500MPa-grade corrosion-resistant pipeline steel containing hydrogen sulfide and used for conveying oil-gas medium and preparation method of 500MPa-grade corrosion-resistant pipeline steel

Abstract

The invention discloses 500 MPa-grade corrosion-resistant pipeline steel containing hydrogen sulfide and used for conveying oil and gas media and a preparation method of the 500 MPa-grade corrosion-resistant pipeline steel. The method comprises the following steps: smelting molten iron in a converter, and carrying out ladle argon blowing treatment on the molten iron after smelting in the converter to obtain molten steel with the temperature of more than 1540 DEG C obtained at the end point of an argon station; the molten steel obtained at the end point of the argon station is subjected to LF refining treatment in an LF refining station at the station entering temperature higher than 1525 DEG C, the components of the molten steel are finely adjusted to target components in the LF furnace molten steel LF refining process, the station exiting temperature of the molten steel in the LF refining station reaches 1585-1620 DEG C, and LF refined molten steel is obtained; the LF refined molten steel is subjected to continuous casting treatment, and a continuous casting slab is obtained; the continuous casting slab is heated and rolled, and rolled steel is obtained; and the rolled steel is subjected to laminar cooling treatment, and the 500 MPa-grade corrosion-resistant pipeline steel for conveying the hydrogen sulfide-containing oil gas medium is prepared.

Description

Technical Field

[0001] The present application belongs to the technical field of steel manufacturing, and in particular relates to a 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide and a preparation method thereof. Background Art

[0002] Hydrogen sulfide is one of the most corrosive and harmful media in oil and gas. The content of hydrogen sulfide in my country's oil and gas products is relatively high, which will cause relatively serious hydrogen sulfide corrosion. Hydrogen sulfide corrosion is often hidden and difficult to detect during normal operation. Once a leak occurs, it will cause huge losses. This puts higher requirements on the hydrogen sulfide corrosion resistance of steel used in oil and gas pipelines. Therefore, it is of great significance to develop pipeline steel with high resistance to hydrogen sulfide corrosion. Summary of the invention

[0003] The embodiment of the present application provides a method for preparing 500 MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, which can solve the problems of insufficient corrosion resistance and high alloy cost of existing corrosion-resistant pipeline steel.

[0004] In a first aspect, the present application provides a method for preparing a 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, comprising:

[0005] The molten iron is subjected to converter smelting, and after the converter smelting, the molten iron is subjected to argon blowing treatment in a ladle to obtain molten steel having a temperature of more than 1540°C controlled at the end point of the argon station;

[0006] The molten steel obtained at the end of the argon station is subjected to LF refining at an inlet temperature of >1520°C in an LF refining station, and the composition of the molten steel is finely adjusted to a target composition during the LF refining of the molten steel in the LF furnace, so that the outlet temperature of the molten steel at the LF refining station reaches 1585°C to 1620°C, thereby obtaining LF refined molten steel;

[0007] Continuously casting the LF refined molten steel to obtain a continuously cast slab;

[0008] The continuous casting slab is heated and rolled to obtain rolled steel;

[0009] The rolled steel is subjected to laminar cooling treatment to obtain 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide.

[0010] According to the embodiment of the first aspect of the present application, the molten iron needs to meet the following composition requirements in terms of mass percentage: P≤0.15% of the molten iron entering the furnace, residual elements As≤0.03%, and Sn≤0.02%.

[0011] According to an embodiment of the first aspect of the present application, the LF refining time is 40 minutes to 45 minutes.

[0012] According to the embodiment of the first aspect of the present application, the process conditions for continuous casting of LF refined steel liquid are: the pulling speed is 1.4m / min to 1.6m / min, and the continuous casting is carried out in a light pressure mode to obtain a continuously cast slab.

[0013] According to the embodiment of the first aspect of the present application, the light reduction mode means that during the solidification process of the continuous casting slab, the continuous casting slab in the solid-liquid dual-phase temperature range is pressed down by 5mm to 10mm along the thickness direction of the continuous casting slab.

[0014] According to an embodiment of the first aspect of the present application, it also includes: subjecting the continuously cast slab to stack cold treatment to reduce the temperature of the continuously cast slab from a hot slab environment of more than 500°C to below 300°C.

