X80MS acid-resistant pipeline steel hot rolled steel strip and manufacturing method thereof

Abstract

The invention discloses an X80MS acid-resistant pipeline steel hot rolled steel strip and a manufacturing method thereof, and relates to the technical field of pipeline steel manufacturing. 0.10% to 0.30% of Si; 0.80% to 1.20% of Mn; p: less than or equal to 0.012%; s: less than or equal to 0.0015%; 0.02 to 0.05 percent of Al; 0.060% to 0.080% of Nb; 0.010% to 0.060% of V; ti: 0.005% to 0.020%; 0.10% to 0.30% of Cr; 0.10% to 0.30% of Ni; 0.10% to 0.30% of Cu; 0.10-0.30% of Mo, and the balance Fe and inevitable impurity elements; meanwhile, Ceq is controlled to be smaller than or equal to 0.43%, and Pcm is controlled to be smaller The highest-level limitation of API standard acid-resistant pipeline steel is broken through, and optimization of high strength and HIC and SSC double corrosion resistance is achieved. A refining process is combined with a continuous casting electromagnetic stirring and soft reduction technology, and a high-purity casting blank with the Mannesmann center segregation rating smaller than or equal to the second level is obtained. And in cooperation with an accurate controlled rolling and controlled cooling process, the product forms a uniform fine-grain low-carbon bainite structure, and the problems that thick-specification pipeline steel is uneven in structure and insufficient in corrosion resistance are effectively solved.

Description

Technical Field

[0001] This application belongs to the field of pipeline steel manufacturing technology, and in particular relates to a hot-rolled steel strip of X80MS acid-resistant pipeline steel and its manufacturing method. Background Technology

[0002] Pipeline transportation, as the core method for long-distance oil and natural gas transport, has become the preferred choice for energy transportation due to its economy, safety, and efficiency. However, as global oil and gas exploration gradually expands into complex environments such as deep seas and high-sulfur formations, the content of hydrogen sulfide (H2S) in the transported media has increased significantly, placing extremely stringent requirements on the corrosion resistance of pipeline steel. Hydrogen-induced cracking (HIC) and sulfide stress corrosion cracking (SSC) caused by hydrogen sulfide not only shorten the service life of steel pipes but may also lead to oil and gas leaks, resulting in safety accidents and huge economic losses. Therefore, the research and development and upgrading of acid-resistant pipeline steel has become an urgent need for the industry.

[0003] Currently, the highest grade of acid-resistant pipeline steel specified by the international API standard is X70MS, and the highest grade for commercial mass application is only X65MS. Commonly used grades are mainly X52MS and X60MS, while mature preparation technology for high-grade X80MS acid-resistant pipeline steel is still lacking. The development of X80MS grade pipeline steel faces multiple technical bottlenecks: on the one hand, there is an inherent contradiction between high strength and resistance to hydrogen sulfide corrosion. Increasing the steel grade and thickness will exacerbate compositional segregation and uneven microstructure, thereby reducing corrosion resistance; on the other hand, existing technical solutions have obvious defects. For example, patent CN107974614A discloses a production method for X80 grade pipeline steel resistant to hydrogen sulfide corrosion cracking, but its C and Mn content is too low. To ensure the performance of products of the same thickness, more alloying elements need to be added, which leads to an increase in production costs. Furthermore, this patent only involves resistance to HIC and does not mention resistance to SSC. In addition, the patent with publication number CN107604249A discloses an economical pipeline steel resistant to HIC and SSCC X80MS, but its product is a hot-rolled medium plate, which cannot meet the industrial application requirements of steel strip, and the Mn content is too high, which easily causes central segregation, resulting in unstable resistance to hydrogen sulfide corrosion.

[0004] Furthermore, acid-resistant pipeline steel has much higher requirements for steel purity, billet uniformity, and weldability than ordinary pipeline steel: impurities such as P and S in the steel are prone to segregation, which worsens corrosion resistance; inclusions such as MnS are the main cause of HIC (High-Intensity Corrosion); uneven microstructure leads to stress concentration and reduces resistance to SSC (Sedimentation-Solid Capacity); at the same time, the composition design of high-grade pipeline steel needs to balance strength and weld toughness, avoiding a decline in weldability due to excessive addition of alloying elements. Therefore, there is an urgent need to develop a manufacturing technology for X80MS-grade acid-resistant hot-rolled steel strip to solve technical problems such as the synergy between high strength and corrosion resistance, and the compatibility of composition and process. Summary of the Invention

[0005] To address some or all of the technical problems existing in the prior art, this application provides a hot-rolled steel strip of X80MS acid-resistant pipeline steel and its manufacturing method.

