WO2024127033A1

WO2024127033A1 - Wire for refining molten metal

Info

Publication number: WO2024127033A1
Application number: PCT/GB2023/053268
Authority: WO
Inventors: Victor Stekly; Ramiro BECERRA
Original assignee: Injection Alloys Limited
Priority date: 2022-12-16
Filing date: 2023-12-15
Publication date: 2024-06-20
Also published as: GB202219049D0

Abstract

A molten metal refining wire (11) which comprises a metal sheath (12) encapsulating a core (14) comprising refining material (14), wherein the refining material (14) comprises calcium carbide which is located at or towards the centre of the core, along at least a part of the length of the core.

Description

WIRE FOR REFINING MOLTEN METAL

This invention relates to wire for refining molten metal with additives, such as metallic material and/or minerals, and an associated method of manufacturing such wire.

Prior to casting a molten metal, such as molten steel, refining wires can be injected into the vessels which hold molten metal such as a ladle, pot or continuous casting tundish, to provide the metal with improved and/or altered characteristics. The purpose of the refining wire is to introduce refining materials and alloying additions, such as metals and/or minerals, encapsulated in the sheath of the wire into the molten metal in accurate quantities and in a controlled manner. This is often contemplated when the refining materials display either a high affinity to oxygen, or a low melting and/or vapour point, or a high vapour pressure, or a low solubility or low density compared to the molten metal, or a combination of these factors. In this regard, it is important to achieve a high percentage of recovery of the refining or alloying material defined as the ratio of the injected material quantity remaining into the molten metal divided by the total material quantity injected. In addition to the recovery, the overall performance measure of the refining wire also takes into consideration the repeatability of the recovery, the inclusion treatment that considers the inclusion composition (the shape, the size and the quantity), the homogeneity of the entire ladle of molten steel, the overall treatment time, the quantity and nature of fume emissions, the reaction that occurs during the introduction of the refining wire that causes ‘splashing’ and means that there may be an increase in the height of the free-board (and a corresponding reduction in the quantity of steel per ladle), and the shelf-life of the refining wire.

In a known method of manufacturing a refining wire, a steel strip is rolled to form a U-shaped section that is filled with refining material in powdered form. The two longitudinal edges of the U- shaped strip section, which have been pre-folded, are then hooked together. In this manner, a refining wire is formed with a steel sheath encapsulating a core of refining material.

Another method of manufacturing a refining wire is the same as above with the exception that the refining material is introduced into the U-shaped section as a solid extruded wire. Refining wires produced by these known methods usually have a sheath thickness in the range of 0.2 mm to 0.6mm due to manufacturing and product constraints. As a result, the wire can be deformed easily by the high pressure of the feeder pinch rolls used to inject the wire through a guide tube into the molten metal vessel, thereby requiring guide tubes with comparatively large inner diameters which are detrimental to guiding the refining wire accurately into the vessel, or requires guide tubes to be positioned closer to the surface of the molten metal which introduces further complications and may require ceramic lining and shielding from the molten metal.

Sometimes also, the refining wire is not sufficiently rigid to penetrate a solidified surface of slag floating on the surface of molten metal, such as molten steel, in the vessel.

Further, the hook-type closure for the steel sheath of refining wires discussed above does not allow for the deep rolling or drawing of such wires down to much smaller diameters, in which case, the core can include excessive and undesirable amounts of air which, during the refining process, is detrimental to the quality of the molten metal as well as the recovery of the core material. Moreover, the refining material can interact with components of the air, thus reducing the shelf life of the wire.

Some of these disadvantages result in part from the fact that the steel sheath of the refining wire is too thin, and secondly, from the encapsulated refining material not being sealed into the sheath in a fluid- tight manner.

In our earlier patent application, published as W02006/079832 we propose a solution to the disadvantage faced by prior art refining wires. In that application we propose a refining wire having a sheath thickness of greater than 0.6mm and a core of refining material which has a density of 95% theoretical or greater.

In the above-identified patent application we disclose the use of, as the refining material, calcium, aluminium or nickel, or a combination thereof, or calcium-silicon alloy, a ferrotitanium alloy, a ferro-boron alloy or a combination thereof. The preferred refining material is powdered calcium. Silicon can also be added to the refining material. In some refining wires we use a mixture of silicon and calcium powders. Whilst our refining wires are very adept at enabling the addition of refining materials into a molten metal held in a vessel (even where the surface of the melt has a slag layer thereon) it can be difficult to retard the reactivity of the calcium (or other refining material) as it is plunged beneath the surface of the melt. The refining wire will cause a reaction or interaction (for example a violent reaction or interaction known as ‘splashing’) at or towards the surface of the melt and/or may lead to less than optimal recovery and create conditions that are sub-optimal performance with oxygen pick-up, and potential unsafe working conditions.

