| 摘要 |
A sand mixture for producing casting mouldings, mould masks and core moulds for metal castings consists of quartz sand (2', 2"), iron oxide (1', 1") and synthetic resin binder (3). It should be prepared without special expenditure and be of such a nature that the cracking, based on the so-called cristobalite discontinuity of the quartz sand and causing casting faults, in the casting moulds, mould masks and core moulds is reliably avoided. For this reason, the iron oxide (1', 1") is added in a fine granular form with porous grain structure and in quantities of more than 8 to 40% by weight to the quartz sand (2', 2"), the iron oxide (1', 1") being provided by the hot enveloping method with the synthetic resin binder (3) exclusively on its surface. <IMAGE>
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