KR20080059654A - Method and apparatus for electromagnetic confinement of molten metal in horizontal casting systems - Google Patents

Abstract

The present invention provides an apparatus for strip casting of molten metal including a pair of casting rollers R1, R2, adapted to receive molten metal M along a horizontal axis, wherein a vertical distance separating the pair of casting rollers defines a molding zone; and an electromagnetic edge containment apparatus 15 positioned on each side of the molding zone having an induction coil wound about a portion of a magnetic member to generate magnetic lines of force upon application of a current, wherein the poles of the magnetic member are positioned distal from to aligned to the planar sidewall of the casting rollers and the current provides magnetic lines of force perpendicular to said horizontal axis that contain the molten metal in contact to the casting rollers without substantially increasing the temperature of the molten metal.

Description

METHOD AND APPARATUS FOR ELECTROMAGNETIC CONFINEMENT OF MOLTEN METAL IN HORIZONTAL CASTING SYSTEMS

The present invention relates to the continuous casting of metal strips, and more particularly to the electromagnetic restraint of molten metal in a continuous casting system.

Continuous casting of the metal is carried out in twin roll casting machines, belt casting machines or combinations thereof. Methods for casting in the horizontal and vertical directions are available. In particular, high speed twin roll strip casting machines have recently been developed in the steel industry which operate in a vertically descending direction.

Until now, mechanical edge dams have been employed to confine molten metal in the casting zone. Such devices include caterpillar type edge dams (with Hazelett casting machines) that move with the strip or fixed edge dams pressed against the surface of the roll. Fixed edge dams are used for casting steel strip twin rolls. This fixed mechanical edge dam is short in life because it is eroded by contact with the cold side walls of the roll. In addition, these mechanical edge dams provide a location for the creation of skulls that tend to be cut and enter the casting strip to create metallographically undesirable microstructures. The caterpillar edge dams are proven to be suitable for thick slab casting but are impractical for twin drum casting machines or thin strip casting machines in the steel industry, which involve a sharp change in cross section along the casting zone.

Electromagnetic edge dams have been employed in the prior art for strip casting of metals in vertical twin drum (twin roll) casting systems. An electromagnetic edge dam of the magnetic system type uses a combination of a magnet assembly and an AC coil to generate restraining forces. The electromagnetic edge dam of the induction system type only depends on the AC coil for generating the restraining force.

The electromagnetic edge dam of such a magnetic system uses a magnetic member that includes a yoke or core connecting two poles arranged opposite to the gap on which the molten metal is constrained. The magnetic element is made of a ferromagnetic material and is surrounded by a coil that allows alternating current over a yoke of a predetermined length. The magnetic flux generated by the flow of current in the coil is transmitted through the yoke to the magnet's poles to form a restraining force on the metal surface in the gap.

In general, some of the magnetic elements in the magnetic system are covered with an electrically conductive shield to minimize leakage of magnetic flux in a direction away from the gap. Such a magnetic restraint system has the advantage that the restraint current does not need to be high compared to a system using only induction coils. If a stronger magnetic field is required, it can be achieved at the same current level by reducing the pole area to focus the magnetic field. But such a system is not without its drawbacks. For example, such systems generally have low operating efficiencies resulting in losses due to magnetic hysteresis and core losses when an alternating magnetic field is applied to the magnetic material. In addition, high temperatures are formed that need to be divergent by cooling to prevent damage to the magnetic system.

Inductive confinement systems typically employ an inductor positioned close to the gap where the molten metal is constrained. The alternating current flowing through the inductor not only forms an induced current but also forms a magnetic field that changes over time on the surface of the molten metal to be constrained. The interaction of the current with the magnetic field provides a binding force. To improve the efficiency, a magnetic member is installed around the inductor to concentrate the current on the inductor surface facing the molten metal. Induction coil systems are generally simpler to design than magnetic systems. However, the induction system is disadvantageously limited in terms of the maximum electrostatic metal head that can be accommodated by the system. The maximum electrostatic metal head that can be supported in an induction coil system is limited because the induction coil system requires very high induction currents to provide adequate restraint, and such high currents are accompanied by an increase in heat generation and thus casting Interfere with or slow the coagulation process.

Referring to FIG. 1, the molten metal head that must be constrained in a vertical twin roll casting machine tends to be very high. Under normal operating conditions, the metal head height H1 is approximately 65% of the radius of the casting roll. Thus, the electromagnetic edge dam device used in a vertical twin roll casting machine must provide a magnetic field strong enough to accommodate a molten metal pool having a head height H1 that is 65% of the radius of the casting roll. This electromagnetic edge dam has not been successfully commercialized for two reasons. First, the high current required to receive the molten metal pool creates a constant wave on the upper surface of the molten metal pool that is too large in size during the casting process. Second, the large electromagnetic force required to receive the molten metal heads formed on top of the vertical roll casting system results in induction heating that hinders the solidification process on the sidewalls of the molten metal pool.

U. S. Patent No. 4,936, 374 discloses a vertical casting system and an electromagnetic restraining device having the aforementioned disadvantages. In addition, U. S. Patent No. 4,936, 374 discloses a casting roll having a rim portion, and the confining magnetic field is conducted through the rim portion of the casting roll. In addition to induction heating and wave generation, the rim portion of the casting roll disclosed in US Pat. No. 4,936,374 forms a ridge in the cast product and thus fails to provide a casting strip with uniform sidewalls (edges). Ridges formed in casting strips made using the apparatus and method disclosed in US Pat. No. 4,936,374 must be processed prior to rolling the casting strip. Further processing is undesirable as it increases the manufacturing cost.

Therefore, for a high speed continuous casting method of metals and alloys, which achieves uniformity of the casting strip surface, provides good confinement of molten metal in the casting zone, and obtains strip edges that can be rolled without the need for trimming. There is a demand.

The present invention overcomes the above mentioned difficulties and disadvantages by providing an electromagnetic restraint device integrated in a horizontal casting device. The magnetic field generated by the position of the electromagnetic restraint device and the alternating current in the present invention provides a metal casting strip having a substantially uniform edge (side wall). The present invention also provides a method and apparatus for manufacturing a metal casting strip having means for adjusting the profile of the sidewall of the metal casting strip.

