METHOD OF OPERATION THEREOF

TECHNICAL FIELD

Embodiments of the present disclosure relate to an electromagnetic stirring apparatus for a metal furnace, particularly for an electric arc furnace, and a method of operation thereof

BACKGROUND

In a metal furnace of the present state of the art, a melt may be stirred using an electromagnetic stirrer (EMS), fa general, a metal furnace is a vessel for metal processing. A metal furnace in the context of the present disclosure may include, but is not limited to, an electric arc furnace ( EA F ) for steelmaking, an electric arc furnace for ferro-alloy (for example, FeMn or FeNi) refining, a ladle furnace for steel refining, an aluminium melting furnace for scrap recycling, an aluminium holding furnace for alloying and casting, a copper anode furnace for copper refining, or a lead melting furnace.

Electromagnetic stirring is beneficial for many reasons. For example, electromagnetic stirring allows for improved melting speed and reduced process time, improx ed temperature homogenization, and reduced energy consumption of the metal furnace. In a typical installation, such as in an EAF, the EMS is mounted below the hearth of the EAF) and the melt is stirred by the application of a magnetic field.

In the present state of the art, a typical EMS has a linear design, comprising a linear core element with two or more windings wound thereon Electric currents arc applied to the w indings so as to generate a magnetic field in the linear direction along the length of the core element. As such, the resulting stirring of the melt is performed only in a linear direction. The melt, when stirred linearly, encounters significant flow resistance when the flow reaches the walls of the hearth. Therefore, the electric energy consumption for stirring a melt using a linear EMS is high. Further, the space available below the hearth of a metal furnace such as an EAF is typically limited, as the hearth is typically mounted on a large frame which allows for tilting of the EAF during tapping. The overall length of a linear EMS is limited by the space available in the frame.

In view of the deficiencies of electromagnetic stirrers in the current state of the art, an improved EMS having reduced energy consumption, improved stirring and a more space efficient design is desired.

SUMMARY

In view of the above challenges and problems arising in the state of the art, improved methods and systems for electromagnetic stirring in a metal furnace are sought.

According to a first aspect of the present disclosure, an electromagnetic stirring apparatus for a metal furnace is provided. The electomagiietic stirring apparatus includes a stirring assembly having a ferromagnetic core arranged in a ring-like configuration, and at least three windings which are wound on the ferromagnetic core such that a w inding avis of each one of the at least three windings extends in a circumferential direction with respect to the ring-like configuration. The electromagnetic stirring apparatus further includes a multiphase AC power supply electrically connected to the at least three windings and a mounting member for mounting the stirring assembly below the metal furnace, wherein the multiphase AC power supply is configured for providing electrical currents to each of the at least three windings, the electrical currents being adapted for generating an electromagnetic stirring field for stirring a melt in the metal furnace when the stirring assembly is mounted below the metal furnace. According to a second aspect of the present disclosure, a metal furnace is provided. The metal furnace includes an electromagnetic stirring apparatus according to the first aspect arranged below the furnace.

According to a third aspect of the present disclosure, a method for stirring a melt in a metal furnace is provided. The method includes providing a stirring assembly below the metal furnace, the stirring assembly having a ferromagnetic core arranged in a ring-like configurationand at least three windings which are wound on the ferromagnetic core such that a winding axis of each one of the at least three windings extends in a circumferential direction with respect to the ring-like configuration. The method further includes providing electrical currents in each of the at least three windings, wherein the electrical currents are adapted for generating an electromagnetic stirring field for stirring the melt in the metal furnace when the stirring assembly is prov ided below the metal furnace.

Aspects of the present disclosure provide apparatus and methods for more energy efficient stirring of a melt in a metal furnace as compared to solutions known in the state of the art. Further, the improved apparatus of the present disclosure allows for increased flexibility and improved stirring of the melt, and allows for a more space efficient design suitable forapplications where space below the hearth of an EAF is restricted.

