800mpa grade marine environment fatigue resistant mine pipeline steel plate and production method thereof

Abstract

The application provides a kind of 800MPa grade marine environment fatigue-resistant mine pipeline steel plate and its production method, the composition of the steel plate is as follows according to percentage by weight: C:0.13%~0.17%, Si:0.15%~0.30%, Mn:0.80%~0.95%, P≤0.015%, S≤0.001%, Cr:0.60%~1.00%, Mo:0.20%~0.40%, Al:0.010%~0.050%, Nb:0.03%~0.07%, V:0.11%~0.20%, Ti:0.005%~0.025%, Ni:0.15%~0.30%, Ce:0.01~0.06%, the balance is Fe and inevitable impurities;Production method includes heating, rolling, accelerated cooling, slow cooling;The steel plate produced by the application-20 ℃ impact energy is greater than or equal to 110J, 10 7 The cycle fatigue strength is greater than or equal to 300MPa, and the abrasion rate in the simulated marine environment is only less than 60% of Q460C steel.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials, and in particular relates to a steel plate for ore transport pipelines with fatigue resistance in marine environments of 800MPa and a method for producing the same. Background Technology

[0002] The deep sea crust contains a variety of mineral resources, and my country possesses several deep-sea mining areas with exclusive exploration and priority mining rights, boasting extremely high resource abundance and economic value. Pipeline-lift mining systems, due to their advantages of continuous operation, high mining efficiency, and relatively low energy consumption, are currently recognized globally as the most promising commercial deep-sea mining and ore transportation technology. The ore transport riser transports the mixture of seabed ore and seawater from the mining equipment to the sea surface at a certain speed and concentration, making it an indispensable piece of equipment for deep-sea mining engineering. The working environment of deep-sea mining requires ore transport pipelines to be wear-resistant, seawater corrosion-resistant, and clog-resistant. Furthermore, they must be able to overcome the complex marine environment, including waves and currents, at depths ranging from the sea surface to hundreds of meters below, exhibiting excellent fatigue resistance.

[0003] Patent application number 202310647877.9 discloses a "Fatigue-Resistant Marine Riser Steel and its Preparation Method," with the following chemical composition: C: 0.04%–0.07%, Si: 0.20%–0.40%, Mn: 1.00%–1.60%, Nb: 0.02%–0.06%, V: 0.030%–0.055%, Ti: 0.01%–0.02%, Cr: 0.10%–0.30%, Ni: 0.10%–0.30%, Mo: 0.05%–0.25%, P: <0.005%, S: <0.005%, with the remainder being Fe and unavoidable impurities. The microstructure is characterized by ultrafine-grained ferrite and acicular ferrite. Its intended use is for transporting oil and natural gas media; however, its low C content results in poor wear resistance, making it unsuitable for transporting high-hardness media such as minerals.

[0004] Patent application number 201710818766.4 discloses a "high fatigue resistance pipe steel, its manufacturing method and welded steel pipe using the same," with the following chemical composition: C: 0.10%~0.15%; Si: 0.30%~0.50%; Mn: 0.8%~1.2%; Nb: 0.01%~0.03%; Cr: 0.5%~0.7%; Ti: 0.01%~0.03%; Cu: 0.1%~0.4%; Ni: 0.1%~0.3%; N≤0.008%; P≤0.025%; S≤0.005%; the balance being Fe and unavoidable impurities. High fatigue resistance steel pipes are obtained by controlling the microstructure to be 50%-80% ferrite + 20%-50% pearlite. Its purpose is to transport oil and natural gas media, but it is not suitable for the highly abrasive environment of mineral transportation and cannot meet the harsh service conditions of deep-sea mineral transportation.

[0005] Patent document with application number 202111192650.7 discloses "Corrosion-resistant and fatigue-resistant underwater oil and gas production pipeline steel and its production method", the chemical composition of which is: C 0.030%~0.055%, Si 0.26%~0.40%, Mn 1.11%~1.18%, P≤0.010%, S≤0.0015%, Nb 0.035%~0.060%, Ti 0.012%~0.025%, V 0.01%~0.04%, Ni 0.10%~0.19%, Cu 0.16%~0.25%, Mo 0.10%~0.19%, Cr<0.25%, Alt 0.010%~0.025%, Ca 0.0015%~0.0050%, with the balance being iron and unavoidable impurities. High fatigue-resistant steel pipes are produced by employing a low-carbon composition design and controlling the microstructure to 15%-60% polygonal ferrite + bainite + a small amount of ferrite / aluminum. These pipes are intended for transporting oil and natural gas media. However, the steel plates have relatively low strength, making them unsuitable for the highly abrasive environments of mineral transport and unable to meet the stringent service conditions of deep-sea mineral transport.

