鋳塊のひけ欠陥に及ぼす結晶組織形態の影響

概要

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A number of shrinkage predictions in castings have been proposed. In many cases, it has been assumed that the critical values of the parameters for shrinkage are independent of cast structures. In this paper, two-dimentional temperature measurements in aluminum alloy castings were carried out to clarify the effect of cast structures on shrinkage predictions. Temperature gradient (G) distribution and temperature gradient divided by the square root of the cooling rate (G√V) distribution proposed previously applied to these castings at several fraction solid (fS). The area of shrinkage porosities correspond to G = 1.0°C/cm and G/√V = 3.0°C1/2 sec1/2/cm for Al-Cu and Al-Si alloy castings. The shrinkage defect could be estimated from the G/√V in the range of about 0.56 to 0.80 fS. Fraction solid fS depended on the averaged grain size of castings, that is, fS decreased with an increasing the grain size. It is considered that fine crystals may be moved with molten metals by fluid flow during solidification. For a more exact prediction of shrinkage, it may be necessary to take account of the cast structures.
Japan Foundry Engineering Societyの論文