A method of manufacturing a 130 ksi grade oil drill pipe joint

Abstract

The present application relates to the technical field of drill pipe joint manufacturing, and particularly relates to a 130Ksi steel grade petroleum drill pipe joint manufacturing method, which comprises the following steps: S1, selecting a steel material as 37CrMnMo; S2, according to the size of a target joint, preparing the 37CrMnMo steel material into a corresponding thick-walled seamless pipe; S3, sawing the thick-walled seamless pipe into a pipe segment with a required length, and the length of the pipe segment is calculated according to the volume of a male joint blank or a female joint blank; S4, heating the pipe segment to 1200+ / -30 DEG C and keeping the temperature for 10 minutes, and then performing multi-step forging forming in a mold to form the male joint blank and / or the female joint blank; and S5, performing heat treatment on the male joint blank and the female joint blank; the present application has the beneficial effect that: through accurate selection of the 37CrMnMo steel material, fine control of a multi-step forging forming process, and optimization of heat treatment parameters, the yield strength and comprehensive mechanical properties of the petroleum drill pipe joint can be significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of drill pipe joint manufacturing, and specifically relates to a method for manufacturing a 130Ksi grade oil drill pipe joint. Background Technology

[0002] Global oil and gas exploration and development is extending to deep wells, ultra-deep wells, and complex geological areas. Traditional drill pipes can no longer meet the demands of high-intensity operations, leading to a continuous increase in the market demand for high-strength drill pipes. Whether it is the development of deep shale gas, ultra-deep wells, and offshore oil and gas, or drilling in high-temperature and extremely cold regions, higher requirements are placed on the tensile strength and fatigue life of drill pipes.

[0003] Currently, the minimum yield strength of high-strength steel for drill pipe bodies has reached 140 ksi and 150 ksi, but the yield strength of joints can only reach 120 ksi. Since 80% of drill pipe failures occur at the joints during drilling operations, improving the quality of drill pipe joints is the key to reducing the accident rate.

[0004] The 37CrMnMo material system has become the most successful joint material due to its suitability for harsh application environments and complex stress conditions. Its production methods are mainly two: one is to roll cast billets into bars, which are then sawed, forged, and heat-treated to produce joint blanks; the other is to roll cast billets into thick-walled seamless steel, which is then heat-treated, sawed, and machined. Joints produced using these two methods at the 120ksi grade can meet basic mechanical performance requirements, but cannot be manufactured at higher grades. How to achieve 130ksi-level comprehensive performance using existing 37CrMnMo materials has become the core bottleneck in the production of high-strength drill pipes.

[0005] Therefore, a manufacturing method for 130Ksi grade oil drill pipe joints is needed to overcome the above-mentioned problems. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for manufacturing 130Ksi grade oil drill pipe joints, thereby achieving the goal of resolving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: a method for manufacturing a 130Ksi grade oil drill pipe joint, characterized by comprising the following steps:

[0008] S1, the selected material is 37CrMnMo steel; S2, according to the size of the target joint, the 37CrMnMo steel is prepared into a corresponding thick-walled seamless pipe; S3, the thick-walled seamless tube is cut into sections of the required length, the length of which is calculated based on the volume of the male or female connector blank. S4, the pipe section is heated to 1200±30℃ and held for 10 minutes, and then subjected to multi-step forging in a mold to form a male connector blank and / or a female connector blank, wherein: S41, the male connector blank is formed by two upsetting, the steps of which include: the pipe section is upsetting once through mold one, the pipe section forms a predetermined outer diameter and inner diameter, and the lower outer side forms an external thread area bevel; then the pipe section is upsetting twice through mold two, the upper outer side forms a 35° shoulder, and the lower outer side forms an external thread area bevel with a sealing shoulder. S42, the female connector blank is formed by three upsetting processes, the steps of which include: first upsetting the pipe section through mold three, forming a predetermined outer diameter and inner diameter, and forming an 18° shoulder slope on the lower outer side; then performing a second upsetting through mold four, forming an internal thread area slope on the upper inner side of the pipe section; finally performing a third upsetting through mold five, forming an internal thread area slope with a sealing shoulder on the upper inner side of the pipe section; S5, the male connector blank and the female connector blank are subjected to heat treatment, the heat treatment includes: quenching and heating to 880±10℃, quenching with water-based quenching fluid, the concentration of the water-based quenching fluid is controlled below 20%, and the average cooling rate before cooling to 300℃ during quenching is 20-50℃ / s; then tempering and heating to 570-600℃.

