Reduce, Redistribute and Restructure the residual stresses

PWHT (Post-Weld Heat Treatment) is performed usually after welding in order to ensure the material strength of a part is retained after welding. Post Weld Heat Treatment is essentially method of altering the physical and sometimes chemical properties of metals and essentially can be defined as a controlled heating and cooling of a metal or metal alloy, in its solid state, to produce certain changes in its properties.

Post Weld Heat Treatment is also known as Stress Relief Heat Treatment, which is performed by heating to a temperature as detailed in the welding code for the appropriate material, and holding at that temperature long enough to achieve the desired reduction in residual stresses. The steel is then cooled at a sufficiently slow rate to avoid formation of excessive thermal stresses.

PWHT is typically essential to reduce residual stresses, as a method of hardness control, or even to enhance material strength.

With a fleet of over 50 PWHT machines, we bolster our specialty services. With a team of highly skilled and experienced PWHT technicians, we serve customers in fabrication and heavy steel industries.

TYPICAL CYCLE OF PWHT

Typical cycle for ASTM A 106 Gr. B

• Heating Rate: 200°C/Hour
• Soaking: 600-620°C for 1 Hour
• Cooling: 200°C/Hour

ADVANTAGES OF PWHT

• Improved ductility of the material
• Improved metallurgical structure
• Improved or reduced hardness
• Reduced risk of brittle fracture
• Relaxed thermal stress
• Tempered metal
• Removal of diffusible hydrogen (to prevent hydrogen induced cracking)