WO2018119333A1

WO2018119333A1 - Adjustable side dam holder

Info

Publication number: WO2018119333A1
Application number: PCT/US2017/068055
Authority: WO
Inventors: Tao Wang; Christopher Quick; Kevin KEOWN
Original assignee: Nucor Corporation
Priority date: 2016-12-23
Filing date: 2017-12-21
Publication date: 2018-06-28

Abstract

Apparatuses and methods for continuous twin roll casting of metal strips are disclosed herein. An apparatus includes a pair of adjustable side dam holders each adapted to retain a side dam during casting. The adjustable side dam holders are vertically and/or horizontally adjustable to permit the side dam to be moved vertically, such as up to 15 mm, and/or horizontally, such as up to 15 mm.

Description

ADJUSTABLE SIDE DAM HOLDER

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to, and the benefit of, U.S. Provisional Patent Application No. 62/438,993, filed December 23, 2016 with the U.S. Patent Office, and which is hereby incorporated by reference.

BACKGROUND

[0002] This invention relates to making thin metal strips and more particularly casting of thin metal strip ("thin strip") by a twin roll caster.

[0003] In a twin roll caster, molten metal is introduced between a pair of counter-rotating casting rolls that are cooled so that metal shells solidify on the moving roll surfaces and are brought together at a nip between them. The term "nip" is used herein to refer to the general region at which the rolls are closest together. The molten metal may be delivered from a ladle into a smaller vessel or series of smaller vessels, from which the molten metal flows through a metal delivery nozzle located above the nip. The molten metal forms a casting pool above the nip, which is supported on the casting surfaces of the rolls immediately above the nip. The casting pool generally extends the length of the nip. As the molten metal forms along the casting rolls into shells, the shells join and pass through the nip between the casting rolls to form a thin metal strip cast downwardly from the nip.

[0004] The casting pool is commonly confined between side dams located at opposing axial ends of the casting rolls, so as to constrain the lengthwise ends of the casting pool, where each of the side dams inhibit leakage of molten metal from the casting pool while also permitting the casting pool to reach a desired depth. As the casting rolls are rotated, the axial ends rotate against each side dam, whereby each side dam experiences frictional wear resulting in the formation of arc-shaped grooves or recesses in each side dam . To compensate for this wear, the side dams are forced in an axial direction of the casting rolls against the ends portions of the casting rolls to provide a seal with the casting rolls for the casting pool. Each side dam is held in place during casting by a side dam holder.

[0005] A typical side dam and side dam holder assembly includes a V-shaped side dam and a stationary or non-adjustable side dam holder into which the side dam may be seated. However, the lack of vertical and horizontal adjustability of the side dam by way of the side dam holder can result in inconsistent contact area between the side dams and the casting rolls over time. As the side dams wear, the contact between casting rolls and the side dams decreases significantly and may ultimately result in a gap between any casting roll and the side dam. In particular, through use the casting rolls themselves develop cracks and other defects and periodically need to be taken out of service, ground down and refurbished. When the casting roll is returned to service, its diameter is smaller than the original diameter, which also can create decreased or inconsistent contact, or even a gap between the casting roll and the side dam. As a result, due to the reduction in contact, friction force generated along the side dam by the rotating casting rollers decreases. This reduction in friction force can cause the side dams to move and become positionally unstable. As a result, "skulls" of solid metal may form near the side dams adjacent the end portions of the casting rolls, which can grow to considerable size. The skulls can drop through the nip of the casting rolls and form defects in the strip known as "snake eggs." When these skulls drop between the roll nip, they may also cause the two solidifying shells at the casting roll nip to "swallow" additional liquid metal between the shells, causing the strip to reheat and break, thereby disrupting the continuous production of coiled strip.

[0006] Snake eggs and skulls may also be detected as visible bright bands across the width of the cast strip, as well as by spikes in the lateral force exerted by skulls on the casting rolls as they pass through the roll nip between the casting rolls. Such resistive forces are exerted against the side dams in addition to the forces from the ferrostatic head of the casting pool.

[0007] An adjustable side dam holder is herein disclosed that can remedy the inconsistency in contact area between the casting rolls and side dams and allow for the use of different diameter casting rolls.

SUMMARY

[0008] Currently disclosed is an adjustable side dam holder configured to receive and retain a side dam formed of refractory material and having edge portions adapted to engage a corresponding end portion of each casting roll of the twin roll caster during casting, the side dam holder being vertically and/or horizontally adjustable relative to the casting rolls to permit the side dam to be moved vertically and/or horizontally, respectively, relative to the end portion of each of the casting rolls to maintain engagement between the side dam and the corresponding end portion of the casting rolls. The adjustable side dam holder may be operatively connected to a side dam plate on which the side dam may be mounted.

[0009] In particular embodiments, the side dam holder is vertically adjustable up to 15 millimeters (mm) or up to 25 mm and horizontally adjustable up to 15 mm or up to 25 mm. It is appreciated that adjustability may occur in either the vertical or horizontal direction. Alternatively, adjustments may be made in both the vertical and horizontal direction, and the adjustments may be made separately or concurrently. For example, adjustments may be made in a first direction (e.g., vertical or horizontal) and then in a second direction (e.g., the other of the vertical or horizontal direction). In another example, adjustments may be made in a direction biased to both the vertical and horizontal direction, such as a direction diagonal to both the vertical and horizontal directions, where the adjustment direction can be parsed into vertical and horizontal vectors (components).

[0010] Also disclosed is a side dam apparatus for a twin roll caster for forming thin metal strips comprising a side dam formed of refractory material and having edge portions adapted to engage an end portion of each casting roll of the twin roll caster; an adjustable side dam holder configured to receive and retain the side dam, the side dam holder being vertically and/or horizontally adjustable relative to the casting rolls to permit the side dam to be moved vertically and/or horizontally relative to the end portion of each of the casting rolls to maintain engagement between the side dam and the corresponding end portion of the casting rolls.

