Double-corrosion-resistant steel for coastal refining sea-entering pipeline and manufacturing method of double-corrosion-resistant steel

Abstract

The invention relates to double-corrosion-resistant steel for a coastal refining sea-entering pipeline and a manufacturing method of the steel. The steel plate comprises the following chemical components: 0.02%-0.06% of C, 0.30%-0.80% of Si, 0.90%-1.30% of Mn, less than or equal to 0.008% of P, less than or equal to 0.002% of S, 1.60%-2.50% of Ni, 0.20%-0.50% of Cu, 0.04%-0.08% of Nb, 0.015%-0.050% of Alt, 0.02%-0.05% of Zr, 0.005%-0.010% of N and the balance of Fe and impurities. On the basis of low C and medium Mn, the contents of harmful elements P and S are strictly controlled, meanwhile, Ni and Cu alloy elements and microalloy elements such as Nb and Zr are added, and through the smelting, rolling and heat treatment processes, the steel plate which is suitable for the coastal pipeline and resistant to seawater and industrial medium double corrosion is produced.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline steel production, and in particular to a dual corrosion resistant steel for coastal refinery pipelines entering the sea and a manufacturing method thereof. Background Art

[0002] In modern large-scale refineries, pipelines, as an important part of the production system, play an irreplaceable role and are called "industrial blood vessels" within the industry. Among them, pipelines connecting offshore refining facilities are usually for the extraction and processing of resources such as crude oil and natural gas at sea. Facilities located in offshore areas transport the mined resources to processing centers or storage facilities on land through pipelines. The transportation media are crude oil, semi-finished oil and finished oil. Some pipelines need to extend into the sea. The outer walls of these pipelines will be corroded by high salt, high humidity and other corrosion, especially the part entering the sea. The corrosion is the most serious. The part of the pipeline entering the sea has experienced the seawater atmosphere zone, splash zone, tidal zone and full immersion zone. Among them, the seawater in the seawater splash zone is in full contact with the air and has the highest oxygen content. Coupled with the scouring of waves, it is the most corrosive. The outer wall of the pipeline in this area mainly suffers from comprehensive corrosion. The inner wall of the pipeline will be affected by the presence of S, CO 2 , H 2 O's crude oil, semi-finished oil or finished oil and sulfur-containing wastewater are prone to hydrogen-induced cracking and sulfide stress corrosion cracking. The corrosion of the inner and outer walls of the refining pipeline into the sea has a great impact on its safe operation, and safety accidents will occur if leakage occurs due to corrosion.

[0003] The Chinese patent application with publication number CN 112111698A discloses "a steel with high corrosion resistance for exposed pipes of refineries and a production method thereof", which is composed of the following chemical components in weight percentage: C 0.09% to 0.12%, Si 0.20% to 0.50%, Mn 0.90% to 1.20%, P ≤ 0.020%, S ≤ 0.005%, Ni 0.20% to 0.40%, Cr 0.80% to 1.10%, Cu 0.20% to 0.40%, Ti 0.02% to 0.05%, Zr 0.01% to 0.03%, Als 0.020% to 0.040%, and the balance is Fe and unavoidable inclusions. The production method is as follows: 1) pretreatment of steel billet, heating temperature is 1200℃~1250℃; 2) recrystallization controlled rolling starting temperature is 1050℃~1150℃, and the end temperature is 950℃~1100℃; 3) non-recrystallization starting temperature is 870℃~910℃, and non-recrystallization end temperature is 780~820℃; 4) first heat treatment 5) second heat treatment 6) tempering treatment. The steel for exposed pipelines of refineries is subjected to organizational control and ultra-fine treatment. Under the premise of meeting the performance requirements, the environmental corrosion resistance of the material itself is improved by changing the composition process. From the perspective of the composition, production method and beneficial effects of the steel, it is mainly used in the industrial atmospheric environment of refineries, and the external environment it contacts is air, which is an aerobic environment, but it is not suitable for corrosive environments such as seawater.

