Method for recycling mixed alloy scrap parts
By diffusing iron to the coating and forming a diffusion coating with high melting temperature, the problem of difficult separation between steel fasteners and aluminum parts in vehicle waste is solved, and efficient vehicle waste recycling of mixed materials is achieved, ensuring the quality and applicability of recycled aluminum alloys.
Patent Information
- Application Number
- CN202411367457.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-10-05
- Filing Date
- 2024-09-29
- Publication Date
- 2025-04-08
AI Technical Summary
The prior art is difficult to efficiently recover vehicle waste including different metal alloys, especially due to the tight connection of steel fasteners to aluminum parts and the complexity of mixed materials, which makes it difficult to efficiently separate and recycle.
By adjusting the mixed material vehicle waste, iron from the steel parts diffuses into the coating to form a diffusion coating that has a melting temperature higher than the aluminum alloy. The mixed material vehicle waste is then heated to a melting temperature above the aluminum alloy but below the melting temperature of the diffusion coating, allowing the steel parts to separate from the aluminum parts.
Efficient separation and recycling of mixed material vehicle waste is achieved, improving the efficiency and quality of the recycling process, especially in limiting the transfer of iron, ensuring the quality and applicability of the recycled aluminum alloy.
Smart Images
Figure CN119776658A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to scrap recycling, and in particular to methods of recycling mixed alloy scrap. Background Art
[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
[0003] Vehicle scrap recycling can be an important part of a more sustainable manufacturing industry. Specifically, aluminum is being used in increasing amounts to reduce the weight of vehicles, but when a vehicle reaches the end of its useful life, aluminum can often benefit from recycling.
[0004] In some cases, vehicles cannot be completely separated by metal type. For example, steel fasteners are often used to fasten aluminum panels together. Depending on the type of fastener and the installation method, the steel fasteners may not be removed from the aluminum in an efficient process. In addition, melting mixed material scrap may result in less usable compositions, especially when high purity alloys are required.
[0005] The present disclosure addresses these issues associated with efficient and effective recycling of vehicle scrap including dissimilar metal alloys. Summary of the invention
[0006] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.
[0007] In one form, the present disclosure provides a method for processing mixed material vehicle scrap. The mixed material vehicle scrap includes 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 the second alloy and a coating disposed over the substrate. The method includes: conditioning the mixed material vehicle scrap so that elements of the second alloy are diffused into the coating to form a diffusion 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 diffusion coating, thereby allowing the second group of parts to be separated from the first group of parts. The diffusion coating has a melting temperature that is higher than the melting temperature of the first alloy.
[0008] In a variation of the method that may be implemented alone or in any combination: the first alloy comprises an aluminum alloy; the first alloy comprises a magnesium alloy; the coating is applied using an electrocoating process; the coating has a thickness between about 2 microns and 10 microns; the diffusion coating comprises a gamma phase component; 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.
[0009] The present disclosure also provides another method for processing mixed material vehicle scrap. The mixed material vehicle scrap includes 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 above the steel substrate. The method includes: conditioning the mixed material vehicle scrap so that iron from the steel parts diffuses into the coating to form a diffusion coating; and heating the mixed material vehicle scrap to a temperature higher than the melting temperature of the aluminum alloy and lower than the melting temperature of the diffusion coating, thereby allowing the steel parts to be separated from the aluminum parts. The diffusion coating has a melting temperature higher than the melting temperature of the aluminum alloy.
[0010] In variations of the method that may be implemented alone or in any combination: the coatings are applied with an electrocoating process; the coatings have a thickness between about 2 microns and 10 microns; and each of the diffusion coatings includes a gamma phase component.
[0011] In yet another form, the present disclosure provides a method for processing mixed material vehicle scrap. The mixed material vehicle scrap includes 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 above 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 about 60 minutes, so that iron from each of the steel parts diffuses into each of the coatings to form a γ-phase diffusion layer, the γ-phase diffusion layer including intermetallic components and having a melting temperature higher than the melting temperature of the aluminum alloy; and heating the mixed material vehicle scrap to a temperature higher than the melting temperature of the aluminum alloy and lower than the melting temperature of the diffusion layer, thereby allowing the steel parts to be separated from the aluminum parts.
