HIGH STRENGTH STEEL PIPE FOR LOW-TEMPERATURE USAGE HAVING EXCELLENT BUCKLING RESISTANCE AND TOUGHNESS OF WELDED HEAT AFFECTED ZONE AND METHOD FOR PRODUCING THE SAME

• US 20120018028A1
• Filed: 02/05/2010
• Published: 01/26/2012
• Est. Priority Date: 02/06/2009
• Status: Active Grant

• Current Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Original Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Inventors: Ishikawa, Nobuyuki, Okatsu, Mitsuhiro, Shikanai, Nobuo, Shimamura, Junji
• Granted Patent: US 8,765,269 B2
• Time in Patent Office: Days
• US Class Current: 138/142
• CPC Class Codes: B21C 37/08 Making tubes with welded or soldered seams with helically arranged seams B21C37/122
• CPC Class Codes: B23K 2101/06 Tubes
• CPC Class Codes: B23K 2103/04 Steel or steel alloys
• CPC Class Codes: B23K 35/30 with the principal constituent melting at less than 1550 degrees C
• CPC Class Codes: B23K 9/0253 for the longitudinal seam of tubes
• CPC Class Codes: B23K 9/18 Submerged-arc welding
• CPC Class Codes: B23K 9/23 taking account of the properties of the materials to be welded
• CPC Class Codes: C21D 2211/002 Bainite
• CPC Class Codes: C21D 2211/008 Martensite
• CPC Class Codes: C21D 6/005 containing Mn
• CPC Class Codes: C21D 8/0205 of ferrous alloys
• CPC Class Codes: C21D 8/0226 Hot rolling
• CPC Class Codes: C21D 8/0247 characterised by the heat treatment
• CPC Class Codes: C21D 8/10 during manufacturing of tubular bodies
• CPC Class Codes: C21D 8/105 of ferrous alloys
• CPC Class Codes: C21D 9/08 for tubular bodies or pipes
• CPC Class Codes: C21D 9/50 for welded joints
• CPC Class Codes: C22C 38/001 containing N
• 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 38/12 : containing tungsten, tantalum, molybdenum, vanadium, or niobium
• CPC Class Codes: C22C 38/14 : containing titanium or zirconium
• CPC Class Codes: Y10T 428/12951 : Fe-base component
• CPC Class Codes: Y10T 428/12958 : Next to Fe-base component
• CPC Class Codes: Y10T 428/12965 : Both containing 0.01-1.7% carbon [i.e., steel]
• CPC Class Codes: Y10T 428/12972 : Containing 0.01-1.7% carbon [i.e., steel]

Abstract

An APIX100-grade high strength steel pipe includes a base material containing, in mass percentage, C: more than 0.03% and 0.08% or less, Si: 0.01% to 0.5%, Mn: 1.5% to 3.0%, P: 0.015% or less, S: 0.005% or less, Al: 0.01% to 0.08%, Nb: 0.005% to 0.025%, Ti: 0.005% to 0.025%, N: 0.001% to 0.010%, O: 0.005% or less, and B: 0.0003% to 0.0020%, further contains one or more of Cu, Ni, Cr, Mo, and V, satisfies 0.19≦P_cm≦0.25, the balance being Fe and unavoidable impurities, and has a TS of 760 to 930 MPa, a uniform elongation of 5% or more, and a YR of 85% or less; the seam weld metal has a specific composition.

Claims

1. A high strength steel pipe for low-temperature usage, comprising:

a base material portion in which a base material has a composition containing, in mass percentage,

C;

more than 0.03% and 0.08% or less,

Si;

0.01% to 0.5%,

Mn;

1.5% to 3.0%,

P;

0.015% or less,

S;

0.003% or less,

Al;

0.01% to 0.08%,

Nb;

0.005% to 0.025%,

Ti;

0.005% to 0.025%,

N;

0.001% to 0.010%,

O;

0.005% or less, and

B;

0.0003% to 0.0020%

and one or more of

Cu;

0.01% to 1%,

Ni;

0.01% to 1%,

Cr;

0.01% to 1%,

Mo;

0.01% to 1%, and

V;

0.01% to 0.1%,

wherein a P_CM value (in %) calculated by a formula (1) below satisfies 0.19 S P_CM≦

0.25, the balance is Fe and unavoidable impurities,

the base material has a tensile strength of 760 MPa or more and 930 MPa or less, a uniform elongation of 5% or more, a yield ratio of 85% or less, and a charpy absorbed energy at a test temperature of −

40°

C. is 210 J or more when the plate thickness is less than 25 mm and is 150 J or more when the plate thickness is 25 mm or more; and

a weld metal portion in which weld metal for seam welding has a composition containing, in mass percentage,

C;

0.03% to 0.10%,

Si;

0.5% or less.

