Method for preparing TMCP-state thick oil and gas transmission pipeline steel plate

Abstract

The invention relates to a method for preparing a TMCP-state thick oil and gas transmission pipeline steel plate, and belongs to the technical field of steel manufacturing. The method comprises the following steps: heating a plate blank with set chemical components; rough rolling is conducted on the heated plate blank, and an intermediate blank is obtained; the rough rolling comprises at least three passes of rolling, after the second pass of rolling is finished, the plate blank is subjected to first cooling, and after the third pass of rolling is finished, the plate blank subjected to first cooling is subjected to second cooling; and the intermediate billet is subjected to finish rolling and third cooling in sequence, and the pipeline steel plate is obtained. Cooling between passes is added in the rough rolling process, the surface temperature is reduced, the deformation resistance of the surface is improved, and deformation of key passes is promoted to effectively permeate into the core, so that defects of the core are eliminated, grains of the core are refined, and the purpose of improving the toughness of the core of the thick steel plate is achieved.

Description

Technical Field

[0001] This application relates to the technical field of steel manufacturing, and particularly to a method for preparing TMCP thick-specification oil and gas transmission pipeline steel plates. Background Art

[0002] In the process of modern industrial development, oil and gas pipelines are important infrastructure for ensuring national energy security and economic development, and are the core part of the "blood vessels" of modern industry, making the pipeline steel used for transporting oil and gas an important raw material relied on by the national economic development.

[0003] In recent years, with the increasing demand for oil and gas resources, it is necessary to improve the transportation capacity of pipelines, making pipeline transportation develop towards large-diameter and high-pressure transportation. Therefore, the pipeline will bear greater pressure, and this goal can be achieved by increasing the pipeline wall thickness and raising the strength level of pipeline steel. At the same time, with the improvement of oil and gas field development technology, oil and gas fields in remote areas are continuously developed, and the pipeline laying will pass through many places with extremely harsh environmental conditions such as extremely cold and frozen areas, and the steel plate is required to have a certain toughness reserve under low-temperature environment. However, in the actual production process, due to factors such as limited reduction ratio during rolling and continuous casting billet quality control, it is very difficult to control the core quality of TMCP thick-specification steel plates, resulting in difficulty in achieving an excellent match between strength and toughness for thick-specification oil and gas transmission steel plates. Although increasing the reduction can effectively improve the deformation in the deformation zone, it is difficult to control the deformation uniformity in the thickness direction of the steel plate. Summary of the Invention

[0004] This application provides a method for preparing TMCP thick-specification oil and gas transmission pipeline steel plates to solve the following technical problem: how to improve the strength and toughness of the core of TMCP thick-specification oil and gas transmission pipeline steel plates.

[0005] The embodiments of this application provide a method for preparing TMCP thick-specification oil and gas transmission pipeline steel plates, and the method includes:

[0006] Heating a slab with a set chemical composition;

[0007] Rough-rolling the heated slab to obtain an intermediate billet; the rough-rolling is at least 3-pass rolling, wherein, after the end of the 2nd pass rolling, the slab is subjected to the first cooling, and after the end of the 3rd pass rolling, the slab after the first cooling is subjected to the second cooling;

[0008] Successively subjecting the intermediate billet to finish rolling and the third cooling to obtain a pipeline steel plate.

[0009] Optionally, the cooling rate of both the first cooling and the second cooling is 18°C / s to 25°C / s.

[0010] Optionally, the final cooling temperatures of both the first cooling and the second cooling are 1060°C to 1100°C.

[0011] Optionally, the rough rolling is carried out in 4 to 6 passes. The starting rolling temperature of the rough rolling is 1160°C to 1200°C, and the final rolling temperature of the rough rolling is 980°C to 1040°C.

[0012] Optionally, the starting rolling temperature of the finish rolling is 830°C to 850°C, and the final rolling temperature of the finish rolling is 790°C to 820°C.

[0013] Optionally, the heating temperature is 1200°C to 1250°C, and the holding time of the heating is ≥ 3 h.

