Metal pipes for oil wells

Abstract

Provided is a metal pipe for an oil well, the metal pipe comprising a Zn-Ni alloy plating layer having excellent seizure resistance.　A metal pipe (1) for an oil well according to the present disclosure comprises a pipe body (10) including a first end part (10A) and a second end part (10B). The pipe body (10) includes a pin (40) formed on the first end part (10A) and a box (50) formed on the second end part (10B). The pin (40) includes a pin contact surface (400) including a male screw part (41). The box (50) includes a box contact surface (500) including a female screw part (51). The metal pipe (1) for an oil well further comprises a Ni plating layer (100) formed on the pin contact surface (400) and / or the box contact surface (500), and a Zn-Ni alloy plating layer (110) formed on the Ni plating layer (100). The deposition amount of the Ni plating layer (100) is larger than or equal to 6.00 g / m 2.

Description

[Technical Field]

[0001] This disclosure relates to metal tubing, and more specifically to metal tubing for oil wells. [Background technology]

[0002] Oil wells and gas wells (hereinafter, oil wells and gas wells are collectively referred to simply as "oil wells") use metal pipes for oil wells. These metal pipes have threaded joints. Specifically, at the oil well extraction site, multiple metal pipes are connected according to the depth of the oil well to form an oil well pipe assembly, such as a casing or tubing. The oil well pipe assembly is formed by screwing the metal pipes together. Inspections may be conducted on the oil well pipe assembly. When an inspection is conducted, the oil well pipe assembly is lifted and the pipes are unscrewed. The metal pipes are then removed from the oil well pipe assembly by unscrewing and inspected. After the inspection, the metal pipes are screwed together again, and the metal pipes are reused as part of the oil well pipe assembly.

[0003] The metal pipe for oil wells comprises a pin and a box. The pin has a pin contact surface including a male thread on the outer circumferential surface of the end of the metal pipe for oil wells. The box has a box contact surface including a female thread on the inner circumferential surface of the end of the metal pipe for oil wells. In this specification, the male thread and the female thread are collectively referred to as the "threaded portion." In this specification, the pin contact surface and the box contact surface are collectively referred to as the "contact surface." The pin contact surface may further include a pin seal surface and a pin shoulder surface, which constitute a pin threadless metal contact portion. Similarly, the box contact surface may further include a box seal surface and a box shoulder surface, which constitute a box threadless metal contact portion.

[0004] The pin contact surfaces and box contact surfaces (contact surfaces) of metal pipes used in oil wells are subjected to repeated strong friction during screw tightening and loosening. As a result, the contact surfaces are prone to golring (irreparable seizure) when repeatedly tightened and loosened. Therefore, metal pipes used in oil wells require sufficient durability against friction, i.e., excellent seizure resistance.

[0005] In the metal pipe for oil wells disclosed in Patent Document 1 (International Publication No. 2016 / 170031), a Zn-Ni alloy plating layer is formed on the pin contact surface or box contact surface instead of compound grease. The Zn in the Zn-Ni alloy plating layer formed on the contact surface of the metal pipe for oil well enhances the corrosion resistance of the metal pipe through sacrificial corrosion protection. Furthermore, Patent Document 1 discloses that the Zn-Ni alloy also has excellent wear resistance properties. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2016 / 170031 [Patent Document 2] Japanese Patent Publication No. 2014-91244 [Patent Document 3] Japanese Patent Publication No. 2017-179510 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, in recent years, there has been a growing demand for metal pipes for oil wells with even better seizure resistance. In particular, with large metal pipes for oil wells, the circumference of the pipe body is longer, requiring longer sliding distances from the start to the completion of fastening. As a result, large metal pipes for oil wells tend to seize up more easily than conventional pipes. Thus, metal pipes for oil wells are now required to have even better seizure resistance than conventional pipes.

[0008] An object of the present disclosure is to provide a metal pipe for oil wells having a Zn-Ni alloy plating layer with excellent seizure resistance.

Means for Solving the Problems

[0009] The metal pipe for oil wells according to the present disclosure includes a pipe body including a first end portion and a second end portion, wherein the pipe body includes a pin formed at the first end portion and a box formed at the second end portion, wherein the pin [[ID=--19]]includes a pin contact surface including a male thread portion, wherein the box includes a box contact surface including a female thread portion, the metal pipe for oil wells further includes a Ni plating layer formed on at least one of the pin contact surface and the box contact surface, and [[ID=2--8]] a Zn-Ni alloy plating layer formed on the Ni plating layer, -- wherein the adhesion amount of the Ni plating layer is 6.00 g / m 2 or more.

Advantages of the Invention

[0010] The metal pipe for oil wells having a Zn-Ni alloy plating layer according to the present disclosure has excellent seizure resistance.

Brief Description of the Drawings

[0011] [[ID=--47]] [Figure 1] FIG. 1 is a diagram showing the relationship between the adhesion amount (g / m2) of the Ni plating layer in an example described later and the sliding distance (mm) which is an index of seizure resistance. [Figure 2] FIG. 2 is a configuration diagram showing an example of the metal pipe for oil wells according to the present embodiment. [Figure 3] FIG. 3 is a partial cross-sectional view showing a cross-section (longitudinal cross-section) parallel to the pipe axis of the coupling of the metal pipe for oil wells shown in FIG. 2. [Figure 4] Note: There seem to be some formatting or content issues in the original text which might affect the translation's comprehensibility. For example, in the original text, there are some consecutive tags without clear text content between them, and in the translation, the numbering in the tags and the text might not match exactly due to potential errors in the original text's structure. However, I've translated it as accurately as possible according to the rules.Figure 4 is a cross-sectional view of the portion of the oil well metal pipe near the pin shown in Figure 3, parallel to the pipe axis direction of the oil well metal pipe. [Figure 5] Figure 5 is a cross-sectional view of the portion of the oil well metal pipe near the box shown in Figure 3, parallel to the pipe axis direction of the oil well metal pipe. [Figure 6] Figure 6 shows an example of a metal pipe for an oil well in which the pin includes a male threaded portion but does not include a pin seal surface or a pin shoulder surface, and the box includes a female threaded portion but does not include a box seal surface or a box shoulder surface. [Figure 7] Figure 7 is a diagram showing the configuration of an integral-type metal pipe for oil wells according to this embodiment. [Figure 8] Figure 8 is a cross-sectional view of the vicinity of the pin contact surface when the Ni plating layer is formed on the pin contact surface. [Figure 9] Figure 9 is a cross-sectional view of the vicinity of the box contact surface when the Ni plating layer is formed on the box contact surface. [Figure 10] Figure 10 is a cross-sectional view of the vicinity of the pin contact surface with a different configuration than that shown in Figure 8. [Figure 11] Figure 11 is a cross-sectional view of the vicinity of the box contact surface with a different configuration from that in Figure 9. [Modes for carrying out the invention]

[0012] This embodiment will be described in detail below with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

[0013] The Zn-Ni alloy plating layer has excellent wear resistance due to its high hardness. Furthermore, when it has excellent wear resistance, it tends to have excellent seizure resistance. For this reason, the Zn-Ni alloy plating layer has been applied to metal pipes for oil wells where seizure resistance is required. On the other hand, as mentioned above, large metal pipes for oil wells with large diameters have longer sliding distances during screw tightening and loosening than conventional metal pipes for oil wells. Therefore, even with metal pipes for oil wells that have a Zn-Ni alloy plating layer, excellent seizure resistance may not be obtained in large metal pipes for oil wells. So the inventors investigated various methods to improve the seizure resistance of metal pipes for oil wells that have a Zn-Ni alloy plating layer. As a result, the inventors obtained the following findings.

