GB2241454A

GB2241454A - Method and apparatus for producing a metal matrix composite

Info

Publication number: GB2241454A
Application number: GB9104134A
Authority: GB
Inventors: Lenni Leander Laakso
Original assignee: Outokumpu Oyj
Current assignee: Outokumpu Oyj
Priority date: 1990-02-28
Filing date: 1991-02-27
Publication date: 1991-09-04
Also published as: ITMI910465A0; GB9104134D0; ITMI910465A1; IT1249646B; FI901001A0; FI901001A

Abstract

Filaments (5) to be incorporated in the continuously cast composite are fed separately and in the casting direction into the casting space through a perforated guide member (3) provided with apertures (4), the number of which corresponds to the number of filaments. Molten metal (1) enters the interior of a member (6) through which the filaments pass from the guide member (3) so as to form a casting (9) extracted vertically upwards. A slightly different arrangement is provided for horizontal casting (Fig. 2, not shown). <IMAGE>

Description

METHOD AND APPARATUS FOR PRODUCING A METAL MATRIX COMPOSITE The present invention relates to a method and apparatus for producing a metal matrix composite by continuous casting.

From the DE application 2,236,640 there is known a method and apparatus for producing a fibre-reinforced continuous casting. According to the said application, a copper or aluminium based matrix is provided with a tungsten or carbon fibre reinforcement structure, which is positioned lengthwise inside the continuous casting. Prior to casting, the fibres have been twisted into a round, netlike structure, which is conveyed, by means of control members, to the continuous casting machine, parallel to the casting, so that the fibre structure forms a reinforcement which is positioned lengthwise and concentrically in the casting. Thus all of the elements in the reinforcing structure of the continuous casting produced according to the DE publication 2,236,640 are throughout the length of the casting essentially at the same distance from the outer surface of the casting.Consequently the reinforcing effect created by the reinforcing structure is directed towards a small area on the transverse surface of the casting only, and never very near to for instance the outer surface thereof.

The object of the present invention is to eliminate some of the drawbacks of the prior art and to realize a metal matrix composite production method, where the composite structure of a continuous casting can be essentially extended throughout the whole transverse surface of the casting. The invention also provides apparatus for use in the method.

The method of the present invention for producing a metal matrix composite by continuous casting comprises feeding filaments to be incorporated in a metal matrix separately and essentially in the casting direction through a perforated guide member into a casting space containing the continuously cast metal of the metal matrix. The apparatus of the invention for use in the new method comprises a die defining a casting space provided with a guide member having apertures the number of which corresponds to the number of filaments to be incorporated in the composite.

According to the present invention, into the molten metal serving as the metal matrix, for instance copper or copper-based metal alloy, there is partly immersed a die, which at the same time serves as the casting space of the continuous casting process. That end of the die which is immersed in the melt is provided with a perforated guide member. In the said perforated guide member there are advantageously arranged apertures for each filament, essentially in the casting direction. The diameter and number of the filaments can vary according to the use of the composite. However, advantageously the number of filaments is larger than one.The apertures provided for the filaments in the guide member are distributed at essentially even intervals throughout the transversal surface of the guide member, and through these apertures the filaments are conducted in an essentially continuous fashion to inside the die. Depending on the employed casting direction, the filaments must be fed through the molten metal, too. In that case the filaments can be conveyed onto the guide member through the melt either as such or in a separate pipe, which if necessary can be connected to the die, and in which pipe a protecting gas also can be used. The molten metal is conducted to inside the die through at least one inlet which is provided in the wall of the die, essentially near to the guide member.

The filaments used in the method of the invention are fibre material with a high melting temperature, for instance metal such as tungsten, or some ceramic fibre.

High melting temperature here means such temperatures that are essentially higher than the melting temperature of the metal or metal alloy used as the metal matrix.

Accordingly, when the filament of the invention gets into contact with the molten metal, the filament essentially maintains its direction and shape. Now the molten metal flows to around the filaments positioned essentially in the casting direction, thus filling the die. In order to realize the continuous casting process in an advantageous fashion, around the end of the die that is located outside the melt, there is arranged a cooling member, so that the casting ejected from the die is solidified at least on its outer surface. This casting also contains the filaments fed in through the guide member provided in the die, which filaments, positioned in the casting direction, for example provide a lengthwise reinforcement for the casting.

