X80M pipeline steel plate and production and manufacturing method thereof

Abstract

The invention relates to an X80M pipeline steel plate and a production and manufacturing method thereof, and belongs to the technical field of steel production. The thick X80M pipeline steel is high in strength, good in toughness and excellent in low-temperature performance. The steel grade of the steel plate is L555 / X80, the thickness is greater than or equal to 40mm, the difference between the strength and the plate is less than or equal to 50MPa, and the average value of the drop-weight shear surface ratio at-20 DEG C is greater than The chemical components comprise C, Si, Mn, P, S, Cr, Ni, Mo, Nb, Ti and Al, and the carbon equivalent Pcm is less than or equal to 0.19%. The production method comprises the steps of molten iron pretreatment, converter smelting, LF refining, RH degassing, CCM continuous casting, slab reheating, rough rolling, finish rolling, accelerated cooling, hot straightening, natural cooling, warm straightening, cold straightening, ultrasonic flaw detection and finishing treatment. By optimizing chemical components and key process steps, the uniformity of the performance of the steel plate is achieved, the production efficiency is improved, the cost is reduced, meanwhile, the internal quality and the welding performance of the steel plate are guaranteed, and the steel plate is suitable for oil and gas transmission under the extreme weather condition.

Description

Technical Field

[0001] The present invention relates to the technical field of steel production, and in particular to an X80M pipeline steel plate and a production method thereof. Background Art

[0002] With the rapid development of the global economy, energy demand continues to grow. As key energy resources, the safe and efficient transportation of oil and natural gas is particularly important. Long-distance oil and gas transportation usually relies on strong and reliable pipeline steel materials, which must meet high strength, good low-temperature toughness and excellent welding performance. In recent years, with the development of TMCP (thermomechanical control process) technology and the advancement of alloy design, the research and development and production of high-performance pipeline steel has become possible.

[0003] Since the 1980s, X80-grade pipeline steel has gradually become the preferred material for new large-scale natural gas pipelines due to its excellent properties, such as high strength, high toughness, low Bauschinger effect and good weldability. In the 1980s, the German Mannesmann company developed and laid a 3.2km X80 test pipeline. Since then, the research and development and application of X80 pipeline steel have continued to expand, especially in Japan, Canada and other countries.

[0004] However, the production of thick X80M pipeline steel still faces many challenges. First, the low-temperature toughness of thick materials is insufficient, which is particularly evident in extreme climate conditions. Second, the existing production process is inefficient, resulting in increased production costs, which limits the widespread application of thick X80M pipeline steel. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an X80M pipeline steel plate and a production method thereof. By optimizing the chemical composition and the production process, the manufacture of high-performance X80M pipeline steel with a thickness greater than or equal to 40 mm is achieved, meeting the requirements of modern oil and gas transportation for pipeline materials.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A X80M pipeline steel plate, the steel grade of the pipeline steel plate is L555 / X80 level, the thickness of the pipeline steel plate is ≥40mm, the strength difference between the same plate is ≤50MPa, the average value of the -20°C drop hammer shear surface ratio is ≥85%, and the chemical composition and corresponding mass percentages are: C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 1.60-1.70%, P: ≤0.015%, S: ≤0.05%, Cr: ≤0.20%, Ni: 0.15-0.25%, Mo: 0.10-0.15%, Nb: 0.05-0.06%, Ti: 0.01-0.02%, Al: 0.02-0.05%, and the rest are iron and unavoidable impurity elements, and the carbon equivalent satisfies Pcm≤0.19%.

