Metal pipe for oil well

Abstract

Provided is a metal pipe for oil wells that has both a high yield torque and excellent wear resistance. The metal pipe for oil wells of the present disclosure has a pipe main body. The pipe main body includes a pin portion (40) formed at a first end portion (10A) and a box portion formed at a second end portion. One of the pin portion contact surface (400) of the pin portion (40) and the box portion contact surface of the box portion, i.e., a first contact surface, is formed with a plating layer, and a solid lubricating layer is formed on the plating layer. The arithmetic mean deviation Ra of the other of the pin portion contact surface (400) and the box portion contact surface, i.e., a second contact surface, is 0.5 to 10.0 μm, and a semisolid or liquid rust-preventive coating film (80) is formed on the second contact surface.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an oil-well metal pipe. BACKGROUND

[0002] An oil-well metal pipe is used for production of an oil field or a natural gas field (hereinafter, the oil field and the natural gas field will be collectively referred to as "oil well"). The oil-well metal pipe has a threaded joint. At an oil well drilling site, a plurality of oil-well metal pipes are connected according to the depth of the oil well, and an oil well pipe string is formed. The oil well pipe string is formed by tightly screwing the oil-well metal pipes to each other. The oil well pipe string is pulled up for inspection and the like, and the threads are loosened. After the inspection, the threads are tightened again, and the oil well pipe string is used again.

[0003] The oil-well metal pipe has a pin and a box. The pin has a pin contact surface on the outer peripheral surface of the end portion of the oil-well metal pipe, and the pin contact surface includes an external thread portion. The box has a box contact surface on the inner peripheral surface of the end portion of the oil-well metal pipe, and the box contact surface includes an internal thread portion.

[0004] The pin contact surface and the box contact surface are repeatedly subjected to strong friction when the oil-well metal pipe is tightly screwed and loosened. If the pin contact surface and the box contact surface do not have sufficient durability against friction, galling (irreparable wear) occurs when the threads are repeatedly tightened and loosened. Therefore, the oil-well metal pipe is required to have sufficient durability against friction, that is, excellent wear resistance.

[0005] In the past, in order to improve the wear resistance, a composite grease containing heavy metals, which is called a dope, has been used. By applying the composite grease to the pin contact surface and / or the box contact surface, the wear resistance of the oil-well metal pipe can be improved. However, the heavy metals such as Pb, Zn, and Cu contained in the composite grease can have an impact on the environment. Therefore, it is desirable to develop an oil-well metal pipe having excellent wear resistance even without using the composite grease.

[0006] To this end, a technology of using a solid lubricating coating film instead of the composite grease has been proposed. For example, a pipe threaded joint proposed in International Publication No. 2009 / 072486 (Patent Literature 1) forms a solid lubricating coating film on the box contact surface and forms a solid anticorrosion coating film composed of an ultraviolet-cured resin on the pin contact surface. The document states that the occurrence of wear can be suppressed even when the threads are repeatedly tightened and loosened by the solid lubricating coating film.

[0007] On the other hand, when the oil well pipe joint body made of a plurality of oil well metal pipes is pressed into an oil well, the oil well pipe joint body is rotated and pressed. However, a stratum (reservoir) in which oil is buried extends in a horizontal direction rather than a vertical direction. For this reason, in order to cover a wide range of reservoirs and improve the efficiency of oil production, the use of oil drilling techniques such as deviated drilling and horizontal drilling is increasing. In deviated drilling and horizontal drilling, an oil well pipe joint body is bent in the ground, and the lower end of the oil well pipe joint body extends in a deviated direction or a horizontal direction. In the case where an oil well extends in a horizontal direction or a deviated direction, the longer the length in the horizontal direction or the length in the deviated direction, the higher the rotational torque required to press the oil well pipe joint body. When such a high rotational torque is applied, there is a possibility that if the oil well metal pipe is plastically deformed, the high air tightness cannot be maintained. Therefore, there is a demand for an oil well metal pipe which is less likely to be plastically deformed even when a high rotational torque is applied, in other words, an oil well metal pipe having a high yield torque.

[0008] Here, the yield torque is defined as follows. Figure 1 is a graph showing the relationship between the number of revolutions of the oil well metal pipe and the torque when the oil well metal pipe is fastened. See Figure 1 When the oil well metal pipe is screwed, the torque initially slowly increases in proportion to the number of revolutions. When the screwing is further performed, the shoulder portions of the oil well metal pipe come into contact with each other. The torque at this time is called a shoulder torque Ts. If the screwing is further performed after the shoulder torque Ts is reached, the torque sharply increases in proportion to the number of revolutions. The fastening is completed when the torque reaches a predetermined value (fastening torque To). At the fastening torque To, the pin contact surface and the box contact surface interfere with each other with a suitable surface pressure. In this case, the air tightness of the oil well pipe joint body made of a plurality of oil well metal pipes is high. However, if the torque applied to the oil well metal pipe is further increased, there is a possibility that the pin and the box are locally yielded and plastically deformed. The torque at this time is called a yield torque Ty.

[0009] It should be noted that if the oil well metal pipe does not have a shoulder portion, that is, in the case of an oil well metal pipe having so-called wedge threads, the relationship between the number of revolutions of the oil well metal pipe and the torque is as shown in Figure 1 In the wedge threads, in the thread advancing direction of the pin, the thread tooth width of the pin portion gradually decreases along the helical line of the thread, and the thread groove width of the pin portion gradually increases along the helical line of the thread. In addition, in the thread advancing direction of the pin, the thread groove width of the box portion gradually decreases along the helical line of the thread, and the thread tooth width of the box portion gradually increases along the helical line of the thread.

[0010] For an oil well metal pipe having a wedge thread without a shoulder portion, as the make-up of the thread proceeds, the load side surfaces of the external thread portion and the internal thread portion come into contact with each other and the stabbing side surfaces come into contact with each other to be locked (to be interference fitted). The torque at which the locking occurs is called a locking torque. The locking torque is equivalent to the shoulder torque of the oil well metal pipe having a shoulder portion. Therefore, in the present specification, unless otherwise specified, the locking torque and the shoulder torque are not distinguished from each other, and are collectively referred to as a shoulder torque. The oil well metal pipe having a wedge thread, like the oil well metal pipe having a shoulder portion, if the make-up of the thread is further performed after the shoulder torque Ts is reached, the torque sharply rises in proportion to the number of revolutions. And, if the make-up of the thread is further performed, the yield torque Ty is generated.

[0011] In view of the above, recently, there is a demand for an oil well metal pipe having a high yield torque, which is less likely to be plastically deformed even when a high rotational torque is applied. International Publication No. 2013 / 176281 (Patent Literature 2) proposes a tubular threaded joint having an excellent high torque fastening performance. The tubular threaded joint disclosed in Patent Literature 2 forms a first solid lubricating coating film on a part of a contact surface of at least one of a pin portion and a box portion including a shoulder portion. And, a second solid lubricating coating film is formed on at least a part of the contact surface on which the first solid lubricating coating film is not formed. The Vickers hardness of the first solid lubricating coating film is higher than the Vickers hardness of the second solid lubricating coating film. At the time of fastening, until the shoulder portion of the pin portion comes into contact with the shoulder portion of the box portion, the second solid lubricating coating film having a low Vickers hardness functions to reduce the coefficient of friction at the time of fastening. Therefore, the shoulder torque is kept at a low level. And, after the shoulder portion of the pin portion comes into contact with the shoulder portion of the box portion, the first solid lubricating coating film having a high Vickers hardness functions to increase the coefficient of friction. Thereby, the yield torque is increased.

[0012] Prior Art Documents

[0013] Patent Literature

[0014] Patent Literature 1: International Publication No. 2009 / 072486

[0015] Patent Literature 2: International Publication No. 2013 / 176281 SUMMARY

[0016] PROBLEMS TO BE SOLVED BY THE INVENTION

[0017] With the technique of Patent Literature 2, the yield torque can be increased. However, the yield torque can also be increased by other techniques. In addition, as described above, the oil well metal pipe also requires wear resistance. Therefore, it is desirable that the high yield torque and the excellent wear resistance can be both satisfied.

[0018] The present disclosure aims to provide a metal pipe for oil wells that can achieve both high yield torque and excellent wear resistance.

[0019] Solution to the problem

[0020] The metal pipe for oil wells provided by the present disclosure has:

[0021] a pipe body including a first end portion and a second end portion,

[0022] the pipe body includes:

[0023] a pin portion formed in the first end portion, and

[0024] a box portion formed in the second end portion,

[0025] the pin portion includes a pin portion contact surface,

[0026] the pin portion contact surface has at least an external thread portion formed on an outer circumferential surface of the first end portion of the pipe body,

[0027] the box portion includes a box portion contact surface,

[0028] the box portion contact surface has at least an internal thread portion formed on an inner circumferential surface of the second end portion of the pipe body,

[0029] one of the pin portion contact surface and the box portion contact surface, i.e., a first contact surface, is formed with a plating layer,

[0030] the plating layer is formed with a solid lubricating layer,

[0031] the other of the pin portion contact surface and the box portion contact surface, i.e., a second contact surface, has an arithmetic mean deviation Ra of 0.5 to 10.0 μm,

[0032] the second contact surface is formed with a semisolid or liquid rust-preventive coating film.

[0033] Effects of the invention

[0034] The metal pipe for oil wells of the present embodiment can achieve both high yield torque and excellent wear resistance. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a graph showing the relationship between the number of revolutions of the metal pipe for oil wells and the torque when the metal pipe for oil wells is fastened.

[0036] Figure 2 is a structural diagram showing one example of the T&C type metal pipe for oil wells of the present embodiment.

[0037] Figure 3 is a graph showingFigure 2 is a partial cross-sectional view of a cross section parallel to the pipe axis direction of the coupling of the metal pipe for oil wells shown in FIG. 1.

[0038] Figure 4 is Figure 3 is a cross-sectional view of a portion near the pin end of the metal pipe for oil wells shown in FIG. 1.

[0039] Figure 5 is Figure 3 is a cross-sectional view of a portion near the box end of the metal pipe for oil wells shown in FIG. 1.

[0040] Figure 6 is a structural view of another T&C type metal pipe for oil wells different from Figure 2

[0041] Figure 7 is a structural view of the integrated metal pipe for oil wells according to the present embodiment.

[0042] Figure 8 is a cross-sectional view for explaining the structure on the first contact surface when the first contact surface is a box end contact surface.

[0043] Figure 9 is a cross-sectional view for explaining the structure on the second contact surface when the second contact surface is a pin end contact surface.

[0044] Figure 10 is Figure 9 is an enlarged view of a portion near the second contact surface Figure 9 which is a pin end contact surface.

[0045] Figure 11 is a cross-sectional view for explaining the structure on the first contact surface when the first contact surface is a pin end contact surface.

[0046] Figure 12 is a cross-sectional view for explaining the structure on the second contact surface when the second contact surface is a box end contact surface.

[0047] Figure 13 is a view showing the structure of the second contact surface including the chemical conversion treatment coating film when the second contact surface is a pin end contact surface.

[0048] Figure 14 is a torque curve diagram for explaining the yield torque measurement test in the example. DETAILED DESCRIPTION

[0049] Hereinafter, the present embodiment will be described in detail with reference to the drawings. Identical or equivalent portions in the drawings are designated by the same reference numerals, and will not be repeatedly described. ​

[0050] The present inventors and others have conducted various studies on oil well metal pipes that can achieve both high yield torque and excellent wear resistance. As a result, the following understanding has been obtained.

[0051] To improve the wear resistance of an oil well metal pipe during fastening, it is preferable to form a plating layer on either one of the contact surface of the pin end (hereinafter referred to as the pin end contact surface) and the contact surface of the box end (hereinafter referred to as the box end contact surface) (hereinafter referred to as the first contact surface), and to form a solid lubricating layer on the plating layer. The solid lubricating layer improves the wear resistance by lubrication. In addition, the plating layer also improves the wear resistance, and a plating layer having high hardness and a high melting point also improves the wear resistance during fastening. For this reason, the present inventors and others have considered that, with respect to one of the pin end contact surface and the box end contact surface, i.e., the first contact surface, it is preferable to form a plating layer and a solid lubricating layer in this order.

