High-Toughness Cold-Drawn Wire Rod Without Heat Treatment
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Solution Overview
Problem
Existing non-heat treated steel wire rods face challenges in achieving high toughness and controlled tensile strength without heat treatment, often requiring expensive alloying elements and specific cooling processes, which are not economically viable or applicable to all steel types.
Innovation Solution
A non-heat treated cold-drawn wire rod composition with specific carbon, silicon, manganese, phosphorus, and sulfur content, along with controlled heating and cooling processes, to form de-generated pearlite, enhancing toughness and allowing tensile strength control through cold drawing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heat treatment process is omitted to reduce manufacturing cost and complexity, then productivity and ease of manufacture are improved, but the strength and toughness of the wire rod deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the steel by precisely controlling the content ranges of C (0.15-0.30%), Si (0.05-0.25%), Mn (2.00-4.00%), P (≤0.035%), and S (≤0.040%). This compositional parameter optimization enables the steel to achieve high strength and toughness without requiring heat treatment, thus resolving the contradiction between productivity improvement and strength maintenance
Solution Approach 2:
The patent creates a composite microstructure consisting of ferrite and de-generated pearlite phases through controlled cooling. This microstructural composite provides both the strength needed to replace heat treatment and the toughness required for high-quality wire rod products, eliminating the need for expensive alloying elements while maintaining mechanical properties
2Strength
If expensive alloying elements like Cr, Mo, V, and Nb are added to improve strength and toughness, then material strength is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive alloying elements (Cr, Mo, V, Nb) with cheaper elements like Si and Mn that can achieve similar or better mechanical properties when used in optimized combinations. This substitution dramatically reduces material cost while maintaining or improving wire rod strength and toughness
Solution Approach 2:
The patent optimizes the concentration parameters of affordable elements (C: 0.15-0.30%, Si: 0.05-0.25%, Mn: 2.00-4.00%) to achieve maximum mechanical performance without expensive additives. This parameter optimization allows common elements to perform the function previously requiring rare and expensive alloying elements
3Strength
If cold working is continuously applied to increase strength, then tensile strength is improved, but ductility continuously decreases
Solution Approach 1:
The patent performs preliminary microstructure optimization during the cooling process after hot rolling, creating a pre-prepared ferrite-de-generated pearlite composite structure. This preliminary microstructural preparation ensures that subsequent cold working can achieve high strength without excessive loss of ductility, as the optimized base structure provides better work hardening characteristics
Solution Approach 2:
The patent creates a composite microstructure of ferrite and de-generated pearlite that combines the advantages of both phases: ferrite provides ductility and formability, while de-generated pearlite provides strength. This microstructural composite allows the material to achieve high tensile strength through cold working while maintaining adequate ductility
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 secures excellent toughness and controlled tensile strength without heat treatment, making it suitable for vehicle components like tie rods and rack bars, with improved impact toughness and ductility, while avoiding the need for expensive alloying elements.
Implementation Method 1
heating a billet within a temperature range of Ae3+150° C. to Ae3+250° C.
Implementation Method 2
cooling the heated billet at a cooling rate of 5-15° C./s
Implementation Method 3
tensile strength may be increased through a cold drawing process
Data Source
AI summary
Provided is a wire rod for use in mechanical structure connections, vehicle components, or the like, and more particularly, to a wire rod which has superior toughness without being subjected to a heat treatment, and the strength of which is ensured through a cold-drawing process. Tot his end, provided are a high-toughness cold-drawn non-heat-treated wire rod and a method for manufacturing the same, wherein the wire rod comprises in % by weight: 0.2 to 0.3% of carbon (C), 0.1 to 0.2% of silicon (Si), 2.5 to 4.0% of manganese (Mn), 0.035% or less (but not 0%) of phosphorus (P), 0.04% or less (but not 0%) of sulfur (S), the remainder being iron (Fe) and unavoidable impurities.