A double carburizing method for 9310 steel spiral bevel gear parts

Abstract

The present application discloses a double carburizing processing method for 9310 steel parts, which adopts the double carburizing superposition technology. By adjusting the process parameters of the first carburizing treatment and the second carburizing treatment, the carburizing time of the two carburizing treatments is different, and the concentration distribution of the two carburizing treatments is controlled, thereby achieving precise control of the carburizing layer depth, surface hardness, and surface carbon concentration, solving the technical problem that the existing technical solutions cannot achieve the three technical index requirements of 9310 steel spiral bevel gear parts.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment processing, in particular to a double carburizing processing method for a 9310 steel spiral bevel gear part. Background Art

[0002] In order to improve the level of independent research and development of domestic engines and transmission systems, the existing product structure cannot meet the requirements for further improvement of power-to-weight ratio. Therefore, lightweight and high-performance components are the future development direction.

[0003] The current product involves a 9310 steel spiral bevel gear component, which requires a carburizing depth of 1.25-1.5mm (measured to HV513) in the first carburizing zone (teeth), a carburizing surface hardness of 81-83 HRA, a carburizing layer depth of ≥0.57mm at HRC60, and a surface carbon concentration of 0.7%-0.9%. The second carburizing zone (outer circle) requires a carburizing layer depth of 0.75-0.85mm (measured to HV513), a carburizing surface hardness of 81-83 HRA, a carburizing layer depth of ≥0.34 at HRC60, and a surface carbon concentration of 0.7%-0.9%. Due to the different carburizing layer requirements for the two locations, a double carburizing process is required to achieve quality control.

[0004] CN 106342096 B discloses a carburizing method for 9310 steel. By carburizing in a controlled atmosphere furnace, adding and removing a copper protective layer during carburizing, and subsequently performing heat treatment and freezing treatment, the method can achieve two different carburizing depths of 1.10 to 1.25 mm and 1.9 to 2.1 mm for the same part. However, according to the process and parameters of this method, the three technical indicators required by the present invention (carburizing depth, hardness, and carbon concentration) cannot be achieved, and in particular, the carbon concentration indicator differs significantly.

[0005] CN 110699632 B discloses a carburizing method for 9310 steel spiral bevel gears. The method achieves the desired target requirements through a single pulse carburizing treatment. However, the flow rates of the carburizing atmosphere and the diffusion atmosphere are large, and the single carburizing time is long, which cannot meet the three technical indicators required by the present invention.

[0006] In summary, the products obtained by the existing carburizing methods cannot achieve the three technical index requirements to be achieved by the present invention, and a carburizing method that can achieve the three technical index requirements is urgently needed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a double carburizing method for 9310 steel spiral bevel gear parts, in which the three indicators of carburizing depth, hardness and carbon concentration can all meet target requirements.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A double carburizing method for a 9310 steel spiral bevel gear part comprises the following steps:

[0010] S1, the first carburizing zone of the machined part;

[0011] S2. Carburize the parts for the first time: keep the parts at a temperature of 927±10℃ for 20-40min, and then carry out the first pulse carburizing treatment after the end of the insulation. The time of each carburizing atmosphere introduction is 50-80s, and the time of each diffusion atmosphere introduction is 200-3000s. The flow rates of each carburizing atmosphere and diffusion atmosphere are 1400-1600Nl / h respectively. The time of the latter diffusion atmosphere introduction is longer than that of the previous diffusion atmosphere introduction. The final diffusion atmosphere is introduced for 7000-10000s. The time of the first pulse carburizing treatment is 8-10h.

[0012] S3. Perform the first tempering treatment on the cooled parts:

[0013] S4, the second carburized zone of the machined part;

[0014] S5. Carburize the parts for the second time: keep the parts at 927±10℃ for 20-40min, and then use pulse carburizing after the end of the heat preservation. The time of each carburizing atmosphere is 30-60s, and the time of each diffusion atmosphere is 100-1000s. The flow rates of each carburizing atmosphere and diffusion atmosphere are 1400-1600Nl / h respectively. The time of the latter diffusion atmosphere is longer than that of the previous diffusion atmosphere. The final diffusion atmosphere is used for 2000-5000s. The time of the second pulse carburizing treatment is 3-5h.

