R-T-B Permanent Magnet with Zr and Concentration Gradient
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Solution Overview
Problem
Existing R-T-B based permanent magnets face challenges in maintaining excellent magnetic properties and corrosion resistance, especially when the Co content is low, as they tend to experience decreased coercive force and corrosion resistance.
Innovation Solution
The R-T-B based permanent magnet incorporates specific elements within defined content ranges, including Zr, Cu, Mn, Al, and Ga, with a concentration gradient of heavy rare earth elements decreasing from the surface to the inside, and a core-shell structure to enhance magnetic properties and corrosion resistance, even with low Co content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Co content is reduced to lower cost, then manufacturing cost decreases, but coercive force and corrosion resistance deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of multiple elements (R: 30.00-32.20 mass%, Co: 0.30-1.30 mass%, Zr: 0.21-0.85 mass%, B: 0.90-1.02 mass%) to achieve optimal magnetic properties and corrosion resistance with low Co content. This systematic parameter optimization resolves the contradiction between cost reduction and performance maintenance.
Solution Approach 2:
The patent creates a composite material system combining rare earth elements (Nd, Pr, Dy, Tb), Fe, Co, Zr, and B in specific proportions. This composite approach allows the material to achieve enhanced coercive force and corrosion resistance through synergistic effects, compensating for the reduced Co content and resolving the technical contradiction.
2Reliability
If heavy rare earth element content is increased to improve coercive force, then magnetic properties improve, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the total content of heavy rare earth elements (Dy and Tb) within the constrained range of 30.00-32.20 mass% combined with light rare earth elements, achieving high coercive force while controlling material cost. This parameter optimization balances performance requirements with economic considerations.
Solution Approach 2:
The patent implements a concentration gradient structure where heavy rare earth elements are distributed non-uniformly, with higher concentration at the surface and lower concentration toward the interior. This local quality approach maximizes the surface magnetic properties and corrosion resistance while minimizing the overall amount of expensive heavy rare earth elements required, resolving the contradiction between coercive force and cost.
Data Source
AI summary
The present invention provides an R-T-B based permanent magnet having excellent magnetic properties and corrosion resistance even when Co content is small.The R-T-B based permanent magnet in which R is a rare earth element including one or more selected from Nd and Pr and one or more selected from Dy and Tb, T is a combination of Fe and Co, and B is boron. The R-T-B based permanent magnet further includes Zr. A total content of Nd, Pr, Dy, and Tb is 30.00 mass % to 32.20 mass %, Co content is 0.30 mass % to 1.30 mass %, Zr content is 0.21 mass % to 0.85 mass %, and B content is 0.90 mass % to 1.02 mass % with respect to 100 mass % of the R-T-B based permanent magnet.