FR2585268A1 - Pilger rolling, drawing and coiling of long tube - Google Patents

Abstract

In a method of pilger rolling, drawing and coiling of tube of great length in one working operation in a rolling mill, with rolling stand moving backwards and forwards and feed and turning of the tube in alternate directions, drawing of the tube takes place through the immediately following coiling in the same working operation. Specifically the tube is drawn by at least 25% redn. and a buffer zone is provided with storage capacity for at least the length of the tube which is rolled without redn. in rolling speed, in the time for prepg. the tube for drawing. The max. storage capacity is available when the tube tip is prepd. for drawing.

Description

The present invention relates to a method for rolling with pilgrim steps, stretching and winding long tubes in a series of operations, as well as a device for carrying out said method.

Already known, from patent DE-OS-3 146 284, a process for rolling with pilgrim steps, stretching and winding long tubes in a series of operations in a rolling mill with rolling mill cage with reciprocating movement calibrated therein, comprising effective intermittent advance and rotation of the tube in the area of one or two dead centers, the reciprocal rotation being the same in each direction and the irregularly cyclic speed of the rolled tube being transformed into a constant output speed in a buffer zone deviating the tube from the direction of rolling and the tube being wound up following the buffer zone.

 It is moreover known, from patent DE-PS-841896, to cold stretch a tube after rolling with pilgrim steps in a series of continuous operations.

The object of the invention is to develop the method of the prior art mentioned above, as well as the corresponding device, in the sense that the extent of the deformations in cross section of the tube in a series of operations can be increased by importantly.

To this end, the process for rolling with pilgrim steps, stretching and winding long tubes in a series of operations, of the type described above, is remarkable, according to the invention, in that stretching the tube has takes place in the same sequence of operations by directly associated winding.

According to another characteristic of the invention, the tube is cold drawn with a reduction in cross section of at least 25%.

According to yet another characteristic of the invention, the storage capacity of the buffer zone corresponds at least to the length of tube, which is rolled without reducing the rolling speed in the time necessary-to grasp, stopper, grease and tender - the tube before the start of drawing and which is sufficient for the transformation of the intermittent rolling speed into a constant rolling speed.

In particular, the maximum storage capacity of the buffer zone is available when the end of the tube is prepared for the drawing process.

According to another characteristic of the invention, the angle of deviation of the buffer zone amounts to at least 600.

According to yet another characteristic of the invention, the drawing speed depends on the average instant rolling speed, the length of stored tube decreases continuously over the time during which it is rolled, as well as drawn, and the speed of stretching is increased after lamination of the tube end until, until the next length of tube is entered, plugged and greased, the previously stretched tube package is discharged and the device is ready to receive the length next tube.

The invention also relates to a device for implementing said method, of the type comprising a rolling mill with cold pilgrim steps with a device for rotating the tube in the area of one or two dead spots, a buffer area for transforming the irregular speed cyclically at a constant speed, as well as an angle device connected to the buffer zone, remarkable in that, according to the invention, a drum stretching machine is provided as a device for 'angle, which is associated, upstream, a device for gripping, plugging and greasing the tube.

In particular, the device for gripping, plugging and greasing the tube is stationary behind the buffer zone, or else, the device for grasping, plugging and greasing the tube can be moved forward as much as possible with a speed corresponding to the rolling speed for the time required to grasp, stopper and grease.

According to yet another characteristic of the invention, the buffer zone is produced in the form of a loop pit known per se, in which the tube, thanks to its self-weight, is deflected first of all outside the rolling plane and , behind the loop pit, is brought back into the rolling plane.

The advantage of the invention consists essentially in that an increase in yield of about 25-50% is obtained depending on the reduction in the stretching machine, when the total deformation of the device according to the invention corresponds to that of rolling mill without cold drawing apparatus and if the cross-sections of tube created are different. In addition, there is the possibility of loading larger magnifying glass cross-sections and thus larger magnifying weights for identical magnifying glass lengths.

This leads to longer tube lengths in the stretching machine and, consequently, to higher profitability. In addition, the larger magnifying glass cross-sections lead to more favorable conditions for the magnifying glass creation sector.

By using magnifying glass cross sections, as provided in the prior art, the extension in the cold rolling mill can be decreased due to the extension in the drum stretching machine and thus an increase in 25-50% advance can be obtained.

As a result, an increase in yield of about 25-50% is possible.

For usual magnifying glass dimensions, extensions and advances, the tube cross-section can be reduced so much that a lower number of draws in the drawing machine leads to higher profitability. In addition, coarser rolling tolerances can be allowed by pre-stretching for low drawing speeds, which have repercussions either on the increase in yield by means of larger advances, or on the reduction of costs. By relatively slow drawing on a flying mandrel, the rolling emulsion outside the tube is removed, so that a rolling emulsion plug in the drawing machine, for high drawing speeds, does not more leads to tube tears.

Finally, another advantage must be mentioned which compensates for a disadvantage of the state of the art.

