Pipeline steel for conveying thickened oil and preparation method thereof

Abstract

The invention relates to pipeline steel for heavy oil conveying and a preparation method, and belongs to the technical field of steel preparation. The pipeline steel for thick oil conveying comprises the following chemical components: C, Si, Mn, P, S, Cr, Nb, Ti, V and a matrix element Fe, the mass part of C is less than or equal to 0.10 part; the mass part of the V is 0.01 to 0.08 part. By optimizing chemical components and controlling the content of C, it is avoided that due to the too high content of C, the center segregation tendency of a plate blank is increased, and the material toughness is reduced, meanwhile, a proper amount of V, Cr, Nb, Ti and other elements are added, and the strength and heat resistance of steel are improved through a solid solution strengthening and precipitation strengthening mechanism. The obtained pipeline steel is suitable for LLHT (electric heat tracing system formed by ultra-long-distance resistance type heating cables) long-distance pipeline heating thickened oil conveying, and can meet the requirement of the maximum 100 DEG C environment in the ultra-long-term service state.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, and particularly relates to a pipeline steel for thick oil transportation and a preparation method. BACKGROUND

[0002] In the face of rapidly growing energy demand worldwide, the world's oil and gas production capacity and production are relatively insufficient, which makes people pay more and more attention to the development and utilization of unconventional oil and gas resources. As an important unconventional oil and gas resource, thick oil has great development potential due to its abundant reserves. However, thick oil has some inherent physical properties, such as high density, high asphaltene content and poor flowability at room temperature, which pose special requirements on the long-distance transportation environment of thick oil. The high viscosity and low flowability of thick oil require special measures to improve its flowability during transportation to ensure smooth transportation. At present, the main ways to improve the viscosity of thick oil in the pipeline include heating and mixing other liquids. Among them, the heating method has become the most widely used thick oil pipeline transportation process because it can significantly reduce the viscosity of thick oil and thus improve the pumping efficiency. Through heating, the temperature of thick oil is increased, the interaction between molecules is weakened, and the flowability is significantly increased, so that thick oil can flow more easily in the pipeline.

[0003] However, although the heating method is effective, it also has the problem of high energy consumption. In order to reduce energy consumption while meeting normal transportation conditions, people usually use the mixed transportation method, that is, mixing thick oil with other low-viscosity liquids to appropriately reduce the transportation temperature. This method reduces energy consumption to some extent, but also limits the transportation distance and efficiency of thick oil. At present, the operating temperature of most thick oil pipelines is controlled at about 70-85℃, which is a relatively economical and feasible temperature range. However, some super-thick oil pipelines have to use higher transportation temperatures due to the extremely high viscosity of thick oil. These high-temperature transportation environments pose higher requirements on the pipeline materials. The traditional pipeline materials may have performance degradation at high temperatures, such as strength reduction and toughness reduction, which cannot meet the safety operation requirements of super-thick oil pipelines. SUMMARY

[0004] The present application provides a pipeline steel for thick oil transportation and a preparation method to solve the technical problem of how to solve the performance requirements of the pipeline steel for thick oil transportation under high-temperature and long-distance service environment.

[0005] In a first aspect, the embodiments of the present application provide a pipeline steel for thick oil transportation, and the chemical components of the pipeline steel for thick oil transportation include C, Si, Mn, P, S, Cr, Nb, Ti, V and base element Fe.

[0006] The mass fraction of C is ≤0.10 parts.

[0007] The mass fraction of V is 0.01-0.08 parts.

[0008] Optionally, the chemical composition of the pipeline steel for transporting heavy oil is, in terms of mass fraction, C: 0.030%-0.080%, Si: 0.10%-0.40%, Mn: 1.20%-1.60%, P≤0.015%, S≤0.005%, V: 0.02%-0.05%, Cr: 0.10%-0.25%, Ti: 0.010%-0.060%, Nb: 0.01%-0.05%, and base element Fe.

[0009] Optionally, the metallurgical structure of the pipeline steel for transporting heavy oil includes ferrite and / or quasi-polygonal ferrite, pearlite.

[0010] Optionally, the pipeline steel for transporting heavy oil satisfies at least one of the following properties at ≤100℃: yield strength≥420MPa, tensile strength≥505MPa.

