Co 2 corrosion resistant pipeline steel plate with high crack arrest toughness and production method therefor

Abstract

A CO2 corrosion resistant pipeline steel plate with high crack arrest toughness and a production method therefor. The chemical components of the steel plate are: C: 0.025%-0.055%, Si: 0.15%-0.30%, Mn: 1.35%-1.55%, P≤0.015%, S≤0.002%, Cr: 0.35%-0.65%, Mo: 0.10%-0.20%, Ni+Cu: 0.40%-0.60%, Nb: 0.040%-0.060%, Ti: 0.010%-0.030%, Al: 0.020%-0.050%, and the balance being Fe and inevitable impurities. The production method for the steel plate comprises the steps of blank heating, rolling, and accelerated cooling. By means of the interaction of all elements in combination with appropriate heating, rolling, and cooling processes, the single structure type of granular bainite is ultimately achieved, and the steel plate has excellent crack arrest toughness and CO2 corrosion resistance.

Description

A CO2 corrosion-resistant pipeline steel plate with high crack arrest toughness and its production method Technical Field

[0001] The present invention relates to the technical field of metal material production, and in particular to a CO2 corrosion-resistant pipeline steel plate with high crack arrest toughness and a production method thereof. Background Art

[0002] Carbon capture, utilization, and storage (CCUS) is a highly promising emerging technology for effectively controlling carbon dioxide emissions. Long-distance pipeline transportation is a key component of CCUS, and supercritical CO2 (temperature > 31°C, pressure > 7.4 MPa) pipeline transportation has rapidly developed due to its optimal economics.

[0003] When supercritical CO2 is transported through a pipeline, if cracks occur in the pipeline, a high stress state will persist at the crack tip, and the crack will continue to expand, leading to long-distance pipeline cracking accidents. During rapid pressure relief, due to the Joule-Thomson effect, the material is exposed to temperatures below the triple point (-56.6°C), and rapidly propagating ductile fractures occur at the same time. This requires the pipe to have excellent low-temperature crack arrest performance. In addition, supercritical CO2 is transported through pipelines at high pressure, and high-pressure service conditions also increase the corrosion rate of the pipe. The existing API carbon steel system pipelines used to transport natural gas may leak and fail in the event of occasional corrosion, reducing the service life of the pipe. Although stainless steel pipelines have good corrosion resistance, they are expensive and difficult to use for long-distance, large-scale CO2 transportation. Therefore, the development of low-alloy carbon steel pipes with high crack arrest toughness and good corrosion resistance is the key to achieving safe long-distance pipeline transportation of supercritical CO2.

[0004] Patent publication number CN202110097162.1 discloses a CO2 corrosion-resistant steel plate and its preparation method. Its chemical composition is: C: 0.03%-0.07%, Cr: 4.0%-6.0%, Ni: 0.15%-2.50%, Nb: 0.01%-0.06%, P ≤ 0.005%, S ≤ 0.005%, with the remainder being Fe and unavoidable impurities. The Cr content in this steel plate exceeds 4%, relying on a high Cr content for enhanced corrosion resistance. The production method utilizes a controlled rolling and cooling process followed by a quenching and tempering heat treatment.

[0005] The invention patent with publication number CN202211192415.4 discloses a low-Cr content CO2 corrosion-resistant oil casing and its preparation method. Its chemical composition is: C: 0.21%-0.29%, Si: 0.25%-0.45%, Mn: 0.90%-1.10%, Cr: 2.95%-5.50%, Mo: 0.35%-0.50%, Ni: 0.15%-0.25%, Cu: 0.15%-0.25%, Nb: 0.05%-0.08%, Ti: 0.02%-0.05%, N: 0.001%-0.010%, Ce: 0.006%-0.010%, Al: 0.005%-0.020%, Ca: 0.005%-0.010%, P≤0.015%, S≤0.005%, O≤0.002%, H≤0.00015%, and the balance is Fe and unavoidable impurities. Its chemical composition contains 0.21%-0.29% of C element, 2.95%-5.50% of Cr element and 0.006%-0.010% of Ce element. The product is a seamless pipe for oil casing, which is produced through hot perforation, hot continuous rolling and heat treatment processes.

