A planetary gear carburizing and quenching process

Abstract

The present invention discloses a planetary wheel carburizing and quenching process method, comprising the following steps: after pre-treatment of the workpiece, stacking is adopted, each stack of workpieces is evenly supported by solid pads, the solid pads can keep each layer of planetary wheel workpieces horizontal, and the distance between each layer of planetary wheel workpieces is not less than 50mm, and the stack spacing between each stack of workpieces is not less than 50mm; carburizing treatment: carburizing the planetary wheel workpieces; quenching furnace loading: after carburizing, all planetary wheel workpieces are turned over, and each stack of planetary wheel workpieces is re-stacked in the reverse order of the original up and down order, and the stack spacing is kept not less than 100mm; tempering treatment is performed on the planetary wheel workpieces after quenching treatment. The present invention can effectively control the deformation amount of the planetary wheel after carburizing and quenching, and improve the production efficiency of the planetary wheel.

Description

Technical Field

[0001] The invention belongs to the technical field of production and processing of planetary gears, and in particular relates to a planetary gear carburizing and quenching process. Background Art

[0002] Deformation is one of the common defects in the carburizing and quenching heat treatment process, accounting for the largest proportion of all quenching defects. Large deformation will increase the subsequent grinding of the gear, resulting in uneven and insufficient hardened layer on the tooth surface, which not only increases the manufacturing cost but also causes a decrease in gear accuracy and load-bearing capacity. Planetary gears are key components of planetary structure gearboxes. They are produced in large quantities and at a tight pace. How to effectively control the carburizing and quenching deformation of planetary gears is very important for improving the quality and efficiency of planetary gear heat treatment. Summary of the invention

[0003] Purpose of the invention: In view of the defects and technical problems existing in the background technology, the present invention provides a planetary gear carburizing and quenching process method, which can effectively control the deformation of the planetary gear after carburizing and quenching, and improve the production efficiency of the planetary gear.

[0004] Technical solution: To achieve the above-mentioned invention object, the present invention adopts the following technical solution: a planetary gear carburizing and quenching process method, comprising the following steps:

[0005] S1, pre-treatment: the planetary gear workpiece is degreased, cleaned and dried;

[0006] S2, carburizing furnace charging: the planetary wheel workpieces are stacked, and each stack of workpieces is evenly supported by solid pads. The solid pads can keep each layer of planetary wheel workpieces level, and the distance between each layer of planetary wheel workpieces is not less than 50mm, and the stack spacing between each stack of workpieces is not less than 50mm;

[0007] S3, carburizing treatment: performing carburizing treatment on the planetary gear workpiece;

[0008] S4, quenching furnace loading: After carburizing is completed, all planetary gear workpieces are turned over and each stack of planetary gear workpieces is re-stacked in the reverse order of the original up and down order, and the stack spacing is kept not less than 100mm;

[0009] S5, quenching treatment: quenching the planetary gear workpiece;

[0010] S6, tempering: After quenching, the workpiece is cleaned and then subjected to two low-temperature tempering treatments.

[0011] Furthermore, the carburizing process in step S3 includes:

[0012] (1) Heating stage: Enter the main furnace and use step-by-step heating, first heating to 650-660℃ and keeping it for 2h, then heating to 820-830℃ and keeping it for 2h, and finally heating to 930±5℃ and keeping it for carburizing;

[0013] (2) Carburizing stage: The workpiece is subjected to strong carburizing and diffusion carburizing. During the strong carburizing and diffusion carburizing processes, the strong carburizing potential is maintained at 1.10±0.05%C, the diffusion carbon potential is maintained at 0.75±0.05%C, and the methanol flow rate is maintained at 55-70mL / min, the nitrogen flow rate is maintained at 55-65L / min, and the acetone flow rate is maintained at 5-15mL / min;

[0014] (3) Cooling stage: After carburizing, the temperature is lowered to 820-830℃ with the furnace, and then cooled to 70±20℃ within 180min by air cooling and oil pipe circulation cooling. During this process, the workpiece shrinks under the structural stress and thermal stress.

[0015] Furthermore, the quenching process steps in step S5 include:

[0016] (1) Heating and holding stage: first, the temperature is raised to 650-660°C and held for 4-6 hours, then the temperature is raised to 820-830°C within 2 hours and held for 4 hours. During this process, the carbon potential is controlled at 0.75%C, and the workpiece structure completes the austenite transformation;

[0017] (2) Quenching stage: The oil temperature of the quenching oil pool is maintained at 70-90°C and stirring is maintained. The workpiece is quenched in the quenching oil pool for 80±10 minutes to cause the workpiece structure to undergo martensitic transformation.

