Mandrel pipe-rolling installation, and method for producing seamless pipes

摘要

The installation for producing seamless pipes consists of a series of rolling units for rolling and stretching pipe blanks (1) with the use of a mandrel (5). It is characterised by the following facts: (a) the first rolling unit in the series is a four-roll unit (2) which serves solely for reducing the outside diameter of the pipe blank (I); (b) the last rolling unit of the series is a second four-roll unit (4) which serves for eliminating wall eccentricities, namely, for eliminating wall thickness deviations of the pipe blank in the circumferential direction; (c) a group pf two-roll units (3a-3d) serving for reduction of the wall thickness of the pipe blank is positioned between the first and second four-roll unit (2,4). The ratio (Di/Dm) of the inside diameter (Di) of the pipe blank at the exit from the four-roll unit (2) and the outside diameter (Dm) of the mandrel is maintained equal to or less than 1.05.