Double-corrosion-resistant coastal refining buried pipeline steel and manufacturing method thereof

Abstract

The invention relates to double-corrosion-resistant steel for a coastal refining buried 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, 0.75%-1.15% of Mn, less than or equal to 0.008% of P, less than or equal to 0.002% of S, 0.20%-0.50% of Mo, 2.10%-3.40% of Ni, 0.04%-0.08% of V, 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 the components of low C, medium Si and medium Mn, the content of harmful elements P and S is strictly controlled, meanwhile, Mo and Ni alloy elements, V, Sb and other microalloy elements are added, smelting, rolling and heat treatment production processes are matched, and the steel plate suitable for the buried pipeline under the coastal area soil and industrial medium double-corrosion condition is developed.

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 buried pipelines and a manufacturing method thereof. Background Art

[0002] With the continuous increase in the exploitation of offshore oil and gas fields, the demand for pipelines for transporting crude oil, natural gas and other resources between the sea and land is increasing, among which the demand for buried pipelines is the largest. The soil in coastal areas is relatively moist and has a high salt content; for example, in the marine plains and sea retreat lands where coastal salt soil is distributed, the average salt content of 1 meter of soil can reach more than 6.0g / kg. The salt content of new land soil formed by land reclamation or tidal flat reclamation is even higher, usually 10.0~20.0g / kg, or even as high as 30.0~40.0g / kg. From the perspective of corrosion, the soil in coastal areas is a special electrolyte, which is not only high in salt and moist, but also usually has stray currents. It can be seen that the steel used for coastal buried pipelines is mainly in multiple corrosion environments such as micro-battery corrosion, macro-battery corrosion and stray current corrosion. Long-term service in multiple corrosion environments makes the corrosion problem of coastal buried pipeline steel more serious. Once the refining buried pipeline is damaged, it will lead to a large loss of the oil products it transports, and may even cause fires, explosions and environmental pollution.

[0003] The complex coastal soil corrosion environment causes serious corrosion on the outer wall of the steel used for buried pipelines, which is prone to corrosion perforation. The inner wall of the pipeline will be affected by sulfur, CO 2 , H 2 O and other crude oil, semi-finished oil or finished oil, as well as sulfur-containing wastewater; the main failure forms of the pipeline inner wall are hydrogen-induced cracking and sulfide stress corrosion cracking.

[0004] In summary, the corrosion environment of coastal refining and buried pipelines is complex and harsh. Once failure occurs, it will cause great harm to social and personal safety, and pipeline maintenance is relatively difficult and costly.

[0005] The Chinese patent application with application publication number CN 112111698A discloses "a steel for exposed pipelines of refineries with high corrosion resistance and a production method thereof". The pipeline steel 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 ending temperature is 950℃~1100℃; 3) non-recrystallization starting temperature is 870℃~910℃, and non-recrystallization ending temperature is 780~820℃; 4) first heat treatment 5) second heat treatment 6) tempering treatment. It improves the environmental corrosion resistance of the material itself by changing the composition process under the premise of meeting the performance through organizational regulation and ultra-fine treatment. From the disclosed steel composition, production method and beneficial effects, the pipeline described is used in the industrial atmospheric environment of the refinery, and the external environment it contacts is air, which is an aerobic environment, but it is not applicable to coastal buried pipelines.

[0006] The Chinese patent application with application publication number CN 103469094A discloses "a steel for pipelines resistant to chloride ion corrosion and a preparation method thereof". The chemical elements contained in the steel are: 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 in underground pipeline projects. The final state of the steel plate is controlled rolling and controlled cooling. Although the product can meet the chloride ion corrosion environment requirements of underground pipelines, it cannot meet the use requirements of refining environments.

[0007] The Chinese patent application with application publication number CN 109023070A discloses "a steel for buried structure resistant to salt soil corrosion and a method for manufacturing the same". The steel contains C: 0.02% to 0.06%, Si: 0.05% to 0.22%, Mn: 0.30% to 1.20%, Nb: 0.010% to 0.030%, Ti: 0.015% to 0.035%, Cr: 2.8% to 4.3%, Cu: 0.40% to 0.60%, Sb: 0.05% to 0.15%, Mo: 0.20% to 0.40%, Ni: 0.20% to 0.40%, Al: 0.01% to 0.04%, P≤0.015%, S≤0.005%, and the balance is iron and unavoidable impurities. The slow cooling time of the ingot off-line is ≥72h, heated to 1230-1260℃, the rough rolling final rolling temperature is 1070-1120℃, the finishing rolling start temperature is 1030-1080℃, the finishing rolling final rolling temperature is 860-930℃, the finishing rolling total reduction rate is ≥65%, the cooling rate is 16-32℃ / s, and the coiling is 720-780℃. The steel plate has good strength and toughness and resistance to saline soil corrosion. However, judging from the disclosed steel composition, production method and beneficial effects, its products are mainly used in buried structural components, which are only exposed to a single soil corrosion environment and cannot meet the application requirements of the oil and chemical corrosion environment inside the pipeline.

