EP3784423B1 - Cross-rolling mill with hydraulic roller actuator - Google Patents

Description

1. Field of the Invention

The invention relates to a cross-rolling mill for rolling an ingot over a mandrel into a hollow ingot, comprising a plurality of work rolls, each of which exerts a substantially radially directed rolling force on the ingot, the work rolls being carried in a roll stand and the gap between the work rolls, preferably also the alignment of the roll axis of at least one of the work rolls relative to the block can be changed. Furthermore, the invention relates to a method for producing a hollow block from a block by means of such a cross-rolling mill. A generic piercing mill and a generic method are out DE 21 56 595 A1 known.

2. State of the art

When rolling a metallic hollow block over a mandrel using the so-called Mannesmann process, a preheated block, in the case of steel a block preheated to approx. 1,250°C, is rolled into a hollow block by means of two or more main work rolls over a mandrel located between the rolls. During the rolling process, the work rolls exert an essentially radially directed rolling force on the block and are mounted and supported for support in a roll stand, a so-called rolling mill stand, in such a way that at least the roll gap between the work rolls is set to the desired wall thickness of the hollow block to be produced can be. For this purpose, mechanical spindle drives have been used for decades, which allow at least one roll gap setting before and after the rolling process. A roll gap setting during the rolling process, in particular an automated roll gap setting during the rolling process itself, is nevertheless not possible as a result.

3. Object of the invention

It was therefore an object of the invention to specify a cross-rolling mill and a method for rolling an ingot over a mandrel to form a hollow ingot, by means of which the problems known from the prior art are solved and automatic compensation of disturbance variables determined, preferably during the rolling process, is made possible .

In the sense of the invention, this object is achieved with a cross-rolling mill comprising the features of claim 1 and a method comprising the features of claim 13 . Advantageous configurations of the invention are set out in the dependent claims and in the following description.

4. Summary of the Invention

According to a first aspect of the invention, a cross-rolling mill for rolling an ingot over a mandrel to form a hollow ingot is specified, in which, instead of the previously used mechanical adjustment elements such as spindle drives, hydraulic adjustment elements, preferably hydraulic capsules, are provided for changing the roll gap, preferably also aligning the roll axis of at least one of the work rolls with respect to the billet. The change in the roll gap by means of hydraulic adjustment elements compared to the block as a workpiece is understood in such a way that the work rolls are realigned to each other as required, whereby the roll gap dimension and geometry also remains variable during the rolling process. During the rolling process, there is an alignment with respect to the block to be formed into a hollow block, between the respective rolling processes and during the rolling processes the alignment of at least one of the roll axes also occurs with respect to the other work roll(s). The hydraulic ones Adjusting elements are preferably connected to chocks in a manner customary in the art, via which the work rolls are mounted adjustably in the respective roll stand.

As a result, a cross-rolling mill is made available for the first time which, due to the hydraulic adjustment elements, allows a change in the roll gap geometry or any other type of disturbance variable compensation even during the rolling process.

According to the invention, the work rolls are preset to a specific distance from one another, the so-called roll gap, via the hydraulic adjustment elements. The mandrel held by a mandrel bar is located symmetrically between the work rolls in the cross-rolling mill according to the invention, over which mandrel the billet is then rolled to form a hollow billet. Due to the inclined position of the work rolls, the ingot is formed into a hollow block via the mandrel fixed in the roll gap and due to the drive applied to the block by the inclined position of the work rolls.

However, enormous forces are generated during rolling, which, among other things, push the work rolls apart. The entire rolling mill stand is stretched in shape by the forces acting on the work rolls or distorted in some other way, which ultimately also leads to a change in the previously set roll gap and its geometry.

