| 摘要 |
<p>PROBLEM TO BE SOLVED: To secure the strength of an original component material for a steel pipe without a re-normalizing and tempering process after bending the steel pipe by high frequency induction heating. SOLUTION: In a bending method in which a ferrite steel pipe 1 is heated while moving the position for high frequency induction heating, in which bending is commenced by starting the high frequency induction heating at a prescribed pipe position ahead of a bending starting point 13 and in which heating is continuously done to a prescribed pipe position after a bending finishing point 14; a strength decreasing zone takes place near the starting point 10 and the finishing point 11 of heating due to hot bending by high frequency induction heating; therefore, this zone is cut off and removed. The cutting position near the starting and the finishing of heating is situated sufficiently outside the starting and the finishing of bending; hence, the cross-sectional shape of the cut-off position is unaffected by bending deformation, thereby making edge preparation easy, and giving no trouble in joining with other straight pipe.</p> |
