DE2657823A1 - Rolling mill for mfr. of seamless tubes from billets - using a skew rolling mill with mandrel or hole press - Google Patents

Abstract

Skew rolling mill or a hole press is used to transform the billet into hollow blocks. The blocks are then prerolled in a rolling mill into short continuous tubes. After this the wall thickness is further reduced by further rolling. Improvement is that the rolling mill in which the hollow blocks are rolled into short cylinders is in the form of a planetary skew rolling mill with a fixed mandrel of which the point projects into the milling zone. The skew rolling mill is in line with the mill in which the wall thickness of the tube is reduced.

Description

Rolling mill for the production of seamless tubes

The invention relates to a rolling mill for the production of seamless Tubes made from round billets, consisting of a piercing mill or a piercing press for reshaping the billets into hollow blocks, one of them or one of these with the interposition of them a transverse transport downstream rolling mill for rolling out the hollow blocks via a mandrel bar to contour tubes, as well as a stretch-reducing mill for the Rolling out the account pipes into finished pipes.

Such rolling mills are already available in various designs known. They differ essentially in their arrangement and training between the piercing mill or piercing press and the stretch-reducing mill arranged rolling mill for the rough rolling of the hollow blocks into tubes.

In the classic design of a tube rolling mill, this is Rolling mill designed as a multi-stand continuous rolling mill, to which the cross rolling mill or hollow blocks coming from the piercing press are fed.

If the round billets are punched into hollow blocks on a cross-rolling mill, then the hollow blocks have to be fed to the continuous rolling mill via a transverse transport will. The piercing mill works with one located on the outlet side A mandrel through which the round billet transforms its longitudinal axis into a hollow block while rotating will. On the one hand, namely the mandrel assigned to the cross-rolling mill on the outlet side leaves a direct entry of the hollow block into the continuous rolling mill is not possible because namely after the completion of the hollow block pulled out of this must become. But even if it is not necessary to pull the mandrel on the outlet side - the hollow block could not enter the continuous rolling mill because it rotates around its longitudinal axis during the shaping in the Schrågnvalzwerk, one such However, rotation in the continuous rolling mill is not desired.

The forming of the hollow block in the continuous rolling mill takes place via a mandrel bar, which must be introduced into the hollow block before the entry side of the continuous rolling mill and which runs along with the continuous tubes in the rolling direction during the rolling process. Therefore this mandrel bar must have a length dimension which is at least the length dimension of the contour tube.

In the case of a rolling mill system equipped with a continuous rolling mill, it is also necessary to have a mandrel bar puller on the outlet side of the continuous rolling mill provide, with the help of which the mandrel after the exit of the contour tube from the Continuous rolling mill pulled out of this and back to the inlet side of the continuous rolling mill is returned for reuse.

The operation of the mandrel bar extractor makes it impossible to the continuous rolling mill in one roll line with the downstream stretch-reducing mill to arrange. Therefore, the continuous tubes must also be arranged downstream of the continuous rolling mill Cross transport are promoted in front of the entry side of the stretch-reducing mill. Due to the relatively long passage of the continuous tubes through the continuous rolling mill and the downstream operation of the mandrel bar extractor cools that down Continuous tube down to a temperature of about 650 C, so that this is before the insertion must be reheated in the stretch-reducing mill. To this end is therefore in the known rolling mill system, a reheating furnace following uen transverse transport provided that the continuous tubes must pass through before they enter the stretch-reducing mill can be introduced.

It is obvious that a rolling mill of the above-described, known design is very expensive because it is in addition to the various rolling mills requires complex auxiliary systems that can only be accommodated in long and wide halls are. In addition, the operating weight of the round billets used for pipe production is also included limited, because the resulting as an intermediate product conti tubes, due to the Design of the auxiliary systems should not exceed a certain length - a maximum of 30 m to be allowed to.

A fully continuous production of seamless tubes is with one such, for example in "Klepzig Fachberichte" 81st year.

(1973), pages 218-221 described, pipe rolling mill plant, not possible.

To reduce the investment in the system is in the magazine "Stahl und Eisen "93. Jhrg. (1973) on page 1026 in the right column already the suggestion was made, instead of the multi-stand continuous rolling mill, a planetary piercing mill to use. Otherwise nothing changes in the overall structure of the rolling mill system, because it is obvious that here, too, the rolling of the contour tubes over a accompanying mandrel takes place and therefore the mandrel rod puller, the associated Cross transport and the reheating furnace upstream of the stretch-reducing mill are retained Need to become.

Rolling mills for the production of seamless tubes are also known from round billets, in which the piercing mill is used to produce the hollow blocks so-called Assel mill is downstream. Forming takes place at the Assel rolling mill the hollow blocks to contour tubes also via a mandrel, which is arranged on the inlet side is. During the rolling process, the rolling stock rotates around its longitudinal axis and the mandrel follows this rotational movement.

