US20220097130A1

US20220097130A1 - Aluminum castings using ultrasonic technology

Info

Publication number: US20220097130A1
Application number: US17/032,518
Authority: US
Inventors: Qigui Wang; Wenying Yang; John M. Kremer; Daniel J. Wilson; Dale A. Gerard; Thomas W. Gustafson
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2022-03-31
Also published as: DE102021110122A1; CN114247874A

Abstract

A ladle, process, and system for casting an aluminum-based alloy includes a casting ladle. The casting ladle includes a cup and the cup defines an opening. The ladle also includes an ultrasonic transducer including an end immersed in the cup, wherein the cup exhibits a first depth and the ultrasonic transducer is immersed in the cup at a second depth in a range of 5 percent to 100 percent of the first depth. An aluminum-based alloy melt is introduced into an opening of a casting ladle, an ultrasonic transducer immersed in the aluminum-based alloy melt is activated, and the aluminum-based alloy melt is transferred onto a casting surface.

Description

Porosity and grain structure of metal alloys have long been recognized as factors affecting mechanical properties, especially alloy ductility and fatigue performance of cast components. Porosity forms, in part, due to solubilized gasses in the liquid melt, which are less soluble in the solid structure and become trapped. In addition, volumetric shrinkage in the transition of the melt from a liquid phase to a solid phase during solidification can contribute to porosity. Unrefined and undesirable grain structures (including large and columnar grain formations) can form if solidification temperatures are not carefully controlled. These problems are particularly acute in the casting of lightweight metal alloys (such as aluminum-based alloys in general and aluminum-silicon alloys (319, 356, 390 or the like in particular) that are used to make—among other things—automotive cylinder blocks and heads.
The evolution of dissolved gases as a result of the significant decrease in solubility of the gases in the solid as compared to the liquid metal is often the primary cause of porosity. This is especially true for aluminum-based castings, where hydrogen-induced porosity is the dominant form due to hydrogen being the gas that is appreciably soluble in molten aluminum. As such, there are several methods that are currently employed to reduce inclusion and hydrogen content in liquid aluminum. These methods include various degassing techniques, including rotary impeller degassing, tablet (such as hexachloroethane (C₂Cl₆)) degassing, vacuum degassing, and spray degassing. Although such degassing methods have demonstrated effectiveness, to varying degrees, in refining aluminum-based melts, they can cause environmental problems (for example, due to Cl₂gas release) or involve significant capital investment.
Further, it is desirable to pursue fine and equiaxed grain structure in aluminum-based castings as a way to minimize shrinkage, hot tearing, and fatigue susceptibility, as well as improve ductility and provide a relatively more uniform distribution of fine scale second phases and microporosity. These in turn improve yield strength, fracture toughness, and other useful mechanical properties. Generally, any factor which increases the number of nucleation sites or reduces growth rate has a tendency to yield fine grains in an as-cast aluminum alloy. Commonly used techniques include using a chill or related insert in the mold to increase local solidification rate (which in turn tends to promote grain size reduction and related mechanical properties). For instance, in a sand-cast engine block, the bulkheads near the crankshaft journal areas are formed with heavy metal chills to assure the required mechanical properties. Unfortunately, when chills are used, undesirable local columnar grain structure may form; such structure can significantly reduce the fatigue performance of the material. Therefore, in practice grain refiners in the form of chemical or elemental additives (such as titanium, boron, carbon, or combinations thereof) are often placed in the liquid metal or mold prior to mold fill when a chill is employed. Because the addition of such a grain refiner to a liquid metal melt in the furnace tends to lead to sludge settling over time, such an approach can significantly contribute to furnace and recirculation pump maintenance costs. Likewise, in-mold grain refinement tends to produce more oxides (which can contribute to undesirable bi-film formation) and microstructure segregation in the casting.
Accordingly, while the current aluminum alloy formation processes achieve their intended purposes, there is a need for a new and improved system and method for processing aluminum alloys to reduce porosity and reduce grain structure.

