EP0787542B1 - Method of manufacturing seamless pipes and mandrel therefor - Google Patents

Description

The invention relates to a method for producing seamless tubes heated solid metal blocks, especially on a Mannesmann cross-rolling mill, as well as an inner tool for this.

In the Mannesmann cross-rolling process, a solid one is heated to rolling heat and usually perforated round metal block and into one in the further course of the process seamless tube ironed. The hole is created by the round block through the inclined rollers are driven and pressed over a rolling mandrel. The The purpose of the rolling mandrel is the so-called Friemel effect of the rollers to widen the loosened core zone of the block, any material tearing open to weld again, the inner surface of the hollow block created smooth and bring 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 extremely stressed and has a limited lifespan. The Since the invention of the cross rolling method, the cross roll has been striving for Extend the life of the mandrels to save costs and improve the quality of the to improve rolled pipes. The service life of the rolling mandrel is approaching At the end, the dome may lose its shape, a damaged surface or get welded material. This also means one Deterioration in pipe quality.

Over the years, many measures to increase tool life have been proposed, such as the execution of the mandrel tips from particularly heat-resistant materials, such as e.g. technical ceramics, the coating of the rolling mandrel surface with Filler materials, controlled oxidation of the surface, frequent replacement the mandrels in connection with water spray or immersion cooling, internal cooling of the Rolling mandrels with water through the rolling rod, to name just a few examples call.

An additional problem with cross rolling occurs due to the scaling of the Inner surface of the hollow block. Tinder leads to an imperfect Welding the tears of the loosened core zone and thus the Further processing of the hollow blocks to form shells and cracks on the Internal pipe surface.

To solve this problem, the injection of inert gas into the hollow block proposed. DE-PS 34 32 288 contains a device with which both water for internal cooling of the rolling mandrel as well as inert gas through the rolling rod are fed. A similar device describes the older Japanese Patent 61-002446. In both devices, the water supply and Water drainage lines and the inert gas supply relatively easy to the rotating Rolling rod can be connected because the rolling rods are fixed to the mandrel abutment are connected and the connections after retracting the mandrel abutment finished rolling need not be released. In these versions, one Cross-rolling mill becomes the rolling rod with mandrel through the rolled hollow block pulled out of this in order to be able to remove the hollow block.

Comparable solutions also result from the Japanese publications 59033010 and 58035005.

For certain materials, e.g. Pipes with high quality Internal surfaces through cold processing directly from a hollow block manufactured, like thin-walled copper pipes, is forbidden Pull the roller rod out of the hollow block because of the on the Internal surface of sliding mandrel damage to the inner surface of the hollow block can cause. For these cases you have a stationary one Mandrel abutment developed against which the rolling rod only turns during rolling loosely supported. After rolling is finished, the mandrel abutment just swung to the side or up or down and the Hollow block pulled off the rolling rod in the rolling direction. Since he is not the more feared that it has to pass through the rolling mandrel Damage.

This device has so far not been able to water and Attach the inert gas connections together because the roller rod is only loose supports against the mandrel abutment. Fixed connections would be here prohibit because there is not enough time to connect and disconnect Available.

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, however, no cooling water for the rolling mandrel is supplied and removed. As A swivel abutment is used for the mandrel abutment.

Another problem occurs when cross-rolling copper. Since that Cross rolling of this material with a relatively poor efficiency based on the effective rolling speed and also the Rolling speed to protect the rolling stock is lower than when rolling of steel, a rolling cycle takes a correspondingly long time. This means for the Rolling mandrel a long dwell time in the rolling stock with strong heating. It could be observed that the rolling mandrel can become red-hot and almost all of its mass. This means an essential one Shortening the lifespan in connection with quality problems for the Rolling.

A significant increase in the service life can be seen in particular in the Cross rolling of copper by cooling the mandrel internally with water to reach. At the same time, however, the injection of inert gas cannot be dispensed with just as little on a swiveling mandrel abutment, i.e. a peeling of the rolled hollow block from the stationary mandrel bar.

