KR102666365B1 - Reduces cracking susceptibility to 7xxx series direct cooled (DC) cast ingots - Google Patents

Abstract

During direct cooling casting of 7xxx series alloys, process control of strong agitation along the solidification front and adjustment of casting speed can reduce the cracking susceptibility of the ingot. Strong agitation control is used to reduce the thickness of the solidification front, promote the agglomeration of hydrogen gas rejected at the solidification front, remove impurities rejected at the solidification front and improve particle size. Strong agitation control is used to operate at faster casting speeds without the risk of increasing the thickness of the solidification front. Selective reheating during casting to promote dispersoid formation is used to create a high-strength zone of dispersoid-enhanced solidified metal around the outside of the ingot, which can further reduce the ingot's susceptibility to cracking.

Description

Reduces cracking susceptibility to 7xxx series direct cooled (DC) cast ingots

Cross-reference to related applications

This application claims the benefit and priority of U.S. Provisional Application No. 62/951,883, filed December 20, 2019, which is incorporated herein by reference in its entirety.

Technology field

The present invention relates generally to metal casting, and more specifically to direct cold casting of difficult aluminum alloys.

In direct cooling (DC) casting, molten metal is delivered into a mold cavity and has a pulsed, or moving, bottom. As molten metal enters the mold cavity, the bottom is lowered, typically at a rate related to the rate of flow of molten metal from the top. Molten metal that has solidified near the sides can be used to retain liquid and partially liquid metal in a molten sump. Metals can be 99.9% solid (e.g., completely solid), 100% liquid, and anywhere in between. The molten sump may take on a V-shape, U-shape, or W-shape because the thickness of the solid region increases as the molten metal cools. The interface between solid and liquid metal is called the solidification interface.

When the molten metal in the melt sump becomes between about 0% solids and about 5% solids, nucleation can occur and small crystals of metal can form. These small (e.g., nanometer-sized) crystals begin to form as nuclei, which continue to grow in a preferred direction to form dendrites as the molten metal cools. When the molten metal cools to the dentrite coherency point (for example, 632°C for 5182 aluminum used in beverage can ends), the dentrites begin to stick together. Depending on the temperature and solids percentage of the molten metal, crystals form different particles, such as particles of FeAl ₆ , Mg ₂ Si, FeAl ₃ , Al ₈ Mg ₅ and gaseous H ₂ in certain alloys of aluminum (e.g. intermetallic compounds). or hydrogen bubbles) or may capture them.

Additionally, when the solidifying aluminum first begins to cool, it cannot support as many alloying elements in its alpha phase, so the molten metal surrounding the solidification interface may have a proportionally higher alloying element concentration. Therefore, different compositions and particles can be formed at or near the solidification interface. Additionally, there may be stagnation regions within the sump, which may lead to preferential accumulation of these particles.

The heterogeneous distribution of alloying elements on the length scale of the crystal is known as microsegregation. In contrast, macrosegregation is chemical heterogeneity on length scales larger than a particle (or multiple particles), such as up to the length scale of a meter.

Certain aluminum alloys, such as the 7xxx series alloys, can be particularly difficult to cast. 7xxx series alloys typically contain numerous alloying elements such as combinations of one or more of zinc, magnesium, copper, chromium, zirconium and other alloying elements. When and immediately after casting 7xxx series alloys, large internal stresses (e.g., compressive and sometimes tensile) can build up, making the cast article susceptible to cracking. Certain alloying elements used in these types of alloys, such as zinc, contract and expand at much different rates than aluminum. In particular, zinc contracts and expands much more than aluminum. Therefore, the same volume of zinc and aluminum at a similar temperature (e.g., 600°C) may have different volumes of zinc and aluminum when cooled (e.g., in the final stage of solidification). These varying rates of expansion and contraction between the alloy elements and the aluminum can cause large internal forces and therefore stresses within articles cast from 7xxx series alloys.

Additionally, 7xxx series alloys are very susceptible to porosity problems that occur when dissolved hydrogen is rejected from the molten alloy, solidifying into microbubbles of gas. Voids due to gas bubbles are often crack initiation sites and can cause significant cracking. Additionally, 7xxx series alloys can be very susceptible to shrinkage porosity due, at least in part, to differences in shrinkage rates as the molten metal solidifies.

In traditional production environments, large internal stresses during solidification can cause hot or cold cracking in cast articles, making the articles unsuitable for further production. For 7xxx series alloys, overall ingot loss increases in conventional production environments compared to other more easily cast products such as 6xxx series alloys.

Additionally, 7xxx series alloy cast articles may rely on a homogenization step continued after casting to achieve the desired internal structure with desired precipitates while reducing post-cast stresses. Homogenization can be used to reduce microsegregation after casting. In some cases, 7xxx series alloy cast articles can be hot rolled to smaller gauges, solutionized, and then aged. In some cases, prolonged aging and additional processing (e.g., solutionizing or recrystallization) can be used to obtain a more desirable microstructure, but these techniques require significant equipment and a significant expenditure of time, resources, and energy.

The terms examples and similar terms are intended to refer broadly to all subject matter of this disclosure and the following claims. Statements containing these terms should not be construed as limiting the subject matter described herein or limiting the meaning or scope of the claims below. Embodiments of the disclosure covered herein are defined by the claims below and not by this summary. This summary is a high-level overview of various aspects of the disclosure and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used separately to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the entire specification of this disclosure, any or all drawings, and each claim, as appropriate.

Embodiments of the present disclosure include a casting method comprising: feeding molten metal into a mold and forming an embryo ingot comprising an outer solid shell and an inner molten core; advancing the embryo ingot in an advance direction away from the casting mold while supplying additional molten metal to the casting mold; directing a supply of liquid coolant to the outer surface of the outer solid shell to extract heat from the embryo ingot between the casting mold and the transient location; and reheating the embryo ingot at the transient position such that at least a portion of the outer solid shell of the embryo ingot at the transient position reaches a temperature (e.g., a reheat temperature) suitable for precipitating the dispersoid and lower than the homogenization temperature of the molten metal. where the transient position is in a plane perpendicular to the advancing direction and intersecting the inner molten core.

In some cases, the reheat temperature, in degrees Celsius, is between 80% and 98% of the homogenization temperature, in degrees Celsius, of the molten metal. In some cases, the temperature in degrees Celsius is between 85% and 90% of the homogenization temperature of the molten metal in degrees Celsius. Optionally, the temperature in degrees Celsius is 80% to 95%, 80% to 90%, 80% to 85%, 80%, 81%, 82%, 83%, 84%, 85%, 86% of the homogenization temperature in degrees Celsius of the molten metal. %, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 98%. In some cases, the temperature is between 400°C and 460°C. In some cases, the temperature is between 410°C and 420°C. Optionally, the temperature is 400°C to 410°C, 400°C to 420°C, 400°C to 430°C, 400°C to 440°C, 400°C to 450°C, 400°C to 460°C. °C, 410°C to 420°C, 410°C to 430°C, 410°C to 440°C, 410°C to 450°C, 410°C to 460°C, 420°C to 430°C , 420°C to 440°C, 420°C to 450°C, 420°C to 460°C, 430°C to 440°C, 430°C to 450°C, 430°C to 460°C, 440 °C to 450°C, 440°C to 460°C, or 450°C to 460°C. In some cases, the method is performed for at least 3 hours, such as 3 hours to 4 hours, 3 hours to 5 hours, 3 hours to 6 hours, 3 hours to 7 hours, 3 hours to 8 hours, 3 hours to 9 hours, 3 hours to 10 hours, 4 hours to 5 hours, 4 hours to 6 hours, 4 hours to 7 hours, 4 hours to 8 hours, 4 hours to 9 hours, 4 hours to 10 hours, 5 hours to 6 hours, 5 hours to 7 hours, 5 hours to 8 hours, 5 hours to 9 hours, 5 hours to 10 hours, 6 hours to 7 hours, 6 hours to 8 hours, 6 hours to 9 hours, 6 hours to 10 hours, 7 hours to 8 maintaining the temperature in the portion of the outer solid shell for a period of time, 7 hours to 9 hours, 7 hours to 10 hours, 8 hours to 9 hours, 8 hours to 10 hours, 9 hours to 10 hours, or longer. . In some cases, reheating the embryo ingot includes removing liquid coolant from the outer surface of the outer solid shell. In some cases, reheating the embryo ingot further includes applying heat to the outer surface of the outer solid shell to replenish latent heat from the inner molten core. In some cases, the method includes performing temperature measurements of the embryo ingot; and dynamically adjusting the transient location based on the temperature measurement. In some cases, the method further includes inducing agitation in the inner molten core adjacent the interface between the inner molten core and the outer solid shell. In some cases, the method further includes performing a temperature measurement of the embryo ingot, and inducing agitation in the internal molten core includes dynamically adjusting the agitation intensity based on the temperature measurement. In some cases, the transitional position is chosen such that the plane intersects the embryo ingot in a cross section where the outer solid shell of the embryo ingot occupies approximately one-third of a line extending from the outer surface to the center of the embryo ingot within the plane. In some cases, the transitional position is chosen such that the plane intersects the embryo ingot in a cross section where the outer solid shell of the embryo ingot occupies no more than 50% of the line extending from the outer surface to the center of the embryo ingot within the plane. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the reheated portion includes a metal plane containing liquid at its center, and the reheat zone causes deposits to grow around the perimeter of the ingot adjacent the surface.

Embodiments of the present disclosure include a method comprising: forming an embryo ingot by feeding molten metal into a mold and extracting heat from the molten metal to form an outer solid shell; solidifying the inner molten core of the embryo ingot as the embryo ingot advances in a forward direction away from the mold, supplying additional molten metal to the mold, wherein solidifying the inner molten core occurs through the outer solid shell. comprising extracting heat from the internal molten core; and continuously forming a high-strength zone within the outer solid shell at a cross-section of the embryo ingot perpendicular to the advancing direction and intersecting the inner molten core, wherein the high-strength zone is between the outer surface of the outer solid shell and the inner molten core. The step of forming the high-strength zone includes reheating the outer solid shell in the cross section to induce dispersoid precipitation in the outer solid shell.

