Mold Casting Surface Cooling

Abstract

The present invention relates to a method, system, and apparatus for improving the efficiency of a continuous casting operation. The continuous casting mold component described herein includes a mold wall substrate having a groove near a bottom of the mold wall substrate, the continuous casting mold component further includes a graphite liner having a bottom edge with a first inclined surface and a top edge with a second inclined surface, the bottom edge being received within the groove of the mold wall substrate, and the continuous casting mold component further includes a clamping element having an inclined clamping surface attached to the mold wall substrate by at least one fastener, the bottom inclined surface of the graphite liner being driven into the groove of the substrate in response to the inclined clamping surface of the clamping element engaging the second inclined surface of the graphite liner and the fastener urging the clamping element toward the mold wall substrate.

Description

[Technical field]

[0001] The present invention relates to methods, systems, and apparatus for improving the efficiency of continuous casting operations, and more particularly to techniques for promoting effective cooling of the casting face of a continuous casting mold wall.

[0002] [Citation to Related Applications] This application claims priority to U.S. Patent Application No. 17 / 651,708, filed February 18, 2022, which is incorporated by reference in its entirety. [Background technology]

[0003] Metal products can be formed in a variety of ways, but numerous forming methods require ingots, billets, etc., to serve as raw materials from which the metal end product can be produced, for example, by rolling or machining. One method of producing an ingot or billet is by a semi-continuous casting process called direct chill casting, in which a vertically oriented mold cavity is placed above a platform that translates vertically down the casting pit. A starter or starter block may be positioned on the platform to form, at least initially, the bottom of the mold cavity to begin the casting process. Molten metal is poured into the mold cavity, where it cools, typically with the use of a cooling fluid. The platform with the starter block on it may be lowered into the casting pit at a predetermined rate, allowing the metal leaving the mold cavity and descending with the starter block to solidify. The platform continues to be lowered as the quantity of molten metal enters the mold cavity, thereby causing the solid metal to exit the mold cavity. This continuous casting process allows metal ingots and billets to be shaped to conform to the mold cavity profile with a length limited only by the casting pit depth and the hydraulic platform moving within the casting pit. Maintaining the casting surfaces of the mold walls below a temperature above the minimum temperature at which the casting surface lubricant will burn or evaporate is important in ensuring casting quality and consistency. Summary of the Invention

[0004] The present invention relates to methods, systems, and apparatus for improving the efficiency of continuous casting operations, and more particularly to techniques for promoting effective cooling of the casting face of a wall of a continuous casting mold. The embodiments described herein employ a graphite casting surface in the form of a graphite liner received at a mold wall substrate. The graphite liner is configured to securely engage the mold wall substrate, thereby maximizing contact between the rear surface of the graphite liner and the mold wall substrate to maximize heat transfer from the graphite liner through the mold wall substrate to a cooling fluid. Embodiments described herein include a continuous casting mold component including a mold wall substrate having a groove near a bottom of the mold wall substrate, the continuous casting mold component further including a graphite liner having a bottom edge with a first inclined surface and a top edge with a second inclined surface, the bottom edge being received into the groove of the mold wall substrate, the continuous casting mold component further including a clamp or clamping element with an inclined clamping surface attached to the mold wall substrate by at least one fastener, the bottom inclined surface of the graphite liner being driven into the groove of the mold wall substrate in response to the inclined clamping surface of the clamping element engaging the second inclined surface of the graphite liner and the fastener pressing the clamping element toward the mold wall substrate.

[0005] According to some embodiments, the graphite liner has a rest state and an installed state, where the graphite liner has a curve along a back face of the graphite liner between a top edge and a bottom edge in the rest state, where the back face is straightened in response to the fasteners pressing the clamping element against the mold wall substrate in the installed state. According to some embodiments, the curve of the back face of the graphite liner has a curve profile, where in the installed state, a force is applied by the graphite liner to the mold wall substrate in response to the fasteners pressing the clamping element against the mold wall substrate. The curve profile of some embodiments is configured to concentrate the force applied by the graphite liner to the mold wall substrate in the installed state at a lower third of the graphite liner.

[0006] In some embodiments, the mold wall substrate further includes a substrate angled surface near the top of the mold wall substrate, and the clamping element includes an angled drive surface that cooperates with the angled drive surface to drive the clamping element toward the bottom of the mold wall substrate in response to the fastener forcing the clamping element toward the mold wall substrate. The fastener in the illustrated embodiment comprises a threaded fastener, and the clamping element includes a slot for receiving the threaded fastener, the threaded fastener being received into a threaded hole in the mold wall substrate. The slot in the clamping element, in some embodiments, has a relatively narrow dimension in an axial direction along which the mold wall substrate extends, and a relatively long dimension extending in a direction toward the bottom of the mold wall substrate. The clamping element in some embodiments is driven toward the bottom of the mold wall substrate in response to the threaded fastener being tightened and threaded into the threaded hole in the mold wall substrate. The graphite liner of example embodiments has a first thickness near a top edge of the graphite liner and a second thickness near a bottom edge, the first thickness being greater than the second thickness. The graphite liner of some embodiments tapers from the first thickness to the second thickness.

