Classifications

• • 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
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
• • 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
  • B22D11/008—Continuous casting of metals, i.e. casting in indefinite lengths of clad ingots, i.e. the molten metal being cast against a continuous strip forming part of the cast product

Definitions

• the present invention relates to clad cast thin metal strip, and to a process for its production.
• the present invention includes an energy effici ⁇ ent, continuous casting procedure capable of producing a hot band crystalline steel strip having a thickness between about 0.03 to 0.375 inches.
• the process utilized in the formation of thin hot band steel strip or sheet usually comprises casting of large slabs of steel (generally S to 16" thick) followed by a number of hot rolling operations (e.g., reheating of the cast slabs and rolling) and cold rolling operations which reduce the thickness of the slab in stages until the desired thin band steel strip is produced.
• hot rolling operations e.g., reheating of the cast slabs and rolling
• cold rolling operations which reduce the thickness of the slab in stages until the desired thin band steel strip is produced.
• the rapidly solidified resulting thin metal strip or sheet has finer grain struct ⁇ ure and is capable of being cold rolled to a final gauge.
• thin metal strip the product of the invention is referred to as thin metal strip, hot band metal strip, or composite thin metal strip, and it is to be understood that those expressions, in so far as they include the word "strip”, do not imply any width or thickness limitations with respect to the thin metal strip product.
• a process for continuously producing thin metal strip comprising the steps of providing at least two metal strips, and introducing molten metal between the metal strips to at least partially bond the metal strips and the molten metal together.
• the molten metal is intro ⁇ quizzed between the metal strips under conditions such that the metal strips do not delaminate during subsequent mechan- ical operations, and it is preferred to conduct the process in an inert gas environment, to minimize oxidation.
• the process of the present invention comprises providing at least two metal strips, preferably stainless steel strips, feeding those metal strips to a gap between a first and second quench surface opposed one to the other, maintaining an inert atmosphere about the area defined by at least the gap and the first and second quench surfaces, and joining the metal strips one to the other at the gap during contact with the first and second quench surfaces by providing a layer of molten metal, preferably carbon steel, therebetween.
• the strips and molten metal are kept in contact with at least one of the first and second quench surfaces for a time sufficient to at least insure partial solidification of the molten metal and at least partial bonding of the strips to the molten metal.
• the partial bond must be of sufficient strength to insure that the strips do not delaminate during subsequent mechanical operations.
• the partially bonded strips are then cooled further by contact with at least a third quench or cooling surface to permanently bond the metal strips.
• the joining of the metal strips is accomplished by providing a layer of rheocast metal slurry between the strips.
• the hot band crystalline metal strip is produced by a continuous casting procedure utilizing a molten metal or a rheocast slurry source.
• the hot band metal strip produced is selected to have a thickness in the range of about .03 to .375 inch .
• the outer two metal strips are selected to have a thickness of about .008 inch (mils) and the resulting hot band metal strip produced has a thickness in the range of about .070 to 080 inch.
• the outer two metal strips are selected to have a thickness of between about .012 to .040 inch and the resulting hot band metal strip produced has a thickness in the range of 0.120 to 0.375 inch.
• the molten to solid ratio is above about 3-4.
• the molten to solid ratio is above 4-2.
• the ratio is generally above about 3.4, preferably above about 5-0.
• the hot band metal strip produced is cold rolled to a thickness of between about .008 to 0.040 inches and a portion of cold rolled product is recycled for use as the outer strip in the process of the present invention.
• the metal strips are fed into the gap between the first and second quench surfaces at a speed of about 500 to 8000 inches/minute. Most preferably, the strip speed is between about 500 to 1900 inches/ minute.
• the quench surfaces have a cooling fluid continuously passing through them.
• the process includes positioning two interme ⁇ diate endless metal support belts between the outer metal strips and at least the first and second quench surfaces.
• composition of the molten metal is selected to be different than the composition of the outer metal strips.
• the composition of the molten metal is selected to be the same as the composition of the outer strips.
• the quench surfaces ar*. selected to included opposed wheels, spaced apart one from the other, each roller having an annular flange at one end, the flanges being located at opposite ends of the rollers, respec ⁇ tively. These flanges facilitate the confinement of the molten or rheocast metal layer.
• the feeding of the metal strips, the joining of the metal strip and initial cooling of the molten or rheocast layer are performed in an inert atmos ⁇ phere such as argon, nitrogen or helium, _
• the metal strips and the molten or rheocast layer are selected to consist of carbon-steel.
