Undercut in welding is primarily characterized by what?

Undercut in welding is primarily characterized by a groove melted into the base metal. This phenomenon occurs when the heat from the welding process causes the base metal to erode, creating a depression along the edge of the weld bead. Undercut can compromise the strength and integrity of the weld joint as it reduces the effective area of the material being joined. Proper technique and heat management during welding are essential to avoid this issue, ensuring that the weld metal adequately fills the joint without over-melting the adjacent base metal.

In contrast, the ideal shape of a weld bead involves a smooth, consistent profile that does not exhibit undercutting. Excessive heat input can contribute to undercut, but it is not the defining characteristic; rather, it is the resultant groove that is the primary concern. Uniform penetration across the weld is also a desirable outcome that is opposite to what undercut represents. Understanding the characteristic feature of undercut is crucial for welders to anticipate and rectify it to maintain weld quality.