224 Modern Welding Copyright Goodheart-Willcox Co., Inc. Stopping and restarting a weld bead is a skill and technique you need to practice. You do not want to create a weld defect because of a poor restart. Weld some additional beads on plate using both stringer and weave beads. Stop along the weld joint but do not fi ll the crater. Clean the weld bead. Properly restart the weld bead and continue welding. You can stop and restart many times on a single bead for practice. Practice both push and drag travel angles while welding with GMAW. There will be times you will need to use one and not the other. FCAW, on the other hand, is almost always done with a drag travel angle. You should also practice GMAW with short circuit- ing and spray transfer. You need to be able to produce quality welds with both transfer methods. 8.9 Shutting Down the Station When welding is stopped for an extended period, the station should be properly shut down. The larger angle prevents excessive penetration. Smaller angles of 10°–20° provide greater penetration. In FCAW–S, the drag travel angle is as little as 5° up to 20°. Smaller angles have better penetration. Too large of a travel angle can cause poor penetration. One difference between FCAW–G and FCAW–S is the slag coating on a completed weld. The slag cover- ing from an FCAW–G electrode can easily be removed. The slag covering from an FCAW–S electrode is much more diffi cult to remove. More chipping is required. Sometimes a power grinder with a wire brush wheel is used to remove the fl ux. The reason the FCAW–S slag is more diffi cult to remove is the material in the fl ux. Remember the fl ux in an FCAW–S electrode must work to remove all oxygen and nitrogen from the weld pool. 8.10.1 Fillet Weld on a Lap Joint The metal should be set up as shown in Figure 8-49. It should be tack welded about every 3″ (75 mm). Tack welds hold the pieces in position while the weld is made. To make the fillet weld, the centerline of the electrode should be held at about a 45° work angle. The electrode and gun should be tilted in the direc- tion of travel, between 15°–25° from a true vertical position. This is a 15°–25° drag travel angle. Procedure Shutting Down a GMAW/FCAW Station To shut down the station, proceed as follows: 1. Close the valve on the shielding gas cylinder or close the valve on the manifold. 2. Pull the gun trigger or press the purge switch to bleed or drain the shielding gas from the system. 3. Turn the wire feeder off. 4. Turn the welding machine off. 5. Neatly coil the cable and hang up the gun. 6. Neatly coil the ground cable and hang up the cable. 8.10 Welding Joints in the Flat Welding Position The face of a weld made in the fl at welding position should be horizontal or nearly horizontal. The weld axis is also horizontal. See Figure 8-49. Any of the metal transfer methods can be used in the fl at weld- ing position. The metal transfer method depends on the metal thickness and other factors. Base metal posi- tions and gun angles apply to both GMAW and FCAW. There is one signifi cant difference between GMAW and FCAW–G compared to FCAW–S. GMAW gun angles are commonly about a 15° drag travel angle and up to about 25°. If the angle is too large, the shielding gas will not cover properly. FCAW–G travel angles are 10° up to 45°. As the base metal gets thinner, a larger travel angle is used. Weld face horizontal Weld axis horizontal Direction of travel 15°–25° travel angle 45° to surface Goodheart-Willcox Publisher Figure 8-49. A fillet weld on a lap joint in the flat welding position. Note the angles used and the deep penetration of the weld. Also, notice that the weld face and axis are horizontal or nearly horizontal.