In blow molding, green sand is blown from the magazine to the cavity using compressed air, and squeezed. In this study, the blow stage is investigated. It is essential to know how the sand particles are moved by airflow during the blow stage. The blow stage is however very complex phenomenon, due to the interaction of the sand particles and airflow. The purpose of this study is thus to develop a process model using the distinct element method (DEM) coupled with airflow analysis. Numerical simulation was performed to predict the behavior of the sand particles during the blow stage, and laboratory experiments for rectangular cavity were carried out to examine the calculated results. The simulation reasonably explains the behavior of green sand flow in the magazine and cavity, which is difficult to be measured by the experiment.

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  The effects of alloying elements on graphite (T_EG) and cementite eutectic temperature (T_EC) of cast iron, and the difference between them (ΔT_E) were investigated. A thermal analysis system consisting of three cups was used to measure eutectic temperature. The order of the expanding effect on ΔT_E is as follows : Si> Al> C_<2.9%> Cu> Co> P> Ni> C_>2.9%. The order of the narrowing effect on ΔT_E is as follows : B> S_>0.44%> V> Cr> S_<0.44%> Mn> Nb> Ti> Sn> W> Mo> Sb. Mn and Ti form sulfide, so that they expand ΔT_E for a low content of element and narrow ΔT_E when the content is less than the transition content. It can be concluded that ΔT_E is not related to carbon activity but to the distribution coefficient of element between cementite and austenite.

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  Ferrite-rimmed spheroidal graphite cast iron composed of ferrite rich structure near the surface and pearlite-rich at the inner part of a cylindrical specimen was developed by a simple heat treatment. The structure formation process was investigated by interrupting the transformation during continuous cooling and isothermal heat treatment around the eutectoid temperature after austenitizing. The optimum heat treatment for the ferrite-rimmed structure consists of slow cooling at a rate of about 10K/min from austenitizing temperature and isothermal holding around 1013K, followed by air cooling. CCT and TTT curves obtained from a small specimen indicate that the optimum cooling rate and the holding temperature correspond to the closeness of the onset of the ferrite and pearlite formations. It was also found that the austenitizing condition affects the thickness of the ferrite-rim. The bending property of the newly developed ferrite-rimmed cast iron is superior to that of a homogeneous ferrite-pearlite cast iron with the same tensile strength.

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  The relationship of tempering temperature with wear resistance and residual stress of 25% Cr cast iron was studied. Abrasion tests were carried out with test pieces tempered at different temperatures. The results show that abrasion tend to increase with the increase in tempering temperature. The increase was especially remarkable when the tempering temperature exceeded 700K. The amount of sand erosion, however, was not noticeably affected by the tempering temperature, remaining at about the same value. Abrasion considered changing with the change in material hardness, whereas, sand erosion do with the change in the amount of carbide in the material. Residual stress after tempering was analyzed with castings of 30mm in diameter. The residual stress generated in the course of air hardening treatment decreased with the increase in the tempering temperature, but, started to increase after showing a minimum value at around 700K. The generation of residual stress is considered due to the cooling after heating and decomposition of the retained austenite over 700K, despite the stress relief effect by heating. Consequently, for reducing residual stress without losing wear resistance, tempering at 700K is recommended.

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  Al-4, 8, or 12 mass % Cu alloy melt flowing out through a small nozzle located at the bottom of the quartz tube container was rapidly solidified in a tube on a rotating copper substrate which was pulled down into water. Fusion-weldability between layers, shape stability and microstructure were investigated as functions of alloy composition, superheat and rotation speed of the substrate. Good weldability between the layers and steady shape forming were achieved with smaller superheat and higher rotation speed. Better shape stability was obtained for hypo-eutectic alloys. The microstructure of the tube specimen subjected to the fused spinning deposition process was found to consist of fine equiaxed grains and the specimen exhibited tensile strength 1.5 times higher than metal-mold cast alloys with a fine columnar structure. The solidification analysis showed that the equiaxed grain structure is formed as a result of the cyclic remelting and solidification process.

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  This is the observation of pin hole defects occurred in cast iron by green sand mold with SEM. All 109 samples (gas hole defects) gathered from 34 foundries are observed. The defects are classified in 4 types as follows : In D), there are still more 3 types defects. A) round pin hole, B) thin & long pin hole, C) fissure pin hole, D) slag pin hole (a : ladle slag, b : inoculant, c : manganese sulfide). Typical SEM photo (A～D) is shown the figure. By standardizing these, SEM photos, it will be possible to classify the pin hole defects occurred in foundries and it will help studying of prevention.

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