Gear heat treatment method and gear

Abstract

The invention relates to the technical field of heat treatment, in particular to a gear heat treatment method and a gear. The gear heat treatment method comprises the following steps that S1, a workpiece is placed in a first heating furnace to be heated to the first preset temperature T1, and heat preservation is conducted for the first preset time t1; s2, the workpiece is taken out of the first heating furnace, and the workpiece is blown to be cooled to a second preset temperature T2; s3, the workpiece is placed in a second heating furnace to be subjected to heat preservation at a second preset temperature T2 for a second preset time t2; s4, the workpiece is kept at the second preset temperature T2, the ultrasonic generator is started to conduct ultrasonic-assisted induction heating on the workpiece, and the heating time is third preset time t3; and S5, the workpiece is taken out of the second heating furnace and air-cooled to the room temperature. The gear prepared through the gear heat treatment method is good in obdurability, hardness and abrasion resistance, the machining process period of the gear can be shortened, and energy consumption can be reduced.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology, and more particularly to a gear heat treatment method and a gear. Background Technology

[0002] Gears are one of the important components in transmission mechanisms. They have the characteristics of transmitting a wide range of power, high transmission efficiency, and the ability to transmit motion and power between two shafts at will. They are an indispensable part in any speed change mechanism.

[0003] Annealing is an indispensable and crucial process in the manufacturing of gear parts. Its core purpose is to reduce the hardness of the steel, refine the grain, and homogenize the microstructure, laying a good foundation for subsequent cutting operations (such as turning, milling, and drilling) and the final carburizing and quenching heat treatment. Currently, isothermal annealing is mostly used for gear parts. Isothermal annealing refers to a process in which the austenite is rapidly cooled to a certain temperature and held isothermally for a certain period of time to transform into pearlite. This process can effectively improve the strength, toughness, and wear resistance of the parts. However, because the parts need to be held at a temperature for a long time, there are problems such as long process cycle, unstable process quality, and high production energy consumption.

[0004] Therefore, there is an urgent need for a gear heat treatment method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a gear heat treatment method and a gear, so as to solve the technical problems of long process cycle, unstable process quality and high production energy consumption in related technologies.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A gear heat treatment method includes the following steps:

[0008] Step S1: Place the workpiece in the first heating furnace and heat it to the first preset temperature T1, and keep it at that temperature for the first preset time t1;

[0009] Step S2: Remove the workpiece from the first heating furnace and cool it down to the second preset temperature T2 by blowing air on it;

[0010] Step S3: Place the workpiece in the second heating furnace and keep it at the second preset temperature T2 for a second preset time t2;

[0011] Step S4: Maintain the second preset temperature T2 and turn on the ultrasonic generator to perform ultrasonic-assisted induction heating on the workpiece, and the heating time is the third preset time t3.

[0012] Step S5: Remove the workpiece from the second heating furnace and air-cool it to room temperature.

[0013] As a preferred embodiment of the gear heat treatment method provided by the present invention, in step S4, the ultrasonic output frequency of the ultrasonic generator is 20kHz~40kHz, the ultrasonic amplitude is 5µm~10µm, and the ultrasonic power is 350w~400w.

[0014] As a preferred embodiment of the gear heat treatment method provided by the present invention, the third preset time t3 is 5 min to 15 min.

[0015] As a preferred embodiment of the gear heat treatment method provided by the present invention, the first preset temperature T1 is 850℃~900℃, and the first preset time t1 is 60min~300min.

[0016] And / or, the second preset temperature T2 is 620℃~680℃, and the second preset time t2 is 60min~360min.

[0017] As a preferred embodiment of the gear heat treatment method provided by the present invention, the first preset temperature T1 is 860℃~880℃, and the first preset time t1 is 60min~90min.

[0018] As a preferred embodiment of the gear heat treatment method provided by the present invention, the second preset temperature T2 is 645℃~660℃, and the second preset time t2 is 60min~90min.

