LU82090A1 - COMPOSITE FOUR YARN FOR THE INTRODUCTION OF ADDITIVES INTO A METAL BATH - Google Patents

Description

Composite cored wire

The present invention relates to a composite cored wire intended for the introduction of additives into metal baths.

The technique of introducing treatment or alloying additives into metal baths, via cored wires, the core of which consists essentially of the additive itself, has been found to be; effective and therefore gaining popularity.

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It is known to introduce into a metal bath a wire, consisting of a core of Fe, Al, Ca, Ni, Mo, Mg, Ti or their 'alloys and an outer metal sheath containing various powdery or granular additives . By using such a cored wire, it is possible to double the effect of a deoxidation of an alloying effect.

However, this introduction technique is not free from technological problems. Thus, according to the shaping 20 of the cored wire there is the risk of a flow or alteration of the additive incorporated in the sheath.

In order to extend said technique to metallurgical applications, such as for example the treatment of metal baths with mixtures of rare earths (Ce, Pr, Nd), means * have been developed which make it possible to ensure that d on the one hand the expensive additive that is the mixture of rare earths does not undergo during its entanglement any oxidation and that on the other hand it is possible to store the shaped cored wire, without there being any alteration 30 due to the conditions prevailing in general in steelworks.

Thus the applicant has described in Luxembourg patent no. 80.118 a metallic cored wire which is waterproof and which also has a high ratio of the volume of the core, therefore of additive, to that of the sheath.

This cored wire which allows the lengths to be reduced to be reduced

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- 2 - for storing a given quantity of additive essentially comprises a metallic sheath, constituted by a thin strip whose edges are curved so that it forms a profile of substantially circular cross section, as well as an enclosed additive inside the sheath. Inside the sheath is a metal sheet with a semicircular profile which, by its curved edges, touches the sides of the sheath and which overlaps the additive so that the center of the sheet lies substantially below the region where the edges of the sheath approach. This sheet has a fold oriented towards the core of the wire and protects the additive when the edges of the sheath are closed by welding.

A wire which makes it possible to further increase the additive / metal sheath ratio has been described by the applicant in Luxembourg patent application no. 81,280. This cored wire comprises in particular a metal sheath constituted by a thin strip whose edges are curved so that it forms a profile of substantially circular cross section, as well as an additive enclosed inside the sheath. It is characterized in that the additive is surrounded at least partially by an envelope of organic or metallic synthetic material in the form of a strip which has a very thin thickness of less than 100 microns.

In fact, thanks to the use of a strip of minimum thickness, it is possible to reduce the metal weight of the cored wire, which is an effective means for improving the rate of re-pleating of the wire as well as for reducing the time required to introduce a given amount of additives into the bath.

If it is proposed to further reduce this time, it is possible either to introduce several wires at the same time, which involves a complicated installation, or to increase the speed of introduction. However, the latter is already for known wires around 2 m / sec. An increase in speed risks

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- 3 - lead to accidents when the wire abuts against the bottom of the container and it can come out of the bath without having had time to melt. Another means would be to simply increase the diameter of the wire, which would however have the effect of substantially increasing the winding radius; the spools necessary to wind such wires would be too large to be used on the reduced surfaces which are available for operations of this kind.

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The object of the invention is therefore to propose a cored wire making it possible to increase the filling rate appreciably and thus to decrease the useful length of the wire and at the same time the time necessary for its introduction into a metal bath. .

This object is achieved by the composite cored wire according to the invention which is characterized in that it comprises in particular a metal sheath constituted by a thin strip 20 whose edges are curved so that it forms a profile of section which is substantially flat, as well as an additive enclosed inside the sheath, the additive being surrounded at least partially by an envelope of organic or metallic synthetic material in the form of a strip 25 which has a thickness of less than 100 microns.

. According to the invention the height of the flat wire is preferably of the order of 10 - 12 mm and its width corresponds to at least three times the said height.

The idea which is the basis of the present invention can be stated as follows: A cored wire with a diameter of 10-12 mm can be wound on coils of an acceptable size for commissioning in steelworks. The limits have been reached with regard to the thickness of the metal sheath of the wire and of the protective strips. So if it is proposed to increase the weight ratio of 11 additive / length of the wire where said length corresponds to the time necessary for the introduction of a given quantity of additive into the bath by means of a single wire, there is hardly any other solution than that of increasing the diameter of the wire. To reconcile this increase with the spans of the 5 conventional coils, the wire according to the invention is proposed which has a flattened shape, preferably produced by rolling.

* The solution of the problems to be solved is an increase in the diameter of the wire, for example three times and a flattening of the wire such that the height is reduced to a value corresponding to the diameters of the conventional wires. Indeed, a wire with a diameter of 30 mm has a section of approximately 700 mm2, while 3 wires with a diameter of 10 mm have a useful section of approximately 240 mm2. By flattening the wire 30 mm in diameter at a height of 10 mm, we therefore arrive at an appreciable gain in storage capacity of additive, while retaining the faculty of winding on reels of viable span, free of 20 problems.

As regards the protection of the additive stored in the wire, there is provided according to the invention a strip of polythene, polyester or polyvinyl chloride, or even a metal strip, Al or light alloy.

This strip constitutes a sealing means for cored wires which makes it possible to dispense with and welding these wires and sealing them by means of a metallic strip of 0.2 mm and more thickness whose weight is considerable. and whose own volume to which must be added that caused by the longitudinal folding acts against the desired maximum filling rate.

In this context, it should be noted that the density of the aforementioned synthetic material is close to 1 and that it is not difficult to manufacture strips, eg of polyester, having thicknesses of the order of 100 microns. , î - 5 - and a sufficient stiffness to lend itself to conventional methods of manufacturing cored wires.

