EP2900394B1 - Deoxidation of cross-rolled hollow blocks - Google Patents

Description

1. Field of the invention

The invention relates to a method for producing a pipe or pipe precursor from a solid body by means of a rolling mill, comprising at least one attacking from the outside of the solid body or the pipe precursor roller, in particular inclined roller, and a hole plug carrying and engaging from inside the pipe or pipe precursor mandrel , Moreover, the invention relates to a rolling mill for carrying out such a method.

2. State of the art

The production of hollow blocks such as pipes or pipe precursors of metallic solid bodies is done for decades by means of the well-known to those skilled Lochdornprozesses in which a perforated plug is supported by a mandrel and continuously transforms a metallic solid body into a hollow block in a hot forming process. The workpiece is usually held in this forming process between two externally attacking skew rollers, via which a rotational movement is applied to the workpiece. The wall thickness of the hollow body is usually determined by the distance between the hole plug and the outer rollers or.

In this hot forming process, due to the forming during the forming surfaces and the contact with the air atmosphere mill scale, the both disrupt the forming process itself and reduce the surface quality of the pipe or pipe precursor.

Therefore, on the one hand attempts to limit the amount of scale formed to a minimum, and on the other hand to remove the still formed mill scale before the next manufacturing process steps again. One approach to removing the mill scale is, for example, the use of fluidized deoxidizers and the injection of inert gases at least to protect the hollow block interior surfaces of the manufactured pipe or pipe precursor. Such methods are for example in the DE 1427828 , of the DE 3405771 , of the CH 655516 as well as the WO 2011/083101 described.

The blowing of the deoxidizer is carried out in a special Deoxidationsstation after Lochwalzvorgang by coupling a Einblasvorrichtung on one side and optionally a suction device on the other side of the hollow block. An alternative to this is in the WO 2011/154133 and the DE 1427828 stimulated, in which at or immediately after punching inert gas or deoxidizer are blown through holes in the support rod of the hole plug or through holes in the hole plug itself into the hollow block.

Although this method has not yet been sufficiently tested, a large number of problems can be expected both on the plant side as well as during the process.

Blowing the deoxidizer in a dedicated deoxidizer station requires large amounts of inert gas to first blow out the loose interior scale formed in the meantime and then push the invaded ambient air out of the cavity block and then express excess deoxidizer since they preferentially settle on the first half of the cavity block , Thus, there is the problem that an unnecessarily large amount of deoxidizer must be used to achieve the entire hollow block length. Excess deoxidizer is partly ejected in the rolling mill, partly it burns under violent flame development.

Those methods in which the deoxidizer is to be blown through the carrier bar during or shortly after the end of the perforation requires a complex construction of the abutment during the oblique rolling, the carrier rod of the perforation plug or the hole plug itself. Furthermore, there is a risk of blockage of the feed line and the outlet channels by the tendency to agglomerate, usually strongly hygroscopic, deoxidizer, in particular also due to the fact that the hole plugs and the support rods are water cooled from the outside and / or inside.

3. Object of the invention

It was therefore an object of the invention to provide a method and an apparatus by means of which the improvement of the application and the uniformity of the application of the deoxidizer on the inner tube surface can be achieved. In addition, the object of the invention was to limit the use of the amount of deoxidizer to the required minimum.

This object is achieved in the sense of the invention by means of a method comprising the features of claim 1, and by means of a rolling mill, comprising the features of claim 9. Advantageous embodiments of the invention are defined in the dependent claims.

4. Summary of the invention

In the context of the invention, immediately after complete punching of the solid body by means of the perforated plug, a fluidized deoxidizer and / or an inert gas is supplied to the side of the pipe or pipe precursor facing the roll, and upon retraction of the piercer through the pipe or pipe precursor into the interior of the pipe or pipe precursor introduced. This means that as soon as the perforation stopper has completely passed through the solid body and an opening of the hollow block, tube or tube precursor is obtained continuously, in particular within a period of 10 seconds after puncturing of the solid body, preferably within 5 seconds, particularly preferably within from one second after complete punching of the solid body, inert gas, deoxidizer or a mixture thereof to the at least one roller, in particular oblique roller, facing side of the tube or tube precursor is supplied and then in particular by the action of retraction of the piercing pin through the tube or tube precursor generated negative pressure in the interior of the pipe or pipe precursor is introduced.

In accordance with the invention, therefore, the negative pressure formed by the retraction of the piercing mandrel in the hollow block is used to draw in inert gas and / or a deoxidizer fluidized by carrier gas. In this case, the deoxidizer and optionally also the inert gas is conveyed through the free, arranged on both sides of the end of the hollow block.

This not only allows the contact of the newly formed pipe inner surface with the atmospheric oxygen limited to the necessary minimum, the supply of deoxidizer and / or inert gas under the effect of the negative pressure generated when retracting the piercer also achieves a lower consumption of deoxidizer and / or Inert gas due to a immediate covering of the hollow block inner surface after punching and turbulence of the deoxidizer and / or inert gas and a distribution in the hollow block without the otherwise usually required excess amounts of carrier gas, inert gas and / or deoxidizer.

