JP2023506836A - Reduced Crack Susceptibility of 7xxx Series Semi-Continuous (DC) Cast Ingots - Google Patents

Abstract

Process control of strong agitation along the solidification front and adjustment of casting speed during semi-continuous casting of 7xxx series alloys can reduce ingot crack susceptibility. Strong stirring control reduces the thickness of the solidification front, promotes aggregation of hydrogen gas expelled in the solidification front, removes impurities expelled in the solidification front, and improves grain size. used for doing Strong stir control is used to operate at higher casting speeds without the risk of increasing the thickness of the solidification front. Optional reheating during casting to promote dispersoid formation is used to create high-strength regions of dispersoid-strengthened solidified metal at the periphery of the ingot, which further reduces the ingot's susceptibility to cracking. can let [Selection drawing] Fig. 1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Application No. 62/951,883, filed December 20, 2019, which is hereby incorporated by reference in its entirety. do.

FIELD OF THE DISCLOSURE The present disclosure relates generally to metal casting, and more specifically to semi-continuous casting of difficult aluminum alloys.

In semi-continuous (DC) casting, molten metal is forced through a mold cavity that has a raised or movable bottom. As the molten metal enters the mold cavity, typically from the top, the raised bottom descends at a velocity related to the velocity of the molten metal flow. Melt that solidifies near the sides can be used to retain liquid and partially liquid metals in the melt pool. The metal can be 99.9% solid (eg, completely solid), 100% liquid, and anything in between. Because the thickness of the solid region increases as the melt cools, the melt puddle can assume a V-shape, a U-shape, or a W-shape. The interface between solid metal and liquid metal is sometimes referred to as the solidification interface.

When the melt in the melt pool is about 0% solids to about 5% solids, nucleation can occur and small crystals of metal can form. These small (eg, nanometer-sized) crystals begin to form nuclei, which continue to grow in their preferred direction to form dendrites as the melt cools. As the melt cools to the dendrite alignment point (eg, 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 melt, the crystals may form various particles (e.g., intermetallic compounds or hydrogen bubbles) such as _FeAl6 , _Mg2Si , _FeAl3 , _{Al8Mg5 and} gaseous in certain alloys of aluminum. It may contain or trap particles of _H2 .

In addition, when the solidifying aluminum first begins to cool, it cannot support just as much the alloying elements in its alpha phase, so the melt surrounding the solidification interface has a proportionately higher concentration of alloying elements. can be high. Therefore, different compositions and particles may be formed at or near the solidification interface. Additionally, there may be stagnant regions within the puddle that may result in preferential accumulation of these particles.

The uneven distribution of alloying elements on the grain length scale is known as fine segregation. In contrast, macrosegregation is chemical heterogeneity over length scales larger than a grain (or a few grains), eg, up to several meters.

Certain aluminum alloys, such as the 7xxx series alloys, can be particularly difficult to cast. 7xxx series alloys generally contain combinations of one or more of a number of alloying elements such as zinc, magnesium, copper, chromium, zirconium and other alloying elements. Large internal stresses (eg, compressive stresses and sometimes tensile stresses) can build up during and immediately after casting 7xxx series alloys, making the casting susceptible to cracking. Certain alloying elements used in these classes of alloys, such as zinc, contract and expand at much different rates than aluminum. Zinc, in particular, contracts and expands significantly more than aluminum. Thus, the same volumes of zinc and aluminum at similar temperatures (eg, 600° C.) can become different volumes of zinc and aluminum, respectively, when cooled (eg, in the final stages of solidification). These different expansion and contraction rates between alloying elements and aluminum can be the cause of large internal forces and hence stresses in castings cast from 7xxx series alloys.

In addition, the 7xxx series alloys are highly susceptible to porosity problems due to dissolved hydrogen being expelled as microbubbles of gas from the solidifying molten alloy. Voids created by gas bubbles are often crack initiation sites and can lead to substantial cracking. In addition, 7xxx series alloys can be highly susceptible to shrinkage porosity due at least in part to differential shrinkage as the melt solidifies.

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

In addition, 7xxx series alloy castings may rely on long post-casting homogenization steps to achieve desired internal structures with desired precipitates while reducing casting stresses. Homogenization can be used to mitigate microsegregation after casting. Optionally, the 7xxx series alloy casting may be hot rolled to smaller gauges, solution treated and then aged. In some cases, long-term aging and further processing (e.g., solution treatment or recrystallization) may be used in an attempt to obtain a more desirable microstructure, but such techniques require considerable equipment and considerable time and effort. Requires consumption of resources and energy.

The term embodiment and like terms are intended to refer broadly to all of the subject matter of this disclosure and the following claims. It should be understood that phrases containing these terms do not limit the subject matter described herein or the scope or meaning of the following claims. The embodiments of the disclosure encompassed herein are defined by the following claims rather than by this summary. This summary is a general overview of various aspects of the present disclosure and is intended to introduce some 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, any or all drawings, and claims of the present disclosure.

An embodiment of the present disclosure is a casting method comprising feeding molten metal into a casting mold to form an embryonic ingot comprising an outer solid shell and an inner molten core; advancing the ingot in a direction of travel away from the casting mold; removing heat from the embryonic ingot between the casting mold and the transition location by directing a supply of liquid coolant to the outer surface of the outer solid shell; and transitioning. at the transition location such that at least a portion of the outer solid shell of the embryonic ingot at the location reaches a temperature suitable for precipitation of dispersoids and below the homogenization temperature of the molten metal (e.g., a reheat temperature). The method comprising reheating the embryonic ingot, wherein the transition location is in a plane perpendicular to the direction of travel and intersecting the internal molten core.

Optionally, the reheating temperature, for example in degrees Celsius, is 80-98% of the homogenization temperature, for example in degrees Celsius, of the melt. Optionally, said temperature, for example in degrees Celsius, is 85-90% of the homogenization temperature, for example in degrees Celsius, of the melt. Optionally, the temperature in degrees Celsius is 80-95%, 80-90%, 80-85%, 80%, 81%, 82%, 83% of the homogenization temperature in degrees Celsius of the melt. %, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98%. Optionally, the temperature is 400-460°C. In some cases the temperature is 410-420°C. Optionally, 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℃, 410-460℃, 420-430℃, 420-440℃, 420-450℃, 420-460℃, 430-440℃, 430-450℃, 430-460℃, 440-450 ℃, 440-460 ℃, or 450-460 ℃. Optionally, the method includes subjecting a portion of the outer solid shell to a temperature for at least 3 hours, such as 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 longer. Optionally, reheating the embryonic ingot includes removing the liquid coolant from the outer surface of the outer solid shell. Optionally, reheating the embryonic ingot further comprises applying heat to the outer surface of the outer solid shell to supplement latent heat heating from the inner molten core. Optionally, the method further includes taking a temperature measurement of the embryonic ingot and dynamically adjusting the transition location based on the temperature measurement. Optionally, the method further comprises inducing agitation in the inner molten core adjacent to the interface between the inner molten core and the outer solid shell. Optionally, the method further comprises taking a temperature measurement of the embryonic ingot, and inducing agitation in the internal molten core comprises dynamically adjusting the intensity of agitation based on the temperature measurement. Optionally, the transition location is such that the plane intersects the embryonic ingot in a cross section in which the outer solid shell of the embryonic ingot occupies approximately one-third of the line extending in the plane from the outer surface to the center of the embryonic ingot. is selected. Optionally, the transition location is selected such that the plane intersects the embryonic ingot in a cross-section in which the outer solid shell of the embryonic ingot occupies no more than 50% of the line extending in the plane from the outer surface to the center of the embryonic ingot. be done. In some cases, the melt is a 7xxx series aluminum alloy. In some cases, the reheated portion includes a liquid-containing metal face in the center, with the reheated region growing the precipitates at the outer perimeter of the ingot adjacent to the surface.

An embodiment of the present disclosure is a method of forming an embryonic ingot by feeding molten metal to a mold and removing heat from the molten metal to form an outer solid shell; Advancing in a receding direction of travel and solidifying an internal molten core of the embryonic ingot as additional molten metal is fed into the mold, solidifying the internal molten core moves from the internal molten core through the external solid shell. removing heat; and continuously forming a high strength region within 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. wherein the high strength region is located between the outer surface of the outer solid shell and the inner molten core, and forming the high strength region reheats the outer solid shell in cross section to disperse in the outer solid shell. including the method comprising inducing the precipitation.

Optionally, reheating the outer solid shell in the cross section comprises reheating a portion of the outer solid shell to a temperature suitable for precipitation of the dispersoids, said temperature being below the homogenization temperature of the molten metal. . Optionally, said temperature, for example in degrees Celsius, is 80-98% of the homogenization temperature, for example in degrees Celsius, of the melt. Optionally, 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 is 300-460°C, such as 400-460°C. In some cases the temperature is 410-420°C. In some cases, temperature ranges of 400-460°C and 410-420°C may be particularly suitable for 7xxx series alloys. In some cases other temperature ranges may be used, for example for 6xxx series alloys. Optionally, the method further comprises maintaining the temperature in the portion of the outer solid shell for at least 3 hours, or 3-10 hours. Optionally, removing heat from the inner molten core through the outer solid shell includes supplying a liquid coolant to the outer surface of the outer solid shell, and reheating the outer solid shell comprises: Including removing the liquid coolant from the outer surface. Optionally, reheating the outer solid shell further comprises applying heat to the outer surface of the outer solid shell to supplement latent heat heating from the inner molten core. Optionally, the method further includes taking a temperature measurement of the embryonic ingot and dynamically adjusting the distance between the mold and the cross-section based on the temperature measurement. Optionally, the method further comprises inducing agitation in the inner molten core adjacent to the interface between the inner molten core and the outer solid shell. Optionally, the method further comprises taking a temperature measurement of the embryonic ingot, and inducing agitation in the internal molten core comprises dynamically adjusting the intensity of agitation based on the temperature measurement. In some cases, the outer solid shell of the embryonic ingot in cross-section occupies approximately one-third of the line extending from the outer surface to the center of the embryonic ingot. Optionally, in cross section the outer solid shell of the embryonic ingot occupies 50% or less of the line extending from the outer surface to the center of the embryonic ingot. In some cases, the melt is a 7xxx series aluminum alloy. In some cases, the high intensity region comprises a higher concentration of dispersoids compared to the rest of the outer solid shell.

An embodiment of the present disclosure is an aluminum metal product comprising a solidified aluminum alloy mass having two ends and an outer surface, the solidified aluminum alloy mass containing a center of the solidified aluminum alloy mass; a core region; an outer region integral with the outer surface; and a high-strength region disposed between the core region and the outer region, the high-strength region having a higher concentration of dispersoids than each of the core region and the outer region. including such aluminum metal products.

