Effects of shake-out time and heat treatment on microstructure and properties of Cr28 cast iron after poured have been investigated. The results indicate that although the hardness and impact toughness of the Cr28 cast iron can be decreased with increasing cooling time in the sand mold

the Cr28 cast iron exhibits higher hardness and impact toughness with air cooling after cooling for 3 h in sand mold. The hardness and impact toughness of the cast iron are more than 56 and 4.5 J

respectively. The microstructure of Cr28 cast iron with varied shake-out time at air cooling is composed of martensite

residual austenite and different shape M7C3 carbide. The Cr28 cast iron can be improved by more than 60 in hardness and more than 2.8J in impact toughness after normalizing at 1040℃ and tempering at 100 ℃ with different shake-out time at air cooling.