LU83557A1 - IMPROVED PROCESS FOR THE MANUFACTURE OF STEEL - Google Patents

Description

y ^ j i i Γ! I 5 C 2156/8107.

i METALLURGICAL RESEARCH CENTER -! CENTRUM V00R RESEARCH IN DE METALLURGIE,

Non-profit association -Vereniging zonder winstoograerk in BRUXELLES, (Belgium).

Improved process for the manufacture of steel.

The present invention relates to an improved process for manufacturing steel. It is particularly suitable for allowing the continuous casting of said steel, once it has been formed into a retort.

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We know that the quality of a steel which has been continuously cast, depends, among other things, on its oxidation state and on the manner in which it has been deoxidized.

The use of silicon leads to these inclusions which, during lime lamination, lengthen and reinforce the anisctropy of the mechanical properties of the product Other disadvantages well CCT-Π-Ε ££ ΉϋΓΞ · £ &Π; £ βρίΐ X CT B CSt Xci G £: 1EJT. L Γ-. e 3 B E ÉrClC OR

/ during subsequent galvanization. /, - / i / i '- 2 -

In addition, the use of aluminum as dexoydant gives rise to inclusions which easily cause plugging of the pouring cups; it can also lead to the production of steels containing hard Al „0 inclusions detrimental 2 3 to good behavior in service.

Such drawbacks arise, for example, when developing a current steel in retort with top refining, one obtains for the latter, a composition of the order of: C = 50.10 ~ 3% 'Fe = 20% slag 0 = 650 ppm.

Indeed, to allow such a steel to be cast in continuous casting, it is necessary to reduce its oxygen content to values of the order of 5 ppm and less, which requires the use of large quantities of deoxidizers (Al , Si) and therefore has the disadvantages mentioned above.

In order to get around these, we have already imagined finishing a retort ripening with a higher C content in steel (for example 80 or 100.10 “- ·%), a lower slag content in Fe (for example 15 to 16%}, but with a final oxygen content in the steel notably lower, for example 200 to 350 ppm. Such a final oxygen content requires A * obviously less deoxidizer to arrive at the desired 5 ppm * for continuous casting, but it is also necessary to reduce the te-neur in C, which is done er, following the elaboration in, retort of a vacuum treatment precede. ·: adding this deoxy dant and the casting continues. Or. fear, in certain ways, to significantly reduce the content of steel in C and also in oxygen.

This result r.‘is however obtained that at the cost of 1 * operat icr. additional this vacuum treatment, which colt, in the case where the C content of 11 a ci. er appeared i had to link emer.t high, y »/ comocrter in addition an injection not c'cxvçene ocur allow a / -, / / - 3 -»>, sufficient elimination of said carbon.

The subject of the present invention is a process by which a steel with a low final content, both in carbon and in oxygen, can be obtained in retort, the latter being sufficiently low that the corresponding amount of deoxidizing agent to be introduced into the steel before casting it continuously cannot! conduct themselves to the disadvantages of the importance of those mentioned above. In addition, this method makes it possible to save on vacuum treatment.

1%! The process which is the subject of the present invention, in which use is made of a converter allowing the blowing of the cast iron from the top and from the bottom, is essentially characterized in that it is blown from the top and / or from below, an oxidizing gas! can be pure oxvcene, up to this eue the content of steel i, * in C is at most 20.10-Ji%, and in this or 'after the drawdown, it causes an energetic stirring of l steel, by in-suffluting an inert gas from below, such as argon.

I According to the invention, the quantity of oxidizing gas blown in through the bottom of the converter is advantageously between 5 t and 15% of the total blown out.

:: It was found that this way of proceeding made it possible to arrive easily at the end of refining at oxygen contents of λ of the order of 200 ppm. A small addition of it or Si brings this ♦ content to 5 ppm and thus makes possible the continuous casting of this steel, without incurring the drawbacks mentioned above.

In the above-mentioned process, it has been mentioned that the injection of oxygen and argon, but it must be understood that in this, as in the refining process, cr.

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Claims (2)

1. Improved process for the manufacture of steel, in which use is made of a converter allowing the blowing of the cast iron from the top and from the bottom, characterized in that one blows from the top and / or from the bottom, an oxidizing gas which can be pure oxygen, until the steel content in C is at most 20.10 "· ^%, and in this gu 'after the drawdown, this steel is vigorously stirred, by injecting an inert gas, such as argon, from below. 2. Method according to claim 1, characterized in that the amount of oxidizing gas blown in from the bottom of the converter is between 5% and 15% of the total blown out. Drawings: - ^ - piencte. · * ____ .. • 5 f rz £ 1 £ r,. T l. p; 3CSS - "-. 'T'" ___ r _3 ~. :? ^ r_ „..... λ - - -;: r- - - - - - r * J 6