EP0908245B1 - Method and apparatus for producing tubes by cold pilgrim rolling - Google Patents

Abstract

Disclosed are a method and apparatus for manufacturing tubes, preferably tubes composed of high-tensile steels or special alloys, using the cold pilger rolling method with two rolling stands which can be moved backward and forward, at least in opposite directions at times and in the rolling direction by means of crank drives. The rolling stands have rollers which are calibrated in a tapering manner and which, driven by toothed racks via cogs, roll over the material to be rolled, with an alternating rotation direction. The majority of the forming work takes place on the first rolling stand and a relatively small portion of the forming work takes place on the second rolling stand and additional smoothing work is carried out. Reduction rolling takes place in both rolling stands via a mandrel which is matched to the roller caliber, and the backward and forward movements of the two rolling stands are matched to one another in such a manner that the angular offset between the crank drives is chosen such that the forming zone of the first stand does not occur at the same time as the forming zone of the second stand.

Description

The invention relates to methods and a device for producing pipes, preferably made of high-strength steels or special alloys according to Cold pilger step method with two at least in the rolling direction by means of crank drives at times counter-rotating roll stands with tapering calibrated rollers, driven by racks via pinions, with alternating Roll the direction of rotation over the rolling stock. As the closest state of the Technology can be seen in JP-A-63-260 607.

A significant share of the costs in the manufacture and operation of Cold pilger rolling mills is due to the necessary turning and feed devices as well as the feeders for the cold pilger rolling process are indispensable. A significant improvement in the cost-performance ratio can be achieved if while maintaining these facilities and without A significant increase in performance can be achieved by reducing the number of scaffolding strokes can. One way to do this is to increase the forming work per scaffold lift and Rolling mill, through which with only a small increase in investment costs significant increase in performance is effected. This statement applies to Cold pilger rolling mills in general and especially for the cold pilger rolling of relative small pipes made of high-strength steels or special alloys.

Known cold pilger rolling mills, in which conventional single-strand rolling is used, suffer compared to modern drawing processes at relatively high investment costs at rather low power. In order to increase performance, it has been suggested Cold pilger rolling mills with several, for example two to four, parallel strands operate. However, this means a higher scaffolding weight with a reduced number of strokes, the effort for the loading and the rotary feed devices becomes clear larger and the tolerance of the rolled tubes leaves something to be desired.

So-called tandem cold pilger rolling mills have also been tried to be used in which two pairs of rollers are combined in a stand are. Here, too, the higher scaffolding weight with a low number of strokes is all in one unfavorable price-performance ratio noticeable, roll both sets of rolls at the same time the advanced tube volume, the second set of rollers the rolled tube length of the first roll set during the feed is supplied, which can lead to compression problems in the pipe with performance and quality losses ..

Finally, with the figures 5 and 6 of the German patent 604 909 Cold pilger rolling mill became known, the two in the rolling direction by means of crank drives shows roll stands that can be reciprocated at times in opposite directions, the rollers of which roll over Racks are driven with alternating directions of rotation. The well-known The arrangement provides for the blank in the first roll stand exclusively and without Reduce the diameter of the dome and then the wall thickness in the second roll stand reduce the pipe over a mandrel. The arrangement of the crank drives is like this chosen that the movements of the two rolling stands together with the Movement of the dome rod and gripping of the rollers feed the tube enable in a certain way.

Although the explanation of the operation of the known mill arrangement the does not reveal the exact procedure when rolling the tubes, is determine that this rolling mill can be operated at low power at best could, which was sufficient at the time, but the demands of one modern cold pilger rolling mill no longer does justice. Hollow rolling in the 1st stand leads to an inadmissible deterioration of the inner surface today and causes if any, only a slight increase in performance; because the essential Wall reduction is only carried out in the second scaffolding.

The object of the present invention is cold pilger rolling and a Device for the production of pipes, in particular from high-strength steels or To create special alloys according to the cold pilger step process, in which a significant increase in rolling performance compared to conventional rolling mills with the least possible additional mechanical effort and without loss of quality becomes possible.

To achieve the object, methods according to claims 1 and 2 are proposed.

The methods according to the invention enable extremely high performance firstly, that in the first roll stand only forming work and none Smoothing is done, which significantly extends the Reduction caliber is usable and no performance reducing Tolerance requirements have to be taken into account while in the second mill stand beside the smoothing work is carried out a significant additional forming work.

