高マンガン厚肉球状黒鉛鋳鉄の組織と機械的性質に及ぼす後期接種の影響

抄録

  In recent years, there has been an increase in the amount of manganese (Mn) contained in cast iron due to changes in raw materials. It is thought that the increase of Mn contents has a bad influence on the mechanical properties of cast iron. This study aims to investigate the effects of Mn content and post inoculation for mechanical properties and structural changes of FCD450-10 with different thicknesses. In this study, spheroidal graphite cast iron was used as specimens with a Mn concentration of 0.3%, 0.6%, 0.9%. The rates of the cooling of specimens to the eutectic temperature were 0.22K/s, 0.12K/s and 0.08K/s, respectively, for different thickness of specimens. It was observed that thick wall specimens with a cooling rate of 0.12K/s or less had large graphite and grain diameters. In addition, when the Mn content was 0.9% or more, coarse cementite occurred in the last region to solidify (intercellular structure) with the segregation of Mn to the cell boundary. On the other hands, for the specimens with post inoculation, graphite nodule count and cell count increased, and the pearlite area decreased. Course cementite also disappeared in the specimens. Mn segregating to cell was concentrated in the pearlite. Mechanical properties decreased with decreasing cooling rate and increasing amount of post inoculant. This is due to chunky graphite formed.