[0015] According to an embodiment of the first aspect of the present application, heating and rolling the continuous casting slab includes:

[0016] heating the continuous casting slab that has been cooled to room temperature to obtain a heated casting slab;

[0017] The heated ingot is rolled by adopting a thermomechanical controlled rolling and air cooling process to obtain rolled steel.

[0018] According to an embodiment of the first aspect of the present application, cooling the continuous casting slab to room temperature comprises:

[0019] The continuous casting slab is heated to 1200°C to 1250°C using a heating furnace, the heating time is required to be 150 minutes to 250 minutes, and the solution time is greater than 30 minutes.

[0020] According to the embodiment of the first aspect of the present application, the heating ingot is rolled by adopting the thermomechanical controlled rolling and controlled cooling process, including: performing rough rolling and finish rolling on the heated ingot, wherein the rough rolling start temperature is 1160℃~1220℃, and the rough rolling final rolling temperature is 1120℃~980℃; the finish rolling start temperature is 1020℃~920℃, and the finish rolling final rolling temperature is 800℃~720℃, to obtain rolled steel.

[0021] According to an embodiment of the first aspect of the present application, laminar cooling treatment of rolled steel includes:

[0022] The cooling rate of the rolled steel is 30°C / s to 40°C / s, and the final cooling is to 550°C to 580°C, thereby obtaining 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide.

[0023] According to an embodiment of the first aspect of the present application, the preparation method of 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide also includes: coiling the rolled steel that has completed laminar cooling treatment to obtain a steel coil; stacking the steel coil, and cross-cutting it flat, and putting it into storage after inspection for storage, transportation or sale.

[0024] In a second aspect, the present application provides a 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, which comprises the following chemical components in mass percentage: C 0.04% to 0.06%; Si 0.15% to 0.25%; Mn 1.0% to 1.2%; Nb 0.045% to 0.055%; Al 0.020% to 0.050%; Cr 0.20% to 0.30%; Ti 0.015% to 0.025%; Cu 0.25% to 0.50%; Sb 0.25% to 0.35%; S 0.020% to 0.035%; P≤0.015%; N≤0.0050%; O≤0.0030%; hydrogen≤0.0015%, and the balance is Fe and unavoidable inclusions.

[0025] According to the embodiment of the second aspect of the present application, a 500MPa-grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide is prepared according to a preparation method of a 500MPa-grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, and has the following properties: yield strength Rel is 500MPa-550MPa, tensile strength Rm is 630MPa-750MPa, elongation A is greater than 15%, -40°C KV2 impact energy is greater than 27J; and hydrogen-induced cracking sensitivity index is less than 0.30.

[0026] The preparation method of 500MPa grade corrosion-resistant pipeline steel for oil and gas medium transportation of hydrogen sulfide in the embodiment of the present application reasonably adds corrosion-resistant elements such as copper and antimony to improve the electrode potential of steel in the complex mineral medium environment such as hydrogen sulfide gas and salt contained in the oil and gas medium, thereby improving the corrosion resistance; in particular, according to the hydrogen-induced cracking problem of hydrogen sulfide in oil and gas, antimony elements are added to improve the corrosion resistance of the corrosion-resistant pipeline steel matrix in the sensitive medium range. Adding Nb with a mass fraction of 0.045wt.% to 0.055% in the corrosion-resistant pipeline steel ensures that the bainite matrix has sufficient NbC second phase precipitation to produce strengthening, thereby ensuring that the yield strength of the corrosion-resistant pipeline steel is above 500MPa and the tensile strength is above 630MPa, significantly improving the resistance to hydrogen sulfide stress corrosion, and having a low sensitivity to stress corrosion cracking, that is, stronger resistance to crack initiation and expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1It is a schematic flow chart of a method for preparing a 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide provided in an embodiment of the present application;

[0029] Figure 2 This is the metallographic structure diagram of the 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide provided in Example 1 of the present application;

[0030] Figure 3 This is the metallographic structure diagram of the 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide provided in Example 2 of the present application.

[0031] Figure 4 This is the metallographic structure diagram of the 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide provided in Example 3 of the present application.

[0032] Figure 5 This is the metallographic structure diagram of the 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide provided in Example 4 of the present application.

