| 摘要 |
<p>PURPOSE:To improve the yield during mandrel bar manufacture, by quenching the rear end chucking part of a mandrel bar by high frequency induction heating, then quenching barrel and top and parts thereof to prevent impression generation on mandrel bar surface. CONSTITUTION:While revolving the mandrel bar 1 by a pinch roll 10, at first, the bar is caried into a heating coil 8 from the rear end chucking part 4, wholly quenched uniformly up to shaft core part while repeating reciprocating motion in shaft direction at relatively rapid rate. Meanwhile, since the barrel part 3 is straight after mechanical working and hard before heating, and is not danced on a roll 9, impression is not caused. Successively, the part from the part 3 to the top end part 2 is carried into the coil 8 in shaft direction while being revolved slowly at low rate to perform surface quenching also in this case, since impactive collision against the roll 9 is avoided in such a way, impression is not caused. Consequently, quality of seamless steel tube is improved by dipping the bar 1 to said tube manufacture.</p> |
