Reading the Weld Bead A welder must be able to visually determine whether a weld is made properly. This can be done by looking at the weld while it is being made and after it is completed. Visual inspection of a weld bead is referred to as reading the weld bead. The process of examining or reading the weld bead can provide information on the following welding variables: • Amperage setting. • Arc length. • Travel speed. Figure 12-16 shows weld beads that have been made under different welding conditions. If the correct amperage is used, a completed stringer bead will have an even width. It will also have evenly spaced, oval-shaped ripples. The weld bead width and height will also be correct, Figure 12-16A. If the welding amperage is too low, the weld bead will be narrow and built up, and will have poor penetration. See Figure 12-16B. Excessive current produces a weld that is wide, low, and has a great deal of spatter (molten metal droplets) on the metal’s surface. See Figure 12-16C. A built-up weld bead with poor penetration is generally caused by a short arc length. Overlap is usually present. See Figure 12-16D. If the arc length is too long, the weld bead will be rough and will have a lot of spatter. It may also have poor penetration and have undercutting at the weld toes, Figure 12-16E. Figure 12-16F shows a weld that was made too slowly. The weld bead is too wide and built up too much. Also notice the round shape of the ripples. A weld that is made too fast will be low and narrow, as shown in Figure 12-16G. The ripples are pointed. These weld characteristics can be seen while the weld is in progress. If you notice any of these poor characteristics while welding, immediately adjust your arc length and welding speed. The effects of these changes should be seen as a more perfect weld bead is formed. If the current needs to be changed, the weld must be stopped. Hang the electrode holder on an insulated hanger before changing the amperage. Then restart the weld after changing the amperage. Exercise 12-1 Running a Weld Bead Using an Open Arc 1. Obtain one low carbon steel plate measuring 1/4″ × 3″ × 6″ (6.4 mm × 75 mm × 150 mm). 2. Also obtain five 1/8″ (3.2 mm) diameter E6013 electrodes. 3. Mark three parallel 6″ (150 mm) long lines on the plate. The lines should be 3/4″ (20 mm) apart. 4. Determine the amperage range and polarity for this electrode. Refer to Chapter 11 or an electrode manufacturer’s guide. 5. Make a safety inspection of the arc welding outfit or station. 6. Set the amperage near the low end of the suggested range. 7. Make certain that the workpiece lead is attached to the worktable or practice plate. 8. Strike the arc using the scratching or pecking method. 9. Run a weld bead of correct width and height along the first marked line. 10. Chip and wire-brush the weld bead. Chipping goggles must be worn. 11. Read the finished weld bead and compare it to Figure 12-16. 12. Change your amperage, arc length, or travel speed as required. Run two additional weld beads. Read each weld bead while it is being made. Clean the completed welds and make changes in your welding method as required. 13. Make three additional weld beads on the opposite side of the metal about 3/4″ (20 mm) apart. Inspection: Each weld bead should be the proper width and height. The ripples should be oval-shaped and evenly spaced. Each weld bead should improve as errors are read and corrected. Tack Welding A tack weld is a small weld used to join two pieces of metal. Tack welds hold the pieces of metal 176 Section 2 Shielded Metal Arc Welding Copyright Goodheart-Willcox Co., Inc.