Metal pipe for oil well

Abstract

Provided is a metal pipe for oil wells having a Zn-Ni alloy plating layer with high adhesion. The metal pipe for oil wells of the present disclosure includes a pipe body including a pin that is formed at a first end portion and has a pin contact surface including an outer threaded portion, a box that is formed at a second end portion and has a box contact surface including an inner threaded portion, and a Zn-Ni alloy plating layer formed on at least one of the pin contact surface and the box contact surface. The Zn-Ni alloy plating layer has an X-ray diffraction intensity that satisfies formula (1). I 18 / (I 18 +I 36 +I 54 ) ≥ 0.60 (1), where the X-ray diffraction intensity of {411} and {330} is substituted into I 18 in formula (1) in units of cps, the X-ray diffraction intensity of {442} and {600} is substituted into I 36 in units of cps, and the X-ray diffraction intensity of {552} is substituted into I 54 in units of cps.

Description

Technical Field

[0001] This disclosure relates to a metal pipe for oil wells, and more specifically to a metal pipe for oil wells having a threaded joint. Background Technology

[0002] For the exploitation of oil and gas fields (hereinafter, oil and gas fields are collectively referred to as "oil wells"), metal pipes for oil wells are used. Specifically, at the oil well exploitation site, multiple metal pipes for oil wells are connected according to the depth of the oil well to form an oil well pipe connection body, represented by casing and tubing. The oil well pipe connection body is formed by threading together threaded joints formed at the ends of the metal pipes for oil wells. There are situations where the oil well pipe connection body needs to be inspected. In the event of an inspection, the oil well pipe connection body is pulled up, and the threads of the threaded joints are loosened. Then, the metal pipes for oil wells that were removed from the oil well pipe connection body due to loosening are inspected. After inspection, the threaded joints of the oil well pipes are re-tightened, and the connection body is reused as part of the oil well pipe connection body.

[0003] The oil well metal pipe has a pipe body including a first end and a second end. The pipe body includes a male thread formed at the first end and a female thread formed at the second end. The male thread has a male thread contact surface including an external thread on the outer circumferential surface of the first end of the pipe body. The female thread has a female thread contact surface including an internal thread on the inner circumferential surface of the end of the pipe body opposite to the male thread (the second end). When the thread is tightened into the threaded joint formed at the end of the oil well metal pipe, the male thread contact surface contacts the female thread contact surface.

[0004] The male and female thread contact surfaces of oil well metal pipes are repeatedly subjected to strong friction during thread tightening and loosening. If these areas lack sufficient durability against friction, adhesion (irreparable sintering) will occur during repeated thread tightening and loosening. Therefore, oil well metal pipes require sufficient durability against friction, i.e., excellent resistance to sintering.

[0005] Previously, composite greases containing heavy metals, known as coatings, were used to improve sintering resistance. Applying composite grease to the male and / or female thread contact surfaces can improve the sintering resistance of metal pipes used in oil wells. However, there is a possibility that the heavy metals such as Pb, Zn, and Cu contained in the composite grease may have environmental impacts. Therefore, it is desirable to develop metal pipes for oil wells that exhibit excellent sintering resistance even without the use of composite grease.

[0006] In the oil well metal pipe disclosed in Patent Document 1 (International Publication No. 2016 / 170031), a Zn-Ni alloy coating is formed on the male or female thread contact surface to replace the composite grease. The Zn in the Zn-Ni alloy coating formed on the contact surface of the oil well metal pipe improves the corrosion resistance of the oil well metal pipe by sacrificing corrosion protection. Furthermore, the Zn-Ni alloy disclosed in Patent Document 1 also exhibits excellent wear resistance.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2016 / 170031 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] However, the Zn-Ni alloy coating is repeatedly subjected to strong friction during the tightening and loosening of the threads of the oil well metal pipe. If a portion of the Zn-Ni alloy coating, subjected to repeated strong friction, peels off, the coefficient of friction of the contact surface increases sharply, and the sintering resistance of the oil well metal pipe decreases drastically. Therefore, the Zn-Ni alloy coating formed on the contact surface of the oil well metal pipe is preferably difficult to peel off even under repeated strong friction. Hereinafter, in this specification, the difficulty in peeling off even under repeated strong friction will be referred to as "high tightness of adhesion".

[0012] According to the technology disclosed in Patent Document 1, the sintering resistance of oil well metal pipes can be improved by forming a Zn-Ni alloy coating on the male or female contact surface. However, Patent Document 1 did not study the tightness of the Zn-Ni alloy coating formed on the contact surface of the oil well metal pipe.

[0013] The purpose of this disclosure is to provide a metal pipe for oil wells with a Zn-Ni alloy coating that has a high degree of tightness in fit.

[0014] Solution for solving the problem

[0015] The metal pipe for oil wells disclosed herein comprises a pipe body, the pipe body including a first end and a second end.

[0016] The pipe body includes:

[0017] Male buckle, which is formed at the first end; and

[0018] The female buckle, which is formed at the second end,

[0019] The male thread has a male thread contact surface including an external thread portion.

[0020] The female buckle has a female buckle contact surface including an internal thread portion.

[0021] The oil well metal pipe also has a Zn-Ni alloy coating formed on at least one of the male thread contact surface and the female thread contact surface.

[0022] The X-ray diffraction intensity of the Zn-Ni alloy coating satisfies equation (1).

[0023] I 18 / (I 18 +I 36 +I 54 )≥0.60 (1)

[0024] In this context, the sum of the squares of the Miller indices is 18, and the X-ray diffraction intensities of {411} and {330} are substituted into I in equation (1) in units of cps. 18 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensities of {442} and {600}, which are 36, into I in equation (1) in units of cps. 36 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensity of {552}, which is 54, into I in equation (1) in units of cps. 54 .

[0025] The effects of the invention

[0026] The Zn-Ni alloy coating of the oil well metal pipe disclosed herein has high tightness of adhesion. Attached Figure Description

[0027] Figure 1 This indicates that Fn1 (=I) in this embodiment 18 / (I 18 +I 36 +I 54 A graph showing the relationship between the fit and the fit evaluation as an indicator of fit.

[0028] Figure 2 This is a structural diagram illustrating an example of a metal pipe for oil wells according to this embodiment.

[0029] Figure 3 It means Figure 2 The diagram shows a partial sectional view of the pipe fitting of a metal pipe for oil wells, taken along the pipe axis (longitudinal section).

[0030] Figure 4 yes Figure 3 The diagram shows a cross-sectional view of the portion of the metal tubing near the male thread, parallel to the axis of the tubing.

[0031] Figure 5 yes Figure 3 The diagram shows a cross-sectional view of the portion of the metal tubing near the female thread, parallel to the axis of the tubing.

[0032] Figure 6 It means and Figure 3 A partial sectional view of the pipe fitting of the oil well metal pipe of this embodiment along the pipe axis (longitudinal section).

[0033] Figure 7 This is a structural diagram of the integral metal pipe for oil wells in this embodiment.

[0034] Figure 8 yes Figure 4 An enlarged view of the male contact surface shown.

[0035] Figure 9 yes Figure 5 An enlarged view of the female buckle contact surface shown.

[0036] Figure 10 Is with Figure 8 Enlarged view of the male contact surface of different structures.

[0037] Figure 11 Is with Figure 9 Enlarged view of the contact surface of the female buckle with different structures.

[0038] Figure 12 Is with Figure 8 and Figure 10 Enlarged view of the male contact surface of different structures.

