Explanation

Add spheroidizing agent and inoculant for treatment. cast iron in which graphite is mainly spherical. It is called ductile iron for short. Common spheroidizing agents include magnesium and its alloy, rare earth, etc. When there are anti spheroidizing elements such as Bi, Ti, Cu, Pb, etc. An appropriate amount of rare earth should be added as a spheroidizing agent. The inoculant is 75% ferrosilicon. Rare earth ferrosilicon also has a certain inoculation effect. As graphite is spherical, its adverse effect of weakening matrix and causing stress concentration is significantly reduced, its strength is high (tensile strength up to 1200MPa) and has good toughness. Nodular cast iron can be subjected to various heat treatment to improve its matrix structure. According to the type of matrix structure, nodular cast iron can be divided into ferrite nodular cast iron, pearlite nodular cast iron and bainite nodular cast iron. The grade of ductile iron (GB/T1348-2009) is QT followed by tensile strength value and elongation value (such as QT500-7 for ductile iron with tensile strength greater than SOOMPa and elongation greater than 7%). The castability of nodular cast iron is better than that of cast steel. The mechanical properties are obviously better than that of ordinary cast iron and close to that of steel. Low production costs and prices. Therefore, it is widely used to manufacture mechanical parts with complex stress and high requirements for strength, toughness and wear resistance, such as crankshaft, gear, engine cylinder liner, automobile chassis parts, etc.

Classification