The choice of the phase angle between the two stands and the design of the Rolling tools are subject to significantly fewer restrictions if the rolls of the release the tube at a second definable time by separately an annular gap is temporarily formed between the tube and the roller. For this purpose provided in a variant of the invention that the second roll stand by 180 Degrees crank angle offset to the first scaffolding and on which Reduction-free return stroke from the material range from the first frame Appropriate annular gap between rolling stock and roll caliber in which the formed tube is inserted in the first roll stand.

It is suggested that the distance of the during the rolling process To change the roller axes cyclically to each other, so that the necessary space in the Roll caliber to create the material supply from the rolling process of the first Rolling mill takes up.

To the mechanical engineering effort for the cyclical generation of the annular gap to save between caliber processing and rolling stock is the invention Alternative suggested that the second mill stand be 90 to 150 degrees Crank angle is offset from the first roll stand and that its rollers are rotationally driven by stationary racks and that the The center distance of the rolls remains constant during rolling.

A device for performing the method is defined in claim 4.

With a cold pilger rolling mill designed in this way, the rolling performance can be compared significantly increase conventional rolling mills. By training the first Roll stand with only working caliber rolls can be Significantly increase the forming work in this stand; because because a smoothing work in This scaffolding does not have to be made, the entire caliber can be processed be used for the forming work. The smoothing work is only carried out in the second roll stand made in the smoothing caliber provided there, but a working caliber is arranged with which an additional, noteworthy reshaping of the Rohres can be accomplished. The mechanical engineering effort remains for receive the rotary and feed drive as well as for loading with new blanks and does not increase compared to a normal simple cold pilger rolling mill. The Arrangement of the crank drive angles to each other allows turning and advancing the slug at favorable times and prevents together with further features of the invention that there is a material jam between the Roll stands comes while the main forming work is on the first roll stand is performed. The opposite direction of rotation of the two cranks allows one favorable balance of mass forces of the first harmonics, making it high Strokes possible compared to a conventional single cold pilger rolling mill do not have to be reduced because the inertia forces due to the chosen construction do not rise.

The mechanical engineering effort for such a crank mechanism is only insignificant higher than for driving a single scaffold. The arrangement of the crank drives with vertical axes of rotation dispenses with deep foundations for the Mass balance. The distance between the two roll stands can be e.g. be minimized if the Push rods of each roll stand in superimposed levels or the two roll stands are arranged above the crank mechanism in such a way that the pivot points for the push rods on the two are furthest apart distant parts of the roll stand.

A common crank mechanism with rotating counterweights on the two opposing crank bends is preferably provided for both roll stands, which counterbalances the first order of the inertial forces, while an at least partial compensation of the inertial forces can take place through the interaction of the stand masses. A phase angle of 90 ° is optimal from the point of view of the balancing of mass forces, because under this condition the second order mass forces also cancel each other out. However, difficulties in rolling technology cannot be ruled out with such an arrangement.
In one constructional variant, the cranks are driven in the same direction of rotation and, with counterweights on the cranks, some of the mass forces of the first order are balanced. The remaining part of this mass force component is compensated not at all or with counterweights on an intermediate shaft connecting the two cranks via gear wheels, which rotates at the crank speed but in the opposite direction.

But it is also possible to have a separate crank drive with each roll stand Allocate mass balance, the drive of the second roll stand then can preferably be made weaker than that of the first roll stand. This makes the drive of the second scaffolding smaller, lighter and cheaper than that of the first roll stand. A change in the phase angle between the two Scaffolding is easy to implement with two separate crank drives.

Furthermore, it is conceivable that the two roll stands in one housing to accommodate driving cranks, but to drive them by separate motors, so that the change in the phase angle of the two cranks is easily possible. The first order mass balance then requires two rotating weights each crank, such that the greater weight is firmly connected to the crank and the smaller one in relation to the crank e.g. than rotatable around the middle of the crank Eccentric is adjustable.

In a further variant of the cold pilger rolling mill according to the invention, the two roll stands of different weights and may even be used moves different strokes, with corresponding counterweights the opposite shafts or cranks for a complete balance of the First order mass forces.

To change the annular gap between caliber processing and rolling stock is provided that at least the racks of the second roll stand with a displacement device for adjusting the Racks are provided in their longitudinal directions.

