Induction heating quenching and tempering both have temperature requirements. Different tempering processes produce different tempered structures.
1. Low-temperature tempering structure: The induction heating tempering temperature is 250-400°C. The quenched martensite decomposes into a complex mixed structure composed of fine carbide precipitation and ferrite. This mixed structure Maintaining the shape of plate-like martensite is called tempered martensite. Tempered martensite has the characteristics of high hardness, high strength and low toughness.
2. Medium temperature tempering: When the induction heating tempering temperature is 400-600°C, the ferrite grains begin to grow, and the fine cementite begins to aggregate and grow, while both remain laths. Martensite shape. The mixed structure composed of two phases is called tempered trotenite. Tempered trostenite steel shows high elastic limit, yield limit and good toughness.
3. High-temperature tempering structure: The induction heating tempering temperature is 600-750°C. The carbon content of ferrite increases, reaches a balanced composition and begins to transform from flaky to equiaxed grains. The lamellar cementite grows into large grains. This complex phase structure composed of equiaxed grain ferrite price policy and coarse carburization is called tempered sorbite. Tempered troostite steel shows excellent comprehensive properties, including certain strength and hardness, as well as good plasticity and toughness.
In short, different tempering processes produce different tempered structures, and different tempered structures have different characteristics. The low temperature tempered structure is suitable for high carbon tool steel; the medium temperature tempered structure is suitable for spring steel; the high temperature tempered structure is suitable for carbon structural steel.