[0014] Due to its high hardness, the Zn-Ni alloy plating layer has lower ductility compared to other plating layers, such as the Cu plating layer. Furthermore, in metal pipes used in oil wells, which are used in harsh environments, the Zn-Ni alloy plating layer is formed thicker than that of plated steel sheets, etc. Therefore, the Zn-Ni alloy plating layer formed on metal pipes used in oil wells tends to have high internal stress. As a result, the inventors hypothesized that the adhesion between the Zn-Ni alloy plating layer and the contact surface tends to decrease in metal pipes used in oil wells, leading to a decrease in seizure resistance. In other words, if the adhesion between the Zn-Ni alloy plating layer and the contact surface can be improved, it may be possible to improve the seizure resistance of metal pipes used in oil wells.

[0015] To date, strike metal plating layers have been used to improve the adhesion between steel materials and the plating layer. Patent Document 2 (Japanese Patent Application Publication No. 2014-91244) discloses a technology for a resin-coated metal plate for containers with a strike metal plating layer formed thereon. Specifically, Patent Document 2 states that "strike metal plating has been carried out mainly for the purpose of improving the adhesion between the base metal and the plating layer" (paragraph

[0023] of Patent Document 2), and that "as for the type of strike metal plating, nickel plating or copper plating is preferred because it has already been established as a practical technology" (paragraph

[0025] of Patent Document 2). On the other hand, "the amount of adhesion is 0.1 g / m 2If the amount is less than 3.0 g / m², it becomes difficult to form a uniform plating layer, and good plating adhesion cannot be obtained. 2 Patent Document 2 states that "when the film thickness exceeds a certain level, the angular electrodeposition on the strike metal plating surface becomes coarser" (paragraph

[0026] of Patent Document 2). Therefore, the amount of plating on the strike metal plating layer should be 0.1 to 3.0 g / m². 2 Patent Document 2 states that this is within the scope of [the specified range].

[0016] Similarly, to improve the adhesion between the steel material and the plating layer, a technique has been used to form a Ni plating layer between the steel material and the plating layer. Patent Document 3 (Japanese Patent Application Publication No. 2017-179510) discloses a technique for forming a Ni plating layer to improve the adhesion of the Cu plating layer. Specifically, Patent Document 3 states that "the amount of Ni plating layer to be attached is preferably 0.4 g / m² from the viewpoint of improving the adhesion between the stainless steel plate and the Cu plating layer." 2 The amount should be "or more," and "preferably 4 g / m² from the viewpoint of improving adhesion between the stainless steel plate and the Cu plating layer." 2 (all paragraphs from Patent Document 3)

[0017] It is stated that this should be done. In other words, by forming a Ni plating layer between the steel material and the Cu plating layer, the adhesion of the Cu plating layer to the steel material can be improved, but a Ni plating layer that is too thick will actually reduce the adhesion of the Cu plating layer to the steel material, as stated in Patent Document 3.

[0017] Based on these prior art techniques, it is possible that forming a thin Ni plating layer between the contact surface of the oil well metal pipe and the Zn-Ni alloy plating layer will improve the adhesion of the Zn-Ni alloy plating layer and enhance the seizure resistance of the oil well metal pipe. Therefore, the inventors manufactured various oil well metal pipes in which a Ni plating layer was formed on the contact surface and a Zn-Ni alloy plating layer was formed on the Ni plating layer, and evaluated their seizure resistance. As a result, contrary to expectations based on prior art, the adhesion amount of the Ni plating layer was 6.00 g / m². 2It has been clarified that if it is increased to the above level, the seizure resistance of the metal pipe for oil wells will be significantly enhanced. This point will be described in detail using the drawings.

[0018] Figure 1 is a diagram showing the relationship between the deposition amount (g / m 2 ) of the Ni plating layer in the examples described later and the sliding distance (mm), which is an index of seizure resistance. Figure 1 was created using the deposition amount (g / m 2 ) of the Ni plating layer formed on a steel plate simulating the contact surface and the sliding distance (mm) in the sliding property evaluation test for the examples described later.

[0019] Referring to Figure 1, when the deposition amount of the Ni plating layer was less than 6.00 g / m 2 , it showed almost the same sliding distance as when the Ni plating layer was not formed. That is, even when a thin Ni plating layer disclosed in the prior art was formed, there was no significant change in the seizure resistance of the metal pipe for oil wells with a Zn-Ni alloy plating layer formed. On the other hand, when the deposition amount of the Ni plating layer was 6.00 g / m 2 or more, the sliding distance was significantly longer compared to the case where a thin Ni plating layer was formed. That is, it has been clarified that by deliberately forming a thick Ni plating layer that has been used from the perspective of adhesion, the seizure resistance of the metal pipe for oil wells is significantly enhanced.

[0020] In addition, the deposition amount of the Ni plating layer formed on the contact surface was 6.00 g / m 2The reason why increasing the thickness to the above level improves the seizure resistance of oil well metal pipes with a Zn-Ni alloy plating layer is not yet clear. However, the inventors speculate as follows: As mentioned above, the Zn-Ni alloy plating layer formed on oil well metal pipes is formed thickly, which tends to increase internal stress. In other words, the effect of internal stress in the formed Zn-Ni alloy plating layer is easily apparent in oil well metal pipes. On the other hand, by forming a thick Ni plating layer, a distance is created between the contact surface and the Zn-Ni alloy plating layer, which may allow for the dispersion of internal stress in the Zn-Ni alloy plating layer. Therefore, the effect of dispersing internal stress in the Zn-Ni alloy plating layer by the thick Ni plating layer may outweigh the decrease in adhesion due to the formation of a thick Ni plating layer, resulting in improved seizure resistance of the oil well metal pipes.

[0021] Through the above mechanism, the amount of Ni plating layer formed on the contact surface was 6.00 g / m². 2 The inventors speculate that increasing the above level will improve the seizure resistance of the Zn-Ni alloy plated metal pipes for oil wells. Furthermore, the amount of Ni plating layer formed on the contact surface was increased to 6.00 g / m² by a mechanism different from the one described above. 2 By increasing the amount above, it is possible that the seizure resistance of the metal pipes for oil wells with a Zn-Ni alloy plating layer has been improved. However, the amount of Ni plating layer formed on the contact surface is 6.00 g / m². 2 As demonstrated by the examples described later, increasing the above levels improves the seizure resistance of metal pipes for oil wells that have a Zn-Ni alloy plating layer formed on them.

