WO2003047792A1

WO2003047792A1 - Device consisting of a heatable casting vessel and a ladle furnace

Info

Publication number: WO2003047792A1
Application number: PCT/DE2002/004407
Authority: WO
Inventors: Günter PHILLIPPS; Ralph Koppenhöfer; Carmen Scherer
Original assignee: INDUGA Industrieöfen und Giesserei-Anlagen GmbH & Co. KG; Daimlerchrysler Ag
Priority date: 2001-12-04
Filing date: 2002-12-02
Publication date: 2003-06-12
Also published as: AU2002360884A1; EP1450974A1; WO2003047792A8; DE10159306A1; DE50203641D1; EP1450974B8; EP1450974B1; ATE297825T1

Abstract

The invention relates to a device consisting of a casting vessel (1) having a heatable, refractory lining and an outer metal jacket for receiving molten metal material, especially aluminum molten materials, and a ladle furnace (2) with a magnetic coil (5), wherein the casting vessel (1) is releasably placed on the stationary ladle furnace (2). According to the invention, the metal jacket of the casting vessel (1) has several openings (13) in the form of slits in the lower area.

Description

description

Device consisting of heatable pouring vessel and a heating stand

The invention relates to a device according to the preamble of claim 1.

In order to bring a metal or a metal alloy into a castable state, the metals first have to be melted, then optionally subjected to a metallurgical intermediate treatment and finally to the casting process itself. The metallic raw materials are mostly melted in a large-volume melting furnace, from where the melts are transferred to a pan and from there to a casting plant. However, many metals or metal alloys are sensitive to temperature fluctuations, and tend to be exposed to oxygen and hydrogen or other substances passing through the air or through contact with the vessels used, e.g. Iron to enter into unwanted reactions that lead to unwanted accompanying substances in the melt. Z.T. form dross, also via undesired chemical reactions at the respective molten metal level. Many of the above-mentioned reactions are promoted by decanting the metal melt one or more times.

This also applies in particular to the material aluminum or its alloys, in which oxidation is largely prevented and any gas absorption is to be prevented as completely as possible. The temperatures up to about 770 ° C during the melting process favor the oxidation of the aluminum, which is particularly serious because the aluminum oxide has the same density as the base material aluminum, so that the resulting Al ₂ O ₃ neither settles in the melt nor through the buoyancy is flushed to the bath surface. The oxides remaining in the aluminum melt are present in the cast as foam or thin skin and can impair the structure of the finished cast part in the sense of a reduction in the strength and tightness of the castings. The risk of aluminum oxide formation during decanting is particularly great the aluminum melt in a downstream transport or treatment vessel or when pouring into the molds. Since the oxide cannot be further reduced under normal foundry conditions, special precautions must be taken to prevent the oxidation process, which is referred to as waste, as far as possible.

Negative effects also occur if the aluminum melt with moisture, e.g. B. moist air comes into contact. Due to the high temperatures, the water splits into its components hydrogen and oxygen, whereby dissolved hydrogen in the melt separates again in the form of enclosed gas bubbles during the solidification process; the pores formed by hydrogen separation interrupt the structure in the casting.

In existing foundries, it is often customary according to the prior art to transfer aluminum or aluminum alloys originating from a large-volume melting furnace into pans which serve as a means of transport for the melt to an intermediate station with one or more holding furnaces. Thereafter, the aluminum or the aluminum alloy is transferred to a casting installation by means of a further transport vessel, so that several transfer operations take place until the actual casting process.

Remedial measures can be provided by so-called induction conveying troughs, which transfer the liquid aluminum or aluminum alloy from a melting furnace into a tiltable treatment and casting furnace. By induction of an alternating magnetic field in the liquid metal, eddy currents are generated, which in interaction can exert a mechanical force on the metal that moves the metal. In addition, the induced eddy currents also heat the liquid metal, so that temperature losses can be compensated for.

