Patent Application
20240198413
The present disclosure relates to metallurgy generally and more specifically to continuous casting of alloy products using continuous casting devices.
Techniques for making metal strip articles, such as metal strips, slabs, or plates, may include using a continuous casting apparatus. For example, aluminum alloy strip products may be cast using continuous casting. Certain continuous casting devices, such as belt casters, can be used to solidify liquid metal as it passes between moving, cooling surfaces of the continuous casting device. These systems typically have a limit in how fast a metal strip can be continuously cast while still achieving acceptable surface quality.
The term embodiment and like terms are intended to refer broadly to all of the subject matter of this disclosure 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 claims below. Embodiments of the present disclosure covered herein are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the disclosure and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used 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 disclosure, any or all drawings and each claim.
In an aspect, described are nosetips for continuous casting of a metal alloy. A nosetip of this aspect may include a first portion having a first surface parallel to a second surface. The second surface may be opposite the first surface. The nosetip may include a second portion having a third surface directed toward an extended first surface. The extended first surface may be in a common plane with the first surface. The nosetip may include a third portion having an arcuate surface connecting the third surface to the extended first surface.
In examples, the arcuate surface may include a point of curvature. The point of curvature may be a vertical distance from the extended first surface. The vertical distance may be configured to limit a maximum meniscus height for liquid metal, cast using the nosetip, between the nosetip and a continuous casting surface.
In examples, the third portion of the nosetip may include a turbulence generating mechanism. The turbulence generating mechanism may be at least one chosen from a plurality of dimples, a plurality of ribs, a plurality of piers, or a surface roughness greater than a surface roughness of the first surface, the second surface, or the extended first surface.
In examples, the nosetip may comprise a refractory material. In some cases, the nosetip may comprise a material coated with a non-wetting substance, such as boron nitride (BN).
In another aspect, described are methods of continuously casting a metal alloy. A method of this aspect may include providing an arcuate nosetip. The arcuate nosetip may include a first portion having a first surface parallel to a second surface, the second surface opposite the first surface; a second portion having a third surface directed toward an extended first surface, the extended first surface in a common plane with the first surface; and a third portion having an arcuate surface connecting the third surface to the extended first surface. The method may include flowing liquid metal, through the arcuate nosetip, to a casting cavity to form a cast product.
In examples, the method may include a meniscus length of the liquid metal flowing through the arcuate nosetip being at most equal to a distance from a point of curvature to a casting surface partially defining the casting cavity. In some examples, the meniscus length may be from 0.5 mm to 2.0 mm.
In examples, the third portion of the arcuate nosetip may further include a turbulence generating mechanism. The turbulence generating mechanism may be at least one chosen from a surface roughness, a plurality of dimples, a plurality of ribs, a plurality of piers, and combinations thereof.
In examples, the method may further include generating turbulence in the liquid metal at the arcuate surface using a magnetic oscillation technique.
In examples of the method, the nosetip may include a refractory material.
In examples, the cast product may have a surface roughness of at most 10 μm. The surface roughness may be measured by 3D image analysis, for example. The cast product may have a composition near the surface having a decrease in Fe and Mn at the cast surface as compared with a reference conventionally cast standard. The composition may be characterized by Glow Discharge Optical Emission Spectroscopy. The cast product may have an exudate frequency of at most 30 exudates/cm2. The exudate frequency may be determined by 3D image analysis, for example.
In examples, the disclosed methods are useful for casting at a speed of greater than 12 m/min.
Other objects and advantages will be apparent from the following detailed description of non-limiting examples.
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.
Described herein are nosetips for continuous casting. The nosetips include an arcuate surface and, optionally, a turbulent flow mechanism. Also described herein are methods of casting using the nosetips, and products formed from aluminum alloys cast using the nosetips. The disclosed nosetips are also referred to as arcuate nosetips interchangeably herein. The disclosed nosetips include an arcuate surface with a point of curvature defining the maximum height, or distance from the belt, that the meniscus can extend. The disclosed nosetips improve upon nosetips, such as nosetip 100 shown in
As shown in
Conventional continuous casting devices can have difficulty in producing a desirable surface of the cast metal article. Surface defects can result in waste (e.g., in cases where the cast metal article cannot be used) or the need for additional downstream processing (e.g., to correct or mitigate any correctable surface defects). The conventional configuration also results in casting rate limitations. For example, conventional casting rates are limited to at most 12 m/min. The casting speed of 12 m/min refers to the cast product exiting the casting device at a rate of 12 m of cast product in the casting direction per minute. The nosetips of the present disclosure can increase stability during casting by reducing the meniscus height to provide a metal article with fewer defects, more uniform heat removal, higher casting speeds, and greater production throughput.
