A production method of L360QS seamless line pipe for gas transmission resistant to hydrogen sulfide corrosion

Abstract

The application discloses a production method of L360QS seamless pipeline pipe for anti-hydrogen sulfide corrosion gas transmission, which comprises the following steps: steel grade component design of the billet; smelting of the billet; short process pure steel smelting technology is adopted, the process is electric arc furnace+external refining+vacuum degassing, the electric arc furnace charge is high-quality scrap steel+molten iron, and the contents of C, P and S during tapping are controlled; hot continuous rolling is carried out; the 508PQF piercing mill unit hot rolling process is adopted, and the heating of the billet is controlled through a ring heating furnace; after rolling, the semi-finished product pipe is subjected to quenching and tempering heat treatment; heating is controlled in a high-temperature furnace, and then tempering is carried out after heat preservation, and then quenching cooling is carried out, the quenching medium is circulating water, and the water pressure, flow rate, flow and time are controlled; after completion, drying is carried out, heating is controlled in a tempering furnace, and then heat preservation is carried out, and then air cooling is carried out. Through the accurate control of the components, inclusions of the billet and the product size and heat treatment process during production, the strict requirements of the project on the anti-hydrogen sulfide corrosion seamless thin-wall pipeline pipe are met.

Description

Technical Field

[0001] This invention relates to the field of seamless pipeline manufacturing technology, specifically to a method for producing L360QS seamless pipeline pipe for gas transmission that is resistant to hydrogen sulfide corrosion. Background Technology

[0002] With the development of large-scale acidic oil and gas fields both domestically and internationally, the demand for gas transmission pipelines in acidic environments is increasing daily. Hydrogen sulfide-resistant steel pipes are one of the development directions for high-performance oil and gas transmission steel pipes. However, the harsh acidic service environment places more stringent requirements on the dimensions and performance indicators of pipeline steel, while also requiring it to meet H2S corrosion resistance testing requirements.

[0003] Therefore, in order to correct the above-mentioned defects, we propose a production method for L360QS seamless pipeline pipes for gas transmission that are resistant to hydrogen sulfide corrosion. Summary of the Invention

[0004] This invention addresses the technical problem by proposing a production method for L360QS seamless pipeline pipes resistant to hydrogen sulfide corrosion for gas transmission. It utilizes low-sulfur, low-carbon steel to roll L360QS thin-walled pipeline pipes designed for acidic service. The main technical challenge lies in meeting the requirements of various application scenarios and performance parameters, including resistance to H2S corrosion, a strength range of only 100 MPa, and an impact shear area ≥90%. By controlling the composition and inclusions of the steel billet, and by precisely controlling the product dimensions and heat treatment process during production, the strict requirements for hydrogen sulfide corrosion-resistant seamless thin-walled pipeline pipes for project use are met.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for producing L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion, comprising the following steps:

[0006] S1. Design of steel grade composition for steel billets;

[0007] S2. Smelting of steel billets: Short-process pure steel smelting technology is adopted, the process is electric arc furnace + ladle refining + vacuum degassing, the electric arc furnace charge is high-quality scrap steel + molten iron, and the content of C, P and S at the time of tapping is controlled.

[0008] S3. Hot continuous rolling: The hot rolling process of the 508PQF piercing mill is adopted, and the heating of the steel billet is controlled by the annular heating furnace;

[0009] S4. After rolling, the billet undergoes heat treatment: it is heated in a high-temperature furnace under controlled temperature and held at that temperature, and then quenched and cooled. The quenching medium is circulating water, with controlled water pressure, flow rate, flow rate, and time. After completion, it is dried and then heated in a tempering furnace under controlled temperature and held at that temperature. Finally, it is cooled in air to obtain the finished steel pipe.

[0010] Furthermore, in step S1, the steel composition includes Mn, Cr content of 0.01-0.20, V, Cu, P, S, and C.

[0011] Furthermore, in step S1, the Mn content is 1.00–1.50%, the Cr content is 0.01–0.20%, the V content is 0.01–0.07%, the Cu content is 0.01–0.07%, the P content is 0.001–0.009%, the S content is 0.001–0.009%, and the C content is ≤0.20%.

[0012] Furthermore, in step S3, the piercing mill unit adopts a two-roll skew rolling guide plate type piercing mill.

[0013] Furthermore, in step S3, the piercing rolls of the piercing mill rotate at a speed of 20–60 rpm, the bite angle is 5–20°, and the top reduction rate is 3–18%, enabling the steel billet to be successfully pierced into a hollow tube. The continuous rolling parameters are controlled using the PQF continuous rolling mill: limit ratio 60–90, rolling force 3000–7500 rpm, and exit speed 1600–4000 rpm.

