Electrical Steel Sheet Coating for Low Iron Loss and Adhesion
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Solution Overview
Problem
The adhesion of insulation coatings on grain-oriented electrical steel sheets without a forsterite film is inadequate, leading to increased iron loss in transformers due to insufficient adhesion and interference with magnetic domain wall movement.
Innovation Solution
A grain-oriented electrical steel sheet with a silicon-based oxide intermediate layer and a phosphate-based coating, containing specific crystalline phosphorus oxides, is developed to enhance adhesion and reduce iron loss without relying on a forsterite film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the forsterite film is removed to smooth the surface and reduce iron loss, then the surface smoothness is improved, but the adhesion of the insulation coating deteriorates
Solution Approach 1:
The patent introduces an intermediate layer between the base steel sheet and the insulation coating. This intermediate layer serves as a mediator that provides both surface smoothness (to reduce iron loss) and adequate adhesion (to ensure coating reliability). The intermediate layer with specific composition (SiO2 content: 20-70 atomic%, O content: 30-80 atomic%, Mg content: <20 atomic%, P content: <5 atomic%, Fe content: <20 atomic%) acts as a bridge that resolves the contradiction between smoothness and adhesion.
Solution Approach 2:
The patent changes the compositional parameters of the intermediate layer to achieve the desired balance. By controlling the SiO2 content to be 20-70 atomic% and limiting Mg content to <20 atomic%, the intermediate layer achieves optimal properties. This parameter control allows the surface to be smooth enough to reduce iron loss while maintaining sufficient adhesion for the insulation coating.
2Loss of energy
If the forsterite film is removed to smooth the surface, then the magnetic domain wall movement is improved, but the adhesion of the insulation coating becomes insufficient
Solution Approach 1:
The intermediate layer acts as a mediator that simultaneously provides surface smoothness for improved magnetic domain wall movement and adequate adhesion for coating quality. The specific composition parameters of the intermediate layer ensure both functions are achieved without compromising either magnetic performance or coating adhesion.
Solution Approach 2:
The intermediate layer has locally optimized properties at the interface between the base steel sheet and the insulation coating. The specific composition (high SiO2, controlled Mg and P content) creates a local region that facilitates both smooth magnetic domain wall movement and strong coating adhesion, addressing different requirements at different interfaces.
3Ease of manufacture
If the insulation coating is applied directly on the base steel sheet without forsterite film, then the manufacturing process is simplified, but the adhesion becomes insufficient
Solution Approach 1:
The intermediate layer serves as a necessary mediator that enables direct coating application on the base steel sheet while ensuring adequate adhesion. Although it adds a layer, it simplifies the overall process by eliminating the need for forsterite film formation through complex annealing separators, while still providing the adhesion function.
Solution Approach 2:
By controlling the compositional parameters of the intermediate layer (SiO2: 20-70 atomic%, O: 30-80 atomic%, with limited Mg, P, and Fe content), the patent achieves sufficient adhesion while maintaining manufacturing simplicity. The specific parameter ranges ensure the intermediate layer provides adequate bonding without requiring additional complex processing steps.
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 provides excellent adhesion of the insulation coating, improving the iron loss characteristics of the steel sheet by applying tension and ensuring effective electrical insulation, even without a forsterite film, thereby enhancing the performance of the steel sheet in transformer applications.
Implementation Method 1
sufficient adhesion is required between the coating and the base steel sheet
Implementation Method 2
the above adhesion has been mainly ensured by the anchor effect derived from the unevenness of an interface between the base steel sheet and the forsterite film
Implementation Method 3
The coating applies the tension to the grain-oriented electrical steel sheet, and thereby, reduces the iron loss as a single steel sheet
Implementation Method 4
the coating ensures interlaminar electrical insulation when the grain-oriented electrical steel sheets are utilized after being laminated
Implementation Method 5
the insulation coating is formed by applying coating solution including, for instance, phosphoric acid or phosphate, colloidal silica, and chromic anhydride or chromate to the steel sheet after final annealing, and by baking and drying it at 300 to 950°° C. for 10 seconds or more
Data Source
AI summary
A grain-oriented electrical steel sheet includes a base steel sheet, an oxide film, and a phosphate-based coating. The phosphate-based coating includes a first crystalline phosphorus oxide whose crystal structure corresponds to Fe2P2O7 and a second crystalline phosphorous oxide whose crystal structure corresponds to Fe7(P2O7)4, and the second crystalline phosphorous oxide includes at least one element selected from a group consisting of V, W, Zr, Co, and Mo.