COLD PILGER ROLLING MILL AND METHOD FOR PRODUCING A PIPE

Abstract

A cold pilger rolling mill including a front mandrel thrust block that has a distance of at least 30 m from a feed chuck, measured with the feed clamping carriage at the rear reversal point thereof. The distance is measured between the rear (in the feed direction of the hollow) end of the chuck of the front mandrel thrust block and the front (in the feed direction of the hollow) end of the feed chuck of the feed clamping carriage at the rear reversal point thereof.

Claims

1. A cold pilger rolling mill for cold working a hollow into a strain-hardened tube comprising: a roll stand comprising rollers rotatably mounted on the roll stand, wherein the roll stand is driven by a motor and is movable back and forth in a direction parallel to a longitudinal axis of the hollow between a front reversal point in a feed direction of the hollow and a rear reversal point in the feed direction of the hollow, and wherein the rollers during a reciprocating motion of the hollow perform a rotational motion, such that the rollers in an operation of the cold pilger rolling mill roll the hollow into a tube, a mandrel, wherein the mandrel is supported by a mandrel bar at a rear end of the mandrel bar in the feed direction of the hollow in such a way that during operation of the cold pilger rolling mill the hollow is rolled by the rollers over the mandrel, at least one feed clamping carriage with a feed chuck mounted thereon to receive the hollo, wherein the feed clamping carriage in a direction parallel to the longitudinal axis of the hollow is movable back and forth between a front reversal point in the feed direction of the hollow and a rear reversal point in the feed direction of the hollow such that the hollow in an operation of the cold pilger rolling mill experiences a stepwise feed in a direction towards the mandrel, and wherein the feed chuck can is openable and closeable in a radial direction in such a way that it releases or clamps the hollow, and at least one mandrel thrust block with a chuck mounted thereon to hold the mandrel bar, wherein a front mandrel thrust block is positioned in front of the feed clamping carriage in the feed direction of the hollow such that the mandrel bar in an operation of the cold pilger rolling mill is holdable by the chuck of the front mandrel thrust block, and wherein the chuck of the front mandrel thrust block is openable in a radial direction, so that a hollow is feedable between the chuck and the mandrel bar, wherein the front mandrel thrust block has a distance of at least 30 m from the feed chuck, measured with the feed clamping carriage at its rear reversal point.

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

3. The cold pilger rolling mill according to claim 1, wherein the mandrel bar has an elongation of 10% or less.

4. The cold pilger rolling mill according to claim 1, wherein the cold pilger rolling mill comprises two feed clamping carriages each having a feed chuck mounted thereon and a controller, wherein the controller is arranged to control the motion of the two feed clamping carriages such that each of the hollows in a continuous operation of the cold pilger rolling mill is alternately clampable by one of the feed chucks and feedable stepwise in the direction towards the mandrel, wherein the front mandrel thrust block has a distance from the rear feed clamping carriage in the feed direction of the hollow of at least 30 m, measured with the feed clamping carriage at its rear reversal point.

5. 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 in the feed direction of the hollow between the front reversal point of the feed clamping carriage and the front mandrel thrust block, wherein the rear mandrel thrust block has a distance of at least 30 m from the front mandrel thrust block, 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.

6. The cold pilger rolling mill according to claim 1, wherein each feed clamping carriage of the cold pilger rolling mill is arranged to feed a hollow with a weight of 100 kg/m or more.

7. The cold pilger rolling mill according to claim 1, wherein a coiling device is arranged in the feed direction of the finished tube behind the rollers of the cold pilger rolling mill, wherein the coiling device for the tube manufactured in the cold pilger rolling mill comprises a bending device to bend the tube so that it can be coiled around a first axis, and a holding frame wherein the bending device and the first axis are pivotably received on the holding frame around a second axis which is perpendicular to the first axis and parallel to a longitudinal axis of a hollow received between the rollers.

8. The cold pilger rolling mill according to claim 1, wherein the cold pilger rolling mill has an uncoiling device, by which a hollow coiled on a spindle about a first axis is uncoilable and feedable to the front mandrel thrust block for a feed into the cold pilger rolling mill.

9. The cold pilger rolling mill according to claim 1, wherein the cold pilger rolling mill has an annealing furnace which is arranged to heat the hollow in a coiled state to a temperature in a range from 1000 C. to 1200 C.