• the two metal strips are selected to have a thickness of from about .008 to .040 inches.
• the molten metal bath is maintained in a .tempera ⁇ ture range of about 2900°F to 298 ⁇ °F.
• the process is conducted so as to minimize entrapment of ambient air or inert gas in the molten metal as the molten metal is introduced between the metal strips.
• Such entrapment is minimized in order to reduce the forma ⁇ tion of bubbles or metal oxides either in the area of the fusion bond between the metal strips and the molten metal or within the molten metal, which would reduce the bonding integrity of the thin strip product and create voids in the cast structure of the core.
• This is achieved by providing a barrier for shielding the molten metal from ambient air or inert gas as the molten metal is introduced between the metal strips.
• the metal strips form at least part of the barrier, and act as a curtain to shield the molten metal from the ambient air or inert gas.
• the metal strips are fed in sliding contact past a tundish nozzle tip into contact with first and second quench surfaces, with the metal strips traveling a distance between the point of contact with the tundish nozzle tip and the point of contact with the quench sur ⁇ faces such that distortion or bursting of the metal strips is avoided. This procedure also prevents or minimizes gene-
• the thin metal strip produced by the process of the invention forms another aspect of the present inven ⁇ tion.
• a clad cast metal strip com ⁇ prising a metal core and exterior metal cladding bonded to the core, with the metal cladding and the core defining a diffusion interface therebetween.
• the grain size is larger in the core than at the diffusion interface in view of the fact that the rate of solidification of molten metal when cooling and bonding to the strips to give the diffusion interface is higher than the rate of solidification of metal towards the center of the core.
• an apparatus for manufacturing thin metal - ⁇ tJRl_T strip comprising at least two quench surfaces defining a gap therebetween for receiving at least two metal strips, feed means for feeding at least two metal strips in spaced- apart configuration into the gap and into contact with at least one of said spaced-apart quench surfaces, and means for supplying molten metal between the metal strips as the metal strips are fed between the quench surfaces and into the gap.
• the process of the present invention substan ⁇ tially reduces the amount of energy required in the produc ⁇ tion of thin strip hot band steel.
• the estimated U.S. market for thin strip (.030 inch thick) steel product is 10 million tons per year and as much as 30 million ton in all thicknesses of strip and sheet.
• the process of the present invention has potential energy saving of as much as 5 million BTU/ton.
• the direct casting procedure of the pre ⁇ sent invention enables improvement in the surface condition of the thin strip. In previous melt drag casting pro ⁇ cedures, the side of the strip which did not contact the quench roll had irregularities.
• the process of the present invention which joins two strips with a maximum amount of molten metal, yields a product having two good external surfaces which retain the surface characteristics of the incoming strip.
• the use of two thin outer strips eliminates the sticking problem associated with the prior attempts to continuously cast strip steel because in the present process the molten metal does not contact the quench roll.
• the process of the present invention is premised upon the use of a superior method of transferring the heat from the molten metal while retaining the molten metal in strip form in a thickness range of .030 to .300 inches.
• Rapid solidification occurs over a time period typically 50 seconds or less, more usually 20 seconds or less, e.g. 5 to 10 seconds, with a temperature drop from about 2800 F to about 2400°F.
• Rapid heat transfer occurs between the molten metal and the clad strip while bonding also occurs.
• the metal-to-metal contact between molten metal with a tempera ⁇ ture of approximately 2800°F and cladding strip with a temperature of less than 500 results in rapid equalization of the composite strip temperature at about 2400 where it is solid.
• the rapid equalization of the composite strip temperature is also important from the standpoint of avoid ⁇ ing wavyness or warping in the final composite strip. If rapid temperature equalization is not obtained, and the metal strips cool at a different rate (typically a higher rate of cooling) than the rate of cooling of the core, then warping or wavyness in the strip may result, which is undesirable. Such warping or wavyness may be reduced by placing a tension on the composite strip after it is completely solidified. The tension may be placed on the strip as it is pulled through the apparatus (for example by arranging the exit speed of the composite strip to be slightly greater than the entry speed), which tension is high enough to eliminate or substantially reduce warping or wavyness without giving rise to melt-through problems. In this way, a more uniform product is obtained and subsequent rolling to reduce thickness is more readily facilitated.
