Production method of submarine hydrogen transmission pipeline steel

Abstract

The invention relates to a production method of seabed hydrogen transmission pipeline steel. The steel comprises the following chemical components in percentage by mass: 0.02%-0.03% of C, 0.10%-0.30% of Si, 1.6%-1.8% of Mn, less than or equal to 0.008% of P, less than or equal to 0.0015% of S, 0.020%-0.050% of Alt, 0.15%-0.25% of Cr, 0.10%-0.15% of Mo, 0.20%-0.30% of Cu, 0.30%-0.50% of Ni, 0.08%-0.15% of Nb + Ti + V, 0.003%-0.006% of N, 0.51% of 1.5 Cr + Mo + 20N, more than or equal to 0.6% and less than or equal to 0.8% of Nb / (Ti + V), and the balance of Fe and inevitable impurities. The key process steps comprise steelmaking, heating, rolling and cooling. According to the invention, the component design of Cr, Mo, N, Nb, Ti and V is combined with a reasonable rolling and cooling process to form a nano-scale (Cr, Mo) (C, N) and (Nb, Ti, V) (C, N) composite precipitated phase, so that the hydrogen trap density reaches 1.5 * 10 < 20 > / cm < 3 >, and the hydrogen trap density is uniformly distributed; and a continuous passivation film is formed in a matrix through Cu, Ni and Cr, and the corrosion resistance is synergistically improved with Nb-Ti-V microalloying.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material manufacturing, and relates to a high-strength and high hydrogen embrittlement resistant pipeline steel suitable for subsea high-pressure hydrogen transmission environment and its production method. Background Art

[0002] To address global climate change, countries around the world are actively promoting the phasing out of fossil fuels; hydrogen energy, as a clean energy with zero carbon emissions, has become a key alternative energy source, especially playing an important role in the industrial, transportation, and power sectors. Given the intermittent nature of wind and solar power generation, effective energy storage technologies are needed to balance supply and demand, and green hydrogen produced by electrolyzing water can be used as an effective cross-regional and cross-seasonal energy storage medium.

[0003] With the rapid global development of the hydrogen energy industry, subsea hydrogen transmission pipelines, as key infrastructure connecting hydrogen energy supplies in different regions, have attracted much attention. However, in a high-pressure hydrogen environment, traditional pipeline steels are prone to hydrogen embrittlement, which significantly reduces the ductility and strength of the materials. In addition, complex factors such as high salinity, high pressure, low temperature, and microbial corrosion in the subsea environment pose more stringent requirements on the corrosion resistance and welding performance of pipeline steels. Summary of the Invention

[0004] The present invention aims to provide a production method for subsea hydrogen transmission pipeline steel to solve the key technologies of steel plates for hydrogen transmission pipelines. The produced steel plates not only have the high strength of conventional pipeline steels but also have good low-temperature performance, low hydrogen diffusivity, and high corrosion resistance: the impact at -60°C ≥ 100 J; the relative cross-sectional shrinkage rate Z of the pipe at a high hydrogen partial pressure of 6.3 MPa H2 / Z Ref ≥ 0.80, the fracture toughness K ⅠC ≥ 70 MPa m 1 / 2 , and the seawater corrosion resistance is more than 1.35 times that of ordinary pipeline steels of the same grade.

