Primary Coating Interface for Grain-Oriented Steel Adhesion
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Solution Overview
Problem
Existing grain-oriented electrical steel sheets face issues with primary coating adhesion during bending operations, leading to peeling and surface defects due to gas release during finish annealing, which are not adequately addressed by existing technologies.
Innovation Solution
The interface structure of the primary coating is controlled by dividing it into two regions: a surface oxide layer and an anchoring oxide layer, with specific morphological features and element compositions, including Y, La, Ce, Ca, Sr, and Ba, to enhance adhesion and prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the primary coating is made thicker to improve adhesion during bending operations, then coating adhesion is improved, but surface defects occur due to gas release during finish annealing
Solution Approach 1:
The primary coating is divided into two distinct layers: a surface oxide layer (5-20 μm thick) and an anchoring oxide layer (20-50 μm thick). This segmentation allows the surface layer to release gas smoothly during annealing while the deeper anchoring layer maintains strong adhesion to the base steel sheet, preventing peeling during bending operations.
Solution Approach 2:
Different regions of the primary coating are given different compositions and functions. The surface oxide layer contains elements like Al, Si, and Mn that facilitate gas release and surface quality, while the anchoring oxide layer contains MgO and other elements that provide strong mechanical interlocking with the base steel sheet, ensuring adhesion during bending.
2Strength
If the interface structure is made more complex to prevent peeling during bending, then coating adhesion is improved, but manufacturing complexity increases
Solution Approach 1:
The dual-layer primary coating structure forms automatically during the finish annealing process through controlled oxidation and diffusion of elements. The surface oxide layer and anchoring oxide layer develop self-organizing patterns that optimize both gas release and adhesion functions without requiring additional manufacturing steps or complex equipment.
3Strength
If elements like Y, La, Ce, Ca, Sr, and Ba are added to control interface structure, then coating adhesion and magnetic properties are improved, but manufacturing precision requirements increase
Solution Approach 1:
Specific elements (Y, La, Ce, Ca, Sr, Ba) are added in controlled amounts to the steel sheet composition before rolling. During finish annealing, these elements diffuse and concentrate at the primary coating interface, automatically forming the desired dual-layer structure with optimal adhesion and magnetic properties. The elements act as diffusion markers that guide the self-organization of the interface structure.
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 improves coating adhesion to both shearing and bending operations while maintaining excellent magnetic properties and reducing surface defects, ensuring high reliability and quality.
Implementation Method 1
the anchoring oxide layer penetrating into the base steel sheet... the anchoring structures of the primary coating causing physical bonding strength between the primary coating and the base steel sheet
Implementation Method 2
the MgO in the annealing separator and the SiO2 in the internal oxide layer formed on the surface of the cold rolled steel sheet at the time of decarburization annealing react whereby a primary coating having forsterite (Mg2SiO4) as a main constituent is formed
Data Source
AI summary
Grain-oriented electrical steel sheet excellent in magnetic properties and adhesion of a primary coating to a base steel sheet and with few defects where the base metal is exposed in point defects and a method for manufacturing grain-oriented electrical steel sheet are provided. This is characterized by being provided with a base steel sheet and a primary coating. The primary coating satisfies (1) Number density D3 of Al concentrated regions: 0.015 to 0.150/μm2, (2) (Area S5 of regions comprised of anchoring oxide layer regions and Al concentrated regions)/(area S3 of Al concentrated regions)≥0.30, (3) Distance H5 of mean value of heights in thickness direction of regions of comprised of anchoring oxide layer regions and Al concentrated regions minus H0: 0.4 to 4.0 μm, (4) (Perimeter L5 of regions comprised of anchoring oxide layer regions and Al concentrated regions)/(observed area S0): 0.020 to 0.500 μm/μm2, and (5) (Area S1 of anchoring oxide layer regions)/(observed area S0)≥0.15.