[0012] In variations of the method that may be implemented alone or in any combination: the coating is applied using 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.
[0013] 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. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In order that the present disclosure may be better understood, various forms of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:
[0015] Figure 1 is a cross-sectional view of a self-piercing rivet according to one aspect of the present disclosure;
[0016] Figure 2 is a flow chart illustrating a method for recycling mixed alloy scrap according to the principles of the present disclosure;
[0017] Figure 3 is a microscopic image of the Fe-Zn diffusion layer; and
[0018] Figure 4 is an iron-zinc phase diagram according to the present disclosure.
[0019] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION
[0020] 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 the same or corresponding parts and features.
[0021] Aluminum alloys are used in large quantities in motor vehicles for both body parts and frame parts. Because recycling aluminum consumes 95% less energy than producing aluminum from raw materials, vehicle scrap is typically recycled at the end of the life of a motor vehicle. During the recycling process, the scrap is separated by metal type as much as possible, and the aluminum scrap is melted into a molten pool. In order to separate the various materials in the vehicle scrap, vehicles at the end of their life are typically shredded and then separated by automated methods including weight separation and magnetic separation. However, smaller and / or closely connected parts to the aluminum parts, such as fasteners, typically slip through the separation process and remain with the aluminum. Although fasteners can be removed manually, such as by, for example, drilling them out, this will not be effective for most cases.
[0022] The quality and utility of recycled aluminum alloys depend on the composition, especially the iron content. Above 0.6 wt. %, the ductility of the resulting aluminum alloy is reduced to below the requirements for use in motor vehicles. Higher quality recycled aluminum alloys have less than 0.2 wt. % iron. Because higher amounts of iron produce alloys that lack the desired formability and structural properties for applications in motor vehicles, the teachings herein provide methods for limiting the transfer of iron from steel fasteners and other steel parts into aluminum alloy parts.
[0023] Reference now Figure 1 , an exemplary fastener is designated by reference numeral 10 and is shown in cross-section. As shown, fastener 10 is a self-piercing rivet; however, a variety of fastener types may be used within the scope of the present disclosure. For example, fastener 10 is used to join an aluminum part 12. Aluminum part 12 is an aluminum motor vehicle part, such as an aluminum panel, an aluminum frame, etc. Fastener 10 includes a steel substrate 14 and a coating 16 disposed about the substrate. Therefore, fastener 10 and aluminum part 12 are "hybrid materials" because they are made of different materials (e.g., aluminum, steel, and a coating), as described below.
[0024] In one variation, the coating is applied using an electrocoating process, which may be electroplated zinc or a zinc alloy. The thickness of the zinc coating is typically between 2 microns and 10 microns. In another form, the coating is a nickel coating having a thickness between 1 micron and 5 microns. Additionally, other metal coatings may be used under the electrocoating process or other coating processes while remaining within the scope of the present disclosure. For example, these other metal coatings include, but are not limited to, cadmium, magnesium, or manganese, etc.
[0025] refer to Figure 2 The present disclosure provides a novel method 20 for recycling a collection of mixed material vehicle scrap, such as, for example, aluminum parts 12 with coated steel fasteners 10 as described above. The mixed material vehicle scrap consists of a first set of parts and a second set of parts.
[0026] The first group of parts includes scrap from bulk parts such as vehicle panels, frames, and panels (e.g., aluminum part 12). Generally, the first group of parts is made of a first alloy. In one form, the first group of parts includes an aluminum alloy as described above, but other materials may be used for the first alloy, such as magnesium, for example, while remaining within the scope of the present disclosure.
