WO2024180941A1

WO2024180941A1 - Metal pipe for oil wells, and composition for forming lubricant coating layer for said metal pipe for oil wells

Info

Publication number: WO2024180941A1
Application number: PCT/JP2024/001593
Authority: WO
Inventors: 知花安倍; 幸司秋岡; 崇夫倉西; 邦夫後藤
Original assignee: 日本製鉄株式会社; バローレック・オイル・アンド・ガス・フランス
Priority date: 2023-02-28
Filing date: 2024-01-22
Publication date: 2024-09-06
Also published as: JP2024121847A

Abstract

Provided is a metal pipe for oil wells, the metal pipe having excellent seizure resistance and excellent high torque performance. The metal pipe (1) for oil wells according to the present disclosure is provided with a pipe body (10) that includes a first end part (10A) and a second end part (10B). The pipe body (10) includes a pin (40) formed in the first end part (10A) and a box (50) formed in the second end part (10B). The pin (40) includes a pin contact surface (400) including a male screw portion (41), and the box (50) includes a box contact surface (500) including a female screw portion (51). The metal pipe (1) for oil wells is further provided with a lubricant coating layer (100) formed as an uppermost layer of at least one of the pin contact surface (400) and the box contact surface (500). The lubricant coating layer (100) contains ZrO2, a metal soap, a wax, and a basic aromatic organic metal salt.

Description

Metallic pipe for oil well and composition for forming lubricating coating layer on said metallic pipe for oil well

This disclosure relates to a metal oil well pipe and a composition for forming a lubricating coating layer on the metal oil well pipe.

Oil wells and gas wells (hereinafter, oil wells and gas wells are collectively referred to simply as "oil wells") use metal oil well pipes. In oil well mining areas, multiple metal oil well pipes are connected according to the depth of the oil well to form an oil well pipe assembly, typically casing or tubing. For this reason, a threaded joint (pin and box) is formed on the pipe body of the metal oil well pipe. In this specification, the pipe body means a pipe body (hollow pipe) with a pin and box formed on the end by machining or the like. In other words, an oil well pipe assembly is formed by connecting a pin formed on the end of the pipe body of a metal oil well pipe to a box formed on the end of the pipe body of another metal oil well pipe by screwing them together.

Here, the pin has a pin contact surface including a male thread portion on the outer peripheral surface of one end of the pipe body. The box has a box contact surface including a female thread portion on the inner peripheral surface of the end of the pipe body of the metal pipe for oil wells where the pin is not formed. In this specification, the male thread portion and the female thread portion are also collectively referred to as the "thread portion". In this specification, the pin contact surface and the box contact surface are also collectively referred to as the "contact surface". Note that the pin contact surface may further include a pin unthreaded metal contact portion including a pin seal surface and a pin shoulder surface. Similarly, the box contact surface may further include a box unthreaded metal contact portion including a box seal surface and a box shoulder surface. Hereinafter, the pin unthreaded metal contact portion and the box unthreaded metal contact portion are also collectively referred to as the "unthreaded metal contact portion". In other words, the contact surface of the pipe body may include only a thread portion, or may include a thread portion and an unthreaded metal contact portion.

Incidentally, inspections may be carried out on the formed oil well pipe connections. When carrying out an inspection, the oil well pipe connection is pulled up and the pin and box are unscrewed. The oil well metal pipe is then removed from the oil well pipe connection by unscrewing and inspected. After inspection, the pin and box are screwed together again and the oil well metal pipe is reused as part of the oil well pipe connection. In this way, when using the oil well metal pipe as an oil well pipe connection, screwing and unscrewing the pin and box may be repeated.

On the other hand, when the pin and box are screwed in and out, the contact surfaces (the pin contact surface and the box contact surface) are repeatedly subjected to strong friction. Therefore, when the pin and box are repeatedly screwed in and out, galling (irreparable seizure) is likely to occur on the contact surfaces. Therefore, metal pipes for oil wells are required to have sufficient durability against friction, i.e., excellent seizure resistance.

　Traditionally, compound grease containing heavy metal powder, called dope, has been used to improve the seizure resistance of metal oil well pipes. The seizure resistance of metal oil well pipes can be improved by applying compound grease to the contact surface. However, there are concerns that the heavy metal powders, such as Pb, Zn, and Cu, contained in compound grease may have a negative impact on the environment. For this reason, there is a need to develop metal oil well pipes that have excellent seizure resistance without using compound grease.

Technologies for improving the seizure resistance of metal pipes for oil wells are proposed, for example, in JP 2002-348587 A (Patent Document 1) and WO 2006/104251 (Patent Document 2).

The oil well metal pipe disclosed in Patent Document 1 has a solid lubricating coating made of a lubricating powder and a binder formed on the contact surface of at least one of the pin and the box. The lubricating powder is made of one or two types selected from molybdenum disulfide powder and tungsten disulfide powder, and graphite powder. The graphite powder accounts for 2 to 20 mass % of the lubricating powder. Patent Document 1 discloses that this oil well metal pipe has excellent seizure resistance.

The oil well metal pipe disclosed in Patent Document 2 has a viscous liquid or semi-solid lubricating coating formed on the contact surface of at least one of the pin and the box, and a dry solid coating formed on top of that. Patent Document 2 discloses that this oil well metal pipe has excellent seizure resistance without the use of compound grease.

JP 2002-348587 A International Publication No. WO 2006/104251

When the pin and box formed on the pipe body of the metal pipe for oil wells are screwed together, the torque at the completion of screwing (hereinafter referred to as the tightening torque) is set so that sufficient sealing surface pressure is obtained regardless of the amount of thread interference. In the final stage of screwing, the surface pressure between the contacting surfaces becomes high. Therefore, even if the surface pressure becomes high, if the torque can be steadily increased without seizing, it becomes easy to adjust the tightening torque. Therefore, it is preferable for the metal pipe for oil wells to be able to steadily increase the torque even if the surface pressure between the contacting surfaces increases. Hereinafter in this specification, being able to steadily increase the torque even if the surface pressure between the contacting surfaces increases is referred to as high torque performance.

In short, it is preferable that metal pipes for oil wells have not only excellent seizure resistance but also excellent high torque performance. However, the above-mentioned

Patent Documents

1 and 2 do not consider the high torque performance of metal pipes for oil wells.

The object of the present disclosure is to provide a metal pipe for oil wells having excellent seizure resistance and excellent high torque performance, and to provide a composition for forming a lubricating coating layer formed on a metal pipe for oil wells having excellent seizure resistance and excellent high torque performance.

The metal pipe for oil well use according to the present disclosure comprises:
a tube body including a first end and a second end;
The tube body includes:
a pin formed on the first end;
a box formed at the second end,
The pin is
a pin contact surface including an external thread;
The box includes:
a box contact surface including an internal thread;
The metal pipe for oil well further comprises:
a lubricating coating layer formed as an uppermost layer on at least one of the pin contact surface and the box contact surface;
The lubricating coating layer is
_ZrO2 ,
Metal soaps,
Wax and
and a basic aromatic organic acid metal salt.

The composition according to the present disclosure comprises:
A composition for forming the lubricating coating layer on the metal oil well pipe, comprising:
_ZrO2 ,
Metal soaps,
Wax and
and a basic aromatic organic acid metal salt.

The metal pipe for oil wells according to the present disclosure has excellent seizure resistance and excellent high torque performance. The composition according to the present disclosure can form a lubricating coating layer formed on the metal pipe for oil wells having excellent seizure resistance and excellent high torque performance.

FIG. 1 is a diagram for explaining the torque-on shoulder resistance ΔT′ in this embodiment. FIG. 2 is a graph showing the relationship between the ZrO ₂ content (mass %) in the lubricating coating layer 100 and the torque-on-shoulder resistance ΔT′ (relative value), which is an index of high torque performance. FIG. 3 is a graph showing the relationship between the _ZrO2 content (mass %) in the lubricating coating layer 100 and the number of make-up and unmake-up cycles, which is an index of seizure resistance. FIG. 4 is a configuration diagram showing an example of the metal oil well pipe 1 according to this embodiment. FIG. 5 is a cross-sectional view (longitudinal cross-sectional view) parallel to the pipe axis direction of the second end 10B of the metal pipe for oil well 1 shown in FIG. FIG. 6 is a cross-sectional view (longitudinal cross-sectional view) of a portion of the pin 40 taken along a line parallel to the tube axis direction. FIG. 7 is a cross-sectional view (longitudinal cross-sectional view) of a portion of the box 50 taken along a line parallel to the tube axis direction. FIG. 8 is a longitudinal sectional view of an example different from FIG. 5 among cross sections (longitudinal sectional views) parallel to the pipe axis direction of the second end 10B of the metal pipe for oil well 1. FIG. 9 is a longitudinal sectional view of an example different from FIG. 5 and FIG. 8, among cross sections (longitudinal sectional views) parallel to the pipe axis direction of the second end 10B of the metal pipe for oil well 1. FIG. 10 is a cross-sectional view (longitudinal cross-sectional view) parallel to the tube axis direction of a part in the vicinity of the pin 40. As shown in FIG. FIG. 11 is a cross-sectional view (longitudinal cross-sectional view) parallel to the tube axis direction of a part in the vicinity of the box 50. As shown in FIG. FIG. 12 is a vertical cross-sectional view of an example different from FIG. 10, among cross-sectional views (vertical cross-sectional views) parallel to the tube axis direction of a part in the vicinity of the pin 40. In FIG. FIG. 13 is a vertical cross-sectional view of an example different from FIG. 11, among cross-sectional views (vertical cross-sectional views) parallel to the tube axis direction of a part in the vicinity of the box 50. In FIG. FIG. 14 is a vertical cross-sectional view of an example different from FIGS. 10 and 12, among cross-sectional views (vertical cross-sectional views) parallel to the tube axis direction of a part in the vicinity of the pin 40. In FIG. FIG. 15 is a diagram for explaining the torque-on-shoulder resistance ΔT′ in this embodiment.

The oil well metal pipe and composition according to this embodiment will be described in detail below with reference to the drawings. The same or corresponding parts in the drawings will be given the same reference numerals and their description will not be repeated.

The inventors of the present invention have conducted various studies on the relationship between the metal pipe for oil wells and the composition for forming the lubricating coating layer of the metal pipe for oil wells, and the seizure resistance and high torque performance of the metal pipe for oil wells. As a result, the following findings were obtained.

As mentioned above, in this specification, the ability to stably increase torque even when the surface pressure between the contact surfaces increases is referred to as high torque performance. Here, the high torque performance of metal pipes for oil wells will be specifically explained using as an example a case in which the contact surfaces have threadless metal contact parts. As mentioned above, the pin threadless metal contact part includes the pin seal surface and the pin shoulder surface, and the box threadless metal contact part includes the box seal surface and the box shoulder surface.