In the prior art, it is necessary to lower the number of cycles when loading into the retainer and the folding apparatus. Thanks to the device according to the invention having a movable device for gripping, etc., this reduction in cycles disadvantageous for the efficiency of the installation no longer exists. It should also be noted that the drive power for the retainer and the bending device of a winding device can be used in the stretching process so that the total energy requirement of the installation s 'lowers.

The figures of the appended drawing will make it clear how the invention can be implemented. In these figures, identical references designate similar elements.

Figure 1 is a schematic view of a first embodiment of the device according to the invention.

Figure 2 is a schematic view of another embodiment with deviation of 900 from the tube.

A copper magnifying glass with an outside diameter of 80mm and a wall thickness of 10mm must be transformed into a tube with an outside diameter of 33mm and a wall thickness of 1.5mm.

Cold rolling pass: 80 x 10 to 40 x 1.9
Elongation coefficient: 9.67
Discount: 89.7%
Feed: 16mm
Laminated tube at each stroke: 155mm
Cycles / min: 145
Rolling speed: 22.5m / min
Drum stretch: 40 x 1.9 to 33 x -1.5
Elongation coefficient: 1.54
Discount: 35%
Drawing speed: 22.5m / min
A length of tube to be stored of 3.75m corresponds to an assumed duration of 10 seconds to plug, grease internally and grasp.

Referring to Figure 1, a magnifying glass 1 is rolled into a cold-rolled tube 4 by means of a rolling mill 2 and a mandrel 3 in the displacement zone ET to AT of the rolling mill stand. The tube 4, in the buffer zone 5, changes direction from 1800 towards the device 6, in which the tube is grasped and greased internally and in which the drawing plug is placed. A drum drawing machine 7 now stretches the tube with a uniform drawing speed into a coil. When the end of the tube reaches device 6, the tube forms a Y loop in the buffer zone, which, at the start of stretching and during stretching, is pushed into position X.

The difference a then corresponds, for a constant radius r to the half-length of the tube to be stored, that is to say 1.87 m for the example chosen.

In the device according to FIG. 2, the tube changes direction by 900. The value a is, in this case, equal to the radius of curvature plus the length of tube to be stored, that is to say that for the example chosen, a = r + 3.75m.

For the two embodiments, there is provided, before the start of the buffer zone, a greater straight distance, for example of 50 m, which compensates for at least part of the torsion of the tube due to the alternating rotation of the tube and which forms a time reserve for removing the wound tube from the stretching drum.

and to prepare the device 6 again.

Claims (10)

1. Method for rolling with pilgrim steps, stretching and winding long tubes in a series of operations in a rolling mill with rolling mill stand with reciprocating movement and calibrated cylinders therein, comprising intermittent effective advance and rotation of the tube in the area of one or two dead centers, the reciprocal rotation being the same in each direction and the irregularly cyclic speed of the rolled tube being transformed into a constant exit speed in a buffer zone deviating the tube from the direction of rolling and the tube being wound up following the buffer zone, characterized in that the stretching of the tube takes place in the same sequence of operations by directly associated winding. 2. Method according to claim 1, characterized in that the tube is cold drawn with a reduction in cross section of at least 25%. 3. Method according to claim 1 or claim 2, characterized in that the storage capacity of the buffer zone corresponds at least to the length of tube, which is rolled without reducing the rolling speed in the time necessary to enter, stopper, grease and tighten the tube before the start of stretching and which is sufficient for the transformation of the intermittent rolling speed into a constant rolling speed. 4. Method according to any one of the preceding claims, characterized in that the maximum storage capacity of the buffer zone is available when the end of the tube is prepared for the drawing process. 5. Method according to any one of the preceding claims, characterized in that the angle of deviation of the buffer zone amounts to at least 600. 6. Method according to any one of the preceding claims, characterized in that the drawing speed depends on the average instant rolling speed, the length of stored tube continuously decreasing in the time during which it is rolled, as well as drawn and the drawing speed is increased after lamination of the tube end until, until the next length of tube is entered, plugged and greased, the previously stretched tube package is discharged and the device is ready to receive the next tube length. 7. Device for implementing the method according to any one of claims 1 to 6, of the type comprising a rolling mill with cold pilgrim steps with a device for rotating the tube in the area or two dead spots, an area buffer for cyclically forming the irregular speed in a constant speed, as well as an angle device connecting to the buffer zone, characterized in that, as an angle device, a stretching machine is provided drum (7), which is associated, upstream, a device (6) for gripping, plugging and greasing the tube (4). 8. Device according to claim 7, characterized in that the device (6) for gripping, plugging and greasing the tube (4) is stationary behind the buffer zone (5). 9. Device according to claim 7, characterized in that the device (6) for gripping, plugging and greasing the tube (4) can be moved forward as much as possible with a speed corresponding to the rolling speed for the time required to grasp, stopper and grease. 10. Device according to claim 7, characterized in that the buffer zone (5) is produced in the form of a loop pit known per se, in which the tube (4), thanks to its own weight, is deviated completely 'first out of the rolling plane and, behind the loop pit, is brought back into the rolling plane.