In some cases, the solidified aluminum alloy mass contains retained heat from the semi-continuous casting process. In some cases, the high strength region is located approximately one third of the depth of a line extending along the cross-section of the solidified aluminum alloy mass from the outer surface to the center of the solidified aluminum alloy mass. In some cases, the high strength region is located at a depth of one-half or less of a line extending along the cross-section of the solidified aluminum alloy mass from the outer surface to the center of the solidified aluminum alloy mass. In some cases, the shape of the solidified aluminum alloy mass is cylindrical. In some cases, the shape of a cross-section of the solidified aluminum alloy mass that is perpendicular to the casting direction of the solidified aluminum alloy mass is rectangular. Optionally, the solidified aluminum alloy mass is a solidified 7xxx series aluminum alloy mass.

An embodiment of the present disclosure 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 an aluminum alloy, the solidified shell extending from the solidification interface to a bottom end in a casting direction. an extending outer surface, the solidified shell including a high strength region disposed between the outer surface and a centerline extending in the casting direction through the center of the liquid molten core and the center of the solidified shell; contains the embryonic ingot having a higher concentration of dispersoids than the rest of the solidified shell.

In some cases, the high intensity region is located approximately one third of the depth of a line extending from the outer surface to the centerline. In some cases, the high intensity region is located at a depth of less than or equal to one-half the line extending from the outer surface to the centerline. In some cases, the shape of the solidified shell is cylindrical. In some cases, the shape of a cross-section of the solidified shell perpendicular to the casting direction is rectangular. Optionally, the aluminum alloy is a 7xxx series aluminum alloy. Optionally, the embryonic ingot was made according to any of the above methods.

An embodiment of the present disclosure is a method of 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, wherein the solidification interface is located between the outer solid shell and the pool of metal; a direction of travel of the embryonic ingot away from the mold while delivering the molten metal and forming the outer solid shell; using the casting speed to determine the intensity of agitation, wherein the intensity of agitation is suitable to produce the target solidification interface profile at the casting speed; The method comprises inducing agitation within the molten pool with an intensity, wherein the inducing agitation within the molten pool causes the solidification interface to exhibit a target solidification interface profile at a casting speed.

In some cases, inducing agitation includes applying an agitation force to the molten metal in the metal pool using a non-contact magnetic stirrer. Optionally, delivering the melt includes delivering the melt through the plurality of nozzles at a mass flow rate, and inducing agitation while maintaining the mass flow rate through the plurality of nozzles. increasing the flow rate of the molten metal through at least one of the plurality of nozzles; Optionally, the method further comprises changing the casting speed; using the updated casting speed to determine an updated intensity of agitation, wherein the updated intensity of agitation is at the updated casting speed suitable for providing a target solidification profile; This results in the solidification interface exhibiting the target solidification interface profile at a given casting speed. In some cases, the melt is a 7xxx series aluminum alloy. Optionally, the method further comprises measuring the temperature of the embryonic ingot, and using the casting speed to determine the intensity of agitation comprises using the measured temperature. In some cases, the target solidification interface profile is predetermined to minimize the risk of cracking. Optionally, the method further comprises continuously forming a high strength region within the outer solid shell in a cross-section of the embryonic ingot that is perpendicular to the direction of travel and intersects the inner molten core. wherein the high strength region is located between the outer surface of the outer solid shell and the inner molten core, and forming the high strength region is performed by reheating the outer solid shell in cross section to cause dispersoid precipitation in the outer solid shell. including inducing In some cases, inducing agitation within the molten metal pool controls the delivery of molten metal into the metal pool such that the jet of molten metal erodes the solidification interface at the bottom of the metal pool to form a depression. and the recess has a diameter sized to match the diameter of the bottom of the metal pool.

An embodiment of the present disclosure is a method of 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, wherein the solidification interface is located between the outer solid shell and the pool of metal; a direction of travel of the embryonic ingot away from the mold while delivering the molten metal and forming the outer solid shell; and controlling the delivery of molten metal into the metal pool to produce a jet of molten metal sufficient to erode at least a portion of the solidification interface at the bottom of the metal pool. , including the method.

Optionally, controlling the delivery of the melt comprises controlling the delivery of the melt such that the jet of melt erodes the solidification interface to a thickness of 10 mm or less. Optionally, delivering the melt includes delivering the melt through the plurality of nozzles at a mass flow rate, and generating the jet of melt maintains the mass flow rate as it passes through the plurality of nozzles. while increasing the flow rate of the melt through at least one of the plurality of nozzles. Optionally, the method further comprises applying a stirring force to the molten metal in the metal pool using a non-contact magnetic stirrer. Optionally, the method further comprises altering the casting speed, wherein controlling the delivery of the molten metal is based on the altered casting speed such that the jet of molten metal reaches the solidification interface at the bottom of the metal pool. including dynamically adjusting to continue to erode at least a portion of the In some cases, the melt is a 7xxx series aluminum alloy. Optionally, the method further comprises measuring a temperature of the embryonic ingot, and controlling the delivery of the molten metal based on the measured temperature causes the jet of molten metal to flow at the bottom of the metal pool. including dynamically adjusting to continue to erode at least a portion of the solidification interface. Optionally, the method further comprises continuously forming a high strength region within the outer solid shell in a cross-section of the embryonic ingot that is perpendicular to the direction of travel and intersects the metal pool. , the high-strength region is located between the outer surface of the outer solid shell and the metal pool, and forming the high-strength region reheats the outer solid shell in cross section to induce dispersoid precipitation in the outer solid shell. including doing

An embodiment of the present disclosure is an embryonic ingot comprising a solidified shell of aluminum alloy extending from a solidification interface to a bottom end in a casting direction, and a liquid molten core of aluminum alloy extending from the top surface to the solidification interface, the liquid molten core includes a jet of aluminum alloy impinging on the solidification interface at the bottom of the liquid molten core to form a depression in the solidification interface.

In some cases, the liquid molten core contains resuspended grains from the solidification interface. In some cases, the liquid molten core contains resuspended hydrogen from the solidification interface. Optionally, the solidified shell includes a high strength region located between the outer surface of the solidified shell and a centerline extending in the casting direction through the center of the liquid molten core and the center of the solidified shell, the high strength region comprising: , has a higher concentration of dispersoids compared to the rest of the solidified shell. Optionally, the aluminum alloy is a 7xxx series aluminum alloy.

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

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

The specification refers to the following accompanying drawings, wherein like reference numbers in different drawings are intended to indicate similar or similar components.

1 is a partial cross-sectional view of a metal casting system for in situ dispersoid precipitation, according to certain aspects of the present disclosure; FIG. 1 is a partial cross-sectional view of a metal casting system for in situ dispersoid precipitation with pool depth control, according to certain aspects of the present disclosure; FIG. 1 is a partial cross-sectional view of a metal casting system for controlled flow agitation in accordance with certain aspects of the present disclosure; FIG. 1 is a partial cross-sectional view of a metal casting system for controlled flow agitation with multiple feed tubes, in accordance with certain aspects of the present disclosure; FIG. 1 is a partial cross-sectional view of a metal casting system for strong stirring with a magnetic stirrer, according to certain aspects of the present disclosure; FIG. FIG. 4 is an enlarged schematic diagram of the bottom of the molten metal pool when there is no strong stirring; 2 is an enlarged schematic diagram of the bottom of a molten metal pool undergoing vigorous agitation, in accordance with certain aspects of the present disclosure; FIG. 4 is a flow diagram illustrating a process for in situ dispersoid precipitation, according to certain aspects of the present disclosure; 4 is a flow diagram illustrating a process for creating high strength regions of precipitated dispersoids in a semi-continuously cast ingot, according to certain aspects of the present disclosure; 1 is an elevated cross-sectional schematic view of an ingot depicting regions of high strength, in accordance with certain aspects of the present disclosure; FIG. 1 is a schematic cross-sectional top view of an ingot depicting regions of high strength, according to certain aspects of the present disclosure; FIG. 1 is a flow diagram illustrating a process for producing a strongly-stirred semi-continuous casting ingot, according to certain aspects of the present disclosure; A and B show schematic diagrams of cross-sections of 7xxx series ingots showing the locations of the sampling sites. 4 shows data showing the composition of a reference ingot at various sampling locations. 4 shows data showing the composition of a first sample ingot at various sampling locations; 4 shows data showing the composition of a first comparative sample ingot at various sampling locations; Figure 3 shows data showing the porosity of a reference ingot at various sampling locations; FIG. 2 shows data showing porosity of first sample ingots at various sampling locations; FIG. Figure 2 shows data demonstrating the mechanical properties of sheet metal made from a second sample ingot;

Certain aspects and features of the present disclosure relate to reducing the cracking susceptibility of semi-continuously cast ingots of certain alloys, such as 7xxx series alloys. Process control of strong agitation along the solidification front and adjustment of casting speed during semi-continuous casting of 7xxx series alloys can reduce ingot crack susceptibility. Vigorous agitation reduces the thickness of the solidification front (eg, the region approximately greater than 0% to less than 100% solid metal, known as the “solidification transition zone”) and drives off hydrogen gas at the solidification front. promotes agglomeration, removes impurities expelled at the front of solidification, and improves grain size. Intense stirring may allow higher casting speeds without the risk of increasing the thickness of the solidification front. Optional reheating during casting to promote dispersoid formation can create a protective region of dispersoid-strengthened solidified metal around the perimeter of the ingot, which can further reduce the ingot's susceptibility to cracking.

In semi-continuous (DC) casting, molten metal is forced through a mold cavity that has a raised or movable bottom. As the molten metal enters the mold cavity, typically from the top, the raised bottom descends at a velocity related to the velocity of the molten metal flow. Melt that solidifies near the sides can be used to retain liquid and partially liquid metals in the melt pool. The metal can be 99.9% solid (eg, completely solid), 100% liquid, and anything in between. Because the thickness of the solid region increases as the melt cools, the melt puddle can assume a V-shape, a U-shape, or a W-shape. The interface between solid metal and liquid metal may be referred to as the solidification interface or solidification front. A metal article resulting from a DC casting process may be referred to as an ingot. Ingots may generally have a rectangular cross-section, but other cross-sections, such as circular or even asymmetric cross-sections, may be used. The term ingot, as used herein, may suitably encompass any DC cast metal article, including billets.

As noted above, when the metal freezes at the solidification front, certain impurities and gases can be driven out of solution and trapped in the solidifying metal. Gases, such as hydrogen, can collect and form bubbles that lead to voids in the solidifying metal, which voids are commonly known as ingot porosity. In addition, dislodgement of impurities at the solidification interface can result in uneven distribution of impurities throughout the ingot.

