The effects of additional elements Mg, Fe and Cu and heat treatment on the mechanical properties and microstructures of pressure die-cast and high-pressure cast Al-Si alloys were examined and compared to those of gravity-die casting.
  (1) All Al-10%Si and Al-5.5%Si alloys, cast in the above mention three ways and T5 treated, showed increase in tensile strength with addition of Mg. But with combined addition of Mg and Cu, very little improvement of tensile strength was seen.
  (2) The elongation of high-pressure castings was about two times longer than that of gravity die-castings.
  (3) In high-pressure castings the elongation remarkably decreased with the addition of Fe and Cu.
  (4) In T6 treated high-pressure casting the tensile strength of Mg containing Al-Si alloys improved remarkably. Its elongation was the same as in gravity castings.

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  This paper is one of the serial investigations on the structure of white cast iron. The specimen, solidified unidirectionally, was prepared by the same method as in the preceding paper.
  In this paper the focus is on the relationship between the primary austenite dendrite and the ledeburite eutectic structure in white cast iron. The influences of the solidification velocity and the chemical composition were also investigated.
  The results obtained were as follows:
  1) The secondary arm spacing of primary austenite dendrite decreased with the Cr content, and increased with the C content.
  2) The thickness of ledeburite eutectic cell increased with the Cr content, and decreased with the C content.
  3) The secondary arm spacing of primary austenite dendrite and the thickness of ledeburite eutectic cell decreased together by addition of 0.2%Ti.
  4) Hyper-eutectic type ledeburite eutectic cell was sometimes observed in hypo-eutectic Fe-C-Cr alloy.
  5) The growth direction of proeutectoid cementite precipitated in primary austenite dendrite was, in many cases, parallel with that of the ledeburite eutectic cell.
  6) The shape and position of the proeutectoid cementite may be influenced by the solidification velocity.

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  In the dry-sliding wear of continuous cast iron, we have already reported in our latest report that the addition of Sn is effective for improving its wear characteristics. The present study, following our latest attempts to compare the wear characteristics and wear tendencies of continuous cast iron without any additive and with addition of Sn, in their lubricated sliding wear, and also to scrutinize the influence of Sn on the wear resistance.
  It has been found that the stable wear limit, obtained through wear characteristic curves within the area of normal wear, of cast iron with Sn addition more precipitation of pearlite, is greater in its pressure and velocity and has less wear rate than cast iron without any additive element. Experiments were conducted to obtain wear tendency curves with wear conditions which under adhesive wear. The result clarified that cast iron with Sn had small rate of wear increase at normal wear stage and excellent wear resistivities. It has been found also that under such conditions in which oxidation constitutes a main factor of wear mechanisms, the influence of existence of ferrite on wear loss is extremely small.

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  It is very important to know the types of eutectic solidification in order to clarify the properties of spheroidal graphite cast iron. Some examples are shrinkage cavity formation and expansion or shrinkage at solidification. In this paper, the type of eutectic solidification of the spheroidal graphite cast iron treated with Ca or Mg spheroidizer and flake graphite cast iron was studied through CRF value t₂/t₁; t₁ is difference of starting time of eutectic solidification between surface and center part in the casting sample and t₂ is time of eutectic solidification for center part of same sample.
  Many researchers have studied the eutectic solidification of cast iron qualitatively and have found that the solidification type of this alloy is mushy. However, quantitative studies had not been done.
  The authors have quantitatively measured the mushiness of this alloy and following results were obtained.
  (1) Eutectic solidification type of spheroidal graphite cast iron and flake graphite cast iron are very different, especially in hyper-eutectic composition alloy, the former is the severe mushy type but the latter is not so. CRF value of spheroidal graphite cast iron is 20∼30, but it is only about 5∼6 in flake graphite cast iron; the former being 5∼6 times larger than the latter. CRF expresses the degree of mushiness and skin type.
  (2) We consider that both solidification types in hypo-eutectic composition alloys are almost identical because the CRF value, eutectic solidification time and expansion mode at solidification of both alloys are nearly the same.
  (3) The eutectic solidification time of hyper-eutectic composition spheroidal graphite cast iron is longer than the flake graphite cast iron of the same composition. The expansion at solidification of spheroidal graphite cast iron is great because of this longer eutectic solidification time and thus affects the mold strength, and graphitization.

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  The effect of feldspar on the interfacial reaction between mold and liquid iron was studied by varying the content of feldspar in silica sand, bonded with sodium silicate, bentonite or fireclay. The products of the interfacial reaction were examined by a polarizing microscope and metallographic microscope.
  The rssults obtained were;
  (1) The thickness of the skin on cast iron was between 0.3∼0.4mm, and the micro-Vickers hardness of the pearlitic skin ranged from 280∼340. This was harder than that of the pearlitic matrix of parent metal which ranged from 250∼280.
  (2) The bond between iron and intermediate layer was composed of fayalite-cristobalite mixtures, and these mixtures were not affected by the content of feldspar in molding sands. In steel castings, however, the bond was composed of wüstite-fayalite mixture, and the addition of feldspar to silica sands promoted the formation of fayalite-cristobalite mixtures.
  (3) Intermediate layer thickness of iron castings was so thin that the retardation of reaction by adding feldspar was not observed. The reaction products in intermediate layer consisted of fayalite and cristobalite, and the addition of feldspar promoted the formation of eutectic of fine structure. The same tendency was observed in steel castings.
  (4) The residual strength of sintered zone was not affected by adding feldspar in iron castings.
  (5) Where easily removed burn-on formed, the bond between iron and intermediate layer was enriched with wüstite. The mechanism of easily burn-on was confirmed by the change in linear dimmensions of reaction products during cooling of castings, and the strength of bonds.
  (6) It is expected that natural silica sands which contain about 30% alkali feldspar, about 87%SiO₂, can be tolerated in iron foundry sands of small castings or thin wall castings.

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