[0019] As a preferred embodiment of the gear heat treatment method provided by the present invention, the first heating furnace is a high-temperature heating furnace; and / or, the second heating furnace is a medium-temperature heating furnace.

[0020] As a preferred embodiment of the gear heat treatment method provided by the present invention, the method further includes the following steps before step S1 and after step S5:

[0021] Step S0: Clean the surface of the workpiece.

[0022] As a preferred embodiment of the gear heat treatment method provided by the present invention, the workpiece is low-carbon alloy carburizing steel or medium-carbon alloy carburizing steel.

[0023] The present invention also provides a gear, which is prepared by the gear heat treatment method described above.

[0024] The beneficial effects of this invention are:

[0025] The gear heat treatment method provided by this invention involves ultrasonic-assisted induction heating of the workpiece during the heat treatment holding stage. On the one hand, the synergistic effect of ultrasonic cavitation, mechanical vibration, and thermal effect promotes grain refinement within the gear, facilitates the transformation of pearlite to austenite, and reduces segregation and structural defects. Simultaneously, ultrasonic vibration increases the defect density within the crystal lattice, thereby significantly reducing the activation energy required for atomic diffusion, accelerating phase transformation, and improving the gear's strength, toughness, hardness, and wear resistance. On the other hand, the ultrasonic vibration during the holding stage penetrates deep into the gear, promoting lattice relaxation and dislocation slip through mechanical excitation, accelerating the release of residual stress, and thus reducing deformation and cracking during subsequent processing and use, improving the gear's dimensional stability and operational reliability. Furthermore, ultrasonic heating has strong energy penetration, enabling synchronous and uniform heating inside and outside the gear, reducing the temperature gradient of traditional heating, thereby shortening the holding time and reducing energy consumption.

[0026] The gear provided by this invention is manufactured using the aforementioned gear heat treatment method. It exhibits good strength, toughness, hardness, and wear resistance, and reduces deformation and cracking during subsequent processing and use, thereby improving gear dimensional stability and operational reliability. Furthermore, it shortens the gear processing cycle and reduces energy consumption. Attached Figure Description

[0027] Figure 1 This is a flowchart of the gear heat treatment method provided by the present invention;

[0028] Figure 2 This is a schematic diagram of the gear heat treatment method provided in an embodiment of the present invention. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] Figure 1 A flowchart of the gear heat treatment method provided in this embodiment is shown. Figure 1 As shown, this embodiment provides a gear heat treatment method, which includes the following steps:

[0033] Step S1: Place the workpiece in the first heating furnace and heat it to the first preset temperature T1, and keep it at that temperature for the first preset time t1;

[0034] Step S2: Remove the workpiece from the first heating furnace and cool it down to the second preset temperature T2 by blowing air on it;

[0035] Step S3: Place the workpiece in the second heating furnace and keep it at the second preset temperature T2 for the second preset time t2;

[0036] Step S4: Maintain the second preset temperature T2 and turn on the ultrasonic generator to perform ultrasonic-assisted induction heating on the workpiece, and the heating time is the third preset time t3.

[0037] Step S5: Remove the workpiece from the second heating furnace and air cool it to room temperature.

[0038] The first heating furnace and the second heating furnace are a high-temperature heating furnace and a medium-temperature heating furnace, respectively, with a first preset temperature T1 greater than a second preset temperature T2. Since the critical temperature values ​​of workpieces made of different materials are different, the first preset temperature T1 greater than the second preset temperature T2 also varies for different materials. The gear heat treatment method provided in this application is applicable to the heat treatment process of gear steel parts made of low-carbon alloy carburized steel and medium-carbon alloy carburized steel.