SUMMARY

According to several aspects, a ladle for casting an aluminum-based alloy includes a casting ladle. The casting ladle includes a cup and the cup defines an opening. The ladle also includes an ultrasonic transducer including an end immersed in the cup, wherein the cup exhibits a first depth and the ultrasonic transducer is immersed in the cup at a second depth in a range of 5 percent to 100 percent of the first depth.
In further aspects, the cup is defined by a ladle wall and the ultrasonic transducer does not directly contact the ladle wall.
In further aspects, the cup is defined by a ladle wall and the ladle further includes a bracket connected to the ladle wall, wherein the ultrasonic transducer is connected to the bracket.
In additional aspects, the bracket defines an aperture and the ultrasonic transducer is positioned in the aperture.
In further aspects, the ultrasonic transducer is secured to a robot arm movable relative to the opening defined in the cup.
In further aspects, the robot arm is connected to the casting ladle.
According to several aspects, a process of casting an aluminum-based alloy, includes introducing an aluminum-based alloy melt into an opening of a casting ladle. The casting ladle includes a cup for receiving the aluminum-based alloy melt and the cup exhibits a first depth. The process further includes activating an ultrasonic transducer immersed in the aluminum-based alloy melt. The ultrasonic transducer is immersed through the opening to a second depth in a range of 5 percent to 100 percent of the first depth of the cup. The process also includes transferring the aluminum-based alloy melt onto a casting surface.
In further aspects, the ultrasonic transducer is activated for a time period in the range of 5 second to 40 seconds.
In further aspects, the process includes applying power to the ultrasonic transducer at levels in a range of 1 kilowatt to 10 kilowatts, at a power density in a range of 10 watts per square centimeter to 500 watts per square centimeter, and at a frequency in a range of 10 kilohertz to 100 kilohertz.
In further aspects, the process includes deactivating the ultrasonic transducer prior to transferring the aluminum-based alloy melt onto the casting surface.
In further aspects, the ultrasonic transducer is immersed in the casting ladle prior to introducing the aluminum-based alloy melt into the opening of the casting ladle.
In additional aspects, the ultrasonic transducer is immersed into the casting ladle by a robot arm after the aluminum-based alloy melt is introduced into the casting ladle.
In further aspects, the casting surface is a mold cavity.
In additional aspects, the casting surface is a belt.
According to several aspects, a system for casting an aluminum-based alloy includes a casting surface for receiving an aluminum-based alloy melt, and a casting ladle for transferring the aluminum-based alloy melt onto the casting surface, the casting ladle including a cup, the cup defining an opening, and an ultrasonic transducer including an end immersed in the cup through the opening, wherein the cup exhibits a first depth and the ultrasonic transducer is immersed in the cup at a second depth in a range of 5 percent to 100 percent of the first depth.
In further aspects, the casting surface includes a mold cavity.
In additional aspects, the casting surface includes a belt.
In further aspects, the system includes a power supply and a controller operatively coupled to the ultrasonic transducer.
In further aspects, the cup is defined by a ladle wall and the system includes a bracket connected to the ladle wall, wherein the ultrasonic transducer is connected to the bracket.
In additional aspects, the ultrasonic transducer is secured to a robot arm and the robot arm is movable relative to the opening defined in the cup.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 illustrates a casting ladle including an ultrasonic transducer according to an exemplary embodiment;

FIG. 2 illustrates a casting ladle including an ultrasonic transducer according to an exemplary embodiment;

FIG. 3 illustrates a process of degassing and refining the grain size of an aluminum-based alloy melt according to an exemplary embodiment;

FIG. 4A illustrates a casting process wherein the aluminum-based alloy melt is poured into a mold according to an exemplary embodiment;

FIG. 4B illustrates a continuous casting process according to an exemplary embodiment;

FIG. 4C illustrates a high pressure die casting process according to an exemplary embodiment;

FIG. 5A illustrates porosity of an untreated alloy according to an exemplary embodiment;

FIG. 5B illustrates porosity of a treated alloy according to an exemplary embodiment;

