Hot-Stamped A-Pillar Outer Panel Geometry to Prevent Cracks and Wrinkles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing high-strength lower A pillar outer panels with vertical walls and flanges in vehicle bodies face challenges such as contradictory relationships between strength and formability, leading to issues like cracks, wrinkles, and increased manufacturing costs, particularly in hot-stamping processes where achieving high tensile strength and small radii of curvature is difficult.
Innovation Solution
A hot-stamping formed article and manufacturing method that incorporates a transition portion with continuous vertical and outward flanges in the corner portion, utilizing a martensitic steel structure and a one-step bending drawing combined forming process to achieve high collision characteristics and rigidity while maintaining a thin sheet thickness and light weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strengthening of steel sheet is implemented to improve collision safety, then tensile strength increases, but formability deteriorates leading to cracks and wrinkles
Solution Approach 1:
The patent applies temperature parameter changes by heating the steel sheet to Ac3 transformation point or higher before forming, then rapidly cooling it during hot stamping. This thermal parameter change enables the steel to be formed in the austenite region with improved formability, followed by martensitic transformation to achieve high tensile strength of 1200 MPa or more, thus resolving the contradiction between strength and formability
Solution Approach 2:
The patent utilizes phase transition of steel from austenite to martensite through controlled heating and rapid cooling during hot stamping. The steel sheet is heated to transform to austenite phase for easy forming, then rapidly cooled in the die to transform to martensite phase, achieving both high formability during forming and high strength in the final product
2Manufacturing precision
If two-step cold forming method is used to create vertical walls with flanges, then manufacturing precision improves, but manufacturing complexity and costs increase
Solution Approach 1:
The patent merges multiple forming operations into a single hot stamping step. The steel blank is heated and then formed in one operation to create both the vertical walls and the outwardly-extending flanges simultaneously, eliminating the need for separate bending operations and reducing manufacturing complexity while maintaining precision
Solution Approach 2:
The patent applies preliminary heating action to the steel blank before forming. By heating the steel to austenite region beforehand, the material becomes more formable, allowing complex shapes with vertical walls and flanges to be formed in one step without requiring multiple subsequent processing steps
3Productivity
If one-step drawing method is used to form vertical walls, then productivity improves, but manufacturing precision deteriorates due to cracks and wrinkles
Solution Approach 1:
The patent changes the temperature parameter during forming by performing hot stamping instead of cold forming. The steel is heated to Ac3 point or higher, transforming it to austenite phase which has superior formability and ductility, allowing one-step drawing to proceed without generating cracks or wrinkles, thus maintaining both high productivity and manufacturing precision
Solution Approach 2:
The patent utilizes phase transition to austenite before forming and to martensite after forming. During the forming step, the steel is in austenite phase which allows large deformations without damage, enabling one-step forming with high productivity. The subsequent rapid cooling transforms it to martensite phase, ensuring high strength and surface quality without defects
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
The solution enables the production of hot-stamping formed articles with high collision characteristics and rigidity, achieving a balance between strength and weight reduction, while avoiding cracks and wrinkles, and reducing manufacturing complexity and costs.
Implementation Method 1
a steel blank, which is a forming material of the lower A pillar outer panel 1, is heated to a temperature of Ac 3 point or higher, thereafter formed with a press die, and then subjected to heat removal and quenching
Implementation Method 2
subjected to heat removal and quenching
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
The present invention provides a hot-stamping formed article made of steel, in which the hot-stamping formed article has at least one of a tensile strength of 1200 MPa or more and a martensitic steel structure and includes a first portion, a corner portion, and a second portion, which are sequentially continuous from one end portion to the other end portion in a longitudinal direction, each of the first portion, the corner portion, and the second portion includes a top sheet and two vertical walls connected to the top sheet when viewed in a cross section perpendicular to the longitudinal direction, the second portion includes a first outwardly-extending flange adjacent to the vertical wall, and the corner portion includes a vertical flange extending from the vertical wall of the first portion, a second outwardly-extending flange adjacent to the vertical wall located on an outer peripheral side of the corner portion out of the two vertical walls, and a transition portion in which the vertical flange and the second outwardly-extending flange are continuous.