250 Section 3 Gas Metal and Flux Cored Arc Welding Copyright Goodheart-Willcox Co., Inc. Holding the Welding Gun Pick up the welding gun. Use a grip that is comfortable, so you can weld for long periods of time without fatigue. Hold the gun so your fi nger or thumb (depending on the type of gun) is on the switch. Find a position that is comfortable. You may want to place the cable across your arm. See Figure 17-5. Press the inch switch on the wire feeder or press the trigger on the welding gun until the electrode sticks out about 2″. Using a pair of welpers or wire cutters, cut the electrode wire to obtain the proper electrode extension. Warning Place one hand over the electrode wire as it is cut to prevent the excess piece from flying through the air. The piece of electrode wire could hit someone in the eye, resulting in injury. Laying a Weld Bead Gas metal arc welding is performed using a backhand or forehand welding method or with the gun held vertically. Flux cored arc welding is performed primarily using the backhand method or with the gun nearly vertical. The backhand welding method pulls or drags the weld pool along the weld axis. The tip of the electrode points opposite the direction of travel. Backhand welding uses a travel angle of about 25°. A backhand travel angle is called a drag angle. See Figure 17-6A. The electrode can be held perpendicular to the workpiece. In such instances, the travel angle is 0°. See Figure 17-6B. The forehand welding method pushes the weld pool, as seen in Figure 17-6C. The tip of the electrode points in the direction of travel. The forehand welding travel angle is called a push angle. The electrode and gun form a push travel angle of about 25°. In all these situations, a work angle of 0° is used. The backhand welding method is used to obtain better penetration than forehand or vertical. It also has a more stable arc and produces less spatter than the other two methods. Position the gun over the area where you will begin welding. Tilt the gun to obtain the desired travel angle. For a drag travel angle, this is about 20°–25° in the backhand position. Touch the electrode wire to the base metal, but do not press the switch. Raise the gun 1/16″ (1.6 mm) or less. Lower your helmet and press the switch. See Figure 17-7. A welding arc will then form. The arc rapidly, almost immediately, melts the base metal and forms a weld pool (depression). The depth of this weld pool is the amount of penetration of the weld. Figure 17-8 shows that penetration is determined by the depth of the weld pool. Begin moving the welding gun in the direction of travel. Metal from the electrode will constantly be added to the pool. The weld pool shape is round to oval. A wider weld bead is obtained by moving the welding gun from side to side. The electrode should be in front of the centerline of the pool. See Figure 17-8. Continue moving the arc and pool until you reach the end of the weld. Keep the nozzle-to- work distance and the angle of the welding gun as constant as possible. The weld pool must be fi lled at the end of the joint or when you are ready to stop. Move the gun backward over the weld pool 1/4″–1/2″ (6 mm–13 mm). This will fi ll the weld pool. Once the Goodheart-Willcox Publisher Figure 17-5. Looping the electrode cable over the arm reduces the weight of the gun and makes it more comfortable to hold the gun.