Galvanized Steel Cooling via Ionic Wind and Solution Spray
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Solution Overview
Problem
The manufacturing of hot-dip galvanized steel sheets often results in surface defects such as pitting marks, drop marks, and linear comb patterns due to inadequate cooling rates, making it difficult to produce sheets with aesthetically pleasing surfaces.
Innovation Solution
A method involving a cooling chamber positioned at the exact point of galvanized layer solidification, where a cooling solution is sprayed using an ionic-wind generator and solution atomizing unit, with air injection and controlled by optical thermometers to optimize cooling efficiency and prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high voltage is applied to attach droplets to the steel sheet surface, then cooling efficiency is improved, but pitting marks and drop marks occur due to droplet collision with the molten galvanized layer
Solution Approach 1:
The patent applies preliminary cooling to reduce the galvanized layer temperature before droplet attachment. The cooling process starts immediately after galvanizing while the layer is still hot, progressively reducing temperature to below the molten state before droplets are attached, preventing collision damage while maintaining cooling efficiency
Solution Approach 2:
The patent dynamically adjusts the timing and conditions of droplet attachment based on the temperature state of the galvanized layer. Instead of static attachment, the system monitors temperature and controls droplet application to occur only when the layer has cooled sufficiently, creating a dynamic process that adapts to changing thermal conditions
2Extent of automation
If optical thermometers are used to measure steel sheet temperature, then temperature monitoring is enabled, but measurement accuracy deteriorates due to emissivity changes during galvanized layer solidification
Solution Approach 1:
The patent introduces a reference object with known and stable emissivity properties as an intermediary for temperature measurement. By measuring the temperature of this reference object rather than directly measuring the galvanized layer whose emissivity changes during solidification, the system achieves accurate temperature monitoring despite the varying optical properties of the molten and solidifying zinc layer
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 method minimizes surface defects, enabling the production of hot-dip galvanized steel sheets with excellent surface quality by precisely controlling the cooling process.
Implementation Method 1
a cooling chamber (4) which has a cooling ability to initiate and complete the solidification of a galvanized layer, and includes an ionic-wind generator (5)
Implementation Method 2
a solution atomizing unit (6) configured to spray a solution
Implementation Method 3
temperature of a steel sheet...measured by optical thermometers
Data Source
AI summary
The present invention relates to a molten metal plated steel sheet manufacturing method for cooling a molten galvanized layer with high efficiency when manufacturing a molten galvanized steel sheet, and the purpose of the present invention is to provide a method for manufacturing a molten galvanized plating, wherein a molten galvanized steel sheet having an aesthetically pleasing surface without fitting defects, drop mark defects, and linear comb-pattern defects can be stably obtained by cooling a galvanized layer with high efficiency during a molten metal plated steel sheet manufacturing process. This method for manufacturing a molten galvanized steel sheet having excellent surface properties is characterized by comprising the steps in which a molten galvanized layer is formed on the surface of a steel sheet while the steel sheet passes through a galvanizing pot, the thickness of the galvanized layer formed on the surface of the steel sheet is adjusted while the steel sheet passes through a gas wiping device, the steel sheet that has had the thickness of the galvanized layer adjusted undergoes a primary cooling while passing through a bottom cooler, and the galvanized steel sheet that has undergone the primary cooling undergoes a secondary cooling while passing through a cooling chamber, wherein: the primary cooling is performed with cooling air blown from the bottom cooler until right before a galvanizing solution of the galvanized layer attached to the surface of the steel sheet becomes solidified, the amount of air blown being adjusted according to the temperature of the galvanized layer attached to the surface of the steel sheet; and the secondary cooling is performed with ionic air generated from an ionic air generator provided in the cooling chamber and a spray solution sprayed from a solution atomization part, the secondary cooling being performed from the start of the solidification of the galvanizing solution until the end of the solidification, and the cooling chamber cooling the galvanized steel sheet while moving up and down according to the temperature of the galvanized layer attached to the surface of the galvanized steel sheet.