Production method of 20crmoa round steel for sucker rod

Abstract

The application discloses a 20CrMoA round steel for sucker rod and a production method thereof, and the mass percentage of the chemical components of the 20CrMoA round steel comprises the following components: C 0.17-0.24%, Si 0.17-0.37%, Mn 0.40-0.70%, P≤0.025%, S≤0.020%, Cr 0.80-1.10%, Mo 0.15-0.25%, Ni≤0.30%, Cu≤0.20%, and the rest is Fe and inevitable impurities, and the total mass percentage is 100%. The application further discloses a production method of the 20CrMoA round steel for sucker rod. Through the control of the processes of converter smelting, LF refining, VD vacuum degassing, continuous casting, casting blank heating furnace heating and round steel rolling, the 20CrMoA round steel for sucker rod with excellent comprehensive mechanical properties is successfully developed.

Description

Technical Field

[0001] This invention belongs to the field of smelting and rolling technology, and particularly relates to a method for producing 20CrMoA round steel for sucker rods. Background Technology

[0002] Global oil demand continues to grow, leading to a surge in demand for high-performance pumping equipment. This is particularly true as oilfield development expands into deeper wells and offshore areas, placing even stricter demands on material performance. Sucker rods withstand immense tensile and compressive forces during well operations, requiring extremely high strength and durability from the round steel used. By optimizing alloy composition and heat treatment processes, steel mills can produce high-strength, wear-resistant, and corrosion-resistant round steel for sucker rods, meeting the demands of harsh working environments. Sucker rods are subjected to frequent cyclic loads during use, making excellent fatigue resistance crucial for long-term reliable operation. Steel mills can utilize advanced metallurgical technologies and precision machining processes to produce round steel with superior fatigue resistance, extending sucker rod lifespan and reducing maintenance and replacement frequency. High-performance sucker rod round steel will become an important material in oilfield equipment manufacturing, with broad market prospects. Improving the performance and lifespan of sucker rod round steel can significantly reduce maintenance and replacement costs for oilfield equipment, increasing extraction efficiency. The high-performance round steel produced by steel mills not only brings economic benefits to oilfield companies but also enhances the market competitiveness and economic returns of the steel mills themselves. Summary of the Invention

[0003] The purpose of this invention is to provide a method for producing 20CrMoA round steel for sucker rods. By utilizing the principle of small-scale Cr and Mo composite alloying, the mechanical properties of hot-rolled round steel are significantly improved while reducing production costs, thereby producing 20CrMoA round steel for sucker rods and significantly improving the overall lifespan and safety of sucker rods.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a method for producing 20CrMoA round steel for sucker rods, the method comprising: converter smelting, LF refining, VD vacuum degassing, continuous casting, billet heating furnace heating, and round steel rolling; wherein:

[0006] The re-blown converter smelting process ensures the smelting materials are dry to prevent moisture from entering the steel and causing white spots; [P] < 0.012%, [S] < 0.030%; during tapping, 4.0 kg of AlMnFe deoxidizer and various high-purity alloys are added per ton for pre-deoxidation and initial adjustment of Si, Mn, Cr, Mo, and other components; slag-blocking and slag-retaining tapping are used to prevent P reversion; 2.5-4 kg of binary synthetic slag is added per ton during tapping; slag blocking is used during tapping, and argon is blown throughout the tapping process;

[0007] Deep desulfurization and alloying of molten steel are carried out in the LF furnace to produce high-basicity slag (R≥3.0) to enhance desulfurization and inclusion removal. The refining process is carried out with stirring throughout.

[0008] After LF refining, a VD circulating degassing device is used for vacuum degassing and impurity removal. The process is maintained under high vacuum for more than 25 minutes to ensure that [H] ≤ 0.0002% and [O] ≤ 0.0020%, and that all components are within the required range.

[0009] A continuous casting machine is used, with mold protective slag. The working speed is 1.5-1.8m / min. The continuous casting of square billets is carried out with full protection throughout the casting process. The billets are placed in a slow cooling pit and the slow cooling time is ≥24 hours.

[0010] The billet heating temperature is 1080~1120℃, the allowable temperature difference is ≤50℃, the total heating time is controlled at 2h, the initial rolling temperature is 1030~1050℃, to prevent overheating, burning and decarburization, the temperature is increased slowly, to ensure uniform billet heating temperature and reduce temperature difference;

[0011] The heat treatment process is quenching at 880℃ and tempering at 500℃;

[0012] The chemical composition of the 20CrMoA round steel includes the following percentages by mass: C 0.17%–0.24%, Si 0.17%–0.37%, Mn 0.40%–0.70%, P ≤ 0.025%, S ≤ 0.020%, Cr 0.80–1.10%, Mo 0.15–0.25%, Ni ≤ 0.30%, Cu ≤ 0.20%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

[0013] Furthermore, pay attention to the condition of the rolls, turning machine, guide plates, roller conveyor, and cover plates, and ensure that they are smooth and free of sharp edges to avoid scratches and dents on the surface of the rolled parts.

