US3693697A - Controlled solidification of case structures by controlled circulating flow of molten metal in the solidifying ingot - Google Patents

Controlled solidification of case structures by controlled circulating flow of molten metal in the solidifying ingot Download PDF

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US3693697A
US3693697A US65611A US3693697DA US3693697A US 3693697 A US3693697 A US 3693697A US 65611 A US65611 A US 65611A US 3693697D A US3693697D A US 3693697DA US 3693697 A US3693697 A US 3693697A
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ingot
flow
pool
molten metal
interface
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Alexander A Tzavaras
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Republic Steel Corp
Ltv Steel Co Inc
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Republic Steel Corp
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Assigned to LTV STEEL COMPANY, INC., reassignment LTV STEEL COMPANY, INC., MERGER AND CHANGE OF NAME EFFECTIVE DECEMBER 19, 1984, (NEW JERSEY) Assignors: JONES & LAUGHLIN STEEL, INCORPORATED, A DE. CORP. (INTO), REPUBLIC STEEL CORPORATION, A NJ CORP. (CHANGEDTO)
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/122—Accessories for subsequent treating or working cast stock in situ using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/114—Treating the molten metal by using agitating or vibrating means
    • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields

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  • the circulation of the molten metal FOREIGN PATENTS 0R APPLICATIONS may be provided by a helical coil which extends about the ingot downstream from the mold and, in the op- 526,455 6/1956 Canada........................164/49 timum arrangement, for Substantially the entire extent 531,772 10/1956 Canada........................164/283 of the molten poo] within the ingot 783,427 9/1957 Great Britain.............164/82 173,173 11/1960 Sweden ................. together164/49 15 Claims, 15 Drawing Figures PATENTEDsms I972 SHEET 1 or 6 INVENTOR. ALEXANDER (4. 72A VAR/4S BY M J? @AJ ATTOEA/EV PATENTEBSEPz I912 Q 3.693.697
  • This invention relates to casting methods and ap paratus, and more particularly to methods and apparatus for improving in a continuous casting process what has generally been termed in the past the grain structure of an ingot.
  • molten metal rotation aggravates problems of segregation inasmuch as the heavier elements in the molten metal tend to be moved by centrifugal force to the outer zone of molten metal movement. Still further, rotation is undesirable because it segregates inclusions at the center of the ingot and prevents them from rising to the surface.
  • Criner U.S. Pat. No. 3,153,820 discloses the stirring of molten metal during ingot fortning through the use of toroidal coils about a mold which induce eddy currents in the melt in order to stir or vibrate the melt. Although vibration may overcome the problems of centerline porosity or shrinkage, inclusions within the melt are not brought to the surface in contact with the slag layer so as to be removed. Further the positioning of stirring coils about the chilling mold is generally not a good location for such coils because of the tendency to disturb the initial skin which is forming on the outer surface of the ingot.
  • British Pat. No. 752,271 purports'to disclose stirring of molten metal in the casting of an ingot through the use of an induction coil positioned adjacent to the mold. Metal movement toward and away from the upper surface of the molten metal is disclosed. The disadvantage of proximity of stirring coil to mold is present in this arrangement.
  • the present invention is directly concerned with casting procedures, and involves microstructure refinement. It has particular application to the continuous casting of an ingot in which the pool of molten metal inside the ingot extends a substantial distance below the chill mold or other mechanism used to form the initial outer skin of the ingot. Such a molten pool may extend, for example, 30 and upwards or even as much as feet below the chill mold in the case of a high speed continuous casting of an ingot.
  • the important parameters which determine the mode of growth for a cast structure are the temperature gradient in the molten metal along the solid/liquid interface, the growth rate of solid material, and the solute concentration in the liquid.
  • a flow of molten metal is utilized substantially to increase the temperature gradient.
  • the typical mushy zone that is normally present along the solid/liquid interface is influenced, greatly reduced or in effect eliminated, changing the solidification characteristics of the ingot so as to produce a more desirable ingot structure.
  • the flow is such as to prevent the growth of columnar dendrites which are known to be undesirable in ingot structure.
  • the fiow of metal that is utilized is a sweeping flow which is along the solid/liquid interface for a selected length thereof or in many cases desirably for substantially the full extent thereof in a first direction that is advantageously the same direction as that of ingot movement; a reverse path of circulation can be used in some cases, but requires substantially greater power for electromagnetically advancing the metal because it must then be moved oppositely to the normal convection flow.
  • a return flow in an opposite direction within the interior of the molten pool is utilized to provide for complete and effective circulation of all the metal within the pool.
  • This sweeping fiow of metal brings hot metal from the top of the molten pool along the solid/liquid interface washing away or substantially dissolving the mushy zone and breaking dendrites before they can form into longer columnar dendrites.
  • the return flow circulates broken dendrites back into the hot melt where they are either re-melted or carried around to be deposited in random orientation and in different locations from where they were broken.