[0052] To maintain the wear resistance while improving the yield torque, the present inventors and others have also studied the structure of the other contact surface, i.e., the second contact surface, of the pin end contact surface and the box end contact surface when a plating layer and a solid lubricating layer are layered on one of the pin end contact surface and the box end contact surface, i.e., the first contact surface.

[0053] On the other hand, an oil well metal pipe is left exposed to the open air in a local yard near the oil well drilling site during the period from after the manufacture to before the use in actual oil well drilling. Therefore, the oil well metal pipe is required not only to have wear resistance but also to have a certain degree of corrosion resistance. For this reason, in the case where a solid lubricating layer is formed on the uppermost layer of the first contact surface of the pin end contact surface and the box end contact surface of the oil well metal pipe in the conventional oil well metal pipe, a well-known solid corrosion-resistant coating film composed of an ultraviolet-cured resin is sometimes formed on the uppermost layer of the second contact surface. However, the solid corrosion-resistant coating film does not have the effect of improving the yield torque.

[0054] For this reason, the present inventors and others have considered not using a solid corrosion-resistant coating film but improving the yield torque by increasing the friction coefficient during fastening by making the surface form (texture) of the second contact surface different from that of the conventional one. As a result of the study, it has been found that, if the second contact surface is made somewhat rough, a high friction coefficient can be obtained by the plating layer under the solid lubricating layer of the first contact surface and the unevenness of the second contact surface when the first contact surface and the second contact surface strongly contact each other during fastening, and as a result, the yield torque increases.

[0055] On the other hand, it is preferable to ensure corrosion resistance on the second contact surface to some extent. However, if a solid corrosion-resistant coating film that has been known heretofore is formed on the second contact surface that is roughened, the unevenness of the second contact surface cannot be reflected on the surface of the solid corrosion-resistant coating film, and the surface of the solid corrosion-resistant coating film is not as rough as the unevenness of the second contact surface.

[0056] To this end, the present inventors and others have considered forming a semisolid or liquid rust-resistant coating film on the second contact surface that is roughened, instead of a solid coating film. In the case where a semisolid or liquid rust-resistant coating film is formed on the roughened second contact surface, the rust resistance of the second contact surface can be ensured by the rust-resistant coating film, and at the same time, at the time of screw fastening, when the first contact surface and the second contact surface come into strong contact, the rust-resistant coating film is easily repelled at the contact portion thereof. As a result, a high coefficient of friction is obtained by the plating layer under the solid lubricating layer of the first contact surface and the unevenness of the second contact surface, and as a result, the yield torque increases.

[0057] The oil well metal pipe of the present embodiment that is completed on the basis of the above knowledge has the following features. [1]

[0059] An oil well metal pipe has:

[0060] a pipe main body including a first end portion and a second end portion,

[0061] the pipe main body includes:

[0062] a pin portion formed on the first end portion, and

[0063] a box portion formed on the second end portion,

[0064] the pin portion includes a pin portion contact surface,

[0065] the pin portion contact surface has at least an external thread portion formed on an outer circumferential surface of the first end portion of the pipe main body,

[0066] the box portion includes a box portion contact surface,

[0067] the box portion contact surface has at least an internal thread portion formed on an inner circumferential surface of the second end portion of the pipe main body,

[0068] a plating layer is formed on one of the pin portion contact surface and the box portion contact surface, i.e., a first contact surface,

[0069] a solid lubricating layer is formed on the plating layer,

[0070] an arithmetic mean deviation Ra of the other of the pin portion contact surface and the box portion contact surface, i.e., a second contact surface, is 0.5 to 10.0 μm,

[0071] A rust-preventive coating film in a semi-solid or liquid state is formed on the second contact surface. [2]

[0073] The metal pipe for oil wells according to [1], wherein

[0074] A chemical conversion treatment coating film is further formed on the second contact surface,

[0075] The rust-preventive coating film is formed on the chemical conversion treatment coating film. [3]

[0077] The metal pipe for oil wells according to [1] or [2], wherein

[0078] The second contact surface is subjected to jet cleaning. [4]

[0080] The metal pipe for oil wells according to any one of [1] to [3], wherein

[0081] The plating layer is composed of a Zn-Ni alloy.

[0082] The metal pipe for oil wells according to the present embodiment will be described below.

[0083] [Structure of Metal Pipe for Oil Wells]

[0084] Before the metal pipe for oil wells according to the present embodiment is described, the structure of the metal pipe for oil wells that is the object of the present embodiment will be described first. The metal pipe for oil wells has a T&C type metal pipe for oil wells and an integrated type metal pipe for oil wells. The metal pipe for oil wells of each type will be described below.

[0085] [When the Metal Pipe for Oil Wells 1 is of the T&C Type]

[0086] Figure 2 is a structural view showing one example of the metal pipe for oil wells 1 according to the present embodiment. Figure 2 is a structural view of a so-called T&C type (Threaded and Coupled) metal pipe for oil wells 1. Referring to Figure 2 , the metal pipe for oil wells 1 has a pipe main body 10.

[0087] The pipe main body 10 extends in the pipe axis direction. The cross section of the pipe main body 10 perpendicular to the pipe axis direction is circular. The pipe main body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is the end portion on the opposite side of the second end portion 10B. Figure 2In the illustrated T&C type oil well metal pipe 1, the pipe body 10 has a pin portion pipe body 11 and a coupling 12. The coupling 12 is attached to one end of the pin portion pipe body 11. More specifically, the coupling 12 is fastened to one end of the pin portion pipe body 11 by a thread.

[0088] Figure 3 is a partial cross-sectional view showing Figure 2 is a partial cross-sectional view showing a cross section (longitudinal cross section) of the coupling 12 of the illustrated oil well metal pipe 1 in a direction parallel to the pipe axis direction. Referring to Figure 2 and Figure 3 , the pipe body 10 includes a pin portion 40 and a box portion 50. The pin portion 40 is formed at a first end portion 10A of the pipe body 10. The pin portion 40 is inserted into a box portion of another oil well metal pipe (not shown) at the time of fastening, and is fastened to the box portion of the other oil well metal pipe by a thread.

[0089] The box portion 50 is formed at a second end portion 10B of the pipe body 10. The box portion 50 is inserted into a pin portion of another oil well metal pipe 1 at the time of fastening, and is fastened to the pin portion of the other oil well metal pipe 1 by a thread.

[0090] [Structure of the Pin Portion 40]

[0091] Figure 4 is Figure 3 is a cross-sectional view of a portion near the pin portion 40 of the illustrated oil well metal pipe 1 in a direction parallel to the pipe axis direction of the oil well metal pipe 1. Figure 4 The dashed portion in Figure 4 , the pin portion 40 has a pin portion contact surface 400 on an outer peripheral surface of the first end portion 10A. The pin portion contact surface 400 contacts a box portion contact surface 500 of the box portion 50 of the other oil well metal pipe 1 at the time of fastening to the other oil well metal pipe 1.

[0092] The pin portion contact surface 400 includes at least an external thread portion 41 formed on the outer peripheral surface of the first end portion 10A. The pin portion contact surface 400 can also include a pin portion sealing surface 42 and a pin portion shoulder surface 43. Figure 4 In , the pin portion sealing surface 42 is disposed on the outer peripheral surface of the first end portion 10A on a top end side of the first end portion 10A further than the external thread portion 41. That is, the pin portion sealing surface 42 is disposed between the external thread portion 41 and the pin portion shoulder surface 43. The pin portion sealing surface 42 is tapered. Specifically, the pin portion sealing surface 42 has an outer diameter that gradually decreases in a length direction (pipe axis direction) of the first end portion 10A from the external thread portion 41 toward the pin portion shoulder surface 43.

[0093] When fastened to other oil well metal pipes 1, the male thread sealing surface 42 contacts the female thread sealing surface 52 (described 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, the male thread 40 is further screwed into the female thread 50 of the other oil well metal pipe 1, and 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, forming a seal based on metal-to-metal contact. Therefore, airtightness can be improved in the mutually fastened oil well metal pipes 1.

[0094] Figure 4 In the middle, the male buckle shoulder surface 43 is disposed on the top surface of the first end portion 10A. That is, in Figure 4 In the male thread portion 40 shown, starting from the center of the pipe body 10 and moving towards the top of the first end portion 10A, an external thread portion 41, a male thread portion sealing surface 42, and a male thread portion shoulder surface 43 are arranged sequentially. When fastened with other oil well metal pipes 1, the male thread portion shoulder surface 43 faces and contacts the female thread portion shoulder surface 53 (described later) of the female thread portion 50 of the other oil well metal pipe 1. More specifically, during fastening, the male thread portion 40 is inserted into the female thread portion 50 of the other oil well metal pipe 1, thereby bringing the male thread portion shoulder surface 43 into contact with the female thread portion shoulder surface 53. As a result, high torque can be obtained during fastening. In addition, the positional relationship between the male thread portion 40 and the female thread portion 50 in the fastened state can be stabilized.

[0095] It should be noted that the male thread contact surface 400 of the male thread portion 40 at least includes the external thread portion 41. That is, the male thread contact surface 400 may include the external thread portion 41, but not the male thread sealing surface 42 and the male thread shoulder surface 43. The male thread contact surface 400 may include the external thread portion 41 and the male thread shoulder surface 43, but not the male thread sealing surface 42. The male thread contact surface 400 may include the external thread portion 41 and the male thread sealing surface 42, but not the male thread shoulder surface 43. For oil well metal pipes with the aforementioned wedge-shaped thread, the male thread portion 40 does not have the male thread shoulder surface 43. It should be noted that if the male thread portion 40 does not have the male thread shoulder surface 43, the female thread portion 50 does not have the female thread shoulder surface 53.

[0096] [Regarding the structure of the female fastener 50]

[0097] Figure 5 yes Figure 3 The cross-sectional view of the portion near the female threaded part 50 of the oil well metal pipe 1, which is parallel to the pipe axis direction of the oil well metal pipe 1. Figure 5 The dashed line in the diagram shows the structure of the male thread 40 of the other oil well metal pipe 1 when it is fastened to the other oil well metal pipe 1. See alsoFigure 5 The box portion 50 is provided with a box portion contact surface 500 on the inner peripheral surface of the second end portion 10B of the pipe body 10. When fastened to the other oil well metal pipe 1, the box portion contact surface 500 comes into contact with the pin portion contact surface 400 of the pin portion 40 of the other oil well metal pipe 1.

[0098] 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. When fastened, the internal thread portion 51 engages with the external thread portion 41 of the pin portion 40 of the other oil well metal pipe.

[0099] The box portion contact surface 500 can further include a box portion sealing surface 52 and a box portion shoulder surface 53. Figure 5 In the present embodiment, the box portion sealing surface 52 is disposed on the inner peripheral surface of the second end portion 10B on the pipe body 10 side further than the internal thread portion 51. That is, the box portion sealing surface 52 is disposed between the internal thread portion 51 and the box portion shoulder surface 53. The box portion sealing surface 52 is tapered. Specifically, the box portion sealing surface 52 is tapered such that the inner diameter gradually decreases toward the box portion shoulder surface 53 from the internal thread portion 51 in the length direction (pipe axis direction) of the second end portion 10B.

[0100] When fastened to the other oil well metal pipe 1, the box portion sealing surface 52 comes into contact with the pin portion sealing surface 42 of the pin portion 40 of the other oil well metal pipe 1. More specifically, when fastened, the pin portion 40 of the other oil well metal pipe 1 is screwed into the box portion 50, whereby the box portion sealing surface 52 comes into contact with the pin portion sealing surface 42; by further screwing, the box portion sealing surface 52 is brought into close contact with the pin portion sealing surface 42. Thus, when fastened, the box portion sealing surface 52 and the pin portion sealing surface 42 are brought into close contact to form a seal based on metal-to-metal contact. Therefore, in the oil well metal pipes 1 fastened to each other, the air tightness can be improved.

