| 摘要 |
PURPOSE:To prevent a cut surface from being nitrided, and to improve the durability of an electrode by starting a plasma cutting by a plasma gas consisting of oxygen and nitrogen of specified mol%, respectively, and subsequently, executing the cutting by switching to an oxygen gas of >= prescribed %. CONSTITUTION:A mixed gas solenoid valve 9 is provided on a leading-in pipe 11 of a mixed gas of 70-10% oxygen and 30-90% nitrogen, and also an oxygen solenoid valve 8 is provided on an oxygen gas leading-in pipe 12 or >=95% oxygen. After the solenoid valves 9, 8 of the leading-in pipes 11, 12, they are unified as a plasma gas feed pipe 10, and connected to a plasma gas passage 7 of a plasma cutting device. When a plasma cutting is started, the solenoid valve 9 is opened, the solenoid valve 8 is closed, and the plasma cutting is executed by a mixed gas. Subsequently, when the start is completed, the solenoid valve 8 is opened, the valve 9 is closed, and the gas is switched to oxygen by a timer. According to this method, a nitrided layer of the cut surface is prevented, and also the durability of an electrode is improved. |