[0007] In some embodiments, the first bevel of the graphite liner is a first chamfer from the aft surface of the graphite liner to the casting surface of the graphite liner, and the second bevel of the graphite liner is a second chamfer from the aft surface of the graphite liner to the casting surface. In some embodiments, the first chamfer forms an angle between the aft surface and the second bevel of about 20°-60°, and the second chamfer forms an angle between the aft surface and the first bevel of about 20°-60°. In some embodiments, the first chamfer forms an angle between the aft surface and the second bevel of about 45°, and the second chamfer forms an angle between the aft surface and the first bevel. In some embodiments, the mold wall substrate has a convex curve between the groove in the mold wall substrate and the clamping element, and the graphite liner is forced to bend around the convex curve in the mold wall substrate when in an attached position fixed relative to the mold wall substrate by the clamping element.

[0008] Embodiments described herein include a method comprising forming a graphite liner for a continuous casting mold, the graphite liner having a rear surface and a casting surface, wherein in a rest state, the graphite liner comprises a convex curve along the rear surface, and comprising attaching the graphite liner to a mold wall substrate, the attaching of the graphite liner to the mold wall substrate comprising inserting a bottom sloping surface of the graphite liner into a groove provided near a bottom of the mold wall substrate, and further comprising engaging a top sloping surface of the graphite liner with a clamping element provided near a top of the mold wall substrate, and clamping the sloping top edge of the graphite liner to the mold wall substrate, wherein in the attached state, the graphite liner comprises a flat rear surface.

[0009] According to an exemplary embodiment, clamping the sloping top edge of the graphite liner to the mold wall substrate includes driving a clamping element toward the mold wall substrate, the clamping element having a sloping clamping surface configured to engage the sloping top edge of the graphite liner and drive into the sloping bottom edge groove of the graphite liner as the clamping element is driven toward the mold wall substrate. Clamping the sloping top edge of the graphite liner to the mold wall substrate includes exerting a force on the mold wall substrate with a convex curve of the mold wall substrate, the force being concentrated near a bottom third of the height of the graphite liner.

[0010] Embodiments described herein include a continuous casting mold having a mold wall substrate and a graphite liner having a rest state and a mounted state, the graphite liner having a rear surface and a casting surface, the graphite liner having a curved portion between a top edge of the graphite liner and a bottom edge of the graphite liner in the rest state, the curved portion being convex along the rear surface, the continuous casting mold further having attachment means for attaching the graphite liner to the mold wall substrate and for flattening the rear surface of the graphite liner against the mold wall substrate in the mounted state, the attachment means having a channel for receiving the bottom edge of the graphite liner and a clamping element configured to clamp the top edge of the graphite liner against the mold wall substrate. The clamping element has a first angled surface and the top edge of the graphite liner has a second angled surface complementary to the first angled surface, the first angled surface engaging the second angled surface to secure the graphite liner to the mold wall substrate. The continuous casting mold component of an example embodiment further includes a fastener configured to secure the graphite liner to the mold wall substrate.

[0011] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 illustrates an exemplary embodiment of a prior art DC casting process. [Diagram 2] FIG. 1 illustrates an ingot formed by a prior art DC casting process. [Diagram 3] FIG. 2 is a top view of a DC casting mold with bendable sides to an uncurved state in accordance with an exemplary embodiment of the present invention. [Figure 4] FIG. 2 is a top view of a DC casting mold with bendable sides into a curved state in accordance with an exemplary embodiment of the present invention. [Diagram 5] FIG. 2 is a cross-sectional view of a mold sidewall having a graphite liner with a casting surface in accordance with an exemplary embodiment of the present invention. [Figure 6] FIG. 13 is another cross-sectional view of a mold sidewall with a graphite liner and clamping mechanism with a casting surface according to an exemplary embodiment of the present invention. [Figure 7] 1A-1C show graphite liners in both rest and installed states along with the forces exerted by the graphite liner in the installed state in accordance with an exemplary embodiment of the present invention. [Figure 8] FIG. 1 is a plot showing the relationship between thermal contact resistance and contact pressure, reflecting heat transfer characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Exemplary embodiments of the present invention will now be described in more detail below with reference to the accompanying drawings, in which some, but not all, embodiments of the present invention are set forth. Indeed, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather, these embodiments are provided so that this disclosure will satisfy applicable statutory requirements. Like reference characters refer to like elements throughout.

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to methods, systems, and apparatus for improving the efficiency of continuous casting operations, and in particular to techniques for facilitating effective cooling of the casting face of the walls of a continuous casting mold. For a casting operation to function effectively and properly, the walls of the continuous casting mold must allow the casting material to pass through the mold as it begins to cool. The walls of the continuous casting mold may be lubricated to facilitate this. Additionally, graphite may be used as the inner surface of the walls of the continuous casting mold to promote smooth flow of the casting material through a low friction surface. According to some embodiments, oil or grease is spread on the inner surface of the walls of the continuous casting mold. The oil or grease is consumed as it travels to the surface of the graphite facing the casting material. It is important that the graphite remains cool and below the operating temperature of the lubricant, or the lubricant will bake onto the surface of the graphite, making it shiny like glass, thereby preventing the oil from migrating in and out of the graphite.

