Patent Application
20240076767
This disclosure relates to the fields of material science, material chemistry, metallurgy, aluminum alloys, aluminum alloy products, aluminum fabrication, and related fields. More specifically, the disclosure provides novel aluminum alloys that can be used in a variety of applications, including, for example, as a fin stock for a heat exchanger.
The automotive heat exchanger industry presents a number of demands on the aluminum alloys used for producing heat exchanger fin stock. For example, when heat exchangers are produced, their parts are typically joined by brazing, which requires aluminum alloys to have good brazing performance, good pre-braze mechanical properties to withstand deformation during brazing cycles, and high post-braze mechanical properties. At the same time, the aluminum alloys needs to be sacrificial and still have adequate corrosion properties. For example, it may be desirable for the heat exchanger fin stock to have a lower corrosion potential than the remainder of the heat exchanger, such that the fin stock acts sacrificially. The fin stock should also withstand slight deformation prior to brazing; therefore, the fin stock should possess good formability and strength in the as-rolled temper. Additionally, in order to make heat exchangers lighter (e.g., to improve automobile fuel efficiency) it is desirable for aluminum alloys for fin stock to be thinner while maintaining the aforementioned combination of properties. Thus, it is difficult to produce aluminum alloys for fin stock having a desired thickness without negatively affecting the pre-braze strength, the post-braze strength, sagging resistance, fin erosion, or formability properties.
Covered embodiments of the invention are defined by the claims, not this summary. This summary is a high-level overview of various aspects of the invention 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, any or all drawings and each claim.
Provided herein are novel aluminum alloys that exhibit high strength and corrosion resistance. The aluminum alloys described herein comprise about 0.20-1.30 wt. % Zn, 0.30-1.25 wt. % Si, 0-0.50 wt. % Fe, 0-0.20 wt. % Cu, 1.00-2.00 wt. % Mn, 0-0.10 wt. % Mg, up to 0.10 wt. % Cr, up to 0.10 wt. % Ti, and up to 0.15 wt. % of impurities, and Al. In some aspects, the aluminum alloy comprises about 0.30-1.10 wt. % Zn, 0.35-1.20 wt. % Si, 0.01-0.40 wt. % Fe, 0.001-0.15 wt. % Cu, 1.20-1.80 wt. % Mn, 0-0.08 wt. % Mg, up to 0.08 wt. % Cr, up to 0.08 wt. % Ti, and up to 0.15 wt. % of impurities, and Al. In some aspects, the aluminum alloy comprises about 0.35-1.00 wt. % Zn, 0.50-1.10 wt. % Si, 0.05-0.35 wt. % Fe, 0.01-0.10 wt. % Cu, 1.30-1.70 wt. % Mn, 0-0.05 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, and Al. In some aspects, the aluminum alloy comprises about 0.50-0.90 wt. % Zn, 0.80-1.10 wt. % Si, 0.05-0.30 wt. % Fe, 0.01-0.05 wt. % Cu, 1.30-1.50 wt. % Mn, 0.001-0.02 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, and Al. In some aspects, the aluminum alloy comprises about 0.75-0.85 wt. %, Zn, 0.80-0.90 wt. % Si, 0-0.30 wt. % Fe, 0-0.03 wt. % Cu, 1.35-1.50 wt. %, Mn, 0-0.05 wt. % Mg, up to 0.01 wt. % Cr, up to 0.03 wt. % Ti, and up to 0.15 wt. % of impurities, and Al. In some aspects, the aluminum alloy is in an H temper. In some aspects, the aluminum alloy has an ultimate tensile strength of the aluminum alloy is at least 140 MPa. In some aspects, the aluminum alloy has a yield strength of the aluminum alloy is at least 155 MPa. In some aspects, the aluminum alloy comprises has an electrical conductivity above 50% based on the international annealed copper standard (IACS). In some aspects, the aluminum alloy has a corrosion potential of from −700 mV to −800 mV. In some aspects, the aluminum alloy comprises 0.80-0.90 wt. % Si, up to 0.30 wt. % Fe, up to 0.03 wt. % Cu, 1.35-1.50 wt. % Mn, up to 0.05 wt. % Mg, 0.75-0.85 wt. % Zn, up to 0.01 wt. % Cr, up to 0.03 wt. % Ti, up to 0.15 wt. % of impurities, and Al, wherein the aluminum alloy has a ultimate tensile strength from 160 MPa to 180 MPa, a yield strength from 150 MPa to 160 MPa, an elongation from 2% to 2.50%, and a conductivity from 55% IACS to 60% IACS. In some aspects, a final gauge of the aluminum alloy is less than 0.10 mm. In some aspects, the aluminum alloy has a sag resistance less than 35 mm, when measured on a sample having a length of 35 mm. In some aspects, a fin stock comprises any of the aluminums alloys described herein. In some aspects, a gauge of the fin stock is 0.10 mm or less. In some aspects, an aluminum alloy product comprises a tube and a fin, wherein the fin comprises any of the aluminums alloys described herein.
In some embodiments, a method of producing an aluminum alloy product is provided. The method comprises casting an aluminum alloy to form a cast aluminum alloy, wherein the aluminum alloy comprises 0.20-1.30 wt. % Zn, 0.30-1.25 wt. % Si, 0-0.50 wt. % Fe, 0-0.20 wt. % Cu, 1.00-2.00 wt. % Mn, 0-0.10 wt. % Mg, up to 0.10 wt. % Cr, up to 0.10 wt. % Ti, and up to 0.15 wt. % of impurities, and Al; preheating the cast aluminum alloy; hot rolling the cast aluminum alloy to produce an aluminum alloy product; cold rolling, in a first cold rolling step, the aluminum alloy to produce to an intermediate gauge aluminum alloy product; inter-annealing the intermediate gauge aluminum alloy product; and cold rolling, in a second cold rolling step, the intermediate gauge aluminum alloy product to a final gauge aluminum alloy product in an H temper. In some aspects, the final gauge aluminum alloy product has an ultimate tensile strength of at least 140 MPa, a yield strength of at least 155 MPa, and an electrical conductivity of at least 50% IACS. In some aspects, the method further comprises brazing the final gauge aluminum alloy product to produce a brazed aluminum alloy product. In some aspects, the brazed aluminum alloy product has an ultimate tensile strength of at least 100 MPa, a yield strength of at least 45 MPa, and an electrical conductivity of at least 45% IACS. In some aspects, the final gauge aluminum alloy product has final gauge less than 0.10 mm. In some aspects, an aluminum alloy product is prepared by the method described herein.
Also provided herein are aluminum alloy products comprising the aluminum alloys described herein. The products can include a fin stock. Optionally, the gauge of the fin stock is 1.0 mm or less (e.g., 0.15 mm or less). Further provided herein are aluminum alloy products comprising a tube and a fin, wherein the fin comprises the aluminum alloys described herein.
Further provided herein are methods of producing an aluminum alloy product. The methods include the steps of casting an aluminum alloy as described herein to form a cast aluminum alloy, preheating the cast aluminum alloy, hot rolling the cast aluminum alloy to produce a rolled product, annealing the rolled product, and cold rolling the rolled product to a final gauge aluminum alloy product. Aluminum alloy products (e.g., heat exchanger fins) obtained according to the methods are also provided herein.
Further aspects, objects, and advantages will become apparent upon consideration of the detailed description of non-limiting examples that follow.
