A L360M grade electric resistance welded pipe suitable for hydrogen service and method of manufacture

Abstract

The present application relates to the technical field of oil and gas pipe, and particularly relates to a L360M steel grade resistance welded pipe suitable for hydrogen transmission and a processing method. The L360M steel grade resistance welded pipe suitable for hydrogen transmission has the following chemical element components in percentage by weight: C: 0.02-0.05%, Si: 0.10-0.30%, Mn: 0.6-1.0%, S: less than or equal to 0.002%, P: less than or equal to 0.010%, Ni: 0.01-0.3%, Cr: 0.01-0.3%, Cu: 0.001-0.05%, Nb: 0.01-0.05%, V: 0.02-0.05%, Ti: less than or equal to 0.02%, Mo: less than or equal to 0.01%, Al: less than or equal to 0.04%, B: less than or equal to 0.0003%, and the balance is Fe and inevitable impurities. The present application optimizes the chemical element component design of the resistance welded pipe, and combines the forming, high-frequency welding and heat treatment processes of the resistance welded pipe, so that the resistance welded pipe has the characteristics of small and uniform grain size, low segregation, high dimensional precision, excellent toughness and easy on-site girth welding of the pipe.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline technology, and in particular to an L360M grade steel resistance welded pipe suitable for hydrogen transportation and its processing method. Background Technology

[0002] Pipeline hydrogen transport is the safest and most efficient mode of transportation, and has become the preferred method for long-distance hydrogen delivery globally. Due to the unique physical and chemical properties of hydrogen, compared to natural gas, hydrogen can cause some damage to pipeline materials, accelerating pipeline failure and damage. In particular, the performance of the pipeline material will significantly decline when there are defects in the pipe material or welds, or under fatigue load conditions.

[0003] Currently, seamless pipes are commonly used in hydrogen transportation pipelines, with steel grades below X52 and transportation pressures below 4.0 MPa. No research reports have been found on the use of ERW welded pipes for medium- and high-pressure pure hydrogen / hydrogen-blended pipeline transportation. Although seamless pipes are widely used in hydrogen pipeline transportation, some problems still exist due to their inherent technological characteristics. First, seamless pipes are formed by heating and piercing steel billets, resulting in large fluctuations in wall thickness and low dimensional accuracy, with wall thickness tolerances ranging from -5% to +10%t. Second, the carbon equivalent of the billet is relatively high, making the billet surface prone to defects such as rolling cracks during the piercing process. Furthermore, weld cracks are easily generated during on-site circumferential welding of the pipeline, making it difficult to guarantee the quality of the circumferential weld joint. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide an L360M grade steel resistance welded pipe suitable for hydrogen transportation and its processing method. By optimizing the chemical element composition of the resistance welded pipe and combining it with processes such as forming, high-frequency welding, and heat treatment, the resistance welded pipe of this invention has the characteristics of fine and uniform grains, low segregation, high dimensional accuracy, excellent toughness, and ease of on-site circumferential welding of pipelines.

[0005] The technical solution of the present invention is: an L360M steel grade resistance welded pipe suitable for hydrogen transportation, wherein the chemical element composition of the resistance welded pipe by weight percentage is: C: 0.02~0.05%, Si: 0.10~0.30%, Mn: 0.6~1.0%, S≤0.002%, P≤0.010%, Ni: 0.01~0.3%, Cr: 0.01~0.3%, Cu: 0.001~0.05%, Nb: 0.01~0.05%, V: 0.02~0.05%, Ti≤0.02%, Mo≤0.01%, Al≤0.04%, B≤0.0003%, with the balance being Fe and unavoidable impurities.

[0006] The carbon equivalent (CE) of the resistance welded pipe pcm Value ≤ 0.12.

[0007] The resistance welded pipe contains Mn and Si by weight percentage greater than 3.0%.