[0015] S6. Perform a second tempering treatment on the cooled parts;

[0016] S7, sequentially performing quenching treatment and cold treatment on the parts after the second tempering treatment;

[0017] S8. Perform a third tempering treatment on the cold-treated parts.

[0018] As a further improvement to the above technical solution:

[0019] In step S1 or step S5, the carburizing atmosphere is C2H2 and the diffusion atmosphere is N2.

[0020] In step S1 or step S5, the first carburizing treatment or the second carburizing treatment is performed in a vacuum furnace.

[0021] In the step S3 or S6, the tempering temperature of the first tempering treatment or the second tempering treatment is 621±14° C., and the tempering time is 3.5 to 4.5 hours.

[0022] In step S7, during the quenching treatment, the quenching temperature is 815±6° C. and the holding time is 120 to 150 minutes.

[0023] In step S7, the quenching treatment is oil cooling quenching.

[0024] In step S7, the temperature of the cold treatment is -90 to -100°C, and the time is 4 to 4.5 hours.

[0025] In step S8, the temperature of the third tempering treatment is 150±6° C., and the time is 4 to 4.5 hours.

[0026] In the step S1, machining the first carburized area of the part refers to finishing the first carburized area of the part to a target size;

[0027] In the step S4, machining the second carburized area of the part refers to finishing the second carburized area of the part to a target size.

[0028] In the step S2 or S5, the time of introducing the diffusion atmosphere is t n , the time of the last diffusion atmosphere introduction is t n+1 , satisfying t n+1 -t n =20~60s.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] The invention discloses a double carburizing processing method for 9310 steel parts. The method adopts a double carburizing superposition technology. By adjusting the process parameters of the first carburizing treatment and the second carburizing treatment, the concentration distribution of the two carburizing treatments is controlled, and the precise control of the carburized layer depth, surface hardness, and surface carbon concentration is achieved. The method ensures that the carburized depth of the first carburizing zone of the 9310 steel spiral bevel gear part is 1.25-1.5 mm (measured to HV513), the carburized surface hardness is 81-83 HRA, the depth at HRC60 is ≥0.57 mm, and the carbon concentration of the first layer is 0.7%-0.9%. The technical requirements of the carburized layer depth of the second carburizing zone is 0.75-0.85 mm (measured to HV513), the carburized surface hardness is 81-83 HRA, the depth at HRC60 is ≥0.34, and the carbon concentration of the first layer is 0.7%-0.9%. The method solves the problem that the three technical indicators are difficult to meet (such as unqualified carbon concentration and low carburized layer depth control accuracy). DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below. Unless otherwise specified, the instruments and materials used in the present invention are commercially available.

[0032] Example 1

[0033] A certain spiral bevel gear part in this embodiment requires that the carburizing depth of the first carburizing zone is 1.25~1.5mm (measured to HV513), the carburizing surface hardness is 81~83HRA, the depth at HRC60 is ≥0.57mm, and the carbon concentration of the first layer is 0.7%~0.9%; the carburizing layer depth of the second carburizing zone is 0.75~0.85mm (measured to HV513), the carburizing surface hardness is 81~83HRA, the depth at HRC60 is ≥0.34, and the carbon concentration of the first layer is 0.7%~0.9%.

