Systems and methods for controlling cracks in cast ingots and increasing casting speed

Abstract

Methods for controlling cracking in an ingot during direct chill casting include introducing molten metal into a mold cavity of a casting mold of a casting system and into a metal sump of the ingot being cast. The method includes creating a plurality of low points in the metal sump. One or more of the low points may be offset from a central axis of the ingot. A casting system may include various means or mechanisms for creating a plurality of low points in the metal sump.

Description

SYSTEMS AND METHODS FOR CONTROLLING CRACKS IN CAST INGOTS AND INCREASING CASTING SPEEDREFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 601,465, filed on November 21, 2023, and entitled SYSTEMS AND METHODS FOR CONTROLLING CRACKS IN CAST INGOTS AND INCREASING CASTING SPEED, the content of which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] This application relates to the casting of metals, and more particularly to systems and methods for controlling crack formation in ingots during casting.BACKGROUND

[0003] In direct chill casting, molten metal is passed into a mold cavity with a false, or moving, bottom. As the molten metal enters the mold cavity, generally from the top, the false bottom lowers at a rate related to the rate of flow of the molten metal. The molten metal that has solidified near the sides can be used to retain the liquid and partially liquid metal in the metal sump. The metal can be 99.9% solid (e.g., fully solid), 100% liquid, and anywhere in between. Traditionally, the metal sump can take on a shape with a single low point, such as a V-shape or U-shape, or a flat sump, due to the increasing thickness of the solid regions as the molten metal cools, and a single low point is generally defined in the metal sump, commonly along the center axis of the ingot. The interface between the solid and liquid metal is sometimes referred to as the solidification front. The metal article resulting from the direct chill casting process can be referred to as an ingot. An ingot may have a generally rectangular cross section, although other cross sections may be used, such as circular or even non-symmetric. The term ingot, as used herein, can be inclusive of any direct chill cast metal article, including billets, as appropriate.

[0004] Traditional approaches of forming the metal sump with a single low point create large internal stresses within the ingot due to shrinkage of the material volume as the metal changes from liquid state to solid state in the solidification front. Such large internal stresses often resultin cracks and / or voids within the material, rendering the ingot unsuitable for further production and / or material waste.SUMMARY

[0005] Embodiments covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various embodiments and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings, and each claim.

[0006] According to certain embodiments, a method of controlling cracking in an ingot includes introducing molten metal into a mold cavity of a casting mold of a casting system and to a metal sump of the ingot being cast and creating a plurality of low points in the metal sump.

[0007] According to some embodiments, a method of controlling cracking in an ingot includes delivering molten metal from a metal source to a metal sump of the ingot being cast in a mold and controlling a sump profile to have a plurality of low points.

[0008] According to various embodiments, a direct chill casting system includes an open- ended mold defining a mold cavity for receiving molten metal in a metal sump of an ingot during casting. The direct chill casting system also includes a bottom block configured to initially close a lower end of the open-ended mold and to move away from the lower end during casting as well as a sump control system for creating a plurality of low points in the metal sump.

[0009] Various implementations described herein can include additional systems, methods, features, and advantages, which cannot necessarily be expressly disclosed herein but will be apparent to one of ordinary skill in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within the present disclosure and protected by the accompanying claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The specification makes reference to the following appended figures, in which use of like reference numerals in different figures is intended to illustrate like or analogous components.

[0011] FIG. 1 illustrates a metal casting system with an ingot having an improved solidification front and sump according to embodiments.

[0012] FIG. 2 illustrates a mold for the casting system of FIG. 1 according to embodiments.

