CN110214060B

CN110214060B - Casting roll and method for casting metal strip with crown control

Info

Publication number: CN110214060B
Application number: CN201880009590.0A
Authority: CN
Inventors: G.霍亨比希勒
Original assignee: Siemens AG Oesterreich
Current assignee: Siemens AG Oesterreich
Priority date: 2017-01-31
Filing date: 2018-01-30
Publication date: 2022-08-30
Anticipated expiration: 2038-01-30
Also published as: JP6865840B2; EP3548207B1; JP2020505236A; KR20190112788A; WO2018141744A1; EP3548207A1; KR102365633B1; CN110214060A

Abstract

The invention relates to a casting roll (12) for casting a metal strip (21) by continuous casting in a twin roll caster, the casting roll comprising: having a casting surface (12A) formed by a substantially cylindrical tube (120); there are axially symmetric expansion elements such as expansion rings (101 to 119) arranged within and adjacent to the cylindrical tube (120), each expansion element being spaced from the other expansion element and adapted to expand the cylindrical tube in response to an increase in radial dimension to vary the roll crown of the casting surfaces of the casting rolls and the thickness profile of the casting strip during casting, and a plurality of axially symmetric expansion elements such as expansion rings (101) and (119) are distributed along the entire length of the cylindrical tube (120), and power switches are located in or on the casting rolls (12) to switch the power supply to the expansion elements (101) and (119) from one or more expansion elements to one or more other expansion elements. The method for continuously casting thin strip by controlling roll crown is characterized in that the radial dimension of at least one expansion element is increased, preferably by heating, to expand the cylindrical tube (120) while the radial dimension of at least one other expansion element is not increased.

Description

Casting roll and method for casting metal strip with crown control

Technical Field

The present invention relates to casting metal strip by continuous casting in a twin roll caster.

In particular, the present invention relates to a casting roll for casting metal strip by continuous casting in a twin roll caster, the casting roll comprising:

-having a casting surface formed by a substantially cylindrical tube,

-having axisymmetric expansion elements, such as expansion rings, arranged inside and adjacent to the cylindrical tube, each expansion element being spaced apart from the other expansion element, and the expansion elements being adapted to increase in radial dimension to cause expansion of the cylindrical tube to vary the roll crown of the casting surfaces of the casting rolls and the thickness profile of the cast strip during casting.

The thickness of the roll-cast tube is often less than 120 mm, for example less than 100 mm or even less than 80 mm. The casting roll tube material is typically selected from the group consisting of copper and copper alloys, optionally with a coating thereon. The casting rolls typically have a plurality of longitudinal water flow passages extending through the cylindrical tubes.

The invention also relates to an apparatus for continuously casting thin strip by controlling roll crown and a method of continuously casting thin strip by controlling roll crown, the apparatus and method comprising:

using a pair of counter-rotating casting rolls having a nip therebetween for delivering cast strip downwardly from the nip, each casting roll having a casting surface formed of a substantially cylindrical tube,

-also using a metal delivery system positioned above the nip to form a casting pool supported on the casting surfaces of the casting rolls, wherein side dams are adjacent to the ends of the nip to delimit the casting pool,

at least one of the casting rolls has axially symmetric expansion elements, such as expansion rings, arranged within and adjacent to the cylindrical tube, each expansion element being spaced apart from the other expansion element and adapted such that an increase in radial dimension causes the cylindrical tube to expand, thereby varying the roll crown of the casting surfaces of the casting rolls and the thickness profile of the cast strip during casting.

In a twin roll caster, molten metal is introduced between a pair of counter-rotating horizontal casting rolls that are cooled so that the metal blanks solidify on the moving roll surfaces, and are brought together at the nip between the roll surfaces to produce a solidified strip product that is delivered downwardly from the nip between the rolls. The term "nip" is used herein to refer to the general area where the rolls are closest together. The molten metal may be poured from a ladle into a smaller vessel or series of smaller vessels from which it flows through metal delivery nozzles located above the nip, forming a casting pool of molten metal supported on the casting surfaces of the rolls immediately above and extending along the length of the nip. The casting pool is typically confined between side plates or dams held in sliding engagement with the end surfaces of the rolls so as to dam the two ends of the casting pool against outflow.

A twin roll caster is capable of continuously producing cast strip from molten steel through a series of ladles positioned on a turntable. Pouring molten metal from the ladle into a tundish and then into a movable tundish before flowing through the metal delivery nozzle enables the empty ladle to be changed over to a full ladle on a turntable without interrupting the production of the cast strip.

Background

In casting thin strip by a twin roll caster, the crown of the casting surfaces of the casting rolls varies during the casting campaign. The convexity of the casting surfaces of the casting rolls in turn determines the strip thickness profile (i.e., cross-sectional shape) of the thin cast strip produced by the twin roll caster. Casting rolls having convex (i.e., positive convexity) casting surfaces produce cast strip having a negative (i.e., concave) cross-sectional shape; and casting rolls having concave (i.e., negative convexity) casting surfaces produce cast strip having a positive (i.e., convex) cross-sectional shape. The casting rolls are typically formed of copper or copper alloys, typically coated with chromium or nickel, with internal passages for circulating cooling water to achieve high heat flux for rapid solidification, with the casting rolls undergoing significant thermal deformation upon exposure to molten metal during the casting campaign.

In thin strip casting, the desired roll crown produces the desired strip cross-sectional thickness profile under typical casting conditions. The casting rolls are typically machined with an initial crown when cold based on the projected crown in the casting surfaces of the casting rolls during casting. However, the difference between the shape of the casting surfaces of the casting rolls when cold and the casting conditions is difficult to predict. Furthermore, the convexity of the casting surfaces of the casting rolls may vary significantly during the casting campaign. The crown of the casting surfaces of the casting rolls may vary during casting due to variations in the temperature of the molten metal supplied to the casting pool of the caster, variations in the casting speed of the casting rolls, and other casting conditions, such as slight variations in the composition of the molten steel.