Described herein are high strength, sag resistant aluminum alloys and methods of making and processing the same. The aluminum alloys described herein exhibit improved mechanical strength, corrosion resistance, corrosion potential and/or formability compared to conventional aluminum alloys for fin stock. In particular, the aluminum alloys described herein display a combination of one or more of the following properties: high pre-braze and post-braze mechanical properties (e.g., tensile strength, yield strength, elongation), sag resistance, thermal conductivity, and corrosion potential. In some embodiments, the aluminum alloys provided herein include higher amounts of Si (e.g., from about 0.3 wt. % to about 1.3 wt. %), Mn (e.g., from about 1.0 wt. % to about 2.0 wt. %) and Mg (e.g., up to about 0.05 wt. %), in comparison to known aluminum alloys for fin stock, that results in high pre-braze strength, which reduces sagging and fin crush problems during brazing. The composition of the aluminum alloys described herein and/or its production process lead to improved properties of the material, such as reduction of fin crush during brazing, higher post-braze strength, improved thermal conductivity, improved sag resistance, and increased anodic corrosion potential.
For automotive heat exchanger applications, aluminum alloy sheets need to retain sufficient strength pre-brazing and post-brazing such that the aluminum alloy sheets do not sag. This strength requirement is a particularly difficult requirement to meet while down-gauging the aluminum alloy sheet thickness in order to make light-weight heat exchangers. In some embodiments, the aluminum alloys described herein possess a combination of characteristics and properties that make the alloys suitable for production of heat exchanger fins, to be used, for example, in heat exchangers, such as those employed in the automotive industry. In one example, the improved aluminum alloys described herein can be produced in a sheet form at desired thickness (gauge) that is suitable for production of light-weight heat exchanger fins for automotive radiators. The aluminum alloys described herein can be brazed and exhibit strength characteristics before, during, and after brazing that make the alloys attractive for automotive heat exchanger applications.
The aluminum alloys described herein also possess sufficiently high thermal conductivity suitable for heat exchanger applications, and have a corrosion potential that is sufficiently negative for the fins to act in a sacrificial manner during corrosion of the heat exchanger. In summary, the improved aluminum alloys described herein possess a combination of suitable pre-braze and post-braze strength, thermal conductivity, and anodic corrosion potential values suitable for automotive fin exchanger applications. At the same time, the aluminum alloys described herein can be produced from input aluminum that is at least in part recycle-friendly.
The aluminum alloys described herein can be especially useful as a sacrificial alloy (e.g., as fin stock material for use in combination with copper or aluminum alloy tubes in heat exchangers). The aluminum alloys described herein provide a material having a balance of mechanical strength as well as sacrificial alloy characteristics. The aluminum alloys described herein can be formed as fin stock and attached mechanically to copper or aluminum alloy tubing. The fin stock can sacrificially corrode, thus protecting the copper or aluminum alloy tubing from corrosion.
The terms “invention,” “the invention,” “this invention,” and “the present invention” used herein 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.
In this description, reference is made to alloys identified by aluminum industry designations, such as “series” or “lxxx.” 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, the meaning of “a,” “an,” or “the” includes singular and plural references unless the context clearly dictates otherwise.
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, less than about 0.3 mm, or less than about 0.1 mm.
Reference is made in this application to alloy temper or condition. For an understanding of the alloy temper descriptions most commonly used, see “American National Standards (ANSI) H35 on Alloy and Temper Designation Systems.” An F condition or temper refers to an aluminum alloy as fabricated. An O condition or temper refers to an aluminum alloy after annealing. An Hxx condition or temper, also referred to herein as an H temper, refers to an aluminum alloy after cold rolling with or without thermal treatment (e.g., annealing). Suitable H tempers include HX1, HX2, HX3 HX4, HX5, HX6, HX7, HX8, or HX9 tempers. For example, the aluminum alloy can be strain hardened to various tempers, for example, H16, H18, or other H1X tempers.
The following aluminum alloys are described in terms of their elemental composition in weight percentage (wt. %) based on the total weight of the alloy. In certain examples of each alloy, the remainder is aluminum, with a maximum wt. % of 0.15% for the sum of the impurities.
As used herein, “electrochemical potential” refers to a material's amenability to a redox reaction. Electrochemical potential can be employed to evaluate resistance to corrosion of aluminum alloys described herein. A negative value can describe a material that is easier to oxidize (e.g., lose electrons or increase in oxidation state) when compared to a material with a positive electrochemical potential. A positive value can describe a material that is easier to reduce (e.g., gain electrons or decrease in oxidation state) when compared to a material with a negative electrochemical potential. Electrochemical potential, as used herein, is a vector quantity expressing magnitude and direction.
As used herein, the meaning of “room temperature” can 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.
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.
Described below are novel aluminum alloy compositions. In certain aspects, the alloys exhibit high pre-braze and post-braze strength, corrosion resistance, conductivity, and corrosion potential that is improved in comparison with known alloys used for fin stock production. The properties of the alloys are achieved due to the elemental compositions of the alloys, and, in some cases, also the methods of processing the alloys to produce the described sheets, plates, and shates. The aluminum alloys are designed to give a high pre-braze and post-braze strength without the addition of excessive amounts of solid solution strengthening elements. With the appropriate process and composition control of the main alloying additions, the resultant microstructure at final gauge exhibits a high number density of dispersoids which substantially increases the strength of the aluminum alloy. Specifically, the Si content (e.g., from about 0.30 wt. % to about 1.30 wt. %) decreases the solubility of Mn (e.g., from about 1.00 wt. % to about 2.00 wt. %) and promotes formation of high density dispersoids to improve pre-braze, strength, post-braze strength, and sagging resistance of the aluminum alloy. The Mn-containing dispersoids in solid solution increases the post-braze strength and plays an important role in controlling the sagging resistance and prevents fin erosion (e.g., liquid core penetration in the fin stock material), thus producing aluminum alloys that have an excellent combination of mechanical properties and corrosion behavior. The formation of dispersoids provides additional post-braze strength through particle strengthening without compromising the electrical conductivity. The Mn-containing dispersoids also control the recrystallization process during the brazing process leading to formation of large recrystallized grains. Additionally, the aluminum alloys described herein can tolerate higher amounts of Mg for additional solute strengthening to improve sag resistance during brazing.
The composition and process described herein ensure that the aluminum alloys, even when rolled to thin gauges (e.g., below 1 mm), have a high sag resistance. When an assembled heat exchanger undergoes controlled atmosphere brazing, the fin stock, tube stock and header stock materials are subject to temperatures in the range of 595° C. to 610° C. At these temperatures, the aluminum components will start to creep. Although the duration for brazing is short, the thin gauge of the aluminum alloys used and the very high temperatures make creep a particular problem for automotive fin stock. This high temperature creep is also referred to as “sag” and the ability of a material to withstand this form of creep is called sag resistance. The sagging of fin stock is a combination of different mechanisms taking place at different temperatures. For example, recovery sagging occurs at lower temperatures and increases with higher amounts of cold deformation, recrystallization sagging occurs at temperatures greater than 300° C., and creep sagging occurs at temperatures greater than 550° C. Creep sagging is due to grain boundary sliding and aluminum alloys are more susceptible to creep sagging if the microstructure of the aluminum alloy has small grain sizes (e.g., below 150 μm to 200 μm). The heating rate during brazing influences creep sagging as a higher rate leads to smaller grains and reduces sagging resistance. Grain boundary sliding increases with decrease in grain length and hence large pancake-shaped grains are preferred over equiaxed grain structures.
