EP0294451B1 - Process and device for continuous casting of metal bars - Google Patents

Abstract

The outflowing casting metal on the path to solidification is no longer subjected to reoxidation and degassing of the casting metal in case of unkilled melts and can immediately be performed ahead of the casting process in a method for continuous casting of metal strands from high-melting metals with cross-sections close to the end dimensions according to the principle of the communicating pipes, and further a temperature and analysis correction can be performed. These conditions are fulfilled by pressing the casting metal from a higher disposed storage container through the communicating channel pipe (8) into a pressure vessel (13) with a gas dome (20), where the casting metal is further transported through an immersion pipe (14), which immerses into the casting metal through the gas dome, into a substantially vertically oscillating independent continuous casting die (15) and where the casting strand formed is deflected in an arc from the vertical direction into the horizontal direction and is withdrawn.

Description

The invention relates to a method and a device for the continuous casting of metal strands from refractory metals, in particular steel strands, with cross-sections close to the final dimensions, according to the principle of the communicating tubes, in which or in which the casting metal in each case from a pressure vessel through a sewer pipe one continuous casting mold is pressed.

A large number of continuous casting processes are known for the production of semi-finished products or primary material for rolling mills. Some of these processes are also used on an industrial scale. These include circular arc continuous casting plants, vertical bending continuous casting plants, die casting processes and horizontal continuous casting processes.

The known methods are either technically problematic or are very complex in plant engineering and still require a high level of personnel and investment costs. Powerful systems are also very inflexible in the product range.

In particular, the requirement for a casting plant corresponding to the above points of view for the production of cross-sections close to final dimensions has been insufficiently met according to the prior art. A known method for producing thin steel strands with a continuous casting mold with a very narrow cross-section suffers from considerable problems of the casting technique, e.g. cleaning the cast metal bath surface in the mold from slag is very difficult due to the narrow cross-section. Furthermore, the problem of casting on at high casting speeds is unsolved.

A problem that has also been unsatisfactorily solved to date is the slag collecting in the continuous casting mold, which not only requires considerable expenditure on the casting powder, but also places considerable demands on the casting team. After that Inadequately trained personnel are the cause of many casting errors.

Another problem with the known continuous casting processes is the reoxidation of the molten steel before and during the casting process. For example, the shadow pipe between the ladle and distributor are removed for several procedures, in which case the re-oxidation of the flowing pouring jet occurs immediately. Significant time and cost problems arise in the area of so-called intermediate distributors. The voluminous distributors have to be precisely aligned over the continuous casting mold, which is becoming increasingly problematic with very narrow strands.

All large-scale casting processes used on an industrial scale have disadvantages of the large personnel expenditure in the casting process (ladle, distributor, mold). In addition to considerable costs, this also results in major deficiencies in process control and in the quality of the products.

The present invention is based on a state of the art, as can be seen in the "Manual of Continuous Casting" from Herrmann Verlag Aluminum, Düsseldorf, edition 1958, page 691 with picture 1930 and page 694 with picture 1940.

According to this, with a system of rising castings and a communicating pipe, a pouring funnel with reoxidation, a fixed vertical or horizontal continuous casting mold and either a steep transition from the vertical to the horizontal or only a vertical strand withdrawal are known.

A method of rising casting is also known (GB-A-2 116 888), which, however, is designed as a semi-continuous casting process, so that no continuously produced cast strand but metal strand castings of finite length, ie of a few meters in length, are produced. The ascent of the cast will not based on the principle of communicating tubes, but by means of an unconnected liquid column. The melt is discontinuously discharged from a melting furnace into a pressure-tight vessel and from there it is pressed by gas pressure onto the melt pool level and through a feed pipe into the mold. The lengths of the individual pieces are determined by chilled molds. This is not a bendable, that is to say a castable casting and, above all, it is not a cross section which can be deformed by low deformation energy to near-net-shape cross-sections and which could form a winding castable. Rather, round or square blocks are produced according to the known method, which have to be processed further according to the conventional methods of the block rolling mills. Use of ladles, avoidance of reoxidation along the entire solidification path, degassing of the melt immediately before casting, temperature and analysis corrections and the control of the pouring metal flow are not taken into account here.