The die used in the apparatus of the invention and the guide member arranged in that end which is immersed into the melt are advantageously made of the same material, for instance graphite. Other suitable materials can also be used, and the die and the guide member do not necessarily have to be of the same material. The inlet for molten metal, one at least, provided in the die is advantageously designed so that the melt flows into the die in essentially perpendicular direction with respect to the filaments positioned in the melt.

The method and apparatus of the present invention for producing metal matrix composite can advantageously be applied for example to vertical and horizontal continuous casting. In vertical continuous casting, it is possible to apply, according to the invention, continuous casting which proceeds either from top to bottom or from bottom to top.

The invention is described in more detail below with reference to the accompanying drawing, where Figure 1 illustrates a preferred embodiment of the invention in vertical continuous casting from bottom to top, seen in partial side-view cross-sectiont and Figure 2 illustrates another preferred embodiment of the invention in horizontal continuous casting, seen in partial side-view cross-section.

According to Figure 1, in the molten metal 1 there is partly immersed the die 2, at the bottom end whereof there is arranged the guide member 3. Through the apertures 4 provided in the guide member 3, the filaments 5 are conducted into the die 2. The filaments 5 are conveyed as separate to the guide member 3, through the molten bath in the pipe 6, so that the filaments 5 do not get into contact with the molten metal before the die. The guide member 3 is tightly set in the die 2, so that the guide member 3 prevents any possible flowing of the melt into the pipe 6. If necessary, some protective gas, such as argon, can be conducted to the pipe 6. The molten metal flows into the die 2 through the opening 7. Around the top part of the die 2 there is arranged the cooling member 8, by means of which the casting 9, cast vertically from bottom to top, and ejected from the die 2, is solidified in the shape determined by the die 2, for instance as wire, bar, or any other metal profile required in each case.

In Figure 2, in the molten metal 11 there is positioned the die 12 for horizontal casting, and the end of the said die that is immersed in the melt is provided with a perforated guide member 13 in order to convey the filaments 14 to inside the die 12 in the casting direction.

Prior to the guide member 13 and the apertures arranged therein, the filaments 14 are conveyed as separate through the molten metal 11 as such, by adjusting the tightness of the filaments by means of roller members 15 to be suitable for the speed of continuous casting. Through the opening 16 provided in the die 12, the molten metal flows to inside the die 12. Around the end of the die 12 that is located outside the molten metal 11, there is arranged a cooling member 17, which causes the casting 18 to be shaped in the form defined by the die 12. Thus the casting 18 contains the lengthwise positioned filaments 14.

In the cases of Figures 1 and 2, the filaments are fed in through the molten metal. It is, however, clear that while employing for instance vertical continuous casting from top to bottom, the filaments can also be fed into the casting space so that it is not necessary to feed the filaments through the molten metal, but the filaments are conducted directly to the casting space through the guide member.

Claims

1. A method for producing a metal matrix composite by continuous casting, which comprises feeding filaments to be incorporated in a metal matrix separately and essentially in the casting direction through a perforated guide member into a casting space containing the continuously cast metal of the metal matrix.

2. The method of claim 1, in which the casting direction is horizontal.

3. The method of claim 1, in which the casting direction is vertical.

4. The method of claim 3, in which the casting direction is from bottom to top.

5. The method of claim 3, in which the casting direction is from top to bottom.

6. The method of any one of the preceding claims to 1 to 5, in which the metal employed as the matrix is copper or a copper-based metal alloy.

7. The method of any one of the preceding claims 1 to 6, in which the filaments are made of metal.

8. The method of claim 7 in which the filaments are made of tungsten.

9. A continuous casting apparatus for realizing the method of claim 1, comprising a die defining a casting space provided with a guide member having apertures the number of which corresponds to the number of filaments to be incorporated in the composite.

10. The apparatus of claim 9, in which the apertures provided in the guide member for the filaments are essentially positioned in the casting direction.

11. The apparatus of claim 9 or 10, in which the apertures provided in the guide member are located in an essentially even distribution throughout the transverse surface of the guide member.

12. The apparatus of claims 9, 10 or 11 in which the guide member and the die defining the casting space are made of the same material.

13. The apparatus of claim 9 substantially as hereinbefore described with reference to Figure 1 or Figure 2.