[0015] A typical continuous casting mold or DC casting mold is water cooled. Water can be used to cool the mold walls through channels that run along the mold walls and direct the cooling water across the back of the mold wall to pull heat out of the mold wall. Using a technique that transfers heat from the mold wall by thermal conduction to the cooling water flowing through channels along the mold wall can help keep the mold sidewalls and graphite at a suitable temperature without risking the lubricant from burning. The embodiments provided herein help transfer heat from the graphite to the mold wall by forcing the graphite into the mold wall, which is typically made of aluminum. The high interface pressure provides good heat transfer.

[0016] Vertical DC casting or continuous casting (sometimes referred to in the art as "semi-continuous casting") is a process used to make ingots that may have large cross sections that can be used in a variety of manufacturing applications. The vertical DC casting process begins with a horizontal table or mold frame having one or more vertically oriented mold cavities. Each of the mold cavities is initially closed at its bottom with a starter block or starter plug to seal the bottom of the mold cavity. Molten metal is introduced into each mold cavity from a metal distribution system to fill the mold cavity. As the molten metal near the bottom of the mold adjacent to the starter block solidifies, the starter block is moved vertically downward along a linear path. The starter block may be moved by hydraulically lowering a platform on which it is mounted. The vertical downward movement of the starter block withdraws solidified metal from the mold cavity while additional molten metal is introduced into the mold cavity. Once initiated, the process proceeds at a relatively steady state and the DC casting process forms a metal ingot having a contour shape defined by the mold cavity and a height determined by the travel depth of the platform and starter block.

[0017] During the DC casting process, the mold itself is cooled to promote solidification of the metal as the starter block is advanced downwardly prior to the metal exiting the mold cavity, and a cooling fluid is introduced to the surface of the metal located near the exit of the mold cavity as the metal is being cast, thereby drawing heat from the cast metal ingot and solidifying the molten metal within the now solidified skin of the ingot. As the starter block is advanced downwardly, a cooling fluid may be sprayed directly onto the ingot, thereby cooling the surface and drawing heat from within the ingot's core.

[0018] DC casting allows ingots to be cast in a variety of sizes and shapes with a variety of profiles. Rectangular ingots are the most common, but other profile shapes are possible. Circular billets benefit from a uniform shape, where the distance from the outer surface to the core around the billet is even all the way around. Rectangular ingots, however, lack this uniformity of surface-to-core depth and thus present additional challenges that must be considered during the DC casting process.

[0019] DC casting molds for producing ingots with rectangular contours do not have perfectly rectangular mold cavities due to deformation of the ingot as it cools after it leaves the mold cavity. The portion of the ingot leaving the mold cavity as the platform and starter block are lowered retains a molten or at least partially molten core within the skin. As the core cools and solidifies, the outer contour of the ingot changes, and as a result, the mold cavity contour does not have the same shape or contour as the final cooled ingot, although this defines the shape of the final cooled ingot.

[0020] FIG. 1 illustrates an exemplary embodiment of a conventional DC casting mold 100 that is received within a table or frame assembly of a DC casting system. As illustrated, the mold 100 has first and second opposing side walls 110, 120 that extend between a first end wall 130 and a second end wall 140 of the mold cavity. The first and second opposing side walls 110, 120 and the first and second end walls 130, 140 combine to form a mold cavity 150 having a generally rectangular contour shape. The first and second opposing side walls 110, 120 are arcuate in shape or have at least some curvature relative to the wall contour shape. This shape allows the cast ingot to have substantially flat opposing sides during the steady state casting operation of the DC casting process. The end walls 130, 140 can also take on a specified shape, such as a curved section, a series of flat sides arranged in an arc, a compound curved section, or a straight side. The "steady state" portion of the casting process described herein is the portion of the casting process after the initial start-up or start-up casting stage and before the end or final casting stage of the casting process. Steady state casting occurs when the temperature distribution of the portion of the ingot exiting the mold cavity remains constant or nearly constant. Different casting control parameters may be desired from the start-up stage to the steady state stage to the end stage based on the type of material being cast. While the exemplary embodiment of FIG. 1 shows an ingot mold shape (e.g., substantially rectangular), the embodiments described herein can employ a billet mold shape (e.g., substantially circular).

[0021] Although DC casting molds have been designed and developed to produce ingots having substantially flat sides with a rectangular profile for the ingot portion produced during the steady state portion of the casting process, the start-up process of the DC casting method presents a challenge in distinguishing the start-up casting stage process and the initial portion of the ingot formed during the start-up casting stage process from the steady state stage of the casting process and the portion of the ingot formed during the steady state casting.

[0022] During the start-up phase of semi-continuous casting, high thermal gradients induce thermal stresses that cause the ingot to deform in a manner distinct from that which occurs during the steady-state phase of casting. Due to the changes in thermal gradients and stresses that occur between the start-up and steady-state phases of casting, a mold cavity of constant contour shape results in a portion of the ingot cast during the start-up phase, also referred to as a butt, and a non-uniform contour shape of the ingot cast during the steady-state casting phase. Since the portion produced during steady-state casting forms the majority of the ingot, the mold contour shape may be designed such that the sides and opposite ends of the ingot are substantially flat. This may result in a butt of ingot that lacks the substantially flat sides formed during the start-up phase, as shown in the cast ingot cross-section of FIG. 2. The illustrated embodiment of FIG. 2 shows a basic cross-section of an ingot mold during the casting process. As shown, molten metal is received in the mold cavity between mold side walls 110, 120, where it transitions to solid metal near the sump indicated by dashed line 163. The start block 157 in the illustrated position has already been lowered with platform 159 in the direction of arrow 162, and casting is now in a steady state phase, with sides 165 of ingot 160 being substantially flat. A portion of ingot 160 produced during the start-up phase is shown adjacent start-up block 157 with a bulging profile 170 relative to the desired flat sides 175 of the steady state casting phase.