Certain aspects of the present disclosure include agitating the molten metal pool. Such agitation can be accomplished in a number of ways, for example, by using contact stirrers, non-contact magnetic stirrers, or adjusting the entry of the liquid metal into the pool. Contact stirrers are often undesirable for use with aluminum alloys, at least because of the risk of impurities and oxides. Non-contact stirrers can include electromagnets and permanent magnet systems designed to induce motion in the melt. In some cases, the molten metal pool is controlled by modulating the entry of the liquid metal into the pool, e.g. can be agitated by feeding as The liquid metal jet can be adjusted by increasing the pressure supplying the liquid metal, adjusting the diameter of the nozzle that delivers the metal, or other techniques such as adding a new liquid metal into the jet created by It can be provided by an eductor nozzle that is used to inject an existing molten pool.

Vigorous agitation in the melt pool can be used to provide agitation along the solidification front. This agitation can sweep away metal crystals that are forming, or parts thereof, impurities, gases, and even some of the liquid metal from the region of the solidification front. Flushing away metal crystals that are forming (e.g., freely moving grains) can help produce finer and more uniform grain sizes, because the crystals that are forming, or fragments thereof, are trapped in the melt pool. This is because it can be resuspended in and serve as additional nucleation sites. Furthermore, agitation of sufficient intensity can lower the bulk liquid temperature of the melt pool, thus creating a favorable environment for the production of fine spherical grains. This fine spherical microstructure is stronger than the typical microstructure found in DC cast ingots. Certain aspects of the present disclosure, such as ingots cast using intensive stirring, may have higher yield strengths and are more susceptible to cold cracking than ingots cast without intensive stirring. It can be hard to accept.

Flushing impurities away from the solidification front can help achieve less macro-segregation (lower degree of macro-segregation) and thus improved homogeneity. This less macro-segregation achieved by agitation can be beneficial in providing desirable protected regions within the ingot. As described in further detail herein, a protected zone may be established by reheating the outer solidified portion of the ingot being cast. Reheating can promote the formation of fine dispersoids within the ingot, which can beneficially strengthen the solidified metal, thus minimizing the ingot's susceptibility to cracking. These fine dispersoids can be approximately 30 nm in diameter, but may be of other sizes. In some cases, these fine dispersoids can be approximately 10-50 nm, 20-40 nm, or 25-35 nm in diameter.

Unexpectedly, it has been found that vigorous agitation within the molten metal pool can reduce or minimize porosity in cast ingots. Vigorous agitation can drive the displaced hydrogen away from the solidification interface, resulting in it being resuspended in the remainder of the melt pool. Resuspended hydrogen may condense with other hydrogen, resulting in the gas being allowed to spread to the surface of the pool, where it may remain or be expelled from the pool. Thus, the use of strong agitation reduces or minimizes porosity in the casting where the displaced hydrogen would have resulted in undesirable porosity in the casting. was found.

Since the presence of impurities and dissolved gases in the molten metal can be a problem during casting, conventional casting techniques generally employ methods to filter out impurities from the liquid metal and/or reduce the amount of dissolved gases (e.g., hydrogen) in the liquid metal. Relies on significant upstream preparation to reduce. Using certain aspects of the present disclosure, this type of upstream preparation to filter out impurities and/or remove dissolved gases can be significantly reduced or eliminated.

Adequate 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, casting speed can be used to control the solidification front. An increase in casting speed can thicken the solidification front, while a decrease in casting speed can narrow the solidification front. If the solidification front is too thick, the melt may not completely penetrate the solidified region of the solidification front, which can create shrinkage cavities and voids. If the solidification front is too thin, hot tearing may occur, where fissures or fissures form between grains due to internal stresses, such as shrinkage-related stresses. Therefore, there is often a trade-off between susceptibility to shrinkage cavities and susceptibility to hot tearing, which can dictate or limit casting speed. In certain alloys that are particularly prone to hot tearing, such as 7xxx series alloys, this trade-off effectively limits the available casting speed and therefore the effective maximum number of ingots that can be cast per day. is provided.

According to certain aspects of the present disclosure, control of the solidification front may be achieved through a combination of agitation control and casting speed control. Intensive stirring can provide a number of advantages that allow for hot tear mitigation while allowing high casting speeds. As noted above, vigorous agitation can help narrow the solidification front. Thus, a DC casting process with intensive stirring can be run at a higher casting speed while maintaining the same solidification front thickness as compared to a DC casting process without intensive stirring. Strong stirring can thus allow for faster casting and therefore greater production capacity per day. In addition, agitation may cause the molten metal pool to expand deeper into the ingot being cast, also referred to herein as the embryonic ingot. In DC casting, the hydrostatic pressure of the melt provides the substantial driving force for the penetration of the liquid metal into the intergranular interstices at the solidification front. A deeper pool of molten metal created by vigorous agitation provides a head region with greater hydrostatic pressure near the bottom of the pool. This head region, which has greater hydrostatic pressure, may facilitate filling of intergranular voids at the solidification front, resulting in reduced or no risk of shrinkage porosity or voids. It may allow a thicker solidification front without concomitant. When intensive stirring is employed, a thicker solidification front can be used, thus increasing the casting rate even further over what would have been available without stirring.

Enhanced agitation can be controlled to result in a nominal reduction in the thickness of the solidification front (eg, solidification interface) to a nominal thickness of the order of several millimeters, eg, approximately 1-5 mm, or approximately 10 mm or less. In some cases, the nominal reduction in thickness is approximately 20 mm or less, 19 mm or less, 18 mm or less; The reduction to the nominal thickness can be 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, a reference to controlling agitation to result in a nominal reduction to a particular nominal thickness will result in a reduction to a particular thickness assuming constant casting speed. It can mean controlling the agitation to a degree. Thus, although enhanced agitation accompanied by an increase in casting speed may result in little or no effective change in solidification interface thickness, the enhanced agitation is nominally Sometimes expressed as providing a certain nominal reduction in thickness. Additionally, as used herein, solidification interface thickness may refer to the minimum, maximum and average thickness, or thickness at applicable points or regions within the embryonic ingot. . For example, a solidification interface having a thickness of 10 mm or less is a solidification interface having a maximum thickness at any point of the solidification interface of 10 mm or less; the solidification interface reaching; the solidification interface where the average thickness across the solidification interface remains no more than 10 mm; It may contain a solidification interface where the average thickness over a region remains no more than 10 mm.

During DC casting, a coolant (eg, water) is sprayed onto the surface of the ingot to remove heat from the ingot as it emerges from the mold. A wiper or other technique may be used to remove the coolant, thus allowing a portion of the ingot to reheat. This reheating can be used in some cases to homogenize the ingot in situ (during casting). In some cases, this in situ homogenization can occur when the metal reaches a recovery temperature of approximately 470°C to approximately 480°C. On the other hand, according to certain aspects of the present disclosure, the reheating can be controlled to provide a lower temperature that is more suitable for precipitation, thereby facilitating the formation of dispersoids at the perimeter of the ingot. Reheating an embryonic ingot to promote precipitate formation during casting may be referred to herein as in situ precipitation.

In some cases, the reheat temperature to achieve the desired in-situ precipitation (e.g., the temperature at which the surface of the embryonic ingot is reheated during casting) is 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., in degrees Celsius, is the final homogenization temperature of the alloy, e.g., in degrees Celsius. It can be about 80% to about 90%, or about 85% to about 98% of the temperature. For example, for a final homogenization temperature of 480°C, the reheat temperature can be approximately 88% of that temperature, or approximately 422°C. To give another example, for a final homogenization temperature of 480°C, the reheat temperature can be approximately 96% of that temperature, or approximately 460°C.

Desirable in situ deposition can be accomplished by reheating the above-identified embryonic ingot and maintaining a constant temperature or allowing the ingot to cool to or towards room temperature over a period of time. The time period can be from about 3 hours to about 5 hours, but in some cases the time may be longer or shorter, eg, deviating within 10% of either endpoint. The in-situ precipitation process may begin during casting of the ingot and may end after the ingot has been cast. Ingots cast using in-situ precipitation can be cooled to or toward room temperature immediately after casting without undergoing quenching. In some cases, a subsequent homogenization step may be performed for a shortened period of time when using in-situ precipitation. For example, in-situ precipitation at 410°C for 3 hours may be homogenized at 475°C for approximately 8 hours to yield the desired small precipitates, whereas ingots cast without in-situ precipitation may be homogenized at 475°C. may require a homogenization period of 10 hours at , which can only result in undesirably large precipitates.

Reheating the embryonic ingot can occur in any suitable manner, such as by applying external heat. However, reheating the embryonic ingot for in-situ homogenization usually reduces the amount of heat removal occurring at the surface of the embryonic ingot and reduces the latent heat of the ingot, particularly the heat of the melt pool. can occur by reheating the exterior of the To achieve the desired in-situ deposition temperature, the point at which reheating begins (eg, the position 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 position of the wiper (moving the wiper closer to the mold), the solid shell will reheat more quickly in cross-sections where the melt pool is wider compared to cross-sections further away from the mold. can be initiated, thus allowing more of the latent heat of the molten pool to reheat the solid shell. In addition to or instead of controlling the point at which reheating begins, the pool depth itself may be controlled to provide precise control of the reheating of the solid shell. For example, by inducing agitation, such as by directing a jet of molten metal to the bottom of the solidification interface, the metal puddle can be extended a greater distance away from the mold than without inducing additional agitation. As the depth of the molten core extends farther from the mold, the solid shell will be subjected to the latent heat of the molten core for a longer period of time after the coolant is removed.

Additionally, control of where reheating is initiated and/or the depth of the molten core may allow control of the surface depth of the dispersoids formed during in situ dispersoid precipitation. As used herein, the term surface depth refers to the depth within an ingot from the outer surfaces (e.g., rolling surfaces and sides) to the center of the ingot (e.g., the longitudinal centerline extending through the center of the ingot in the casting direction). can indicate depth. In some cases, reheating of the solid shell and/or control of the depth of the molten core is controlled in an area (e.g., high strength area) of approximately one-third (33%) of the distance from the surface of the ingot to the longitudinal centerline. ) with the highest concentration of dispersoids. In some cases, this region can be at or about 1/2 (50%) of the way from the surface of the ingot to the longitudinal centerline. In some cases, this region is approximately 5%, 10%, 15%, 20% or 25%, and approximately 25%, 30%, 35%, 40%, It can fall at 45% or 50%. In some cases, this region may extend from the surface of the ingot to the depth described above.

In some cases, the highest concentration of dispersoids and/or high intensity regions may be regions of the ingot that have a concentration of dispersoids that is greater than the average concentration of dispersoids throughout the ingot. In some cases, the highest concentration of dispersoids and/or the high intensity region reduces the average concentration of dispersoids throughout the ingot to at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4. It can be defined as the region of the ingot that has a concentration of dispersoids above the standard deviation. High-strength regions (eg, regions with relatively high concentrations of precipitated dispersoids) can serve as protection from cracking as the ingot cools toward room temperature.