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.
As used herein, the terms “top” and “bottom” can be associated with vertical positions when the continuous casting device is casting in a horizontal direction. However, in some cases, the continuous casting device may be used in a non-horizontal direction, in which case the terms “top” and “bottom” may refer to positions in a plane perpendicular to the casting direction of the continuous casting device.
A continuous caster or continuous casting device can include a pair of opposing cooling assemblies forming a casting cavity therebetween. In some cases, additional features, such as side dams, can further define the extent of the casting cavity. Each cooling assembly can include at least one cooling surface for extracting heat from liquid metal within the casting cavity, as well as additional equipment related to operation of the cooling surface or cooling assembly (e.g., cooling pads, motors, coolant piping, sensors, and other such equipment).
Some continuous casters, such as belt casters, can comprise two counter-rotating belts (e.g., opposing cooling surfaces) that, along with side dams, form a casting cavity into which liquid metal can be fed. The belts can be water-cooled (e.g., cooled with deionized water) or cooled using other fluids. Liquid metal entering the casting cavity at an entrance to the casting cavity can solidify, through heat extraction via the cooled belts, as it moves distally towards the exit of the casting cavity, where it exits as solidified metal (e.g., a continuously cast article). The metal can move through the casting device at approximately the same rate of movement of the belts, thus minimizing or eliminating shear forces between the solidifying metal and the belts. Cooling pads may be utilized for control of casting. Cooling pads may include multiple nozzles located along a surface of the cooling pad and arranged in a pattern, such as a hexagonal or other pattern. In some cases, a cooling pad can include at least one linear nozzle extending across the width of the cooling pad and/or substantially or entirely across a width of the casting cavity.
In this description, reference is made to alloys identified by AA numbers and other related designations, such as “series” or “7xxx.” 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.
As used herein, a plate generally has a thickness of greater than about 15 mm. For example, a plate may refer to an aluminum product having a thickness of greater than about 15 mm, greater than about 20 mm, greater than about 25 mm, greater than about 30 mm, greater than about 35 mm, greater than about 40 mm, greater than about 45 mm, greater than about 50 mm, or greater than about 100 mm.
As used herein, a shate (also referred to as a sheet plate) generally has a thickness of from about 4 mm to about 15 mm. For example, a shate may have a thickness of about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm, about 14 mm, or about 15 mm.
As used herein, a sheet generally refers to an aluminum product having a thickness of less than about 4 mm. For example, a sheet may have a thickness of less than about 4 mm, less than about 3 mm, less than about 2 mm, less than about 1 mm, less than about 0.5 mm, or less than about 0.3 mm (e.g., about 0.2 mm).
As used herein, terms such as “cast aluminum alloy product,” “cast product,” “cast aluminum alloy product,” “cast article,” and the like are interchangeable and can refer to a product produced by direct chill casting (including direct chill co-casting) or semi-continuous casting, continuous casting, electromagnetic casting, hot top casting, or any other casting method, but herein particularly refer to those products produced by continuous casting (including, for example, by use of a twin belt caster, a twin roll caster, a block caster, or any other continuous caster). Cast articles described herein can be processed by any means known to those of ordinary skill in the art. Such processing steps include, but are not limited to, homogenization, hot rolling, cold rolling, solution heat treatment, and an optional pre-aging step.
Aluminum alloy products, including strips, slabs, sheets, shates, or plates, made using continuous casters employing arcuate nosetips described herein, can be used in automotive applications and other transportation applications, including aircraft and railway applications. For example, disclosed aluminum alloy products can be used to prepare automotive structural parts and formed parts, such as bumpers, side beams, roof beams, cross beams, pillar reinforcements (e.g., A-pillars, B-pillars, and C-pillars), inner panels, outer panels, side panels, inner hoods, outer hoods, or trunk lid panels. The aluminum alloy products and methods described herein can also be used in aircraft or railway vehicle applications, to prepare, for example, external and internal panels.