[0011] Optionally, the strength of the pipeline steel for transporting heavy oil is X65 steel grade.

[0012] In a second aspect, the embodiment of the present application provides a preparation method of the pipeline steel for transporting heavy oil in the first aspect, and the method comprises the following steps:

[0013] obtaining a slab with the chemical composition;

[0014] heating the slab so that the slab reaches a tapping temperature;

[0015] sequentially rolling, cooling and coiling the heated slab to obtain the pipeline steel for transporting heavy oil.

[0016] Optionally, the center segregation rating of the slab is ≤2.0.

[0017] Optionally, the tapping temperature is 1100-1280℃.

[0018] Optionally, the final rolling temperature of the rolling is 830-920℃.

[0019] Optionally, the coiling temperature is 400-600℃.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The embodiment of the present application provides a pipeline steel for heavy oil transportation, and the chemical components of the pipeline steel for heavy oil transportation include: C, Si, Mn, P, S, Cr, Nb, Ti, V and base element Fe; the mass fraction of the C is less than or equal to 0.10 parts; and the mass fraction of the V is 0.01 parts to 0.08 parts. By optimizing the chemical components, the content of the C is controlled, so that the tendency of slab center segregation is increased and the toughness of the material is reduced due to too high C content is avoided, meanwhile, the V, Cr, Nb, Ti and other elements are appropriately added, so that the strength and hot strength of the steel are improved through solid solution strengthening and precipitation strengthening mechanism. The obtained pipeline steel is suitable for LLHT (electric heat tracing system formed by super long distance resistance heating cable) long distance pipeline heating heavy oil transportation, and can meet the requirement of maximum 100 DEG C environment under the super long term service state. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings incorporated in the specification and forming a part thereof illustrate the embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows, and obviously, other drawings can be obtained by those of ordinary skill in the art without any creative labor under the premise of the drawings.

[0024] Figure 1 A flowchart of a preparation method of the pipeline steel for heavy oil transportation provided by the embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those of ordinary skill in the art without any creative labor are within the protection scope of the present application.

[0026] Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the range described has been specifically disclosed all possible sub-ranges and single values within the range; for example, it should be considered that the range description from 1 to 6 has been specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it refers to any cited number (fraction or integer) within the indicated range.

[0027] In this document, the term includes "includes" and the like means "including, but not limited to". The relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between such entities or operations. The "and / or", which describes the association relationship of the associated objects, means that there can be three kinds of relationships, for example, A and / or B can represent: A exists alone, A and B exist together, B exists alone; Where A, B can be singular or plural. "One or more" means one or more, "multiple" means two or more; "at least one", "at least one of the following" or the like means any combination of the items, including single item or combination of multiple items; for example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, c can be single or multiple. The "parts ratio" such as weight parts, mass parts, etc. represents the proportional relationship between components. In the proportional relationship described herein, the parameters that need to be described by proportion should be understood as the front item of the proportional form according to the order of description, and the proportional number should be understood as the rear item of the proportional form, for example, the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should be one-to-one corresponding in the proportional form according to the description order, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0028] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used herein can be purchased from the market or can be prepared by existing methods.

[0029] In a first aspect, the embodiments of the present application provide a pipeline steel for heavy oil transportation, the chemical composition of the pipeline steel for heavy oil transportation comprises: C, Si, Mn, P, S, Cr, Nb, Ti, V, and base element Fe;

[0030] the mass fraction of C is ≤0.10 parts;

[0031] the mass fraction of V is 0.01 parts to 0.08 parts.

[0032] Positive effect of limiting the mass fraction of C to ≤0.10 parts: C is a basic strengthening element of steel materials, and has a significant impact on the mechanical properties of steel, such as strength, hardness, and toughness. In the embodiments of the present application, the mass fraction of C is greater than 0.10 parts, which is easy to form center segregation in the slab, i.e., the uneven distribution of carbon elements at the grain boundaries or interdendritic, resulting in uneven material organization and performance degradation. In addition, in high-temperature service environments, the thermal strength of the material is particularly important. Controlling the mass fraction of C to ≤0.10 parts, combined with the addition of other alloying elements, can improve the thermal stability and creep resistance of the steel, so that the pipeline steel can still maintain good mechanical properties and organizational stability at high temperatures. Exemplarily, the mass fraction of C can be 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.10 parts, etc.

