Samarium-Iron-Nitrogen Magnet Sintering With Zinc Coating
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Solution Overview
Problem
Conventional methods for producing samarium-iron-nitrogen-based rare earth magnets face challenges in achieving high-density sintered bodies and sufficient residual magnetization due to nitrogen dissociation and insufficient density during pressure sintering, even when using zinc-containing powders.
Innovation Solution
A production method involving forming a zinc-containing coating on the particle surface of samarium-iron-nitrogen-based magnetic powder, mixing with a binder powder having a lower melting point, and pressure-sintering at specific temperatures to promote powder flow and increase density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If pressure sintering is performed on samarium-iron-nitrogen-based magnetic powder without zinc-containing powder, then sintering temperature can be raised, but nitrogen dissociates and sintering cannot be performed
Solution Approach 1:
Metallic zinc powder acts as an intermediary substance that enables sintering at lower temperatures. The zinc powder forms a eutectic mixture with the magnetic powder, allowing liquid-phase sintering to occur at temperatures below the nitrogen dissociation point, thus mediating between the conflicting requirements of high temperature sintering and nitrogen retention
Solution Approach 2:
The addition of zinc powder changes the thermal parameters of the sintering process. By introducing a material with lower melting point and forming eutectic compositions, the sintering temperature parameter is shifted to a range where nitrogen remains stable in the magnetic powder while still enabling effective sintering
2Temperature
If metallic zinc powder is added as binder, then sintering can be performed at lower temperature, but the process complexity increases
Solution Approach 1:
The metallic zinc powder serves multiple functions simultaneously: it acts as a binder to hold particles together, as a flux to lower the sintering temperature, and as a modifying agent to improve the properties of the sintered body. This multi-functionality reduces the need for separate additives and simplifies the overall formulation
Solution Approach 2:
The binder and temperature-lowering functions are merged into a single material (metallic zinc powder) rather than using separate substances. This consolidation reduces the number of components and simplifies the production process while achieving the desired low-temperature sintering
3Productivity
If sintering temperature is increased to improve density, then manufacturing efficiency improves, but nitrogen dissociation occurs and coercive force decreases
Solution Approach 1:
The sintering temperature parameter is changed from high temperature (which would dissociate nitrogen) to a lower temperature range enabled by the zinc powder. This parameter change allows efficient sintering to proceed while maintaining the nitrogen content and thus the coercive force of the magnetic powder
4Ease of manufacture
If oxygen and αFe phase are present in magnetic powder, then manufacturing is easier, but coercive force is reduced
Solution Approach 1:
The metallic zinc powder acts as a modifying intermediary that reacts with oxygen and αFe phase during sintering. It forms zinc oxides and modifies the iron phase, thereby removing the harmful elements that reduce coercive force while allowing the magnetic powder to be produced through conventional easier methods
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 enhances the density of the sintered body and improves residual magnetization by reducing friction and promoting particle flow during pressure sintering.
Implementation Method 1
a zinc component in the metallic zinc powder undergoes solid-phase or liquid-phase diffusion on the particle surface of the samarium-iron-nitrogen-based magnetic powder
Implementation Method 2
mixing with a binder powder having a lower melting point, and pressure-sintering at specific temperatures to promote powder flow and increase density
Data Source
AI summary
The production method of a rare earth magnet of the present disclosure includes a coated magnetic powder preparation step, a mixed powder preparation step, and a pressure sintering step. In the coated magnetic preparation step, a zinc-containing coating 12 is formed on the particle surface of a samarium-iron-nitrogen-based magnetic powder to obtain a coated magnetic powder 14. In the mixed powder preparation step, a binder powder 20 having a melting point not higher than the melting point of the coating 12 and the coated magnetic powder 14 are mixed to obtain a mixed powder. In the pressure sintering step, denoting as T1° C. the temperature at which the peak disappears in an X-ray diffraction pattern of the binder powder 20 and as T2° C. the temperature at which the magnetic phase in the samarium-iron-nitrogen-based magnetic powder 10 decomposes, the mixed powder is pressure-sintered at T1° C. or more and (T2−50° C.) or less.