[0009] As a further improvement to the above technical solution: The composition of the 37CrMnMo steel selected in step S1, by mass percentage, is as follows: C: 0.35%–0.38%, Si: 0.15%–0.30%, Mn: 0.85%–1.00%, P: ≤0.013%, S: ≤0.005%, Cr: 1.10%–1.20%, Mo: 0.28%–0.33%, Ni: ≤0.25%, N: ≤0.009%, Sol Al: 0.015%–0.040%, Cu: ≤0.20%, V: ≤0.03%, Ti: ≤0.010%, B: ≤0.0001%, Nb: ≤0.05%, with the balance being Fe and unavoidable impurities.

[0010] In step S41, when the male connector blank is formed in one upsetting: the pipe section is heated to 1200±30℃, kept warm for 10 minutes, placed in mold one, and the punch is pressed down to complete one upsetting.

[0011] In step S4, the mold for forming the male connector blank includes a first punch mold and a first outer mold. The first punch mold is a conical mandrel, the first outer mold is barrel-shaped, and the lower part of the first outer mold is a conical surface.

[0012] In step S4, the mold for forming the male connector blank includes a second punch mold, a 35° shoulder forming mold with a hole, and a second outer mold. The second punch mold is a conical mandrel. The middle and upper parts of the second outer mold are barrel-shaped with equal diameters, and the lower part of the second outer mold is an inclined surface with a sealing shoulder.

[0013] In step S42, when the female connector blank is formed in one upsetting: the pipe section is heated to 1200±30℃, kept warm for 10 minutes, placed in mold three, and the punch is pressed down to complete one upsetting.

[0014] In step S4, the mold three for forming the female connector blank includes a third punch mold and a third outer mold. The third punch mold is a conical mandrel, the upper part of the third outer mold is barrel-shaped with equal diameter, and the lower part of the third outer mold is an inclined surface.

[0015] In step S4, the mold for forming the female connector blank includes a first inner mold consisting of a mandrel that is a combination of a frustum and a cylinder. The upper part of the first inner mold is an inclined surface, and the lower part of the first inner mold is a cylinder with a tapered diameter.

[0016] In step S4, the mold five for forming the female connector blank includes a second inner mold with a mandrel that is a combination of a frustum and a cylinder. The upper part of the second inner mold is an inclined surface with a sealing shoulder, and the lower part of the second inner mold is a cylinder with a tapered diameter.

[0017] The beneficial effects of the embodiments of the present invention are as follows: The manufacturing method for 130Ksi grade oil drill pipe joints in this embodiment effectively overcomes the bottleneck of traditional methods in achieving 130Ksi grade joint performance through precise selection of 37CrMnMo steel, meticulous control of multi-step forging processes, and optimization of heat treatment parameters. This method can significantly improve the yield strength and comprehensive mechanical properties of oil drill pipe joints, thereby meeting the needs of high-intensity operations in deep wells, ultra-deep wells, and complex geological areas, and reducing the risk of joint failure during drilling operations. Attached Figure Description

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 A flowchart illustrating the manufacturing process of a male connector blank; Figure 2 This is a flowchart illustrating the manufacturing process of the female connector blank.

[0019] In the diagram: 1. Pipe section; 2. Mold 1; 3. Mold 2; 4. Mold 3; 5. Mold 4; 6. Mold 5; 21. First punch die; 22. First outer die; 31. Second punch die; 32. Shoulder forming die; 33. Second outer die; 41. Third punch die; 42. Third outer die; 51. First inner mold; 61. Second inner mold. Detailed Implementation

[0020] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0021] See Figures 1 to 2 This invention discloses a method for manufacturing a 130Ksi grade oil drill pipe joint, the main steps of which include: selecting 37CrMnMo steel; preparing a thick-walled seamless pipe according to the target joint size; sawing the thick-walled seamless pipe into pipe segments 1 of the required length; heating the pipe segments 1 and performing multi-step forging to form a male joint blank and / or a female joint blank, wherein the male joint blank is formed by two upsetting and the female joint blank is formed by three upsetting; and finally, heat treating the male joint blank and the female joint blank, including quenching and tempering.