[0006] This application provides a hot-rolled X80MS acid-resistant pipeline steel strip with the following chemical composition by mass percentage: C: 0.03-0.06%; Si: 0.10-0.30%; Mn: 0.80-1.20%; P: ≤0.012%; S: ≤0.0015%; Al: 0.02-0.05%; Nb: 0.060-0.080%; V: 0.010-0.060%; Ti: 0.005-0.020%; Cr: 0.10-0.30%; Ni: 0.10-0.30%; Cu: 0.10-0.30%; Mo: 0.10-0.30%, with the balance being Fe and unavoidable impurity elements; while controlling Ceq ≤0.43% and Pcm ≤0.20%.

[0007] Preferably, the Ca content in the chemical composition is controlled to be below 0.006%.

[0008] This application provides a method for manufacturing X80MS acid-resistant pipeline steel hot-rolled strip, characterized by comprising the following steps performed sequentially: Step S1: In the steelmaking stage, during the converter production process, the molten iron meets the pretreatment endpoint conditions of S≤0.005% and slag thickness≤30mm, and the molten iron temperature entering the furnace is ≥1250℃; aluminum shot is added for deoxidation treatment when the steel is tapped from the converter; 500-800kg of lime and 100-300kg of fluorite are added during the LF process, and the total treatment time of the LF furnace is ≥45min. Argon blowing in the LF furnace is used to avoid the molten steel being exposed; during the RH vacuum treatment, the vacuum degree is controlled at ≤4mbar, and the circulation time is not less than 15 minutes. Step S2: In the continuous casting stage, protective casting is adopted, and a four-stage roller electromagnetic stirring and light reduction process is used. The tundish temperature is controlled at 1540-1550℃, and the casting speed is controlled at 0.80-1.25m / min. Step S3: In the hot rolling stage, the slab heating temperature is 1160~1220℃, and the furnace dwell time is 180~220min; the rolling is divided into two stages: roughing and finishing. The finishing temperature of roughing is ≤970℃, and the finishing temperature is 800~850℃; laminar flow cooling is adopted after rolling, with a cooling rate ≥20℃ / s, and the target coiling temperature is controlled at 300~500℃.

[0009] Preferably, in step S1, temperature-controlled deep desulfurization and composition fine-tuning are performed during the LF process.

[0010] Preferably, in step S2, at least one sample is taken from the tail end of the first billet in each pour for low-magnification inspection, and graded according to the Mannesmann center segregation standard, with an acceptance standard of ≤2.

[0011] The X80MS acid-resistant pipeline steel hot-rolled strip and its manufacturing method of this application have the following advantages and positive effects: This application breaks through the highest level limit of API standard acid-resistant pipeline steel, achieving synergistic optimization of high strength and dual corrosion resistance against HIC and SSC. By combining refining processes with continuous casting electromagnetic stirring and light reduction technology, a high-purity billet with a Mannesmann center segregation rating of ≤2 was obtained. Coupled with precise controlled rolling and cooling processes, the product forms a uniform, fine-grained, low-carbon bainitic microstructure with a grain size >10, effectively solving the industry problem of uneven microstructure and insufficient corrosion resistance in thick-gauge pipeline steel. Simultaneously, controlling Ceq ≤0.43% and Pcm ≤0.20% ensures excellent weldability, and the composition design avoids excessive alloying, achieving both economic efficiency and practicality. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for further understanding of the embodiments of this application and constitute a part of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a low-magnification photograph of the X80MS acid-resistant pipeline steel billet of Embodiment 1 of this application; Figure 2 This is a low-magnification photograph of the X80MS acid-resistant pipeline steel billet of Embodiment 2 of this application; Figure 3 This is a photograph of the edge microstructure of the 21.4mm thick X80MS acid-resistant pipeline steel hot-rolled strip of this application; Figure 4 This is a micrograph of the hot-rolled steel strip of the 21.4mm thick X80MS acid-resistant pipeline steel at half its thickness. Figure 5 This is a photograph showing the completion of the HIC test on the X80MS acid-resistant pipeline steel of Example 1 of this application; Figure 6 This is a photograph showing the completion of the HIC test on the X80MS acid-resistant pipeline steel in Example 2 of this application. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0014] This application provides a hot-rolled X80MS acid-resistant pipeline steel strip with the following chemical composition by mass percentage: C: 0.03–0.06%; Si: 0.10–0.30%; Mn: 0.80–1.20%; P: ≤0.012%; S: ≤0.0015%; Al: 0.02–0.05%; Nb: 0.060–0.080%; V: 0.010–0.060%; Ti: 0.005–0.020%; Cr: 0.10–0.30%; Ni: 0.10–0.30%; Cu: 0.10–0.30%; Mo: 0.10–0.30%, with the balance being Fe and unavoidable impurities; and Ceq ≤ 0.43%. The X80MS acid-resistant pipeline steel strip of this application exceeds the highest grade of API standard acid-resistant pipeline steel.

