Creating a level of abrasion resistance and soft brain and stiffness in structural components
Structural components that are under abrasion and bent or twisting.
In low carbon steels, ie, stiff steels, by thermal treatment, carbon annealing penetrate the surface of the work piece. At the time of the quenching, carbonated surface is hardened up to 0.8%, while its brains (0.1- 0.2% C) Remains soft and stiff. The depth of hardness depends on the following factors:
Carbonation materials (solid, liquid or gas),
Type of steel (Carburetor steel – alloy or non-alloy).
Basically, the work piece after the carbonization operation is slowly cool, then up to the hardness, warm, and eventually in the water or oil is quenched. The next return at temperatures between 150 ° C and 200 ° C will increase toughness and reduce hardness.
In direct work after carbonization, the quench operation is performed. This method is economical for energy consumption, but because of the coarse grain structure, the structure is used only for low stress components. Fine grain steels, which are reluctant to be coarse grains structure, are used only for low stressed components. Fine grain steels that are unwilling to be coarse grain, are hardened straightforward.
The best result is obtained by intermediate annealing, after carbonation and before quench.
This process, which is costly, is called double hardening.
|Stage of work||Process||Goal|
|1||Slow cooling||Structure détente
|2||Brain normalization||Fine grain structure in brain|
|3||Quench in oil warm bath||Stability of the brain fine grain structure
(The work piece surface can be hardened)
|4||Intermediate annealing and slow cooling||Most tensions are repulsed.
The machining is possible
|5||Surface hardening||The surface area becomes hard|
|6||Return||Structural stress reduction, very high hardness, are decreased hardly desirable application.|