EP0846510B1 - Use of a mould for producing bars of light metal or their alloys, especially magnesium or magnesium alloy - Google Patents

Abstract

Casting method for extrusion billets of light metal or alloy, especially magnesium or magnesium alloy, with a diameter of 60 to 400 mm, using a tubular metal mould with an internal diameter or cross section corresponding to the required billet. Corresponding equipment is also claimed.

Description

The invention relates to the use of a mold for producing bars from light metal or with a light metal alloy, especially made of magnesium or a magnesium alloy a diameter of 60 to 400 mm.

The manufacture of light metal bars, especially magnesium bars, is carried out according to the current status the art usually by casting strands with a large diameter, preferably 400 up to 600 mm in diameter can be cast using known continuous casting processes, as they do for example, described in US-A-4 071 072. Here, the melt is broken down into a short water-cooled mold, and the strand emerging from the mold is sprayed cooled with water or by immersing in a water bath until completely solidified. Thereafter, machining of the surface of the cast strands to remove the Cast edge shell take place. Finally, the casting strand is extruded to the desired one Dimensions of the ingot brought.

The name of the bars produced in this way is "pre-ex (pre-extruded) bars".

The conventional, water-cooled continuous casting of magnesium or magnesium alloy is included Small formats are not suitable due to the associated risk of explosion.

• Eine ungünstige Ausbringung durch die lange Prozeßkette:
• 1. Das Stranggießen von Gießsträngen mit großem Durchmesser mit etwa 80 % Ausbringung.
• 2. Die spanende Bearbeitung mit etwa 90 % Ausbringung.
• 3. Das Strangpressen auf die gewünschten Abmessungen des Barrens mit etwa 70 % Ausbringung.
  Das ergibt dann insgesamt eine Ausbringung von nur etwa 50 %.
Die Folgen sind ein äußerst hoher Energieverbrauch für den Fertigungsprozeß und zusätzlich für die Wiederaufbereitung des Rücklaufmaterials.
• Weiterhin entsteht ein hoher Energieverbrauch durch den notwendigen Betrieb einer Strangpresse, die für das Strangpressen der großformatigen Barren eine Preßkraft in der Größenordnung um 10.000 t und mehr aufweisen muß. Da Strangpressen in dieser Größenordnung nur an wenigen Stellen in der Welt betrieben werden, ergibt sich daraus die Tatsache, daß nur wenige Firmen weltweit in der Lage sind, diese "Pre-ex"-Barren zu fertigen.
• Ein weiterer Nachteil dieses mehrstufigen Verfahrens liegt darin, daß kleinere Bedarfsmengen nicht wirtschaftlich gefertigt werden können. Auch kurzfristige Bedarfsdeckungen sind wegen des mehrstufigen Verfahrens nicht möglich.

Disadvantages of the prior art are in particular:

• An unfavorable application due to the long process chain:
• 1. The continuous casting of casting strands with a large diameter with about 80% output.
• 2. The machining with about 90% output.
• 3. The extrusion to the desired dimensions of the billet with about 70% output.
  This results in a total yield of only about 50%.
The consequences are an extremely high energy consumption for the manufacturing process and additionally for the reprocessing of the return material.
• Furthermore, a high energy consumption arises from the necessary operation of an extrusion press, which must have a pressing force in the order of magnitude of 10,000 t and more for the extrusion of the large-format ingots. Since extrusion presses of this size are only operated at a few locations in the world, this means that only a few companies worldwide are able to manufacture these "pre-ex" bars.
• Another disadvantage of this multi-stage process is that smaller quantities cannot be produced economically. Even short-term coverage is not possible due to the multi-stage process.

Bars of light metal or a light metal alloy, in particular magnesium or one Magnesium alloy can be used for experimental purposes with conventional casting techniques, e.g. B. in Sand casting processes are produced. However, the structural properties are extreme because of the low solidification speeds for further processing, especially extrusion unfavorable. A one-off production requires a very high manual effort for the Mold production and further processing of the cast blank. The casting blank must be and running system are freed and processed all round to the finished size for further processing become. Due to the large-volume sprue and riser system as well as the machining there is also a very low output in the order of magnitude for the sand casting process 50%. The sand casting process is therefore not suitable for mass production of bars.

