Hot-dip aluminized steel fine spangle control
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Solution Overview
Problem
The production of hot-dip aluminized steel sheets with fine spangles is hindered by the difficulty in uniformly dispersing high-specific-gravity additives in the aluminum-based coating bath, leading to unstable spangle formation during continuous industrial operations, as these additives tend to precipitate at the bottom due to differences in specific gravity.
Innovation Solution
The method involves adjusting the boron, titanium, and vanadium concentrations in the aluminum-based coating bath to specific ranges, ensuring the boron concentration is not less than 0.005 mass % and the sum of titanium and vanadium concentrations is not more than 0.03 mass %, which enhances the spangle-size-reducing effect and stabilizes spangle density across different coating lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-specific-gravity additives (Ti, Nb, TiC, TiB2, TiAl3) are added to the Al-based coating bath to increase spangle nuclei and reduce spangle size, then the spangle size decreases, but the additives precipitate at the bottom of the bath due to specific gravity difference, causing non-uniform dispersion and unstable spangle formation
Solution Approach 1:
The patent uses aluminum boride (AlB2) or aluminum nitride (AlN) as intermediary substances that have specific gravity close to aluminum (2.7). These intermediaries act as spangle nuclei without precipitating to the bottom of the coating bath, thereby maintaining uniform dispersion and stable spangle formation while still achieving fine spangle size. This resolves the contradiction by finding a mediator that provides the desired nucleation effect without the harmful sedimentation effect.
Solution Approach 2:
The patent changes the key parameter of specific gravity by selecting additives (AlB2 or AlN) whose specific gravity matches that of aluminum. This parameter change ensures that the additives remain uniformly dispersed in the coating bath during continuous production, preventing precipitation and maintaining reliable spangle formation while achieving the desired fine spangle size.
2Shape
If conventional additives (Ti, Nb, TiC, TiB2, TiAl3) are used to form fine spangles, then spangle size is reduced, but uniform dispersion in the coating bath cannot be achieved due to density difference
Solution Approach 1:
Aluminum boride (AlB2) or aluminum nitride (AlN) serves as an intermediary substance with specific gravity matching aluminum. These intermediaries provide the necessary spangle nucleation function while remaining uniformly distributed in the coating bath, thus achieving fine spangles with uniform composition throughout the bath during continuous operation.
Solution Approach 2:
The patent achieves homogeneity by selecting additives whose specific gravity (2.7) matches that of aluminum. This density matching ensures that AlB2 or AlN particles remain uniformly dispersed throughout the coating bath without separating or precipitating, thereby maintaining consistent additive distribution and producing uniform fine spangles across the entire production run.
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
This approach allows for the consistent production of hot-dip aluminized steel sheets with fine spangles, improving surface appearance and corrosion resistance by controlling the spangle density and size, thereby overcoming the limitations of existing methods.
Implementation Method 1
the nucleus of the spangle (i.e., spangle nucleus) occurs. Then, a primary dendrite arm grows from the spangle nucleus
Implementation Method 2
a primary dendrite arm grows from the spangle nucleus. Subsequently, a secondary dendrite arm develops from the primary dendrite arm
Data Source
AI summary
Provided is a hot-dip aluminized steel sheet with fine-sized spangles produced in a different way from conventional methods, and a method of producing a hot-dip aluminized steel sheet with fine-sized spangles in a different way from conventional methods. The hot-dip aluminized steel sheet includes: a substrate steel sheet; and an aluminum-based coating which is formed by a hot-dip method on the surface of the substrate steel sheet and in which the average B concentration is not less than 0.005 mass % and the sum of the average Ti concentration and the average V concentration is not more than 0.03 mass %.