Nodular cast iron is widely used in automobile parts, such as wheel hub, differential case, bracket, steering knuckle, main cover, etc. in order to improve the strength or toughness of nodular cast iron, it was realized by adjusting the matrix structure of nodular cast iron in the past. In recent years, a number of domestic articles have introduced: through the method of high silicon solid solution strengthening, the ductile iron with high strength, high toughness and full ferrite matrix has been obtained, which solves the problems of low elongation and large hardness gradient existing in the mixed matrix ductile iron with alloyed pearlite and ferrite such as copper or manganese. In order to solve the problem of uneven strength and hardness of Puma main cover and v348 differential shell nodular iron castings, a foundry of an automobile company applied the technology of silicon strengthened ferrite nodular iron to the practice of the product and achieved good results.
1) By increasing the silicon content of nodular cast iron, the final silicon can reach 3.3% ～ 4.3%, realizing the solid solution strengthening of silicon to nodular cast iron matrix, so as to improve the strength and toughness of castings.
2) Through silicon solution strengthening, the strength and toughness of the casting are improved, the hardness gradient of the casting is effectively reduced, the wall thickness sensitivity of the casting is reduced, the machining performance of the casting is improved, and the tool wear is reduced.
3) Silicon solid solution strengthened ductile iron reduces the difficulty and cost of realizing high grade ductile iron.