[0004] The Chinese patent application with publication number CN 103469094A discloses “a steel for pipelines resistant to chloride ion corrosion and a method for preparing the same”, which contains the following chemical elements: C: 0.008-0.02wt%, Si: 0.05-0.15wt%, Mn: 0.50-0.85wt%, P: less than 0.01wt%, S: less than 0.01wt%, Mo: 0.8-2.0wt%, Al: 0.001-0.02wt%, Ni: 0.50-1.2wt%, W: 0.02-0.08wt%, and the remainder is composed of Cr, Fe and inevitable impurities, and the Cr content satisfies the following inequality: 2.4-0.49[Mo]+11.8[C]+12.2[W]≤[Cr]≤3.2-0.57[Mo]+9.8[C]+7.2[W]. The tensile strength of the steel is higher than 800MPa, and it has excellent resistance to chloride ion corrosion stress cracking in soil with high chloride ion content, and is suitable for buried pipeline steel in coastal ports and other areas with high chloride ion environment. From the disclosed steel composition, production method and beneficial effects, the corrosive medium involved is a chloride ion environment, and it is used for underground pipeline projects. The final state of the steel plate is controlled rolling and controlled cooling. Although the steel plate can meet the chloride ion corrosion environment requirements of underground pipelines, it does not have a protective effect against oil medium corrosion in refineries.

[0005] The Chinese patent application with publication number CN 103103455A discloses "a steel plate for a 600MPa grade hydroelectric pressure steel pipe and a manufacturing method thereof". The chemical composition of the steel plate is C: 0.06-0.09%, Si: 0.20-0.40%, Mn: 1.4-1.6%, P: ≤0.015%, S: ≤0.005%, Nb: 0.02-0.04%, Ni: 0.20-0.40%, Cr: 0.10-0.30%, Mo: 0.10-0.30%, V: 0.03-0.05%, Ti: 0.01-0.02%, and the balance is Fe and unavoidable impurities. The manufacturing method is: using molten iron and scrap steel that have been pre-treated by desulfurization as raw materials, and obtaining a 600MPa grade steel plate for hydroelectric pressure steel pipe through converter smelting, LF refining, RH vacuum treatment, continuous casting, heating, rolling and cooling, quenching and tempering heat treatment and other processes. Its advantages are: tensile strength greater than 600MPa, good plasticity, excellent low-temperature impact toughness and welding performance, and excellent anti-lamellar tearing performance, and can be widely used in the manufacture of water diversion pressure pipes, primary ribs, bifurcated pipes, volutes and other auxiliary facilities in hydropower station dams. From the disclosed steel composition, production method and beneficial effects, its products are mainly used in water conservancy environments, which are pure inland industrial water quality, and have no corrosion resistance to high-chlorine seawater and industrial oil and chemical products.

[0006] The above-mentioned public documents involve simple addition of alloy elements to the steel used for pipelines, which can only meet the needs of single medium environments such as petrochemical media or soil, and cannot be applied to coastal refining and offshore environments. Summary of the invention

[0007] The present invention provides a dual-corrosion resistant steel for coastal oil and gas refinery pipelines entering the sea and a manufacturing method thereof. The steel adopts a unique chemical composition design and a suitable production process. The chemical composition strictly controls the contents of harmful elements P and S on the basis of low C and medium Mn, and simultaneously adds Ni and Cu alloy elements, as well as micro-alloy elements such as Nb and Zr. Through smelting, rolling and heat treatment processes, a steel plate suitable for coastal oil and gas pipelines entering the sea and resistant to dual corrosion by seawater and industrial media is produced, thereby meeting the requirements of coastal oil and gas refineries for pipeline safety and long-term service.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A dual corrosion resistant steel for coastal refining and sea-going pipelines. The chemical composition of the steel plate is as follows by weight: C 0.02%-0.06%, Si 0.30%-0.80%, Mn 0.90%-1.30%, P≤0.008%, S≤0.002%, Ni1.60%-2.50%, Cu 0.20%-0.50%, Nb 0.04%-0.08%, Alt 0.015%-0.050%, Zr0.02%-0.05%, N 0.005%-0.010%, and the balance is Fe and unavoidable impurities.