[0011] Optionally, the side dam may further comprise a pocket between 5 and 50 mm in depth formed in each side dam between the edge portions and forming shoulder portions in the body between the edge portions, and the pocket adapted to be worn as a casting campaign continues until the pocket is reached and continuing to be worn away at level of base portions of the pocket until casting is completed. Furthermore, the shoulder portions of each side dam may be between 10 and 20 mm in width. Alternatively, the shoulder portions of each side dam may be between 12 and 18 mm in width. The pocket formed in each side dam between the edge portions may be between 5 and 35 mm in depth. Further, the pocket formed in each side dam between the edge portions may be between 5 and 25 mm in depth. Even further, the pocket formed in each side dam between the edge portions may be between 10 and 20 mm in depth. [0012] Also disclosed is a method of casting metal strip comprising: counter-rotating a pair of casting rolls laterally positioned to form a nip there between through which thin metal strip can be cast; where each of a pair of confining side dams are arranged adjacent to a corresponding end portion of the pair of casting rolls and thereby confine a casting pool of molten metal supported on casting surfaces of the pair of casting rolls above the nip, each side dam of the pair of side dams having edge portions adapted to engage end portions of the pair of casting rolls; where a side dam holder is arranged adjacent to each side dam of the pair of side dams, each side dam holder configured to receive one side dam of the pair of side dams in a mounted configuration and being vertically and/or horizontally adjustable to permit the side dam holder and mounted side dam to be moved vertically and/or horizontally, respectively, relative to the corresponding end portion of each of the casting rolls; and, vertically and/or horizontally adjusting the side dam holder to move the side dam holder and mounted side dam relative to the corresponding end portion of each of the casting rolls to maintain engagement between each side dam and the corresponding end portion of the casting roll.

[0013] In particular embodiments of the casting methods, the side dam holder is vertically adjustable up to 15 millimeters (mm) or up to 25 mm and horizontally adjustable up to 15 mm or up to 25 mm. It is appreciated that adjustability may occur only in one direction, that is, in either the vertical or horizontal direction. Adjustments may be made in both the vertical and horizontal direction, and also may be made separately or concurrently. For example, adjustments may be made in a first direction (e.g., vertical or horizontal) and then in a second direction (e.g., the other of the vertical or horizontal direction). In another example, adjustments may be made in a direction biased to both the vertical and horizontal direction, such as a direction diagonal to both the vertical and horizontal directions, where the adjustment direction can be parsed into vertical and horizontal vectors (components).

[0014] Optionally, each side dam in the method may have formed therein a pocket between 5 and 50 mm in depth between the edge portions and with shoulder portions between the edge portions and the pocket adapted to be worn as a casting campaign continues until the pocket is reached and continuing to be worn away at level of base portions of the pocket until casting is completed. The shoulder portions of each refractory body may be between 10 and 20 mm in width. Alternatively, the shoulder portions of each refractory body may be between 12 and 18 mm in width.

[0015] The pocket formed in the side dam between the edge portions may be between 5 and 35 mm in depth. Further, the pocket formed in each side dam between the edge portions may be between 5 and 25 mm in depth. Furthermore, the pocket formed in each side dam between the edge portions may be between 10 and 20 mm in depth.

[0016] In an alternative embodiment, the continuous twin roll caster may include an oscillation mechanism and the method may include laterally oscillating each side dam and side dam holder together at a frequency between 2 and 50 hertz and with an amplitude between 100 μηι and 2000 μιη during a casting campaign. The lateral oscillation may further facilitate elimination of defects, such as snake egg and skull defects as described above, and may be used in conjunction with the adjustable side dam holder to allow both horizontal and vertical adjustment of a side dam relative to twin casting rolls and to allow oscillation of the side dam to eliminate defects in the cast metal strips.

BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is a diagrammatical side view of a twin roll caster plant in accordance with one or more aspects of the present invention;

[0018] FIG. 2 is a partial sectional view through the casting rolls mounted in a roll cassette in the casting position of the caster of FIG. 1, in accordance with one or more aspects of the present invention;

[0019] FIGS. 3 A and 3B depict a front and side view, respectively, of side dam in accordance with one or more aspects of the present invention;

[0020] FIGS. 4A and 4B depict a front and a side view, respectively, of another embodiment of a side dam holder plate, in accordance with one or more aspects of the present invention;

[0021] FIGS. 5A-5C depict front, side, and top views, respectively, of an embodiment of a side dam plate mount, in accordance with one or more aspects of the present invention; [0022] FIGS. 6A and 6B depict front and side views, respectively, of an embodiment of an adjustable side dam support, in accordance with one or more aspects of the present invention;

[0023] FIG. 7A is an assembly drawing showing the side dam holder apparatus partially assembled, in accordance with a particular embodiment of the invention;

[0024] FIG. 7B is an assembly drawing showing the side dam holder of FIG. 7A in assembled form.

[0025] FIG. 7C is a section view taken along line 7C-7C in FIG. 7B;

[0026] FIGS. 8A-8C shows a side dam within a portion of an adjustable side dam apparatus in use with differently sized of casting rolls, in accordance with one or more aspects of the present invention;

[0027] FIG. 9A are related graphs showing snake eggs recorded during the casting campaign using a non-adjustable side dam holder;

[0028] FIGS. 9B and 9C are graphs recorded during casting campaigns using an adjustable side dam holder in accordance with the currently claimed invention;

[0029] FIG. 10 shows sample side dams used in continuous casting processes, illustrating some advantages of using an adjustable side dam holder in accordance with one or more aspects of the present invention.