As described above, the pin and box of the metal oil well pipe are screwed together to form an oil well pipe connector. When the contact surfaces have unthreaded metal contact portions, the pin shoulder surface and the box shoulder surface come into contact as the pin and box are screwed together. Further screwing causes the pin seal surface and the box seal surface to interfere with each other, increasing the airtightness between the pin contact surface and the box contact surface. The torque generated when the pin shoulder surface and the box shoulder surface come into contact is called shouldering torque. As described above, the torque generated when the screwing of the pin and the box is completed is called tightening torque. Note that if the screwing is further performed after the tightening torque is reached, there is a concern that at least one of the pin and the box of the pipe body may undergo plastic deformation. The torque generated when the pin and/or the box undergo plastic deformation is called yield torque.

As mentioned above, the tightening torque is set so that sufficient seal surface pressure is obtained regardless of the amount of thread interference. That is, in an oil well metal pipe having an unthreaded metal contact portion, after the pin shoulder surface and the box shoulder surface come into contact, that is, in the final stage of screw tightening, the pin contact surface and the box contact surface slide while receiving a high frictional force. Here, if the pin contact surface and the box contact surface can maintain sliding without seizing even under high frictional force, the difference between the shouldering torque and the yield torque can be made large. Hereinafter, the difference between the shouldering torque and the yield torque is referred to as the torque-on-shoulder resistance ΔT'.

The torque on shoulder resistance ΔT' will be explained in more detail with reference to the drawings. FIG. 1 is a diagram for explaining the torque on shoulder resistance ΔT' in this embodiment. Referring to FIG. 1, when the metal oil well pipe is screwed, the torque first increases in proportion to the rotation speed (solid line at the bottom left in FIG. 1). At this time, the rate of increase in torque according to the rotation speed is low. When the pipe is screwed further, the pin shoulder surface and the box shoulder surface come into contact. At this time, the torque generated in the metal oil well pipe is the shouldering torque (denoted as "Ts" in FIG. 1).

When the torque reaches the shouldering torque (Ts), further tightening of the screw causes the torque to increase further in accordance with the rotation speed (solid line in the center of Figure 1). At this time, the rate of increase in torque in accordance with the rotation speed is high. When the screw is further tightened, the torque reaches a predetermined fastening torque (shown as "To" in Figure 1). When the screw is further tightened, plastic deformation occurs in the pin and/or box (solid line in the upper right corner of Figure 1). The torque generated in the oil well metal pipe at this time is the yield torque (shown as "Ty" in Figure 1).

Referring to FIG. 1, the greater the difference between the yield torque Ty and the shouldering torque Ts (torque-on-shoulder resistance ΔT'), the wider the range in which the tightening torque To can be set. In other words, if the torque-on-shoulder resistance ΔT' can be made larger, the tightening torque can be set higher. In other words, when the metal pipe for oil wells has an unthreaded metal contact portion, if the torque-on-shoulder resistance ΔT' is large, the torque can be increased stably even if the surface pressure between the contact surfaces increases. In other words, when the metal pipe for oil wells has an unthreaded metal contact portion, the torque-on-shoulder resistance ΔT' is an indicator of the high torque performance of the metal pipe for oil wells.

Based on the above findings, the present inventors have studied various methods for improving the high torque performance of metal pipes for oil wells. First, the present inventors have studied forming a lubricating coating layer as the uppermost layer on the contact surface of the pipe body of the metal pipe for oil wells. As a result of detailed studies by the present inventors, it was thought that a lubricating coating layer containing metal soap, wax, and a basic aromatic organic acid metal salt could improve the high torque performance of the metal pipe for oil wells. As a result of further detailed studies by the present inventors, it was revealed that if _ZrO2 is further contained in the lubricating coating layer containing metal soap, wax, and a basic aromatic organic acid metal salt, the torque-on-shoulder resistance ΔT′, which is an index of the high torque performance of the metal pipe for oil wells, can be improved. This point will be specifically explained using the drawings.

FIG. 2 is a diagram showing the relationship between the _ZrO2 content (mass%) in the lubricating coating layer and the torque-on-shoulder resistance ΔT' (relative value), which is an index of high torque performance. FIG. 2 was created using the _ZrO2 content (mass%) in the lubricating coating layer and the torque-on-shoulder resistance ΔT' (relative value) in the examples described later. Note that the torque-on-shoulder resistance ΔT' was determined as a relative value with the value of the torque-on-shoulder resistance ΔT' when a compound grease standardized by API (American Petroleum Institute) was used instead of the lubricating coating layer in test number 11 of the examples described later as the standard (100). Note that the white circle mark ○ in FIG. 2 indicates the torque-on-shoulder resistance ΔT' (relative value) of the test number in which the lubricating coating layer was formed in the examples. The triangle mark Δ in FIG. 2 indicates the torque-on-shoulder resistance ΔT′ (reference value) of test number 11 in which a compound grease was used instead of the lubricating coating layer among the examples (denoted as “API doped” in FIG. 2).

2, if the lubricating coating layer contains even a small amount of _ZrO2 , the torque-on-shoulder resistance ΔT' exceeds 100. In other words, it has become clear that if the lubricating coating layer contains even a small amount of _ZrO2 , the high torque performance of the metal oil well pipe can be improved to at least the same level as when compound grease is used.

The present inventors further conducted a detailed study on the relationship between the _ZrO2 content in the lubricating coating layer and the seizure resistance of the metal pipe for oil well use. As a result, it was revealed that the seizure resistance of the metal pipe for oil well use can be improved by forming a lubricating coating layer as the uppermost layer on the contact surface of the pipe body of the metal pipe for oil well use and by making the lubricating coating layer contain _ZrO2 . This point will be specifically explained with reference to the drawings.

Figure 3 is a diagram showing the relationship between the _ZrO2 content (mass%) in the lubricating coating layer and the number of times of tightening and unscrewing, which is an index of seizure resistance. Figure 3 was created using the _ZrO2 content (mass%) in the lubricating coating layer and the number of times that the screw could be tightened and unscrewed without irrecoverable seizure in the threaded portion or seizure on the seal surface (pin seal surface and/or box seal surface) in the examples described below. As in Figure 2, the white circle mark ○ in Figure 3 indicates the number of times of tightening and unscrewing for the test number in the examples in which the lubricating coating layer was formed. The triangle mark △ in Figure 3 indicates the number of times of tightening and unscrewing for the test number 11 in the examples in which compound grease was used instead of the lubricating coating layer (indicated as "API dope" in Figure 3).

3, the inclusion of even a small amount of _ZrO2 in the lubricating coating layer resulted in a greater number of screwing and unscrewing operations than the number of times with API doping (5 times). In other words, it was revealed that the inclusion of even a small amount of _ZrO2 in the lubricating coating layer can increase the seizure resistance of metal oil well pipes to at least the same level as when compound grease is used.

Therefore, the metal pipe for oil well use according to the present embodiment forms a lubricating coating layer containing _ZrO2 , metal soap, wax, and a basic aromatic organic acid metal salt as the uppermost layer on at least one of the pin contact surface and the box contact surface. As a result, the metal pipe for oil well use according to the present embodiment has excellent seizure resistance and excellent high torque performance. Furthermore, the composition according to the present embodiment contains _ZrO2 , metal soap, wax, and a basic aromatic organic acid metal salt. As a result, the composition according to the present embodiment can form a lubricating coating layer of the metal pipe for oil well use having excellent seizure resistance and excellent high torque performance.

The essential features of the oil well metal pipe and composition according to this embodiment, which were developed based on the above findings, are as follows:

[1]
A metal pipe for oil wells, comprising:
a tube body including a first end and a second end;
The tube body includes:
a pin formed on the first end;
a box formed at the second end,
The pin is
a pin contact surface including an external thread;
The box includes:
a box contact surface including an internal thread;
The metal pipe for oil well further comprises:
a lubricating coating layer formed as an uppermost layer on at least one of the pin contact surface and the box contact surface;
The lubricating coating layer is
_ZrO2 ,
Metal soaps,
Wax and
A basic aromatic organic acid metal salt,
Metal pipe for oil wells.

[2]
The metal pipe for oil well according to [1],
The lubricating coating layer is
When the total content of the _ZrO2 , the metal soap, the wax, the basic aromatic organic acid metal salt, and the lubricating powder is 100 mass%,
ZrO ₂ :0.2-8.0%,
Metal soap: 2-30%,
Wax: 2-30%,
Basic aromatic organic acid metal salt: 12.0 to 80.0%, and
Lubricating powder: 0 to 20.0%,
Metal pipe for oil wells.

[3]
The metal pipe for oil well according to [2],
The lubricating coating layer is
Lubricating powder: 0.1 to 20.0%,
Metal pipe for oil wells.

[4]
The metal pipe for oil well use according to any one of [1] to [3],
The metal pipe for oil well further comprises:
a metal plating layer disposed between at least one of the pin contact surface and the box contact surface and the lubricating coating layer;
Metal pipe for oil wells.

[5]
The metal pipe for oil well use according to any one of [1] to [4],
At least one of the pin contact surface and the box contact surface is
The surface is blasted or pickled.
Metal pipe for oil wells.

[6]
The metal pipe for oil well use according to any one of [1] to [5],
The metal pipe for oil well further comprises:
a chemical conversion layer disposed between at least one of the pin contact surface and the box contact surface and the lubricating coating layer, the chemical conversion layer having a surface in contact with the lubricating coating layer;
Metal pipe for oil wells.

[7]
The metal pipe for oil well use according to any one of [1] to [6],
The pin contact surface further comprises:
a pin seal surface and a pin shoulder surface;
The box contact surface further comprises:
Including a box seal surface and a box shoulder surface.
Metal pipe for oil wells.

[8]
A composition for forming the lubricant coating layer of the metal oil well pipe according to any one of [1] to [7],
_ZrO2 ,
Metal soaps,
Wax and
A basic aromatic organic acid metal salt,
Composition.

[9]
The composition according to [8],
The composition further comprises:
Contains a lubricating powder,
Composition.

[10]
The composition according to [8] or [9],
The composition further comprises:
Contains volatile organic solvents,
Composition.

　The metal oil well pipe according to this embodiment will be described in detail below.

[Configuration of metal pipe for oil wells]
First, the configuration of the metal pipe for oil well use of the present embodiment will be described. The metal pipe for oil well use has a well-known configuration. There are T&C type metal pipe for oil well use and integral type metal pipe for oil well use. Each type of metal pipe for oil well use will be described in detail below.

[When the oil well metal pipe is T&C type]
Fig. 4 is a configuration diagram showing an example of the metal pipe for oil well use 1 according to the present embodiment. Fig. 4 is a configuration diagram of a so-called T&C type (Threaded and Coupled) metal pipe for oil well use 1. Referring to Fig. 4, the metal pipe for oil well use 1 includes a pipe body 10.

The pipe body 10 extends in the pipe axial direction. The cross section of the pipe body 10 perpendicular to the pipe axial direction is circular. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is the end opposite the second end 10B. In the T&C type oil well metal pipe 1 shown in FIG. 4, the pipe body 10 includes a pin pipe body 11 and a coupling 12. The coupling 12 is attached to one end of the pin pipe body 11. More specifically, the coupling 12 is fastened to one end of the pin pipe body 11 by a screw.