[0033] It should be noted that Figures 2 to 5 The unit length in is 20 μm. DETAILED DESCRIPTION

[0034] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0035] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0036] In order to solve the problems of the prior art, the present invention provides a method for preparing 500MPa corrosion-resistant pipeline steel for transporting oil and gas containing hydrogen sulfide. The following first introduces the method for preparing 500MPa corrosion-resistant pipeline steel for transporting oil and gas containing hydrogen sulfide provided in the present invention. Figure 1 A schematic flow chart of a method for preparing a 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide provided in one embodiment of the present application is shown.

[0037] like Figure 1 As shown, the preparation method of 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide according to an embodiment of the present application includes: smelting molten iron in a converter, and the molten iron is subjected to argon blowing treatment in a ladle after smelting in the converter to obtain molten steel with a temperature of >1540°C controlled at the end of the argon station; subjecting the molten steel obtained at the end of the argon station to LF refining at an LF refining station with an inlet temperature of >1520°C, and fine-tuning the composition of the molten steel to the target composition during LF refining of the molten steel in the LF furnace, so that the outlet temperature of the molten steel at the LF refining station reaches 1585°C to 1620°C, to obtain LF refined molten steel; continuously casting the LF refined molten steel to obtain a continuously cast slab; heating and rolling the continuously cast slab to obtain a rolled steel; and laminar cooling the rolled steel to obtain a 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide.

[0038] The preparation method of 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide in the embodiment of the present application reasonably adds corrosion-resistant elements such as copper and antimony to improve the electrode potential of steel in the complex mineral medium environment such as hydrogen sulfide gas and salt contained in the oil and gas medium, thereby improving the corrosion resistance of the corrosion-resistant pipeline steel; in particular, according to the hydrogen-induced cracking problem of hydrogen sulfide in oil and gas, antimony elements are added to improve the corrosion resistance of the corrosion-resistant pipeline steel matrix in the sensitive medium range. Adding Nb with a mass fraction of 0.045wt.% to 0.055% in the corrosion-resistant pipeline steel ensures that there are enough NbC second phase particles precipitated in the bainite matrix structure to produce strengthening, thereby ensuring that the yield strength of the corrosion-resistant pipeline steel is above 500MPa and the tensile strength is above 630MPa. Under the same oil and gas transmission pressure, the 500MPa-grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide prepared by the preparation method of 500MPa-grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide in the embodiment of the present application is used as the steel for making oil and gas pipelines. This can save more than 30% of steel usage, reduce the overall investment by 20%, increase the service life of the corrosion-resistant pipeline steel to at least 20 years, and effectively reduce the pipeline maintenance cost.

[0039] It should be noted that during the LF refining process of molten steel in the LF furnace, the composition of the molten steel is fine-tuned to the target composition, that is, the composition and content of the refined molten steel meet the composition requirements of 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide.

[0040] In some embodiments of the present application, the molten iron needs to meet the following composition requirements in terms of mass percentage: P≤0.15%, residual element As≤0.03%, Sn≤0.02%. If phosphorus or residual elements cannot meet the requirements, the next step of production will not be arranged until the content of phosphorus or residual toxic or harmful elements meets the standard requirements, reducing the harm of toxic elements to the environment; and the stress corrosion resistance of corrosion-resistant pipeline steel may be reduced due to excessive content of harmful P or Sn elements.

[0041] In some embodiments of the present application, the LF refining time is 40 minutes to 45 minutes.

[0042] In some embodiments of the present application, the process conditions for continuous casting of LF refined molten steel are as follows: a pulling speed of 1.4 m / min to 1.6 m / min, and a light reduction mode is adopted to obtain a continuously cast slab.

[0043] In some embodiments of the present application, the light pressure reduction mode refers to pressing down 5mm to 10mm along the thickness direction of the continuous casting slab in the solid-liquid dual-phase temperature range during the solidification process of the continuous casting slab, that is, the continuous casting slab cast by continuous casting of LF refined steel liquid is pressed down with a pressure reduction of 5mm to 10mm. The light pressure reduction mode is used to apply a slight pressure at the end of the solidification of the continuous casting slab to optimize the solidification process, improve the internal quality of the continuous casting slab, and reduce defects such as center segregation and shrinkage.

[0044] Illustratively, continuous casting can be carried out at a continuous casting speed of 1.4, 1.45, 1.5, 1.55, 1.58, or 1.6 m / min and a reduction of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 mm.

