Anti-corrosion seamless steel pipe and preparation method and application thereof

Abstract

The invention provides a corrosion-resistant seamless steel tube and a preparation method and application thereof. The preparation method comprises the steps that S1, raw materials are prepared, specifically, the corrosion-resistant seamless steel pipe comprises, by weight, 0.07%-0.13% of C, 0.5%-0.8% of Si, 0.5%-0.8% of Mn, smaller than or equal to 0.005% of S, smaller than or equal to 0.005% of P, 0.5%-0.9% of W, 0.3%-0.5% of Mo, 0.3%-0.5% of V, 0.06%-0.12% of Nb and the balance Fe and impurities, and Ni and Cr are not included; s2, smelting, vacuum degassing and casting treatment; step S3, annealing treatment; step S4, peeling and surface spraying treatment; and S5, annular furnace heat treatment, normalizing treatment and tempering treatment are conducted. The steel pipe capable of resisting hydrogen, nitrogen and ammonia in the high-temperature and high-pressure state is manufactured.

Description

Technical Field

[0001] The present invention relates to the technical field of alloys, and in particular to a corrosion-resistant seamless steel pipe, a preparation method thereof and applications thereof. Background Art

[0002] The rapid development of the chemical industry and the petroleum refining industry has placed increasingly stringent requirements on the performance of the materials used. Taking the cracking reaction in the chemical industry as an example, its related equipment often requires materials to have multiple properties such as resistance to high temperature, high pressure, and corrosion. In the fertilizer industry, steel pipes are accompanied by the combined effects of multiple conditions during their service, which can easily cause material corrosion failure. At the same time, in various application scenarios of steel pipes, it is generally not just hydrogen corrosion, but also includes the ammonia synthesis process and the combined effects of nitrogen and ammonia.

[0003] In the past, austenitic stainless steel was usually used for high temperature and high pressure conditions, as well as in service scenarios containing media such as hydrogen, nitrogen, and ammonia. Although this type of steel has good hydrogen resistance, it is severely nitrided. At the same time, austenitic stainless steel is expensive due to its high alloy content.

[0004] Based on this, since the seamless steel pipes prepared by the existing technology have the problem of difficulty in having both good mechanical properties and corrosion resistance, it is necessary to design their composition and the corresponding preparation method so that they can meet the use requirements of seamless steel pipes in various fields, especially in high temperature, high pressure and high corrosion environments. Summary of the invention

[0005] The main purpose of the present invention is to provide a corrosion-resistant seamless steel pipe, a preparation method and application thereof, so as to solve the problem that the seamless steel pipe prepared by the prior art is difficult to have both good mechanical properties and corrosion resistance, and is difficult to meet the application requirements in high temperature, high pressure and high corrosion environments.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for preparing a corrosion-resistant seamless steel pipe, which comprises: step S1, preparing raw materials according to the following composition: in terms of weight percentage, the components of the corrosion-resistant seamless steel pipe include: 0.07% to 0.13% C, 0.5% to 0.8% Si, 0.5% to 0.8% Mn, S≤0.005%, P≤0.005%, 0.5% to 0.9% W, 0.3% to 0.5% Mo, 0.3% to 0.5% V, 0.06% to 0.12% Nb, and the remainder is Fe and impurities, but excluding Ni and Cr; step S2, the raw materials are successively smelted, vacuum degassed and cast to obtain an initial billet; step S3, the initial billet is annealed to obtain an annealed billet; step S4, the annealed billet is successively peeled and surface sprayed to obtain a billet to be heat treated with a protective layer on the surface; step S5, the billet to be heat treated is successively subjected to annular furnace heat treatment, normalizing treatment and tempering treatment to obtain a corrosion-resistant seamless steel pipe; the surface coating used for the surface spraying treatment includes Al2O3, SiO2 and SiC, and the thickness of the protective layer is 1.5mm~2.2mm.

[0007] Furthermore, in the composition of the corrosion-resistant seamless steel pipe, the sum of the weights of W and Mo is 1% to 1.2%, and the weight ratio of V to C is (4 to 6):1, calculated by weight percentage.

[0008] Furthermore, in the surface coating, the weight ratio of Al2O3 to SiO2 is (1.0-1.2):1; taking the sum of the weights of Al2O3 and SiO2 as 100%, the content of SiC is 4%-6%.

