ひけ巣傾向を表す熱分析パラメータθに及ぼす各種因子の影響

抄録

  The angle of cooling rate curve at the end of solidification θ was studied in this research. Results of solidification simulation reveal that latent heat is the reason why θ occurs, and that it affects the size of θ, that is the greater the latent heat or the longer the eutectic solidification time, the smaller is θ.

  θ varies with change in the graphite microstructure. Flake graphite iron has a higher cooling rate and a narrower angle at the end of solidification when compared with spheroidal graphite iron. This is due to the differences in their solidification kinetics and heat transfer coefficient between gray iron and ductile iron. When a D Type graphite or chill structure generates in gray iron, θ increases.

  θ is a good indicator of the shrinkage tendency in ductile iron. That is, a larger angle indicates a higher shrinkage tendency. When shrinkage occurs around the thermo-couple in the shell cup, the cooling rate becomes slower due to the heat transfer deterioration. Finally, the difference in the cooling curves between the ATAS Cup and SP Cup resulted from the difference in the quartz tube diameter used in the two cups.