[0014] Optionally, the thickness of the intermediate billet is 1.5 to 2.5 times the thickness of the pipeline steel plate.

[0015] Optionally, the starting cooling temperature of the third cooling is 770°C to 790°C, the cooling rate of the third cooling is 20°C / s to 30°C / s, and the final cooling temperature of the third cooling is 350°C to 550°C.

[0016] Optionally, the specified chemical composition includes: C: 0.060% to 0.10%, Si: 0.2% to 0.4%, Mn: 1.20% to 1.90%, P ≤ 0.01%, S ≤ 0.0030%, Alt: 0.02% to 0.05%, Ni: 0.15% to 0.25%, Nb: 0.025% to 0.085%, Mo: 0.1% to 0.3%, and the matrix element Fe.

[0017] Optionally, the thickness of the pipeline steel plate is 20 mm to 65 mm.

[0018] Optionally, the pipeline steel plate is any one of X80 and X90.

[0019] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0020] The present application provides a method for preparing a TMCP-state thick-specification oil and gas transmission pipeline steel plate. The method includes: heating a slab with a set chemical composition; rough rolling the heated slab to obtain an intermediate slab; the rough rolling is at least three-pass rolling, wherein, after the end of the second pass rolling, the slab is subjected to a first cooling, and after the end of the third pass rolling, the slab after the first cooling is subjected to a second cooling; the intermediate slab is successively subjected to finish rolling and a third cooling to obtain a pipeline steel plate. By adding cooling between passes during rough rolling, the surface temperature is reduced, the deformation resistance of the surface is increased, and the deformation in the key passes effectively penetrates into the core, thereby eliminating core defects and refining the core grains, so as to achieve the purpose of improving the strength and toughness of the core of the thick-specification steel plate. Description of the Drawings

[0021] The drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic flow chart of a method for preparing a TMCP-state thick-specification oil and gas transmission pipeline steel plate provided by an embodiment of the present application. Detailed Embodiments

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0025] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0026] In this document, terms including "comprising" and the like mean "including but not limited to". Relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the associated relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "a plurality" means two or more; "at least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single items (pieces) or plural items (pieces); for example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both mean: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively. "Parts representation method" such as parts by weight, parts by mass, etc. represents the proportional relationship between each component. In the proportional relationships involved in this document, the parameters that need to be described by proportion should be understood as the antecedents of the proportional formula in the order of description, and the proportional numbers should be understood as the consequents of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0027] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in this document can be obtained through market purchases or can be prepared by existing methods.

[0028] Figure 1 It is a schematic flow diagram of a method for preparing a TMCP - state thick - specification steel plate for oil and gas transmission pipelines provided for the embodiments of the present application.

[0029] As Figure 1 shown, the present application provides a method for preparing a TMCP state thick specification oil and gas transmission pipeline steel plate, and the method includes:

[0030] S1. Heating a slab with a set chemical composition;

[0031] Heating a slab with a set chemical composition is the primary step in preparing a TMCP state thick specification oil and gas transmission pipeline steel plate. This step directly affects the microstructure evolution and final mechanical properties of the steel plate during subsequent rolling and cooling processes.

[0032] In some embodiments, the set chemical composition includes: C: 0.060% - 0.10%, Si: 0.2% - 0.4%, Mn: 1.20% - 1.90%, P ≤ 0.01%, S ≤ 0.0030%, Alt: 0.02% - 0.05%, Ni: 0.15% - 0.25%, Nb: 0.025% - 0.085%, Mo: 0.1% - 0.3%, and the matrix element Fe.

[0033] Fe is the matrix element, and the specific content / content range of Fe can be obtained through the upper and lower limit formulas of the components, that is:

[0034] The sum of the percentage contents of each component in a composition should be equal to 100%, and the content ranges of several components should meet the following conditions: the upper limit value of a certain component + the lower limit values of other components ≤ 100; the lower limit value of a certain component + the upper limit values of other components ≥ 100.

[0035] Obtaining a slab with a set chemical composition can lay a solid foundation for subsequent rolling and heat treatment processes. The optimized combination of these chemical components helps to achieve high strength, high toughness, and excellent comprehensive properties of the TMCP state thick specification oil and gas transmission pipeline steel plate.

