EP0787542A2 - Mandrel and mandrel bar for skew-rolling mills - Google Patents

Abstract

A method for cooling a mandrel (2) and protecting the inner surface of a blank (10) against oxidation comprises: (a) returning the water used for internal cooling of the mandrel and directing it into the space between the bar (1) and the inner surface of the hollow blank to quench the latter from inside; and (b) supplying at the same time the forming zone around the mandrel with an inert gas to prevent oxidation of the blank inner surface within this zone, forming a barrier against water flow into this zone. Also claimed is an inner pipe-forming tool implementing the above method.

Description

The invention relates to a method and an apparatus for performing the rolling for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, in which the block is driven through the inclined rolls and pressed over an internal tool that comes from an internally cooled roll dome exists, which is releasably attached to a rolling rod through which both water for cooling the rolling dome and inert gas for introduction into the resulting hollow block can be passed, the rolling rod being supported against a mandrel abutment during rolling with its end facing away from the rolling mandrel.

In the Mannesmann cross-rolling process, a solid and usually round metal block heated to the rolling heat is punched and later stretched into a seamless tube. The hole is created by driving the round block through the inclined rollers and pressing it over a rolling mandrel. The roll dome has the task of widening the core zone of the block, which is loosened up by the so-called Friemel effect of the rolls, welding any material tears open again, smoothing the inner surface of the hollow block produced and bringing its wall thickness to the desired level.

Since the piercing mandrel has to do its work under the influence of the rolling heat, it is subjected to extreme stress and has a limited lifespan. Since the invention of the cross rolling process, the cross roll has been endeavoring to extend the service life of the rolling mandrels, to save costs and improve the quality of the rolled pipes. If the service life of the roll mandrel is nearing its end, the roll mandrel can lose its shape, get a damaged surface or welded material. This also means a deterioration in the pipe quality.

In the course of time, many measures to increase the service life have been proposed, such as the execution of the mandrel tips from particularly heat-resistant materials, e.g. technical ceramics, the coating of the surface of the mandrel with filler materials, a controlled oxidation of the surface, frequent replacement of the mandrels in connection with water spray or immersion cooling, internal cooling of the mandrels with water through the roller rod, to name just a few examples.

An additional problem with cross rolling occurs due to the scaling of the inner surface of the hollow block. Tinder leads to imperfect welding of the tears in the loosened core zone and thus to the formation of shells and cracks on the inner surface of the tube during further processing of the hollow blocks.

In order to solve this problem, the blowing of inert gas into the hollow block has been proposed. DE-PS 34 32 288 contains a device with which both water for internal cooling of the rolling mandrel and inert gas are supplied through the rolling rod. The same Japanese device describes the same device 61-002446. In both devices, the water supply and drainage lines and the inert gas supply could be connected to the rotating roller rod relatively easily, because the roller rods are firmly connected to the mandrel abutment and the connections do not have to be loosened when the dome abutment moves back after the rolling has ended. In these versions of an oblique rolling system, the rolling rod with the roll dome is pulled out of the rolled hollow block in order to be able to remove the hollow block.

For certain materials, e.g. Pipes with high-quality inner surfaces are produced directly from a hollow block by cold processing, such as thin-walled copper pipes, pulling out the rolling rod from the hollow block is prohibited because the rolling mandrel that slides on the inner surface can cause damage to the inner surface of the hollow block. For these cases, a stationary mandrel abutment has been developed, against which the rolling rod is only loosely supported during rolling. After rolling is completed, the dome abutment is simply pivoted away to the side or up or down and the hollow block is pulled off the rolling rod in the rolling direction. Since he no longer has to pass through the rolling mandrel, the feared damage is eliminated.

With this device, however, water and inert gas connections have so far not been able to be brought together because the roller rod is only loosely supported against the mandrel abutment. Fixed connections would be prohibited here because there is not enough time available for coupling and decoupling.

A partial solution to the problem is described in DE-OS 31 23 645. Here, inert gas is blown into the hollow block through the rolling rod, but no cooling water for the rolling mandrel is supplied and removed. A swivel abutment is used as the mandrel abutment.

