A High-Efficiency Forming Method for Titanium Alloy Drill Pipe Joints

Abstract

This invention provides an efficient forming method for titanium alloy drill pipe joints, comprising: 1) heating steel bars in the order of steel bar-titanium alloy bar; 2) sequentially transferring the above materials to a first mold and performing a first die forging and upsetting on the titanium alloy bar, with a deformation of 39-42%; 3) transferring the titanium alloy bar to a second mold and performing a second die forging and upsetting, with a deformation of 17-20%, and punching the titanium alloy bar; 4) transferring the titanium alloy bar to a third mold and performing a third die forging and upsetting, with a deformation of 12-15%, and punching the titanium alloy bar again; 5) transferring the titanium alloy bar to a fourth mold and performing a fourth die forging and upsetting, with a deformation of 0-2%, and then punching the titanium alloy bar again to form a through hole. This invention can improve the forming quality and mechanical properties of titanium alloy joints, reduce surface defects during the forming process, and increase material utilization.

Description

Technical Field

[0001] This invention relates to the field of oil drill pipe technology, and more specifically, to a highly efficient forming method for titanium alloy drill pipe joints. Background Technology

[0002] Titanium alloys possess numerous advantages, including high specific strength, non-magnetic properties, low elastic modulus, excellent fatigue and corrosion resistance, and low thermal conductivity, making them a focal point for the research and development of lightweight drill pipes for deep wells, ultra-deep wells, and special well conditions with high sulfur content. Currently, the development of titanium alloy drill pipes in my country is in its initial stage, and in-depth research has not yet been conducted on the forming methods of titanium alloy drill pipes.

[0003] Currently, the main forming methods for titanium alloy drill pipe joints are: 1) Direct machining using bars or thick-walled tubes. This method has disadvantages such as low material utilization and high forging costs, making it unsuitable for mass production; 2) Drawing inspiration from steel drill pipe joint forming. However, due to the significant differences in material properties between the two, titanium alloy drill pipe joints produced by this method are prone to surface cracking during the forming process, and the joint performance may fail to meet standards. This greatly increases manufacturing costs and cannot meet the requirements for mass production applications.

[0004] To address this, Chinese Patent Application No. 202111594857.7 discloses a novel forging process for titanium alloy drill pipe joints. This process uses die pressing and forward and reverse extrusion to elongate the workpiece, which can improve the utilization rate of raw materials. However, the surface is prone to cracking during the forming process, and Widmanstätten structure is easily formed when the forming temperature is higher than the phase transformation point. This needs to be avoided as much as possible in engineering applications.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One of the problems solved by this invention is how to further suppress the formation of surface defects during the joint forming process, thereby improving the forming quality of the drill pipe joint; another problem solved by this invention is how to further improve the mechanical properties of the drill pipe joint; and a third problem solved by this invention is how to further improve material utilization and reduce manufacturing costs.

[0007] To address the aforementioned issues, this invention employs upsetting to suppress reverse pull-out of the titanium alloy joint and die forging to control the deformation dimensions of the titanium alloy drill pipe joint, thereby ensuring the forming quality of the titanium alloy drill pipe joint and improving its mechanical properties.

[0008] This invention provides a highly efficient forming method for titanium alloy drill pipe joints, comprising:

[0009] 1) Heat the steel bars in the order of steel bar-steel bar-titanium alloy bar, with a heating time of 2-5 minutes and a heating temperature of 900-1000℃.

[0010] 2) Transfer the above materials sequentially to the first mold, and perform the first die forging and upsetting of the titanium alloy bar, with a deformation of 39-42%;

[0011] 3) Transfer the titanium alloy bar to the second mold and perform a second die forging and upsetting. After the deformation is 17-20%, punch holes in the titanium alloy bar.

[0012] 4) Transfer the titanium alloy bar to the third mold for a third die forging and upsetting, with a deformation of 12-15%, and then punch the titanium alloy bar again;

[0013] 5) Transfer the titanium alloy bar to the fourth mold for the fourth die forging and upsetting, with a deformation of 0-2%. Then, punch the titanium alloy bar again to form a through hole.