[0010] A method for manufacturing dual-corrosion resistant steel for coastal refining and sea-going pipelines includes billet heating, rolling and heat treatment processes; the specific control process is as follows:

[0011] 1) Billet heating: The billet heating temperature is controlled at 1200-1250°C, and the total heating time is 4.0-6.5h;

[0012] 2) Rolling: The final rolling temperature in the recrystallization zone is ≥1000°C, and the cumulative reduction rate is ≥50%; the starting rolling temperature in the non-recrystallization zone is 860-920°C, the final rolling temperature is 780-820°C, the single-pass deformation rate is 25%-35%, and the cumulative reduction rate is ≥65%;

[0013] 3) Heat treatment: quenching temperature is 960-1030℃, holding time is 10-20min, and after taking out of the furnace, it is quickly cooled to room temperature at a cooling rate of 30-50℃ / s; tempering temperature is 520-560℃, and holding time is 40-80min.

[0014] The thickness of the finished steel plate is 10 to 50 mm, and the thickness of the rolling intermediate billet is 2.0 to 3.0 times the thickness of the finished steel plate.

[0015] The mechanical properties of the finished steel plate are: at room temperature, 400MPa≤R el ≤450MPa、600MPa≤R m ≤680MPa、30%≤A 50mm ≤35.0%; KV at -20℃ 2 ≥150J.

[0016] The corrosion resistance of the finished steel plate is as follows: the crack sensitivity ratio CSR of the hydrogen induced cracking HIC test based on solution A at room temperature is 0, and the crack sensitivity ratio of the hydrogen induced cracking HIC test based on solution A at 100°C is 0; solution A is the standard solution A in GBT 4157-2017 "Laboratory Test Method for Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion Cracking in Hydrogen Sulfide Environments"; the sulfide stress corrosion SSCC test specimen loaded for 2160h at 100°C and 4MPa pressure did not break; the corrosion rate of the pipeline in the ocean splash zone is 0.4mm / a.

[0017] The structure of the finished steel plate is troostite, and the grain size is 9.0 to 10.0.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention fully considers the mechanical properties and corrosion resistance of steel for refining pipelines in the composition design. On the basis of the composition of "low C + medium Si + medium Mn", the content of harmful elements P and S is strictly controlled. By adding alloy elements such as Mo, Ni, Nb, Zr and N in combination with the manufacturing process, a fine, uniform, dense and stable matrix structure formed by nano-scale dispersed precipitation of second phase particles and martensite tempering structure is obtained, and the grain size grade is 9.0-10.0, which ensures the mechanical properties and corrosion resistance of steel for pipelines.

[0020] (2) Through the unique chemical composition and production process, the mechanical properties of the steel used for coastal refining and offshore pipelines are as follows: at room temperature, 400MPa≤R el ≤450MPa、600MPa≤R m ≤680MPa、30%≤A 50mm ≤35.0%、(-20℃)KV 2 ≥150J.

[0021] (3) The inner wall of the refinery pipeline into the sea is resistant to H 2 S, CO 2 , Cl - The outer wall is resistant to seawater corrosion in single or mixed media. The performance is as follows: the crack sensitivity ratio CSR of the hydrogen-induced cracking HIC test at room temperature is 0, and the crack sensitivity ratio CSR of the hydrogen-induced cracking HIC test at 100°C is 0; the sulfide stress corrosion SSCC test specimen loaded for 2160h at 100°C and 4MPa pressure did not break; the corrosion rate of the refining pipeline in the ocean splash zone is ≤0.4mm / a.

[0022] (4) The manufacturing method of the present invention is used to obtain a steel with excellent corrosion resistance and a thickness of 10 to 50 mm for coastal refining and sea-going pipelines. The steel is resistant to dual corrosion from seawater and industrial media, and meets the requirements of coastal oil refineries for pipeline safety and long-term service. DETAILED DESCRIPTION

[0023] The invention discloses a dual corrosion resistant steel for coastal refining and sea-going pipelines, wherein the chemical composition of the steel plate is as follows by weight: C 0.02%-0.06%, Si 0.30%-0.80%, Mn 0.90%-1.30%, P≤0.008%, S≤0.002%, Ni1.60%-2.50%, Cu 0.20%-0.50%, Nb 0.04%-0.08%, Alt 0.015%-0.050%, Zr 0.02%-0.05%, N 0.005%-0.010%, and the balance is Fe and unavoidable impurities.