[0008] A processing method for L360M grade steel resistance welded pipe suitable for hydrogen transportation includes the following steps: S1: Uncoiling and welding: Align the ends of the strip steel with the front and rear ends; S2: Edge milling: Precision milling the edge of the strip into an I-shape, precisely controlling the perpendicularity of the strip to 90° and the width to be controlled within the range of 1273~1274 mm; S3: Forming: Roller forming is adopted. During the forming process, the height of the side extrusion roller is adjusted to 196~200mm, the height of the outer roller is controlled at 230~235mm, and the height of the inner roller is controlled at 8.4~10mm. A small opening angle of 3~5° and a small extrusion amount of 5.5~6.5mm are used, and the sizing amount is 9mm. S4: Preheating before welding: The continuously produced tube blank is heated in a heat treatment furnace at a temperature of 350℃~400℃ for a time of not less than 20 seconds. S5: High-frequency welding: High-frequency induction resistance welding is adopted, with a welding power of 360~400KW, an induction welding frequency of 400KHZ, a welding speed of 12~16m / min, and an opening angle controlled at 3~5°. S6: Heat treatment: After welding, the weld is subjected to post-weld normalizing heat treatment at a temperature of 920~960℃. After normalizing heat treatment, it is air-cooled to below 300℃. After the weld structure no longer changes, it is sprayed with water to cool to below 70℃. The water spraying cooling rate is controlled at 2±0.5℃ / s. S7: Sizing and straightening; S8: Ultrasonic and X-ray inspection: 100% UT and X-ray inspection of the weld seam and heat-affected zone on both sides of the weld seam of the resistance welded pipe after welding; S9: Pressure test: Perform a hydrostatic pressure test on each resistance welded pipe. The test pressure shall not be lower than the minimum test pressure value required by the standard. No leakage or bursting is allowed during the entire test process. S10: Beveling at the pipe ends: The pipe ends of the resistance welded pipe are beveled according to standard requirements; S11: Finished Product Inspection: Before products are delivered to the warehouse, the appearance quality and dimensions of all resistance welded pipes are inspected according to standard requirements.

[0009] In the S1 strip metallographic structure, the levels of non-metallic inclusions of types A, B, C, D, and DS are all no greater than 1.0, the banded structure is no greater than 1.5, and the grain size is 9 or above.

[0010] In S3, after molding, the circumferential opening of the tube body is measured using the ring-cutting method, and the range is -20 to -10 mm.

[0011] In S5, the extrusion amount of the weld seam during high-frequency welding is controlled at 5.5~6.5mm.

[0012] The resistance welded pipe can be used for conveying pure hydrogen or hydrogen-doped pipes with a pressure of 6.3 MPa and below. When used in hydrogen-doped pipes, the volume ratio of hydrogen doping should not exceed 30%.

[0013] The beneficial effects of this invention are as follows: 1. The resistance welded pipe of this invention adopts an ultra-low C and ultra-low Mn, low S and P composition design, with the addition of appropriate amounts of Si and trace amounts of alloying elements such as Mo, Nb, and Cr, which inhibits the formation of banded inclusions, improves segregation, and enhances HIC resistance. At the same time, the Mn / Si ratio is controlled to be greater than 3.0, facilitating the rapid removal of oxides and inclusions. 2. The resistance welded pipe of this invention uses strip steel with A, B, C, D, and DS type non-metallic inclusions of level A, B, C, D, and DS all not exceeding level 1.0, banded structure not exceeding level 1.5, and grain size of level 9 or above. The strip steel adopts a roll forming rolling process, which can effectively reduce the size of non-metallic inclusions and banded structure, reduce the places where hydrogen atoms accumulate in the grains, and prevent the local accumulation of hydrogen atoms. 3. The resistance welded pipe of this invention can be used in pure hydrogen or hydrogen-doped environments, and can be used for pure hydrogen and hydrogen-doped pipeline transportation with pressure of 6.3 MPa and below. When used in hydrogen-doped pipelines, the hydrogen doping ratio is not greater than 30%.

[0014] The following will provide further explanation in conjunction with the accompanying drawings. Attached Figure Description

[0015] Figure 1 This is a microstructure image of the L360M Φ406.4×10.8mm resistance welded pipe in an embodiment of the present invention.

[0016] Figure 2 This is a microstructure diagram of the L360M Φ406.4×10.8mm resistance welded pipe in Comparative Example 1 of the present invention.

[0017] Figure 3 This is a microstructure diagram of the L360M Φ406.4×10.8mm resistance welded pipe in Comparative Example 2 of the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to embodiments: Example 1 An L360M grade steel resistance welded pipe suitable for hydrogen transportation, characterized in that: the chemical element composition of the resistance welded pipe by weight percentage is: C: 0.02~0.05%, Si: 0.10~0.30%, Mn: 0.6~1.0%, S≤0.002%, P≤0.010%, Ni: 0.01~0.3%, Cr: 0.01~0.3%, Cu: 0.001~0.05%, Nb: 0.01~0.05%, V: 0.02~0.05%, Ti≤0.02%, Mo≤0.01%, Al≤0.04%, B≤0.0003%, with the balance being Fe and unavoidable impurities.

