IGNITION METHOD FOR MAIN PLASMA ARC IN NON-KEY HOLE TYPE PLASMA ARC WELDING

摘要

PURPOSE:To enable the use of nonconsumable electrode for a long period without its readjustment by adding inpulsive center shock gas to center gas and enlarging the flow rate of center gas in an instant in case of igniting the main plasma arc. CONSTITUTION:A pilot arc is ignited by the DC power source 11 for the pilot arc between a nonconsumable electrode 1 and constraining nozzle electrode 2. The plasma welding is then performed without forming a key hole on the body 12 to be welded by igniting the main plasma arc via a plasma flow between the nonconsumable electrode 1 and the body 12 to be welded by the DC power source 10 for welding. In case of this plasma arc ignition, the center gas is fed from a flow paths 13, and the impulsive center shock gas is added from a flow path 15 to the center gas to enlarge the flow rate of the center gas in an instant. The ignition of the main plasma arc is thus made easy by projecting the pilot arc to the external part from the tip of the constraining nozzle electrode 2.