Grain-Oriented Steel Sheet Annealing Separator Composition
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Solution Overview
Problem
Existing methods for manufacturing grain-oriented electrical steel sheets face challenges in achieving high secondary coating adhesion without impairing magnetic characteristics, and some methods require intermediate annealing, which increases manufacturing load.
Innovation Solution
A manufacturing method that includes specific chemical compositions and controlled atmospheric conditions during annealing to form a Fe-Al-P-O compound at the interface between the base steel sheet and secondary coating, ensuring high coating adhesion without intermediate annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a primary coating is formed through conventional finish annealing, then adhesion of secondary coating is improved, but magnetic characteristics deteriorate due to non-magnetic phase and complicated interface structure
Solution Approach 1:
The invention extracts and eliminates the primary coating (glass coating containing forsterite) from the conventional structure by controlling the annealing separator composition to prevent its formation. This removes the harmful non-magnetic phase and complicated interface structure while preserving the necessary secondary coating adhesion through direct bonding to the steel sheet surface.
Solution Approach 2:
The invention creates a locally optimized interface structure where the secondary coating directly bonds to the steel sheet surface without forming a thick primary coating layer. By controlling the annealing separator composition (MgO: 0.01-5.0 mass%, Al2O3: 95.0-99.99 mass%), the interface achieves both good adhesion and minimal interference with magnetic domain wall motion.
2Strength
If intermediate annealing is performed to improve coating adhesion, then secondary coating adhesion is enhanced, but manufacturing complexity and production time increase
Solution Approach 1:
The invention performs preliminary action by optimizing the annealing separator composition before the finish annealing step to ensure that the secondary coating will adhere properly without requiring intermediate annealing. The controlled composition (low MgO, high Al2O3) prepares the steel sheet surface in advance to accept secondary coating directly after finish annealing and pickling.
Solution Approach 2:
The invention maintains continuous production flow by eliminating the intermediate annealing step. The process proceeds continuously from finish annealing → pickling → secondary coating application, maintaining productivity while achieving the desired coating adhesion through the optimized annealing separator composition.
3Reliability
If no primary coating is formed by adding chloride to annealing separator, then magnetic characteristics are improved, but secondary coating adhesion becomes insufficient
Solution Approach 1:
The invention changes the compositional parameters of the annealing separator by strictly limiting MgO content (0.01-5.0 mass%) and maximizing Al2O3 content (95.0-99.99 mass%). This parameter optimization ensures that the separator prevents primary coating formation (improving magnetic characteristics) while still enabling sufficient secondary coating adhesion through direct surface bonding.
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 produces a grain-oriented electrical steel sheet with improved coating adhesion and magnetic characteristics by forming a Fe-Al-P-O compound, enhancing iron loss characteristics and surface smoothness.
Implementation Method 1
MgO in the annealing separator reacts with SiO2 in an internal oxide layer formed on the surface of the cold-rolled steel sheet during the decarburization annealing, such that a glass coating (also referred to as 'primary coating') containing forsterite (Mg2SiO4) as a main component is formed on the surface of the base steel sheet
Implementation Method 2
a steel sheet that contains silicon (Si) in an amount of about 0.5 mass% to 7 mass% and has crystal orientations integrated in an {110} orientation (Goss orientation) by utilizing a phenomenon called secondary recrystallization
Implementation Method 3
a baking step of subjecting the surface-treated steel sheet coated with the insulating coating forming solution to a heat treatment to form a tension-applying insulating coating
Data Source
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AI summary
A method for manufacturing a grain-oriented electrical steel sheet includes a tension-applying insulating coating forming step including an insulating coating chemical solution applying step of applying an insulating coating forming solution to a surface of a surface-treated steel sheet whose surface has been pickled, and a baking step of subjecting the surface-treated steel sheet coated with the insulating coating forming solution to a heat treatment to form a tension-applying insulating coating on the surface of the surface-treated steel sheet, in which the heat treatment in the baking step includes a temperature rising process and a soaking process, in the temperature rising process, the average temperature rising rate of the steel sheet in a steel sheet temperature range of 100°C to 600°C is 10°C/s to 400°C/s in an atmosphere having an oxygen concentration of 1 vol% to 21 vol% and a dew point of 0°C to 30°C, and in the soaking process, a holding time, at a constant steel sheet temperature in a range of 800°C to 1000°C and in a soaking atmosphere whose hydrogen concentration is 1 vol% to 15 vol% and whose atmosphere dew point is a constant value in a range of -20°C to +40°C, is 5 seconds to 200 seconds.