In some cases, reheating the outer solid shell in cross section includes reheating a portion of the outer solid shell to a temperature suitable to precipitate the dispersoid, the temperature being less than the homogenization temperature of the molten metal. In some cases, for example in degrees Celsius, the temperature is between 80% and 98% of the homogenization temperature of the molten metal, for example in degrees Celsius. In some cases, for example in degrees Celsius, the temperature is between 85% and 90% of the homogenization temperature of the molten metal, for example in degrees Celsius. In some cases, the temperature is between 300°C and 460°C, for example between 400°C and 460°C. In some cases, the temperature is between 410°C and 420°C. In some cases, temperature ranges of 400°C to 460°C and 410°C to 420°C may be particularly suitable for 7xxx series alloys. In some cases, other temperature ranges may be used, such as when using 6xxx series alloys. In some cases, the method further includes maintaining the temperature of the outer solid shell portion for at least 3 hours or for 3 to 10 hours. In some cases, extracting 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 includes applying a liquid coolant to the outer surface of the outer solid shell. and removing the liquid coolant. In some cases, reheating the outer solid shell further includes applying heat to the outer surface of the outer solid shell to replenish latent heat from the inner molten core. In some cases, the method includes performing temperature measurements of the embryo ingot; and dynamically adjusting the distance between the mold and the cross section based on the temperature measurement. In some cases, the method further includes inducing agitation in the inner molten core adjacent the interface between the inner molten core and the outer solid shell. In some cases, the method further includes performing a temperature measurement of the embryo ingot, and inducing agitation in the internal molten core includes dynamically adjusting the agitation intensity based on the temperature measurement. In some cases, the outer solid shell of the embryo ingot in cross section occupies approximately one-third of a line extending from the outer surface of the embryo ingot to its center. In some cases, the outer solid shell of the embryo ingot in cross section accounts for less than 50% of the line extending from the outer surface of the embryo ingot to the center. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the high-strength zone contains a higher concentration of dispersoid than the remainder of the outer solid shell.

Embodiments of the invention include an aluminum metal product, the product comprising: a solidified aluminum alloy lump having two ends and an outer surface, wherein the solidified aluminum alloy lump has: a core region containing the centroid; an external region comprising an external surface; and a high intensity zone disposed between the core region and the outer region, wherein the high intensity region has a higher concentration of dispersoid than each of the core region and the outer region.

In some cases, the solidified mass of aluminum alloy contains retained heat from the direct cool casting process. In some cases, the high-strength zone is located at a depth of about one-third 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 zone is located at a depth of less than half 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 solidified mass of aluminum alloy is cylindrical in shape. In some cases, the cross-section of the solidified aluminum alloy mass perpendicular to the casting direction of the solidified aluminum alloy mass is rectangular in shape. In some cases, the solidified mass of aluminum alloy is a solidified mass of series 7xxx aluminum alloy.

Embodiments of the invention include an embryo ingot comprising: a liquid molten core of aluminum alloy extending from the top surface to the solidification interface; and a solidified shell of an aluminum alloy, the solidified shell comprising an outer surface extending from the solidification interface to a bottom end in the casting direction, the solidified shell having a center of the liquid molten core and a center of the solidified shell. and a high-strength zone disposed between the outer surface and a center line extending in the casting direction through the high-strength zone, wherein the high-strength zone has a higher concentration of dispersoid than the remainder of the solidified shell.

In some cases, the high intensity zone is located approximately one-third deep in a line extending from the outer surface to the center line. In some cases, the high-intensity zone is located less than half the depth of the line extending from the outer surface to the center line. In some cases, the solidified shell is cylindrical in shape. In some cases, the cross-section of the solidified cells perpendicular to the casting direction is rectangular in shape. In some cases, the aluminum alloy is a series 7xxx aluminum alloy. In some cases, embryo ingots are prepared according to one of the previously mentioned methods.

Embodiments of the present disclosure include a method comprising: transferring molten metal from a metal source to a metal sump of an embryo ingot being cast in a mold; extracting heat from the metal sump to form an outer solid shell of solidified metal, wherein the solidification interface is located between the outer solid shell and the metal sump; advancing the embryo ingot at a casting speed in an advance direction away from the mold while delivering the molten metal and forming an outer solid shell; determining the agitation intensity using the casting speed, wherein the agitation intensity is appropriate to achieve the target solidification interface profile at the casting speed; and inducing agitation within the melt sump at the determined intensity, wherein inducing agitation within the melt sump causes the solidification interface to assume the target solidification interface profile at the casting speed.

In some cases, inducing agitation includes applying an agitation force to the molten metal in the metal sump using a non-contact magnetic stirrer. In some cases, delivering the molten metal includes delivering the molten metal at a mass flow rate through a plurality of nozzles, and inducing agitation includes delivering the molten metal at a mass flow rate through the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles. and increasing the flow rate of molten metal through at least one. In some cases, the method includes modifying the casting speed; determining an updated agitation intensity using the updated casting speed, wherein the updated agitation intensity is suitable to achieve the target solidification profile at the updated casting speed; and inducing agitation within the melt sump at the updated intensity, wherein inducing agitation within the melt sump at the updated intensity causes the solidification interface to assume the target solidification interface profile at the updated casting rate. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the method further includes measuring the temperature of the embryo ingot, wherein determining the agitation intensity using the casting speed includes using the measured temperature. In some cases, the target solidification interface profile is predetermined to minimize the risk of cracking. In some cases, the method further includes continuously forming high-strength zones within the outer solid shell at a cross-section of the embryo ingot perpendicular to the advancing direction and intersecting the inner molten core, wherein the high-strength zones are formed on the outer surface and interior of the outer solid shell. Located between the molten cores, where forming the high strength zone includes reheating the outer solid shell in the cross section to induce dispersoid precipitation in the outer solid shell. In some cases, inducing agitation within the molten sump includes controlling delivery of the molten metal into the metal sump such that the jet of molten metal erodes a depression from the bottom of the metal sump to the solidification interface, the depression being It has a diameter that matches the diameter of the bottom of the metal sump.

Embodiments of the present disclosure include a method comprising: transferring molten metal from a metal source to a metal sump of an embryo ingot being cast in a mold; extracting heat from the metal sump to form an outer solid shell of solidified metal, wherein the solidification interface is located between the outer solid shell and the metal sump; advancing the embryo ingot at a casting speed in an advance direction away from the mold while delivering the molten metal and forming an outer solid shell; and controlling the delivery of molten metal into the metal sump to produce a jet of molten metal sufficient to erode at least a portion of the solidification interface at the bottom of the metal sump.

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

Embodiments of the present invention include an embryo ingot, the embryo ingot comprising: a solidified shell of aluminum alloy extending from the solidification interface to the bottom end in the casting direction; and a liquid molten core of aluminum alloy extending from the top surface to the solidification interface, the liquid molten core comprising a jet of aluminum alloy that impinges on the solidification interface at the bottom of the liquid molten core and forms a depression in the solidification interface.

In some cases, the liquid melt core contains particles resuspended at the solidification interface. In some cases, the liquid molten core contains hydrogen resuspended at the solidification interface. In some cases, the solidified shell includes a high-strength zone disposed between the outer surface of the solidified shell and the center of the liquid molten core and a centerline extending in the casting direction through the center of the solidified shell, wherein the high-strength zone is a portion of the solidified shell. It has a higher concentration of dispersoids than the rest of the shell. In some cases, the aluminum alloy is series 7xxx aluminum alloy.

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

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

This specification refers to the following accompanying drawings, wherein the use of like reference numerals in the different drawings is intended to illustrate identical or similar elements.
1 is a partial cutaway view of a metal casting system for in-situ dispersoid precipitation according to certain aspects of the disclosure.
2 is a partial cutaway view of a metal casting system for in situ dispersoid precipitation with sump depth control in accordance with certain aspects of the present disclosure.
3 is a partial cutaway view of a metal casting system for controlled flow vigorous agitation in accordance with certain aspects of the present disclosure.
4 is a partial cutaway view of a metal casting system for controlled flow vigorous agitation using multiple feed tubes in accordance with certain aspects of the present disclosure.
FIG. 5 is a partial cutaway view of a metal casting system for vigorous agitation with a magnetic stirrer in accordance with certain aspects of the present disclosure.
Figure 6 is an enlarged schematic view of the bottom of a melt sump without strong agitation.
FIG. 7 is an enlarged schematic diagram of the bottom of a melt sump undergoing intense agitation according to certain aspects of the present disclosure.
8 is a flow diagram illustrating a process for in situ dispersoid precipitation according to certain aspects of the present disclosure.
9 is a flow diagram illustrating a process for creating a high-strength zone of precipitated dispersoid in a direct cool cast ingot according to certain aspects of the present disclosure.
10 is a schematic cross-sectional elevation view of an ingot illustrating high-strength zones according to certain aspects of the disclosure.
11 is a schematic cross-sectional plan view of an ingot illustrating high-strength zones according to certain aspects of the present disclosure.
FIG. 12 is a flow diagram illustrating a process for making strongly agitated direct cool casting ingots in accordance with certain aspects of the present disclosure.
Figures 13A and 13B provide schematic diagrams of a cross section of a 7xxx series ingot showing arrangements of sampling locations.
Figure 14 provides data representing the composition of a reference ingot at various sampling locations.
Figure 15 provides data representing the composition of the first sample ingot at various sampling locations.
Figure 16 provides data representing the composition of a first comparative sample ingot at various sampling locations.
Figure 17 provides data representing the porosity of a reference ingot at various sampling locations.
Figure 18 provides data representing the porosity of a first sample ingot at various sampling locations.
Figure 19 provides data showing the mechanical properties of sheet metal produced from a second sample ingot.

Certain aspects and features of the present invention relate to reducing the cracking susceptibility of direct cool cast ingots of certain alloys, such as 7xxx series alloys. During direct cooling casting of 7xxx series alloys, process control of vigorous agitation along the solidification front and adjustment of casting speed can reduce the cracking susceptibility of the ingot. Strong agitation reduces the thickness of the solidification front (e.g., a region of about >0% to <100% solid metal, known as the “mushy zone”) and promotes agglomeration of hydrogen gas rejected at the solidification front. Promotes, removes rejected impurities at the coagulation front and improves particle size. Strong agitation can allow faster casting speeds without the risk of increasing the thickness of the solidification front. Selective reheating during casting to promote dispersoid formation can create a protective zone of dispersoid-enhanced solidified metal around the exterior of the ingot, which can further reduce the ingot's susceptibility to cracking.

In direct cooling (DC) casting, molten metal is delivered into a mold cavity with a pulsed or moving bottom. As molten metal enters the mold cavity, the bottom of the pulse is lowered, typically at a rate related to the flow rate of molten metal from the top. Molten metal that has solidified near the sides can be used to retain liquid and partially liquid metal in the melt sump. Metals can be 99.9% solid (e.g., completely solid), 100% liquid, and anywhere in between. The molten sump may take on a V-shape, U-shape, or W-shape because the thickness of the solid region increases as the molten metal cools. The interface between solid and liquid metal is sometimes called the solidification interface or solidification front. Metal articles produced in the DC casting process can be referred to as ingots. The ingot may generally have a rectangular cross-section, although other cross-sections such as circular or asymmetric may be used. As used herein, the term ingot may include any DC cast metal product, suitably including a billet.

As the metal solidifies at the solidification front as described above, certain impurities and gases may be rejected from solution and become trapped within the solidified metal. Gases such as hydrogen can form bubbles, creating voids in the solidified metal, commonly known as ingot porosity. Additionally, if impurities are rejected at the solidification interface, they may be unevenly distributed throughout the ingot.

