Wound Iron Core Bending With Heated Steel Sheet to Reduce Iron Loss

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Solution Overview

Problem

Existing wound core manufacturing methods face challenges in suppressing iron loss, particularly due to damage and strain-induced coating peeling during the bending process, which affects the magnetic properties and efficiency of the core.

Innovation Solution

A manufacturing method involving coated grain-oriented electrical steel sheets, where the bending is performed with the bent region heated to 45°C or higher and 500°C or lower, and a controlled temperature gradient in the adjacent flat region to minimize deformation twins and coating damage, resulting in a wound core with reduced iron loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the steel sheet is bent to form corner portions with small radius of curvature (3 mm or less), then the manufacturing process is simplified and shape retention is improved, but deformation twins increase and coating damage occurs leading to increased iron loss

Engineering Contradiction:
Improvemanufacturing process simplicityVSAvoidiron loss
Core Design Contradiction:
Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent applies parameter changes by controlling the temperature of the steel sheet during bending to be 150°C or higher and 500°C or lower. This temperature parameter modification suppresses the formation of deformation twins and prevents coating peeling, thereby reducing iron loss while maintaining the simplified bending manufacturing process with small radius of curvature corner portions

Inventive Principle:
Principle #35Parameter changes

2Device complexity

If the steel sheet is bent at room temperature, then the manufacturing process is simpler without heating, but deformation twins increase and coating peeling occurs

Engineering Contradiction:
Improveheating equipment requirementVSAvoidcoating integrity
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent changes the temperature parameter from room temperature to 150°C or higher and 500°C or lower during the bending process. This parameter modification prevents coating peeling and deformation twin formation, ensuring coating integrity while accepting the addition of heating equipment

Inventive Principle:
Principle #35Parameter changes

3Productivity

If conventional bending methods are used without temperature control, then manufacturing is faster and easier, but iron loss increases due to deformation twins and coating damage

Engineering Contradiction:
Improvemanufacturing speedVSAvoidiron loss
Core Design Contradiction:
ProductivityVSLoss of energy

Solution Approach 1:

The patent implements temperature parameter control at 150°C or higher and 500°C or lower during bending operations. This enables rapid manufacturing through simplified bending processes while simultaneously suppressing deformation twins and coating damage, thereby reducing iron loss without sacrificing productivity

Inventive Principle:
Principle #35Parameter changes

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 effectively suppresses iron loss by maintaining a high coating soundness rate and reducing deformation twins, leading to improved magnetic performance and efficiency in wound cores.

Implementation Method 1

a portion of the bent body to be the bent region is heated to 45°C or higher and 500°C or lower

Methodology Applied
Scientific EffectThermal heating: Heating

Implementation Method 2

a temperature gradient at any position of a portion to be the flat region within the strain affected region in the longitudinal direction of the coated grain-oriented electrical steel sheet is less than 400°C/mm

Methodology Applied
Scientific EffectTemperature gradient control: Temperature Gradient

Data Source

PatentEP3961665B1Method for producing wound iron core
Publication Date: 2024.02.28 NIPPON STEEL CORPORATION
  • EP3961665B1 patent drawingFigure 1~2
  • EP3961665B1 patent drawingFigure 3~4
  • EP3961665B1 patent drawingFigure 5~6

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.