• melt drag process and similar processes which extract heat from molten metal by brief contact between the cooling drum and the molten metal are limited in the thickness of metal which can be rapidly solidified. In these practices, heat extraction from the molten metal to the cooling drum is the predominant source of solidifica ⁇ tion.
• Figure 1 is a schematic side view of a first preferred embodiment of the present invention.
• Figures 2a and 2b are schematic side view of two preferred embodiments of the present invention.
• Figures 3a and 3b are cross sectional views of two preferred configurations for the quenching surfaces used in the process of the present invention, taken along the lines III-III in Figure 1.
• Figure 3c is a schematic side view of an arrange ⁇ ment for edge crimping of thin metal strip products.
• Figure 4 is a schematic side view of a third preferred embodiment of the present invention.
• Figure 5 is a schematic side elevation illu ⁇ strating a fifth preferred embodiment of the present inven ⁇ tion.
• Figure 6 is a schematic view illustrating the internal structure of clad cast metal strip of the present invention.
• metal strips 2 and 3 having a thickness of .008 inch, are provided from suitable sources 90 (e.g., coiled on reels) for feeding into gap 9 located between quenching surfaces (e.g., wheels) 4 and 5.
• suitable sources 90 e.g., coiled on reels
• the area defined by gap 9 and wheels 4 and 5 is maintained under inert atmospheric conditions by passing an inert gas into the chamber (not shown) containing bath 1 and wheels 4 and 5.
• the inert gas is selected from the group consisting of N 2 , Ar, He. It should be understood that the sources for strips 2 and 3 may also be placed in the chamber.
• inert as used herein means not giving rise to any conditions or products which would adversely affect the structure, strength and/or integrity of the thin strip product of this invention.
• inert atmos ⁇ pheric conditions preferably means non-oxidizing or sub ⁇ stantially non-oxidizing conditions.
• New strips 2 and 3 may also be provided by utilizing conventional continuous casting procedures such as those set forth in detail in published European Patent " ⁇ RE_ ⁇ Applications 040,070; 040,072, and 040,009 herein incor ⁇ porated by reference.
• Molten metal from bath 1 is distributed between metal strips 2 and 3 at gap 9, while strips 2 and 3 are in contact with quench surfaces 4 and 5-
• the ratio of molten to solid is maintained at above 3-4-
• Strips 2 and 3 and the molten metal layer must remain in contact with at least one quench wheel 4 and/or 5 for a time sufficient to enable partial solidification and cooling of the molten layer enabling strips 2 and 3 to join, one to the other, in sufficient strength to ensure that strips 2 and 3 will not delaminate during subsequent mechanical operations.
• Joined strips 2 and 3 are further cooled by contact with a third cooling wheel 6 and support surface(s) 7 to ensure permanent bonding of strip 2 and 3 producing a thin hot band crystalline metal strip 8 suitable for imme ⁇ diate cold reduction or coiling.
• the thickness of strip 8 is between about .03 to .125 in. Most preferably, the thickness is between about .070 to .080 inch.
• Support surfaces 7 are also fluid cooled (e.g., water or steam) to aid in the solidification of the molten metal layer.
• cool air blast may be supplied to the partially bonded metal strip at appropriate locations. For example, air blast may be positioned between adjacent support surfaces 7-
• a rheocast metal slurry may be utilized as the means of joining strips 2 and 3 • Accordingly, molten metal bath 1 may be replaced by a conventional rheocast slurry source.
• the strip speed for strips 2 and 3 may be within the range of 500 to 8000 inches/min. Most preferably, 500 to 1900 inches/minute should be utilized.
• Quench surfaces , 5 and 6, respectively, are preferably fluid (e.g., water or steam) cool wheels capable of maintaining the outer surfaces of strips 2 and 3 at a temperature low enough to maintain the integrity of the strips and to provide proper heat transfer from the laminate.
• the metal strips 2 and 3 are carbon-steel and the molten metal bath is carbon steel maintained at a temperature of between about 2900 to 2980 F.
• the distribution of the molten metal or rheocast metal slurry between strips 2 and 3 is performed in an inert atmosphere such as He, Ar and N ⁇ .
• metal strips 2 and 3 may be selected of various thicknesses depending upon the ultimate thickness desired in the resulting thin band crystalline metal strip 8. For example, strips 2 and 3 should have a thickness of between aabout .012 and .016 inch for the production of thin band strip 8 having a thickness in the range of .120 and .125 inch.
• the critical factor in the process of the present invention is to maintain the molten to solid ratio below the point where melt through of strips 2 and 3 occur. The molten solid ratio must be maintained above 3-4 and preferably is about 4.2.
