The present disclosure generally relates to permanent magnets; more specifically, the present disclosure relates to a method of manufacturing permanent magnets comprising a powdered metal alloy contained within an enclosed volume of a container of any desired cross sectional shape.
Permanent magnets with high energy products, such as neodymium-iron-boron magnets, are conventionally produced with a modified powdered metallurgical process in simple geometrical forms like discs, cuboids and parallelepiped. A conventional process of manufacturing an exemplary combination of metals, neodymium-iron-boron, is shown and described with reference to
First, powdered metals are created. To do this, the appropriate amounts of neodymium, iron, and boron are combined and heated to the melting point under vacuum. As used herein, “alloy” is used to refer to the resulting substance in both liquid and solid states. The vacuum prevents any chemical reaction between air and the melting materials that might contaminate the final metal alloy. Once the metal alloy has cooled and solidified, it is broken up and crushed into small pieces, which are ground into a fine powder creating a powdered metal alloy.
Next, the powdered metal alloy is pressed. In this process, the powder is placed in a die that has the shape of the finished magnet. A magnetic field is applied to the powder to line up the powder particles. While the magnetic force is being applied, the powder is pressed from the top and bottom with hydraulic or mechanical rams to compress it to within about 0.125 inches (0.32 cm) of its final intended thickness. Typical pressures are about 10,000 psi to 15,000 psi (70 MPa to 100 MPa). Some shapes are made by placing the powder in a flexible, air-tight, evacuated container and pressing it into shape with liquid or gas pressure. This is known as isostatic compaction.
Once compressed, the powdered metal alloy is heated. The metal alloy is removed from the die and placed in an oven for sintering, which fuses the powder into a solid piece. The process usually consists of three stages. In the first stage, the alloy is heated at a low temperature to slowly drive off any moisture or other contaminants that may have become entrapped during the pressing process. In the second stage, the temperature is raised to about 70-90% of the melting point of the metal alloy and held there for a period of several hours or several days to allow the small particles to fuse together. Finally, the alloy is slowly cooled down in controlled, step-by-step temperature increments.
The sintered metal alloy then undergoes a second controlled heating and cooling process known as annealing. This process removes any residual stresses within the alloy and strengthens it.
Then, a finishing process takes place. The annealed metal alloy is very close to the finished shape and required dimensions. A final machining process removes any excess material and produces a smooth surface. The alloy is then given a protective coating to seal the surfaces.
Once in its finished form, the metal alloy is magnetized. Up to this point, the metal alloy is just a piece of compressed and fused metal. Even though it was subjected to a magnetic force during pressing, that force did not magnetize the alloy, it simply lined up the loose powder particles. To turn it into a magnet, the alloy is placed between the poles of a powerful electromagnet and oriented in the desired direction of magnetization. The electromagnet is then energized for a period of time. The magnetic force aligns the groups of atoms, or magnetic domains, within the material to transform the alloy into a strong permanent magnet.
Each step of the conventional manufacturing process is monitored and controlled. The sintering and annealing processes are especially critical to the final mechanical and magnetic properties of the magnet, and the variables of time and temperature must be closely controlled.
The standard geometrical forms produced by this conventional method are insufficient for many applications. More complex shapes and magnetization directions are needed. For example, Halbach arrays formed from permanent magnets use complex shapes and magnetization directions. To create permanent magnets for Halbach arrays using conventional methods either complex molds (dies) are needed to produce the permanent magnets or the standard geometrical forms have to be machined to yield the required shapes. Both of these manufacturing processes are complex and expensive. Machining of permanent magnet materials, in particular, is difficult, since the material is very hard and brittle, causing wear-out and breakage of cutting tools. The manufacture of large permanent magnet arrays is further complicated by a difficult assembly process, in which substantial repulsive or attractive magnetic forces have to be overcome during manufacturing processes.
Therefore, what is needed in the art is a more efficient manufacturing method that can create permanent magnets of more complex shapes and magnetization directions and results in permanent magnets which are more structurally robust and are able to resist structural failure under point or distribute loads that may be experienced during manufacture, shipping, assembly and use.
In accordance with the teachings disclosed herein, embodiments related to a method of manufacturing permanent magnets are disclosed.