[0019] The carbon equivalent (CE) of the resistance welded pipe pcm Value ≤ 0.12.

[0020] The resistance welded pipe contains Mn and Si by weight percentage greater than 3.0%.

[0021] This invention compensates for the strength loss caused by ultra-low C and ultra-low Mn, low S and P, and adds appropriate amounts of Si and trace amounts of Mo, Nb, Cr and other alloying elements. The ultra-low C content reduces core segregation and banded structure, and inhibits the formation of large carbides; the ultra-low Mn content reduces MnS formation and eliminates Mn segregation, inhibiting the formation of banded inclusions; controlling the Mn / Si ratio to be greater than 3.0 yields complete liquid deoxidation products, improving the fluidity of molten steel, and also rapidly removing oxides and inclusions generated during welding; the low S and P content effectively reduces inclusions and segregation; adding appropriate amounts of Si and trace amounts of Mo, Nb, Cr and other alloying elements can transform low-melting-point banded FeS / MnS into high-melting-point spherical structures, further refining the microstructure, improving segregation, and enhancing HIC performance.

[0022] Example 2 A processing method for L360M grade steel resistance welded pipe suitable for hydrogen transportation includes the following steps: S1: Uncoiling and welding: Align the ends of the strip steel with the front and rear ends; S2: Edge milling: Precision milling the edge of the strip into an I-shape, precisely controlling the perpendicularity of the strip to 90° and the width to be controlled within the range of 1273~1274 mm; S3: Forming: Roller forming is adopted. During the forming process, the height of the side extrusion roller is adjusted to 196~200mm, the height of the outer roller is controlled at 230~235mm, and the height of the inner roller is controlled at 8.4~10mm. A small opening angle of 3~5° and a small extrusion amount of 5.5~6.5mm are used to make a small over-bending of the outermost edge of the strip steel, so that the edge is fully formed and the sizing amount is 9mm. S4: Preheating before welding: The continuously produced tube blank is heated in a heat treatment furnace at a temperature of 350℃~400℃ for a time of not less than 20 seconds. This removes residual impurities such as hydrogen and oxygen from the tube blank, controls the intake of hydrogen and oxygen during subsequent welding, reduces the hydrogen content in the tube body and weld, and improves weld quality. S5: High-frequency welding: High-frequency induction resistance welding is adopted, with a welding power of 360~400KW, an induction welding frequency of 400KHZ, a welding speed of 12~16m / min, and an opening angle controlled at 3~5°. S6: Heat treatment: After welding, the weld is subjected to post-weld normalizing heat treatment at a temperature of 920~960℃. The normalizing heat treatment temperature should be matched with the welding speed to ensure that the weld microstructure is completely austenitized. After normalizing heat treatment, the weld is air-cooled to below 300℃. After the weld microstructure no longer undergoes transformation, it is water-cooled to below 70℃. The water-cooling rate is controlled at 2±0.5℃ / s. The weld microstructure after heat treatment is a multiphase structure with polygonal ferrite as the main component and a small amount of pearlite as the auxiliary component. This makes the weld microstructure relatively consistent with the base metal microstructure, thereby refining the weld microstructure and improving the resistance to HIC. S7: Sizing and straightening; S8: Ultrasonic and X-ray inspection: 100% UT and X-ray inspection of the weld seam and heat-affected zone on both sides of the weld seam of the resistance welded pipe after welding; S9: Pressure test: Perform a hydrostatic pressure test on each resistance welded pipe. The test pressure shall not be lower than the minimum test pressure value required by the standard. No leakage or bursting is allowed during the entire test process. S10: Beveling at the pipe ends: The pipe ends of the resistance welded pipe are beveled according to standard requirements; S11: Finished Product Inspection: Before products are delivered to the warehouse, the appearance quality and dimensions of all resistance welded pipes are inspected according to standard requirements.

[0023] In the S1 strip metallographic structure, the levels of non-metallic inclusions of types A, B, C, D, and DS are all no greater than 1.0, the banded structure is no greater than 1.5, and the grain size is 9 or above.