[0023] The deformation 170 of the ingot portion created during the start-up phase may not be usable depending on the end use of the ingot, and therefore the portion of the ingot formed during the start-up period may be sacrificed (i.e., cut off from the ingot and repurposed / recast). This sacrificial butt portion of the ingot may be quite large in size, especially in DC casting molds with relatively large profile shapes, and the butt may be recast, so that no material is lost, but the high temperature rate of the semi-continuous casting process is reduced as a result of the lost portion of the ingot and the loss of time, reheat / remelt costs and labor associated with the reduced maximum size availability of one ingot. Similar problems may occur at the end of the casting when forming the "head" of the ingot or billet, where the casting is no longer at steady state and may require specific control parameters to maximize the usable portion of the ingot and reduce waste.

[0024] To solve or ameliorate the above problems, DC casting molds may employ flexible opposing sidewalls that can be dynamically moved during the casting process to eliminate the butt swelling of conventional semi-continuous ingot casting molds, reducing waste, and increasing ingot casting efficiency. The DC casting molds described herein may have a pair of opposing casting surfaces on the flexible mold sidewalls that allow the sidewalls to change shape while the mold is casting the ingot. Each of the opposing sidewalls may include two or more contact portions or force-receiving elements, each configured to receive a force that dynamically moves the opposing sidewalls of the mold to change shape during the casting process. The forces applied to the two or more contact areas may be independent and may include forces in opposite directions, as further described below. The contact areas may optionally be repositionable along the length of the opposing sidewalls to allow greater control over the shape of the sidewalls due to the applied forces.

[0025] FIGURE 3 is a top view of a DC casting mold assembly 200 configured with a variable profile to improve casting quality and consistency. As shown, the mold assembly 200 includes first and second opposing sidewall assemblies 210, 220 and first and second end wall assemblies 230, 240. Each of the opposing sidewall assemblies 210, 220 includes a sidewall of the mold assembly 250 that cooperates with the end walls of the end wall assemblies 230, 240 to define a mold cavity contour shape that is the shape of the perimeter of the mold cavity. FIGURE 4 is a top view of the DC casting mold assembly 200 of FIGURE 3, where a curvature or curved portion is provided in the sidewall assemblies 210, 220.

[0026] Various mechanisms may be used to impart curvature or curves to the sidewall assemblies of the DC casting mold. In practice, however, DC casting molds are often arranged in a set of DC casting molds positioned adjacent to one another above a casting pit. The size of the casting pit and the frame above the casting pit that supports the DC casting molds limits the number of DC casting molds that can be used during a single casting run. By positioning the DC casting molds as close together as practicable, the capacity of the casting pit and the system is increased, thereby increasing the overall efficiency of the casting operation.

[0027] As mentioned above, a graphite casting surface in the form of a graphite liner can be used as a casting surface for molten aluminum. A lubricant, such as oil or grease, spread on the surface of the graphite will soak into the porous graphite. During the casting process, the oil or grease is consumed as it moves from the inside of the graphite liner to the casting surface where it is carried away or burned by the ingot. It is important that the graphite remains cool relative to the ingot so that it remains below the working temperature of the lubricant. If the temperature of the graphite liner becomes too high, the lubricant may burn onto the surface of the graphite, making it shiny, preventing the oil from migrating into or out of the graphite.

[0028] 5 shows a cross section of the sidewall 210. The mold sidewall 210 has two cooling fluid channels 250, 255. The illustrated embodiment described herein shows two fluid chambers (250 and 255), however, more or less fluid chambers may be provided based on desired design configurations. A single fluid chamber may be used in some embodiments to allow for cooling fluid flow through the sidewall 210. Optionally, more than two fluid chambers may be used, especially in embodiments where different flow rates or flow pressures through the orifices associated with each of the fluid chambers may be desirable.

[0029] During the casting process, as the material exits the mold cavity in response to the downward advancement of the starter block 157 as shown in FIG. 2, cooling of the material exiting the mold cavity is necessary to properly form the ingot 160. This cooling is accelerated by the use of a cooling fluid or agent sprayed from orifices located near the bottom of the sidewall 210 in the direction of the material exiting the mold cavity. Also shown is a fluid chamber 261 that is formed in the rear side of the sidewall 210 and is separated from the fluid chambers 250, 255. The fluid chamber 261 in the illustrated embodiment is configured to convey a lubricating fluid (e.g., oil or grease) along the length of the sidewall 210, and is in fluid communication with a number of orifices 262 (a cross section of one of which is shown in FIG. 5) that provide the lubricating fluid to the casting surface 211 of the sidewall 210. The lubricating fluid may be provided to the fluid chamber 261 at a relatively high pressure, and the lubricating fluid may be released into the mold at a more uniform and lower pressure. The lubricating fluid does not spray outwardly from the sidewall 210, but exits the orifice 262 flowing generally downward along the casting surface 211 of the sidewall 210 to provide a lubricating layer between the ingot and the casting surface 211 of the sidewall 210. The multiple orifices 262 for providing the lubricating fluid to the face of the sidewall 211 may each be configured to allow the lubricating fluid to flow substantially evenly over the entire length of the sidewall 210, with as many or as few lubricating fluid orifices as deemed appropriate for the mold and size of the material to be cast. Optionally, the lubricant may be applied to the casting surface 211 between ingots, rather than being delivered through the fluid chamber 261.