DETAILED DESCRIPTION

[0030] This disclosure concerns improvements to the casting of metal strips, where the improvements include providing a side dam that is positionally adjustable relative to casting rolls employed in the casting process. Embodiments include adjustable side dam holders and apparatus for a twin roll continuous caster and methods of continuously casting metal strip utilizing the inventive adjustable side dam holders.

[0031] While exemplary side dams are discussed herein in accordance with particular embodiments, other types of side dams may be configured to move to accomplish the positional adjustments contemplated herein. It is appreciated that a variety of side dam designs may be configured or adapted to move, or, in other words, positionally adjust, as desired in accordance with the teachings of this invention. This adjustability may occur in preparation for a casting operation, and/or during a casting operation. It is appreciated that adjustment may be accomplished manually or automatically. For example, in certain exemplary embodiments, a side dam apparatus forms an assembly including a side dam operably attached to a side dam holder including a side dam plate operably mounted on a side dam plate mount. In these embodiments, each side dam holder is vertically and/or horizontally adjustable to permit the side dam holder and supported side dam to be moved vertically and/or horizontally, respectively, relative to the corresponding end portion of each of the casting rolls to maintain a desired engagement between each side dam and the corresponding end portion of a casting roll. The side dam may be retained on the side dam plate according to any desired manner. In one embodiment, each side dam includes a plurality of pins extending from the back side of the side dam, each of which slide into one of a plurality of recesses extending into the side dam plate from a top side. The side dam plate further includes a plurality of apertures for mounting the side dam plate to a side dam plate mount that includes a corresponding plurality of pins, whereby each aperture of the plurality of apertures of the side dam plate is configured to receive a corresponding pin from the plurality of pins of the side dam plate. Other mounting arrangements also are contemplated, such as, for example, where the plurality of pins are arranged along the side dam plate, and the plurality of corresponding apertures are instead arranged along the side dam plate mount. It is appreciated that the side dam can be attached to the side dam holder manually or automatically through, for example, use of robotic positioning adjustment.

[0032] Exemplary embodiments of these methods will now be discussed in association with the drawings showing exemplary apparatus for performing these methods.

[0033] Referring to FIGS. 1 and 2, a twin roll caster is shown for continuously casting thin steel strip. A main machine frame 10 stands up from the factory floor and supports a roll cassette module 11 on which a pair of counter-rotatable casting rolls 12 are mounted. The casting rolls 12 having casting surfaces 12A are laterally positioned to form a nip 18 therebetween. The roll cassette 11 facilitates rapid movement of the casting rolls 12 as a unit from a setup position, to operative casting position, and rapid removal of the casting rolls from the casting position when the casting rolls are to be replaced. The configuration of the roll cassette may be as desired, so long as it performs that function of facilitating movement and positioning of the casting rolls 12 between the set up position and the operative casting position [0034] Molten metal is supplied from a ladle 13 through a metal delivery system, such as a movable tundish 14 and a transition piece or distributor 16. From the distributor 16, the molten metal flows to at least one metal delivery nozzle 17, also called a core nozzle, positioned between the casting rolls 12 above the nip 18. Molten metal discharged from the delivery nozzle or nozzles 17 forms a casting pool 19 of molten metal supported on the casting surfaces 12A of the casting rolls 12 above the nip 18. This casting pool 19 is confined at the end portions of the casting rolls 12 by a pair of side closures or confining plate side dams 20 (shown in dotted line in FIG. 2). The upper surface of the casting pool 19 (generally referred to as the "meniscus" level) typically rises above the bottom portion of the delivery nozzle 17 so that the lower part of the delivery nozzle 17 is immersed in the casting pool 19. The casting area above the casting pool 19 provides the addition of a protective atmosphere to inhibit oxidation of the molten metal before casting.

[0035] The ladle 13 typically is of a conventional construction supported on a rotating turret 40. For metal delivery, the ladle 13 is positioned above a movable tundish 14 in the casting position as shown in FIG. 1 to deliver molten metal to movable tundish 14. The movable tundish 14 may be positioned on a tundish car 66 capable of transferring the tundish from a heating station (not shown), where the tundish is heated to near a casting temperature, to the casting position. A tundish guide, such as rails, may be positioned beneath the tundish car 66 to enable moving the movable tundish 14 from the heating station to the casting position. An overflow container 38 may be provided beneath the movable tundish 14 to receive molten material that may spill from the tundish. As shown in FIG. 1, the overflow container 38 may be movable on rails 39 or another guide such that the overflow container 38 may be placed beneath the movable tundish 14 as desired in casting locations.

[0036] The movable tundish 14 may be fitted with a slide gate 25, actuable by a servo mechanism, to allow molten metal to flow from the tundish 14 through the slide gate 25, and then through a refractory outlet shroud 15 to a transition piece or distributor 16 in the casting position. From the distributor 16, the molten metal flows to the delivery nozzle 17 positioned between the casting rolls 12 above the nip 18.

[0037] The casting rolls 12 are internally water cooled so that as the casting rolls 12 are counter-rotated, shells solidify on the casting surfaces 12A as the casting surfaces 12A rotate into contact with and through the casting pool 19 with each revolution of the casting rolls 12. The shells are brought together at the nip 18 between the casting rolls 12 to produce a solidified thin cast strip product 21 delivered downwardly from the nip 18. The gap between the casting rolls is configured to maintain separation between the solidified shells at the nip so that semi- solid metal is sandwiched between the shells through the nip, and delivered downwardly as part of the strip below the nip.

[0038] FIG. 1 shows the twin roll caster producing the thin strip 21, which passes from the casting rolls across a guide table 30 to a pinch roll stand 31, comprising pinch rolls 31 A. Upon exiting the pinch roll stand 31 the thin strip passes through a hot rolling mill 32, comprising a pair of work rolls 32A, and backup rolls 32B capable of hot rolling the strip delivered from the casting rolls. In the hot rolling mill 32, the strip is hot rolled to reduce the strip to a desired thickness, improve the strip surface, and improve the strip flatness. The work rolls 32A have work surfaces relating to the desired strip profile across the work rolls. The hot rolled strip then passes onto a run-out 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 strip may then pass through a second pinch roll stand 91 having rollers 91 A to provide tension on the strip, and then to a coiler 92. The thickness of strip may be typically between about 0.3 and about 3 millimeters in thickness after hot rolling.