There is another one to consider when cross-rolling copper Quality requirement. For a good cold processing ability of the copper is a fine grain advantageous. So the norms make a certain fine one Grain size prescribed, on the other hand, a fine grain structure increases Stretchability of the material to produce a thin-walled finished pipe before an intermediate annealing process must be switched on. One tries therefore that Rolled stock immediately after hot forming to quench a restrict subsequent grain growth if possible. For this the Hollow block behind the rolling zone cooled down as quickly as possible by water showers or inserted directly into a pool of water to quench the material. This can only be done at a certain distance behind the rolling zone, because that Material under the rollers must still have the rolling temperature, that is, up to Deterring valuable time is lost. A disadvantage of the conventional Quenching is also the fact that the water attack on the hollow block is only from takes place outside and all the heat must be dissipated to the outside. succeed on the other hand, additional internal cooling of the hollow block could also be done by the achieve a finer grain more quickly.

The object of the invention is therefore to create a method and an internal tool, that combines all of the above advantages without the disadvantages übemehmen.

This object is achieved with a 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 via an internal tool, which consists of an internally cooled rolling mandrel, which is releasable a rolling rod is fastened, through which both water for cooling the rolling mandrel 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 which
the water is cooled to cool the mandrel and is conducted at a position as close as possible behind the forming zone of the rolls to quench the hollow block inside into the space between the rolling rod and the hollow block inside, at the same time the forming zone around the rolling mandrel is placed under inert gas to prevent oxidation of the hollow block surface, whereby the inert gas acts as a barrier against the ingress of water into the forming zone between the dome and the hollow block and the hollow block is withdrawn from the rod in the rolling direction immediately after the rolling.

By combining these process steps in the invention Both the service life of the rolling mandrels and the quality of the Improve pipe significantly. While by introducing the inert gas the harmful oxidation inside the hollow block safely suppressed and at the same time the penetration of water is prevented, the water cools the rolling mandrel in conventional way to increase the service life. Both measures will combined with the possibility of removing the hollow block from the mandrel in Rolling direction, i.e. over the roller rod so that damage to the Hollow block inner surface can be prevented by the mandrel.

According to a development of the method, at least the Water for cooling the rolling mandrel through the mandrel abutment into the Rolling rod takes place during the rolling process by a to load the Watz bar swivel abutment removable from the rolling line in a stationary Position can be determined.

For the first time, it has been possible to supply the cooling water through a interchangeable roll bar to allow by the roll bar during the Rolling is pressed against a pivotable abutment abutment for loading and no fixed water connections stripping the hollow blocks and loading the Obstacle to the rolling rod and its replacement.

The inner tool is designed according to the invention so that for the supply of Inert gas and forwarding to outlet holes on the mandrel abutment facing end of the rolling rod is sealed by sealing rings coaxially around the Rolling rod rotatable sleeve is attached to the end of the rolling rod in the there are radially drilled holes, which on the one hand lead to a Rolling rod provided ring channel that connects to the lines inside the Rolling rod is connected and on the other hand lead to an annular channel on the inside of a releasable gripping around the rolling rod Inert gas supply is provided. The sleeve that grips around the rolling rod in the manner of 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 embodiments of the invention it is proposed that the derivation of the through the mandrel abutment in the rolling rod cooling water also through the mandrel abutment is made through. It is also conceivable that the derivation of the Cooling water supplied through the mandrel abutment through in the roller rod provided radial holes in the area behind the rolling dome. Finally can also be provided that the derivation of the through the mandrel abutment in the Rolled cooling water directed from the roll rod can optionally be switched by the mandrel abutment through or through radial bores provided in the roller rod into the area behind the wadding mandrel. In all cases, the cooling water is supplied through through the mandrel abutment without the additional connections to be loosened with the Roll rod must be connected.

The optional switching of the cooling water discharge can be done by moving the reach the cooling water conducting inner tube through which in the Moving end positions closed the corresponding outlet openings or are open.

Conveniently, according to another feature of the invention, the intensity of the Internal cooling of the hollow block via the amount of the emerging from the rolling rod Control water.

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

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 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 roller 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 of a main elements Rolling rod 1 with the screwed rolling mandrel 2 and Swivel abutment 3.