From the "Handbook on Continuous Casting", 1980, Aluminum-Verlag Düsseldorf, page 290, Fig. 1656, the generic method described at the outset is also known, the principle of communicating tubes being used. There, the casting metal is pressed out of a pressure vessel arranged in the hallway through a sewer pipe into a fixed arc mold, although induction pumps are used in the sewer pipe to generate pressure. Another method (Fig. 1658) also uses arc molds. Here, the cast strand is therefore used during cooling, i.e. bent during solidification and not cast and cooled when stretched.

The casting of hollow strands is known from the "Patents Abstracts of Japan", Vol.6, No.178 (M-155) dated 11.9.82 and JP-A-57-85 655, with melt being degassed in an upstream treatment vessel . Since the melt then goes from a lower melt level into the vertical stationary mold is promoted, there is no system of communicating tubes and no continuous liquid column between the furnace and the mold. The tubes are neither bendable nor windable.

In contrast, the invention has for its object to design a ladle insert in such a way that the pouring pouring metal on the way to solidification is no longer exposed to reoxidation, degassing the pouring metal (including unsteady melting) immediately before the casting process to be able to make a temperature and analysis correction shortly before pouring and to achieve the control of the flow of casting metal to the continuous casting mold without additional manual or apparatus expenditure.

The object is achieved on the basis of the method described at the outset in that the casting metal is pressed from a higher-level storage container through the communicating sewer pipe into a pressure vessel with a gas dome, that the casting metal is passed through a vertical immersion pipe which is immersed in the casting metal through the gas dome , is transported into a substantially vertically oscillating, independent continuous casting mold and that the casting strand which is being formed is deflected in an arc from the vertical into the horizontal and drawn off. This process combines the advantage of the air being completely sealed off from the casting metal until the largely solidified metal strand emerges at the exit from the continuous casting mold. The metal inflow can be easily controlled by pressure control via the gas dome. With the rising casting, a dense, gap-free structure is created. The casting metal can be degassed immediately before the actual casting process without significant temperature losses. There is also no slag fishing in front of the mold. According to the process, semi and unsteady steels can also be cast.

An improvement results from the fact that the pressure generated in the gas dome is controlled in coordination with the continuous casting mold oscillation. The solidification conditions in the continuous casting mold, i.e. the formation of the strand shell can be influenced advantageously with this step.

Further advantages result from the fact that a metallostatic pressure difference of at least 780 Torr is maintained continuously between the solidification front in the cast metal strand and the cast metal surface in the pressure vessel or the cast metal surface in the vacuum chamber. These measures ensure the production of a dense structure, whereby degassing processes can be suppressed at this point.

The device for carrying out the method is based on a pressure vessel and a continuous casting mold connected by means of a sewer pipe.

Such an object is improved according to the further invention in that an exchangeable pan vessel is connected upstream of the pressure vessel via the sewer pipe, that an immersion tube is immersed through a gas dome in the casting metal located in the pressure vessel and is attached to an oscillatable continuous casting mold arranged above the pressure vessel and that a sealing compensator for the mold oscillation movement is arranged between the pressure vessel and the continuous casting mold. The idea of a gas dome in connection with the pressure vessel allows the casting metal to be kept away from parts sealing against the continuous casting mold in connection with an increasing and reoxidation-free casting.

The casting metal can advantageously be degassed during the casting process by connecting a vacuum chamber with airtight connection connections between the pan vessel and the pressure vessel.

According to further features of the invention, it is provided that the sewer pipe opens into the pressure vessel in the region of the pressure vessel bottom. Advantageously, the shape and the length of the sewer pipe can hereby be influenced or determined or selected.