Certain aspects of the disclosure include agitating the melt sump. This agitation can be achieved in a variety of ways, such as using a contact stirrer, non-contact stirrer, or adjusting the way the liquid metal enters the sump. Contact stirrers are often undesirable for use with aluminum alloys, not least because of the risk of impurities and oxides. Non-contact stirrers may include electromagnets and permanent magnet systems designed to induce movement in the molten metal. In some cases, it is possible to agitate the molten sump by adjusting the way the liquid metal enters the sump, such as providing the liquid metal with a powerful jet of liquid metal, such as a jet powerful enough to penetrate to the bottom of the sump. Liquid metal jets are created by increasing the pressure at which the liquid metal is delivered, adjusting the diameter of the nozzle through which the metal is delivered, or an eductor nozzle used to inject an existing melt sump into the jet created by the newly added liquid metal. This can be achieved through other techniques, such as an eductor nozzle.

Vigorous agitation in the melt sump can be used to provide agitation along the solidification front. This agitation can wash away any of the metal crystals or portions thereof, impurities, gases or liquid metals that form in the solidification front area. Washing of the forming metal crystals (e.g., free-moving particles) is helpful in achieving a finer, more uniform particle size because the forming crystals or their broken parts can be resuspended in the melt sump and act as additional nucleation sites. It can be helpful. Additionally, agitation of sufficient intensity can lower the bulk liquid temperature in the melt sump, creating an appropriate environment for the production of purified spherical particles. This refined spherical microstructure is stronger than the typical microstructure found in DC cast ingots. Ingots cast using certain aspects of the invention, such as vigorous agitation, may have higher yield strengths and may be less susceptible to cold cracking than ingots cast without vigorous agitation.

Washing away impurities from the solidification front can help achieve lower macrosegregation (e.g., lower macrosegregation degree) and thus increased homogeneity can be achieved. This lower macrosegregation achieved through agitation can be advantageous in achieving desirable protection zones within the ingot. As explained in more detail herein, the protection zone can be established by reheating the external solidified portion of the ingot being cast. Reheating can promote the formation of fine dispersoids within the ingot, which can advantageously strengthen the solidified metal and minimize the susceptibility of the ingot to cracking. These microdispersoids may be approximately 30 nm in diameter, but may be assigned other sizes. In some cases, these microdispersoids may be approximately 10 to 50 nm, 20 to 40 nm, or 25 to 35 nm in diameter.

It was unexpectedly found that strong agitation within the melt sump can reduce or minimize the porosity of the cast ingot. Strong agitation can wash rejected hydrogen away from the solidification interface and resuspend it in the remainder of the melt sump. The resuspended hydrogen may clump with other hydrogen, causing the gas to propagate to the melt sump surface and remain there or to escape from the melt sump. Accordingly, the use of vigorous agitation has been found to reduce or minimize the porosity of the cast product when the rejected hydrogen would otherwise have resulted in undesirable porosity in the cast product.

Because the presence of impurities and dissolved gases in the molten metal can be problematic during casting, traditional casting techniques typically require considerable effort to filter out impurities from the liquid metal and reduce the amount of gases (e.g., hydrogen) dissolved in the liquid metal. Depends on upstream preparation. 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.

Proper control of the solidification front can be critical to achieving 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. Increasing casting speed can thicken the solidification front, while decreasing casting speed can narrow the solidification front. If the solidification front is too thick, the molten metal may not fully penetrate through the solidification zone of the solidification front, resulting in shrinkage porosity and voids. If the solidification front is too thin, internal stresses, such as shrinkage-related stresses, can cause hot cracking, where gaps or cracks form between particles. There is therefore often a tradeoff between susceptibility to shrinkage porosity and susceptibility to hot cracking, which can define or limit the casting speed. In certain alloys that are particularly prone to hot cracking, such as the 7xxx series alloys, this compromise effectively limits the usable casting speed, setting the effective maximum to the number of ingots that can be cast per day.

According to certain aspects of the disclosure, control of the solidification front may be achieved through a combination of agitation control and casting speed control. Intensive agitation can provide numerous advantages, allowing high casting speeds while mitigating hot cracking. As described above, vigorous agitation can help narrow the coagulation front. Therefore, a DC casting process with strong agitation can operate at higher casting speeds than a DC casting process without strong agitation while maintaining the same solidification front thickness. Therefore, strong agitation allows for faster casting and thus more production capacity per day. Additionally, agitation can cause the molten sump to expand deeper into the ingot being cast (also referred to herein as the embryo ingot). In DC casting, the hydrostatic pressure of the molten metal provides the actual driving force to penetrate the liquid metal into the interstitial spaces at the solidification front. A deeper melt sump achieved with strong agitation provides a larger hydrostatic head area near the bottom of the sump. This larger hydrostatic head area facilitates filling the gaps between particles at the solidification front, allowing for a thicker solidification front with reduced or no risk of shrinkage porosity or voids. Because thicker solidification fronts are available when strong agitation is used, casting speeds can be increased significantly beyond what is available without agitation.

The increased agitation can be controlled to achieve a nominal reduction in the thickness of the solidification front (e.g., the solidification interface) on the order of a few millimeters, to a nominal thickness of between about 1 mm and 5 mm, or up to about 10 mm. In some cases the nominal reduction in thickness is approximately 20mm, 19mm, 18mm 17mm, 16mm, 15mm, 14mm, 13mm, 12mm, 11mm, 10mm, 9mm, 8mm, 7mm, 6mm, 5mm, 4mm, 3mm, 2mm or 1mm or less nominal. It can be thick. As used herein, reference to controlling agitation to achieve a nominal reduction to a particular nominal thickness may refer to controlling agitation to the extent that, given a constant casting speed, results in a reduction to a particular thickness. Therefore, increased agitation with increased casting speed may achieve little or no effective change in the solidification interface thickness, but increased agitation may be described as achieving a certain nominal reduction in the thickness of the solidification interface to the nominal thickness. You can. Additionally, the thickness of the solidification interface herein may refer to the minimum thickness, maximum thickness, and average thickness, or the thickness at the corresponding point or region within the embryo ingot. For example, a solidification interface having a thickness of 10 mm or less is a solidification interface having a maximum thickness of 10 mm or less at any point on the solidification interface; A solidification interface where the minimum thickness at any point of the solidification interface reaches a thickness of 10 mm or less; Solidification interface where the average thickness of the entire solidification interface is maintained below 10 mm; or a region at or near the bottom of the solidification interface (e.g., the region furthest from the mold), or other suitable point or region, where the average thickness of the solidification interface is maintained below 10 mm.

During DC casting, heat is extracted from the ingot by spraying a coolant (e.g., water) on the surface of the ingot as it exits the mold. The coolant can be removed using a wiper or other technique, allowing part of the ingot to be reheated. This reheating may in some cases be used for in-situ (e.g. during casting) homogenization of the ingot. In some cases, this in situ homogenization can occur when the metal reaches a reaction temperature between about 470°C and about 480°C. However, according to certain embodiments of the invention, reheating can be controlled to achieve lower temperatures more suitable for precipitation, forming dispersoids in the outer periphery of the ingot. Reheating the embryo ingot to promote sediment formation during casting may be referred to herein as in situ sedimentation.

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

The desired in situ precipitation can be achieved by reheating the embryo ingot and maintaining a constant temperature as identified above, or by cooling the ingot to or toward room temperature over a period of time. The time period may be between approximately 3 hours and approximately 5 hours, although in some cases the time may be more or less within a 10% deviation of either endpoint. The in situ precipitation process can begin while casting the ingot and end after the ingot has been cast. Ingot casting using in situ precipitation can be allowed to cool to room temperature or toward room temperature immediately after casting without quenching. In some cases, if in situ precipitation is used, a subsequent homogenization step can be performed for a reduced amount of time. For example, in situ precipitation at 410 °C for 3 h can be homogenized at 475 °C for approximately 8 h to obtain desirable, small precipitates, whereas ingot casting without in situ precipitation requires 10 h at 475 °C. Homogenization periods of 100% may be required and only undesirable large deposits may be obtained.

Reheating of the embryo ingot can occur in any suitable manner, such as by applying external heat. However, reheating of the embryo ingot for in situ homogenization generally reduces the amount of heat extraction occurring at the surface of the embryo ingot and can occur by allowing the latent heat of the ingot, particularly the latent heat of the melt sump, to reheat the outside of the ingot. To achieve the desired in situ deposition temperature, the point at which reheating begins (e.g., the position of a wiper that removes coolant) can be controlled and/or the depth of the molten core can be controlled. For example, by increasing the position of the wiper (e.g., moving the wiper closer to the mold), the solid shell can heat up much faster because the melt sump can begin to reheat earlier in a larger cross-section compared to a cross-section further away from the mold. The latent heat of the large melt sump can reheat the solid shell. In addition to or instead of controlling the point at which reheating begins, the depth of the melt sump itself can be controlled to precisely control reheating of the solid shell. For example, by inducing agitation, such as directing a jet of molten metal to the bottom of the solidification interface, the metal sump can be extended further in the mold than if no additional agitation was induced. The farther the depth of the molten core is from the mold, the longer the solid shell will retain the latent heat of the molten core after the coolant is removed.

Additionally, controlling the location at which reheating begins and/or the depth of the molten core can control the surface depth of the dispersoid formed during in situ dispersoid precipitation. As used herein, the term surface depth refers to the depth of the ingot from the outer surface (e.g., rolling face and sides) toward the center of the ingot (e.g., the longitudinal centerline extending in the casting direction through the center of the ingot). It can refer to the depth within. In some cases, reheating of the solid shell and/or controlling the depth of the molten core results in the highest strength in a region (e.g., high-strength zone) that falls approximately one-third (33%) from the surface of the ingot toward the longitudinal centerline. It can provide dispersoids of high concentration. In some cases, this area is approximately one way from the surface of the ingot toward the longitudinal centerline. It may be at (50%). In some cases, this area is between about 5%, 10%, 15%, 20%, or 25% and about 25%, 30%, 35%, 40%, 45%, or 50% from the ingot surface toward the longitudinal centerline. may be in In some cases, this area may extend from the surface of the ingot to the previously mentioned depth.

In some cases, the highest concentration of dispersoid and/or the high intensity zone may be an area of the ingot that has a greater dispersoid concentration than the average dispersoid concentration of the entire ingot. In some cases, the highest concentration dispersoid and/or high strength zone is an ingot having a dispersoid concentration of at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4 standard deviations relative to the average dispersoid concentration of the entire ingot. It can be defined as the area of . High-strength zones (e.g., areas of relatively high concentration of precipitated dispersoids) can serve as protection against cracking when the ingot is cooled to room temperature.

