Metal Wire Hardness Gradient for Strength and Ductility
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Solution Overview
Problem
Conventional metal wires produced by typical drawing methods have sufficient mechanical strength but insufficient ductility, necessitating the development of wires with improved mechanical strength and ductility.
Innovation Solution
A metal wire with a specific hardness distribution in its cross-section, where the hardness decreases towards the peripheral portions from the central portion, is achieved through axial extension and secondary processing, ensuring a balanced mechanical strength and ductility by softening the peripheral areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic material is subjected to typical drawing and extended axially to increase mechanical strength, then the crystal grains change into fine isometric grains improving strength, but the ductility remains insufficient
Solution Approach 1:
The patent applies local quality by creating a non-uniform hardness distribution across the wire cross-section. The peripheral portion is specifically softened through controlled reheating to a temperature below the recrystallization point, creating a gradient where the center maintains high hardness (fine isometric grains) while the periphery has lower hardness. This local differentiation resolves the contradiction by preserving strength at the center while improving ductility at the periphery where it is most needed for forming operations.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the reheating temperature to be below the recrystallization point (specifically 100-200°C below). This temperature parameter control allows the peripheral portion to soften and improve ductility without triggering full recrystallization that would reduce strength. The selective temperature treatment creates the desired hardness gradient that simultaneously achieves both high strength and improved ductility.
2Ease of operation
If the peripheral portion hardness is reduced to improve ductility, then the wire becomes more formable, but the mechanical strength may be compromised
Solution Approach 1:
The patent resolves this contradiction through local quality by spatially differentiating the hardness properties. The peripheral portion (within 1mm from the surface) is softened to improve ductility and formability, while the central core maintains high hardness and fine isometric grain structure to preserve mechanical strength. This local differentiation allows the wire to exhibit both high strength and improved ductility simultaneously.
Solution Approach 2:
The patent applies asymmetry by creating an asymmetric hardness distribution across the wire cross-section. Rather than uniform treatment, the peripheral region receives selective thermal treatment to reduce hardness, while the center remains unchanged. This asymmetric property distribution optimizes both strength (center) and ductility (periphery) in their respective zones.
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 metal wire exhibits improved ductility and resistance to cracking, preventing breakage during manufacturing, particularly when used in twisted wire configurations, thereby enhancing production efficiency and reducing costs.
Implementation Method 1
a drawing is known as a manufacturing method of the metal wire, where a metallic material is extended to be thin through dies while being stretched in an axial direction
Implementation Method 2
the metal wire obtained by such bending has an increased mechanical strength due to a change of crystal grains contained in a conductor into fine isometric grains
Implementation Method 3
the hardness of the specific peripheral portion becomes less than the hardness of the central portion by means of a secondary processing performed after the extension
Data Source
AI summary
To provide a metal wire and an electric wire of high mechanical strength and high ductibility that have sufficiently increased ductibility as well as sufficiently increased mechanical strength. A metal wire manufactured at least by being subjected to an extension in which a metal wire is extended in an axial direction, and having a hardness distribution in which hardness decreases toward a specific peripheral portion from a central portion in a cross-section orthogonal to axis, whereby a softened peripheral portion becomes to show a good malleability as well as a high resistance to cracking, so as to attain an improvement of mechanical strength and ductibility.