Carbon steel castings
Changes in mechanical properties: Tempering can eliminate quenching internal stress, reduce hardness and strength, and improve toughness and plasticity. For example, high carbon steel castings have high hardness and high brittleness after quenching. After low temperature tempering, they can greatly improve toughness while maintaining a certain hardness, so that they can meet the use requirements of tools and other tools with high hardness and toughness.
Organizational transformation: The organization of carbon steel castings after quenching is mainly martensite and residual austenite. During tempering, martensite will decompose to form tempered martensite and other organizations, making the organizational structure of the casting more stable and improving dimensional accuracy.

Alloy steel castings
Changes in mechanical properties: Different alloying elements have different effects on the tempering process. Elements such as chromium and molybdenum can improve the tempering stability of steel, so that alloy steel castings can still maintain high hardness and strength when tempered at higher temperatures. Nickel elements can improve the toughness of steel, and the toughness of alloy steel is further improved after tempering.
Organizational transformation: Alloy elements will change the formation and aggregation rate of carbides. For example, alloy steel castings containing vanadium, titanium and other elements will form fine, dispersed carbides during the tempering process, resulting in secondary hardening, which significantly improves the hardness and wear resistance of the steel.

Stainless steel castings
Changes in mechanical properties: Tempering can eliminate some processing stresses and improve the mechanical properties of stainless steel castings. For austenitic stainless steel, tempering generally has little effect on strength, but can improve its plasticity and toughness to a certain extent. For martensitic stainless steel, tempering can significantly reduce its hardness and strength and improve toughness.
Changes in corrosion resistance: A reasonable tempering process can improve the corrosion resistance of stainless steel castings. For example, for precipitation-hardened stainless steel, a specific tempering treatment can be used to make the strengthening phase precipitate uniformly, which can not only improve strength but also improve corrosion resistance. However, if the tempering process is improper, carbides of alloying elements such as chromium may precipitate at the grain boundaries, reducing the chromium content near the grain boundaries, thereby reducing the corrosion resistance of the casting.

Heat-resistant steel castings
Changes in mechanical properties: Tempering helps to adjust the strength and toughness of heat-resistant steel castings to meet high-temperature use requirements. Generally speaking, the strength will be reduced after tempering, but the toughness will be improved, so that the casting has better fatigue resistance and creep resistance at high temperature.
Organization stability: When heat-resistant steel is used for a long time at high temperature, the organization stability is very important. Tempering can promote organization homogenization, eliminate organization defects generated during the casting process, and improve organization stability, thereby ensuring the long-term stable operation of heat-resistant steel castings in high temperature environments.