There is often no relationship between the initial, as-cast microstructure and the final machined microstructure due to recrystallization of the microstructure during hot working and subsequent processing. However, in certain alloys, such as certain 7xxx series alloys, recrystallization can be suppressed using dispersoids, such as adding elements such as Cr or Zr. By inducing the formation of such dispersoids in the microstructure of the casting, the dispersoids can inhibit recrystallization or at least a substantial change in average grain size during recrystallization. Because recrystallization is suppressed, the final machined microstructure can be related to, and more specifically similar to, the initial, as-cast microstructure.

This ability to relate the microstructure of a casting to the final machined microstructure can make techniques for improving the microstructure of a casting particularly useful. The addition of particle refiners can be used to reduce particle size to some extent, but after the saturation limit is reached the effectiveness of additional particle refiners is limited. However, using aspects of the present disclosure, such as vigorous agitation, even more desirable particle refinement can be achieved. The microstructure of this fine casting carries over to the microstructure of the final product and can have many advantages, such as corrosion resistance and strength advantages.

In some cases, certain embodiments of the invention may be particularly suitable for 7xxx series alloys, but may also be advantageous for use with 5xxx or other series alloys. Certain aspects of the present disclosure may help resist “orange peel” defects, such as in the 7xxx series. These "orange peel" defects are surface defects that appear after deformation of metal products and are characterized by surface roughness that appears as an orange-colored outer surface. These defects are often a result of large particle size. By reducing the final grain size, this defect can become less pronounced after deformation.

As used herein, the terms “invention,” “the invention,” “this invention,” and “the present invention” are intended to broadly refer to all subject matter of this patent application and the following claims. Descriptions containing these terms should be understood not as limiting the subject matter described herein or limiting the meaning or scope of the patent claims below.

In this description, reference is made to alloys identified by their AA numbers and other related designations such as "series" or "7xxx". For an understanding of the numbering systems most commonly used to name and identify aluminum and its alloys, see “International Alloy Nomenclature and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys” or “Aluminum Alloys in Cast and Ingot Form.” See “Records of Registration of Alloy Names and Chemical Composition Limits of the Aluminum Society for”, both published by the Aluminum Society.

As used herein, “room temperature” means from about 15°C to about 30°C, for example about 15°C, about 16°C, about 17°C, about 18°C, about 19°C, about 20°C. °C, about 21°C, about 22°C, about 23°C, about 24°C, about 25°C, about 26°C, about 27°C, about 28°C, about 29°C, or about May contain temperatures up to 30°C. As used herein, the meaning of “ambient conditions” may include a temperature of about room temperature, a relative humidity of about 20% to about 100%, and an atmospheric pressure of about 975 millibars (mbar) to about 1050 millibars. 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 10 40 mbar, approximately 1045 mbar , about 1050 mbar, or any value in between.

All ranges disclosed herein should be understood to include any and all subranges subsumed therein. For example, a stated range of “1 to 10” should be considered to include all subranges between the minimum value of 1 and the maximum value of 10; That is, it includes all subranges that have a minimum value greater than or equal to 1, for example from 1 to 6.1, and a maximum value of 10 or less, for example, ending with 5.5 to 10. Unless otherwise specified, the expression "up to" when referring to compositional amounts of an element means that the element is optional and includes 0% composition of that particular element. Unless otherwise specified, all composition percentages are expressed as weight percentages (wt.%).

As used herein, the singular terms “a”, “an” and “the” include singular and plural references unless the context clearly dictates otherwise.

In the following examples, aluminum alloy products and their components are described in terms of elemental composition in weight percent (wt.%). In each alloy, the remainder is a maximum of 0.15% wt. of the sum of all impurities. It is aluminum with %.

Additional elements, such as particle refiners and deoxidizers, or other additives, may be present in the invention and may on their own add other properties without departing from or significantly altering the properties of the alloys described herein or the alloys described herein. You can. However, it should be understood that the scope of the disclosure should not/cannot be circumvented through the mere addition of ancillary elements or elements in amounts that will not alter the desired characteristics of the disclosure.

There may be a small amount of unavoidable impurities in the alloy, such as aluminum's inherent properties or leaching due to contact with processing equipment. Some impurities commonly found in aluminum include iron and silicon. As explained, the alloy contains approximately 0.25 wt of any element, excluding alloying elements, minor elements and unavoidable impurities. It may contain less than %.

As used herein, the term “slab” refers to an alloy thickness greater than 15 mm. For example, slab may mean an aluminum product with a thickness greater than 15 mm, greater than 20 mm, greater than 25 mm, greater than 30 mm, greater than 35 mm, greater than 40 mm, greater than 45 mm, greater than 50 mm, or greater than 100 mm. You can.

As used herein, plates typically have a thickness ranging from 5 mm to 50 mm. For example, plate may refer to an aluminum product having a thickness of approximately 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm.

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

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

Cast ingots may be processed by any means known to those skilled in the art. Sheets may be manufactured using optional processing steps. These processing steps include, but are not limited to, homogenization, hot rolling, cold rolling, solution heat treatment, and any preliminary aging steps known to those skilled in the art.

In the homogenization step, the cast product described herein is heated to a temperature ranging from about 400°C to about 500°C. For example, the product may be rated at approximately 400°C, approximately 410°C, approximately 420°C, approximately 430°C, approximately 440°C, approximately 450°C, approximately 460°C, approximately 470°C, approximately 480°C. , can be heated to a temperature of about 490°C, or about 500°C. The product is then steeped (i.e. held at the indicated temperature) for a period of time. In some examples, the total time of the homogenization step, including the heating and soaking steps, can be up to 24 hours. For example, the product can be heated and soaked up to 500°C for up to 18 hours for a homogenization step. Optionally, the product may be heated and soaked below 490°C for a total of 18 hours or more for the homogenization step. In some cases, the homogenization step involves multiple processes. In some non-limiting examples, the homogenization step includes heating the product to a first temperature for a first period of time and then to a second temperature for a second period of time. For example, the product may be heated to about 465°C for about 3.5 hours and then to about 480°C for about 6 hours.

A hot rolling step may be performed after the homogenization step. Before hot rolling begins, the homogenized product can be cooled to a temperature between 300°C and 450°C. For example, the homogenized product may be cooled to a temperature of 325°C to 425°C or 350°C to 400°C. The products are then hot rolled at a temperature between 300°C and 450°C to cut into sizes between 3 mm and 200 mm, e.g. , 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 90mm, 200mm, or It can form hot rolled plate, hot rolled sheet or hot rolled sheet having a gauge of any value in between.

The plate, sheet or sheet can then be cold rolled into sheets using conventional cold rolling mills and techniques. The cold rolled sheet may have a gauge of about 0.5 to 10 mm, for example about 0.7 to 6.5 mm. Optionally cold rolled sheets are available in 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, 4.5mm, 5.0mm, 5.5mm, 6.0mm, 6.5mm, 7.0mm, 7.5mm , can have gauges of 8.0mm, 8.5mm, 9.0mm, 9.5mm or 10.0mm. Perform cold rolling to reduce gauge by up to 85% (e.g. up to 10%, up to 20%, up to 30%, up to 40%, up to 50%, up to 60%, up to 70%, up to 80% or up to 85%) % reduction) can be obtained. Optionally, an interannealing step may be performed during the cold rolling step. The interannealing step may be performed at 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). °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 interannealing step involves multiple processes. In some non-limiting examples, the interannealing step includes heating the plate, sheet, or sheet to a first temperature for a first period of time and then to a second temperature for a second period of time. For example, a plate, sheet, or sheet may be heated to about 410°C for about 1 hour and then to about 330°C for about 2 hours.

The plate, sheet or sheet may then undergo a solution heat treatment step. The solution heat treatment step can be any conventional treatment for the sheet that results in solutionization of the soluble particles. The plate, sheet or sheet may be heated to a peak metal temperature (PMT) of up to 590°C (e.g., 400°C to 590°C) and immersed at that temperature for a period of time. For example, plates, sheets or sheets may be soaked for a soaking time of up to 30 minutes (e.g., 0 seconds, 60 seconds, 75 seconds, 90 seconds, 5 minutes, 10 minutes, 20 minutes, 25 minutes, 30 minutes). Can be immersed at 480°C. After heating and immersion, the plate, sheet or sheet is rapidly cooled to a temperature between 500 and 200°C at a rate of more than 100°C/s. In one example, the plate, sheet or sheet has a quench rate of greater than 200°C/s at a temperature between 450°C and 200°C. Optionally in other cases the cooling rate may be faster.

After quenching, the plate, shape or sheet may optionally undergo a pre-aging treatment by reheating the plate, shape or sheet prior to coiling. The pre-aging treatment may be performed at a temperature of about 70°C to about 125°C for a period of up to 6 hours. For example, 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. °C, about 115°C, about 120°C, or about 125°C. Optionally, the pre-aging treatment can be performed 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 performed by passing the plate, sheet or sheet through a heating device, such as a device that emits radiant heat, convective heat, inductive heat, infrared heat, etc.

The cast products described herein may also be used to make plate-shaped products or other suitable products. For example, a plate comprising a product as described herein may be produced by subjecting the ingot in a homogenization step followed by a hot rolling step. In the hot rolling step, the cast product may be hot rolled to a thickness gauge of 200 mm or less (eg, from about 10 mm to about 200 mm). For example, the cast product may be a plate having a final gauge thickness 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. Can be hot rolled.

The aluminum alloy products described herein may be used in automotive applications and other transportation applications, including aircraft and rail applications. For example, the disclosed aluminum alloy products include bumpers, side beams, roof beams, cross beams, pillar reinforcements (e.g., A pillars, B pillars and C pillars), interior panels, exterior panels, side panels, interior hoods, exterior It can be used to manufacture automotive structural parts such as hoods or trunk lid panels. The aluminum alloy products and methods described herein may also be used in aircraft or rail vehicle applications, for example, to manufacture exterior and interior panels.

The aluminum alloy products and methods described herein may also be used in electronic applications. For example, the aluminum alloy products and methods described herein can be used to manufacture housings for electronic devices, including cell phones and tablet computers. In some examples, aluminum alloy products can be used to manufacture housings for cell phones (e.g., smartphones), tablet bottom chassis, and external casings of other portable electronic devices.

These illustrative examples are provided to introduce the reader to the general subject matter discussed herein and are not intended to limit the scope of the disclosed concepts. The following sections describe various additional features and examples with reference to the drawings where like numbers represent like elements, and directional descriptions are used to describe example embodiments, but, like the example embodiments, are used to limit the disclosure. It shouldn't be. Elements included in the drawings of this specification may not be drawn to scale. For example, a drawing depicting a metal sump may include features that are exaggerated for illustrative purposes.

