US20220017997A1

US20220017997A1 - Aluminum alloys for structural high pressure vacuum die casting applications

Info

Publication number: US20220017997A1
Application number: US17/428,844
Authority: US
Inventors: Kevin Haney; Mike BLOW; Benjamin C. PROBERT; Zach Brown; Brian Springer; Andrea HILL; Xiaoping Niu; Randy Beals
Original assignee: Magna International of America Inc
Current assignee: Magna International of America Inc
Priority date: 2019-02-08
Filing date: 2020-02-07
Publication date: 2022-01-20
Also published as: EP3921449A4; WO2020163707A1; CN113423853B; EP3921449A1; CN113423853A

Abstract

A vehicle part formed at least in part of a blended material is provided. The blended material is formed by mixing an improved aluminum alloy and a recycled aluminum alloy. The recycled aluminum alloy can be obtained from road wheels. The blended alloy preferable meets the Aural series alloy specifications. The blended material can be cast under high pressure and a vacuum to form a part designed for use in a chassis or structural body of a vehicle, for example a front subframe, a front shock tower, a rear rail, a front kick-down rail, a front body hinge pillar, a tunnel, a front body hinge pillar, or a rear shock mount.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This PCT International Patent application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/803,000, filed Feb. 8, 2019, titled “Aluminum Alloys For Structural High Pressure Vacuum Die Casting Applications,” the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an aluminum alloy, a part produced from at least partially recycled material and an aluminum alloy, and methods of manufacturing the same.

2. Related Art

This section provides background information related to the present disclosure which is not necessarily prior art.
Casting, extruding, and forging are popular production processes wherein material is melted, shaped, and allowed to cool and solidify into an article. One material used in such processes is aluminum, and more particularly, an Aural series aluminum alloy, which has been shown to exhibit excellent mechanical properties, good castability (fluidity), and an ability to be hardened via heat treatment (precipitation hardening). Articles produced from the Aural series alloys are typically formed by a high pressure die casting process. While exhibiting these qualities, the Aural series alloys are expensive and are typically produced in lower volumes than other more common aluminum alloys. Moreover, workability of the Aural series alloys can be difficult during certain processes, such as smelting.
There have been attempts to eliminate the above noted shortcomings of the Aural series alloys. Some efforts include developing different alloys that are easier and cheaper to produce but that still replicate the material qualities of the Aural series alloys. Other efforts included improvements to the process of producing the Aural series alloys to make the production process cheaper and more efficient. For example, one attempt included using recycled material as a raw material. Reused or recycled material is also known as scrap or “dirty material” and can greatly decrease the cost of production, particularly for more expensive materials like aluminum. Aluminum is endlessly recyclable and the recycling process uses only 5% of the energy required in the production of primary aluminum. As a result, the carbon footprint of recycled aluminum is only 5% of that of primary aluminum. During some traditional production processes, the recycled material is added to molten Aural series alloy material in the furnace and mixed. The recycled material is added at a specific ratio to total molten material, based on differences in chemical composition. In addition to the recycled material, master alloy additions, such as silicon, manganese, magnesium, and strontium, are also added to compensate for the differences between the composition of the recycled material and the Aural series alloy material.
While this recycling process can produce an alloy comparable to an Aural series alloy at a lower cost, there are certain drawbacks. For example, the master alloys are expensive, and they are intended for small adjustments. Master alloys also have the tendency to at least partially burn off during introduction into the furnace. In addition, during the process of recycling material, it takes time to accurately measure the composition in the furnace, for example using chemical spectroscopy disc and/or other optical emission spectroscopy machines. There is also a risk that the alloy produced may be out of the desired specification for the particular Aural series alloy chemical composition. In this case, all castings made with the alloy would not meet material property requirements and would have to be scrapped.
Accordingly, there is a continuing desire to develop and further refine processes that are capable of producing alloys within the Aural series alloys specifications using recycled material.

SUMMARY

This section provides a general summary of the inventive concepts associated with this disclosure and is not intended to be interpreted as a complete and comprehensive listing of all of its aspects, objectives, features, and advantages.
One aspect of the invention provides a method of manufacturing a blended material. The method comprises mixing a recycled aluminum alloy with an improved aluminum alloy to form a blended material. The recycled aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the recycled aluminum alloy, 6.5 wt. % to 7.5 wt. % silicon, up to 0.25 wt. % iron, up to 0.2 wt. % copper, up to 0.1 wt. % manganese, 0.25 wt. % to 0.45 wt. % magnesium, up to 0.1 wt. % zinc, up to 0.2 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum. The blended material comprises, in weight percent (wt. %) based on the total weight of the blended material, 6.0 to 8.0 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.03 wt. % strontium, and up to 0.15 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum; or the blended material comprises, in weight percent (wt. %) based on the total weight of the blended material, 9.5 to 11.5 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.025 wt. % strontium, and up to 0.12 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum.
Another aspect of the invention provides a blended material comprising, in weight percent (wt. %) based on the total weight of the blended material, 6.0 to 8.0 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.03 wt. % strontium, and up to 0.15 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum; or the blended material comprises, in weight percent (wt. %) based on the total weight of the blended material, 9.5 to 11.5 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.025 wt. % strontium, and up to 0.12 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum. The blended material is formed by mixing a recycled aluminum alloy and an improved aluminum alloy. The recycled aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the recycled aluminum alloy, 6.5 wt. % to 7.5 wt. % silicon, up to 0.25 wt. % iron, up to 0.2 wt. % copper, up to 0.1 wt. % manganese, 0.25 wt. % to 0.45 wt. % magnesium, up to 0.1 wt. % zinc, up to 0.2 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum.
Another aspect of the invention provides a method of manufacturing a part for a vehicle. The part is formed of a blended material comprising, in weight percent (wt. %) based on the total weight of the blended material, 6.0 to 8.0 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.03 wt. % strontium, and up to 0.15 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum; or the blended material comprises, in weight percent (wt. %) based on the total weight of the blended material, 9.5 to 11.5 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.025 wt. % strontium, and up to 0.12 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum. The blended material is formed by mixing a recycled aluminum alloy and an improved aluminum alloy. The recycled aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the recycled aluminum alloy, 6.5 wt. % to 7.5 wt. % silicon, up to 0.25 wt. % iron, up to 0.2 wt. % copper, up to 0.1 wt. % manganese, 0.25 wt. % to 0.45 wt. % magnesium, up to 0.1 wt. % zinc, up to 0.2 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum. The method further includes casting the blended material to form the part.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purpose of illustration only and are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and are not intended to limit the scope of the present disclosure. The inventive concepts associated with the present disclosure will be more readily understood by reference to the following description in combination with the accompanying drawings wherein:

