A general feeding method for sand castings, the "three rules", is routinely used in France. While two of the these three rules can in theory be transposed to precision casting in ceramic shells moulds, this is not true of the "feed distance" rule. This rule determines, for a casting or a part of a casting, the. number of identical optimized feeders and their respective distances. Schematically, this reflects the ability of a feeder to deliver molten metal at a given distance, in a given time. It is directly related to the thickness and shape of the castings, to the pouring temperature, and to the type of alloy, in particular its mode of solidification, which depends among other things on the moulding process. C.T.I.F and MICROSTEEL accordingly conducted a joint experimental study to determine numerical values of the feeding distances for two grades of steel and one superalloy cast in ceramic shell moulds. The results were analysed with reference to the quality levels of the ASTM E192 radiographic standards and enabled to establish feed distance curves for each of these three alloys. Nowadays, MICROSTEEL uses these values sytematically when designing the feeding of castings in these grades, used in aircraft, aerospace and military or surgical applications.
展开▼