[0039] At the start of the casting campaign, a short length of imperfect strip is typically produced as casting conditions stabilize. After continuous casting is established, the casting rolls 12 are moved apart slightly and then brought together again to cause the leading end of the thin strip to break away forming a clean head end for the following strip to cast. The imperfect material drops into a scrap receptacle 26, which is movable on a scrap receptacle guide. The scrap receptacle 26 is located in a scrap receiving position beneath the caster and forms part of a sealed enclosure 27 as described below. The enclosure 27 is typically water cooled. At this time, a water-cooled apron 28 that normally hangs downwardly from a pivot 29 to one side in the enclosure 27 is swung into position to guide the clean end of the strip 21 onto the guide table 30 and feed the strip 21 through the pinch roll stand 31. The apron 28 is then retracted back to the hanging position to allow the strip 21 to hang in a loop beneath the casting rolls in enclosure 27 before the strip passes to the guide table 30 where it engages a succession of guide rollers. [0040] The sealed enclosure 27 is formed by a number of separate wall sections that fit together with seal connections to form a continuous enclosure that permits control of the atmosphere within the enclosure. Additionally, the scrap receptacle 26 may be capable of attaching with the enclosure 27 so that the enclosure is capable of supporting a protective atmosphere immediately beneath the casting rolls 12 in the casting position. The enclosure 27 includes an opening in the lower portion of the enclosure, lower enclosure portion 44, providing an outlet for scrap to pass from the enclosure 27 into the scrap receptacle 26 in the scrap receiving position. The lower enclosure portion 44 may extend downwardly as a part of the enclosure 27, the opening being positioned above the scrap receptacle 26 in the scrap receiving position. As used in the specification and claims herein, "seal", "sealed", "sealing", and "sealingly" in reference to the scrap receptacle 26, enclosure 27, and related features may not be completely sealed so as to prevent atmospheric leakage, but rather may provide a less than perfect seal appropriate to allow control and support of the atmosphere within the enclosure as desired with some tolerable leakage.

[0041] A rim portion 45 may surround the opening of the lower enclosure portion 44 and may be movably positioned above the scrap receptacle, capable of sealingly engaging and/or attaching to the scrap receptacle 26 in the scrap receiving position. The rim portion 45 may be movable between a sealing position in which the rim portion engages the scrap receptacle, and a clearance position in which the rim portion 45 is disengaged from the scrap receptacle. Alternately, the caster or the scrap receptacle may include a lifting mechanism to raise the scrap receptacle into sealing engagement with the rim portion 45 of the enclosure, and then lower the scrap receptacle into the clearance position. When sealed, the enclosure 27 and scrap receptacle 26 are filled with a desired gas, such as nitrogen, to reduce the amount of oxygen in the enclosure and provide a protective atmosphere for the strip 21.

[0042] The enclosure 27 may include an upper collar portion 27A supporting a protective atmosphere immediately beneath the casting rolls in the casting position. When the casting rolls 12 are in the casting position, the upper collar portion is moved to the extended position closing the space between a housing portion adjacent the casting rolls 12, as shown in FIG. 2, and the enclosure 27. The upper collar portion may be provided within or adjacent the enclosure 27 and adjacent the casting rolls, and may be moved by a plurality of actuators (not shown) such as servo-mechanisms, hydraulic mechanisms, pneumatic mechanisms, and rotating actuators.

[0043] As illustrated in FIGS. 3 A and 3B, in one exemplary embodiment, a side dam 20 comprises a body 102 formed of refractory material and generally shaped to a triangular form. The body 102 has: (1) opposing edge portions 106 spaced apart in a widthwise direction, each of which area adapted to engage end portions of casting rolls 12 of the twin roll caster (as shown for example in FIG. 2); (2) a nip portion 126 adapted to be adjacent the nip 18 between the casting rolls 12 (as shown in FIG. 2); and, (3) an upper portion 103 extending across the side dam 20 to form a lateral restraint for forming a casting pool 19 (see FIG. 2) of molten metal during operation in a twin roll caster. Side dam 20, as well as body 102, has a front side 102F for engaging the end portion of any casting roll, and a rear side 102R from which mounting pins 108 extend for use in mounting the side dam onto a side dam holder. Of course, other mechanisms other than, or in addition to, mounting pins 108 may be employed for mounting any side dam onto a side dam holder. As further described below, the center of side dam 20, and in particular nip portion 126, may be kept horizontally centered relative to nip 18 by side-to-side adjustment (also referred to as "horizontal adjustment") of side dam 20. Vertical adjustment to the position of the side dam relative to the pair of casting rolls is employed to maintain proper alignment of the side dam relative the outer diameter of the casting rolls, which may change or vary over time, such as when each side dam wears over time during its use or when replacing a casting roll with a differently sized casting roll. Positional adjustment of the side dam provides improved casting performance by providing better balanced friction forces between each casting roll (the entry and delivery rolls) and the side dam.

[0044] With continued reference to FIGS. 3 A and 3B, optionally, side dam 20 may have a pocket 105 between 5 and 50 mm in depth formed in the body between edge portions 106 and forming shoulder portions 104 in the body between the edge portions 106. The pocket 105 is adapted to be worn as a casting campaign continues until the pocket is reached, and continues to be worn away at level of base portions of the pocket until casting is completed. The pocket 105 may be between 5 and 35 mm in depth. Alternatively, the pocket 105 may be between 5 and 25 mm in depth or between 10 and 20 mm in depth. The shoulder portions 104, which start from the edge portions 106 of the body 102 and ends at the edge of the pocket 105 may be between 10 and 20 mm in width. Alternatively, the shoulder portions may be between 12 and 18 mm. These widths of the shoulder portions are measured at the upper start of the shoulder portions (identified as 121) and a location 3 mm up from the bottom of the pocket (identified as 123). It should be noted that the shoulder portions are typically not the same along their respective lengths.