[0022] Based on the above findings, the gist of the metal pipe for oil wells according to this embodiment is as follows:

[0023] [1] Metal pipes for oil wells, It comprises a pipe body including a first end and a second end, The aforementioned pipe body is The pin formed at the first end, Including a box formed at the second end, The aforementioned pin is, Including the pin contact surface including the male thread portion, The aforementioned box is Including the box contact surface including the female thread portion, The aforementioned metal pipe for the oil well further, A Ni plating layer is formed on at least one of the pin contact surface and the box contact surface, The Ni plating layer is formed on the Ni plating layer, comprising a Zn-Ni alloy plating layer, The amount of the Ni plating layer is 6.00 g / m². 2 That's all. Metal pipes for oil wells.

[0024] [2] [1] The metal pipe for oil wells described above, The aforementioned metal pipe for the oil well further, A lubricating film layer is provided on or above the Zn-Ni alloy plating layer. Metal pipes for oil wells.

[0025] The metal pipe for oil wells according to this embodiment will be described in detail below.

[0026] [Configuration of metal pipes for oil wells] First, the configuration of the metal tubing for oil wells in this embodiment will be described. The metal tubing for oil wells has a well-known configuration. There are two types of metal tubing for oil wells: T&C type and integral type. The following describes each type of metal tubing for oil wells in detail.

[0027] [When the metal pipe 1 for the oil well is of the T&C type] Figure 2 is a configuration diagram showing an example of a metal pipe 1 for an oil well according to this embodiment. Figure 2 is a configuration diagram of a so-called T&C type (Threaded and Coupled) metal pipe 1 for an oil well. Referring to Figure 2, the metal pipe 1 for an oil well comprises a pipe body 10.

[0028] The pipe body 10 extends in the direction of the pipe axis. The cross-section of the pipe body 10 perpendicular to the direction of the pipe axis is circular. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is the end opposite to the second end 10B. In the T&C type oil well metal pipe 1 shown in Figure 2, the pipe body 10 comprises a pin pipe body 11 and a coupling 12. The coupling 12 is attached to one end of the pin pipe body 11. More specifically, the coupling 12 is fastened to one end of the pin pipe body 11 by screw.

[0029] Figure 3 is a partial cross-sectional view showing a cross-section (longitudinal section) parallel to the pipe axis direction of the coupling 12 of the oil well metal pipe 1 shown in Figure 2. Referring to Figures 2 and 3, the pipe body 10 includes a pin 40 and a box 50. The pin 40 is formed at the first end 10A of the pipe body 10. When fastening, the pin 40 is inserted into the box 50 of another oil well metal pipe 1 (not shown) and fastened to the box 50 of the other oil well metal pipe 1 by screw.

[0030] The box 50 is formed at the second end 10B of the pipe body 10. During fastening, the pin 40 of the other oil well metal pipe 1 is inserted into the box 50 and fastened with the pin 40 of the other oil well metal pipe 1 by screw.

[0031] [Regarding the configuration of pin 40] Figure 4 is a cross-sectional view of the oil well metal pipe 1 shown in Figure 3, near the pin 40, parallel to the pipe axis direction of the oil well metal pipe 1. The dashed line in Figure 4 shows the configuration of the box 50 of the other oil well metal pipe 1 when fastened with another oil well metal pipe 1. Referring to Figure 4, the pin 40 has a pin contact surface 400 on the outer circumferential surface of the first end 10A of the pipe body 10. When fastened with another oil well metal pipe 1, the pin contact surface 400 is screwed into the box 50 of the other oil well metal pipe 1 and comes into contact with the box contact surface 500 (described later) of the box 50.

[0032] The pin contact surface 400 includes at least a male threaded portion 41 formed on the outer circumferential surface of the first end portion 10A. The pin contact surface 400 may further include a pin seal surface 42 and a pin shoulder surface 43. In Figure 4, the pin shoulder surface 43 is located on the tip surface of the first end portion 10A, and the pin seal surface 42 is located on the outer circumferential surface of the first end portion 10A, closer to the tip of the first end portion 10A than the male threaded portion 41. In other words, the pin seal surface 42 is located between the male threaded portion 41 and the pin shoulder surface 43. The pin seal surface 42 is tapered. Specifically, on the pin seal surface 42, the outer diameter gradually decreases in the longitudinal direction (pipe axis direction) of the first end portion 10A, from the male threaded portion 41 towards the pin shoulder surface 43.

[0033] When fastening to another oil well metal pipe 1, the pin seal surface 42 comes into contact with the box seal surface 52 (described later) of the box 50 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 is inserted into the box 50 of the other oil well metal pipe 1, causing the pin seal surface 42 to come into contact with the box seal surface 52. Then, as the pin 40 is further screwed into the box 50 of the other oil well metal pipe 1, the pin seal surface 42 comes into close contact with the box seal surface 52. As a result, when fastening, the pin seal surface 42 comes into close contact with the box seal surface 52, forming a seal based on metal-to-metal contact. Therefore, the airtightness of the oil well metal pipes 1 fastened to each other can be improved.

[0034] In Figure 4, the pin shoulder surface 43 is located on the tip surface of the first end 10A. In other words, in the pin 40 shown in Figure 4, the male thread portion 41, the pin seal surface 42, and the pin shoulder surface 43 are arranged in that order from the center of the pipe body 10 toward the first end 10A. When fastening with another oil well metal pipe 1, the pin shoulder surface 43 faces and contacts the box shoulder surface 53 (described later) of the box 50 of the other oil well metal pipe 1. More specifically, when fastening, the pin shoulder surface 43 comes into contact with the box shoulder surface 53 as the pin 40 is inserted into the box 50 of the other oil well metal pipe 1. This allows for high torque to be obtained when fastening. It also allows for stabilization of the positional relationship between the pin 40 and the box 50 when fastened.

[0035] Furthermore, the pin contact surface 400 of the pin 40 includes at least the male threaded portion 41. In other words, the pin contact surface 400 includes the male threaded portion 41 but does not include the pin seal surface 42 and the pin shoulder surface 43. The pin contact surface 400 includes the male threaded portion 41 and the pin shoulder surface 43 but does not include the pin seal surface 42. The pin contact surface 400 includes the male threaded portion 41 and the pin seal surface 42 but does not include the pin shoulder surface 43.

[0036] [Regarding the configuration of Box 50] Figure 5 is a cross-sectional view of the portion of the oil well metal pipe 1 near the box 50 shown in Figure 3, parallel to the pipe axis direction of the oil well metal pipe 1. The dashed line in Figure 5 shows the configuration of the pin 40 of the other oil well metal pipe 1 when fastened with another oil well metal pipe 1. Referring to Figure 5, the box 50 has a box contact surface 500 on the inner circumferential surface of the second end 10B of the pipe body 10. When fastened with another oil well metal pipe 1, the pin 40 of the other oil well metal pipe 1 is screwed into the box contact surface 500 and comes into contact with the pin contact surface 40 of the pin 40.

[0037] The box contact surface 500 includes at least a female threaded portion 51 formed on the inner circumferential surface of the second end portion 10B. When fastened, the female threaded portion 51 engages with the male threaded portion 41 of the pin 40 of the other oil well metal pipe 1.

[0038] The box contact surface 500 may further include a box seal surface 52 and a box shoulder surface 53. In Figure 5, the box seal surface 52 is located on the inner circumferential surface of the second end portion 10B, on the side of the pipe body 10 that is closer to the female thread portion 51. In other words, the box seal surface 52 is located between the female thread portion 51 and the box shoulder surface 53. The box seal surface 52 is tapered. Specifically, in the box seal surface 52, the inner diameter gradually decreases in the longitudinal direction (pipe axis direction) of the second end portion 10B, from the female thread portion 51 toward the box shoulder surface 53.

