Strip casting apparatus

Information

  • Patent Grant
  • 6397924
  • Patent Number
    6,397,924
  • Date Filed
    Monday, October 30, 2000
    24 years ago
  • Date Issued
    Tuesday, June 4, 2002
    22 years ago
Abstract
Apparatus for continuously casting metal strip comprises a pair of parallel casting rolls (16). In use of the apparatus molten metal is delivered between the casting rolls which are rotated to deliver cast strip product downwardly from the rolls. Casting rolls (16) are mounted on a roll module (13) installed in and removable from the caster as a unit. Module (13) is movable horizontally from a stand-by position to an intermediate position beneath a casting position of the rolls and can be hoisted from the intermediate position by operation of hoists (71) to lift the rolls (16) into their casting position.
Description




BACKGROUND OF THE INVENTION




This invention relates to the casting of metal strip. It has particular application to the casting of metal strip by continuous casting in a twin roll caster.




In a twin roll caster molten metal is introduced between a pair of contra-rotated horizontal casting rolls which are cooled so that metal shells solidify on the moving roll surfaces and are brought together at the nip between them to produce a solidified strip product delivered downwardly from the nip between the rolls. The term “nip” is used herein to refer to the general region at which the rolls are closest together. The molten metal may be poured from a ladle into a smaller vessel or series of vessels from which it flows through a metal delivery nozzle located above the nip so as to direct it into the nip between the rolls, so forming a casting pool of molten metal supported on the casting surfaces of the rolls immediately above the nip and extending along the length of the nip. This casting pool is usually confined between side plates or dams held in sliding engagement with end surfaces of the rolls so as to dam the two ends of the casting pool against outflow, although alternative means such as electromagnetic barriers have also been proposed.




The change-over of the casting rolls in a twin roll caster is a significant problem. The rolls may need to be changed between casts so as to allow a different width of strip to be cast and the rolls must be replaced if the casting surfaces are in any way damaged or deteriorate during casting. If the rolls have to be changed in situ, a significant amount of potential casting time is lost waiting for the casting components and the area surrounding them to cool. The new set of rolls, once in place, has to be calibrated prior to casting so that the nip width can be pre-set.




When casting ferrous metals, it is necessary to preheat the refractory components of the metal delivery and pool confinement means to very high temperatures before casting commences. For these reasons it has been proposed to build twin roll casters with demountable components so that the rolls and preheated refractory components can be rapidly brought together into an operative assembly and casting started before the preheated components cool significantly. One example of a caster with moveable rolls and refractory components is disclosed in our Australian Pat. No. 631728 and 637548 and corresponding U.S. Pat. No. 5,184,668 and 5,277,243.




The present invention enables a twin roll strip caster to be built with a modular construction in which the casting rolls are installed in a moveable module readily moveable into and out of the machine. A previous proposal for mounting the rolls on a moveable module is described in Japanese Patent Publication JP-B93-9185 of Mitsubishi Heavy Industries Ltd. In that proposal the rolls and the pool confining side plates are mounted together on a frame which is carried on a wheeled car moveable horizontally into and out of the machine along rails. The present invention provides a different arrangement in which a roll module is moved horizontally into an intermediate position beneath the final casting position and is ;then lifted into the casting position. This enables the rolls to be quickly manoeuvred into the casting position without requiring movement of any ancillary equipment or components. In a preferred embodiment of the invention the rolls can be lifted into position between a pair of pool confinement side plates without the need to move the side plates.




SUMMARY OF THE INVENTION




According to the present invention there is provided an apparatus for continuously casting metal strip which includes: a pair of parallel casting rolls forming a nip between them; metal delivery means to deliver molten metal into the nip between the rolls to form a casting pool of molten metal supported on casting roll surfaces immediately above the nip; pool confining means at the ends of the rolls confining the pool against outflow from the ends of the nip; and roll drive mean's to drive the casting rolls in counter-rotational directions to produce a solidified strip of metal delivered downwardly from the nip; wherein the casting rolls are mounted on a roll module installed in and removable from the caster as a unit and movable horizontally transversely to a casting direction from a stand-by position to an intermediate position beneath a casting position of the rolls and thereafter vertically to lift the rolls to the,casting position; and wherein the apparatus includes a lifting means for lifting the roll module and rolls mounted thereon from the intermediate position to the casting position.




