| 摘要 |
PURPOSE: To provide the corrosion resistance of the same degree as that of the base metal to the weld zone by achieving the postheating treatment of a weld seam part after forming the duplex stainless steel strip in an open-tube shape, and achieving the laser beam welding of both edge parts under the prescribed condition. CONSTITUTION: The steel strip stuck made of duplex stainless steel is continuously formed in an open-tube shape, and each edge of the steel strip is butted to each other by a squeeze roll. This butted part is irradiated with the laser beam to achieve the tube-making welding under the condition expressed by the inequalities of P>=0.4Vt/exp(aT)>=20, where P is the laser beam output (KW), V is the welding speed (m/min), (t) is the thickness (mm) of the stock steel strip, T is the preheating temperature ( deg.C) at each edge part of the steel strip, and (a) is the constant (=0.0006), and T=0 deg.C in the case without preheating. After the laser beam welding, the weld seam part is postheated at 1000-1100 deg.C, and the ferritic ratio of the structure of the weld metal is adjusted so that the ferrite ratio as large as that base metal may be approximately 50%. |
