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ELECTRODE WELDING AND GOUGING

Welding Techniques

Having examined the necessary equipment and studied the safety precautions which must be carefully followed, we shall now look at the actual welding operation.

In order to obtain a good weld we must ensure that the following points are correct:

Surface welded at correct current value. Current output too high, even, but coarsely

• The current • The length of the arc • The angle of the electrode • Electrode travel

beaded surface.

Current

Settings

Current output is the most important factor in arc welding, and this is where most mistakes are made. It is a good rule to use slightly more current than required rather than risk using too little. If the current output is insufficient, fusing with the base material will be unsatisfactory. Slag may become embedded in the weld, and other faults are likely to occur. When current, electrode travel and angle are correct, the molten pool of the weld will proceed smoothly and slag will form behind the pool. Approximate current values are given in the descriptions of the different types of electrodes, and are also shown on the electrode package labels.

The table gives the ampere limits for the most important electrode diameters, as well as rules of thumb for calculating them. The values given are only valid for unalloyed and low-alloy electrodes and for the stated electrode lengths. For root-welding, vertical-up and overhead welding the welder should use the lower limit. For fillet-welding in horizontal and flat positions and also for vertical-down welding, the amperage is set near to the upper limit.

Welding surface appearance at different current values:

Current value too low, uneven surface.

Diameter

2.0

2.5

3.25

Length

250/300

350

350/450 350/450

4.0

5.0

6.0

450

450

Amperage

40-80

50-100 90-150 120-200 180-270 220-360

Length of arc

When arc welding with electrodes, it is important that the arc be kept as short as possible in order to avoid the formation of pores and to prevent slag becoming embedded in the weld. A short arc prevents the formation of molten slag ahead of the molten pool. This is of particular importance when welding with basic electrodes. The guiding rule is that the arc gap should be equal to the diameter of the wire core of the electrode.

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