According to a further embodiment of the invention, it is proposed that the cast metal level in the vacuum chamber run higher than the top of the horizontally removable metal strand. The desired pressure conditions in the cast metal or in the solidifying metal strand are thereby set.

In a further development of the device it is provided that a casting tract is connected upstream of the pressure vessel, which has a degassing device and / or a pressure accumulator and / or an alloy addition device and / or a heating device. These features are in the sense of advantageous pretreatment measures for the cast metal, e.g. to avoid unwanted elimination processes.

It is also provided that slides are arranged next to the vacuum chamber and in front of the pressure vessel. These ensure that the pressure is maintained in parts of the system if there is a drop in pressure in other areas.

Another group of features consists of the fact that the pressure vessel has a considerably larger cross section than the sewer pipe or the immersion pipe. This measure allows the formation of the gas dome. Elimination and degassing processes, if desired, as well as purification processes can be facilitated.

Another proposal is that the pressure vessel is provided with a slag tapping device in the upper region. This means that residual slag can be removed without any special effort.

An interchangeability of the dip tube is advantageously achieved and facilitated in that a frame is arranged between the compensator and the continuous casting mold, which is carried or driven by a mold oscillation drive and which also carries the continuous casting mold.

The formation of the cast strand or metal strand is also favored in that the continuous casting mold formed from cooled copper plates is provided at the inlet with semi-permeable strips and that these strips are provided with lubricant channels which are connected to a high-pressure lubricant pump. This reduces the friction of the metal strand and at the same time supports the detachment of the strand shell being formed.

According to further features, a slide is arranged between the continuous casting mold and the dip tube. This measure allows the continuous casting mold to be changed without changing the immersion tube, e.g. when changing from a format of the metal strand to a new format.

The mold oscillation with a moving immersion tube requires new ways of construction. For this purpose, it is proposed that the compensator consists of a labyrinth lower part fastened to the pressure vessel and a labyrinth upper part fastened to the continuous casting mold or to the slide, that the labyrinth lower part and the labyrinth upper part are provided with interacting teeth, the latter of which The stroke of movement corresponds to the stroke of the continuous casting mold. The mold oscillation can thus advantageously be absorbed and the sealing elements are protected from damage in emergencies.

Advantageous features for the sealing elements are that the lower part of the labyrinth and the upper part of the labyrinth form a cylindrical, external seal. Such a seal can be better controlled.

According to another proposal, the seal can be formed either in the manner of a piston ring seal or in the manner of an annular bellows.

One measure to protect against the operating heat is that the seal is cooled. Such cooling can take place from the outside or from the inside or on both sides.

The invention is not restricted to the use of a single-core continuous casting installation. It is therefore proposed that several parallel metal strands can be generated, wherein one or two pan vessels are provided and that a track runs in front of the continuous casting molds across the metal strands, on which one or more manipulators for changing continuous casting molds, compensators or dip tubes can be moved. Only one casting section is therefore necessary for all continuous casting molds. This arrangement also allows casting to be interrupted on any strand without having to stop pouring on the other strands.

Finally, it is also advantageous that an emergency casting device is arranged under the pressure vessel or the connected sewer pipe.

• Fig. 1 eine Gesamtansicht der Stranggießvorrichtung im Aufriß von der Seite gesehen,
• Fig.2 einen Ausschnitt bezüglich einer Bogenstranggießkokille mit Tauchrohr und Druckgefäß im senkrechten Schnitt, gegenüber Fig.l in einem vergrößerten Maßstab,
• Fig.3 ein Detail zwischen Bogenstranggießkokille und Tauchrohr im Längsschnitt wie Fig.2, jedoch in einem noch mehr vergrößerten Maßstab,
• Fig.4 einen Teil-Querschnitt durch den Kompensator in einer ersten Ausführungsform,
• Fig.5 einen Teil-Querschnitt wie Fig.4 durch den Kompensator in einer zweiten Ausführungsform,
• Fig.6 einen Grundriß für eine Mehrstranggießanlage in einer ersten Ausführungsform und
• Fig.7 einen Grundriß wie Fig.6 für eine Mehrstranggießanlage in einer zweiten Ausführungsform.

