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CN-121992178-A - Preparation method of corrosion-resistant L555-level submarine pipeline steel

CN121992178ACN 121992178 ACN121992178 ACN 121992178ACN-121992178-A

Abstract

The invention discloses a preparation method of corrosion-resistant L555-level submarine pipeline steel, belongs to the technical field of submarine pipeline steel manufacturing, and aims to solve the problem that the strength, toughness and corrosion resistance of pipeline steel are difficult to cooperatively improve due to the fact that the existing preparation method of the L555-level submarine pipeline steel is insufficient in tissue regulation and control capability. The invention provides a preparation method of corrosion-resistant L555-level submarine pipeline steel, which comprises the following steps of step 1, smelting and continuous casting, step 2, controlling a rolling process, heating a continuous casting billet to 1180 ℃ plus or minus 10 ℃ and preserving heat for 30-60min, step 3, performing a three-stage temperature-controlled cooling process, sequentially performing a first-stage rapid cooling, a second-stage medium-speed cooling, an isothermal maintaining stage and a third-stage air cooling treatment on a rolled plate blank, step 4, performing online self-tempering treatment on the submarine pipeline steel after rolling, and performing 450-480 ℃ multiplied by 3-8min online tempering treatment on a steel plate after cooling. The invention can obviously improve the corrosion resistance of the L555-level submarine pipeline steel.

Inventors

  • JIA SHUJUN
  • ZHANG ZHIHUI
  • LIU QINGYOU
  • MAO CHUNLIANG
  • ZHANG HESONG
  • Suo Donghua

Assignees

  • 钢铁研究总院有限公司

Dates

Publication Date
20260508
Application Date
20260302

Claims (10)

  1. 1. The preparation method of the corrosion-resistant L555-level submarine pipeline steel is characterized by comprising the following steps of: Step 1, smelting and continuous casting processes; smelting according to the design components of the L555-level submarine pipeline steel, and adopting converter smelting, LF refining, RH vacuum degassing technology and continuous casting; step2, controlling a rolling process; firstly heating the continuous casting blank to 1180+/-10 ℃ and preserving heat for 30-60min; Step 3, a three-stage temperature control cooling process; the rolled slab is subjected to first-stage rapid cooling, second-stage medium-speed cooling-isothermal holding and third-stage air cooling in sequence; the first stage of rapid cooling, namely cooling the rolled slab to 480-520 ℃ at a cooling rate of 20-35 ℃ per second; step 4, performing on-line self-tempering treatment on the rolled submarine pipeline steel; the online self-tempering treatment process is that the steel plate is subjected to online tempering treatment for 450-480 ℃ multiplied by 3-8min after being cooled.
  2. 2. The method for producing a corrosion resistant type L555 grade subsea pipeline steel according to claim 1, wherein in step 3, the second stage moderate speed cooling-isothermal holding stage comprises a moderate speed cooling stage and an isothermal holding stage; and the medium-speed cooling stage is used for cooling the steel plate from 480-520 ℃ to 400-450 ℃ after the rapid cooling of the first stage at a cooling rate of 8-12 ℃ per second.
  3. 3. The method for producing a corrosion resistant type L555 grade subsea pipeline steel according to claim 2, wherein in step 3, the isothermal holding stage is an isothermal holding stage for 5-10min after the steel sheet reaches 400-450 ℃, followed by slow cooling to 320-380 ℃ at a cooling rate of 1-3 ℃ per second.
  4. 4. A method for producing corrosion resistant grade L555 subsea pipeline steel according to claim 3, characterized in that in said step 3, the third stage of air cooling comprises naturally cooling the steel sheet from 320-380 ℃ to room temperature.
  5. 5. The method for producing a corrosion resistant grade L555 subsea pipeline steel according to claim 1, wherein [ O ] is not more than 0.003% and the inclusion grade is not more than 1.0 during the smelting and continuous casting in said step 1.
  6. 6. The method for producing a corrosion resistant grade L555 subsea pipeline steel according to claim 1, wherein in step 1, the thickness of the continuous casting billet is 200-220mm, and the center segregation is controlled within grade C1.0.
  7. 7. The method for producing a corrosion resistant type grade L555 subsea pipeline steel according to claim 6, wherein in step 1, the initial temperature is 1450-1600 ℃ during the converter smelting stage, and then converting is performed for 20-45 min, and tapping is performed after converting, and tapping temperature is 1650-1710 ℃.
  8. 8. The method for producing a corrosion resistant grade L555 subsea pipeline steel according to claim 7, wherein in step 1, the molten steel temperature is 1600-1650 ℃ and refining time is 15-40 min in the LF refining stage.
  9. 9. The method for producing a corrosion resistant type L555-grade subsea pipeline steel according to claim 8, wherein in step 4, the steel sheet is subjected to an on-line tempering treatment at 450-480 ℃ x 3-8min after cooling.
  10. 10. A corrosion-resistant type L555-grade subsea pipeline steel, characterized by being prepared by the preparation method of the corrosion-resistant type L555-grade subsea pipeline steel according to any one of claims 1 to 9; The corrosion-resistant L555-level submarine pipeline steel comprises the following components in percentage by mass ：C：0.03-0.07%、Mn：1.60-2.20%,Ni：0.10-0.80%,Cu：0.10-0.45%,Cr：0-0.30%,Nb：0-0.06%,Ti 0-0.02%,P≤0.008%,S≤0.002%,N≤0.004%, of Fe and unavoidable impurities.

