CA1194269A - Strip casting nozzle - Google Patents
Strip casting nozzleInfo
- Publication number
- CA1194269A CA1194269A CA000377152A CA377152A CA1194269A CA 1194269 A CA1194269 A CA 1194269A CA 000377152 A CA000377152 A CA 000377152A CA 377152 A CA377152 A CA 377152A CA 1194269 A CA1194269 A CA 1194269A
- Authority
- CA
- Canada
- Prior art keywords
- slot
- casting
- nozzle
- set forth
- strip
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
-
- 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
- B22D11/005—Continuous casting of metals, i.e. casting in indefinite lengths of wire
-
- 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
- B22D11/0637—Accessories therefor
- B22D11/064—Accessories therefor for supplying molten metal
- B22D11/0642—Nozzles
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
- Inspection Of Paper Currency And Valuable Securities (AREA)
- Recording Or Reproducing By Magnetic Means (AREA)
- Credit Cards Or The Like (AREA)
Abstract
STRIP CASTING NOZZLE
Abstract of the Disclosure An apparatus for continuously casting metallic strip material is disclosed, comprising a tundish, and a nozzle comprising a slotted element, with the slot having substantially uniform cross-sectional dimensions throughout the longitudinal extent thereof. Disposed outside the nozzle is a cooled casting surface movable past the nozzle in a direction substantially perpendicular to the longitudinal axis of the slot. The slot is defined between first and second lips of the nozzle which have inside surfaces facing one another at least at an inner portion of the slot. The facing inside surfaces diverge from one another at an outer portion of the slot. The first and second lips are further provided with bottom surfaces facing the casting surface at a standoff distance less than 0.120 inch.
Abstract of the Disclosure An apparatus for continuously casting metallic strip material is disclosed, comprising a tundish, and a nozzle comprising a slotted element, with the slot having substantially uniform cross-sectional dimensions throughout the longitudinal extent thereof. Disposed outside the nozzle is a cooled casting surface movable past the nozzle in a direction substantially perpendicular to the longitudinal axis of the slot. The slot is defined between first and second lips of the nozzle which have inside surfaces facing one another at least at an inner portion of the slot. The facing inside surfaces diverge from one another at an outer portion of the slot. The first and second lips are further provided with bottom surfaces facing the casting surface at a standoff distance less than 0.120 inch.
Description
Brief Summary of the Invention Releva~t subject matter is dIsclosed in co-filed Canadian Patent Applications entitled "Strip Casting Apparatus" Serial Number 366,164; "Method and Apparatus for Strip Casting" Serial Number 377,201; "Method of Repetitiously Marking Continuously Cast Metallic Strip Material" Serial Number 377,216; and "Apparatus :Eor Strip Casting" Serial Number 377,134, all of which are assigned to Battelle Development Corporation.
The present invention relates to the casting of strip material at high quench rates and at high production rates. More particularly, the present invention is directed to an apparatus for rapidly cas-ting thin metallic strip material characterized by an outwardly diverging nozzle design.
The apparent advantages and economic significance of producing thin metallic strip material by a casting process, as compared to the conventional rolling or reducing operations, are numerous. The fact that strip casting may be performed at such high quench rates to produce amorphous material is even more meaningful. However, it is equally apparent that there are a multitude of strip casting parameters which must be controlled or monitored to assure that the cast strip is of acceptable quality and of uniform composikion and structure. For these reasons, those skilled in the art appreciate the intricacy involved in the development of a commercially successful strip casting apparatus.
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1 The general concept of casting thin metallic materials suc~ a~ sheet, foil, strip ~nd ribbon was disclosed ~n the early l900's. For example, U.S. Patents 905~758 and 993,904 teach processes wherein molten material flows onto a moving cool surface and the material is drawn and hardened thereon into a continuous thin 6tripO These references teach that molten metal may be poured onto ~he smooth peripheral surface of a rotating liquid cooled copper dr~m or disc to form strip materials. Despite early disclosure of such ~oncept, there i~ no evidence of commercial success of strip casting during the early part of the 20th century.
Recently, in U~S. Patents 3,522,836 and 3,605,863 a method for manufacturing a continuous product, such as metallic wire or strip from molten metal has been disclosed.
These references teach that a convex meniscus of molten material should project from a nozæle. A heat extracting surface, such as a water-cooled drum, is moved in a path substantially parallel to the outlet orifice and into contact with the meniscus of molten met:al to continuously draw material from the meniscus to form a uniform continuous product. The above-described method is commonly called the nmelt drag" process as the heat extracting surface moving pas~ the meni~cus of molten metal at the nozzle orifice actually has an effect on the rate of molten metal flow, or drag, through the nozzle.
More recent strip casting developmen~s ocus on relat~vely narrow refinements ln the metallic s~rip casting art. ~or exa~ple, U.`S. Patent 4~142,571 is particularly , L~
1 directed to a ~lot construction in a metal strip casting nozzle having ~tringent dimen~ional requirements. Also, U.S. Patent 4,077,462 pertains to the provision of a specific construction for a stationary housing above the peripheral 6urface of a chill roll used for strip cast.ing.
There are a number of other rapid ~uenching techniques known in the art. For example, melt spinning processes of producing metallic filament by cooling a fine molten stream either in Pree flight or against a chill block have been practiced. Also known are melt extraction techniques, such as crucible melt extraction disclosed in U.S. Patent 3,838,185 and pendant drop melt extraction techniques taught in U.S. Patent 3,896,203. It has been found difficult to produce uniform heet or strip by such alternative techniques of raFid casting. There are many factors, such as casting temperature and pressure, auxiliary surface cooling rates, ~urface coatings for the casting surface, and the like which appear to affect the product thickness and the quality of rapidly cast strip material.
Despite the relatively long history o the art of ~trip casting, and the recent developmen~s in this area, strip casting is not a widely accepted and commercially significant operation at the present time. I~ appears that various improvements, modification~ and innovations are required in the art to effectuate a significant commercial ~mpact in the art of ~trip casting. In particular, proper relationships among such variables as molten metal tundish construction, nozzle orifice ~ize and dimensions~ spacing 1 from a ca~ting surface, ~peed at which uch surface is moved, quench rates, metal temperature and feed rates, and the like may requlre more accurate identification and interrelation in order to accompli~h the uniformity and consi~tency required for successful, commercial production o~ cast strip In particular, certain nozzle and 610t structures and their dimensional relationship to the casting surface onto which strip material is cast, h~ve been found to be inadequate to yield uniform strip castin~ results when utilized in various casting parameters.
Accordingly, a new and improved apparatus for casting relatively wide, thin strip material is desired which overcomes the disadvantages of the prior art structures. Such desired apparatus should be reliable, more efficient and more effective than the structures disclosed in the prior art, and should lead to reproducibility, uniformity and consistency in strip casting.
~he present invention may be summarized as providing a new and improved apparatus for continuously casting metallic strip material. Such appar~tus comprises a tundish and a nozzle comprising a slotted element, with the slot having substantially uniform cross~sectional dimensions throughout the longitudinal extent thereof. Di~posed outside the nozzle is a cooled casting surface movable past the nozzle in a directon ~ubstantially perpendicular to the longitudinal axis of the slot. ~he slot is defined between first and second lips of the nozzle which have inside ~urfaces facing one ~nother at least at an inner portion 1 of the slot. The facing ~nside surfaces diverge from one another at an outer port~on of the slot. The Pirst and ~econd lips are further provided with bottom sufaces facing the casting surface at a standoff distance less than 0.120 inch.
Among the advantages of the present invention is the provision of a strip casting apparatus which is capable of continuously casting metallic strip material of substantially uniform dimension and substantially uniform Quality throughout its length.
Another advantage of the present invention is the provision of a strip casting apparatus having an outwardly diverging nozzle construction which promotes the efficient rapid casting of metal strip material.
An objective of the present invention is to provide a strip casting apparatus capable of reproducing successful strip casting operations.
Another objective of this invention is to provide a strip ca~ting apparatus which can effec~uate sufficiently rapid quenching of the produced strip to result in the production o amorphous strip. ~owever, it should be understood that the production of continuously cas~ ceystalline material is also comprehended by the present invention.