Alternatively, at least the rollers are excited to adjust the center distance to provide a cyclically usable wedge mechanism of the second roll stand.

The crank drives with a phase angle of To operate 180 ° so that both dead centers are rotated and advanced can. Twisting and pushing twice would be the same as usual Rolling mills are known to further increase both production quantity and quality. In this case, however, the second order mass forces and the Cyclic generation of an annular gap between the rolling stock and the caliber processing appears necessary during the return stroke of the second scaffold.

Cold pilgrims of thin-walled tubes with small diameters are possible with any, for example also with non-incremental rotating and feed movements. When using a rolling mill according to the invention, this thin-walled tube is completed by the second rolling stand. Since the tube can be fed to the second roll stand in any way in this case, the rotation and feed movement can be determined independently of the phase position of the two roll stands only according to the requirements of the first roll stand, for example also as turning and advancing at both dead centers.
With these thin-walled products, the cold pilger process also allows the tube to be turned and pushed forward, even though the rollers still touch the tube on the smooth caliber. This means that the caliber of the rolls of the second roll stand can also be extended to the outlet dead center of this roll stand.

Since the mechanical engineering effort for the rotary and feed drive as well as for the Loaded with new slugs compared to a normal single cold pilger rolling mill is not increased, the rolling mill can be manufactured with a good price-performance ratio become. The rolling mill can be operated with high stroke rates compared to a normal single rolling mill does not have to be reduced because the Mass forces do not increase due to the scaffolding and crank mechanism arrangement. The mechanical engineering effort for the crank drive is only slightly higher than that for the drive of just one scaffold. Of particular note is the fact that the Caliber length of the first stand can be fully used for the forming, since a smoothing caliber is not required here and tolerance requirements are not taken into account can stay. This results in a notable increase in performance, the thereby additionally increasing that a further forming in the second stand takes place. At the same time, there is the possibility compared to previous ones Rolling tools a much longer smoothing caliber in the second mill stand preserved and so the manufacturing tolerances despite the increased production volume further restrict.

Figur 1

eine grob schematische Seitenansicht eines Walzwerkes,

Figur 2

eine Draufsicht auf das Walzwerk nach Figur 1

The invention is explained with reference to a drawing, which is described below. It shows:

Figure 1

a rough schematic side view of a rolling mill,

Figure 2

a plan view of the rolling mill of Figure 1

Table 1 also shows a tabular comparison of two exemplary embodiments

The two roll stands 1 and 2 are so by a common crank mechanism 3 driven that the mass forces of the first order of the two roll stands completely compensate. The counter-rotating counterweights 4 and 5 (FIG. 2) only the rotary ones are the same in this exemplary embodiment Imbalance from cranks and push rods.

Each roll stand 1 and 2 is only by one of the push rods 11 and 12th driven, which move in superimposed levels. this will thereby causes the articulation point to the first roll stand 1 under the same and to the second roll stand 2 is provided in front of this. Enter ET in the dead center both sets of rolls 7 and 8 free the rolling stock for turning and advancing The rolling outlet dead center AT is at most short for an additional turning Approved.

While on the preliminary stroke of the roll stand 1 from ET to AT that Feed volume is rolled out and extended accordingly, the Rolling 7 of the roll stand 2 located on the return stroke by means of a Adjustment device 9 for the racks 10 rotated so that the rollers 8 of the Roll stand 2 when moving from AT to ET not or only insignificantly have a reducing effect. The adjustment mechanism 9 does this in the inlet area Undo adjustment. On the way from ET to AT if that Roll stand 1 on the return stroke practically without plastic deformation work is in the mill stand 2 that on the preliminary stroke of the roll stand 1 before extended feed volume with the length of feed times the extension of the first Scaffold 1 rolled out.

The illustrated rolling mill, which is about twice the performance of a conventional rolling mill, is characterized in that the entire turning, Feed and loading device remains unchanged that the oscillating Compensating masses of a conventional rolling mill with a second rolling stand are replaced, and that only the additional roller axes with their Rack and pinion drives are added.