Those skilled in the art will recognise additional features and adv antages upon reading the following detailed description, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the figures are not necessarily to scale, instead emphasis being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts. In the drawings: Fig. 1 illustrates a schematic side view of an electric arc furnace having an electromagnetic stirring apparatus according to embodiments of the present invention;

Fig. 2a illustrates a schematic top view of an electric arc tanace having an electromagnetic stirring apparatus according to the current state of the art;

Fig. 2b illustrates a schematic top view of a melt flow in an electric arc tanace having an electromagnetic stirring apparatus according to the current state of the art;

Fig. 3 a illustrates a schematic top view of an electric arc tanace having an electromagnetic stirring apparatus according to embodiments of the present invention;

Fig. 3b illustrates a schematic top view of a melt flow in an electric arc furnace having an electromagnetic stirring apparatus according to embodiments of the present invention;

Fig. 4a-4d illustrate schematic top views of an electromagnetic stirring apparatus according to embodiments of the present invention;

Fig. 5 illustrates a schematic top view of an electromagnetic stirring apparatus according to embodiments of the present invention; and

Fig. 6 illustrates a schematic front view of an electric arc furnace having an electromagnetic stirring apparatus according to embodiments of the present invention. DETAILED DESCRIPTION

Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by w ay of explanation and is not meant as a limitation For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment.

It is intended that the present disclosure includes such modifications and variations.

Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment applies to a corresponding part or aspect in another embodiment as well.

Reference will first be made to Fig. 1, which shows an exemplary side section view of a metal furnace. The metal furnace as exemplarily shown in the figures is an electric arc furnace ( EAF ) 100, however the present disclosure is not limited thereto. For example, the metal furnace may include any one of an electric arc furnace ( EAF) for steelmaking, an electric arc furnace for ferro-alloy (for example, FeMn or FeNi) refining, a ladle furnace for steel refining, an aluminium melting furnace for scrap recycling, an aluminium holding furnace for alloying and casting, a copper anode furnace for copper refining, a lead melting furnace, or any other suitable metal furnace known in the art.

In the context of the present disclosure, the term “a melt” refers to a volume of material being processed in a metal furnace. Particularly, the melt is a volume of material in a metal furnace which is to be stirred by an electromagnetic stirrer. The melt may refer to a volume of material which is completely molten, or may refer to a v olume of material w hich is partially molten and partially solid. The material may include a metal or a metal alloy Particularly the volume of material is an electrically conductive metal, or may include electrically conductive metal in at least a portion of the volume of material. The electric arc furnace 100 includes a hearth 101 having a bowl shape, particularly having an egg-shaped cross section when v iewed from above. The hearth 101 is lined w ith a refractory lining 102 and a working lining 103 In the ease of a DC EAF , the working lining 103 may be a conductiv e lining, c.g a graphite lining. The hearth 101 contains the melt M. which is the material to be melted in the metal furnace Graphite electrodes 105 arc mov able mounted to the roof (not shown) of the electric arc furnace 100, and arc configured for generating one or more electric arcs to provide heat to the melt M. The EAF 100 exemplarily shown in the figures is an AC EAF which includes three electrodes 105. The electrodes 105 are configured to be movable in the vertical direction in order to control the arc generation as the electrodes 105 wear

The electric arc furnace 100 max be configured for tapping or pouring the melt M In this arrangement, the electric arc furnace 100 is mounted on a frame configured for tilting the electric arc furnace 100 m a tapping or pouring process, \n eccentric bottom tap-hole (EBT) 104 is prov ided at one end of the hearth 101 for the melt M to flow from the hearth 101Arranged below the hearth 101 of the electric arc furnace 100 is an electromagnetic stirrer (EMS) 200, 300, 400, 500. The EMS is configured to generate magnetic fields which penetrate the shell of the hearth 101 and the respectiv e linings 102, 103 and act on the melt M By applying magnetic fields, the meh M can be stirred so as to liquefy the material in the melt M faster more effectiv ely and with better temperature homogeneity The EMS typically includes an AC power supply, which may be mounted io the EMS or may be external to the LMS. to apply electrical currents and generate the magnetic fields.

