COLD PILGER ROLLING MILL AND METHOD FOR PRODUCING A PIPE

Abstract

Cold pilger rolling mill for cold forming a hollow into a strain hardened tube with a roll stand with rollers mounted pivotably thereon. Efficient milling of long hollows is enabled without reducing the quality of the manufactured tubes. The cold pilger rolling mill has an unwinding device, wherein the unwinding device is arranged and in the feed direction of the hollow is located in front of the front mandrel thrust block such that at the unwinding device a spindle being rotatable around an axis being perpendicular to the feed direction of the hollow with the hollow wound thereon is receivable and in an operation of the cold pilger rolling mill the hollow is unwindable and feedable between the chuck of the front mandrel thrust block and the mandrel bar into the feed clamping sledge and the roll stand.

Claims

1. A cold pilger rolling mill for cold forming of a hollow into a strain hardened tube comprising: a roll stand with rollers rotatably mounted thereon, wherein the roll stand is motor driven and moveable back and forth in a direction parallel to a longitudinal axis of the hollow between an in a feed direction of the hollow front point of return and an in the feed direction of the hollow rear point of return, and wherein the rollers during a back and forth movement of the roll stand carry out a rotational motion, such that the rollers during operation of the cold pilger rolling mill, mill the hollow into a tube, a mandrel, wherein the mandrel is mounted by mandrel bar at an in the feed direction of the hollow rear end of the mandrel bar, such that during operation of the cold pilger rolling mill the hollow is milled by the rollers over the mandrel, at least one feed clamping sledge with a feed chuck mounted thereon to receive the hollow, wherein the feed clamping sledge is moveable back and forth in a direction parallel to the longitudinal axis of the hollow between an in the feed direction of the hollow front point of return and an in the feed direction of the hollow rear point of return such that the hollow during operation of the cold pilger rolling mill experiences a stepwise feed in a direction towards the mandrel, and wherein the feed chuck is openable and closeable in a radial direction such that the hollow is released or clamped, and at least one mandrel thrust block with a chuck for mounting the mandrel bar, wherein a front mandrel thrust block is located in the feed direction of the hollow in front of the feed clamping sledge such that the mandrel bar during operation of the cold pilger rolling mill is mountable by the chuck of the front mandrel thrust block, wherein the chuck of the front mandrel thrust block is openable in a radial direction, such that a hollow is feedable between chuck and the mandrel bar, wherein the cold pilger rolling mill comprises an unwinding device, wherein the unwinding device is arranged and located in the feed direction of the hollow in front of the front mandrel thrust block such that a spindle with the hollow wound thereon is receivable at the unwinding device being rotatable about an axis being perpendicular to the feed direction of the hollow and during the operation of the cold pilger rolling mill the hollow is unwindable and feedable between the chuck of the front mandrel thrust block and the mandrel bar to the feed clamping sledge and to the roll stand.

2. The cold pilger rolling mill according to claim 1, wherein the front mandrel thrust block has a distance from the feed clamping sledge, measured with the feed clamping sledge at its rear point of return, of at least 30 m.

3. The cold pilger rolling mill according to claim 1, wherein the mandrel bar a tensile strength of 1000 N or more.

4. The cold pilger rolling mill according to claim 1, wherein the mandrel bar comprises a strain of 10% or less

5. The cold pilger rolling mill according to claim 1, wherein the cold pilger rolling mill comprises two feed clamping sledges with a feed chuck mounted on each of the feed clamping sledges as well as a controller, wherein the controller is arranged such that the controller controls the motion of the two feed clamping sledges such that the hollow in a continuous operation of the cold pilger rolling mill is clampable alternately by one of the feed chucks and such that the hollows are stepwise feedable towards the mandrel, and wherein the front mandrel thrust block comprises a distance of at least 30 m from the feed chuck of the in the feed direction of the hollow rear feed clamping sledge, measured with the feed clamping sledge at its rear point of return.

6. The cold pilger rolling mill according to claim 1, wherein the cold pilger rolling mill comprises a rear mandrel thrust block with a chuck for mounting the mandrel bar between the front point of return of the feed clamping sledge and the front mandrel thrust block when viewed in the feed direction of the hollow, wherein the rear mandrel thrust block comprises a distance from the front mandrel thrust block of at least 30 m such that the mandrel bar during operation of the cold pilger rolling mill is mountable by at least one chuck of the front mandrel thrust block or of the rear mandrel thrust block.

