3. Heat treatments to give the product its final characteristics

3.1 Relaxation treatment

Residual stresses resulting from work hardening can sometimes be troublesome and cause :

• distortion during machining or cutting, resulting from residual stress imbalance;

• instability in the in-service behaviour of leaf or wire springs subjected to permanent stress;

• metal susceptibility to stress corrosion (season cracking) or fire cracking (hot cracking).

Stress corrosion results from the presence of internal stresses. The most dangerous corrosive agents are ammoniacal vapors and solutions, mercury salt solutions, certain molten metals, etc. It is also known as seasonal corrosion, because it was originally observed...