[0008] The alloy elements of the above pipeline steel are simply added, and can only meet the corrosion environment of a single medium such as petrochemical medium or soil, and cannot meet the use requirements of coastal refining buried pipelines. Summary of the invention

[0009] The present invention provides a steel plate for buried pipelines in coastal refineries resistant to dual corrosion and a manufacturing method thereof. The steel plate adopts a unique chemical composition design and a suitable production process. On the basis of the composition of "low C + medium Si + medium Mn", the contents of harmful elements P and S are strictly controlled. Meanwhile, alloy elements Mo and Ni, and micro-alloy elements such as V and Zr are added. The steel plate is matched with smelting, rolling and heat treatment production processes to develop a steel plate for buried pipelines suitable for dual corrosion conditions of soil and industrial media in coastal areas, which meets the requirements of coastal oil refineries for safe and long-term service of pipelines.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A steel for buried coastal refining pipelines resistant to double corrosion, the chemical composition of the steel plate is as follows by weight: C 0.02%-0.06%, Si 0.30%-0.80%, Mn 0.75%-1.15%, P≤0.008%, S≤0.002%, Mo0.20%-0.50%, Ni 2.10%-3.40%, V 0.04%-0.08%, Alt 0.015%-0.050%, Zr0.02%-0.05%, N0.005%-0.010%, and the balance is Fe and unavoidable impurities.

[0012] A method for manufacturing steel for coastal refining and chemical buried pipelines resistant to dual corrosion, including billet heating, rolling and heat treatment processes; the specific control process is as follows:

[0013] 1) Billet heating: The billet heating temperature is controlled at 1200-1250°C, and the total heating time is 4.0-6.5h;

[0014] 2) Rolling: The final rolling temperature in the recrystallization zone is ≥1000°C, and the cumulative reduction rate is ≥55%; the starting rolling temperature in the non-recrystallization zone is 890-950°C, the final rolling temperature is 820-880°C, the single-pass deformation rate is 25%-30%, and the cumulative reduction rate is ≥60%;

[0015] 3) Heat treatment: quenching temperature is 960-1010℃, 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 560-620℃, and holding time is 60-100min.

[0016] 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.

[0017] The mechanical properties of the finished steel plate are: at room temperature, 370MPa≤R el ≤420MPa、530MPa≤R m ≤630MPa、30%≤A 50mm ≤35.0%;(-20)℃KV 2 ≥100J.

[0018] 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 buried pipeline in the coastal soil corrosion test is ≤80mm / a, and there is no perforation.

[0019] The structure of the finished steel plate is tempered bainite with a grain size of 9.0 to 10.0.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) On the basis of the "low C + medium Si + medium Mn" composition, the contents of harmful elements P and S are strictly controlled, and Mo, Ni, V, and Zr alloy elements are added in combination. Combined with appropriate manufacturing processes, a fine, uniform, dense, and stable matrix structure formed by nano-scale dispersed second phase particles and tempered bainite structure is obtained, with a grain size grade of 9.0 to 10.0, which ensures the mechanical properties and corrosion resistance of pipeline steel.

[0022] (2) The unique chemical composition and production process have resulted in the following mechanical properties for the coastal refining buried pipeline steel: 370MPa≤R el ≤420MPa、530MPa≤R m ≤630MPa、30%≤A 50mm ≤35.0%;(-20℃)KV 2 ≥200J.

[0023] (3) The inner wall of the buried pipeline of the refinery can withstand H 2 S, CO 2 , Cl - Single medium or mixed medium corrosion, the outer wall is resistant to coastal soil corrosion, specifically micro-cell corrosion, macro-cell corrosion and stray current corrosion. Performance: 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; the sulfide stress corrosion SSCC test specimen loaded for 2160h at 100°C and 4MPa pressure did not break; the corrosion rate of the buried pipeline in the coastal soil corrosion test is ≤80mm / a, and there is no perforation.