  • the return flow also sweeps the molten metal into contact with the underside of the slag layer, by which many inclusions are easily removed.
  • the downward sweeping flow of hot metal along the interface also tends to redissolve inclusion elements, even to the extent of preventing their deposit as inclusions until solidification of the trailing end of a continuously cast strand.
  • the metal circulation further promotes coagulation of small inclusions, and aids their separation, as larger bodies, into the slag layer.
  • the sweeping flow which takes place in accordance with the invention and which moves in the interior of the molten pool reduces segregation and centerline porosity or shrinkage that is present when rotation about the ingot axis is employed as in prior art stirring techniques during ingot formation.
  • the sweeping flow may advantageously be for the full extent of the molten pool and thus extends many feet downstream of the chill mold or other chilling means.
  • the sweeping flow of molten metal is achieved through the use of helical coils positioned along the ingot downstream of the chill mold. Optimum flow of molten metal is believed to be achieved when the effect of the coils covers the full length of the mo]- ten pool.
  • Reference to a helical coil thus means a coil in which the turns form a helix around the ingot or strand, i.e., a helix (whether having square or oblong turns, with rounded corners, or circular turns or other shape suited to the ingot) that is substantially coaxial with the ingot and its path of travel.
  • the coils are energized in known fashion by a polyphase source of excitation to achieve the desired circulation of molten metal.
  • Each of these flow rates is characterized by a growth structure which is different from that which would be present under the same thermodynamic conditions without any forced fluid flow.
  • the invention has for a primary object the achieving of improved solidification microstructures.
  • FIG. 1 is a perspective view of representative apparatus in accordance with the invention, shown in greatly simplified and somewhat schematic manner.
  • FIG. 2 is a sectional view taken along the section 2- 2 of FIG. 1.
  • FIGS. 3a, 3b, 4a, 4b, 5a, and 5b are scanning electron microscope photographs of difierent microstructures in accordance with the invention.
  • FIG. 6 is a series of curves showing the relationship between different growth structures as a function of solute concentration, temperature gradient and growth rate.
  • FIG. 7 is a series of curves relating the growth structure to initial temperature and flow rate or power input.
  • FIG. 8 is a micrograph (magnification 65x) of a section taken parallel to the direction of growth (i.e., growth from a chilled surface), showing a broken columnar microstructure, of equiaxed character.
  • FIG. 9 is a micrograph (magnification 65x) of a section parallel to growth, showing a thamnitic microstructure.
  • FIGS. 10a and 10b are micrographs (magnification 65x, reduced for reproduction) of sections respectively taken parallel and perpendicular to the direction of growth, showing a fibrous microstructure.
  • FIG. 11 is a micrograph (magnification 65X, reduced for reproduction) of a section parallel to growth, which proceeded as from left to right, showing dendritic microstructure except for a band across the growing solid where the molten metal was subjected to flow as in accordance with the invention, there producing a thamnitic microstructure.
  • Dendrite growth is characterized by a resultant microstructure which is somewhat tree-like in appearance, having primary and secondary arms.
  • the primary arm of a dendrite extends in one direction similar to the trunk of a tree, and the secondary arms extend generally perpendicular thereto as do the branches of a tree.
  • the secondary arms themselves may have further arms extending perpendicular thereto.
  • Columnar dendrite structures are characterized by relatively long primary dendrite arms which align themselves substantially parallel to each other. Columnar dendritic structures are undesirable in a cast structure since at least the ductility varies according to direction; it is strongest in the growth direction of the primary dendrite arms and is poor across the growth direction.
  • Inclusions formed prior to solidification are mainly oxides stable at high temperatures. Inclusions formed during solidification are most sulfides, tellurides, arsenides, nitrides and some oxides.
  • the usual inclusions in steel are compounds of various solutes or deoxidizers used in steel combined with oxygen, sulfur, and less frequently with nitrogen. If rotary stirring about an ingot axis or local agitation is employed, inclusions, if affected at all, will still remain throughout the structure, or will tend to concentrate at the center during the solidification process.
  • Segregation is characterized by concentrations of elements at zones within the ingot and is aggravated in particular by rotary stirring, which tends to create segregation bands about the ingot axis because of centrifugal force.
  • Macrosegregation is usually associated with large castings and refers to local changes in the solute concentration in a macroscale.
  • Microsegregation is the difference in solute concentration between the center of the dendrite and the interdendritic areas. It will be understood that references to solutes mean, for example in steel, other elements than iron, such as alloying elements, contained in the desired composition.
  • the chill mold is supplied with a coolant via a supply line 16, which coolant circu-- lates within the interior l0a of the mold and exits therefrom via outlet 18.
  • the chill mold is conventional in construction and is typically 2 or 3 feet long in the direction of the ingot movement, which is downwardly in FIG. 2.
  • An ingot 20 is formed containing a pool 22 of molten metal therein.
  • the bottom of the ingot is generally supported by a support structure 24 and by rollers 26 along the sides thereof.
