Permanent Magnet MIM Debinding with Rare Earth Inertization
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Solution Overview
Problem
The production of complex-shaped permanent magnets with rare earth elements, such as neodymium, is hindered by their high reactivity with oxygen and carbon during the debinding process in metal powder injection molding, leading to the formation of oxides or carbides that deteriorate the hard magnetic properties.
Innovation Solution
Converting the rare earth element into an inert compound before the debinding step in the MIM process, ensuring it remains non-reactive with oxygen and carbon, and then reconverting it back after debinding to maintain the magnet's properties, thereby preventing oxide and carbide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic binder material is used in MIM process, then the binder can be removed through thermal debinding, but oxides or carbides of rare earth metal form during debinding
Solution Approach 1:
A coating layer comprising rare earth metal oxide is applied to the starting material before debinding. This coating layer acts as an intermediary barrier that prevents direct contact between the rare earth metal and oxygen/carbon during thermal debinding, thereby preventing oxide and carbide formation while allowing the debinding process to proceed normally
Solution Approach 2:
The coating layer creates an inert protective environment around the rare earth metal particles during the debinding process. By forming a stable oxide layer beforehand, the rare earth metal is protected from further oxidation or carbide formation when exposed to the oxygen and carbon released from the organic binder during thermal decomposition
2Reliability
If rare earth element is kept in reactive form, then magnetic properties are maintained, but reactivity with oxygen and carbon increases during debinding
Solution Approach 1:
The rare earth metal is pre-oxidized to form a stable coating layer before the debinding process. This preliminary action protects the rare earth metal from harmful reactions during debinding, and the coating is subsequently removed or transformed during sintering to restore the magnetic properties
Solution Approach 2:
The chemical state of the rare earth metal is temporarily changed from metallic form to oxide form during debinding for protection, then restored back to metallic form during sintering to regain magnetic properties. This parameter change allows the material to be in a protective state during vulnerable processing steps
3Loss of substance
If MIM process is used for complex geometries, then material efficiency is improved, but hard magnetic properties deteriorate due to oxide and carbide formation
Solution Approach 1:
The rare earth metal oxide coating serves as a protective intermediary during the entire MIM process, particularly during debinding. This allows the MIM process to be used for complex geometries with high material efficiency while preventing the oxide and carbide formation that would otherwise deteriorate the hard magnetic properties
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the production of low-oxide and carbide-free permanent magnets with high energy product, allowing for efficient use of raw materials and cost-effective production of complex geometries without material waste.
Implementation Method 1
the rare earth element present in the starting material is converted into an inerted compound before a debinding step of the metal powder injection molding process
Implementation Method 2
it is not in its highly reactive form towards oxygen and carbon in the debinding step, but rather in a more inert form
Data Source
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AI summary
The invention relates to a method for producing a permanent magnet comprising a rare earth element, wherein a starting material is processed in a metal injection molding method and a rare earth metal present in the starting material is converted into an inertised compound prior to a binder removal step.