2005 Volume 23 Issue 2 Pages 220-229
Stable sliding contact is the most important factor for stable arc discharge of solid wire. If the contact tube wore seriously, arc discharge would become unstable and wire position would be shifted. Ordinary non-Cu-coated solid wire has much wear of contact tube about ten times comparing to Cu-coated solid wire. The mechanism of contact tube wear is not only friction at high temperature but also molten bridge formed between contact tube and wire surface. Some 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 interface layer on inner surface of contact tube, and the layer prevents the transfer of molten Cu to wire surface. The interface layer mainly consists of FeO and complex oxides.