Holding steel below Ac1, commonly 550 to 675 °C for carbon and low-alloy grades, then cooling slowly so residual stresses relax by local yielding and creep. It is done after heavy machining, welding or straightening to keep parts from moving later. On hardened parts, stress relief has to stay below the last tempering temperature or hardness will drop.
Weldment goes to stress relief at 1,150 before the boring mill touches it.
Rough, stress relieve, then finish. Relieving after the finish cut only moves the warp onto finished surfaces.
Also heard as
- stress relief
- stress relieve
- SR
Related terms
Tempering
Reheating hardened steel below its lower critical temperature to trade some hardness for toughness.
Distortion
Unwanted change in shape or size of a part during heat treatment, such as bowing, warping or ovality.
Annealing
Heating metal and cooling it slowly to soften it, relieve stress and make it easier to machine or form.
Potato chip
Shop name for a thin, flat part that warps into a dished or wavy shape during the quench.