Zn-Plated Hot-Stamped Steel Layer Control for Hexagonal Pattern Suppression
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Solution Overview
Problem
Zn-plated hot stamped products face issues with sacrificial corrosion resistance and plating adhesion, and there is a need for improved appearance quality, particularly in visually noticeable automotive applications.
Innovation Solution
Control the formation of a hexagonal pattern by managing the Mn content ratio and the thickness ratio between the upper and lower layers of the Zn-based plating layer, which includes a Γ phase and an Fe-Zn solid solution, to enhance corrosion resistance and plating adhesion while suppressing the hexagonal pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zn-based plated steel sheet is used for hot stamping, then corrosion resistance is improved, but a hexagonal pattern is generated on the surface deteriorating appearance quality
Solution Approach 1:
The invention changes the chemical composition parameters of the plated layer by controlling the mass ratio of Mn to Zn to be 0.03 to 0.08, and controlling the content of specific elements (Al: 0.005-0.05%, Si: 0.005-0.05%, P: 0.005-0.05%). These parameter changes suppress the formation of the hexagonal pattern while maintaining corrosion resistance, thereby resolving the contradiction between appearance quality and corrosion resistance
Solution Approach 2:
The invention creates a composite plated layer structure containing multiple elements (Zn, Mn, Al, Si, P) with specific compositional ratios. This composite material approach allows the plated layer to simultaneously achieve good appearance quality by suppressing hexagonal pattern formation and maintaining excellent corrosion resistance through the synergistic effects of different elements
2Manufacturing precision
If the Mn content is increased to suppress hexagonal pattern, then appearance quality is improved, but plating adhesion deteriorates
Solution Approach 1:
The invention precisely controls the Mn content through the Mn/Zn mass ratio parameter (0.03-0.08) rather than simply increasing Mn content. This optimized parameter change suppresses hexagonal pattern formation while maintaining plating adhesion, resolving the contradiction between appearance quality and plating adhesion
Solution Approach 2:
The invention uses a composite plated layer with multiple elements (Zn, Mn, Al, Si, P) in specific ratios. The synergistic interaction between these elements allows suppression of hexagonal pattern at moderate Mn levels while maintaining plating adhesion, resolving the contradiction between appearance and adhesion
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 solution achieves excellent corrosion resistance, plating adhesion, and appearance quality, making the Zn-plated hot stamped products suitable for both functional and aesthetic requirements in automotive applications.
Implementation Method 1
Both the Γ phase and the Fe-Zn solid solution are not excellent in both sacrificial corrosion resistance and plating adhesion
Implementation Method 2
a hexagonal pattern is formed by local oxidation of Mn
Implementation Method 3
a change in volume and a flow due to a change in plating phase under the oxide
Data Source
Figure 1
Figure 2~2(c)
Figure 3~4
AI summary
This Zn-plated hot stamped product includes a steel, a Zn-based plating layer, and an oxide layer, in which an upper layer which is a region on a surface side of the Zn-based plating layer has a two-phase structure of a Γ phase and an Fe-Zn solid solution, and a lower layer which is a region of the Zn-based plating layer excluding the upper layer has a single-phase structure of an Fe-Zn solid solution, an upper layer thickness and a lower layer thickness satisfy the following expression, a Mn content ratio of Max. Mn/Min. Mn, which is a ratio of a maximum value Max. Mn to a minimum value Min. Mn of an Mn content on a surface of the Zn-plated hot stamped product, is 10.0 or less, and an average value Ave. Mn is 0.5 to 7.5% by mass%. 0.20≤upperlayerthickness/upperlayerthickness+lowerlayerthickness≤0.80