Magnesium Oxide Annealing Separator for Uniform Forsterite Coating
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Solution Overview
Problem
Existing annealing separators containing copper diffuse into the steel sheet during high temperature annealing, affecting the magnetic properties of grain-oriented electromagnetic steel sheets.
Innovation Solution
The use of magnesium oxide with a specific particle structure, comprising reticular and plate-shaped particles, and controlled trace elements, allows for even coating and minimizes copper diffusion, ensuring uniform application and improved magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copper is added to the annealing separator to improve forsterite film properties, then film uniformity and adhesiveness are improved, but copper diffuses into the steel sheet during high temperature annealing, degrading magnetic properties
Solution Approach 1:
The patent extracts copper from the annealing separator composition entirely, using magnesium oxide with specific particle morphology (reticular and plate-shaped particles in 1:99 to 20:80 ratio) instead. This removes the source of copper diffusion while maintaining film formation capability through the specialized particle structure that enables uniform forsterite coating.
Solution Approach 2:
The patent changes the physical and chemical parameters of magnesium oxide by controlling particle size distribution (D10: 0.65-1.7 μm, D50: 1.5-3.6 μm, D90: 2.0-14 μm) and particle morphology (reticular with multiple depressions and plate-shaped). These parameter changes enable uniform slurry application and forsterite film formation without requiring copper addition.
2Strength
If copper is added to the annealing separator to improve forsterite film adhesiveness, then film adhesiveness is improved, but copper content in steel sheet increases, adversely affecting magnetic properties
Solution Approach 1:
The patent removes copper from the annealing separator formulation entirely, achieving film adhesiveness through the interfacial interaction between the specialized magnesium oxide particle structure and the steel sheet surface, followed by forsterite film formation during annealing. This eliminates copper transfer to the steel sheet while maintaining adequate adhesiveness.
3Area of stationary object
If copper is added to the annealing separator to improve forsterite film occupancy factor, then film coverage is improved, but copper diffusion into steel sheet increases, degrading magnetic properties
Solution Approach 1:
The patent achieves uniform film coverage by optimizing magnesium oxide particle size distribution (D10: 0.65-1.7 μm, D50: 1.5-3.6 μm, D90: 2.0-14 μm) and morphology. The reticular particles with multiple depressions and plate-shaped particles in specific ratios enable homogeneous slurry application and complete surface coverage during the annealing process without requiring copper addition.
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 magnesium oxide enables uniform coating of the steel sheet, forming a forsterite coating film with satisfactory properties, resulting in improved magnetic properties of the grain-oriented electromagnetic steel sheet.
Implementation Method 1
an annealing separator composed mainly of magnesium oxide is coated onto surfaces of a decarburized annealed steel sheet. This forms a forsterite coating film on the surfaces of the steel sheet
Implementation Method 2
it is important for the annealing separator slurry to be uniformly applied onto the steel sheet
Implementation Method 3
a large amount of copper to diffuse throughout the steel sheet during the high temperature annealing step
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3~4
AI summary
Provided is a magnesium oxide for an annealing separator that allows a slurry of the magnesium oxide for an annealing separator to be evenly applied onto a steel sheet. The magnesium oxide for an annealing separator comprises reticular particles having multiple depressions on the surfaces, and plate-shaped particles. A proportion of the number of plate-shaped particles and the number of reticular particles is 1:99 to 20:80.