[0008] A method for producing X80M pipeline steel plate specifically comprises the following steps:

[0009] Prepare molten iron according to the predetermined chemical composition requirements of 0.30%≤Si≤0.60%, Mn≤0.40%, S≤0.040%, P≤0.120%;

[0010] The hot metal was pretreated for desulfurization using the KR stirring method;

[0011] The pretreated molten iron is poured into a BOF converter for smelting, and the process conditions are controlled to convert the molten iron into molten steel. When the BOF converter is tapped, ferrosilicon → metallic manganese → aluminum ingot → lime are added in sequence to adjust the chemical composition of the molten steel;

[0012] Refining the molten steel by LF furnace to further adjust and optimize the chemical composition of the molten steel;

[0013] Degassing and vacuuming the molten steel by means of an RH furnace, and controlling process parameters to remove gas impurities in the molten steel;

[0014] The molten steel is continuously casted into a solid slab through CCM;

[0015] The slab is subjected to a reheating treatment, during which the heating temperature and the time in the furnace are controlled;

[0016] Before rough rolling, steel is tapped 2 to 5 minutes in advance to pre-warm the slab;

[0017] Rough rolling is performed on the slab to widen it and form an intermediate slab;

[0018] The intermediate billet after rough rolling is placed in a waiting zone for cooling to obtain a suitable organizational state of the intermediate billet;

[0019] The cooled intermediate billet is finish rolled to lengthen it and form a steel plate;

[0020] The MULPIC accelerated cooling system is used to cool the steel plate and control the cooling rate to ensure that the steel plate obtains a uniform microstructure;

[0021] Hot straightening is performed on the steel plate after accelerated cooling to improve the plate shape;

[0022] The hot straightened steel plate is naturally cooled to room temperature on a cooling bed;

[0023] After natural cooling, the steel plate is subjected to warm and cold straightening to further improve the plate shape;

[0024] Cooling the steel plate offline for subsequent ultrasonic flaw detection;

[0025] Conduct ultrasonic testing on steel plates to detect internal defects and ensure the internal quality of the steel plates;

[0026] The steel plates that pass the flaw detection are subjected to final finishing treatment to form finished steel plates, including size verification, steel plate marking and warehousing. The thickness of the finished steel plates is ≥40mm.

[0027] Furthermore, the process parameters of the RH degassing are controlled as follows: vacuum degree <2mbar, H <2.0ppm; vacuum degree <2mBar, degassing time ≥12 minutes, 150m of seamless calcium silicon wire is fed into the RH furnace, the soft stirring time after the seamless calcium silicon wire is fed is not less than 12 minutes, the RH furnace is hydrogenated before the molten steel breaks through the air, H ≤ 2ppm, and the vacuum tank on the RH furnace is cleaned regularly to keep the thickness of the cold steel ≤ 30cm.

[0028] Furthermore, when the BOF converter is tapping steel, there is a corresponding relationship between the amount of aluminum ingot added and the oxygen content in the molten steel, specifically:

[0029] When the oxygen content is 0-500PPm, add 14Kg of aluminum ingot per ton of molten steel;

[0030] When the oxygen content is 501-600PPm, add 15Kg of aluminum ingot per ton of molten steel;

[0031] When the oxygen content is 601-700PPm, add 16Kg of aluminum ingot per ton of molten steel;

[0032] When the oxygen content is 701-800PPm, add 17Kg of aluminum ingot per ton of molten steel;

[0033] When the oxygen content is greater than 800PPm, add 18Kg of aluminum ingot per ton of molten steel.

[0034] Furthermore, when the molten steel is refined by the LF furnace, an appropriate amount of lime and / or fluorite is added to adjust the slag according to the slag condition during the power-on period, and calcium carbide is added to diffusely deoxidize the molten steel to further reduce the oxygen content in the molten steel. Alloy materials are selected to fine-tune the composition of the molten steel. The alloy materials include: silicon alloy, manganese alloy, ferroniobium, ferromolybdenum, ferrochrome, and nickel plate.

[0035] Furthermore, when the slab is reheated, the cross-section of the slab is 320 mm; the slab is reheated by step heating, the temperature of the preheating section is controlled at 1000-1150°C, the temperature of the first heating section is controlled at 1100-1200°C, the temperature of the second heating section is controlled at 1170-1230°C, the temperature of the soaking section is controlled at 1170-1220°C, and the time in the furnace is not less than 1.2 min / mm.

[0036] Furthermore, during the CCM continuous casting process, a long shroud, a tundish covering agent, an immersed shroud and a seal are used for full protection casting.

