SK5082000A3 - Apparatus and method for the secondary refinement of metals - Google Patents

Abstract

Apparatus for use in the secondary refinement of a metal, particularly steel, is disclosed, which includes an elongated vessel (10) of which the length to width ratio is greater than 2, the vessel (10) being provided with at least one channel type inductor (13) adapted for heating the vessel (10), and the vessel (10) being adapted in operation to be located with its long side substantially horizontally disposed. The invention also includes a method of refining a metal such as steel, using the aforesaid apparatus.

Description

Technical field

The present invention relates to an apparatus and method for performing secondary refining of metals, in particular steel.

BACKGROUND OF THE INVENTION

In the steel industry, steel ladle furnaces are used to a large extent to control the temperature of the steel fed from the steelmaking furnace and to refine it before casting it into a continuous casting plant. In such a refining process, steel ladle furnaces are arranged below the lid and an electric arc heating is applied to the surface of the molten steel in the ladle, while at the same time the molten steel is bubbled with argon to distribute heat throughout the metal.

By introducing fluxes such as quicklime, aluminum oxide, silicon oxide and the like into the steel, a slag layer is formed which floats on the steel surface.

The aforementioned bubbling of steel with argon is usually effected by blowing such gas through one or more porous elements expediently disposed at the bottom of the ladle. Said argon bubbling is necessary to ensure satisfactory conditions of volume concentration and heat transfer between steel and slag. In some cases, electromagnetic stirring may be used to provide additional additional benefits.

Steel ladles are vertically arranged cylindrical vessels, the depth / diameter ratio of which is usually greater than 1 and less than 2. It is understood that one of the main reasons for the vertical arrangement of such vessels is the effort to achieve the minimum specific surface of the bath and the resulting energy conservation. in a metal bath volume.

The expedient positioning of the aforementioned porous elements in such containers is also important in order to obtain the best possible mixing effects. In addition, it is also known that the use of containers with smaller size depth / diameter ratios results in poorer mixing ratios, and that such shallow containers, for example oxygen containers with basic lining, require the arrangement of several such porous elements to achieve efficient mixing.

A further disadvantage found in connection with such a vertically disposed container is that the surface to volume ratio of the metal bath in the container is relatively small.

In addition, since to minimize metal leakage during agitation, the vessel must be reasonably maintained above the bath surface, removing the slag from impregnation from such a vessel is difficult to remove. In the case where the slag removal is performed, for example, by tilting the container, the specific surface of the metal / slag bath increases, thereby reducing the thickness of the slag layer. In addition, in arrangements in which a scraper blade is used to pull the slag towards the edge of the container, the substantially circular configuration of the surface of the slag layer constitutes a limitation on the width of the blade in that the blade is wide enough to span the entire width. the slag layer near the edge of the container is too narrow in width at a position farther away from the edge, and in this state allows the slag to escape around its ends.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention to provide an apparatus and method for performing secondary refining of metals, in particular steel, through which the aforementioned deficiencies are either completely eliminated or at least reduced to a minimum.

The apparatus of the present invention for performing secondary refining of metals, in particular steel, comprises an elongate vessel having a length / width ratio greater than two, the vessel being equipped with at least one channel type inductor adapted to heat the vessel and in operation it is positioned such that its longer side is substantially horizontal.

It must be understood that although the container is arranged horizontally, the size ratio of the metal / slag bath will be within the container, i. a ratio of the length of the bath surface area to the width of the bath surface area, greater than two. In addition, it must be understood that the specific surface area of such a metal / slag bath will be much larger compared to a conventionally used vertically arranged vessel so as to provide a much larger contact area for reaction with the additive chemicals introduced into the bath for secondary metal refining and / or or removing sulfur from the metal bath and / or interacting between the metal bath and the slag layer thereon.

Furthermore, according to the present invention, the device is provided with at least one inductor which is arranged substantially in the central region of the underside of the horizontally arranged vessel.