The aluminum alloy products and methods described herein can also be used in electronics applications. For example, the aluminum alloy products and methods described herein can be used to prepare housings for electronic devices, including mobile phones and tablet computers. In some examples, the aluminum alloy products can be used to prepare housings for the outer casing of mobile phones (e.g., smart phones), tablet bottom chassis, and other portable electronics.
The aluminum alloy products and methods described herein can be used in any other desired application.
All ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “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 beginning with a minimum value of 1 or more, e.g. 1 to 6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10. Unless stated otherwise, the expression “up to” when referring to the compositional amount of an element means that element is optional and includes a zero percent composition of that particular element. Unless stated otherwise, all compositional percentages are in weight percent (wt. %).
As used herein, the meaning of “a,” “an,” and “the” includes singular and plural references unless the context clearly dictates otherwise.
These illustrative examples are given to introduce the reader to the general subject matter discussed herein and are not intended to limit the scope of the disclosed concepts. The following sections describe various additional features and examples with reference to the drawings in which like numerals indicate like elements, and directional descriptions are used to describe the illustrative embodiments but, like the illustrative embodiments, should not be used to limit the present disclosure. The elements included in the illustrations herein may not be drawn to scale. In particular, the angles of attack illustrated herein have been exaggerated for illustrative purposes.
Nosetips for continuous casting are described herein, such as an arcuate nosetip.
While
The belt 208 can be made of any suitable thermally-conductive material, such as copper, steel, or aluminum. The belts 208 of the top belt assembly 202 and the bottom belt assembly 204 can rotate in opposite directions to one another, such that the surfaces of the belts 208 that come into contact with the liquid metal 252 in the casting cavity 250 move in a downstream direction 254. The top belt assembly 202 and the bottom belt assembly 204 can further include additional equipment as necessary, such as motors and other equipment.
Liquid metal 252 can enter the casting cavity 250 via nozzle 214. Within the casting cavity 250, the liquid metal 252 can solidify as heat is extracted via the belts 208 of the top belt assembly 202 and the bottom belt assembly 204. The liquid metal 252 and solidifying liquid metal move in direction 254 within the casting cavity 250. After sufficient heat has been extracted, the liquid metal 252 will have become solid and can exit the casting cavity 250 as a continuously cast article 206. The continuously cast article 206 will exit the continuous casting device 200 at an exit temperature. The nozzle 214 may be at least one linear nozzle extending across the width of a cooling pad and/or substantially or entirely across a width of the casting cavity 250. Nozzle 214 may include a nosetip, such as an arcuate nosetip, as described herein.
The casting cavity 250 is bounded by an entrance (e.g., at the nozzle 214), an exit (e.g., where the continuously cast article 206 exits the casting cavity 250), side dams, the top belt assembly 202, and the bottom belt assembly 204. More specifically, because the belts 208 of the top and bottom belt assemblies 202, 204 are in motion, the top and bottom of the casting cavity 250 are bounded by the exterior surfaces 256 of the belts 208 that lie between the entrance and the exit of the casting cavity 250 at any particular point in time. The path of these exterior surfaces 256 can be adjusted, such as by pushing against them from within the top and bottom belt assemblies 202, 204 (e.g., from opposite the belts 208 from the casting cavity 250). As depicted in
Nosetip 300 can have a first portion 322 having a first surface 321 parallel or substantially parallel to a second surface 323. Second surface 323 is opposite the first surface 321. Nosetip 300 has a second portion 326 having a third surface 327 directed toward an extended first surface 325, the extended first surface 325 in a common plane with the first surface 321. As shown in
Arcuate surface 329 includes a point of curvature p. Liquid metal 352 will travel toward belt B from this point of curvature p. Line L extends from point p to the belt external surface 308. The point of curvature p is a distance h from belt B along line L. Distance h is configured to be a maximum height for meniscus 350 and is the height of the liquid metal to be in contact with the nosetip 300 and the belt B.