[0013] FIG. 3 illustrates a process of casting an ingot according to embodiments.DETAILED DESCRIPTION

[0014] Described herein are systems and methods for controlling a solidification front and sump in an ingot to have a plurality of low points during direct chill casting. Compared to traditional casting systems and methods in which the sump has a single low point, often aligned with the center axis of the ingot, the sump with multiple low points may reduce internal stresses and reduce susceptibility of the ingot to crack formation that traditionally occurs as solidification takes place. In some cases, while traditional approaches may result in crack formation along the center of the ingot (and even after casting has completed), the multiple low points in the sump may decrease susceptibility to cracking by moving any cracks formed in the ingot to the side of the ingot and may heal the cracks, thereby providing an improved cast product compared to traditional approaches. In certain embodiments, creating the sump with multiple low points may also allow for an increased casting speed compared to traditional approaches. The systems and methods described herein may be useful for reducing cracking susceptibility in various metals and may be particularly useful in the casting of aluminums alloys. In certain embodiments, the systems and methods described herein may be utilized for the casting of difficult to cast aluminum alloys, such as but not limited to 7xxx series aluminum alloys. Various other benefits and advantages may be realized with the systems and methods described herein, and the aforementioned benefits and advantages should not be considered limiting.

[0015] FIG. 1 illustrates an example of a direct chill (DC) casting system 100 for forming an ingot 101 according to embodiments. The DC casting system 100 generally includes an open- ended mold 102, a metal supply system 104, and a bottom block 106.

[0016] The mold 102 includes a top end 108, a bottom end 110, and mold walls 112 defining a mold cavity 114. The mold 102 may be surrounded by a cooling jacket through which a coolant 130, such as but not limited to water, is circulated to provide external cooling of the mold walls 112. Optionally, in some embodiments, external cooling may be blocked and / or insulated from the liquid metal. As non-limiting examples, if the ends of the mold are lower than the middle, there may be a deeper pool of metal towards the ends, and it may be advantageous to minimize cooling on the ends of the mold 102 until just before the metal leaves the mold 102. In other embodiments, other control of external cooling may be implemented as desired.

[0017] The bottom block 106 may be initially positioned within or proximate to the bottom end 110 of the mold 102 to close the mold cavity 114 at the bottom end 110. The bottom block 106 may have various shapes or profiles as desired, including but not limited to a flat shape or profile, a non-linear or non-planar (e.g., curved) profile, combinations thereof, and / or as otherwise desired. Optionally, a shape of the bottom block 106 may match and / or be complimentary to a shape of the mold 102. In certain embodiments, the mold cavity 114 may be a generally rectangular shape, although in other embodiments the mold cavity 114 may have various shapes as desired.

[0018] The metal supply system 104 may be various suitable devices or mechanisms for supplying molten metal to the mold cavity 114. The molten metal may be various metals as desired, including but not limited to aluminum, aluminum alloys, steel, or other metals as desired. In some examples, the molten metal may be an aluminum or an aluminum alloy in the Ixxx series, 2xxx series, 3xxx series, 4xxx series, 5xxx series, 6xxx series, 7xxx series, 8xxx series and / or any other aluminum or aluminum alloy as desired.

[0019] In certain embodiments, the metal supply system 104 may include a metal source 116, such as but not limited to a tundish or trough, which may supply molten metal through a spout 118 into the mold cavity 114. Optionally, a flow controller 120 may be included to control the flow of molten metal through the spout 118. Non-limiting examples of flow controllers 120 include, but are not limited to, control pins, magnetic pumps, electric pumps, and / or any suitable device for controlling the flow of molten metal through the spout 118, including increasing the flow, decreasing the flow, and / or terminating the flow. Optionally, a skimming device 122 and / or any other device or mechanism may be provided to facilitate distribution of the molten metal and / or direct the flow of metal. In one non-limiting example, such devices may be below the metal level and may be removed at the end of casting. In some embodiments,metal distribution and / or flow may be utilized to minimize and / or prevent defects and / or other characteristics in the finished product. As non-limiting examples, metal flow may be controlled to distribute pre-solidified particles, which may otherwise have a tendency to settle at a lowest point. Other control of metal flow and / or distribution may be implemented as desired.

