Alloys or metallic compositions – Containing over 50 per cent metal but no base metal
Patent
1990-11-09
1991-08-06
Dean, R.
Alloys or metallic compositions
Containing over 50 per cent metal but no base metal
420578, 420581, C22C 3500
Patent
active
050376098
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to metallurgy and has specific reference to the materials for refining steel of multi-purpose application.
BACKGROUND OF THE INVENTION
Steel of multi-purpose application is a term used in reference to the steel of the following composition, % by mass:
______________________________________ carbon 0.05-0.5
manganese 0.25-2
iron the balance.
______________________________________
Steel of multi-purpose application may also contain (% by mass) such elements as:
______________________________________ silicon up to 0.6
aluminium up to 0.08
chromium up to 2
vanadium up to 0.2
titanium up to 0.2.
______________________________________
The presence of other elements is not excluded as well.
In world steelmaking practice, confined to the ladle are now the following operations: alloying, desulphurisation, modification and the removal on nonmetallic inclusions, degassing, i.e. the reduction of oxygen, nitrogen and hydrogen content.
The alloying and refining are carried out in succession. The steel is alloyed by adding various ferroalloys and then it is refined by such techniques as the application of vacuum or the introduction of powdered material with the aid of a jet of an inert gas.
Considerable heat losses are involved during each operation of alloying and refining. To compensate for the losses, the metal must be overheated in the furnace and tapped at a temperature above normal or it must be heated up in the ladle, using certain means.
However, both ways are irrational in the making of steel for multi-purpose application. Firstly, an increase in the solubility of oxygen at high temperatures results in a higher than normal oxidation of the metal. This calls for using more deoxidisers which contaminate the steel by the nonmetallic inclusions resulting from the reaction and impair product quality. Secondly, the extra heating up with special means adds to the costs, for such means must be purchased and installed, and also extends the period of treatment, reducing plant capacity.
All in all, the cost of steel rises--a fact which is not justifiable as far as the production of steel for multi-purpose application is concerned.
Known in the art is a material for the refining of molten metal (EP, A1, 0192090) which has a composition (% by mass) as follows:
______________________________________ silicon 40-80
titanium 10-20
magnesium 1.5-3
calcium 0-0.5
aluminium 0-2
rare-earth elements
0-2
iron the balance.
______________________________________
However, the known material is ineffective in removing sulphur and nonmetallic inclusions, for the percentage of the oxygen dissolved in the molten metal is low.
The content of reactive agents, i.e. deoxidisers--aluminium, magnesium, calcium and rare-earth elements--which are also strong desulphurising additives and strong modifiers of nonmetallic inclusions, is low in the known material. The available deoxidisers effectively eliminate the oxygen dissolved in the molten metal when the known material is added thereto but they appear to be in short supply for the desulphurisation and modification to take place.
Apart from that, the titanium which is present in the known material for refining forms high-melting oxides. Rising to the surface, these oxides render the slag more viscous and less effective as the sorbent of sulphur and nonmetallic inclusions. These unwanted substances remain in the metal, impairing the quality thereof.
The known refining material, if used as the source of alloying elements reduced form oxides contained therein, is of no avail in producing metal of a conditioned composition. The silicon contained in the known refining material has a high affinity for oxygen but it is also a reducing agent of a strength inferior to that of aluminium, magnesium and calcium. Therefore, the reaction yields acidic oxides of silicon which increase the viscosity of the slag and reduce the reactivity of the alloying element contained in the slag. This has an adverse effect on the reduction of all
REFERENCES:
patent: 963345 (1910-07-01), Willson et al.
patent: 4162159 (1979-07-01), Peregudov et al.
Kolpakov Vasily S.
Nakonechny Anatoly Y.
Tolymbekov Manat Z.
Vyatkin Jury F.
Zaitsev Alexandr J.
Dean R.
Ip Sikyin
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