Laser Polarization Angle for Grain-Oriented Steel Domain Refinement
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Solution Overview
Problem
Laser magnetic domain control in grain-oriented electromagnetic steel sheets faces challenges due to varying absorptance of the laser beam, leading to increased risk of defects in the glass coating film, especially at the edges where the laser beam path length increases, resulting in higher absorption and potential rust formation.
Innovation Solution
The use of a linearly polarized laser beam with an angle between the polarization direction and scanning direction set between 45° and 90° reduces absorptance at the edges, minimizing defects in the glass coating film by optimizing the path length and power distribution, thereby reducing core loss and preventing rust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the laser beam is scanned along the width direction of the steel sheet, then magnetic domains are refined and anomalous eddy-current loss is reduced, but the path length of the laser beam increases at the edges, causing increased absorption and defects in the glass coating film
Solution Approach 1:
The patent applies different laser beam polarization orientations at different positions across the scanning width. The polarization direction is angled relative to the scanning direction, creating local variations in absorptance that compensate for the position-dependent path length differences, thereby uniformizing the heating effect across the entire scanned area
Solution Approach 2:
The patent changes the polarization parameter of the laser beam by orienting it at a specific angle (between 10° and 70°) relative to the scanning direction. This parameter change modifies the absorptance characteristics of the laser beam by the glass coating film, allowing compensation for the varying path lengths and preventing edge defects
2Manufacturing precision
If the laser beam power is increased to ensure sufficient heating at the edges, then magnetic domain refinement is improved, but defects in the glass coating film and insulating coating film increase
Solution Approach 1:
The patent creates local variations in laser beam absorptance by orienting the polarization direction at an angle to the scanning direction. This results in different effective absorptance values at different positions across the scanning width, allowing uniform heating without excessive power that would cause coating film defects
Solution Approach 2:
The patent converts the potentially harmful effect of increased path length at edges (which would normally cause excessive absorption and defects) into a beneficial control mechanism. By using polarized light at an angle, the position-dependent absorptance variations are harnessed to achieve uniform heating across the scanning width, preventing both under-heating and overheating defects
3Loss of energy
If a narrow beam spot size is used to reduce circulating current magnetic domain width, then hysteresis loss is reduced, but the laser beam absorption by coating films increases, raising defect risk
Solution Approach 1:
The patent changes the polarization parameter of the laser beam, orienting it at an angle between 10° and 70° relative to the scanning direction. This parameter change reduces the absorptance of the laser beam by the coating films, allowing narrow beam spot sizes to be used for reducing hysteresis loss without increasing the risk of coating film defects
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 effectively suppresses defects in the glass coating film across the entire scanning width, maintains core loss reduction efficacy, and prevents rust formation, thereby reducing production costs and enhancing the energy efficiency of electromagnetic steel sheets.
Implementation Method 1
the surface of a grain-oriented electromagnetic steel sheet in which an insulating coating film is formed is irradiated with a laser beam
Implementation Method 2
a thermal history having a steep temperature gradient along a thickness direction is generated in the outermost surface of the grain-oriented electromagnetic steel sheet through the scanning with the laser beam
Implementation Method 3
due to an increase in temperature caused by the laser beam irradiation, defects may be generated on the insulating coating film and the glass coating film
Data Source
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AI summary
In a laser processing apparatus for refining magnetic domains of a grain-oriented electromagnetic steel sheet by setting a laser beam to be focused on the grain-oriented electromagnetic steel sheet and scanned in a scanning direction, the laser beam focused on the grain-oriented electromagnetic steel sheet is linearly polarized light, and an angle between a linear polarization direction and the scanning direction is higher than 45° and equal to or lower than 90°.