The effects of thermomechanical treatment on the ausferritic transformation process and the toughness of ductile cast iron were studied. Rolling at the austempering temperature remarkably accelerates the ausferritic transformation, resulting in very fine and uniform matrix microstructure and increasing in strength. Rolling at the austenitizing temperature slightly delays the kinetics of the transformation. Beneficial effects are the elimination of γ-pool and increase in ductility. The refinement of the matrix microstructure, while promoting strength, also retults in flat fracture surface and drop in ductility concomitant with higher strength values. Thus, in order to achieve maximum toughness, it is desirable to have optimum fineness in the matrix microstructure. Maximum toughness and ductility were obtained by 19.3 % (total reduction ratio) rolling at both the austenitizing and austempering temperatures. Maximum strength and hardness were obtained by 24.0 % rolling at the austemperig temperature.

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  This study attempts to provide a prototype of a system software for identifying casting defects. The system employs an expert system consisting of unprecedented logical data bank. The database is built up by classifying complex defect causes. The system works satisfactorily for speculating the causes of copper alloy casting defects. Another advantage of this system is that it helps users understand more about the causes of defect not only through ordinary literal explanations but also through accompanying high resolution photographs as well. In constructing rules, considerable differences were observed between the computer and human performance. In constructing dependable truth table, it is necessary to obtain more data on logically selected attributes and fitting arrangement of those attributes. A more logical representation of attribute values also should be discussed.

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  The remelt-chilled cast iron, which is remelted locally on the surface using tungsten inert gas (TIG) arc as a heat source and self-cooled, is widely being used in sliding parts. Rolling contact fatigue property of remelt-chilled spheroidal graphite cast iron having excellent wear resistance is compared with that of cast irons which are treated by various surface-hardening process. Compared with other cast irons, the remelt-chilled spheroidal graphite cast iron has excellent rolling contact fatigue strength. While a high frequency induction-hardened flake graphite iron which raises the surface hardness does not cause fatigue strength in proportion to the increase in hardness, when matrix hardness is high. The TIG arc remelting process provides remarkably high rolling contact fatigue strength to the cast iron. Especially, the remelt-chilled spheroidal graphite cast iron is free from spalling which may cause heavy exfoliation, and holds its service life until it is damaged by the pitting. Occurrence of the pitting in gears usually does not mean that the service life ends, and they can have a much longer fatigue life.

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  In the rolling stock, a brake shoe of phosphoric cast iron had a wear resistance and a higher friction coefficient, therefore, phosphorus was a very important element for the performance improvement of brake shoe. In this study, the specimens were made with phosphorus contents between 0.05 % and 9.5 %, and the effect of phosphorus was studied in detail by using a friction tester and a full-scale brake tester. When phosphorus content was in the range of approximately 1-3 mass % at an initial brake speed level of less than 95 km/h, the friction coefficient of brake shoe had the highest peak. The effect of phosphorus to decrease the wear rate of brake shoe turned out the larger at the lower speed. The worn particles of phosphoric cast irons were a plate-like form as the result of fragments being crushed between the frictional surfaces, while columnar worn particles turned up at a speed greater than 10 m/s.

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