High Strength Steel Sheet with Enhanced Young's Modulus
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing high-strength steel sheets with high Young's modulus struggle to achieve tensile strength of 780 MPa or more while maintaining rigidity and deep drawability, often requiring expensive chemical elements and failing to provide isotropic Young's modulus in all directions.
Innovation Solution
Hot-rolling steel with Ti and Nb or Ti and V additions, followed by controlled coiling and cold rolling to precipitate carbides, then annealing to grow α-fiber and γ-fiber textures, which enhances Young's modulus and deep drawability across all directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the steel sheet is reduced to reduce automobile weight, then weight reduction is achieved, but the rigidity of automobile bodies decreases
Solution Approach 1:
The patent changes the material parameters by increasing the Young's modulus from conventional values (206 GPa) to 220 GPa or more through specific grain orientation control, allowing the steel sheet to maintain rigidity even at reduced thickness
Solution Approach 2:
The patent creates a composite microstructure containing both ferrite and martensite phases with specific orientations, achieving enhanced rigidity that combines the benefits of different material phases in a controlled configuration
2Strength
If grain orientation anisotropy is provided to increase Young's modulus in a specific direction, then Young's modulus increases in that direction, but the steel sheet cannot achieve high Young's modulus in all directions due to load requirements from various directions
Solution Approach 1:
The patent applies different grain orientations to different regions of the steel sheet - α-fiber texture in the rolling direction and γ-fiber texture in the transverse direction - so that each region is optimized for its specific loading conditions while collectively providing high Young's modulus in all directions
Solution Approach 2:
The patent transitions from conventional single-direction texture optimization to multi-directional texture design by introducing both α-fiber and γ-fiber orientations, adding the transverse dimension to the traditional rolling direction focus
3Weight of moving object
If high strength steel sheet with tensile strength of 780 MPa or more is used to reduce weight, then weight reduction is achieved, but the deep drawability and workability deteriorate
Solution Approach 1:
The patent optimizes the chemical composition parameters (C: 0.06-0.15%, Si: 0.50-2.20%, Mn: 1.00-3.00%, Al: 0.01-2.50%) and microstructural parameters (ferrite area ratio: 20-80%, martensite area ratio: 20-70%, average grain size: 5-50 μm) to achieve the right balance between strength and formability
Solution Approach 2:
The patent creates a composite microstructure with ferrite providing ductility and deep drawability while martensite provides strength, achieving both ease of manufacture and weight reduction through the synergistic combination of these phases
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 method achieves a high-strength steel sheet with tensile strength of 780 MPa or more, Young's modulus of 205 GPa or more in the rolling direction and 220 GPa or more at 45°, and excellent deep drawability, effectively reducing automobile weight while maintaining structural rigidity.
Implementation Method 1
followed by controlled coiling and cold rolling to precipitate carbides
Implementation Method 2
then annealing to grow α-fiber and γ-fiber textures
Data Source
AI summary
A high strength steel sheet having a high Young's modulus, the steel sheet having a chemical composition including, by mass %, C: 0.060% or more and 0.150% or less, Si: 0.50% or more and 2.20% or less, Mn: 1.00% or more and 3.00% or less, and one or both of Ti: 0.001% or more and 0.200% or less and Nb: 0.001% or more and 0.200% or less, in which the contents of C, N, S, Ti, and Nb satisfy the equation 500≤C*≤1300. The steel sheet has a microstructure including ferrite in an amount of 20% or more and martensite in an amount of 5% or more, in terms of area ratio, such that the average grain size of the ferrite is 20.0 μm or less and the inverse intensity ratio of γ-fiber for α-fiber is 1.00 or more in the ferrite and the martensite.