[0101] The box portion shoulder surface 53 is disposed on the pipe axis direction central side of the pipe body 10 further than the box portion sealing surface 52. That is, in the box portion 50, the box portion shoulder surface 53, the box portion sealing surface 52, and the internal thread portion 51 are disposed in this order from the pipe axis direction center of the pipe body 10 toward the top end of the second end portion 10B. When fastened to the other oil well metal pipe 1, the box portion shoulder surface 53 opposes and comes into contact with the pin portion shoulder surface 43 of the pin portion 40 of the other oil well metal pipe 1. More specifically, when fastened, the box portion shoulder surface 53 comes into contact with the pin portion shoulder surface 43 by inserting the pin portion 40 of the other oil well metal pipe 1 into the box portion 50. Thus, when fastened, a high torque can be obtained. In addition, the positional relationship of the pin portion 40 and the box portion 50 in the fastened state can be stabilized.

[0102] The female contact surface 500 includes at least the female internal thread portion 51. At the time of fastening, the female contact surface 500 of the female 50 contacts the male contact surface 400 of the male 40. The female sealing surface 52 contacts the male sealing surface 42. The female shoulder surface 53 contacts the male shoulder surface 43.

[0103] When the male contact surface 400 includes the male external thread portion 41 and the male shoulder surface 43 and does not include the male sealing surface 42, the female contact surface 500 includes the female internal thread portion 51 and the female shoulder surface 53 and does not include the female sealing surface 52. When the male contact surface 400 includes the male external thread portion 41 and the male sealing surface 42 and does not include the male shoulder surface 43, the female contact surface 500 includes the female internal thread portion 51 and the female sealing surface 52 and does not include the female shoulder surface 53.

[0104] The male contact surface 400 can include a plurality of male external thread portions 41, can include a plurality of male sealing surfaces 42, and can include a plurality of male shoulder surfaces 43. For example, the male contact surface 400 of the male 40 can be configured with the male shoulder surface 43, the male sealing surface 42, the male external thread portion 41, the male sealing surface 42, the male shoulder surface 43, and the male sealing surface 42 in this order from the top end of the first end portion 10A toward the center of the pipe body 10. In this case, the female contact surface 500 of the female 50 can be configured with the female internal thread portion 51, the female sealing surface 52, the female shoulder surface 53, the female sealing surface 52, the female internal thread portion 51, the female sealing surface 52, and the female shoulder surface 53 in this order from the top end of the second end portion 10B toward the center of the pipe body 10.

[0105] Figure 4 and Figure 5 The male 40 includes the male external thread portion 41, the male sealing surface 42, and the male shoulder surface 43, and the female 50 includes the female internal thread portion 51, the female sealing surface 52, and the female shoulder surface 53. However, as described above, the male 40 can include the male external thread portion 41 and does not include the male sealing surface 42 and the male shoulder surface 43. In this case, the female 50 includes the female internal thread portion 51 and does not include the female sealing surface 52 and the female shoulder surface 53. Figure 6is a drawing showing one example of the oil well metal pipe 1 in which the pin portion 40 includes the external thread portion 41 and does not include the pin portion sealing surface 42 and the pin portion shoulder surface 43, and the box portion 50 includes the internal thread portion 51 and does not include the box portion sealing surface 52 and the box portion shoulder surface 53.

[0106] [Oil well metal pipe 1 is integrated type]

[0107] Figure 2 Figure 3 Figure 6 The oil well metal pipe 1 shown in FIG. 1 is a so-called T&C type oil well metal pipe 1 in which the pipe body 10 includes the pin portion pipe body 11 and the coupling 12. However, the oil well metal pipe 1 of the present embodiment can not be a T&C type, but an integrated type.

[0108] Figure 7 is a structural drawing of the integrated type oil well metal pipe 1 provided by the present embodiment. Referring to Figure 7 , the integrated type oil well metal pipe 1 is provided with the 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 disposed on the opposite side of the second end portion 10B. As described above, in the T&C type oil well metal pipe 1, the pipe body 10 is provided with the pin portion pipe body 11 and the coupling 12. That is, in the T&C type oil well metal pipe 1, the pipe body 10 is constituted by fastening two independent components (the pin portion pipe body 11 and the coupling 12). In contrast, in the integrated type oil well metal pipe 1, the pipe body 10 is integrally formed.

[0109] The pin portion 40 is formed at the first end portion 10A of the pipe body 10. At the time of fastening, the pin portion 40 is inserted into the box portion 50 of the other integrated type oil well metal pipe 1 and screwed in, and is fastened to the box portion 50 of the other integrated type oil well metal pipe 1. The box portion 50 is formed at the second end portion 10B of the pipe body 10. At the time of fastening, the box portion 50 is inserted into the pin portion 40 of the other integrated type oil well metal pipe 1 and screwed in, and is fastened to the pin portion 40 of the other integrated type oil well metal pipe 1.

[0110] The structure of the pin portion 40 of the integrated type oil well metal pipe 1 is the same as that of the pin portion 40 of the T&C type oil well metal pipe 1 shown in FIG. 1. Similarly, the structure of the box portion 50 of the integrated type oil well metal pipe 1 is the same as that of the box portion 50 of the T&C type oil well metal pipe 1 shown in FIG. 1. Note that, Figure 4 Figure 5 Figure 7 ​​​​In the embodiment, on the pin portion 40, from the top end of the first end portion 10A toward the center of the pipe axis direction of the pipe body 10, a pin portion shoulder surface, a pin portion sealing surface, an external thread portion, a pin portion sealing surface, a pin portion shoulder surface, a pin portion sealing surface, and an external thread portion are arranged in this order. Therefore, on the box portion 50, from the top end of the second end portion 10B toward the center of the pipe axis direction of the pipe body 10, an internal thread portion, a box portion sealing surface, a box portion shoulder surface, a box portion sealing surface, an internal thread portion, a box portion sealing surface, and a box portion shoulder surface are arranged in this order. However, the pin portion contact surface 400 of the pin portion 40 of the integral type oil well metal pipe 1 can include at least the external thread portion 41. Also, the box portion contact surface 500 of the box portion 50 of the integral type oil well metal pipe 1 can include at least the internal thread portion 51. Figure 4 Similarly, the pin portion contact surface 400 of the pin portion 40 of the integral type oil well metal pipe 1 can include at least the external thread portion 41. Also, the box portion contact surface 500 of the box portion 50 of the integral type oil well metal pipe 1 can include at least the internal thread portion 51. Figure 5 Similarly, the pin portion contact surface 400 of the pin portion 40 of the integral type oil well metal pipe 1 can include at least the external thread portion 41. Also, the box portion contact surface 500 of the box portion 50 of the integral type oil well metal pipe 1 can include at least the internal thread portion 51.

[0111] In summary, the oil well metal pipe 1 of the embodiment can be a T&C type or an integral type.

[0112] The oil well metal pipe 1 can be a steel pipe composed of an Fe-based alloy or an alloy pipe typified by a Ni-based alloy pipe. The steel pipe is, for example, a low alloy steel pipe, a martensitic stainless steel pipe, a duplex stainless steel pipe, or the like.

[0113] [Structure on the Pin Portion Contact Surface 400 or the Box Portion Contact Surface 500]

[0114] In the oil well metal pipe 1 of the embodiment, a plating layer 60 is formed on one of the pin portion contact surface 400 and the box portion contact surface 500, i.e., a first contact surface, and a solid lubricating layer 70 is formed on the plating layer 60. Also, the arithmetic average deviation Ra of the other of the pin portion contact surface 400 and the box portion contact surface 500, i.e., a second contact surface, is 0.5 to 10.0 μm, and a semi-solid or liquid rust-preventive coating film 80 is formed on the second contact surface.

[0115] Hereinafter, the structure on the first contact surface and the structure on the second contact surface will be described when the first contact surface is the box portion contact surface 500 and the second contact surface is the pin portion contact surface 400. However, the structure on the first contact surface and the structure on the second contact surface are the same when the first contact surface is the pin portion contact surface 400 and the second contact surface is the box portion contact surface 500.

[0116] [Structure on the First Contact Surface]

[0117] Figure 8 is a cross-sectional view for explaining the structure on the first contact surface when the first contact surface is the box portion contact surface 500. Referring to Figure 8The plating layer 60 is formed on the first contact surface. Further, a solid lubricating layer 70 is formed on the plating layer 60. Hereinafter, the plating layer 60 and the solid lubricating layer 70 will be described.

[0118] [About the plating layer 60]

[0119] The kind of the plating layer 60 is not particularly limited. The plating layer 60 can be, for example, a Zn plating layer, a Ni plating layer, a Cu plating layer, a Zn-Ni alloy plating layer, a Zn-Co alloy plating layer, a Ni-W alloy plating layer, and a Cu-Sn-Zn alloy plating layer. The plating layer 60 can be formed by laminating a plurality of plating layers. For example, a Ni plating layer can be formed on the first contact surface, and a Zn-Ni plating layer can be further laminated on the Ni plating layer.

[0120] In the case where the plating layer 60 is a Cu-Sn-Zn alloy plating layer, the chemical composition of the Cu-Sn-Zn alloy coating film is, for example, 40 to 70 mass% of Cu, 20 to 50 mass% of Sn, 2 to 20 mass% of Zn, and the balance including impurities. In the case where the plating layer 60 is a Cu plating layer, the chemical composition of the Cu plating layer includes, for example, Cu and impurities.

[0121] It is preferable that the plating layer 60 be composed of a Zn alloy plating layer including one or more selected from the group consisting of Ni, Fe, Mg, and Mn, and Zn. These Zn alloy plating layers have high hardness and high melting points. Therefore, they exhibit excellent wear resistance. Further, Zn is a metal that is less noble than steel, which is the base material of the pipe body 10, and thus functions as a sacrificial corrosion protection. Therefore, in the case where the plating layer 60 is composed of a Zn alloy plating layer, the plating layer 60 exhibits not only wear resistance but also excellent corrosion resistance.

[0122] It is further preferable that the plating layer 60 be a Zn-Ni alloy plating layer. The Zn-Ni alloy plating layer is composed of a Zn-Ni alloy. The Zn-Ni alloy includes zinc (Zn) and nickel (Ni). The Zn-Ni alloy sometimes contains impurities. Here, the impurities of the Zn-Ni alloy mean substances other than Zn and Ni, and substances contained in the Zn-Ni alloy plating layer within a range that does not affect the effects of the present embodiment in the manufacturing process of the metal pipe for oil wells and the like. The Zn-Ni alloy has not only excellent corrosion resistance, as described above, but also high hardness and high melting points, and has excellent wear resistance.

[0123] In the Zn-Ni alloy plating layer, it is preferable to contain 10 to 20 mass% of Ni, based on 100 mass% of the total of Zn and Ni. The preferable lower limit of the Ni content in the Zn-Ni alloy plating layer is 11 mass%, and it is further preferable to be 12 mass%. The preferable upper limit of the Ni content in the Zn-Ni alloy plating layer is 18 mass%, and it is further preferable to be 16 mass%, and it is further preferable to be 15 mass%.

[0124] [Method for measuring chemical composition of Zn-Ni alloy plating layer]

[0125] When the plating layer 60 is a Zn-Ni alloy plating layer, the chemical composition of the plating layer 60 can be measured from the cross section of the plating layer using an energy dispersive X-ray (EDX) analysis device. In work management at the time of manufacture, it is preferable that the measurement be non-destructive and simple. For this reason, the measurement of the chemical composition of the Zn-Ni alloy plating layer can also be performed from the surface of the plating layer using, for example, a fluorescent X-ray analysis device. In this case, a standard sample of which the chemical composition is known in advance is used, and appropriate correction is performed.

[0126] [Thickness of the plating layer 60]

[0127] The thickness of the plating layer 60 is not particularly limited. The thickness of the plating layer 60 is, for example, 1 to 20 μm. When the thickness of the plating layer 60 is 1 μm or more, sufficient wear resistance can be obtained. On the other hand, even when the thickness of the plating layer 60 exceeds 20 μm, the above-mentioned effects are saturated. The lower limit of the thickness of the plating layer 60 is preferably 3 μm, and further preferably 5 μm. The upper limit of the thickness of the plating layer 60 is preferably 18 μm, and further preferably 15 μm.

