| 摘要 |
1327992 Casting and foundry moulding processes UNITED AIRCRAFT CORP 5 May 1971 [1 June 1970] 13145/71 Heading B3F A mould for producing directionally solidified cast articles includes a first mould portion 4 having an article (turbine blade) forming cavity 5, 8, 10, 12 and beneath this cavity a columnar crystal growth starting cavity 14 having an open bottom. A second mould portion 2 (see Fig. 10) surrounds the first poition 4 to define a pair of cavities 18 (see Fig. 7) at opposed sides of the article-forming cavity 5. The cavities 18 are connected towards the base of the mould where they surround and may open into the open bottom of the crystal growth starting cavity 14. A chill plate 3 closes the base of the cavity formed by the second mould portion 2 about the article and crystal growth starting cavities. In operation, the mould is preheated and molten alloy poured in a vacuum through a sprue 47 into the cavities 18. The molten alloy enters the article-forming cavity 5 through the columnar crystal growth starting cavity 14. Alternatively, the alloy can be poured into article-forming cavity 5 and from there enter cavities 18. Upward solidification is induced from the chill plate, the helical part of the crystal growth starting cavity 14 selecting a single crystal to grow into the article-forming cavity 5. In an alternative embodiment, the article-forming cavity is not interconnected with outer cavities 18, and consequently the crystal growth starting portion (42) is extended downwardly so that its open bottom is closed by a chill plate (36). In this embodiment a cheaper alloy may be poured into the cavities 18 and may be used to surround the article formed. To separate the cast article from the sheath cast about it in cavities 18 and the crystal growth casting portions, a single saw cut is made across the base of the article just below a line 13. Moulding processes.-To form the mould a wax pattern of the article, crystal growth cavity and sprue is first invested to form a first shell mould portion 4. A wax overlay is then provided on the first portion 4 to form the cavities 18 and their extension (19) that surrounds the crystal growth cavity. The assembly of patterns and first portion 4 is once again iuvested to form a second shell portion 2 and the wax patterns melted out. |
