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I. Strengthening of graphite cast iron fineness-inoculation treatment
In order to refine the structure of gray cast iron and improve the mechanical properties of Si-Ba inoculant cast iron to make it uniform, generally a small amount of inoculant is used to improve the quality of cast iron. This process is called incubation process. Add hot metal. The breeding gray cast iron is called breeding cast iron.
The inoculant often used is an iron alloy containing 75% Si. According to the strength of the casting, the inoculant is added in an amount of about 0.2% to 0.5%. Its role is to promote the non-spontaneous nucleation of graphite. Therefore, the inoculated cast iron structure is a fine pearlite matrix, and the fine graphite is evenly distributed. Its tensile strength can reach 300-400MPa, hardness can reach HB170-270, αk can reach 3-8 Jcm2, and elongation can reach about 0.5%, which are all higher than ordinary gray sieve cast iron.
Second, graphite spheroidizing strengthening of cast iron-spheroidizing treatment
1. Production of ductile cast iron
Ductile iron is referred to as ductile iron. Ductile iron is made by spheroidizing and nurturing molten iron with gray components.
2, the structure and performance characteristics of ductile iron
Graphite in spheroidal graphite cast iron is spherical, with little damage to the substrate, and the strength utilization of the substrate can reach 70% -90%. After being heat treated, spheroidal graphite cast iron can fully exert the potential performance of the substrate, and has good mechanical properties. Up to 150x107Nm2, elongation up to 25%, and high yield, αk can reach 8-15Jcm2.
3. Ductile iron grade, chemical composition and application
According to Chinese standards, ductile iron is divided into eight grades, of which "QT" is the Chinese pinyin prefix of the two words ductile iron, followed by two numbers indicating low tensile strength and low elongation.
Ductile iron has the above-mentioned excellent mechanical properties. Sometimes it can replace carbon steel for heavy-duty, complicated structure parts. Such as automobile, tractor crankshaft, connecting rod, camshaft and other commonly used pearlite ball heads, can also be used as working cylinders, cylinders, pistons and other large hydraulic machines, ferritic ductile iron is mainly used for the production of pressure valves, rear axle vehicles Bearings, etc. use.
The above is the way to improve the performance of Si-Ba inoculant cast iron in this issue. Follow us and learn more about inoculants!