[0045] In some embodiments of the present application, the method for preparing 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide also includes: subjecting the continuous casting slab to stack cold treatment to cool the continuous casting slab from a hot slab environment above 500°C to below 300°C.

[0046] In some embodiments of the present application, heating and rolling the continuous casting slab includes:

[0047] heating the continuous casting slab that has been cooled to room temperature to obtain a heated casting slab;

[0048] The heated ingot is rolled by adopting a thermomechanical controlled rolling and air cooling process to obtain rolled steel.

[0049] In some embodiments of the present application, heating the continuous casting slab cooled to room temperature comprises:

[0050] The continuous casting slab is heated to 1200°C to 1250°C using a heating furnace. The heating time is required to be 150 minutes to 250 minutes, and the solution time is greater than 30 minutes to obtain the heated casting slab.

[0051] In some embodiments of the present application, the thermomechanical controlled rolling and controlled cooling process is used to roll the heated ingot, including: performing rough rolling and finish rolling on the heated ingot, wherein the start temperature of the rough rolling is 1160℃~1220℃, and the final temperature of the rough rolling is 1120℃~980℃; the start temperature of the finish rolling is 1020℃~920℃, and the final temperature of the finish rolling is 800℃~720℃, to obtain rolled steel.

[0052] It should be noted that the rough rolling uses a 5- or 7-stand rough rolling mill to perform rough rolling on the heated ingot.

[0053] In the embodiments of the present application, hot rolling is based on metal deformation, phase change and other processes, and solid solution strengthening, precipitation strengthening, dislocation strengthening and other hardening measures are completed under the specified deformation and temperature conditions to obtain good mechanical properties and corrosion resistance. And reduce the manufacturing cost, make full use of the rolling and cooling capacity of the continuous rolling mill, and produce 500MPa grade corrosion-resistant pipeline steel for oil and gas medium transportation containing hydrogen sulfide by controlled rolling and accelerated cooling. The best mechanical effect is obtained by the coupling effect of deformation recrystallization in the high-temperature austenite zone, deformation in the low-temperature austenite non-recrystallization zone, and accelerated cooling after rolling. In the high-temperature austenite zone, corrosion-resistant elements such as Cr, Cu, and Sb are dissolved into the matrix, and controlled rolling and controlled cooling technology are used to ensure that the alloy elements are in a solid solution state, and the passivation film has sufficient alloy elements to participate in the film formation, thereby improving the corrosion resistance of the corrosion-resistant pipeline steel.

[0054] In some embodiments of the present application, laminar cooling treatment of rolled steel includes: laminar cooling of rolled steel at a cooling rate of 30°C / s to 40°C / s, and final cooling to 550°C to 580°C, to produce 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide.

[0055] In the embodiments of the present application, the bainite starting transformation temperature is 600°C, and the bainite transformation termination temperature is about 530°C. The corrosion-resistant pipeline steel can be transformed into a low-temperature bainite structure after finishing rolling through a reasonable cooling rate at a cooling rate greater than 30°C / s to 40°C / s, that is, the structure of the steel after finishing rolling is controlled to provide a basic structure for high-strength mechanical properties.

[0056] In some embodiments of the present application, the preparation method of 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide also includes: coiling the rolled steel that has completed laminar cooling treatment to obtain a steel coil; stacking the steel coil, and cross-cutting it flat, and storing it after inspection, etc., to obtain 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide that meets the use requirements and specifications.

[0057] In a second aspect, the present application provides a 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, which comprises the following chemical components in mass percentage: C 0.04% to 0.06%; Si 0.15% to 0.25%; Mn 1.0% to 1.2%; Nb 0.045% to 0.055%; Al 0.020% to 0.050%; Cr 0.20% to 0.30%; Ti 0.015% to 0.025%; Cu 0.25% to 0.50%; Sb 0.25% to 0.35%; S 0.020% to 0.035%; P≤0.015%; N≤0.0050%; O≤0.0030%; hydrogen≤0.0015%, and the balance is Fe and unavoidable inclusions.