[0014] This setup employs upsetting to suppress reverse pull-out of the titanium alloy joint and die forging to control the deformation dimensions of the titanium alloy drill pipe joint, ensuring the forming quality of the titanium alloy drill pipe joint, improving the mechanical properties of the joint, and effectively avoiding the shortcomings of reverse pull-out leading to easy surface cracking and easy formation of Widmanstätten structure at high temperatures; it also has high material utilization to further reduce production costs.

[0015] Preferably, steps 2) and / or 3) and / or 4) further include: inspecting the surface forming quality of the titanium alloy bar and determining whether there are any defects. If so, the bar is ground with an angle grinder to eliminate the defects and then the process returns to the previous step; otherwise, the process proceeds to the next step. This setup ensures a high yield rate for the finished product and maximizes overall efficiency.

[0016] Preferably, the defects include the presence of obvious pits and / or deformation defects.

[0017] Preferably, the heating method in step 1) is as follows: the material is heated in a medium-frequency induction heating furnace, and a section of material is pushed into the furnace from one end for about 1.2-1.5 minutes, while the heated billet is pushed out from the other end for continuous production. The production process corresponding to this efficient forming method for titanium alloy drill pipe joints is a continuously cyclical process. While the previous bar is undergoing its second upsetting die forging, the next bar is heated and begins its first upsetting die forging. This cycle repeats, reducing the forming time of a single drill pipe joint to 1.5 minutes. Up to 40 titanium alloy joints can be forged and upsetting within one hour, improving production efficiency and further reducing production costs.

[0018] Preferably, the deformation amounts of the die forging and upsetting in steps 2), 3), and 4) are 41%, 18.2%, and 13.93%, respectively. This setting, combined with the deformation temperature, can further improve the mechanical properties of the titanium alloy joint.

[0019] Preferably, for a 5.5-inch titanium alloy drill rod connector, in step 2), the upsetting pressure of the titanium alloy rod is 35mm, the punching diameter is φ60mm, and the hole depth is 110mm; in step 3), the punching diameter is φ90mm and the depth is 255mm; in step 4), the punching diameter is φ90mm and the depth is 160mm.

[0020] Preferably, step 1) further includes: pre-extracting the steel bar or titanium alloy bar by mechanical drawing.

[0021] Preferably, in steps 3), 4), and 5), two steel bars are used to preheat the die before the die forging and upsetting. The purpose of using steel bars for die forging and upsetting is mainly to preheat the die, reduce heat loss of the titanium alloy joint during the die forging and upsetting process; using two steel bars can shorten the preheating time of each process and improve production efficiency.

[0022] Preferably, the efficient forming method of the titanium alloy drill pipe joint further includes: 6) machining the treated titanium alloy rod to form threads.

[0023] Compared with the prior art, the efficient forming method of titanium alloy drill pipe joint of the present invention has the following beneficial effects: 1) The surface forming quality of the titanium alloy joint is good, and the non-destructive testing meets the requirements of coloring and ultrasonic Class I; 2) The mechanical properties of the titanium alloy drill pipe joint are improved, with the yield strength increased by more than 8%, the tensile strength increased by more than 20%, the elongation increased by more than 25%, and the impact energy at -10℃ increased by more than 20% compared with the original bar stock; 3) The material utilization rate in the process of finishing the titanium alloy drill pipe joint is more than 70%. Attached Figure Description

[0024] Figure 1 This is a cross-sectional schematic diagram of the titanium alloy drill pipe joint according to an embodiment of the present invention;

[0025] Figure 2 This is a physical image of the titanium alloy drill pipe joint described in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the titanium alloy bar material described in an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the original bar stock after one die forging and upsetting according to an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the original bar stock after secondary die forging and upsetting according to an embodiment of the present invention;

[0029] Figure 6 This is a schematic diagram of the original bar stock after three die forging and upsetting according to an embodiment of the present invention;

[0030] Figure 7 This is a schematic diagram of the original bar stock after four die forging and upsetting according to an embodiment of the present invention;

[0031] Figure 8 This is a cross-sectional schematic diagram of the first mold in an embodiment of the present invention;

[0032] Figure 9 This is a cross-sectional schematic diagram of the second mold according to an embodiment of the present invention;

[0033] Figure 10 This is a cross-sectional schematic diagram of the third mold described in an embodiment of the present invention;

[0034] Figure 11 This is a cross-sectional schematic diagram of the fourth mold described in an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Lower mold; 2. Annular abutment block; 3. Telescopic part. Detailed Implementation

[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Without conflict, the features in the embodiments of the present invention can be combined with each other.

