THICKNESS CONTROLLING METHOD OF SEAMLESS PIPE

摘要

PURPOSE:To make thickness distribution in longitudinal direction of a seamless pipe after elongation surely uniform by controlling a piercer from bulge width distribution in longitudinal direction of a mandrel mill that elongates a hollow blank pipe pierced by a piercer. CONSTITUTION:In a mandrel mill 20 that manufactures a seamless pipe using a mandrel bar 18 and plural rolls 20a from a hollow blank pipe 16 obtained by piercing by a piercer 14 using a piercing plug mandrel 14b, the piercer 14 is controlled by a controlling device 32 through a plug positioning device 14d and a working roll clearance fixing device 14e to obtain target thcikness distribution in longitudinal direction of the pipe after percing basing on bulge width distribution in longitudinal direction of the blank pipe 16 during rolling obtained by measuring with a photoelectric bulge width meter 30 provided on the intermediate stand or by guessing from the rolling load in a proper stand.