Two kinds of heat treatment in casting

Two kinds of heat treatment in casting
Because of the difference of purpose, there are many heat treatment ways, that can be divided into two major categories basicly. The first category is that the organization structure will not change by heat treatment or should not change and the second category is that the basic organization structure changes. The first heat treatment procedure is mainly used to eliminate internal stress and the internal stress due to different cooling conditions in the process of stainless steel casting. The organization, strength and other mechanical properties has no obvious changes due to heat treatment.
For the second type of heat treatment, matrix structure has an obvious change, that can be roughly divided into five categories:
softening annealing: The purpose is to decompose carbide, reduced its hardness, and improve the processing performance. For ductile iron, Its aim is to gain more ferrite.
normalizing treatment:The main purpose is to obtain pearlite and sorbite structure and to improve the mechanical properties of the stainless steel casting.
quenching:It’s main purpose is to obtain higher hardness and wear and tear strengthpearlite and at the same time to obtain the higher surface wear-resistant characteristics.
surface-hardening treatment:Mainly to obtain the higher surface hardening layer, and get very high surface wear-resisting properties.
precipitation hardening treatment:Mainly to obtain high strength and elongation and not drastic changed.