[0014] Furthermore, in step S4, the minimum quenching temperature is 916℃ and the maximum tempering temperature is 728℃.

[0015] Furthermore, in step S4, the temperature is maintained in a high-temperature furnace for 20 to 40 minutes, the temperature of the circulating water during quenching is between 15 and 30°C, the cooling rate is controlled between 8°C / s and 20°C / s, and the temperature is maintained in a tempering furnace for 30 to 80 minutes.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The L360QS acidic service thin-walled pipeline production method of the present invention obtains qualified pipeline dimensions through strict control of the chemical composition of steel billets, electric arc furnace + ladle refining + vacuum degassing processes, and reasonable rolling process parameters. By adopting reasonable hot continuous rolling temperature, rolling tools, and heat treatment quenching temperature, tempering temperature and cooling rate, the tensile strength, impact, hardness, corrosion resistance and other properties of the steel pipe meet the standards and user requirements, and meet the needs of acidic oil and gas field projects. The finished product has a microstructure of ferrite and bainite. The characteristic of this metallographic structure is that fine bainite is evenly distributed on the ferrite surface and is relatively stable. The use of low-content alloy design helps to reduce production costs. Attached Figure Description

[0017] Figure 1 A curve measured after tempering heat treatment of seamless pipeline tubes;

[0018] Figure 2 This is a graph showing the impact toughness of a seamless pipeline. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a technical solution:

[0021] A method for producing L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion includes the following steps:

[0022] 1. Chemical composition design

[0023] The steel composition design uses a base of Mn content of 1.00–1.50, incorporating low-content alloying elements such as Cr content of 0.01–0.20, V content of 0.01–0.07, and Cu content of 0.01–0.07 for microalloying design; controlling the P content of 0.001–0.009 and S content of 0.001–0.009 to reduce segregation, reduce inclusion content, and control the morphology of inclusions; controlling the carbon content to a low level and ensuring that the carbon equivalent CEpcm ≤ 0.20% to improve its welding performance for project use.

[0024] 2. Steel billet smelting methods

[0025] The process employs a short-process pure steel smelting technology, with the main steps being electric arc furnace + ladle refining + vacuum degassing. The electric arc furnace charge consists of high-quality scrap steel and molten iron. The content of C, P, and S during tapping is further precisely controlled to enhance the control of chemical composition and segregation during the refining process, ensuring sufficient vacuum and degassing time. Inclusion spheroidization treatment is performed to reduce inclusions, improve the cleanliness of the molten steel, and ensure the quality of the billet.

[0026] 3. Hot continuous rolling method

[0027] The tube rolling process utilizes the 508PQF hot rolling mill. Heating of the billet is controlled via a ring furnace, with precise control over heating time, temperature, and discharge rhythm to ensure uniform heating and optimal discharge temperature. The piercing mill employs a two-roll skew-guide piercing mill, with appropriate rolling tools designed and selected, and piercing parameters controlled: piercing roll speed 20–60 rpm, bite angle 5–20 rpm, and top reduction rate 3–18%, successfully piercing the billet into a hollow tube. The PQF continuous rolling mill then controls the rolling parameters: limit ratio 60–90, rolling force 3000–7500 rpm, and exit speed 1600–4000 rpm, ensuring uniform wall thickness control within -10% to +15% of the tube, guaranteeing the inner surface quality of the steel tube. Finally, the sizing mill reduces the diameter and slightly thickens the tube, controlling the outer surface quality to achieve suitable dimensions.

[0028] 4. Heat treatment methods

[0029] After rolling, pipeline pipes that pass the initial inspection need to undergo quenching and tempering heat treatment, based on the measured C-curve (see...). Figure 1 The minimum quenching temperature is 916℃, and the maximum tempering temperature is 728℃. Based on small-batch trial production and verification, and through continuous improvement, a suitable heat treatment process was determined: Heating is performed in a high-temperature furnace under controlled temperature for 20–40 minutes, followed by quenching and cooling. Circulating water is used as the quenching medium, with a temperature between 15–30℃. Water pressure, flow rate, flow volume, and time are controlled, and the cooling rate is controlled between 8℃ / s and 20℃ / s. After completion, the material is dried and then placed in a tempering furnace for controlled temperature heating and holding for 30–80 minutes, followed by air cooling to finally obtain the finished steel pipe.