• FIGS 2a and 2b illustrate alternative embodi ⁇ ments of the process of the present invention.:
• the cor ⁇ responding reference numerals appearing in Figures 1, 2a and 2b designate corresponding elements.
• Figure 2b illustrates an embodiment which is similar to that shown in Figure 2a, except that an upper support belt 115 is provided which passes around the periph ⁇ eries of wheels 5, 6 and 113.
• support surfaces 7 are provided around cooling wheel 6, and may be fluid cooled (e.g., with water) to aid in the solidification of the molten metal layer, as described above in connection with Figure 1.
• the upper support belt 115 provides support for the thin metal strip as it progresses through the area X of greatest vulnerability, and thereby lessens the chance of any melt-through of the molten metal through the metal strips 2 and 3-
• the thickness of the strip 2 to be slightly greater than the thickness of the strip 3.
• the thickness of strip 2 may be between 0.18 to 0.25 inch, typically 0.19 to 0.21 inch
• the thickness of strip 3 may be 0.008 to 0.16 inch, typically 0.12 to 0.16 inch.
• the thin metal strip is subject to its greatest vulner ⁇ ability to melt-through in the area designated by the letter X and the chance of melt-through -is reduced by utilizing thicker metal strip for the strip 2 than for the strip 3•
• a further feature which can be appreciated from Figures 1, 2a and 2b is that the composite thin metal strip, after passing between quench surfaces 4 and 5 moves along a tortuous multi- deflectional path around wheels 4, 6 and 13• As the thin metal strip moves along this tortuous path, it is subject to the constant directional force of gravity while the cast core is still molten, and this results in any bubbles and/or slag in the molten metal, typically non-metallic solid particles such as aluminates and silicates, to be more evenly dispersed throughout the molten metal, and not to collect and be deposited in the interface between the core and the clad strips, as solidifi ⁇ cation occurs.
• any entrapped gas bubbles and/or solid impurities in the molten metal having a different specific gravity or weight to that of the molten metal will be dispersed throughout the molten metal as solidification occurs.
• the solid particles e.g., non-metallic aluminates and silicates
• the solid particles have a similar effect as gas bubbles in that they form voids in the continuity of the solidified core of the thin metal product, and must be dispersed to prevent accumulations of such particles or voids which might give rise to weaknesses in the tensile strength of the thin metal product or starting sources of delamination.
• Figures 3(a) and 3(b) are cross-sectional illustrations of two preferred embodiments of quench wheels 4 and 5.
• Wheels 4 and 5 comprise opposed circular surfaces spaced apart one from the other, forming gap 9.
• Wheel 4 has an annular flange 11.
• Wheel 5 has an annular flange 10.
• Flanges 10 and 11 are located at opposite ends of rolls 4 and 5, respectively.
• the function of flanges 10 and 11, respectively, is to aid in the confinement of the molten metal or rheocast metal slurry material during distribution between metal strips 2 and 3- Gap 9 provided between flanges 10 and 11 respectively, provides an area where strips 2 and 3 and molten or rheostat metal are maintained during the partial solidification and bonding of strips 2 and 3.
• Gap 9 provided between flanges 10 and 11 respectively, provides an area where strips 2 and 3 and molten or rheostat metal are maintained during the partial solidification and bonding of strips 2 and 3.
• other configurations for quenching surfaces 4 and 5 may
• the strips 2 and 3 are wider than the distance between flanges 10 and 11, so that edges 120, 122 are crimped at 124 through an angle of approximately 90 .
• molten metal is prevented from leaking out between edges 120, 122, and a thin strip product of even width and thickness is subsequently obtained by trim ⁇ ming the edges to remove edges 120 from 122 after cooling and solidification of the molten metal.
• flanges 10 and 11 force edges 120, 122 closer together without crimping through an angle of approximately 90° as occurs in the embodiment illustrat ⁇ ed in Figure 3(a).
• a floating seal arrangement 126 is provided which urges the edges 120, 122 towards each other to prevent leakage of metal between edges 120, 122.
• the result of the edges 120, 122 being urged towards one another by the floating seal arrangement 126 is that very little molten metal is allowed to pene ⁇ trate between edges 102, 122, so that generally only a film thickness of molten metal is present between edges 120, 122. This, in turn, results in solidification of the thin film of metal almost instantaneously to seal edges 120, 122 together.