1 is a partial cutaway view of a metal casting system 100 for in-situ dispersoid precipitation in accordance with certain aspects of the disclosure. A metal source 102, such as a tundish, may supply molten metal down the supply tube 104 and out of the nozzle 106. An optional skimmer 108 may be used around the feed tube 104 to distribute the molten metal and reduce the formation of metal oxides on the upper surface of the melt sump 110. Bottom block 120 may be lifted by hydraulic cylinder 122 to meet the wall of mold cavity 112. As the molten metal begins to solidify within the mold, bottom block 120 may be steadily lowered at the casting rate. The embryonic ingot 116 may include solidified sides 118 while molten metal added to the casting may be used to continuously extend the embryonic ingot 116. Embryo ingot 116 may include a bottom end 136. In some cases, the walls of the mold cavity 112 define a hollow space and may contain a coolant 114, such as water. Coolant 114 may escape as a jet from the hollow space and flow down the sides 118 of the embryo ingot 116 to help solidify the embryo ingot 116. Embryo ingot 116 may include an outer solid shell 128, a transitional metal region (e.g., solidification interface 126), and a molten metal core 124.

To begin promoting dispersoid precipitation, the solidified shell 128 of the embryo ingot 116 is placed at the bottom of the mold cavity 112 (e.g., where the embryo ingot 116 exits the mold cavity 112). Reheating occurs starting from the reheater distance 130, which is defined as the distance from the solid shell 118 to the position at which reheating begins. Reheater distance 130 may be the distance between the mold and a location where reheating begins (e.g., the location of a reheating device, such as a wiper 142 used to remove coolant 114). The location where reheating begins can be referred to as the transition location.

Although various techniques may be used to reheat the solid shell 128, Figure 1 shows the removal of coolant 114 from the embryo ingot 116 using a wiper 142. Wiper 142 in FIG. 1 is shown as a solid wiper, but other wipers may also be used, such as fluid-based wipers (eg, air knives). Coolant 114 is removed from the embryo ingot 116 at the cross section where the core of the embryo ingot 116 is still molten. Accordingly, the latent heat from the molten metal core 124, particularly the region of the molten metal core 124 between the reboiler distance 130 and the molten metal distance 132 (defined below), is transferred to the solid shell 128. ) can be reheated. Accordingly, by adjusting the reheater distance 130 and/or the molten metal distance 132, as described in more detail herein, the timing and amount of reheating can be precisely controlled.

Reboiler distance 130 may be shorter than molten metal distance 132 and sump distance 134. Molten metal distance 132 may be defined as the distance from the bottom of mold cavity 112 to the bottom of molten metal core 124. Sump distance 134 may be defined as the distance from the bottom of mold cavity 112 to the bottom of solidification interface 126.

In some cases, the difference between the molten metal distance 132 and the reboiler distance 130 may be achieved, for example, by inducing a change in the shape of the molten metal core 132 (e.g., by changing the casting speed and/or stirring It can be controlled by adjusting the molten metal distance 132 or by moving the wiper 142 to adjust the reheater distance 130. These casting speed, agitation and/or wiper 142 adjustments may be controlled by a 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, such as temperature measurements taken by sensor 144. Sensor 144 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 144 in FIG. 1 is shown adjacent to solid shell 128 for measuring the surface of solid shell 128, but this need not be the case. In some cases, the sensor(s) can be placed in different locations and different ingot measurements such as sump temperature or coolant temperature can be obtained.

An optional flow controller 140 may be positioned to control the flow of molten metal through the feed tube 104. Examples of suitable flow controllers 140 include retractable pins to slow and/or stop metal flow, magnetic pumps, electric pumps, or any suitable device to increase and/or decrease metal flow through feed tube 104. Includes devices.

Although a wiper system is shown in FIG. 1 , other types of reheating techniques may be used in the reheater street 130 instead of or in addition to the wiper system. For example, direct flame impingement, rotating magnetic heaters, or other devices may be used to heat the solid shell 128 in addition to any latent heat from the molten metal core 124. In some cases, these techniques for applying heat to the solid shell 128 can be controlled, such as controlling the amount of heat provided and/or the location where the heat is provided. This control may be performed by controller 138.

2 is a partial cutaway view of a metal casting system 200 for in situ dispersoid precipitation with sump depth control in accordance with certain aspects of the disclosure. Metal casting system 200 may be similar to metal casting system 100 of FIG. 1 . Metal source 202 may supply molten metal down supply tube 204 and out of nozzle 206 through flow controller 240 . Flow controller 240 may provide increased flow from metal source 202 to molten metal core 224. This increased flow of molten metal through feed tube 204 may result in increased flow 246 within molten metal core 224. Increased flow 246 may be or correspond to an increased volumetric flow rate, an increased linear flow rate, or both an increased volumetric flow rate and an increased linear flow rate compared to the flow configuration shown in FIG. 1 .

This increased flow 246 can provide strong agitation and act as a jet that can erode part of the solidification interface 226. The jet may create a depression within the solid shell 228 and solidification interface 226 at the bottom of the metal sump (e.g., the lowest portion of the liquid metal core 224). By doing so, the molten metal distance 232 and sump distance 234 may be increased.

Accordingly, if the wiper 242 is located at the same reboiler distance 230 from the mold 212 as the wiper 142 in FIG. 1, the solid shell 228 of the embryo ingot 216 is as shown in FIG. More heating can be experienced from the molten metal core 224 because the difference between the molten metal distance 232 and the reheater distance 230 is greater.

The intensity of agitation and/or amount of flow 246 may be controlled by controller 238 coupled to any suitable actuator (e.g., 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, such as temperature measurements taken by sensor 244. Sensor 244 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 244 in FIG. 2 is shown adjacent to solid shell 228 for measuring the surface of solid shell 228, but this need not be the case. In some cases, the sensor(s) can be placed in different locations and different ingot measurements such as sump temperature or coolant temperature can be obtained.

3 is a partial cutaway view of a metal casting system 300 for controlled flow vigorous agitation in accordance with certain aspects of the present disclosure. Various aspects of metal casting system 300 may be similar to aspects of metal casting system 100 of FIG. 1 where appropriate. A metal source 302 may supply molten metal down a supply tube 304 and out of a nozzle 306 through a flow controller 340 . Flow controller 340 may provide increased flow from metal source 302 to molten metal core 324. This increased flow of molten metal through feed tube 304 may result in increased flow 346 within molten metal core 324.

This increased flow 346 can provide strong agitation and act as a jet that can erode part of the solidification interface 326. The jet may create a depression within the solid shell 328 and solidification interface 326 at the bottom of the metal sump (e.g., the lowest portion of the liquid metal core 324). The intensity of flow 346 and the resulting jet can be controlled to achieve a depression of the desired shape. If the flow is too little, no depressions may be present or small diameter depressions may be created. If the flow is too high, the diameter of the depression may be too large. However, the preferred depression would have a diameter that matches the diameter of the sump bottom, resulting in a sump with a smooth, graduated shape. The shape of the sump with depressions can facilitate the flow of molten metal over the sides of the solidification interface 326, which facilitates the removal of rejected impurities and hydrogen from the solidification interface 326 as well as reproducing particles. Finer particles can be achieved by resuspending and improving particle structure.

The intensity of agitation and/or amount of flow 346 may be controlled by controller 338 coupled to any suitable actuator (e.g., 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, such as temperature measurements taken 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 take action to achieve or maintain the desired solidification interface profile. Sensor 344 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 344 in FIG. 3 is shown adjacent to solid shell 328 for measuring the surface of solid shell 328, but this need not be the case. In some cases, it is possible to place sensors in different locations and obtain different ingot measurements, such as sump temperature or coolant temperature.

4 is a partial cutaway view of a metal casting system 400 for controlled flow vigorous agitation with multiple feed tubes in accordance with certain aspects of the present disclosure. Metal casting system 400 may be similar to metal casting system 300 of FIG. 3 . Metal source 402 may feed molten metal down multiple feed tubes 404, 450, 454. As shown in Figure 4, three feed tubes are used, but any number of feed tubes can be used. Each supply tube 404, 450, 454 may be associated with a flow controller 440, 456, 452, respectively. Flow controllers 440, 456, 452 are shown as pin valves, but any suitable flow controller may be used. When multiple feed tubes 404, 450, 454 are used to supply molten metal to the molten metal core 424, increased flow 446 is directed to one or more feed tubes (e.g., feed tubes 450 , 454), and increasing flow through one or more remaining feed tubes (e.g., feed tube 404). As shown in FIG. 4 , flow controllers 452 and 456 are closed and flow controller 440 is open to allow more fluid to flow through central feed tube 404 and increase the amount of fluid within molten metal core 424. Create flow 446.

This increased flow 446 can provide strong agitation and act as a jet that can erode part of the solidification interface 426. The jet may create a depression within the solid shell 428 and solidification interface 426 at the bottom of the metal sump (e.g., the lowest portion of the liquid metal core 424). The intensity of flow 446, and therefore the resulting jet, can be controlled (e.g., by actuating any of the flow controllers 452, 440, 456) to achieve a depression of the desired shape. If the flow is too little, no depressions may be present or small diameter depressions may be created. If there is too much flow, the diameter of the depression may be too large. However, the preferred depression would have a diameter that matches the diameter of the sump bottom, resulting in a sump with a smooth, graduated shape. The shape of the sump with depressions can facilitate the flow of molten metal over the sides of the solidification interface 426, which facilitates the removal of rejected impurities and hydrogen from the solidification interface 426 as well as reproducing particles. By turbidizing and improving particle structure, finer particles can be achieved.

The intensity of agitation and/or amount of flow 446 may be controlled by a controller 438 coupled to any suitable actuator (e.g., 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, such as temperature measurements taken 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 take action to achieve or maintain the desired solidification interface profile. Sensor 444 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 444 in FIG. 4 is shown adjacent to solid shell 428 to measure the surface of solid shell 428, but this need not be the case. In some cases, it is possible to place sensors in different locations and obtain different ingot measurements, such as sump temperature or coolant temperature.

5 is a partial cutaway view of a metal casting system 500 for vigorous agitation with a magnetic stirrer in accordance with certain aspects of the present disclosure. Metal casting system 500 may be similar to metal casting system 300 of FIG. 3 . Metal source 502 may supply molten metal down feed tube 504 and out of nozzle 506. In some cases flow controllers may be used, but none are shown in Figure 5.

Non-contact magnetic stirrers 560 are positioned adjacent the molten metal core 524 to create surface flows 566, 568. Non-contact magnetic stirrer 560 can be electromagnetic or permanent magnet. In an example, permanent magnet non-contact magnetic stirrers 560 may be positioned on opposite sides of feed tube 504 and oriented in appropriate directions 562, 564 to create surface flows 566, 568 toward feed tube 504. can be rotated. This surface flow 556, 568 can interact with the molten metal flowing out of the feed tube 504 and provide increased flow 546 within the molten metal core 524.

