[0103] 1.4. Heat the component to 815℃, keep warm for 120min, and quench in oil (oil temperature 50℃);

[0104] 1.5. Cool the component to -70℃, keep it warm for 120min, take it out and return it to room temperature in the air;

[0105] 1.6. Heat the component to 150℃, keep it warm for 180 minutes, and air cool it to room temperature.

[0106] Figure 1Schematic diagram of the microstructure of the carburized layer of the low alloy 9310 carburized gear steel component after treatment in Example 1. Figure 1 It can be seen that the carburized layer of the low alloy 9310 carburized gear steel component has a uniform structure, and the precipitates such as carbides, nitrides and carbonitrides are finely dispersed, with no network structure and no coarse precipitates.

[0107] Figure 2 Schematic diagram of the microstructure of the core of the low alloy 9310 carburized gear steel component after treatment in Example 1. Figure 2 It can be seen that the core structure of the low alloy 9310 carburized gear steel component is lath martensite structure.

[0108] The hardness of the low alloy 9310 carburized gear steel components after treatment in Example 1 and Comparative Example 1 was tested:

[0109] The Vickers hardness test standard is GB / T 4340.1, and the test equipment is a micro Vickers hardness tester. The results are as follows: Figure 3 shown. Figure 3 Schematic diagram of the Vickers hardness gradient of the 9310 steel low alloy carburized gear component after treatment in Example 1 and Comparative Example 1 respectively.

[0110] The Rockwell hardness test standard is GB / T 230.1, and the testing equipment is a Rockwell hardness tester. The results are shown in Table 1. Table 1 shows three data points on the same sample.

[0111] Table 1 Surface hardness of low alloy 9310 carburized gear steel components after treatment in Example 1 and Comparative Example 1

[0112]

[0113] from Figure 3 As shown in Table 1, after being treated with the method of the present invention, the surface hardness of the 9310 steel component reached 65HRC, which is 3-4HRC higher than the hardness after being treated with the traditional method. As can be seen from the hardness curve, the hardness of the component's infiltration layer gradually decreases with the distance from the surface, and the depth at HV550 reaches 1.4mm. When it is less than 2.5mm from the surface, the hardness returns to the matrix hardness. Compared with the hardness gradient of the 9310 steel component treated with the traditional method disclosed in Comparative Example 1, it can be seen that the hardness of each position of the infiltration layer of the 9310 steel component is significantly improved after being treated with the method of the present invention, and the depth of the infiltration layer (the depth at the HV550 hardness) increases by 0.3-0.4mm.

[0114] The above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should all be covered by the protection scope of the present invention.

Claims

1. A heat treatment method for low alloy 9310 carburized gear steel, comprising the following steps: S1. Clean the low alloy 9310 carburized gear steel components to be processed; S2. After the component treated in step S1 is kept at 910-930°C, it is carburized with the carbon potential controlled at 1.25±0.05C% for 350-410 minutes. After that, the carbon potential is adjusted to 1.0±0.05C%, and the component is cooled to 860-880°C. S3, mixing the component treated in step S2 with ammonia, and performing carbonitriding at 860-880°C, with the ammonia flow rate controlled at 5±1m 3 / h, the carbon potential is controlled at 1.0±0.05C%, and the carbonitriding time is 220-260min, followed by oil quenching; S4, performing high temperature annealing on the oil-quenched component; S5. Heat the component treated in step S4 to 815±5°C, mix it with ammonia and carburizing medium, and control the ammonia flow rate at 5±1m 3 / h, carbon potential controlled at 0.9±0.05C%, heat preservation for 60~120min, oil quenching; S6, cold-treating the component after the treatment in step S5; S7. Perform low-temperature tempering on the component processed in step S6.

2. The heat treatment method according to claim 1, characterized in that In step S2, the carburizing medium is propane gas; The insulation time is 20 to 30 minutes.

3. The heat treatment method according to claim 1, characterized in that In step S3, during the carbonitriding, the carburizing medium is propane gas.

4. The heat treatment method according to claim 1, characterized in that In step S3, the temperature of the oil quenching is 70±2° C., and the stirring frequency is 48-52 Hz.

5. The heat treatment method according to claim 1, characterized in that In step S4, the high temperature annealing is: The oil-quenched component is heated to 700-730° C., kept at this temperature for 180-240 minutes, and then cooled to room temperature.

6. The heat treatment method according to claim 5, characterized in that The method of cooling to room temperature is: After the furnace temperature drops to 645-655°C, it is cooled by nitrogen filling until the temperature drops below 100°C, and then taken out of the furnace and air-cooled to room temperature.

7. The heat treatment method according to claim 1, characterized in that In step S5, the carburizing medium is propane gas; The temperature of the oil quenching is 50±2°C.

8. The heat treatment method according to claim 1, wherein In step S6, the cold treatment is: The component treated in step S5 is cooled to -70 to -90°C, kept warm for 120 to 180 minutes, taken out, and returned to room temperature in air.

9. The heat treatment method according to claim 1, characterized in that In step S7, the low temperature tempering is: Heat the component to 150±10℃, keep it warm for 180~300min, and air cool it to room temperature.

10. The heat treatment method according to claim 1, characterized in that In step S1, the cleaning method is washing and drying; The surface roughness of the component after cleaning is Ra≤0.4 μm.

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