Hot-dip Zn Alloy Plating Cooling via Aqueous Inhibitor
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Solution Overview
Problem
The production of hot-dip Zn alloy-plated steel sheets is restricted by the need to cool the surface of the plating layer to a specified temperature before water quenching, reducing productivity, and the addition of readily oxidizable elements complicates the production process by forming dross and requiring complex concentration control.
Innovation Solution
Reducing the ratio of Zn(OH)2 at the surface of the plating layer and using a cooling aqueous solution with a water-soluble corrosion inhibitor to cool the plating layer, ensuring the temperature is above 100°C but below the solidifying point of the plating layer, thereby suppressing blackening without compromising productivity or requiring complex bath component control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface of the plating layer is cooled to a specified temperature before water quenching, then blackening resistance is improved, but productivity is reduced due to slower feed rates required for thick plated steel sheets
Solution Approach 1:
The invention changes the temperature parameter control strategy by allowing the plating layer surface temperature to be above 100°C during water quenching, rather than requiring it to be cooled to a specified lower temperature first. This parameter change enables simultaneous achievement of blackening resistance and high productivity
Solution Approach 2:
The invention applies preliminary action by forming a specific plating layer composition (Zn-5-15mass%Al-0.1-5mass%Mg-0.003-0.05mass%B) before water quenching that inherently provides blackening resistance. This preliminary composition control eliminates the need for subsequent temperature reduction, maintaining high production speed
2Reliability
If readily oxidizable elements are added into the plating bath to prevent blackening, then blackening resistance is improved, but the production process becomes complicated due to dross formation and concentration control requirements
Solution Approach 1:
The invention changes the chemical composition parameters of the plating layer by specifying precise ranges of Al (5-15mass%), Mg (0.1-5mass%), and B (0.003-0.05mass%). This parameter optimization provides inherent blackening resistance without requiring additional readily oxidizable elements, thereby simplifying the production process
Solution Approach 2:
The invention extracts the blackening prevention function from the readily oxidizable elements (which cause dross and complexity) and transfers it to the optimized Zn-Al-Mg-B plating layer composition. This extraction eliminates the need for complex concentration control while maintaining blackening resistance
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 allows for the production of hot-dip Zn alloy-plated steel sheets with excellent blackening resistance at high productivity, maintaining a Zn(OH)2 ratio of 40% or less, which effectively prevents surface darkening and maintains the metallic luster.
Implementation Method 1
contacting a cooling aqueous solution with the surface of the plated steel sheet to cool the plated steel sheet having a raised temperature through formation of the plated steel sheet
Implementation Method 2
cooling aqueous solution containing a water-soluble corrosion inhibitor to cool the plating layer, ensuring the temperature is above 100°C but below the solidifying point of the plating layer, thereby suppressing blackening
Data Source
AI summary
A method of producing a hot-dip Zn alloy-plated steel sheet includes: dipping a base steel sheet in a hot-dip Zn alloy plating bath to form a hot-dip Zn alloy plating layer on a surface of the base steel sheet; and contacting an aqueous solution containing a water-soluble corrosion inhibitor with a surface of the hot-dip Zn alloy plating layer to cool the base steel sheet and the hot-dip Zn alloy plating layer having a raised temperature through formation of the hot-dip Zn alloy plating layer. A temperature of the surface of the hot-dip Zn alloy plating layer when the aqueous solution is to be contacted with the surface of the hot-dip Zn alloy plating layer is equal to or more than 100° C. and equal to or less than a solidifying point of the plating layer. The aqueous solution containing the water-soluble corrosion inhibitor satisfies the Equation [{(Z0−Z1)/Z0}100≥20].