Preferably the lifting means includes a fluid cylinder actuated hoist.




Preferably the apparatus includes drive coupling means which automatically couple the roll drive means to the casting rolls when the roll module is in the intermediate position.




Preferably the apparatus includes water coupling means which automatically couple a water cooling means to the rolls when the roll module is in the intermediate position.




Preferably the roll module further includes a module frame and roll carriers moveable on the module frame to permit bodily movement of the rolls toward and away from one another to vary the nip between them.




Preferably the apparatus further includes a roll biasing means operable when the roll module is in the casting position to move the casting; rolls from an open position towards each other to vary the width of the nip.




Preferably the pool confining means is in the casting position prior to moving the roll module from stand-by position to the intermediate position and thereafter to the casting position. Moving the roll module to the intermediate position beneath the casting position and holding the casting rolls in the open position ensures that there is no contact between the rolls and the pool confining means during the installation of the rolls.




Preferably the roll biasing means is operable to move the casting rolls away from each other.




Preferably the roll module further includes an adjustable stop means disposed beneath the nip and between the roll carriers to serve as a spacer stop for engagement with the roll carriers to pre-set the minimum width of the nip between the rolls and adjustable in width to vary the minimum width of the nip.




Preferably the roll biasing means is operable to move the casting rolls from an open position to the stop means and thereafter to bias the rolls against the stop means.




Preferably, the roll module further includes a means for holding the roll carriers, in the open position.




Preferably the holding means includes a locking pin assembly having locking pins carried by the module frame that can be received in openings in the roll carriers.




Preferably the locking pins are fixed relative to the roll carriers so that when the roll carriers and the rolls thereon are lifted from the intermediate position to the casting position the roll carriers are moved clear of and therefore are not retained by the locking pins.




The roll carriers may comprise a pair of roll end support structures for each of the rolls disposed generally beneath the ends of the respective roll.




Each pair of roll end support structures may carry journal bearings mounting the respective roll ends for rotation about a central roll axis.




The roll end support structures may be mounted on the module frame for generally horizontal movement of the rolls toward and away from one another.




The module frame may be moveable horizontally on linear bearings into and out of the intermediate position in the caster.




The roll module may be firmly clamped vertically by operation of the fluid cylinder actuated hoist described above lifting the roll module so that stop surfaces on the roll module contact fixed stop surfaces on the caster.




Appropriate indexing means May be provided for indexing of the module frame with the main machine frame when the module frame is hoisted so as to provide for accurate positioning of the module frame longitudinally of the rolls.




The roll biasing means may include a pair of biasing units for each roll and the biasing units being connectable to the roll carriers.




The biasing units may be carried on moveable mountings on the caster so that they can be readily moved into and out of operative inter-engagement with the roll carriers.




The invention also provides apparatus for continuously casting metal strip comprising a pair of parallel casting rolls forming a nip between them; metal delivery means to deliver molten metal into the nip between the rolls to form a casting pool of molten metal supported on casting roll surfaces immediately above the nip; pool confining means at the ends of the rolls against outflow from the ends of the nip; and roll drive means to drive the casting rolls in counter-rotational directions to produce a solidified strip of metal delivered downwardly from the nip; wherein the casting rolls are mounted on a roll module installed in and removable from the caster as a unit, said module comprising a module frame; roll carriers moveable on the module frame to permit bodily movement of the rolls toward and away from one another to vary the nip between them; and adjustable stop means disposed beneath the nip and between the roll carriers to serve as a spacer stop for engagement with the roll carriers to pre-set the minimum width of the nip between the rolls and adjustable in width to vary the minimum width of the nip.