[0030] The casting surface 211 is the surface of the graphite liner 300 engaged with the mold sidewall 210. The graphite liner 300 provides a porous lubricated casting surface on the sidewall facing the mold cavity. This porous lubricated surface (casting surface 211) promotes smooth flow of the ingot as it exits the mold cavity. Graphite as the material of the graphite liner can allow for the flow of lubricant through the graphite liner 270, for example from the fluid chamber 261, or the graphite material can have a lubricant applied to the casting surface 211 prior to the casting operation where the lubricant is absorbed into the graphite liner.

[0031] As mentioned above, embodiments may include any number of cooling fluid chambers, where each cooling fluid chamber may feed one or more sets of orifices to provide cooling fluid to the ingot as it exits the mold. As shown in FIG. 5, the cooling fluid chambers 250, 255 may be configured to convey cooling fluid to two sets of cooling orifices 264, 266. Both orifices 264, 266 are visible in the cross-sectional view of FIG. 5 along with the fluid flow path for each, but it will be understood that both orifices and associated fluid flow paths may not be visible in the cross-sectional view in their natural physical state. The cross-sectional view of FIG. 5 is provided for illustrative purposes and ease of understanding. Although the orifices 264, 266 are illustrated as round, embodiments may include elongated orifices 264, 266 along the sidewall 210. This allows for different cooling fluid flow patterns from the orifices to cool the ingot as it exits the mold.

[0032] According to the illustrated embodiment, the fluid chamber 255 may be in fluid communication with cooling orifices 264, each of which may be positioned at a first angle relative to the sidewall 210, as indicated by arrow 265 indicating the direction of fluid exiting the first plurality of cooling orifices 264. The second plurality of cooling orifices 266 may be positioned to direct the cooling fluid at a different angle, as indicated by arrow 267. However, the second plurality of cooling orifices may be in fluid communication with the cooling fluid chamber 250 rather than the chamber 255. A channel 270 may be machined or otherwise formed in the rear face of the sidewall 210 to supply cooling fluid from the cooling fluid chamber 250 to the plurality of orifices 266. A channel 270 may be provided for each of the second set of cooling orifices 266, or alternatively, the channels 270 may be present at multiple locations along the length of the sidewall 221 in cooperation with channels extending longitudinally along the sidewall 210 in a manifold structure with the channels 270 positioned near the second set of cooling orifices 266.

[0033] According to the illustrated embodiment, the flow of cooling fluid through each of the first plurality of orifices 264 and the plurality of orifices 266 may be independently provided by a corresponding cooling fluid chamber 250, 255. In this configuration, a cooling profile can be created depending on the type of material being cast with the appropriate flow rate and spray pattern from the corresponding set of cooling orifices.

[0034] In addition to providing cooling fluid to the orifices 264, 266, the cooling fluid chambers 250, 255 provide a cooling effect to the sidewall 210 itself as well as to the graphite liner 300 and its casting surface 211. The cooling fluid chambers 250, 255 are positioned in a manner that facilitates the extraction of heat from the back face of the sidewall 210 to the cooling fluid. This cooling effect of the sidewall further reduces the temperature of the graphite liner 300 and the casting surface 211 of the sidewall 210, thereby avoiding overheating of the lubricating fluid, which may result in premature evaporation or burnout of the lubricating fluid. Cooling the sidewall 210 using the cooling fluid chambers 250, 255 further reduces the risk and extent to which the lubricating fluid will burn out or evaporate as it flows down the casting surface 211 with the casting material. Heat from the ingot passes through the casting surface of the graphite liner 300, is drawn through the mold walls, and is carried away via the cooling fluid in the cooling chamber. Thus, it is important to maximize the heat transfer between components to maximize the cooling effect on the graphite liner.

[0035] The graphite liner 300 in the exemplary embodiment described herein is removably attached to the mold sidewall 210. The graphite liner 300 is a consumable item that may require replacement in some embodiments. Additionally, since the mold sidewall 210 is made entirely of aluminum, the graphite liner 300 must be attached or secured to the mold sidewall 210. According to the exemplary embodiment of FIG. 5, the graphite liner 300 has a sloped bottom edge 305 that is received within a complementary channel 310 in the sidewall 210. The bottom edge 305 received within the channel 310 provides support for the graphite liner 300 as the ingot exits the mold cavity. A similar configuration is provided on the top surface of the graphite liner 300, where the sloped top edge 315 is received within a complementary channel 320 in the removable top edge 330 of the mold sidewall 210. The removable top edge 330 is secured to the mold sidewall 210 by fasteners 335, one of which is shown in cross section in Figure 5. Replacement of the graphite liner 300 is accomplished by removing the top edge 330 of the mold sidewall 210, removing the worn or defective graphite liner 300, and replacing the graphite liner. The top edge 330 is then replaced and secured by fasteners 335.

