OA21494A

OA21494A - Metal pipe for oil well and method of manufacturing metal pipe for oil well.

Info

Publication number: OA21494A
Application number: OA1202300052
Authority: OA
Inventors: Keishi Matsumoto; Tomoka ABE; Ken Tomiyasu; Mamoru OCHIAI
Original assignee: Nippon Steel Corporation; Vallourec Oil And Gas France
Priority date: 2020-08-20
Filing date: 2021-08-16
Publication date: 2024-07-31

Abstract

An oil-well metal pipe according to the present disclosure can be fastened with high torque even when the oil-well metal pipe has a large diameter. An oil-well metal pipe (1) according to the present disclosure has a pipe main body (10) including a first end portion (10A) and a second end portion (10B). The pipe main body (10) includes a pin (40) formed at the first end portion (l0A), and a box (50) fom1ed at the second end portion (10B). The pin (40) includes a pin contact surface (400) including an external thread part (41), and the box (50) includes a box contact surface (500) including an internal thread part (51). The oil-well metal pipe (1) according to the present disclosure also includes a resin coating (100) containing a resin, a solid lubricant powder, and copper phthalocyanine on or above at least one of the pin contact surfaces (400) and the box contact surface (500).

Description

DESCRIPTION

TITLE OF INVENTION

METAL PIPE FOR OIL WELL AND METHOD OF MANUFACTURING METAL PIPE FOR

OIL WELL

TECHNICAL FIELD

The présent disclosure relates to an oil-well métal pipe and method for producing an oilwell métal pipe.

BACKGROUND ART

An oil-well métal pipe is used for drilling in oil fîelds and natural gas fields (hereinafter, oil fields and natural gas fields are collectively referred to as oil wells). An oil-well métal pipe has a threaded connection. Specifically, at the oil well drilling site, a plurality of oil-well métal pipes are connected to form an oil country tubular goods connected body as typified by a casing pipe or a tubing pipe. An oil country tubular goods connected body is formed by fastening oil-well métal pipes to each other. Inspections are sometimes conducted on oil country tubular goods connected bodies. When conducting an inspection, the oil country tubular goods connected body is lifted up and loosened. Oil-well métal pipes are then detached from the oil country tubular goods connected body by loosening, and inspected. After the inspection, the oil-well métal pipes are refastened to each other, and the oil-well métal pipes are reused as a part of the oil country tubular goods connected body.

An oil-well métal pipe includes a pin and a box. The pin has a pin contact surface including an extemal thread part on an outer peripheral surface of an end portion of the oil-well métal pipe. The box has a box contact surface including an internai thread part on an inner peripheral surface of an end portion of the oil-well métal pipe. In the présent description, the extemal thread part and the internai thread part may also be collectively referred to as thread parts. Note that, in some cases the pin contact surface may also include a pin unthreaded métal contact portion including a pin sealing surface and a pin shoulder surface. Likewise, in some cases the box contact surface may also include a box unthreaded métal contact portion including a box sealing surface and a box shoulder surface.

The pin contact surface and the box contact surface repeatedly expérience strong friction during fastening and loosening of the oil-well métal pipe. Therefore, galling (unrepairable galling) is liable to occur at the pin contact surface and the box contact surface during repeated fastening and loosening. Accordingly, an oil-well métal pipe is required to hâve sufficient durability with respect to friction, that is, to hâve excellent galling résistance.

Heretofore, heavy métal powder-containing compound greases, which are referred to as dopes, hâve been used to improve the galling résistance of an oil-well métal pipe. Application of a compound grease to the pin contact surface and/or the box contact surface can improve the galling résistance of an oil-well métal pipe. However, heavy métal powder contained in compound greases, such as Pb, Zn and Cu, may affect the environment. For this reason, the development of an oil-well métal pipe that is excellent in galling résistance even without the use of a compound grease is desired.

Technology for enhancing the galling résistance of an oil-well métal pipe is proposed in, for example, International Application Publication No. WO2014/042144 (Patent Literature 1) and International Application Publication No. WO2017/047722 (Patent Literature 2).

