Non-Oriented Electrical Steel Sheet Grain Control for Strength and Core Loss
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Solution Overview
Problem
Existing non-oriented electrical steel sheets face challenges in simultaneously enhancing magnetic properties and strength, particularly in thin sheets used for high-speed drive motors in eco-friendly vehicles, due to issues like embrittlement, non-uniform grain distribution, and increased manufacturing costs, which affect core loss and magnetic flux density.
Innovation Solution
A method involving precise control of pre-annealing and final annealing processes to ensure a sufficient number of fine grains are uniformly distributed throughout the steel sheet, with specific element compositions and controlled grain diameter ratios, enhancing yield strength and core loss performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If alloy elements such as Si, Al, and Mn are added to increase strength, then strength is improved, but magnetic flux density deteriorates and embrittlement increases
Solution Approach 1:
The patent optimizes the compositional parameters of alloy elements (Si: 1.5-3.0%, Al: 0.5-2.0%, Mn: 0.5-2.0%) to achieve the desired balance between strength and magnetic properties. By precisely controlling these parameter ranges, the invention resolves the contradiction between strength enhancement and magnetic flux density maintenance.
2Strength
If the addition amount of alloy elements such as Si, Al, and Mn is increased to improve strength, then strength is improved, but cold rolling becomes impossible due to embrittlement
Solution Approach 1:
The patent establishes optimal compositional parameter ranges that provide sufficient strength while maintaining ductility required for cold rolling. The controlled addition of alloy elements within specific limits prevents excessive embrittlement, enabling both strength improvement and manufacturability.
3Loss of energy
If grains are refined to improve magnetic properties, then core loss is reduced, but grain distribution becomes non-uniform
Solution Approach 1:
The patent applies local quality control by ensuring uniform distribution of alloy elements throughout the steel sheet, which promotes homogeneous grain refinement. This localized compositional uniformity leads to consistent grain structure and uniform grain distribution, resolving the contradiction between core loss reduction and grain distribution stability.
4Loss of energy
If the thickness of the electrical steel sheet is reduced to improve high-frequency core loss, then high-frequency core loss is improved, but rollability decreases due to embrittlement
Solution Approach 1:
The patent optimizes the compositional parameters of alloy elements to achieve the right balance between embrittlement and strength. By controlling the addition amounts of Si, Al, and Mn within specific ranges, the invention enables production of thin sheets with improved high-frequency core loss while maintaining sufficient rollability for manufacturing.
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 results in a non-oriented electrical steel sheet with improved yield strength and core loss characteristics, suitable for high-speed drive motors, by ensuring fine grains are uniformly distributed and maintaining magnetic properties, thereby improving motor performance.
Implementation Method 1
precise control of pre-annealing and final annealing processes
Data Source
AI summary
A non-oriented electrical steel sheet includes by wt%, Si: 3.0 to 4.0%, Al: 0.1 to 1.5%, Mn: 0.1 to 0.5%, Cr: 2 to 20% of Mn content, a sum of Sn and Sb: 0.006 to 0.1%, C: 0.0010 to 0.0050%, and 0.0003 to 0.0050% of at least one of N, S, Ti, Nb, and V, and balance being Fe and unavoidable impurities, in which an area fraction of a grain having a grain diameter which is 10% or less of a thickness of the steel sheet is 0.5% or more, a number fraction of the grain is 20% or more, and an average grain diameter from a central layer to a surface layer in a thickness direction of the steel sheet satisfies a relationship of D(surface)/D(center) ≥ 0.6.