[0037] Furthermore, in the rough rolling, the rough rolling temperature is controlled at 950-1050°C, the single-pass reduction rate in the rough rolling stage is ≥10%, the rolling force is not less than 5500 tons, and after rough rolling, the thickness of the intermediate billet is 3.5 to 4.5 times the thickness of the finished steel plate.

[0038] Furthermore, during the finishing rolling process, the starting temperature of the finishing rolling is ≤770°C, the first pass of the finishing rolling is also the first pass of the elongation, and the reduction in a single pass is ≥12%; the reduction in a single pass of the last two passes in the finishing rolling stage is ≤10%; the final rolling temperature of the steel plate is controlled at 750±20°C, and the total compression ratio in the finishing rolling stage is ≥70%.

[0039] Furthermore, the MULPIC accelerated cooling system is configured so that during the cooling process, the cooling water ratio of the upper and lower surfaces of the steel plate is ≥0.90, the cooling rate is controlled at 20-30°C / s, the proportion of cooling water shielding is ≥90%, the shielding distance parameters of the head and tail of the steel plate are both ≥4m, and the distance parameter for gradually recovering to the set cooling water volume after shielding is set to ≥3m, which effectively improves the strength difference of the same plate and makes the strength distribution of the whole plate more uniform.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention reasonably adjusts the chemical composition and process of the steel plate to make the X80M pipeline steel plate have good drop weight performance, thereby achieving a combination of high strength and good toughness, reaching the performance of L555 / X80 level, and meeting the requirements of modern oil and gas transportation for pipeline construction materials.

[0042] (2) The steel plate of the present invention has an average drop weight shear surface ratio of more than 85% at -20°C, showing excellent low-temperature toughness and is suitable for oil and gas transportation under extreme climatic conditions.

[0043] (3) By optimizing the production process, such as accurately controlling the rolling temperature, reduction ratio and cooling rate, the steel plate of the present invention achieves a strength difference of ≤50MPa, thereby ensuring the uniformity of material properties.

[0044] (4) The present invention introduces innovative process control methods in key process steps, such as seamless calcium silicon wire feeding during RH degassing, controlling the corresponding relationship between the amount of aluminum ingot added and the oxygen content during BOF converter tapping,

[0045] Fine-tuning of alloy materials during LF refining further improves the performance of the steel plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the microstructure of a X80M pipeline steel cross section at 1 / 2 of the thickness of the present invention;

[0047] Figure 2 This is a schematic diagram of the microstructure of a X80M pipeline steel cross section at 1 / 4 of the thickness of the present invention;

[0048] Figure 3 It is a schematic diagram of the microstructure at the surface of the cross section of an X80M pipeline steel of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0050] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0051] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0052] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0053] like Figure 1 to Figure 3 As shown, an X80M pipeline steel plate, the steel grade of the pipeline steel plate is L555 / X80, the thickness of the pipeline steel plate is ≥40mm, the strength is uniform, the strength difference between the same plate is ≤50MPa, the average value of the shear surface ratio of the -20℃ drop hammer is ≥85%, and it has good low temperature toughness. Its chemical composition and corresponding mass percentage are: C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 1.60-1.70%, P: ≤0.015%, S: ≤0.05%, Cr: ≤0.20%, Ni: 0.15-0.25%, Mo: 0.10-0.15%, Nb: 0.05-0.06%, Ti: 0.01-0.02%, Al: 0.02-0.05%, the rest are iron and unavoidable impurity elements, and the carbon equivalent satisfies Pcm≤0.19%.

[0054] Specifically, the consideration strategy for chemical composition and corresponding mass percentage is as follows:

[0055] C: 0.03~0.06%, C≤0.06% has a significant improvement effect on the component segregation in the steel billet, thereby reducing the formation of banded structure in the steel plate. The steel is less likely to crack when deformed, thereby improving the drop weight toughness.

[0056] Si: 0.15-0.25%. Si is added for deoxidation. However, if the addition amount exceeds 0.40%, the toughness of the base material and the weld heat affected zone will be significantly reduced, so the Si amount is set to 0.40% or less. The range of 0.10% to 0.25% is selected.