In one embodiment of the present invention, the position of the electromagnetic restraint device relative to the forming zone of the horizontal casting device as well as the current applied through the electromagnetic restraint device is selected to provide a metal casting strip having a substantially uniform edge, The sidewalls of the metal casting strip may be substantially flat or concave or convex with respect to the centerline of the metal casting strip. The substantially uniform edge of the metal casting strip allows the metal casting strip to be rolled without further processing. An apparatus of one embodiment of the present invention is:

(a) a pair of casting rolls adapted to receive molten metal along a horizontal axis;

(b) an electromagnetic edge restraining device including an induction coil wound around a portion of the magnetic member to generate magnetic force lines upon application of current and located on each side of the forming zone; And

(c) means for supplying molten metal from the tundish along the horizontal axis to the forming zone while ensuring that the molten metal remains substantially unoxidized,

A vertical distance separating the pair of casting rolls forms the forming zone, the magnetic member comprising a first magnetic pole and a second magnetic pole positioned and aligned away from the sidewalls of the pair of casting rolls and the current Defines a molten metal in contact with the casting roll without increasing the temperature of the molten metal and provides a magnetic force line orthogonal to the horizontal axis, the tundish forming zone to substantially eliminate wave generation in the tundish caused by the magnetic force line. Away from you.

In another embodiment of the apparatus of the present invention, a horizontal roll casting apparatus is provided, through which the restraint of molten metal is provided by a combination of a mechanical edge dam and an electromagnetic edge dam. The casting apparatus of the present invention is:

(a) the pair of casting rolls in which a vertical distance separating the pair of casting rolls forms a forming zone and is adapted to receive molten metal along a horizontal axis;

(b) a discharge tip structure positioned to supply molten metal from the tundish along the horizontal axis to a forming zone while ensuring that the molten metal remains substantially unoxidized; And

(c) an edge restraint device located on each side of the forming zone;

The edge limiter is:

A mechanical edge dam extending partially towards the forming zone and positioned to at least cover an end of the discharge tip structure; and

An electromagnetic edge dam covering a portion of the mechanical edge dam extending partially towards the forming zone and including an aligned first pole and a second pole positioned away from the sidewalls of the pair of casting rolls; The electromagnetic edge dam provides a line of magnetic force orthogonal to the horizontal axis that defines a molten metal in contact with the casting roll.

In each embodiment, the vertical distance separating the pair of casting rolls arranged horizontally is a metal head height that allows the receipt of the molten metal by the magnetic force lines provided by the electromagnetic restraint device without increasing the temperature of the molten metal. To provide. For purposes of explanation, the expression "located and aligned away from the sidewalls of said pair of casting rolls" as used herein refers to a plane in which the magnetic poles of the electromagnetic edge dams define the sidewalls of the casting rolls towards the casting device centerline. It does not extend beyond, but is intended to indicate that it is located very close to the sidewall of the casting roll to provide a sufficient magnetic field to confine the molten metal in the forming zone. The magnetic poles of the electromagnetic edge dams can be adjusted to any distance from the side wall in the vicinity of the side wall of the casting roll, provided that sufficient restraint force is provided by the magnetic poles to the forming zone. In an embodiment, the sidewalls of the cast roll can be substantially planar. The expression “substantially flat” in relation to the sidewall of the casting roll indicates that the casting roll does not incorporate the lip portion. In an embodiment, the electromagnetic force lines are made by alternating current having a frequency of 40 Hz to 10,000 Hz through the electromagnetic edge receiving device.

In another embodiment of the present invention, there is provided a belt casting system employing an electromagnetic edge receiving device and manufacturing a metal strip having a substantially uniform edge, wherein the substantially uniform edge is a metal casting strip without further processing. Allow it to be rolled. The belt casting system of the present invention for strip casting molten metal is:

(a) a pair of opposing circulating metal belts passing over the rolls and having a perimeter aligned along the sidewalls of the rolls and having a surface for receiving molten metal;

(b) an electromagnetic edge restraint device comprising an induction coil wound around a portion of the magnetic member to generate magnetic field lines upon application of current and located on each side of the forming zone; And

(c) means for feeding the molten metal from the tundish along the horizontal axis to the forming zone,

A vertical distance separating the pair of circulating metal belts forms a forming zone and the current draws molten metal within a width in contact with at least a portion of the pair of circulating metal belts without increasing the temperature of the molten metal. Providing a defining magnetic force line, the tundish being spaced from the forming zone to substantially eliminate the occurrence of waves in the tundish caused by the magnetic force line.

In another aspect of the present invention, there is provided a metal casting strip that can be formed by the casting device. Metal casting strips:

(a) a first shell;

(b) a second shell; And

(c) a central portion between the first shell and the second shell, the central portion comprising grains with equiaxed texture, and the metal casting strip has a substantially uniform sidewall edge.

In another aspect of the present invention, a method for casting a metal strip is provided in which a magnetic field is used to control the geometry of the sidewalls of the metal strip. The method of the present invention is:

Providing molten metal to the forming zone along the horizontal axis;

Confining the molten metal within the forming zone by magnetic confinement means; And

Casting the molten metal into a metal casting strip, wherein the geometry of the sidewalls of the metal casting strip is formed by adjusting the magnetic restraining means.

The magnetic field can be adjusted to provide the geometry of the metal casting strip sidewalls that are concave or convex with respect to the centerline of the flat or metal casting strip. In one embodiment, the magnetic restraining means may comprise an induction coil wound around the magnetic member to produce a line of magnetic force upon application of current. The magnetic member has a first magnetic pole and a second magnetic pole positioned and adjacent to the molding zone.

The magnetic force lines produced by the magnetic restraint means can be adjusted by increasing or decreasing the current flowing through the induction coil or by changing the position of the magnetic restraint means relative to the forming zone. Positioning the first and second magnetic poles of the magnetic restraining means adjacent to the forming zone can produce a metal casting strip having concave sidewalls, and the first and second magnetic poles of the magnetic restraining means are separated from the forming zone. Positioning can produce metal casting strips with convex sidewalls.

1 is a schematic side cross-sectional view of a portion of a vertical roll casting device showing a pair of rolls and a molten metal head operated in accordance with the prior art;

2A is a schematic side cross-sectional view of one embodiment of a horizontal casting apparatus having an electromagnetic edge dam in accordance with the present invention.

2B is a side cross-sectional view showing one embodiment of a pair of belt casting machines with electromagnetic edge dam devices according to the present invention.

3 is a side cross-sectional view showing a forming zone of the horizontal casting apparatus of the present invention.

4 shows a table summarizing the magnetic field densities required to accommodate a molten pool of aluminum at different head heights.

5 shows the magnetic field strength produced by the electromagnetic restraint device according to the invention at a distance and a variable current measured from the sidewall of the caster roll.

FIG. 6 is a side cross-sectional view showing the cross section taken along line 2-2 of FIG. 2A, showing the position of the electromagnetic edge modem relative to the side wall of the roll casting machine. FIG.

7A-7D are side views showing different magnetic pole angles and orientations in accordance with the present invention.

8A to 8C are cross-sectional views of the electromagnetic edge dam apparatus of the present invention showing the path of magnetic force lines for the roll casting machine of the horizontal roll casting machine casting device.

