Roll pass design for a pipe reducing rolling mill

Details Roll pass design for a pipe reducing rolling mill Roll pass design for a pipe reducing rolling mill

1997-08-14

1998-10-06

Hail, III, Joseph J.

Metal deforming

By use of roller or roller-like tool-element

Included in roller-cluster

72235, 72181, B21B 1310

Patent

active

058160922

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention is directed to a roll pass design for the sets of rolls of a non-mandrel type multiple-stand pipe reducing rolling mill. Each set of rolls has three rolls, in which the concave groove contours of the rolls are curved out in a convex manner at both sides of every roll.
2. Description of the Prior Art
In pipe reducing rolling mills, especially stretch-reducing mills which operate without an internal die, a phenomenon referred to as corner formation or polygon formation occurs as a result of the rolling process. With this phenomenon, the inner diameter of the pipe has a shape which diverges from the circular cross section and which can be described as a rectangular cross-sectional shape with rounded edges when using two roll passes and as a hexagonal cross-sectional shape with rounded edges when using a three-roll pass.
Various suggestions have been made for preventing this so-called polygon formation in the interior of the pipe. However, in essence, these suggestions have yielded inadequate results or require heavy expenditure.
A meaningful suggestion for this problem is described in German Patent 24 48 158. Based on the realization that the extent of the inner polygon becomes less pronounced as the quantity of roll sets used in the pipe reducing mill increases, the known prior art suggests approximating the deformation ratios of a roll set formed of three rolls to the deformation ratios of a roll set formed of six rolls. For this purpose, the groove contours of the rolls are curved out at the sides of the rolls.
The suggestion made in the prior art known from DE 24 48 158 does not take into account the fact that the proposed roll pass shape is not suitable by itself to render the deformation state homogeneous. Accordingly, the known solution incorrectly predicts the effect of the roll pass shape on the material flow. Disadvantageous tension states are brought about in the pipe during rolling and result in thickened locations in the finished pipe along the circumference of the pipe.


SUMMARY OF THE INVENTION

Proceeding from German Patent 24 48 158 and based on the roll pass shape suggested therein, the object of the present invention is to improve the roll pass design for a pipe reducing mill so that the flow of material in the pipe is acted upon locally in such a way that the occurrence of local thickening of the pipe wall at critical points along the circumference of the pipe during reduction is decreased so as to prevent the thickened locations encountered on the finished pipe.
In order to meet this object, the invention proposes that the magnitude of the curvature of the roll pass flanks in the known groove contour design be increased by constant amounts or by equal percentages in the rolling direction of successive sets of rolls. This suggestion is based on the insight that the known curvature has no effect on the flow of material if the reduction in the roll pass flanks brought about by the curvature does not exceed the reduction occurring in the groove base or roll pass gap in each stand of a plurality of successive working stands. Consequently, the height of the curvature must be increased from one stand to the next in the series of passes. The inventive suggestion results in the advantage that the local curvature increases the local contact pressure in every stand so as to counteract a thickening of material in the center of the roll pass flank. If polygon formation occurs in the finished pipe, that is, if the present invention is not applied, the wall thickness will be enlarged in the finished pipe at this location compared with the rest of the pipe circumference. The steps suggested by the invention counteract this thickening.
According to an advantageous embodiment of the invention, the increase in curvature corresponds to 1 to 5% of the pipe wall thickness of the pipe to be rolled in the roll pass.
In a further embodiment of the invention, the summit or apex of the curvature of each roll pass flank is shifted by 30 to 35 degr

REFERENCES:
patent: 3952570 (1976-04-01), Demny et al.
patent: 4099402 (1978-07-01), Biller
patent: 4277967 (1981-07-01), Staat et al.

Affiliated with

Also associated with

Rating

Roll pass design for a pipe reducing rolling mill does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Roll pass design for a pipe reducing rolling mill, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Roll pass design for a pipe reducing rolling mill will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-67978