[0038] Oil and gas exploration and development are expanding into areas previously considered "infeasible," with an increasing number of complex wells, including deep wells, ultra-deep wells, and ultra-short radius horizontal wells. Titanium alloy drill pipe joints effectively address the shortcomings of steel materials in these harsh environments, offering the following advantages: 1) High specific strength: Under the same strength conditions, titanium alloy has only 56% of the specific gravity of steel; this significantly improves the safety factor of the drill string and its ability to handle complex accidents; it also significantly reduces drilling rig power requirements and drilling energy consumption. 2) Non-magnetic: Titanium alloy has non-magnetic properties, which can significantly reduce the impact on downhole tools and instruments, improving operational safety. 3) Low elastic modulus: The elastic modulus of titanium alloy is only 50% of that of steel drill pipe. In short-radius and horizontal well operations such as window drilling in older wells, titanium alloy has advantages over steel drill pipe. 4) Excellent fatigue performance and corrosion resistance: In environments containing H2S, CO2, and Cl... - Titanium alloys exhibit excellent corrosion resistance under operating conditions; in corrosive conditions, the fatigue life of titanium alloy drill pipes is 100 times that of steel drill pipes. 5) Low thermal conductivity: Downhole temperatures in the Sichuan-Chongqing region are generally around 150℃. To ensure tool life and normal instrument operation, the low thermal conductivity of titanium alloys helps to better reduce downhole temperatures.

[0039] This invention is for the production of 5.5-inch titanium alloy drill pipe connectors with an outer diameter of 127mm, such as... Figure 1-2As shown, the titanium alloy rod used has dimensions of φ140*445mm and a total weight of 30.81Kg. Figure 3 As shown; prepare two additional 140*445mm steel bars for later use; calculate the deformation amount according to the following formula: Deformation amount = Volume of deformed metal / Total volume * 100%.

[0040] For ease of explanation, the molds used in this application are first described as follows: the first mold, the second mold, the third mold, and the fourth mold have largely the same structure, but their specific dimensions differ to control the deformation size and amount of deformation in a single die forging and upsetting process. The first mold is described below as an example: the first mold includes a lower mold 1, which has a cavity for placing the bar stock; an annular abutment block 2 is provided on the lower mold 1, which is connected to the drive structure. The annular abutment block 2 can move up and down and abut against the bar stock, thereby effectively controlling the reverse pulling of the bar stock; a telescopic part 3 is provided inside the annular abutment block 2, which is vectored and parallel to the power component and can move up and down relative to the annular abutment block 2 to perform die forging and upsetting on the bar stock. The specific structure and working principle of the drive structure and power component are existing technologies and will not be elaborated here.

[0041] Example 1

[0042] A highly efficient forming method for titanium alloy drill pipe joints, comprising:

[0043] 1) Mechanically draw the steel bars and titanium alloy bars, and then put them into the medium frequency induction heating furnace in the order of steel bar-steel bar-titanium alloy bar for heating. The heating time is 3 minutes and the heating temperature is 1020℃.

[0044] 2) Place the above materials sequentially onto the first mold, as shown in the image. Figure 8 As shown, the steel plate is used for preheating and heat preservation of the mold, and for the first die forging and upsetting of the titanium alloy bar. The upsetting pressure of the bar is 35mm to make the bar length consistent with the final product; at the same time, a φ60mm hole with a depth of 110mm is punched in the core of the bar; at this time, the outer diameter of the upper part of the bar becomes φ160mm, as shown. Figure 4 As shown, the deformation amount of the first die forging upsetting is: 282743.339 / 6850242.781 = 41%.