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

The inert gas passes through the annular gap 23 and the bores 24 and 25 the rolling mandrel 2 and leaves the rolling rod 1 through the outlet bores 27, which are located in the intermediate piece 6. To the transition of the inert gas from To ensure intermediate piece 7 in the intermediate piece 6 is between the two an annular channel 26 is arranged. The outlet bores 27 for the inert gas are located closer to the mandrel 2 than the holes 22 for the cooling water. By the Overpressure of the inert gas is achieved so that the cooling water does not enter the Forming zone of the hollow block 10 can penetrate. A circumferential bead 28 on the intermediate piece 7 also narrows the annular gap between the roller rod 1 and the hollow block 10 and thus further reduces the risk of water or steam get into the forming zone. The forming zone is through the rollers 43 and the mandrel 2 are formed. The inert gas leaves on the same paths as the cooling water the hollow block 10.

The inflow of cooling water and inert gas into the rolling rod 1 is shown in FIG. 2 shown. This is the place where the loose and in the rolling position Roll rod 1 is supported against the turntable 29 of the pivot abutment 3. The The turntable 29 has the conical centering 30 Inlet bore 31, the cooling water in the central bore 19 of the Rolling rod 1 initiated and fed through the tube 11 to the rolling mandrel 2. The water and inert gas connections must be separated from each other locally so that none Water can flow into the inert gas line. For this purpose, the end piece is 18th the rolling rod 1 loosely attached a sleeve 32 which on the end piece 18th can rotate and which is sealed by the sealing rings 33. In the sleeve 32 there are radially provided bores 34.

In order to introduce the inert gas into the rolling rod 1, as in FIG. 3 shown - an opening and closing pliers-like Inert gas supply 35 pressed onto the sleeve 32, the inert gas through the Ring channel 36 and the holes 34 enters the ring channel 38. From here the gas flows through a plurality of radially arranged bores 39 and is passed through the annular gap 44 transported in the front part of the rolling rod 1. The 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 rolling rod-mandrel system according to Fig.4 and Fig.5 is based on the internal cooling of the hollow block 10 with water waived. For this purpose, the water inside the roller rod 1 again returned and emerges at the rear end of the rod. 4 that Water is fed into the rolling mandrel 2 via the pipe 11 and runs through it Tube 13, which envelops tube 11, back to the rod end. The Tube 11 is centered by spacers 12 in intermediate piece 6 and secured against shifting in the longitudinal direction. In the intermediate piece 7 the tube 13 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 become.

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

The opposite end of the rolling rod 1 is shown in FIG. 5. Here is the intermediate piece 16 is welded to the pipe 15 and via the thread 17th connected to the end piece 18. The tube 11 extends into the end piece 18th into it and through the central bore 19 enables the water supply. The Water flowing back through the pipe 13 reaches the area of the end piece 18 in the annular gap 44 and is derived via the holes 20. The Turntable 29 with its conical centering 30 is to catch the Return water additionally equipped with the annular space 46, which the water collects and through the holes 47 in a manner not shown on Turntable 29 arranged rotating connection feeds into one Hose connection passes over. For completeness, it remains to be mentioned that the incoming water by means of hose connection and Slewing ring is connected to the turntable 29. 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, the holes 39 go into the Longitudinal bores 40 over. From here, the inert gas passes through the annular gap 23 passed to the front part of the rolling rod 1.

In a further embodiment of the device it is possible according to FIG. temporarily switching off the cooling water from the rolling rod 1, so that only certain lengths of the hollow block are cooled from the inside become. For this purpose, the tube 13 is displaceable in the longitudinal direction. In the advanced position - drawn in the upper half of Fig. 6 are Bores 22 covered. Thus, the cooling water flows 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 back to the rear part of the rolling rod 1. In advanced position - as drawn in the lower part of Fig. 6 - be the holes 22 released and the water can now pass through them Flow the holes out of the roller rod 1. So that it doesn't continue flows between tube 11 and tube 13, is (not shown in the drawing) on the end of the roller rod the drain is closed by a switching valve. It is also possible, however, by throttling the backflow Water flow is the ratio of the amounts of the from the roller bar escaping water and flowing back inside the roller rod Taxes. This can influence the intensity of the internal cooling of the Hollow blocks can be taken.