In some examples, the arcuate nosetips of the present disclosure include a turbulence generating mechanism. Turbulence generating mechanisms are generally defined herein as any mechanism to provide turbulent flow around a curved body.
This concept of the turbulent eddies' effect on ball-shaped bodies is applied to the arcuate nosetips of the present disclosure. In some examples, the arcuate nosetip has a third portion that includes a turbulence generating mechanism.
In some examples, the turbulence generating mechanism 520 includes, but is not limited to, at least one chosen from a surface roughness, a plurality of dimples, a plurality of ribs, a plurality of piers, or similar structures, and combinations thereof. Additionally or alternatively in some examples, a turbulence generating mechanism includes magnetic oscillation, such as where a controllable electromagnet is used to interact with the liquid metal at the location of turbulence generating mechanism 520 depicted in
Optionally, portion 630 may include a turbulence generating mechanism 620 as previously described. Meniscus 650 may change shape or length as compared with that of meniscus 350 depicted in
The nosetips of the present disclosure, such as nosetip 300 of
The aluminum alloys and aluminum alloy products described herein can be continuous cast using any suitable continuous casting method known to those of ordinary skill in the art using the nosetips described herein, such as arcuate nosetips 300, 500, and 600 of
Continuous casting of the aluminum alloys described herein can provide a cast product having a surface roughness, or Ra value, that is less than the surface roughness of a cast product using a conventional nosetip. Surface roughness may be alternatively measured as a defect count that includes defect size and distribution, for example, by image analysis. Defect count may provide a better representation for surface roughness of the cast product due to greater sampling area, because Ra value is measured over a relatively small area. Therefore, if the defects are not evenly distributed over the surface there can be a large variation in Ra from one measurement location to another. In some examples, the cast product of the present disclosure has a surface demonstrating few surface defects and providing an Ra value of at most 10 μm, at most 5.0 μm, at most 3.5 μm, at most 2.5 μm, at most 2.0 μm, or at most 1.5 μm.
The methods described herein can result in fewer surface defects at or near the surface of the cast product. Defects may include exudates. An exudate is a surface defect that results from re-heating of the near surface regions of the solidifying cast slab as the slab shrinks away from the cooling surface. The density of exudates may be alloy dependent, with 6xxx alloys being more prone to exudation. The exudates may be about 50 μm or less in diameter depending upon the alloy. In some examples, the cast aluminum alloys have an exudate frequency of at most 30 exudates/cm2 as measured by image analysis. Exudate heights range from about 5 μm to about 100 μm. Roughness may be measured by measuring defect (exudate) height by 3D imaging (Keyence).
The methods described herein can provide a casting speed of greater than 12 m/min, greater than 14 m/min, greater than 16 m/min, or greater than 18 m/min. The casting speed may be improved up to fifty percent or greater as compared with the casting speed using a conventional nosetip, which is limited to up to 12 m/min.
The cast product according to the present disclosure can provide a composition near the surface having fewer defects and impurities. The near-surface composition may be analyzed by Glow Discharge Optical Emission Spectroscopy (GDOES) to get a measure of elemental concentration as a function of depth. The near-surface composition may be characterized by GDOES for elemental analysis to a desired depth, such as up to 1 μm, up to 2 μm, up to 5 μm, up to 10 μm, up to 15 μm, or to larger or smaller depths, for example. Conventional continuous cast products may include the presence of Fe and Mn on the continuous cast final gauge product surface with a subsurface denuded zone, which is in contrast to standard direct casting processed products. This is likely due to the presence of Fe and/or Mn containing surface intermetallics resulting from continuous casting. The cast product has a composition near the surface having a decrease in Fe and Mn as compared with a reference conventionally cast standard.
In some examples, the number of surface defects including exudates in the near-surface composition is less, thereby decreasing the Fe and Mn contents at the cast surface.
As used below, any reference to a series of aspects (e.g., “Aspects 1-4”) or non-enumerated group of aspects (e.g., “any previous or subsequent aspect”) is to be understood as a reference to each of those aspects disjunctively (e.g., “Aspects 1-4” is to be understood as “Aspects 1, 2, 3, or 4”).
