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Food can body welding machine
The main type of resistance welds used are (a) butt welds; (b) spot
welds; and (c) seam welds. When considering any of these it
must be remembered that in all types of resistance welding the
basic principle is the fusion of two metals together.
When a sufficiently heavy electric current flows through a high
resistance, intense heating takes place. This fact, of course, is
employed in the common fuse, a thin piece of wire which is
melted and breaks the circuit, if the current flowing exceeds the
amount for which the fuse is designed.
In resistance welding, two electrodes, or two clamps, are incorporated in a circuit of low resistance and the metals to be welded together are pressed between the electrodes or held in the two clamps.
The circuit is thus completed and the electrical resistance at the
joint of the metals to be welded together is so high, in
comparison with the rest of the circuit, that if the current is
heavy enough the joint of the metals is heated to a
plastic state necessary for the welding to take place