By measuring the microstructure and mechanical properties of low carbon equivalent grey cast iron treated by different processes, the mechanism of inoculation strengthening low carbon equivalent grey cast iron with rare earth ferrosilicon is discussed, and the following conclusions are drawn:
- By observing the metallographic structure, it is found that with the increase of rare earth ferrosilicon inoculation, the overall change trend of graphite structure of low carbon equivalent gray cast iron is mainly E-type undercooled graphite, the graphite sheet is relatively coarse, gradually becomes fine and evenly distributed flake A-type graphite, and then changes to e, D-type, vermicular and spherical graphite. Graphite itself has no strength, but the distribution, shape and quantity of graphite can affect the properties of gray cast iron. The graphite becomes fine and then turns into vermicular and spherical, so as to reduce the splitting effect on the matrix and improve the strength of low carbon equivalent gray cast iron.
- Comparing the matrix structure of different rare earth alloy addition, it can be found that in a certain range, rare earth can greatly reduce the content of cementite in low carbon equivalent gray cast iron, increase the content of pearlite and greatly improve the mechanical properties of gray cast iron; Pearlite can also strengthen the matrix. When the content of rare earth alloy is 0.1% and 0.2%, the amount of pearlite is large and flake; This shows that the addition of rare earth alloy can significantly increase the undercooling of molten iron, reduce the carbon concentration required to form cementite, and increase the growth rate of alloy cementite in cementite, so as to reduce the thickness of ferrite sheet, speed up the eutectoid transformation, and finally reduce the sheet spacing of pearlite sheet, strengthen the matrix and improve the mechanical properties of gray cast iron.
- Comparing the eutectic structure of different rare earth alloy additions, it can be found that after the modification of rare earth alloy, the number of eutectic clusters per unit area increases with the increase of rare earth alloy additions; After eutectic refinement, the mechanical properties of gray cast iron can be effectively improved under the same matrix conditions.