FIG. 5 is a cross-sectional view (longitudinal cross-sectional view) parallel to the pipe axis direction of the second end 10B of the metal pipe for oil wells 1 shown in FIG. 4. Referring to FIGS. 4 and 5, the pipe body 10 includes a pin 40 and a box 50. The pin 40 is formed at the first end 10A of the pipe body 10. The box 50 is formed at the second end 10B of the pipe body 10. When fastening, the pin 40 is inserted into the box 50 of another metal pipe for oil wells 1 (not shown) and fastened to the box 50 of the other metal pipe for oil wells 1 by a screw. When fastening, the pin 40 of the other metal pipe for oil wells 1 is inserted into the box 50 and fastened to the pin 40 of the other metal pipe for oil wells 1 by a screw.

[Configuration of pin 40]
Fig. 6 is a cross-sectional view (longitudinal cross-sectional view) of a part of the pin 40, parallel to the pipe axis direction. The dashed line portion in Fig. 6 shows the configuration of a box 50 of another metal pipe for oil well use 1 when fastening with another metal pipe for oil well use 1. Referring to Fig. 6, the pin 40 has a pin contact surface 400 on the outer circumferential surface of the first end 10A of the pipe body 10. When fastening with the other metal pipe for oil well use 1, the pin contact surface 400 is screwed into the box 50 of the other metal pipe for oil well use 1, and comes into contact with a box contact surface 500 (described later) of the box 50.

The pin contact surface 400 includes at least the male thread portion 41 formed on the outer peripheral surface of the first end portion 10A. The pin contact surface 400 may further include a pin seal surface 42 and a pin shoulder surface 43. In FIG. 6, the pin shoulder surface 43 is disposed on the tip surface of the first end portion 10A, and the pin seal surface 42 is disposed on the outer peripheral surface of the first end portion 10A, closer to the tip side of the first end portion 10A than the male thread portion 41. In other words, the pin seal surface 42 is disposed between the male thread portion 41 and the pin shoulder surface 43. The pin seal surface 42 is tapered. Specifically, the outer diameter of the pin seal surface 42 gradually decreases from the male thread portion 41 to the pin shoulder surface 43 in the longitudinal direction (pipe axis direction) of the first end portion 10A.

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

In FIG. 6, the pin shoulder surface 43 is disposed on the tip surface of the first end 10A. That is, the pin 40 shown in FIG. 6 is disposed in the order of the male thread portion 41, the pin seal surface 42, and the pin shoulder surface 43 from the center of the pipe body 10 toward the first end 10A. When fastening with another oil well metal pipe 1, the pin shoulder surface 43 faces and contacts a box shoulder surface 53 (described later) of the box 50 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 is inserted into the box 50 of the other oil well metal pipe 1, so that the pin shoulder surface 43 contacts the box shoulder surface 53. This allows a high torque to be obtained when fastening. In addition, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

The pin contact surface 400 of the pin 40 includes at least the male thread portion 41. In other words, the pin contact surface 400 may include the male thread portion 41, and not include the pin seal surface 42 and the pin shoulder surface 43. The pin contact surface 400 may include the male thread portion 41 and the pin shoulder surface 43, and not include the pin seal surface 42. The pin contact surface 400 may include the male thread portion 41 and the pin seal surface 42, and not include the pin shoulder surface 43.

[Regarding the configuration of box 50]
Fig. 7 is a cross-sectional view (longitudinal cross-sectional view) parallel to the pipe axis direction of a part of the box 50. The dashed line portion in Fig. 7 shows the configuration of the pin 40 of the other metal pipe for oil well use 1 when fastening with the other metal pipe for oil well use 1. Referring to Fig. 7, the box 50 has a box contact surface 500 on the inner peripheral surface of the second end portion 10B of the pipe body 10. When fastening with the other metal pipe for oil well use 1, the pin 40 of the other metal pipe for oil well use 1 is screwed into the box contact surface 500, and the box contact surface 500 comes into contact with the pin contact surface 400 of the pin 40.

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

The box contact surface 500 may further include a box seal surface 52 and a box shoulder surface 53. In FIG. 7, the box seal surface 52 is located on the inner circumferential surface of the second end 10B closer to the pipe body 10 than the female thread portion 51. In other words, the box seal surface 52 is located between the female thread portion 51 and the box shoulder surface 53. The box seal surface 52 is tapered. Specifically, the inner diameter of the box seal surface 52 gradually decreases from the female thread portion 51 toward the box shoulder surface 53 in the longitudinal direction (pipe axial direction) of the second end 10B.

When fastening with another metal oil well pipe 1, the box seal surface 52 comes into contact with the pin seal surface 42 of the pin 40 of the other metal oil well pipe 1. More specifically, when fastening, the pin 40 of the other metal oil well pipe 1 is screwed into the box 50, so that the box seal surface 52 comes into contact with the pin seal surface 42, and when further screwed, the box seal surface 52 comes into close contact with the pin seal surface 42. As a result, when fastening, the box seal surface 52 comes into close contact with the pin seal surface 42 to form a seal based on metal-metal contact. Therefore, the airtightness of the metal oil well pipes 1 fastened to each other can be improved.

The box shoulder surface 53 is disposed closer to the pipe body 10 than the box seal surface 52. In other words, in the box 50, the box shoulder surface 53, the box seal surface 52, and the female threaded portion 51 are disposed in this order from the center of the pipe body 10 toward the tip of the second end 10B. When fastening with another oil well metal pipe 1, the box shoulder surface 53 faces and contacts the pin shoulder surface 43 of the pin 40 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 of the other oil well metal pipe 1 is inserted into the box 50, so that the box shoulder surface 53 contacts the pin shoulder surface 43. This allows a high torque to be obtained when fastening. In addition, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

The box contact surface 500 includes at least a female thread portion 51. During fastening, the female thread portion 51 of the box contact surface 500 of the box 50 corresponds to the male thread portion 41 of the pin contact surface 400 of the pin 40 and contacts the male thread portion 41. The box seal surface 52 corresponds to the pin seal surface 42 and contacts the pin seal surface 42. The box shoulder surface 53 corresponds to the pin shoulder surface 43 and contacts the pin shoulder surface 43.

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

The pin contact surface 400 may include multiple male threads 41, multiple pin seal surfaces 42, and multiple pin shoulder surfaces 43. For example, the pin contact surface 400 of the pin 40 may be arranged in the following order from the tip of the first end 10A toward the center of the pipe body 10: pin shoulder surface 43, pin seal surface 42, male thread 41, pin seal surface 42, pin shoulder surface 43, pin seal surface 42, male thread 41. In this case, the box contact surface 500 of the box 50 is arranged in the following order from the tip of the second end 10B toward the center of the pipe body 10: female thread 51, box seal surface 52, box shoulder surface 53, box seal surface 52, female thread 51, box seal surface 52, box shoulder surface 53.

6 and 7 show a so-called premium joint in which the pin 40 includes the male thread portion 41, the pin seal surface 42, and the pin shoulder surface 43, and the box 50 includes the female thread portion 51, the box seal surface 52, and the box shoulder surface 53. However, as described above, the pin 40 may include the male thread portion 41 and not include the pin seal surface 42 and the pin shoulder surface 43. In this case, the box 50 includes the female thread portion 51 and does not include the box seal surface 52 and the box shoulder surface 53. FIG. 8 is a longitudinal sectional view of an example of a cross section (longitudinal sectional view) parallel to the pipe axis direction of the second end 10B of the metal pipe for oil wells 1, which is different from FIG. 5. FIG. 8 shows an example of a metal pipe for oil wells 1 in which the pin 40 includes the male thread portion 41, does not include the pin seal surface 42, and does not include the pin shoulder surface 43, and the box 50 includes the female thread portion 51, and does not include the box seal surface 52 and the box shoulder surface 53.

[When the metal oil well pipe 1 is an integral type]
The metal oil well pipe 1 shown in Figures 4, 5 and 8 is a so-called T&C type metal oil well pipe 1 in which a pipe body 10 includes a pin pipe body 11 and a coupling 12. However, the metal oil well pipe 1 of the present embodiment may be an integral type instead of a T&C type.

9 is a longitudinal sectional view of an example different from those of FIG. 5 and FIG. 8, among cross sections (longitudinal sectional views) parallel to the pipe axis direction of the second end 10B of the metal pipe for oil wells 1. FIG. 9 is a longitudinal sectional view of an integral type metal pipe for oil wells 1. Referring to FIG. 9, in the integral type metal pipe for oil wells 1, the pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is disposed on the opposite side to the second end 10B. As described above, in the T&C type metal pipe for oil wells 1, the pipe body 10 includes a pin pipe body 11 and a coupling 12. That is, in the T&C type metal pipe for oil wells 1, the pipe body 10 is configured by fastening two separate members (the pin pipe body 11 and the coupling 12). In contrast, in the integral type metal pipe for oil wells 1, the pipe body 10 is integrally formed.

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

The configuration of the pin 40 of the integral type metal pipe for oil wells 1 is the same as that of the pin 40 of the T&C type metal pipe for oil wells 1 shown in FIG. 6. Similarly, the configuration of the box 50 of the integral type metal pipe for oil wells 1 is the same as that of the box 50 of the T&C type metal pipe for oil wells 1 shown in FIG. 7. In FIG. 6, the pin shoulder surface 43, the pin seal surface 42, and the male thread portion 41 are arranged in this order in the pin 40 from the tip of the first end 10A toward the center of the pipe body 10. Therefore, in the box 50, the female thread portion 51, the box seal surface 52, and the box shoulder surface 53 are arranged in this order from the tip of the second end 10B toward the center of the pipe body 10. However, like the pin contact surface 400 of the pin 40 of the T&C type metal pipe for oil wells 1, the pin contact surface 400 of the pin 40 of the integral type metal pipe for oil wells 1 only needs to include at least the male thread portion 41. Also, like the box contact surface 500 of the box 50 of the T&C type metal pipe for oil wells 1, the box contact surface 500 of the box 50 of the integral type metal pipe for oil wells 1 only needs to include at least the female thread portion 51.

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

[Chemical composition of the tube body]
The chemical composition of the pipe body 10 of the metal pipe for oil well use 1 according to the present embodiment is not particularly limited. That is, in the present embodiment, the steel type of the pipe body 10 of the metal pipe for oil well use 1 is not particularly limited. The pipe body 10 may be formed of, for example, carbon steel, stainless steel, alloy, or the like. That is, the pipe body 10 may be a steel pipe made of an Fe-based alloy, or an alloy pipe represented by a Ni-based alloy pipe. Here, the steel pipe is, for example, a low alloy steel pipe, a martensitic stainless steel pipe, a ferritic stainless steel pipe, an austenitic stainless steel pipe, a duplex stainless steel pipe, or the like. The alloy pipe is, for example, a Ni-based alloy pipe, a NiCrFe alloy pipe, or the like.