Embodiments of the invention are shown in the drawing and are described in more detail below. Show it

• 1 is an overall view of the continuous casting device in elevation seen from the side,
• 2 shows a detail with respect to a continuous sheet casting mold with a dip tube and pressure vessel in a vertical section, compared to FIG. 1 on an enlarged scale,
• 3 shows a detail between the continuous casting mold and the dip tube in longitudinal section as in FIG. 2, but on an even more enlarged scale,
• 4 shows a partial cross section through the compensator in a first embodiment,
• 5 shows a partial cross section like FIG. 4 through the compensator in a second embodiment,
• 6 shows a floor plan for a multi-strand caster in a first embodiment and
• 7 shows a floor plan like FIG. 6 for a multi-strand casting installation in a second embodiment.

The casting metal flows from a pan vessel 1, regulated by a pan slide 2, into a one arranged below the pan vessel 1 Vacuum chamber 3. The vacuum chamber 3 is connected to a machine (not shown) that generates the vacuum by means of a suction pipe 4.

An alloy addition device 5 for alloying agents and / or scrap is also provided on the vacuum chamber 3. A gas-permeable insert 6 is arranged in the bottom region of the vacuum chamber 3. A slide 7 arranged in the bottom area forms the bottom closure of the vacuum chamber 3 at the beginning of the casting process and, if necessary.

Following a pouring nozzle 7a of the vacuum chamber 3 there is a sewer pipe 8 made of refractory material, which consists of a vertically downward section 8a, a horizontal section 8b and a vertically upward section 8c. The sewer pipe 8 is provided at a suitable point with a heating device 36 in order to heat up the casting metal if necessary. In the region of the deflection of the section 8b into the section 8c, a closure device 11 is provided which, if necessary, enables the drainage of the sewer pipe 8. The end of section 8c is formed by a slide 12. This slide 12 can also serve as a bottom closure of a pressure vessel 13. It is also possible to provide a second slide. The pressure vessel 13 is used to hold the liquid casting metal shortly before entering a dip tube 14, which in turn feeds the casting metal to a continuous casting mold 15, which can basically consist of an arcuate casting mold or also of a straight continuous casting mold. There are special advantages associated with both systems.

The dip tube 14 is designed according to the format of the metal strand 10 to be cast or the corresponding continuous casting mold 15. The pressure vessel 13 is enlarged in cross section with respect to the sewer pipe 8 and is under a gas pressure which is built up in a gas dome 20 and which hates the continuous casting mold 15 and a mold oscillation drive 30 partially compensated. Furthermore, the enlarged cross-section serves to calm the flow of the casting metal and to separate metal-accompanying substances, which are drawn off from time to time.

The gas pressure depends on the distance of the cast metal mirror 9 above the top of the horizontally removable metal strand 10.

A compensator 16 and a slide 17 are arranged above the pressure vessel 13. The compensator 16 compensates for the mold stroke in relation to the fixed pressure vessel 13 and consists of a lower labyrinth part 16a and an upper labyrinth part 16b.

According to FIG. 4 (a first embodiment), the gas-tight closure of lower part 16a and upper part 16b is achieved by means of piston rings 16d. The lower part 16a and the upper part 16b are supplied with coolant via a line system 16e. The gas pressure established in the pressure vessel 13 is controlled and monitored via a gas line 16f. In the event of failure or an inadmissible drop in the gas pressure in the pressure vessel 13, the labyrinth upper part 16b automatically falls on the labyrinth lower part 16a and, as a result of a toothing 16g, blocks the flow of the casting metal and prevents the piston rings 16d from being damaged.
The lower labyrinth part 16a and the upper labyrinth part 16b form a cylindrical, outer seal 16h (FIG. 4). This seal 16h is formed either in the manner of a piston seal 16d (FIG. 4) or in the manner of an annular bellows 16c (FIG. 5).

