Electric Welding
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-432
2025-12-17
25
The heating effect of the current is used effectively in electric welding. For this purpose heavy currents are used, such as are supplied from the low-voltage side of a step-down transformer. ….
Demonstration. - Couple two insulated copper bell wires to a 110-volt circuit in series with a 110-volt lamp; hold them touching end to end: The current passing through the high resistance of the junction of the two wires will produce so great heat that the ends will melt and on being pushed together the wires will become welded and form a single conductor.
This is an example of what is known as resistance welding. The pieces to be welded are held together end to end and when the metal becomes plastic the ends are pushed together and the current turned off. Special machines are used to perform these operations in regular succession.
Another type of electric welding, called spot welding, is used to weld one sheet of metal to another. Two large electrodes are used to press the metal surfaces together and to localize the heat of the current. These electrodes are shown at E in Fig. 1. The pieces to be welded are placed between the electrodes and on pulling down the lever L or pressing down the treadle T the pressure is applied and the current turned on for the few seconds necessary.
Another form of welding, called seam welding, makes use of the great heat of the electric arc.
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