A further objective of this invention $s to identify certain design and dimensional requirements, particularly with regard to an outwardly diverging nozzle 1 structure, which permit continuous and repetitious rapid casting of ~etallic strlp material of uniform dimension and unlform quality.
These and other objectives and advantages will be more fully understood and appreciated with reference to the following detailed description and the accompanying drawings .
Brief Description of the Drawings Figure 1 is an elevation view, partially in cross-section, illustrating a typical apparatus used for continuously casting strip material, Figure 2 is a cross-sectional view of an outwardly diverging nozzle in a strip casting apparatus of the present invention.
Figures 3r 4 and 5 are cross-sectional views of alternative outwardly diverging nozzles in strip casting apparatu~ of the present invention.
Detailed Description Referring particularly to the drawings, Figure 1 generally illustrates an apparatus for casting metallic strlp material 10 in ~ccordance with the present invention.
This apparatus includes an element 12 upon which the str ip 10 i~ cast. In a preferred embodiment a con~lnuous strip 10 1~ caEt onto a ~mooth, outer peripheral surface 14 of a circular drum or wheel as ~hown ln Figure 1. It 6hould be ?!$ ~
1 understood that confi~uration~ other than circular may be employed. Por example, a wheel with a smooth, frustoconical outer peripheral surface (not 6hown) may be employed. Also, a belt capable of rotating through a generally ovular path may also be employed as the casting element. Regardless of the configuration employed, the cooled casting urface ~hould ~e at least as wide as the trip to be cast.
In a preferred embodiment, the casting element 12 comprises a water cooled, precipitation hardened copper alloy wheel containing about 98% copper and about 2~
chromium~ Copper and copper alloys are chosen for their high thermal conductivity and wear resistance, however, berillium copper alloys, steel, brass~ aluminum, aluminu~
alloys or other materials may be utilized alone, or in combination. For example, multipiece wheels having sleeves of molybdenum or other material may be employed. Likewise, cooling may be accomplished with the use of a medium other than water. Water is typically chosen for its low cost and its ready availability.
In the operation of the strip casting apparatus of the present invention, the surface 14 of the casting wheel 12 must be able to absor~ the heat generated by contact with molten metal at the initial castiny location 16, and ~uch heat must be conducted substantially in~o the copper wheel during each rotation of the wheel. The initial ca6tlng point 16 refer to the approximate location on the casting 6urface 14 where molten metal 20 from ~he tundish 22 fir~t contact~ the casting ~urface 14. Cooling, by heat 1 conduction, may be accomplished by delivering a 6uf~icient qu~ntity of water through lnternal passageways located near the periphery of the casting wheel 12. Alternatively, the cooling medium may be delivered directly to the underside of the ca~ting surface. Understandably, refrlger~tion techniques and the like may be employed to accelerate or decelerate cooling rates, and/or to effectuate wheel expan~ion or contraction during strip casting.
Whether a drum, wheel or belt is employed for casting, the casting surface should be generally smooth and symmetrical to maximize uniformity in strip casting. For example, in certain strip castiny operations the distance between the outer peripheral casting surface 14 and the surfaces defining the orifice of the nozzle which is feeding the molten material onto the casting surface 14 must not deviate from a desired or set distance during the casting operation. This distance shall hereinafter be called standoff distance or gap. It is understandable that the gap 6hould be substantially maintained throughout the casting operation when it is the intention to cast uniform strip material.
It ~hould be understood that lf the casting element is a drum or a wheel, the element should be carefully constructed ~o as not to be out~of-round during operation to insure uniformity in strip casting. Along these l~nes, it has been found that a drum or wheel which is out-of-round by about 0.020 inch, or more, may have a magnitude of dimencional in~tability which unless corrected g_ 1 or compensated during operation~ ~ay be unacceptable for certain strip casting operations. It has been found that acceptable dimen6ional symmetry, as well as the elimination of problems associated with weld porosity may be more readily acco~plished by fabricating a wheel or drum from a single, integral slab of cold rolled or forged copper alloy. ~owever, as mentioned above alternative materials, including ~leeves and co~tings may be employed.
The molten material 20 to be cast in the apparatus described herein is pref2rably retained in a crucible 22, or tundish, which is provided with a pOULin9 orifice 24 or nozzle. The noz~le is typically, though not necessarily, located at a lower portion of the tundish 22 as shown in Figure 1. As will be appreciated from the foregoing discussion, the nozzle 24 may be a separate element in the tundish 22, or, the nozzle 24 and tundish 22 may be monolithic, i.e. integrally formed, with all or any portion of the tundish 22.
The nozzle 24, located in or forming a lower portion of the tundish 22 may comprise a slotted element~ as best ~hown in Figure 2. The slot 30 is preferably substantially centrally located in the nozzle element 24.
Such approximate central location of the slot 30 helps ~o asure uniformity as the pressure of the molten metal bearing thereagainst i8 ~ubstantially equali~ed during the casting operation. It should be understood, however, that the slot 30 may be located in off-center posi~ions as may be desired.
1 The longitudinal extent o~ the ~lot 30 should approximate the width of the strip to be cast. There does not appear to be a limitation on the longitudinal extent of the ~lot, ~nd, slots as long as thirty ix inches, or longer, are comprehended by the present lnvention. It is highly desired that the molten metal flow uniformly through the slot 30 in the noz21e 24 ~f the present invention in order to produce uniform, high quality strip material. In an alternative embodiment, strip of various widths may be simultaneously produced by cutting multiple longitudinally aligned slots 30 of appropriate longitudinal extent in the nozzle area of a tundish 22, as opposed to a single slot 30. Regardless of the ~ize of the slot 30, or slots, the cross-sectional dimensions of each 610t 30 should be substantially uniform throughout the longitudinal extent thereof to produce strip material having uniform dimensions. In the operation of the str ip casting apparatus of the present invention, the cooled casting ~urface 14 moves past the slot 30 in a direction 6ubstantially perpendicular to the longitudinal axis of the slot~
As shown in Figure 2, the slot 30 is defined between a flrst lip 32 and a second lip 34 of the no~zle 24 The first lip 32 i located at the downstream edge of the ~lot 30, ~ith re~pect to the direction of movement of the casting surface 14 indicated by the arrow in ~igure 2. The ~econd lip 34 i3 located at an upstream edge of the slot with re~pect to the casting direction.
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1 The fixst lip 32 and the second lip 34 have inside surfaces 36 and 3~, respe~t~vely, which are ~ubstantially parallel to and acing one another at least at an inner portion of the slot 30. The inner portion refers to that portion which is near the molten metal holding portion of the tundish, while ~n outer portion of the slot 30 refers to that portion near the casting surface 14. I~
should be understood that the innermost portion of the slot may be relieved or tapered. For example, the innermost portion of the fir6t lip 32 and/or the ~econd lip 34 may be cut into a general V-shape, or a more rounded U-shape creating an initial funnel type structure for the slot as illustrated in Figures 3 and 5. Such relief of the innermost portion of the slot 30 may assist in maintaining uniform molten metal flow patterns and minimizing irregularities or turbulence during strip casting. What is required by the present invention is that the inside surfaces 36 and 38 are facing and parallel at least at some inner portion of the slot 30~
Beyond such inner, parallel, facing portion, ! in the direction of the casting surface 14, the inside surfaces diverge outwardly from one another at an outer portion of the slot 30. Preferred outwardly diverging ~urfaces are indicated by reference numerals 40 and 42 in . Figure 2. Such outward divergence of the inside surfaces may be accomplished by alternative structure~ ~u~h as those ~hown in Flgures 3, 4 and 5. It should be noted that only one of the in~ide surfaces need to diverge to create the 1 necessary relation~hip o outward divergence therebetween a~
~hown in Figures 3 and 4. Also, curved ~urface~9 radiused either inwardly 40 or outwardly 4~ a~ ~hown in Figure 5, may eQtablish 6uch outward divergence.
