Ring Permanent Magnet Extrusion for Uniform Radial Magnetization
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Solution Overview
Problem
The production of ring-shaped permanent magnets with radial magnetization is challenging due to difficulties in achieving radial magnetization through traditional sintering, which results in waste and limitations on the size of the magnets, and existing methods like hot pressing lead to uneven shapes and significant material loss.
Innovation Solution
A method involving transverse extrusion of a magnetic material blank using cross punches to deform projections, aligning the magnetic moments radially, allowing for the production of rotationally symmetrical magnets with reduced waste and no need for additional shaping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sintering is used to produce ring-shaped permanent magnets, then the magnetic material can be formed into a solid body, but radial magnetization is difficult to achieve and significant material loss occurs due to cracking
Solution Approach 1:
The invention changes the fundamental forming parameter from sintering (heating below melting point with pressure) to hot extrusion (heating to near melting point with uniaxial pressure). This parameter change enables radial magnetization without cracking because the extrusion process creates a homogeneous microstructure without the differential shrinkage that causes cracking in sintered magnets.
Solution Approach 2:
The invention utilizes the phase transition of the magnetic material to a semi-fluid state at high temperature (near melting point) during hot extrusion. This allows the material to flow and be formed into the desired shape, then solidifies upon cooling, eliminating the cracking problem associated with sintering while enabling radial magnetization.
2Reliability
If hot pressing is used to form magnetic material at high temperature, then radial magnetization can be achieved, but the final shape is uneven and significant material loss occurs
Solution Approach 1:
The invention changes the forming mechanism from hot pressing (isotropic compression) to hot extrusion (directional uniaxial pressure). This creates uniform material flow and consistent density throughout the magnet body, eliminating the uneven shape and material loss associated with hot pressing while maintaining radial magnetization quality.
3Reliability
If radial magnetization is achieved through sintering with field displacement, then magnetic field lines run radially, but only small radial thickness and axial height can be produced
Solution Approach 1:
The invention changes the forming process from sintering to hot extrusion, which eliminates the limitation on radial thickness and axial height. The extrusion process can produce magnets of any size within the capabilities of the equipment, as it does not rely on the long-distance effect of external electromagnetic fields during forming.
4Stability of the object's composition
If sintered magnets are produced with different crystal axis shrinkage, then the material forms a solid body, but the magnets are under tension and prone to cracking
Solution Approach 1:
The invention uses the phase transition to a semi-fluid state during hot extrusion to achieve homogeneous material flow and uniform density. This eliminates the differential shrinkage that occurs during sintering, where different crystal axes shrink by different amounts, creating internal tensions and cracks. The extruded magnets have uniform microstructure and no internal stresses.
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 approach minimizes waste and allows for the production of magnets with consistent radial magnetization over the entire length, reducing material requirements and eliminating the need for post-processing shaping, thus enhancing efficiency and size flexibility.
Implementation Method 1
The forming process causes the magnetic material to flow, which is why the process is also known as extrusion. The pressure and flow align the crystal axes of the magnetic material, namely in such a way that the magnetic preferred direction is formed perpendicular to the flow direction.
Implementation Method 2
The magnetic material is consequently shaped so that it flows in the axial direction. This is possible by so-called forward extrusion or by backward extrusion.
Data Source
Figure 1~1a
Figure 2a~4
Figure 5A~5E
AI summary
The invention relates to a method and a press (50) for producing a rotationally symmetrical, in particular ring-shaped, permanent magnet (30) with radially preferred magnetization (38) by extrusion of a blank (2) made of magnetic material. It is provided that the extrusion is carried out transversely to the blank axis (27) by transverse dies (6) deforming projections (21) of the blank (2) such that the volume of material forming the projections (21) flows in the circumferential direction. The invention further relates to a blank (2) for use in the method.