Grain-Oriented Electrical Steel Coating With Retained Scale Layer
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Solution Overview
Problem
The existing production processes for grain-oriented electrical steel sheets face challenges in forming a uniform insulation coating layer and ensuring adequate adhesion between the steel sheet and the coating due to the presence of Fe on the surface after pickling.
Innovation Solution
A grain-oriented electrical steel sheet is developed with a substrate, a scale layer, and a metal oxide layer containing a forsterite compound, where the F content is between 0.1 to 3 wt%. The manufacturing method involves hot-rolling, cold-rolling, primary and secondary recrystallization annealing, and the use of an annealing separator containing magnesium oxide or magnesium hydroxide and fluoride.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pickling process is used to remove surface scale after hot rolling, then the surface cleanliness is improved, but the adhesion between the steel sheet and insulation coating layer deteriorates
Solution Approach 1:
The patent extracts only part of the surface scale rather than removing all of it. By selectively retaining a portion of the scale layer after hot rolling, the surface provides adequate binding sites for oxide formation while maintaining sufficient cleanliness for coating application, thus resolving the contradiction between surface cleanliness and adhesion.
Solution Approach 2:
The patent changes the parameter of scale layer thickness from complete removal to partial retention. By controlling the remaining scale thickness to form an appropriate oxide film, the surface properties are optimized to provide both cleanliness and adhesion, solving the contradiction between these two requirements.
2Manufacturing precision
If all surface scale is removed to improve surface quality, then the surface uniformity is improved, but the binding force with functional groups O and OH decreases
Solution Approach 1:
The patent extracts only the excessive or harmful portion of the scale layer while retaining a controlled amount that provides sufficient binding sites. This selective extraction maintains surface uniformity for coating application while preserving the chemical binding capability with O and OH groups.
Solution Approach 2:
The patent creates local quality variation in the surface treatment, where different regions or depths of the surface have different characteristics. The retained scale provides binding sites while the overall surface maintains uniformity, allowing both requirements to be satisfied simultaneously through spatial differentiation of surface properties.
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 proposed solution improves the adhesion between the steel sheet and the insulation coating layer, reduces iron loss due to thermal expansion differences, and provides insulating properties, while preventing fusion during winding and ensuring uniform metal oxide layer formation.
Implementation Method 1
reduces iron loss due to thermal expansion differences
Implementation Method 2
annealing the cold-rolled sheet coated with the annealing separator through secondary recrystallization, wherein the annealing separator includes magnesium oxide (MgO) or magnesium hydroxide (MgOH) and fluoride
Implementation Method 3
the binding force with functional groups O and OH does not act greatly on the surface of the steel sheet
Data Source
AI summary
Provided is a manufacturing method of a grain-oriented electrical steel sheet including preparing a hot-rolled sheet by hot-rolling a slab; removing some of scales formed on the hot-rolled sheet and leaving a scale layer having a thickness of 10 nm or more to prepare a hot-rolled sheet on which the scale layer remains; preparing a cold-rolled sheet by cold-rolling the hot-rolled sheet on which the scale layer remains; preparing the decarburization annealed cold-rolled sheet by decarburization annealing the cold-rolled sheet; coating an annealing separator on the decarburization annealed cold-rolled sheet to form a metal oxide layer; and final annealing the steel sheet on which the metal oxide layer is formed, wherein the annealing separator includes magnesium oxide (MgO) or magnesium hydroxide (MgOH) and fluoride.