The same inductive effect is also used in so-called induction crucible furnaces, in which both a melt bath movement is achieved by means of the existing magnetic coil generated as well as keeping warm is guaranteed. In the case of the above-mentioned induction channels as well as the furnaces, it is necessary for the inner wall to consist of non-magnetic, electrically non-conductive, refractory material, so that the magnetic fields are not impaired and the heat development occurs directly in the melting material.

Induction troughs for conveying molten metal between two metallurgical vessels are, however, constructional and costly. In addition, these channels require space and do not allow any flexibility.

The transport vessels that are still used in foundry technology have the disadvantage that, due to the lack of their own heating system, a not inconsiderable temperature loss of the melt during transport has to be accepted. In principle, it would be possible to provide the transport containers with an inductively operating heater, but this has the disadvantage that the power supply line, including the cooling devices for the coil, must then be carried along. In addition, a heating device installed in the lower region of a transport vessel would considerably increase the weight and volume of this transport vessel and thus make it considerably more difficult to handle.

From DE 20 35 221 B a device for keeping metallic melts warm in a ladle is known, which is lined with refractory material and which has a fixed, designed as an independent structural unit, an electro-inductive heating device and a portable ladle which can be inserted therein, the jacket of which is entirely or at least in the area of action of the heating device made of electrically non-conductive material. The shell of the ladle can consist entirely or at least in the area of the action of the heating device made of a plastic, preferably reinforced by inserts such as glass fibers, or of longitudinally laminated sheets, between each of which a plastic insulating layer is provided. This measure is intended to prevent damage to the ladle during the electro-inductive heating of the molten metal contained therein, but the casting vessel is very complex in terms of construction. It is therefore an object of the present invention to provide an inductively heatable vessel which avoids the aforementioned disadvantages and can be used flexibly both as a holding and / or degassing oven and as a transport vessel and, under certain circumstances, also as a casting vessel.

This object is achieved by the inductively heatable vessel according to claim 1.

The advantage of this design is that this vessel can be used both as a transport vessel and as a holding, alloying and / or degassing vessel and possibly also as a casting vessel, from which the desired batches are removed using a ladle. The molten metal transferred from a melting vessel into the casting vessel is transferred to a heating station, where the casting vessel is placed or used and the melt is inductively heated and a bath movement is generated. In this station, post-treatments such as degassing, grain refinement or even alloy settings can be carried out before the casting vessel is removed from the heating stand and led to the casting plant, which can be a rotary table system for permanent mold casting or a continuous casting plant. Since the molten metal remains in one and the same vessel from melting to the casting station, decanting processes are also eliminated, so that the dreaded burn-up (oxidation) or other gas absorption, in particular hydrogen, is excluded to this extent. The pouring vessels preferably have a filling volume of 1 to 3 tons. The vessel structure is basically known from ladle metallurgy, ie the vessels have a refractory lining and an outer metal jacket, which, however, must not be ferromagnetic in the lower area in order not to impair the desired magnetic field structure and the generation of eddy currents in the melt. According to the invention, the metal jacket has slot-shaped openings in the lower region, which are located at the level of the magnetic coil when the casting vessel is attached. The slots mentioned prevent a large-scale generation of eddy currents in a structurally simple manner, which could lead to overheating and damage to the ladle. The length of the slots is preferably between 120% and 150% of the length of the magnetic coil, ie the slots protrude above and below the magnetic coil in the axial direction. The number of slots, which are preferably arranged equidistantly in the vessel jacket, is essentially determined by the casting vessel diameter. With the filling volumes specified above, there should be 4, 6, 8 or more slots in the metal jacket.

As is known in principle from the prior art, the magnetic coil is preferably surrounded by an iron core (yoke). According to a further embodiment of the invention, the position of the slots in the casting vessel jacket is approximately congruent in height with the position of the yokes.

The width of the slots is between 2 mm and 10 mm. Such a slot width on the one hand effectively prevents the formation of large eddy currents, on the other hand the slot width is so small that the stability of the casting vessel is not impaired.

