RU2819336C1 - Reduced susceptibility to cracking of cast ingots of 7xxx series, obtained by continuous casting into crystallizer (dc) - Google Patents

Abstract

FIELD: foundry.

SUBSTANCE: invention relates to continuous casting. Method of continuous casting of aluminium alloy includes supply of molten aluminium alloy from source into hole for melting of initial ingot in crystallizer, Formation of outer solid shell and advance of initial ingot from crystallizer at casting speed. Mixing is induced in the melt cavity with the help of casting speed, the intensity of which is determined for acceptance of the target profile by the solidification boundary of the alloy. At that, supply of molten aluminium alloy is controlled so that its jet destroys solidification boundary to thickness equal to or less than 10 mm. Said mixing allows to reduce thickness of hardening front, promotes agglomeration of gaseous hydrogen emitted at hardening front, and removal of impurities emitted at hardening front. Control of intensive mixing is used to increase casting speed without increasing thickness of hardening front.

EFFECT: reduced sensitivity of ingot to cracking.

21 cl, 19 dwg, 1 ex

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of U.S. Provisional Patent Application 62/951,883, filed December 20, 2019, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This invention relates generally to metal casting and, more particularly, to continuous mold casting of complex aluminum alloys.

BACKGROUND OF THE ART

In continuous mold casting (DC; direct chill), the molten metal passes into the cavity of the mold with a complex, or movable, bottom. When molten metal enters the mold cavity, preferably from above, the false bottom descends at a speed related to the flow rate of the molten metal. Molten metal solidified near the walls can be used to hold liquid and partially liquid metal in the melt well. A metal can be 99.9% solid (such as completely solid), 100% liquid, or anything in between. The melt well may be V-shaped, U-shaped, or W-shaped due to the thickening of the solid regions as the molten metal cools. The boundary between solid metal and liquid metal is sometimes called the solidification boundary.

When the molten metal in the melt well is between about 0% solids and about 5% solids, nucleation may occur and small metal crystals may be formed. These small (e.g., nanometer-sized) crystals begin to form as nuclei that continue to grow in preferred directions to form dendrites as the molten metal cools. When the molten metal is cooled to the point of dendritic coherence (for example, 632°C in 5182 aluminum used for the ends of beverage cans), the dendrites begin to stick together. Depending on the temperature and percentage of solids in the molten metal, the crystals may contain or trap various particles (for example, intermetallic compounds or hydrogen bubbles), such as FeAl ₆ , Mg ₂ Si, FeAl ₃ , Al ₈ Mg ₅ particles and H ₂ gas. in some aluminum alloys.

Additionally, when solidifying aluminum first begins to cool, it may not contain as many alloying elements in its alpha phase, and thus the molten metal surrounding the solidifying interface may have a proportionately higher concentration of alloying elements. Thus, various compositions and particles may form at or near the solidification surface. Additionally, there may be areas of stagnation within the socket, which may result in the preferential accumulation of these particles.

The non-uniform distribution of alloying elements along the length of the grain is known as microsegregation. In contrast, macrosegregation is chemical heterogeneity on a length scale larger than a grain (or number of grains), such as up to a length scale of meters.

Some aluminum alloys, such as the 7xxx series alloys, can be particularly difficult to cast. 7xxx series alloys advantageously contain multiple alloying elements, such as combinations of one or more of zinc, magnesium, copper, chromium, zirconium and other alloying elements. When casting 7xxx series alloys and immediately after it, large internal stresses (for example, compressive and sometimes tensile) can occur, which makes the cast product susceptible to cracking. Some alloying elements used in these types of alloys, such as zinc, contract and expand at far different rates than aluminum. In particular, zinc contracts and expands much more than aluminum. Thus, the same volumes of zinc and aluminum at similar temperatures (e.g., 600°C) may result in different volumes of zinc and aluminum upon cooling (e.g., in the final stages of solidification). These different rates of expansion and contraction between the alloying elements and the aluminum can cause large internal forces and therefore stresses in a product cast from a 7xxx series alloy.

In addition, 7xxx series alloys are very sensitive to porosity problems caused by dissolved hydrogen escaping from the solidifying molten alloy in the form of microgas bubbles. Voids created by gas bubbles are often crack initiation sites and can lead to significant cracking. In addition, 7xxx series alloys can be very sensitive to shrinkage porosity, at least in part due to differences in shrinkage percentages as the molten metal solidifies.

In traditional manufacturing environments, large internal stresses during solidification can cause hot or cold cracking of the cast product, rendering the product unsuitable for further production. When using 7xxx series alloys under traditional production conditions, there is increased loss of the entire ingot compared to other, more easily cast products, such as 6xxx series alloys.

In addition, 7xxx series alloy castings can be subjected to an extended homogenization step after casting to achieve the desired internal structure with the desired precipitates while reducing casting stresses. Homogenization can be used to reduce microsegregation after casting. In some cases, 7xxx series alloy castings may be hot rolled to a smaller size, dissolved, and subsequently aged. In some cases, long periods of aging and further processing (such as dissolution or recrystallization) can be used to obtain more desirable microstructures, but such methods require significant equipment and a significant investment of time, resources and energy.

SUMMARY OF THE INVENTION

The term “embodiment” and similar terms are intended to broadly denote the entire scope of this invention and the following claims. Statements containing these terms are to be understood as not limiting the scope of the invention described herein or limiting the meaning or scope of the claims below. The embodiments of the present invention disclosed herein are defined by the claims below and not by this summary section. This summary section provides a general overview of the various aspects of the invention and introduces some of the concepts that are further described below in the Detailed Description of the Invention section. This section of the summary of the invention is not intended to define the key or significant distinguishing features of the claimed subject matter of the invention, nor is it intended to separately determine the scope of the claimed subject matter of the invention. The subject matter of the invention should be understood by reference to the relevant portions of the entire specification of this invention, any possible drawings, and each claim.

Embodiments of the present invention include a casting method comprising: feeding molten metal into a mold and forming an initial ingot comprising an outer hard shell and an inner molten core; advancing the initial ingot in the direction of advancement away from the mold while simultaneously feeding additional molten metal into the mold; removing heat from the initial ingot between the mold and the transition point by directing the supply of liquid coolant to the outer surface of the outer hard shell; and reheating the initial ingot at the transition location such that at least a portion of the outer hard shell of the initial ingot at the transition location reaches a temperature (e.g., reheat temperature) suitable for particulate release and below the homogenization temperature of the molten metal, wherein the transition location lies in a plane perpendicular to the direction of advancement and intersecting the internal molten core.

In some cases, the reheat temperature, eg in degrees Celsius, is from 80% to 98% of the homogenization temperature, eg in degrees Celsius, of the molten metal. In some cases, the temperature, eg in degrees Celsius, is 85% to 90% of the homogenization temperature, eg in degrees Celsius, of the molten metal. Optionally, temperature in degrees Celsius is 80% to 95%, 80% to 90%, 80% to 85%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98% of the homogenization temperature of the molten metal in degrees Celsius. In some cases the temperature ranges from 400°C to 460°C. In some cases, the temperature is from 410°C to 420°C. Optionally, the temperature is from 400°C to 410°C, from 400°C to 420°C, from 400°C to 430°C, from 400°C to 440°С, from 400°С to 450°С, from 400°С to 460°С, from 410°С to 420°С, from 410°С to 430°С, from 410°С to 440°С, from 410°С to 450°С, from 410°С to 460°С, from 420°С to 430°С, from 420°С to 440°С, from 420°С to 450°С, from 420°С to 460 °С, from 430°С to 440°С, from 430°С to 450°С, from 430°С to 460°С, from 440°С to 450°С, from 440°С to 460°С or from 450 °C to 460 °C. In some cases, the method further includes maintaining the temperature at the outer hard shell portion for at least 3 hours, for example from 3 hours to 4 hours, from 3 hours to 5 hours, from 3 hours to 6 hours, from 3 hours to 7 hours, from 3 hours to 8 hours, from 3 hours to 9 hours, from 3 hours to 10 hours, from 4 hours to 5 hours, from 4 hours to 6 hours, from 4 hours to 7 hours, from 4 hours to 8 hours, from 4 hours to 9 hours, from 4 hours to 10 hours, from 5 hours to 6 hours, from 5 hours to 7 hours, from 5 hours to 8 hours, from 5 hours to 9 hours, from 5 hours to 10 hours, from 6 hours to 7 hours, from 6 hours to 8 hours, from 6 hours to 9 hours, from 6 hours to 10 hours, from 7 hours to 8 hours, from 7 hours to 9 hours, from 7 hours up to 10 hours, from 8 hours to 9 hours, from 8 hours to 10 hours, from 9 hours to 10 hours or more. In some cases, reheating the initial ingot involves removing liquid coolant from the outer surface of the outer hard shell. In some cases, reheating the initial ingot further involves applying heat to the outer surface of the outer solid shell in addition to latent heat from the inner molten core. In some cases, the method further includes measuring the temperature of the starting ingot; and dynamically adjusting the transition location based on temperature measurements. In some cases, the method further includes mixing the inner molten core near the interface between the inner molten core and the outer solid shell. In some cases, the method further includes taking temperature measurements of the initial ingot, wherein inducing stirring in the inner molten core involves dynamically adjusting the stirring intensity based on the temperature measurements. In some cases, the transition location is chosen so that the plane intersects the initial ingot in a cross section where the outer solid shell of the initial ingot occupies about one-third of a line extending from the outer surface to the center of the initial ingot within the plane. In some cases, the transition location is chosen so that the plane intersects the initial ingot in a cross section in which the outer hard shell of the initial ingot occupies no more than 50% of the line passing from the outer surface to the center of the initial ingot within the plane. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the reheated portion includes a plane of metal containing liquid in the center, with a reheated zone in which said precipitates grow along the periphery of the ingot adjacent to the surface.

Embodiments of the present invention include a method comprising: forming an initial ingot by feeding molten metal into a mold and removing heat from the molten metal to form an outer hard shell; solidifying the inner molten core of the initial ingot as the initial ingot is advanced in a forward direction away from the mold and additional molten metal is supplied to the mold, wherein solidifying the inner molten core includes removing heat from the inner molten core through the outer solid shell; and continuously forming a high-strength zone within the outer hard shell in a cross-section of the initial ingot perpendicular to the advance direction and intersecting the inner molten core, wherein the high-strength zone is located between the outer surface of the outer hard shell and the inner molten core, wherein the formation of the high-strength zone includes reheating the outer solid shell in cross section to induce the release of dispersed particles in the outer hard shell.

In some cases, reheating the outer solid shell cross-section involves reheating a portion of the outer solid shell to a temperature suitable for particulate release, a temperature below the homogenization temperature of the molten metal. In some cases, the temperature, eg in degrees Celsius, is 80% to 98% of the homogenization temperature, eg in degrees Celsius, of the molten metal. In some cases, the temperature, eg in degrees Celsius, is 85% to 90% of the homogenization temperature, eg in degrees Celsius, of the molten metal. In some cases, the temperature is from 300°C to 460°C, for example, from 400°C to 460°C. In some cases the temperature ranges from 410°C to 420°C. In some cases, the 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 can be used, for example for 6xxx series alloys. In some cases, the method further includes maintaining a temperature at a portion of the outer hard shell for at least 3 hours or from 3 hours to 10 hours. In some cases, removing heat from the inner molten core through the outer solid shell involves applying liquid coolant to the outer surface of the outer solid shell, while reheating the outer solid shell involves removing liquid coolant from the outer surface of the outer solid shell. In some cases, reheating the outer hard shell further involves applying heat to the outer surface of the outer hard shell in addition to latent heat from the inner molten core. In some cases, the method further includes measuring the temperature of the starting ingot; and dynamic adjustment of the distance between the mold and the cross section based on temperature measurements. In some cases, the method further includes mixing the inner molten core near the interface between the inner molten core and the outer solid shell. In some cases, the method further includes taking temperature measurements of the initial ingot, wherein inducing stirring in the inner molten core involves dynamically adjusting the stirring intensity based on the temperature measurements. In some cases, in cross-section, the outer hard shell of the initial ingot occupies about one-third of a line extending from the outer surface to the center of the initial ingot. In some cases, in cross-section, the outer hard shell of the initial ingot occupies no more than 50% of the line running from the outer surface to the center of the initial ingot. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the high-strength zone contains a higher concentration of dispersed particles than the rest of the outer hard shell.