There is often no relationship between the initial cast microstructure and the final wrought material microstructure, which is at least partially due to microstructural recrystallization during hot working and subsequent working. It is the cause. However, in certain alloys, for example certain 7xxx series alloys, recrystallization can be inhibited by using dispersoids, for example by adding elements such as Cr or Zr. By inducing the formation of such dispersoids in the cast microstructure, the dispersoids can inhibit recrystallization, or at least significant changes in average grain size during recrystallization. Because recrystallization is suppressed, the final wrought material microstructure can be that associated with, or more specifically similar to, the initial cast microstructure.

This ability to relate the cast microstructure to the final stretch microstructure can make techniques for improving the cast microstructure particularly beneficial. Addition of grain refiners is sometimes used to reduce grain size to a certain degree, but the effectiveness of additional grain refiners after the saturation limit is reached is limited. On the other hand, using aspects of the present disclosure, such as vigorous agitation, further and more desirable grain refinement can be achieved. This finer cast microstructure results in a finer microstructure for the final product, which can have many advantages such as corrosion resistance and strength.

In some cases, certain aspects of the present disclosure may be particularly suitable for 7xxx series alloys, but may also be useful for use with 5xxx series or other series of alloys. Certain aspects of the present disclosure can also help to withstand "orange peel" defects, for example in 7xxx systems. This "orange peel" defect is a surface defect that appears after deformation of a metal article and is characterized by a rough cast surface that has the appearance of an orange outer surface. This defect is often the result of large grain size. By reducing the final grain size, this defect can become less noticeable after deformation.

As used herein, the terms "invention," "the invention," "this invention," and "the present invention" refer broadly to this patent application and It is intended to refer to all subject matter of the following claims. It should be understood that phrases containing these terms do not limit the subject matter described herein or the scope or meaning of the following claims.

This document refers to alloys identified by AA number and other related designations, such as "series" or "7xxx". For an understanding of the numbering systems most commonly used in naming and identifying aluminum and its alloys, see International Alloy Designations and Chemical Compositions Limits for Wrought Aluminum and Aluminum, both published by The Aluminum Association. Wrought Aluminum Alloys" or "Registration Record of Aluminum Association Alloy Designations and Chemical Compositions Limits for Aluminum Alloys in the Forms of Casting".

As used herein, "room temperature" means about 15°C to about 30°C, such as about 15°C, about 16°C, about 17°C, about 18°C, about 19°C, about 20°C, C., about 21.degree. C., about 22.degree. C., about 23.degree. C., about 24.degree. C., about 25.degree. As used herein, the meaning of "ambient conditions" can include temperatures of about room temperature, relative humidity of about 20% to about 100%, and atmospheric pressure of about 975 millibars (mbar) to about 1050 mbar. . For example, the relative humidity is 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 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 is 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 1040 mbar, , about 1050 mbar, or any value in between.

All ranges disclosed herein are to be understood to encompass any and all subranges therein. For example, a range labeled "1 to 10" means any and all subranges between a minimum value of 1 and a maximum value of 10 (including the endpoints), i. and ending with a maximum value of 10 or less, eg, 5.5 to 10. Unless otherwise noted, the phrase "or less" when referring to a compositional amount of an element means that the element is optional and includes zero percent composition of that particular element. All compositional percentages are expressed in weight percent (wt.%) unless otherwise noted.

As used herein, the meanings of "a," "an," and "the" include their singular and plural meanings, unless the context clearly indicates otherwise.

In the following examples, the aluminum alloy products and their constituents are represented by their elemental composition in weight percent (wt.%). The balance is aluminum in each alloy and the sum of all impurities is 0.15% wt. %.

Incidental elements, such as grain refiners and deoxidizers, or other additives, may be present in the present invention and may result from the alloys described herein or properties of the alloys described herein. It may itself add other attributes without deviating or significantly changing it. However, it should be understood that the scope of the present disclosure should not/cannot be circumvented by the mere addition of amounts of one or more incidental elements that would not alter the properties desired in the present disclosure. is.

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

As used herein, the term "slab" refers to alloy thickness greater than 15 mm. For example, the slab may be 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. It can refer to an aluminum product with thickness.

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

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

As used herein, sheet generally refers to aluminum products having a thickness of less than about 4 mm. For example, the sheet can 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.

Cast ingots may be processed by any means known to those skilled in the art. Optionally, a processing step that produces thin sheets can be used. Such processing steps include, but are not limited to, homogenization, hot rolling, cold rolling, solution heat treatment, and optional pre-aging steps, as known to those skilled in the art.

During the homogenization step, the castings described herein are heated to a temperature in the range of about 400°C to about 500°C. For example, the product may be exposed 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. can be heated to The product is then ignited (ie held at a specified temperature) for a period of time. In some examples, the total time for the homogenization step can be 24 hours or less, including the heating and ignition period. For example, the product may be heated to 500° C. or less and sintered for a total time of 18 hours or less for the homogenization step. Optionally, the product may be heated and sintered below 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 can be heated to about 465°C for about 3.5 hours and then heated to about 480°C for about 6 hours.

A hot rolling step may be performed following the homogenization step. The homogenized product may be cooled to a temperature of 300-450° C. before starting hot rolling. For example, the homogenized product can be cooled to a temperature of 325-425°C, or 350-400°C. The product is then hot rolled at a temperature of 300-450° C. to obtain a , 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, or any in between value of ) to form hot-rolled flat plate, hot-rolled plate or hot-rolled sheet.

The flat plate, slate or sheet may then be cold rolled into sheet using conventional cold rolling mills and techniques. Cold rolled sheet may have standard dimensions of about 0.5-10 mm, such as about 0.7-6.5 mm. Optionally, the cold rolled sheet is 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 reduces the standard dimension by 85% or less (e.g., 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). ), resulting in a final standard thickness dimension corresponding to 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, shaft 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, a flat plate, slate, or sheet can be heated to about 400° C. for about 1 hour and then heated to about 330° C. for about 2 hours.

The flat plate, slate or sheet may then undergo a solution heat treatment step. The solution heat treatment step can be any conventional treatment for sheet metal that results in solutionization of the soluble particles. A slab, slate, or sheet can be heated to a peak metal temperature (PMT) of 590° C. or less (eg, 400-590° C.) and ignited at that temperature for a period of time. For example, the slab, slate or sheet is annealed at 480° C. for an anneal 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). can be After heating and firing, the slab, slate or sheet is quenched to a temperature of 500-200°C at a rate greater than 100°C/sec. In one example, the quenching rate of a flat plate, shaft or sheet is greater than 200°C/sec at a temperature of 450-200°C. Optionally, the cooling rate may be faster in other instances.

After quenching, the flat plate, shaft or sheet may optionally undergo a pre-aging treatment by reheating the flat plate, shaft or sheet prior to winding. 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 is 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 it can be carried out at a temperature of about 125°C. Optionally, the pre-aging treatment can 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. Pre-aging treatment can be carried out by passing the plate, shaft or sheet through a heating device, for example, a device that emits radiant, convective, inductive, infrared heat, or the like.

The castings described herein may also be used to make products in the form of flat plates or other suitable products. For example, flat plates, including the products described herein, can be made by processing an ingot in a homogenization process followed by a hot rolling process. In the hot rolling process, the cast product may be hot rolled to a standard thickness dimension of 200 mm or less (eg, about 10 mm to about 200 mm). For example, the cast product has 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. It can be hot rolled into flat plate.

The aluminum alloy products described herein may 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 in 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 hood, outer hood or trunk lid panel. The aluminum alloy products and methods described herein can also be used in aircraft or rail vehicle applications, for example, to make exterior and interior panels.

The aluminum alloy products and methods described herein may also be used in electronic device 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, aluminum alloy products can be used to make housings for cell phone (eg, smart phone) outer frames, tablet bottom frames, and other portable electronic devices.

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 this disclosure. The following sections describe various additional features and examples with reference to drawings in which like numerals indicate like elements, and the indicative descriptions are provided to illustrate exemplary embodiments. Although used, it should not be used to limit the present disclosure, as with the exemplary embodiment. Elements included in the illustrations herein may not be drawn to scale. For example, figures depicting metal puddle may contain exaggerated features for illustrative purposes.

FIG. 1 is a partial cross-sectional view of a metal casting system 100 for in situ dispersoid precipitation, according to certain aspects of the present disclosure. A metal source 102 , such as a tundish, may supply 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 melt and reduce metal oxide formation on the upper surface of the melt pool 110 . The bottom block 120 can be lifted by a hydraulic cylinder 122 to conform to the walls of the mold cavity 112 . As the molten metal begins to solidify in the mold, the bottom block 120 can be steadily lowered at the casting speed. Embryonic ingot 116 may include solidified sides 118 while molten metal added to the mold may be used to continuously lengthen embryonic ingot 116 . Embryonic ingot 116 may include bottom end 136 . In some cases, the walls of the mold cavity 112 define hollow spaces and may contain a coolant 114, such as water. The coolant 114 may jet out of the hollow space and flow down the sides 118 of the embryonic ingot 116 to help solidify the embryonic ingot 116 . Embryonic ingot 116 may include outer solid shell 128 , transitional metal regions (eg, solidification interface 126 ), and melt core 124 .

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

Although various techniques may be used to reheat solid shell 128 , FIG. 1 depicts the use of wiper 142 to remove coolant 114 from embryonic ingot 116 . Although wiper 142 in FIG. 1 is depicted as a solid wiper, other wipers, such as fluid-based wipers (eg, air knives), can be used as well. The coolant 114 is removed from the embryonic ingot 116 at the cross section where the core of the embryonic ingot 116 is still molten. Thus, latent heat from melt core 124 , particularly from regions of melt core 124 between reheater distance 130 and melt distance 132 (defined below), may reheat solid shell 128 . Accordingly, the timing and amount of reheat can be precisely controlled by adjusting reheater distance 130 and/or melt distance 132, as described in further detail herein.

Reheater distance 130 may be shorter than melt distance 132 and pool distance 134 . Melt distance 132 may be defined as the distance from the bottom of mold cavity 112 to the bottom of melt core 124 . A puddle distance 134 may be defined as the distance from the bottom of the mold cavity 112 to the bottom of the solidification interface 126 .

In some cases, for example, by inducing a change in the shape of the melt core 132 (e.g., by changing the casting speed and/or inducing agitation) to adjust the melt distance 132, or by moving the wiper 142. By adjusting reheater distance 130, the difference between melt distance 132 and reheater distance 130 can be controlled. Such casting speed, agitation and/or wiper 142 adjustment may be controlled by controller 138 coupled to any suitable actuator. In some cases, controller 138 may perform operations based on preset routines. In some cases, controller 138 may perform operations based on dynamic feedback from the casting process, eg, from temperature measurements made by sensor 144 . Sensor 144 may be any suitable temperature sensor, such as a contact or non-contact sensor. Although sensor 144 in FIG. 1 is depicted adjacent solid shell 128 to make measurements of the surface of solid shell 128, this need not be the case. In some cases, the sensor(s) may be placed elsewhere to make other ingot measurements, such as puddle temperature or coolant temperature measurements.

