Production method of 35CrMoA round steel for sucker rod

Abstract

The invention discloses a production method of 35CrMoA round steel for a sucker rod, the production method comprises converter smelting, LF refining, continuous casting, casting blank heating furnace heating and round steel rolling, and the round steel comprises the following chemical components in percentage by mass: 0.32%-0.40% of C, 0.17%-0.37% of Si, 0.40%-0.70% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, 0.80%-1.10% of Cr, 0.15%-0.25% of Mo and the balance of Fe and inevitable impurities, and the total mass fraction is 100%. According to the production method, the mechanical property of the hot-rolled round steel is remarkably improved on the premise of reducing the production cost by utilizing the process which is synergistically optimized according to the Cr and Mo composite alloying principle, so that the 35CrMoA round steel for the sucker rod is produced, and the overall service life and the safety of the sucker rod are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of smelting and rolling, and particularly relates to a production method of 35CrMoA round steel for sucker rods. BACKGROUND

[0002] With the continuous growth of global oil demand, the demand for high-performance sucker rod equipment is also increasing. Especially as oilfield exploitation expands to deep wells and the sea, the performance requirements for materials are more stringent. Sucker rods need to withstand huge tension and pressure in oil well operations, so there are very high requirements for the strength and durability of round steel. By optimizing alloy composition and heat treatment process, steel mills can produce high-strength, wear-resistant, corrosion-resistant round steel for sucker rods to meet the demands of harsh working environments. Sucker rods will be subjected to frequent cyclic loads during use, and good fatigue resistance is the key to ensuring their long-term reliable operation. Steel mills can produce round steel with excellent fatigue resistance through advanced metallurgical techniques and precision machining processes, extending the service life of the sucker rod and reducing maintenance and replacement frequency. High-performance round steel for sucker rods will become an important material in the field of oilfield equipment manufacturing, with broad market prospects. By improving the performance and service life of round steel for sucker rods, the maintenance and replacement costs of oilfield equipment can be significantly reduced, and the efficiency of exploitation can be improved. High-performance round steel produced by steel mills not only brings economic benefits to oilfield companies, but also enhances the market competitiveness and economic benefits of steel mills themselves. SUMMARY

[0003] The purpose of the present application is to provide a production method of 35CrMoA round steel for sucker rods, which utilizes the Cr-Mo composite alloying principle and optimized process to significantly improve the mechanical properties of hot-rolled round steel under the premise of reducing production costs, thereby producing 35CrMoA round steel for sucker rods, and further significantly improving the overall service life and safety of the sucker rod.

[0004] To solve the above technical problems, the present application adopts the following technical scheme:

[0005] The production method of 35CrMoA round steel for sucker rods of the present application comprises converter smelting, LF refining, continuous casting, casting blank heating furnace heating, and round steel rolling, and is characterized in that:

[0006] Converter smelting: combined blown converter smelting, ensure that the smelting material is dry to avoid water vapor entering the steel to produce white spots; require [P] < 0.012%, [S] < 0.030%; add AlMnFe deoxidizer and multiple high-purity alloys per ton at the time of tapping to pre-deoxidize and initially adjust the Si, Mn, Cr, Mo components, use slag blocking and slag leaving to prevent P back; add 2.5-4 kg of binary synthetic slag per ton at the time of tapping; block the slag at the time of tapping, and blow argon throughout the tapping process;

[0007] LF refining: deep desulfurization and alloying of molten steel in LF furnace, high basicity slag strengthening desulfurization and inclusion removal, full process stirring is adopted in the refining process;

[0008] Continuous casting: using continuous casting machine, using mold powder, working speed is 1.5-1.8 m / min, full protection casting is realized, and the billet enters the slow cooling pit, and the slow cooling time is greater than or equal to 24 hours;

[0009] Billet heating furnace heating: billet heating temperature is 1080-1120℃, allowable temperature difference is less than or equal to 50℃, total heating time is controlled to be 1.5-2.5h (preferably 2h), and the opening rolling temperature is 1030-1050℃, so as to prevent overheating, overburning and decarburization, slowly increase the temperature, and ensure that the billet heating temperature is uniform and the temperature difference is reduced;

[0010] Round steel rolling: pay attention to the condition of the roller, the steel turning machine, the guide plate, the roller way and the cover plate, and ensure that they are smooth and have no sharp corners, so as to avoid scratches and scratches on the surface of the rolled piece.

[0011] Further, the rolled product specification is φ150mm.

[0012] Further, the heat treatment system is 850℃ quenching and 550℃ tempering.

[0013] Further, the mass percentage of the chemical composition of the round steel includes: C 0.32%-0.40%, 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%, the rest is Fe and inevitable impurities, and the mass fraction is 100%.

[0014] Further, the mass percentage of the chemical composition of the round steel includes: C 0.37%, Si 0.27%, Mn 0.63%, P 0.017%, S 0.003%, Cr 1.02%, Mo 0.19%, the rest is Fe and inevitable impurities, and the mass fraction is 100%.

[0015] Further, the mass percentage of the chemical composition of the round steel includes: C 0.39%, Si 0.28%, Mn 0.66%, P 0.013%, S 0.004%, Cr 1.04%, Mo 0.21%, the rest is Fe and inevitable impurities, and the mass fraction is 100%.

