Austenitic Stainless Steel Foil Stretch Formability
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Solution Overview
Problem
Ultrathin stainless steel foils used in battery cases face challenges with deformation anisotropy and reduced forming depth due to crystal grain orientation and surface hardening issues, limiting their ability to achieve both thin thickness and high formability for compact electronic devices.
Innovation Solution
The development of austenitic stainless steel foils with controlled crystal grain orientation, reduced dislocation density through high-pressure rolling and annealing, and minimized surface nitriding, ensuring random grain orientation and adequate plastic deformability, along with a recrystallization rate of 90% or more, to enhance stretch formability and reduce deformation anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of stainless steel foil is reduced to 60 μm or less, then weight and size are reduced for compact electronic devices, but deformation anisotropy increases and forming depth decreases
Solution Approach 1:
The patent applies parameter changes by controlling the crystal grain size to be 10 μm or less and adjusting the composition parameters (Ni: 8-12 mass%, Cr: 17-20 mass%, Mn: 1.5-3.0 mass%) to achieve uniform deformation characteristics in ultrathin stainless steel foil, thereby improving stretch formability while maintaining reduced thickness
Solution Approach 2:
The patent applies local quality by creating a specific microstructure with uniformly distributed fine crystal grains throughout the foil, ensuring consistent mechanical properties and deformation behavior across the entire material, which eliminates deformation anisotropy in the ultrathin foil
2Weight of moving object
If the thickness of stainless steel foil is reduced to 60 μm or less, then weight and size are reduced, but forming depth during press forming decreases
Solution Approach 1:
The patent changes the microstructural parameters by controlling crystal grain size to 10 μm or less and optimizing compositional parameters, which fundamentally alters the deformation mechanism to enable adequate forming depth even in ultrathin foil with thickness of 60 μm or less
3Ease of operation
If stainless steel foil is subjected to high-pressure rolling to reduce dislocation density, then stretch formability improves, but production complexity increases
Solution Approach 1:
The patent applies preliminary action by performing high-pressure rolling during the manufacturing process to pre-reduce dislocation density and establish the desired microstructure before final foil production, thereby improving stretch formability while integrating the process into existing manufacturing workflows
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 austenitic stainless steel foils demonstrate excellent stretch formability with reduced deformation anisotropy, allowing for increased forming depth and improved battery capacity in compact electronic devices, even at thicknesses of 60 µm or less.
Implementation Method 1
a recrystallization rate of 90% or more
Implementation Method 2
reduced dislocation density through high-pressure rolling
Data Source
AI summary
Provided is an austenitic stainless steel foil that demonstrates a high degree of stretch formability and little deformation anisotropy with respect to stretch forming despite having a sheet thickness of 60 µm or less. The austenitic stainless steel foil of the present invention has a sheet thickness of 5 µm to 60 µm, a recrystallization rate of 90% to 100%, and a texture in which the total of the area ratio of a crystal orientation in which the difference in orientation from the {112}<111> orientation is within 10°, the area ratio of a crystal orientation in which the difference in orientation from the {110}<112> orientation is within 10°, and the area ratio of a crystal orientation in which the difference in orientation from the {110}<001> orientation is within 10°, in a measuring field thereof, is 20% or less.