A sheet metal mold is described in US-A-2 264 456. It rests on a lowerable Table in a spray zone or a water bath. The mold has clamp elements for Hold / fix the free ends of the sheets. They are topped up to the same extent as the Casting table is lowered.

All processes have in common that in principle an intensive liquid cooling of the mold and / or the ingot is provided.

The invention is based on the problem of a method and an apparatus for producing Ingots, in particular pressed bars made of light metal or a light metal alloy, in particular made of Magnesium or a magnesium alloy, with a diameter of 60-400 mm, which is both for series production and for one-off production for small quantities and short-term coverage is suitable. The ingots are said to be without further processing have the desired dimensions so that machining of the bar surfaces can be eliminated or reduced to a minimum. Finally, the total output is supposed to about 80% and above.

Based on this problem, the use of a tubular, extruded, metal mold with high thermal conductivity only exposed to still air, with a desired diameter or cross section of the ingot corresponding inner diameter or Internal cross section, a bottom plate closing the mold, at least one of the desired Length of the bar corresponding length for the production of pressed bars from light metal or one Light metal alloy, in particular made of magnesium or a magnesium alloy, with a Proposed diameters from 60 to 400 mm.

Preferably, an extruded metal mold made of aluminum or an aluminum alloy used. Surprisingly, it has been shown that the cooling rate in one such a mold is so high that the cooling effect in still air due to the high Thermal conductivity of the mold material is completely sufficient and even for the production of bars made of aluminum and its alloys is suitable without the mold melting. In order to increase the cooling effect of the metal mold, the mold can preferably be equipped with cooling fins be provided.

Such molds can be quickly extruded with any internal diameter or internal cross-section as well as with cooling fins, so that the manufactured by means of this mold Ingot already has the respective dimensions required for further processing, without that additional processing steps are required. The preferred mold used Aluminum or an aluminum alloy already has such a high cooling effect in still air, that additional cooling is not required.

The inner surface of the metal mold can be provided with a conventional size, and as Chill material can be metals that can be formed by extrusion and one have high thermal conductivity. Aluminum or preferably therefore come for the mold Aluminum alloys in question.

The light metal or light metal alloy melt, in particular the magnesium or Magnesium alloy melt, is from above into the extrusion profile used as a mold filled with rising metal mirror. One serves as the lower end or bottom for the mold Metal plate, preferably a steel plate, which can also be cooled. To be a quiet one The metal is fed during to achieve metal feed without vortex and turbulence the casting always below the melt surface and preferably in such a way that a constant distance of a melt nozzle immersed in the melt from the Melt surface using a float by lowering the mold or lifting the Melt nozzle is set.

A quiet metal feed without vortex and turbulence can also be done without using a Floats can be achieved by lowering the mold or lifting the melt nozzle in Dependence of the mold filling speed is controlled so that the melt nozzle is always in the Melt remains immersed.

A light metal-resistant filter in the melt nozzle can also be a quiet metal feed cause and also reduces or avoids the introduction of oxides and / or Contamination in the mold.

By shrinking the light metal or the light metal alloy, especially the Magnesium or the magnesium alloy, during the solidification the bars can easily be released remove the extruded profile used as the mold. That used as a mold Extruded profile does not require any rework and is immediately available for further use Available.

The mold is characterized by a very high output because of the necessary waste at most is limited to the lowest area of the ingot, where it is at the initial Filling the light metal or light metal alloy melt, in particular the magnesium or Magnesium alloy melt, there is turbulence and oxide inclusions and therefore alone must be separated if there are appropriate cleanliness requirements. The rest of it Material up to the upper metal mirror can be used directly for further processing. In addition, the surface of the cast blank can optionally be cleaned by blasting or even slightly machined to get a clean metallic surface, if appropriate There are requirements for the products to be manufactured, in particular extruded profiles.

