Metal Sheet Crystal Orientation for Roughness-Resistant Forming
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Solution Overview
Problem
Conventional methods for molding metal sheets into complex shapes with deep drawing or overhang molding often result in abnormal surface roughness due to protrusions and recesses, limiting the sheet thickness decrease rate to less than 10% to avoid surface roughness issues, which restricts the production of more intricate automobile exterior sheet products.
Innovation Solution
A metal sheet with specific crystal grain orientations and sizes, controlled through conditions such as area fraction and Taylor Factor values, is used to inhibit surface roughness by allowing a sheet thickness decrease rate of 10% to 30% during plane strain tensile and biaxial tensile deformation, thereby enabling the production of molded products with improved surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If molding is conducted at a large machining amount (sheet thickness decrease rate of 10% or more) to produce complicated shapes, then the shape complexity is improved, but protrusions and recesses are formed on the surface resulting in abnormal surface roughness
Solution Approach 1:
The invention changes the crystallographic parameters of the metal sheet by controlling the area fraction of crystal grains with specific orientations (15° or less relative to (001) plane: 0.20-0.35) and average crystal grain size (15 μm or less). This parameter change in the material structure enables the sheet to withstand large machining amounts (10-30% thickness decrease) during plane strain and biaxial tensile deformation without forming surface protrusions and recesses, thus resolving the contradiction between shape complexity and surface roughness
2Manufacturing precision
If the sheet thickness decrease rate is limited to less than 10% to avoid abnormal surface roughness, then the surface quality is improved, but the production of more intricate molded products is restricted
Solution Approach 1:
By modifying the material parameters through controlled crystal grain orientation (area fraction 0.20-0.35 within 15° of (001) plane) and fine crystal grain size (≤15 μm), the invention expands the processable range of sheet thickness decrease rate from the conventional <10% limit to 10-30%, thereby enhancing the adaptability to produce intricate molded products while maintaining excellent surface quality
3Shape
If conventional molding methods are used for deep drawing or overhang molding, then complex shapes can be produced, but fine protrusions and recesses are likely to be formed on the surface
Solution Approach 1:
The invention changes the fundamental material parameters by controlling crystal grain characteristics (orientation and size) to create a metal sheet that is inherently resistant to surface defect formation during large deformation molding processes. This enables complex shapes to be produced through plane strain and biaxial tensile deformation with sheet thickness decrease rates of 10-30% while maintaining smooth surface finish without the fine protrusions and recesses characteristic of conventional molding
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 proposed method effectively inhibits surface roughness in molded products with bcc and fcc structures, allowing for more complex shapes and increased sheet thickness reduction without compromising surface quality, making it suitable for automobile exterior applications.
Implementation Method 1
molding the metal sheet to cause plane strain tensile deformation and biaxial tensile deformation and allowing at least a part of the metal sheet to have a sheet thickness decrease rate of from 10% to 30%
Data Source
Figure 1~3
Figure 4A
Figure 4B
AI summary
Provided are a metal sheet, a method of producing a metal sheet, a method of producing a molded product of a metal sheet, and a molded product of a metal sheet, in which occurrence of surface roughness is inhibited. Provided are a metal sheet satisfying conditions (a1), (b1) or (c1) at the surface and a method for producing the metal sheet. Also provided are a method for producing a molded product of a metal sheet using the metal sheet, and a molded product of the metal sheet. (a1) The area fraction of crystal grains having a crystal orientation divergent by 20° or more from a (111) plane and by 20° or more from a (001) plane is from 0.25 to 0.35, and the average crystal grain size is less than 16 µm. (b1) The area fraction of crystal grains having a crystal orientation divergent by 20° or more from a (111) plane and by 20° or more from a (001) plane is from 0.15 to 0.30, and the average crystal grain size is 16 µm or more. (c1) The area fraction of crystal grains with a Taylor Factor value from 3.0 to 3.4, when assuming plane strain tensile deformation in the transverse direction, is from 0.18 to 0.40.