[0033] Positive effect of limiting the mass fraction of V to 0.01 parts to 0.08 parts: the addition of V can improve the strength of the steel through two mechanisms of solid solution strengthening and precipitation strengthening. Through micro-alloying of element V, stable carbides and nitrides are formed, which prevent grain growth and dislocation movement at high temperatures, maintain the stability of the organizational structure of the steel, and thus improve the thermal strength of the steel, so that the safety service of the pipeline can be maintained at a higher temperature. Exemplarily, the mass fraction of V can be 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, etc.

[0034] In some embodiments, the chemical composition of the pipeline steel for transporting thick oil, in terms of mass fraction, is: C: 0.030% to 0.080%, Si: 0.10% to 0.40%, Mn: 1.20% to 1.60%, P ≤ 0.015%, S ≤ 0.005%, V: 0.02% to 0.05%, Cr: 0.10% to 0.25%, Ti: 0.010% to 0.060%, Nb: 0.01% to 0.05%, and base element Fe.

[0035] Advantages of limiting the mass fraction of Si to 0.10% to 0.40%: Si is a common deoxidizer in steel smelting. In the steelmaking process, Si can combine with oxygen in the steel to form stable silicates or silicon dioxide, thereby reducing the oxygen content in the steel and reducing the hot brittleness and crack sensitivity caused by excessive oxygen content. Si can be solid-solved in ferrite to form a solid solution, which has a certain strengthening effect on the strength of the steel. At the same time, Si can also promote the formation of carbides in the steel, further increasing the hardness of the steel. For pipeline steels used for heavy oil transportation that need to serve in high temperature environments, heat resistance and oxidation resistance are crucial. Si can improve the stability and oxidation resistance of the steel at high temperatures, reduce oxidation and decarburization of the steel at high temperatures, and thus prolong the service life of the material. For example, the mass fraction of Si can be 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, etc.

[0036] Advantages of limiting the mass fraction of Mn to 1.20% to 1.60%: Mn is an important alloying element in steel, which can effectively improve the strength and hardness of the steel. In pipeline steels for heavy oil transportation, 1.20% to 1.60% of Mn can increase the yield strength and tensile strength of the steel, ensuring the stability and safety of the pipeline steel under high pressure and high temperature conditions. The addition of Mn also helps to improve the toughness and plasticity of the steel. When subjected to external forces, Mn can enhance the deformation ability of the steel, prevent sudden breakage of the steel, and improve the durability of the pipeline steel in complex stress environments. For example, the mass fraction of Mn can be 1.20%, 1.30%, 1.40%, 1.50%, 1.60%, etc.

[0037] Advantages of limiting the mass fraction of Cr to 0.10% to 0.25%: Cr is one of the key elements for enhancing the corrosion resistance of steel. In the process of heavy oil transportation, pipeline steels may come into contact with corrosive media such as sulfur compounds and moisture. Controlling the mass fraction of Cr within the range of 0.10% to 0.25% can significantly improve the corrosion resistance of the pipeline steel and prolong its service life. Cr can also improve the oxidation resistance of the steel, especially in high temperature environments. In the process of heavy oil transportation, the pipeline steel may be in a high temperature state and prone to oxidation. A dense oxide film can be formed on the surface of the steel with 0.10% to 0.25% of Cr, preventing further oxidation and protecting the steel from high temperature oxidation damage. As an alloying element, Cr also has a positive effect on the hardness and strength of the steel. In pipeline steels for heavy oil transportation, 0.10% to 0.25% of Cr can be solid-solved in ferrite to form solid solution strengthening, thereby improving the yield strength and tensile strength of the steel. For example, the mass fraction of Cr can be 0.10%, 0.13%, 0.16%, 0.19%, 0.22%, 0.25%, etc.