[0014] Furthermore, the rolled product specification is φ120mm.

[0015] Furthermore, the 20CrMoA round steel used for producing sucker rods meets the following requirements: longitudinal mechanical properties Rm≥735MPa, ReL≥930MPa, A≥12.0%, Z≥50%, impact energy KU2≥78J, austenite grain size≥8, and the steel surface is free of cracks, scabs, folds, or inclusions.

[0016] Furthermore, the chemical composition of the 20CrMoA round steel includes the following mass percentages: C 0.19%, Si 0.26%, Mn 0.58%, P 0.012%, S 0.0058%, Cr 0.92%, Mo 0.20%, Ni 0.03%, Cu 0.04%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

[0017] Furthermore, the chemical composition of the 20CrMoA round steel includes the following mass percentages: C 0.23%, Si 0.28%, Mn 0.62%, P 0.014%, S 0.0075%, Cr 0.95%, Mo 0.23%, Ni 0.05%, Cu 0.03%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

[0018] Furthermore, the chemical composition of the 20CrMoA round steel includes the following mass percentages: C 0.20%, Si 0.27%, Mn 0.60%, P 0.013%, S 0.0055%, Cr 0.93%, Mo 0.21%, Ni 0.04%, Cu 0.05%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] (1) The steel of this invention has the advantage of high strength; (2) This invention optimizes the preparation process, using a converter instead of an electric furnace to reduce preparation costs, and performs degassing and removal of inclusions to improve the cleanliness of the material, thereby significantly improving the strength, toughness, and lifespan of the steel. The preparation method is simple, has low energy consumption, and is suitable for existing industrial equipment levels.

[0021] The 20CrMoA round steel for sucker rods produced using the chemical composition and process flow of this invention has been tested and found to have longitudinal mechanical properties that meet the R standard. m ≥735MPa, R eL ≥930MPa, A≥12.0%, Z≥50%, impact energy KU2≥78J, austenite grain size of steel≥8 grade, and no cracks, scabs, folds or inclusions on the surface of the steel. Detailed Implementation

[0022] The following provides a more detailed description of the 20CrMoA round steel used for sucker rods and its production method according to the present invention.

[0023] Example:

[0024] The sucker rod of this embodiment uses 20CrMoA round steel and its production method. The chemical composition by mass percentage includes: C 0.17%~0.24%, Si 0.17%~0.37%, Mn 0.40%~0.70%, P≤0.025%, S≤0.020%, Cr 0.80~1.10%, Mo 0.15~0.25%, Ni≤0.30%, Cu≤0.20%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

[0025] The production method of 20CrMoA round steel for sucker rods in this embodiment is as follows: converter smelting, LF refining, VD vacuum degassing, continuous casting, billet heating furnace heating, and round steel rolling.

[0026] The re-blown converter smelting process ensures the smelting materials are dry to prevent moisture from entering the steel and causing white spots; [P] < 0.012%, [S] < 0.030%; during tapping, 4.0 kg of AlMnFe deoxidizer and various high-purity alloys are added per ton for pre-deoxidation and initial adjustment of Si, Mn, Cr, Mo, and other components; slag-blocking and slag-retaining tapping are used to prevent P reversion; 2.5-4 kg of binary synthetic slag is added per ton during tapping; slag blocking is used during tapping, and argon is blown throughout the tapping process;

[0027] Deep desulfurization and alloying of molten steel are carried out in the LF furnace to produce high-basicity slag (R≥3.0) to enhance desulfurization and inclusion removal. The refining process is carried out with stirring throughout.

[0028] After LF refining, a VD circulating degassing device is used for vacuum degassing and impurity removal. The process is maintained under high vacuum for more than 25 minutes to ensure that [H] ≤ 0.0002% and [O] ≤ 0.0020%, and that all components are within the required range.

[0029] A continuous casting machine is used, with mold protective slag. The working speed is 1.5-1.8m / min. The continuous casting of square billets is carried out with full protection throughout the casting process. The billets are placed in a slow cooling pit and the slow cooling time is ≥24 hours.

[0030] The billet heating temperature is 1080~1120℃, the allowable temperature difference is ≤50℃, the total heating time is controlled at 2h, the initial rolling temperature is 1030~1050℃, to prevent overheating, burning and decarburization, the temperature is increased slowly, to ensure uniform billet heating temperature and reduce temperature difference;

[0031] Pay attention to the condition of the rolls, turning machine, guide plates, roller conveyor, and cover plates, ensuring they are smooth and free of sharp edges to avoid scratches, dents, or other defects on the surface of the rolled workpiece. The finished product specification is φ120mm. The heat treatment process is quenching at 880℃ and tempering at 500℃.

[0032] The 20CrMoA round steel for sucker rods produced using the chemical composition and process of this invention has the following longitudinal mechanical properties: Rm≥735MPa, ReL≥930MPa, A≥12.0%, Z≥50%, impact energy KU2≥78J, austenite grain size ≥8, and no cracks, scabs, folds, or inclusions on the steel surface.

