Non-oriented electrical steel sheet with low Al and Cu control
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Solution Overview
Problem
Current methods for reducing iron loss in non-oriented electrical steel sheets, especially when high-temperature final annealing is performed, do not adequately improve magnetic properties in low-Al steel, as they focus on grain growth at lower temperatures and do not effectively address the pinning effect caused by Cu sulfides and selenides.
Innovation Solution
A non-oriented electrical steel sheet with a specific chemical composition, including C: 0.005% or less, Si: 1.0% to 4.5%, Mn: 0.02% to 2.0%, Sol. Al: 0.001% or less, P: 0.2% or less, S+Se: 0.0010% or less, and Cu: 0.02% to 0.30%, subjected to hot rolling, cold rolling, and final annealing at a heating rate of 40° C/s or higher, with a temperature of 900° C to 1100° C, to minimize the pinning effect and enhance magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high-temperature final annealing (900°C or higher) is performed to coarsen grains and reduce iron loss, then magnetic properties improve, but the pinning effect from Cu sulfides and selenides hinders grain growth and reduces effectiveness
Solution Approach 1:
The patent extracts and eliminates the harmful Cu sulfides and selenides from the steel sheet through strict control of S and Se content (total ≤0.0010%). By removing these pinning particles, the final annealing process can effectively coarsen grains and improve magnetic properties without interference, resolving the contradiction between reducing iron loss and maintaining magnetic properties.
Solution Approach 2:
The patent changes the chemical composition parameters by strictly limiting S and Se content while controlling Cu content within specific ranges. This parameter control prevents the formation of excessive Cu sulfides and selenides, allowing high-temperature final annealing to work effectively for grain coarsening and iron loss reduction while maintaining excellent magnetic properties.
2Loss of energy
If Al content is increased to reduce iron loss and improve blanking workability, then magnetic properties improve, but recyclability deteriorates due to electrode degradation in electric furnaces
Solution Approach 1:
The patent changes the Al content parameter to a low range (0.001% or less) while compensating for iron loss reduction through strict control of S and Se content and optimized Cu content. This alternative parameter adjustment achieves the desired magnetic properties and blanking workability without the harmful effects of high Al content on recyclability.
Solution Approach 2:
The patent replaces the traditional Al-based solution with a low-Al alternative that uses controlled Cu, S, and Se content to achieve similar or better performance. This substitute approach maintains effectiveness while eliminating the recyclability problems associated with Al-added steel.
3Manufacturing precision
If Cu content is increased to control inclusions, then inclusion formation increases, but fine Cu sulfides and selenides cause pinning effect that hinders grain growth
Solution Approach 1:
The patent optimizes the Cu content parameter within a specific range (0.01-0.10% in the example, 0.02-0.30% in the claim) and combines it with strict limits on S and Se content. This parameter optimization ensures sufficient inclusion control benefits from Cu while preventing excessive formation of fine Cu sulfides and selenides that would cause pinning effects and hinder grain growth during annealing.
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 approach results in a steel sheet with excellent magnetic properties and reduced iron loss, even when formed from low-Al steel and subjected to high-temperature annealing, by controlling the content of Cu, S, and Se to eliminate pinning effects and promote recrystallization textures.
Implementation Method 1
when the final annealing is performed at a high temperature of 900° C. or higher, grains in the steel sheet are coarsened, grain boundaries that inhibit domain wall displacement are reduced, and as a result the iron loss decreases
Implementation Method 2
final annealing at a heating rate from 100° C. to 700° C. of 80° C./s in which the steel sheet is retained at 970° C. for 10 s
Implementation Method 3
If fine Cu sulfides or Cu selenides are present in the steel sheet microstructure, a pinning effect is caused during a heat treatment such as final annealing. When a pinning effect occurs, growth of secondary recrystallized grains during final annealing is hindered
Implementation Method 4
final annealing at a heating rate from 100° C. to 700° C. of 80° C./s
Data Source
AI summary
Disclosed is a non-oriented electrical steel sheet that is low in iron loss and exhibits excellent magnetic properties even when subjected to final annealing at high temperature. The non-oriented electrical steel sheet can be obtained from a steel (low-Al steel) having a chemical composition containing, in mass %, C: 0.005% or less, Si: 1.0% to 4.5%, Mn: 0.02% to 2.0%, Sol. Al: 0.001% or less, P: 0.2% or less, S+Se: 0.0010% or less, N: 0.005% or less, O: 0.005% or less, and Cu: 0.02% to 0.30%, and the balance consisting of Fe and incidental impurities.