7. The cold pilger rolling mill according to claim 1, wherein each feed clamping sledge of the cold pilger rolling mill is arranged such that it can feed a hollow with a weight of 100 kg/m or more.

8. The cold pilger rolling mill according to claim 1, wherein a winding device is located in the feed direction of the finished tube behind the rollers of the cold pilger rolling mill, wherein the winding device comprises a bending device for the tube manufactured in the cold pilger rolling mill to bend the tube such that the tube is windable around a first axis, and mounting frame, and wherein the bending device and the first axis are pivotably mounted at the mounting frame about a second axis which is essentially perpendicular to the first axis and which is parallel to a longitudinal axis of a hollow received between the rollers.

9. The cold pilger rolling mill according to claim 1, wherein the cold pilger rolling mill comprises an annealing furnace, and wherein the annealing furnace is arranged such that the annealing furnace during an operation of the cold pilger rolling mill heats the hollow to a temperature in a range from 1000? C. to 1200? C.

10. A method for manufacturing a tube by cold forming of a hollow in a cold pilger rolling mill with a roll stand with rollers pivotably mounted thereon, a mandrel mounted by a mandrel bar, at least one mandrel thrust block mounting the mandrel bar and at least one feed clamping sledge with a feed chuck for receiving the hollow, comprising the steps: a) opening a chuck of an in a feed direction of the hollow front mandrel thrust block in a radial direction and feeding a first hollow through the front mandrel thrust block between the chuck of the front mandrel thrust block and the mandrel bar, b) after completely feeding of the first hollow through the front mandrel thrust block closing the chuck of the front mandrel thrust block in the radial direction such that the front mandrel thrust block mounts the mandrel bar carrying the mandrel, c) feeding the first hollow to a feed clamping sledge and receiving the first hollow by opening the feed chuck in the radial direction and clamping the first hollow by closing the feed chuck in the radial direction at an in the feed direction of the hollow front point of return of the feed clamping sledge, and d) milling the first hollow by the rollers over the mandrel into a strain hardened tube by stepwise feeding the first hollow by means of the feed clamping sledge and oscillatory back and forth movement of the roll stand with the rollers between a front point of return and a rear point of return, further comprising prior to step a) in a step a) providing the first hollow wound up on a spindle and unwinding of the first hollow from the spindle with an unwinding device is carried out.

11. The method for manufacturing a tube according to claim 10, wherein the first hollow comprises a length of 30 m or more.

12. The method for manufacturing a tube according to claim 10, wherein the method comprises the following step after step a) and prior to step b): e) opening of a chuck of an in the feed direction of the hollow rear mandrel thrust block, located between the front point (of return of an in the feed direction of the hollow front feed clamping sledge and the front mandrel thrust block, in a radial direction, wherein the rear mandrel thrust block comprises a distance of at least 30 m from the front mandrel thrust block, and feeding a first hollow through the rear mandrel thrust block, wherein the milling of the first hollow by the rollers over the mandrel into a strain hardened tube in step c) is caused by stepwise feeding the first hollow intermittently by means of the front feed clamping sledge from a front point of return (to a rear point of return of the front feed clamping sledge and by means of an in the feed direction of the hollow rear feed clamping sledge from a front point of return to a rear point of return of the rear feed clamping sledge and oscillatorily moving the roll stand back and forth between a front point of return and a rear point of return of the rollers, and wherein the method in addition comprises the steps of: f) after completely feeding the first hollow through the rear mandrel thrust block closing the chuck of the rear mandrel thrust block in a radial direction such that the rear mandrel thrust block mounts the mandrel bar carrying the mandrel, g) during the milling of the first hollow unwinding a second hollow, wherein the second hollow is wound on a spindle being rotatable around an axis being perpendicular to the feed direction of the hollow, h) opening the chuck of the front mandrel thrust block and feeding the second hollow through the front mandrel thrust block into an area between the front mandrel thrust block and the rear mandrel thrust block, i) after completely feeding the second hollow through the front mandrel thrust block closing the chuck of the front mandrel thrust block such that the front mandrel thrust block mounts the mandrel bar carrying the mandrel, j) opening the chuck of the rear mandrel thrust block, k) feeding the second hollow through the rear mandrel thrust block, l) feeding the second hollow to the front feed clamping sledge and receiving the second hollow in the feed chuck of the front feed clamping sledge and clamping the second hollow by closing the feed chuck of the front feed clamping sledge in a radial direction, m) opening the feed chuck of the rear feed clamping sledge in a radial direction, n) stepwise feeding the second hollow (intermittently by means of the front feed clamping sledge and by the rear feed clamping sledge while the second hollow is clamped, o) after completely discharging of the finished tube milled out of the first hollow from the roll stand inserting the second hollow into the roll stand and p) milling the second hollow by the rollers over the mandrel into a strain hardened tube by stepwise feeding the second hollow intermittently by means of the rear feed clamping sledge and of the front feed clamping sledge and oscilatorilly moving back and forth the roll stand between a front point of return and a rear point of return with the rollers.