[0015] The roles and effects of each component in the X80MS acid-resistant pipeline hot-rolled steel strip of this application are as follows: Carbon (C) is an extremely effective interstitial solid solution strengthening element, significantly improving the strength of steel. However, increased C content exacerbates C segregation in steel, increasing the failure rate of HIC testing. Simultaneously, excessive C forms carbides, intensifying localized corrosion. Furthermore, increased C content reduces the toughness and weldability of steel. Considering all factors, the design composition is set at 0.03%–0.06%.

[0016] Silicon (Si): In pipeline steel, Si plays two main roles: firstly, it has a certain deoxidizing effect; secondly, it can stabilize and improve strength to a certain extent. However, its content must be strictly controlled, because excessive silicon (usually >0.5%) will significantly increase the material's brittleness and may also worsen the plasticity and toughness of the weld heat-affected zone, thus affecting the overall weldability and corrosion resistance. Taking all factors into consideration, the design composition is determined to be 0.10%–0.30%.

[0017] Manganese (Mn): As an alloying element, it can significantly enhance the strength and toughness of steel, refine grains, and improve hot workability. However, in acid-resistant pipeline steel, its content must be strictly controlled (usually 0.8%–1.4%). Excessive manganese can easily cause segregation, forming banded structures, thereby increasing susceptibility to HIC and SSC. Given the high strength and inherent high corrosion susceptibility of X80MS, after comprehensive consideration, the design composition is set at 0.80%–1.20%.

[0018] Phosphorus (P): An unavoidable impurity element in steel, and its content should be as low as possible. Phosphorus is prone to segregation, which affects its resistance to hydrogen sulfide corrosion. This application controls the P content to below 120 ppm.

[0019] Sulfur (S): A highly harmful element that can induce hydrogen sulfide corrosion (HIC). MnS inclusions formed from sulfur (S) and manganese (Mn) are the most likely sites for HIC formation. Ca (Carbon Dioxide) can alter the morphology of inclusions, making them dispersed spherical bodies, thereby enhancing the steel's resistance to H2S corrosion. However, the Ca content must be precisely controlled within a certain range to avoid the formation of Ca sulfides or oxides that are sensitive to H2S. This application controls the S content to below 15 ppm and the Ca content to below 0.006%.

[0020] Niobium (Nb), Vanadium (V), and Titanium (Ti): Niobium has the most significant grain-refining effect, increasing strength while lowering the ductile-brittle transition temperature. Solid-solution Nb undergoes strain-induced precipitation during subsequent hot rolling, precipitating at dislocations, subgrain boundaries, and grain boundaries. After controlled rolling and cooling, it transforms into fine phase transformation products. The Nb content added in this application is 0.060–0.080%. Vanadium produces precipitation strengthening, thereby increasing yield strength, but it also increases the ductile-brittle transition temperature; therefore, the V content in this application is within 0.035%. Titanium combines with N at high temperatures to form very stable TiN particles, which can control the austenite grain size at relatively high temperatures. It also helps control the grain size of the heat-affected zone during welding, which is very beneficial for improving the toughness of the weld heat-affected zone. This application improves the weldability of steel by adding 0.005%–0.020% Ti.

[0021] Copper (Cu) and nickel (Ni): possess certain corrosion resistance and can improve the strength of steel through solid solution strengthening. The addition of Ni can effectively improve the hot brittleness that Cu easily induces in steel and can also lower the ductile-brittle transition temperature. Therefore, in this application, the content of Cu and Ni is increased by 0.10% to 0.30%.

[0022] Chromium (Cr) is an effective element for increasing the hardenability of steel and improving the uniformity of its microstructure. Microstructure uniformity is one of the important factors affecting the resistance of steel to hydrogen sulfide corrosion. Cr can also improve the strength of low-carbon steel. However, excessive addition of Cr will reduce weldability and weld toughness. In this application, the Cr content is 0.10–0.30%.

