fresa para mandril, método de operação desta e método de produção de tubo sem costura.

摘要

The object of the present invention is to provide a mandrel mill capable of producing a seamless pipe without flaws such as necking. The mandrel mill of the present invention includes a plurality of consecutively provided grooved-roll stands and a mandrel bar 3 provided in a roll groove array formed by the grooved-roll stands so as to continuously elongate a hollow shell 2. Roll grooves 4 of at least a first stand and a second stand are arranged so as to satisfy conditions represented by the following formulas (1) to (4): b ‰¤ 10 �¢ a + 1.5 b ‰¤ - a + 1.5 b ‰¥ 10 �¢ a - 0.2 b ‰¥ - a + 1.15 wherein a = S/R1, b = C/(R1-S).