| 摘要 |
PROBLEM TO BE SOLVED: To obtain a formed steel tube in which removal of residual stress and recovery of toughness can be attained, and twisting, bending and deformation hardly occur. SOLUTION: At a heat treatment part, a plurality of heating zones 25A to 25c and hold zones 26A to 26C are alternately arranged, respectively. Each cold-formed steel tube 1 is alternately moved to each heating zone and hold zone in succession, is stepwise heated-up in the group of the heating zones 25A to 25C, and is further held in the group of the hold zones 26A to 26C in the condition of the temperature raised by the heating zones 25A to 25C. The heated formed steel tube 1 discharged from the hold zone 26C in the final stage is annealed. COPYRIGHT: (C)2006,JPO&NCIPI
|
