Sm2Co17 Magnet Surface Composition for High-Temperature Demagnetization
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Solution Overview
Problem
Conventional Sm2Co17 type permanent magnets used in motors and power generators experience high-temperature demagnetization due to reduced Sm concentration at the surface, leading to performance degradation under high temperatures.
Innovation Solution
A permanent magnet design with a magnet main body and a surface portion having distinct compositions, where the surface portion has a higher concentration of rare-earth elements like Sm to suppress demagnetization, achieved by adjusting atomic ratios and using heat treatment to diffuse Sm, ensuring higher Sm concentration at the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional Sm2Co17 type magnet is applied to a motor and power generator, then high coercive force and high magnetic flux density are achieved, but demagnetization occurs in the surface portion under high temperatures
Solution Approach 1:
The patent applies local quality by creating a surface portion with higher Sm concentration specifically at the surface of the magnet, while the interior maintains the standard Sm2Co17 composition. This localized compositional difference suppresses demagnetization at the surface under high temperatures while preserving the high coercive force and magnetic flux density of the bulk material.
Solution Approach 2:
The patent employs preliminary action by performing heat treatment before final magnet assembly to diffuse Sm from the surface inward, establishing a protective high-Sm concentration gradient in advance. This pre-established compositional structure prevents demagnetization during subsequent high-temperature operation without requiring post-assembly modifications.
2Reliability
If the Sm concentration at the surface is increased to suppress demagnetization, then heat resistance is improved, but manufacturing complexity increases due to additional heat treatment and polishing steps
Solution Approach 1:
The patent performs the Sm diffusion heat treatment as a preliminary step before final magnet assembly and inspection. By establishing the high-Sm surface layer during manufacturing rather than requiring post-assembly surface modification, the process integrates the protective layer creation into the base manufacturing flow, reducing the need for separate polishing or coating operations.
Solution Approach 2:
The patent utilizes parameter changes by controlling the heat treatment temperature and duration to achieve optimal Sm diffusion depth and concentration gradient. By adjusting these thermal parameters, the desired surface Sm enrichment is achieved without excessive material removal or complex multi-step processing.
3Reliability
If excessive polishing is performed to remove the surface portion with low Sm concentration, then demagnetization is suppressed, but manufacturing costs increase and material is wasted
Solution Approach 1:
The patent performs Sm diffusion heat treatment as a preliminary action to enrich the surface with Sm before final magnet assembly. This creates a protective surface layer that inherently resists demagnetization, eliminating the need for excessive polishing to remove low-Sm surface material and thereby reducing both material waste and manufacturing costs.
Solution Approach 2:
The patent converts the naturally low-Sm surface layer (which would normally be harmful and require removal) into a beneficial feature by reversing the concentration gradient through heat treatment. The surface, initially deficient in Sm, becomes enriched through diffusion, transforming what would be discarded material into a protective demagnetization-resistant layer.
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 design effectively suppresses high-temperature demagnetization, maintaining magnetic properties and reducing manufacturing costs by avoiding excessive polishing, thus enhancing the performance of motors and power generators under high-temperature conditions.
Implementation Method 1
The surface portion has a composition expressed by a following composition formula 2... it effectively suppresses high-temperature demagnetization, maintaining magnetic properties
Implementation Method 2
achieved by adjusting atomic ratios and using heat treatment to diffuse Sm, ensuring higher Sm concentration at the surface
Data Source
AI summary
In one embodiment, a permanent magnet includes a magnet main body and a surface portion provided on a surface of the magnet main body. The magnet main body has a composition expressed by a composition formula 1: R(Fep1Mq1Cur1Co1-p1-q1-r1)z1. The surface portion has a composition expressed by a composition formula 2: R(Fep2Mq2Cur2Co1-p2-q2-r2)z2. In the composition formulas 1 and 2, R is at least one element selected from rare earth elements, M is at least one element selected from Ti, Zr and Hf, p1 and p2 are 0.25 to 0.45, q1 and q2 are 0.01 to 0.05, r1 and r2 are 0.01 to 0.1, z1 is 6 to 9, and z2 satisfies 0.8≦z2/z1≦0.995.