Non-oriented electrical steel sheet grain control
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Solution Overview
Problem
Existing methods to improve iron loss in non-oriented electrical steel sheets, such as increasing alloy content or reducing thickness, lead to increased production costs and reduced productivity, making it difficult to effectively reduce iron loss in the rolling direction.
Innovation Solution
A non-oriented electrical steel sheet with controlled grain size distribution and dislocation density, manufactured through specific alloy compositions and controlled heat treatment processes, including hot-rolling, cold-rolling, and annealing with precise tensile stress application, to achieve uniform grain distribution and reduced iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If alloy content is increased to improve iron loss, then iron loss is reduced, but production cost increases and cold rollability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alloy composition within specific ranges (Si: 1.5-3.5 wt%, Al: 0.003-2.0 wt%, Mn: 0.03-2.0 wt%, C: 0.003-0.030 wt%) rather than simply increasing alloy content. This optimized parameter combination achieves iron loss reduction while maintaining cold rollability and avoiding the detrimental effects of excessive alloying.
2Loss of energy
If steel sheet thickness is reduced to improve iron loss, then eddy current loss decreases, but heat treatment time increases and productivity decreases
Solution Approach 1:
The patent changes the parameter of steel sheet thickness to a specific optimized range (0.15-0.30 mm) that balances eddy current loss reduction with productivity maintenance. This parameter optimization achieves effective iron loss reduction without the excessive heat treatment time and productivity loss associated with thinner sheets.
3Loss of energy
If impurity levels are minimized to improve iron loss, then magnetic domain structure improves, but steelmaking time extends and productivity decreases
Solution Approach 1:
The patent applies parameter changes by setting specific impurity level thresholds (S: 0.003-0.030 wt%, P: 0.003-0.030 wt%, N: 0.003-0.030 wt%) rather than pursuing extreme minimization. This balanced approach achieves sufficient improvement in magnetic domain structure and iron loss reduction while avoiding excessive steelmaking time and productivity loss.
4Loss of energy
If grain size is reduced to improve iron loss, then magnetic properties improve, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by controlling grain size through optimized alloy composition and processing parameters during manufacturing, establishing a uniform fine-grained structure before final heat treatment. This preliminary grain control simplifies subsequent heat treatment processes while achieving the desired fine grain size for reduced iron loss.
Solution Approach 2:
The patent changes the grain size parameter to a specific optimized range through controlled alloying and processing, achieving uniform fine-grained structure that reduces iron loss without requiring excessively complex manufacturing processes.
5Loss of energy
If dislocation density is controlled to improve iron loss, then magnetic domain movement improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by optimizing alloy composition (Si: 1.5-3.5 wt%, Al: 0.003-2.0 wt%, Mn: 0.03-2.0 wt%) and processing parameters to achieve appropriate dislocation density levels. This balanced approach improves magnetic domain movement and reduces iron loss without requiring excessively precise manufacturing control.
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 results in a steel sheet with improved iron loss properties, reduced manufacturing costs, and increased productivity by optimizing grain size fractions and dislocation distribution, enhancing magnetic properties and reducing core loss across various frequencies.
Implementation Method 1
As the specific resistance of the steel increases through the addition of the alloying elements, the eddy current loss decreases, thereby lowering the overall iron loss
Implementation Method 2
a cold-rolled steel sheet annealing step of annealing the cold-rolled steel sheet, wherein in the cold-rolled steel sheet annealing step, a tensile stress of more than 0.01 to less than 1.0 kgf/mm2
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
The present invention relates to a non-oriented electrical steel sheet and a method of manufacturing the same, and according to the non-oriented electrical steel sheet, an area fraction of grains having a grain size of less than 1/3 times an average grain size may be less than 5%, and an area fraction of grains having a dislocation density of more than 1012/m2 and less than or equal to 1016/m2 is less than 5% of a total area.