Heat treatment process is one of the most import technology for investment casting desgin. Heat treatment can help to improve the properties of the casting materials to achieve certain mechanical property requirements, such as high strength, hardness or wear resistance, by changing the inner structure of the materials.
Heat treatment contains several process to meet different required mechanical properties:
1)One process is heat-treating the investment castings without changing the inner structure of the castings. Usually used is relieving of internal stress, which might be caused by no enough time for cooling or other air condition problems.
2)The other heat treatment process will change the inner structure of the materials. The main technics are as below,
The main function for this heat treatment process is to decompose the carbide, thus to reduce the hardness of the castings. This can help to machine the castings easily. For ductile iron castings, tempering treatment can help to get more ferritic structure to increase the quality of the castings.
The main function for this heat treatment process is to get the pearlite and sorbite structure of the castings, thus to increase the mechanical properties of the investment castings.
The main function of hardening treatment is to get higher hardness, thus to increase the wear resistance property.
The main function of surface-hardening treatment is to get a hardened layer on surface of the castings, thus to increase the wear resistance of the castings. Compare with hardening treatment, surface-hardening treatment are usually used for some special areas of castings. Induction hardening is widely used for this surface treatment process.
e.Precipitation hardening treatment
The precipitation hardening treatment is used to increase the strength of the castings, without changing the elongation property of the castings.