Metal pipe for oil wells and composition for forming lubrication coating layer thereof

Abstract

Provided is a metal pipe for oil wells which has excellent anti-seizure properties, low shouldering torque, and high high-torque performance. A metal pipe (1) for oil wells according to the present disclosure comprises a pipe body (10). The pipe body is provided with: a pin (40) which is formed at a first end (10A) and which has a pin contact surface (400) that includes a male thread portion (41); and a box (50) which is formed at a second end (10B) and which has a box contact surface (500) that includes a female thread portion (51). A lubrication coating layer (100) which is formed as the uppermost layer of at least one contact surface of the pin contact surface (400) and the box contact surface (500) contains 12.0-35.0% of metal particles, 2.0-30.0% of metal soap, 2.0-30.0% of a wax, 20.0-80.0% of a basic metal salt of an aromatic organic acid, 2.0-30.0% of a pine resin substance, and 0.1-10.0% of a lubricating powder. The Vickers hardness of the metal particles is not greater than the Vickers hardness of the pipe body (10).

Description

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

[0001] The present disclosure relates to a metal oil well tubular article and a composition for forming a lubricating coating layer on the metal oil well tubular article.

[0002] Metallic oil well pipes are used in oil wells and gas wells (hereinafter, oil wells and gas wells are collectively referred to simply as "oil wells"). At oil well drilling sites, multiple metallic oil well pipes are connected to form an oil well pipe assembly, typically casing or tubing, depending on the depth of the oil well. For this purpose, threaded joints (pins and boxes) are formed on the pipe body of the metallic oil well pipe. In this specification, the term "pipe body" refers to a pipe body (hollow pipe) having a pin and a box formed on the end thereof by machining or the like. That is, an oil well pipe assembly is formed by connecting a pin formed on the end of the pipe body of one metallic oil well pipe to a box formed on the end of the pipe body of another metallic oil well pipe by screwing them together.

[0003] 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 both a thread portion and an unthreaded metal contact portion.

[0004] Incidentally, there are cases where an inspection is carried out on the formed oil well tubular goods connected body. When carrying out the inspection, the oil well tubular goods connected body is pulled up, and the pin and the box are unscrewed. Then, the oil well metal pipe is removed from the oil well tubular goods connected body by unscrewing, and then inspected. After the inspection, the pin and the box are screwed together again, and the oil well metal pipe is reused as a part of the oil well tubular goods connected body. In this way, when the oil well metal pipe is used as an oil well tubular goods connected body, screwing and unscrewing of the pin and the box may be repeated.

[0005] On the other hand, when the pin and the box are screwed together or unscrewed, the contact surfaces (the pin contact surface and the box contact surface) are repeatedly subjected to strong friction. Therefore, when the pin and the box are repeatedly screwed together and unscrewed, 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.

[0006] Conventionally, compound grease containing heavy metal powder, called dope, has been used to improve the seizure resistance of oil well metal pipes. The application of compound grease to the contact surface can improve the seizure resistance of oil well metal pipes. However, there are concerns that the heavy metal powders, such as Pb, Zn, and Cu, contained in the compound grease may have a negative impact on the environment. Therefore, there is a need for the development of oil well metal pipes that have excellent seizure resistance without using compound grease.

[0007] Techniques for improving the galling resistance of metal pipes for oil wells have been proposed, for example, in Japanese Patent Laid-Open No. 2002-348587 (Patent Document 1) and International Publication No. 2006 / 104251 (Patent Document 2).

[0008] The oil well metal pipe disclosed in Patent Document 1 has a solid lubricating coating composed 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 composed 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.

[0009] The metal oil well pipe disclosed in Patent Document 2 has a viscous liquid or semi-solid lubricating coating and a dry solid coating formed thereon on the contact surface of at least one of the pin and the box. Patent Document 2 discloses that this metal oil well pipe can achieve excellent seizure resistance without using compound grease.

[0010] Patent Document 1: JP 2002-348587 A, International Publication No. 2006 / 104251

[0011] Incidentally, when a pin and a box formed on the pipe body of a metal oil well pipe are screwed together, the torque changes depending on the screw-tightening rotation speed. This point will be specifically explained using drawings. FIG. 1 is a diagram showing the relationship between the rotation speed and torque of a metal oil well pipe. The change in torque with respect to the rotation speed shown in FIG. 1 is also called a torque chart. Referring to FIG. 1, when screwing together the pin and the box, there are a stage where the torque chart has a gentle slope (initial stage), a stage where the torque chart becomes steep (steep slope stage), and a stage where the torque chart becomes gentle again (over-torque stage). Note that in the over-torque stage, plastic deformation occurs in parts of the pin and the box, resulting in a smaller slope of the torque chart.

[0012] 1 , in this specification, the torque at which the torque chart changes to a steep slope is also referred to as shouldering torque Ts (denoted as "Ts" in FIG. 1 ). Furthermore, the torque at which the torque chart again becomes gently sloped is also referred to as yield torque Ty (denoted as "Ty" in FIG. 1 ). Here, in the steep slope stage where the torque is greater than shouldering torque Ts, the pin and box are screwed together with a high torque, improving the airtightness performance. On the other hand, in the over-torque stage where the torque is greater than yield torque Ty, plastic deformation occurs in at least a portion of the pin and box.

[0013] Therefore, as shown in FIG. 1, the engagement torque To is set between the shouldering torque Ts and the yield torque Ty. From the above perspective, a larger difference between the shouldering torque Ts and the yield torque Ty is preferable, as this widens the range of torque that can be set as the engagement torque To. In this specification, the difference between the shouldering torque Ts and the yield torque Ty is also referred to as the "torque-on-shoulder resistance ΔT'." Furthermore, in this specification, a large torque-on-shoulder resistance ΔT' is also referred to as "high high-torque performance."

[0014] Here, in order to improve the high torque performance of the metal oil well pipe, it is effective to reduce the shouldering torque Ts or increase the yield torque Ty. However, it is generally known that the shouldering torque Ts and the yield torque Ty exhibit similar behavior. Therefore, if the friction coefficient of the surface of the metal oil well pipe is increased in order to increase the yield torque Ty, the yield torque Ty and the shouldering torque Ts will also increase. In this case, it becomes necessary to set the make-up torque To high.

[0015] On the other hand, the fastening of oil well metal pipes is carried out using, for example, power tongs. Therefore, if the set fastening torque To is too high, it may exceed the applicable range of a jig, such as a power tong. In other words, even if the high torque performance of the oil well metal pipe is improved, it is not desirable for the shouldering torque Ts to be too high.

[0016] That is, there has been a demand for a metallic oil well pipe having excellent seizure resistance and achieving both a low shouldering torque Ts and high high torque performance. Meanwhile, as described above, the techniques disclosed in Patent Documents 1 and 2 can improve the seizure resistance of a metallic oil well pipe. However, Patent Documents 1 and 2 do not consider achieving both a low shouldering torque Ts and high high torque performance.

[0017] An object of the present disclosure is to provide a metal oil well pipe having excellent seizure resistance and achieving both low shouldering torque and high torque performance, and to provide a composition for forming a lubricating coating layer on the metal oil well pipe.

[0018] The metal oil well pipe according to the present disclosure comprises a pipe body having a first end and a second end, the pipe body including a pin formed at the first end and a box formed at the second end, the pin including a pin contact surface including a male thread portion, and the box including a box contact surface including a female thread portion, the metal oil well pipe further comprising 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 comprising, in mass %, the following, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the lubricating coating layer is taken as 100 mass %: metal particles: 12.0 to 35.0%, metal soap: 2.0 to 30.0%, wax: 2.0 to 30.0%, basic aromatic organic acid metal salt: 20.0 to 80.0%, rosin-based substance: 2.0 to 30.0%, and The lubricating powder contains 0.1 to 10.0%, and the Vickers hardness of the metal particles is equal to or lower than the Vickers hardness of the pipe body.

[0019] The composition according to the present disclosure is a composition for forming a lubricating coating layer provided on the above-mentioned metal pipe for oil well use, and contains, in mass %, the following, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder is taken as 100 mass %, and the Vickers hardness of the metal particles is equal to or less than the Vickers hardness of the pipe body.

[0020] The metal oil well pipe according to the present disclosure has excellent seizure resistance and achieves both low shouldering torque and high high torque performance. The composition according to the present disclosure can form a lubricating coating layer on the metal oil well pipe.