In our patent application, published as CN106834601 , we propose a solution to the disadvantage faced by known refining wires. In that application we propose a refining wire comprising a metal sheath encapsulating a core comprising refining material and iron metal. The inclusion of iron metal within the core was shown to retard the activity of the refining material.

As well as the refining material reacting with components of the air, the refining material may interact with other materials, such as moisture or oxidising agents, reducing the shelf life of the wire.

It is an object of the present invention to provide a refining wire that overcomes, or at least substantially reduces, the disadvantage associated with the known refining wires discussed above whilst allowing the use of new or different refining materials.

As such it may be desirable to use refining materials which are less stable than the above- mentioned refining materials. For example, certain desirable refining materials may react with air or with moisture (and moisture in the air) and so their use in known refining materials has been limited or avoided altogether.

A first aspect of the invention provides a molten metal refining wire comprising a metal sheath encapsulating a core comprising refining material, wherein the core is sealed within the sheath in a fluid-tight manner and wherein the refining material comprises a refining material which readily reacts in the presence of heat, moisture, air and/or other atmospheric agents.

Accordingly, another aspect of the invention provides a molten metal refining wire comprising a metal sheath encapsulating a core comprising refining material, wherein the core is sealed within the sheath in a fluid-tight manner and wherein the refining material comprises pure calcium carbide, or a combination of calcium carbide with other refining materials, wherein calcium carbide makes up at least 10 wt.% of the refining material and/or at least 10 wt.% of the core.

A further aspect of the invention provides a molten metal refining wire comprising a metal sheath encapsulating a core comprising refining material, wherein the refining material comprises calcium carbide which is located at or towards the centre of the core, along at least a part of the length of the core.

Preferably, having the calcium carbide at least at (or at least towards) the centre of the core can ensure that the calcium carbide (or at least some of it) is less likely to react with moisture or other atmospheric components. For example, the calcium carbide can be radially surrounded within a wire by another element and/or may be longitudinally bound by another element.

The calcium carbide may extend along a major proportion of the length of the core, for example more than 55%, more than 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%. The calcium carbide may extend along the entire length of the core.

Whilst calcium carbide has been suggested as a deoxidizing agent in a ladle and for use in the production of low carbon steel (e.g. Metallurgist 48, 557-561 (2004)) it has not been proposed as a constituent of a refining wire.

It is known that calcium carbide (also known as calcium acetylide) undergoes a violent, highly exothermic hydrolysis reaction with even mere traces of water, or moisture, to form calcium oxide and acetylene (Equation 1), a highly flammable gas. Further, if there is an insufficient quantity of water, the resulting acetylene can spontaneously combust.

CaC₂(s) + 2H₂O(I) - C₂H₂(g) + Ca(OH)₂(s) Equation 1

We understand that calcium carbide has previously not been used as a refining material in a refining wire because such refining wires typically have a long shelf-life and may remain in stock within a mill or foundry for a period of time before use. As such, the chemical nature of calcium carbide mitigates against its use in a refining wire. The product will degrade in conventional wire form, and therefore will potentially no longer provide any effective treatment reagent, and/or provide unreliable treatment performance dependent on the tightness of the seal and the length of time it is stored, and in what storage conditions.

Its use is also precluded on the basis that any air and/or moisture ingress into a refining wire containing calcium carbide would lead to the rapid degradation of the product or more dangerously to the production of acetylene within the steel plant or foundry. On safety grounds alone using calcium carbide in a conventional wire would be unacceptable.

The refining material may comprise 10 to 100 w/w% of the core. For example, the refining material may comprise from 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95 w/w% of the core to 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 w/w% of the core.

The core may comprise a mixture of materials, i.e. one or more additional materials, in addition to calcium carbide, may be present.

The said one or more additional materials may comprise or be a material suitable for refining molten metal, for example molten steel, such materials including, inter alia, pure calcium or silicon, aluminium or nickel metal or any combination thereof, a calcium-silicon alloy (CaSi), a ferro-titanium alloy (FeTi), a ferro-niobium alloy (FeNb), a ferro-boron alloy (FeB), iron powder or any combination thereof, calcium and silicon powders, for example, mixed or separate.

Additionally or alternatively, the said one or more additional materials may comprise or be a material which does not take part in the refining of molten metal, for example molten steel.

The said one or more additional materials may comprise carbon powder, iron powder, sulphur, lead, selenium and vanadium.

Advantageously, one or more of the additional materials, may be present within the core to retard the activity of the refining material, for example, allowing the refining material to penetrate further into the molten metal, for example in accordance with our earlier patent application CN 106834601. As such, the core may, in an embodiment, comprise iron, for example unalloyed iron metal, which may be powdered iron. The one or more additional materials, e.g. powdered iron, may have a particle size of from 0-1 mm (/.e. a number average particle size of from 0-1 mm and/or preferably over 50% of the particles falling in the range of particle sizes 0-1 mm.

