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Technology has been developed to increase the fatigue strength of powder-forged connecting rods. The fatigue strength of powder-forged materials was increased without adding special alloy components or lowering workability by adjusting the ratios of the conventional main mixed powders (iron, carbon, copper). In addition to solid solution strengthening of the ferrite using copper, reducing porosity, which is a material surface defect, is also an effective method of increasing fatigue strength. Reducing carbon content greatly reduced the occurrence of defects in the forging stage. The results of this research showed that the fatigue strength of high strength powder-forged connecting rods can be increased by 30% or more over that of conventional materials, allowing powder-forged connecting rods to be applied to even higher output and higher load engines than before.

Filiform corrosion phenomenon and its prevention method for 5000 series aluminum alloy sheet have been investigated. The painted aluminum alloy sheets were subject significantly to filiform corrosion caused by formation of a mottled and coarse zinc phosphate film during chemical conversion process. On the other hand, galvanized aluminum alloy sheet showed an uniform and fine phosphate film in a brief time and the filiform corrosion resistance was improved markedly. The test results of press-forming and corrosion for the prototype engine hoods made of this newly developed galvanized sheets have revealed a good formability and an excellent filiform corrosion resistance.

This paper summarizes a laboratory study aimed at revealing the effect of chemical elements. Si, Cr, Mo and V, on the sag resistance and developing new steels with all the characteristics required for suspension coil spring in comparison with AISI 9260. It was found that as far as sag resistance is concerned an optimum silicon content exist (1.5 silicon) and chromium deteriorates sag resistance and molybdenum and vanadium improve it. Further studies showed that Si-Cr-V steels are the best spring steels available, particularly 1.5Si-0.5Cr-G.2V steel has all the required characteristics, e.g., good sag resistance, good decarburizing resistance and sufficient hardenability.