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PD ISO TR 945-3:2016 pdf free

PD ISO-TR 945-3:2016 pdf free.Microstructure of cast irons – Matrix structures
Acicular ferrite is a microstructure of ferrite that is characterized by needle shaped crystallites or grains when viewed in two dimensions. The grains, actually three dimensional in shape, have a thin lenticular shape. This microstructure is advantageous over other microstructures because of its chaotic ordering, which increases toughness.
Ausferrite is a special type of multi-phase microstructure that occurs when cast irons with a silicon content of about 2 % or higher are austempered.
Austempering consists of rapidly cooling the fully austenitic iron to avoid the formation of pearlite to a temperature above that of martensite formation and holding for the time necessary to precipitate the ausferrite matrix. This microstructure consists primarily of acicular ferrite in carbon enriched austenite.
Bainite is a multi-phase microstructure, consisting of acicular ferrite and cementite that forms in cast irons during rapid cooling. It is one of the decomposition products that can form when austenite is cooled rapidly below the eutectoid temperature, but above the martensitic starting (M3) temperature. Bainite can also form from the decomposition of ausferrite upon extended heating above the temperature at which it was formed.
In the iron-carbon system cementite is a common constituent because ferrite contains maximum 0,02 % by mass of carbon. Therefore, in cast irons that are slowly cooled, a part of these elements is in the form of cementite. In the case of white cast irons, cementite precipitates directly from the melt. In grey cast irons or spheroidal graphite cast irons, cementite forms either from austenite during cooling or from martensite during tempering, or from the decomposition of ausferrite. An intimate mixture of cementite with ferrite, the other product of austenite, forms a lamellar structure called pearlite (see 2..2).
The location from which samples are taken should be agreed between the manufacturer and purchaser and should take into account the requirements specified in the appropriate material standard. If an examination report is required, the location from where the final sample is taken shall be recorded.
The sample should be of sufficient size to provide a true representation of the matrix structure in the agreed location from which it is taken.PD ISO TR 945-3 pdf free.

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