[0006] Patent document with application number 202111194029.4 discloses "Heat-resistant and fatigue-resistant precipitation-strengthened pipeline steel and its production method", the chemical composition of which is: C 0.04%~0.06%, Si 0.26%~0.45%, Mn 1.50%~1.69%, P≤0.012%, S≤0.002%, Cr 0.16%~0.30%, Mo 0.21%~0.29%, Ni<0.15%, Cu<0.15%, Al 0.010%~0.025%, Nb 0.056%~0.070%, V 0.01%~0.04%, Ti 0.012%~0.025%, Ca 0.0015%~0.0045%, with the balance being iron and unavoidable impurities. The steel pipe employs a low-carbon composition design, achieving high fatigue resistance by controlling the microstructure to 40%-70% polygonal ferrite + bainite + a small amount of M / A. However, it lacks design considerations for improved abrasion resistance, making it unsuitable for the highly abrasive environments of mineral transportation and unable to meet the stringent service conditions of deep-sea mineral transportation.

[0007] Patent application number 201810492367.8 discloses "A High-Strength Steel Resistant to Seawater Corrosion and Its Production Method," with the following chemical composition: C≤0.09%, Si≤0.40%, Mn0.80%~0.90%, P0.090%~0.10%, S≤0.005%, Cu0.52%~0.58%, Ni0.42%~0.48%, Ti0.030%~0.050%, Al0.02%~0.06%, Re0.01%~0.05%, with the balance being Fe and unavoidable impurities. By employing a Cu-P-Ni composition system design and proportioning, along with process matching, seawater corrosion resistance is achieved. However, this steel, used for manufacturing seawater corrosion-resistant pile pipes, does not possess wear resistance or fatigue resistance.

[0008] In summary, there is currently no material design that matches the comprehensive performance of wear resistance and fatigue resistance to the characteristics of mineral transportation and marine service conditions. It is not suitable for the highly abrasive environment of mineral transportation and cannot meet the harsh service conditions of deep-sea mineral transportation. Summary of the Invention

[0009] The purpose of this invention is to overcome the above-mentioned problems and deficiencies and provide a steel plate for marine environment fatigue-resistant mineral transport pipelines with excellent comprehensive performance of wear resistance and fatigue resistance, meeting the stringent service conditions of deep-sea mineral transport. The steel plate and its production method are as follows.

[0010] The objective of this invention is achieved as follows:

[0011] A type of 800MPa grade marine environment fatigue-resistant ore transport pipeline steel plate, the composition of which is as follows by weight percentage: C: 0.13%~0.17%, Si: 0.15%~0.30%, Mn: 0.80%~0.95%, P≤0.015%, S≤0.001%, Cr: 0.60%~1.00%, Mo: 0.20%~0.40%, Al: 0.010%~0.050%, Nb: 0.03%~0.07%, V: 0.11%~0.20%, Ti: 0.005%~0.025%, Ni: 0.15%~0.30%, Ce: 0.01~0.06%, with the balance being Fe and unavoidable impurities.

[0012] Furthermore, the Cr+Mo content in the steel plate is ≥0.95%.

[0013] Furthermore, the Nb / Ce ratio in the steel plate is ≥1.

[0014] Furthermore, the V / Ce ratio in the steel plate is ≥2.3.

[0015] Furthermore, the microstructure of the steel plate is a mixed structure of bainite, fine-grained ferrite, and nanoscale V-containing precipitates, which are expressed as follows by volume percentage: the volume fraction of bainite is 80% to 90%, the proportion of nanoscale precipitates is 1% to 2%, and more than 90% of the precipitates are ≤50nm in size and are diffusely distributed.

[0016] Further details: steel plate thickness 12-20mm; yield strength 610-680MPa, tensile strength 850-960MPa, elongation ≥24%. Impact energy at -20℃ ≥110J. 7 The cycle fatigue strength is ≥300MPa, the hardness is ≥300HBW, and the wear rate in a simulated marine environment is less than 60% of that of Q460C steel.