There is another problem with cross rolling copper. Since the cross-rolling of this material runs with a relatively poor efficiency in relation to the effective rolling speed and, moreover, the rolling speed to protect the rolling stock is lower than when rolling steel, a rolling cycle takes a correspondingly long time. For the rolling mandrel, this means a long dwell time in the rolling stock with strong heating. It could be observed that the rolling dome can become red-hot and almost with its entire mass. This means a significant reduction in the service life in connection with quality problems for the rolling stock.

A significant increase in the service life can be achieved, in particular when cross-rolling copper, by internally cooling the roll dome with water. At the same time, however, the blowing in of inert gas cannot be dispensed with, just as little as there is no pivotable dome abutment, i.e. withdrawing the rolled hollow block from the stationary mandrel bar.

Another quality requirement has to be considered when cross-rolling copper. A fine grain is advantageous for good cold processing capability of the copper. This is how the standards become one. certain fine grain size prescribed, on the other hand, a fine grain structure increases the stretchability of the material for producing a thin-walled finished tube before an intermediate annealing process must be switched on. Efforts are therefore made to immediately quench the rolled material after hot forming in order to limit subsequent grain growth if possible. For this purpose, the hollow block behind the rolling zone is cooled as quickly as possible by water showers or introduced directly into a water basin to quench the material. However, this can only be done at a certain distance behind the rolling zone, because the material under the rollers must still have the rolling temperature, which means that valuable time is lost until the quenching. Another disadvantage of conventional quenching is the fact that the water attack on the hollow block occurs only from the outside and all the heat has to be dissipated to the outside. If, on the other hand, additional internal cooling of the hollow block is successful, the grain can be quenched even more quickly thanks to the faster quenching effect.

The object of the invention is therefore to provide a method and a device which combines all of the aforementioned advantages without accepting the disadvantages.

To achieve the object, a method using a generic system for the production of pipes is proposed, which is characterized in that the water is returned for cooling the rolling mandrel and at a position as close as possible behind the forming zone of the rolls for quenching the inside of the hollow block into the space between Roll rod and hollow block inside is passed, that at the same time the forming zone around the rolling mandrel is placed under inert gas to prevent oxidation of the hollow block inner surface, the inert gas acting as a barrier against the ingress of water into the forming zone between the dome and the hollow block and that the hollow block immediately after is pulled from the rod in the rolling direction.

By combining these process steps in the manner according to the invention, both the service life of the rolling mandrels and the quality of the tube can be significantly improved. While the harmful oxidation inside the hollow block is reliably suppressed by the introduction of the inert gas and at the same time the penetration of water is prevented, the water cools the rolling mandrel in a conventional manner to increase the service life. Both measures are combined with the possibility of pulling the hollow block from the mandrel in the rolling direction, i.e. over the roller rod so that damage to the inner surface of the hollow block is prevented by the mandrel.

An internal tool device for carrying out the method is characterized in that at least the water for cooling the rolling dome is fed through the mandrel abutment into the rolling rod, which is in a stationary position during the rolling process by means of a pivoting abutment which can be removed from the rolling line for loading the rolling rod is definable.

For the first time, it has been possible to supply the cooling water with an exchangeable roller rod, in that the roller rod is pressed against a dome abutment that can be swiveled away for loading and no fixed water connections hinder the stripping of the hollow blocks and the loading of the roller rod and its replacement.

To introduce the inert gas is provided according to another feature of the invention that for supplying the inert gas and forwarding to outlet bores at the end of the rolling rod facing the dome end, a sleeve sealed by sealing rings and coaxially rotatable around the rolling rod is attached to the end piece of the rolling rod, in which radially attached Holes are located on the one hand to an annular channel provided in the rolling rod, which is connected to the lines inside the rolling rod and, on the other hand, lead to an annular channel which is provided on the inside of a releasable inert gas supply which engages around the rolling rod. The sleeve surrounding the roller rod like a pliers can be easily released by opening the "pliers ^" and thereby also allows unhindered handling of the roller rod and the hollow block when stripping.

In further refinements of the invention, it is proposed that the cooling water conducted through the mandrel abutment into the rolling rod also be drained through the dome abutment. It is also conceivable that the cooling water supplied through the dome abutment is carried out through radial bores provided in the roll rod into the area behind the roll dome. Finally, it can also be provided that the cooling water conducted through the dome abutment into the rolling rod is selectively switchable through the dome abutment or through radial bores provided in the rolling rod into the area behind the rolling mandrel. In all cases, the cooling water is supplied through the mandrel abutment without the need to connect additional connections to the roll rod.

