Non-Oriented Electrical Steel Sheet Annealing for Strength and Cold Rolling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing non-oriented electrical steel sheets struggle to simultaneously enhance magnetic properties and yield strength at low and high temperatures, often resulting in increased manufacturing costs, decreased productivity, and quality deviations due to brittleness and non-uniformity issues.
Innovation Solution
A method involving twice hot-rolled sheet annealing and twice cold-rolled sheet annealing with controlled residence times in specific temperature ranges, along with precise alloy compositions (2.5-4.0% Si, 0.1-1.5% Al, 0.1-1.5% Mn, and additional elements) to achieve optimal grain size distribution and strength, while maintaining magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If alloy elements (Si, Al, Mn) are added to increase resistivity and strength, then eddy current loss is reduced and strength is increased, but magnetic flux density deteriorates and brittleness increases making cold rolling impossible
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ranges of alloy elements (Si: 2.0-4.5%, Al: 0.1-2.0%, Mn: 0.1-2.0%) and implementing specific annealing temperature ranges (950-1150°C for first hot-rolled annealing, 900-1100°C for first cold-rolled annealing) with controlled residence times. This optimization balances the strengthening effect with maintaining sufficient ductility for cold rolling, resolving the contradiction between strength enhancement and manufacturability.
2Strength
If alloy element content is increased to improve strength, then yield strength increases, but brittleness increases and quality uniformity deteriorates
Solution Approach 1:
The patent optimizes alloy element content within specific ranges rather than using excessive amounts, and controls annealing parameters (temperature and residence time) to achieve uniform microstructure. The double annealing process with controlled residence times ensures homogeneous grain structure and property distribution throughout the steel sheet, maintaining quality uniformity while achieving high yield strength.
Solution Approach 2:
The patent employs periodic action through the double annealing process, where the steel sheet undergoes two distinct annealing cycles (hot-rolled annealing followed by cold-rolled annealing) with different temperature ranges and residence times. This periodic heat treatment ensures uniform microstructure development and property homogenization, improving quality uniformity while achieving the desired high strength characteristics.
3Loss of energy
If magnetic properties are improved by alloy addition, then iron loss is reduced, but strength at high temperature deteriorates
Solution Approach 1:
The patent creates a composite microstructure through the combination of multiple alloy elements (Si, Al, Mn) working synergistically. Si increases resistivity to reduce eddy current loss, Al and Mn provide solid solution strengthening and form precipitates for age hardening. This composite approach at the microstructural level achieves both low iron loss and high high-temperature strength simultaneously.
Solution Approach 2:
The double annealing process with controlled residence times enables periodic microstructure evolution that develops both magnetic properties and strength. The first annealing cycle establishes the base microstructure for good magnetic properties, while the second cycle optimizes precipitate distribution for high-temperature strength, achieving both objectives simultaneously.
4Loss of energy
If grain size is reduced to improve magnetic properties, then iron loss decreases, but yield strength at high temperature decreases
Solution Approach 1:
The patent creates a composite microstructure combining fine grains with age-hardening precipitates. The fine grain structure (achieved through controlled rolling and annealing) provides good magnetic properties and low iron loss, while the precipitates formed during controlled cooling and second annealing provide age-hardening that maintains high yield strength at elevated temperatures, resolving the contradiction between grain size and 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 method effectively produces non-oriented electrical steel sheets with improved iron loss, yield strength, and magnetic flux density, enabling stable high-speed motor operation across a wide temperature range, enhancing the efficiency of eco-friendly vehicle drive motors.
Implementation Method 1
twice hot-rolled sheet annealing and twice cold-rolled sheet annealing with controlled residence times in specific temperature ranges
Implementation Method 2
If the resistivity of the steel is increased through the addition of these alloy elements, the eddy current loss may be reduced
Implementation Method 3
the alloy element is employed as a substitutional element to iron to cause a strengthening effect, thereby increasing the strength
Data Source
AI summary
A non-oriented electrical steel sheet according to an embodiment of the present invention may include, by wt %, 2.5 to 4.0% of Si, 0.1 to 1.5% of A1, 0.1 to 1.5% of Mn, and the remainder of Fe and inevitable impurities.In the non-oriented electrical steel sheet according to an embodiment of the present invention, an average grain size is 50 to 100 μm, and an area ratio of grains having a grain size of 20 μm or less is 0.5% or more.