Chapter 17 GMAW and FCAW: Flat Welding Position 253 Copyright Goodheart-Willcox Co., Inc. A travel speed that is too high produces a high convex bead with rough or uneven edges. If the travel speed is too low, especially in FCAW, slag inclusions will result. Changing the contact tube-to-work distance changes the welding current. A longer contact tube- to-work distance decreases the welding current, and a short distance increases the current. A longer contact tube-to-work distance causes the electrode to preheat more and reduces the penetration of the weld. GMAW can be performed with a push travel angle, a drag travel angle, or with the gun perpendicular to the surface. The drag travel angle is most common in GMAW and FCAW. When the drag angle is too high, porosity and spatter increase. Also, penetration is reduced and the weld bead can become high, narrow, and convex. These variables interact. For example, consider two welders, both using the same voltage and wire feed speed. The fi rst welder passes a welding qualifi cation test. The second welder does not pass the test. The second welder may be using too large of a gun angle, producing low penetration and porosity. This welder may also be using a higher travel speed, producing a narrower bead. These are not acceptable. Welding takes practice to properly control the weld pool. Controlling the weld pool requires properly setting the voltage and wire feed speed on the welding equipment. It also requires using the correct gun angle, distance to the work, and travel speed. Proper weld technique produces an excellent weld bead with GMAW and FCAW. The skills learned welding a bead on plate apply to making fi llet welds and groove welds in fl at and in out-of-position welding. Making a Fillet Weld A fi llet weld made with GMAW or FCAW looks similar to one made with other welding processes. The two legs should be equal in size. The weld face should be convex or fl at with evenly spaced ripples. Undercutting, porosity, and cracks should not be visible. Figure 17-10 shows a good fi llet weld made with GMAW. Figure 17-11 shows a good fi llet weld made with FCAW. One difference in making a GMAW or FCAW weld is the travel speed. The trailing edge of a weld made with GMAW or FCAW processes will have a pointed shape. Slower welding processes create more of a round trailing edge. Goodheart-Willcox Publisher Figure 17-10. This is a well-formed fillet weld on a lap joint. The weld bead is slightly convex. Goodheart-Willcox Publisher Figure 17-11. A—Self-shielded FCAW being used to weld an outside corner joint. Drag, or backhand, is being used by a left-handed welder. B—Close-up view of a partially completed weld. A B