| 摘要 |
PROBLEM TO BE SOLVED: To provide the inexpensive and simple manufacturing method of a seamless steel tube by which the 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, a material to be pierced has a through hole in the center part of a cross section and, furthermore, a lubricant is blown into the inside of the through hole from the rear end of the material to be pierced on the inlet side of a skew piercing machine before piercing.
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