Cold-Heading Wire Rod Composition for Shorter Spheroidizing
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Solution Overview
Problem
The existing wire rod manufacturing process for cold heading requires lengthy spheroidizing heat treatment, increasing manufacturing costs and reducing ductility, while non-normalized steel omits necessary heat treatments, leading to defects and decreased product quality.
Innovation Solution
A wire rod composition with specific elemental percentages (C: 0.15-0.5%, Si: 0.1-0.4%, Mn: 0.3-1.5%, Cr: 0.1-1.5%, Al: 0.02-0.05%, N: 0.004-0.02%, Nb: 0.001-0.03%, V: 0.01-0.3%, Mo: 0.01-0.5%, Ti: 0.001-0.03%) and microstructure, including pearlite colonies and carbonitride precipitates, is developed, along with a hot rolling and cooling process to minimize heat treatment time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If spheroidizing heat treatment is performed to increase rolling life, then the rolling life is improved, but the process time increases and manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by controlling the microstructure during hot rolling to achieve a spheroidized cementite distribution before the actual rolling process. The wire rod is manufactured with a controlled pearlite colony structure and spheroidized cementite morphology (long and short axis ratio of 5:1 or less) through specific hot rolling parameters (finishing temperature 700-780°C, cooling rate 5-20°C/s), which prepares the material in advance to reduce or eliminate the need for subsequent spheroidizing heat treatment, thereby reducing process time while maintaining rolling life
Solution Approach 2:
The patent applies parameter changes by optimizing the chemical composition (C: 0.15-0.5%, Si: 0.1-0.4%, Mn: 0.3-1.5%, Cr: 0.1-1.5%, Al: 0.02-0.05%, N: 0.004-0.02%, and microalloying elements) and hot rolling parameters (temperature, cooling rate) to directly achieve the desired microstructure. This allows the material to possess the required spheroidized cementite morphology from the outset, eliminating the need for additional heat treatment processes and reducing manufacturing time while maintaining excellent rolling life
2Duration of action of stationary object
If spheroidizing heat treatment is performed to increase rolling life, then the rolling life is improved, but the manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by manufacturing the wire rod with a pre-controlled microstructure that includes spheroidized cementite morphology and appropriate pearlite colony size through optimized hot rolling parameters. This preliminary structuring during manufacturing eliminates the need for subsequent spheroidizing heat treatment, thereby reducing manufacturing cost while maintaining excellent rolling life
Solution Approach 2:
The patent applies parameter changes by optimizing chemical composition (including microalloying elements Nb, V, Mo, Ti) and hot rolling parameters (finishing temperature 700-780°C, cooling rate 5-20°C/s) to directly achieve the desired microstructure with spheroidized cementite. This approach eliminates additional heat treatment processes, reducing manufacturing cost while ensuring superior rolling life
3Ease of manufacture
If continuous cold processing is performed without heat treatment to reduce manufacturing cost, then manufacturing cost is reduced, but ductility decreases
Solution Approach 1:
The patent applies preliminary action by establishing the optimal microstructure (pearlite colonies with spheroidized cementite, maximum size 5μm or less) during hot rolling. This preliminary microstructural control ensures that the material maintains adequate ductility throughout continuous cold processing without requiring intermediate heat treatments, thereby reducing manufacturing cost while preserving ductility
Solution Approach 2:
The patent applies parameter changes by optimizing chemical composition (C: 0.15-0.5%, Si: 0.1-0.4%, Mn: 0.3-1.5%, Cr: 0.1-1.5%, Al: 0.02-0.05%, N: 0.004-0.02%, and microalloying elements) and hot rolling parameters to achieve a balanced microstructure. The controlled pearlite colony size (≤5μm) and spheroidized cementite morphology provide both strength and ductility, enabling continuous cold processing without intermediate heat treatments while maintaining adequate ductility
4Ease of manufacture
If omitted heat treatment is performed to reduce manufacturing cost, then manufacturing cost is reduced, but product quality decreases due to defects
Solution Approach 1:
The patent applies preliminary action by controlling the microstructure during hot rolling to achieve uniform pearlite colonies with spheroidized cementite morphology and appropriate size distribution. This preliminary microstructural control prevents common defects such as banding, coarse grain structure, and non-uniform properties that would otherwise require heat treatment to correct, thereby maintaining high product quality while reducing manufacturing cost
Solution Approach 2:
The patent applies parameter changes by optimizing chemical composition (including microalloying elements Nb, V, Mo, Ti at controlled levels) and hot rolling parameters (finishing temperature 700-780°C, cooling rate 5-20°C/s) to achieve a balanced microstructure with fine pearlite colonies (≤5μm) and spheroidized cementite. This controlled microstructure ensures uniform mechanical properties, adequate ductility, and high product quality without requiring additional heat treatment processes
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 significantly reduces spheroidizing heat treatment time, enhancing economic efficiency and maintaining strength and ductility, thus improving the manufacturing process for cold heading applications.
Implementation Method 1
the wire rod includes a pearlite colony as microstructure, and the long and short axis ratio of cementite present in the pearlite colony is 200:1 or less
Implementation Method 2
The wire rod may include at least one precipitate of Al-based carbonitride, Nb-based carbonitride, V-based carbonitride, Mo-based carbonitride, and Ti-based carbonitride
Data Source
AI summary
The present disclosure provides a wire rod for cold heading that can shorten the spheroidizing heat treatment time, processed products using the same, and manufacturing method thereof. A wire rod for cold heading according to an embodiment of present disclosure includes, in percent (%) by weight of the entire composition, C: 0.15 to 0.5%, Si: 0.1 to 0.4%, Mn: 0.3 to 1.5%, Cr: 0.1 to 1.5%, Al: 0.02 to 0.05%, N: 0.004 to 0.02%, at least one selected from the group consisting of Nb: 0.001 to 0.03%, V: 0.01 to 0.3%, Mo: 0.01 to 0.5%, Ti: 0.001 to 0.03%, and the remainder of iron (Fe) and other inevitable impurities, and the microstructure has a long and short axis ratio of cementite present in pearlite colonies of 200:1 or less.