[0009] Further, in step S2, the annealing treatment includes a first annealing treatment and / or a second annealing treatment, and the temperature of the first annealing treatment is 900°C to 920°C, and the temperature of the second annealing treatment is 700°C to 720°C.

[0010] Further, in step S5, the annular furnace heat treatment includes the following steps in sequence: preheating treatment at a temperature of 600-700°C for 4.0h-7.0h; first-stage heating treatment at a temperature of 1020±10°C for 2.0h-3.0h; second-stage heating treatment at a temperature of 1160±10°C for 1.5h-2.0h; third-stage heating treatment at a temperature of 1175±10°C for 1.5h-2.0h; fourth-stage heating treatment at a temperature of 1250±10°C for 1.5h-2.0h; and final heating treatment at a temperature of 1250±10°C for 1.5h-2.0h.

[0011] Furthermore, in step S5, before normalizing, the billet after the ring furnace heat treatment is subjected to rolling treatment to obtain a rolled tube billet with a wall thickness of 52±4 mm.

[0012] Furthermore, the rolling process includes a hot rolling piercing process at a temperature of 1200° C. to 1250° C. and a cycle rolling process at a temperature of 1020° C. to 1100° C. performed sequentially.

[0013] Further, in step S5, the normalizing temperature is 970°C to 990°C, the time is the normalizing time parameter × wall thickness, and the normalizing time parameter is 3.0 min / mm to 3.5 min / mm; the tempering temperature is 730°C to 750°C, the time is the tempering time parameter × wall thickness, and the tempering time parameter is 4.0 min / mm to 4.5 min / mm.

[0014] The second aspect of the present invention provides a corrosion-resistant seamless steel pipe, which is produced by the above-mentioned method for producing the corrosion-resistant seamless steel pipe.

[0015] The third aspect of the present invention provides an application of the above-mentioned corrosion-resistant seamless steel pipe as a pipe in the fields of oil and gas exploration, chemical production and fertilizer industry, and the application environmental conditions are: temperature of 350°C to 380°C, pressure of 32MPa to 35MPa, gas environment of H2:N2=(2~3):1, NH3 volume fraction=(15±2)%.

[0016] By applying the technical solution of the present invention, a low-cost seamless steel pipe material with good high-temperature and high-pressure gas corrosion resistance and a manufacturing method thereof are provided. By comprehensively designing the composition formula, process flow and parameter conditions of the seamless steel pipe, introducing the technology of surface spraying to form an anti-oxidation protective layer, and combining the heat treatment process, the manufacture of steel pipes that can resist hydrogen, nitrogen and ammonia under high temperature and high pressure is realized. The obtained corrosion-resistant seamless steel pipe has both good mechanical properties and corrosion resistance, and can meet the application requirements in multiple fields and harsh environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 This is a metallographic photograph of the corrosion-resistant seamless steel pipe obtained in Example 1. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0020] As described in the background technology, the seamless steel pipe prepared by the prior art has the problem that it is difficult to have both good mechanical properties and corrosion resistance, and it is difficult to meet the application requirements in high temperature, high pressure and high corrosion environments. In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing a corrosion-resistant seamless steel pipe, and the method for preparing a corrosion-resistant seamless steel pipe comprises:

[0021] Step S1, preparing raw materials according to the following composition: by weight percentage, the components of the corrosion-resistant seamless steel pipe include: 0.07% to 0.13% C, 0.5% to 0.8% Si, 0.5% to 0.8% Mn, S≤0.005%, P≤0.005%, 0.5% to 0.9% W, 0.3% to 0.5% Mo, 0.3% to 0.5% V, 0.06% to 0.12% Nb, the balance is Fe and impurities, and does not include Ni and Cr; Step S2, the raw materials are sequentially After smelting, vacuum degassing and casting treatment, an initial billet is obtained; in step S3, the initial billet is annealed to obtain an annealed billet; in step S4, the annealed billet is successively subjected to peeling and surface spraying treatment to obtain a billet to be heat treated with a protective layer on the surface; in step S5, the billet to be heat treated is successively subjected to ring furnace heat treatment, normalizing treatment and tempering treatment to obtain a corrosion-resistant seamless steel pipe; the surface coating used for the surface spraying treatment includes Al2O3, SiO2 and SiC, and the thickness of the protective layer is 1.5mm to 2.2mm.

