Reduced final grain size of non-crystallized wrought materials produced via the semi-continuous casting (DC) route

Abstract

To provide a casting method for improving a grain size of a deliverable metal product.SOLUTION: A grain size of a deliverable metal product can be improved by pre-setting recrystallization-suppressing dispersoids during casting. The outer regions of a direct chill cast embryonic ingot can undergo reheating before casting is complete. Through unique wiper placement and / or other reheating techniques, the temperature of the ingot can be permitted to reheat (e.g., up to approximately 410°C to approximately 420°C), allowing dispersoids to form. Stirring and / or agitation of the molten sump can facilitate formation of a deeper sump and desirably fine grain size as-cast. The formation of dispersoids during and / or immediately after casting can pin the grain boundaries at the desirably fine grain size, encouraging the same grain sizes even after a later recrystallization and / or solutionizing step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Application No. 62 / 951,884, filed December 20, 2019, which is hereby incorporated by reference in its entirety.

[0002] The present disclosure relates generally to metal casting, and more specifically to semi-continuous casting of difficult aluminum alloys. [Background technology]

[0003] In semi-continuous (DC) casting, the molten metal is forced through a mold cavity that has a false bottom or movable bottom. As the molten metal enters the mold cavity, typically from the top, the false bottom descends at a rate related to the speed of the molten metal flow. The molten metal that solidifies near the sides can be used to hold the liquid and partially liquid metal in the pool. The metal can be 99.9% solid (i.e. completely solid), 100% liquid, and ranges in between. As the molten metal cools, the thickness of the solid region increases, so the pool can assume a V-, U-, or W-shape. The interface between the solid metal and the liquid metal is sometimes referred to as the solidification interface.

[0004] When the molten metal in the pool is between approximately 0% solids and approximately 5% solids, nucleation can occur and small crystals of metal can form. These small (e.g., nanometer-sized) crystals begin to nucleate, which continue to grow in preferred directions as the molten metal cools to form dendrites. When the molten metal cools to the dendrite alignment point (e.g., 632°C for 5182 aluminum used for beverage can ends), the dendrites begin to stick together. Depending on the temperature and percent solids of the molten metal, the crystals may form various particles (e.g., intermetallic compounds or hydrogen bubbles), e.g., FeAl in certain alloys of aluminum. 6 , Mg 2 Si, FeAl 3 , Al 8 Mg 5 and gaseous H 2The particles may include or be trapped.

[0005] In addition, as the solidifying aluminum first begins to cool, it cannot support just as many alloying elements in its alpha phase, so the melt surrounding the solidification interface may be proportionally more concentrated in alloying elements. Thus, different compositions and particles may form at or near the solidification interface. Additionally, there may be stagnation regions within the pool that may result in preferential accumulation of these particles.

[0006] The non-uniform distribution of alloying elements on the length scale of the grains is known as microsegregation. In contrast, macrosegregation is a chemical non-uniformity over length scales larger than the grains (or a few grains), for example up to several meters.

[0007] Certain aluminum alloys, such as the 7xxx series alloys, can be particularly difficult to cast. The 7xxx series alloys generally contain a number of alloying elements, such as one or more combinations of zinc, magnesium, copper, chromium, zirconium, and other alloying elements. Large internal stresses (e.g., compressive and sometimes tensile) can build up during and shortly after casting of the 7xxx series alloys, making the castings susceptible to cracking. Certain alloying elements used in these types of alloys, such as zinc, contract and expand at rates much different from aluminum. In particular, zinc contracts and expands significantly more than aluminum. Thus, zinc and aluminum that are the same volume at similar temperatures (e.g., 600° C.) can have different volumes of zinc and aluminum, respectively, when cooled (e.g., during the final stages of solidification). These different rates of expansion and contraction of the alloying elements and aluminum can be the source of large internal forces, and therefore stresses, in castings cast from the 7xxx series alloys.

[0008] In addition, the 7xxx series alloys are highly susceptible to porosity problems caused by dissolved hydrogen being expelled from the solidifying molten alloy as tiny gas bubbles. The voids created by the gas bubbles are often crack initiation sites and can result in substantial cracking. In addition, the 7xxx series alloys can be highly susceptible to shrinkage cavities caused, at least in part, by differences in the rate of contraction as the molten alloy solidifies.

[0009] In a conventional manufacturing environment, large internal stresses during solidification can cause hot or cold cracks in the casting, making it unsuitable for further manufacturing. Conventional manufacturing environments for 7xxx series alloys result in increased overall ingot losses compared to other more easily cast castings, such as the 6xxx series alloys.

[0010] In addition, 7xxx series alloy castings may rely on an extensive homogenization step after casting to achieve the desired internal structure with the desired precipitates while reducing casting stresses. Homogenization may be used to mitigate microsegregation after casting. In some cases, 7xxx series alloy castings may be hot rolled to smaller gauges, solution treated, and then aged. In some cases, extensive aging and further processing (e.g., solutionizing or recrystallization) may be used in an attempt to obtain a more desirable microstructure, but such techniques require significant equipment and the expenditure of significant time, resources, and energy. Summary of the Invention

[0011] The term "embodiments" and similar terms are intended to broadly refer to all of the subject matter of the present disclosure and the following claims. It should be understood that phrases incorporating these terms are not intended to limit the subject matter described herein or the scope or meaning of the following claims. The embodiments of the present disclosure contained herein are defined by the following claims, not this summary. This summary is a broad overview of various aspects of the disclosure and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this disclosure, any or all drawings, and the claims.

[0012] An embodiment of the present disclosure includes a casting method including: supplying molten metal to a casting mold to form an embryonic ingot including an outer solid shell and an inner molten core; advancing the embryonic ingot in a traveling direction away from the casting mold while supplying additional molten metal to the casting mold; removing heat from the embryonic ingot between the casting mold and a transfer location by directing a supply of liquid coolant against an outer surface of the outer solid shell; and reheating the embryonic ingot at the transfer location such that at least a portion of the outer solid shell of the embryonic ingot at the transfer location reaches a temperature suitable for precipitation of a dispersed phase and lower than a homogenization temperature of the molten metal (e.g., a reheat temperature), wherein the transfer location is in a plane perpendicular to the traveling direction and intersecting the inner molten core.

[0013] In some cases, the reheat temperature, for example in degrees Celsius, is 80-98% of the homogenization temperature, for example in degrees Celsius, of the melt. In some cases, the temperature, for example in degrees Celsius, is 85-90% of the homogenization temperature, for example in degrees Celsius, of the melt. Optionally, the temperature, for example in degrees Celsius, is 80-95%, 80-90%, 80-85%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98% of the homogenization temperature, for example in degrees Celsius, of the melt. In some cases, the temperature is 400-460°C. In some cases, the temperature is 410-420°C. In some cases, the temperature is 400-410°C, 400-420°C, 400-430°C, 400-440°C, 400-450°C, 400-460°C, 410-420°C, 410-430°C, 410-440°C, 410-450°C, 410-460°C, 420-430°C, 420-440°C, 420-450°C, 420-460°C, 430-440°C, 430-450°C, 430-460°C, 440-450°C, 440-460°C, or 450-460°C. In some cases, the method further includes maintaining the temperature in a portion of the outer solid shell for at least 3 hours, e.g., 3-4 hours, 3-5 hours, 3-6 hours, 3-7 hours, 3-8 hours, 3-9 hours, 3-10 hours, 4-5 hours, 4-6 hours, 4-7 hours, 4-8 hours, 4-9 hours, 4-10 hours, 5-6 hours, 5-7 hours, 5-8 hours, 5-9 hours, 5-10 hours, 6-7 hours, 6-8 hours, 6-9 hours, 6-10 hours, 7-8 hours, 7-9 hours, 7-10 hours, 8-9 hours, 8-10 hours, 9-10 hours, or more. In some cases, reheating the embryonic ingot includes removing liquid coolant from an exterior surface of the outer solid shell. In some cases, reheating the embryonic ingot further includes applying heat to an exterior surface of the outer solid shell to supplement the latent heat heating from the inner molten core. In some cases, the method further includes taking a temperature measurement of the embryonic ingot and dynamically adjusting the transition location based on the temperature measurement.In some cases, the method further includes inducing stirring in the inner molten core adjacent an interface between the inner molten core and the outer solid shell. In some cases, the method further includes taking a temperature measurement of the embryonic ingot, and inducing stirring in the inner molten core includes dynamically adjusting the intensity of the stirring based on the temperature measurement. In some cases, the transition location is selected such that the plane intersects the embryonic ingot at a cross section where the outer solid shell of the embryonic ingot occupies approximately one third of a line extending in the plane from the outer surface to the center of the embryonic ingot. In some cases, the transition location is selected such that the plane intersects the embryonic ingot at a cross section where the outer solid shell of the embryonic ingot occupies 50% or less of a line extending in the plane from the outer surface to the center of the embryonic ingot. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the reheated portion includes a surface of metal containing liquid in the center, and the reheated portion grows the precipitates at the periphery of the ingot adjacent the surface.

[0014] Embodiments of the present disclosure include a method comprising forming an embryonic ingot by supplying molten metal to a mold and removing heat from the molten metal to form an outer solid shell; solidifying an inner molten core of the embryonic ingot as the embryonic ingot advances in a travel direction away from the mold and additional molten metal is supplied to the mold, where solidifying the inner molten core comprises removing heat from the inner molten core through the outer solid shell; and further comprising continuously forming high strength sites in the outer solid shell at a cross section of the embryonic ingot perpendicular to the travel direction and intersecting the inner molten core, where the high strength sites are located between an outer surface of the outer solid shell and the inner molten core, and where forming the high strength sites comprises reheating the outer solid shell at the cross section to induce dispersed phase precipitation in the outer solid shell.

[0015] Optionally, reheating the outer solid shell at the cross section includes reheating a portion of the outer solid shell to a temperature suitable for precipitation of the dispersed phase, the temperature being lower than the homogenization temperature of the molten metal. Optionally, the temperature, for example, expressed in degrees Celsius, is 80-98% of the homogenization temperature, for example, expressed in degrees Celsius, of the molten metal. Optionally, the temperature, for example, expressed in degrees Celsius, is 85-90% of the homogenization temperature, for example, expressed in degrees Celsius, of the molten metal. Optionally, the temperature is 300-460°C, for example, 400-460°C. Optionally, the temperature is 410-420°C. Optionally, the temperature ranges of 400-460°C and 410-420°C may be particularly suitable for 7xxx series alloys. Optionally, other temperature ranges may be used, for example, for 6xxx series alloys. Optionally, the method further includes maintaining the temperature in the portion of the outer solid shell for at least 3 hours, or 3-10 hours. In some cases, removing heat from the inner molten core through the outer solid shell includes providing a liquid coolant to an exterior surface of the outer shell, and reheating the outer solid shell includes removing the liquid coolant from the exterior surface of the outer solid shell. In some cases, reheating the outer solid shell further includes applying heat to the exterior surface of the outer solid shell to supplement the latent heating from the inner molten core. In some cases, the method further includes taking a temperature measurement of the embryonic ingot and dynamically adjusting a distance between the mold and the cross section based on the temperature measurement. In some cases, the method further includes inducing stirring in the inner molten core adjacent an interface between the inner molten core and the outer solid shell. In some cases, the method further includes taking a temperature measurement of the embryonic ingot and inducing stirring in the inner molten core includes dynamically adjusting an intensity of the stirring based on the temperature measurement. In some cases, in a cross section, the outer solid shell of the embryonic ingot occupies approximately one third of a line extending from the exterior surface to a center of the embryonic ingot. In some cases, in a cross-section, the outer solid shell of the embryonic ingot occupies 50% or less of a line extending from the outer surface to the center of the embryonic ingot. In some cases, the molten metal is a 7xxx series aluminum alloy.In some cases, the high strength regions contain a higher concentration of dispersed phase compared to the remainder of the outer solid shell.