This increased flow 546 can provide strong agitation and act as a jet that can erode part of the solidification interface 526. The jet may create a depression within the solid shell 528 and solidification interface 526 at the bottom of the metal sump (e.g., the lowest portion of the liquid metal core 524). The intensity of flow 546 and the resulting jet can be controlled to achieve a depression of the desired shape. Too little flow may result in no depressions or small diameter depressions. If the flow is too high, the diameter of the depression may be too large. However, the preferred depression would have a diameter that matches the diameter of the sump bottom, resulting in a sump with a smooth, graduated shape. The shape of the sump with the depression can facilitate the flow of molten metal over the sides of the solidification interface 526, which not only facilitates the removal of rejected impurities and hydrogen from the solidification interface 526, but also facilitates the removal of particles. Finer particles can be achieved by resuspending and improving particle structure.

The intensity of agitation and/or amount of flow 546 may be controlled by a controller 538 coupled to any suitable actuator (e.g., non-contact stirrer 560). In some cases, 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, such as temperature measurements taken 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 take action to achieve or maintain the desired solidification interface profile. Sensor 544 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 544 in FIG. 5 is shown adjacent to solid shell 528 for measuring the surface of solid shell 528, but this need not be the case. In some cases, it is possible to place sensors in different locations and obtain different ingot measurements, such as sump temperature or coolant temperature.

Figure 6 is an enlarged schematic view of the bottom of the melt sump 600 without vigorous agitation. The bottom of the molten metal core 624 and solidification interface 626, as well as adjacent portions of the solid shell 628, may take on an uneven, built-up shape due to settling of suspended particles as well as other factors. As a result, the molten metal may remain somewhat stagnant near this area. This bottom region of the melt sump may have a width 670 that can be roughly defined between the regions where the sloping walls of the solidification interface 626 reach their maximum depth.

FIG. 7 is an enlarged schematic diagram of the bottom of a melt sump 700 undergoing intense agitation according to certain aspects of the present disclosure. The bottom of the molten metal core 724 and solidification interface 726, as well as the adjacent portion of the solid shell 728, adopt a uniform U-shaped or parabolic profile due to the increased flow 746 of molten metal. Flow 746 of molten metal may erode depression 774 into solidification interface 726 and solid shell 728. This depression 774 extends from the bottom of the sump prior to agitation (e.g., as shown in FIG. 6) during agitation (e.g., as shown in FIG. 7) to the bottom of the depression 774. It can have depth (772). The depression 774 may have a diameter 770 (e.g., the largest diameter) that is approximately the same as the diameter before sump agitation (e.g., diameter 670 in FIG. 6).

The flow 746 of molten metal is at least at or adjacent to the bottom of the solidification interface 726 to erode the solidification interface 726 to a thickness of several millimeters, for example between approximately 1 mm and 5 mm or up to about 10 mm. It can be controlled. In some cases, flow 746 extends solidification interface 726 at least at or adjacent to the bottom of solidification interface 726 by approximately 20 mm, 19 mm, 18 mm, 17 mm, 16 mm, 15 mm, 14 mm, 13 mm, 12 mm, 11 mm, 10 mm, 9 mm. , can be controlled to erode to a thickness of 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm or less than 1 mm. 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 embryo ingot being formed in the mold is advanced in the casting direction. At block 806, heat is continuously extracted from the shell between the bottom of the mold where the embryo ingot exits the mold and the reheat location. At block 808, the embryo ingot is reheated. Reheating may be initiated from the reheat location. In some cases, reheating may include removing the coolant supplied to the surface of the embryo ingot during block 806. At block 810, the embryo ingot may be maintained at the reheat temperature for a period of time, such as about 3 hours. In some cases, instead of maintaining the ingot at the reheat temperature, the ingot is allowed to gradually cool in block 812. The ingot may be cooled gradually to room temperature, such as over a period of at least approximately 3 hours.

In some cases, agitation may be selectively induced at block 816. Agitation can be induced to influence the reheating performed in block 808 by lowering the depth of the melt sump as well as improving various properties of the ingot being cast.

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

9 is a flow diagram illustrating a process 900 for creating a high-strength zone of precipitated dispersoid in a direct cool cast ingot according to certain aspects of the present disclosure. At block 902, an embryo ingot may be formed or may begin to form. At block 904, at least a portion of the inner molten core of the embryo ingot may solidify to form a solid shell of the embryo ingot. At block 906, high-strength zones of precipitated dispersoid may be continuously formed.

Continuously forming a high-strength zone of precipitated dispersoid in block 906 may include reheating the outer solid shell at a reheater distance in block 908. In some cases, the temperature of the ingot may be measured at block 910. This measurement can be used to adjust the reboiler distance in block 912 and/or the molten metal distance in block 916. Adjusting the reheater distance at block 912 may include moving the reheater (e.g., a wiper) at block 914. Adjusting the molten metal distance in block 916 may include inducing agitation in block 918.

FIG. 10 is a schematic cross-sectional elevation view of an ingot 1016 illustrating a high-strength zone 1074 in accordance with certain aspects of the disclosure. High-strength zone 1074 is shown at or near the surface of ingot 1016 extending to a surface depth less than half the distance from the surface of ingot 1016 to the longitudinal centerline 1016 of ingot 1016.

11 is a schematic cross-sectional plan view of an ingot 1116 illustrating a high-strength zone 1174 according to certain aspects of the present disclosure. High-strength zone 1174 is located at or near the surface (e.g., rolling surface and/or side surface) of ingot 1016 from the surface of ingot 1116 to the associated centerline, e.g., at the rolling surface of ingot 1116. It is shown extending from the surface to the lateral centerline 1180 and less than half the surface depth from the side of the ingot 1116 to the rolling face centerline 1178.

FIG. 12 is a flow diagram illustrating a process 1200 for making strongly agitated direct cool casting ingots in accordance with 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 as heat is extracted from the molten metal. At block 1206, the ingot may be advanced out of the mold at the casting speed. At block 1208, the intensity of agitation may be determined using the address speed. Agitation intensity can 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 a flow controller and/or a non-contact agitator, although other techniques may be used. At block 1212, the casting speed may be modified. When modifying the casting speed, the agitation intensity may be determined again at block 1208 based on the updated casting speed from block 1212. Agitation can then be induced at the newly determined intensity. In optional block 1214, the temperature of the embryo ingot may be monitored. When monitoring the ingot temperature, the agitation intensity may again be determined at block 1208 based at least in part on the temperature measured at block 1214. Agitation can then be induced at the newly determined intensity.

In optional block 1216, high intensity zones of sediment dispersoids may be continuously formed as disclosed herein.

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

Example 1 - Analysis of an ingot

Several different aluminum alloy ingots were obtained, including reference ingots and sample ingots made according to the technique described herein with induced agitation during casting. The ingots were all 7xxx series aluminum alloy.

The standard ingot is 0.08wt.% Si, 0.15wt.% Fe, 1.58wt.% Cu, 0.02wt.% Mn, 2.52wt.% Mg, 0.193wt.% Cr, 0.01wt.% Ni, 5.61wt.% Zn. , 0.012wt.% V, 0.019wt.% Ti, 0.001wt.% Ca, 0.010wt.% Zr, and the remainder was aluminum. The reference ingot was cast using conventional DC casting and then used a conventional homogenization process. One-inch thick pieces were obtained at 50-inch, 100-inch, and 150-inch casting lengths 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. It had a composition of % Zn, 0.019 wt.% V, 0.03 wt.% Ti, 0.005 wt.% Ca, 0.010 wt.% Zr, and the remainder was aluminum. The first sample ingot was cast using non-contact agitation as described herein and then homogenized at 480°C for 4 hours. A first comparative sample ingot was cast using non-contact agitation as described herein without homogenization so that as-cast properties could be evaluated. One-inch thick pieces were obtained at 50-inch, 100-inch, and 150-inch casting lengths 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.%. It had a composition of % Ti, 0.02 wt.% Zr, 0.02 wt.% Sr, and the remainder aluminum. A second sample ingot was cast using non-contact agitation as described herein, followed by a multi-step homogenization: initially the second sample ingot was heated to 465°C at a rate of approximately 50°C/hr and then heated to 465°C. kept at C for 4 hours; The second sample ingot was then heated from 465°C to 480°C at 5°C/hr and held at 480°C for 16 hours. The second sample ingot was subjected to a conventional rolling process to obtain a sheet metal sample.

Cross-sectional views of 1 inch thick slices of the reference ingot 1300 and the first sample ingot 1350 are shown in FIGS. 13A and 13B, respectively. A slice of reference ingot 1300 has a width 1301 of approximately 1690 mm and a thickness 1302 of approximately 602 mm; A slice of the first sample ingot 1350 has a width 1351 of approximately 1750 mm and a thickness 1352 of approximately 519 mm. Analysis of the reference ingot 1300 and the first sample ingot 1350 comprised a grid of sampling locations spanning nine columns (columns 1 through 9) and four rows (rows A through D). It was carried out using The fifth row E of the reference ingot 1300 was not fully analyzed because this row was partially cut off at the edge of the reference ingot 1300. The sampling locations of the reference ingot 1300 were approximately 45 mm in diameter, with location 9A corresponding to the center of the reference ingot 1300 and the first sample ingot 1350. In the reference ingot 1300, the sampling positions of column 1 were located approximately 30 mm away from the edge, and the sampling positions of column 1 were located approximately 58 mm away from the edge of the first sample ingot 1350. The columns of the reference ingot 1300 are spaced apart from each other by approximately 62 mm and the rows of the standard ingot 1300 are spaced apart from each other by approximately 42 mm. The columns of the first sample ingot 1350 are spaced apart from each other by approximately 61 mm and the rows of the first sample ingot 1350 are spaced apart from each other by approximately 28 mm.

Macrosegregation of Fe, Zn, Cr, Mg, and Cu across sampling locations for the reference ingot 1300 and the first sample ingot 1350 was analyzed using X-ray fluorescence (XRF) spectroscopy. For each of the slices (50 inches, 100 inches, 150 inches) of the first sample ingot, the compositions of Fe, Zn, Cr, Mg, and Cu were generally stable across rows A through D and columns 1 through 9. .

The reference ingot showed significant amounts of macrosegregation for most of these elements. A plot showing the Fe, Zn, Cr, Mg and Cu composition for a 100 inch slice of a reference ingot as a function of position is depicted in Figure 14. In contrast, macrosegregation in the first sample ingot was limited. A plot showing the Fe, Zn, Cr, Mg and Cu composition for a 100 inch slice of the first sample ingot as a function of position is depicted in Figure 15.

However, since the first sample ingot was homogenized after casting, the composition of the first comparative sample ingot was analyzed in the same manner to evaluate macrosegregation of the ingot cast before homogenization. Although the concentrations of Fe, Zn, Cr, Mg, and Cu were slightly different between the first and first comparison sample ingots, macrosegregation was similarly limited in the first comparison sample ingot, indicating that casting using non-contact stirring did not cause macrosegregation. It shows that it can help limit A plot showing the Fe, Zn, Cr, Mg and Cu composition for a 100 inch slice of the first comparative sample ingot as a function of position is depicted in Figure 16.