[0039] Figure 13 Is with Figure 9 and Figure 11 Enlarged view of the contact surface of the female buckle with different structures. Detailed Implementation

[0040] Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings. The same or equivalent parts in the drawings will be labeled with the same reference numerals and will not be described repeatedly.

[0041] The inventors have conducted a detailed study on a method to improve the tightness of a Zn-Ni alloy coating formed on at least one of the male and female thread contact surfaces of a metal pipe used in oil wells. As a result, the inventors have obtained the following insights.

[0042] The physical and chemical properties of metallic materials are influenced by the fine structure represented by the crystallographic structure and surface morphology of the material. Therefore, the inventors focused on the microstructure of Zn-Ni alloy coatings as metallic materials and conducted a detailed study on methods to improve the adhesion of Zn-Ni alloy coatings. As a result, the inventors obtained the following insight: the adhesion varies due to the orientation of the crystals in the Zn-Ni alloy coating. In this specification, the distribution of the crystal orientation in the Zn-Ni alloy coating is also referred to as the "orientation of the Zn-Ni alloy coating." In other words, the inventors believe that if the orientation of the Zn-Ni alloy coating can be appropriately controlled, it is possible to improve the adhesion of the Zn-Ni alloy coating.

[0043] X-ray diffraction analysis (XRD) is one method for evaluating the orientation of metallic materials. XRD analyzes the diffraction caused by the scattering and interference of X-rays by electrons surrounding atoms. Therefore, XRD can obtain a unique diffraction pattern based on the arrangement of atoms in the material. In other words, the size of the crystal and the orientation of the material can be evaluated based on the diffraction pattern obtained through XRD.

[0044] Therefore, the inventors manufactured various oil well metal pipes with Zn-Ni alloy coatings formed on their contact surfaces, evaluated the orientation of the Zn-Ni alloy coatings using XRD, and investigated the relationship between the orientation of the Zn-Ni alloy coatings and their tightness of adhesion. The results showed that if the X-ray diffraction intensity of the Zn-Ni alloy coating satisfies the following equation (1), the tightness of the Zn-Ni alloy coating is significantly improved.

[0045] I 18 / (I 18 +I 36 +I 54 )≥0.60 (1)

[0046] In this context, the sum of the squares of the Miller indices is 18, and the X-ray diffraction intensities of {411} and {330} are substituted into I in equation (1) in units of cps. 18 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensities of {442} and {600}, which are 36, into I in equation (1) in units of cps. 36 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensity of {552}, expressed in units of cps, into I in equation (1). 54 .

[0047] Defined as Fn1 = I 18 / (I 18 +I36 +I 54 Fn1 is an index representing the orientation tendency of {411} and {330}. That is, the larger Fn1 is, the more {411} and {330} tend to be in the same direction. Further detailed research by the inventors has clarified that if Fn1 is 0.60 or higher, the adhesion of the Zn-Ni alloy coating is significantly improved. This will be specifically illustrated using the accompanying drawings.

[0048] Figure 1 This indicates that Fn1 (=I) in this embodiment 18 / (I 18 +I 36 +I 54 A graph showing the relationship between the fit and the fit evaluation as an indicator of fit. Figure 1 It was made using the embodiments described below. The X-ray diffraction intensity and tightness evaluation for determining Fn1 were obtained using the methods described below. Furthermore, for the tightness evaluation, "0" is given in the case of minimal peeling and "5" is given in the case of maximum peeling.

[0049] Reference Figure 1 If Fn1 is 0.60 or higher, the tightness evaluation decreases sharply. In other words, if Fn1 is 0.60 or higher, the tightness of the Zn-Ni alloy coating is significantly improved. Therefore, in the oil well metal pipe of this embodiment, Fn1 is set to 0.60 or higher in the Zn-Ni alloy coating formed on the contact surface.

[0050] Furthermore, the reasons for the improved adhesion of the Zn-Ni alloy coating when Fn1 is set to 0.60 or higher are not clear. However, the inventors speculate as follows: As mentioned above, the physical and chemical properties of metallic materials are affected by the crystallographic structure of the material. That is, if the orientation of the Zn-Ni alloy coating is different, the ease with which strain remains in the crystal lattice may also change. In particular, when {411} and {330} tend to be in the same direction, strain may be difficult to retain. As a result, the inventors believe that if Fn1 is increased to 0.60 or higher, the residual tensile stress in the Zn-Ni alloy coating can be reduced, thereby improving the adhesion.

[0051] Based on the above mechanism, the inventors hypothesize that setting Fn1 to 0.60 or higher will improve the tightness of the Zn-Ni alloy coating. Furthermore, based on a different mechanism, it is also possible that setting Fn1 to 0.60 or higher will improve the tightness of the Zn-Ni alloy coating. However, the improvement in the tightness of the Zn-Ni alloy coating by setting Fn1 to 0.60 or higher is demonstrated by the examples discussed later.

[0052] Based on the above insights, the main idea of ​​the metal pipe for oil wells in this embodiment is as follows.

[0053] [1] A metal pipe for oil wells, wherein the metal pipe for oil wells comprises a pipe body, the pipe body including a first end and a second end,

[0054] The pipe body includes:

[0055] Male buckle, which is formed at the first end; and

[0056] The female buckle, which is formed at the second end,

[0057] The male thread has a male thread contact surface including an external thread portion.

[0058] The female buckle has a female buckle contact surface including an internal thread portion.

[0059] The oil well metal pipe also has a Zn-Ni alloy coating formed on at least one of the male thread contact surface and the female thread contact surface.

[0060] The X-ray diffraction intensity of the Zn-Ni alloy coating satisfies equation (1).

[0061] I 18 / (I 18 +I 36 +I 54 )≥0.60 (1)

[0062] In this context, the sum of the squares of the Miller indices is 18, and the X-ray diffraction intensities of {411} and {330} are substituted into I in equation (1) in units of cps. 18 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensities of {442} and {600}, which are 36, into I in equation (1) in units of cps. 36 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensity of {552}, which is 54, into I in equation (1) in units of cps. 54 .

[0063] [2] According to the metal pipe for oil wells described in [1], wherein,

[0064] The thickness of the Zn-Ni alloy coating is 5 μm to 25 μm.

[0065] [3] According to [1] or [2], the metal pipe for oil wells, wherein,

[0066] A lubricating coating is provided on or above the Zn-Ni alloy coating.

[0067] The following section discusses in detail the metal pipe for oil wells according to this embodiment.

[0068] [Structure of metal pipes for oil wells]

[0069] First, the structure of the oil well metal pipe of this embodiment will be described. Oil well metal pipes have a well-known structure. Oil well metal pipes include T&C type oil well metal pipes and integral type oil well metal pipes. The following will discuss each type of oil well metal pipe in detail.

[0070] [For oil wells using T&C type metal tubing]

[0071] Figure 2 This is a structural diagram showing an example of the metal pipe 1 for oil wells according to this embodiment. Figure 2 This is a structural diagram of the so-called T&C type (Threaded and Coupled) metal pipe for oil wells. (Refer to...) Figure 2 The oil well metal pipe 1 has a pipe body 10.

[0072] The tube body 10 extends along the tube axis. The cross-section of the tube body 10 perpendicular to the tube axis is circular. The tube 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. Figure 2 In the T&C type oil well metal pipe 1 shown, the pipe body 10 has a male threaded pipe body 11 and a pipe fitting 12. The pipe fitting 12 is installed at one end of the male threaded pipe body 11. More specifically, the pipe fitting 12 is fastened to one end of the male threaded pipe body 11 by threads.

