Patent Application
20070246132
The present invention relates generally to casting processes and casting alloys. More particularly, the present invention is directed to an aluminum alloy for use with a high pressure casting technique.
It is conventional in the casting industry to produce products that require high strength, wear resistance, hardness, and/or ductility, using aluminum alloys, such as A356, in conjunction with the gravity permanent mold (GPM) casting process. The GPM casting technique involves heating a metal and pouring the molten metal into permanent metal molds while allowing gravity to fill the mold cavity with the molten metal.
However, there are specific problems associated with the A356 aluminum alloy when utilized as a casting metal. For example, the casting melting temperature of A356 is approximately 1320 degrees Fahrenheit (“° F.”) or 716 degrees Celsius (“° C.”). When castings are produced with the alloys having a casting metal temperature of 1320° F. (716° C.), soldering may occur. Soldering refers to the adherence of aluminum to the cavity of a mold or die, which, after a period of time, renders the mold or die unusable. This leads to repeated and costly replacements of the dies.
Accordingly, it is desirable to provide an alloy that has beneficial properties but does not cause soldering. It is also desirable to provide an alloy that allows for the production of cast parts with high strength, wear resistance, hardness and/or ductility without having to repeatedly replace the dies that may be damaged. Furthermore, it is desirable to produce cast parts with little or no soldering.
The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an alloy is provided that in some embodiments produces cast parts with high strength, wear resistance, hardness and/or ductility, with little or no soldering.
An embodiment of the present invention relates to a rear suspension component for an automobile. The rear suspension component includes an ADC12 aluminum alloy. The ADC12 aluminum alloy is squeeze cast to generate the rear suspension component. The ADC12 aluminum alloy consists essentially of the following constituents by percentage of weight: 9.6 to 12.0 percent silicon; 0.0 to 1.3 percent iron; 1.5 to 3.5 percent copper; 0.0 to 0.5 percent manganese; 0.0 to 0.3 percent magnesium; 0.0 to 1.0 percent zinc; 0.0 to 0.5 percent nickel; 0.0 to 0.3 percent tin; 0.0 to 0.15 percent one or more other elements; and aluminum as the remainder. The cast rear suspension component is T4 tempered.
Another embodiment of the present invention pertains to an apparatus for casting a rear suspension component for an automobile. The apparatus includes a means for heating an ADC12 aluminum alloy to liquefy the ADC12 aluminum alloy, means for injecting the ADC12 aluminum alloy into a die corresponding to the rear suspension component, means for solidifying the ADC12 aluminum alloy to generate the rear suspension component, and means for tempering the rear suspension component. The ADC12 aluminum alloy consists essentially of the following constituents by percentage of weight: 9.6 to 12.0 percent silicon; 0.0 to 1.3 percent iron; 1.5 to 3.5 percent copper; 0.0 to 0.5 percent manganese; 0.0 to 0.3 percent magnesium; 0.0 to 1.0 percent zinc; 0.0 to 0.5 percent nickel; 0.0 to 0.3 percent tin; 0.0 to 0.15 percent one or more other elements; and aluminum as the remainder. The apparatus further includes a means for tempering the cast rear suspension component.
Yet another embodiment of the present invention relates to a method of casting a rear suspension component for an automobile. In this method, an ADC12 aluminum alloy is heated to liquefy the ADC12 aluminum alloy, the ADC12 aluminum alloy is injected into a die corresponding to the rear suspension component, and the ADC12 aluminum alloy is solidified to generate the rear suspension component. In addition, the rear suspension component is tempered. The ADC12 aluminum alloy consists essentially of the following constituents by percentage of weight: 9.6 to 12.0 percent silicon; 0.0 to 1.3 percent iron; 1.5 to 3.5 percent copper; 0.0 to 0.5 percent manganese; 0.0 to 0.3 percent magnesium; 0.0 to 1.0 percent zinc; 0.0 to 0.5 percent nickel; 0.0 to 0.3 percent tin; 0.0 to 0.15 percent one or more other elements; and aluminum as the remainder.
There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. An embodiment in accordance with the present invention provides a rear suspension component of an automobile that is cast from ADC12 aluminum alloy utilizing a high pressure, slow velocity casting technique such as, for example, squeeze casting, semi-solid metal (SSM) casting, and the like. This rear suspension component is further T4 tempered. As used herein, ADC12 aluminum alloy with a T4 temper is referred to as ADC12-T4.