[0038] The positive effects of limiting the mass fraction of Ti to 0.010% to 0.060%: Ti can combine with element C in the steel to form stable carbide (TiC), which can effectively hinder the movement of grain boundaries, thereby inhibiting the growth of grains. By refining the grains, the strength and toughness of the steel can be improved, and the mechanical properties of the steel can be improved. The carbide of Ti is a hard point, which can be dispersedly distributed in the steel matrix to play a role of dispersion strengthening. This strengthening mechanism can increase the yield strength and tensile strength of the steel, and improve the carrying capacity of the steel. Finally, Ti can combine with harmful elements such as S and P in the steel to reduce their adverse effects on the welding quality, and at the same time, the refined grains can help to reduce the brittleness tendency of the welding heat affected zone, and improve the strength and toughness of the welded joint. For example, the mass fraction of Ti can be 0.010%, 0.020%, 0.030%, 0.040%, 0.050%, 0.060%, etc.

[0039] The positive effects of limiting the mass fraction of Nb to 0.01% to 0.05%: Nb is a strong carbide-forming element, which can combine with C in the steel to form fine NbC particles. These particles are very stable at high temperatures and can effectively hinder the growth of austenite grains, thereby refining the grains of the steel. The refined grains can improve the strength and toughness of the steel, and improve the mechanical properties of the steel. The NbC particles in the steel can play a role of precipitation strengthening. These particles are dispersedly distributed in the matrix, which can hinder the movement of dislocations, thereby improving the strength of the steel. This strengthening method can not only improve the yield strength and tensile strength of the steel, but also can not reduce the toughness of the steel. In addition, the addition of Nb can reduce the segregation of harmful elements such as sulfur and phosphorus in the steel, reduce the crack sensitivity of the welding heat affected zone, and at the same time, the refined grains can help to reduce the brittleness tendency of the welding heat affected zone, and improve the strength and toughness of the welded joint. For example, the mass fraction of Nb can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, etc.

[0040] In some embodiments, the metallurgical structure of the heavy oil pipeline steel includes ferrite and / or quasi-polygonal ferrite, pearlite.

[0041] In some embodiments, the heavy oil pipeline steel satisfies at least one of the following properties at ≤100℃: yield strength ≥420MPa, tensile strength ≥505MPa.

[0042] The yield strength is the minimum stress value at which the material begins to deform plastically. In the process of transporting heavy oil, the pipeline steel needs to withstand the pressure from the oil flow and various stresses from the external environment. A yield strength of ≥420MPa can ensure that the pipeline steel does not easily deform plastically when facing these stresses, thereby maintaining the integrity and stability of the pipeline.

[0043] Tensile strength is the maximum tensile stress that a material can withstand during tensile testing, which reflects the material's ability to resist fracture. During the transportation of heavy oil, the pipeline steel may be subjected to sudden impact or overload, and a tensile strength ≥ 505 MPa can ensure that the pipeline steel does not easily fracture when faced with these extreme conditions, thereby preventing safety accidents such as pipeline leakage or rupture.

[0044] In the embodiments of the present application, the pipeline steel for heavy oil transportation meets the above mechanical property requirements at a temperature not exceeding 100°C, which can ensure that it maintains stable mechanical properties and reliable working conditions in harsh service environments. This not only improves the safety and reliability of the pipeline, but also prolongs the service life of the pipeline, reduces maintenance costs and environmental risks. It is suitable for LLHT long-distance pipeline electric heating systems. The LLHT system provides heat to the pipeline through resistance heating cables to prevent heavy oil from solidifying during transportation due to excessively low temperature.

[0045] In some embodiments, the pipeline steel for heavy oil transportation has a strength of X65 steel grade.

[0046] The pipeline steel for heavy oil transportation has a strength of X65 steel grade, which is a standard for high-strength pipeline steel that can withstand large internal pressure and external load, ensuring the safety and reliability of the pipeline in harsh environments.

[0047] Figure 1 A flowchart of a preparation method of a pipeline steel for heavy oil transportation according to an embodiment of the present application is shown.

[0048] Please refer to Figure 1 , in a second aspect, the present application provides a preparation method of the pipeline steel for heavy oil transportation in the first aspect, the method comprises:

[0049] S1, obtaining a slab with the chemical composition;

[0050] Obtaining a slab with a specific chemical composition is the first step in manufacturing pipeline steel for heavy oil transportation, which ensures that the steel material can meet the expected performance requirements in the subsequent processing process.

