Annealing Separator for Grain Oriented Steel Sheet
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Solution Overview
Problem
Existing annealing separators for grain-oriented electrical steel sheets cause surface roughness and film defects due to the formation of local projections on the forsterite film, which also reduce the stacking factor and gas flowability during final annealing.
Innovation Solution
An annealing separator composed of magnesia with specific properties, including controlled particle size and the addition of a water-insoluble compound like titania or silica, to maintain gas flowability and prevent surface roughness, with a composition of Cl: 0.01-0.05 mass%, B: 0.05-0.15 mass%, CaO: 0.1-2 mass%, P2O3: 0.03-1.0 mass%, and a water-insoluble compound with particle diameters between 45 µm and 150 µm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If magnesia containing particles passing through a 100-mesh sieve but not through a 325-mesh sieve (44 μm to 150 μm) is used as an annealing separator, then gas flowability in the coil is improved, but surface roughness occurs due to local projections formed on the forsterite film surface
Solution Approach 1:
The annealing separator is segmented into two functional components: fine magnesia particles (44-150 μm) that ensure gas flowability, and water-insoluble compound particles (45-150 μm) that prevent surface roughness. This segmentation allows each component to perform its specific function without interfering with the other, resolving the contradiction between gas flowability and surface quality
Solution Approach 2:
The invention uses a composite annealing separator comprising magnesia mixed with water-insoluble compounds (such as titania or silica). This composite structure combines the advantages of both materials: magnesia provides gas flowability through its particle size distribution, while the water-insoluble compounds prevent surface roughness by maintaining film uniformity. The composite material approach directly resolves the technical contradiction
2Quantity of substance
If magnesia containing particles passing through a 100-mesh sieve but not through a 325-mesh sieve (44 μm to 150 μm) is used as an annealing separator, then gas flowability is improved, but stacking factor is reduced due to surface roughness and film defects
Solution Approach 1:
The annealing separator is segmented into two functional components: fine magnesia particles (44-150 μm) that ensure gas flowability, and water-insoluble compound particles (45-150 μm) that prevent surface roughness. This segmentation allows each component to perform its specific function without interfering with the other, resolving the contradiction between gas flowability and surface quality
Solution Approach 2:
The invention uses a composite annealing separator comprising magnesia mixed with water-insoluble compounds (such as titania or silica). This composite structure combines the advantages of both materials: magnesia provides gas flowability through its particle size distribution, while the water-insoluble compounds prevent surface roughness by maintaining film uniformity. The composite material approach directly resolves the technical contradiction
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 solution enables the formation of a uniform and smooth forsterite film, enhancing the stacking factor and film properties of grain-oriented electrical steel sheets while maintaining gas flowability during final annealing.
Implementation Method 1
the magnesia also serves to react with an oxide layer mainly composed of SiO 2 , which layer is formed on a surface of the steel sheet during the decarburization annealing (primary recrystallization annealing) prior to the final annealing, to thereby form a forsterite (Mg 2 SiO 4 ) film on the surface
Implementation Method 2
it is a common practice to apply, to the steel sheet prior to the final annealing, an annealing separator mainly composed of magnesia, the annealing separator being applied as a slurry which is obtained by suspending the annealing separator with water, in order to prevent sticking of inner and outer wraps of the coiled steel sheet
Data Source
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AI summary
Provided is an annealing separator for a grain oriented electrical steel sheet, which does not inhibit the flowability of an atmospheric gas during the final annealing of the coil-shaped product and can prevent the occurrence of surface roughness. The annealing separator contains 0.01-0.05 mass% of Cl, 0.05-0.15 mass% of B, 0.1-2 mass% of CaO and 0.03-1.0 mass% of P2O3, and is mainly composed of magnesia having: a degree of activity of citric acid of 30-120 seconds as measured at 40 % CAA; a specific surface area of 8-50 m2/g as measured by a BET method; an amount of hydration of 0.5-5.2 mass% as measured in terms of ignition loss; and a content of particles each having a particle diameter of 45 µm or more of 0.1 mass% or less, the annealing separator further containing a water-insoluble compound having a particle diameter of 45-150 µm inclusive in an amount of 0.05-20 mass% inclusive.