Mandrel mill and method of tube rolling by using the same
AssigneeSumitomo Metal Industries, Ltd.
InventorMasayuki Yamada
Life of this patent
Estimating the term…
Abstract
In a mandrel mill for elongating and rolling a hollow shell, with a mandrel bar inserted, by passing the hollow shell, a four-roll stand for diameter reduction used to reduce only the outer diameter of the hollow shell is disposed as the first stand, a group of two-roll stands for wall thickness reduction used to reduce the wall thickness of the hollow shell is disposed following the four-roll stand, and a four-roll stand for eccentric wall cancellation used to cancel any nonuniform wall thickness in the circumferential direction of the hollow shell is disposed as the final stand. The ratio (D.sub.i /D.sub.m) between inner diameter D.sub.i of the hollow shell on the outlet side of the four-roll stand as the first stand and outer diameter D.sub.m of the mandrel bar is 1.05 or less.
Claims8
A mandrel mill having a row of stands comprising a plurality of caliber roll stands for elongating and rolling a hollow shell having an outer diameter and a wall thickness, with a mandrel bar inserted, by passing the hollow shell through the roll stands, comprising:
- a first four-roll stand for diameter reduction disposed as a first stand of the row of the stands to reduce only the outer diameter of the hollow shell;
- a second four-roll stand for eccentric wall cancellation disposed as a final stand of the row of the stands to cancel wall thickness variations in a circumferential direction of the hollow shell;
- and
- a group of two-roll stands disposed between said first four-roll stand and said second four-roll stand to reduce the wall thickness of the hollow shell.
A method of tube rolling for elongating and rolling a hollow shell having an outer diameter and wall thickness, with a mandrel bar inserted, by passing the hollow shell through a mandrel mill having a plurality of caliber roll stands, comprising the following steps:
- passing the hollow shell through a first four-roll stand to reduce only the outer diameter of the hollow shell;
- passing the hollow shell through a group of two-roll stands to reduce the wall thickness of the hollow shell;
- and
- passing the hollow shell through a second four-roll stand to reduce wall thickness variations in a circumferential direction of the hollow shell.
Dependencies are inferred from the claim text.