The heating station has a magnetic coil, which preferably contains at least two windings and which is surrounded by an iron core (yokes). The multiple winding of the magnetic coil creates the advantage that the height of the heating stand can be minimized, e.g. to 150 to 300 mm, since the multilayer of the winding enables a correspondingly higher desired performance to be achieved. The magnetic coil and the yokes are preferably arranged in a frame, which then form the heating station.

According to a further embodiment of the invention, the heating position is adjustable in height, which has the advantage that the vessel placed and centered on existing supports or a frame is then coupled to the heating position by the heating position being raised around the lower area or before the further transport of the Vessel is lowered. For this purpose, the heating station preferably consists of an annular base in which the magnet coil is integrated. The vessel shows its lower area has an outer shape which is adapted to the inner jacket of the annular base, ie that when the vessel is placed or inserted, an air gap which is adapted to the dimensions remains between the magnet coil and the vessel jacket. If the frame with yokes and coil is to be placed around the lower area of the vessel by hydraulic lifting after positioning the inductive vessel, a frame is used as a support or supports are provided which have a support surface adapted to the vessel.

The transition region of the vessel from the lower part into the upper part with a larger cross section can, according to an alternative embodiment, be designed as a collar-shaped contact surface corresponding to the roof surface of the annular base. This type of training is designed for fixed, not height-adjustable heating stations.

According to a further embodiment of the invention, the vessel described above is used as a transport, holding, alloying, degassing and / or casting vessel for molten metals, in particular made of aluminum or aluminum alloys, preferably in such a way that the casting vessel is used on a rotary table system with several working positions or linear system for permanent mold casting is used.

Further refinements of the invention and advantages resulting therefrom are explained with reference to the exemplary embodiment shown in the drawing. Show it:

Fig. 1 shows a cross section through a casting vessel, which is coupled to a heating station and

2 shows a further partially sectioned view of the casting vessel according to FIG. 1.

The vessel 1 shown is placed on a heating stand 2. The vessel 1 has an upper region with a diameter Di of 1100 mm, an intermediate area rich, in which the diameter tapers and a lower area with a diameter D ₂ of 500 mm, which is adapted to the geometry of the ladle used. The dimensions result in a filling capacity of approx. 2 to (2000 kg) aluminum. The vessel 1 has an insulating refractory lining and an outer metal jacket. The metal jacket 4 in the lower area consists of a non-ferromagnetic material, for example VA steel. Around the lower, for example cylindrical outer jacket made of VA steel, a double-layer magnetic coil 5 is arranged at a distance from an air gap 6 and is enclosed by an iron core (yokes 7). The coil 5 and the yokes 7 are installed in a common frame 8 which can be raised and lowered, as is made visible by the double arrow 9. Existing lifting devices, not shown, preferably operate hydraulically. In the present case, three supports 10 serve as supports for the vessel 1, which support the vessel in the conical intermediate region.

If a heating and lowering heating device 2 is to be dispensed with, the collar-shaped area 11 can also serve as a support surface on a corresponding annular bearing surface of the heating station. An essential feature of the present invention, however, for both alternative embodiments, is that the vessel 1 is detachably connected to the heating station 2. If the vessel 1 is placed on or in the heating station 2 in the manner shown, a field is induced by means of the magnetic coil 5, which causes a bath movement in the melt and supplies heat to the melt. The heating station 2 can be arranged next to a casting carousel with a plurality of casting molds, so that the desired batch can be removed from the vessel 1 and poured from it by means of a ladle 12.

As can be seen from FIG. 2, the outer metal jacket of the casting vessel is slotted in the lower region, ie at the level of the magnet coil 5. The slots 13 run longitudinally axially and project above the magnetic coil or their longitudinal axial height at the top and bottom, the length of the slots being at least 1.2 times the longitudinal axial length of the magnetic coil. The magnetic coil is surrounded by yokes 7, which (in height) are approximately congruent with the slots 13. Preferably, and as shown in FIG. 2, the slots project above and below the yokes, respectively.

