Production method of 25MnVA round steel for sucker rod

Abstract

The invention discloses a production method of 25MnVA round steel for a sucker rod. The 25MnVA round steel comprises the following chemical components in percentage by mass: 0.21-0.30% of C, 0.17-0.37% of Si, 1.30-1.70% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, 0.05-0.15% of V, less than or equal to 0.35% of Cr, less than or equal to 0.10% of Mo and less than or equal to 0.20% of Cu. The production method comprises the steps of converter smelting, LF refining, continuous casting, casting blank heating furnace heating and round steel rolling. Wherein the billet heating temperature is 1200-1250 DEG C, the allowable temperature difference is smaller than or equal to 50 DEG C, the total heating time is controlled to be 2 h, the rolling starting temperature is 1050-1100 DEG C, and the heat treatment system is that quenching is conducted at 880 DEG C, and tempering is conducted at 500 DEG C. The 25MnVA round steel for the sucker rod with excellent comprehensive mechanical performance is successfully adopted and developed.

Description

Technical Field

[0001] The invention relates to the technical field of smelting and rolling, and in particular to a production method of 25MnVA round steel for pumping rods. Background Art

[0002] The sucker rod bears the huge tension and pressure in the oil well, and needs to have high strength, excellent toughness and stable deformation ability. Therefore, the steel must have excellent mechanical properties to ensure the reliability and safety of the sucker rod in oil well operations. The sucker rod needs to move up and down frequently in oil well operations, and the steel must have excellent fatigue resistance and withstand repeated loading for a long time without breaking or damage. The sucker rod is placed in a high-salinity, high-pressure, and acidic environment during oil production, so the selected steel must have excellent corrosion resistance. The developed steel for the sucker rod should be able to resist the erosion of corrosive media such as salt water and acid to ensure its long-term stable operation in harsh environments. The use of high-performance steel can extend the service life of the sucker rod and reduce maintenance and replacement costs. This can not only improve the efficiency and safety of oilfield operations, but also save costs for oilfield enterprises and improve economic benefits. Global oil demand continues to grow, and the demand for high-performance and high-reliability pumping equipment is also increasing. The development of steel for sucker rods that meets market demand will be widely used and recognized in the oilfield equipment manufacturing field. Therefore, the promotion and application of steel for pumping rods by steel mills has clear feasibility and broad prospects. By meeting the market's requirements for performance, quality and cost, steel mills can gain an important position in the oil industry and obtain considerable market share and economic benefits. Summary of the invention

[0003] The purpose of the present invention is to provide a production method of 25MnVA round steel for pumping rods, and successfully adopt and develop 25MnVA round steel for pumping rods with excellent comprehensive mechanical properties.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a production method of 25MnVA round steel for oil pumping rods, wherein the mass percentage of the chemical components thereof includes: C 0.21% to 0.30%, Si 0.17% to 0.37%, Mn 1.30%~1.70%, P≤0.025%, S≤0.020%, V0.05~0.15%, Cr≤0.35%, Mo≤0.10%, Cu≤0.20%, the rest are Fe and inevitable impurities, with a total mass fraction of 100%; its production method includes: converter smelting, LF refining, continuous casting, billet heating furnace heating, round steel rolling; wherein: the billet heating temperature is 1200~1250℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1050~1100℃, overheating, overburning and decarburization are prevented, the temperature is slowly increased to ensure that the billet heating temperature is uniform and the temperature difference is reduced; the heat treatment system is 880℃ quenching and 500℃ tempering.