Mn;

1.5% to 3.0%,

P;

0.015% or less,

S;

0.005% or less,

Al;

0.05% or less,

Nb;

0.005% to 0.05%,

Ti;

0.005% to 0.03%,

N;

0.010% or less,

O;

0.015% to 0.045%, and

B;

0.0003% to 0.0050%

and one or more of

Cu;

0.01% to 1%,

Ni;

0.01% to 2.5%,

Cr;

0.01% to 1%,

Mo;

0.01% to 1.5%, and

V;

0.1% or less, and

the balance is Fe and unavoidable impurities,

wherein a microstructure of a welded heat affected zone in which a prior austenite grain size is 50 μ

m or more near a fusion line in a seam weld zone of the steel pipe is a lower bainite structure or a multi-phase structure containing lower bainite having an area fraction of 50% or more and upper bainite and/or martensite,

P_CM(%)=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5×

B 

 

(1)

where each element represents content (mass %).

2. The high strength steel pipe according to claim 1, wherein, in the seam weld zone of the steel pipe in which a layer on an internal side and a layer on an external side are welded in a longitudinal direction of the steel pipe, the welded heat affected zone near the fusion line on the external side has a hardness satisfying a formula (2) below,

250≦

HV(98N)≦

350 

 

(2)

where HV(98N) represents a Vickers hardness measured with 10 kgf.

3. The high strength steel pipe according to claim 1, wherein the seam weld zone of the steel pipe has a joint strength of 760 MPa or more and 930 MPa or less.

4. The high strength steel pipe according to claim 1, wherein a microstructure of the base material portion of the steel pipe is mainly constituted of a bainite structure containing island martensite having an area fraction of 4% or more and 12% or less, the island martensite contained has a long axis size of 2 μ

m or less, and bainitic ferrite surrounded by boundaries having a misorientation of 15°

or more in the microstructure of the base material portion has a long axis size of 20 μ

m or less.

5. The high strength steel pipe according to claim 1, wherein the chemical composition of the base material portion and/or the weld metal portion further contains, in mass percentage, one or more of

Ca:

0.0005% to 0.1%,

REM;

0.0005% to 0.02%,

Zr;

0.0005% to 0.03%, and

Mg;

0.0005% to 0.01%.

6. The high strength steel pipe according to claim 4, wherein the steel pipe has a uniform elongation of 5% or more and a yield ratio of 85% or less even after the steel pipe is subjected to a strain ageing treatment at a temperature of 250°

C. or less for 30 minutes or less.

7. A method for producing a steel plate for a high strength steel pipe for low-temperature usage comprising:

subjecting a steel having the base material composition according to claim 1 to hot rolling such that the steel is heated at a temperature of 1000°

C. to 1300°

C., a cumulative rolling reduction at more than 950°

C. is 10% or more, a cumulative rolling reduction at 750°

C. or less is 75% or more, and a finish rolling temperature is 650°

C. or more;

then subjecting the steel to accelerated cooling to a temperature of 450°

C. or more and less than 650°

C. at a cooling rate of 10°

C./s or more; and

immediately after the accelerated cooling, reheating the steel to a temperature of 500°

C. to 750°

C. at a heating rate of 0.5°

C./s or more, the temperature being equal to or more than a stopping temperature of the accelerated cooling.

8. The method according to claim 7, wherein, in the hot rolling, a cumulative rolling reduction at a temperature of more than 750°

C. and 950°

C. or less is 20% or more.

9. A method for producing a high strength welded steel pipe for low-temperature usage, wherein the steel plate obtained by the method according to claim 7 is formed into a pipe shape, and, in welding of abutting portions of the formed steel plate by welding an internal layer and an external layer of the steel plate, internal welding heat input and external welding heat input is each 80 kJ/cm or less, and a heat input balance between the external heat input and the internal heat input satisfies a formula (3) below,

internal heat input≦

external heat input 

 

(3).

10. The method according to claim 9, wherein, after the internal layer and the external layer are welded in a longitudinal direction of the steel pipe, the steel pipe is subjected to pipe expansion at an expansion ratio of 0.4% or more and 2.0% or less.

11. The high strength steel pipe according to claim 2, wherein the seam weld zone of the steel pipe has a joint strength of 760 MPa or more and 930 MPa or less.