[0024] The non-metallic inclusions of types A, B, C, D, and DS in the metallographic structure of the welded pipe strip of the present invention are all no greater than grade 1.0, the banded structure is no greater than grade 1.5, and the grain size is grade 9 or above. This can strictly control the morphology and size of non-metallic inclusions and banded structures, effectively reduce the places where hydrogen atoms are enriched in the grains, and prevent the local accumulation of hydrogen atoms.

[0025] In step S3, after forming, the circumferential opening of the pipe body is measured using the ring-cutting method, which ranges from -20 to -10 mm, ensuring that the welded pipe has excellent ellipticity and low residual stress after forming.

[0026] In S5, the extrusion amount of the weld seam during high-frequency welding is controlled at 5.5~6.5mm.

[0027] Because L360M strip steel has a low carbon content and good ductility and extensibility, the extrusion amount before and after welding should be strictly controlled to ensure that inclusions can be effectively extruded after the edge melts and recrystallization occurs at the weld. At the same time, it is also necessary to prevent the extrusion amount from being too small, which would result in the inclusions not being effectively extruded and thus causing the weld to have too low impact toughness. During the welding process, the extrusion amount of the weld should be controlled at 5.5~6.5mm to generate a weld metal flow ascent angle of about 70°, which can ensure that the weld has good performance.

[0028] The resistance welded pipe can be used for conveying pure hydrogen or hydrogen-doped pipes with a pressure of 6.3 MPa and below. When used in hydrogen-doped pipes, the volume ratio of hydrogen doping should not exceed 30%.

[0029] This invention optimizes the chemical composition of resistance welded pipes and combines it with processes such as forming, high-frequency welding, and heat treatment to give the resistance welded pipes the characteristics of fine and uniform grains, low segregation, high dimensional accuracy, excellent toughness, and ease of on-site circumferential welding.

[0030] Example 3 The processing method for L360M steel grade resistance welded pipe suitable for hydrogen transportation, as described in Example 2, is used to process L360M Φ406.4×10.8mm resistance welded pipe. The specific process is as follows: (1) Raw materials: L360M hot-rolled steel strip with a wall thickness of 10.8mm was used, as shown in Example 3. The comparative examples are Comparative Example 1 and Comparative Example 2. The chemical composition weight percentage of the hot-rolled steel strip in Example 3, Comparative Example 1 and Comparative Example 2 is shown in Table 1 (wt%).

[0031] Table 1. Chemical composition (wt%) of hot-rolled steel strips in Example 3, Comparative Example 1, and Comparative Example 2 C Si Mn S P Cu Al B Nb+V+Ti Ni+Cr+Mo <![CDATA[CE pcm ]]> Example 3 0.03 0.17 0.65 0.001 0.009 0.004 0.035 0.0001 0.074 0.021 0.07 Comparative Example 1 0.07 0.14 1.27 0.003 0.013 0.010 0.027 0.0001 0.036 0.034 0.13 Comparative Example 2 0.22 0.33 1.27 0.005 0.020 0.070 0.030 0.0004 0.058 0.082 0.22 (2) Pipe manufacturing: Φ406.4×10.8mm resistance welded pipes are produced using L360M hot-rolled steel strips. After uncoiling and welding, and milling, the width of the steel strip is precisely controlled at 1273~1274mm. Roll forming is used to control the waveform of the strip steel, and the weld seam extrusion amount is adjusted and controlled at 6mm. The opening angle is controlled at 5° and the welding speed is 15m / min. The strips are welded into resistance welded pipes with an outer diameter of 406.4mm and a wall thickness of 10.8mm. Subsequently, the weld seam of the L360M Φ406.4×10.8mm resistance welded pipe is subjected to online normalizing heat treatment at 950±10℃, air-cooled to below 300℃, and then sprayed with water to cool to below 70℃. The water spray cooling rate is controlled at 2±0.5℃ / s. Finally, the resistance welded pipe is manufactured through processes such as sizing and straightening, ultrasonic and X-ray inspection, water pressure, pipe end chamfering, and finished product inspection.

[0032] Metallographic structures of resistance-welded pipes in Example 3, Comparative Example 1, and Comparative Example 2 are shown below. Figures 1-3 As shown in the figure, the analysis results are shown in Table 2.

[0033] Table 2. Metallographic analysis of resistance welded pipes in Example 3, Comparative Example 1, and Comparative Example 2.

