Ultra-High-Strength Steel Sheet With High Yield Ratio and Bendability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing ultra-high strength steel sheets with high yield ratios and excellent bendability face challenges such as shape quality deterioration, material defects, and reduced formability due to temperature deviations, which limit their application in cold stamping processes.
Innovation Solution
A steel sheet composition with specific elemental content (C: 0.1-0.3%, Mn: 1.0-2.3%, Si: 0.05-1.0%, P: 0.1% or less, S: 0.03% or less, Al: 0.01-0.5%) and a manufacturing process involving heat treatment, primary cooling, secondary cooling, and reheating and overaging to achieve a yield ratio greater than 0.73 and excellent bending properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If water cooling during continuous annealing is used to increase yield strength, then yield ratio is improved, but shape quality deteriorates and material defects occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling alloying element compositions (C: 0.15-0.30%, Mn: 1.50-2.50%, Si: 0.10-0.60%, Al: 0.015-0.050%, Ti: 0.010-0.050%, Nb: 0.010-0.050%, V: 0.010-0.050%, B: 0.0005-0.0050%) and heat treatment parameters (tempering temperature 150-250°C, holding time 5-30 minutes) to achieve high yield ratio while preventing shape quality deterioration and material defects
Solution Approach 2:
The patent uses composite material principles by creating a multi-element alloy system combining C, Mn, Si, Al, Ti, Nb, V, and B to achieve synergistic effects that simultaneously improve strength, control carbide precipitation, and maintain shape quality during heat treatment
2Strength
If strength of steel sheet is increased, then yield strength is improved, but elongation decreases and forming processability deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the balance between strength-enhancing elements (C, Mn, Si) and microstructure-controlling elements (Ti, Nb, V, B), along with precise heat treatment parameters (tempering temperature 150-250°C, holding time 5-30 minutes), to achieve high yield strength while maintaining sufficient elongation and forming processability
3Strength
If hot press forming method is used to secure high strength, then strength is improved, but equipment investment increases and process costs increase
Solution Approach 1:
The patent applies the principle of using simpler, more economical processing methods by developing a cold-rolled steel sheet that achieves high strength through controlled alloying and heat treatment, eliminating the need for expensive hot press forming equipment while maintaining comparable strength levels
Solution Approach 2:
The patent uses parameter changes in composition and heat treatment to enable cold stamping processability, providing a cost-effective alternative to hot press forming by achieving high strength through material design rather than expensive forming equipment
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 solution provides a steel sheet with high strength, high yield ratio, and excellent bending properties, suitable for use as a body-in-white structural member, while maintaining weldability and securing good crash performance.
Implementation Method 1
heat treating the cold-rolled steel sheet at a temperature of Ac3 or higher for 30 seconds or more
Implementation Method 2
primarily cooling the cold-rolled steel sheet to a temperature within a range of 500 to 750° C. at an average cooling rate of 1 to 10° C./s after the heat treatment
Implementation Method 3
reheating and overaging by heating the secondarily-cooled steel sheet to a temperature within a range of greater than secondary cooling end temperature+30° C. and less than 270° C., and holding the same for 1 to 20 minutes
Data Source
AI summary
Provided is an ultra high strength steel sheet having a high yield ratio, and a method for manufacturing same and, more specifically, to a steel sheet having ultra high strength, a high yield ratio and excellent bendability, and a method for manufacturing same.