Alloy Flake Cooling Roll Surface Texture for Magnet Phase Control
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Solution Overview
Problem
Current methods for producing rare earth sintered magnets fail to suppress the generation of chill crystals and achieve uniform 2-14-1-based main phase shapes and R-rich phase dispersion, affecting the magnetic properties of the final product.
Innovation Solution
The production of raw material alloy flakes for rare earth sintered magnets involves strip casting with a cooling roll having a surface roughness of 2 to 15 µm and a specific surface texture, resulting in alloy flakes with controlled crystal growth, suppressing chill crystal formation and ensuring uniform phase dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional strip casting with smooth cooling roll surface is used, then production efficiency is high, but chill crystals are generated and phase dispersion is non-uniform
Solution Approach 1:
The cooling roll surface is designed with specific local characteristics including roughness Rz of 3-30μm and linear irregularities at 30-60° angle to the rotational direction. These localized surface features control nucleation and crystal growth in specific regions, achieving uniform phase dispersion and suppressing chill crystals while maintaining production efficiency.
Solution Approach 2:
The invention changes the surface parameters of the cooling roll, specifically setting roughness Rz to 3-30μm and creating linear irregularities at specific angles. These parameter changes transform the surface from a smooth state to one that actively controls solidification, resolving the contradiction between production efficiency and phase uniformity.
2Manufacturing precision
If rapid cooling is applied to suppress chill crystals, then crystal structure control improves, but production speed decreases
Solution Approach 1:
The linear irregularities on the cooling roll surface create periodic contact points between the molten alloy and the roll surface during rotation. This periodic action promotes uniform nucleation at regular intervals, controlling crystal structure while maintaining continuous production flow and high production speed.
3Manufacturing precision
If cooling roll surface roughness is increased to control crystal growth, then phase uniformity improves, but surface quality of alloy flakes deteriorates
Solution Approach 1:
The cooling roll surface features asymmetric linear irregularities at specific angles (30-60°) rather than symmetric patterns. This asymmetric design creates controlled nucleation sites that promote uniform phase distribution while the directional nature of the irregularities helps maintain relatively smooth alloy flake surfaces by guiding crystal growth in favorable directions.
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 produces rare earth sintered magnets with excellent magnetic properties and allows for industrial-scale production of alloy flakes with controlled crystal structures, enhancing coercivity and remanent magnetization.
Implementation Method 1
strip casting with a cooling roll having a surface roughness of 2 to 15 µm
Implementation Method 2
resulting in alloy flakes with controlled crystal growth, suppressing chill crystal formation
Data Source
Figure 1~2
Figure 3~4
AI summary
Provided are raw material alloy flakes for a rare earth sintered magnet and a method for producing the same, which flakes have undergone suppressed generation of chill crystals, and have quite uniform 2-14-1-based main phase shapes and R-rich phase dispersion. The alloy flakes of the present invention have a roll-cooled face, are obtained by strip casing with a cooling roll, and satisfy the following requirements (1) to (3): (1) the alloy flakes contain at least one R selected from rare earth metal elements including Y, B, and the balance M including iron, at a particular ratio; (2) the alloy flakes, as observed in a micrograph at a magnification of 100× of its roll-cooled face, have not less than 5 crystals each of which is a dendrite grown radially from a point of crystal nucleation, has particular aspect ratio and grain size, and crosses a line segment corresponding to 880 µm; (3) the alloy flakes, as observed in a micrograph at a magnification of 200x of its section taken generally perpendicularly to its roll-cooled face, have an average distance between R-rich phases of not less than 1 µm and less than 10 µm.