As the gauge of fin stock is reduced, the ability of the fin stock to withstand sagging during the brazing operation becomes more important. The aluminum alloy composition described herein having a balance of alloying elements delays recrystallization of the grain structure, thus reducing the tendency to form small equiaxed grains. The fine distribution of dispersoids present after casting and rolling to final gauge prevents grains growing through the sheet thickness, but allows the growth of grains in the rolling plane to form long pancake-shaped grains. The delay of recrystallization and the promotion of grain growth in the rolling direction enables the aluminum alloy to develop pancake-shaped grains that provide excellent sag resistance.
In some embodiments, the aluminum alloys and methods described herein can be used in industrial applications including sacrificial parts, heat dissipation, packaging, and building materials. The alloys described herein can be employed as industrial fin stock for heat exchangers. The industrial fin stock can be provided such that it is more resistant to corrosion than currently employed industrial fin stock alloys (e.g., AA7072 and AA1100) and will still preferentially corrode, protecting other metal parts incorporated in a heat exchanger.
In some examples, the aluminum alloys can have the following elemental composition as provided in Table 1.
In some examples, the aluminum alloys can have the following elemental composition as provided in Table 2.
In some examples, the aluminum alloys can have the following elemental composition as provided in Table 3.
In some examples, the aluminum alloys can have the following elemental composition as provided in Table 4.
In some examples, the alloy includes zinc (Zn) in an amount from about 0.20% to about 1.30% (e.g., from about 0.30% to about 1.10%, from about 0.35% to about 1.00%, from about 0.50% to about 0.90%, or from about 0.70% to about 0.85%) based on the total weight of the alloy. For example, the alloy can include about 0.20%, about 0.21%, about 0.22%, about 0.23%, about 0.24%, about 0.25%, about 0.26%, about 0.27%, about 0.28%, about 0.29%, about 0.30%, about 0.31%, about 0.32%, about 0.33%, about 0.34%, about 0.35%, about 0.36%, about 0.37%, about 0.38%, about 0.39%, about 0.40%, about 0.41%, about 0.42%, about 0.43%, about 0.44%, about 0.45%, about 0.46%, about 0.47%, about 0.48%, about 0.49%, about 0.50%, about 0.51%, about 0.52%, about 0.53%, about 0.54%, about 0.55%, about 0.56%, about 0.57%, about 0.58%, about 0.59%, about 0.60%, about 0.61%, about 0.62%, about 0.63%, about 0.64%, about 0.65%, about 0.66%, about 0.67%, about 0.68%, about 0.68%, about 0.70%, about 0.71%, about 0.72%, about 0.73%, about 0.74%, about 0.75%, about 0.76%, about 0.77%, about 0.78%, about 0.79%, about 0.80%, about 0.81%, about 0.82%, about 0.83%, about 0.84%, about 0.85%, about 0.86%, about 0.87%, about 0.88%, about 0.89%, about 0.90%, about 0.91%, about 0.92%, about 0.93%, about 0.94%, about 0.95%, about 0.96%, about 0.97%, about 0.98%, about 0.99%, about 1.00%, about 1.01%, about 1.02%, about 1.03%, about 1.04%, about 1.05%, about 1.06%, about 1.07%, about 1.08%, about 1.09%, about 1.10%, about 1.11%, about 1.12%, about 1.13%, about 1.14%, about 1.15%, about 1.16%, about 1.17%, about 1.18%, about 1.19%, about 1.20%, about 1.21%, about 1.22%, about 1.23%, about 1.24%, about 1.25%, about 1.26%, about 1.27%, about 1.28%, about 1.29%, or about 1.30% Zn. All percentages are expressed in wt. %. The Zn content can be reduced compared to conventional fin stock alloys. Aluminum alloys including the claimed amount of Zn are able to act sacrificially when attached to copper or other aluminum alloy tubes, thus providing cathodic protection to the tubes. Zn is known to affect the anodic potential of aluminum alloys. Zn additions will cause an aluminum alloy to become more electronegative (sacrificial). In heat exchanger units, it is preferable that the fin material is sacrificial to the tube material, which depends on the composition of the tube material itself. By using an aluminum alloy having a low content of Zn for fin stock, the difference in corrosion potential between the tubes and fin stock can be tailored for an adequate level of protection. The Zn content can improve the corrosion resistance of the aluminum alloys described herein. Specifically, when zinc is incorporated at a level as described herein, such as from about 0.20% to about 1.30%, the alloys exhibit enhanced corrosion resistance as compared to fin stock typically used in industrial processes (e.g., lxxx series and 7xxx series alloys), which require a much higher content of Zn to achieve the same corrosion resistance. In some further examples, Zn can decrease resistance to corrosion when incorporated at weight percentages exceeding those described herein. In still further examples, Zn can be incorporated in an aluminum alloy in an optimal amount, as described herein, to provide an alloy suitable for use as an industrial fin. For example, at Zn levels higher than those described herein, the alloys for use as fins can corrode more rapidly than for fins containing the described amount of Zn, resulting in perforations in the fin. As a result, the mechanical integrity and thermal performance of the heat exchanger can be compromised, thus affecting the service life of the heat exchanger.
In some examples, the alloy includes silicon (Si) in an amount from about 0.30% to about 1.25% (e.g., from about 0.35% to about 1.20%, from about 0.50% to about 1.10%, from about 0.80% to about 1.10%, or from about 0.80% to about 0.90%) based on the total weight of the alloy. For example, the alloy can include about 0.30%, about 0.31%, about 0.32%, about 0.33%, about 0.34%, about 0.35%, about 0.36%, about 0.37%, about 0.38%, about 0.39%, about 0.40%, about 0.41%, about 0.42%, about 0.43%, about 0.44%, about 0.45%, about 0.46%, about 0.47%, about 0.48%, about 0.49%, about 0.50%, about 0.51%, about 0.52%, about 0.53%, about 0.54%, about 0.55%, about 0.56%, about 0.57%, about 0.58%, about 0.59%, about 0.60%, about 0.61%, about 0.62%, about 0.63%, about 0.64%, about 0.65%, about 0.66%, about 0.67%, about 0.68%, about 0.68%, about 0.70%, about 0.71%, about 0.72%, about 0.73%, about 0.74%, about 0.75%, about 0.76%, about 0.77%, about 0.78%, about 0.79%, about 0.80%, about 0.81%, about 0.82%, about 0.83%, about 0.84%, about 0.85%, about 0.86%, about 0.87%, about 0.88%, about 0.89%, about 0.90%, about 0.91%, about 0.92%, about 0.93%, about 0.94%, about 0.95%, about 0.96%, about 0.97%, about 0.98%, about 0.99%, about 1.00%, about 1.01%, about 1.02%, about 1.03%, about 1.04%, about 1.05%, about 1.06%, about 1.07%, about 1.08%, about 1.09%, about 1.10%, about 1.11%, about 1.12%, about 1.13%, about 1.14%, about 1.15%, about 1.16%, about 1.17%, about 1.18%, about 1.19%, about 1.20%, about 1.21%, about 1.22%, about 1.23%, about 1.24%, or about 1.25% Si. As described above, the Si content promotes formation of dispersoids to improve pre-braze and post-braze strength of the aluminum alloy, thus producing alloys that have excellent mechanical properties and corrosion potential. Specifically, Si combines with Mn and results in a high density of dispersoids particles which promotes high strength and good sagging resistance. However, a high level of Si (e.g. greater than 1.25 wt. %) increases the risk of fin stock erosion during brazing.