[0021] FIG. 1 is a diagram showing the relationship between the rotation speed and torque of a metal oil well pipe. FIG. 2 is a structural diagram showing an example of a metal oil well pipe 1 according to this embodiment. FIG. 3 is a cross-sectional view (longitudinal cross-sectional view) parallel to the pipe axis direction of the second end 10B of the metal oil well pipe 1 shown in FIG. 2. FIG. 4 is a cross-sectional view (longitudinal cross-sectional view) parallel to the pipe axis direction of a part of a pin 40. FIG. 5 is a cross-sectional view (longitudinal cross-sectional view) parallel to the pipe axis direction of a part of a box 50. FIG. 6 is a longitudinal cross-sectional view of an example of cross-sectional views (longitudinal cross-sectional views) parallel to the pipe axis direction of the second end 10B of the metal oil well pipe 1, different from FIG. 3. FIG. 7 is a longitudinal cross-sectional view of an example of cross-sectional views (longitudinal cross-sectional views) parallel to the pipe axis direction of the second end 10B of the metal oil well pipe 1, different from FIG. 3 and FIG. 6. FIG. 8 is a cross-sectional view (longitudinal cross-sectional view) parallel to the pipe axis direction of a part in the vicinity of the pin 40. Fig. 9 is a cross-sectional view (longitudinal cross-sectional view) parallel to the tube axis direction of a portion near the box 50. Fig. 10 is a longitudinal cross-sectional view of an example of cross-sectional views (longitudinal cross-sectional views) parallel to the tube axis direction of a portion near the pin 40, different from Fig. 8. Fig. 11 is a longitudinal cross-sectional view of an example of cross-sectional views (longitudinal cross-sectional views) parallel to the tube axis direction of a portion near the box 50, different from Fig. 9. Fig. 12 is a longitudinal cross-sectional view of an example of cross-sectional views (longitudinal cross-sectional views) parallel to the tube axis direction of a portion near the pin 40, different from Figs. 8 and 10. Fig. 13 is a longitudinal cross-sectional view of an example of cross-sectional views (longitudinal cross-sectional views) parallel to the tube axis direction of a portion near the box 50, different from Figs. 9 and 11.

[0022] The metallic oil well pipe and composition according to the present embodiment will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0023] The present inventors have conducted various studies on the relationship between a metallic oil well pipe and a composition for forming a lubricating coating layer on the metallic oil well pipe, and the seizure resistance, shouldering torque Ts, and high torque performance of the metallic oil well pipe, and have obtained the following findings.

[0024] As described above, simply increasing the friction coefficient of the lubricating coating layer to improve the high-torque performance of an oil well tubular product increases not only the yield torque Ty but also the shouldering torque Ts. Therefore, the present inventors investigated ways to improve the high-torque performance of an oil well tubular product by introducing particles into the lubricating coating layer. As a result of detailed investigations, the present inventors discovered that the high-torque performance of an oil well tubular product can be improved by incorporating particles having a certain level of hardness into the lubricating coating layer.

[0025] The present inventors therefore evaluated the particles incorporated into the lubricating coating layer and the high torque performance, shouldering torque Ts, and seizure resistance of the resulting metal oil well pipes. This will be explained in detail using a table showing some of the examples.

[0026]

[0027] Table 1 is a table of excerpts from some of the examples described below. Referring to Table 1, Test No. 1 is an example in which the lubricating coating layer did not contain particles. On the other hand, Test Nos. 2, 3, 7, and 10 are examples in which the lubricating coating layer contained particles. In Table 1, "E (Excellent)" in the "Seizure Resistance" column indicates that the specimen had excellent seizure resistance. In Table 1, "NA (Not Acceptable)" in the "Seizure Resistance" column indicates that the specimen did not have excellent seizure resistance.

[0028] Referring to Table 1, comparing Test Nos. 1 and 2 with Test Nos. 3, 7, and 10, it can be seen that torque-on-shoulder resistance ΔT' increases when the lubricating coating contains particles in excess of 10.0 mass %. Further referring to Table 1, comparing Test No. 3 with Test Nos. 7 and 10, it can be seen that when the lubricating coating contains particles that are harder than the pipe body, torque-on-shoulder resistance ΔT' increases, but shouldering torque Ts also increases. Test No. 3 also had excellent seizure resistance.

[0029] In other words, as a result of detailed studies by the present inventors, it has become clear that if the lubricating coating layer contains more than 10.0 mass % of metal particles that have an appropriate hardness but are lower in hardness than the pipe body, it is possible to obtain a metal oil well pipe that has excellent seizure resistance and achieves both low shouldering torque Ts and high high torque performance.

[0030] The details of why the inclusion of more than 10.0 mass% of metal particles with a lower hardness than the pipe body in the lubricating coating can provide an OCTG with excellent seizure resistance and achieve both low shouldering torque Ts and high torque performance are not clear. However, the inventors speculate as follows: If the lubricating coating contains hard particles, the hard particles may be pressed against the pipe body when two OCTGs are fastened together, generating resistance. Therefore, it is speculated that the torque-on-shoulder resistance ΔT′ increases if the lubricating coating contains more than 10.0 mass% of metal particles with a certain degree of hardness. On the other hand, if the particles in the lubricating coating are too hard, scratches may easily occur in the pipe body when the hard particles are pressed against it. If scratches occur in the pipe body, the base materials of the pipe bodies may come into contact with each other, potentially increasing the likelihood of seizure. If scratches occur on the pipe body, the friction coefficient may increase, and the shouldering torque Ts may become higher.

[0031] In other words, if the lubricating coating contains more than 10.0 mass% of metal particles that are moderately hard and have a lower hardness than the pipe body, not only can the yield torque Ty be stably increased while maintaining a low shouldering torque Ts, but seizure due to flaws in the pipe body is also less likely to occur. As a result, the inventors speculate that it is possible to obtain a metal oil well pipe with excellent seizure resistance and both a low shouldering torque Ts and high high-torque performance. It is possible that a metal oil well pipe with excellent seizure resistance and both a low shouldering torque Ts and high high-torque performance could be obtained by a mechanism other than the above. However, the fact that a metal oil well pipe with excellent seizure resistance and both a low shouldering torque Ts and high high-torque performance can be obtained by containing more than 10.0 mass% of metal particles that are moderately hard and have a lower hardness than the pipe body in the lubricating coating is proven by the examples described below.

[0032] Therefore, the metal oil well pipe according to this embodiment has a lubricating coating layer formed as an uppermost layer on at least one of the pin contact surface and the box contact surface, and the lubricating coating layer contains, in mass %, 12.0 to 35.0% of metal particles, 2.0 to 30.0% of metal soap, 2.0 to 30.0% of wax, 20.0 to 80.0% of basic aromatic organic acid metal salt, 2.0 to 30.0% of rosin-based substance, and 0.1 to 10.0% of lubricating powder, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the lubricating coating layer is taken as 100% by mass, and further the Vickers hardness of the metal particles is equal to or less than the Vickers hardness of the pipe body. As a result, the metal oil well pipe according to this embodiment has excellent seizure resistance and achieves both low shouldering torque Ts and high high torque performance.

[0033] The metallic oil well pipe and composition according to the present embodiment, which have been completed based on the above findings, are summarized as follows.

[0034] [1] A metal pipe for oil well use, comprising: a pipe body having a first end and a second end, the pipe body including: a pin formed at the first end; and a box formed at the second end, the pin including a pin contact surface including a male thread portion, and the box including a box contact surface including a female thread portion, the metal pipe for oil well use further comprising: 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 comprising, in mass %, the following, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the lubricating coating layer is taken as 100 mass %: metal particles: 12.0 to 35.0%, metal soap: 2.0 to 30.0%, wax: 2.0 to 30.0%, basic aromatic organic acid metal salt: 20.0 to 80.0%, rosin-based substance: 2.0 to 30.0%, and A metal pipe for oil well use, comprising: 0.1 to 10.0% of a lubricating powder, wherein the Vickers hardness of the metal particles is equal to or lower than the Vickers hardness of the pipe body.

[0035] [2] The metal pipe for oil well use according to [1], wherein the chemical composition of the metal particles contains, in mass %, Fe: 50% or more.

[0036] [3] The metal pipe for oil well use according to [1] or [2], wherein the particle diameter of the metal particles is 15 to 250 μm.

[0037] [4] The metal oil well pipe according to any one of [1] to [3], wherein the lubricating coating layer has a thickness of 10 to 500 μm.

[0038] [5] The metallic oil well pipe according to any one of [1] to [4], further comprising one or more layers selected from the group consisting of a metal plating layer and a chemical conversion coating layer, which are formed as layers below the lubricating coating layer.

[0039] [6] The metal oil well pipe according to any one of [1] to [5], wherein the pin contact surface further includes a pin seal surface and a pin shoulder surface, and the box contact surface further includes a box seal surface and a box shoulder surface.

[0040] [7] A composition for forming the lubricating coating layer provided on the metal oil well pipe according to any one of [1] to [6], the composition containing, in mass %, the following, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder is taken as 100 mass %, and the Vickers hardness of the metal particles is equal to or less than the Vickers hardness of the pipe body.

[0041] [8] The composition according to [7], further comprising a volatile organic solvent.

[0042] The metallic oil well pipe according to this embodiment will be described in detail below.

