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Welding Procedures Before you begin the welding process, be sure to observe the following preliminary steps: 1. Check all electrical circuit connections to make sure they are tight. 2. Check for proper diameter electrode and cup size. 3. Adjust the electrode so that it extends the appropriate distance beyond the edge of the gas cup for the particular joint being welded. 4. Check the electrode to be certain that it is firmly held in the collet. If the electrode moves in the nozzle, tighten the collet holder or gas cup. Be careful not to overtighten the gas cup because this will strip the threads. 5. Set the machine for the correct welding amperage. 6. If a water-cooled torch is to be used, turn on the water. 7. Turn on the inert gas and set it to the correct flow. STARTING THE ARC. If you are using an ac machine, the electrode should not touch the met alto start the arc. To strike the arc, first turn on the welding current and hold the torch in a horizontal position about 2 inches above the work. Angle the end of the torch toward the work piece so the end of the electrode is 1/8 inch above
Figure 15-46.-Breaking the arc. the plate. Figure 15-45 shows the procedure for starting the arc. The high-frequency current will jump the gap between the electrode and the plate, establishing the arc. Be sure the downward motion is made rapidly to provide the maximum amount of gas protection to the weld zone. If a dc machine is used, hold the torch in the same position; but in this case, the electrode can touch the plate to start the arc. When the arc is struck, withdraw the electrode so it is about 1/8 inch above the work piece. STOPPING THE ARC. To stop an arc on the ac or dc machine, swing the electrode back to the horizontal position, as shown in figure 15-46. Make this movement rapidly to avoid marring or damaging the weld surface. Some machines are equipped with a foot pedal to permit a gradual decrease of current. With such control, it is easier to fill the crater completely and prevent crater cracks.CAUTION If you are using a water-cooled cup, do not allow the cup to come in contact with the work when the current is on. The hot gases may cause the arc to jump the electrode to the cup instead of the plate, thereby damaging the cup. Be sure that the water flow is set according to the manufacture's recom-mendations. |
 
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