In the current state of the art, the electromagnetic stirrer provided beneath the hearth 101 is a linear EMS 200. A linear EMS 200 according to the current state of the art is exemplarily show in Fig, 2a. w hich show s a top v iew of a hearth 101 of a metal furnace. The metal furnace includes a linear EMS 200 arranged below the hearth 101. A typical linear EMS 200 includes a ferromagnetic core 201 and a plurality of windings 202a-f wound around the ferromagnetic core 201. A multiphase AC power supply provides electrical currents to each one of the plurality of windings 202a-f such that a magnetic field is generated and applied to the melt M inside the hearth 101 of the metal furnace. Fig. 2a further shows an exemplary shape of the hearth 101 and the location of the eccentric bottom tap-hole 104.

The resulting flow pattern of the melt being stirred by the exemplary linear EMS 200 is illustrated in Fig. 2b. Since the magnetic field generated by the linear EMS 200 is only Ale to be applied to the melt M in a linear direction, the melt M can only be directed in a direction along the length of the linear EMS 200 and directly towards the wall of the hearth 101. When the melt flow impinges on the wall of the hearth 101, the flow changes direction to flow aroundand parallel to the wall of the hearth 101 . The melt flow encounters significant resistance when reaching the wall of the hearth 101. and the electric energy consumed by the linear EMS 200 to overcome the melt flow resistance is high.

In addition to the high electric energy consumption, the dimensions of the linear EMS 200 may also be disadvantageous for implementing electromagnetic stirring on the metal furnace.

Particularly, a linear EMS 200 of the present state of fee art has a larger size to generate sufficient force to overcome the melt flow resistance, and challenges may arise when allocating space below the metal furnace due to the excessive length of the linear EMS 200 For example, it may be challenging to provide sufficient space for a linear EMS 200 in a support frame design for the metal furnace, particularly a metal furnace mounted on a support frame designed to be lilted during a tapping or pouring process.

The present disclosure provides an EMS and methods for stirring a melt to solve the problems associated with the use of a linear EMS in metal furnaces. An EMS according to embodiments of the present disclosure offers reduced electric energy consumption, improved flexibility and more compact dimensions by implementing a ring-like configuration. An EMS according to the present disclosure is exemplarily shown in Fig. 3a.

According to an aspect of the present disclosure, an electromagnetic stirring apparatus for a metal furnace including a stirring assembly having a ferromagnetic core arranged in a ring-like configuration and at least three windings which are wound on the ferromagnetic core such that a winding axis of each one of the at least three windings extends in a circumferential direction with respect to the ring-like configuration. The electromagnetic stirring apparatus farther includes a multiphase AC powersupply electrically connected to the at least three windings and a mounting member for mounting the stirring assembly below the metal furnace (e.g. with the mounting member mechanically connected to the core and extending therefrom e.g.. upw ardly

- to atach the stirring apparatus to the metal furnace above), wherein the multiphase AC power supply is configured for pro\ iding electrical currents in each of the at least three w indings, the electrical currents being adapted for generating an electromagnetic stirring field for stirring a melt in the metal furnace when the stirring assembly is mounted below the metal furnace. According to a farther aspect, the stirring apparatus is used below the metal furnace, i.e, below the melt contained in the metal furnace.

According to a further aspect of the present disclosure, a metal furnace having a hearth and the electromagnetic stirring apparatus as described herein is provided, wherein the electromagnetic stirring apparatus is arranged bclov the furnace. Particularly, the electromagnetic stirring apparatus is arranged below the heart of the metal furnace. The metal furnace may be any one of an electric arc furnace for ferro-alloy (for example, FcMn or FcNi ) refining, a ladle furnace for steel refining, an aluminium melting furnace for scrap recycling, an aluminium holding furnace for alloy inti and casting, a copper anode furnace for copper refining, a lead melting furnace. In a preferred embodiment, the metal furnace is an electric arc furnace. According to a yet further aspect of the present disclosure, a method for stirring a melt in a metal furnace is provided. Particularly the method relates to stirring a melt in a metal fomace using the electromagnetic stirring apparatus described herein. The method includes providing a stirring assembly below the metal furnace, the stirring assemble having a ferromagnetic corearranged in a ring-like configuration and at least three windings which are wound on the ferromagnetic core such that a winding axis of each one of the at least three windings extends in a circumferential direction with respect to the ring-like configuration. The method further includes providing electrical currents in each of the at least three windings, wherein the electrical currents are adapted for generating an electromagnetic stirring field for stirring the melt in the metal furnace when the stirring assembly is provided below the metal furnace. According to embodiments of the present disclosure, the method for stirring a melt in a metal furnace is provided, wherein the metal furnace is an electric are fomace.