  • the ingot i.e., the cast strand
  • the ingot is square, although this is simply representative.
  • lnterposed between the rollers 26 are a series of helically wound coil sections 28a, 28b, 28c, 28d, 28e, 28f 28n. Water for cooling purposes may be supplied as shown around the coil sections and rollers.
  • the coil sections 28 are energized by a source of alternating current potential (not shown) such that the excitation of the sections varies in phase in a predetermined manner as will be readily understood. Any number of phases may be employed for the excitation. What is desired is a moving magnetic field which causes a flow of metal as shown by arrows 30 in FIG. 2.
  • Electromagnetic stirring has been employed in connection with the melting and refining of molten metal. See for example the following references which deal with such electromagnetic stirring: Williamson U.S. Pat. No. Re. 24,463, issued Apr. 22, I958; Dreyfus U.S. Pat. No. Re. 24,462, issued Apr. 22, 1958; Dreyfus U.S. Pat. No. 2,774,803, issued Dec. 18, 1956; Tostmann U.S. Pat. No. 2,968,685, issued Jan. 17, 1961; I-Iokanson U.S. Pat. No. 3,239,204, issued Mar. 8, 1966; Jones U.S. Pat. No. 2,686,823, issued Aug. 17, 1954 and Magnetic Traveling Fields for Metallurgical Processes by Yngve Sundberg (IEEE Spectrum, May 1969, pages 79 through 88).
  • the stirring of molten metal by electromagnetic means is, as just noted, well known.
  • the stirring mechanism involves the development of eddy currents within the molten metal by the varying magnetic field, which eddy currents themselves set up magnetic fields which interact with the applied magnetic field to cause movement of the molten metal.
  • pulses of motive force are given to the molten metal progressively from section to section in the desired direction, so that the metal is caused to flow continuously downward along its outermost regions, in effect parallel to the axis of the coils.
  • the flow of molten metal may be as shown by the arrows 30, namely, sweeping downwardly over the solid/liquid interface of the ingot, as indicated by arrows 30a and 30b and upwardly through the center of the molten pool, as indicated by arrows 30c and 30d.
  • the flow along the solid/liquid interface increases the temperature gradient in the liquid at the interface and reduces or eliminates the extent of the mushy zone normally present in a solidifying ingot at the interface,
  • the flow rate is a function of the viscosity of the molten metal and the power applied to the coil sections 28.
  • an opposite flow could be achieved with respect to that shown in FIG. 2, namely, upwardly along the solid/liquid interface and downwardly in the center of the molten pool.
  • the flow in FIG. 2 is to be greatly desired, namely, downwardly along the solid/liquid interface and upwardly in the interior of the molten pool, inasmuch as this flow is the same as and aids the normal convection flow that occurs in an ingot during solidification.
  • the molten pool 22 extends a substantial distance below the chill mold l0, and this distance may be as great as feet in some cases, depending upon the speed of ingot formation and movement.
  • the bottom portion 22a of the molten pool is rounded or even flattened and not pointed as when no flow is present. This flattening effect is produced by the circulation of hot molten metal from the top of the pool along the sides of the pool to and across the bottom of the pool.
  • the shape of the molten pool is frustoconical and not conical with a sharply pointed bottom as when no forced flow is present. It is believed that the volume of the force flow molten pool is the same as that of the non-forced flow molten pool.
  • the length of the molten pool is much less than that present with no forced flow.
  • One advantage of a shorter molten pool is that at the end of a continuous casting process, when the feed of molten metal to the ingot, i.e., the strand, is stopped, the wasted end length is shorter than that which would normally be present.
  • a further advantage is that when successive lengths are cut from the continuously cast strand, there is much less danger that the plane of cut will intersect a pointed end of the liquid pool and allow molten metal to escape.
  • the electromagnetic field will not be present to a substantial degree within the chill mold. This is helpful because it is desired to reduce turbulence and agitation within the mold at the location where the outer skin of the ingot is initially formed.
  • the upwardly directed outlet 12a from the supply pipe 12 aids in the flow of metal in this regard, causing a full sweep of liquid on the underside of the slag layer so as to remove inclusions.
  • the flow from the nozzle is directed generally toward or just below the intersection of the slag layer with the sides of the mold so as to avoid any turbulence in the slag layer.
  • the coil may be continuously wound and may include taps at various points for connection to the various phases of excitation.
  • a plurality of conductor strands may be wound helically about the ingot adjacent each other, each strand carrying an individual phase of excitation.
  • the electromagnetic coils may be made of copper tubing, carrying a coolant for the purpose of heat dissipation from the electromagnetic structure. The effect of the electromagnetic structure should cover at least some part, and for special advantage, substantially the full length of the liquid pool in the downstream direction below the mold, the latter condition being desirable to achieve the full benefits of stirring of the pool of molten metal.