[0128] The thickness of the plating layer 60 can be measured by the following method. A sample including the cross section of the plating layer 60 is collected. The thickness of the plating layer 60 is measured at any three points of the cross section of the plating layer 60. The arithmetic mean of the measured thicknesses is defined as the thickness (μm) of the plating layer 60. In addition to the above-mentioned method, the thickness of the plating layer 60 can also be measured from the surface of the plating layer using a fluorescent X-ray analysis device, as in the above-mentioned measurement of the chemical composition of the plating layer. In this case, a standard sample of which the chemical composition is known in advance is used, and appropriate correction is performed.

[0129] [Solid lubricating layer 70]

[0130] A solid lubricating layer 70 is further formed on the plating layer 60. The solid lubricating layer 70 improves the lubricity of the pin connection portion 40 and the box connection portion 50 of the oil well metal pipe 1 at the time of fastening. The solid lubricating layer 70 is a coating film that is solid at normal temperature (20°C ± 15°C).

[0131] In this specification, solid, semi-solid, and liquid are defined as follows, respectively. Solid means a state in which the shape is fixed at normal temperature, and the shape is maintained without deformation even when an external force is applied, or at least a part is broken. Semi-solid means a state in which the shape is maintained at normal temperature, but at least a part subjected to an external force is easily deformed without being broken when the external force is applied. In this specification, grease-like and semi-dry are included in semi-solid. Liquid means a state of a liquid. Note that a state in which a volatile component is evaporated from a liquid, and a non-volatile component having viscosity remains is equivalent to "semi-solid or liquid".

[0132] The solid lubricating layer 70 contains, for example, a solid lubricating powder and a binder as a base material. That is, the solid lubricating layer 70 is a layer composed of a heterogeneous coating film formed by binding the solid lubricating powder with the binder.

[0133] [Solid lubricating powder]

[0134] The solid lubricating powder refers to a powder exhibiting a lubricating action. The solid lubricating powder can use a known material conventionally used as a solid lubricant. As the solid lubricating powder, a material having no adverse effect on the environment is preferable.

[0135] The preferable solid lubricating powder contains, for example, one or more selected from the group consisting of molybdenum disulfide (MoS2), tungsten disulfide (WS2), graphite, boron nitride (BN), carbon black, polytetrafluoroethylene (PTFE) powder, and fluorinated graphite (CF X ). Molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are inorganic powders having a graphite-type crystal structure. The average particle diameter of the solid lubricating powder is not particularly limited. The average particle diameter of the solid lubricating powder is, for example, 0.5 to 15 μm.

[0136] The preferable mass ratio of the total amount of the solid lubricating powder to the total amount of the binder in the solid lubricating layer 70 is 0.3 to 0.9. When the mass ratio of the total amount of the solid lubricating powder to the total amount of the binder is 0.3 or more, the wear resistance of the solid lubricating layer 70 is further improved. When the mass ratio of the total amount of the solid lubricating powder to the total amount of the binder is 0.9 or less, the adhesion of the solid lubricating layer 70 is further improved, and the strength of the solid lubricating layer 70 is further improved.

[0137] The solid lubricating layer 70 can further contain a powder other than the solid lubricating powder. The solid lubricating layer 70 contains, for example, the solid lubricating powder and silica. The other powder is, for example, an inorganic powder having no graphite-type crystal structure. When the solid lubricating layer 70 contains the solid lubricating powder and the other powder, the preferable mass ratio of the total amount of the solid lubricating powder and the other powder to the total amount of the binder is 0.9 or less.

[0138] [Binder]

[0139] The binder in the solid lubricating layer 70 is composed of an organic resin and / or an inorganic high molecular compound.

[0140] The organic resin as the binder preferably has heat resistance, moderate hardness, and moderate abrasion resistance. The organic resin as the binder is composed of, for example, one or more selected from the group consisting of thermosetting resins and thermoplastic resins. The organic resin is composed of one or more selected from the group consisting of epoxy resins, polyimide resins, polyamide-imide resins, polycarbodiimide resins, polyether sulfone, polyether ether ketone, phenol-aldehyde resins, furan resins, polyvinyl resins, acrylic resins, polyurethane resins, polyethylene resins, silicone resins, and fluorine resins.

[0141] From the viewpoint of improving the adhesion of the solid lubricating layer 70, a raw material of the solid lubricating layer 70, a liquid composition containing a solid lubricating powder and a binder (hereinafter also referred to as an organic liquid composition) can be subjected to a heat curing treatment to form the solid lubricating layer 70. The temperature of the heat curing treatment is preferably 80°C or higher, and further preferably 150 to 380°C. The treatment time is preferably 5 minutes or longer, and further preferably 20 to 60 minutes. The heat curing treatment can include a pre-drying step and a baking step. In the pre-drying step, it is held at 80 to 100°C for 2 to 15 minutes. The baking step is performed after the pre-drying step. In the baking step, it is held at 150 to 380°C for 10 to 50 minutes.

[0142] The inorganic high molecular compound as the binder is, for example, a compound having a three-dimensionally crosslinked structure of metal-oxygen bonds such as Ti-O, Si-O, Zr-O, Mn-O, Ce-O, and Ba-O. Such an inorganic high molecular compound can be formed by hydrolysis and condensation of a hydrolyzable metal compound such as a metal alkoxide or a metal chloride. The inorganic high molecular compound can be formed using a hydrolyzable metal compound containing a functional group such as an amine group, an epoxy group, or the like. The hydrolyzable metal compound containing a functional group such as an amine group, an epoxy group, or the like is, for example, a silane coupling agent or a titanate coupling agent.

[0143] The solid lubricating layer 70 containing the inorganic high molecular compound as the binder is formed, for example, by the following method. A liquid composition containing a solvent of a hydrolyzable metal compound or a partial hydrolyzate thereof and a solid lubricating powder (hereinafter referred to as an inorganic liquid composition) is applied to the plating layer 60. The applied liquid composition is subjected to a humidity treatment and / or a heat treatment. Through the above procedures, the solid lubricating layer 70 containing the inorganic high molecular compound as the binder is formed.

[0144] As described above, in order to promote the hydrolysis of the hydrolysable metal compound, a humidification treatment can be performed. In the humidification treatment, the coated liquid composition is left in the atmosphere, preferably in a humidified atmosphere having a relative humidity of 70% or more, for a prescribed period of time. The heating is preferably performed after the humidification treatment. By the heating, the hydrolysis of the metal compound and the condensation of the resulting hydrolysate are promoted, and the discharge of the by-products of the hydrolysis (alcohol when the metal compound is a metal alkoxide) and the condensation (water) is promoted. As a result, the solid lubricating layer 70 can be formed in a short period of time. In addition, by the heating after the humidification treatment, the adhesion of the solid lubricating layer 70 formed becomes strong. The heating after the humidification treatment is preferably performed after the evaporation of the solvent remaining in the coating film. The heating temperature at the time of the heating after the humidification treatment is preferably a temperature of 50 to 200°C close to the boiling point of the by-product alcohol. The heating in a hot-air oven is more effective.

[0145] The thickness of the solid lubricating layer 70 is 3 to 50 μm. The preferable thickness of the solid lubricating layer 70 is 10 to 40 μm. When the thickness of the solid lubricating layer 70 is 10 μm or more, the high lubricity can be further stably obtained. On the other hand, when the thickness of the solid lubricating layer 70 is 40 μm or less, the adhesion of the solid lubricating layer 70 further stabilizes. When the thickness of the solid lubricating layer 70 is 40 μm or less, the thread tolerance (clearance) of the sliding surface further increases. In this case, the surface pressure at the time of sliding decreases. Therefore, the excessive increase in the fastening torque can be suppressed. Therefore, the preferable thickness of the solid lubricating layer 70 is 10 to 40 μm. The further preferable lower limit of the thickness of the solid lubricating layer 70 is 15 μm, and the further preferable upper limit is 30 μm.

[0146] The thickness of the solid lubricating layer 70 is measured by the following method. A sample including the first contact surface on which the solid lubricating layer 70 is formed is collected. Of the surface of the sample, one surface corresponds to a cross section perpendicular to the axial direction (lengthwise direction) of the metal pipe for oil wells. Hereinafter, this cross section is referred to as an observation surface. In the observation surface, the region including the solid lubricating layer 70 is subjected to microscopic observation. The magnification of the microscopic observation is 500 times. In any 10 fields of view, the thickness of the solid lubricating layer 70 is found. In each field of view, the thickness of the solid lubricating layer 70 is measured at any 3 sites. The arithmetic mean of the thickness of the solid lubricating layer 70 in the 10 fields of view (30 in total) is defined as the thickness of the solid lubricating layer 70 (μm).

[0147] [Structure on the second contact surface]

[0148] Figure 9 is a cross-sectional view for illustrating the structure on the second contact surface when the second contact surface is the pin portion contact surface 300. Referring to Figure 9The arithmetic mean deviation Ra of the second contact surface is 0.5–10.0 μm. And on the second contact surface ( Figure 9 A semi-solid or liquid anti-rust coating 80 is formed on the male contact surface 400. The arithmetic mean deviation Ra of the second contact surface and the anti-rust coating 80 will be explained below.

[0149] [Arithmetic mean deviation Ra of the second contact surface]

[0150] Second contact surface ( Figure 9 The arithmetic mean deviation Ra of the male thread contact surface (400) was determined using the arithmetic mean deviation measurement method specified in JIS B 0601 (2013). Specifically, on the second contact surface, 10 arbitrary locations were selected as measurement locations along the extension direction of the thread teeth (thread cutting direction). At each measurement location, the arithmetic mean deviation Ra was measured using an evaluation length extending along the pipe axis. The evaluation length was 5 times the reference length (cutoff wavelength). The arithmetic mean deviation Ra was measured using a stylus-type roughness gauge at a measurement speed of 0.5 mm / second. Among the 10 arithmetic mean deviations Ra obtained, the largest, second largest, smallest, and second smallest arithmetic mean deviations Ra were removed, and the arithmetic mean of the remaining 6 arithmetic mean deviations Ra was defined as the arithmetic mean deviation Ra. The contact-type roughness gauge was, for example, the SURFTEST SJ-301 (trade name) surface roughness measuring instrument manufactured by Mitutoyo Co., Ltd.

[0151] The arithmetic mean deviation of the second contact surface after thread cutting is less than 0.1 μm. If the arithmetic mean deviation Ra of the second contact surface is 0.5–10.0 μm, the second contact surface can be roughened by performing a surface treatment. Such surface treatment is, for example, blasting.

[0152] Preferably, the second contact surface is subjected to blasting cleaning. Blasting cleaning refers to a process in which abrasive material (abrasive) is impacted onto the second contact surface using a blasting device. Blasting cleaning includes, for example, sandblasting, shot blasting, or edge-peening. Blasting cleaning involves mixing abrasive material (abrasive) with compressed air and projecting it onto the second contact surface. By adjusting the abrasive material used in blasting cleaning and the projection speed, the roughness of the second contact surface can be appropriately set.

[0153] [Rust-proof coating 80]

[0154] A rust-preventive coating 80 is formed on the second contact surface. The rust-preventive coating 80 is semi-solid or liquid at room temperature (20℃±15℃).

[0155] Figure 10 yes Figure 9The second contact surface (here, the male screw contact surface 400) is formed with minute irregularities having an arithmetic mean deviation Ra of 0.5 to 10 μm. By the irregularities, the coefficient of friction of the male screw contact surface 400 and the female screw contact surface 500 is increased at the time of tightening, and the yield torque is increased. Figure 9 An enlarged view of a portion near the male screw contact surface 400. Referring to FIG. 4, the second contact surface (here, the male screw contact surface 400) is formed with minute irregularities having an arithmetic mean deviation Ra of 0.5 to 10 μm. By the irregularities, the coefficient of friction of the male screw contact surface 400 and the female screw contact surface 500 is increased at the time of tightening, and the yield torque is increased. Figure 10

[0156] [Type of rust-preventive coating 80]

[0157] The rust-preventive coating 80 can be any one of the following two types.

[0158] (A) Liquid rust-preventive coating

[0159] (B) Semi-solid rust-preventive coating

[0160] The liquid rust-preventive coating and the semi-solid rust-preventive coating will be described below.

