RH Diffusion Source for Sintered R-T-B Magnet Coercivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for increasing the coercivity of sintered R-T-B based magnets with heavy rare-earth elements result in low diffusion rates and adhesion issues at high temperatures, and excessive use of heavy rare-earth elements leads to decreased remanence.
Innovation Solution
A diffusion source alloy comprising 0.2-18% light rare-earth elements (Nd or Pr), 40-70% Fe, and a balance of heavy rare-earth elements (Dy or Tb) is used, allowing for efficient diffusion of heavy rare-earth elements within a wide temperature range of 700-1000°C without adhesion, maintaining high remanence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare-earth element RH is added to increase coercivity, then coercivity (HcJ) increases, but remanence (Br) decreases
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of heavy rare-earth elements through diffusion from the surface inward. The surface region has higher RH concentration for enhanced coercivity, while the interior maintains lower RH concentration to preserve remanence. This spatial variation in composition resolves the contradiction between improving coercivity and maintaining remanence.
Solution Approach 2:
The patent changes the concentration parameter of heavy rare-earth elements from uniform distribution to gradient distribution. By controlling diffusion temperature (500-850°C) and time, the RH concentration varies spatially, with higher concentration at the surface and lower concentration in the interior, thereby achieving both high coercivity and maintained remanence.
2Productivity
If diffusion temperature is increased to improve diffusion rate, then diffusion efficiency increases, but adhesion between magnet body and diffusion source occurs
Solution Approach 1:
The patent optimizes the diffusion temperature parameter to a specific range (500-850°C) that achieves sufficient diffusion rate while preventing adhesion. This temperature control resolves the contradiction between improving productivity through faster diffusion and avoiding harmful adhesion effects.
3Strength
If heavy rare-earth element RH is added in large amounts to achieve high coercivity at high temperature, then coercivity (HcJ) increases, but resource consumption increases
Solution Approach 1:
The patent applies local quality by concentrating heavy rare-earth elements only where needed (at the surface region) rather than uniformly throughout the entire magnet body. This localized enrichment achieves the required coercivity while minimizing overall RH consumption, addressing the contradiction between high coercivity performance and resource conservation.
Solution Approach 2:
The patent uses partial action by applying heavy rare-earth element diffusion only to the surface region rather than the entire volume. This partial treatment achieves sufficient coercivity enhancement while using minimal amounts of heavy rare-earth elements, resolving the contradiction between performance and resource consumption.
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 significantly increases coercivity (HcJ) of sintered R-T-B based magnets while maintaining high remanence (Br) and preventing adhesion during the diffusion process.
Implementation Method 1
the heavy rare-earth element RH can be supplied from the RH diffusion source and then diffused inward through the grain boundary
Implementation Method 2
heating the sintered R-T-B based magnet body and the RH diffusion source to a temperature of 500° C. to 850° C. for 10 minutes or more
Data Source
AI summary
A method for producing a sintered R-T-B based magnet includes providing a sintered R-T-B based magnet body, where T is mostly Fe; providing an RH diffusion source that includes 0.2 mass % to 18 mass % of a light rare-earth element RL; 40 mass % to 70 mass % of Fe; and a heavy rare-earth element RH as the balance; and performing an RH diffusion process by loading the sintered R-T-B based magnet body, a stirring aid member, and the RH diffusion source into a chamber, and by heating the sintered R-T-B based magnet body, the stirring aid member, and the RH diffusion source to a temperature of 700° C. to 1000° C. while rotating or rocking the chamber. The Fe/RH ratio is within a range from two to seven and is defined by a mass fraction of Fe when a mass fraction of the heavy rare-earth element RH in the RH diffusion sources is three.