The one or more additional materials, e.g. iron powder, may have a bulk density of less than 4kg/dm³, for example less than 4kg/dm³, less than 3kg/dm³, less than 2kg/dm³, and preferably less than 1.5kg/dm³. In one embodiment the one or more additional materials, e.g. iron powder, has a bulk density of about 1.4kg/dm³. Even though the one or more additional materials, e.g. iron powder, may have a relatively low bulk density (e.g. as compared to the theoretical density of iron, namely 7.86 g/cm³) it is readily compressible once mixed with refining material. Accordingly, the mixture of the one or more additional materials, e.g. iron powder, and refining material is capable, when using methods of the prior art (e.g. W02006/079832), of being compressed to high relative densities (as compared to theoretical).

Preferably the one or more additional materials, e.g. iron powder, is substantially pure, by which is meant impurities may be less than 5%, preferably less than 4, 3, 2, 1 %.

Although we neither wish nor intend to be bound by any theory, we believe that the inclusion of a retarding agent(s), e.g. iron powder, has two distinct effects. The first is that it acts as a diluent for the refining material which means that as the wire is plunged into the melt there is less refining material to contact per unit length and hence a gentler reaction/inter-reaction between the melt and the core is achieved. The second is that the one or more additional materials, e.g. iron, acts as a heat sink, again ensuring a less rigorous reaction. In this regard, we may also consider calcium carbide to be a retardant agent and may in fact be added as such to refining wire containing pure Ca metal (or other refining materials).

The one or more additional materials may comprise 0 to 90 w/w% of the core. For example, the one or more additional materials may comprise from 0, 5 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85 w/w% of the core to 5, 10 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85 or 90 w/w% of the core. Although the amount of refining material may be reduced by the use of one or more retarding agents, e.g. iron metal, we believe that the overall recovery of refining material is improved due to the presence of the additional material(s), e.g. iron.

The refining material may comprise 10 to 100 w/w% calcium carbide, i.e. such that the refining material comprises 90 to 0 w/w% of the said one or more additional materials.

For example, the refining material may comprise from 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95 w/w% calcium carbide to 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 w/w% calcium (and/or other known additional refining agent).

For example, the refining material may comprise from 0, 5 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85 w/w% of the one or more additional materials to 5 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85 or 90 w/w% of the one or more additional materials.

The one or more additional materials may be mixed with the calcium carbide before it is introduced into the sheath. The encapsulated core of refining material may comprise a mix of calcium carbide and one or more additional materials. The mix may be a homogenous, or at least substantially homogeneous, mix.

For example, the core may comprise calcium carbide, one or more additional refining material and one or more additional retarding agents, for example the core may comprise 10-90 w/w% calcium carbide, 10-90 w/w calcium or calcium/silicon (and/or another additional refining material) and 10-90 w/w iron powder (an/or another additional retarding agent), the whole making 100 w/w% of the core.

The refining wire will typically have a first end and a second end.

It is preferred that the refining wire comprises protection means or protection to at least partially inhibit, for example to prohibit, the reaction of calcium carbide with air, moisture or other atmospheric agents or to otherwise limit the reduction of available calcium carbide.

Protection means or protection may take many forms. In one embodiment, at least one of the first and second ends of the refining wire may be closed. At least one of the first and second ends may be welded, crimped or shut to at least partially close the respective at least one of the first and second ends to inhibit the contact of calcium carbide with air, moisture or other atmospheric agents. Said protection or protection means may be applied to the ends of the refining wire, for example a coating or sealant may be applied to the free ends. Plural protection or protection means may be applied to the refining wire.

Additionally or alternatively, the calcium carbide may be located towards the longitudinal centre of the refining wire and may not be present at one or both of said first and second ends. For example, said one or more additional materials may be located at least at one of the first and second ends, thereby to at least partially inhibit the contact of calcium carbide with air, moisture or other atmospheric agents.

Additionally or alternatively, the calcium carbide may be surrounded by said one or more additional materials. That is, the core may comprise an elongate central region comprising calcium carbide which is radially or peripherally bounded by said one or more additional materials.

Advantageously, the protection means or protection may stop, reduce or prevent reactions with the air or other materials, such as moisture or oxidising agents, e.g. by forming a barrier between the refining material (e.g. the calcium carbide and/or one or more additional refining materials) and the air or other materials, such as moisture or oxidising agents. For example, the one or more additional materials, e.g. non-refining materials or retarding agents, may form a fluid-tight barrier or seal between the refining material, e.g. the calcium carbide and/or one or more additional refining materials, and the air or other materials.

Advantageously, the provision of protection or protection means will increase the shelf-life of the refining wire and will seek to ensure optimum delivery of calcium carbide to the molten metal.

Surprisingly then, the refining wire can be made economically whilst not compromising performance. The additional materials(s), e.g. refining materials, non-refining materials or retarding agents (e.g. iron metal), may be mixed with the calcium carbide before it is introduced into the sheath. The so-formed mixture may be a homogeneous, or at least a substantially homogeneous mix.

