Casting process and product

Details Casting process and product Casting process and product

2002-03-19

2004-09-07

King, Roy (Department: 1742)

Metal treatment

Stock

Age or precipitation hardened or strengthened

C148S438000, C420S537000

Reexamination Certificate

active

06786983

ABSTRACT:

FIELD OF THE INVENTION
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.
BACKGROUND OF THE INVENTION
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 356 secondary and A356.2, 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. The primary difference between permanent mold casting and conventional die casting, which is high pressure and high velocity casting, is that the molten metal is simply poured into the mold without any external mechanical forces, rather than injected into a die, as is done in conventional die casting. 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.
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 commonly 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.
In particular, the 356 secondary and A356.2 aluminum alloys are commonly used with the GPM casting technique to produce products requiring high strength, wear-resistance, hardness and/or ductility. The chemistries of the 356 secondary and A356.2 aluminum alloys are as follows:
A356.2
356 Secondary
Percent of
Percent of
Element
Weight
Element
Weight
Silicon
6.5-7.5
Silicon
6.5-7.5
Iron
0.12 max
Iron
 0.6 max
Manganese
0.05 max
Manganese
0.35 max
Magnesium
0.30-0.45
Magnesium
0.20-0.45
Zinc
0.50 max
Zinc
0.35 max
Titanium
0.20 max
Titanium
0.25 max
Strontium
0.03 max
Strontium
0.03 max
Copper
0.10 max
Copper
0.25 max
Other
0.15 max
Other
0.15 max
Aluminum
Balance
Aluminum
Balance
However, there are specific problems associated with the 356 secondary and A356.2 aluminum alloys when utilized as a casting metal. For example, the casting melting temperature of 356 secondary and A356.2 is approximately 1320 degrees Fahrenheit (715.5 degrees Celsius). When castings are produced with the alloys having a casting metal temperature of 1320 degrees Fahrenheit, soldering occurs. 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.
It is common in the automotive industry to produce master cylinders and components of antilock braking systems (ABS) from the 356 secondary and A356.2 aluminum alloys using GPM. Braking systems are utilized to reduce a vehicle's speed, to bring the vehicle to a stop, or to keep the vehicle stationary if the vehicle is already at rest. The master cylinder is one of the control devices for braking systems in vehicles, such as passenger cars and light utility vehicles that is utilized to apply pressure to the wheel cylinders. ABS components are control devices within a braking system that prevent wheel lock-up during braking by controlling force to the wheel cylinders to maintain stability of the vehicle.
Accordingly, because of the purposes for which master cylinders and ABS components serve, they are required to have high mechanical properties in the areas of strength, wear resistance and hardness. Further, ABS components also are required to be ductile, i.e., has the ability to undergo permanent deformation prior to failure.
Typically, subsequent to the casting of master cylinders and/or ABS components, the master cylinders and/or ABS components are heat treated for increased strength and hardness, and anodized for increased corrosion resistance. The products are heat treated to deliver the minimum property requirements for the required components as shown below:
Minimum Properties for master cylinders:
Yield strength=~23 ksi
Tensile strength=~35 ksi
Percent elongation=~1%
Hardness=~80 BHN
Minimum properties for ABS components:
Yield strength=~25 ksi
Tensile strength=~35 ksi
Percent elongation=~3%
Hardness=~80 BHN
Master cylinders and ABS components produced utilizing GPM and 356 secondary and A356.2 aluminum alloys are typically heat treated to ensure that the products satisfy the minimum property requirements for the respective product. Commonly, master cylinders are heat treated according to a T6 temper. A typical T6 temper consists of solution treating the casting at 1,000 degrees Fahrenheit (537.7 degrees Celsius) plus or minus ten degrees Fahrenheit for ten hours, water quenching the casting, and artificially aging the casting at 340 degrees Fahrenheit (171.1 degrees Celsius) plus or minus ten degrees Fahrenheit for four to five hours.
SUMMARY OF THE INVENTION
Accordingly, it is desirable to provide, at least to some extent, a casting product, which exceeds in mechanical properties and costs, casting products manufactured according to the GPM casting technique utilizing the 356 secondary or A356.2 aluminum alloys.
In one aspect of the invention, an aluminum alloy product is provided that includes an ADC12 aluminum alloy, wherein the ADC12 aluminum alloy is cast into the product utilizing a high pressure, slow velocity casting technique.
In another aspect of the present invention, a braking system is provided that includes a brake component, wherein the brake component is made from an ADC12 aluminum alloy, and wherein the ADC12 aluminum alloy is cast into a brake component according to a high pressure, slow velocity casting technique.
In yet another aspect of the present invention, a method for manufacturing an aluminum alloy component is provided that includes injecting an ADC12 aluminum alloy into a die and applying a high pressure, slow velocity casting technique.
In another aspect of the present invention, a casting apparatus is provided that includes a means for injecting an ADC12 aluminum alloy into a die, and a means for applying a high pressure casting technique.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features 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 other embodiments and of being practiced and carried out in various ways. Als

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