9. Hold the torch at the correct angle about 1/8″ (3 mm) above the work. 10. Press the foot pedal or thumb switch. The arc will start. 11. Move the electrode closer to the work, so it is about 1/16″ (1.5 mm) above the base metal. Watch the weld pool as it forms into a C shape. When it reaches the correct size and shape, add the welding rod. Begin moving the torch forward. 12. Maintain the same size weld pool, adding welding rod as needed, as you steadily move along the plate. Keep the electrode a constant distance above the work. 13. Stop welding at the end of the joint. 14. Weld the other side of the joint. Inspection: The weld bead should be straight with even ripples. There should not be any overlap or porosity. Exercise 22-2 Making a Horizontal Fillet Weld on a T-Joint 1. Obtain two pieces of carbon steel measuring 1/8″ × 1 1/2″ × 6″ (3.2 mm × 40 mm × 150 mm). 2. Clean one long edge on one piece and one face on the other piece. 3. Set up the welding machine for welding carbon steel. Set the shielding gas flow rate. 4. Select, prepare, and install the electrode. Select the correct welding rod. 5. Tack weld the two pieces together to form a T-joint. 6. Weld both sides of the T-joint. Watch the weld pool to make sure both surfaces melt. Add the welding rod to form a 1/8″ (3 mm) fillet weld. The bead should be slightly convex. Inspection: The completed weld should have even ripples. The bead should be even in width along the entire joint. There should not be any defects in the weld. Compare your completed weld to the one shown in Figure 22-4. Butt Weld Molten metal in a horizontal butt weld will sag downward due to the force of gravity. If the weld sags, it will have a poor appearance. It also can be weakened by undercutting or underfi lling of the weld joint. Overlap may also occur. These defects are shown in Figure 22-5. Welding with a small weld pool and a short arc length will help prevent defects such as these. The angles of the torch and welding rod are shown in Figure 22-6. Notice that the welding rod is held 15°–20° above the axis of the weld. The welding rod is added to the front upper part of the weld pool. Adding the fi ller metal to the top of the pool reduces undercut and underfi ll. The tip of the torch is angled upward 5°–15°. Pointing the electrode up helps keep the weld pool from sagging. Butt joints require full-penetration welds. Point the arc at the root of the weld. Heat the weld joint with the arc so both pieces begin to melt evenly. They should melt all the way to the root of the joint. You can then add the welding rod. Move the torch forward at a uniform speed, keeping both pieces molten. The root of the weld will look like a keyhole, as shown in Figure 22-7. The back and the sides of the weld are molten. Keep the keyhole size the same as the weld progresses. Goodheart-Willcox Publishing Figure 22-5. Common weld defects that may occur on a horizontal butt weld. Undercut is caused by an incorrect electrode angle. When not enough filler metal is added, underfill occurs. Overlap or sagging occurs when too much welding rod is used or if the bead is overheated. Undercut Underfill Overlap and sagging 326 Section 4 Gas Tungsten Arc Welding Copyright Goodheart-Willcox Co., Inc.