The metal sheath may be formed of a metal strip. The longitudinal edges of the so-formed sheath may be sealed together to encapsulate the refining material, e.g. calcium carbide and/or one or more additional materials.

The sheath may be made of any suitable metallic material but when the refining wire is used for refining molten steel, the sheath is preferably a low carbon, low silicon steel, although may also be any suitable grade of metal that may be welded by the said method.

The thickness of the sheath may be up to 2.0 mm, e.g. from 0.6 to 2.0 mm or from 0.6 to 1.5 mm, e.g. 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4 or 1.5 mm. The thickness of the sheath may be greater than 1 .0 mm, for example from greater than 1 .0 to 2.0 mm, say from greater than 1.0 mm to 1.5 mm.

The wire may have an external diameter from 5 to 20 mm, or from 9 to 15 mm, or from 10 to 14 mm.

Advantageously, a wire with an outside diameter from 10 to 14 mm (with a sheath thickness of from 0.6 to 2 mm, preferably from 0.6 to 1.5 mm) is particularly useful in terms of the balance between cost, strength and addition of materials.

The edges of the sheath may be welded, e.g. butt welded together, and both longitudinal edges may be sealed together in a fluid-tight manner.

Where the edges of the sheath are welded together it may be appropriate, as protection means or protection, to at least partially surround the calcium carbide with one or more of said additional materials to at least partially protect the calcium carbide from the heat of the welding operation.

The one or more additional materials and calcium carbide may alternate along the length of the refining wire. For example, the one or more additional materials may be located at a first zone and a third zone, and the calcium carbonate may be located in a second zone (or vice versa), located between the first and third zone, the first second and third zones defining at least a part of the core and being longitudinally spaced along the wire.

Additionally the first zone and third zones may comprise a preponderance of said one or more additional materials (e.g. 51-99 w/w%, say 90 - 99 w/w %) and a minor proportion of calcium carbide (e.g. 1 - 49 w/w%, say 1-10 w/w%), whereas the second zone may comprise a preponderance of calcium carbide (e.g. 51-99 w/w%, say 90 - 99 w/w %) and a minor proportion of said one or more additional materials (e.g. 1 - 49 w/w%, say 1-10 w/w%).

The zone (or zones) comprising calcium carbide may comprise a major longitudinal proportion of the core whereas the zone (or zones) free of calcium carbide (or containing a minor proportion of calcium carbide) may comprise a minor longitudinal proportion of the core.

Preferably, the ends of the wire will correspond to a part of the core having no (0 w/w%), or only a minor amount of (< 50 w/w%, preferably less than 40, 30, 20, 10, 5 w/w%), calcium carbide.

The metal sheath may comprise one or more marks or indicators on the exterior surface of the refining wire to indicate the actual or approximate location of the calcium carbide and/or the one or more additional materials.

Another aspect of the invention provides a molten metal refining wire having a first end and a second end and comprising a metal sheath encapsulating a core comprising refining material, wherein the core is sealed within the sheath in a fluid-tight manner, the metal sheath having an external surface which comprises one or more marks or indicators between the first end and the second end, wherein said marks or indicators indicate the extent of at least one component of said refining material.

For example, if the refining wire comprises a length, and the additional material is located at at least one of the first and second ends and at a location between the first and second ends, the metal sheath may comprise a mark or indicator to indicate the end point of the additional material at the at least one of the first and second ends and another mark or indicator to indicate the location of the additional material at the location between the first and second ends. In this way an operative is provided with a visual cue to recognise the limit of the extent of the calcium carbide and can easily expose calcium carbide at an end of the refining wire or can cut the refining wire at a location of the additional material so as not to expose the calcium carbide to air, moisture or other atmospheric agents.

A second aspect of the invention resides in a method of manufacturing a molten metal refining wire comprising a metallic sheath encapsulating a core comprising refining material, wherein the core is encapsulated within the sheath in a fluid-tight manner, and wherein the refining material comprises calcium carbide.

A third aspect of the invention resides in a method of manufacturing a molten metal refining wire comprising a metallic sheath encapsulating a core comprising refining material, the method comprising forming a metal strip into a sheath with refining material comprising calcium carbide encapsulated therein, and sealing together, the longitudinal edges of the so-formed sheath.

The method may comprise locating the calcium carbide on a metal strip and forming a sheath, wherein one or more of locating the calcium carbide and/or forming the sheath are carried out under an inert atmosphere, for example under vacuo or, preferably using an inert and/or dry gas, such as argon and/or nitrogen

A fourth aspect of the invention comprises a use of a refining wire in the refining or molten steel, the refining wire comprising a metallic sheath encapsulating a core comprising refining material which comprises calcium carbide, the use comprising providing at an exposed end of the refining wire calcium carbide.

