Non-oriented Electrical Steel Sheet Inner Oxidation Layer
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Solution Overview
Problem
Conventional electrical steel sheets face challenges in achieving simultaneous excellent insulation characteristics, workability, and magnetism due to insufficient addition of P, Cr, and Mg elements, leading to inefficiencies in motor performance and producibility issues.
Innovation Solution
A non-oriented electrical steel sheet is developed by adding appropriate amounts of P, Cr, and Mg elements to form an inner oxidation layer within the steel sheet, optimizing the composition to include Si: 2.5 to 6.0%, Al: 0.2 to 3.5%, Mn: 0.2 to 4.5%, Cr: 0.01 to 0.2%, P: 0.005 to 0.08%, and Mg: 0.0005 to 0.05%, with a specific ratio and forming an inner oxidation layer of 0.2 to 5 μm thickness, which enhances insulation and magnetism while minimizing the insulating layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the insulating coating layer is increased to improve insulation and reduce eddy current loss, then motor efficiency is improved, but the stacking factor deteriorates and mold damage occurs during punching
Solution Approach 1:
The insulation function is segmented into two parts: an inner oxidation layer formed within the steel sheet itself and an outer insulating coating applied to the surface. The inner oxidation layer (0.2 to 5 μm thick) provides base insulation and allows the outer coating to be applied thinner (0.5 to 2.0 μm), thus maintaining insulation while improving stacking factor and reducing mold damage during punching.
Solution Approach 2:
The inner oxidation layer is nested within the steel sheet structure, forming an integrated insulation system. This nested approach allows the insulation function to be embedded in the material itself rather than relying solely on an external coating, enabling thinner overall insulation structures that improve stacking factor while maintaining electrical insulation.
2Reliability
If the thickness of the insulating coating layer is increased to secure insulation, then eddy current loss is reduced, but producibility deteriorates due to foreign material formation during punching
Solution Approach 1:
The insulation system is divided into an inner oxidation layer and an outer insulating coating. The inner layer provides structural insulation that prevents excessive coating thickness, thereby reducing foreign material formation during punching operations and improving overall producibility.
Solution Approach 2:
The inner oxidation layer is formed during the steel sheet manufacturing process before the insulating coating is applied. This preliminary formation of the oxidation layer ensures proper insulation characteristics are built into the material itself, allowing for thinner coatings and reduced punching-related defects.
3Reliability
If appropriate amounts of P, Cr, and Mg elements are added to form an inner oxidation layer, then insulation characteristic and magnetism are simultaneously improved, but manufacturing complexity increases
Solution Approach 1:
The formation of the inner oxidation layer is merged with the existing steel sheet manufacturing process, specifically during the final annealing stage. By combining the oxidation layer formation with the standard annealing process (using controlled atmosphere and temperature), no separate manufacturing step is required, thus avoiding increased manufacturing complexity while achieving improved insulation and magnetic properties.
Solution Approach 2:
The final annealing process serves multiple functions: it completes the steel sheet production, controls microstructure for magnetic properties, and simultaneously forms the inner oxidation layer for insulation. This multi-functionality eliminates the need for additional dedicated oxidation steps, maintaining manufacturing simplicity.
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 solution results in improved motor efficiency, increased stacking factor, and enhanced producibility by securing excellent insulation and magnetism characteristics, suitable for environmentally-friendly automotive motors and high-efficiency household appliances.
Implementation Method 1
forming an inner oxidation layer inside the steel sheet
Data Source
AI summary
A non-oriented electrical steel sheet according to an exemplary embodiment of the present invention includes, by weight %, Si: 2.5 to 6.0%, Al: 0.2 to 3.5%, Mn: 0.2 to 4.5%, Cr: 0.01 to 0.2%, P: 0.005 to 0.08%, Mg: 0.0005 to 0.05%, and a remainder including Fe and inevitable impurities, while satisfying Equation 1 below, and formed with an inner oxidation layer of a 0.2 to 5 μm thickness inside a base steel sheet.−2.5≤[P]/[Cr]−[Mg]×100≤6.5 [Equation 1](In Equation 1, [P], [Cr], and [Mg] respectively represent a content (by wt %) of P, Cr, and Mg).