Non-Heat-Treated Steel Wire Rod Composition for Cold Forging
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Solution Overview
Problem
Non-heat-treated steel wire rods experience continuous work hardening during cold drawing and forging, leading to reduced ductility and toughness, and variations in mechanical properties, which diminish the benefits of omitting heat treatment processes.
Innovation Solution
A non-heat-treated steel wire rod composition with controlled chemical elements and manufacturing processes, including precise rolling and cooling conditions, to achieve excellent cold forgeability and uniform tensile strength without heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment processes (quenching and tempering) are performed after cold forging, then material strength and toughness are enhanced, but process complexity and manufacturing cost increase
Solution Approach 1:
The patent applies preliminary action by optimizing the chemical composition and microstructure of the steel wire rod before cold forging to achieve the desired strength and toughness without subsequent heat treatment. The steel composition is specifically designed with controlled carbon content (0.25-0.45 wt%) and alloying elements, along with controlled rolling and cooling processes, to pre-establish the mechanical properties needed for the final product, thereby eliminating the need for quenching and tempering operations.
2Device complexity
If heat treatment processes are omitted to simplify manufacturing, then process complexity and cost are reduced, but work hardening continuously occurs during cold drawing and forging leading to reduced ductility and toughness
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (carbon: 0.25-0.45 wt%, silicon: 0.10-0.30 wt%, manganese: 1.30-1.60 wt%, and other alloying elements) and processing parameters (rolling temperature, cooling rate) to achieve a balanced microstructure that provides both strength and toughness. This compositional and microstructural optimization allows the steel to maintain adequate ductility and toughness even without heat treatment, resolving the contradiction between process simplification and mechanical property maintenance.
3Loss of time
If heat treatment is omitted, then manufacturing cost and process time are reduced, but variations in mechanical properties increase due to dependence on raw material properties
Solution Approach 1:
The patent applies parameter changes by establishing tight control ranges for chemical composition (carbon: 0.25-0.45 wt%, silicon: 0.10-0.30 wt%, manganese: 1.30-1.60 wt%, phosphorus: ≤0.05 wt%, sulfur: ≤0.05 wt%, and controlled amounts of Cr, Ni, Mo, V, Nb, Ti, Al, Cu, and B) and processing parameters to minimize variations in mechanical properties. This precise parameter control ensures consistent tensile strength (≥900 MPa) and other mechanical properties across production batches, compensating for the absence of heat treatment that would otherwise be used to standardize properties.
4Strength
If continuous work hardening occurs during cold drawing and forging, then product strength increases, but ductility and toughness continuously decrease and mold life is reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition (particularly carbon content at 0.25-0.45 wt% and alloying elements like Mn at 1.30-1.60 wt%) to achieve an optimal balance between strength and workability. This compositional optimization allows the steel to undergo cold drawing and forging with controlled work hardening that achieves sufficient product strength while maintaining adequate ductility and extending mold life, resolving the contradiction between strength development and tooling durability.
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 steel wire rod with consistent tensile strength of 900 MPa or more, enhanced toughness, and reduced variations in mechanical properties, maintaining excellent cold forgeability and mold life.
Implementation Method 1
work hardening continuously occurs during the cold drawing step S21 and the cold forging step S23
Implementation Method 2
forming a billet by reheating a steel material... forming a wire rod by rolling the reheated billet
Data Source
AI summary
Provided are a non-heat-treated steel wire rod with excellent cold forgeability and a method of manufacturing the same, the non-heat-treated steel wire rod including carbon: 0.20 to 0.40 wt %, silicon: 0.10 to 0.30 wt %, manganese: 1.30 to 1.60 wt %, phosphorus: more than 0 wt % and up to 0.05 wt %, sulfur: more than 0 wt % and up to 0.05 wt %, chromium: 0.02 to 0.30 wt %, nickel: 0.02 to 0.30 wt %, molybdenum: 0.02 to 0.30 wt %, vanadium: 0.01 to 0.15 wt %, niobium: 0.01 to 0.05 wt %, aluminum: 0.005 to 0.060 wt %, titanium: 0.005 to 0.020 wt %, copper: 0.01 to 0.30 wt %, boron: 0.0001 to 0.0020 wt %, nitrogen: 0.005 to 0.015 wt %, and a balance of iron and other unavoidable impurities, wherein a sum of Nb and V is 0.02 to 0.2 wt %, and wherein the non-heat-treated steel wire rod satisfies a tensile strength of 900 MPa or more.