[0006] Furthermore, double-blowing converter smelting ensures that the smelting materials are dry to avoid water vapor entering the steel to produce white spots; requirements [P] < 0.012%, [S] < 0.030%; nitrogen and argon are switched at the bottom of the converter to ensure that the carbon is hit once and to avoid post-blowing, and the final carbon is controlled to be > 0.10%, reducing the oxidation of the molten steel and reducing decarburization; the final [P] ≤ 0.020%; slag is blocked during steel tapping, and argon is blown throughout the steel tapping process; white slag is refined, and the molten steel must not be exposed throughout the process; calcium feeding wire is used to deform the inclusions to avoid nozzle nodules; Do not add any slag after feeding the calcium wire to purify the molten steel. The soft blowing time should be ≥10min to ensure that the inclusions float fully. Strictly implement the tundish baking system to ensure the tundish baking time and baking temperature. The molten steel outside the long water nozzle cannot be exposed to prevent secondary oxidation of the molten steel. Ensure that the crystallizer is centered, and use weak cooling for the second cooling and constant pulling speed. Use electromagnetic stirring to improve the surface quality of the ingot. Pay attention to the conditions of the rolls, steel turning machines, guide plates, roller tables and cover plates, and ensure that they are smooth and have no sharp edges to avoid scratches and bumps on the surface of the rolled piece.

[0007] Furthermore, the specification of the rolled product is φ123mm.

[0008] Furthermore, the mass percentage of its chemical composition includes: C 0.27%, Si 0.24%, Mn 1.33%, P0.012%, S 0.0058%, V 0.08%, Cr 0.25%, Mo 0.007%, Cu 0.04%, and the rest is Fe and inevitable impurities, with a total mass fraction of 100%.

[0009] Furthermore, the mass percentage of its chemical composition includes: C 0.28%, Si 0.23%, Mn 1.35%, P0.014%, S 0.0075%, V 0.09%, Cr 0.27%, Mo 0.010%, Cu 0.03%, and the rest is Fe and inevitable impurities, with a total mass fraction of 100%.

[0010] Furthermore, the mass percentage of its chemical composition includes: C 0.27%, Si 0.25%, Mn 1.34%, P0.013%, S 0.0055%, V 0.08%, Cr 0.26%, Mo 0.009%, Cu 0.05%, and the rest is Fe and inevitable impurities, with a total mass fraction of 100%.

[0011] Compared with the prior art, the beneficial technical effects of the present invention are:

[0012] (1) By reducing the carbon content and introducing vanadium and chromium, 25MnVA significantly improves the toughness and impact resistance of the material while maintaining high strength, which is particularly prominent under extreme working conditions. (2) The optimized quenching and tempering process makes the strength of 25MnVA significantly better than 35Mn2A, effectively extending the service life of the sucker rod under high-frequency alternating stress environment. (3) By optimizing the alloy composition and smelting process, 25MnVA reduces the dependence on the precious alloy element Mo, reduces the production cost while ensuring performance, and has better market competitiveness. DETAILED DESCRIPTION

[0013] The 25MnVA round steel for sucker rods and the production method thereof in the present invention comprises the following chemical components in percentage by weight: C 0.21%-0.30%, Si 0.17%-0.37%, Mn 1.30%-1.70%, P≤0.025%, S≤0.020%, V0.05-0.15%, Cr≤0.35%, Mo≤0.10%, Cu≤0.20%, and the rest are Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0014] The production method of 25MnVA round steel for pumping rod in this embodiment is: converter smelting, LF refining, continuous casting, heating in a casting heating furnace, and round steel rolling.

[0015] Combined blowing converter smelting ensures that the smelting materials are dry to avoid water vapor entering the steel to produce white spots; requirements [P] < 0.012%, [S] < 0.030%; switch to nitrogen and argon blowing at the bottom of the converter to ensure that the carbon is hit once and avoid post-blowing, and the end point carbon is controlled to be > 0.10%, reducing the oxidation of molten steel and reducing decarburization; the end point [P] ≤ 0.020%; slag blocking during steel tapping, and argon blowing throughout the steel tapping process;

[0016] During the refining of white slag, the molten steel must not be exposed throughout the whole process; the calcium feeding line is used to deform the inclusions to avoid nozzle nodules; no slag is added after the calcium feeding line to purify the molten steel, and the soft blowing time is ≥10min to ensure that the inclusions fully float;

[0017] Strictly implement the tundish baking system to ensure the tundish baking time and baking temperature; the molten steel outside the long nozzle cannot be exposed to prevent secondary oxidation of the molten steel; ensure that the crystallizer is centered, the secondary cooling adopts weak cooling and constant casting speed; use electromagnetic stirring to improve the surface quality of the ingot;

[0018] The billet heating temperature is 1200-1250℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1050-1100℃, prevent overheating, overburning and decarburization, and heat up slowly to ensure uniform billet heating temperature and reduce temperature difference;

[0019] Pay attention to the condition of the rolls, steel turning machine, guide plate, roller table and cover plate, and ensure that they are smooth without sharp edges and corners to avoid scratches and knocks on the surface of the rolled piece. The specification of the rolled product is φ123mm. The heat treatment system is quenching at 880℃ and tempering at 500℃.