[0016] An embodiment of the present disclosure includes an aluminum metal product comprising a solidified aluminum alloy block having two ends and an outer surface, the solidified aluminum alloy block comprising a core region containing a center of the solidified aluminum alloy block; an outer region integral with the outer surface; and a high strength section disposed between the core region and the outer region, the high strength section having a higher concentration of dispersed phase compared to each of the core region and the outer region.

[0017] In some cases, the solidified aluminum alloy block includes retained heat from the semi-continuous casting process. In some cases, the high strength portion is located at a depth of approximately one third of a line extending along a cross section of the solidified aluminum alloy block from an outer surface to a center of the solidified aluminum alloy block. In some cases, the high strength portion is located at a depth of less than one half of a line extending along a cross section of the solidified aluminum alloy block from an outer surface to a center of the solidified aluminum alloy block. In some cases, the solidified aluminum alloy block is cylindrical in shape. In some cases, a cross section of the solidified aluminum alloy block perpendicular to a casting direction of the solidified aluminum alloy block is rectangular in shape. In some cases, the solidified aluminum alloy block is a solidified 7xxx series aluminum alloy block.

[0018] An embodiment of the present disclosure includes an embryonic ingot including a liquid molten core of an aluminum alloy extending from a top surface to a solidification interface, and a solidified shell of the aluminum alloy, the solidified shell including an outer surface extending from the solidification interface to a bottom end in a casting direction, the solidified shell including a high strength region disposed between the outer surface and a centerline extending in the casting direction through a center of the liquid molten core and a center of the solidified shell, the high strength region having a higher concentration of a dispersed phase compared to a remainder of the solidified shell.

[0019] Optionally, the high strength region is located at a depth of approximately one third of a line extending from the outer surface to the center line. Optionally, the high strength region is located at a depth of one half or less of a line extending from the outer surface to the center line. Optionally, the solidified shell is cylindrical in shape. Optionally, a cross-section of the solidified shell perpendicular to the casting direction is rectangular in shape. Optionally, the aluminum alloy is a 7xxx series aluminum alloy. Optionally, the embryonic ingot is made according to any of the methods described above.

[0020] An embodiment of the present disclosure includes a method including delivering molten metal from a metal source to a metal pool of an embryonic ingot being cast into a mold; forming an outer solid shell of solidified metal by removing heat from the metal pool, a solidification interface being located between the outer solid shell and the metal pool; advancing the embryonic ingot at a casting speed in an advancing direction away from the mold while delivering molten metal and forming the outer solid shell; determining an intensity of stirring using the casting speed, the intensity of stirring suitable to result in a target solidification interface profile at the casting speed; and further including inducing stirring in the molten metal pool at the determined intensity, wherein inducing stirring in the molten metal pool results in the solidification interface assuming the target solidification interface profile at the casting speed.

[0021] In some cases, inducing stirring includes applying a stirring force to the molten metal in the metal pool using a non-contact magnetic stirrer. In some cases, delivering the molten metal includes delivering the molten metal through a plurality of nozzles at a mass flow rate, and inducing stirring includes increasing the flow rate of the molten metal through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles. In some cases, the method further includes modifying the casting speed; determining an updated intensity of stirring using the updated casting speed, the updated intensity of stirring being suitable for resulting in a target solidification profile at the updated casting speed; and further includes inducing stirring in the molten metal pool at the updated intensity, and inducing stirring in the molten metal pool at the updated intensity results in the solidification interface exhibiting the target solidification interface profile at the updated casting speed. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the method further includes measuring a temperature of the embryonic ingot, and determining the intensity of stirring using the casting speed includes using the measured temperature. In some cases, the target solidification interface profile is predetermined to minimize risk of cracking. In some cases, the method further includes continuously forming high strength regions in the outer solid shell at a cross section of the embryonic ingot perpendicular to the direction of advancement and intersecting the inner molten core, the high strength regions being located between an outer surface of the outer solid shell and the inner molten core, and forming the high strength regions includes reheating the outer solid shell at the cross section to induce dispersed phase precipitation in the outer solid shell. In some cases, inducing stirring in the molten metal pool includes controlling delivery of molten metal into the metal pool such that a jet of molten metal erodes the solidification interface at a bottom of the metal pool to form a depression, the depression having a diameter sized to match a diameter of the bottom of the metal pool.

[0022] An embodiment of the present disclosure includes a method comprising: delivering molten metal from a metal source to a metal pool of an embryonic ingot being cast into a mold; forming an outer solid shell of solidified metal by removing heat from the metal pool, a solidification interface being located between the outer solid shell and the metal pool; advancing the embryonic ingot at a casting speed in an advancing direction away from the mold while delivering molten metal and while forming the outer solid shell; and controlling the delivery of molten metal into the metal pool to generate a jet of molten metal sufficient to erode at least a portion of the solidification interface at the bottom of the metal pool.

[0023] In some cases, controlling the delivery of the molten metal includes controlling the delivery of the molten metal such that the jet of molten metal erodes the solidification interface to a thickness of 10 mm or less. In some cases, delivering the molten metal includes delivering the molten metal through a plurality of nozzles at a mass flow rate, and generating the jet of molten metal includes increasing the flow rate of the molten metal through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles. In some cases, the method further includes applying a stirring force to the molten metal in the metal pool using a non-contact magnetic stirrer. In some cases, the method further includes modifying a casting speed, and controlling the delivery of the molten metal includes dynamically adjusting the delivery of the molten metal based on the modified casting speed such that the jet of molten metal continues to erode at least a portion of the solidification interface at the bottom of the metal pool. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the method further includes measuring a temperature of the embryonic ingot, and controlling the delivery of the molten metal includes dynamically adjusting the delivery of the molten metal based on the measured temperature such that the jet of molten metal continues to erode at least a portion of the solidification interface at the bottom of the metal pool. In some cases, the method further includes continuously forming high strength regions in the outer solid shell at a cross section of the embryonic ingot perpendicular to the direction of advancement and intersecting the metal pool, the high strength regions being located between an outer surface of the outer solid shell and the metal pool, and forming the high strength regions includes reheating the outer solid shell at the cross section to induce dispersed phase precipitation in the outer solid shell.

[0024] An embodiment of the present disclosure includes an embryonic ingot including a solidified shell of an aluminum alloy extending from a solidification interface to a bottom end in a casting direction, and a liquid molten core of an aluminum alloy extending from a top surface to the solidification interface, the liquid molten core including a jet of aluminum alloy that impacts the solidification interface at a bottom of the liquid molten core to form a depression in the solidification interface.

[0025] In some cases, the liquid molten core includes resuspended grains from the solidification interface. In some cases, the liquid molten core includes resuspended hydrogen from the solidification interface. In some cases, the solidified shell includes a high strength region disposed between an outer surface of the solidified shell and a centerline extending in a casting direction through a center of the liquid molten core and a center of the solidified shell, the high strength region having a higher concentration of dispersed phase relative to the remainder of the solidified shell. In some cases, the aluminum alloy is a 7xxx series aluminum alloy.

[0026] Embodiments of the present disclosure include aluminum metal products made according to any of the above methods.

[0027] Other objects and advantages will become apparent from the following detailed description of non-limiting examples.

[0028] DETAILED DESCRIPTION OF THE DRAWINGS This specification refers to the following accompanying drawings, in which like reference numbers in different drawings are intended to indicate like or similar elements. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a partial cross-sectional view of a metal casting system for in situ dispersed phase precipitation according to certain aspects of the present disclosure. [Diagram 2] FIG. 1 is a partial cross-sectional view of a metal casting system for in situ dispersed phase precipitation with pool depth control in accordance with certain aspects of the present disclosure. [Diagram 3] FIG. 1 is a partial cross-sectional view of a metal casting system for flow-controlled intensive stirring in accordance with certain aspects of the present disclosure. [Figure 4] FIG. 1 is a partial cross-sectional view of a metal casting system for flow-controlled intensive stirring with multiple feed tubes according to certain aspects of the present disclosure. [Diagram 5] FIG. 1 is a partial cross-sectional view of a metal casting system for intensive stirring with a magnetic stirrer, according to certain aspects of the present disclosure. [Figure 6] FIG. 2 is an enlarged schematic diagram of the bottom of a molten metal pool when there is no strong stirring. [Figure 7]FIG. 1 is a schematic diagram of an enlarged view of the bottom of a puddle of molten metal undergoing intensive stirring, according to certain aspects of the present disclosure. [Figure 8] 1 is a flow diagram illustrating a process for in situ dispersed phase precipitation according to certain aspects of the present disclosure. [Figure 9] 1 is a flow diagram illustrating a process for producing high strength sections of precipitated dispersed phases in a semi-continuously cast ingot according to certain aspects of the present disclosure. [Figure 10] FIG. 2 is a schematic cross-sectional elevation view of an ingot depicting a high strength region according to certain embodiments of the present disclosure. [Figure 11] FIG. 2 is a schematic cross-sectional plan view of an ingot depicting a high strength region according to certain embodiments of the present disclosure. [Figure 12] 1 is a flow diagram illustrating a process for producing an intensive stir semi-continuous cast ingot according to certain aspects of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Certain aspects and features of the present disclosure relate to improving the grain size of shippable metal products by pre-providing a recrystallization-inhibiting dispersed phase during casting. The outer regions of the semi-continuously cast embryonic ingot may be reheated before casting is completed. The temperature of the ingot may be reheated (e.g., to about 410°C to about 420°C) by a unique wiper arrangement and / or other reheating techniques, allowing for the formation of the dispersed phase. Stirring and / or agitation of the molten pool may facilitate the formation of a deeper pool and a desirably fine cast grain size. The formation of the dispersed phase during and / or immediately after casting may pin the grain boundaries to a desirably fine grain size, thereby promoting the same grain size even after a subsequent recrystallization and / or solutionizing step.

[0031] In semi-continuous (DC) casting, the molten metal is passed through a mold cavity having a false bottom or movable bottom. As the molten metal enters the mold cavity, typically from the top, the false bottom descends at a rate related to the rate of flow of the molten metal. The molten metal solidifies near the sides and can be used to hold the liquid and partially liquid metal in the pool. The metal can be 99.9% solid (e.g., completely solid), 100% liquid, and ranges in between. As the molten metal cools, the thickness of the solid region increases, so the pool can assume a V-, U-, or W-shape. The interface between the solid metal and the liquid metal can be referred to as the solidification interface or solidification front. The metal article resulting from the DC casting process can be referred to as an ingot. Ingots can generally have a rectangular cross-section, although other cross-sections, such as circular or even asymmetric cross-sections, can be used. The term ingot, as used herein, can suitably encompass any DC cast metal article, including billets.

[0032] As mentioned above, as the metal solidifies at the solidification front, certain impurities and gases may be expelled from solution and trapped in the solidifying metal. Gases, such as hydrogen, may collect and form bubbles that result in voids in the solidifying metal, commonly known as porosity in the ingot. In addition, impurities expelled at the solidification interface may result in uneven distribution of impurities throughout the ingot.

[0033] Certain aspects of the present disclosure include stirring the molten metal pool. Such stirring can be accomplished in many ways, for example, by using contact stirrers, non-contact magnetic stirrers, or by adjusting the ingress of liquid metal into the pool. Contact stirrers are often undesirable for use with aluminum alloys because of, at least, the risk of impurities and oxides. Non-contact stirrers can include electromagnet and permanent magnet systems designed to induce motion in the molten metal. In some cases, the molten metal pool can be stirred by adjusting the ingress of liquid metal into the pool, for example, by delivering the liquid metal as a powerful jet of liquid metal, for example, a jet powerful enough to penetrate to the bottom of the pool. The liquid metal jet can be provided by increasing the pressure delivering the liquid metal, adjusting the diameter of the nozzle delivering the metal, or other techniques, for example, an eductor nozzle used to inject the existing molten metal pool into the jet created by the newly added liquid metal.

