Heavy wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes

• US 9,644,248 B2
• Filed: 04/08/2014
• Issued: 05/09/2017
• Est. Priority Date: 04/08/2013
• Status: Active Grant

• Current Assignee: Dalmine SPA (Tenaris SA)
• Original Assignee: Dalmine SPA (Tenaris SA)
• Inventors: Anelli, Ettore, Paravicini Bagliani, Emanuele, Fare, Stefano
• Primary Examiner(s): KLEMANSKI, HELENE G
• Application Number:
  US14/248,116
• Publication Number:
  US 20140299235A1
• Time in Patent Office: 1,127 Days
• Field of Search: 148504, 148330, 148332, 148335
• CPC Class Codes: C21D 2211/002 Bainite
• CPC Class Codes: C21D 2211/005 Ferrite
• CPC Class Codes: C21D 8/105 of ferrous alloys
• CPC Class Codes: C21D 9/08 for tubular bodies or pipes
• 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 38/42 with copper
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/48 with niobium or tantalum
• CPC Class Codes: C22C 38/50 with titanium or zirconium
• CPC Class Codes: F16L 9/02 of metal F16L9/16 - F16L9/22 take precedence

Abstract

Disclosed herein are embodiments of a seamless quenched and tempered steel pipe having a wall thickness (WT) higher than or equal to 35 mm and lower than or equal to 80 mm. Embodiments of the steel pipe can comprise C, Mn, Cr, Ni, Mo, Al, Ca, N, Nb, Ti, Zr, and Ta. Further, for some embodiments of the steel pipe wherein, defining a first parameter P1=50×C+Cr+10×Mo+70×V, the chemical composition can satisfy a first condition P1≦8.0.

Claims

1. A seamless quenched and tempered steel pipe comprising:

a yield strength from 415 MPa to 635 MPa and a wall thickness (WT) higher than or equal to 35 mm and lower than or equal to 80 mm;

wherein the steel pipe has a chemical composition consisting of;

0.050-0.085 wt % C;

0.80-1.65 wt % Mn;

0.10-0.45 wt % Si;

0.10-0.70 wt % Cr;

0.08-0.45wt % Ni;

0.08-0.40 wt % Mo;

0.015-0.040 wt % Al;

0.0008-0.0050 wt % Ca;

0.0030-0.0090 wt % N;

0.000-0.040 wt % Nb;

0.000-.020 wt % Ti;

0.000-0.030 wt % Zr;

0.000-0.030 wt % Ta;

0.000-0.010 wt % V;

0.000-0.25 wt % Cu;

0.000-0.003 wt % S;

0.000-0.015 wt % P; and

0.000-0.0005 wt % B;

the remainder being Fe;

wherein CE_IIW=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15) is in the range of 0.36% to 0.43%;

wherein, defining a first parameter P1=50×

C+Cr+10×

Mo+70×

V, the chemical composition satisfies a first condition 4.2<

P1<

8.0;

wherein the quenched and tempered steel pipe has, at mid thickness, a microstructure comprising, in volume percentage, tempered bainite greater than or equal to 50% and ferrite (V_F) lower than or equal to 50%,

wherein the quenched and tempered steel pipe has, at a distance up to 2 mm starting from outer and inner surfaces of the steel pipe, a microstructure comprising, in volume percentage, tempered martensite lower than 70% and tempered bainite higher than 30%;

wherein the microstructure of the quenched and tempered steel pipe has an average prior austenite grain size, measured by ASTM Standard E112, smaller than 25 μ

m;

and wherein the maximum hardness values, measured at 1.5-2.0 mm depth from the outer and inner surfaces, are not higher than 235 HV₁₀.

2. The seamless quenched and tempered steel pipe of claim 1, wherein, at a distance up to 2 mm starting from outer and inner surfaces of the steel pipe, the microstructure comprises tempered martensite lower than 40% and tempered bainite higher than 60%.

3. The seamless quenched and tempered steel pipe of claim 2, wherein, at a distance up to 2 mm starting from outer and inner surfaces of the steel pipe, the microstructure comprises tempered martensite lower than 20% and tempered bainite higher than 80%.

