NdFeB Magnet Powder Hydrogen Staging for Uniform Crushing
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Solution Overview
Problem
Conventional hydrogen treatment processes for preparing NdFeB magnetic powders result in uneven hydrogen absorption, leading to difficulties in grinding and low material utilization rates due to oxidation and nitridation of ultrafine powders.
Innovation Solution
A method involving controlled hydrogen absorption temperatures to separately crush the neodymium-rich and main phases during hydrogen treatment, followed by jet milling, which improves particle size distribution and grinding efficiency, and reduces material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen treatment is performed at conventional temperatures, then hydrogen absorption occurs, but uneven hydrogen absorption results leading to poor grinding performance and low material utilization
Solution Approach 1:
The hydrogen treatment process is divided into three distinct temperature stages: first stage at 400-480°C for initial hydrogen absorption, second stage at 200-400°C for continued absorption, and third stage at -50°C to 200°C for final absorption. This segmentation of the temperature profile ensures uniform hydrogen distribution throughout the alloy flakes, preventing the uneven absorption that plagues conventional single-temperature processes and thereby improving both hydrogen absorption uniformity and subsequent grinding efficiency.
Solution Approach 2:
The invention systematically varies the temperature parameter throughout the hydrogen treatment process, transitioning from high temperature (400-480°C) to medium temperature (200-400°C) to low temperature (-50°C to 200°C) stages. This parameter change strategy enables controlled hydrogen absorption at different rates and depths, achieving uniform hydrogen distribution that directly addresses the uneven absorption problem and improves manufacturing precision.
2Manufacturing precision
If hydrogen treatment is performed to crush the alloy, then particle size is reduced, but ultrafine powders are easily oxidized and nitrided leading to material waste
Solution Approach 1:
The invention performs preliminary protective actions by conducting the entire multi-stage hydrogen treatment process in a controlled atmosphere that prevents oxidation and nitridation. The gradual temperature reduction and controlled hydrogen exposure create a protective environment before the alloy is subjected to jet milling, ensuring that ultrafine powders generated during grinding do not oxidize or nitride, thereby preserving material and improving utilization rate.
Solution Approach 2:
The hydrogen treatment process is conducted in an inert or controlled atmosphere environment that protects the alloy from oxidation and nitridation. This inert environment protection throughout the multi-stage temperature process prevents harmful reactions with oxygen and nitrogen, especially during the particle size reduction stages, thereby reducing material loss and improving the utilization rate of the expensive NdFeB alloy.
3Reliability
If heavy rare earth elements are added to improve coercivity, then magnetic performance increases, but material cost increases significantly
Solution Approach 1:
The invention enables the NdFeB alloy to achieve improved coercivity through self-optimization via controlled hydrogen absorption at multiple temperature stages. The process induces selective phase transformations and microstructural changes that enhance magnetic performance without requiring external addition of expensive heavy rare earth elements. The alloy essentially serves itself to improve coercivity through the hydrogen treatment-induced microstructural evolution, eliminating the need for costly material substitutions.
Solution Approach 2:
The invention changes the physical and chemical parameters of the NdFeB alloy through controlled hydrogen absorption at varying temperatures, inducing phase transformations and microstructural modifications that enhance coercivity. By adjusting temperature and hydrogen pressure parameters during treatment, the process optimizes magnetic properties without adding heavy rare earth elements, thereby improving reliability while maintaining cost-effectiveness.
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
The method achieves a more uniform particle size distribution, enhances magnetic properties, and increases the yield of magnetic powder to at least 99.1%, while reducing material waste and processing costs.
Implementation Method 1
the neodymium-rich phase and the main phase are respectively crushed under control of the hydrogen absorption temperature during hydrogen treatment process
Implementation Method 2
after hydrogen is introduced at room temperature, the alloy flakes start to absorb hydrogen and occur exothermic reaction, and the temperature can reach about 200°C
Data Source
Figure 1
AI summary
The present invention refers to a method of preparing a NdFeB magnet powder. The method includes a hydrogen treatment process including the steps of: a) charging NdFeB alloy flakes into a hydrogen treatment furnace, wherein the NdFeB alloy flakes include a neodymium-rich phase and a main phase; b) performing a hydrogen absorption by heating the hydrogen treatment furnace in a first stage to a temperature at which only the neodymium-rich phase undergoes a hydrogen absorption reaction, then introducing and maintaining hydrogen at a predetermined pressure until the hydrogen absorption of the neodymium-rich phase is finished, then stop heating of the hydrogen treatment furnace in a second stage, where the temperature falls to a temperature at which the main phase undergoes a hydrogen absorption reaction; and c) when the hydrogen absorption of step b) is finished, performing a vacuum dehydrogenation of the obtained coarse magnet powder.