(1) Ductile iron samples with silicon content of 2.9%~4.6% were prepared by EPC process, and the matrix structure was ferrite. When the silicon content was 2.92%, the average diameter of spherical graphite of QT450-10samples was about 35.6 μ m. The average number of graphite balls per unit area is about 151/mm2, and the average size of ferrite grains is about 43.766 2 μ m; When the silicon content is 4.59%, the average diameter of spheroidal graphite of high silicon ductile iron sample is about 26 μ m. The average number of graphite balls per unit area is about 223/mm2, and the average size of ferrite grains is about 35.381 1 μm。
(2) QT450-10 ductile iron with silicon content of 2.92%, tensile strength of 441 MPa, Brinell hardness of 128 HBW, elongation of 17%; The high silicon ductile iron with silicon content of 4.59% has a tensile strength of 683 MPa, Brinell hardness of 186.1 HBW, elongation of 17.5%, and high comprehensive mechanical properties.
(3) For the high silicon ductile iron sample with silicon content of 3.5%~4.6%, the increase of silicon content makes the graphite ball finer and more uniform, and the effect of spherical graphite on the metal matrix is reduced; The grain size of ferrite decreases, which enhances the fine grain strengthening effect of silicon on ferrite; Silicon can replace solid solution in ferrite matrix to form solid solution strengthening, but with the increase of silicon content, its segregation index value on ferrite grain boundary becomes larger and larger, that is, the segregation phenomenon becomes more and more serious, which reduces the lattice constant of ferrite and increases the lattice distortion. Therefore, with the increase of silicon content, the mechanical properties of high silicon ductile iron are improved.