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CN-121992303-A - Nb-V-B anti-fatigue L555-level submarine pipeline steel and preparation method thereof

CN121992303ACN 121992303 ACN121992303 ACN 121992303ACN-121992303-A

Abstract

The invention discloses Nb-V-B anti-fatigue L555-grade submarine pipeline steel and a preparation method thereof, belongs to the technical field of submarine pipeline steel, and aims to solve the problems that the existing L555-grade submarine pipeline steel still has defects in the aspect of crack resistance caused by poor fatigue fracture resistance and tissue uniformity under cyclic load, and cannot meet the service requirement of deep sea dynamic load. The Nb-V-B anti-fatigue L555-level submarine pipeline steel provided by the invention comprises the following components in percentage by weight ：C：0.045-0.055%,Mn：1.60-1.75%,Si：0.20-0.30%,Nb：0.060-0.080%,V：0.070-0.090%,B：0.0010-0.0015%,Cr：0.05-0.10%,Ni≤0.05%,P≤0.008%,S≤0.002%,N≤0.004%, of Fe and unavoidable impurities. The submarine pipeline steel provided by the invention can meet the severe service requirements of deep sea dynamic loads.

Inventors

  • JIA SHUJUN
  • ZHANG ZHIHUI
  • LIU QINGYOU
  • LI BA
  • WANG BING
  • CHEN XIAOPING

Assignees

  • 钢铁研究总院有限公司

Dates

Publication Date
20260508
Application Date
20260302

Claims (10)

  1. 1. A Nb-V-B anti-fatigue L555-grade submarine pipeline steel is characterized by comprising the following components in percentage by weight of ：C：0.045-0.055%,Mn：1.60-1.75%,Si：0.20-0.30%,Nb：0.060-0.080%,V：0.070-0.090%,B：0.0010-0.0015%,Cr：0.05-0.10%,Ni≤0.05%,P≤0.008%,S≤0.002%,N≤0.004%, and the balance of Fe and unavoidable impurities.
  2. 2. The Nb-V-B fatigue resistant L555 grade subsea pipeline steel according to claim 1, wherein the composition comprises ：C：0.047-0.050%,Mn：1.65-1.70%,Si：0.22-0.25%,Nb：0.065-0.080%,V：0.075-0.090%,B：0.0010-0.0015%,Cr：0.06-0.08%,Ni≤0.05%,P≤0.008%,S≤0.002%,N≤0.004%, balance Fe and unavoidable impurities in weight percent.
  3. 3. A method for preparing Nb-V-B fatigue resistant L555-grade subsea pipeline steel, characterized by being used for preparing Nb-V-B fatigue resistant L555-grade subsea pipeline steel according to claim 1 or 2, the method comprising the steps of: s1, smelting and continuous casting; Smelting and continuous casting are carried out by adopting a converter smelting, LF refining and RH vacuum degassing process; S2, controlling rolling; Heating the slab to 1160-1180 ℃ with a heat preservation time of 30-60 min, then sequentially performing rough rolling, medium rolling and finish rolling, wherein the whole rolling process adopts multi-pass deformation, the single-pass rolling reduction is 10-15%, and the accumulated rolling reduction is more than 80%; s3, accelerating cooling control; the cooling rate is set to 15-25 ℃ per second; s4, online self-tempering; the steel plate is subjected to on-line self-tempering treatment after being subjected to accelerated controlled cooling, the self-tempering temperature is 420-480 ℃, and the tempering time is 3-10min.
  4. 4. A method for producing Nb-V-B fatigue resistant L555-grade subsea pipeline steel according to claim 3 wherein in step S1 the converter smelting temperature is 1600-1650 ℃.
  5. 5. The method for producing a Nb-V-B fatigue resistant L555-grade subsea pipeline steel according to claim 4, wherein in the step S1, the LF refining temperature is 1450-1550 ℃.
  6. 6. The method for producing a steel for a subsea pipeline at level L555 with fatigue resistance as claimed in claim 5, wherein in said step S1, [ O ] < 0.003% is controlled during the smelting and continuous casting, the thickness of the ingot is controlled to 180-220 mm, and the center segregation is controlled to within level C1.0.
  7. 7. A method for producing Nb-V-B fatigue resistant L555 grade subsea pipeline steel according to claim 3 wherein in said step S2 the finishing temperature of the rough rolling zone is 1000-1060 ℃.
  8. 8. The method for producing a Nb-V-B fatigue resistant L555 grade subsea pipeline steel according to claim 7, wherein in the step S2, the finishing temperature of the mid-rolling zone is 860 to 920 ℃.
  9. 9. The method for producing a Nb-V-B fatigue resistant L555-grade subsea pipeline steel according to claim 8, wherein in the step S2, the finish rolling temperature in the finish rolling zone is 740 to 820 ℃.
  10. 10. Process for the preparation of Nb-V-B fatigue resistant L555 grade subsea pipeline steel according to any of claims 3 to 9, characterized in that in step S3 the final cooling temperature is controlled between 350-420 ℃.