[0043] [Configuration of Oil Well Metal Tubing] First, the configuration of the oil well metal tubing of this embodiment will be described. The oil well metal tubing has a well-known configuration. There are two types of oil well metal tubing: T&C type oil well metal tubing and integral type oil well metal tubing. Each type of oil well metal tubing will be described in detail below.

[0044] [When the oil well metal pipe 1 is a T&C type] Fig. 2 is a structural diagram showing an example of the oil well metal pipe 1 according to this embodiment. Fig. 2 is a structural diagram of a so-called T&C type oil well metal pipe 1. Referring to Fig. 2, the oil well metal pipe 1 includes a pipe body 10.

[0045] The pipe body 10 extends in the pipe axis direction. A cross section of the pipe body 10 perpendicular to the pipe axis direction is circular. The pipe body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is the end portion opposite the second end portion 10B. In the T&C type metal oil well pipe 1 shown in FIG. 2 , 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.

[0046] Figure 3 is a partial cross-sectional view showing a cross section (longitudinal cross section) parallel to the pipe axis direction of the coupling 12 of the metal oil well pipe 1 shown in Figure 2. With reference to Figures 2 and 3, the pipe body 10 includes a pin 40 and a box 50. The pin 40 is formed at a first end 10A of the pipe body 10. When fastening, the pin 40 is inserted into a box 50 of another metal oil well pipe 1 (not shown) and fastened to the box 50 of the other metal oil well pipe 1 by a screw.

[0047] The box 50 is formed at the second end 10B of the pipe body 10. At the time of fastening, the pin 40 of another metal pipe for oil well use 1 is inserted into the box 50, and the box 50 is fastened to the pin 40 of the other metal pipe for oil well use 1 by a screw.

[0048] [Configuration of pin 40] Fig. 4 is a cross-sectional view parallel to the pipe axis direction of the metal oil well pipe 1 of a portion near the pin 40 of the metal oil well pipe 1 shown in Fig. 3. The dashed line portion in Fig. 4 shows the configuration of a box 50 of another metal oil well pipe 1 when fastening to another metal oil well pipe 1. Referring to Fig. 4, the pin 40 has a pin contact surface 400 on the outer circumferential surface of the first end 10A of the pipe body 10. When fastening to another metal oil well pipe 1, the pin contact surface 400 is screwed into the box 50 of the other metal oil well pipe 1 and comes into contact with a box contact surface 500 (described later) of the box 50.

[0049] The pin contact surface 400 includes at least a male thread portion 41 formed on the outer circumferential surface of the first end portion 10A. The pin contact surface 400 may further include a pin seal surface 42 and a pin shoulder surface 43. In FIG. 4 , the pin shoulder surface 43 is located on the distal end surface of the first end portion 10A, and the pin seal surface 42 is located on the outer circumferential surface of the first end portion 10A closer to the distal end of the first end portion 10A than the male thread portion 41. In other words, the pin seal surface 42 is located 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.

[0050] When fastening another oil well metal pipe 1, the pin seal surface 42 comes into contact with a box seal surface 52 (described later) of the box 50 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 is inserted into the box 50 of the other oil well metal pipe 1, 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 oil well metal pipe 1, the pin seal surface 42 comes into close contact with the box seal surface 52. As a result, when fastening, the pin seal surface 42 comes into close contact with the box seal surface 52, forming a seal based on metal-metal contact. Therefore, the airtightness of the oil well metal pipes 1 fastened together can be improved.

[0051] In Fig. 4, the pin shoulder surface 43 is disposed on the tip surface of the first end portion 10A. That is, in the pin 40 shown in Fig. 4, the male thread portion 41, the pin seal surface 42, and the pin shoulder surface 43 are disposed in this order from the center of the pipe body 10 toward the first end portion 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 during fastening. Furthermore, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

[0052] 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, but not the pin seal surface 42 or the pin shoulder surface 43. The pin contact surface 400 may include the male thread portion 41 and the pin shoulder surface 43, but not the pin seal surface 42. The pin contact surface 400 may include the male thread portion 41 and the pin seal surface 42, but not the pin shoulder surface 43.

[0053] [Configuration of the box 50] Fig. 5 is a cross-sectional view parallel to the pipe axis direction of the metal oil well pipe 1 of a portion near the box 50 of the metal oil well pipe 1 shown in Fig. 3. The dashed line portion in Fig. 5 shows the configuration of the pin 40 of another metal oil well pipe 1 when fastening to another metal oil well pipe 1. Referring to Fig. 5, the box 50 has a box contact surface 500 on the inner circumferential surface of the second end 10B of the pipe body 10. When fastening to another metal oil well pipe 1, the pin 40 of the other metal oil well pipe 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.

[0054] 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. During fastening, the female thread portion 51 meshes with the male thread portion 41 of the pin 40 of another oil well metal pipe 1.

[0055] The box contact surface 500 may further include a box seal surface 52 and a box shoulder surface 53. In FIG. 5 , the box seal surface 52 is located on the inner circumferential surface of the second end portion 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 portion 10B.

[0056] When fastening 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, forming a seal based on metal-metal contact. Therefore, the airtightness of the metal oil well pipes 1 fastened to each other can be improved.

[0057] The box shoulder surface 53 is located closer to the pipe body 10 than the box seal surface 52. That is, in the box 50, the box shoulder surface 53, the box seal surface 52, and the female thread portion 51 are located in this order from the center of the pipe body 10 toward the tip of the second end 10B. When fastening 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 during fastening. Furthermore, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

[0058] The box contact surface 500 includes at least an internal thread portion 51. During fastening, the internal thread portion 51 of the box contact surface 500 of the box 50 corresponds to and contacts the external thread portion 41 of the pin contact surface 400 of the pin 40. The box seal surface 52 corresponds to and contacts the pin seal surface 42. The box shoulder surface 53 corresponds to and contacts the pin shoulder surface 43.

[0059] When the pin contact surface 400 includes the male thread portion 41 but does not include the pin seal surface 42 or the pin shoulder surface 43, the box contact surface 500 includes the female thread portion 51 but does not include the box seal surface 52 or the box shoulder surface 53. When the pin contact surface 400 includes the male thread portion 41 and the pin shoulder surface 43 but does not include the pin seal surface 42, the box contact surface 500 includes the female thread portion 51 and the box shoulder surface 53 but does not include the box seal surface 52. When the pin contact surface 400 includes the male thread portion 41 and the pin seal surface 42 but does not include the pin shoulder surface 43, the box contact surface 500 includes the female thread portion 51 and the box seal surface 52 but does not include the box shoulder surface 53.

[0060] The pin contact surface 400 may include a plurality of male thread portions 41, a plurality of pin seal surfaces 42, or a plurality of pin shoulder surfaces 43. For example, on the pin contact surface 400 of the pin 40, the pin shoulder surface 43, the pin seal surface 42, the male thread portion 41, the pin seal surface 42, the pin shoulder surface 43, the pin seal surface 42, and the male thread portion 41 may be arranged in this order from the tip of the first end 10A toward the center of the pipe body 10. In this case, on the box contact surface 500 of the box 50, the female thread portion 51, the box seal surface 52, the box shoulder surface 53, the box seal surface 52, 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.

[0061] 4 and 5 illustrate a so-called premium joint in which the pin 40 includes a male thread portion 41, a pin seal surface 42, and a pin shoulder surface 43, and the box 50 includes a female thread portion 51, a box seal surface 52, and a box shoulder surface 53. However, as described above, the pin 40 may include the male thread portion 41 but not the pin seal surface 42 or the pin shoulder surface 43. In this case, the box 50 includes the female thread portion 51 but not the box seal surface 52 or the box shoulder surface 53. Fig. 6 is a diagram showing an example of a metal oil well pipe 1 in which the pin 40 includes the male thread portion 41 but not the pin seal surface 42 or the pin shoulder surface 43, and the box 50 includes the female thread portion 51 but not the box seal surface 52 or the box shoulder surface 53.

[0062] [When the oil well metal pipe 1 is an integral type] The oil well metal pipe 1 shown in Figures 2, 3 and 6 is a so-called T&C type oil well metal pipe 1 in which the pipe body 10 includes a pin pipe body 11 and a coupling 12. However, the oil well metal pipe 1 of this embodiment may be an integral type instead of a T&C type.

[0063] Fig. 7 is a structural diagram of an integral-type metal oil well pipe 1 according to this embodiment. Referring to Fig. 7, the integral-type metal oil well pipe 1 includes a pipe body 10. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is located on the opposite side to the second end 10B. As described above, in the T&C type metal oil well pipe 1, the pipe body 10 includes a pin pipe body 11 and a coupling 12. That is, in the T&C type metal oil well pipe 1, the pipe body 10 is formed by fastening two separate members (the pin pipe body 11 and the coupling 12). In contrast, in the integral-type metal oil well pipe 1, the pipe body 10 is integrally formed.