9 illustrates an exemplary embodiment of the present invention in which the magnetic member has a split core design.

10 illustrates an exemplary embodiment of the present invention in which the magnetic member is of laminate design.

11 illustrates an exemplary embodiment of the present invention in which a mechanical edge dam is used in conjunction with an electromagnetic edge dam.

12 shows a side wall of a casting strip.

FIG. 13 is a table showing data on push of an electromagnetic edge dam. FIG.

14A and 14B show the edges of a strip made of high magnetic force in an electromagnetic dam.

15 shows a casting strip having a flat edge shape (straight edge).

FIG. 16 shows the casting strip after 87% thickness reduction (acceptable level of edge cracking).

The present invention provides an electromagnetic edge dam that confines molten metal in a forming zone horizontally placed in a roll casting system or a belt casting system with a magnetic field created by a current lower than the alternating current previously possible. By providing sufficient electromagnetic restraining means at lower alternating currents, the present invention utilizes electromagnetic restraint without generating a substantial increase in the temperature of the molten metal or the effects of wave generation.

As described above, in the conventional vertical casting method with a large molten metal head height, a larger magnetic force is required to suppress the higher pressure generated by the molten metal, and generally a larger magnetic force generates a higher current that generates heat. Need. For example, in the case of a general vertical casting method, a magnetic field strength of at least 0.24 T is required to accommodate molten aluminum at a height of 300 mm. In the present invention, the metal head height is kept low by the horizontally placed casting system so that the necessary suppression can be met with a relatively low magnetic field strength. For example, a 50 mm head height in a horizontal casting device according to the invention requires a magnetic field strength of only 0.055 T to accommodate molten aluminum in a horizontal position during casting. The invention is now described in more detail with reference to the accompanying drawings in the specification. In the accompanying drawings, the same and / or corresponding elements are denoted by the same reference numerals.

Referring to FIG. 2A, in one embodiment of the present invention, the horizontal roll casting device 10 has an electromagnetic edge positioned to provide a line of magnetic force for confining molten metal M in the forming zone 20 of the device 10. It has a dam 15. The magnetic field lines extend along a plane perpendicular to the plane through which the cast product exits. The horizontal roll casting apparatus 10 is performed using a pair of rotary cooling rolls R1 and R2 which rotate in opposite directions in the directions of the arrows A1 and A2, respectively. The term horizontal is meant to express that the casting strip is produced along a horizontal plane, where the horizontal plane is parallel to the section line 2-2 or approximately 30 ° plus or minus an angle from the horizontal plane.

Referring to FIG. 2B, in one embodiment of the present invention, the horizontal belt casting device 10 ′ is electromagnetically positioned to provide a line of magnetic force for confining molten metal M within the forming zone 20 of the device 10 ′. Edge dam 15. The magnetic field lines extend along a plane perpendicular to the plane through which the cast product exits. The horizontal belt casting apparatus 10 'is implemented using a pair of rotating belts B1 and B2 which rotate in opposite directions in the directions of the arrows A1 and A2, respectively. Although subsequent figures are directed to the horizontal roll casting apparatus 10 shown in FIG. 2A, the following description is in contact with the belts B1 and B2 which are reversely rotated instead of contacting the molten metal with the rolls R1 and R2. The same applies to the horizontal belt casting apparatus 10 'shown in FIG. 2B except that. Other differences between the horizontal roll casting device 10 and the belt casting device 10 'can be seen through the following description.

Referring to FIG. 3, molten metal M is supplied to the forming zone 20 by a feed tip T, which may be made of a suitable ceramic material. The feed tip T distributes the molten metal M in the direction of arrow B directly on casting rolls R1 and R2 which respectively rotate in the direction of arrows A1 and A2. The gaps G1 and G2 between the feed tip T and the respective rolls R1 and R2 are kept as small as possible to prevent the molten metal from leaking and to minimize the exposure of the molten metal to the atmosphere. Suitable gaps G1 and G2 have dimensions of about 0.01 inch (0.25 mm). The plane L passing through the center of the rolls R1 and R2 passes through a region of minimum clearance between the rolls R1 and R2 called roll nips N.

The molten metal M discharged from the feed tip T is in direct contact with the cooling rolls R1, R2 in the zones 18, 19, respectively. Upon contact with the rolls R1 and R2, the molten metal M cools and starts to solidify. The cooled metal produces an upper shell 16 of metal solidified near roll R1 and a lower shell 17 of metal solidified near roll R2. As the molten metal M proceeds toward the nip N, the thicknesses of the shells 16 and 17 increase. A large dendrite 21 of solidified metal is made at the interface between each of the upper and lower shells 16, 17 and molten metal M. Large dendrite 21 is pulled into the central portion 12 of the flow of broken and slowly moving molten metal M and conveyed in the direction of arrows C1 and C2.

Traction action of the flow causes the large dendrite 21 to break into smaller dendrite 22 (not shown to scale). At the central portion 12 upstream of the nip N, the metal M is a semi-solid comprising a solid component and a molten metal component comprising the solidified small dendrite 22. The metal M in zone 23 is thick because partly the small dendrite 22 is dispersed therein. At the position of the nip N, part of the molten metal is pressed back in the opposite direction to the arrows C1, C2. The forward rotation of the rolls R1, R2 in the nip N is essentially a solid part of the metal (upper and lower shells 16, 17 and central) so that the metal solidifies as it exits the point of the nip N. Only the small dendrite 22 in (12) is advanced while forcing the molten metal in the central portion 12 upstream from the nip (N).

Downstream of the nip N, the central portion 13 is a solid center layer 13 comprising a small dendrite 22 sandwiched between the upper shell 16 and the lower shell 17. In the central layer 13, the small dendrite 22 is about 20-50 microns in size and has a generally equiaxed shape (spherical) as opposed to having a columnar shape. The solidified center layer 13 and the three layers of the upper and lower shells 16, 17 constitute a solid casting strip.

The rolls R1 and R2 serve as heat sinks for the heat of the molten metal M. In the present invention, heat is transferred in a uniform manner from the molten metal M to the rolls R1 and R2 in order to ensure the uniformity of the surface of the casting strip. The surfaces D1, D2 of each roll R1, R2 can be made of a material having good thermal conductivity, such as steel or copper or other metal material, can be composed of a surface in the form of a fabric, and the molten metal M Surface irregularities (not shown) in contact with the substrate. Surface irregularities may serve to increase heat transfer from surfaces D1 and D2. Rolls R1 and R2 may be coated with a material such as chromium or nickel to facilitate separation of the casting strips from rolls R1 and R2. In a preferred embodiment, the rolls R1, R2 comprise the surfaces D1, D2 and comprise a ferromagnetic material. In embodiments of the invention in which the rolls R1 and R2 do not comprise a ferromagnetic material, the cast surfaces D1 and D2 of the roll as well as the sidewalls of the roll may be coated with a ferromagnetic material.

