Ductile Iron is spheroidal graphite obtained through sp […]
Ductile Iron is spheroidal graphite obtained through spheroidization and inoculation, which effectively improves the mechanical properties of cast iron, especially the plasticity and toughness, thus obtaining higher strength than carbon steel.
Ductile Iron Castings, as shaft parts, requires comprehensive mechanical properties with high strength and good toughness, and carries out quenching and tempering treatment on cast iron parts. The process comprises the following steps of: heating iron castings to 860-900 DEG C, keeping the temperature to make the matrix austenite, cooling in oil or molten salt to realize quenching, and tempering at 500-600 DEG C to obtain tempered sorbite structure, wherein the form of the original spherical graphite is unchanged. After treatment, the strength and toughness match well and are suitable for the working conditions of shaft parts.
The annealing heat treatment of Ductile Iron Castings is to improve the overall properties of iron castings. Common heat treatment processes include annealing, normalizing, quenching, etc.
1, annealing: obtaining a ferrite matrix, improving plasticity and toughness, eliminating stress and improving cutting performance.
2. Normalizing: pearlite matrix is obtained to improve strength and wear resistance.
3. Quenching and tempering: obtain the matrix structure of tempered sorbite and good comprehensive mechanical properties, such as main shaft, crankshaft, connecting rod, etc.
4. Isothermal quenching: The parts with complex appearance and high comprehensive performance requirements can obtain the matrix structure of lower bainite, as well as high strength, high hardness, high toughness and other comprehensive mechanical properties to avoid cracking during heat treatment.
As shaft parts, Ductile Castings needs higher hardness. Iron castings are often quenched and tempered at low temperature. The treated Ductile Iron Castings have high hardness and certain toughness, retain the lubricating property of graphite and improve the wear resistance. Therefore, in order to produce high-quality products, the above precautions need to be understood.
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