Steel plate for 1000MPa-grade marine environment anti-fatigue ore conveying pipeline and production method of steel plate

Abstract

The invention belongs to the field of metal materials, and provides a steel plate for a 1000 MPa grade marine environment anti-fatigue ore conveying pipeline and a production method thereof.The steel plate comprises, by weight, 0.13%-0.17% of C, 0.31%-0.50% of Si, 0.96%-1.20% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.001% of S, 0.70%-1.10% of Cr, 0.25%-0.45% of Mo, 0.010%-0.050% of Al, 0.08%-0.12% of Nb, 0.11%-0.20% of V, 0.005%-0.025% of Ti, 0.31%-0.50% of Ni, 0.01%-0.06% of Ce and the balance Fe and inevitable impurities, and the production method comprises the steps of heating, rolling, accelerated cooling and slow cooling. The steel plate produced by using the method has good obdurability, abrasion resistance and excellent fatigue resistance.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and in particular relates to a 1000MPa-level marine environment fatigue-resistant steel plate for an ore conveying pipeline and a production method thereof. Background Art

[0002] The deep-sea crust contains the vast majority of the Earth's ultra-high-grade metal minerals, including manganese, cobalt, copper, and nickel. Its widespread distribution, high grade, and vast reserves far exceed those on land. Deep-sea mining will become a crucial component of future mineral resource development. Mineral transportation is a crucial component of deep-sea mining. Pipeline-lift deep-sea mining systems, proven through numerous sea trials, offer the greatest commercial potential. Deep-sea mineral resource development faces extremely complex and harsh operating environments, including typhoons, huge waves, and internal waves. Deep-sea mining, in particular, involves transporting minerals from underwater to the surface via pipelines. These pipelines, connected at both ends to surface platforms and seabed ore collection systems, hang suspended in the deep sea. These pipelines are subject to not only internal wear and tear from mineral transportation but also the harsh effects of external ocean currents, swaying caused by wind and waves, and the drag of gravity. This demands that the pipelines, in addition to being resistant to wear and seawater corrosion, possess excellent fatigue resistance.

[0003] Patent application number 202310647877.9 discloses "A Fatigue-Resistant Offshore Riser Steel and Its Preparation Method." Its chemical composition is as follows: 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. Its microstructure is characterized by ultrafine-grained ferrite and acicular ferrite. It is intended for transporting oil and natural gas. However, its low C content results in poor wear resistance, making it unsuitable for transporting high-hardness media such as minerals.

[0004] Patent document 201811584851.X discloses "High-Strength, Toughness, and Fatigue-Resistant Nanoprecipitate-Reinforced Martensite-Austenite Duplex Steel and Its Preparation Method." Its chemical composition is as follows: C: 0.06%–0.20%; Si: 0.05%–0.20%; Mn: 2.50%–5.00%; P ≤ 0.01%; S ≤ 0.01%; Cu: ≤ 1.00%; Ni: ≤ 2.00%; Mo: 0.20%–0.50%; Cr: 1.00%–1.50%; V: 0.10%–0.80%; the remainder being Fe and unavoidable impurities. Through quenching and tempering heat treatment, tempered martensite and reversed austenite are obtained, resulting in excellent fatigue and corrosion resistance. However, the high content of alloying elements in the steel, particularly Mn exceeding 2.5%, not only significantly increases the alloy cost but also adversely affects the steel's weldability.

[0005] Patent document 202410698271.2 discloses "An Ultrafine Bainite Wear-Resistant Steel NM300 and Its Production Method." Its chemical composition is: C 0.13% to 0.15%, Si 0.4% to 0.6%, Mn 1.3% to 1.5%, Alt 0.3% to 0.5%, Nb 0.01% to 0.03%, Ti 0.01% to 0.03%, B 0.001% to 0.004%, with the remainder being Fe and trace impurity elements. By adding the B element and achieving a cooling rate ≥ 80°C / s, an ultrafine bainite + retained austenite structure is obtained, giving the steel plate with a thickness of 2-8mm good wear resistance. However, this design does not have seawater corrosion resistance, and the steel plate wall thickness is too small, resulting in poor crush resistance. It is not suitable for deep-sea high-pressure environments and the highly abrasive environment of seawater-containing mineral transportation, and cannot meet the harsh service conditions of deep-sea mineral transportation.