[0022] The above-mentioned preparation method provided by the present invention, by designing the composition of the corrosion-resistant seamless steel pipe, coordinating the process flow and adjusting the relevant condition parameters, successfully realizes the manufacture of corrosion-resistant seamless steel pipes with good mechanical properties and corrosion resistance, and capable of resisting hydrogen, nitrogen and ammonia under high temperature and high pressure. Specifically, for the composition of the corrosion-resistant seamless steel pipe provided, due to the requirements of multiple fields for the high temperature and high pressure corrosion resistance of steel pipes, a small amount of P and S are added to reduce its intergranular brittle tendency. Mn is an austenite stabilizing element and also a matrix strengthening element, which can improve the strength through precipitation strengthening. The 0.5% to 0.8% Mn added by the present invention can also improve the hardenability of the material. If it is too low, the strength will not meet the requirements, and if it is too high, it will affect the toughness of the material. S is easy to form precipitate MnS with the metal element Mn, reducing the low-temperature toughness of the material; P is easy to segregate at the grain boundary, reducing the grain boundary crack propagation resistance and reducing corrosion resistance. Therefore, S and P are both harmful elements to corrosion resistance. The present invention controls the content of both of them to be no more than 0.005% based on the overall alloy formula.

[0023] Considering the requirements of high temperature, high pressure, resistance to hydrogen, nitrogen, ammonia and hydrogen corrosion, the present invention further adds 0.3% to 0.5% V, 0.3% to 0.5% Mo, 0.5% to 0.9% W, and 0.06% to 0.12% Nb on the basis of the above-mentioned component dosages. This is because the inventors have found through a large number of experiments that these elements can form stable carbides with 0.07% to 0.13% carbon in the above-mentioned alloy formula provided by the present invention, which are dispersed on the ferrite body and play a role in dispersion strengthening. At the same time, the content of V, Mo, W, and Nb elements with the above-mentioned specific content is higher than that of existing hot-strength alloy steels. The main purpose is to improve the high temperature performance and corrosion resistance of the corrosion-resistant seamless steel pipe obtained by the present invention. In addition, adding 0.06% to 0.12% of the trace element Nb can also simplify the heat treatment process, better adapt to the above-mentioned preparation method provided by the present invention, and thus improve the processing performance of the corrosion-resistant seamless steel pipe during the preparation process.

[0024] In particular, the corrosion-resistant seamless steel pipe provided by the present invention does not include Ni and Cr. The inventors found after a large number of experiments and comparisons that, based on the alloy composition formula provided by the present invention, if the above two elements are added alone or in combination, while complicating the alloy composition and the corresponding preparation process, the performance of the obtained corrosion-resistant seamless steel pipe will not be improved, and may even be deteriorated to a certain extent, as follows:

[0025] The addition of Ni element can improve the impact toughness and corrosion resistance of low carbon steel under normal heat treatment conditions, but the preparation method provided by the present invention will obtain a martensitic martensite structure. If Ni element is present in it, it will affect the low-temperature impact toughness; Cr element is generally believed in the art to be able to effectively improve the oxidation resistance and corrosion resistance of heat-resistant steel, and can also be dissolved in the matrix to play a solid solution strengthening role, but for the low carbon corrosion-resistant steel provided by the present invention, if this element is present in the normalizing cooling process, it is easy to obtain a martensitic structure, which leads to a decrease in impact toughness.

[0026] On this basis, for the composition formula of the above-mentioned corrosion-resistant seamless steel pipe, the inventor has conducted a large number of experiments, comprehensively considered and designed the corresponding preparation process as above, especially the annealed billet after preliminary annealing is peeled to keep the surface clean and smooth, and remove the oxide scale formed on the surface during the previous step of forming and the previous step of heat treatment, to ensure that the subsequent surface spraying and forming of the protective layer can proceed smoothly. The coating used for the anti-oxidation protective layer includes Al2O3 and SiO2, which are the basic raw materials of the coating, different from other types of oxides, and can better cooperate with the above-mentioned alloy formula to play a significant protective role. On this basis, SiC is further added to increase the anti-decarburization ability. At the same time, in order to comprehensively consider the dimensional accuracy, surface properties, corrosion resistance, mechanical properties and service life of the obtained corrosion-resistant seamless steel pipe, the inventors have controlled the thickness of the above-mentioned anti-oxidation protective layer formed by surface spraying to be 1.5mm~2.2mm through a large number of experiments. The anti-oxidation coating of this thickness can also effectively prevent the tube blank from forming oxide scale during subsequent high-temperature heating, maintain its surface cleanliness, thereby improving the surface finish and corrosion resistance of the seamless steel pipe, and finally obtaining a corrosion-resistant seamless steel pipe with excellent comprehensive performance.

