What are the main properties of ductile cast iron?

　　Ductile iron, a high-strength cast iron material developed in the 1950s, boasts mechanical properties that closely match those of steel. Thanks to its outstanding performance, it has been successfully used to cast complex components requiring high strength, excellent toughness, and superior wear resistance. Today, ductile iron has rapidly emerged as the second most widely used cast iron material after gray iron. The phrase "using iron instead of steel" primarily refers to ductile iron.

　　Ductile cast iron achieves spherical graphite through spheroidalization and inoculation processes, effectively enhancing the mechanical properties of cast iron—particularly improving its ductility and toughness—while also delivering higher strength compared to carbon steel.

　　What are the components of ductile iron?

　　Cast iron is an iron-carbon alloy with a carbon content exceeding 2.11%. Industrial pig iron, scrap steel, and other steel and alloy materials are transformed into cast iron through high-temperature melting and casting processes. In addition to iron, these processes also cause the carbon in cast iron to precipitate out as graphite. If the precipitated graphite forms a flake-like structure, the resulting cast iron is known as gray cast iron; when the graphite appears in a vermicular form, it’s called ductile (or malleable) cast iron; and if the graphite solidifies into a blocky, nodular shape, the cast iron is classified as malleable iron.

　　The chemical composition, aside from ductile iron, typically includes a carbon content of 3.0% to 4.0%, a silicon content of 1.8% to 3.2%, and a total amount of manganese, phosphorus, and sulfur kept below 3.0%. It also contains适量 of spheroidizing elements such as rare earths and magnesium.

　　What are the main properties of ductile cast iron?

　　Ductile iron castings have been applied in nearly every major industrial sector where strength, ductility, toughness, wear resistance, thermal and mechanical shock resistance, performance under high or low temperatures, corrosion resistance, and dimensional stability are critical. To meet these varying application requirements, ductile iron is available under numerous brand names, offering a wide range of mechanical and physical properties.

　　Most ductile iron castings specified by the International Organization for Standardization ISO 1083 are produced primarily in a non-alloyed state. Clearly, this range includes high-strength grades with tensile strengths exceeding 800 newtons per square millimeter and elongation rates of at least 2%. Another category is the high-plasticity grade, characterized by elongation rates above 17% and relatively lower strength (at least 370 newtons per square millimeter). However, strength and elongation are not the primary criteria designers rely on when selecting materials; other critical properties include yield strength, elastic modulus, wear resistance, fatigue strength, hardness, and impact performance. Additionally, corrosion resistance, oxidation resistance, and electromagnetic properties may also be crucial considerations for designers. To meet these specialized application requirements, a unique class of austenitic ductile iron has been developed—commonly known as Ni-1 Resis ductile iron. This type of austenitic ductile iron is primarily alloyed with nickel, chromium, and manganese, and it has now been incorporated into international standards.

　　Pearlite-type ductile iron boasts excellent secondary strength, moderate toughness, high ductility, superior overall performance, wear resistance, vibration damping, and excellent castability. Its properties can be tailored through various heat treatments. It is primarily used in manufacturing key components for power machinery, such as crankshafts, camshafts, connecting shafts, connecting rods, gears, clutch housings, hydraulic cylinder bodies, and other critical parts.