[0006] Patent application number 201710182924.1 discloses "Ultra-High Strength Steel Plate with Excellent Seawater Corrosion Resistance, Fatigue Resistance, and Environmental Brittleness Resistance, and Its Manufacturing Method." Its chemical composition is as follows: C 0.025%-0.055%, Si ≤ 0.10%, Mn 0.45%-0.85%, P ≤ 0.013%, S ≤ 0.0050%, Cr 11%-16%, Mo 0.85%-1.25%, Ni 4.50%-6.50%, Nb 0.05%-0.08%, Ti 0.008%-0.018%, Ca 0.0015%-0.0040%, with the balance being iron and unavoidable impurities. By designing a high Cr, Mo, and Ni composition, an ultra-high-strength steel plate with excellent fatigue resistance and environmental brittleness resistance is achieved. However, an alloy content exceeding 16% not only increases the alloy cost but also negatively impacts the formability and weldability of the steel plate.

[0007] In summary, the current production of steel for ore transport risers does not have a matching design for the comprehensive performance of material wear resistance and fatigue resistance based on 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

[0008] The object of the present invention is to overcome the above problems and deficiencies and to provide a 1000MPa grade marine environment fatigue resistant steel plate for ore transportation pipelines having good toughness, abrasion resistance and excellent fatigue resistance and a production method thereof.

[0009] The object of the invention is achieved like this:

[0010] A 1000MPa-grade steel plate for fatigue-resistant ore transportation pipelines in marine environments. The steel plate has the following components by weight: C: 0.13%-0.17%, Si: 0.31%-0.50%, Mn: 0.96%-1.20%, P≤0.015%, S≤0.001%, Cr: 0.70%-1.10%, Mo: 0.25%-0.45%, Al: 0.010%-0.050%, Nb: 0.08%-0.12%, V: 0.11%-0.20%, Ti: 0.005%-0.025%, Ni: 0.31%-0.50%, Ce: 0.01%-0.06%, and the balance being Fe and unavoidable impurities.

[0011] Furthermore, Cr+Mo in the steel plate is ≥ 1.10%.

[0012] Furthermore, Nb / Ce in the steel plate is ≥ 1.8.

[0013] Furthermore, V / Ce in the steel plate is ≥ 2.2.

[0014] Furthermore, the microstructure of the steel plate is a mixed structure of lower bainite + lath martensite + nano-scale V-containing precipitates, which is recorded as follows in mass percentage: lower bainite 30%~50%; nano-scale precipitates 1.0%~2.0%, of which more than 90% of the precipitates have a size of ≤40nm.

[0015] Further; the steel plate yield strength 1000~1100MPa, tensile strength 1150~1250MPa, elongation ≥18%; steel plate -20 ℃ impact energy ≥110J, 10 7 Cyclic fatigue strength ≥250MPa, hardness ≥370HBW.

[0016] The reasons for the composition design of the present invention are as follows:

[0017] C: A fundamental strengthening element in steel, it plays a key role in ensuring strength and hardness in the present invention. Adding an appropriate amount of C can significantly improve the strength and hardness of steel plates. C also combines with V and Nb to form fine granular precipitates, further enhancing the steel's toughness. However, excessive C levels are detrimental to the steel's weldability, toughness, and ductility. Therefore, considering factors such as cost and performance, the present invention limits the C content to 0.13% to 0.17%.

[0018] Si: Si is an essential element for deoxidation during the steelmaking process. It has a strong solid solubility in steel and can increase the strength and hardness of steel, thereby improving the wear resistance of steel. Adding an appropriate amount of Si to steel can cause carbides to become smaller and dispersed in the matrix and enriched around the carbides, inhibiting the precipitation of cementite, hindering the growth of carbides, improving the fatigue resistance of steel and further improving the wear resistance of steel. However, a higher content of Si is not conducive to low-temperature toughness, which will reduce the low-temperature toughness of the steel plate, deteriorate the toughness of the steel material, and reduce the plasticity. The content of Si in the present invention is controlled at 0.31~0.50%.