The thickness profile measured across the width of the strip is continuously variable. If the strip profile is measured somewhere between the nip of the casting rolls and the entrance of the first hot rolling stand, the strip profile shows a variation of up to 30 or even 40 microns across the strip width. Peaks or valleys of up to 15 to 30 strip thickness can be found across the entire strip width. On physical tape edges, the so-called edge drop (= local thickness variation in the direction of tape width close to the tape edge) may even have a value of up to 100 microns or more.

Accordingly, there is a need for a reliable and efficient way to directly and closely control the shape of the crown in the casting surfaces of the casting rolls during casting and thereby control the cross-sectional thickness profile of the thin cast strip produced by a twin roll caster.

WO 2016/083506 a1 discloses a method of controlling the crown of the casting rolls and in turn the cross-sectional strip thickness profile by controlling the crown in the casting surfaces by expansion rings positioned within and adjacent to the cylindrical tubes forming the casting rolls. The expansion rings are electrically heated here at the edges of the casting rolls and/or in the center of the casting rolls. This method has shown some positive effect of controlling the edge drop.

Disclosure of Invention

It is an object of the present invention to further reduce the peaks and valleys of the belt surface across the width of the belt.

According to the invention, this can be achieved by the casting rolls in case a large number of axisymmetric expansion elements, such as expansion rings, are distributed along the entire length of the cylindrical pipe and power switches are located in or on the casting rolls in order to switch the power supply of the expansion elements from one or more expansion elements to one or more other expansion elements.

Switching the power supply from one or more expansion elements to one or more other expansion elements means that the power fed into one or more expansion elements decreases while the power fed into one or more other expansion elements increases. When the power fed into one or more expansion elements is reduced, the reduction in power for a particular expansion element may (but in most cases will not) be reduced to zero. On the other hand, when starting to increase the power fed in one or more other expansion elements, a particular expansion element may have received power at that time, or it may not have received power at that time.

Since the expansion elements are distributed along a cylindrical tube (which is also referred to as a casting sleeve), it is possible to vary the diameter of the casting surface and/or the temperature of the casting surface for the entire casting surface and not just for the edges or the center. A large number of expansion elements are required to locally change the diameter of the casting surface and/or the temperature of the casting surface. Although the present invention requires at least two expansion elements per casting roll, it is preferred to provide at least three expansion elements. Still more preferred are more than ten, more than fifteen or even more than twenty expansion elements per casting roll. Thus, a typical number of expansion elements is sixteen to thirty axisymmetric expansion elements, such as expansion rings.

In a preferred embodiment of the invention, axially symmetric expansion elements, such as expansion rings, are distributed along the entire length of the cylindrical tube, including the end portions of the casting surfaces.

According to the invention, the power switch is located in or on the casting roll in order to distribute the fully available power to the casting roll for heating expansion elements, for example, in equal parts or in different percentages to many of the connected expansion elements. Each expansion element can be heated individually by using electricity and thus the temperature can be controlled individually.

Since such a power switch is integrated in the casting roll, there is no need for 10 or more slip rings for power supply and sensor signal transmission, wherein a respective control unit is used for each expansion element, which slip rings would require a longer axis of the casting roll, thus significantly elongating the casting roll on one end. Due to the power switch only one control line is required for directing the respective control signal into the casting rolls, i.e. to the power switch.

In a preferred embodiment of the invention, the expansion elements (preferably a multitude of expansion elements, in particular each expansion element) have a width (measured parallel to the axis of the casting rolls) of between 40 and 150 mm, preferably between 40 and 100 mm, more preferably between 50 and 85 mm. The expansion element may have the form of a ring, which by definition has a central aperture, or the expansion element may have the form of a disk without a central annular aperture. In any event, the outer diameter of the expansion element should be a tolerance fit with the inner diameter of the roller tube.

In a preferred embodiment of the invention, each expansion ring has a radial ring thickness (i.e. the difference between the outer and inner diameters of the ring) of between 40 and 150 mm, preferably between 40 and 100 mm, more preferably 45 to 75 mm.

The expansion ring may be mounted on an inner tube, preferably having a wall thickness of at least 10 to 50 mm and an outer diameter of at least not less than 110 mm, the expansion ring being tolerance fitted on the inner tube. The axial position of the expansion ring on the inner tube can be fixed by spacers between the rings or by corresponding press-fit tolerances of the rings (e.g. shrink-fitted rings).

The outer diameter of the expansion element may be increased by heating. Thus, the preferred embodiment of the invention is: each expansion element is equipped with a resistance heating element capable of supplying up to 15 kW, preferably 3 to 10 kW of heating power to the expansion loop. The resistive heating element may be a wire or rod in the form of a ring in contact with the expansion element.

The total electrical power provided for all expansion elements together may be up to 70 kW, preferably not more than 35 kW, per metre of the outer circumferential portion of the casting roll.

The preferred embodiment of the invention is: the centrally mounted expansion element is configured to be permanently heated. This ensures contact between the outer surface of the expansion element and the inner surface of the cylindrical tube (casting roll shell) or even an outward bulging of the cylindrical tube superimposed to the local (thermal) convexity. The centrally mounted expansion element may have the same width as most of the other expansion rings, or may have a width significantly greater than all of the other expansion rings, for example up to 150 up to 400 mm.

In addition to this, it is preferred that the expansion element at the end portion of the casting surface is constructed to be permanently heated. Again, this ensures contact between the outer surfaces of the two expansion elements and the inner surface of the cylindrical tube (casting sleeve) or even an outward bulging of the cylindrical tube at the end of the cylindrical tube superimposed to the local (thermal) convexity.

The preferred embodiment of the invention is: the controller is configured to control the radial dimension of each expansion element at least in response to a temperature process model of the casting rolls and/or expansion rings or in response to temperature measurements foreseen by the respective temperature sensor in some or all of the expansion elements. The expansion elements may thus each be equipped with at least one temperature sensor for providing a corresponding signal to the controller.

The preferred embodiment of the invention is: the expansion elements are each equipped with at least one RFID tag for identifying the expansion elements when temperature information is sent to a controller, preferably a controller located in-situ with the casting rolls.