If we compare these values with those presented by the 5 steel strips, whose density is seven times greater and whose thickness is 200 to 300 microns, we understand the scope of the advantages of composite flux cored wire. according to the invention.

A first embodiment of the composite cored wire according to the invention provides that the additive is completely surrounded by a strip whose edges overlap mu-v so much over a distance which corresponds to at least one tenth of the outer circumference of the wire.

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In this execution the overlapping edges of the strip are located below the region where the edges of the sheath touch.

Thanks to this measure, the only critical region where there is a possibility of additive loss is sealed by two layers of strip.

Another embodiment provides that the additive is re-covered by a strip of semi-circular profile positioned so that its center line is below the region where the edges of the sheath touch.

In this embodiment it may be advantageous to use a self-adhesive strip whose sticky surface is directed towards the metal sheath.

According to a particularly advantageous embodiment, the synthetic strip is a strip which contracts under the effect of heat. In this case, it suffices to heat the region where the edges of the metal sheath touch each other to hot air, for example at 40 - 50 ° C, so that the strip contracts. The gap between the edges of the metal sheath is somehow sealed by the strip at the end of the contraction, so that the use of a contractable synthetic strip constitutes an inexpensive and easy-to-use means of closure.

Apart from the increase in the filling rate offered by the cored wire according to the invention, the latter also presents the possibility of giving the wire in the process of unwinding a twist, which makes it possible to use rolls of son at place of coils.

A non-limiting illustration of a preferred embodiment of the cored wire according to the invention is provided by way of the drawings, in which FIG. 1 shows a section through the wire, while FIGS. 2 and _3 illustrate the advantages achievable according to the invention, by showing a section of a wire of large diameter with respect to the same flattened wire, in which 3 conventional wires have been inscribed.

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In fig. 1 there is a metallic sheath (1) which contains the additive (3), the latter being protected by a very thin strip (2) whose edges overlap below the zone where the edges of the sheath (1) getting closer.

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We realize that the cored wire according to the invention which has a height corresponding to that of a conventional cored wire, can be made to measure, in random widths, although the illustrated ratio of the height and 30 of the width corresponds to a form of execution recognized as preferable in practice.

In fig. 2 a flattened wire is illustrated, corresponding in useful capacity to the wire shown in FIG. 3. It is realized that by affixing 3 conventional wires realizing the width of the wire according to the invention, an appreciable amount of storage capacity is lost, depending on the surfaces (A) in such unusable cases.

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A graphic illustration of the advantages offered by the use of the cored wire according to the invention is provided by means of the diagrams in FIG. 4, 5 and 6 which relate the diameter of cored wires to 5 the storage capacity resp. the injectable quantities with the speed of introduction of the wires into the bath, for wires of different diameters.

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In fig. 4 the relationship between the dia-10 meter (0) of wires and the storage capacity (C) is shown - we considered wires with diameters of 12, 17 and * 30 mm, the latter in flattened form according to the invention, the strip constituting the envelope having a thickness of 0.5 mm. The stored powders have an average density of 1.3 g / cm 3. The curves illustrating said relationship were drawn, (0) being expressed in mm and (C) either in g / meter of wire, or as filling rate in%.

It can be seen that by passing from a diameter (0) of 12 to 30 mm, we increase (C) from 120 g / m to about 800 g / m, resp. from 45% to 70%.

We note in addition that 3 wires of 12 rnm (0) used * 25 at the same time, which is difficult and complicated, only allow to achieve less than half of (C) which is achievable using a wire 30 mm (0) equivalent.

It is understood that the 30 mm wire (0) must be formed according to the invention in flattened form, to be used in steelworks in a rational manner.

In fig. 5 there is shown the relationship between the quantity of injectable additive (Q) in g / sec with the diameter of the wire (0) in mm for an introduction speed of 1 m / sec. We distinguish the area (Z) which corresponds to the possibilities

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- 8 - injection of additives, offered by the introduction technique using a lance and a carrier gas.

The use of the cored wire according to the invention makes it possible to exceed the quantities injectable by conventional means using lances and this at the fairly modest speed of 1 m / sec.

• In fiq. 6 there is shown the relationship between (Q) and the speed (V) of introduction of the wires, in m / sec, for wires of (0) different. It can be seen that the use of flattened 30 mm (0) wire makes it possible to introduce large quantities of additives while remaining within reasonable speeds (1-1.5 m / sec).

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Claims (6)

1. Composite cored wire intended for the introduction of additives into a metal bath, characterized in that it comprises in particular a metal sheath constituted by a thin strip whose edges are curved so that it forms a profile of substantially flat section, as well as an additive enclosed inside the sheath, the additive being surrounded at least partially by an envelope of organic or metallic synthetic material in the form of a film which has a thickness less than 100 microns. 2. Cored wire according to claim 1, characterized in that its height is of the order of 10 - 12 mm and that its width corresponds to at least three times the said height. 15 3) Cored wire according to claims 1-2, characterized in that the additive is completely surrounded by a strip whose edges overlap each other over a distance which corresponds to at least one tenth of the outer circumference of the wire. 20 4. Cored wire according to claims 1-3, characterized in that the edges of the overlapping strip are located below the region where the edges of the sheath touch. 25 5) Cored wire according to claims 1-2, characterized in that the additive is covered by a strip which is positioned so that its center line is located below the region where the edges of the sheath touch . 30 6) Cored wire according to claims 1, 2 and 4, characterized in that the strip is a self-adhesive strip whose sticky face is directed towards the metal sheath. 1 cored wire according to claims 1-6, characterized in that the strip is contractible under the effect of heat.