With the development of industrial technology, the performance requirements of gray cast iron are higher and higher in various fields. Ordinary gray cast iron can not fully meet the production requirements. Gray iron castings at home and abroad usually ensure their tensile strength by controlling carbon equivalent and adding a certain amount of alloy elements [9]. Although the addition of alloy elements improves the mechanical properties and meets the requirements of control indicators, the addition of alloy elements greatly increases the cost. In addition, the low carbon equivalent and added alloy elements affect the solidification mode, feeding capacity and other casting properties and cutting properties of gray cast iron, resulting in a large number of waste castings and serious deterioration of cutting properties. After effective inoculation, gray cast iron can refine the matrix structure, reduce the tendency of white cast iron, eliminate the sensitivity of wall thickness and improve the machinability. Therefore, inoculation treatment will be a practical method to improve the machinability of gray iron castings. In this chapter, the effects of four inoculants 75sife, SRSI, basi, sisR (80%) + 75fesi (20%) on the machinability of gray cast iron are quantitatively analyzed and studied. Combined with the mechanical properties and microstructure of the samples, the relationship between the microstructure and properties of Gray Cast Iron Inoculated with different inoculants is analyzed and explained.
The effects of four inoculants 75sife, SRSI, basi, sisR (80%) + 75fesi (20%) on the machinability of gray cast iron were quantitatively analyzed and studied. Combined with the mechanical properties and microstructure of the samples, the relationship between the microstructure and properties of Gray Cast Iron Inoculated with different inoculants was analyzed and explained. The main results are as follows:
1.High performance cast iron ht350 can be obtained by low alloying and effective inoculation with appropriate inoculant. 75 ferrosilicon inoculated gray iron castings have higher tensile strength, lower hardness and lower section sensitivity. The gray iron castings inoculated with sisR (80%) + 75fesi (20%) composite inoculant have the highest hardness, but their section sensitivity is large. The strength and hardness of gray cast iron samples inoculated with inoculants basi and SRSI in the same furnace are basically the same, but the section sensitivity and microstructure uniformity of gray cast iron treated with SRSI inoculant are better than those treated with basi inoculant.
2.From the comparison of microstructure photos of castings after inoculation treatment, it can be seen that the graphite of gray iron castings with composite inoculation treatment is smaller and bent than that of gray iron castings with single inoculation treatment, and the matrix structure has good uniformity, so the processing performance is better. Therefore, improving the graphite morphology and structure uniformity in the structure of gray iron castings is conducive to the improvement of processing performance of gray iron castings. The machinability of the sample has a close corresponding relationship with the structure of the casting. The more the content of type a graphite in the gray iron castings, the more uniform the matrix structure, and the better the machinability of the gray iron castings, indicating that the uniformity of microstructure has a great influence on the machinability of the gray iron castings.
3.Under the same cutting conditions, the three-dimensional cutting force and cutting force of gray cast iron sample inoculated with basi are the largest; The cutting force of the sample treated by composite inoculation is the smallest. Under the same strength, the three-dimensional cutting force and cutting force of the gray cast iron sample inoculated with basi are significantly higher than those inoculated with SRSI.