| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To produce a heat-treated steel material by heating a steel material that has a closed cross-sectional shape while transferring the same in its axial direction and suppressing change of heating temperature in the longitudinal and/or circumferential direction. <P>SOLUTION: A production apparatus 10 includes: an induction heating coil 12a that heats a steel pipe 17 to a temperature equal to or higher than the Ac<SB POS="POST">3</SB>point, wherein the induction heating coil 12a is installed at a first position A away from an outside surface 17c of the steel pipe 17 being longitudinally transferred with its first longitudinal end 17a in the forefront; a cooling system 13 that sprays cooling water 13b to the outside surface 17c of the steel pipe 17 at a second position B located at the downstream side relative to the first position A in the transfer direction of the steel pipe 17, thereby quenching the steel pipe 17 while forming a red-hot part 17d between a heating position P1 of the steel pipe 17 heated by the induction heating coil 12a and the spraying position P2 of the steel pipe 17 to which cooling water 13b is sprayed; a temperature measurement system 14 for the red-hot part 17d; and an input power control system 15 that performs feedback control of power input into the induction heating coil 12a based on the measurement result of the temperature measurement system 14. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