  • the amount of current carried in the coils will vary depending upon the degree of stirring desired and the material forming the molten pool. As will be explained, varying flow rates may be desired, in which case the current will be appropriately varied. Further, the frequency of excitation should be chosen to provide good depth of penetration throughout the pool to achieve appropriate fluid flow throughout all portions of the pool. The variations of these parameters will be understood by those skilled in the art.
  • phase of pulsing will normally be varied among the different coil sections or segments, i.e., in progressively timed manner along the desired direction of flow vertically downward, in order to achieve the appropriate movement of molten metal within the pool in the ingot.
  • the frequency of excitation is generally of low magnitude, typically in the order of 60 hertz or less. However, it may be desirable to limit the excitation of the coils so that periodic excitation is employed.
  • the molten metal may be made to flow in the pattern shown in FIG. 2 by continuous A.C. or pulsed D.C. excitation of the coils which is then rendered intermittent once the inertia of the moving liquid is sufficient to continue fluid flow without the use of an outside field. Selective energization of the coils is then carried out in order to keep the molten metal moving.
  • variation of the magnetic field turns) among the different coil sections may be employed, if desired, or the use of a coil arrangement only over a part of rather than almost the whole of the molten pool may also be employed.
  • FIG. 2 a typical chill mold 10 has been shown, with the direction of ingot movement being in the vertical direction. It should be noted that ingot movement in any direction is possible and a typical chill mold need not be employed. Specifically, moving belt apparatus as disclosed in Hazelett et al., U.S. Pat. No. 3,036,348 may be utilized for ingot formation. Hence the mold 10 in FIG. 2 should be taken to represent any mold means suitable for the formation of a continuously cast structure.
  • the molten metal flow rate varies the growth structure in an ingot.
  • three basic growth structures are possible, namely, equiaxed, thamnitic or flow-modified, and fibrous.
  • Equiaxed dendritic structure is characterized by: (l) discernible dendrites having primary and secondary arms in which the dendrites are broken and moved to new positions by the forced fluid flow remote from the breaking positions and (2) by a random orientation of primary arms.
  • the equiaxed dendritic microstructure is the same as free dendritic microstructure except for the fact that the breaking of dendrites is involved, and it is thus composed of broken and randomly oriented dendrites.
  • The'equiaxed microstructure is produced by flow within the molten pool.
  • FIGS. 3a and 3b are scanning electron microscope photographs of a solid/liquid interface of structure rendered equiaxed by laminar like flow, with the magnification x in FIG. 3a and 5001 in FIG. 3b.
  • FIGS. 4a and 4b are scanning electron microscope photographs of the solid/liquid interface of a thamnitic or flow-modified structure produced by turbulent fluid flow. The magnification in these figures is respectively 50x and 200x. The lack of any symmetry in the thamnitic or flowmodified structure is evident.
  • dendritic growth normally proceeds into a flow, such flow being unidirectional; it is now found that where the flow becomes turbulent, lacking local directional characteristics, the solid metal can correspondingly grow in a random multitude of directions resulting in the defined thamnitic structure, the term thamnitic being intended to mean bush-like.
  • the plane-section micrograph of FIG. 9 shows the random, closely abutting and variously connected rounded shapes of this microstructure; their appearance is substantially the same when viewed in a plane perpendicular to growth.
  • Fibrous microstructure is formed under intense turbulent flow.
  • the structure is characterized by unidirectional primary structural elements only, without any secondary structural elements or secondary arms. There is an apparent braiding or interknitting of the primary structural elements by virtue of the continuously changing growth conditions in the boundary layer (in the liquid phase) because of the extremely intense turbulent flow.
  • FIGS. 5a and 5b are scanning electron microscopephotographs of the solid/liquid interface of fibrous structure produced by turbulent flow. The magnifications are respectively 1001: and 2001:.
  • FIGS. 3, 4 and 5 were taken of statically cast ingots.
  • the ingot material was A181 4335 steel.
  • a cylindrical crucible 4 inches in diameter and 6 inches high was employed which was rotatable about a horizontal axis by The chill for the ingot was at the bottom thereof.
  • An induction coil about the ingot provided the necessary circulation of molten metal.
  • the well known decanting technique was used to reveal the solid/liquid interface of ingot structure. Specifically, the crucible was rotated by 180 at a given time during L la.
  • FIG. 11 Shows an experiment in region of FIG.
  • FIG. 6 is a graphical representation of the various growth regimes with no flow as a function of solute concentration C and the critical ratio G/R, in which G is the temperature gradient in the molten pool at the solid/liquid interface and R is the growth rate of solid material in a direction perpendicular to the solid/liquid interface.
  • G free dendritic growth
  • R the critical ratio of solid material in a direction perpendicular to the solid/liquid interface.
  • the present invention operates with a liquid pool within an ingot in which the factors of solute concentration and critical ratio would normally thermodynamically result in columnar dendritic growth, e.g., as at point a in FIG. 6.
  • columnar dendritic growth e.g., as at point a in FIG. 6.