[0058] The 500MPa grade corrosion-resistant pipeline steel for oil and gas medium transportation containing hydrogen sulfide provided in the embodiment of the present application has a lower crack sensitivity level, crack length rate and crack width rate. Under the same oil and gas transportation pressure, it can save more than 30% of steel, reduce the comprehensive investment by 20%, and increase the service life of oil and gas pipeline steel to at least 20 years, effectively reducing the pipeline maintenance cost. The 500MPa grade corrosion-resistant pipeline steel for oil and gas medium transportation containing hydrogen sulfide prepared by the preparation method in the embodiment of the present application has significantly improved hydrogen sulfide stress corrosion resistance than the existing steel grade X52M, and has a lower sensitivity to stress corrosion cracking, that is, it has a stronger resistance to crack initiation and expansion. Among them, the service life of the existing steel grade X52M is 8 to 10 years, that is, less than 20 years, while the service life of the 500MPa grade corrosion-resistant pipeline steel for oil and gas medium transportation containing hydrogen sulfide provided in the embodiment of the present application reaches more than 20 years.

[0059] The design ideas of each component in this application are:

[0060] Carbon: Carbon is the most easily available and economical alloying element in steel. Low carbon content design can ensure good welding performance of corrosion-resistant pipeline steel on the one hand, and cooperate with titanium and niobium in steel to form second-phase particles for strengthening, ensuring the strength performance of steel plate. With the corresponding cooling rate, full bainite structure can be obtained, ensuring that the matrix structure of corrosion-resistant pipeline steel has good strength, good toughness and good corrosion resistance. Therefore, the carbon content of corrosion-resistant pipeline steel is controlled at 0.04% to 0.06% in this application.

[0061] Silicon: Silicon can be deoxidized during the smelting process, but too high a content of silicon will affect the weldability and toughness of the corrosion-resistant pipeline steel. In this application, the content of silicon is controlled within a range of 0.15% to 0.25%.

[0062] Manganese: Manganese is beneficial to improving the high temperature brittleness of corrosion-resistant pipeline steel, but it is easy to form MnS inclusions in the steel, which are harmful to impact toughness and welding performance. Therefore, the corrosion-resistant pipeline steel of the present application controls its content within 1.0% to 1.20%.

[0063] Niobium: Adding more than 0.015% Nb to corrosion-resistant pipeline steel can significantly refine the grains, improve the strength of the corrosion-resistant pipeline steel, and also improve its low-temperature toughness. Therefore, it is more appropriate to control the niobium content to 0.045% to 0.055% in this application.

[0064] Aluminum: Too much aluminum will damage the toughness and isotropy of mechanical properties of corrosion-resistant pipeline steel. Its content is controlled at 0.025% to 0.050%.

[0065] Chromium: A chromium content greater than 0.2% can improve the corrosion resistance of corrosion-resistant pipeline steel, while enhancing the hardenability of the steel, which is beneficial to the formation of bainite, and can promote the transformation of the rust layer structure from porous β-Fe2O3 to dense α-Fe2O3, which can effectively isolate the contact between the corrosive liquid medium and the substrate, so that the steel is effectively protected. Taking into account the performance and cost, this application controls the Cr content to 0.20% to 0.30%.

[0066] Titanium: During the continuous casting solidification process, titanium combines with nitrogen to form TiN, which reduces the influence of boron nitride. The presence of fine TiN can inhibit the coarsening of grains in the welding heat affected zone. Preferably, the Ti content is controlled at 0.015% to 0.025%.

[0067] Copper: Adding 0.25% to 0.50% copper can increase the electrode potential of the corrosion-resistant pipeline steel matrix. After adding antimony elements to the copper-containing corrosion-resistant steel, the Cu-Sb elements work together to form a Cu2Sb precipitation phase, which later forms a denser Sb2O5 film after contacting with a sulfuric acid medium. A dense passivation film is formed, which inhibits the segregation of Sb elements at grain boundaries and improves grain boundary brittleness.

[0068] Antimony: Antimony is the chemical element that has the most significant effect in improving the corrosion resistance of corrosion-resistant pipeline steel in a sulfuric acid environment. Sb significantly improves the corrosion resistance of steel. However, Sb is an element that has an adverse effect on the strength, toughness, plasticity and weldability of steel. Sb added to the metal surface can form Sb2O5 in the corrosive medium, which has higher stability than a single steel matrix and is beneficial to prevent the metal matrix from being further corroded by the corrosive medium. In this application, the antimony content is controlled at 0.25% to 0.35%, which has good corrosion resistance without damaging strength and toughness.