[0057] Mn: 1.60-1.70%. Mn is mainly added to increase the strength of the base material. It is also a necessary deoxidizer and reducing agent. However, if the addition amount is too small, the effect is not sufficient. In addition, if the addition amount exceeds 5.0%, not only the toughness of the base material deteriorates, but also the center segregation is promoted, making the center of the billet loose and large. The range of 1.60-1.70% is appropriate.

[0058] P: ≤0.015%. P is a harmful element in steel. It has high solubility in Fe and has a strong solid solution strengthening effect, but it will significantly reduce toughness, especially low-temperature toughness. Therefore, the P content in steel should not be too high, preferably not higher than 0.015%.

[0059] S: ≤0.05%. S is also one of the harmful elements. Sulfur exists in steel in the form of iron sulfide. The steel is prone to hot brittleness during processing, which reduces the ductility and toughness of the steel, is not good for welding performance, and reduces corrosion resistance. Therefore, S: ≤0.05% is appropriate.

[0060] Cr: ≤0.20%. Cr can increase the hardenability of steel and have a secondary hardening effect, which can improve the strength and hardness of steel and reduce the elongation and cross-sectional shrinkage. Therefore, Cr should not be too much, and ≤0.20% is appropriate.

[0061] Ni: 0.15-0.25%. Ni can significantly improve the strength of steel, and on the other hand, it can maintain a high level of toughness of the steel plate. However, if the amount added is too much, the economic efficiency will be significantly reduced. Therefore, 0.15-0.25% of Ni is appropriate.

[0062] Mo: 0.10-0.15%. Mo in steel can improve hardenability and heat strength and prevent temper brittleness. The Mo content should not be too high. Excessive Mo will increase the brittleness of the steel and reduce its toughness. Therefore, 0.10-0.15% Mo is appropriate.

[0063] Nb: 0.05-0.06%. A small amount of Nb can improve the strength of steel without affecting the plasticity and toughness of the steel.

[0064] Ti: 0.01-0.02%. Ti can refine grains and improve strength and toughness of steel plates. When Ti exceeds 0.020%, Ti nitrides coarsen and thus reduce toughness of the base material. Therefore, Ti should be within the range of 0.10-0.15%.

[0065] Al: 0.02-0.05%. Al can combine with the oxygen element in steel and effectively absorb other non-metallic inclusions to achieve the effect of deoxidation. Adding an appropriate amount of Al can improve the strength and toughness of steel. Excessive Al is prone to thermal cracking, reducing toughness and affecting welding performance. Therefore, Al should be 0.02-0.05%.

[0066] A method for producing X80M pipeline steel plate specifically comprises the following steps:

[0067] Prepare molten iron according to the predetermined chemical composition requirements of 0.30%≤Si≤0.60%, Mn≤0.40%, S≤0.040%, P≤0.120%;

[0068] The hot metal was pretreated for desulfurization using the KR stirring method;

[0069] The pre-treated molten iron is poured into the BOF converter for smelting. The process conditions are controlled to convert the molten iron into molten steel. When the BOF converter is tapping steel, ferrosilicon → metallic manganese → aluminum ingots → lime are added in sequence to adjust the chemical composition of the molten steel.

[0070] The molten steel is refined through the LF furnace to further adjust and optimize the chemical composition of the molten steel;

[0071] Degassing and vacuuming the molten steel in an RH furnace, controlling process parameters to remove gas impurities in the molten steel;

[0072] The molten steel is continuously cast into a solid slab through CCM;

[0073] The slab is reheated, and the heating temperature and the time in the furnace are controlled during the process;

[0074] Before rough rolling, steel is tapped 2 to 5 minutes in advance to pre-warm the slab;

[0075] The slab is roughly rolled to widen it and form an intermediate slab;

[0076] The intermediate billet after rough rolling is placed in a waiting zone for cooling to obtain a suitable organizational state of the intermediate billet;

[0077] The cooled intermediate billet is finish rolled to lengthen it and form a steel plate;