12. The high strength steel pipe according to claim 2, wherein a microstructure of the base material portion of the steel pipe is mainly constituted of a bainite structure containing island martensite having an area fraction of 4% or more and 12% or less, the island martensite contained has a long axis size of 2 μ

m or less, and bainitic ferrite surrounded by boundaries having a misorientation of 15°

or more in the microstructure of the base material portion has a long axis size of 20 μ

m or less.

13. The high strength steel pipe according to claim 3, wherein a microstructure of the base material portion of the steel pipe is mainly constituted of a bainite structure containing island martensite having an area fraction of 4% or more and 12% or less, the island martensite contained has a long axis size of 2 μ

m or less, and bainitic ferrite surrounded by boundaries having a misorientation of 15°

or more in the microstructure of the base material portion has a long axis size of 20 μ

M or less.

14. The high strength steel pipe according to claim 2, wherein the chemical composition of the base material portion and/or the weld metal portion further contains, in mass percentage, one or more of

Ca:

0.0005% to 0.1%,

REM;

0.0005% to 0.02%,

Zr;

0.0005% to 0.03%, and

Mg;

0.0005% to 0.01%.

15. The high strength steel pipe according to claim 3, wherein the chemical composition of the base material portion and/or the weld metal portion further contains, in mass percentage, one or more of

Ca:

0.0005% to 0.1%,

REM;

0.0005% to 0.02%,

Zr;

0.0005% to 0.03%, and

Mg;

0.0005% to 0.01%.

16. The high strength steel pipe according to claim 4, wherein the chemical composition of the base material portion and/or the weld metal portion further contains, in mass percentage, one or more of

Ca:

0.0005% to 0.1%,

REM;

0.0005% to 0.02%,

Zr;

0.0005% to 0.03%, and

Mg;

0.0005% to 0.01%.

17. The high strength steel pipe according to claim 5, wherein the steel pipe has a uniform elongation of 5% or more and a yield ratio of 85% or less even after the steel pipe is subjected to a strain ageing treatment at a temperature of 250°

C. or less for 30 minutes or less.

18. A method for producing a steel plate for a high strength steel pipe for low-temperature usage comprising:

subjecting a steel having the base material composition according to claim 2 to hot rolling such that the steel is heated at a temperature of 1000°

C. to 1300°

C., a cumulative rolling reduction at more than 950°

C. is 10% or more, a cumulative rolling reduction at 750°

C. or less is 75% or more, and a finish rolling temperature is 650°

C. or more;

then subjecting the steel to accelerated cooling to a temperature of 450°

C. or more and less than 650°

C. at a cooling rate of 10°

C./s or more; and

immediately after the accelerated cooling, reheating the steel to a temperature of 500°

C. to 750°

C. at a heating rate of 0.5°

C./s or more, the temperature being equal to or more than a stopping temperature of the accelerated cooling.

19. A method for producing a steel plate for a high strength steel pipe for low-temperature usage comprising:

subjecting a steel having the base material composition according to claim 3 to hot rolling such that the steel is heated at a temperature of 1000°

C. to 1300°

C., a cumulative rolling reduction at more than 950°

C. is 10% or more, a cumulative rolling reduction at 750°

C. or less is 75% or more, and a finish rolling temperature is 650°

C. or more;

then subjecting the steel to accelerated cooling to a temperature of 450°

C. or more and less than 650°

C. at a cooling rate of 10°

C./s or more; and

immediately after the accelerated cooling, reheating the steel to a temperature of 500°

C. to 750°

C. at a heating rate of 0.5°

C./s or more, the temperature being equal to or more than a stopping temperature of the accelerated cooling.

20. A method for producing a steel plate for a high strength steel pipe for low-temperature usage comprising:

subjecting a steel having the base material composition according to claim 4 to hot rolling such that the steel is heated at a temperature of 1000°

C. to 1300°

C., a cumulative rolling reduction at more than 950°

C. is 10% or more, a cumulative rolling reduction at 750°

C. or less is 75% or more, and a finish rolling temperature is 650°

C. or more;

then subjecting the steel to accelerated cooling to a temperature of 450°

C. or more and less than 650°

C. at a cooling rate of 10°

C./s or more; and

immediately after the accelerated cooling, reheating the steel to a temperature of 500°

C. to 750°

C. at a heating rate of 0.5°

C./s or more, the temperature being equal to or more than a stopping temperature of the accelerated cooling.