[0033] Table 1 shows the chemical composition of three embodiments of the present invention, and Tables 2 and 3 further illustrate the present invention.

[0034] Table 1. Chemical composition (mass percentage) of various examples of 20CrMoA round steel used for sucker rods.

[0035] Example C Si Mn P S Cu Cr Ni Mo Example 1 0.19 0.26 0.58 0.012 0.0058 0.04 0.92 0.03 0.20 Example 2 0.23 0.28 0.62 0.014 0.0075 0.03 0.95 0.05 0.23 Example 3 0.20 0.27 0.60 0.013 0.0055 0.05 0.93 0.04 0.21

[0036] Table 2 Mechanical property indicators of 20CrMoA round steel for sucker rods in various examples

[0037]

[0038]

[0039] Table 3. Non-metallic inclusions and austenite grain size of various examples of 20CrMoA round steel used for sucker rods.

[0040]

[0041] As can be seen from Tables 1-3, the 20CrMoA round steel used for the sucker rod of this invention has excellent mechanical properties.

[0042] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing 20CrMoA round steel for sucker rods, characterized in that, Its production methods include: converter smelting, LF refining, VD vacuum degassing, continuous casting, billet heating furnace heating, and round steel rolling; among which: The re-blown converter smelting process ensures the smelting materials are dry to prevent moisture from entering the steel and causing white spots; [P] < 0.012%, [S] < 0.030%; during tapping, 4.0 kg of AlMnFe deoxidizer and various high-purity alloys are added per ton for pre-deoxidation and initial adjustment of Si, Mn, Cr, and Mo compositions; slag-blocking and slag-retaining techniques are used during tapping to prevent P reversion; 2.5-4 kg of binary synthetic slag is added per ton during tapping; slag blocking is used during tapping, and argon is blown throughout the tapping process; Deep desulfurization and alloying of molten steel are carried out in the LF furnace to create high-basicity slag to enhance desulfurization and remove inclusions. The refining process is carried out with full stirring. After LF refining, a VD circulating degassing device is used for vacuum degassing and impurity removal. The process is maintained under high vacuum for more than 25 minutes to ensure that [H] ≤ 0.0002% and [O] ≤ 0.0020%, and that all components are within the required range. A continuous casting machine is used, with mold protective slag. The working speed is 1.5-1.8m / min. The continuous casting of square billets is carried out with full protection throughout the casting process. The billets are placed in a slow cooling pit and the slow cooling time is ≥24 hours. The billet heating temperature is 1080~1120℃, the allowable temperature difference is ≤50℃, the total heating time is controlled at 2h, the initial rolling temperature is 1030~1050℃, to prevent overheating, burning and decarburization, the temperature is increased slowly, to ensure uniform billet heating temperature and reduce temperature difference; The heat treatment process is quenching at 880℃ and tempering at 500℃; The chemical composition of the 20CrMoA round steel includes the following percentages by mass: C 0.17%–0.24%, Si 0.17%–0.37%, Mn 0.40%–0.70%, P ≤ 0.025%, S ≤ 0.020%, Cr 0.80–1.10%, Mo 0.15–0.25%, Ni ≤ 0.30%, Cu ≤ 0.20%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

2. The method for producing 20CrMoA round steel for sucker rods according to claim 1, characterized in that, Pay attention to the condition of the rolls, turning machine, guide plates, roller conveyor, and cover plates, and ensure that they are smooth and free of sharp edges to avoid scratches and dents on the surface of the rolled parts.

3. The method for producing 20CrMoA round steel for sucker rods according to claim 1, characterized in that, The rolled product has a diameter of φ120mm.

4. The method for producing 20CrMoA round steel for sucker rods according to claim 1, characterized in that, The sucker rods produced using 20CrMoA round steel meet the following requirements: longitudinal mechanical properties Rm≥735MPa, ReL≥930MPa, A≥12.0%, Z≥50%, impact energy KU2≥78J, austenite grain size≥8, and the steel surface is free of cracks, scabs, folds, or inclusions.

5. The method for producing 20CrMoA round steel for sucker rods according to claim 1, characterized in that, The chemical composition of the 20CrMoA round steel includes the following percentages by mass: C 0.19%, Si 0.26%, Mn 0.58%, P 0.012%, S 0.0058%, Cr 0.92%, Mo 0.20%, Ni 0.03%, Cu 0.04%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

6. The method for producing 20CrMoA round steel for sucker rods according to claim 1, characterized in that, The chemical composition of the 20CrMoA round steel includes the following percentages by mass: C 0.23%, Si 0.28%, Mn 0.62%, P 0.014%, S 0.0075%, Cr 0.95%, Mo 0.23%, Ni 0.05%, Cu 0.03%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

7. The method for producing 20CrMoA round steel for sucker rods according to claim 1, characterized in that, The chemical composition of the 20CrMoA round steel includes the following percentages by mass: C 0.20%, Si 0.27%, Mn 0.60%, P 0.013%, S 0.0055%, Cr 0.93%, Mo 0.21%, Ni 0.04%, Cu 0.05%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

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