Heat treatment process of round steel for 35Mn2A sucker rod

Abstract

The invention discloses a heat treatment process of 35Mn2A round steel for sucker rods, which comprises the following steps: putting a rough-machined round steel blank sample for the 35Mn2A sucker rods into a heating furnace, heating to 830-850 DEG C, preserving heat for 50-70 minutes, and then quenching with water; and putting the quenched sample into a heating furnace, heating to 490-510 DEG C, preserving heat for 120-150 minutes, then taking out, and cooling in water. According to the heat treatment process of the round steel for the 35Mn2A sucker rod, the round steel for the 35Mn2A sucker rod has the good comprehensive mechanical property, the overall service life of the round steel for the sucker rod is remarkably prolonged, the safety of the round steel for the sucker rod is remarkably improved, mechanical property inspection is conducted on a sample obtained after heat treatment, and the requirements that the yield strength is larger than or equal to 735 MPa, the tensile strength is larger than or equal to 885 MPa, and the ductility is larger than or equal to 12% are met at the normal temperature. The percentage reduction of area is not less than 45%; the impact absorption KU2 is more than or equal to 55J, and various non-metallic inclusions are less than or equal to 1.5 grades.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing round steel for sucker rods, and particularly to a heat treatment process for round steel of 35Mn2A sucker rods. Background Art

[0002] As a key component in the process of oil extraction, sucker rods are often exposed to high-salinity, high-pressure, and acidic environments. Therefore, the developed steel must have excellent corrosion resistance to withstand the erosion of corrosion media such as brine and acid solutions, and maintain the stability and durability of the material. Sucker rods have to bear huge tensile and compressive forces in oil wells and also need to have good bending performance. Therefore, the selected steel must have excellent mechanical properties, including high strength, good toughness, and stable deformation ability, to ensure the reliability and safety of sucker rods during oil well operations. Therefore, it is particularly important to formulate a suitable heat treatment process to ensure that the round steel for sucker rods has good properties. Through research on the phase transformation points of round steel for 35Mn2A sucker rods, it is found that the austenitizing temperature for the heat treatment of round steel for sucker rods should preferably be controlled at 830°C - 850°C. Selecting water with a higher cooling rate as the quenching medium can obtain high strength and good toughness. The tempering temperature should preferably be controlled at 490 - 510°C. The tempering temperature has a greater impact on the properties of the material. As the tempering temperature increases, the strength of the material decreases, while the plasticity and toughness increase, and it has better comprehensive mechanical properties at around 490 - 510°C. Summary of the Invention

[0003] The purpose of the present invention is to provide a heat treatment process for round steel of 35Mn2A sucker rods, so as to endow it with good comprehensive mechanical properties, and thus significantly improve the overall life and safety of the round steel for sucker rods. The mechanical properties of the heat-treated samples are tested and meet the following requirements at room temperature: yield strength ≥ 735 MPa, tensile strength ≥ 885 MPa, elongation ≥ 12%, reduction of area ≥ 45%; impact absorption energy KU2 ≥ 55 J, and all types of non-metallic inclusions are ≤ grade 1.5.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] For the heat treatment process of round steel of 35Mn2A sucker rods of the present invention, the rough-machined blank sample of round steel for 35Mn2A sucker rods is placed in a heating furnace, heated to 830°C - 850°C, held for 50 - 70 min, and then quenched with water; the quenched sample is placed in a heating furnace, heated to 490°C - 510°C, held for 120 - 150 min, and then taken out and cooled in water.

[0006] Further, place the rough - processed round steel blank sample of the 35Mn2A sucker rod into a heating furnace, raise the temperature to 830 °C, hold for 50 min, and then quench with water; place the quenched sample into the heating furnace, heat to 490 °C, hold for 120 min, then take out the sample and cool it in water.

[0007] Further, place the rough - processed round steel blank sample of the 35Mn2A sucker rod into a heating furnace, raise the temperature to 850 °C, hold for 70 min, and then quench with water; place the quenched sample into the heating furnace, heat to 510 °C, hold for 150 min, then take it out and cool it in water.

[0008] Further, place the rough - processed round steel blank sample of the 35Mn2A sucker rod into a heating furnace, raise the temperature to 840 °C, hold for 60 min, and then quench with water; place the quenched sample into the heating furnace, heat to 500 °C, hold for 130 min, then take it out and cool it in water.

[0009] Further, the chemical components of the round steel for the 35Mn2A sucker rod by mass percentage include: C 0.35%, Si 0.25%, Mn 0.53%, Cr 0.97%, Mo 0.21%, and the rest is Fe and inevitable impurities.

[0010] Further, the chemical components of the round steel for the 35Mn2A sucker rod by mass percentage include: C 0.34%, Si 0.27%, Mn 0.55%, Cr 0.95%, Mo 0.22%, and the rest is Fe and inevitable impurities.