[0019] Mn: It is a common strengthening element in steel and can be dissolved in the Fe matrix in large quantities to improve strength through solid solution strengthening. Manganese can reduce the critical cooling rate of steel, promote the formation of martensite, greatly improve the hardenability, and at the same time significantly reduce the brittle transition temperature of steel, improve impact toughness, and refine the microstructure of steel. It is an important strengthening and toughening element. However, if the Mn content is too high, it is easy to form segregation in the steel, which has an adverse effect on the fatigue and corrosion properties of the steel. Taking all factors into consideration, the present invention controls the range of Mn to be 0.96%~1.20%.

[0020] Cr and Mo: They can improve the hardenability and bainitization tendency of steel, effectively increasing the strength, hardness, and fatigue strength of the steel, and achieving good wear resistance and fatigue resistance. Adding a certain amount of Cr and Mo to the steel can also effectively fill the gaps formed by pitting corrosion caused by chloride ions in the marine environment, forming a dense protective film that prevents further pitting corrosion and thus provides corrosion resistance in the marine environment. The present invention controls the Cr content within the range of 0.70% to 1.10%, and the Mo content within the range of 0.25% to 0.45%, preferably; Cr + Mo ≥ 1.10%.

[0021] Nb: It is a grain refining element. When heated, the carbon and nitride particles of undissolved Nb are distributed on the austenite grain boundaries, which can hinder the growth of austenite grains when the steel is heated. It can effectively delay the recrystallization of deformed austenite, prevent the growth of austenite grains, refine the ferrite grains, improve the impact toughness of steel and lower its brittle transition temperature. Nb can also increase the solid solubility of rare earths such as Ce in steel. When Nb and Ce are added in combination, Ce can be fully dissolved in the steel, thereby improving the corrosion resistance of the steel. An appropriate amount of Nb can further increase the non-recrystallization temperature window of steel, enable non-recrystallization rolling at higher temperatures, and reduce the rolling load of the rolling mill. The present invention controls the Nb content to 0.08%~0.12%, preferably, Nb / Ce≥1.8.

[0022] V: V is a strong carbide-forming element and has a strong affinity with C and N. The carbide dispersion of vanadium is very high and extremely stable, which can improve the strength and toughness of steel by refining the structure and grain of steel, while improving fatigue resistance. V combines with C and N to form second-phase particles that precipitate during welding, which can ensure the strength of the heat-affected zone of steel and significantly reduce the softening of the heat-affected zone of welding. Under certain C content conditions, the combined addition of V and Nb can form dispersed nano-scale carbide particles in the steel, which significantly improves the strength and hardness of the steel without deteriorating the toughness, thereby improving the wear resistance of the steel. V can also increase the solid solubility of rare earth elements such as Ce in steel, thereby improving the corrosion resistance of steel. In the present invention, its content is controlled at 0.11-0.20%, and V / Ce≥2.2.

[0023] Ti: A strong nitrogen-binding element, adding trace amounts of Ti to aluminum-containing steel can significantly reduce corrosion rates. Ti also preferentially bonds 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, deteriorating low-temperature toughness. Therefore, the Ti content in this invention is preferably between 0.010% and 0.025%.

[0024] Al: Commonly used as a deoxidizer in steel, too low an aluminum content results in inadequate deoxidation, causing easily oxidizable elements like Ti to form oxides. Excessive aluminum content increases the formation of aluminum oxide inclusions, degrading steel cleanliness and adversely affecting fatigue resistance. Therefore, the present invention controls the Al content within a range of 0.010% to 0.050%.

[0025] Nickel (Ni) increases steel strength, lowers critical cooling temperature, facilitates microstructure control and grain refinement, and improves low-temperature toughness and fatigue resistance. However, Ni is relatively expensive, so excessive addition is not recommended. The present invention controls the Ni content to 0.31%-0.50%.