Among alloys, so-called high alloys such as Ni-based alloys and duplex stainless steels containing alloying elements such as Cr, Ni, and Mo have high corrosion resistance. Therefore, if these high alloys are used as the pipe body 10, excellent corrosion resistance can be obtained in a corrosive environment containing hydrogen sulfide, carbon dioxide, etc. If the pipe body 10 is a stainless steel pipe, the seizure resistance is more likely to decrease compared to when the pipe body 10 is a low-alloy steel pipe. However, in the metal pipe for oil wells 1 according to this embodiment, a lubricating coating layer, which will be described later, is formed as the uppermost layer on at least one of the contact surfaces 400, 500. As a result, the metal pipe for oil wells 1 according to this embodiment exhibits excellent seizure resistance even if the pipe body 10 is a stainless steel pipe.

[Lubricating film layer 100]
The metal oil well pipe 1 according to the present embodiment is provided with a lubricating coating layer as the uppermost layer on at least one of the pin contact surface 400 and the box contact surface 500. Here, the metal oil well pipe 1 according to the present embodiment is provided with a lubricating coating layer There may or may not be other layers between the contact surfaces 400, 500.

Specifically, Figs. 10, 12, and 14 are cross-sectional views (longitudinal cross-sectional views) parallel to the tube axis direction of a portion near the pin 40. Furthermore, Figs. 11 and 13 are cross-sectional views (longitudinal cross-sectional views) parallel to the tube axis direction of a portion near the box 50. With reference to Fig. 10, the lubricating coating layer 100 may be formed directly on the pin contact surface 400. With reference to Fig. 11, the lubricating coating layer 100 may be formed directly on the box contact surface 500. With reference to Figs. 12 and 14, the lubricating coating layer 100 may be formed on another layer formed on the pin contact surface 400. Furthermore, with reference to Fig. 13, the lubricating coating layer 100 may be formed on another layer formed on the box contact surface 500.

The lubricating coating layer 100 contains _ZrO2 , metal soap, wax, and a basic metal salt of an aromatic organic acid. The lubricating coating layer 100 may further contain a lubricating powder. That is, the lubricating powder is an optional component in the lubricating coating layer 100. Each component will be described below. Note that, unless otherwise specified, "%" for each component refers to the content (mass %) of each component when the total content of _ZrO2 , metal soap, wax, basic metal salt of an aromatic organic acid, and lubricating powder in the lubricating coating layer 100 is taken as 100 mass %.

[ _ZrO2 ]
_ZrO2 is a white solid particle at room temperature and has a melting point of about 2700°C. _ZrO2 is generally used as a heat-resistant ceramic material. As described above, even if only a small amount of _ZrO2 is contained in the lubricating coating layer 100, the seizure resistance and high torque performance of the metal pipe for oil well 1 can be improved to the same level or higher than that of compound grease.

That is, the _ZrO2 content in the lubricating coating layer 100 is more than 0%. In order to stably obtain the above-mentioned effect of _ZrO2 , the preferable lower limit of the _ZrO2 content in the lubricating coating layer 100 is 0.2%. The more preferable lower limit of the _ZrO2 content in the lubricating coating layer 100 is 0.5%, more preferably 1.0%, more preferably 2.0%, and even more preferably 3.0%. If the _ZrO2 content is 0.5% or more, the high torque performance of the metal pipe for oil well 1 is significantly improved. The upper limit of the _ZrO2 content in the lubricating coating layer 100 is not particularly limited. However, if the _ZrO2 content in the lubricating coating layer 100 is too high, the lubricating coating layer 100 becomes difficult to form. Therefore, the upper limit of the _ZrO2 content in order to stably form the lubricating coating layer 100 is less than 10.0%. A more preferable upper limit of the _ZrO2 content in the lubricating coating layer 100 is 8.0%, even more preferably 7.0%, and even more preferably 6.5%.

In this embodiment, the Mohs hardness of ZrO ₂ is about 6 to 9. If the Mohs hardness is too high, the seizure resistance of the metal pipe for oil well use 1 may not be sufficiently improved. On the other hand, if the Mohs hardness is too low, the high torque performance of the metal pipe for oil well use 1 may not be sufficiently improved. That is, since ZrO ₂ has a moderate Mohs hardness, it is possible to improve the seizure resistance and high torque performance of the metal pipe for oil well use 1. On the other hand, for example, among the metal oxides, TiO ₂ has a lower Mohs hardness than ZrO _2. Therefore, it is expected that, among the metal oxides, TiO ₂ is less likely to achieve the effect of improving the high torque performance than ZrO _2. As described above, metal oxides have significantly different properties depending on the type, and therefore cannot be easily replaced.

The Mohs hardness of ZrO ₂ is preferably 6 to 8.5, more preferably 6 to 7, and even more preferably 6.5 to 7. In this embodiment, the Mohs hardness of ZrO ₂ is measured by the following method. The standard material is rubbed with the sample material (ZrO ₂ ) to check for scratches. The standard material is a mineral that is generally used as a standard material for Mohs hardness measurement. The Mohs hardness is measured on a 10-point scale using talc (Mg ₃ (Si ₄ O ₁₀ ) (OH) ₂ ) with a Mohs hardness of 1 to diamond (diamond) with a Mohs hardness of 10. ZrO ₂ has a hardness between orthoclase (KAlSi ₃ O ₈ ) with a Mohs hardness of 6 and corundum (Al ₂ O ₃ ) with a Mohs hardness of 9. Preferably, _ZrO2 has a hardness between that of orthoclase, which has a hardness of 6 on the Mohs scale, and that of quartz ( _SiO2 ), which has a hardness of 7 on the Mohs scale.

In addition, the above-mentioned method for measuring the Mohs hardness of ZrO ₂ involves forming scratches on ZrO ₂ before it is processed into a powder state. On the other hand, since it is difficult to form scratches on ZrO ₂ powder, it is difficult to directly measure the Mohs hardness of ZrO ₂ powder. Therefore, in this embodiment, when determining the Mohs hardness from ZrO ₂ powder, it is estimated from the Vickers hardness. Specifically, first, a sample is prepared by embedding and fixing ZrO ₂ powder in a resin and polishing the surface. A diamond triangular pyramid-shaped indenter is pressed into the surface of the prepared sample, and a load-unload test is performed while controlling the test force and the load rate. The Vickers hardness can be obtained by using the test force and the indentation depth curve obtained from the load-unload test. As a Vickers tester used for the load-unload test, for example, a dynamic ultra-microhardness tester (DUH-211S) manufactured by Shimadzu Corporation can be used.

When the Vickers hardness of the _ZrO2 powder obtained by the above method is 600 to 780 Hv, the Mohs hardness is 6 to 7, when the Vickers hardness is 780 to 1250 Hv, the Mohs hardness is 7 to 8, and when the Vickers hardness is 1250 to 1900 Hv, the Mohs hardness is estimated to be 8 to 9.

In this embodiment, the preferred particle size of _ZrO2 is 20 to 2000 nm. If the particle size of _ZrO2 is 20 to 2000 nm, the dispersion state of _ZrO2 in the lubricating coating layer 100 is improved, and the seizure resistance and high torque performance of the metal pipe for oil well 1 can be stably improved. A more preferred lower limit of the particle size of _ZrO2 is 100 nm, more preferably 300 nm, more preferably 500 nm, and even more preferably 1000 nm. A more preferred upper limit of the particle size of _ZrO2 is 1800 nm, more preferably 1600 nm, and even more preferably 1500 nm.

In this embodiment, the particle size of _ZrO2 is measured by the following method. A particle size distribution measurement is performed on the sample material ( _ZrO2 ) by a laser diffraction/scattering method. The particle size distribution measurement can be performed by a well-known method. The arithmetic mean value of the effective diameter distribution obtained using, for example, a Shimadzu SALD series particle size distribution measuring device is taken as the particle size of _ZrO2 in this embodiment.

As described above, even if only a small amount of ZrO ₂ is contained in the lubricating coating layer 100, the high torque performance of the metal pipe for oil well 1 is improved. As described above, high torque performance means that the torque can be stably increased even if the surface pressure between the contact surfaces increases. In other words, ZrO ₂ may have the effect of increasing friction at high surface pressure. Therefore, it is preferable that the surface of ZrO ₂ is not covered with a coating (for example, a coating containing F).

[Metal soap]
Metal soaps are salts of aliphatic acids and metals. Here, fatty acids refer to aliphatic organic acids. That is, aromatic organic acids are not included in fatty acids by definition.

In this embodiment, the fatty acid of the metal soap may be a mixture of fatty acids or a single compound. Examples of fatty acid mixtures include beef tallow, lard, wool fat, palm oil, rapeseed oil, and coconut oil. Examples of single compound fatty acids include lauric acid, tridecylic acid, myristic acid, palmitic acid, lanopalmitic acid, stearic acid, isostearic acid, 12-hydroxystearic acid, oleic acid, elaidic acid, arachic acid, behenic acid, erucic acid, lignoceric acid, lanoceric acid, ricinoleic acid, montanic acid, linoleic acid, linolenic acid, ricinolenic acid, octylic acid, and sebacic acid. The fatty acid according to this embodiment may be one or more selected from the group consisting of the examples of fatty acids described above. Preferably, the fatty acid according to this embodiment has a carbon number of 12 to 30. Examples of fatty acids having 12 to 30 carbon atoms include lauric acid, tridecylic acid, myristic acid, palmitic acid, lanopalmitic acid, stearic acid, isostearic acid, 12-hydroxystearic acid, oleic acid, elaidic acid, arachic acid, behenic acid, erucic acid, lignoceric acid, lanoceric acid, ricinoleic acid, montanic acid, linoleic acid, linolenic acid, and ricinolenic acid.

In this embodiment, the metal of the metal soap is not particularly limited as long as it can form a salt with the fatty acid. Examples of the metal of the metal soap are calcium, sodium, magnesium, zinc, and barium. In this embodiment, the metal soap may be a neutral salt or a basic salt. In other words, the metal soap according to this embodiment is not particularly limited as long as it is a salt of the above-mentioned fatty acid and the above-mentioned metal.

In the lubricating coating layer 100 according to this embodiment, the content of the metal soap is not particularly limited. Preferably, the content of the metal soap in the lubricating coating layer 100 is 2 to 30%. If the content of the metal soap is 2% or more, the seizure resistance and rust prevention of the metal oil well pipe 1 can be stably improved. If the content of the metal soap is 30% or less, the adhesion and strength of the lubricating coating layer 100 can be stably improved. Therefore, the content of the metal soap in the lubricating coating layer 100 is preferably 2 to 30%. A more preferable lower limit of the content of the metal soap in the lubricating coating layer 100 is 5%, more preferably 7%, and even more preferably 10%. A more preferable upper limit of the content of the metal soap in the lubricating coating layer 100 is 28%, more preferably 25%, and even more preferably 20%.

