Mechanical properties: The mechanical properties of gray cast iron are related to the microstructure of the Matrix and the morphology of graphite. The flake graphite in gray cast iron has serious fragmentation to the matrix, so it is easy to cause stress concentration at the angle of graphite, so that the tensile strength, plasticity and toughness of gray iron is much lower than that of steel, but the compressive strength is the same as that of steel, and it is the most common cast iron. At the same time, the matrix has a certain influence on the mechanical properties of gray cast iron, ferrite matrix Gray cast iron graphite flake, the lowest strength and hardness, so the application is less; the graphite flakes of the pearlite matrix Gray cast iron are small, have high strength and hardness, and are mainly used to manufacture the more important castings The graphite sheet of ferrite-pearlite gray cast iron is slightly thicker than pearlite gray cast iron, and its performance is inferior to pearlite gray cast iron.
Therefore, the industrial use of the pearlite matrix of gray cast iron.
Other performance: Gray cast iron has good casting performance, good vibration damping, good wear resistance, good cutting performance, low notch sensitivity.
factors affecting the performance of gray cast iron Effects of ① chemical constituents. Production is mainly to control the quality of carbon and silicon fractions. Carbon, silicon mass fraction is too low, cast iron easy to appear white tissue, mechanical properties and casting performance are very low; When the mass fraction of carbon and silicon is too high, the graphite sheet is too thick, and even the graphite floats on the surface of molten iron, which reduces the performance and quality of the castings. Therefore, the content of carbon and silicon in gray cast iron is generally controlled in 2%~ 4%c; 1.0%~2.0%si;
0.5%~1.4%mn. The effect of ② cooling rate: Under certain casting conditions, the cooling rate of castings has a great influence on the degree of graphitization. With the increase of wall thickness, the cooling speed slows down and the carbon atom has sufficient diffusion time, it is propitious to the graphitization process and the formation of gray iron structure in room temperature. But the thin-walled parts in the cooling process of cold speed too fast, easy to form deforming tissue.