[0022] For ease of understanding, the following explains some key terms in this embodiment: 130Ksi grade oil drill pipe joints refer to oil drill pipe connection components with a yield strength of 130Ksi (approximately 900MPa). They are designed to withstand high-intensity stresses during drilling operations in deep wells, ultra-deep wells, and complex geological areas.

[0023] 37CrMnMo steel is an alloy structural steel. Due to its excellent strength, toughness and hardenability, it is often used to manufacture high-strength and high-wear-resistant mechanical parts, especially suitable for components such as oil drill pipe joints that are subjected to complex stress environments.

[0024] Thick-walled seamless pipes refer to pipes with relatively large wall thickness and no weld seams. They are manufactured through processes such as piercing and rolling, and have good mechanical properties and dimensional accuracy. They are ideal starting materials for manufacturing high-strength joint blanks.

[0025] Multi-step forging is a processing technology that gradually changes the shape of metal materials through multiple forging passes using dies. This process can densify the internal structure of the metal, improve grain flow lines, and thus enhance the mechanical properties of the parts. It is particularly suitable for manufacturing joint blanks with complex shapes.

[0026] Male and female connector blanks are semi-finished products of oil drill pipe fittings before final processing. Male connector blanks typically have external threads and a shoulder structure, while female connector blanks have internal threads and a shoulder structure. The two are connected to the drill pipe through threaded connection.

[0027] Heat treatment is a comprehensive process that alters the internal structure of metallic materials through heating, holding, and cooling, thereby improving their mechanical properties. For high-strength steel, heat treatment is a crucial step in obtaining the desired strength, hardness, and toughness, typically involving two main stages: quenching and tempering.

[0028] Water-based quenching fluid is a quenching medium based on water, with its cooling performance adjusted by adding polymers and other components. Compared to oil-based quenching fluids, water-based quenching fluids have advantages such as faster cooling speed, lower cost, and environmental friendliness, making them suitable for quenching processes with specific requirements for cooling rate.

[0029] This embodiment provides a method for manufacturing a 130Ksi grade oil drill pipe joint, the specific implementation process of which is as follows: First, in step S1, 37CrMnMo steel is selected as the base material for manufacturing the joint. This steel is chosen based on its excellent comprehensive performance under high temperature and high stress conditions.

[0030] Subsequently, in step S2, the selected 37CrMnMo steel is processed into a corresponding thick-walled seamless tube according to the specific size requirements of the target joint. This processing can be achieved through various existing technologies, such as piercing rolling, extrusion, or cold drawing, to obtain seamless tubes with the required outer diameter, inner diameter, and wall thickness.

[0031] Further, in step S3, the prepared thick-walled seamless tube is sawn into tube segments 1 of the required length. The length of tube segment 1 is precisely calculated based on the volume of the final male or female connector blank to ensure material utilization and forming accuracy in the subsequent forging process.

[0032] Next, in step S4, pipe segment 1 is heated to 1200±30℃ and held at that temperature for 10 minutes, followed by multi-step forging in a mold to form a male connector blank and / or a female connector blank. The heating process aims to improve the plasticity of the steel, facilitating subsequent plastic deformation. Forging involves applying pressure to the heated pipe segment 1 using a mold, gradually deforming it to a predetermined shape.

[0033] Specifically, in step S41, the male connector blank is formed using a two-upsetting method. First, the pipe section 1 is upset using mold 2 to form a predetermined outer and inner diameter, and an external threaded area bevel is formed on the lower outer side. This upsetting process can be achieved by placing the pipe section 1 in mold 2 and applying appropriate pressure. Subsequently, the pipe section 1 is upset again using mold 3 to form a 35° shoulder on the upper outer side and an external threaded area bevel with a sealing shoulder on the lower outer side.