In the production of continuous tubes in the Assel rolling mill, there is one Mandrel bar pull-out device is not required, but the contour tube can also be used here do not enter the stretch-reducing mill directly, mainly therefore not because there is a rotational movement of the tube in the stretch-reducing mill is undesirable. The Assel mill must therefore also have a cross transport and a Reheating furnace can be assigned, so that the system costs even in this case is considerable.

In the Assel rolling mill, the entry-side bearing of the mandrel prepares considerable difficulties because this rotates with the rolling stock and therefore he must be kept on expensive thrust bearings.

For the sake of completeness, it should be noted that for the production of more seamless Tubes also so-called pilgrim step mills are in use. The mode of action the same lies, so to speak, between the two types of rolling mill described above, because the rolling stock does not rotate continuously, but rotated intermittently will. The pipes emerging from the pilgrim step rolling mills cannot therefore either run directly into a downstream stretch-reducing mill.

The purpose of the invention is to overcome the disadvantages of all of the above Avoid rolling mills for the production of seamless tubes from round billets. Therefore, it is based on the task of a rolling mill of the type mentioned Generate genus for the production of seamless tubes from round billets, with the the hollow blocks prefabricated in a piercing mill or on a piercing press fully continuously rolled out into finished tubes in one heat. Simultaneously an increase in the operating weight for the round billets should also be made possible, so that the production output of the rolling mill is improved accordingly.

The solution to this complex problem is essentially achieved according to the invention achieved in that the continuous tube rolling mill as a planetary piercing mill with a arranged on the inlet side, stationary with the mandrel tip during the rolling process formed into the deformation zone protruding mandrel bar and in the same roll line is arranged with the stretch reducing mill.

Since in such a rolling mill system, on the one hand, the rotation of the continuous tube is avoided during the rolling process and, on the other hand, the mandrel bar is stationary Position, the contour tube can leave the planetary piercing mill directly, i.e. without an intermediate stop enter the stretch-reducing mill. Because the contour tube in the planetary piercing mill is subject to deformation work only over a relatively short distance and because of The mandrel rod, which is stationary on the inlet side, has no mandrel rod pull-out device on the outlet side is required, no transverse transport and no reheating furnace is required. Therefore can according to a further feature of the invention, the planetary piercing mill directly be arranged in front of the entry side of the stretch-reducing mill. This results in the advantage that the rolling hall can be built much shorter and narrower can.

So that a perfect operation of the planetary piercing mill at the Rolling out of the hollow blocks to the contour tubes is ensured after a Another feature of the invention is the mandrel bar on the inlet side of the planetary piercing mill arranged axially displaceably around the length of the hollow blocks.

This measure enables the hollow blocks to be used as a cross rolling mill or from the piercing press by a transverse transport in front of the inlet side of the planetary piercing mill bring, whereupon the mandrel tange with the mandrel tip through the hollow block up can be advanced into the deformation zone of the planetary piercing mill. By subsequent advance of the hollow block is its' front end into the deformation zone of the planetary piercing mill and there continuously over the fixed mandrel tip with a large degree of stretch formed into a tube in a roll pass, which then goes straight to the stretch-reducing mill to manufacture the finished pipe comes in.

The invention is to be described in detail with the aid of a drawing will. It shows Fig. F in a purely schematic plan view of a conventional one Tube rolling mill plant with a between the piercing mill and the stretch-reducing mill switched on continuous rolling mill, while in Fig. 2 also in a schematic plan view a tube rolling mill according to the invention is shown.

In both figures of the drawing, a rotary hearth furnace 1 is from one Storage location 2, e.g. via a roller table 3 and a cross conveyor 4 on the entry side 5 are fed cyclically with round billets 6, which after they have been heated, also cyclically be discharged on the discharge side 7 of the rotary hearth furnace 1. Get from there it is first transferred to a centering device 9 via a transverse transport 8 and from there from in turn via transverse transports 1o and 12 and a roller table 11 in front of the inlet side a cross rolling mill 13. In this cross rolling mill, the round billets 6 are then in a known manner via a mandrel 14 held on the outlet side to form hollow blocks 15 reshaped. After the hollow block 15 has left the piercing rolling mill 13 completely has, the mandrel 14 is pulled out of the hollow block 15 away from the outlet side. The hollow block 15 then again arrives at a transverse transport 16 and via a Roller table 17 to a further transverse transport 18. In the case of the one shown in FIG In the tube rolling mill, the hollow block 15 is moved by the transverse transport 18 in front of the inlet side a multi-stand continuous rolling mill 19 brought. First there is a long thorn rod 20 pushed through the rear end into the hollow block 15, after which the The hollow block 15 with the mandrel bar 20 enters the continuous rolling mill 19.

