Chapter 17 GMAW and FCAW: Flat Welding Position 257 Copyright Goodheart-Willcox Co., Inc. gun. Move the gun forward when the pool forms. Keep the keyhole and the pool as consistent as possible. 7. Continue welding the butt joint to the end of the plate. Fill the weld pool at the end of the weld. Inspection: A butt weld should have complete penetration. The weld root should indicate complete penetration. This penetration and the face of the weld should have evenly spaced ripples. The weld bead should be consistent in width. Signs of defects should not be visible. The weld bead should be built up slightly higher than the base metal. Excessive spatter on the surface is not acceptable. Welding Aluminum Welding aluminum involves a few problems that are not present when welding mild steel. These include frequent bird’s nests and the forming of aluminum oxide. The electrode wire in the wire feeder may become tangled, producing a bird’s nest. The number of bird’s nests may be reduced by: • Selecting the correct electrode wire. • Adjusting the equipment properly. Aluminum electrode wire is very soft. U-grooved drive rolls are used in the wire feeder because they will not damage the soft wire. Bird’s nests can be avoided by selecting the largest possible diameter electrode wire when welding aluminum. A large-diameter wire is stiffer than a smaller-diameter wire. Use an aluminum alloy electrode that is stiffer. This allows the electrode to be pushed through the cable to the welding gun without kinking. Two common aluminum electrode wires are ER5356 and ER4043. ER5356 is stiffer than ER4043 and results in fewer bird’s nests. ER5356 and ER4043 are different alloys and must be selected correctly, depending on the base metal being welded and the desired weld properties. Proper equipment adjustment is an important consideration in reducing the number of bird’s nests. One necessary adjustment is to position the guide tubes in the wire feeder as close to the drive rolls as possible. Because aluminum electrode wire is soft, it cannot easily be pushed through a long cable to the welding gun. Use the shortest cable assembly possible from the 10 9 8 7 6 5 4 3 2 1 4th layer 3rd layer 2nd layer 1st layer (root pass) Goodheart-Willcox Publisher Figure 17-17. Notice the penetration of each weld bead on this multiple-pass weld. Each weld bead or pass must melt into the base metal and any previous weld beads. This weld has four layers and ten weld passes. Goodheart-Willcox Publisher Figure 17-16. A three-pass FCAW butt weld. The root pass requires a keyhole to ensure proper fusion and penetration. All flux must be removed before the next bead is created.