Wire Rod Cold Forgeability via Hardness Control
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Solution Overview
Problem
Existing wire rods require additional spheroidizing annealing heat treatment to achieve excellent cold forgeability, which increases costs and reduces manufacturing efficiency, necessitating the development of a wire rod with enhanced cold workability without additional heat treatment.
Innovation Solution
A wire rod composition of carbon (0.02-0.15 wt%), silicon (0.05-0.3 wt%), manganese (0.5-1.2 wt%), chromium (0.3-0.9 wt%), phosphorus (0.02 wt% or less), sulfur (0.02 wt% or less), soluble aluminum (0.01-0.05 wt%), and nitrogen (0.01 wt% or less) with specific hardness ratios and carbon equivalent ranges, allowing for hot-rolling and cooling processes to achieve excellent cold forgeability without additional heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If spheroidizing annealing heat treatment is performed to improve cold workability, then ductility is improved and deformation resistance is reduced, but additional costs are incurred and manufacturing efficiency is reduced
Solution Approach 1:
The patent applies preliminary action by controlling the composition and microstructure of the wire rod before cold working. Specifically, it controls the hardness to 150 Hv or less and the hardness ratio between center and outer peripheral portions to 1.20 or less through controlled cooling and composition design, preparing the material in advance to have the necessary ductility and low deformation resistance without requiring subsequent heat treatment, thus eliminating the spheroidizing annealing step and improving manufacturing efficiency
2Ease of operation
If spheroidizing annealing heat treatment is performed to improve cold workability, then ductility is improved and deformation resistance is reduced, but additional costs are incurred
Solution Approach 1:
The patent eliminates the need for additional heat treatment by preliminarily designing the wire rod composition and processing parameters. By controlling C content at 0.05-0.15%, Mn at 1.50-3.00%, Cr at 0.50-1.50%, and applying controlled cooling after hot rolling to achieve specific hardness values and hardness ratios, the material is prepared in advance with optimal cold workability, removing the costly spheroidizing annealing step
Solution Approach 2:
The patent applies parameter changes by precisely controlling chemical composition parameters (C: 0.05-0.15%, Mn: 1.50-3.00%, Cr: 0.50-1.50%, and other elements) and processing parameters (finish rolling temperature, cooling rate, hardness Hv≤150, hardness ratio ≤1.20). These parameter optimizations enable the wire rod to achieve excellent cold workability inherently, eliminating the need for additional heat treatment and associated costs
3Strength
If high strength is maintained in wire rod, then structural integrity is improved, but deformation resistance increases and cold workability deteriorates
Solution Approach 1:
The patent applies local quality by creating a controlled hardness distribution across the wire rod cross-section. It specifies that the hardness at the center portion should be 5-15 Hv lower than at the outer peripheral portion, and the hardness ratio between center and outer peripheral portions should be 1.20 or less. This localized hardness control allows the outer regions to provide strength while the center region maintains lower deformation resistance, enabling both high strength and good cold workability
Solution Approach 2:
The patent resolves the strength-cold workability contradiction through parameter optimization: controlling overall hardness to 150 Hv or less, maintaining specific alloy content (C: 0.05-0.15%, Mn: 1.50-3.00%, Cr: 0.50-1.50%), and enforcing the hardness ratio constraint (center/outer peripheral ≤1.20). These parameters enable the wire rod to achieve both adequate strength for structural integrity and sufficiently low deformation resistance for excellent cold workability without requiring heat treatment
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 wire rod effectively suppresses deformation resistance during cold working, maintaining strength and preventing cracking, thereby ensuring excellent cold forgeability without the need for spheroidizing annealing heat treatment.
Implementation Method 1
obtaining the wire rod by hot-rolling the billet having been heated under the conditions of a finish rolling temperature of 900° C. to 1000° C.
Implementation Method 2
cooling, after winding the wire rod
Data Source
AI summary
Disclosed are a wire rod and a manufacturing method therefor. The wire rod comprises in percentage by weight: 0.02 to 0.15% of C; 0.05 to 0.3% of Si; 0.5 to 1.2% of Mn; 0.3 to 0.9% of Cr; 0.02% or less of P; 0.02% or less of S; 0.01 to 0.05% of sol. Al; 0.01% or less of N; Fe as the remainder; and unavoidable impurities, wherein the wire rod satisfies following formulas 1 and 2, wherein, when the hardness of the wire rod measured in 1/2d position and in 1/4d position in the diameter direction of the wire rod is Hv,1/2d(Hv) and Hv,1/4d(Hv), respectively (here, d is the diameter of the wire).(Hv,1/2d+Hv,1/4d)/2≤150 [Formula 1]Hv,1/2d/Hv,1/4d≤1.2 [Formula 2]