| 摘要 |
PURPOSE:To simplify a stage for joining cores by calcining a separately molded shell core and the other core and fitting the shell core held at the calcination temp. and the other core cooled to an ordinary temp., then cooling the shell core. CONSTITUTION:The composite core 17 is constituted with the 2nd core 11 and the 3rd core 13 integrally to be joined to the 1st annular core 10 as the shell core so as to enclose the core 10. The core 10 provided with a projecting part 10a and the cores 11, 13 respectively provided with recesses 11a, 13a are separately formed and are calcined at the time of molding. The cores 11, 13 are then held at the calcination temp. and while the core 10 is kept cooled down to the ordinary temp., the recesses 11a, 13a of the cores 11, 13 are fitted into the projecting part 10a of the core 10. The cores 11, 13 are thereafter cooled to integrally join the cores 10, 11, 13. The stage for joining the cores is thereby simplified and the quick joining of the cores is executed.
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