The porosity of the reference ingot and the first sample ingot was also characterized by scanning a 3D surface profilometer across the surface of a slice of the ingot and identifying areas where the surface profile had depressions greater than a given depth as pores. The overall porosity plots for each of the sampling locations of the reference ingot and the first sample ingot in the 100 inch slice are depicted in Figures 17 and 18, respectively. The reference ingot exhibited greater porosity than the first sample ingot.

The grain structures of the reference ingot and the first sample ingot were also characterized. Optical microscopy images were obtained for each sampling location to evaluate particle structure. Both ingots showed a relatively coarser primary Al particle structure closer to the ingot center, and a relatively finer particle structure towards the ingot surface. Grain boundary precipitates and fine MgZn ₂ precipitates were observed in the reference ingot and the 11th sample ingot. More grain boundary precipitates were 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 assess the presence and composition of intermetallic compounds, precipitates, and eutectics. It has been done. DSC data showed a clear presence of low-temperature melt phases (e.g. MgZn ₂ and Al ₂ CuMg) at locations closer to the surface (e.g. rows B, C and D), but closer to the center of the ingot. Locations (e.g., Row A) showed no evidence of cold melting in the DSC data. However, _the XRD and DSC data for the first comparative ingot showed evidence of several low temperature melt phases including MgZn ₂ , Al ₂ MgC and Mg ₂ Si, including locations close to the center of the ingot.

A sample of the rolled sheet metal of the second sample ingot was mechanically tested for analysis. Rolled sheet metal was manufactured under two conditions: T6 temper condition and T6 temper condition followed by paint baking (T6 + PB). Samples were evaluated from the center and both edges of the ingot. T6 temper condition centroid samples were 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, mean yield stress (YS) (offset 0.2%), mean ultimate tensile stress (TS), mean maximum axial strain (AS) and mean uniform elongation (UE) are summarized in the plot shown in Figure 19.

Exemplary Aspects

As used below, references to a series of aspects are to be construed as separate references to each such instance (e.g., “aspects 1 to 4” to “aspects 1, 2, 3, or 4”) ").

Embodiment 1 is a method, such as a casting method, comprising supplying molten metal into a casting mold and forming an embryo ingot comprising an outer solid shell and an inner molten core; advancing the embryo ingot in a forward direction away from the casting mold while supplying additional molten metal to the casting mold; directing a supply of liquid coolant to the outer surface of the outer solid shell to extract heat from the embryo ingot between the casting mold and the transient position; and reheating the embryo ingot at the transient position such that at least a portion of the outer solid shell of the embryo ingot at the transient position reaches a temperature suitable for precipitating a dispersoid and below the homogenization temperature of the molten metal. and the transient position is in a plane perpendicular to the advancing direction and intersecting the inner molten core.

Aspect 2 is the method of any preceding or subsequent aspect, wherein the temperature, e.g. in degrees Celsius, is between 80% and 98% of the homogenization temperature of the molten metal, e.g. in degrees Celsius.

Aspect 3 is the method of any preceding or subsequent aspect, wherein the temperature, e.g. in degrees Celsius, is between 85% and 90% of the homogenization temperature of the molten metal, e.g. in degrees Celsius.

Aspect 4 is the method of any preceding or succeeding aspect, wherein the temperature is between 400°C and 460°C.

Aspect 5 is the method of any preceding or succeeding aspect, wherein the temperature is between 410°C and 420°C.

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

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

Aspect 8 is the method of any preceding or subsequent aspect, wherein reheating the embryo ingot further comprises applying heat to the outer surface of the outer solid shell to replenish latent heat from the inner molten core.

Aspect 9 is the method of any preceding or subsequent aspect, comprising: performing temperature measurements of the embryo ingot; and dynamically adjusting the transient location based on the temperature measurement.

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

Aspect 11 is the method of any preceding or subsequent aspect, further comprising: performing a temperature measurement of the embryo ingot, wherein inducing agitation in the inner molten core dynamically adjusts the intensity of agitation based on the temperature measurement. Includes an adjustment step.

Aspect 12 is the method of any preceding or subsequent aspect, wherein the transitional position is such that the plane is about one-third of a line where the outer solid shell of the embryo ingot extends from the outer surface to the center of the embryo ingot within the plane. It is selected to intersect the embryo ingot in a cross-section that occupies it.

Aspect 13 is the method of any preceding or subsequent aspect, wherein the transitional position is such that the plane is such that the outer solid shell of the embryo ingot occupies no more than 50% of a line extending from the outer surface to the center of the embryo ingot in the plane. The cross section is selected to intersect the embryo ingot.

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

Aspect 15 is a method comprising: forming an embryo ingot by supplying molten metal to a mold and extracting heat from the molten metal to form an outer solid shell; solidifying the inner molten core of the embryo ingot as the embryo ingot advances in an advance direction away from the mold and additional molten metal is supplied to the mold, wherein solidifying the inner molten core causes the outer solid shell comprising extracting heat from the internal molten core via -; and continuously forming a high-strength zone within the outer solid shell at a cross-section of the embryo ingot that intersects the inner molten core and is perpendicular to the advancing direction, wherein the high-strength zone is formed between the outer surface of the outer solid shell and the Located between the inner molten core, forming the high strength zone includes reheating the outer solid shell at the cross-section to induce dispersoid precipitation in the outer solid shell.

Aspect 16 is the method of any preceding or subsequent aspect, wherein reheating the outer solid shell in the cross section comprises reheating a portion of the outer solid shell to a temperature suitable for precipitating the dispersoid, and wherein the temperature is lower than the homogenization temperature of the molten metal.

Embodiment 17 is the method of any preceding or subsequent aspect, wherein the temperature, e.g. in degrees Celsius, is between 80% and 98% of the homogenization temperature of the molten metal, e.g. in degrees Celsius.

Embodiment 18 is the method of any preceding or subsequent aspect, wherein the temperature, e.g. in degrees Celsius, is between 85% and 90% of the homogenization temperature of the molten metal, e.g. in degrees Celsius.

Embodiment 19 is the method of any preceding or subsequent aspect, wherein the temperature is between 400°C and 460°C.

Embodiment 20 is the method of any preceding or subsequent aspect, wherein the temperature is between 410°C and 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 3 hours to 10 hours.

Aspect 22 is the method of any preceding or subsequent aspect, wherein extracting heat from the inner molten core through the outer solid shell comprises supplying a liquid coolant to the outer surface of the outer solid shell, Reheating the outer solid shell includes removing the liquid coolant from the outer surface of the outer solid shell.

Aspect 23 is the method of any preceding or subsequent aspect, wherein reheating the outer solid shell further comprises applying heat to the outer surface of the outer solid shell to replenish latent heat from the inner molten core. .

Aspect 24 is the method of any preceding or subsequent aspect, comprising: performing temperature measurements of the embryo ingot; and dynamically adjusting the distance between the mold and the cross section based on the temperature measurement.

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

Embodiment 26 is the method of any preceding or subsequent aspect, further comprising: performing a temperature measurement of the embryo ingot, wherein inducing agitation in the inner molten core dynamically adjusts the intensity of agitation based on the temperature measurement. Includes an adjustment step.

Aspect 27 is the method of any preceding or subsequent aspect, wherein, in the cross-section, the outer solid shell of the embryo ingot occupies about one-third of a line extending from the outer surface to the center of the embryo ingot.

Aspect 28 is the method of any preceding or subsequent aspect, wherein, in the cross-section, the outer solid shell of the embryo ingot occupies no more than 50% of a line extending from the outer surface to the center of the embryo ingot.

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

Embodiment 30 is the method of any preceding or subsequent aspect, wherein the high intensity zone comprises a higher concentration of dispersoid than the remainder of the outer solid shell.

Embodiment 31 is an aluminum metal product comprising a mass of solidified aluminum alloy having two ends and an outer surface, wherein the mass of solidified aluminum alloy has: A core region containing; an external region comprising the external surface; and a high intensity zone disposed between the core region and the outer region, the high intensity region having a higher concentration of dispersoid than each of the core region and the outer region.

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

Aspect 33 is the aluminum metal product of any preceding or subsequent aspect, wherein the high strength zone is about 1/3 of a line extending along a cross-section of the solidified aluminum alloy lump from the outer surface to the center of the solidified aluminum alloy lump. It is located at a depth of 3.

Aspect 34 is the aluminum metal product of any preceding or subsequent aspect, wherein the high strength zone is one half of a line extending along a cross-section of the solidified aluminum alloy lump from the outer surface to the center of the solidified aluminum alloy lump. It is located at a depth below.

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

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

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

Aspect 38 is an aluminum metal product of any preceding or subsequent aspect, made according to the method of any preceding or succeeding aspect.

Embodiment 39 is an embryo ingot comprising a liquid molten core of aluminum alloy extending from the upper surface to the solidification interface; and a solidified shell of the aluminum alloy, the solidified shell comprising an outer surface extending from the solidification interface to a bottom end in a casting direction, the solidified shell being positioned between the center of the liquid molten core and the solidified shell. and a high-strength zone disposed between the outer surface and a center line extending in the casting direction through the center of the shell, the high-strength zone having a higher concentration of dispersoid than the remainder of the solidified shell.

Embodiment 40 is the embryo ingot of any preceding or subsequent embodiment, wherein the high intensity zone is located at a depth of about one-third of the line extending from the outer surface to the center line.

Embodiment 41 is the embryo ingot of any preceding or subsequent embodiment, wherein the high intensity zone is located at a depth of less than one-half of a line extending from the outer surface to the centerline.

Embodiment 42 is the embryo ingot of any preceding or subsequent embodiment, wherein the solidified shell is cylindrical in shape.

Embodiment 43 is the embryo ingot of any preceding or subsequent embodiment, wherein the cross-section of the solidified cells perpendicular to the casting direction is rectangular in shape.

Embodiment 44 is the embryo ingot of any preceding or subsequent embodiment, wherein the aluminum alloy is a series 7xxx aluminum alloy.

Aspect 45 is an embryo ingot of any preceding or subsequent aspect, wherein the embryo ingot is made according to the method of any preceding or subsequent aspect.

Aspect 46 is a method comprising: transferring molten metal from a metal source to a metal sump of an embryo ingot being cast in a mold; forming an outer solid shell of solidified metal by extracting heat from the metal sump, wherein the solidification interface is located between the outer solid shell and the metal sump; advancing the embryo ingot at a casting speed in an advance direction away from the mold while delivering the molten metal and forming an outer solid shell; determining the intensity of agitation using the casting speed, wherein the intensity of agitation is appropriate to achieve the target solidification interface profile at the casting speed; and inducing agitation within the melt sump at the determined intensity, wherein inducing agitation within the melt sump causes the solidification interface to assume the target solidification interface profile at the casting speed.

