Heat Treatment Specialist Offers:Liquid Nitriding, Gas Nitriding, Case Hardening, Direct Hardening, Stress Relieving and Blackening Services

Stress-Relieving or Post Weld Heat Treatment

To relieve stresses that remain locked in a structure as a consequence of Post Welding . Postweld heat treating is to provide, in addition to the relief of residual stresses. For example, most ferritic weldments are given postweld heat treatment to improve the fracture toughness of the heat-affected zones (HAZ). Moreover, austenitic and nonferrous alloys are frequently postweld heat treated to improve resistance to environmental damage. Stress-relief heat treating is the uniform heating of a structure, or portion thereof, to a suitable temperature below the transformation range (Ac1 for ferritic steels), holding at this temperature for a predetermined period of time, followed by uniform cooling. Care must be taken to ensure uniform cooling, particularly when a component is composed of variable section sizes.

  1. Thermal Stress Relieving is generally applied to metallic materials that have been cold-worked, formed, machined, flame-cut, or weld-fabricated to reduce residual stresses for dimensional stability or reduced risk of premature failure in service.
  2. Stress relieving heat treating can reduce distortion and high stresses from welding that can affect service performance.
  3. The presence of residual stresses can lead to stress-corrosion cracking (SCC) near welds and in regions of a component that has been cold strained during processing
  4. Thermal Treatment performed at typically 150-200°C relieves peak stresses after hardening without significantly reducing hardness (e.g. case-hardened components, bearings, etc.)
  5. Treatment performed at typically 550-680°C (e.g. after welding, machining etc.) provides virtually complete stress relief.

Sources of Residual Stress

Different Furnace Capacity