Aluminum-Plated Steel Sheet for Coating Adhesion After Hot Stamping
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Solution Overview
Problem
Existing aluminum-plated steel sheets for hot stamping lack sufficient corrosion resistance after coating, primarily due to inadequate adhesion of the coating material and insufficient reactivity between the oxide film and chemical conversion agents.
Innovation Solution
An aluminum-plated steel sheet with a plating layer containing specific A group elements (such as Be, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and a controlled average grain size, which enhances the adhesion of the electrodeposition coating film and improves corrosion resistance after coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the sheet thickness of steel sheets is reduced to reduce weight, then the weight of vehicle bodies is reduced, but the strength of structures decreases
Solution Approach 1:
The patent applies parameter changes by heating the steel sheet to high temperature (Ac3 transformation point or higher) to alter its microstructure and enable forming, then rapidly cooling it to achieve martensitic transformation and high strength. This thermal parameter change allows thin sheets to achieve both formability and high strength simultaneously
Solution Approach 2:
The patent utilizes phase transitions of steel during hot stamping: heating transforms the microstructure to austenite, enabling plastic deformation; rapid cooling then transforms it to martensite, achieving high strength. This phase transition mechanism resolves the contradiction between thinning for weight reduction and maintaining strength
2Weight of moving object
If the sheet thickness of steel sheets is reduced to reduce weight, then the weight of vehicle bodies is reduced, but the formability of the material deteriorates
Solution Approach 1:
The patent changes the temperature parameter of the steel sheet from ambient to high temperature (Ac3 point or higher), which fundamentally alters the material's formability. At elevated temperature, the steel sheet becomes soft and easily formable, allowing complex shapes to be achieved even with reduced thickness
Solution Approach 2:
The patent exploits the phase transition from ferrite/pearlite to austenite upon heating, which dramatically improves ductility and formability. This phase change enables thin sheets to be formed into complex shapes without cracking or thinning during the forming process
3Reliability
If a chemical conversion film is formed on the surface of hot-stamped members to improve corrosion resistance, then the adhesion of coating material is insufficient, but corrosion resistance is required
Solution Approach 1:
The patent changes the chemical composition parameters of the plating layer by adding specific elements (Al: 5-15 mass%, Si: 3-15 mass%, Mn: 0.5-3.0 mass%) to create a plating layer with enhanced reactivity. This compositional parameter change ensures both good adhesion and corrosion resistance after hot stamping and coating
Solution Approach 2:
The patent creates a composite plating layer structure containing multiple elements (Al-Si-Mn system) that work synergistically: Al provides base protection, Si enhances oxidation resistance and reactivity, and Mn improves adhesion. This composite material approach resolves the contradiction between adhesion and corrosion 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
The proposed solution significantly improves the adhesion of the electrodeposition coating film and enhances the corrosion resistance after coating of hot-stamped members, making the aluminum-plated steel sheet more suitable for applications in the vehicle manufacturing industry.
Implementation Method 1
a surface layer area of a plated steel sheet before hot stamping, and the proportion of A group elements in an oxide film layer that is formed on a surface of a hot-stamped member
Implementation Method 2
a material that is a forming subject is heated to a high temperature, and a steel sheet softened by heating is formed by pressing and, after the forming (or almost at the same time as the forming), cooled
Implementation Method 3
the mechanical strength of the material can be increased by the quenching effect of the cooling after forming
Data Source
AI summary
This aluminum-plated steel sheet has a steel sheet and a plating layer formed on a surface of the steel sheet, the plating layer contains one or more A group elements selected from a group consisting of Be, Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, a remainder of Al, Fe, and impurities, a thickness t of the plating layer is 10 to 60 μm, and an average grain size is 2t/3 or less and 15 μm or less in a thickness range from an outermost surface of the plating layer to a ⅔ thickness t position.