[wax]
Wax is a general term for organic matter that is solid at room temperature and becomes liquid when heated. In this embodiment, the wax is one or more selected from the group consisting of animal, vegetable, mineral, and synthetic wax. Examples of animal waxes are beeswax and spermaceti. Examples of vegetable waxes are Japan wax, carnauba wax, candelilla wax, and rice wax. Examples of mineral waxes are paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokerite, and ceresin. Examples of synthetic waxes are oxidized wax, polyethylene wax, Fischer-Tropsch wax, amide wax, and hardened castor oil (castor wax). As an example, the molecular weight of the wax is 1000 or less. Preferably, the wax is paraffin wax with a molecular weight of 150 to 500.

That is, the wax is, for example, one or more selected from the group consisting of beeswax, spermaceti, Japan wax, carnauba wax, candelilla wax, rice wax, paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokerite, ceresin, oxidized wax, polyethylene wax, Fischer-Tropsch wax, amide wax, and hardened castor oil (castor wax). The wax is preferably one or more selected from the group consisting of paraffin wax, microcrystalline wax, and oxidized wax.

In the lubricating coating layer 100 according to this embodiment, the wax content is not particularly limited. Preferably, the wax content in the lubricating coating layer 100 is 2 to 30%. If the wax content is 2% or more, the friction of the lubricating coating layer 100 can be reduced, and the seizure resistance of the metal oil well pipe 1 can be stably improved. If the wax content is 30% or less, the adhesion and strength of the lubricating coating layer 100 can be stably improved. Therefore, the wax content in the lubricating coating layer 100 is preferably 2 to 30%. A more preferable lower limit of the wax content in the lubricating coating layer 100 is 5%, more preferably 7%, and even more preferably 10%. A more preferable upper limit of the wax content in the lubricating coating layer 100 is 28%, more preferably 25%, and even more preferably 20%.

[Basic aromatic organic acid metal salt]
The basic metal salt of an aromatic organic acid is a basic salt of an aromatic organic acid and a metal. The basic metal salt of an aromatic organic acid is, for example, a grease-like or semi-solid substance at room temperature.

In this embodiment, the aromatic organic acid is, for example, a sulfonate, a phenate, or a salicylate. In this embodiment, the metal of the basic aromatic organic acid metal salt is an alkali metal (lithium, sodium, potassium, rubidium, cesium, or francium) or an alkaline earth metal (beryllium, magnesium, calcium, barium, or radium). Preferably, the metal of the basic aromatic organic acid metal salt is one or more selected from the group consisting of sodium, potassium, calcium, barium, or magnesium. More preferably, the metal of the basic aromatic organic acid metal salt is one or more selected from the group consisting of calcium, barium, or magnesium.

In other words, the basic aromatic organic acid metal salt is, for example, one or more selected from the group consisting of basic sodium sulfonate, basic potassium sulfonate, basic magnesium sulfonate, basic calcium sulfonate, basic barium sulfonate, basic sodium phenate, basic potassium phenate, basic magnesium phenate, basic calcium phenate, basic barium phenate, basic sodium salicylate, basic potassium salicylate, basic magnesium salicylate, basic calcium salicylate, and basic barium salicylate.

The higher the base number of the basic aromatic organic metal salt, the higher the amount of fine metal salt particles that function as a solid lubricant. Therefore, by using a basic aromatic organic metal salt with a high base number, the seizure resistance of the oil well metal pipe 1 is further improved. Furthermore, if the base number is increased to a certain level or higher, the effect of neutralizing the acid component is obtained. Therefore, by using a basic aromatic organic metal salt with a high base number, the rust prevention ability of the oil well metal pipe 1 is further improved. Therefore, it is preferable that the basic aromatic organic metal salt has a base number (JIS K2501) (when two or more types are used, the weighted average value of the base number taking into account the amount) of 50 to 500 mg KOH/g.

If the base number of the basic aromatic organic metal salt is 50 mgKOH/g or more, the above effects can be sufficiently obtained. If the base number is 500 mgKOH/g or less, the hydrophilicity can be reduced and sufficient rust prevention properties can be obtained. A more preferred lower limit of the base number of the basic aromatic organic metal salt is 100 mgKOH/g, more preferably 200 mgKOH/g, and even more preferably 250 mgKOH/g. A more preferred upper limit of the base number of the basic aromatic organic metal salt is 450 mgKOH/g.

In the lubricating coating layer 100 according to this embodiment, the content of the basic aromatic organic metal salt is not particularly limited. As described above, the basic aromatic organic metal salt is a grease-like or semi-solid substance, and also functions as a base for the lubricating coating layer 100. Therefore, the content of the basic aromatic organic metal salt in the lubricating coating layer 100 can be increased up to 80.0%. That is, in this embodiment, the content of the basic aromatic organic metal salt in the lubricating coating layer 100 is 12.0 to 80.0%.

In this embodiment, a more preferred lower limit for the content of the basic aromatic organic metal salt in the lubricating coating layer 100 is 20.0%, more preferably 30.0%, and even more preferably 40.0%. A more preferred upper limit for the content of the basic aromatic organic metal salt in the lubricating coating layer 100 is 75.0%, more preferably 71.0%, and even more preferably 70.0%.

[Lubricant powder]
The lubricating coating layer 100 according to this embodiment may further contain a lubricating powder in addition to _ZrO2 , metal soap, wax, and basic aromatic organic acid metal salt. That is, the lubricating powder is an optional component and does not have to be contained in the lubricating coating layer 100. In this specification, the lubricating powder is a general term for solid powders that have lubricity. In this embodiment, a well-known solid powder that has lubricity can be used as the lubricating powder.

Specifically, as an example, lubricating powders are roughly classified into the following four types.
(1) Materials that exhibit lubricity due to having a specific slippery crystal structure, such as a hexagonal layered crystal structure (e.g., graphite, amorphous graphite, zinc oxide, boron nitride, and talc);
(2) Those that exhibit lubricity by having a reactive element in addition to a crystal structure (for example, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfide, bismuth sulfide, and organic molybdenum),
(3) Those that exhibit lubricity due to chemical reactivity (e.g., thiosulfate compounds);
(4) Those that exhibit lubricity due to plastic or viscoplastic behavior under frictional stress (e.g., polytetrafluoroethylene (PTFE), polyamide, copper (Cu), and melamine cyanurate (MCA)).

Preferably, the lubricating powder contains one or more selected from the group consisting of (1) to (4) above. That is, preferably, the lubricating powder is one or more selected from the group consisting of graphite, amorphous graphite, zinc oxide, boron nitride, talc, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfide, bismuth sulfide, organic molybdenum, thiosulfate compounds, polytetrafluoroethylene (PTFE), polyamide, copper (Cu), and melamine cyanurate (MCA). More preferably, the lubricating powder is one or more selected from the group consisting of molybdenum disulfide, graphite, polytetrafluoroethylene (PTFE), and graphite fluoride. Even more preferably, the lubricating powder is one or two selected from the group consisting of graphite and polytetrafluoroethylene (PTFE).

In this embodiment, the content of lubricating powder in the lubricating coating layer 100 is 0 to 20.0%. A more preferred lower limit of the content of lubricating powder in the lubricating coating layer 100 is 0.5%, more preferably 3.0%, and even more preferably 5.0%. A more preferred upper limit of the content of lubricating powder in the lubricating coating layer 100 is 18.0%, more preferably 15.0%, and even more preferably 12.0%.

[Other ingredients]
The lubricating coating layer 100 may contain other components in addition to _ZrO2 , metal soap, wax, basic aromatic organic acid metal salt, and lubricating powder, such as well-known anti-rust additives, preservatives, color pigments, and impurities.

If the lubricating coating layer 100 contains a rust-preventive additive, the rust-preventive properties of the metal pipe for oil wells 1 are improved. If the rust-preventive properties of the metal pipe for oil wells 1 are improved, rusting of the metal pipe for oil wells 1 due to long-term storage can be suppressed. Examples of the rust-preventive additive include aluminum tripolyphosphate, aluminum phosphite, and calcium ion-exchanged silica. Other commercially available reactive water repellents can also be used as rust-preventive additives.

If the lubricating coating layer 100 contains a preservative, the corrosion resistance of the metal oil well pipe 1 is increased. If the corrosion resistance of the metal oil well pipe 1 is increased, corrosion of the metal oil well pipe 1 due to long-term storage can be suppressed. Furthermore, the lubricating coating layer 100 may contain, as impurities, trace amounts of volatile organic solvents contained in the composition described below. In this embodiment, the total content of other components in the lubricating coating layer 100 is 0 to 10%.

[Composition for forming lubricating coating layer 100]
In this embodiment, the composition for forming the lubricating coating layer 100 contains _ZrO2 , metal soap, wax, and a basic metal salt of an aromatic organic acid. The composition according to this embodiment may further contain a lubricating powder. Preferably, when the total content of _ZrO2 , metal soap, wax, basic metal salt of an aromatic organic acid, and lubricating powder is taken as 100 mass%, the composition contains _ZrO2 : 0.2 to 8.0%, metal soap: 2 to 30%, wax: 2 to 30%, basic metal salt of an aromatic organic acid: 12.0 to 80.0%, and lubricating powder: 0 to 20.0%. In short, the content of _ZrO2 , metal soap, wax, basic metal salt of an aromatic organic acid, and lubricating powder in the composition is the same as that of the lubricating coating layer 100.

The composition according to this embodiment may further contain a volatile organic solvent. When coating is performed at room temperature, the composition is prepared by adding a volatile organic solvent to a mixture of the components of the lubricating coating layer 100. Unlike substances contained in the composition, the volatile organic solvent evaporates almost entirely during the process of forming the lubricating coating layer 100. However, the volatile organic solvent may remain as an impurity in the lubricating coating layer 100 according to this embodiment. In this specification, "volatile" means that it shows a tendency to evaporate at temperatures from room temperature to 150°C.

In this embodiment, the type of volatile organic solvent is not particularly limited. The volatile organic solvent is, for example, a petroleum-based solvent. The petroleum-based solvent is, for example, one or more selected from the group consisting of solvent equivalent to industrial gasoline specified in JIS K2201 (2006), mineral spirits, aromatic petroleum naphtha, xylene, and cellosolve. The volatile organic solvent preferably has a flash point of 30°C or higher, an initial boiling point of 150°C or higher, and an end point of 210°C or lower. In this case, the volatile organic solvent is relatively easy to handle, evaporates quickly, and requires a short drying time.

In this embodiment, the content of the volatile organic solvent may be adjusted as appropriate so that the viscosity of the composition can be adjusted appropriately depending on the application method of the composition. For example, the content of the volatile organic solvent is 20 to 50 g when the total amount of the non-volatile components is 100 g.