The optional switching of the cooling water discharge can be achieved by shifting the inner pipe that conducts the cooling water, by means of which the corresponding outlet openings are closed or opened in the shifting end positions.

According to another feature of the invention, the intensity of the internal cooling of the hollow block can advantageously be controlled via the amount of water emerging from the roller rod.

It has proven to be advantageous if the inner surface of the mandrel is corrugated for better heat transfer

Figur 1:

das vordere Walzstangenende mit Walzdorn sowie Inertgas- und Wasseraustritt hinter dem Walzdorn,

Figur 2:

das hintere Walzstangenende mit Wassereintritt und Inertgasanschluß als Fortsetzung zu Fig. 1,

Figur 3:

einen Querschnitt durch die Walzstange und Anschlußzange für die Inertgaszuführung,

Figur 4:

das vorderes Walzstangenende mit Walzdorn, Inertgasaustritt und innerem Wasserumlauf,

Figur 5:

das hintere Stangenende mit Wasserein- und Austritt und Inertgasanschluß als Fortsetzung zu Fig. 4 und

Figur 6:

eine Alternative mit verschließbarem Wasserausfluß.

An embodiment of the invention is shown in the drawing and is described below. It shows:

Figure 1:

the front end of the rolling rod with a mandrel and inert gas and water outlet behind the mandrel,

Figure 2:

the rear roll rod end with water inlet and inert gas connection as a continuation to Fig. 1,

Figure 3:

a cross section through the rolling rod and connecting pliers for the inert gas supply,

Figure 4:

the front end of the rod with a mandrel, inert gas outlet and internal water circulation,

Figure 5:

the rear rod end with water inlet and outlet and inert gas connection as a continuation to Fig. 4 and

Figure 6:

an alternative with closable water outflow.

The device according to the invention consists in the main elements of a rolling rod 1 with the screwed-on rolling dome 2 and the swivel abutment 3.

1, the mandrel 2 is hollow and relatively thin-walled for effective internal cooling. To improve the heat transfer, the inner surface 4 of the mandrel is corrugated. The rolling mandrel 2 is screwed onto the intermediate piece 6 of the rolling rod 1 with a thread 5. Since no cooling water may penetrate to the outside at the screwing point, a sealing ring 8 is inserted into a groove 9 of the intermediate piece 6. The same is repeated for the intermediate piece 7 with the sealing ring 50. The sealing rings 8 and 50 can consist of a squeezable metal due to the action of heat. The intermediate piece 6 is connected to the intermediate piece 7 by the thread 14. The cooling water is passed through the pipe 11 into the rolling dome 2, runs outside on the pipe 11 back into the annular gap 21 and from there passes through the outlet bores 22 into the annular gap which is formed between the rolling rod 1 and the hollow block 10. The tube 11 is secured by the stop 51 against slipping in the longitudinal direction and sealed by the seal 52. From the point at which the water emerges from the bores 22 of the intermediate piece 7, the hollow block 10 is cooled from the inside. The water leaves the hollow block 10 in the rolling direction.

The inert gas passes through the annular gap 23 and the bores 24 and 25 in front of the rolling mandrel 2 and leaves the rolling rod 1 through the outlet bores 27 which are located in the intermediate piece 6. In order to ensure the transition of the inert gas from the intermediate piece 7 into the intermediate piece 6, an annular channel 26 is arranged between the two. The exit bores 27 for the inert gas are closer to the mandrel 2 than the bores 22 for the cooling water. The overpressure of the inert gas ensures that the cooling water cannot penetrate into the forming zone of the hollow block 10. A circumferential bead 28 on the intermediate piece 7 also narrows the annular gap between the rolling rod 1 and the hollow block 10 and thus further reduces the risk of water or water vapor entering the forming zone. The forming zone is formed by the rollers 43 and the mandrel 2. The inert gas leaves the hollow block 10 in the same way as the cooling water.

