Research on Application of High Strength and High Toughness Austempered Spheroidal Graphite Cast Iron to Environmental Material

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This research is in the aim of the development of the austempered spheroidal graphite cast iron which considers high strength, a high toughness, and corrosion resistance.The first research planned the construction of a handy evaluation system from the viewpoint of prevention and the diagnosis of corrosion in the metallic surface. The system analyzes the corrosion distribution, the form, and the progress degree of the metallic surface by using a digital image processing. The second research evaluated the corrosion resistance of the developed material by the electrochemical corrosion test. It was a natural potential measurement and an anodic polarization measurement.The test material prepared the Ni-Cu alloy spheroidal graphite cast iron to expect the corrosion resistance improvement. In addition, the spheroidal graphite cast iron, the high Si content spheroidal graphite cast iron, the white cast iron, and the carbon steel were used as the comparison material. In addition, the effect on various matrixes of the cast iron which showed an excellent property in corrosion resistance was examined in the experiment.The Cu-Ni alloy spheroidal graphite cast iron obstructed the progress of corrosion by the protection film formation of Cu. This material showed the most excellent corrosion resistance. The martensite and the ausferite structure made minute become small no movement maintenance current density, and have improved corrosion resistance.On the other hand, the corrosion evaluation of the metallic surface was able to be analyzed by a digital image processing which used the fractal dimension analysis. The research in the future is to make the objective evaluation judgment standard from the viewpoint of the corrosion prevention and the diagnosis and the evaluation by using a digital image processing.