Multilayer Electrical Steel Sheet Si Gradient
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Solution Overview
Problem
Conventional gradient Si magnetic materials used in high-frequency applications have high hysteresis loss, and electrical steel sheets require excellent elongation for workability when processed into motor cores.
Innovation Solution
A multilayer electrical steel sheet with surface layers and an inner layer, where the surface layers have specific chemical compositions and a controlled Si content gradient, reducing magnetostriction differences and optimizing Si content and thickness ratios to achieve low high-frequency iron loss and high magnetic flux density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Si content is increased to reduce high-frequency iron loss, then specific resistance increases and eddy current loss decreases, but saturation magnetization decreases
Solution Approach 1:
The patent applies local quality by creating a Si concentration gradient where the surface layers have higher Si content (5-8 mass%) than the mid-thickness part (3.0-4.5 mass%). This allows the surface layers to provide high specific resistance for reduced eddy current loss, while the inner core maintains lower Si content for higher saturation magnetization, thus resolving the contradiction between reducing iron loss and maintaining magnetic flux density.
Solution Approach 2:
The steel sheet is segmented into three distinct regions: two surface layers with high Si content and a mid-thickness core layer with lower Si content. This segmentation allows each region to perform its specialized function - surface layers for electrical resistance and eddy current reduction, and the core for magnetic flux density - thereby resolving the contradiction between iron loss reduction and magnetization maintenance.
2Strength
If electrical steel sheets are stacked and interlocked for motor core processing, then structural integrity is ensured, but elongation requirements must be met for workability
Solution Approach 1:
The patent controls the Si content within specific ranges (3.0-4.5 mass% in core, 5-8 mass% in surface layers) to maintain appropriate mechanical properties. By optimizing these compositional parameters, the steel achieves a balance between structural integrity for stacking and interlocking, and sufficient elongation for workability during motor core fabrication.
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 multilayer electrical steel sheet exhibits excellent elongation and workability, along with reduced high-frequency iron loss and high magnetic flux density, making it suitable for high-frequency applications such as motor cores in hybrid electric vehicles and other equipment.
Implementation Method 1
To reduce the high-frequency iron loss, it is effective to increase specific resistance. Therefore, high-Si steel having increased specific resistance through the increase in the Si content has been developed.
Implementation Method 2
since Si is a non-magnetic element, the increase in the Si content leads to lower saturation magnetization
Implementation Method 3
the inventors made intensive studies of a method of solving the problem, and as a result, found that in order to reduce high-frequency iron loss, it is important to reduce the difference in magnetostriction between surface layers and an inner layer of a steel sheet
Data Source
AI summary
Provided is a multilayer electrical steel sheet having low high-frequency iron loss and high magnetic flux density. The multilayer electrical steel sheet has an inner layer and surface layers provided on both sides of the inner layer, in which the surface layers and inner layer have predetermined chemical compositions, the multilayer electrical steel sheet having: ΔSi of 0.5 mass % or more, ΔSi being defined as a difference between a Si content in the surface layer [Si]1 and a Si content in the inner layer [Si]0 represented by [Si]1−[Si]0; Δλ1.0/400 of 1.0×10−6 or less, Δλ1.0/400 being defined as an absolute value of the difference between a magnetostriction of the surface layer λ1.0/400,1 and a magnetostriction of the inner layer λ1.0/400,0; a sheet thickness t of 0.03 mm to 0.3 mm, and a ratio of a total thickness of the surface layers t1 to t of from 0.10 to 0.70.