Copyright Goodheart-Willcox Co., Inc. Chapter 17 Welding Procedures, Defects, and Corrective Actions 151 Undercut. Lack of filler material at the toe of the weld. fi How to correct: • Decrease the travel speed. • Increase the dwell time at the edge of the joint on weave beads. • Decrease the voltage. • Decrease the amperage. • Change the gun angle. Convex crown. A weld that is peaked in the center. How to correct: • Change the gun angle. • Increase the current. • Decrease the electrode stickout. • Use a weave bead technique, with a dwell time at the edge of joint. Craters. Depressions formed at the end of a weld bead due to a lack of fi ller metal or weld shrinkage. fi How to correct: • Do not stop welding at the end of the joint (use run-off tabs). • Using the same gun travel angle, move the gun backward a quarter inch, over the completed weld, to backfi the crater before stopping the weld. fill Cracks. Fractures caused by cooling stresses in the weld and/or base metal. How to correct: • Use electrode wire with a lower tensile strength or different chemistry. • Increase joint preheat to slow the weld cooling rate. • Allow the joint to expand and contract during heating and cooling. Increase the size of the weld. Goodheart-Willcox Publisher Goodheart-Willcox Publisher Praphan Jampala/Shutterstock.com Goodheart-Willcox Publisher