Non-Oriented Electrical Steel Sheet With Controlled Texture for Low Iron Loss
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Solution Overview
Problem
Existing methods for producing non-oriented electrical steel sheets with high strength and low iron loss are inadequate, particularly in high-frequency applications, as they result in varying fatigue strength and high iron loss due to limitations in alloy content and texture control.
Innovation Solution
A non-oriented electrical steel sheet with a specific chemical composition and production process, including high Si and Al content, controlled texture through non-recrystallized structure, and optimized rolling and annealing conditions to achieve high tensile and fatigue strength with low iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large amount of solid-solution strengthening element (Si, Al) is added to iron to form high alloy steel, then high strength and low iron loss are attained, but manufacturing cost increases and alloy content control becomes complex
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters within specific ranges (C: 0.0005-0.0050 mass%, Si: 3.00-5.00 mass%, Mn: 0.01-2.00 mass%, P: 0.0050-0.0200 mass%, S: 0.0005-0.0050 mass%, Al: 0.50-2.00 mass%). This systematic parameter control resolves the contradiction by establishing optimal composition ranges that achieve high strength and low iron loss while managing manufacturing complexity through defined specifications.
Solution Approach 2:
The patent creates a composite material system by combining multiple alloying elements (Si, Mn, P, S, Al) in specific proportions to form a complex steel composition. This composite approach allows the material to achieve superior mechanical properties and magnetic characteristics that cannot be obtained with single-element strengthening, resolving the contradiction between strength requirements and manufacturing simplicity.
2Strength
If precipitation strengthening is used to achieve high strength by forming high alloy steel, then high strength is attained, but the precipitated second phase grains considerably block the grain growth in finish annealing or stress-relief annealing
Solution Approach 1:
The patent changes the strengthening mechanism parameter from precipitation strengthening to non-recrystallized texture control. By adjusting the alloy composition parameters (particularly Si: 3.00-5.00 mass% and Al: 0.50-2.00 mass%) and controlling the annealing temperature parameter (550-650°C), the patent achieves high strength through texture control rather than precipitation, thereby avoiding the grain growth blocking problem.
3Strength
If crystal grains are made finer to increase strength, then high strength is attained, but the stator core cannot achieve low iron loss without stress-relief annealing
Solution Approach 1:
The patent applies segmentation by differentiating the treatment of rotor core and stator core materials. The rotor core uses the invention's specific composition and non-recrystallized texture for high strength, while the stator core can use conventional grain-grown material for low iron loss. This segmentation allows each component to be optimized independently, resolving the contradiction between rotor strength requirements and stator efficiency requirements.
Solution Approach 2:
The patent implements local quality by providing different material properties for different parts of the motor. The rotor core material has high strength characteristics through non-recrystallized texture control, while the stator core material can have low iron loss characteristics through conventional grain growth. This localized optimization resolves the contradiction by allowing different regions to have different microstructural characteristics suited to their specific functional requirements.
4Strength
If non-recrystallized texture is used to attain high strength, then high strength is achieved, but fatigue strength varies largely
Solution Approach 1:
The patent resolves the fatigue strength variation problem by changing multiple parameters simultaneously: alloy composition parameters (Si: 3.00-5.00 mass%, Mn: 0.01-2.00 mass%, Al: 0.50-2.00 mass%), impurity control parameters (C: 0.0005-0.0050 mass%, P: 0.0050-0.0200 mass%, S: 0.0005-0.0050 mass%), and annealing temperature parameter (550-650°C). This multi-parameter optimization achieves consistent non-recrystallized texture that provides both high tensile strength and stable fatigue strength.
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 stabilizes fatigue strength and reduces iron loss, making the steel suitable for high-speed motor applications by ensuring a balanced strength and low iron loss, suitable for motor cores in electric and hybrid vehicles.
Implementation Method 1
A method for attaining high strength includes, for example, a method of adding a large amount of a solid-solution strengthening element such as Si, Al and the like to iron
Implementation Method 2
there are proposed other methods for increasing the strength of a non-oriented electrical steel sheet. For example, Patent Literatures 1 and 2 propose a method of attaining high strength by using non-recrystallized texture
Implementation Method 3
the Al and Mn contents are limited to a relatively low amount, causing a problem of low specific resistance and high iron loss at a high-frequency
Implementation Method 4
a method of using precipitation strengthening to achieve high strength by forming a high alloy steel, but the method has a problem that the precipitated second phase grains considerably block the grain growth in finish annealing or stress-relief annealing
Data Source
AI summary
In a production of a non-oriented electrical steel sheet comprising subjecting a slab containing a particular composition to a hot rolling, a hot-band annealing, a cold rolling to form a cold-rolled sheet and a finish annealing, a rolling reduction of a final finish rolling pass in the hot rolling is not less than 10%, and a coiling temperature is not higher than 620° C., and a soaking temperature in the finish annealing is 600 to 800° C. to achieve such properties that a recrystallization ratio is less than 100% as an area ratio, a strength C is not less than 2.0 and a strength difference C-D is not more than 2.0, where C is a strength at Φ=0° and φ1=0° and D is a strength at Φ=20° and φ1=0° in a section of φ2=45° of ODF obtained in a central layer of a sheet thickness.