[0027] In addition, the preparation method provided by the present invention also includes performing ring furnace heat treatment, normalizing treatment and tempering treatment on the tube blank with an anti-oxidation protective layer formed on the surface, so as to better uniformize the composition, refine the grains, and improve the mechanical properties, especially toughness, and corrosion resistance of the obtained corrosion-resistant seamless steel pipe.

[0028] In several typical embodiments, in the composition of the corrosion-resistant seamless steel pipe, the weight sum of W and Mo is 1% to 1.2% by weight percentage. This is because W and Mo can not only fix the carbon in the steel, but also partially integrate into the ferrite, play a role in solid solution strengthening, and improve the thermal strength and tempering stability. Based on the consideration that W and Mo elements will affect the low-temperature impact performance and solid solubility in steel, the inventor has preferred the content of W+Mo to be 1% to 1.2% after a large number of experiments to more significantly improve the mechanical strength of the obtained corrosion-resistant seamless steel pipe, especially the impact performance. And, in the composition of the corrosion-resistant seamless steel pipe, the weight ratio of V to C is (4 to 6): 1 by weight percentage. The inventor has found through a large number of experiments that under this ratio, V can form V4C3 with C, and at the same time, in conjunction with a variety of reasonable heat treatment processes in the subsequent process, V4C3 can be obtained as the main phase precipitated carbide, which improves the hydrogen resistance of the steel pipe under high temperature service conditions, and more effectively avoids the reduction of the toughness of the obtained steel pipe.

[0029] In order to make the anti-oxidation protective layer coated on the outer surface of the corrosion-resistant seamless steel pipe, the inventors have optimized the weight ratio of Al2O3 to SiO2 in the surface coating to be (1.0-1.2):1 through a large number of experiments. By coordinating these two oxides that play a major protective role under this dosage relationship, a seamless steel pipe that can take into account the corrosion resistance of multiple media is obtained. The obtained seamless steel pipe can show excellent resistance to hydrogen, nitrogen and ammonia corrosion under high temperature and high pressure conditions. And in order to strengthen the anti-decarburization brought by the anti-oxidation protective layer, further improve the corrosion resistance of the obtained seamless steel pipe, and enhance its service safety, it is preferred that the content of SiC is 4% to 6% based on the sum of the weight of Al2O3 and SiO2 as 100%.

[0030] In several typical implementations, in step S2, the annealing treatment includes a first annealing treatment and / or a second annealing treatment, and the temperature of the first annealing treatment is 900° C. to 920° C., and the temperature of the second annealing treatment is 700° C. to 720° C. Heat treating the initial billet within the above temperature range can better eliminate the internal stress of the initial billet during the casting process, improve its mechanical properties, make it show better processability in the subsequent process flow, and ultimately improve the comprehensive performance of the obtained corrosion-resistant seamless steel pipe.

[0031] Further, in step S5, the annular furnace heat treatment includes the following steps in sequence: preheating treatment at a temperature of 600-700°C for 4.0h-7.0h; first-stage heating treatment at a temperature of 1020±10°C for 2.0h-3.0h; second-stage heating treatment at a temperature of 1160±10°C for 1.5h-2.0h; third-stage heating treatment at a temperature of 1175±10°C for 1.5h-2.0h; fourth-stage heating treatment at a temperature of 1250±10°C for 1.5h-2.0h; and final heating treatment at a temperature of 1250±10°C for 1.5h-2.0h. After a large number of experiments, the inventors regulated and optimized the process steps of the ring furnace heat treatment and the temperature and time involved in each step, and obtained the above-mentioned process procedure, and found that this process procedure can better adapt to the above-mentioned alloy composition formula provided by the present invention, so as to more effectively promote the precipitation of each dispersion strengthening phase, significantly optimize the metallographic structure of the seamless steel pipe, and ultimately improve its comprehensive performance, especially corrosion resistance. And further, with respect to the heating rate of each heating stage during the ring furnace heat treatment process, the inventors, after a large number of experiments, preferably when the temperature is below 900°C, the heating rate is 10±2°C / min, and when it is above 900°C, the heating rate is 20±2°C / min. This heating method can improve the temperature uniformity of the tube blank during heat treatment, and at the same time can also reduce the defects caused by unreasonable heating rate during the heating process.