In some examples, the alloy also includes iron (Fe) in an amount from 0% to about 0.50% (e.g., from 0.05% to about 0.35%, from 0.05% to 0.30%, or from 0.05% to 0.20%) based on the total weight of the alloy. For example, the alloy can include 0%, about 0.01%, about 0.02%, about 0.03%, about 0.04%, about 0.05%, about 0.60%, about 0.07%, about 0.08%, about 0.09%, about 0.10%, about 0.11%, about 0.12%, about 0.13%, about 0.14%, about 0.15%, about 0.16%, about 0.17%, about 0.18%, about 0.19%, about 0.20%, about 0.21%, about 0.22%, about 0.23%, about 0.24%, 0.25%, about 0.26%, about 0.27%, about 0.28%, about 0.29%, about 0.3%, about 0.31%, about 0.32%, about 0.33%, about 0.34%, about 0.35%, about 0.36%, about 0.37%, about 0.38%, about 0.39%, about 0.4%, about 0.41%, about 0.42%, about 0.43%, about 0.44%, about 0.45%, about 0.46%, about 0.47%, about 0.48%, about 0.49%, or about 0.50% Fe. All percentages are expressed in wt. %. In some instances, a large amount of Fe (e.g., greater than 0.50 wt. %) can have an adverse effect on the properties of the aluminum alloy as it increases the risk forming large intermetallic constituent particles during solidification. This can lead to issues with material perforation or holes when the aluminum alloy is rolled to a final gauge.
In some examples, the disclosed alloy includes copper (Cu) in an amount from 0% to about 0.20% (e.g., from 0% to about 0.15%, from about 0.001% to about 0.15%, from about 0.01% to about 0.10%, or from about 0.01% to about 0.05%) based on the total weight of the alloy. For example, the alloy can include 0%, about, 0.001%, about 0.002%, about 0.003%, about 0.004%, about 0.005%, about 0.006%, about 0.007%, about 0.008%, about 0.009%, 0.01%, about 0.02%, about 0.03%, about 0.04%, about 0.05%, about 0.06%, about 0.07%, about 0.08%, about 0.09%, about 0.10%, about 0.11%, about 0.12%, about 0.13%, about 0.14%, about 0.15%, about 0.16%, about 0.17%, about 0.18%, about 0.19%, or about 0.20% Cu. All percentages are expressed in wt. %. A small addition of Cu increases the post-brazing strength and may contribute to the formation of the large pancake grains which improve the sag resistance properties. In some instances, a Cu content above 0.20 wt. % may lead to corrosion problems as it leads to positive corrosion potentials which is not desirable for fin stock materials.
In some examples, the alloy can include manganese (Mn) in an amount from about 1.00% to about 2.00% (e.g., from about 1.20% to about 1.80%, from about 1.30% to about 1.70%, or from about 1.30% to about 1.50%) based on the total weight of the alloy. For example, the alloy can include about 1.00%, about 1.01%, about 1.02%, about 1.03%, about 1.04%, about 1.05%, about 1.06%, about 1.07%, about 1.08%, about 1.09%, about 1.10%, about 1.11%, about 1.12%, about 1.13%, about 1.14%, about 1.15%, about 1.16%, about 1.17%, about 1.18%, about 1.19%, about 1.20%, about 1.21%, about 1.22%, about 1.23%, about 1.24%, about 1.25%, about 1.26%, about 1.27%, about 1.28%, about 1.29%, about 1.30%, about 1.31%, about 1.32%, about 1.33%, about 1.34%, about 1.35%, about 1.36%, about 1.37%, about 1.38%, about 1.39%, about 1.40%, about 1.41%, about 1.42%, about 1.43%, about 1.44%, about 1.45%, about 1.46%, about 1.47%, about 1.48%, about 1.49%, about 1.50%, about 1.51%, about 1.52%, about 1.53%, about 1.54%, about 1.55%, about 1.56%, about 1.57%, about 1.58%, about 1.59%, about 1.60%, about 1.61%, about 1.62%, about 1.63%, about 1.64%, about 1.65%, about 1.66%, about 1.67%, about 1.68%, about 1.69%, about 1.70%, about 1.71%, about 1.72%, about 1.73%, about 1.74%, about 1.75%, about 1.76%, about 1.77%, about 1.78%, about 1.79%, about 1.80%, about 1.81%, about 1.82%, about 1.83%, about 1.84%, about 1.85%, about 1.86%, about 1.87%, about 1.88%, about 1.89%, about 1.90%, about 1.91%, about 1.92%, about 1.93%, about 1.94%, about 1.95%, about 1.96%, about 1.97%, about 1.98%, about 1.99%, or about 2.00% Mn. All percentages are expressed in wt. %. Mn largely remains in solid solution while a small amount is precipitated during hot rolling and interannealing as fine dispersoids. The effect of this microstructure is that, when the material is heated to 600° C. as in a brazing operation, the material retains strength due to the solid solution strengthening effects of the Mn. In this way the addition of Mn is optimized to provide a useful balance of properties. Mn, (optionally, in combination with Cu), is added to the aluminum alloy to provide strength, sagging resistance, and avoid fin erosion, but not so much to adversely affect the electrical and thermal conductivity.
In some examples, the alloy can include magnesium (Mg) in an amount from 0% to about 0.10% (e.g., from 0% to about 0.08%, from 0% to about 0.05%, or from about 0.001% to about 0.02%) based on the total weight of the alloy. For example, the alloy can include 0%, about 0.001%, about 0.002%, about 0.003%, about 0.004%, about 0.005%, about 0.006%, about 0.007%, about 0.008%, about 0.009%, about 0.01%, about 0.02%, about 0.03%, about 0.04%, about 0.05%, about 0.06%, about 0.07%, about 0.08%, about 0.09%, or about 0.10% Mg. All percentages are expressed in wt. %.
In some examples, the alloy includes chromium (Cr) in an amount up to about 0.10% (e.g., from 0% to about 0.05%, from about 0.001% to about 0.04%, or from about 0.01% to about 0.03%) based on the total weight of the alloy. For example, the alloy can include about 0.001%, about 0.002%, about 0.003%, about 0.004%, about 0.005%, about 0.006%, about 0.007%, about 0.008%, about 0.009%, about 0.01%, about 0.02%, about 0.03%, about 0.04%, about 0.05%, about 0.06%, about 0.07%, about 0.08%, about 0.09%, or about 0.1% Cr. In some cases, Cr is not present in the alloy (i.e., 0%). All percentages are expressed in wt. %.
In some examples, the alloy includes titanium (Ti) in an amount up to about 0.10% (e.g., from 0% to about 0.05%, from about 0.001% to about 0.04%, or from about 0.01% to about 0.03%) based on the total weight of the alloy. For example, the alloy can include about 0.001%, about 0.002%, about 0.003%, about 0.004%, about 0.005%, about 0.006%, about 0.007%, about 0.008%, about 0.009%, about 0.01%, about 0.02%, about 0.03%, about 0.04%, about 0.05%, about 0.06%, about 0.07%, about 0.08%, about 0.09%, or about 0.1% Ti. In some cases, Ti is not present in the alloy (i.e., 0%). All percentages are expressed in wt. %.
