Plasma arc welding method

摘要

A method of operating a plasma welding apparatus producing a plasma arc and having valve means arranged to control gas flow for the plasma arc and power supply means arranged to control welding current for the plasma arc, wherein the plasma arc current, gas flow to the plasma arc and the feed of a filler material to the arc are coordinated for producing a weld. The gas flow and welding current are maintained at a steady rate during the weld run. The gas flow is reduced at a constant rate to a minimum valve of about 30 % of the steady flow rate at the conclusion of the welding run and the welding current is subsequently reduced at a constant rate from the steady value of the welding current. At the start of the weld run, the gas flow is initiated at a rate of about 50 % of the steady flow rate, the plasma arc current is initiated and is increased at a constant rate to the steady value from an initial value sufficient to strike the arc and the gas flow is increased at a constant flow rate to the steady flow rate as soon as the plasma arc has established a keyhole. The feed of filler material is at a constant rate and is initiated immediately before the plasma arc has established the keyhole and continued until the welding current decreases by substantially 20 % from its steady value.