FIG. 1 illustrates an example part at least partially formed from a blended material that includes a recycled alloy and an improved aluminum alloy and which meets Aural series alloy specifications;

FIG. 2 shows fragments of the recycled aluminum alloy according to an example embodiment;

FIGS. 3A and 3B provide microscopic views illustrating porosity of the recycled aluminum alloy according to an example embodiment;

FIGS. 4A through 4D illustrate dendrite arm spacing (DAS) of the blended material after various processing steps according to an example embodiment;

FIG. 5A-5I illustrate steps of a high pressure vacuum die casting process according to an example embodiment;

FIG. 6 is a chart illustrating differences between conventional high pressure die casting HPDC, vacuum assist high pressure die casting, and high vacuum high pressure vacuum die casting;

FIGS. 7A-7H are example parts that can be formed from the blended material; and

FIG. 8 provides a description of a sludge factor for aluminum alloys.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments will now be described more fully with reference to the accompanying drawings. In general, the subject embodiments are directed to a part produced from at least partially recycled material and an improved alloy, the improved alloy, and a method of blending the improved alloy with the recycled material. However, the example embodiments are only provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The present disclosure provides a blended material formed of a recycled aluminum alloy and an improved aluminum alloy, a method of producing the blended material from the recycled aluminum alloy and an improved aluminum alloy, a part formed of the blended material, and a method of producing the part from the blended material. The method allows for relatively inexpensive and efficient production of parts exhibiting excellent material properties, preferably similar or identical to parts formed of Aural series alloys.
FIG. 1 shows a part 20 made from the blended material formed of the recycled aluminum alloy and the improved aluminum alloy. In this example, the part is a structural component for a body of a vehicle, specifically a front body hinge pillar. The blended material could be used to form various other parts used for vehicle applications. The parts are at least partially formed, but preferably entirely formed, from the blended material.
The chemical composition of the recycled aluminum alloy can be measured, for example, via an optical emission spectroscopy machine, and the composition of the improved aluminum alloy can be set to achieve the blended material with the desirable composition. The resulting blended material typically and preferably meets the specifications of Aural 2, Aural 5S, or another Aural series alloy.
The recycled aluminum alloy used to form the parts is preferably cleaned and shredded before introduction into a furnace. In one preferred embodiment, the recycled aluminum alloy includes recycled 356 aluminum alloy, preferably A356.2 aluminum obtained from used wheels and/or rims, as shown in FIG. 2. The used wheels or rims are crushed, shredded (or fragmented), and cleaned, without requiring melting and casting into ingots, further reducing the carbon footprint. After fragmentation, the recycled aluminum alloy placed in the furnace, melted, and blending with the improved aluminum alloy.
Castings formed of aluminum alloys can be greatly affected by the presence of oxide films and impurities in the molten blended alloy. With the increased surface area of fragmented and crushed wheels, a slightly higher potential risk of oxides and other inclusions may occur in certain embodiments. In order to meet ASTM requirements for tensile testing, proper cleaning of the melt, grain refining additions and modifications prior to casting or blending of the recycled aluminum alloy can be included in the method.
The following paragraphs provide example embodiments of both the recycled alloy. However, these example embodiments are provided for purposes of illustration and not intended to be exhaustive or to limit the disclosure. These compositions can be measured on site, for example by using a Optical Emission Spectrometry.
The recycled aluminum alloy typically is a recycled 356.2 aluminum alloy and has a composition very similar to that of raw and unused A356.2. The only typical exception is the Fe content, which is typically in the range, in weight percent (wt. %) based on the total weight of the alloy, of 0.11-0.14% on average (compared to the 0.12% limit of A356.2). When wheels are made from A356.2, they often contain an even higher purity specification with respect to Fe than the 0.12% limit. Recycled 356.2 alloy is currently available in the form of sacks suitable for improved handling and logistics. If necessary, the method may include mixing/diluting the recycled 356.2 alloy with primary aluminum to comply exactly with the A356.2 chemistry, although for most embodiments this is not necessary.
According the embodiment wherein the recycled aluminum alloy is 356.2 aluminum, and the recycled 356.2 aluminum approximately or exactly comprises, in weight percent (wt. %) based on the total weight of the alloy:silicon (6.81 wt. %); iron (0.156 wt. %); copper (0.0467 wt. %,); manganese (0.0213 wt. %); magnesium (0.353 wt. %); zinc (0.0072 wt. %); titanium (0.1015 wt. %); and the remainder being aluminum and other trace elements.
According to another embodiment, the recycled 356.2 aluminum approximately or exactly comprises, in weight percent (wt. %) based on the total weight of the alloy:silicon (7.0 wt. %); Iron (0.11 wt. %); copper (0.004 wt. %,); manganese (0.006 wt. %); magnesium (0.334 wt. %); zinc (0.005 wt. %); titanium (0.12 wt. %); other elements (0.03 wt. %); and the remainder being aluminum.
In the embodiments which include the recycled 356.2 aluminum alloy, it is preferred that the furnace is hot enough so that after melting, the recycled 356.2 aluminum alloy approximately or exactly comprises, in weight percent (wt. %) based on the total weight of the alloy:silicon (7.0 wt. %); iron (0.15 wt. %); copper (0.011 wt. %,); manganese (0.006 wt. %); magnesium (0.348 wt. %); zinc (0.005 wt. %); titanium (0.10 wt. %); other elements (0.03 wt. %); and the remainder being aluminum.
It is more preferable yet that in embodiments which include recycled 356.2 aluminum alloy, that the recycled 356.2 aluminum alloy is degassed. For example, the recycled 356.2 aluminum alloy can be argon degassed with a Palmer rotary degasser for approximately 20 minutes. After being degassed, the recycled 356.2 aluminum alloy approximately or exactly comprises, in weight percent (wt. %) based on the total weight of the alloy:silicon (7.0 wt. %); iron (0.15 wt. %); copper (0.006 wt. %,); manganese (0.006 wt. %); magnesium (0.338 wt. %); zinc (0.005 wt. %); titanium (0.13 wt. %); other elements (0.03 wt. %); and the remainder being aluminum.
In summary, the recycled 356.2 aluminum alloy typically includes the following preferred ranges and approximate values of the following elements (which are typical in recycled road wheels and can represent a nominal composition within the preferred embodiment), in weight percent (wt. %) based on the total weight of the recycled aluminum alloy:silicon (minimum 6.5 wt. %, maximum 7.5 wt. %); iron (minimum 0.13 wt. %, maximum 0.25 wt. %); copper (0.2 wt. % max or 0.10 wt. % max); manganese (0.1 wt. % max or 0.05 wt. % max); magnesium (0.25 wt. % to 0.45 wt. % or 0.3 wt. % to 0.45 wt. %); zinc (0.05 wt. % max or 0.1 wt. % max), titanium (0.1 wt. % max or 0.2 wt. % max); and the remainder being aluminum and other trace elements.
The following Tables 1-3 provide specific example compositions of the recycled aluminum alloy. The recycled aluminum alloy could include any composition within the ranges of the A356.0 ASTM B108, A356.1 ASTM B179, or A356.2 ASTM B179 specifications.