[0032] In several typical implementations, in step S5, before normalizing, the billet after the ring furnace heat treatment is also subjected to rolling treatment to obtain a rolled tube billet with a wall thickness of 52±4 mm, so as to better meet the use requirements for seamless steel pipes in various fields.

[0033] Furthermore, the rolling treatment includes a hot rolling piercing treatment at a temperature of 1200°C to 1250°C and a periodic rolling treatment at a temperature of 1020°C to 1100°C. The hot rolling piercing treatment temperature of 1200°C to 1250°C can better improve the plasticity and fluidity of the seamless steel pipe during the hot rolling process, thereby improving the dimensional accuracy and surface quality of the obtained seamless steel pipe, while the periodic rolling at a temperature of 1020°C to 1100°C can improve its dimensional accuracy and surface finish while maintaining the performance of the corrosion-resistant seamless steel pipe.

[0034] As for the normalizing and tempering treatment in step S5, in several typical implementations, the normalizing temperature is 970℃~990℃, and the time is (3.0min / mm~3.5min / mm)×wall thickness. The normalizing temperature range of 970℃~990℃ can more effectively improve the internal structure of the corrosion-resistant seamless steel pipe, improve its comprehensive performance, and enable it to better withstand the test of high pressure and high temperature in application. The time is (3.0min / mm~3.5min / mm)×wall thickness. This method of controlling time can better improve the uniformity and stability of the internal structure of the seamless steel pipe, so that it exhibits higher corrosion resistance. In several typical implementations, the tempering temperature is 730℃~750℃, and the time is (4.0min / mm~4.5min / mm)×wall thickness. Tempering treatment under this temperature range can more effectively eliminate the residual stress generated by the corrosion-resistant seamless steel pipe after normalizing, stabilize its internal structure, and further improve its mechanical properties and extend its service life. This temperature control method can also better improve the uniformity and stability of the internal structure of the seamless steel pipe, and ultimately improve the comprehensive performance of the resulting corrosion-resistant seamless steel pipe.

[0035] The second aspect of the present invention provides a corrosion-resistant seamless steel pipe, which is prepared by the above-mentioned method for preparing a corrosion-resistant seamless steel pipe. The obtained corrosion-resistant seamless steel pipe not only exhibits high tensile strength, yield strength, good toughness and impact resistance, but also has high high-temperature strength and resistance to hydrogen, nitrogen and ammonia corrosion under high temperature and high pressure. It can completely replace or even be superior to stainless steel pipes of the same grade, and the manufacturing cost is also lower.

[0036] The third aspect of the present invention provides an application of the above-mentioned corrosion-resistant seamless steel pipe as a pipe in the fields of oil and gas exploration, chemical production and fertilizer industry, and the environmental conditions of the application are: temperature of 350°C to 380°C, pressure of 32MPa to 35MPa, gas environment of H2:N2=(2-3):1, NH3 volume fraction=(15±2)%. The obtained corrosion-resistant seamless steel pipe has excellent comprehensive performance, so it can meet the use requirements of various fields, especially for the application in the above-mentioned high temperature, high pressure and various corrosive gas environments.

[0037] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0038] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing a corrosion-resistant seamless steel pipe:

[0041] S1. Prepare the raw materials according to the following alloy composition: C=0.01%, Si=0.72%, Mn=0.75%, S=0.001%, P=0.002%, W=0.6%, Mo=0.4%, V=0.4%, Nb=0.10%, and the balance is Fe and impurities (see Table 1); wherein W+Mo=1.0%, V / C=4.

[0042] S2. Billet smelting and VD treatment: the raw materials are smelted, refined, vacuum degassed and then processed by electromagnetic stirring continuous casting to obtain round tube billets. The initial blank;

[0043] S3, annealing treatment, the billet is subjected to high temperature diffusion annealing, the diffusion annealing temperature is 920°C, the time is the diameter of the round tube × 6 min / mm, that is, 500 mm × 6 min / mm, 50 hours.