[0161] [Regarding (A) Liquid rust-preventive coating]

[0162] The liquid rust-preventive coating is a rust-preventive coating in a liquid state. Here, the liquid state means a state of a liquid. Note that a state in which a volatile component in a liquid is evaporated and a non-volatile component having viscosity remains is also equivalent to the "liquid state". The liquid rust-preventive coating can be formed by applying a commercially available rust-preventive lubricant also called light oil such as WD-40 (trade name). The chemical composition of the liquid rust-preventive coating contains, for example, 50 to 75% by mass of mineral spirit and 25% by mass or less of petroleum-based oil.

[0163] [Mineral spirit]

[0164] The mineral spirit is a solvent equivalent to Industrial Spirit No. 4 specified in JIS K 2201 (1991). The lower limit of the content of the mineral spirit is preferably 52% by mass, further preferably 54% by mass, further preferably 56% by mass, further preferably 58% by mass. The upper limit of the content of the mineral spirit is preferably 70% by mass, further preferably 68% by mass, further preferably 66% by mass, further preferably 64% by mass, further preferably 62% by mass.

[0165] [Petroleum-based oil]

[0166] ​The petroleum oil is an oil obtained by purifying crude oil. The petroleum oil is composed of, for example, one or two or more selected from the group consisting of paraffin oil, naphthene oil, and aromatic oil. The lower limit of the content of the petroleum oil is preferably 2% by mass, further preferably 4%, further preferably 6%, further preferably 8%. The upper limit of the content of the petroleum oil is preferably 22% by mass, further preferably 20%, further preferably 18%, further preferably 16%.

[0167] [Anti-rust additive]

[0168] The anti-rust coating film 80 can contain an anti-rust additive in addition to the mineral oil and the petroleum oil. The anti-rust additive is a general term for additives having corrosion resistance. The anti-rust additive contains, for example, one or two or more selected from the group consisting of aluminum tripolyphosphate, aluminum phosphite, and calcium ion-exchanged silica. It is preferable that the anti-rust additive contain at least one selected from the group consisting of calcium ion-exchanged silica and aluminum phosphite. As the anti-rust additive, a publicly known (commercially available) reaction water repellent can also be contained.

[0169] The content of the anti-rust additive in the anti-rust coating film 80 is preferably 10% by mass or less. The upper limit of the anti-rust additive in the anti-rust coating film 80 is preferably 9%, further preferably 8%, further preferably 5%. The lower limit of the anti-rust additive in the anti-rust coating film 80 is preferably 2%, further preferably 3%. Note that the anti-rust coating film 80 can not contain the above-described anti-rust additive. That is, the chemical composition of the anti-rust coating film 80 can be such that the mineral oil and the petroleum oil are contained, and the balance is impurities.

[0170] Note that the anti-rust coating film 80 does not substantially contain heavy metal powder. That is, in the anti-rust coating film 80, heavy metals are impurities. The heavy metal powder is, for example, Pb, Cu, Zn, or the like. The anti-rust coating film 80 also does not contain a chlorine-based compound. Therefore, the metal pipe for oil wells of the present embodiment can be used in offshore oil wells in which the use of greases and the like containing heavy metals and chlorine-based compounds is prohibited.

[0171] [About the (B) semi-solid anti-rust coating film]

[0172] The semi-solid anti-rust coating film is an anti-rust coating film that, although maintaining a certain shape at ordinary temperature, is easily deformed in a state in which at least the portion subjected to external force is not broken (cracks are not generated) when an external force is applied. The semi-solid anti-rust coating film can be greasy or semi-dry.

[0173] The chemical composition of the semi-solid anti-rust coating film is, for example, 20 to 30% by mass of purified mineral oil, 8 to 13% by mass of petroleum wax, 3 to 5% by mass of graphite, and 5 to 10% by mass of rosin, and the balance is calcium sulfonate and impurities.

[0174] The purified mineral oil is a hydrocarbon compound obtained by purifying petroleum, natural gas, etc. The petroleum-based wax is a wax collected from petroleum. The wax is an organic substance that is solid at ordinary temperature and becomes liquid by heating. The rosin is a resin obtained by removing turpentine from pine resin by steam distillation.

[0175] Note that the semi-solid rust-preventive coating film can be a publicly known yellow paint or a publicly known green paint.

[0176] The rust-preventive coating film 80 is semi-solid or liquid. Therefore, when the rust-preventive coating film 80 is formed on the second contact surface, a special device is not generally required as compared with when a solid coating film is formed. Depending on the properties and specifications of the rust-preventive coating film 80, heating drying can be performed.

[0177] The rust-preventive coating film 80 formed on the second contact surface is semi-solid or liquid. When the metal pipe for oil wells is fastened, the semi-solid or liquid rust-preventive coating film 80 deforms or flows along with the fastening. As a result, the surface roughness of the rust-preventive coating film 80 formed on the second contact surface is substantially the same as the surface roughness of the second contact surface.

[0178] Note that the second contact surface is not provided with a plating layer. When a plating layer is formed on the second contact surface that is roughened and the rust-preventive coating film 80 is further formed on the formed plating layer, the unevenness of the second contact surface is not reflected on the surface of the plating layer. That is, the surface roughness of the plating layer is smaller than the surface roughness of the second contact surface. Therefore, the yield torque cannot be sufficiently increased at the time of fastening. In addition, if the plating layer is formed on the second contact surface, the surface of the plating layer is roughened, and then the rust-preventive coating film 80 is formed, the production cost increases. Therefore, in the metal pipe for oil wells of the present embodiment, the second contact surface is not provided with a plating layer.

[0179] [When the pin contact surface is the first contact surface and the box contact surface is the second contact surface]

[0180] In the above description, the structure of the first and second contact surfaces has been described with the box contact surface 500 as the first contact surface and the pin contact surface 400 as the second contact surface. However, as described above, the pin contact surface 400 can also be the first contact surface and the box contact surface 500 can also be the second contact surface. In this case, as shown in FIG. 6, a plating layer 60 is formed on the pin contact surface 400 (the first contact surface), and a solid lubricating layer 70 is formed on the plating layer 60. In addition, as shown in FIG. 7, the surface of the box contact surface 500 (the second contact surface) is roughened, and the arithmetic mean deviation Ra of the box contact surface 500 is 0.5 to 10.0 μm. Furthermore, a rust-preventive coating film 80 is formed on the box contact surface 500. Figure 11 Figure 12 In the above description, the structure of the first and second contact surfaces has been described with the box contact surface 500 as the first contact surface and the pin contact surface 400 as the second contact surface. However, as described above, the pin contact surface 400 can also be the first contact surface and the box contact surface 500 can also be the second contact surface. In this case, as shown in FIG. 6, a plating layer 60 is formed on the pin contact surface 400 (the first contact surface), and a solid lubricating layer 70 is formed on the plating layer 60. In addition, as shown in FIG. 7, the surface of the box contact surface 500 (the second contact surface) is roughened, and the arithmetic mean deviation Ra of the box contact surface 500 is 0.5 to 10.0 μm. Furthermore, a rust-preventive coating film 80 is formed on the box contact surface 500.​

[0181] As described above, in the oil well metal pipe 1 of the present embodiment, a plating layer 60 is formed on one of the pin contact surface 400 and the box contact surface 500, i.e., a first contact surface, and a solid lubricating layer 70 is formed on the plating layer 60. Also, a second contact surface opposite to the first contact surface at the time of fastening is roughened, and the arithmetic mean deviation Ra of the second contact surface is 0.5 to 10.0 μm. Also, on the second contact surface roughened, a semisolid or liquid rust-preventive coating film 80 is formed. By the plating layer 60 and the solid lubricating layer 70 of the first contact surface, the wear resistance at the time of fastening can be improved. Further, in the case where the semisolid or liquid rust-preventive coating film 80 is formed on the second contact surface roughened, a high friction coefficient can be obtained by the plating layer 60 under the solid lubricating layer 70 of the first contact surface and the irregularities of the second contact surface. As a result, the yield torque is increased.

[0182] [About the chemical conversion treatment coating film 90 formed on the second contact surface]

[0183] The second contact surface of the oil well metal pipe 1 of the present embodiment can also be such that a chemical conversion treatment coating film is formed on the second contact surface, and a rust-preventive coating film 80 is formed on the chemical conversion treatment coating film. Figure 13 is a view showing the structure of the second contact surface including the chemical conversion treatment coating film 90 when the second contact surface is the pin contact surface 400. Referring to Figure 13 On the second contact surface whose roughness is adjusted to the range of the arithmetic mean deviation Ra = 0.5 to 10.0 μm, a chemical conversion treatment coating film 90 is formed, and a rust-preventive coating film 80 is formed on the chemical conversion treatment coating film 90. At this time, the chemical conversion treatment coating film 90 is formed in contact with the second contact surface, and the rust-preventive coating film 80 is formed in contact with the chemical conversion treatment coating film 90.

[0184] The chemical conversion treatment coating film 90 is composed of, for example, one or more selected from the group consisting of a phosphate chemical conversion treatment coating film, an oxalate chemical conversion treatment coating film, and a borate chemical conversion treatment coating film. It is preferable that the chemical conversion treatment coating film 90 be a phosphate chemical conversion treatment coating film.

[0185] The chemical conversion treatment coating film 90 is porous. Therefore, if the rust-preventive coating film 80 is formed on the chemical conversion treatment coating film 90, the adhesion (retention) of the rust-preventive coating film 80 on the second contact surface is improved by so-called "anchoring effect". In this case, the corrosion resistance of the second contact surface is improved. The thickness of the chemical conversion treatment coating film 90 is not particularly limited. The preferable thickness of the chemical conversion treatment coating film 90 is 5 to 40 μm. When the thickness of the chemical conversion treatment coating film 90 is 5 μm or more, the corrosion resistance is further improved. When the thickness of the chemical conversion treatment coating film is 40 μm or less, the adhesion of the rust-preventive coating film 80 is further stably improved.

[0186] Note that, Figure 13 The case where the second contact surface is the pin portion contact surface 400 is shown in FIG. 4. However, even if the second contact surface is the box portion contact surface 500, the chemical conversion treatment coating film 90 can be formed on the second contact surface, and the rust-preventive coating film 80 can be formed on the chemical conversion treatment coating film 90.

[0187] Note that, the rust-preventive coating film 80 can also be formed directly on the second contact surface, and the chemical conversion treatment coating film 90 can also not be formed on the second contact surface. Preferably, when the Cr content in the chemical composition of the oil well metal pipe 1 is 1.00% or less by mass, the chemical conversion treatment coating film 90 is formed on the second contact surface, and the rust-preventive coating film 80 is formed on the chemical conversion treatment coating film 90. When the Cr content in the chemical composition of the oil well metal pipe 1 is 1.00% or less by mass, the base material itself of the oil well metal pipe 1 has low corrosion resistance. When the Cr content in the chemical composition of the oil well metal pipe 1 is 1.00% or less by mass, if the chemical conversion treatment coating film 90 is formed on the second contact surface, and the rust-preventive coating film 80 is formed on the chemical conversion treatment coating film 90, the corrosion resistance of the second contact surface can be improved.

[0188] [Manufacturing Process]

[0189] One example of the manufacturing method of the oil well metal pipe of the present embodiment having the above structure will be described. Note that, the manufacturing method described below is one example of the manufacturing method of the oil well metal pipe of the present embodiment. Therefore, the manufacturing method is not particularly limited as long as the oil well metal pipe of the present embodiment can be manufactured. The manufacturing method described below is one preferable example of manufacturing the oil well metal pipe of the present embodiment.

[0190] The manufacturing method of the oil well metal pipe of the present embodiment includes: a process of preparing a threaded pipe blank (threaded pipe blank preparation process); a process of forming a plating layer 60 on a first contact surface (plating layer formation process); a process of forming a solid lubricating layer 70 on the plating layer 60 (solid lubricating layer formation process); a process of adjusting the surface roughness of a second contact surface (second contact surface roughness adjustment process); and a process of forming a rust-preventive coating film on the second contact surface whose roughness has been adjusted (rust-preventive coating film formation process). Each process will be described in detail below.

[0191] [Threaded pipe blank preparation process]

[0192] In the pipe blank preparation process, a threaded joint pipe blank is prepared. Here, the threaded joint pipe blank refers to the pipe body 10. When the oil well metal pipe is of the T&C type, the pipe body 10 includes the pin portion pipe body 11 and the coupling 12. When the oil well metal pipe is of the integrated type, the pipe body 10 is formed integrally.