TABLE 1

	Si	Fe	Cu	Mn	Mg	Zn	Ti	Others

356.2 As	7.0	0.11	0.004	0.006	0.334	0.005	0.12	0.03
received
356.2 As	7.0	0.15	0.011	0.006	0.348	0.005	0.10	0.03
melted
356.2	7.0	0.15	0.006	0.006	0.338	0.005	0.13	0.03
degassed melt
A356.0	6.5-7.5	0.20 max	0.20 max	0.10 max	0.25-0.45	0.10 max	0.20 max	0.15 max
ASTM B108
A356.1	6.5-7.5	0.15 max	0.20 max	0.10 max	0.30-0.45	0.10	0.20 max	0.10 max
ASTM B179
A356.2	6.5-7.5	0.12 max	0.10 max	0.05 max	0.30-0.45	0.05	0.20 max	0.10 max
ASTM B179

TABLE 2

Element	Si	Fe	Cu	Mn	Mg	Ni	Zn	Ti	Pb	Sn	Sr

Wt. %	6.81	0.156	0.0467	0.0213	0.352	0.0033	0.0072	0.1015	—	0	0

TABLE 3

Element	Si	Fe	Cu	Mn	Mg	Zn

Wt. %	6.5-7.5	0.13-0.25	0.10	0.05	0.3-0.45	0.05

The following paragraphs provide example embodiments of both the improved aluminum alloy. However, these example embodiments are provided for purposes of illustration and not intended to be exhaustive or to limit the disclosure. These compositions can be measured on site, for example by using a Optical Emission Spectrometry.
The improved aluminum alloy preferably consists of a chemical composition that, when blended with the recycled aluminum alloy in a furnace, does not need any additional elements or materials to form the desired blended material. More specifically, there is no need to add additional master alloys, such as silicon, manganese, magnesium, and strontium into the furnace during the blending. The improved aluminum alloy is typically formed into an ingot before introduction into the furnace.
A first example embodiment of the improved aluminum alloy, referred to as E5.50, comprises in weight percent (wt. %) based on the total weight of the alloy:silicon (minimum 7.4 wt. %, maximum 7.9 wt. %); copper (maximum 0.01 wt. % or maximum 0.25 wt. %); iron (minimum 0.16 wt. %, maximum 0.2 wt. %); magnesium (no minimum, maximum 0.1 wt. %); zinc (no minimum, maximum 0.03 wt. %); manganese (minimum 0.92 wt. %, maximum 1.0 wt. %); titanium (no minimum, maximum 0.06 wt %); strontium (minimum 0.03 wt. %, maximum 0.04 wt. %); nickel (trace amounts); chromium (trace amounts); tin (trace amounts); other elements (combined maximum 0.1 wt. %, individual maximum 0.03 wt. %); and the remainder being aluminum. This example improved aluminum alloy preferably has a sludge factor of approximately 1.8. When combined in a furnace with the recycled 356.2 aluminum, this improved aluminum alloy is hypoeutectic.
A second example embodiment of the improved aluminum alloy, referred to as E2.50, comprises in weight percent (wt. %) based on the total weight of the improved aluminum alloy:silicon (minimum 12.5 wt. %, maximum 13 wt. %); copper (maximum 0.01 wt. % or maximum 0.25 wt. %); iron (minimum 0.16 wt. %, maximum 0.2 wt. %); magnesium (minimum 0.27 wt,%, maximum 0.33 wt. %); zinc (no minimum, maximum 0.03 wt. %); manganese (minimum 0.92 wt. %, maximum 1.0 wt. %); titanium (no minimum, maximum 0.06 wt. %); strontium (minimum 0.03 wt. %, maximum 0.04 wt. %); nickel (trace amounts); chromium (trace amounts); tin (trace amounts); other elements (combined maximum 0.1 wt. %, individual maximum 0.03 wt. %); and the remainder being aluminum. This improved aluminum alloy preferably has a sludge factor of approximately 1.8. When combined in a furnace with the recycled 356.2 aluminum alloy, this improved aluminum alloy is eutectic.
A third example embodiment of the improved aluminum alloy, referred to as E2.70, comprises in weight percent (wt. %) based on the total weight of the improved aluminum alloy:silicon (minimum 17 wt. %, maximum 17.5 wt. %); copper (maximum 0.01 wt. %); iron (minimum 0.16 wt. %, maximum 0.2 wt. %); magnesium (minimum 0.27 wt. %, maximum 0.33 wt. %); zinc (no minimum, maximum 0.03 wt. %); manganese (minimum 1.65 wt. %, maximum 1.70 wt. %); titanium (no minimum, maximum 0.06 wt. %); strontium (minimum 0.06 wt. %, maximum 0.07 wt. %); nickel (trace amounts); chromium (trace amounts); tin (trace amounts); other elements (combined maximum 0.1 wt. %, individual maximum 0.03 wt. %); and the remainder being aluminum. This improved aluminum alloy preferably has a sludge factor of approximately 1.8. When combined in a furnace with the recycled 356.2 aluminum alloy, this improved aluminum alloy is hypereutectic.
Table 4 provides specific example compositions of the improved aluminum alloys E5.50, E2.50, and E2.70. The “trace amount” disclosed above for the nickel, chromium and tin of the improved aluminum alloys and listed below is up to 0.05 wt. %. The improved aluminum alloys can include trace amounts of nickel, chromium and tin. The total amount of these trace elements is preferably not greater than 0.15 wt. %. FIG. 8 provides a description of the “sludge factor” and how it is calculated.

TABLE 4

Alloy E5.50	Wt %	Ally E2.50	Wt %	Alloy E2.70	Wt %

Si	7.4-7.9	Si	12.5-13	Si	17-17.5
Cu	0.01 max.	Cu	0.01 max.	Cu	0.01 max.
Fe	0.16-0.2	Fe	0.16-0.2	Fe	0.16-0.2
Mg	0-0.1	Mg	0.27-0.33	Mg	0.27-0.33
Zn	0.03 max	Zn	0.03 max	Zn	0.03 max
Mn	0.92-1.0	Mn	0.92-1.0	Mn	1.65-1.7
Ni	Trace	Ni	Trace	Ni	Trace
Cr	Trace	Cr	Trace	Cr	Trace
Sn	Trace	Sn	Trace	Sn	Trace
Ti	0-0.06	Ti	0-0.06	Ti	0-0.06
Sr	0.03-0.04	Sr	0.03-0.04	Sr	0.06-0.07
Sludge	1.8	Sludge	1.8	Sludge	1.8
factor		factor		factor
Other each	0.03 max	Other each	0.03 max	Other each	0.03 max
Other total	0.1	Other total	0.1	Other total	0.1
Al	Remainder	Al	Remainder	Al	Remainder