[0073] Figure 3 It means Figure 2 A partial sectional view of the pipe fitting 12 of the oil well metal pipe 1, parallel to the pipe axis (longitudinal section). (Refer to...) Figure 2 and Figure 3 The pipe body 10 includes a male thread 40 and a female thread 50. The male thread 40 is formed at the first end 10A of the pipe body 10. During tightening, the male thread 40 is inserted into the female thread 50 of another oil well metal pipe (not shown) and tightened with the female thread 50 of the other oil well metal pipe 1 by means of threads.

[0074] The female thread 50 is formed at the second end 10B of the pipe body 10. During tightening, the male thread 40 of another oil well metal pipe 1 is inserted into the female thread 50 and tightened by the thread with the male thread 40 of the other oil well metal pipe 1.

[0075] [Regarding the structure of the public buckle]

[0076] Figure 4 yes Figure 3 A cross-sectional view of the portion near the male thread 40 of the oil well metal pipe 1, shown, parallel to the pipe axis direction of the oil well metal pipe 1. Figure 4 The dashed line indicates the structure of the female thread 50 of the other oil well metal pipe 1 when it is fastened to other oil well metal pipes 1. (Refer to...) Figure 4 The male thread 40 includes a male thread contact surface 400 on the outer peripheral surface of the first end 10A of the pipe body 10. The male thread contact surface 400 contacts the female thread 50 of the other oil well metal pipe 1 when fastened to it.

[0077] The male contact surface 400 includes at least an external threaded portion 41 formed on the outer peripheral surface of the first end 10A. Alternatively, the male contact surface 400 may also include a male sealing surface 42 and a male shoulder surface 43. Figure 4 In this configuration, the male thread sealing surface 42 is positioned on the outer peripheral surface of the first end portion 10A, closer to the top end of the first end portion 10A than the external thread portion 41. That is, the male thread sealing surface 42 is positioned between the external thread portion 41 and the male thread shoulder surface 43. The male thread sealing surface 42 is tapered. Specifically, in the male thread sealing surface 42, along the length direction (pipe axis direction) of the first end portion 10A, the outer diameter gradually decreases from the external thread portion 41 toward the male thread shoulder surface 43.

[0078] When fastened to other oil well metal pipes 1, the male thread sealing surface 42 contacts the female thread sealing surface 52 (discussed later) of the female thread 50 of the other oil well metal pipe 1. More specifically, during fastening, the male thread 40 is inserted into the female thread 50 of the other oil well metal pipe 1, thereby bringing the male thread sealing surface 42 into contact with the female thread sealing surface 52. Then, by further screwing the male thread 40 into the female thread 50 of the other oil well metal pipe 1, the male thread sealing surface 42 and the female thread sealing surface 52 are tightly fitted together. Thus, during fastening, the male thread sealing surface 42 and the female thread sealing surface 52 are tightly fitted together to form a seal based on metal-metal contact. Therefore, in the mutually fastened oil well metal pipes 1, air tightness can be improved.

[0079] exist Figure 4 In the middle, the male buckle shoulder surface 43 is disposed on the top surface of the first end 10A. That is to say, in Figure 4In the male thread 40 shown, an external thread portion 41, a male thread sealing surface 42, and a male thread shoulder surface 43 are sequentially arranged from the center of the pipe body 10 toward the first end 10A. When fastened to other oil well metal pipes 1, the male thread shoulder surface 43 faces and contacts the female thread shoulder surface 53 (discussed later) of the female thread 50 of the other oil well metal pipe 1. More specifically, during fastening, the male thread 40 is inserted into the female thread 50 of the other oil well metal pipe 1, thereby bringing the male thread shoulder surface 43 into contact with the female thread shoulder surface 53. This allows for a higher torque during fastening. In addition, the positional relationship between the male thread 40 and the female thread 50 in the fastened state can be stabilized.

[0080] Furthermore, the male contact surface 400 of the male thread 40 includes at least the external thread portion 41. That is, the male contact surface 400 may also include the external thread portion 41 but exclude the male sealing surface 42 and the male shoulder surface 43. Alternatively, the male contact surface 400 may include the external thread portion 41 and the male shoulder surface 43 but exclude the male sealing surface 42. Alternatively, the male contact surface 400 may include the external thread portion 41 and the male sealing surface 42 but exclude the male shoulder surface 43.

[0081] [Regarding the structure of the female buckle]

[0082] Figure 5 yes Figure 3 The cross-sectional view of the portion near the female thread 50 in the oil well metal pipe 1 shown is parallel to the pipe axis direction of the oil well metal pipe 1. Figure 5 The dashed line indicates the structure of the male thread 40 of the other oil well metal pipe 1 when it is fastened to other oil well metal pipes 1. (Refer to...) Figure 5 The female thread 50 includes a female thread contact surface 500 on the inner circumferential surface of the second end 10B of the pipe body 10. The female thread contact surface 500 is used to screw in the male thread 40 of the other oil well metal pipe 1 when fastened to it, and contacts the male thread contact surface 400 of the male thread 40.

[0083] The female thread contact surface 500 includes at least an internal thread portion 51 formed on the inner circumferential surface of the second end 10B. During tightening, the internal thread portion 51 engages with the external thread portion 41 of the male thread 40 of the other well metal pipe 1.

[0084] Alternatively, the female contact surface 500 may also include a female sealing surface 52 and a female shoulder surface 53. Figure 5In this configuration, the female thread sealing surface 52 is positioned on the inner circumferential surface of the second end 10B, closer to the pipe body 10 than the internal thread portion 51. That is, the female thread sealing surface 52 is positioned between the internal thread portion 51 and the female thread shoulder surface 53. The female thread sealing surface 52 is tapered. Specifically, in the female thread sealing surface 52, along the length direction (pipe axis direction) of the second end 10B, the inner diameter gradually decreases from the internal thread portion 51 towards the female thread shoulder surface 53.

[0085] When fastened to other oil well metal pipes 1, the female thread sealing surface 52 contacts the male thread sealing surface 42 of the male thread 40 of the other oil well metal pipe 1. More specifically, during fastening, by screwing the male thread 40 of the other oil well metal pipe 1 into the female thread 50, the female thread sealing surface 52 contacts the male thread sealing surface 42, and by further screwing, the female thread sealing surface 52 and the male thread sealing surface 42 are tightly fitted together. Thus, during fastening, the female thread sealing surface 52 and the male thread sealing surface 42 are tightly fitted together to form a seal based on metal-metal contact. Therefore, in the mutually fastened oil well metal pipes 1, air tightness can be improved.

[0086] The female thread shoulder surface 53 is positioned closer to the pipe body 10 than the female thread sealing surface 52. That is, in the female thread 50, the female thread shoulder surface 53, the female thread sealing surface 52, and the internal thread portion 51 are sequentially arranged from the center of the pipe body 10 toward the top of the second end 10B. When fastened to other well metal pipes 1, the female thread shoulder surface 53 faces and contacts the male thread shoulder surface 43 of the male thread 40 of the other well metal pipe 1. More specifically, during fastening, the female thread shoulder surface 53 contacts the male thread shoulder surface 43 by inserting the male thread 40 of the other well metal pipe 1 into the female thread 50. This allows for a higher torque during fastening. Furthermore, it ensures a stable positional relationship between the male thread 40 and the female thread 50 during the fastened state.

