Post Weld Heat Treatment Service (PWHT), also commonly referred to as stress relieving, is the application of controlled heat applied after the welding is complete. During the welding of metals, the high temperatures and rapid cool down creates stresses in the molecular structure of the parts being welded.

When the weld has a PWHT carried out the metallurgical structures and molecules of the weld and parent metal blend together during the heat up, soak period, and cool down to create a finished product that meets the intended design criteria of the parts being heated.

Learn more about weld heat treating and the science behind the process.

Without proper PWHT, the welded joint can be susceptible to issues such as distortion, cracking, and stress corrosion cracking. The primary benefit is the reduction of residual stress in the welded joint. As the metal cools down, the contraction is more uniform throughout the entire joint, reducing the overall stress levels.

This is particularly important for industries such as petrochemical, aerospace and marine, where corrosion resistance is critical. PWHT applies equally to new welds and to weld repairs on components that have previously been heat treated.

By following best practices, PWHT can be optimized for maximum stress relief, resulting in improved mechanical properties and increased reliability of the welded joint. It is important to consider the environmental factors and the intended usage of the structure after the welding process.