Heated Bending of Coated Wound Cores to Suppress Iron Loss
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Solution Overview
Problem
Existing wound core manufacturing methods fail to effectively suppress iron loss due to coating damage and strain-induced deterioration, particularly in the flat regions adjacent to bent regions during the bending process.
Innovation Solution
A wound core is formed by laminating bent bodies of coated grain-oriented electrical steel sheets, where the bending is performed under controlled temperature conditions (45°C to 500°C) with a gentle temperature gradient in the flat regions, ensuring a high coating soundness rate and minimizing deformation twins, thereby reducing iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the steel sheet is bent to form corner portions with a radius of curvature of 3 mm or less, then the manufacturing process is simplified and shape retention is improved, but coating damage and strain-induced deterioration occur in the flat regions adjacent to bent regions
Solution Approach 1:
The patent applies temperature control as a parameter change to resolve the contradiction. By heating the steel sheet to 150°C or higher and 500°C or lower before bending, the material becomes more ductile and less prone to coating damage and strain-induced deterioration. This temperature parameter modification allows the bending process to proceed with smaller radius of curvature (3 mm or less) while maintaining coating integrity and reducing harmful effects in the flat regions adjacent to bent regions.
Solution Approach 2:
The patent implements preliminary heating before the bending operation. By pre-heating the steel sheet to the specified temperature range (150-500°C) prior to bending, the material properties are modified in advance to prevent coating damage and strain-induced deterioration during the subsequent bending process. This preliminary thermal treatment ensures that when the steel sheet is bent to form corner portions with small radius of curvature, the flat regions adjacent to bent regions do not suffer from coating damage or excessive strain.
2Device complexity
If the steel sheet is bent at room temperature, then the manufacturing process is simpler without heating equipment, but deformation twins increase and iron loss is not effectively suppressed
Solution Approach 1:
The patent changes the temperature parameter from room temperature to 150-500°C to suppress deformation twin formation. By heating the steel sheet before bending, the crystal structure becomes more resistant to forming deformation twins during the bending process. This parameter change effectively reduces iron loss caused by deformation twins in the bent regions, while the heating process itself is integrated into the manufacturing flow to minimize additional equipment complexity.
3Reliability
If the steel sheet is heated to high temperature for bending, then coating damage is reduced, but energy consumption increases
Solution Approach 1:
The patent optimizes the temperature parameter to a specific range of 150-500°C, avoiding both room temperature (which causes coating damage) and excessive high temperatures (which waste energy). Within this optimized range, the steel sheet achieves sufficient ductility and coating protection while minimizing energy consumption. The lower bound (150°C) ensures adequate thermal activation to prevent coating damage, while the upper bound (500°C) prevents excessive energy use and potential material degradation.
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 method significantly suppresses iron loss by maintaining coating integrity and reducing strain in the flat regions, leading to a wound core with improved magnetic characteristics and reduced eddy currents.
Implementation Method 1
the coated grain-oriented electrical steel sheet is bent in a state where a portion of the bent body to be a bent region is 150° C. or higher and 500° C. or lower
Implementation Method 2
a wound core formed by laminating a plurality of bent bodies obtained by forming a coated grain-oriented electrical steel sheet in which a coating is formed on at least one surface of a grain-oriented electrical steel sheet so that the coating is on an outside, in a sheet thickness direction
Data Source
AI summary
Provided is a wound core formed by laminating a plurality of bent bodies obtained by forming a coated grain-oriented electrical steel sheet in which a coating is formed on at least one surface of a grain-oriented electrical steel sheet so that the coating is on an outside, in a sheet thickness direction, in which the bent body has a bent region obtained by bending the coated grain-oriented electrical steel sheet and a flat region adjacent to the bent region, the number of deformation twins present in the bent region in a side view is five or less per 1 mm of a length of a center line in the sheet thickness direction in the bent region, and when a region extending 40 times a sheet thickness to both sides in a circumferential direction from a center of the bent region on an outer circumferential surface of the bent body is defined as a strain affected region, a proportion of an area where the coating is not damaged at any position along the circumferential direction in a flat region within the strain affected region is 90% or more.