  • fragmentation or breaking of dendrites takes place so as to reduce the width of the columnar zone that would normally be present by at least two mechanisms: dynamic shearing of dendrites and the dissolution of dendrite stems by it will be noted then that the flow rate determines the ingot microstructure and, depending upon the type of structure desired, the flow rate is chosen accordingly.
  • FIG. 7 is a graphical representation of the flow speed required for the three individual and different microstructures described above, namely, equiaxed (at least partially equiaxed), flow-modified or thamnitic, and fibrous, as a function of an initial temperature.
  • the flow rate is directly correlated with the power input to the coils that cause the molten metal flow, and hence the ordinate in FIG. 7 is characterized as flow rate or power input to stirring coils.
  • the equiaxed regime is the area under curve 40.
  • the flow-modified or thamnitic regime is the area between curves 40 and 42.
  • the fibrous regime is the area above curve 42.
  • induced fluid flow of low velocity produces laminar-like flow conditions that change a columnar dendritic structure to an equiaxed dendritic structure at higher thermal gradients or shorter distances from an established chill than obtained under static solidification conditions.
  • the velocity of the induced flow increases (up to 25 cm/sec) the amount of fragmentation of the columnar dendritic structure increases in unidirectionally solidified ingots until this columnar structure is completely eliminated.
  • the induced flow becomes turbulent and the morphology of the solidified structures becomes flow-modified or thamnitic with local growth proceeding in multidirections.
  • Turbulent fluid flow of very high velocity (above 55 cm/sec) produces a fibrous structure with an appearance similar to a cellular structure.
  • Turbulent fluid flow past the growing solid minimizes the width of the mushy zone, eliminates macrosegregation and reduces the severity of microsegregation.
  • Turbulent flow of at least the velocity necessary for the formation of flow-modified or thamnitic structure prevents the coarsening of inclusions that usually occurs as the distance from the chill increases; at the higher flow velocities which form fibrous structure, the inclusion volume fraction in the solid decreases as the distance from the chill increases.
  • the tensile properties of the flow-modified structure are similar to the statically cast columnar dendritic close to the chill, but do not exhibit the loss in ductility (mass effect) at greater distances from the chill of the statically solidified structure.
  • the fibrous structure is similar in tensile properties to the columnar and flow-modified or thamnitic structure.
  • interdendritic distances are much less in the equiaxed dendritic structure than they are in the columnar dendritic structure, providing less space for segregates and inclusions to be trapped in the microstructure. This spacing becomes less between the elements of growth in the thamnitic microstructure and very much less in the fibrous microstructure.
  • mushy zone of relatively substantial extent between the growing solid and the truly liquid metal.
  • segregation occurs involving localized increased concentration of solutes, and is manifested in the product, both on a microscale (as defined above), and on a macro-scale by a resulting continuity of the increased solute concentration over a considerable area or distance.
  • formation of inclusions i.e., socalled indigenous inclusions, is greatly promoted in the mushy zone as to atoms of elements such as oxygen and sulfur which there become concentrated in the liquid phase, and combine with metallic elements in the mushy zone.
  • the extent or thickness of the mushy zone is reduced, indeed essentially to none in the case of the intense flow that creates a fibrous structure, and the motion of the metal carries away the localized portions of high solute concentration and the localized content of inclusion-forming elements, so that the latter are dissolved and the former redistributed in normal intended concentration in the liquid.
  • the reduction of the mushy zone is aided or characterized by the reduction of spacing between growing solid structures, such as dendrites, thus cooperating in the elimination of segregation and inclusion problems.
  • the thermodynamic conditions between solid and liquid phases are altered by the movement of liquid and its proximity to the solid phase, in a direction toward greater equality of solute concentration in adjacent solid and liquid regions, as is most desirable for avoidance of segregation in the ultimate cast body.
  • An advantage of the forced flow of molten metal in the pool inside a continuously cast ingot is that segregates and inclusions tend to be confined to the pool. The result is that at the end of a casting run, the pool is rich in solutes and segregates. As noted above, the end of the ingot which is last cast and which is unusable is shorter than that involved when no forced flow of fluid is provided.
  • the laminar or turbulent metal flow sweeping along the solid/liquid interface carries away elements of the mushy zone, and in particular tends to carry away solute remaining between growth elements, thus counteracting segregation and reducing or preventing formation of inclusions (from segregated inclusion elements) at the locality of solidification.
  • the reduced spacing between growing solid structures necessarily limits the size of inclusions even if left to grow in such spaces.
  • the return flow preferably carries such inclusions back up to the underside of the slag layer.
  • the path of circulating flow is preferably carried up into the mold beneath the slag layer, and then is initiated downwardly along the solidifying metal, being advanced effectively along such interface below the mold by the described nature of magnetic field.
  • the employment of turbulent flow is markedly effective in obviating occurrence of unwanted inclusions in the product, and likewise in reducing or obviating both microand macro-segregation.
