Metal pipe for oil well

Abstract

Provided is a metal pipe for oil wells, which is provided with a Zn-Ni alloy plating layer having excellent sintering resistance. This oil well metal pipe (1) is provided with a pipe body (10) comprising a first end (10A) and a second end (10B), the pipe body (10) comprising: a pin part (40) formed at the first end (10A); a metal pipe (1) for an oil well, the metal pipe (1) being provided with a first end portion (10A), a second end portion (10B), a pin portion (40) formed at the first end portion (10A), and a box portion (50) formed at the second end portion (10B), the pin portion (40) having a pin portion contact surface (400) including a male thread portion (41), the box portion (50) having a box portion contact surface (500) including a female thread portion (51), the metal pipe (1) being further provided with: an Ni plating layer (100) formed on at least one of the pin portion contact surface (400) and the box portion contact surface (500); and a Zn-Ni alloy plating layer (110) formed on the Ni plating layer (100), the amount of the Ni plating layer (100) deposited being 6.00 g / m2 or more.

Description

Technical Field

[0001] The present disclosure relates to a metal pipe, and more particularly to a metal pipe for oil wells. Background Art

[0002] Oil well metal pipes are used in oil wells and gas wells (hereinafter collectively referred to as oil wells and gas wells and simply referred to as "oil wells"). Oil well metal pipes have threaded joints. Specifically, at the oil well mining site, a plurality of oil well metal pipes are connected according to the depth of the oil well to form an oil well pipe connection body represented by casing and pipes. The oil well pipe connection body is formed by threading the oil well metal pipes together. In addition, there are cases where the oil well pipe connection body is inspected. In the case of an inspection, the oil well pipe connection body is pulled up and the threads are loosened. In addition, the oil well metal pipe is removed from the oil well pipe connection body by loosening the threads and inspected. After the inspection, the oil well metal pipes are threaded together again, and the oil well metal pipe is reused as a part of the oil well pipe connection body.

[0003] The metal pipe for oil wells comprises a pin buckle part and a box buckle part. The pin buckle part has a pin buckle part contact surface including an external threaded part on the outer peripheral surface of the end of the metal pipe for oil wells. The box buckle part has a box buckle part contact surface including an internal threaded part on the inner peripheral surface of the end of the metal pipe for oil wells. In the present specification, the external threaded part and the internal threaded part are also collectively referred to as "threaded part". In the present specification, the pin buckle part contact surface and the box buckle part contact surface are also collectively referred to as "contact surface". In addition, the pin buckle part contact surface also includes a metal contact part without a pin buckle part thread, and the metal contact part without a pin buckle part thread includes a pin buckle part sealing surface and a pin buckle part shoulder surface. Similarly, the box buckle part contact surface also includes a metal contact part without a box buckle part thread, and the metal contact part without a box buckle part thread includes a box buckle part sealing surface and a box buckle part shoulder surface.

[0004] The contact surface of the pin part and the contact surface of the box part (contact surface) of the metal pipe for oil wells are repeatedly subjected to strong friction when the threads are tightened and loosened. Therefore, the contact surface is prone to galling and seizure (irreparable seizure) when the threads are tightened and loosened repeatedly. Therefore, sufficient durability against friction, that is, excellent seizure resistance is required for the metal pipe for oil wells.

[0005] In the oil well metal pipe disclosed in Patent Document 1 (International Publication No. 2016 / 170031), a Zn-Ni alloy plating layer is formed on the contact surface of the pin buckle part or the contact surface of the box buckle part instead of the composite grease. The Zn in the Zn-Ni alloy plating layer formed on the contact surface of the oil well metal pipe improves the corrosion resistance of the oil well metal pipe due to sacrificial corrosion protection. In addition, Patent Document 1 discloses that the wear resistance of the Zn-Ni alloy is also excellent.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2016 / 170031

[0009] Patent Document 2: Japanese Patent Application Publication No. 2014-91244

[0010] Patent Document 3: Japanese Patent Application Publication No. 2017-179510 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] However, in recent years, oil well metal pipes with better seizure resistance have been sought. In particular, in large oil well metal pipes, the circumference of the pipe body becomes longer, so a longer sliding distance is required from the start of tightening to the completion of tightening. As a result, there is a tendency for large oil well metal pipes to be more easily seizure-prone than before. Thus, oil well metal pipes are required to have better seizure resistance than before.

[0013] An object of the present disclosure is to provide a metal pipe for oil wells having a Zn—Ni alloy plating layer having excellent seizure resistance.

[0014] Solutions for solving problems

[0015] The oil well metal pipe disclosed herein includes a pipe body including a first end portion and a second end portion.

[0016] The pipe body comprises:

[0017] a male buckle portion formed at the first end portion; and

[0018] a female buckle portion formed at the second end portion,

[0019] The pin portion has a pin portion contact surface including an external thread portion,

[0020] The box portion has a box portion contact surface including an internal thread portion,

[0021] The metal pipe for oil wells further comprises:

[0022] A Ni plating layer formed on at least one of the pin portion contact surface and the box portion contact surface; and

[0023] A Zn-Ni alloy plating layer is formed on the Ni plating layer,

[0024] The adhesion amount of the Ni plating layer is 6.00 g / m 2 above.

[0025] Effects of the Invention

[0026] The oil well metal pipe provided with the Zn—Ni alloy plating layer of the present disclosure has excellent seizure resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the coating weight (g / m 2 ) and the sliding distance (mm) which is an indicator of seizure resistance.

[0028] Figure 2 It is a structural diagram showing an example of the metal pipe for oil wells according to the present embodiment.

[0029] Figure 3 Yes means Figure 2 The illustrated partial cross-sectional view is a cross-sectional view of a pipe joint for an oil well metal pipe, taken along a section (longitudinal section) parallel to the pipe axis direction.

[0030] Figure 4 yes Figure 3 A cross-sectional view of a portion near a pin portion of the oil well metal pipe shown in FIG. 1 , parallel to the pipe axis direction of the oil well metal pipe.

[0031] Figure 5 yes Figure 3 A cross-sectional view of a portion near a box portion of the oil well metal pipe shown in FIG. 1 , parallel to the pipe axis direction of the oil well metal pipe.

[0032] Figure 6 This is a diagram showing an example of a metal pipe for oil wells in which a pin portion includes an external thread portion but does not include a pin portion sealing surface and a pin portion shoulder surface, and a box portion includes an internal thread portion but does not include a box portion sealing surface and a box portion shoulder surface.

[0033] Figure 7 This is a structural diagram of the integral oil well metal pipe according to the present embodiment.

[0034] Figure 8 It is a cross-sectional view of the vicinity of the pin contact surface in the case where a Ni plating layer is formed on the pin contact surface.

[0035] Fig. 9 It is a cross-sectional view of the vicinity of the contact surface of the box portion in the case where a Ni plating layer is formed on the contact surface of the box portion.

[0036] Fig.10 is with Figure 8 Cross-sectional views near the contact surface of the male buckle parts of different structures.

