The main component of the electric welding machine is a step-down transformer. The two ends of the secondary coil are welded workpiece and electrode, igniting arc when working, and welding the welding rod into the gap of the workpiece at the high temperature of the arc. Because the core of the welding transformer has its own characteristics, it has the characteristic of rapid voltage drop, that is, the voltage will decrease after the ignition of the electrode, and the voltage will decrease sharply when the electrode is adhered to short circuit. In the welding operation, although the current in the circuit is same, but because all resistance is not the same, not in the fixed contact resistance (the maximum resistance called contact resistance), according to the thermal effect of the current law (also called Joule's law), Q=IR.t indicated that in the current phase, the resistance is more large parts of the heat is high, so the welding electrode contact, the contact resistance was the metal body of the contact at the maximum, electric heating is generated in this part of the most naturally, and the electrode is alloy with low melting point, easy to melt. After melting, the alloy electrode is glued to the welded object, and the welding object is glued to one piece after cooling.
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