S From that outwardly diverging ~urface,~ 40 ~nd 42 the first and second lips 32 and 34 extend to bottom ~urfaces 44 and 46 respectively. Such bottom surfaces 44 and 46 of the lips 32 and 34 face the casting surface 14~
and are located at a standoff distance, or gap, of less than about 0.120 inch from the casting surface. In a preferred embodiment, the standoff distance e be~ween the bottom surface 44 of the first lip 32 and the castins surface 14 is as small as possible consistent with permitting ~he casting surface 14 to move thereunder in an unobstructed path. In any event, the gap e between the bottom surface 44 of the first lip 32 and the casting surface 14 must be small enough at the nozzle orifice to prevent significant molten metal backflow therebetween during casting. The gap d between the casting surface 14 and the bottom surface 46 of the second lip 34 is preferably less than 0.080 inch, and for casting certain alloys into thin gage strip may be less than 0.010 inch.
Preferably, at least a portion of the bo~tom surfaces 4~ and 46 are in sub~tantially complete parallelism with the c~sting ~urface 14 movable therebelow, at least at the nozzle orificeO When utilizing a drum or wheelt and a refractory nozzle 24, such parallism may be accompll~hed by placing a sheet of ~andpaper, or the like, against the -1 ca~ting ~urface 14 with the grit ~ide of the sandpapex facing the nozzle 2~. By moving the nozzle 2A into tight contact wlth the casting 6urface 14, with the ~andpaper disposed therebetween, and by movin9 the casting surface 14 and ~andpaper 6imultaneously past the nozzle 24, the bottom surfaces 44 and 46 are ground by the grit into substantially complete parallelism with the casting surface 14. Such parallelism may be achieved even when round or other curvilinear casting surfaces are employed. To achieve such parallelism on most refractory nozzles by this procedure, 400 or 600 grit sandpaper has been Eound to be adequate.
It has also been found that the corners between the surfaces defining the slot 30 may be radiused to minimize molten metal turbulence during casting. In certain instances sharp corners may be subjected to various pre~s~re and flow patterns which could create stress conditions for nozzles 24 made of certain materials, and in some instances, may break, crack or wear during casting in a manner which may upset balanced strip casting conditions. Providing ~uch rounded corners may minimize the adver~e affects of such turbulence and flow through the nozzle 24.
The crucible 22 is preferably constructed of a ma~erial having superior insulating ability. If the insulating ability is not sufficient to retain the mol~en ~aterial at a relatively constant temperature, auxiliary heaters ~uch as indu~tion coils may have to be provided in ~nd/or around the crucible 22, or resistance elemen~s 6uch 1 as wires may be provided. A convenient material for the crucible is an insulating board made from fiberized kaolin, a naturally occurring, high purity, alumina-silica fire clay. Such insulating material is available as KAOWOOL
(a trade mark for fiberized kaolin block) HS board. However, for sustained operations~ and for casting certain high melting temperature alloys, various other materials may have to be employed for construc-ting the crucible or the nozzle including graphite, alumina graphlte, quartz, clay graphite, boron nitride, silicon nitride, silicon carbide, boron carbide, alumina zirconia and various combinations or mixtures of such materials. It should be understood that these materials may be strengthened; for example, fiberized kaolin may be strengthened by impregnating with a silica gel or the like.
It is imperative that the orifice of the nozzle 24 remain open and its configuration remain substantiall~ stable throughout at least one, and preferably many strip casting operations. It is understandable that the orifice should not erode or clog, significantly, during strip casting.
Along these lines, it appears that certain i~sulating matierals may not be able to maintain their dimensional stability over long casting periods. To obviate this problem, lips 32 and 3~ forming th~ orifice oE the nozzle 2 may be constructed of a material which is better able to maintain dimensional stability and integrity during e~posure to high molten metal temperatures for prolonged time periods.
Such materials may take the form of a single, generally ., ~.
1 semi-circular element with a slot 30 cut therethrough or a pair of insert6 held in the crucible to form a slot 30 therebetween. In a prferred embodimen~ the slot or slots in single elements may be cut ultrasonically to in~ure that the desired ~lot dimen~ions are accurately provided. Such nozzles 24 may be constructed of materials ~uch as quartz, graphite, clay graphite, boron nitride, alumina graphite, silicon carbide, stabili~ed zirconia ~ilicate, zirconia, magnesia, alumina or other similar molten metal resistan~
material. Such nozzle6 24 may be held in the orifice of the crucible mechanically, with pressure, and/or with the aid of adhesives such as various refractory cements, ~prinq biased mechanisms, or the like.
The drive system and housing for the drum, wheel or other casting surface 14 of the pre~ent invention should be rigidly c~nstructed to permit drum rotation without structural instability which could cause the drum to slip or vibrate. In particular, care should be taken to avoid resonant freguences at the operating speeds for the casting &urfce 14. The casting surface 14 should be capable of moving at a ~urface speed of from about 200 linear surface feet per minute to more that about 10,000 linear ~urface feet per minute. When utilizing a drum having a circumference of about 8 feet~ this rate calculates to a drum speed from about 25 rpm to about 1250 rpm. A three horsepower variable speed rever~ible~ dynamically braked motor provide~ ~n adequate drive ~ystem for an lntegral copper alloy casting drum ~pproximately 2 inches thick and about 8 eet in circumference.
1~
1 In one embodimellt, the casting surEace 14 on the wheel or drum of the apparatus of the present invention is smooth. It has been Eound tha-t in cer-tain applications, such as for producing amorphous materials, finishing the peripheral surface 14 of a casting drum 12 with 400-grit paper and preferably with 600-grit paper may yield improved product uniformity.
In a preferred embodiment as illustrated in Figure 2, the nozzle 24 is defined by an insert made of clay graphite, a molten metal resistant material, held in the - walls of the crucible 22. The slot 30 is cut ultrasonically in the clay graphite nozzle 24. The first lip 32 and the second lip 34 of the nozzle 24 define the slot 30 therebetween. As alternative preferred examples of nozzle 24 materials, a plate made of quartz or VYCOR (a trade mark for thermally resistant laboratory glass) material,or an insert of boron nitride may be employed. The desired slot forming the orifice 46, may be accurately cut therein with an ultrasonic drill. A preEerred one piece element forming a nozzle, as best illustrated in Figure 2, may ~e constructed of a semi-circular ring of molten metal resistant material. In this example, a slot having a width of about 0.010 to about 0.080 inch between the facing, parallel inside surfaces 36 and 38 may be ultrasonically drilled into a clay graphite insert material, and the insert is held in the crucible 22. It should be understood that the design of the insert~may be modified to assist in holding the insert forming the nozzle 24 in the crucible 22.
1 A preferred nozzle 24 of the ~pparatus of the pre~ent invention i~ shown ln enlarged cross~section in Figure 2. In one embodiment of this apparatus, the dimensions indicated in Fi~ure 2 h~ve the following preferred li~itations.
Ji more preferred preferred dimension designation limitation limitation a bottom surface at least .001 .25 - .50 inch of first lip inch b width of slot .020 - .200 inch 0.125 inch at maximum divergence c bottom surface .01 - .16 inch .02 - .06 inch of second lip d standoff .01 - .080 inch less than .010 distance be- inch tween first lip and ca~ting ~urface e standoff .01 - .080 inch less than .010 dlstance be- inch tween ~econd lip and casting surface f width of slot .010 - .080 inch .025 - .035 inch between parallel, facing ~urfaces g depth of diverg- ~050 - .200 inch .125 inch ing area of slot h depth of para- .050 - .200 inch .125 inch llel area of slot ., In the production of amorphous strip ma~erials the width of the slot f is typically in the range of from about 0.010 to 0.040 inch~ In the production OL cry6talline strip material~ cuch a~ stainless ~t~el, the width of the 1 ~lot f may be greater, perhaps a5 high as about 0.080 inch if thick strip is being unifor~ly produced in accordance with the present invention. Al~o, the primary purpose of a relief at an ~nner portion of the slot 30, such as i6 shown in Figures 3 and 5 is to eliminate clogging of molten metal in the orifice during strip casting.
