Deoxidized steel

Source: Wikipedia, the free encyclopedia.

Deoxidized steel (Also known as killed steel) is

deoxidizing agents
to the melt either before or after it is tapped, or by vacuum treatment, in which carbon dissolved in the steel is the deoxidizer.

Elements used for deoxidizing steel

Aluminium, silicon, and manganese are the most widely used elements for the deoxidation of steel.[1] Usually, aluminium is added in the form of pellets or wire, while silicon and manganese in the form of ferroalloys. The reaction products obtained following the deoxidation of the liquid steel bath are respectively alumina, silica and manganese oxide:

2 Al + 3 O → Al2O3
Si + 2 O → SiO2
Mn + O → MnO

The products of the deoxidation reaction are distributed within the slag produced by the steel deoxidation treatment. The slag can be skimmed off, therefore removing the dissolved oxygen from the liquid steel bath.

Types

There are four types, ranging from fully deoxidized to slightly deoxidized: killed, semi-killed, rimmed, and capped.[2] Note that none of the various types are better than the other as each is useful in its own regard.[3][needs update]

Killed steel

Killed steel is steel that has been completely deoxidized by the addition of an agent before

gas porosities. The steel is said to be "killed" because it will quietly solidify in the mould, with no gas bubbling out. It is marked with a "K" for identification purposes.[4]

For

heat treatments. For steels of the same grade a killed steel will be harder than rimmed steel.[5]

The main disadvantage of killed steel is that it suffers from deep

hot top. Typical killed-steel ingots have a yield of 80% by weight.[3][needs update
]

Commonly killed steels include alloy steels,[4] stainless steels,[4] heat resisting steels,[4] steels with a carbon content greater than 0.25%, steels used for forgings, structural steels with a carbon content between 0.15 and 0.25%, and some special steels in the lower carbon ranges.[5] It is also used for any steel castings.[6] Note that decrease in carbon content increases the problems with non-metallic inclusions.[7][needs update]

Continuous casting and strip-casting technologies have largely superseded ingot casting techniques in recent times. Through these methods, all steel is killed and the resulting yields are close to 96%.

Semi-killed

Semi-killed steel is mostly deoxidized steel, but the carbon monoxide leaves blowhole type porosity distributed throughout the ingot. The porosity eliminates the pipe found in killed steel and increases the yield to approximately 90% by weight. Semi-killed steel is commonly used for structural steel with a carbon content between 0.15 and 0.25% carbon, because it is rolled, which closes the porosity. It is also used for drawing applications.[4][8][needs update]

Characteristics of SEMI KILLED steels.

  • Structural steels containing 0.15 to 0.25% carbon are generally semi-killed.
  • In semi-killed steel, the aim is to produce metal free from surface blowhole and pipe.
  • The surface should have a sound skin of considerable thickness.
  • They are used for general structural applications.
  • During solidification of semi-killed steel, gas is evolved in the body of the ingot, tending to compensate in part or entirely for the shrinkage accompanying solidification.
  • Since pipe cavities are minimized, semi-killed steels are usually cast in big-end-down molds without hot-tops.
  • This type of steel is suitable for drawing operation (except severe drawing).

Rimmed

Rimmed steel, also known as drawing quality steel, has little

hot-working applications.[4][6][8][needs update][10]

Capped

Capped steel starts as rimmed steel but part way through the solidification the ingot is capped. This can be done by literally covering the ingot mold or by adding a deoxidizing agent. The top of the ingot then forms into a solid layer of steel, but the rim of the rest of the ingot is thinner than in a rimmed steel. Also there is less segregation of impurities.[8][needs update]

The yield of rimmed and capped steel is slightly better than that of semi-killed steel. These types of steels are commonly used for sheet and strip metal because of their excellent surface condition.[8][needs update] It is also used in most cold-working applications.[6]

Due to production processes, as the carbon content of rimmed and capped steel increases above 0.08%, the cleanliness decreases.[11][needs update]

See also

  • Decarburized steel

References

  1. ^ Henderieckx, Staf. "Deoxidizing of Steel" (PDF). Gietech B.V.
  2. ^ Types of Steel according to deoxidation practice, archived from the original on 2009-05-01, retrieved 2010-02-06.
  3. ^ a b American Institute of Mining and Metallurgical Engineers 1951, p. 52.
  4. ^ a b c d e f Types of steel according to deoxidation practice, archived from the original on 2009-05-01, retrieved 2010-02-28.
  5. ^ a b Steels - Killed Steels, 2002-10-14, retrieved 2009-11-17.
  6. ^ a b c Carbon steel, archived from the original on 2010-01-07, retrieved 2010-02-28.
  7. ^ American Institute of Mining and Metallurgical Engineers 1951, p. 58.
  8. ^ a b c d American Institute of Mining and Metallurgical Engineers 1951, p. 53.
  9. ISBN 978-0-278-00057-5
    .
  10. ^ Basics of Arc Welding, archived from the original on 2010-03-04, retrieved 2010-02-28.
  11. ^ American Institute of Mining and Metallurgical Engineers 1951, pp. 57–58.

Bibliography

Retrieved from "https://en.wikipedia.org/w/index.php?title=Deoxidized_steel&oldid=1161423923"