Such a controller (e.g., a microcontroller) may be part of the main controller of the control system and may be connected to the RFID tag for detecting and evaluating temperature values. The microcontroller may emit the thermal profile over all expansion elements (i.e. over the width of the casting rolls) every two to sixty seconds, preferably every five to thirty seconds, and send it to the main controller, which uses this temperature profile (e.g. in combination with the thermal profile calculated by the process model) as an input for controlling which expansion elements are to be increased, i.e. heated.

An apparatus for continuously casting thin strip by controlling roll crown according to the present invention comprises:

a pair of counter-rotating casting rolls having a nip therebetween and capable of delivering cast strip downwardly from the nip, each casting roll having a casting surface formed of a substantially cylindrical tube,

a metal delivery system positioned above the nip and configured to form a casting pool supported on the casting surfaces of the casting rolls, wherein side dams are adjacent to ends of the nip to define the casting pool,

and is characterized in that at least one casting roll is designed according to the invention.

The objects of the invention are also achieved by a method for continuously casting thin strip by controlling roll crown, which method comprises controlling roll crown

Using a pair of counter-rotating casting rolls having a nip therebetween to deliver cast strip downwardly from the nip, each casting roll having a casting surface formed of a substantially cylindrical tube,

-also using a metal delivery system positioned above the nip to form a casting pool supported on the casting surfaces of the casting rolls, wherein side dams are adjacent to the ends of the nip to define the casting pool,

at least one of the casting rolls has axisymmetric expansion elements, such as expansion rings, arranged inside and adjacent to a cylindrical tube, each expansion element being spaced apart from the other expansion element and adapted to expand the cylindrical tube with an increase in radial dimension to vary the roll crown of the casting surfaces of the casting rolls and the thickness profile of the cast strip during casting,

while at least one expansion element is expanded in radial dimension, preferably by heating, to expand the cylindrical tube, while at least one other expansion element is not increased in radial dimension, controlling which expansion elements are increased is based on:

recorded temperature profile of the cast strip, and/or

Measured strip thickness profile of the cast strip, and/or

Measured thermal crown of the casting rolls, and/or

Temperature profile of one or both of the casting rolls, and/or

-the measured temperature of the expansion element.

If controlling which expansion elements are to be increased is based on the measured temperatures of the expansion elements, the temperature of two or more expansion elements of one casting roll is measured, or the temperature of two or more expansion elements of two casting rolls is measured.

Thus, there will be a switching of the power supply among at least some of the expansion elements. Although this switching can be done at a high frequency, it is preferred to switch between different expansion elements only every two to sixty seconds, preferably every five to thirty seconds.

In a preferred embodiment of the invention, the temperature profile of one or both of the casting rolls is given by a process model that outputs in real time a two-dimensional or three-dimensional temperature field of the interior of the cylindrical tube.

Alternatively, in another preferred and simpler embodiment of the invention, the temperature profile of one or both of the casting rolls is given by a process model which outputs the average temperature of each expansion element in real time.

The process model delivers in real time the actual state of the two-dimensional or three-dimensional temperature field within the cylindrical pipe (casting sleeve) and/or the average temperature of each expansion element (e.g., each expansion ring). In addition, the process model delivers both convexity and thermal profile information. Based on these facts, a selection is made of, for example, three, four, or five expansion elements that obtain electric power (= to be heated). It must be taken into account that those expansion elements which have been heated before do not cool down immediately.

The process model calculates in real time the two-dimensional or three-dimensional temperature field within the cylindrical pipe (casting sleeve) and/or the average temperature of each expansion element in a calculation cycle lasting at least one second, two seconds or up to fifteen seconds, and the average temperature of the cylindrical pipe (casting sleeve) in a circular cross section, and can therefore predict, by means of the deformation field calculations for the cylindrical pipe (casting sleeve) and for the expansion elements, which expansion elements are touching the cylindrical pipe and have to be heated and thus more or less enlarged to eliminate certain strip profile valleys or strip surface temperature points.

The process model for the temperature field in the cylindrical pipe (casting sleeve) and the process model for the average temperature of each expansion element can be designed as separate models and can therefore be used and calculated separately. The process model for the temperature field in the cylindrical pipe (casting sleeve) can contribute to the saving of external sensors. A process model for the average temperature of each expansion element may help to save temperature sensors within the expansion elements.

In addition to physical-mathematical process models, artificial intelligence or machine learning methods and models (e.g., in the form of neural network algorithms or symbolic regression algorithms, etc.) can be used to fine-tune the selection of thermal rings for heating. Thus, the preferred embodiment of the invention is: artificial intelligence, for example in the form of a neural network algorithm or a symbolic regression algorithm, is additionally used to determine which expansion elements have to be enlarged, preferably heated.

It is also preferred to enlarge, preferably heat, only three to nine, more preferably three to five expansion elements at a time.

A preferred embodiment of the invention provides that only the centrally mounted expansion element is permanently enlarged, preferably heated. In addition, it is possible that the expansion element at the end portion of the casting surface is permanently enlarged, preferably heated.

For the above method, it is preferred that at least one of the casting rolls is designed according to the claimed casting rolls.

Drawings

The invention will be explained in more close detail by reference to preferred embodiments, which are schematically depicted in the drawings.

FIG. 1 is a diagrammatic side view of a twin roll casting machine of the present disclosure;

FIG. 2A is an enlarged, partial cross-sectional view of a portion of the twin roll casting machine of FIG. 1 including a strip inspection device for measuring the profile of the strip;

FIG. 2B is a schematic illustration of a portion of the twin roll casting machine of FIG. 2A;

FIG. 3A is a cross-sectional view longitudinally through a portion of one of the prior art casting rolls of FIG. 2A, with the expansion ring corresponding to a central portion of the cast strip;

FIG. 3B is a cross-sectional view of the remainder of the prior art casting roll joined on line A-A longitudinally through FIG. 3A;

FIG. 4 is an end view of the prior art casting roll of FIG. 3A on line 4-4 and showing partial internal detail in phantom;

FIG. 5 is a cross-sectional view of the prior art casting roll of FIG. 3A on line 5-5;

FIG. 6 is a cross-sectional view of the prior art casting roll of FIG. 3A on line 6-6;

FIG. 7 is a cross-sectional view of the prior art casting roll of FIG. 3A on line 7-7;

FIG. 8 is a cross-sectional view longitudinally through a portion of one of the prior art casting rolls of FIG. 2 with two expansion rings spaced from the edge portions of the cast strip;

FIG. 9 is a cross-sectional view longitudinally through a portion of a prior art casting roll with expansion rings spaced from edge portions of the cast strip;

FIG. 10 is a cross-sectional view longitudinally through a portion of one of the prior art casting rolls of FIG. 2 with two expansion rings spaced from edge portions of the cast strip and one expansion ring corresponding to a central portion of the cast strip;

FIG. 11 is a cross-sectional view longitudinally through a casting roll having nineteen expansion rings in accordance with the present invention;

FIG. 12 is a graph of profile correction for half-band thickness versus length (μm vs. mm) along a cylindrical tube.

