Composite Plating Layer for Hot Press Forming Weldability
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Solution Overview
Problem
High-strength steels used in automobiles face challenges with weldability and corrosion resistance due to surface oxides formed during hot press forming (HPF), as zinc-based plating provides inadequate sacrificial protection and excessive zinc oxides hinder welding, while aluminum-based plating lacks sufficient corrosion protection.
Innovation Solution
A plated steel sheet with a composite plating layer consisting of alternately formed Mn-based and Al-based layers, where the Al-based layer is the uppermost, providing a thin surface oxide layer for high weldability and forming alloys like Fe—Mn-based alloys that offer sacrificial corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zinc-based plating is used to provide sacrificial corrosion protection, then corrosion resistance is improved, but zinc oxides form on the surface during HPF which worsen weldability
Solution Approach 1:
The plating layer is segmented into multiple functional layers: an inner Zn-based plating layer for corrosion protection and an outer Al-based plating layer for oxide suppression. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between corrosion resistance and weldability
Solution Approach 2:
The invention uses a composite plating structure combining Zn-based and Al-based materials. The Zn-based layer provides sacrificial corrosion protection while the Al-based layer forms a thin, weldable oxide layer during HPF, creating a composite system that achieves both corrosion resistance and good weldability
2Ease of manufacture
If aluminum-based plating is used to suppress oxide formation and improve weldability, then spot weldability is improved, but sacrificial corrosion protection becomes insufficient
Solution Approach 1:
The plating is segmented into an inner Zn-based layer that provides corrosion protection and an outer Al-based layer that suppresses oxide formation. This segmentation allows the Al-based layer to improve weldability while the Zn-based layer maintains corrosion resistance
Solution Approach 2:
The Zn-based plating layer acts as an intermediary between the steel substrate and the Al-based plating layer. It provides the sacrificial corrosion protection that aluminum alone cannot provide, while the Al-based layer mediates the interaction with the environment by forming a protective oxide barrier
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 high spot weldability and corrosion resistance by forming thin surface oxides and alloys that protect the steel sheet, reducing manufacturing costs and improving the quality of formed components.
Implementation Method 1
If a steel sheet is plated with aluminum (Al) having a high degree of heat resistance and is then subjected to an HPF process, a product formed by the HPF process does not have surface oxides or has very low amounts of surface oxides
Implementation Method 2
an alloy layer formed on an iron surface of the plated steel sheet is electrochemically less noble than iron (Fe) of the plated steel sheet, and thus provides sacrificial corrosion protection to iron (Fe) of the plated steel sheet
Implementation Method 3
the alloy layer formed on an iron surface of the plated steel sheet is electrochemically less noble than iron (Fe) of the plated steel sheet, and thus provides sacrificial corrosion protection to iron (Fe) of the plated steel sheet
Data Source
AI summary
The present invention relates to a plated steel sheet for hot press forming, a hot-press forming member manufactured using the same, and a manufacturing method thereof. The plated steel sheet comprises: a base steel sheet and a composite plated layer that is formed on at least one surface of the base steel sheet, and has a Mn-based plated layer and an Al-based plated layer alternately formed therein, an Al-based plated layer being formed on the uppermost layer thereof, wherein the composite plated layer has a total thickness of 5 to 30 μm, and in this case, the Mn-based plated layer accounts for 5 to 60% of the total thickness.