Appropriate control, maintenance and selection of rolls R1 and R2 may affect the workability of the present invention. The roll speed determines the speed at which the molten metal M advances toward the nip N. If the speed is too slow, the large dendrite 21 will not attract enough force to be drawn into the central portion 12 and to break into the small dendrite 22. Thus, the present invention is suitable for operation at high speeds such as about 25 to about 400 feet per minute, about 100 to about 400 feet per minute or about 150 to about 300 feet per minute. The leading speed at which the molten aluminum is directed to the rolls R1 and R2 may be less than the speeds of the rolls R1 and R2 or approximately one quarter in the roll. The high speed continuous casting according to the invention can be partially achieved since the surfaces D1, D2 in the form of fabrics ensure uniform heat transfer from the molten metal M.

Roll separation force may be a parameter in practicing the present invention. Roll separation force is the force present between rolls because there is a strip in the roll gap. Roll separation is particularly high when the strip is plastically deformed by the roll during roll casting. An important advantage of the present invention is that no solid strip is made until the metal reaches the nip (N). The thickness is determined by the dimensions of the nip N between the rolls R1 and R2. The roll separation force may be large enough to press the molten metal upstream from the nip N. Excess molten metal passing through the nip (N) may cause the solid central portion 13 and the layers of the upper and lower fins 16, 17 to fall apart from one another and become misaligned. Failure of sufficient molten metal to reach the nip N may result in the formation of the strip too early, as occurs in conventional roll casting processes. Suitable roll separation forces are about 25 to about 300 pounds per inch of casting width or about 100 pounds per inch of casting width. In general, slow casting speeds may be required when casting thick dimension aluminum alloys to remove heat from thick aluminum alloys. Unlike conventional roll casting, this slow casting rate does not result in excessive roll separation force in the present invention because no solid aluminum strip is made upstream of the nip.

In the conventional manner, the roll separation force was a limiting factor in producing a small thickness aluminum alloy strip product, but in the present invention, the roll separation force is not so limited because it is smaller than the conventional manner. The aluminum alloy strip can be made to a thickness of approximately 0.1 inches or less at a speed of about 25 to about 400 feet per minute. The method of the present invention can also be used to make aluminum alloy strips of thick dimension, for example about 1/4 inch thick.

The aluminum alloy strip 20 continuously cast according to the invention comprises a first layer of aluminum alloy and a second layer of aluminum alloy (corresponding to the shells 16, 17) and an interlayer therebetween (solidified center layer 13). ) Is included. Since the force exerted by the roll is small (300 pounds per inch or less), the grains in the aluminum alloy strip of the present invention are substantially undeformed. The strip is not solid until it reaches the nip N and is therefore not hot rolled by conventional twin roll casting and subjected to the usual thermo-mechanical treatment. There is no conventional hot rolling in the casting apparatus, so that the grains of the strip 20 remain substantially undeformed and retain the initial crystal structure obtained during solidification, ie spherical structure like spherical shape.

Continuous casting of aluminum according to the invention is achieved by initially selecting the dimensions of the nip N corresponding to the desired thickness of the strip S. The speed of the rolls R1, R2 can be increased at a rate lower than the rate at which the roll separation force increases to a level that indicates the desired production rate or plastic deformation of the cast strip occurs between the rolls R1, R2. Casting at the speed intended by the present invention (i.e., about 25 to about 400 feet per minute) solidifies the aluminum alloy strip about 1000 times faster than aluminum alloy casting, such as ingot casting, and more than the characteristics of an aluminum alloy cast product such as ingot. To improve the properties of the strip.

Molten metal (M) discharged from the feed tip (T) is confined in the forming zone (20) by an electromagnetic edge dam (15) positioned to face a line of magnetic force perpendicular to the plane (2-2) to which the casting is directed. do. In one embodiment, an electromagnetic edge dam 15 is located on each side of the casting device. In the preferred embodiment as shown in FIGS. 6 and 11, the molten metal M is molded zone 20 during casting by a mechanical edge dam 55 used in combination with the electromagnetic edge dam 15. Constrained within, the mechanical edge dam 55 is located near the feed tip T and the electromagnetic edge dam 15 is positioned overlapping the mechanical edge dam 55 to restrain the force along the entire length of the forming zone 20. To provide.

The current and / or frequency used by the electromagnetic edge dam 15 to maintain the molten metal M in the forming zone 20 is more than normally required in conventional casting equipment using electromagnetic edge dams. Practically small. Conventional casting equipment using electromagnetic edge dams requires high magnetic field forces to receive the molten metal and consequently results in induction heating of the molten metal, negatively affecting the solidification process. By reducing the magnitude of the electromagnetic force required in the present invention, the current and / or frequency conducted through the electromagnetic edge dam is also reduced, advantageously reducing the occurrence of induction heating to the side of the molten metal in the forming zone.

In the description of the present invention, but not by way of limitation, the reduction of the electromagnetic force required to accommodate the metal in the forming zone is due to the fact that the molten metal pool is located above the roll casting device of the conventional vertical casting device as shown in FIG. In contrast to the larger height H1, it is thought to be related to the reduced height H ₂ of molten metal from the feed tip T as shown in FIG. 3. As described above, the height H1 (or depth) of the melt pool above the vertically positioned casting rolls as shown in FIG. 1 is approximately 65% of the height of the casting rolls R1 and R2 and is between 8 inches and 20 inches. It can be in the range of inches. Referring to FIG. 3, the height H ₂ of the molten metal may be about 1 inch when guided from the feed tip T to the forming zone 20 in the present invention, and in some instances is further reduced to 0.5 inch. Can be. In the future, the difference between the vertical position of the metal level in the tundish and the vertical position in the center of the cast strip is referred to as the "molten metal head".

The relationship between the height of the molten metal head H ₂ and the magnetic field density required to accommodate molten aluminum at different head levels is well explained through the following equations. First, the pressure exerted by the molten metal head that the magnetic field must receive in the forming zone 20 is calculated from the following equation.

p = ρgH ₂

Where p is the magnetic pressure in Pa (Pascals), ρ is the density of the metal, g is the acceleration of gravity, and H ₂ is the height of the molten metal head. The pressure generated by the molten metal head determines the strength of the magnetic field that must be generated by the electromagnetic edge restraint device to receive the molten metal head in the forming zone 20. In the present invention, the height of the molten metal head H ₂ guided horizontally to the forming zone 20 by the feed tip T may be as low as 0.5 inches. The pressure generated by the molten metal head of varying height H ₂ from the feed tip T of the horizontal roll casting device 10 of the present invention was determined using the above-described formula and is shown in the table shown in FIG. It is described. The pressure ranges from about 125 Pa for a metal head height H ₂ of approximately 0.5 inches (12.7 mm) to about 2,492 Pa pressure ranges for a metal head height H ₂ of approximately 10 inches (254 mm).