• the floating seal arrangement 126 is shown in more detail in Figure 3(c), wherein a floating seal 128 is urged against edge 120 of strip 2 by an adjustable pressure roller 130.
• a satisfactory seal between edges 120, 122 is produced without the necessity of crimping the ssttrriippss 22,, 33 tthhrroouugghh 9900° oorr ooff uuttiilliizziinngg a separate crimping apparatus to facilitate such deformation,
• Figure 4 illustrates another preferred embodiment of the present invention.
• Metal strips 20 and 22 are positioned to enter gap 23 located between quench surfaces 25 and 27.
• Belts 29 and 31 are maintained at
• OMPI substantially the same temperature as quench surfaces 25 and 27 and are mounted about quench surfaces 25, 27, 33, 35, 37 and 39 to provide an endless moveable support surface for strips 20 and 22.
• Supplemental quench surfaces (wheels 41(a) and 4Kb)) may be provided between quench sur ⁇ faces 25 and 33, and 27 and 37, respectively.
• the thin metal strip does not tra ⁇ verse a tortuous path as described above in connection with the embodiments illustrated in Figures 1, 2a and 2b, but insteai moves along an approximately straight path between quench surfaces 25, 27, 33, 41(a), 4Kb) and 35.
• Such an embodiment is particularly useful when "clean" steel is utilized as the molten material, i.e. steel which does not contain significant amounts of slag and has not been sub ⁇ jected to turbulence or other conditions giving rise to bubbles in the molten metal, since, in that instance, the need to disperse the bubbles or slag throughout the molten metal is lessened.
• metal strips 20 and 22 having a thickness of about .008 inch are fed into gap 23 located between quench surfaces 25 and 27.
• Strips 20 and 22 are cooled and supported by endless belts 29 and 31 positioned about surfaces 25, 27, 33, 35, 37 and 39- Molten metal (43) is fed into gap 23 into contact with strips 20 and 22.
• the ratio of molten to solid is maintained at above 3-4.
• Strips 20 and 22 having molten metal 41 therebetween is passed through gap 23 between quench surface 25 and 27 while in contact with cooled endless support belts 29 and 31.
• the olten layer remains in contact with support belts 29 and 31 for a time sufficient to ensure at least partial solidi ⁇ fication of the molten metal and the formation of a bond at least strong enough to ensure that strips 20 and 22 do not delaminate.
• the resulting cast strip 43 has a thickness in the range of .070 to .080 inch.
• Figure 5 illustrates a further preferred embodi ⁇ ment in which metal strips 50, 52 are advanced past a tundish 53 in sliding contact with the tundish nozzle tip 54 towards a gap 56 between quench surfaces 58, 60.
• the strips touch or bear upon the tundish nozzle tip 54 at contact points 62, 64 before the clad strips come into contact with the quench surfaces 58, 60 on the opposite sides of the two clad strips.
• the distance between the contact points 62, 64 an contact points 66, 68 where the strips contact the quench surfaces 58, 60 is variable and can be controlled, and is generally in the range 0.05 to 2 inches, usually no more than 0.1 inch, depending on the thickness of the strips 50, 52.
• the distance Is suffici ⁇ ently short as compared with the thickness of the strips 50, 52 to ensure that the strips 50, 52 have sufficient tensile strength to prevent bulging or bursting under the head pressure of molten metal 70 entering the gap 56 through the nozzle tip 54-
• the head pressure of the molten metal is controlled by the depth X of the molten metal in the tundish.
• Another function of this distance between con ⁇ tact points 62, 64 and contact points 66, 68 Is to prevent the nozzle tip 54 from bearing downward, in the direction of the metal flow and onto the quench surfaces 5 ⁇ >, 60 through the strips 50, 52. This prevents the nozzle tip 54 from being swept into pinch point 5.
• the downward head pressure of the molten metal flowing from the tundish 53 through the nozzle tip 54 operates to reliably and continu ⁇ ously fill the region between the nozzle tip 54 and the pinch point 55 to continuously provide a layer of molten metal having a depth at least equal to the depth X referred to above.
• the clad strips form a barrier between the molten metal flowing from the tundish nozzle tip 54 into the gap 56 and shield the molten metal from ambient air or the inert gas atmosphere and thereby minimize entrapment of inert gas or air in the molten metal as it passes into the gap 56.
