| 摘要 |
1,256,058. Casting processes. UNITED AIRCRAFT CORP. 9 March, 1970 [13 March, 1969], No. 11114/70. Heading B3F. [Also in Division B1] Apparatus for use in casting single crystal articles comprises a shell 12 having an open bottom, a chill plate 10, and a mould 14 within the shell and spaced from the chill plate, the mould 14 having an opening 17 in its bottom surface and a non-rectilinear tube 18 extending from said opening towards the chill plate. In use, the apparatus is placed in a vacuum chamber and heated to a temperature above the melting point of the alloy to be cast. The molten metal is then poured through the sprue 24 until the shell 12 and mould 14 are filled to the required level and solidification initiated by the chill plate 10. The tube 18 is of such a shape e.g. helical, that it allows only one of the directionally solidified grains to grow into the mould 14 and initiate solidification therein. The heating of the mould 14 and shell is gradually reduced from the bottom to the top to maintain a substantially horizontal solid-liquid interface during solidification. In an embodiment, a ring of insulating material (30) is located under and spaced from the mould and a ring of filler cement (34) located on the top surface of the mould. The mould 14 may be somewhat porous to allow the escape of air during the filling process. |