[0030] Product Performance

[0031] Tensile properties

[0032] According to the standard, the tensile test was conducted using a longitudinal plate-shaped specimen with dimensions b0 = 38.1 mm and L0 = 50 mm. The test results showed that the yield strength fluctuated between 400 MPa and 470 MPa, the tensile strength fluctuated between 500 MPa and 560 MPa, the yield-to-tensile ratio fluctuated between 0.77 and 0.85, and the elongation fluctuated between 38% and 44%, indicating relatively small performance fluctuations.

[0033] Impact toughness

[0034] According to the standard, the impact test specimens were 3 / 4 standard size transverse specimens, the test temperature was -10℃, and the impact energy of all specimens was above 250J. The specimens exhibited good impact toughness, and showed good ductile-brittle transition at -60℃ to +20℃. (See...) Figure 2 .

[0035] Hardness properties

[0036] The Vickers hardness was measured at three locations: inside, middle, and outside the steel pipe, for a total of 12 hardness points. The internal hardness ranged from 160 HV10 to 210 HV10, while the middle and outer hardness ranged from 150 HV10 to 200 HV10, which was slightly lower than the internal hardness. The difference in hardness between the inside, middle, and outside was within 30 HV10.

[0037] Metallographic analysis

[0038] Table 1 shows the metallographic analysis results of the pipeline pipe in terms of inclusions, structure, and grain size. It can be seen that the pipeline pipe has a low content of non-metallic inclusions, a uniform structure, and a fine grain size. This structural characteristic is stable and beneficial to the corrosion resistance of the steel pipe.

[0039] Table 1 Metallographic Analysis Results of Steel Pipes

[0040]

[0041] Corrosion resistance test

[0042] Corrosion resistance tests were conducted using both HIC and SSC (four-point bending) tests. The HIC test involved an immersion time of 96 hours. The SSC test (four-point bending) used solution A, with an initial pH of 3.0 and an ending pH of 3.3. The test temperature ranged from 23℃ to 26℃, and the test period was 720 hours. Specific standard requirements and test results are shown in Table 2.

[0043] Table 2 Corrosion Resistance of Steel Pipes

[0044]

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion, characterized in that: Includes the following steps: S1. Design of steel grade composition for steel billets; S2. Smelting of steel billets: Short-process pure steel smelting technology is adopted, the process is electric arc furnace + ladle refining + vacuum degassing, the electric arc furnace charge is high-quality scrap steel + molten iron, and the content of C, P and S at the time of tapping is controlled. S3. Hot continuous rolling: The hot rolling process of the 508PQF piercing mill is adopted, and the heating of the steel billet is controlled by the annular heating furnace; S4. After rolling, the billet undergoes heat treatment: it is heated in a high-temperature furnace under controlled temperature and held at that temperature, and then quenched and cooled. The quenching medium is circulating water, with controlled water pressure, flow rate, flow rate, and time. After completion, it is dried and then heated in a tempering furnace under controlled temperature and held at that temperature. Finally, it is cooled in air to obtain the finished steel pipe.

2. The production method of L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion according to claim 1, characterized in that: In step S1, the steel composition includes Mn, Cr content of 0.01-0.20, V, Cu, P, S, and C.

3. The production method of L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion according to claim 2, characterized in that: In step S1, the content of Mn is 1.00-1.50, the content of Cr is 0.01-0.20, the content of V is 0.01-0.07, the content of Cu is 0.01-0.07, the content of P is 0.001-0.009, the content of S is 0.001-0.009, and the content of C is ≤0.20%.

4. The production method of L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion according to claim 1, characterized in that: In step S3, the piercing unit adopts a two-roll skew rolling guide plate type piercing machine.

5. The method for producing L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion according to any one of claims 1 or 4, characterized in that: In step S3, the piercing rolls of the piercing mill rotate at a speed of 20–60 rpm, the bite angle is 5–20°, and the top reduction rate is 3–18%, enabling the steel billet to be successfully pierced into a hollow tube. The continuous rolling parameters are controlled using the PQF continuous rolling mill: limit ratio 60–90, rolling force 3000–7500 rpm, and exit speed 1600–4000 rpm.

6. The production method of L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion according to claim 1, characterized in that: In step S4, the minimum quenching temperature is 916℃ and the maximum tempering temperature is 728℃.

7. The production method of L360QS seamless pipeline pipe for gas transmission resistant to hydrogen sulfide corrosion according to claim 1, characterized in that: In step S4, the temperature is maintained in a high-temperature furnace for 20 to 40 minutes, the temperature of the circulating water during quenching is between 15 and 30°C, the cooling rate is controlled between 8°C / s and 20°C / s, and the temperature is maintained in a tempering furnace for 30 to 80 minutes.

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