[0037] Fig.11 is with Fig. 9Cross-sectional views near the contact surface of the female buckle parts with different structures. DETAILED DESCRIPTION

[0038] Hereinafter, the present embodiment will be described in detail with reference to the drawings. The same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0039] Zn-Ni alloy coating has excellent wear resistance due to its higher hardness. In addition, when having excellent wear resistance, there is a tendency to obtain excellent sintering resistance. Therefore, Zn-Ni alloy coating is suitable for oil well metal pipes requiring sintering resistance. On the other hand, as mentioned above, large oil well metal pipes with large diameter have a longer sliding distance when the threads are tightened and the threads are loosened than the previous oil well metal pipes. Therefore, even if there is a metal pipe for oil wells with Zn-Ni alloy coating, in large oil well metal pipes, there is also a situation where excellent sintering resistance cannot be obtained. Therefore, the inventors have studied various methods to improve the sintering resistance of metal pipes for oil wells with Zn-Ni alloy coatings. As a result, the inventors have obtained the following insights.

[0040] Zn-Ni alloy coating is due to its higher hardness, compared with other coatings, such as Cu coating, etc., ductility is lower. In addition, for the metal pipe for oil wells used in severe environment, compared with coated steel plate, etc., Zn-Ni alloy coating is formed thicker. Therefore, the internal stress of the Zn-Ni alloy coating formed in the metal pipe for oil wells is easy to become high. As a result, the inventors of the present invention etc. consider that: in the metal pipe for oil wells, the adhesion between the Zn-Ni alloy coating and the contact surface is easy to reduce, and the sintering resistance is easy to reduce. That is, if the adhesion between the Zn-Ni alloy coating and the contact surface can be improved, the sintering resistance of the metal pipe for oil wells may be improved.

[0041] Hitherto, flash metal plating has been used for the purpose of improving the adhesion between steel and the plating. Patent Document 2 (Japanese Patent Publication No. 2014-91244) discloses a technology for forming a resin-coated metal plate for a container with a flash metal plating. Specifically, Patent Document 2 states the following: "Hitherto, metal flash plating has been implemented mainly for the purpose of improving the adhesion between the base metal and the plating" (paragraph

[0023] of Patent Document 2); and "As types of metal flash plating, nickel plating or copper plating has been determined as a practical technology and is therefore more preferred" (paragraph

[0025] of Patent Document 2). On the other hand, Patent Document 2 states that "when the adhesion amount is less than 0.1 g / m 2 In the case of , it is difficult to form a uniform coating and good coating adhesion cannot be obtained"; and "the flash metal coating is formed by a plating bath with low cathode deposition efficiency. Therefore, if it becomes greater than 3.0g / m2 The thickness of the flash metal plating layer is increased by 0.1 to 3.0 g / m. 2 the content of the scope.

[0042] Similarly, in order to improve the adhesion between the steel material and the plating layer, a technology of forming a Ni plating layer between the steel material and the plating layer is used. Patent document 3 (Japanese Patent Publication No. 2017-179510) discloses a technology of forming a Ni plating layer to improve the adhesion of the Cu plating layer. Specifically, the following content is recorded in Patent Document 3: "From the perspective of improving the adhesion between the stainless steel plate and the Cu plating layer, the adhesion amount of the Ni plating layer is preferably set to 0.4g / m 2 "From the viewpoint of improving the adhesion between the stainless steel plate and the Cu plating layer, preferably 4 g / m 2 "Below" (all are paragraphs

[0017] of Patent Document 3). That is, Patent Document 3 records the following: 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 is improved, but an excessively thick Ni plating layer instead reduces the adhesion of the Cu plating layer to the steel material.

[0043] With reference to these prior arts, if a thinner Ni coating is formed between the contact surface of the metal pipe for oil wells and the Zn-Ni alloy coating, there is a possibility that the adhesion of the Zn-Ni alloy coating is improved, and the sintering resistance of the metal pipe for oil wells is improved. Therefore, the inventors of the present invention manufactured various metal pipes for oil wells having a Ni coating formed on the contact surface and a Zn-Ni alloy coating formed on the Ni coating, and evaluated their sintering resistance. The results, contrary to the expectations derived from the prior art, clearly showed that: if the adhesion amount of the Ni coating is increased to 6.00 g / m 2 As described above, the seizure resistance of the metal pipe for oil wells is significantly improved. This point will be described in detail using the drawings.

[0044] Figure 1 It is the coating weight (g / m 2 ) and the sliding distance (mm) as an indicator of seizure resistance. For the examples described below, the adhesion amount (g / m 2 ) and the sliding distance (mm) in the sliding evaluation test. Figure 1 .

[0045] Reference Figure 1 , the adhesion of Ni plating is less than 6.00g / m 2When the Ni coating is formed, the sliding distance is almost the same as that when the Ni coating is not formed. That is, even if the thin Ni coating disclosed in the prior art is formed, the seizure resistance of the oil well metal pipe formed with the Zn-Ni alloy coating does not change much. On the other hand, when the Ni coating adhesion amount is 6.00 g / m 2 In the above case, the sliding distance is significantly longer than when a thin Ni plating layer is formed. That is, it is clear that the seizure resistance of the oil well metal pipe is significantly improved by deliberately making the thin Ni plating layer, which has been used so far for the purpose of adhesion, thicker.

[0046] In addition, by increasing the adhesion amount of the Ni plating layer formed on the contact surface to 6.00 g / m 2 Above, the reason that the sintering resistance of the metal pipe for oil wells formed with Zn-Ni alloy coating is improved, the details are not clear. However, the inventors etc. speculate as follows. As mentioned above, the Zn-Ni alloy coating formed by the metal pipe for oil wells is formed thicker, so the internal stress is easy to become high. That is, in the metal pipe for oil wells, the influence of the internal stress of the formed Zn-Ni alloy coating is easy to show. On the other hand, by forming the Ni coating thicker, there is the possibility of forming the distance between the contact surface and the Zn-Ni alloy coating, and the internal stress of the Zn-Ni alloy coating is dispersed. Therefore, compared with the reduction of the tightness caused by forming a thicker Ni coating, the effect of the internal stress dispersion of the Zn-Ni alloy coating is improved by utilizing a thicker Ni coating, and as a result, there is the possibility of improving the sintering resistance of the metal pipe for oil wells.

[0047] The inventors of the present invention speculate that, based on the above mechanism, by increasing the adhesion amount of the Ni plating layer formed on the contact surface to 6.00 g / m 2 In addition, there is also a mechanism different from the above mechanism, by increasing the adhesion amount of the Ni plating layer formed on the contact surface to 6.00 g / m 2 However, by increasing the adhesion amount of the Ni plating layer formed on the contact surface to 6.00 g / m 2 As described above, the improvement in the seizure resistance of the oil well metal pipe having the Zn—Ni alloy plating layer is demonstrated by the examples described below.

[0048] The gist of the metal pipe for oil wells of the present embodiment completed based on the above findings is as follows.

[0049] [1] A metal pipe for oil wells, comprising a pipe body including a first end portion and a second end portion,

[0050] The pipe body comprises:

[0051] a male buckle portion formed at the first end portion; and

[0052] a female buckle portion formed at the second end portion,

[0053] The pin portion has a pin portion contact surface including an external thread portion,

[0054] The box portion has a box portion contact surface including an internal thread portion,

[0055] The metal pipe for oil wells further comprises:

[0056] A Ni plating layer formed on at least one of the pin portion contact surface and the box portion contact surface; and

[0057] A Zn-Ni alloy plating layer is formed on the Ni plating layer,

[0058] The adhesion amount of the Ni plating layer is 6.00 g / m 2 above.