[0006] Patent publication number CN02137308.6 discloses a low-alloy steel resistant to carbon dioxide and hydrogen sulfide corrosion. Its chemical composition is: C: 0.15%-0.30%, Si: 0.01%-1.0%, Mn: 0.10%-2.0%, Cr: 0.50%-3.0%, Mo: 0.01%-1.0%, Ce: 0.005%-0.25%, V: 0.005%-0.1%, Cu: 0.05%-1.02%, Al: 0.01%-0.10%. Small amounts of Nb and other elements may be added as needed, with the balance being iron and other unavoidable impurities. The steel contains 0.15%-0.30% C, 0.005%-0.25% Ce, and 0.005%-0.1% V. The product is a seamless oil well pipe with a sorbite microstructure.

[0007] Patent publication number CN201310217916.8 discloses a method for preparing CO2 corrosion-resistant pipeline steel for surface gathering and transportation. Its chemical composition is: C: 0.01%-0.08%, Si: 0.10%-0.50%, Mn: 0.50%-1.50%, P ≤ 0.02%, S ≤ 0.006%, Nb + V + Ti ≤ 0.1%, Cr: 1.0%-3.0%, Mo: 0.10%-0.30%, Cu: 0.10%-0.50%, Ni: 0.10%-0.50%, with the balance being Fe and unavoidable impurities. The steel contains V and 1.0%-3.0% Cr, which enhances corrosion resistance due to the high Cr content. Its metallographic structure is a duplex structure of acicular ferrite and granular bainite. In addition, the service condition of the steel plate described in this invention is an oil and gas transportation environment where the total gas pressure is normal pressure.

[0008] Patent publication number CN202010105910.1 discloses an 8-15mm thick, corrosion-resistant, high-crack-arrest submarine pipeline steel, X65MO, and its production method. Its chemical composition is as follows: C: 0.05%-0.08%, Si: 0.10%-0.20%, Mn: 1.00%-1.20%, P ≤ 0.015%, S ≤ 0.002%, Nb: 0.025%-0.035%, Ti: 0.015%-0.025%, Cr: 0.15%-0.25%, Ce: 0.0010%-0.0020%, H ≤ 2.0 ppm, O ≤ 30 ppm, N ≤ 60 ppm, with the remainder being Fe and unavoidable impurities. Its chemical composition contains 1.00%-1.20% Mn and 0.0010%-0.0020% Ce elements. The product is a steel coil with a thickness of 8-15mm. The metallographic structure is a dual-phase structure of polygonal ferrite and acicular ferrite. The finished product has H2S corrosion resistance and does not involve CO2 corrosion resistance.

[0009] Patent publication number CN200410066297.8 discloses an acicular ferrite X70 pipeline steel with high crack arrest toughness and its manufacturing method. Its chemical composition is: C: 0.020%-0.060%, Mn: 1.45%-1.75%, Si: 0.100%-0.500%, S ≤ 0.0020%, P: 0.004%-0.012%, Nb: 0.050%-0.080%, Ti: 0.005%-0.025%, V: 0.010%-0.060%, Mo: 0.10%-0.30%, Ca: 0.0015%-0.0040%, N ≤ 0.0080%, Al: 0.015%-0.045%. Its chemical composition contains 0.010%-0.060% of V element and no Cr element. Its organizational characteristics are acicular ferrite. In addition, there is no mention of CO2 corrosion resistance.

[0010] Patent publication number CN201710196157.X discloses a high-strength thick steel plate with excellent crack arrestability and its manufacturing method. Its chemical composition is as follows: C: 0.04%-0.16%, Si: 0.1%-0.5%, Mn: 0.9%-1.6%, Cu: 0.1%-0.3%, Ni: 0.2%-0.9%, P ≤ 0.02%, S ≤ 0.02%, Al: 0.01%-0.05%, N: 0.002%-0.010%, Nb: 0.02%-0.05%, Ti: 0.01%-0.03%, and the remainder is Fe and unavoidable impurities. Its chemical composition does not contain Mo and Cr elements. Its production process adopts low-temperature heating, low-temperature rolling and low-temperature cooling. The maximum heating temperature does not exceed 1150℃, the final rolling temperature does not exceed 760℃, the cooling temperature does not exceed 400℃, and it needs to be slowly cooled for 24 hours. In addition, the finished product is container ship steel with a thickness of 50-90mm, and does not involve CO2 corrosion resistance.