[0027] The second group of parts are small components that cannot be easily separated from the first group of parts, including those described above and in Figure 1 10. Each of the second set of parts includes a substrate and a coating disposed over the substrate. Generally, the substrate is made of a second alloy. The second alloy includes components that should be limited to recycled aluminum or other first alloys, such as but not limited to iron. In one form, the substrate is a steel alloy and the coating is a zinc alloy, as previously described. Other materials, such as, for example, non-steel alloys or non-ferrous alloys, may be employed while remaining within the scope of the present disclosure.
[0028] like Figure 2 As shown, the first step of the method is to condition or heat the mixed material vehicle scrap. In one form, the conditioning is completed by heating the mixed material vehicle scrap to a temperature between about 450°C and about 600°C for about 60 minutes. During conditioning, iron from the steel substrate diffuses into the coating on the second group of parts to form a diffusion coating on each part. For example, iron from the steel substrate 14 of the fastener 10 diffuses into the coating 16 of the fastener 10. More generally, the components or chemical elements of the second alloy diffuse from the substrate into the coating to form a diffusion coating. The diffusion coating has a melting temperature that is higher than the melting temperature of the substrate and higher than the melting temperature of aluminum or other first alloys. As described in more detail below, the difference in melting temperature inhibits the second alloy from melting into the first alloy and allows the first group of parts to be separated from the second group of parts.
[0029] In one specific form where the second alloy is steel and the coating is zinc, iron from the steel diffuses into the zinc coating to form a diffusion coating having a zinc-iron solid solution diffusion layer. The zinc-iron diffusion layer includes an intermetallic composition layer composed of different alloy phases when the percentage of iron in the zinc varies. The zinc-iron diffusion layer does not react with aluminum.
[0030] In one form, the diffusion coating comprises a gamma phase diffusion layer comprised of a gamma phase intermetallic component. Figure 3 An example of a zinc-iron diffusion layer is shown including a gamma phase diffusion layer indicated by reference numeral 20. The gamma phase intermetallic component of the zinc-iron layer has a melting temperature higher than the melting temperature of aluminum and / or the temperature of the aluminum recovery bath. Figure 4 A zinc-iron phase diagram is shown, which shows that the melting point of the gamma phase is 782°C.
[0031] In other variations where the substrate or coating has a different composition, the diffusion coating includes different solid solution diffusion layers that include intermetallic components in the phase layer. 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 diffusion coating do not react with the first alloy and have a melting temperature that is higher than the melting temperature of the aluminum or other first alloy. In one form, the diffusion layer has a thickness between 2 microns and 10 microns, depending on the temperature and duration of the conditioning.
[0032] Return to reference Figure 2 In the next step of the method, the conditioned mixed material vehicle scrap is heated to a temperature above the melting temperature of the first alloy and below the melting temperature of the diffusion coating. Thus, the first group of parts becomes molten. For example, the aluminum and steel scrap are heated to a temperature that melts the first group of aluminum parts into an aluminum molten pool. In one form, the aluminum molten pool and the mixed material vehicle scrap are heated to above 700°C. Because the second group of parts has a diffusion coating with a melting temperature higher than the molten pool temperature, the diffusion coating provides a barrier between the molten aluminum and the steel substrate. The diffusion coating limits the amount of iron mixed with the molten aluminum from the second group of parts. In one form, the second group of parts is separated from the molten aluminum. Steel fasteners are denser than aluminum and therefore sink to the bottom of the aluminum molten pool, where they can be collected and removed. Other separation methods may include a magnetic collector.
[0033] Unless otherwise expressly indicated herein, all numerical values indicating mechanical / thermal properties, composition percentages, dimensions and / or tolerances or other characteristics when describing the scope of the present disclosure should be understood to be modified by the word "about" or "approximately". Such modifications are desirable for a variety of reasons, including: industrial practice; material, manufacturing and assembly tolerances; and testing capabilities.
[0034] 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."
[0035] The description of the present disclosure is merely exemplary in nature, and thus, variations that do not depart from the essence of the present disclosure are intended to be within the scope of the present disclosure. Such variations should not be regarded as a departure from the spirit and scope of the present disclosure.