[0017] The rationale for the design of the components in this invention is as follows:

[0018] Carbon (C): A fundamental strengthening element in steel, C is the main element ensuring strength and hardness in the technical solution of this invention. Adding an appropriate amount of C can significantly improve the strength and hardness of the steel plate. C can also combine with V and Nb to form fine granular precipitates, further enhancing the strength and toughness of the steel. However, excessive C is detrimental to the welding, toughness, and plasticity of the steel plate. Therefore, considering factors such as cost and performance, the range of C in this invention is controlled to be 0.13% to 0.17%.

[0019] Si (Si): Si can improve the strength and hardness of steel plates through solid solution strengthening. It also improves the hardenability of materials. Adding an appropriate amount of Si to steel can promote the formation of a protective rust layer on the steel surface, thereby improving corrosion resistance. Under certain carbon content conditions, Si can also inhibit the precipitation of cementite and accumulate around carbides, hindering carbide growth and promoting the finer and more dispersed distribution of carbides in the matrix. This results in finer abrasive particles generated during wear, thus reducing the degree of wear. However, higher Si content tends to cause graphitization in steel, making it brittle, reducing plasticity, and deteriorating toughness. In this invention, the Si content is controlled at 0.15%–0.30%.

[0020] Mn (manganese) is a common strengthening element in steel. It can dissolve in large quantities in the Fe matrix, increasing strength through solid solution strengthening. Manganese can lower the critical cooling rate of steel, promote martensite formation, significantly improve hardenability, and significantly lower the brittle transition temperature of steel, improve impact toughness, and refine the microstructure of steel, making it an important strengthening and toughening element. However, excessive Mn content can easily lead to segregation in steel, which has adverse effects on the fatigue and corrosion properties of steel. Taking all factors into consideration, this invention controls the Mn content to be in the range of 0.80%–0.95%.

[0021] Cr and Mo: These elements improve the hardenability of steel, accelerating the transformation of the microstructure at medium and low temperatures through accelerated cooling at high temperatures. This increases the strength and hardness of the steel plate, significantly improving its wear resistance. Adding a certain amount to the steel can also effectively fill the voids formed by pitting corrosion caused by chloride ions in marine environments, forming a dense protective film that prevents further pitting corrosion and thus provides corrosion resistance in marine environments. In this invention, the Cr content is controlled within the range of 0.60%–1.00%, and the Mo content is controlled within the range of 0.20%–0.40%, with Cr+Mo ≥ 0.95%.

[0022] Nitrogen (Nb) is a grain-refining element. When heated, undissolved Nb carbon and nitride particles are distributed along the austenite grain boundaries, hindering austenite grain growth during heating. It effectively delays the recrystallization of deformed austenite, prevents austenite grain growth, refines ferrite grains, improves the impact toughness of steel, and lowers its brittle-to-ductile transition temperature. Nb can also increase the solid solubility of rare earth elements such as Ce in steel. Since Ce has a much higher solid solubility in austenite than in ferrite, and Nb can lower the austenite-to-ferrite phase transformation temperature and expand the temperature range of the austenite phase, when Nb and Ce are added together, Ce can be fully dissolved in the steel, thereby improving the corrosion resistance of the steel. In this invention, the Nb content is controlled at 0.03%~0.07%, and the Nb / Ce ratio is ≥1.

[0023] Vanadium (V) has a strong affinity for both carbon (C) and nitrogen (N), forming stable compounds with them. In steel, vanadium mainly exists as carbides, its primary function being to refine the steel's microstructure and grain size, thereby improving its strength and toughness. In particular, the combination of V with C and N to form second-phase particles that precipitate during welding ensures the strength of the heat-affected zone (HAZ) and significantly reduces HAZ softening. Under certain C content conditions, the combined addition of V and Nb can create dispersed nanoscale carbide precipitates in the steel, significantly improving its strength and hardness without deteriorating toughness, thus enhancing its wear resistance. Similar to Nb, V can increase the solid solution content of rare earth elements such as Ce in steel, thereby improving its corrosion resistance. To ensure the effective precipitation of nanoscale carbides, the V content is controlled at 0.11–0.20%, with a V / Ce ratio ≥ 2.3.

[0024] Ti is a strong nitrogen-containing element. Adding trace amounts of Ti to Al-containing steel can significantly reduce the corrosion rate, and Ti preferentially combines with nitrogen in the steel, reducing the amount of AlN and improving weldability. However, when the Ti content exceeds a certain value, the TiN particles coarsen, causing a deterioration in low-temperature toughness. Therefore, this invention selects a Ti content of 0.010% to 0.025%.

