Electrical news and engineering . the production of a hightemperature ranging from 6300°F. to 7300°F. Arc welding is specially suited to such work as (.a* join-ing of plates or broken parts; (b) building up parts worn byuse: (c) filling blowholes in defective parts; (d) caulkingjoints. Before proceeding to make a repair or to build up wornparts by the electric arc welding process, the material must December 1, 1919 THE ELECTRICAL NEWS be prepared for the operation. All scale, grease and dirtmust be removed from the part on which the welding is tobe done in order to avoid impurities in the weld
Electrical news and engineering . the production of a hightemperature ranging from 6300°F. to 7300°F. Arc welding is specially suited to such work as (.a* join-ing of plates or broken parts; (b) building up parts worn byuse: (c) filling blowholes in defective parts; (d) caulkingjoints. Before proceeding to make a repair or to build up wornparts by the electric arc welding process, the material must December 1, 1919 THE ELECTRICAL NEWS be prepared for the operation. All scale, grease and dirtmust be removed from the part on which the welding is tobe done in order to avoid impurities in the weld. For this,a file, chisel, wire brush or sand blast may be used. Thematerial must then be shaped in such a way that the newmetal being added will touch the original metal over a fairlylarge surface giving opportunity for good fusion to producea strong weld. For electric are welding, both direct current and alter-nating current are used. As these differ widely in the na-ture of the equipment used, and more or less widely in the. T^S Fig. 3—Butt weld. results obtained, it seems advisable to discuss each separ-ately, taking first the one most commonly used, namely, di-rect current. Having prepared the material in the part to be welded,the two leads from the direct current welding panel arebrought along and the positive lead connected securely tothe piece of metal on which the work is to be done; the jobthen becomes the positive electrode. The negative lead isconnected to the electrode holder, a device for gripping apiece of welding wire or stick of carbon, and sufficientlylight in weight to be manipulated with one hand by theoperator. The carbon electrode demands a much more mas-sive holder than the metallic electrode on account of thegreater heat generated with the carbon. This negative elec-trode, either carbon or metallic, will hereafter be referred tosimply as the electrode. The polarity as just mentioned is a very important is estimated that seventy-five per cent
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