Rolling mill and rolling method

Abstract

In order to improve the quality of pipe-like work pieces, a rolling mill has at least two successive consecutive rolling stages that have mandrel rods. A threading line for the mandrel rod of the second rolling stage can lie on an extraction line for the mandrel rod of the first rolling stage. The same advantage can be achieved in a rolling method for the production of pipe-like work pieces, comprising at least two successive consecutive rolling stages, wherein the two rolling stages perform the rolling with the use of mandrel rods. The work piece is brought from the mandrel rod of the first rolling stage onto the mandrel rod of the second rolling stage, without entirely emptying an interior of the work piece and/or without changing the direction of movement of the work piece or braking the work piece in the meantime and accelerating it once again.

Claims

1. A rolling method for the production of a pipe-like work piece, using at least two successive consecutive rolling stages, wherein the two rolling stages perform the rolling with a mandrel rod in the first rolling stage and another mandrel rod in the second rolling stage, the method comprising: rolling a work piece in the first rolling stage being a cross-roll piercing method using the mandrel rod of the first rolling stage in order to form the work piece from a block into a hollow block with the mandrel rod of the first stage located in an interior of the work piece; bringing the work piece from the mandrel rod of the first rolling stage onto the mandrel rod of the second rolling stage by inserting the mandrel rod of the second rolling stage into the interior of the work piece without entirely removing the mandrel rod of the first rolling stage from the interior of the work piece and without changing a direction of movement of the work piece and without braking the work piece and accelerating the work piece once again, wherein the mandrel rod of the second rolling stage moves with the work piece during the second rolling stage, and wherein the second rolling stage is a mandrel rolling method.

2. The rolling method according to claim 1, wherein the work piece is brought from the mandrel rod of the first rolling stage, while the mandrel rod of the first rolling stage is still situated in the work piece, onto the mandrel rod of the second rolling stage, and/or wherein the work piece is brought from the mandrel rod of the first rolling stage, while the mandrel rod of the first rolling stage is still situated in the work piece, onto an intermediate rod and from the intermediate rod, while the intermediate rod is still situated in the work piece, onto the mandrel rod of the second rolling stage.

3. The rolling method according to claim 1, wherein the mandrel rods touch during the step of bringing the work piece from the first rolling stage to the second rolling stage.

4. The rolling method according to claim 1, wherein the rods put tensile or pressure stress on one another during the step of bringing the work piece from the first rolling stage to the second rolling stage.

5. The rolling method according to claim 1, wherein an interior of the work piece is provided with a deoxidation agent and/or lubricant during extraction of the mandrel rod of the first rolling stage.

6. The rolling method according claim 1, wherein the two rolling stages follow one another without interposition of a further forming stage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.

(2) In the drawings, wherein similar reference characters denote similar elements throughout the several views:

(3) FIG. 1 shows a schematic top view of a first rolling mill;

(4) FIG. 2 shows the schematic method sequence of a rolling method carried out on the rolling mill according to FIG. 1;

(5) FIG. 3 shows a schematic top view of a second rolling mill; and

(6) FIG. 4 shows the schematic method sequence of a rolling method carried out on the rolling mill according to FIG. 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) Referring now in detail to the drawings, the rolling mill 1 shown in FIG. 1 rolls a work piece 2, proceeding from a block, in a first rolling stage 10 that is configured as a cross-roll piercing mill 15, first into a hollow block 4 and then, in a second rolling stage 20, which is configured as a mandrel rolling mill 25, to produce a shell 5.

(8) Both the first rolling stage 10 and the second rolling stage 20 have mandrel rods 11, 21. The mandrel rod 11 of the first rolling stage 10 comprises a piercer 12 and a rod 13, which is held by way of a counter-bearing 14 as a run-up mandrel rod 11, counter to the direction of movement of the work piece 2 through the first rolling stage 10.

(9) The work piece 2 or the hollow block 4, respectively, after being rolled in the first rolling stage 10, is brought, by way of a transverse transport 17 that is not shown in any detail and is sufficiently known, from a rolling line 16 of the first rolling stage 10 onto an extraction line 19, on which the mandrel rod 11 of the first rolling stage 10 is extracted from the hollow block 4 by means of a hold-back mechanism 18 and a longitudinal work piece transport 8, in that the hollow block 4 is moved along the extraction line 19. Also, the extraction line 19 lies directly on a threading line 29 of the second rolling stage, so that the longitudinal work piece transport 8 can move the work piece 2 from an extraction start position all the way to a threading end position on the second mandrel rod 21, without changing the direction of movement of the work piece 2 or braking the work piece in the meantime and accelerating it again. In this connection, the threading line 29 lies directly on the rolling line 26 of the second rolling stage 20, so that after threading of the mandrel rod 21 of the second rolling stage 20, a retainer 24 merely needs to grasp the mandrel rod 21 with the second rolling stage and to guide it through the mandrel rolling mill 25 in known manner.

