Medium carbon steel gears are quenched and heat treated using an energy-saving medium frequency induction heating machine with good results

In the machine tool manufacturing industry, medium carbon steel induction quenching has long been used. However, in engineering machinery, carburized gears are still widely used. Recently, a company in my country successfully used medium carbon steel induction quenching to replace the original 20CrMnTi carburizing and quenching for large internal ring gears. , which solves the problem of large shrinkage and deformation of the original process gear.

The original process is: blanking, forging, normalizing, rough turning, fine turning, gear shaping, carburizing, shot blasting, fine turning, quenching and tempering. The new process is: blanking, forging, normalizing, rough turning, quenching and tempering, shot blasting, fine turning, gear shaping, induction quenching and tempering. The depth of the hardened layer is changed from 1.2-2.4mm to the tooth top 1.9-12.4mm, the pitch circle 2.4-5.0mm, and the tooth root 1.5-3.0mm. The surface hardness is changed from 58-63HRC to 52-60HRC, and the matrix hardness is 248-293HBW. Compared with carburizing heat treatment, the surface hardness of the workpiece is slightly lower, but the depth of the hardened layer is deeper, the grain size and martensite level are the same, but it does not contain carbides with higher wear resistance. The main engine was dismantled and inspected after 3000 hours of operation. It was found that the wear of the inner ring gear was very small, no problems, and fully met the service requirements.

The new process uses a 1200kw energy-saving medium-frequency induction heating machine, a large gear induction quenching machine tool, and a dedicated internal ring gear inductor. The inductor directly sprays the quenching cooling medium (AQ25 I with a mass fraction of 5%-7%). The effect of this process is obvious, the process cycle is reduced from 46 hours to 9.5 hours, which is energy-saving, environmentally friendly and greatly reduces production costs.

Using an energy-saving medium frequency induction heating machine to perform quenching heat treatment on medium carbon steel gears not only greatly improves workers' productivity, but also improves the quenching effect of the gears, avoids defects such as oxidation, decarburization, cracks, and deformation, and improves gear's life.