• the reduced exposure of the molten metal to oxygen in the ambient air reduces the formation of metal oxides which, in turn, improves the bonding integrity and tensile strength of the resulting product, and reduces any tendency for the product to undergo delamination when subjected to further mechanical operations such as rolling and bending.
• the use of the metal strips 50, 52 as a barrier or curtain prevents or minimizes entrapment of inert gases in the molten metal which subsequently can give rise to voids in the metal after it solidifies.
• a further advantage arising from the arrangment illustrated in Figure 5 is that the entry of the strips 50, 52 past the tundish nozzle tip 54 reduces molten metal turbulence in the presence of ambient air or inert gases which would result in such atmospheres being entrapped in the molten metal, and giving rise to oxide metal formation or void formation, as described above.
• C metal is introduced between the strips 2, 3, in a chamber so that the metal can be introduced between the metal strips in an inert gas atmosphere.
• the metal strips form a barrier and the process is conducted under a shroud of inert gas in the region where the molten metal is intro ⁇ quizd between the metal strips, then sufficient protection is generally afforded by the shroud, and it -is possible to dispense with the chamber for housing the apparatus.
• the prevention of oxide entry into the molten metal can be further accomplished by passing the strips 50, 52 through a pickling acid bath in order to remove metal oxide present on the strip.
• Pickling is preferably con ⁇ ducted immediately prior to feeding the metal strips 50, 52 into the gap 56, and this removes metal oxide deposits adhering to the surface of the strips 50, 52.
• Figure 6 illustrates in cross section the clad cast metal strip of the invention.
• the strip comprises a metal core 70 and exterior metal cladding 72, 74 bonded to the core 70 by a fusion bond generally identified by the numeral 76.
• the fusion bond 76 is formed as the strips 50, 52 come into contact with the molten metal and at least a molecular thickness of the surface layer of the metal strip melts to give rise to bonding upon cooling and solidifica ⁇ tion of the molten metal.
• the fusion bond 76 defines a diffusion interface 78 between the cladding 72, 74 and the core 70, and the grain structure 80 in the core is general ⁇ ly larger than the grain structure 82 in the diffusion interface in view of the fact that the metal in the diffusion interface underwent more rapid cooling than the metal towards the center of the core.
• the apparatus comprises at least two quench surfaces 4,5 defining a gap 9 there ⁇ between for receiving at least two feed metal strips 2, 3-
• the apparatus also includes feed means 90 for feeding the at least two feed metal strips 2, 3 in spaced-apart con ⁇ figuration into gap 9 and into contact with at least one of said quench surfaces 4, 5 -
• Means 1 is also provided for supplying molten metal between the feed strips 2,3 as the strips 2, 3 are fed between quench surfaces 4, 5 into gap 9.
• the process of the present invention produces a 'hot band crystalline metal strip which has sufficient strength and thickness to enable immediate cold rolling of the strip.
• the product can be partially recycled reducing substantially the energy expenditure as ⁇ sociated with past hot band strip formation techniques.
• the potential energy savings by the use of the process are as much as 10 million BTU/ton.
• the direct casting procedure of the present invention produces a continuous strip product having both surfaces retaining the original surface charac ⁇ teristics of the metal strips while simultaneously elimi ⁇ nating the sticking problem associated with previous cast ⁇ ing techniques.
• the outer strips prevent molten metal con ⁇ tact with the cooling surfaces, thereby eliminating the sticking problem associated with prior casting techniques.
• a critical aspect of the present invention is that the two metal strips and molten metal are retained in contact with the quenching surfaces under appropriate conditions and for a time sufficient to produce an adequate bond between these strips so that delamination of the strips will not occur during the subsequent operation such as cold rolling.
• the molten metal may be the same as that of the metal strip, for example carbon steel in each instance, or the molten metal used may be different to that of the metal strip, for example copper cladding on a steel core.
• the metal strip may be of a different compo ⁇ sition to the molten metal, for example the strip may be of an alloy of the metal present in the core, e.g., stainless steel cladding on a carbon steel core, or a high purity aluminum alloy on a high tensile strength- aluminum alloy core.
• the quench surface may be varied in size. For example, wheels 4 and 5 shown in Figure 1 may be made as large as wheel 6.

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• 1984
  • 1984-10-31 WO PCT/US1984/001770 patent/WO1985001901A1/en unknown
  • 1984-10-31 AU AU36109/84A patent/AU3610984A/en not_active Abandoned
  • 1984-10-31 EP EP19840904058 patent/EP0160081A1/de not_active Withdrawn

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