According to FIG. 5 (a second embodiment), the lower labyrinth part 16a and the upper labyrinth part 16b are connected by means of a flexible element, ie with a ring collar 16c, which is protected from damage by the toothing 16g.

The pressure vessel 13 has a gas inlet 18 and a slag tapping device 19.

For a modified control technology, the continuous casting mold 15 is equipped with a second slide, not shown, which lies above the slide 17.

The continuous casting mold 15 also has copper plates 22 (FIG. 2) which form the format for the metal strand. They can be designed for a block, tube or plate continuous casting mold 15 and are cooled from the outside.

At the inlet part 22a of the continuous casting mold 15 (FIG. 3), semipermeable strips 23 are arranged in a ring, which serve to supply and distribute suitable lubricants. The strips 23 have channels 24. The channels 24 are segmented and are supplied with lubricant through a line 38 by means of a multi-cylindrical injection pump (not shown). Between the compensator 16 and the continuous casting mold 15 there is an internally cooled frame 26 which is carried or driven by the mold oscillation drive 30 and which also carries the continuous casting mold 15.

6 and 7, several systems for metal strands 10 can be arranged side by side. In this case, the sewer pipe 8 runs in each case in the axis of symmetry of the continuous casting molds 15, i.e. perpendicular to the strand extraction direction 31. For high-performance systems, two ladle containers 1 are expediently provided on the left and right of the system. This enables a smooth change of the ladle vessels 1 without the need for a conventional ladle turret with inevitable ladle changing times.

• des Tauchrohrs 14
• des Kompensators 16
• des Schiebers 17
• der Stranggießkokille 15
• von Segmenten 29 der Strangführung.

The pouring stand front 27 (FIG. 1) facing away from the plant part of the strand discharge 37 generally serves to control the plant and the service. For this purpose, a manipulator 28 is provided on rails 28a to enable the following and other devices to be handled:

• of the dip tube 14
• of the compensator 16
• the slide 17
• the continuous casting mold 15
• of segments 29 of the strand guide.

The mold oscillation drive 30 and segment drives (not shown) are located under the strand discharge 37.

A slag receiving device 32, which can be moved transversely to the metal strands 10, is provided directly next to the slag accumulating in the pressure vessel 13.

A tapping device 33 is provided for receiving the casting metal from the casting tract in an emergency and for other cases. It can be moved across by means of a trolley 34 and is disposed of outside the casting area by crane.

A reel device 35 is provided in the strand discharge 36 for handling thin metal strands 10.

Claims (20)

1. PROCESS for the continuous casting of high-melting metals, particularly steel, into strands with cross-sections close to finished dimensions, in accordance with the principle of communicating pipes, wherein the metal to be cast is in each case forced from a pressure vessel via a channel pipe into a mould,
characterised by:
the casting metal being forced from an elevated reservoir via a communicating channel pipe into a pressure vessel having a dome of gas and being transported in a vertical immersion pipe passing through the gas dome, this immersion pipe being submerged in the casting metal, the latter being transferred into an essentially vertically oscillating independent continuous casting mould and the forming strand being deflected in the curved arc from the vertical to the horizontal prior to withdrawal.

2. PROCESS to Claim 1,
characterised by:
the pressure generated in the gas dome being controlled in coordination with mould oscillation.

3. PROCESS to Claim 1 or Claim 2,
characterised by:
the metallostatic pressure differential of at least 780 Torr being continuously maintained between the solidification front in the cast metal strand and the casting metal surface in the pressure vessel or in the vacuum chamber.