[0045] With reference now to an exemplary embodiment of a side dam holder, which is configured to receive the side dam previously described, in particular embodiments, FIG. 4A and FIG. 4B depict front-facing and side views, respectively, of an exemplary embodiment of a side dam holder plate 130 (also referred to more simply as a "side dam plate"), which forms a portion of a side dam holder, such as is shown in FIGS. 7 A and 7B. The side dam plate 130 includes horizontally opposed and spaced-apart side edges 131 that correspond to the edge portions 106 of the side dam 20 (see FIG. 3). The side dam plate also includes plurality of apertures 132 into which mounting pins of a side dam holder plate mount (such as describe below) may be secured. While apertures 132 may be cylindrical or any other shape, in the embodiment shown, apertures are elongated in a horizontal direction, such as to form elliptic cylinders in certain instances. Apertures 132 are arranged to correspond to an arrangement of pins on the side dam holder plate mount to permit the insertion of each pin into a corresponding aperture. Guides 134 receive corresponding pins extending from the back surface of the side dam to permit the side dam to operably engage the side dam plate.

[0046] An exemplary embodiment of a side dam holder plate mount 140 is shown in FIGS. 5A-5C. As noted previously, side dam holder plate mount 140 (also referred to more simply as a "side dam plate mount") is configured to receive the side dam plate 130 shown in FIGS. 4A and 4B. Side dam plate mount 140 has a body having a generally triangularly- shaped body 141 from which a plurality of pins 142 extend from along a front face 143 of the side dam plate mount. Body 141 can be described as having horizontally spaced-apart, opposing sides 144, which is similarly shaped to and arranged as side edges 131 of side dam plate 130 (see FIGS. 4A, 4B), although this is not necessary so long as body 141 is shaped so not to contact any of the casting rolls during use. The plurality of pins 142 is arranged to correspond to the apertures of any side dam plate (such as with apertures 132 of side dam plate 130 in FIGS. 4A, 4B) for the purpose of receiving and maintaining a side dam plate in an installed arrangement thereon. As FIGS. 5B and 5C show, while the plurality of pins 142 extend from front face 143 of the side dam plate mount 140, a first mounting structure 146 extends outwardly from back face 145, where front face 143 and back face 145 define the thickness of body 141. First mounting structure 146 is configured to attach side dam plate mount 140 to a side dam support that also engages a side dam cylinder on the opposing side (opposite) the side dam holder plate mount. In particular, at least a portion of the first mounting structure 146 includes features configured to interoperate or interconnect with corresponding features arranged along a side dam support. For example, first mounting structure 146 includes a projection 147 having an aperture 148 configured to receive a fastening member (not shown) for both (1) securing the side dam plate mount 140 to a side dam support (e.g., see 160 in FIG. 6A, 6B) and (2) vertically adjusting the position of the side dam plate mount 140 (and therefore the side dam plate) relative to the side dam support. In certain embodiments, the fastening member, and therefore, the aperture, is threaded, although other alternatives known to one of ordinary skill for the purpose of securing and altering the relative position between the side dam plate mount and side dam support may be employed. Other portions of the mounting structure may be adapted to permit vertical movement between the side dam plate mount and the side dam support when desiring to adjust the vertical position of the side dam plate and side dam plate mount, or more generally, the side dam. For example, passage 149, which is configured to receive a shaft (not shown) used in part to attach the side dam holder plate mount to the side dam support, is vertically elongated to permit vertical movement of the shaft when needing to vertically adjust the side dam relative to the casting rolls.

[0047] An exemplary embodiment of a side dam support 160 is shown in FIGS. 6 A and 6B. Side dam support 160 is configured to operably attach to the side dam plate mount 140 shown in FIGS. 5A-5C. The side dam support 160 includes a body 161 and is configured to engage a side dam cylinder (not shown) within a cylindrical recess 163 arranged along a front face 162 of the side dam support body 161. Extending outwardly from a back side 164 of the side dam support body 161 is second mounting structure 165, said mounting structure being at least partially configured to cooperatively interconnect with at least a portion of the first mounting structure 146 of the side dam plate mount 140 (see FIG. 5B) to facilitate attachment between the side dam plate mount 140 and the side dam support 160. Specifically, in the embodiment shown, second mounting structure 165 includes a projection 166 extending from back side 164 and having an aperture 167 configured to receive a fastening member (not shown) for both (1) securing the side dam holder plate mount to a side dam support and (2) vertically adjusting the position of the side dam holder plate mount relative to the side dam support. In certain embodiments, the fastening member, and therefore, the aperture, is threaded, although other alternatives known to one of ordinary skill for the purpose of securing and altering the relative position between the side dam holder plate mount and side dam support may be employed. Other portions of the mounting structure may be adapted to permit vertical movement between the side dam holder plate mount and the side dam support when desiring to adjust the vertical position of the side dam plate and side dam holder plate mount, and thus the side dam itself is positionally adjusted. In the embodiment shown, second mounting structure 165 includes additional structure 168 configured for attaching the side dam support to the side dam holder plate mount. In particular, structure 168 forms a pair of projections where each projection includes an aperture 169 configured to receive a shaft, which may be a fastening member in certain instances. The shaft, as discussed above in association with an embodiment of the side dam holder plate mount, also extends through a passage 149 in the side dam holder plate mount first mounting structure 146 (see FIG. 5B) when the side dam holder plate mount and the side dam support are attached to one another. Just as passage 149 may be optionally elongated to facilitate vertical adjustments of the side dam relative the casting rolls, optionally each aperture 169 may be vertically elongated to facilitate the same vertical adjustments.

