Rare-Earth Magnet Sintering with Carbon Reduction Sequencing
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Solution Overview
Problem
Current methods for manufacturing rare earth permanent magnets do not fully elucidate the factors contributing to high performance, leading to ongoing discussions and trials for enhancing magnetic performance.
Innovation Solution
A method involving a green compact of raw materials with specific elements, including rare earth elements, boron, and certain metals, undergoes a degreasing and carbon reduction process in a vacuum at controlled temperatures and humidity, followed by a sintering step to create a crystal structure with substituted boron atoms, enhancing magnetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional manufacturing methods are used without detailed process control, then manufacturing simplicity is maintained, but magnetic performance cannot be optimized
Solution Approach 1:
The patent applies preliminary action by performing carbon reduction and degreasing treatments before the main sintering process. The green compact undergoes carbon reduction at 100-300°C for 1-24 hours, followed by degreasing at 200-400°C for 1-4 hours, to remove carbon and organic binders in advance. This preliminary preparation ensures optimal magnetic performance by preventing carbon contamination during sintering, while keeping each individual step simple and controllable.
2Reliability
If carbon content is not reduced before degreasing, then manufacturing process is simpler, but magnetic performance deteriorates due to carbon contamination
Solution Approach 1:
The patent segments the heat treatment process into distinct stages: carbon reduction (100-300°C, 1-24 hours) followed by degreasing (200-400°C, 1-4 hours). This segmentation allows each process to be optimized independently - carbon reduction removes carbon contaminants at lower temperatures before organic binders are removed in the degreasing stage. The sequential segmentation prevents carbon re-contamination and ensures clean grain boundaries, improving magnetic performance while maintaining process simplicity through clear stage separation.
3Reliability
If degreasing is performed before carbon reduction, then process sequence is simpler, but carbon contaminates the magnet during degreasing
Solution Approach 1:
The patent applies preliminary anti-action by performing carbon reduction before degreasing to prevent carbon contamination. The carbon reduction step at 100-300°C removes carbon and hydrocarbon contaminants from the green compact surface and pores before the degreasing process begins. This preliminary protective action prevents carbon from entering the magnet during subsequent high-temperature degreasing, eliminating the need for complex carbon filtration systems and ensuring clean grain boundaries for optimal magnetic performance.
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 results in rare earth permanent magnets with improved residual magnetic flux density and coercive force, achieving high magnetic performance and energy efficiency.
Implementation Method 1
a carbon reduction step of reducing a carbon content in the green compact
Implementation Method 2
a degreasing step of retaining, in vacuum, the green compact
Implementation Method 3
a degassing step of retaining the green compact at a temperature of 100°C or lower for one hour or longer
Implementation Method 4
a drying step of retaining the green compact in an atmosphere of a dew point of -60°C or lower
Implementation Method 5
followed by a sintering step to create a crystal structure with substituted boron atoms
Data Source
Figure 1~1(b)
Figure 2~2(b)
Figure 3
AI summary
A rare earth permanent magnet includes a main phase containing: a rare earth element R of one or more types including Nd; an element L of one or more types selected from a group consisting of Co, Be, Li, Al, and Si; B; and Fe, wherein crystals which form the main phase belong to P42/mnm; some of B atoms occupying a 4f site of the crystals are substituted with atoms of the element L; each distribution of Nd atoms and the atoms of the element L appears along a C-axis direction of the crystals in a plurality of cycles; and the rare earth permanent magnet includes an area where a cycle of the atoms of the element L matches a cycle of the Nd atoms.