Metal wire and electric wire

Patent metadata

Field	Value
Publication number	US-10293397-B2
Application number	US-201414495138-A
Country	US
Kind code	B2
Filing date	Sep 24, 2014
Priority date	Mar 29, 2012
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

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.

First claim

The invention claimed is:

1. A metal wire comprising
a hardness distribution in which hardness decreases toward a specific peripheral portion in a specific radial direction from a central portion in a cross-section orthogonal to an axis,
wherein the metal wire is manufactured at least by subjecting a metallic material to bending at an approximate right angle in an axial direction with a single feed roller of a bending-stretching mold,
wherein the bending is subjected only once,
wherein the bending-stretching mold includes an insertion hole bent at an approximate right angle,
wherein the single feed roller is arranged inside of a bending portion of the insertion hole and applies a frictional force to an inner circumferential surface of a flexural portion on a circumferential surface of the metallic material at the bending portion,
wherein the metal wire has a metallographic structure with a grain size equal to or less than 1 μm,
wherein a hardness distribution of the specific peripheral portion and another hardness distribution of an opposing peripheral portion that opposes to the specific peripheral portion in a radial direction of the metal wire with reference to the central portion are a bilaterally asymmetrical shape with respect to the center portion in the radial direction of the metal wire,
wherein the hardness of the specific peripheral portion decreases by equal to or more than 10% of that of the central portion at a circumferential surface side being beyond at least ½ of the radius from the center, and
wherein the another hardness of an opposing peripheral portion falls within plus and minus 10% of that of the central portion, and the another hardness of the opposing peripheral portion is higher than the hardness of the specific peripheral portion.

2. The metal wire according to claim 1 , wherein the hardness of the peripheral portion in the radial direction after the extension is higher than the hardness of the central portion, and 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.

3. The metal wire according to claim 2 , wherein the hardness of the central portion after the secondary processing is higher than the hardness of the central portion before the secondary processing, and the hardness of the specific peripheral portion after the secondary processing decreases by more than 10% with reference to the hardness of the specific peripheral portion before the secondary processing.

4. An electric wire comprising one or more of the metal wire in claim 1 .

5. The metal wire according to claim 1 , wherein the metal wire is selected from a group consisting of a copper wire, an annealed copper wire made of copper alloy, a tinned copper wire, a nickel-plated copper line, an aluminum wire made of aluminum and an aluminum alloy wire made of aluminum alloy.

6. The metal wire according to claim 1 , wherein the frictional force is not applied to an outer circumferential surface of the flexural portion of the metallic material and wherein a tension caused by bending is applied to the outer circumferential surface of the flexural portion of the metallic material.

7. A method for producing a metal wire according to claim 1 comprising steps of:
drawing a metallic material and stretching the metallic material in an axial direction;
bending the metallic material at an approximate right angle in the axial direction;
applying a frictional force of a single feed roller of a bending-stretching mold to an inner circumferential surface of a bent portion of the metallic material;
obtaining a metallographic structure in the metallic material with a grain size equal to or less than 1 μm;
obtaining a first hardness of a first part of the metallic material in a cross section outer than a half of a radius of the metallic material from a center of the metallic material in a radial direction to be equal to or 10% more decreased than that of the center of the metallic material;
obtaining a second hardness of a second part of the metallic material opposing to the first part in the radial direction with respect to the center to be higher than the first hardness and to be within plus and minus 10% of that of the center; and
subsequently obtaining the metal wire from the metallic material.

Assignees

• Yazaki Corp
• Univ Tokyo

Inventors

• Tokutomi Junichiro
• Hanazaki Kenichi
• Yanagimoto Jun

Classifications

• C21D7/02

  by cold working · CPC title

• B21F99/00

  Subject matter not provided for in other groups of this subclass · CPC title

• B21C1/003

  Drawing materials of special alloys so far as the composition of the alloy requires or permits special drawing methods or sequences · CPC title

• C21D1/02

  Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation · CPC title

• C21D7/10

  of the whole cross-section, e.g. of concrete reinforcing bars · CPC title