The invention is a novel and enabling process for economical production of permanent magnets, having the potential to revolutionize permanent magnet manufacturing; lower cost product, lower cost and safer assembly of magnet-based products, enabler for the application of future permanent magnet materials and enabling new magnet-based products having potential for high-impact solutions for energy, medical, transportation and environmental industries. The novel Permanent Magnet (PM) manufacturing technology of the invention, termed PM-Wire, overcomes many inherent issues with conventional magnet production methods. The process of the invention enables mass-produced, cost-effective PM products, which are more robust, easily assembled into products and enables new “wire like” shapes and significantly increases energy density. The novel process comprises a “powder-in-tube” process that is continuous and may utilize drawing, packing and shaping processes, allows for mass production of permanent magnets of any desired shape or cross section, produces permanent magnets continuously that may be cut to any length, and may, in an embodiment, result in magnets with a desired magnetization direction.
In an embodiment, a method manufacturing a permanent magnet comprises heating a plurality of magnetic metals to their melting point under vacuum to create a metal alloy, allowing the metal alloy to cool and solidify and then grounding the metal alloy into a fine powder. The plurality of magnetic metals may be neodymium, iron and boron. The metal alloy powder is then placed in a tube or other shaped container. The tube or other shaped container may comprise a non-magnetic metal. A magnetic field is applied to the metal alloy while the metal alloy and tube it is contained in are compressed. The process of compressing the metal alloy and tube may comprise swaging the metal alloy and tube or other shaped container. The metal alloy and tube are then sintered and cooled. After cooling, the metal alloy is magnetized. Magnetization may comprise placing the metal alloy between two poles of an electromagnet and energizing the electromagnet.
In another embodiment, a permanent magnet is prepared by the above process.
The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating the preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings:
In the figures, like item callouts refer to like elements.
A detailed description of the embodiments for a method of manufacturing permanent magnets will now be presented with reference to
As used herein, “tube” includes within its definition any desired shape enclosing an interior volume.
As used herein, “PM Wire” is used to refer to any permanent magnet shape or configuration produced by the inventive method, and is therefore not limited only to “wire” constructs or shapes.
Embodiments of the manufacturing process disclosed herein overcome some of the inherent issues with the conventional manufacturing method and, in particular, enable cost effective manufacturing of complex magnetic arrays, such as Halbach arrays. Embodiments of the manufacturing process enable mass production of permanent magnets that are more mechanically robust than conventional permanent magnets and more easily assembled into complex arrays. In some cases, permanent magnets created can be bent into arcs.
An exemplary embodiment of the inventive process for manufacturing a permanent magnet is shown and described with reference to
Referring now to
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Still referring to
As an alternative to the sintering process of steps 102 and 202, a bonding agent, such as a chemical bonding agent, epoxy, or the like may be mixed with the powdered metal alloy. The bonding agent is then cured, producing a permanent magnet of a desired shape that is ready for final finishing.
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With this powder-in-tube process depicted in
Using the resulting tubes of permanent magnets, complex assemblies such as, for example, Halbach arrays can be produced. The surrounding support tube, or other-shaped container, provides mechanical strength, which aids in the handling of the permanent magnets created using the powder-in-tube process. Included within the scope of the invention are Halbach arrays comprising permanent magnets produced by the processes and methods described herein.
For powder-in-tube magnets with large aspect ratios of tube length to diameter, for example a length of 500 mm and an outer tube diameter of 5 mm, or wires, a slight bending of the final magnet is possible, creating an arc.
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In
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Having now described the invention, the construction, the operation and use of preferred embodiments thereof, and the advantageous new and useful results obtained thereby, the new and useful constructions, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.
Within the scope of the invention are both the processes and methods described herein and the products produced thereby.
This international application for patent claims the benefit of United States provisional patent application No. 62/315,622 filed in the United States Patent and Trademark Office (USPTO) titled METHOD OF MANUFACTURING PERMANENT MAGNETS on Mar. 30, 2016, which is hereby incorporated herein by reference in its entirety; and this application claims the benefit of priority of United States provisional patent application No. 62/314,991 titled DUAL-ROTOR SYNCHRONOUS ELECTRICAL MACHINES filed in the USPTO on Mar. 30, 2016, which is hereby also incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2017/025212 | 3/30/2017 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2017/173186 | 10/5/2017 | WO | A |
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Number | Date | Country | |
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20190122818 A1 | Apr 2019 | US |
Number | Date | Country | |
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62315622 | Mar 2016 | US | |
62314991 | Mar 2016 | US |