Which weld type is defined by its need for more heat application?

The groove weld is characterized by its design that allows for a more substantial and deeper fusion between the base materials. This type of weld is typically used in thicker materials and configurations where a strong, penetrating weld is essential. To achieve this, welding processes require higher heat application to melt through the material's thickness and fill the joint adequately.

Groove welds create a joint that can fully penetrate the members being welded, which necessitates careful control over heat input to ensure an effective bond without overheating the material, which could lead to warping or other issues. This penetrating weld type is especially valuable in critical applications that demand high strength.

In contrast, the other types of welds mentioned don't require the same level of heat application. For example, fillet welds and plug welds generally involve joining edges without the same depth or thermal input. Backing welds, while they do aid in achieving penetration, are not as demanding regarding heat application compared to groove welds.