Detailed Description

Referring now to fig. 1, 2A and 2B, there is illustrated a twin roll caster comprising a main machine frame 10, the main machine frame 10 standing from the plant floor and supporting a pair of counter-rotatable casting rolls 12 mounted in modules in a roll cassette 11. The casting rolls 12 are mounted in a roll cassette 11 for ease of handling and movement, as described below. The roll cassette 11 facilitates rapid movement of the casting rolls 12, which are in reserve for casting, as a unit from a set-up position into an operating casting position in the caster, and easy removal of the casting rolls 12 from the casting position when the casting rolls 12 are to be replaced. There is no particular configuration of the roll cassette 11 desired as long as it performs the function of facilitating the movement and positioning of the casting rolls 12 as described herein.

A casting apparatus for continuously casting thin steel strip includes a pair of counter-rotatable casting rolls 12 having casting surfaces 12A positioned laterally to form a nip 18 therebetween. Molten metal is supplied from the ladle 13 through a metal delivery system to metal delivery nozzles 17 (core nozzles) positioned between the casting rolls 12 above the nip 18. The molten metal thus delivered forms a casting pool 19 of molten metal supported on the casting surfaces 12A of the casting rolls 12 above the nip 18. The casting pool 19 is bounded in the casting zone at the ends of the casting rolls 12 by a pair of side closure plates or side dams 20 (shown in phantom in fig. 2A and 2B). The upper surface of the casting pool 19 (commonly referred to as the "meniscus" level) may rise above the lower ends of the delivery nozzles 17 such that the lower ends of the delivery nozzles 17 are submerged within the casting pool 19. The casting zone includes the addition of a protective atmosphere above the casting pool 19 to inhibit oxidation of the molten metal in the casting zone.

Ladle 13 is generally of conventional construction supported on a rotating turret 40. For metal delivery, the ladle 13 is positioned above the movable tundish 14 in the casting position to fill the tundish 14 with molten metal. The removable tundish 14 may be positioned on a tundish car 66, and the tundish car 66 may be capable of transferring the tundish 14 from a heating station (not shown) where the tundish 14 is heated to near the casting temperature to the casting position. A tundish guide (such as rails 39) may be positioned below the tundish car 66 to enable the movable tundish 14 to be moved from the heating station to the casting position.

The movable tundish 14 may be fitted with a sliding gate valve 25, the sliding gate valve 25 being actuatable by a servo mechanism to allow molten metal to flow from the tundish 14 through the sliding gate valve 25 and then through the refractory outlet shroud 15 to the transition piece or distributor 16 in the casting position. The molten metal flows from the distributor 16 to delivery nozzles 17 positioned between the casting rolls 12 above the nip 18.

The side dam 20 may be made of a refractory material such as zirconia graphite, graphite alumina, boron nitride-zirconia, or other suitable composite material. The side dams 20 have surfaces (face surfaces) that are in physical contact with the casting rolls 12 and the molten metal in the casting pool 19. The side dams 20 are mounted in side dam holders (not shown) that are movable to engage the side dams 20 with the ends of the casting rolls 12 by side dam actuators (not shown), such as hydraulic or pneumatic cylinders, servos, or other actuators. In addition, the side dam actuators are capable of positioning the side dams 20 during casting. During a casting operation, the side dams 20 form end closures for the molten metal pool on the casting rolls 12.

FIG. 1 shows a twin roll caster producing cast strip 21, with the cast strip 21 being transferred across a guide table 30 to pinch roll stand 31 comprising pinch rolls 31A. Upon exiting the pinch roll stand 31, the thin cast strip 21 may pass through a hot rolling mill 32, the hot rolling mill 32 comprising a pair of work rolls 32A and back-up rolls 32B, forming a gap capable of hot rolling the cast strip 21 delivered from the casting rolls 12, wherein the cast strip 21 is hot rolled to reduce the strip to a desired thickness, improve the strip surface, and improve strip flatness. The work roll 32A has a work surface associated with a desired belt profile across the work roll 32A. The hot rolled cast strip 21 then passes onto an output table 33 where it may be cooled by contact with a coolant (such as water) supplied via water jets 90 or other suitable means, and by convection and radiation. In any event, the hot rolled cast strip 21 may then pass through a second pinch roll stand 91 to provide tension to the cast strip 21 and then to a coiler 92. The thickness of the cast strip 21 may be between about 0.3 and 2.0 millimeters prior to hot rolling.

At the start of a casting operation, short lengths of defective strip are typically produced when casting conditions are stable. After continuous casting is established, the casting rolls 12 are slightly removed and then brought together again to disengage the leading end of the cast strip 21 to form a flawless leading end of the following cast strip 21. The defective material falls into a waste receptacle 26 that is movable on a waste receptacle guide. The scrap receptacle 26 is located in a scrap receiving position below the caster and forms part of a sealed enclosure 27 as described below. The housing 27 is typically water cooled. At this point, the water cooled apron 28 is normally suspended from the pivot 29 down to one side in the enclosure 27 and swung into position to guide the flaw free end of the cast strip 21 onto the guide table 30, which guide table 30 feeds the strip to the pinch roll stand 31. The apron plates 28 are then withdrawn to their hanging position to allow the strip 21 to hang in loops in the enclosure 27 beneath the casting rolls 12, and the strip then passes to a guide table 30 where it engages a series of guide rolls at the guide table 30.