[0034] A double carburizing method for a 9310 steel spiral bevel gear part according to this embodiment includes the following steps:

[0035] (1) Rough machining of 9310 steel spiral bevel gear parts, and finishing of the first carburized area of the parts to the target size;

[0036] (2) The parts are carburized for the first time: the carburizing equipment uses a vacuum furnace, which is kept at 927°C for 20 minutes. After the end of the heat preservation, the atmosphere is introduced in a pulsed manner. The carburizing atmosphere is C2H2, and the diffusion atmosphere is N2. The C2H2 flow rate is 1500Nl / h and the N2 flow rate is 1500Nl / h. The carburizing treatment is completed in the order of C2H2-N2-C2H2-N2. The time for introducing C2H2 in each step is 60s (in other embodiments, 50-80s can achieve the same or similar results). Similar technical effects), the N2 introduction time gradually increases with the increase in the number of introductions, and the time is 200s, 240s, 260s, ... 2900s (the first time increases by 40s, the second time increases by 20s, the third time increases by 40s, the fourth time increases by 20s, and each time increases by 20s to 60s (20s, 40s pulse increase), and so on). The last step is N2 as the final diffusion atmosphere, the introduction time is 8000s, and the total carburizing time is 560min (8h). After carburizing is completed, the parts are transferred to the air cooling chamber and cooled to below 100°C under the protection of nitrogen atmosphere for 60 minutes before being taken out of the furnace;

[0037] (3) The parts are subjected to high temperature tempering: tempering temperature 621℃, tempering time 4.5h;

[0038] (4) Finishing the second carburized area of the part to the target size;

[0039] (5) The parts are carburized for the second time: the carburizing equipment uses a vacuum furnace, which is kept at 927℃ for 20 minutes. After the insulation is completed, the atmosphere is introduced in a pulsed manner. The carburizing atmosphere is C2H2 and the diffusion atmosphere is N2. The C2H2 flow rate is 1500Nl / h and the N2 flow rate is 1500Nl / h. The carburizing treatment is completed in the order of C2H2-N2-C2H2-N2. The introduction time of C2H2 in each step is 60s (in other embodiments, 50-80s can achieve the same or similar technical effects). The introduction time of N2 gradually increases with the increase in the number of introductions, and the time is 100s, 120s, 140s, ... 900s (each time increases by 20s, and so on. In other embodiments, each time increases by 20s to 60s can achieve the same technical effects). In the last step, N2 is the final diffusion atmosphere, and the introduction time is 4000s. The total carburizing time is 250min. After carburizing is completed, the parts are transferred to the air cooling chamber and cooled to below 100℃ in a nitrogen atmosphere for 60 minutes before being taken out of the furnace;

[0040] (6) The parts are subjected to high temperature tempering: tempering temperature 621℃, tempering time 4.5h;

[0041] (7) Quenching of parts: The parts are placed stably in a box-type heating furnace, the quenching temperature is 815℃, the temperature is kept for 125min, and the parts are oil-cooled;

[0042] (8) After quenching, the parts are cold treated within 1 hour at a temperature of -95°C for 4 hours;

[0043] (9) After the parts are cooled to room temperature, they are tempered at 150°C for 4 hours and then air-cooled to room temperature.

[0044] Final inspection revealed that the first carburized zone had a carburized depth of 1.48mm (measured to HV513), a carburized surface hardness of 83HRA, a depth of 0.83mm at HRC60, and a first-layer carbon concentration of 0.89%. The second carburized zone had a carburized layer depth of 0.83mm (measured to HV513), a carburized surface hardness of 83HRA, a depth of 0.45mm at HRC60, and a first-layer carbon concentration of 0.75%. Conclusion: Pass.

[0045] The present invention does not perform copper plating on the carburized area during the two carburizing treatments. After rough processing, the first carburized area is fine-processed to the target size. During the second carburizing treatment, the second carburized area is fine-processed to the target size. Finally, the other parts are fine-processed to the target gear, avoiding the copper plating and removal steps, which is simpler.

[0046] Comparative Example 1

[0047] The double carburizing processing method of a 9310 steel spiral bevel gear part in this comparative example is roughly the same as that in Example 1, except that: during the first carburizing and second carburizing treatments, the flow rate of the carburizing atmosphere or diffusion atmosphere is 1800Nl / h, the first carburizing treatment time is 12h, and the second carburizing treatment time is 5.5h.