The vessel shown serves in the present case as a means of transport for the melt volume filled therein as well as an alloy, holding and degassing vessel. The liquid metal or metal alloy removed from a melting furnace remains in one and the same container during transport, any intermediate storage or an intermediate treatment, namely degassing until pouring, so that pouring into other vessels or furnaces is avoided. If the metal melt cannot be transferred directly from the melting furnace to the casting plant for procedural or operational reasons, a further heating station 2 can be installed stationary at an intermediate station, on which the vessel 1 is placed in the manner shown and kept at the desired temperature by appropriate inductive heating , Metallurgical treatments of the melt are possible at this intermediate station.

In a specific application, the alloy removed from the melting furnace is transferred to a pan, which is transported to an intermediate station with a heating station, where the pan is placed on existing supports and then the heating station is raised hydraulically until the lower area of the pan is surrounded by the magnetic coil is. The metal melt is degassed in this intermediate station, for example by injecting nitrogen or argon. Any temperature losses are compensated for by the heating energy introduced via the heating station. After sufficient degassing (or another desired metallurgical treatment), the molten metal is slagged off as required and the pan is transported to a casting plant, where it is centered in a corresponding manner as described above on an existing heating station and then coupled to it by lifting the heating station , The ladle can then be successively removed from the metal melt in batches for casting in molds, which are arranged, for example, on a casting carousel, using a ladle become. The lower tapering of the vessel to a diameter adapted to the ladle serves the purpose that the pan can be practically completely emptied.

Basically, the combination of the vessel and the heating stand according to the invention can be used for any metal or metal alloy melts, in particular if casting processes are to be avoided as far as possible.

Claims

claims

1. From a heatable, a fireproof lining and an outer metal jacket casting vessel (1) for metallic melting material, in particular for aluminum melts, and a heating station (2) with a magnetic coil (5) existing device in which the casting vessel (1) on the stationary heating station (2) is detachably mounted, characterized in that the metal jacket of the casting vessel (1) has a plurality of slot-shaped openings (13) in the lower region.

2. Device according to claim 1, characterized in that the outer metal jacket of the casting vessel (1) has a plurality of slots (13), preferably arranged axially axially, which are located at the level of the magnetic coil (5) when the casting vessel (1) is in place.

3. Device according to claim 2, characterized in that the length of the slots (13) is between 120% and 150% of the length of the magnet coil (5).

4. The device according to claim 2 or 3, characterized in that the slots (13) are arranged at an equidistant distance and / or that at least 4 slots are present.

5. Device according to one of claims 2 to 4, characterized in that the magnetic coil (5) is surrounded by an iron core (yokes) (7) and that the position of the slots (13) when the casting vessel (1) is in place approximately in height is congruent with the position of the yokes (7).

6. Device according to one of claims 2 to 5, characterized in that the width of the slots (13) is between 2 mm and 10 mm.

7. Device according to one of claims 2 to 6, characterized in that the heating stand (2) has a magnetic coil (5), which preferably contains at least two windings, and is surrounded by an iron core (7).

8. Device according to one of claims 2 to 7, characterized in that the heating position (2) is adjustable in height, preferably hydraulically adjustable in height.

9. Device according to one of claims 2 to 8, characterized in that the heating stand consists of an annular base in which the magnet coil (5) is integrated and that the vessel (1) has an outer shape in its lower region, which the Inner jacket of the annular base (8) is adapted.

10. The device according to one of claims 2 to 9, characterized in that the transition of the vessel from the lower region into the larger cross-sectional upper region of the vessel is designed as a collar-shaped support surface corresponding to the roof surface of the annular base (8).

11. Use of the vessel (1) according to one of claims 2 to 10 as a transport, holding, alloying, degassing and / or casting vessel for molten metals, in particular made of aluminum or aluminum alloys.

12. Use of the casting vessel according to claim 11, on a rotary table system with several working positions or on a linear line with metal removal, ladle removal and degassing position.