[0078] The MULPIC accelerated cooling system is used to cool the steel plate and control the cooling rate to ensure that the steel plate obtains a uniform microstructure;

[0079] Hot straightening is performed on the steel plate after accelerated cooling to improve the plate shape;

[0080] The hot straightened steel plate is naturally cooled to room temperature on a cooling bed;

[0081] After natural cooling, the steel plate is subjected to warm and cold straightening to further improve the plate shape;

[0082] The steel plates are stacked and cooled offline for subsequent ultrasonic flaw detection;

[0083] Conduct ultrasonic testing on steel plates to detect internal defects and ensure the internal quality of the steel plates;

[0084] The steel plates that pass the flaw detection are subjected to final finishing treatment to form finished steel plates, including size verification, steel plate marking and warehousing. The thickness of the finished steel plates is ≥40mm.

[0085] Specifically, the process parameters of RH degassing are controlled as follows: vacuum degree <2mbar, H <2.0ppm; vacuum degree <2mBar, degassing time ≥12 minutes, 150m of seamless calcium silicon wire is fed into the RH furnace, the soft stirring time after the seamless calcium silicon wire is fed is not less than 12 minutes, the RH furnace is hydrogenated before the molten steel breaks through the air, H≤2ppm, and the vacuum tank on the RH furnace is cleaned regularly to keep the thickness of the cold steel ≤30cm.

[0086] Specifically, when the BOF converter is tapping steel, there is a corresponding relationship between the amount of aluminum ingot added and the oxygen content in the molten steel, specifically:

[0087] When the oxygen content is 0-500PPm, add 14Kg of aluminum ingot per ton of molten steel;

[0088] When the oxygen content is 501-600PPm, add 15Kg of aluminum ingot per ton of molten steel;

[0089] When the oxygen content is 601-700PPm, add 16Kg of aluminum ingot per ton of molten steel;

[0090] When the oxygen content is 701-800PPm, add 17Kg of aluminum ingot per ton of molten steel;

[0091] When the oxygen content is greater than 800PPm, add 18Kg of aluminum ingot per ton of molten steel.

[0092] Furthermore, when the molten steel is refined by the LF furnace, an appropriate amount of lime and / or fluorite is added to adjust the slag according to the slag condition during the power-on period, and calcium carbide is added to diffuse deoxidize the molten steel to further reduce the oxygen content in the molten steel. Alloy materials are selected to fine-tune the composition of the molten steel. The alloy materials include: silicon alloy, manganese alloy, ferroniobium, ferromolybdenum, ferrochrome, and nickel plate.

[0093] Specifically, when the slab is reheated, the cross section of the slab is 320mm; the slab is reheated by step-by-step heating to perform high-temperature solution treatment, the preheating section temperature is controlled at 1000-1150°C, the first heating temperature is controlled at 1100-1200°C, the second heating temperature is controlled at 1170-1230°C, the soaking section temperature is controlled at 1170-1220°C, and the furnace time is not less than 1.2min / mm. When the heating temperature is increased to 1200°C, the solid solution amount of Nb in the steel is the largest, while the solid solution amount of Ti is extremely low, so Ti still exists in the form of second phase particles. When heated below 1200°C, the austenite grains are relatively small and grow slowly. To obtain a finer austenite grain size, and to make the micro-alloy elements have a higher solid solution amount, improve the center segregation, and improve the toughness of the steel plate.

[0094] Specifically, during the CCM continuous casting process, a long shroud, a tundish covering agent, an immersed shroud and a seal are used for full protection casting.

[0095] Furthermore, during rough rolling, the rough rolling temperature is controlled at 950-1050°C, the single-pass reduction rate in the rough rolling stage is ≥10%, the rolling force is not less than 5500 tons, and after rough rolling, the thickness of the intermediate billet is 3.5 to 4.5 times the thickness of the finished steel plate.

[0096] Specifically, during the finishing rolling process, the starting temperature of the finishing rolling is ≤770°C, the first pass of the finishing rolling is also the first pass of the elongation, and the reduction in a single pass is ≥12%; the reduction in the last two passes of the finishing rolling stage is ≤10%; the final rolling temperature of the steel plate is controlled at 750±20°C, and the total compression ratio in the finishing rolling stage is ≥70%.

