Material selection and technical requirements for heat treatment of worm by medium frequency induction heating machine

The steering mechanism of low-horsepower tractors adopts a worm gear structure, and the steering gear worm is an important component of the tractor. Its function is to drive the worm wheel to rotate through the rotation of the worm, and then turn the front wheels through the steering linkage mechanism to achieve the purpose of tractor steering. The quality of its parts directly affects the performance of the entire machine.

The working conditions of the tractor are complex. During the working process of the worm, the working surface of the gear teeth is subject to large compressive stress and friction, which will cause contact fatigue damage and deep peeling. In addition, due to the frequent impact on the steering tooth surface, the teeth Partially damaged. The main failure mode of worm gear is tooth wear or broken teeth. Therefore, the heat treatment of the worm with a medium frequency induction heating machine can achieve this effect, so that the worm has high bending strength and contact fatigue strength, high surface hardness and wear resistance, and sufficient strength and toughness in the core to ensure a long service life. The following are the material selection and technical requirements for the heat treatment of the worm by the medium frequency induction heating machine:

(1) Material selection

The carbon content should be controlled within a certain range to ensure that the core has sufficiently high toughness and plasticity. After appropriate heat treatment, the surface layer has high hardness and strength to ensure that the entire part has good comprehensive mechanical properties. Based on the above Based on specific practice, 20Cr is selected as the material of the worm. Its material composition is: C 0.17% to 0.24%, Cr 0.70% to 1.0%, Si 0.20% to 0.40%, Mn 0.50% to 0.80%. The low carbon content meets the requirements for high core toughness and good plasticity. Quenching and low-temperature tempering after carburization can meet the requirements for high surface hardness and good wear resistance of the parts; if the carbon content is too high, the toughness will It will deteriorate, and the carbon content is too low, which will cause insufficient core hardness of the part and the strength cannot meet the requirements.

(2) Worm production process route

Blanking - forging - normalizing - roughing - carburizing - finishing - quenching - journal grinding. Technical requirements: The depth of the carburized layer on the tooth surface is 0.8~1.2mm; after quenching, the hardness of the carburized area is 58-64HRC, the hardness of the core is not greater than 45HRC, and the surface is not allowed to have cracks, burns and other defects.