On the device side, a device for supplying and introducing fluidized deoxidizer and / or inert gas to the at least one side of the tube or tube precursor facing the roller is provided for this purpose in accordance with the invention. The effects obtainable with the device are the same as those already described above with respect to the method.

In a preferred embodiment of the invention, the supply of fluidized deoxidizer and / or inert gas already takes place before retracting the piercer, so that it is ensured that by retracting the piercer no ambient air, but only inert gas, deoxidizer or a mixture thereof by means of negative pressure in the Hohlblockinnere is introduced.

It is particularly preferred that process control simultaneously start the retraction of the piercing mandrel and the supply of fluidized deoxidizer and / or inert gas to thereby minimize the consumption of inert gas and / or deoxidizer to the required minimum.

It is also preferred if the inflow of air into the interior of the pipe or pipe precursor is at least largely prevented, at least until the beginning of the supply of fluidized deoxidizer and / or inert gas. This can be achieved, for example, by introducing inert gas through the side of the workpiece facing away from the roller, in particular the oblique roller, during the hole mandrel process which has not yet been completed.

According to a preferred embodiment of the invention, the supply of fluidized deoxidizer and / or inert gas under an overpressure of not more than one bar, preferably not more than 0.25 bar. As a result, only the supply of fluidized deoxidizer and / or inert gas is advantageously supported, but the introduction and distribution of deoxidizer and / or inert gas within the hollow block is largely effected by the negative pressure generated by the hole plug.

Since the perforation plug is usually only slightly smaller than the inner diameter of the hollow block, a negative pressure forms on retraction of the plug on the side facing away from the abutment of the perforated plug, thus the side facing the roller of the perforated plug. By this negative pressure, the suction effect is utilized to draw inert gas and / or fluidized deoxidizer in the hollow block itself. Because in this case the injected media does not first have to overcome the resistance of an air mass present in the hollow block and a strong turbulence is generated by the suction effect of the perforated plug, less inert gas and / or deoxidant and a more uniform distribution of the latter are expected in the hollow block. In addition, since the introduction of inert gas and / or deoxidizer takes place with constant enlargement of the space available within the hollow block, it is also not observed in practice occasionally repelling the media stream by the sudden expansion of the gaseous media in contact with the hot hollow block interior ,

It is preferred if a carrier gas is added to the deoxidizer. As a result, the supply and distribution of the deoxidizer to the workpiece and within the hollow block is supported particularly advantageous. In particular, by the carrier gas, the fluidization of the deoxidizer can be achieved by mixing with a gaseous medium.

It is also preferred if the deoxidizer is pneumatically supplied. As a result, a particularly simple and manageable method is used, in which the supply of deoxidizer with particularly easy and precisely adjustable pressures and reliable to the workpiece is guaranteed.

According to a second aspect of the invention, a rolling mill for carrying out the method according to the invention according to the first aspect of the invention is disclosed as already described. The rolling mill comprises at least one roller acting on the outside of the solid body or the pipe precursor, in particular a skew roll, and a mandrel bar carrying a hole plug and engaging the pipe or pipe precursor from the inside. An apparatus for supplying and introducing fluidized deoxidizer and / or inert gas is provided, which preferably comprises a means for at least one side sealing of the pipe or pipe precursor to the ambient atmosphere. Such means can be obtained, for example, in the form of a lid which completely covers the through-hole created by the hole plug.

In a further preferred embodiment of the invention, a storage for an inert gas and a storage for a deoxidizer and valves for controlling the supply from the respective storage to the pipe or pipe precursor are provided.

In this connection, it is particularly preferred if a process control unit is provided for controlling the supply of deoxidizer and / or inert gas and for controlling the perforated stopper. Through this process control unit, the supply of inert gas and / or deoxidizer can be adjusted to the movement of the perforated plug, whereby a secure process management with optimized supply of inert gas and / or deoxidizer depending on the process condition is achievable.

5. Brief description of the drawings

Figur 1

eine schematische Ansicht des Verfahrens zum Herstellen eines Rohres oder Rohrvorprodukts aus einem Vollkörper mit einem Walzwerk gemäß dem Stand der Technik,

Figur 2

eine schematische Ansicht eines erfindungsgemäßen Walzwerks vor Beginn des erfindungsgemäßen Verfahrens, und

Figur 3

eine schematische Ansicht auf ein erfindungsgemäßes Walzwerk bei Durchführung des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to three figures. In the figures shows

FIG. 1

a schematic view of the method for producing a pipe or pipe precursor from a solid body with a rolling mill according to the prior art,

FIG. 2

a schematic view of a rolling mill according to the invention before the start of the inventive method, and

FIG. 3

a schematic view of a rolling mill according to the invention in carrying out the method according to the invention.

6. Detailed description of the figures

• FIG. 1 shows a schematic view of a rolling mill 1 for punching a workpiece 2 by means of a piercer 3 carrying mandrel rod 4. Under the action of two externally applied oblique rollers 5a, 5b, the workpiece 2 is rotated and simultaneously conveyed in the direction of arrow 6, so as continuously Form a metallic solid block a pipe 2 or pipe precursor with a newly produced by the hole plug 3 inner surface 7.
• FIG. 2 shows a schematic view of a rolling mill 1 according to the invention, in which a device 8 for supplying deoxidizer and inert gas to the rollers 5a, 5b facing the end of the tube 2 is provided. The hole plug 3 has just completely pushed through the body 2 and the supply of the device 8 takes place along the direction indicated by the arrow 9 direction. The device 8 comprises a lid 10 for covering the roller facing Side of the tube 2 and valves 11, 12 for controlling the supply of deoxidizer and inert gas through the device 8 into the tube 2 inside.
• FIG. 3 Finally, FIG. 1 shows a state in which the rolling mill 1 carries out the method according to the invention. While the hole plug 3 is pulled out of the tube 2 along the direction of the arrow 13 together with the mandrel rod 4, deoxidizer and nitrogen is fed as inert gas from the reservoirs 14, 15 via the device 8 in the tube 2 and here under the influence of negative pressure within promoted by the mandrel 4 released space in the interior of the tube 2 and on the inner tube wall 7 out and swirled. The device 8 also includes a valve 16 through which the supply of nitrogen from the reservoir 15 into the deoxidizer powder storage 14 can be controlled so as to convert the deoxidizer powder from the storage 15 to the fluidized state by the nitrogen. In this preferred embodiment, the nitrogen from the reservoir 15 thus also serves as a carrier gas for the deoxidation powder from the reservoir 14.

LIST OF REFERENCE NUMBERS

1

rolling mill

2

pipe

3

hole plug

4

mandrel

5a

roller

5b

roller

6

arrow

7

Inner tube wall

8th

contraption

9

arrow

10

cover

11

Valve

12

Valve

13

arrow

14

Storage

15

Storage

16

Storage

Claims (12)

1. Method of producing a tube (2) or tube pre-product from a solid body by means of a rolling mill (1), comprising at least one roll (5) engaging the solid body or the tube pre-product from the outside and a mandrel rod (4) carrying a piercing head (3) and engaging in the tube (2) or tube pre-product from the inside,
   characterised in that
   directly after complete piercing of the solid body by means of the piercing head (3) a fluidised deoxidising agent and/or an inert gas is fed to the side of the tube (2) or the tube pre-product facing the roll (3) and is introduced into the interior of the tube (2) or tube pre-product when retraction of the piercing head (3) through the tube (2) or tube pre-product takes place.
2. Method according to claim 1, characterised in that the feed of fluidised deoxidising agent and/or an inert gas begins before the retraction of the piercing head (3).
3. Method according to one of the preceding claims, characterised in that the feed of fluidised deoxidising agent and/or an inert gas takes place within 10 seconds, preferably within 5 seconds, particularly preferably within 1 second, after complete piercing of the solid body.
4. Method according to any one of the preceding claims, characterised in that a process control starts the retraction of the piercing head (3) and the feed of fluidised deoxidising agent and/or inert gas at the same time.
5. Method according to any one of the preceding claims, characterised in that the inflow of air into the interior of the tube (2) or tube pre-product is at least substantially prevented up to the start of feed of fluidised deoxidising agent and/or inert gas.
6. Method according to any one of the preceding claims, characterised in that the feed of fluidised deoxidising agent and/or inert gas takes place under an excess pressure of not more than 1 bar, preferably not more than 0.25 bars.
7. Method according to any one of the preceding claims, characterised in that a carrier gas is admixed with the deoxidising agent.
8. Method according to any one of the preceding claims, characterised in that the deoxidising agent is fed pneumatically.
9. Rolling mill (1) for carrying out the method according to any one of the preceding claims, comprising at least one roll (5) engaging the solid body or the tube pre-product from the outside and a mandrel rod (4) carrying a piercing head (3) and engaging in the tube (2) or tube pre-product from the inside, characterised in that a device (8) for feeding and introducing fluidised deoxidising agent and/or inert gas to the side of the tube (2) or tube pre-product facing the at least one roll (5) is provided.
10. Rolling mill (1) according to claim 9, characterised in that the device (8) comprises means (10) for sealing the tube (2) or tube pre-product at least at one an relative to the ambient atmosphere.
11. Rolling mill (1) according to one of claims 9 and 10, characterised in that a reservoir (15) for an inert gas and a reservoir (14) for a deoxidising agent as well as valves (11, 12) for controlling the feed from the respective reservoirs (14, 15) to the tube (2) or tube pre-product are provided.
12. Rolling mill (1) according to any one of claims 9 to 11, characterised in that a process control unit for controlling the feed of deoxidising agent and/or inert gas as well as for control of the piercing head (3) is provided.

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