| 摘要 |
<p>PURPOSE:To easily draw out a mandrel from a steel pipe, by controlling the number of revolutions of rolling rolls to the specified value to surely keep the gap between the rolled seamless steel pipe and the mandrel, in manufacturing a seamless steel pipe by a mandrel mill. CONSTITUTION:In manufacturing a seamless steel pipe by a semi-floating system which restricts a mandrel to the specified speed; when an unbalance of speed occurs between the (i-1)th stand and the (i)th stand, a tension is produced at the same time when a material (a) to be rolled is bitten by the (i)th stand, and the current values of roll motors of the (i-1)th and (i)th stands change. The front tension is detected by said changed current values, and the number of revolutions of the rolls of the stand in biting is changed so as to return the condition to the condition before biting in order to surely keep the gap between mandrel (b) and a hole of the material (a), thereby easily drawing out the mandrel (b) from the steel pipe (a) and improving the dimensional accuracy of a seamless steel pipe product.</p> |