[0011] Patent publication number EP3239330B1 discloses a high-strength steel with excellent brittle crack arrest properties and its production method. Its chemical composition is: C: 0.05%-0.1%, Mn: 0.9%-1.5%, Ni: 0.8%-1.5%, Nb: 0.005%-0.1%, Ti: 0.005%-0.1%, Cu: 0.1%-0.6%, Si: 0.1%-0.4%, P ≤ 100ppm, S ≤ 40ppm, with the remainder being Fe and unavoidable impurities. Its chemical composition is high in Ni and contains no Mo or Cr. Its production process utilizes low-temperature heating, with the maximum heating temperature not exceeding 1100°C, and the steel plate cooling temperature not exceeding 700°C. Furthermore, the finished product does not demonstrate CO2 corrosion resistance.

[0012] Patent publication WO2021109439A1 discloses a pipeline steel with both HIC resistance and large deformation resistance, and its manufacturing method. Its chemical composition is as follows: C: 0.015%-0.039%, Si: 0.15%-0.35%, Mn: 1.6%-1.9%, S ≤ 0.002%, P ≤ 0.012%, Al: 0.02-0.045%, Cr: 0.15%-0.35%, Nb + V + Ti ≤ 0.1% (Nb, V, and Ti are all non-zero), Ni: 0.15%-0.50%, Cu: 0.01%-0.25%, Ca ≤ 0.002%, N ≤ 0.0046%, Mo: 0.01%-0.20%, and the remainder is Fe and unavoidable impurities. Its chemical composition has a high Mn content. Although its microstructure is characterized by a bainite single-phase structure, its production process uses relatively low heating and final cooling temperatures. The maximum heating temperature does not exceed 1160°C, and the final cooling temperature is below 280°C. In addition, its finished product is resistant to H2S corrosion, but does not involve CO2 corrosion resistance.

[0013] In summary, the current CO2 corrosion resistant steel plates mainly have the following problems:

[0014] Compositions with CO2 corrosion resistance have high Cr contents, relying on this element to improve the steel's corrosion resistance. Furthermore, the steel's crack arrest toughness is not mentioned, and no specific solutions have been designed to improve this. Pipeline steels with high crack arrest toughness do not address CO2 corrosion resistance and lack CO2 corrosion resistance. Furthermore, the transport medium and material service conditions are all based on low-CO2 oil and gas field environments, not the high-pressure environments of supercritical CO2 transport.

[0015] Summary of the Invention

[0016] In response to the above-mentioned problems and deficiencies, the present invention aims to provide a CO2 corrosion-resistant pipeline steel plate with high crack arrest toughness and a production method thereof. Through the design of the steel plate's composition, manufacturing process, and microstructural control, the ideal internal quality is achieved, harmful elements and impurities are reduced, and the steel plate's microstructure and grain size are effectively improved. By refining and controlling the microstructural composition through appropriate processes, the steel plate's excellent combined crack arrest toughness and CO2 corrosion resistance is ensured.

[0017] In order to achieve the above object, the technical solution of the present invention is as follows:

[0018] On one hand, the present invention provides a CO2 corrosion-resistant pipeline steel plate with high crack arrest toughness. The chemical composition of the steel plate is as follows, by weight percentage: C: 0.025%-0.055%, Si: 0.15%-0.30%, Mn: 1.35%-1.55%, P≤0.015%, S≤0.002%, Cr: 0.35%-0.65%, Mo: 0.10%-0.20%, Ni+Cu: 0.40%-0.60%, Nb: 0.040%-0.060%, Ti: 0.010%-0.030%, Al: 0.020%-0.050%, and the balance is Fe and unavoidable impurities.

[0019] In the above technical solution, further, in terms of weight percentage, Ni / Cu≥0.6.

[0020] The composition design reasons of the present invention are as follows:

[0021] C: The most essential and economical strengthening element in steel. A high C content can easily cause center segregation in steel plates, negatively impacting the steel's corrosion resistance and crack arrest toughness. Therefore, the present invention controls the C content to 0.025%-0.055%.

[0022] Si: It can improve the strength of steel plates through solid solution strengthening, and has the effect of improving the hardenability and corrosion resistance of the material. Among all alloying elements, Si is abundant in resources and relatively inexpensive. Adding an appropriate amount of Si to steel can also inhibit the precipitation of cementite. At the same time, Si will be enriched around carbides, hindering the growth of carbides, causing carbides to become small and dispersed in the matrix, which is beneficial to improving strength. However, a higher content of Si makes steel tend to graphitize, making the steel brittle, reducing plasticity, and worsening toughness. The Si content of the present invention is controlled at 0.15-0.30%.

[0023] Mn: It is a common strengthening element in steel and can be dissolved in the Fe matrix in large quantities to increase strength through solid solution strengthening. Manganese can reduce the critical cooling rate of steel, 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 plasticity, toughness and corrosion resistance of the steel. Taking all factors into consideration, the present invention controls the range of Mn to be 1.35%-1.55%.

