| 摘要 |
PURPOSE: To manufacture by laser welding a welded tube the welded zone of which is free from breaking under a high degree of working. CONSTITUTION: In welding by laser welding both ends in the width direction of a metallic belt 1 formed cylindrically, assume the thickness of the metallic belt 1 is t (mm), outer diameter of the welded tube to be manufactured D (mm), output of a laser welding machine P (kW), and tubing speed V (m/min). With a relation between the thickness ratio t/D and the hardness HVS of the base material expressed as HVS=f (t/D), and with a relation between the output ratio P/(V.t) and the hardness HVW of the welding zone as HVW=g[P/(V.t)], the output ratio P/(V.t) is determined so that the difference ΔH(=HVWHVS) between the hardness of the base material HVS and that of the welding zone HVW may be larger than 0 but not larger than 100 desirably 10 to 80. Even under a high degree of working such as bulging and pipe-exponding, the welding zone is free from cracks, enabling the working in various shapes depending on the use. |