In an exemplary operation of the apparatus of the present invention, molten metal is delivered to a heated crucible 22. It i8 understood that a heater, such as induction coils of resistance wire, may be provided in and above the crucible 22 to maintain relatively constant molten metal temperatures as may be desired. Alternatively, the molten metal may be poured direc~ly into a preheated crùcible. The preheat temperature should prevent free~ing or clogging of the slot 30 during the initial casting operation, and the temperature of the flowing metal should thereafter keep the crucible 22 and nozzle 24 at sufficient temperature to insure uninterrupted mo~ten metal flow through the orifice. In certain applications, the nozzle itself may be externally heated throughout the casting operation~ Also, the metal which is fed to the crucible 22 may be superheated to allow a certain degree of temperature loss without adversely affecting metal flow through the no~le 24.
Also, a metallostatic head helght ~n the tundish 22 is preferably maintained at a relatively constant level, typically ~t a level of less ~han ten inches abo~e the nozzle 24, throughout the casting oper~tion to a~sure that a
The present invention relates to the casting of strip material at high quench rates and at high production rates. More particularly, the present invention is directed to an apparatus for rapidly cas-ting thin metallic strip material characterized by an outwardly diverging nozzle design.
The apparent advantages and economic significance of producing thin metallic strip material by a casting process, as compared to the conventional rolling or reducing operations, are numerous. The fact that strip casting may be performed at such high quench rates to produce amorphous material is even more meaningful. However, it is equally apparent that there are a multitude of strip casting parameters which must be controlled or monitored to assure that the cast strip is of acceptable quality and of uniform composikion and structure. For these reasons, those skilled in the art appreciate the intricacy involved in the development of a commercially successful strip casting apparatus.
.~..".~,",. ;.
, ~ ..
1 The general concept of casting thin metallic materials suc~ a~ sheet, foil, strip ~nd ribbon was disclosed ~n the early l900's. For example, U.S. Patents 905~758 and 993,904 teach processes wherein molten material flows onto a moving cool surface and the material is drawn and hardened thereon into a continuous thin 6tripO These references teach that molten metal may be poured onto ~he smooth peripheral surface of a rotating liquid cooled copper dr~m or disc to form strip materials. Despite early disclosure of such ~oncept, there i~ no evidence of commercial success of strip casting during the early part of the 20th century.
Recently, in U~S. Patents 3,522,836 and 3,605,863 a method for manufacturing a continuous product, such as metallic wire or strip from molten metal has been disclosed.
These references teach that a convex meniscus of molten material should project from a nozæle. A heat extracting surface, such as a water-cooled drum, is moved in a path substantially parallel to the outlet orifice and into contact with the meniscus of molten met:al to continuously draw material from the meniscus to form a uniform continuous product. The above-described method is commonly called the nmelt drag" process as the heat extracting surface moving pas~ the meni~cus of molten metal at the nozzle orifice actually has an effect on the rate of molten metal flow, or drag, through the nozzle.
More recent strip casting developmen~s ocus on relat~vely narrow refinements ln the metallic s~rip casting art. ~or exa~ple, U.`S. Patent 4~142,571 is particularly , L~
1 directed to a ~lot construction in a metal strip casting nozzle having ~tringent dimen~ional requirements. Also, U.S. Patent 4,077,462 pertains to the provision of a specific construction for a stationary housing above the peripheral 6urface of a chill roll used for strip cast.ing.
There are a number of other rapid ~uenching techniques known in the art. For example, melt spinning processes of producing metallic filament by cooling a fine molten stream either in Pree flight or against a chill block have been practiced. Also known are melt extraction techniques, such as crucible melt extraction disclosed in U.S. Patent 3,838,185 and pendant drop melt extraction techniques taught in U.S. Patent 3,896,203. It has been found difficult to produce uniform heet or strip by such alternative techniques of raFid casting. There are many factors, such as casting temperature and pressure, auxiliary surface cooling rates, ~urface coatings for the casting surface, and the like which appear to affect the product thickness and the quality of rapidly cast strip material.
Despite the relatively long history o the art of ~trip casting, and the recent developmen~s in this area, strip casting is not a widely accepted and commercially significant operation at the present time. I~ appears that various improvements, modification~ and innovations are required in the art to effectuate a significant commercial ~mpact in the art of ~trip casting. In particular, proper relationships among such variables as molten metal tundish construction, nozzle orifice ~ize and dimensions~ spacing 1 from a ca~ting surface, ~peed at which uch surface is moved, quench rates, metal temperature and feed rates, and the like may requlre more accurate identification and interrelation in order to accompli~h the uniformity and consi~tency required for successful, commercial production o~ cast strip In particular, certain nozzle and 610t structures and their dimensional relationship to the casting surface onto which strip material is cast, h~ve been found to be inadequate to yield uniform strip castin~ results when utilized in various casting parameters.
Accordingly, a new and improved apparatus for casting relatively wide, thin strip material is desired which overcomes the disadvantages of the prior art structures. Such desired apparatus should be reliable, more efficient and more effective than the structures disclosed in the prior art, and should lead to reproducibility, uniformity and consistency in strip casting.
~he present invention may be summarized as providing a new and improved apparatus for continuously casting metallic strip material. Such appar~tus comprises a tundish and a nozzle comprising a slotted element, with the slot having substantially uniform cross~sectional dimensions throughout the longitudinal extent thereof. Di~posed outside the nozzle is a cooled casting surface movable past the nozzle in a directon ~ubstantially perpendicular to the longitudinal axis of the slot. ~he slot is defined between first and second lips of the nozzle which have inside ~urfaces facing one ~nother at least at an inner portion 1 of the slot. The facing ~nside surfaces diverge from one another at an outer port~on of the slot. The Pirst and ~econd lips are further provided with bottom sufaces facing the casting surface at a standoff distance less than 0.120 inch.
Among the advantages of the present invention is the provision of a strip casting apparatus which is capable of continuously casting metallic strip material of substantially uniform dimension and substantially uniform Quality throughout its length.
Another advantage of the present invention is the provision of a strip casting apparatus having an outwardly diverging nozzle construction which promotes the efficient rapid casting of metal strip material.
An objective of the present invention is to provide a strip casting apparatus capable of reproducing successful strip casting operations.
Another objective of this invention is to provide a strip ca~ting apparatus which can effec~uate sufficiently rapid quenching of the produced strip to result in the production o amorphous strip. ~owever, it should be understood that the production of continuously cas~ ceystalline material is also comprehended by the present invention.
A further objective of this invention $s to identify certain design and dimensional requirements, particularly with regard to an outwardly diverging nozzle 1 structure, which permit continuous and repetitious rapid casting of ~etallic strlp material of uniform dimension and unlform quality.
These and other objectives and advantages will be more fully understood and appreciated with reference to the following detailed description and the accompanying drawings .
Brief Description of the Drawings Figure 1 is an elevation view, partially in cross-section, illustrating a typical apparatus used for continuously casting strip material, Figure 2 is a cross-sectional view of an outwardly diverging nozzle in a strip casting apparatus of the present invention.
Figures 3r 4 and 5 are cross-sectional views of alternative outwardly diverging nozzles in strip casting apparatu~ of the present invention.
Detailed Description Referring particularly to the drawings, Figure 1 generally illustrates an apparatus for casting metallic strlp material 10 in ~ccordance with the present invention.
This apparatus includes an element 12 upon which the str ip 10 i~ cast. In a preferred embodiment a con~lnuous strip 10 1~ caEt onto a ~mooth, outer peripheral surface 14 of a circular drum or wheel as ~hown ln Figure 1. It 6hould be ?!$ ~
1 understood that confi~uration~ other than circular may be employed. Por example, a wheel with a smooth, frustoconical outer peripheral surface (not 6hown) may be employed. Also, a belt capable of rotating through a generally ovular path may also be employed as the casting element. Regardless of the configuration employed, the cooled casting urface ~hould ~e at least as wide as the trip to be cast.
In a preferred embodiment, the casting element 12 comprises a water cooled, precipitation hardened copper alloy wheel containing about 98% copper and about 2~
chromium~ Copper and copper alloys are chosen for their high thermal conductivity and wear resistance, however, berillium copper alloys, steel, brass~ aluminum, aluminu~
alloys or other materials may be utilized alone, or in combination. For example, multipiece wheels having sleeves of molybdenum or other material may be employed. Likewise, cooling may be accomplished with the use of a medium other than water. Water is typically chosen for its low cost and its ready availability.