[0039] By applying ultrasonic-assisted induction heating to the workpiece during the heat treatment holding stage, the cavitation effect, mechanical vibration, and thermal effect of ultrasound can promote grain refinement within the gear, accelerate the transformation of pearlite to austenite, and reduce segregation and structural defects. Simultaneously, ultrasonic vibration increases the defect density within the crystal lattice, significantly reducing the activation energy required for atomic diffusion, accelerating phase transformation, and improving the gear's strength, toughness, hardness, and wear resistance. Furthermore, the ultrasonic vibration during the holding stage penetrates deep into the gear, promoting lattice relaxation and dislocation slip through mechanical excitation, accelerating the release of residual stress, thereby reducing deformation and cracking during subsequent processing and use, and improving the gear's dimensional stability and operational reliability. In addition, ultrasonic heating has strong energy penetration, enabling simultaneous and uniform heating inside and outside the gear, reducing the temperature gradient of traditional heating, thus shortening the holding time and reducing energy consumption.

[0040] In some embodiments, the holding temperature of the workpiece in the high-temperature heating furnace, i.e., the first preset temperature T1, can be 850℃~900℃ to austenitize the internal grains of the workpiece. Exemplarily, the first preset temperature T1 can be 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, 880℃, 885℃, 890℃, 885℃, 900℃, etc. Of course, the specific value of the first preset temperature T1 is not limited to the above range; designers can adaptively adjust the first preset temperature T1 according to actual process requirements and the material and volume of the workpiece. Further, the first preset temperature T1 is preferably 860℃~880℃ to reduce the first preset temperature T1 while ensuring that the internal grains of the workpiece can be austenitized, thereby further saving energy consumption of the high-temperature heating furnace.

[0041] In some embodiments, the holding time of the workpiece in the high-temperature heating furnace, i.e., the first preset time t1, is 60 min to 300 min, to achieve complete austenitization and obtain uniform and fine austenite grains. For example, the first preset time t1 can be 60 min, 90 min, 120 min, 150 min, 180 min, 210 min, 240 min, 270 min, 300 min, etc. Of course, the specific value of the first preset time t1 is not limited to the above range; designers can adaptively adjust the first preset time t1 according to actual process requirements and the material and volume of the workpiece. Further, the first preset time t1 is preferably 60 min to 90 min, for example, it can be 65 min, 70 min, 75 min, 80 min, 85 min, or 90 min, to shorten the first preset time t1 while ensuring complete austenitization of the grains inside the workpiece, thereby shortening the gear's process cycle.

[0042] In some embodiments, the holding temperature of the workpiece in the medium-temperature heating furnace, i.e., the second preset temperature T2, can be 620℃~680℃ to fix fine austenite grains and generate a uniform fine pearlite structure. Exemplarily, the second preset temperature T2 can be 620℃, 625℃, 630℃, 635℃, 640℃, 645℃, 650℃, 655℃, 660℃, 665℃, 670℃, 675℃, 680℃, etc. Of course, the specific value of the second preset temperature T2 is not limited to the above ranges; designers can adaptively adjust the second preset temperature T2 according to actual process requirements and the material and volume of the workpiece. Further, the second preset temperature T2 is preferably 645℃~660℃ to reduce the energy consumption of the medium-temperature heating furnace while ensuring the formation of a uniform fine pearlite structure inside the workpiece.

[0043] In some embodiments, the holding time of the workpiece in the medium-temperature heating furnace, i.e., the second preset time t2, can be 60 min to 360 min to ensure complete austenite transformation and thus ensure the uniformity of the microstructure within the gear. For example, the second preset time t2 can be 60 min, 90 min, 120 min, 150 min, 180 min, 210 min, 240 min, 270 min, 300 min, 330 min, 360 min, etc. Of course, the specific value of the second preset time t2 is not limited to the above range; designers can adaptively adjust the second preset time t2 according to actual process requirements and the material and volume of the workpiece. Further, the second preset time t2 is preferably 60 min to 90 min, for example, it can be 65 min, 70 min, 75 min, 80 min, 85 min, or 90 min, to shorten the second preset time t2 while ensuring complete austenite transformation, thereby shortening the gear's processing cycle.

[0044] In some embodiments, the heating time of the workpiece in the medium-temperature heating furnace using ultrasonic-assisted induction heating, i.e., the third preset time t3, is 5 min to 15 min, to promote grain refinement inside the gear and facilitate the rapid transformation of pearlite to austenite. Exemplarily, the third preset time t3 can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, etc. Of course, the specific value of the third preset time t3 is not limited to the above range; designers can adaptively adjust the third preset time t3 according to actual process requirements and the material and volume of the workpiece.

