Rare Earth Magnet Sintering With Dual-Size SmFeN and Zinc Binder
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Solution Overview
Problem
The production methods for Sm—Fe—N-based rare earth magnets often result in reduced magnetization due to the decomposition of SmFeN powder during sintering, and the use of modifiers like metallic zinc helps but does not consistently achieve high magnetization levels.
Innovation Solution
A production method involving a specific particle size distribution and volume ratio of SmFeN powder with a modifier powder, compression-molding in a magnetic field, and pressure-sintering at controlled temperatures and pressures, along with a modification-inhibiting coating and heat treatment, to enhance magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If pressureless sintering is used to avoid decomposition of SmFeN powder, then the sintering temperature can be reduced, but the sintering time must be extended to 6 hours or more to achieve high density
Solution Approach 1:
The invention changes the sintering parameters by applying pressure during sintering (pressure sintering) while controlling the temperature range. This allows achieving high density in shorter time (0.1-5 hours) compared to pressureless sintering (6+ hours), while avoiding SmFeN powder decomposition by maintaining temperature below 900°C
Solution Approach 2:
The invention uses a composite powder mixture containing SmFeN magnetic powder and metallic zinc powder. The metallic zinc acts as a binder that facilitates sintering at lower temperatures and shorter times, enabling high density achievement without decomposing the SmFeN powder
2Loss of time
If pressure sintering is applied to reduce sintering time, then high density can be achieved in 0.1 to 5 hours, but the SmFeN powder may decompose due to heat
Solution Approach 1:
The invention optimizes the sintering temperature parameter to range from 600°C to 800°C (or up to 900°C) during pressure sintering. This temperature control prevents SmFeN powder decomposition while still enabling high density achievement in 0.1-5 hours through applied pressure
Solution Approach 2:
Metallic zinc powder serves as an intermediary binder that facilitates sintering at lower temperatures. The zinc component diffuses to the magnetic powder surface during sintering, enabling bonding without requiring high temperatures that would decompose the SmFeN powder
3Loss of time
If metallic zinc powder is added as a binder to enable low temperature sintering, then sintering time is reduced, but the magnetization is reduced by the amount of zinc content
Solution Approach 1:
The invention optimizes the metallic zinc powder content to be 1-30 mass% relative to the SmFeN powder. This parameter optimization balances the competing requirements: enough zinc to act as an effective binder for low-temperature sintering, but limited enough to minimize magnetization reduction
4Volume of stationary object
If high temperature sintering (900°C or more) is used for pressureless sintering to achieve high density, then sintering time can be extended, but the SmFeN powder decomposes
Solution Approach 1:
Metallic zinc powder acts as an intermediary binder that enables density achievement without high temperatures. The zinc diffuses to SmFeN powder surfaces during sintering, creating strong bonds that achieve high density while keeping the temperature below the decomposition point of SmFeN powder
Solution Approach 2:
The invention changes the sintering temperature parameter from conventional high temperatures (900°C or more) to a lower range (600-800°C, up to 900°C) when using pressure sintering with metallic zinc binder, thereby preventing SmFeN powder decomposition while still achieving high density
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
This method increases the density and magnetization of the rare earth magnet by optimizing the particle distribution and sintering conditions, leading to improved magnetic properties.
Implementation Method 1
compression-molding the mixed powder in a magnetic field to obtain a magnetic-field molded body
Implementation Method 2
pressure-sintering the magnetic-field molded body to obtain a sintered body
Implementation Method 3
the zinc component in the metallic zinc powder diffuses to the magnetic powder surface during sintering
Implementation Method 4
absorbs oxygen in the SmFeN powder to enhance the coercive force
Implementation Method 5
heat treatment, to enhance magnetization
Data Source
AI summary
The present invention is a method for producing a rare earth magnet, including preparing a magnetic powder and a modifier powder, mixing them to obtain a mixed powder, compression-molding the mixed powder in a magnetic field to obtain a magnetic-field molded body, and pressure-sintering the magnetic-field molded body to obtain a sintered body, wherein the magnetic powder includes a first particle group and a second particle group, the D50 values of the first particle group and the second particle group are denoted by d1 μm and d2 μm, respectively, d1 and d2 satisfy the relationship of 0.350≤d2/d1≤0.500, and the ratio between the total volume of the first particle group and the total volume of the second particle group is from 9:1 to 4:1; and a rare earth magnet obtained by the production method.