In embodiments including the improved alloy E5.50 or alloy E2.50, it is preferable that the method includes adding equal parts of the improved aluminum alloy and the recycled 356.2 aluminum alloy to the furnace, and blending the resulting molten material. In embodiments including the improved alloy of E2.70 alloy, it is preferable that the method includes a longer melting period, in addition to adding more E2.70 alloy than recycled 356.2 aluminum alloy to the furnace, and blending the resulting molten material. In some embodiments, the method includes slight adjustments of the composition of the blended material in the furnace after melting.
In one preferred embodiment, the recycled aluminum alloy includes recycled 356 aluminum alloy, preferably A356.2 aluminum obtained from used wheels and/or rims; and the improved alloy is an aluminum alloy contains at least 7%, in weight percent (wt. %), silicon. In another embodiment, the recycled aluminum alloy includes silicon in an amount of 6.81 wt. %, iron in a amount of 0.156 wt. %, manganese in an amount of 0.021 wt. %, magnesium in an amount of 0.325 wt. %, titanium in an amount of 0.102 wt. %, and copper in an amount of 0.047 wt. %, based on the total weight of the improved aluminum alloy; and the recycled alumni alloy is mixed with the improved aluminum alloy E5.50 to achieve the blended material comprising silicon in an amount of 7.31 wt. %, iron in a amount of 0.16 wt. %, manganese in an amount of 0.544 wt. %, magnesium in an amount of 0.164 wt. %, strontium in an amount of 0.011 wt. %, titanium in an amount of 0.064 wt. %, and, in some embodiments, copper in an amount of 0.01 wt. %, based on the total weight of the blended material.
According to some preferred embodiments, the blended material comprises any composition within the Aural 5S specification. In this case, the blended material comprises, in weight percent (wt. %) based on the total weight of the blended material, 6.0 to 8.0 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.03 wt. % strontium, and up to 0.15 wt. % titanium, other elements each in an amount up to 0.05 wt. %, other elements in a total amount up to 0.15 wt. %, and a balance of aluminum.
According to other preferred embodiments, the blended material comprises any composition within the Aural 2 specification. In this case, the blended material comprising, in weight percent (wt. %) based on the total weight of the blended material, 9.5 to 11.5 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.025 wt. % strontium, and up to 0.12 wt. % titanium, other elements each in an amount up to 0.05 wt. %, other elements in a total amount up to 0.15 wt. %, and a balance of aluminum.
The recycled aluminum alloy and/or the improved aluminum alloy can undergo additional processing before, during, or after being blended. For example, the alloys could be degassed, fluxed, filtered, and grain boundary strengthened during the production process. In one embodiment, the step of degassing includes argon degassing with a Palmer rotary degasser for 20 minutes.
The blended material could also undergo one or more of the aforementioned additional processing steps. Furthermore, the resulting blended material can undergo heat treating after casting. For example, the blended material could be heat treated to T6 according to, American Society for Testing and Materials (ASTM), ASTM B917 and T61 with slight modification to ASTM B917 to increase elongation. For the T6 treatment, the blended material can be sand casted and annealed to 540° C. for 9 h, quenched in water at 25° C., and aged to 155° C. for 4 hours the day after. For the T61 treatment, the blended material can be permanently cast into bars, solution annealed to 540° C. for 9 h, quenched in water at 25° C., then aged at 162° C. for 9 hours. The blended material may further be treated by hot isostatic pressing at 535° C. 15000 psi for 2 hours. In addition, the blended material can be heated to a temperature of 730° C. and melted, then may further undergo T7 treatment at 860° F. for 75 minutes, and forced air quenched at a 14° C. per second for two hours at 215° C. (419° F.). These process steps can achieve the microstructure shown in FIGS. 4A-4D, which is the center of a cross-section exhibiting fine alpha aluminum grains and spheroidized eutectic silicon. Furthermore, in some embodiments the molten blended material is grain refined with 0.05% Ti (Al %5Ti1B).
According to alternative embodiments, the recycled aluminum alloy is modified, and the modifications of the recycled alloy, in certain cases, result in improvements to the blended material. While the specific material properties described in the following paragraphs are related to the recycled aluminum alloy, it should be appreciated that any of the methods of modifying material properties can also be applied to the improved aluminum alloy and/or the blended material before, after, or during, the blending or casting of the part 20. It should also be appreciated that these methods steps can be combined in different variations.
Table 1 above compares the compositions of three variations of the recycled 356.2 aluminum alloy to ASTM required specifications of A356.0 at ASTM B 108, A356.1 at ASTM B179, and A356.2 at ASTM B179. An experiment was conducted to evaluate the alloys and the blended material. The recycled 356.2 aluminum alloy was melted in a Dynarad MG260 75 kW resistance furnace with a silicon carbide crucible. After preheating at 275° C., melting was completed in about 3 hours 25 minutes. Typically, melting smaller crushed wheel pieces is faster than larger ingots, sows, or T-bars due to increased surface area. At the end of the melting, some floating skins of the last pieces of the recycled 356.2 aluminum alloy were visible on the melt surface. Those oxides were skimmed off before sampling the untreated melt; total skim removed was 0.66 lbs. or 0.5% of the charge, which is within a normal range for most types of charge materials.
A chemical analysis of the 356.2 recycled aluminum alloy as received was completely within the A356.2 specification in terms of purity, particularly due to the cleaning step and the composition of the wheels/rims (with likely even higher purity specification with respect to Fe than the 0.12% limit). The measured composition of the 356.2 aluminum alloy is provided in Table 2. During melting, the recycled aluminum alloy was slightly contaminated with some Fe in the crucible (hence the 0.15% Fe in the as melted recycled alloy), but this did not have any significant impact other than putting it essentially within the A356.1 specification. Strontium modification was not performed on the melt, since a residual level of 88 ppm strontium in the melt was measured before degassing and 79 ppm after degassing.
The blended material achieves an ultimate tensile strength of greater than 180, a yield strength of greater than 120, and an elongation of greater than 5%. The following Table 5 includes material properties of the blended material that comprises E.250 and the recycled A356.2 aluminum alloy obtained from the road wheels after heat treatment.

