Grain-Oriented Steel Sheet Nitridation for Stable Recrystallization
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Solution Overview
Problem
Existing methods for producing grain-oriented electrical steel sheets face challenges such as unstable secondary recrystallization, coarse grain formation, and high energy consumption due to ultra-high slab heating temperatures, which affect magnetic properties and productivity.
Innovation Solution
A method involving high-temperature slab heating using AlN as a primary inhibitor, followed by controlled nitridation and annealing processes to achieve uniform inhibitor strength and optimal magnetic properties, without the need for extreme temperatures or specialized equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultra-high slab heating temperature (≥1300°C) is used to achieve complete solid solution and uniform inhibitor distribution, then magnetic properties and secondary recrystallization stability are improved, but energy consumption increases and coarse grain formation occurs
Solution Approach 1:
The patent changes the heating temperature parameter from ultra-high (≥1300°C) to moderate (900-1200°C) range, combined with extended holding time (30-180 seconds) to achieve complete solid solution of AlN inhibitors without the energy waste and coarse grain problems of conventional methods
2Stability of the object's composition
If ultra-high slab heating temperature (≥1300°C) is used to secure uniform solid solution state and productivity, then inhibitor distribution uniformity is improved, but coarse grain formation and streak-like poor secondary recrystallization occur
Solution Approach 1:
The patent changes the heating temperature parameter from ultra-high (≥1300°C) to moderate (900-1200°C) range, combined with extended holding time (30-180 seconds) to achieve complete solid solution of AlN inhibitors without the energy waste and coarse grain problems of conventional methods
Solution Approach 2:
The patent performs preliminary complete solid solution of AlN inhibitors at moderate temperature before the final annealing process, ensuring uniform inhibitor distribution is achieved in advance, which prevents coarse grain formation during subsequent processing
3Quantity of substance
If nitridation is performed after decarburization annealing to supplement inhibitors, then inhibitor amount is increased, but Goss orientation sharpness deteriorates
Solution Approach 1:
The patent performs preliminary complete solid solution of AlN inhibitors at moderate temperature before the final annealing process, ensuring uniform inhibitor distribution is achieved in advance, which prevents coarse grain formation during subsequent processing
Solution Approach 2:
The patent extracts the nitridation step from the conventional sequence and performs it at a specific stage (after decarburization annealing but with controlled parameters) to supplement inhibitors without allowing excessive nitrogen to form that would harm Goss orientation sharpness
4Use of energy by moving object
If slab heating temperature is reduced below 1280°C to avoid ultra-high temperature problems, then energy consumption decreases, but incomplete solid solution and non-uniform inhibitor distribution occur
Solution Approach 1:
The patent changes the heating temperature parameter from ultra-high (≥1300°C) to moderate (900-1200°C) range, combined with extended holding time (30-180 seconds) to achieve complete solid solution of AlN inhibitors without the energy waste and coarse grain problems of conventional methods
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
This approach results in a grain-oriented electrical steel sheet with enhanced magnetic flux density and improved production efficiency, overcoming fluctuations in inhibitor content and achieving stable secondary recrystallization.
Implementation Method 1
making a ratio of precipitation of the N contained in the steel strip after the hot rolling as AlN 20% or less
Implementation Method 2
nitriding it after the decarburization annealing in a mixed gas of hydrogen, nitrogen, and ammonia in the strip running state
Implementation Method 3
reheating a slab to 1280°C or more and a solid solution temperature of the inhibitor substances or more
Implementation Method 4
decarburization annealing it
Data Source
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AI summary
Reheating a grain-oriented electrical steel sheet slab comprising predetermined components to 1280°C or more and a solid solution temperature of inhibitor substances or more, hot rolling, annealing, and cold rolling it, decarburization annealing it, nitriding it in a strip running state, coating an annealing separator, and finish annealing it during which making a precipitation ratio of N as AlN after hot rolling 20% or less, making a mean grain size of primary recrystallization 7 µm to less than 20 µm, and making a nitrogen increase ΔN in the nitridation within a range of Equation (1) and making nitrogen contents σN1 and σN2 (front and back, mass%) of a 20% thickness portion of one surface of the steel strip (sheet) within a range of Equation (2): 0.007-N-14/48×Ti≤ΔN≤solAl×14/27-N-14/48×Ti+0.0025 σN1-σN2/ΔN≤0.35