[0026] Ce preferentially reacts with O and S during the steelmaking process to form stable oxides and sulfides, transforming strip-shaped MnS inclusions into spherical ones. This promotes the full flotation of these compounds in the molten steel, further facilitating inclusion removal. This reduces the formation of large inclusions and mitigates the disruptive effects of irregular and large inclusions on the matrix, purifying the molten iron and significantly improving fatigue resistance. During solidification, Ce also acts as a nucleation core, increasing the number of crystal nuclei and thereby refining the grain size, further enhancing the steel's toughness and fatigue resistance. The Ce content in this invention is controlled to 0.01%-0.06%.

[0027] 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 the present invention, the P and S contents are required to be controlled within P≤0.015% and S≤0.001%, respectively.

[0028] The second technical solution of the present invention is to provide a 1000MPa grade fatigue resistant steel plate for ore transportation pipeline in marine environment and its production method, which includes: heating, rolling, accelerated cooling, and slow cooling;

[0029] Heating: The slab adopts a multi-stage stepped temperature heating method, in which the high-temperature heating section temperature is 1200-1250℃, the soaking section temperature is 1180-1220℃, and the high-temperature heating section + soaking section time is not less than 120 minutes.

[0030] The design of the heating process is 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. At the same time, it effectively controls 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 roughing stage ends at a temperature ≥1050°C, and the reduction ratio for each of the last two roughing passes is ≥14% to fully crush and refine the original austenite grains. The intermediate bar thickness for the finishing stage is 3.5-4.0t, where t is the thickness of the finished steel plate (12-20mm). The starting rolling temperature is 850-900°C, and the reduction ratio for each of the first three finishing passes is ≥13%. The final rolling temperature is 780-820°C.

[0032] Rolling temperature design primarily considers minimizing deformation resistance during rough and finish rolling, achieving a greater degree of deformation, and ensuring full penetration of the rolling effect through the thickness, resulting in excellent through-thickness microstructure uniformity and improved fatigue resistance. This, in turn, promotes the formation of nanoscale precipitates, pinning grain boundaries and dislocations for grain refinement. A high single-pass reduction is employed to fully crush and flatten the austenite grains, while a relatively low finish rolling temperature is used to increase dislocation density in the steel, ultimately improving strength and toughness through grain refinement and dislocation strengthening.

[0033] Accelerated cooling: After rolling, the steel plate undergoes accelerated cooling, which is carried out in two stages. The first stage begins at a temperature range of 760-800°C, with a cooling rate of 5-10°C / s and a cooling time of 8-10 seconds. This cooling process aims to inhibit the transformation of austenite to ferrite and achieve a granular bainite structure at an appropriate cooling rate. The second stage, with no significant time or distance difference from the first, has an increased cooling rate of 15-20°C / s and a final cooling temperature of 360-430°C.

[0034] Slow cooling: After accelerated cooling, the steel plate is slowly cooled in a stacking process at a cooling rate of ≤0.2°C / s until it reaches room temperature. This is to slowly release the internal stress in the steel and prevent cracking caused by a sharp increase in stress due to drastic changes in the steel's structure caused by the high concentration of C and the strong hardenability elements Cr and Mo after accelerated cooling.

[0035] The goal is to suppress the formation of lamellar martensite and promote the formation of short, lath-like martensite through appropriate cooling rates and final cooling temperatures, ultimately achieving a mixed structure of lower bainite, lath-like martensite, and nanoscale V-containing precipitates. The lower bainite content ranges from 30% to 50%, while the nanoscale precipitates account for 1.0% to 2.0%. Over 90% of the precipitates are dispersed and ≤40nm in size. The lower bainite and short, lath-like martensite in the final structure provide excellent strain coordination, effectively managing the traction and stretching of the steel pipe caused by floating body motion, alleviating stress concentration caused by cyclical reciprocating deformation, and effectively resisting fatigue crack initiation. They also effectively absorb energy from crack initiation, hindering further crack growth and improving crack arrest performance. The lath-like martensite enhances the strength and wear resistance of the steel plate. Martensite, as a hard phase, is surrounded by bainite, enhancing the steel's strength without degrading its fatigue properties. The dispersed nano-scale V-containing precipitates as hard phase particles not only significantly improve the wear resistance of the steel, but also maintain the dispersed precipitation state during the welding process, ensuring the strength of the heat-affected zone, significantly improving the softening of the heat-affected zone, improving the overall performance uniformity of the steel pipe, and thus improving the fatigue fracture resistance of the steel pipe. The cooled steel plates are stacked and slowly cooled to room temperature to fully release the internal stress of the steel plates.

