Elliptical Laser Beam Orientation for Grain-Oriented Steel Core Loss
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Solution Overview
Problem
High-speed production of grain-oriented electrical steel sheets faces challenges in maintaining effective laser irradiation width and reducing core loss, as the focused spot size becomes too narrow, leading to increased hysteresis loss and uneven stress distribution, especially when the steel sheet moves rapidly.
Innovation Solution
Adjusting the slant angle of an elliptical laser beam spot relative to its scan direction to minimize the effective irradiated width on the steel sheet, using equations to optimize the production line speed and scan speed, and employing an elliptical beam shaping unit with a cylindrical lens telescope and slant angle adjustment mechanism to maintain a stable, narrow focused spot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the production line speed is increased to improve productivity, then the output increases, but the effective laser irradiation width becomes insufficient leading to inadequate stress distribution
Solution Approach 1:
The elliptical focused spot geometry with asymmetric orientation (long axis parallel to sheet movement direction, short axis parallel to scan direction) enables the laser to maintain adequate irradiation width in the movement direction even at high line speeds, while keeping the scan direction width narrow for precise domain control.
Solution Approach 2:
The patent utilizes the time dimension by extending the focused spot along the movement direction, effectively increasing the residence time of the laser on each point of the sheet. This dimensional extension in the movement direction compensates for the high speed movement, ensuring sufficient stress distribution without reducing productivity.
2Use of energy by moving object
If the focused spot is made circular with small size to concentrate stress, then the power density increases, but the beam residence time becomes too short for sufficient heat transfer
Solution Approach 1:
The elliptical focused spot creates asymmetric energy distribution where high power density is maintained in the scan direction (short axis) for precise stress concentration, while the extended length in the movement direction (long axis) provides sufficient residence time for heat transfer, resolving the contradiction between energy concentration and exposure duration.
Solution Approach 2:
The patent changes the focused spot from a circular shape with uniform dimensions to an elliptical shape with different dimensions in different directions. By controlling the elliptical parameters (aspect ratio, orientation), the patent independently optimizes power density in the scan direction while ensuring adequate residence time through the extended length in the movement direction.
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 allows for consistent improvement in magnetic properties and reduced core loss, even at high production speeds, by ensuring the laser beam's impact area matches the short axis of the elliptical spot, thereby minimizing hysteresis loss and maintaining effective stress distribution.
Implementation Method 1
irradiating the surface of grain-oriented electrical steel sheet with a laser beam to improve its magnetic properties
Implementation Method 2
By giving periodic stress in a linear form substantially vertical to the rolling direction and in the rolling direction near the surface of the steel sheet, the distance between 180° domain walls becomes narrower
Implementation Method 3
focusing a laser beam to an elliptical spot on grain-oriented electrical steel sheet
Implementation Method 4
employing an elliptical beam shaping unit with a cylindrical lens telescope
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3(a)~3(c)
AI summary
Technology scanning and irradiating grain-oriented electrical steel sheet moving in a rolling direction at a speed V1 with an elliptical spot formed by a laser beam in the width direction at Vc to improve the core loss of the grain-oriented electrical steel sheet, which adjusts the angle θs formed by the scan direction of the elliptical beam and the long axis of the ellipse based on the equation θs=tan-1 (Vl/Vc) and which constructs the system for adjusting the θs by an optical system for laser irradiation comprised of a cylindrical lens telescope, scan mirror, and fθ lens arranged in that order, a system for changing the angle of the cylindrical lens telescope with respect to the scan direction of the scan mirror, and a system for changing the distance between lenses.