Classification by structure.
The steel structure - less steady classification sign as depends on speed of
cooling (thickness of the casting wall), degree of an alloying, a mode of heat
treatment and other changing factors, but structure of the finished article allows
to estimate its quality objectively.
Steel on structure classify in conditions after annealing and normalization.
In the annealed condition of steel subdivide on:
190
- 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
191
- 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
Достарыңызбен бөлісу: |