Spangle-Free Hot-Dip Galvanized Steel Sheet Manufacturing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hot-dip galvanized steel sheets suffer from inferior corrosion resistance, oil stain resistance, and blackening resistance compared to electro-galvanized steel sheets due to their coarse spangle texture and non-uniform crystal orientation, which affects their surface appearance and mechanical properties.
Innovation Solution
A spangle-free hot-dip galvanized steel sheet is manufactured with an average crystalline texture particle diameter of 10 to 88 μm, where at least 50% aluminum is present around the grain boundaries, and the height difference between hills and valleys on the coating layer is less than 25% of the coating thickness, achieved through a process involving a zinc-coating solution with aluminum, air-wiping, water or aqueous solution spraying, and passing liquid droplets through a high-voltage charged mesh-like electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hot-dip galvanization is used to achieve low manufacturing cost, then production cost is reduced, but surface appearance quality deteriorates due to coarse spangle texture
Solution Approach 1:
The patent applies parameter changes by controlling the aluminum content in the zinc coating solution within a specific range (0.03-0.15 wt%) and controlling the cooling rate during solidification. These parameter changes result in fine crystalline grain structure with average particle diameter of 10-88 μm, eliminating coarse spangles while maintaining hot-dip galvanization's cost advantage.
2Device complexity
If conventional hot-dip galvanization process is used, then manufacturing simplicity is maintained, but corrosion resistance deteriorates due to non-uniform crystal orientation
Solution Approach 1:
The patent applies local quality by ensuring aluminum distribution around grain boundaries through controlled solidification. This creates localized aluminum enrichment at critical grain boundary regions, providing enhanced corrosion resistance specifically where it is most needed, while maintaining overall process simplicity.
3Manufacturing precision
If rapid solidification is used to reduce spangle size, then surface appearance improves, but manufacturing precision deteriorates due to non-uniform thickness from dendrite growth
Solution Approach 1:
The patent applies parameter changes by optimizing the cooling rate during solidification and controlling aluminum content in the molten zinc. This combination prevents dendrite formation and promotes uniform equiaxed grain structure, achieving both fine spangle size (10-88 μm) and uniform coating thickness without hills and valleys.
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 resulting steel sheet exhibits superior corrosion resistance, oil stain resistance, and blackening resistance, along with a favorable surface appearance, making it suitable for applications in car bodies, household appliances, and building materials.
Implementation Method 1
passing liquid droplets through a high-voltage charged mesh-like electrode
Implementation Method 2
served as solidification nuclei of molten zinc
Data Source
AI summary
A spangle-free, hot-dip galvanized steel sheet, and a method and device for manufacturing the same. The hot-dip galvanized steel sheet is characterized in that a solidified zinc crystal of hot-dip galvanized layer has an average crystalline texture particle diameter of 10 to 88 μm and there is no solidification traces of dendrites upon observing under a microscope at a magnification of 100×. The method comprises dipping a steel sheet in a bath of a zinc-coating solution containing 0.13 to 0.3% by weight of aluminum; air-wiping the steel sheet to remove an excess of the coating solution; spraying water or an aqueous solution on the air-wiped steel sheet, using a steel sheet temperature in the range of a hot-dip galvanization temperature to 419 ° C. as a spray initiation temperature and using a steel sheet temperature in the range of 417 ° C. to 415 ° C. as a spray completion temperature; passing sprayed liquid droplets of water or aqueous solution through a mesh-like high-voltage charged electrode which is electrically charged with a high voltage of −1 to −50 kV; and allowing the electrode-passed liquid droplets to be bound to the surface of the steel sheet and hereby being served as solidification nuclei of molten zinc.