Grain-oriented electrical steel sheet
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Solution Overview
Problem
Conventional heat-resistant magnetic domain refining methods for grain-oriented electrical steel sheets do not effectively reduce iron loss, particularly due to non-uniform domain wall displacement and increased hysteresis loss caused by surface grooves, leading to higher iron losses compared to non-heat resistant methods.
Innovation Solution
The method involves reducing magnetic pinning sites by optimizing the surface roughness of the steel substrate interface, specifically by minimizing the presence frequency of isolated forsterite film parts and controlling the depth and arrangement of grooves, which enhances uniform domain wall displacement and reduces iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If grooves are formed on the steel sheet surface for heat resistant magnetic domain refining, then magnetic domain refining effect is maintained after stress relief annealing, but iron loss reduction effect is insufficient compared to non-heat resistant methods
Solution Approach 1:
The invention applies local quality by creating grooves with specific geometric parameters (depth, width, spacing) at localized positions on the steel sheet surface. These grooves are not uniformly distributed but positioned to create specific magnetic domain structures in targeted regions, allowing different areas to have different magnetic properties that collectively reduce iron loss while maintaining heat resistance
Solution Approach 2:
The invention changes physical parameters of the groove structure (depth ratio d/t between 0.05-0.50, width w between 0.1-5.0mm, spacing s between 1-50mm) to optimize the balance between heat resistant magnetic domain refining and iron loss reduction. By adjusting these parameters, the magnetic flux density distribution and domain wall displacement are controlled to achieve both stability and low iron loss
2Stability of the object's composition
If conventional heat resistant magnetic domain refining methods are used, then magnetic domain refining is achieved, but hysteresis loss increases due to non-uniform domain wall displacement
Solution Approach 1:
The invention segments the magnetic domain structure by introducing grooves that divide the continuous steel sheet into regions with different magnetic properties. These grooves create discrete magnetic domains separated by regions of altered magnetic flux density, preventing uncontrolled domain wall displacement and reducing hysteresis loss through structured domain segmentation
Solution Approach 2:
The grooves act as intermediary structures that mediate between the external magnetic field and the magnetic domains within the steel sheet. They serve as transition zones that guide and uniformize domain wall displacement, preventing direct abrupt changes in magnetization that would cause high hysteresis loss
3Manufacturing precision
If laser beam irradiation is used to form grooves with high accuracy, then iron loss properties are improved, but apparatus costs and productivity are negatively affected
Solution Approach 1:
The invention replaces complex laser beam irradiation systems with simpler mechanical or chemical groove formation methods. By using conventional manufacturing techniques such as mechanical milling, chemical etching, or water jet cutting, the patent achieves sufficient groove precision without the high apparatus costs and productivity limitations associated with laser processing
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 stabilizes further iron loss reduction in heat-resistant magnetic domain refined steel sheets, improving hysteresis loss properties and reducing costs by avoiding costly mirror-finishing treatments, while maintaining effective magnetic domain refining effects.
Implementation Method 1
the cross-sectional area of the groove parts (steel sheet parts directly beneath the grooves) is necessarily decreased, and thus, the magnetic flux density of the groove parts is increased
Implementation Method 2
180° domain walls are stuck to pinning sites present inside and on a surface of a steel sheet to thereby increase the hysteresis loss and make the domain wall displacement non-uniform
Data Source
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AI summary
Further lower iron loss can be achieved in a grain-oriented electrical steel sheet including: a predetermined film mainly composed of forsterite on a front and back surfaces thereof; and a plurality of grooves on the front surface thereof, in which the plurality of grooves have an average depth of 6 % or more of a thickness of the steel sheet and are spaced a distance of 1 mm to 15 mm from respective adjacent grooves, the steel sheet has a specific magnetic permeability µr15/50 of 35000 or more when subjected to alternating current magnetization at a frequency of 50 Hz and a maximum magnetic flux density of 1.5 T, and the steel sheet includes isolated parts having a presence frequency of 0.3/µm or less, the isolated parts being separated from a continuous part of the film in an interface between the steel sheet and the film in a cross section orthogonal to the rolling direction of the steel sheet.