FIG. 5C illustrates porosity of a treated alloy according to an exemplary embodiment;

FIG. 6A illustrates grain structure of an untreated alloy according to an exemplary embodiment;

FIG. 6B illustrates grain structure of a treated alloy according to an exemplary embodiment;

FIG. 6C illustrates grain structure of a treated alloy according to an exemplary embodiment;

FIG. 7A illustrates grain structure of an untreated alloy according to an exemplary embodiment;

FIG. 7B illustrates primary silicon particle size distribution of the untreated alloy according to an exemplary embodiment;

FIG. 7C illustrates grain structure of a treated alloy according to an exemplary embodiment; and

FIG. 7D illustrates primary silicon particle size distribution of the treated alloy according to an exemplary embodiment.

DETAILED DESCRIPTION

The present disclosure is directed to a casting ladle and process for forming aluminum castings using ultrasonic technology as well as a method for processing aluminum-based alloys and, in aspects, improving the quality and mechanical performance of aluminum-based alloy castings using ultrasonic technology. In aspects, the casting ladles described herein are used with a number of casting processes.
FIG. 1 illustrates an aspect of the casting ladle 100, including an ultrasonic transducer 102 held in position within the aluminum-based alloy melt 104 in the ladle 100. In the illustrated aspect, the ultrasonic transducer 102 is held in the ladle 100 with a mounting bracket 106 connected to the ladle 100. In alternative aspects, such as those illustrated in FIG. 2, the ultrasonic transducer 102 is held in the ladle 100 using a robotic arm 108, which is moveable and positions the ultrasonic transducer 102 in the ladle 100 or removes the ultrasonic transducer 102 from the ladle 100.
With reference to FIGS. 1 and 2, the casting ladle 100 defines an opening 112 in a cup 114 that is formed by a ladle wall 116. In the illustrated aspect, the opening 112 is defined in the top 118 of the ladle 100. In aspects (not illustrated), the ladle 100 may include a lid that at least partially, or completely, covers the opening 112. In aspects, the casting ladle 100 is a pouring ladle, which is understood as a ladle 100 that is used to pour liquid melt into a casting mold or onto a conveyor. When filled, the aluminum-based alloy melt 104 fills at least a portion of the volume 120 defined by the cup 114. In aspects, the casting ladle 100 is formed from tool steel, ceramic, or other materials that retain structural integrity at the working temperatures of the castable metal materials.
The ultrasonic transducer 102 is positioned within the volume 120 of the cup 114, such that an end 124 of the ultrasonic transducer 102 is immersed in the aluminum-based alloy melt 104, from the top 118 of the ladle 100, either before or after the aluminum-based alloy melt 104 is introduced into the ladle 100. Accordingly, in aspects, the end 124 of the ultrasonic transducer 102 is immersed into the ladle through the opening 112 of the cup 114. The cup 114 exhibits a first depth d and the ultrasonic transducer 102 is immersed at a second depth that is at least 5 percent of the first depth d of the cup 114, including all values and ranges from 5 percent to 100 percent of the first depth d of the cup 114, such as 5 percent to 75 percent, 10 percent to 50 percent, etc. In aspects, the ultrasonic transducer 102 does not directly contact the ladle wall 116, including at the bottom 136 of the cup 114. In addition, the ultrasonic transducer 102 is configured to operate at power levels in the range of 1 kilowatt to 10 kilowatts, including all values and ranges therein, a power density in the range of 10 watts per square centimeter to 500 watts per square centimeter, including all values and ranges therein, and a frequency of 10 kilohertz to 100 kilohertz, including all values and ranges therein.
In aspects, such as the aspect illustrated in FIG. 1, the ultrasonic transducer 102 is held in the ladle 100 with a bracket 106. In the illustrated aspect, the bracket 106 is mounted to the interior 130 of the cup 114. However, in other aspects, the bracket 106 may be mounted to the exterior 132 of the cup 114, or both the interior 130 and exterior 132 of the cup 114. The bracket 106 extends over the opening 112 of the ladle 100, to position the ultrasonic transducer 106 a distance away from the ladle wall 116.
