The mechanical properties of grey cast iron are related to the microstructure of the matrix and the morphology of the graphite. The flake graphite in gray cast iron is severely cracked on the substrate, and it tends to cause stress concentration at the sharp corners of the graphite. The tensile strength, plasticity and toughness of the gray cast iron are much lower than that of the steel, but the compressive strength is equivalent to that of the steel. The worst mechanical cast iron in the piece. At the same time, the matrix structure has a certain influence on the mechanical properties of gray cast iron. The graphite sheet of ferrite matrix gray cast iron is coarse, with the lowest strength and hardness, so it is less applied.
The graphite sheet of the pearlite matrix gray cast iron is small, has high strength and hardness, and is mainly used to manufacture more important castings; the graphite sheet of the ferrite-pearlite matrix gray cast iron is slightly thicker than the pearlite gray cast iron, and the performance is not as good as that of pearlite. grey cast iron. Therefore, the gray cast iron of the pearlite matrix is used more in the industry.
Gray cast iron has good casting properties, good vibration damping, good wear resistance, good cutting performance and low notch sensitivity.
The influence of the chemical composition of gray cast iron. The production is mainly to control the mass fraction of carbon and silicon. The carbon and silicon mass fraction is too low, the cast iron is prone to white mouth structure, and the mechanical properties and casting properties are very low. When the carbon and silicon mass fraction is too high, the graphite flakes are too large and coarse, and even the graphite floats on the surface of the molten iron. Reduce the performance and quality of castings. Therefore, the carbon and silicon contents in the gray cast iron are generally controlled at 2% to 4% C; 1.0% to 2.0% Si; 0.5% to 1.4% Mn.