A composition disclosed in Patent Literature 1 is a composition for forming a solid coating on a surface of a threaded connection of an oil-well métal pipe. The composition contains, in a mixed solvent including water and a dipolar aprotic solvent, a powdery organic resin which is at least partially soluble in the dipolar aprotic solvent. In the composition, the powdery organic resin is présent in a dissolved State or a dispersed State in the mixed solvent.

A composition disclosed in Patent Literature 2 is a composition for forming a solid lubricant coating on a threaded connection of an oil-well métal pipe. The composition contains a binder, a lubricant addition agent, an anti-rust addition agent and a plasticizer.

CITATION LIST

PATENT LITERATURE

Patent Literature 1: International Application Publication No. WO2014/042144 Patent Literature 2: International Application Publication No. WO2017/047722

SUMMARY OF INVENTION

TECHNICAL PROBLEM

In this connection, varions sizes (diameters) are used for an oil-well métal pipe. Therefore, it is désirable for it to be difficult for fastening together of oil-well métal pipes to become loose, irrespective of whether the size of the oil-well métal pipe is large or small. In this regard, a high fastening torque is set in advance for a large-diameter oil-well métal pipe so that oil-well métal pipes that were fastened do not become loose.

In the case of fastening large-diameter oil-well métal pipes with high torque, it is désirable that high torque performance is high. The phrase high torque performance is high means, in other words, that torque on shoulder résistance is large. The tenu torque on shoulder résistance means the différence between a yield torque at which one part of a threaded connection yields, and a shouldering torque at which interférence between threaded connections rapidly increases. On the other hand, even when the technologies disclosed in Patent Literature 1 and Patent Literature 2 are used, in some cases the torque on shoulder résistance is small. In such a case, it is difficult to fasten large-diameter oil-well métal pipes with high torque.

An objective of the présent disclosure is to provide an oil-well métal pipe that can be fastened with high torque even when the oil-well métal pipe has a large diameter, and a method for producing the oil-well métal pipe.

SOLUTION TO PROBLEM

An oil-well métal pipe according to the présent disclosure includes:

a pipe main body including a first end portion and a second end portion, wherein: the pipe main body includes:

a pin formed at the first end portion, and a box formed at the second end portion;

the pin includes:

a pin contact surface including an extemal thread part; and the box includes:

a box contact surface including an internai thread part;

the oil-well métal pipe fürther including:

a resin coating containing a resin, a solid lubricant powder and copper phthalocyanine on or above at least one of the pin contact surface and the box contact surface.

A method for producing the oil-well métal pipe according to the présent disclosure includes the steps of:

preparing an oil-well métal pipe having a pipe main body that includes a pin including a pin contact surface that includes an extemal thread part, and a box including a box contact surface that includes an internai thread part;

applying a composition containing a resin, a solid lubricant powder and copper phthalocyanine onto at least one of the pin contact surface and the box contact surface; and hardening the composition that is applied to form a resin coating.

ADVANTAGEOUS EFFECTS OF INVENTION

The oil-well métal pipe according to the présent disclosure can be fastened with high torque even when the oil-well métal pipe has a large diameter. The method for producing an oil-well métal pipe according to the présent disclosure can produce the aforementioned oil-well métal pipe.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a graph illustrating the relation between the number of tums of an oil-well métal pipe that has a shoulder part and the torque, when the oil-well métal pipe is fastened. [FIG. 2A] FIG. 2A is a graph illustrating the relation between the content of copper phthalocyanine in a resin coating and high torque performance.

[FIG. 2B] FIG. 2B is an enlarged view of a part of a graph illustrating the relation between the content of copper phthalocyanine in a resin coating and high torque performance shown in Fig. 2A.

[FIG. 3] FIG. 3 is a configuration diagram illustrating one example of an oil-well métal pipe according to the présent embodiment.

[FIG. 4] FIG. 4 is a partial cross-sectional view illustrating a cross section (longitudinal cross section) parallel to a pipe axis direction of a coupling of the oil-well métal pipe illustrated in FIG.3.

[FIG. 5] FIG. 5 is a cross-sectional view parallel to the pipe axis direction of the oil-well métal pipe illustrated in FIG. 4, that illustrâtes a portion in the vicinity of a pin of the oil-well métal pipe.