[0059] [2] The metal pipe for oil wells according to [1], wherein

[0060] The oil well metal pipe further includes a lubricating coating layer on or above the Zn—Ni alloy plating layer.

[0061] Hereinafter, the oil well metal pipe according to the present embodiment will be described in detail.

[0062] [Structure of metal pipe for oil wells]

[0063] First, the structure of the metal pipe for oil wells of this embodiment is described. The metal pipe for oil wells has a well-known structure. There are T&C type metal pipe for oil wells and integral type metal pipe for oil wells. The following describes each type of metal pipe for oil wells in detail.

[0064] [When the metal pipe for oil well 1 is of T&C type]

[0065] Figure 2 It is a structural diagram showing an example of the oil well metal pipe 1 according to the present embodiment. Figure 2 This is a structural diagram of a so-called T&C type (Threaded and Coupled) oil well metal pipe 1. Figure 2 The oil well metal pipe 1 includes a pipe body 10 .

[0066] The pipe body 10 extends in the pipe axis direction. The cross section of the pipe body 10 perpendicular to the pipe axis direction is circular. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is an end on the opposite side of the second end 10B. Figure 2 In the illustrated T&C type oil well metal pipe 1, the pipe body 10 includes a pin pipe body 11 and a pipe joint 12. The pipe joint 12 is attached to one end of the pin pipe body 11. More specifically, the pipe joint 12 is fastened to one end of the pin pipe body 11 by screws.

[0067] Figure 3 Yes means Figure 2 The cross-sectional view of the pipe joint 12 of the oil well metal pipe 1 shown is a partial cross-sectional view of a section (longitudinal section) parallel to the pipe axis direction. Figure 2 and Figure 3 The pipe body 10 includes a pin part 40 and a box part 50. The pin part 40 is formed at the first end 10A of the pipe body 10. When fastening, the pin part 40 is inserted into the box part 50 of another oil well metal pipe 1 (not shown) and fastened to the box part 50 of the other oil well metal pipe 1 by using threads.

[0068] The box portion 50 is formed at the second end portion 10B of the pipe body 10. When fastening, the pin portion 40 of another oil well metal pipe 1 is inserted into the box portion 50 and fastened to the pin portion 40 of another oil well metal pipe 1 by the threaded box portion 50.

[0069] [Structure of the male buckle portion 40]

[0070] Figure 4 yes Figure 3 The cross-sectional view of the vicinity of the pin portion 40 of the oil well metal pipe 1 is parallel to the pipe axis direction of the oil well metal pipe 1 . Figure 4 The dotted line portion in shows the structure of the box buckle portion 50 of the other oil well metal pipe 1 when fastened to the other oil well metal pipe 1. Figure 4 The pin part 40 includes a pin part contact surface 400 on the outer peripheral surface of the first end portion 10A of the pipe body 10. When the pin part 40 is fastened to another oil well metal pipe 1, the pin part 40 is screwed into the box part 50 of the other oil well metal pipe 1, and the pin part contact surface 400 contacts the box part contact surface 500 (described later) of the box part 50.

[0071] The pin contact surface 400 includes at least an external thread portion 41 formed on the outer peripheral surface of the first end portion 10A. Alternatively, the pin contact surface 400 may further include a pin sealing surface 42 and a pin shoulder surface 43. Figure 4In the embodiment, the male buckle shoulder surface 43 is arranged at the top end surface of the first end portion 10A, and the male buckle sealing surface 42 is arranged at a position on the outer peripheral surface of the first end portion 10A, closer to the top end side of the first end portion 10A than the external thread portion 41. In other words, the male buckle sealing surface 42 is arranged between the external thread portion 41 and the male buckle shoulder surface 43. The male buckle sealing surface 42 is set to be conical. Specifically, in the male buckle sealing surface 42, in the longitudinal direction (tube axis direction) of the first end portion 10A, the outer diameter gradually decreases as it moves from the external thread portion 41 toward the male buckle shoulder surface 43.

[0072] When fastened to other metal pipes 1 for oil wells, the male buckle sealing surface 42 contacts the female buckle sealing surface 52 (described later) of the female buckle 50 of the other metal pipes 1 for oil wells. More specifically, when fastening, the male buckle 40 is inserted into the female buckle 50 of the other metal pipes 1 for oil wells, so that the male buckle sealing surface 42 contacts the female buckle sealing surface 52. Then, by further screwing the male buckle 40 into the female buckle 50 of the other metal pipes 1 for oil wells, the male buckle sealing surface 42 and the female buckle sealing surface 52 are in close contact. Thus, when fastening, the male buckle sealing surface 42 and the female buckle sealing surface 52 are in close contact to form a seal based on metal-to-metal contact. Therefore, in the metal pipes 1 for oil wells that are fastened to each other, the air tightness can be improved.

[0073] exist Figure 4 In the embodiment, the male buckle shoulder surface 43 is arranged at the top end surface of the first end portion 10A. Figure 4 In the pin buckle part 40 shown, an external threaded part 41, a pin buckle sealing surface 42, and a pin buckle shoulder surface 43 are sequentially arranged from the center of the pipe body 10 toward the first end 10A. When tightened with other metal pipes 1 for oil wells, the pin buckle shoulder surface 43 is opposite to and in contact with the female buckle shoulder surface 53 (described later) of the female buckle part 50 of the other metal pipes 1 for oil wells. More specifically, when tightening, the pin buckle part 40 is inserted into the female buckle part 50 of the other metal pipes 1 for oil wells, so that the pin buckle shoulder surface 43 is in contact with the female buckle shoulder surface 53. As a result, a higher torque can be obtained during tightening. In addition, the positional relationship between the pin buckle part 40 and the female buckle part 50 in the tightened state can be stabilized.

[0074] In addition, the pin part contact surface 400 of the pin part 40 includes at least the external threaded portion 41. In other words, the pin part contact surface 400 may include the external threaded portion 41, but not include the pin part sealing surface 42 and the pin part shoulder surface 43. The pin part contact surface 400 may include the external threaded portion 41 and the pin part shoulder surface 43, but not include the pin part sealing surface 42. The pin part contact surface 400 may include the external threaded portion 41 and the pin part sealing surface 42, but not include the pin part shoulder surface 43.

[0075] [Structure of the female buckle portion 50]

[0076] Figure 5 yes Figure 3 The cross-sectional view of the portion near the box portion 50 of the oil well metal pipe 1 is parallel to the pipe axis direction of the oil well metal pipe 1 . Figure 5 The dotted line portion in shows the structure of the male buckle portion 40 of another oil well metal pipe 1 when fastened to another oil well metal pipe 1. Figure 5 The box portion 50 includes a box portion contact surface 500 on the inner peripheral surface of the second end portion 10B of the pipe body 10. The box portion contact surface 500 is screwed into the male portion 40 of the other oil well metal pipe 1 when fastened to the other oil well metal pipe 1, and contacts the male portion contact surface 400 of the male portion 40.

[0077] The box portion contact surface 500 includes at least an internal thread portion 51 formed on the inner peripheral surface of the second end portion 10B. During fastening, the internal thread portion 51 meshes with the external thread portion 41 of the pin portion 40 of the other oil well metal pipe 1.