[0036] Attachment of the graphite liner 300 to the mold sidewall 210 is not a trivial process, especially in embodiments where the mold sidewall is flexed during the casting operation. Heat transfer between the graphite liner and the mold sidewall to the cooling chambers 250, 255 is essential to maintaining the temperature at the casting surface 211 below a level that would burn off the lubricant.

[0037] Graphite is less ductile than aluminum, and a relatively thin graphite liner may be used for a wide range of flexibility. However, a relatively thin graphite liner is more difficult to secure to the mold sidewall, particularly using the mechanisms described with reference to FIG. 5, because the surface and area to be clamped is small. The clamping or clamping mechanism may be varied, for example, by changing the fastener orientation or reducing the fastener size. However, the area of ​​the graphite liner available for applying a clamping force remains small. The embodiments described herein employ a novel mechanism for forming the graphite liner and attaching it to the mold sidewall.

[0038] FIG. 6 shows a portion of a mold sidewall with a graphite liner 400. The portion of the mold sidewall shown includes a substrate 440 that is bonded to or part of an assembly with the mold sidewall. As shown, the graphite liner 400 has a beveled bottom edge 405. The angle formed may be about 20°-60°, or more specifically, about 45°, relative to the casting surface 411 of the graphite liner. The beveled bottom edge 405 may form a chamfer or bevel between the back surface 410 of the graphite liner and the casting surface 411, as shown in FIG. 6. A groove 410 having a supplemental angle is formed in the substrate 440 to receive the beveled bottom edge 400 of the graphite liner 400. The graphite liner 400 of the illustrated embodiment further includes a beveled top edge 415, which may also be at an angle of about 20° to 60°, and more specifically about 45°, relative to the casting surface 411. The beveled top edge 415 may form a chamfer or bevel between the back surface 412 of the graphite liner and the casting surface 411, as shown in FIG.

[0039] A clamping element 420, including a complementary sloped element that engages the sloped top edge 415 of the graphite liner 400, is secured to the substrate by a fastener 425. The fastener may be, for example, a threaded fastener (threaded fastener) received within a threaded hole in the mold wall substrate 440. The threaded fastener 425 may be secured with a locking feature to reduce the risk of the fastener unfastening inadvertently. The locking feature may be, for example, a thread locking compound. Optionally, the threaded fastener may be engaged with a lock washer, for example, a split lock washer, a spring washer (e.g., a Belleville washer), or a wedge washer. The lock washer may help to prevent loosening of the clamping element, which may result in poor contact between the graphite liner 400 and the mold wall substrate 440, thereby reducing heat transfer efficiency.

[0040] The clamp element 420 further has an upper angled face 430 that engages a complementary substrate angled face 435. When the fastener 425 is tightened to drive the clamp element 420 towards the substrate 440, the substrate angled face 435 presses against the clamp element upper angled face 430, thereby forcing the clamp element down towards the graphite liner 400. A slot 427 formed in the clamp element 420 allows some vertical movement of the clamp element relative to the substrate 440. The fastener 425 may include a shoulder fastener, where the shoulder prevents the clamp element 420 from getting stuck in the groove 427 as it is tightened. When the clamp element is driven towards the graphite liner 400, the angled top edge 415 of the graphite liner engages and is driven downward, driving the angled bottom edge 405 into the groove 410 of the substrate 440 with a complementary angle. This system secures the graphite liner 400 to the substrate 440 and facilitates the realization of a thermal interface between the graphite liner 400 and the substrate 440 to allow the transfer of heat from the graphite liner to the substrate of the mold sidewall.

[0041] The clamping mechanism of the embodiment of Figure 6 allows the graphite liner 400 to flex with the mold sidewall when it flexes as described above. A groove 410 located near the bottom of the mold wall substrate 440 grips the graphite liner along its length, and a clamping element 420 can extend longitudinally along the mold wall substrate near the top of the mold wall substrate. Optionally, the clamping element can be one of multiple clamping elements disposed along the length of the mold sidewall substrate, the clamping elements being sufficiently close to each other to ensure that the top edge of the graphite liner is kept in contact with the mold sidewall substrate during the casting operation and when the mold sidewall is flexing.

[0042] According to another exemplary embodiment described herein, the mold wall substrate may be shrink fitted. According to such an exemplary embodiment, the clamping element 420 may be secured to the mold wall substrate 440 or a portion of the mold wall substrate. The mold may be heated to expand across the distance between the clamping element 440 and the groove 410, and the graphite liner 400 may then slide into engagement with the mold wall substrate with the top edge 415 and bottom edge 405 received within the groove formed by the clamping element 420 and the groove 410 along the bottom of the mold wall substrate 440. In response to cooling of the mold wall substrate, the distance between the clamping element 420 and the groove 410 may decrease (due to thermal expansion and contraction) and the graphite liner 400 may become tightly gripped into engagement with the mold wall substrate.

[0043] Although the exemplary embodiment of FIG. 6 can provide a thermal interface between the graphite liner 400 and the substrate 440, the graphite liner may not provide complete contact along the back face of the graphite liner to the substrate. Strong contact between the graphite liner and the substrate results in more efficient heat transfer, which reduces the temperature at the casting surface of the graphite liner and reduces the risk of lubricant burnout or evaporation. The embodiments provided herein further include a graphite liner with a curve machined into the back face of the graphite liner to promote improved contact between the back face of the graphite liner and the substrate. FIG. 7 shows a graphite liner 500 with a casting surface 511 and a back face 512 with curves. The casting surface 511 has a concave curve as shown when the graphite liner is not attached to the mold wall, whereas the back face 512 or back side has a convex curve. The graphite liner 500 is shown in a "rest" or uninstalled state, where the profile of the graphite liner 500 shown in FIG. 7 remains as it was when the graphite liner was fabricated or manufactured.