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

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

FIG. 2 is a partial cross-sectional view of a metal casting system 200 for in situ dispersoid precipitation with pool depth control, according to certain aspects of the present disclosure. Metal casting system 200 may be similar to metal casting system 100 of FIG. Metal source 202 may supply molten metal down feed tube 204 , through flow controller 240 and out nozzle 206 . Flow controller 240 may provide increased flow from metal source 202 into melt core 224 . This increased flow of melt through feed tube 204 may result in increased flow 246 within melt core 224 . Increased flow 246 can be or correspond to increased volumetric flow rate, increased linear flow rate, or both increased volumetric flow rate and increased linear flow rate, for example, when compared to the flow arrangement depicted in FIG. obtain.

Such increased flow 246 can result in strong agitation and can act as jets that can erode portions of solidification interface 226 . The jet may create depressions within the solid shell 228 and within the solidification interface 226 at the bottom of the metal pool (eg, the lowest portion of the liquid metal core 224). By doing so, both the melt distance 232 and the pool distance 234 may be increased.

Thus, for wiper 242 located at the same reheater distance 230 from mold 212 and wiper 142 of FIG. 224 because the difference between melt distance 232 and reheater distance 230 is greater.

The intensity of agitation and/or the amount of flow 246 may be controlled by controller 238 coupled to any suitable actuator (eg, flow controller 240). In some cases, controller 238 may perform operations based on preset routines. In some cases, controller 238 may perform operations based on dynamic feedback from the casting process, eg, from temperature measurements made by sensor 244 . Sensor 244 may be any suitable temperature sensor, such as a contact or non-contact sensor. Although sensor 244 in FIG. 2 is depicted adjacent solid shell 228 to take measurements of the surface of solid shell 228, this need not be the case. In some cases, the sensor(s) may be placed elsewhere to make other ingot measurements, such as puddle temperature or coolant temperature measurements.

FIG. 3 is a partial cross-sectional view of a metal casting system 300 for controlled flow agitation in accordance with certain aspects of the present disclosure. Various aspects of metal casting system 300 may be similar to appropriate aspects of metal casting system 100 of FIG. Metal source 302 may supply molten metal down feed line 304 , through flow controller 340 and out nozzle 306 . Flow controller 340 may provide increased flow from metal source 302 into melt core 324 . This increased flow of melt through feed tube 304 may result in increased flow 346 into melt core 324 .

Such increased flow 346 can result in strong agitation and can act as jets that can erode portions of solidification interface 326 . The jet may create depressions within the solid shell 328 and within the solidification interface 326 at the bottom of the metal pool (eg, the lowest portion of the liquid metal core 324). The strength of the flow 346, and hence the strength of the resulting jet, can be controlled to produce the desired shape of the depression. If the flow is too weak, either no pits or pits of small diameter can be created. If the flow is too strong, the depression may have too large a diameter. On the other hand, the desired indentation may have a diameter that matches the diameter of the bottom of the puddle, resulting in a smooth, gradual shape of the puddle. A puddle shape with dimples may facilitate the flow of molten metal up the sides of the solidification interface 326, which removes impurities and hydrogen displaced from the solidification interface 326, as well as reduces the grain size. It may facilitate resuspension to improve grain structure resulting in finer grains.

The intensity of agitation and/or the amount of flow 346 may be controlled by controller 338 coupled to any suitable actuator (eg, flow controller 340). In some cases, controller 338 may perform operations based on preset routines. In some cases, controller 338 may perform operations based on dynamic feedback from the casting process, eg, from temperature measurements made by sensor 344 . In some cases, feedback from sensor 344 can be used to infer the solidification interface profile (e.g., the shape of the solidification interface) and to implement actions to provide or maintain the desired solidification interface profile. . Sensor 344 may be any suitable temperature sensor, such as a contact or non-contact sensor. Although sensor 344 in FIG. 3 is depicted adjacent solid shell 328 to make measurements of the surface of solid shell 328, this need not be the case. In some cases, the sensor(s) may be placed elsewhere to make other ingot measurements, such as puddle temperature or coolant temperature measurements.

FIG. 4 is a partial cross-sectional view of a metal casting system 400 for controlled flow agitation with multiple feed tubes, according to certain aspects of the present disclosure. Metal casting system 400 may be similar to metal casting system 300 of FIG. Metal source 402 may supply molten metal down a plurality of feed tubes 404 , 450 , 454 . Although three feed tubes are used as depicted in FIG. 4, any number of feed tubes may be used. Each feed tube 404, 450, 454 may be associated with a controller 440, 456, 452, respectively. Flow controllers 440, 456, 452 are depicted as pin valves, but any suitable flow controller may be used. reducing flow through one or more of the feed tubes (e.g., feed tubes 450, 454) when multiple feed tubes 404, 450, 454 are used to supply melt to the melt core 424; Increased flow 446 may be provided by increasing flow through one or more of the remaining feed tubes (eg, feed tube 404). As depicted in FIG. 4, flow controllers 452 and 456 are closed while flow controller 440 is open, allowing more fluid to flow out of central feed tube 404. , thus creating an increased flow 446 within the melt core 424 .

Such increased flow 446 can result in strong agitation and can act as jets that can erode portions of solidification interface 426 . The jet may create depressions within the solid shell 428 and within the solidification interface 426 at the bottom of the metal pool (eg, the lowest portion of the liquid metal core 424). The strength of the flow 446, and hence the strength of the resulting jet, can be controlled (eg, by activating any of the flow controllers 452, 440, 456) to produce the desired shape of the depression. If the flow is too weak, either no pits or pits of small diameter can be created. If the flow is too strong, the depression may have too large a diameter. On the other hand, the desired indentation may have a diameter that matches the diameter of the bottom of the puddle, resulting in a smooth, gradual shape of the puddle. A puddle shape with dimples may facilitate the flow of molten metal up the sides of the solidification interface 426, which removes impurities and hydrogen displaced from the solidification interface 426, as well as reduces the grain size. It may facilitate resuspension to improve grain structure resulting in finer grains.

The intensity of agitation and/or amount of flow 446 may be controlled by controller 438 coupled to any suitable actuator (eg, flow controllers 440, 452, 456). In some cases, controller 438 may perform operations based on preset routines. In some cases, controller 438 may perform operations based on dynamic feedback from the casting process, eg, from temperature measurements made by sensor 444 . In some cases, feedback from sensor 444 can be used to infer the solidification interface profile (e.g., the shape of the solidification interface) and to implement actions to provide or maintain the desired solidification interface profile. . Sensor 444 may be any suitable temperature sensor, such as a contact or non-contact sensor. Although sensor 444 in FIG. 4 is depicted adjacent solid shell 428 to make measurements of the surface of solid shell 428, this need not be the case. In some cases, the sensor(s) may be placed elsewhere to make other ingot measurements, such as puddle temperature or coolant temperature measurements.

FIG. 5 is a partial cross-sectional view of a metal casting system 500 for high agitation with a magnetic stirrer, according to certain aspects of the present disclosure. Metal casting system 500 may be similar to metal casting system 300 of FIG. Metal source 502 may supply molten metal down feed tube 504 and out nozzle 506 . Although not depicted in FIG. 5, a flow controller may optionally be used.

A non-contact magnetic stirrer 560 is positioned adjacent the melt core 524 to generate surface flows 566,568. Non-contact magnetic stirrer 560 can be an electromagnet or a permanent magnet. In one example, a permanent magnet non-contact magnetic stirrer 560 can be placed on the opposite side of the feed tube 504 and can rotate in directions 562, 564 suitable to generate surface flows 566, 568 toward the feed tube 504. . Surface flows 556 , 568 may interact with molten metal flowing out of feed tube 504 and may provide increased flow 546 into molten metal core 524 .

Such increased flow 546 can result in strong agitation and can act as jets that can erode portions of solidification interface 526 . The jet may create depressions within the solid shell 528 and within the solidification interface 526 at the bottom of the metal pool (eg, the lowest portion of the liquid metal core 524). The strength of the flow 546, and hence the strength of the resulting jet, can be controlled to produce a depression of desired shape. If the flow is too weak, either no pits or pits of small diameter can be created. If the flow is too strong, the depression may have too large a diameter. On the other hand, the desired indentation may have a diameter that matches the diameter of the bottom of the puddle, resulting in a smooth, gradual shape of the puddle. A puddle shape with dimples may facilitate the flow of molten metal up the sides of the solidification interface 526, which removes impurities and hydrogen displaced from the solidification interface 526, as well as reduces the grain size. It may facilitate resuspension to improve grain structure resulting in finer grains.

The intensity of agitation and/or amount of flow 546 may be controlled by controller 538 coupled to any suitable actuator (eg, non-contact agitator 560). In some cases, controller 538 may perform operations based on preset routines. In some cases, controller 538 may perform operations based on dynamic feedback from the casting process, eg, from temperature measurements made by sensor 544 . In some cases, feedback from sensor 544 can be used to infer the solidification interface profile (e.g., the shape of the solidification interface) and to implement actions to provide or maintain the desired solidification interface profile. . Sensor 544 may be any suitable temperature sensor, such as a contact or non-contact sensor. Although sensor 544 in FIG. 5 is depicted adjacent solid shell 528 to make measurements of the surface of solid shell 528, this need not be the case. In some cases, the sensor(s) may be placed elsewhere to make other ingot measurements, such as puddle temperature or coolant temperature measurements.

FIG. 6 is an enlarged schematic diagram of the bottom of the molten metal pool 600 when there is no strong stirring. The bottom of the melt core 624 and the solidification interface 626, as well as adjacent portions of the solid shell 628, may exhibit uneven layered topography, which may be due to settling of suspended grains, as well as other factors. have a nature. As a result, the melt may remain somewhat stagnant near this region. This bottom region of the melt pool may have a width 670 that may be roughly defined between the regions where the sloped walls of the solidification interface 626 reach their maximum depth.

FIG. 7 is an enlarged schematic diagram of the bottom of a molten pool 700 undergoing vigorous agitation, according to certain aspects of the present disclosure. The bottom of the melt core 724 and the solidification interface 726, as well as adjacent portions of the solid shell 728, may exhibit an uneven U-shaped or parabolic contour due to the increased flow 746 of melt. Molten metal flow 746 may erode solidification interface 726 and solid shell 728 to form depression 774 . The depression 774 can have a depth 772 that extends from the bottom before agitation (eg, as seen in FIG. 6) to the bottom of the depression 774 during agitation (eg, as seen in FIG. 7). Depression 774 can have a diameter 770 (eg, maximum diameter) approximately equal to the diameter of the puddle prior to agitation (eg, diameter 670 in FIG. 6).