The work rolls, for example the upper and lower work rolls, usually move to different extents in different spatial directions. This is all the more true when one or more of the work rolls is firmly connected to the roll stand and/or the foundation and is therefore only subject to minimal movements under load. In the process, the previously set arrangement of both the work rolls and, if applicable, the mandrel is lost. The roll gap increases as a result and the symmetry of the arrangement of the The work rolls and possibly the mandrel are shifted relative to one another, in particular since, for example, the upper and lower work rolls are shifted to different extents, for example upwards or downwards, due to the design. Ultimately, the center of the work rolls shifts to one another and to the mandrel and thus to the outlet side of the cross-rolling mill, which leads to undesirable effects on the quality of the hollow billet produced. In the wall thickness distribution of the hollow block, eccentricities occur to a greater extent due to the displacement of the work roll centers relative to one another, and these can ultimately also be found in the finished rolled tube.

Until now, such disturbances could only be determined after the end of the rolling process and compensated for by readjusting the work rolls relative to one another before a subsequent rolling process. Dynamic compensation for disturbance variables, in particular compensation for manipulated variables during the rolling process on the basis of measurement data determined online, was previously not possible. The use of hydraulic adjustment elements according to the invention overcomes this disadvantage of previously existing cross-rolling mills.

According to the invention, the use of hydraulic adjusting elements, preferably hydraulic capsules, enables the dynamic minimization or complete compensation of the column expansion and the associated shifting of the roll positions relative to one another. In particular, it is now possible for the first time even with changing load conditions, e.g. B. during rolling, preferably in real time, to compensate for the disturbance variables of the roll gap changes and roll gap shifts by suitable changes in the roll gap, preferably also the alignment of the roll axis of at least one of the work rolls with respect to the block or any other work roll, preferably as far as possible.

Disturbance variable adjustments, which act in the x-direction horizontally transverse to the rolling direction, in the γ-direction vertically to the rolling direction and in the z-direction in the rolling direction towards the outlet side, are preferably used as manipulated variables for the hydraulic adjustment elements of the work rolls.

According to the first aspect of the invention, the cross-rolling mill according to the invention preferably has, in addition to the work rolls, preferably the upper and lower work rolls, disks or guide shoes that laterally limit the roll gap, via which a central positioning of the billet and the outgoing hollow billet within the roll gap can be influenced. These so-called Diescher disks usually have a circumferential profile in the shape of the hollow billet to be rolled and are arranged within the cross-rolling mill such that they can be set against the hollow billet. In this context, it is preferred if the Diescher disks or the guide shoes also have hydraulic adjustment elements, which preferably support or can bring about a dynamic and online-acting disturbance variable compensation.

In a further preferred embodiment of the cross-rolling mill according to the invention, a measuring device is provided with which a change in the roll gap geometry and/or the roll gap shift and/or the position of the work rolls in space and their change during rolling operation can be determined. In this context, it is particularly preferred if this measuring device is connected to an evaluation unit that is suitable for determining the disturbance variables to be compensated for. This provides a cross-rolling mill which is able to dynamically and permanently determine any change in the rolling process, for example using a stand expansion to be measured and the associated change in the arrangement of the work rolls and possibly the mandrel relative to one another. In principle, the measuring device can be arranged at any point of the roll stand or of its built-in elements essentially direct measurement on the work rolls is preferred, an indirect measurement, for example on a guide element such as a Diescher disk or a guide shoe, nevertheless allows conclusions to be drawn about the position of the work rolls or the individual guide elements in the roll stand under load via a corresponding correlation analysis.

It is particularly preferred if the measuring means comprises an optical image acquisition unit, which makes it possible to separate the measuring unit away from the roll stand and the circumstances that otherwise act on the measuring unit there and have a disruptive effect on the measurement result. It is particularly preferred if the measuring means comprises a camera, preferably a CCD camera. Using such a camera, the measuring unit can be positioned in the rolling mill in almost any position relative to the rolling stand and at the same time, if necessary after a corresponding calibration, provide all desired measurement results.

