| 摘要 |
PURPOSE:To save the amt. of a gaseous mixture for preheating by providing plural groups of gaseous mixture holes for preheating of a nozzle and selectively using the gas hole groups in accordance with need. CONSTITUTION:Gaseous mixture hole groups 11, 12 for primary preheating and secondaty preheating are provided respectively on the outside circumference of a cutting oxygen hole 10 of a nozzle concentrically in order from the inner side. When a large amt. of a gaseous mixture for pregeating is necessary, for example, in the case of groove cutting, the work is preheated with the groups 11, 12, and even after the start of cutting with the hole 10, the preheating flames of the groups 11, 12 are continued in succession. On the other hand, if te gaseous mixtre for preheating is required in a small amt., for example, in the case of I type cutting, the work is preheated for a constant time with the groups 11, 12, after which the preheating flame from the group 12 is put out upon starting of cutting with the hole 10, and the cutting is accomplished only by the preheating flame from the group 11. |