The molten metal flow 746 may be controlled to erode the solidification interface 726 to a thickness on the order of a few millimeters, eg, approximately 1-5 mm, or approximately 10 mm or less, at least at or adjacent to the bottom of the solidification interface 726 . In some cases, the flow 746 causes the solidification interface 726 at least at or adjacent to the bottom of the solidification interface 726 to be 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. It can be controlled to erode to a thickness of 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. FIG. 8 is a flow diagram illustrating a process 800 for in situ dispersoid precipitation, according to certain aspects of the present disclosure. At block 802, molten metal is supplied to the mold. At block 804, the embryonic ingot to be formed in the mold is advanced in the casting direction. At block 806, heat is continuously removed from the shell between the bottom of the mold as the embryonic ingot emerges from the mold and the reheat location. At block 808, the embryonic ingot is reheated. Reheating can be initiated at the reheating position. In some cases, reheating may include removing coolant supplied to the surface of the embryonic ingot during block 806 . At block 810, the embryonic ingot may be held at the reheat temperature for a period of time, eg, approximately 3 hours. Optionally, instead of holding the ingot at the reheat temperature, the ingot is gradually cooled at block 812 . The ingot can be gradually cooled to room temperature, for example, over a period of at least approximately 3 hours.

In some cases, agitation may optionally be induced at block 816 . Agitation may be induced to improve various properties of the as-cast ingot and to increase the depth of the pool of molten metal and thus affect the reheating performed at block 808 .

In some cases, temperature measurement monitoring may optionally be performed at block 814 . The results of temperature measurement monitoring can be used to adjust the amount of agitation induced at block 816 and the reheat position used with respect to block 808 . Temperature measurement monitoring at block 814 can occur continuously.

FIG. 9 is a flow diagram illustrating a process 900 for creating high strength regions of precipitated dispersoids in a semi-continuously cast ingot, according to certain aspects 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 internal molten core of the embryonic ingot may solidify to form a solid shell of the embryonic ingot. At block 906, high strength regions of precipitated dispersoids may be continuously formed.

Continuously forming high strength regions of precipitated dispersoids at block 906 may include reheating the outer solid shell at a reheater distance at block 908 . Optionally, the temperature of the ingot may be measured at block 910 . This measurement can 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 the reheater (eg, wiper) at block 914 . Adjusting the melt distance at block 916 may include inducing agitation at block 918 .

FIG. 10 is a schematic cross-sectional elevational view of ingot 1016 depicting regions of high strength 1074, according to certain aspects of the present disclosure. High strength region 1074 is depicted extending from or near the surface of ingot 1016 to a surface depth of less than half the surface of ingot 1016 to longitudinal centerline 1016 of ingot 1016 .

FIG. 11 is a schematic cross-sectional plan view of ingot 1116 depicting regions of high strength 1174, according to certain aspects of the present disclosure. High strength regions 1174 extend from or near the surface of ingot 1016 (eg, rolled surface and/or sides) to less than halfway from the surface of ingot 1116 to the associated centerline, e.g., from the rolled surface of ingot 1116 to the lateral centerline. 1180 and extending from the side of the ingot 1116 to less than half the surface depth to the rolling face centerline 1178 .

FIG. 12 is a flow diagram illustrating a process 1200 for producing a strongly-stirred semi-continuous casting ingot, according to certain aspects of the present disclosure. At block 1202, molten metal may be delivered to the mold. At block 1204, an outer solid shell may be formed when heat is removed from the melt. At block 1206, the ingot may be advanced out of the mold at the casting speed. At block 1208, the casting speed may be used to determine the agitation intensity. Agitation intensity may be based on a sensed or known casting speed. At block 1210 , agitation may be induced at the intensity determined at block 1208 . Inducing agitation may include using flow controllers and/or non-contact agitators, although other techniques may be used. At block 1212, the casting speed may be changed. Upon changing the casting speed, the agitation intensity may again be determined at block 1208 based on the updated casting speed from block 1212 . Agitation can then be induced at the newly determined intensity. At optional block 1214, the temperature of the embryonic ingot may be instrumented and monitored. Once the ingot temperature has been metered and monitored, the agitation intensity can again be determined at block 1208 based at least in part on the temperature measured at block 1214 as well. Agitation can then be induced at the newly determined intensity.

At optional block 1216, high strength regions of precipitated dispersoids may be continuously formed as disclosed herein.

Aspects of the present invention may be further understood by reference to the following non-limiting examples.

Example 1 - Analysis of Ingots Several different aluminum alloy ingots were obtained, including a reference ingot and sample ingots made according to the techniques described herein in which agitation was induced during casting. All ingots were 7xxx series aluminum alloys.

The reference ingot was 0.08 wt. % Si, 0.15 wt. % Fe, 1.58 wt. % Cu, 0.02 wt. % Mn, 2.52 wt. % Mg, 0.193 wt. % Cr, 0.01 wt. % Ni, 5.61 wt. % Zn, 0.012 wt. % V, 0.019 wt. % Ti, 0.001 wt. % Ca, 0.010 wt. % Zr and balance aluminum. A reference ingot was cast using conventional DC casting followed by a conventional homogenization process. One inch thick flakes were obtained at casting lengths of 50 inches, 100 inches and 150 inches and analyzed as described below.

The first sample ingot was 0.09 wt. % Si, 0.20 wt. % Fe, 1.45 wt. % Cu, 0.04 wt. % Mn, 2.35 wt. % Mg, 0.20 wt. % Cr, 0.004 wt. % Ni, 5.45 wt. % Zn, 0.019 wt. % V, 0.03 wt. % Ti, 0.005 wt. % Ca, 0.010 wt. % Zr and balance aluminum. A first sample ingot was cast using non-contact stirring as described herein followed by homogenization at 480° C. for 4 hours. A comparative first sample ingot was cast using non-contact stirring as described herein without homogenization to allow evaluation of as-cast properties. One inch thick flakes were obtained at casting lengths of 50 inches, 100 inches and 150 inches and analyzed as described below.

The second sample ingot was 0.11 wt. % Si, 0.20 wt. % Fe, 1.57 wt. % Cu, 0.05 wt. % Mn, 2.39 wt. % Mg, 0.18 wt. % Cr, 5.73 wt. % Zn, 0.03 wt. % Ti, 0.02 wt. % Zr, 0.02 wt. % Sr and balance aluminum. A second sample ingot was cast using non-contact stirring followed by multi-stage homogenization as described herein: first, the second sample ingot was heated to 465° C. at a rate of about 50° C./hour, Hold at 465°C for 4 hours; then a second sample ingot was heated from 465°C to 480°C at 5°C/hr and held at 480°C for 16 hours. A second sample ingot was subjected to a conventional rolling process to obtain a sheet metal sample.

Cross-sectional depictions of 1 inch thick slices of reference ingot 1300 and first sample ingot 1350 are shown in FIGS. 13A and 13B, respectively. The slice of reference ingot 1300 has a width 1301 of about 1690 mm and a thickness 1302 of about 602 mm; the slice of reference ingot 1350 has a width 1351 of about 1750 mm and a thickness 1352 of about 519 mm. rice field. Analysis of the reference ingot 1300 and first sample ingot 1350 was performed using a grid of sampling locations spanning nine columns (columns 1-9) and four rows (rows AD). The fifth row E of reference ingot 1300 was not fully analyzed because this row was partially cut and was at the edge of reference ingot 1300 . The sampling location was approximately 45 mm in diameter on the reference ingot 1300 and location 9A corresponded to the center of the reference ingot 1300 and the first sample ingot 1350 .

The first row of sampling locations was located approximately 30 mm from the edge in the reference ingot 1300 , while the first row of sampling locations was located approximately 58 mm from the edge of the first sample ingot 1350 . was The columns were spaced about 62 mm from each other in the reference ingot 1300 and the rows were spaced from each other about 42 mm in the reference ingot 1300 . The columns were spaced about 61 mm from each other in the first sample ingot 1350 and the rows were spaced from each other about 28 mm in the first sample ingot 1350 .

The macrosegregation of Fe, Zn, Cr, Mg and Cu across the sampling sites of the reference ingot 1300 and the first sample ingot 1350 was analyzed using x-ray fluorescence (XRF) spectroscopy. The composition of Fe, Zn, Cr, Mg and Cu for each of the first sample ingot (50″, 100″, 150″) flakes was generally stable across rows AD and columns 1-9. .

The reference ingot exhibited moderate amounts of macrosegregation for most of these elements. A graph of Fe, Zn, Cr, Mg and Cu composition as a function of position for a 100 inch slice of the reference ingot is shown in FIG. In contrast, macrosegregation in the first sample ingot was limited. A graph of Fe, Zn, Cr, Mg and Cu composition as a function of position for a 100 inch slice of the first sample ingot is shown in FIG.

However, since the first sample ingot was subjected to homogenization following casting, the composition of the first comparative sample ingot was analyzed in the same manner to assess macrosegregation in the as-cast ingot prior to homogenization. bottom. Although the concentrations of Fe, Zn, Cr, Mg and Cu were slightly different between the first sample ingot and the first comparative sample ingot, the macro-segregation was similarly limited in the first comparative sample ingot and non-contact stirring have shown that casting using A graph of Fe, Zn, Cr, Mg and Cu composition as a function of position for a 100 inch slice of the first comparative sample ingot is shown in FIG.

A reference ingot and a first sample by scanning a 3D surface profiler across the surface of the ingot slice and identifying areas where the surface profile has depressions larger than a given depth as cavities. Ingot porosity characterization was also performed. Graphs of total porosity for each of the sampling locations of the 100 inch slices of the reference ingot and the first sample ingot are shown in FIGS. 17 and 18, respectively. The reference ingot exhibited a higher porosity than the first sample ingot.

The grain structure of the reference ingot and the first sample ingot was also characterized. Optical microscope images were obtained for each of the sampling locations to assess the grain structure. Both ingots exhibited a relatively coarser primary Al grain structure closer to the ingot center and a relatively finer grain structure toward the ingot surface. Grain boundary precipitates and fine _MgZn2 precipitates are observed in the reference ingot and the first sample ingot. A greater proportion of grain boundary precipitates was observed in the first comparative sample ingot.

