| 摘要 |
PURPOSE:To prevent the formation of a button head having an inadequate shape by preheating the tip of a heading punch up to the saturation temp. of the heading punch shown by a heading cycle time in the stage of starting the operation of a warm heading machine. CONSTITUTION:A heading punch 2 is driven prior to a heading sequence and the tip 21 of the punch 2 is inserted into the prescribed position in an induction heating coil C. The coil C is then energized to preheat the tip 21 until said part is uniformly heated up to the saturation temp. of the punch 2 substantially higher than 450 deg.C which is the formable line for the button head of a normal shape. Thereafter the punch 2 is advanced to a position L in a direction (a) and a PC steel bar W is inserted in a direction (d) up to the position L and is held by a chuck mechanism 1. The bar W is heated to a prescribed temp. by the coil C and the punch 2 is slowly advanced in the direction (a), thereby forming a button head WH to the bar W. |