In the operation of the strip casting apparatus of the present invention, the surface 14 of the casting wheel 12 must be able to absor~ the heat generated by contact with molten metal at the initial castiny location 16, and ~uch heat must be conducted substantially in~o the copper wheel during each rotation of the wheel. The initial ca6tlng point 16 refer to the approximate location on the casting 6urface 14 where molten metal 20 from ~he tundish 22 fir~t contact~ the casting ~urface 14. Cooling, by heat 1 conduction, may be accomplished by delivering a 6uf~icient qu~ntity of water through lnternal passageways located near the periphery of the casting wheel 12. Alternatively, the cooling medium may be delivered directly to the underside of the ca~ting surface. Understandably, refrlger~tion techniques and the like may be employed to accelerate or decelerate cooling rates, and/or to effectuate wheel expan~ion or contraction during strip casting.
Whether a drum, wheel or belt is employed for casting, the casting surface should be generally smooth and symmetrical to maximize uniformity in strip casting. For example, in certain strip castiny operations the distance between the outer peripheral casting surface 14 and the surfaces defining the orifice of the nozzle which is feeding the molten material onto the casting surface 14 must not deviate from a desired or set distance during the casting operation. This distance shall hereinafter be called standoff distance or gap. It is understandable that the gap 6hould be substantially maintained throughout the casting operation when it is the intention to cast uniform strip material.
It ~hould be understood that lf the casting element is a drum or a wheel, the element should be carefully constructed ~o as not to be out~of-round during operation to insure uniformity in strip casting. Along these l~nes, it has been found that a drum or wheel which is out-of-round by about 0.020 inch, or more, may have a magnitude of dimencional in~tability which unless corrected g_ 1 or compensated during operation~ ~ay be unacceptable for certain strip casting operations. It has been found that acceptable dimen6ional symmetry, as well as the elimination of problems associated with weld porosity may be more readily acco~plished by fabricating a wheel or drum from a single, integral slab of cold rolled or forged copper alloy. ~owever, as mentioned above alternative materials, including ~leeves and co~tings may be employed.
The molten material 20 to be cast in the apparatus described herein is pref2rably retained in a crucible 22, or tundish, which is provided with a pOULin9 orifice 24 or nozzle. The noz~le is typically, though not necessarily, located at a lower portion of the tundish 22 as shown in Figure 1. As will be appreciated from the foregoing discussion, the nozzle 24 may be a separate element in the tundish 22, or, the nozzle 24 and tundish 22 may be monolithic, i.e. integrally formed, with all or any portion of the tundish 22.
The nozzle 24, located in or forming a lower portion of the tundish 22 may comprise a slotted element~ as best ~hown in Figure 2. The slot 30 is preferably substantially centrally located in the nozzle element 24.
Such approximate central location of the slot 30 helps ~o asure uniformity as the pressure of the molten metal bearing thereagainst i8 ~ubstantially equali~ed during the casting operation. It should be understood, however, that the slot 30 may be located in off-center posi~ions as may be desired.
1 The longitudinal extent o~ the ~lot 30 should approximate the width of the strip to be cast. There does not appear to be a limitation on the longitudinal extent of the ~lot, ~nd, slots as long as thirty ix inches, or longer, are comprehended by the present lnvention. It is highly desired that the molten metal flow uniformly through the slot 30 in the noz21e 24 ~f the present invention in order to produce uniform, high quality strip material. In an alternative embodiment, strip of various widths may be simultaneously produced by cutting multiple longitudinally aligned slots 30 of appropriate longitudinal extent in the nozzle area of a tundish 22, as opposed to a single slot 30. Regardless of the ~ize of the slot 30, or slots, the cross-sectional dimensions of each 610t 30 should be substantially uniform throughout the longitudinal extent thereof to produce strip material having uniform dimensions. In the operation of the str ip casting apparatus of the present invention, the cooled casting ~urface 14 moves past the slot 30 in a direction 6ubstantially perpendicular to the longitudinal axis of the slot~
As shown in Figure 2, the slot 30 is defined between a flrst lip 32 and a second lip 34 of the no~zle 24 The first lip 32 i located at the downstream edge of the ~lot 30, ~ith re~pect to the direction of movement of the casting surface 14 indicated by the arrow in ~igure 2. The ~econd lip 34 i3 located at an upstream edge of the slot with re~pect to the casting direction.
~ ~34 ~ ~
1 The fixst lip 32 and the second lip 34 have inside surfaces 36 and 3~, respe~t~vely, which are ~ubstantially parallel to and acing one another at least at an inner portion of the slot 30. The inner portion refers to that portion which is near the molten metal holding portion of the tundish, while ~n outer portion of the slot 30 refers to that portion near the casting surface 14. I~
should be understood that the innermost portion of the slot may be relieved or tapered. For example, the innermost portion of the fir6t lip 32 and/or the ~econd lip 34 may be cut into a general V-shape, or a more rounded U-shape creating an initial funnel type structure for the slot as illustrated in Figures 3 and 5. Such relief of the innermost portion of the slot 30 may assist in maintaining uniform molten metal flow patterns and minimizing irregularities or turbulence during strip casting. What is required by the present invention is that the inside surfaces 36 and 38 are facing and parallel at least at some inner portion of the slot 30~
Beyond such inner, parallel, facing portion, ! in the direction of the casting surface 14, the inside surfaces diverge outwardly from one another at an outer portion of the slot 30. Preferred outwardly diverging ~urfaces are indicated by reference numerals 40 and 42 in . Figure 2. Such outward divergence of the inside surfaces may be accomplished by alternative structure~ ~u~h as those ~hown in Flgures 3, 4 and 5. It should be noted that only one of the in~ide surfaces need to diverge to create the 1 necessary relation~hip o outward divergence therebetween a~
~hown in Figures 3 and 4. Also, curved ~urface~9 radiused either inwardly 40 or outwardly 4~ a~ ~hown in Figure 5, may eQtablish 6uch outward divergence.
S From that outwardly diverging ~urface,~ 40 ~nd 42 the first and second lips 32 and 34 extend to bottom ~urfaces 44 and 46 respectively. Such bottom surfaces 44 and 46 of the lips 32 and 34 face the casting surface 14~
and are located at a standoff distance, or gap, of less than about 0.120 inch from the casting surface. In a preferred embodiment, the standoff distance e be~ween the bottom surface 44 of the first lip 32 and the castins surface 14 is as small as possible consistent with permitting ~he casting surface 14 to move thereunder in an unobstructed path. In any event, the gap e between the bottom surface 44 of the first lip 32 and the casting surface 14 must be small enough at the nozzle orifice to prevent significant molten metal backflow therebetween during casting. The gap d between the casting surface 14 and the bottom surface 46 of the second lip 34 is preferably less than 0.080 inch, and for casting certain alloys into thin gage strip may be less than 0.010 inch.
Preferably, at least a portion of the bo~tom surfaces 4~ and 46 are in sub~tantially complete parallelism with the c~sting ~urface 14 movable therebelow, at least at the nozzle orificeO When utilizing a drum or wheelt and a refractory nozzle 24, such parallism may be accompll~hed by placing a sheet of ~andpaper, or the like, against the -1 ca~ting ~urface 14 with the grit ~ide of the sandpapex facing the nozzle 2~. By moving the nozzle 2A into tight contact wlth the casting 6urface 14, with the ~andpaper disposed therebetween, and by movin9 the casting surface 14 and ~andpaper 6imultaneously past the nozzle 24, the bottom surfaces 44 and 46 are ground by the grit into substantially complete parallelism with the casting surface 14. Such parallelism may be achieved even when round or other curvilinear casting surfaces are employed. To achieve such parallelism on most refractory nozzles by this procedure, 400 or 600 grit sandpaper has been Eound to be adequate.
It has also been found that the corners between the surfaces defining the slot 30 may be radiused to minimize molten metal turbulence during casting. In certain instances sharp corners may be subjected to various pre~s~re and flow patterns which could create stress conditions for nozzles 24 made of certain materials, and in some instances, may break, crack or wear during casting in a manner which may upset balanced strip casting conditions. Providing ~uch rounded corners may minimize the adver~e affects of such turbulence and flow through the nozzle 24.
