R-Fe-B Sintered Magnet Powder with R-Al-Cu Oxide Control
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Solution Overview
Problem
Existing methods for producing NdFeB-based magnets face challenges such as long pulverization processes, irregular particle shapes, and the formation of oxide films during the reduction-diffusion process, which deteriorate the magnetic properties of sintered magnets.
Innovation Solution
A method involving the production of R—Fe—B-based magnet powder using a reduction-diffusion process, with the addition of a R—Al—Cu powder as a sintering agent to form a mixed powder, which is then sintered to produce a sintered magnet, where R can be Nd, Pr, Dy, or Ce, and the process includes mixing, agglomerating, and heat-treating the precursor in an argon atmosphere to lower the melting temperature and prevent oxide film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a reduction-diffusion process is used to produce magnet powder, then uniform fine particles can be produced, but oxide films form on the particles making sintering difficult and deteriorating magnetic properties
Solution Approach 1:
The patent applies preliminary action by adding a sintering aid (CaB6 or CaAlSiN3) before the sintering process to prevent oxide film formation on the magnet powder particles. The sintering aid is mixed with the magnet powder in advance, and during sintering, it reacts with the oxide films to form a protective layer that prevents further oxidation and facilitates sintering. This preliminary preparation resolves the contradiction by addressing the oxide film issue before it deteriorates the magnetic properties.
Solution Approach 2:
The patent uses a sintering aid as an intermediary substance that mediates between the magnet powder and the oxidation environment. The sintering aid (CaB6 or CaAlSiN3) acts as a protective intermediary that reacts with oxygen to form a barrier layer, preventing direct oxidation of the magnet powder particles. This intermediary approach allows the uniform fine particles produced by reduction-diffusion to be sintered successfully without oxide film deterioration.
2Productivity
If traditional strip/mold casting or melt spinning methods are used, then magnets can be produced, but long pulverization processes are required and particle shapes become irregular
Solution Approach 1:
The patent applies parameter changes by modifying the production method from traditional melt-based processes to a reduction-diffusion process. This fundamental parameter change in the manufacturing approach produces magnet powder with uniform, regular particle shapes directly, eliminating the need for lengthy pulverization processes. The reduction-diffusion method controls the formation of Nd2Fe14B phase particles to achieve both productivity and shape regularity simultaneously.
3Reliability
If high temperature sintering is performed to sinter magnet powder, then dense sintered magnets can be obtained, but oxide films form and magnetic properties deteriorate
Solution Approach 1:
The patent uses a sintering aid as an intermediary substance that mediates between the magnet powder and the oxidation environment. The sintering aid (CaB6 or CaAlSiN3) acts as a protective intermediary that reacts with oxygen to form a barrier layer, preventing direct oxidation of the magnet powder particles. This intermediary approach allows the uniform fine particles produced by reduction-diffusion to be sintered successfully without oxide film deterioration.
Solution Approach 2:
The patent converts the harmful effect of high temperature (which causes oxidation) into a beneficial effect by using the sintering aid to react with oxygen at high temperature. The sintering aid preferentially reacts with oxygen to form a protective layer, converting the harmful oxidation into a beneficial protective mechanism. This allows high temperature sintering to achieve dense sintered magnets while preventing oxide film formation through the controlled reaction of the sintering aid.
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 improves the magnetic properties of sintered magnets by preventing oxide film formation and reducing the melting temperature, resulting in enhanced coercive force and magnetic flux density, while also reducing production costs and simplifying the process.
Implementation Method 1
sintering the mixed powder to form a sintered magnet
Implementation Method 2
the obtained lump is subjected to coarse pulverization
Implementation Method 3
producing an R—Fe—B-based magnet powder by a reduction-diffusion method
Implementation Method 4
reduction-diffusion process in which Nd2O3, Fe, and B are mixed and reduced
Implementation Method 5
an oxide film may be formed in the process of removing a reducing agent
Data Source
AI summary
A sintered magnet and a method for producing the same are provided. The method includes producing an R—Fe—B-based magnet powder by a reduction-diffusion method, adding a R—Al—Cu powder as a sintering agent to the R—Fe—B-based magnet powder to form a mixed powder, wherein the R—Al—Cu powder is an alloy of R, Al and Cu, and R is Nd, Pr, Dy, Tb or Ce, and sintering the mixed powder to form a sintered magnet.