| 摘要 |
PURPOSE:To start an arc stably by generating the arc in the gaseous Ar atmosphere formed between the work and an electrode and including a dissimilar gas in said gas after stabilization of this arc. CONSTITUTION:Prior to arc starting, gaseous Ar which is low in potential inclination and is easy to generate arcs is ejected as the 1st working gas G1 through the leading end of a plasma torch 1. After the time T1 when the Ar is filled, a pilot arc is fired between the nozzle electrode 1b and nozzle electrode 1a on the inner side of a torch 1. When this pilot arc transfers to the plasma arc 2 generated between the electrode 1a and the work 5, the output current from an electric power source 4 increases and therefore it is detected with a current detector 7. After the time T3 from this detection, the supply of the 2nd working gas G2 consisting of dissimilar gases of Ar+H2, Ar+N2 or N2 is started and is mixed with the gas G1. After the supply of the gas G2, the work 5 and the torch 1 are moved relatively. |
