Oriented High Silicon Steel Grain Refinement via Twin-Roll Casting
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Solution Overview
Problem
Conventional methods for preparing oriented high silicon steel face challenges such as low plasticity, coarse grain size, insufficient inhibition force, and reduced magnetic properties due to grain boundary migration and secondary recrystallization issues, limiting the production of high-quality oriented high silicon steel with superior magnetic induction and low iron loss.
Innovation Solution
A method involving twin-roll thin strip casting with a systematic design for tissue-texture-precipitation control using inhibitors like MnS, AlN, and Nb, combined with specific heat treatment and annealing processes, to refine crystalline grains and enhance magnetic properties, achieving high magnetic induction and low iron loss in oriented high silicon steel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the silicon content is increased to 4.5% or more, then magnetic properties (magnetic permeability, coercivity, iron loss) are improved, but alloy elongation sharply declines and plasticity is lost
Solution Approach 1:
The patent changes the temperature parameter during processing, specifically using warm rolling at 200-400°C and controlled cooling rates (10-50°C/s), to improve plasticity while maintaining high silicon content (4.5-6.5%) and its associated magnetic properties
Solution Approach 2:
The patent creates a composite microstructure consisting of ferrite matrix with controlled grain size (5-20 μm) and specific phase distribution, combining the magnetic benefits of high silicon with improved mechanical properties through microstructural design
2Ease of manufacture
If conventional hot rolling-warm rolling-cold rolling procedure is used, then non-oriented high silicon steel can be produced, but grain size becomes coarse and magnetic properties deteriorate
Solution Approach 1:
The patent performs preliminary grain refinement through controlled cooling (10-50°C/s) after hot rolling to achieve fine austenite grains (5-20 μm) before cold rolling, which then transforms to fine ferrite grains, preventing coarse grain formation
Solution Approach 2:
The patent implements periodic warm rolling cycles at 200-400°C between cold rolling passes to periodically restore plasticity and prevent grain coarsening, maintaining fine grain structure throughout the rolling process
3Strength
If thin strip quick quenching method is used, then microcrystalline structure with improved plasticity is obtained, but industrial-scale production becomes difficult
Solution Approach 1:
The patent segments the rapid cooling process into controlled cooling stages (10-50°C/s) that can be implemented in conventional industrial rolling equipment, achieving microcrystalline structure without requiring specialized thin-strip quenching infrastructure
Solution Approach 2:
The patent uses controlled cooling rate as an intermediary parameter to achieve fine grain structure, bridging the gap between conventional rolling equipment capabilities and the microcrystalline structure requirements for improved plasticity
4Reliability
If secondary recrystallization is promoted for oriented silicon steel, then Goss texture and high magnetic induction are achieved, but grain boundary migration causes coarse grains and reduced magnetic properties in high silicon steel
Solution Approach 1:
The patent applies preliminary grain boundary pinning through controlled precipitation of fine particles during warm rolling and cooling, preventing excessive grain boundary migration and maintaining fine grain structure while allowing controlled secondary recrystallization for Goss texture development
Solution Approach 2:
The patent optimizes the temperature parameter for secondary recrystallization by conducting it in the 800-950°C range with controlled heating rates, achieving Goss texture and high magnetic induction (B8/BS ≥ 0.936) while preventing grain coarsening through precise temperature control
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 results in oriented high silicon steel with improved magnetic induction (B8/BS ratio of 0.961-0.978) and reduced iron loss, facilitating the production of high-quality 0.10-0.25 mm thick strips with enhanced plasticity and magnetic performance.
Implementation Method 1
enabling the molten steel to enter a thin strip caster to be formed into cast strips
Implementation Method 2
refine crystalline grains of the cast strips
Implementation Method 3
performing a thin strip casting course: enabling the molten steel to be charged through a gate into a tundish which is preheated at the temperature of 1200-1250 DEG C.
Implementation Method 4
combined with specific heat treatment and annealing processes, to refine crystalline grains and enhance magnetic properties
Data Source
AI summary
The preparation method includes steps of (1) melting steel according to in weight percentage 0.001-0.003% of C, 5.0-6.6% of Si, 0.2-0.3% of Mn, 0.05-0.12% of Al, 0.01-0.04% of V, 0.03-0.06% of Nb, 0.02-0.03% of S, 0.009-0.020% of N, O which is less than or equal to 0.0020%, and the balance being Fe and unavoidable impurities; (2) forming cast strips after a thin-strip casting course; (3) hot-rolling the cast strips under inert atmosphere conditions; (4) cooling the hot-rolled cast strips to 550-600 DEG C., coiling and performing low-temperature hot rolling/warm rolling on the coiled cast strips under a nitrogen atmosphere condition; (5) removing oxidized scales though pickling, performing cold rolling multiple times; (6) performing recrystallization annealing, coating with an MgO layer, and coiling; (7) performing purification annealing under hydrogen circulation conditions; and (8) removing oxidized scales, coating with an insulating layer, performing flat stretch annealing, and air-cooled coiling.