Embodiments of the present invention include an aluminum metal product comprising: a solidified aluminum alloy mass having two ends and an outer surface, the solidified aluminum alloy mass comprising: a core region containing a center of mass of the solidified aluminum alloy; an outer region including an outer surface; and a high-strength zone located between the core region and the outer region, wherein the high-strength zone has a higher particulate concentration than each of the core region and the outer region.

In some cases, the mass of solidified aluminum alloy contains residual heat from the continuous mold casting process. In some cases, the high-strength zone is located at a depth of about one-third of a line running from the outer surface to the center of the mass of the solidified aluminum alloy along the cross-section of the mass of the solidified aluminum alloy. In some cases, the high-strength zone is located at a depth of no more than half a line running from the outer surface to the center of mass of the solidified aluminum alloy along the cross-section of the mass of the solidified aluminum alloy. In some cases, the mass of solidified aluminum alloy has a cylindrical 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 mass of solidified aluminum alloy is the mass of solidified 7xxx series aluminum alloy.

Embodiments of the present invention include a starter ingot comprising: a liquid molten aluminum alloy core extending from a top surface to a solidification surface; and a solidified shell of aluminum alloy, wherein the solidified shell has an outer surface extending from the solidification boundary to a lower end in the casting direction, wherein the solidified shell contains a high-strength zone located between the outer surface and a center line extending in the casting direction through the center of the liquid molten the core and center of the hardened shell, with the high-strength zone having a higher concentration of dispersed particles than the rest of the hardened shell.

In some cases, the high-strength zone is located at a depth of about one-third of a line extending from the outer surface to the centerline. In some cases, the high-strength zone is located at a depth of no more than half a line running from the outer surface to the center line. In some cases, the hardened shell has a cylindrical shape. In some cases, the cross-section of the hardened deposit, perpendicular to the casting direction, has a rectangular shape. In some cases, the aluminum alloy is a 7xxx series aluminum alloy. In some cases, the initial ingot is made by any of the above methods.

Embodiments of the present invention include a method comprising: supplying molten metal from a metal source to a metal well of a starting ingot being cast into a mold; forming an outer hard shell of solidified metal by extracting heat from the metal socket, wherein the solidification surface is located between the outer hard shell and the metal socket; advancing the initial ingot in the direction of advancement from the mold at a casting speed while supplying molten metal and forming an outer hard shell; determining the stirring intensity using the casting speed, where the stirring intensity is suitable to achieve the target solidification interface profile at the casting speed; and inducing stirring in the melt well at a certain intensity, wherein stirring in the melt well causes the solidification boundary to adopt a target solidification surface profile at the casting speed.

In some cases, inducing stirring involves applying stirring forces to the molten metal in a metal well using a non-contact magnetic stirrer. In some cases, supplying molten metal includes feeding molten metal at a mass flow rate through a plurality of nozzles, wherein inducing mixing includes increasing the flow rate of molten metal through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles. In some cases, the method further includes changing the casting speed; determining an updated stirring intensity using the updated casting speed, wherein the updated stirring intensity is suitable to achieve a target solidification profile at the updated casting speed; and initiating mixing in the melt well at the updated intensity, wherein mixing in the melt well at the updated intensity causes the solidification boundary to adopt a target solidification surface profile at the updated casting speed. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the method further includes measuring the temperature of the starting ingot, wherein determining the stir rate using the casting speed includes using the measured temperature. In some cases, the target curing surface profile is pre-determined to minimize the risk of cracking. In some cases, the method further includes continuously forming a high-strength zone within the outer hard shell in a cross-section of the initial ingot that is perpendicular to the direction of advance and which intersects the inner molten core, wherein the high-strength zone is located between the outer surface of the outer hard shell and the inner molten core, and wherein forming the high-strength zone involves reheating the outer hard shell in cross section to induce the release of dispersed particles in the outer hard shell. In some cases, inducing agitation within the melt well involves controlling the flow of molten metal into the metal well such that the jet of molten metal erodes a solidification surface depression at the bottom of the metal well, the depression having a diameter corresponding to the diameter of the bottom of the metal well.

Embodiments of the present invention include a method comprising: supplying molten metal from a metal source to a metal well of a starting ingot being cast into a mold; forming an outer hard shell of solidified metal by extracting heat from the metal socket, wherein the solidification surface is located between the outer hard shell and the metal socket; advancing the initial ingot in the direction of advancement from the mold at a casting speed while supplying molten metal and forming an outer hard shell; and controlling the flow of molten metal into the metal well to create a jet of molten metal sufficient to destroy at least a portion of the solidification surface at the bottom of the metal well.

In some cases, controlling the supply of molten metal includes controlling the supply of molten metal such that the jet of molten metal erodes the solidification surface to a thickness equal to or less than 10 mm. In some cases, supplying molten metal includes delivering molten metal at a mass flow rate through a plurality of nozzles, wherein creating a jet of molten metal includes increasing the flow rate of molten metal through at least one of the plurality of nozzles while maintaining a mass flow rate through the plurality of nozzles. In some cases, the method further includes applying stirring forces to the molten metal in the metal well using a non-contact magnetic stirrer. In some cases, the method further includes varying the casting speed, wherein controlling the supply of molten metal includes dynamically adjusting the supply of molten metal based on the changed casting speed such that the jet of molten metal continues to erode at least a portion of the solidifying surface at the bottom of the metal socket. In some cases, the molten metal is a 7xxx series aluminum alloy. In some cases, the method further includes measuring the temperature of the initial ingot, wherein controlling the supply of molten metal includes dynamically adjusting the supply of molten metal based on the measured temperature such that the stream of molten metal continues to erode at least a portion of the solidification boundary at the bottom of the metal crater. In some cases, the method further includes continuously forming a high-strength zone within the outer hard shell in a cross section of the initial ingot perpendicular to the feed direction and intersecting the metal dimple, wherein the high-strength zone is located between the outer surface of the outer hard shell and the metal dimple, and wherein forming the high-strength zone includes reheating the outer hard shell in cross section to induce the release of dispersed particles in the outer hard shell.

Embodiments of the present invention include a starter ingot comprising: a solidified aluminum alloy shell extending from a solidification surface to a lower end in a casting direction; and a liquid molten aluminum alloy core extending from the top surface to a solidification boundary, the liquid molten core including an aluminum alloy jet impinging on a solidification surface at the bottom of the liquid molten core to form a depression at the solidification boundary.

In some cases, the liquid molten core contains resuspended grains from the solidification boundary. In some cases, the liquid molten core contains re-suspended hydrogen from the solidification boundary. In some cases, the solidified shell contains a high-strength zone located 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 the center of the solidified shell, the high-strength zone having a higher concentration of dispersed particles than the rest of the solidified shell. In some cases, the aluminum alloy is a 7xxx series aluminum alloy.

Embodiments of the present invention include an aluminum metal product manufactured in accordance with any of the methods described above.

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

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

In the description, reference is made to the following accompanying drawings, in which the use of like reference numerals in different figures is intended to illustrate like or similar components.

In fig. 1 is a partial cross-sectional view of an in-situ particulate recovery metal casting system in accordance with certain aspects of the present invention.

In fig. 2 is a partial cross-sectional view of a metal casting system for in-situ particulate recovery with dimple depth control in accordance with certain aspects of the present invention.

In fig. 3 is a partial cross-sectional view of a controlled flow intensive mixing metal casting system in accordance with certain aspects of the present invention.

In fig. 4 is a partial cross-sectional view of a controlled flow intensive mixing metal casting system with multiple feed tubes in accordance with certain aspects of the present invention.

In fig. 5 is a partial cross-sectional view of a high-intensity magnetic stirring metal casting system in accordance with certain aspects of the present invention.

In fig. Figure 6 shows an enlarged schematic view of the bottom of the melt well without intensive stirring.

In fig. 7 is a schematic close-up view of the bottom of a hot melt well in accordance with certain aspects of the present invention.

In fig. 8 is a flow diagram illustrating an in-situ particulate separation process in accordance with certain aspects of the present invention.

In fig. 9 is a flow diagram depicting a process for creating a high strength zone of separated dispersed particles in a continuous casting ingot in accordance with certain aspects of the present invention.

In fig. 10 is a schematic cross-sectional side view of an ingot depicting a high strength zone in accordance with certain aspects of the present invention.

In fig. 11 is a schematic cross-sectional top view of an ingot depicting a high strength zone in accordance with certain aspects of the present invention.

In fig. 12 is a flow diagram depicting a process for producing a continuous stir casting ingot in accordance with certain aspects of the present invention.

In fig. 13A and FIG. 13B is a schematic cross-sectional view of 7xxx series ingots showing the positions of the sampling locations.

In fig. Figure 14 presents data showing the composition of the reference ingot at various sampling locations.

In fig. Figure 15 presents data showing the composition of the first sample ingot at various sampling points.

In fig. 16 presents data showing the composition of the ingot of the first comparative sample at various sampling locations.

In fig. Figure 17 presents data showing the porosity of the reference ingot at various sampling locations.

In fig. 18 shows data showing the porosity of the first sample ingot at various sampling locations.

In fig. 19 presents data showing the mechanical properties of sheet metal made from the second sample ingot.

DETAILED DESCRIPTION OF THE INVENTION

Certain aspects and features of the present invention relate to reducing the crack sensitivity of continuous mold castings of certain alloys, such as the 7xxx series alloys. Controlling the process of intensive mixing along the solidification front and adjusting casting speeds during continuous casting of 7xxx series alloys into a mold can reduce the sensitivity of the ingot to cracking. Vigorous mixing reduces the thickness of the solidification front (e.g., the region from approximately >0% to <100% of solid metal, known as the "quasi-equilibrium two-phase zone"), promotes agglomeration of hydrogen gas emitted at the solidification front, removes impurities emitted at the solidification front, and improves grain size. Intensive mixing can provide higher casting speeds without the risk of increasing solidification front thickness. Optional reheating during casting to promote particulate formation can create a protective zone of particulate-strengthened solidified metal at the outer periphery of the ingot, which can further reduce the ingot's susceptibility to cracking.

In continuous mold casting (DC), the molten metal flows into a mold cavity with a false, or moving, bottom. When molten metal enters the mold cavity, preferably from above, the false bottom descends at a speed related to the flow rate of the molten metal. Molten metal solidified near the walls can be used to hold liquid and partially liquid metal in the melt well. A metal can be 99.9% solid (such as completely solid), 100% liquid, or anything in between. The melt well may be V-shaped, U-shaped, or W-shaped due to the thickening of the solid regions as the molten metal cools. The boundary between solid and liquid metal is sometimes called the solidification boundary or solidification front. The metal product resulting from the DC casting process can be called an ingot. The ingot may have a predominantly rectangular cross-section, although other cross-sections such as circular or even asymmetrical may be used. As used herein, the term "ingot" can include any DC cast metal product, including blanks as appropriate.