[0020] During casting, the molten metal is introduced into the casting cavity 114, and as the molten metal begins to solidify within the mold, the bottom block 106 may be lowered at a casting speed. The ingot 101 emerging from the bottom end 110 of the mold 102 may include an external solid shell 124, a solidifying front 126, and a metal sump 128. In other words, the pool of molten metal within the mold 102 extends downwardly for some distance below the mold 102. In some embodiments, the metal sump 128 may have a progressively decreasing cross-section in the downward direction as the ingot 101 solidifies inwardly from the outer surface 132 of the ingot 101 until its core portion becomes completely solid. In other examples, as the metal changes phases from liquid to solid, the shell wall thickness may decrease for a period of time, which is sometimes referred to as “reheat.” Coolant 130, which may be the same as or different from the coolant 130 used to chill the mold walls 112, may be brought into direct contact with the outer surface 132 of the advancing ingot 101 directly below the mold 102, thereby causing direct chilling of the metal. This direct chilling of the surface 132 of the ingot 101 serves both to maintain the peripheral portion of the ingot 101 in solid state and to promote internal cooling and solidification of the ingot 101.

[0021] In various embodiments, the DC casting system 100 includes a sump control system 136 for creating a plurality of (i.e., two or more) low points 138 in the metal sump 128. While traditional casting techniques create a metal sump with a single low point or line towards a bottom 141 of the ingot 101 (and generally aligned with a center axis 134 of the ingot 101), it has been found that, unexpectedly, creating the plurality of low points 138 reduce internal stresses in the ingot 101 as solidification takes place, thereby reducing susceptibility of the ingot 101 to crack formation. In some embodiments, the plurality of low points 138 may allow for liquid metal in the metal sump 128 to feed voids created as the material volume shrinks while changing from a liquid to solid state. In certain embodiments, creating the plurality of low points 138 may allow for faster casting and therefore more production capability per day.

[0022] In the embodiment illustrated in FIG. 1, the sump control system 136 creates two low points 138 in the metal sump 128 on either side of a raised center portion 139 of the metal sump 128. However, the number of low points 138 and / or the profile of the metal sump 128 with the plurality of low points 138 should not be considered limiting. As a non-limiting example, inother embodiments, the sump control system 136 may create three low points 138, four low points 138, five low points 138, or more than five low points 138 in the metal sump 128. In certain embodiments, at least one of the low points 138 of the plurality of low points 138 may be offset from the center axis 134 of the ingot 101. Optionally, a distance between at least one of the low points 138 of the plurality of low points 138 and the outer surface 132 of the ingot 101 is less than a distance between the particular low point 138 and the center axis 134. In some embodiments, each low point 138 need not have a same distance from the outer surface 132. In one non-limiting example, one or more low points may be proximate to the center axis. In a further non-limiting examples, a plurality of low points may be created in an ingot or billet being cast using a circular mold.

[0023] The sump control system 136 may include various devices or mechanisms for creating the plurality of low points 138 in the metal sump 128. As a non-limiting example, and referring to FIG. 2, the sump control system 136 may include a mold 142 having an arcuate mold surface 144 extending between opposing wall portions 146, 148 of the mold 142. In this embodiment, a height of the mold surface 144 at a center 151 of the mold 142 may be greater than a height of the mold at the wall portions 146, 148, and the mold surface 144 proximate to the wall portions 146, 148 may form the two low points 138 illustrated in FIG. 1 (movement represented by arrow 147). In other embodiments, a geometry or profile of the mold surface 144 may be controlled to create any number of low points 138 as desired and may have various or surfaces as desired, such as but not limited to linear portions, arcuate portions, combinations thereof, etc. Moreover, while the mold 142 is illustrated as generally rectangular, it need not be in other embodiments. As examples, the mold 142 may be circular shaped, oval shaped, and / or as otherwise desired. In such embodiments,

[0024] Additionally, or alternatively, the sump control system 136 may be devices or mechanisms for controlling aspects of the casting process to create the plurality of low points 138 in the metal sump 128. Optionally, the sump control system 136 includes a controller 140 (processor and / or memory) for controlling one or more pieces of equipment and / or processes for creating the plurality of low points 138.