[0024] Cr: It can improve the hardenability of steel, strengthen the cooling effect of steel plates, improve the uniformity of the structure in the thickness direction, and make up for the strength loss of the steel plates due to low C and low Mn. The price of Cr alloys is not high. It can not only replace precious metal elements such as Mo and V that have a strengthening effect to reduce the cost of the alloy, but also its hardenability effect is not as strong as Mo under similar content conditions. An appropriate amount of Cr can more stably control the formation of the medium-temperature transformation structure - granular bainite. However, a higher content of Cr will make the hardenability of steel too high, forming too much hardenable structure, making the lamellar structure of the structure obvious, and worsening the crack arrest toughness of the steel plate. Taking all factors into consideration, the present invention controls the range of Cr to be 0.35%-0.65%.

[0025] Mo: Mo improves the hardenability of steel, has a certain grain-refining effect, effectively increases steel strength, promotes low-temperature microstructural transformation, and inhibits ferrite transformation. Combined with elements such as Ni and Cu, it can improve the corrosion resistance of steel plates. Mo is relatively expensive, and adding too much will significantly increase alloy cost. It can also increase hardenability, promote the formation of a large amount of lamellar shear structure, and hinder crack arrest performance. The present invention controls the Mo content within a range of 0.10%-0.20%.

[0026] Ni, Cu: Ni can improve the strength of steel, lower the critical cooling temperature, delay pearlite transformation, facilitate microstructure control and grain refinement, and improve low-temperature toughness. Adding an appropriate amount of Cu can improve the strength, low-temperature toughness and corrosion resistance of steel. However, too high a Cu content can easily cause embrittlement of the steel plate, generate thermal cracks, and reduce toughness. Due to the high price of Ni, it is not advisable to add too much. The combined addition of Ni and Cu can fully play their respective beneficial roles. The present invention controls Ni / Cu to be no less than 0.6, and the range of Ni+Cu is 0.40%-0.60%.

[0027] Nb: A grain-refining element. During heating, undissolved Nb carbon and nitride particles are distributed on the austenite grain boundaries, hindering austenite grain growth during heating. This effectively delays recrystallization of deformed austenite, refines grains, improves steel toughness, and lowers its brittle transition temperature. The present invention controls the Nb content within a range of 0.040% to 0.060%.

[0028] Ti: A strong nitrogen-binding element, adding trace amounts of Ti to aluminum-containing steel can significantly reduce corrosion rates. Ti also preferentially combines with nitrogen in the steel, reducing the amount of AlN and improving weldability. However, when the Ti content exceeds a certain value, the TiN particles coarsen, deteriorating low-temperature toughness. Therefore, the Ti content in this invention is preferably between 0.010% and 0.030%.

[0029] 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. Too high an aluminum content increases aluminum oxide inclusions, reducing the cleanliness of the steel. Therefore, the present invention controls the Al content within a range of 0.020% to 0.050%.

[0030] P and S: As impurity elements, P and S 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 the range of P≤0.015% and S≤0.002%, respectively.

[0031] In the above technical solution, further, the yield strength of the steel plate is 470-570 MPa, the tensile strength is 550-640 MPa, the average impact energy of the steel plate at -60°C is ≥250J, and the average DWTT at -30°C is ≥90%.

[0032] In the above technical solution, further, the final structure of the steel plate is a single granular bainite structure, and the average crystal grain size of the bainite is ≤8μm.

[0033] In the above technical solution, further, the thickness of the finished steel plate is 15-25 mm.

[0034] Another aspect of the present invention provides a method for producing the above-mentioned CO2 corrosion-resistant pipeline steel plate with high crack arrest toughness, comprising heating the billet, rolling and accelerated cooling;

[0035] Billet heating: The billet heating temperature is 1160-1220℃, and the holding time is not less than 120min;

[0036] The design of the heating process is mainly to ensure the full solid solution of elements such as Mn, Cr, Ni, Cu, and Nb, so that they can play a role in subsequent rolling and accelerated cooling, and at the same time, effectively control the growth of austenite grains; the heating time can ensure the heating effect and temperature uniformity;

