Common use of ductile iron is in assembly parts for the auto and agricultural industries, such as flanges, gears, hubs, suspension parts, and in the flow control industry, such as for valves, meters and pumps.
Ductile iron is often used as a cost effective alternative to steel castings. Ductile iron improves the resistance to cracking which may occur in gray iron and ductile iron may be able to reduce overall dimensions and mass of a casting without sacrificing performance characteristics. Ductile iron provides high tensile strength, with improved ease of machining, vibration damping, surface hardening, and resistance to damage from impact, corrosion resistance and wear resistance, all at a competitive price. Relative to gray iron, ductile iron provides an improved strength-to-weight ratio, resistance to impact, corrosion and wear resistance, with an improved modulus of elasticity.
Typical ductile iron classes, designated by ASTM A536 are:
Ductile iron castings may be austempered, producing structures of acicular ferrite and high carbon structures, to achieve specific mechanical properties. Austempering is accomplished by maintaining the casting at the quenching temperature for an extended period of time. The casting is then cooled rapidly to avoid formation of pearlite structures.