[0051] In some embodiments, the center segregation rating of the slab is ≤ 2.0 level.

[0052] Center segregation is a key indicator of internal quality of steel, which reflects the segregation of solute elements (such as carbon, sulfur, phosphorus, etc.) at grain boundaries or interdendritic during the solidification process. The higher the degree of center segregation, the more uneven the internal structure of the steel, which can easily lead to problems such as mechanical property degradation, toughness reduction, and welding performance deterioration. Center segregation rating is a method to evaluate the severity of element enrichment segregation band in the center of the slab. Rating the center segregation to accurately assess its impact on steel quality is an important part of steel production and quality control. In the embodiments of the present application, the center segregation of the slab is rated using the Mannesmann standard.

[0053] S2, heating the slab to make the slab reach a tapping temperature;

[0054] In some embodiments, the tapping temperature is 1100℃-1280℃.

[0055] Heating the slab in this temperature range can ensure that the internal structure of the steel reaches a uniform state, reducing internal stress and defects and improving the overall performance of the steel. On the other hand, the tapping temperature is one of the important factors affecting the rolling process. A temperature higher than 1280℃ can cause uneven deformation of the steel during rolling, and even overheating and burning phenomena; while a temperature lower than 1100℃ can increase the difficulty of rolling and affect the finished product quality of the steel. Therefore, setting the tapping temperature at 1100℃-1280℃ can ensure the smooth progress of the rolling process and obtain high-quality hot-rolled plates. For example, the tapping temperature can be 1100℃, 1130℃, 1160℃, 1190℃, 1220℃, 1250℃, 1280℃, etc.

[0056] S3, sequentially rolling, cooling and coiling the heated slab to obtain a pipeline steel for thick oil transportation.

[0057] Through rolling, the heated slab is calendered to the required thickness and width, while improving its internal structure and mechanical properties.

[0058] In some embodiments, the finish rolling temperature of the rolling is 830℃-920℃.

[0059] The finishing temperature directly affects the deformation and recrystallization behavior of the steel during rolling, and thus affects the final microstructure. Finishing at a temperature in the range of 830°C to 920°C helps to form the desired microstructure. On the other hand, the finishing temperature in the range of 830°C to 920°C can improve the mechanical properties of the steel, such as yield strength, tensile strength, and elongation. This is because the plastic deformation capacity and work hardening effect of the steel reach an optimal balance at this temperature range. Exemplary finishing temperatures for rolling can be 830°C, 845°C, 860°C, 875°C, 890°C, 905°C, 920°C, etc.

[0060] The microstructure and properties of the steel are adjusted by controlling the cooling. The cooled steel is sent to a coiler for coiling to facilitate storage, transportation, and subsequent processing.

[0061] In some embodiments, the coiling temperature is in the range of 400°C to 600°C.

[0062] The coiling temperature directly affects the final microstructure and properties of the steel, and coiling in the range of 400°C to 600°C helps the steel to form the desired microstructure. Exemplary coiling temperatures can be 400°C, 440°C, 480°C, 520°C, 560°C, 600°C, etc.

[0063] The product of the method for preparing the heavy oil transportation pipeline steel is the heavy oil transportation pipeline steel described above. Since the method for preparing the heavy oil transportation pipeline steel employs some or all of the technical solutions of the heavy oil transportation pipeline steel embodiments, it at least has all the beneficial effects brought by the technical solutions of the heavy oil transportation pipeline steel embodiments, which will not be repeated here.

[0064] The present application will be further described below in conjunction with specific examples. The experimental methods in the following examples, if not specified, are generally determined according to national standards / industry standards; if there is no corresponding national standard / industry standard, they are determined according to the general international standards, conventional conditions, or according to the conditions suggested by the manufacturers.

[0065] A slab with a specific chemical composition is obtained, and the chemical composition of the slab is shown in Table 1.

