Chromium(III) Phosphate Coating for Grain-Oriented Steel
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Solution Overview
Problem
The use of chromium(VI) in phosphate layers for grain-oriented electrical steel is hazardous and difficult to replace without compromising the material's properties, leading to issues with chemical resistance, tensile stress, and optical quality.
Innovation Solution
A chromium(VI)-free phosphate solution is developed using chromium(III) compounds, colloid stabilizers, and pickling inhibitors to maintain the material's properties, with chromium(III) nitrate being particularly effective in transferring tensile stress and improving optical quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium(VI) is used in the phosphate solution, then corrosion resistance and chemical resistance are improved, but toxicity and environmental hazard increase
Solution Approach 1:
The patent changes the oxidation state parameter of chromium from +6 to +3, transforming chromium(VI) compounds into chromium(III) compounds. This parameter change maintains the protective function of the phosphate layer while dramatically reducing toxicity and environmental hazard, as chromium(III) is significantly less toxic than chromium(VI)
Solution Approach 2:
The patent replaces the hazardous chromium(VI) with chromium(III) compounds, using a safer, more environmentally friendly alternative that achieves the same protective function without the severe health and environmental risks associated with chromium(VI)
2Object-affected harmful factors
If chromium(VI) is omitted from the phosphate solution, then toxicity is reduced, but chemical resistance and tensile stress transfer deteriorate
Solution Approach 1:
The patent changes the oxidation state parameter of chromium from +6 to +3, transforming chromium(VI) compounds into chromium(III) compounds. This parameter change maintains the protective function of the phosphate layer while dramatically reducing toxicity and environmental hazard, as chromium(III) is significantly less toxic than chromium(VI)
Solution Approach 2:
The patent creates a composite phosphate solution system containing chromium(III) compounds combined with colloidal oxide compounds (such as silica sol) and organic additives. This composite formulation achieves both chemical resistance and tensile stress transfer properties while maintaining low toxicity, overcoming the limitations of simple chromium-free formulations
3Object-affected harmful factors
If chromium-free phosphate solution is used without additives, then environmental safety is improved, but optical quality and layer homogeneity worsen
Solution Approach 1:
The patent creates a composite phosphate solution system containing chromium(III) compounds combined with colloidal oxide compounds (such as silica sol) and organic additives. This composite formulation achieves both chemical resistance and tensile stress transfer properties while maintaining low toxicity, overcoming the limitations of simple chromium-free formulations
Solution Approach 2:
The patent introduces colloidal oxide compounds and organic additives as intermediary substances that mediate between the chromium-free phosphate solution and the steel surface. These intermediaries ensure proper layer formation, homogeneity, and optical quality without requiring toxic chromium(VI), facilitating successful coating even in the absence of traditional harmful chemicals
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 improved optical properties and higher tensile stress compared to chromium-free alternatives, while being safer and more environmentally friendly, effectively replacing chromium(VI) without significant drawbacks.
Implementation Method 1
the omission of chromium(VI) results in a significant chemical reaction between the phosphate solution and the metal, a pickling reaction
Implementation Method 2
prevent iron from dissolving in the solution state
Implementation Method 3
phosphoric acid released when baking the phosphate solution bind to chromium phosphate
Data Source
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AI summary
The invention relates to a method for producing a grain-oriented electric strip coated with a phosphate layer, in that a phosphate solution comprising a colloid component and at least one colloid stabilizer (A), and/or at least one etching inhibitor (B) is applied to the electric strip, wherein the phosphate solution comprises at least one compound comprising chromium at the oxidation level III (Chromium (III) compounds). Grain-oriented electric strips produced by means of the method according to the invention are characterized by excellent optical properties and high tensile stress.