[0034] Intensive stirring in the molten pool can be used to provide stirring along the solidification front. This stirring can sweep away forming metal crystals or parts thereof, impurities, gases, and even some of the liquid metal from the solidification front region. Sweeping away forming metal crystals (e.g., free moving grains) can help to produce finer and more uniform grain size, since the forming crystals or their fragments can be resuspended in the molten pool and serve as additional nucleation sites. Furthermore, stirring of sufficient intensity can reduce the bulk liquid temperature of the molten pool, thus creating a favorable environment for the generation of fine globular grains. This fine globular microstructure is stronger than the typical microstructure found in DC cast ingots. Ingots cast using certain embodiments of the present disclosure, such as intensive stirring, can have higher yield strength and be less susceptible to cold cracking compared to ingots cast without intensive stirring.

[0035] Sweeping impurities away from the solidification front can help achieve less macrosegregation (lower degree of macrosegregation) and therefore improved homogeneity. This less macrosegregation achieved by stirring can be beneficial in providing desirable protective sites within the ingot. As described in more detail herein, the protective sites can be established by reheating the outer solidified portion of the ingot being cast. Reheating can promote the formation of fine dispersed phases within the ingot, which can beneficially strengthen the solidified metal, thus minimizing the susceptibility of the ingot to cracking. These fine dispersed phases can be approximately 30 nm in diameter, but can be other sizes as well. In some cases, these fine dispersed phases can be approximately 10-50 nm, 20-40 nm, or 25-35 nm in diameter.

[0036] It has been unexpectedly discovered that vigorous stirring in the pool can reduce or minimize porosity in the cast ingot. Vigorous stirring can sweep the displaced hydrogen away from the solidification interface, causing it to be resuspended in the remainder of the pool. The resuspended hydrogen can condense with other hydrogen, causing the gas to spread to the surface of the pool where it remains or is vented from the pool. Thus, it has been discovered that the use of vigorous stirring reduces or minimizes porosity in the casting where the displaced hydrogen would otherwise result in undesirable porosity in the casting.

[0037] Because the presence of impurities and dissolved gases in the molten metal can be problematic during casting, conventional casting techniques generally rely on significant upstream preparations to filter impurities from the liquid metal and / or reduce the amount of dissolved gases (e.g., hydrogen) in the liquid metal. Using certain embodiments of the present disclosure, this type of upstream preparation to filter out impurities and / or remove dissolved gases can be significantly reduced or eliminated.

[0038] Proper control of the solidification front can be important to achieve successful casting, especially when using difficult alloys such as the 7xxx series alloys. In conventional DC casting, the casting speed can be used to control the solidification front. Increasing the casting speed can thicken the solidification front, while decreasing the casting speed can narrow the solidification front. If the solidification front is too thick, the molten metal may not completely penetrate the solidified region of the solidification front, which can result in shrinkage cavities and voids. If the solidification front is too thin, hot tearing can occur, where fissures or cracks form between grains due to internal stresses, such as shrinkage-related stresses. Thus, there is often a tradeoff between susceptibility to shrinkage cavities and susceptibility to hot tearing, which can dictate or limit the casting speed. In certain alloys that are particularly prone to hot tearing, such as the 7xxx series alloys, this tradeoff effectively limits the available casting speed, and therefore places an effective maximum on the number of ingots that can be cast in a day.

[0039] According to certain aspects of the present disclosure, control of the solidification front may be achieved by a combination of stirring control and casting speed control. Intensive stirring may provide numerous advantages that allow for high casting speeds while mitigating hot cracking. As discussed above, intensive stirring may help narrow the solidification front. Thus, a DC casting process with intensive stirring may be run at a higher casting speed while maintaining the same thickness of the solidification front compared to a DC casting process without intensive stirring. Intensive stirring may thus allow for faster casting and therefore a higher production capacity per day. Additionally, stirring may result in a deeper extension of the molten metal pool into the ingot being cast, also referred to herein as an embryonic ingot. In DC casting, the hydrostatic pressure of the molten metal provides a substantial driving force for the penetration of the liquid metal into the intergranular gaps at the solidification front. The deeper molten metal pool provided by intensive stirring provides a head area with greater hydrostatic pressure near the bottom of the pool. This head region with greater hydrostatic pressure may facilitate filling of gaps between grains at the solidification front, resulting in a thicker solidification front with reduced or no risk of shrinkage cavities or voids. When strong stirring is employed, a thicker solidification front can be used, allowing for even greater increases in casting speed than would be available without stirring.

[0040] The enhanced stirring may be controlled to result in a nominal reduction in thickness at the solidification front (e.g., solidification interface) of the order of a few millimeters, e.g., about 1-5 mm, or about 10 mm or less to a nominal thickness. In some cases, the nominal reduction in thickness may be a reduction to a nominal thickness of about 20 mm or less, 19 mm or less, 18 mm or less, 17 mm or less, 16 mm or less, 15 mm or less, 14 mm or less, 13 mm or less, 12 mm or less, 11 mm or less, 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less. As used herein, references to controlling stirring to result in a nominal reduction to a particular nominal thickness may mean controlling stirring to an extent that would result in a reduction to the particular thickness assuming a constant casting speed. Thus, although the enhanced stirring associated with an increased casting speed may result in little or no effective change in the thickness of the solidification interface, the enhanced stirring may be expressed as resulting in a certain nominal reduction in the thickness of the solidification interface to a nominal thickness. In addition, as used herein, the thickness of the solidification interface may refer to a minimum thickness, a maximum thickness, and an average thickness, or a thickness at an applicable point or region within the embryonic ingot. For example, a solidification interface having a thickness of 10 mm or less may include a solidification interface whose maximum thickness at any point of the solidification interface is 10 mm or less; a solidification interface whose minimum thickness at any point of the solidification interface reaches a thickness of 10 mm or less; a solidification interface whose average thickness throughout the solidification interface remains 10 mm or less; or a solidification interface whose average thickness at a region at or near the bottom of the solidification interface (e.g., the region furthest from the mold) or any other suitable point or region remains 10 mm or less.

[0041] During DC casting, a coolant (e.g., water) is sprayed onto the surface of the embryonic ingot as it emerges from the mold to remove heat from the ingot. The coolant may be removed using wipers or other techniques, thus allowing a portion of the ingot to be reheated. This reheating may in some cases be used to homogenize the ingot in situ (e.g., during casting). In some cases, this in situ homogenization may occur when the metal reaches a recovery temperature of approximately 470°C to approximately 480°C. On the other hand, according to certain embodiments of the present disclosure, the reheating may be controlled to provide a lower temperature that is more suitable for precipitation, thereby allowing the formation of a dispersed phase at the periphery of the ingot. Reheating an embryonic ingot to promote precipitate formation during casting may be referred to herein as in situ precipitation.

[0042] In some cases, the reheat temperature to achieve the desired in-situ precipitation (e.g., the temperature at which the surface of an embryonic ingot is reheated during casting) may be from about 400°C to about 460°C, from about 405°C to about 425°C, or from about 410°C to about 420°C. In some cases, the reheat temperature may be expressed as a percentage of the final homogenization temperature for the alloy, where the reheat temperature, e.g., when expressed in degrees Celsius, may be from about 80% to about 90%, or from about 85% to about 98% of the final homogenization temperature, e.g., when expressed in degrees Celsius, for the alloy. For example, for a final homogenization temperature of 480°C, the reheat temperature may be about 88% of that temperature, or about 422°C. As another example, for a final homogenization temperature of 480°C, the reheat temperature may be about 96% of that temperature, or about 460°C.

[0043] The desired in-situ precipitation may be accomplished by reheating the embryonic ingot identified above and maintaining a constant temperature or allowing the ingot to cool to or toward room temperature over a period of time. The period may be from about 3 hours to about 5 hours, although in some cases the period may be longer or shorter, for example, deviating from either end point by no more than 10%. The in-situ precipitation process may be initiated during the casting of the ingot and may be terminated after the ingot is cast. Ingots cast using in-situ precipitation may be cooled to or toward room temperature immediately after casting without undergoing a quench. In some cases, the subsequent homogenization step when using in-situ precipitation may be performed for a shortened period of time. For example, a 3 hour in situ precipitation at 410°C may be homogenized at 475°C for approximately 8 hours to result in desired small precipitates, whereas an ingot cast without in situ precipitation may require a 10 hour homogenization period at 475°C, which may only result in undesirable large precipitates.

[0044] Reheating the embryonic ingot can occur in any suitable manner, such as by application of external heat. However, reheating the embryonic ingot for in situ homogenization typically occurs by reducing the amount of heat removal occurring at the surface of the embryonic ingot and allowing the ingot's latent heat, particularly the heat of the molten pool, to reheat the exterior of the ingot. To achieve a desired in situ precipitation temperature, the point at which reheating begins (e.g., the location of the wiper that removes the coolant) can be controlled and / or the depth of the molten core can be controlled. For example, by raising the wiper location (moving the wiper closer to the mold), the solid shell can begin reheating earlier at sections where the molten pool is wider compared to sections further from the mold, thus allowing more of the molten pool's latent heat to reheat the solid shell. In addition to or instead of controlling the point at which reheating begins, the molten pool depth itself may be controlled to provide precise control of the reheating of the solid shell. By inducing stirring, such as by directing a jet of molten metal to the bottom of the solidification interface, the metal pool can be extended a greater distance from the mold than would be the case if no additional stirring were induced. As the depth of the molten core extends farther from the mold, the solid shell will be exposed to the latent heat of the molten core for a longer period of time after the coolant is removed.

[0045] In addition, controlling where reheating begins and / or the depth of the molten core may allow control of the surface depth of the dispersed phase formed during in-situ dispersed phase precipitation. As used herein, the term surface depth may refer to the depth within the ingot from the outer surface (e.g., the rolling surface and side surface) toward the center of the ingot (e.g., the longitudinal centerline running through the center of the ingot in the casting direction). In some cases, reheating the solid shell and / or controlling the depth of the molten core may result in the highest concentration of dispersed phase in a region (e.g., a high strength region) that is approximately 1 / 3 (33%) of the way from the surface of the ingot toward the longitudinal centerline. In some cases, this region may be 1 / 2 (50%) or approximately 1 / 2 (50%) of the way from the surface of the ingot toward the longitudinal centerline. In some cases, this region may be approximately 5%, 10%, 15%, 20% or 25% of the way from the surface of the ingot toward the longitudinal centerline, and approximately 25%, 30%, 35%, 40%, 45% or 50% of the way from the surface of the ingot toward the longitudinal centerline. In some cases, this region may extend from the surface of the ingot to the depth.

[0046] In some cases, the highest concentration of dispersed phase and / or high strength sites may be regions of an ingot having a concentration of dispersed phase greater than the average concentration of dispersed phase throughout the ingot. In some cases, the highest concentration of dispersed phase and / or high strength sites may be defined as regions of an ingot having a concentration of dispersed phase that is at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4 standard deviations above the average concentration of dispersed phase throughout the ingot. High strength sites (e.g., sites with a relatively high concentration of precipitated dispersed phase) may act as protection from cracking as the ingot cools toward room temperature.

[0047] There is often no relationship between the initial cast microstructure and the final wrought microstructure, which is due, at least in part, to recrystallization of the microstructure during hot working and subsequent processing. However, in certain alloys, e.g., certain 7xxx series alloys, recrystallization can be inhibited by the use of dispersed phases, e.g., by the addition of elements such as Cr or Zr. By inducing the formation of such dispersed phases in the cast microstructure, the dispersed phases can inhibit recrystallization, or at least a significant change in average grain size during recrystallization. Because recrystallization is inhibited, the final wrought microstructure can be related to, or more specifically similar to, the initial cast microstructure.