(10) As is directly evident, the cold mandrel rod 21 of the second rolling stage 20 remains within the hollow block 4 for only a relatively short time, until this block is processed in the mandrel rolling mill 25, so that cooling, which ultimately could impair the quality of the work piece 2, is avoided.

(11) Furthermore, the entire method sequence is extremely time-saving, so that for this reason, as well, cooling of the work piece 2 between the two rolling stages 10, 20 is reduced to a minimum.

(12) Depending on the concrete implementation of this exemplary embodiment, the mandrel rods 11 and 21 can be connected with one another by tension, so that the hold-back mechanism 18, in particular, can also hold back the mandrel rod 21 of the second rolling stage 20, counter to the movement of the hollow block 4, during the mandrel rod change-over. Preferably, there is a particularly small distance between the two mandrel rods 11, 21, so that for one thing, as little air as possible is drawn into the interior of the hollow block 4, and for another, the risk that rolling peels get into the interior of the hollow block 4 is reduced to a minimum.

(13) In an alternative embodiment, the mandrel rod 21 of the second rolling stage 20 is supported in the region of the rolls of the mandrel rolling mill 25—and, if necessary, actually helps to support the mandrel rod 11 of the first rolling stage 10, if both of them interact end to end, with or without an intermediate rod.

(14) The method sequence described above, as such, is shown in detail in FIG. 2.

(15) The threading line 29 of the second rolling stage lies on the extraction line 19 of the first rolling stage 10 also in the arrangement according to FIGS. 3 and 4. However, in this embodiment, the two lines 19, 29 lie on the rolling line 16 of the first rolling stage, so that the hollow block 4 can be released from the mandrel rod 11 of the first rolling stage 10 directly after rolling, from the end position, by means of the longitudinal work piece transport 8, and can be brought over the mandrel rod 21 of the second rolling stage 20. In order to counter the forces that occur in this connection, this arrangement has a counter-bearing 28 that supports both the mandrel rod 21 of the second rolling stage 20 and the mandrel rod 11 of the first rolling stage 10, whereby the counter-bearing 14 of the first rolling stage 10 is still pivoted away before threading, and the two mandrel rods 11, 21 are brought end to end with one another.

(16) After threading of the mandrel rod 21 of the second rolling stage 20, the hollow block 4, together with the threaded mandrel rod 21, is transferred to the rolling line 26 of the second rolling stage 20 by means of the transverse transport 27, in order to then be rolled in known manner.

(17) Here, too, FIG. 4 shows the method sequence schematically.

(18) The arrangement shown in FIGS. 3 and 4 can be operated at higher cycle times, because in view of the length of the mandrel rod 21 of the second rolling stage 20, a work piece 2 that has previously passed through the rolling mill 1 can still be rolled in the second rolling stage 20 while the work piece 2 is already being threaded onto the mandrel rod 21.

(19) It is understood that if necessary, a transfer of the work piece 2 from the one mandrel rod 11 to the other mandrel rod 21 can also take place in intermediate positions between the rolling line 16 of the first rolling stage and the rolling line 26 of the second rolling stage. This is particularly possible during a transport, in which not only the mandrel rods 11, 21 but also the work piece 2 are being moved.

(20) In both embodiments, the mandrel rod 11 of the first rolling stage 10 is configured in such a manner that it can bring deoxidation agents or lubricants into the interior of the hollow block 4. In this manner, scale formation can be prevented to an even greater extent. Furthermore, it is possible to eliminate a further intermediate step for lubrication, if applicable. It is understood that a corresponding apparatus for application of the deoxidation agent or lubricant can also be provided at a different location, for example on an intermediate rod.

(21) Accordingly, while only a few embodiments of the present invention have been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.

REFERENCE SYMBOL LIST

(22) 1 rolling mill 2 work piece 3 block 4 hollow block 5 shell 6 longitudinal work piece transport 10 first rolling stage 11 mandrel rod 12 piercer 13 rod 14 counter-bearing 15 cross-roll piercing mill 16 rolling line of the first rolling stage 17 transverse transport 18 hold-back mechanism 19 extraction line 20 second rolling stage 21 mandrel rod 24 retainer 25 mandrel rolling mill 26 rolling line of the second rolling stage 27 transverse transport 28 counter-bearing 29 threading line