HEAVY WALL ELECTRIC RESISTANCE WELDED STEEL PIPE FOR LINE PIPE AND METHOD FOR MANUFACTURING THE SAME (AS AMENDED)

• US 20160153063A1
• Filed: 07/08/2014
• Published: 06/02/2016
• Est. Priority Date: 07/09/2013
• Status: Active Grant

• Current Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Original Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Inventors: Goto, Sota, Toyoda, Shunsuke, Okabe, Takatoshi
• Granted Patent: US 10,385,417 B2
• Time in Patent Office: Days
• CPC Class Codes: B23K 11/0873 of the longitudinal seam of tubes
• CPC Class Codes: C21D 1/42 Induction heating
• CPC Class Codes: C21D 2211/002 Bainite
• CPC Class Codes: C21D 6/004 containing Cr and Ni
• CPC Class Codes: C21D 6/005 containing Mn
• CPC Class Codes: C21D 6/008 containing Si
• CPC Class Codes: C21D 8/0205 of ferrous alloys
• CPC Class Codes: C21D 8/0226 Hot rolling
• CPC Class Codes: C21D 8/0236 Cold rolling
• CPC Class Codes: C21D 8/0263 following hot rolling
• CPC Class Codes: C21D 8/105 of ferrous alloys
• CPC Class Codes: C21D 9/08 for tubular bodies or pipes
• CPC Class Codes: C21D 9/085 Cooling or quenching
• CPC Class Codes: C21D 9/50 for welded joints
• CPC Class Codes: C21D 9/505 Cooling thereof
• 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 38/12 : 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 38/22 : 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 38/38 : with more than 1.5% by weight of manganese
• CPC Class Codes: C22C 38/58 : with more than 1.5% by weight of manganese
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

By using, as a raw material, a thick hot-rolled steel sheet having a chemical composition containing, by mass %, C: 0.02% or more and 0.10% or less, Si: 0.05% or more and 0.30% or less, Mn: 0.80% or more and 2.00% or less, and Nb: 0.010% or more and 0.100% or less and satisfying the condition that a carbon equivalent Ceq is 0.25% or more and 0.50% or less, a microstructure including a bainitic ferrite phase and/or a bainite phase, a high strength of 52 ksi or more in terms of yield strength and a high toughness of −45° C. or lower in terms of fracture transition temperature vTrs, and satisfying the condition that the ratio of the average crystal grain size of the coarsest-grain portion to the average crystal grain size of the finest-grain portion is 2.0 or less in every portion in the wall thickness direction is obtained

Claims

1. A heavy wall electric resistance welded steel pipe for a line pipe, the steel pipe being a heavy wall electric resistance welded steel pipe which is formed from a thick hot-rolled steel sheet as a raw material and which has a base metal zone and an electric resistance weld zone,

wherein the base metal zone has a chemical composition containing, by mass %, C:

0.02% or more and 0.10% or less, Si;

0.05% or more and 0.30% or less, Mn;

0.80% or more and 2.00% or less, and Nb;

0.010% or more and 0.100% or less and satisfying the condition that a carbon equivalent Ceq defined by equation (1) below is 0.25% or more and 0.50% or less, and a microstructure including a bainitic ferrite phase and/or a bainite phase,

wherein the base metal zone has a high strength of 360 MPa or more in terms of yield strength and a high toughness of −

45°

C. or lower in terms of fracture transition temperature vTrs in a Charpy impact test,

wherein the electric resistance weld zone has a microstructure including a bainitic ferrite phase and/or a bainite phase and satisfying the condition that the ratio of the average crystal grain size of a portion in the wall thickness direction having the largest grain size to the average crystal grain size of a portion in the wall thickness direction having the smallest grain size, that is, (the average crystal grain size of the coarsest-grain portion)/(the average crystal grain size of the finest-grain portion) is 2.0 or less in every portion in the wall thickness direction, and

wherein the electric resistance weld zone has high toughness, and 0.80 mm or more in terms of critical opening displacement δ

at a testing temperature of −

25°

C. in a CTOD test;

Ceq (%)=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15 

 

(1),

where C, Mn, Cr, Mo, V, Cu, Ni respectively represent the contents of the corresponding chemical elements (mass %).