The electromagnetic stirring apparatus 300 includes a stirring assembly, which is arranged below the hearth 101 of the metal furnace. The stirring assembly includes the elements which are configured for generating magnetic fields w hich are used to stir the melt M. Particularly, the stirring assembly includes a ferromagnetic core 301 arranged in a ring-like configuration, and at least three windings 302a-f wound on the ferromagnetic core. When a current is applied to the at least three windings 302a-f such that a phase difference exists between the currents in two or more windings, a magnetic field is generated for stirring the melt M. In the EMS 300 exemplarily shown in Fig. 3a. six w indings 302a-f are provided. and the ferromagnetic core has a hexagonal ring-like configuration.

The ferromagnetic core 301 of the stirring apparatus may include at least one core element arranged in a ring-like configuration. In the most basic sense, the ferromagnetic core may include a single element having a ring-like shape. For example, the ferromagnrtic rare may include a single piece of ferromagnetic metal formed into a closed ring, for example, a toroid shape. However, a single core element may be impractical for a number of reasons, including challenging manufacturing and assembly of the windings 302a-f thereon. Thus, in preferred embodiments, the ferromagnetic core 301 may include a plurality of core elements arranged in a ring-like configuration. For example, a ferromagnetic core 301 may be formed by arranging a plurality of core elements each having a longitudinal shape into a ring-like configuration in the shape of a polygon. Alternatively foe plurality of core elements may each have an arc shape which, when arranged in a ring-like configuration, form the shape of a circle.

The plurality of core elements of the ferromagnetic core 301 may be arranged so that they join and abut each other at their respective ends, so that the ferromagnetic core 301 is a closed loop. Alternatively, the plurality of core elements may be arranged with a gap therebetween. In both cases, the ferromagnetic core 301 essentially forms an arrangement where the ferromagnetic core 301 is a magnetic loop, wherein the magnetic field within the ferromagnetic core 301 is a closed loop around the ring-like configuration.

In the context of the present disclosure, the term “ring-like configuration” refers to the overall shape of a ring. The ring-like configuration may be uniform or non-uniform. Particularly the ring-likc configuration refers to an arrangement of at least one object lying on a contour having a start point, where said contour circumscribes a circuit, and returns to an end point which is the same as the start point. For example, the ring-like configuration may be an arrangement of objects lying on a ring-like contour, such as a circle, an oval or a polygon. The arrangement of objects on the contour may be continuous, for example, where the objects join or abut to one mother to form a closed circuit, or the arrangement of objects on the contour may be discontinuous, for example, where the objects have spaces therebetween.

Further, the ring-like configuration defines a circumferential direction, which is the direction along the contour of the ring-like configuration. For example, for a ring-like configuration having a contour in a circular shape, the circumferential direction is the direction around the circle. As a further example, for a ring-like configuration having a contour in a polygonal shape, the circumferential direction is the direction around the polygon.

The w indings 302 a-f of the stirring apparatus arc arranged on the ferromagnetic core 301 such that a magnetic field is generated when electric currents are provided to two respective windings 302a-f Each respective winding 302a-f is wound on the ferromagnetic core 301 such that a winding axis of each respective winding 302a-f extends in a circumferential direction with respect to the ring-like configuration. The respective windings 302a-f are wound around the ferromagnetic core 301. Preferably, the windings 302a-f are evenly spaced around the ring-like configuration in the circumferential direction.

When referring to an axis extending in the circumferential direction with respect to the ringlike configuration, the axis is defined as a line extending tangential to the circumferential direction at a point around the contour of the ring-like configuration. For example, for a ringlike configuration having a contour in a circular shape, the axis extending in the circumferential direction is a line extending tangential to the circle. As a further example, for a ring-like configuration having a contour in a polygonal shape, the axis extending in the circumferential direction is a line extending coincident with a line segment of the polygon.

