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- proeutectoid, having in structure superfluous ferrite.,
- eutectoid which structure consists of a pearlite.,
- hupereutectoid in which structure there are the secondary carbides which are
allocating from austenite.,
- ledeburite which structure contains primary carbides.,
- austenitic.,
- ferrite
After normalization of steel subdivide into the following structural classes:
- pearlite.,
- austenitic.,
- ferrite.
Formation of structure of steel is influenced most by carbon.
Classification by direction
.
By classification steel share on three groups:
- constructional steel, intended for manufacturing of details of cars and elements
of construction designs which are subdivided on:
- ordinary quality.,
- the improved.,
- the carburizing.,
- the automatic.,
- the high-strength.,
- the spring roll.
- tool steel, subdivide into subgroups on manufacturing:
- the cutting tool.,
- measuring tool.,
- Stamping-pressure equipment.
- steel of a special purpose with special physical and mechanical characteristics:
- the corrosion-proof.,
- the heat resisting.,
- the heat proof.,
- the wear-resisting.
Classification by quality.
On quality of steel classify on:
- ordinary quality, contain to 0,06 % of sulfur and 0,07 % phosphorus.,
- qualitative sulfurs containing to 0,035 % and 0,035 % of phosphorus.,
- the high-quality - no more than 0,025 % are gray and 0,025 % of phosphorus.,
- the especially high-quality - no more than 0,015 % are gray and 0,025 % of
phosphorus.
Quality is understood as set of properties of the steel defined by metallurgical
process of its production. Uniformity of a chemical composition, a structure and
properties of steel depend on the content of harmful impurity and gases.
Classification by de-oxidation level.
The steel classify on the
level of the de-oxidation
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- the killed steel,
- the semi-killed steel.,
- the rimming steel.
De-oxidation is named the process of removal of oxygen of liquid steel.
Keeled steel deoxidize with manganese, aluminum and silicon in the melting
furnace and a ladle. They harden in a mold quietly, without gas evolution, with
piping in the top part of ingots of a shrinkable sink.
Rimming steel deoxidize only with manganese that isn't enough. Before
casting they contain increased amount of oxygen which when hardening ingot
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