The effects of padding and chilling, the typical measures of promoting directional solidification, on sound zones of ceramic shell mold castings were investigated. Sound zone distances in tapered ceramic shell mold castings of SCS13 were found to be predictable from the following equations using two parameters ; casting modulus (V/S, mm) and taper angle (θ, degree).
  a (edge effect, mm)=7.38×(V/S)×(0.51×θ^0.51+1) and
  b (riser effect, mm)=5.50×(V/S)×(0.19×θ^1.36+1),
where pouring temperature and riser modulus ratio were fixed at 1,600°C and 1.4, respectively. Reviewing the published data with tapered sand mold castings, it was found that edge effect distances were determined from the same two parameters. As for chilling, effects of finning, local air-blowing and SiC local staccoing were compared with each other. These chilling techniques exhibited little effects of practical significance on promoting edge effects. But when they were applied to promote riser effects, a marked effect was observed only with SiC local staccoing technique, which was concluded to be the simplest and most effective method.

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  In metallic mold casting, temperature variation during melt flow greatly affects the soundness of castings. This paper presents a numerical technique for estimating the melt temperature, which takes into consideration the convection in the melt, conduction in the mold, solidification and remelting. This technique was applied to the heat transfer analysis of the flow of molten Al-11.5wt% Si alloy in a metallic mold runner with an inner diameter of 15mm and with mold coating of 200μm in thickness. The measured melt temperatures agreed well with the calculated ones derived by using melt velocity measured by an electromagnetic flow meter and the heat transfer coefficient between the melt and the mold wall of 0.03cal/cm²·s·deg. The analysis with a constant mold wall temperature resulted in 20 to 100% error. The proposed technique based on the direct finite difference method, which can use triangular elements, may be applied to metallic and sand mold castings with complicated shapes, if the melt velocity is known.

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  Nucleation and growth during solidification of the primary austenite were investigated, paying attention to the degree of undercooling for nucleation, the degree of nucleation and the growth morphology of austenite. The experiment was conducted on hypo-eutectic iron of Fe-C system inoculated with ferro-silicon or calcium-silicide and held at the molten state. Inoculation effect and fading phenomenon were observed in the nucleation of graphite eutectic with Fe-Si or Ca-Si addition, in agreement with the previous studies. Nucleation of primary austenite is promoted by adding Ca-Si, but is hindered by adding Fe-Si. Inoculation effect on the solidification of primary austenite differs from that on the graphite eutectic.

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  The effect of ferritizing heat treatment on the embrittlement associated with dynamic strain aging or fine carbide precipitation was studied in the tensile testing temperature range from room temperature to 500°C to investigate the mechanism of 400°C embrittlement. A relationship among the amount and size of fine carbide precipitates, frequency of serrations and tendency to embrittlement at 400°C was observed. The precipitation of fine carbides by the dynamic strain aging and dependence of strain rate on the ductile minimum temperature suggested that the precipitation of the fine carbides is one of the important metallurgical factors causing the 400°C embrittlement by intergranular fracture in the ferritic spheroidal graphite cast iron.

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  Two problems associated with the molding processes in foundry shops aroused our interrest. The one was the alleviation of pollution and the improvement of the disagreeable working environment due to noise, dust and hot air occurring in the molding shops. The other was the reclamation of the used sand. In order to solve these problems by using water-soluble mold, an exothermic self-hardening and water-soluble alumina sand mold was examined. The mold was produced by adding sodium aluminate solution and aluminum powder as binder. This study was carried out to establish a reclamation process of the mold materials.
  1) Mold sand hardened by the exothermic reaction as well as those heated up to 1,100°C could be cleaned out to a suitable state for reuse by a few minutes of scrabbing in water.
  2) Sodium aluminate as binder could be reclaimed by electrodialyzing the washing water after separating aluminum hydrate colloid as a reaction product by thickening and filtering.
  3) The reclaimed mold sand and binder showed no harmful influence for reuse.
  4) From these results, a system to recycle the water-soluble mold materials was conceived.

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  Castings with as-cast high dimensional accuracy and superior surface quality can be produced by precision casting. There are two methods of precision casting ; one is the investment casting method using lost pattern, e. g. lost wax process, and the other is the ceramic mold casting method, e. g. Shaw process or C. M. process. Our laboratory has been engaged in research to produce products with high added value and complicated shapes. We have especially concentrated on developing the yet unexploited field of large size precision casting and in 1963 we finally succeeded in developing the CM process which is a kind of ceramic mold process. Since then we have made large steam turbine nozzles used for steam power generators, etc. However, the degree of precision inherent to ceramic mold was not quite satisfactory. We then proceeded with our research activity to develop a precision casting method to make castings with higher demensional accuracy. Our all-out efforts have been crowned with success by the development of the DPM process (Disposable Pattern Mold) with which we can produce large size precision castings. Outline of the process is described in this paper.

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