Grain Oriented Steel Sheet Warpage Control
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Solution Overview
Problem
Grain oriented electrical steel sheets face challenges in reducing iron loss while minimizing warpage after artificial magnetic domain refining treatments, which can lead to deterioration in handling and magnetic properties.
Innovation Solution
Applying a tension-applying insulating coating or base film on both surfaces of the steel sheet before strain-introducing treatment, with specific tension ratios to control warpage and maximize iron loss reduction, using techniques like electron beam or continuous laser irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If large thermal energy is introduced to the surface of the steel sheet to perform magnetic domain refining treatment, then iron loss reduction is achieved, but warpage occurs toward the strain-introduced surface
Solution Approach 1:
A coating layer is applied to the surface of the steel sheet before magnetic domain refining treatment to prevent warpage. The coating layer has different thermal expansion characteristics than the steel substrate, creating preliminary counteracting stress that opposes the warpage tendency during subsequent thermal processing, thereby maintaining flatness while allowing iron loss reduction
Solution Approach 2:
The coating layer acts as an intermediary between the thermal energy input and the steel substrate. It mediates the thermal stress distribution and prevents direct transmission of warpage-inducing stresses to the bulk material, enabling magnetic domain refinement without excessive warpage
2Reliability
If strain-introducing treatment is performed to reduce magnetic domain width and iron loss, then magnetic properties improve, but handling ability deteriorates due to warpage
Solution Approach 1:
The coating layer is applied in advance to counteract warpage effects before they fully develop during or after magnetic domain refining treatment, preserving both improved magnetic properties and adequate handling ability
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 effectively reduces iron loss to low values (W17/50 ≤ 0.70 W/kg) while minimizing warpage to within 1-10 mm, maintaining the steel sheet's handling and magnetic properties.
Implementation Method 1
a tension-applying insulating coating on both surfaces of the steel sheet, wherein tension applied to the both surfaces of the steel sheet by the tension-applying insulating coating before strain-introducing treatment satisfies a relation of Formula (1)
Implementation Method 2
JP 06-072266 B proposes a technique for controlling the magnetic domain width by means of electron beam irradiation
Implementation Method 3
JP 57-002252 B proposes a technique for reducing iron loss by irradiating a final product steel sheet with a laser
Data Source
AI summary
A grain oriented electrical steel sheet has sufficiently low iron loss and having less conventionally-concerned warpage of the steel sheet even after the steel sheet is subjected to artificial magnetic domain refining treatment, where strain-introducing treatment is conducted with high energy so that an iron loss-reducing effect can be maximized. The grain oriented electrical steel sheet is obtained by adjusting tension to be applied to a tension-applying insulating coating, or to both surfaces of the steel sheet by the tension-applying insulating coating, before strain-introducing treatment in the range of Formula (1):1.0≦(tension applied to non-strain-introduced surface)/(tension applied to strain-introduced surface)≦2.0 (1),and by controlling the amount of warpage of the steel sheet toward the strain-introduced surface side after strain-introducing treatment in the range of 1 mm or more and 10 mm or less.