[0039] When fastening with another oil well metal pipe 1, the box seal surface 52 comes into contact with the pin seal surface 42 of the pin 40 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 of the other oil well metal pipe 1 is screwed into the box 50, causing the box seal surface 52 to come into contact with the pin seal surface 42, and as it is screwed in further, the box seal surface 52 comes into close contact with the pin seal surface 42. As a result, when fastening, the box seal surface 52 comes into close contact with the pin seal surface 42, forming a seal based on metal-to-metal contact. Therefore, the airtightness of the oil well metal pipes 1 fastened together can be improved.

[0040] The box shoulder surface 53 is positioned closer to the pipe body 10 than the box seal surface 52. In other words, in the box 50, the box shoulder surface 53, the box seal surface 52, and the female thread portion 51 are arranged in that order from the center of the pipe body 10 toward the tip of the second end portion 10B. When fastening with another oil well metal pipe 1, the box shoulder surface 53 faces and contacts the pin shoulder surface 43 of the pin 40 of the other oil well metal pipe 1. More specifically, when fastening, the box shoulder surface 53 comes into contact with the pin shoulder surface 43 when the pin 40 of the other oil well metal pipe 1 is inserted into the box 50. This allows for high torque to be obtained during fastening. It also allows for stabilization of the positional relationship between the pin 40 and the box 50 when fastened.

[0041] The box contact surface 500 includes at least a female threaded portion 51. When fastened, the female threaded portion 51 of the box contact surface 500 of the box 50 corresponds to and contacts the male threaded portion 41 of the pin contact surface 400 of the pin 40. The box seal surface 52 corresponds to and contacts the pin seal surface 42. The box shoulder surface 53 corresponds to and contacts the pin shoulder surface 43.

[0042] If the pin contact surface 400 includes the male thread portion 41 but does not include the pin seal surface 42 and the pin shoulder surface 43, the box contact surface 500 includes the female thread portion 51 but does not include the box seal surface 52 and the box shoulder surface 53. If the pin contact surface 400 includes the male thread portion 41 and the pin shoulder surface 43 but does not include the pin seal surface 42, the box contact surface 500 includes the female thread portion 51 and the box shoulder surface 53 but does not include the box seal surface 52. If the pin contact surface 400 includes the male thread portion 41 and the pin seal surface 42 but does not include the pin shoulder surface 43, the box contact surface 500 includes the female thread portion 51 and the box seal surface 52 but does not include the box shoulder surface 53.

[0043] The pin contact surface 400 may include a plurality of male threaded portions 41, a plurality of pin sealing surfaces 42, or a plurality of pin shoulder surfaces 43. For example, on the pin contact surface 400 of the pin 40, the pin shoulder surface 43, pin sealing surface 42, male threaded portion 41, pin sealing surface 42, pin shoulder surface 43, pin sealing surface 42, and male threaded portion 41 may be arranged in that order from the tip of the first end 10A toward the center of the pipe body 10. In this case, on the box contact surface 500 of the box 50, the female threaded portion 51, box sealing surface 52, box shoulder surface 53, box sealing surface 52, female threaded portion 51, box sealing surface 52, and box shoulder surface 53 may be arranged in that order from the tip of the second end 10B toward the center of the pipe body 10.

[0044] Figures 4 and 5 illustrate a so-called premium joint in which the pin 40 includes a male threaded portion 41, a pin seal surface 42, and a pin shoulder surface 43, and the box 50 includes a female threaded portion 51, a box seal surface 52, and a box shoulder surface 53. However, as described above, the pin 40 may include the male threaded portion 41 but not the pin seal surface 42 and the pin shoulder surface 43. In this case, the box 50 includes the female threaded portion 51 but not the box seal surface 52 and the box shoulder surface 53. Figure 6 shows an example of a metal pipe 1 for an oil well in which the pin 40 includes the male threaded portion 41 but not the pin seal surface 42 and the pin shoulder surface 43, and the box 50 includes the female threaded portion 51 but not the box seal surface 52 and the box shoulder surface 53.

[0045] [When the metal pipe 1 for the oil well is of the integral type] The metal pipe 1 for oil wells shown in Figures 2, 3, and 6 is a so-called T&C type metal pipe 1 for oil wells, in which the pipe body 10 includes a pinned pipe body 11 and a coupling 12. However, the metal pipe 1 for oil wells in this embodiment may be of an integral type instead of a T&C type.

[0046] Figure 7 is a diagram showing the configuration of an integral-type oil well metal pipe 1 according to this embodiment. Referring to Figure 7, the integral-type oil well metal pipe 1 comprises a pipe body 10. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is located on the opposite side from the second end 10B. As described above, in the T&C type oil well metal pipe 1, the pipe body 10 comprises a pin pipe body 11 and a coupling 12. In other words, in the T&C type oil well metal pipe 1, the pipe body 10 is constructed by fastening two separate components (the pin pipe body 11 and the coupling 12). In contrast, in the integral-type oil well metal pipe 1, the pipe body 10 is formed integrally.

[0047] The pin 40 is formed at the first end 10A of the pipe body 10. During fastening, the pin 40 is inserted into and screwed into the box 50 of the other integral-type oil well metal pipe 1, and fastened to the box 50 of the other integral-type oil well metal pipe 1. The box 50 is formed at the second end 10B of the pipe body 10. During fastening, the pin 40 of the other integral-type oil well metal pipe 1 is inserted into and screwed into the box 50, and fastened to the pin 40 of the other integral-type oil well metal pipe 1.

[0048] The configuration of the pin 40 of the integral type oil well metal pipe 1 is the same as the configuration of the pin 40 of the T&C type oil well metal pipe 1 shown in Figure 4. Similarly, the configuration of the box 50 of the integral type oil well metal pipe 1 is the same as the configuration of the box 50 of the T&C type oil well metal pipe 1 shown in Figure 5. In Figures 4 and 5, the pin 40 is arranged in the order of pin shoulder surface 43, pin seal surface 42, and male thread portion 41, starting from the tip of the first end 10A toward the center of the pipe body 10. Therefore, in the box 50, the female thread portion 51, box seal surface 52, and box shoulder surface 53 are arranged in the order of female thread portion 51, box seal surface 52, and box shoulder surface 53, starting from the tip of the second end 10B toward the center of the pipe body 10. However, similar to the pin contact surface 400 of the pin 40 of the T&C type oil well metal pipe 1, the pin contact surface 400 of the pin 40 of the integral type oil well metal pipe 1 only needs to include at least the male thread portion 41. Furthermore, similar to the box contact surface 500 of the box 50 of the T&C type oil well metal pipe 1, the box contact surface 500 of the box 50 of the integral type oil well metal pipe 1 only needs to include at least the female thread portion 51.

[0049] In short, the metal pipe 1 for the oil well in this embodiment may be of the T&C type or the integral type.