[0016] Furthermore, the chemical composition of the round steel includes the following mass percentages: C 0.38%, Si 0.29%, Mn 0.64%, P 0.015%, S 0.005%, Cr 1.03%, Mo 0.20%, with the remainder being Fe and unavoidable impurities, totaling 100% by mass.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0018] (1) The steel of this invention has the advantage of high strength; (2) By optimizing the preparation process, this invention uses a converter instead of an electric furnace to reduce the preparation cost, and performs degassing and removal of inclusions to improve the cleanliness of the material, thereby significantly improving the strength and toughness of the steel and the service life of the material. The preparation method is simple, has low energy consumption, and is suitable for the current level of industrial equipment. Detailed Implementation

[0019] The following provides a more detailed description of the 35CrMoA round steel used for sucker rods and its production method according to the present invention.

[0020] Example: This example is a preferred embodiment of the various embodiments of the present invention.

[0021] The sucker rod of this embodiment uses 35CrMoA round steel and its production method. The chemical composition by mass percentage includes: C 0.32%~0.40%, 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%, with the remainder being Fe and unavoidable trace impurities, totaling 100% by mass.

[0022] The production method of 35CrMoA round steel for sucker rods in this embodiment is as follows: converter smelting, LF refining, continuous casting, billet heating furnace heating, and round steel rolling; specifically:

[0023] 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 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;

[0024] 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.

[0025] 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.

[0026] 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;

[0027] 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 φ150mm. The heat treatment process is quenching at 850℃ and tempering at 550℃.

[0028] The 35CrMoA round steel for sucker rods produced using the chemical composition and process flow of this invention has the following longitudinal mechanical properties: Rm≥885MPa, ReL≥1030MPa, A≥12.0%, Z≥45%, impact energy KU2≥63J, austenite grain size ≥8, and no cracks, scabs, folds, or inclusions on the steel surface.

[0029] Table 1 shows the chemical composition of three embodiments of the present invention, and Tables 2 and 3 further illustrate the present invention. Table 1. Chemical composition (mass percentage) of various examples of 35CrMoA round steel for sucker rods.

[0030]

[0031] Table 2 Mechanical property indicators of 35CrMoA round steel for sucker rods in various examples

[0032]

[0033] Table 3. Non-metallic inclusions and austenite grain size of various examples of 35CrMoA round steel used for sucker rods.

[0034]

[0035] As can be seen from Tables 1-3, the 35CrMoA round steel used for the sucker rod of this invention has excellent mechanical properties and a high yield strength ratio.

[0036] 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 production method of 35CrMoA round steel for sucker rod, comprising converter smelting, LF refining, continuous casting, heating of casting blank in a heating furnace, and round steel rolling, characterized in that, Specifically: Converter smelting: combined blowing converter smelting, ensuring smelting material dryness to avoid water vapor entering the steel to produce white spots; requiring [P]<0.012%, [S]<0.030%; adding AlMnFe deoxidizer and multiple high-purity alloys per ton at tapping to pre-deoxidize and initially adjust Si, Mn, Cr, Mo components, using slag blocking and slag leaving at tapping to prevent P backflow; adding binary synthetic slag 2.5-4 kg per ton at tapping; blocking slag at tapping, blowing argon throughout the tapping process; LF refining: deep deoxidization and alloying in the LF furnace, creating high-alkalinity slag to strengthen S removal and inclusion removal, using full-range stirring during the refining process; Continuous casting: using a continuous casting machine, using a mold powder, and implementing full-range full-protection casting production of continuous casting billets at a working casting speed of 1.5-1.8 m / min, with the billet entering the slow cooling pit, and the slow cooling time being ≥24 hours; Billet heating furnace heating: billet heating temperature 1080-1120℃, allowable temperature difference ≤50℃, total heating time controlled to be 1.5-2.5h, rolling start temperature 1030-1050℃, preventing overheating, overburning and decarburization, slowly increasing the temperature to ensure uniform billet heating temperature and reduce temperature difference; Round steel rolling: paying attention to the condition of the rolls, the steel turning machine, the guide plate, the roller and the cover plate, and ensuring smoothness, no sharp corners, to avoid scratches and scuffs on the surface of the rolled piece.

2. The method for producing 35CrMoA round steel for sucker rod according to claim 1, characterized in that, The rolled product specification is φ150mm.

3. The method for producing 35CrMoA round steel for sucker rod according to claim 1, characterized in that, The heat treatment system is 850℃ quenching and 550℃ tempering.

4. The method for producing 35CrMoA round steel for sucker rod according to any one of claims 1-3, characterized in that, The mass percentage of the chemical composition of the round steel includes: C 0.32%-0.40%, 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%, the rest being Fe and unavoidable impurities, with the mass fraction totaling 100%.

5. The method for producing 35CrMoA round steel for sucker rod according to claim 4, characterized in that, The mass percentage of the chemical composition of the round steel includes: C 0.37%, Si 0.27%, Mn 0.63%, P 0.017%, S 0.003%, Cr 1.02%, Mo 0.19%, the rest being Fe and unavoidable impurities, with the mass fraction totaling 100%.

6. The method for producing 35CrMoA round steel for sucker rod according to claim 4, characterized in that, The mass percentage of the chemical composition of the round steel includes: C 0.39%, Si 0.28%, Mn 0.66%, P 0.013%, S 0.004%, Cr 1.04%, Mo 0.21%, the rest being Fe and unavoidable impurities, with the mass fraction totaling 100%.

7. The method for producing 35CrMoA round steel for sucker rod according to claim 4, characterized in that, The mass percentage of the chemical composition of the round steel includes: C 0.38%, Si 0.29%, Mn 0.64%, P 0.015%, S 0.005%, Cr 1.03%, Mo 0.20%, the rest being Fe and unavoidable impurities, with the mass fraction totaling 100%.

Images