[0034] Meanwhile, in step S42, the female connector blank is formed using a three-upsetting method. First, the pipe section 1 is upset once using mold three 4 to form the predetermined outer and inner diameters, and to form an 18° shoulder slope on the lower outer side. This first upsetting process can also be achieved by placing the pipe section 1 in mold three 4 and applying appropriate pressure. Subsequently, the pipe section 1 is upset twice using mold four 5 to form an internal thread area slope on its upper inner side. Finally, the pipe section 1 is upset three times using mold five 6 to form an internal thread area slope with a sealing shoulder on its upper inner side. The synergistic effect of molds three 4, four 5, and five 6 ensures the precise forming of the complex internal cavity structure of the female connector blank.

[0035] Finally, in step S5, the formed male and female connector blanks are heat-treated. This heat treatment includes two stages: quenching and tempering. During quenching, the blank is heated to 880±10℃ and quenched using a water-based quenching fluid with a concentration controlled below 20%. The average cooling rate before cooling to 300℃ is 20-50℃ / s. Quenching aims to obtain a high-hardness martensitic structure. Subsequently, tempering is performed, in which the blank is heated to 570-600℃. Tempering aims to eliminate quenching stress, improve the toughness of the material, and adjust its strength to the target 130Ksi steel grade.

[0036] The manufacturing method for 130Ksi grade oil drill pipe joints in this embodiment effectively overcomes the bottleneck of traditional methods in achieving 130Ksi grade joint performance through precise selection of 37CrMnMo steel, meticulous control of multi-step forging processes, and optimization of heat treatment parameters. This method can significantly improve the yield strength and comprehensive mechanical properties of oil drill pipe joints, thereby meeting the needs of high-intensity operations in deep wells, ultra-deep wells, and complex geological areas, and reducing the risk of joint failure during drilling operations.

[0037] In some embodiments described above in this application, a method for manufacturing 130Ksi grade oil drill pipe joints is proposed, wherein 37CrMnMo steel is selected as the raw material. However, if the composition of the 37CrMnMo steel is not precisely controlled, the mechanical properties of the steel may fluctuate significantly, making it difficult to consistently achieve the strength, toughness, and fatigue resistance required for 130Ksi grade oil drill pipe joints. In particular, during subsequent heat treatment and forging processes, its microstructure uniformity and hardenability may not be effectively guaranteed, thereby affecting the reliability of the final product.

[0038] In this regard, this application further proposes that the composition of the 37CrMnMo steel selected in step S1, by mass percentage, is as follows: C: 0.35%-0.38%, Si: 0.15%-0.30%, Mn: 0.85%-1.00%, P: ≤0.013%, S: ≤0.005%, Cr: 1.10%-1.20%, Mo: 0.28%-0.33%, Ni: ≤0.25%, N: ≤0.009%, Sol Al: 0.015%-0.040%, Cu: ≤0.20%, V: ≤0.03%, Ti: ≤0.010%, B: ≤0.0001%, Nb: ≤0.05%, with the balance being Fe and unavoidable impurities.

[0039] When manufacturing the male connector blank (such as...) Figure 1 (as shown) First, calculate the required length of pipe section 1 based on the volume of the final male connector blank; the calculation method is as follows: L1=4X / [3.14 (D1) 2 -d1 2 )]; X is the volume of the male connector blank, D1 is the inner diameter of the thick-walled seamless pipe, d1 is the outer diameter of the thick-walled seamless pipe, and L1 is the length of pipe segment 1 for which the male connector blank needs to be prepared.

[0040] Next, heat the pipe section to 1200±30℃, keep it warm for 10 minutes, put it into mold 2, press it down, and complete the first upsetting.

[0041] Finally, pipe section 1 is subjected to a second upsetting using mold 23.

