Post Weld Heat Treatment

Post Weld Heat Treatment (PWHT), or stress relief as it is sometimes known, is a method for reducing and redistributing the residual stresses in the material that have been introduced by welding.

The extent of relaxation of the residual stresses depends on the material type and composition, the temperature of PWHT and the soaking time at that temperature. A commonly used guideline for PWHT is that the joint should be soaked at peak temperature for 1 hour for each 25mm (1 inch) of thickness, although for certain cases a minimum soak time will be specified.

In addition to reduction and redistribution of residual stresses, PWHT at higher temperatures permits some tempering, precipitation or ageing effects to occur. These metallurgical changes can reduce the hardness of the as-welded structure, improving ductility and reducing the risks of brittle fracture. In some steels, however, ageing/precipitation processes can cause deterioration in the mechanical properties of the steel, in which case, specialist advice should be taken on the appropriate times and temperatures to use.

ITIS offers post weld heat treatment by using electricity as source of heating for stress relieving of weld joints.
All ITIS heat treatment Services are designed to minimize downtime, improve structural integrity, and enhance effective plant life. Additionally, depending on the mobility of the required equipment many of our heating processes can be applied On-site or at your facility.

ITIS has specialized personnel and equipment to carry out a wide range of heat treatment processes like post weld heat treatment of vessels, piping, spheres and fabricated spools.