The use may comprise forcing the exposed end of refining wire into a melt of molten metal.

In the methods or use set out above, the core may comprise any of the one or more additional materials as set out above in relation to the first aspect.

The methods set out above may comprise providing protection means or protection to at least partially inhibit, for example to prohibit, the reaction of calcium carbide with air, moisture or other atmospheric agents or to otherwise limit the reduction in available calcium carbide.

In one embodiment, the methods may comprise closing at least one of the first and second ends. At least one of the first and second ends may be welded, crimped or shut to at least partially close the respective at least one of the first and second ends to at least partially inhibit the contact of calcium carbide with air, moisture or other atmospheric agents.

Additionally or alternatively, the methods may comprise locating the calcium carbide towards the longitudinal centre of the refining wire and may comprise not locating the calcium carbide at one or both of said first and second ends. For example, said one or more additional materials may be located at at least one of the first and second ends, thereby to at least partially inhibit the contact of calcium carbide with air, moisture or other atmospheric agents.

Additionally or alternatively, the methods may comprise surrounding the calcium carbide by said one or more additional materials. That is, the core may comprise a elongate central region comprising calcium carbide which is at least partially (and preferably totally) radially or peripherally bounded by said one or more additional materials.

For example, calcium carbide may be located towards the middle of a wire and a retarding agent (and/or a less or non-reactive refining material) may be located towards (or at) the ends of the refining wire. Additionally, the calcium carbide may be radially bound by an additional material (e.g. refining material and/or retarding agent). In a preferred embodiment, calcium carbide is at least located along the central longitudinal axis of the core, along at least a part of the length of the core. Accordingly, that portion of the core will comprise the highest amount (w/w) of calcium carbide.

Said protection or protection means may be (and typically are) applied to the ends of the refining wire, for example a coating or sealant may be applied to the free ends. Plural protection or protection means may be applied to the refining wire.

In any aspect of the method or use defined above, the sheath may be made of any suitable metallic material but when the refining wire is used for refining molten steel, the sheath is preferably a low carbon, low silicon steel.

The edges of the sheath are preferably butt welded together, and both longitudinal edges may be sealed together in a fluid-tight manner.

In order to reduce oxygen, air or other deleterious gases remaining in the sheath of the so- formed wire, the wire can be deep rolled or drawn to a smaller diameter, thereby expelling such gases from the wire, without detriment to the integrity thereof, whilst also tending to close the sheath around the core more tightly. In this manner, the refining material of the core may achieve an apparent density ratio of over 80% of the theoretical solid core equivalent.

A further aspect of the invention provides a method of refining molten metal, comprising forcing, e.g. injecting, into molten metal a refining wire in accordance with the aspects of the invention or a wire manufactured in accordance with the further aspects of the invention defined above.

The method may comprise exposing at least one end of the refining wire, e.g. prior to injecting the refining wire into the molten metal. Exposing at least one end of the refining wire may comprise cutting a portion of the refining wire, e.g. to expose the refining material.

A further aspect of the invention provides a method of storing and/or transporting calcium carbide, the method comprising locating calcium carbide, which may be in the form or powder or granules, on an elongate length of metal having a first elongate side and a second elongate side and bringing the first elongate side and second elongate side into proximity to form a hollow structure, whereby the calcium carbide is located within the hollow structure and is at least partially protected from atmospheric reactants.

The first side and the second side may be welded, thereby to form a sealed tube. The calcium carbide may be located within the metal sheath under a non-reactive atmosphere, for example in a dry and inert atmosphere, for example in an atmosphere of nitrogen or argon gas. The ends of the tube may comprise protection to at least partially inhibit the reaction of calcium carbide with air, moisture and/or other atmospheric agents. For example the ends of the tube may be crimped or welded shut. Additionally or alternatively, the calcium carbide may be preferentially located towards the centre of the tube and another species (/.e. one which is less reactive to air, moisture and/or other atmospheric agent than is calcium carbide) is located towards or at the end of the tube.

Although the above has mainly focussed on refining wires comprising calcium carbide, the use of protection (or protection means) is not limited to the use of calcium carbide and may be used with other desired refining materials (or reactive species) which have not heretofore been used due to their reactivity. Accordingly, the references above to calcium carbide may be replaced by a desired refining material, say of relatively high reactivity, in a refining wire with addition protection (or protection means).

In each of the aspects set out above, preferably the core does not comprise a solid metallic central core, for example a core of solid metallic calcium, iron or other metal. Further, the wire will preferably provide a single central compartment for the core, rather than a plurality of zones subdivided by concentric tubes. The sheath is preferably in the form of a single metal layer. One or more of these features allow for the maximum payload of core materials whilst minimising the amount of sheath material (notwithstanding the preferable dimensions of the sheath mentioned above).

