Oriented Electromagnetic Steel Sheet Grain Boundary Segregation
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Solution Overview
Problem
The challenge is to manufacture grain-oriented electrical steel sheets with improved bend properties without deteriorating magnetic properties, using a slab composition with reduced S and Se, while minimizing manufacturing costs and avoiding the adverse effects of high-temperature processes.
Innovation Solution
Incorporating specific grain boundary segregation elements like Sn, Sb, Cr, P, Mo, and B into the steel composition, controlling their content to suppress silicon nitride precipitation at grain boundaries, and optimizing the annealing process to retain these elements post-purification annealing, thereby enhancing bend properties without compromising magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature slab reheating (1300°C or higher) is performed to dissolve inhibitor components, then secondary recrystallization can be achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature slab reheating (1300°C or higher) to low-temperature slab reheating (900-1100°C), fundamentally altering the thermal processing regime to eliminate the need for expensive high-temperature equipment and energy consumption while achieving the same secondary recrystallization effect through alternative mechanisms
Solution Approach 2:
The patent extracts and removes the high-temperature processing step from the conventional manufacturing flow, replacing it with a low-temperature process that uses grain boundary segregation elements (Ti, Nb, V, B, P, Al) to control precipitate formation and inhibit grain growth without requiring slab reheating to 1300°C or higher
2Reliability
If S and Se content in slab composition is reduced to improve magnetic properties, then magnetic quality improves, but bend properties deteriorate
Solution Approach 1:
The patent introduces grain boundary segregation elements (Ti, Nb, V, B, P, Al) as intermediary substances that mediate between the reduced S and Se content and the steel matrix, controlling precipitate formation at grain boundaries to maintain both improved magnetic properties and acceptable bend properties through controlled microstructure development
Solution Approach 2:
The patent creates a composite microstructure by combining low S and Se content steel with controlled precipitates of grain boundary segregation elements, forming a multi-phase system where TiN, NbN, VN, B2O3, P2O5, or Al2O3 precipitates are distributed at grain boundaries to simultaneously achieve good magnetic properties and bend resistance
3Strength
If grain boundary segregation elements are added to control precipitate formation, then bend properties improve, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent establishes specific compositional parameter ranges for grain boundary segregation elements (Ti: 0.003-0.05%, Nb: 0.003-0.05%, V: 0.003-0.05%, B: 0.0005-0.005%, P: 0.005-0.05%, Al: 0.003-0.03%) to precisely control precipitate formation, transforming the manufacturing challenge into a controlled compositional design problem with defined tolerance ranges
Solution Approach 2:
The patent implements compositional feedback control by specifying exact content ranges for multiple alloying elements that work synergistically, where the combined effect of Ti, Nb, V, B, P, and Al creates a self-regulating system for precipitate formation that maintains manufacturing precision through compositional balance rather than relying on difficult-to-control single-element additions
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 grain-oriented electrical steel sheets with significantly improved bend properties, maintaining magnetic quality, and reducing manufacturing costs by minimizing high-temperature processing requirements.
Implementation Method 1
Incorporating specific grain boundary segregation elements like Sn, Sb, Cr, P, Mo, and B into the steel composition, controlling their content to suppress silicon nitride precipitation at grain boundaries
Implementation Method 2
performing final annealing at 1200°C for around 5 hours for secondary recrystallization and purification of inhibitor components
Implementation Method 3
precipitates i.e. inhibitor components such as MnS, MnSe and AlN are contained in the slab stage, and are temporarily dissolved by slab reheating at a high temperature of 1300°C or higher
Implementation Method 4
nitrogen diffuses into the steel and, when the temperature exceeds 900°C, precipitates as substantially uniform Al-containing nitrides in the sheet thickness direction, which provides a full-thickness grain growth inhibiting capability
Data Source
AI summary
The disclosure contains, in mass% or mass ppm: C: 0.005 % or less, Si: 2.0 % to 5.0 %, Mn: 0.01 % to 0.5 %, sol.Al: 10 ppm or less, N: 15 ppm or less, S and Se: each 10 ppm or less, and three or more selected from Sn, Sb, Cr, P, Mo and B whose contents satisfy a relational expression of 0.16 ≤ [%Sn] + [%Sb] + [%Cr] + 2 × [%P] + [%Mo] + [%B] ≤ 0.50, the balance being Fe and inevitable impurities, where a number of times of repeated bending in a bend test is 10 or more.