Grain Oriented Steel Sheet Deflection Control
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Solution Overview
Problem
Grain oriented electrical steel sheets used in transformers experience noise due to magnetostrictive behavior and electromagnetic vibrations, which are difficult to completely eliminate through clamping alone, and are prone to deflection and cracking during annealing, affecting iron loss properties.
Innovation Solution
Thermal strain-imparting magnetic domain refinement is applied to the steel sheets using electron beam or laser irradiation, with specific conditions to reduce crack length and deflection, thereby improving iron loss properties and reducing noise by correcting the shape of the steel sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If flattening annealing is performed at high temperature to correct deflection, then shape accuracy is improved, but creep deformation occurs causing film cracking
Solution Approach 1:
The patent changes the temperature parameter from high temperature (800°C or higher) to low temperature (500°C or lower) flattening annealing, thereby correcting deflection while preventing creep deformation and film cracking that occur at high temperatures
Solution Approach 2:
The patent replaces the conventional high-temperature thermal correction method with a low-temperature method combined with mechanical tension control, using tension application and release to correct deflection without causing thermal creep deformation
2Manufacturing precision
If in-furnace tension is increased during flattening annealing to enhance correcting effect, then shape accuracy is improved, but creep deformation is facilitated causing film cracking
Solution Approach 1:
The patent changes the temperature parameter to low temperature (500°C or lower) where creep deformation is suppressed, allowing the application of tension during annealing to correct deflection without causing film cracking that would occur at high temperatures with increased tension
3Loss of energy
If electron beam or laser irradiation is used for magnetic domain refinement, then iron loss is reduced, but thermal strain causes deflection and film cracking
Solution Approach 1:
The patent performs magnetic domain refinement by electron beam or laser irradiation at low temperature (500°C or lower) during flattening annealing, thereby achieving iron loss reduction through magnetic domain subdivision while preventing thermal strain-induced deflection and film cracking that would occur at high temperatures
Solution Approach 2:
The patent combines flattening annealing, magnetic domain refinement, and tension control into a single integrated low-temperature process, achieving shape correction, iron loss reduction, and film integrity preservation simultaneously without the adverse effects of separate high-temperature processes
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 approach effectively reduces iron loss and noise in transformers by minimizing crack formation and deflection, allowing for better stacking and handling of steel sheets, while maintaining low iron loss properties.
Implementation Method 1
thermal strain-imparting magnetic domain refinement... introduction of thermal strain is carried out by irradiation of electron beam... irradiation of laser
Implementation Method 2
heating by irradiation and subsequent rapid cooling of the portion... residual tensile stress generated through magnetic domain refinement
Implementation Method 3
magnetostrictive behavior occurring when an electrical steel sheet is magnetized... alternately magnetized in positive/negative magnetization direction... iron core repeats expanding and shrinking movements
Data Source
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AI summary
The present invention proposes measures to decrease noise generated by an iron core of a transformer when grain oriented electrical steel sheets each having realized low iron loss through magnetic domain refinement are stacked to constitute the iron core. Specifically, the present invention proposes a method for manufacturing a grain oriented electrical steel sheet, comprising: subjecting a grain oriented electrical steel sheet comprising 2.0 mass% to 8.0 mass% Si and having a forsterite film on a steel sheet surface to flattening annealing at 800°C or higher wherein an in-furnace tension during flattening annealing is 10 MPa or less, and subjecting the grain oriented electrical steel sheet to magnetic domain refinement after final annealing such that thermal strain is introduced in a linear like manner in a direction intersecting a rolling direction of the steel sheet, with magnetic domain refinement interval D (mm) in the rolling direction, from a side of the steel sheet corresponding to the winding outer peripheral side of a coiled steel sheet at the stage of the final annealing, such that a deflection of the grain oriented electrical steel sheet is 3 mm or less per unit length: 500 mm in the rolling direction of the steel sheet,