[0048] To facilitate horizontal adjustments of the side dam relative to the casting rolls, in the embodiment shown in FIGS. 6A and 6B, horizontal adjustment is accomplished by moving horizontally the side dam support relative 160 to the side dam cylinder (not shown) when extending into recess 163 on front face 162 during use. With regard to the embodiment shown, this is accomplished, at least in part, by use of horizontal adjustment members (not shown) which extend through apertures 171 in horizontal side structure 170 to engage opposing horizontal sides of the side dam cylinder and to adjust the horizontal position of the side dam cylinder within and relative to the recess. In the present embodiment, a horizontal adjustment member (not shown) comprises a fastener, such as a threaded bolt with or without one or more nuts, configured to selectively extend through any such aperture 171, which may or may not be threaded as accommodate any such horizontal adjustment member. Recess 163 is oversized to permit horizontal movement of the side dam cylinder within recess 163. By adjusting the horizontal location of the side dam cylinder within recess 163, the side dam support 160 together with the side dam plate mount 140 and side dam plate 130 move horizontally to adjust the side dam horizontal position relative to the casting rolls. In the embodiment shown horizontal side structures 170 form tabs or projections; however, it is contemplated that other structures may be employed within which to arrange apertures 171. For example, apertures may be arranged within body 161 such to extend into the recess from a horizontal side of the recess, such as when the recess is sufficiently deep to provide a side sufficiently sized to accommodate the aperture. Optionally, vertical adjustment members arranged on opposing vertical sides of the recess may be employed to control the vertical position of the side dam cylinder within a sufficiently oversized recess. This optional vertical adjustment mechanism may be employed in addition to or in the alternative to the vertical adjustment mechanism discussed previously, for the purpose of adjusting the vertical position of the side dam relative to the casting rolls. It is also noted that projections may extend from an end of the side dam cylinder (not shown) and extend into apertures 172 arranged within recess 163 to better constrain the side dam cylinder within the recess. These projections may form a portion of the side dam cylinder or may form other structures, such as fasteners or pins, extending into the end of the side dam cylinder. To facilitate horizontal movement of the side dam support relative to the side dam cylinder, apertures 172 may be horizontally elongated.

[0049] With reference now to FIG. 7A, side dam 20, side dam plate 130, side dam plate mount 140, and side dam support 160 are shown partially assembled. In particular, side dam 20 is shown mounted onto side dam plate 130, while side dam plate mount 140 is shown operably attached to side dam support 160, with a side dam cylinder 180 arranged within recess 163 of side dam support 160. Side dam plate 130 is shown for installation upon side dam plate mount 140. With reference to FIG. 7B, the side dam plate is shown installed upon side dam plate mount 140. In each figure, consistent with the prior description, a fastener 173 with a nut is arranged within the aperture extending through projection 166 to facilitate vertical adjustments. Likewise, consistent with the prior description, horizontal adjustment members 174 comprising threaded bolts with nuts are arranged to extend through structure 170 and into engagement with side dam cylinder 180 to facilitate horizontal adjustments. This is also shown in an alternative view in FIG. 7C. By adjusting the extent by which each of fastener 173 and horizontal adjustment members 174 extend through each corresponding aperture, corresponding vertical and horizontal adjustments may be accomplished. Such unequal gaps or contact may remain even after vertical adjustment of the side dam. Through vertical and/or horizontal adjustment of the adjustable side dam plate mount 140, the position of a side dam 20 can be changed during continuous casting to minimize extra ledge thicknesses, eliminate snake egg and skull defects, and increase the useful life of casting rolls as the casting rolls are periodically ground down and refurbished, as further described herein.

[0050] As previously explained, adjusting the side dam holder allows for consistent contact area between the casting rolls and the side dams. In particular, an adjustable side dam holder extends the diameter range for casting rolls that may be used with the side dam while maintaining a minimum contact area between a casting roll and the side dam. FIGS. 8A-8C provide exemplary illustrations of how an adjustable side dam holder, as described herein, can extend the range of diameters for casting rolls that may be used in casting campaigns, and that can extend the useful life of casting rolls, which for example have been machined or ground out to remove cracks and other defects resulting in a reduced diameter. FIG. 8A illustrates a side dam 20 positioned in relation to a casting roll 201 having an original diameter of 500 mm and casting roll 202 has a diameter of 476 mm. Generally, an optimal gap distance of about 2.5 mm should be maintained between a casting roll and side dam pocket to minimize extra ledge thickness of the continuous strip formed at the side dam; extra ledge thickness at the side dam can significantly increase the formation of skulls and snake egg defects, as described above. When adjusting from the first casting roll 201 of 500 mm diameter to the second casting roll 202 of 476 mm diameter, the gap distance increases from 2.5 mm to about 4.1 mm, allowing an extra ledge thickness of about 1.6 mm to form as extra molten metal gathers in the gap between the casting roll and the side dam. As depicted further in FIG. 8A, below, this additional 1.6 mm gap distance can significantly increase incidences of snake egg defects in the steel strip. As illustrated by FIG. 8B, however, by adjusting side dam 20 downward by 3 mm the gap distance between casting roll 202 and the side dam pocket is reduced to result in an extra ledge thickness of only 0.3 mm, a negligible increase over the optimal 2.5 mm gap that facilitates minimizing snake egg defects. This is further depicted in FIG. 8C, as described below. [0051] FIG. 8C depicts side dam 20 in relation to casting roll 202, having a diameter of 476 mm, and in relation to a third casting roll 203, having a further reduced diameter of 466 mm.