[Thickness of lubricating coating layer 100]
In this embodiment, the thickness of the lubricating coating layer 100 is not particularly limited. Preferably, the thickness of the lubricating coating layer 100 is 20 to 80 μm. If the thickness of the lubricating coating layer 100 is 20 μm or more, the lubricity of the lubricating coating layer 100 is stably increased. On the other hand, if the thickness of the lubricating coating layer 100 is 80 μm or less, the adhesion of the lubricating coating layer 100 is stably increased. Therefore, in this embodiment, the thickness of the lubricating coating layer 100 is preferably 20 to 80 μm.

In this embodiment, the thickness of the lubricating coating layer 100 is measured by the following method. A wet gauge is brought into contact with the pin contact surface 400 or the box contact surface 500 on which the lubricating coating layer 100 is formed. The wet gauge includes a number of end faces corresponding to the thickness. The wet gauge is brought into contact with the lubricating coating layer 100, and it is confirmed which end face of the wet gauge the lubricating coating layer 100 is attached to. In this manner, the thickness of the lubricating coating layer 100 is determined. The measurement points are 12 points (12 points at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°) around the circumference of the metal oil well pipe 1. The arithmetic mean value of the measurement results at the 12 points is regarded as the thickness of the lubricating coating layer 100.

[Arrangement of lubricating coating layer 100]
In this embodiment, the lubricating coating layer 100 is formed as the uppermost layer on at least one of the pin contact surface 400 and the box contact surface 500. In other words, in this embodiment, the lubricating coating layer 100 is disposed as the outermost layer on at least one of the pin contact surface 400 and the box contact surface 500.

The lubricating coating layer 100 may be formed as the entire top layer of at least one of the pin contact surface 400 and the box contact surface 500, or may be formed as the top layer only on a part of the surface. When the pipe body 10 has a pin seal surface 42, a box seal surface 52, a pin shoulder surface 43, and a box shoulder surface 53, the surface pressure of the seal surfaces 42, 52 and the shoulder surfaces 43, 53 is particularly high in the final stage of screw tightening. Therefore, when the lubricating coating layer 100 is partially formed as the top layer of at least one of the contact surfaces 400, 500 having the seal surfaces 42, 52 and the shoulder surfaces 43, 53, the lubricating coating layer 100 may be formed as the top layer of at least one of the seal surfaces 42, 52 and the shoulder surfaces 43, 53. On the other hand, if the lubricating coating layer 100 is formed as the entire top layer of at least one of the contact surfaces 400, 500, the production efficiency of the metal pipe for oil wells 1 is improved.

The lubricating coating layer 100 may be a single layer or multiple layers. Multiple layers refers to a state in which the lubricating coating layer 100 is laminated in two or more layers as the uppermost layer of the

contact surface

400 or 500. Specifically, by repeatedly applying and drying the composition, two or more lubricating coating layers 100 can be formed.

[Other layers]
The metal oil well pipe 1 according to this embodiment may have a layer other than the lubricating coating layer 100 formed on or above the contact surfaces 400, 500. The other layer is, for example, a metal plating layer and a chemical conversion layer.

[Metal plating layer 110]
The metal oil well pipe 1 according to this embodiment may further include a metal plating layer between the lubricating coating layer 100 and at least one of the pin contact surface 400 and the box contact surface 500. Specifically, with reference to Fig. 12, the metal plating layer 110 may be formed on the pin contact surface 400 as an underlayer of the lubricating coating layer 100. Similarly, with reference to Fig. 13, the metal plating layer 110 may be formed on the box contact surface 500 as an underlayer of the lubricating coating layer 100. In this way, when both the lubricating coating layer 100 and the metal plating layer 110 are formed, the metal plating layer 110 is formed between at least one of the contact surfaces 400, 500 and the lubricating coating layer 100.

In this embodiment, the type of the metal plating layer 110 is not particularly limited. The metal plating layer 110 may be a single-layer plating layer or a multi-layer plating layer (two-layer plating layer or three-layer plating layer). When the metal plating layer 110 is a single-layer plating layer, the metal plating layer 110 is, for example, a single-layer plating layer of Cu, Sn, or Ni metal, a single-layer plating layer of a Zn-Ni alloy, a Cu-Sn alloy, or a Cu-Sn-Zn alloy. When the metal plating layer 110 is a multi-layer plating layer, the metal plating layer 110 is, for example, a two-layer plating layer of a Cu layer and a Sn layer, a three-layer plating layer of a Ni layer, a Cu layer, and a Sn layer, or a multi-layer plating layer that combines the above single-layer plating layers.

Preferably, the hardness of the metal plating layer 110 is 200 or more in micro Vickers. If the hardness of the metal plating layer 110 is 200 or more, the corrosion resistance of the metal pipe for oil wells 1 is further stably increased. In this embodiment, the hardness of the metal plating layer 110 is measured as follows. Five arbitrary regions are identified in the metal plating layer 110 formed on the contact surfaces 400, 500 of the metal pipe for oil wells 1. For each identified region, the Vickers hardness (HV) is measured in accordance with JIS Z2244 (2009). The test conditions are, for example, a test temperature of room temperature (25°C) and a test force of 2.94 N (300 gf). The arithmetic mean value of the obtained values is defined as the hardness of the metal plating layer 110.

In this embodiment, the thickness of the metal plating layer 110 is not particularly limited. However, when forming a multi-layer plating layer as the metal plating layer 110, it is preferable that the bottom plating layer has a film thickness of less than 1 μm. In addition, it is preferable that the thickness of the metal plating layer 110 (total thickness in the case of a multi-layer plating layer) is 5 to 15 μm.

The thickness of the metal plating layer 110 in this embodiment is measured as follows. A probe of an eddy current phase type film thickness gauge conforming to ISO (International Organization for Standardization) 21968 (2005) is brought into contact with the contact surfaces 400, 500 on which the metal plating layer 110 is formed. The phase difference between the high-frequency magnetic field on the input side of the probe and the eddy currents excited by it on the metal plating layer is measured. This phase difference is converted into the thickness of the metal plating layer 110.

[Chemical conversion layer 120]
The metal oil well pipe 1 according to this embodiment may further include a chemical conversion layer disposed between at least one of the pin contact surface 400 and the box contact surface 500 and the lubricant coating layer 100, and having a surface in contact with the lubricant coating layer 100. Specifically, with reference to FIG. 14 , the chemical conversion layer 120 may be formed on the metal plating layer 110 formed on the pin contact surface 400, as a lower layer of the lubricant coating layer 100. Although not shown, the chemical conversion layer 120 may be formed on the metal plating layer 110 formed on the box contact surface 500, as a lower layer of the lubricant coating layer 100. Similarly, although not shown, the chemical conversion layer 120 may be formed on the pin contact surface 400, as a lower layer of the lubricant coating layer 100. Similarly, although not shown, the chemical conversion layer 120 may be formed on the box contact surface 500, as a lower layer of the lubricant coating layer 100.

In this embodiment, the type of the chemical conversion layer 120 is not particularly limited. The chemical conversion layer 120 may be, for example, a phosphate chemical conversion layer, an oxalate chemical conversion layer, a borate chemical conversion layer, a chromate chemical conversion layer, or a zirconium chemical conversion layer. Here, the chemical conversion layer 120 is porous. Therefore, if the lubricating coating layer 100 is formed on the chemical conversion layer 120, the adhesion of the lubricating coating layer 100 is further increased due to the so-called anchor effect. Furthermore, in this embodiment, the thickness of the chemical conversion layer 120 is not particularly limited. The preferred thickness of the chemical conversion layer 120 in this embodiment is 5 to 40 μm.

[Surface that has been blasted or pickled]
In the metal pipe for oil well use 1 according to the present embodiment, the contact surfaces 400, 500 may be blasted or pickled. That is, the surface of the metal pipe for oil well use 1 on which the lubricating coating layer 100 is formed as the uppermost layer may be a surface that has been blasted or pickled. That is, the contact surfaces 400, 500 of the pipe body 10 of the metal pipe for oil well use 1 may be blasted or pickled, and the lubricating coating layer 100 may be formed thereon. In addition, when the metal pipe for oil well use 1 has a metal plating layer 110, the metal pipe for oil well use 1 may have a

contact surface

400, 500 that has been blasted or pickled, and the metal plating layer 110 thereon, and the lubricating coating layer 100 may be provided on or above the metal plating layer 110. In addition, when the metal pipe for oil well use 1 has a metal plating layer 110, the metal pipe for oil well use 1 may further have a metal plating layer 110 that has been blasted or pickled, and the lubricating coating layer 100 thereon.

Surfaces that have been blasted or pickled have increased surface roughness. Specifically, the preferred surface roughness of the surface that comes into contact with the lubricating coating layer 100 is an arithmetic mean roughness Ra of 1 to 8 μm (reference length 2.5 mm). If the arithmetic mean roughness Ra of the surface that comes into contact with the lubricating coating layer 100 is 1 μm or more, the adhesion of the lubricating coating layer 100 is further increased. If the arithmetic mean roughness Ra of the surface that comes into contact with the lubricating coating layer 100 is 8 μm or less, the lubricating coating layer 100 is less likely to peel off.

In this embodiment, the arithmetic mean roughness Ra is measured based on JIS B0601 (2013). For example, it can be measured using a scanning probe microscope SPI3800N manufactured by SII Nanotechnology. The measurement conditions are, for example, a 2 μm×2 μm area of the sample as a unit of the number of acquired data, and 1024×1024 acquired data. The reference length is 2.5 mm. The larger the arithmetic mean roughness Ra, the larger the contact area with the lubricating coating layer 100. Therefore, the anchor effect increases the adhesion with the lubricating coating layer 100. If the adhesion of the lubricating coating layer 100 is increased, the seizure resistance of the metal pipe for oil wells 1 will be further improved.

[Production method]
Hereinafter, a method for producing the metal oil well pipe 1 according to the present embodiment will be described.

The manufacturing method for the oil well metal pipe 1 according to this embodiment includes a preparation process and a lubricating coating layer formation process.

[Preparation process]
In the preparation step, a metal pipe for oil well use 1 is prepared, which includes a pipe body 10 including a pin 40 including a pin contact surface 400 including a male thread portion 41, and a box 50 including a box contact surface 500 including a female thread portion 51. As described above, the metal pipe for oil well use 1 according to the present embodiment has a well-known configuration. That is, in the preparation step, it is sufficient to prepare a metal pipe for oil well use 1 having a well-known configuration.

[Lubricating film layer formation process]
In the lubricating coating layer formation process, first, a composition containing the above-mentioned components is prepared. The composition for forming the lubricating coating layer 100 contains _ZrO2 , metal soap, wax, and basic aromatic organic solvent. The composition is liquefied by adding a solvent and/or by heating, and is applied onto or above at least one of the pin contact surface 400 and the box contact surface 500. If necessary, the applied composition is The composition is dried to form the lubricant coating layer 100.

Specifically, first, a composition containing the above-mentioned components is prepared. For example, a solventless composition can be produced by heating a mixture of the components of the above-mentioned composition and kneading them in a molten state. A powder mixture in which all components are mixed in powder form may be used as the composition. For example, a solvent-based composition can be produced by dissolving or dispersing _ZrO2 , a metal soap, a wax, and a basic aromatic organic acid metal salt in a volatile organic solvent and mixing them.

