Wire Rod Composition for High Tensile Strength and Corrosion Resistance
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Solution Overview
Problem
High-strength steel wires face challenges with strain aging, delamination, corrosion, and hydrogen embrittlement, particularly during wire drawing processing, which affects their tensile strength and torsion properties, and existing solutions do not adequately address these issues simultaneously.
Innovation Solution
A wire rod with a specific chemical composition, including C, Si, Mn, Cu, Ni, and N, optimized to achieve a pearlite structure with controlled hardness variation, enhancing corrosion resistance, hydrogen embrittlement resistance, and torsion properties, while maintaining high tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tensile strength of the steel wire is increased to 1700 MPa or more, then the strength requirement is met, but strain aging occurs during wire drawing processing causing brittleness and reduced torsion properties
Solution Approach 1:
The invention changes the chemical composition parameters by strictly controlling C content to 0.70-1.00%, Si to 0.10-2.00%, and adding specific amounts of Cu (0.10-2.00%) and Ni (0.10-2.00%). These parameter changes modify the material's strain aging behavior, allowing high tensile strength while maintaining ductility and torsion properties after wire drawing processing.
Solution Approach 2:
The invention creates a composite alloy system by combining Fe with specific amounts of Cu and Ni along with C and Si. This composite material approach provides synergistic effects where Cu and Ni work together with C and Si to suppress strain aging while achieving the required tensile strength of 1700 MPa or more.
2Strength
If the strength of the steel wire is increased to achieve high tensile strength, then the strength requirement is met, but the risk of breakage due to corrosion or hydrogen embrittlement increases
Solution Approach 1:
The invention changes the chemical composition by adding Cu (0.10-2.00%) and Ni (0.10-2.00%) which are known to improve corrosion resistance. Simultaneously, the controlled C content (0.70-1.00%) and Si content (0.10-2.00%) are optimized to achieve high strength while maintaining resistance to hydrogen embrittlement, thus resolving the contradiction between strength and corrosion/hydrogen embrittlement resistance.
3Strength
If high-strength steel wire is produced to meet tensile strength requirements, then strength is achieved, but delamination occurs during torsion testing reducing manufacturability
Solution Approach 1:
The invention optimizes the chemical composition parameters, particularly controlling C at 0.70-1.00% and adding Cu (0.10-2.00%) and Ni (0.10-2.00%), to achieve a balanced microstructure that provides high tensile strength while preventing delamination during torsion testing. This compositional optimization ensures both strength and manufacturability.
Data Source
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AI summary
This wire rod has a predetermined chemical composition, satisfies the following (1) to (3), contains a pearlite structure having 90% or more of a metal structure, and satisfies the following (4) in a case in which a value of a Vickers hardness at a surface layer portion for each sample is HVsi with respect to each of eight samples si collected at arbitrary equal intervals in a longitudinal direction of the wire rod, and an average value and maximum value of HVsi are respectively Hvsiave and Hvsimax: Cu/Ni>1.00 1.70≤Y1≤4.50 Y1=3×Cr+5×Mn+Cu+Ni Y2<1.81 Y2=C+Si/10+A A satisfies A = a in a case in which a value of a = 350 × ([N] - 0.29 × [Ti]) satisfies a ≥ 0, and A = 0 in a case in which the value satisfies a < 0 Hvsimax−Hvsiave≤50.