What common method is used for controlling expansion when welding a joint?

Placing tack welds along the length of the joint is a common method used to control expansion and distortion during the welding process. Tack welds are small, temporary welds that help to hold the workpieces in place and provide a reference point for the welder. By using tack welds, the welder can effectively manage the heat input during the welding operation. This, in turn, minimizes the effects of thermal expansion and contraction that can lead to warping or misalignment of the joint.

When the main weld is applied, these tack welds help to maintain the position of the components, allowing for a more controlled and even distribution of heat. This method is particularly important in situations where the materials being welded have different thermal expansion properties or when dealing with larger assemblies that are more prone to distortion from heat.

In contrast, while cooling the metal beforehand, adjusting the welding speed, or welding in a circular pattern may have effects on the welding process, they do not directly address the need to manage thermal expansion and the integrity of the joint as effectively as tack welding does. Tack welding stands out as a practical and widely-used technique in various welding applications to ensure proper alignment and to mitigate issues related to heat-induced deformation.