MANUFACTURE OF SEAMLESS STEEL TUBE AND SEAMLESS STEEL TUBE HAVING EXCELLENT INNER SURFACE QUALITY

摘要

PROBLEM TO BE SOLVED: To provide a manufacturing method of a seamless steel tube capable of stably obtaining a product tube of 0.2 mm or less in depth of a flaw in an inner surface and the seamless steel tube having excellent inner surface quality which is obtained by the method. ;SOLUTION: When thinning is applied to a hollow tube stock after piercing and rolling with a stretch mill which is provided witch an inner surface control tool, the inner surface of the hollow tube stock is purged with inert gas, a lubricant whose main component is univalent alkali metal borate and which does not incorporate phosphorus is uniformly coated at 50-300 g/m2 onto the inner surface of the tube just after that, and thereafter stretch rolling is executed.;COPYRIGHT: (C)2000,JPO