13. The method for manufacturing a tube according to claim 10, wherein a winding of an already completely milled part of the hollow simultaneously with the milling of a part of the hollow to be milled into the strain hardened tube with the steps: bending of a part of the hollow which is already completely milled in a bending device, spirally winding up the already completely milled part of the hollow around a first axis, and pivoting of the bending device mounted at a mounting frame and the first axis around the second axis being essentially perpendicular to the first axis and being essentially parallel to a longitudinal axis of a hollow (located between the rollers such that the pivoting occurs with the same angular velocity as a pivoting of the hollow around its longitudinal axis during the milling of the hollow.

14. The method for manufacturing a tube according to claim 10, wherein prior to the feeding of the hollow through the front mandrel thrust block the hollow located wound up on a spindle is heated to a temperature in a range from 1000? C. to 1200? C.

15. The method for manufacturing a tube according to claim 14, wherein to the heating of the hollow a further cold forming of the hollow in a second cold pilger rolling mill is carried out such that the finished tube is manufactured by multiple cold forming of a hollow.

Description

[0087] Further advantages, features and applications of the present invention become apparent from the following description of embodiments thereof as well as the appended figures.

[0088] FIG. 1 shows a schematic side view of the arrangement of a cold pilger rolling mill with an unwinding device according to an embodiment of the present invention.

[0089] FIG. 2 shows a schematic side view of a design of a cold pilger rolling mill with an unwinding device, a front mandrel thrust block and a rear mandrel thrust block as well as two feed clamping sledges according to a further embodiment of the present invention.

[0090] FIG. 3 shows a schematic side view of an arrangement of a cold pilger rolling mill with an unwinding device, a front mandrel thrust block and a rear mandrel thrust block, two feed clamping sledges and a winding device according to a further embodiment of the present invention.

[0091] In the figures, identical elements are denoted by identical reference numbers.

[0092] In FIG. 1, the design of an inventive cold pilger rolling mill is schematically shown in a side view. The cold pilger rolling mill 7 consists of a roll stand 1 with an upper roller 2 and a lower roller 3, a calibrated mandrel 4 (in the figure, the position of the mandrel is denoted by reference number 4), a mandrel bar 8 carrying the mandrel 4, a feed clamping sledge 5 with a feed chuck 12 to receive a hollow 11, a front mandrel thrust block 15 with a chuck 19 as well as a discharge clamping sledge 18 with a chuck 22. In the embodiment shown, the cold pilger rolling mill comprises a linear motor 6 as a direct drive for the feed clamping sledge 5.

[0093] Like in all embodiments of FIGS. 1 to 3 the cold pilger rolling mill 7 comprises an unwinding device 26 for the provision of the hollow 11. The unwinding device 26 is arranged such that a hollow located wound up around an axis 28 being perpendicular to the feed direction of the hollow 11 on a spindle 27 is unwound. Thereby the spindle 27 is rotated driven by a motor around the first axis 28 in direction of the arrow shown such that the hollow located wound up on the spindle 27 is guided between five bending rollers 32a. Three bending rollers 32a thereby are located in an upper row and two bending rollers 32a are located in a lower row. The bending rollers 32a bend the hollow fit through homogeneously and in opposite directions each such that the hollow is bend straight and is straightened between the bending rollers 32a prior to the hollow being fed through the chuck 19 of the front mandrel thrust block 15. The straightening of the hollow 11 in the initial state thereby is carried out during the loading of the hollow 11 through the front mandrel thrust block 15 into the cold pilger rolling mill 7.

