Maintenance Technician 2026 Complete Practice Test

Post Weld Heat Treatment (PWHT) is recommended to prevent residual stress in welded metals because it helps to relieve the internal stresses that develop as the metal cools after welding. During the welding process, the rapid heating and cooling of the material can result in uneven thermal expansion and contraction, which may introduce significant residual stresses in the weld and the surrounding base metal.

PWHT works by subjecting the welded metal to a controlled heating process followed by a slow cooling phase. This allows the microstructure of the metal to adjust and stabilize, effectively redistributing and reducing these stresses. This treatment can enhance the ductility and toughness of the weld, as well as improve the overall mechanical properties of the material.

In contrast, cooling the metals quickly can actually exacerbate residual stresses because it can lead to more rapid contractions and thermal shocks. Holding the welded metals under high pressure is not a standard method for reducing residual stress and might not address the underlying issues of thermal distortion. Galvanizing is a process that involves coating metal with zinc for corrosion resistance and does not relate to managing residual internal stresses from welding.

Therefore, PWHT is the established method you would employ to mitigate the issues associated with residual stress in welded joints.