Goal:
Creating a level of abrasion resistance and soft brain and stiffness in structural components
Application:
Structural components that are under abrasion and bent or twisting.
Methods:
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),
- Carbonation time,
- Annealing temperature
- Type of steel (Carburetor steel – alloy or non-alloy).
Heat treatment:
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.
| Goal | Process | Stage of work |
| Structure détente
|
Slow cooling | 1 |
| Fine grain structure in brain | Brain normalization | 2 |
| Stability of the brain fine grain structure
(The work piece surface can be hardened) |
Quench in oil warm bath | 3 |
| Most tensions are repulsed.
The machining is possible |
Intermediate annealing and slow cooling | 4 |
| The surface area becomes hard | Surface hardening | 5 |
| Structural stress reduction, very high hardness, are decreased hardly desirable application. | Return | 6 |
In pieces that require machining in addition to grinding, after the carburetor hardening, for example, the screwdriver in the drill bush, the process is carried out in the following order:
The initial milling, while taking into account the overload of the corresponding location, the carbonation operation, the turning of the corresponding milling (and the removal of carbon from the above point, which should remain soft in hardness), hardening, grinding and twisting.
Tip:
In simple parts, the points that need to remain soft could be covered with copper or coated copper, so carbonation can’t be performed until carbonization occurs.