[0018] Furthermore, the tempering temperature in step S6 is 180-200°C.

[0019] Furthermore, in steps S2 and S4, the number of each stack of planetary gear workpieces is three.

[0020] Furthermore, the specifications of the planetary gear workpiece are a tooth top circle diameter of 400mm-600mm and a distance between the two end faces of 200mm-300mm.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0022] (1) Carburizing and quenching are performed in a multi-purpose furnace. After carburizing, the temperature is lowered to 820℃ and the workpiece is moved from the rear chamber to the front chamber and then raised to the set position for gas quenching. During the gas quenching process, the deformation law of the workpiece is as follows: the shrinkage of the single workpiece is greater than the upper end face than the lower end face, the cone becomes smaller at the top and larger at the bottom, and the taper size of the stacked three-layer workpiece is the uppermost layer>middle layer>lowest layer; the oil pool of the multi-purpose furnace is a fully enclosed structure with a small capacity. When the oil is cooled, the stirrers at the four corners are turned on, and the quenching oil flow trajectory starts to cool the workpiece from the lower end face. Under the combined effect of quenching oil cooling and the workpiece's own heat transfer, the expansion law is as follows: lower end face>upper end face, lowermost layer>middle layer>uppermost layer.

[0023] (2) By using the influence of carburizing and quenching processes on the deformation of planetary gears, all the stacked planetary gears are turned over after carburizing, and the top carburized planetary gear is swapped with the bottom carburized planetary gear, and then quenched, thereby effectively controlling the deformation of the planetary gear after carburizing and quenching. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the carburizing process curve of the planetary gear carburizing and quenching process method of the present invention.

[0025] Figure 2 This is the quenching and tempering process curve of the planetary gear carburizing and quenching process method of the present invention.

[0026] Figure 3 It is a schematic diagram of a carburizing furnace and a quenching furnace in an embodiment of the present invention.

[0027] Figure 4 It is a single value diagram of the carburizing taper and quenching taper of Example 1# of the present invention.

[0028] Figure 5 This is a single value diagram of the quenching expansion of Example 1# of the present invention.

[0029] Figure 6 It is a single value diagram of the carburizing taper and quenching taper of Example 2# of the present invention.

[0030] Figure 7 This is a single value diagram of the quenching expansion of Example 2# of the present invention.

[0031] Figure 8 It is a single value diagram of the carburizing taper and quenching taper of Example 3# of the present invention.

[0032] Fig. 9 This is a single value diagram of the quenching expansion of Example 3# of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0034] The planetary gear carburizing and quenching process of the present invention is suitable for the carburizing and quenching of planetary gears with a tooth top diameter of 400mm-600mm and a distance between the two end faces of 200mm-300mm. Figure 1 and 2 As shown, the process steps of the present invention mainly include:

[0035] S1, workpiece pretreatment: The planetary gear should be thoroughly cleaned and degreased before carburizing. After cleaning, it should be naturally dried or air-dried or baked. It should be completely dried before carburizing.

[0036] S2, carburizing furnace loading method: stacking, one stack on the front and one on the back of the tray, the stack spacing is not less than 50mm, there are 3 workpieces in each stack, each piece is evenly supported at three points by a 50mm solid pad of the same height (the three points are evenly distributed, and the contact area between each point and the part should be kept as equal as possible and greater than 80%), and the supporting parts of each stack of three layers are kept vertical to produce the same force support.

[0037] S3, carburizing process is as follows:

[0038] Heating stage: step heating, first heating to 650-660℃ and keeping warm for 2h, then heating to 820-830℃ and keeping warm for 2h, and finally heating to 930±5℃ and keeping warm for carburizing.

[0039] Carburizing stage: Carburizing and diffusion carburizing are carried out according to the carburizing layer depth requirements. The oxygen probe controls the carbon potential, the strong carburizing potential is 1.10%C, the diffusion carbon potential is 0.75%C, the carbon potential fluctuation is controlled within the range of ±0.05%C, and the methanol flow rate is adjusted to 55-70mL / min, the nitrogen flow rate is 55-65L / min, and the acetone flow rate is 5-15mL / min (or the natural gas flow rate is 10-20L / min).

