Grain-Oriented Steel Oxide Layer for Coating Adhesion and Low Iron Loss
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Solution Overview
Problem
Grain oriented electrical steel sheets without a glass film face challenges in achieving stable adhesion of tension-insulation coatings and consistent improvement in iron loss characteristics, as existing methods fail to ensure adequate adhesion and magnetic performance.
Innovation Solution
A method involving a washing treatment with sulfuric acid and heat treatment in a specific atmosphere to form a favorable oxide layer, which enhances the adhesion of the tension-insulation coating and stabilizes iron loss reduction by controlling the layering structure and incorporating specific oxides like magnetite, hematite, and fayalite, without the need for a glass film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a glass film is formed on the steel sheet surface, then the adhesion of the tension-insulation coating is improved, but the iron loss increases due to the non-magnetic nature and intruding structure of the glass film
Solution Approach 1:
The invention removes the glass film (forsterite film) from the steel sheet surface, extracting the harmful non-magnetic layer that causes intruding structure and increases iron loss, while maintaining coating adhesion through alternative oxide layers
Solution Approach 2:
The invention changes the chemical composition parameters of the oxide layer by controlling the content of Fe, Si, and Cr elements, transforming the oxide layer from a glass film structure to a magnetite-hematite-fayalite based structure that provides both adhesion and magnetic compatibility
2Loss of energy
If the glass film formation is suppressed, then the iron loss decreases due to reduced intruding structure, but the adhesion of the tension-insulation coating deteriorates
Solution Approach 1:
The invention introduces an intermediary oxide layer composed of magnetite, hematite, and fayalite that mediates between the steel sheet base and the tension-insulation coating, providing adhesion without the harmful effects of glass film
Solution Approach 2:
The invention creates a composite oxide layer structure combining multiple oxides (magnetite Fe3O4, hematite Fe2O3, and fayalite Fe2SiO4) that collectively provide both coating adhesion and magnetic compatibility, replacing the single-phase glass film
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 ensures excellent adhesion of the tension-insulation coating and stable reduction in iron loss, improving magnetic characteristics and maintaining consistent performance even without the glass film, by forming a controlled oxide layer that supports the coating and domain wall motion.
Implementation Method 1
the intruding structure tends to suppress domain wall motion when the grain oriented electrical steel sheet is magnetized
Implementation Method 2
a washing treatment, a pickling treatment, and a heat treatment in turn are conducted for the final annealed steel sheet
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A grain oriented electrical steel sheet includes a base steel sheet, an oxide layer, and a tension-insulation coating. When a glow discharge spectroscopy is conducted in a region from a surface of the tension-insulation coating to an inside of the base steel sheet, a sputtering time Fe0.5 at which a Fe emission intensity becomes 0.5 times as compared with a saturation value thereof and a sputtering time Fe0.05 at which a Fe emission intensity becomes 0.05 times as compared with the saturation value satisfy (Fe0.5 - Fe0.05) / Fe0.5 ≥ 0.35. A maximal point of a Cr emission intensity is included between the Fe0.05 and the Fesat. Moreover, a magnetic flux density B8 in a rolling direction of the grain oriented electrical steel sheet is 1.90 T or more.