Galvanized Steel Sheet Composition for Oxide-Free Plating Adhesion
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Solution Overview
Problem
Existing hot-dip galvanized steel sheets face issues with non-plating and peeling of the plating layer due to surface oxides formed during annealing, particularly from elements like Mn and Si, leading to poor plating quality and potential linear defects.
Innovation Solution
A steel sheet composition with controlled concentration profiles of Mn and Si, combined with an Fe plating layer and specific annealing conditions, including a high dew point atmosphere, to suppress surface oxide formation and enhance plating adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If elements such as Mn, Si, Al, Cr, and B are added to secure physical properties of the steel sheet, then the physical properties are improved, but surface oxides are formed during annealing which reduces reactivity and causes non-plating
Solution Approach 1:
The patent removes the harmful surface oxides formed during annealing by controlling the annealing atmosphere to prevent oxide formation at the surface, while allowing the beneficial alloying elements (Mn, Si, Al, Cr, B) to remain in the steel sheet to maintain its physical properties. This extraction of the harmful surface oxide layer resolves the contradiction between maintaining physical properties and preventing non-plating.
Solution Approach 2:
The patent changes the annealing atmosphere parameters (controlling oxygen potential, dew point, and gas composition) to prevent oxide formation at the steel sheet surface during annealing. By adjusting these atmospheric parameters, the process prevents the formation of harmful surface oxides while allowing the steel sheet to retain its alloying elements and physical properties, thus resolving the contradiction.
2Object-generated harmful factors
If elements diffuse to surfaces during annealing to form oxides, then oxide formation is achieved, but reactivity of the surface is reduced causing non-plating
Solution Approach 1:
The patent uses a controlled annealing atmosphere with limited oxygen potential to prevent oxide formation at the steel sheet surface. By creating an inert or low-oxygen environment during annealing, the process prevents the diffusion of alloying elements to the surface and subsequent oxide formation, thereby maintaining surface reactivity and preventing non-plating while still allowing necessary internal oxidation for physical property enhancement.
3Object-generated harmful factors
If surface oxides are formed during annealing, then oxidation of alloying elements is achieved, but wettability with zinc is reduced causing poor plating adhesion
Solution Approach 1:
The patent converts the potential harm of oxide formation into a benefit by controlling the annealing process to form oxides only at specific depths within the steel sheet rather than at the surface. This controlled internal oxidation enhances the physical properties of the steel sheet while the surface remains free of oxides, maintaining good wettability and adhesion with zinc during hot-dip galvanizing.
4Strength
If alloying elements are added to improve physical properties, then strength and ductility are enhanced, but linear defects occur due to uneven alloying during heat treatment
Solution Approach 1:
The patent applies local quality control by ensuring uniform distribution of alloying elements throughout the steel sheet thickness and controlling their diffusion to the surface during annealing. By managing the local concentration profiles of Mn, Si, Al, Cr, and B elements, the process prevents uneven alloying and linear defects on the surface while maintaining the physical property enhancements provided by these elements.
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 method results in a hot-dip galvanized steel sheet with improved plating adhesion and surface quality, preventing non-plating and linear defects, even after alloying heat treatments.
Implementation Method 1
oxidizing the steel sheet in a direct flame furnace in an oxidizing atmosphere to form an iron oxide including Si, Mn or Al alone or complex oxides to a certain depth inside the steel sheet
Implementation Method 2
reducing and annealing the iron oxide in a reducing atmosphere
Implementation Method 3
insufficient formation of an alloying inhibition layer (Fe2Al5) required to secure adhesion of the plating layer during a hot-dip plating process
Data Source
AI summary
The steel sheet according to an aspect of the present invention has a GDS profile of an Mn element and a GDS profile of an Si element, which are observed from the surface to the depth, sequentially including a maximum point and a minimum point, wherein a difference of converted concentration of Mn is 80% or more, and a difference of converted concentration of Si is 50% or more.