The mechanical properties of a product are not only dependent on the casting technique utilized, but are also dependent on the casting alloy that is utilized. Aluminum alloys are used in the casting industry because they are adaptable to many of the most commonly used casting methods, can readily be cast in metal molds or dies and have a high resistance to corrosion.
As a casting material, aluminum alloys also provide good fluidity, i.e., most aluminum alloys flow with ease. This is particularly important because if the metal, when in its molten state, does not flow at a rate that is sufficient to fill the die cavity or mold before the molten metal solidifies, then the metal may have difficulty filling, for example, thin sections of a mold or die.
Additionally, aluminum alloys have relatively low melting points. Accordingly, the heat required to melt aluminum alloys is less than the heat required for some metals and thus, the cost of producing aluminum alloy castings is less. Further, there is less heat to transfer from the molten aluminum alloy to the mold. As a result, the cycle time required for casting an aluminum alloy product is reduced. In addition, the lifetime of the mold is increased by utilizing aluminum alloys because the molds are subjected to less stress from heat.
Rear suspension components for automotive vehicles are required to have high mechanical properties in the areas of strength, wear resistance and hardness. Further, they are also are required to be ductile, i.e., have the ability to undergo permanent deformation prior to failure.
Rear suspension components produced utilizing GPM and the A356 aluminum alloy are typically heat treated to ensure that the products satisfy the minimum property requirements for the respective product. Commonly, rear suspension components are heat treated according to a T6 temper. A typical T6 temper consists of solution treating the casting at 1,000° F. (538° C.) plus or minus 10° F. (5.6° C.) for ten hours, water quenching the casting, and artificially aging the casting at 340° F. (171° C.) plus or minus 10° F. (5.6° C.) for four to five hours. In contrast, a T4 temper includes heating to about 930° F. (499° C.), soaking for about seven hours and then water quenching at temperatures between 110° F. (43° C.) and 160° F. (71° C.).
In accordance with the present invention, an aluminum alloy, ADC12-T4, is utilized with a high pressure, slow velocity casting technique to produce casting products for rear suspension components. Such components include knuckles and upper and lower control arms, among others.
High pressure, slow velocity casting techniques, such as squeeze casting, SSM casting and the like, involve injecting molten metal into a mold via a hydraulically powered piston, at a slow rate into the mold/die cavity, and applying and maintaining a high pressure until after the metal has solidified in the mold/die cavity. When the applied high pressure thrusts the molten metal to the walls of the mold/die cavity, the air gap between the molten metal and the walls of the mold/die cavity is quickly minimized.
Therefore, there is a rapid transfer of heat between the metal and the mold/die cavity. Consequently, because of the use of the rapid heat transfer process involved in high pressure casting, the metal cools to a solid state quickly. As a result of the rapid solidification, the grain structure of the casting is small, i.e., refined.
In GPM, the molten metal is poured into the mold without any external mechanical forces. In contrast, in conventional die casting, which includes high pressure and high velocity casting, the metal is injected into a die. Typically, products manufactured by the GPM casting technique tend to be higher in strength and are less porous than products produced by conventional die casting.
According to an embodiment of the invention, rear suspension components are squeeze cast, SSM cast or otherwise utilized with a high pressure, slow velocity casting technique to cast with the ADC12-T4 alloy. Rear suspension components cast in this manner exhibit mechanical properties that are higher than the. mechanical properties of products manufactured according to GPM casting techniques utilizing the A356 aluminum alloy. ADC12-T4 includes the below-listed elements, by percentage of weight, as follows:
As shown from the chart immediately above, the ADC12-T4 aluminum alloy does not require strontium. Strontium is utilized in an aluminum alloy as a modifying agent to, for example, improve the ductility of the aluminum alloy. Strontium is often utilized along with casting processes that involve slower solidification rates, such as GPM and sand casting.
The ADC12-T4 alloy, when utilized with a high pressure, slow velocity casting technique, has a higher solidification rate because of the rapid heat transfer rates that are characteristic of high pressure casting techniques. Thus, because the products derive high ductility from being manufactured according to a high pressure, slow velocity casting technique, strontium is not required with the use of the ADC12-T4 alloy.
As a result, the aluminum content is increased in ADC12-T4 alloy products. The cost of the aluminum is cheaper than the cost of strontium. Accordingly, the cost of ADC12-T4 alloy products is cheaper than products made with added strontium. However, beneficial properties are still retained.