[0037] Rolling: The billet is rolled directly after being discharged from the furnace, and a three-stage rolling process is adopted, wherein the rough rolling is carried out in two stages. The first stage rolling ends at a temperature ≥1100℃, and then air-cooled to wait for the temperature. The second stage starts at a rolling temperature of 1060-1080℃, and the single-pass reduction rate of the last two passes before the end of rolling is ≥16%. The third stage is finishing rolling, and the finishing rolling start temperature is 870-920℃, the single-pass reduction rate of the first three passes is ≥14%, and the final rolling temperature is Ar3+60℃-Ar3+90℃;

[0038] The two-stage rough rolling process design can fully crush and refine the original austenite grains. In particular, the second stage is rolled at a relatively low temperature, which can effectively reduce the driving force for austenite grain growth and inhibit excessive grain growth. The design of the finishing rolling process can, on the one hand, ensure that the austenite is fully flattened and deformed and accumulate deformation energy. On the other hand, it can promote the induction precipitation of fine Nb precipitates, pinning grain boundaries and dislocations, increasing nucleation sites, and further refining grains.

[0039] Accelerated cooling: After the steel plate is rolled, it is accelerated and cooled in two stages. The first stage starts at a temperature range of Ar3+30℃-Ar3+60℃, with a cooling rate of 25-30℃ / s and a cooling time of 5-8s. After the first stage of cooling, the second stage of cooling is carried out directly. The cooling rate of the second stage is 8-12℃ / s and the final cooling temperature is M s +30℃-M s +80℃;

[0040] The purpose of the first stage cooling process is to inhibit the transformation of austenite to ferrite and to obtain bainite structure in the steel plate at a faster cooling rate; the purpose of the second stage cooling is to control the structure type of bainite transformation, inhibit the generation of coarse lamellar structure, promote the formation of small irregular block structure, and finally obtain a single type of granular bainite structure with an average grain size of ≤8μm; the irregular structure of granular bainite causes the crack propagation path to turn along the irregular grain boundary when the steel plate cracks, consuming the energy of crack propagation, significantly reducing the crack driving force and achieving effective crack arrest; the single type of structure causes the steel plate to corrode uniformly in a supercritical CO2 environment, forming a corrosion passivation film attached to the surface of the steel plate; due to the single and uniform distribution of the structure type, the corrosion conditions at all positions on the surface of the steel plate are the same, and local corrosion is not easy to occur; the formed corrosion passivation film can effectively hinder the further occurrence of corrosion, significantly reduce the corrosion rate, and play a good corrosion resistance role.

[0041] In the above technical solution, further, the thickness of the intermediate billet after rough rolling is 3.3t-4.2t, wherein t is the thickness of the finished steel plate.

[0042] In the above technical solution, further, in the rolling process, the finishing rolling temperature is 820-850°C.

[0043] In the above technical solution, further, in the accelerated cooling process, the first stage of cooling is 790-820°C, and the second stage of final cooling is 490-550°C.

[0044] The beneficial effects of the present invention are:

[0045] This invention utilizes inexpensive elements such as C, Mn, Cr, and Cu, along with trace amounts of Nb and Ni. Through the interaction of these elements and appropriate heating, rolling, and cooling processes, a single microstructure of granular bainite is ultimately achieved. Compared to existing CO2 transport steels and their production technologies, this invention utilizes a targeted microstructure design to improve crack arrest toughness and CO2 corrosion resistance, resulting in a steel plate with both excellent crack arrest toughness and CO2 corrosion resistance.

[0046] The steel plate of the present invention has a yield strength of 470-570 MPa and a tensile strength of 550-640 MPa, reaching X65 grade strength. The steel plate also has an average impact energy of ≥250 J at -60°C, an average DWTT of ≥90% at -30°C, and a uniform corrosion rate of ≤0.07 mm / a in a supercritical CO2 environment. These performance characteristics meet the technical requirements for manufacturing X65-grade steel plate for supercritical CO2 pipeline transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG1 is a metallographic photograph of the steel in Example 5 of the present invention;

[0048] FIG2 is a SEM image of the steel in Example 5 of the present invention. DETAILED DESCRIPTION

[0049] The following examples are only some of the best embodiments of the present invention and do not limit the scope of the above invention and technical means.

[0050] Smelting was carried out according to the designed chemical composition range. The chemical compositions of the steels of Examples 1-9 and Comparative Examples 1-5 are shown in Table 1.

[0051] Table 1 Chemical composition of steels of the present invention and comparative examples (wt%)

[0052] The obtained molten steel is cast to obtain a billet, and the billet is subjected to heating-rolling-accelerated cooling to obtain the steel plate of the present invention;

[0053] The billet heating, rolling and accelerated cooling processes of Examples 1-9 and Comparative Examples 1-5 are shown in Tables 2 to 4.