Further, in the illustrated aspect, the bracket 106 defines an aperture 134, in which the ultrasonic transducer 102 is mounted. In aspects, the ultrasonic transducer 102 is mechanically coupled to the bracket 106 using one or more mechanical fasteners, such as nuts, bolts, screws, or clamps. Alternatively, or additionally, the ultrasonic transducer 102 is retained in the bracket 106 by an interference fit between the ultrasonic transducer 102 and the aperture 134 in which the ultrasonic transducer 102 is positioned. In further aspects, the ultrasonic transducer 102 is coupled to the bracket 106 in an adjustable manner, wherein the transducer 102 may be raised and lowered relative to the bottom 136 the cup 114. It should be appreciated that adjustable mounting is useful when the amount of aluminum-based alloy melt 104 within the ladle 100 varies from casting process to casting process or product application to product application. In aspects, a gasket (not illustrated) is positioned in the aperture 134 between the ultrasonic transducer 102 and the bracket 106, dampening the vibration of the ultrasonic transducer 102 to prevent damage to the bracket 106 and ladle 100.
With reference now to FIG. 2, the ultrasonic transducer 102 is positioned in the ladle 100 by a robot arm 108. In such aspects, the ultrasonic transducer 102 is secured to the robot arm 108 and the robot arm 108 raises and lowers the ultrasonic transducer 102 relative to the opening 112 of the cup 114. In aspects, the robot arm 108 is secured to the ultrasonic transducer by a clamp or mechanical fasteners. Further, while only two linkages 140, 142 of the robot arm 108 are illustrated, more than two linkages may be present, such as 3 or 4 depending on the level and degree of movement required to position the ultrasonic transducer 102 within the ladle 100. Further, while the robot arm 108 is illustrated as being connected to the ladle wall 116, it should be appreciated that in aspects the robot arm 108 is not connected directly on the ladle 100, such that the ladle 100 can move relative to the robot arm 108. In aspects, the robot arm 108 lowers the ultrasonic transducer 102 into the ladle 100 after the liquid melt 104 has been introduced into the ladle 100. In further aspects, 108, dampening pads (not illustrated) are positioned between the robot arm 108 and the ultrasonic transducer 102, which may dampen the vibration of the ultrasonic transducer 102 and prevent damage to the robot arm 108.
While FIGS. 1 and 2 illustrate the use of an ultrasonic transducer 102, in alternative aspects (not illustrated), more than one ultrasonic transducer 102 may be present, such as in the range of 2 transducers to 10 transducers, including all values and ranges therein. The additional ultrasonic transducers 102 may be held in placed by one or more brackets 106 or immersed into the aluminum-based alloy melt 104 by one or more robotic arms 108.
An ultrasonic transducer 102 is understood as a wave generator, which generates waves by converting electrical energy or, in some aspects, mechanical energy, into sound energy by mechanically vibrating. Accordingly, in aspects, such as the aspect illustrated in FIG. 1, a system for using a casting ladle and process for forming aluminum castings using ultrasonic technology includes a power supply 148 for providing electrical energy to the ultrasonic transducer 102. In further aspects, the system includes a controller 150 for regulating and modulating the power provided by the power supply 148 to the ultrasonic transducer 102. The power supply 148 and controller 150 are operatively coupled to the ultrasonic transducer 102. Further, in aspects, the ultrasonic transducer is a piezoelectric transducer, magneto-strictive transducer, electromagnetic transducer, etc. In additional aspects, the ultrasonic transducers are insulated by, for example, coating with a layer of ceramic.
In aspects, the ladle 100 is used to reduce porosity and refine grain structures while casting aluminum-based alloys into various components, such as automatic components. Grains are understood herein as relatively small regions of a metal, unalloyed or alloyed, having a given and continuous crystal lattice orientation. Each grain represents a single crystal. The aluminum-based alloys are, in aspects, aluminum casting alloys, which include, but are not limited to, aluminum silicon alloys, aluminum copper alloys, aluminum magnesium alloys and aluminum zinc alloys. Aluminum silicon alloys include for example, near eutectic aluminum-silicon alloys such as 336, 339, 369, 384, 385. Aluminum silicon alloys also include, for example, hypereutectic aluminum-silicon alloys such as 390, A390, B390, 392, and 393. Aluminum silicon alloys further