[0044] S4, peeling the annealed blank obtained in S3 to make the outer surface of the blank clean and free of oil and scale; then spraying the peeled blank to coat the outer surface of the blank with an anti-oxidation protective layer, the anti-oxidation coating uses Al2O3 and SiO2 (Al2O3:SiO2=1:1, weight ratio) as the basic raw materials of the coating, and adds 5% SiC compared to the total weight of Al2O3 and SiO2 to increase the anti-decarburization ability, and uses potassium silicate aqueous solution as a binder. The above raw materials are mixed into a paste according to proportion, and applied on the surface of the blank to form an anti-oxidation protective layer with a thickness of 1.8 mm, that is, the blank to be heat treated.

[0045] S5-1. The blank to be heat treated is heated in the following order: annular furnace heating: preheating - four-stage heating - uniform heating: preheating temperature is 600℃ with furnace temperature, time is 4 hours; heating temperature of the first stage is 1020℃, time is 2 hours, heating temperature of the second stage is 1060℃, time is 1.8 hours, heating temperature of the third stage is 1175℃, time is 1.8 hours, heating temperature of the fourth stage is 1250℃, time is 1.8 hours; uniform heating temperature of the first stage is 1250℃, time is 1.5 hours.

[0046] S5-2, hot rolling piercing: hot rolling piercing is carried out at 1200℃, and 500mm round billets are pierced into capillaries.

[0047] S5-3, Cycle rolling and sizing: The temperature is 1120℃. Rough tube rolling The rough pipe is then heated to 920℃ in a stepping furnace and sized to After cooling, the finished steel pipe is Steel pipe.

[0048] S5-4. Income The steel pipe was sequentially subjected to normalizing treatment at a temperature of 980°C and a holding time of 3.0 min / mm×52mm=156 min, and tempering treatment at a temperature of 740°C and a holding time of 4.5 min / mm×52mm=234 min.

[0049] S6: Final treatment: After straightening, finishing, size and surface quality inspection of the tempered steel pipe, a corrosion-resistant seamless steel pipe is obtained.

[0050] The metallographic structure of the obtained corrosion-resistant seamless steel pipe is shown in Figure 1 .

[0051] Examples 2 to 11

[0052] The difference between Examples 2 to 11 and Example 1 is that the steel pipe composition ratios and process parameters are different, wherein the composition is shown in Table 1, and the differences among step S4, step S5-1 and step S5-3 in the process parameters are shown in Tables 2-1 and 2-2, and the remaining steps not mentioned in the table are the same as those in Example 1.

[0053] Comparative Examples 1 to 8

[0054] The difference between Comparative Examples 1 to 8 and Example 1 is that the steel pipe composition ratios and process parameters are different, wherein the composition is shown in Table 1, and the differences among step S4, step S5-1 and step S5-3 in the process parameters are shown in Table 2-1 and Table 2-2, and the remaining steps not mentioned in the table are the same as those in Example 1.

[0055] Table 1

[0056]

[0057] The examples and comparative examples not listed in Table 1 have the same element types and contents as those in Example 1. Meanwhile, Comparative Example 3 has 0.05% Ni added to the components in the table, and Comparative Example 4 has 0.05% Cr added to the components in the table.

[0058] Table 2-1

[0059]

[0060]

[0061] For the embodiments and comparative examples not listed in Table 2-1, the experimental conditions involved in this table are the same as those in Example 1.

[0062] Table 2-2

[0063]

[0064] For the embodiments and comparative examples not listed in Table 2-2, the experimental conditions involved in this table are the same as those in Example 1.

[0065] The steel pipes with a specification of Φ406×52 mm obtained in the above embodiments and comparative examples were subjected to performance tests in accordance with the requirements of GB / T6479. The results are shown in Table 3.

[0066] In addition, the experimental conditions for the corrosion resistance test are temperature 380°C, pressure 32MPa, H2:N2=3:1, NH3=15%. After 5000 hours to 10000 hours of corrosion, the changes in tensile strength and yield strength before and after corrosion are tested. The results are shown in Table 3.

[0067] Table 3

[0068]

[0069]

[0070] From the above description, it can be seen that the above embodiments of the present invention realize the manufacture of corrosion-resistant seamless steel pipes having good mechanical properties and corrosion resistance and capable of resisting hydrogen, nitrogen and ammonia under high temperature and high pressure conditions. The obtained steel pipes can meet the application requirements in multiple fields and harsh environments.

