| 摘要 |
<p>A contact tube guides and supplies current to the wire electrode in an arc welding machine. The tube is preferably copper, with a central bore through which the wire passes. The end of the tube where the electrode emerges is covered by an electrically insulating protective piece, to which molten metal from the weld pool does not adhere. It is made of high temperature refractory, such as alumina or chromium dioxide, and held in place by a sheath of similar material pushed over it and also protecting the sides of the tube. Spring loaded balls, held in place by the sheath, ensure good electrical contact between wire and tube. Protecting the end of the contact tube reduces problems due to the build-up of splashed weld metal. Deposits around the central bore restrict the regulated advance of the welding wire. Where a gas shield is provided by a surrounding nozzle they can also restrict its flow.</p> |