The light metal or light metal alloy melt, in particular the magnesium or Magnesium alloy melt can also from below into the extrusion profile used as a mold be filled with rising metal levels. For this come z. B. the low pressure casting process or the gravity casting process with increasing mold filling in question.

The mold can be in one part or can be composed of several parts from extruded profile segments.

To keep a constant distance from the melt when filling the mold To ensure immersed melt nozzle from the melt surface, a float be provided, which controls the melt supply.

A light metal-resistant filter can be arranged in the melt nozzle.

Bars with a length corresponding to the height of the mold can be produced.

To counteract the formation of voids in the upper area of the ingot, the Thermal insulation may be provided in the upper region of the mold. This thermal insulation can be used as arranged on the inside and / or the outside of the mold in the upper area, heat-insulating coating can be formed. Instead of or in addition to this coating a heat-insulating attachment can also be provided on the mold. This essay can be made a piece of pipe made of molding sand, which preferably tapers conically upwards is exist.

For a series production in the form of a band production or carousel production, several can arranged on the belt or the carousel. The important thing here is Cooling section that is required until the bar solidifies and the ingot is removed from the mold. It can also be cast in multiple strands at the same time by using an appropriate Distribution pan is worked above several molds.

Fig. 1

eine Schnittansicht einer erfindungsgemäßen Kokille mit Darstellung des angewandten Gießverfahrens,

Fig. 2

eine Draufsicht auf eine erste Ausführungsform einer Kokille,

Fig. 3

eine Draufsicht auf eine zweite Ausführungsform einer Kokille,

Fig. 4

eine Schnittansicht einer erfindungsgemäßen Kokille mit Darstellung des angewandten Gießverfahrens und einer gekühlten Bodenplatte,

Fig. 5

eine Schnittansicht einer erfindungsgemäßen Kokille mit Darstellung des angewandten Gießverfahrens und eines leichtmetallresistenten Filters,

Fig. 6

eine Schnittansicht einer erfindungsgemäßen Kokille mit Darstellung des angewandten Gießverfahrens und eines anders angeordneten, leichtmetallresistenten Filters,

Fig. 7

eine Schnittansicht einer erfindungsgemäßen Kokille mit Darstellung des angewandten Gießverfahrens und einer Wärmeisolierung im oberen Bereich der Kokille und

Fig. 8

eine Schnittansicht einer erfindungsgemäßen Kokille mit Darstellung des angewandten Gießverfahrens und einer anderen Ausführungsform einer Wärmeisolierung im oberen Bereich der Kokille.

The invention is explained below with reference to several exemplary embodiments shown in the drawing. The drawing shows:

Fig. 1

2 shows a sectional view of a mold according to the invention, showing the casting method used,

Fig. 2

a plan view of a first embodiment of a mold,

Fig. 3

a plan view of a second embodiment of a mold,

Fig. 4

2 shows a sectional view of a mold according to the invention, showing the casting method used and a cooled base plate,

Fig. 5

2 shows a sectional view of a mold according to the invention, showing the casting method used and a light metal-resistant filter,

Fig. 6

2 shows a sectional view of a mold according to the invention, showing the casting method used and a differently arranged, light metal-resistant filter,

Fig. 7

a sectional view of a mold according to the invention with representation of the casting process used and thermal insulation in the upper region of the mold and

Fig. 8

a sectional view of a mold according to the invention showing the applied casting process and another embodiment of thermal insulation in the upper region of the mold.

An extruded mold 1 made of aluminum or an aluminum alloy has a tube wall 2 with an inner diameter corresponding to the desired diameter of the ingot and radial Cooling fins 3. The mold 1 rests on a base plate 4 made of metal, and the whole of a lowering device 10 worn. The bottom plate 4 can, as shown in Fig. 4, cooling channels 16 have. A melt nozzle 6 protrudes into the mold 1 and consists of a light metal, especially magnesium-resistant material. A float 7 stands with the nozzle 6 also made of light metal, especially magnesium-resistant material in combination, for this ensures that light metal or light metal alloy melt or the magnesium or Magnesium alloy melt 8 always at a uniform distance from one Melt surface 9 is introduced into the mold 1.