In order that the invention may be more fully understood, a refining wire in accordance therewith will now be described by way of example only and with reference to the accompanying Examples and drawings in which:

Figures 1A and 1 B are cross-sectional views of wires for refining molten steel in accordance with embodiments of the invention; Figures 2A to 2C show wires for refining molten steel, in accordance with the invention;

Figures 3A and 3B are schematics of further wires for refining molten steel, in accordance with a further embodiment of the invention; and

Figures 4A and 4B are schematics of yet further wires for refining molten steel, in accordance with a further embodiment of the invention.

Referring firstly to the refining wire, as indicated generally at 1 in Figure 1 A, there comprises a steel sheath 2 which has been formed from a steel strip whose longitudinal edges have each been bent into the form of a hook 3. The steel sheath is formed from a steel strip which is bent into a U-shape for receiving therein a powdered refining material 4, wherein the refining material 4 comprises calcium carbide. The two pre-folded edges 3 are then hooked together, so that the refining material 4 is encapsulated within the sheath 2 as a core.

The refining material 4 may comprise a mixture of materials, i.e. the refining material 4 may comprise one or more additional materials, in addition to calcium carbide. The said one or more additional materials may comprise or be a material suitable for refining molten metal, for example molten steel, such materials including, inter alia, pure calcium or silicon, aluminium or nickel metal or any combination thereof, a calcium-silicon alloy (CaSi), a ferrotitanium alloy (FeTi), a ferro-niobium alloy (FeNb), a ferro-boron alloy (FeB), iron powder or any combination thereof which may be mixed or separate, for example calcium and silicon powders. In one embodiment, said one or more additional materials may be selected from nickel, calcium, silicon, or calcium-silicon alloy (CaSi), a ferro-titanium alloy (FeTi), a ferro- niobium alloy (FeNb), a ferro-boron alloy (FeB) or combinations thereof.

Turning to Figure 1 B, the refining wire T of Figure 1 B is the same as the refining wire 1 in Figure 1A except that the refining material 4’, comprises calcium carbide, which is surrounded by one or more additional materials 5’, which may be one or more refining materials or retarding materials, for example.

The one or more additional materials 5’ may be or comprise a protection means or protection to at least partially inhibit, for example to prohibit, the reaction of calcium carbide with air, moisture or other atmospheric agents or to otherwise limit the reduction in available calcium carbide. Referring now to Figure 2A, there is shown a schematic of a refining wire 11 in accordance with the invention, wherein the steel sheath 12 is formed from a strip of steel having been first formed into a generally U-shape into which the refining material 14, which comprises calcium carbide, of the core has been provided. Typically the calcium carbide is located on the strip of metal under an inert atmosphere, for example an atmosphere provided by a blanket of an inert gas such as argon or nitrogen.

The refining material 14 may comprise a mixture of materials, i.e. the refining material 14 may comprise one or more additional materials, in addition to calcium carbide. The said one or more additional materials may comprise or be a material suitable for refining molten metal, for example molten steel, such materials including, inter alia, additional refining materials, for example pure calcium or silicon, aluminium or nickel metal or any combination thereof, a calcium-silicon alloy (CaSi), a ferro-titanium alloy (FeTi), a ferro-niobium alloy (FeNb), a ferro-boron alloy (FeB), and/or additional retarding agents, such as iron powder or any combination thereof which may be mixed or separate, for example calcium and silicon powders and iron powders.

In contrast to the first refining wire 1 , T discussed above in relation to Figures 1A and 1 B, the confronting or abutting longitudinal edges 15 of the sheath 12 are sealed together in a fluid type manner by welding (see Figure 2B which shows a cross section of the wire 11 of Figure 2A through the line A-A). Thus, this so-formed welded seam 13 encapsulates the refining material 14 within the core of wire 11 within the sheath 12 in a sealed, fluid-tight manner, thus reducing the possibility of, and preferably preventing, any undesirable oxygen or other gas or material from entering the interior of the sheath 12 during a molten metal refining process.

Also, any air, oxygen or other gas present in the sheath 12 can be reduced by expelling it from the sheath interior if the wire 11 is deep rolled or drawn down in diameter. This also tends to close the sheath 12 more tightly around the refining material 14 within the core.

Further, and in accordance with the embodiment set out in Figure 1 B, the refining material 14, which comprises calcium carbide, may be surrounded by one or more additional materials, which may be one or more additional refining materials and/or retarding materials, for example. In this embodiment such protection may help to limit the exposure of calcium carbide to atmospheric agents and/or any heat generated in the butt-welding process.

Turning to Figure 2C, this embodiment differs from the embodiment of Figure 2A in that at least one, and preferably both of the first and second ends 11a, 11 b of the wire 11 are closed, i.e. welded, crimped or shut to at least partially occlude the respective at least one of the first and second ends 11a, 11 b to at least partially inhibit the contact of the refining material 14 comprising calcium carbide with air, moisture or other atmospheric agents.