According to the present invention there is also provided a method of positioning casting rolls in a continuous strip caster which includes the steps of: moving a roll module carrying a pair of parallel casting rolls horizontally in a direction transverse to a casting direction from a stand-by position to an intermediate position; coupling the rolls to a roll drive means and a water cooling unit at the intermediate position; and lifting the roll module to a casting position.




Preferably, the roll drive means and the water cooling unit are automatically coupled to the rolls when the roll module is moved to the intermediate position.




Preferably, after lifting the roll module to the casting position, the method further includes moving the rolls inwardly to a pre-set nip position.




Preferably, the rolls are held apart prior to being lifted to the casting position and the lifting movement releases the rolls for inward movement.











BRIEF DESCRIPTION OF THE DRAWINGS




In order that the invention may be fully explained one particular embodiment will be described in some detail with reference to the accompanying drawings in which:





FIG. 1

is a vertical cross section through a strip caster constructed in accordance with the present invention;





FIG. 2

is a side elevation of the caster shown in

FIG. 1

with the tundish and distributor removed for clarity and with the casting roll module in an intermediate position and the casting rolls in an open position;





FIG. 3

is the same side elevation as shown in

FIG. 2

but with the roll module/casting rolls separated from the caster for clarity;





FIG. 4

is a further side elevation of the caster with the roll module in a raised casting position and the rolls in an open position;





FIG. 5

is a further side elevation of the caster with the roll module in the raised casting position and the rolls at a pre-set nip spacing.





FIG. 6

is a top plan view of the caster;





FIG. 7

is a top plan view illustrating in detail an end section of the roll module/casting rolls and the coupling of the rolls to water supply hoses and roll drive spindles; and





FIG. 8

is a side elevation of the section of the caster shown in FIG.


7


.











DESCRIPTION OF PREFERRED EMBODIMENT




The illustrated caster comprises a main machine frame


11


which supports a casting roll module in the form of a roll cassette


13


which can be moved into an operative position in the caster as a unit but can readily be removed when the rolls are to be replaced. Cassette


13


carries a pair of parallel casting rolls


16


to, which molten metal is supplied during a casting operation from a ladle (not shown) via a ladle outlet nozzle


46


, a tundish


17


, a distributor


18


and a delivery nozzle


19


to create a casting pool


30


which is confined by the rolls


16


and by a pair of side closure plates


18


. Casting rolls


16


are water cooled so that shells solidify on the moving roll surfaces and are brought together at the nip between them to produce a solidified strip product


20


at the roll outlet. This product may be fed to a standard coiler.




The illustrated twin roll caster as thus far described is of the kind which is illustrated and described in some detail in Australian Patent 664670 and U.S. Pat. No. 5,488,988 and reference may be made to those patents for appropriate constructional details which form no part of the present invention.




Casting rolls


16


are contra-rotated through drive shafts


41


from an electric motor and transmission which includes drive spindles


128


mounted on the main machine frame. The drive shafts


41


can be disconnected from the transmission when the cassette


13


is to be removed from the caster. Rolls


16


have copper peripheral walls formed with a series of longitudinally extending and circumferentially spaced water cooling passages (not shown) supplied with cooling water through the roll ends from water supply ducts (not shown) in the roll drive shafts


41


which are connected to water supply hoses


42


through rotary glands


43


. The rolls may typically be about 500 mm diameter and up to 2000 mm long in order to produce strip product approximately the width of the rolls.




The ladle is of entirely conventional construction and is supported on a rotating turret (not shown) whence it can be brought into position over the tundish


17


to fill the tundish. The tundish may be fitted with a sliding gate valve


47


actuable by a servo cylinder to allow molten metal to flow from the tundish


17


through the valve


47


and the refractory shroud


48


into the distributor


18


.




