Casting industry characteristics

Casting is a more economical method of forming blanks, for the complex shape of the parts can show its economy. Such as the cylinder block and cylinder head of automobile engines, ship propellers and delicate works of art. Some difficult to cut parts, such as combustion turbines, nickel-based alloy parts without casting method can not be formed.

For casting engineers and mechanical structure design engineers, heat treatment is a very meaningful, and has a very high value to improve the quality of the material method, through heat treatment can change or affect the organization and properties of cast iron, and at the same time can obtain higher strength, hardness, and improve its resistance to wear and tear and so on.

Because of the different purposes, heat treatment of very many types, basically can be divided into two main categories:

The first category is the organization structure will not be changed or should not be changed by heat treatment, and the second is the basic organization structure changes. The first heat treatment program, mainly for the elimination of internal stress, and this internal stress is caused by the casting process due to different cooling conditions and conditions. Organization, strength and other mechanical properties, etc., not due to heat treatment and significant changes.

For the second type of heat treatment, the base organization has changed significantly, can be broadly divided into five categories:

(1) Softening annealing: its purpose is mainly to decompose carbide, will reduce its hardness, and improve the machinability. For ductile iron, its purpose is to obtain more ferrite organization.

(2) Normalizing treatment: the main purpose is to obtain pearlite and sohnite organization to improve the mechanical properties of castings.

(3) Quenching: The main purpose is to obtain higher hardness or wear strength, and at the same time to the very high surface wear characteristics.

(4) Surface hardening treatment: mainly to obtain the surface hardening layer, and at the same time get very high surface wear characteristics.

(5) Precipitation hardening treatment: Mainly to obtain high strength without drastic changes in elongation.

Casting surface defects treatment: casting defects such as porosity, shrinkage holes, sand holes, sticky sand and cracks. Casting defects has been the casting industry can not be avoided and difficult to solve the problem. Repair of unqualified castings, the conventional method is mainly to carry out welding, which requires skilled workers, time-consuming, and consumes a lot of material.