| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive and simple manufacturing method of a seamless steel tube by which damage in the body part of a plug is prevented when performing skew piercing of a billet of high alloy steel or the like. SOLUTION: In a Mannesmann skew piercing process, using a hollow billet having a through hole in the center part of a cross section, when the billet is pierced and a lubricant supply tube is inserted into the through hole from the rear end of the billet, thereby supplying a lubricant into the through hole.
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