[0193] The pipe body 10 can be prepared using a product provided by a third party, or the pipe body 10 can be manufactured. In the case of manufacturing the pipe body 10, for example, the following method is used.

[0194] A billet is manufactured from molten steel. Specifically, a cast blank (slab, bloom, or billet) is manufactured from molten steel by continuous casting. A ingot can also be manufactured from molten steel by ingot casting. As necessary, the slab, bloom, or ingot can be roughed to manufacture a steel billet (billet). The billet (slab, bloom, or billet) is manufactured by the above process. The prepared billet is subjected to hot working to manufacture a pipe blank. The hot working method can be piercing based on the Mannesmann method, or a hot extrusion method. The pipe blank after hot working is subjected to known quenching and known tempering to adjust the strength of the pipe blank. The pipe blank is manufactured by the above process. Note that when the oil well metal pipe is of the T&C type, a pipe blank for the coupling 12 is also prepared. The manufacturing method of the pipe blank for the coupling 12 is the same as the manufacturing method of the pipe blank described above.

[0195] When the oil well metal pipe is of the T&C type, the outer surface of both end portions of the pipe blank for the pin portion pipe body 11 is subjected to thread cutting processing to form a pin portion contact surface 400. In addition, the inner surface of both end portions of the pipe blank for the coupling 12 is subjected to thread cutting processing to form a box portion contact surface 500. The pin portion of one end of the pipe blank for the pin portion pipe body 11 is inserted into the box portion of one end of the pipe blank for the coupling 12 and screwed in. The pipe body including the pin portion pipe body 11 and the coupling 12 (threaded joint pipe blank) is manufactured by the above process.

[0196] When the oil well metal pipe is of the integrated type, the outer surface of the first end portion 10A of the pipe blank corresponding to the pipe body 10 is subjected to thread cutting processing to form a pin portion contact surface 400. In addition, the outer surface of the second end portion 10B of the pipe blank corresponding to the pipe body 10 is subjected to thread cutting processing to form a box portion contact surface 500. The pipe body 10 including the pin portion and the box portion (threaded joint pipe blank) is prepared by the above process.

[0197] [Plating layer forming process]

[0198] A plating layer 60 is formed on one of the pin portion contact surface 400 and the box portion contact surface 500 of the prepared pipe body, i.e., the first contact surface. The formation of the plating layer 60 can be performed using a known method. The formation of the plating layer 60 can be performed using an electroplating method, or a chemical plating method.

[0199] For example, when the plating layer 60 composed of a Zn-Ni alloy is formed by an electroplating method, a plating bath contains zinc ions and nickel ions. The composition of the plating bath is preferably 1 to 100 g / L of zinc ions and 1 to 50 g / L of nickel ions. The conditions of the electroplating method are, for example, 1 to 10 of the pH of the plating bath, 25 to 80°C of the temperature of the plating bath, 1 to 100 A / dm2of the current density, and 0.1 to 30 minutes of the processing time. For example, when the plating layer 60 composed of a Cu-Sn-Zn alloy is formed by an electroplating method, a plating bath contains 1 to 50 g / L of copper ions, 1 to 50 g / L of tin ions, and 1 to 50 g / L of zinc ions. The conditions of the electroplating can be the same as those described above for forming the plating layer 60 composed of a Zn-Ni alloy. When the plating layer 60 is composed of Cu or a Cu alloy, it can be manufactured by a known method. 2 For example, when the plating layer 60 composed of a Zn-Ni alloy is formed by an electroplating method, a plating bath contains zinc ions and nickel ions. The composition of the plating bath is preferably 1 to 100 g / L of zinc ions and 1 to 50 g / L of nickel ions. The conditions of the electroplating method are, for example, 1 to 10 of the pH of the plating bath, 25 to 80°C of the temperature of the plating bath, 1 to 100 A / dm

[0200] [Formation of solid lubricating layer]

[0201] In the formation of solid lubricating layer, a solid lubricating layer 70 is formed on the plating layer 60. The formation of solid lubricating layer includes a coating step and a curing step.

[0202] [Coating step]

[0203] In the coating step, a composition for forming the solid lubricating layer 70 on the plating layer 60 is coated on the plating layer 60 by a known method.

[0204] For example, when the composition is the above-described organic liquid composition, the organic liquid composition is coated on the first contact surface by spraying. In this case, the viscosity of the organic liquid composition is adjusted to be sprayable in a normal temperature and pressure environment. The coating method can also be brush coating and dipping, etc. instead of spraying. The same applies when the composition is the above-described inorganic liquid composition.

[0205] [Curing step]

[0206] When the composition is the organic liquid composition, in the curing step, the coated organic liquid composition is cured to form the solid lubricating layer 70. The solid lubricating layer 70 is formed by drying and / or heat curing the coating resin solution coated on the plating layer 60. The drying and / or heat curing can be performed by a known method according to the type of the binder. The preferred conditions are as described above. When the composition is the inorganic liquid composition, in the curing step, the inorganic liquid composition is subjected to the above-described humidification treatment and / or heat treatment.

[0207] By performing the above-described coating step and curing step, the solid lubricating layer 70 is formed on the plating layer 60.

[0208] [Second contact surface roughness adjustment step]

[0209] In the second contact surface roughness adjustment step, the surface roughness of the second contact surface among the pin contact surface 400 and the box contact surface 500 of the pipe body 10 is adjusted so that the arithmetic average deviation Ra of the second contact surface is 0.5 to 10.0 μm.

[0210] The adjustment of the surface roughness is, for example, the implementation of blasting.

[0211] [blasting]

[0212] The blasting is a process of making the surface rough by impinging the second contact surface with a blasting material (abrasive) using a blasting device. The blasting is, for example, a sandblasting process. The sandblasting process is a process of mixing a blasting material (abrasive) with compressed air and projecting the mixture to the second contact surface. The blasting material is, for example, a spherical bead material and an angular sand material. The sandblasting process can be implemented by a known method. For example, the compressed air is compressed by a compressor and mixed with the blasting material. The material of the blasting material is, for example, stainless steel, aluminum, ceramic, and alumina, etc. The conditions such as the projection speed of the sandblasting process can be appropriately set. By appropriately selecting the blasting material of the blasting and appropriately adjusting the conditions such as the projection speed in the blasting, the arithmetic average deviation Ra of the second contact surface can be adjusted to 0.5 to 10.0 μm.

[0213] [anti-rust coating film forming step]

[0214] In the anti-rust coating film forming step, an anti-rust lubricant for forming a semi-solid or liquid anti-rust coating film is applied to the second contact surface of the pipe body 10 after the second contact surface roughness adjustment step. The anti-rust coating film is not a solid but a semi-solid or liquid. Therefore, if the anti-rust lubricant in a semi-solid or liquid state is applied to the second contact surface, the semi-solid or liquid anti-rust coating film can be easily formed. The method of applying the anti-rust lubricant in a semi-solid or liquid state is not particularly limited as long as the anti-rust coating film can be formed on the second contact surface. For example, the anti-rust lubricant can be applied by spraying. The anti-rust lubricant can also be applied by brushing. The anti-rust lubricant can also be applied to the second contact surface to form the anti-rust coating film by other known methods.

[0215] [optional step]

[0216] [chemical conversion treatment coating film forming step]

[0217] In the case where the chemical conversion treatment coating film 90 is formed on the second contact surface, the chemical conversion treatment coating film forming step can be implemented after the second contact surface roughness adjustment step and before the anti-rust coating film forming step. That is, the chemical conversion treatment coating film forming step is an optional step and can not be implemented.

[0218] In the case where the chemical conversion treatment coating film formation step is performed, a publicly known chemical conversion treatment is performed in the chemical conversion treatment coating film formation step to form a chemical conversion treatment coating film 90 on the second contact surface after the roughness adjustment. The chemical conversion treatment can be performed by a publicly known method. As the treatment liquid, a conventional chemical conversion treatment liquid can be used. For example, in the case where the chemical conversion treatment coating film 90 is a phosphate chemical conversion treatment coating film, a zinc phosphate 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 exemplified. As the chemical conversion treatment, a manganese phosphate chemical conversion treatment liquid can also be used. The liquid temperature is, for example, normal temperature to 100°C. The treatment time can be appropriately set according to the desired film thickness, and is, for example, 5 to 20 minutes. In order to promote the formation of the chemical conversion treatment coating film, surface adjustment can be performed before the chemical conversion treatment. The surface adjustment refers to a treatment of immersion in a surface adjustment aqueous solution containing colloidal titanium. After the chemical conversion treatment, drying is preferably performed after water washing or hot water washing.

[0219] By the above manufacturing procedure, the oil well metal pipe of the present embodiment can be manufactured.

[0220] Example

[0221] Hereinafter, examples will be described. The oil well metal pipe of the present embodiment is not limited to the examples. In the examples, % means mass % unless otherwise specified.

[0222] [Example 1]

[0223] Oil well metal pipes of various structures were prepared. Using the prepared oil well metal pipes, the following tests were performed to measure the yield torque (ft·lb). First, oil well metal pipes as shown in Table 1 were prepared.

[0224] [Table 1]

[0225] Table 1

[0226]

[0227] The oil well metal pipes of Test Nos. 11 to 16 had an outer diameter of 7 inches (177.80 mm) and a wall thickness of 10.36 mm. The chemical composition of the oil well metal pipes was equivalent to L80 prescribed by API-5CT.

[0228] In Test Nos. 11 to 16, the first contact surface was provided as the female coupling portion contact surface, and the second contact surface was provided as the male coupling portion contact surface. A Zn-Ni alloy plating layer was formed on the first contact surface in each of the Test Nos. The first contact surface was immersed in a plating solution to perform electroplating, thereby forming a Zn-Ni alloy plating layer on the first contact surface. The Zn-Ni alloy plating solution was a product of DAIN ZIN ALLOY N2-PL manufactured by DAINICHI KASEI CO., LTD. The chemical composition of the Zn-Ni alloy plating layer formed by the above procedure was a chemical composition containing 10 to 16 mass% of Ni and the balance of Zn in all the Test Nos. Note that the thickness of the Zn-Ni alloy plating layer in each of the Test Nos. was in the range of 5 to 15 μm.

[0229] Further, a solid lubricating layer was formed on the Zn-Ni alloy plating layer. Specifically, an organic liquid composition was applied to the Zn-Ni alloy plating layer. The organic liquid composition contained an epoxy resin, pure water, ethylene glycol mono-n-butyl ether, isopropyl alcohol, 1-butanol, and PTFE particles. After the organic liquid composition was sprayed on the Zn-Ni alloy plating layer, a publicly known curing treatment was performed to form a solid lubricating layer. Specifically, as the curing treatment, pre-drying (10 minutes at 85°C) and baking (20 minutes at 210°C) were performed. The average film thickness of the obtained solid lubricating layer was in the range of 20 to 30 μm in all the Test Nos.

[0230] The second contact surface of Test Nos. 13 to 16 was subjected to a sand blasting treatment. The arithmetic mean deviation Ra of the second contact surface after the sand blasting treatment was measured in accordance with the method for measuring arithmetic mean deviation prescribed in JIS B 0601 (2013). Specifically, 10 arbitrary parts of the second contact surface were used as measurement sites. The arithmetic mean deviation Ra was measured in each measurement site in an evaluation length extending in the pipe axial direction. The evaluation length was 5 times the reference length (cutoff wavelength). The measurement of the arithmetic mean deviation Ra was performed using a stylus-type roughness meter at a measurement speed of 0.5 mm / sec. Among the 10 arithmetic mean deviations Ra obtained, the largest arithmetic mean deviation Ra, the second largest arithmetic mean deviation Ra, the smallest arithmetic mean deviation Ra, and the second smallest arithmetic mean deviation Ra were removed, and the arithmetic mean of the remaining 6 arithmetic mean deviations Ra was defined as the arithmetic mean deviation Ra. As the contact-type roughness meter, a surface roughness meter SURFTEST SJ-301 (trade name) manufactured by Mitutoyo Corporation was used. The arithmetic mean deviation Ra (μm) obtained is shown in Table 1. Note that the second contact surfaces of Test Nos. 11 and 12 were not subjected to the sand blasting treatment (indicated as "-" in the "blast cleaning" column of Table 1). The arithmetic mean deviation Ra of the second contact surface of the oil well metal pipe of Test Nos. 11 and 12, which were not subjected to the sand blasting treatment, was about 0.2 μm, which was less than 0.5 μm. The arithmetic mean deviation Ra of the second contact surface of the oil well metal pipe of Test Nos. 13 to 16 was 2.7, which was in the range of 0.5 to 10.0 μm.

