| 摘要 |
PURPOSE:To maufacture a steel rod which is excellent in its relaxation characteristics, without deteriorating the characteristics of uniform elongation, by applying very small bending stress to a steel rod heated to a tempering temperature by a stress applying device, in a heat treatment line of the steel rod. CONSTITUTION:A steel rod W fed in the direction as indicated with an arrow by pinch rolls 1, 4 and 11 is made to have linearity by a longitudinal stage roll 2 and a lateral stage roll 3 for correction at first, subsequently, is heated to 900-1,000 deg.C quenching temperature by a high frequency induction heating coil 5, and after that, it quenched and hardened by a water-cooling jacket 6. Subsequently, the steel rod W is heated to a tempering temperature by a high frequency induction heating coil 7, very small <=2% bending stress is applied to the steel rod W by upper and lower, and horizontal stress applying devices 8, 9 consisting of fixed rolls 81, 82, 83 and 84, and moving rolls 85, 86 and 87, and after that, the rod is quenched and tempered by a water-cooling jacket 10, by which it is possible to obtain a steel rod for PC concrete, which is excellent in its various characteristics. |