[0044] Specifically, the curves formed on the back face 512 of the graphite liner 500 of FIG. 7 are configured to press the graphite liner back face into engagement with the substrate when attached to the substrate of the mold wall when in the "attached state." For example, the curves may be optimized to provide maximum pressure according to the stiffness of the shape of the bottom third of the graphite liner. The curves on the back face of the graphite liner in the rest state may be, for example, a single radius, a compound curve, or a spline. The curves may include a location of peak bend or minimum radius that may help concentrate the force exerted by the graphite liner when actuated into the attached state. The curves on the back face of the graphite liner may optionally be non-uniform along the length of the graphite liner along the mold wall substrate. For example, the back face of the graphite liner may have a first curve profile near the center of the mold wall and a different curve profile near the edge of the mold wall. According to some embodiments, the mold wall substrate can have a curved portion, such as a convex curved portion, for interfacing with the back face of the graphite liner, such that in the installed position, the back face of the graphite liner is driven into contact with the curved portion of the mold wall substrate while the casting surface of the graphite liner achieves a substantially flat casting surface.

[0045] During casting, the bottom third of the graphite liner is where the steady state casting is occurring at the mold wall and therefore where the graphite is prone to high temperatures. With reference to graphite liner 500 in Figure 7, when the graphite liner is attached to substrate 440 as shown in Figure 6, the result is that the graphite liner reaches an "attached state" that achieves the shape of the attached graphite liner shown in Figure 6, but due to the curvature of the back face 512, it exerts a force against the substrate, particularly in the bottom third of the graphite liner, when the beveled bottom edge 505 of the graphite liner engages the complementary beveled bottom edge 405 and the clamping element 402 clamps the beveled top edge 515 of the graphite liner into the mold wall.

[0046] FIG. 7 further illustrates a graphite liner 600 fabricated with curves, similar to that of the graphite liner 500 in an installed orientation, where a first clamping force 607 is applied at the beveled bottom edge 615 and a second clamping force 617 is applied at the beveled top edge 615 by the elements described with reference to FIG. 6. In the installed orientation, the clamping of the graphite liner 600 results in a force exerted by the back face 612 of the liner on the mold wall substrate. The force exerted is determined by the curves of the manufactured or machined graphite liner and where the peak radius or sharpest bend occurs. The force arrow 620 in FIG. 7 indicates the magnitude of the force, which is greatest in the first third of the back face 612 of the graphite liner 600. As discussed above, this is where the greatest heat transfer needs to occur from the hottest portion of the graphite liner to the substrate. This relatively high force in the lower third region ensures maximum contact between the back face of the graphite liner and the substrate, thereby facilitating improved heat transfer.

[0047] The embodiments described herein facilitate heat transfer from the casting surface of the graphite liner (or other liner material) through the mold wall substrate to which the graphite liner is attached. By applying a force between the graphite liner and the mold wall substrate as described above, improved contact between the graphite liner and the mold wall substrate is maintained, thereby enhancing heat transfer between the graphite liner and the mold wall. FIG. 8 is an exemplary measurement normalized to show the effect of thermal contact resistance on contact pressure. As shown, as the contact pressure increases along the x-axis, the thermal contact resistance decreases along the y-axis, thereby enhancing heat transfer across the interface. As shown, a greased interface improves the heat transfer characteristics across the graphite liner / mold wall substrate interface. Although a greased interface is illustrated, alternative fluids, such as thermally conductive liquids, adhesives or gels, that can be used between the graphite liner and the mold wall substrate can also facilitate heat transfer across the interface. However, both the dry and greased interfaces provide improvements to heat transfer with increased contact pressure between the graphite liner and the mold wall substrate. Thus, the force applied between the graphite liner and the mold wall substrate by the exemplary embodiments described herein enhances the heat transfer characteristics in transferring heat away from the casting surface of the graphite liner to the mold wall substrate.

[0048] The above-described embodiments may be employed with any mold wall, whether the mold wall is a side wall or an end wall. Additionally, the embodiments are configured to function with the mold wall being flexible and capable of being deflected to impart a radius to the mold wall. In some embodiments, a conductive material, such as a liquid, adhesive, or gel, may be used between the graphite liner and the substrate, as described above. In an exemplary embodiment, a grease may be used between the mold wall substrate and the graphite liner. The grease of the exemplary embodiment may improve the contact between the mold wall substrate and the graphite liner. Other materials, such as the liquid or gel described above, or a deformable gasket made of a thermally conductive material, may be used at the interface between the graphite liner and the mold wall substrate to improve surface contact of the surfaces at the interface with the gap material, thereby increasing the area for heat transfer.

[0049] Many variations and other embodiments of the inventions described herein will be apparent to one skilled in the art having the benefit of the teachings provided in the foregoing descriptions and the associated drawings. It is therefore to be understood that the invention is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the invention as defined by the appended claims. Although specific terms are employed herein, such terms are used in a generic and descriptive sense only and are not intended to be limiting of the invention.