Below are two exemplary embodiments for further explanation of the invention described, which are listed in Table 1. Example 1 describes a classic stainless steel rolling for heat exchanger tubes, Example 2 explains the exploitation of the great ductility of austenitic steels for one greater cross-sectional reduction.

example 1

In the table there is a classic stainless steel rolling for the "Example 1" Heat exchanger tube 16 x 1 listed, the experience with about 18 mm rolled tube length per stand stroke, which together with 320 Strokes per minute leads to a rolling capacity of theoretically 346 m / h. Here are from the total caliber length of 370 mm 100 mm smooth caliber provided, d. H. approx. 27% that practically do not contribute to the transformation.

In a rolling mill according to the invention, there is no smoothing caliber in the first stand required so that the forming zone is extended accordingly to 370 mm. This and the fact that in the first scaffolding only a reduction from 33 x 3.5 to 20 x 1.5 is provided, allow an at least 15% increase in emissions in mm per scaffold stroke, because not only the finished tube length per stroke but also the Pipe cross section increased from 16 x 1 to 20 x 1.5, there is an increase the weight enforced from 128 to 272 kg / h, d. H. 113% performance gain.

The 5.6 mm advance in the first stand occurs when the 1st stand is in the Infeed and the 2nd scaffold are in the dead center; d. H. the forming in the 1st Scaffolding essentially takes place on its forward stroke when the 2nd scaffolding is on the Return stroke is located. The latter will be in its exit dead center area Feed volume 20 x 1.5 with 5.6 mm length added, which during its Return stroke extended to 20.7 mm. Thus, the second scaffold is given before its Vorhubes fed a feed of 20.7 mm, which at 1.85 times the extension in 2. Roll out the stand to 38 mm.

A problem to be solved is of course that the rolling stock during the return stroke of the second scaffold can also be pushed forward without disability. For this are in the present embodiment by means of cyclic adjustment of the Rolling rotationally driving racks the rolls so that they turn on release the pipe on the return stroke. Then in the switching area of the inlet dead center this adjustment withdrawn again. This is before rolling begins 20.6 mm feed takes place on the feed stroke and the rollers are back in the correct position Roll position. On the advance stroke, the 20.6 mm feed is now 1.85 times larger Extension to 38 mm tube length per stroke. The performance of the Rolling mill according to the invention thus increases to 2.13 times one conventional rolling mill.

Example 2

While the first example the performance gain with unchanged pipe cross-section shows, in the second example the great ductility of austenitic steels for an increase the stretching can be used by the rolling mill according to the invention.

"Example 2" shows the rolling 33 x 3.5 to 16 x 1 from "Example 1" for the conventional rolling mill, but 33 x 3.5 to 12 x 1 for the rolling mill according to the invention. Even here, the output in m doubles / h and the throughput in kg / h increases by almost 50% despite the lower meter weight. example 1 Conventional rolling mill Rolling mill according to the invention same aspect ratio 1. Scaffolding 2.Gerüst Luppen outer diam. mm 33 33 20 Luppen Wall mm 3.5 3.5 1.5 External pipe diameter. mm 16 20 16 Tube wall mm 1 1.5 1 stretching --- 6.88 3.72 1.85 strokes min ^ -1 320 320 320 Total caliber length mm 370 370 370 Reduzierkaliberlänge mm 270 370 270 Glättkaliberlänge mm 100 0 100 Tube per stroke mm 18 20.7 38 part extension --- 6.88 3.72 1.85 feed mm 2.6 5.6 20.7 Theor. power m / h 346 397 735 kg / h 128 272 272 % 100 115 213 Example 2 Conventional rolling mill Rolling mill according to the invention increased stretch 1. Scaffolding 2.Gerüst Luppen outer diam. mm 33 33 16 Luppen Wall mm 3.5 3.5 1.3 External pipe diameter, mm 16 16 12 Tube wall mm 1 1.3 1 stretching --- 6.88 5.40 1.74 strokes min ^ -1 320 320 320 Total caliber length mm 370 370 370 Reduzierkaliberlänge mm 270 370 270 Glättkaliberlänge mm 100 0 100 Tube per stroke mm 18 21 36 part extension --- 6.88 5.40 1.74 feed mm 2.6 3.9 21.0 Theor. power m / h 346 403 700 kg / h 128 190 190 % 100 117 203

Claims (8)