[0045] 3) Inspect the surface forming quality of the titanium alloy bar and determine whether there are any defects. If so, grind it with an angle grinder and return to step 2 after the defects are eliminated; otherwise, proceed to step 4). The defects include obvious pits and / or diameter variation defects.

[0046] 4) Transfer the titanium alloy bar to the second die in sequence for a second die forging and upsetting. The second die is as follows: Figure 9 As shown, the titanium alloy bar is then punched with a diameter of φ90mm and a depth of 255mm, consistent with the final product; at this point, the upper part of the bar is 181mm, as shown. Figure 5 As shown, the deformation amount of the second die forging upsetting is (1526814.030-282743.339) / 6850242.781=18.2%.

[0047] The two steel bars are transferred to the second mold in sequence and then to the third mold. After the two steel bars leave the second mold, the titanium alloy bars are transferred to the second mold in sequence for processing.

[0048] 5) Inspect the surface forming quality of the titanium alloy bar and determine whether there are any defects. If so, grind it with an angle grinder and remove the defects before returning to step 4; otherwise, proceed to step 6.

[0049] 6) Transfer the titanium alloy bar to the third die in sequence for a third die forging and upsetting, wherein the third die is as follows: Figure 10 As shown, the titanium alloy bar is then punched, with a punching diameter of φ90mm and a depth of 160mm. At this point, the bar's dimensions are essentially fully deformed. Figure 6 As shown; the deformation amount of the third die forging upsetting is: (2481072.798-1526814.030) / 6850242.781=13.93%.

[0050] 7) Inspect the surface forming quality of the titanium alloy bar and determine whether there are any defects. If so, grind it with an angle grinder and remove the defects before returning to step 6; otherwise, proceed to step 8).

[0051] 8) Transfer the titanium alloy bar to the fourth die in sequence for the fourth die forging and upsetting, wherein the fourth die is as follows: Figure 10 As shown, a φ90mm through hole is formed in the center of the titanium alloy bar, and the deformation amount of the fourth die forging upsetting is 0%.

[0052] 9) The titanium alloy bar processed in step 8 is machined to form threads.

[0053] The forming method of the titanium alloy drill pipe joint described in this invention employs a forming process of preheating a steel joint and forging and upsetting a titanium alloy joint. On the one hand, this process suppresses the formation of surface defects during the joint forming process, thus improving the forming quality of the drill pipe joint. On the other hand, by reducing the deformation temperature and controlling the deformation amount during the forming process, the mechanical properties of the drill pipe joint are improved. At the same time, the material utilization rate of the drill pipe joint is significantly increased to 70%, greatly reducing the manufacturing cost of the drill pipe joint.

[0054] Example 2

[0055] The titanium alloy drill pipe joint was prepared using the same method as in Example 1, except that the heating temperature in step 1) was 980°C.

[0056] The weight of each of the above joints was 24.64 kg. Their forming quality was tested, and the surface forming quality was good. Non-destructive testing met the coloring grade I requirements of NB / T 47013-2015 standard. The final upset joint is as follows: Figure 2 As shown in Table 1, the mechanical properties of the joint were tested.

[0057] Table 1 Results of Mechanical Property Tests

[0058]

[0059]

[0060] The material utilization rate of titanium alloy drill pipe joints obtained by different processes was calculated, and the results are shown in Table 2.

[0061] Table 2. Dimensions and Weights of Raw Materials and Finished Products Joints

[0062] Molding method Bar machining Thick-walled tube machining Example 1 Material specifications (mm) φ180*415 φ180*45*415 φ140*445 Material weight (Kg) 47.5 41.05 30.81 Material utilization rate 49.26％ 57.00％ 79.97％

[0063] Comparative Example 1

[0064] The 5-inch titanium alloy drill pipe joints 3 and 4 were prepared using the technical solution of Example 1 in Chinese Patent Application No. 202111594857.7, and the mechanical property test results are shown in Table 3.