As exemplarily shown in Fig. 3a, the number of windings 302a-f is six. However, the present disclosure is not limited thereto. In general, the minimum number of windings 302a-f to achieve appropriate stirring is three. There is a balance to be made between the number of windings 3()2a-f and the size of the windings 302 a-f, as more windings may allow for a more ring-like magnetic field and resulting stirring action, but may restrict the size of the windings and the strength of the magnetic field which may be applied. The number of windings may also depend on the shape of the ring-like con figuration, and/or the number of core elements included in the ferromagnetic core 301. Preferably, the number of windings 302a-f is at least six windings. More preferably the number of windings 302a-f is at least one winding per core element included in the ferromagnetic core 301.

The resulting flow pattern of the melt being stirred by the EMS 300 according to the present disclosure is illustrated in Fig. 3b. The magnetic fields generated by the EMS 300 allow for a rotational flow of the melt M, such that the melt M is stirred around the hearth 101 instead of end-to-end as with a linear EMS. As a result, the melt M is not directed such that the melt flow impinges directly on the wall of the hearth 101. This rotational flow of the melt M exhibits si gni flcantl y lower flow resistance as compared to the end-to-end flow caused by a linear EMS.

As a result, the strength of the magnetic field for stirring the melt M may be reduced, and consequently, the electric energy consumption of the EMS 300 is significantly reduced The

EMS 300 according to embodiments of the present disclosure thus allows for improved stirring efficiency. Further still, due to the reduced strength of the magnetic field for stirring the melt M, the EMS 300 may be reduced in size as compared to a linear EMS, allowing for the EMS 300 to be more compact. Particularly, the EMS 300 may be easily adaptable to metal furnaces configured for tilting in a tapping or pouring process, which typically would have a sizeable mounting frame below the hearth 101 .

Reference will now be made to Figs. 4A-4D, which exemplarily show electromagnetic stirrers 400-1, 400-22, 400-3, 400-4 according to embodiments of the present disclosure. The exemplary electromagnetic stirrers 400-1, 400-2, 400-3, 400-4 include different arrangements of ferromagnetic cores 301 and windings 302 arranged in different ring-like configurations.

According to embodiments, which may be combined with other embodiments described herein, the electromagnetic stirring apparatus includes at least three core elements, wherein the at least three core elements have a longitudinal shape extending tangentially to the circumferential direction, and the ring-like configuration is preferably a polygonal configuration having at least three sides. Fig. 4 A exemplarily shows an EMS 400-1 having a ring-like configuration in the shape of a triangle. The ferromagnetic core includes three core elements 401a-c extending along the cireumferential direction of the ring-like configuration, and six windings 402a-f are wound thereon. Each of the three core elements 401 a-c are shown as having a gap therebetween, however the arrangement of the three core elements in a ring-like configuration forms a magnetic circuit through the ferromagnetic core. The exemplary EMS 400-1 has advantages in low complexity and a compact design suitable for smaller metal furnaces, or metal furnaces with restricted space beneath foe hearth. The triangular ring-type configuration may also be more suitable for stirring a melt in an egg-shaped hearth due to their similar shapes. Fig 4B exemplary show s an EMS 400-2 ha\ ing a ring-type configuration in the shape ofa four- sided polygon, particularly a square. The four-sided polygon, however; may instead be a rectangle or an irregular quadrilateral. The ferromagnetic core includes four core elements 401a-d arranged to form a magnetic circuit through the ferromagnetic core Such an EMS 400-2 may be suitable for maximising the use of av ailable space beneath metal furnaces having a mounting frame, as such a frame typically provides a rectangular-shaped area for the EMS.

Similar to the example EMS 400-1 shown in Fig. 4A, the EMS 400-2 includes two windings 302a-h per core element 301 a-d for a total of eight windings 302a-h. With a higher number of windings 302a-h, this configuration may allow for more flexibility in control, e.g, by allowing for more variety in winding pairings to be configured. Fig. 4C exemplarily shows an EMS 400-3 having a ring-type configuration in the shape of a six-sided polygon, particularly a hexagon. The ferromagnetic core includes six core elements 401a-fr and six windings 402a-f are wound thereon. A configuration having one winding per core element allows for largerw indings to bc installed, w hich may allow for a stronger magnetic field for stirring the melt. The two examples shown in Fig. 4B and 4C further allow for a space to be provided at the centre of the ring-like configuration . These designs may be advantageous for use in a DC EAF having a large electrode protruding from the botom of the hearth.