[0036] In some embodiments, the heating temperature is 1200°C - 1250°C, and the holding time of the heating is ≥ 3h.

[0037] Within the heating temperature range of 1200°C - 1250°C, the metal atoms inside the slab can obtain sufficient energy for diffusion and rearrangement, thereby optimizing its microstructure. At the same time, this temperature range can also effectively eliminate the internal stress and tissue defects generated during the solidification process of the slab, improving the overall performance of the material. Exemplarily, the heating temperature can be 1200°C, 1210°C, 1220°C, 1230°C, 1240°C, 1250°C, etc.

[0038] A holding time of not less than 3 hours can ensure that the slab reaches a uniform temperature from the surface to the core, avoiding thermal stress and non-uniformity of the microstructure caused by excessive temperature gradient. In addition, sufficient holding time helps further diffusion and rearrangement of metal atoms inside the slab, thereby refining the grains and improving the strength and toughness of the material. Exemplarily, the holding time for heating can be 3h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, etc.

[0039] S2. Rough roll the heated slab to obtain an intermediate billet; the rough rolling is at least 3-pass rolling. Among them, after the end of the second pass rolling, the slab is subjected to the first cooling, and after the end of the third pass rolling, the slab after the first cooling is subjected to the second cooling;

[0040] After heating is completed, the slab enters the rough rolling stage. In the process of manufacturing TMCP state thick-specification oil and gas transmission pipeline steel plates, the rough rolling stage mainly occurs in the recrystallization zone. By precisely controlling the rolling temperature and the number of rolling passes, the purpose of refining the grains, improving the microstructure uniformity, and enhancing the material properties can be achieved.

[0041] Rolling in the recrystallization zone refers to the rolling area where the internal structure of the steel undergoes recrystallization during rolling. During rough rolling, the metal undergoes strong plastic deformation, increasing the dislocation density inside it and forming work hardening. However, during rolling in the recrystallization zone, these dislocations are consumed by the recrystallization process, thus avoiding the accumulation of work hardening. At the same time, within the recrystallization zone, due to the relatively high rolling temperature, the dislocation density inside the rolled piece decreases, and dynamic recovery and recrystallization processes occur, making the microstructure of the rolled steel more uniform and finer.

[0042] In some embodiments, the rough rolling is 4-pass to 6-pass rolling, the starting rolling temperature of the rough rolling is 1160°C to 1200°C, and the finishing rolling temperature of the rough rolling is 980°C to 1040°C.

[0043] The starting rolling temperature is set to 1160°C to 1200°C to ensure that the metal has sufficient plasticity before rolling, facilitating deformation, and at the same time avoiding grain coarsening caused by too high a temperature. Exemplarily, the starting rolling temperature of the rough rolling can be 1160°C, 1165°C, 1170°C, 1175°C, 1180°C, 1185°C, 1190°C, 1195°C, 1200°C, etc.; the selection of the finishing rolling temperature is crucial for refining the grains, improving the microstructure uniformity, and enhancing the comprehensive properties of the material. In the embodiments of the present application, the finishing rolling temperature is controlled at 980°C to 1040°C. If the finishing rolling temperature is lower than 980°C, it may lead to work hardening, while if the finishing rolling temperature is higher than 1040°C, it may cause the grains to coarsen again. Exemplarily, the finishing rolling temperature of the rough rolling can be 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, etc.

[0044] In the embodiment of the present application, the rough rolling stage is 4 to 6 passes of rolling. Through multiple passes of rolling, the original ingot structure can be gradually refined to form more uniform and fine grains. Fine grains help to improve the strength and toughness of the material because the grain boundaries can hinder the movement of dislocations, thereby improving the deformation resistance of the material. In the rough rolling stage, water cooling control is performed between the second and third passes and between the third and fourth passes, that is, the first cooling and the second cooling.

[0045] In some embodiments, the cooling rates of the first cooling and the second cooling are both 18° C. / s to 25° C. / s.