  • one such coil unit disposed around the descending strand (i.e., ingot) of a continuous casting operation
  • one such coil unit consisted of three IO-turn sections of copper tubing, carrying cooling water, arranged in continuing immediate succession along the strand path, the turns being square with rounded comers and positioned helically around the square-section strand.
  • apparatus casting steel e.g., an 8 inch by ten inch ingot at a rate of ingot descent of 44 inches per minute downward through a chill mold having a height of 3 feet
  • the sections were respectively connected to the phases of a conventional three-phase A.C.
  • phase difference (120) being progressive down the unit, in such order as to effect molten metal flow downward (from a region above to a region below the unit) along the solid/liquid interface and back up the center of the liquid metal pool. It will be understood that the speed of downward flow induced in the molten metal in all cases is faster than the downward speed of the ingot and its pool as a whole, e.g., of different, higher order of velocity.
  • the electromagnetic influence of the coils covers at least a substantially longer portion of the molten pool (which may reach 35 feet or more below the mold), indeed preferably most or all of it; for instance, another like coil unit, in the above apparatus, can be effectively interposed between the mold and the unit located as above, and preferably one or more further such units disposed below the latter along the descending strand.
  • the method for improving the subsequent solidification structure of the molten metal comprising causing a circulating flow of said molten metal within said pool that:
  • the method for improving the solidification structure of the ingot comprising causing a circulating flow of molten metal within said pool that is:
  • said flow of molten metal being produced by a moving magnetic field downstream of said mold means, said moving magnetic field being produced by polyphase excitation of successive coil sections which are arranged along and coaxial with the path of ingot movement, and of which each section is a coil helically coaxial with said path.
  • a method according to claim 2 in which molten metal is initially supplied to said mold means from a central zone underneath the slag layer, with the introduced metal being directed outwardly and generally toward the underside of the slag layer.
  • the method for improving the solidification structure of the ingot comprising: causing, by the application of force created by a moving magnetic field extending downwardly throughout a zone along the ingot for at least a 30-foot length of said pool below about the first 2 feet thereof that comprise said location at which the outer skin of the ingot is formed, a circulating flow of molten metal within said pool that is:
  • said moving magnetic field being produced by polyphase excitation of successive coil sections which are arranged along and coaxial with the path of ingot movement, and of which each section is a coil helically coaxial with said path,
  • the continuous casting 0 an ingot in which there is present within the ingot a pool of molten metal which extends downstream a substantial distance from the mold means within which the outer skin of the ingot is formed, the method for improving the solidification structure of the ingot comprising producing, by a moving magnetic field downstream of said mold means, a circulating flow of molten metal within said pool that is:
  • the molten metal being initially supplied to said mold means from a central zone underneath the slag layer, with the introduced metal being directed outwardly and generally toward the underside of the slag layer, said directing of the introduced metal and the aforesaid flow-producing action of the magnetic field downstream of the mold means coacting to carry said circulating flow along a path within said mold means whereby the return direction flow extends centrally up to and outwardly under the slag and thence the first direction flow along the interface extends downwardly within the mold means,
  • said first direction flow of molten metal below the mold means being turbulent flow, effected by producing said moving magnetic field with sufficient electrical power to provide turbulent flow velocity of above 25 cm/sec.
  • the molten metal being initially supplied to said mold means from a central zone underneath the slag layer, with the introduced metal being directed outwardly and generally toward the underside of the slag layer, said directing of the introduced metal and the aforesaid flow-producing action of the magnetic field downstream of the mold means coacting to carry said circulating flow along a path within said mold means whereby the return direction flow extends centrally up to and outwardly under the slag and thence the first direction flow along the interface extends downwardly within the mold means,
  • said first direction flow of molten metal below the mold means being turbulent flow, effected by producing said moving magnetic field with sufficient electrical power to provide turbulent flow velocity of above 25 cm/sec.

