Rare-Earth Cobalt Magnet Composition for High-Temperature Squareness
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Solution Overview
Problem
Existing rare-earth cobalt permanent magnets do not achieve superior magnetic characteristics, particularly in terms of squareness ratio, and there is a need for improved resistance to degradation in high-temperature environments.
Innovation Solution
A rare-earth cobalt permanent magnet composition comprising 24 to 26% rare-earth element R, 25 to 27% Fe, 4.0 to 7.0% Cu, 2.0 to 3.5% Zr, and Co, with a cell phase of Th2Zn17 structure and cell wall of RCo5 structure, manufactured through specific heat treatment and aging processes to enhance magnetic coercive force and squareness ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rare-earth cobalt permanent magnet compositions are used, then the magnets exhibit basic magnetic properties, but the squareness ratio and magnetic coercive force are insufficient for high-performance applications
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of rare-earth elements (Sm, Nd, Pr), Fe, Cu, and Zr within specific ranges. The rare-earth element content is optimized at 24-26 mass%, Fe at 25-27 mass%, Cu at 4.0-7.0 mass%, and Zr at 2.0-3.5 mass%. This systematic parameter optimization resolves the contradiction by achieving high magnetic coercive force through controlled composition rather than trial-and-error manufacturing.
Solution Approach 2:
The patent employs composite materials by creating a dual-phase microstructure consisting of a Th2Zn17-type crystalline phase (60-80 mass%) and an RCo5-type crystalline phase (20-40 mass%). This composite structure at the microstructural level enables simultaneous achievement of high squareness ratio (≥63%) and magnetic coercive force, resolving the performance limitations of conventional single-phase magnets.
2Reliability
If the rare-earth element concentration is increased to improve magnetic properties, then the magnetic coercive force increases, but the manufacturing precision required to maintain optimal phase distribution increases
Solution Approach 1:
The patent applies local quality by creating distinct regions with different compositions and structures: a Th2Zn17-type crystalline phase region providing high squareness ratio (60-80 mass%) and an RCo5-type crystalline phase region providing magnetic coercivity (20-40 mass%). The rare-earth element concentration is specifically optimized at 24-26 mass% to ensure proper phase separation and distribution. This local differentiation resolves the contradiction by allowing each phase to contribute its optimal properties without requiring ultra-precise uniform composition control throughout the entire material.
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 described manufacturing method results in a rare-earth cobalt permanent magnet with a high squareness ratio of at least 63% and improved magnetic domain pinning, suitable for use in high-temperature environments.
Implementation Method 1
a step (IV) of sintering the molded body into a sintered body by heating the molded body at 1190 to 1225° C. for 0.5 to 3.0 hours
Implementation Method 2
a step (V) of solution heat treating the sintered body by heating the sintered body at 1120 to 1180° C. for 20 to 100 hours
Implementation Method 3
a step (VI) of rapidly cooling the sintered body to 600° C. or lower at a cooling rate of no less than 60° C./min at least from the solution heat treatment temperature
Implementation Method 4
a step (VII) of aging treating the rapidly cooled sintered body to form a cell phase that includes a crystalline phase of a Th2Zn17 structure and a cell wall that includes a crystalline phase of an RCo5 structure
Data Source
AI summary
A rare-earth cobalt permanent magnet according to the present disclosure comprises: 24 to 26 mass % of a rare-earth element R including Sm; 25 to 27 mass % of Fe; 4.0 to 7.0 mass % of Cu; 2.0 to 3.5 mass % of Zr; and Co and an unavoidable impurity as a remainder. The rare-earth element R is any one of a combination of Sm and Nd, a combination of Sm and Pr, or a combination of Sm, Nd, and Pr. The rare-earth cobalt permanent magnet includes a cell phase that includes a crystalline phase of a Th2Zn17 structure and a cell wall that includes a crystalline phase of an RCo5 structure enclosing the cell phase, and the concentration of the rare-earth element R in the cell wall is higher than the concentration of the rare-earth element R in the cell phase by no less than 25 atomic %.