[0094] Integration of the unwinding device 26 into the cold pilger rolling mill as shown in the figures and thus of the unwinding into the milling process is in particular advantageous for hollows with a length of more than 30 m. By unwinding of the hollow 11 located wound up on the spindle 27 and by simultaneously feeding the hollow 11 to and through the front mandrel thrust block 15, a large space in a workshop in which the cold pilger rolling mill is located, can be saved.

[0095] During the cold pilger milling in the cold pilger rolling mill shown in FIG. 1 the hollow 11 experiences a stepwise feed in a direction towards the mandrel 4 and over the mandrel, while the rollers 2, 3 are moved horizontally back and forth over the mandrel 4 and thus over the hollow 11. Thereby the horizontal motion of the rollers 2, 3 is guided by the roll stand 1 at which the rollers 2, 3 are pivotably mounted. The roll stand 1 is moved back and forth by means of a crank drive 23 via a push rod 24 in a direction parallel to the longitudinal axis of the hollow between the in the feed direction of the hollow 11 front point of return 9, which is denoted as the feed dead center ET, and an in the feed direction of the hollow 11 rear point of return 10, which is also denoted as the discharge dead center AT. The rollers 2, 3 in turn receive their rotating motion from a tooth bar (not shown) which relatively to the roll stand 1 is fixed, in which tooth bar gear wheels (not shown) fixedly mounted on the roller axis engage. The feed of the hollow 11 over the mandrel 4 is carried out by means of the feed clamping sledge 5, which enables a translational motion in the direction parallel to the axis of the hollow 11. The feed clamping sledge 5 thereby carries out a motion back and forth between an in the feed direction of the hollow 11 front point of return 13 and an in the feed direction of the hollow 11 rear point of return 14. The path of the feed clamping sledge 5 between the two points of return 13, 14 in the embodiment of FIG. 1 amounts to 24 m.

[0096] As soon as the hollow 11 is released from the front mandrel thrust block 15 the chuck 19 of the front mandrel thrust block 15 is closed in a radial direction such that the chuck 19 fixedly clamps the mandrel bar 8. Thereby, the front mandrel thrust block 15 in FIG. 1 comprises a distance from the feed chuck 12 of the feed clamping sledge 5 when the feed clamping sledge 5 is located at its rear point of return 14 of 36 m. This distance is measured between the rear end of the chuck 19 of the front mandrel thrust bar 15 in the feed direction of the hollow and the front end of the feed chuck 12 of the feed clamping sledge in the feed direction of the hollow when the feed clamping sledge is located at its rear point of return 14. Consequently, a hollow with a maximum length of 36 m could be located between the front mandrel thrust block 15 and the feed chuck 12 of the feed clamping sledge 5 located at its rear point of return 14 without the hollow being clamped by the chuck 19 of the front mandrel thrust block 15 or the chuck 12 of the feed clamping sledge 5.

[0097] The mandrel bar 8 in FIG. 1 consists of a raw material 30 CrNiMo 8 and comprises a tensile strength of 1000 N/mm.sup.2 as well as a strain of 8%.

[0098] At the in the feed direction of the hollow 11 front point of return 9 of the roll stand 1 the hollow 11 enters between the rollers 2, 3 and is received by the receiving pocket (not depicted) of the rollers 2, 3. The conically calibrated rollers 2, 3 arranged above each other at the roll stand 1 mill the hollow 11 by rolling back and forth on the hollow 11 in the feed direction of the feed clamping sledge 5. The pair of rollers during a milling stroke moves by a path L from the front point of return 9 of the roll stand 1 (feed dead center ED in the feed direction to the rear point of return 10 (discharge dead center AT) of the roll stand 1 in the feed direction of the hollow.