[0050] [Chemical composition of the tube body] The chemical composition of the pipe body 10 of the oil well metal pipe 1 according to this embodiment is not particularly limited. That is, in this embodiment, the type of steel used for the pipe body 10 of the oil well metal pipe 1 is not particularly limited. The pipe body 10 may be made of, for example, carbon steel, stainless steel, or alloys. In other words, the oil well metal pipe 1 may be a steel pipe made of Fe-based alloy, or an alloy pipe represented by Ni-based alloy pipe. Here, steel pipes include, for example, low-alloy steel pipes, martensitic stainless steel pipes, ferritic stainless steel pipes, austenitic stainless steel pipes, and duplex stainless steel pipes. Alloy pipes include, for example, Ni-based alloy pipes and NiCrFe alloy pipes. On the other hand, among alloys, so-called high alloys such as Ni-based alloys and duplex stainless steel containing alloying elements such as Cr, Ni, and Mo have high corrosion resistance. Therefore, if these high alloys are used for the pipe body 10, excellent corrosion resistance can be obtained in corrosive environments containing hydrogen sulfide, carbon dioxide, etc.

[0051] [Ni plating layer] In the metal pipe 1 for oil wells according to this embodiment, a Ni plating layer is formed on at least one of the contact surfaces, the pin contact surface 400 and the box contact surface 500. That is, the Ni plating layer is formed on the pin contact surface 400 and does not have to be formed on the box contact surface 500. The Ni plating layer is also formed on the box contact surface 500 and does not have to be formed on the pin contact surface 400. The Ni plating layer may further be formed on both the pin contact surface 400 and the box contact surface 500.

[0052] [Zn-Ni alloy plating layer] In the metal pipe 1 for oil wells according to this embodiment, a Zn-Ni alloy plating layer is formed on a Ni plating layer. That is, if the Ni plating layer is formed on the pin contact surface 400, the Zn-Ni alloy plating layer is formed on the Ni plating layer formed on the pin contact surface 400. In this case, the box contact surface 500 may have a Ni plating layer, a Zn-Ni alloy plating layer, or no plating layer at all. Also, if the Ni plating layer is formed on the box contact surface 500, the Zn-Ni alloy plating layer is formed on the Ni plating layer formed on the box contact surface 500. In this case, the pin contact surface 400 may have a Ni plating layer, a Zn-Ni alloy plating layer, or no plating layer at all. In other words, in this embodiment, it is sufficient that a Ni plating layer is formed on at least one of the pin contact surface 400 and the box contact surface 500, and that a Zn-Ni alloy plating layer is formed on the Ni plating layer.

[0053] The following explanation describes the configuration on the pin contact surface 400 when the Ni plating layer is formed on the pin contact surface 400, and the configuration on the box contact surface 500 when the Ni plating layer is formed on the box contact surface 500.

[0054] [Configuration on the pin contact surface when the Ni plating layer is formed on the pin contact surface] Figure 8 is a cross-sectional view of the vicinity of the pin contact surface 400 when the Ni plating layer 100 is formed on the pin contact surface 400. Referring to Figure 8, in this case the oil well metal pipe 1 further comprises a Ni plating layer 100 formed on the pin contact surface 400 of the pin 40 and a Zn-Ni alloy plating layer 110 formed on the Ni plating layer 100.

[0055] The Ni plating layer 100 and the Zn-Ni alloy plating layer 110 may be formed on a portion of the pin contact surface 400, or they may be formed on the entire pin contact surface 400. Note that the pin seal surface 42 experiences particularly high surface pressure during the final stage of screw tightening. Therefore, when the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are partially formed on the pin contact surface 400, it is preferable that the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are formed on at least the pin seal surface 42.

[0056] [Configuration on the box contact surface when the Ni plating layer is formed on the box contact surface] Figure 9 is a cross-sectional view of the vicinity of the box contact surface 500 when the Ni plating layer 100 is formed on the box contact surface 500. Referring to Figure 9, in this case the oil well metal pipe 1 further comprises a Ni plating layer 100 formed on the box contact surface 500 of the box 50 and a Zn-Ni alloy plating layer 110 formed on the Ni plating layer 100.

[0057] The Ni plating layer 100 and the Zn-Ni alloy plating layer 110 may be formed on a portion of the box contact surface 500, or they may be formed on the entire box contact surface 500. Note that the box seal surface 52 experiences particularly high surface pressure during the final stage of screw tightening. Therefore, when the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are partially formed on the box contact surface 500, it is preferable that the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are formed on at least the box seal surface 52.

[0058] [Amount of Ni plating layer and Zn-Ni alloy plating layer] In this embodiment, the amount of Ni plating layer 100 deposited is 6.00 g / m². 2 That concludes the report. The amount of Ni plating layer 100 deposited is 6.00 g / m². 2 In the above case, the amount of Ni plating layer 100 attached is 6.00 g / m². 2Compared to the case where the amount is less, the seizure resistance of the oil well metal pipe 1 is significantly improved. Therefore, in the oil well metal pipe 1 according to this embodiment, the amount of Ni plating layer 100 formed on at least one of the pin contact surface 400 and the box contact surface 500 is 6.00 g / m 2 This concludes the explanation. As a result, the internal stress of the Zn-Ni alloy plating layer 110 formed on the Ni plating layer 100 is relieved, and the seizure resistance of the oil well metal pipe 1 is improved.

[0059] In this embodiment, the preferred lower limit for the amount of Ni plating layer 100 is 6.50 g / m². 2 And more preferably 7.00 g / m 2 And more preferably 8.00 g / m 2 And more preferably 9.00 g / m 2 And more preferably 9.30 g / m 2 And more preferably 10.00 g / m 2 The upper limit of the amount of Ni plating layer 100 is not particularly limited, but for example, 60.00 g / m² 2 That is the case.

[0060] In this embodiment, the amount of Zn-Ni alloy plating layer 110 is not particularly limited. However, the Zn-Ni alloy plating layer 110 formed on the oil well metal pipe 1 tends to be formed relatively thickly in order to obtain excellent anti-seizure properties. Specifically, the amount of Zn-Ni alloy plating layer 110 in this embodiment is, for example, 20 to 160 g / m². 2 Therefore, the Zn-Ni alloy plating layer 110, formed to this thickness, exhibits excellent wear resistance, but is prone to high internal stress. 2 By forming the above Ni plating layer 100 as a lower layer, the internal stress of the Zn-Ni alloy plating layer 110 is relaxed, and as a result, the seizure resistance of the oil well metal pipe 1 is expected to be improved.

[0061] The amount of Ni plating layer 100 and Zn-Ni alloy plating layer attached can be determined using the film dissolution method. Specifically, a sample containing Ni plating layer 100 and Zn-Ni alloy plating layer 110 (including the contact surface on which Ni plating layer 100 and Zn-Ni alloy plating layer 110 are formed) is taken from the oil well metal pipe 1. The areas of Ni plating layer 100 and Zn-Ni alloy plating layer 110 formed on the taken sample are measured in advance. The Zn-Ni alloy plating layer 110 is dissolved in the taken sample using a dilute hydrochloric acid solution to obtain a solution of Zn-Ni alloy plating layer 110. Then, the Ni plating layer 100 is dissolved in the sample from which the Zn-Ni alloy plating layer 110 has been removed by dissolution using a dilute nitric acid solution to obtain a solution of Ni plating layer 100.