As described above, as the metal solidifies at the solidification front, some impurities and gas may be forced out of solution and trapped within the solidifying metal. Gases such as hydrogen can collect to form bubbles, resulting in the formation of voids in the solidified metal, commonly referred to as ingot porosity. In addition, removing impurities at the solidification boundary can lead to uneven distribution of impurities throughout the ingot.

Some aspects of the present invention include stirring the melt well. This mixing can be achieved in many ways, such as using contact stirrers, non-contact stirrers, or adjusting the way the liquid metal enters the well. Contact agitators are often undesirable for use with aluminum alloys, at least due to the risk of forming impurities and oxides. Non-contact stirrers may include electromagnetic and permanent magnet systems configured to create movement in the molten metal. In some cases, the molten sump may be agitated by adjusting the manner in which the liquid metal enters the socket, such as by delivering the liquid metal in the form of a powerful jet of liquid metal, such as a jet powerful enough to penetrate to the bottom of the socket. A jet of liquid metal can be produced by increasing the pressure at which the liquid metal is injected, by adjusting the diameter of the nozzle through which the metal is injected, or by other methods such as an ejector nozzle used to inject an existing melt well into a newly created jet. added liquid metal.

Vigorous mixing in the melt well can be used to provide mixing along the solidification front. This stirring can wash out the resulting metal crystals or parts thereof, impurities, gases, or even part of the liquid metal from the region of the solidification front. Washing out the resulting metal crystals (e.g., free-moving grains) can help produce a finer and more uniform grain size because the resulting crystals or broken pieces can be resuspended in the melt well and act as additional nuclei. In addition, sufficiently vigorous stirring can reduce the overall temperature of the liquid in the melt well, thereby creating a favorable environment for the formation of refined spherical grains. This refined spherical microstructure is stronger than the typical microstructure found in DC cast ingots. Ingots cast using certain aspects of the present invention, such as high agitation, may have a higher yield strength and may be less susceptible to cold cracking than ingots cast without intense agitation.

Washing out impurities from the solidification front can help reduce macrosegregation (eg, lower degree of macrosegregation) and thus improve uniformity. This lower macrosegregation achieved through mixing can be beneficial in achieving the required protective zone within the ingot. As described in more detail herein, a protective zone can be created by reheating the outer solidified portion of the cast ingot. Reheating can result in the formation of fine dispersed particles within the ingot, which can positively strengthen the solidified metal, thus minimizing the susceptibility of the ingot to cracking. These fine dispersed particles can have a diameter of about 30 nm, although they can be of other sizes. In some cases, these fine dispersed particles may have a diameter of about 10-50 nm, 20-40 nm or 25-35 nm.

It has been surprisingly discovered that vigorous stirring in the melt well can reduce or minimize the porosity of the cast ingot. Vigorous agitation can wash away the released hydrogen from the solidification surface, re-suspending it in the rest of the melt well. The re-suspended hydrogen can agglomerate with other hydrogen, allowing the gas to spread to the surface of the melt well, where it remains or exits the melt well. Thus, in cases where the release of hydrogen would otherwise result in undesirable porosity of the cast product, it has been found that the use of vigorous agitation reduces or minimizes the porosity of the cast product.

Because the presence of impurities and dissolved gases in the molten metal can become a problem during casting, traditional casting methods typically rely on significant prior preparation to filter impurities from the liquid metal and/or reduce the amount of dissolved gases (eg, hydrogen) in the liquid metal. Using certain aspects of the present invention, this type of prior preparation for filtering impurities and/or removing dissolved gases can be significantly reduced or eliminated.

Proper control of the solidification front can be essential to achieving successful casting, especially when using difficult alloys such as the 7xxx series alloys. In traditional DC casting, the casting speed can be used to control the solidification front. Increasing the casting speed can thicken the solidification front, while decreasing the casting speed can narrow the solidification front. If the solidification front is too thick, molten metal may not completely flow through the solidification regions of the solidification front, which can result in shrinkage porosity and voids. If the solidification front is too thin, hot cracking can occur, where gaps or cracks form between the grains due to internal stresses, such as those due to shrinkage. Therefore, there is often a trade-off between sensitivity to shrinkage porosity and sensitivity to hot cracking, which can determine or limit casting speed. In some alloys particularly prone to hot cracking, such as the 7xxx series alloys, this ratio effectively limits the available casting speed, thereby setting an effective maximum on the number of ingots that can be cast in a day.

In accordance with some aspects of the present invention, control of the solidification front can be achieved by combining stir control and casting speed control. Intensive mixing can provide numerous benefits that mitigate hot cracking while allowing for high casting speeds. As described above, vigorous agitation can help narrow the solidification front. Thus, the DC casting process with intense stirring can operate at a higher casting speed than the DC casting process without vigorous stirring, while maintaining the same thickness of the solidification front. Thus, intensive mixing can result in faster casting and therefore more production per day. In addition, stirring may cause the melt well to penetrate deeper into the cast ingot, which is also referred to herein as the starting ingot. In DC casting, the hydrostatic pressure of the molten metal provides a significant driving force for liquid metal to infiltrate into the grain gaps at the solidification front. The deeper melt well achieved by vigorous agitation provides a larger area of hydrostatic head near the bottom of the well. This large area of hydrostatic head can facilitate filling of grain gaps at the solidification front, providing a thicker solidification front with no or no risk of shrinkage porosity or voids. Because a thicker solidification front can be used with vigorous agitation, casting speeds can be increased even more than would be possible without agitation.

The enhanced agitation can be adjusted to achieve a nominal reduction in the thickness of the solidification front (eg, solidification interface) to a nominal thickness on the order of several millimeters, for example, from about 1 mm to 5 mm, or at or less than about 10 mm. In some cases, nominal thickness reduction may occur to a nominal thickness equal to or less than about 20 mm, 19 mm, 18 mm, 17 mm, 16 mm, 15 mm, 14 mm, 13 mm, 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm or 1 mm. As used herein, the term "controlling stirring to achieve a nominal reduction to a specific nominal thickness" may refer to controlling stirring to such an extent that will result in reduction to a particular thickness at a constant casting speed. Therefore, while increased mixing accompanied by increased casting speed may result in little or no effective change in the thickness of the solidifying interface, such increased mixing can be described as achieving a certain nominal reduction in the thickness of the solidifying interface to the nominal thickness. In addition, as used herein, solidification interface thickness may refer to the minimum thickness, maximum thickness, and average thickness or thickness at an applicable point or region within the initial ingot. For example, a solidification surface with a thickness of 10 mm or less may include a solidification boundary such that the maximum thickness at any point on the solidification surface is 10 mm or less; the solidification boundary at which the minimum thickness at any point of the solidification boundary reaches a thickness of 10 mm or less; a solidification boundary at which the average thickness of the entire solidification boundary remains 10 mm or less; or a solidification boundary such that the average thickness at or near the bottom of the solidification boundary (eg, the region furthest from the mold), or any other suitable point or region, is still 10 mm or less.

During DC casting, when the initial ingot exits the mold, a coolant (such as water) is sprayed onto the surface of the ingot to remove heat from the ingot. A purifier or other method can be used to remove the coolant, allowing a portion of the ingot to be reheated. This reheating can be used in some cases to homogenize the ingot in situ (for example, during casting). In some cases, such in situ homogenization may occur when the metal reaches a rebound temperature of about 470°C to about 480°C. However, in accordance with some aspects of the present invention, the reheat can be adjusted to achieve a lower temperature more suitable for release, which allows the formation of dispersed particles on the outer periphery of the ingot. Reheating the initial ingot to promote precipitate formation during casting may be referred to herein as in-situ precipitation.

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

The required in situ release can be achieved by reheating the initial ingot as above and either maintaining a constant temperature or allowing the ingot to cool to or near room temperature over a period of time. The time period may range from about 3 hours to about 5 hours, although in some cases the time may be longer or shorter, for example within a 10% deviation from either endpoint. The in-situ precipitation process may begin during the casting of the ingot and may end after the casting of the ingot. An ingot cast using in-situ precipitation can be cooled to or near room temperature without quenching immediately after casting. In some cases where in situ isolation is used, the later homogenization step can be performed in less time. For example, a three-hour in-situ release at 410°C may be homogenized for about 8 hours at 475°C and produce the required small releases, whereas a casting of an ingot without in-situ precipitation may require a 10-hour homogenization period at 475°C and may will only lead to unwanted large discharge.

Reheating the initial ingot can be accomplished by any suitable method, for example by applying external heat. However, reheating the initial ingot for in-situ homogenization can generally be accomplished by reducing the amount of heat rejection occurring at the surface of the initial ingot and allowing the latent heat of the ingot, especially the heat of the melt well, to reheat the outer portion of the ingot. To achieve the desired release temperature, the point at which reheating begins can be controlled in situ (eg, the position of the purifier removing the coolant) and/or the depth of the molten core can be controlled. For example, by increasing the position of the purifier (e.g., by moving the purifier closer to the mold), the solid shell may begin to reheat earlier in a cross section where the melt well is larger than in a cross section further away from the mold, allowing latent heat to be generated even more parts of the melt well to reheat the solid shell. In addition to, or instead of, controlling the point at which reheating begins, the depth of the melt well itself can be adjusted to provide precise control of solid shell reheating. For example, by causing agitation, for example by directing a stream of molten metal to the bottom of the solidification boundary, the metal well can be expanded to a greater distance from the mold than without additional agitation. As the depth of the molten core extends further from the mold, the solid shell will be exposed to the latent heat of the molten core for longer periods of time after the coolant is removed.

In addition, control of the location where reheating begins and/or the depth of the molten core may allow control of the surface depth of particulate matter that is formed during in situ release of particulate matter. As used herein, the term "surface depth" may refer to the depth of the ingot from the outer surface (eg, rolling surfaces and sides of the mold) to the center of the ingot (eg, the longitudinal centerline passing through the center of the ingot in the casting direction). In some cases, controlling the reheating of the solid shell and/or the depth of the molten core can provide the highest particulate concentrations in an area (eg, high strength zone) that accounts for about 1/3 (33%) of the longitudinal axis path from the ingot surface. In some cases, this area may be about ½ (50%) of the way to the longitudinal centerline from the surface of the ingot. In some cases, this area may be between about 5%, 10%, 15%, 20%, or 25% and about 25%, 30%, 35%, 40%, 45%, or 50% of the way to the longitudinal centerline from the surface of the ingot. . In some cases, this area may extend from the surface of the ingot to the aforementioned depths.

In some cases, the highest particulate concentrations and/or high strength zone may be a region of the ingot having a particulate concentration greater than the average particulate concentration of the entire ingot. In some cases, the highest concentration of dispersed particles and/or high-strength zone can be considered an area of the ingot with a concentration of dispersed particles of at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4 standard deviation units based on the average concentration of dispersed particles of the entire ingot. A high-strength zone (for example, a zone of relatively high concentrations of released dispersed particles) can act as protection against cracking when the ingot is cooled to room temperature.

Often there is no relationship between the initial microstructure after casting and the final wrought microstructure, at least in part due to recrystallization of the microstructures during hot working and post-processing. However, in some alloys, such as some of the 7xxx series alloys, recrystallization can be inhibited by the use of dispersed particles, for example by the addition of elements such as Cr or Zr. By causing the formation of such dispersed particles in the cast microstructure, the dispersed particles can suppress recrystallization or at least significant changes in average grain size during recrystallization. Since recrystallization is suppressed, the final forged microstructure can be related to, and more specifically similar to, the original microstructure after casting.

