LU82305A1 - PROCESS FOR DESULFURIZING A FUSED METAL - Google Patents

Description

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The present invention relates to an improvement relating to a process for the desulfurization of a molten metal, in particular of pig iron.

It is believed that an easy and convenient process is important for the use of a desulfurization agent for molten metals. As desulphurizing agents most suitable for use in a presetting process, mention will be made of those of the type of alkali metal oxides which are fast reacting and have a low melting point in the form of slag, i.e. agents such as sodium carbonate, caustic soda, potassium carbonate and caustic potash or their mixtures with small amounts of calcium fluoride, sodium fluoride, iron oxide, aluminum fluoride , sodium aluminum fluoride, potassium aluminum fluoride and magnesium fluoride.

Known desulfurization agents such as lime, calcium carbonate, nitrogen lime and metallic magnesium are not suitable for the desulfurization operation by the presetting process because they react too slowly or too quickly and that 'They must be added to the hot melt using a large device, so they are not economical desulfurization agents. In the case of the use of a desulfurization agent of the type of an alkali metal oxide, a desulfurization reaction of a molten metal is theoretically carried out in the joint presence of a reducing element. In other words, from the reaction formula it can be assumed that a free alkali metal is formed from the alkali oxide by means of reducing agents such as carbon, silicon, aluminum , magnesium titanium and zirconium, to then bind to the sulfur content 3 ί _ tr j -_______ _ i * r -n -i 3 __ * t _ \ metal. From the phase diagram of a Fe-Al alloy, it is obvious that aluminum is precisely the element which is fusible in cast iron and which is most likely to exert a desulfurizing action until its extinction. On the other hand, magnesium which is a highly reactive metal, melts in a smaller quantity in the cast iron, so that its reactivity is appreciably lower. In addition, when used for the desulphurization of pig iron, aluminum offers an advantage in that it does not reduce the basicity of the slag, so that the desulphurization reaction takes place continuously under the same conditions.

The object of the present invention is to provide a desulfurization agent which is best suited to the presetting process, the implementation of which is easy and convenient for the desulfurization of molten metals, in particular of pig iron, as well as a process. suitable for the addition of this desulfurization agent. In other words, the desulfurization process consists either of previously melting aluminum in the molten pig iron to then react it with a desulfurization agent, or of simultaneously incorporating the aluminum and the desulfurization agent for molten pig iron. However, aluminum is preferably added to the molten pig iron before the desulfurization agent.

As the desulfurization agent of the type of an alkali metal oxide which exerts the desired effects for the presetting process, any type of powder is used in the form of a powder, grains, mass or flakes. anhydrous substance, hydrate and hydrogen carbonate of one or more elements chosen from the group comprising potassium carbonate, sodium carbonate, caustic soda, caustic potash and sodium potassium carbonate. In addition, \ or a mass, it can be added with a small amount of an organic binder such as starch, dextrin, glue, a natural resin or a synthetic resin, or a binder inorganic such as cement, water glass, clay, colloidal silica or aluminum phosphate.

The metallic aluminum in the form of a mass, of grains or of a granulated powder element is charged or introduced into the hot molten mass but, in order to delay the reaction, provision may be made, at the external periphery of this mass , of these grains or of this granulated element, a receptacle, a coating or a support made of a material which may not exert a contrary influence on the refractory interior wall of the container containing the hot molten mass or on it.

In the desulfurization process according to the present invention, a desulfurization agent of the type of an alkali metal oxide, as well as metallic aluminum, are either mixed just before use, or loaded simultaneously in the form of separate packages. Alternatively, a process can be adopted in which the hot molten mass is poured after having previously introduced metallic aluminum into a treatment vessel, while a desulfurization agent of the type of an alkali metal oxide is then charged and added to the casting stream, in the middle of the casting process of the melt. The utilization ratio between metallic aluminum and the total weight of the desulfurization agent is from 1 to 301 by weight. With an amount of metallic aluminum of less than 1%, the reducing action does not influence the desulphurizing agent while, with an amount greater than 30¾, the amount of the desulphurizing agent decreases, so that the latter must be used in large quantities. As a result, aluminum oxide is produced in an amount such that the fluidity of - s - \

The desulfurization process of the invention will be described below by comparative examples.

In each of these examples, the effects of desulphurization exerted by the addition and absence of addition of aluminum are compared using pig iron of the same composition, as well as a ladle of hot metal the same capacity and by adopting a preset process. The capacity of this hot metal ladle is 250 tonnes, while 240 tonnes of molten pig iron are poured into this ladle by means of a mixing trolley, so as to carry out a desulphurization treatment.

From these examples, it will be understood that the desulfurization agent used in conjunction with metallic aluminum provides a desulfurization greater by 5 - 12¾ than that of the agent used alone. J

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Claims (3)

1. Desulfurization process for molten pig iron, characterized in that it consists in using jointly with i a desulfurization agent of the type of an alkali metal oxide, tii * of metallic aluminum in an amount ranging from 1 to 301, calculated on the total weight of this agent. 2. Desulphurization process according to claim 1, characterized in that the desulphurizing agent and the metallic aluminum are introduced beforehand into a treatment container before the hot metal is poured. 3. Desulfurization method according to claim 1, characterized in that the metallic aluminum is introduced beforehand into the treatment container before the hot metal is poured, while the desulfurization agent is added to the casting stream of the latter. Drawings: - p.nr.ches% çznor dent ... ri ......... r ^ e de garde S d -? CnDtior, .... / ..... .... description c —- Charles München »Y