The pressure required to receive the molten metal head H _{2 in the} forming zone 20 is used in the equation below to determine the required magnetic field density B.

p = B ² / 2μ _o

Where p is the magnetic pressure in Pa, B is the magnetic field density in T (Tesla), and μ _o is the permeability of air (= 4π x 10 ^-7 H / m). Referring to FIG. 4, the magnetic field density required for a relatively high molten metal head height H _{2 of} approximately 254 mm (10 inches) for the feed tip T from the above equation is calculated as 0.079 T (790 Gauss). And the required magnetic field density for a molten metal head height H ₂ of approximately 12.7 mm (0.5 inch) is about 0.0177 T. As shown in FIG. 4, reducing the molten metal head height H ₂ reduces the magnetic field density required to receive the molten metal M in the forming zone 20. The magnetic field density required to accommodate molten metal head height in accordance with the present invention can be obtained by electromagnets of relatively low current levels. In one embodiment, the electromagnetic edge dam operates approximately 2000 amps (ie, 10 wound coils running 200 A).

In another aspect of the present invention, the physical positioning of the electromagnetic edge dam, the molten metal head height, and the strength of the magnetic field can be changed to control the edge position of the molten metal in the forming zone with respect to the roll casting device sidewalls. The strength of the magnetic field at different distances from the surface (edge) of the roll casting device can be calculated by the following equation.

Where B _L = magnetic field strength at the distance L (m) of the gap from the roll surface.

nI = number of coils wound and current.

w = roll gap (l = (μ _r ) in the relationship between the relative transmission of the steel casting apparatus roll (μ _r ) (taken at 600), the skin depth (δ) for the steel of the casting apparatus roll, and the roll gap (w) δw / 2) ^1/2 ).

D = distance between electromagnet pole and roll surface.

H = height of the magnetic pole.

Referring to FIG. 5, the magnetic field strength was calculated using the above equation and is expressed as a function of the frequency (Hz) of current conducted through the electromagnetic edge dam 15, the distance calculated for the magnetic field strength is the 10 mm to 80 mm inward from the side wall (baseline 1 is 10 mm, baseline 2 is 20 mm, baseline 3 is 30 mm, baseline 4 is 40 mm, baseline 5 is 50 mm, baseline 6 is 60 mm). In each calculation, the height H of the poles was set to 8 mm, the distance D between the electromagnet poles and the roll surface was set to 4 mm, and the roll gap w was set to 4 mm. In addition, the reference lines constructed to indicate minimizing the magnetic field required to accommodate the metal head are 250 mm (baseline 7), 150 mm (baseline 8), 100 mm (baseline 9) and 50 mm (baseline 11). It has the same height (H ₂ ). The figure shown in FIG. 5 shows that the 0.079 T magnetic field density required for the 250 mm metal head 8 can be produced by an electromagnet at a distance of 20 mm into the roll gap.

Therefore, if desired, the edge of the casting strip can be received inward from the casting rolls R1, R2 surface by increasing the current in the edge dam. The magnetic field density decreases sharply at further distances from the roll surface, and a small metal head height as high as 50 mm can be accommodated at a distance of 40 mm or more by operation of the edge dam at 2000 amps. If necessary, the confinement range can be further extended by increasing the magnetic force (nI) for the edge dam. When increasing the magnetic force, it is necessary to take into account the considerations given to the heating effect of the edge dam.

The diagram shown in FIG. 5 also shows that the electromagnetic edge dams can effectively operate at any selected frequency when used in the present invention. The loss of magnetic field is only pronounced when operating at frequencies above 10 kHz.

In addition to the molten metal head height and magnetic field density, the position of the electromagnetic edge dam relative to the casting roll can be adjusted to provide an electromagnetic force line for confining the molten metal M in the forming zone 20. Referring to FIG. 6, an electromagnetic edge dam 15 may be positioned such that the magnetic poles of the magnetic members are aligned with the sidewalls 13 of the casting rolls R1 and R2. In one embodiment, an electromagnetic edge dam can be positioned at the distal end of the magnetic member magnetic pole of each casting roll R1, R2. In an embodiment of the invention in which a horizontal belt casting device is employed as shown in FIG. 2A, each magnetic pole of the magnetic member is aligned adjacent to the sidewall from the end with respect to the sidewalls of the casting belts B1, B2, and is electromagnetic Edge dam 15 may be located. For this purpose, the expression “aligned adjacent to the sidewall from the end to the sidewall of the casting belt” does not extend toward the casting device centerline beyond the plane defined by the sidewall of the casting belt. It is intended to indicate that it is located very close to the sidewall of the casting belt to provide a magnetic field sufficient to receive molten metal in the forming zone.

The electromagnetic edge dams of the present invention can also be implemented in nonmagnetic materials (nonferromagnetic materials) such as copper. However, when the roll comprises a nonmagnetic material, the penetration of the magnetic field in the roll gap can be limited, so that the limitation generally occurs in the plane near the end of the roll. As shown in FIG. 8D, it is possible to infiltrate the gap by coating the end surface and casting surface 200 of the roll with ferromagnetic material (iron, nickel or cobalt) to the required defined depth.

In general, conventional casting devices form the magnetic rolls and casting rolls of the electromagnetic device to focus the magnetic field towards the forming zone. In one example, a conventional cast roll employs a lip extending from the sidewall of each roll and may further include a magnetic pole having a geometry corresponding to the extended lip of a conventional cast roll. Unlike conventional casting apparatus, the present invention does not require a specially configured casting roll to facilitate concentration of the magnetic field generated by the electromagnetic edge dam. In one embodiment of the invention, the sidewalls 113 of the casting rolls R1, R2 may be substantially planar. Moreover, the electromagnetic edge dam 15 of the present invention can be positioned such that the surface of the electromagnetic edge restraint device is aligned with the surface of the side wall 113 which is the plane of the casting roll, where the electromagnetic edge dam 15 is Mainly close to the rolls R1 and R2. The electromagnetic edge dam 15 may also be located distal from the side wall 113 of the casting roll. Regardless of the position of the electromagnetic edge dam 15, the electromagnetic edge dam 15 is positioned to provide sufficient electromagnetic force to receive the molten metal M in the forming zone 20.

The position of the edge dam 15 depends on the current or frequency used for the edge dam. For example, a low current provides a small electromagnetic force line, thus requiring the edge dam 15 to be located closer to the forming zone 20. The greater the current conducted through the electromagnetic edge dam, the larger the size of the electromagnetic force lines, and thus the electromagnetic edge dam can be located further away from the forming zone 20.