An overflow receptacle 38 may be provided below the movable tundish 14 to receive molten material that may overflow from the tundish 14. As shown in fig. 1, the overflow receptacle 38 may be movable on rails 39 or another guide so that the overflow receptacle 38 may be placed under the movable tundish 14 as desired in the casting position. Additionally, the distributor 16 may be provided with an optional overflow container (not shown) adjacent to the distributor 16.

The sealed enclosure 27 is formed from a number of separate wall sections that fit together at various sealed connections to form a continuous enclosure wall that permits control of the atmosphere within the enclosure 27. In addition, the scrap receptacle 26 may be attachable to the enclosure 27 such that the enclosure 27 is capable of supporting a protective atmosphere immediately below the casting rolls 12 in the casting position. The housing 27 includes an opening in a lower portion of the housing 27 (the lower housing portion 44) providing an outlet for waste material to pass from the housing 27 into the waste receptacle 26 in the waste receiving position. The lower housing portion 44 may extend downwardly as part of the housing 27 with the opening positioned above the waste receptacle 26 in the waste receiving position. As used herein in the specification and claims, "seal", "sealed", "sealing" and "sealingly" in relation to the waste receptacle 26, the outer shell 27 and related features may not be a complete seal to prevent leakage, but rather a generally less than perfect seal as the case may be to allow the atmosphere within the outer shell 27 to be controlled and supported by some tolerable leakage as desired.

A rim portion 45, which may surround the opening of the lower housing portion 44 and may be removably positioned above the waste receptacle 26, can sealingly engage and/or attach to the waste receptacle 26 in the waste receiving position. The rim portion 45 is movable between a sealing position (wherein the rim portion 45 engages the waste receptacle 26) and a clearance position (wherein the rim portion 45 is separated from the waste receptacle 26). Alternatively, the caster or waste receptacle 26 may include a lifting mechanism to raise the waste receptacle 26 into sealing engagement with the rim portion 45 of the housing 27 and then lower the waste receptacle 26 into the clearance position. When sealed, the enclosure 27 and the scrap receptacle 26 are filled with a desired gas (such as nitrogen) to reduce the amount of oxygen in the enclosure 27 and provide a protective atmosphere for the cast strip 21.

The enclosure 27 may include an upper collar portion 43, the collar portion 43 supporting a protective atmosphere immediately below the casting rolls 12 in the casting position. When the casting rolls 12 are in the casting position, the upper collar portions 43 are moved to the extended position, thereby closing the space between the shell portions 53 (shown in FIG. 2) and the shells 27 adjacent the casting rolls 12. The upper collar portions 43 may be disposed within or adjacent to the housings 27 and adjacent to the casting rolls 12 and may be moved by a plurality of actuators (not shown), such as servos, hydraulic mechanisms, pneumatic mechanisms, and rotary actuators.

The casting rolls 12 are internally water cooled as described below so that when the casting rolls 12 are counter-rotated, the billet solidifies on the casting surfaces 12A as the casting surfaces 12A move into contact with the casting pool 19 and through the casting pool 19 with each rotation of the casting rolls 12. The billets are packed closely together at the nip 18 between the casting rolls 12 to produce a thin cast strip product 21 delivered downwardly from the nip 18. Thin cast strip product 21 is formed from the billet at the nip 18 between the casting rolls 12 and is delivered downwardly and moves downstream as described above.

Referring now to fig. 3A-3B, each casting roll 12 comprises a cylindrical tube 120 of a metal selected from the group consisting of copper and copper alloys, optionally having a coating (e.g., chromium or nickel) thereon to form a casting surface 12A. In FIG. 3A, an expansion ring 220 may be positioned within and adjacent to cylindrical tube 120, according to the prior art, at a location where expansion ring 220 corresponds to the center portion of the cast strip formed on the casting surfaces of the casting rolls during casting.

Each cylindrical tube 120 may be mounted between a pair of

stub shaft assemblies

121 and 122.

Stub shaft assemblies

121 and 122 have

end portions

127 and 128, respectively (shown in fig. 4-6),

end portions

127 and 128 fitting snugly within the ends of cylindrical tubes 120 to form casting rolls 12. Thus, cylindrical tube 120 is supported by

end portions

127 and 128 having

flange portions

129 and 130, respectively, to form a bore 163 therein and to support the assembled casting rolls between

stub shaft assemblies

121 and 122.

The cylindrical outer surface of each cylindrical tube 120 is the roll casting surface 12A. The radial thickness of the cylindrical tube 120 may be no greater than 80 millimeters thick. The thickness of the tube 120 may range between 40 and 80 millimeters in thickness, or may range between 60 and 80 millimeters in thickness.

Each cylindrical tube 120 is provided with a series of longitudinal water flow passages 126, the longitudinal water flow passages 126 being formed by drilling long holes through the circumferential thickness of the cylindrical tube 120 from one end to the other. The ends of these holes are then closed by end plugs 141, the end plugs 141 being attached to the

end portions

127 and 128 of the

stub shaft assemblies

121 and 122 by fasteners 171. The water flow passage 126 is formed through the thickness of the cylindrical tube 120 and has an end plug 141. The number of stub shaft fasteners 171 and end plugs 141 may be selected as desired. The end plugs 141 may be arranged to provide single pass cooling from one end of the roll 12 to the other using water channels in the stub shaft assembly described below, or alternatively arranged to provide multi-pass cooling in which, for example, the flow channels 126 are connected to provide three-way cooling water through adjacent flow channels 126, which is then returned to the water supply either directly or through the cavity 163.

A water flow passage 126 through the thickness of the cylindrical tube 120 may be connected to a water supply in series with the cavity 163. The water flow channel 126 may be connected to a water supply such that cooling water first passes through the cavity 163 and then through the water supply channel 126 to the return line, or first passes through the water supply channel 126 and then through the cavity 163 to the return line.

The cylindrical tube 120 may be provided with circumferential steps 123 at the ends to form shoulders 124, with the working portions of the roll casting surfaces 12A of the rolls 12 between the shoulders 124. The shoulder 124 is arranged to engage the side dam 20 and delimit the casting pool 19 during a casting operation as described above.

