Post Weld Heat Treatment

Welding and machining induces changes in the chemical/mechanical properties of the base material which could result in distortion, cracking and misalignment (of precision machined holes, for instance).

To minimize this affect, controlled heat treatment is undertaken to lower the temperature gradually over a defined period to reduce the stress within the heat affected zone as well as the area immediately adjacent to it, thereby reducing metal hardness and improving ductility across the worked on area. By uniformly heating the base metal (pipe, vessel, etc) to a sufficiently high temperature, just below the metal transformation temperature range, then reducing the temperature over a prolonged, controlled period (dependent on material thickness), the base metal can return to the normal operating temperature and the pre-stressed state.