[0048] This ability to relate the cast microstructure to the final wrought microstructure can make techniques to improve the cast microstructure particularly beneficial. Although the addition of grain refiners may be used to reduce grain size to a certain extent, there is a limited effect of additional grain refiners after the saturation limit is reached. On the other hand, using aspects of the present disclosure, such as intensive stirring, further and more desirable grain refinement can be achieved. This finer cast microstructure leads to a finer microstructure for the final product, which can have many advantages, such as corrosion resistance and strength advantages.

[0049] In some cases, certain embodiments of the present disclosure may be particularly suited for 7xxx series alloys, but may also be useful for use with 5xxx series or other series alloys. Certain embodiments of the present disclosure may also help resist "orange peel" defects, for example in the 7xxx series. The "orange peel" defect is a surface defect found after deformation of a metal article, characterized by a rough casting surface having the exterior appearance of an orange. The defect is often the result of large grain size. By reducing the final grain size, the defect may be less noticeable after deformation.

[0050] As used herein, the terms "invention," "the invention," "this invention," and "the present invention" are intended to refer broadly to all of the subject matter of this patent application and the claims that follow. It is to be understood that phrases incorporating these terms are not intended to be limiting of the subject matter described herein or of the scope or meaning of the claims that follow.

[0051] This document refers to alloys identified by AA numbers and other related designations, such as "series" or "7xxx." For an understanding of the number designation systems most commonly used in naming and identifying aluminum and its alloys, please refer to "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys" or "Registration Record of Aluminum Association Alloy Designations and Chemical Compositions Limits for Aluminum Alloys in the Form of Castings and Ingot," both published by The Aluminum Association.

[0052] As used herein, the meaning of "room temperature" can include temperatures of about 15° C. to about 30° C., e.g., about 15° C., about 16° C., about 17° C., about 18° C., about 19° C., about 20° C., about 21° C., about 22° C., about 23° C., about 24° C., about 25° C., about 26° C., about 27° C., about 28° C., about 29° C., or about 30° C. As used herein, the meaning of "ambient conditions" can include temperatures of about room temperature, a relative humidity of about 20% to about 100%, and an atmospheric pressure of about 975 millibars (mbar) to about 1050 mbar. For example, the relative humidity may be about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%, about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about 39%, about 40%, about 41%, about 42%, about 43%, about 44%, about 45%, about 46%, about 47%, about 48%, about 49%, about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%, about 59%, about 60%, about The concentration may be 61%, about 62%, about 63%, about 64%, about 65%, about 66%, about 67%, about 68%, about 69%, about 70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, or any value in between. For example, atmospheric pressure can be about 975 mbar, about 980 mbar, about 985 mbar, about 990 mbar, about 995 mbar, about 1000 mbar, about 1005 mbar, about 1010 mbar, about 1015 mbar, about 1020 mbar, about 1025 mbar, about 1030 mbar, about 1035 mbar, about 1040 mbar, about 1045 mbar, about 1050 mbar, or any value in between.

[0053] All ranges disclosed herein should be understood to include any and all subranges therein. For example, a range stated as "1-10" should be considered to include any and all subranges between a minimum value of 1 and a maximum value of 10 (including the endpoints), i.e., all subranges beginning with a minimum value of 1 or more, e.g., 1-6.1, and ending with a maximum value of 10 or less, e.g., 5.5-10. Unless otherwise noted, the phrase "less than" when referring to a compositional amount of an element means that the element is optional and includes a zero percent composition of that particular element. Unless otherwise noted, all compositional percentages are expressed as weight percent (wt.%).

[0054] As used herein, the meanings of "a," "an," and "the" are inclusive of the singular and plural meanings, unless the context clearly indicates otherwise.

[0055] In the following examples, aluminum alloy products and components thereof are referred to by their elemental composition expressed in weight percent (wt.%), with the balance being aluminum in each alloy, and the sum of all impurities being a maximum of 0.15% wt.%.

[0056] Incidental elements, such as grain refiners and deoxidizers, or other additives, may be present in the present invention and may themselves add other properties without departing from or significantly altering the alloys described herein or the properties of the alloys described herein, however, it should be understood that the scope of the present disclosure should not / cannot be circumvented by the mere addition of one or more incidental elements in amounts that would not change the properties desired in the present disclosure.

[0057] Small amounts of unavoidable impurities, including substances or elements due to the inherent properties of aluminum or leaching from contact with processing equipment, may be present in the alloy. Some impurities typically found in aluminum include iron and silicon. The alloys described may contain up to about 0.25 wt.% of any element in addition to the alloying elements, incidental elements, and unavoidable impurities.

[0058] As used herein, the term "slab" refers to an alloy thickness greater than 15 mm. For example, slab can refer to an aluminum product having a thickness greater than 15 mm, greater than 20 mm, greater than 25 mm, greater than 30 mm, greater than 35 mm, greater than 40 mm, greater than 45 mm, greater than 50 mm, or greater than 100 mm.

[0059] As used herein, a flat plate generally has a thickness in the range of 5 to 50 mm. For example, a flat plate may refer to an aluminum product having a thickness of about 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, or 50 mm.

[0060] As used herein, shate (also referred to as sheet metal) generally has a thickness of about 4 mm to about 15 mm. For example, shate may have a thickness of 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, or 15 mm.

[0061] As used herein, sheet generally refers to an aluminum product having a thickness of less than about 4 mm. For example, sheet may have a thickness of less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, less than 0.5 mm, less than 0.3 mm, or less than 0.1 mm.

[0062] The cast ingots may be processed by any means known to those skilled in the art. Optionally, processing steps to produce sheet metal may be used, including, but not limited to, homogenization, hot rolling, cold rolling, solution heat treatment, and optional pre-aging steps, as known to those skilled in the art.

[0063] In the homogenization step, the cast article described herein is heated to a temperature ranging from about 400°C to about 500°C. For example, the article may be heated to a temperature of about 400°C, about 410°C, about 420°C, about 430°C, about 440°C, about 450°C, about 460°C, about 470°C, about 480°C, about 490°C, or about 500°C. The article is then soaked (i.e., held at a specified temperature) for a period of time. In some instances, the total time for the homogenization step, including the heating and soaking periods, may be 24 hours or less. For example, the article may be heated and soaked at 500°C or less for a total time of 18 hours or less for the homogenization step. In some cases, the article may be heated and soaked at less than 490°C for a total time of 18 hours or less for the homogenization step. In some cases, the homogenization step includes multiple processes. In some non-limiting examples, the homogenization step includes heating the product to a first temperature for a first period of time, followed by heating to a second temperature for a second period of time. For example, the product may be heated to about 465° C. for about 3.5 hours, followed by heating to about 480° C. for about 6 hours.

[0064] The homogenization step may be followed by a hot rolling step. Before starting the hot rolling, the homogenized product may be cooled to a temperature of 300-450°C. For example, the homogenized product may be cooled to a temperature of 325-425°C, or 350-400°C. The product may then be hot rolled at a temperature of 300-450°C to form a hot rolled plate, hot rolled shate or hot rolled sheet having a standard dimension of 3-200 mm (e.g., 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, or any value in between).

[0065] The plate, shate or sheet may then be cold rolled into a sheet using conventional cold rolling machines and techniques. The cold rolled sheet may have a standard dimension of about 0.5 to 10 mm, for example about 0.7 to 6.5 mm. Optionally, the cold rolled sheet may have a standard dimension of 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, 8.0 mm, 8.5 mm, 9.0 mm, 9.5 mm or 10.0 mm. Cold rolling may be performed to provide a final gauge dimension corresponding to a gauge reduction of 85% or less (e.g., a reduction of 10% or less, 20% or less, 30% or less, 40% or less, 50% or less, 60% or less, 70% or less, 80% or less, or 85% or less). Optionally, an intermediate annealing step may be performed during the cold rolling step. The intermediate annealing step may be performed at a temperature of about 300°C to about 450°C (e.g., about 310°C, about 320°C, about 330°C, about 340°C, about 350°C, about 360°C, about 370°C, about 380°C, about 390°C, about 400°C, about 410°C, about 420°C, about 430°C, about 440°C, or about 450°C). In some cases, the intermediate annealing step includes multiple processes. In some non-limiting examples, the intermediate annealing step includes heating the plate, shate or sheet to a first temperature for a first period of time followed by heating to a second temperature for a second period of time. For example, the plate, shate or sheet can be heated to about 410° C. for about 1 hour and then to about 330° C. for about 2 hours.

[0066] The plate, shate or sheet may then be subjected to a solution heat treatment step. The solution heat treatment step may be any conventional process for the sheet that results in the solution of soluble particles. The plate, shate or sheet may be heated to a peak metal temperature (PMT) of 590°C or less (e.g., 400-590°C) and annealed at that temperature for a period of time. For example, the plate, shate or sheet may be annealed at 480°C for a annealing time of 30 minutes or less (e.g., 0 seconds, 60 seconds, 75 seconds, 90 seconds, 5 minutes, 10 minutes, 20 minutes, 25 minutes or 30 minutes). After heating and annealing, the plate, shate or sheet is quenched at a rate of greater than 100°C / s to a temperature of 500-200°C. In one example, the quenching rate of the plate, shate or sheet is greater than 200°C / s at a temperature of 450-200°C. Optionally, in other instances the cooling rate may be faster.

[0067] After quenching, the plate, shate or sheet may optionally be subjected to a pre-aging treatment by reheating the plate, shate or sheet before coiling. The pre-aging treatment may be carried out at a temperature of about 70°C to about 125°C for a period of 6 hours or less. For example, the pre-aging treatment may be carried out at a temperature of about 70°C, about 75°C, about 80°C, about 85°C, about 90°C, about 95°C, about 100°C, about 105°C, about 110°C, about 115°C, about 120°C or about 125°C. Optionally, the pre-aging treatment may be carried out for about 30 minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours or about 6 hours. The pre-aging treatment may be carried out by passing the plate, shate or sheet through a heating device, for example, a device that emits radiant heat, convective heat, induction heat, infrared heat, etc.

[0068] The cast products described herein may also be used to make products in the form of plates or other suitable products. For example, plates, including the products described herein, may be made by processing an ingot in a homogenization step followed by a hot rolling step. In the hot rolling step, the cast product may be hot rolled to a standard thickness dimension of 200 mm or less (e.g., about 10 mm to about 200 mm). For example, the cast product may be hot rolled to a plate having a final standard thickness dimension of about 10 mm to about 175 mm, about 15 mm to about 150 mm, about 20 mm to about 125 mm, about 25 mm to about 100 mm, about 30 mm to about 75 mm, or about 35 mm to about 50 mm.

[0069] The aluminum alloy products described herein can be used in automotive applications and other transportation applications, such as aircraft and railroad applications. For example, the aluminum alloy products of the present disclosure can be used to make automotive structural components, such as bumpers, side beams, roof beams, cross beams, pillar reinforcements (e.g., A-pillars, B-pillars, and C-pillars), inner panels, outer panels, side panels, inner hoods, outer hoods, or trunk lid panels. The aluminum alloy products and methods described herein can also be used in aircraft or railroad vehicle applications, for example, to make exterior and interior panels.

[0070] The aluminum alloy products and methods described herein can also be used in electronics applications. For example, the aluminum alloy products and methods described herein can also be used to make housings for electronic devices, including mobile phones and tablet computers. In some examples, the aluminum alloy products can be used to make the outer frames of mobile phones (e.g., smart phones), tablet bottom frames, and housings for other portable electronic devices.

[0071] These examples are provided to introduce the reader to the general subject matter discussed herein and are not intended to limit the scope of the concepts of the present disclosure. The following sections describe various additional features and examples with reference to the drawings in which like numbers refer to like elements, and descriptive descriptions are used to describe the exemplary embodiments, but as with the exemplary embodiments, should not be used to limit the present disclosure. Elements included in the examples herein may not be drawn to scale. For example, a drawing depicting a metal pool may include exaggerated features for illustrative purposes.