[0024] A method for manufacturing dual-corrosion resistant steel for coastal refining and sea-going pipelines includes billet heating, rolling and heat treatment processes; the specific control process is as follows:

[0025] 1) Billet heating: The billet heating temperature is controlled at 1200-1250°C, and the total heating time is 4.0-6.5h;

[0026] 2) Rolling: The final rolling temperature in the recrystallization zone is ≥1000°C, and the cumulative reduction rate is ≥50%; the starting rolling temperature in the non-recrystallization zone is 860-920°C, the final rolling temperature is 780-820°C, the single-pass deformation rate is 25%-35%, and the cumulative reduction rate is ≥65%;

[0027] 3) Heat treatment: quenching temperature is 960-1030℃, holding time is 10-20min, and after taking out of the furnace, it is quickly cooled to room temperature at a cooling rate of 30-50℃ / s; tempering temperature is 520-560℃, and holding time is 40-80min.

[0028] The thickness of the finished steel plate is 10 to 50 mm, and the thickness of the rolling intermediate billet is 2.0 to 3.0 times the thickness of the finished steel plate.

[0029] The mechanical properties of the finished steel plate are: at room temperature, 400MPa≤R el ≤450MPa、600MPa≤R m ≤680MPa、30%≤A 50mm ≤35.0%; KV at -20℃ 2 ≥150J.

[0030] The corrosion resistance of the finished steel plate is as follows: the crack sensitivity ratio CSR of the hydrogen induced cracking HIC test based on solution A at room temperature is 0, and the crack sensitivity ratio of the hydrogen induced cracking HIC test based on solution A at 100°C is 0; solution A is the standard solution A in GBT 4157-2017 "Laboratory Test Method for Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion Cracking in Hydrogen Sulfide Environments"; the sulfide stress corrosion SSCC test specimen loaded for 2160h at 100°C and 4MPa pressure did not break; the corrosion rate of the pipeline in the ocean splash zone is 0.4mm / a.

[0031] The structure of the finished steel plate is troostite, and the grain size is 9.0 to 10.0.

[0032] In the dual corrosion resistant steel for coastal refinery pipelines entering the sea, the limited ranges and reasons for each chemical element are as follows:

[0033] C: is the most important and cheap strengthening element. Adding a certain amount of C can ensure the matrix strength of pipeline steel, but too high a carbon content will increase carbide segregation, causing a difference in hardness between the segregation zone and the surrounding structure, leading to HIC corrosion. In addition, too high a carbon content is not conducive to the welding performance of the pipeline and the corrosion resistance of the weld. Therefore, the present invention limits the C content range to 0.02% to 0.06%.

[0034] Mn: A certain amount of Mn can play a role in solid solution strengthening of the pipeline matrix, but the segregation caused by excessive Mn is likely to produce high-strength, low-toughness microstructures such as martensite and bainite in the weld and heat-affected zone, showing extremely high hardness, increasing the tendency of post-weld structural cracking, and being extremely detrimental to the SSC resistance of the pipeline. Therefore, it is necessary to control the upper limit of Mn; the present invention limits the Mn content range to 0.90% to 1.30%.

[0035] Si: A certain amount of Si is added to the steel of the present invention to play the role of a deoxidizer. However, when the Si element content is too high, the hardness of the weld and the heat-affected zone is relatively high. At the same time, the Si element is easy to segregate at the grain boundary, promote the formation of intergranular cracks, and increase the corrosion risk of the pipeline. Therefore, the present invention limits the Si content range to 0.30% to 0.80%.

[0036] P: Even when the P content is very low, cracks can nucleate and propagate on MnS, oxide inclusions and grain boundaries, so the present invention limits the P content range to ≤0.008%.

[0037] S: forms MnS band distribution and FeS non-metallic inclusions in the steel, resulting in local microstructure looseness and increasing the sensitivity of HIC or SOHIC in a wet hydrogen sulfide environment. Therefore, the present invention limits the S content range to ≤0.002%.

[0038] Ni: A certain amount of Ni can ensure the strength of the refining pipeline steel while shifting the self-corrosion potential of the bare steel positively, increasing the stability of the steel matrix. At the same time, Ni can be enriched in the rust layer, refine the rust layer grains and increase its density. In addition, Ni can also promote the formation of nano-scale, superparamagnetic α-FeOOH in the inner rust layer, blocking Cl - Penetration makes the rust layer protective, so Ni plays an important role in the present invention in resisting seawater corrosion, but Ni is relatively expensive, and excessive addition leads to a significant increase in cost; therefore, the present invention limits the Ni content range to 1.6% to 2.50%.

