Ultrahigh-Strength Steel Sheet Composition for Weldable Ductility
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Solution Overview
Problem
Current steel sheet manufacturing techniques struggle to produce ultrahigh-strength steel sheets with high ductility, crashworthiness, and weldability, limiting their use in complex automotive components due to issues with work hardening, weldability, and strength levels below 1300 MPa.
Innovation Solution
Controlled alloying elements such as manganese, carbon, aluminum, and silicon, combined with a re-rolling process to induce work hardening, resulting in a steel sheet with a microstructure optimized for strength, ductility, and weldability, achieving tensile strengths above 1300 MPa and yield strengths above 1000 MPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large amount of manganese is added to steel to obtain high ductility, then ductility is improved, but work hardening occurs severely in deformed portions and the steel sheet is easily fractured
Solution Approach 1:
The patent applies parameter changes by precisely controlling the manganese content within a specific range (1.5-3.0%) rather than using a large amount, and by adjusting the silicon content (0.01-1.0%) to balance the properties. This optimization of compositional parameters resolves the contradiction between ductility and fracture resistance.
2Stability of the object's composition
If a large amount of silicon is added to steel to obtain intended ductility, then ductility is improved, but the characteristics for electroplating and hot dip plating become poor
Solution Approach 1:
The patent optimizes the silicon content within a controlled range (0.01-1.0%) to achieve the desired ductility while maintaining good plating characteristics. This parameter optimization allows the steel sheet to satisfy both formability requirements and manufacturing process requirements.
3Strength
If the yield strength of steel sheet is increased to improve crashworthiness, then crashworthiness is improved, but the formability and workability of the steel sheet deteriorate
Solution Approach 1:
The patent achieves a balance between yield strength and formability by optimizing the compositional parameters (manganese: 1.5-3.0%, silicon: 0.01-1.0%) and controlling the microstructure. This results in steel sheets with yield strength of 1000-1500 MPa while maintaining adequate formability for automotive applications.
4Strength
If the tensile strength of steel sheet is increased to achieve ultrahigh-strength level, then strength is improved, but the weldability and delayed fracture resistance deteriorate
Solution Approach 1:
The patent controls the carbon equivalent (Ceq) by limiting the contents of alloying elements, specifically maintaining manganese at 1.5-3.0% and silicon at 0.01-1.0%. This parameter control achieves ultrahigh tensile strength (1300-1800 MPa) while preserving weldability and delayed fracture resistance.
5Strength
If current steel sheet manufacturing techniques are used to produce high-strength steel, then strength is improved, but it is difficult to manufacture steel sheets with tensile strength of 1300 MPa or greater that are processable through cold pressing or roll forming
Solution Approach 1:
The patent optimizes the compositional parameters (particularly manganese and silicon content) to achieve a microstructure that provides both ultrahigh strength and good formability. This allows the steel sheets to be processed through cold pressing and roll forming while achieving tensile strength of 1300 MPa or greater.
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 enables the production of ultrahigh-strength steel sheets suitable for complex automotive components, offering improved formability, crashworthiness, and weldability, while maintaining economic viability.
Implementation Method 1
performing a re-rolling process after a cold rolling process or a plating process so as to induce work hardening and thus to impart tensile strength on the level of 1300 MPa or greater and yield strength on the level of 1000 MPa
Data Source
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AI summary
The present invention relates to an ultrahigh-strength steel sheet and a manufacturing method therefor. More specifically, the present invention can provide an ultra-high strength steel sheet which can ensure weldability and a delayed fracture resistance property by controlling the contents of elements affecting platability along with the contents of austenite-stabilizing elements and increasing twin formation through re-rolling, and simultaneously improve impact characteristics and workability by ensuring excellent yield strength and ductility.