The prepared composition is applied on or above at least one of the contact surfaces 400, 500. Specifically, in the case of a solvent-free composition, the composition can be applied using a hot melt method. In the hot melt method, the composition is heated and melted to a low-viscosity fluid state. The fluidized composition is then sprayed from a spray gun having a temperature maintenance function. In this case, the composition is heated and melted in a tank equipped with an appropriate stirring device, and is supplied to the spray head of the spray gun (maintained at a predetermined temperature) via a metering pump by a compressor, and sprayed. The heating temperature is, for example, 90 to 130°C. The holding temperature in the tank and the spray head is adjusted according to the melting point of the composition. The application method may be brush coating, immersion, etc. instead of spray coating. The heating temperature of the composition is preferably 10 to 50°C higher than the melting point of the composition. When applying the composition, it is preferable to heat the surface to which the composition is to be applied (the

contact surface

400, 500, the surface of the metal plating layer 110, or the surface of the chemical conversion layer 120) to a temperature higher than the melting point of the base.

In the case of a solvent-based composition, the composition is made into a solution state by adding a solvent, and is applied by spray application or the like to at least one of the contact surfaces 400, 500. In this case, the viscosity of the composition is adjusted so that the composition can be spray applied under an environment of normal temperature and pressure.

In the case of a solvent-free composition, the composition applied to at least one of the pin contact surface 400 and the box contact surface 500 is cooled, whereby the molten composition dries to form the lubricating coating layer 100. The composition can be cooled by a known method. For example, cooling is allowed to stand in the air and air cooling. In the case of a solvent-based composition, the composition applied to or above the contact surfaces 400, 500 is dried to form the lubricating coating layer 100. The composition can be dried by a known method. For example, drying is allowed to stand in the air, air drying at low temperature, and vacuum drying.

The above-mentioned cooling may be performed by rapid cooling using a nitrogen gas and carbon dioxide gas cooling system, etc. When rapid cooling is performed, cooling is performed indirectly from the opposite side of the contact surface. Specifically, when forming the lubricating coating layer 100 as the top layer of the pin contact surface 400, cooling is performed from the inner surface side of the pipe body 10. Similarly, when forming the lubricating coating layer 100 as the top layer of the box contact surface 500, cooling is performed indirectly from the outer surface side of the pipe body 10.

The lubricating coating layer 100 may be a single layer or multiple layers. Multiple layers means that the lubricating coating layer 100 is laminated in two or more layers in the radial direction of the pipe body 10 from the contact surfaces 400, 500 side. By repeating the application and drying of the composition, two or more lubricating coating layers 100 can be formed. The lubricating coating layer 100 may be formed directly on at least one of the contact surfaces 400, 500, or may be formed after carrying out the base treatment described below.

The above steps produce the metal oil well pipe 1 according to this embodiment.

[Other steps]
The method for producing the metal oil well pipe 1 according to the present embodiment may further include other steps. The other steps are, for example, a metal plating step, a chemical conversion treatment step, a blasting treatment step, and a pickling treatment step. Each step will be described below.

[Metal plating process]
The method for manufacturing the metal oil well pipe 1 according to this embodiment may further include a metal plating step prior to the step of forming the lubricating coating layer 100. The metal plating layer 110 can be formed by, for example, electroplating or impact plating.

[Electroplating process]
In this embodiment, the electroplating process is a process for forming the metal plating layer 110 by electroplating. As described above, the metal plating layer 110 is, for example, a single-layer plating layer of Cu, Sn, or Ni metal, a single-layer plating layer of a Zn-Ni alloy, a Cu-Sn alloy, or a Cu-Sn-Zn alloy, a two-layer plating layer of a Cu layer and a Sn layer, a three-layer plating layer of a Ni layer, a Cu layer, and a Sn layer, or a multi-layer plating layer combining the above single-layer plating layers.

The electroplating process can be carried out by a known method. For example, a plating bath containing ions of the metal elements contained in the alloy plating is prepared. Next, at least one of the contact surfaces 400, 500 is immersed in the plating bath. Furthermore, electricity is passed through at least one of the contact surfaces 400, 500 to form a metal plating layer 110 on at least one of the contact surfaces 400, 500. The conditions of the plating bath, such as the temperature and plating time, can be set as appropriate.

More specifically, for example, when a Cu-Sn-Zn alloy plating layer is formed, the plating bath contains copper ions, tin ions, and zinc ions. In this case, the plating bath preferably has a composition of Cu: 1-50 g/L, Sn: 1-50 g/L, and Zn: 1-50 g/L. The electroplating conditions are, for example, plating bath pH: 1-10, plating bath temperature: 60°C, current density: 1-100 A/ ^dm2 , and treatment time: 0.1-30 minutes.

Similarly, for example, when a Zn-Ni alloy plating layer is formed, the plating bath contains zinc ions and nickel ions. In this case, the plating bath preferably has a composition of Zn: 1 to 100 g/L and Ni: 1 to 50 g/L. The electroplating conditions are, for example, plating bath pH: 1 to 10, plating bath temperature: 60°C, current density: 1 to 100 A/ ^dm2 , and treatment time: 0.1 to 30 minutes.

[Impact plating process]
Impact plating is a process that can be carried out by mechanical plating, in which particles and the object to be plated are collided in a rotating barrel, or projection plating, in which particles are collided with the object to be plated using a blasting device.

[Chemical conversion treatment process]
The method for producing a metal oil well pipe 1 according to this embodiment may include a chemical conversion treatment step prior to the lubricant coating layer-forming step. In the chemical conversion treatment step, a chemical conversion treatment is carried out to form a chemical conversion layer 120 as an underlayer of the lubricant coating layer 100, the chemical conversion layer 120 having a surface in contact with the lubricant coating layer 100.

In this embodiment, the chemical conversion treatment can be performed by a known method. A general chemical conversion treatment liquid can be used as the treatment liquid. For example, a zinc phosphate-based chemical conversion treatment liquid containing 1 to 150 g/L of phosphate ions, 3 to 70 g/L of zinc ions, 1 to 100 g/L of nitrate ions, and 0 to 30 g/L of nickel ions can be used. Alternatively, a manganese phosphate-based chemical conversion treatment liquid can be used. In addition, a chemical conversion treatment liquid can be used depending on the chemical conversion treatment layer 120 to be formed. The liquid temperature of the treatment liquid is, for example, room temperature to 100°C. The treatment time of the chemical conversion treatment can be appropriately set depending on the desired film thickness, for example, 15 minutes. When forming a phosphate conversion treatment layer, surface conditioning may be performed before the phosphate conversion treatment in order to promote the formation of the chemical conversion treatment layer. Surface conditioning refers to a treatment of immersing in a surface conditioning aqueous solution containing colloidal titanium. After the phosphate conversion treatment, it is preferable to wash with water or hot water and then dry.

[Blast treatment process]
In this embodiment, the blasting process is, for example, a process of colliding particles using a blasting device. The blasting process is, for example, a sandblasting process. The sandblasting process is a process of mixing a blasting material (abrasive) and compressed air and projecting the mixture. The blasting material is, for example, a spherical shot material and an angular grid material. The sandblasting process can increase the surface roughness of the contact surfaces 400, 500 and the surface of the metal plating layer 110.

In this embodiment, the sandblasting process can be performed by a known method. In the sandblasting process, for example, air is compressed with a compressor and the compressed air is mixed with a blasting material. The blasting material can be made of, for example, stainless steel, aluminum, ceramic, alumina, etc. In addition, the conditions of the sandblasting process, such as the projection speed, can be set appropriately.

[Pickling treatment process]
In this embodiment, the pickling process refers to a process of roughening the surface by immersing in a strong acid solution such as sulfuric acid, hydrochloric acid, nitric acid, or hydrofluoric acid. That is, by immersing the contact surfaces 400, 500 and the surface of the metal plating layer 110 in a strong acid solution, the surface roughness of these surfaces can be increased.

The metal pipe for oil wells and the composition according to this embodiment will be explained in more detail below using examples. However, the metal pipe for oil wells and the composition according to this embodiment are not limited to the examples explained below. In the examples below, the pin contact surface is referred to as the pin surface, and the box contact surface is referred to as the box surface. In addition, % in the examples means mass % unless otherwise specified.

In this example, VAM (registered trademark) 21HT manufactured by Nippon Steel Corporation was used. VAM (registered trademark) 21HT is a metal pipe for oil wells with an outer diameter of 177.80 mm (7 inches) and a wall thickness of 11.506 mm (0.453 inches). The steel type was 13Cr stainless steel. The composition of the 13Cr steel was C: 0.19%, Si: 0.25%, Mn: 0.80%, P: 0.02%, S: 0.01%, Cu: 0.04%, Ni: 0.10%, Cr: 13.0%, Mo: 0.04%, and the remainder was Fe and impurities.

First, the pin surface and box surface of each test number were ground to finish. Of the pin surfaces of each test number that had been ground to finish, test numbers 8 and 9 were further sandblasted. For the sandblasting, Mesh 100 abrasive was used to create a surface roughness. As shown in Table 1, a metal plating layer was formed on the box surface of each test number other than test number 11, which had been ground to finish, as shown in Table 1. The type of metal plating layer formed and its film thickness are listed in the "Preparation" column for the box surface in Table 1. A "-" in the "Preparation" column for the box surface means that no metal plating layer was formed. The film thickness of the metal plating layer was measured using the method described above.

For the test numbers in which a Zn-Ni alloy plating layer was formed as the metal plating layer, Zn-Ni alloy plating was performed by electroplating to form the Zn-Ni alloy plating layer. The Zn-Ni alloy plating bath used was Dainjin Alloy N-PL, a product name of Daiwa Kasei Co., Ltd. The electroplating conditions were plating bath pH: 6.5, plating bath temperature: 25°C, current density: 2 A/dm ² , and treatment time: 18 minutes. The composition of the Zn-Ni alloy plating layer was Zn: 85% and Ni: 15%.

In test number 7, in which a Cu-Sn-Zn alloy plating layer was formed as the metal plating layer, Ni strike plating was first formed by electroplating. Then, the Cu-Sn-Zn alloy plating layer was formed. The Cu-Sn-Zn alloy plating bath used was a plating bath manufactured by Nippon Kagaku Sangyo Co., Ltd.

The arithmetic mean roughness Ra of the pin surface and box surface after the base treatment for each test number is as shown in Table 1. The arithmetic mean roughness Ra was measured based on JIS B 0601 (2013). The arithmetic mean roughness Ra was measured using a scanning probe microscope SPI3800N manufactured by SII Nanotechnology. The measurement conditions were as follows: the unit of data acquisition was a 2 μm x 2 μm area of the sample, and the number of data acquisitions was 1024 x 1024.

