Electric resistance welded steel pipe

• US 9,726,305 B2
• Filed: 09/27/2013
• Issued: 08/08/2017
• Est. Priority Date: 09/27/2012
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: Shinohara, Yasuhiro, Nagai, Kensuke, Ozaki, Masakazu
• Primary Examiner(s): Yee, Doborah
• Application Number:
  US14/420,971
• Publication Number:
  US 20150219249A1
• Time in Patent Office: 1,411 Days
• Field of Search: None
• CPC Class Codes: B23K 11/002 specially adapted for particular articles or work
• CPC Class Codes: B23K 11/0873 of the longitudinal seam of tubes
• CPC Class Codes: B23K 35/38 Selection of media, e.g. special atmospheres for surrounding the working area
• CPC Class Codes: C21D 2211/005 Ferrite
• CPC Class Codes: C21D 2211/008 Martensite
• CPC Class Codes: C21D 9/46 for sheet metals
• CPC Class Codes: C21D 9/50 for welded joints
• CPC Class Codes: C22C 38/00 Ferrous alloys, e.g. steel alloys cast-iron alloys C22C37/00
• 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 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• 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 38/12 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 38/18 containing chromium
• CPC Class Codes: C22C 38/26 with niobium or tantalum
• CPC Class Codes: C22C 38/28 : with titanium or zirconium
• CPC Class Codes: F16L 9/02 : of metal F16L9/16 - F16L9/22 take precedence
• CPC Class Codes: Y10T 428/12292 : Workpiece with longitudinal passageway or stopweld material [e.g., for tubular stock, etc.]

Abstract

An electric resistance welded steel pipe which has sufficient strength and low-temperature toughness and a low yield ratio and which is suitable as a line pipe to be laid in depths of the sea, characterized in that: the composition of the base material contains, in mass %, 0.05 to 0.10% of C, 1.00 to 1.60% of Mn, and 0.005 to less than 0.035% of Nb, and has a Ceq value of 0.23 to 0.38; and the metal microstructure of the base material contains 3 to 13% of martensite in area fraction with the balance being ferrite.

Claims

1. An electric resistance welded pipe comprising a base material having a chemical composition comprising, by mass %,

C:

0.05 to 0.10%,

Mn;

1.00 to 1.60%,

Ti;

0.005 to 0.030%,

Nb;

0.005% to less than 0.035%, and

N;

0.001 to 0.008%,

further comprising one or both of

Si;

0.01 to 0.60% and

Al;

0.001 to 0.10%, and

a balance of iron and unavoidable impurities, wherein contents are restricted to

P;

0.02% or less and

S;

0.005% or less, and

a Ceq, represented by the following formula 1, satisfies 0.23≦

Ceq≦

0.38, and having a metal microstructure comprising, by area ratio, 3 to 13% of martensite, and a balance of ferrite, an average value of an equivalent circle diameter of the martensite being 0.5 to 1.5 μ

m;

Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 

 

(formula

     1)

where, in formula 1, C, M, Cr, Mo, V, Ni, and Cu are values which represent the contents of the elements by mass %.

2. The electric resistance welded pipe according to claim 1 wherein the chemical composition of the base material further comprises, by mass %, one or more of

Ni:

1.0% or less,

Cu;

1.0% or less,

Cr;

1.0% or less,

Mo;

0.5% or less,

V;

0.2% or less,

Ca;

0.006% or less, and

REM;

0.006% or less.

3. The electric resistance welded pipe according to claim 1 wherein the chemical composition of the base material satisfies

Mn:

1.00 to 1.50% and

Si;

0.40% or less and

further satisfies

0.23≦

Ceq≦

0.30,

and

a tensile strength of the steel pipe is 490 to 760 MPa.

4. The electric resistance welded pipe according to claim 3 wherein the chemical composition of the base material satisfies

Nb:

0.005 to 0.020%.

5. The electric resistance welded pipe according to claim 3 wherein the chemical composition of the base material further comprises, by mass %, one more of

Ni:

0.5% or less,

Cu;

0.5% or less,

Cr;

0.5% or less,

Mo;

0.2% or less,

V;

0.1% or less,

Ca;

0.006% or less, and

REM;

0.006% or less.

6. The electric resistance welded pipe according to claim 4 wherein the chemical composition of the base material further comprises, by mass %, one more of

Ni:

0.5% or less,

Cu;

0.5% or less,

Cr;

0.5% or less,

Mo;

0.2% or less,

V;

0.1% or less,

Ca;

0.006% or less, and

REM;

0.006% or less.

7. The electric resistance welded pipe according to claim 1, wherein the electric resistance weld pipe has a Charpy absorption energy at −

30°

C. of 190 J or more.

8. The electric resistance welded pipe according to claim 2, wherein the electric resistance weld pipe has a Charpy absorption energy at −

30°

C. of 190 J or more.

9. The electric resistance welded pipe according to claim 3, wherein the electric resistance weld pipe has a Charpy absorption energy at −

30°

C. of 190 J or more.

10. The electric resistance welded pipe according to claim 4, wherein the electric resistance weld pipe has a Charpy absorption energy at −

30°

C. of 190 J or more.

11. The electric resistance welded pipe according to claim 5, wherein the electric resistance weld pipe has a Charpy absorption energy at −

30°

C. of 190 J or more.

12. The electric resistance welded pipe according to claim 6, wherein the electric resistance weld pipe has a Charpy absorption energy at −

30°

C. of 190 J or more.