[0023] This application provides a method for manufacturing X80MS acid-resistant pipeline steel hot-rolled strip, comprising the following steps performed sequentially: Step S1: In the steelmaking stage, during the converter production process, the molten iron meets the pretreatment endpoint conditions of S≤0.005% and slag thickness≤30mm, and the molten iron temperature entering the furnace is ≥1250℃; aluminum shot is added for deoxidation treatment when the steel is tapped from the converter; 500-800kg of lime and 100-300kg of fluorite are added during the LF process, and the total LF furnace treatment time is ≥45min. Argon blowing in the LF process avoids the molten steel from being exposed, and temperature adjustment, deep desulfurization, and composition fine-tuning are carried out at the same time; during RH vacuum treatment, the vacuum degree is controlled at ≤4mbar, and the circulation time is not less than 15 minutes. Step S2: In the continuous casting stage, protective pouring is adopted, and a four-stage roller electromagnetic stirring and light reduction process are used. The tundish temperature is controlled at 1540-1550℃, and the casting speed is controlled at 0.80-1.25m / min. At least once per casting, a sample is taken from the tail of the first billet of each flow for low-magnification inspection. The sample is rated according to the Mannesmann center segregation standard, and the acceptance standard is ≤2.

[0024] Step S3: In the hot rolling stage, the slab heating temperature is 1160~1220℃, and the furnace dwell time is 180~220min; the rolling is divided into two stages: roughing and finishing. The finishing temperature of roughing is ≤970℃, and the finishing temperature is 800~850℃; laminar flow cooling is adopted after rolling, with a cooling rate ≥20℃ / s, and the target coiling temperature is controlled at 300~500℃.

[0025] The specific implementation methods of this application are described in detail below with reference to the embodiments, but the specific implementation methods of this application are not limited to the following embodiments.

[0026] Example 1: This embodiment provides an acid-resistant pipeline steel with the following chemical composition and mass percentage: C: 0.050%; Si: 0.16%; Mn: 1.10%; P: 0.008%; S: 0.0014%; Al: 0.023%; Nb: 0.07%; V: 0.027%; Ti: 0.013%; Cu: 0.22%; Cr: 0.23%; Ni: 0.21%; Mo: 0.25%; N: 0.0036%; Ca: 0.0046%; the balance is Fe and impurities. Ceq: 0.36%; Pcm: 0.16%.

[0027] The production steps for the aforementioned acid-resistant pipeline steel are as follows: Step S1: In the steelmaking stage, during the converter production process, the molten iron meets the pretreatment endpoint conditions of S≤0.005% and slag thickness≤30mm, and the molten iron temperature entering the furnace is 1280℃; when tapping steel from the converter, 500kg of lime is added, along with appropriate amounts of aluminum shot and fluorite; the total treatment time in the LF furnace is ≥45min, and argon blowing in the LF furnace prevents the molten steel from being exposed, while temperature regulation, deep desulfurization, and composition fine-tuning are carried out simultaneously; during RH vacuum treatment, the vacuum degree is controlled at ≤4mbar, and the circulation time is 20 minutes. Step S2: In the continuous casting stage, protective casting is adopted, and a four-section roller electromagnetic stirring and light reduction process are used. The tundish temperature is controlled at 1543℃ and the casting speed is controlled at 1.05m / min.

[0028] Step S3: In the hot rolling stage, the slab heating temperature is 1180℃ and the furnace dwell time is 190min; the rolling is divided into two stages: roughing and finishing. The finishing temperature of roughing is ≤950℃ and the finishing temperature is 820℃; laminar flow cooling is adopted after rolling, with a cooling rate ≥20℃ / s, and the coiling target temperature is controlled at 320℃ to obtain an ideal fine-grained low-carbon bainite structure.

[0029] As shown in Table 1 below, the mechanical and technological properties of the acid-resistant pipeline steel in Example 1 can be seen.

[0030] Table 1 ; As shown in Table 2 below, the HIC and SSC properties of the acid-resistant pipeline steel in Example 1 can be seen.

[0031] Table 2 ; Appendix Figure 1 The photograph was taken using low magnification to visually demonstrate the macroscopic morphology and internal quality of the cast billet. It clearly shows that the cast billet has no obvious macroscopic defects such as center segregation, porosity, shrinkage cavities and inclusions, confirming that the cast billet of Example 1 meets the technical requirement of Mannesmann center segregation rating ≤ 2.

