A control pin for controlling the flow of liquid metal in a casting process includes an elongate body member, the body member being made at least partially of a composite ceramic material that includes a fibrous reinforcing material embedded within a ceramic matrix, and a failsafe element embedded within the composite ceramic material.
1. A control pin that controls the flow of liquid metal in a casting process, the control pin comprising an elongate body member and a wear-resistant tip at one end of the elongate body member, the body member being made at least partially of a laminated composite ceramic material that includes multiple layers of a reinforcing fabric embedded within a cast ceramic matrix, and a failsafe element embedded within the composite ceramic material.
2. A control pin according to claim 1 , wherein the failsafe element extends along substantially the whole length of the elongate body member.
3. A control pin according to claim 1 , wherein the failsafe element is made of a material that is resistant to high temperatures.
4. A control pin according to claim 1 , wherein the failsafe element is made of a material that is resistant to oxidation.
5. A control pin according to claim 1 , wherein the failsafe element is made of a metallic material.
6. A control pin according to claim 1 , wherein the failsafe element comprises a metallic wire.
7. A control pin according to claim 1 , wherein the failsafe element comprises a helical element.
8. A control pin according to claim 1 , wherein the failsafe element comprises a mesh.
9. A control pin according to claim 1 , wherein the failsafe element is embedded between layers of the reinforcing fabric.
10. A control pin according to claim 1 , wherein the reinforcing fabric comprises a woven reinforcing fabric.
11. A control pin according to claim 1 , wherein the reinforcing fabric is made of glass.
12. A control pin according to claim 1 , wherein the matrix material is selected from the group consisting of fused silica, alumina, mullite, silicon carbide, silicon nitride, silicon aluminium oxy-nitride, zircon, magnesia, zirconia, graphite, calcium silicate, boron nitride, aluminium nitride, titanium diboride, and mixtures thereof.
13. A control pin according to claim 1 , wherein the matrix material is calcium based.
14. A control pin according to claim 1 , wherein the matrix material comprises calcium silicate and silica.
15. A control pin according to claim 1 , wherein the matrix material comprises Wollastonite and colloidal silica.
16. A control pin according to claim 1 , wherein the control pin comprises a non-stick surface coating.
17. A control pin according to claim 16 , wherein the coating comprises boron nitride.
18. A control pin according to claim 1 , wherein the elongate body member is substantially cylindrical.
19. A control pin according to claim 1 , wherein the elongate body member is at least partially hollow.
20. A control pin according to claim 19 , wherein the elongate body member comprises a circumferential wall having a wall thickness from 1-10 mm.
21. A control pin according to claim 1 , wherein the wear-resistant tip is inserted at least partially into one end of the elongate body member.
22. A control pin according to claim 1 , wherein the wear-resistant tip is made of a ceramic material.
23. A control pin according to claim 22 , wherein the wear-resistant tip is made of a material selected from the group consisting of fused silica, alumina, mullite, silicon carbide, silicon nitride, silicon aluminium oxy-nitride, zircon, magnesia, zirconia, graphite, calcium silicate, boron nitride, aluminium titanate, aluminium nitride and titanium diboride.
24. A control pin according to claim 1 , wherein the wear-resistant tip is made of a material having a density in the range 1800-3000 kg/m 3 .
25. A control pin according to claim 1 , wherein the wear-resistant tip is made of a material having a density in the range 1900-2500 kg/m 3 .
26. A control pin according to claim 1 , wherein the control pin has a length in the range 200-1000 mm.
27. A control pin according to claim 1 , wherein the control pin has a diameter in the range 20-75 mm.