What is the first pass of a weld referred to as?

The first pass of a weld is referred to as the "root." This term describes the initial layer of welding material that is deposited into the joint between two pieces of base metal. The root pass establishes the foundation for the weld, ensuring that the joint is adequately fused together from the start. Achieving a good root pass is critical, as it directly influences the integrity and quality of the entire weld. Proper technique during the root pass helps to prevent defects such as porosity or incomplete fusion, which can compromise the strength of the welded joint.

In welding, subsequent passes build upon the root, adding layers to fill the joint and cap it off, but the focus of the first pass is minimalist—creating a solid connection at the deepest part of the joint before any other materials are added. This foundational aspect underscores the importance of a well-executed root pass in the overall quality of the weld.