[0032] Combined with appendix Figure 5 As can be seen, there were no visible cracks on the sample surface and cross section, which is consistent with the test results in Table 2 where CLR, CTR, and CSR were all 0, directly verifying the excellent hydrogen-induced cracking resistance of the product in Example 1; at the same time, no cracks were generated in the SSC test, filling the gap in the existing technology that only focuses on HIC and ignores SSC, and achieving synergistic dual corrosion resistance performance.

[0033] Example 2: This embodiment provides an acid-resistant pipeline steel with the following chemical composition and mass percentages: C: 0.053%; Si: 0.15%; Mn: 1.10%; P: 0.008%; S: 0.0010%; Al: 0.030%; Nb: 0.072%; V: 0.025%; Ti: 0.011%; Cu: 0.22%; Cr: 0.23%; Ni: 0.21%; Mo: 0.24%; N: 0.0033%; Ca: 0.0034%; the balance being Fe and impurities. Ceq: 0.36%; Pcm: 0.16%.

[0034] The production steps for the aforementioned acid-resistant pipeline steel are as follows: Step S1: In the steelmaking stage, during the converter production process, the molten iron meets the pretreatment endpoint conditions of S≤0.005% and slag thickness≤30mm, and the molten iron temperature entering the furnace is 1280℃; when tapping steel from the converter, 500kg of lime is added, along with appropriate amounts of aluminum shot and fluorite; the total treatment time in the LF furnace is ≥45min, and argon blowing in the LF furnace prevents the molten steel from being exposed, while temperature regulation, deep desulfurization, and composition fine-tuning are carried out simultaneously; during RH vacuum treatment, the vacuum degree is controlled at ≤4mbar, and the circulation time is 20 minutes. Step S2: In the continuous casting stage, protective casting is adopted, and a four-section roller electromagnetic stirring and light reduction process are used. The tundish temperature is controlled at 1543℃ and the casting speed is controlled at 1.05m / min.

[0035] Step S3: In the hot rolling stage, the slab heating temperature is 1180℃ and the furnace dwell time is 190min; the rolling is divided into two stages: roughing and finishing rolling. The finishing rolling temperature is 945℃ and the finishing rolling temperature is 824℃; laminar flow cooling is adopted after rolling, with a cooling rate ≥20℃ / s, and the coiling target temperature is controlled at 300℃ to obtain an ideal fine-grained low-carbon bainite structure.

[0036] As shown in Table 3 below, the mechanical and technological properties of the acid-resistant pipeline steel in Example 2 can be obtained.

[0037] Table 3 ; As shown in Table 4 below, the HIC and SSC properties of the acid-resistant pipeline steel in Example 2 can be obtained.

[0038] Table 4 ; Appendix Figure 2 With appendix Figure 1 With the same observation objective, the macroscopic quality state of the billet in Example 2 was displayed through low-magnification macroscopic photography, verifying that the billet in this example also had no significant macroscopic defects, and the Mannesmann center segregation rating was ≤2, further proving the stability and reliability of the billet preparation process of this application.

[0039] Combined with appendix Figure 6 As can be seen, the sample had no visible cracks, which is consistent with the test results in Table 4, proving that the technical solution of this application can stably produce products with HIC and SSC resistance performance meeting the standards.

[0040] Appendix Figure 3 The example provided shows a steel strip with an actual thickness of 21.4 mm. The photograph, taken with a metallographic microscope, illustrates the microstructure of the strip's edge, revealing a uniform, fine-grained, low-carbon bainite structure with a grain size >10, verifying the refinement and uniformity of the microstructure at the edge of the thick-gauge steel strip. (Attached) Figure 4 With appendix Figure 3 Correspondingly, focusing on the microstructure of the central region of the steel strip, the photograph shows that the central region also has a fine-grained low-carbon bainite structure, consistent with the edge structure and without obvious segregation, confirming that the composition design and controlled rolling and cooling process of this application can achieve the uniformity of the overall microstructure of thick steel strips.

[0041] In summary, Tables 1 and 3 show that the yield strength of the product in this application is between 575 and 580 MPa, and the tensile strength is between 700 and 720 MPa, fully meeting the strength requirements of X80 steel grade. Its elongation reaches 41% to 42%, far exceeding the standard value of ≥21%, demonstrating excellent plasticity. The yield-to-tensile strength ratio is only 0.81 to 0.82, far below the limit of ≤0.93, providing higher safety for pipeline welding construction. At -20℃, the impact energy is above 400 J, exhibiting excellent toughness.