The distributor


18


is formed as a wide dish made of a refractory material such as magnesium oxide (MgO). One side of the distributor


18


receives molten metal from the tundish


17


and the other side of the distributor


18


is provided with a series of longitudinally spaced metal outlet openings (not shown). The lower part of the distributor


18


carries mounting brackets (not shown) for mounting the distributor onto the main caster frame when the cassette is installed in its casting position.




Delivery nozzle


19


is formed as an elongate body made of a refractory material such as alumina graphite. Its lower part is tapered so as to converge inwardly and downwardly so that it can project into the nip between the casting rolls


16


. Its upper part is formed with outwardly projecting side flanges (not shown) which locate on a mounting bracket (not shown) which forms part of the main frame.




Nozzle


19


may have a series of horizontally spaced generally vertically extending flow passages (not shown) to produce a suitably low velocity discharge of metal throughout the width of the rolls


16


and to deliver the molten metal into the nip between the rolls without direct impingement on the roll surfaces at which initial solidification occurs. Alternatively, the nozzle


19


may have a single continuous slot outlet (not shown) to deliver a low velocity curtain of molten metal directly into the nip between the rolls


16


and/or it may be immersed in the molten metal pool.




Side closure plates


18


are made of a strong refractory material, for example boron nitride, and have scalloped side edges to match the curvature of stepped ends of the rolls.




During a casting operation the sliding gate valve


47


is actuated to allow molten metal to pour from the tundish


17


to the distributor


18


and,through the metal delivery nozzle


19


whence it flows onto the casting rolls. The head end of the strip product


20


is guided to the jaws of a coiler (not shown).




In accordance with the invention, the roll cassette


13


is movable:




(i) horizontally in a direction that is transverse to the casting direction of the caster (in the casting direction is denoted by the arrow A in the Figures) from a stand-by position located on one side of the caster to an intermediate position beneath a casting position; and thereafter




(ii) vertically to the casting position.





FIG. 2

shows the roll cassette


13


at the intermediate position and

FIGS. 4 and 5

show the roll cassette


13


at the raised casting position.




Movement of the roll cassette


13


to the intermediate position bring the casting rolls


16


.into contact with and automatically couples the rolls


16


to the drive spindles


128


and the water supply hoses


42


.




The roll cassette


13


is constructed so that the casting rolls


16


can be set up and the nip between them pre-set at the stand-by position before the cassette is installed in position in the caster.




Roll cassette


13


includes a large frame


102


supported on four wheels


121


which carries the rolls


16


and upper part (not shown) of the refractory enclosure for enclosing the cast strip below the nip. The caster includes a pair of rails


89


for guiding the wheels


121


between the stand-by position and the intermediate position. Rolls


16


are mounted on roll supports


104


which carry roll end bearings (not shown) by which the rolls are mounted for rotation about their longitudinal axes in parallel relationship with one another. The two pairs of roll supports


104


are mounted on the roll cassette frame


102


by means of linear bearings


106


whereby they can slide laterally of the cassette frame to provide for bodily movement of the rolls


16


toward and away from one another thus permitting separation and closing movement of the two parallel rolls between an open position shown in

FIG. 4 and a

pre-set nip position shown in FIG.


5


.




The caster includes a lifting means in the form of four fluid cylinder actuated hoists


71


supported by the machine frame


11


and located to underlie the corner regions of the roll cassette frame


102


when the roll cassette


13


is at the intermediate position - as can best be seen in

FIGS. 2

,


4


and


5


. Actuation of the hoists


71


lifts the roll cassette


13


to the casting position. The upward movement of the roll cassette


13


is limited by inwardly extending flanges


75


on the guide rails


89


which are contacted by outwardly extending flanges


77


on the roll cassette frame


102


.




The rolls


16


are retained at the open position shown in

FIG. 4

by four locking pin assemblies housed in vertical openings in the base of roll cassette frame


102


. Each pin assembly includes a locking pin


83


which is biased upwardly by means of a spring


85


. In the open position of the rolls


16


shown in

FIG. 4

the locking pins


83


extend into openings


87


in the base of roll supports


104


. Upward movement of the roll cassette frame


102


relative to the locking pins


83


moves the roll cassette frame


102


clear of the pins and thereby releases the rolls


16


for movement inwardly by the action of roll biasing units


51


described hereinafter to bring the rolls


16


to the pre-set nip position shown in FIG.