[0069] Sulfur: Sulfur can form a CuS passivation film during the contact between the corrosion-resistant pipeline steel and the acid medium, which can effectively isolate the contact between the acid and the corrosion-resistant pipeline steel matrix medium. Therefore, the content of sulfur is controlled within the range of 0.020% to 0.035% in this application.

[0070] Phosphorus: Too high phosphorus will cause grain boundary segregation and increase the brittleness of the steel. Therefore, the phosphorus content is controlled to ≤0.015% in this application.

[0071] In addition, nitrogen, oxygen, hydrogen and other gas elements are extremely detrimental to the performance stability of corrosion-resistant pipeline steel used for transporting oil and gas media containing hydrogen sulfide, and should be strictly controlled. Therefore, the content of the three elements in steel should be controlled as follows: nitrogen ≤ 0.00060%, oxygen ≤ 0.00015%, hydrogen ≤ 0.0015%.

[0072] In some embodiments of the present application, a 500MPa-grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide is prepared according to a preparation method of a 500MPa-grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, and has the following properties: yield strength Rel is 500MPa-550MPa, tensile strength Rm is 630MPa-750MPa, elongation A is greater than 15%, -40°C KV2 impact energy is greater than 27J; and hydrogen-induced cracking sensitivity index is less than 0.30.

[0073] In some embodiments of the present application, 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide can be manufactured into pipes, storage tanks and other equipment for transportation, and used for the transportation and storage of high-sulfur oil and gas media (the volume concentration of H2S in the high-sulfur oil and gas media is 5% v / v to 15% v / v).

[0074] The technical solutions and beneficial effects of the present application are described in detail below using specific embodiments and comparative examples.

[0075] Examples 1-4

[0076] The molten iron is desulfurized by KR and then smelted in a 210-ton converter to obtain molten iron. In terms of mass percentage, the molten iron meets the following composition requirements: P≤0.15% of the molten iron entering the furnace, residual element As≤0.03%, Sn≤0.02%, and then argon blowing in the ladle, LF furnace refining, RH vacuum treatment and continuous casting into a continuous casting slab with a thickness of 230 mm; the continuous casting slab is stacked and cooled to room temperature after 48 hours of stacking, and then the continuous casting slab is heated, roughed by a rough rolling mill for 5 passes, and then thermomechanical controlled rolling and controlled cooling are carried out by a 7-stand 2250 continuous rolling unit. The thickness specifications of the hot-rolled coils are: 12mm, 18mm, and 24mm respectively. The specific composition of the corrosion-resistant pipeline steel of Examples 1-4 is shown in Table 1 below, the specific process parameters are shown in Table 2 below, the results of the mechanical property test of Examples 1-3 are shown in Table 3, and the anti-HIC stress corrosion performance test is shown in Table 4.

[0077] Comparative Example 1

[0078] Comparative Example 1 uses X52MS steel, and its composition, preparation process parameters, mechanical property tests and HIC stress corrosion resistance tests are shown in Tables 1 to 4, respectively.

[0079] Table 1 Comparison of the composition of the corrosion-resistant pipeline steel continuous casting slabs of Examples 1-4 and Comparative Example 1

[0080] serial number Thickness, mm C Si Mn S P Ti Nb Example 1 10 0.053 0.19 1.05 0.023 0.013 0.019 0.048 Example 2 12 0.052 0.18 1.08 0.025 0.012 0.018 0.05 Example 3 18 0.051 0.17 1.1 0.022 0.012 0.019 0.048 Example 4 24 0.052 0.2 1.12 0.03 0.013 0.02 0.047 Comparative Example 1 18 0.048 0.2 1.1 0.0012 0.012 0.018 0.042 serial number Thickness, mm Cr Cu Al Sb N O H Example 1 10 0.29 0.45 0.038 0.33 0.0046 0.0020 0.0011 Example 2 12 0.25 0.43 0.036 0.32 0.0044 0.0028 0.0012 Example 3 18 0.28 0.46 0.042 0.3 0.0043 0.0025 0.0013 Example 4 24 0.26 0.48 0.044 0.31 0.0045 0.0022 0.0014 Comparative Example 1 18 0.22 —— —— —— 0.0045 0.002 0.0013