[0065] Table 3 Results of Mechanical Property Tests

[0066] Yield strength / MPa Tensile strength / MPa elongation Impact energy at -10℃ / J raw bar stock 758 793 10 41 Drill pipe joint 3 769 900 12.5 45 Drill pipe joint 4 788 904 13.0 46 Changes 2.7％ 13.7％ 27.5％ 10.9％

[0067] The solution requires 31.55 kg of titanium alloy rods, and the corresponding weight for preparing the 5-inch drill pipe joint is 21.46 kg, with a material utilization rate of 68.02%.

[0068] The efficient forming method for titanium alloy drill pipe joints described in this invention employs a multi-stage die forging and upsetting process to strictly control the forming process of the joint, thereby improving the mechanical properties of the drill pipe joint. It has advantages such as good forming quality, excellent dimensional accuracy, high material utilization, and low cost, thus meeting the quality and mechanical performance requirements of titanium alloy drill pipe joints.

[0069] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A highly efficient forming method for titanium alloy drill pipe joints, characterized in that, Includes the following steps: 1) Heat the steel bars in the order of steel bar-steel bar-titanium alloy bar, with a heating time of 2-5 minutes and a heating temperature of 900-1000℃. 2) Transfer the steel bars-steel bars-titanium alloy bars sequentially to the first mold, and perform the first die forging and upsetting on the titanium alloy bars, with a deformation of 39-42%; 3) Transfer the titanium alloy bar to the second mold and perform a second die forging and upsetting, with a deformation of 17-20%, and then punch holes in the titanium alloy bar; 4) Transfer the titanium alloy bar to the third mold for a third die forging and upsetting, with a deformation of 12-15%, and then punch the titanium alloy bar again; 5) Transfer the titanium alloy bar to the fourth mold for the fourth die forging and upsetting, with a deformation of 0-2%. Then punch the titanium alloy bar again to form a through hole. The heating method in step 1) is as follows: the billet is heated in a medium-frequency induction heating furnace. A section of steel bar or titanium alloy bar is pushed into the furnace from one end for 1.2-1.5 minutes, and the heated billet is pushed out from the other end for continuous production. The first mold includes a lower mold (1), which has a cavity for placing titanium alloy bars; an annular abutment block (2) is provided on the lower mold (1), the annular abutment block (2) is connected to the drive structure, the annular abutment block (2) can move up and down and abut against the titanium alloy bars, thereby effectively controlling the reverse pulling of the titanium alloy bars; a telescopic part (3) is provided inside the annular abutment block (2), the telescopic part (3) is connected to the power component and can move up and down relative to the annular abutment block (2) to perform die forging and upsetting of the titanium alloy bars; In steps 3), 4), and 5), the die is preheated using two steel bars before the forging and upsetting.

2. The efficient forming method for titanium alloy drill pipe joints according to claim 1, characterized in that, Step 2), and / or Step 3) and / or Step 4) further include: inspecting the surface forming quality of the titanium alloy bar and determining whether there are any defects. If so, the bar is polished with an angle grinder and the defects are eliminated before returning to Step 1); otherwise, proceed to the next step.

3. The efficient forming method for titanium alloy drill pipe joints according to claim 2, characterized in that, The defects include the presence of obvious pits and / or deformation defects.

4. The efficient forming method for titanium alloy drill pipe joints according to claim 1, characterized in that, In steps 2), 3), and 4), the deformation amounts of the die forging and upsetting are 41%, 18.2%, and 13.93%, respectively.

5. The efficient forming method for titanium alloy drill pipe joints according to claim 4, characterized in that, For a 5.5-inch titanium alloy drill pipe joint, in step 2), the upsetting depth of the titanium alloy rod is 35mm, the punching diameter is φ60mm, and the depth is 110mm; in step 3), the punching diameter is φ90mm and the depth is 255mm; in step 4), the punching diameter is φ90mm and the depth is 160mm.

6. The efficient forming method for titanium alloy drill pipe joints according to claim 4, characterized in that, Step 1) also includes: pre-processing the steel bar and titanium alloy bar with mechanical polishing.

7. The efficient forming method for titanium alloy drill pipe joints according to claim 1, characterized in that, The efficient forming method for the titanium alloy drill pipe joint further includes: 6) machining the treated titanium alloy bar to form threads.

Images