Non-Oriented Electrical Steel Composition for Stable Magnetic Properties
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Solution Overview
Problem
Current methods for producing non-oriented electrical steel sheets struggle to achieve low iron loss and high magnetic flux density while maintaining cost-effectiveness, as they often require special processes that increase production costs or result in unstable magnetic properties.
Innovation Solution
A non-oriented electrical steel sheet with a specific chemical composition, including controlled amounts of C, Si, Mn, Al, Ti, Nb, V, Zr, N, S, B, and Sn, and a production process involving hot rolling and annealing conditions to manage B and AlN formation, ensuring good grain growth and magnetic properties without excessive costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-grade starting materials with increased Si and Al content are used to increase resistivity and crystal grain size, then magnetic performance is improved, but production cost increases significantly
Solution Approach 1:
The invention changes the chemical composition parameters by strictly controlling Si content to 1.50% or less and Al content to 0.05% or less, while adding specific microalloying elements (Ti: 0.0005-0.0050%, Nb: 0.0005-0.0050%, V: 0.0005-0.0050%, Zr: 0.0005-0.0050%) and B (0.0003-0.0030%). This parameter optimization achieves low iron loss and high magnetic flux density without requiring high Si-Al content, thus reducing production cost while maintaining magnetic performance.
2Reliability
If special processes are applied to promote grain growth during stress relief annealing, then iron loss is reduced, but production cost increases
Solution Approach 1:
The invention performs preliminary grain growth promotion during hot rolling by holding the slab temperature at 1000-1050°C for 30 minutes or more before rolling, and by controlling the accumulative rolling ratio within 900-1000°C to be 70% or more. This preliminary grain growth action eliminates the need for additional special processes during stress relief annealing, reducing production cost while achieving the required grain size for low iron loss.
Solution Approach 2:
The invention optimizes hot rolling parameters including holding temperature (1000-1050°C for 30+ minutes), accumulative rolling ratio (70% or more within 900-1000°C), and post-rolling holding (700-780°C for 30+ minutes). These parameter changes promote grain growth during the hot rolling process itself, achieving low iron loss without requiring expensive special processes.
3Reliability
If Al content is increased to promote grain growth, then magnetic properties improve, but scrap castability deteriorates
Solution Approach 1:
The invention strictly limits Al content to 0.05% or less, which is sufficient for deoxidation but low enough to ensure good scrap castability. Instead of relying on high Al content for grain growth, the invention achieves grain growth through controlled hot rolling parameters and microalloying with Ti, Nb, V, Zr, and B, thus maintaining both magnetic properties and scrap castability.
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 provides a non-oriented electrical steel sheet with favorable iron loss and magnetic flux density after stress relief annealing, ensuring stable production at a low cost by optimizing grain growth and magnetic properties through precise chemical composition and processing.
Implementation Method 1
before performing hot rolling, a temperature of the slab is held within a range of 1000 to 1050° C. for 30 minutes or more
Implementation Method 2
after hot rolling is performed, a temperature of the hot-rolled steel sheet is held within a range of 700° C. or more to less than 780° C. for 30 minutes or more
Implementation Method 3
the cold-rolled steel sheet is heated to a highest temperature reached of 800° C. or more to less than 850° C. at an average heating rate of 20° C./s or more
Implementation Method 4
the number of oxide particles having a size with a diameter ranging from 0.5 pm or more to 5 μm or less in the steel is 1000 particles or more to 50000 particles or less per cm2
Data Source
AI summary
A non-oriented electrical steel sheet is provided which has a chemical composition including, in mass %, C: 0.0010 to 0.0050%, Si: 1.50% or less, Mn: 0.10 to 1.50%, sol. Al: 0.010 to 0.040%, Ti: 0.0030% or less, Nb: 0.0030% or less, V: 0.0030% or less, Zr: 0.0030% or less, N: 0.0030% or less, S: 0.0040% or less, B: 0.0045% or less, and the balance: Fe and impurities, and which satisfies [0.0020≤Ti+Nb+V+Zr≤0.0120], [0.5≤B/N≤1.5], [sol. B≤0.0005], and [NAlN≤0.0005].