[0046] If the cooling rate of the first cooling is lower than 18°C / s, it is easy to cause grain coarsening, and the coarsened grains will be inherited in the entire TMCP process, which will cause the final microstructure grain size to be too large, which will have an adverse effect on fracture toughness; if the cooling rate of the first cooling is higher than 25°C / s, it is easy to cause rapid cooling of the surface, and a large stress will be generated in the core, which will have an adverse effect on fracture toughness. Exemplarily, the cooling rate of the first cooling can be 18°C / s, 19°C / s, 20°C / s, 21°C / s, 22°C / s, 23°C / s, 24°C / s, 25°C / s, etc.

[0047] If the cooling rate of the second cooling is lower than 18°C / s, it will cause the austenite grains to coarsen, which will have an adverse effect on the performance of the steel plate; if the cooling rate of the second cooling is higher than 25°C / s, it is easy to cause uneven cooling along the thickness direction, and the hardness difference between the organizations is greater, which will have an adverse effect on the uniformity of strength and fracture toughness. Exemplarily, the cooling rate of the second cooling can be 18°C / s, 19°C / s, 20°C / s, 21°C / s, 22°C / s, 23°C / s, 24°C / s, 25°C / s, etc.

[0048] In some embodiments, the final cooling temperature of the first cooling and the second cooling are both 1060°C to 1100°C.

[0049] If the final cooling temperature of the first cooling is lower than 1060°C, mixed crystal structure is likely to appear, and the waiting time is long, which affects the production efficiency; if the final cooling temperature of the first cooling is higher than 1100°C, grain coarsening is likely to occur, which will have an adverse effect on the final fracture toughness of the steel plate. Exemplarily, the final cooling temperature of the first cooling can be 1060°C, 1065°C, 1070°C, 1075°C, 1080°C, 1085°C, 1090°C, 1095°C, 1100°C, etc.

[0050] If the final cooling temperature of the second cooling is lower than 1060°C, the target austenite grain size cannot be obtained, and a long waiting time will reduce production efficiency; if the final cooling temperature of the second cooling is higher than 1100°C, austenite grain coarsening is likely to occur, which will have an adverse effect on the final fracture toughness of the steel plate. Exemplarily, the final cooling temperature of the second cooling can be 1060°C, 1065°C, 1070°C, 1075°C, 1080°C, 1085°C, 1090°C, 1095°C, 1100°C, etc.

[0051] For thick - gauge steel plates, due to the limitations of thickness and rolling capacity, temperature changes and rolling deformation are difficult to penetrate to the core; in the embodiment of the present application, cooling between passes is added during rough rolling to reduce the surface temperature and increase the surface deformation resistance. At this time, due to the large thickness of the steel plate, the core temperature is still relatively high and it is easy to deform. This will promote the effective penetration of the deformation in the key passes of the rough rolling stage to the core, which is beneficial to eliminating the defects in the core and at the same time refining the grain size of the core to achieve the purpose of improving the strength and toughness of the core of the thick - gauge steel plate.

[0052] In some embodiments, the thickness of the intermediate billet is 1.5 to 2.5 times the thickness of the pipeline steel plate.

[0053] A reasonable thickness of the intermediate billet helps to ensure that the steel plate can obtain a uniform and fine microstructure during finish rolling, thereby improving its strength and toughness. In the embodiment of the present application, the thickness of the intermediate billet is limited to 1.5 to 2.5 times the thickness of the finished pipeline steel plate.

[0054] S3. Subject the intermediate billet to finish rolling and third cooling in sequence to obtain a pipeline steel plate.

[0055] In the embodiment of the present application, the finish rolling stage is rolling in the non - recrystallization zone. The non - recrystallization zone refers to the region where, after the metal is plastically deformed, due to the relatively low temperature, the recrystallization process cannot be triggered, thus maintaining the deformed microstructure. When rolling in the non - recrystallization zone, due to the low temperature, the dislocations and deformation structures inside the metal are retained and not eliminated by the recrystallization process. This helps to refine the grains because the deformation promotes the multiplication and interaction of dislocations, thereby increasing the nucleation sites and being beneficial to the formation of new grains. The steel plate after finish rolling also needs to be cooled, that is, the third cooling stage.

