High strength steel pipe for line pipe superior in low temperature toughness and high strength steel plate for line pipe and methods of production of the same

• US 20100236668A1
• Filed: 07/02/2007
• Published: 09/23/2010
• Est. Priority Date: 07/04/2006
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: Terada, Yoshio, Hara, Takuya, Asahi, Hitoshi
• Granted Patent: US 8,764,918 B2
• Time in Patent Office: Days
• US Class Current: 148/521
• CPC Class Codes: B23K 35/30 with the principal constituent melting at less than 1550 degrees C
• CPC Class Codes: C21D 8/02 during manufacturing of plates or strips C21D8/12 takes precedence
• CPC Class Codes: C21D 8/10 during manufacturing of tubular bodies
• CPC Class Codes: C21D 9/08 for tubular bodies or pipes
• 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 38/16 containing copper
• CPC Class Codes: C22C 38/20 with copper
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/24 with vanadium
• CPC Class Codes: C22C 38/26 with niobium or tantalum
• CPC Class Codes: C22C 38/28 with titanium or zirconium
• CPC Class Codes: C22C 38/32 with boron
• CPC Class Codes: C22C 38/38 with more than 1.5% by weight of manganese
• CPC Class Codes: C22C 38/42 with copper
• CPC Class Codes: C22C 38/44 : with molybdenum or tungsten
• CPC Class Codes: C22C 38/46 : with vanadium
• CPC Class Codes: C22C 38/48 : with niobium or tantalum
• CPC Class Codes: C22C 38/50 : with titanium or zirconium
• CPC Class Codes: C22C 38/54 : with boron
• CPC Class Codes: C22C 38/58 : with more than 1.5% by weight of manganese
• CPC Class Codes: F16L 9/02 : of metal F16L9/16 - F16L9/22 take precedence

Abstract

The present invention provides high strength steel pipe for line pipe superior in low temperature toughness suppressed in drop of toughness of the HAZ and a method of production of the same, more particularly high strength steel plate for line pipe used as a material for high strength steel pipe for line pipe and a method of production of the same, in particular high strength steel pipe for line pipe superior in low temperature toughness characterized in that the chemical compositions of the base metal is, by mass %, C: 0.020 to 0.080%, Si: 0.01 to 0.50%, Mo: 0.01 to 0.15%, Al: 0.0005 to 0.030%, and Nb: 0.0001 to 0.030% contained in a range of C+0.25Si+0.1Mo+Al+Nb: 0.100% or less and the mixture of austenite and martensite present along prior austenite grain boundaries of the reheated part of the heat affected zone has a width of 10 μm or less and a length of 50 μm or less.

Claims

1. A high strength steel pipe for line pipe superior in low temperature toughness characterized by comprising a steel plate shaped into a tube with seam portions of the steel plate welded by one layer each at the inner side and outer side, a base metal of the steel pipe having a chemical compositions containing, by mass %,

C:

0.020 to 0.080%,

Si;

0.01 to 0.50%,

Mo;

0.01 to 0.15%,

Al;

0.0005 to 0.030%, and

Nb;

0.0001 to 0.030%

in a range of

C+0.25Si+0.1Mo+Al+Nb;

0.100% or less

further containing,

Mn;

1.50 to 2.50%,

Ti;

0.003 to 0.030%, and

B;

0.0001 to 0.0030%, and

limiting

P;

0.020% or less and

S;

0.0030% or less,

with the balance of Fe and unavoidable impurities, the mixture of austenite and martensite present along prior austenite grain boundaries of the reheated parts of the heat affected zone having a width of 10 μ

m or less and a length of 50 μ

m or less.

2. A high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 1 characterized in that the base metal has a tensile strength in the circumferential direction of 900 MPa or more.

3. A high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 1 characterized in that the weld metal has a chemical compositions containing, by mass %,

C:

0.010 to 0.100%,

Si;

0.01 to 0.50%,

Mn;

1.00 to 2.00%,

Ni;

1.30 to 3.20%,

Al;

0.0005 to 0.100%,

Ti;

0.003 to 0.050%, and

0;

0.0001 to 0.0500%

further containing

a total of one or more of Cr, Mo, and V;

1.00 to 2.50%,

limiting

P;

0.020% or less and

S;

0.0100% or less

with the balance of Fe and unavoidable impurities.

4. A high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 3 characterized in that the weld metal has a chemical compositions containing, by mass %, B:

0.0001 to 0.0050%.

