Carburizing and Quenching Method for Automobile Transmission Gear
An automobile gearbox, carburizing and quenching technology, applied in the field of heat treatment, can solve problems such as spalling, carbon potential fluctuations in the furnace, and gears prone to grinding cracks, etc., to improve tooth surface hardness and wear resistance, and smooth carbon concentration gradient , the effect of improving the service life
Active Publication Date: 2019-09-27
CRRC QISHUYAN INSTITUTE CO LTD
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Problems solved by technology
Due to the high carburizing potential of this carburizing and quenching method, a large amount of carbon black is easily deposited in the furnace, which will cause fluctuations in the carbon potential in the furnace at the carburizing temperature, causing great difficulties in controlling the carbon potential
At the same time, the strong infiltration time of this method is long and at the same temperature. Since the carbide-forming elements such as Cr, Mo, Ti, and W in the steel will form stable alloy carbides with carbon, the carbon absorption ability is strong, and the carburized layer The increase of carbon concentration is not conducive to the diffusion of carbon elements. The concentration gradient of the carburized layer becomes steeper, and large block and network carbides are prone to appear, which destroys the continuity of the matrix structure and seriously affects the quality of the carburized layer. Grinding cracks are easy to occur in the subsequent grinding process, and the gears are prone to fatigue under the action of periodic contact stress, forming pitting and surface peeling
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[0019] See figure 1 Shown, the carburizing and quenching method of automobile gearbox gear of the present invention comprises the following steps,
[0020] ⑴. Heating step, place the gear in a carburizing furnace and heat it to 930±5°C for multi-stage cooling and carbon potential reduction at the rear.
[0021] (2) In the first carburizing step, the gear is maintained at 930±5°C with the furnace, and the carburizing agent is passed into the carburizing furnace for carburizing, and the carbon potential CP is controlled at 1.15±0.05C%, and the temperature is kept for 5-6h. CP is controlled by adjusting the flow of carburizing agent.
[0022] (3) In the second carburizing step, lower the furnace temperature, the gear will drop to 920±5°C along with the furnace, put the carburizing agent into the carburizing furnace for carburizing, the carbon potential CP will drop to 1.05±0.05C%, and keep warm for 5-6h , the same carbon potential CP is controlled by adjusting the flow of carb...
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The invention relates to a carburizing and quenching method for an automobile transmission gear. The method comprises the following steps of (1) heating, (2) first carburizing, (3) second carburizing, (4) third carburizing, (5) fourth carburizing, (6) temperature reduction, (7) quenching and (8) low-temperature tempering. According to the carburizing and quenching method for the automobile transmission gear, the multiple stage temperature-lowering carbon-decreasing potential method is adopted, the problem that the carburized layer of the surface of the gear easily generates large block and network carbide can be effectively solved, harmful carbide can be eliminated, and dispersedly-distributed fine granular carbide is obtained; and a metallographic structure is optimized, the hardness and abrasive resistance of the surface of the gear are improved, and the service life of the gear is improved.
Description
technical field [0001] The invention relates to a carburizing and quenching method for an automobile transmission gear, belonging to the technical field of heat treatment. Background technique [0002] Automobile transmission gear is one of the parts with the highest technical requirements in the automobile transmission system. During the operation of the gear, there are both rolling and sliding between the tooth surfaces that mesh with each other. At the same time, the gear is also subjected to pulse stress and alternating bending stress. Therefore, the gears are required to undergo heat treatment to have good hardness, wear resistance, fatigue resistance, high dimensional accuracy, and low noise performance during operation. [0003] At present, the most important heat treatment method for surface strengthening of automobile gearbox gears is carburizing and quenching. The existing gearbox gear carburizing method is two-stage carburizing, such as figure 2 As shown, it is ...
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IPC IPC(8): C23C8/22C21D1/18C21D9/32
Inventor 刘聪敏吴国庆樊洋王晓华
Owner CRRC QISHUYAN INSTITUTE CO LTD