[0056] In some embodiments, the starting rolling temperature of the finish rolling is 830°C to 850°C, and the final rolling temperature of the finish rolling is 790°C to 820°C.

[0057] The starting rolling temperature of finish rolling is set at 830°C to 850°C. The selection of this temperature range helps the metal to undergo uniform plastic deformation during finish rolling, laying a good foundation for the subsequent cooling and coiling processes. Exemplarily, the starting rolling temperature of finish rolling can be 830°C, 835°C, 840°C, 845°C, 850°C, etc.

[0058] The finishing rolling temperature of finish rolling is set at 790°C to 820°C. Within this temperature range, dislocations and deformation energy within the metal are fully released and re-arranged, which helps to form a fine and uniform microstructure. At the same time, the finishing rolling temperature of 790°C to 820°C can also ensure that no adverse microstructure transformation occurs during the cooling of the steel plate, such as the formation of brittle phases, etc. Exemplarily, the finishing rolling temperature of finish rolling can be 790°C, 795°C, 800°C, 805°C, 810°C, 815°C, 820°C, etc.

[0059] In some embodiments, the starting cooling temperature of the third cooling is 770°C to 790°C, the cooling rate of the third cooling is 20°C / s to 30°C / s, and the final cooling temperature of the third cooling is 350°C to 550°C.

[0060] The starting cooling temperature of the steel plate is set at 770°C to 790°C. The selection of this temperature range aims to ensure that the steel plate has appropriate plasticity before cooling, avoiding excessive internal stress and cracks during cooling. At the same time, the starting cooling temperature of 770°C to 790°C also helps to refine the microstructure after cooling and improve the comprehensive performance of the steel plate. Exemplarily, the starting cooling temperature of the third cooling can be 770°C, 775°C, 780°C, 785°C, 790°C, etc.

[0061] The cooling rate is controlled between 20°C / s and 30°C / s. The selection of this speed range is for rapid cooling, thereby refining the microstructure, increasing strength and hardness. A cooling rate of 20°C / s to 30°C / s helps to inhibit the growth of grains and promote the formation of favorable microstructures. However, a cooling rate faster than 30°C / s may also lead to an increase in internal stress and the generation of cracks. Exemplarily, the cooling rate of the third cooling can be 20°C / s, 22°C / s, 24°C / s, 26°C / s, 28°C / s, 30°C / s, etc.

[0062] The final cooling temperature is set to 350°C to 550°C. This temperature range is selected to ensure that no adverse microstructure transformation occurs during the cooling process of the steel plate, such as the formation of brittle phases. At the same time, the final cooling temperature of 350°C to 550°C also helps to reduce internal stress and crack generation. After cooling to 350°C to 550°C, the steel plate is air-cooled to room temperature, and the process of air-cooling to room temperature further releases the residual stress inside the steel plate and improves the stability of the steel plate. Exemplarily, the final cooling temperature of the third cooling can be 350°C, 370°C, 390°C, 410°C, 430°C, 450°C, 470°C, 490°C, 510°C, 530°C, 550°C, etc.

[0063] In some embodiments, the thickness of the pipeline steel plate is 20 mm to 65 mm.

[0064] In the embodiments of the present application, the manufactured TMCP-state thick-specification oil and gas transmission pipeline steel plate has a specific thickness range of 20 mm to 65 mm. Exemplarily, the thickness of the pipeline steel plate can be 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, etc.

[0065] In some embodiments, the pipeline steel plate is any one of X80 and X90.

[0066] In the embodiments of the present application, the manufactured TMCP-state thick-specification oil and gas transmission pipeline steel plate is any one of X80 and X90.

[0067] The following further elaborates the present application in conjunction with specific embodiments. The experimental methods without specific conditions noted in the following embodiments are generally determined according to national standards / industry standards; if there are no corresponding national standards / industry standards, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0068] A slab with a set chemical composition (wt%) is obtained, as shown in Table 1.