[0042] Tables 2 and 4 show that the crack length ratio (CLR), crack thickness ratio (CTR), and crack sensitivity ratio (CSR) of the product in this application are all 0 in the HIC test, and no visible cracks are found in the SSC test. This demonstrates both HIC and SSC performance, overcoming the shortcomings of products that only resist HIC. Furthermore, by controlling the Mn content to 0.80-1.20%, the problem of center segregation caused by high Mn content is avoided. The consistent corrosion resistance of the two embodiments proves the stability of the technical solution.

[0043] This application breaks through the highest level limit of API standard acid-resistant pipeline steel, achieving synergistic optimization of high strength and dual corrosion resistance against HIC and SSC. By combining refining processes with continuous casting electromagnetic stirring and light reduction technology, a high-purity billet with a Mannesmann center segregation rating of ≤2 was obtained. Coupled with precise controlled rolling and cooling processes, the product forms a uniform, fine-grained, low-carbon bainitic microstructure with a grain size >10, effectively solving the industry problem of uneven microstructure and insufficient corrosion resistance in thick-gauge pipeline steel. Simultaneously, controlling Ceq ≤0.43% and Pcm ≤0.20% ensures excellent weldability, and the composition design avoids excessive alloying, achieving both economic efficiency and practicality.

[0044] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely 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. At the same time, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. In addition, the terms "front," "rear," "left," "right," "upper," and "lower" in this document refer to the placement states shown in the accompanying drawings.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A hot-rolled steel strip of X80MS acid-resistant pipeline steel, characterized in that, The chemical composition, by mass percentage, is as follows: C: 0.03–0.06%; Si: 0.10–0.30%; Mn: 0.80–1.20%; P: ≤0.012%. S: ≤0.0015%; Al: 0.02~0.05%; Nb: 0.060~0.080%; V：0.010～0.060%； Ti: 0.005~0.020%; Cr: 0.10~0.30%; Ni: 0.10~0.30%; Cu: 0.10~0.30%; Mo: 0.10~0.30%, with the balance being Fe and unavoidable impurity elements; while controlling Ceq≤0.43% and Pcm≤0.20%.

2. The X80MS acid-resistant pipeline steel hot-rolled strip according to claim 1, characterized in that, The Ca content in the chemical composition is controlled to be below 0.006%.

3. A method for manufacturing X80MS acid-resistant pipeline steel hot-rolled strip as described in claim 1 or 2, characterized in that, The following steps are performed sequentially: Step S1: In the steelmaking stage, during the converter production process, the molten iron meets the pretreatment endpoint conditions of S≤0.005% and slag thickness≤30mm, and the molten iron temperature entering the furnace is ≥1250℃; aluminum shot is added for deoxidation treatment when the steel is tapped from the converter; 500-800kg of lime and 100-300kg of fluorite are added during the LF process, and the total treatment time of the LF furnace is ≥45min. Argon blowing in the LF furnace is used to avoid the molten steel being exposed; during the RH vacuum treatment, the vacuum degree is controlled at ≤4mbar, and the circulation time is not less than 15 minutes. Step S2: In the continuous casting stage, protective casting is adopted, and a four-stage roller electromagnetic stirring and light reduction process is used. The tundish temperature is controlled at 1540-1550℃, and the casting speed is controlled at 0.80-1.25m / min. Step S3: In the hot rolling stage, the slab heating temperature is 1160~1220℃, and the furnace dwell time is 180~220min; the rolling is divided into two stages: roughing and finishing. The finishing temperature of roughing is ≤970℃, and the finishing temperature is 800~850℃; laminar flow cooling is adopted after rolling, with a cooling rate ≥20℃ / s, and the target coiling temperature is controlled at 300~500℃.

4. A method for manufacturing X80MS acid-resistant pipeline steel hot-rolled strip according to claim 3, characterized in that, In step S1, temperature-controlled deep desulfurization and composition fine-tuning are performed during the LF process.

5. A method for manufacturing X80MS acid-resistant pipeline steel hot-rolled strip according to claim 3, characterized in that, In step S2, at least one sample is taken from the tail of the first billet in each pour for low-magnification inspection, and graded according to the Mannesmann center segregation standard, with an acceptance standard of ≤2.

Images