[0024] (4) The steel for buried coastal refining pipelines with a thickness of 10 to 50 mm obtained by the method of the present invention has excellent corrosion resistance, can withstand the dual corrosion effects of soil and industrial media in coastal areas, and can meet the requirements of coastal oil refineries for safe and long-term service of pipelines. DETAILED DESCRIPTION

[0025] The invention discloses a steel for buried coastal refining pipelines resistant to double corrosion, wherein the chemical composition of the steel plate is as follows by weight: C 0.02%-0.06%, Si 0.30%-0.80%, Mn 0.75%-1.15%, P≤0.008%, S≤0.002%, Mo0.20%-0.50%, Ni 2.10%-3.40%, V 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.

[0026] The present invention discloses a method for manufacturing a dual corrosion resistant steel for buried coastal refinery pipelines, comprising the steps of heating, rolling and heat treatment of steel billets; the specific control process is as follows:

[0027] 1) Billet heating: The billet heating temperature is controlled at 1200-1250°C, and the total heating time is 4.0-6.5h;

[0028] 2) Rolling: The final rolling temperature in the recrystallization zone is ≥1000°C, and the cumulative reduction rate is ≥55%; the starting rolling temperature in the non-recrystallization zone is 890-950°C, the final rolling temperature is 820-880°C, the single-pass deformation rate is 25%-30%, and the cumulative reduction rate is ≥60%;

[0029] 3) Heat treatment: quenching temperature is 960-1010℃, 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 560-620℃, and holding time is 60-100min.

[0030] 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.

[0031] The mechanical properties of the finished steel plate are: at room temperature, 370MPa≤R el ≤420MPa、530MPa≤R m ≤630MPa、30%≤A 50mm ≤35.0%;(-20)℃KV 2 ≥200J.

[0032] 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 buried pipeline in the coastal soil corrosion test is ≤80mm / a, and there is no perforation.

[0033] The structure of the finished steel plate is tempered bainite with a grain size of 9.0 to 10.0.

[0034] In the dual corrosion resistant steel for buried coastal refinery pipelines of the present invention, the limited ranges and reasons of each chemical element are as follows:

[0035] C: is the most important and cheapest strengthening element. A certain amount of C can ensure the matrix strength of pipeline steel, but too high a carbon content can cause structural segregation, resulting in differences in segregation zone structures and 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%.

[0036] 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%.

[0037] 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, the present invention limits the Mn content range to 0.75% to 1.15%.

[0038] P: It is easy to segregate at the austenite grain boundary, which weakens the bonding force between atoms at the grain boundary of the matrix material and causes the material to have high temper brittleness. Therefore, the P content range is set to ≤0.008% in the present invention.

[0039] 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%.

[0040] Mo: Molybdenum forms fine carbide, nitride or carbonitride precipitation phases with carbon, nitrogen and other elements, such as Mo 2 C, MoN, etc. These precipitated phases are dispersed in the steel matrix, hindering dislocation movement, playing a role of precipitation strengthening, further improving the strength of the steel, while maintaining good toughness and enhancing the pipe's ability to resist deformation in the soil environment. In addition, molybdenum can synergize with the iron element in steel to form a dense and stable passivation film on the metal surface. This passivation film is mainly composed of iron and molybdenum oxides and hydroxides, such as MoO 3 It has good self-repairing ability and can effectively prevent corrosive media such as moisture, oxygen, and salt in the soil from contacting the metal matrix, thereby improving the soil corrosion resistance of the material. At the same time, molybdenum can reduce the micro-area corrosion current density of steel in the soil and inhibit the occurrence and development of local corrosion, such as pitting and crevice corrosion. This is because the addition of molybdenum improves the stability and repair ability of the passivation film, makes the potential distribution of the metal surface more uniform, reduces the local potential difference, and thus reduces the sensitivity of local corrosion. Therefore, the present invention limits the Mo content range to 0.2% to 0.5%.

[0041] 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 soil corrosion resistance in the steel of the present invention, but Ni is relatively expensive, and excessive addition will lead to a significant increase in costs. Therefore, the present invention limits the Ni content range to 2.10% to 3.40%.

[0042] V vanadium forms fine carbide, nitride or carbonitride precipitation phases with carbon, nitrogen and other elements, such as VC, VN, etc. These precipitation phases are dispersed in the steel matrix, hindering dislocation movement and playing a role in precipitation strengthening. While improving strength, they can also maintain good toughness. In addition, vanadium can combine with oxygen in steel to form a dense and stable oxide film on the surface of steel, such as V 2 O 5 This oxide film can prevent external corrosive media such as oxygen, water, acid, alkali, etc. from further contacting the steel matrix, thereby improving the corrosion resistance of the corrosion-resistant steel. Therefore, the present invention sets the V content range to 0.04-0.08%.

[0043] 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%.

[0044] Alt: Aluminum plays a major role in deoxidation and grain refinement in steel. 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 its 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%.

