Grain-Oriented Electrical Steel Coating Stack for Annealing Adhesion
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Solution Overview
Problem
Grain oriented electrical steel sheets face issues with coating adhesion and magnetic properties after stress relief annealing, as ceramic coatings tend to peel off due to reaction products forming during high-temperature stress relief, leading to poor coating adhesion and magnetic performance.
Innovation Solution
A grain oriented electrical steel sheet with a metal coating containing elements like Y, Zr, Nb, Mo, Hf, or W, having an atomic radius rate of 10% or more, and a ceramic coating with a nitride or carbonitride, where the metal coating is thin (1.0 to 10.0 nm) and the ceramic coating is formed using methods like ion irradiation or chemical vapor deposition, ensuring excellent adhesion and magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic coating is formed on a steel sheet to apply tensile stress and improve magnetic properties, then magnetic properties are improved, but the ceramic coating peels off during stress relief annealing due to reaction product formation
Solution Approach 1:
A metal coating layer is introduced as an intermediary between the steel sheet and the ceramic coating layer. This intermediate metal layer prevents direct reaction between the ceramic coating and steel sheet during stress relief annealing, eliminating the formation of reaction products that cause coating peeling, while still allowing the ceramic coating to provide the necessary tensile stress for improved magnetic properties.
Solution Approach 2:
The invention uses a composite coating structure consisting of a metal coating layer and a ceramic coating layer. The metal coating layer (containing elements like Ti, Cr, Ni, Co, Cu, or their alloys) combined with the ceramic coating layer creates a multi-layer composite structure that combines the adhesion benefits of metal with the tensile stress benefits of ceramic, resolving the contradiction between coating adhesion and magnetic property improvement.
2Reliability
If a forsterite coating is used to apply tensile stress, then magnetic properties improve, but the smoothness of the steel sheet surface deteriorates due to the anchoring effect
Solution Approach 1:
The metal coating layer serves as an intermediary that decouples the functions of surface smoothing and tensile stress application. The metal coating can be applied smoothly without anchoring effects, and the ceramic coating can be applied over it to provide tensile stress, thus maintaining surface smoothness while improving magnetic properties.
3Reliability
If CVD or PVD methods are used to form ceramic coating, then tensile stress can be applied, but manufacturing costs increase significantly
Solution Approach 1:
The invention changes the material parameters by using a metal coating layer with specific compositions (Ti, Cr, Ni, Co, Cu or their alloys) that can be applied using conventional, cost-effective coating methods. This alternative material selection reduces manufacturing costs compared to traditional CVD or PVD ceramic coatings while still achieving the desired tensile stress and magnetic property improvement.
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 coating adhesion and magnetic properties after stress relief annealing, with improved tensile stress and reduced iron loss, maintaining the smoothness of the steel sheet surface and enhancing transformer performance.
Implementation Method 1
the metal coating is formed by irradiating the steel sheet with metal ions to attach the metal ions to the steel sheet
Implementation Method 2
by attaching, to the steel sheet, metal element ejected from a filament during irradiation of the steel sheet with inert gas ions
Implementation Method 3
the coating layer A is formed by a chemical vapor deposition method or a physical vapor deposition method
Implementation Method 4
the coating layer A is formed by a chemical vapor deposition method or a physical vapor deposition method
Implementation Method 5
the coating layer B is formed by applying a coating chemical solution on the coating layer A with an application roll, followed by baking in a nitrogen atmosphere
Implementation Method 6
when a demander or the like subjects the grain oriented electrical steel sheet to stress relief annealing
Implementation Method 7
the silicon phosphate coating having a lower thermal expansion coefficient than that of the steel sheet is formed at high temperature and cooled to room temperature, whereby a tensile stress is applied to the steel sheet using a difference in thermal expansion coefficient
Data Source
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Figure 3
AI summary
Provided are: a grain-oriented electrical steel sheet that has an excellent magnetic property and coating adhesiveness after stress relief annealing; and a production method therefor. This grain-oriented electrical steel sheet has: a steel sheet; a metal coating which contains a metal element and which is disposed on the steel sheet; a coating layer A which is a ceramic coating having an oxide content of less than 30 mass% and which is disposed on the metal coating; and a coating layer B which is an insulating tensile coating containing an oxide and which is disposed on the coating layer A, wherein the metal coating has a thickness of 1.0-10.0 nm, and in the metal element, the atomic radius ratio represented by formula (1) is at least 10%, when the atomic radius of iron is defined as RFe and the atomic radius of the metal element as RA. Formula (1): (|RFe-RA|/RFe)×100.