The crucible 22 is preferably constructed of a ma~erial having superior insulating ability. If the insulating ability is not sufficient to retain the mol~en ~aterial at a relatively constant temperature, auxiliary heaters ~uch as indu~tion coils may have to be provided in ~nd/or around the crucible 22, or resistance elemen~s 6uch 1 as wires may be provided. A convenient material for the crucible is an insulating board made from fiberized kaolin, a naturally occurring, high purity, alumina-silica fire clay. Such insulating material is available as KAOWOOL
(a trade mark for fiberized kaolin block) HS board. However, for sustained operations~ and for casting certain high melting temperature alloys, various other materials may have to be employed for construc-ting the crucible or the nozzle including graphite, alumina graphlte, quartz, clay graphite, boron nitride, silicon nitride, silicon carbide, boron carbide, alumina zirconia and various combinations or mixtures of such materials. It should be understood that these materials may be strengthened; for example, fiberized kaolin may be strengthened by impregnating with a silica gel or the like.
It is imperative that the orifice of the nozzle 24 remain open and its configuration remain substantiall~ stable throughout at least one, and preferably many strip casting operations. It is understandable that the orifice should not erode or clog, significantly, during strip casting.
Along these lines, it appears that certain i~sulating matierals may not be able to maintain their dimensional stability over long casting periods. To obviate this problem, lips 32 and 3~ forming th~ orifice oE the nozzle 2 may be constructed of a material which is better able to maintain dimensional stability and integrity during e~posure to high molten metal temperatures for prolonged time periods.
Such materials may take the form of a single, generally ., ~.
1 semi-circular element with a slot 30 cut therethrough or a pair of insert6 held in the crucible to form a slot 30 therebetween. In a prferred embodimen~ the slot or slots in single elements may be cut ultrasonically to in~ure that the desired ~lot dimen~ions are accurately provided. Such nozzles 24 may be constructed of materials ~uch as quartz, graphite, clay graphite, boron nitride, alumina graphite, silicon carbide, stabili~ed zirconia ~ilicate, zirconia, magnesia, alumina or other similar molten metal resistan~
material. Such nozzle6 24 may be held in the orifice of the crucible mechanically, with pressure, and/or with the aid of adhesives such as various refractory cements, ~prinq biased mechanisms, or the like.
The drive system and housing for the drum, wheel or other casting surface 14 of the pre~ent invention should be rigidly c~nstructed to permit drum rotation without structural instability which could cause the drum to slip or vibrate. In particular, care should be taken to avoid resonant freguences at the operating speeds for the casting &urfce 14. The casting surface 14 should be capable of moving at a ~urface speed of from about 200 linear surface feet per minute to more that about 10,000 linear ~urface feet per minute. When utilizing a drum having a circumference of about 8 feet~ this rate calculates to a drum speed from about 25 rpm to about 1250 rpm. A three horsepower variable speed rever~ible~ dynamically braked motor provide~ ~n adequate drive ~ystem for an lntegral copper alloy casting drum ~pproximately 2 inches thick and about 8 eet in circumference.
1~
1 In one embodimellt, the casting surEace 14 on the wheel or drum of the apparatus of the present invention is smooth. It has been Eound tha-t in cer-tain applications, such as for producing amorphous materials, finishing the peripheral surface 14 of a casting drum 12 with 400-grit paper and preferably with 600-grit paper may yield improved product uniformity.
In a preferred embodiment as illustrated in Figure 2, the nozzle 24 is defined by an insert made of clay graphite, a molten metal resistant material, held in the - walls of the crucible 22. The slot 30 is cut ultrasonically in the clay graphite nozzle 24. The first lip 32 and the second lip 34 of the nozzle 24 define the slot 30 therebetween. As alternative preferred examples of nozzle 24 materials, a plate made of quartz or VYCOR (a trade mark for thermally resistant laboratory glass) material,or an insert of boron nitride may be employed. The desired slot forming the orifice 46, may be accurately cut therein with an ultrasonic drill. A preEerred one piece element forming a nozzle, as best illustrated in Figure 2, may ~e constructed of a semi-circular ring of molten metal resistant material. In this example, a slot having a width of about 0.010 to about 0.080 inch between the facing, parallel inside surfaces 36 and 38 may be ultrasonically drilled into a clay graphite insert material, and the insert is held in the crucible 22. It should be understood that the design of the insert~may be modified to assist in holding the insert forming the nozzle 24 in the crucible 22.
1 A preferred nozzle 24 of the ~pparatus of the pre~ent invention i~ shown ln enlarged cross~section in Figure 2. In one embodiment of this apparatus, the dimensions indicated in Fi~ure 2 h~ve the following preferred li~itations.
Ji more preferred preferred dimension designation limitation limitation a bottom surface at least .001 .25 - .50 inch of first lip inch b width of slot .020 - .200 inch 0.125 inch at maximum divergence c bottom surface .01 - .16 inch .02 - .06 inch of second lip d standoff .01 - .080 inch less than .010 distance be- inch tween first lip and ca~ting ~urface e standoff .01 - .080 inch less than .010 dlstance be- inch tween ~econd lip and casting surface f width of slot .010 - .080 inch .025 - .035 inch between parallel, facing ~urfaces g depth of diverg- ~050 - .200 inch .125 inch ing area of slot h depth of para- .050 - .200 inch .125 inch llel area of slot ., In the production of amorphous strip ma~erials the width of the slot f is typically in the range of from about 0.010 to 0.040 inch~ In the production OL cry6talline strip material~ cuch a~ stainless ~t~el, the width of the 1 ~lot f may be greater, perhaps a5 high as about 0.080 inch if thick strip is being unifor~ly produced in accordance with the present invention. Al~o, the primary purpose of a relief at an ~nner portion of the slot 30, such as i6 shown in Figures 3 and 5 is to eliminate clogging of molten metal in the orifice during strip casting.
In an exemplary operation of the apparatus of the present invention, molten metal is delivered to a heated crucible 22. It i8 understood that a heater, such as induction coils of resistance wire, may be provided in and above the crucible 22 to maintain relatively constant molten metal temperatures as may be desired. Alternatively, the molten metal may be poured direc~ly into a preheated crùcible. The preheat temperature should prevent free~ing or clogging of the slot 30 during the initial casting operation, and the temperature of the flowing metal should thereafter keep the crucible 22 and nozzle 24 at sufficient temperature to insure uninterrupted mo~ten metal flow through the orifice. In certain applications, the nozzle itself may be externally heated throughout the casting operation~ Also, the metal which is fed to the crucible 22 may be superheated to allow a certain degree of temperature loss without adversely affecting metal flow through the no~le 24.
Also, a metallostatic head helght ~n the tundish 22 is preferably maintained at a relatively constant level, typically ~t a level of less ~han ten inches abo~e the nozzle 24, throughout the casting oper~tion to a~sure that a
2~
1 relatiYely constant stat~c head pressure may be maintained at the nozzle 24. This may be accomplished ~y initially pouring the molten metal into the crucible to the ~esired height ~nd thereafter controlling the rate at which additional molten metal i8 poured into the crucible to maintain the metallostatic head. It is understandable that the rate at which additional molten metal is fed to the crucible 22 ~hould be in substantial conformity with the rate at which metal flows from the no~zle orifice onto the casting surface 14 in forming strip material. Maintenance of a relatively constant height of metal in the crucible assures that the molten metal flow pressure through the orifice is maintained relatively constant so as not to adversely affect the casting operation or the quality of the strip material. Alternatively, externally applied pressure may be employed to control the pressure at the noz21e.
The nozzle 24 of the present invention is characterized by ~n outwardly diverginy lip surfaces 40 and 42 at the outer portion of the slot 30. Such structure ~acilitates increa6ed molten metal flow to a moving casting surface 14, resulting in improved lateral flow of molten metal onto a casting surface 14, and in the formation of high quality 6trip material 10. In a preferred embodiment the width b of the orifice of the slot 30 at the outermost divergent portion may be as wide as about .200 inch~ which may be in ~ceEs of about four times the width f of the slot 30 as measured between the inner, parallel facing surface6 of the 810t 30. Such ~tructure provides a relatively l~rge castlng cavity ~t the outer portion of the ~~ - ~
1 noz~le 24, fed by a relatively narr~w internal orifice.