[0087] The female contact surface 500 includes at least an internal thread portion 51. During tightening, the internal thread portion 51 of the female contact surface 500 corresponds to and contacts the external thread portion 41 of the male contact surface 400. The female sealing surface 52 corresponds to and contacts the male sealing surface 42. The female shoulder surface 53 corresponds to and contacts the male shoulder surface 43.

[0088] When the male contact surface 400 includes an external thread portion 41 but does not include the male sealing surface 42 and the male shoulder surface 43, the female contact surface 500 includes an internal thread portion 51 but does not include the female sealing surface 52 and the female shoulder surface 53. When the male contact surface 400 includes an external thread portion 41 and the male shoulder surface 43 but does not include the male sealing surface 42, the female contact surface 500 includes an internal thread portion 51 and the female shoulder surface 53 but does not include the female sealing surface 52. When the male contact surface 400 includes an external thread portion 41 and the male sealing surface 42 but does not include the male shoulder surface 43, the female contact surface 500 includes an internal thread portion 51 and the female sealing surface 52 but does not include the female shoulder surface 53.

[0089] The male thread contact surface 400 may include multiple external thread portions 41, multiple male thread sealing surfaces 42, and multiple male thread shoulder surfaces 43. For example, on the male thread contact surface 400 of the male thread 40, the male thread shoulder surface 43, male thread sealing surface 42, external thread portion 41, male thread sealing surface 42, male thread shoulder surface 43, male thread sealing surface 42, and external thread portion 41 may be arranged sequentially from the top of the first end 10A toward the center of the tube body 10. In this case, on the female thread contact surface 500 of the female thread 50, the internal thread portion 51, female thread sealing surface 52, female thread shoulder surface 53, female thread sealing surface 52, internal thread portion 51, female thread sealing surface 52, and female thread shoulder surface 53 may be arranged sequentially from the top of the second end 10B toward the center of the tube body 10.

[0090] exist Figure 4 and Figure 5 The diagram illustrates a so-called advanced connector where the male thread 40 includes an external thread portion 41, a male thread sealing surface 42, and a male thread shoulder surface 43, and the female thread 50 includes an internal thread portion 51, a female thread sealing surface 52, and a female thread shoulder surface 53. However, it is also possible, as described above, that the male thread 40 includes the external thread portion 41 but excludes the male thread sealing surface 42 and the male thread shoulder surface 43. In this case, the female thread 50 includes the internal thread portion 51 but excludes the female thread sealing surface 52 and the female thread shoulder surface 53. Figure 6 This figure shows an example of an oil well metal pipe 1 in which the male thread 40 includes an external thread portion 41 but does not include the male thread sealing surface and the male thread shoulder surface, and the female thread 50 includes an internal thread portion 51 but does not include the female thread sealing surface and the female thread shoulder surface. The oil well metal pipe 1 of this embodiment may also have… Figure 6 The structure shown.

[0091] [When the metal tubing for oil wells is a single piece]

[0092] Figure 2 , Figure 3 as well as Figure 6The oil well metal pipe 1 shown is a so-called T&C type oil well metal pipe 1, with the pipe body 10 including a male threaded pipe body 11 and a pipe joint 12. However, the oil well metal pipe 1 of this embodiment may not be T&C type, but may be integral type.

[0093] Figure 7 This is a structural diagram of the integral oil well metal pipe 1 according to this embodiment. (Refer to...) Figure 7 The integral type oil well metal pipe 1 includes 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 side opposite to the second end 10B. As described above, in the T&C type oil well metal pipe 1, the pipe body 10 includes a male threaded pipe body 11 and a pipe fitting 12. That is, in the T&C type oil well metal pipe 1, the pipe body 10 is constructed by fastening two separate components (male threaded pipe body 11 and pipe fitting 12). In contrast, in the integral type oil well metal pipe 1, the pipe body 10 is formed integrally.

[0094] A male thread 40 is formed at the first end 10A of the pipe body 10. During tightening, the male thread 40 is inserted into and screwed into the female thread 50 of another integral type oil well metal pipe 1, thus securing it to the other integral type oil well metal pipe 1. A female thread 50 is formed at the second end 10B of the pipe body 10. During tightening, the male thread 40 of another integral type oil well metal pipe 1 is inserted into and screwed into the female thread 50, thus securing the female thread 50 to the other integral type oil well metal pipe 1.

[0095] The structure of the male thread 40 of the integral metal pipe 1 for oil wells is similar to Figure 4 The male thread 40 of the T&C type oil well metal pipe 1 shown has the same structure. Similarly, the female thread 50 of the integral type oil well metal pipe 1 has the same structure. Figure 5 The female thread 50 of the T&C type oil well metal pipe 1 shown has the same structure. Furthermore, in Figure 7 In the male thread 40, a male thread shoulder, a male thread sealing surface, and an external thread portion 41 are sequentially arranged from the top of the first end 10A toward the center of the tube body 10. Therefore, in the female thread 50, an internal thread portion 51, a female thread sealing surface, and a female thread shoulder are sequentially arranged from the top of the second end 10B toward the center of the tube body 10. However, compared with… Figure 4 Similarly, the male thread contact surface 400 of the male thread 40 of the integral oil well metal pipe 1 should at least include the external thread portion 41. Additionally, with... Figure 5 Similarly, the female thread contact surface 500 of the female thread 50 of the integral metal pipe 1 for oil wells may include at least the internal thread portion 51.

[0096] In summary, the metal pipe 1 for oil wells in this embodiment can be either T&C type or integral type.

[0097] [Regarding the chemical composition of the tube body]

[0098] In the oil well metal pipe 1 of this embodiment, the chemical composition of the pipe body 10 is not particularly limited. The pipe body 10 may have a chemical composition equivalent to carbon steel or stainless steel.

[0099] [For Zn-Ni alloy coatings]

[0100] In the oil well metal pipe 1 of this embodiment, a Zn-Ni alloy coating is formed on at least one of the contact surfaces of the male thread contact surface 400 and the female thread contact surface 500. That is, the Zn-Ni alloy coating may be formed on the male thread contact surface 400 but not on the female thread contact surface 500. Alternatively, the Zn-Ni alloy coating may be formed on the female thread contact surface 500 but not on the male thread contact surface 400. Furthermore, the Zn-Ni alloy coating may be formed on both the male thread contact surface 400 and the female thread contact surface 500.

[0101] In the following description, the structure on the male contact surface 400 when the Zn-Ni alloy coating is formed on the male contact surface 400 and the structure on the female contact surface 500 when the Zn-Ni alloy coating is formed on the female contact surface 500 will be described.

[0102] [Structure on the male contact surface when a Zn-Ni alloy coating is formed on the male contact surface]

[0103] Figure 8 This is an enlarged view of the area near the male contact surface 400, where the Zn-Ni alloy plating 100 is formed on the male contact surface 400. (Refer to...) Figure 8 In this case, the oil well metal pipe 1 also has a Zn-Ni alloy coating 100 formed on the male thread contact surface 400 of the male thread 40.

[0104] The Zn-Ni alloy plating 100 can be formed partially on the male contact surface 400 or entirely on the male contact surface 400. The surface pressure on the male sealing surface 42 becomes particularly high during the final stage of thread tightening. Therefore, when the Zn-Ni alloy plating 100 is partially formed on the male contact surface 400, it is preferable that the Zn-Ni alloy plating 100 is formed at least on the male sealing surface 42. As described above, the Zn-Ni alloy plating 100 can also be formed entirely on the male contact surface 400.

