Molded Metal Sheet Microstructure for High-Strain Surface Quality
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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 high machining amounts, which limits the sheet thickness decrease rate to less than 10% to prevent 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) or (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 abnormal grain growth and surface defects occur
Solution Approach 1:
The patent applies preliminary action by controlling the crystal grain structure and orientation of the metal sheet before molding. Specifically, the metal sheet is prepared with a controlled area fraction of crystal grains having specific orientations (e.g., <100> orientation within 15 degrees of the normal direction) and controlled average crystal grain size (e.g., 5 μm to 20 μm) prior to the molding process. This preliminary control of microstructure prevents abnormal grain growth during subsequent high-machiningAmount molding operations, enabling sheet thickness decrease rates of 10% to 30% while maintaining surface quality.
2Manufacturing precision
If the sheet thickness decrease rate is limited to less than 10% to prevent abnormal grain growth, then surface quality is maintained, but the range of achievable shapes and design freedom are restricted
Solution Approach 1:
The patent applies parameter changes by modifying the crystallographic parameters of the metal sheet material. The invention specifies controlling the area fraction of crystal grains with specific orientations (e.g., <100> orientation within 15 degrees of the normal direction) and controlling the average crystal grain size. By changing these microstructural parameters before molding, the material can withstand sheet thickness decrease rates of 10% to 30% without abnormal grain growth, thereby expanding design freedom while maintaining surface quality.
3Shape
If high machining amount molding is performed to achieve complicated shapes, then design freedom is improved, but protrusions and recesses form on the surface resulting in abnormal grain growth
Solution Approach 1:
The patent applies preliminary anti-action by pre-controlling the crystal grain structure to counteract the harmful effects of high-machiningAmount molding. The metal sheet is prepared with controlled crystal grain orientation (e.g., <100> orientation within 15 degrees of normal direction) and controlled average grain size (5 μm to 20 μm) before molding. This preliminary microstructural control creates resistance against abnormal grain growth during high-machiningAmount operations, enabling sheet thickness decrease rates of 10% to 30% while preventing surface 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
This approach enables the production of molded products with excellent design and surface texture by preventing abnormal grain growth, even at higher sheet thickness decrease rates, thereby expanding the range of achievable shapes and reducing the limitations on machining amounts.
Implementation Method 1
molding the metal sheet to cause plane strain tensile deformation and biaxial tensile deformation
Implementation Method 2
crystal grains having a crystal orientation of 15° or less relative to a (001) plane parallel to the surface of a metal sheet are deformed in a prioritized manner
Data Source
AI summary
The method includes treating a metal sheet having a bcc structure and a surface satisfying conditions (a) or (b), 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%. Condition (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. Condition (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, the average crystal grain size thereof is 15 μm or less. The molded product satisfies conditions (a) or (b).