Automotive Outer Plate Blank Orientation to Reduce Ghost Lines
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Solution Overview
Problem
Existing technologies fail to effectively reduce ghost lines in press-formed automobile panel components, which are visually undesirable streaks caused by the preferential deformation of soft and hard phases in steel sheets.
Innovation Solution
The solution involves manufacturing a steel sheet with a specific chemical composition and rolling direction, where the rolling direction aligns with the vehicle body left-right direction to minimize preferential deformation of the soft phase, thereby reducing ghost lines. The steel sheet composition includes elements like C, Mn, Si, Al, P, S, N, O, and others, with controlled ranges to enhance strength and formability. The manufacturing process includes blanking the sheet so that the rolling direction extends along the longitudinal direction of the blank sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high-strengthening and thinning of panel components is implemented to reduce weight and improve collision safety, then weight reduction and collision safety are improved, but appearance quality deteriorates due to visible surface defects
Solution Approach 1:
The invention changes the orientation parameter of the steel sheet by rotating it 90 degrees before blanking, so that the rolling direction becomes the longitudinal direction of the blank sheet. This parameter change in orientation prevents ghost lines from forming in the visual field during press forming, thereby maintaining high appearance quality while using high-strength thin steel sheets for weight reduction.
2Strength
If high-strengthening steel sheets are used to improve collision safety, then collision safety is improved, but appearance quality deteriorates due to ghost lines caused by preferential deformation
Solution Approach 1:
The invention changes the orientation parameter of the steel sheet by rotating it 90 degrees before blanking. This causes the rolling direction to align with the longitudinal direction of the blank sheet, which prevents ghost lines from forming in the visual field during press forming of high-strength steel, thereby maintaining appearance quality while ensuring collision safety.
3Stability of the object's composition
If the rolling direction is aligned with the sheet width direction during press forming, then deformation is more uniform, but ghost lines occur due to preferential deformation of soft phase in the longitudinal direction
Solution Approach 1:
The invention inverts the conventional blanking orientation by rotating the steel sheet 90 degrees. Instead of aligning the rolling direction with the sheet width direction, the rolling direction is aligned with the longitudinal direction of the blank sheet. This inversion prevents ghost lines from forming in the visual field during press forming.
4Weight of moving object
If thin steel sheets are used to reduce weight, then weight reduction is achieved, but formability and dent resistance deteriorate
Solution Approach 1:
The invention changes the orientation parameter to prevent ghost line formation, which enables the use of thin high-strength steel sheets for weight reduction. By eliminating the appearance quality issue that would otherwise prevent using thin sheets, the invention indirectly improves formability and dent resistance while achieving weight reduction.
Data Source
AI summary
A blank sheet which is a material for an outer plate component for an automobile includes a steel sheet. A rolling direction of the steel sheet extends along a longitudinal direction of the blank sheet, and a thickness is 0.6 mm or less. The steel sheet may have a chemical composition in which arithmetic average waviness Wa is 0.10 to 0.30 μm. The steel sheet may have a chemical composition in which ΔC calculated from C20 that is a C content at a depth position of 20 μm from a surface, C60 that is a C content at a depth position of 60 μm from the surface, and Expression (1) is 0.20 to 0.90 mass %/mm, and a tensile strength is 500 MPa or greater,ΔC=(C60−C20)/(0.04) (1).