[0078] Alternatively, the female buckle portion contact surface 500 further includes a female buckle portion sealing surface 52 and a female buckle portion shoulder surface 53. Figure 5 In the embodiment, the box buckle portion sealing surface 52 is arranged on the inner peripheral surface of the second end portion 10B, at a position closer to the pipe body 10 than the internal thread portion 51. That is, the box buckle portion sealing surface 52 is arranged between the internal thread portion 51 and the box buckle portion shoulder surface 53. The box buckle portion sealing surface 52 is set to be tapered. Specifically, in the box buckle portion sealing surface 52, the inner diameter gradually decreases from the internal thread portion 51 toward the box buckle portion shoulder surface 53 in the longitudinal direction (pipe axis direction) of the second end portion 10B.

[0079] When fastened to other metal pipes 1 for oil wells, the sealing surface 52 of the female buckle part contacts the sealing surface 42 of the male buckle part 40 of the other metal pipes 1 for oil wells. More specifically, when fastened, the male buckle part 40 of the other metal pipes 1 for oil wells is screwed into the female buckle part 50, so that the sealing surface 52 of the female buckle part contacts the sealing surface 42 of the male buckle part, and by further screwing in, the sealing surface 52 of the female buckle part and the sealing surface 42 of the male buckle part are in close contact. Thus, when fastened, the sealing surface 52 of the female buckle part and the sealing surface 42 of the male buckle part are in close contact to form a seal based on metal-metal contact. Therefore, in the metal pipes 1 for oil wells that are fastened to each other, the airtightness can be improved.

[0080] The shoulder surface 53 of the box buckle part is arranged at a position closer to the pipe body 10 side than the sealing surface 52 of the box buckle part. That is, in the box buckle part 50, the box buckle part shoulder surface 53, the box buckle part sealing surface 52, and the internal thread part 51 are arranged in sequence from the center of the pipe body 10 toward the top of the second end 10B. When fastened with other metal pipes 1 for oil wells, the shoulder surface 53 of the box buckle part is opposite to and in contact with the shoulder surface 43 of the male buckle part 40 of the other metal pipes 1 for oil wells. More specifically, when fastening, by inserting the male buckle part 40 of the other metal pipes 1 for oil wells into the box buckle part 50, the shoulder surface 53 of the box buckle part is in contact with the shoulder surface 43 of the male buckle part. As a result, a higher torque can be obtained during fastening. In addition, the positional relationship between the male buckle part 40 and the box buckle part 50 in the fastened state can be stabilized.

[0081] The box contact surface 500 includes at least an internal thread portion 51. When tightened, the internal thread portion 51 of the box contact surface 500 of the box 50 corresponds to and contacts the external thread portion 41 of the pin contact surface 400 of the pin 40. The box sealing surface 52 corresponds to and contacts the pin sealing surface 42. The box shoulder surface 53 corresponds to and contacts the pin shoulder surface 43.

[0082] In the case where the pin part contact surface 400 includes the external threaded portion 41, excluding the pin part sealing surface 42 and the pin part shoulder surface 43, the box part contact surface 500 includes the internal threaded portion 51, excluding the box part sealing surface 52 and the box part shoulder surface 53. In the case where the pin part contact surface 400 includes the external threaded portion 41 and the pin part shoulder surface 43, excluding the pin part sealing surface 42, the box part contact surface 500 includes the internal threaded portion 51 and the box part shoulder surface 53, excluding the box part sealing surface 52. In the case where the pin part contact surface 400 includes the external threaded portion 41 and the pin part sealing surface 42, excluding the pin part shoulder surface 43, the box part contact surface 500 includes the internal threaded portion 51 and the box part sealing surface 52, excluding the box part shoulder surface 53.

[0083] The pin contact surface 400 may include a plurality of external threaded portions 41, a plurality of pin sealing surfaces 42, or a plurality of pin shoulder surfaces 43. For example, the pin shoulder surface 43, the pin sealing surface 42, the external threaded portion 41, the pin sealing surface 42, the pin shoulder surface 43, the pin sealing surface 42, and the external threaded portion 41 may be sequentially arranged on the pin contact surface 400 of the pin 40 from the top of the first end 10A toward the center of the pipe body 10. In this case, the internal threaded portion 51, the box sealing surface 52, the box shoulder surface 53, the box sealing surface 52, the internal threaded portion 51, the box sealing surface 52, and the box shoulder surface 53 may be sequentially arranged on the box contact surface 500 of the box 50 from the top of the second end 10B toward the center of the pipe body 10.

[0084] exist Figure 4 and Figure 5 In the figure, the pin part 40 includes an external threaded portion 41, a pin part sealing surface 42, and a pin part shoulder surface 43, and the box part 50 includes an internal threaded portion 51, a box part sealing surface 52, and a box part shoulder surface 53, which is a so-called advanced joint. However, as described above, the pin part 40 may include an external threaded portion 41, but not include a pin part sealing surface 42 and a pin part shoulder surface 43. In this case, the box part 50 includes an internal threaded portion 51, but not include a box part sealing surface 52 and a box part shoulder surface 53. Figure 6 1 is a diagram showing an example of a metal pipe 1 for oil wells as follows: a pin portion 40 includes an external thread portion 41, excluding a pin portion sealing surface 42 and a pin portion shoulder surface 43, and a box portion 50 includes an internal thread portion 51, excluding a box portion sealing surface 52 and a box portion shoulder surface 53.

[0085] [When the metal pipe for oil well 1 is of integral type]

[0086] Figure 2 , Figure 3 as well as Figure 6 The oil well metal pipe 1 shown is a so-called T&C type oil well metal pipe 1 in which the pipe body 10 includes a pin pipe body 11 and a pipe joint 12. However, the oil well metal pipe 1 of this embodiment may not be a T&C type but an integral type.

[0087] Figure 7 1 is a structural diagram of an integral oil well metal pipe 1 according to the present embodiment. Figure 7The integral type metal pipe for oil wells 1 includes a pipe body 10. The pipe body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is arranged on the side opposite to the second end portion 10B. As described above, in the T&C type metal pipe for oil wells 1, the pipe body 10 includes a male buckle portion pipe body 11 and a pipe joint 12. That is, in the T&C type metal pipe for oil wells 1, the pipe body 10 is formed by fastening two separate components (male buckle portion pipe body 11 and pipe joint 12). In contrast, in the integral type metal pipe for oil wells 1, the pipe body 10 is formed integrally.

[0088] 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 the other integral metal pipe for oil wells 1 and screwed in, and fastened to the box 50 of the other integral metal pipe for oil wells 1. The box 50 is formed at the second end 10B of the pipe body 10. When fastening, the pin 40 of the other integral metal pipe for oil wells 1 is inserted into the box 50 and screwed in, and the box 50 is fastened to the pin 40 of the other integral metal pipe for oil wells 1.