[0064] The pin 40 is formed at a first end 10A of the pipe body 10. At the time of fastening, the pin 40 is inserted into and screwed into a box 50 of another integral type metal pipe for oil well use 1, and is fastened to the box 50 of another integral type metal pipe for oil well use 1. The box 50 is formed at a second end 10B of the pipe body 10. At the time of fastening, the pin 40 of another integral type metal pipe for oil well use 1 is inserted into and screwed into the box 50, and is fastened to the pin 40 of another integral type metal pipe for oil well use 1.

[0065] The configuration of the pin 40 of the integral type metal oil well pipe 1 is the same as the configuration of the pin 40 of the T&C type metal oil well pipe 1 shown in Fig. 4. Similarly, the configuration of the box 50 of the integral type metal oil well pipe 1 is the same as the configuration of the box 50 of the T&C type metal oil well pipe 1 shown in Fig. 5. In Figs. 4 and 5, in the pin 40, the pin shoulder surface 43, the pin seal surface 42, and the male thread portion 41 are arranged in this order 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 oil well pipe 1, it is sufficient that the pin contact surface 400 of the pin 40 of the integral type metal oil well pipe 1 includes at least the male thread portion 41. Furthermore, like the box contact surface 500 of the box 50 of the T&C type metal pipe for oil well use 1, the box contact surface 500 of the box 50 of the integral type metal pipe for oil well use 1 may include at least the female thread portion 51.

[0066] The metal oil well pipe 1 of this embodiment may be a T&C type or an integral type.

[0067] [Chemical Composition of Pipe Body] The chemical composition of the pipe body 10 of the oil well metal pipe 1 according to this embodiment is not particularly limited. That is, in this embodiment, the steel type of the pipe body 10 of the oil well metal pipe 1 is not particularly limited. The pipe body 10 may be formed of, for example, carbon steel, stainless steel, an 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, examples of steel pipes include low-alloy steel pipes, martensitic stainless steel pipes, ferritic stainless steel pipes, austenitic stainless steel pipes, and duplex stainless steel pipes. Examples of alloy pipes include Ni-based alloy pipes and NiCrFe alloy pipes.

[0068] 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, so if these high alloys are used for the pipe body 10, excellent corrosion resistance can be obtained in corrosive environments containing hydrogen sulfide, carbon dioxide, etc.

[0069] [Lubricant Coating Layer 100] The oil well metal pipe 1 according to this embodiment is provided with a lubricant coating layer 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 lubricant coating layer may be formed directly on at least one of the contact surfaces 400, 500, or some other layer may be formed on at least one of the contact surfaces 400, 500 and the lubricant coating layer may be formed on top of that. In other words, another layer may or may not be formed between the lubricant coating layer and the contact surface 400, 500.

[0070] 8, 10, and 12 are cross-sectional views (longitudinal cross-sections) parallel to the pipe axis direction of a portion near the pin 40. Furthermore, FIGS. 9, 11, and 13 are cross-sectional views (longitudinal cross-sections) parallel to the pipe axis direction of a portion near the box 50. With reference to FIG. 8, the lubricating coating layer 100 may be formed directly on the pin contact surface 400. With reference to FIG. 9, the lubricating coating layer 100 may be formed directly on the box contact surface 500. With reference to FIGS. 10 and 12, one or more other layers may be formed between the lubricating coating layer 100 and the pin contact surface 400. With reference to FIGS. 11 and 13, one or more other layers may be formed between the lubricating coating layer 100 and the box contact surface 500.

[0071] There are no particular restrictions on the thickness of the lubricating coating 100, but it is, for example, 10 to 500 μm. If the thickness of the lubricating coating 100 is 10 μm or greater, the above effects are stably achieved. On the other hand, if the thickness of the lubricating coating 100 is 500 μm or less, the adhesion of the lubricating coating 100 is improved. Therefore, taking productivity into consideration, the thickness of the lubricating coating in this embodiment is 10 to 500 μm.

[0072] In this embodiment, the thickness of the lubricating coating 100 can be measured by the following method. A wet gauge is placed in contact with the pin contact surface 400 or the box contact surface 500 on which the lubricating coating 100 is formed. The wet gauge includes multiple end faces corresponding to the desired thickness. The wet gauge is placed in contact with the lubricating coating 100, and it is determined which end face of the wet gauge the lubricating coating 100 is attached to. In this manner, the thickness of the lubricating coating 100 is determined. Measurements are taken at 12 locations around the circumferential direction of the metal oil well pipe 1 (12 locations: 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°). The arithmetic mean of the measurement results at the 12 locations is defined as the thickness of the lubricating coating 100.

[0073] The lubricating coating 100 contains, in mass %, 12.0 to 35.0% metal particles, 2.0 to 30.0% metal soap, 2.0 to 30.0% wax, 20.0 to 80.0% basic aromatic organic acid metal salt, 2.0 to 30.0% rosin-based substance, and 0.1 to 10.0% lubricating powder, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the lubricating coating 100 is taken as 100% by mass. The lubricating coating 100 may also contain components other than the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder. The total content (mass %) of components other than the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder is 0 to 10.0%. In other words, the lubricating coating 100 of this embodiment may be a lubricating coating layer containing, in mass %, 12.0 to 35.0% metal particles, 2.0 to 30.0% metal soap, 2.0 to 30.0% wax, 20.0 to 80.0% basic aromatic organic acid metal salt, 2.0 to 30.0% rosin-based substance, 0.1 to 10.0% lubricating powder, and 0 to 10.0% other components, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the lubricating coating 100 is taken as 100% by mass. Each component is described below. Unless otherwise specified, the "%" for each component refers to the content (mass %) of each component when the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the lubricating coating layer 100 is taken as 100 mass %.

[0074] [Metal Particles] In this embodiment, metal particles refer to particles primarily composed of metal. That is, in this embodiment, the metal particles may contain impurities in addition to the metal. The metal may be a single metal or an alloy containing two or more metals. Preferably, the chemical composition of the metal particles contains, by mass %, 50% or more Fe. That is, the metal particles are preferably pure iron or an Fe-based alloy. More specifically, the metal of the metal particles is preferably one or more selected from the group consisting of pure iron, carbon steel, and alloy steel as defined by JIS G 0203:2009. More preferably, the metal of the metal particles is stainless steel as defined by JIS G 0203:2009.

[0075] In this embodiment, the Vickers hardness of the metal particles is equal to or lower than the Vickers hardness of the pipe body. As described above, the chemical composition of the pipe body according to this embodiment is not particularly limited, but examples thereof include carbon steel, stainless steel, and alloys. That is, in this embodiment, the metal particles can be selected according to the chemical composition of the pipe body. Furthermore, the Vickers hardness of the metal particles is not particularly limited, but is, for example, 130 to 250 Hv. If the Vickers hardness of the metal particles is 130 to 250 Hv, this is preferable because it allows for a stable lower Vickers hardness compared to pipe bodies widely used as metal pipes for oil wells.

[0076] As described above, the metal particles are preferably made of stainless steel. Furthermore, if the metal particles are made of austenitic stainless steel, the Vickers hardness can be stably reduced. Examples of austenitic stainless steel include SUS301, SUS301L, SUS301J1, SUS302, SUS302B, SUSXM15J1, SUS303, SUS303Cu, SUS304, SUS304L, SUS304LN, SUS304N1, SUS304N2, SUS304Cu, SUSXM7, SUS304J1, SUS304J2, and SUS304Cu. 05, SUS305J1, SUS309S, SUS310S, SUS315J1, SUS315J2, SUS316, SUS316L, SUS316N, SUS316LN, SUS316J1, SUS316J1L, SUS317, SUS317J1, SUS317L, SUS312L, SUS836L, SUS890L, SUS321, and SUS 347. More preferably, the metal of the metal particles is SUS316L.

[0077] In this embodiment, the Vickers hardness of metal particles can be measured by the following method. Specifically, metal particles are collected from the lubricating coating layer 100 of the metal oil well pipe 1 according to this embodiment. Those skilled in the art can separate the metal particles from other components. The collected metal particles are embedded and fixed in resin, and the surface is polished to prepare a sample. A diamond triangular pyramidal indenter is pressed into the surface of the prepared sample, and a load-unload test is performed while controlling the test force and loading rate. The Vickers hardness (Hv) can be determined using the test force and indentation depth curve obtained from the load-unload test. A Vickers testing machine used for the load-unload test can be, for example, a dynamic ultra-microhardness tester (DUH-211S) manufactured by Shimadzu Corporation.