Aspect 1 is a nosetip for continuous casting of a metal alloy, the nosetip comprising: a first portion having a first surface parallel to a second surface, the second surface opposite the first surface; a second portion having a third surface directed toward an extended first surface, the extended first surface in a common plane with the first surface; and a third portion having an arcuate surface connecting the third surface to the extended first surface.
Aspect 2 is the nosetip of any previous or subsequent aspect, wherein the arcuate surface includes a point of curvature.
Aspect 3 is the nosetip of any previous or subsequent aspect, wherein the point of curvature is a vertical distance from the extended first surface, the vertical distance configured to limit a maximum meniscus height for liquid metal, cast using the nosetip, between the nosetip and a continuous casting surface.
Aspect 4 is the nosetip of any previous or subsequent aspect, wherein the third portion includes a cutback between the point of curvature and the extended first surface.
Aspect 5 is the nosetip of any previous or subsequent aspect, wherein the third portion includes a turbulence generating mechanism.
Aspect 6 is the nosetip of any previous or subsequent aspect, wherein the turbulence generating mechanism is at least one chosen from a plurality of dimples, a plurality of ribs, a plurality of piers, or a surface roughness greater than a surface roughness of the first surface, the second surface, or the extended first surface.
Aspect 7 is the nosetip of any previous or subsequent aspect, wherein the nosetip comprises a refractory material.
Aspect 8 is a method of continuous casting a metal alloy, the method comprising: providing an arcuate nosetip, the arcuate nosetip including: a first portion having a first surface parallel to a second surface, the second surface opposite the first surface; a second portion having a third surface directed toward an extended first surface, the extended first surface in a common plane with the first surface; and a third portion having an arcuate surface connecting the third surface to the extended first surface; and flowing liquid metal, through the arcuate nosetip, to a casting cavity to form a cast product.
Aspect 9 is the method of any previous or subsequent aspect, wherein a meniscus length of the liquid metal flowing through the arcuate nosetip is at most equal to a distance from a point of curvature to a casting surface partially defining the casting cavity.
Aspect 10 is the method of any previous or subsequent aspect, wherein the meniscus length is from 0.5 mm to 2.0 mm.
Aspect 11 is the method of any previous or subsequent aspect, wherein the third portion of the arcuate nosetip further comprises a turbulence generating mechanism.
Aspect 12 is the method of any previous or subsequent aspect, wherein the turbulence generating mechanism is at least one chosen from a surface roughness, a plurality of dimples, a plurality of ribs, a plurality of piers, and combinations thereof.
Aspect 13 is the method of any previous or subsequent aspect, further comprising generating turbulence in the liquid metal at the arcuate surface using a magnetic oscillation technique.
Aspect 14 is the method of any previous or subsequent aspect, wherein the nosetip is a refractory material.
Aspect 15 is the method of any previous or subsequent aspect, wherein the cast product has a surface roughness of at most 10 μm.
Aspect 16 is the method of any previous or subsequent aspect, wherein the surface roughness is measured by 3D image analysis.
Aspect 17 is the method of any previous or subsequent aspect, wherein the cast product has a composition near the surface having a decrease in Fe and Mn at the cast surface as compared with a reference conventionally cast standard.
Aspect 18 is the method of any previous or subsequent aspect, wherein the composition is characterized by Glow Discharge Optical Emission Spectroscopy.
Aspect 19 is the method of any previous or subsequent aspect, wherein the cast product has an exudate frequency of at most 30 exudates/cm2.
Aspect 20 is the method of any previous or subsequent aspect, wherein the exudate frequency is determined by 3D image analysis.
Aspect 21 is the method of any previous aspect, wherein the method provides a casting speed of greater than 12 m/min.
Aspect 22 is the method of any previous aspect, wherein the arcuate nosetip is the nosetip of any previous aspect.
All patents, publications and abstracts cited above are incorporated herein by reference in their entirety. The foregoing description of the embodiments, including illustrated embodiments, has been presented only for the purpose of illustration and description and is not intended to be exhaustive or limiting to the precise forms disclosed. Numerous modifications, adaptations, and uses thereof will be apparent to those skilled in the art.
This application claims the benefit of and priority to U.S. Provisional Application No. 63/195,731, filed on Jun. 2, 2021, which is hereby incorporated by reference in its entirety for all purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/072689 | 6/1/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63195731 | Jun 2021 | US |