[0052] Generally, as shown in FIG. 8C, it is generally desirable to maintain a contact size 202a, 203a between side dam 20 and a side of a casting roll of about 7.5 mm; contact sizes lower than 7.5 mm may produce defects in the steel strip, as described above. In casting systems where side dam 20 cannot be adjusted, the smallest casting roll diameter that can be used is about 476 mm, such as second casting roll 202, as the contact size 202a between the side dam and the casting roll is about 7.5 mm. By adjusting side dam 20 downward by about 2.9 mm, as shown in FIG. 8C, third casting roll 203 with a diameter of about 466 mm can be used while still maintaining a contact size 203a of about 7.5 mm between the third casting roll 203 and side dam 20. The adjustable side dam 20 thus permits use of smaller casting rolls than are currently usable in casting systems with static, non-adjustable side dams. Typically, casting rolls are ground down from an initial diameter, such as about 500 mm, to a smaller diameter to remove cracks and other defects caused by continuous use of the casting rolls in casting campaigns. Smaller, casting rolls can continue to be ground down and refurbished and re-used until they are too small to effectively be used further. In current casting systems with non- adjustable side dams, casting rolls can be refurbished through multiple casting cycles until they are ground down to about 476 mm, below which the casting rolls cannot maintain sufficient contact with the side dams. By adjusting the side dams downward, casting rolls can be reused through several more casting cycles until they have ground down below 476 mm. In the example illustrated by FIG. 8C, extending the use of casting rolls from 476 mm down to 466 mm, through use of the adjustable side dams, increases the effective useful life of casting rolls by about 40%, which may represent significant cost savings as casting rolls can be reused longer without needing complete replacement.

[0053] As illustrated by the graphs depicted in FIG. 9A, inconsistent contact between the casting roll and the side dam (in this case a pocket side dam) results in side dam instability and movement, which results in the formation of snake eggs. The molten metal accumulates in the gap between the casting roll and the side dam forming skulls, which eventually drop and form snake eggs. The presence of the snake eggs is evident by the spikes in the graphs. The presence of skulls is detected by the lateral forces they exert on the casting rolls as they pass between them at the nip. Skulls also cause visible bright bands, i.e., snake eggs, to be formed across the width of the strip, which are defects in the surface of the cast strip. During testing, the presence of snake egg forming skulls was monitored by measuring the drive-side (DS) casting roll force (Newtons) and the work-side (WS) casting roll force (Newtons).

[0054] FIG. 9A, includes two graphs, a work-side (top graph) and a drive-side (bottom graph) of casting roll force measured over time when using previous standard side dams. The drive-side casting roll force showed peaks in excess of 12500 N. The work-side casting roll force showed peaks in excess of 15000 N. Each peak represents one or more skulls dropping and travelling through the nip of the casting rolls, causing snake eggs, and exerting a lateral pressure on the casting rolls measured by a force detector. When these skulls drop between the roll nip, they may cause the two solidifying shells at the casting roll nip to "swallow" additional liquid metal between the shells, and may cause the strip to reheat and break disrupting the continuous production of casted strip. As illustrated in FIG. 9A, multiple strip break peaks were observed, as illustrated by the spikes corresponding to sudden increases in gap force (vertical axes) during casting over time (horizontal axes). As both the two graphs of FIG. 9A also show, the frequency and size of the spikes both increased as casting continued over time and the gap between casting roll and side dam increased, indicating increased defects in the cast steel.

[0055] In contrast, as illustrated in FIGS. 9B and 9C, when an adjustable side dam holder is used, the distance between the side dam and the casting roll may be adjusted to minimize or even eliminate incidences of snake egg defects. The adjustable side dam holder permits for the side dam holder and supported adjacent side dam to be moved vertically up to 15 mm or up to 25 mm and horizontally up to 15 mm or up to 25 mm to accommodate for different diameter casting rolls. For example, the side dam may be moved vertically and/or horizontally to maintain or increase the contact area between the casting roll and side dam as desired, such as to allow the use of casting rolls down to about 466 mm in diameter. An adjustable side dam holder can selectively maintain the same or similar gap between the side dam pocket edge and casting roll edge different diameter rolls are applied against the pocket side dam. Therefore, with an adjustable side dam holder it is not necessary to change the pocket size for different sized casting rolls. For example, and with particular reference to FIG. 8C, an extra 1.6 mm ledge was created on the side dam when a large diameter casting roll is switched to a small diameter casting roll and an adjustable side dam was not utilized. The extra 1.6 mm ledge on the pocket side dam has the potential to create serious snake eggs break. As indicated in FIGS. 8A-8B, an adjustable side dam is capable of maintaining the gap between the side dam pocket and the casting roll edge when switching between different sized rolls. In the present examples, the optimal gap distance that works for both casting rolls is 2.5 mm. In contrast to the casting campaign illustrated by the graphs in FIG. 9A, no significant spikes appear in the graphs of FIG. 9B aside from the beginning spike, indicating that the adjustment of the side dam relative to the casting rolls eliminated skulls and snake egg defects in the steel. FIG. 9C depicts graphs illustrating another casting campaign with no side dam adjustment. In this example, occasional spikes near the beginning of the campaign (magnified in the cut-out graphs to the left) as well as a few spikes near the end of the campaign (magnified in the cut-out graphs to the right) correspond to the snake eggs created due to the extra ledges being broken off the side dam without side dam adjustment. The amount of roll gap open indicates the size of snake egg caused by the extra ledge going through the nip point which are shown in the bottom of two magnified figures.