5


.




Roll cassette frame


102


also carries two adjustable spacers


107


(shown only in

FIGS. 2 and 3

) in the form of a worm or screw driven jack disposed beneath the rolls


16


about a central vertical plane between the rolls


16


and located between the two pairs of roll supports


104


so as to serve as stops limiting inward movement of the two roll supports thereby to define the pre-set nip position, ie the minimum width of the nip between the rolls. The roll biasing units


51


act continuously to bias the roll supports


104


inwardly toward these central stops to permit outward springing movement of the rolls against preset biasing forces.




There are four roll biasing units


51


disposed in two pairs acting one pair on the supports


104


of each roll


16


. Each roll biasing unit


51


includes a spring housing


111


containing a biasing spring


112


acting on a thrust rod


113


which is connected at its forward end to the respective roll support


104


The forward end of each thrust rod


113


has an enlarged head


115


located in a keyhole opening


117


in a side of one of the roll supports


104


. The heads


115


of the thrust rods


113


are positioned in the keyholes


117


as the roll cassette


13


moves from the stand-by position to the intermediate position. The vertical dimension of the keyholes


117


is larger than the diameter of the enlarged heads


115


to accommodate vertical movement of the roll cassette


13


relative to the roll biasing units


51


as the roll cassette


13


is lifted from the intermediate position to the casting position. Each unit


51


is supported at its forward end on the main machine frame


11


by a linear, bearing


116


. When the roll cassette


13


is in the casting position shown in

FIG. 4

the thruster rods


113


can be translated inwardly by operation of hydraulic cylinder units so that the units


51


can move the rolls


16


to the preset nip position shown in FIG.


5


and then provide a biasing action against the rolls. The spring biasing force of each roll biasing unit


51


can be adjusted by operation of a motor


117


which actuates a screw thread on spring plunger


118


to move the plunger and thereby adjust the compression in the spring


112


.




The illustrated caster construction enables the rolls to be accurately set up out of the machine or off-line and rapidly installed when required. Accordingly it is possible to set up rolls between casts in replacement cassettes and to accurately preset the nip spacing. Because the spacing between the rolls is accurately set by the centralised stops and the roll biasing forces bias the rolls inwardly against the stops, it is also possible to preload the rolls with appropriate biasing forces as soon as the cassette is installed and it is not necessary as in previous casters to wait for metal to pass through the rolls to develop reactive forces resisting roll separation. The direct coupling of the roll biasing units between the cassette frame and the roll supports also virtually eliminates friction in the spring control mechanism.




The illustrated caster construction also enables change-over of rolls quickly and effectively without interference with pre-positioned pool confining end plates.




The illustrated caster has been advanced by way of example only and it could be modified considerably. For example it is not essential that the roll supports be mounted on linear bearings for strict linear movement. They could alternatively be supported from the cassette frame on pivot arms to allow arcuate movement providing the necessary lateral movement of the rolls to permit appropriate springing movement. This arrangement would enable further reduction of the effective friction on roll movement. Similarly the roll biasing units


51


could be mounted on pivot arms and brought into position for connection with the installed cassette by actuation of hydraulic or pneumatic cylinder units acting on the supporting pivot arms. The precise manner in which the cassette is transported into and out of the casting machine could also be varied.




Moreover, the spring biasing units could be incorporated into the moveable cassette. However, this would require more moveable components and since each change of cassette would also involve a change of load cells, the cells would need to be recalibrated at each change. It is therefore preferred to mount a single set of biasing units and load cells on the main frame and to connect them to the roll supports when the cassette is moved into its operative position.




It is accordingly to be understood that the invention is in no way limited to the constructional details of the illustrated apparatus and that many modifications and variations may be made without departing from the scope of the appended claims.