This ability to link the cast microstructure to the final forged microstructure can make methods for improving the cast microstructure particularly useful. The addition of grain refiners can be used to reduce grain size to a certain extent, but the effects of additional grain refiner become limited once the saturation limit is reached. However, using aspects of the present invention, such as intensive mixing, further and more desirable grain refinement can be achieved. This finer cast microstructure results in a finer microstructure in the final product, which can have many benefits, such as advantages in corrosion resistance and strength.

In some cases, certain aspects of the present invention may be particularly suitable for 7xxx series alloys, but may also be useful for use with 5xxx series alloys or other alloys. Certain aspects of the present invention may help combat orange peel defects such as those found in the 7xxx series. These "orange peel" defects are surface defects that are visible after deformation of a metal product and are characterized by surface roughness with an orange-like appearance on the outer surface. These defects are often the result of large grain sizes. By reducing the final grain size, this defect may become less pronounced after deformation.

As used herein, the terms “invention,” “recited invention,” “this invention,” and “the present invention” broadly refer to the entire scope of this patent application and the claims set forth below. Statements containing these terms are to be understood as not limiting the scope of the invention described herein or limiting the meaning or scope of the claims set forth below.

In this specification, reference is made to alloys designated by AA numbers and other appropriate designations such as "series" or "7xxx". For an understanding of the number system most commonly used to name and identify aluminum and its alloys, see International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys* "Registration Record of Aluminum Association Alloy Designations and Chemical Compositions Limits for Aluminum Alloys in the Form of Castings and Ingots" "), published by the Aluminum Industry Association.

As used herein, the term "room temperature" may include a temperature of 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, about 21°C, about 22°C, about 23°C, about 24°C, about 25°C, about 26°C, about 27°C, about 28°C, about 29°C or about 30°C. As used herein, the term "ambient conditions" may include temperature around room temperature, relative humidity from about 20% to about 100%, and barometric pressure from about 975 millibars (mbar) to about 1050 mbar. For example, the relative humidity may be about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%, about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about 39%, about 40%, about 41%, about 42%, about 43 %, about 44%, about 45%, about 46%, about 47%, about 48%, about 49%, about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%, about 59%, about 60%, about 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 anything in between. For example, barometric pressure may be about 975 mbar, about 980 mbar, about 985 mbar, about 990 mbar, about 995 mbar, about 1000 mbar, about 1005 mbar, about 1010 mbar, about 1015 mbar, about 1020 mbar, about 1025 mbar, about 1030 mbar, about 1035 mbar, about 1040 mbar, about 1045 mbar, about 1050 mbar or any value in between.

It should be understood that all ranges disclosed herein cover any and all sub-ranges included herein. For example, the stated range "1 to 10" should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges starting with a minimum value of 1 or more, such as 1 to 6.1, and ending with a maximum value of 10 or less, such as 5.5 to 10. Unless otherwise noted, the expression "to" when applied to compositional quantity of an element means that the element is optional and includes zero percent of the composition of that particular element. Unless otherwise stated, all composition percentages are given in percent by weight (wt%).

As used herein, the singular form includes references to the singular and plural unless the context clearly indicates otherwise.

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

Incidental elements such as grain refiners and deoxidizers or other additives may be present in this invention and may themselves add other characteristics without departing from or substantially changing the characteristics of the alloy described herein or the characteristics of the alloy described herein. However, it should be understood that the scope of this invention should not/cannot be avoided by simply adding a random element or elements in quantities that would not change the properties required by this invention.

Unavoidable impurities, including materials or elements, may be present in the alloy in trace amounts due to the inherent properties of aluminum or leaching upon contact with processing equipment. Some impurities commonly found in aluminum include iron and silicon. The alloy as described may contain no more than about 0.25 wt. % of any element except alloying elements, incidental elements and unavoidable impurities.

As used herein, the term "slab" means an alloy thickness greater than 15 mm. For example, slab may refer to 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.

As used herein, the term "slab" generally means a slab having a thickness in the range of 5 mm to 50 mm. For example, slab may refer to an aluminum product with a thickness of about 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm.

The sheet used herein (also called sheet plate) typically has a thickness of from 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.

The sheet used herein advantageously refers to an aluminum product 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.

The cast ingot can be processed by any means known to those skilled in the art. Optionally, processing steps can be used to prepare sheets. Such processing steps include, but are not limited to, homogenization, hot rolling, cold rolling, solution heat treatment and an optional pre-aging step known to those skilled in the art.

During the homogenization step, the cast product described herein is heated to a temperature in the range of about 400°C to about 500°C. For example, the product can be heated to a temperature of about 400°C, about 410°C, about 420°C, about 430°C, about 440°C, about 450°C, about 460°C, about 470°C, about 480° C, about 490°C or about 500°C. The product is then simmered (i.e. kept at a specified temperature) for a certain period of time. In some examples, the total time of the homogenization step, including the heating and simmering phases, can be up to 24 hours. For example, the product can be heated to 500°C and simmered for a total time of up to 18 hours for the homogenization stage. Optionally, the product may be heated to a temperature below 490°C and subjected to simmering for a total time of more than 18 hours during the homogenization step. In some cases, the homogenization step involves several processes. In some non-limiting examples, the homogenization step includes heating the article to a first temperature for a first period of time followed by heating to a second temperature for a second period of time. For example, the article can be heated to about 465°C for about 3.5 hours and then heated to about 480°C for about 6 hours.

After the homogenization step, a hot rolling step can be performed. Before hot rolling, the homogenized product can be allowed to cool to a temperature in the range of 300°C to 450°C. For example, the homogenized product can be allowed to cool to a temperature in the range of 325°C to 425°C or 350°C to 400°C. Then the product can be hot rolled at a temperature of 300°C to 450°C to form a hot rolled plate, hot rolled plate or hot rolled sheet with a thickness of 3 mm to 200 mm (for example, 3 mm, 4 mm, 5 mm, 6 mm, 7mm, 8mm, 9mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm , 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm or any value in between) .

The slab, plate or sheet can then be cold rolled using conventional mills and cold rolling technology to form the sheet. The cold rolled sheet may have a thickness of from about 0.5 mm to 10 mm, for example from about 0.7 mm to 6.5 mm. Optionally, the cold rolled sheet can have a thickness of 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, 8.0 mm, 8.5 mm, 9.0 mm, 9.5 mm or 10.0 mm. Cold rolling may be performed to obtain a final dimensional thickness that corresponds to a thickness reduction of 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). Optionally, an intermediate annealing step may be performed during the cold rolling step. The intermediate annealing step can be carried out at a temperature of from about 300°C to about 450°C (for example, about 310°C, about 320°C, about 330°C, about 340°C, about 350°C, about 360°C, about 370°C, about 380°C, about 390°C, about 400°C, about 410°C, about 420°C, about 430°C, about 440°C or about 450°C). In some cases, the intermediate annealing step involves multiple processes. In some non-limiting examples, the intermediate annealing step includes heating the plate, plate, or sheet to a first temperature for a first period of time, followed by heating to a second temperature for a second period of time. For example, the plate, sheet metal, or sheet may be heated to about 410°C for about 1 hour and then heated to about 330°C for about 2 hours.

The board, sheet plate or sheet may then be subjected to a solution heat treatment step. The solution heat treatment step may be any conventional sheet treatment that results in the dissolution of soluble particles. The slab, plate, or sheet may be heated to a peak metal temperature (PMT) of 590° C. (eg, 400° C. to 590° C.) and simmered for a specified period of time at that temperature. For example, a slab, sheet, or sheet may be simmered at 480° C. for a simmer time of up to 30 minutes (e.g., 0 seconds, 60 seconds, 75 seconds, 90 seconds, 5 minutes, 10 minutes, 20 minutes, 25 minutes, or 30 minutes). After heating and simmering, the slab, plate or sheet is rapidly cooled at a rate of more than 100°C/s to a temperature in the range of 500°C to 200°C. In one example, the board, plate or sheet has a hardening rate greater than 200°C/sec at a temperature of from 450°C to 200°C. Optionally, the cooling rate may be higher in other cases.

After hardening, the board, sheet plate or sheet may optionally be subjected to a pre-aging treatment by reheating the board, sheet plate or sheet before coiling. The pre-aging treatment can be carried out at a temperature of from about 70°C to about 125°C for a period of up to 6 hours. For example, pre-aging can be carried out at a temperature of about 70°C, about 75°C, about 80°C, about 85°C, about 90°C, about 95°C, about 100°C, about 105°C, about 110°C, about 115°C, about 120°C or about 125°C. Optionally, the pre-aging treatment can be carried out for about 30 minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, or about 6 hours. The pre-aging treatment can be carried out by passing the board, sheet metal or sheet through a heating device such as a radiant heat device, convective heat device, induction heat device, infrared heat device and the like.

The cast products described herein can also be used to make products in the form of slabs or other suitable products. For example, slabs, including the products described herein, can be produced by treating 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 of 200 mm or less (eg, about 10 mm to about 200 mm). For example, the cast product may be hot rolled to form a slab having a final dimensional thickness of from about 10 mm to about 175 mm, from about 15 mm to about 150 mm, from about 20 mm to about 125 mm, from about 25 mm to about 100 mm, from about 30 mm to about 75 mm or from about 35 mm to about 50 mm.

The aluminum alloy products described herein can be used in the automotive industry and other transportation-related applications, including the aircraft and rail industries. For example, the described aluminum alloy products can be used to make automotive structural parts such as bumpers, side beams, roof beams, cross beams, pillar reinforcements (such as A-pillars, B-pillars and C-pillars), interior panels, exterior panels, side panels, inner hoods, outer hoods or trunk lid panels. The aluminum alloy products and processes described herein can also be used in aircraft or railway vehicles to produce, for example, exterior and interior panels.

The products and methods described herein for aluminum alloys can also be used in electronic applications. For example, the aluminum alloy products and methods described herein can be used to make housings for electronic devices, including mobile phones and tablet computers. In some examples, aluminum alloy products can be used to make housings for the outer casings of mobile phones (such as smartphones), the lower casings of tablets, and other portable electronics.

These illustrative examples are provided to familiarize the reader with the general subject matter of the invention discussed herein and are not intended to limit the scope of the concepts disclosed. The following sections describe various additional features and examples with reference to the drawings, in which like numerals denote like elements and directional descriptions are used to describe illustrative embodiments, but, like the illustrative embodiments, are not to be used to limit the present invention. Items included in illustrations herein may not be to scale. For example, figures representing metal holes may include exaggerated elements for illustrative purposes.

In fig. 1 is a partial cross-sectional view of an in-situ particulate recovery metal casting system 100 in accordance with certain aspects of the present invention. A metal source 102, such as a tundish, may supply molten metal through the feed pipe 104 and through the nozzle 106. An optional collector 108 can be used around the feed pipe 104 to help distribute the molten metal and reduce the formation of metal oxides on the top surface of the melt well 110. The lower block 120 can be lifted by a hydraulic cylinder 122 until it contacts the walls of the mold cavity 112. As the molten metal begins to solidify within the mold, the lower block 120 can be gradually lowered at the casting speed. The initial ingot 116 may include sides 118 that have solidified, and molten metal added to the casting may be used to continuously extend the initial ingot 116. The initial 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 coolant 114 such as water. Coolant 114 may spray out of the hollow space and flow down the sides 118 of the initial ingot 116 to assist in solidifying the initial ingot 116. The initial ingot 116 may comprise an outer hard shell 128, a transition metal region (e.g., a solidification boundary 126), and a molten core 124 metal

To begin releasing particulates, the solidified shell 128 of the initial ingot 116 is reheated starting at a distance 130 from the preheater, defined as the distance from the bottom of the mold cavity 112 (e.g., where the initial ingot 116 exits the mold cavity 112) to the point where the solid the shell 118 begins to reheat. The preheater distance 130 may be the distance between the mold and the location where reheating begins (eg, the location of a preheater device, such as the purifier 142 used to remove the coolant 114). The point where reheating begins may be known as the transition point.

