Chapter 8 Gas Metal and Flux Cored Arc Welding 229 Copyright Goodheart-Willcox Co., Inc. 8.12 Welding Joints in the Vertical Welding Position GMAW in the vertical welding position is performed with the short circuiting or pulsed spray transfer method. In the vertical welding position, the weld axis and the weld face are both vertical. Vertical welding use is common in structural welding. GMAW welds can be made downhill (from the top down) or uphill (from the bottom up). Downhill welding is used on thin sheet metal. Because down- hill welding requires a faster travel speed, it produces less penetration. Therefore, it is better for welding on thin base metal. It is also used on the root pass of a groove weld. Downhill welding uses a drag travel angle of 10°–25°. A downhill root pass of a groove weld can be welded with a stringer bead or a weave bead. A slight weave along with short circuiting metal transfer is excellent to bridge a root opening. A skilled welder using these settings can overcome a poor fi t-up or uneven base metal. The welder can manipulate the weld pool to make a good root pass with proper fusion into both pieces of base metal and good root penetration. With both GMAW and FCAW, welding is always done uphill for 3/8″ (9.6 mm) and thicker base metal. The solidifi ed weld bead provides a shelf to support the molten weld pool. Uphill welding is usually done with a push angle. This is easier for the welder than trying to weld with a drag travel angle. A push angle of 5°–15° is used. A larger push angle produces less penetration. Keep the arc at or near the leading edge of the weld pool. Vertical FCAW travels uphill. Make sure the FCAW electrode is designated for welding in all positions. There will be a number 1 in a carbon-steel or low-alloy steel electrode. An example is E71T-11. The 1 after the 7 indicates this electrode can be used for all-position welding. FCAW does not work well traveling downhill. The molten fl ux can run ahead of the weld pool and get trapped in the weld. Trapped fl ux is unacceptable in a weld therefore, FCAW is performed uphill. Welds can be made with stringer or weave beads. Most commonly a weave is used. A small weave in the root of a groove weld melts the root face of both pieces. A weave in the root of a groove weld also ensures that both pieces are melting. Watch the weld pool and observe that both pieces of base metal are being melted. A larger weave is needed for intermediate weld passes in both groove and fillet welds. An oval, Z-weave, or W-weave pattern can be used. There are also other weave patterns that make an excellent bead. The weld pool remains relatively cool when weld- ing is done with short circuiting metal transfer. A properly adjusted pulsed spray arc will maintain a properly sized weld pool that can be controlled. Both short circuiting and pulsed spray produce quality welds in the vertical position when used by a skilled welder. Practice is necessary to master the welding skills necessary to produce quality welds in the verti- cal welding position with GMAW and FCAW. 8.12.1 Fillet Weld on a Lap Joint Downhill GMAW is used on thin base metal to pre- vent burn through or excessive penetration. The gun angle is a 10°–25° drag travel angle. Keep the arc near the leading edge of the weld pool. Figure 8-63 shows a multipass fi llet weld being made in the vertical uphill welding position. The gun is pointed up at a 5°–15° push angle. Stringer or weave beads can be made. A work angle of 45° should be used. If the edge of the metal melts too rapidly, adjust the work angle and point the electrode more toward the fl at surface. A weave action helps prevent exces- sive melting of the top edge of a lap joint. 15° travel angle 45° work angle Goodheart-Willcox Publisher Figure 8-63. A fillet weld on a lap joint in the vertical position. The second weld pass is in progress. Notice that the weld axis and bead face are vertical.