include, for example, hypoeutectic aluminum-silicon alloys such as 356, A356, B356, C356, 357, A357, B357, C357, D357, 360, A369, 380, A380, B380, 383 and 384. Aluminum copper alloys include, for example, 206, A206, 208, 212, and 224. Aluminum magnesium alloys include, for example, 511, 512, 513, 514, 515, 516, 518, 520, A535, B535 and 535. Aluminum zinc alloys include, for example, 705, 707, 710, 712, 713, 771 and 772. In particular aspects, the alloys are hyper-eutectic aluminum-silicon alloys, including aluminum present in the range of 70 weight percent to 81 weight percent, including all values and ranges therein, copper present in the range of 0.4 to 5.0 weight percent, including all values and ranges therein, iron present in the range of less than, up to and including 1.3 weight percent, including all values and ranges between 0 to 1.3 weight percent, magnesium present in the range of 0.4 weight percent to 1.3 weight percent, including all values and ranges therein, manganese present in the range of less than, up to, and including 0.6 weight percent, including all values and ranges between 0 and 0.6 weight percent, silicon present in the range of 16 weight percent to 23 weight percent, including all values and ranges therein, titanium present in the range of less than, up to, and including 0.2 weight percent, including all values and ranges between 0 and 0.2 weight percent, zinc present in the range of less than, up to, and including 0.4 weight percent, including all values and ranges between 0 and 0.4 weight percent. It is noted that some hyper-eutectic aluminum-silicon alloys include one or more of the following: up to 2.5 weight percent nickel, up to 0.3 weight percent tin, and in the range of 0.08 to 0.15 vanadium. Other elements may be present in the alloy compositions at a total of 0.5 weight percent for any other elements, unspecified above, combined. Further, the elemental ranges noted above total 100 percent of combined elements for a given alloy composition, selected from the ranges above.
Turning now to FIG. 3, with further reference to FIGS. 1 and 2, the figure illustrates a process 300 for casting an aluminum-based alloy using the casting ladle 100 described above to degas the alloy, reduce porosity, and refine the alloy grain structure. At block 302, an aluminum-based alloy melt 104 is poured into a casting ladle 100. The ultrasonic transducer 102 being immersed in the casting ladle and aluminum-based alloy melt, as described above. It should be appreciated from the above that an end of the ultrasonic transducer is immersed in the casting ladle before or after the aluminum-based alloy melt is added. At block 304, an end 124 of the ultrasonic transducer 102 is immersed in the ladle 100 either before or after the aluminum-based alloy melt 104 is poured into the ladle 100. As mentioned above, the ultrasonic transducer 102 is held immersed in the ladle 100 by a bracket 106 or the ultrasonic transducer 102 is immersed by a robot arm 108.
With the aluminum-based alloy melt 104 in the ladle 100, power is applied to the ultrasonic transducer 102 and the ultrasonic transducer 102 is activated, at block 306, for a period of time in the range of 5 seconds to 40 seconds, including all values and ranges therein, such as 10 seconds to 40 seconds, 10 seconds to 35 seconds, etc. In aspects, the aluminum-based alloy melt 104 is treated in the melt (liquid) state. As alluded to above, the power is applied at levels in the range of 1 kilowatt to 10 kilowatts, including all values and ranges therein, at a power density in the range of 10 watts per square centimeter to 500 watts per square centimeter, including all values and ranges therein, and at a frequency of 10 kilohertz to 100 kilohertz, including all values and ranges therein. When activated, the ultrasonic transducer 102 imparts vibrations to the aluminum-based alloy melt 104. At the end of the time period at block 308, the transducer is turned off and the aluminum-based alloy melt 104 is transferred from the ladle 100 onto a casting surface, such as by pouring the aluminum-based alloy melt 104 into a mold cavity or onto a belt, discussed further herein. It was discovered that even though the activation of the ultrasonic transducer was short, the aluminum-based alloy melt 104 is degassed and the grain structure is refined as discussed further below.