Lateral movement of the molten metal inside such cavity during ~trip casting ha~ been found to improYe the uniformity with which metal is ~upplied to the ca~ting ~urface 14, and thus improve the quality of the 6~rip 10 ca6t thereon. As discussed above, the presence of such cavity further reduces the tendency ~or nozzle blockage caused by freezing because the narrow metering orifice is located further from the cool casting surface 14.
Various alloys may be successfully cast usin~
the apparatus of the present invention, including certain brazing alloys, including nickel based brazing alloys, stainless steel and certain silicon steel grades. In certain applications, the cast alloy ha~ been shown to be amorphous, and in other applisations, the cast strip material has been shown to be crystalline.
During casting of strip material, the tendency of the strlp 10 to adhere to the casting surface 14 for a significant di~tance, such as several Eeet or more, beyond the nozzle ha~ been observed. It is understandable that if the strip material remains on a rotating casting drum or wheel 12 for a full revolution damaye to the crucible 22, particularly to the no~zle orifice could resul~. It has been found that the u~e of a doctor blade ~ ~uch as a knife ype element rlding at or near the drum surface 14, or an air wlper, approximately 2.5 to 6 feet from the orifice, or more, ea~ily counters ~uch adherence. With ~uch an arrangement, the cast strip may be removed from the drum !
26~
1 by such doctor blade. Such doctor blade has been found particularly useful in the produc~ion of thinner amorphous strip mater~als which appear to have a greater tendency to adhere to the casting surface 14 than do the cry talline strip materials~ It i6 believed that the force wb~ch retains the strip on the casting surface may reflect the quality of the thermal contact between the strip and the casting surface~
The casting of relatively high quality strip material including amorphous material, which for the purpose of this invention includes materials which are at least 25%
amorphous, is feasible and practical using the apparatus and procedures described above. Understandably, the quench rates must be higher for amorphous material as compared to crystalline material~ Quench rates may be accelerated such as by increasin~ the speed of the casting surface, or the like.
Whereas the preferred embodiment has been described above for the purposes of illustration, it will be apparent to those skilled in the art that numerous variations of the details may be made without departing from the invention.
I claim:
1 relatiYely constant stat~c head pressure may be maintained at the nozzle 24. This may be accomplished ~y initially pouring the molten metal into the crucible to the ~esired height ~nd thereafter controlling the rate at which additional molten metal i8 poured into the crucible to maintain the metallostatic head. It is understandable that the rate at which additional molten metal is fed to the crucible 22 ~hould be in substantial conformity with the rate at which metal flows from the no~zle orifice onto the casting surface 14 in forming strip material. Maintenance of a relatively constant height of metal in the crucible assures that the molten metal flow pressure through the orifice is maintained relatively constant so as not to adversely affect the casting operation or the quality of the strip material. Alternatively, externally applied pressure may be employed to control the pressure at the noz21e.
The nozzle 24 of the present invention is characterized by ~n outwardly diverginy lip surfaces 40 and 42 at the outer portion of the slot 30. Such structure ~acilitates increa6ed molten metal flow to a moving casting surface 14, resulting in improved lateral flow of molten metal onto a casting surface 14, and in the formation of high quality 6trip material 10. In a preferred embodiment the width b of the orifice of the slot 30 at the outermost divergent portion may be as wide as about .200 inch~ which may be in ~ceEs of about four times the width f of the slot 30 as measured between the inner, parallel facing surface6 of the 810t 30. Such ~tructure provides a relatively l~rge castlng cavity ~t the outer portion of the ~~ - ~
1 noz~le 24, fed by a relatively narr~w internal orifice.
Lateral movement of the molten metal inside such cavity during ~trip casting ha~ been found to improYe the uniformity with which metal is ~upplied to the ca~ting ~urface 14, and thus improve the quality of the 6~rip 10 ca6t thereon. As discussed above, the presence of such cavity further reduces the tendency ~or nozzle blockage caused by freezing because the narrow metering orifice is located further from the cool casting surface 14.
Various alloys may be successfully cast usin~
the apparatus of the present invention, including certain brazing alloys, including nickel based brazing alloys, stainless steel and certain silicon steel grades. In certain applications, the cast alloy ha~ been shown to be amorphous, and in other applisations, the cast strip material has been shown to be crystalline.
During casting of strip material, the tendency of the strlp 10 to adhere to the casting surface 14 for a significant di~tance, such as several Eeet or more, beyond the nozzle ha~ been observed. It is understandable that if the strip material remains on a rotating casting drum or wheel 12 for a full revolution damaye to the crucible 22, particularly to the no~zle orifice could resul~. It has been found that the u~e of a doctor blade ~ ~uch as a knife ype element rlding at or near the drum surface 14, or an air wlper, approximately 2.5 to 6 feet from the orifice, or more, ea~ily counters ~uch adherence. With ~uch an arrangement, the cast strip may be removed from the drum !
26~
1 by such doctor blade. Such doctor blade has been found particularly useful in the produc~ion of thinner amorphous strip mater~als which appear to have a greater tendency to adhere to the casting surface 14 than do the cry talline strip materials~ It i6 believed that the force wb~ch retains the strip on the casting surface may reflect the quality of the thermal contact between the strip and the casting surface~
The casting of relatively high quality strip material including amorphous material, which for the purpose of this invention includes materials which are at least 25%
amorphous, is feasible and practical using the apparatus and procedures described above. Understandably, the quench rates must be higher for amorphous material as compared to crystalline material~ Quench rates may be accelerated such as by increasin~ the speed of the casting surface, or the like.
Whereas the preferred embodiment has been described above for the purposes of illustration, it will be apparent to those skilled in the art that numerous variations of the details may be made without departing from the invention.
I claim:
Claims (12)
1. An apparatus for continuously casting metal strip comprising:
a tundish for receiving and holding molten metal, a nozzle comprising a slotted element disposed in the tundish with the longitudinal extent of the slot approximating the width of the strip to be cast, said slot having substantially uniform cross-sectional dimensions throughout the longitudinal extent thereof, a cooled casting surface at least as wide as the strip to be cast, disposed outside the nozzle, movable past the nozzle in a direction substantially perpendicular to the longitudinal axis of the slot, said slot defined between a first lip and a second lip of the nozzle, and having an inner portion near the tundish and an outer portion adjacent the casting surface, said first lip and said second lip having sub-stantially planar inside sufaces, facing one another at the inner portion of the slot, said inside surfaces are parallel to one another at least at the inner portion of the slot and diverging from one another at the outer portion of the slot, the width of the outermost divergent portion being in excess of four times the width of said slot, as measured between inner parallel facing surfaces, and said first lip and said second lip having bottom surfaces facing the casting surface at a standoff distance less than about 0.120 inch, the bottom surface of said first lip having a length at least twice the width of said inner portion of said slot.
a tundish for receiving and holding molten metal, a nozzle comprising a slotted element disposed in the tundish with the longitudinal extent of the slot approximating the width of the strip to be cast, said slot having substantially uniform cross-sectional dimensions throughout the longitudinal extent thereof, a cooled casting surface at least as wide as the strip to be cast, disposed outside the nozzle, movable past the nozzle in a direction substantially perpendicular to the longitudinal axis of the slot, said slot defined between a first lip and a second lip of the nozzle, and having an inner portion near the tundish and an outer portion adjacent the casting surface, said first lip and said second lip having sub-stantially planar inside sufaces, facing one another at the inner portion of the slot, said inside surfaces are parallel to one another at least at the inner portion of the slot and diverging from one another at the outer portion of the slot, the width of the outermost divergent portion being in excess of four times the width of said slot, as measured between inner parallel facing surfaces, and said first lip and said second lip having bottom surfaces facing the casting surface at a standoff distance less than about 0.120 inch, the bottom surface of said first lip having a length at least twice the width of said inner portion of said slot.