[0025] Al: Commonly used as a deoxidizer in steel, insufficient deoxidation leads to the formation of oxides from easily oxidized elements such as Ti; excessive aluminum content increases alumina inclusions, deteriorating the cleanliness of the steel and negatively impacting its fatigue resistance. Therefore, this invention controls the Al content to be in the range of 0.01% to 0.05%.

[0026] Ni (Ni): It can improve the strength of steel, lower the critical cooling temperature, facilitate microstructure control and grain refinement, and improve low-temperature toughness and fatigue resistance. However, Ni is expensive and should not be added in excess. This invention controls the Ni content to be 0.15%–0.30%.

[0027] Ce: Adding a small amount of Ce to steel can improve its quality by altering the morphology and distribution of inclusions. Ce has a strong affinity for O and S, preferentially reacting with them to form stable oxides and sulfides. It can also transform strip-shaped MnS inclusions into spherical shapes and promote the flotation of these compounds in molten steel, thereby reducing the formation of large inclusions and mitigating the cutting effect of irregular and large inclusions on the matrix, thus purifying the molten iron. During the solidification process, Ce acts as a nucleation core, increasing the number of crystal nuclei and refining the grains, significantly improving the steel's strength, toughness, fatigue resistance, and corrosion resistance. This invention controls the Ce content to be 0.01%–0.06%.

[0028] P and S: As impurity elements, phosphorus and sulfur significantly deteriorate the toughness, plasticity and weldability of steel, so their content in steel should be reduced as much as possible. In this invention, the content of P and S is required to be controlled at P≤0.015% and S≤0.001%, respectively.

[0029] The second technical solution of the present invention is to provide a method for producing steel plates for ore transport pipelines with fatigue resistance in marine environments of 800MPa grade, including heating, rolling, accelerated cooling, and slow cooling;

[0030] Heating: The slab adopts a multi-stage stepped temperature heating method; the high-temperature heating section is 1200-1250℃, the soaking section is 1180-1220℃, and the time for the high-temperature heating section plus the soaking section is not less than 120min; the heating process is designed mainly to ensure the solid solution of elements such as Mn, Cr, Mo, Ni, Cu, Nb, and V, so that they can play a role in subsequent rolling and accelerated cooling, while effectively controlling the growth of austenite grains; the heating time can ensure the heating effect and temperature uniformity.

[0031] Rolling: Steel plate rolling is carried out in two stages: roughing and finishing. The finishing temperature of the roughing stage is ≥1050℃, and the single-pass reduction rate of the last two passes of roughing is ≥14%, so as to fully break down and refine the original austenite grains. The intermediate billet thickness of the finishing stage is 3.0~3.5t, where t is the thickness of the finished steel plate (12~20mm). The initial rolling temperature is 880~930℃, the single-pass reduction rate of the first three passes of finishing is ≥13%, and the final rolling temperature is 820~860℃.

[0032] The design of the roughing rolling process primarily considers the full deformation of steel at high temperatures, especially with the last two passes employing large single-pass reductions. The aim is to increase the dislocation density within the grain nuclei, causing existing large grains to split into new, smaller nuclei due to dislocation fragmentation. This results in austenite grain fragmentation and further refinement, suppressing excessive austenite grain growth between the end of roughing and the beginning of finishing. The finishing rolling process is designed to ensure sufficient flattening and deformation of austenite through the thickness of the intermediate slab, accumulating deformation energy. Furthermore, the large single-pass reduction promotes the induced precipitation of nanoscale Nb and V phases, pinning grain boundaries and dislocations, increasing nucleation sites, and further refining the grains. By controlling the initial and final rolling temperatures, the steel completes the deformation process within a relatively low temperature range, achieving a good balance of strength and toughness while avoiding ferrite coarsening, which negatively impacts fatigue resistance.

[0033] Accelerated cooling: After the steel plate is rolled, it is subjected to accelerated cooling. The initial cooling temperature is 760-800℃, the accelerated cooling rate is 15-25℃ / s, and the final cooling temperature is 550-600℃.

[0034] The microstructure ultimately achieved through accelerated cooling is a mixed microstructure consisting of bainite, a small amount of fine-grained ferrite, and nanoscale V-containing precipitates. The volume fraction of bainite is 80%–90%. The proportion of nanoscale precipitates is 1%–2%, with over 90% of the precipitates having a size ≤50 nm and exhibiting a diffuse distribution.