[0072] FIG. 1 is a partial cross-sectional view of a metal casting system 100 for in situ dispersed phase precipitation according to certain embodiments of the present disclosure. A metal source 102, e.g., a tundish, may provide molten metal down a feed tube 104 and out a nozzle 106. An optional skimmer 108 may be used around the feed tube 104 to help distribute the molten metal and mitigate metal oxide formation on the top surface of the molten metal pool 110. A bottom block 120 may be raised by a hydraulic cylinder 122 to conform to the wall of the mold cavity 112. As the molten metal begins to solidify in the mold, the bottom block 120 may be steadily lowered at the casting speed. The embryonic ingot 116 may include a solidified side 118, while molten metal added to the mold may be used to continue to lengthen the embryonic ingot 116. The embryonic ingot 116 may include a bottom end 136. In some cases, the walls of the mold cavity 112 define a hollow space that may contain a coolant 114, such as water. The coolant 114 may exit the hollow space as a jet and flow down the sides 118 of the embryonic ingot 116 to aid in solidification of the embryonic ingot 116. The embryonic ingot 116 may include an outer solid shell 128, a transition metal region (e.g., solidification interface 126), and a molten metal core 124.

[0073] To begin promoting dispersed phase precipitation, reheating of the solidified shell 128 of the embryonic ingot 116 begins at a reheater distance 130, which is defined as the distance from the bottom of the mold cavity 112 (e.g., where the embryonic ingot 116 exits the mold cavity 112) to the location where reheating of the solid shell 118 begins. The reheater distance 130 may be the distance between the mold and the location where reheating begins (e.g., the location of a reheating device such as wiper 142 used to remove coolant 114). The location where reheating begins may be known as the transition location.

[0074] While various techniques may be used to reheat the solid shell 128, FIG. 1 depicts the use of a wiper 142 to remove the coolant 114 from the embryonic ingot 116. While the wiper 142 in FIG. 1 is depicted as a solid wiper, other wipers, such as fluid-based wipers (e.g., air knives), may be used as well. The coolant 114 is removed from the embryonic ingot 116 at cross sections where the core of the embryonic ingot 116 is still molten. Thus, latent heat from the molten core 124, particularly from the region of the molten core 124 between the reheater distance 130 and the molten metal distance 132 (defined below), may reheat the solid shell 128. Thus, the timing and amount of reheating may be precisely controlled by adjusting the reheater distance 130 and / or the molten metal distance 132, as described in more detail herein.

[0075] The reheater distance 130 may be less than the molten metal distance 132 and the pool distance 134. The molten metal distance 132 may be defined as the distance from the bottom of the mold cavity 112 to the bottom of the molten metal core 124. The pool distance 134 may be defined as the distance from the bottom of the mold cavity 112 to the bottom of the solidification interface 126.

[0076] In some cases, the difference between the molten metal distance 132 and the reheater distance 130 may be controlled, for example, by inducing a change in the shape of the molten metal core 132 (e.g., by changing the casting speed and / or inducing stirring) to adjust the molten metal distance 132, or by moving the wiper 142 to adjust the reheater distance 130. Such adjustments of the casting speed, stirring, and / or wiper 142 may be controlled by a controller 138 coupled to any suitable actuator. In some cases, the controller 138 may perform operations based on a pre-set routine. In some cases, the controller 138 may perform operations based on dynamic feedback from the casting process, for example, from temperature measurements made by the sensor 144. The sensor 144 may be any suitable temperature sensor, for example, a contact or non-contact sensor. Although the sensor 144 in FIG. 1 is depicted adjacent to the solid shell 128 to perform measurements of the surface of the solid shell 128, this is not required. Optionally, the sensor(s) may be placed in other locations to take other ingot measurements, such as puddle temperature or coolant temperature.

[0077] An optional flow controller 140 may be positioned to control the flow rate of molten metal through the feed tube 104. Examples of suitable flow controllers 140 include retractable pins for slowing and / or stopping the flow of metal, magnetic pumps, electric pumps, or any suitable device for increasing and / or decreasing the flow of metal through the feed tube 104.

[0078] 1, other types of reheating techniques may be used in place of or in addition to a wiper system at the reheater distance 130. For example, heat may be applied to the solid shell 128 using direct flame impingement, rotary magnetic heaters, or other devices in addition to any latent heat from the molten metal core 124. In some cases, these techniques for applying heat to the solid shell 128 may be controlled, for example, the amount of heat provided and / or where the heat is provided may be controlled. Such control may be performed by a controller 138.

[0079] 2 is a partial cross-sectional view of a metal casting system 200 for in situ dispersed phase deposition with pool depth control according to certain embodiments of the present disclosure. The metal casting system 200 may be similar to the metal casting system 100 of FIG. 1. A metal source 202 may provide molten metal down a feed tube 204, through a flow controller 240, and out a nozzle 206. The flow controller 240 may provide an increased flow from the metal source 202 into the molten metal core 224. This increased flow of molten metal through the feed tube 204 may result in an increased flow 246 in the molten metal core 224. The increased flow 246 may be or correspond to an increased volumetric flow rate, an increased linear flow rate, or both an increased volumetric flow rate and an increased linear flow rate, for example, when compared to the flow arrangement depicted in FIG. 1.

[0080] Such increased flow 246 may result in strong agitation and may act as a jet that may erode a portion of the solidification interface 226. The jet may create a depression in the solid shell 228 and in the solidification interface 226 at the bottom of the metal pool (e.g., the lowest portion of the liquid metal core 224). By doing so, both the molten metal distance 232 and the pool distance 234 may increase.

[0081] Thus, for a wiper 242 located at the same reheater distance 230 from the mold 212 and wiper 142 in FIG. 1, the solid shell 228 of the embryonic ingot 216 may receive more heat from the molten metal core 224 than depicted in FIG. 1 because the difference between the molten metal distance 232 and the reheater distance 230 is greater.

[0082] The intensity of the stirring and / or the amount of flow 246 may be controlled by a controller 238 coupled to any suitable actuator (e.g., flow controller 240). In some cases, the controller 238 may perform operations based on a pre-set routine. In some cases, the controller 238 may perform operations based on dynamic feedback from the casting process, such as from temperature measurements made by the sensor 244. The sensor 244 may be any suitable temperature sensor, such as a contact or non-contact sensor. Although the sensor 244 in FIG. 2 is depicted adjacent to the solid shell 228 to perform measurements of the surface of the solid shell 228, this is not required. In some cases, the sensor(s) may be located elsewhere and may perform other ingot measurements, such as measurements of the sump temperature or coolant temperature.

[0083] 3 is a partial cross-sectional view of a metal casting system 300 for flow-controlled intensive stirring, according to certain embodiments of the present disclosure. Various embodiments of the metal casting system 300 may be similar to appropriate embodiments of the metal casting system 100 of FIG. 1. A metal source 302 may provide molten metal down a feed tube 304, through a flow controller 340, and out a nozzle 306. The flow controller 340 may provide an increased flow from the metal source 302 into the molten metal core 324. This increased flow of molten metal through the feed tube 304 may result in an increased flow 346 within the molten metal core 324.

[0084] Such increased flow 346 may result in strong agitation and may act as a jet that may erode a portion of the solidification interface 326. The jet may create a depression in the solid shell 328 and in the solidification interface 326 at the bottom of the metal pool (e.g., the lowest portion of the liquid metal core 324). The strength of the flow 346, and thus the strength of the resulting jet, may be controlled to result in a depression of a desired shape. If the flow is too weak, either no depression or a depression with a small diameter may be created. If the flow is too strong, the depression may have a diameter that is too large. On the other hand, a desired depression may have a diameter that matches the diameter of the bottom of the pool, resulting in a smooth and gradual shape of the pool. The shape of the pool with the depression may facilitate the flow of the molten metal up the sides of the solidification interface 326, which may facilitate the removal of impurities and hydrogen dislodged from the solidification interface 326, as well as the resuspending of grains to improve the grain structure resulting in finer grains.

[0085] The intensity of the stirring and / or the amount of flow 346 may be controlled by a controller 338 coupled to any suitable actuator (e.g., flow controller 340). In some cases, the controller 338 may perform operations based on a preset routine. In some cases, the controller 338 may perform operations based on dynamic feedback from the casting process, such as from temperature measurements made by the sensor 344. In some cases, feedback from the sensor 344 may be used to infer the solidification interface profile (e.g., the shape of the solidification interface) and to perform actions to provide or maintain a desired solidification interface profile. The sensor 344 may be any suitable temperature sensor, for example, a contact or non-contact sensor. Although the sensor 344 in FIG. 3 is depicted adjacent to the solid shell 328 to perform measurements of the surface of the solid shell 328, this is not required. In some cases, the sensor(s) may be located elsewhere and may perform other ingot measurements, such as measurements of the sump temperature or coolant temperature.

[0086] 4 is a partial cross-sectional view of a metal casting system 400 for flow-controlled intensive stirring with multiple feeds, according to certain embodiments of the present disclosure. The metal casting system 400 may be similar to the metal casting system 300 of FIG. 3. A metal source 402 may deliver molten metal down multiple feeds 404, 450, 454. Although three feeds are used as depicted in FIG. 4, any number of feeds may be used. Each feed 404, 450, 454 may be associated with a controller 440, 456, 452, respectively. Although the flow controllers 440, 456, 452 are depicted as pin valves, any suitable flow controller may be used. When multiple feeds 404, 450, 454 are used to supply molten metal to the molten metal core 424, increased flow 446 can be produced by reducing the flow through one or more of the feeds (e.g., feeds 450, 454) and increasing the flow through the remaining feed or feeds (e.g., feed 404). As depicted in FIG. 4, flow controllers 452 and 456 are closed while flow controller 440 is open, resulting in more fluid being allowed to flow out of the central feed 404, thus creating increased flow 446 within the molten metal core 424.

[0087] Such increased flow 446 may result in strong agitation and may act as a jet that may erode a portion of the solidification interface 426. The jet may create a dimple in the solid shell 428 and in the solidification interface 426 at the bottom of the metal pool (e.g., the lowest portion of the liquid metal core 424). The strength of the flow 446, and thus the strength of the resulting jet, may be controlled (e.g., by actuating any of the flow controllers 452, 440, 456) to result in a dimple of a desired shape. If the flow is too weak, either no dimple may be created or a dimple of a small diameter may be created. If the flow is too strong, the dimple may have a diameter that is too large. On the other hand, the desired dimple may have a diameter that matches the diameter of the bottom of the pool, resulting in a smooth, gradual shape of the pool. The recessed pool shape may facilitate the flow of molten metal up the sides of the solidification interface 426, which may facilitate removing impurities and hydrogen dislodged from the solidification interface 426, as well as resuspending the grains and improving the grain structure resulting in finer grains.

[0088] The intensity of the stirring and / or the amount of flow 446 may be controlled by a controller 438 coupled to any suitable actuators (e.g., flow controllers 440, 452, 456). In some cases, the controller 438 may perform operations based on a preset routine. In some cases, the controller 438 may perform operations based on dynamic feedback from the casting process, such as from temperature measurements made by the sensor 444. In some cases, feedback from the sensor 444 may be used to infer the solidification interface profile (e.g., the shape of the solidification interface) and to perform actions to provide or maintain a desired solidification interface profile. The sensor 444 may be any suitable temperature sensor, for example, a contact or non-contact sensor. Although the sensor 444 in FIG. 4 is depicted adjacent to the solid shell 428 to perform measurements of the surface of the solid shell 428, this is not required. In some cases, the sensor(s) may be located elsewhere and may perform other ingot measurements, such as measurements of the sump temperature or coolant temperature.

[0089] 5 is a partial cross-sectional view of a metal casting system 500 for intensive stirring with a magnetic stirrer, according to certain embodiments of the present disclosure. The metal casting system 500 may be similar to the metal casting system 300 of FIG. 3. A metal source 502 may provide molten metal down a feed tube 504 and out a nozzle 506. Although not depicted in FIG. 5, a flow controller may be used in some cases.