[0011] Further, the chemical components of the round steel for the 35Mn2A sucker rod by mass percentage include: C 0.36%, Si 0.24%, Mn 0.52%, Cr 0.98%, Mo 0.20%, and the rest is Fe and inevitable impurities.

[0012] Compared with the prior art, the beneficial technical effects of the present invention:

[0013] (1) Through the optimized heat treatment process (quenching temperature 830 - 850 °C, tempering temperature 490 - 510 °C), the present invention can enable the yield strength, tensile strength, ductility, and impact toughness of the 35Mn2A round steel to reach or exceed the expected performance standards. Especially when used in the harsh environment of oil wells, it has higher reliability and service life. (2) The process parameters of the present invention are finely designed, making the production process more stable, while reducing energy consumption and raw material waste, significantly reducing the overall production cost, and being suitable for large-scale industrial production. (3) By precisely controlling the quenching and tempering processes, the present invention effectively avoids the problems of grain coarsening and material softening, ensuring the tissue uniformity and consistency of the workpieces in mass production, thereby improving the quality stability of the products. Detailed Embodiments

[0014] The heat treatment process of the round steel for sucker rods of the present invention will be further described in detail below.

[0015] Example 1:

[0016] The steel part in the heat treatment process of the present invention is the round steel for 35Mn2A sucker rods, and it is carried out according to the following steps:

[0017] (1) Quenching: Put the rough-machined round steel blank sample for sucker rods into the heating furnace, heat it up to 830 °C, hold for 50 min, and then quench it with water;

[0018] (2) Tempering: Put the quenched sample into the heating furnace, heat it to 490 °C, hold for 120 min, and then take out the sample and cool it in water.

[0019] Example 2:

[0020] The steel part in the heat treatment process of the present invention is the round steel for 35Mn2A sucker rods, and it is carried out according to the following steps:

[0021] (1) Quenching: Put the rough-machined round steel blank sample for sucker rods into the heating furnace, heat it up to 850 °C, hold for 70 min, and then quench it with water;

[0022] (2) Tempering: Put the quenched sample into the heating furnace, heat it to 510 °C, hold for 150 min, and then take out the sample and cool it in water.

[0023] Example 3:

[0024] The steel part in the heat treatment process of the present invention is the round steel for 35Mn2A sucker rods, and it is carried out according to the following steps:

[0025] (1) Quenching: Put the rough-machined round steel blank sample for sucker rods into the heating furnace, heat it up to 840 °C, hold for 60 min, and then quench it with water;

[0026] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 500 °C, hold for 140 min, then take out the sample and cool it in water.

[0027] Comparative Example 1:

[0028] The steel part in the heat treatment process of the present invention is round steel for 35Mn2A sucker rods, and the steps are as follows:

[0029] (1) Quenching: Put the rough-machined round steel blank sample for sucker rods into a heating furnace, heat it up to 800 °C, hold for 60 min, and then quench it with water;

[0030] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 450 °C, hold for 130 min, then take out the sample and cool it in water.

[0031] Comparative Example 2:

[0032] The steel part in the heat treatment process of the present invention is round steel for 35Mn2A sucker rods, and the steps are as follows:

[0033] (1) Quenching: Put the rough-machined round steel blank sample for sucker rods into a heating furnace, heat it up to 900 °C, hold for 70 min, and then quench it with water;

[0034] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 550 °C, hold for 120 min, then take out the sample and cool it in water.

[0035] Comparative Example 3:

[0036] The steel part in the heat treatment process of the present invention is round steel for 35Mn2A sucker rods, and the steps are as follows:

[0037] (1) Quenching: Put the rough-machined round steel blank sample for sucker rods into a heating furnace, heat it up to 830 °C, hold for 70 min, and then quench it with water;

[0038] (2) Tempering: Put the quenched sample into a heating furnace, heat it to 450 °C, hold for 120 min, then take out the sample and cool it in water.

[0039] Comparative Example 4:

[0040] The steel part in the heat treatment process of the present invention is round steel for 35Mn2A sucker rods, and the steps are as follows:

[0041] Quenching: Put the rough-machined round steel blank sample for sucker rods into a heating furnace, heat it up to 840 °C, hold for 70 min, and cool it in air.

[0042] After the heat treatment is completed, finish machining is carried out on the rough-machined blank sample, and various performance inspections are carried out. Table 1 shows the chemical compositions of each example and comparative example, and the inspection results are shown in Tables 2, 3, and 4. It can be seen from Tables 2, 3, and 4 that all performance indicators are higher than the required indicators, and the performance of the sample after heat treatment is qualified.