[0034] from Figures 1-3 As can be seen, compared with Comparative Examples 1 and 2, Example 3 has a fine and uniform microstructure, low microstructure segregation and banded structure grade, and the grades of non-metallic inclusions of types A, B, C, D, and DS are all no greater than grade 1.0, the banded structure is no greater than grade 1.5, and the grain size is grade 9 or above, which is beneficial to reduce the enrichment and nucleation of hydrogen atoms in the crystal.

[0035] (3) Physical and chemical properties: The physical and chemical properties of the welded pipes were tested according to CDP-S-NGP-PL-006-2019-4 "Technical Specifications for Steel Pipes for Natural Gas Pipeline Engineering". The test results are shown in Table 3. The mechanical properties all meet the standard requirements and have a high margin of safety. The test results are as follows: Pipe body yield strength R... t0.5 450~490MPa; Pipe body tensile strength R m :535~560MPa; pipe body yield ratio R t0.5 / R m : 0.86~0.90; pipe elongation A: 33~38%; weld tensile strength R m Impact strength: 525~575MPa; Transverse impact energy of pipe body at -10℃: 398~485J; Impact energy of weld at -10℃: 280~352J; Impact energy of heat-affected zone at -10℃: 318~357J; Hardness of welded joint: 158~186HV 10The springback of the L360M resistance welded pipe body was measured to be -15mm after cutting the pipe ring; the 0° and 90° flattening tests of the weld were both qualified.

[0036] Table 3 Physicochemical properties of Example 3, Comparative Example 1, and Comparative Example 2

[0037] Compared with Comparative Examples 1 and 2, Example 3 shows that the yield strength and tensile strength of the pipe body are more uniform and stable, with lower upper and lower limit deviations, and significant advantages in impact toughness. The impact energy of the pipe body in the transverse direction, weld center, and heat-affected zone is about 80J~160J higher than that of Comparative Examples 1 and 2.

[0038] (4) HIC corrosion resistance: HIC tests were conducted using NACE TM0284 standard A solution. The crack length ratio (CLR) of the three cross sections was 0, the crack thickness ratio (CTR) was 0, and the crack sensitivity ratio (CSR) was 0, indicating excellent HIC corrosion resistance. The test results are shown in Table 4. Table 4. Test results of HIC sensitivity parameters in Example 3, Comparative Example 1, and Comparative Example 2.

[0039] Compared with Comparative Examples 1 and 2, Example 3 showed that the crack length (CLR), crack thickness ratio (CTR), and crack sensitivity ratio (CSR) of the three cross sections were all 0. In the comparative examples, the weld center and heat-affected zone showed high values ​​that did not meet the standards. Example 3 showed excellent resistance to HIC corrosion.

[0040] (5) Evaluation of slow strain rate tensile adaptability in high-pressure hydrogen environment: The slow strain rate tensile adaptability of the welded pipe body and weld seam in hydrogen environment was evaluated according to GB / T 34542.2-2018 "Test method for compatibility of metallic materials with hydrogen in hydrogen storage and transportation system". The test results of the base material and weld seam are shown in Tables 5 and 6. The test results all meet the standard requirements, indicating that L360M Φ406.4×10.8mm resistance welded pipe has excellent plasticity in a 6.3MPa pure hydrogen environment and a hydrogen-doped environment with a total pressure of 6.3MPa and a hydrogen doping ratio of 30%.

[0041] Table 5. Results of slow strain rate tensile tests on the tube base materials of Example 3, Comparative Example 1, and Comparative Example 2.

[0042] Table 6 Results of slow strain rate tensile tests on welded pipe seams in Example 3, Comparative Example 1, and Comparative Example 2

[0043] Compared with Comparative Examples 1 and 2, Example 3 exhibits excellent plasticity in both a pure hydrogen environment at 6.3 MPa and a hydrogen-doped environment at a total pressure of 6.3 MPa with a hydrogen doping ratio of 30%.

[0044] (6) Fatigue life test and evaluation in high-pressure hydrogen environment: The fatigue life of the welded pipe body and weld was tested and evaluated in hydrogen environment according to GB / T 34542.2-2018 "Test method for compatibility of metallic materials with hydrogen in hydrogen storage and transportation system". The test results of the base material and weld are shown in Table 7. The test results all meet the standard requirements, indicating that the L360M Φ406.4×10.8mm resistance welded pipe has excellent fatigue resistance in 6.3MPa pure hydrogen environment and hydrogen-doped environment with a total pressure of 6.3MPa and a hydrogen doping ratio of 30%.