The inflow of cooling water and inert gas into the rolling rod 1 is shown in FIG. 2. This is the point at which the loose rolling rod 1 lying in the rolling position is supported against the turntable 29 of the swivel abutment 3. For this purpose, the turntable 29 has the conical centering 30. The cooling water is introduced into the central bore 19 of the rolling rod 1 through the inlet bore 31 and fed to the rolling mandrel 2 through the pipe 11. The water and inert gas connections must be separated from each other so that no water can flow into the inert gas line. For this purpose, a sleeve 32 is loosely attached to the end piece 18 of the rolling rod 1, which sleeve can rotate on the end piece 18 and which is sealed by the sealing rings 33. Radial holes 34 are provided in the sleeve 32.

In order to introduce the inert gas into the rolling rod 1, an opening and closing pincer-like inert gas supply 35 is pressed onto the sleeve 32, as shown in FIG. 3, the inert gas passing through the annular channel 36 and the bores 34 into the annular channel 38. From here, the gas flows through a plurality of radially provided bores 39 and is transported through the annular gap 44 into the front part of the rolling rod 1. The device is supplied with inert gas via the hose connection 49.

The inert gas supply 35 is sealed according to FIG. 2 on the sleeve 32 by the seals 37. The end piece 18 is screwed to the intermediate piece 16 via the thread 17, which in turn is welded to the pipe 15.
The inert gas supply 35 is opened together with the swivel abutment 3 when a hollow block is to be pulled off the roller rod.

In a modified version of the roller rod-mandrel system according to FIGS. 4 and 5, the internal cooling of the hollow block 10 with water is dispensed with. For this purpose, the water inside the roller rod 1 is returned and exits at the rear end of the rod. 4, the water is fed into the rolling mandrel 2 via the pipe 11 and runs back through the pipe 13, which surrounds the pipe 11, back to the rod end. The tube 11 is centered by the spacers 12 in the intermediate piece 6 and secured against displacement in the longitudinal direction. In the intermediate piece 7, the tube 13 is sealed by means of the sealing rings 45. The intermediate piece 6 is screwed together with the intermediate piece 7 via the thread 14. The intermediate piece 7 is in turn welded to the tube 15 of the rolling rod 1. The tubes 11 and 13 can be removed by unscrewing the end piece 18.

The inert gas passes through the annular gap 23 into the front part of the rolling rod 1 and leaves it through the outlet bores 27a, which are arranged in the intermediate piece 7.

The opposite end of the rolling rod 1 is shown in FIG. 5. Here, the intermediate piece 16 is welded to the pipe 15 and connected to the end piece 18 via the thread 17. The tube 11 extends into the end piece 18 and enables the water to be supplied through the central bore 19. The water flowing back through the pipe 13 reaches the annular gap 44 in the region of the end piece 18 and is discharged via the bores 20. The turntable 29 with its conical centering 30 is additionally equipped for collecting the return water with the annular space 46, which collects the water and feeds it through the holes 47 in a manner not shown to a rotary connection arranged on the turntable 29, which in one Hose connection merges. For the sake of completeness, it remains to be mentioned that the incoming water is also connected to the turntable 29 by means of a hose connection and rotary connection. A seal 48 seals the rod seat in the turntable 29.

The connection of the inert gas is carried out in the manner already described. As a result of the additional tube 13, however, the bores 39 merge into the longitudinal bores 40. From here, the inert gas is passed through the annular gap 23 to the front part of the rolling rod 1.

In a further embodiment of the device it is possible, according to FIG. 6, to temporarily switch off the exit of the cooling water from the rolling rod 1, so that only certain longitudinal sections of the hollow block are cooled from the inside. For this purpose, the tube 13 is displaceable in the longitudinal direction. In the advanced position - drawn in the upper half of FIG. 6 - the bores 22 are covered. Thus, the cooling water flows back through the annular gap 21 and in the further course between the outer wall of the tube 11 and the inner wall of the tube 13 to the rear part of the rolling rod 1. In the advanced position - as drawn in the lower part of FIG. 6 - the holes 22 are released and the water can now flow out of the roller rod 1 through these holes. So that it does not continue to flow between tube 11 and tube 13, the drain is closed by a switching valve (not shown in the drawing) at the rear end of the roller rod. However, it is also possible to control the ratio of the quantities of the water emerging from the roller rod and flowing back inside the roller rod by deliberately throttling the backflow of water. This can influence the intensity of the internal cooling of the hollow block.