Legend

1

rolling bar

2

rolling mandrel

3

swiveling mandrel abutment

4

corrugated mandrel surface

5

thread

6

connecting piece

7

connecting piece

8th

sealing ring

9

groove

10

hollow block

11

inner tube

12

spacer

13

pipe

14

thread

15

pipe

16

connecting piece

17

thread

18

tail

19

central bore

20

drilling

21

annular gap

22

exit holes

23

annular gap

24

drilling

25

drilling

26

annular channel

27

exit holes

27a

exit holes

28

bead

29

turntable

30

centering

31

inlet bore

32

shell

33

seals

34

drilling

35

inert gas

36

annular channel

37

seals

38

annular channel

39

drilling

40

longitudinal bores

43

roller

44

annular gap

45

seals

46

annulus

47

drilling

48

poetry

49

hose connection

50

sealing ring

51

attack

52

poetry

Claims (8)

1. Process for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann oblique-rolling mill, in which the block moves though the oblique rolls (43) and is expanded by an internal tool consisting of an internally cooled rolling mandrel (2) which is detachably fixed on a rolling bar (1), through which both water for cooling the rolling mandrel (2) and also inert gas for introduction into the hollow block (10) being produced can be passed, the said rolling bar (1) being supported at its end facing away from the rolling mandrel (2) against a mandrel thrust-block (3),
   such that
   the water for cooling the rolling mandrel (2) is recycled and passes into the space between the rolling bar (1) and the inside of the hollow block at a position as near as possible behind the deformation zone of the rolls (43) in order to quench the inside of the hollow block, and at the same time the deformation zone around the rolling mandrel (2) is kept under inert gas in order to prevent oxidation of the inside surface of the hollow block, the inert gas also acting to prevent the penetration of water into the deformation zone between the mandrel (2) and the hollow block (10), and the hollow block (10) being drawn though by the bar (1) in the rolling direction immediately after rolling.
2. Internal tool for the production of seamless tubes from heated solid metal blocks, in particular on a Mannesmann oblique-rolling mill, according to Claim 1, consisting of an internally cooled rolling mandrel (2) which is detachably fixed on a rolling bar (1) through which both water for cooling the rolling mandrel (2) and also inert gas for introduction into the inside of the hollow block (10) being produced can be passed, the said rolling bar (1) being supported at its end facing away from the rolling mandrel (2) against a mandrel thrust-block (3),
   such that
   at least the feed of water for cooling the rolling mandrel (2) takes place through the mandrel thrust-block (3) into the rolling bar (1), which during the rolling process can be fixed in a stationary position by a swivelling thrust-block (3) that can be detached from the rolling line for loading the rolling bar (1), and for the inert gas feed and its further passage to outlet holes (27) at the front end of the rolling bar (1) a sleeve (32) that can be rotated coaxially around the rolling bar (1) and is sealed by sealing rings (33) is attached to the end-piece (18) of the rolling bar (1), in which there are radial holes (34) which on the one hand lead into an annular channel (38) provided in the rolling bar (1) which communicates with an annular gap (44) on the inside of the rolling bar (1) via the holes (39), and on the other hand lead to an annular channel (36) which is provided on the inside of an inert gas feed element (35) that surrounds the rolling bar (1) in the manner of a clamp but can be released therefrom, and the cooling water passed through the mandrel thrust-block (3) drains out through radial holes (outlet holes 22) provided in the area behind the rolling mandrel (2).
3. Internal tool according to Claim 2,
   characterised in that
   the cooling water passing through the mandrel thrust-block (3) into the rolling bar (1) also drains away though the mandrel thrust-block (3).
4. Internal tool according to Claim 2,
   characterised in that
   the draining of the cooling water passing through the mandrel thrust-block (3) into the rolling bar (1) can optionally be directed though the mandrel thrust-block (3) or through the radial holes (outlet holes 22) provided in the rolling bar (1) in the area behind the rolling mandrel (2).
5. Internal tool according to Claim 4,
   characterised in that
   to direct the cooling water draining, an internal tube (13) carrying the cooling water can be moved and, at the limits of its movement, the corresponding outlet holes (22) are closed or opened by the internal tube (13).
6. Internal tool according to Claims 2 to 5,
   characterised in that
   the intensity of the internal cooling of the hollow block (10) can be controlled by regulating the quantity of water emerging from the rolling bar (1).
7. Internal tool according to Claims 2 to 6,
   characterised in that
   to improve the heat transfer, the inside surface (4) of the mandrel is corrugated.
8. Internal tool according to any one or more of the preceding claims,
   characterised in that
   the space between the rolling mandrel (2) and the hollow block (10) that can be filled with inert gas, can largely be sealed by an outwardly convex annular bead (28) of the rolling bar (1).

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