[0025] As a non-limiting example, the sump control system 136 may create the plurality of low points 138 by controlling the casting speed of the casting process. In these examples, the sump control system 136 may be one or more actuators suitable for controlling the vertical position of the bottom block 106 and / or otherwise as desired.

[0026] In another non-limiting example, the sump control system 136 may create the plurality of low points by controlling a location of the spout 118 and / or a number of spouts 118 at a top 150 of the ingot 101. In such embodiments, the sump control system 136 may be one or more actuators for controlling the location of the spout(s) 118 at the top 150, a submergence depth of the spout(s) 118 within the metal sump 128, an arrangement of the spouts 118 at the top 150, combinations thereof, and / or otherwise as desired.

[0027] In another non-limiting example, the sump control system 136 may create the plurality of low points 138 by at least partially controlling the flow rate of molten metal into the metal sump 128. In such embodiments, the sump control system 136 may include the flow controller 120 and / or other actuators for controlling the flow rate (e.g., to increase the flow rate of the molten metal, decrease the flow rate of the molten metal, and / or terminate the flow of the molten metal into the mold 102).

[0028] As another non-limiting example, the sump control system 136 may create the plurality of low points 138 by controlling the application of the coolant 130 on the ingot 101. In such embodiments, the sump control system 136 may include one or more actuators for controlling a coolant flow rate (e.g., by controlling a flow control valve), an angle at which coolant is directed onto the ingot 101, a spray pattern of the coolant on the ingot 101, removal of the coolant from the ingot 101, combinations thereof, and / or as otherwise desired to create the plurality of low points 138.

[0029] In a further non-limiting example, the sump control system 136 may create the plurality of low points 138 by inducing stirring of the molten metal in the metal sump 128. In such embodiments, the sump control system 136 may include actuators for controlling one or more stirrers, such as but not limited to contact stirrers and / or non-contact stirrers (e.g., stirrers that induce stirring without contacting the molten metal). Controlling of the one or more stirrers may include controlling a direction of the stirring, a location of the stirring within the metal sump 128, an intensity of the stirring, combinations thereof, and / or as otherwise desired to create the plurality of low points 138.

[0030] In other embodiments, additional and / or alternative devices, systems, and / or methods may be utilized by the sump control system 136 during the casting process to generate the plurality of low points 138 in the metal sump 128, and the aforementioned examples should not be considered limiting.

[0031] Optionally, the controller 140 may control the sump control system 136 to create and / or control the plurality of low points 138 based on information from one or more sensors monitoring various aspects of the casting process. As a non-limiting example, one or more sensors may be one or more temperature sensors for measuring a temperature of the outer surface 132, a temperature of the metal sump 128, and / or a temperature of the coolant 130, and the controller 140 may control the sump control system 136 based on information from the one or more sensors. As a non-limiting example, based on the temperature of the metal sump 128, the controller 140 may control the mold 142, cooling of the ingot using liquid coolant, delivery of the molten metal into the metal sump 128, and / or stirring of the molten metal to create and / or maintain the plurality of low points 138 and / or otherwise control the profile of the metal sump 128 as desired. In other embodiments, other types of sensors for measuring other characteristics of the casting process may be utilized as feedback for the sump control system 136.

[0032] FIG. 3 illustrates a method of forming a DC cast ingot according to embodiments. In a block 302, the method includes supplying molten metal into the mold 102 of the DC casting system 100. At block 304, the ingot 101 may be formed or may start to form, and at least a portion of the molten metal may be solidified into the sold shell 124.