Legend

1

Rolling rod

2nd

Walzdom

3rd

swiveling dome abutment

4th

corrugated dome surface

5

thread

6

Spacer

7

Spacer

8th

Sealing ring

9

Groove

10th

Hollow block

11

Inner tube

12th

Spacers

13

pipe

14

thread

15

pipe

16

Spacer

17th

thread

18th

Tail

19th

Central bore

20th

Holes

21

Annular gap

22

Exit holes

23

Annular gap

24th

Holes

25th

Holes

26

Ring channel

27

Exit holes

27a

Exit holes

28

bead

29

Turntable

30th

centering

31

Inlet bore

32

Sleeve

33

Sealing rings

34

Holes

35

Inert gas supply

36

Ring channel

37

Seals

38

Ring channel

39

Holes

40

Longitudinal bores

43

roller

44

Annular gap

45

Sealing rings

46

Annulus

47

Holes

48

poetry

49

Hose connection

50

Sealing ring

51

attack

52

poetry

Claims (10)

Process for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, in which the block is driven through the inclined rolls and pressed over an internal tool consisting of an internally cooled rolling mandrel, which is detachably attached to a rolling rod which can be passed through both water for cooling the roll dome and inert gas for introduction into the resulting hollow block, the roll rod being supported against a mandrel abutment during rolling with its end facing away from the roll dome,
characterized,
that the water is returned to the cooling of the roll dome and directed at a position as close as possible behind the forming zone of the rolls to quench the inside of the hollow block into the space between the rolling rod and the inside of the ingot, that the forming zone around the rolling dome is simultaneously placed under inert gas to prevent oxidation of the inside of the block , wherein the inert gas acts as a barrier against the ingress of water into the forming zone between the mandrel and the hollow block and that the hollow block is pulled off the rod immediately after rolling in the rolling direction. Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, in which the block is driven through the inclined rolls and pressed over the inner tool, which consists of an internally cooled roll dome, which is detachably attached to a roll rod which can be passed through both water for cooling the roll dome and inert gas for introduction into the interior of the hollow block being formed, the roller rod being supported against a dome abutment during rolling with its end facing away from the roll dome,
characterized,
that at least the water for cooling the rolling dome (2) is fed through the mandrel abutment (3) into the rolling rod (1), which during the rolling process is carried out by a pivoting abutment (3) which can be removed from the rolling line for loading the rolling rod (1) can be fixed in a stationary position. Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to claim 1 or 2,
characterized,
that for supplying the inert gas and forwarding it to outlet bores (27) at the front end of the roller rod (1), a sleeve (32), which is sealed by sealing rings (33) and can be rotated coaxially about the roller rod (1), on the end piece (18) of the roller rod (1) is attached, in which there are radially arranged bores (34) which, on the one hand, lead to an annular channel (38) provided in the roller rod (1), which through the bores (39) with the annular gap (44) inside the roller rod (1 ) is connected and, on the other hand, lead to an annular channel (36) which is provided on the inside of a detachable inert gas supply (35) which engages around the roller rod (1) in the manner of pliers. Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to claim 2 or 3,
characterized,
that the discharge of the cooling water conducted through the dome abutment (3) into the roller rod (1) also takes place through the dome abutment (3). Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to claim 2 or 3,
characterized,
that the cooling water is discharged through the dome abutment (3) through radial bores (outlet bores 22) provided in the rolling rod (1) into the area behind the rolling mandrel (2). Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to claim 2 or 3,
characterized,
that the discharge of the cooling water conducted through the mandrel abutment (3) into the rolling rod (1) can be switched either through the dome abutment (3) or through radial bores (outlet bores 22) provided in the rolling rod (1) into the area behind the rolling mandrel (2) he follows. Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to claim 6,
characterized,
that to switch the cooling water discharge, the inner tube (13) which conducts the cooling water is displaceable and in the shifting end positions the corresponding outlet bores (22) are closed or opened by the inner tube (13). Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to claims 2 to 7,
characterized
that the intensity of the internal cooling of the hollow block (10) can be controlled via the amount of water emerging from the roller rod (1). Internal tool for producing seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to claims 2 to 8,
characterized
that the mandrel inner surface (4) is corrugated for better heat transfer Internal tool for producing seamless tubes from heated solid metal blocks, in particular on a Mannesmann cross-rolling mill, according to one or more of the preceding claims,
characterized
that the space which can be filled with inert gas between the roll dome (2) and the hollow block (10) can be largely sealed off by a radially outwardly curved annular bead (28) of the roll rod (1).

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