TABLE 5

Location	UTS	YS	Elong

1	196	124	18.7
2	198	124	17.6
2	201	130	16.0
1	195	124	18.8
2	194	123	15.1
1	195	123	15.9
2	195	121	15.9
1	196	125	16.4
2	199	127	14.6
1	196	123	17.5
1	189	121	17.1
2	198	126	17.5
1	195	125	18.7
2	195	125	15.9
1	197	129	18.8
2	198	129	17.1
1	195	129	14.9
AVE	196	125.18	16.85
St Dev	2.57	2.79	1.40

FIGS. 3A and 3B are microscopic views that illustrate porosity of the recycled aluminum alloy. Porosity was evaluated by image analysis of the surface. As shown in 3A (from left to right), porosity in the permanent mold bar was 0.67% for the untreated melt, 0.36% for the degassed melt, and 0.02% in the degassed after hipping. Hipping has closed porosity and substantially improved mechanical properties, hence exhibiting improved results for certain embodiments (e.g., from low pressure/counter pressure casting or squeeze casting). Porosity in a sand cast test bar is illustrated in 3B and includes an average value of tensile properties at 0.53%. The lower speed of solidification or in the resin sand mold is the reason for the higher porosity content when compared to permanent mold results presented in FIG. 3A
FIGS. 4A through 4D are microscopic views of the blended material illustrating dendrite arm spacing. Dendrite arms spacing is correlated to solidification speed and efficiency. The fast cooling in metal molds produces a finer structure than in a sand mold. Modification by a step of adding strontium is made to transform the acicular eutectic silicon to rounded shapes, which improves elongation.
A test bar cast from the blended material including E.250 and the recycled aluminum alloy that is T7 treated is shown in FIG. 4A. A test bar cast from blended material including E.5.50 and recycled alloy after T5 heat treatment is shown in FIG. 4B. A test bar cast from blended alloy including E.2.50 and recycled alloy after T5 heat treatment is shown in FIGS. 4C and 4D.
The step of cleaning the recycled aluminum alloy can include an assessment of cleanliness. The metal cleaning can be started with Kmold during the testing. Recycled alloy cleanliness is ideally assessed with a hot porous disk filtration apparatus (PoDFA) in the degassed melt. The PoDFA can be used for a molten cleanliness assessment, wherein the molten metal is forced under vacuum to flow through a ceramic filter. The amount of inclusion per kg filtered and inclusion type is measured by metallography and expressed in mm2/kg. PoDFA results of methods that include the recycled 356.2 aluminum alloy have shown excellent results.
As referenced above, after the step of degassing, the recycled aluminum alloy can undergo a step of fluxing. The step of fluxing is carried out with 0.8 g/kg of Promag SI flux, then argon degassed with the Palmer degasser for 20 minutes. An amount of 1.7 lb of dross can be generated. Magnesium in the melt was almost unchanged with 0.32% after melt treatment (including the 4 hours of operation for pouring and testing the degassed alloy). Strontium fell to 20 ppm after fluxing and degassing.
Tests were conducted on fluxed and degassed bars all cast in a permanent mold that were heat treated along with the degassed and untreated series and 50% were hipped. Tensile results shown in Table 5 do not particularly differ from the degassed melt results. However, the results indicate that the melt was already clean enough, and that degassing was sufficient and fluxing is not necessary in certain embodiments. In foundries and die casting operations, filtering the any of the recycled alloy or the blended material can also be implemented.
Various recycled alloys, including the recycled 356.2 aluminum alloy are available in large quantities. Blending with an the improved aluminum alloy in accordance with the above teachings provides the benefit of a lower price point, and eliminates one or more production steps (such as the addition of master alloys) resulting in improvements to logistics, handling, etc. For certain parts and products, the cost saving associated with raw materials of lighter weight aluminum casting alternatives could make economic sense for OEMs, thereby enabling them to replace heavier alternatives with lighter castings and contribute to overall vehicle light weighting. Moreover, reduction in weight results in a beneficial effect on emissions generation and fuel consumption by vehicles. While the example recycled alloy is A356, it could also include a multitude of die casting processes and materials. For example, certain die castings are made from primary alloys (e.g., 365 or A365) which can also be used and undergo the above method and exhibit a similar positive economical and environmental impact. In addition, a multitude of components currently made by die casting (in secondary alloys) could benefit from the higher quality and competitive input material that the recycled 356.2 alloy blended with the improved alloy provides. With improved mechanical properties, these die cast parts can be redesigned in a way that reduces the overall weight of vehicles. Additionally, the die cast parts formed of the blended material with improved properties could be used to replace heavier aluminum (e.g., in permanent mold castings made with thicker walls, or other heavier metal castings). Significantly more weight saving in vehicles and hence the reduction of fuel consumption and emission generation can be achieved. As with any charge material, the charging and melting time of the recycled 356.2 alloy will depend on the furnace type and arrangement and the way it is charged. In most cases, there will be little difference in terms of charging time between small ingots, T-bars, or sows if the charging is done in the appropriate way, e.g., with complete sacks (replacing T-bars or sows). Melting time can also depend on the surface area to mass ratio, which is much greater compared to ingots and especially T-bars or sows, so generally shredded recycled material will melt faster, especially if the charge is immersed into molten metal. These features can all be calculated for refining various method steps.