The

end portions

127 and 128 of the

stub shaft assemblies

121 and 122, respectively, generally sealingly engage the ends of the cylindrical tube 120 and have radially extending

water passages

135 and 136 shown in fig. 4-6 to deliver water to the water flow passage 126 extending through the cylindrical tube 120. The

radial flow passages

135 and 136 are connected to the ends of at least some of the water flow passages 126, for example in a threaded arrangement, depending on whether the cooling is a single-pass or multi-pass cooling system. The remaining ends of the water flow channels 126 may be closed by, for example, a threaded end plug 141 as described above, wherein the water cooler is a multi-pass system.

As shown in detail by fig. 7, the cylindrical tubes 120 may be positioned in an annular array within the thickness of the cylindrical tubes 120, depending on the desired single-pass or multiple-pass array of water flow passages 126. The water flow passages 126 are connected at one end of the casting rolls 12 to the annular gallery 140 and in turn to the radial flow passages 135 of the end portion 127 in the stub shaft assembly 120 through radial ports 160, and are connected at the other end of the casting rolls 12 to the annular gallery 150 and in turn to the radial flow passages 136 of the end portion 128 in the stub shaft assembly 121 through radial ports 161. Water supplied through one

annular gallery

140 or 150 at one end of the roll 12 may flow in parallel through all of the water flow passages 126 to the other end of the roll 12 in a single pass and out through the

radial passages

135 or 136 and the other

annular gallery

150 or 140 at the other end of the cylindrical tube 120. The directional flow may be reversed by appropriate connection of the supply and return lines, as desired. Alternatively or additionally, a selected one of the water flow passages 126 may optionally connect or block the

radial passages

135 and 136 to provide a multi-pass arrangement (such as a tee).

The stub shaft assembly 122 may be longer than the stub shaft assembly 121 and the stub shaft assembly 122 is provided with two sets of

water flow ports

133 and 134. The

water flow ports

133 and 134 are connectable with rotary

water flow couplings

131 and 132 with which water is delivered to and from the casting rolls 12 by passing axially through the stub shaft assemblies 122 to and from the casting rolls 12 using the rotary

water flow couplings

131 and 132. In operation, cooling water passes through the

radial passages

135 and 136 to and from the water flow passage 126 in the cylindrical tube 120, the

radial passages

135 and 136 extending through the

end portions

127 and 128 of the

stub shaft assemblies

121 and 122, respectively. The stub shaft assembly 121 houses axial tubes 137 to provide fluid communication between the radial passages 135 in the end portions 127 and the central cavities within the casting rolls 12. The stub shaft assembly 122 is fitted with an axial space tube 138 to separate a central water conduit 138 in fluid communication with the central cavity 163 from an annular water flow conduit 139 in fluid communication with the radial passage 136 in the end portion 122 of the stub shaft assembly 122. The central water conduit 138 and the annular water conduits 139 are capable of providing an inflow of cooling water to the casting rolls 12 and an outflow of cooling water from the casting rolls 12.

In operation, incoming cooling water may be supplied through the supply line 131 through the port 133 to the annular conduit 139 (which in turn is in fluid communication with the radial passage 136, the gallery 150 and the water flow passage 126), and then returned through the gallery 140, the radial passage 135, the axial tube 137, the central cavity 163 and the central water conduit 138 to the outer flow line 132 through the water flow port 134. Alternatively, the water flow to the casting rolls 12, from the casting rolls 12, and through the casting rolls 12 may be in opposite directions, as desired. The

water flow ports

133 and 134 may be connected to water supplies and return lines so that water may flow to and from the water flow passages 126 in the cylindrical tubes 120 of the casting rolls 12 in either direction as desired. Depending on the direction of flow, cooling water flows through cavity 163 either before or after flowing through flow channel 126.

According to the present invention, each cylindrical tube 120 is typically provided with more than three expansion rings. As illustrated in fig. 8 (which is of the prior art), each cylindrical tube 120 may be provided with at least two expansion rings 210, the expansion rings 210 being spaced apart on opposite end portions of the cylindrical tube 120 within 450 mm inward of edge portions of the cast strip formed on the opposite end portions of the casting rolls during the casting campaign. FIG. 9 (which is also of the prior art) shows a cross-sectional view longitudinally through a portion of a casting roll with expansion rings 210 spaced from the edge portions of the cast strip.

Alternatively, as shown in fig. 10 (which again is of the prior art), two expansion rings 210 may be spaced apart on the opposite end portions of the cylindrical tube within 450 mm of the edge portions of the cast strip formed on the opposite end portions of the casting rolls during the casting campaign, and an additional expansion ring 200 may be positioned within and adjacent to the cylindrical tube 120 at a location corresponding to the central portion of the cast strip formed on the casting surfaces of the casting rolls during casting.

A power line 222 and a control line 224 extend from the slip ring 220 to each expansion loop. The power line 222 supplies energy to power the

expansion loops

200, 210. The control line 224 modulates the energy used to provide power to the expansion loop.

FIG. 11 is a cross-sectional view longitudinally through a casting roll having nineteen expansion rings 101-119 according to the present invention, with interior portions of the casting roll 12 omitted. In this example, the expansion rings 101 to 119 have approximately the same width and the same ring thickness. Expansion rings 101 and 119 are located at the edges of the casting surface 12A. Viewed in the axial direction, a portion of the expansion rings 101, 119 is located inside the casting surface 12A and a portion of the expansion rings 101, 119 is located outside the casting surface 12A. Here, the distance of the

expansion ring

101, 119 at the edge of the casting surface 12A to the

next expansion ring

102, 118 is greater than the distance between two adjacent inner expansion rings 102 to 118. In this example, the distance of an

expansion ring

101, 119 to the

next expansion ring

102, 118 at the edge of the casting surface 12A is between 1.0 and 1.5 of the width of one expansion ring 101 to 119. The distance between two adjacent inner expansion rings 102 to 118 is smaller than the width of one expansion ring 101 to 119, here approximately between 0.5 and 0.8 of the width of one expansion ring 101 to 119.

The expansion rings 101 to 119 are mounted on the outer surface of the inner tube 180, for example by shrink fitting. The inner tube 180 may contain wires or cables for providing electrical energy from the wires 181 to each of the expansion loops 101-119. Also, a power switch may be located in the inner tube 180 to switch the supply of power from one or more expansion loops to one or more other expansion loops. Similar to fig. 4-7, the inner tube 180 may also contain a portion of a water cooler.

