Wear mechanism in contact tube

Stable sliding contact is the most important factor in the stable arc discharge of solid wire. If the contact tube wears seriously, arc discharge will become unstable and the wire position will be shifted. Ordinary non-Cu-coated solid wire causes much wear of the contact tube, about 10 times that caused by Cu-coated solid wire. The mechanism of contact tube wear is not only friction at high temperature, but also a molten bridge formed between the contact tube and wire surface. A complex of superfine particles decreases the amount of contact tube wear. For example, the mixture of graphite and magnetite reduces the amount of contact tube wear by 80%. These particles form an interface layer on the inner surface of the contact tube, and the layer prevents the transfer of molten Cu to the wire surface. The interface layer mainly consists of FeO and complex oxides.