4. APPARATUS for performing the process to one or more of Claims 1 to 3, comprising a pressure vessel and a mould linked by a channel pipe,
characterised by:
the pressure vessel (13) being preceded via the channel pipe (8) by a replaceable ladle (1), and an immersion pipe (14) being submerged in the casting metal in the pressure vessel (13) via a gas dome (20) and being mounted at a continuous casting mould (15) capable of being oscillated, such mould being arranged above the said pressure vessel (13), and a sealing compensator (16) for the continuous casting mould oscillation movement being arranged between the pressure vessel (13) and the mould (15).

5. APPARATUS to Claim 4,
characterised by:
a vacuum chamber (3) with air-tight connections being interposed between the ladle (1) and the pressure vessel (13).

6. APPARATUS to Claim 4,
characterised by:
the channel pipe (8) ending in the bottom zone at the pressure vessel (13).

7. APPARATUS to Claims 4 to 6,
characterised by:
the casting metal level (9) in the vacuum chamber (3) being higher than the upper side of the horizontally withdrawable metal strand (10).

8. APPARATUS to Claims 4 to 7,
characterised by:
a casting section being located in front of the pressure vessel (13) and featuring a degassing facility and/or a pressure accumulator (3a) and/or an alloyant charging device (5) and/or a heating device (36).

9. APPARATUS to Claim 8,
characterised by:
slides (7; 12) being arranged adjacent to the vacuum chamber (3) and ahead of the pressure vessel (13).

10. APPARATUS to one or more of Claims 4 to 9,
characterised by:
the pressure vessel (13) having a substantially larger cross-section relative to the channel pipe (8) and/or the immersion pipe (14).

11. APPARATUS to Claims 4 to 10,
characterised by:
the pressure vessel (13) being provided in its upper zone with a slag tapping device (19).

12. APPARATUS to one or more of Claims 4 to 11,
characterised by:
a frame (26) being arranged between the compensator (16) and the continuous casting mould (15) in such manner as to be supported or driven by a mould oscillator drive (30) which likewise carries the continuous casting mould (15).

13. APPARATUS to Claims 4 to 12,
characterised by:
the continuous casting mould (15) formed by cooled copper plates (22) featuring semi-permeable stripos (23) at the inlet (22a) and these strips (23) being provided with lubricant ducts (24) connected to a high-pressure lube pump.

14. APPARATUS to Claims 4 to 13,
characterised by:
a slide (17) being arranged between the continuous casting mould (15) and the immersion pipe (14).

15. APPARATUS to a pluralty of Claims 4 to 14,
characterised by:
the compensator (16) consisting of a lower labyrinth part (16a) mounted at the pressure vessel (13) and a labyrinth upper part (16b) mounted at the continuous casting mould (15) or at the slide (17), and the labyrinth lower and upper parts (16a and 16b), featuring co-active meshing toothing (16g) whereof the motion stroke corresponds to that of the continuous casting mould (15).

16. APPARATUS to Claim 15,
characterised by:
labyrinth lower and upper parts (16a and 16b) forming a cylindrical external seal (16h).

17. APPARATUS to Claims 15 and 16,
characterised by:
the seal (16h) being designed either as a piston ring seal (16d) or in the nature of a ring bellows (16c).

18. APPARATUS to Claims 15 to 17,
characterised by:
the seal (16h) being cooled.

19. APPARATUS to one or more of Claims 4 to 18,
characterised by:
a pluralty of parallel metal strands (10) being achievable to work in conjunction with a ladle or two ladles (1), a rail track (28a) being arranged ahead of the continuous casting moulds (15) in order to permit travel of a manipulator or several manipulators (28) for changing the continuous casting moulds (15), compensators (16) or immersion pipes (14).

20. APPARATUS to Claims 4 to 19,
characterised by:
an emergency casting device (33 or 34) being arranged under the pressure vessel (1) and/or the connected channel pipe (8).

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