[0045] Table 7. Evaluation results of fatigue life testing of welded pipe body and weld in Example 3, Comparative Example 1, and Comparative Example 2.

[0046] Compared with Comparative Examples 1 and 2, Example 3 exhibits superior fatigue resistance in both a pure hydrogen environment (6.3 MPa) and a hydrogen-doped environment (6.3 MPa with a 30% hydrogen doping ratio).

[0047] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An L360M grade steel resistance welded pipe suitable for hydrogen transportation, characterized in that: The chemical element composition of resistance welded pipe, by weight percentage, is as follows: C: 0.02~0.05%, Si: 0.10~0.30%, Mn: 0.6~1.0%, S≤0.002%, P≤0.010%, Ni: 0.01~0.3%, Cr: 0.01~0.3%, Cu: 0.001~0.05%, Nb: 0.01~0.05%, V: 0.02~0.05%, Ti≤0.02%, Mo≤0.01%, Al≤0.04%, B≤0.0003%, with the balance being Fe and unavoidable impurities. The processing method of resistance welded pipe includes the following steps: S1: Uncoiling and welding: Align the ends of the strip steel with the front and rear ends; S2: Edge milling: Precision milling the edge of the strip into an I-shape, precisely controlling the perpendicularity of the strip to 90°, and the width to be controlled within the range of 1273~1274mm; S3: Forming: Roller forming is adopted. During the forming process, the height of the side extrusion roller is adjusted to 196~200mm, the height of the outer roller is controlled at 230~235mm, and the height of the inner roller is controlled at 8.4~10mm. A small opening angle of 3~5° and a small extrusion amount of 5.5~6.5mm are used, and the sizing amount is 9mm. S4: Preheating before welding: The continuously produced tube blank is heated in a heat treatment furnace at a temperature of 350℃~400℃ for a time of not less than 20 seconds. S5: High-frequency welding: High-frequency induction resistance welding is adopted, with a welding power of 360~400KW, an induction welding frequency of 400KHZ, a welding speed of 12~16m / min, and an opening angle controlled at 3~5°. S6: Heat treatment: After welding, the weld is subjected to post-weld normalizing heat treatment at a temperature of 920~960℃. After normalizing heat treatment, it is air-cooled to below 300℃. After the weld structure no longer changes, it is sprayed with water to cool to below 70℃. The water spraying cooling rate is controlled at 2±0.5℃ / s. S7: Sizing and straightening; S8: Ultrasonic and X-ray inspection: 100% UT and X-ray inspection of the weld seam and heat-affected zone on both sides of the weld seam of the resistance welded pipe after welding; S9: Pressure test: Perform a hydrostatic pressure test on each resistance welded pipe. The test pressure shall not be lower than the minimum test pressure value required by the standard. No leakage or bursting is allowed during the entire test process. S10: Beveling at the pipe end: Beveling the pipe end of the resistance welded pipe; S11: Finished Product Inspection: Inspect the appearance quality and dimensions of all resistance welded pipes.

2. The L360M steel grade resistance welded pipe suitable for hydrogen transportation according to claim 1, characterized in that: Carbon equivalent (CE) of resistance welded pipe pcm Value ≤ 0.

12.

3. The L360M steel grade resistance welded pipe suitable for hydrogen transportation according to claim 1, characterized in that: The weight percentage of chemical elements Mn and Si contained in resistance welded pipes is greater than 3.0%.

4. The L360M steel grade resistance welded pipe suitable for hydrogen transportation according to claim 1, characterized in that: In the S1 strip metallographic structure, the levels of non-metallic inclusions of types A, B, C, D, and DS are all no greater than 1.0, the banded structure is no greater than 1.5, and the grain size is 9 or above.

5. The L360M steel grade resistance welded pipe suitable for hydrogen transportation according to claim 1, characterized in that: In S3, after molding, the circumferential opening of the tube body is measured using the ring-cutting method, and the range is -20 to -10 mm.

6. The L360M steel grade resistance welded pipe suitable for hydrogen transportation according to claim 1, characterized in that: In S5, the extrusion amount of the weld seam during high-frequency welding is controlled at 5.5~6.5mm.

7. The L360M steel grade resistance welded pipe suitable for hydrogen transportation according to claim 1, characterized in that: The resistance welded pipe can be used for conveying pure hydrogen or hydrogen-doped pipes with a pressure of 6.3 MPa and below. When used in hydrogen-doped pipes, the volume ratio of hydrogen doping should not exceed 30%.

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