In this context, it is particularly preferred if the measuring device is able to detect an image element associated with the roll stand, preferably one or more image elements associated with the adjustment elements for the work rolls, and is then able to determine their position and/or Determine shape change during the rolling process. In this context, it is particularly preferred if the at least one picture element is an active luminous body which, in an extremely preferred embodiment of the invention, is circular and has a defined diameter or is oval with a defined shape. It is also preferred if the image element is square or rectangular, in which case, for example, the evaluation of the change in one or more image element diagonals under load allows an indication of the rolling stand expansion or distortion.

On the one hand, this creates the possibility of measuring each roll stand expansion and/or distortion directly and immediately, on the other hand, the design of the picture element as an active luminous body advantageously supports image acquisition with particularly simple means. Finally, the preferred configuration of the picture element with a circular shape and defined diameter or oval with a predetermined shape or square or rectangular with known diagonal dimensions supports calibration of the measurement with particularly simple means on the one hand, and on the other hand also creates the possibility of not only changing the position of the picture element during roll stand expansion, but also any deformation of the pixel due to any other type of roll stand distortion. This can be used to particular advantage when the optical image capture is not just the center point (in the case of a circular shape) or the point of intersection of the main axes (in the case of an oval shape) or the point of intersection of the surface diagonals (in the case of a square or rectangular shape) of a picture element, but its entire surface, but at least the pixel edge and its center is able to detect. The advantage of this measuring method is that it creates the possibility of being able to evaluate many points of the flat image element in order to determine a single point. This reduces the susceptibility to interference compared to a conventional laser measurement, which only allows a single point observation. The area consideration also allows a one-time calibration of the measuring device, regardless of its location, the position of the measuring device can thus be freely selected and even changed from one measurement to the next if necessary.

According to a second aspect of the invention, there is provided a method for producing a hollow billet from a billet by means of a cross mill for rolling a billet over a mandrel, more preferably a cross mill according to the first aspect of the invention. According to the invention, hydraulic adjustment elements, preferably hydraulic capsules, which are connected directly or indirectly to the work rolls, for example via roll chocks, change during the Rolling process the roll gap, as well as the alignment of the roll axis of at least one of the work rolls relative to the block. In this way, a method is made available which, for the first time, makes it possible to make changes to the roll gap geometry during the rolling process and thereby counteract any disturbance variables that may be determined for the purpose of quality assurance or quality optimization of the rolling process.

It is particularly preferred if the change in the roll gap, as described above, is brought about when disturbance variables are determined in advance by an evaluation unit by means of measured changes in the roll gap geometry and/or the roll gap displacement and/or the position of the work rolls in space and their change during rolling operation have been. In a particularly advantageous manner, a suitable control and regulation unit interacts with the evaluation unit to output a signal for manipulated variable compensation to the hydraulic adjustment elements. In this context, it is particularly preferred if the evaluation unit is connected to a measuring device, preferably an optical measuring device arranged at a distance from the roll stand, in particular a measuring device with an optical image acquisition unit. In a preferred embodiment of the invention, this measuring device can detect an image element connected to the roll stand, preferably one or more image elements connected to the adjustment elements for the work rolls, and determine their position and/or shape changes during the rolling process. The movement of the image elements is preferably dynamically recorded with high precision using the optical measuring device, with the changes Δ×1(t) and Δy1(t) of the upper work roll or Δx2(t), Δy2(t) of the lower work roll preferably being determined online and using the evaluation unit is transmitted to the control and regulation unit for minimizing or compensating for the manipulated variables. New manipulated variables for the hydraulic adjustment elements of the upper work roll and/or the lower work roll is calculated and the respective roll positions adjusted in such a way that the absolute roll gap error is minimized and symmetry to the original center can be restored.

This provides a method that allows very precise and highly dynamic disturbance variable compensation with simple, error-free and accurate means that can be used online, which means that for the first time during the rolling process in the cross-rolling mill an influence can be exerted on the rolling operation currently running.

For this purpose, it is also advantageous if, in addition to the position of the work rolls, preferably the upper and/or lower work rolls, also or exclusively the position and/or location of the mandrel and, in addition to this or independently of other changes, the position and/or location of the Diescher disks for Block or hollow block is changed dynamically in order to effect or at least support the compensation of previously determined disturbance variables.