[0231] Further, for Test Nos. 11, 13, and 15, the second contact surface (pin contact surface) was immersed in a zinc phosphate chemical conversion treatment liquid (trade name Palbond 181X manufactured by Nippon Parkerizing Co., Ltd.) at 75 to 85°C for 10 minutes to form a zinc phosphate chemical conversion treatment layer. The thickness of the zinc phosphate chemical conversion treatment layer was 12 μm. Note that the zinc phosphate chemical conversion treatment layer was not formed on the second contact surface of Test Nos. 12, 14, and 16 (indicated as "-" in the "zinc phosphate" column of Table 1).

[0232] A rust-preventive coating was formed on the zinc phosphate chemical conversion treatment layers in tests 11 and 13. Specifically, a liquid rust-preventive coating was formed on the zinc phosphate chemical conversion treatment layers in tests 11 and 13. Additionally, a semi-solid (grease-like) rust-preventive coating was formed on the second contact surfaces in tests 12 and 14. A semi-solid rust-preventive coating composed of yellow paint was formed on the second contact surfaces in tests 15 and 16. In all tests, a liquid or semi-solid rust-preventive lubricant was sprayed from a distance of 300 mm from the surface of the zinc phosphate chemical conversion treatment layer or the second contact surface, forming a liquid or semi-solid rust-preventive coating. Alternatively, a liquid or semi-solid rust-preventive lubricant was brushed onto the surface of the zinc phosphate chemical conversion treatment layer or the second contact surface, forming a liquid or semi-solid rust-preventive coating. During the spraying process, the metal pipe for the oil well is rotated around the central axis, forming a liquid or semi-solid anti-rust coating on the entire surface or the second contact surface of the zinc phosphate chemical conversion treatment layer.

[0233] It should be noted that the liquid rust inhibitor lubricant contains 50-75% mineral oil and less than 25% petroleum-based oil by mass. The semi-solid rust inhibitor lubricant contains 20-30% purified mineral oil, 8-13% petroleum-based wax, 3-5% graphite, and 5-10% rosin by mass, with the balance being calcium sulfonate. As mentioned above, in tests 15 and 16, a yellow coating (manufactured by Bestolife Co., Ltd., trade name BoL4010NM) was used as the semi-solid rust inhibitor lubricant.

[0234] Through the above manufacturing process, metal pipes for oil wells with test numbers 11 to 16 were manufactured.

[0235] [Yield Torque Measurement Test]

[0236] The yield torque was determined using a pair (2 pipes) of well tubing (well tubing with wedge threads but without a shoulder) of each test number, as follows. Specifically, the tightening torque was slowly increased at a tightening speed of 0.5 rpm, and the test ended when the material yielded. The torque was measured while tightening the threads, and fabricated as follows: Figure 14 The torque curve shown. Figure 14 In this context, Ts represents the shoulder torque. Line segment L is a straight line with the same slope as the linear region of the torque curve after shoulder formation, but with 0.2% more revolutions per minute compared to the linear region. In this embodiment, the torque value at the intersection of line segment L and the torque curve is defined as the yield torque Ty. The ratio (%) of the yield torque Ty of each test number to the yield torque Ty of test number 11 (without sandblasting treatment of the second contact surface) is defined as the "yield torque ratio". The yield torque ratios are shown in Table 1.

[0237] [Evaluation Results]

[0238] Referring to Table 1, in Test Nos. 13 to 16, the Zn-Ni alloy plating layer and the solid lubricating layer were laminated on the first contact surface, the second contact surface was subjected to the sand blasting treatment, the surface roughness was 0.5 to 10.0 μm, and the semisolid or liquid rust-preventive coating film was formed on the second contact surface. Therefore, the yield torque ratio was higher than that of Test Nos. 11 and 12 in which the second contact surface was not subjected to the sand blasting treatment. That is, the excellent high torque performance was obtained.

[0239] [Example 2]

[0240] A metal pipe for oil well was prepared as shown in Table 2.

[0241] [Table 2]

[0242] Table 2

[0243]

[0244] The metal pipe for oil well of Test Nos. 21 to 24 had an outer diameter of 7 inches (177.80 mm) and a wall thickness of 10.36 mm. The chemical composition of the metal pipe for oil well was equivalent to that of L80-13CR prescribed in API-5CT.

[0245] In Test Nos. 21 to 24, the first contact surface was set to the box contact surface, and the second contact surface was set to the pin contact surface. On the first contact surface of each Test No., the Zn-Ni alloy plating layer was formed in the same manner as in Example 1. The chemical composition of the Zn-Ni alloy plating layer was the same in all Test Nos., and contained 10 to 16 mass% of Ni and the balance of Zn. The thickness of the Zn-Ni alloy plating layer of each Test No. was in the range of 5 to 15 μm.

[0246] Further, on the Zn-Ni alloy plating layer, the solid lubricating layer was formed in the same manner as in Example 1. The average film thickness of the obtained solid lubricating layer was in the range of 20 to 30 μm in all Test Nos.

[0247] On the other hand, the sand blasting treatment was performed on the second contact surface of Test Nos. 23 and 24 in the same manner as in Example 1. The arithmetic mean deviation Ra of the second contact surface after the sand blasting treatment was measured in the same manner as in Example 1. The obtained arithmetic mean deviation Ra (μm) is shown in Table 2. Note that the second contact surface of Test Nos. 21 and 22 was not subjected to the sand blasting treatment (indicated as "-" in the column of "blast cleaning" in Table 2). The arithmetic mean deviation Ra of the second contact surface of the metal pipe for oil well of Test Nos. 21 and 22 which was not subjected to the sand blasting treatment was about 0.2 μm, which was less than 0.5 μm.

[0248] A rust-preventive coating film was formed on the second contact surface of each test number. Specifically, on the second contact surface of test numbers 21 and 23, a liquid rust-preventive coating film was formed. In addition, on the second contact surface of test numbers 22 and 24, a semi-solid rust-preventive coating film was formed. The forming method was the same as in Example 1. By the above manufacturing procedure, the oil well metal pipes of test numbers 21 to 24 were manufactured.

[0249] [Yield torque measurement test]

[0250] The yield torque ratio of the oil well metal pipe of each test number was calculated in the same manner as in Example 1.

[0251] [Results of evaluation]

[0252] Referring to Table 2, in test numbers 23 and 24, the Zn-Ni alloy plating layer and the solid lubricating layer were laminated on the first contact surface, the second contact surface was subjected to sand blasting treatment, the surface roughness was 0.5 to 10.0 μm, and a liquid or semi-solid rust-preventive coating film was formed on the second contact surface. Therefore, as compared with test numbers 21 and 22 in which the second contact surface was not subjected to sand blasting treatment, the yield torque ratio was high. That is, excellent high torque performance was obtained.

[0253] [Example 3]

[0254] An oil well metal pipe as shown in Table 3 was prepared.

[0255] [Table 3]

[0256] Table 3

[0257]

[0258] The oil well metal pipes of test numbers 31 and 32 had an outer diameter of 9-5 / 8 inches (244.475 mm) and a wall thickness of 13.84 mm. The chemical composition of the oil well metal pipe was equivalent to P110 prescribed in API-5CT.

[0259] In test numbers 31 and 32, the first contact surface was set to the box contact surface, and the second contact surface was set to the pin contact surface. On the first contact surface of each test number, a Zn-Ni alloy plating layer was formed in the same manner as in Example 1. The chemical composition of the Zn-Ni alloy plating layer was the same in all test numbers, and contained 10 to 16 mass% of Ni and the balance of Zn. The thickness of the Zn-Ni alloy plating layer of each test number was in the range of 5 to 15 μm.

[0260] In addition, on the Zn-Ni alloy plating layer, a solid lubricating layer was formed in the same manner as in Example 1. The average film thickness of the obtained solid lubricating layer was in the range of 20 to 30 μm in all test numbers.

[0261] On the other hand, the second contact surface of Test No. 32 was subjected to the sand blasting treatment in the same manner as in Example 1. The arithmetic mean deviation Ra of the second contact surface after the sand blasting treatment was measured in the same manner as in Example 1. The arithmetic mean deviation Ra (μm) obtained is shown in Table 3. Note that the second contact surface of Test No. 31 was not subjected to the sand blasting treatment (indicated as "-" in the column of "blasting cleaning" in Table 3). The arithmetic mean deviation Ra of the second contact surface of the oil well metal pipe of Test No. 31 not subjected to the sand blasting treatment was about 0.2 μm, which was less than 0.5 μm.

[0262] A rust-preventive coating film was formed on the second contact surface of each of the test numbers. Specifically, on the second contact surfaces of Test Nos. 31 and 32, a liquid rust-preventive coating film was formed. The formation method was the same as in Example 1. Through the above manufacturing procedures, the oil well metal pipes of Test Nos. 31 and 32 were manufactured.

[0263] [Yield torque measurement test and evaluation results]

[0264] The yield torque ratio of the oil well metal pipe of each of the test numbers was calculated in the same manner as in Example 1. Referring to Table 3, in Test No. 32, the Zn-Ni alloy plating layer and the solid lubricating layer were laminated on the first contact surface, the second contact surface was subjected to the sand blasting treatment, the surface roughness was 0.5 to 10.0 μm, and a liquid rust-preventive coating film was formed on the second contact surface. Therefore, the yield torque ratio was higher than that of Test No. 31 in which the second contact surface was not subjected to the sand blasting treatment. That is, an excellent high torque property was obtained.

[0265] [Example 4]

[0266] An oil well metal pipe as shown in Table 4 was prepared.

[0267] [Table 4]

[0268] Table 4

[0269]

[0270] The oil well metal pipes of Test Nos. 41 to 43 had an outer diameter of 7 inches (177.80 mm) and a wall thickness of 11.51 mm. The oil well metal pipe used was a product name SM13CRS-110 manufactured by Nippon Steel Corporation.

[0271] In Test Nos. 41 to 43, the first contact surface was provided as the female coupling portion contact surface, and the second contact surface was provided as the male coupling portion contact surface. In the first contact surface of each Test No., a Zn-Ni alloy plating layer was formed in the same manner as in Example 1. The chemical composition of the Zn-Ni alloy plating layer was the same in all Test Nos., and was a chemical composition containing 10 to 16 mass% of Ni and the balance being Zn. The thickness of the Zn-Ni alloy plating layer of each Test No. was in the range of 5 to 15 μm.

[0272] Further, on the Zn-Ni alloy plating layer, a solid lubricating layer was formed in the same manner as in Example 1. The average film thickness of the obtained solid lubricating layer was in the range of 20 to 30 μm in all Test Nos.

[0273] On the other hand, the second contact surface of Test No. 43 was subjected to sand blasting treatment in the same manner as in Example 1. The arithmetic mean deviation Ra of the second contact surface after the sand blasting treatment was measured in the same manner as in Example 1. The obtained arithmetic mean deviation Ra (μm) is shown in Table 4. Note that the second contact surfaces of Test Nos. 41 and 42 were not subjected to sand blasting treatment (indicated as "-" in the "blast cleaning" column of Table 4). The arithmetic mean deviation Ra of the second contact surface of the oil well metal pipe of Test Nos. 41 and 42, which were not subjected to sand blasting treatment, was about 0.2 μm, which was less than 0.5 μm.

[0274] A rust-preventive film was formed on the second contact surface of each Test No. Specifically, on the second contact surface of Test Nos. 41 and 43, a semi-solid rust-preventive film was formed. In addition, on the second contact surface of Test No. 42, a liquid rust-preventive film was formed. The formation method was the same as in Example 1. Through the above manufacturing procedures, the oil well metal pipes of Test Nos. 41 to 43 were manufactured.

