| 摘要 |
<p>A chilled mould is coated prior to the centrifugal casting of copper or its alloys, using a suspension of powders to form a thin layer. The novelty is that to form a thermally-conducting layer which is permeable to gas, the suspension contains ZrO2 and an inorganic binder. Inorganic binder is pref. unsintered alumina, the pref. suspension consisting of water contg. fine-grained ZrO2, and the finest Al2O3 slurry, forming a layer on the internal wall of the mould with a uniform thickness of 0.1-0.3 mm. During coating with the suspension, the mould is pref. rotated at a slower speed than that used during centrifugal casting, and the mould is pref. preheated to 150 degrees C, before using the suspension. Amt. of gas inclusions on the outside surface of the casting is reduced, and the amt. of oxide and unsoundness in the bore of the casting is also reduced. Lower casting temps. can be employed so casting times are less and mould life is increased. Improvement in casting quality means that only a small amt. of the casting must be removed by machining.</p> |
