The effects of chemical composition, microstructure and testing conditions on the so-called 673K embrittlement in spheroidal graphite cast irons were examined in detail. The observation of fracture process shows that the embrittlement is not due to dynamic strain aging (blue embrittlement) but intergranular fracture. It is found that the embrittlement can be suppressed by reducing the Mg/P ratio to less than 1.5.
