Post Weld Heat Treatment (PWHT)
PWHT is a controlled process when material that has to be be welded is reheated to a temperature below its lower critical transformation temperature, and then it is held at that temperature for a specified period of time; however, it has a specific meaning in the oil, gas, and petrochemical industries. Industry codes, such as the ASME Pressure Vessel and Piping Codes, often require mandatory performance of PWHT on certain materials to ensure a safe design with optimal mechanical and metallurgical properties.
Advantages:
- Improving the ductility of the materials
- Reducing the instances brittle fractures
- Tempered metal
- Improves and reduces the metal’s hardness in some cases
- Improve metallurgical properties
- The prevention of cracking caused by hydrogen by its removal