[0039] Cu: Copper will undergo oxidation reaction in seawater, and a protective film mainly composed of basic copper chloride, copper oxide, etc. will be formed on the surface. This film has a certain stability and density, which can prevent corrosive media such as chloride ions and oxygen in seawater from further contacting the metal matrix, thereby slowing down the corrosion rate. In addition, there are a large number of microorganisms in seawater, such as sulfate-reducing bacteria, which will adhere to the metal surface to form biofilms and cause microbial corrosion. Copper ions have a certain bactericidal effect, which can inhibit the growth and reproduction of microorganisms in seawater, reduce the formation of microbial films, and thus reduce the risk of microbial corrosion. Therefore, the present invention sets the Cu content range to 0.20% to 0.50%.

[0040] Nb: Niobium can react with oxygen, nitrogen and other elements in steel to form a dense oxide film or nitride film on the surface of the steel, such as Nb 2 O 5 This protective film can effectively block the contact between the external corrosive medium and the steel matrix, slow down the corrosion process, and improve the corrosion resistance of the corrosion-resistant steel in various corrosive environments. In addition, the present invention comprises Nb and carbon and nitrogen element compounds. These compounds refine the grains, reduce grain boundary defects, and reduce the corrosion sensitivity of the grain boundaries, thereby improving the intergranular corrosion resistance of the corrosion-resistant steel. Therefore, the present invention sets the Nb content range to 0.04%-0.08%.

[0041] Zr: It can generate highly dispersed strong carbide ZrC, which can strongly hinder the growth of austenite grains, refine grains, improve the density and strength of pipeline steel matrix, and play a role in corrosion resistance. However, Zr is a precious metal element, and excessive addition will lead to increased costs. Therefore, the present invention limits the Zr content range to 0.02% to 0.05%.

[0042] Alt: Aluminum in steel mainly plays the role of deoxidation and grain refinement; when the aluminum content reaches a certain value, the surface of the steel will be passivated, making the steel corrosion-resistant in oxidizing acids and improving the corrosion resistance to hydrogen sulfide. However, excessive aluminum will promote the graphitization tendency of steel when used for a medium or long time. Therefore, the present invention limits the Alt content range to 0.015% to 0.050%.

[0043] N: forms nitrides with Nb and Zr elements, precipitates at grain boundaries, pins grain boundaries and refines grains. The effect of refining grains can increase the density of the rust layer on the pipeline surface and improve the corrosion resistance of steel; therefore, the present invention limits the N content to 0.005% to 0.010%.

[0044] The manufacturing method and principle of the dual corrosion resistant steel for coastal refining and sea-going pipelines described in the present invention are as follows:

[0045] 1. Billet heating process: By controlling the heating process parameters of the billet, ensure that the alloy elements are fully dissolved and effectively inhibit the growth of the original austenite grains. The billet heating temperature is controlled at 1200-1250°C and the total heating time is 4.0-6.5h.

[0046] 2. Rolling process: The final rolling temperature in the recrystallization zone is ≥1000℃, the cumulative reduction rate is ≥50%, and the intermediate billet thickness is 2.0-3.0 times the thickness of the finished steel plate; the starting rolling temperature in the non-recrystallization zone is 860-920℃, the final rolling temperature is 780-820℃, the single-pass deformation rate is 25%-35%, and the cumulative reduction rate is ≥65%. Through the organic combination of Nb and Zr microalloy elements added to the steel with C and N elements, the dispersion strengthening and grain refinement effects are maximized. At the same time, the single-pass large deformation in the non-recrystallization zone is conducive to grain crushing, increasing grain distortion energy, and further refining grains. The thickness of the finished steel plate is 10-50mm.

[0047] 3. Heat treatment process: The toughness and corrosion resistance of the pipeline steel of the present invention require not only the reasonable design of chemical composition, but also the organic combination of production processes, especially the heat treatment process. The present invention obtains ultra-fine martensitic structure and dispersed fine second phase particles through the "ultra-high temperature short-time quenching + tempering" process to form a dense organizational structure, thereby improving the toughness and overall corrosion resistance of the steel.