Description

Preparation method of corrosion-resistant L555-level submarine pipeline steel Technical Field The invention belongs to the technical field of submarine pipeline steel manufacturing, and particularly relates to a preparation method of corrosion-resistant L555-level submarine pipeline steel. Background The submarine pipeline is used as a key infrastructure for the development and transportation of ocean oil and gas resources, and is used in a severe ocean environment with high salt, high humidity and high pressure and rich in corrosive media such as Cl -、H2S、CO2, and the safety and reliability of the submarine pipeline are directly related to the stable operation of the whole oil and gas exploitation system and the protection of the ocean ecological environment. At present, the traditional L555-grade pipeline steel preparation method still has a certain limitation in the aspect of tissue regulation. The conventional preparation method of L555-level pipeline steel is insufficient in control of rolling process parameters, insufficient in refining degree of austenite grains in the conventional rolling process and poor in matching degree of cooling speed and phase change process, so that coarse pearlite or netlike carbide is easy to appear in a steel structure, the low-temperature toughness of materials is influenced, the risk of brittle fracture possibly exists under the deep sea low-temperature condition, in addition, the conventional preparation method is lack of targeted corrosion resistance strengthening treatment, the conventional process is insufficient in promotion of formation and stability of passivation films on the steel surface, and corrosion of chloride ions in a submarine environment cannot be effectively resisted, so that local corrosion phenomena such as pitting corrosion and crevice corrosion are frequent. Disclosure of Invention In view of the above analysis, the embodiment of the invention aims to provide a preparation method of corrosion-resistant L555-stage submarine pipeline steel, and solves the problem that the strength, toughness and corrosion resistance of the pipeline steel are difficult to cooperatively improve due to insufficient tissue regulation capability in the existing preparation method of the L555-stage pipeline steel. The aim of the invention is mainly realized by the following technical scheme: the invention provides a preparation method of corrosion-resistant L555-level submarine pipeline steel, which comprises the following steps: Step 1, smelting and continuous casting processes; Smelting according to the design components of the L555-level submarine pipeline steel, and adopting converter smelting, LF refining, RH vacuum degassing technology and continuous casting; step2, controlling a rolling process; firstly heating the continuous casting blank to 1180+/-10 ℃ and preserving heat for 30-60min; Step 3, a three-stage temperature control cooling process; the rolled slab is subjected to first-stage rapid cooling, second-stage medium-speed cooling-isothermal holding and third-stage air cooling in sequence; The first stage of rapid cooling, namely cooling the rolled plate blank to 480-520 ℃ at a cooling rate of 20-35 ℃ per second; step 4, performing on-line self-tempering treatment on the rolled submarine pipeline steel; the online self-tempering treatment process is that the steel plate is subjected to online tempering treatment for 450-480 ℃ multiplied by 3-8min after being cooled. Further, in step 3, the second stage moderate cooling-isothermal holding stage includes a moderate cooling stage and an isothermal holding stage; And a medium-speed cooling stage, namely cooling the steel plate from 480-520 ℃ to 400-450 ℃ after the rapid cooling of the first stage at a cooling rate of 8-12 ℃ per second. Further, in step 3, the isothermal holding stage is to isothermal hold for 5-10min after the steel sheet reaches 400-450 ℃, and then slowly cool to 320-380 ℃ at a cooling rate of 1-3 ℃ per second. Further, in the step 3, the third stage of air cooling is to naturally cool the steel plate from 320-380 ℃ to room temperature. Further, in the step 1, during smelting and continuous casting, the [ O ] is controlled to be less than or equal to 0.003 percent, and the inclusion grade is controlled to be less than or equal to 1.0 grade. Further, in step 1, the thickness of the continuous casting billet is 200-220mm, and center segregation is controlled within class C1.0. Further, in the step 1, in the converter smelting stage, the initial temperature is 1450-1600 ℃, then the blowing is carried out, the blowing time is 20-45 min, the tapping is carried out after the blowing, and the tapping temperature is 1650-1710 ℃. Further, in step 1, in the LF refining stage, the molten steel temperature is 1600-1650 ℃ and the refining time is 15-40 min. Further, in step 4, the steel sheet is subjected to an on-line tempering treatment at 450-480 ℃ for 3-8min after cooling. The invention also provides cor