[0005] The technical solution of the present invention: A production method of submarine hydrogen transmission pipeline steel, the mass percentage of the chemical components of the steel is C = 0.02% - 0.03%, Si = 0.10% - 0.30%, Mn = 1.6 - 1.8%, P ≤ 0.008%, S ≤ 0.0015%, Alt = 0.020% - 0.050%, Cr = 0.15% - 0.25%, Mo = 0.10% - 0.15%, Cu = 0.20% - 0.30%, Ni = 0.30% - 0.50%, Nb + Ti + V = 0.08% - 0.15%, N = 0.003% - 0.006%, 1.5Cr + Mo + 20N = 0.51%, 0.6 ≤ Nb / (Ti + V) ≤ 0.8, and the balance is Fe and unavoidable impurities; the main process steps include: (1) Steelmaking: The C content of the molten steel tapped from the converter is ≤ 0.04%, the O content is ≥ 0.05%, the tapping temperature is ≥ 1630 °C, and no deoxidizing alloy is added during the tapping process; the molten steel enters the RH for treatment, and the circulation time is 15 - 18 minutes, of which the holding time under a vacuum degree below 67 Pa is ≥ 10 minutes; after the molten steel is treated by RH, it enters the LF for heating, slag formation, deoxidation and alloying treatment; the molten steel with qualified chemical components is cast into qualified billets through the protective casting technology; (2) Heating: The heating temperature is 1150 - 1200 °C, and the heating time is 280 - 320 min; (3) Rolling: The rolling temperature in the first stage is 1050 - 1150 °C, and the cumulative reduction ratio is ≥ 60%; the rolling temperature in the second stage is 880 - 910 °C, and the cumulative reduction ratio is ≥ 40%; (4) Cooling: Relax for 30 - 60 s after the second stage of rolling, start cooling at a temperature of 750 - 830 °C, the cooling rate before 540 °C is 18 - 21 °C / s, the cooling rate from 540 °C to 300 °C is 8 - 10 °C / s, and the final cooling temperature is 300 °C.

[0006] The beneficial effects of the present invention: 1) For the first time, the hydrogen trap design is unified with the demand for seawater corrosion resistance. Through the composition design of Cr(0.15% - 0.25%) + Mo(0.10% - 0.15%) + N(0.003% - 0.006%) and Nb + Ti + V = 0.08% - 0.15%, nano-scale (Cr,Mo)(C,N) and (Nb,Ti,V)(C,N) composite precipitation phases are formed, and the ratio relationship of 1.5Cr + Mo + 20N = 0.51% and 0.6 ≤ Nb / (Ti + V) ≤ 0.8 is precisely controlled, so that the hydrogen trap density reaches 1.5x10 20 / cm 3 ; while that of the conventional pipeline steel is about 8x10 19 / cm 3By forming a continuous passivation film in the matrix with Cu (0.20% - 0.30%) + Ni (0.30% - 0.50%) + Cr, the corrosion resistance is synergistically improved in combination with Nb - Ti - V microalloying. 2) Ultra - low interstitial atom control: C < 0.03% and N ≤ 0.006% reduce the lattice distortion energy to 12 kJ / mol (about 18 kJ / mol for ordinary X70 pipeline steel). 3) Relax for 30 - 60 s after two - stage rolling to promote dislocation recombination, and then perform two - stage cooling. The cooling rate is 18 - 21 °C / s before 540 °C and 8 - 10 °C / s from 540 - 300 °C, forming a microstructure of 75% - 85% acicular ferrite + 15% - 25% granular bainite. The produced hydrogen - transporting pipeline steel not only meets the mechanical properties of conventional pipelines, with an impact value of ≥ 100 J at - 60 °C, and the relative cross - sectional shrinkage rate Z H2 / Z Ref ≥ 0.80, and the fracture toughness K ⅠC ≥ 70 MPa m 1 / 2 , and the seawater corrosion resistance is more than 1.35 times that of ordinary pipeline steel of the same grade. Detailed implementation mode

[0007] The content of the present invention will be further described below in conjunction with embodiments.

[0008] Example 1: Production of 12.9 mm submarine hydrogen - transporting pipeline steel The mass percentage content of the chemical composition of the steel is C = 0.02%, Si = 0.25%, Mn = 1.65%, P = 0.008%, S = 0.0013%, Alt = 0.025%, Cr = 0.17%, Mo = 0.15%, Cu = 0.23%, Ni = 0.35%, Nb + Ti + V = 0.085%, N = 0.0052%, and the balance is Fe and unavoidable impurities; the technological steps are as follows: (1) Steelmaking: The C content in the converter - tapped steel is 0.04%, the O content is 0.055%, the tapping temperature is 1640 °C, no deoxidizing alloy is added during tapping, the molten steel enters RH for treatment, the circulation time is 17 minutes, and the holding time under a vacuum of less than 67 Pa is 13 minutes; after RH treatment of the molten steel, it enters LF for temperature - raising, slag - forming, deoxidizing and alloying treatment; the molten steel with qualified chemical composition is cast into qualified billets through protective casting technology.