10. A method for manufacturing a tube by cold working a hollow in a cold pilger rolling mill with a roll stand having rollers rotatably mounted thereon, a mandrel supported by a mandrel bar, at least one mandrel thrust block holding the mandrel bar and at least one feed clamping carriage with a feed chuck to receive the hollow comprising the steps of: a) opening a chuck of a front mandrel thrust block in the feed direction the hollow in a radial direction and feeding a first hollow through the front mandrel thrust block, b) after completely feeding 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 holds the mandrel bar supporting the mandrel, c) feeding the first hollow to a feed clamping carriage 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 a front reversal point of the feed clamping carriage in the feed direction of the hollow, d) rolling of the first hollow by the rollers over the mandrel into a strain-hardened tube by stepwise feeding of the first hollow by means of the feed clamping carriage and an oscillating motion of the roll stand with the rollers back and forth between a front reversal point and a rear reversal point, wherein the first hollow has a length of 30 m or more.

11. The method for manufacturing a tube according to claim 10, further comprising an additional step after step b) and before step c): e) opening in a radial direction a chuck of an rear mandrel thrust block in the feed direction of the hollow positioned in the feed direction of the hollow between the front reversal point of a front feed clamping carriage and the front mandrel thrust block, wherein the rear mandrel thrust block has a distance of at least 30 m from the front mandrel thrust block, and feeding the first hollow through the rear mandrel thrust block, wherein rolling of the first hollow by the rollers over the mandrel into a strain-hardened tube in step d) is carried out by stepwise feeding the first hollow alternately by means of the front feed clamping carriage from a front reversal point to a rear reversal point of the front feed clamping carriage and by means of a in the feed direction of the hollow rear feed clamping carriage from a front reversal point to a rear reversal point of the rear feed clamping carriage and oscillating the roll stand with the rollers back and forth between a front and a rear reversal point, and wherein the method additionally comprises the steps: f) after completely feeding the first hollow through the rear mandrel thrust block closing the chuck of the rear mandrel thrust block in the radial direction so that the rear mandrel thrust block holds the mandrel bar supporting the mandrel, g) during rolling of the first hollow opening the chuck of the front mandrel thrust block and feeding a second hollow through the front mandrel thrust block into the area between the front mandrel thrust block and the rear mandrel thrust block, h) after the second hollow has been fed completely through the front mandrel thrust block, closing the chuck of the front mandrel thrust block so that the front mandrel thrust block holds the mandrel bar supporting the mandrel, i) opening the chuck of the rear mandrel thrust block, j) feeding the second hollow through the rear mandrel thrust block, k) feeding the second hollow to the front feed clamping carriage and receiving the second hollow in the feed chuck of the front feed clamping carriage and clamping the second hollow by closing the feed chuck of the front feed clamping carriage in the radial direction, l) opening the feed chuck of the rear feed clamping carriage in the radial direction, m) stepwise feeding the second hollow alternately by means of the front feed clamping carriage and the rear feed clamping carriage with the second hollow being clamped, n) after the complete discharge of the finished tube rolled of the first hollow from the roll stand inserting the second hollow into the roll stand, and o) rolling the second hollow by the rollers over the mandrel into a strain-hardened tube by stepwise feeding the second hollow alternately using the rear feed clamping carriage and the front feed clamping carriage and oscillating the roll stand with the rollers back and forth between a front and a rear reversal point.

12. The method for manufacturing a tube according to claim 10, further comprising coiling an already completely rolled section of the hollow during the rolling of a section of the hollow to be rolled into a strain-hardened tube with the steps: bending an already completely rolled section of the hollow in a bending device, spirally coiling an already completely rolled section of the hollow about a first axis, and pivoting the bending device received on a support frame and the first axis about a second axis being substantially perpendicular to the first axis and being substantially parallel to a longitudinal axis of a hollow received between the rollers such that the pivoting occurs at the same angular velocity as a pivoting of the hollow about its longitudinal axis during the rolling of the hollow.

13. The method for manufacturing a tube according to claim 10, wherein an uncoiling of a coiled hollow from a spindle about a first axis occurs in an uncoiling device, so that an already uncoiled section of the hollow is fed through the front mandrel thrust block.

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 coiled 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 prior to heating the hollow a further cold working of the hollow is carried out in a second cold pilger rolling mill such that the finished tube is manufactured by cold working of a hollow multiple times.

Description

[0084] Further advantages, features and applications of the present invention will become apparent from the following description of embodiments thereof and the accompanying drawings.

[0085] FIG. 1 shows a schematic side view of the layout of a cold pilger rolling mill with a front mandrel thrust block according to an embodiment of the present invention.

[0086] FIG. 2 shows a schematic side view of the layout of a cold pilger rolling mill with a front and a rear mandrel thrust block and two feed clamping carriages according to a further embodiment of the present invention.