[0040] Cooling stage: After carburizing, the temperature is lowered to 820-830℃ with the furnace. The workpiece is moved from the rear chamber of the multi-purpose furnace to the front chamber and raised to the set position for gas quenching for 180 minutes, that is, the fan on the top of the front chamber and the oil pipe circulation are turned on for cooling. In this process, the workpiece shrinks under the action of tissue stress and thermal stress. The deformation law of the workpiece is: the shrinkage of the single workpiece upper end face ≥ the lower end face, the cone becomes smaller at the top and larger at the bottom, and the taper size of the stacked three layers is the uppermost layer> the middle layer> the lowermost layer.

[0041] S4, quenching furnace loading method: after carburizing is completed, the workpieces are taken out of the furnace and reloaded into the furnace. All workpieces are turned over (upper and lower end faces are reversed). The loading method is the same as step 3 except for the following two points: first, the stack spacing is not less than 100mm, and second, the order of workpieces is changed, the carburized uppermost layer workpiece is placed on the quenching lowermost layer, the carburized middle layer workpiece is placed on the quenching middle layer, and the carburized lowermost layer workpiece is placed on the quenching uppermost layer.

[0042] S5, quenching process is as follows:

[0043] a) Heating and holding stage: step heating, first heating to 650-660℃ and holding for 4-6h, then heating to 820-830℃ and holding for 4h, the carbon potential is controlled at 0.75%C, and during the holding stage of 820-830℃, the austenite transformation of the workpiece is completed.

[0044] b) Quenching stage: Turn on the agitators at the four corners of the quenching oil pool 30 minutes in advance. After the insulation is completed, the workpiece is moved from the rear chamber of the multi-purpose furnace to the front chamber and lowered into the oil pool for quenching for 80 minutes. The oil temperature is maintained at 70-90°C during the quenching process. During the quenching process, the cooling rate of the workpiece is greater than the critical cooling rate of martensitic transformation, and the workpiece structure undergoes martensitic transformation. The quenching oil flow trajectory starts to cool the planetary gear from the lower end face. Under the combined effect of quenching oil cooling and the heat transfer of the planetary gear itself, the workpiece expansion law is as follows: lower end face > upper end face, bottom layer > middle layer > top layer.

[0045] S6, tempering: After quenching, clean the workpiece, and then perform two low-temperature temperings at a tempering temperature of 180-200℃ for 10h.

[0046] Implementation example Figure 3 As shown, in this embodiment, each stack of workpieces on the material tray has three layers. The workpieces are numbered when loaded into the furnace for carburizing, and are turned over when loaded into the furnace for quenching, and the up-and-down order is reversed.

[0047] After the planetary gear is carburized and cooled to room temperature, and after tempering and cooled to room temperature, measure the diameter of the planetary gear tooth top circle. Specific measurement method: select a tooth with a "1" mark on the upper and lower end faces, and a "2" mark on the upper and lower end faces at 90°, and measure the tooth top circle diameter at the "1" and "2" mark positions each time, and measure 4 times. The measured data is processed to obtain deformation data, and the deformation data processing regulations are as follows: upper / lower end face ellipticity = absolute value of (2 point value - 1 point value), 1 / 2 point taper = 1 / 2 point value of lower end face - 1 / 2 point value of upper end face, 1 / 2 point expansion = 1 / 2 point value after tempering - 1 / 2 point value after carburizing. Table 1 is the deformation data collected by 3 furnaces according to the present invention.

[0048] Table 1 Data collected after carburizing, quenching and tempering of three furnaces using the present invention

[0049]

[0050]

[0051] It can be seen from the table that there is no obvious regularity in the ovality after carburizing and quenching and the deformation is small. The taper after carburizing is affected by the carburizing position. Figure 4-9 To conduct a statistical analysis of the three practical examples, it can be seen from the figure that the deformation law of the carburizing taper of the workpiece is: the taper becomes smaller at the top and larger at the bottom, and the taper size of the three layers stacked is the top layer> middle layer> bottom layer; the workpiece expansion law is: lower end surface> upper end surface, bottom layer> middle layer> top layer. After three furnaces of carburizing and quenching, the method of the present invention is used to correct the taper after quenching, and the deformation of the planetary gear after carburizing and quenching is effectively controlled. For the planetary gear workpiece of the specifications described in the present invention, the carburizing and quenching process of the present invention has the following advantages in terms of compensating and controlling deformation:

[0052] (1) The carburizing process of the present invention adopts a step-by-step heating and cooling method to control the deformation law of the workpiece: the three-stage heating method makes the workpiece heat and the structure transformation uniform during the heating stage, and the deformation taper produced is smaller. After carburizing, the temperature is lowered to 820-830℃ with the furnace to reduce the irregular high-temperature creep produced by the workpiece in the high-temperature stage; after the temperature is lowered to 820-830℃, the workpiece is moved from the rear chamber of the multi-purpose furnace to the front chamber and rises to the set position. It is quickly cooled under the action of oil pipe circulation cooling and air cooling, producing regular shrinkage deformation.