[0045] N: forms nitride with V element, precipitates at grain boundaries, pins grain boundaries and refines grains, increases the density of pipelines, and improves the corrosion resistance of steel. Therefore, the present invention limits the N content to 0.005% to 0.010%.

[0046] The manufacturing method and principle of the dual corrosion resistant steel for buried coastal refining pipelines of the present invention are as follows:

[0047] 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.

[0048] 2. Rolling process: The final rolling temperature of the recrystallization zone is ≥1000℃, the cumulative reduction rate is ≥55%, and the intermediate billet thickness is 2.0-3.0 times the thickness of the finished steel plate; the starting rolling temperature of the non-recrystallization zone is 890-950℃, the final rolling temperature of the non-recrystallization zone is 820-880℃, the single-pass deformation rate is 25%-30%, and the cumulative reduction rate is ≥60%. The V and Zr microalloying elements added to the steel are organically combined with the C and N elements to maximize their dispersion strengthening and grain refinement effects. 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.

[0049] 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 bainite 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.

[0050] Specific process: Quenching temperature is selected at A C3In the above 100-150℃ range, the alloy elements can be fully dissolved in the matrix at this temperature, and the coarse and uneven organizational types after rolling can be eliminated, the final organizational uniformity can be improved, and the potential difference caused by organizational differences 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 960-1010℃, and the holding time is 10-20min; after being taken out of the furnace, a cooling rate of 30-50℃ / s is used to quickly cool to room temperature to obtain an ultra-fine lath bainite structure.

[0051] 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 560-620℃, and the holding time is 60-100min. Under this process, the composite carbides formed by microalloy elements such as V and Zr in the steel and C and N are fully precipitated, and the nano-scale dispersed second phase particles and tempered bainite structure form a small, uniform, dense and stable matrix structure; finally, the pipeline using the steel of the present invention not only has the ability to resist pressure explosion in application, but also has the dual corrosion resistance of internal oil and chemical corrosion and external coastal soil corrosion.

[0052] 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.

[0053] [Example]

[0054] 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) at 25°C and 100°C of the finished steel plates in each embodiment, Table 6 shows the four-point bending test results (Solution A) of the finished steel plates in each embodiment, and Table 7 shows the corrosion rate of the finished steel plates in each embodiment in the coastal soil environment.

[0055] In each embodiment, an electrochemical test is used to measure the corrosion rate of the finished steel plate in the coastal soil environment. The electrochemical test adopts a three-electrode system, in which the sample is the working electrode, the reference electrode is the Ag / AgCl electrode, and the auxiliary electrode is the Pt electrode. The maximum polarization current density is 200A / m 2 , the maximum reverse current density is 100A / m 2The interference signal periods are 60s, 120s, 180s, 300s, 600s and 900s respectively, and the experimental time is 24h. After the experiment, the corrosion rate is calculated by weight loss method. The simulated soil solution composition is 6g / kg NaCl, 0.2g / kg CaCl 2 、2g / kg MgCl·6H 2 O, 0.22 g / L Na 2 SO 4 , 0.016 g / kg NaHCO 3 and 0.50g / L KNO 3 , pH value is 8.

[0056] Table 1 Chemical composition of steel (wt, %)

[0057] Example C Si Mn P S Mo Ni V Alt N Zr 1 0.02 0.33 1.10 0.006 0.001 0.50 2.3 0.07 0.017 0.006 0.04 2 0.04 0.44 0.85 0.006 0.002 0.45 3.1 0.06 0.032 0.009 0.02 3 0.05 0.70 0.80 0.008 0.001 0.30 2.5 0.07 0.024 0.008 0.04 4 0.03 0.30 1.06 0.005 0.001 0.40 3.3 0.04 0.050 0.007 0.05 5 0.03 0.78 0.75 0.006 0.002 0.31 3.0 0.06 0.019 0.006 0.03 6 0.06 0.80 0.90 0.005 0.001 0.20 2.2 0.08 0.045 0.010 0.05 7 0.04 0.53 1.15 0.007 0.001 0.45 2.1 0.04 0.031 0.005 0.02 8 0.05 0.46 0.88 0.006 0.001 0.43 2.9 0.05 0.022 0.006 0.03 9 0.06 0.59 0.95 0.007 0.002 0.36 3.4 0.06 0.050 0.010 0.05 10 0.05 0.66 0.99 0.005 0.001 0.25 2.7 0.08 0.024 0.007 0.02