Optionally, the alloy compositions can further include other minor elements, sometimes referred to as impurities, in amounts of about 0.05% or below, 0.04% or below, 0.03% or below, 0.02% or below, or 0.01% or below each. These impurities may include, but are not limited to, Na, Ga, V, Ni, Sc, Ag, B, Bi, Zr, Li, Pb, Sn, Ca, Hf, Sr, or combinations thereof. Accordingly, Na, Ga, V, Ni, Sc, Ag, B, Bi, Zr, Li, Pb, Sn, Ca, Hf, or Sr may be present in an alloy in amounts of 0.05% or below, 0.04% or below, 0.03% or below, 0.02% or below, or 0.01% or below. In certain aspects, the sum of all impurities does not exceed 0.15% (e.g., 0.1%). All percentages are expressed in wt. %. In certain aspects, the remaining percentage of the alloy is aluminum.
In some embodiments, exemplary aluminum alloys as described herein can include about 0.36-0.46% Si, up to about 0.30% Fe, up to about 0.02% Cu, about 1.36-1.50% Mn, up to about 0.03% Mg, about 0.65-0.75 Zn, up to about 0.01% Cr, up to about 0.03% Ti, and up to about 0.15% of impurities, and Al. In some embodiments, exemplary aluminum alloys as described herein can include about 0.36-0.46% Si, up to about 0.30% Fe, up to about 0.02% Cu, about 1.36-1.50% Mn, up to about 0.03% Mg, about 0.95-1.05% Zn, up to about 0.01% Cr, up to about 0.03% Ti, and up to about 0.15% of impurities, and Al. In some embodiments, exemplary aluminum alloys as described herein can include about 0.55-0.65% Si, up to about 0.30% Fe, up to about 0.02% Cu, about 1.50-1.70% Mn, up to about 0.03% Mg, about 1.10-1.30% Zn, up to about 0.01% Cr, up to about 0.03% Ti, and up to about 0.15% of impurities, and Al. In some embodiments, exemplary aluminum alloys as described herein can include about 0.80-0.90% Si, up to about 0.30% Fe, about 0.07-0.09% Cu, about 1.25-1.40% Mn, up to about 0.05% Mg, about 0.65-0.75% Zn, up to about 0.01% Cr, up to about 0.03% Ti, and up to about 0.15% of impurities, and Al. In some embodiments, exemplary aluminum alloys as described herein can include about 0.80-0.90% Si, up to about 0.30% Fe, up to about 0.03% Cu, about 1.35-1.50% Mn, up to about 0.05% Mg, about 0.75-0.85% Zn, up to about 0.01% Cr, up to about 0.03% Ti, and up to about 0.15% of impurities, and Al. In some embodiments, exemplary aluminum alloys as described herein can include about 1.00-1.20% Si, up to about 0.30% Fe, about 0.04-0.08% Cu, about 1.25-1.40% Mn, up to about 0.05% Mg, about 0.95-1.05% Zn, up to about 0.01% Cr, up to about 0.03% Ti, and up to about 0.15% of impurities, and Al. All percentages are expressed in wt. %.
In some embodiments, an exemplary alloy includes 0.85% Si, 0.08% Fe, 0.014% Cu, 1.41% Mn, 0.002% Mg, 0.001% Cr, 0.81% Zn, 0.01% Ti, and up to 0.15% total impurities, with the remainder as Al. In some embodiments, an exemplary alloy includes 1.10% Si, 0.08% Fe, 0.05% Cu, 1.37% Mn, 0.001% Mg, 0.001% Cr, 0.99% Zn, 0.01% Ti, and up to 0.15% total impurities, with the remainder as Al. All percentages are expressed in wt. %.
The processes of producing aluminum alloys described herein lead to an aluminum material that can be described as “strain-hardened,” “cold-worked,” and/or having or being in “H1X” temper (e.g., H16 temper). The mechanical properties of the aluminum alloy can be controlled by various processing conditions depending on the desired use. The alloy can be produced (or provided) in an H temper (e.g., HX1, HX2, HX3, HX4, HX5, HX6, HX7, HX8, or HX9 tempers). As one example, the alloy can be produced (or provided) in the H16 temper. It is to be understood that a particular range of properties is associated with the temper designation. It is also to be understood that the temper designation refers to the pre-braze properties of the aluminum alloy.
In some non-limiting examples, the disclosed alloys have high strength, corrosion potential, and conductivity in the H tempers (e.g., H16 temper) and post-brazing. In some non-limiting examples, the disclosed alloys have good corrosion resistance in the H tempers (e.g., H16 temper) and post-braze compared to conventional 7xxx and lxxx series aluminum alloys employed as industrial fin stock. As a result of controlling the composition and microstructure as described herein, the aluminum alloy exhibits the following balance of properties. For example, the ultimate tensile strength (UTS) is greater than 100 MPa and the electrical conductivity is greater than 48% IACS after brazing at 600° C.
In certain aspects, the aluminum alloys can have a yield strength (YS) of at least about 30 MPa. In non-limiting examples, the yield strength is at least about 30 MPa, at least about 35 MPa, at least about 40 MPa, at least about 45 MPa, at least about 50 MPa, at least about 60 MPa, at least about 70 MPa, at least about 80 MPa, at least about 90 MPa, at least about 100 MPa, at least about 110 MPa, at least about 120 MPa, at least about 130 MPa, at least about 140 MPa, at least about 150 MPa, at least about 160 MPa, at least about 170 MPa, at least about 180 MPa, or anywhere in between. In some cases, the yield strength is from about 30 MPa to about 180 MPa. For example, the yield strength can be from about 35 MPa to about 170 MPa, from about 40 MPa to about 160 MPa, from about 50 MPa to about 155 MPa, from about 55 MPa to about 150 MPa, or from about 60 MPa to about 140 MPa.
The yield strength will vary based on the tempers of the alloys. In some examples, the alloys described herein provided in an H temper can have a yield strength of from at least about 100 MPa to about 170 MPa. In non-limiting examples, the yield strength of the alloys in H temper is at least about 110 MPa, at least about 120 MPa, at least about 125 MPa, at least about 130 MPa, at least about 135 MPa, at least about 140 MPa, at least about 145 MPa, at least about 150 MPa, at least about 155 MPa, at least about 160 MPa, at least about 165 MPa, at least about 170 MPa, or anywhere in between.
In some further examples, the alloys described herein, after brazing, can have a yield strength of at least about 30 MPa, at least about 35 MPa, at least about 40 MPa, at least about 45 MPa, at least about 50 MPa, at least about 55 MPa, at least about 60 MPa, at least about 65 MPa, at least about 70 MPa, at least about 75 MPa, at least about 80 MPa, at least about 85 MPa, at least about 90 MPa, at least about 100 MPa, or anywhere in between.
In certain aspects, the aluminum alloys can have an ultimate tensile strength (UTS) of at least about 70 MPa. In non-limiting examples, the yield strength is at least about 70 MPa, at least about 80 MPa, at least about 90 MPa, at least about 100 MPa, at least about 110 MPa, at least about 120 MPa, at least about 130 MPa, at least about 140 MPa, at least about 150 MPa, at least about 160 MPa, at least about 170 MPa, at least about 180 MPa, at least about 190 MPa, at least about 200 MPa, or anywhere in between. In some cases, the yield strength is from about 70 MPa to about 200 MPa. For example, the yield strength can be from about 75 MPa to about 190 MPa, from about 80 MPa to about 185 MPa, from about 85 MPa to about 180 MPa, from about 90 MPa to about 175 MPa, or from about 95 MPa to about 170 MPa.