The lowering device 10 is lowered according to the casting speed until the mold is filled with molten metal. The melt is cooled in still air.

If the cooling effect is sufficient, the mold can also be used as a smooth tube without cooling fins be trained.

With the described method, bars with a height corresponding to the mold can be produced Create length. Of course, it is possible to use the nozzle 6 according to the Raising the casting speed instead of lowering the mold 1.

The embodiment shown in FIG. 3 shows an existing of mold segments 11 Mold, in the tube wall 12 channels 13 are arranged. In addition, outer cooling fins 14 shown. In the example shown, the mold consists of four mold segments 11, which, for. B. are positively connected to one another by means of a dovetail connection 15, however the mold can also consist of fewer or more mold segments.

Of course, other connection options such. B. possible by welding.

To ensure that the light metal or the light metal alloy adheres to the inner surface of the To avoid mold tube wall, this can be treated with a conventional size.

The cross section of the mold can be circular, as shown, but can also be other Have cross-sectional shapes.

The cooling rate on the wall 2 of the mold is so great that that of aluminum or an aluminum alloy extruded mold 1 also for the production of bars from aluminum or an aluminum alloy is suitable.

5, a light metal-resistant filter 17 can be used to control the mold filling speed between the float 7 and the melt nozzle 6 or as shown in FIG. 6 instead of the float the melt nozzle 6 may be arranged. This allows the introduction of oxides and others Reduce or even avoid contamination in the melt.

In order to counteract the formation of voids in the upper area of the ingot, in the upper area the mold 1, inside and / or outside, a heat-insulating coating 18, 19 may be applied. The same purpose can also be achieved by an attachment 20 shown in FIG Reach conical pipe piece made of molding sand, which alone or in addition to the coating 18, 19 in FIG. 7 forms the thermal insulation.

Claims (15)

1. The use of a tubular, extruded chill (1,) exposed only to resting air, of metal with a high thermal conductivity with an internal diameter or internal cross-section corresponding to the desired diameter or cross-section of a bar which is to be produced, a base plate (4) closing the chill (1), a length corresponding to the desired length of the bar for the production of press bars of light metal or of a light metal alloy, in particular of magnesiun or of a magnesium alloy, with a diameter of 60 to 400 mm.
2. The use of a chill according to Claim 1 with cooling ribs on the outer surface.
3. The use of a chill according to Claim 1 or 2 of aluminium or of an aluminium alloy.
4. The use of a chill according to Claim 2 or 3, which is composed in several parts of extrusion profile segments (11).
5. The use of a chill according to Claim 1, 2, 3 or 4 with a base of a metal plate (4) as base for the chill (1;11).
6. The use of a chill according to Claim 5, in which the metal plate (4) is able to be cooled.
7. The use of a chill according to one of Claims 1 to 6 with a thermal insulation (18, 19, 20) in the upper region.
8. The use of a chill according to Claim 7 with a thermally insulating coating (18, 19) on the inner face and/or on the outer face of the upper region.
9. The use of a chill according to Claim 7 or 8 with a thermally insulating attachment (20) on the upper region.
10. The use of a chill according to Claim 9, in which the thermally insulating extension (20) consists of a pipe piece of casting sand.
11. The use of a chill according to Claim 10, in which the pipe piece (20) is constructed narrowing conically upwards.
12. The use of a chill according to any of Claims 1 to 11, in which the melt is able to be supplied by means of a melt nozzle (6) during casting always beneath the melt surface (9).
13. The use of a chill according to Claim 12, in which a constant spacing of the melt nozzle (6), immersed in the melt, from the melt surface (9) is able to be set by means of a float (7) by lowering the chill (1) or raising the melt nozzle (6).
14. The use of a chill according to one of more of Claims 10 to 13 with a mounting for the chill (1;11) and a lowering device (10) for the metal plate (4).
15. The use of a chill according to one of Claims 1 to 14, in which the melt is able to be supplied by means of a melt nozzle (6) provided with a light metal-resistant filter (17).

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