JPS574309A - Rolling method for metallic pipe - Google Patents

Abstract

PURPOSE:To improve the production efficiency and product quality as securing the uniformity of cross sectional dimensions of a pipe along its longitude, by controlling the tip of mandrel to a prescribed position during a rolling pass and at the end point of the rolling pass, at practicing a piercing work with a semi-floating mandrel. CONSTITUTION:A mandrel 1 is previously applied with a lubricant oil and is placed in a stand-by position on the upstream side of a piercing mill 3, and a hollow blank pipe MT is laid upon a roller table arranged between a rolling stand 31 and the mandrel 1. The mandrel 1, being detachably held by mandrel holder 2 and controlledly moved forward and backward against the mill 3, is fed forward and is passed through the hollow part of the blank pipe MT and then the mill 3; the tip of mandrel 1 is stopped at a position of a required length l projecting from a stand 38. The length l is optionally selected correspondingly to the material quality of the mandrel 1 and the kind of lubricant oil. The blank pipe MT is then fed to the mill 3; at an optional point of time after starting the rolling work, the mandrel 1 is backward moved until the rear end of the blank pipe MT passes over the stand 38 finishing the rolling work. By the present metod, the metal-to-metal seizure and the abrasion are prevented; the length of tip of the mandrel 1 fitted in the pipe SP at the end point of the rolling work is taken as about 0.3-1m. The mandrel 1 is then released from the mandrel holder 2 and is discharged to the downstream side.