[0056] FIG. 10 shows a comparison between two side dams after casting. On the left side, side dam 310 was used and assembled with a non-adjustable side dam holder; on the right side, side dam 320 was used and assembled with an adjustable side dam holder, such as an adjustable side dam holder as described herein. Side dam 320 was lowered by 5 mm relative to casting rolls during a continuous casting campaign to maintain a desired contact area between the side dam and the casting roll. As observed, the inner edge 325 of the side dam 320 has a straight, evenly worn appearance. The even wear of side dam 320 may correspond, for example, to the casting campaign illustrated in the graphs of FIG. 9B. By contrast, side dam 310 shows a step 315 and tilted line 312 on the edge 311 of the side dam. The step and tilted line on the edge of the side dam indicate that there was insufficient contact between the side dam and the casting roll during casting. The side dam was not stable. The uneven wear of side dam 310 might be expected to be similar to the casting campaigns illustrated in the graphs of FIG. 9A in which the side dam was not adjusted during casting.

[0057] While it has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from its scope. Therefore, it is intended that it not be limited to the particular embodiments disclosed, but that it will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMS What is claimed is:

1. An adjustable side dam holder configured to receive and retain a side dam formed of refractory material and having edge portions adapted to engage a corresponding end portion of each casting roll of the twin roll caster during casting, the side dam holder being vertically and/or horizontally adjustable relative to the casting rolls to permit the side dam to be moved vertically and/or horizontally, respectively, relative to the end portion of each of the casting rolls to maintain engagement between the side dam and the corresponding end portion of the casting rolls.

2. The adjustable side dam holder of claim 1, wherein the holder is operatively

connected to a side dam plate on which the side dam may be mounted.

3. The adjustable side dam holder of claim 1, wherein the holder is vertically adjustable up to 15-25 millimeters (mm).

4. The adjustable side dam holder of claim 1, wherein the holder horizontally adjustable up to 15-25 mm.

5. A side dam apparatus for a twin roll caster for forming thin metal strips comprising:

(a) a side dam formed of refractory material and having edge portions adapted to engage an end portion of each casting roll of the twin roll caster; and,

(b) an adjustable side dam holder configured to receive and retain the side dam, the side dam holder being vertically and/or horizontally adjustable relative to the casting rolls to permit the side dam to be moved vertically and/or horizontally relative to the end portion of each of the casting rolls to maintain engagement between the side dam and the corresponding end portion of the casting rolls.

6. The side dam apparatus of Claim 5, where the side dam holder includes a side dam plate upon which the side dam is mounted and a side dam plate mount that includes a plurality of pins, and where the side dam plate includes a plurality of apertures each configured to receive a corresponding pin of the plurality of pins of the side dam plate mount.

7. The side dam apparatus of Claim 5, where the side dam plate mount is configured for operable attachment to a side dam support, where operable attachment is vertically adjustable to provide vertical adjustment of the side dam plate mount.

8. The side dam apparatus of Claim 7, where the operable attachment includes a

threaded fastener extending vertically through each of the side dam plate mount and the side dam support.

9. The side dam apparatus of Claim 5, where the side dam plate mount is configured to be operably attached to a side dam support, and where the side dam support is configured to engage a side dam cylinder, where the side dam support includes a pair of horizontal adjustment members extending between the side dam support and the side dam cylinder, the pair of horizontal adjustment members configured to selectively move the side dam support horizontally relative to the side dam cylinder to provide horizontal adjustment of the side dam holder.

10. The side dam apparatus of Claim 9, where each of the pair of horizontal adjustment members includes a threaded fastener extending horizontally through an aperture in the side dam plate mount.

11. The side dam apparatus of Claim 5, where the side dam is a first side dam and further comprising a second side dam, wherein the first side dam is installed with the second side dam on the twin roll caster.

12. The side dam apparatus of Claim 5, where each side dam includes a pocket between 5 and 50 mm in depth arranged between the edge portions and forming shoulder portions in the body between the edge portions and the pocket.

13. A method of casting metal strip comprising: counter-rotating a pair of casting rolls laterally positioned to form a nip there between through which thin metal strip can be cast;

where each of a pair of confining side dams are arranged adjacent to a corresponding end portion of the pair of casting rolls and thereby confine a casting pool of molten metal supported on casting surfaces of the pair of casting rolls above the nip, each side dam of the pair of side dams having edge portions adapted to engage end portions of the pair of casting rolls;

where a side dam holder is arranged adjacent to each side dam of the pair of side dams, each side dam holder configured to receive one side dam of the pair of side dams in a mounted configuration and being vertically and/or horizontally adjustable to permit the side dam holder and mounted side dam to be moved vertically and/or horizontally, respectively, relative to the corresponding end portion of each of the casting rolls, and

vertically and/or horizontally adjusting the side dam holder to move the side dam holder and mounted side dam relative to the corresponding end portion of each of the casting rolls to maintain engagement between each side dam and the corresponding end portion of the casting roll.

The method of casting metal strip of Claim 13, wherein each side dam holder includes a side dam plate mount and a side dam plate configured to receive one of the pair of side dams in the mounted configuration, the side dam plate mount including a plurality of pins and the side dam plate including a plurality of apertures each configured to receive a corresponding pin of the plurality of pins from the side dam holder.

The method of casting metal strip of Claim 13, where each side dam plate mount is operably attached to a side dam support, where operable attachment is vertically adjustable to provide vertical adjustment of the side dam plate mount.

The method of casting metal strip of Claim 15, where the operable attachment includes a threaded fastener extending vertically through each of the side dam plate mount and the side dam support.

The method of casting metal strip of Claim 15, where the side dam support engages a side dam cylinder, where the side dam support includes a pair of horizontal adjustment members extending between the side dam support and the side dam cylinder, the pair of horizontal adjustment members configured to selectively move the side dam support horizontally relative to the side dam cylinder to provide horizontal adjustment of the side dam plate mount.

18. The method of casting metal strip of Claim 17, where each of the pair of horizontal adjustment members includes a threaded fastener extending horizontally through an aperture in the side dam plate mount.

19. The method of casting metal strip of Claim 13 where each side dam has formed therein a pocket between 5 and 50 mm in depth between the edge portions and with shoulder portions between the edge portions.