Overlapped Hot-Stamp Blank Coating Layout for Uniform Heating
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Solution Overview
Problem
The use of aluminum-based plated steel sheets in hot stamping faces challenges in achieving uniform temperature increasing rates between overlapped and one-sheet parts, leading to inadequate corrosion resistance and potential liquid-metal embrittlement issues due to differences in temperature increasing rates.
Innovation Solution
The solution involves optimizing the plating coating weight and structure of aluminum-based plated steel sheets, where the first steel sheet has a higher plating coating weight and the second steel sheet has a lower plating coating weight, with a specific ratio and thickness relationship, along with spot welding and additional coatings like carbon-based coatings or ZnO/TiO2 to enhance emissivity and uniform heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum-based plated steel sheets are used in hot stamping, then corrosion resistance is improved, but temperature increasing rate becomes non-uniform between overlapped and one-sheet parts
Solution Approach 1:
The patent applies different plating coating weights to different regions: the first steel sheet (one-sheet part) has a higher plating coating weight (W1) while the second steel sheet (overlapped part) has a lower plating coating weight (W2). This local differentiation ensures uniform temperature increasing rates across both regions during hot stamping, while maintaining adequate corrosion resistance through the higher plating on the one-sheet part.
2Reliability
If the plating coating weight is increased to improve corrosion resistance, then liquid-metal embrittlement is prevented, but temperature increasing rate becomes non-uniform
Solution Approach 1:
The patent implements local quality by setting W1 > W2, where the higher plating coating weight on the first steel sheet provides adequate protection against liquid-metal embrittlement and corrosion, while the lower plating coating weight on the second steel sheet ensures uniform temperature increasing rate during hot stamping.
Solution Approach 2:
The patent changes the plating coating weight parameter differently for overlapped and one-sheet parts. By optimizing W1 and W2 within specific ranges and establishing their relationship through the formula (W1/W2)²×(t1/t2)≥1.5, the patent achieves both adequate corrosion/embrittlement resistance and uniform temperature distribution.
3Ease of manufacture
If uniform plating coating weight is used across all steel sheets, then manufacturing is simplified, but temperature increasing rate becomes non-uniform leading to poor corrosion resistance
Solution Approach 1:
The patent applies local quality by differentiating plating coating weights between the first steel sheet (W1) and second steel sheet (W2). This regional differentiation optimizes both corrosion resistance and temperature distribution, while the clear specification of weight relationships maintains manufacturing feasibility.
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
This approach effectively addresses the temperature rate disparity, improving corrosion resistance and preventing liquid-metal embrittlement by ensuring consistent alloying reactions and enhanced emissivity across the overlapped and one-sheet parts during hot stamping.
Implementation Method 1
the Zn-based plating becomes Zn—Fe-based plating and the Al-based plating becomes Al—Fe-based plating after the hot-stamping heating by the alloying reaction of diffusing Fe in the plating
Implementation Method 2
additional coatings like carbon-based coatings or ZnO/TiO2 to enhance emissivity and uniform heating
Implementation Method 3
heating a steel sheet up to an Ac3 point or higher (for example, 800° C. or higher) to make it into austenite
Implementation Method 4
rapidly cooling it down to an Ms point or lower (for example, 400° C. or lower) by a metal mold during keeping it at a bottom dead center to make the material into martensite to thereby quench it
Implementation Method 5
a first steel sheet; and at least one second steel sheet connected to a surface of the first steel sheet via a welding point
Data Source
AI summary
To solve the problem about the difference in temperature increasing rate between an overlapped part and a one-sheet part so as to further improve the corrosion resistance of plating after hot stamping. An overlapped blank for hot stamping includes: a first steel sheet; and at least one second steel sheet connected to a surface of the first steel sheet via a welding point and smaller in area than the first steel sheet, wherein: the first steel sheet is a plated steel sheet having an aluminum-based plated layer on both faces of the first steel sheet, and the second steel sheet is a plated steel sheet having an aluminum-based plated layer on both faces of the second steel sheet; a coating weight of the aluminum-based plated layer on the first steel sheet is W1 (g/m2) in terms of an average coating weight on both the faces; a coating weight of the aluminum-based plated layer on a surface on a side not in contact with the first steel sheet in the second steel sheet is W2 (g/m2); and each of the W1 and the W2 is within a range of 20 g/m2 or more and 120 g/m2 or less, and satisfies relationships of Expression (1) and Expression (2).