Overlapped Hot-Stamping Blank With Black Coating for Faster Heating
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Solution Overview
Problem
The use of Al-based plated steel sheets in overlapped blanks for hot stamping faces challenges such as a slow temperature increasing rate and a difference in temperature increasing rate between overlapped and non-overlapped parts, leading to decreased productivity and spot weldability issues.
Innovation Solution
The solution involves optimizing the lightness (L*) and coating weights of Al-based plated steel sheets, with a carbon-based black coating on one side, to enhance heat absorption and maintain metallic luster, thereby improving temperature increasing rates and weldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Al-based plated steel sheets are used for overlapped blanks, then oxidation resistance is improved and metallic luster is maintained, but temperature increasing rate becomes slow and productivity decreases
Solution Approach 1:
The patent applies a black coating layer on the Al-based plated steel sheet surface. This black coating has high light absorption properties, converting optical energy to thermal energy more efficiently, thereby increasing the temperature increasing rate during hot stamping while maintaining the underlying Al-based plating's oxidation resistance
Solution Approach 2:
The patent creates a composite structure by combining Al-based plated steel sheet with a black coating layer. This composite material structure leverages the oxidation resistance of Al-based plating and the high heat absorption capability of the black coating, achieving both protective and thermal functions simultaneously
2Reliability
If Al-based plated steel sheets are used for overlapped blanks, then corrosion resistance is improved, but difference in temperature increasing rate between overlapped and non-overlapped parts increases
Solution Approach 1:
The patent applies the black coating selectively to specific regions of the Al-based plated steel sheet, particularly to the overlapped portions. This local application creates different thermal absorption characteristics in different areas, compensating for the reduced heat absorption in overlapped regions and reducing temperature differences across the blank
3Productivity
If carbon-based black coating is applied to enhance heat absorption, then temperature increasing rate is improved, but spot weldability may be affected
Solution Approach 1:
The black coating is applied selectively to specific areas rather than uniformly across the entire surface. This localized application allows heat absorption enhancement where needed while leaving other areas with good spot weldability characteristics
Solution Approach 2:
The patent applies the black coating to a limited extent or thickness that provides sufficient heat absorption benefit without creating excessive carbon content that would interfere with spot welding operations
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 enhances the productivity and spot weldability of Al-based plated steel sheets by addressing the slow temperature increasing rate and rate differences, ensuring effective hot stamping processes.
Implementation Method 1
optimizing the lightness (L*) and coating weights of Al-based plated steel sheets, with a carbon-based black coating on one side, to enhance heat absorption
Implementation Method 2
the Zn-based plating becomes Zn—Fe-based plating and the Al-based plating becomes Al-Fe-based plating after hot stamping heating by the alloying reaction of Fe diffusing into the plating
Data Source
AI summary
To improve both the slow temperature increasing rate of an overlapped part and the difference in temperature increasing rate between an overlapped part and a one-sheet part when an Al-based plated steel sheet is used as a raw material. An overlapped blank for hot stamping according to the present invention includes: a first Al-based plated steel sheet having a sheet thickness t1; and a second Al-based plated steel sheet having a sheet thickness t2, the second Al-based plated steel sheet overlapped and welded on the first steel sheet, having a smaller area than the first steel sheet, and including a carbon-based black coating as an upper layer of an Al-based plated layer on the side not in contact with the first Al-based plated steel sheet, in which the overlapped blank for hot stamping satisfies (1) Expression to (5) Expression.