[0078] In this embodiment, the preferred particle size of the metal particles is 15 to 250 μm. When the particle size of the metal particles is 15 μm or more, the effect of increasing the yield torque Ty while maintaining a low shouldering torque Ts increases as the content increases. In other words, when the particle size of the metal particles is 15 μm or more, high torque performance is likely to be further improved while maintaining a low shouldering torque Ts. On the other hand, metal particles with a particle size of 15 μm or more are likely to cause scratches on the pipe body 10 when metal oil well pipes 1 are fastened together. Therefore, when metal oil well pipes 1 formed with a lubricating coating layer 100 containing metal particles with a particle size of 15 μm or more are fastened together, seizure resistance tends to be easily reduced.

[0079] Therefore, the metal particles in this embodiment have a Vickers hardness equal to or less than that of the pipe body 10. As a result, even if the metal particles in this embodiment have a particle diameter of 15 μm or more, deterioration in seizure resistance is unlikely. On the other hand, if the particle diameter of the metal particles is too large, the adhesion of the lubricating coating layer 100 may decrease. Therefore, in this embodiment, the preferred particle diameter of the metal particles is 15 to 250 μm.

[0080] In this embodiment, the particle size of the metal particles can be measured by the following method. Metal particles are collected using a method similar to that for measuring Vickers hardness, and particle size distribution is measured by a laser diffraction / scattering method. The particle size distribution can be measured by a well-known method. The arithmetic mean value of the effective diameter distribution obtained using, for example, a SALD series particle size distribution measuring device manufactured by SHIMADZU is used as the particle size of the metal particles in this embodiment.

[0081] The metal particle content required to effectively achieve the above effects is 12.0 to 35.0%. If the metal particle content is too low, the above effects will not be fully achieved. On the other hand, if the metal particle content is too high, the adhesion of the lubricating coating 100 may decrease. Therefore, the metal particle content in the lubricating coating 100 of this embodiment is 12.0 to 35.0%. A preferred lower limit for the metal particle content in the lubricating coating 100 is 13.0%, more preferably 14.0%, even more preferably 15.0%, and even more preferably 16.0%. A preferred upper limit for the metal particle content in the lubricating coating 100 is 34.0%, even more preferably 32.0%, even more preferably 30.0%, and even more preferably 29.0%.

[0082] Metal soaps are salts of fatty acids and metals. Here, fatty acids refer to aliphatic organic acids. That is, aromatic organic acids are not included in fatty acids by definition.

[0083] 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 tallow, 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, arachidic 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 of this embodiment may be one or more selected from the group consisting of the above-mentioned examples of fatty acids. Preferably, the fatty acid of this embodiment has 12 to 30 carbon atoms. 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.

[0084] 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 include 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.

[0085] In this embodiment, the metal soap content in the lubricating coating 100 is 2.0 to 30.0%. A metal soap content of 2.0% or more consistently improves the galling resistance and rust prevention properties of the metal oil well tubular product 1. A metal soap content of 30.0% or less consistently improves the adhesion and strength of the lubricating coating 100. Therefore, the metal soap content in the lubricating coating 100 of this embodiment is 2.0 to 30.0%. A preferred lower limit for the metal soap content in the lubricating coating 100 is 5.0%, more preferably 7.0%, and even more preferably 10.0%. A preferred upper limit for the metal soap content in the lubricating coating 100 is 28.0%, more preferably 25.0%, and even more preferably 20.0%.

[0086] [Wax] Wax is a general term for organic substances that are solid at room temperature and become liquid when heated. In this embodiment, the wax is one or more selected from the group consisting of animal, vegetable, mineral, and synthetic waxes. Examples of animal waxes include beeswax and spermaceti. Examples of vegetable waxes include Japan wax, carnauba wax, candelilla wax, and rice wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokerite, and ceresin. Examples of synthetic waxes include oxidized wax, polyethylene wax, Fischer-Tropsch wax, amide wax, and hydrogenated castor oil (castor wax). For example, the molecular weight of the wax is 1,000 or less. Preferably, the wax is paraffin wax with a molecular weight of 150 to 500.

[0087] 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 hydrogenated castor oil (castor wax). The wax is preferably one or more selected from the group consisting of paraffin wax, microcrystalline wax, and oxidized wax.

[0088] In this embodiment, the wax content in the lubricating coating 100 is 2.0 to 30.0%. A wax content of 2.0% or more reduces friction in the lubricating coating 100, thereby consistently improving the seizure resistance of the metal oil well tubular product 1. A wax content of 30.0% or less consistently improves the adhesion and strength of the lubricating coating 100. Therefore, the wax content in the lubricating coating 100 of this embodiment is 2.0 to 30.0%. A preferred lower limit for the wax content in the lubricating coating 100 is 5.0%, more preferably 7.0%, and even more preferably 10.0%. A preferred upper limit for the wax content in the lubricating coating 100 is 28.0%, more preferably 25.0%, and even more preferably 20.0%.

[0089] [Basic Metal Salt of an Aromatic Organic Acid] A 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.

[0090] 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, and 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, and magnesium.

[0091] That is, 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.

[0092] The higher the base number of the basic aromatic organic metal salt, the higher the amount of fine particle metal salt that functions as a solid lubricant. Therefore, by using a basic aromatic organic metal salt with a high base number, the seizure resistance of the metal oil well pipe 1 is further improved. Furthermore, by increasing the base number to a certain level or more, the effect of neutralizing acid components is obtained. Therefore, by using a basic aromatic organic metal salt with a high base number, the rust prevention ability of the metal oil well pipe 1 is further improved. Therefore, the basic aromatic organic metal salt preferably has a base number (JIS K2501) (when two or more types are used, the weighted average value of the base numbers taking into account the amounts) of 50 to 500 mgKOH / g.

[0093] When the base number of the basic aromatic organic acid metal salt is 50 mgKOH / g or more, the above-mentioned effects can be sufficiently obtained. When the base number is 500 mgKOH / g or less, 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 acid 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 acid metal salt is 450 mgKOH / g.

[0094] As described above, the basic metal salt of an aromatic organic acid is a grease-like or semi-solid substance that also functions as the base of the lubricating coating 100. As a result, the content of the basic metal salt of an aromatic organic acid in the lubricating coating 100 can be increased up to 80.0%. That is, in the lubricating coating 100 of this embodiment, the content of the basic metal salt of an aromatic organic acid is 20.0 to 80.0%.

[0095] In this embodiment, the preferred lower limit of the basic aromatic organic acid metal salt content in the lubricating coating 100 is 30.0%, more preferably 35.0%, and even more preferably 40.0%. The preferred upper limit of the basic aromatic organic acid metal salt content in the lubricating coating 100 is 75.0%, more preferably 71.0%, and even more preferably 70.0%.

[0096] [Pine resin-based substance] Pine resin-based substance is a compound selected from pine resin and derivatives of pine resin. In this specification, pine resin means a natural resin secreted from trees of the genus pine. Pine resin is a compound selected from C ２０ H ３０ O ２ Resin acid (rosin acid) represented by C ｎ H ｎ＋１０ O ４ The rosin-based substance is mainly composed of colophenic acid represented by the formula (I). Examples of rosin derivatives among the rosin-based substances include rosin ester, hydrogenated rosin, polymerized rosin, and disproportionated rosin. That is, in this embodiment, the rosin-based substance is, for example, one or more selected from the group consisting of rosin, which is a natural resin, rosin ester, hydrogenated rosin, polymerized rosin, and disproportionated rosin.

[0097] In this embodiment, the content of the rosin-based substance in the lubricating coating 100 is 2.0 to 30.0%. A rosin-based substance content of 2.0% or more reduces the friction of the lubricating coating 100, thereby consistently improving the seizure resistance of the metal oil well tubular product 1. A rosin-based substance content of 30.0% or less consistently improves the adhesion and strength of the lubricating coating 100. Therefore, the rosin-based substance content in the lubricating coating 100 of this embodiment is 2.0 to 30.0%. A preferred lower limit for the rosin-based substance content in the lubricating coating 100 is 5.0%, more preferably 7.0%, and even more preferably 10.0%. A preferred upper limit for the rosin-based substance content in the lubricating coating 100 is 28.0%, more preferably 25.0%, and even more preferably 20.0%.

[0098] [Lubricant Powder] The lubricant powder is a general term for solid powders having lubricity. In this embodiment, a well-known solid powder having lubricity can be used as the lubricant powder.

[0099] Specifically, as an example, lubricating powders are broadly classified into the following four types: (1) those that exhibit lubricity due to 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 due to a reactive element in addition to a crystal structure (e.g., 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), and (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)).

[0100] Preferably, the lubricating powder contains one or more materials selected from the group consisting of (1) to (4) above. That is, preferably, the lubricating powder is one or more materials 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 materials selected from the group consisting of molybdenum disulfide, graphite, polytetrafluoroethylene (PTFE), and graphite fluoride. Even more preferably, the lubricating powder is one or two materials selected from the group consisting of graphite and polytetrafluoroethylene (PTFE).