The reference ingot, first sample ingot and second sample ingot were also characterized using differential scanning calorimetry (DSC) and x-ray diffraction (XRD) to determine the presence and composition of intermetallics, precipitates and eutectics. evaluated. DSC showed a distinct presence of low temperature melting phases (e.g. _MgZn2 and _Al2CuMg ) at locations closer to the surface (e.g. rows B, C and D), while locations closer to the center of the ingot (e.g. row A row) showed no evidence of low temperature melting in the DSC data. However, the XRD data showed the presence of _MgZn2 , possibly in the form of fine precipitates, at locations closer to the center of the ingot (eg row A). XRD and DSC data for the first comparative sample ingot showed evidence of several low temperature melting phases including _MgZn2 , _Al2MgC and _Mg2Si , including locations near the center of the ingot.

A sample of rolled sheet metal from the second sample ingot was subjected to mechanical testing for analysis. Rolled sheet metal was produced in two conditions: a T6 temper condition, and a T6 temper condition followed by a paint bake (T6+PB). Samples from the center and both edges of the ingot were evaluated. The center sample for the T6 temper condition was evaluated along the transverse (T), longitudinal (L) and diagonal (D) directions. Edge samples and T6+PB samples were evaluated along the longitudinal direction only. The measured properties, average yield stress (YS) (0.2% offset), average maximum tensile stress (TS), average maximum axial strain (AS), and average uniform elongation (UE) are shown in FIG. Plot it in a graph.

Exemplary Embodiments As used below, any reference to a series of embodiments should be understood as a separate reference to each of those examples (e.g., "embodiments 1-4" becomes "embodiments 1, 2, 3 or 4”).

Aspect 1 is a method, such as a casting method, wherein molten metal is fed into a casting mold to form an embryonic ingot comprising an outer solid shell and an inner molten core; advancing the embryonic ingot in a direction of travel away from the casting mold; transferring heat from the embryonic ingot between the casting mold and a transition location by directing a supply of liquid coolant against the outer surface of the outer solid shell; and so that at least a portion of the outer solid shell of the embryonic ingot at the transition location reaches the temperature suitable for precipitation of dispersoids and below the homogenization temperature of the molten metal. and reheating the embryonic ingot at the transition location, wherein the transition location is in the plane perpendicular to the direction of travel and intersecting the internal molten core. is.

Aspect 2 is the method of any preceding or subsequent aspect, wherein said temperature, eg, expressed in degrees Celsius, is 80-90% of said homogenization temperature, eg, expressed in degrees Celsius, of said melt.

Aspect 3 is the method of any preceding or subsequent aspect, wherein said temperature, eg, expressed in degrees Celsius, is 85-90% of said homogenization temperature, eg, expressed in degrees Celsius, of said melt.

Aspect 4 is the method of any preceding or following aspect, wherein said temperature is from 400 to 460°C.

Aspect 5 is the method of any preceding or following aspect, wherein said temperature is 410-420°C.

Aspect 6 is the method of any preceding or subsequent aspect, further comprising maintaining said temperature in said portion of said outer solid shell for at least 3 hours.

Aspect 7 is the method of any preceding or subsequent aspect, wherein reheating the embryonic ingot comprises removing the liquid coolant from the outer surface of the outer solid shell.

Aspect 8 is any preceding or following wherein reheating the embryonic ingot further comprises applying heat to the outer surface of the outer solid shell to supplement latent heat heating from the inner molten core. A method according to an embodiment.

Aspect 9 is the method of any preceding or subsequent aspect, further comprising taking a temperature measurement of the embryonic ingot and dynamically adjusting the transition location based on the temperature measurement.

Aspect 10 is the method of any preceding or subsequent aspect, further comprising inducing agitation in the internal molten core adjacent to the interface between the internal molten core and the external solid shell.

Aspect 11 further comprises taking a temperature measurement of the embryonic ingot, and wherein inducing agitation in the internal molten core comprises dynamically adjusting an intensity of agitation based on the temperature measurement.Optional A method according to any preceding or subsequent aspect of A.

Aspect 12 is characterized in that the surface is the embryonic ingot in cross-section in which the outer solid shell of the embryonic ingot occupies approximately one-third of the line extending from the outer surface to the center of the embryonic ingot in the surface. A method according to any preceding or succeeding aspect, wherein said transition locations are selected to intersect.

In a thirteenth aspect, the outer solid shell of the embryonic ingot occupies 50% or less of the line extending from the outer surface to the center of the embryonic ingot in the plane, and the plane intersects the embryonic ingot in the cross section. A method according to any preceding or subsequent aspect, wherein said transition location is selected as so.

Aspect 14 is the method of any preceding or subsequent aspect, wherein the melt is a 7xxx series aluminum alloy.

Aspect 15 is a method comprising: forming an embryonic ingot by feeding a molten metal to a mold and removing heat from the molten metal to form an outer solid shell; advancing in a receding direction of travel and solidifying an internal molten core of the embryonic ingot as additional molten metal is fed into the mold, solidifying the internal molten core through the external solid shell; removing heat from said internal molten core; comprising continuously forming a high-strength region, said high-strength region being located between an outer surface of said outer solid shell and said inner molten core; reheating the outer solid shell in to induce dispersoid precipitation in the outer solid shell.

Aspect 16, wherein reheating the outer solid shell in the cross section comprises reheating a portion of the outer solid shell to a temperature suitable for dispersoid precipitation, wherein the temperature is sufficient to homogenize the melt. A method according to any preceding or subsequent aspect wherein the temperature is lower than the temperature.

Aspect 17 is the method of any preceding or subsequent aspect, wherein said temperature, eg, expressed in degrees Celsius, is 80-98% of said homogenization temperature, eg, expressed in degrees Celsius, of said melt.

Aspect 18 is the method of any preceding or subsequent aspect, wherein said temperature is 85-90% of said homogenization temperature of said melt.

Aspect 19 is the method of any preceding or following aspect, wherein said temperature is 400-460°C.

Aspect 20 is the method of any preceding or following aspect, wherein said temperature is 410-420°C.

Aspect 21 is the method of any preceding or subsequent aspect, further comprising maintaining said temperature in said portion of said outer solid shell for at least 3 hours, such as from 3 to 10 hours.

Aspect 22, removing heat from the inner molten core through the outer solid shell comprises supplying a liquid coolant to the outer surface of the outer shell, and reheating the outer solid shell. A method according to any preceding or subsequent aspect, comprising removing the liquid coolant from the outer surface of the outer solid shell.

Aspect 23 is any preceding or following wherein reheating said outer solid shell further comprises applying heat to said outer surface of said outer solid shell to supplement latent heat heating from said inner molten core. A method according to an embodiment.

Aspect 24 of any preceding or following aspect, further comprising taking a temperature measurement of the embryonic ingot and dynamically adjusting the distance between the mold and the cross-section based on the temperature measurement. is the method described in

Aspect 25 is the method of any preceding or subsequent aspect, further comprising inducing agitation in the internal molten core adjacent an interface between the internal molten core and the external solid shell.

Aspect 26 further comprises taking a temperature measurement of the embryonic ingot, and wherein inducing agitation in the internal molten core comprises dynamically adjusting an intensity of agitation based on the temperature measurement.Optional A method according to any preceding or subsequent aspect of A.

Aspect 27. Aspect 27 as recited in any preceding or following aspect, wherein the outer solid shell of the embryonic ingot in the cross-section occupies approximately one-third of a line extending from the outer surface to the center of the embryonic ingot. method.

Aspect 28. The method of any preceding or subsequent aspect, 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 the center of the embryonic ingot. is.

Aspect 29 is the method of any preceding or subsequent aspect, wherein said melt is a 7xxx series aluminum alloy.

Aspect 30 is the method of any preceding or subsequent aspect, wherein the high intensity region comprises a higher concentration of dispersoids relative to the remainder of the outer solid shell.

Aspect 31 is an aluminum metal product comprising a solidified aluminum alloy mass having two ends and an outer surface, said solidified aluminum alloy mass containing a center of said solidified aluminum alloy mass; an outer region integral with an outer surface; and a high strength region disposed between said core region and said outer region, said high strength region being higher than each of said core region and said outer region. The aluminum metal product having a concentration of dispersoids.

Aspect 32 is the aluminum metal product of any preceding or subsequent aspect, wherein said solidified aluminum alloy mass includes retained heat from a semi-continuous casting process.

Aspect 33 optionally wherein said high strength region is located at a depth of approximately one third of a line extending along a cross-section of said solidified aluminum alloy mass from said outer surface to said center of said solidified aluminum alloy mass. 3. An aluminum metal article according to any preceding or subsequent aspect of .

Aspect 34 optionally wherein said 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 said solidified aluminum alloy mass from said outer surface to said center of said solidified aluminum alloy mass. 3. An aluminum metal article according to any preceding or subsequent aspect of .

Aspect 35 is the aluminum metal article of any preceding or subsequent aspect, wherein the shape of said solidified aluminum alloy mass is cylindrical.

Aspect 36. The aluminum of any preceding or subsequent aspect, wherein the shape of the cross-section of the solidified aluminum alloy mass perpendicular to the casting direction of the solidified aluminum alloy mass is rectangular. It is a metal product.

Aspect 37 is the aluminum metal article of any preceding or subsequent aspect, wherein the solidified aluminum alloy mass is a solidified 7xxx series aluminum alloy mass.

Aspect 38 is the aluminum metal article of any preceding or subsequent aspect made according to the method of any preceding or subsequent aspect.

Embodiment 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 said aluminum alloy, said solidified shell extending from said solidification interface to a bottom end in the casting direction. an extending outer surface, the solidifying shell defining a high strength region disposed between the outer surface and a centerline extending in the casting direction through the center of the liquid molten core and the center of the solidifying shell; wherein said high strength region has a higher concentration of dispersoids than the rest of said solidified shell.

Aspect 40 is the embryonic ingot of any preceding or succeeding aspect, wherein the high strength region is located at a depth of approximately one third of a line extending from the outer surface to the centerline.

Aspect 41 is the embryonic ingot of any preceding or succeeding aspect, wherein the high strength region is located at a depth of one-half or less of a line extending from the outer surface to the centerline.

Aspect 42 is the embryonic ingot according to any preceding or subsequent aspect, wherein said solidified shell is cylindrical in shape.

Aspect 43 is the embryonic ingot of any preceding or subsequent aspect, wherein a cross-section of said solidified shell perpendicular to said casting direction is rectangular in shape.

Embodiment 44 is an embryonic ingot according to any preceding or subsequent embodiment, wherein said aluminum alloy is a 7xxx series aluminum alloy.

Aspect 45 is an embryonic ingot according to any preceding or subsequent aspect made according to the method according to any preceding or subsequent aspect.

Aspect 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 a shell, wherein a solidification interface is located between said outer solid shell and said pool of metal; advancing at a casting speed in a direction of travel away from; using said casting speed to determine an intensity of agitation, said intensity of agitation being suitable to provide a target solidification interface profile at said casting speed. A; further comprising inducing agitation within the pool of molten metal at the determined intensity, wherein at the casting speed the solidification interface conforms to the target solidification interface profile is the method described above, resulting in exhibiting

Aspect 47 is the method of any preceding or subsequent aspect, wherein inducing agitation comprises applying an agitation force to the molten metal in the metal pool using a non-contact magnetic stirrer. .