[0090] A non-contact magnetic stirrer 560 is positioned adjacent to the molten metal core 524 to generate surface flows 566, 568. The non-contact magnetic stirrer 560 can be an electromagnet or a permanent magnet. In one example, the permanent magnet non-contact magnetic stirrer 560 can be positioned on the opposite side of the feed tube 504 and can rotate in a direction 562, 564 suitable to generate surface flows 566, 568 toward the feed tube 504. The surface flows 556, 568 can interact with the molten metal flowing out of the feed tube 504 and can result in an increased flow 546 within the molten metal core 524.

[0091] Such increased flow 546 may provide strong agitation and may act as a jet that may erode a portion of the solidification interface 526. The jet may create a depression in the solid shell 528 and in the solidification interface 526 at the bottom of the metal pool (e.g., the lowest portion of the liquid metal core 524). The strength of the flow 546, and thus the strength of the resulting jet, may be controlled to provide a depression of a desired shape. If the flow is too weak, either no depression or a depression with a small diameter may be created. If the flow is too strong, the depression may have a diameter that is too large. On the other hand, a desired depression may have a diameter that matches the diameter of the bottom of the pool, resulting in a smooth and gradual shape of the pool. The shape of the pool with the depression may facilitate the flow of the molten metal up the sides of the solidification interface 526, which may facilitate the removal of impurities and hydrogen dislodged from the solidification interface 526, as well as the resuspending of grains to improve the grain structure resulting in finer grains.

[0092] The intensity of the stirring and / or the amount of flow 546 may be controlled by a controller 538 coupled to any suitable actuator (e.g., non-contact stirrer 560). In some cases, the controller 538 may perform operations based on a preset routine. In some cases, the controller 538 may perform operations based on dynamic feedback from the casting process, such as from temperature measurements made by the sensor 544. In some cases, feedback from the sensor 544 may be used to infer the solidification interface profile (e.g., the shape of the solidification interface) and to perform actions to provide or maintain a desired solidification interface profile. The sensor 544 may be any suitable temperature sensor, for example, a contact or non-contact sensor. Although the sensor 544 in FIG. 5 is depicted adjacent to the solid shell 528 to perform measurements of the surface of the solid shell 528, this is not required. In some cases, the sensor(s) may be located elsewhere and may perform other ingot measurements, such as measurements of the sump temperature or coolant temperature.

[0093] 6 is a close-up schematic diagram of the bottom of the molten metal pool 600 in the absence of strong stirring. The bottom of the molten metal core 624 and solidification interface 626, as well as the adjacent portion of the solid shell 628, may exhibit a non-uniform layered shape, which may be due to settling of suspended grains and other factors. As a result, the molten metal may remain somewhat stagnant near this region. This bottom region of the molten metal pool may have a width 670 that may be roughly defined between the regions where the sloping walls of the solidification interface 626 reach their maximum depth.

[0094] 7 is a schematic diagram of an enlarged bottom of a pool of molten metal 700 undergoing strong stirring, according to certain embodiments of the present disclosure. The bottom of the molten metal core 724 and solidification interface 726, as well as adjacent portions of the solid shell 728, may exhibit an uneven U-shaped or parabolic profile due to the increased flow 746 of molten metal. The flow 746 of molten metal may erode the solidification interface 726 and solid shell 728 to form a depression 774. The depression 774 may have a depth 772 that extends from the bottom before stirring (e.g., as seen in FIG. 6) to the bottom of the depression 774 during stirring (e.g., as seen in FIG. 7). The depression 774 may have a diameter 770 (e.g., maximum diameter) approximately equal to the diameter of the pool before stirring (e.g., diameter 670 in FIG. 6).

[0095] The flow of molten metal 746 can be controlled to erode the solidification interface 726 to a thickness on the order of a few millimeters, such as approximately 1-5 mm, or approximately 10 mm or less, at least at or adjacent the bottom of the solidification interface 726. In some cases, the flow of molten metal 746 can be controlled to erode the solidification interface 726 to a thickness of approximately 20 mm or less, 19 mm or less, 18 mm or less, 17 mm or less, 16 mm or less, 15 mm or less, 14 mm or less, 13 mm or less, 12 mm or less, 11 mm or less, 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less, at least at or adjacent the bottom of the solidification interface 726. FIG. 8 is a flow diagram illustrating a process 800 for in situ dispersed phase precipitation according to certain embodiments of the present disclosure. At block 802, molten metal is provided to a mold. At block 804, the embryonic ingot being formed in the mold is advanced in a casting direction. At block 806, heat is continuously removed from a shell between the bottom of the mold as the embryonic ingot emerges from the mold and a reheating location. At block 808, the embryonic ingot is reheated. Reheating may be initiated at the reheating location. In some cases, reheating may include removing the coolant provided to the surface of the embryonic ingot during block 806. At block 810, the embryonic ingot may be held at a reheating temperature for a period of time, for example, approximately three hours. In some cases, instead of holding the ingot at the reheating temperature, the ingot is gradually cooled at block 812. The ingot may be gradually cooled to room temperature, for example, over a period of at least approximately three hours.

[0096] In some cases, stirring may be optionally induced at block 816. Stirring may be induced to improve various characteristics of the as-cast ingot and to increase the depth of the molten metal pool and therefore affect the reheating performed at block 808.

[0097] In some cases, temperature metrology monitoring may optionally be performed at block 814. The results of the temperature metrology monitoring may be used to adjust the amount of agitation induced at block 816 and / or the reheat location used for block 808. The temperature metrology monitoring at block 814 may occur continuously.

[0098] 9 is a flow diagram illustrating a process 900 for producing high strength sections of precipitated dispersed phases in a semi-continuously cast ingot according to certain embodiments of the present disclosure. At block 902, an embryonic ingot may be formed or may begin to be formed. At block 904, at least some of the inner molten core of the embryonic ingot may solidify to form a solid shell of the embryonic ingot. At block 906, high strength sections of precipitated dispersed phases may be continuously formed.

[0099] Continuously forming high strength regions of precipitated dispersed phase at block 906 may include reheating an outer solid shell at a reheater distance at block 908. Optionally, a temperature of the ingot may be measured at block 910. This measurement may be used to adjust the reheater distance at block 912 and / or adjust the melt distance at block 916. Adjusting the reheater distance at block 912 may include moving a reheater (e.g., wiper) at block 914. Adjusting the melt distance at block 916 may include inducing agitation at block 918.

[0100] 10 is a schematic cross-sectional elevation view of an ingot 1016 depicting a high strength region 1074 according to certain embodiments of the present disclosure. The high strength region 1074 is depicted extending from at or near the surface of the ingot 1016 to a surface depth less than halfway from the surface of the ingot 1016 to the longitudinal centerline 1016 of the ingot 1016.

[0101] 11 is a schematic planar cross-sectional view of an ingot 1116 depicting a high strength region 1174 according to certain embodiments of the present disclosure. The high strength region 1174 is depicted extending from at or near the surface of the ingot 1116 (e.g., the rolling surface and / or side) to a surface depth less than halfway from the surface of the ingot 1116 to an associated centerline, such as less than halfway from the rolling surface to a lateral centerline 1180 of the ingot 1116 and from a side of the ingot 1116 to a rolling surface centerline 1178.

[0102] FIG. 12 is a flow diagram illustrating a process 1200 for producing an intensively stirred semi-continuously cast ingot according to certain embodiments of the present disclosure. In block 1202, molten metal may be delivered to a mold. In block 1204, an outer solid shell may be formed as heat is removed from the molten metal. In block 1206, the ingot may advance out of the mold at a casting speed. In block 1208, a stirring intensity may be determined using the casting speed. The stirring intensity may be based on a sensed or otherwise known casting speed. In block 1210, stirring may be induced at the intensity determined in block 1208. Inducing stirring may include using a flow controller and / or a non-contact stirrer, although other techniques may be used. In block 1212, the casting speed may be changed. Upon changing the casting speed, the stirring intensity may again be determined in block 1208 based on the updated casting speed from block 1212. Stirring may then be induced at the newly determined intensity. In optional block 1214, the temperature of the embryonic ingot may be monitored. Once the ingot temperature has been monitored, the stirring intensity may again be determined in block 1208 based at least in part on the temperature measured in block 1214. Stirring may then be induced at the newly determined intensity.

[0103] In optional block 1216, the high strength regions of the precipitated dispersed phase may be formed continuously as disclosed herein.

[0104] Exemplary embodiments As used hereinafter, any reference to a series of embodiments should be understood as a separate reference to each of those examples (e.g., "embodiments 1-4" should be understood as "embodiments 1, 2, 3 or 4").

[0105] Aspect 1 is a method, such as a casting method, that includes supplying molten metal to a casting mold to form an embryonic ingot including an outer solid shell and an inner molten core; advancing the embryonic ingot in a traveling direction away from the casting mold while supplying additional molten metal to the casting mold; removing heat from the embryonic ingot between the casting mold and a transfer location by directing a supply of liquid coolant against an outer surface of the outer solid shell; and reheating the embryonic ingot at the transfer location such that at least a portion of the outer solid shell of the embryonic ingot at the transfer location reaches a temperature suitable for precipitation of a dispersed phase, the temperature being lower than a homogenization temperature of the molten metal, wherein the transfer location is in a plane perpendicular to the traveling direction and intersecting the inner molten core.

[0106] Aspect 2 is a method according to any preceding or succeeding aspect, wherein the temperature, eg, in degrees Celsius, is 80-98% of the homogenization temperature, eg, in degrees Celsius, of the molten metal.

[0107] Aspect 3 is a method according to any preceding or succeeding aspect, wherein the temperature, eg, in degrees Celsius, is 85-90% of the homogenization temperature, eg, in degrees Celsius, of the molten metal.

[0108] Aspect 4 is the method according to any preceding or following aspect, wherein the temperature is 400 to 460°C.

[0109] Aspect 5 is the method according to any preceding or following aspect, wherein the temperature is 410 to 420°C.

[0110] Example 6 is the method of any preceding or following example, further comprising maintaining said temperature in said portion of said outer solid shell for at least 3 hours.

[0111] Example 7 is the method of any preceding or following example, wherein reheating the embryonic ingot includes removing the liquid coolant from the exterior surface of the outer solid shell.

[0112] Example 8 is the method of any preceding or following example, wherein reheating the embryonic ingot further comprises applying heat to the exterior surface of the outer solid shell to supplement latent heating from the inner molten core.

[0113] Example 9 is the method of any preceding or following example, further comprising: taking a temperature measurement of the embryonic ingot; and dynamically adjusting the transition location based on the temperature measurement.

[0114] Example 10 is the method of any preceding or following example, further comprising inducing agitation in the inner molten core adjacent an interface between the inner molten core and the outer solid shell.

[0115] Example 11 is the method of any preceding or following example, further comprising performing a temperature measurement of the embryonic ingot, and wherein inducing stirring in the internal molten core comprises dynamically adjusting a strength of stirring based on the temperature measurement.

[0116] Example 12 is a method as described in any preceding or following example, wherein the transition location is selected such that the plane intersects the embryonic ingot at a cross section in which the outer solid shell of the embryonic ingot occupies approximately one-third of a line extending within the plane from the outer surface to the center of the embryonic ingot.

[0117] Example 13 is a method as described in any preceding or following example, wherein the transition location is selected such that the plane intersects the embryonic ingot at a cross section in which the outer solid shell of the embryonic ingot occupies less than 50% of a line extending within the plane from the outer surface to a center of the embryonic ingot.

[0118]

[0036] Example 14 is the method of any preceding or following example, wherein the molten metal is a 7xxx series aluminum alloy.