[0089] The structure of the male buckle part 40 of the integral oil well metal pipe 1 is Figure 4 The structure of the male buckle part 40 of the T&C type oil well metal pipe 1 shown in FIG. Figure 5 The structure of the female buckle portion 50 of the T&C type oil well metal pipe 1 shown is the same. Figure 4 and Figure 5 In the embodiment, in the pin part 40, the pin part shoulder surface 43, the pin part sealing surface 42, and the external threaded portion 41 are sequentially arranged from the top end of the first end 10A toward the center of the pipe body 10. Therefore, in the box part 50, the internal threaded portion 51, the box part sealing surface 52, and the box part shoulder surface 53 are sequentially arranged from the top end of the second end 10B toward the center of the pipe body 10. However, like the pin part contact surface 400 of the pin part 40 of the T&C type oil well metal pipe 1, the pin part contact surface 400 of the pin part 40 of the integral type oil well metal pipe 1 only needs to include at least the external threaded portion 41. Also, like the box part contact surface 500 of the box part 50 of the T&C type oil well metal pipe 1, the box part contact surface 500 of the box part 50 of the integral type oil well metal pipe 1 only needs to include at least the internal threaded portion 51.

[0090] In short, the oil well metal pipe 1 of the present embodiment may be of the T&C type or of the integral type.

[0091] [Chemical composition of the tube body]

[0092] The chemical composition of the pipe body 10 of the metal pipe for oil wells 1 of the present embodiment is not particularly limited. That is, in the present embodiment, the steel type of the pipe body 10 of the metal pipe for oil wells 1 is not particularly limited. The pipe body 10 can also be formed of carbon steel, stainless steel, alloy, etc., for example. That is, the metal pipe for oil wells 1 can be a steel pipe composed of an Fe-based alloy, or an alloy pipe represented by a Ni-based alloy pipe. Among them, the steel pipe is, for example, a low-alloy steel pipe, a martensitic stainless steel pipe, a ferritic stainless steel pipe, an austenitic stainless steel pipe, and a duplex stainless steel pipe. The alloy pipe is, for example, a Ni-based alloy pipe and a NiCrFe alloy pipe. On the other hand, among alloys, the so-called high alloys such as Ni-based alloys and duplex stainless steels containing alloy elements such as Cr, Ni and Mo have higher corrosion resistance. Therefore, if these high alloys are used as the pipe body 10, excellent corrosion resistance can be obtained in a corrosive environment containing hydrogen sulfide, carbon dioxide, etc.

[0093] [Ni plating]

[0094] In the oil well metal pipe 1 of the present embodiment, a Ni plating layer is formed on the contact surface of at least one of the pin part contact surface 400 and the box part contact surface 500. That is, the Ni plating layer may be formed on the pin part contact surface 400, but not on the box part contact surface 500. In addition, the Ni plating layer may be formed on the box part contact surface 500, but not on the pin part contact surface 400. The Ni plating layer may be formed on both the pin part contact surface 400 and the box part contact surface 500.

[0095] [Zn-Ni alloy plating]

[0096] In the metal pipe for oil wells 1 of the present embodiment, a Zn-Ni alloy plating layer is formed on the Ni plating layer. That is, in the case where the Ni plating layer is formed on the male buckle contact surface 400, a Zn-Ni alloy plating layer is formed on the Ni plating layer formed on the male buckle contact surface 400. In this case, a Ni plating layer may be formed on the female buckle contact surface 500, a Zn-Ni alloy plating layer may be formed, or no plating layer may be formed. In addition, in the case where the Ni plating layer is formed on the female buckle contact surface 500, a Zn-Ni alloy plating layer is formed on the Ni plating layer formed on the female buckle contact surface 500. In this case, a Ni plating layer may be formed on the male buckle contact surface 400, a Zn-Ni alloy plating layer may be formed, or no plating layer may be formed. That is, in the present embodiment, a Ni plating layer is formed on at least one of the pin portion contact surface 400 and the box portion contact surface 500 , and a Zn—Ni alloy plating layer is formed on the Ni plating layer.

[0097] In the following description, the structure on the pin part contact surface 400 where the Ni plating layer is formed on the pin part contact surface 400 and the structure on the box part contact surface 500 where the Ni plating layer is formed on the box part contact surface 500 will be described.

[0098] [Structure on the contact surface of the pin portion in the case where the Ni plating layer is formed on the contact surface of the pin portion]

[0099] Figure 8 1 is a cross-sectional view of the vicinity of the male buckle contact surface 400 in a case where the Ni plating layer 100 is formed on the male buckle contact surface 400. Figure 8 In this case, the oil well metal pipe 1 further includes 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 .

[0100] 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 on the entire pin contact surface 400. In addition, the surface pressure of the pin sealing surface 42 is particularly high in the final stage of thread tightening. Therefore, in the case where the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are partially formed on the pin contact surface 400, the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are preferably formed at least on the pin sealing surface 42.

[0101] [Structure on the contact surface of the female buckle portion in the case where the Ni plating layer is formed on the contact surface of the female buckle portion]

[0102] Fig. 9 1 is a cross-sectional view of the vicinity of the female buckle contact surface 500 in a case where the Ni plating layer 100 is formed on the female buckle contact surface 500. Fig. 9 In this case, the oil well metal pipe 1 further includes a Ni plating layer 100 formed on the box portion contact surface 500 of the box portion 50 and a Zn—Ni alloy plating layer 110 formed on the Ni plating layer 100 .

[0103] 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 on the entire box contact surface 500. In addition, the surface pressure of the box sealing surface 52 is particularly high in the final stage of thread tightening. Therefore, in the case where the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are partially formed on the box contact surface 500, the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are preferably formed at least on the box sealing surface 52.

[0104] [Ni plating and Zn-Ni alloy plating adhesion]

[0105] In this embodiment, the deposition weight of the Ni plating layer 100 is 6.00 g / m 2 The adhesion amount of the Ni plating layer 100 is 6.00 g / m 2 In the above case, the adhesion amount of the Ni plating layer 100 is less than 6.00 g / m 2 Therefore, in the oil well metal pipe 1 of the present embodiment, the adhesion amount of the Ni plating layer 100 formed on at least one of the pin part contact surface 400 and the box part contact surface 500 is set to 6.00 g / m 2 As a result, the internal stress of the Zn—Ni alloy plating layer 110 formed on the Ni plating layer 100 can be relaxed, and the seizure resistance of the oil well metal pipe 1 is improved.

[0106] In this embodiment, the lower limit of the amount of Ni plating layer 100 is preferably 6.50 g / m 2 , more preferably 7.00 g / m 2 , more preferably 8.00 g / m 2 , further preferably 9.00 g / m 2 , further preferably 9.30g / m 2 , more preferably 10.00 g / m 2 The upper limit of the amount of Ni plating layer 100 is not particularly limited, and is, for example, 60.00 g / m 2 .

[0107] In the present 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 thick in order to obtain excellent sintering resistance. Specifically, the amount of Zn-Ni alloy plating layer 110 in the present embodiment is, for example, 20 to 160 g / m 2 The Zn-Ni alloy plating layer 110 formed thickly to this extent exhibits excellent wear resistance, but on the other hand, the internal stress tends to become high. Therefore, it is considered that by setting the deposition amount to 6.00 g / m 2 The Ni plating layer 100 described above is formed in the lower layer, and the internal stress of the Zn—Ni alloy plating layer 110 can be relaxed, and as a result, the seizure resistance of the oil well metal pipe 1 is improved.

