Chromium-Free Coating for Grain-Oriented Steel
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Solution Overview
Problem
Existing coating solutions for grain-oriented electrical steel sheets either contain hexavalent chromium, leading to environmental concerns, or use expensive additives that result in insulating films with poor denseness, corrosion resistance, and water resistance, and insufficient film tension.
Innovation Solution
A coating solution comprising hydrous silicate powders with an average particle size of 2 μm or less and phosphoric acids/phosphates, where the ratio of metal ions to phosphorus satisfies specific conditions, is applied and baked at high temperatures to form a dense insulating film with improved tension, corrosion resistance, and water resistance without using chromium compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a coating solution containing hexavalent chromium is used to form an insulating film, then the film characteristics such as tension are excellent, but the work environment deteriorates and equipment considerations are required
Solution Approach 1:
The invention extracts and removes the harmful hexavalent chromium component from the coating solution while retaining the essential functional components (colloidal silica and monophosphate) that provide good film characteristics. This eliminates the work environment problems associated with chromium while maintaining film tension and other performance properties.
Solution Approach 2:
The invention replaces expensive and harmful chromium-based additives with more economical and environmentally friendly alternatives (colloidal silica and monophosphate combination), achieving comparable or superior film characteristics without the need for special equipment or safety measures.
2Object-affected harmful factors
If a coating solution containing no chromic acid and using other additives is used, then the work environment is improved, but the film tension becomes smaller
Solution Approach 1:
The invention changes the chemical parameters of the coating solution by using a specific combination of colloidal silica and monophosphate in optimized proportions. This parameter optimization ensures that the insulating film achieves sufficient film tension and other characteristics comparable to chromium-based solutions, while maintaining an improved work environment.
3Object-affected harmful factors
If expensive additives are used instead of chromic acid, then the work environment is improved, but the film characteristics such as denseness, corrosion resistance, and water resistance deteriorate
Solution Approach 1:
The invention uses a composite coating system combining colloidal silica and monophosphate that work synergistically to provide excellent film characteristics including denseness, corrosion resistance, and water resistance. This composite approach eliminates the need for expensive chromium-based additives while achieving superior reliability and protection properties.
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 achieves a grain-oriented electrical steel sheet with enhanced film tension, space factor, corrosion resistance, and water resistance, while reducing iron loss, without the use of chromium compounds, thus addressing the limitations of previous technologies.
Implementation Method 1
A coating solution comprising hydrous silicate powders with an average particle size of 2 μm or less and phosphoric acids/phosphates, where the ratio of metal ions to phosphorus satisfies specific conditions, is applied and baked at high temperatures to form a dense insulating film
Implementation Method 2
A coating solution comprising hydrous silicate powders with an average particle size of 2 μm or less and phosphoric acids/phosphates, where the ratio of metal ions to phosphorus satisfies specific conditions
Data Source
AI summary
A coating solution for forming an insulating film for a grain-oriented electrical steel sheet which contains one or more types of hydrous silicate powders having an average particle size of 2 μm or less, and one or more types of phosphoric acids and phosphates satisfying a relation of ΣniMi/ΣPi≤0.5, and satisfies (Formula 1).1.5≤(ΣniMi+Σn′jM′j)/ΣPi≤15 (Formula 1)(P represents the number of moles of phosphorus, M represents the number of moles of metal ions derived from the phosphate, n represents the valence of the metal ions derived from the phosphate, i represents the number of types of phosphates, M′ represents the number of moles of metal elements in the hydrous silicate, n′ represents the valence of the metal elements in the hydrous silicate, and j represents the number of types of hydrous silicates).