[0036] The beneficial effects of the present invention are:

[0037] 1) This invention adds appropriate amounts of alloying elements, including Cr, Mo, Ni, Nb, and V, to C and Mn. Through the interaction of these elements and a suitable heating, rolling, and cooling process, the resulting composite structure is composed of lower bainite, lath-shaped martensite, and nanoscale V-containing precipitates. Compared to existing technologies, this invention specifically designs the composition and microstructure to enhance the fatigue and wear resistance of the steel plate. The resulting steel plate exhibits excellent strength, toughness, wear resistance, and fatigue resistance.

[0038] 2) The steel plate has excellent comprehensive mechanical properties, with a yield strength of 1000-1100 MPa, a tensile strength of 1150-1250 MPa, and an elongation of ≥18%. The steel plate also has an impact energy of ≥110 J at -20°C, a 107-cycle fatigue strength of ≥250 MPa, and a hardness of ≥370 HBW. In a simulated marine environment, the abrasion rate is less than 50% of that of Q460C steel. These performance characteristics meet the technical requirements for 1000 MPa-grade ore pipelines in marine environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a metallographic diagram of the microstructure of Example 1 of the present invention.

[0040] Figure 2 This is a characteristic diagram of the nanoscale precipitation phase in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below by way of examples.

[0042] The embodiment of the present invention performs smelting, continuous casting, heating, rolling, accelerated cooling, and slow cooling according to the component ratio of the technical solution.

[0043] Heating: The slab adopts a multi-stage stepped temperature heating method, where the high temperature heating section is at 1200~1250℃ and the soaking section is at 1180~1220℃.

[0044] Rolling: Steel plate rolling is carried out in two stages: rough rolling and finishing rolling. The end temperature of the rough rolling stage is ≥1050℃, and the single pass reduction rate of the last two passes of rough rolling is ≥14%. The thickness of the intermediate bar in the finishing rolling stage is 3.5~4.0t, where t is the thickness of the finished steel plate. The starting rolling temperature is 850~900℃, the single pass reduction rate of the first three passes of finishing rolling is ≥13%, and the final rolling temperature is 780~820℃.

[0045] Accelerated cooling: After the steel plate is rolled, it is accelerated and cooled in two stages. The first stage has a cooling temperature of 760~800℃, a cooling rate of 5~10℃ / s, and a cooling time of 8~10s. The second stage has a cooling rate of 15~20℃ / s and a final cooling temperature of 360~430℃.

[0046] Slow cooling: After the steel plate completes accelerated cooling, it is slowly cooled in a stacking manner with a cooling rate of ≤0.2℃ / s until it cools to room temperature.

[0047] Furthermore, the high temperature heating section + soaking section time is not less than 120 minutes.

[0048] The compositions of the steels and example steels of the present invention are shown in Table 1. The main process parameters for heating the steels and example steels of the present invention are shown in Table 2. The main process parameters for rolling the steels and example steels of the present invention are shown in Table 3. The main process parameters for cooling the steels and example steels of the present invention are shown in Table 4. The properties of the steels and example steels of the present invention are shown in Table 5. The microstructures of the steels and example steels of the present invention are shown in Table 6.

[0049] Table 1 Composition of Example Steel and Example Steel of the Present Invention

[0050]

[0051] Table 2 Main process parameters for heating of the embodiment of the present invention and the embodiment steel

[0052]

[0053] Table 3 Main process parameters of the rolling of the embodiment of the present invention and the embodiment steel

[0054]

[0055] Table 4 Main process parameters for cooling of the embodiment of the present invention and the embodiment steel

[0056]

[0057] Table 5 Properties of Example Steel and Example Steel of the Present Invention

[0058]

[0059] Table 6 Structure of Example Steel and Example Steel of the Present Invention

[0060]

[0061] The steel plate produced using this invention has a microstructure consisting of a mixture of lower bainite, lath-shaped martensite, and nanoscale V-containing precipitates. The microstructure, by mass percentage, is as follows: 30% to 50% lower bainite; 1.0% to 2.0% nanoscale precipitates, with at least 90% of the precipitates ≤40 nm in size. The steel plate has a yield strength of 1000 to 1100 MPa, a tensile strength of 1150 to 1250 MPa, and an elongation of ≥18%. The steel plate also has an impact energy of ≥110 J at -20°C, a fatigue strength of ≥250 MPa at 107 cycles, and a hardness of ≥370 HBW.