[0105] [Structure on the contact surface of the female buckle when a Zn-Ni alloy coating is formed on the contact surface of the female buckle]

[0106] Figure 9 This is an enlarged view of the vicinity of the female contact surface 500, where the Zn-Ni alloy coating 100 is formed on the female contact surface 500. (Refer to...) Figure 9 In this case, a Zn-Ni alloy plating 100 is formed on the female contact surface 500. The Zn-Ni alloy plating 100 can be formed partially or entirely on the female contact surface 500. The surface pressure of the female sealing surface 52 becomes particularly high during the final stage of thread tightening. Therefore, when the Zn-Ni alloy plating 100 is partially formed on the female contact surface 500, it is preferable that the Zn-Ni alloy plating 100 is formed at least on the female sealing surface 52.

[0107] [Composition of Zn-Ni alloy coating]

[0108] As described above, the Zn-Ni alloy coating 100 is formed on the contact surface of at least one of the male contact surface 400 and the female contact surface 500. The Zn-Ni alloy coating 100 is formed of a Zn-Ni alloy. Specifically, the Zn-Ni alloy contains zinc (Zn) and nickel (Ni). There are cases where the Zn-Ni alloy contains impurities. Impurities in the Zn-Ni alloy refer to substances other than Zn and Ni, and are substances present in the Zn-Ni alloy coating 100 during the manufacturing process of the oil well metal pipe 1, etc., in amounts that do not affect the effectiveness of this embodiment.

[0109] The Zn-Ni alloy coating 100 contains Zn. Compared to Fe, Zn is a base metal. Therefore, the Zn-Ni alloy coating 100 preferentially corrodes compared to steel (sacrificial corrosion protection). As a result, the corrosion resistance of the oil well metal pipe 1 is improved.

[0110] The chemical composition of the Zn-Ni alloy coating 100 can be determined using the following method: A sample containing the Zn-Ni alloy coating 100 (including the contact surface where the Zn-Ni alloy coating 100 is formed) is collected from an oil well metal pipe 1. The Zn-Ni alloy coating 100 in the collected sample is dissolved in 10% hydrochloric acid to obtain a solution. Elemental analysis of the obtained solution is performed using inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine the Ni content (mass%) and Zn content (mass%) in the Zn-Ni alloy coating 100.

[0111] [Thickness of Zn-Ni alloy coating 100]

[0112] The thickness of the Zn-Ni alloy coating 100 is not particularly limited. The thickness of the Zn-Ni alloy coating 100 is, for example, 1 μm to 20 μm. If the thickness of the Zn-Ni alloy coating 100 is 1 μm or more, the sintering resistance can be further improved. Even if the thickness of the Zn-Ni alloy coating 100 exceeds 20 μm, the above effect saturates. The lower limit of the thickness of the Zn-Ni alloy coating 100 is preferably 3 μm, more preferably 5 μm. The upper limit of the thickness of the Zn-Ni alloy coating 100 is preferably 18 μm, more preferably 15 μm.

[0113] In this embodiment, the thickness of the Zn-Ni alloy coating 100 can be determined using the following method. The thickness of the Zn-Ni alloy coating 100 is measured at any four locations on the male contact surface 400 or female contact surface 500 where the Zn-Ni alloy coating 100 is formed, using an eddy current phase thickness gauge PHASCOPE PMP10 manufactured by Helmut Fischer GmbH. The measurement is performed according to the method of ISO (International Organization for Standardization) 21968 (2005). The measurement locations are four locations (0°, 90°, 180°, and 270°) along the circumferential direction of the oil well tubing 1. The arithmetic mean of the measurement results is taken as the thickness of the Zn-Ni alloy coating 100.

[0114] [Microstructure of Zn-Ni alloy coating 100]

[0115] The Zn-Ni alloy coating 100 contains a γ phase. Specifically, the Zn-Ni alloy formed through electroplating contains an η phase, a γ phase, and an α phase. The η phase refers to the phase with the chemical formula Zn and a hexagonal crystal structure. The γ phase refers to the phase with the chemical formula Ni5Zn. 21 Furthermore, it has a body-centered cubic crystal structure. The α phase refers to the phase with the chemical formula Ni and a face-centered cubic crystal structure. The Zn-Ni alloy coating 100 of this embodiment may also be a mixture of the η phase, γ phase, and α phase. Preferably, the Zn-Ni alloy coating 100 is a single γ phase. In this specification, "single γ phase" means that the phases other than the γ phase (that is, the η phase and the α phase) are so few as to be negligible.

[0116] Orientation of Zn-Ni alloy coating 100

[0117] The X-ray diffraction intensity of the Zn-Ni alloy coating 100 in this embodiment satisfies the following formula (1).

[0118] I 18 / (I 18 +I 36 +I54 )≥0.60 (1)

[0119] In this context, the sum of the squares of the Miller indices is 18, and the X-ray diffraction intensities of {411} and {330} are substituted into I in equation (1) in units of cps. 18 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensities of {442} and {600}, which are 36, into I in equation (1) in units of cps. 36 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensity of {552}, expressed in units of cps, into I in equation (1). 54 .

[0120] Fn1(=I 18 / (I 18 +I 36 +I 54 Fn1 is an index representing the orientation tendency of {411} and {330}. That is, the larger Fn1 is, the more {411} and {330} tend to be in the same direction. Furthermore, if Fn1 is 0.60 or higher, the tightness of the Zn-Ni alloy coating 100 is significantly improved. Therefore, in this embodiment, Fn1, determined based on the X-ray diffraction intensity of the Zn-Ni alloy coating 100, is set to 0.60 or higher.

[0121] The preferred lower limit for Fn1 is 0.65, more preferably 0.70, further preferably 0.75, further preferably 0.80, further preferably 0.85, and further preferably 0.90. Furthermore, the upper limit for Fn1 is not particularly limited. Fn1 can also be 1.00. However, in the oil well metal pipe 1 of this embodiment, the upper limit for Fn1 is substantially 0.99.

[0122] As described above, in this specification, the orientation of the Zn-Ni alloy coating 100 refers to the distribution of the orientation of the crystals in the Zn-Ni alloy coating. Furthermore, the orientation of the material can be evaluated using XRD. On the other hand, in XRD, there are cases where some planes cannot be separated. Specifically, the Miller index of any plane is expressed as (hkl). In this case, the diffraction line is not obtained for each plane (hkl), but rather for the sum of squares of each Miller index, s(=hkl). 2 +k 2 +l 2 One line is obtained by taking the value of s. That is, a diffraction ray originating from a surface with the same sum of squares of Miller indices is obtained as one diffraction ray.

[0123] Furthermore, the surfaces (411), (141), and (114) that are in a symmetric relationship are collectively referred to as {411}. Similarly, the surfaces (330), (303), and (033) that are in a symmetric relationship are collectively referred to as {330}. For both {411} and {330}, s = 18. Therefore, the diffraction ray with s = 18 is a superposition of the diffraction ray originating from {411} and the diffraction ray originating from {330}. In addition, for the surfaces (442), (424), and (244) that are in a symmetric relationship, {442} and the surfaces (600), (060), and (006) that are in a symmetric relationship, {600}, s = 36. Therefore, the diffraction ray with s = 36 is a superposition of the diffraction ray originating from {442} and the diffraction ray originating from {600}.

[0124] Thus, I in equation (1) 18 It becomes the sum of the X-ray diffraction intensities of {411} and {330}. Similarly, I in equation (1) 36 This becomes the sum of the X-ray diffraction intensities of {442} and {600}. Additionally, I in equation (1) 54 It becomes the sum of the X-ray diffraction intensities of {552} of the plane (552), plane (525), and plane (255) which are in a symmetric relationship.