[0048] Specific process: Quenching temperature is selected at A C3 In the above 150-200℃ range, the alloy elements can be fully dissolved in the matrix at this temperature, and the coarse and uneven structure type after rolling can be eliminated, the final structure uniformity can be improved, and the potential difference caused by the structure difference can be reduced; but due to the high temperature, the heating temperature should not be too long to prevent grain coarsening; therefore, the heating temperature of ultra-high temperature quenching is limited to 980-1030℃, the holding time is 10-20min, and after taking out of the furnace, it is cooled to room temperature at a cooling rate of 30-50℃ / s to obtain ultra-fine lath martensite structure.

[0049] After quenching, the steel plate has high strength and large internal stress, and needs to be regulated by tempering heat treatment process for organization and performance. The tempering temperature designed by the present invention is 520-560°C, and the holding time is 40-80min. Under this process, the composite carbides formed by microalloying elements such as Nb and Zr in the steel and C and N are fully precipitated. This nano-scale dispersed second phase particles and martensite tempering structure form a small, uniform, dense and stable matrix organization structure. Finally, the pipeline using the steel of the present invention not only has the ability to resist seawater corrosion in application, but also has the ability to resist internal oil and chemical corrosion, that is, it has dual corrosion resistance.

[0050] In order to more intuitively embody the present invention, the embodiments of the present invention are further described in conjunction with examples. The following examples are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution that can be obviously obtained by a person skilled in the art within the technical scope disclosed in the present invention, including simple changes or equivalent replacements, is within the protection scope of the present invention.

[0051] [Example]

[0052] Table 1 shows the chemical composition of the steel in each embodiment, Table 2 shows the process parameters of each embodiment, Table 3 shows the structure and properties of the finished steel plates in each embodiment, Table 4 and Table 5 show the hydrogen induced cracking HIC test results (Solution A) of the finished steel plates in each embodiment at 25°C and 100°C, respectively, and Table 6 shows the four-point bending test results (Solution A) of the finished steel plates in each embodiment.

[0053] In each embodiment, a cyclic corrosion test chamber is used to measure the corrosion rate of steel used for refinery pipelines entering the sea in the ocean splash zone, and the experimental time is 360 hours. After the experiment, the corrosion rate is calculated using the weight loss method. The simulated ocean solution is 3.5% NaCl.

[0054] Table 1 Chemical composition of steel (wt, %)

[0055] Example C Si Mn P S Ni Cu Nb Zr Alt N 1 0.05 0.33 0.97 0.006 0.001 1.87 0.24 0.06 0.02 0.045 0.006 2 0.03 0.59 0.90 0.006 0.001 2.20 0.50 0.05 0.04 0.034 0.005 3 0.05 0.50 1.10 0.005 0.002 2.33 0.34 0.06 0.02 0.015 0.006 4 0.03 0.44 1.19 0.007 0.001 1.89 0.47 0.05 0.04 0.050 0.010 5 0.05 0.30 1.26 0.006 0.002 1.60 0.20 0.07 0.05 0.037 0.007 6 0.04 0.67 1.30 0.006 0.001 1.77 0.28 0.04 0.03 0.015 0.008 7 0.02 0.80 0.90 0.008 0.001 2.50 0.39 0.06 0.05 0.045 0.009 8 0.04 0.72 0.95 0.006 0.001 2.45 0.42 0.08 0.02 0.023 0.006 9 0.04 0.36 1.04 0.708 0.002 2.11 0.35 0.05 0.03 0.028 0.006 10 0.03 0.53 1.07 0.006 0.001 2.09 0.22 0.08 0.05 0.019 0.007

[0056] Table 2 Production process parameters

[0057]

[0058] Table 3 Microstructure and properties of finished steel plate

[0059] Example <![CDATA[R el / MPa]]> <![CDATA[R m / MPa]]> A / ％ <![CDATA[(-20℃)KV 2 / J]]> Grain size grade 1 420 630 34.5 152 9.5 2 427 644 34.0 169 10.0 3 408 610 35.0 183 9.5 4 425 633 34.0 191 10.0 5 440 678 31.0 159 9.5 6 430 665 32.0 162 10.0 7 434 670 31.0 173 9.5 8 450 680 30.0 159 9.0 9 414 631 35.0 182 9.5 10 447 666 33.0 174 9.0