4. The seamless quenched and tempered steel pipe of claim 2, wherein, at a distance up to 2 mm starting from outer and inner surfaces of the steel pipe, the microstructure only comprises tempered bainite.

5. The seamless quenched and tempered steel pipe of claim 1, wherein, at mid thickness, the microstructure comprises tempered bainite greater than or equal to 60% and ferrite (V_F) lower than or equal to 40%.

6. The seamless quenched and tempered steel pipe of claim 1, wherein, at mid thickness, the microstructure comprises tempered bainite greater than or equal to 80% and ferrite (V_F) lower than or equal to 20%.

7. The seamless quenched and tempered steel pipe of claim 1, wherein, at mid thickness, the microstructure comprises ferrite (V_F) lower than or equal to 50% for a pipe of grade X60, ferrite (V_F) lower than or equal to 40% for a pipe of grade X65, ferrite (V_F) lower than or equal to 20% for a pipe of grade X70.

8. The seamless quenched and tempered steel pipe of claim 1, wherein, defining a second parameter P2=10×

C+Mn+Cr+4×

Mo+16×

V, the chemical composition satisfies a second condition P2>

2.3.

9. The seamless quenched and tempered steel pipe of claim 8, wherein the second parameter P2 satisfies the following conditions:

P2>

2.3 in order to meet the minimum yield strength required by the grade X60Q (415 MPa);

P2>

2.7 in order to meet the minimum yield strength required by the grade X65Q (450 MPa); and

P2>

3.5 in order to meet the minimum yield strength required by the grade X70Q (485 MPa).

10. The seamless quenched and tempered steel pipe of claim 8, wherein the second parameter P2 is lower than or equal to 4.0.

11. The seamless quenched and tempered steel pipe of claim 1, wherein:

CE_PCM=C+Si/30+Mn/20+Cr/20+Cu/20+Ni/60+Mo/15+V/10+5×

B is in the range of 0.17% to 0.22%.

12. The seamless quenched and tempered steel pipe of claim 1, wherein the chemical composition consists of:

0.050-0.085 wt % C;

0.95-1.30 wt % Mn;

0.10-0.35 wt % Si;

0.20-0.50 wt % Cr;

0.15-0.40 wt % Ni;

0.15-0.40 wt % Mo;

0.000-0.010 wt % V;

0.020-0.040 wt % Al;

0.0008-0.0030 wt % Ca;

0.020-0.040 wt % Nb;

0.000-0.015 wt % Ti;

0.0030-0.0070 wt % N;

0.00-0.20 wt % Cu;

0.0000-0.0020 wt % S;

0.000-0.015 wt % P;

0.0000-0.0005 wt % B;

0.000-0.015 wt % Zr; and

0.000-0.015 wt % Ta;

the remainder being Fe.

13. The seamless quenched and tempered steel pipe of claim 1, wherein the chemical composition consists of:

0.060-0.080 wt % C;

1.00-1.20 wt % Mn;

0.10-0.30 wt % Si;

0.30-0.40 wt % Cr;

0.25-0.35 wt % Ni;

0.30-0.35 wt % Mo;

0.000-0.010 wt % V;

0.020-0.030 wt % Al;

0.0015-0.0030 wt % Ca;

0.020-0.030 wt % Nb;

0.000-0.015 wt % Ti;

0.0030-0.0060 wt % N;

0.00-0.15 wt % Cu;

0.0000-0.0010 wt % S;

0.000-0.011 wt % P;

0.0000-0.0005 wt % B;

0.000-0.010 wt % Zr; and

0.000-0.010 wt % Ta;

the remainder being Fe.

14. The seamless quenched and tempered steel pipe of claim 1, wherein the chemical composition consists of:

0.060-0.085 wt % C;

0.95-1.30 wt % Mn;

0.10-0.35 wt % Si;

0.20-0.40 wt % Cr;

0.25-0.40 wt % Ni;

0.25-0.35 wt % Mo;

0.000-0.010 wt % V;

0.020-0.040 wt % Al;

0.0008-0.0030 wt % Ca;

0.020-0.040 wt % Nb;

0.000-0.015 wt % Ti;

0.0030-0.0070 wt % N;

0.00-0.20 wt % Cu;

0.0000-0.0020 wt % S;