[0058] Table 2 Production process parameters

[0059] Example 1 2 3 4 5 6 7 8 9 10 Heating temperature / ℃ 1220 1200 1240 1200 1218 1210 1235 1250 1245 1240 Total heating time / h 4.5 6.0 6.5 5.5 6.0 5.0 4.0 5.5 6.0 5.0 Recrystallization final rolling temperature / ℃ 1012 1013 1017 1021 1009 1007 1020 1028 1023 1013 Cumulative reduction rate of recrystallization / % 56 57 58 55 56 60 56 57 55 55 Thickness ratio of intermediate billet to finished product 2.0 2.0 3.0 2.5 3.0 3.0 2.0 3.0 2.5 2.0 Non-recrystallization rolling temperature / ℃ 901 897 912 934 911 893 950 904 900 898 Final rolling temperature without recrystallization / ℃ 861 826 865 851 850 842 880 833 869 864 Single pass deformation rate in non-recrystallized zone / % 26 26 29 25 29 28 30 30 27 28 Cumulative reduction rate in non-recrystallized area / % 61 64 63 66 65 61 63 62 65 65 Quenching temperature / ℃ 970 960 1010 960 975 980 1000 995 985 980 Insulation time / min 10 14 20 15 20 16 17 20 18 10 Cooling rate ℃ / S 50 40 32 45 40 35 45 30 30 50 Tempering temperature / ℃ 600 660 600 560 565 590 560 590 560 610 Insulation time / min 100 60 60 70 80 75 90 66 100 100

[0060] Table 3 Structure and properties of finished steel plate

[0061] Example <![CDATA[R el / MPa]]> <![CDATA[R m / MPa]]> A / ％ <![CDATA[(-20℃)KV 2 / J]]> Grain size grade 1 385 595 32.0 259 9.5 2 370 625 33.0 234 9.0 3 392 591 32.5 225 9.0 4 420 630 33.5 232 9.0 5 415 630 32.5 211 9.0 6 390 604 35.0 228 10.0 7 417 545 34.5 239 9.5 8 381 595 32.5 227 10.0 9 373 581 35.0 234 9.0 10 410 627 34.5 243 9.5

[0062] Table 4 25℃ Hydrogen Induced Cracking HIC Test Results (Solution A)

[0063]

[0064] Table 5 HIC test results at 100°C (solution A)

[0065]

[0066] Table 6 Four-point bending test results (Solution A)

[0067] Example Sample conditions 1 Unbroken 2 Unbroken 3 Unbroken 4 Unbroken 5 Unbroken 6 Unbroken 7 Unbroken 8 Unbroken 9 Unbroken 10 Unbroken

[0068] Table 7 Corrosion rate in coastal soil corrosion test

[0069] Example Corrosion rate Perforation 1 50.62 none 2 60.97 none 3 55.12 none 4 53.38 none 5 43.20 none 6 62.14 none 7 43.63 none 8 56.32 none 9 66..87 none 10 57.42 none

[0070] From the above results, it can be concluded that the steel for buried pipelines of coastal refineries manufactured by the method of the present invention has a strength of 370MPa≤Rel≤420MPa, 530MPa≤Rm≤630MPa, and 30%≤A 50mm ≤35.0%; KV at -20℃ 2 ≥200J. Pipe inner wall resistance to H 2 S, CO 2 , Cl- The outer wall is resistant to coastal soil corrosion in single or mixed media. The performance is that the CSR of 25℃ HIC is 0, and the CSR of 100℃ HIC is 0; the SSCC specimen loaded at 4MPa pressure at 100℃ for 2160h does not break; the corrosion rate of buried sea pipeline steel in coastal soil corrosion environment is ≤80mm / a, and there is no perforation.

[0071] 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 buried coastal refining 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 0.75%~1.15%, P≤0.008%, S≤0.002%, Mo 0.20%~0.50%, Ni 2.10%~3.40%, V 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 buried coastal refinery pipelines 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 ≥55%; The starting rolling temperature in the non-recrystallization zone is 890-950°C, the final rolling temperature is 820-880°C, the single-pass deformation rate is 25%-30%, and the cumulative reduction rate is ≥60%; 3) Heat treatment: quenching temperature is 960-1010℃, 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 560-620℃, and holding time is 60-100min.

3. The method for manufacturing a dual corrosion resistant steel for buried 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 buried coastal refinery pipelines according to claim 2, characterized in that: The mechanical properties of the finished steel plate are: at room temperature, 370MPa≤R el ≤420MPa、530MPa≤R m ≤630MPa、30%≤A 50mm ≤35.0%; KV2≥100J at -20℃.

5. The method for manufacturing a dual corrosion resistant steel for buried coastal refinery pipelines 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 buried pipeline in the coastal soil corrosion test is ≤80mm / a, and there is no perforation.

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

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