Overall, according to the two aspects explained in more detail above, the invention enables the dynamic compensation of the expansion of the rolling mill during rolling and the reduction or elimination of defects in the tube to be produced by the cross-rolling mill. The measurement values are preferably recorded without contact and away from the roll stand, thus free from the influences that interfere with the measurement result near the roll gap, and allows the greatest possible flexibility in the arrangement of the measuring device to the roll stand, depending on local conditions. During the rolling process, movements of the roll stand can be recorded and compensated for during subsequent rolling operations, if necessary also during the ongoing rolling process. In order to acquire the data required for the compensation, measurements can be taken at several points simultaneously, and the measuring means can also be installed in a fixed manner, but can also be designed to be mobile.

Optical image acquisition using the ^CaliView® measuring device can be used for the measurement in a highly preferred manner. This can measure contours from a distance of 8 m to 40 m with an accuracy of 0.1 mm, whereby CaliView ^® also has a serial image function to check the measurement.

The measurement can thus record movements of the roll stand determined during the rolling process and changes in the roll gap and the roll gap geometry resulting therefrom and use them during operation to readjust the work rolls or other manipulated variables. Due to the preferably known shape and dimension of the image element on the roll stand, an angular offset can also be provided when arranging the measuring device in relation to the roll stand, which should then be taken into account when calibrating the measuring device. In this way, the influence of the vapors occurring during the cross-rolling process and other influences that interfere with the measurement result can be limited to the unavoidable minimum.

5. Short description of the figures

Figur 1

zeigt eine schematische Ansicht eines Teils eines Schrägwalzwerks gemäß einer ersten Ausführungsform der Erfindung,

Figur 2

zeigt eine schematische Darstellung eines Teils eines Schrägwalzwerks gemäß einer zweiten Ausführungsform der Erfindung, und

Figur 3

zeigt ein Ablaufschaubild zur Anwendung eines erfindungsgemäßen Verfahrens.

The invention is explained in more detail below with reference to a series of drawings, these figures only showing exemplary and schematic representations of the invention.

figure 1

shows a schematic view of part of a cross-rolling mill according to a first embodiment of the invention,

figure 2

shows a schematic representation of part of a cross-rolling mill according to a second embodiment of the invention, and

figure 3

shows a flow chart for the application of a method according to the invention.

6. Detailed description of the figures

figure 1 shows a first embodiment of the mode of operation of a cross-rolling mill, comprising an upper work roll 1 and a lower work roll 2. The upper and lower work rolls 1, 2 are designed in the form of two truncated cones connected to one another at their large end faces and act during the forming of a billet 3 in a direction from left to right (z-direction) in figure 1 together with a mandrel 5 arranged on a mandrel rod 4 . With a suitable adjustment of the upper and lower work rolls 1, 2 relative to the block 3, the block 3 is pushed through the roll gap between the upper and lower work rolls 1, 2 and conveyed over the mandrel 5 from the input side 6 to the output side 7 . Hydraulic adjustment elements 8a, 8b and 9a, 9b are arranged at the respective ends of the upper and lower work rolls 1, 2, via which the position of the work rolls 1, 2 in relation to one another and in relation to the block 3 can be changed in almost any way, in particular in in a γ-direction vertical to the rolling direction as shown. The vertical adjustment of the hydraulic adjustment elements 8a, 8b, 9a, 9b can also change the roll gap between the upper and lower work rolls 1, 2, at least both in the γ direction and in the z direction.

figure 2 12 shows another embodiment of an essential part of a rolling mill according to the invention, comprising an upper work roll 1 and a lower work roll 2, each showing a truncated cone shape with an unsteady jacket profile. Between the upper and lower work rolls 1, 2 there is again a roll gap 10, into which the billet 3 enters by moving in direction z towards the mandrel 5 and there in the interaction of the upper and lower work rolls 1, 2 with the locally fixed piercer mandrel 5 is formed into a hollow block (not shown). At both ends of the upper and lower work rolls 1, 2 there are hydraulic adjustment elements 8a, 8b or 9a, 9b, by means of which the roll gap 10 and the local position of the roll axes 1a, 1b can be changed.

