Cooling Roll Segmentation for Rare-Earth Magnet Alloy Flakes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing alloy flakes for rare earth sintered magnets fail to achieve uniform intervals, size, and orientation of the R-rich region and dendrites of the 2-14-1 phase, leading to the formation of chill crystals and limitations in crystal grain size, which affect the magnetic properties of the final product.
Innovation Solution
A method involving a cooling roll with linear nucleation inhibiting and nucleating portions, where the nucleation inhibiting portions have a width of more than 100 μm, controls the formation of dendrites and chill crystals, resulting in alloy flakes with a dendrite content of not lower than 80 vol % and a chill crystal content of not higher than 1 vol %, with uniform crystal grain sizes and intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional rapid solidification methods are used to produce alloy flakes, then the production process is simple, but the intervals, size, and orientation of the R-rich region and dendrites are non-uniform, and chill crystals form
Solution Approach 1:
The cooling roll surface is segmented into distinct functional zones: nucleation inhibiting portions (with width >100 μm) that prevent unwanted crystal formation, and nucleating portions that promote controlled dendrite formation. This segmentation allows different regions of the roll to perform different functions, achieving uniform alloy flake structure through localized control of solidification processes.
Solution Approach 2:
Different surface regions of the cooling roll are given different properties: the nucleation inhibiting portions have specific width dimensions (>100 μm) and surface characteristics that inhibit nucleation, while the nucleating portions have properties that promote nucleation. This local differentiation of properties enables precise control over where and how dendrites form in the alloy flakes.
2Manufacturing precision
If the primary cooling rate is increased to reduce intervals between R-rich regions, then the intervals are reduced, but the crystal grain size is also reduced and chill crystals form
Solution Approach 1:
The cooling roll surface is pre-configured with nucleation inhibiting portions and nucleating portions before the alloy melt contacts it. The nucleation inhibiting portions (width >100 μm) are positioned to prevent nucleation in specific zones, while nucleating portions are positioned to promote nucleation in controlled locations. This preliminary arrangement ensures that when solidification occurs, dendrites form only in desired locations with controlled spacing and size, preventing chill crystal formation even at high cooling rates.
3Reliability
If the dendrite content is increased to not lower than 80 vol % to improve magnetic properties, then the magnetic remanence improves, but it becomes difficult to control crystal grain size and prevent chill crystals
Solution Approach 1:
The cooling roll acts as an intermediary tool that mediates between the alloy melt and the desired microstructure. Its surface with nucleation inhibiting portions (width >100 μm) and nucleating portions serves as a controlled interface that directs where dendrites form and how they grow. This intermediary structure enables the production of alloy flakes with ≥80 vol % dendrite content while maintaining controlled crystal grain sizes and preventing chill crystal formation, thereby achieving both high magnetic remanence and manufacturing precision.
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 alloy flakes that can be easily pulverized into uniform powder, allowing for compacted products with controlled shrink ratios and achieving excellent magnetic properties in the resulting rare earth sintered magnets.
Implementation Method 1
supplying and solidifying the alloy melt prepared in step (A) on a cooling roll, wherein the cooling roll has on a roll surface a plurality of linear nucleation inhibiting portions for inhibiting formation of dendrites of a R2Fe14B phase and chill crystals, and a plurality of nucleating portions for formation of the dendrites
Implementation Method 2
solidifying the alloy melt prepared in step (A) on a cooling roll
Implementation Method 3
nucleation inhibiting portions for inhibiting formation of dendrites of a R2Fe14B phase and chill crystals
Data Source
AI summary
The invention provides a method for producing alloy flakes for rare earth sintered magnets, which makes uniform the intervals, size, orientation, and shape of the R-rich region and the dendrites of the 2-14-1 phase, which inhibits formation of chill, and which produces flakes that are pulverized into powder of a uniform particle size in the pulverization step in the production of a rare earth sintered magnet, and that are pulverized into powder compactable into a product with a controlled shrink ratio, and alloy flakes for a rare earth sintered magnet obtained by the method, and a rare earth sintered magnet having excellent magnetic properties. The present method includes preparing an alloy melt of a composition consisting of R of rare earth metal elements and the balance M including B and Fe, and supplying and solidifying the alloy melt on a cooling roll, wherein the roll has on its surface linear nucleation inhibiting portions for inhibiting formation of dendrites or the like, and nucleating portions for formation of the dendrites, and wherein the inhibiting portions have a region with a width of more than 100 μm.