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1. (WO1997018339) FILTRATION DEVICE FOR FILTERING MOLTEN METAL
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1. A filtration device for filtering molten metal comprising a body defining a cavity for receiving molten metal, an outlet for the molten metal from the body, and means for holding a filter between the cavity and outlet for concentrating inclusions in the metal in the cavity, characterised in that the body comprises refractory fibrous material.

2. A filtration device according to claim 1 wherein, the fibrous material comprises a ceramic such as alumino-silicate fibres.

3. A filtration device according to claim 1 or 2 wherein the body comprises a fluid impermeable Iayer such as a masked or coated region, adjacent the outlet

4 A filtration device according to claim 3 wherein the fluid impermeable Iayer is thick enough to prevent gas leakage therethrough.

5. A filtration device according to claim 3 or 4 wherein the fluid impermeable Iayer extends at least across the base of the device to form a complete fillet at the junction at the outlet between the filter and the base of the body

6. A filtration device according to claim 5 wherein the fluid impermeable Iayer extends some distance up the outside edges of the body.

7. A filtration device according to claim 6 wherein the device compnses a gasket on the outside of the body proximal the outlet, and the fluid impermeable Iayer extends some distance beyond the gasket up the outside edges of the body

8. A filtration device according to any of claims 3 to 7 wherein the fluid impermeable Iayer is in the order of or less than 1 mm thick.

9. A filtration device according to any of claims 3 to 8 wherein the fluid impermeable Iayer comprises diluted Fraxbond.

10. A filtration device according to any preceding claim wherein the filter holding means compnses a ledge in the body, which ledge is preferably annular and preferably substantially smooth.

11. A filtration device according to claim 10 wherein the filter is fixed to the holding means by a cement such as Fraxbond 715.

12. A filtration device according to any preceding claim wherein the filter has a first surface operably presented to the cavity, which surface is partially masked to provide an active filtration area in use.

13. A filtration device according to claim 12 wherein the mask comprises refractory material impermeable to molten metal.

14 A filtration device according to claim 13 wherein the film comprises flake or platelets and a refractory cement.

15. A filtration device according to any of claims 12 to 14 wherein the film comprises mica or kaolin.

16 A filtration device according to any of claims 13 to 15 wherein the mask extends beyond the filter onto the body surface adjacent thereto

17. A filter for inhibiting the flow of inclusions in molten metal, comprising sintered granules, such as alumina or zirconia.

18. A filter according to claim 17 compnsing a granule bonding agent such as silica, silica carbide or sintered metal.

19. A filter according to claim 17 or 18 compnsing a first surface which operably contacts the molten metal, the surface comprising an active region which operably allows flow of molten metal thorugh the filter and which region is unfinished.

20. A filter according to claim 19 wherein the active region is unground after sintering.

21. A filter according to claim 20 or 21 wherein the active region is defined by a film on the first surface, which film is impermeable to molten metal.

22. A filter according to claim 21 wherein the film comprises platelet mateπal such as mica or kaolin

23. A filter according to any of claims 17 to 22 comprising a second surface through which molten metal leaves the filter, the second surface compnsing a region which is unfinished and preferably unground.

24. A filter according to claim 23 wherein the active region of the second surface is defined by a film of platelet material such as mica or kaolin.

25. A filter according to any of claims 17 to 24 or independently thereof, wherein the average pore size is in the region of 50 to 200 (μm) and preferably about 90 (μm).

26. A method of making a filtration device for separating inclusions from molten metals, comprising the step of fabricating a body, defining a cavity for the molten metal, of refractory fibrous matenal.

27. A method according to claim 26 wherein the body is formed by bonding the fibrous material together using a binder which is fixed for example during firing.

28. A method according to claim 25 or 26 wherein the fibrous material is alumino silicate and the binder is an organic material.

29. A method according to claim 26, 27 or 28 further compnsing the step of rigidisiπg the body by impregnation of a ngidizer.

30. A method according to any of claims 26 to 29 comprising the step of forming means within the body for holding a filter.

31. A method according to the previous claim comprising the step of fixing a filter in the holding means using an adhesive.

32. A method according to any preceding claim comprising the step of sealing the body adjacent an outlet for the molten metal thereby to inhibit flow of fluids, such as air, through the body.

33 A method according to any of claims 26 to 32 comprising the step of temporaπly masking an active region of the filter while applying a film to the filter, thereby operably to allow molten metal to flow through the active area but not the film

34 A method according to the preceding claim compnsing the step of extending the film across the body adjacent to the filter

35 Use of a filtration device according to any of claims 1 to 16 to enable the rapid melting of a solid metal sample in the device to form a representative liquid metal sample which can then be filtered.

36 A filtration device for filtering molten metal comprising a body defining a cavity for receiving molten metal, an outlet from the body for the molten metal, and a filter positionable adjacent the outlet to concentrate inclusions in the molten metal above the filter which filter is in accordance with any of claims 17 to 25