FIG. 4A illustrates a system and process for casting of the aluminum-based alloys by transferring the aluminum-based alloy melt 104 into a mold 154, wherein the type of mold 154 depends on the casting process used. The mold 154 includes a cavity 156, which receives and shapes the aluminum-based alloy melt 104 into the desired component. As noted above, component formed by the processes discussed herein may include various automotive components such as an engine block, cylinder head, transmission covers, transmission cases, drive unit housing, knuckles, cradles, control arms, or panels. In some aspects, the mold 154 may include a parting line 158 for opening the mold 154 and removing the part without damaging the mold 154. Examples of casting processes using molds include, for example, sand casting, plaster casting, shell mold casting, investment casting, evaporative-pattern casting, lost foam-casting, permanent mold casting, semi-permanent mold casting, die casting, squeeze casting, and centrifugal casting. Another casting system and process that uses a mold includes high pressure die casting, an example of which is illustrated in FIG. 4C. In this process, the aluminum-based alloy melt 104 is poured from the ladle 100 into a shot sleeve 160. A plunger 162 then transfers the aluminum-based alloy melt 104 into the cavity 156 under pressure. FIG. 4B illustrates a continuous casting system and process in which the aluminum-based alloy melt 104 is poured onto a belt 164. This process is often used to make sheets or ribbon of the aluminum-based alloy. Additional rollers or belts 166 may be present for sandwiching the solidifying aluminum-based alloy melt 104 as it cools, reducing the thickness of the aluminum-based alloy melt 104. Various cooling methods may optionally be used in either process to control the cooling rate of the aluminum-based alloy melt 104 into a solidified part, including quenching baths, cooling lines in the molds 154, cooling in the rollers or belts 164, 166, etc.
It was found herein that the above described casting ladle 100 and processes 300 resulted in a reduction of porosity, a refinement in the grain structure of the aluminum-based alloys described herein as well as an increase in the ductility of the aluminum-based alloys, even though the aluminum-based alloys were poured from the casting ladle 100 onto the casting surfaces.
In the case of hyper-eutectic aluminum-based alloys, porosity is reduced from an average area of porosity, as measured across a given plane of the solidified aluminum-based alloy, from greater than 5%, untreated, to less than 1% after treatment. Further, the largest pore size of the treated alloy is reduced to less than 15% of the untreated pore size. The average area of a pore is less than 120,000 micrometers after ultrasonic vibration treatment in the ladle 100. In addition, the average grain size of hyper-eutectic aluminum-based alloys is reduced to less than 20% of the grain size of the untreated alloy, and in some aspects with treatment times of in the range of 33 to 35 seconds, 10% of the untreated grain size. Depending on the hyper-eutectic aluminum-based alloys, in aspects, the average grain size is less than 1.0 millimeter, and in some aspects, less than 40 micrometers, after ultrasonic vibration treatment in the ladle. An increase in mechanical properties was also found in hyper-eutectic aluminum-based alloys after ultrasonic vibration treatment in the ladle 100 and, particularly, an increase in the ductility is observed, wherein the treated alloys exhibited a ductility of more than 2% and, in some aspects up to 3%.
Reference is made herein to FIGS. 5A through 5C, which illustrate a reduction in porosity of an aluminum-based 319 alloy. The images were taken at about 5 times magnification and the scale represents 5,000 micrometers in length. The melt temperature of the treated samples was 750° C. when the samples were treated. Further the power applied to the ultrasonic transducer was 2 kilowatts, the power density was approximately 100 water per square centimeter and the frequency was 30 kilohertz. Treatment times are references herein. FIG. 5A illustrates an untreated sample. The untreated sample includes a number of relatively large dark, porous regions. The average area percent of porosity, that is the average area of porosity for a given area measured across a given plane of the solidified aluminum alloy, was found to be 5.53%, the largest pore size was found to be 786,103 square micrometers, and the largest ferret diameter, which is understood to be a measure of an object size between two parallel planes, was found to be 2,415 micrometers. FIG. 5B illustrates a sample that was treated with ultrasonic vibration for 15 seconds. As can be seen, the size of the dark, porous regions has been significantly reduced. The average area percent of porosity for a given area was found to be 0.73%, the largest pore size was found to be 112,586 square micrometers, and the largest ferret diameter was found to be 902 micrometers. FIG. 5C illustrates a sample that was treated with ultrasonic vibration for 34 seconds. The average area percent of porosity for a given area was found to be 0.53%, the largest pore size was found to be 112,089 square micrometers, and the largest ferret diameter was found to be 798 micrometers.