[0101] In this embodiment, the lubricating powder content in the lubricating coating 100 is 0.1 to 10.0%. A lubricating powder content of 0.1% or more reduces friction in the lubricating coating 100, thereby consistently improving the seizure resistance of the metal oil well tubular product 1. A lubricating powder content of 10.0% or less consistently improves the adhesion and strength of the lubricating coating 100. Therefore, the lubricating powder content in the lubricating coating 100 of this embodiment is 0.1 to 10.0%. A preferred lower limit for the lubricating powder content in the lubricating coating 100 is 0.5%, more preferably 1.0%, and even more preferably 2.0%. A preferred upper limit for the lubricating powder content in the lubricating coating 100 is 8.0%, more preferably 7.0%, and even more preferably 6.0%.

[0102] [Other Components] In addition to the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder, the lubricating coating layer 100 may contain other components, such as well-known anti-rust additives, preservatives, color pigments, and impurities.

[0103] If the lubricating coating layer 100 contains a rust-preventive additive, the rust-preventive properties of the metal oil well pipe 1 are improved. If the rust-preventive properties of the metal oil well pipe 1 are improved, rust development in the metal oil well pipe 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 the rust-preventive additive.

[0104] If the lubricating coating layer 100 contains an antiseptic, the corrosion resistance of the oil well metal pipe 1 is improved. If the corrosion resistance of the oil well metal pipe 1 is improved, corrosion of the oil well metal pipe 1 due to long-term storage can be suppressed. Furthermore, the lubricating coating layer 100 may contain trace amounts of volatile organic solvents contained in the composition described below as impurities. In the lubricating coating layer 100 of this embodiment, the total content of other components is 0 to 10.0%.

[0105] [Composition for Forming Lubricating Coating Layer 100] In this embodiment, the composition for forming the lubricating coating layer 100 contains, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder is taken as 100 mass %, the composition contains 12.0 to 35.0% metal particles, 2.0 to 30.0% metal soap, 2.0 to 30.0% wax, 20.0 to 80.0% basic aromatic organic acid metal salt, 2.0 to 30.0% rosin-based substance, and 0.1 to 10.0% lubricating powder. In other words, the content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the composition is the same as that of the lubricating coating layer 100.

[0106] 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 tends to evaporate at temperatures from room temperature to 150°C.

[0107] In this embodiment, the type of volatile organic solvent is not particularly limited. The volatile organic solvent may be, for example, a petroleum-based solvent. The petroleum-based solvent may be, for example, one or more solvents selected from the group consisting of solvents equivalent to industrial gasoline as defined 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.

[0108] In this embodiment, the content of the volatile organic solvent may be adjusted appropriately 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, assuming that the total amount of the nonvolatile components is 100 g.

[0109] [Other Layers] The metal oil well pipe 1 according to this embodiment may have layers other than the lubricating coating layer 100 formed on the contact surfaces 400, 500. The other layers are, for example, metal plating layers and chemical conversion layers.

[0110] [Metal Plating Layer 110] The oil well metal 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. 10 , the metal plating layer 110 may be formed on the pin contact surface 400 as an underlying layer of the lubricating coating layer 100. Similarly, with reference to FIG. 11 , the metal plating layer 110 may be formed on the box contact surface 500 as an underlying layer of the lubricating coating layer 100. In this manner, when both the lubricating coating layer 100 and the metal plating layer 110 are formed, the metal plating layer 110 is formed between the lubricating coating layer 100 and at least one of the contact surfaces 400, 500.

[0111] In the present 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 (a two-layer plating layer or a three-layer plating layer). When the metal plating layer 110 is a single-layer plating layer, the metal plating layer 110 may be, for example, a single-layer plating layer of Cu, Sn, or Ni metal, or 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 may be, 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 combining the above single-layer plating layers.

[0112] Preferably, the hardness of the metal plating layer is 200 or more in micro Vickers. If the hardness of the metal plating layer is 200 or more, the corrosion resistance of the metal oil well pipe 1 is further stably improved. In this embodiment, the hardness of the metal plating layer 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 oil well pipe 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.

[0113] In this embodiment, the thickness of the metal plating layer 110 is not particularly limited. However, when a multi-layer plating layer is formed as the metal plating layer 110, it is preferable that the thickness of the bottom plating layer be less than 1 μm. Furthermore, it is preferable that the thickness of the metal plating layer 110 (total thickness in the case of a multi-layer plating layer) be 5 to 15 μm.

[0114] The thickness of the metal plating layer 110 according to this embodiment is measured as follows. A probe of an eddy current phase-based film thickness gauge conforming to ISO (International Organization for Standardization) 21968 (2005) is brought into contact with the contact surface 400, 500 on which the metal plating layer 110 is formed. The phase difference between the high-frequency magnetic field at the input side of the probe and the eddy currents excited thereby on the metal plating layer is measured. This phase difference is converted into the thickness of the metal plating layer 110.

[0115] [Chemical Conversion Layer 120] The oil well metal pipe 1 according to this embodiment may further include a chemical conversion layer disposed between the lubricating coating layer 100 and at least one of the pin contact surface 400 and the box contact surface 500. The chemical conversion layer 120 has a surface in contact with the lubricating coating layer 100. Specifically, with reference to FIG. 12 , the chemical conversion layer 120 may be formed on the metal plating layer 110 formed on the pin contact surface 400, as an underlying layer of the lubricating coating layer 100. With reference to FIG. 13 , the chemical conversion layer 120 may be formed on the metal plating layer 110 formed on the box contact surface 500, as an underlying layer of the lubricating coating layer 100. Similarly, although not shown, the chemical conversion layer 120 may be formed on the pin contact surface 400, as an underlying layer of the lubricating coating layer 100. Similarly, although not shown, the chemical conversion layer 120 may be formed on the box contact surface 500, as an underlying layer of the lubricating coating layer 100.

[0116] In this embodiment, the type of 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, or a borate chemical conversion layer. 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 improved due to the so-called anchor effect. Furthermore, in this embodiment, the thickness of the chemical conversion layer 120 is not particularly limited. A preferred thickness of the chemical conversion layer 120 in this embodiment is 5 to 40 μm.

[0117] [Blast-treated surface or pickled surface] In the oil well metal pipe 1 according to this embodiment, the contact surfaces 400, 500 may be blast-treated or pickled. That is, in the oil well metal pipe 1, the surface on which the lubricating coating layer 100 is formed as the uppermost layer may be blast-treated or pickled. That is, the contact surfaces 400, 500 of the pipe body 10 of the oil well metal pipe 1 may be blast-treated or pickled, and the lubricating coating layer 100 may be formed thereon. Furthermore, when the oil well metal pipe 1 has the metal plating layer 110, the oil well metal pipe 1 may have the contact surfaces 400, 500 that have been blast-treated or pickled, and the metal plating layer 110 thereon, and the lubricating coating layer 100 may be formed on the metal plating layer 110. Furthermore, when the oil well metal pipe 1 has the metal plating layer 110, the oil well metal pipe 1 may further have a blasted or pickled metal plating layer 110 and a lubricating coating layer 100 thereon.

[0118] A blasted or pickled surface has increased surface roughness. Specifically, the preferred surface roughness of the surface that comes into contact with the lubricating coating 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 100 is 1 μm or more, the adhesion of the lubricating coating 100 is further improved. If the arithmetic mean roughness Ra of the surface that comes into contact with the lubricating coating 100 is 8 μm or less, the lubricating coating 100 is less likely to peel off.

[0119] In this embodiment, the arithmetic mean roughness Ra is measured in accordance with JIS B0601 (2001). For example, it can be measured using a scanning probe microscope SPI3800N manufactured by SII Nanotechnology Inc. Measurement conditions include, for example, a 2 μm × 2 μm area of ​​the sample, with 1024 × 1024 data points acquired. The reference length is 2.5 mm. The greater the arithmetic mean roughness Ra, the greater the contact area with the lubricating coating layer 100. This results in improved adhesion with the lubricating coating layer 100 due to the anchor effect. The improved adhesion of the lubricating coating layer 100 further improves the seizure resistance of the metal oil well pipe 1.

[0120] [Manufacturing Method] Hereinafter, a manufacturing method of the metal oil well pipe 1 according to this embodiment will be described.

[0121] The method for manufacturing the metal oil well pipe 1 according to this embodiment includes a preparation step and a lubricating coating layer forming step.

[0122] [Preparation Step] In the preparation step, a metal oil well pipe 1 is prepared, which includes a pipe body 10 including a pin 40 having a pin contact surface 400 including a male thread portion 41, and a box 50 having a box contact surface 500 including a female thread portion 51. As described above, the metal oil well pipe 1 according to this embodiment has a well-known configuration. That is, in the preparation step, it is sufficient to prepare a metal oil well pipe 1 having a well-known configuration.