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US65611A 1970-08-20 1970-08-20 Controlled solidification of case structures by controlled circulating flow of molten metal in the solidifying ingot Expired - Lifetime US3693697A (en)

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Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3804147A (en) * 1971-03-30 1974-04-16 Etudes De Centrifugation Continuous rotary method of casting metal utilizing a magnetic field
JPS4996927A (enrdf_load_stackoverflow) * 1973-01-22 1974-09-13
US3862659A (en) * 1972-05-29 1975-01-28 Schloemann Ag Method and apparatus for conveying a strand through a continuous casting installation
US3882923A (en) * 1972-06-08 1975-05-13 Siderurgie Fse Inst Rech Apparatus for magnetic stirring of continuous castings
US3941183A (en) * 1973-10-19 1976-03-02 Institut De Recherches De La Siderurgie Francaise (Irsid) Liquid cooled electromagnetic continuous casting mold
US3981345A (en) * 1973-05-21 1976-09-21 Institut De Recherches De La Siderurgie Francaise (Irsid) Method to improve the structure of cast metal during continuous casting thereof
US3995678A (en) * 1976-02-20 1976-12-07 Republic Steel Corporation Induction stirring in continuous casting
US4030534A (en) * 1973-04-18 1977-06-21 Nippon Steel Corporation Apparatus for continuous casting using linear magnetic field for core agitation
US4042007A (en) * 1975-04-22 1977-08-16 Republic Steel Corporation Continuous casting of metal using electromagnetic stirring
US4106546A (en) * 1974-02-27 1978-08-15 Asea Aktiebolag Method for inductively stirring molten steel in a continuously cast steel strand
US4178979A (en) * 1976-07-13 1979-12-18 Institut De Recherches De La Siderurgie Francaise Method of and apparatus for electromagnetic mixing of metal during continuous casting
US4183395A (en) * 1977-02-03 1980-01-15 Asea Aktiebolag Multi-phase stirrer
DE2830523A1 (de) * 1978-07-12 1980-01-31 Technicon Instr Verfahren und vorrichtung zum giessen eines metallgegenstands in einer kokille
US4200137A (en) * 1975-04-22 1980-04-29 Republic Steel Corporation Process and apparatus for the continuous casting of metal using electromagnetic stirring
US4321958A (en) * 1979-01-30 1982-03-30 Cem Compagnie Electro-Mecanique Electromagnetic inductor for generating a helical field
US4495984A (en) * 1980-05-19 1985-01-29 Asea Aktiebolag Continuous casting mold stirring
US4515203A (en) * 1980-04-02 1985-05-07 Kabushiki Kaisha Kobe Seiko Sho Continuous steel casting process
US4714103A (en) * 1986-10-10 1987-12-22 Mannesmann Demag Corporation Continuous casting mold
US20040089435A1 (en) * 2002-11-12 2004-05-13 Shaupoh Wang Electromagnetic die casting
US7509993B1 (en) 2005-08-13 2009-03-31 Wisconsin Alumni Research Foundation Semi-solid forming of metal-matrix nanocomposites
EP1932931A3 (en) * 2006-12-04 2009-04-22 Heraeus, Inc. Magnetic pulse-assisted casting of metal alloys and metal alloys produced thereby
US20090242165A1 (en) * 2008-03-25 2009-10-01 Beitelman Leonid S Modulated electromagnetic stirring of metals at advanced stage of solidification
US20140202654A1 (en) * 2011-09-02 2014-07-24 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Continuous casting equipment for titanium or titanium alloy slab
CN105935752A (zh) * 2016-07-08 2016-09-14 东北大学 一种控制铸坯中心质量的立式电磁搅拌方法
CN106925762A (zh) * 2015-12-29 2017-07-07 北京有色金属研究总院 一种高剪切强电磁搅拌熔体处理的装置和方法
EP3238856A1 (en) 2016-04-29 2017-11-01 Marcela Pokusova A method of controlling the solidification process of continuously cast metals and alloys and a device for implementing the method

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Publication number Priority date Publication date Assignee Title
DE2743505C3 (de) * 1977-09-23 1984-09-20 Aeg-Elotherm Gmbh, 5630 Remscheid Einrichtung zur Erzeugung eines elektromagnetischen Wanderfeldes innerhalb der Stützrollenbahn einer Brammengießanlage
US4229210A (en) * 1977-12-12 1980-10-21 Olin Corporation Method for the preparation of thixotropic slurries
FR2426516A1 (fr) * 1978-05-23 1979-12-21 Cem Comp Electro Mec Prodede de brassage electromagnetique de billettes ou blooms coules en continu
FR2437900A1 (fr) * 1978-10-05 1980-04-30 Siderurgie Fse Inst Rech Procede de coulee continue des metaux avec brassage dans la zone du refroidissement secondaire

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CA526455A (en) * 1956-06-19 Allmanna Svenska Elektriska Aktiebolaget Arrangement in the production of steel and other metals
CA531772A (en) * 1956-10-16 Continuous Metalcast Co. Method and apparatus for the continuous casting of metal
GB783427A (en) * 1953-07-30 1957-09-25 Boehler & Co Ag Geb Process for continuous casting especially for the continuous casting of metals of high melting point
US2877525A (en) * 1953-08-27 1959-03-17 Schaaber Otto Casting process