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

Aspect 48 is a method of any preceding or subsequent aspect, wherein delivering the molten metal comprises delivering the molten metal at a mass flow rate through the plurality of nozzles, and inducing agitation comprises delivering the molten metal at a mass flow rate through the plurality of nozzles. and increasing the flow rate of molten metal through at least one of the plurality of nozzles while maintaining the flow rate.

Aspect 49 is a method of any preceding or successor aspect, comprising: modifying an address rate; determining an updated agitation intensity using the updated casting speed, wherein the updated agitation intensity is suitable to achieve the target solidification profile at the updated casting speed; and inducing agitation within the melt sump at the updated intensity, wherein inducing agitation within the melt sump at the updated intensity causes the solidification interface to assume the target solidification interface profile at the updated casting rate.

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

Aspect 51 is the method of any preceding or subsequent aspect, further comprising measuring the temperature of the embryo ingot, and determining the agitation intensity using the casting speed includes using the measured temperature.

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.

Embodiment 53 is the method of any preceding or subsequent aspect, further comprising continuously forming a high-strength zone within the outer solid shell at a cross-section of the embryo ingot perpendicular to the advancing direction and intersecting the inner molten core, wherein the high-strength zone is: Located between the outer surface of the outer solid shell and the inner molten core, forming the high strength zone includes reheating the outer solid shell in cross section to induce dispersoid precipitation in the outer solid shell.

Aspect 54 is the method of the preceding or subsequent aspect, wherein inducing agitation within the molten sump includes controlling delivery of the molten metal into the metal sump such that the jet of molten metal erodes a depression into the solidification interface of the bottom of the metal sump. And, the depression has a diameter that matches the diameter of the bottom of the metal sump.

Aspect 55 is a method comprising: transferring molten metal from a metal source to a metal sump of an embryo ingot being cast in a mold; extracting heat from the metal sump to form an outer solid shell of solidified metal, wherein the solidification interface is located between the outer solid shell and the metal sump; advancing the embryo ingot at a casting speed in an advance direction away from the mold while delivering the molten metal and forming an outer solid shell; and controlling the delivery of molten metal into the metal sump to produce a jet of molten metal sufficient to erode at least a portion of the solidification interface at the bottom of the metal sump.

Aspect 56 is the method of any preceding or subsequent aspect, wherein controlling the delivery of the molten metal includes controlling the delivery of the molten metal such that the jet of molten metal erodes the solidification interface to a thickness of 10 mm or less.

Aspect 57 is the method of the preceding or subsequent aspect, wherein delivering the molten metal comprises delivering the molten metal at a mass flow rate through a plurality of nozzles, and generating a jet of molten metal comprises delivering a jet of molten metal through the plurality of nozzles. and increasing the flow rate of molten metal through at least one of the plurality of nozzles while maintaining the 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 sump using a non-contact magnetic stirrer.

Aspect 59 is the method of any preceding or subsequent aspect, further comprising modifying the address rate, and controlling delivery of the molten metal such that the jet of molten metal continues at least a portion of the solidification interface at the bottom of the metal sump. and dynamically adjusting the delivery of molten metal based on the casting speed modified to erode.

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

Aspect 61 is the method of any preceding or subsequent aspect, further comprising measuring the temperature of the embryo ingot, and controlling the delivery of molten metal, wherein the jet of molten metal is positioned at least at the solidification interface at the bottom of the metal sump. and dynamically adjusting the delivery of molten metal based on the measured temperature to continue eroding the portion.

Aspect 62 is the method of any preceding or subsequent aspect, further comprising continuously forming a high-strength zone within the outer solid shell at a cross-section of the embryo ingot intersecting the metal sump and perpendicular to the advancing direction, wherein the high-strength zone is: Positioned between the outer surface of the outer solid shell and the metal sump, forming a high strength zone includes reheating the outer solid shell in cross section to induce dispersoid precipitation in the outer solid shell.

Aspect 63 is an aluminum metal product made according to the method of the preceding or subsequent aspect.

Embodiment 64 is an embryo ingot comprising: a solidified shell of aluminum alloy extending from the solidification interface to the bottom end in the casting direction; and a liquid molten core of aluminum alloy extending from the top surface to the solidification interface, the liquid molten core comprising a jet of aluminum alloy that impinges on the solidification interface at the bottom of the liquid molten core and forms a depression in the solidification interface.

Embodiment 65 is the embryo ingot of any preceding or subsequent aspect, wherein the liquid molten core comprises particles resuspended from the solidification interface.

Embodiment 66 is the embryo ingot of any preceding or subsequent embodiment, wherein the liquid molten core includes hydrogen resuspended from the solidification interface.

Embodiment 67 is the embryo ingot of any preceding or subsequent embodiment, wherein the solidified shell has a high strength zone disposed between the outer surface of the solidified shell and a center line extending in the casting direction through the center of the solidified shell and the center of the liquid molten core. and the high-strength zone has a higher concentration of dispersoids than the rest of the solidified shell.

Embodiment 68 is the embryo ingot of any preceding or subsequent embodiment, wherein the aluminum alloy is a series 7xxx aluminum alloy.

All patents and publications cited herein are incorporated by reference in their entirety. The foregoing description of embodiments, including illustrative embodiments, has been presented for purposes of illustration and description only and is not intended to be exhaustive or to limit the precise form disclosed. Numerous modifications, adaptations and uses will be apparent to those skilled in the art.

Claims (23)

In the method,
transferring molten metal from a metal source to a metal sump of an embryonic ingot being cast in a mold;
forming an outer solid shell of solidified metal by extracting heat from the metal sump, wherein a solidification interface is located between the outer solid shell and the metal sump;
advancing the embryo ingot at a casting speed in an advance direction away from the mold while delivering the molten metal and forming the outer solid shell;
determining the intensity of agitation using the casting speed; and
inducing agitation within the melt sump at a determined intensity so that the bottoms of the molten metal core, solidification interface and adjacent portions of the solid shell form a uniform U-shape or parabolic shape at the casting speed;
Inducing agitation includes applying an agitation force to the molten metal in the metal sump using a non-contact magnetic stirrer located on an opposite side of the feed tube. delete The method of claim 1, wherein delivering the molten metal includes delivering the molten metal at a mass flow rate through a plurality of nozzles, and inducing agitation while maintaining the mass flow rate through the plurality of nozzles. A method comprising increasing the flow rate of molten metal through at least one of the plurality of nozzles. According to paragraph 1,
modifying the casting speed;
determining an updated agitation intensity using the updated casting speed; and
Inducing agitation within the melt sump at the updated intensity so that the bottoms of the molten metal core, solidification interface, and adjacent portions of the solid shell form a uniform U-shape or parabolic shape at the updated casting speed. , method. The method of claim 1, wherein the molten metal is a 7xxx series aluminum alloy. The method of claim 1, further comprising measuring the temperature of the embryo ingot, wherein determining the agitation intensity using the casting speed includes using the measured temperature. delete According to paragraph 1,
Continuously forming a high-strength zone within the outer solid shell at a cross-section of the embryo ingot that intersects the inner molten core and is perpendicular to the advancing direction, wherein the high-strength zone is adjacent to the outer surface of the outer solid shell and the inner melt. Between the cores, forming the high strength zone comprises reheating the outer solid shell at the cross-section to induce dispersoid precipitation in the outer solid shell. 2. The method of claim 1, wherein the step of inducing agitation within the melt sump causes the molten metal to flow into the metal sump such that a jet of the molten metal erodes a depression into the solidification interface at the bottom of the metal sump. Controlling the delivery of metal, wherein the depression has a diameter sized to match the diameter of the bottom of the metal sump. In the method,
transferring molten metal from a metal source to a metal sump of an embryo ingot being cast in a mold;
forming an outer solid shell of solidified metal by extracting heat from the metal sump, wherein a solidification interface is located between the outer solid shell and the metal sump;
advancing the embryo ingot at a casting speed in an advance direction away from the mold while delivering the molten metal and forming the outer solid shell; and
controlling the delivery of the molten metal into the metal sump to produce a jet of molten metal sufficient to erode at least a portion of the solidification interface at the bottom of the metal sump,
Delivering the molten metal includes delivering the molten metal at a mass flow rate through a plurality of nozzles, and generating the jet of molten metal while maintaining the mass flow rate through the plurality of nozzles. A method comprising increasing the flow rate of molten metal through at least one of the plurality of nozzles. 11. The method of claim 10, wherein controlling the delivery of molten metal comprises controlling the delivery of the molten metal such that the jet of molten metal erodes the solidification interface to a thickness of less than 10 mm. delete 11. The method of claim 10, further comprising applying a stirring force to the molten metal in the metal sump using a non-contact magnetic stirrer. 11. The method of claim 10, further comprising modifying the casting speed, wherein controlling the delivery of molten metal causes the jet of molten metal to continue to erode at least a portion of the solidification interface at the bottom of the metal sump. Dynamically adjusting the delivery of molten metal based on the modified casting speed so as to. 11. The method of claim 10, wherein the molten metal is a 7xxx series aluminum alloy. 11. The method of claim 10, further comprising measuring the temperature of the embryo ingot, and controlling the delivery of molten metal such that the jet of molten metal passes at least a portion of the solidification interface at the bottom of the metal sump. Dynamically adjusting the delivery of molten metal based on the measured temperature to continue eroding. According to clause 10,
Continuously forming a high-strength zone within the outer solid shell at a cross-section of the embryo ingot that intersects the metal sump and is perpendicular to the advancing direction, wherein the high-strength zone is formed between the outer surface of the outer solid shell and the metal. Located between sumps, forming the high strength zone comprises reheating the outer solid shell in cross section to induce dispersoid precipitation in the outer solid shell. delete In the embryo ingot,
a solidified shell of aluminum alloy extending from the solidification interface to the bottom end in the casting direction; and
An embryo ingot comprising a liquid molten core of the aluminum alloy extending from an upper surface to the solidification interface, wherein the bottoms of the molten metal core, the solidification interface and adjacent portions of the solid shell form a uniform U-shape or parabolic shape. 20. The embryo ingot of claim 19, wherein the liquid molten core comprises resuspended particles from the solidification interface. 20. The embryo ingot of claim 19, wherein the liquid molten core comprises resuspended hydrogen from the solidification interface. 20. The method of claim 19, wherein the solidified shell comprises a high strength zone disposed between the outer surface of the solidified shell and a center line extending in the casting direction through the center of the liquid molten core and , wherein the high-strength zone has a higher concentration of dispersoid than the remainder of the solidified shell. 20. The embryo ingot of claim 19, wherein the aluminum alloy is a series 7xxx aluminum alloy.