In some examples, the alloys described herein provided in an H temper can have an UTS of from at least about 140 MPa to about 200 MPa. In non-limiting examples, the UTS of the alloys in H temper is at least about 140 MPa, at least about 145 MPa, at least about 150 MPa, at least about 155 MPa, at least about 160 MPa, at least about 165 MPa, at least about 170 MPa, at least about 175 MPa, at least about 180 MPa, at least about 190 MPa, at least about 200 MPa, or anywhere in between.
In some examples, the alloys described herein provided, after brazing, can have an UTS of from at least about 70 MPa to about 140 MPa. In some further examples, the alloys described herein, after brazing, can have an UTS of at least about 70 MPa, at least about 75 MPa, at least about 80 MPa, at least about 85 MPa, at least about 90 MPa, at least about 95 MPa, at least about 100 MPa, at least about 105 MPa, at least about 110 MPa, at least about 115 MPa, at least about 120 MPa, at least about 125 MPa, at least about 130 MPa, at least about 135 MPa, at least about 140 MPa, or anywhere in between.
In certain aspects, the alloys described herein provided in an H temper has sufficient formability to meet an elongation of about 2% or greater. In certain examples, the alloys described herein provided in an H temper can have an elongation of about 2% or greater, about 2.25% or greater, about 2.50% or greater, about 2.75% or greater, about 3% or greater, about 3.25% or greater, about 3.50% or greater, about 3.75% or greater, about 4% or greater, about 4.25% or greater, about 4.50% or greater, about 4.75% or greater, about 5.0% or greater, about 5.25% or greater, about 5.50% or greater, about 5.75% or greater, about 6.0% or greater, or anywhere in between.
In certain aspects, the alloys described herein, after brazing, has sufficient formability to meet an elongation of about 7% or greater (e.g., about 9% or greater). In certain examples, the alloys described herein, after brazing, can have an elongation of about 7% or greater, about 7.25% or greater, about 7.50% or greater, about 7.75% or greater, about 8% or greater, about 8.25% or greater, about 8.50% or greater, about 8.75% or greater, about 9% or greater, about 9.25% or greater, about 9.50% or greater, about 9.75% or greater, about 10.0% or greater, about 10.25% or greater, about 10.50% or greater, about 10.75% or greater, about 11.0% or greater, about 11.25% or greater, about 11.50% or greater, about 11.75% or greater, about 12.0 or greater, about 12.25% or greater, about 12.50% or greater, about 12.75% or greater, about 13.0% or greater, or anywhere in between.
In some examples, the alloys described herein provided in an H temper can have an average conductivity value of above about 50% based on the international annealed copper standard (IACS) (e.g., from about 50% IACS to about 60% IACS). For example, the alloy can have an average conductivity value of about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%, about 59%, about 60%, or anywhere in between. All values in % IACS.
In some examples, the alloys described herein, after brazing, can have an average conductivity value of above about 40% based on the international annealed copper standard (IACS) (e.g., from about 40% IACS to about 55% IACS). For example, the alloy can have an average conductivity value of 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%, or anywhere in between. All values in % IACS.
In certain aspects, the alloys described herein can have a corrosion resistance that provides a negative corrosion potential or electrochemical potential (Ecorr) of about −700 mV or less when tested according to the ASTM G69 standard. In certain cases, an open corrosion potential value vs. Standard Calomel Electrode (SCE) can be about −700 mV or less, about −710 mV or less, about −720 mV or less, about −730 mV or less, about −740 mV or less, about −750 mV or less, about −760 mV or less, about −770 mV or less, about −780 mV or less, about −790 mV or less, about −800 mV or less, or anywhere in between. For example, the aluminum alloy can have an open corrosion potential of from about −700 mV to about −800 mV (e.g., from about −715 mV to about −775 mV or from about −725 mV to about −770 mV).
In certain aspects, the alloys described herein have excellent sag resistance. The sag resistance was measured by placing an aluminum alloy in a custom built rig including a clamping device that suspends the aluminum alloy perpendicular to the ground. Samples between about 1 inch to 2 inches wide were cut across the rolling direction and the sample length along the rolling direction was adapted to the thickness of the fin being tested. The initial height at the tip of the sample was measured. A simulated braze cycle was applied to the aluminum alloy. The distance from the tip of the brazed aluminum alloy to the ground is measured to determine the amount of deflection of the sample. In certain aspects, the alloys described herein can have an average sag distance of about 1 mm, about 1.20 mm, about 1.40 mm, about 1.60 mm, about 1.80 mm, about 2 mm, about 2.20 mm, about 2.40 mm, about 2.60 mm, about 2.80 mm, about 3 mm, about 3.20 mm, about 3.40 mm, about 3.60 mm, about 3.80 mm, about 4 mm, or anywhere in between. In some embodiments, the sagging distance may be between 0 mm to about 100 mm (e.g., less than about 35 mm) depending on the initial sample length. For example, for an aluminum alloy having a thickness less about 0.1 mm (e.g., from about 0.05 mm to 1 mm) and a length of 35 mm, the sag resistance is less than 35 mm.
In some embodiments, exemplary aluminum alloys having about 0.80-0.90% Si, up to about 0.30% Fe, up to about 0.03% Cu, about 1.35-1.50% Mn, up to about 0.05% Mg, about 0.75-0.85 Zn, up to about 0.01% Cr, up to about 0.03% Ti, and up to about 0.15% of impurities, and Al, exhibited a pre-braze ultimate tensile strength of about 160 MPa to 180 MPa, a yield strength of about 150 MPa to 160 MPa, an elongation from 2% to 2.50%, and a conductivity from 55% IACS to 60% IACS. After brazing, the aforementioned aluminum alloy exhibited a ultimate tensile strength of about 120 MPa to 130 MPa, a yield strength of about 40 MPa to 50 MPa, an elongation from 11% to 12%, and a conductivity from 45% IACS to 50% IACS.
In certain aspects, the disclosed alloy composition is a product of a disclosed method. Without intending to limit the disclosure, aluminum alloy properties are partially determined by the formation of microstructures during the alloy's preparation. In certain aspects, the method of preparation for an alloy composition may influence or even determine whether the alloy will have properties adequate for a desired application.
In some embodiments, an exemplary method for producing the aluminum alloys described herein may include the following steps. The method may include direct chill (DC) casting an aluminum alloy into an ingot. Following casting, the process comprises hot rolling of the ingot. The ingots produced by casting are preheated for hot rolling. The preheating temperature and duration of hot rolling are finely controlled to preserve a large grain size and high strength after the aluminum alloy is brazed. In the process for hot rolling, the ingots can be preheated to up to about 560° C. (e.g., from about 450° C. to about 480° C.) in a furnace at a suitable heating rate (e.g., about 60° C./hr), followed by maintaining the temperature (“soak” or “soaking”) from about 450° C. to about 560° C. (e.g., about 450° C. to about 480° C.) for about 4 hours to about 16 hours. Following preheating and soaking, the ingots are hot rolled in the range of about 450° C. to about 500° C. to a thickness less from about 2 mm to about 15 mm, which may be referred to as “exit gauge” after hot rolling. After hot rolling, the aluminum alloy product is cold rolled in a two-stage cold rolling process. In the first cold rolling step, the aluminum alloy product is cold rolled to an intermediate gauge thickness (e.g., less than about 1 mm) aluminum alloy product in a number of cold rolling passes. The intermediate gauge thickness aluminum alloy product can optionally be inter-annealed at an annealing temperature from about 250° C. to about 400° C. (e.g., about 400° C.) at a heating rate (e.g., 50° C./hr) for about 3 hours to about 5 hours. The intermediate gauge thickness aluminum alloy product is cold rolled in a second cold step to produce a final gauge aluminum alloy product (e.g., about 0.05 mm to about 0.10 mm).