[0123] [Lubricating Coating Layer 100 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 metal particles, metal soap, wax, a basic aromatic organic acid metal salt, a rosin-based substance, and a lubricating powder. The composition is liquefied by adding a solvent and / or by heating, and then applied to at least one of the pin contact surface 400 and the box contact surface 500. If necessary, the applied composition is dried to form the lubricating coating layer 100.

[0124] Specifically, first, a composition containing the above-mentioned components is prepared. A solventless composition can be produced, for example, 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 can also be used as the composition. A solvent-based composition can be produced, for example, by dissolving or dispersing metal particles, a metal soap, a wax, a basic aromatic organic acid metal salt, a rosin-based substance, and a lubricating powder in a volatile organic solvent and mixing them.

[0125] The prepared composition is applied to at least one of the contact surfaces 400, 500. Specifically, in the case of a solventless composition, the composition can be applied using a hot melt method. In the hot melt method, the composition is heated to melt it and become a low-viscosity fluid state. The fluidized composition is then sprayed from a spray gun with a temperature maintenance function. In this case, the composition is heated and melted in a tank equipped with an appropriate stirring device, and then supplied to the spray head of the spray gun (maintained at a predetermined temperature) via a metering pump using a compressor, where it is sprayed. The heating temperature is, for example, 90 to 130°C. The temperatures inside the tank and the spray head are adjusted according to the melting point of the composition. Instead of spray application, brush coating, immersion, and other application methods may also be used. 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 that the surface to which the composition is to be applied (the contact surfaces 400, 500, the surface of the metal plating layer 110, or the surface of the chemical conversion coating layer 120) be heated to a temperature higher than the melting point of the base.

[0126] 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 normal pressure.

[0127] In the case of a solventless 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 cooling of the composition can be carried out by a well-known method. Examples of cooling methods include standing to cool in the atmosphere and air cooling. In the case of a solvent-based composition, the composition applied to the contact surfaces 400, 500 is dried to form the lubricating coating layer 100. The drying of the composition can be carried out by a well-known method. Examples of drying methods include air drying, low-temperature air drying, and vacuum drying.

[0128] The cooling described above may also be performed by rapid cooling using a nitrogen gas or carbon dioxide gas cooling system. When rapid cooling is performed, indirect cooling is performed from the opposite side of the contact surface. Specifically, when forming the lubricating coating layer 100 as the top layer on the pin contact surface 400, cooling is performed from the inside surface of the pipe body 10. Similarly, when forming the lubricating coating layer 100 as the top layer on the box contact surface 500, indirect cooling is performed from the outside surface of the pipe body 10.

[0129] The lubricating coating layer 100 may be a single layer or multiple layers. "Multiple layers" refers to a state in which two or more layers of the lubricating coating layer 100 are stacked radially of the pipe body 10 from the contact surfaces 400, 500 side. Two or more lubricating coating layers 100 can be formed by repeatedly applying and drying the composition. The lubricating coating layer 100 may be formed directly on at least one of the contact surfaces 400, 500, or may be formed after performing the surface preparation described below.

[0130] Through the above steps, the metal oil well pipe 1 according to this embodiment is manufactured.

[0131] [Other Steps] The method for manufacturing the metal oil well pipe 1 according to this embodiment may further include other steps. The other steps include, for example, a metal plating step, a chemical conversion treatment step, a blasting step, and a pickling step. Each step will be described below.

[0132] [Metal Plating Step] The method for manufacturing the metal oil well pipe 1 according to this embodiment may further include a metal plating step prior to the lubricating coating layer forming step. The metal plating layer 110 can be formed by, for example, electroplating or impact plating.

[0133] [Electroplating Process] In the present embodiment, the electroplating process is a process of 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 an Sn layer, a three-layer plating layer of a Ni layer, a Cu layer, and an Sn layer, or a multi-layer plating layer that combines the above single-layer plating layers.

[0134] The electroplating process can be performed 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. Further, a current is passed through at least one of the contact surfaces 400, 500 to form the metal plating layer 110 on at least one of the contact surfaces 400, 500. The conditions, such as the temperature of the plating bath and the plating time, can be set as appropriate.

[0135] 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 to 50 g / L, Sn: 1 to 50 g / L, and Zn: 1 to 50 g / L. The electroplating conditions are, for example, plating bath pH: 1 to 10, plating bath temperature: 60° C., and current density: 1 to 100 A / dm ２ The treatment time is 0.1 to 30 minutes.

[0136] Similarly, for example, when forming a Zn—Ni alloy plating layer, 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 / dm ２ The treatment time is 0.1 to 30 minutes.

[0137] [Impact Plating] Impact plating is a treatment that can be carried out by mechanical plating, in which particles collide with the object to be plated in a rotating barrel, or projection plating, in which particles are collided with the object to be plated using a blasting device.

[0138] [Chemical Conversion Treatment Step] The method for manufacturing the metal oil well pipe 1 according to this embodiment may include a chemical conversion treatment step prior to the lubricating coating layer formation step. In the chemical conversion treatment step, a chemical conversion treatment is carried out to form a chemical conversion layer 120, which serves as an underlying layer of the lubricating coating layer 100 and has a surface that comes into contact with the lubricating coating layer 100.

[0139] In this embodiment, the chemical conversion treatment can be performed using a known method. A typical chemical conversion treatment solution can be used. For example, a zinc phosphate-based chemical conversion treatment solution 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 solution can be used. Other chemical conversion treatment solutions can be used depending on the desired chemical conversion treatment layer 120. The temperature of the treatment solution is, for example, room temperature to 100°C. The treatment time for 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 to promote the formation of the chemical conversion treatment layer. Surface conditioning refers to a treatment in which the substrate is immersed in a surface conditioning aqueous solution containing colloidal titanium. After the phosphate conversion treatment, it is preferable to rinse with water or hot water and then dry.

[0140] [Blasting 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, sandblasting. The sandblasting process is a process of projecting a mixture of blasting material (abrasive) and compressed air. The blasting material is, for example, spherical shot material and angular grit material. The sandblasting process can increase the surface roughness of the contact surfaces 400, 500 and the surface of the metal plating layer 110.

[0141] In this embodiment, the sandblasting process can be performed by a well-known method. For example, in the sandblasting process, air is compressed with a compressor and the compressed air is mixed with a blasting material. The blasting material may be made of stainless steel, aluminum, ceramic, alumina, or the like. In addition, the conditions of the sandblasting process, such as the projection speed, can be set appropriately.

[0142] In the present embodiment, the pickling process refers to a process of roughening the surface by immersion 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.

[0143] The metallic oil well pipe and composition according to the present embodiment will be described in more detail below using examples. However, the metallic oil well pipe and composition according to the present embodiment are not limited by the examples described below. In the examples below, the pin contact surface will be referred to as the pin surface, and the box contact surface will be referred to as the box surface. Furthermore, % in the examples means mass % unless otherwise specified.

[0144] In this example, VAM21 (registered trademark) manufactured by Nippon Steel Corporation was used as the pipe body. The VAM21 (registered trademark) pipe body had an outer diameter of 177.80 mm (7 inches) and a wall thickness of 11.506 mm (0.453 inches). The steel type was carbon steel. The carbon steel had a composition of 0.250% C, 0.29% Si, 0.85% Mn, 0.008% P, 0.0040% S, 0.02% Cu, 1.14% Cr, 0.03% Ni, 0.33% Mo, and the balance being Fe and impurities. The Vickers hardness of the pipe body used in this example was 254 Hv.

[0145] For the pipe body, specimen 1 was prepared for the repeated fastening test, and specimen 2 was prepared for the yield torque Ty measurement. The pin surfaces of specimen 1 of test numbers 1 to 9 were ground and finished, and then a zinc phosphate chemical conversion coating layer was formed. The pin surfaces of specimen 1 of test number 10 were ground and finished. The box surfaces of specimen 1 of test numbers 1 to 10 were ground and finished, and then a manganese phosphate chemical conversion coating layer was formed. The pin surfaces of specimen 2 of test numbers 1 to 10 were ground and finished. The box surfaces of specimen 2 of test numbers 1 to 10 were ground and finished, and then a manganese phosphate chemical conversion coating layer was formed.

[0146] In this example, the zinc phosphate conversion treatment layer was formed by the following method. Specifically, the test material was immersed in a zinc phosphate conversion treatment solution at 75 to 85°C for 10 minutes to form a zinc phosphate conversion treatment layer with a thickness of 12 μm (surface roughness of 8 μm). In this example, the manganese phosphate conversion treatment layer was formed by the following method. Specifically, the test material was immersed in a manganese phosphate conversion treatment solution at 80 to 95°C for 10 minutes to form a manganese phosphate conversion treatment layer with a thickness of 15 μm (surface roughness of 12 μm).

[0147] 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. The "Lubricating Coating Layer Composition" column in Table 2 shows the content of each component in mass %, with the total content of particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder taken as 100 mass %, except for the "Type" and "Particle Size" columns in the "Particle" column. The composition used to form the lubricating coating layer for each test number was the same as the lubricating coating layer composition shown in Table 2.