[0009] (2) Heating: The heating temperature is 1150 - 1200 °C, and the heating time is 310 min; (3) Rolling: The temperature of the first - stage rolling is 1060 - 1130 °C, the cumulative reduction ratio is 65%, the temperature of the second - stage rolling is 885 - 910 °C, and the cumulative reduction ratio is 50%; (4) Cooling: After two-stage rolling, relax for 32 s. The starting cooling temperature is 780 °C, the cooling rate is 18 - 21 °C / s before 540 °C, the cooling rate is 8 - 10 °C / s between 540 - 300 °C, and the final cooling temperature is 300 °C.

[0010] Comparative Example 1: Production of 12.9 mm ordinary pipeline steel The mass percentage content of the chemical composition of the steel is: C = 0.05%, Si = 0.32%, Mn = 1.55%, P = 0.010%, S = 0.002%, Alt = 0.052%, Nb = 0.035%, Ti = 0.015%, Cr = 0.27%, and the balance is Fe and unavoidable impurities; the process steps are as follows: (1) Steelmaking: The tapping C of the converter is 0.045%, O is 0.049%, the tapping temperature is 1610 °C, 150 kg of Al-Fe is added during tapping for deoxidation, and it is subjected to LF heating, slag-making, deoxidation, and alloying treatment; then it enters RH for treatment, with a cycle time of 14 minutes, and the holding time under a vacuum of 67 Pa or less is 9 minutes; the molten steel with qualified chemical composition is cast into qualified billets through the protective casting technology.

[0011] (2) Heating: The heating temperature is 1210 - 1230 °C, and the heating time is 270 min; (3) Rolling: The rolling temperature in the first stage is 960 - 1040 °C, the cumulative reduction rate is 55%, the rolling temperature in the second stage is 840 - 870 °C, and the cumulative reduction rate is 60%; (4) Cooling: After two-stage rolling, cool in water. The starting cooling temperature is 835 - 860 °C, the cooling rate is 12 °C / s, and the final cooling temperature is 520 °C.

[0012] Example 2: Production of 17.7 mm submarine hydrogen transmission pipeline steel The mass percentage content of the chemical composition of the steel is: C = 0.03%, Si = 0.20%, Mn = 1.78%, P = 0.006%, S = 0.0011%, Alt = 0.033%, Cr = 0.20%, Mo = 0.12%, Cu = 0.28%, Ni = 0.45%, Nb + Ti + V = 0.085%, N = 0.0045%, and the balance is Fe and unavoidable impurities. The properties of the steel are shown in Table 1, and the process steps are as follows: (1) Steelmaking: The tapping C of the converter is 0.035%, O is 0.057%, the tapping temperature is 1635 °C, no deoxidation alloy is added during tapping, the molten steel enters RH for treatment, with a cycle time of 16 minutes, and the holding time under a vacuum of 67 Pa or less is 12 minutes; after the molten steel is treated by RH, it enters LF for heating, slag-making, deoxidation, and alloying treatment; the molten steel with qualified chemical composition is cast into qualified billets through the protective casting technology.

[0013] (2) Heating: Heating temperature is 1150 - 1200 °C, heating time is 300 min; (3) Rolling: The rolling temperature in the first stage is 1065 - 1135 °C, the cumulative reduction ratio is 67%, the rolling temperature in the second stage is 882 - 905 °C, and the cumulative reduction ratio is 48%; (4) Cooling: Relax for 35 s after the second-stage rolling, start cooling at 810 °C, the cooling rate before 540 °C is 18 - 21 °C / s, the cooling rate from 540 - 300 °C is 8 - 10 °C / s, and the final cooling temperature is 300 °C.