2. The heavy wall electric resistance welded steel pipe for a line pipe according to claim 1, wherein the chemical composition is a chemical composition containing, by mass %, C:

0.02% or more and 0.10% or less, Si;

0.05% or more and 0.30% or less, Mn;

0.80% or more and 2.00% or less, P;

0.030% or less, S;

0.0050% or less, Nb;

0.010% or more and 0.100% or less, Ti;

0.001% or more and 0.025% or less, Al;

0.01% or more and 0.08% or less, Ca;

0.0005% or more and 0.0050% or less, and the balance being Fe and inevitable impurities and satisfying the condition that a carbon equivalent Ceq defined by equation (1) above is 0.25% or more and 0.50% or less.

3. The heavy wall electric resistance welded steel pipe for a line pipe according to claim 2, wherein the chemical composition further contains, by mass %, one, two, or more selected from among Cu:

0.5% or less, Ni;

0.5% or less, Cr;

0.5% or less, Mo;

0.5% or less, and V;

0.10% or less.

4. The heavy wall electric resistance welded steel pipe for a line pipe according to claim 1, wherein the average crystal grain size of the finest-grain portion is 10 μ

m or less.

11. The heavy wall electric resistance welded steel pipe for a line pipe according to any one of claim 2, wherein the average crystal grain size of the finest-grain portion is 10 μ

m or less.

12. The heavy wall electric resistance welded steel pipe for a line pipe according to any one of claim 3, wherein the average crystal grain size of the finest-grain portion is 10 μ

m or less.

5. A method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe, the method being a method for manufacturing a heavy wall electric resistance welded steel pipe including using a heavy wall electric resistance welded steel pipe as a starting material and performing an in-line heat treatment process for an electric resistance weld zone on the electric resistance weld zone of the heavy wall electric resistance welded steel pipe,

wherein the heavy wall electric resistance welded steel pipe as the starting material is a high-strength heavy wall electric resistance welded steel pipe having a chemical composition containing, by mass %, C:

0.02% or more and 0.10% or less, Si;

0.05% or more and 0.30% or less, Mn;

0.80% or more and 2.00% or less, and Nb;

0.010% or more and 0.100% or less and satisfying the condition that a carbon equivalent Ceq defined by equation (1) below is 0.25% or more and 0.50% or less, a microstructure including a bainitic ferrite phase and/or a bainite phase in every portion in the wall thickness direction, and having a high strength of 360 MPa or more in terms of yield strength and a high toughness of −

45°

C. or lower in terms of fracture transition temperature vTrs in a Charpy impact test in every portion in the wall thickness direction,

wherein the heat treatment process for an electric resistance weld zone is a process including performing a heat treatment for an electric resistance weld zone such that every portion in the wall thickness direction of the electric resistance weld zone has a temperature of 850°

C. or higher and 1150°

C. or lower and performing a cooling treatment for an electric resistance weld zone to a cooling stop temperature of 550°

C. or lower such that an average cooling rate is 10°

C./s or more and 70°

C./s or less in every portion in the wall thickness direction of the electric resistance weld zone, and

wherein the electric resistance weld zone has high toughness, and 0.80 mm or more in terms of critical opening displacement δ

at a testing temperature of −

25°

C. in a CTOD test;

Ceq (%)=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15 

 

(1),

where C, Mn, Cr, Mo, V, Cu, Ni respectively represent the contents of the corresponding chemical elements (mass %).

6. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 5, wherein the heat treatment process for an electric resistance weld zone is a process using an induction heating device and a water cooling device which are placed on the outer surface side of the heavy wall electric resistance welded steel pipe,

wherein the heat treatment for an electric resistance weld zone is a treatment including performing heating such that an outer surface temperature of the steel pipe is 1150°

C. or lower and such that an inner surface temperature of the steel pipe is 830°

C. or higher, and

wherein the cooling treatment for an electric resistance weld zone is a treatment including performing cooling such that an average cooling rate is 70°

C./s or less in terms of outer surface temperature of the steel pipe when an outer surface temperature of the steel pipe is 800°

C. or lower and 500°

C. or higher and such that an average cooling rate is 10°

C./s or more in terms of inner surface temperature of the steel pipe when an inner surface temperature of the steel pipe is 750°

C. or lower and 650°

C. or higher.

7. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 6, wherein the cooling device is a device using cooling water, wherein a water flow rate of the cooling water is 1.2 m³/m² min or more and 5.0 m³/m² min or less, and wherein the cooling width is ±

50 mm or more in the circumferential direction from the center of the electric resistance weld zone.

8. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 5, wherein the chemical composition is a chemical composition containing, by mass %, C:

0.02% or more and 0.10% or less, Si;

0.05% or more and 0.30% or less, Mn;

0.80% or more and 2.00% or less, P;

0.030% or less, S;

0.0050% or less, Nb;

0.010% or more and 0.100% or less, Ti;

0.001% or more and 0.025% or less, Al;

0.01% or more and 0.08% or less, Ca;

0.0005% or more and 0.0050% or less, and the balance being Fe and inevitable impurities and satisfying the condition that a carbon equivalent Ceq defined by equation (1) above is 0.25% or more and 0.50% or less.

9. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 8, wherein the chemical composition further contains, by mass %, one, two, or more selected from among Cu:

0.5% or less, Ni;

0.5% or less, Cr;

0.5% or less, Mo;

0.5% or less, and V;

0.10% or less.

10. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 5, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

13. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 6, wherein the chemical composition is a chemical composition containing, by mass %, C:

0.02% or more and 0.10% or less, Si;

0.05% or more and 0.30% or less, Mn;

0.80% or more and 2.00% or less, P;

0.030% or less, S;

0.0050% or less, Nb;

0.010% or more and 0.100% or less, Ti;

0.001% or more and 0.025% or less, Al;

0.01% or more and 0.08% or less, Ca;

0.0005% or more and 0.0050% or less, and the balance being Fe and inevitable impurities and satisfying the condition that a carbon equivalent Ceq defined by equation (1) above is 0.25% or more and 0.50% or less.

14. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 7, wherein the chemical composition is a chemical composition containing, by mass %, C:

0.02% or more and 0.10% or less, Si;

0.05% or more and 0.30% or less, Mn;

0.80% or more and 2.00% or less, P;

0.030% or less, S;

0.0050% or less, Nb;

0.010% or more and 0.100% or less, Ti;

0.001% or more and 0.025% or less, Al;

0.01% or more and 0.08% or less, Ca;

0.0005% or more and 0.0050% or less, and the balance being Fe and inevitable impurities and satisfying the condition that a carbon equivalent Ceq defined by equation (1) above is 0.25% or more and 0.50% or less.

15. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 13, wherein the chemical composition further contains, by mass %, one, two, or more selected from among Cu:

0.5% or less, Ni;

0.5% or less, Cr;

0.5% or less, Mo;

0.5% or less, and V;

0.10% or less.

16. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 14, wherein the chemical composition further contains, by mass %, one, two, or more selected from among Cu:

0.5% or less, Ni;

0.5% or less, Cr;

0.5% or less, Mo;

0.5% or less, and V;

0.10% or less.

17. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 6, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

18. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 7, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

19. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 8, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

20. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 13, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

21. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 14, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

22. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 9, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

23. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 15, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.

24. The method for manufacturing a heavy wall electric resistance welded steel pipe for a line pipe according to claim 16, wherein the high-strength heavy wall electric resistance welded steel pipe is an electric resistance welded steel pipe which is formed from a high-strength thick hot-rolled steel sheet as a raw material, and

wherein the high-strength thick hot-rolled steel sheet is manufactured by performing a heating process including heating a steel raw material having the chemical composition at a heating temperature of 1100°

C. or higher and 1280°

C. or lower, by performing a hot rolling process including rough rolling and finishing rolling with a cumulative rolling reduction ratio of 20% or more in a no-recrystallization temperature range, which is equal to or higher than the Ar₃ transformation point and 930°

C. or lower, and after the finishing rolling has been performed, by performing a cooling process including cooling the hot-rolled steel sheet to a cooling stop temperature of 650°

C. or lower at an average cooling rate of 10°

C./s or more and 100°

C./s or less in terms of the temperature of the central portion in the thickness direction and coiling the cooled steel sheet into a coil shape.