4. Heat and mechanical treatments after forming and welding

4.1 Heat treatment after cold forming

In boiler making, shaped parts are then assembled by welding. During welding operations, the work-hardened metal ages. Hardening and ageing result in a hardening of the metal, accompanied by a reduction in ductility and impact strength.

Knowledge of the degraded characteristics of cold-formed sheet metal and of the restoration obtained by heat treatment is necessary when the products are used for pressure vessels or safety parts.

The various construction codes and specifications define, for each steel grade, the maximum allowable deformation without heat treatment (see table