The alloy described herein can be cast using a casting method as known to those of skill in the art. For example, the casting process can include a direct chill (DC) casting process. The DC casting process is performed according to standards commonly used in the aluminum industry as known to one of skill in the art. The DC process can provide an ingot. Optionally, the ingot can be scalped before downstream processing. Optionally, the casting process can include a continuous casting (CC) process.
The cast aluminum alloy can then be subjected to further processing steps. For example, the processing methods as described herein can include the steps of homogenization, hot rolling, cold rolling, and/or annealing.
The preheating step can include heating a cast aluminum alloy as described herein to attain a preheating temperature of about, or at least about, 400° C. (e.g., at least about 410° C., at least about 420° C., at least about 430° C., at least about 440° C., at least about 450° C., at least about 460° C., at least about 470° C., at least about 480° C., at least about 490° C., at least about 500° C., at least about 510° C., at least about 520° C., at least about 530° C., at least about 540° C., at least about 550° C., at least about 560° C., or anywhere in between). For example, the cast aluminum alloy can be heated to a temperature of from about 400° C. to about 560° C., from about 420° C. to about 550° C., from about 440° C. to about 540° C., from about 450° C. to about 530° C., or from about 450° C. to about 480° C. In some cases, the heating rate to the preheating temperature can be about 10° C./hour or greater, about 20° C./hour or greater, about 30° C./hour or greater, about 40° C./hour or greater, about 50° C./hour or greater, about 60° C./hour or greater, or about 70° C./hour or greater. In other cases, the heating rate to the preheating temperature can be from about 10° C./min to about 100° C./min (e.g., about 10° C./min to about 90° C./min, about 20° C./min to about 80° C./min, about 30° C./min to about 70° C./min, from about 40° C./min to about 65° C./min, from about 45° C./min to about 60° C./min, or from about 50° C./min to about 60° C./min).
The cast aluminum alloy is then allowed to soak (i.e., held at the indicated temperature) for a period of time at the preheating temperature range. According to one non-limiting example, the cast aluminum alloy is allowed to soak for up to about 16 hours (e.g., from about 10 minutes to about 16 hours, inclusively). For example, the cast aluminum alloy can be soaked at a temperature from about 450° C. to about 560° C. for about 10 minutes, about 30 minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, about 11 hours, about 12 hours, about 13 hours, about 14 hours, about 15 hours, about 16 hours, or anywhere in between. In some embodiments, the cast aluminum alloy is soaked at a preheating temperature from about 480° C. to about 560° C. for about 5 hours to about 7 hours.
Following the preheating step, a hot rolling step can be performed. The cast aluminum alloy can be hot rolled at a temperature from about 450° C. to about 560° C. (e.g., from about 460° C. to about 550° C., from about 470° C. to about 540° C., from about 480° C. to about 530° C., or from about 490° C. to about 520° C.). In some examples, the hot rolling temperature is about 450° C., about 460° C., about 470° C., about 480° C., about 490° C., about 500° C., about 510° C., about 520° C., about 530° C., about 540° C., about 550° C. or about 560° C. If the hot rolling temperature is too cold (e.g., less than 450° C.), the hot roll loads are too high and may be susceptible to cracking. If the hot rolling temperature is too hot (e.g., greater than 560° C.), the aluminum alloy may be too soft and break up in the hot rolling mill. In some embodiments, the cast aluminum alloy can be hot rolled at a temperature from about 450° C. to about 500° C.
In certain cases, the cast aluminum alloy can be hot rolled to an about 2 mm to about 15 mm thick gauge (e.g., from about 2.5 mm to about 12 mm thick gauge). For example, the cast aluminum alloy can be hot rolled to an about 2 mm thick gauge, about 2.5 mm thick gauge, about 3 mm thick gauge, about 3.5 mm thick gauge, about 4 mm thick gauge, about 5 mm thick gauge, about 6 mm thick gauge, about 7 mm thick gauge, about 8 mm thick gauge, about 9 mm thick gauge, about 10 mm thick gauge, about 11 mm thick gauge, about 12 mm thick gauge, about 13 mm thick gauge, about 14 mm thick gauge, or about 15 mm thick gauge. In certain cases, the cast aluminum alloy can be hot rolled to a gauge greater than 15 mm (i.e., a plate). In other cases, the cast aluminum alloy can be hot rolled to a gauge less than 4 mm (i.e., a sheet).
Following the hot rolling step, a cold rolling step can be performed. In some examples, the cold rolling step is a two-stage cold rolling step. The two-stage cold rolling step can comprise a first cold rolling step, an optional intervening inter-annealing step, and a second cold rolling step. Optionally, the method can further comprise annealing the rolled product after the second cold rolling step. In certain aspects, the hot rolled products can be cold rolled to an intermediate gauge thickness in a first cold rolling step, i.e., into a first cold rolled product. In certain aspects, the hot rolled product is cold rolled to an intermediate gauge aluminum alloy product (e.g., a sheet or a shate) in the first cold rolling step. In some examples, the intermediate gauge aluminum alloy product has a thickness ranging from about 0.10 mm to 6 mm (e.g., from about 0.20 mm to about 5 mm, from about 0.25 mm to about 4 mm, from about 0.30 mm to about 3 mm, from about 0.40 mm to about 2 mm, from about 0.10 mm to about 1 mm, from about 0.15 mm to about 0.75 mm).
A second cold rolling step can be performed on the intermediate gauge aluminum alloy product. In certain aspects, the second cold rolling step can be performed after an optional inter-annealing step (described below). In certain aspects, the intermediate gauge aluminum alloy product is cold rolled to a final gauge aluminum alloy product (e.g., a sheet, such as a lower gauge sheet). In some examples, the final gauge aluminum alloy product has a thickness ranging from about 0.01 mm to 1 mm (e.g., from about 0.02 mm to about 0.90 mm, from about 0.03 mm to about 0.80 mm, from about 0.04 mm to about 0.70 mm, from about 0.05 mm to about 0.60 mm, from about 0.06 mm to about 0.50 mm, from about 0.08 mm to about 0.40 mm, from about 0.10 mm to about 0.30 mm, or from about 0.15 mm to about 0.25 mm).
In some non-limiting examples, an optional inter-annealing step can be performed during the two-stage cold rolling step. For example, the hot rolled product can be cold rolled to an intermediate gauge aluminum alloy product (first cold rolling step), optionally coiled, annealed, and subsequently cold rolled to a final gauge aluminum alloy product (second cold rolling step). In some aspects, the optional inter-annealing can be performed in a batch process (i.e., a batch inter-annealing step) or in a continuous process. The inter-annealing step can be performed at a temperature of from about 250° C. to about 450° C. (e.g., about 250° C., about 260° C., about 270° C., about 280° C., about 290° C., about 300° C., 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 heating rate in the inter-annealing step can be about 100° C./hour or less, 75° C./hour or less, 50° C./hour or less, 40° C./hour or less, 30° C./hour or less, 25° C./hour or less, 20° C./hour or less, or 15° C./hour or less. In other cases, the heating rate can be from about 10° C./min to about 100° C./min (e.g., from about 10° C./min to about 90° C./min, from about 10° C./min to about 70° C./min, from about 10° C./min to about 60° C./min, from about 20° C./min to about 90° C./min, from about 30° C./min to about 80° C./min, from about 40° C./min to about 70° C./min, or from about 50° C./min to about 60° C./min).
