NdFeB Magnet Production Without Dehydrogenation Heating
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Solution Overview
Problem
In the grain boundary diffusion method for producing NdFeB system sintered magnets, the carbon-rich phase formed from organic lubricants impedes the diffusion of rare-earth elements, leading to reduced coercive force and maximum energy product.
Innovation Solution
A method that omits dehydrogenation heating and evacuation, allowing hydrogen to remain in the alloy powder, which reduces carbon content and enables deeper diffusion of rare-earth elements through the rare-earth rich phase in the grain boundaries, using a press-less production method in an oxygen-free atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dehydrogenation heating and evacuation are performed to remove hydrogen from alloy powder, then oxidation resistance improves, but carbon content increases due to organic lubricant decomposition, which impedes rare-earth element diffusion and reduces coercive force
Solution Approach 1:
The patent performs pulverization and mixing of alloy powder with organic lubricant before sintering, but omits the dehydrogenation heating step that would decompose the lubricant into carbon. By preparing the powder mixture in advance and proceeding directly to sintering in an oxygen-free atmosphere, the lubricant serves its lubricating function without decomposing into harmful carbon deposits that would block grain boundary diffusion paths.
Solution Approach 2:
The patent conducts sintering in an oxygen-free atmosphere (vacuum or inert gas) without performing dehydrogenation heating. This inert environment prevents oxidation of the hydrogen-containing alloy powder while avoiding the thermal decomposition of organic lubricants that would otherwise occur at high temperatures in the presence of oxygen, thereby eliminating carbon-rich phase formation.
2Quantity of substance
If dehydrogenation heating is performed to desorb hydrogen, then hydrogen content decreases, but production time increases and production cost increases
Solution Approach 1:
The patent extracts (omits) the dehydrogenation heating step from the conventional production process. By removing this unnecessary intermediate step and proceeding directly from powder preparation to sintering in an oxygen-free atmosphere, the production time is significantly reduced while maintaining control over hydrogen content through the oxygen-free environment that prevents both oxidation and uncontrolled hydrogen loss.
Solution Approach 2:
The patent maintains continuous production flow by eliminating the dehydrogenation heating step. The alloy powder is prepared with organic lubricant and sintered continuously in an oxygen-free atmosphere, avoiding interruptions for hydrogen desorption. This continuous process reduces production time and increases productivity while the oxygen-free environment ensures proper hydrogen management throughout the process.
3Ease of manufacture
If organic lubricant is added to alloy powder for pulverization, then pulverization efficiency improves, but carbon-rich phase forms in grain boundaries that blocks rare-earth element diffusion
Solution Approach 1:
The patent performs sintering in an oxygen-free atmosphere without dehydrogenation heating, which prevents the thermal decomposition of organic lubricants into carbon. The oxygen-free environment ensures that the organic lubricant remains stable and does not form carbon-rich phases that would block grain boundaries, while still allowing the lubricant to serve its intended function during pulverization and mixing.
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 approach results in NdFeB system sintered magnets with higher coercive force and reduced carbon content, simplifying the production process, shortening production time, and reducing costs while maintaining high magnetic properties.
Implementation Method 1
coarse powder of a NdFeB system alloy is prepared by coarsely pulverizing a lump of NdFeB system alloy by making this lump occlude hydrogen
Implementation Method 2
heating the base material to diffuse RH from the surface of the base material into inner regions through the grain boundaries inside the base material
Data Source
AI summary
A method for producing a NdFeB system sintered magnet. The method includes: a hydrogen pulverization process, in which coarse powder of a NdFeB system alloy is prepared by coarsely pulverizing a lump of NdFeB system alloy by making this lump occlude hydrogen; a fine pulverization process, in which fine powder is prepared by performing fine pulverization for further pulverizing the coarse powder; a filling process, in which the fine powder is put into a filling container; an orienting process, in which the fine powder in the filling container is oriented; and a sintering process, in which the fine powder after the orienting process is sintered as held in the filling container. The processes from hydrogen pulverization through orienting are performed with neither dehydrogenation heating nor evacuation each for desorbing hydrogen occluded in the hydrogen pulverization process. The processes from hydrogen pulverization through sintering are performed in an oxygen-free atmosphere.