Magnetic Lamination Layering to Reduce Sintering Stress
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Solution Overview
Problem
Existing two-component magnetic laminations produced by stencil printing face issues with mechanical stresses due to differing thermal expansion coefficients, leading to bulges or cracks, which impair mechanical and magnetic properties, particularly at high rotor speeds.
Innovation Solution
An additively manufactured magnetic lamination with symmetrical layering of material components, where a first material with an austenitic microstructure is radially inner and a second material with high iron content is radially outer, and a transition region with discrete subregions, to compensate for thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If two-component magnetic laminations are produced by stencil printing to achieve higher mechanical strength, then mechanical strength is improved, but different coefficients of thermal expansion cause high mechanical stresses, bulges, or cracks during sintering and cooling
Solution Approach 1:
The patent applies local quality by creating a symmetrical arrangement of material components around a center plane, with radially inner and outer regions having different material compositions. This local differentiation allows each region to accommodate thermal expansion differently while maintaining overall structural integrity, preventing the mechanical stresses and defects that would occur with uniform material distribution.
Solution Approach 2:
The patent employs asymmetry in the radial distribution of materials within each layer, placing different material components in radially inner and outer regions. This asymmetric arrangement, combined with symmetry across the center plane, creates a balanced structure that compensates for differential thermal expansion between materials, resolving the contradiction between mechanical strength and reliability.
2Strength
If high-strength steel with coefficient of expansion 16×10−6 K−1 is used to increase mechanical strength, then mechanical strength is improved, but the difference in thermal expansion with soft-magnetic material (10-12×10−6 K−1) causes mechanical stresses in connecting regions
Solution Approach 1:
The patent addresses thermal expansion stress by creating local quality variations through symmetrical arrangement of different materials in radially inner and outer regions. This allows the high-strength steel and soft-magnetic materials to be positioned where their different expansion coefficients can be accommodated by the symmetrical structure, reducing mechanical stresses in connecting regions.
Solution Approach 2:
The symmetrical arrangement of material components acts as a counterbalancing mechanism for thermal expansion stresses. The equal distribution of materials on both sides of the center plane creates opposing forces that compensate for differential expansion, reducing net mechanical stress in the structure during temperature changes.
3Productivity
If stencil printing is used to produce two-component magnetic laminations, then productivity is improved, but the method cannot adequately address thermal expansion differences between materials
Solution Approach 1:
The patent enhances manufacturing precision by implementing a symmetrical arrangement of material components with specific radial positioning. This structured approach to material distribution allows stencil printing to efficiently produce complex multi-component laminations while maintaining precise control over material placement and thermal expansion management.
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 magnetic lamination achieves higher mechanical stability and reduced intrinsic stresses, minimizing bulging and maintaining magnetic properties, suitable for high-speed applications.
Implementation Method 1
different coefficients of thermal expansion. Thus, for example, a high-strength steel constituting a subcomponent for the mechanical strength of the magnetic lamination has a coefficient of expansion of 16×10−6 K−1. A further soft-magnetic material in this respect has a coefficient of thermal expansion of between 10-12×10−6 K−1
Implementation Method 2
the screen printing technique results in production of a green body, which after a further heat treatment firstly generally has the binder removed and then is fed to a sintering process at a higher temperature, the metallic powder grains being sintered to one another such that a structured lamination, the magnetic lamination, is produced
Data Source
AI summary
Various embodiments of the teachings herein include an additively produced magnetic lamination for a laminated core of an electric machine. An example includes at least three layers connected by sintering, wherein each layer contains at least two material components separate from one another in planar extent. The arrangement of the material components in their planar extent in a respective layer is symmetrical to a center plane of the magnetic lamination. A ratio of material contents of the first material component and of the second material component is modified over the layer sequence. The first material component is arranged in a radially inner region of the respective layer and the second material component is arranged in a radially outer region of a respective layer. The first material component comprises an iron alloy with an austenitic microstructure of at least 25% by volume.