It has been found by the Applicants that the fact that the bath in such a vessel is heated from the bottom in combination with the facts regarding the existence of a relatively low metallographic pressure height of the metal together with the resulting effect of heat transfer ensures that sufficiently agitating effects of mixing near the inductor (or inductors) resulting in a highly efficient interaction at the slag / metal interface and an even distribution of the refined metal and the impurity saturated slag.

In addition, the fluxes and alloying agents required for the refining process may be fed in a semi-gas stream to the surface of the metal bath directly into the region above the inductor (s), i.e. the inducer (s). to the area where the most efficient mixing movement is achieved.

It will be appreciated that any such fluxes and similar additives that are required for refining a metal bath can be fed into the metal bath by the same standard procedure by means of one or more inlet pipes passing through and passing into the metal bath.

In addition, any additional or required heating may be accomplished using standard means, for example by means of one or more plasma torches and / or electrodes for producing an electric arc powered by a three-phase current.

Further, according to the present invention, the vessel has a circular configuration in cross-section.

Still further, according to the present invention, the vessel is provided with an opening towards at least one of its shorter ends through which a bucket or the like can be inserted to sweep the slag waste from the surface of the metal bath in the vessel.

It will be appreciated that a scoop that substantially spans the entire width of the slag layer over substantially the entire length of the slag layer may be used for slag raking because the surface of the slag layer has a substantially rectangular configuration in plan view.

By shifting or contracting such a blade along the slag layer, the waste slag can be removed in a highly efficient manner from the surface of the metal bath.

For the purpose of removing waste slag, at least one of said shorter ends of the container may be provided with a tap-hole.

Preferably, the width of the vane is slightly less than the width of the container so that narrow clearance gaps remain between the outer ends of the vane and the container walls to ensure free, unrestricted movement of the vane in the container.

Advantageously, air or nitrogen may be blown into these passage gaps to prevent slag from escaping through the gaps during displacement of the vane along the slag layer in the vessel.

The present invention further relates to a method of performing secondary metal refining using the apparatus described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The apparatus of the present invention will be further elucidated by way of a detailed description of one exemplary embodiment thereof in conjunction with the accompanying drawings, in which FIG. 1 is a schematic side view of a device according to the present invention;

Fig. 2 is a schematic view of the device of FIG. 1 in cross-section taken along line I-I in FIG. 1; and FIG. 3 is a schematic view of the device of FIG. 1 in a plan view in the direction of the arrow A of FIG. First

DETAILED DESCRIPTION OF THE INVENTION

Apparatus for performing secondary refining of metals, such as steel, according to a preferred embodiment of the present invention, comprises a horizontally arranged and refractory liner equipped with a vessel 10 whose length / diameter ratio is greater than 2. For example, according to one embodiment of the present invention the length of the vessel 10 of the order of 8 m and the diameter of the vessel of the order of 2 m, it being assumed that the vessel will be filled with molten metal to a height of the order of 1 m.

It will be appreciated that although the container 10 shown in cross-section has a circular configuration, such a container may be formed with any other and suitable cross-sectional configuration, such as substantially square, triangular, and the like.

The container 10 is provided on its top wall with a filling opening 12 through which fluxes and similar additives can be introduced. The vessel 10 is further equipped, in the central region of its underside, with at least one 3 MW channel-type inductor 13.

In addition, the top wall of the container 10 at its opposed ends is provided with apertures 14 through which an elongated-shaped blade 15 designed to retract the slag, which is operated by the handling handle 16 and whose width is slightly smaller than the diameter, can be introduced into the container. containers 10.

The apertures 14 are provided with hatches (not shown).

The vessel 10 is further provided with a lead-in tube 17 which is guided from above and passes into a metal bath T1 and through which argon and / or nitrogen can be blown into the bath 11 for stirring purposes.

In addition, if desired, the vessel 10 may further be provided with one or more porous elements through which argon and / or nitrogen may be introduced into the vessel to additionally promote mixing of the bath T1. In FIG. 1, only one such element, indicated by 18, is shown in broken line.

In operation, the molten metal to be refined is fed into the vessel 10 through an opening 14 to form a bath with a depth of the order of 1 m, and the desired fluxes are charged through the feed opening 12.

