Metal Stress Relief is a type of heat treatment used to reduce or remove internal stress induced into metal components from various manufacturing methods.
Why does metal need Stress Relief
Machining induces stresses in parts. The bigger and more complex the part, the more the stresses. These stresses can cause distortions in the part long term. If the parts are clamped in service, then cracking could occur. Also hole locations can change causing them to go out of tolerance. For these reasons, stress relieving is often necessary.
Typically, the parts that benefit from stress relieving are large and complex weldments, castings with a lot of machining, parts with tight dimensional tolerances and machined parts that have had a lot of stock removal performed.
The Stress Relieving Process
Stress Relieving is done by heating the part 75 ºC, below the transformation temperature, line A1 on the diagram, which is about 727 ºC of steel. Stress Relieving is done at about 650 ºC for about one hour or till the whole part reaches the temperature. This removes more than 90% of the internal stresses. Alloy steels are Stress Relieved at higher temperatures. After removing from the furnace the parts are air cooled in still air.
For more information see DIECUT’s Stress Relief services
references: Efunda materials online magazine.