[0033] At a block 306, the method includes forming the plurality of low points 138 in the metal sump 128 of the ingot 101. In some embodiments, block 306 includes forming the plurality of low points 138 in the metal sump 128 using the mold 142 and / or other molds as desired. Optionally, the geometry and / or profile of the mold surface 144 may be adjusted and / or a mold having a desired geometry and / or profile may be selected to control the creation of the plurality of low points 138. Additionally, or alternatively, block 306 may include forming the plurality of flow points 138 in the metal sump 128 by controlling a stirring of the molten metal using a contact and / or non-contact stirrer. Additionally, or alternatively, block 306 may include forming the plurality of flow points 138 in the metal sump 128 by controlling delivery of the molten metal into the top 150 of the metal sump 128. Controlling delivery of the molten metal may include, but is not limited to, controlling a location of the spout 118, controlling a number of spouts 118, controlling a submergence of the spout 118, controlling a flow rate using the flow controller 120, combinations thereof, and / or as otherwise desired. Additionally, or alternatively, block 306 may include forming the plurality of low points 138 in the metal sump 128 by controlling application of the coolant on the ingot 101. Controlling application of the coolant may include, but is not limited to, controlling a flow rate of the coolant, a location of the coolant on the ingot 101, a spray pattern of the coolant on the ingot 101, a temperature ofthe coolant, combinations thereof, and / or as otherwise desired. Additionally, or alternatively, block 306 may include forming the plurality of flow points 138 in the metal sump 128 by controlling the casting speed. In other embodiments, block 306 includes various controls for creating the plurality of low points 138 in the metal sump 128 as desired.

[0034] A collection of exemplary embodiments is provided below, including at least some explicitly enumerated as an “Illustration” providing additional description of a variety of example embodiments in accordance with the concepts described herein. These illustrations are not meant to be mutually exclusive, exhaustive, or restrictive; and the disclosure not limited to these example illustrations but rather encompasses all possible modifications and variations within the scope of the issued claims and their equivalents.

[0035] Illustration 1. A method of controlling cracking in an ingot, the method comprising: introducing molten metal into a mold cavity of a casting mold of a casting system and to a metal sump of the ingot being cast; and creating a plurality of low points in the metal sump.

[0036] Illustration 2. The method of any preceding or subsequent illustration or combination of illustrations, wherein at least one low point of the plurality of low points is offset from a center axis of the ingot.

[0037] Illustration 3. The method of any preceding or subsequent illustration or combination of illustrations, wherein creating the plurality of low points in the metal sump comprises using a mold.

[0038] Illustration 4. The method of any preceding or subsequent illustration or combination of illustrations, further comprising controlling the plurality of low points by controlling a geometry of a surface of the mold.

[0039] Illustration 5. The method of any preceding or subsequent illustration or combination of illustrations, wherein creating the plurality of low points in the metal sump comprises controlling an application of coolant on the ingot.

[0040] Illustration 6. The method of any preceding or subsequent illustration or combination of illustrations, wherein creating the plurality of low points in the metal sump comprises controlling at least one of a delivery of the molten metal into the metal sump or a casting speed.

[0041] Illustration 7. The method of any preceding or subsequent illustration or combination of illustrations, wherein creating the plurality of low points in the metal sump comprises stirring the molten metal.

[0042] Illustration 8. The method of any preceding or subsequent illustration or combination of illustrations, wherein creating the plurality of low points comprises forming at least three low points.

[0043] Illustration 9. The method of any preceding or subsequent illustration or combination of illustrations, wherein creating the plurality of low points comprises forming at least two low points, wherein a distance between a first low point of the at least two low points and a central axis of the ingot is different from a distance between a second low point of the at least two low points and the central axis of the ingot.

[0044] Illustration 10. A method of controlling cracking in an ingot, the method comprising: delivering molten metal from a metal source to a metal sump of the ingot being cast in a mold; and controlling a sump profile to have a plurality of low points.