Although various methods can be used to reheat the hard shell 128, FIG. 1 illustrates the use of a purifier 142 to remove coolant 114 from a starting ingot 116. The purifier 142 shown in FIG. 1 is depicted as a solid cleaner, however other cleaners such as liquid based cleaners (eg air knives) can be used. Coolant 114 is removed from the initial ingot 116 in a cross section where the core of the initial ingot 116 is still in a molten state. Thus, latent heat from the molten metal core 124, especially from the regions of the molten metal core 124 between the preheater distance 130 and the molten metal distance 132 (defined below), can reheat the solid shell 128. Thus, as described in more detail herein, by adjusting the distance 130 from the preheater and/or the distance 132 from the molten metal, the time and degree of reheating can be precisely controlled.

The distance 130 to the preheater may be shorter than the distance 132 to the molten metal and the distance 134 to the well. The molten metal distance 132 may be defined as the distance from the bottom of the mold cavity 112 to the bottom of the molten metal core 124. The dimple distance 134 can be defined as the distance from the bottom of the mold cavity 112 to the bottom of the solidification boundary 126.

In some cases, the difference between the distance 132 to the molten metal and the distance 130 to the preheater can be controlled, for example, by inducing changes in the shape of the molten metal core 132 (for example, changing the casting speed and/or inducing stirring) to adjust the distance 132 to the molten metal or by moving the purifier 142 to adjust the distance 130 to the heater. Such adjustments to the casting speed, agitation, and/or cleaner 142 may be controlled by a controller 138 coupled to any associated drives. In some cases, controller 138 may perform operations based on a preset procedure. In some cases, controller 138 may perform operations based on dynamic feedback from the casting process, such as temperature measurements obtained by sensor 144. Sensor 144 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 144 shown in FIG. 1 is shown next to the hard shell 128 to measure the surface of the hard shell 128, but this is not necessary. In some cases, the sensor(s) may be placed in other locations and may perform other measurements of the ingot, such as crater temperature or coolant temperature.

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

Although in FIG. 1 depicts a purifier system, other types of reheat methods may be used at 130 to the preheater instead of or in addition to the purifier system. For example, direct flame, rotating magnetic heaters, or other devices may be used to provide heat to the solid shell 128 in addition to any latent heat from the molten metal core 124. In some cases, these methods of applying heat to the solid shell 128 can be controlled, for example, by controlling the amount of heat applied and/or the location to which the heat is applied. Such control may be performed by controller 138.

In fig. 2 is a partial cross-sectional view of a metal casting system 200 for in situ particulate recovery with crater depth control in accordance with certain aspects of the present invention. The metal casting system 200 may be similar to the metal casting system 100 in FIG. 1. Metal source 202 may supply molten metal through feed pipe 204 through flow controller 240 from nozzle 206. Flow controller 240 may provide increased flow from metal source 202 to molten metal core 224. This increased flow of molten metal through the feed pipe 204 may result in an increased flow 246 within the molten metal core 224. Increased flow 246 may be or correspond to increased volumetric flow, increased linear flow, or both increased volumetric flow and increased linear flow, for example, compared to the flow configuration depicted in FIG. 1.

This increased flow 246 can provide intense mixing and can act as a jet capable of disrupting part of the solidification boundary 226. The jet may create a depression in the solid shell 228 and a solidification boundary 226 at the bottom of the metal well (eg, the lowest portion of the liquid metal core 224). In this way, it is possible to increase the distance 232 to the molten metal, as well as the distance 234 to the hole.

Thus, with purifiers 242 located at the same preheater distance 230 from mold 212 and purifiers 142 shown in FIG. 1, the solid shell 228 of the initial ingot 216 may be subject to greater heat from the molten metal core 224 than that shown in FIG. 1, since the difference between the distance 232 to the molten metal and the distance 230 to the preheater is greater.

The mixing intensity and/or volume of flow 246 may be controlled by controller 238 coupled to any associated actuators (eg, flow controller 240). In some cases, controller 238 may perform operations based on a preset procedure. In some cases, controller 238 may perform operations based on dynamic feedback from the casting process, such as temperature measurements obtained by sensor 244. Sensor 244 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 244 shown in FIG. 2 is shown next to the hard shell 228 to measure the surface of the hard shell 228, but this is not necessary. In some cases, the sensor(s) may be placed in other locations and may perform other measurements of the ingot, such as crater temperature or coolant temperature.

In fig. 3 is a partial cross-sectional view of a high-mix controlled flow metal casting system 300 in accordance with certain aspects of the present invention. Various aspects of the metal casting system 300 may be similar to aspects of the metal casting system 100 shown in FIG. 1, depending on the circumstances. Metal source 302 may supply molten metal through feed pipe 304, through flow controller 340 from nozzle 306. Flow controller 340 may provide increased flow from metal source 302 to molten metal core 324. This increased flow of molten metal through the feed pipe 304 may result in an increased flow 346 within the molten metal core 324.

This increased flow 346 can provide intense mixing and can act as a jet capable of disrupting part of the solidification boundary 326. The jet may create a depression in the solid shell 328 and a solidification boundary 326 at the bottom of the metal well (eg, the lowest portion of the liquid metal core 324). The intensity of the flow 346, and therefore the resulting jet, can be controlled to achieve the desired recess shape. If the flow is too low, a recess may not form, or the recess may have a small diameter. If the flow is too intense, the diameter of the recess may be too large. However, the desired recess may have a diameter that matches the diameter of the bottom of the well, resulting in the well having a smooth, flowing shape. The dimple shape may promote the flow of molten metal up the sides of the solidification boundary 326, which may assist in removing expelled impurities and hydrogen from the solidification boundary 326, as well as re-suspending the grains and improving the grain structure to produce finer grains.

The mixing intensity and/or volume of flow 346 can be controlled by a controller 338 coupled to any associated actuators (eg, flow controller 340). In some cases, controller 338 may perform operations based on a preset procedure. In some cases, controller 338 may perform operations based on dynamic feedback from the casting process, such as temperature measurements obtained by sensor 344. In some cases, feedback from sensor 344 may be used to determine the solid boundary profile (e.g., the shape of the solid boundary) and performing actions to achieve or maintain the required solidification boundary profile. Sensor 344 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 344 shown in FIG. 3 is depicted next to the hard shell 328 to measure the surface of the hard shell 328, but this is not necessary. In some cases, the sensor(s) may be placed in other locations and may perform other measurements of the ingot, such as crater temperature or coolant temperature.

In fig. 4 is a partial cross-sectional view of a variable flow intensive mixing metal casting system 400 with multiple feed tubes in accordance with certain aspects of the present invention. The metal casting system 400 may be similar to the metal casting system 300 shown in FIG. 3. The metal source 402 may supply molten metal through multiple feed pipes 404, 450, 454. As shown in FIG. 4, three feed pipes are used, although any number of feed pipes may be used. Each supply pipe 404, 450, 454 may be associated with a flow controller 440, 456, 452, respectively. Flow controllers 440, 456, 452 are depicted as needle valves, although any suitable flow controller can be used. When multiple feed pipes 404, 450, 454 are used to supply molten metal to the molten metal core 424, increasing the flow 446 can be achieved by reducing the flow through one or more feed pipes (e.g., feed pipes 450, 454) and increasing the flow through one or more remaining feed pipes (eg, feed pipe 404). As shown in FIG. 4, flow controllers 452 and 456 are closed while flow controller 440 is open, allowing more fluid to flow through the central feed pipe 404, thereby creating increased flow 446 within the molten metal core 424.

This increased flow 446 can provide intense mixing and can act as a jet capable of disrupting part of the solidification boundary 426. The jet may create a depression in the solid shell 428 and a solidification boundary 426 at the bottom of the metal well (eg, the lowest portion of the liquid metal core 424). The intensity of the flow 446, and therefore the resulting jet, can be controlled (eg, by actuating any of the flow controllers 452, 440, 456) to achieve a desired recess shape. If the flow is too low, a recess may not form, or the recess may have a small diameter. If the flow is too intense, the diameter of the recess may be too large. However, the desired recess may have a diameter that matches the diameter of the bottom of the well, resulting in the well having a smooth, flowing shape. The dimple shape may promote the flow of molten metal up the sides of the solidification boundary 426, which may help remove expelled impurities and hydrogen from the solidification boundary 426, as well as re-suspend the grains and improve the grain structure to produce finer grains.

The mixing intensity and/or volume of flow 446 can be controlled by controller 438 coupled to any appropriate actuators (eg, flow controllers 440, 452, 456). In some cases, the controller 438 may perform operations based on a preset procedure. In some cases, controller 438 may perform operations based on dynamic feedback from the casting process, such as temperature measurements obtained by sensor 444. In some cases, feedback from sensor 444 may be used to determine the solid boundary profile (e.g., the shape of the solid boundary) and performing actions to achieve or maintain the required solidification boundary profile. Sensor 444 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 444 shown in FIG. 4 is shown next to the hard shell 428 to measure the surface of the hard shell 428, but this is not necessary. In some cases, the sensor(s) may be placed in other locations and may perform other measurements of the ingot, such as crater temperature or coolant temperature.

In fig. 5 is a partial cross-sectional view of a magnetic stirring metal casting system 500 in accordance with certain aspects of the present invention. The metal casting system 500 may be similar to the metal casting system 300 shown in FIG. 3. Metal source 502 may supply molten metal through feed pipe 504 from nozzle 506. In some cases, a flow controller may be used, although not shown in FIG. 5.

Non-contact magnetic stirrers 560 are positioned adjacent to the molten metal core 524 to create surface flow 566, 568. Non-contact magnetic stirrers 560 may be electromagnetic or permanent magnets. For example, a non-contact permanent magnet magnetic stirrer 560 may be positioned on opposite sides of the feed pipe 504 and may be rotated in suitable directions 562, 564 to create a surface flow 566, 568 towards the feed pipe 504. This surface flow 556, 568 may interact with the molten metal. , flowing from the supply pipe 504, and provide increased flow 546 within the molten metal core 524.

This increased flow 546 can provide intense mixing and can act as a jet capable of disrupting part of the solidification boundary 526. The jet may create a depression in the solid shell 528 and a solidification boundary 526 at the bottom of the metal well (eg, the lowest portion of the liquid metal core 524). The intensity of the flow 546, and therefore the resulting jet, can be controlled to achieve the desired recess shape. If the flow is too low, a recess may not form, or the recess may have a small diameter. If the flow rate is too high, the diameter of the recess may be too large. However, the desired recess may have a diameter that matches the diameter of the bottom of the well, resulting in the well having a smooth, flowing shape. The dimple shape may promote the flow of molten metal up the sides of the solidification boundary 526, which may assist in removing expelled impurities and hydrogen from the solidification boundary 526, as well as re-suspending the grains and improving the grain structure to produce finer grains.

The stirring intensity and/or volume of flow 546 can be controlled by a controller 538 coupled to any appropriate drives (eg, touchless stirrers 560). In some cases, the controller 538 may perform operations based on a preset procedure. In some cases, controller 538 may perform operations based on dynamic feedback from the casting process, such as temperature measurements obtained by sensor 544. In some cases, feedback from sensor 544 may be used to determine the solid boundary profile (e.g., the shape of the solid boundary) and performing actions to achieve or maintain the required solidification boundary profile. Sensor 544 may be any suitable temperature sensor, such as a contact or non-contact sensor. Sensor 544 shown in FIG. 5 is shown next to the hard shell 528 to measure the surface of the hard shell 528, but this is not necessary. In some cases, the sensor(s) may be placed in other locations and may perform other measurements of the ingot, such as crater temperature or coolant temperature.