[0020] The 25MnVA round steel for sucker rod and the production method thereof of the present invention are further described in detail below in conjunction with specific embodiments.

[0021] Table 1 shows the chemical compositions of three examples of the present invention, and Tables 2 and 3 further illustrate the present invention and the comparison among three comparative examples.

[0022] Table 1 Chemical composition of various examples of 25MnVA round steel for sucker rods (mass percentage / %)

[0023] Example C Si Mn P S Cu Cr Ni Mo V Example 1 0.27 0.24 1.33 0.012 0.0058 0.04 0.25 0.007 0.08 Example 2 0.28 0.23 1.35 0.014 0.0075 0.03 0.27 0.010 0.09 Example 3 0.27 0.25 1.34 0.013 0.0055 0.05 0.26 0.009 0.08 Comparative Example 1 0.37 0.34 1.73 0.012 0.0058 0.14 0.05 0.13 0.037 Comparative Example 2 0.38 0.33 1.75 0.014 0.0075 0.13 0.07 0.14 0.040 Comparative Example 3 0.37 0.35 1.64 0.013 0.0055 0.11 0.06 0.12 0.039

[0024] Table 2 Mechanical properties of 25MnVA round steel for pumping rod

[0025]

[0026] Table 4 Non-metallic inclusions and austenite grain size of various examples of 25MnVA round steel for sucker rods

[0027]

[0028]

[0029] It can be seen from Tables 1-4 that the 25MnVA round steel for the sucker rod of the present invention has excellent mechanical properties.

[0030] The production method of 25MnVA round steel embodies the non-obviousness of the technical solution in the following aspects:

[0031] Ingenious combination of alloy components: By scientifically optimizing the ratio of alloy elements (such as the introduction of vanadium and chromium), the common brittle fracture problem is avoided while improving the mechanical properties of the material. This combination is difficult to foresee in the existing 35Mn2A process because its alloy component ratio has a unique synergistic effect.

[0032] In the production process of 25MnVA, the heat treatment process is crucial to achieve the target performance. Experimental data show that the influence of different temperatures on the performance of 25MnVA is much greater than that of 35Mn2A. This sensitivity and strict requirements on process parameters make the production method of 25MnVA innovative.

[0033] Through multiple sets of comparative experiments, it is proved that after the process optimization, the comprehensive performance of 25MnVA is significantly better than that of 35Mn2A, such as higher tensile strength and lower manufacturing cost. These data strongly prove the superiority and unpredictability of the 25MnVA process.

[0034] Compared with the production method of 35Mn2A round steel, the production method of 25MnVA round steel has significant differences in the following aspects:

[0035] 1. 25MnVA round steel reduces the Mn content to 1.20%-1.50%, and introduces appropriate amounts of V (vanadium) and Cr to enhance the refinement and strengthening effects of the material, while the Ni and Mo contents may be reduced accordingly.

[0036] 2. The heat treatment process of 25MnVA is 880℃ quenching + 500℃ tempering, and the tempering temperature can be set in the range of 450℃-500℃ to improve the toughness and fatigue strength of the material. The heat treatment process of 35Mn2A is 840℃ quenching and 500℃ tempering.