Claims
  • 1. A method of installing a roll module in a continuous strip caster, said module comprising a module frame, roll carriers movable on the module frame to permit bodily movement of the rolls toward and away from one another to vary the nip between them, and adjustable stop means disposed on the module frame beneath the nip and between the roll carriers to serve as a spacer stop for engagement with the roll carriers to pre-set the minimum width of a nip between the rolls and adjustable in width to vary the minimum width of the nip; said method including the steps of adjusting the stop means on the module frame to pre-set the minimum width of the nip between the rolls, moving the roll module into a casting position in the strip caster, and connecting roll biasing means to the module to bias the rolls against the stop means.
  • 2. A method as claimed in claim 1, wherein the biasing means is connected to the roll carriers so as to act on the roll carriers.
  • 3. A method as claimed in claim 2, wherein the biasing means is a pair of spring biasing units carried on movable mountings on the caster and the method includes the step of moving the spring biasing units on said mountings, following installation of the roll module, into operative interengagement with the roll carriers.
  • 4. A method as claimed in claim 1, wherein a pair of casting pool confinement plates are mounted on the strip caster one to either side of the space occupied by the roll module when in the casting position, and wherein the moving of the roll modulel into the casting position causes the casting rolls to move relative to the pool confinement plates so as to be located between those plates, and the confinement plates are subsequently biased against ends of the rolls.
  • 5. Apparatus for continuously casting metal strip comprising a pair of parallel casting rolls forming a nip between them; metal delivery means to deliver molten metal into the nip between the rolls to form a casting pool of molten metal supported on casting roll surfaces immediately above the nip; pool confining means at the ends of the rolls to confine the casting pool against outflow from the ends of the nip; and roll drive means to drive the casting rolls in counter-rotational directions to produce a solidified strip of metal delivered downwardly from the nip; wherein the casting rolls are mounted on a roll module installed in and removable from the caster as a unit, said module comprising a module frame, roll carriers moveable on the module frame to permit bodily movement of the rolls toward and away from one another to vary the nip between them, and adjustable stop means disposed on the module frame beneath the nip and between the roll carriers to serve as a spacer stop for engagement with the roll carriers to pre-set the minimum width of the nip between the rolls and adjustable in width to vary the minimum width of the nip, and roll biasing means operable when the module is installed to bias the roll carriers against the stop means.
  • 6. Apparatus as claimed in claim 5, wherein the roll biasing means is mounted on the caster so as to be connectable with the roll carriers when the module is installed to bias the roll carriers toward the adjustable stop means.
  • 7. Apparatus as claimed in claim 5, wherein the roll biasing means comprises a pair of biasing units for each roll, each biasing unit being connectable to the module to provide spring biasing of the respective roll when the module is in its position but releasable from the module to enable the module to be removed from the caster.
  • 8. Apparatus as claimed in claim 7 wherein the spring biasing units are carried on moveable mountings on the caster so that they can be moved into and out of operative interengagement with the module.
Priority Claims (2)
Number Date Country Kind
PO9253 Sep 1997 AU
PP3752 May 1998 AU
Parent Case Info

This is a continuation application of Ser. No. 09/154,209, filed Sept. 16, 1998, now U.S. Pat. No. 6,164,366.

US Referenced Citations (5)
Number Name Date Kind
3621694 Greenberger Nov 1971 A
4308741 Ishii et al. Jan 1982 A
5184668 Fukase et al. Feb 1993 A
5277243 Fukase et al. Jan 1994 A
5488988 Fukase et al. Feb 1996 A
Non-Patent Literature Citations (1)
Entry
Patent Abstract of Japan vol. 009, No. 311 Dec. 7, 1985 and JP 60 145253 A (Mitsubishi Jukogyo KK), Jul. 31, 1985, “Method for Exchanging Water Cooled Casting Roll in Continuous Casting Device”.
Continuations (1)
Number Date Country
Parent 09/154209 Sep 1998 US
Child 09/698054 US