What Does Stress Relieving Mean?
Stress relieving is a heat treatment process in which a metal is subjected to a constant temperature that is below the metal's critical temperature, followed by controlled cooling.
Drawing, forming and machining induce stresses in materials. A stress relief operation is typically used to remove internal (residual) stresses that have accumulated in the material. These stresses can cause loss of tolerance, cracking and distortion, and contribute to in-service failures. For these reasons, stress relieving is often necessary or even mandatory.
Corrosionpedia Explains Stress Relieving
The stress relief process is performed by heating in an oven or furnace to a temperature below the critical temperature (different materials have different temperatures) and holding it at that temperature long enough to achieve the desired reduction in residual stresses. Temperature, time and time held at the temperature are key process variables, if necessary stress relieving can be performed in a furnace with protective gas, to protect surfaces from oxidation. In extreme conditions vacuum furnaces can be used.
The advantages of stress relief include:
- It relieves internal stresses without causing any color change.
- It returns the material to a strength level approximately equivalent to where it was prior to forming.
- It increases mechanical strength of the material.
- Welded structures can be made tension free by stress relieving.