[0037] 3. In order to adapt to the special composition of 25MnVA, the heating temperature and rolling temperature of the steel billet need to be adjusted, requiring stricter temperature control and more precise rolling speed (the heating temperature of the steel billet needs to be precisely controlled within an appropriate range, between 1200°C and 1250°C, and the rolling start temperature should be controlled between 1050°C and 1100°C to ensure the plasticity of the steel while preventing cracks or other defects during the rolling process. The final rolling temperature needs to be controlled between 850°C and 900°C to ensure that the rolled steel has a uniform microstructure and good mechanical properties; the rolling speed is controlled within the range of 2.0 to 2.5 m / s; too fast rolling speed may lead to uneven temperature distribution and affect the uniformity of the steel's organization; while too slow speed may cause excessive cooling of the material, increase the difficulty of rolling and affect the dimensional accuracy and surface quality of the final product) to ensure the performance of the finished product.

[0038] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing 25MnVA round steel for sucker rods, characterized in that: The mass percentage of its chemical composition includes: C 0.21%-0.30%, Si 0.17%-0.37%, Mn 1.30%-1.70%, P≤0.025%, S≤0.020%, V 0.05-0.15%, Cr≤0.35%, Mo≤0.10%, Cu≤0.20%, and the rest is Fe and inevitable impurities, with a total mass fraction of 100%. Its production method includes: converter smelting, LF refining, continuous casting, billet heating furnace heating, and round steel rolling; wherein: the billet heating temperature is 1200-1250°C, the allowable temperature difference is ≤50°C, the total heating time is controlled to be 2h, the rolling temperature is 1050-1100°C, overheating, overburning and decarburization are prevented, the temperature is slowly increased, the billet heating temperature is guaranteed to be uniform, and the temperature difference is reduced; the heat treatment system is 880°C quenching and 500°C tempering.

2. The method for producing 25MnVA round steel for sucker rod according to claim 1, characterized in that: Combined blowing converter smelting ensures that the smelting materials are dry to avoid water vapor entering the steel to produce white spots; requirements [P] < 0.012%, [S] < 0.030%; nitrogen and argon are switched to the bottom blowing of the converter to ensure that the carbon is hit once and to avoid post-blowing. The final carbon control is > 0.10%, which reduces the oxidation of the molten steel and reduces decarburization; the final [P] ≤ 0.020%; slag is blocked during steel tapping, and argon is blown throughout the steel tapping process; white slag refining operation, the molten steel must not be exposed throughout the process; calcium feeding line is used to deform the inclusions to avoid nozzle nodules; calcium feeding line Do not add any slag at the end to purify the molten steel, the soft blowing time is ≥10min, and ensure that the inclusions float fully; strictly implement the tundish baking system to ensure the tundish baking time and baking temperature; the molten steel outside the long nozzle cannot be exposed to prevent the secondary oxidation of the molten steel; ensure that the crystallizer is centered, and the secondary cooling adopts weak cooling and constant pulling speed; use electromagnetic stirring to improve the surface quality of the casting; pay attention to the conditions of the rolling rollers, steel turning machines, guide plates, roller tables and cover plates, and ensure that they are smooth and have no sharp edges to avoid scratches and knocks on the surface of the rolled piece.

3. The method for producing 25MnVA round steel for sucker rod according to claim 1, characterized in that: The specification of the rolled product is φ123mm.

4. The method for producing 25MnVA round steel for sucker rod according to claim 1, characterized in that: The mass percentages of its chemical components include: C 0.27%, Si 0.24%, Mn 1.33%, P 0.012%, S 0.0058%, V 0.08%, Cr 0.25%, Mo 0.007%, Cu 0.04%, and the rest are Fe and unavoidable impurities, with a total mass fraction of 100%.

5. The method for producing 25MnVA round steel for sucker rod according to claim 1, characterized in that: The mass percentages of its chemical components include: C 0.28%, Si 0.23%, Mn 1.35%, P 0.014%, S 0.0075%, V 0.09%, Cr 0.27%, Mo 0.010%, Cu 0.03%, and the rest are Fe and unavoidable impurities, with a total mass fraction of 100%.

6. The method for producing 25MnVA round steel for sucker rod according to claim 1, characterized in that: The mass percentages of its chemical components include: C 0.27%, Si 0.25%, Mn 1.34%, P 0.013%, S 0.0055%, V 0.08%, Cr 0.26%, Mo 0.009%, Cu 0.05%, and the rest are Fe and unavoidable impurities, with a total mass fraction of 100%.

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