[0148]

[0149] In this example, "S316L" in the "Type" column of the "Particle" column refers to metal particles made of SUS316L steel manufactured by Sanyo Special Steel Co., Ltd., product name: PSS316L, chemical composition: Fe-13Ni-17Cr-2Mo. The Vickers hardness of S316L was 205 Hv. In addition, "SiO ２ " refers to quartz particles manufactured by AGC Inc., product name: Sunsphere, chemical composition: SiO ２ It means SiO ２ The Vickers hardness of the SPM30 particles was 600 Hv. The "SPM30" listed in the "Type" column of the "Particle" column refers to metal particles manufactured by Sanyo Special Steel Co., Ltd., product name: SPM30, chemical composition: Fe-1.3C-4Cr-5Mo-3V-6W-8Co. The Vickers hardness of the SPM30 particles was 755 Hv.

[0150] In this example, zinc stearate was used as the metal soap, paraffin wax was used as the wax, basic Ca sulfonate was used as the basic aromatic organic acid metal salt, rosin was used as the rosin-based substance, and graphite was used as the lubricating powder.

[0151] The pin surfaces and box surfaces for each test number were prepared in the above manner. Fastening tests were carried out using the obtained pin surfaces and box surfaces.

[0152] [Fastening Test] A cyclic fastening test was conducted using Test Material 1, and a fastening test was conducted using Test Material 2 until plastic deformation occurred. Specifically, in the cyclic fastening test using Test Material 1, the screw was repeatedly tightened and loosened at room temperature (20°C) while measuring the torque. The tightening torque during fastening was 24,350 N m. The pin surface and box surface were visually observed after each tightening and loosening. The occurrence of seizure on the threaded portion and seal surface was confirmed through visual observation. The test was terminated when seizure occurred on the seal surface. If the seizure on the threaded portion was minor and could be repaired by maintenance such as filing, the seizure flaw was repaired and the test continued. The test was also terminated at that point if irreparable seizure occurred on the threaded portion.

[0153] In this example, the maximum number of times that the screw could be made up without irreversible seizure occurring in the threaded portion or on the seal surface was defined as the number of times that the screw could be made up (times). Note that for test number 11, compound grease was reapplied after each tightening and loosening cycle before use. A torque chart such as that shown in Figure 1 was created for each number of tightening cycles, and the shouldering torque Ts for each test number was determined. The maximum value of the shouldering torque Ts obtained during each tightening cycle was defined as the shouldering torque Ts (ft-lbs).

[0154] Furthermore, in the make-up test using Test Material 2, the screw was tightened at room temperature (20°C) while measuring the torque until Test Material 2 underwent plastic deformation. A torque chart such as that shown in Figure 1 was created, and the yield torque Ty for each test number was determined. Specifically, the torque at which, after reaching shouldering torque Ts, the linearity of the torque change with the progression of rotation is lost and the torque begins to deviate from the linear region was defined as the yield torque Ty (ft-lbs).

[0155] The shouldering torque Ts (ft-lbs) obtained for each test number is shown in the "Ts (ft-lbs)" column of Table 3. The yield torque Ty (ft-lbs) obtained for each test number is shown in the "Ty (ft-lbs)" column of Table 3. The torque-on-shoulder resistance ΔT' (= Ty - Ts) was calculated from the yield torque Ty and shouldering torque Ts obtained for each test number. The torque-on-shoulder resistance ΔT' (ft-lbs) obtained for each test number is shown in the "ΔT' (ft-lbs)" column of Table 3. The number of make-up times (times) obtained for each test number is shown in Table 3.

[0156]

[0157] Referring to Tables 2 and 3, the lubricating coating layers of the test materials of Test Nos. 3 to 5 contained 12.0 to 35.0% metal particles with a Vickers hardness equal to or lower than that of the pipe body. As a result, the shouldering torque Ts of these test materials was as low as that of Test No. 1, which contained no metal particles. Furthermore, these test materials had high high-torque performance, with torque-on-shoulder resistance ΔT' exceeding 1,800 ft-lbs. Furthermore, these test materials had excellent seizure resistance, with no seizure occurring even after repeated screw tightening and loosening 10 times.

[0158] On the other hand, the lubricating coating layer of the specimen of Test No. 1 did not contain metal particles. As a result, this specimen had a torque-on-shoulder resistance ΔT' of less than 1,800 ft-lbs, and did not have high high-torque performance.

[0159] The lubricating coating layer of the specimen No. 2 had too low a content of metal particles. As a result, the shouldering torque Ts of this specimen was significantly higher than that of Test No. 1, which contained no metal particles. Furthermore, this specimen had a torque-on-shoulder resistance ΔT' of less than 1,800 ft-lbs, and did not have high high-torque performance.

[0160] The lubricating coating layers of the test materials of test numbers 6 and 7 contained particles with a Vickers hardness higher than that of the pipe body. As a result, the shouldering torque Ts of these test materials was significantly higher than that of test number 1, which did not contain metal particles. Furthermore, these test materials did not have high high-torque performance, with torque-on-shoulder resistance ΔT' being less than 1,800 ft-lbs. Furthermore, these test materials did not exhibit excellent seizure resistance, with seizure occurring before the test materials were repeatedly tightened and loosened 10 times.

[0161] The lubricating coating layer of the specimen of test number 8 contained particles with a Vickers hardness higher than that of the pipe body. As a result, this specimen began to seize before it was repeatedly screwed in and out 10 times, and did not exhibit excellent seizure resistance.

[0162] The lubricating coating layers of the test materials Nos. 9 and 10 contained particles with a Vickers hardness higher than that of the pipe body. As a result, the shouldering torque Ts of these test materials was significantly higher than that of Test No. 1, which contained no metal particles. Furthermore, these test materials did not have high high-torque performance, with torque-on-shoulder resistance ΔT' being less than 1,800 ft-lbs. Furthermore, these test materials did not exhibit excellent seizure resistance, with seizure occurring before the test materials were repeatedly tightened and loosened 10 times.

[0163] The test material of test number 11 was not formed with a lubricating coating layer and instead used compound grease. As a result, the shouldering torque Ts of this test material was significantly higher than that of test number 1, which did not contain metal particles.

[0164] The embodiments of the present disclosure have been described above. 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 appropriately modifying the above-described embodiments within the scope of the present disclosure.

[0165] REFERENCE SIGNS LIST 1 Metal pipe for oil well 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 coating layer 400 Pin contact surface 500 Box contact surface

Claims

1. A metal pipe for oil well use comprising a pipe body having a first end and a second end, the pipe body including: a pin formed at the first end; and a box formed at the second end, the pin including a pin contact surface including a male thread portion, and the box including a box contact surface including a female thread portion, the metal pipe for oil well use further comprising 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 comprising, in mass %, the following, where the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder in the lubricating coating layer is taken as 100 mass %: metal particles: 12.0 to 35.0%, metal soap: 2.0 to 30.0%, wax: 2.0 to 30.0%, basic aromatic organic acid metal salt: 20.0 to 80.0%, rosin-based substance: 2.0 to 30.0%, and A metal pipe for oil well use, comprising: 0.1 to 10.0% of a lubricating powder, wherein the Vickers hardness of the metal particles is equal to or lower than the Vickers hardness of the pipe body.

2. A metal pipe for oil well use according to claim 1, wherein the chemical composition of the metal particles contains, by mass %, 50% or more of Fe.

3. A metal pipe for oil well use according to claim 1 or 2, wherein the particle diameter of the metal particles is 15 to 250 μm.

4. A metal oil well pipe according to any one of claims 1 to 3, wherein the lubricating coating layer has a thickness of 10 to 500 μm.

5. A metallic oil well pipe according to any one of claims 1 to 4, further comprising one or more layers selected from the group consisting of a metal plating layer and a chemical conversion coating layer, which are formed as layers below the lubricating coating layer.

6. A metal oil well pipe according to any one of claims 1 to 5, wherein the pin contact surface further includes a pin seal surface and a pin shoulder surface, and the box contact surface further includes a box seal surface and a box shoulder surface.

7. A composition for forming the lubricating coating layer provided on the metal oil well pipe according to any one of claims 1 to 6, comprising, when the total content of the metal particles, metal soap, wax, basic aromatic organic acid metal salt, rosin-based substance, and lubricating powder is taken as 100% by mass, the composition contains, in mass %, the following: metal particles: 12.0 to 35.0%, metal soap: 2.0 to 30.0%, wax: 2.0 to 30.0%, basic aromatic organic acid metal salt: 20.0 to 80.0%, rosin-based substance: 2.0 to 30.0%, and lubricating powder: 0.1 to 10.0%, and the Vickers hardness of the metal particles is equal to or less than the Vickers hardness of the pipe body.

8. The composition according to claim 7, further comprising a volatile organic solvent.

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