7A-7C, in one embodiment the location of the electromagnetic edge dam 15 and the size of the electromagnetic force lines are substantially flat sidewalls (FIG. 7A), convex sidewalls (M) in the molten metal M in the forming zone 20. 7B) or to form a concave sidewall (FIG. 7C). In one example, a current of 2200 amps / turns produces a casting strip having concave sidewalls, a current of 1200 amps produces a casting strip having substantially flat or straight sidelines, and a 1200 amp count level. The current in produces a cast strip having substantially convex sidewalls. The above examples are for illustrative purposes and are not intended to limit the present invention, and any current may be applied to the present invention unless the current brakes sufficient restraining force on the forming zone 20 and results in excessive induction heating. . In a preferred embodiment of the invention where the sidewalls of the casting strip are concave or convex, the curvature of the sidewalls may be defined by a radius that is approximately half the height of the molten metal head.

In another embodiment, the electromagnetic edge dam 15 can be configured to provide molten metal to the forming zone with sidewalls that are convex with respect to the centerline of the molten metal M in the forming zone 20. Preferably, the sidewalls of the molten metal in the forming zone are substantially aligned with the surface of the plane of the roll casting apparatus as shown in FIGS. 8A and 8C. Alternatively, as shown in FIGS. 8B and 8D, the electromagnetic edge dam 15 may be configured to transmit magnetic field lines primarily beyond the sidewalls 113 of the roll, where the molten metal is an edge of the roll casting device. It is bound inside.

The structure of the electromagnetic edge dam 15 is shown in detail in FIG. 8A which shows a cross-sectional view of the device of the edge dam 15 shown in FIG. 2A. In a preferred embodiment of the present invention, the electromagnetic edge dam 15 is a magnet type restraint system and includes a C-shaped magnetic member as a whole. Accordingly, the magnetic member 30 includes an upper arm 34 or a magnetic pole and a lower arm 36 or a core 32 having a magnetic pole extending to form a C shape as a whole. The core 32 includes an induction coil winding 38 consisting of a coil wound around the core 32 of the magnetic member 30 to form an induction coil. Thus, the winding consists of a plurality of conductors wound around the core 32 of the magnetic member 30. The core winding 38 around the core 32 may be made of a solid metal such as copper wire.

Referring to FIG. 8A, the upper arm 34 terminates at the pole surface 42, while the lower arm 36 terminates at the pole surface 44 with molten metal M retained therebetween. Thus, the magnetic pole surfaces 42, 44 are formed by the magnetic member 30 as shown by magnetic field lines 48 as the induction coil 38 passes from one magnetic pole surface 42 to another magnetic pole surface 44. It defines the surface on which magnetic lines of force occur.

9A-9C illustrate different magnetic pole surface 44 angles and orientations in accordance with the present invention. As will be apparent to those skilled in the art, the intensity of the magnetic field across the gap decreases when the gap 43 between the magnetic pole surfaces increases. 9A shows a cross section of the magnetic member 30, wherein the magnetic pole surfaces 42, 44 have a negative angle with respect to the vertical plane that is substantially orthogonal to the plane where casting is to be made. Negative angle means that the gap 43 between the magnetic pole surfaces is smaller at the outer edge of each magnetic pole surface than the inner edge of each magnetic pole surface. As a result, the restraining force generated by the magnetic member shown in Fig. 9C is stronger at the outer edge than at the inner edge of each magnetic pole surface. 9B shows a cross section of the magnetic member 30, wherein the magnetic pole surfaces 42, 44 are not angled with respect to the vertical plane that is substantially orthogonal to the plane where casting is to be made. Angular zero means that the gap 43 between the magnetic pole surfaces is the same at the inner edge of each magnetic pole surface and at the outer edge of each magnetic pole surface. Therefore, the magnetic field generated by the magnetic member shown in FIG. 9A is relatively uniform across each magnetic pole surface. 9C shows a cross section of a magnetic member having magnetic pole surfaces 42, 44 that are partially parallel and not partially parallel. The inner region of the pole surfaces 42, 44 has a negative angle with respect to the horizontal direction.

In one embodiment of the invention, magnetic member 30 is formed of a ferromagnetic material, such as silicon steel, and may be formed as a solid piece of such ferromagnetic material. Alternatively, magnetic member 30 may be formed of a plurality of ferromagnetic materials, such as the split core design shown in FIG. 10. In another embodiment, the magnetic member 30 may be formed of a series of laminated elements that are processed and secured together using mechanical, adhesive, or similar means to produce the desired structure as shown in FIG. In many instances, the use of such a laminate design is desirable because the lamination scheme distributes the magnetic flux more evenly in the magnetic member and reduces the loss due to saturation of the magnetic member. In addition, in a magnetic member made of laminated ferromagnetic material, heat-dissipated electrical energy is also uniformly distributed and more easily removed, particularly with good thermal conductivity when using an adhesive to hold the laminated elements together.

Referring again to FIGS. 8A-8D, surrounding magnetic member 30 is an outer shield 50, which is preferably made of a metal, more preferably a metal having structural stiffness and extremely high electrical and thermal conductivity. . Preferably, the outer shield 50 is made of copper although other metals such as gold and silver may likewise be used. The high electrical conductivity of the outer shield 50 facilitates confining the lines of magnetic force within the magnetic member while good thermal conductivity promotes the dissipation of heat from the entire device. As will be appreciated by those skilled in the art, the outer shield 50 may be equipped with a tube for dispensing cooling fluid through the cooling channel or outer shield surface or surface to the outer shield to further facilitate the removal of heat generated by the electromagnetic field. have. For example, an inlet may be employed to allow cooling fluid to pass through the outer shield and be removed from the discharge port when additional cooling capability is required. Thus, cooling fluid can pass through conduits in the outer shield to remove heat generated by the electromagnetic field.

The electromagnetic edge dam of the present invention also includes an inner shield 56 dimensioned to fit within the C-shaped magnetic member 30. Similarly, the inner shield 56 serves to limit the magnetic force lines generated by the coil 38 of the magnetic member 30 and ensure that the magnetic force lines are maintained in the magnetic member 30. In addition, it is also possible and sometimes desirable to include conduit means for passing cooling fluid through the inner shield where it is desired to increase the ability to dissipate heat from the magnet. It is also possible to allow heat to dissipate into the inner shield, especially when using silicon steel laminates having a grain orientation that is desirable for magnetic fields to flow in the laminate.