[0087] FIG. 3 shows a schematic side view of the layout of a cold pilger rolling mill with a front and a rear mandrel thrust block, two feed clamping carriages, an uncoiling device and a coiling device according to another embodiment of the present invention.

[0088] In FIG. 1, the layout of a cold pilger rolling mill according to the invention is shown schematically 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 supporting the mandrel 4, a feed clamping carriage 5 with a feed chuck 12 for receiving a hollow 11, a front mandrel thrust block 15 with a chuck 19 and a discharge clamping carriage 18 with a chuck 22. In the illustrated embodiment, the cold pilger rolling mill has a linear motor 6 as a direct drive for the feed clamping carriage 5.

[0089] During cold pilgering in the cold pilger rolling mill shown in FIG. 1, the hollow 11 experiences a stepwise feed in the direction towards the mandrel 4 or beyond the mandrel 4, while the rollers 2, 3 are rotationally moved back and forth in a horizontal direction over the mandrel 4 and thus over the hollow 11. The horizontal motion of the rollers 2, 3 is defined by the roll stand 1, on which the rollers 2, 3 are rotatably mounted. The roll stand 1 is reciprocated by means of a crank drive 23 via a push rod 24 in a direction parallel to the longitudinal axis of the hollow between a front reversal point 9 in the feed direction of the hollow 11 and a rear reversal point 10 in the feed direction of the hollow 11. The rollers 2, 3 in turn receive their rotational motion by a gear rack (not shown) being fixed with respect to the roll stand 1, wherein gear wheels (not shown) fixedly mounted on the roller axes comb with the gear rack. The feed of the hollow 11 over the mandrel 4 is carried out with the aid of the feed clamping carriage 5, which allows a translational motion in a direction parallel to the axis of the hollow 11. The feed clamping carriage 5 performs a reciprocating motion between a front reversal point 13 in the feed direction of the hollow 11 and a rear reversal point 14 in the feed direction of the hollow 11. In the embodiment of FIG. 1, the path of travel of the feed clamping carriage 5 between the two reversal points 13, 14 amounts to 24 m.

[0090] Once the hollow 11 has left the front mandrel thrust block 15, the chuck 19 of the front mandrel thrust block 15 is closed in the radial direction, so that the chuck 19 clamps the mandrel bar 8 firmly. In this case, the front mandrel thrust block 15 in FIG. 1 comprises a distance of 36 m from the feed chuck 12 of the feed clamping carriage 5, when the feed clamping carriage 5 is positioned at its rear reversal point 14. This distance is measured between the front end of chuck 19 of the front mandrel thrust block 15 and the front end of the feed chuck 12 of the feed clamping carriage 5 in the feed direction when the feed clamping carriage is at its rear reversal point 14. A hollow with a maximum length of 36 m could thus be arranged between the front mandrel thrust block 15 and the feed chuck 12 of the feed clamping carriage 5 positioned at its rear reversal point 14, without the hollow being pinched or clamped by the chuck 19 of the front mandrel thrust block 15 or the feed chuck 12 of the feed clamping carriage 5.

[0091] The mandrel bar 8 in FIG. 1 consists of the material 30 CrNiMo 8 and has a tensile strength of 1000 N/mm.sup.2 and an elongation of 8%.

[0092] At the front reversal point 9 of the roll stand 1 in the feed direction of the hollow 11, i.e. at the inlet dead center ET of the roll stand, the hollow 11 enters between the rollers 2, 3 and is received by the infeed pockets (not shown) of the rollers 2, 3. The conically calibrated rollers 2, 3 stacked on top of each other in the roll stand 1 are rolled over the hollow 11 by rolling back and forth on the hollow 11 in the feed direction of the feed clamping carriage 5. The pair of rollers 2, 3 moves during a rolling stroke by a distance L from the inlet dead center ET to the rear reversal point 10 of the rolling stand in the feed direction of the hollow, i.e. to the discharge dead center AT of the roll stand. In FIG. 1 this corresponds to a rotation of the rollers by an angle of 280. The pair of rollers 2, 3 stretches the hollow 11 over the mandrel 4 held in the interior of the hollow 11. The rollers 2, 3 and the mandrel 4 are calibrated such that the gap between the rollers 2, 3 and mandrel 4 in the working caliber zone of the rollers 2, 3 is steadily reduced from the wall thickness of the hollow 11 to the wall thickness of the finished rolled tube 25. In addition, the outer diameter defined by the rollers decreases from the outer diameter of the hollow 11 to the outer diameter of the finished tube 25 and the inner diameter defined by the mandrel 4 decreases from the inner diameter of the hollow 11 to the inner diameter of the finished tube 25. After the working caliber zone of the rollers 2, 3 follows the smoothing caliber zone of the rollers 2, 3, in which a smoothing of the surface of the tube 25 to be manufactured takes place. Upon reaching the rear reversal point 10 of the roll stand 1, the discharge pocket (not shown) of the rollers 2, 3 releases the finished rolled tube.