[0097] Furthermore, the MULPIC accelerated cooling system is configured so that during the cooling process, the cooling water ratio of the upper and lower surfaces of the steel plate is ≥0.90, the cooling rate is controlled at 20-30°C / s, the proportion of cooling water shielding is ≥90%, the shielding distance parameters of the head and tail of the steel plate are both ≥4m, and the distance parameter for gradually recovering to the set cooling water volume after shielding is set to ≥3m, which effectively improves the strength difference of the same plate and makes the strength distribution of the whole plate more uniform. Among them, along the rolling direction of the steel plate, the head is rolled out first, and the tail is rolled out later.

[0098] Taking 40mmX80M as an example, the smelting composition of the embodiment smelting furnace is shown in Table 1, the smelting furnace and the mother plate rolling process control parameters of the embodiment are shown in Table 2, the mechanical properties of the embodiment mother plate are shown in Table 3, and the hardness value of the embodiment mother plate is shown in Table 4:

[0099]

[0100] Table 1: Chemical composition of smelting furnaces in the example

[0101]

[0102] Table 2: Control parameters of smelting furnaces and mother plate rolling process in the embodiment

[0103]

[0104] Table 3: Mechanical properties of motherboard in the embodiment, Note: SA - shear surface ratio of drop weight fracture

[0105] It can be seen that the final rolling temperature of Example 1 is too high, resulting in unsatisfactory drop hammer performance. The chromium and molybdenum elements in Examples 1 and 2 are higher than those in Examples 3 and 4, which reduces their toughness. The final rolling temperature of Example 2 is low, but the drop hammer performance is poor, which shows that the composition design is particularly important. In order to ensure the stability of the rolling process, the waiting thickness of Examples 3 and 4 is slightly changed, and the drop hammer performance is better than that of Examples 1 and 2. At the same time, the strength difference between the same plate is reduced, and the performance of the steel plate is more uniform.

[0106] In summary, it can be concluded that the X80M pipeline steel plate of the present invention solves the problems of poor drop hammer performance, large strength difference between the same plate, uneven strength distribution of the whole plate, low toughness and poor low temperature resistance of the conventional thick-walled X80M pipeline steel. The production method of the present invention has high efficiency in producing finished steel plates, good plate shape and good drop hammer performance.

[0107] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An X80M pipeline steel plate, characterized in that: The thickness of the pipeline steel plate is ≥40mm, and its chemical composition and corresponding mass percentage are: C: 0.03-0.06%, Si: 0.15-0.25%, Mn: 1.60-1.70%, P: ≤0.015%, S: ≤0.05%, Cr: ≤0.20%, Ni: 0.15-0.25%, Mo: 0.10-0.15%, Nb: 0.05-0.06%, Ti: 0.01-0.02%, Al: 0.02-0.05%, and the rest are iron and unavoidable impurity elements, and the carbon equivalent satisfies Pcm≤0.19%.

2. A method for producing the X80M pipeline steel plate according to claim 1, comprising the following steps: Prepare molten iron according to the chemical composition requirements of 0.30%≤Si≤0.60%, Mn≤0.40%, S≤0.040%, P≤0.120%; The hot metal was pretreated for desulfurization using the KR stirring method; The pretreated molten iron is poured into a BOF converter for smelting, and the process conditions are controlled to convert the molten iron into molten steel. When the BOF converter taps the steel, ferrosilicon, metallic manganese, aluminum ingots and quicklime are sequentially added to adjust the chemical composition of the molten steel; Refining the molten steel by a LF furnace; Degassing and vacuuming the molten steel by means of an RH furnace, and controlling process parameters to remove gas impurities in the molten steel; The molten steel is continuously casted into a solid slab through CCM; reheating the slab; Preheat the slab for 2 to 5 minutes; Rough rolling is performed on the slab to widen it and form an intermediate slab; The intermediate billet after rough rolling is placed in a waiting zone for cooling; The cooled intermediate billet is finish rolled to lengthen it and form a steel plate; Use MULPIC accelerated cooling system to cool the steel plate and control the cooling rate; Hot straightening is performed on the steel plate after accelerated cooling to improve the plate shape; The hot straightened steel plate is naturally cooled to room temperature on a cooling bed; After natural cooling, the steel plate is subjected to warm and cold straightening to further improve the plate shape; Cooling the steel plate offline for subsequent ultrasonic flaw detection; Conduct ultrasonic testing on steel plates to detect internal defects and ensure the internal quality of the steel plates; The steel plates that pass the flaw detection are subjected to final finishing treatment to form finished steel plates, including size verification, steel plate marking and warehousing. The thickness of the finished steel plates is ≥40mm.

3. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: The process parameters of the RH degassing are controlled as follows: vacuum degree <2mbar, H <2.0ppm; vacuum degree <2mBar, degassing time ≥12 minutes, 150m of seamless calcium silicon wire is fed into the RH furnace, the soft stirring time after the seamless calcium silicon wire is fed is not less than 12 minutes, the RH furnace is hydrogenated before the molten steel breaks through the air, H ≤ 2ppm, and the vacuum tank on the RH furnace is cleaned regularly to keep the thickness of the cold steel ≤ 30cm.

4. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: When the BOF converter is tapping steel, there is a corresponding relationship between the amount of aluminum ingot added and the oxygen content in the molten steel, specifically: When the oxygen content is 0-500PPm, add 14Kg of aluminum ingot per ton of molten steel; When the oxygen content is 501-600PPm, add 15Kg of aluminum ingot per ton of molten steel; When the oxygen content is 601-700PPm, add 16Kg of aluminum ingot per ton of molten steel; When the oxygen content is 701-800PPm, add 17Kg of aluminum ingot per ton of molten steel; When the oxygen content is greater than 800PPm, add 18Kg of aluminum ingot per ton of molten steel.

5. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: When the molten steel is refined by the LF furnace, lime and / or fluorite are added to adjust the slag during the power-on period, and calcium carbide is added to diffuse deoxidize the molten steel to further reduce the oxygen content in the molten steel. Alloy materials are selected to fine-tune the composition of the molten steel. The alloy materials include: silicon alloy, manganese alloy, ferroniobium, ferromolybdenum, ferrochrome, and nickel plate.

6. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: When the slab is reheated, the cross-section of the slab is 320 mm; the slab is reheated by step heating, the temperature of the preheating section is controlled at 1000-1150°C, the temperature of the first heating section is controlled at 1100-1200°C, the temperature of the second heating section is controlled at 1170-1230°C, the temperature of the soaking section is controlled at 1170-1220°C, and the time in the furnace is not less than 1.2 min / mm.

7. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: During the CCM continuous casting process, a large ladle with a long shroud, a tundish covering agent, an immersed shroud and a seal are used for full protection casting.

8. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: In the rough rolling, the rough rolling temperature is controlled at 950-1050°C, the single-pass reduction rate in the rough rolling stage is ≥10%, the rolling force is not less than 5500 tons, and after rough rolling, the thickness of the intermediate billet is 3.5-4.5 times the thickness of the finished steel plate.

9. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: During the finishing rolling process, the starting temperature of the finishing rolling is ≤770°C, the first pass of the finishing rolling is also the first pass of the elongation, and the reduction in a single pass is ≥12%; the reduction in a single pass of the last two passes of the finishing rolling stage is ≤10%; the final rolling temperature of the steel plate is controlled at 750±20°C, and the total compression ratio in the finishing rolling stage is ≥70%.

10. The method for producing X80M pipeline steel plate according to claim 2, characterized in that: The MULPIC accelerated cooling system is configured so that during the cooling process, the cooling water ratio of the upper and lower surfaces of the steel plate is ≥0.90, the cooling rate is controlled at 20-30°C / s, the proportion of cooling water shielding is ≥90%, the shielding distance parameters of the head and tail of the steel plate are both ≥4m, and the distance parameter for gradually recovering to the set cooling water volume after shielding is set to ≥3m.

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