[0071] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a corrosion-resistant seamless steel pipe, characterized in that: The method for preparing the corrosion-resistant seamless steel pipe comprises: Step S1, preparing raw materials according to the following composition: by weight percentage, the components of the corrosion-resistant seamless steel pipe include: 0.07% to 0.13% C, 0.5% to 0.8% Si, 0.5% to 0.8% Mn, S≤0.005%, P≤0.005%, 0.5% to 0.9% W, 0.3% to 0.5% Mo, 0.3% to 0.5% V, 0.06% to 0.12% Nb, the balance is Fe and impurities, and does not include Ni and Cr; Step S2, the raw material is sequentially smelted, vacuum degassed and cast to obtain an initial blank; Step S3, the initial blank is annealed to obtain an annealed blank; Step S4, the annealed blank is subjected to peeling and surface spraying treatments in sequence to obtain a blank to be heat treated with a protective layer on the surface; Step S5, the blank to be heat treated is sequentially subjected to a ring furnace heat treatment, a normalizing treatment and a tempering treatment to obtain the corrosion-resistant seamless steel pipe; The surface coating used for the surface spraying treatment includes Al2O3, SiO2 and SiC, and the thickness of the protective layer is 1.5mm to 2.2mm.

2. The method for preparing a corrosion-resistant seamless steel pipe according to claim 1, characterized in that: In the composition of the corrosion-resistant seamless steel pipe, the sum of the weights of W and Mo is 1% to 1.2%, and the weight ratio of V to C is (4 to 6):

1.

3. The method for preparing a corrosion-resistant seamless steel pipe according to claim 1 or 2, characterized in that: In the surface coating, the weight ratio of Al2O3 to SiO2 is (1.0-1.2):1; Taking the sum of the weight of Al2O3 and SiO2 as 100%, the content of SiC is 4% to 6%.

4. The method for preparing a corrosion-resistant seamless steel pipe according to any one of claims 1 to 3, characterized in that: In step S2, the annealing treatment includes a first annealing treatment and / or a second annealing treatment, and the temperature of the first annealing treatment is 900°C to 920°C, and the temperature of the second annealing treatment is 700°C to 720°C.

5. The method for preparing a corrosion-resistant seamless steel pipe according to any one of claims 1 to 4, characterized in that: In step S5, the annular furnace heat treatment includes the following steps performed in sequence: Preheating treatment, temperature is 600~700℃, time is 4.0h~7.0h; One stage heating treatment, temperature is 1020±10℃, time is 2.0h~3.0h; Second stage heating treatment, temperature is 1160±10℃, time is 1.5h~2.0h; Three-stage heating treatment, temperature is 1175±10℃, time is 1.5h~2.0h; Four-stage heating treatment, temperature is 1250±10℃, time is 1.5h~2.0h; The final heating treatment is performed at a temperature of 1250±10°C for 1.5h to 2.0h.

6. The method for preparing a corrosion-resistant seamless steel pipe according to any one of claims 1 to 5, characterized in that: In step S5, before the normalizing treatment, the process further includes rolling the billet after the heat treatment in the annular furnace to obtain a rolled tube billet with a wall thickness of 52±4 mm.

7. The method for preparing a corrosion-resistant seamless steel pipe according to claim 6, characterized in that: The rolling process includes a hot rolling piercing process at a temperature of 1200° C. to 1250° C. and a periodic rolling process at a temperature of 1020° C. to 1100° C. performed sequentially.

8. The method for preparing a corrosion-resistant seamless steel pipe according to claim 6 or 7, characterized in that: In step S5, The normalizing treatment temperature is 970°C to 990°C, the time is the normalizing treatment time parameter × the wall thickness, and the normalizing treatment time parameter is 3.0min / mm to 3.5min / mm; The tempering treatment temperature is 730° C. to 750° C., the time is the tempering treatment time parameter×the wall thickness, and the tempering treatment time parameter is 4.0 min / mm to 4.5 min / mm.

9. A corrosion-resistant seamless steel pipe, characterized in that: The corrosion-resistant seamless steel pipe is prepared by the method for preparing the corrosion-resistant seamless steel pipe according to any one of claims 1 to 8.

10. An application of the corrosion-resistant seamless steel pipe according to claim 9 as a pipe in the fields of oil and gas exploration, chemical production and fertilizer industry, wherein the environmental conditions of the application are: temperature of 350°C to 380°C, pressure of 32MPa to 35MPa, gas environment of H2:N2=(2-3):1, NH3 volume fraction=(15±2)%.

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