[0125] In this embodiment, Fn1 can be determined as follows: A test piece is prepared from the male thread contact surface 400 or female thread contact surface 500 of the oil well metal pipe 1 of this embodiment, on which a Zn-Ni alloy coating 100 is formed. The size of the test piece is not particularly limited, for example, 15mm × 15mm × 2mm thickness. X-ray diffraction measurement is performed on the surface of the Zn-Ni alloy coating 100 of the test piece using an X-ray diffraction apparatus. The X-ray diffraction measurement can be performed using well-known methods. The X-ray diffraction apparatus is not particularly limited, for example, the RINT-2500 manufactured by Rigaku Corporation of Japan can be used. In addition, in this embodiment, the target of the X-ray diffraction apparatus is not particularly limited. For example, Co (CoKα line) can also be used as the target of the X-ray diffraction apparatus.

[0126] The diffraction peaks corresponding to s = 18, 36, and 54 were determined from the X-ray diffraction spectra obtained by X-ray diffraction. The intensities of the determined diffraction peaks were calculated, and the intensity of the diffraction peak was defined as I. 18 I 36 and I 54 Able to determine the value of I based on the obtained information. 18 I 36 and I 54 Find Fn1.

[0127] [For any other structure of the metal pipe 1 for oil wells in this embodiment]

[0128] [For chemical conversion treatment coating]

[0129] Alternatively, the oil well metal pipe 1 of this embodiment may also have a chemical conversion coating 110 on top of the Zn-Ni alloy plating 100. (See reference...) Figure 10 Alternatively, if the Zn-Ni alloy plating 100 is formed on the male contact surface 400, a chemical conversion coating 110 may be formed on the Zn-Ni alloy plating 100. Furthermore, refer to... Figure 11 Alternatively, when the Zn-Ni alloy coating 100 is formed on the female contact surface 500, a chemical conversion coating 110 is formed on the Zn-Ni alloy coating 100.

[0130] The chemical conversion coating 110 is not particularly limited, but is preferably a well-known chemical conversion coating. For example, the chemical conversion coating 110 can be an oxalate chemical conversion coating, a phosphate chemical conversion coating, a borate chemical conversion coating, or a chromate coating. When the chemical conversion coating 110 is a chromate coating, it is preferable that the chromate coating does not contain hexavalent chromium.

[0131] The metal pipe 1 for oil wells may be stored outdoors for extended periods until it is actually used at the oil extraction site. The chemical conversion coating 110 improves the corrosion resistance of the male thread contact surface 400 during prolonged outdoor exposure to the atmosphere, inhibiting rusting (white rust) on the male thread contact surface 400. The thickness of the chemical conversion coating 110 is not particularly limited. For example, the thickness of the chemical conversion coating 110 is 10 nm to 200 nm.

[0132] [Lubricating Coating]

[0133] In the oil well metal pipe 1, a lubricating coating 120 may also be provided on the Zn-Ni alloy coating 100, the chemical conversion coating 110, or on the contact surface where the Zn-Ni alloy coating 100 is not formed (on the male thread contact surface 400 or the female thread contact surface 500). The lubricating coating 120 further improves the lubricity of the oil well metal pipe 1.

[0134] Reference Figure 12When the Zn-Ni alloy plating 100 is formed on the male contact surface 400, the lubricating coating 120 can also be formed on the chemical conversion coating 110 formed on the Zn-Ni alloy plating 100. That is, the lubricating coating 120 can also be formed on top of the Zn-Ni alloy plating 100. Furthermore, refer to... Figure 13 When the Zn-Ni alloy plating 100 is formed on the female contact surface 500, the lubricating coating 120 can also be formed on the Zn-Ni alloy plating 100. That is to say, the lubricating coating 120 can also be formed on the Zn-Ni alloy plating 100.

[0135] Furthermore, the configuration of the lubricating coating 120 is not limited to... Figure 12 and Figure 13 In other words, the lubricating coating 120 can be formed on or above the male contact surface 400 where the Zn-Ni alloy coating 100 is not formed, or on or above the female contact surface 500 where the Zn-Ni alloy coating 100 is not formed, or on or above the Zn-Ni alloy coating 100 formed on the male contact surface 400, or on or above the Zn-Ni alloy coating 100 formed on the female contact surface 500.

[0136] The lubricating coating can be solid, semi-solid, or liquid. Commercially available lubricants can be used in the lubricating coating. The lubricating coating may contain, for example, lubricating particles and a binder. The lubricating coating may also contain solvents and other components as needed. There are no particular limitations on whether the lubricating particles are lubricating. The lubricating particles may be, for example, one or more selected from the group consisting of graphite, MoS2 (molybdenum disulfide), WS2 (tungsten disulfide), BN (boron nitride), PTFE (polytetrafluoroethylene), CFx (fluorinated graphite), and CaCO3 (calcium carbonate).

[0137] 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. Thermosetting resins are, for example, one or more selected from the group consisting of polyethylene resin, polyimide resin, and polyamide-imide resin. Inorganic binders are, for example, one or two selected from the group consisting of alkoxysilanes and compounds containing siloxane bonds. Commercially available lubricants include, for example, SEAL-GUARD ECF (trade name) manufactured by JET-LUBE Co., Ltd. Other lubricating coatings include, for example, lubricating coatings containing rosin, metallic soap, wax, and lubricating powder.

[0138] [Manufacturing method of metal pipe 1 for oil wells]

[0139] The manufacturing method of the oil well metal pipe 1 according to this embodiment will be described below. Furthermore, if the oil well metal pipe 1 of this embodiment has the above-described structure, the manufacturing method is not limited to the method described below. However, the manufacturing method described below is a preferred example of manufacturing the oil well metal pipe 1 of this embodiment.

[0140] The manufacturing method of the metal pipe 1 for oil wells includes a preparation step (S1) for preparing a pipe blank having a male thread 40 or a female thread 50 and a Zn-Ni alloy coating formation step (S2). Hereinafter, each step of the manufacturing method of the metal pipe 1 for oil wells according to this embodiment will be described in detail.

[0141] [Preparation Process (S1)]

[0142] In the preparation process (S1), a tube blank with male thread 40 or female thread 50 is prepared. In this specification, "tube blank with male thread or female thread" refers to any one of the tube body 10, male thread tube body 11 in the T&C type oil well metal pipe 1, and the tube body 10 of the integral type oil well metal pipe 1.

[0143] For example, a tube blank with a male thread 40 or a female thread 50 is manufactured using the following method. Molten steel is used to manufacture the raw material. Specifically, molten steel is used to manufacture castings (slabs, blooms, or billets) using a continuous casting method. Molten steel can also be used to manufacture ingots using an ingot casting method. Alternatively, steel plates, ingots, or billets can be rolled to produce steel sheets (billets) as needed. The raw material (slab, ingot, or billet) is manufactured through the above process. The prepared raw material is hot-worked to manufacture the tube blank. The hot-working method can be piercing rolling based on the Mannesmann process or hot extrusion. The hot-worked tube blank is subjected to well-known quenching and tempering to adjust its strength. The tube blank is manufactured through the above process. Furthermore, in the case where the oil well metal pipe 1 is of type T&C, a tube blank for pipe fitting 12 is also prepared. The manufacturing method for the tube blank for pipe fitting 12 is the same as the manufacturing method for the tube blank described above.

