152 GMAW/FCAW Handbook Copyright Goodheart-Willcox Co., Inc. Porosity. Small internal voids in the weld caused by gas bubbles that did not have enough time to rise to the surface of the molten weld pool before it froze. How to correct: • Remove all heavy rust, paint, oil, or scale on the joint before welding. • Remove any oxide fi lm (GMAW) or slag (FCAW) fi from the previous passes or layers of the weld. • Increase the electrode stickout distance for FCAW. • Check the gas flow. fl • Protect the welding area from wind. • Remove spatter from the interior of the gas nozzle. • Check the gas hoses for leaks. • Check the gas supply for contamination. Linear porosity. Small voids that form in a line along the root of the weld at the center of the joint where penetration is very shallow. How to correct: • Make sure the root faces are clean. • Increase the current. • Decrease the voltage. • Decrease the electrode stickout. • Decrease the travel speed. Burn-through. A widened gap that forms in the weld joint or a hole that forms where the metal is thin. It is caused by excessive heat in a concentrated area. How to correct: • Decrease the current. • Increase the voltage. • Increase the electrode stickout. • Increase the travel speed. • Decrease the root opening. Whiskers. Pieces of electrode wire that extend through the completed weld joint. Occurs where there is a root spacing that the wire slips into. How to correct: • Keep the arc on solidified metal and base metal. fi • Do not allow the electrode to slip into the root opening. Goodheart-Willcox Publisher Goodheart-Willcox Publisher Goodheart-Willcox Publisher Goodheart-Willcox Publisher