[0119] Example 15 is a method comprising forming an embryonic ingot by supplying molten metal to a mold and removing heat from the molten metal to form an outer solid shell; solidifying an internal molten core of the embryonic ingot as the embryonic ingot advances in a travel direction away from the mold and additional molten metal is supplied to the mold, where solidifying the internal molten core comprises removing heat from the internal molten core through the outer solid shell; and further comprising continuously forming high strength sites in the outer solid shell at a cross section of the embryonic ingot perpendicular to the travel direction and intersecting the internal molten core, where the high strength sites are located between an outer surface of the outer solid shell and the inner molten core, and where forming the high strength sites comprises reheating the outer solid shell at the cross section to induce dispersed phase precipitation in the outer solid shell.

[0120] Example 16 is the method of any preceding or following example, wherein reheating the outer solid shell at the cross section includes reheating a portion of the outer solid shell to a temperature suitable for precipitation of a dispersed phase, the temperature being less than a homogenization temperature of the molten metal.

[0121] Example 17 is the method of any preceding or following example, wherein the temperature, e.g., in degrees Celsius, is 80-98% of the homogenization temperature, e.g., in degrees Celsius, of the molten metal.

[0122] Example 18 is the method of any preceding or following example, wherein the temperature is 85-90% of the homogenization temperature of the molten metal.

[0123] Aspect 19 is the method according to any preceding or following aspect, wherein the temperature is 400 to 460°C.

[0124] A twenty-first aspect is the method according to any preceding or following aspect, wherein the temperature is 410 to 420°C.

[0125] Example 21 is the method of any preceding or following example, further comprising maintaining said temperature in said portion of the outer solid shell for at least 3 hours, e.g., from 3 to 10 hours.

[0126] Example 22 is the method of any preceding or following example, wherein removing heat from the inner molten core through the outer solid shell includes supplying a liquid coolant to the exterior surface of the outer shell, and reheating the outer solid shell includes removing the liquid coolant from the exterior surface of the outer solid shell.

[0127] Example 23 is the method of any preceding or following example, wherein reheating the outer solid shell further comprises applying heat to the exterior surface of the outer solid shell to supplement the latent heating from the inner molten core.

[0128] Example 24 is the method of any preceding or following example, further comprising: measuring a temperature of the embryonic ingot; and dynamically adjusting a distance between the mold and the cross section based on the temperature measurement.

[0129] Example 25 is the method of any preceding or following example, further comprising inducing agitation in the inner molten core adjacent an interface between the inner molten core and the outer solid shell.

[0130] Example 26 is the method of any preceding or following example, further comprising performing a temperature measurement of the embryonic ingot, and inducing stirring in the internal molten core comprises dynamically adjusting a strength of stirring based on the temperature measurement.

[0131] Example 27 is the method of any preceding or following example, wherein in the cross-section, the outer solid shell of the embryonic ingot occupies approximately one-third of a line extending from the outer surface to a center of the embryonic ingot.

[0132] Example 28 is the method of any preceding or following example, wherein in the cross-section, the outer solid shell of the embryonic ingot occupies 50% or less of a line extending from the outer surface to a center of the embryonic ingot.

[0133] Example 29 is the method of any preceding or following example, wherein the molten metal is a 7xxx series aluminum alloy.

[0134] Example 30 is the method of any preceding or following example, wherein the high strength region comprises a higher concentration of dispersed phase relative to the remainder of the outer solid shell.

[0135] Example 31 is an aluminum metal product comprising a solidified aluminum alloy block having two ends and an outer surface, the solidified aluminum alloy block comprising a core region containing a center of the solidified aluminum alloy block; an outer region integral with the outer surface; and a high strength section disposed between the core region and the outer region, the high strength section having a higher concentration of dispersed phase compared to each of the core region and the outer region.

[0136] Example 32 is the aluminum metal product of any preceding or following example, wherein the solidified aluminum alloy mass includes retained heat from a semi-continuous casting process.

[0137]

[0023] Example 33 is the aluminum metal product of any preceding or following example, wherein the high strength region is located at a depth of approximately one-third of a line extending along a cross section of the solidified aluminum alloy block from the exterior surface to the center of the solidified aluminum alloy block.

[0138]

[0023] Example 34 is the aluminum metal product of any preceding or following example, wherein the high strength region is located at a depth less than or equal to one-half of a line extending along a cross section of the solidified aluminum alloy block from the outer surface to the center of the solidified aluminum alloy block.

[0139]

[0035] Example 35 is the aluminum metal product of any preceding or following example, wherein the solidified aluminum alloy mass is cylindrical in shape.

[0140]

[0036] Example 36 is the aluminum metal product of any preceding or following example, wherein a cross-section of the solidified aluminum alloy block perpendicular to a casting direction of the solidified aluminum alloy block is rectangular in shape.

[0141] Example 37 is the aluminum metal product of any preceding or following example, wherein the solidified aluminum alloy mass is a solidified 7xxx series aluminum alloy mass.

[0142] Example 38 is the aluminum metal product of any preceding or following embodiment, made according to the method of any preceding or following embodiment.

[0143] Example 39 is an embryonic ingot comprising a liquid molten core of an aluminum alloy extending from a top surface to a solidification interface, and a solidified shell of the aluminum alloy, the solidified shell comprising an outer surface extending from the solidification interface to a bottom end in a casting direction, the solidified shell comprising a high strength portion disposed between the outer surface and a centerline extending in the casting direction through a center of the liquid molten core and a center of the solidified shell, the high strength portion having a higher concentration of a dispersed phase relative to a remainder of the solidified shell.

[0144] Example 40 is the embryonic ingot of any preceding or following example, wherein the high strength region is located at a depth of approximately one-third of the line extending from the outer surface to the center line.

[0145] Example 41 is the embryonic ingot of any preceding or following example, wherein the high strength region is located at a depth equal to or less than one-half of a line extending from the outer surface to the center line.

[0146] Example 42 is the embryonic ingot of any preceding or following example, wherein the solidified shell is cylindrical in shape.

[0147]

[0036] Example 43 is the embryonic ingot of any preceding or following example, wherein a cross-section of the solidified shell perpendicular to the casting direction has a rectangular shape.

[0148] Example 44 is the embryonic ingot of any preceding or following example, wherein the aluminum alloy is a 7xxx series aluminum alloy.

[0149] Example 45 is an embryonic ingot as described in any preceding or subsequent embodiment, made according to a method as described in any preceding or subsequent embodiment.

[0150] Example 46 is a method comprising: delivering molten metal from a metal source to a metal pool of an embryonic ingot being cast into a mold; forming an outer solid shell of solidified metal by removing heat from the metal pool, a solidification interface being located between the outer solid shell and the metal pool; advancing the embryonic ingot at a casting speed in an advancement direction away from the mold while delivering the molten metal and while forming the outer solid shell; determining an intensity of stirring using the casting speed, the intensity of stirring suitable for resulting in a target solidification interface profile at the casting speed; and further comprising inducing stirring in the molten metal pool at the determined intensity, wherein inducing stirring in the molten metal pool results in the solidification interface assuming the target solidification interface profile at the casting speed.

[0151] Example 47 is the method of any preceding or following example, wherein inducing stirring includes applying a stirring force to the molten metal in the metal reservoir using a non-contact magnetic stirrer.

[0152] Example 48 is the method of any preceding or following example, wherein delivering the molten metal includes delivering the molten metal through a plurality of nozzles at a mass flow rate, and inducing agitation includes increasing the flow rate of the molten metal through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles.

[0153] Example 49 is the method of any preceding or following example, further comprising: changing the casting speed; determining an updated intensity of stirring using the updated casting speed, the updated intensity of stirring suitable for resulting in the target solidification profile at the updated casting speed; and further comprising inducing stirring in the molten metal pool at the updated intensity, wherein inducing stirring in the molten metal pool at the updated intensity results in the solidification interface assuming the target solidification interface profile at the updated casting speed.

[0154] Example 50 is the method of any preceding or following example, wherein the molten metal is a 7xxx series aluminum alloy.

[0155] Example 51 is the method of any preceding or subsequent example, further comprising measuring a temperature of the embryonic ingot, and determining the intensity of stirring using the casting speed comprises using the measured temperature.

[0156]

[0036] Example 52 is the method of any preceding or following example, wherein the target solidification interface profile is predetermined to minimize risk of cracking.

[0157] Example 53 is the method of any preceding or following example, further comprising continuously forming high strength sites in the outer solid shell at a cross section of the embryonic ingot that is perpendicular to the direction of travel and intersects the inner molten core, the high strength sites being located between an outer surface of the outer solid shell and the inner molten core, and forming the high strength sites comprises reheating the outer solid shell at the cross section to induce dispersed phase precipitation in the outer solid shell.

[0158] Example 54 is the method of any preceding or following example, wherein inducing stirring in the molten metal pool includes controlling delivery of the molten metal into the metal pool such that a jet of molten metal erodes the solidification interface at a bottom of the metal pool to form a depression, the depression having a diameter dimensioned to match a diameter of the bottom of the metal pool.

[0159] Example 55 is a method comprising: delivering molten metal from a metal source to a metal pool of an embryonic ingot being cast into a mold; forming an outer solid shell of solidified metal by removing heat from the metal pool, a solidification interface being located between the outer solid shell and the metal pool; advancing the embryonic ingot at a casting speed in an advancing direction away from the mold while delivering the molten metal and while forming the outer solid shell; and controlling delivery of the molten metal into the metal pool to generate a jet of molten metal at a bottom of the metal pool sufficient to erode at least a portion of the solidification interface.

[0160] Example 56 is the method of any preceding or following example, wherein controlling the delivery of the molten metal includes controlling the delivery of the molten metal such that the jet of molten metal erodes the solidification interface to a thickness of 10 mm or less.

[0161] Example 57 is the method of any preceding or following example, wherein delivering the molten metal includes delivering the molten metal through a plurality of nozzles at a mass flow rate, and generating the jet of molten metal includes increasing a flow rate of the molten metal through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles.

[0162] Example 58 is the method of any preceding or following example, further comprising applying a stirring force to the molten metal in the metal reservoir using a non-contact magnetic stirrer.

[0163] Example 59 is the method of any preceding or following example, further comprising changing the casting speed, wherein controlling the delivery of the molten metal comprises dynamically adjusting the delivery of the molten metal based on the changed casting speed so that the jet of molten metal continues to erode at least a portion of the solidification interface at the bottom of the metal pool.

[0164] Example 60 is the method of any preceding or following example, wherein the molten metal is a 7xxx series aluminum alloy.

[0165] Example 61 is the method of any preceding or following example, further comprising measuring a temperature of the embryonic ingot, and controlling the delivery of the molten metal comprises dynamically adjusting the delivery of the molten metal based on the measured temperature so that the jet of molten metal continues to erode at least the portion of the solidification interface at the bottom of the metal pool.

[0166] Example 62 is the method of any preceding or subsequent example, further comprising continuously forming high strength sites in the outer solid shell at a cross section of the embryonic ingot that is perpendicular to the direction of travel and intersects the metal pool, the high strength sites being located between an outer surface of the outer solid shell and the metal pool, and forming the high strength sites comprises reheating the outer solid shell at the cross section to induce dispersed phase precipitation in the outer solid shell.

[0167] Embodiment 63 is an aluminum metal product made according to the method of any preceding or following embodiment.

[0168] Example 64 is an embryonic ingot comprising a solidified shell of an aluminum alloy extending from a solidification interface to a bottom end in a casting direction, and a liquid molten core of the aluminum alloy extending from a top surface to the solidification interface, the liquid molten core comprising a jet of the aluminum alloy at a bottom of the liquid molten core that impacts the solidification interface to form a depression in the solidification interface.

[0169] Example 65 is the embryonic ingot of any preceding or following example, wherein the liquid molten core comprises resuspended grains from the solidification interface.

[0170] Example 66 is the embryonic ingot of any preceding or following example, wherein the liquid molten core includes resuspended hydrogen from the solidification interface.

[0171] Example 67 is an embryonic ingot according to any preceding or following example, wherein the solidified shell includes a high strength region disposed between an outer surface of the solidified shell and a centerline extending in the casting direction through a center of the liquid molten core and a center of the solidified shell, the high strength region having a higher concentration of a dispersed phase compared to a remainder of the solidified shell.