5. A high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 1 characterized in that the base metal has a chemical compositions containing, by mass %, one or both of

Cu:

0.05 to 1.50% and

Ni;

0.05 to 5.00%.

6. A high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 1 characterized in that the base metal has a chemical compositions containing, by mass %, one or more of

Cr:

0.02 to 1.50%,

W;

0.01 to 2.00%,

V;

0.010 to 0.100%,

Zr;

0.0001 to 0.0500%, and

Ta;

0.0001 to 0.0500%.

7. A high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 1 characterized in that the base metal has a chemical compositions containing, by mass %, one or more of

Mg:

0.0001 to 0.0100%,

Ca;

0.0001 to 0.0050%,

REM;

0.0001 to 0.0050%,

Y;

0.0001 to 0.0050%,

Hf;

0.0001 to 0.0050%, and

Re;

0.0001 to 0.0050%.

8. A high strength steel plate for line pipe superior in low temperature toughness characterized by comprising high strength steel plate for line pipe used as a material for high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 1 and having a chemical compositions containing, by mass %,

C:

0.020 to 0.080%,

Si;

0.01 to 0.50%,

Mo;

0.01 to 0.15%,

Al;

0.0005 to 0.030%, and

Nb;

0.0001 to 0.030%

in a range of

C+0.25Si+0.1Mo+Al+Nb;

0.100% or less and

further containing

Mn;

1.50 to 2.50%,

Ti;

0.003 to 0.030%, and

B;

0.0001 to 0.0030%, and

limiting

P;

0.020% or less,

S;

0.0030% or less

with a balance of Fe and unavoidable impurities.

9. A high strength steel plate for line pipe superior in low temperature toughness characterized by comprising high strength steel plate for line pipe used as a material for high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 8 and having a chemical compositions containing, by mass %, one or both of

Cu:

0.05 to 1.50% and

Ni;

0.05 to 5.00%.

10. A high strength steel plate for line pipe superior in low temperature toughness characterized by comprising high strength steel plate for line pipe used as a material for high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 8 and having a chemical compositions containing, by mass %, one or more of

Cr:

0.02 to 1.50%,

W;

0.01 to 2.00%,

V;

0.010 to 0.100%,

Zr;

0.0001 to 0.0500%, and

Ta;

0.0001 to 0.0500%.

11. A high strength steel plate for line pipe superior in low temperature toughness characterized by comprising high strength steel plate for line pipe used as a material for high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 8 and having a chemical compositions containing, by mass %, one or more of

Mg:

0.0001 to 0.0100%,

Ca;

0.0001 to 0.0050%,

REM;

0.0001 to 0.0050%,

Y;

0.0001 to 0.0050%,

Hf;

0.0001 to 0.0050%, and

Re;

0.0001 to 0.0050%.

12. A method of production of a high strength steel plate for line pipe superior in low temperature toughness as set forth in claim 8, said method of production of a high strength steel plate for line pipe superior in low temperature toughness characterized by melting and casting steel comprising the chemical compositions as set forth in claim 8, reheating a steel slab to 1000°

C. or more, hot rolling by a reduction ratio in a nonrecrystallization temperature region of 3 or more, and stopping water cooling at 500°

C. or lower.

13. A method of production of high strength steel pipe for line pipe superior in low temperature toughness characterized by comprising a method of production of high strength steel pipe for line pipe superior in low temperature toughness and by shaping the high strength steel plate for line pipe superior in low temperature toughness produced by the method as set forth in claim 12 to a tube, welding the seam portions, and then enlarging it.

14. A method of production of high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 13 characterized by shaping the steel plate into a tube by a UO process, welding the seam portions from the inner side and outer side by submerged arc welding, then enlarging the pipe.

15. A method of production of a high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 14 characterized in that a welding wire used for the submerged arc welding has a chemical compositions containing, by mass %,

C:

0.01 to 0.12%,

Si;

0.05 to 0.50%,

Mn;

1.00 to 2.50%, and

Ni;

2.00 to 8.50%

further containing one or more of Cr, Mo, and V in a range of

Cr+Mo+V;

1.00 to 5.00%

with a balance of Fe and unavoidable impurities.

16. A method of production of high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 15 characterized in that the chemical compositions of the welding wire is, by mass %, B:

0.0001 to 0.0050%.

17. A method of production of high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 13 characterized by heat treating the weld zone and heat affected zone after welding and before pipe expansion.

18. A method of production of high strength steel pipe for line pipe superior in low temperature toughness as set forth in claim 17 characterized in that the heating temperature when heat treating the weld zone and heat affected zone is 200 to 500°

C.