figure 3 shows a schematic flowchart of the method according to the invention using a cross-rolling mill 11 according to the invention, which carries an upper work roll 1 and a lower work roll 2 . Image elements MM1 and MM2 are arranged on the roll stands of the roll stand 11 and are constantly monitored with high precision and dynamically during the rolling operation, both in terms of their position and their shape, by a remotely arranged camera that is not shown in the picture. Each change in position in the x-direction and y-direction Dx1(t), Δy1(t) for the upper work roll 1 and Dx2(t), Δy2(t) for the lower work roll 2 are recorded by the measuring unit (not shown) and an an evaluation unit (also not shown) is transmitted. In this evaluation unit, it is in turn determined whether the changes in position of the picture elements MM1, MM2 detected by the picture unit (not shown) are to be regarded as manipulated variables to be compensated. If this is the case, the disturbance variables determined by the evaluation unit are forwarded to the HGC controller as the control and regulation unit (hydraulic gap control controller). Further process parameters go into the control and regulation unit (HGC), so that control commands Y1, Y2 are output to the hydraulic adjustment elements 8, 9 on the basis of predefined algorithms. By adjusting the upper work roll 1 and/or the lower work roll 2 in relation to the mandrel (not shown), these hydraulic adjustment elements 8, 9 change the roll gap geometry and, if necessary, the alignment of the (not shown) roll axes to each other. This makes it possible to output control and regulation commands online during the rolling process in a highly dynamic manner with constant acquisition and evaluation of measurement data, which are able to positively influence the rolling result and the course of the cross-rolling process.

Reference List

1

stripper

1a, b

roller axis

2

stripper

2a, b

roller axis

3

block

5

mandrel

8th

adjustment element

8a, 8b

adjustment element

9

adjustment element

9a, 9b

adjustment element

10

roll gap

11

cross rolling mill

H.G.C

Hydraulic gap control

MM1

picture element

MM2

picture element

Claims (19)

