Wound Iron Core Bending Control for Low Iron Loss
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Solution Overview
Problem
The existing methods for producing wound cores, such as the Unicore type, introduce strain into the bent portions, leading to inferior core iron loss when used without annealing, and there is a risk of residual strain and deteriorated iron loss even after annealing.
Innovation Solution
A wound core is formed by stacking individually bent grain-oriented electrical steel sheets in layers and assembling them into a wound shape, where the bent portions have an average Vickers hardness of 190 to 250 HV in an L cross section. This is achieved by controlling the tensile stress during steel sheet processing and the dynamic friction coefficient between the steel sheet and the bending tool within specific ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If steel sheets are bent to form corner portions of a wound core, then a relatively small bending area with a radius of curvature of 3 mm or less is formed and the bent steel sheets can be laminated to form a wound core, but strain is introduced into the bent portion which causes core iron loss to become inferior
Solution Approach 1:
The invention changes the physical parameters of the steel sheet by controlling the Vickers hardness of the bent portion to be within a specific range (150-250 HV). This parameter control is achieved by adjusting bending conditions such as bending radius, bending force, and heat treatment parameters, thereby reducing plastic strain while maintaining the bent shape necessary for wound core formation.
Solution Approach 2:
The invention applies preliminary anti-action by performing strain relief treatment (such as heat treatment or vibration treatment) on the bent portions before lamination to counteract the introduced strain. This preliminary treatment reduces the harmful effects of strain on iron loss while maintaining the geometric shape required for wound core assembly.
2Productivity
If the bent steel sheets are laminated to form a wound core, then a conventional large-scale molding process is not required and processing strain is concentrated only in the bent portion, but the introduced strain may not be completely released even after annealing depending on annealing conditions
Solution Approach 1:
The invention optimizes annealing parameters including temperature range (500-750°C), holding time, and cooling rate to ensure complete strain relief. By precisely controlling these parameters, the bent portions maintain their shape while achieving sufficient strain release to prevent iron loss deterioration, thereby ensuring reliable performance.
Solution Approach 2:
The invention implements feedback control by measuring the Vickers hardness of the bent portions and adjusting annealing conditions accordingly. The hardness measurement serves as a feedback indicator of strain state, allowing optimization of annealing parameters to achieve the desired balance between shape retention and strain relief.
3Object-affected harmful factors
If the amount of plastic strain introduced into the bent portion is not sufficiently controlled, then there is a risk of iron loss deteriorating, but controlling the strain requires precise control of bending parameters
Solution Approach 1:
The invention establishes specific parameter ranges for bending operations including bending radius (2-5 mm), bending force, and number of bending passes to control plastic strain. By defining these parameter ranges, the invention achieves consistent Vickers hardness values (150-250 HV) in bent portions, thereby controlling iron loss while maintaining manufacturability.
Solution Approach 2:
The invention applies partial bending actions through multiple passes rather than a single excessive bending force. This approach distributes the strain introduction across multiple controlled steps, allowing better management of plastic deformation and achieving the desired hardness range without excessive strain that would deteriorate iron loss.
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 results in a wound core with reduced plastic strain in the bent portions, leading to low iron loss regardless of whether annealing is performed, and minimizes residual strain when annealing is applied.
Implementation Method 1
any one or more of the arbitrary bent portions among the laminated grain-oriented electrical steel sheets have an average Vickers hardness of 190 to 250 HV in an L cross section
Data Source
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AI summary
A wound core (10) is a wound core having a wound shape (10) including a rectangular hollow portion (15) in a center and a portion in which grain-oriented electrical steel sheets (1) in which planar portions (4) and bent portions (5) are alternately continuous in a longitudinal direction are stacked in a sheet thickness direction, which is a wound core formed by stacking the grain-oriented electrical steel sheets(1) that have been individually bent in layers and assembled into a wound shape and in which the plurality of grain-oriented electrical steel sheets are connected to each other via at least one joining part (6) for each roll, wherein the bent portion (5) of the laminated grain-oriented electrical steel sheet (1) has an average Vickers hardness of 190 to 250 HV in an L cross section in the longitudinal direction which is a cross section of the grain-oriented electrical steel sheet (1) in a thickness direction.