2. An apparatus as set forth in claim 1 wherein the facing inside surfaces of said first and second lips are parallel to one another at least at an inner portion of the slot.
3. An apparatus as set forth in claim 2 wherein the gap between the facing parallel inside surfaces of the first and second lips is from about .010 to about .040 inch.
4. An apparatus as set forth in claim 2 wherein the gap between the inside surfaces of the first and second lips at the outer portion of the slot is at least .010 inch greater than the gap between the facing parallel inside surfaces of the first and second lips.
5. An apparatus as set forth in claim 1 wherein the gap between the inside surfaces of the first and second lips at the outer diverging portion of the slot is from about .04 to about .18 inch.
6. An apparatus as set forth in claim 1 wherein the gap betwen the inside surfaces of the first and second lips at the outer diverging portion of the slot is from about .10 to about .15 inch.
7. An apparatus as set forth in claim 1 wherein the casting surface is movable past the nozzle at a rate of from about 200 to about 10,000 linear surface feet per minute.
8. An apparatus as set forth in claim 1 wherein the casting surface is movable past the nozzle at a rate of from about 1,800 to about 4,000 linear surface feet per minute.
9. An apparatus as set forth in claim 1 wherein the casting surface comprises the peripheral surface of a water cooled wheel.
10. An apparatus as set forth in claim 9 wherein the wheel is made of a metal selected from the group consisting of copper, copper alloy, aluminum, aluminum alloy, steel, molybdenum and combinations thereof.
11. An apparatus as set forth in claim 1 wherein the nozzle is constructed of a material selected from the group consisting of graphite, alumina graphite, clay graphite, quartz, fiberized kaolin, boron nitride, silicon nitride, silicon carbide, boron carbide, alumina, zirconia, stabilized zirconia silicate, magnesia and combinations thereof.
12. An apparatus as set forth in claim 1 wherein at least a portion of the bottom surfaces of the first and second lip are in complete parallelism with casting surfaces therebelow.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US14844180A | 1980-05-09 | 1980-05-09 | |
| US148,441 | 1980-05-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194269A true CA1194269A (en) | 1985-10-01 |
Family
ID=22525784
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000377152A Expired CA1194269A (en) | 1980-05-09 | 1981-05-08 | Strip casting nozzle |
Country Status (15)
| Country | Link |
|---|---|
| EP (1) | EP0040073B1 (en) |
| JP (1) | JPS574359A (en) |
| KR (1) | KR830005930A (en) |
| AR (1) | AR227668A1 (en) |
| AT (1) | ATA206281A (en) |
| AU (1) | AU6997681A (en) |
| BR (1) | BR8102820A (en) |
| CA (1) | CA1194269A (en) |
| DE (1) | DE3163362D1 (en) |
| ES (1) | ES8307138A1 (en) |
| GB (1) | GB2214679B (en) |
| HU (1) | HU183418B (en) |
| MX (1) | MX154957A (en) |
| NO (1) | NO156818C (en) |
| PL (1) | PL231046A1 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4330025A (en) * | 1980-09-11 | 1982-05-18 | Allegheny Ludlum Steel Corporation | Nozzle in a strip casting apparatus |
| WO1984003852A1 (en) * | 1983-03-28 | 1984-10-11 | Tdk Corp | Apparatus and method for producing thin metal strip |
| AU578968B2 (en) * | 1984-09-13 | 1988-11-10 | Allegheny Ludlum Steel Corp. | Method and apparatus for direct casting of crystalline strip by radiantly cooling |
| US4715428A (en) * | 1984-09-13 | 1987-12-29 | Allegheny Ludlum Corporation | Method and apparatus for direct casting of crystalline strip by radiant cooling |
| US5063988A (en) * | 1990-06-22 | 1991-11-12 | Armco Inc. | Method and apparatus for strip casting |
| GB2290897B (en) * | 1994-06-28 | 1998-07-01 | Lee Ming Cheng | Magnetic cards |
| GB2294790B (en) * | 1994-09-02 | 1998-02-18 | Andrew David Lewis | Article characterisation method and apparatus |
| US5842511A (en) * | 1996-08-19 | 1998-12-01 | Alliedsignal Inc. | Casting wheel having equiaxed fine grain quench surface |
| JP4517386B2 (en) | 2004-06-30 | 2010-08-04 | 住友電気工業株式会社 | Casting nozzle |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2059171A5 (en) * | 1969-08-25 | 1971-05-28 | Smiths Industries Ltd | |
| CH581359A5 (en) * | 1974-10-01 | 1976-10-29 | Grey Lab Establishment | |
| US4013894A (en) * | 1975-05-27 | 1977-03-22 | Addressograph Multigraph Corporation | Secure property document and system |
| GB1541579A (en) * | 1976-10-16 | 1979-03-07 | Emi Ltd | Security material and examination theroef |
| US4142571A (en) * | 1976-10-22 | 1979-03-06 | Allied Chemical Corporation | Continuous casting method for metallic strips |
| US4257830A (en) * | 1977-12-30 | 1981-03-24 | Noboru Tsuya | Method of manufacturing a thin ribbon of magnetic material |
| GB2021835B (en) * | 1978-05-30 | 1982-08-04 | Emi Ltd | Making and examining security documents |
| DE3000560C2 (en) * | 1980-01-09 | 1986-10-09 | Hermann 7742 St Georgen Stockburger | Method for checking the authenticity of a data carrier and device for carrying out the method |
| IT1159459B (en) * | 1983-06-14 | 1987-02-25 | Urmet Spa | RECORDING AND READING SYSTEM OF MAGNETIC CARDS VALUED PARTICULARLY FOR PUBLIC TELEPHONY |
| US4626669A (en) * | 1983-12-28 | 1986-12-02 | Fairview Partners | Intercept system for intercepting stolen, lost and fraudulent cards |
-
1981
- 1981-04-29 AU AU69976/81A patent/AU6997681A/en not_active Abandoned
- 1981-05-04 KR KR1019810001544A patent/KR830005930A/en unknown
- 1981-05-05 HU HU811171A patent/HU183418B/en unknown
- 1981-05-07 BR BR8102820A patent/BR8102820A/en unknown
- 1981-05-08 PL PL23104681A patent/PL231046A1/xx unknown
- 1981-05-08 CA CA000377152A patent/CA1194269A/en not_active Expired
- 1981-05-08 MX MX187184A patent/MX154957A/en unknown
- 1981-05-08 JP JP6843881A patent/JPS574359A/en active Granted
- 1981-05-08 EP EP81302063A patent/EP0040073B1/en not_active Expired
- 1981-05-08 ES ES502052A patent/ES8307138A1/en not_active Expired
- 1981-05-08 NO NO811578A patent/NO156818C/en unknown
- 1981-05-08 AT AT0206281A patent/ATA206281A/en not_active Application Discontinuation
- 1981-05-08 DE DE8181302063T patent/DE3163362D1/en not_active Expired
- 1981-05-30 AR AR285162A patent/AR227668A1/en active
-
1989
- 1989-01-12 GB GB8900646A patent/GB2214679B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| BR8102820A (en) | 1982-02-02 |
| PL231046A1 (en) | 1982-01-04 |
| HU183418B (en) | 1984-05-28 |
| JPS574359A (en) | 1982-01-09 |
| NO156818C (en) | 1987-12-02 |
| EP0040073A1 (en) | 1981-11-18 |
| AR227668A1 (en) | 1982-11-30 |
| GB8900646D0 (en) | 1989-03-08 |
| MX154957A (en) | 1988-01-14 |
| EP0040073B1 (en) | 1984-05-02 |
| GB2214679B (en) | 1992-07-22 |
| NO811578L (en) | 1981-11-10 |
| DE3163362D1 (en) | 1984-06-07 |
| KR830005930A (en) | 1983-09-14 |
| NO156818B (en) | 1987-08-24 |
| JPH0341258B2 (en) | 1991-06-21 |
| ES502052A0 (en) | 1983-06-16 |
| AU6997681A (en) | 1981-11-12 |
| GB2214679A (en) | 1989-09-06 |
| ATA206281A (en) | 1986-07-15 |
| ES8307138A1 (en) | 1983-06-16 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |