Abstract: A process for applying a weld overlay to a tube with a single pass of a weld head. An inverter-type alternating current pulsed power source, composed of a primary inverter and a secondary inverter, is used to control the melting rate of welding wire during welding of the overlay to the tube. The primary inverter controls the value of output current, and the second inverter changes the polarity of output current between electrode negative. For a given welding current, the wire melting rate increases significantly as the electrode negative ratio increases, and this makes a relatively high welding speed attainable. Increasing the electrode negative ratio at a fixed, predetermined wire feed rate decreases the weld penetration depth, which correspondingly lowers the dilution rate and results in a smooth and narrow welding bead.

Abstract: A process for applying weld overlay material to a tube with a single pass of a weld head. A gas tungsten arc welding process with high frequency wave pulse current is preferably used to apply the overlay material. The overlay material is preferably in the form of weld wire and is pre-heated and mechanically fed into the resultant weld pool on the tube. The wire is preferably resistance-heated to a temperature lower than its melting point prior to contact of the wire with the molten weld pool, and the weld pool is preferably oscillated during the overlay process. Use of the gas tungsten arc welding process provides sufficient weld fusion to allow the overlaid tube to be subsequently bent and formed, and use of the high frequency wave pulse current provides for reduced dilution of the overlay.