[0054] Table 2 Billet heating process of the steel of the embodiment of the present invention and the comparative example

[0055] Table 3 Rolling process of the steel of the embodiment of the present invention and the comparative example

[0056] Table 4 Accelerated cooling process of the steel of the embodiment of the present invention and the comparative example

[0057] Conventional mechanical property tests and microstructure characteristic tests were performed on the steels of Examples 1-9 of the present invention and Comparative Examples 1-5. The results are shown in Tables 5 and 6.

[0058] Table 5 Tensile properties of steels in the embodiments of the present invention and comparative examples

[0059] Table 6 CO2 corrosion resistance and microstructure characteristics of the steels of the embodiments of the present invention and the comparative examples

[0060] Note: Corrosion test conditions: test temperature 40℃, pressure 10MPa, corrosion medium is supercritical CO2.

[0061] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A CO-resistant pipeline steel plate with high crack arrest toughness 2 ​ It is characterized in that: The chemical composition of the steel plate is as follows by weight percentage: C: 0.025% - 0.055%, Si: 0.15% - 0.30%, Mn: 1.35% - 1.55%, P ≤ 0.015%, S ≤ 0.002%, Cr: 0.35% - 0.65%, Mo: 0.10% - 0.20%, Ni + Cu: 0.40% - 0.60%, Nb: 0.040% - 0.060%, Ti: 0.010% - 0.030%, Al: 0.020% - 0.050%, and the balance is Fe and unavoidable impurities.

2. The corrosion-resistant pipeline steel plate with high crack arrest toughness according to claim 1 2 ​ It is characterized in that: By weight percentage, Ni / Cu ≥ 0.

6.

3. The corrosion-resistant pipeline steel plate with high crack arrest toughness according to claim 1 2 ​ It is characterized in that: The yield strength of the steel plate is 470 - 570 MPa, the tensile strength is 550 - 640 MPa, the average impact energy of the steel plate at -60°C is ≥ 250 J, and the average value of -30°C DWTT is ≥ 90%.

4. The CO-resistant pipeline steel plate with high crack arrest toughness according to claim 1 2 ​ It is characterized in that: The final structure of the steel plate is a single structure of granular bainite, and the average crystal grain size of bainite is ≤ 8 μm.

5. The CO-resistant pipeline steel plate with high crack arrest toughness according to claim 1 2 ​ It is characterized in that: The thickness of the finished steel plate is 15 - 25 mm.

6. A production method of a pipeline steel plate resistant to CO corrosion with high crack arrest toughness according to any one of claims 1-5 2 ​ It is characterized in that: It includes blank heating, rolling, and accelerated cooling; Blank heating: The temperature of blank heating is 1160 - 1220°C, and the holding time is not less than 120 min; Rolling: After the steel billet is taken out of the furnace, it is directly rolled, and a three-stage rolling process is adopted. Among them, rough rolling is carried out in two stages. The finishing temperature at the end of the first stage is ≥1100°C, and then it is air-cooled to wait for the temperature. The starting rolling temperature in the second stage is 1060 - 1080°C, and the single-pass reduction rate in the last two passes before the end of rolling is ≥16%. The third stage is finish rolling. The starting rolling temperature for finish rolling is 870 - 920°C, and the single-pass reduction rate in the first three passes is ≥14%. The finishing temperature is Ar 3 +60°C - Ar 3 +90°C; Accelerated cooling: After the steel plate rolling is completed, accelerated cooling is carried out. The accelerated cooling is carried out in two stages. The starting cooling temperature in the first stage is Ar 3 +30°C - Ar 3 +60°C, the cooling rate is 25 - 30°C / s, the cooling time is 5 - 8 s. After the first stage of cooling, the second stage of cooling is carried out directly. The cooling rate is 8 - 12°C / s, and the final cooling temperature is M s +30°C -M s +80℃。 7. According to the production method described in claim 6, It is characterized in that: In the rolling process, the thickness of the intermediate billet after rough rolling is 3.3t - 4.2t, where t is the thickness of the finished steel plate.

8. According to the production method described in claim 6, It is characterized in that: In the rolling process, the finishing rolling temperature is 820 - 850°C.

9. According to the production method described in claim 6, It is characterized in that: In the accelerated cooling process, the starting cooling temperature in the first stage is 790 - 820°C, and the final cooling temperature in the second stage is 490 - 550°C.

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