Reference is now made to FIGS. 6A through 6C, which illustrate reduction in grain size of the aluminum 319 alloy upon ultrasonic vibration treatment. Similar to the images of FIGS. 5A through 5C, the images were taken at about 5 times magnification and the scale represents 5,000 micrometers in length. The melt temperature of the treated samples was 750° C. when the samples were treated. Further the power applied to the ultrasonic transducer was 2 kilowatts, the power density was approximately 100 water per square centimeter and the frequency was 30 kilohertz. Treatment times are references herein. FIG. 6A illustrates the solidified aluminum-based alloy melt, untreated with ultrasonic vibration. Again, the relatively large dark, porous regions are visible. Further the average grain size was measured to be approximately 5 mm in length. FIG. 6B illustrates a sample of the solidified aluminum-based alloy melt, treated with ultrasonic vibration for 15 seconds. The average grain size was measured to be approximately 0.8 mm in length. FIG. 6C illustrates a sample of the solidified aluminum-based alloy melt, treated with ultrasonic vibration for 34 seconds. The average grain size was measured to be approximately 0.5 mm in length.
Reference is further made to FIGS. 7A through 7D, which illustrate the effect of ultrasonic vibration treatment on aluminum B390 Alloy. Note that the scales on FIGS. 7A and 7C are 100 micrometers. As illustrated in FIG. 7A, the untreated alloy exhibits relatively large grains including a relatively substantial fraction of needle like grains. FIG. 7B illustrates the primary silicon particle size distribution in the alloy. The yield strength of the alloy was found to be 246 megapascals. The ultimate tensile strength was found to be 273 megapascals. In addition, the percent elongation was found to be 0.8. The yield strength and percent elongation were measured using ASTM testing method E8 with a 1% per minute strain at room temperature. FIG. 7C illustrates a micrograph of the alloy depicting a significant reduction of grain size, reducing the needle-like structures. FIG. 7D illustrates the primary silicon particle size distribution in the alloy. The yield strength of the alloy was found to be 248 megapascals. The ultimate tensile strength was found to be 306 megapascals. In addition, the percent elongation was found to be 2.3 percent.
While casting ladles are referred to herein, the aspects described herein are applicable to other ladles as well, including transfer ladles and treatment ladles. In aspects, the aluminum-based alloy melt 104 is processed with the ultrasonic transducer 102 in the ladle 100 immediately before being poured into, or onto, the casting surface.
The casting ladle and process for forming aluminum castings using ultrasonic technology as well as a method for processing hypereutectic aluminum-silicon alloys offer several advantages. In aspects, the use of the casting ladle, including ultrasonic technology, in the process of forming a hypereutectic aluminum-silicon alloy improves the quality and mechanical performance of hypereutectic aluminum alloy castings through the reduction of porosity and microstructure refinement. In further aspects, the advantages include reduction in the hydrogen content in the liquid melt, reducing the porosity. In further aspects, these advantages include the achievement of ductility in the range of up to 2% elongation to 3% elongation, greater than the ductility presently achieved by hypereutectic aluminum-silicon alloys. In yet further aspects, these advantages include the use of the ladle described herein with a variety of casting processes. In yet further aspects, as the liquid aluminum-based alloy melt is processed with ultrasonic vibration just prior to pouring, melt processing efficiency is improved. Further, in aspects, the reduced complexity of the casting ladle reduces cost. These advantages further include the flexibility of employing the casting ladle with various casting processes.
The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.