However, one consideration with increased surface area to mass (i.e., faster melting) also creates more oxide surfaces and hence more dross generation. Testing shows that for the recycled 356.2 aluminum alloy, melt loss was low and comparable to ingots. In a series of example method steps that include a 275-lb melt, steps and results include: first, skimming 0.66 lb or 0.5% of the charge; second, skimming after degassing 5.97 lb or 2.17% of the charge, amounting to 2.67% of the charge loss in dross. With clean and dry charge materials like ingots or T-bars, this loss can be in the range of 1-2%. In general, using shredded the recycled 356.2 alloy will lead to approximately 1% more dross than ingots, which is offset by its lower price point and high melting rate energy savings. Oxide testing of a part formed from the blended material can be included in the method via a Kmold Oxide Measurement, for example after mixing E2.50 and the recycled aluminum alloy before a fluxing operation.
In general, melting loss/dross generation depends on equipment and processing of the metal, surface area to mass ratio of the charge material, and the condition of the surface of the charge material. In the case of shredded recycled 356.2 alloy, its surface condition is excellent and extremely clean, so it does not contribute additionally to melt loss/dross generation. The recycled 356.2 aluminum alloy is a material that can allow foundries and die casters to achieve very good quality castings—close to 450 MPa (in permanent mould casting).
As indicated above, various parts can be formed from the blended material, including the recycled aluminum alloy and the improved aluminum alloy. According to a preferred embodiment, the parts are formed by high pressure vacuum die casting. During this process, molten metal is injected at high velocity and high pressure into a steel mold (die) cavity. The metal is typically injected at a velocity ranging from 90 to 200 feet per second and at a pressure of 5 to 15 ksi. The cavity (die) fill time ranges from a few milliseconds to as long as one half second. Die casting machines are typically rated in clamping tons equal to the amount of pressure they can exert on the die. Machine sizes range from 400 tons to 4000+ tons. The metal dies are fabricated from alloy tool steels, usually H13 in the heat treated condition (hardened) condition. Die cavity temperatures are maintained at about 450 to 500° F., and the temperature of the molten alloys is closely controlled to ensure adequate fluidity and die cavity fill.
FIG. 5A-5I illustrate steps of the high pressure vacuum die casting process according to an example embodiment. FIG. 5A shows the start position of a die. In the step of FIG. 513, the die is closed and molten aluminum alloy is poured into a cold chamber. In the step of FIG. 5C, a vacuum is applied to remove the atmosphere inside a die cavity and shot chamber. In the step of FIG. 5D, hydraulic pistons push the metal slowly toward the die cavity. In the step of FIG. 5E, the die cavity is filled in a fraction of a second. In the step of FIG. 5F, the metal solidifies under pressure to form a casting. In the step of FIG. 5G, the die is opened and the casting is removed. In the step of FIG. 5H, a release agent is applied to the die. In the step of 5I, the casting apparatus is ready for the next cycle
FIG. 6 is a chart illustrating differences between conventional high pressure die casting HPDC, vacuum assist high pressure die casting, and high pressure vacuum die casting.
FIGS. 7A-7H are example parts that can be formed from the blended material. FIG. 7A is a chassis component, particularly a front subframe. FIG. 7B is a structural body component, specifically a front shock tower. FIG. 7C is a structural body component, specifically a rear rail. FIG. 7D is a structural body components, specifically a front kick-down rail. FIG. 7E is a structural body component, specifically a front body hinge pillar. FIG. 7F is a structural body component, specifically a tunnel. FIG. 7G is a structural body component, specifically a front body hinge pillar. FIG. 7H is a structural body component, specifically a rear shock mount.
While the present disclosure is intended to produce a part with minimum treatment steps, depending on the required chemistry and casting properties, small additions of Mg and Sr or potential dilution with primary A356.2 (or higher purity) ingots might be required in certain cases. In some circumstances, fluxing the melt does not change tensile results, which indicates that the recycled aluminum alloy is very clean.
It should be appreciated that the foregoing description of the embodiments has been provided for purposes of illustration. In other words, the subject disclosure it is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varies in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of disclosure.

