Structural Steel Plate With Through-Thickness Texture for High Rigidity
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Solution Overview
Problem
Current methods for achieving high strength and rigidity in steel materials for structural applications, such as automobile structures, often require additional elements or increased manufacturing costs, and struggle to balance strength and toughness while maintaining moldability and resistance to tensile deformation.
Innovation Solution
A high-strength and high-rigidity steel plate is manufactured using a composition of 0.05% to 0.4% C, 1.65% Mn, 0.55% Si, and 0.040% P, with a balanced Fe and impurities, and rolled using a large-diameter work roll in a warm temperature range to refine crystal grains and control texture orientation, thereby achieving a Young's modulus of 210 GPa or more and a yield strength of 580 MPa or more without additional elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If dispersed particles with high elastic constant are added to increase rigidity, then rigidity is improved, but manufacturing cost increases and raw material procurement becomes unstable
Solution Approach 1:
The invention extracts and eliminates the need for additional dispersed particles (such as boride particles containing titanium) from the steel plate composition. Instead of adding external particles, the patent achieves high rigidity through controlled crystal orientation (texture) of the steel matrix itself, specifically by increasing the Young's modulus in the rolling direction through texture control with 30° to 75° orientation relative to the rolling direction.
Solution Approach 2:
The invention changes the physical parameters of the steel plate by controlling crystal orientation (texture) rather than changing chemical composition. By adjusting rolling conditions and heat treatment to achieve specific crystal orientation angles (30° to 75° relative to rolling direction), the Young's modulus in the rolling direction is increased to 130 GPa or more, achieving high rigidity without adding particles.
2Stress or pressure
If crystal orientation is adjusted to increase Young's modulus in a specific direction, then rigidity is improved, but strength decreases during heat treatment
Solution Approach 1:
The invention optimizes the crystal orientation parameters to achieve a balance between rigidity and strength. By controlling the texture to have 30° to 75° orientation relative to the rolling direction, the patent achieves a Young's modulus of 130 GPa or more in the rolling direction while maintaining adequate strength properties through controlled rolling and heat treatment processes.
3Stress or pressure
If Al content is increased to control texture and improve Young's modulus, then rigidity is improved, but toughness decreases
Solution Approach 1:
The invention changes the approach from chemical composition control to physical process control. Instead of increasing Al content to control texture, the patent achieves the desired crystal orientation (30° to 75° relative to rolling direction) through optimized rolling conditions and heat treatment parameters, thereby avoiding the toughness degradation associated with high Al addition.
4Strength
If strength of steel plate is increased to improve structural performance, then strength is improved, but moldability and resistance to tensile deformation worsen
Solution Approach 1:
The invention applies local quality by creating different properties in different directions through controlled texture. The steel plate exhibits high strength and high Young's modulus in the rolling direction (where structural support is needed) while maintaining adequate ductility and moldability in other directions, allowing the material to meet both structural performance and formability requirements.
5Strength
If shot peening is performed to impart residual compressive stress and prevent fracture, then fracture resistance is improved, but manufacturing cost increases due to additional process
Solution Approach 1:
The invention performs preliminary action by incorporating the necessary texture control and crystal orientation adjustments during the primary rolling and heat treatment processes, before secondary working such as press molding. This preliminary optimization of the steel plate's anisotropic properties ensures both high strength and good moldability from the start, eliminating the need for subsequent shot peening or other fracture prevention treatments.
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 results in a steel plate with a fine crystal grain structure, different textures at the plate thickness center and surface layers, and enhanced strength and rigidity, along with a residual compressive stress of 100 MPa or more in the surface layer, suitable for structural applications like automobiles, while maintaining cost-effectiveness.
Implementation Method 1
rolled using a large-diameter work roll in a warm temperature range to refine crystal grains
Implementation Method 2
refine crystal grains and control texture orientation, thereby achieving a Young's modulus of 210 GPa or more
Implementation Method 3
control texture orientation, thereby achieving a Young's modulus of 210 GPa or more and a yield strength of 580 MPa or more
Implementation Method 4
increase the resistance force with respect to elastic deformation in order to secure the firm rigidity of vehicle body
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention provides a steel material which has a plate shape and achieves both high strength and high rigidity by imparting large nonuniform deformation to the steel material utilizing rolling using a large-diameter work roll. The steel plate according to an embodiment of the present invention is produced by performing rolling using a rolling mill having a work roll diameter of 650 mm or more in a warm temperature region so that a nonuniform metallographic structure is formed in a plate thickness direction and thus the steel plate of the present invention is a high-strength and high-rigidity steel plate in which a yield strength is 580 MPa or more and a Young's modulus at a plate thickness center portion or a surface layer portion is 210 GPa or more and a difference in Young's moduli at the plate thickness center portion and the surface layer portion is 5 GPa or more in a case in which a tensile direction in a tensile test is at least any one of a rolling direction, a plate width direction, or a direction forming an angle difference of 45 degrees from the rolling direction and the plate width direction.