[0093] In order to obtain a uniform shape of the finished tube 25, the hollow 11 in addition to a stepwise feed experiences a rotation about its longitudinal axis. The rotation of the hollow 11 takes place at both reversal points 9, 10 of the roll stand 1, i.e. at the inlet dead center ET and at the discharge dead center AT. By repeatedly rolling over each tube section a uniform wall thickness and roundness of the tube and uniform inner and outer diameters are achieved.

[0094] The finished tube 25 is received by a chuck 22 of a discharge clamping carriage 18 and is pulled out of the cold pilger rolling mill 7.

[0095] FIG. 2 shows a schematic layout of another cold pilger rolling mill 7 according to the invention in a side view. In contrast to FIG. 1, however, the cold pilger rolling mill 7 illustrated in FIG. 2 has two feed clamping carriages 5, 5, each with a feed chuck 12, 12 to receive a hollow 11. The two feed clamping carriages 5, 5 can each be moved by 12 m between their front 13, 13 and rear reversal points 14, 14 and are therefore distinguished by a smaller path of travel in comparison with the feed clamping carriage 5 shown in FIG. 1.

[0096] The front feed clamping carriage 5 in the feed direction of the hollow 11 has already advanced the hollow towards its rear reversal point 14 in the direction towards the mandrel 4. The rear feed clamping carriage 5 in the feed direction of the hollow 11 approaches the front feed clamping carriage 5 in the feed direction of the hollow, so that the front feed clamping carriage 5, when it arrives at its rear reversal point 14, can pass over the hollow to the rear feed clamping carriage 5 at the front reversal point 13 of the rear feed clamping carriage 5. After the clamping of the hollow 11 by the rear feed clamping carriage 5, the rear feed clamping carriage 5 would in the next step feed the hollow 11 stepwise towards the mandrel 4, while the front feed clamping carriage 5 would return to its front reversal point 13 to receive another hollow 11. In this way, a continuous operation of the cold pilger rolling mill is enabled, which avoids dead times during the return of a single feed clamping carriage 5 from its rear reversal point 14 to its front reversal point 13 as shown in FIGS. 1 and 2.

[0097] In contrast to the cold pilger rolling mill 7 shown in FIG. 1, the cold pilger rolling mill 7 of FIG. 2 in addition to the front mandrel thrust block 15, also has a rear mandrel thrust block 16 in the feed direction of the hollow 11. The rear mandrel thrust block 16 is arranged between the front reversal point 13 of the front feed clamping carriage 5 and the front mandrel thrust block 15 and, like the front mandrel thrust block 15, has a chuck 20 for holding the mandrel bar 8. The hollow 11 in FIG. 2 has left the front mandrel thrust block 15 already, so that the chuck 19 of the front mandrel thrust block 15 is closed and the mandrel 8 is firmly clamped. The chuck 20 of the rear mandrel thrust block 16, however, is opened and allows the hollow 11 to pass between the chuck 20 and the mandrel bar 8.

[0098] In FIG. 2, the distance between the front mandrel thrust block 15, measured at the rear end of the chuck 19 in the feed direction of the hollow, and the rear mandrel thrust block 16, measured at the front end of the chuck 20, amounts to 38 m, while the hollow 11 depicted in FIG. 2 has a length of 37 m. Accordingly, the hollow 11 can be arranged between the front 15 and 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 pinching the hollow 11.

[0099] In FIG. 3, a cold pilger rolling mill 7 according to an embodiment of 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 carriages 5, 5, the front 15 and the rear mandrel thrust blocks 16 comprises an uncoiling device 26 and a coiling device 30.

[0100] The uncoiling device 26 ensures that a hollow 11 arranged on a spindle 27 and coiled around a first axis 28 is uncoiled. In this case, a motor-driven rotation of the spindle 27 occurs about the first axis 28 in the direction of the arrow depicted, so that the hollow arranged and coiled on the spindle 27 is fed between five bending rollers 32a. Three bending rollers 32a are arranged in an upper row and two bending rollers 32a are arranged in a lower row. The bending rollers 32a bend the hollow 11 passing uniformly and in opposite directions so that the hollow 11 is bent and straightened between the bending rollers 32a before being fed through the chuck 19 of the front mandrel thrust block 15. The straightening of the hollow 11 from its curved initial shape takes place during the loading of the hollow 11 through the front mandrel thrust block 15 in the cold pilger rolling 7.