[0053] (2) The quenching temperature rise stage of the present invention is kept at 650-660°C for 4-6 hours, which has a spheroidizing effect on the cementite in the structure, thereby having a homogenizing effect on the deformation during the quenching process and reducing the deformation ellipticity.

[0054] (3) The influence of the furnace loading of the present invention on quenching deformation: a multi-purpose furnace with a working area specification of 1500mm*1200mm*1200mm is used. The specifications of the workpieces adapted in the present invention are a tooth top circle diameter of 400mm-600mm, a distance between the two end faces of 200mm-300m, and carburizing and quenching are both stacked. Each stack of workpieces is evenly supported by solid pads, and the distance between each layer of planetary gear workpieces is not less than 50mm and does not exceed 3 layers. The combination of the specifications of the heat treatment furnace and the specifications of the workpieces, as well as the furnace loading method, causes the workpiece to expand and deform regularly after quenching under the combined effects of quenching oil cooling and the workpiece's own heat transfer, so that the expansion and deformation law can be effectively utilized to quickly adjust the furnace loading in the two stages of carburizing and quenching, thereby quickly compensating and reducing the deformation of the workpiece.

[0055] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A planetary gear carburizing and quenching process, characterized in that: The following steps are involved: S1, pre-treatment: the planetary gear workpiece is degreased, cleaned and dried; S2, carburizing furnace charging: the planetary wheel workpieces are stacked, and each stack of workpieces is evenly supported by solid pads. The solid pads can keep each layer of planetary wheel workpieces level, and the distance between each layer of planetary wheel workpieces is not less than 50mm, and the stack spacing between each stack of workpieces is not less than 50mm; S3, carburizing treatment: performing carburizing treatment on the planetary gear workpiece; S4, quenching furnace loading: After carburizing is completed, all planetary gear workpieces are turned over and each stack of planetary gear workpieces is re-stacked in the reverse order of the original up and down order, and the stack spacing is kept not less than 100mm; S5, quenching treatment: quenching the planetary gear workpiece; S6, tempering: After quenching, the workpiece is cleaned and then subjected to two low-temperature tempering treatments.

2. The planetary gear carburizing and quenching process according to claim 1, characterized in that: The process steps of the carburizing treatment in step S3 include: (1) Heating stage: Enter the main furnace and use step-by-step heating, first heating to 650-660℃ and keeping it for 2h, then heating to 820-830℃ and keeping it for 2h, and finally heating to 930±5℃ and keeping it for carburizing; (2) Carburizing stage: The workpiece is subjected to strong carburizing and diffusion carburizing. During the strong carburizing and diffusion carburizing processes, the strong carburizing potential is maintained at 1.10±0.05%C, the diffusion carbon potential is maintained at 0.75±0.05%C, and the methanol flow rate is maintained at 55-70mL / min, the nitrogen flow rate is maintained at 55-65L / min, and the acetone flow rate is maintained at 5-15mL / min; (3) Cooling stage: After carburizing, the temperature is lowered to 820-830℃ with the furnace, and then cooled to 70±20℃ within 180min by air cooling and oil pipe circulation cooling. During this process, the workpiece shrinks under the structural stress and thermal stress.

3. The planetary gear carburizing and quenching process according to claim 1, characterized in that: The quenching process steps in step S5 include: (1) Heating and holding stage: first, the temperature is raised to 650-660°C and held for 4-6 hours, then the temperature is raised to 820-830°C within 2 hours and held for 4 hours. During this process, the carbon potential is controlled at 0.75%C, and the workpiece structure completes the austenite transformation; (2) Quenching stage: The oil temperature of the quenching oil pool is maintained at 70-90°C and stirring is maintained. The workpiece is quenched in the quenching oil pool for 80±10 minutes to cause the workpiece structure to undergo martensitic transformation.

4. The planetary gear carburizing and quenching process according to claim 1, characterized in that: The tempering temperature in step S6 is 180-200°C.

5. The planetary gear carburizing and quenching process according to claim 1, characterized in that: In steps S2 and S4, the number of each stack of planetary gear workpieces is three.

6. The planetary gear carburizing and quenching process according to claim 1, characterized in that: The specifications of the planetary gear workpiece are that the diameter of the tooth top circle is 400mm-600mm and the distance between the two end faces is 200mm-300mm.

Images