[0042] Mold 1 (2) and Mold 2 (3) are as follows: Die 1 2 includes: a first punch die 21 and a first outer die 22; the first punch die 21 (moving downwards for upsetting) is designed as a conical mandrel, with the upper diameter equal to the required inner diameter of pipe section 1, and the lower diameter 1mm smaller than the upper diameter, so as to facilitate the first punch die 21 being pulled out of the upsetting pipe section 1; the first outer die 22 is designed as a barrel shape with an equal outer diameter, and the lower part of the first outer die 22 is designed as a conical surface, which is adapted to the inclined surface of the external thread area; the minimum diameter D4 is equal to the minor diameter of the male connector blank thread D5 + 4mm.

[0043] Die 2 3 includes: a second punch die 31, a 35° shoulder forming die 32 with a hole, and a second outer die 33; the second punch die 31 (moving downwards for upsetting) is designed as a conical mandrel, with the upper diameter being 1mm larger than the lower diameter to facilitate punch extraction, and the upper diameter being 2mm smaller than the inner diameter of the male connector blank; the second punch die 31 passes through the shoulder forming die 32 and moves downwards together for upsetting; the lower part of the second punch die 31 is designed as a conical surface with a shoulder, so that when pressed down, the lower part of the male connector blank forms a sealing surface with a sealing shoulder.

[0044] During the manufacturing of the female connector blank (such as...) Figure 2 (as shown) First, calculate the required length of pipe section 1 based on the volume of the final female connector blank; the calculation method is as follows: L2=4Y / [(3.14 (D1) 2 -d1 2 )]; Y represents the volume of the female connector blank, D1 represents the inner diameter of the thick-walled seamless pipe, d1 represents the outer diameter of the thick-walled seamless pipe, and L2 represents the length of pipe segment 1 from which the female connector blank needs to be prepared.

[0045] Next, heat the pipe section to 1200±30℃, keep it warm for 10 minutes, put it into mold 34, press it down, and complete the first upsetting.

[0046] Then, the second upsetting is completed using mold 45.

[0047] Finally, the three blocks were completed using mold 56.

[0048] Molds 3 and 4, Mold 4 and 5, and Mold 5 and 6 are detailed below: The mold 3 4 includes the third punch mold 41 (pressing downwards) designed as a conical mandrel, with the upper diameter equal to the inner diameter of the connector blank and the lower diameter 1mm smaller than the connector blank size to facilitate connector extraction; the upper part of the third outer mold 42 is designed as a barrel shape, with the upper and lower diameters being equal, and the lower part of the third outer mold 42 is designed as a conical surface similar to the 18° shoulder of the connector.

[0049] Mold 4.5 is a combination mandrel consisting of a frustum and a cylinder. The upper mandrel is a conical surface that matches the inclined surface of the internal thread area, and the lower part is a cylinder with a tapered diameter. The diameter of the cylindrical mandrel is larger at the top and smaller at the bottom to facilitate the removal of the mandrel.

[0050] Mold 56 is a combination mandrel of frustum and cylinder. The upper mandrel has a threaded area forming slope and a sealing shoulder surface, while the lower part is a cylinder with a tapered diameter. The diameter of the cylindrical mandrel is larger at the top and smaller at the bottom to facilitate the removal of the mandrel.

[0051] The performance test data of the NC50 connector manufactured using the above method are shown in the table below:

[0052] Tensile test conditions: room temperature; Impact test conditions: longitudinal normal temperature, transverse -20℃.

[0053] Meanwhile, when the joint with beveled forming is machined, the metal flow lines at the shoulder will be cut off, which will affect the fatigue life of the sealing surface. In this invention, the shoulder is formed by forging during the secondary forming process, and most of the metal flow lines are retained, thereby improving the fatigue life of the sealing surface.

[0054] The terms “first” and “second” are used to distinguish similar objects, rather than to describe or indicate a specific order or sequence.

