R-T-B Rare Earth Sintered Magnet Composition
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Solution Overview
Problem
Nd-Fe-B magnets suffer from reduced coercive force when nickel is substituted for iron to improve corrosion resistance, and existing solutions fail to maintain magnetic properties while enhancing corrosion resistance.
Innovation Solution
The addition of silicon (Si) and copper (Cu) along with nickel in the composition of rare earth sintered magnets, specifically in the R-T-B system, improves corrosion resistance without sacrificing coercive force, with optimal weight percentages of 0.1-2% Ni, 0.1-3% Si, and 0.05-1% Cu, and a primary phase of R2-T14-B1 with an average grain size of 3.0 to 10.0 µm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel is substituted for iron to improve corrosion resistance, then corrosion resistance is improved, but coercive force is reduced
Solution Approach 1:
The patent changes the compositional parameters by adding specific amounts of silicon (0.1-3.0 wt%) and copper (0.05-1.0 wt%) alongside nickel to modify the magnetic properties and corrosion resistance balance in the R-T-B magnet system
Solution Approach 2:
The patent creates a composite alloy system combining rare earth elements (R), transition metals (T including Fe and Co), boron (B), nickel (Ni), silicon (Si), copper (Cu), and optional minor elements (M) to achieve both improved corrosion resistance and maintained coercive force through synergistic interactions between components
2Reliability
If multiple substitution of Co and Ni for Fe is used to improve corrosion resistance, then corrosion resistance is improved, but magnet suffers substantial loss of coercive force
Solution Approach 1:
The patent optimizes the substitution parameters by limiting Ni to 0.1-2.0 wt% and adding Si (0.1-3.0 wt%) and Cu (0.05-1.0 wt%) to compensate for coercive force loss while maintaining corrosion resistance improvements
Solution Approach 2:
The patent develops a multi-element composite system where the combination of R (26-36 wt%), T (balance), B (0.5-1.5 wt%), Ni (0.1-2.0 wt%), Si (0.1-3.0 wt%), Cu (0.05-1.0 wt%), and M (0.05-4.0 wt%) creates synergistic effects that preserve magnetic properties while enhancing corrosion resistance
Data Source
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AI summary
A rare earth sintered magnet consists essentially of 26-36 wt% R, 0.5-1.5 wt% B, 0.1-2.0 wt% Ni, 0.1-3.0 wt% Si, 0.05-1.0 wt% Cu, 0.05-4.0 wt% M, and the balance of T and incidental impurities wherein R is a rare earth element, T is Fe or Fe and Co, M is selected from Ga, Zr, Nb, Hf, Ta, W, Mo, Al, V, Cr, Ti, Ag, Mn, Ge, Sn, Bi, Pb, and Zn. Simultaneous addition of Ni, Si, and Cu ensures magnetic properties and corrosion resistance.