The path of the magnetic field of the present invention is shown in Figures 8A-8D. In FIG. 8A, the magnetic field flows from one pole of the edge dam to the other in a plane parallel to the side of the roll. This is applicable to non-ferromagnetic metal rolls such as copper. The magnetic field creates a restraining force on the end surface of the roll. 8B shows a case where a magnetic field penetrates into the gap and receives molten metal inward from the roll surface. This is the case for ferromagnetic rolls and strong magnetic fields. As shown in FIG. 8D, it may also be achieved by applying a ferromagnetic coating 200 of sufficient depth to the end surface of the roll material and the end of the casting surface that is not ferromagnetic.

In designing the electromagnetic restraint device employed in the present invention, various other techniques may be used to dissipate heat generated by the electromagnetic field. As shown in FIG. 8C, the winding 40 may be formed of a circular conductor having a central opening 41. Thus, it is possible to allow the coolant to pass through the central opening of the winding 40 to promote the dissipation of heat generated by the electromagnetic field. As shown in FIG. 12, the core 30 may also have a cooling conduit 47, in which the cooling fluid passes through the cooling conduit 47 to promote the dissipation of heat generated by the electromagnetic field. do.

FIG. 12 shows a preferred embodiment of the present invention wherein a mechanical edge dam 55 is used with an electromagnetic edge dam 15 having a magnetic member 30. Magnetic member 30 lies in front of mechanical edge dam 55. In order to reduce the magnetic resistance at the inlet of the forming zone, the mechanical edge dam 55 should ideally have a ceramic free surface and contain magnetic material. Ceramic materials can also be used to make mechanical edge dams 55 if the process conditions make it impossible to use metal materials. In one embodiment of the invention, a mechanical edge dam 55 is positioned to ensure that the molten metal is confined within the casting apparatus while it is led from the tundish H to the feed tip. Once the molten metal M reaches the feed tip T, the restraining force is provided by the electromagnetic edge dam 15. In this arrangement, the life of the mechanical edge dam 55 is increased by the electromagnetic edge dam 15 because the electromagnetic edge dam 15 is located in the worst environmental part of the casting apparatus.

The examples described below are intended to illustrate further description of the present invention and the advantages presented in accordance with the present invention. It is not intended that the invention be limited to the specific examples described.

Example 1. Electromagnetic Push  Confirm

An aluminum strip was cast in accordance with the present invention using a casting apparatus with steel rolls. The strip was tested metallographically to identify the effect of electromagnetic forces on the molten metal within the forming zone. Test samples were made using a combination of electromagnetic edge dams and mechanical edge dams according to the present invention and a horizontal roll casting apparatus. Three different thickness (2.44 mm, 2.29 mm, 2.16 mm) casting strips were cast by operating an electromagnetic edge dam at 2180 amps. The sample was cut at the edge of the strip and prepared for metallographic examination. It was confirmed that the center of the cast strip was pushed inward as compared to the outer surface of the strip as shown in FIGS. 14A and 14B. This observation confirms the restraining effect of the electromagnetic edge dams during casting, since the central part of the strip solidifies the latest.

The depth of restraint effect in the roll gap was evaluated by first measuring the width of the casting strip at room temperature, with the width of the casting strip being approximately 400.5 mm. From these measurements, the width of the strip in the forming zone can be estimated at 406 mm by adding the shrinkage that occurs during solidification and cooling to room temperature.

Given that the casting rolls are approximately 432 mm wide, the magnetic field is approximately 13 mm (13 mm = ((432 (width of roll)-406) from the casting roll surface on each side of the casting roll. It is evident that it is pushed by a distance of) / 2) More specifically, subtracting the calculated width of the casting strip in the forming zone from the width of the casting roll calculates the overall displacement caused by the electromagnetic edge dam. The amount of displacement caused by a single edge dam is calculated by the number of edge dams used, in which two electromagnetic edge dams were used at opposite ends of the casting rolls, as summarized in the table shown in FIG. Similarly, similar electromagnetic push effects were observed for three different strip thicknesses: The degree of magnetic field push was measured as the depth of the center portion of the strip relative to the strip edge. Since the narrow roll gap creates greater magnetic field density at a given distance, the magnetic field push for the thinner strip appeared somewhat larger .. As summarized in Figure 13, the two sides (drive side) of the casting rolls were summarized. The difference in magnetic field push between the and operator side is thought to be due to the change in the position of the electromagnetic edge dam and the mechanical edge dam.

Example 2. Control of Casting Strip Edge Profile

The edge profiles of the cast strips were examined for operation at different magnetomotive force levels in the electromagnets. If the edge was not trimmed before rolling, the edge profile obtained at 2180 amps shown in FIG. 14 was judged not suitable for subsequent rolling of the strip. In order to provide a casting strip with an edge profile suitable for rolling without further processing, the electromagnet of the electromagnet has been reduced to reduce the magnetic field push on the central part of the casting strip so that the edge profile of the strip becomes flat or slightly convex.

The flat edge profile was obtained in a cast strip in which a current of 180 amps (or 1620 amp times) was applied to the electromagnet. To obtain a flat edge profile, the magnetic field should be chosen to offset the pressure caused by the molten metal in the forming zone caused by the metal head where the roll pressure contribution is small. Referring to Figure 15, the edges of the casting strips made under these conditions were flat to allow rolling the edges of the casting strips without trimming or other additional processing.

This strip was successfully inline rolled through a four-stage rolling mill. The cast strip was rolled to a thickness of approximately 0.36 mm (0.014 inch) at a thickness of the cast state of 2.7 mm (0.107 inch), which corresponds to a 87% thickness reduction. Referring to Fig. 16, the plate made by this method showed only small cracks at the edges, which can be removed by trimming before winding into the rolling coil.

With proper control of the electromagnetic edge dams, high quality edge profiles that can be rolled at high rolling rates have been obtained in the casting strips, which increase production yield and improve process efficiency.

While the invention has been shown and described with respect to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Therefore, it is intended that the present invention not be limited to the forms and contents illustrated and described, but fall within the scope of the claims.

