What are the advantages and disadvantages of spheroidal graphite cast iron?
Therefore, ductile iron pressure containing parts are treated with a ferritizing annealing cycle, the globular structure of ductile iron internal can also eliminate the crack phenomenon of iron easy to produce graphite flakes within the. In microscopic photographs of ductile iron, cracks can be seen and terminated after the parade of graphite balls. In the ductile iron industry, these graphite balls are called "crack terminator" because they have the ability to prevent fracture.
As a substitute for steel, man developed ductile iron in 1949. The carbon content of cast steel is less than 0.3%, while that of cast iron and ductile iron is at least 3%. The low carbon content in cast steels makes the carbon free of graphite free of structural flakes. The natural form of carbon in cast iron is the form of free graphite flakes. In ductile iron, the graphite flakes change into tiny spheres by special treatment. The improved sphere makes ductile iron more superior in physical properties than cast iron or steel. It is the globular microstructure of this kind of carbon that makes ductile iron more ductile and impact resistant, while the thin form of cast iron causes the cast iron to be free of ductility. The best ductility can be obtained by ferrite matrix.
Compared with cast iron, ductile iron has an absolute advantage in strength. The tensile strength of ductile iron is 60K, while the tensile strength of cast iron is only 31k. The yield strength of ductile iron is 40K, while the cast iron does not show yield strength, and eventually breaks. The strength to cost ratio of ductile iron is far superior to that of cast iron.