[0101] The integration of an uncoiling device 26, as shown in FIG. 4, is particularly advantageous in case of hollows 5 having a length of 30 m or more. By uncoiling a coiled hollow 11 from the spindle 27 and simultaneously feeding the hollow 11 to the front mandrel thrust block 15 and passing the hollow 11 through the front mandrel thrust block 15, a lot of space can be saved in a workshop in which the cold pilger mill 7 is installed.

[0102] In order to be able to coil the finished tube 25 behind the roll stand 1 into a shape to be shipped, a coiling device 30 is additionally provided in the cold pilger rolling mill 7 shown in FIG. 3. The coiling device 30, which is shown schematically in FIG. 3, consists of a holding frame 33 and a bending device 31. The bending device 31 has three bending rollers 32b, which in the illustrated embodiment are all motor-driven and frictionally engaged with the finished tube 25.

[0103] The already completely rolled section of the hollow, i.e. the section of the already finished tube 25, is first received by a chuck 22 of a discharge clamping carriage 18 and is pulled in the direction towards the coiling device 30. As soon as a section of the already finished tube 25 runs between the bending rollers 32b of the bending device 31 of the coiling device 30, this section of the finished tube 25 is first bent by two bending rollers 32b arranged above the finished tube 25 and a bending roll 32b arranged below the finished tube 25. As a result of a motor-driven rotation of the coiling device 30 in the direction of the arrow depicted in FIG. 3, the curved portion of the finished tube 35 is coiled spirally around a first axis 34.

[0104] In addition, the bending device 31 and the three bending rollers 32b are pivotally mounted on the holding frame 33 about a second axis 35, which coincides with the longitudinal axis of the finished tube 25 leaving the discharge clamping carriage 18. In this case, the pivoting motion of the bending rollers 32b about the second axis 35 occurs by means of a motor drive. The pivoting occurring simultaneously with the coiling is carried at the same angular velocity as the pivoting motion of the hollow 11 about its longitudinal axis during the rolling of the hollow 11. Both pivoting motions therefore take place synchronously with respect to each other. This has the advantage that a twisting of the finished tube 25 during coiling is completely, but at least substantially, avoided and the finished tube 25 is coiled without any torsional stresses during rolling.

[0105] In addition, an annealing furnace 29 is provided in the same workshop in which the hollow 11 is annealed prior to entry into the pilger rolling mill 7 and after a first rolling in a second cold pilger rolling mill.

[0106] For purposes of the original disclosure, it is to be understood that all features as will become apparent to those skilled in the art from the present description, drawings, and claims, even though they have been specifically described in connection with certain further features, both individually and separately can be combined in any combination with others of the features or groups of features disclosed herein, unless this has been expressly excluded or technical conditions make such combinations impossible or pointless. For brevity and readability of the description a comprehensive, explicit representation of all conceivable combinations of features has been omitted. While the invention has been illustrated and described in detail in the drawings and in the foregoing description, such illustration and description is exemplary only and is not intended to limit the scope of protection as it is defined by the claims. The invention is not limited to the disclosed embodiments.

[0107] Variations of the disclosed embodiments will be apparent to those skilled in the art from the drawings, the description and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain features are claimed in different claims does not exclude their combination. Reference signs in the claims are not intended to limit the scope of protection.

LIST OF REFERENCE NUMBERS

[0108] 1 roll stand

[0109] 2, 3 upper, lower roller

[0110] 4 mandrel

[0111] 5 feed clamping carriage

[0112] 6 linear motor

[0113] 7, 7, 7 cold pilger rolling mill

[0114] 8 mandrel bar

[0115] 9 front reversal point of the roll stand

[0116] 10 rear reversal point of the roll stand

[0117] 12 feed chuck

[0118] 13 front reversal point of the feed clamping carriage

[0119] 14 rear reversal point of the feed clamping carriage

[0120] 15 front mandrel thrust block

[0121] 16 rear mandrel thrust block

[0122] 18 discharge clamping carriage for finished tube

[0123] 19, 20, 22 chuck

[0124] 23 crankshaft

[0125] 24 pushrod

[0126] 25 finished tube

[0127] 26 uncoiling device

[0128] 27 spindle

[0129] 28 first axis (uncoiling device)

[0130] 29 annealing furnace

[0131] 30 coiling device

[0132] 31 bending device

[0133] 32a, 32b bending roller

[0134] 33 holding frame

[0135] 34 first axis (coiling device)

[0136] 35 second axis (coiling device)

[0137] ET inlet dead center

[0138] AT outlet dead center