GB2145021A

GB2145021A - Rolling mill

Info

Publication number: GB2145021A
Application number: GB08420732A
Authority: GB
Inventors: Klaus-Peter Schirmag; Manfred Bellman; Horst Biller
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1983-08-15
Filing date: 1984-08-15
Publication date: 1985-03-20
Also published as: IT8421850A1; IT1174607B; GB8420732D0; DE3329763A1; IT8421850A0; FR2550718A1; JPS6044109A

Abstract

A rolling mill for reducing and sizing rolling of pipes has several roll stands arranged successively in the direction of rolling. Each roll stand has two driven rolls 1 and the rolls in successive stands are arranged rotated through 90 DEG about the rolling axis with respect to each other. Non-driven rolls 2 are arranged between the two driven rolls 1 in each stand, and the looping angle 8 of the driven rolls 1 is greater than that of the non- driven rolls 2. Groove wear is substantially reduced, so that with respect to the relative speed between roll and pipe, rolling conditions are produced similar to those of a 3-roll stand but with a much simpler initiation of moment of rotation and roll mounting. <IMAGE>

Description

SPECIFICATION Rolling mill for the reducing and sizing rolling of pipes The invention relates to rolling mills for the sizing rolling and/or reducing of pipes. Parti cularly it relates to such mills in which succes sive roll stands with driven rolls are arranged for the passage therethrough of the material to be rolled.

A rolling mill of the above type is known from German Patent No: 366 710 for the reducing of pipes, which has four driven rolls per stand. The roll gap of the stands placed one behind the other is rotated in each case through 45 with respect to each other, so that the roll gap marking on the rolled material lies in the groove base of the following stand. This results in considerable groove wear. In this mill, mounting of the rolls is difficult, and initiation of moment of rotation is expensive.

In the pipe reducing rolling mill disclosed in German Patent No: 675 180, two driven rolls are provided per stand, and the rolls of stands lying one behind the other are rotated in each case through 90". In this arrangement the roll gap marking likewise always lies in the groove base of the following stand. The consequence of this is again a high degree of roll wear and a relatively poor pipe surface. The groove wear is also intensified by the high relative speed between the rolls and the pipe.

The present invention seeks to reduce groove wear in rolling mills of the above general type so that with respect to the relative speed between roll and pipe, rolling conditions are produced as in rolling with a 3-roll stand, but with a much simpler initiation of moment of rotation and mounting of the rolls.

According to the invention a rolling mill for the reducing and sizing rolling of pipes has a plurality of roll stands arranged successively in the direction of rolling, each roll stand comprising two driven rolls and two rolls arranged as drag rolls, the looping angle of the driven rolls being greater than that of the rolls running as drag rolls, and the driven rolls in successive stands being arranged rotated through 90 about the rolling axis with respect to each other.

It is preferred that the looping angle of the driven rolls is so much greater than that of the rolls running as drag rolls that the direction of the roll gaps from the rolling axis forms an angle of approximately 1 5 to 35 to the plane of the drag rolls. The preferred looping angle of the rolls running as drag rolls is thus in the range 30 to 70 . It is also preferred that the diameter in the groove base on the driven rolls is greater than that on the rolls running as drag rolls.

In a typicai embodiment of the invention the rolling mill is broadly of the universal rolling mill type. The rolls forming a groove deviating from this however, are mounted between two plate-shaped half stands and the stands mounted in a larger number in a stand frame. In each case two rolls of a stand are driven. The stands are arranged at a small distance from each other in the direction of rolling.

It was recognized early in the development of pipe rolling techniques that the forming conditions are better, the more rolls form a groove. However, already in the 3-roll groove the structural expenditure rose so much through the use of bevel gears that suggestions with more than three rolls for a groove came to be used as individual special section roll stands.

In rolling mills according to the invention, no roll need have a substantially greater looping angle than the rolls of a 3-roll-groove and thereby no greater relative speed is produced between roll and pipe. With respect to groove wear and the deformation, it is also advantageous that the marking of the roll gap on the rolled material does not run into the groove base of the rolls of the subsequent stand. The wall thickness of the rolled material consequently is very regular in its circumference. This regularity is further enhanced by appropriate selection of the diameter of the drag rolls which can differ from that of the driven rolls. We have also found that the surface quality of pipes rolled on an installation according to the invention is greatly improved in comparison with prior techniques, and can in some circumstances be substantially flawless.

In addition to the above benefits, the structural expenditure in a mill according to the invention corresponds substantially to that of a rolling mill with roll stands having only two rolls. This applies whether the roll axes of the driven rolls are arranged alternately horizontally and vertically in successive stands, intersecting each other at 45 to the horizontal, or at any other angle.

The invention will now be described by way of example and with reference to the accompanying schematic drawings wherein: Figure 1 shows a view of a roll stand in rolling direction without a front plate, Figure 2 shows a perspective view of the two sets of rolls A and B standing one behind the other.

Each stand of the rolling mill according to the invention consists of a plate-like stand half 3 and four rolls, namely of two driven rolls 1 and two rolls 2 running as drag rolls. The rolls are mounted on both sides in bearings 4 between the stand halves 3. The driven rolls 1 are drawn here with an horizontal axis and are driven via the gear coupling 5 from a drive not shown.

The rolls 1 and 2 form a groove, the radius of which, except in the case of the last respective sizing stand, increases somewhat from the groove base 6 toward the roll gap 7.

The looping angle 8 of the driven rolls 1 is greater than that of the rolls 2 running as drag rolls, preferred angles being 1 10 to 150 and 30 to 70 respectively. As shown, each roll 1,2 has bevelled edges, the bevel surfaces defining the respective looping angles, and substantially parallel roll gaps.

In the embodiment shown in Fig. 1, initiation of the moment of rotation takes place into the driven rolls 1, specificaily to both rolls from one stand side via the couplings 5. Thus a compact structure is ensured, with simple handling even on changing stands.

According to the invention the driven rolls 1 and hence also the rolls 2, running as drag rolls, are arranged rotated through 90 about the rolling axis on successive stands. This is shown in Fig. 2 on successive stands A and B. For clarity, the structure of the respective stands is not shown. With this arrangement, and with the looping angles of the driven rolls and those running as drag rolls not being equal, the roll jump marking on the rolled material changes in successive stands, but does not lie in the groove base of the following stand.

Claims

1. A rolling mill for the reducing and sizing rolling of pipes having a plurality of roll stands arranged successively in the direction of rolling, each roll stand comprising two driven rolls and two rolls arranged as drag rolls, the looping angle of the driven rolls being greater than that of the rolls running as drag rolls, and the driven rolls in successive stands being arranged rotated through 90 about the rolling axis with respect to each other.

2. A rolling mill according to Claim 1 wherein the looping angle of the rolls running as drag rolls are each in the range 30 to 70'.

3. A rolling mill according to Claim 1 or Claim 2 wherein the diameter in the groove base on the driven rolls is greater than that on the rolls running as drag rolls.

4. A rolling mill for the reducing and sizing rolling of pipes substantially as described herein with reference to the accompanying drawings.