Dual-Phase Steel Composition for Low-Cost 80 kg Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing dual-phase steels face challenges in achieving high mechanical performances while maintaining low cost, due to high contents of alloying elements like Si, Mn, and Mo, which affect weldability, surface quality, and phosphatability, and result in increased production costs.
Innovation Solution
A dual-phase steel composition comprising C: 0.09%-0.11%, Si: 0.1%-0.3%, Mn: 1.4%-1.6%, Al: 0.01%-0.03%, Nb: 0.01%-0.03%, Ti: 0.01%-0.03%, and B: 0.0020%-0.0030%, with a hardenability factor YQ of 1.9≤YQ≤2.1, and a manufacturing process involving smelting, hot rolling, cold rolling, annealing, and tempering, to achieve a 80 kg-grade strength without Mo and Cr.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high content of Mn and Si is added to achieve high strength, then mechanical performance is improved, but weldability and surface quality deteriorate
Solution Approach 1:
The patent precisely controls the content ranges of alloying elements (C: 0.23-0.38%, Si: 0.10-0.30%, Mn: 1.30-1.70%) to achieve the optimal balance between strength and weldability. By adjusting these parameters within specific ranges, the steel attains tensile strength ≥780 MPa while maintaining good weldability and surface quality.
Solution Approach 2:
The patent creates a dual-phase composite microstructure consisting of ferrite and martensite phases. This composite structure combines the ductility of ferrite with the high strength of martensite, achieving tensile strength ≥780 MPa with elongation ≥10%, while the controlled composition ensures good weldability without excessive alloying.
2Strength
If high content of alloying elements (Si, Mn, Mo, Cr) is used to achieve high strength, then mechanical performance is improved, but production cost increases
Solution Approach 1:
The patent optimizes the composition parameters by setting specific ranges for each element (C: 0.23-0.38%, Si: 0.10-0.30%, Mn: 1.30-1.70%, Mo: 0.05-0.50%, Cr: 0.05-1.00%) to achieve the minimum required strength with controlled cost. The patent notably restricts expensive elements like Mo to low levels (0.05-0.50%) while maintaining high strength through the dual-phase microstructure and precise composition control.
Solution Approach 2:
The patent replaces expensive alloying elements (Mo, Cr, Ni) with more cost-effective compositions by relying on the dual-phase microstructure control and precise C-Si-Mn composition optimization. This approach achieves high strength without heavy dependence on costly alloying, reducing production cost while maintaining tensile strength ≥780 MPa.
3Adaptability or versatility
If high content of Si is added to improve formability, then hole expansion ratio is improved, but phosphatability and weldability deteriorate
Solution Approach 1:
The patent precisely controls Si content within 0.10-0.30% to achieve the optimal balance between formability and phosphatability. This controlled Si level provides sufficient hole expansion ratio and bendability while avoiding the negative effects of excessive Si on phosphating and welding performance.
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 results in a dual-phase steel with excellent mechanical properties, including yield strength of ≥420 MPa, tensile strength of ≥800 MPa, and A50-gauge-length elongation at break of ≥18%, while maintaining low production costs and ensuring good weldability and formability.
Implementation Method 1
a dual-phase steel comprising a ferrite matrix and martensite islands
Implementation Method 2
heating the steel slab to a temperature Ta of Ac3+30° C.-Ac3+50° C.
Implementation Method 3
cooling the steel slab at a cooling rate of 10° C./s-50° C./s in the temperature range from As to Af
Data Source
AI summary
Disclosed in the present invention is dual-phase steel, comprising, in addition to 90% or more of Fe and inevitable impurities, the following components in percentages by mass: C: 0.09-0.11%, Si: 0.1-0.3%, Mn: 1.4-1.6%, Al: 0.01-0.03%, Nb: 0.01-0.03%, Ti: 0.01-0.03%, and B: 0.0020-0.0030%. In the present invention, by rationally controlling the chemical components of steel, dual-phase steel with both low cost and high mechanical properties is obtained. Further disclosed in the present invention is a manufacturing method for the dual-phase steel.