Claims

What is claimed is:

1. A ladle for casting an aluminum-based alloy, comprising:

a casting ladle, the casting ladle including a cup, the cup defining an opening; and

an ultrasonic transducer including an end immersed in the cup, wherein the cup exhibits a first depth and the ultrasonic transducer is immersed in the cup at a second depth in a range of 5 percent to 100 percent of the first depth.

2. The ladle of claim 1, wherein the cup is defined by a ladle wall and the ultrasonic transducer does not directly contact the ladle wall.

3. The ladle of claim 1, wherein the cup is defined by a ladle wall, further comprising a bracket connected to the ladle wall, wherein the ultrasonic transducer is connected to the bracket.

4. The ladle of claim 3, wherein the bracket defines an aperture and the ultrasonic transducer is positioned in the aperture.

5. The ladle of claim 1, wherein the ultrasonic transducer is secured to a robot arm movable relative to the opening defined in the cup.

6. The ladle of claim 5, wherein the robot arm is connected to the casting ladle.

7. A process of casting an aluminum-based alloy, comprising:

introducing an aluminum-based alloy melt into an opening of a casting ladle, wherein the casting ladle includes a cup for receiving the aluminum-based alloy melt and the cup exhibits a first depth;

activating an ultrasonic transducer immersed in the aluminum-based alloy melt, wherein the ultrasonic transducer is immersed through the opening to a second depth in a range of 5 percent to 100 percent of the first depth of the cup; and

transferring the aluminum-based alloy melt onto a casting surface.

8. The process of claim 7, wherein the ultrasonic transducer is activated for a time period in the range of 5 second to 40 seconds.

9. The process of claim 7, further comprising applying power to the ultrasonic transducer at levels in a range of 1 kilowatt to 10 kilowatts, at a power density in a range of 10 watts per square centimeter to 500 watts per square centimeter, and at a frequency in a range of 10 kilohertz to 100 kilohertz.

10. The process of claim 7, further comprising deactivating the ultrasonic transducer prior to transferring the aluminum-based alloy melt onto the casting surface.

11. The process of claim 7, wherein the ultrasonic transducer is immersed in the casting ladle prior to introducing the aluminum-based alloy melt into the opening of the casting ladle.

12. The process of claim 7, wherein the ultrasonic transducer is immersed into the casting ladle by a robot arm after the aluminum-based alloy melt is introduced into the casting ladle.

13. The process of claim 7, wherein the casting surface is a mold cavity.

14. The process of claim 7, wherein the casting surface is a belt.

15. A system for casting an aluminum-based alloy, comprising:

a casting surface for receiving an aluminum-based alloy melt; and

a casting ladle for transferring the aluminum-based alloy melt onto the casting surface, the casting ladle including a cup, the cup defining an opening, and an ultrasonic transducer including an end immersed in the cup through the opening, wherein the cup exhibits a first depth and the ultrasonic transducer is immersed in the cup at a second depth in a range of 5 percent to 100 percent of the first depth.

16. The system of claim 15, wherein the casting surface includes a mold cavity.

17. The system of claim 15, wherein the casting surface includes a belt.

18. The system of claim 15, further comprising a power supply and a controller operatively coupled to the ultrasonic transducer.

19. The system of claim 15, wherein the cup is defined by a ladle wall, further comprising a bracket connected to the ladle wall, wherein the ultrasonic transducer is connected to the bracket.

20. The system of claim 15, wherein the ultrasonic transducer is secured to a robot arm and the robot arm is movable relative to the opening defined in the cup.