Coating of functional and thicker layer on iron castings was prepared by using mixture of ferrochromium alloy powder and three kinds of Ni based alloy powders having low melting point as coating powder on the mold. The main results obtained were as follows : (1) The best coating layer which contains a little amount of porosity and is 2-3 mm in thickness and 800-900 numbers in Vickers hardness, can be obtained by a suitable mixing ratio (ferrochromium powder/self-fused Ni based alloy powder) at each location of the mold. The ratio should be lower in order to get well sintering coating layer powder, thus more liquid can be supplied at such rapid cooling location as edge corner of mold. (2) When Ni-P or Ni-P-Cr powder was mixed, the large pores have a tendency to remain in the coating layer because the liquids have poor wettability with ferrochromium.

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  A thin surface layer of flake graphite cast irons with A and D type graphite were once melted by applying tungsten inert gas arc (TIG) and solidified. Some properties of the hardened chilled are related to the parameter ƒ(J) = (I⁴/E²ν)^1/3 for remelting condition, where I is arc current, E is arc voltage and ν is rate of melting. Depth, p, aspect ratio, b/p and surface hardness, HV of chilled layer are proportional to the parameter ƒ(J) and are given by the equations.
  For A type graphite iron : p=0.043ƒ(J) +0.06, b/p=-0.036ƒ(J) +5.6, HV=-5.8ƒ(J) +964
  For D type graphite iron : p=0.056ƒ(J) +0.10, b/p=-0.040ƒ(J) +5.0, HV=-5.8ƒ(J) +1056
  The blow holes which remained in the chilled layer are present in A type iron in much greater amount than can be permitted in D type iron. The blow holes are produced by CO gas formed by reducing SiO₂ with carbon in a temperature range higher than the critical point of CO-SiO₂ equilibrium. Addition of aluminum during remelting is particularly beneficial for the prevention of blow holes, because aluminum has a high ability of reducing SiO₂ and its reaction product is not reduced during remelting.

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  The solidification and falling flow behavior are studied to develope the process for producing a container without cores by the vertical centrifugal casting. The solidification time of the center zone of a side wall was more than that of outer and inner peripheral zones. The falling temperature and solid fraction for the falling flow are greatly influenced by the falling volume of castings. The critical solid fraction for the falling flow of AC4C alloys is estimated as 0.38-0.45 according to the cooling rate of the just falling part.

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  The foamed aluminum with varying porosity was produced by using titanium hydride as a blowing agent. The effects of porosity on physical properties of foamed aluminum were experimentally investigated. The percentage of the porosity of foamed aluminum was varied from 76.5 % to 86.6 % . The results were summarized as follow : (1) The mechanical properties and the electromagnetic shielding characteristics of foamed aluminum decreased as the porosity increased, but the thermal insulation was improved. (2) The peak of normal absorption percentage was shifted to the lower frequency region as the porosity decreased or the thickness of the air gap layer increased. (3) The effect of sound absorption was improved as the cellular size decreased when the porosity was higher than 80 % . (4) A higher normal absorption percentage was obtained over a wide frequency range by forming through-holes in cell walls of the gas permeable foamed aluminum with high porosity.

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  The wear resistance of spheroidal graphite cast irons can be markedly improved by boriding, but softening of the unborided core substrate may occur in certain boriding process. In such cases it is required to strengthen the unborided core substrate with the subsequent heat treatment, such as austempering and induction hardening. Although it is suspected that those treatments damage the boride layers. Hence, the influence of austempering and induction hardening on wear resistance of borided spheroidal graphite cast iron was studied. Some specimens were austempered in a Pb bath at 648 K immediately followed by boriding in fluidized bed furnace, others were induction-quenched in cold water followed by furnace cooling after boriding in fluidized bed furnace. The tests were made on the hardness, the microscopy, X-ray diffractometry, the SEM and the sliding wear characteristics. Both austempering and induction hardening after the boriding reduced only slightly the hardness of the boride layers, but these phenomena did not always deteriorate the sliding wear resistance.

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  The effect of graphite nodule count and Mn content on successive austempering process, which was developed for the production of more tough austempered ductile iron (ADI), was investigated. This process is a characteristic heat-treatment cycle in different holding time combination with high and low austempering temperature (HLAT) to improve the toughness of hardenable Mn alloyed ductile iron. Higher impact energy was obtained in the better combination structure with maximum retained austenite and minimum untransformed austenite volume (UAV). The better graphite nodule count was, the higher toughness was obtained, while about 0.6 mass % Mn alloyed ductile iron was optimum. The relationship between impact toughness (Y) and UAV (X) was able to be expressed by the following representation : Y = 111 × X^-0.55 . Impact toughness was quite sensitive to the lower range of UAV.

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  Expansion and shrinkage behaviors in freezing flake and spheroidal graphite cast irons have been investigated by the float method using a laser dilatometer. The volumetric expansion of flake graphite cast irons on eutectic solidification was given by a linear function of the modified carbon equivalent CE∗ [=(mass % C) + (mass % Si) /5] ; ΔV/V(%) = 1.57(CE∗-2.08). For S. G. irons, no distinct dependence of expansion on composition was observed but the amount of expansion varied with cooling rate. From the observed expansion values, expansion pressures need to suppress entirely the expansion during eutectic solidification were estimated on the assumption that the cast irons are homogeneous isotropic elasticities. It has been suggested that the predicted expansion pressure amounts to be 3∼4.5 GPa when the expansion value is 3 % and has been predicted from the pressure dependence of eutectic temperature that the transition of solidification structure from expanding graphite eutectic to shrinking ledeburite may bring about at less pressures.

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