In fig. 6 is an enlarged schematic view of the bottom of a melt well 600 without vigorous stirring. The bottom of the melt core 624 and solidification boundary 626, as well as the adjacent portion of the solid shell 628, may take on an uneven, built-up shape, which may be due to the release of suspended grains, as well as other factors. As a result, the molten metal may stagnate somewhat near this area. This lower region of the melt well may have a width 670, which may be approximately defined between the regions where the sloping walls of the solidification boundary 626 reach their maximum depth.

In fig. 7 is an enlarged schematic view of the bottom of a melt well 700 undergoing intense agitation, in accordance with certain aspects of the present invention. The bottom of the molten metal core 724 and solidification boundaries 726, as well as the adjacent portion of the solid shell 728, may have a flat, U-shaped, or parabolic profile due to the increased molten metal flow 746. The molten metal flow 746 may erode a recess 774 in the solidification boundary 726 and solid shell 728. This recess 774 may have a depth 772 extending from the bottom of the premix well (e.g., as seen in FIG. 6) to the bottom of the recess 774 during mixing (e.g. , as seen in Fig. 7). Recess 774 may have a diameter 770 (eg, largest diameter) approximately equal to the diameter of the premix well (eg, diameter 670 in FIG. 6).

The molten metal flow 746 can be controlled to erode the solidification boundary 726 at least at or near the bottom of the solidification boundary 726 to a thickness on the order of several millimeters, such as about 1 mm to 5 mm, or at or less than about 10 mm. In some cases, the flow 746 can be controlled to erode the solidification boundary 726 at at least the bottom or near the bottom of the solidification boundary 726 to a thickness equal to or less than about 20 mm, 19 mm, 18 mm, 17 mm, 16 mm, 15 mm, 14mm, 13mm, 12mm, 11mm, 10mm, 9mm, 8mm, 7mm, 6mm, 5mm, 4mm, 3mm, 2mm or 1mm. In fig. 8 is a flow diagram depicting an in situ particulate separation method 800 in accordance with certain aspects of the present invention. At block 802, molten metal is fed into the mold. At initial block 804, the ingot formed in the mold is advanced in the casting direction. At block 806, heat is continuously removed from the shell between the bottom of the mold where the initial ingot exits the mold and the reheat point. At block 808, the initial ingot is reheated. Reheating may begin at the reheating location. In some cases, reheating may include removing the coolant supplied to the surface of the initial ingot at block 806. At block 810, the initial ingot may be maintained at the reheating temperature for a period of time, such as about 3 hours. In some cases, instead of holding the ingot at the reheat temperature, the ingot is allowed to gradually cool in block 812. The ingot may be gradually cooled to room temperature, for example, over a period of time of at least about 3 hours.

In some cases, shuffle may be further invoked at block 816. The stirring may be caused to improve various characteristics of the cast ingot, as well as to reduce the depth of the melt well, which affects the reheat performed at block 808.

In some cases, temperature control may additionally be performed at block 814. The results of the temperature control may be used to adjust the amount of agitation caused at block 816 and/or the reheat position used in relation to block 808. Temperature control at block 814 may be performed continuously .

In fig. 9 is a flow diagram depicting a method 900 for creating a high-strength zone of separated dispersed particles in a continuous casting ingot, in accordance with certain aspects of the present invention. At block 902, an initial bar may be formed or begin to form. At block 904, at least a portion of the inner molten core of the initial ingot may solidify to form a solid shell of the initial ingot. At block 906, a high-strength zone of separated dispersed particles may be continuously formed.

Continuously forming a high-strength zone of separated particulate matter in block 906 may include reheating the outer solid shell in block 908 at a distance from the preheater. In some cases, the temperature of the ingot may be measured at block 910. This measurement may be used to adjust the distance to the preheater at block 912 and/or to adjust the distance to the molten metal at block 916. Adjusting the distance to the preheater at block 912 may involve moving the preheater (eg , purifier) at block 914. Adjusting the distance to the molten metal at block 916 may involve inducing agitation at block 918.

In fig. 10 is a schematic cross-sectional side view of ingot 1016 depicting high strength zone 1074 in accordance with certain aspects of the present invention. The high strength zone 1074 is depicted as extending from the surface or near the surface of the ingot 1016 to a surface depth that is less than half the way from the surface of the ingot 1016 to the longitudinal centerline 1016 of the ingot 1016.

In fig. 11 is a schematic top cross-sectional view of an ingot 1116 depicting a high strength zone 1174 in accordance with certain aspects of the present invention. The high strength zone 1174 is depicted as extending from or near the surface (e.g., the rolling surface and/or side surface) of the ingot 1016 to the depth of the surface less than half the way from the surface of the ingot 1116 to the corresponding center lines, such as from the rolling surface of the ingot 1116 to the side centerline 1180 and from the side surface of the ingot 1116 to the center line 1178 of the rolling surface.

In fig. 12 is a flow diagram depicting a method 1200 for producing a continuous stir casting ingot in accordance with certain aspects of the present invention. At block 1202, molten metal may be delivered to the mold. At block 1204, an outer solid shell may be formed as heat is removed from the molten metal. At block 1206, the ingot may be advanced from the mold at casting speed. At block 1208, the stirring intensity can be determined using the casting speed. The stirring intensity may be based on the measured or otherwise known casting speed. At block 1210, mixing may be induced at an intensity determined at block 1208. Inducing mixing may involve the use of a flow controller and/or non-contact stirrers, although other methods may be used. At block 1212, the casting speed may be changed. After changing the casting speed, the stirring intensity can be again determined at block 1208 based on the updated casting speed from block 1212. Stirring can then be induced at the newly determined intensity. At optional block 1214, the temperature of the starting ingot can be controlled. After monitoring the temperature of the ingot, the stirring intensity at block 1208 can again be determined, at least in part, also based on the temperature measured at block 1214. Stirring can then be induced at the newly determined intensity.

At an optional block 1216, a high-strength zone of particulate ejecta may be continuously formed, as described herein.

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

EXAMPLE 1 - ANALYSIS OF INGOTS

Several different aluminum alloy ingots were produced, including a master ingot and reference ingots made in accordance with the methods described herein where stirring was induced during casting. All ingots were aluminum alloys of the 7xxx series.

The reference ingot had a composition of 0.08 wt. % Si, 0.15 wt. % Fe, 1.58 wt. % Cu, 0.02 wt. % Mn, 2.52 wt. % Mg, 0.193 wt. % Cr, 0.01 wt. % Ni, 5.61 wt. % Zn, 0.012 wt. % V, 0.019 wt. % Ti, 0.001 wt. % Ca, 0.010 wt. % Zr and the rest of aluminum. The reference ingot was cast using conventional DC casting followed by a conventional homogenization process. Sections 2.54 cm (1 in.) thick were obtained at casting lengths of 127 cm, 254 cm, and 381 cm (50 in., 100 in., and 150 in.) and analyzed as described below.

The ingot of the first sample had a composition of 0.09 wt. % Si, 0.20 wt. % Fe, 1.45 wt. % Cu, 0.04 wt. % Mn, 2.35 wt. % Mg, 0.20 wt. % Cr, 0.004 wt. % Ni, 5.45 wt. % Zn, 0.019 wt. % V, 0.03 wt. % Ti, 0.005 wt. % Ca, 0.010 wt. % Zr and the rest of aluminum. The first sample ingot was cast using non-contact mixing as described herein, followed by homogenization at 480°C for 4 hours. The comparative first sample ingot was cast using non-contact stirring as described herein, without homogenization, so that as-cast properties could be assessed. Sections 2.54 cm (1 in.) thick were obtained at casting lengths of 127 cm, 254 cm, and 381 cm (50 in., 100 in., and 150 in.) and analyzed as described below.

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

Cross sections of 2.54 cm (1 inch) thick sections of reference ingot 1300 and first sample ingot 1350 are shown in FIG. 13A and FIG. 13 V accordingly. The sections of the reference ingot 1300 had a width 1301 of about 1690 mm and a thickness 1302 of about 602 mm; The sections of the reference ingot 1350 had a width 1351 of about 1750 mm and a thickness of 1352 about 519 mm. Analysis of the reference ingot 1300 and the first sample ingot 1350 was performed using a grid of sampling locations ranging from 9 columns (columns 1-9) and 4 rows (rows A-D). The fifth row E of reference ingot 1300 was not fully analyzed because this row was partially cut off and was located at the edge of reference ingot 1300. The sampling locations in reference ingot 1300 were approximately 45 mm in diameter, with position 9A corresponding to the center of reference ingot 1300 and first ingot 1350 sample. In reference ingot 1300, the column 1 sampling points were located about 30 mm from the edge, and the column 1 sampling points were located about 58 mm from the edge of the first sample ingot 1350. The columns in the 1300 reference ingot were spaced about 62 mm apart and the rows in the 1300 reference ingot were spaced about 42 mm apart. The columns in the first sample ingot 1350 were spaced about 61 mm apart, and the rows in the first sample ingot 1350 were spaced about 28 mm apart.

The macrosegregation of Fe, Zn, Cr, Mg and Cu at the sampling sites for the reference ingot 1300 and the first sample ingot 1350 was analyzed using X-ray fluorescence (XRF; x-ray fluorescence) spectrometry. For each of the ingot cuts of the first sample (127 cm, 254 cm and 381 cm (50 inch, 100 inch, 150 inch)), the compositions of Fe, Zn, Cr, Mg and Cu were predominantly stable in rows A-D and columns 1-9.

The reference ingot exhibited significant macrosegregation for most of these elements. Graphs showing the compositions of Fe, Zn, Cr, Mg and Cu for a 254 cm (100 inch) section of a reference ingot as a function of position are presented in FIG. 14. In contrast, macrosegregation in the first sample ingot was limited. Graphs showing the compositions of Fe, Zn, Cr, Mg and Cu for a 254 cm (100 inch) section of the first sample ingot as a function of position are presented in FIG. 15.

However, since the first sample ingot was homogenized after casting, the first comparative sample ingot was also analyzed for composition in the same manner to evaluate macrosegregation in the cast ingot before homogenization. While the concentrations of Fe, Zn, Cr, Mg and Cu were slightly different between the first sample ingot and the first comparative ingot, macrosegregation was similarly limited in the first comparative ingot, indicating that non-contact stir casting can be beneficial for restrictions on macrosegregation. Graphs showing the compositions of Fe, Zn, Cr, Mg and Cu for a 254 cm (100 inch) section of the first comparative sample ingot as a function of position are presented in FIG. 16.

The porosity of the reference ingot and the first sample ingot was also characterized by scanning a three-dimensional surface profiler along the cut surfaces of the ingots and identifying areas where the surface profile had depressions greater than a given depth in the form of a pore. Total porosity plots for each of the reference ingot and first sample ingot sampling locations on 100-inch slices are shown in FIG. 17 and fig. 18 respectively. The reference ingot showed greater porosity than the first sample ingot.

The grain structure of the reference ingot and the first sample ingot was also characterized. Optical micrographs were obtained for each sampling location to evaluate grain structure. Both ingots exhibited relatively larger primary AI grain structures towards the center of the ingot and relatively finer grain structures towards the surface of the ingot. Precipitations along grain boundaries and small precipitations of MgZn ₂ were observed in the reference ingot and the ingot of the first sample. In the ingot of the first comparative sample, a large proportion of precipitates was observed at the grain boundaries.