[0062] Elemental analysis of each obtained solution is performed using inductively coupled plasma atomic emission spectrometry (ICP-AES). For the Ni plating layer 100, the Ni content obtained from the elemental analysis and the area of ​​the Ni plating layer 100 formed in the sample are used to determine the amount of Ni plating layer 100 deposited (g / m²). 2 The amount of Zn-Ni alloy plating layer 110 (g / m²) can be determined using the Ni content and Zn content obtained from elemental analysis of the Zn-Ni alloy plating layer 110, and the area of ​​the Zn-Ni alloy plating layer 110 formed in the sample. 2 ) can be calculated.

[0063] [Chemical composition of the Ni plating layer and the Zn-Ni alloy plating layer] The Ni plating layer 100 has a chemical composition consisting of Ni and impurities. The Zn-Ni alloy plating layer 110 is composed of a Zn-Ni alloy and has a chemical composition consisting of Ni: 5-25%, with the remainder being Zn and impurities. Here, impurities in the chemical composition of the Ni plating layer refer to substances other than Ni, which are contained in the Ni plating layer 100 through the manufacture of the oil well metal pipe 1, etc., and are included in a content range that does not affect the effect of the oil well metal pipe 1 according to this embodiment. Furthermore, impurities in the chemical composition of the Zn-Ni alloy plating layer 110 refer to substances other than Zn and Ni, which are contained in the Zn-Ni alloy plating layer 110 through the manufacture of the oil well metal pipe 1, etc., and are included in a content range that does not affect the effect of the oil well metal pipe 1 according to this embodiment.

[0064] Here, the Zn-Ni alloy plating layer 110 contains Zn. Zn is a less noble metal compared to Fe. Therefore, the Zn-Ni alloy plating layer 110 is corroded preferentially over the steel (sacrificial corrosion protection). This enhances the corrosion resistance of the oil well metal pipe 1. The chemical composition of the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 can be identified simultaneously when determining the amount of adhesion using the film dissolution method described above.

[0065] [Other optional configurations of the oil well metal pipe 1 in this embodiment] [Chemical conversion coating] The oil well metal pipe 1 of this embodiment may further have a chemical conversion coating on the Zn-Ni alloy plating layer 110. For example, if the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are formed on the pin contact surface 400, the chemical conversion coating may be formed on the Zn-Ni alloy plating layer 110. Alternatively, if the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are formed on the box contact surface 500, the chemical conversion coating may be formed on the Zn-Ni alloy plating layer 110.

[0066] The chemical conversion coating is not particularly limited and may be any well-known chemical conversion coating. The chemical conversion coating may be, for example, an oxalate chemical conversion coating, a phosphate chloride chemical conversion coating, a borate chemical conversion coating, or a chromate coating. If the chemical conversion coating is a chromate coating, it is preferable that the chromate coating does not contain hexavalent chromium.

[0067] The metal pipes 1 used for oil wells may be stored outdoors for long periods before being actually used at the oil extraction site. The chemical conversion coating enhances the corrosion resistance of the pin contact surface 400 and suppresses the occurrence of rust (white rust) on the pin contact surface 400 when the metal pipes 1 used for oil wells are exposed to the atmosphere outdoors for long periods. The thickness of the chemical conversion coating is not particularly limited. For example, the thickness of the chemical conversion coating is 10 to 200 nm.

[0068] [Lubricating film layer] In the oil well metal pipe 1, a lubricating coating layer may be provided on the Zn-Ni alloy plating layer 110, on the chemical conversion coating, or on a contact surface where the Zn-Ni alloy plating layer 110 is not formed (on the pin contact surface 400 or on the box contact surface 500). The lubricating coating layer further enhances the lubricity of the oil well metal pipe 1. Referring to Figure 10, when the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are formed on the pin contact surface 400, the lubricating coating layer 120 may be formed on the Zn-Ni alloy plating layer 110. Also, referring to Figure 11, when the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are formed on the box contact surface 500, the lubricating coating layer 120 may be formed on the Zn-Ni alloy plating layer 110.

[0069] The lubricating film layer 120 may be solid, semi-solid, or liquid. The lubricating film layer 120 can be formed using commercially available lubricants. The lubricating film layer 120 may, for example, contain lubricating particles and a binder. The lubricating film layer 120 may further contain a solvent and other components as needed.

[0070] The lubricating particles are not particularly limited as long as they are particles that have lubricating properties. For example, the lubricating particles are one or more selected from the group consisting of graphite, MoS2 (molybdenum disulfide), WS2 (tungsten disulfide), BN (boron nitride), PTFE (polytetrafluoroethylene), CFx (graphite fluoride), and CaCO3 (calcium carbonate).

[0071] The binder is, for example, one or two selected from the group consisting of organic binders and inorganic binders. The organic binder is, for example, one or two selected from the group consisting of thermosetting resins and thermoplastic resins. The thermosetting resin is, for example, one or more selected from the group consisting of polyethylene resins, polyimide resins and polyamide-imide resins. The inorganic binder is, for example, one or two selected from the group consisting of alkoxysilanes and compounds containing siloxane bonds.

[0072] A commercially available lubricant is, for example, SEAL-GUARD ECF (product name) manufactured by JET-LUBE Corporation. Other lubricating film layers 120 include, for example, rosin, metal soap, wax, and lubricating powder.

[0073] [Manufacturing method for metal pipes 1 for oil wells] The manufacturing method for the oil well metal pipe 1 of this embodiment will be described below. Note that the manufacturing method for the oil well metal pipe 1 of this embodiment is not limited to the method described below, as long as it has the above configuration. However, the manufacturing method described below is a preferred example for manufacturing the oil well metal pipe 1 according to this embodiment.

[0074] The manufacturing method for the oil well metal pipe 1 comprises a preparation step (S1) of preparing a raw pipe on which a pin 40 or box 50 is formed, a Ni plating layer formation step (S2), and a Zn-Ni alloy plating layer formation step (S3). The manufacturing steps of the oil well metal pipe 1 according to this embodiment will be described in detail below.

[0075] [Preparation process (S1)] In preparation step (S1), a raw pipe having a pin 40 or a box 50 formed on it is prepared. In this specification, "raw pipe having a pin or a box formed on it" means either the pipe body 10 or pin pipe body 11 in a T&C type oil well metal pipe 1, or the pipe body 10 in an integral type oil well metal pipe 1.

[0076] The base tube on which the pin 40 or box 50 is formed is manufactured, for example, by the following method: The material is manufactured using molten steel. Specifically, a slab (slab, bloom, or billet) is manufactured using molten steel by continuous casting. An ingot may also be manufactured using molten steel by ingot forming. If necessary, a billet may be manufactured by bloc rolling of the slab, bloom, or ingot. The material (slab, bloom, or billet) is manufactured by the above process. The prepared material is hot-worked to manufacture the base tube. The hot-working method may be perforation rolling by the Mannesmann method or hot extrusion. The strength of the base tube is adjusted by performing well-known quenching and tempering on the base tube after hot-working. The base tube is manufactured by the above process. If the metal pipe 1 for the oil well is of the T&C type, a base tube for the coupling 12 is also prepared. The method for manufacturing the base tube for the coupling 12 is the same as the method for manufacturing the base tube described above.

