Grain-Oriented Steel Sheet Secondary Recrystallization Control
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Solution Overview
Problem
Current production methods for grain-oriented electrical steel sheets face challenges in achieving stable magnetic properties and glass film formation due to nonuniform temperature and atmosphere history during secondary recrystallization annealing, leading to unstable secondary recrystallization and inadequate glass film formation.
Innovation Solution
A method involving intermediate slab heating, controlled oxygen and atmosphere conditions in primary and secondary recrystallization annealing, and regulated hydrated water and chlorine content in the annealing separator to enhance Goss orientation and glass film formation, utilizing AlN as the main inhibitor and incorporating other inhibitors like MnS, MnSe, Cu-S, and Cu-Se to achieve multi-inhibitor strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxygen content of the decarburization-annealed steel sheet is increased to form a good glass film, then glass film formation is improved, but secondary recrystallization becomes unstable
Solution Approach 1:
The patent applies parameter changes by precisely controlling the oxygen content within a specific range (50-200 ppm) rather than simply increasing it. This optimized parameter range allows sufficient glass film formation while preventing excessive oxidation that would consume aluminum and impair secondary recrystallization stability.
Solution Approach 2:
The patent applies local quality by differentiating the oxygen content requirements for different functional aspects: sufficient oxygen (50-200 ppm) for glass film formation while limiting excess oxygen that would cause aluminum oxidation and destabilize secondary recrystallization. This localized control of oxygen distribution and concentration resolves the contradiction between glass film quality and recrystallization stability.
2Reliability
If oxygen content is reduced to stabilize secondary recrystallization, then secondary recrystallization stability is improved, but glass film formation becomes insufficient
Solution Approach 1:
The patent identifies and applies parameter changes by establishing the optimal oxygen content range (50-200 ppm) that simultaneously satisfies both secondary recrystallization stability and glass film formation requirements. This precise parameter optimization resolves the contradiction by finding the sweet spot where neither oxygen deficiency nor excess occurs.
3Reliability
If AlN is used as the main inhibitor for secondary recrystallization, then secondary recrystallization control is improved, but glass film formation becomes insufficient without increased oxygen content
Solution Approach 1:
The patent applies parameter changes by optimizing the oxygen content parameter to 50-200 ppm, which provides sufficient oxygen for glass film formation while maintaining AlN inhibitor effectiveness for secondary recrystallization control. This resolves the contradiction by finding the optimal oxygen level that supports both functions simultaneously.
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 excellent magnetic properties and improved glass film formation, achieving high magnetic flux density and stable secondary recrystallization, while minimizing defects and ensuring consistent product quality across the coil.
Implementation Method 1
the kinds of inhibitor used is, for example, AlN, MnS, MnSe, Cu-S or Cu-Se, and downstream nitriding is essential
Implementation Method 2
complete solid solution, non-nitriding
Implementation Method 3
secondary recrystallization
Implementation Method 4
when excessive oxygen is present, Al oxidation inevitably occurs at the sheet surface and excessive nitrogen comes to be present in the nitrided sheet surface layer
Implementation Method 5
intermediate slab heating at 1280°C or higher
Implementation Method 6
complete solid solution
Implementation Method 7
decarburization-annealed steel sheet
Data Source
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AI summary
The invention provides a method of producing a grain-oriented electrical steel sheet of the complete solid solution nitrided type that is good in glass film formation and excellent in magnetic properties, which method comprises: C: 0.025 to 0.09%, hot-rolling the steel slab containing Si: 2.5 to 4.0% and acid-soluble Al into a hot-rolled steel strip; controlling the rate at which N contained in the hot-rolled steel strip is precipitated as AlN to a precipitation rate of 20% or less; conducting hot-rolled strip annealing and cold rolling conducting decarburization-annealing combined with primary recrystallization by during the former part of the process in an atmosphere whose PH2O/ PH2 is 0.30 to 0.70 and then during the latter part thereof in an atmosphere whose PH2O/PH2 is 0.20 or less, thereby making the circular equivalent average grain diameter of the primary recrystallization grains 7 µm to less than 18 µm; nitriding the strip as it travels in a mixed gas of hydrogen, nitrogen and ammonia; controlling the steel strip oxygen concentration before secondary recrystallization annealing calculated based on strip thickness of 0.30 mm (oxygen content: So) to 450 ppm to 700 ppm inclusive; applying a coat of annealing separator; and then conducting secondary recrystallization annealing in an atmosphere that, while the temperature at the hottest coil outer periphery point is between room temperature and 950 °C, is controlled to a nitrogen atmosphere containing oxygen: 25 to 75% wherein the balance is hydrogen and PH2O/ PH2 is 0.01 to 0.15.