A series of experiments was carried out under mass production conditions with the pullback of plungers in order to investigate in detail how pressure is transmitted in cavities during die casting. When the plunger pulled back rapidly, the melt pressure in cavities was able to follow the pullback and descend. However, when it pulled back slowly, the melt pressure could not follow the pullback with slow pressure decrease. This indicates that the pressure of the plunger is transmitted into cavities sufficiently through gates at an early stage. The time required for the transmission of the pressure depended on the occlusion of the gate, when the thickness of the gate was thinner than standard. On the other hand, the transmission time depended on the solidification in cavities or in the pressure transmissions path, when the gate thickness was thick. The transmission time of the pressure increased with the gate thickness, improving product quality.

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  This paper proposes a cast-in insert process to improve wear resistance of aluminum castings by alumina dispersion composite structure on casting surfaces. This process uses thermite reaction heat and employs Al-CuO mixed powder compacts as a reaction system. Poured aluminum melt ignites the thermite reaction to produce alumina dispersion Al-Cu alloy composites through the strong reaction heat generated. Use of the heat yields a complete cast-in insert. Such a process requires rapid reaction at relatively low temperature provided by aluminum melt during casting. This paper examines influences of compact pressure, Al/CuO ratio, and additional elements (Mg, Mg-Al alloy and Ni) on reaction initiation. Various powder compacts heated in a constant heating rate environment were examined to measure initial and maximum reaction temperatures. In addition, DTA measurements clarified temperature of liquid appearance in compacts.
  This study found that Al-CuO reaction requires high compact pressure and sufficient aluminum metal fraction ; also, additional 10 mass% of magnesium in compacts was indispensable. Comparative experiments of cast-in inserts using compacts of proper conditions and compacts without magnesium addition confirmed the magnesium effect and presented the possibility that reaction heat aided the cast-in insert process. These results indicate that reaction of adhered Al and CuO cannot start unless the Mg-CuO reaction produces sufficient heat prior to Al-CuO reaction.

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  Surface hardening of 27 mass%Cr white cast iron was studied by an inserting method with mixture block of crushed TiC-Mo₂C-Ni cermet powder (<200μm) and some kinds of additional metallic powder (<60μm). After a white cast iron rod was placed on the mixture block, inserting process was studied by melting to penetrate the white cast iron into the mixture block. The results showed that inserted layers could not be formed by using cermet powder only, but could be formed by using the mixture of cermet powder and additional Ni powder or Cr powder above 50 vol.%. In the case of additional Ni powder, high hardness of inserted layer was not obtained because increasing Ni content in the binder phase of cermet powder caused the morphology of the cermet powder to collapse and disperse TiC particles of the cermet powder over a wide region of the inserted layer. In the case of additional Cr powder however, high hardness of the inserted layer was obtained in comparison with additional Ni powder, because of the formation of large amounts of M₇C₃ carbide precipitates on the inserted layer and dispersion hardening of TiC particles. Additional Mo powder and Co powder did not show any effects for the formation of the inserted layer.

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  The effects of wetting on the transfer of a particle into molten metal were investigated using three theoretical models. The effects of particle diameter and contact angle between the particle and molten metal on the force for particle transfer were also calculated. Using these theoretical models, for any arbitrary value of the three interfacial energies (solid/vapor, solid/liquid and liquid/vapor), contact angle, particle radius, ratio of dipped length, particle and liquid density, the actual force required for the particle transfer can be obtained. Furthermore, these equations were verified using water solutions and paraffin coated steel balls with a 1mm radius in experiments where the contact angle was varied from 0° to 105° by changing the concentration of the surfactant (sodium lauryl sulfate). The surface tension of these aquasolutions were measured by the maximum bubble pressure method.

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  Cast simulation using computer is useful for designing cast technology of complicated iron castings, and analyses of fluid and solidification are carried out in routine work for reference. Using the function of solidification analysis, methods differing from common ones were established in this study. Prediction and optimization of shake-out timing for large-sized iron castings, prediction of temperature distribution in casting during heat treatment process, and prediction of residual stress in casting using simple models. were carried out. The results proved that these analyses are useful in iron casting production.

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  CO₂ laser beam was applied to the cladding of WC dispersed hastelloy on carbon steel by a preplaced powder method. The hardness and microstructure of the clad layer were investigated by changing the power of laser, number of clad layers and overlapped width of the laser beam. The average hardness of matrix in the clad layer was 400 to 420HV 0. 1 under the following conditions : laser power of 2500W to 3100W, cladding speed of 400mm/min, defocusing distance of 30mm, oscillation width of 7mm and argon gas shielding. The microstructure of the clad layer was observed to transform into fine dendrites with secondary dendrite arm spacing of 2μm and fine eutectic structure because of rapid solidification, and tungsten carbide particles were dispersed in the matrix. A heat affected zone was produced near the boundary of the clad layer on the surface of the carbon steel and martensitic structure was observed. The clad layer was then heat treated again with CO₂ laser beam, but the hardness of the clad layer did not change. EPMA line analysis indicated that an alloyed layer with a thickness of 20μm exists between the clad layer and the heat affected zone of the carbon steel. These results suggest that CO₂ laser beam cladding of WC dispersed hastelloy is a useful surface treatment process.

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