0.000-0.015 wt % P;

0.0000-0.0005 wt % B;

0.000-0.015 wt % Zr; and

0.000-0.015 wt % Ta;

the remainder being Fe;

and satisfies the following additional conditions;

P1=50×

C+Cr+10×

Mo+70×

V in the range from 6.3 to 8.0;

P2=10×

C+Mn+Cr+4×

Mo+16×

V in the range from 2.75 to 3.8;

CE_IIW=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15 in the range from 0.38% to 0.43%; and

CE_PCM=C+Si/30+Mn/20+Cr/20+Cu/20+Ni/60+Mo/15+V/10+5×

B in the range from 0.17% to 0.21%.

15. The seamless quenched and tempered steel pipe according to claim 1, wherein the chemical composition consists of:

0.050-0.080 wt % C;

0.95-1.20 wt % Mn;

0.10-0.35 wt % Si;

0.10-0.30 wt % Cr;

0.15-0.35wt % Ni;

0.15-0.30 wt % Mo;

0.000-0.010 wt % V;

0.020-0.040 wt % Al;

0.0008-0.0030 wt % Ca;

0.020-0.040 wt % Nb;

0.000-0.015 wt % Ti;

0.0030-0.0070 wt % N;

0.00-0.20 wt % Cu;

0.0000-0.0020 wt % S;

0.000-0.015 wt % P;

0.0000-0.0005 wt % B;

0.000-0.015 wt % Zr; and

0.000-0.015 wt % Ta;

the remainder being Fe;

and satisfies the following additional conditions;

P1=50×

C+Cr+10×

Mo+70×

V in the range from 4.2 to 7.5;

P2=10×

C+Mn+Cr+4×

Mo+16×

V in the range from 2.31 to 3.66

CE_IIW=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15 in the range from 0.36% to 0.41%; and

CE_PCM=C+Si/30+Mn/20+Cr/20+Cu/20+Ni/60+Mo/15+V/10+5×

B in the range from 0.16% to 0.21%.

17. A pipe bend, obtained by a seamless steel pipe of claim 1, having maximum hardness values, measured at 1.5 mm to 2 mm depth from the surface, not higher than 235 HV₁₀.

18. The pipe bend of claim 17, having a maximum hardness values, measured at 1.5 mm to 2 mm depth from the surface, not higher than 230 HV₁₀.

16. A method for manufacturing a seamless quenched and tempered steel pipe comprising:

hot forming a seamless steel pipe having a wall thickness (WT) higher than or equal to 35 mm and lower than or equal to 80 mm and a chemical composition consisting of;

0.050-0.085 wt % C;

0.80-1.65 wt % Mn;

0.10-0.45 wt % Si;

0.10-0.70 wt % Cr;

0.08-0.45 wt % Ni;

0.08-0.40 wt % Mo;

0.015-0.040 wt % Al;

0.0008-0.0050 wt % Ca;

0.0030-0.0090 wt % N;

0.000-0.040 wt % Nb;

0.000-0.020 wt % Ti;

0.000-0.030 wt % Zr;

0.000-0.030 wt % Ta;

0.000-0.010 wt % V;

0.00-0.25 wt % Cu;

0.000-0.003 wt % S;

0.000-0.015 wt % P; and

0.0000-0.0005 wt % B;

the remainder being Fe;

cooling in air the seamless steel pipe down to reach room temperature;

heating the seamless steel pipe, with a first heating rate between 0.1°

C./s and 10°

C./s, to an austenitizing temperature above the Ac3 transformation point, in a range between 880°

C. and 980°

C., and providing a soaking time between 180 s and 5400 s;

quenching the seamless steel pipe using external and internal cooling, with a cooling rate greater than 6°

C./s and up to 30°

C./s at mid thickness of the pipe, and with a cooling rate of 100-200°

C./s in proximity of the outer and inner surfaces of the pipe;

heating the seamless steel pipe, with a second heating rate between 0.1°

C./s and 10°

C./s, to a tempering temperature comprised in a predetermined range, and providing a holding time at said tempering temperature between 600 s and 7200 s;

wherein said predetermined range is calculated with a tolerance of ±

20°

C. using the following equation;