Molded Metal Sheet Texture Control for Complex Forming Surfaces
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Solution Overview
Problem
Current methods for molding metal sheets into complex shapes, such as deep drawing or overhang molding, often result in abnormal grain growth and impaired appearance due to the formation of protrusions and recesses, especially at large machining amounts, which limits the sheet thickness decrease rate to less than 10% to avoid these issues.
Innovation Solution
Controlling the area fraction and average crystal grain size of specific crystal orientations in the metal sheet, such as those relative to the (001) and (111) planes, to inhibit the formation of protrusions and recesses during plane strain tensile deformation and biaxial tensile deformation, allowing for a sheet thickness decrease rate of 10% to 30% without abnormal grain growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the sheet thickness decrease rate is increased to achieve more complicated molded product shapes, then the design freedom and shape complexity are improved, but protrusions and recesses form on the surface resulting in abnormal grain growth and impaired appearance
Solution Approach 1:
The patent applies preliminary action by controlling the crystal texture of the metal sheet before molding to prevent abnormal grain growth during subsequent large-deformation molding processes. Specifically, the metal sheet is prepared with controlled crystal orientations (Taylor factor between 2.0-2.5) prior to molding, which enables the material to withstand sheet thickness decrease rates of 10% or more without forming protrusions and recesses on the surface.
2Manufacturing precision
If the sheet thickness decrease rate is limited to less than 10% to avoid abnormal grain growth, then the surface quality and appearance are maintained, but the design freedom and shape complexity are restricted
Solution Approach 1:
The patent applies parameter changes by modifying the crystal texture parameters of the metal sheet, specifically controlling the Taylor factor to be between 2.0 and 2.5. This parameter change in the material's microstructure enables the metal sheet to undergo large deformations (sheet thickness decrease rate of 10% or more) while maintaining surface quality and preventing abnormal grain growth, thus resolving the contradiction between surface quality and shape complexity.
3Ease of manufacture
If conventional molding methods are used for deep drawing or overhang molding, then the production process is simple, but protrusions and recesses form on the surface resulting in abnormal grain growth
Solution Approach 1:
The patent applies preliminary action by preparing the metal sheet with controlled crystal texture (Taylor factor 2.0-2.5) before the molding process. This preliminary control of material microstructure enables conventional molding processes to achieve large sheet thickness decrease rates (10% or more) without forming protrusions and recesses, thereby maintaining both process simplicity and surface quality.
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 molded products with improved design by preventing abnormal grain growth, maintaining excellent appearance, and allowing for more significant sheet thickness reduction, thus expanding the range of complex shapes that can be achieved in metal sheet molding.
Implementation Method 1
molding the metal sheet to cause plane strain tensile deformation and/or biaxial tensile deformation
Implementation Method 2
the area fraction of crystal grains having a crystal orientation of 15° or less relative to a (001) plane parallel to a surface of the metal sheet
Implementation Method 3
protrusions and recesses are likely to be formed on the surface of a molded product, resulting in abnormal grain growth
Implementation Method 4
the average crystal grain size of the crystal grains is 15 μm or less
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
The following is provided based on the disclosure: a method of producing a molded product: including treating a metal sheet having a bcc structure and a surface that satisfies either of the following conditions (a) or (b); and molding the metal sheet to cause plane strain tensile deformation and biaxial tensile deformation and allowing at least one part of the metal sheet to have a sheet thickness decrease rate of from 10% to 30%: (a) an area fraction of crystal grains having a crystal orientation of 15° or less relative to a (001) plane parallel to a surface of the metal sheet is from 0.20 to 0.35; (b) the area fraction of crystal grains having a crystal orientation of 15° or less relative to a (001) plane parallel to a surface of the metal sheet is 0.45 or less, and the average crystal grain size thereof is 15 µm or less; or a molded product that satisfies either of the conditions (a) or (b).