Claims (31)

As a device for strip casting of molten metal, (a) a pair of casting rolls adapted to receive molten metal along a horizontal axis; (b) an electromagnetic edge restraining device including an induction coil wound around a portion of the magnetic member to generate magnetic force lines upon application of current and located on each side of the forming zone; And (c) means for supplying molten metal from a tundish along the horizontal axis to the forming zone while ensuring that the molten metal remains substantially unoxidized, A vertical distance separating the pair of casting rolls defines the forming zone, the magnetic member comprising a first magnetic pole and a second magnetic pole positioned and aligned away from the sidewalls of the pair of casting rolls; The current defines the molten metal in contact with the casting roll without increasing the temperature of the molten metal and provides a magnetic force line orthogonal to the horizontal axis, wherein the tundish is shaped to substantially eliminate wave generation in the tundish caused by the magnetic force line. Strip casting apparatus for molten metal, characterized in that it is spaced apart from the zone. 2. The apparatus of claim 1, wherein the current includes alternating current having a frequency in the range of 40 Hz to 10,000 Hz. 2. The apparatus of claim 1, wherein the current is less than 2,000 amps. The apparatus of claim 1, comprising shielding means positioned around the magnetic member. 2. The apparatus of claim 1, wherein the magnetic member is generally C-shaped and includes a core portion and parallel magnetic poles extending integrally. 6. The apparatus of claim 5, wherein an induction coil is wound around the core of the magnetic member, and the induction coil is wound 1 to 100 times around the magnetic member. The method of claim 1, wherein the vertical distance separating the pair of casting rolls permits defining the molten metal between the casting rolls by the lines of magnetic force at the current without causing a substantial increase in the temperature of the molten metal from the lines of magnetic force. Strip casting apparatus of molten metal, characterized by providing a metal head height. The apparatus of claim 1, wherein the vertical distance separating the pair of chiefly rolls is less than 1.0 inch. 2. The apparatus of claim 1, wherein a magnetic member is positioned in the forming zone to position the lines of magnetic force to form convex sidewalls, concave sidewalls or substantially flat sidewalls in the molten metal in the forming zone. The apparatus of claim 1, wherein the magnetic member is formed of a laminate in which ferromagnetic materials are bonded or mechanically bonded, or the magnetic member is formed of a solid core of ferromagnetic material. 2. The molten metal of claim 1, wherein the pair of cast rolls comprises a ferromagnetic material, a non-ferromagnetic material, or a non-ferromagnetic material coated with at least a ferromagnetic material on the casting surface and sidewalls of the casting roll. Strip casting device. The apparatus of claim 1, wherein the sidewalls of the pair of cast rolls are substantially planar. As a device for strip casting of molten metal, (a) a pair of opposing circulating metal belts passing over the rolls and having a perimeter aligned along the sidewalls of the rolls and having a surface for receiving molten metal; (b) an electromagnetic edge restraint device comprising an induction coil wound around a portion of the magnetic member to generate magnetic field lines upon application of current and located on each side of the forming zone; And (c) means for feeding the molten metal from the tundish along the horizontal axis to the forming zone, A vertical distance separating the pair of circulating metal belts forms a forming zone and the current draws molten metal within a width in contact with at least a portion of the pair of circulating metal belts without increasing the temperature of the molten metal. Providing a confining magnetic force line, wherein the tundish is spaced from the forming zone to substantially eliminate wave generation in the tundish by the magnetic force line. 14. The magnetic member of claim 13 wherein the magnetic member includes an upper magnetic pole and a lower magnetic pole, wherein an induction coil is wound around a portion of the magnetic member to generate a line of magnetic force passing from one of the upper magnetic pole and the lower magnetic pole to the other. And a magnetic member positioned to act on a line of magnetic force forming a constraining force at the edges of the pair of opposing circulating metal belts to confine the molten metal between the circulating metal belts facing the lower magnetic poles. Strip casting device. 15. The method of claim 13, wherein the vertical distance separating the pair of circulating metal belts melts between the pair of circulating metal belts by the lines of magnetic force at the current without causing a substantial increase in temperature of the molten metal from the lines of magnetic force. A device for casting strips of molten metal, characterized by providing a metal head height that allows for confining the metal. 14. The apparatus of claim 13, wherein the minimum vertical distance for separating a pair of opposing circulating metal belts from the nip of the casting apparatus ranges from about 0.025 inches to about 0.25 inches. 14. The apparatus of claim 13, wherein a magnetic member is positioned in the forming zone to position the lines of magnetic force to form convex sidewalls, concave sidewalls or substantially flat sidewalls in the molten metal in the forming zone. As a cast metal strip, (a) a first shell; (b) a second shell; And (c) a central portion between the first shell and the second shell, wherein the central portion comprises grains with equiaxed texture, and the cast metal strip has a substantially uniform sidewall edge. Characterized by a cast metal strip. 19. The cast metal strip of claim 18, wherein the first shell is an upper shell and the second shell is a lower shell. 19. The cast metal strip of claim 18, wherein the cast metal strip can be rolled without machining the sidewall edges. 19. The cast metal strip of claim 18, wherein the cast metal strip comprises aluminum and other light metals such as magnesium and zinc. 19. The cast metal strip of claim 18, wherein the equiaxed tissue is generally spherical. As a casting device, (a) the pair of casting rolls in which a vertical distance separating the pair of casting rolls forms a forming zone and is adapted to receive molten metal along a horizontal axis; (b) a discharge tip structure positioned to supply molten metal from the tundish along the horizontal axis to a forming zone while ensuring that the molten metal remains substantially unoxidized; And (c) an edge restraint device located on each side of the forming zone; The edge restraint device is: A mechanical edge dam extending partially towards the forming zone and positioned to at least cover an end of the discharge tip structure; and An electromagnetic edge dam covering a portion of the mechanical edge dam extending partially towards the forming zone and including an aligned first pole and a second pole positioned away from the sidewalls of the pair of casting rolls; And wherein said electromagnetic edge dam provides a line of magnetic force orthogonal to said horizontal axis defining a molten metal in contact with a casting roll. 24. The casting apparatus of claim 23, wherein the discharge tip structure has a length that substantially eliminates generation of waves in the turnash caused by the lines of magnetic force. 25. The apparatus of claim 24, wherein the electromagnetic edge dam includes an induction coil wound around the magnetic member to generate magnetic force lines upon application of current. 27. The apparatus of claim 25, wherein the current provides a line of magnetic force that defines the molten metal in contact with the casting roll without increasing the temperature of the molten metal. As a method for producing a cast metal strip, Providing molten metal to the forming zone along the horizontal axis; Confining the molten metal within the forming zone by magnetic confinement means; And Casting the molten metal into a cast metal strip, wherein the geometry of the sidewalls of the cast metal strip is formed by adjusting the magnetic restraining means. 28. The method of claim 27 wherein the geometry of the sidewalls is flat or concave or convex with respect to the centerline portion of the cast metal strip. 29. The apparatus of claim 28, wherein the magnetic restraining means includes an induction coil wound around a magnetic member to generate magnetic lines of force upon application of current, wherein the magnetic member is located and adjacent to the forming zone firstly. A method for producing a cast metal strip comprising a magnetic pole and a second magnetic pole. 30. The method of claim 29, wherein adjusting the magnetic restraint means includes increasing or decreasing the current flowing in the induction coil. 30. The method of claim 29, wherein adjusting the magnetic restraining means moves the first magnetic pole and the second magnetic pole away from or adjacent to the forming zone.

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