Non-Oriented Electrical Steel Grain Control for Iron Loss and Strength
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Solution Overview
Problem
Existing non-oriented electrical steel sheets fail to simultaneously achieve low iron loss and high strength required for motors in electric vehicles and hybrid vehicles, as previous technologies are insufficient in realizing these characteristics without compromising yield or mechanical properties.
Innovation Solution
A non-oriented electrical steel sheet with a specific chemical composition and grain size, including Si, Mn, and Al, and an insulation coating, which balances magnetic and mechanical properties by optimizing electric resistance, grain size, and annealing processes to enhance strength and reduce iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a non-oriented electrical steel sheet is designed for low iron loss (excellent magnetic characteristics), then magnetic performance is improved, but strength deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (Si: 3.0-5.0%, Mn: 0.10-2.0%, P: 0.030% or less, S: 0.0050% or less, C: 0.0050% or less) and processing parameters (grain size: 40-120 μm, annealing temperature: 800-1050°C, annealing time: 1-300 seconds) to simultaneously achieve low iron loss and high strength. The specific composition ranges and processing conditions create an optimal balance between magnetic properties and mechanical strength.
Solution Approach 2:
The patent creates a composite microstructure through controlled grain size (40-120 μm) and specific phase distribution achieved by the annealing process. The combination of Si and Mn in specific ratios creates a composite effect that simultaneously improves magnetic characteristics and strength, while the grain boundary structure acts as a composite feature that enhances both properties.
2Reliability
If separate non-oriented electrical steel sheets are produced for stator and rotor to satisfy different characteristics, then performance requirements are met, but manufacturing yield deteriorates
Solution Approach 1:
The patent achieves universality by developing a single non-oriented electrical steel sheet composition and processing regime that can be used for both stator and rotor applications. The steel sheet simultaneously provides excellent magnetic characteristics for the stator and high strength for the rotor, eliminating the need for separate material specifications and improving manufacturing yield.
3Loss of energy
If stress relieving annealing is performed to achieve low iron loss for stator, then magnetic characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating alloying elements (Si: 3.0-5.0%, Mn: 0.10-2.0%) during steelmaking that pre-establish the conditions for low iron loss. This preliminary compositional design allows the steel to achieve excellent magnetic characteristics with simpler subsequent annealing treatment compared to conventional steels that require more complex stress relieving processes.
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 achieves a non-oriented electrical steel sheet with high strength and excellent magnetic characteristics, suitable for both stator and rotor applications, improving energy efficiency and manufacturing feasibility.
Implementation Method 1
the average grain size of the base metal is more than 40 μm and 120 μm or less
Implementation Method 2
an insulation coating on a surface of the base metal
Data Source
AI summary
This non-oriented electrical steel sheet includes a base metal having a predetermined chemical composition satisfying the expression [Si+0.5×Mn≥4.3], and an average grain size of the base metal is more than 40 μm and 120 μm or less.