[0172] Example 68 is the embryonic ingot of any preceding or following example, wherein the aluminum alloy is a 7xxx series aluminum alloy.

[0173] All patents and publications cited herein are incorporated by reference in their entirety. The above description of the embodiments, including the exemplified embodiments, has been provided for purposes of illustration and description only and is not intended to be exhaustive or limited to the precise forms disclosed. Numerous modifications, adaptations and uses thereof will be apparent to those skilled in the art. The present disclosure includes the following inventive aspects: <Aspect 1> A casting method comprising the steps of: delivering the molten metal to a casting mold to form an embryonic ingot comprising an outer solid shell and an inner molten core; advancing said embryonic ingot in a forward direction away from said mold while supplying additional molten metal to said mold; removing heat from said embryonic ingot between said mold and a transfer location by directing a supply of liquid coolant to an exterior surface of said outer solid shell; and reheating the embryonic ingot at the transfer location such that at least a portion of the outer solid shell of the embryonic ingot at the transfer location reaches a temperature suitable for precipitation of a dispersed phase, the temperature being lower than a homogenization temperature of the molten metal. wherein the transition location is in a plane perpendicular to the direction of travel and intersects the inner molten core. <Aspect 2> 2. The method of claim 1, wherein the temperature, in degrees Celsius, is 80-98% of the homogenization temperature, in degrees Celsius, of the molten metal. <Aspect 3> 2. The method of claim 1, wherein the temperature, in degrees Celsius, is 85-90% of the homogenization temperature, in degrees Celsius, of the molten metal. <Aspect 4> 2. The method according to aspect 1, wherein the temperature is 400 to 460°C. <Aspect 5> 2. The method according to aspect 1, wherein the temperature is 410 to 420° C. <Aspect 6> 2. The method of claim 1, further comprising maintaining said temperature in said portion of said outer solid shell for at least 3 hours. <Aspect 7> reheating the embryonic ingot removing the liquid coolant from the exterior surface of the outer solid shell. 2. The method of embodiment 1, comprising: <Aspect 8> reheating the embryonic ingot applying heat to the exterior surface of the outer solid shell to supplement the latent heating from the inner molten core; 8. The method of embodiment 7, further comprising: <Aspect 9> measuring the temperature of the embryonic ingot; and Dynamically adjusting the transition location based on the temperature measurements. 2. The method of embodiment 1, further comprising: <Aspect 10> inducing agitation in the inner molten core adjacent an interface between the inner molten core and the outer solid shell. 2. The method of embodiment 1, further comprising: <Aspect 11> Measuring the temperature of the embryonic ingot and inducing agitation in the inner molten core further comprises: Dynamically adjusting the intensity of the stirring based on said temperature measurements. 11. The method of embodiment 10, comprising: <Aspect 12> 2. The method of claim 1, wherein the transition location is selected such that the plane intersects the embryonic ingot at a cross section in which the outer solid shell of the embryonic ingot occupies approximately one-third of a line extending within the plane from the outer surface to a center of the embryonic ingot. <Aspect 13> 2. The method of claim 1, wherein the transition location is selected such that the plane intersects the embryonic ingot at a cross section in which the outer solid shell of the embryonic ingot occupies less than 50% of a line extending within the plane from the outer surface to a center of the embryonic ingot. <Aspect 14> 2. The method of claim 1, wherein the molten metal is a 7xxx series aluminum alloy. <Aspect 15> 1. A method comprising: forming an embryonic ingot by delivering molten metal to a mold and removing heat from said molten metal to form an outer solid shell; solidifying an internal molten core of the embryonic ingot as the embryonic ingot advances in a forward direction away from the mold and additional molten metal is supplied to the mold. and solidifying the inner molten core comprises: removing heat from said inner molten core through said outer solid shell; and forming a continuous high strength region within the outer solid shell at a cross section of the embryonic ingot perpendicular to the direction of travel and intersecting the inner molten core. wherein the high strength region is located between an exterior surface of the outer solid shell and the inner molten core, and forming the high strength region comprises reheating the outer solid shell at the cross section to induce dispersed phase precipitation in the outer solid shell. <Aspect 16> reheating the outer solid shell at the cross section; reheating a portion of said outer solid shell to a temperature suitable for precipitation of the dispersed phase; wherein the temperature is below a homogenization temperature of the molten metal. <Aspect 17> 17. The method of claim 16, wherein the temperature, in degrees Celsius, is 80-98% of the homogenization temperature, in degrees Celsius, of the molten metal. <Aspect 18> 17. The method of claim 16, wherein the temperature, in degrees Celsius, is 85-90% of the homogenization temperature, in degrees Celsius, of the molten metal. <Aspect 19> 17. The method according to aspect 16, wherein the temperature is 400 to 460°C. <Aspect 20> 17. The method according to claim 16, wherein the temperature is 410 to 420° C. <Aspect 21> 17. The method of embodiment 16, further comprising maintaining said temperature in said portion of said outer solid shell for at least 3 hours. <Aspect 22> removing heat from the inner molten core through the outer solid shell; providing a liquid coolant to said exterior surface of said outer shell; and reheating the outer solid shell comprises: removing the liquid coolant from the exterior surface of the outer solid shell. 16. The method of embodiment 15, comprising: <Aspect 23> reheating the outer solid shell applying heat to the exterior surface of the outer solid shell to supplement the latent heating from the inner molten core; 23. The method of embodiment 22, further comprising: <Aspect 24> measuring the temperature of the embryonic ingot; and dynamically adjusting the distance between the mold and the cross section based on the temperature measurements. 16. The method of embodiment 15, further comprising: <Aspect 25> inducing agitation in the inner molten core adjacent an interface between the inner molten core and the outer solid shell. 16. The method of embodiment 15, further comprising: <Aspect 26> Measuring the temperature of the embryonic ingot and inducing agitation in the inner molten core further comprises: Dynamically adjusting the intensity of the stirring based on said temperature measurements. 26. The method of embodiment 25, comprising: <Aspect 27> 16. The method of claim 15, wherein in the cross-section, the outer solid shell of the embryonic ingot occupies approximately one-third of a line extending from the outer surface to a center of the embryonic ingot. <Aspect 28> 16. The method of claim 15, wherein in the cross-section, the outer solid shell of the embryonic ingot occupies 50% or less of a line extending from the outer surface to a center of the embryonic ingot. <Aspect 29> The method of embodiment 15, wherein the molten metal is a 7xxx series aluminum alloy. <Aspect 30> 16. The method of embodiment 15, wherein the high strength regions comprise a higher concentration of dispersed phase relative to the remainder of the outer solid shell. <Aspect 31> An aluminum metal product comprising: A solidified block of aluminum alloy having two ends and an outer surface. and the solidified aluminum alloy mass comprises: a core region containing the center of the solidified aluminum alloy mass; an outer region integral with said outer surface; and A high strength section disposed between the core region and the outer region. wherein the high strength section has a higher concentration of dispersed phase compared to each of the core region and the outer region. <Aspect 32> The solidified aluminum alloy block is Retained heat from the semi-continuous casting process 32. The aluminum metal product of embodiment 31, comprising: <Aspect 33> 32. The aluminum metal product of claim 31, wherein the high strength portion is located at a depth of approximately one-third of a line extending along a cross section of the solidified aluminum alloy block from the outer surface to the center of the solidified aluminum alloy block. <Aspect 34> 32. The aluminum metal product of claim 31, wherein the high strength region is located at a depth of less than or equal to one-half of a line extending along a cross section of the solidified aluminum alloy block from the outer surface to the center of the solidified aluminum alloy block. <Aspect 35> 32. The aluminum metal product of embodiment 31, wherein the solidified aluminum alloy chunk is cylindrical in shape. <Aspect 36> 32. The aluminum metal product of claim 31, wherein a cross-section of the solidified aluminum alloy block perpendicular to a casting direction of the solidified aluminum alloy block is rectangular in shape. <Aspect 37> 32. The aluminum metal product of embodiment 31, wherein the solidified aluminum alloy chunk is a solidified 7xxx series aluminum alloy chunk. <Aspect 38> 32. The aluminum metal product of claim 31, made according to the method of claim 1 or claim 15. <Aspect 39> An embryonic ingot, a liquid molten core of the aluminum alloy extending from the upper surface to the solidification interface; and Solidified shell of the aluminum alloy The solidified shell includes an outer surface extending from the solidification interface to a bottom end in a casting direction, and the solidified shell includes a high strength portion disposed between the outer surface and a center line extending in the casting direction through a center of the liquid molten core and a center of the solidified shell; wherein the high strength portion has a higher concentration of dispersed phase compared to the remainder of the solidified shell. <Aspect 40> 40. The embryonic ingot of claim 39, wherein the high strength portion is located at a depth of approximately one-third of a line extending from the outer surface to the center line. <Aspect 41> 40. The embryonic ingot of claim 39, wherein the high strength portion is located at a depth equal to or less than half of a line extending from the outer surface to the center line. <Aspect 42> 40. The embryonic ingot of claim 39, wherein the solidified shell is cylindrical in shape. <Aspect 43> 40. The embryonic ingot of claim 39, wherein a cross-section of the solidified shell perpendicular to the casting direction has a rectangular shape. <Aspect 44> 40. The embryonic ingot of claim 39, wherein the aluminum alloy is a 7xxx series aluminum alloy. <Aspect 45> 40. The embryonic ingot of embodiment 39, made according to the method of embodiment 1 or embodiment 15.

Claims

1. An aluminum metal product comprising: A solidified aluminum alloy mass having two ends and an outer surface. and the solidified aluminum alloy mass comprises: a core region containing a center of the solidified aluminum alloy mass; an outer region integral with the outer surface; and A high strength section disposed between the core region and the outer region. wherein the high strength section has a higher concentration of dispersed phase compared to each of the core region and the outer region.

2. 2. The aluminum metal product of claim 1, wherein the high strength region is located approximately one-third of a depth along a line extending along a cross section of the solidified aluminum alloy mass from the outer surface to the center of the solidified aluminum alloy mass.

3. 2. The aluminum metal product of claim 1, wherein the high strength region is located at a depth of less than or equal to one-half of a line extending along a cross section of the solidified aluminum alloy mass from the outer surface to the center of the solidified aluminum alloy mass.

4. The aluminum metal product of claim 1 , wherein the solidified aluminum alloy mass is cylindrical in shape.

5. 2. The aluminum metal product of claim 1, wherein a cross-section of the solidified aluminum alloy ingot perpendicular to a casting direction of the solidified aluminum alloy ingot is rectangular in shape.

6. 2. The aluminum metal product of claim 1, wherein the solidified aluminum alloy mass is a solidified 7xxx series aluminum alloy mass.

7. An embryonic ingot, a liquid molten core of the aluminum alloy extending from the upper surface to the solidification interface; and Solidified shell of said aluminum alloy The solidified shell includes an outer surface extending from the solidification interface to a bottom end in a casting direction, and the solidified shell includes a high strength portion disposed between the outer surface and a center line extending in the casting direction through a center of the liquid molten core and a center of the solidified shell; wherein the high strength portion has a higher concentration of dispersed phase compared to the remainder of the solidified shell.

8. 8. The embryonic ingot of claim 7, wherein said high strength portion is located at a depth approximately one-third of a line extending from said outer surface to said center line.

9. 8. The embryonic ingot of claim 7, wherein the high strength portion is located at a depth equal to or less than half a line extending from the outer surface to the center line.

10. 8. The embryonic ingot according to claim 7, wherein the solidified shell is cylindrical in shape.

11. 8. The embryonic ingot according to claim 7, wherein a cross section of the solidified shell perpendicular to the casting direction has a rectangular shape.

12. 8. The embryonic ingot of claim 7, wherein the aluminum alloy is a 7xxx series aluminum alloy.

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