Gravity die casting plant for metal-foam mouldings

Abstract

Claims

2. Gravity die casting plant (1) for metal-foam mouldings according to claim 1, wherein the gate box (7) comprises a plurality of gate regions (8, 9, 10).

3. Gravity die casting plant (1) for metal-foam mouldings according to claim 1, wherein the metering and mixing device (11, 12, 13) for metering and mixing the foam-generating medium with the melt is arranged in each of a plurality of gate regions (8, 9, 10) of the gate box (7).

4. Gravity die casting plant (1) for metal-foam mouldings according to claim 3, wherein each of a plurality of dies (2, 3, 4) is arranged so as to be connectable to a gate region (8, 9, 10).

5. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein at least one gate region (8, 9, 10) is arranged so as to be connectable to each die (2, 3, 4).

6. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein each die (2, 3, 4) has a different geometry.

7. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein the gate regions (8, 9, 10) in the gate box (7) are arranged so as to be spatially separated from one another.

8. Gravity die casting plant (1) for metal-foam mouldings according to claim 4, wherein the dies (2, 3, 4) and/or the gate box (7) are/is designed with a heating and/or cooling system.

9. Method for the production of metal-foam mouldings in a gravity die casting plant according to claim 1, comprising the steps of: feed of the melt in the reservoir (16), build-up of pressure in the gravity die casting plant (1), the melt being pressed from the reservoir into the gate box (7) and into the die (2, 3, 4), introduction of gas into the melt, discharge of pressure from the gravity die casting plant (1), and adherence to a holding time for cooling the die (2, 3, 4), wherein the gas is introduced by means of an impeller agitator (11, 12, 13) in the die (2, 3, 4) filled with melt, and in that, during the casting operation, at least the method parameters comprising the density of the metal foam and the temperature in the gate box (7), in the gate region (8, 9, 10) and in the die (2, 3, 4) can be set and controlled independently of one another in each gate box (7), in each die (2, 3, 4) and in each gate region (8, 9, 10).

Description

[0001] This patent application claims the benefit of priority from European Application No. 05 022 025.0 filed Oct. 10, 2005.

BACKGROUND OF THE INVENTION

[0002] The invention relates to a gravity die casting plant for metal-foam mouldings, comprising at least one die, one reservoir for the metal melt and at least one metering and mixing device for metering and mixing the foam-generating medium with the melt.

[0003] In motor vehicle construction, in order to save weight, increasing use is made of castings and mouldings which are produced in part from metal foam. The foam-generating medium used is a gas, for example air or inert gas, or a medium generating gas at the casting temperature. By means of an impeller, as it is known, the gas or the gas-generating medium is supplied to the melt in a gate box and is distributed uniformly into the melt.

[0004] EP 1259344 B1 discloses a generic device for the production of metal-foam mouldings. A mould for the metal-foam mouldings has a widening inlet port which remains submerged in the melt during filling with the metal foam. An impeller agitator is arranged below the inlet port in the melt. A gas supply is provided in the axis of rotation of the impeller agitator or directly adjacently to the agitator. The intensity of intermixing and the foam content of the metal melt can be set.

[0005] Proceeding from this prior art, the object of the invention is to specify a gravity die casting plant for metal-foam mouldings, in which the method parameters can be set as flexibly as possible.

SUMMARY OF THE INVENTION

[0006] The object is achieved by means of a gravity die casting plant for metal-foam mouldings, comprising at least one die, one reservoir for the metal melt and at least one metering and mixing device for metering and mixing the foam-generating medium with the melt, at least one gate box being arranged between the die and the reservoir, and the metering and mixing device being arranged in the gate box.

[0007] It is advantageous that a plurality of metal-foam mouldings having different properties can be produced simultaneously in each casting cycle. This is achieved in that the gate box has a plurality of gate regions. This is also achieved in that a metering and mixing device for metering and mixing the foam-generating medium with the melt is arranged in each gate region.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] An exemplary embodiment of the invention is described with reference to the figures in which:

[0009] FIG. 1 shows a perspective view of a gravity die casting plant according to the invention, and

[0010] FIG. 2 shows a section through the gravity die casting plant of FIG. 1.