According to embodiments, which may be combined with other embodiments described herein, the electromagnetic stirring apparatus includes at least tw o core elements, wherein the at least two core elements have an arc shape extending in the cireumferential direction, and the ringlike configuration is preferably a circular configuration or an oval configuration.

Fig. 4D exemplarily shows an EMS 400-4 having a ring-type configuration in the shape of a circle. This example di tiers from the examples of Figs. 4A-4C in that the ferromagnetic core includes a plurality of arc-shaped core elements 401a-f Arc-shaped core elements 401a-f may generate a more uniformly circular magnetic field, allowing for uniform circular stirring of the melt, which may be more efficient than an EMS having longitudinal-shaped core elements. Further, the ends of each respective core element 401a-f are joined and abuted to each other, forming a closed loop ferromagnetic core. Abuting the core elements may improve the strength of the magnetic fields generated by the EMS 400-4.

Reference w ill now be made to Fig 5. w hich show s a top schematic view of an electromagnetic stirring apparatus 500 in a preferred configuration. The electromagnetic stirring apparatus 500 includes a ferromagnetic core having six core elements 501a-f arranged in a ring-like configuration having a hexagonal shape. Each of the six core elements 501a-f have a longitudinal shape extending in the circumferential direction, and arc configured to join and abut each other at respective ends. Six windings 502a-f are wound on the ferromagnetic core such that the winding axis of each one of the six w indings 5n2a-f extends in the circumferential direction.

An electromagnetic stirring apparatus according to aspects and embodiments of the present disclosure is adapted to be mounted below a metal furnace, particularly below a hearth of a metal furnace. Referring now to Fig, 6, which shows a side view of a metal furnace having an electromagnetic stirring apparatus according to embodiments of the present disclosure, a metal furnace 100 having a hearth 101 is supported by a furnace frame 111 , Hearth mounting members 1 10 max be prov ided to mount the hearth 101 to the furnace frame 1 1 1 In the embodiment shown in Figs. 5 and 6, fee electromagnetic stirring apparatus 500, particularly the stirring assembly of the electromagnetic stirring apparatus 500, is adapted to be mounted below a metal furnace with a mounting member 503. Mounting member 503 may further include a fastening means adapted for fastening the mounting member 503 to the furnace frame 111, for example, a bolted connection or a clamp connection. In exemplary embodiments, the electromagnetic stirring apparatus is mounted to a frame of the metal furnace. However, the present disclosure is not limited thereto, and the dectrornagnetic stirring apparatus may be mounted on a frame separate to the metal furnace. For example, the electromagnetic stirring apparatus may be mounted on a frame which is fastened to a floor below the metal furnace. Alternatively, the electromagnetic stirring apparatus may be mounted to a mov able frame w hich is configured to be positioned below a metal furnace, allow ing for the electromagnetic stirring apparatus to be mox ed from one metal furnace to another.

The electromagnetic stirring apparatus according to embodiments of the present disclosure include a multiphase AC power supply electrically connected to the at least three windings. The multiphase AC power supply is configured to providing electrical currents in each of the at least three w indings to generate an electromagnetic stirring field for stirring a melt in the metal furnace. The multiphase AC power supply may include any power supply capable of pro\ iding alternating current to each one of the at least three windings, such that the electrical current in one of the at least three windings may be adapted to be out of phase w ith the electrical current in another of the at least three windings. By applying out-of-phase electrical Currents to a pair of the at least three windings, the windings generate a positive magnetic polarity and a negative magnetic polarity, generating a magnetic field which may be used to stir the melt.

According to embodiments, which may be combined with other embodiments described herein, the multiphase AC power supply may be configured to provide a first electrical current in one of the at least three windings and a second electrical current in another one of the at least three windings, wherein the phase of the first electrical current is offset from the phase of the second electrical current.

