Oriented Steel Sheet Coating Adhesion via Cr Gradient
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Solution Overview
Problem
Conventional grain oriented electrical steel sheets face issues with coating adhesion and magnetic properties after stress relief annealing, particularly due to the peeling of non-oxide ceramic coatings and degradation of magnetic properties, which are costly and inefficiently addressed by existing thin ceramic coatings.
Innovation Solution
A grain oriented electrical steel sheet with a non-oxide ceramic coating of thickness not more than 0.400 μm and an insulation tension coating of silicon phosphate glass, where the Cr content is strategically distributed to enhance adhesion and magnetic properties, using specific deposition methods and structures to prevent peeling and diffusion issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a non-oxide ceramic coating is formed to be thin (≤0.400 μm) to reduce manufacturing cost, then manufacturing cost is reduced, but coating adhesion deteriorates and peeling occurs after stress relief annealing
Solution Approach 1:
The patent applies local quality by creating a non-oxide ceramic coating with non-uniform Cr content distribution: the region adjacent to the steel sheet has low Cr content (≤25 at%) for strong adhesion, while the outer region has high Cr content (≥25 at%) for oxidation resistance. This local variation in composition allows the thin coating (≤0.400 μm) to maintain both adhesion and protective functions without peeling after stress relief annealing.
Solution Approach 2:
The patent changes the compositional parameter of Cr content across the coating thickness to resolve the contradiction. By controlling Cr content to be ≤25 at% near the steel sheet interface and ≥25 at% in the outer region, the coating achieves optimal adhesion strength while maintaining oxidation resistance, enabling thin coating design that survives stress relief annealing without peeling.
2Reliability
If a forsterite coating is formed to apply tensile stress to the steel sheet, then magnetic properties are improved, but the steel sheet surface smoothness deteriorates
Solution Approach 1:
The patent extracts the forsterite coating layer from the coating structure, replacing it with a non-oxide ceramic coating (such as TiN, CrN, or their alloys). This non-oxide ceramic coating maintains the ability to apply tensile stress for improving magnetic properties while preserving the surface smoothness that was degraded by the forsterite coating. The extraction of the problematic forsterite layer resolves the contradiction between magnetic property enhancement and surface smoothness maintenance.
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, reducing manufacturing costs and maintaining performance, with improved tensile stress application and magnetic domain stability.
Implementation Method 1
a non-oxide ceramic coating containing a non-oxide and having a thickness of not more than 0.400 μm formed on a steel sheet
Implementation Method 2
a non-oxide ceramic coating containing a non-oxide and having a thickness of not more than 0.400 μm formed on a steel sheet
Implementation Method 3
the silicon phosphate glass 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
Implementation Method 4
when a demander or the like subjects the grain oriented electrical steel sheet to stress relief annealing
Data Source
AI summary
Provided are: an oriented electromagnetic steel sheet with outstanding coating adhesion and magnetic properties after stress relief annealing; and a method for manufacturing the oriented electromagnetic steel sheet. The oriented electromagnetic steel sheet comprises: a steel sheet; a non-oxide ceramic coating disposed on the steel sheet and containing a non-oxide; and an insulating tensile coating disposed on the non-oxide ceramic coating and containing an oxide. The thickness of the non-oxide ceramic coating is 0.020-0.400 μm. The thickness of the insulating tensile coating is at least 1.0 μm. The chromium content on the steel plate side of the non-oxide ceramic coating is less than 25 atomic %, and the chromium content on the insulating tensile coating side of the non-oxide ceramic coating is at least 25 atomic %.