Technical requirements for heat treatment of railway vehicle bearings using medium frequency induction heating machine

Passenger car bearings

The hardness after quenching by medium frequency induction heating machine is 62~66HRC, and the hardness after tempering is 60~64HRC. The hardness difference of the same part after quenching and tempering should be ≤2HRC; the structure after quenching and tempering should be cryptocrystalline and fine crystalline horse. Stenite and uniformly distributed fine particle carbides, without decarburization (carbon-poor layer <0.05mm), soft spots and cracks.

Truck bearings

Finished parts made of 20CrNi2MoA carburized steel require a carburized layer depth of 1.5~2.3mm. After heat treatment with a medium frequency induction heating machine, the effective carburized hardened layer depth is 1.8~2.6mm (measured to 50HRC); the carbon content on the surface of the part ( Mass fraction) is 0.85%~l.05%; the surface hardness after secondary quenching is 62~66HRC, the surface hardness after secondary quenching and tempering is 60~64HRC, and the core hardness after secondary quenching is 35~45HRC; 2. After subquenching and tempering, the surface microstructure is fine martensite and uniformly distributed granular carbides. Reticular or massive carbides are not allowed to appear. The core structure is lath martensite and lumpy iron is not allowed to appear. Body structure; the hardness difference of the same workpiece after quenching and tempering should be ≤2HRC; the parts should not have soft spots and cracks after quenching and tempering, and the carbon-poor layer should be less than 0.06mm.

The technical requirements for conventional heat treatment of GCr15 and GCr15SiMn steel are the same as those of passenger car bearings. There have been experiments using bainitic austempering, with good results and a hardness of 58-62HRC.