| 摘要 |
A mandrel mill for rolling a tubing in a pass between a mandrel bar and a plurality of serially arranged roll stands. Each roll stand has a plurality of pairs of grooved rolls whose grooves are paired to define a part of the pass. The grooves of the rolls of a first roll stand define a hole having a circumference of not more than 1.12 times the outer circumference of a tubing at the exit of the final roll stand. The grooves of the second-stand rolls define a hole having a circumference of not more than 1.06 times that outer circumference, and those of the third-stand rolls define a hole having a circumference of not more than 1.02 times that outer circumference. Thus, the mandrel mill is capable of preventing stripping miss even when the billet is of a high-alloy steel. <IMAGE>
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