[0081] Table 2 Partial process parameters of corrosion-resistant pipeline steel of Examples 1-4 and Comparative Example 1

[0082]

[0083] Mechanical properties test

[0084] The mechanical properties of the corrosion-resistant pipeline steels of Examples 1-4 and Comparative Example 1 were tested, and the mechanical properties of the corrosion-resistant pipeline steels of Examples 1-4 and Comparative Example 1 are shown in Table 3 below. Among them, various mechanical property tests were conducted according to the following standards:

[0085] (1) Yield strength, tensile strength and elongation are tested in accordance with the standard number: GB / T228.1-2010, standard name: Part 1 of "Tensile Test of Metallic Materials";

[0086] (2) The longitudinal impact energy at -40°C is tested in accordance with Part 1 of GB / T 229-2020, Charpy Pendulum Impact Test Method for Metallic Materials.

[0087] Table 3 Mechanical properties test table of corrosion resistant pipeline steel of Examples 1-4 and Comparative Example 1

[0088]

[0089] It can be concluded from Table 3 that the yield strength of the corrosion-resistant pipeline steel of the same thickness prepared by the preparation method of the 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas containing hydrogen sulfide in the embodiment of the present application is equivalent to the yield strength of the corrosion-resistant pipeline steel of Comparative Example 1, which is within 30MPa; the tensile strength is significantly higher than the tensile strength of the corrosion-resistant pipeline steel of Comparative Example 1 by 100MPa to 150MPa; only the elongation and the impact work at -40°C are slightly weaker than the elongation and the impact work at -40°C of the corrosion-resistant pipeline steel of Comparative Example 1. Among them, Figure 2 This is a metallographic structure diagram of the corrosion-resistant pipeline steel obtained in Example 1 of the present application, wherein the metallographic structure is 85% to 90% ferrite and 10% to 15% pearlite; Figure 2 The black particles dispersed in the sample are the second phase precipitates, i.e. the second phase particles. Figure 3 is the metallographic structure diagram of the corrosion-resistant pipeline steel prepared in Example 2 of the present application, Figure 4 is the metallographic structure diagram of the corrosion-resistant pipeline steel obtained in Example 3 of the present application, Figure 5 This is the metallographic structure diagram of the corrosion-resistant pipeline steel prepared in Example 4 of the present application. Figures 3 to 5 The black particles dispersed in the steel are all second phase precipitates, that is, the second phase particles, bainite structure and second phase particles are dispersed and strengthened in the matrix structure, which makes the steel have high strength and good plasticity and toughness, and improves the resistance of corrosion-resistant pipeline steel to crack initiation and propagation.

[0090] HIC hydrogen embrittlement resistance test

[0091] The corrosion-resistant pipeline steels of Examples 1-4 and Comparative Example 1 were tested for HIC hydrogen embrittlement resistance using the standard of the International Association of Corrosion Engineers, wherein the standard number is: NACETM0284-96, and the A solution in the standard is 5wt.% NaCl+0.5wt.% acetic acid+saturated H2S aqueous solution.

[0092] Table 4 Corrosion resistance test table of corrosion resistant pipeline steel of Examples 1-4 and Comparative Example 1

[0093]

[0094] The crack sensitivity level refers to a quantitative index of the material's resistance to crack initiation and expansion, reflecting the material's tendency to brittle fracture or plastic failure when there are small defects. Highly sensitive materials tend to fail quickly under small defects, while low-sensitivity materials show higher toughness and crack resistance. The crack length rate refers to the rate of change of the crack length over time, a(t) = da / dt, and the crack width rate refers to the rate of change of the crack width over time, W(t) = da / dt.

[0095] It can be concluded from Table 4 that the test results of the HIC hydrogen embrittlement resistance test of the corrosion-resistant pipeline steel prepared by the preparation method of 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide in the embodiment of the present application are all small, and the test results of its crack sensitivity level, crack length rate, and crack width rate are all significantly weaker than the test results of the crack sensitivity level, crack length rate, and crack width rate of the corrosion-resistant pipeline steel in Comparative Example 1, indicating that the corrosion-resistant pipeline steel prepared by the preparation method of 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide in the embodiment of the present application has good corrosion resistance to oil and gas media containing hydrogen sulfide, and its stress corrosion cracking sensitivity is low, that is, it has stronger resistance to crack initiation and propagation, and exhibits higher toughness and crack resistance.

