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

• US 9,689,053 B2
• Filed: 11/12/2015
• Issued: 06/27/2017
• Est. Priority Date: 03/25/2008
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: Yamasaski, Shingo, Nishida, Seiki
• Primary Examiner(s): Yang, Jie
• Application Number:
  US14/939,848
• Publication Number:
  US 20160145713A1
• Time in Patent Office: 593 Days
• Field of Search: 148599
• CPC Class Codes: B21C 1/003 Drawing materials of special alloys so far as the composition of the alloy requires or permits special drawing methods or sequences
• CPC Class Codes: C21D 2211/009 Pearlite
• CPC Class Codes: C21D 6/004 containing Cr and Ni
• CPC Class Codes: C21D 6/005 containing Mn
• CPC Class Codes: C21D 6/007 containing Co
• CPC Class Codes: C21D 6/008 containing Si
• CPC Class Codes: C21D 8/065 of ferrous alloys
• CPC Class Codes: C21D 9/525 for wire, for rods C21D9/54 takes precedence
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/08 containing nickel C22C38/105 takes precedence
• CPC Class Codes: C22C 38/10 containing cobalt
• CPC Class Codes: C22C 38/12 containing tungsten, tantalum, molybdenum, vanadium, or niobium
• CPC Class Codes: C22C 38/14 containing titanium or zirconium
• CPC Class Codes: C22C 38/16 containing copper
• CPC Class Codes: C22C 38/20 with copper
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/26 : with niobium or tantalum
• CPC Class Codes: C22C 38/28 : with titanium or zirconium
• CPC Class Codes: C22C 38/30 : with cobalt
• CPC Class Codes: C22C 38/32 : with boron
• CPC Class Codes: C22C 38/54 : with boron
• CPC Class Codes: D07B 1/066 : the wires being made from special alloy or special steel composition
• CPC Class Codes: D07B 2205/3035 : Pearlite
• CPC Class Codes: D07B 2205/3057 : having a high carbon content, e.g. greater than 0,8 percent respectively SHT or UHT wires
• CPC Class Codes: D07B 2801/10 : Smallest filamentary entity of a rope or strand, i.e. wire, filament, fiber or yarn

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/mm² or less.

Claims

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.