[0077] If the metal pipe 1 for the oil well is of the T&C type, threading is performed on the outer surfaces of both ends of the base pipe for the pin pipe body 11 to form a pin 40 including a pin contact surface 400. Through the above process, a base pipe (pin pipe body 11) with the pin 40 formed is prepared for the case where the metal pipe 1 for the oil well is of the T&C type. In addition, if the metal pipe 1 for the oil well is of the T&C type, a coupling 12 may also be prepared. Specifically, threading is performed on the inner surfaces of both ends of the base pipe for the coupling 12 to form a box 50 including a box contact surface 500. Through the above process, the coupling 12 is manufactured.

[0078] If the metal pipe 1 for the oil well is of the integral type, threading is performed on the outer surface of the first end 10A of the pipe to form a pin 40 including a pin contact surface 400. Furthermore, threading is performed on the inner surface of the second end 10B of the pipe to form a box 50 including a box contact surface 500. Through these steps, a pipe (pipe body 10) with the pin 40 and box 50 formed is prepared for the case where the metal pipe 1 for the oil well is of the integral type.

[0079] [Other optional steps] The preparation step (S1) of this embodiment may further include a grinding step.

[0080] In the preparation step (S1) according to this embodiment, if a grinding process is performed, the grinding process may include, for example, sandblasting and mechanical grinding. Sandblasting is a process in which a mixture of blasting material (abrasive) and compressed air is projected onto the contact surface. The blasting material may be, for example, spherical shot material or angular grid material. Sandblasting can increase the surface roughness of the contact surface. Sandblasting can be performed by well-known methods. For example, air is compressed with a compressor and mixed with the blasting material. The material of the blasting material may be, for example, stainless steel, aluminum, ceramic, and alumina. The projection speed and other conditions of the sandblasting process are not particularly limited and can be adjusted as appropriate under well-known conditions.

[0081] [Ni plating layer formation process (S2)] In the Ni plating layer formation process (S2), a Ni plating layer 100 is formed by electroplating on the pin contact surface 400 of the raw tube on which the pins 40 are formed after the preparation process (S1), and / or on the box contact surface 500 of the raw tube on which the box 50 is formed.

[0082] In the Ni plating layer formation step (S2), a Ni plating layer 100 is formed by electroplating using a plating bath containing nickel ions. The counteranion of the nickel ion is not particularly limited. For example, chloride ions, sulfate ions, or sulfamate ions may be used as the counteranion of the nickel ion. In other words, in the Ni plating layer formation step (S2) according to this embodiment, a chloride bath, a sulfuric acid bath, or a sulfamic acid bath may be used as the plating bath.

[0083] The following describes a specific example of a plating bath, specifically using a chloride bath. When using a chloride bath, for example, a chloride bath containing nickel chloride: 240 g / L and hydrochloric acid: 125 mL / L can be used. As mentioned above, the Ni plating layer formation process (S2) according to this embodiment is not limited to a chloride bath, and other baths can also be used.

[0084] The electroplating conditions in the Ni plating layer formation process (S2) are not particularly limited and can be adjusted as appropriate using well-known conditions. Specifically, the electroplating conditions are: plating bath pH: 1~10, plating bath temperature: 10~60℃, current density: 1~100A / dm 2 Furthermore, the processing time can be set to 6.0 to 1800.0 seconds. As mentioned above, the Ni plating layer 100 according to this embodiment has an adhesion amount of 6.00 g / m². 2 This concludes the explanation. At this time, the amount of Ni plating layer 100 can be adjusted by adjusting the electroplating current density and processing time. That is, depending on the type of plating bath used and the electroplating conditions such as the temperature of the plating bath, the amount of Ni plating layer 100 can be adjusted to 6.00 g / m². 2 You can adjust it as described above.

[0085] [Zn-Ni alloy plating layer formation process (S3)] In the Zn-Ni alloy plating layer formation step (S3), the Zn-Ni alloy plating layer 110 is formed on the Ni plating layer 100 after the Ni plating layer formation step (S2) by electroplating. As described above, the Zn-Ni alloy plating layer 110 may also be formed on the pin contact surface 400 or the box contact surface 500 where the Ni plating layer 100 has not been formed.

[0086] In the Zn-Ni alloy plating layer formation step (S3), a Zn-Ni alloy plating layer 110 is formed by electroplating using a well-known plating bath containing zinc ions and nickel ions. For example, a plating bath containing zinc ions: 1 to 100 g / L and nickel ions: 1 to 100 g / L can be used. Furthermore, the counteranions of zinc ions and nickel ions are not particularly limited. For example, chloride ions or sulfate ions may be used as counteranions. In other words, in the Zn-Ni alloy plating layer formation step (S3) according to this embodiment, a chloride bath or a sulfuric acid bath may be used as the plating bath.

[0087] The electroplating conditions in the Zn-Ni alloy plating layer formation process (S3) are not particularly limited and can be appropriately adjusted using well-known conditions. Examples of electroplating conditions include: plating bath pH: 1-10, plating bath temperature: 10-60°C, current density: 1-100 A / dm². 2 The processing time is 0.1 to 30 minutes. When forming the Zn-Ni alloy plating layer 110 on the Ni plating layer 100 formed on the pin contact surface 400, the pin contact surface 400 is immersed in the above-mentioned plating bath and electroplating is performed. Similarly, when forming the Zn-Ni alloy plating layer 110 on the Ni plating layer 100 formed on the box contact surface 500, the box contact surface 500 is immersed in the above-mentioned plating bath and electroplating is performed.

[0088] Through the above manufacturing process, the oil well metal pipe 1 of this embodiment having the above-described configuration is manufactured. Note that the above-described manufacturing process is an example of the manufacturing process for the oil well metal pipe 1 according to this embodiment, and the manufacturing method for the oil well metal pipe 1 according to this embodiment is not limited to the above-described method.

[0089] [Other optional steps] The manufacturing method for the oil well metal pipe 1 according to this embodiment may further include at least one of the following steps: a chemical treatment step and a film formation step. These steps are optional. Therefore, these steps do not need to be performed.

[0090] [Chemical treatment process] The manufacturing method of this embodiment may optionally include a chemical conversion treatment step. In other words, the chemical conversion treatment step is an optional step. When the chemical conversion treatment step is performed, a chemical conversion treatment film is formed on the Zn-Ni alloy plating layer 110. In the chemical conversion treatment step, any well-known chemical conversion treatment may be performed. The chemical conversion treatment may be, for example, an oxalate chemical conversion treatment, a phosphate chlorination treatment, or a borate chemical conversion treatment. For example, when performing a phosphate chlorination treatment, a chemical conversion treatment using zinc phosphate may be performed, a chemical conversion treatment using manganese phosphate may be performed, or a chemical conversion treatment using zinc calcium phosphate may be performed.

[0091] Specifically, when performing zinc phosphate conversion treatment, a conversion treatment solution containing, for example, 1 to 150 g / L of phosphate ions, 3 to 70 g / L of zinc ions, 1 to 100 g / L of nitrate ions, and 0 to 30 g / L of nickel ions can be used as the treatment solution. In this case, the temperature of the conversion treatment solution is, for example, 20 to 100°C. By performing the conversion treatment under these well-known conditions as appropriate, a conversion treatment film can be formed.