The hollow block 15 then becomes one here over the mandrel bar 20 Contour tube 21 rolled out. The contour tube 21 now arrives at a transverse transport 22 and is then brought up to a mandrel bar puller. The mandrel bar puller 23 now pulls the mandrel rod out of the contour tube 21 and conveys it backwards to a transverse transport 24. Via the transverse transport 24, the mandrel bar 2o brought again in front of the inlet side of the continuous rolling mill 19.

The stripped contour tube 21 is conveyed further on the transverse transport and arrives from there via a roller table 25 into a reheating furnace 26, because it has meanwhile has cooled to a temperature of 650 ° C.

In the reheating furnace 26, the contour tube 21 is during a transversely directed Transport motion warmed up to 95oOC again. From there it then arrives via one Roller table 27 in a stretch reducing mill 28 with a large number of rolling stands and it is based on the final wall thickness and the required diameter rolled.

It is readily apparent that a tube rolling mill of the type shown in Fig. 1 is very complex and because of the complicated workflow The round stick 6 can only be operated with a very limited operating weight. The mandrel bar extractor 23 also causes considerable noise and through their operation leads to the fact that the contours 21 cool down to a temperature which makes reheating necessary before the continuous tube goes into the stretch-reducing mill 28 can enter.

In the tube rolling mill installation according to FIG. 2, instead of a multi-stand Continuous rolling mill 19, a planetary piercing mill 29 is provided. Through the transverse transport 18, the hollow block 15 is brought in front of the inlet side of the planetary piercing mill 29. A mandrel rod 30 is then passed through the hollow block 15 from the rear with its mandrel tip 31 into the deformation zone of the planetary piercing mill 29 advanced and then fixed in place. About the mandrel bar 30 is now the hollow block 15 with its front end in the deformation zone of the Planetary piercing mill 29 advanced and there over the stationary mandrel tip 31 formed into a contour tube with a high degree of stretch. As the pass distance the hollow blocks 15 through the planetary piercing mill 29 is only very short and that Continuous tube runs free from the mandrel tip 31 of the mandrel rod 30, it can do so directly run into the stretch reducing mill 28 and then to the final wall thickness and the required diameter can be rolled out to the finished pipe without interruption.

The hollow blocks 15 coming from the piercing mill 13 are rolled out so here fully continuously, i.e. without interruption, in a single one Rolling heat Through the use of the planetary piercing mill 29 with the inlet side The mandrel bar 30, which can be fixed in a fixed position, is not only used for the transverse transports 22 and 24 and the roller tables 25 and 27 but in particular also the reheating furnace 26 in the absence.

In addition, the operating weight for the round stick 6 can also be significant increased, for example tripled, because the in the planetary piercing mill 29 as an intermediate product manufactured pipes are not rolled over a rotating mandrel bar. By the increase in the operating weight of the round billets can therefore be a considerable Achieve improved output on finished pipes.

Finally, it should be mentioned that in the tube rolling mill plant 2 Octagonal continuous cast ingots can also be used as feed material. These are then not rolled into hollow blocks 15 by a cross rolling mill 13, but pierce with a punch press. These octagonal hollow blocks can then directly introduced into the planetary piercing mill 29 and fixed on the inlet side fixable mandrel bar 30 are rolled out.

Another advantage of the planetary piercing mill 29 with the inlet side fixable mandrel rod 30 is that this works with a degree of stretching of 12, while an ex.

eight-stand continuous rolling mill 19 only reached a degree of stretching of 4. The use of the planetary piercing mill 29 also results in a high surface quality has already been achieved on the continuous tubes produced as intermediate products.

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Claims (3)

Claims rolling mill for the production of seamless tubes from round billets or the like, consisting of a piercing mill or a piercing press for reshaping the billets into hollow blocks, one of them or one of these with the interposition of them a transverse transport downstream rolling mill for pre-rolling the hollow blocks over a mandrel bar for contour tubes and a stretch-reducing mill for rolling the continuous tubes to finished tubes, characterized in that the continuous tube rolling mill as a planetary piercing mill (29) with an inlet side arranged during the Rolling process with the mandrel tip (31) projecting stationary into the deformation zone Mandrel bar (30) formed and in the same rolling line with the stretch reducing mill (28) is arranged (Fig. 2). 2. Rolling mill installation according to claim 1, d a d u r c h g e k e n n ze i c h n e t that the planetary piercing mill (29) is immediately in front of the inlet side of the Stretch reducing mill (28) is arranged and with this a fully continuous Tube rolling mill forms. 3. Rolling mill according to Claims 1 and 2, characterized in that that the mandrel bar (30) on the inlet side of the planetary piercing mill x (29) at least is arranged axially displaceable by the length of the hollow blocks (15).