In some embodiments, the intermediate gauge aluminum alloy product is allowed to soak for a period of time during the inter-annealing step. In some examples, the intermediate gauge aluminum alloy product is allowed to soak for up to about 5 hours (e.g., from about 30 minutes to about 4 hours, from about 45 minutes to about 3 hours, or from about 1 hour to about 2 hours, inclusively). For example, the intermediate gauge aluminum alloy product can be soaked at a temperature of from about 250° C. to about 450° C. for about 20 minutes, about 30 minutes, about 45 minutes, about 1 hour, about 1.5 hours, about 2 hours, about 3 hours, about 4 hours, about 5 hours, or anywhere in between. In some examples, the intermediate gauge aluminum alloy product can be soaked at a temperature of about 400° C. for about 4 hours.
The aluminum alloys and methods described herein can be used in industrial applications including sacrificial parts, heat dissipation, packaging, and building materials. The aluminum alloys described herein can be used in various applications, for example, for manufacturing fins for heat exchangers. In one example, the improved aluminum alloys described herein are useful for high performance, light weight automotive heat exchangers. More generally, the aluminum alloys described herein can be used in motor vehicle heat exchangers such as radiators, condensers and evaporators. As discussed above, the compositions and the processes for producing the improved aluminum alloys described herein lead to a material possessing a combination of beneficial characteristics and properties that make it suitable for manufacturing heat exchanger fins. However, the uses and applications of the improved aluminum alloys described herein are not limited to automotive heat exchangers and other uses are envisioned. It is to be understood that the characteristics and properties of the aluminum alloys described herein can also be beneficial for uses and applications other than the production of automotive heat exchanger fins. For example, the improved aluminum alloys described herein can be used for manufacture of various devices employing heat exchangers and produced by brazing, such as devices employed in heating, ventilation, and air conditioning (HVAC).
The aluminum alloys disclosed herein are suitable substitutes for metals conventionally used in indoor and outdoor HVAC units. As used herein, the meaning of “indoor” refers to a placement contained within any structure produced by humans with controlled environmental conditions. As used herein, the meaning of “outdoor” refers to a placement not fully contained within any structure produced by humans and exposed to geological and meteorological environmental conditions comprising air, solar radiation, wind, rain, sleet, snow, freezing rain, ice, hail, dust storms, humidity, aridity, smoke (e.g., tobacco smoke, house fire smoke, industrial incinerator smoke and wild fire smoke), smog, fossil fuel exhaust, bio-fuel exhaust, salts (e.g., high salt content air in regions near a body of salt water), radioactivity, electromagnetic waves, corrosive gases, corrosive liquids, galvanic metals, galvanic alloys, corrosive solids, plasma, fire, electrostatic discharge (e.g., lightning), biological materials (e.g., animal waste, saliva, excreted oils, vegetation), wind-blown particulates, barometric pressure change, and diurnal temperature change. The aluminum alloys described herein provide better corrosion performance and higher strength as compared to alloys currently employed.
The following examples will serve to further illustrate the present invention without, however, constituting any limitation thereof. On the contrary, it is to be clearly understood that resort may be had to various embodiments, modifications and equivalents thereof which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the invention. During the studies described in the following examples, conventional procedures were followed, unless otherwise stated. Some of the procedures are described below for illustrative purposes.
Alloys 1, 2, 3, 4, 5, 6 are exemplary alloys produced according to methods described below. Alloy A is a comparative alloy prepared according to methods described below. Alloy A is a conventional aluminum alloy which is currently employed as an industrial fin stock in commercial applications.
Alloys 1, 2, 3, 4, 5, 6 and Alloy A, as shown in Table 5, were direct chill cast into ingots. The ingots were preheated to 480° C. at a heating rate of 60° C./h and soaked for 6 hours. After preheating, the ingots were hot rolled resulting in an aluminum alloy product having a gauge reduction from 76 mm to 2.5 mm. In a first cold rolling step, the aluminum alloy product was cold rolled to an intermediate gauge thickness (e.g., about 0.18 mm) aluminum alloy product in five cold rolling passes. The intermediate gauge thickness aluminum alloy product was inter-annealed at an annealing temperature of about 400° C. at a heating rate of about 50° C./hr for about 4 hours. The intermediate gauge thickness aluminum alloy product was cold rolled in a second cold step to produce a final gauge aluminum alloy product in an H16 temper having a final gauge of 0.09 mm. Alloys 1, 2, 3, 4, 5, 6 and Alloy A were brazed using a standard brazing cycle at 600° C. for 3 minutes.
The mechanical properties of the exemplary alloys and comparative alloy were determined according to ASTM B557. Specifically, the alloys were subjected to tensile, yield strength, elongation, and conductivity tests. The yield strength (YS), ultimate tensile strength (UTS), percent elongation (EI), and percent of the International Annealed Copper Standard (% IACS) were determined. The test results are summarized in Table 6.
As shown in Table 6, Example Alloys 4-6 exhibited excellent pre-braze strength compared to Comparative Example A currently employed as industrial fin stock. Example Alloys 4-6 each exhibited a tensile strength greater than 165 MPa and a yield strength greater than 155 MPa. Surprisingly, after brazing, Example Alloys 4-6 exhibited a tensile strength greater than 120 MPa and yield strength greater than 45 MPa. Each of Examples Alloys 1-6 also achieved an electrical conductivity greater than 45% IACS, which was significantly greater than the electrical conductivity of Comparative Example A. As shown above in Table 6, the exemplary alloys described herein display exceptional mechanical properties as compared to the comparative alloy and can be excellent commercial alloys employed in industrial fin stock applications.
The corrosion properties and sag resistance of exemplary alloys described herein and the comparative alloy described herein, elemental compositions of which are provided in Table 5, were determined. The open circuit potential corrosion values were measured according to ASTM G69. The sag resistance values were measured according to the methods described herein. Corrosion and sag resistance of the exemplary alloys and comparative alloy were determined after a simulated brazing cycle at temperature of about 605° C. and subsequent cooling to room temperature in about 20 minutes. Corrosion and sag resistance test results are summarized in Table 7.
The exemplary alloys exhibited electrochemical potential values comparable to electrochemical potential values of tube alloys. Conventional aluminum tube alloys have an average open corrosion potential value vs. SCE of −741 mV. The differences between Alloys 1-6 and aluminum tube alloys ranged from 4-27 mV. In comparison, Comparative Alloy A had a large difference in electrochemical potential values of tube alloys. The data show that Alloys 1-6 are acceptable to prepare fins that act as sacrificial anodes. Additionally, Alloys 1-6 exhibited excellent sagging resistance, while still maintaining a balance of desired mechanical and corrosion properties.
The aluminum alloys described herein provide sacrificial corrosion characteristics and mechanical characteristics which enable the manufacture of aluminum alloy fin stock of reduced thickness. The fin stock of reduced thickness maintains sacrificial protection for the copper or aluminum alloy tubes in contact with the fins. The aluminum alloys described herein can also be used in other situations where mechanical strength in combination with sacrificial characteristics are desired.
All patents, publications and abstracts cited above are incorporated herein by reference in their entireties. Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptions thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention as defined in the following claims.
This application claims the benefit of and priority to U.S. Provisional Application No. 63/199,900, filed Feb. 1, 2021, which is incorporated herein by reference in its entirety for all intents and purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/070150 | 1/12/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63199900 | Feb 2021 | US |