According to embodiments, which may be combined with other embodiments described herein, the phases of the respective electrical currents for each of the at least three windings are selected for generating an electromagnetic stirring field for producing a rotational stirring motion of the melt in the metal furnace when the electromagnetic stirring apparatus is mounted below the metal furnace. In the context of the present disclosure, the term “electromagnetic stirring field” refers to one or more magnetic fields being generated by the electromagnetic stirring apparatus which cause the melt in the metal furnace to be moved in a stirring motion. According to an aspect, the electromagnetic stirring field is adapted for rotational stirring about an axis of rotation, preferably a single vortex or axis of rotation, e.g., a predominantly vertical axis at a center region of the furnace.

According to embodiments, which may be combined with other embodiments described herein, the at least three windings comprise pairs of windings, wherein the electrical currents have a predetermined constant phase difference between each pair of windings. Particularly, each winding has a co rresponding other winding which forms a pair. The plurality of windings may respectively include a plurality of pairs of windings. The predetermined constant phase difference may be constant throughout the plurality of pairs of windings, i.e. the predetermined constant phase difference is the same for all pairs of windings. According to embodiments, which may be combined with other embodiments described herein, the phase of the electrical current in an n ^{t h} winding is selected to be offset from the phase of the electrical current in an (n+m) ^th winding, where n is an integer corresponding to the number of the winding in the circumferential direction, and m is an integer which is less than half of the total number of windings. For example, in an electromagnetic stirring apparatus having six windings, the 1 ^st winding may be adjusted to be out of phase with either the 2 ^nd winding (m=l) or the 3 ^rd winding (m=2). As a further example, in an electromagnetic stirring apparatus having eight windings, the 1 ^st winding may be adjusted to be out of phase with either the 2 ^nd winding (m=1), the 3 ^rd winding (m=2) or the 4* winding (m=3). Further; the configuration of pairs or windings may be adjusted depending on a stirring mode.

In embodiments of the present disclosure, the mul tiphase AC power suppl y may be a component mounted to the stirring assembly, or may be a component which is separate to the stirring assembly. The multiphase AC power supply may be configured for providing a number of phases corresponding to a factor of the number of windings. For example, an electromagnetic stirring apparatus having six windings may include a multiphase AC power supply being configured for providing three-phase AC current. The multiphase AC power supply may be configured for providing electrical current having a frequency of 0.1 Hz or more, and/or 10 Hz or less. Particularly, the multiphase AC power supply may be configured for providing electrical current having a variable frequency in the range of 0.1 Hz to 10 Hz. According to embodiments, which may be combined with other embodiments described herein, foe multiphase AC power supply is adapted for providing a total power of at least 10 kW and/or at most 1000 kW. Particularly the multiphase AC power supply may be adapted for providing electrical current having a variable power in the range of 10 kW to 1000 kW.

According to embodiments, which may be combined with other embodiments described herein, the electromagnetic stirring apparatus max further include a controller configured for adjusting the phase of the electrical current in each of the at least three windings. The controller may be further adapted for adjusting the frequency and/or the magnitude of the electrical current in each of the at least three windings. The controller may include any suitable controller known in the state of the art which is capable of adjusting the parameters of the mul tiphase AC power supply For example, the electromagnetic stirring apparatus may include one of a programmable logic controller (PLC), a digital signal processor (DSP), a distributed control system (DCS) or an analogue control system.

Although various exemplary embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the ad\ antages of the invention w ithout departing from the spirit and scope of the invention. It will be obvious to those reasonably skilled in the art that other components performing the same functions may be suitably substituted. It should be mentioned that features explained with reference to a specific figure may be combined with features of other figures, even in those cases in which this has not explicitly been mentioned. Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper” and the like are used for case of description io explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc. andare also not intended to be limiting, Like terms refer to like elements throughout the description.

As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional dements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise . With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equi valents. Reference numbers

100 Metal furnace

101 Hearth

102 Refractory lining

103 Working lining 104 Eccentric bottom tap-hole (EBT)

105 Electrodes

110 Hearth mounting member

111 Furnace frame

200, 300, 400, 500 Electromagnetic stirring apparatus 201, 301 Ferromagnetic core

202a-f 302a-f, 402a-h Winding

401a-f, 501a-f Core element

503 Mounting member

M Melt