[0045] In some embodiments, in step S4, the ultrasonic output frequency of the ultrasonic generator is 20kHz~40kHz, the ultrasonic amplitude is 5µm~10µm, and the ultrasonic power is 350w~400w.

[0046] The ultrasonic generator's output frequency is in the low-frequency range, which can effectively promote lattice relaxation and dislocation slip, accelerating the release of residual stress. For example, the ultrasonic generator's output frequency can be 20kHz, 21kHz, 22kHz, 23kHz, 24kHz, 25kHz, 26kHz, 27kHz, 28kHz, 29kHz, 30kHz, 31kHz, 32kHz, 33kHz, 34kHz, 35kHz, 36kHz, 37kHz, 38kHz, 39kHz, or 40kHz. Of course, the ultrasonic generator's output frequency is not limited to the above ranges; designers can adaptively adjust the ultrasonic generator's output frequency according to actual process requirements and the material and volume of the workpiece.

[0047] The ultrasonic amplitude of an ultrasonic generator is the displacement amplitude of ultrasonic vibration, which directly determines the intensity of mechanical vibration. It can enhance the lattice vibration intensity inside gears, accelerate dislocation movement, and improve the efficiency of microstructure homogenization. Simultaneously, it strengthens the mechanical excitation in stress concentration areas, accelerating the release of residual stress. For example, the ultrasonic amplitude of the ultrasonic generator can be 5µm, 5.5µm, 6µm, 6.5µm, 7µm, 7.5µm, 8µm, 8.5µm, 9µm, 9.5µm, or 10µm. Of course, the ultrasonic amplitude of the ultrasonic generator is not limited to the above ranges; designers can adaptively adjust the ultrasonic amplitude according to actual process requirements and the material and volume of the workpiece.

[0048] The ultrasonic power of an ultrasonic generator is a total indicator of ultrasonic energy input. Appropriately increasing the ultrasonic power can improve the penetration depth and intensity of the ultrasonic waves, ensuring that both the inner and outer layers of the gear receive sufficient vibration energy. Simultaneously, moderate power input will be accompanied by a certain thermal effect, helping to maintain temperature uniformity during the heat preservation stage. For example, the ultrasonic power of the ultrasonic generator can be 350W, 355W, 360W, 365W, 370W, 375W, 380W, 385W, 390W, 395W, or 400W. Of course, the ultrasonic power of the ultrasonic generator is not limited to the above ranges; designers can adaptively adjust the ultrasonic power of the ultrasonic generator according to actual process requirements and the material and volume of the workpiece.

[0049] like Figure 1 As shown, the steps before step S1 and after step S5 also include:

[0050] Step S0: Clean the surface of the workpiece.

[0051] Specifically, before step S1, the workpiece surface is cleaned, mainly to remove adhering substances such as oxides and cutting fluid debris from the machining process. Optionally, high-pressure spray cleaning is the primary cleaning method. After step S5, the workpiece surface is cleaned again, mainly to remove a small amount of oxide scale, thereby ensuring the quality of the finished product and improving the stability of gear performance.

[0052] To further illustrate this application, see the following references. Figure 2 The gear heat treatment method provided in this application is described in detail with reference to the embodiments and comparative examples shown in Table 1 and the test results shown in Table 2, but these should not be construed as limiting the scope of protection of this application.

[0053] Table 1 Heat treatment parameters of Examples 1-3 and Comparative Examples 1-2

[0054]

[0055] Table 2. Performance parameters and process cycles after heat treatment of Examples 1-3 and Comparative Examples 1-2.

[0056]

[0057] It should be explained that Examples 1 to 3 and Comparative Examples 1 to 2 in Table 1 all use 20CrMnTiH gears as examples and employ the heat treatment method provided in this application for heat treatment.

