Treatment of medium carbon steel

The final heat treatment methods of medium carbon steel include tempering, low temperature tempering after quenching, low temperature tempering after high-frequency quenching, isothermal quenching and medium temperature tempering after quenching.

(1) tempering. The tissue is tempered sorbite. This kind of structure has good comprehensive mechanical properties, high strength, good plasticity and toughness. Tempering steel should have good hardenability to ensure uniform organization and performance on the entire section of the tempering part. Compared with alloy steel, carbon steel has poor hardenability, so it is only suitable for tempering medium carbon steel parts with small cross-section size.

(2) tempering at low temperature after quenching. The structure is tempered martensite, which has high strength and appropriate plasticity and toughness.

(3) Low temperature tempering after high-frequency quenching. The microstructure of high-frequency quenching layer is very fine hidden needle martensite, tempered martensite is obtained after low temperature tempering, and the effect of this treatment can be similar to that of carburizing treatment. Tempering or normalizing is generally carried out before high-frequency quenching. Therefore, after high-frequency quenching and tempering, the core of the part has high strength, good plasticity and toughness, and the surface hardness is high and the wear resistance is good. In addition, the surface surface of high-frequency quenched parts produces compressive stress, which has high fatigue limit and long service life.

(4) isothermal quenching. The structure is bainite, which has high strength and good plasticity and toughness.

(5) Tempering at medium temperature after quenching. The tissue is tempered sorbite.