226 Modern Welding Copyright Goodheart-Willcox Co., Inc. 8.10.3 Groove Weld on a Butt Joint Square-groove welds can be made on metal up to 3/8″ (10 mm) thick without edge preparation. Butt joints of any thickness can be made using the GMAW and FCAW processes, as long as the edges of the metal are properly shaped. The groove angle on a V-groove butt joint can be less than the angle used with SMAW. Short circuiting is often used for the root pass. Short circuiting has less penetration than SMAW or GMAW spray transfer. Therefore, the root face for GMAW is often 1/16″–3/32″ (1.6 mm–2.4 mm). The root opening is 3/32″–1/8″ (2.4 mm–3.2 mm) and sometimes even a little wider. The root face is on the small end of an SMAW root face. The root opening is toward the larger range of an SMAW root opening. Figure 8-53 shows a completed butt joint. A 0° work angle is used to make a butt joint. The centerline of the welding wire should be directly over the axis of the weld. A drag travel angle of between 15°–25° is correct for the backhand welding method. See Figure 8-54. Adjusting the travel angle to near zero reduces the penetration. A push travel angle (forehand welding) can be used to further reduce or control the penetration on thin metals. A keyhole in the weld pool indicates that com- plete penetration is occurring. One problem that may occur in a groove weld made with GMAW is whis- kers. Whiskers are lengths of welding wire that stick through the root side of a groove weld. Whiskers are an undesirable result that occurs when the welding wire is advanced ahead of the weld pool. The wire goes through the weld root and burns off. The burned-off length is left stuck in the weld, pro- truding from the bottom side of the joint. Whiskers can be prevented by using the oval or W-weave pattern. The arc is directed at each piece during the weave. The weave stays at the front edge of the weld pool but is not directed over the unwelded gap between the pieces being welded. Another way to prevent whiskers is to slow the welding speed. Whiskers can also be pre- vented by reducing the wire feed speed, which requires a slower travel speed. Frequently, FCAW butt joints (and sometimes GMAW butt joints) are welded with backing. Backing is a piece of the same type of base metal that is tack welded to the root side of the joint. The root gap between the two pieces of base metal has this backing piece behind the base metal. The backing is welded to the two pieces of base metal and is ground off after welding. There are no whiskers when a backing is used on the butt joint. Higher welding currents are used to weld a groove weld with backing. The root pass must melt the toes of each piece of base metal and must melt into the backing. 8.10.4 Groove Weld on an Outside Corner Joint An outside corner joint is set up as shown in Figure 8-55. A square- or prepared-groove weld may be used. The electrode angles are the same as those used for welds made on a butt joint. Since groove welds are made on the outside corner joint, whiskers can occur. 8.11 Welding Joints in the Horizontal Welding Position The face of a weld made in the horizontal welding position is vertical or nearly vertical. In the horizon- tal welding position, the centerline of the weld axis is horizontal or nearly horizontal. See Figure 8-56. Goodheart-Willcox Publisher Figure 8-53. A completed GMAW butt joint. This is a single pass weld on 3/16″ (4.8 mm) carbon steel. Direction of travel 15°–25° travel angle Goodheart-Willcox Publisher Figure 8-54. A V-groove weld on a butt joint in the flat welding position. Note the narrow (45°) groove possible with GMAW.