Overlapped Hot Stamping Heating Control to Minimize Sheet Warpage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of Al-based plated steel sheets as raw materials for manufacturing overlapped hot stamp molded bodies results in warpage due to differences in temperature raising rates between overlapped and non-overlapped parts, leading to reduced productivity and potential corrosion issues.
Innovation Solution
By controlling the heating rate, sheet thickness, and chemical composition of the Al-based plated steel sheets, specifically setting the total sheet thickness to 2.5-5.0 mm, heating at a rate of 1.0-4.0°C/s, and ensuring equalized sheet temperatures, the warpage is minimized, and corrosion resistance is enhanced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Al-based plated steel sheets are used as raw materials for overlapped hot stamp molded bodies, then corrosion resistance is improved, but warpage occurs due to differences in temperature raising rates between overlapped and non-overlapped parts
Solution Approach 1:
The patent applies parameter changes by controlling the heating rate (1.0-4.0°C/s), sheet thickness (2.5-5.0 mm total), and chemical composition (C: 0.10-0.50%, Si: 0.01-2.00%, Mn: 0.30-5.00%, Al: 0.500% or less, B: 0.0002-0.0100%) to minimize warpage while maintaining corrosion resistance of Al-based plated steel sheets
Solution Approach 2:
The patent applies preliminary action by pre-heating the overlapped blank at a controlled rate before final hot stamping, which equalizes the temperature distribution and prevents warpage from developing during the heating process
2Productivity
If the heating rate is increased to improve productivity, then manufacturing time is reduced, but warpage increases due to unequal temperature distribution
Solution Approach 1:
The patent optimizes the heating rate parameter to a specific range (1.0-4.0°C/s) that balances productivity and warpage prevention, representing a parameter change that resolves the contradiction between speed and precision
3Strength
If the sheet thickness is increased to improve strength, then collision resistant property is enhanced, but temperature equalization becomes more difficult leading to increased warpage
Solution Approach 1:
The patent sets the total sheet thickness to a specific range (2.5-5.0 mm) that provides sufficient collision resistance while allowing effective heat penetration and temperature equalization, resolving the contradiction between strength and thermal uniformity
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 improves productivity by reducing warpage and maintains corrosion resistance, ensuring stable manufacturing processes and high-quality overlapped hot stamp molded bodies.
Implementation Method 1
heating at a rate of 1.0-4.0°C/s, and ensuring equalized sheet temperatures
Implementation Method 2
warpage due to differences in temperature raising rates between overlapped and non-overlapped parts
Implementation Method 3
rapidly cooling it down to an Ms point or lower (for example, 400°C or lower) by a die during keeping it at a bottom dead center to make the material into martensite to thereby quench it
Data Source
Figure 1~2
Figure 3~4(b)
Figure 5~6
AI summary
To solve a problem about warpage of a steel sheet due to a difference in temperature raising rate between an overlapped part and a one-sheet part. This manufacturing method includes: a step of heating an overlapped blank; a step of transferring the heated overlapped blank; and a step of performing presswork on the heated overlapped blank by using a die, in which in the heating step, when sheet thicknesses of the first and second steel sheets are set to t1 and t2, respectively, and an average heating rate at a sheet temperature from 20 to 800°C of a portion with a total sheet thickness (tl + t2) of an overlapped portion, and that of a non-overlapped portion are set to V and vl, respectively, the total sheet thickness (tl + t2) is 2.5 to 5.0 mm, a maximum length L of the overlapped portion is 100 to 1100 mm, an area S1 of the first steel sheet, an area S2 of a portion, of the second steel sheet, which is overlapped with the first steel sheet, and the average heating rates V and v1 satisfy Expressions (1) to (3), and the heating is performed at a heating temperature and for a heating time within a specific range on a plane of coordinates defined by the heating time and the heating temperature.