Stress Relief and Heat Treatment of Weldments

18 December 2020

Industries such as automotive, construction, and others have been utilising welding as it can significantly help them gain access to essential materials and carry out more processes. Welding, in general, is a process of joining two parts together by subjecting them under high heat without using a separate binder material. With this process, the mentioned industries can easily create modern assemblies and finish projects like skyscrapers, vehicles, aeroplanes, and many more.

Welding has helped industries form and construct components and structures that cannot be processed by other material binding processes. In fact, almost 70% of the products that are manufactured today are made through the welding process. Given its importance, industries ensure that it will be carried out optimally without causing any problems and issues.

The Significance of Stress Relief

One way to maintain and produce high-quality weldments is through stress relief. Stress relief is a form of post-weld heat treatment that is intended to eliminate residual stresses, lessen distortion, and recover dimensional tolerance. Without performing the necessary stress relief treatment, the weldments can easily obtain stress-corrosion cracking near welds and in some areas that have been cold-strained during the welding process, which then affects the overall production of structures and components.

You see, distortion among weldments and the surrounding bare metal normally occurs whenever they are subjected under rapid and uneven heating and cooling. Once the molten weld metal cools down, their structure contracts at a rate that is different from the base metal around them. The different cooling rates between these parts, especially if they are restrained, will then result in the presence of residual stresses. If they are not restrained, however, both parts will obtain some noticeable distortion.

The presence of welding stresses to materials can increase their susceptibility to brittle fracture and reduce their dimensional stability. They can also cause deformation of the structure and make their form factor and appearance to become out of shape.

Ways to Minimise Welding Stress

Fortunately, there are various ways of minimising welding stress. For one, the welded structures are exposed to vibrations so they can effectively relieve up to 25% of residual stress. Distortion can also be reduced with the use of vibratory stress relief treatment, all without changing the mechanical properties of the weldment. Another way of minimising welding stress is through thermal treatment. This specific treatment is done by heating the parent metal uniformly until it reaches the appropriate temperature. Once the temperature has been reached, the material will then be subjected to uniform cooling.

Peening is also one way of minimising welding stress. This process elongates the outer portion of the weld and is controlled through a pneumatic chisel with a blunt round edge. With preening, it can easily reduce the internal stress of the weldments. It must, however, be done optimally to avoid hardening the weld metal or bending and cracking the weld. Minimising and countering residual stresses can likewise be done through thermomechanical stress relief treatment. This treatment utilises uses thermal expansion in countering residual stresses and other possible issues.

If you want to know more about the process and benefits of stress relief, feel free to contact us at Alpha Detroit Heat Treatment. Our expertise allows us to suggest the most appropriate process for your heat treatment requirements.

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