| 摘要 |
When a body of startup material (70) has been interposed in the cavity (4) between the starter block (60) and a first cross-sectional plane (72) of the cavity transverse the axis (12) thereof, the starter block has commenced reciprocating along the axis, and the body of startup material has commenced reciprocating in tandem with it, through a series of second cross-sectional planes (74), layers (76) of molten metal are successively superimposed on the body of startup material adjacent the first cross- sectional plane of the cavity, and the layers promptly distend relatively periperally outwardly from the axis under the inherent splaying forces therein. The invention confines the relatively peripheral outward distention of layers with a casting surface (62) which is peripherally outwardly flared about the axis of the cavity, so that the thermal contraction forces arising in each layer can counterbalance the splaying forces.
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