[0144] When the oil well metal pipe 1 is of type T&C, the outer surfaces of both ends of the pipe blank for the male thread pipe body 11 are threaded to form a male thread 40 including a male thread contact surface 400. Through the above process, a pipe blank (male thread pipe body 11) with the male thread 40 formed is prepared when the oil well metal pipe 1 is of type T&C. Alternatively, when the oil well metal pipe 1 is of type T&C, a pipe fitting 12 may also be prepared. Specifically, the inner surfaces of both ends of the pipe blank for the pipe fitting 12 are threaded to form a female thread 50 including a female thread contact surface 500. The pipe fitting 12 is manufactured through the above process.

[0145] When the oil well metal pipe 1 is integral, the outer surface of the first end 10A of the pipe blank is threaded to form a male thread 40 including a male thread contact surface 400. Furthermore, the inner surface of the second end 10B of the pipe blank is threaded to form a female thread 50 including a female thread contact surface 500. Through the above processes, a pipe blank (pipe body 10) with male thread 40 and female thread 50 formed is prepared when the oil well metal pipe 1 is integral.

[0146] [Any other process]

[0147] Alternatively, the preparation step (S1) of this embodiment may also include at least one of the following steps: a grinding process and a Ni flash plating process.

[0148] When a grinding process is performed in the preparation step (S1) of this embodiment, the grinding process may include, for example, sandblasting and mechanical grinding finishing. Sandblasting is a process in which abrasive material (abrasive) is mixed with compressed air and sprayed onto the contact surface. The abrasive material may be, for example, spherical shot or angular abrasive particles. Sandblasting can increase the surface roughness of the contact surface. Sandblasting can be performed using well-known methods. For example, compressed air is mixed with the abrasive material using a compressor. The material of the abrasive material may be, for example, stainless steel, aluminum, ceramic, or alumina. The spray speed and other conditions of the sandblasting process are not particularly limited and can be appropriately adjusted using well-known methods.

[0149] In the Ni flash plating process, a Ni flash plating layer is formed on the surface of the tube blank. This Ni flash plating layer is a very thin base layer, improving the adhesion of the Zn-Ni alloy plating layer 100, which will be discussed later. Furthermore, the plating solution used in the Ni flash plating process is not particularly limited, and well-known solutions can be used. Additionally, the conditions for forming the Ni flash plating layer are not particularly limited and can be appropriately adjusted.

[0150] Furthermore, when the Ni flash plating process is performed, a Ni flash plating layer is formed between the pipe body 10 and the Zn-Ni alloy plating layer 100. On the other hand, the thickness of the formed Ni flash plating layer is negligible compared to the thickness of the Zn-Ni alloy plating layer 100. In other words, in the oil well metal pipe 1 of this embodiment, a Ni flash plating layer can also be included in the Zn-Ni alloy plating layer 100.

[0151] [Zn-Ni alloy coating formation process (S2)]

[0152] In the Zn-Ni alloy coating forming process (S2), a Zn-Ni alloy coating 100 is formed by electroplating on the male contact surface 400 of the tube blank with male thread 40 formed after the preparation process (S1) and / or on the female contact surface 500 of the tube blank with female thread 50 formed.

[0153] In the Zn-Ni alloy coating formation step (S2), an electroplating solution containing zinc ions and nickel ions is used to form the Zn-Ni alloy coating 100. The balancing anion for zinc ions and nickel ions is not particularly limited. For example, chloride ions or sulfate ions can be used as the balancing anion. That is, in the Zn-Ni alloy coating formation step (S2) of this embodiment, either a chloride electroplating solution or a sulfuric acid electroplating solution can be used as the electroplating solution.

[0154] The following describes, specifically, an example of using a chlorinated plating solution as the plating bath. When using a chlorinated plating solution, it is preferable that the plating solution does not contain brighteners. In this case, it is further preferable that the concentration of metal ions in the plating solution is high. That is, when using a chlorinated plating solution, specifically, it is preferable that the sum of the zinc ion concentration and the nickel ion concentration is 30 g / L or higher, and that the zinc ion concentration (g / L) is higher than the nickel ion concentration (g / L), and that it does not contain brighteners. In this case, in the formed Zn-Ni alloy plating layer 100, Fn1 can be stably set to 0.60 or higher.

[0155] More specifically, in the Zn-Ni alloy coating formation step (S2) of this embodiment, for example, an electroplating solution containing zinc ions: 40 g / L, nickel ions: 30 g / L, and ammonium chloride: 240 g / L, and without brightener, can be used. Furthermore, as described above, in the Zn-Ni alloy coating formation step (S2) of this embodiment, the electroplating solution is not limited to a chlorinated electroplating solution; a sulfuric acid solution or other electroplating solutions can be used.

[0156] The electroplating conditions in the Zn-Ni alloy coating formation process (S2) are not particularly limited and can be appropriately adjusted using well-known conditions. Examples of electroplating conditions include: electroplating solution pH: 1–10; electroplating solution temperature: 10℃–60℃; current density: 1 A / dm³. 2 ~100A / dm 2The processing time is 0.1 minutes to 30 minutes. When the Zn-Ni alloy plating layer 100 is formed on the male contact surface 400, the male contact surface 400 is immersed in the aforementioned electroplating solution for electroplating. Conversely, when the Zn-Ni alloy plating layer 100 is formed on the female contact surface 500, the female contact surface 500 is immersed in the aforementioned electroplating solution for electroplating.

[0157] The oil well metal pipe 1 of this embodiment, having the above-described structure, is manufactured through the above manufacturing process. Furthermore, the above manufacturing process is only one 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-described manufacturing method.

[0158] [Any other process]

[0159] Alternatively, the manufacturing method of the oil well metal pipe 1 in this embodiment may further include at least one of the following steps: a chemical conversion treatment step and a film formation step. These steps are arbitrary. Therefore, these steps may not be performed.

[0160] [Chemical conversion treatment process]

[0161] The manufacturing method of this embodiment can also include a chemical conversion treatment step as needed. That is, the chemical conversion treatment step is arbitrary. When performing the chemical conversion treatment step, a chemical conversion treatment coating 110 is formed on the Zn-Ni alloy plating layer 100. In the chemical conversion treatment step, a well-known chemical conversion treatment can be performed. The chemical conversion treatment can be, for example, oxalate chemical conversion treatment, phosphate chemical conversion treatment, or borate chemical conversion treatment. For example, when performing phosphate chemical conversion treatment, a chemical conversion treatment using zinc phosphate, a chemical conversion treatment using manganese phosphate, or a chemical conversion treatment using zinc-calcium phosphate can be performed.

[0162] Specifically, when performing the zinc phosphate chemical conversion treatment, the treatment solution can, for example, contain 1 g / L to 150 g / L of phosphate ions, 3 g / L to 70 g / L of zinc ions, 1 g / L to 100 g / L of nitrate ions, and 0 to 30 g / L of nickel ions. In this case, the temperature of the chemical conversion treatment solution is, for example, 20°C to 100°C. Thus, by appropriately setting well-known conditions and performing the chemical conversion treatment, a chemical conversion coating 110 can be formed.

[0163] [Film Forming Process]

[0164] The manufacturing method of this embodiment can also include a film-forming process as needed. That is, the film-forming process is arbitrary. In the film-forming process, a lubricating coating is formed on the Zn-Ni alloy coating 100, and / or the chemical conversion treatment coating 110, and / or the contact surface (male contact surface 400 or female contact surface 500) where the Zn-Ni alloy coating 100 is not formed.