The inducer (s) 13, when actuated, serve not only to heat the bath 11, but at the same time, through the resulting effect of heat transfer and electromagnetic forces, also to induce agitation of the bath U.

If desired, the aforementioned mixing may be supplemented by blowing argon and / or nitrogen into the bath 11 via the lance 17 (or porous element (s) 18).

As a result of the melting of the fluxes and their interaction, a slag layer 19 is formed on the surface of the metal bath 11, which subsequently acts on and influences the molten metal in the bath T1.

Since, due to the horizontal arrangement of the vessel 10, the specific metal / slag bath surface exhibits the aforementioned size ratio, and since the bath 11 is heated mainly from below, it will be appreciated that all advantages related to the above mentioned chemical refining efficiency of the metal and mixing of the bath can be achieved precisely using the apparatus of the present invention.

When the waste slag layer 19 has to be removed from the container 10, a paddle 15 is inserted into the container through one of its openings 14, and the slag layer 19 is swollen and pushed through the tap holes (not shown) at the outer ends of the container 10.

The width of the vane 15 is slightly smaller than the diameter of the transverse cross-section of the container 10 such that when the vane 15 engages the slag layer 19, narrow clearance gaps 20 remain between the outer ends of the vane 15 and the inner side walls of the container 10. the vanes 15 in the interior of the container 10.

The blowing of air or nitrogen into the passage gaps 20 serves to prevent slag from escaping from the slag layer 19 through these gaps 19 during said movement of the blade 15.

It must be understood that the described arrangement completely overcomes or at least reduces to a minimum the above-mentioned disadvantages of removing the waste slag layer from the container.

In addition, it must be understood without any doubt that various variants of the individual detailed components of the apparatus and method for performing secondary metal refining according to the present invention can be made without departing from the spirit and / or claimed scope defined in the appended claims. claims.

Claims (13)

PATENT CLAIMS Apparatus for performing secondary refining of metals, in particular steel, comprising an elongated vessel having a length / width ratio greater than two, said vessel having at least one channel type inductor adapted to heat the vessel, and in operation, the container is positioned such that its longer side is substantially horizontal. Device according to claim 1, characterized in that the at least one inductor is arranged substantially in the central region of the underside of the horizontally arranged vessel. Apparatus according to claim 1 or 2, characterized in that the vessel comprises at its upper end an opening through which any flux can be introduced in the semi-continuous flow to the surface of the metal bath, substantially directly into the area above the inductor (s). and alloying additives required for the refining process. Apparatus according to any one of the preceding claims, characterized in that it comprises at least one inlet pipe directed from above and passing into a metal bath by means of which fluxes and / or alloying additives can be introduced into the bath. Apparatus according to any one of the preceding claims, characterized in that it comprises at least one lance or porous mixing element by means of which argon and / or nitrogen can be blown into the bath to induce supplementary mixing. Apparatus according to any one of the preceding claims, characterized in that it comprises at least one plasma torch and / or an electrode for generating an electric arc, fed by a three-phase current, to induce additional or possibly required heating. Device according to any one of the preceding claims, characterized in that the container has a circular configuration in cross-section. Apparatus according to any one of the preceding claims, characterized in that the receptacle is provided with an opening towards at least one of its shorter ends, and that the apparatus comprises a vane which can be inserted into said receptacle through said opening and removed therefrom from the metal bath surface. waste slag. Apparatus according to claim 8, characterized in that the width of the blade is slightly smaller than the diameter of the vessel cross-section so that, when the blade is engaged in the slag layer between the blade ends and the inner walls of the vessel, narrow passage gaps are formed. container. Apparatus according to claim 9, characterized in that it is adapted to blow air and / or nitrogen into said passage gaps, which serve to prevent slag from escaping through these gaps during movement of the blade along the slag layer. Apparatus according to any one of the preceding claims, characterized in that at least one of the shorter ends of the vessel is provided with a tap hole through which waste slag can be removed from the vessel. Device according to any one of the preceding claims, characterized in that the metal to be treated is steel. Method for carrying out secondary refining of metals, in particular steel, characterized in that it is carried out using a device according to any one of the preceding claims.