[0069] Table 1 Chemical composition of the slab (wt%)

[0070]

[0071]

[0072] Based on the chemical composition of the slab, this embodiment also provides a method for preparing a TMCP-state thick-specification oil and gas transmission pipeline steel plate, including the following steps:

[0073] Heat the slab with a set chemical composition.

[0074] The heated slab is rough rolled to obtain an intermediate slab; the rough rolling is at least 3 - pass rolling. Among them, after the second - pass rolling is completed, the slab is subjected to the first cooling, and after the third - pass rolling is completed, the slab after the first cooling is subjected to the second cooling;

[0075] The intermediate slab is successively subjected to finish rolling and the third cooling to obtain a pipeline steel plate. For the process parameters of the preparation of the pipeline steel plate, please refer to Table 2.

[0076] Table 2 Process parameters for the preparation of the pipeline steel plate

[0077]

[0078] The pipeline steel plates provided in the examples and comparative examples are subjected to performance tests, and the results are shown in Table 3.

[0079] Table 3

[0080]

[0081]

[0082] As can be seen from Tables 1 - 3, the examples have excellent strength - toughness matching. In Comparative Examples 1 - 2, there is no water cooling in the rough rolling stage, the Charpy impact at - 40°C does not reach 200 J, and the drop - weight DWTT of the center at - 15°C does not reach 85%, so they do not have excellent matching of strength and toughness.

[0083] In addition, one or more technical solutions in the embodiments of the present invention at least further have the following technical effects or advantages:

[0084] The pipeline steel plate prepared in the embodiment of the present invention effectively solves the problem of great difficulty in controlling the quality of the center of thick - gauge steel plates, and ensures the uniformity and fine - graining of the center structure.

[0085] The above - mentioned are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features claimed in the present application.

Claims

1. A method for preparing a TMCP thick-gauge oil and gas pipeline steel plate, the method comprising: heating a slab having a set chemical composition; Rough rolling the heated slab to obtain an intermediate slab; The rough rolling is performed by at least three rolling passes, wherein after the second rolling pass, the slab is first cooled, and after the third rolling pass, the slab after the first cooling is second cooled; The intermediate billet is sequentially subjected to finish rolling and third cooling to obtain a pipeline steel plate.

2. The method according to claim 1, characterized in that The cooling rates of the first cooling and the second cooling are both 18°C / s to 25°C / s; and / or, The final cooling temperatures of the first cooling and the second cooling are both 1060°C to 1100°C.

3. The method according to claim 1, characterized in that The rough rolling is performed in 4 to 6 passes, the starting rolling temperature of the rough rolling is 1160° C. to 1200° C., and the finishing rolling temperature of the rough rolling is 980° C. to 1040° C.

4. The method according to claim 1, characterized in that: The start rolling temperature of the finishing rolling is 830°C to 850°C, and the final rolling temperature of the finishing rolling is 790°C to 820°C.

5. The method according to claim 1, characterized in that The heating temperature is 1200° C. to 1250° C., and the heating insulation time is ≥3h.

6. The method according to claim 1, characterized in that The thickness of the intermediate billet is 1.5 to 2.5 times the thickness of the pipeline steel plate.

7. The method according to claim 1, characterized in that The start temperature of the third cooling is 770°C to 790°C, the cooling rate of the third cooling is 20°C / s to 30°C / s, and the final cooling temperature of the third cooling is 350°C to 550°C.

8. The method according to claim 1, characterized in that The set chemical composition includes: C: 0.060% to 0.10%, Si: 0.2% to 0.4%, Mn: 1.20% to 1.90%, P≤0.01%, S≤0.0030%, Alt: 0.02% to 0.05%, Ni: 0.15% to 0.25%, Nb: 0.025% to 0.085%, Mo: 0.1% to 0.3%, and matrix element Fe.

9. The method according to claim 1, characterized in that: The thickness of the pipeline steel plate is 20 mm to 65 mm.

10. The method according to claim 1, characterized in that The pipeline steel plate is any one of X80 and X90.

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