Carbon steel wire with high strength and excellent ductility and fatigue resistance, process for producing the same, and method of evaluating the same

Patent metadata

Field	Value
Publication number	US-9403200-B2
Application number	US-200913126578-A
Country	US
Kind code	B2
Filing date	Oct 30, 2009
Priority date	Oct 30, 2008
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

A carbon steel wire with unprecedentedly high strength and excellent ductility and fatigue resistance, a process for producing the same, and a method of evaluating the same are provided. Provided is a carbon steel wire having a carbon content of 0.50 to 1.10% by mass, wherein the ratio of the hardness of the surface layer portion on a cross section and the hardness of the surface layer portion on a longitudinal section is represented by a coefficient X 1 , and the ratio of the hardness of the center portion on the cross section and the hardness of the center portion on the longitudinal section is represented by a coefficient X 2 , wherein X 1 and X 2 satisfy the following expressions: 0.9<coefficient X 1 ≦1.10, and 0.9<coefficient X 2 ≦1.10, and wherein the carbon steel wire has a tensile strength of 4000 MPa or higher.

First claim

The invention claimed is:

1. A process for producing a carbon steel wire having a carbon content of 0.50 to 1.10% by mass, wherein a ratio of a hardness of a surface layer portion on a cross section orthogonal to a longitudinal direction and a hardness of a surface layer portion on a longitudinal section in the longitudinal direction is represented by a coefficient X 1 , and a ratio of a hardness of a center portion on the cross section and a hardness of a center portion on the longitudinal section is represented by a coefficient X 2 ,
wherein X 1 and X 2 satisfy the following expressions:
0.9<coefficient X 1≦1.10, and

0.9<coefficient X 2≦1.10,

and wherein the carbon steel wire has a tensile strength of 4000 MPa or higher,
wherein, in a final wet wire drawing process, when a carbon steel wire having a carbon content of 0.50 to 1.10% by mass and having a pearlite structure is subjected to a wire drawing process in each die, the number of dies in which a coefficient A represented by the following formula composed of the die reaction and the diameter at the die exit:
coefficient A =(die reaction (kgf)/diameter at the die exit (mm) 2 )

 is 90 or lower is all the dies, and wherein a processing strain ε larger than 2.5 is applied in the final wet wire drawing process.

2. The production process according to claim 1 , wherein the carbon content is 0.50 to 0.74% by mass.

3. The production process according to claim 1 , wherein the carbon content is 0.50 to 0.70% by mass.

4. The production process according to claim 1 , wherein the carbon content is 0.50 to 0.60% by mass.

5. The production process according to claim 1 , wherein the carbon content is 0.50 to 0.55% by mass.

Assignees

• Shimizu Wataru
• Bridgestone Corp

Inventors

• Shimizu Wataru

Classifications

• C21D8/06

  during manufacturing of rods or wires · CPC title

• C21D2211/009

  Pearlite · CPC title

• D07B2205/3057

  having a high carbon content, e.g. greater than 0,8 percent respectively SHT or UHT wires · CPC title

• D07B2801/10

  Smallest filamentary entity of a rope or strand, i.e. wire, filament, fiber or yarn · 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