[0014] Comparative Example 2: Production of 17.7 mm ordinary pipeline steel The mass percentage content of the chemical composition of the steel is C = 0.06%, Si = 0.33%, Mn = 1.53%, P = 0.011%, S = 0.0021%, Alt = 0.055%, Nb = 0.036%, Ti = 0.017%, Cr = 0.28%, and the balance is Fe and unavoidable impurities; the process steps are as follows: (1) Steelmaking: The converter tapping C = 0.05%, O = 0.045%, the tapping temperature is 1615 °C, 150 kg of Al - Fe is added during tapping for deoxidation, and it undergoes LF heating, slag - making, deoxidation, and alloying treatment; then enter RH for treatment, the circulation time is 13 minutes, and the holding time under a vacuum of less than 67 Pa is 9 minutes; the molten steel with qualified chemical composition is cast into qualified billets through protective casting technology.

[0015] (2) Heating: Heating temperature is 1205 - 1230 °C, heating time is 275 min; (3) Rolling: The rolling temperature in the first stage is 965 - 1042 °C, the cumulative reduction ratio is 53%, the rolling temperature in the second stage is 845 - 875 °C, and the cumulative reduction ratio is 55%; (4) Cooling: Cool in water after the second-stage rolling, start cooling at 836 - 865 °C, the cooling rate is 11.8 °C / s, and the final cooling temperature is 510 °C.

[0016] The performance test results of the X65MH steel produced in the examples and the ordinary X65M steel produced in the comparative examples are shown in Table 1.

[0017] Table 1 Performance test results of the X65MH steel produced in the examples and the ordinary X65M steel produced in the comparative examples 。

Claims

1. A production method of submarine hydrogen pipeline steel, characterized in that: The mass percentage of the chemical composition of the steel is C = 0.02% - 0.03%, Si = 0.10% - 0.30%, Mn = 1.6 - 1.8%, P ≤ 0.008%, S ≤ 0.0015%, Alt = 0.020% - 0.050%, Cr = 0.15% - 0.25%, Mo = 0.10% - 0.15%, Cu = 0.20% - 0.30%, Ni = 0.30% - 0.50%, Nb + Ti + V = 0.08% - 0.15%, N = 0.003% - 0.006%, 1.5Cr + Mo + 20N = 0.51%, 0.6 ≤ Nb / (Ti + V) ≤ 0.8, and the balance is Fe and inevitable impurities; The key process steps include: (1) Steelmaking: The C content of the molten steel tapped from the converter is ≤ 0.04%, the O content is ≥ 0.05%, the tapping temperature is ≥ 1630°C, and no deoxidizing alloy is added during tapping; the molten steel enters the RH for treatment, and the circulation time is 15 - 18 minutes, and the holding time under a vacuum of less than 67 Pa is ≥ 10 minutes; after the molten steel is treated in the RH, it enters the LF for heating, slag formation, deoxidation and alloying treatment; the molten steel with qualified chemical composition is cast into qualified billets through the protective casting technology; (2) Heating: The heating temperature is 1150 - 1200°C, and the heating time is 280 - 320 min; (3) Rolling: The rolling temperature in the first stage is 1050 - 1150°C, and the cumulative reduction ratio is ≥ 60%; the rolling temperature in the second stage is 880 - 910°C, and the cumulative reduction ratio is ≥ 40%; (4) Cooling: After relaxation for 30 - 60 s after the second-stage rolling, the starting cooling temperature is 750 - 830°C, the cooling rate before 540°C is 18 - 21°C / s, the cooling rate from 540 - 300°C is 8 - 10°C / s, and the final cooling temperature is 300°C.

2. The production method of a submarine hydrogen pipeline steel according to claim 1, characterized in that The mechanical properties of the produced hydrogen transmission pipeline steel are as follows: impact at -60°C ≥ 100 J, relative reduction of area Z H2 / Z Ref ≥ 0.80, fracture toughness K ⅠC ≥ 70 MPa m 1 / 2 .