[0043] Table 1 Chemical Compositions of Each Example and Comparative Example (%)

[0044]

[0045]

[0046] Table 2 Room Temperature Mechanical Properties after Heat Treatment

[0047]

[0048] Table 3 Impact Toughness after Heat Treatment

[0049]

[0050] Table 4 Non-Metallic Inclusions after Heat Treatment

[0051]

[0052]

[0053] It can be seen from the above examples and comparative examples that: (1) Compared with the recommended quenching temperature range (830 - 850 °C) and tempering temperature range (490 - 510 °C) of the present invention, the low quenching and tempering temperatures in Comparative Example 1 led to a slight decrease in strength and toughness, and the mechanical properties failed to reach the required indicators (yield strength ≥ 735 MPa, tensile strength ≥ 885 MPa, elongation ≥ 12%, impact toughness KU2 ≥ 55 J). This indicates that when the quenching temperature is lower than 830 °C and the tempering temperature is lower than 490 °C, the austenite transformation is insufficient, resulting in a decrease in the strength and toughness of the material. (2) In Comparative Example 2, the quenching temperature of 900 °C led to grain coarsening, resulting in a decrease in the strength and toughness of the material. In addition, the too high tempering temperature (550 °C) softened the material, further reducing the yield strength. (3) In Comparative Example 3, the tempering temperature (450 °C) was slightly lower than the recommended range (490 - 510 °C), resulting in a decrease in elongation and toughness. Although the tensile strength and yield strength were close to the required values, the overall performance still did not reach the optimum. (4) In Comparative Example 4, although air cooling is a more economical and simple process, it cannot provide rapid cooling to obtain high strength and toughness. The slower cooling rate led to the formation of pearlite and ferrite, making the mechanical properties far inferior to those of quenching + tempering.

[0054] The heat treatment process of the round steel for sucker rods of the present invention determines a heat treatment system that can ensure the stable performance of the steel by studying the influence of heat treatment heating systems, including quenching temperature, tempering temperature, and holding time, etc. on the structure and properties; on the premise of ensuring the structure and properties after heat treatment, the heating temperature range is narrowed, the holding time is reduced, the energy consumption of heat treatment is lowered, and the efficiency of heat treatment is improved. The key difference between the present invention and the comparative examples lies in the selection of quenching and tempering temperatures, the cooling medium, and the control of the holding time. By selecting optimized parameters (quenching temperature 830 - 850 °C, tempering temperature 490 - 510 °C, water as the quenching medium), the present invention shows significant superiority in terms of strength, toughness, and ductility. The heat treatment process of the present invention is significantly superior to each comparative example, especially in terms of yield strength, tensile strength, and impact toughness, and its comprehensive mechanical properties far exceed the level of the comparative examples, especially showing better performance in the actual application in the oil well environment.

[0055] The embodiments described above are only used to describe the preferred mode of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solution of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A heat treatment process for 35Mn2A round steel for sucker rod, characterized in that: The rough-machined 35Mn2A round steel blank for sucker rod is placed in a heating furnace, heated to 830℃-850℃, kept warm for 50-70min, and then quenched with water; the quenched sample is placed in a heating furnace, heated to 490℃-510℃, kept warm for 120-150min, then taken out and cooled in water.

2. The heat treatment process of 35Mn2A round steel for sucker rod according to claim 1 is characterized in that: The rough-machined 35Mn2A sucker rod round steel blank sample is placed in a heating furnace, heated to 830°C, kept warm for 50 minutes, and then quenched with water; the quenched sample is placed in a heating furnace, heated to 490°C, kept warm for 120 minutes, and then the sample is taken out and cooled in water.

3. The heat treatment process of 35Mn2A round steel for sucker rod according to claim 1, characterized in that: The rough-machined 35Mn2A sucker rod round steel blank sample is placed in a heating furnace, heated to 850°C, kept warm for 70 minutes, and then quenched with water; the quenched sample is placed in a heating furnace, heated to 510°C, kept warm for 150 minutes, then taken out and cooled in water.

4. The heat treatment process of 35Mn2A round steel for sucker rod according to claim 1, characterized in that: The rough-machined 35Mn2A sucker rod round steel blank sample is placed in a heating furnace, heated to 840°C, kept warm for 60 minutes, and then quenched with water; the quenched sample is placed in a heating furnace, heated to 500°C, kept warm for 130 minutes, then taken out and cooled in water.

5. The heat treatment process of 35Mn2A round steel for sucker rod according to claim 2, characterized in that: The chemical composition of the 35Mn2A round steel for sucker rods includes, by mass percentage, 0.35% C, 0.25% Si, 0.53% Mn, 0.97% Cr, 0.21% Mo, and the rest is Fe and unavoidable impurities.

6. The heat treatment process of 35Mn2A round steel for sucker rod according to claim 3, characterized in that: The chemical composition of the 35Mn2A round steel for sucker rods includes, by mass percentage, 0.34% C, 0.27% Si, 0.55% Mn, 0.95% Cr, 0.22% Mo, and the rest is Fe and unavoidable impurities.

7. The heat treatment process of 35Mn2A round steel for sucker rod according to claim 4, characterized in that: The chemical composition of the 35Mn2A round steel for sucker rods includes, by mass percentage, 0.36% C, 0.24% Si, 0.52% Mn, 0.98% Cr, 0.20% Mo, and the rest is Fe and unavoidable impurities.

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