[0099] This in FIG. 1 corresponds to a rotation of the rollers by an angle of 280?. Thereby, the pair of rollers 2, 3 stretches the hollow 11 over the mandrel 4 mounted inside the hollow 11. The rollers 2, 3 and the mandrel 4 are calibrated such that the gap between the roller 2, 3 and the mandrel 4 is reduced in the working caliber zone of the rollers 2, 3 continuously from the wall thickness of the hollow 11 to the wall thickness of the finished milled tube 25. Furthermore, the outer diameter defined by the rollers is reduced from the outer diameter of the hollow to the outer diameter of the finished tube and the inner diameter defined by the mandrel is reduced from the inner diameter of the hollow to the inner diameter of the tube. After the working caliber zone of the rollers 2, 3 the planing caliber zone of the rollers 2, 3 follows in which a planning of a surface of the tube 25 to be manufactured is carried out. When reaching the rear point of return 10 of the roll stand 1 the discharge pocket (not shown) of the rollers 2, 3 releases the finished milled tube.

[0100] In order to obtain a homogenous shape of the finished tube 25, the hollow 11 besides a feed experiences an intermittent rotation around its longitudinal axis. The rotation of the hollow 11 occurs at both point of returns 9, 10 of the roll stand 1. By multiply milling each tube section a homogenous wall thickness and roundness of the tube as well as homogenous inner and outer diameters are achieved.

[0101] The finished tube 25 is received by a chuck 22 of a discharge clamping sledge 18 and is drawn out of the cold pilger rolling mill 7.

[0102] FIG. 2 shows a schematic design of a further cold pilger rolling mill according to the invention in a side view. In contrast to FIG. 1 the cold pilger rolling mill 7 depicted in FIG. 2 comprises two feed clamping sledges 5, 5 with a feed chuck 12, 12 each for receiving a hollow 11. Both feed clamping sledges 5, 5 are each moveable between their front 13, 13 and rear points of return 14, 14 by 12 m and are thus characterized by a smaller travelling distance when compared to the feed clamping sledge 5 shown in FIG. 1. The in the feed direction of the hollow 11 front feed clamping sledge 5 has already forwarded the hollow in a direction towards the mandrel 4 to a point slightly in front of its rear point of return 14. The in the feed direction of the hollow 11 rear feed clamping sledge 5 moves towards the front feed clamping sledge 5 in a direction opposite to the feed direction such that the front feed clamping sledge 5 once it has arrived at its rear point of return 14 can hand over the hollow 11 to the rear feed clamping sledge 5 at its front point of return 13. After the hollow 11 has been received by the rear feed clamping sledge 5 the rear feed clamping sledge 5 in a next step would forward the hollow 11 stepwise in a direction towards the mandrel 4 while the front feed clamping sledge 5 would return to its front point of return 13 in order to receive a further hollow 11. This way a continuous operation of the mill is possible which avoids dead times during return of a single feed clamping sledge 5 as it is shown in FIGS. 1 and 2 from its rear point of return to its front point of return.

[0103] In contrast to the cold pilger rolling mill 7 shown in FIG. 1 the cold pilger rolling mill 7 of FIG. 2 further comprises another, in the feed direction of the hollow 11 rear mandrel thrust block 16 in addition to the front mandrel thrust block 15. The rear mandrel thrust block 16 is located between the front point of return 13 of the front feed clamping sledge 5 and the front mandrel thrust block 15 and like the front mandrel thrust block 15 comprises a chuck 20 for mounting the mandrel bar 8. The hollow 11 in FIG. 2 has already left the front mandrel thrust block 15 such that the chuck 19 of the front mandrel thrust block 15 is closed and the mandrel bar 8 is fixedly clamped. The chuck 20 of the rear mandrel thrust block 16 in contrast is open and lets the hollow 11 pass between the chuck 20 and the mandrel bar 8.

[0104] In FIG. 2 the distance between the front mandrel thrust block 15 measured at the in the feed direction of the hollow rear end of the chuck 19 and the rear mandrel thrust block 16 amounts to 38 m, while the hollow 11 shown in FIG. 2 comprises a length of 37 m. Consequently, the hollow 11 can be located between the front mandrel thrust block 15 and the rear mandrel thrust block 16 and the chucks 19, 20 of both mandrel thrust blocks 15, 16 can be closed without the chucks 19, 20 clamping the hollow 11.