US3354935A (en) * 1963-04-13 1967-11-28 Fuchs Kg Otto Manufacture of light-metal castings
US3517726A (en) * 1969-08-04 1970-06-30 Inland Steel Co Method of introducing molten metal into a continuous casting mold

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Publication number Priority date Publication date Assignee Title
CA526455A (en) * 1956-06-19 Allmanna Svenska Elektriska Aktiebolaget Arrangement in the production of steel and other metals
CA531772A (en) * 1956-10-16 Continuous Metalcast Co. Method and apparatus for the continuous casting of metal
GB783427A (en) * 1953-07-30 1957-09-25 Boehler & Co Ag Geb Process for continuous casting especially for the continuous casting of metals of high melting point
US2877525A (en) * 1953-08-27 1959-03-17 Schaaber Otto Casting process
US3354935A (en) * 1963-04-13 1967-11-28 Fuchs Kg Otto Manufacture of light-metal castings
US3517726A (en) * 1969-08-04 1970-06-30 Inland Steel Co Method of introducing molten metal into a continuous casting mold

Cited By (29)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3804147A (en) * 1971-03-30 1974-04-16 Etudes De Centrifugation Continuous rotary method of casting metal utilizing a magnetic field
US3862659A (en) * 1972-05-29 1975-01-28 Schloemann Ag Method and apparatus for conveying a strand through a continuous casting installation
US3882923A (en) * 1972-06-08 1975-05-13 Siderurgie Fse Inst Rech Apparatus for magnetic stirring of continuous castings
JPS4996927A (enrdf_load_stackoverflow) * 1973-01-22 1974-09-13
US4030534A (en) * 1973-04-18 1977-06-21 Nippon Steel Corporation Apparatus for continuous casting using linear magnetic field for core agitation
US3981345A (en) * 1973-05-21 1976-09-21 Institut De Recherches De La Siderurgie Francaise (Irsid) Method to improve the structure of cast metal during continuous casting thereof
US3941183A (en) * 1973-10-19 1976-03-02 Institut De Recherches De La Siderurgie Francaise (Irsid) Liquid cooled electromagnetic continuous casting mold
US4106546A (en) * 1974-02-27 1978-08-15 Asea Aktiebolag Method for inductively stirring molten steel in a continuously cast steel strand
US4042007A (en) * 1975-04-22 1977-08-16 Republic Steel Corporation Continuous casting of metal using electromagnetic stirring
US4200137A (en) * 1975-04-22 1980-04-29 Republic Steel Corporation Process and apparatus for the continuous casting of metal using electromagnetic stirring
US3995678A (en) * 1976-02-20 1976-12-07 Republic Steel Corporation Induction stirring in continuous casting
US4178979A (en) * 1976-07-13 1979-12-18 Institut De Recherches De La Siderurgie Francaise Method of and apparatus for electromagnetic mixing of metal during continuous casting
US4183395A (en) * 1977-02-03 1980-01-15 Asea Aktiebolag Multi-phase stirrer
DE2830523A1 (de) * 1978-07-12 1980-01-31 Technicon Instr Verfahren und vorrichtung zum giessen eines metallgegenstands in einer kokille
US4321958A (en) * 1979-01-30 1982-03-30 Cem Compagnie Electro-Mecanique Electromagnetic inductor for generating a helical field
US4515203A (en) * 1980-04-02 1985-05-07 Kabushiki Kaisha Kobe Seiko Sho Continuous steel casting process
US4495984A (en) * 1980-05-19 1985-01-29 Asea Aktiebolag Continuous casting mold stirring
US4714103A (en) * 1986-10-10 1987-12-22 Mannesmann Demag Corporation Continuous casting mold
US20040089435A1 (en) * 2002-11-12 2004-05-13 Shaupoh Wang Electromagnetic die casting
US6994146B2 (en) 2002-11-12 2006-02-07 Shaupoh Wang Electromagnetic die casting
US7509993B1 (en) 2005-08-13 2009-03-31 Wisconsin Alumni Research Foundation Semi-solid forming of metal-matrix nanocomposites
EP1932931A3 (en) * 2006-12-04 2009-04-22 Heraeus, Inc. Magnetic pulse-assisted casting of metal alloys and metal alloys produced thereby
US20090242165A1 (en) * 2008-03-25 2009-10-01 Beitelman Leonid S Modulated electromagnetic stirring of metals at advanced stage of solidification
US20140202654A1 (en) * 2011-09-02 2014-07-24 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Continuous casting equipment for titanium or titanium alloy slab
EP2752259A4 (en) * 2011-09-02 2015-06-17 Kobe Steel Ltd CONTINUOUS CASTING EQUIPMENT FOR PLATE OF TITANIUM OR TITANIUM ALLOY
CN106925762A (zh) * 2015-12-29 2017-07-07 北京有色金属研究总院 一种高剪切强电磁搅拌熔体处理的装置和方法
EP3238856A1 (en) 2016-04-29 2017-11-01 Marcela Pokusova A method of controlling the solidification process of continuously cast metals and alloys and a device for implementing the method
CN105935752A (zh) * 2016-07-08 2016-09-14 东北大学 一种控制铸坯中心质量的立式电磁搅拌方法
CN105935752B (zh) * 2016-07-08 2019-07-23 东北大学 一种控制铸坯中心质量的立式电磁搅拌方法

Also Published As

Publication number Publication date
CA975926A (en) 1975-10-14
FR2104863A1 (enrdf_load_stackoverflow) 1972-04-21
FR2104863B1 (enrdf_load_stackoverflow) 1976-02-13
DE2141868A1 (de) 1972-02-24

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