R-T-B Sintered Magnet Pulverization With Humidified Inert Gas
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Solution Overview
Problem
Existing methods for producing sintered R-T-B based magnets with low oxygen content fail to achieve high performance due to reduced pulverization efficiency and deterioration of magnetic characteristics when using inert gases like nitrogen, especially when attempting to reduce powder particle size.
Innovation Solution
Pulverization of R-T-B based magnet alloy powder is performed using humidified inert gas to maintain an oxygen content between 1000 ppm and 3500 ppm, resulting in a fine-pulverized powder with a size range of 2.0 μm to 4.5 μm, which suppresses nitriding and oxidation, allowing for improved magnetic characteristics and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If highly pure nitrogen gas is used to prevent oxidation during pulverization, then oxygen content decreases, but pulverization efficiency deteriorates and magnetic characteristics worsen
Solution Approach 1:
The patent changes the parameters of the inert gas by introducing controlled amounts of water vapor (humidification) and allowing specific oxygen content (1000-3500 ppm) rather than using highly pure dry nitrogen. This parameter modification resolves the contradiction by maintaining pulverization efficiency while achieving the required low oxygen content in the final product through controlled gas composition during the pulverization process
Solution Approach 2:
The patent uses humidified inert gas (nitrogen or argon) with controlled oxygen content (1000-3500 ppm) to create an optimized inert atmosphere during pulverization. This modified inert environment prevents excessive oxidation while avoiding the negative effects of completely dry highly pure nitrogen, thereby maintaining both pulverization efficiency and magnetic characteristics
2Manufacturing precision
If powder particle size is reduced to improve performance, then magnetic characteristics improve, but pulverization efficiency decreases
Solution Approach 1:
The patent modifies the gas parameters (humidification and oxygen content control) to enable efficient pulverization that produces particles within the optimal size range (2.0-4.5 μm average diameter). The controlled humidified inert gas environment allows achieving fine particle size distribution without sacrificing pulverization efficiency, resolving the contradiction between particle size reduction and productivity
3Object-affected harmful factors
If inert gas is used during pulverization, then oxidation is suppressed, but nitriding occurs and magnetic characteristics deteriorate
Solution Approach 1:
The patent changes the inert gas parameters by introducing controlled water vapor (humidification to -40°C to 0°C dew point) and maintaining specific oxygen content (1000-3500 ppm). This modification suppresses nitriding by creating a more reactive gas environment that prevents nitrogen incorporation, while still preventing excessive oxidation through the inert atmosphere, thereby eliminating the harmful effect of nitriding
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 produces sintered R-T-B based magnets with enhanced magnetic properties and increased pulverization efficiency by controlling oxygen, carbon, and nitrogen content within specific ranges, ensuring high compressibility and reduced die wear.
Implementation Method 1
use of a low oxygen content may inhibit achievement of the intended high level of performance... The inert gas is in a humidified state... the sintered R-T-B based magnet contains oxygen at a content not lower than 1000 ppm by mass and not higher than 3500 ppm by mass
Implementation Method 2
use of inert gas such as the highly pure nitrogen gas or the like... use of a low oxygen content may inhibit achievement of the intended high level of performance... suppresses nitriding and oxidation
Implementation Method 3
pulverizing the coarse-pulverized powder to obtain a fine-pulverized powder... by use of a jet mill
Implementation Method 4
The alloy powder obtained by such a pulverization step is subjected to solid-gas separation performed by, for example, a cyclone collection device
Implementation Method 5
a step of sintering the powder compact... forming a sintered body of the fine-pulverized powder
Data Source
AI summary
A method for manufacturing an R-T-B based sintered magnet according the present disclosure comprises: a step for preparing a coarse ground powder which is made from an alloy for R-T-B based sintered magnets and which has an average particle size of 10-500 μm; a step for obtaining a fine powder having an average particle size of 2.0-4.5 μm, by feeding the coarse ground powder to a jet mill device that has a grinding chamber filled with inert gas and grinding the coarse ground powder; and a step for producing a sintered body of the fine powder, wherein the inert gas has been humidified, and the oxygen content of the R-T-B based sintered magnet is 1000-3500 ppm by mass.