[0275] [Yield torque measurement test and evaluation results]

[0276] The yield torque ratio of the oil well metal pipe of each Test No. was calculated in the same manner as in Example 1. Referring to Table 4, in Test No. 43, the Zn-Ni alloy plating layer and the solid lubricating layer were laminated on the first contact surface, the second contact surface was subjected to sand blasting treatment, the surface roughness was 0.5 to 10.0 μm, and a semi-solid rust-preventive film was formed on the second contact surface. Therefore, the yield torque ratio was high as compared with Test Nos. 41 and 42, in which the second contact surface was not subjected to sand blasting treatment. That is, excellent high torque performance was obtained.

[0277] [Example 5]

[0278] An oil well metal pipe as shown in Table 5 was prepared.

[0279] [Table 5]

[0280] Table 5

[0281]

[0282] The oil well metal pipes of Test Nos. 51 to 54 had an outer diameter of 4-1 / 2 inches (114.3 mm) and a wall thickness of 6.88 mm. The chemical composition of the oil well metal pipes was equivalent to that of L80-13CR prescribed in API-5CT.

[0283] In Test Nos. 51 to 54, the first contact surface was set to the box contact surface, and the second contact surface was set to the pin contact surface. On the first contact surface of each Test No., a Zn-Ni alloy plating layer was formed in the same manner as in Example 1. The chemical composition of the Zn-Ni alloy plating layer was the same in all Test Nos., and was a chemical composition containing 10 to 16 mass% of Ni and the balance of Zn. The thickness of the Zn-Ni alloy plating layer of each Test No. was in the range of 5 to 15 μm.

[0284] Further, on the Zn-Ni alloy plating layer, a solid lubricating layer was formed in the same manner as in Example 1. The average film thickness of the obtained solid lubricating layer was in the range of 20 to 30 μm in all Test Nos.

[0285] On the other hand, the second contact surface of Test Nos. 53 and 54 was subjected to sand blasting treatment in the same manner as in Example 1. The arithmetic mean deviation Ra of the second contact surface after the sand blasting treatment was measured in the same manner as in Example 1. The obtained arithmetic mean deviation Ra (μm) is shown in Table 5. Note that the second contact surface of Test Nos. 51 and 52 was not subjected to sand blasting treatment (indicated as "-" in the column of "blast cleaning" in Table 5). The arithmetic mean deviation Ra of the second contact surface of the oil well metal pipes of Test Nos. 51 and 52, which were not subjected to sand blasting treatment, was about 0.2 μm, which was less than 0.5 μm.

[0286] On the second contact surface of each Test No., a rust-preventive coating film was formed. Specifically, on the second contact surface of Test Nos. 51 and 53, a liquid rust-preventive coating film was formed. In addition, on the second contact surface of Test Nos. 52 and 54, a semi-solid rust-preventive coating film was formed. The formation method was the same as in Example 1. Through the above manufacturing procedures, the oil well metal pipes of Test Nos. 51 to 54 were manufactured.

[0287] [Yield torque measurement test and evaluation results]

[0288] The yield torque ratio of the oil well metal pipe of each test number was calculated in the same manner as in Example 1. As shown in Table 5, in test numbers 53 and 54, the Zn-Ni alloy plating layer and the solid lubricating layer were laminated on the first contact surface, the second contact surface was subjected to sand blasting treatment, the surface roughness was 0.5 to 10.0 μm, and a semisolid or liquid rust-preventive coating film was formed on the second contact surface. Therefore, the yield torque ratio was high as compared with test numbers 51 and 52 in which the second contact surface was not subjected to sand blasting treatment. That is, excellent high torque performance was obtained.

[0289] [Example 6]

[0290] An oil well metal pipe was prepared as shown in Table 6.

[0291] [Table 6]

[0292] Table 6

[0293]

[0294] The oil well metal pipes of test numbers 61 to 64 had an outer diameter of 4-1 / 2 inches (114.3 mm) and a wall thickness of 6.88 mm. The oil well metal pipe used was a product name SM13CRS-110 manufactured by Nippon Steel Corporation.

[0295] In test numbers 61 to 64, the first contact surface was set to the box contact surface, and the second contact surface was set to the pin contact surface. On the first contact surface of each test number, a Zn-Ni alloy plating layer was formed in the same manner as in Example 1. The chemical composition of the Zn-Ni alloy plating layer was the same in all test numbers, and was a chemical composition containing 10 to 16 mass% of Ni and the balance Zn. The thickness of the Zn-Ni alloy plating layer of each test number was in the range of 5 to 15 μm.

[0296] Further, on the Zn-Ni alloy plating layer, a solid lubricating layer was formed in the same manner as in Example 1. The average film thickness of the obtained solid lubricating layer was in the range of 20 to 30 μm in all test numbers.

[0297] On the other hand, the second contact surface of test numbers 63 and 64 was subjected to sand blasting treatment in the same manner as in Example 1. The arithmetic mean deviation Ra of the second contact surface after the sand blasting treatment was measured in the same manner as in Example 1. The obtained arithmetic mean deviation Ra (μm) is shown in Table 6. Note that the second contact surface of test numbers 61 and 62 was not subjected to sand blasting treatment (indicated as "-" in the column of "blast cleaning" in Table 6). The arithmetic mean deviation Ra of the second contact surface of the oil well metal pipes of test numbers 61 and 62 which were not subjected to sand blasting treatment was about 0.2 μm, which was less than 0.5 μm.

[0298] A rust preventive coating film was formed on the second contact surface of each test number. Specifically, on the second contact surface of test numbers 61 and 63, a liquid rust preventive coating film was formed. In addition, on the second contact surface of test numbers 62 and 64, a semi-solid rust preventive coating film was formed. The forming method was the same as in Example 1. Through the above manufacturing process, the oil well metal pipes of test numbers 61 to 64 were manufactured.

[0299] [Yield torque measurement test and evaluation results]

[0300] The yield torque ratio of the oil well metal pipe of each test number was calculated in the same manner as in Example 1. Referring to Table 6, in test numbers 63 and 64, the Zn-Ni alloy plating layer and the solid lubricating layer were laminated on the first contact surface, the second contact surface was subjected to sand blasting treatment, the surface roughness was 0.5 to 10.0 μm, and a semi-solid or liquid rust preventive coating film was formed on the second contact surface. Therefore, the yield torque ratio was high as compared with test numbers 61 and 62 in which the second contact surface was not subjected to sand blasting treatment. That is, excellent high torque performance was obtained.

[0301] [Example 7]

[0302] Oil well metal pipes of various structures were prepared. Using the prepared oil well metal pipes, the following repeated fastening test was performed, and the wear resistance was evaluated. First, the oil well metal pipes shown in Table 7 were prepared.

[0303] [Table 7]

[0304] Table 7

[0305]

[0306] The oil well metal pipes of test numbers 71 to 83 had an outer diameter of 7 inches (177.80 mm) and a wall thickness of 11.51 mm or 12.65 mm. The oil well metal pipes of test numbers 71 to 83 were a product name SM13CRS-110 manufactured by Nippon Steel Corporation.

[0307] In test numbers 71 to 83, the first contact surface was set to the box contact surface, and the second contact surface was set to the pin contact surface. On the first contact surface of each test number, a Zn-Ni alloy plating layer was formed in the same manner as in Example 1. The chemical composition of the Zn-Ni alloy plating layer was a chemical composition containing 10 to 16 mass% of Ni and the balance of Zn in all test numbers. The thickness of the Zn-Ni alloy plating layer of each test number was in the range of 5 to 15 μm.

[0308] In addition, on the Zn-Ni alloy plating layer, a solid lubricating layer was formed in the same manner as in Example 1. The average film thickness of the obtained solid lubricating layer was in the range of 20 to 30 μm in all test numbers.

[0309] On the other hand, the second contact surfaces of Test Nos. 73 to 78, 81 and 82 were subjected to the sand blasting treatment in the same manner as in Example 1. The arithmetic mean deviation Ra of the second contact surfaces after the sand blasting treatment was measured in the same manner as in Example 1. The arithmetic mean deviation Ra obtained was about 2.5 μm, which was in the range of 0.5 to 10.0 μm. Note that the second contact surfaces of Test Nos. 71, 72, 79 and 80 were not subjected to the sand blasting treatment (indicated as "-" in the "blast cleaning" column of Table 7). The arithmetic mean deviation Ra of the second contact surfaces in the tests not subjected to the sand blasting treatment was about 0.2 μm, which was less than 0.5 μm.

[0310] A rust-preventive coating film was formed on the second contact surface of each test number. Specifically, a liquid rust-preventive coating film was formed on the second contact surface of Test Nos. 71, 73, 75, 77, 79 and 81. In addition, a semi-solid rust-preventive coating film was formed on the second contact surface of Test Nos. 72, 74, 76, 78, 80 and 82. The formation method was the same as in Example 1. Note that in Test No. 83, a yellow paint was applied to form a semi-solid rust-preventive coating film. Through the above manufacturing procedures, the metal pipes for oil wells of Test Nos. 71 to 83 were manufactured.

[0311] [Evaluation Test of Wear Resistance]

[0312] The evaluation of wear resistance was performed by a repeated tightening test. In Test Nos. 71 to 83 in Table 7, one pair (two) of the metal pipes for oil wells was used for each test number, and the tightening and loosening of the threads were repeated at room temperature (20°C) to evaluate the wear resistance. The tightening torque was 24,350 N-m. Each time the tightening and loosening of the threads were performed, the contact surfaces of the pin and the box were observed by visual inspection. The occurrence of wear on the thread portions, the pin sealing surface and the box sealing surface was confirmed by visual observation. When wear was confirmed on the pin sealing surface and the box sealing surface, the test was ended. In the thread portions, when the wear was slight and could be restored by polishing or the like, the wear defect was repaired and the test was continued. The maximum number of repeated tightening was 10. The evaluation index of wear resistance was the maximum number of tightening (maximum 10) at which no wear occurred on the thread portions and no wear occurred on the pin sealing surface and the box sealing surface. The results are shown in the "tightening number" column of Table 7. The API standard specifies that the tightening number of a 7-inch casing pipe is 3 or more. Therefore, when the tightening number was 3 or more, the wear resistance was judged to be excellent.

[0313] [Results of Evaluation]

[0314] As shown in Table 7, the tightening number of each of Test Nos. 71 to 83 was 3 or more, and the wear resistance was excellent.

[0315] The above describes embodiments of the present application. However, the above-described embodiments are merely examples for implementing the present application. Therefore, the present application is not limited to the above-described embodiments, and the above-described embodiments can be appropriately modified without departing from the scope of the present application.

[0316] Reference Signs Description

[0317] 1 metal pipe for oil well

[0318] 10 pipe body

[0319] 10A first end portion

[0320] 10B second end portion

[0321] 11 pin portion pipe body

[0322] 12 coupling

[0323] 40 pin portion

[0324] 50 box portion

[0325] 60 plating layer

[0326] 70 solid lubricating layer

[0327] 80 rust-preventive film

[0328] 90 chemical conversion treatment film

[0329] 400 pin portion contact surface

[0330] 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 including: a pin portion formed at the first end portion, and a box portion formed at the second end portion, the pin portion including a pin portion contact surface, the pin portion contact surface having at least an external thread portion formed on an outer peripheral surface of the first end portion of the pipe body, the box portion including a box portion contact surface, the box portion contact surface having at least an internal thread portion formed on an inner peripheral surface of the second end portion of the pipe body, one of the pin portion contact surface and the box portion contact surface, i.e., a first contact surface, being formed with a plating layer, the plating layer being formed with a solid lubricating layer, the other of the pin portion contact surface and the box portion contact surface, i.e., a second contact surface, having an arithmetic mean deviation Ra of 0.5 to 10.0 μm, and the second contact surface being formed with a semisolid or liquid rust-preventive coating film.

2. The metal pipe for oil wells according to claim 1, wherein: the second contact surface is further formed with a chemical conversion treatment coating film, and the rust-preventive coating film is formed on the chemical conversion treatment coating film.

3. The metal pipe for oil wells according to claim 1 or claim 2, wherein: the second contact surface is subjected to blast cleaning.

4. The metal pipe for oil wells according to claim 1, wherein: the plating layer is composed of a Zn-Ni alloy. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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