Stress Relieving

What is stress relieving?

Stress relieving minimises residual stresses in the part, reducing the risk of dimensional changes in later production stages or in service.

Why is it needed?

Machining, cutting, plastic forming and welding create residual stresses in the material. If these stresses are released in an uncontrolled way during a later heat treatment or in service, they cause unwanted dimensional changes and distortion. Stress relieving reduces this risk in advance; welded structures can also be made stress-free by stress relieving.

How is it done?

The part is heated below the transformation temperature of the steel, usually to 550–650 °C for steels that have not been hardened, held there for a time that depends on its section, and cooled slowly, usually in the furnace, so that no new stresses form. Stress relieving does not change the structure of the material and does not significantly affect its hardness.

For hardened and tempered parts, it should be done about 50 °C below the tempering temperature so that hardness does not change. Before nitrocarburising, stress relieving should be carried out above 600 °C.

When is it done?

Stress relieving is normally done after rough machining and before final machining, such as polishing or grinding. It is recommended for parts with tight tolerances that will go through another process such as nitriding, for dies and for welded structures.

For a quote

State the steel grade, the current condition of the part (rough machined, welded, or hardened and tempered), the tempering temperature if known, and the part dimensions and weight in the quote form.