Referring now to Figure 3A, there is shown a schematic of a further refining wire 1 T. The wire 1 T is similar to the wire 11 of Figures 2A to 2C. Like features are denoted with like reference numerals except followed by a prime and will not be described further.

The refining wire 1 T differs from the refining wire 11 of Figures 2A to 2C in that the wire 1 T comprises additional materials 16a’, 16b’ located at at least one, but preferably both, of the ends (11a’, 11b’) of the refining wire 1 T. The additional materials 16a’, 16b’ may be refining materials, non-refining materials or retarding agents (but do not comprise calcium carbide).

Advantageously, one or more of the additional materials 16a’, 16b’, may be present within the core to retard the activity of the refining material 14’, for example, allowing the refining material 14’ to penetrate further into the molten metal, for example in accordance with our earlier patent application CN 106834601.

The additional materials 16a’, 16b’ may be the same as each other or they may be different.

In this embodiment the refining material 14’ is located towards the longitudinal centre of the wire 11’and the additional materials 16a’, 16b’ are located at the first and second ends 11a, 11 b of the wire 11 (wherein the dashed lines represent the boundary of refining material 14 and additional materials 16a’, 16b’, see Figure 3A). Advantageously, locating the additional materials 16a’, 16b’ at the first and second ends 11a’, 11 b’ of the wire 1 T stops, or at least reduces, reactions of the refining material 14’, i.e. the calcium carbide or mixture of refining materials which include calcium carbide, with the air or other materials, such as moisture or oxidising agents. Advantageously, the provision of the additional materials 16a’, 16b’ will further increase the shelf-life of the wire 1 T and will seek to ensure optimum delivery of refining material 14’, i.e. the calcium carbide or mixture of refining materials which include calcium carbide, to the molten metal.

Turning to Figure 3B, the steel sheath 12’ of this embodiment has marks 17a’, 17b’ marking the boundary between the refining material 14’, i.e. the calcium carbide or mixture of refining materials which include calcium carbide, and the additional materials 16a’, 16b’. The marks 17a’, 17b’ of this embodiment are indents in the sheath 12’. The marks 17a’, 17b’ may provide a convenient visual marker to allow the operator (or a machine) to remove the additional materials 16a’ or 16b’ prior to use, if desired.

Referring now to Figures 4A and 4B there is shown a further refining wire 11”. The refining wire 11” is similar to the wire 1 T of Figures 3A and 3B. Like features are denoted with like reference numerals except followed by prime and will not be described further.

The wire 11” comprises alternating sections of refining material 14” and further components 16”. In this embodiment, there are three segments of refining material 14a”, 14b” and 14c”. In this embodiment, there are four segments of a further component 16a”, 16b”, 16c” and 16d”.

The refining material 14” in each of the sections 14a’”, 14b’ and 14c” may be different or it may be the same. The refining material may comprise 100% calcium carbide or it may comprise a mixture of calcium carbide and one or more additional components.

The further components in each of the sections 16a”, 16b”, 16’c’ and 16d” may be different or they may be the same. It will be appreciated that there may be fewer or greater than the number shown.

In this embodiment each section of refining material 14” is located between sections of the further component(s) 16”.

Marks 17” indicate the location of the refining material 14” and/or the additional material 16”. The marks 17” may be indents in the sheath 12”, or marks applied to the sheath 12”. As shown in Figure 4A, marks 17a” to 17f” indicate the boundaries between the refining materials 14a” to 14c”, i.e. the calcium carbide or mixture of refining materials which include calcium carbide, and the additional materials 16a” to 16d”.

As shown in Figure 4B, mark 17a” marks the boundary between the refining material 14a” and the additional material 16a” and mark 17d” marks the boundary between the refining material 14c” and the additional material 16d”. Whereas, marks 17b” and 17c” mark the central point (and not the boundary/end points) of the additional materials 16b” and 16c”, respectively.

In this way an operative is provided with a visual cue to be able to determine the extent of the refining material 14”, i.e. calcium carbide or mixture comprising calcium carbide, and can easily expose the refining material 14”, e.g. calcium carbide or mixture comprising calcium carbide, at an end of the refining wire 11” or can cut the refining wire 11”at a location of the additional material 16” so as not to expose the calcium carbide to, for example, air, moisture or other atmospheric agents.

Additionally, the ends of the refining wire 1 T or 11 ” may be welded or crimped as explained in relation to the refining wire of Figure 2C.

Deep rolling or drawing of the wires is usually necessary to provide smaller diameter wires, in dependence upon operating conditions of the refining process, whilst also tending to close the sheaths more tightly around the wire cores.

Thus, it can be seen that the invention provides refining wires which improve metal refining techniques, in that, inter alia, they reduce impurities being injected into molten metals, whilst retaining their overall integrity, particularly during the process of being fed to the molten metal vessel and their penetration into the molten metal through the slag floating on the molten metal surface.

