Steel rod and high strength steel wire having superior ductility and methods of production of same

Patent metadata

Field	Value
Publication number	US-9689053-B2
Application number	US-201514939848-A
Country	US
Kind code	B2
Filing date	Nov 12, 2015
Priority date	Mar 25, 2008
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

The present invention inexpensively provides with high productivity and good yield a steel rod superior in drawability and a steel wire superior in twistability using the same as a material, that is, draws a high strength steel rod superior in ductility where the chemical components contain C: 0.80 to 1.20%, Si: 0.1 to 1.5%, Mn: 0.1 to 1.0%, Al: 0.01% or less, Ti: 0.01% or less, one or both of W: 0.005 to 0.2% and Mo: 0.003 to 0.2%, N: 10 to 30 ppm, B: 4 to 30 ppm (of which, solute B is 3 ppm or more), and O: 10 to 40 ppm, which has a balance of Fe and unavoidable impurities, has an area percentage of pearlite structures of 97% or more, has a balance of non-pearlite structures, and has a total of the area percentage of the non-pearlite structures and the area percentage of the coarse pearlite structures of 15% or less, to obtain high strength steel wire superior in ductility having a tensile strength of 3600 MPa or more and a number density of voids of lengths of 5 μm or more at the center of 100/mm 2 or less.

First claim

The invention claimed is:

1. A method of producing a steel rod for steel wire superior in ductility, comprising:
hot rolling a steel billet into a steel rod having a diameter of 3 to 7 mm,
coiling the steel rod at a temperature in the region of 800 to 950° C.,
then patenting the steel rod at a cooling rate of 20° C./s or more from 800° C. to 700° C., wherein
the steel billet comprises, by mass % or mass ppm,
C: 0.80 to 1.20%,
Si: 0.1 to 1.5%,
Mn: 0.1 to 1.0%,
Al: 0.01% or less,
Ti: 0.01% or less,
one or both of W: 0.005 to 0.2% and
Mo: 0.003 to 0.2%,
N: 10 to 30 ppm,
B: 4 to 30 ppm, wherein solute B is present in an amount of at least 3 ppm,
O: 10 to 40 ppm, and
a balance of Fe and unavoidable impurities, and wherein
the steel rod has an area percentage of pearlite structures of 97% or more,
a balance of non-pearlite structures comprising bainite, degenerated pearlite, and proeutectoid ferrite, and
a total of the area percentage of non-pearlite structures and coarse pearlite structures of no more than 15%, wherein an apparent lamellar spacing is 600 nm or more.

2. The method of producing steel rod as set forth in claim 1 , wherein the steel billet further comprises, by mass %, at least one of Cr: 0.5% or less, Ni: 0.5% or less, Co: 0.5% or less, V: 0.5% or less, Cu: 0.2% or less, or Nb: 0.1% or less.

3. A method of producing a steel wire superior in ductility comprising:
hot rolling a steel billet into a steel rod having a diameter of 3 to 7 mm,
coiling the steel rod at a temperature in the region of 800 to 950° C.,
then patenting the steel rod at a cooling rate of 20° C./s or more from 800° C. to 700° C.,
drawing the steel rod,
then intermediate patenting the drawn steel rod, and
then further cold drawing the patented drawn steel rod, wherein
the steel billet comprises, by mass % or mass ppm,
C: 0.80 to 1.20%,
Si: 0.1 to 1.5%,
Mn: 0.1 to 1.0%,
Al: 0.01% or less,
Ti: 0.01% or less,
one or both of W: 0.005 to 0.2% and
Mo: 0.003 to 0.2%,
N: 10 to 30 ppm,
B: 4 to 30 ppm, wherein solute B is present in an amount of at least 3 ppm,
O: 10 to 40 ppm, and
a balance of Fe and unavoidable impurities, and wherein
the steel rod has an area percentage of pearlite structures of 97% or more,
a balance of non-pearlite structures comprising bainite, degenerated pearlite, and proeutectoid ferrite, and
a total of the area percentage of non-pearlite structures and coarse pearlite structures of no more than 15%, wherein an apparent lamellar spacing is 600 nm or more.

4. The method of producing a steel wire as set forth in claim 3 , wherein the steel billet further comprises, by mass %, at least one of Cr: 0.5% or less, Ni: 0.5% or less, Co: 0.5% or less, V: 0.5% or less, Cu: 0.2% or less, or Nb: 0.1% or less.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Yamasaski Shingo
• Nishida Seiki

Classifications

• C21D8/06

  during manufacturing of rods or wires · CPC title

• C22C38/28

  with titanium or zirconium · CPC title

• C22C38/26

  with niobium or tantalum · CPC title

• C22C38/08

  containing nickel {(C22C38/105 takes precedence)} · CPC title

• C21D6/008

  containing Si · CPC title