Multi-directional Rolling for Variable Thickness Vehicle Parts
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Solution Overview
Problem
Current methods for manufacturing vehicle body parts with varying thicknesses and strengths using hot stamping face challenges, particularly with coated steel sheets, as they often result in strength reduction and surface oxidation issues, and existing technologies like TWB and TRB have limitations in applying to coated steel sheets for hot stamping.
Innovation Solution
A method involving rolling a blank in multiple directions, incorporating holes and flanges to manage deformation and thickness variations, and omitting preheating to prevent surface cracks, allowing for the use of coated steel sheets like Al-coated steel for hot stamping without seam formation, enabling the production of vehicle parts with multiple regions of different thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If TWB technology is used to manufacture vehicle body parts with varying thicknesses, then parts with different thicknesses can be produced, but strength reduction occurs in welded portions and coated steel sheets cannot be applied
Solution Approach 1:
The blank is divided into multiple regions with different thicknesses through localized rolling operations. The rolling process is segmented into multiple passes with different roll gaps to create specific thickness distributions in different areas of the blank, enabling complex geometry without welding.
Solution Approach 2:
Different regions of the blank are given different thicknesses and material properties through localized rolling. The rolling parameters (pressure, duration, roll gap) are adjusted for each specific region to achieve the desired local thickness and mechanical properties, allowing optimization of each area for its specific function.
2Object-affected harmful factors
If Al-coated steel sheets are used for hot stamping, then surface oxidation is reduced, but laser welding causes strength reduction in welded portions
Solution Approach 1:
The welding operation is completely eliminated from the manufacturing process. Instead of joining separate parts through laser welding, the invention creates a single integral part by forming different thickness regions directly in the blank before hot stamping, thus avoiding the harmful effect of welded portion strength reduction.
Solution Approach 2:
Multiple parts that would traditionally be separately manufactured and welded together are merged into a single integral blank with varying thickness. The blank is designed to incorporate multiple functional regions (different thicknesses) that correspond to different part requirements, all formed in one piece without seams.
3Shape
If TRB technology is used to control thickness, then thickness can be adjusted in rolling direction, but thickness cannot be varied in other directions and applicability to various vehicle parts is limited
Solution Approach 1:
The rolling process is made dynamic and flexible through multiple passes with varying parameters. Instead of a single fixed rolling operation, the process adapts through sequential passes with different roll gaps, pressures, and durations to create complex three-dimensional thickness distributions that go beyond simple one-directional control.
Solution Approach 2:
The thickness control is extended from one-dimensional (TRB rolling direction only) to two or three dimensions by applying rolling operations in multiple directions and sequences. This creates complex thickness patterns across the blank surface that can accommodate various vehicle part geometries and functional requirements.
4Object-affected harmful factors
If preheating is performed before rolling to oxidize coated layer, then surface oxidation is controlled, but fine cracks occur on blank surface during rolling
Solution Approach 1:
The blank is prepared in advance by creating the desired thickness distribution through rolling operations at ambient or elevated temperature before the hot stamping process. This preliminary forming eliminates the need for subsequent oxidation or preheating steps that would compromise surface integrity, as the complex geometry is established while the material is still ductile and crack-resistant.
Solution Approach 2:
The rolling process parameters (temperature, pressure, strain rate) are optimized to achieve the desired thickness distribution without causing surface cracking. By carefully controlling these parameters, the material undergoes plastic deformation to create varying thicknesses while maintaining surface integrity, eliminating the need for oxidation-inducing preheating.
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 enables the production of vehicle body parts with varied thicknesses and strengths without seams, effectively addressing the limitations of existing technologies by preventing surface cracks and maintaining strength, while allowing for the use of coated steel sheets, thus enhancing collision performance and production efficiency.
Implementation Method 1
the blank is heated to an austenitization temperature or more, for example, up to 950°C
Implementation Method 2
the microstructure of a steel blank has to be transformed from austenite to martensite by the quenching process
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~4C
AI summary
Provided is a method for manufacturing vehicle body parts, including: rolling a blank (10) such that the blank (10) has two or more regions with different thicknesses; trimming the rolled blank (10); and performing hot press forming on the trimmed blank (10), and cooling the trimmed blank (10). The blank (10) to be rolled has an absorption hole (11), and a flange (22) protrudes from an edge region of the blank (10) corresponding to a position of the absorption hole (11). The blank (10) is rolled in two or more different directions.