Aspect 48, delivering the melt comprises delivering the melt through the plurality of nozzles at a mass flow rate, and inducing agitation maintains the mass flow rate as it passes through the plurality of nozzles. A method according to any preceding or subsequent aspect, comprising increasing the flow rate of the molten metal through at least one of said plurality of nozzles while at the same time.

Aspect 49 further comprises changing said casting speed; using said updated casting speed to determine an updated intensity of agitation, wherein said updated intensity of agitation is equal to said updated casting speed; further comprising inducing agitation within the molten metal pool with the updated intensity, inducing agitation within the molten metal pool with the updated intensity A method according to any preceding or subsequent aspect, wherein performing causes the solidification interface to exhibit the target solidification interface profile at the updated casting speed.

Aspect 50 is the method of any preceding or subsequent aspect, wherein the melt is a 7xxx series aluminum alloy.

Aspect 51 further comprises measuring a temperature of said embryonic ingot, and determining said intensity of agitation using said casting speed comprises using said measured temperature. The method according to the mode.

Aspect 52 is the method of any preceding or subsequent aspect, wherein the target solidification interface profile is predetermined to minimize the risk of cracking.

Aspect 53 comprises continuously forming a high strength region within the outer solid shell in a cross section of the embryonic ingot that is perpendicular to the direction of travel and intersects the inner molten core. Further comprising, wherein the high strength region is located between an outer surface of the outer solid shell and the inner molten core, and wherein forming the high strength region comprises reheating the outer solid shell in the cross section. A method according to any preceding or subsequent aspect, comprising inducing dispersoid precipitation in said outer solid shell.

Aspect 54 is characterized in that inducing agitation within the pool of molten metal forces the molten metal into the pool such that a jet of molten metal erodes the solidification interface at the bottom of the pool of metal to form a depression. A method according to any preceding or subsequent aspect, comprising controlling delivery, wherein the depression has a diameter sized to match the diameter of the bottom of the metal puddle.

Aspect 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 a shell, wherein a solidification interface is located between said outer solid shell and said pool of metal; and controlling the delivery of the molten metal into the metal pool sufficient to erode at least a portion of the solidification interface at the bottom of the metal pool. the method comprising generating a jet of

Aspect 56 is any preceding or following wherein controlling delivery of said molten metal comprises controlling delivery of said molten metal such that said jet of molten metal erodes said solidification interface to a thickness of 10 mm or less. A method according to an embodiment.

Aspect 57, delivering said molten metal comprises delivering said molten metal at a mass flow rate through a plurality of nozzles, and generating said jet of molten metal when passing through said plurality of nozzles. A method according to any preceding or subsequent aspect, comprising increasing a flow rate of molten metal through at least one of said plurality of nozzles while maintaining said mass flow rate.

Aspect 58 is the method of any preceding or subsequent aspect, further comprising applying a stirring force to the molten metal in the metal pool using a non-contact magnetic stirrer.

Aspect 59 further comprises altering the casting speed, wherein controlling the delivery of the molten metal comprises controlling the delivery of the molten metal based on the altered casting speed to cause the jet of molten metal to flow into the pool of metal. A method according to any preceding or subsequent aspect, comprising dynamically adjusting to continue to erode at least said portion of said solidification interface at the bottom.

Aspect 60 is the method of any preceding or subsequent aspect, wherein the melt is a 7xxx series aluminum alloy.

Aspect 61 further comprises measuring a temperature of the embryonic ingot, and controlling the delivery of the molten metal comprises controlling the delivery of the molten metal based on the measured temperature so that the jet of molten metal reaches the metal pool. A method according to any preceding or subsequent aspect, comprising dynamically adjusting to continue to erode at least said portion of said solidification interface at said bottom of the.

Aspect 62 further comprises continuously forming a high strength region within the outer solid shell in a cross section of the embryonic ingot that is perpendicular to the direction of travel and intersects the metal pool. wherein said high strength region is located between an outer surface of said outer solid shell and said pool of metal, and forming said high strength region comprises reheating said outer solid shell in said cross section to form said outer solid shell. A method according to any preceding or subsequent aspect comprising inducing dispersoid precipitation in a solid shell.

Embodiment 63 is an aluminum metal product made according to the method described in any preceding or subsequent embodiment.

Embodiment 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 said aluminum alloy extending from a top surface to said solidification interface, said liquid molten core is said embryonic ingot comprising a jet of said aluminum alloy impinging said solidification interface at the bottom of said liquid molten core to form a depression in said solidification interface.

Embodiment 65 is an embryonic ingot according to any preceding or subsequent embodiment, wherein said liquid molten core comprises resuspended grains from said solidification interface.

Aspect 66 is an embryonic ingot according to any preceding or subsequent aspect, wherein said liquid molten core comprises resuspended hydrogen from said solidification interface.

Aspect 67, the solidified shell includes a high strength region located between the outer surface of the solidified shell and a centerline extending in the casting direction through the center of the liquid molten core and the center of the solidified shell. 10. An embryonic ingot according to any preceding or subsequent aspect, wherein said high strength region has a higher concentration of dispersoids compared to the remainder of said solidified shell.

Embodiment 68 is the embryonic ingot according to any preceding or subsequent embodiment, wherein said aluminum alloy is a 7xxx series aluminum alloy.

All patents and publications cited herein are incorporated by reference in their entirety. The above description of embodiments, including illustrated embodiments, is provided for purposes of illustration and description only and is not intended to be exhaustive or restrictive to the precise forms disclosed. I have no intention of doing so. Many modifications, adaptations and uses thereof will be apparent to those skilled in the art.

Claims (23)

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 said puddle of metal, said forming wherein a solidification interface is located between said outer solid shell and said puddle of metal;
advancing the embryonic ingot at a casting speed in a direction of travel away from the mold while delivering the molten metal and forming the outer solid shell;
determining an intensity of agitation using the casting speed, wherein the intensity of agitation is suitable for achieving a target solidification interface profile at the casting speed;
inducing agitation in the molten pool at the determined intensity, wherein inducing agitation in the molten pool causes the solidification interface to exhibit the target solidification interface profile at the casting speed; A method comprising: inducing, said inducing. Inducing the agitation
2. The method of claim 1, comprising applying a stirring force to the molten metal in the metal pool using a non-contact magnetic stirrer. delivering the molten metal
inducing the agitation comprising delivering the melt through a plurality of nozzles at a mass flow rate;
2. The method of claim 1, comprising increasing the flow rate of the melt through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles. changing the casting speed;
determining an updated intensity of agitation using the updated casting speed, wherein the updated intensity of agitation is suitable for achieving the target solidification profile at the updated casting speed; said determining;
Inducing agitation within the molten metal pool with the updated intensity, wherein inducing agitation within the molten metal pool with the updated intensity causes the solidification interface at the updated casting speed. 2. The method of claim 1, further comprising: inducing to exhibit the target solidification interface profile. 2. The method of claim 1, wherein the molten metal is a 7xxx series aluminum alloy. 2. The method of claim 1, further comprising measuring the temperature of the embryonic ingot, and wherein using the casting speed to determine the intensity of the agitation comprises using the measured temperature. 2. The method of claim 1, wherein the target solidification interface profile is predetermined to minimize the risk of cracking. further comprising continuously forming high-strength regions within the outer solid shell in a cross-section of the embryonic ingot perpendicular to the direction of travel and intersecting the inner molten core, wherein the high-strength regions are aligned with the located between the outer surface of the outer solid shell and the inner molten core and forming the high strength region reheats the outer solid shell at the cross-section to cause dispersoid precipitation in the outer solid shell; 2. The method of claim 1, comprising provoking. Inducing agitation within the molten metal pool controls the delivery of the molten metal into the metal pool such that the jet of molten metal erodes the solidification interface at the bottom of the metal pool to form a depression. and wherein said recess has a diameter sized to match the diameter of said bottom of said metal puddle. 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 said puddle of metal, said forming wherein a solidification interface is located between said outer solid shell and said puddle of metal;
advancing the embryonic ingot at a casting speed in a direction of travel away from the mold while delivering the molten metal and forming the outer solid shell;
and controlling delivery of said molten metal into said pool of metal to produce a jet of said molten metal sufficient to erode at least a portion of said solidification interface at the bottom of said pool of metal. controlling the delivery of the molten metal,
11. The method of claim 10, comprising controlling delivery of the molten metal such that the jet of molten metal erodes the solidification interface to a thickness of 10 mm or less. delivering the molten metal
generating a jet of said molten metal comprising delivering said molten metal at a mass flow rate through a plurality of nozzles;
11. The method of claim 10, comprising increasing the flow rate of the melt through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles. 11. The method of claim 10, further comprising applying a stirring force to the molten metal in the metal pool using a non-contact magnetic stirrer. controlling the delivery of the molten metal, further comprising varying the casting speed;
dynamically adjusting the delivery of the molten metal based on the altered casting speed such that the jet of molten metal continues to erode at least the portion of the solidification interface at the bottom of the metal pool; 11. The method of claim 10. 11. The method of claim 10, wherein said molten metal is a 7xxx series aluminum alloy. further comprising measuring the temperature of the embryonic ingot, and controlling the delivery of the molten metal;
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 the portion of the solidification interface at the bottom of the pool of metal. Item 11. The method according to Item 10. further comprising continuously forming a high strength region within the outer solid shell in a cross-section of the embryonic ingot perpendicular to the direction of travel and intersecting the puddle of metal; positioned between the outer surface of the outer solid shell and the metal pool and forming the high strength region;
11. The method of claim 10, comprising reheating the outer solid shell in the cross section to induce dispersoid precipitation in the outer solid shell. An aluminum metal product made according to the method of claim 1 or claim 10. 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, wherein the liquid molten core solidifies at the bottom of the liquid molten core. An embryonic ingot comprising a jet of said aluminum alloy impinging on an interface and forming a depression at said solidification interface. 20. The embryonic ingot of claim 19, wherein said liquid molten core comprises resuspended grains from said solidification interface. 20. The embryonic ingot of claim 19, wherein said liquid molten core contains resuspended hydrogen from said solidification interface. wherein the solidified shell includes a high strength region located between an outer surface of the solidified shell and a centerline extending in the casting direction through the center of the liquid molten core and the center of the solidified shell; 20. The embryonic ingot of claim 19, wherein a region has a higher concentration of dispersoids than the rest of the solidified shell. 20. The embryonic ingot of claim 19, wherein said aluminum alloy is a 7xxx series aluminum alloy.

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