[0062] In order to describe the present invention, the present invention has been appropriately and fully illustrated through the examples above. The above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made should be included in the scope of protection of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A 1000MPa grade marine environment fatigue resistant steel plate for ore transportation pipeline, characterized in that: The composition of the steel plate is as follows by weight percentage: C: 0.13%~0.17%, Si: 0.31%~0.50%, Mn: 0.96%~1.20%, P≤0.015%, S≤0.001%, Cr: 0.70%~1.10%, Mo: 0.25%~0.45%, Al: 0.010%~0.050%, Nb: 0.08%~0.12%, V: 0.11%~0.20%, Ti: 0.005%~0.025%, Ni: 0.31~0.50%, Ce: 0.01~0.06%, and the balance is Fe and unavoidable impurities.

2. The 1000MPa grade marine environment fatigue-resistant steel plate for ore transportation pipeline according to claim 1, characterized in that: Cr+Mo in steel plate ≥1.10%.

3. The 1000MPa grade marine environment fatigue-resistant steel plate for ore transportation pipeline according to claim 1, characterized in that: Nb / Ce in steel plate ≥1.

8.

4. The 1000MPa grade marine environment fatigue-resistant steel plate for ore transportation pipeline according to claim 1, characterized in that: V / Ce in steel plate ≥ 2.

2.

5. The 1000MPa grade marine environment fatigue-resistant steel plate for ore transportation pipeline according to claim 1, characterized in that: The microstructure of the steel plate is a mixed structure of lower bainite + lath martensite + nano-scale V-containing precipitates, which is recorded as follows by area percentage: lower bainite 30%~50%; nano-scale precipitates 1.0%~2.0%, of which more than 90% of the precipitates have a size of ≤40nm.

6. The 1000MPa grade marine environment fatigue resistant steel plate for ore transportation pipeline according to claim 1, characterized in that: The steel plate has a yield strength of 1000~1100MPa, a tensile strength of 1150~1250MPa, and an elongation of ≥18%; the steel plate has an impact energy of ≥110J at -20℃, 10 7 Cyclic fatigue strength ≥250MPa, hardness ≥370HBW.

7. A method for producing a 1000 MPa grade marine environment fatigue-resistant steel plate for a mineral transportation pipeline according to any one of claims 1 to 6, comprising smelting, continuous casting, heating, rolling, accelerated cooling, and slow cooling; characterized in that: Heating: The slab adopts a multi-stage stepped temperature heating method, where the high temperature heating section is at 1200~1250℃ and the soaking section is at 1180~1220℃. Rolling: Steel plate rolling is carried out in two stages: rough rolling and finishing rolling. The end temperature of the rough rolling stage is ≥1050℃, and the single pass reduction rate of the last two passes of rough rolling is ≥14%. The thickness of the intermediate bar in the finishing rolling stage is 3.5~4.0t, where t is the thickness of the finished steel plate. The starting rolling temperature is 850~900℃, the single pass reduction rate of the first three passes of finishing rolling is ≥13%, and the final rolling temperature is 780~820℃. Accelerated cooling: After the steel plate is rolled, it is accelerated and cooled in two stages. The first stage has a cooling temperature of 760-800°C, a cooling rate of 5-10°C / s, and a cooling time of 8-10s. The second stage has a cooling rate of 15-20°C / s and a final cooling temperature of 360-430°C. Slow cooling: After the steel plate completes accelerated cooling, it is slowly cooled in a stacking manner with a cooling rate of ≤0.2℃ / s until it cools to room temperature.

8. The method for producing a 1000 MPa grade marine environment fatigue-resistant steel plate for a mineral transportation pipeline according to claim 7, characterized in that: The high temperature heating section + soaking section time shall not be less than 120 minutes.

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