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. DSC data showed clear presence of low temperature melting phases (eg MgZn ₂ and Al ₂ CuMg) at positions closer to the surface (eg rows B, C and D), while positions closer to the center of the ingot (eg row A) did not showed signs of low-temperature melting according to DSC data. However, XRD data showed the presence of MgZn ₂ , possibly as fine precipitates at positions closer to the center of the ingot (eg row A). XRD and DSC data for the first comparative ingot showed the presence of several low temperature melting phases, including MgZn ₂ , Al ₂ MgC and Mg ₂ Si, including at positions close to the center of the ingot.

Samples of rolled sheet metal from the second sample ingot were subjected to mechanical tests for analysis. Rolled sheet metal was prepared in two states: a T6 hardness state and a T6 hardness state followed by paint annealing (T6+PB). Samples were evaluated from the center and from both edges of the ingot. Samples from the center of the T6 hardness state were evaluated in the transverse (T), longitudinal (L) and diagonal (D) directions. Edge samples and T6 + PB samples were evaluated only in the longitudinal direction. Measured properties, mean yield stress (YS; yield stress) (0.2% displacement), mean maximum tensile stress (TS; tensile stress), mean maximum axial strain (AS; axial strain) and mean uniform elongation (UE; uniform elongation ) are summarized in the graph shown in FIG. 19.

ILLUSTRATIVE ASPECTS

As used below, any reference to a number of aspects should be understood as a reference to each of those examples individually (for example, “Aspects 1-4” should be understood as “Aspects 1,2,3 or 4”).

Aspect 1 is a method, such as a casting method, including: supplying molten metal to a mold and forming an initial ingot containing an outer hard shell and an inner molten core; advancing the initial ingot in the direction of advancement away from the mold while simultaneously feeding additional molten metal into the mold; removing heat from the initial ingot between the mold and the transition point by directing the supply of liquid coolant to the outer surface of the outer hard shell; and reheating the initial ingot at the transition location such that at least a portion of the outer hard shell of the initial ingot at the transition location reaches a temperature suitable for particulate release and below the homogenization temperature of the molten metal, wherein the transition location lies in a plane perpendicular to the direction of advancement and crossing the inner molten core.

Aspect 2 is a method according to any preceding or subsequent aspect, characterized in that the temperature, for example in degrees Celsius, is from 80% to 90% of the homogenization temperature, for example in degrees Celsius, of the molten metal.

Aspect 3 is a method according to any preceding or subsequent aspect, characterized in that the temperature, for example in degrees Celsius, is from 85% to 90% of the homogenization temperature, for example in degrees Celsius, of the molten metal.

Aspect 4 is a method according to any preceding or subsequent aspect, characterized in that the temperature is from 400°C to 460°C.

Aspect 5 is a method according to any preceding or subsequent aspect, characterized in that the temperature is from 410°C to 420°C.

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

Aspect 7 is a method according to any preceding or subsequent aspect, characterized in that reheating the initial ingot includes removing liquid coolant from the outer surface of the outer hard shell.

Aspect 8 is a method according to any preceding or subsequent aspect, wherein reheating the initial ingot further includes applying heat to the outer surface of the outer hard shell in addition to latent heating from the inner molten core.

Aspect 9 is a method according to any preceding or subsequent aspect, further comprising: measuring the temperature of the starting ingot; and dynamically adjusting junction location based on temperature measurements.

Aspect 10 is a method according to any preceding or subsequent aspect, further comprising: causing mixing of the inner molten core near 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: taking temperature measurements of the initial ingot, wherein inducing stirring in the internal molten core includes dynamically adjusting stirring intensity based on the temperature measurements.

Aspect 12 is a method according to any preceding or subsequent aspect, characterized in that the transition location is selected such that the plane intersects the initial ingot in a cross section where the outer hard shell of the initial ingot occupies approximately one-third of a line extending from the outer surface to the center of the initial ingot within the plane.

Aspect 13 is a method according to any preceding or subsequent aspect, characterized in that the transition location is selected such that the plane intersects the initial ingot in a cross section where the outer hard shell of the initial ingot occupies no more than 50% of a line extending from the outer surface to the center initial ingot within the plane.

Aspect 14 is a method according to any of the preceding or following aspects, characterized in that the molten metal is a 7xxx series aluminum alloy.

Aspect 15 is a method including: forming an initial ingot by feeding molten metal into a mold and removing heat from the molten metal to form an outer hard shell; solidifying the inner molten core of the seed ingot as the seed ingot is advanced in a direction away from the mold and additional molten metal is supplied to the mold, wherein solidifying the inner molten core involves removing heat from the inner molten core through the outer solid shell; and continuously forming a high-strength zone within the outer hard shell on a cross-section of the initial ingot perpendicular to the advance direction and intersecting the inner molten core, wherein the high-strength zone is located between the outer surface of the outer hard shell and the inner molten core, wherein the formation of the high-strength zone includes reheating the outer solid shell in cross section to induce the release of dispersed particles in the outer hard shell.

Aspect 16 is a method according to any preceding or subsequent aspect, wherein reheating the outer solid shell in cross section includes reheating a portion of the outer solid shell to a temperature suitable for releasing particulates, the temperature being below the homogenization temperature of the molten metal.

Aspect 17 is a method according to any preceding or subsequent aspect, characterized in that the temperature, for example in degrees Celsius, is from 80% to 98% of the homogenization temperature, for example in degrees Celsius, of the molten metal.

Aspect 18 is a method according to any preceding or subsequent aspect, characterized in that the temperature is from 85% to 90% of the homogenization temperature of the molten metal.

Aspect 19 is a method according to any preceding or subsequent aspect, characterized in that the temperature is from 400°C to 460°C.

Aspect 20 is a method according to any preceding or subsequent aspect, characterized in that the temperature is from 410°C to 420°C.

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

Aspect 22 is a method according to any preceding or subsequent aspect, characterized in that removing heat from the inner molten core through the outer solid shell includes applying liquid coolant to an outer surface of the outer shell, and wherein reheating the outer hard shell includes removing liquid coolant from the outer shell. surface of the outer hard shell.

Aspect 23 is a method according to any preceding or subsequent aspect, wherein reheating the outer hard shell further includes applying heat to the outer surface of the outer hard shell in addition to latent heating from the inner molten core.

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

Aspect 25 is a method according to any preceding or subsequent aspect, further comprising: causing mixing of the inner molten core near the interface between the inner molten core and the outer solid shell.

Aspect 26 is the method of any preceding or subsequent aspect, further comprising: taking temperature measurements of the starting ingot; wherein inducing stirring in the inner molten core involves dynamically adjusting stirring intensity based on temperature measurements.

Aspect 27 is a method according to any preceding or subsequent aspect, characterized in that, in cross-section, the outer hard shell of the starting ingot occupies approximately one-third of a line extending from the outer surface to the center of the starting ingot.

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

Aspect 29 is a method according to any of the preceding or following aspects, characterized in that the molten metal is a 7xxx series aluminum alloy.

Aspect 30 is a method according to any preceding or subsequent aspect, characterized in that the high strength zone includes a higher concentration of particulate matter than the rest of the outer hard shell.

Aspect 31 is an aluminum metal product comprising: a solidified aluminum alloy mass having two ends and an outer surface, the solidified aluminum alloy mass comprising: a core region containing a center of the solidified aluminum alloy mass; an outer region including an outer surface; and a high-strength zone located between the core region and the outer region, wherein the high-strength zone has a higher particulate concentration than each of the core region and the outer region.

Aspect 32 is an aluminum metal product according to any preceding or subsequent aspect, characterized in that the mass of solidified aluminum alloy contains residual heat from the continuous mold casting process.

Aspect 33 is the aluminum metal product of any preceding or subsequent aspect, characterized in that the high strength zone is located at a depth of approximately one-third of a line extending from the outer surface to the center of the solidified aluminum alloy mass along a cross-section of the solidified aluminum alloy mass.

Aspect 34 is the aluminum metal product of any preceding or subsequent aspect, characterized in that the high strength zone is located at a depth of no more than half a line extending from the outer surface to the center of the mass of the solidified aluminum alloy along a cross-section of the mass of the solidified aluminum alloy.

Aspect 35 is an aluminum metal product according to any preceding or subsequent aspect, characterized in that the mass of solidified aluminum alloy is cylindrical in shape.

Aspect 36 is an aluminum metal product according to any preceding or subsequent aspect, characterized in that a cross-section of the solidified aluminum alloy body perpendicular to the casting direction of the solidified aluminum alloy body is rectangular in shape.

Aspect 37 is an aluminum metal product according to any preceding or subsequent aspect, characterized in that the mass of solidified aluminum alloy is the mass of solidified aluminum alloy of the 7xxx series.

Aspect 38 is an aluminum metal product of any preceding or subsequent aspect, manufactured in accordance with the method of any preceding or subsequent aspect.

Aspect 39 is an initial ingot containing: a liquid molten aluminum alloy core extending from the top surface to the solidification line; and a solidified shell of aluminum alloy, wherein the solidified shell has an outer surface extending from the solidification boundary to a lower end in the casting direction, wherein the solidified shell contains a high-strength zone located between the outer surface and a center line extending in the casting direction through the center of the liquid molten the core and center of the hardened shell, with the high-strength zone having a higher concentration of dispersed particles than the rest of the hardened shell.

Aspect 40 is the initial ingot of any preceding or subsequent aspect, characterized in that the high strength zone is located at a depth of approximately one third of a line extending from the outer surface to the centerline.

Aspect 41 is the initial ingot of any preceding or subsequent aspect, characterized in that the high strength zone is located at a depth of no more than half a line extending from the outer surface to the centerline.

Aspect 42 is the initial ingot of any preceding or subsequent aspect, characterized in that the solidified shell is cylindrical in shape.

Aspect 43 is the initial ingot of any preceding or subsequent aspect, characterized in that the cross-section of the solidified shell perpendicular to the casting direction is rectangular in shape.

Aspect 44 is the initial ingot of any preceding or subsequent aspect, characterized in that the aluminum alloy is a 7xxx series aluminum alloy.

Aspect 45 is the initial ingot of any preceding or subsequent aspect, manufactured in accordance with the method of any preceding or subsequent aspect.

Aspect 46 is a method comprising: supplying molten metal from a metal source to a metal well of a starting ingot being cast into a mold; forming an outer hard shell of solidified metal by removing heat from the metal hole, with the solidification boundary located between the outer hard shell and the metal hole; advancing the initial ingot in the direction of advancement from the mold at a casting speed while supplying molten metal and forming an outer hard shell; determining the stirring intensity using the casting speed, wherein the stirring intensity is suitable to achieve the target solidification boundary profile at the casting speed; and inducing stirring within the melt well at a certain intensity, wherein stirring within the melt well induces the solidification boundary to adopt a target solidification boundary profile at the casting speed.

Aspect 47 is a method according to any preceding or subsequent aspect, characterized in that inducing stirring involves applying stirring forces to the molten metal in the metal well using a non-contact magnetic stirrer.

Aspect 48 is a method according to any preceding or subsequent aspect, characterized in that feeding molten metal includes feeding molten metal at a mass flow rate through a plurality of nozzles, and wherein inducing mixing includes increasing the flow rate of molten metal through at least one of the plurality of nozzles while maintaining the mass flow rate through the set of nozzles.

Aspect 49 is a method according to any preceding or subsequent aspect, further comprising: changing the casting speed; determining an updated stirring intensity using the updated casting speed, wherein the updated stirring intensity is appropriate to achieve a target solidification profile at the updated casting speed; and inducing mixing within the melt well at the updated intensity, wherein inducing mixing within the melt well at the updated intensity causes the solidification boundary to adopt a target solidification boundary profile at the updated casting speed.

