| 摘要 |
PROBLEM TO BE SOLVED: To provide a forged pipe not cracked from a joint even when performing severe working such as flaring.SOLUTION: A forged pipe is manufactured by heating a steel strip across its full width by a heating furnace, increasing the temperature of its edges by high frequency heating and/or with heat of oxidation by oxygen or air spraying, and thereafter abutting and forging the edges. In the forged pipe which is excellent in workability, a flattening height (H) by a flattening test in which a joint of the forged pipe is set to be the vicinity of one end in a crushing direction is not more than a critical flattening height ratio (HL2) defined by the following <1> formula using a ratio (R2) of a bead part maximum thickness to a pipe thickness. <1>: HL2=-6.0×R2+6.56. |