The ADC12-T4 alloy has a silicon content of 9.6 to 12.0 percent of its weight and is higher than the silicon content of the A356 aluminum alloy, which is 6.5 to 7.5 percent of its weight. A356 includes the following components:
The higher silicon content of the ADC12-T4 alloy leads to the ADC12-T4 alloy having a metal casting temperature of 1250° F. (677° C.), which is lower than the metal casting temperature of approximately 1320° F. (715° C.) for the A356 aluminum alloy. Accordingly, less energy is required to melt the ADC12-T4 alloy than is required to melt the A356 aluminum alloy. Thus, the cost associated with manufacturing ADC12-T4 products is less than the cost associated with manufacturing the A356 product.
Additionally, the lower metal casting temperature of the ADC12-T4 alloy leads to approximately 35% less dross formation than that produced by the A356 aluminum alloy. Dross refers to the metal oxide that is formed when the molten metal reacts with air. Dross formation typically occurs before the molten metal is transferred to the mold/die cavity. If the dross enters the mold/die cavity and becomes a part of the casting, it can lead to a defective casting because the casting will not consist purely of the intended alloy.
Additionally, the lower metal casting temperature of the ADC12-T4 alloy leads to less occurrences of soldering, approximately 15% less, than that produced by the A356 aluminum alloy. Accordingly, utilizing the ADC12-T4 alloy over the A356 alloy reduces soldering and prolongs the life of the mold/die cavity.
Further, the ADC12-T4 alloy has a higher tensile strength than the A356 aluminum alloys. The tensile strength corresponds to the maximum load bearing ability of the metal before the metal breaks down. Thus, the ADC12-T4 alloy has a higher resistance to applied forces. The higher strength of the ADC12-T4 alloy is attributed, at least in part, to the refined microstructure, i.e., the smaller grain size of the casting that is developed from use of a high pressure, slow velocity casting technique. Accordingly, the ADC12-T4 alloy is stronger than the A356 aluminum alloy and therefore, is more suitable for products requiring high strength, for example, components of rear suspension systems, such as knuckles and upper and lower control arms.
When the T4 temper was applied to the ADC12-T4 alloy, the ADC12-T4 alloy outperformed the A356 alloy in wear resistance. The higher wear resistance, i.e., lower volume loss of material, is attributed, at least in part, to the refined microstructure, i.e., the smaller grain size of the casting that is developed from use of high pressure, slow velocity casting technique.
Products, for example, knuckles and upper and lower control arms have been anodized to increase the wear resistance of those products. By utilizing the ADC12-T4 alloy in conjunction with a high pressure casting technique, the amount of anodizing is reduced or eliminated, leading to yet more efficiency.
In addition, ADC12-T4 has a maximum iron content of 1.3 percent of its weight that is higher than the iron content of the A356 alloy. When the iron content of an ADC12-T4 casting is greater than the maximum iron content of the A356 alloy, the ADC12-T4 product is easier to machine than an A356 product.
The high iron content of the ADC12-T4 alloy product also facilitates chip formation, i.e., the generation of shavings, as the product is machined. Accordingly, less force or pressure has to be applied to the machine tool when feeding/thrusting the machine/cutting tool onto the ADC12-T4 alloy product to make the initial cut into the ADC12-T4 product, and also when cutting the ADC12-T4 alloy product, than when performing the same actions on an A356 alloy product. Accordingly, the machine/cutting tool is subjected to less stress and the lifetime of the machine/cutting tool is prolonged with the ADC12-T4 alloy. Moreover, the higher iron content of the ADC12-T4 also leads to less soldering, thereby lengthening the life of the dies.
Further, the cost of ADC12-T4 alloy stock/ingots is less expensive than the cost of the A356 stock or ingot. Accordingly, when the ADC12-T4 alloy is utilized in conjunction with a high pressure casting technique to manufacture products, for example, rear suspension components, the products have high mechanical properties and are less expensive to produce.
The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
This application claims priority to provisional U.S. patent application entitled, SQUEEZE CAST REAR SUSPENSION COMPONENTS USING ADC12-T4 ALUMINUM ALLOY, filed Mar. 27, 2006, having a Ser. No. 60/786,020, the disclosure of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60786020 | Mar 2006 | US |