[0096] The above is only a specific implementation method of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application.

Claims

1. A method for preparing 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, characterized in that: include: The molten iron is subjected to converter smelting, and the molten iron is subjected to argon blowing treatment in a ladle after converter smelting to obtain molten steel having a temperature greater than 1540° C. controlled at an argon station end point; The molten steel obtained at the end of the argon station is subjected to LF refining treatment at an inlet temperature of >1525°C in an LF refining station, and the composition of the molten steel is finely adjusted to a target composition during LF refining of the molten steel in an LF furnace, so that the outlet temperature of the molten steel at the LF refining station reaches 1585°C to 1620°C, thereby obtaining LF refined molten steel; Continuously casting the LF refined molten steel to obtain a continuously cast slab; The continuous casting slab is heated and rolled to obtain rolled steel; The rolled steel is subjected to laminar cooling treatment to obtain 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide.

2. The preparation method according to claim 1, characterized in that: In terms of mass percentage, the molten iron needs to meet the following composition requirements: P≤0.15% of the molten iron, residual elements As≤0.03%, and Sn≤0.02%.

3. The preparation method according to claim 1, characterized in that: The process conditions for continuous casting the LF refined steel liquid are as follows: a drawing speed of 1.4 m / min to 1.6 m / min, and a light reduction mode is used for continuous casting to obtain a continuously cast slab.

4. The preparation method according to claim 1, characterized in that: The soft reduction mode means that during the solidification process of the continuous casting slab, the continuous casting slab in the solid-liquid dual-phase temperature range is pressed down by 5 mm to 10 mm along the thickness direction of the continuous casting slab.

5. The preparation method according to claim 1, characterized in that: Also includes: The continuous casting slab is subjected to stack cooling treatment to reduce the temperature of the continuous casting slab from a hot slab environment of more than 500° C. to less than 300° C.

6. The preparation method according to claim 1, characterized in that: The heating and rolling treatment of the continuous casting slab includes: heating the continuous casting slab to obtain a heated casting slab; The heated ingot is rolled by adopting a thermomechanical controlled rolling and air cooling process to obtain a rolled steel product.

7. The preparation method according to claim 6, characterized in that: The continuous casting slab comprises: using a heating furnace to heat the continuous casting slab to 1200° C. to 1250° C., with a heating time of 150 minutes to 250 minutes and a solution time of more than 30 minutes; and / or The step of rolling the heated ingot by adopting a thermomechanical controlled rolling and controlled cooling process comprises: The heated ingot is subjected to rough rolling and finish rolling, wherein the starting temperature of the rough rolling is 1160°C to 1220°C, and the finishing temperature of the rough rolling is 1120°C to 980°C; the starting temperature of the finish rolling is 1020°C to 920°C, and the finishing temperature of the finish rolling is 800°C to 720°C, to obtain rolled steel.

8. The preparation method according to claim 1, characterized in that: The laminar cooling treatment of the rolled steel comprises: The cooling rate of the rolled steel is 30°C / s to 40°C / s, and the rolled steel is finally cooled to 550°C to 580°C to obtain 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide.

9. A 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide, characterized in that: According to the preparation method according to any one of claims 1 to 8, the 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide contains the following chemical components in mass percentage: C 0.04% to 0.06%; Si 0.15% to 0.25%; Mn 1.0% to 1.2%; Nb 0.045% to 0.055%; Al 0.020% to 0.050%; Cr 0.20% to 0.30%; Ti 0.015% to 0.025%; Cu 0.25% to 0.50%; Sb 0.25% to 0.35%; S 0.020% to 0.035%; P≤0.015%; N≤0.0050%; O≤0.0030%; hydrogen≤0.0015%, and the balance is Fe and unavoidable inclusions.

10. The 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas containing hydrogen sulfide according to claim 1, characterized in that: The properties of the 500MPa grade corrosion-resistant pipeline steel for transporting oil and gas media containing hydrogen sulfide are: yield strength Rel is 500MPa-550MPa, tensile strength Rm is 630MPa-750MPa, elongation A is greater than 15%, -40°C KV2 impact energy is greater than 27J; and hydrogen-induced cracking sensitivity index is less than 0.30.

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