Claims

1. A method of manufacturing a blended material, comprising the steps of:

mixing a recycled aluminum alloy with an improved aluminum alloy to form a blended material;

the recycled aluminum alloy comprising, in weight percent (wt. %) based on the total weight of the recycled aluminum alloy, 6.5 wt. % to 7.5 wt. % silicon, up to 0.25 wt. % iron, up to 0.2 wt. % copper, up to 0.1 wt. % manganese, 0.25 wt. % to 0.45 wt. % magnesium, up to 0.1 wt. % zinc, up to 0.2 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum; and

the blended material comprising, in weight percent (wt. %) based on the total weight of the blended material, 6.0 to 8.0 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.03 wt. % strontium, and up to 0.15 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum; or

the blended material comprising, in weight percent (wt. %) based on the total weight of the blended material, 9.5 to 11.5 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.025 wt. % strontium, and up to 0.12 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum.

2. The method of claim 1, wherein the blended material has an ultimate tensile strength of greater than 180, a yield strength of greater than 120, and an elongation of greater than 5%.

3. The method of claim 1, wherein the improved aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the improved aluminum alloy, 7.4 wt. % to 7.9 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, up to 0.1 wt. % magnesium, up to 0.03 wt. % zinc, 0.92 wt. % to 1.0 wt. % manganese, up to 0.06 wt. % titanium, and 0.03 wt. % to 0.04 wt. % strontium.

4. The method of claim 1, wherein the improved aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the improved aluminum alloy, 12.5 wt. % to 13 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, 0.27 to 0.33 wt. % magnesium, up to 0.03 wt. % zinc, 0.92 wt. % to 1.0 wt. % manganese, up to 0.06 wt. % titanium, and 0.03 wt. % to 0.04 wt. % strontium.

