Patent ID: 6248972
Filing Date: 2001-06-19
Classification: B23K

Abstract:
A method of cutting a work using a plasma arc, comprising the steps of:supplying working gas between an electrode and nozzle;igniting a pilot arc between said electrode and said nozzle;shifting said pilot arc into a main arc between said electrode and the work;cutting said work using said main arc; andextinguishing said main arc when cutting off said work has been completed; in which said step of supplying the working gas comprises the steps of:(1) supplying nitrogen gas, air, or a mixed gas of nitrogen concentration higher than that of air in a pre-flow interval when the pilot arc is ignited; and(2) supplying a mixed gas containing oxygen and nitrogen in a main flow interval by supplying a mixed gas with an oxygen concentration of 70 to 95 mol % and a nitrogen concentration of 30 to 5 mol % when said work is being cut.