What is Residual Stress in Welding?

Residual stress is the stress remaining in a structure or member, as a result of thermal and/or mechanical treatment. Stress arises in fusion welding primarily because the melted material contracts on cooling from the solidus to room temperature. This contraction produces tensile stresses that are opposed by the compressive stresses set up by the surrounding metal. The opposing stresses result in a weld that is in a state of residual stress.

How can I control residual stress?

There are several ways to control residual stress in welding:

One is to use low-stress (also called relaxed) welding techniques. These techniques include using larger electrode sizes, lower currents, and shorter arc lengths.
Another way to control residual stress is to use post-weld heat treatment (PWHT). PWHT helps to relieve stresses by allowing the metal to expand and contract evenly as it is heated and cooled. Still, another way to control residual stress is to use special welding fixtures or jigs. These fixtures help to support the weldment during cooling and prevent distortion.
Finally, it is important to select the proper filler metal for the welding application. Some filler metals are more resistant to creating residual stress than others. For example, austenitic stainless steel filler metals are less likely to create residual stress than ferritic stainless steel filler metals.

In summary, residual stress is the stress remaining in a structure or member as a result of thermal and/or mechanical treatment.

What causes residual stress?

Residual stress is caused by the contraction of the weld metal as it cools from the solidus to room temperature. This contraction produces tensile stresses that are opposed by the compressive stresses set up by the surrounding metal. The opposing stresses result in a weld that is in a state of residual stress.

Types of residual stress in welding

There are two types of residual stress in welding: static and dynamic. Static stress is the result of the contraction of the weld metal as it cools from the solidus to room temperature. Dynamic stress is the result of the movement of the welding torch or electrode during welding.

How can I minimize residual stress?

There are several ways to minimize residual stress in welding, including using low-stress welding techniques, post-weld heat treatment, special welding fixtures or jigs, and selecting the proper filler metal.

What are the effects of residual stress?

Residual stress can have a significant effect on the performance of a weldment. It can cause warping and distortion, cracking, and other problems. Therefore, it is important to understand how to control and minimize residual stress in welding.