[0035] The fine-grained ferrite in the final microstructure plays a good role in coordinating strain, improving the plasticity of the steel, and effectively coping with the traction and tension of the steel pipe caused by the movement of the floating body. Moreover, its low dislocation density can reduce stress concentration caused by cyclic deformation of the material, effectively resisting fatigue crack initiation. At the same time, it can also effectively absorb the energy of continued crack propagation after crack initiation, hindering further crack propagation and improving crack arrest performance. Bainite can increase the strength of the steel plate without deteriorating its fatigue resistance. The dispersed nanoscale V-containing precipitates, as hard phase particles, not only significantly improve the wear resistance of the steel, but also maintain a dispersed precipitation state during welding, significantly improving the softening of the heat-affected zone.

[0036] Slow cooling: After the steel plates have undergone accelerated cooling, they are slowly cooled using a stacking method at a cooling rate of ≤0.2℃ / s until they reach room temperature. The purpose is to slowly release the internal stress in the steel and prevent cracking caused by a sharp increase in stress due to the drastic changes in the steel's microstructure caused by the high C content and the presence of hardenable elements such as Cr and Mo after accelerated cooling.

[0037] The beneficial effects of this invention are as follows:

[0038] (1) Based on C and Mn, this invention adds appropriate amounts of alloying elements such as Cr, Mo, Ni, Nb, and V. Through the interaction between these elements and with suitable heating, rolling, and cooling processes, a mixed microstructure of bainite + a small amount of fine-grained ferrite + nanoscale V-containing precipitates is finally obtained. Compared with the prior art, this invention conducts targeted composition and microstructure design to improve the fatigue resistance and wear resistance of steel plates, and the produced steel plates have good strength, toughness, wear resistance, and excellent fatigue resistance.

[0039] (2) The steel plate possesses excellent comprehensive mechanical properties, with a yield strength of 610–680 MPa, a tensile strength of 850–960 MPa, and an elongation ≥24%. The impact energy of the steel plate at -20℃ is ≥110 J. 7 The cycle fatigue strength is ≥300MPa, the hardness is ≥300HBW, and the abrasion rate in a simulated marine environment is only less than 60% of that of Q460C steel. All properties meet the technical requirements for ore transport pipelines in marine environments with a pressure rating of 800MPa.

[0040] (3) The present invention refines the microstructure by using appropriate processes, controls the microstructure composition and precipitated phase characteristics, and ensures the steel plate has good comprehensive performance in terms of strength, toughness, wear resistance and fatigue resistance. Attached Figure Description

[0041] Figure 1 This is a metallographic image of the microstructure of Embodiment 1 of the present invention.

[0042] Figure 2 This is a characteristic diagram of the nanoscale precipitated phase in Example 1 of the present invention. Detailed Implementation

[0043] The present invention will be further illustrated below through examples.

[0044] According to the component ratio of the technical solution, the present invention performs heating, rolling, accelerated cooling, and slow cooling.

[0045] Heating: The slab adopts a multi-stage stepped temperature heating method; the high-temperature heating section has a temperature of 1200~1250℃, and the soaking section has a temperature of 1180~1220℃.

[0046] Rolling: Steel plate rolling is carried out in two stages: roughing and finishing. The finishing temperature of the roughing stage is ≥1050℃, and the single-pass reduction rate of the last two passes of roughing is ≥14%. The intermediate billet thickness of the finishing stage is 3.0~3.5t, where t is the thickness of the finished steel plate. The initial rolling temperature is 880~930℃, the single-pass reduction rate of the first three passes of finishing is ≥13%, and the final rolling temperature is 820~860℃.

[0047] Accelerated cooling: After the steel plate is rolled, it is subjected to accelerated cooling. The initial cooling temperature is 760~800℃, the cooling rate of accelerated cooling is 15~25℃ / s, and the final cooling temperature is 550~600℃.

[0048] Slow cooling: After the steel plates have completed accelerated cooling, they are slowly cooled by stacking, with a cooling rate of ≤0.2℃ / s, until they reach room temperature.

[0049] Furthermore, the time for the high-temperature heating section plus the heat spread section shall not be less than 120 minutes.

[0050] The composition of the steels in the embodiments and comparative examples of this invention is shown in Table 1. The main process parameters for heating the steels in the embodiments and comparative examples of this invention are shown in Table 2. The main process parameters for rolling and cooling the steels in the embodiments and comparative examples of this invention are shown in Table 3. The properties of the steels in the embodiments of this invention are shown in Table 4. The microstructure of the steels in the embodiments and comparative examples of this invention is shown in Table 5.

