Non-oriented electrical steel sheet with Cr oxide layer
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Solution Overview
Problem
Current non-oriented electrical steel sheets face challenges in minimizing core loss across a wide range of frequencies, particularly at high and low frequencies, while maintaining productivity and cost-effectiveness, as existing methods either increase hardness and brittleness or lead to red shortness issues with Cr addition.
Innovation Solution
A non-oriented electrical steel sheet with specific chemical composition ratios of Si, Al, and Cr, along with controlled sheet thickness and Cr oxide layer formation, to optimize resistivity and magnetic properties, thereby reducing core loss across frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If sheet thickness is decreased to reduce high-frequency core loss, then core loss is reduced, but productivity decreases and manufacturing cost increases
Solution Approach 1:
The invention changes the chemical composition parameters by adding Cr element (0.03-5 mass%) along with Si and Al, which increases electrical resistivity and reduces eddy current loss, allowing the use of thicker sheets without sacrificing high-frequency core loss performance
2Loss of energy
If Si and Al are added to increase resistivity, then resistivity increases, but hardness increases and the steel sheet becomes brittle
Solution Approach 1:
The invention creates a composite alloy system combining Si, Al, and Cr elements where Cr serves to increase resistivity without the harmful side effect of excessive hardening and embrittlement that occurs with Si and Al alone
Solution Approach 2:
The invention optimizes the composition parameters by limiting Si to 2-4.5 mass% and Al to 0.3-2.5 mass% while adding Cr at 0.03-5 mass%, achieving the desired resistivity increase while maintaining acceptable mechanical properties
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 excellent core loss performance across a wide frequency range, maintaining saturation magnetic flux density and preventing internal oxidation, thus enhancing the steel sheet's magnetic properties and reducing eddy and hysteresis losses.
Implementation Method 1
a Cr oxide layer is formed on a surface of the steel sheet... preventing internal oxidation
Implementation Method 2
it is effective to decrease a sheet thickness and have high resistivity by high alloying
Implementation Method 3
an effect of decreasing an eddy current loss
Implementation Method 4
core loss (iron loss) is evaluated
Data Source
AI summary
A non-oriented electrical steel sheet includes: C: 0.005 mass% or less; S: 0.003 mass% or less; N: 0.003 mass% or less; Si: 2.0 mass% or more and less than 4.5 mass%; Al: 0.15 mass% or more and less than 2.5 mass%; and Cr: 0.3 mass% or more and less than 5.0 mass%; and a balance being composed of Fe and inevitable impurities; and a Cr-oxide-containing layer having a thickness of not less than 0.01 µm nor more than 0.5 µm on a surface side, in which when [Si], [Al], and [Cr] are set to the Si content, the Al content, and the Cr content (mass%) of the non-oriented electrical steel sheet respectively, and t is set to a sheet thickness (mm) of the non-oriented electrical steel sheet, 10 mass% ≦ 2[Si] + 2[Al] + [Cr] < 15 mass% and (2[Al] + [Cr])/2[Si] - 10t2 ≦ 0.35 are satisfied.