[0108] The coating dissolution method can be used to obtain the adhesion amount of the Ni plating 100 and the Zn-Ni alloy plating. Specifically, a sample including the Ni plating 100 and the Zn-Ni alloy plating 110 (including the contact surface formed with the Ni plating 100 and the Zn-Ni alloy plating 110) is collected from the metal pipe 1 for oil wells. The area of ​​the Ni plating 100 and the Zn-Ni alloy plating 110 formed on the collected sample is measured in advance. The collected sample is dissolved by using a dilute hydrochloric acid solution to obtain a solution of the Zn-Ni alloy plating 110. Afterwards, the sample from which the Zn-Ni alloy plating 110 is removed by dissolution is dissolved by using a dilute nitric acid solution to obtain a solution of the Ni plating 100.

[0109] Each of the obtained solutions was subjected to elemental analysis by 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 can be used to determine the adhesion amount (g / m 2 For the Zn-Ni alloy plating layer 110, the Ni content and Zn content obtained from the result of elemental analysis and the area of ​​the Zn-Ni alloy plating layer 110 formed in the sample can be used to determine the adhesion amount (g / m 2 ).

[0110] [Chemical composition of Ni plating layer and Zn-Ni alloy plating layer]

[0111] The Ni plating layer 100 has a chemical composition consisting of Ni and impurities. The Zn-Ni alloy plating layer 110 is formed of a Zn-Ni alloy, and has Ni: 5 to 25%, and the balance: Zn and impurities. Among them, the impurities in the chemical composition of the Ni plating layer refer to substances other than Ni, and are substances contained in the Ni plating layer 100 due to the manufacture of the metal pipe 1 for oil wells, etc., and are contained in a range of contents that do not affect the effects of the metal pipe 1 for oil wells of the present embodiment. Moreover, the impurities in the chemical composition of the Zn-Ni alloy plating layer 110 refer to substances other than Zn and Ni, and are substances contained in the Zn-Ni alloy plating layer 110 due to the manufacture of the metal pipe 1 for oil wells, etc., and are contained in a range of contents that do not affect the effects of the metal pipe 1 for oil wells of the present embodiment.

[0112] Among them, the Zn-Ni alloy plating layer 110 contains Zn. Compared with Fe, Zn is a base metal. Therefore, the Zn-Ni alloy plating layer 110 is corroded preferentially than the steel material (sacrificial corrosion protection). As a result, the corrosion resistance of the metal pipe for oil wells 1 is improved. In addition, the chemical composition of the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 can be determined simultaneously when the adhesion amount is obtained by the above-mentioned film dissolution method.

[0113] [Other Arbitrary Structures of the Oil Well Metal Pipe 1 of the Present Embodiment]

[0114] [Chemical conversion coating]

[0115] The oil well metal pipe 1 of the present embodiment may further include a chemical conversion coating on the Zn-Ni alloy plating layer 110. For example, when 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. In addition, when 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.

[0116] The chemical conversion coating is not particularly limited and may be a well-known chemical conversion coating. The chemical conversion coating may be, for example, an oxalate chemical conversion coating, a phosphate chemical conversion coating, a borate chemical conversion coating, or a chromate coating. When the chemical conversion coating is a chromate coating, it is preferred that the chromate coating does not contain hexavalent chromium.

[0117] There are cases where the metal pipe for oil wells 1 is stored outdoors for a long period of time until it is actually used at an oil production site. The chemical conversion coating can improve the corrosion resistance of the male buckle contact surface 400 when the metal pipe for oil wells 1 is exposed to the atmosphere outdoors for a long period of time, and inhibit the generation of rust (white rust) on the male buckle contact surface 400. The film thickness of the chemical conversion coating is not particularly limited. The film thickness of the chemical conversion coating is, for example, 10 to 200 nm.

[0118] [Lubricating coating layer]

[0119] The oil well metal pipe 1 may also include a lubricating coating layer on the Zn-Ni alloy plating layer 110, on the chemical conversion coating, or on the contact surface (on the male buckle contact surface 400 or the female buckle contact surface 500) where the Zn-Ni alloy plating layer 110 is not formed. The lubricating coating layer further improves the lubricity of the oil well metal pipe 1. Fig.10In the case where the Ni plating layer 100 and the Zn-Ni alloy plating layer 110 are formed on the male buckle contact surface 400, the lubricating coating layer 120 may also be formed on the Zn-Ni alloy plating layer 110. Fig.11 In the case where the Ni plating layer 100 and the Zn—Ni alloy plating layer 110 are formed on the female buckle portion contact surface 500 , the lubricating coating layer 120 may also be formed on the Zn—Ni alloy plating layer 110 .

[0120] The lubricating coating layer 120 may be solid, semi-solid or liquid. The lubricating coating layer 120 may be formed using a commercially available lubricant. The lubricating coating layer 120 may contain lubricating particles and a binder, for example. The lubricating coating layer 120 may also contain a solvent or other components as required.

[0121] The lubricating particles are not particularly limited as long as they are particles having lubricity. The lubricating particles are, for example, 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).

[0122] The binder is, for example, one or two selected from the group consisting of an organic binder and an inorganic binder. The organic binder is, for example, one or two selected from the group consisting of a thermosetting resin and a thermoplastic resin. The thermosetting resin is, for example, one or more selected from the group consisting of a polyethylene resin, a polyimide resin, and a polyamide-imide resin. The inorganic binder is, for example, one or two selected from the group consisting of an alkoxysilane and a compound containing a siloxane bond.

[0123] An example of a commercially available lubricant is SEAL-GUARD ECF (trade name) manufactured by JET-LUBE Co., Ltd. Another lubricating coating layer 120 is a lubricating coating layer 120 containing rosin, metal soap, wax, and lubricating powder, for example.

[0124] [Method for manufacturing metal pipe 1 for oil well]

[0125] The following describes a method for manufacturing the oil well metal pipe 1 of the present embodiment. If the oil well metal pipe 1 of the present embodiment has the above-mentioned structure, the manufacturing method is not limited to the following manufacturing method. However, the manufacturing method described below is a preferred example for manufacturing the oil well metal pipe 1 of the present embodiment.

[0126] The method for manufacturing the oil well metal pipe 1 includes a preparation step (S1) of preparing a tube blank having a pin 40 or a box 50 formed thereon, a Ni plating layer forming step (S2), and a Zn-Ni alloy plating layer forming step (S3). The steps of the method for manufacturing the oil well metal pipe 1 according to the present embodiment will be described in detail below.

[0127] [Preparation process (S1)]

[0128] In the preparation step (S1), a pipe blank having a pin portion 40 or a box portion 50 formed thereon is prepared. In the present specification, "a pipe blank having a pin portion or a box portion formed thereon" refers to any of the pipe body 10, the pin portion pipe body 11, and the pipe body 10 of the T&C type oil well metal pipe 1, and the integral type oil well metal pipe 1.

[0129] The tube blank formed with the male buckle portion 40 or the female buckle portion 50 is manufactured, for example, by the following method. Molten steel is used to manufacture a billet. Specifically, a cast sheet (slab, billet, or billet) is manufactured by continuous casting using molten steel. It is also possible to use molten steel and manufacture an ingot by an ingot casting method. It is also possible to manufacture a billet by performing initial rolling on a slab, billet, or ingot as required. The above process is used to manufacture a billet (slab, billet, or billet). The prepared billet is hot-worked to manufacture a tube blank. The hot working method may be either piercing and rolling based on the Mannesmann method or hot extrusion. The tube blank after hot working is subjected to well-known quenching and well-known tempering to adjust the strength of the tube blank. The tube blank is manufactured by the above process. In addition, when the metal pipe 1 for oil wells is a T&C type, a tube blank for the pipe joint 12 is also prepared. The method for manufacturing the tube blank for the pipe joint 12 is the same as the method for manufacturing the tube blank described above.

