Patent Application
20250115976
The present disclosure relates to scrap recycling and in particular to methods of recycling mixed alloy scrap.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Vehicle scrap recycling can be an important component of a more sustainable manufacturing industry. In particular, aluminum is used in increasing amounts to lower the weight of vehicles but can often benefit from recycling when the vehicle reaches the end of its useful life.
In some situations, a vehicle cannot be completely separated by metal type. For example, steel fasteners are often used to fasten aluminum panels together. The steel fasteners may not be able to be removed from the aluminum in an efficient process based on the type of fastener and installation method. Further, melting mixed-material scrap may result in less useable composition, particularly when a high purity alloy is needed.
The present disclosure addresses these issues related to efficiently and effectively recycling vehicle scrap comprising different metal alloys.
This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.
In one form, the present disclosure provides a method of processing mixed-material vehicle scrap. The mixed-material vehicle scrap comprises a first group of parts and a second group of parts. The first group of parts includes a first alloy and the second group of parts has a substrate of a second alloy and a coating disposed over the substrate. The method includes conditioning the mixed-material vehicle scrap such that an element of the second alloy is diffused into the coating to form a diffused coating and heating the mixed-material vehicle scrap to a temperature above the melting temperature of the first alloy and below the melting temperature of the diffused coating, thereby allowing the second group of parts to separate from the first group of parts. The diffused coating has a melting temperature greater than a melting temperature of the first alloy.
In variations of this method, which may be implemented individually or in any combination: the first alloy comprises an aluminum alloy; the first alloy comprises a magnesium alloy; the coating is applied with an electrocoating process; the coating has a thickness between about 2 microns and 10 microns; the diffused coating comprises gamma phase constituents; and conditioning the mixed-material vehicle scrap comprises heating the mixed-material vehicle scrap to a temperature between about 450° C. and about 600° C. for up to about 60 minutes.
The present disclosure further provides another method of processing mixed-material vehicle scrap. The mixed-material vehicle scrap comprises aluminum parts made of an aluminum alloy and steel parts made of a steel alloy. Each of the steel parts includes a steel substrate and a coating disposed over the steel substrate. The method includes conditioning the mixed-material vehicle scrap such that iron from the steel parts is diffused into the coating to form a diffused coating and heating the mixed-material vehicle scrap to a temperature above the melting temperature of the aluminum alloy and below the melting temperature of the diffused coating, thereby allowing the steel parts to separate from the aluminum parts. The diffused coating has a melting temperature greater than a melting temperature of the aluminum alloy.
In variations of this method, which may be implemented individually or in any combination: the coating is applied with an electrocoating process; the coating has a thickness between about 2 microns and 10 microns; and each of the diffused coatings comprises gamma phase constituents.
In yet another form, the present disclosure provides a method of processing mixed-material vehicle scrap. The mixed-material vehicle scrap comprises aluminum parts made of an aluminum alloy and steel parts made of a steel alloy. Each of the steel parts includes a steel substrate and a coating disposed over the steel substrate. The method includes conditioning the mixed-material vehicle scrap by heating the mixed-material vehicle scrap to a temperature between about 450° C. and about 600° C. for up to about 60 minutes such that iron from each of the steel parts is diffused into each of the coatings to form a gamma phase diffusion layer, the gamma phase diffusion layer comprising intermetallic constituents and having a melting temperature greater than a melting temperature of the aluminum alloy; and heating the mixed-material vehicle scrap to a temperature above the melting temperature of the aluminum alloy and below the melting temperature of the diffusion layer, thereby allowing the steel parts to separate from the aluminum parts.
In variations of this method, which may be implemented individually or in any combination: the coating is applied with an electrocoating process; the coating has a thickness between about 2 microns and 10 microns; and the diffusion layer has a thickness between about 2 microns and 10 microns.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
Aluminum alloys are used in significant quantities in motor vehicles, both for body and frame parts. Because recycling aluminum takes 95% less energy than producing aluminum from raw materials, vehicle scrap is often recycled at the end of the life of a motor vehicle. During the recycling process, the scrap is separated by type of metal as far as possible, and the aluminum scrap is melted into a bath. In order to separate various materials in vehicle scrap, vehicles at the end of life are typically shredded and then separated by automated methods including weight separation and magnetic separation. However, parts that are small and/or tightly connected to aluminum parts, such as fasteners, often slip past the separation processes and remain with the aluminum. Although fasteners could be manually removed, such as by drilling out for example, it would not be efficient for the majority of circumstances.
The quality and utility of the recycled aluminum alloy is dependent on the composition, especially the iron content. Above 0.6 wt. % iron content, the ductility of the resulting aluminum alloy is reduced below the requirements for use in motor vehicles. The higher quality recycled aluminum alloys have less than 0.2 wt. % iron. Because higher amounts of iron produce alloys which lack the desired formability and structural properties for applications in motor vehicles, methods of limiting iron transfer from steel fasteners and other steel parts into the aluminum alloy parts are provided by the teachings herein.
Referring now to
In one variation, the coating is applied with an electrocoating process, which may be an electrogalvanized zinc or a zinc alloy. The thickness of the zinc coating is typically between 2 and 10 microns. In another form, the coating is a nickel coating with a thickness between 1 and 5 microns. In addition, other metal coatings may be used, with the electrocoating process or other coating process, while remaining within the scope of this disclosure. For example, these other metal coatings include but are not limited to cadmium, magnesium, or manganese, among others.
Referring to
The first group of parts includes scrap from bulk parts such as vehicle panels, frames, and panels (e.g., the aluminum parts 12). Generally, the first group of parts is made of a first alloy. In one form, the first group of parts comprises an aluminum alloy as set forth above, but other materials may be employed for the first alloy, such as by way of example, magnesium, while remaining within the scope of the present disclosure.
The second group of parts are small components which cannot be easily separated from the first group of parts, including fasteners 10 as set forth above and shown in
As shown in
In one specific form in which the second alloy is steel and the coating is zinc, iron from the steel diffuses into the zinc coating to form a diffused coating with a zinc-iron solid solution diffusion layer. The zinc-iron diffusion layer includes layers of intermetallic constituents made up of different alloy phases as the percentage of iron within the zinc changes. The zinc-iron diffusion layer does not react with the aluminum.
In one form, the diffused coating contains a gamma phase diffusion layer made up of gamma phase intermetallic constituents.
In other variations, in which the substrate or the coating has a different composition, the diffused coating includes a different solid solution diffusion layer including intermetallic constituents in phase layers. For example, if the second alloy forming the substrate is a magnesium alloy and the coating is a nickel alloy, magnesium diffuses into the nickel layer to form a nickel-magnesium diffusion layer. As with the zinc-iron diffusion layer, other variations on the diffused coating do not react with the first alloy and have a melting temperature higher than the melting temperature of the aluminum or other first alloy. In one form, the diffusion layer has a thickness of between 2 and 10 microns, dependent on the temperature and length of the conditioning.
Referring back to
Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.
As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”
The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.