The centrally mounted expansion loop (which in this case would be expansion loop 110) may be permanently connected to wires 181 so as to be permanently heated, or a power switch is constructed or programmed or controlled so as to permanently heat the centrally mounted expansion loop 110. The same applies to the expansion rings 101 and 119 located at the edge of the casting surface 12A.

Each expansion loop 101 to 119 is equipped with a resistive heating element supplying each expansion loop with a heating power of up to 15 kW, preferably 3 to 10 kW, via a wire 181, the wire 181 leading to and from a slip ring (not visible here). The total electrical power provided by the slip rings of one casting roll may amount to up to 70 kW, preferably up to 35 kW, per meter of the outer circumferential portion of the respective casting roll.

The controller may be located outside of the casting rolls 12 and may be connected to the heating elements of the expansion rings 101 through 119 or to power switches in the inner tubes 180 via control wires (not shown). The controller controls the radial dimension of each of the expansion rings 101-119 by controlling the electrical energy provided to each expansion ring 101-119, for example at least in response to a temperature process model of the casting rolls 12 and/or the expansion rings 101-119 and/or in response to a measured expansion ring temperature.

The deformation of the convexity of the casting surface can be controlled by adjusting the radial dimensions of the respective expansion rings 101 to 119 located inside the cylindrical tube 120. The radial dimension of the expansion rings 101 through 119 can be controlled by adjusting the temperature of the expansion rings. Further, the thickness profile of the cast strip may be controlled by controlling the convexity of the casting surfaces 12A of the casting rolls 12. Because the circumferential thickness of the cylindrical tube 120 is typically made to be no greater than 120 mm in thickness, the convexity of the casting surface 12A may deform in response to changes in the radial dimension of the expansion rings 101 to 119.

Each expansion ring 101 to 119 is adapted to increase in radial dimension to expand the cylindrical tube 120 to vary the convexity of the casting surface 12A and the thickness profile of the cast strip 21 during casting.

Each expansion ring is electrically heated to increase the radial dimension. Each expansion loop 101 to 119 can provide a heating input of up to 15 kW; preferably 3 to 10 kW. The force created by the increase in radial dimension will be applied to the cylindrical tube 120 to expand the cylindrical tube, thereby changing the convexity of the casting surface and the thickness profile of the cast strip. FIG. 12 illustrates the effect of expansion loop temperature on cast strip thickness profile. FIG. 12 is a graph of profile correction for half-band thickness versus length (mm) along a cylindrical tube for expansion temperatures from 40 ℃ to 200 ℃. To achieve the desired thickness profile via control of the radial dimensions of the expansion rings 101-119 and control of the casting speed, a strip thickness profile sensor 71 may be positioned downstream to detect the thickness profile of the cast strip 21, as shown in FIGS. 2 and 2A. Strip thickness sensors 71 are typically provided between the nip 18 and the pinch rolls 31A to provide direct control of the casting rolls 12. The sensor may be an x-ray meter or other suitable device capable of periodically or continuously measuring the thickness profile directly across the width of the strip. Alternatively, a plurality of non-contact type sensors are arranged across the cast strip 21 at the roll stand 30 and combinations of thickness measurements from multiple locations across the cast strip 21 are processed by the controller 72 to periodically or continuously determine the strip thickness profile. The thickness profile of the cast strip 21 may be determined periodically or continuously from this data, as desired.

The radial dimension of each expansion ring 101 to 119 may be controlled independently of the radial dimensions of the other expansion rings. The sensor 71 generates a signal indicative of the thickness profile of the cast strip 21. The radial dimension of each expansion ring 101 to 119 is controlled in accordance with the signals generated by the sensors, which in turn controls the roll crown of the casting surfaces 12A of the casting rolls 12 during the casting campaign.

Further, the casting roll drive may be controlled in response to electrical signals received from the sensors 71 to vary the rotational speed of the casting rolls while also varying the radial dimensions of the expansion rings 101-119 to control the roll crown of the casting surfaces of the casting rolls during the casting campaign.

In each embodiment, the expansion ring may be made of austenitic stainless steel (such as 18/8 austenitic stainless steel). Each expansion ring may have an annular dimension of between 40 and 100 millimeters. Each expansion loop 101 to 119 may have a width of up to 200 mm, preferably between 50 and 100 mm, more preferably between 60 and 85 mm. However, the centrally mounted expansion ring 110 may have a width greater than all other expansion rings, for example up to 150 up to 400 mm.

Claims

1. Casting roll (12) for casting a metal strip (21) by continuous casting in a twin roll caster, the casting roll comprising:

-having a casting surface (12A) formed by a substantially cylindrical tube (120),

-having axisymmetric expansion elements (101-119) arranged inside and adjacent to said cylindrical tube (120), each expansion element being spaced apart from the other expansion element and adapted to expand said cylindrical tube by an increase in radial dimension so as to vary the roll crown of said casting surfaces of said casting rolls and the thickness profile of the cast strip during casting,

characterized in that a number of axisymmetric expansion elements (101) are distributed along the entire length of the cylindrical tube (120), and that a power switch is located in the casting roll (12) or on the casting roll (12) in order to switch the power supply of the expansion elements (101) 119 from one or more expansion elements to one or more other expansion elements,

wherein each expansion element (101-119) is equipped with a resistive heating element capable of supplying a heating power of up to 15 kW to the expansion element, and

wherein the centrally mounted expansion element (110) is constructed to be permanently heated.

2. Casting roll (12) according to claim 1, characterized in that the expansion elements (101-119) have a width between 40 and 150 mm.

3. Casting roll (12) according to claim 1, characterized in that the expansion elements (101-119) have a width between 40 and 100 mm.

4. Casting roll (12) according to claim 1, characterized in that the expansion elements (101-119) have a width between 50 and 85 mm.

5. Casting roll (12) according to claim 1, characterized in that each expansion element (101-119) is equipped with a resistive heating element capable of supplying the expansion element with a heating power of 3-10 kW.

