Why can residual stresses cause a welded structure to bow or distort?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Welder in a blue uniform and protective helmet using shielded metal arc welding to join metal pieces, with bright sparks and smoke visible at the welding point. — welding Shielded metal arc welding.

Residual stresses in a welded structure arise primarily from the thermal cycles inherent in the welding process. As the weld metal cools and contracts, and as the heat-affected zone undergoes cycles of expansion and subsequent contraction, the surrounding unheated base metal acts as a restraint.

Because the weld metal is prevented from contracting freely, internal forces are built up within the joint. These forces are known as residual stresses. If these stresses are not properly managed through techniques such as the use of jigs and fixtures, specific fabrication procedures, or post-weld heat treatment, the imbalance of these internal forces causes the structure to bow or distort.1