Also because the sheaths are sealed and have regular, continuous, generally smooth circumferences, they can be readily deep rolled or drawn into smaller diameters without detriment to their integrity, whilst also expelling air, oxygen or any other undesirable gas from the sheath interiors. Moreover, the use of inert atmospheres during production can help to limit the loss of calcium carbide (or other reactive materials used). The provision of various protection means can increase the shelf-life or the reactive material.

Further, deep rolling or drawing of the refining wires to smaller diameters can provide for a core material keeping an apparent density or compression ratio of over 80% of the theoretical solid core equivalent.

Moreover, by using the techniques set out herein, the use of additional refining materials is facilitated, for example refining materials such as calcium carbide, which may be susceptible to reaction with atmospheric agents. Further, the disclosed methods make it possible to safely store and/or transport reactive materials such as calcium carbide.

Claims

CLAIMS A molten metal refining wire comprising a metal sheath encapsulating a core comprising refining material, wherein the refining material comprises calcium carbide which is located at or towards the centre of the core, along at least a part of the length of the core. A wire according to Claim 1 , wherein the refining material comprises 10-100 w/w% of the core. A wire according to any of Claims 1 or 2, wherein the refining material comprises 10-100 w/w% calcium carbide. A wire according to any preceding Claim, wherein the core or the refining material further comprises one or more additional materials. A wire according to Claim 4, wherein the one or more additional materials comprise a material suitable for refining molten metal. A wire according to Claim 5, wherein said one or more additional materials are selected from pure calcium or silicon, aluminium or nickel metal or any combination thereof, calcium-silicon alloy (CaSi), a ferro-titanium alloy (FeTi), a ferro-niobium alloy (FeNb), a ferro-boron alloy (FeB), or combinations thereof, calcium and silicon powders, for example, mixed or separate. A wire according to Claim 4, 5 or 6, wherein the one or more additional materials comprise carbon powder, iron powder, sulphur, lead, selenium and vanadium. A wire according to any of Claims 4 to 7, wherein said one or more additional or further materials comprise 0-90 w/w% of the core. A wire according to any of Claims 4 to 8, wherein the calcium carbide extends longitudinally along the core and is surrounded by said one or more additional materials. A wire according to any of Claims 4 to 9, wherein the wire has a first end and a second end A wire according to Claim 10, wherein said one or more additional materials are located at at least one of the first and second ends. A wire according to Claim 10 or 11 , wherein at least one of the first and second ends are closed, e.g. at least one of the first and second ends are welded, crimped or shut to at least partially close the respective at least one of the first and second ends. A wire according to any of Claims 4 to 12, wherein the calcium carbide and said one or more additional materials alternate along the length of the refining wire. A wire according to any preceding Claim, wherein the sheath has a thickness of from 0.6 to 2.0 mm and/or wherein the outside diameter of the wire is from 5 to 20 mm, preferably from 9 to 15 mm and most preferably from 10 to 14 mm. A wire according to any preceding Claim, the wire having an external surface and one or ore indicators on the exterior surface, whereby the indictors indicate the extent of the calcium carbide within the core. A method of manufacturing a molten metal refining wire comprising a metallic sheath encapsulating a core of refining material, comprising encapsulating the core within the sheath in a fluid-tight manner, and wherein the refining material comprises calcium carbide. A method according to Claim 16, comprising locating the calcium carbide towards the centre of the refining wire. A method according to any of Claims 16 or 17, comprising closing at least one of the first and second ends of the refining wire, e.g. crimping, welding or shutting the respective at least one of the first and second ends. A method according to any of Claims 16, 17, 18, comprising encapsulating the core by welding facing edges of the sheath. A method according to any of Claims 16 to 19, comprising locating the calcium carbide on the sheath and/or encapsulating the calcium carbide within the sheath under a non-reactive atmosphere. Use of a refining wire in the refining of molten steel, the refining wire comprising a metallic sheath encapsulating a core comprising refining material which refining material comprises calcium carbide. Use of a refining wire according to Claim 21 , comprising , providing at an exposed end of the refining wire calcium carbide and forcing the exposed end of refining wire into a melt of molten metal. A method or use according to any of Claims 16 to 22, comprising providing one or more additional materials, e.g. pure calcium or silicon, aluminium or nickel metal or any combination thereof, calcium-silicon alloy (CaSi), a ferro-titanium alloy (FeTi), a ferro-niobium alloy (FeNb), a ferro-boron alloy (FeB), or combinations thereof, calcium and silicon powders, for example, mixed or separate, carbon powder, iron powder, sulphur, lead, selenium and vanadium. A method or use according to Claim 23, comprising surrounding the calcium carbide with said one or more additional materials. A method or use according to any of Claims 16 to 24, comprising exposing at least one end of the refining wire, prior to injecting the refining wire into the molten metal.