[0130] When the metal pipe 1 for oil wells is of T&C type, the outer surfaces of both ends of the pipe blank for the pin part body 11 are threaded to form the pin part 40 including the pin part contact surface 400. The pipe blank (pin part body 11) formed with the pin part 40 is prepared by the above process when the metal pipe 1 for oil wells is of T&C type. In addition, when the metal pipe 1 for oil wells is of T&C type, the pipe joint 12 may also be prepared in advance. Specifically, the inner surfaces of both ends of the pipe blank for the pipe joint 12 are threaded to form the box part 50 including the box part contact surface 500. The pipe joint 12 is manufactured by the above process.

[0131] When the oil well metal pipe 1 is a one-piece type, the outer surface of the first end portion 10A of the tube is threaded to form a pin portion 40 including a pin portion contact surface 400. Furthermore, the inner surface of the second end portion 10B of the tube is threaded to form a box portion 50 including a box portion contact surface 500. In the case where the oil well metal pipe 1 is a one-piece type, a tube (tube body 10) on which the pin portion 40 and the box portion 50 are formed is prepared by the above steps.

[0132] [Other optional processes]

[0133] The preparation step ( S1 ) of the present embodiment may further include a grinding step.

[0134] In the case where a grinding process is implemented in the preparation process (S1) of the present embodiment, in the grinding process, for example, sandblasting and mechanical grinding finishing are implemented. Sandblasting is a process in which a sandblasting material (abrasive) and compressed air are mixed and projected onto the contact surface. Sandblasting materials are, for example, spherical shot and block-shaped blocks. Sandblasting can be used to increase the surface roughness of the contact surface. Sandblasting can be implemented using well-known methods. For example, air is compressed using a compressor to mix compressed air with sandblasting materials. The material of the sandblasting material is, for example, stainless steel, aluminum, ceramics, and alumina. Conditions such as the projection speed of the sandblasting are not particularly limited and can be appropriately adjusted using well-known conditions.

[0135] [Ni plating layer forming step (S2)]

[0136] In the Ni plating forming step (S2), the Ni plating layer 100 is formed by electroplating on the pin portion contact surface 400 of the tube blank on which the pin portion 40 is formed after the preparation step (S1) and / or on the box portion contact surface 500 of the tube blank on which the box portion 50 is formed.

[0137] In the Ni plating formation step (S2), a plating bath containing nickel ions is used to form the Ni plating layer 100 by electroplating. The counter anion of the nickel ion is not particularly limited. For example, as the counter anion of the nickel ion, chloride ions, sulfate ions, or aminosulfonic acid ions can be used. That is, in the Ni plating formation step (S2) of the present embodiment, as the plating bath, a chlorinated bath, a sulfuric acid bath, or an aminosulfonic acid bath can be used.

[0138] Specifically, the case where a chlorinated bath is used as an example of a plating bath is described below. When a chlorinated bath is used, for example, a chlorinated bath containing 240 g / L of nickel chloride and 125 mL / L of hydrochloric acid can be used. In addition, as described above, in the Ni plating layer forming step (S2) of the present embodiment, it is not limited to a chlorinated bath, and other baths can also be used.

[0139] The electroplating conditions in the Ni plating layer forming step (S2) are not particularly limited and can be appropriately adjusted using well-known conditions. Specifically, the electroplating conditions can be set to plating bath pH: 1 to 10, plating bath temperature: 10 to 60°C, and current density: 1 to 100 A / dm 2 , and treatment time: 6.0 to 1800.0 seconds. As described above, the adhesion amount of the Ni plating layer 100 of this embodiment is 6.00 g / m 2 At this time, the amount of Ni plating layer 100 can be adjusted by adjusting the current density and treatment time of the electroplating. That is, the amount of Ni plating layer 100 can be adjusted to 6.00 g / m by appropriately adjusting the current density and treatment time of the electroplating according to the type of plating bath used, the temperature of the plating bath, and other electroplating conditions. 2 That’s all.

[0140] [Zn-Ni alloy plating layer forming step (S3)]

[0141] In the Zn-Ni alloy plating layer forming step (S3), a Zn-Ni alloy plating layer 110 is formed by electroplating on the Ni plating layer 100 after the Ni plating layer forming step (S2). In addition, as described above, the Zn-Ni alloy plating layer 110 may be formed on the male buckle portion contact surface 400 or the female buckle portion contact surface 500 on which the Ni plating layer 100 is not formed.

[0142] In the Zn-Ni alloy plating forming step (S3), a well-known plating bath containing zinc ions and nickel ions is used to form the Zn-Ni alloy plating layer 110 by electroplating. For example, a plating bath containing zinc ions: 1 to 100 g / L and nickel ions: 1 to 100 g / L can be used. In addition, the counter anions of the zinc ions and the nickel ions are not particularly limited. For example, chloride ions can be used, and sulfate ions can also be used as counter anions. That is, in the Zn-Ni alloy plating forming step (S3) of the present embodiment, a chlorinated bath can be used, and a sulfuric acid bath can also be used as a plating bath.

[0143] The electroplating conditions in the Zn-Ni alloy plating layer forming step (S3) are not particularly limited and can be appropriately adjusted using well-known conditions. The electroplating conditions are, for example, a plating bath pH of 1 to 10, a plating bath temperature of 10 to 60°C, and a current density of 1 to 100 A / dm 2, and treatment time: 0.1 to 30 minutes. When the Zn-Ni alloy plating layer 110 is formed on the Ni plating layer 100 formed on the male buckle contact surface 400, the male buckle contact surface 400 is immersed in the above-mentioned plating bath to perform electroplating. Similarly, when the Zn-Ni alloy plating layer 110 is formed on the Ni plating layer 100 formed on the female buckle contact surface 500, the female buckle contact surface 500 is immersed in the above-mentioned plating bath to perform electroplating.

[0144] The above manufacturing process is an example of the manufacturing process of the oil well metal pipe 1 of this embodiment, and the manufacturing method of the oil well metal pipe 1 of this embodiment is not limited to the above manufacturing method.

[0145] [Other optional processes]

[0146] The method for manufacturing the oil well metal pipe 1 of the present embodiment may further perform at least one of the following chemical conversion treatment step and film forming step. These steps are arbitrary steps. Therefore, these steps may not be performed.

[0147] [Chemical conversion treatment process]

[0148] The manufacturing method of the present embodiment may also implement a chemical conversion treatment process as needed. That is, the chemical conversion treatment process is an arbitrary process. When the chemical conversion treatment process is implemented, a chemical conversion treatment film is formed on the Zn-Ni alloy plating layer 110. In the chemical conversion treatment process, a well-known chemical conversion treatment may be implemented. The chemical conversion treatment may be, for example, an oxalate chemical conversion treatment, a phosphate chemical conversion treatment, or a borate chemical conversion treatment. For example, when a phosphate chemical conversion treatment is implemented, a chemical conversion treatment using zinc phosphate may be implemented, a chemical conversion treatment using manganese phosphate may be implemented, or a chemical conversion treatment using zinc calcium phosphate may be implemented.

