Squeezing from the bottom side of a sand mold, which we call under-squeezing, is a more efficient method of compacting sand than other conventional method, such as jolt-squeezing and air impaction. The friction of sand against the walls of the flask impedes the efficiency and precision of sand molds compacted from the upper side with these conventional methods. By contrast, under-squeezing that causes this friction is efficient for compacting sand near the bottom of the flask and pattern faces. We performed experiments on changing the flask height and pattern forms. We clarified the efficiency of compacting sand with molding machines used in factories that are equipped with functions that can change the under-squeezing strokes. The results of the experiments show that under-squeezing compacts molding sand uniformly regardless of the pattern forms and flask height.

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  The coating on iron castings was prepared using a mixture of ferrochromium alloy powder and self-fused Ni based alloy powder with low melting point as the coating powder on the mold. The temperature of the coating powder layer after casting was measured, and several functional properties of the coated iron castings obtained were tested. The main conclusions drawn are : (1) The highest temperature attained in the coating powder layer, which determines the degree of sintering in this layer, is greatly affected by the thickness of the layer and castings. (2) Alumina powder used as heat-retaining material is very effective for maintaining high temperarure in thick coating powder layers and thin castings. (3) The coated iron castings obtained have substantial hardness and good resistance to wet abrasion. corrosion and oxidation at high temperatures.

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  The effects of H₂ gas content on fatigue strength of aluminum cast alloys (AC4CH) and improvement by atmosphric pressure casting, 1MPa pressure casting and 773K-100MPa HIP treatment were investigated from the veiwpoint of defects, a method for evaluating the conservative fatigue limit was proposed. The main results obtained were ; (1) 1MPa pressure casting and HIP treatment were effective in improving the fatigue limit of AC4CH, bcause the defect size in 1MPa pressure casting and HIP treatment is smaller than that in atmospheric pressure casting. (2) The fracture origin proceeds from microshrinkage to adjoining blow holes as H₂ gas content increases, but the size of each blow hole is the same as that of the microshrinkage. Consequently, H₂ gas content has little effect on fatigue strength. (3) The conservative fatigue limit of aluminum cast alloys can be evaluated by substituting √area_max estimated by extreme statistics in the following equation. σ_w=α·σ_B/(√area_max)^0.161

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  Tin is effective for reducing the grain size of pure zinc castings, but on the contrary causes intergranular corrosion of the castings when more than 0.05% is added. The cast structure of Zn-0.05%Sn alloy solidified in stirring was investigated. To observe the effects of stirring on the movement of liquid, a solution of water and 60% glycerin with 66 nylon balls were stirred in an acryl vessel at various conditions. The results obtained are as follows. Granular crystals that had separated accumulated at the bottom of vessel when the effects of stirring on the water or solution were not observed at the bottom of vessel. But columnar crystals were seen to develop from the bottom of vessel when they were indicating, stirring at 2∼3s^-1 was effective for reducing grain size.

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  A twin disk-rolling-sliding contact machine was used to investigate the cold wear property of the tool materials, SKD11, Cast-HSS (High Speed Steel), and HIP-HSS. According to the test results, HIP-HSS, which was harder and had smaller carbide particles, showed better wear resistance than the other two materials. A strong correlation was seen between cold wearing, hardness and microstructure, especially carbide size. Through the observations of the wear surface and cross section, the cold wearing mechanism is assumed as follows. Under heavy load conditions, plastic deformation occurs and microcracks initiate from the near-surface material where the carbide particles have broken. Cracks then propagate and finally the near-surface material disintegrate into flakes. Based on these phenomena, new steel pipe reforming rolls were produced using HIP-HSS, which demonstrated four times longer life than conventional SKD11 rolls.

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  The toughness of ceramic cutting tools made of silicon nitride (Si₃N₄) is improving in recent years. The nose of tool, however, wears out when cutting is performed at high speed condition, and consequently the life of the tool comes to an end. In order to reduce nose wear, the effects of coating with hard materials on the resistance of the Si₃N₄ ceramic tool to wear were investigated. Coating the Si₃N₄ tool with TiN+TiC+Al (ON) using the chemical vapor deposition (CVD) method proved effective for reducing nose wear as compared to when it was not coated and coated with Al₂O₃. The nose wear of the TiN+TiC+Al (ON) -coated Si₃N₄ tool was reduced most effectively when applied with 6-layer coating. The nose wear in the coated Si₃N₄ tool was found to be determined by the coating in the tool land and wear end of tool. Based on the obtained knowledge described above, a novel coating method was developed in which 3-layer coating was applied to the land part of the tool, and 6-layer coating to the other part.

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  Semi-solid cast irons were pressure-cast by using vertical and horizontal die casting machines. Series of experiments were carried out on flaky graphite cast irons. In the rheocasting method. semi-solid slurry (fraction solid is about 0.2) was subjected to the vertical die casting machine. Flat plates of 6mm thick were produced. Surface quality, microstructure of product and die temperature were investigated. The reduction of heat shock of the die was also ensured. In the thixocasting method, as the raw materials, sand mold cast irons were heated to have a solid fraction of 0.2 and then die cast. Flat plates of 6mm thick were produced. The microstructure obtained after die casting was found to be primary austenite (ferrite and pearlite at room temperature) distributing in the structure and it was also found that the liquid phase section became austenite-cementite eutectic. When this eutectic was heat-treated, the cementite shortly changed to fine graphite spheres. The mechanical properties of the tested cast irons were improved by die casting and post heat treatment.

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