A lubricating coating layer having the composition shown in Table 2 was formed on the pin and box surfaces of each test number prepared as described above. In Table 2, the parentheses in the "Lubricating Coating Layer Composition" column indicate the content of each component in mass % when the total content of _ZrO2 , metal soap, wax, basic aromatic organic acid metal salt, and lubricating powder is taken as 100 mass %. The composition for forming the lubricating coating layer of each test number except for test numbers 7 and 11 contained a volatile organic solvent in addition to the lubricating coating layer composition shown in Table 2. The content of the volatile organic solvent was 30% when the total content of _ZrO2 , metal soap, wax, basic aromatic organic acid metal salt, and lubricating powder is taken as 100 mass %. The composition for forming the lubricating coating layer of test numbers 7 and 11 was the same as the lubricating coating layer composition shown in Table 2.

In this embodiment, the particle diameter of _ZrO2 used was 1000 nm. The Mohs hardness of _ZrO2 used in each test number is shown in Table 2. Test number ₁₀ contained _Cr2O3 instead of _ZrO2 . The content of _Cr2O3 was 10.0 mass%. Here, the content _of _Cr2O3 means the content of _Cr2O3 when the total content of _Cr2O3 _, metal soap _, wax, and basic aromatic organic acid metal salt is ₁₀₀ mass%.

In this example, _ZrO2 was Zirconium Oxide (product name: MIZ ₎ manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd. _Cr2O3 was Green F3 manufactured by Nippon Kagaku Kogyo Co., Ltd. The particle size of this _Cr2O3 was 1500 nm. In this example, Ca- _STEARATE manufactured by DIC Corporation was used as Ca stearate. Zn-STEARATE manufactured by DIC Corporation was used as Zn stearate. Na-STEARATE manufactured by DIC Corporation was used as Na stearate.

Furthermore, in this embodiment, the carnauba wax used was XAQUASOROUT-0013, a product of Nippon Seiro Co., Ltd. The paraffin wax used was paraffin wax manufactured by Nippon Seiro Co., Ltd. The microcrystalline wax used was Hi-Mic-1080, a product of Nippon Seiro Co., Ltd. The basic Ca sulfonate used was Calcinate (registered trademark) C400CLR (base number 400 mg KOH/g), a product of LANXESS Corporation. The basic Ca phenate used had a base number of 100 mg KOH/g, a soap concentration of 40%, and a metal ratio of 10. The basic Ca salicylate used was MD9A01, a product of Nippon Lubrizol Co., Ltd. The graphite used was graphite powder manufactured by Nippon Graphite Industries Co., Ltd., product name Blue P (ash content 3.79%, crystallinity 96.9%, average particle size 7 μm). The PTFE used was Lubron (registered trademark) L-5F, a product of Daikin Industries, Ltd. The volatile organic solvent used was Exxsol (registered trademark) D40, a product of Exxon.

In test number 11, a lubricating coating layer was not formed, and BESTOLIFE API Modified 304-ST (hereafter referred to as API dope) was applied with a brush. API dope contains, by mass, 15-40% lead, 7-13% zinc, and 3-7% copper. This API dope contains heavy metals such as lead, which may have adverse effects on the human body and the environment, but it has good lubricity, so it was used as the standard for the high torque performance evaluation described below.

　The pin surfaces and box surfaces for each test number were prepared using the above method. The resulting pin surfaces and box surfaces were used to carry out the seizure resistance evaluation test and high torque performance evaluation test described below.

[Seizure resistance evaluation test]
The seizure resistance evaluation was performed by a repeated fastening test. Specifically, the pin surface and the box surface of each test number were used to repeatedly tighten and unscrew the screws at room temperature (20°C) to evaluate the seizure resistance. The fastening torque in the screw tightening was 24,350 N·m. After each tightening and unscrewing, the pin surface and the box surface were visually observed. The occurrence of seizure on the threaded portion and the seal surface was confirmed by visual observation. The test was terminated when seizure occurred on the seal surface. In cases where the seizure on the threaded portion was minor and could be restored by care such as filing, the seizure defects were repaired and the test was continued. In cases where irreparable seizure occurred on the threaded portion, the test was also terminated at that point.

The evaluation index for seizure resistance was the maximum number of times the screws were tightened without causing irreversible seizure in the threads or seizure on the seal surface. The results of the seizure resistance evaluation test are shown in Table 3. Note that for test number 6, the composition for forming the lubricating coating layer was not applied properly, resulting in poor formation of the lubricating coating layer. For this reason, the test could not be carried out for test number 6.

In addition, in test number 11, a new layer of API dope was applied each time the screw was tightened and loosened. This is because API dope is usually reapplied each time the screw is tightened and loosened. In addition, this is the only intended use of API dope. On the other hand, in test numbers 1 to 10 and 12, the test was continued without re-forming the lubricating coating layer until the end of the test.

[High torque evaluation test]
The torque-on-shoulder resistance ΔT' was measured using the pin surface and box surface of each test number. Specifically, the pin and the box were screwed together at a screwing speed of 10 rpm and a screwing torque of 42.8 kN m. The torque was measured during screwing, and a torque chart was created as shown in FIG.

FIG. 15 is a diagram for explaining the torque on shoulder resistance ΔT' in this embodiment. Ts in FIG. 15 means shouldering torque. MTV in FIG. 15 represents the torque value where line segment L intersects with the torque chart. Line segment L in FIG. 15 is a straight line that has the same slope as the slope of the linear region in the torque chart after shouldering, and has 0.2% more rotation speed than the linear region. Normally, Ty (yield torque) is used to measure the torque on shoulder resistance ΔT'. However, in this embodiment, the yield torque (the boundary between the linear region and the nonlinear region in the torque chart after shouldering) was unclear. Therefore, line segment L was used to define MTV. The difference between MTV and Ts was taken as the torque on shoulder resistance ΔT' in this embodiment.

In this example, the torque on shoulder resistance ΔT' for each test number was calculated as a relative value, with the torque on shoulder resistance ΔT' for test number 11 when API dope was used instead of the lubricating coating layer being set as the standard (100). The torque on shoulder resistance ΔT' (relative value) obtained for each test number is shown in Table 3. As mentioned above, for test number 6, the composition for forming the lubricating coating layer was not applied properly, resulting in poor formation of the lubricating coating layer. Therefore, the test could not be performed for test number 6.

[Evaluation Results]
Referring to Tables 1 to 3, the lubricating coating layers of the metal pipes for oil wells of Test Nos. 1 to 5 and 7 to 9 and the compositions for forming the lubricating coating layers contained _ZrO2 . Therefore, the metal pipes for oil wells of Test Nos. 1 to 5 and 7 to 9 did not experience galling even after being repeatedly screwed in and unscrewed eight times, and thus exhibited excellent galling resistance. Furthermore, the metal pipes for oil wells of Test Nos. 1 to 5 and 7 to 9 had torque-on-shoulder resistance ΔT' (relative value) exceeding 100, and thus exhibited excellent high torque performance.

Furthermore, the oil well metal pipes of Test Nos. 2 to 5 and 7 to 9 had a _ZrO2 content of 0.5 to 8.0% in the lubricating coating layer and in the composition for forming the lubricating coating layer. Therefore, the oil well metal pipes of Test Nos. 2 to 5 and 7 to 9 showed even more excellent high torque performance than the oil well metal pipe of Test No. 1.

On the other hand, the lubricating coating layer of the metal oil well pipe of test number 10 and the composition for forming the lubricating coating layer contained Cr ₂ O ₃ instead of ZrO _2. As a result, after the pipe was repeatedly screwed in and out eight times, seizure occurred, and the pipe did not exhibit excellent seizure resistance.

The lubricating coating layer of the metal oil well pipe of test number 12 and the composition for forming the lubricating coating layer did not contain _ZrO2 . As a result, after five repeated screwing and unscrewing cycles, seizure occurred, and excellent seizure resistance was not exhibited. Furthermore, the torque-on-shoulder resistance ΔT' was less than 100, and excellent high torque performance was not exhibited.

The above describes the embodiments of the present disclosure. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by modifying the above-described embodiments as appropriate within the scope of the spirit of the present disclosure.

REFERENCE SIGNS LIST 1 Metal pipe for oil wells 10 Pipe body 10A First end 10B Second end 11 Pin pipe body 12 Coupling 40 Pin 41 Male threaded portion 42 Pin seal surface 43 Pin shoulder surface 50 Box 51 Female threaded portion 52 Box seal surface 53 Box shoulder surface 100 Lubricating coating layer 110 Metal plating layer 120 Chemical conversion layer 400 Pin contact surface 500 Box contact surface

Claims

A metal pipe for oil wells, comprising:
a tube body including a first end and a second end;
The tube body includes:
a pin formed on the first end;
a box formed at the second end,
The pin is
a pin contact surface including an external thread;
The box includes:
a box contact surface including an internal thread;
The metal pipe for oil well further comprises:
a lubricating coating layer formed as an uppermost layer on at least one of the pin contact surface and the box contact surface;
The lubricating coating layer is
ZrO2 ,
Metal soaps,
Wax and
A basic aromatic organic acid metal salt,
Metal pipe for oil wells.
The metal pipe for oil well according to claim 1,
The lubricating coating layer is
When the total content of the ZrO2 , the metal soap, the wax, the basic aromatic organic acid metal salt, and the lubricating powder is 100 mass%,
ZrO 2 :0.2-8.0%,
Metal soap: 2-30%,
Wax: 2-30%,
Basic aromatic organic acid metal salt: 12.0 to 80.0%, and
Lubricating powder: 0 to 20.0%,
Metal pipe for oil wells.
The metal pipe for oil well according to claim 2,
The lubricating coating layer is
Lubricating powder: 0.1 to 20.0%,
Metal pipe for oil wells.
The metal pipe for oil well according to any one of claims 1 to 3,
The metal pipe for oil well further comprises:
a metal plating layer disposed between at least one of the pin contact surface and the box contact surface and the lubricating coating layer;
Metal pipe for oil wells.
The metal pipe for oil well according to any one of claims 1 to 4,
At least one of the pin contact surface and the box contact surface is
The surface is blasted or pickled.
Metal pipe for oil wells.
The metal pipe for oil well according to any one of claims 1 to 5,
The metal pipe for oil well further comprises:
a chemical conversion layer disposed between at least one of the pin contact surface and the box contact surface and the lubricating coating layer, the chemical conversion layer having a surface in contact with the lubricating coating layer;
Metal pipe for oil wells.
The metal pipe for oil well according to any one of claims 1 to 6,
The pin contact surface further comprises:
a pin seal surface and a pin shoulder surface;
The box contact surface further comprises:
Including a box seal surface and a box shoulder surface.
Metal pipe for oil wells.
A composition for forming the lubricating coating layer provided on the metal oil well pipe according to any one of claims 1 to 7,
ZrO2 ,
Metal soaps,
Wax and
A basic aromatic organic acid metal salt,
Composition.
9. The composition of claim 8,
The composition further comprises:
Contains a lubricating powder,
Composition.
10. The composition according to claim 8 or claim 9,
The composition further comprises:
Contains volatile organic solvents,
Composition.