[0051] Table 1. Composition of steels in the embodiments and comparative examples of the present invention.

[0052]

[0053] Table 2 Main process parameters for heating steel in the embodiments and comparative examples of the present invention.

[0054]

[0055] Table 3. Main process parameters for steel rolling and cooling in the embodiments and comparative examples of the present invention.

[0056]

[0057] Table 4 Properties of steel in embodiments of the present invention

[0058]

[0059] Table 5. Microstructure of steels in embodiments and comparative examples of the present invention.

[0060]

[0061] The steel plate produced using this invention possesses excellent comprehensive mechanical properties, with a yield strength of 610~680MPa, tensile strength of 850~960MPa, and elongation ≥24%. The steel plate has an impact energy of ≥110J at -20℃. 7 The cycle fatigue strength is ≥300MPa, the hardness is ≥300HBW, and the abrasion rate in a simulated marine environment is only less than 60% of that of Q460C steel. All properties meet the technical requirements for ore transport pipelines in marine environments with a pressure rating of 800MPa.

[0062] To illustrate the present invention, the present invention has been appropriately and sufficiently described above through embodiments. The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A steel plate for ore transport pipelines with fatigue resistance in marine environments (800MPa grade), characterized in that, The composition of the steel plate by weight percentage is as follows: C: 0.13%~0.17%, Si: 0.15%~0.30%, Mn: 0.80%~0.95%, P≤0.015%, S≤0.001%, Cr: 0.60%~1.00%, Mo: 0.20%~0.40%, Al: 0.010%~0.050%, Nb: 0.03%~0.07%, V: 0.11%~0.20%, Ti: 0.005%~0.025%, Ni: 0.15%~0.30%, Ce:

0. 0.01%~0.06%, with the balance being Fe and unavoidable impurities; the microstructure of the steel plate is a mixed structure of bainite + a small amount of fine-grained ferrite + nano-sized V-containing precipitates, expressed as follows by volume percentage: bainite accounts for 80%~90% of the volume, and nano-sized precipitates account for 1%~2%, of which more than 90% of the precipitates are ≤50nm in size and are diffusely distributed; the yield strength of the steel plate is 610~680MPa, the tensile strength is 850~960MPa, and the elongation is ≥24%; the impact energy of the steel plate at -20℃ is ≥110J, 10 7 The cycle fatigue strength is ≥300MPa, the hardness is ≥300HBW, and the wear rate in a simulated marine environment is less than 60% of that of Q460C steel.

2. The steel plate for ore transportation pipelines with 800MPa grade marine environment fatigue resistance according to claim 1, characterized in that, The steel plate contains Cr+Mo≥0.95%.

3. The steel plate for ore transportation pipelines with 800MPa grade marine environment fatigue resistance according to claim 1, characterized in that, The Nb / Ce ratio in the steel plate is ≥1.

4. The steel plate for ore transportation pipelines with 800MPa grade marine environment fatigue resistance according to claim 1, characterized in that, The V / Ce ratio in the steel plate is ≥2.

3.

5. A method for producing an 800MPa grade marine environment fatigue-resistant ore transport pipeline steel plate as described in any one of claims 1-4, comprising heating, rolling, accelerated cooling, and slow cooling; characterized in that: Heating: The slab adopts a multi-stage stepped temperature heating method; the high-temperature heating section has a temperature of 1200~1250℃, and the soaking section has a temperature of 1180~1220℃. Rolling: Steel plate rolling is carried out in two stages: roughing and finishing. The finishing temperature of the roughing stage is ≥1050℃, and the single-pass reduction rate of the last two passes of roughing is ≥14%. The intermediate billet thickness of the finishing stage is 3.0~3.5t, where t is the thickness of the finished steel plate. The initial rolling temperature is 880~930℃, the single-pass reduction rate of the first three passes of finishing is ≥13%, and the final rolling temperature is 820~860℃. Accelerated cooling: After the steel plate is rolled, it is accelerated cooled. The initial cooling temperature is 760~800℃, the cooling rate is 15~25℃ / s, and the final cooling temperature is 550~600℃. Slow cooling: After the steel plates have completed accelerated cooling, they are slowly cooled by stacking, with a cooling rate of ≤0.2℃ / s, until they reach room temperature.

6. The method for producing an 800MPa grade marine environment fatigue-resistant ore transport pipeline steel plate according to claim 5, characterized in that, The time for the high-temperature heating section plus the soaking section shall not be less than 120 minutes.

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