DETAILED DESCRIPTION

[0011] FIGS. 1 and 2 illustrate diagrammatically a gravity die casting plant 1 for the production of metal-foam mouldings, with three dies 2, 3, 4 next to one another. FIG. 1 shows a perspective illustration and FIG. 2 a longitudinal section through the casting plant of FIG. 1. The dies 2, 3, 4 are constructed in each case from two die halves 2a, 2b, 3a, 3b, 4a, 4b. The dies 2, 3, 4 are installed between two insulating walls 5, 6. Heating or coolant lines may be installed in the insulating walls 5, 6. What is achieved thereby is that the dies 2, 3, 4 can be cooled or heated in a controlled way before and/or after the casting operation. What is achieved thereby is that the structure of the metal-foam moulding can be influenced by adherence to a temperature/time program. If the lines to each die 2, 3, 4 are activated separately, three mouldings with different structures and/or qualities can be produced in one casting operation. One moulding with three or more different regions may also be produced, however, if one large die is installed between the insulating walls 5, 6, instead of three smaller dies.

[0012] A gate box 7 can be seen below the dies 2, 3, 4. The gate box 7 has three gate regions 8, 9, 10 arranged next to one another. Each die 2, 3, 4 is thus assigned a gate region 8, 9, 10. If a large die is used, a larger metal-foam body with three differently formed regions can be produced in one casting operation.

[0013] Three impeller agitators 11, 12, 13 are illustrated in FIG. 1 perpendicularly to the plane of FIG. 2 and more clearly. The impeller agitators 11, 12, 13 are in each case assigned to a gate region 8, 9, 10. The metal melt is agitated and gassed by means of the impeller agitator 11, 12, 13. For the formation of foam, a gaseous or foam-forming medium, for example air or inert gas, is supplied to the melt in the die through ports in the impeller agitator 11, 12, 13. The impeller agitator 11, 12, 13 consists of a hollow rotatable shaft which projects into the respective gate region 8, 9, 10 from the side into the metal melt and which drives at the shaft end a vane wheel or an impeller having gas outlet ports. By means of the impeller agitator 11, 12, 13, in each gate region 8, 9, 10, air or inert gas or another foam-generating medium is supplied or metered in a defined quantity ratio to the melt and mixed with the metal melt. By the impeller agitator 11, 12, 13 being arranged directly below the die 2, 3, 4, the formation of foam takes place in the die 2, 3, 4 already filled with melt. As a result of the excess pressure which is generated by the impeller by means of the gas supply, part of the melt is driven out of the die 2, 3, 4 back into the gate box 7.

[0014] Foam formation and the stabilization of the foam can be improved if the melt has added to it solid particles which have a beneficial influence on the surface tension at the interface between the gas and the metal melt. Instead of the impeller agitator 11, 12, 13, another suitable metering and mixing device may also be installed. It is also conceivable that a plurality of gate regions 8, 9, 10 are operated by means of one impeller agitator 11, 12, 13, so that two cast mouldings having the same properties can be produced simultaneously.

[0015] The gate box 7 has on the underside a connection 14 for a riser pipe 15 or another line for connecting the metal melt to a reservoir 16. In the already known rising low-pressure casting method, as it is referred to, the riser pipe 15 is immersed in the reservoir 16, and the reservoir 16 is closed off and acted upon by pressure, for example by inert gas. Owing to the pressure on the melt surface in the reservoir 16, the metal melt rises into the riser pipe 15 and into the gate box 7. It is also conceivable to fill via a plurality of riser pipes 15 a plurality of gate boxes 7 which could then, in turn, fill one or more dies 2, 3, 4. The metal melt may be a light-metal melt, for example an aluminium or magnesium melt. The gravity die casting plant 1 may, however, also be designed for other metals. The solid particles which may be added for foam formation are administered in the reservoir 16 or in the melting furnace for the melt.

[0016] By means of the gravity die casting plant 1 described here, the method parameters for each gate region 8, 9, 10 and for each die 2, 3, 4 can be set separately. The chemical parameters of the melt can be varied by additions in the gate box 7. The temperature of the melt or of the metal foam can be varied by the preheating or precooling of the die 2, 3, 4 or by additional heating which may be installed in each gate region 8, 9, 10 of the gate box 7. By the action of pressure upon the reservoir 16, the casting speed can be set. Foam formation and foam consistency can be set by means of the gas quantity and the impeller speed. A separate temperature/time curve can be achieved for each die 2, 3, 4 by means of a control of the holding times.

[0017] Metal-foam bodies with different geometries can be produced simultaneously or, if one large die is connected to a plurality of gate regions 8, 9, 10, a larger metal-foam body with differently foamed regions can be produced. Larger castings may also be produced, which are foamed in some regions, but in other regions are not foamed, that is to say are filled completely.