Which parts are suitable for surface quenching? What is the purpose of surface quenching?

Surface quenching of steel parts is mostly used for machine tool transmission gears, machine tool spindles, internal combustion engine crankshafts, camshafts and other parts. The materials used are medium carbon steel or medium carbon low alloy steel. After normalizing or quenching and tempering, the surface is quenched and tempered at low temperature. In the working process, the working conditions of these parts are bending alternating load or torsion alternating load, which requires good surface wear resistance and impact resistance at the same time, and can run safely and reliably for a long time.

According to the above requirements, the surface structure of the parts after quenching is tempered martensite structure, and the hardness is above 50HRC, so it has good wear resistance. Because the specific volume of tempered martensite is smaller than the original structure, compressive stress is generated on the surface of the parts after quenching, which can significantly improve the bending performance and fatigue resistance of the parts. But the microstructure of the center is fine pearlite or tempered sorbite, which can ensure good comprehensive mechanical properties.

In addition, cold rolls with certain requirements for wear resistance and contact fatigue resistance are mostly made of high carbon steel, which can better meet their mechanical properties after surface quenching.