6. Casting roll (12) according to claim 1, characterized in that the expansion elements (101-119) are expansion rings.

7. Casting roll (12) according to claim 6, characterized in that each expansion ring has a radial ring thickness between 40 and 150 mm.

8. Casting roll (12) according to claim 6, characterized in that each expansion ring has a radial ring thickness between 40 and 100 mm.

9. Casting roll (12) according to any of claims 1-5, characterized in that the expansion elements have the form of rings or have the form of discs.

10. Casting roll (12) according to any of claims 1-6, characterized in that the total electric power provided for all expansion elements (101-119) together is up to 70 kW per meter of the outer circumferential portion of the casting roll (12).

11. Casting roll (12) according to any of claims 1-6, characterized in that the total electrical power provided for all expansion elements (101-119) together is not more than 35 kW per meter of the outer circumferential portion of the casting roll (12).

12. Casting roll (12) according to any of claims 1-6, characterized in that more than fifteen axially symmetric expansion elements (101-119) are arranged inside and adjacent to the cylindrical tube (120).

13. Casting roll (12) according to any of claims 1-6, characterized in that sixteen to thirty axisymmetric expansion elements (101-119) are arranged inside and adjacent to the cylindrical tube (120).

14. Casting roll (12) according to any of claims 1-6, characterized in that a number of axisymmetric expansion elements (101) are distributed along the entire length of the cylindrical tube (120), including the end portions of the casting surface (12A).

15. Casting roll (12) according to any of claims 1-6, characterized in that the power switch is configured to switch the power supply between different expansion elements (101-119) every two to thirty seconds.

16. Casting roll (12) according to any of claims 1-6, characterized in that the power switch is configured to switch the power supply between different expansion elements (101-119) every five to fifteen seconds.

17. The casting roll (12) according to any one of claims 1-6, characterized in that the expansion elements (101, 119) at end portions of the casting surface (12A) are configured to be permanently heated.

18. Casting roll (12) according to any of claims 1-6, characterized in that the expansion elements (101-119) are each equipped with at least one temperature sensor for providing a corresponding signal to a controller.

19. Casting roll (12) according to any of claims 1-6, characterized in that the expansion elements (101-119) are each equipped with at least one RFID tag for identifying the expansion elements when sending temperature information to the controller.

20. Casting roll (12) according to any of claims 1-6, characterized in that the expansion elements (101-119) are each equipped with at least one RFID tag for identifying the expansion elements when sending temperature information to a controller located within the casting roll (12).

21. Casting roll (12) according to any of claims 1-6, characterized in that the controller is configured to control the radial dimension of each of the expansion elements (101-119) at least in response to a temperature process model of the casting roll (12) and/or a temperature process model of the expansion elements (101-119) and/or in response to a measured temperature change for the expansion elements (101-119).

22. An apparatus for continuously casting thin strip by controlling roll crown, the apparatus comprising:

-a pair of counter-rotating casting rolls (12) having a nip (18) therebetween and capable of delivering a cast strip (21) downwardly from the nip, each casting roll having a casting surface (12A) formed by a substantially cylindrical tube (120),

-a metal delivery system positioned above the nip (18) and capable of forming a casting pool (19) supported on the casting surfaces of the casting rolls (12), with side dams (20) adjacent the ends of the nip to delimit the casting pool,

characterized in that the at least one casting roll (12) is a casting roll according to any one of claims 1-21.

23. A method of continuously casting thin strip by controlling roll crown, the method comprising:

-using a pair of counter-rotating casting rolls (12) having a nip (18) therebetween for delivering a cast strip (21) downwardly from the nip, each casting roll having a casting surface (12A) formed by a substantially cylindrical tube (120),

-also using a metal delivery system positioned above the nip (18) to form a casting pool (19) supported on the casting surfaces (12A) of the casting rolls (12), with side dams (20) adjacent the ends of the nip to define the casting pool,

-at least one casting roll (12) has axially symmetric expansion elements (101-119) arranged inside and adjacent to said cylindrical tube (120), each expansion element being spaced apart from the other and adapted to expand said cylindrical tube (120) by an increase in radial dimension so as to vary the roll crown of the casting surfaces of said casting rolls and the thickness profile of the cast strip (21) during casting,

characterized in that the radial dimension of at least one expansion element is increased by heating, thereby expanding the cylindrical tube (120) while the radial dimension of at least one other expansion element is not increased, and controlling which expansion elements are to be increased is based on:

-the recorded temperature profile of the casting strip (21), and/or

-a measured strip thickness profile of the casting strip (21), and/or

-measured thermal crown of the casting rolls (12), and/or

-a temperature profile of one or both of the casting rolls (12), and/or

-the measured temperature of the expansion element,

24. Method according to claim 23, characterized in that each expansion element (101-119) is equipped with a resistive heating element capable of supplying 3-10 kW of heating power to the expansion element.

25. Method according to claim 23, wherein said expansion element (101-119) is an expansion ring.

26. Method according to any of claims 23-25, wherein switching between different expansion elements (101-119) is performed every two to sixty seconds.

27. Method according to any of claims 23-25, characterized in that switching is performed between different expansion elements (101-119) every five to thirty seconds.

28. The method according to any of claims 23-25, characterized in that the temperature profile of one or both of the casting rolls (12) is given by a process model that outputs in real time a two-dimensional or three-dimensional temperature field of the interior of the cylindrical tube (120).

29. Method according to any of claims 23-25, wherein the temperature profile of one or both of the casting rolls (12) is given by a process model which outputs in real time the average temperature of each expansion element (101-119).

30. Method according to any one of claims 23-25, characterized in that additionally an artificial intelligence in the form of a neural network algorithm or a symbolic regression algorithm is used for determining which expansion elements (101-119) have to be heated.

31. The method of any one of claims 23-25, wherein only three to nine expansion elements are heated at a time.

32. The method of any one of claims 23-25, wherein only three to five expansion elements are heated at a time.

33. The method according to any of the claims 23-25, characterized in that the expansion elements (101, 119) at the end portions of the casting surface (12A) are permanently heated.

34. Method according to any one of claims 23-25, characterized in that at least one of the casting rolls (12) is a casting roll according to any one of claims 1-21.