Claims

1. 1. A continuous casting mold component comprising: a mold wall substrate, the mold wall substrate having a groove disposed near a bottom thereof; a graphite liner having a bottom edge with a first beveled surface and a top edge with a second beveled surface, said bottom edge being received into said groove in said mold wall substrate; a clamping element having an inclined clamping surface attached to the mold wall substrate by at least one fastener; the bottom angled surface of the graphite liner is driven into the groove of the mold wall substrate in response to the angled clamping surface of the clamping element engaging the second angled surface of the graphite liner and the fastener urging the clamping element toward the mold wall substrate; 1. A continuous casting mold component comprising: a graphite liner having a rest state and an installed state, the graphite liner having a curve along a back face of the graphite liner between the top edge and the bottom edge in the rest state; and the back face being straightened in the installed state in response to the fastener pressing the clamp element toward the mold wall substrate.

2. 2. The continuous casting mold component of claim 1 , wherein the curved portion of the back face of the graphite liner has a curved portion profile such that in the installed condition, a force is applied by the graphite liner to the mold wall substrate in response to the fastener pressing the clamp element against the mold wall substrate.

3. 3. The continuous casting mold component of claim 2, wherein the curvature profile is configured to concentrate forces applied by the graphite liner to the mold wall substrate in the installed condition at a lower third of the graphite liner.

4. 2. The continuous casting mold component of claim 1, wherein the mold wall substrate further comprises a substrate inclined surface near a top of the mold wall substrate, and the clamping element includes an inclined drive surface, the substrate inclined surface cooperating with the inclined drive surface to drive the clamping element toward the bottom of the mold wall substrate in response to the fastener urging the clamping element toward the mold wall substrate.

5. 5. The continuous casting mold component of claim 4, wherein the fastener comprises a threaded fastener, the clamp element having a slot for receiving the threaded fastener, the threaded fastener being received into a threaded hole in the mold wall substrate.

6. 6. The continuous casting mold component of claim 5, wherein the slot in the clamping element has a relatively narrow dimension in an axial direction along which the mold wall substrate extends and a relatively long dimension extending in a direction toward the bottom of the mold wall substrate.

7. 7. The continuous casting mold component of claim 6, wherein the clamping element is driven in a direction toward the bottom of the mold wall substrate in response to the threaded fastener being tightened and threaded into the threaded hole in the mold wall substrate.

8. 2. The continuous casting mold component of claim 1, wherein the graphite liner has a first thickness near the top edge and a second thickness near the bottom edge of the graphite liner, the first thickness being greater than the second thickness.

9. The continuous casting mold component of claim 8 , wherein the graphite liner tapers from the first thickness to the second thickness.

10. 2. The continuous cast mold component of claim 1 , wherein the first sloping surface of the graphite liner is a first chamfer from the aft surface of the graphite liner to the casting surface of the graphite liner and the second sloping surface of the graphite liner is a second chamfer from the aft surface of the graphite liner to the casting surface.

11. 11. The continuous casting mold component of claim 10, wherein the first chamfer defines an angle between the trailing surface and the second angled surface of about 20° to 60°, and the second chamfer defines an angle between the trailing surface and the first angled surface of about 20° to 60°.

12. 2. The continuous casting mold component of claim 1, wherein the mold wall substrate has a convex curve between the groove in the mold wall substrate and the clamping element, and the graphite liner is forced to bend around the convex curve in the mold wall substrate when in an attached position secured to the mold wall substrate by the clamping element.

13. 1. A graphite liner for a continuous casting mold, comprising: a bottom edge having a first beveled surface; a top edge having a second beveled surface; A graphite liner having a rest state and an installed state, the graphite liner having a curve along a back face of the graphite liner between the top edge and the bottom edge in the rest state, and the back face being straightened in the installed state.

14. The graphite liner of claim 13 , wherein in the installed condition, the graphite liner is clamped to the continuous casting mold at the top edge and the bottom edge.

15. The graphite liner of claim 14 , wherein in the installed condition, the bottom edge of the graphite liner is received within a groove of the continuous casting mold and the top edge of the graphite liner is clamped to the continuous casting mold by a clamping element.

16. 16. The graphite liner of claim 15, wherein in the installed condition, the bottom edge of the graphite liner is driven into the groove of the continuous casting mold in response to the clamping element pressing the top edge of the graphite liner toward the continuous casting mold.

17. 14. The graphite liner of claim 13, wherein the curved portion of the back face of the graphite liner has a curved portion profile, and in the installed state, a force is applied by the graphite liner to the continuous casting mold in response to a clamping element pressing the top edge of the graphite liner toward the continuous casting mold.

18. 14. The graphite liner of claim 13, wherein the graphite liner has a first thickness near the top edge and a second thickness near the bottom edge of the graphite liner, the first thickness being greater than the second thickness.

19. The graphite liner of claim 18 , wherein the graphite liner tapers from the first thickness to the second thickness.

20. 1. A graphite liner for a continuous casting mold, comprising: A bottom edge; a top edge; A graphite liner having a rest state and an installed state, the graphite liner having a curve along a back face of the graphite liner between the top edge and the bottom edge in the rest state, and the back face being straightened in the installed state.

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