[0149] Specifically, when zinc phosphate chemical conversion treatment is performed, as the treatment liquid, for example, a chemical conversion treatment liquid containing phosphate ions 1 to 150 g / L, zinc ions 3 to 70 g / L, nitrate ions 1 to 100 g / L, and nickel ions 0 to 30 g / L can be used. In this case, the liquid temperature of the chemical conversion treatment liquid is, for example, 20 to 100° C. In this way, by appropriately setting well-known conditions to perform chemical conversion treatment, a chemical conversion treatment film can be formed.

[0150] [Film forming process]

[0151] The manufacturing method of this embodiment may also implement a film forming process as needed. That is, the film forming process is an arbitrary process. In the film forming process, a lubricating coating layer 120 is formed on the Zn-Ni alloy plating layer 110, and / or on the chemical conversion treatment film, and / or on the contact surface (male buckle part contact surface 400 or female buckle part contact surface 500) where the Zn-Ni alloy plating layer 110 is not formed.

[0152] In the film forming step, a composition or lubricant containing the above-mentioned lubricating film components is applied. In this way, the lubricating film layer 120 can be formed. The coating method is not particularly limited. The coating method is, for example, spraying, brushing, and dipping. In the case of spraying, the composition or lubricant can also be heated and sprayed in a state with increased fluidity. The composition or lubricant is dried to form the lubricating film layer 120.

[0153] The oil well metal pipe 1 of this embodiment will be described in more detail below using examples. The conditions in the following examples are one condition example adopted to confirm the feasibility and effect of the oil well metal pipe 1 of this embodiment. Therefore, the oil well metal pipe 1 of this embodiment is not limited to this one condition example.

[0154] Example

[0155] In this embodiment, Ni plating and Zn-Ni alloy plating were formed on a steel plate simulating a contact surface to evaluate the sintering resistance of the steel plate. Specifically, the steel plate refers to a cold-rolled steel plate having a chemical composition of C≤0.15%, Mn≤0.60%, P≤0.100%, S≤0.050%, and the remainder: Fe and impurities.

[0156] The steel sheets of each test number were subjected to electrolytic degreasing and immersion pickling as base treatment. The plating baths listed in Table 1 were used at the current densities (A / dm 2 ) and treatment time (seconds) to form a Ni plating layer relative to the steel plate of each test number after the substrate treatment. In addition, the "-" in the "plating bath" column, the "current density" column, and the "treatment time" column in Table 1 means that no Ni plating layer is formed.

[0157] [Table 1]

[0158] Table 1

[0159]

[0160] Specifically, the plating baths "A" and "B" are as follows.

[0161] [Plating bath A]

[0162] A chlorinated bath was used as plating bath A. 240 g / L of nickel chloride and 125 mL / L of hydrochloric acid were contained in plating bath A. The electroplating conditions when plating bath A was used were plating bath pH: 1.5 or less and plating bath temperature: 25°C.

[0163] [Plating bath B]

[0164] A sulfuric acid bath was used as the plating bath B. The plating bath B contained 240 to 300 g / L of nickel sulfate, 40 to 70 g / L of nickel chloride, and 30 to 45 g / L of boric acid. The electroplating conditions when using the plating bath B were set to a plating bath pH of 3 to 4 and a plating bath temperature of 40 to 50°C.

[0165] The steel sheet after forming the Ni coating was subjected to a Zn-Ni alloy coating forming step. The coating bath used in the Zn-Ni alloy coating forming step was a commercially available and well-known coating bath. Other Zn-Ni alloy coating forming steps were performed under the above-mentioned preferred conditions. The steel sheets of each test number were manufactured using the above manufacturing process.

[0166] The produced steel sheets of each test number were subjected to measurement of coating adhesion and a seizure resistance test.

[0167] [Measurement of coating adhesion]

[0168] The above-mentioned coating dissolution method was used to measure the adhesion amount of Ni plating and Zn-Ni alloy plating on the steel plates of each test number. Specifically, samples including Ni plating and Zn-Ni alloy plating were collected from the steel plates of each test number, and the Zn-Ni alloy plating and Ni plating were dissolved respectively using dilute hydrochloric acid solution and dilute nitric acid solution. The obtained dissolved solution was subjected to elemental analysis by ICP-AES. The adhesion amount of Ni plating (g / m 2 The obtained Ni content and Zn content and the area of ​​the Zn-Ni alloy plating layer formed in the sample were used to obtain the Zn-Ni alloy plating layer adhesion amount (g / m 2 In this embodiment, the adhesion amount of the Zn-Ni alloy plating layer is 80g / m 2 .

[0169] [Seizing resistance test]

[0170] For the steel plates of each test number, a lubricating coating layer was formed on the Zn-Ni alloy coating and a sintering resistance test was implemented. Specifically, a commercially available solid lubricating coating layer was formed on the Zn-Ni alloy coating of the steel plates of each test number. The thickness of the solid lubricating coating layer formed is 30μm. While keeping the state of pressing the steel ball on the steel plates of each test number pasted on the rotating disk at 60N (Hertz surface pressure 1.25GPa) unchanged, the rotating disk is rotated under the sliding condition of a sliding speed of 31.4mm / s. The rotating disk is rotated with a reciprocating swing of 90 degrees. In addition, the sliding was implemented under the conditions of no oiling and room temperature. The friction coefficient μ of the steel ball in the sliding is measured, and the sliding distance (mm) until the friction coefficient μ is greater than 0.3 is calculated. The calculated sliding distance is shown in Table 1.

[0171] [Evaluation results]

[0172] Referring to Table 1, the amount of Ni plating on the steel sheets of test numbers 5 to 9 was 6.00 g / m 2 As a result, the sliding distance in the seizure resistance test was 9000 mm or more. That is, the steel sheets of test numbers 5 to 9 had excellent seizure resistance.

[0173] On the other hand, the Ni plating weight of the steel sheets of test numbers 1 to 4 was less than 6.00 g / m 2 As a result, the sliding distance in the seizure resistance test was less than 9000 mm. That is, the steel sheets of test numbers 1 to 4 did not have excellent seizure resistance.

[0174] The embodiments of the present disclosure have been described above. However, the above embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above embodiments, and the above embodiments can be appropriately modified and implemented within the scope of the present disclosure.

[0175] Description of Reference Numerals

[0176] 1. Metal pipe for oil well; 10. Pipe body; 10A. First end; 10B. Second end; 40. Pin portion; 41. External thread portion; 50. Box portion; 51. Internal thread portion; 100. Ni plating; 110. Zn-Ni alloy plating; 120. Lubricating coating layer; 400. Pin portion contact surface; 500. Box portion contact surface.

Claims

1. A metal pipe for oil wells, comprising a pipe body including a first end portion and a second end portion, The pipe body comprises: a male buckle portion formed at the first end portion; and a female buckle portion formed at the second end portion, The pin portion has a pin portion contact surface including an external thread portion, The box portion has a box portion contact surface including an internal thread portion, The metal pipe for oil wells further comprises: A Ni plating layer formed on at least one of the pin portion contact surface and the box portion contact surface; and A Zn-Ni alloy plating layer is formed on the Ni plating layer, The adhesion amount of the Ni plating layer is 6.00 g / m 2 above.

2. The metal pipe for oil wells according to claim 1, wherein: The oil well metal pipe further includes a lubricating coating layer on or above the Zn—Ni alloy plating layer.

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