[0066] Table 1 Chemical composition of the slab (wt%), the balance being Fe and unavoidable impurities

[0067] Group C Si Mn P S Cr Nb Ti V Example 1 0.04 0.25 1.60 0.010 0.0010 0.20 0.03 0.02 0.02 Example 2 0.06 0.15 1.50 0.012 0.0018 0.15 0.04 0.015 0.03 Example 3 0.08 0.10 1.40 0.012 0.0030 0.10 0.05 0.01 0.04

[0068] Based on the chemical composition of the slab of the embodiment, the present embodiment also provides a method for preparing a heavy oil transportation pipeline steel, comprising the following steps:

[0069] obtaining a slab with the chemical composition;

[0070] The slab is heated so that the slab reaches a tapping temperature;

[0071] The heated slab is sequentially rolled, cooled and coiled to obtain a pipeline steel for heavy oil transportation. The preparation process parameters are shown in Table 2.

[0072] Table 2 Preparation process parameters of the pipeline steel for heavy oil transportation

[0073] Group Temperature at tapping (°C) Temperature at finish rolling (°C) Coiling temperature (°C) Center segregation rating of slab Example 1 1200 840 480 1.0 Example 2 1200 850 520 1.0 Example 3 1180 850 540 1.0

[0074] The pipeline steel for heavy oil transportation obtained in the example is tested for performance at 100 DEG C, and the results are shown in Table 3.

[0075] Table 3 Performance results of the pipeline steel for heavy oil transportation

[0076] Group Yield strength (MPa) Tensile strength (MPa) Yield ratio Elongation after break (%) Example 1 Example 2 540 630 0.86 37 Example 3 535 630 0.85 41 ​ 525 615 0.85 41

[0077] Based on the existing data accumulation, the attenuation of the yield strength and the tensile strength under the service environment of the material with temperature should be considered in the engineering design. In the example, the yield strength is greater than or equal to 420 MPa, and the tensile strength is greater than or equal to 505 MPa at 100 DEG C.

[0078] The one or more technical solutions in the example have at least the following technical effects or advantages:

[0079] The pipeline steel for heavy oil transportation provided in the example meets at least one of the following performances: the yield strength is greater than or equal to 420 MPa, and the tensile strength is greater than or equal to 505 MPa under the condition of less than or equal to 100 DEG C.

[0080] The above is only the specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A pipeline steel for transporting heavy oil, the chemical composition of the pipeline steel for transporting heavy oil comprising: C, Si, Mn, P, S, Cr, Nb, Ti, V, and base element Fe; the mass fraction of the C is ≤0.10 parts; the mass fraction of the V is 0.01 parts to 0.08 parts.

2. The heavy oil service line pipe steel according to claim 1, characterized in that, The chemical composition of the pipeline steel for transporting heavy oil is, in mass fraction: C: 0.030% to 0.080%, Si: 0.10% to 0.40%, Mn: 1.20% to 1.60%, P ≤0.015%, S ≤0.005%, V: 0.02% to 0.05%, Cr: 0.10% to 0.25%, Ti: 0.010% to 0.060%, Nb: 0.01% to 0.05%, and base element Fe.

3. The heavy oil service line pipe steel of claim 1, characterized in that, The metallographic structure of the pipeline steel for transporting heavy oil includes ferrite and / or quasi-polygonal ferrite, and pearlite.

4. The heavy oil service line pipe steel of claim 1, characterized by, The pipeline steel for transporting heavy oil satisfies at least one of the following properties at ≤100℃: yield strength ≥420MPa, tensile strength ≥505MPa.

5. The heavy oil service line pipe steel of claim 1, characterized in that, The strength of the pipeline steel for transporting heavy oil is X65 steel grade.

6. A method for preparing the pipeline steel for transporting heavy oil according to any one of claims 1 to 5, the method comprising: obtaining a slab with the chemical composition; heating the slab so that the slab reaches a tapping temperature; sequentially rolling, cooling and coiling the heated slab to obtain the pipeline steel for transporting heavy oil.

7. The method of claim 6, wherein, The center segregation rating of the slab is ≤2.0 grade.

8. The method of claim 6, wherein, The tapping temperature is 1100℃ to 1280℃.

9. The method of claim 6, wherein, The finishing temperature of the rolling is 830℃ to 920℃.

10. The method of claim 6, wherein, The coiling temperature is 400℃ to 600℃.

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