1. Cross-rolling mill (11) for rolling a billet (3) over a mandrel (5) to form a hollow billet, comprising a plurality of work rolls (1, 2) which each exert a substantially radially directed rolling force on the billet (3), wherein the work rolls (1, 2) are carried in a roll stand and the rolling gap (10) between the work rolls (1, 2) and the orientation of the roll axis (1a, 2a) of at least one of the work rolls (1, 2) relative to the billet (3) are variable, wherein hydraulic adjusting elements (8, 9), preferably hydraulic capsules, are provided for the purpose of varying the rolling gap (10) during the rolling process, characterised in that the hydraulic adjusting elements (8, 9) are also provided for the purpose of producing the orientation of the roll axis (1a, 2a) of at least one of the work rolls (1, 2) relative to the billet (3) during the rolling process.
2. Cross-rolling mill (11) according to claim 1, characterised in that the hydraulic adjusting elements (8, 9) are in a position of providing compensation for roll stand expansion during rolling operation through varying the adjustment of the work rolls (1, 2) relative to one another, preferably additionally through orientation of the roll axis (1a, 2a) of at least one of the work rolls (1, 2) relative to the billet (3).
3. Cross-rolling mill (11) according to one of the preceding claims, characterised in that in addition to the work rolls (1, 2) discs laterally bounding the rolling gap (10), i.e. so-called Diescher discs and/or guide discs, which preferably are similarly connected with hydraulic adjusting elements, are provided.
4. Cross-rolling mill (11) according to any one of the preceding claims, characterised in that in addition a measuring means is provided by which a variation of the rolling gap geometry and/or rolling gap displacement and/or the position of the work rolls (1, 2) in three dimensions as well as variation thereof during rolling operation is determinable.
5. Cross-rolling mill (11) according to claim 4, characterised in that the measuring means is connected with an evaluating unit suitable for the purpose of ascertaining disturbance variables.
6. Cross-rolling mill (11) according to any one of the preceding claims, characterised in that a controlling and regulating unit (HGC) is provided, which is so connected with the hydraulic adjusting elements (8, 9) that it is possible to counteract variations determined beforehand in rolling gap geometry and/or rolling gap displacement and/or position of the work rolls (1, 2) in three dimensions as well as variation thereof during rolling operation through change in the rolling gap (10), preferably also the orientation of the roll axis (1a, 1b) of at least one of the work rolls (1, 2) relative to the billet (3).
7. Cross-rolling mill (11) according to claim 6, characterised in that the controlling and regulating unit (HGC) is connected with the evaluating unit according to claim 5.
8. Cross-rolling mill (11) according to any one of claims 4 to 7, characterised in that the measuring means comprise an optical image detecting unit.
9. Cross-rolling mill (11) according to any one of claims 4 to 8, characterised in that the measuring means is in a position of detecting an image element (MM1, MM2) connected with the roll stand, preferably one or more image elements (MM1, MM2) connected with the adjusting elements (8, 9) for the work rolls (1, 2), as well as ascertaining the change in position and/or shape thereof.
10. Cross-rolling mill (11) according to any claim 9, characterised in that the at least one image element (MM1, MM2) is an active light-emitting body.
11. Cross-rolling mill (11) according to one of claims 8 and 9, characterised in that the image element (MM1, MM2) is circularly round with a defined diameter or square or rectangular with known diagonal dimensions, or oval with a definitive form.
12. Cross-rolling mill (11) according to preceding claims, characterised in that the position of the mandrel (5) within the rolling gap (10) is variable.
13. Method of producing a hollow billet from a billet (3) by means of a cross-rolling mill (11) for rolling a billet (3) over a mandrel (5), wherein the cross-rolling mill (11) comprises a plurality of work rolls (1, 2) which each exert a substantially radially directed rolling force on the billet (3), wherein the work rolls (1, 2) are carried in a roll stand and the rolling gap (10) between the work rolls (1, 2) and the orientation of the roll axis (1a, 2a) of at least one of the work rolls (1, 2) relative to the billet (3) are variable, wherein hydraulic adjusting elements (8, 9), preferably hydraulic capsules, are provided for the purpose of varying the rolling gap (10) during the rolling process, characterised in that the hydraulic adjusting elements (8, 9) also vary the orientation of the roll axis of at least one of the work rolls relative to the billet during the rolling process.
14. Method according to claim 13, characterised in that the variation of the rolling gap (10), preferably also the orientation of the roll axis (1a, 2a) of at least one of the work rolls (1, 2) relative to the billet (3), is produced when variations, which are measured beforehand by way of a measuring means, of the rolling gap geometry and/or rolling gap displacement and/or the position of the work rolls (1, 2) in three dimensions as well as the variation thereof during rolling operation, have been ascertained by an evaluating unit and classified as disturbance variables.
15. Method according to claim 14, characterised in that a controlling and regulating unit (HGC) is connected with the evaluating unit and issues signals for disturbance-variable compensation to the hydraulic adjusting elements (8, 9).
16. Method according to one of claims 14 and 15, characterised in that the evaluating unit is connected with a measuring means, preferably an optical measuring means arranged remotely from the roll stand, particularly a measuring means with an optical detecting unit.
17. Method according to claim 16, characterised in that the measuring means detects an image element connected with the roll stand, preferably one or more image elements (MM1, MM2) connected with the adjusting elements (8, 9) for the work rolls (1, 2), as well as ascertains the change in position and/or shape thereof during the rolling process.
18. Method according to any one of claims 14 to 17, characterised in that the position and/or orientation of the mandrel (5) within the rolling gap (10) is or are varied during the rolling process to provide compensation for disturbance variables ascertained beforehand.
19. Method according to any one of claims 13 to 18, characterised in that it is performed by a cross-rolling mill (11) according to any one of claims 1 to 12.

Images