[0058] Based on Tables 1 and 2, in Examples 1 to 3, when T1, T2, T3, t1, t2, ultrasonic output frequency, ultrasonic amplitude, and ultrasonic power are all within the specified range, the hardness of the heat-treated gear is greater than 170 HBW, the hardness variation of the same workpiece is less than 10 HBW, the isothermal annealing metallographic level is 1 to 3, and the entire process cycle is less than 150 min, which greatly shortens the heat treatment process cycle of the gear.

[0059] In Comparative Example 1, when T1, T2, T3, t1, and t2 are equal to the corresponding T1, T2, T3, t1, and t2 in Example 1, but ultrasonic-assisted induction heating is not performed during the gear heat preservation stage, the hardness of the heat-treated gear is 170 HBW, the hardness difference of the same workpiece is 15 HBW, the isothermal annealing metallographic level is 2 to 4, and the entire process cycle is 130 minutes, resulting in poor gear quality after heat treatment.

[0060] In Comparative Example 2, when T1, T2, and T3 are equal to the corresponding T1, T2, and T3 in Example 1, and t1 and t2 are increased accordingly, and ultrasonic-assisted induction heating is not performed during the gear heat preservation stage, the hardness of the heat-treated gear is 160 HBW, the hardness difference of the same workpiece is 9 HBW, the isothermal annealing metallographic level is 1~3, and the entire process cycle is 270 min, the heat treatment process cycle of the gear is significantly increased.

[0061] This application also provides a gear that undergoes heat treatment using the aforementioned gear heat treatment method. This results in gears with good strength, toughness, hardness, and wear resistance, and reduces deformation and cracking during subsequent processing and use, thereby improving gear dimensional stability and operational reliability. Furthermore, it shortens the gear processing cycle and reduces energy consumption.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method of heat treating a gear, characterized by, Includes the following steps: Step S1: Place the workpiece in the first heating furnace and heat it to the first preset temperature T1, and keep it at that temperature for the first preset time t1; Step S2: Remove the workpiece from the first heating furnace and cool it down to the second preset temperature T2 by blowing air on it; Step S3: Place the workpiece in the second heating furnace and keep it at the second preset temperature T2 for a second preset time t2; Step S4: Maintain the second preset temperature T2 and turn on the ultrasonic generator to perform ultrasonic-assisted induction heating on the workpiece, and the heating time is the third preset time t3. Step S5: Remove the workpiece from the second heating furnace and air-cool it to room temperature.

2. The gear heat treatment method according to claim 1, characterized in that, In step S4, the ultrasonic output frequency of the ultrasonic generator is 20kHz~40kHz, the ultrasonic amplitude is 5µm~10µm, and the ultrasonic power is 350w~400w.

3. The gear heat treatment method according to claim 1, characterized in that, The third preset time t3 is 5 min to 15 min.

4. The gear heat treatment method according to claim 1, characterized in that, The first preset temperature T1 is 850℃~900℃, and the first preset time t1 is 60min~300min; And / or, the second preset temperature T2 is 620℃~680℃, and the second preset time t2 is 60min~360min.

5. The gear heat treatment method according to claim 4, characterized in that, The first preset temperature T1 is 860℃~880℃, and the first preset time t1 is 60min~90min.

6. The gear heat treatment method according to claim 4, characterized in that, The second preset temperature T2 is 645℃~660℃, and the second preset time t2 is 60min~90min.

7. The gear heat treatment method according to claim 1, characterized in that, The first heating furnace is a high-temperature heating furnace; and / or, the second heating furnace is a medium-temperature heating furnace.

8. The gear heat treatment method according to claim 1, characterized in that, The steps before and after step S5 also include: Step S0: Clean the surface of the workpiece.

9. The gear heat treatment method according to any one of claims 1 to 8, characterized in that, The workpiece is made of low-carbon alloy carburized steel or medium-carbon alloy carburized steel.

10. A gear, characterized in that, The gear is prepared by the gear heat treatment method as described in any one of claims 1 to 9.

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