Description

Nb-V-B anti-fatigue L555-level submarine pipeline steel and preparation method thereof Technical Field The invention belongs to the technical field of submarine pipeline steel, and particularly relates to Nb-V-B anti-fatigue L555-level submarine pipeline steel and a preparation method thereof. Background With the development of global oil gas entering into a deep sea ultra-deep water stage (water depth is more than 1500 m), a marine riser and a riser are used as key bearing components of a drilling and production system and are used in a complex marine environment for a long time, and the effects of internal and external pressure difference, tensile-compressive alternating stress, ocean current induced vibration (VIV), low-temperature impact and the like are required to be borne. The existing L555-level pipeline steel still has defects in the aspects of fatigue fracture resistance and stress corrosion crack resistance under cyclic load, and cannot meet the service requirements of deep sea dynamic load. Disclosure of Invention In view of the above analysis, the embodiment of the invention aims to provide the Nb-V-B anti-fatigue L555-grade submarine pipeline steel and the preparation method thereof, which are used for solving the problems that the existing L555-grade submarine pipeline steel still has defects in the aspects of fatigue fracture performance and stress corrosion crack resistance under cyclic load and cannot meet the service requirement of deep sea dynamic load. The aim of the invention is mainly realized by the following technical scheme: On the one hand, the invention provides Nb-V-B anti-fatigue L555-grade submarine pipeline steel, which comprises ：C：0.045-0.055%,Mn：1.60-1.75%,Si：0.20-0.30%,Nb：0.060-0.080%,V：0.070-0.090%,B：0.0010-0.0015%,Cr：0.05-0.10%,Ni≤0.05%,P≤0.008%,S≤0.002%,N≤0.004%, of Fe and unavoidable impurities in percentage by weight. In one possible design, the composition comprises ：C：0.047-0.050%,Mn：1.65-1.70%,Si：0.22-0.25%,Nb：0.065-0.080%,V：0.075-0.090%,B：0.0010-0.0015%,Cr：0.06-0.08%,Ni≤0.05%,P≤0.008%,S≤0.002%,N≤0.004%, parts by weight of Fe and unavoidable impurities. On the other hand, the invention also provides a preparation method of the Nb-V-B anti-fatigue L555-level submarine pipeline steel, which is used for the Nb-V-B anti-fatigue L555-level submarine pipeline steel, and comprises the following steps: s1, smelting and continuous casting; Smelting and continuous casting are carried out by adopting a converter smelting, LF refining and RH vacuum degassing process; S2, controlling rolling; Heating the slab to 1160-1180 ℃ with a heat preservation time of 30-60 min, then sequentially performing rough rolling, medium rolling and finish rolling, wherein the whole rolling process adopts multi-pass deformation, the single-pass rolling reduction is 10-15%, and the accumulated rolling reduction is more than 80%; s3, accelerating cooling control; the cooling rate is set to 15-25 ℃ per second; s4, online self-tempering; the steel plate is subjected to on-line self-tempering treatment after being subjected to accelerated controlled cooling, the self-tempering temperature is 420-480 ℃, and the tempering time is 3-10min. Further, in step S1, the temperature during converter smelting is 1600-1650 ℃. Further, in step S1, the furnace temperature at the time of LF refining is 1450-1550 ℃. Further, in the step S1, during smelting and continuous casting, the [ O ] is controlled to be less than or equal to 0.003 percent, the thickness of the continuous casting billet is controlled to be 180-220 mm, and the center segregation is controlled to be within class C1.0. Further, in step S2, the finishing temperature of the rough rolling zone is 1000 to 1060 ℃. Further, in step S2, the finishing temperature of the intermediate rolling zone is 860-920 ℃. Further, in step S2, the finish rolling temperature of the finish rolling zone is 740 to 820 ℃. Further, in step S3, the final cooling temperature is controlled to 350-420 ℃. Compared with the prior art, the invention has at least one of the following beneficial effects: (1) The traditional L555-level pipeline steel microalloy is single in design (mainly comprising Nb and Ti) and lacks of precipitation strengthening regulation and control, and the high fatigue life and the tissue uniformity of the L555-level submarine pipeline steel are realized by combining a Nb-V-B composite microalloy strengthening system and a three-stage TMCP (rough rolling, medium rolling and finish rolling) process. The yield strength of the prepared L555-level submarine pipeline steel is 560-610 MPa, the tensile strength is 630-690 MPa, the yield ratio is less than or equal to 0.90, The impact energy (transverse direction) at 40 ℃ is more than or equal to 380J,The DWTT shearing area at 30 ℃ is more than or equal to 85 percent, the fatigue crack propagation threshold delta Kth is more than or equal to 12 MPa.m 1/2, the HAZ hardness peak value is less than or equal to 260 HV, and