[0045] Illustration 11. The method of any preceding or subsequent illustration or combination of illustrations, wherein controlling the sump profile comprises creating at least three low points.

[0046] Illustration 12. The method of any preceding or subsequent illustration or combination of illustrations, wherein controlling the sump profile comprises using a mold comprising an arcuate surface extending between two wall portions of the mold.

[0047] Illustration 13. The method of any preceding or subsequent illustration or combination of illustrations, wherein controlling the sump profile comprises creating the plurality of low points at locations offset from a central axis of the ingot.

[0048] Illustration 14. The method of any preceding or subsequent illustration or combination of illustrations, wherein, for at least one low point of the plurality of low points, a distance between the low point and the central axis of the ingot is greater than a distance between the low point and an outer surface of the ingot.

[0049] Illustration 15. The method of any preceding or subsequent illustration or combination of illustrations, wherein controlling the sump profile comprises controlling at least one of a geometry of a mold, an application of coolant on the ingot, or delivery of the molten metal into the metal sump.

[0050] Illustration 16. A direct chill casting system comprising: an open-ended mold defining a mold cavity for receiving molten metal in a metal sump of an ingot during casting; a bottom block configured to initially close a lower end of the open-ended mold and to move away fromthe lower end during casting; and a sump control system for creating a plurality of low points in the metal sump.

[0051] Illustration 17. The direct chill casting system of any preceding or subsequent illustration or combination of illustrations, wherein the sump control system for creating the plurality of low points in the metal sump comprises a mold with a mold surface configured to create the plurality of low points in the metal sump.

[0052] Illustration 18. The direct chill casting system of any preceding or subsequent illustration or combination of illustrations, wherein the mold surface is an arcuate surface extending between two wall portions of the mold, and wherein a height of the mold surface at a center of the mold is greater than a height of the mold surface at the two wall portions.

[0053] Illustration 19. The direct chill casting system of any preceding or subsequent illustration or combination of illustrations, wherein the sump control system for creating the plurality of low points in the metal sump comprises a coolant system configured to supply liquid coolant to an outer surface of the ingot.

[0054] Illustration 20. The direct chill casting system of any preceding or subsequent illustration or combination of illustrations, wherein the sump control system for creating the plurality of low points in the metal sump comprises a flow controller for controlling a flow and delivery of the molten metal into the metal sump.

[0055] Illustration 21. The direct chill casting system of any preceding or subsequent illustration or combination of illustrations, wherein the sump control system for creating the plurality of low points in the metal sump comprises a stirrer for inducing stirring in the molten metal.

[0056] Illustration 22. An ingot formed by the method of any preceding or subsequent illustration or combination of illustrations or using the direct chill casting system of any preceding or subsequent illustration or combination of illustrations.

[0057] As used herein, the terms “invention,” “the invention,” “this invention,” and “the present invention” are intended to refer broadly to all of the subject matter of this patent application and the claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below.

[0058] In this description, reference is made to alloys identified by AA numbers and other related designations, such as “series” or “5xxx.” For an understanding of the number designation system most commonly used in naming and identifying aluminum and its alloys, see “International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys” or “Registration Record of Aluminum Association Alloy Designations and Chemical Compositions Limits for Aluminum Alloys in the Form of Castings and Ingot,” both published by The Aluminum Association.

[0059] As used herein, the meaning of “a,” “an,” and “the” includes singular and plural references unless the context clearly dictates otherwise.

[0060] The elements included in the illustrations herein may not be drawn to scale. For example, figures depicting metal sumps may include exaggerated features for illustrative purposes.

[0061] The subject matter of embodiments of the present disclosure is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. Directional references such as “up,” “down,” “top,” “bottom,” “left,” “right,” “vertical,” “horizontal,” “lateral,” “longitudinal,” “front,” and “back,” among others, are intended to refer to the orientation as illustrated and described in the figure (or figures) to which the components and directions are referencing.

