Hot-Stamped Soft Region Ribs for Dimensional Stability
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Solution Overview
Problem
Existing methods for forming local soft regions in hot stamped parts face challenges with severe dimensional deviations and poor stability due to large temperature differences between soft and hard regions during cooling, leading to inconsistent part sizes and high maintenance costs.
Innovation Solution
A production method involving thermoforming with ribs in the soft region, where the ribs shrink to compensate for dimensional changes, ensuring the soft region's performance and stability by pressing them lower and wider until they match the digital product model.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If soft region formation technology is applied to hot stamped parts, then the hardness problem at connection positions is solved and energy-absorbing effect is improved, but severe dimensional deviations and poor dimensional stability occur
Solution Approach 1:
The patent applies preliminary anti-action by designing ribs with predetermined dimensions in the soft region that will shrink during cooling to counteract the dimensional changes caused by temperature differences. The ribs are intentionally designed with larger initial dimensions so that their shrinkage compensates for the overall part shrinkage, thereby maintaining dimensional stability despite the presence of soft regions with different cooling characteristics.
Solution Approach 2:
The patent utilizes parameter changes by controlling the temperature parameters during the hot stamping process. The soft region is maintained at a higher temperature (500-550°C) while the hard region is cooled to lower temperatures (100-250°C), creating deliberate temperature differences that enable differential cooling rates and controlled microstructure formation, thus achieving both hardness requirements and dimensional stability.
2Strength
If large area soft region and transition region are designed in hot stamped parts, then the hardness distribution is improved, but the size and performance of parts cannot be both ensured
Solution Approach 1:
The patent applies local quality by creating distinct regions with different properties within the hot stamped part. The soft region with ferrite or bainite microstructure provides ductility and energy absorption, while the hard region with martensite microstructure provides strength and hardness. The rib structures are locally positioned in the soft region to provide localized dimensional compensation, allowing large area soft regions to be implemented without compromising overall part size control.
3Stability of the object's composition
If temperature difference between soft region and hard region is maintained during cooling, then the microstructure transformation is achieved, but the soft region and hard region shrink to different sizes causing dimensional instability
Solution Approach 1:
The patent converts the harmful effect of differential shrinkage caused by temperature differences into a beneficial effect. The ribs in the soft region are intentionally designed to shrink during cooling, and this shrinkage is harnessed to compensate for the overall dimensional changes in the part. The temperature difference that causes problematic differential shrinkage is also the mechanism that enables the ribs to provide dimensional compensation, thus converting a harm into a benefit.
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
Ensures dimensional stability and performance of the soft region, addressing severe deviations and stability issues while reducing equipment investment and maintenance costs.
Implementation Method 1
heating a slab in a heating furnace to fully austenitize the same
Implementation Method 2
the soft region cools and shrinks
Implementation Method 3
the temperature of a soft region of a part is about 500 to 550 degrees Celsius, but the temperature of a hard region is 100 to 250 degrees Celsius. After cooling, both the temperature of the soft region and the temperature of the hard region are lowered to room temperature, and a large temperature difference therebetween causes the soft region and the hard region to shrink to different sizes
Implementation Method 4
the ribs of the soft region being pressed lower and wider when pressure is applied, until they are the same shape as a digital product model
Data Source
AI summary
A method and die for a hot stamped member comprising a local soft region, and a hot stamped member, is provided. The method comprises moving an austenitized slab into a TTP thermoforming die, the TTP thermoforming die pressing out several ribs at a soft region position, moving a thermoformed member from the TTP thermoforming die into a shaping die, and pressing, when pressure is applied, the ribs of the soft region lower and wider until they are the same shape as a digital product model. A soft region is provided with ribs during thermoforming, and the ribs shrink during shaping to compensate for a dimensional change caused by the soft region cooling and shrinking, thereby not only ensuring the performance of a soft region of a part, but also solving the problems of severe dimensional deviation and poor dimensional stability after TTP formation.