Effects of Thermal and Pressure Factors on Surface Formation of Cast Alloys

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In response to the needs for castings of thinner section thickness, solidification behavior of molten metal in flowing fields was studied for promoting the basic understanding of the processes of cast surface formation.(1) Fluidity of aluminum alloys in thin sections : Fluidity of Al-Si-Cu alloy wa studied by means of the suction test method. Effects of section thickness, suction pressure, mold materials, surface treatment, pouring temperature and mold atmosphere were studied. Effects of surface tension were discussed.(2) Fluidity of cast iron : Effects of section thickness, pouring temperature, inoculation and suction pressure on the fluidity of cast iron were studied. By examining the solidification structure, non-uniformity due to flow was found.(3) Fluidity in Titanium castings : Effects of section thickness, pouring temperature and deoxidation were studied. An indirect indication was obtained on the possible effects of deoxidation on fluidity.(4) Computer simulation of solidification under forced fluid flow : Solidification of water under fluid flow was modeled in 2-dimensional section and compared with visualization experiments with a satisfactory agreement.(5) Deformation of unidirectionally solidified Pb-Sn alloy discs : Buckling deformation was measured on the bottom of unidirectionally solidified discs. Thermal stress in the already solidified layer was found to be the major cause of the deformation.(6) Deformation study of initial solidification layer by means of drop method : Various pure metals and binary alloys were studied. Deformation of pure metals was found to depend only on thermal stress in the solidified layer. Abnormally large positive or negative deformation was found with alloys near eutectic compositions. The cause was either thermal shrinkage or expansion due to precipitation in solid solution.