[0105] In FIG. 3 a cold pilger rolling mill 7 according to the invention is shown in a schematic side view, which in comparison to the cold pilger rolling mill 7 shown in FIG. 2 in addition to the two feed clamping stages 5, 5, the front mandrel thrust block 15 and the rear mandrel thrust block 16 also comprises a winding device 30.

[0106] In order to wind up the finished tube 25 behind the roll stand 1 into a transportable shape the cold pilger rolling mill 7 shown in FIG. 3 also comprises a winding device 30. The winding device 30 which in FIG. 3 is shown schematically consists of a mounting frame 33 and a bending device 31. The bending device 31 comprises three bending rollers 32b which in the shown embodiment all three are motor driven and are frictionally engaged with the finished tube 25.

[0107] The already finished milled part of the hollow, i.e. the part of the already finished tube 25 first is received by a chuck 22 of a discharge clamp sledge 18 and is drawn in a direction towards the winding device 30. As soon as a part of the already finished tube 25 enters between the bending rollers 32b of the bending device 31 of the winding device 30 this part of the finished tube 25 is bend by two bending rollers 32b above the finished tube 25 and a bending roller 32b below the finished tube 25. Due to a motor driven rotation of the bending device 30 in a direction of the arrow drawn in FIG. 3 the bend part of the finished tube 35 is spirally wound up around a first axis 34.

[0108] The bending device 31 and the three bending rollers 32b furthermore are pivotably mounted at the mounting frame 33 around a second axis 35 which coincides with the longitudinal axis of the finished tube 25 exiting the discharge clamping sledge 18. Thereby the pivoting motion of the bending rollers 32b around the second axis 35 is carried out by means of a motor drive. The pivoting motion occurring simultaneously with the winding up is carried out with the same angular velocity as the pivoting motion of the hollow 11 around its longitudinal axis during the milling of the hollow 11. Consequently, both pivoting motions occur synchronous with each other. This has the advantage that a twisting of the finished tube 35 during winding up is avoided entirely, at least essentially and the finished tube 35 is wound up without torsional stresses during milling.

[0109] In addition in the same workshop an annealing furnace 29 is provided in which the hollow is annealed prior to the feeding into the cold pilger rolling mill 7 and after a first milling in a second cold pilger rolling mill.

[0110] For purposes of the original disclosure it is pointed out that all features which are apparent for a person skilled in the art from the present description, from the figures and from the claims, even if they are only disclosed in combination with certain further features, are combinable on their own as well as in arbitrary combinations with other features and feature groups disclosed herein as far as this I not explicitly excluded or technical circumstances make such combination impossible or useless. A full explicit description of all possible combinations of features is only omitted to provide a short and readable description. While the invention is shown in detail in the figures and the above description this representation and description is only an example and is not considered a restriction of the scope of protection as it is defined by the claims. The invention is not restricted to the disclosed embodiments.

[0111] Modifications of the disclosed embodiments are apparent for a person skilled in the art from the figures, the description and the dependent claims. In the claims the word comprises does not exclude other elements or steps. The indefinite article a or an does not exclude a plurality. The mere fact that some features are claimed in different claims does not exclude their combination. Reference signs in the claims are not considered as a restriction of the scope of protection.

REFERENCE LIST

[0112] 1 roll stand [0113] 2, 3 upper, lower roller [0114] 4 mandrel [0115] 5 feed clamping sledge [0116] 6 linear motor [0117] 7, 7, 7 cold pilger rolling mill [0118] 8 mandrel bar [0119] 9 front point of return of the roll stand [0120] 10 rear point of return of the roll stand [0121] 11 hollow [0122] 12 feed chuck [0123] 13 front point of return of the feed clamping sledge [0124] 14 rear point of return of the feed clamping sledge [0125] 15 front mandrel thrust block [0126] 16 rear mandrel thrust block [0127] 18 discharge clamping sledge for the finished tube [0128] 19, 20, 22 chuck [0129] 23 crank drive [0130] 24 push rod [0131] 25 finished tube [0132] 26 unwinding device [0133] 27 spindle [0134] 28 first axis (unwinding device) [0135] 29 annealing furnace [0136] 30 winding device [0137] 31 bending device [0138] 32a, 32b bending roller [0139] 33 mounting frame [0140] 34 first axis (winding device) [0141] 35 second axis (winding device)