In welding, what contributes to defective welds during the start-stop process?

• A. Excess weld metal
• B. Crater pipe formation
• C. Improper drainage of slag
• D. Overheating

Answer: (B)

The start-stop process in welding can lead to several defects, but crater pipe formation is a primary concern. When welding begins and ends, especially in processes like gas tungsten arc welding (GTAW) or gas metal arc welding (GMAW), there is a tendency for a crater to form at the start or stop points due to incomplete fusion or penetration, insufficient heat input to properly melt and fuse the weld metal, or rapid solidification of weld metal.

This crater, if not properly managed, can lead to a defect called a crater pipe, which is a small, conical depression often filled with a mixture of weld metal and slag that appears at the termination point of the weld. This defect can compromise the integrity and appearance of the weld joint, affecting its mechanical properties and overall strength.

While excess weld metal, improper drainage of slag, and overheating can contribute to possible defects in the welding process, crater pipe formation specifically relates to the unique challenges presented during the transitions at the start and stops of the welding operation. It is this formation that often requires specific techniques, such as a proper technique for weaving, controlling the heat input, and ensuring a smooth transition to avoid such defects.