Jiro Wada

Study on improving quality of aluminium die-casting

The mechanical properties of die-castings, the effects of casting conditions upon these, and the relation between the microstructure and the strength of the products have been studied. The results are summarized as follows.1. The mechanical properties of the die-cast tensile specimens were sensitively affected by the casting temperature, but not by the die-temperature.2. The injection pressure affects upon the mechanical properties. A sufficiently high pressure is needed for improving the strength.3. The proof stress at 0.2 percent offset of the silumin die-cast tensile specimens lies almost within the range between 12 and 14kg/mm2, and was nearly constant regardress of the tensile strength when its strength was above 17kg/mm2.4. The average elongation in 50mm of the above-mentioned specimens was 2.8% for the nominal tensile strength (24.5kg/mm2 of ASTM), which was lower than the nominal value.5. The relation between the microstructure and the mechanical properties of the die-cast automobile parts were examined, but the difference of strength which depended on the micro-structures could not exactly be decided.6. The roughness of surface of the die-casting and the die cavity was tested. It is considered from these tests that the roughness of surface of the davity is propertional to numbers of shot.

Effects of low-temperature deformation on recovery phenomena of aluminium

Measurements of decreases in electric resistance of polycrystalline commercial aluminium and superpure aluminium annealed at various temperatures after deformation at liquid-nitrogen temperature reveal that some form of recovery occurs. The apparent activation energies for these recovery processes are 0.55ev for -80--50°C in commercial and superpure aluminium, 0.75ev for -50-0°C in commercial aluminium and for -50--25°C in superpure aluminium, and 0.4ev for -25-0°C in superpure aluminium. The activation energies are discussed in comparison with the recovery processes of copper.Measurements of X-ray patterns of polycrystalline commercial aluminium annealed at recrystallization temperature after prior deformation at liquid-nitrogen temperature reveal that there are much more subgrains and finer recrystallized grains than that annealed at recrystallization temperature after prior deformation at room temperature.

Study on quality improvement of die-casting

In order to improve quality of the die-cast, it is important to control heat (temperature) together with the design of dies, character of die-casting machine, etc., and we studied the effects of shot number and water cooling on variation of distribution of die-temperature.A method of qualitative improvement for uniform temperature of cavity might be found and an equation for efficiency of water cooling might be proposed by the measurement of die temperature.

Study on the Pickling Inhibitors

A quantitative relation between the cathode potential rise with the addition of inhibitor and its inhibition efficiency is suggested and proved. The difference in functions between nitrogen-contai fling organic inhibitors and inorganic inhibitors is pointed out. The function of inorganic inhibitors may beto due not only the high hydrogen overvoltage of deposited metal which covers the original cathode by replacement, but also. the formation of various cathode films such as metastable Sb4O3 (OH)3Cl3 in antimony trichloride-containing hydrochloric acid solution at higher temperature. The inhibition efficiency increases with the concentration of inhibitor in solution. Thiourea may be the more useful and efficient inhibitor than monoaliphatic amines and nitrogen-containing aromatic compounds of the short hydrocarbon chains.

Study on the Finishing of Zinc Base Alloys used for Die Casting

Among the finishing of zinc base alloys used for die casting, the electroplating has been applied for general uses. Owing to the intercrystalline corrosion and surface corrosion of zinc alloy die castings, the metal coating must have the thickness sufficient to prevent their corrosion. Therefore, we investigated on the direct nickel plating and copper plating, and we could find that it was necessary to have the thick and compact copper coating, in order to prevent the corrosion and make the mass production.