[0048] The test results of the 9310 steel spiral bevel gear produced in this comparative example were: the carburized depth in the first carburized zone was 1.58mm (measured to HV513), the carburized surface hardness was 84.5HRA, the depth at HRC60 was 0.98mm, and the carbon concentration in the first layer was 1.05%. The carburized layer depth in the second carburized zone was 0.92mm (measured to HV513), the carburized surface hardness was 83.5HRA, the depth at HRC60 was 0.56mm, and the carbon concentration in the first layer was 0.94%. The test results showed that all three technical indicators were not met, and the part failed.

[0049] Although the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, utilize the technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A double carburizing method for 9310 steel spiral bevel gear parts, characterized by: The following steps are involved: S1, the first carburizing zone of the machined part; S2. Carburize the parts for the first time: keep the parts at 927±10℃ for 20-40min, and then carry out the first pulse carburizing treatment. The time for each carburizing atmosphere is 50-80s, and the time for each diffusion atmosphere is 200-3000s. The flow rates of each carburizing atmosphere and diffusion atmosphere are 1400-1600Nl / h respectively. Finally, the diffusion atmosphere is introduced for 7000-10000s. The time for the first pulse carburizing treatment is 8-10h. S3. Perform the first tempering treatment on the cooled parts: S4, the second carburized zone of the machined part; S5. Carburize the parts for the second time: keep the parts at 927±10℃ for 20-40min, and then use pulse carburizing after the end of the heat preservation. The time of each carburizing atmosphere is 30-60s, and the time of each diffusion atmosphere is 100-1000s. The flow rates of each carburizing atmosphere and diffusion atmosphere are 1400-1600Nl / h respectively. Finally, the diffusion atmosphere is introduced for 2000-5000s. The time of the second pulse carburizing treatment is 3-5h. S6. Perform a second tempering treatment on the cooled parts; S7, sequentially performing quenching treatment and cold treatment on the parts after the second tempering treatment; S8, performing a third tempering treatment on the cold-treated parts; In step S3 or S6, the tempering temperature of the first tempering treatment or the second tempering treatment is 621±14° C., and the tempering time is 3.5 to 4.5 hours; In step S7, during the quenching treatment, the quenching temperature is 815±6°C and the holding time is 120-150 minutes; In step S8, the temperature of the third tempering treatment is 150±6° C., and the time is 4 to 4.5 hours.

2. The double carburizing method of 9310 steel spiral bevel gear parts according to claim 1, characterized in that: In step S1 or step S5, the carburizing atmosphere is C2H2 and the diffusion atmosphere is N2.

3. The double carburizing method of 9310 steel spiral bevel gear parts according to claim 1, characterized in that: In step S1 or step S5, the first carburizing treatment or the second carburizing treatment is performed in a vacuum furnace.

4. The double carburizing method for a 9310 steel spiral bevel gear part according to any one of claims 1 to 3, characterized in that: In step S7, the quenching treatment is oil cooling quenching.

5. The double carburizing method for 9310 steel spiral bevel gear parts according to any one of claims 1 to 3, characterized in that: In step S7, the temperature of the cold treatment is -90 to -100°C, and the time is 4 to 4.5 hours.

6. The double carburizing method for a 9310 steel spiral bevel gear part according to any one of claims 1 to 3, characterized in that: In the step S1, machining the first carburized area of the part refers to finishing the first carburized area of the part to a target size; In the step S4, machining the second carburized area of the part refers to finishing the second carburized area of the part to a target size; The first carburized area is the tooth portion, and the second carburized area is the outer circle.

7. The double carburizing method for a 9310 steel spiral bevel gear component according to any one of claims 1 to 3, characterized in that: In the step S2 or S5, the time of introducing the diffusion atmosphere is t n , the time of the last diffusion atmosphere introduction is t n+1 , satisfying t n+1 -t n =20~60s.