Hot-Press Steel Sheet Coating for Oxidation and Corrosion Control
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Solution Overview
Problem
Existing hot stamping steel sheets face challenges with oxidation during high-temperature processing, leading to reduced corrosion resistance and increased complexity in forming complex shapes due to spring back phenomena.
Innovation Solution
A steel sheet for hot pressing is developed with a plated layer comprising 20 wt % to 45 wt % zinc (Zn), 0.2 wt % to 3 wt % magnesium (Mg), 1 wt % to 5 wt % silicon (Si), and 0.01 wt % to 0.5 wt % strontium (Sr), along with an Sr-based oxide layer and a corrosion resistance reinforcement layer to enhance sacrificial anti-corrosion properties and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If aluminum-plated layer is used to prevent oxidation during hot press forming, then oxidation resistance is improved, but molding workability and corrosion resistance deteriorate due to plated layer cracking and detachment
Solution Approach 1:
The invention uses a composite plated layer containing Al-Si-Zn-Mg-Sr alloy instead of pure aluminum plating. The multiple elements work synergistically: Al provides oxidation resistance, Si reduces plated layer hardness and prevents cracking, Zn enhances corrosion resistance through sacrificial protection, Mg improves ductility, and Sr forms protective oxide layers. This composite material approach resolves the contradiction by maintaining oxidation resistance while improving molding workability and corrosion resistance simultaneously.
Solution Approach 2:
The invention changes the chemical composition parameters of the plated layer by adding specific amounts of Si (3-11 wt%), Zn (2-10 wt%), Mg (0.5-3 wt%), and Sr (0.05-0.5 wt%). These parameter changes transform the plated layer properties: Si reduces hardness to prevent cracking during molding, Zn provides sacrificial corrosion protection, and the combined composition prevents both oxidation during hot pressing and plated layer detachment, thereby improving both oxidation resistance and molding workability.
2Object-affected harmful factors
If Al-Si-based plating is used for hot stamping, then oxidation resistance is improved, but corrosion resistance deteriorates due to plated layer loss during processing
Solution Approach 1:
The invention employs an Al-Si-Zn-Mg-Sr composite plated layer where Zn provides sacrificial corrosion protection through galvanic action, protecting the underlying steel substrate. The Sr element forms stable oxide layers that seal the surface, preventing corrosive agent penetration. This composite structure maintains oxidation resistance during hot pressing while significantly improving corrosion resistance compared to Al-Si plating alone, resolving the contradiction between these two properties.
Solution Approach 2:
The Sr element acts as an intermediary that forms stable oxide layers (SrO, SrSiO3) on the plated layer surface. These oxide layers serve as a protective barrier that prevents both oxidation during hot pressing and corrosion in service environments. The intermediary oxide layer mediates between the metal plated layer and the external environment, providing dual protection that resolves the contradiction between oxidation resistance and corrosion resistance.
3Reliability
If Zn-based plating is used to improve corrosion resistance, then sacrificial anti-corrosion properties are enhanced, but high-temperature processability deteriorates due to volatility and oxidation
Solution Approach 1:
The invention uses an Al-Si-Zn-Mg-Sr composite plated layer where Al and Si form a stable matrix that suppresses Zn volatility and oxidation at high temperatures. The Al-Si base provides high-temperature stability, while Zn dispersed within this matrix provides sacrificial corrosion protection. This composite structure allows the plated layer to maintain both excellent corrosion resistance and high-temperature processability, resolving the contradiction between these two properties.
Solution Approach 2:
The Al-Si matrix acts as an intermediary that confines and stabilizes Zn at high temperatures. The Al-Si phase prevents Zn from volatilizing and oxidizing excessively during hot pressing by providing a stable chemical environment. This intermediary matrix allows Zn to maintain its corrosion protection function while preventing its high-temperature degradation, thereby resolving the contradiction between corrosion resistance and high-temperature processability.
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 proposed solution provides a steel sheet with improved sacrificial anti-corrosion properties and excellent processability, effectively preventing oxidation and enhancing the ability to form complex shapes without spring back issues.
Implementation Method 1
since the aluminum-plated layer is present on the surface of the steel sheet, it is possible to prevent the surface of the steel sheet from being oxidized by heating the steel sheet
Implementation Method 2
Zn-based hot stamping plating technology in which metal materials in the plated layer have sacrificial anti-corrosion properties
Implementation Method 3
since quenching is performed through a mold, the strength of a molded product may be secured
Data Source
AI summary
An embodiment of the present invention discloses a hot-stamped part including: a base steel sheet; and a plated layer provided on the base steel sheet and including zinc (Zn), magnesium (Mg), silicon (Si), aluminum (Al), strontium (Sr), and the balance of iron (Fe) and other inevitable impurities, wherein the plated layer includes an alloying blocking layer, an intermediate alloy layer, and a corrosion resistance reinforcement layer which are sequentially stacked from the base steel sheet, and the corrosion resistance reinforcement layer includes an Sr-containing surface oxide layer.