[0092] [Film forming process] The manufacturing method of this embodiment may optionally include a film formation step. In other words, the film formation step is an optional step. In the film formation step, a lubricating film layer 120 is formed on the Zn-Ni alloy plating layer 110 and / or on the chemical conversion treatment film and / or on a contact surface (pin contact surface 400 or box contact surface 500) where the Zn-Ni alloy plating layer 110 is not formed.

[0093] In the film formation process, a composition or lubricant containing the above-mentioned lubricating film components is applied. In this way, a lubricating film layer 120 can be formed. The application method is not particularly limited. For example, application methods include spray application, brush application, and immersion. When spray application is used, the composition or lubricant may be heated to increase its fluidity before spraying. The composition or lubricant is dried to form the lubricating film layer 120.

[0094] The metal pipe 1 for oil wells of this embodiment will be described in more detail below with reference to examples. The conditions in the following examples are just one example of conditions adopted to confirm the feasibility and effectiveness of the metal pipe 1 for oil wells of this embodiment. Therefore, the metal pipe 1 for oil wells of this embodiment is not limited to this one example of conditions. [Examples]

[0095] In this example, a Ni plating layer and a Zn-Ni alloy plating layer were formed on a steel sheet simulating a contact surface, and the seizure resistance of the steel sheet was evaluated. Specifically, the steel sheet was a cold-rolled steel sheet, with a chemical composition of C ≤ 0.15%, Mn ≤ 0.60%, P ≤ 0.100%, S ≤ 0.050%, and the remainder being Fe and impurities.

[0096] For each test number of steel sheet, electrolytic degreasing and immersion pickling were performed as surface preparation. After surface preparation, each test number of steel sheet was plated using the plating baths listed in Table 1, with the current densities (A / dm²) listed in Table 1. 2 A Ni plating layer was formed using the following method: ) and processing time (seconds). Note that in Table 1, a "-" in the "Plating Bath", "Current Density", and "Processing Time" columns means that a Ni plating layer was not formed.

[0097] [Table 1]

[0098] Specifically, the plating baths "A" and "B" were as follows:

[0099] [Plating bath A] A chloride bath was used as plating bath A. Plating bath A contained 240 g / L of nickel chloride and 125 mL / L of hydrochloric acid. The electroplating conditions when using plating bath A were: plating bath pH: 1.5 or less, and plating bath temperature: 25°C.

[0100] [Plating bath B] A sulfuric acid bath was used as plating bath B. Plating bath B contained 240-300 g / L of nickel sulfate, 40-70 g / L of nickel chloride, and 30-45 g / L of boric acid. The electroplating conditions when using plating bath B were: plating bath pH: 3-4, plating bath temperature: 40-50°C.

[0101] A Zn-Ni alloy plating layer formation process was carried out on the steel sheet after the Ni plating layer was formed. The plating bath used in the Zn-Ni alloy plating layer formation process was a commercially available, well-known plating bath. The other conditions for the Zn-Ni alloy plating layer formation process were carried out under the preferred conditions described above. Steel sheets of each test number were manufactured using the above manufacturing process.

[0102] For each steel plate with a test number that was manufactured, the amount of plating adhesion was measured, and a seizure resistance test was performed.

[0103] [Measuring the amount of plating adhesion] For each test number of steel plate, the amount of Ni plating layer and Zn-Ni alloy plating layer was measured using the film dissolution method described above. Specifically, samples containing both the Ni plating layer and the Zn-Ni alloy plating layer were taken from each test number of steel plate, and the Zn-Ni alloy plating layer and the Ni plating layer were dissolved in dilute hydrochloric acid solution and dilute nitric acid solution, respectively. Elemental analysis of the resulting solutions was performed using ICP-AES. The amount of Ni plating layer (g / m²) was calculated using the obtained Ni content and the area of ​​the Ni plating layer formed in the sample. 2 The amount of Ni plating layer deposited was determined. The amount of Ni plating layer deposited is shown in Table 1. Similarly, using the obtained Ni content and Zn content, and the area of ​​the Zn-Ni alloy plating layer formed in the sample, the amount of Zn-Ni alloy plating layer deposited (g / m²) was calculated.2 The amount of Zn-Ni alloy plating layer was determined to be 80 g / m² in all cases. 2 That was the case.

[0104] [Seizure Resistance Test] For each steel plate with a test number, a lubricating film layer was formed on the Zn-Ni alloy plating layer, and an anti-seizure test was conducted. Specifically, a commercially available solid lubricating film layer was formed on the Zn-Ni alloy plating layer of each steel plate with a test number. The thickness of the formed solid lubricating film layer was 30 μm in all cases. A steel ball was pressed against each steel plate with a test number, which was attached to a rotating disk, with a pressure of 60 N (Hertz surface pressure of 1.25 GPa), and the disk was rotated at a sliding speed of 31.4 mm / s. The rotating disk was rotated with a 90-degree reciprocating oscillation. The sliding was performed without oil and at room temperature. The coefficient of friction μ of the steel ball during sliding was measured, and the sliding distance (mm) until the coefficient of friction μ exceeded 0.3 was determined. The determined sliding distances are shown in Table 1.

[0105] [Evaluation Results] Referring to Table 1, the steel plates with test numbers 5-9 had a Ni plating layer adhesion of 6.00 g / m². 2 The above was the result. As a result, the sliding distance in the anti-seizure test was 9000 mm or more. In other words, the steel plates from test numbers 5 to 9 had excellent anti-seizure properties.

[0106] On the other hand, the steel plates with test numbers 1-4 had a Ni plating layer adhesion of 6.00 g / m². 2 The result was less than 9000 mm. In other words, steel plates numbered 1 to 4 did not have good seizure resistance.

[0107] The embodiments of this disclosure have been described above. However, the embodiments described above are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the embodiments described above, and the embodiments described above can be modified as appropriate without departing from the spirit of this disclosure. [Explanation of Symbols]

[0108] 1 Metal pipe for oil well 10 Pipe body 10A 1st end 10B 2nd end 40 pins 41 Male threaded section 50 boxes 51 Female thread section 100 Ni plating layer 110 Zn-Ni alloy plating layer 120 Lubricating film layer 400 pin contact surface 500 Box Contact Surface

Claims

1. Metal pipes for oil wells, The pipe body comprises a first end and a second end, The aforementioned pipe body is The pin formed at the first end, Including a box formed at the second end, The aforementioned pin is, Including the pin contact surface including the male thread portion, The aforementioned box is Including the box contact surface including the female thread portion, The aforementioned metal pipe for the oil well further, A Ni plating layer is formed on at least one of the pin contact surface and the box contact surface, The Ni plating layer is formed on the Ni plating layer, and comprises a Zn-Ni alloy plating layer. The amount of Ni plating layer is 6.00 g / m². ２ The above is 60.00 g / m² or less. Metal pipes for oil wells.

2. A metal pipe for an oil well according to claim 1, The aforementioned metal pipe for the oil well further, A lubricating film layer is provided above or above the Zn-Ni alloy plating layer. Metal pipes for oil wells.

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