| 摘要 |
PROBLEM TO BE SOLVED: To provide a method which prevents heat deformation of a steel member, and ensures the cutting quality at the starting point of gas cutting by cutting of the steel member after completion of the preheating process. Preheating is applied to a target position of the steel member after positioning the burnt gas flame for preheating in an incised hole which is formed by laser beam in the steel member. SOLUTION: A preheating process and a cutting process of the steel member 6 using a gas cutting torch is carried out after the incised hole 7 is formed with the laser cutting torch 5 in the steel member 6. In the cutting process of the incised hole, the incised hole 7 for starting gas cutting is formed in the steel member 6 by the laser beam 9 which is emitted from a laser cutting torch 5. The incised hole 7 consists of a circular hole 10 which is 10-50 millimeter in diameter and a cut groove 12. In the preheating process, the steel member 6 is preheated by positioning the burnt gas flame for the preheating in the boundary between the formed circular hole 10 of the incised hole 7 and the cut groove 12. In this case, the preheating time of the steel member 6 is shortened, because the edge formed in the boundary between the circular hole 10 and the cut groove 12 is heated intensively. |