[0036] According to the present invention, a method for processing mixed-material vehicle scrap, including aluminum parts and steel parts, each of the steel parts including a steel substrate and a coating layer disposed over the steel substrate, the method comprising: conditioning the mixed-material vehicle scrap so that iron from each of the steel parts diffuses into each of the coating layers to form a diffusion layer having a melting temperature higher than that of the aluminum parts; and heating the mixed-material vehicle scrap to a temperature higher than the melting temperature of the aluminum parts and lower than the melting temperature of the diffusion layer, thereby allowing the steel parts to be separated from the aluminum parts.
[0037] In one aspect of the invention, the coating is applied using an electrocoating process.
[0038] In one aspect of the invention, the coating comprises a zinc alloy.
[0039] In one aspect of the invention, the coating has a thickness between about 2 and 10 microns.
[0040] In one aspect of the invention, the diffusion layer includes a gamma phase component.
[0041] In one aspect of the invention, conditioning the mixed material vehicle waste includes heating the mixed material vehicle waste to a temperature between about 450° C. and about 600° C. for up to about 60 minutes.
[0042] In one aspect of the invention, mixed material vehicle scrap is heated to above 700°C and the aluminum parts become molten.
[0043] According to the present invention, a method for processing mixed-material vehicle scrap includes an aluminum alloy, and each of the steel parts includes a steel substrate and a coating, the method comprising: 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 about 60 minutes so that iron from each of the steel parts diffuses into each of the coatings to form a gamma-phase diffusion layer, the gamma-phase diffusion layer including intermetallic components and having a melting temperature higher than the melting temperature of the aluminum alloy; heating the mixed-material vehicle scrap to a temperature higher than the melting temperature of the aluminum alloy and lower than the melting temperature of the diffusion layer, thereby allowing the steel parts to be separated from the aluminum parts.
[0044] In one aspect of the invention, the coating is applied using an electrocoating process.
[0045] In one aspect of the invention, the coating comprises a zinc alloy.
[0046] In one aspect of the invention, the coating has a thickness between about 2 and 10 microns.
[0047] In one aspect of the invention, the diffusion layer has a thickness between about 2 microns and 10 microns.
Claims
1. A method of processing mixed-material vehicle scrap, the mixed-material vehicle scrap comprising a first group of parts and a second group of parts, the first group of parts comprising a first alloy and the second group of parts comprising a second alloy, each of the second group of parts having a substrate comprising the second alloy and a coating disposed over the substrate, the method comprising: conditioning the mixed material vehicle scrap material such that elements of the second alloy are diffused into the coating to form a diffusion coating having a melting temperature greater than a melting temperature of the first alloy; as well as The mixed material vehicle scrap is heated to a temperature above the melting temperature of the first alloy and below the melting temperature of the diffusion coating, thereby allowing the second group of parts to be separated from the first group of parts.
2. The method of claim 1, wherein the first alloy comprises an aluminum alloy.
3. The method of claim 2, wherein the mixed material vehicle scrap is heated to above 700°C and the aluminum part becomes molten. The method of claim 1 , wherein the first alloy comprises a magnesium alloy.
5. The method of claim 1, wherein the coating is applied using an electrocoating process.
6. The method of claim 1, wherein the coating comprises a zinc alloy.
7. The method of claim 1, wherein the coating has a thickness between about 2 microns and 10 microns.
8. The method of claim 1, wherein the diffusion coating comprises a gamma phase component.
9. The method of claim 1, wherein 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.
10. The method of claim 1, wherein the second alloy comprises a steel alloy.
11. The method of claim 10, wherein the mixed material vehicle scrap is conditioned so that iron from each of the steel alloys is diffused into each of the coatings to form a diffusion layer having a melting temperature higher than the melting temperature of the first alloy.
12. The method of claim 11, wherein the diffusion layer is a gamma phase diffusion layer.
13. The method of claim 11, wherein the diffusion layer has a thickness between approximately 2 microns and 10 microns.