[0055] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0056] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a 130Ksi grade oil drill pipe joint, characterized in that, Includes the following steps: S1, the selected material is 37CrMnMo steel; S2, according to the size of the target joint, the 37CrMnMo steel is prepared into a corresponding thick-walled seamless pipe; S3, the thick-walled seamless pipe is cut into pipe segments (1) of the required length, the length of which is calculated based on the volume of the male or female connector blank. S4, the pipe section (1) is heated to 1200±30℃ and held for 10 minutes, and then subjected to multi-step forging in a mold to form a male connector blank and / or a female connector blank, wherein: S41, the male connector blank is formed by two upsetting, the steps include: the pipe section (1) is upset once by mold one (2), the pipe section (1) forms a predetermined outer diameter and inner diameter, and the lower outer side forms an external thread area slope; then the pipe section (1) is upset twice by mold two (3), the upper outer side forms a 35° shoulder, and the lower outer side forms an external thread area slope with a sealing shoulder; S42, the female connector blank is formed by three upsetting, the steps include: the pipe section (1) is upset once by mold three (4), the pipe section (1) forms a predetermined outer diameter and inner diameter, and an 18° shoulder slope is formed on the lower outer side; then the pipe section (1) is upset twice by mold four (5), and an internal thread area slope is formed on the upper inner side of the pipe section (1); finally the pipe section (1) is upset three times by mold five (6), and an internal thread area slope with a sealing shoulder is formed on the upper inner side of the pipe section (1); S5, the male connector blank and the female connector blank are subjected to heat treatment, the heat treatment includes: quenching and heating to 880±10℃, quenching with water-based quenching fluid, the concentration of the water-based quenching fluid is controlled below 20%, and the average cooling rate before cooling to 300℃ during quenching is 20-50℃ / s; then tempering and heating to 570-600℃.

2. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, The composition of the 37CrMnMo steel selected in step S1, by mass percentage, is as follows: C: 0.35%–0.38%, Si: 0.15%–0.30%, Mn: 0.85%–1.00%, P: ≤0.013%, S: ≤0.005%, Cr: 1.10%–1.20%, Mo: 0.28%–0.33%, Ni: ≤0.25%, N: ≤0.009%, Sol Al: 0.015%–0.040%, Cu: ≤0.20%, V: ≤0.03%, Ti: ≤0.010%, B: ≤0.0001%, Nb: ≤0.05%, with the balance being Fe and unavoidable impurities.

3. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, In step S41, when the male connector blank is formed in one upsetting: the pipe section (1) is heated to 1200±30℃, kept warm for 10 minutes, placed in mold one (2), and the punch is pressed down to complete one upsetting.

4. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, In step S4, the mold 1 (2) for forming the male connector blank includes a first punch mold (21) and a first outer mold (22). The first punch mold (21) is a conical mandrel, the first outer mold (22) is barrel-shaped, and the lower part of the first outer mold (22) is a conical surface.

5. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, In step S4, the mold 2 (3) used for forming the male connector blank includes a second punch mold (31), a 35° shoulder forming mold (32) with a hole, and a second outer mold (33). The second punch mold (31) is a conical mandrel. The middle and upper parts of the second outer mold (33) are barrel-shaped with equal diameters, and the lower part of the second outer mold (33) is an inclined surface with a sealing shoulder.

6. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, In step S42, when the female connector blank is formed in one upsetting: the pipe section (1) is heated to 1200±30℃, kept warm for 10 minutes, placed in mold three (4), and the punch is pressed down to complete one upsetting.

7. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, In step S4, the mold three (4) for forming the female connector blank includes a third punch mold (41) and a third outer mold (42). The third punch mold (41) is a conical mandrel. The upper part of the third outer mold (42) is barrel-shaped with equal diameters, and the lower part of the third outer mold (42) is an inclined surface.

8. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, In step S4, the mold four (5) for forming the female connector blank includes a first inner mold (51) with a mandrel in the shape of a frustum and a cylinder. The upper part of the first inner mold (51) is inclined, and the lower part of the first inner mold (51) is a cylinder with a tapered diameter.

9. The method for manufacturing 130Ksi grade oil drill pipe joints according to claim 1, characterized in that, In step S4, the mold five (6) for forming the female connector blank includes a second inner mold (61) with a mandrel in the form of a frustum and a cylinder. The upper part of the second inner mold (61) is an inclined surface with a sealing shoulder, and the lower part of the second inner mold (61) is a cylinder with a tapered diameter.

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