5. The method of claim 1, wherein the improved aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the improved aluminum alloy, 17 wt. % to 17.5 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, 0.27 to 0.33 wt. % magnesium, up to 0.03 wt. % zinc, 1.65 wt. % to 1.70 wt. % manganese, up to 0.06 wt. % titanium, and 0.06 wt. % to 0.07 wt. % strontium.

6. The method of claim 1 including recycling a first aluminum alloy to obtain the recycled aluminum alloy.

7. A blended material comprising, in weight percent (wt. %) based on the total weight of the blended material, 6.0 to 8.0 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.03 wt. % strontium, and up to 0.15 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum; or

8. The blended material of claim 16, wherein the improved aluminum alloy comprises, in wt. % based on the total weight of the improved aluminum alloy, 7.4 wt. % to 7.9 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, up to 0.1 wt. % magnesium, up to 0.03 wt. % zinc, 0.92 wt. % to 1.0 wt. % manganese, up to 0.06 wt. % titanium, and 0.03 wt. % to 0.04 wt. % strontium.

9. The blended material of claim 16, wherein the improved aluminum alloy comprises, in wt. % based on the total weight of the improved aluminum alloy, 12.5 wt. % to 13 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, 0.27 to 0.33 wt. % magnesium, up to 0.03 wt. % zinc, 0.92 wt. % to 1.0 wt. % manganese, up to 0.06 wt. % titanium, and 0.03 wt. % to 0.04 wt. % strontium.

10. The blended material of claim 16, wherein the improved aluminum alloy comprises, in wt. % based on the total weight of the improved aluminum alloy, 17 wt. % to 17.5 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, 0.27 to 0.33 wt. % magnesium, up to 0.03 wt. % zinc, 1.65 wt. % to 1.70 wt. % manganese, up to 0.06 wt. % titanium, and 0.06 wt. % to 0.07 wt. % strontium.

11. A method of manufacturing a part for a vehicle, comprising the steps of:

the recycled aluminum alloy comprising, in wt. % based on the total weight of the recycled aluminum alloy, 6.5 wt. % to 7.5 wt. % silicon, up to 0.25 wt. % iron, up to 0.2 wt. % copper, up to 0.1 wt. % manganese, 0.25 wt. % to 0.45 wt. % magnesium, up to 0.1 wt. % zinc, up to 0.2 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum;

the blended material comprising, in weight percent (wt. %) based on the total weight of the blended material, 9.5 to 11.5 wt. % silicon, up to 0.25 wt. % iron, 0.40 to 0.60 wt. % manganese, 0.1 to 0.60 wt. % magnesium, 0.01 to 0.025 wt. % strontium, and up to 0.12 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum; and

casting the blended material to form the part.

12. The method of claim 11, wherein the part has an ultimate tensile strength of greater than 180, a yield strength of greater than 120, and an elongation of greater than 5%.

13. The method of claim 11, wherein the casting step includes injecting the blended material into a cavity of a die at a velocity ranging from 90 to 200 feet per second and at a pressure of 5 to 15 ksi.

14. The method of claim 11, wherein the part is designed for a chassis or structural body of a vehicle.

15. The method of claim 14, wherein the part is a front subframe, a front shock tower, a rear rail, a front kick-down rail, a front body hinge pillar, a tunnel, a front body hinge pillar, or a rear shock mount.

16. The blended material of claim 7, wherein the blended material is formed by mixing a recycled aluminum alloy and an improved aluminum alloy, the recycled aluminum alloy comprising, in wt. % based on the total weight of the recycled aluminum alloy, 6.5 wt. % to 7.5 wt. % silicon, up to 0.25 wt. % iron, up to 0.2 wt. % copper, up to 0.1 wt. % manganese, 0.25 wt. % to 0.45 wt. % magnesium, up to 0.1 wt. % zinc, up to 0.2 wt. % titanium, other elements in an amount up to 0.15 wt. %, and a balance of aluminum.

17. The method of claim 11, wherein the improved aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the improved aluminum alloy, 7.4 wt. % to 7.9 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, up to 0.1 wt. % magnesium, up to 0.03 wt. % zinc, 0.92 wt. % to 1.0 wt. % manganese, up to 0.06 wt. % titanium, and 0.03 wt. % to 0.04 wt. % strontium.

18. The method of claim 11, wherein the improved aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the improved aluminum alloy, 12.5 wt. % to 13 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, 0.27 to 0.33 wt. % magnesium, up to 0.03 wt. % zinc, 0.92 wt. % to 1.0 wt. % manganese, up to 0.06 wt. % titanium, and 0.03 wt. % to 0.04 wt. % strontium.

19. The method of claim 11, wherein the improved aluminum alloy comprises, in weight percent (wt. %) based on the total weight of the improved aluminum alloy, 17 wt. % to 17.5 wt. % silicon, up to 0.01 wt. % copper, 0.16 wt. % to 0.2 wt. % iron, 0.27 to 0.33 wt. % magnesium, up to 0.03 wt. % zinc, 1.65 wt. % to 1.70 wt. % manganese, up to 0.06 wt. % titanium, and 0.06 wt. % to 0.07 wt. % strontium.

20. The method of claim 11 including recycling a first aluminum alloy to obtain the recycled aluminum alloy.