Overlapped Hot-Stamp Blank Heating to Suppress Warpage
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Solution Overview
Problem
The use of Al-based plated steel sheets in manufacturing overlapped hot stamp molded bodies leads to warpage due to differences in temperature raising rates between overlapped and non-overlapped portions, which hinders productivity in hot-stamping heating processes.
Innovation Solution
To address the warpage issue, the method involves heating the overlapped blank at controlled average heating rates, optimizing the sheet thickness and area ratios of the overlapped and non-overlapped portions, and ensuring a specific range of heating times and temperatures to equalize sheet temperatures and reduce warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Al-based plated steel sheets are used in overlapped hot stamp molding, then corrosion resistance is improved, but warpage occurs due to differences in temperature raising rates between overlapped and non-overlapped portions
Solution Approach 1:
The patent applies parameter changes by controlling the heating rate within a specific range (3-15°C/s) to equalize temperature distribution between overlapped and non-overlapped portions. This parameter optimization prevents thermal expansion differences that cause warpage, while maintaining the corrosion resistance benefits of Al-based plated steel sheets.
2Productivity
If high heating rates are used to improve productivity, then heating time is reduced, but warpage increases due to temperature differences between overlapped and non-overlapped portions
Solution Approach 1:
The patent identifies an optimal heating rate range (3-15°C/s) that balances productivity and shape stability. This parameter optimization allows sufficiently fast heating to maintain productivity while preventing excessive temperature differences that would cause warpage, resolving the contradiction between heating efficiency and dimensional stability.
3Strength
If the overlapped portion area is increased to enhance reinforcement, then collision resistance is improved, but warpage increases due to larger temperature differences
Solution Approach 1:
The patent uses parameter changes in heating rate to compensate for the increased warpage tendency caused by larger overlapped areas. By optimizing the heating rate within the specified range, the patent enables the use of larger overlapped portions for enhanced collision resistance while maintaining shape stability through controlled thermal expansion.
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 suppresses warpage during heating, improves the stability of transferring the steel sheet, and enhances the productivity of the hot-stamping process while maintaining the corrosion resistance of the overlapped hot stamp molded body.
Implementation Method 1
heating the overlapped blank in a heating furnace
Implementation Method 2
carrying the heated overlapped blank out of the heating furnace and transferring it to a pressing apparatus
Implementation Method 3
performing presswork on the heated overlapped blank by using a die provided to the pressing apparatus
Data Source
AI summary
A manufacturing method includes: heating an overlapped blank; transferring the heated overlapped blank; and a step of performing presswork on the heated overlapped blank by using a die. In the heating step, when sheet-thicknesses of the first and second steel sheets are set, respectively, and an average heating rate at a sheet temperature from 20 to 800° C. of a portion with a total sheet thickness of an overlapped portion, and a non-overlapped portion are set, the total sheet thickness is 2.5 to 5.0 mm, a maximum length of the overlapped portion is 100 to 1100 mm, an area of the first steel sheet, an area of a portion, of the second steel sheet, overlapped with the first steel sheet, and the average heating rates satisfy Expressions (1) to (3), and heating is performed at a temperature and for a time within a specific range on a plane of coordinates.