Aspect 50 is a method according to any preceding or subsequent aspect, characterized in that the molten metal is a 7xxx series aluminum alloy.

Aspect 51 is the method of any of the preceding or subsequent aspects, further comprising measuring the temperature of the starting ingot, wherein determining the intensity of stirring using the casting speed includes using the measured temperature.

Aspect 52 is a method according to any preceding or subsequent aspect, characterized in that the target solidification boundary profile is predetermined to minimize the risk of cracking.

Aspect 53 is a method according to any preceding or subsequent aspect, further comprising: continuously forming a high-strength zone within the outer hard shell in a cross-section of the initial ingot that is perpendicular to the direction of advance and which intersects the inner molten core, the high-strength zone located between the outer surface of the outer hard shell shell and an inner molten core, and wherein forming a high strength zone includes reheating the outer hard shell in cross section to induce the release of dispersed particles in the outer hard shell.

Aspect 54 is a method according to any preceding or subsequent aspect, characterized in that inducing agitation within the melt well includes controlling the flow of molten metal into the metal well such that the jet of molten metal destroys a depression at the solidification boundary at the bottom of the metal well, wherein the depression has a diameter the size of which corresponds to the diameter of the bottom of the metal hole.

Aspect 55 is a method comprising: supplying molten metal from a metal source to a metal well of a starting ingot being cast into a mold; forming an outer hard shell of solidified metal by removing heat from the metal hole, with the solidification boundary located between the outer hard shell and the metal hole; advancing the initial ingot in the direction of advancement from the mold at a casting speed while supplying molten metal and forming an outer hard shell; and controlling the flow of molten metal into the metal well to create a jet of molten metal sufficient to destroy at least a portion of the solidification boundary at the bottom of the metal well.

Aspect 56 is a method according to any preceding or subsequent aspect, characterized in that controlling the supply of molten metal includes controlling the supply of molten metal such that the jet of molten metal erodes the solidification boundary to a thickness equal to or less than 10 mm.

Aspect 57 is a method according to any preceding or subsequent aspect, wherein supplying molten metal includes supplying molten metal at a mass flow rate through a plurality of nozzles, and wherein creating a jet of molten metal includes increasing the flow rate of molten metal through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles.

Aspect 58 is the method of any of the preceding or following aspects, further comprising applying stirring forces to the molten metal in the metal well using a non-contact magnetic stirrer.

Aspect 59 is a method according to any preceding or subsequent aspect, further comprising varying the casting speed, wherein controlling the supply of molten metal includes dynamically adjusting the supply of molten metal based on the changed casting speed such that the jet of molten metal continues to erode at least a portion of the solidification boundary at the bottom of the metal hole.

Aspect 60 is a method according to any preceding or subsequent aspect, characterized in that the molten metal is a 7xxx series aluminum alloy.

Aspect 61 is a method according to any preceding or subsequent aspect, further comprising measuring the temperature of the initial ingot, wherein controlling the supply of molten metal includes dynamically adjusting the supply of molten metal based on the measured temperature such that the stream of molten metal continues to destroy at least a portion of the solidification boundary at the bottom of the metal hole.

Aspect 62 is a method according to any preceding or subsequent aspect, further comprising: continuously forming a high-strength zone within the outer hard shell in a cross-section of the initial ingot that is perpendicular to the direction of advance and which intersects the metal dimple, wherein the high-strength zone is located between the outer surface of the outer hard shell and a metal dimple, wherein forming the high strength zone involves reheating the outer hard shell in cross section to induce release of particulate matter in the outer hard shell.

Aspect 63 is an aluminum metal product manufactured in accordance with the methods of any preceding or subsequent aspect.

Aspect 64 is an initial ingot comprising: a solidified aluminum alloy shell extending from the solidification boundary to a lower end in the casting direction; and a liquid molten aluminum alloy core extending from the top surface to a solidification boundary, the liquid molten core including a jet of aluminum alloy impinging on the solidification boundary for days of the liquid molten core forming a depression at the solidification boundary.

Aspect 65 is the initial ingot of any preceding or subsequent aspect, characterized in that the liquid molten core includes re-suspended grains from the solidification boundary.

Aspect 66 is the initial ingot of any preceding or subsequent aspect, characterized in that the liquid molten core includes re-suspended hydrogen from the solidification boundary.

Aspect 67 is an ingot blank according to any preceding or subsequent aspect, characterized in that the solidified shell comprises a high-strength zone located between the outer surface of the solidified shell and a centerline extending in the casting direction through the center of the liquid molten core and the center of the solidified shell, wherein the high-strength the zone has a higher concentration of dispersed particles than the rest of the solidified shell.

Aspect 68 is the initial ingot of any preceding or subsequent aspect, characterized in that the aluminum alloy is a 7xxx series aluminum alloy.

All patents and publications cited herein are incorporated by reference in their entirety. The foregoing description of embodiments, including the illustrated embodiments, is presented for purposes of illustration and description only and is not intended to be exhaustive or to limit the invention to the specific forms disclosed. Numerous modifications, adaptations and applications thereof will be apparent to those skilled in the art.

Claims (40)

1. A method for continuous casting of aluminum alloy, including: supplying molten aluminum alloy from the aluminum alloy source to the melt well of the initial ingot cast in the mold; forming an outer hard shell of the solidified aluminum alloy by extracting heat from the melt well, wherein a solidification surface is located between the outer hard shell and the melt well; advancing the initial ingot in the direction of advancement from the mold at a casting speed while supplying molten aluminum alloy and forming an outer hard shell; determining the stirring intensity using the casting speed, wherein the stirring intensity is suitable to achieve the target solidification boundary profile at the casting speed; and inducing stirring within the melt well at a certain intensity, wherein inducing stirring within the melt well causes the solidification boundary to adopt a target solidification boundary profile at the casting speed, wherein the supply of molten aluminum alloy is controlled such that the jet of molten aluminum alloy destroys the solidification boundary to a thickness equal to or less than 10 mm. 2. The method according to claim 1, characterized in that inducing stirring involves applying stirring forces to the molten aluminum alloy in the melt well using a non-contact magnetic stirrer. 3. The method of claim 1, wherein feeding the molten aluminum alloy comprises feeding the molten aluminum alloy at a mass flow rate through a plurality of nozzles, and wherein inducing mixing includes increasing the flow rate of the molten aluminum alloy through at least one of the plurality of nozzles at maintaining the mass flow rate through the set of nozzles. 4. The method according to claim 1, additionally including: changing the casting speed; determining an updated stirring intensity using the updated casting speed, wherein the updated stirring intensity is appropriate to achieve a target solidification profile at the updated casting speed; and inducing mixing within the melt well at the updated intensity, wherein inducing mixing within the melt well at the updated intensity causes the solidification boundary to adopt a target solidification boundary profile at the updated casting speed. 5. The method according to claim 1, characterized in that the molten aluminum alloy is an aluminum alloy of the 7xxx series. 6. The method of claim 1, further comprising measuring the temperature of the starting ingot, wherein determining the mixing intensity using the casting speed includes using the measured temperature. 7. Method according to claim 1, characterized in that the target solidification boundary profile is predetermined to minimize the risk of cracking. 8. The method according to claim 1, additionally including: continuous formation of a high-strength zone within the outer hard shell on a cross-section of the initial ingot perpendicular to the direction of advance and intersecting the internal molten core, while the high-strength zone is a region of the ingot having a concentration of dispersed particles exceeding the average concentration of dispersed particles of the entire ingot, and is located between the outer surface a hard shell and an inner molten core, wherein forming a high-strength zone includes reheating the outer hard shell in cross section to induce the release of dispersed particles in the outer hard shell. 9. The method of claim 1, wherein inducing mixing within the melt well includes controlling the supply of molten aluminum alloy into the melt well such that the stream of molten aluminum alloy forms a depression at the solidification boundary at the bottom of the melt well, the depression having diameter, the size of which corresponds to the diameter of the bottom of the melt well. 10. A method for continuous casting of aluminum alloy, including: supplying molten aluminum alloy from the aluminum alloy source to the melt well of the initial ingot cast in the mold; forming an outer hard shell of the solidified aluminum alloy by extracting heat from the melt well, wherein a solidification surface is located between the outer hard shell and the melt well; advancing the initial ingot in the direction of advancement from the mold at a casting speed while supplying molten aluminum alloy and forming an outer hard shell; and controlling the supply of molten aluminum alloy to the melt well to create a jet of molten aluminum alloy sufficient to destroy at least a portion of the solidification boundary at the bottom of the melt well, wherein controlling the supply of the molten aluminum alloy includes controlling the supply of the molten aluminum alloy such that the jet of molten aluminum alloy destroys the solidification boundary to a thickness equal to or less than 10 mm. 11. The method of claim 10, wherein supplying the molten aluminum alloy includes supplying the molten aluminum alloy at a mass flow rate through a plurality of nozzles, and wherein creating a jet of molten aluminum alloy includes increasing the flow rate of the molten aluminum alloy through at least one of the plurality of nozzles while maintaining the mass flow rate through the plurality of nozzles. 12. The method according to claim 10, further comprising applying stirring forces to the molten aluminum alloy in the melt well using a non-contact magnetic stirrer. 13. The method of claim 10, further comprising varying the casting speed, wherein controlling the flow of molten aluminum alloy includes dynamically adjusting the flow of molten aluminum alloy based on the changed casting speed such that the jet of molten aluminum alloy continues to erode at least a portion of the solidification boundary at bottom of the melt well. 14. The method according to claim 10, characterized in that the molten aluminum alloy is a 7xxx series aluminum alloy. 15. The method of claim 10, further comprising measuring the temperature of the starting ingot, wherein controlling the supply of molten aluminum alloy includes dynamically adjusting the supply of molten aluminum alloy based on the measured temperature such that the stream of molten aluminum alloy continues to erode at least a portion of the solidification boundary at bottom of the melt well. 16. The method according to claim 10, additionally including: the continuous formation of a high-strength zone within the outer hard shell on a cross-section of the initial ingot perpendicular to the direction of advance and intersecting the melt well, wherein the high-strength zone is an area of the ingot having a particulate concentration greater than the average particulate concentration of the entire ingot and is located between the outer surface the outer hard shell and the melt well, wherein forming the high strength zone includes reheating the outer hard shell in cross section to induce release of particulate matter in the outer hard shell. 17. An initial ingot with a liquid core for the production of a continuously cast ingot of an aluminum alloy, containing: a solidified aluminum alloy shell extending from the solidification boundary to the lower end in the casting direction; and a liquid molten aluminum alloy core extending from the top surface to a solidification boundary, the liquid molten core including a jet of aluminum alloy impinging on the solidification boundary at the bottom of the liquid molten core to form a depression at the solidification boundary, wherein the solidification boundary is destroyed by said jet of molten aluminum alloy to a thickness equal to or less than 10 mm. 18. The initial ingot according to claim 17, characterized in that the liquid molten core contains re-suspended grains from the solidification boundary. 19. The initial ingot according to claim 17, characterized in that the liquid molten core contains re-suspended hydrogen from the solidification boundary. 20. The initial ingot according to claim 17, characterized in that the solidified shell contains a high-strength zone, which is an area of the ingot having a concentration of dispersed particles exceeding the average concentration of dispersed particles of the entire ingot, and is located between the outer surface of the solidified shell and the center line passing in the casting direction through the center of the liquid molten core and the center of the solidified shell. 21. Initial ingot according to claim 17, characterized in that the aluminum alloy is an aluminum alloy of the 7xxx series.