Abstract
The structure dependence of the 673 K embrittlement of ferritic spheroidal graphite cast iron with a constant graphite volume fraction and with various ones was investigated. Experimental results show that the fracture strain at room temperature and 473 K tends to increase as the structure size increases. At 673 K, the ductility tends to decrease extremely by the onset of intergranular (I.G.) fracture, as the structure size increases, but only the specimen of the smallest structure shows the ductile fracture without I.G. fracture. I.G. fracture becomes easier to occur, accompanied with the ductility decrease at 673 K, as the carbon content or the graphite volume fraction decreased. The suppressible effect of graphite nodules on the embrittlement due to I.G. fracture or cleavage fracture was considered. It was deduced that a larger triaxiality built at the matrix of a lower carbon content of ferritic spheroidal graphite cast iron leads to more embrittlement.
