Stress relieving is a heat treatment process used to reduce residual stresses locked inside a component or fabricated structure as a result of welding, machining, cold working, grinding, bending or other manufacturing operations. In welded components, this treatment is commonly referred to as Post Weld Heat Treatment (PWHT).
In this process, the component is heated uniformly to a suitable temperature below the transformation range, held for a predetermined time and then cooled in a controlled and uniform manner. The objective is to reduce harmful internal stresses without significantly changing the essential shape or dimensions of the component.
Stress relieving is widely used where dimensional stability, reduced risk of cracking, improved service reliability and better structural performance are required after fabrication or welding.
Residual stresses are generated when different portions of a component undergo uneven heating, cooling, plastic deformation or phase-related strain during manufacturing. In welded fabrications, steep thermal gradients between the weld zone, heat-affected zone (HAZ) and surrounding base metal can create high residual tensile and compressive stresses.
During stress relieving, the material is heated to a controlled temperature below the lower critical transformation range. At this temperature, localized internal stresses are reduced through stress relaxation, limited creep response and redistribution of locked-in strain energy. In ferritic steels, this treatment is also often used after welding to improve the condition of the heat-affected zone and reduce the risk associated with brittle behavior in restrained structures.
Proper stress relieving depends on control of:
Particular care is required where the component has variable section sizes, because non-uniform cooling can itself generate fresh stress or distortion if the thermal cycle is not properly managed.
Goswami Heat Treatment Centre provides controlled stress relieving and post weld heat treatment services for fabricated parts, welded assemblies and engineering components requiring reduction of residual stress and improved dimensional stability.
Stress relieving is suitable for components and structures where residual stresses may affect service performance, dimensional accuracy, cracking tendency or subsequent machining behavior.
Common sources of residual stress include:
The main purpose is to reduce harmful residual stresses created during welding, machining, grinding, bending or fabrication, thereby improving dimensional stability and service reliability.
Is stress relieving the same as hardening?No. Hardening is used to increase hardness and strength, whereas stress relieving is primarily used to reduce locked-in internal stress without aiming for a hardened structure.
Why is PWHT important after welding?PWHT helps reduce weld-related residual stresses and may improve the condition of the heat-affected zone, which is important for fracture resistance, dimensional stability and service performance.
Why must heating and cooling be uniform during stress relieving?Non-uniform heating or cooling can create additional thermal gradients, which may introduce new stresses or distortion instead of relieving them.
Can stress relieving help reduce warping risk?Yes. By reducing internal residual stress, stress relieving can help lower the tendency of some parts to warp during machining or in later service, especially in restrained or thin components.
Do you provide stress relieving job work for welded and fabricated components?Yes. We provide stress relieving and post weld heat treatment services for suitable engineering, fabricated and welded components subject to size, material and process requirement.