[0060] Table 4 25℃ Hydrogen Induced Cracking HIC Test Results (Solution A)

[0061]

[0062] Table 5 100℃ HIC test results (Solution A)

[0063]

[0064] Table 6 Four-point bending test results (Solution A)

[0065] Example Sample conditions 1 Unbroken 2 Unbroken 3 Unbroken 4 Unbroken 5 Unbroken 6 Unbroken 7 Unbroken 8 Unbroken 9 Unbroken 10 Unbroken

[0066] According to the above results, it can be concluded that the steel for coastal refining and sea-going pipelines provided by the present invention has a strength of 400MPa≤R el ≤450MPa、600MPa≤R m ≤680MPa、30%≤A 50mm ≤35.0%、(-20℃)KV 2 ≥150J. The inner wall of the refinery pipeline into the sea is resistant to H 2 S, CO 2 , Cl - Single medium or mixed medium corrosion, the outer wall is resistant to seawater corrosion. It is manifested as the CSR of HIC at 25℃ is 0, and the CSR of HIC at 100℃ is 0; the SSCC test specimen loaded at 100℃ and 4MPa pressure for 2160h does not break; the corrosion rate of the refining pipeline in the ocean splash zone is ≤0.4mm / a.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A dual corrosion resistant steel for coastal refining and sea-going pipelines, characterized in that: The chemical composition of the steel plate is calculated by weight percentage: C 0.02%~0.06%, Si 0.30%~0.80%, Mn 0.90%~1.30%, P≤0.008%, S≤0.002%, Ni 1.60%~2.50%, Cu 0.20%~0.50%, Nb 0.04%~0.08%, Alt 0.015%~0.050%, Zr 0.02%~0.05%, N 0.005%~0.010%, and the balance is Fe and unavoidable impurities.

2. A method for manufacturing the dual corrosion resistant steel for coastal refinery pipelines entering the sea as claimed in claim 1, characterized in that: Including billet heating, rolling and heat treatment processes; the specific control process is as follows: 1) Billet heating: The billet heating temperature is controlled at 1200-1250°C, and the total heating time is 4.0-6.5h; 2) Rolling: Final rolling temperature in recrystallization zone ≥1000°C, cumulative reduction rate ≥50%; The starting rolling temperature in the non-recrystallization zone is 860-920°C, the final rolling temperature is 780-820°C, the single-pass deformation rate is 25%-35%, and the cumulative reduction rate is ≥65%; 3) Heat treatment: quenching temperature is 960-1030℃, holding time is 10-20min, and after taking out of the furnace, it is quickly cooled to room temperature at a cooling rate of 30-50℃ / s; tempering temperature is 520-560℃, and holding time is 40-80min.

3. The method for manufacturing a dual corrosion resistant steel for coastal refinery pipelines according to claim 2, characterized in that: The thickness of the finished steel plate is 10 to 50 mm, and the thickness of the rolling intermediate billet is 2.0 to 3.0 times the thickness of the finished steel plate.

4. The method for manufacturing a dual corrosion resistant steel for coastal refinery pipelines according to claim 2, characterized in that: The mechanical properties of the finished steel plate are: at room temperature, 400MPa≤R el ≤450MPa、600MPa≤R m ≤680MPa、30%≤A 50mm ≤35.0%; KV2≥150J at -20℃.

5. The method for manufacturing a dual corrosion resistant steel for coastal refinery pipelines entering the sea according to claim 2, characterized in that: The corrosion resistance of the finished steel plate is as follows: the crack sensitivity ratio CSR of the hydrogen induced cracking HIC test based on solution A at room temperature is 0, and the crack sensitivity ratio of the hydrogen induced cracking HIC test based on solution A at 100°C is 0; solution A is the standard solution A in GBT 4157-2017 "Laboratory Test Method for Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion Cracking in Hydrogen Sulfide Environments"; the sulfide stress corrosion SSCC test specimen loaded for 2160h at 100°C and 4MPa pressure did not break; the corrosion rate of the pipeline in the ocean splash zone is 0.4mm / a.

6. The method for manufacturing a dual corrosion resistant steel for coastal refinery pipelines according to claim 2, characterized in that: The finished steel plate structure is troostite with a grain size of 9.0 to 10.0.

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