156 GMAW/FCAW Handbook Copyright Goodheart-Willcox Co., Inc. Linear porosity. Voids that form along the root of the joint interface. How to correct: • Use the suggestions provided for groove weld linear porosity. Worm tracks. Surface voids usually between 1/4″ to 1″ ″ in length found beneath the slag covering of FCAW-G ″ welds. Shielding gas pockets that are trapped beneath the slag coating as it hardens form these surface voids. How to correct: • Use the suggestions provided for groove weld worm tracks. Plug Weld Defects Lack of penetration. Failure of the fi ller metal to reach the proper depth in the bottom plate. fi How to correct: • Increase the amperage. • Decrease the voltage. • Decrease the electrode stickout. • Start the weld in the center of the plug hole, and fi ll it in a circular pattern. fi Excessive penetration. A weld root that extends too far into the bottom sheet of the assembly. How to correct: • Decrease the amperage. • Increase the voltage. • Increase the electrode stickout. • Move the gun in a circular pattern and shorten the duration of the welding operation. Cracks. Fractures that occur at the center of the weld nugget and are caused by rapid cooling of weld metal. How to correct: • Use an electrode of a lower tensile strength or different chemistry. • Increase the preheat to slow the cooling rate. • Increase the size of the weld. 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: • Use the suggestions provided for groove weld porosity. Goodheart-Willcox Publisher Goodheart-Willcox Publisher