1. Method of producing tubes, preferably from high-tensile steels or special alloys, using the cold pilger rolling method with two roll stands (1,2) which can be moved in the rolling direction by means of crank drives (3) to and fro in opposite directions at least intermittently, said stands having rollers (7,8) which are calibrated in a tapering manner and which roll over the material to be rolled with an alternating direction of rotation, wherein
   the major part of the forming work takes place on the first roll stand (1) and a smaller part of the forming work and additional smoothing work on the second roll stand (2), reduction rolling being carried out in both stands (1, 2) via a mandrel which is matched to the roller calibre, and the angular offset of the crank drives (3) is selected such that the forming zone of the first stand (1) does not coincide in time with the forming zone of the second stand (2),
   characterised in that
   the second stand (2) is disposed offset from the first stand (1) by a crank angle of 90 to 150 degrees, in that its rollers (8) are driven in rotation by stationary toothed racks (10), and in that the distance between the roller (8) axes remains constant during the rolling.
2. Method of producing tubes, preferably from high-tensile steels or special alloys using the cold pilger rolling method with two roll stands (1,2) which can be moved in the rolling direction by means of crank drives (3) to and fro in opposite directions at least intermittently, said stands having rollers (7,8) which are calibrated in a tapering manner and which roll over the material to be rolled with an alternating direction of rotation, wherein
   the major part of the forming work takes place on the first roll stand (1) and a smaller part of the forming work and additional smoothing work on the second roll stand (2), reduction rolling being carried out in both stands (1, 2) via a mandrel which is matched to the roller calibre, and the angular offset of the crank drives (3) is selected such that the forming zone of the first stand (1) does not coincide in time with the forming zone of the second stand (2),
   characterised in that
   the rollers (7, 8) are driven by toothed racks via pinions,
   in that the second roll stand (2) is disposed offset from the first stand by a crank angle of 180 degrees and on the return stroke, during which there is no reduction, opens up between the material to be rolled and the roller calibre an annular gap which corresponds to the material supplied from the first (1) stand, and into which the tube formed in the first stand (1) is introduced, and
   in that the distance between the roller (7,8) axes is altered cyclically during the rolling process.
3. Method of producing tubes according to claim 1,
   characterised in that
   the toothed racks (10) for driving the rollers in rotation can be displaced horizontally in a cyclical manner.
4. Apparatus for producing tubes, preferably from high-tensile steels or special alloys, using the cold pilger rolling method with two roll stands (1,2) which can be moved in the rolling direction by means of crank drives (3) to and fro in opposite directions at least intermittently, said stands having rollers (7,8) which are calibrated in a tapering manner and which roll over the material to be rolled with an alternating direction of rotation, wherein
   the first roll stand (1) is configured as a break-down stand with rollers (7) which only have the working calibre, the rollers (8) of the second stand (2) have working and smoothing calibres, the rollers (7,8) of both stands (1,2) cooperate with correspondingly calibrated rolling mandrels and the crank drives (3), which are offset at an angle from one another, are designed to drive the roll stands (1,2) via individual push rods (11,12) allocated to each stand (1,2) and having vertical axes of rotation,
   characterised in that
   the rollers (7, 8) are driven by toothed racks via pinions and
   in that a cyclically adjustable wedge mechanism is provided to adjust the distance between the axes at least of the rollers (7, 8) of the second roll stand (2), or
   in that at least the toothed racks (10) of the second stand (2) are provided with a displacement device (9) to adjust the toothed racks (10) in the direction of their longitudinal extension.
5. Apparatus for producing tubes according to claim 4,
   characterised in that
   the push rods (11, 12) of each roll stand (1,2) circulate in planes which lie the one above the other.
6. Apparatus for producing tubes according to claims 4 and 5,
   characterised in that
   a common crank drive (3) is provided for both roll stands (1,2) which has contra-rotating crank drives and rotating balance weights (4, 5) at the two crank bends, the rotating counterweights completely compensating for the first-order mass forces and there being partial compensation for the higher-order mass forces through the interaction of the stand masses.
7. Apparatus for producing tubes according to claims 4 and 5,
   characterised in that
   the cranks are driven in the same direction of rotation and with counterweights on the cranks in each case a portion of the first-order mass forces is compensated for, and the remaining portion of this mass force component is compensated for either not at all or with counterweights at an intermediate shaft which connects the two cranks via gearwheels and rotates at the same speed as the cranks but in the opposite direction of rotation.
8. Apparatus for producing tubes according to claim 4,
   characterised in that
   there is associated with each roll stand (1 and 2) its own crank drive with mass balancing, the drive of the second stand (2) being preferably configured weaker than that of the first stand (1).

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