[0062] The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0063] The above-described aspects are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the present disclosure. Manyvariations and modifications can be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the present disclosure. All such modifications and variations are intended to be included herein within the scope of the present disclosure, and all possible claims to individual aspects or combinations of elements or steps are intended to be supported by the present disclosure. Moreover, although specific terms are employed herein, as well as in the claims that follow, they are used only in a generic and descriptive sense, and not for the purposes of limiting the described embodiments, nor the claims that follow.

Claims

CLAIMSThat which is claimed:

1. A method of controlling cracking in an ingot, the method comprising: introducing molten metal into a mold cavity of a casting mold of a casting system and to a metal sump of the ingot being cast; and creating a plurality of low points in the metal sump.

2. The method of claim 1, wherein at least one low point of the plurality of low points is offset from a center axis of the ingot.

3. The method of claim 1, wherein creating the plurality of low points in the metal sump comprises using a mold.

4. The method of claim 3, further comprising controlling the plurality of low points by controlling a geometry of a surface of the mold.

5. The method of claim 1, wherein creating the plurality of low points in the metal sump comprises controlling an application of coolant on the ingot.

6. The method of claim 1, wherein creating the plurality of low points in the metal sump comprises controlling at least one of a delivery of the molten metal into the metal sump or a casting speed.

7. The method of claim 1, wherein creating the plurality of low points in the metal sump comprises stirring the molten metal.

8. The method of claim 1, wherein creating the plurality of low points comprises forming at least three low points.

9. The method of claim 1, wherein creating the plurality of low points comprises forming at least two low points, wherein a distance between a first low point of the at least twolow points and a central axis of the ingot is different from a distance between a second low point of the at least two low points and the central axis of the ingot.

10. A method of controlling cracking in an ingot, the method comprising: delivering molten metal from a metal source to a metal sump of the ingot being cast in a mold; and controlling a sump profile to have a plurality of low points.

11. The method of claim 10, wherein controlling the sump profile comprises creating at least three low points.

12. The method of claim 10, wherein controlling the sump profile comprises using a mold comprising an arcuate surface extending between wall portions of the mold.

13. The method of claim 10, wherein controlling the sump profile comprises creating the plurality of low points at locations offset from a central axis of the ingot.

14. The method of claim 13, wherein, for at least one low point of the plurality of low points, a distance between the low point and the central axis of the ingot is greater than a distance between the low point and an outer surface of the ingot.

15. The method of claim 10, wherein controlling the sump profile comprises controlling at least one of a geometry of a mold, an application of coolant on the ingot, or delivery of the molten metal into the metal sump.

16. A direct chill casting system comprising: an open-ended mold defining a mold cavity for receiving molten metal in a metal sump of an ingot during casting; a bottom block configured to initially close a lower end of the open-ended mold and to move away from the lower end during casting; and a sump control system for creating a plurality of low points in the metal sump.

17. The direct chill casting system of claim 16, wherein the sump control system for creating the plurality of low points in the metal sump comprises a mold with a mold surface configured to create the plurality of low points in the metal sump.

18. The direct chill casting system of claim 17, wherein the mold surface is an arcuate surface extending between wall portions of the mold, and wherein a height of the mold surface at a center of the mold is greater than a height of the mold surface at the wall portions.

19. The direct chill casting system of claim 16, wherein the sump control system for creating the plurality of low points in the metal sump comprises a coolant system configured to supply liquid coolant to an outer surface of the ingot.

20. The direct chill casting system of claim 16, wherein the sump control system for creating the plurality of low points in the metal sump comprises a flow controller for controlling a flow and delivery of the molten metal into the metal sump.

21. The direct chill casting system of claim 16, wherein the sump control system for creating the plurality of low points in the metal sump comprises a stirrer for inducing stirring in the molten metal.

22. An ingot formed by the method of claim 1, the method of claim 10, or using the direct chill casting system of claim 16.

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