Effect of modifier content on Microstructure and properties of high strength gray cast iron

Modification is a method of adding a small amount of elements or their compounds to the molten metal to control the crystallization process and change the solidification structure, so as to refine the grains. If the crystallization process of gray cast iron can be controlled and the solidification structure of gray cast iron can be changed, gray cast iron can have high mechanical properties.

The effects of different modifier contents on the microstructure, mechanical properties and thermal fatigue properties of high strength gray cast iron were studied. The conclusions are as follows:

1) The addition amount of modification is from 0.8wt.% Increase to 1.0wt.% It can refine the graphite in the structure of gray cast iron, make the graphite more curved and fine, increase the quantity, and increase the amount of modifier. It can also refine pearlite and reduce the lamellar spacing of pearlite.

2) The modification treatment can change the growth process of primary austenite, promote the development of primary austenite as a spatial network, limit the space of Eutectic Transformation of gray cast iron, reduce the size of eutectic cluster, provide a premise for obtaining fine bent graphite, and the addition amount of modifier is from 0.8wt% Increase to 1.0wt.% It makes the network structure of primary austenite more complex and the number of eutectic clusters more.

3) Due to the increase of the amount of modifier, the graphite will become fine and curved, the network frame structure of primary austenite will be more complex, and the lamellar spacing of pearlite will be reduced. Therefore, the mechanical properties of gray cast iron will be improved. After modification, the thermal fatigue properties of gray cast iron are improved, and the more the modifier is added, the better the thermal fatigue resistance is.