[0165] In the film-forming process, a composition or lubricant containing the aforementioned lubricating coating components is applied. This forms a lubricating coating. The application method is not particularly limited. Application methods include, for example, spraying, brushing, and dipping. When using spraying, the composition or lubricant may be heated to improve its fluidity before spraying. The composition or lubricant is then dried to form a lubricating coating.

[0166] The following describes the oil well metal pipe 1 of this embodiment in more detail using examples. The conditions in the following examples are examples adopted to confirm the feasibility and effectiveness 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 example.

[0167] Example

[0168] In this embodiment, the tightness of the Zn-Ni alloy coating was evaluated by simulating the formation of a Zn-Ni alloy coating on a steel plate at the contact surface. Specifically, the steel plate refers to a cold-rolled steel plate with the following chemical composition: C≤0.15%, Mn≤0.60%, P≤0.100%, S≤0.050%, with the remainder being Fe and impurities.

[0169] Electrolytic degreasing, hydrochloric acid pickling, and Ni flash plating were performed on the steel plates for each test number as substrate treatments. The Ni flash plating treatment time is shown in the "Substrate Treatment (minutes)" column of Table 1. Furthermore, a "-" in the "Substrate Treatment (minutes)" column of Table 1 indicates that Ni flash plating was not performed.

[0170] [Table 1]

[0171] Table 1

[0172]

[0173] For the steel plates of each test number, a Zn-Ni alloy coating was formed using the electroplating solutions listed in Table 1. Furthermore, the thickness of the Zn-Ni alloy coating was approximately 10 μm regardless of the electroplating solution used. Moreover, the Ni ratio in the Zn-Ni alloy coating was 12% to 16% by mass. Specifically, electroplating solutions "A" and "B" are as follows.

[0174] [Electroplating Solution A]

[0175] As plating solution A, the product name DAIN ZIN ALLOYN2-PL manufactured by Daiwa Chemical Research & Development Co., Ltd. was used. Plating solution A is a chlorinated plating solution and does not contain brighteners. In plating solution A, the sum of the zinc ion concentration and the nickel ion concentration is still above 30 g / L, and the zinc ion concentration (g / L) is higher than the nickel ion concentration (g / L). Furthermore, the plating conditions using plating solution A are set as follows: plating solution pH: 5.8, plating solution temperature: 40°C, current density: 6 A / dm³. 2 And processing time: 8 minutes.

[0176] [Electroplating Solution B]

[0177] As plating solution B, the product name DAIN ZIN ALLOYN-PL manufactured by Daiwa Chemical Research & Development Co., Ltd. was used. Plating solution B is a chlorinated plating solution containing a brightener. In plating solution B, the sum of the zinc ion concentration and the nickel ion concentration is still above 30 g / L, and the zinc ion concentration (g / L) is lower than the nickel ion concentration (g / L). Furthermore, the plating conditions using plating solution B were set as follows: plating solution pH: 6.4, plating solution temperature: 25°C, current density: 2 A / dm³. 2 Processing time: 20 minutes.

[0178] X-ray diffraction intensity measurement and tightness test were performed on steel plates with Zn-Ni alloy coatings as shown above for each test number.

[0179] [X-ray diffraction intensity measurement test]

[0180] Fn1 was determined by performing X-ray diffraction intensity measurements on steel plates of each test number using the method described above. Specifically, X-ray diffraction measurements were performed on steel plates of each test number using an X-ray diffraction apparatus. The X-ray diffraction apparatus used was a RINT-2500 manufactured by Rigaku Corporation, Japan. Furthermore, in the X-ray diffraction measurements, the target was set to Co (CoKα line). Based on the X-ray diffraction spectra obtained through the X-ray diffraction measurements, diffraction peaks corresponding to s = 18, 36, and 54 were determined. The intensity of the determined diffraction peaks was calculated and defined as I. 18 I 36 and I 54 Based on the obtained I 18 I 36 and I 54 Calculate Fn1. For the steel plates of each test number, obtain I... 18 I 36 I 54 Fn1 and Fn1 are represented in Table 1.

[0181] [Fitness Test]

[0182] A tightness test was performed on the steel plates of each test number using the cross-cutting method specified in JIS K 5600-5-6 (1999). Specifically, cuts were made on the Zn-Ni alloy coating of each test number steel plate using a blade in an orientation perpendicular to the Zn-Ni alloy coating. After making six parallel cuts at approximately 1 mm intervals, six cuts were made at approximately 1 mm intervals, alternating the direction by 90°. After applying transparent adhesive tape to the cut areas, the tape was removed within 5 minutes. The surface of each test number steel plate after the tape was removed was visually observed, and the test results were classified into six grades from 0 to 5 according to the JIS K 5600-5-6 (1999) standard. Furthermore, the grade with the least peeling was "0", and the grade with the most peeling was "5". The obtained test results are shown in the "Tightness Evaluation" column of Table 1.

[0183] [Evaluation Results]

[0184] Referring to Table 1, the X-ray diffraction intensity of the Zn-Ni alloy coating in the steel plates of test numbers 1 to 6 satisfies equation (1). As a result, the tightness evaluation of the tightness test is 0 to 2. That is, the Zn-Ni alloy coatings of test numbers 1 to 6 have high tightness.

[0185] On the other hand, in the steel plates of test numbers 7 to 9, the X-ray diffraction intensity of the Zn-Ni alloy coating did not satisfy equation (1). As a result, the tightness evaluation of the tightness test was 4 or 5. That is, the Zn-Ni alloy coatings of test numbers 7 to 9 did not have high tightness.

[0186] The embodiments of this disclosure have been described above. However, the above embodiments are merely illustrative examples for implementing this disclosure. Therefore, this disclosure is not limited to the above embodiments, and can be implemented by appropriately modifying the above embodiments without departing from its spirit.

[0187] Explanation of reference numerals in the attached figures

[0188] 1. Metal pipe for oil wells; 10. Pipe body; 10A. First end; 10B. Second end; 40. Male thread; 41. External thread; 50. Female thread; 51. Internal thread; 100. Zn-Ni alloy coating; 110. Chemical conversion coating; 120. Lubricating coating; 400. Male thread contact surface; 500. Female thread contact surface.

Claims

1. A metal pipe for oil wells, wherein, The metal pipe for the oil well has a pipe body, which includes a first end and a second end. The pipe body includes: Male buckle, which is formed at the first end; and The female buckle, which is formed at the second end, The male thread has a male thread contact surface including an external thread portion. The female buckle has a female buckle contact surface including an internal thread portion. The oil well metal pipe also has a Zn-Ni alloy coating formed on at least one of the male thread contact surface and the female thread contact surface. The X-ray diffraction intensity of the Zn-Ni alloy coating satisfies equation (1). I 18 / (I 18 +I 36 +I 54 )≥0.60 (1) In this context, the sum of the squares of the Miller indices is 18, and the X-ray diffraction intensities of {411} and {330} are substituted into I in equation (1) in units of cps. 18 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensities of {442} and {600}, which are 36, into I in equation (1) in units of cps. 36 Substituting the sum of the squares of the Miller indices to the X-ray diffraction intensity of {552}, which is 54, into I in equation (1) in units of cps. 54 .

2. The metal pipe for oil wells according to claim 1, wherein, The thickness of the Zn-Ni alloy coating is 5 μm to 25 μm.

3. The metal pipe for oil wells according to claim 1 or 2, wherein, A lubricating coating is provided on or above the Zn-Ni alloy coating.

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