[FIG. 6] FIG. 6 is a cross-sectional view parallel to the pipe axis direction of the oil-well métal pipe illustrated in FIG. 4, that illustrâtes a portion in the vicinity of a box of the oil-well métal pipe.

[FIG. 7] FIG. 7 is a partial cross-sectional view illustrating a cross section (longitudinal cross section) parallel to the pipe axis direction of a coupling of the oil-well métal pipe according to the présent embodiment, that is different from FIG. 4.

[FIG. 8] FIG. 8 is a configuration diagram illustrating an intégral type oil-well métal pipe according to the présent embodiment.

[FIG. 9] FIG. 9 is an enlarged view of a pin contact surface illustrated in FIG. 5.

[FIG. 10] FIG. 10 is an enlarged view of a box contact surface illustrated in FIG. 6.

[FIG. 11] FIG. 11 is an enlarged view of a pin contact surface according to the présent embodiment, that is different from FIG. 9.

[FIG. 12] FIG. 12 is an enlarged view of a pin contact surface according to the présent embodiment, that is different from FIG. 9 and FIG. 11.

[FIG. 13] FIG. 13 is an enlarged view of a pin contact surface according to the présent embodiment, that is different from FIG. 9, FIG. 11 and FIG. 12.

[FIG. 14] FIG. 14 is a graph illustrating the relation between a plating layer and results of the Bowden test as an index of galling résistance.

[FIG. 15] FIG. 15 is an enlarged view of a box contact surface according to the présent embodiment, that is different from FIG. 10.

[FIG. 16] FIG. 16 is an enlarged view of a pin contact surface according to the présent embodiment, that is different from FIG. 9, FIG. 11, FIG. 12 and FIG. 13.

[FIG. 17] FIG. 17 is an enlarged view of a pin contact surface according to the présent embodiment, that is different from FIG. 9, FIG. 11, FIG. 12, FIG. 13 and FIG. 16.

[FIG. 18] FIG. 18 is an enlarged view of a pin contact surface according to the présent embodiment, that is different from FIG. 9, FIG. 11, FIG. 12, FIG. 13, FIG. 16 and FIG. 17. [FIG. 19] FIG. 19 is a view for describing a torque on shoulder résistance ΔΤ with respect to the examples.

DESCRIPTION OF EMBODIMENTS

The présent embodiment will be described in detail below with reference to the accompanying drawings. The same reference symbols will be used throughout the drawings to refer to the same or like parts, and description thereof will not be repeated.

The présent inventors conducted varions studies regarding the relation between an oilwell métal pipe and fastening torque. As a resuit, the présent inventors obtained the following findings.

[High torque performance]

When fastening oil-well métal pipes to each other, the optimal torque to end the fastening is determined in advance. FIG. 1 is a graph illustrating the relation between the number of tums of an oil-well métal pipe that has a shoulder part and the torque, when the oil-well métal pipe is fastened. Referring to FIG. 1, when oil-well métal pipes are fastened, initially the torque increases moderately in proportion to the number of tums. As fastening continues, the shoulder parts corne in contact with each other. The torque at such time is referred to as shouldering torque Ts. Aller the shouldering torque Ts is reached, when fastening is continued, the torque rapidly increases in proportion to the number of tums. The fastening is completed at a time point at which the torque reaches a predetermined value (fastening torque To). At the fastening torque To, métal seal portions interfère with each other with an appropriate interfacial pressure. In this case, high gas tightness is obtained with respect to the oil-well métal pipes. After reaching the fastening torque To, if the oil-well métal pipes are further fastened excessively, a torque will be reached a yield torque and a portion of the pin and the box will yield. In the présent description, the différence between the shouldering torque Ts and the yield torque Ty is referred to as torque on shoulder résistance ΔΤ.

Note that, as a different form of an oil-well métal pipe, an oil-well métal pipe which has a wedge thread and does not hâve a shoulder part is available. In the case of such kind of oil-well métal pipe that has a wedge thread also, similarly to an oil-well métal pipe that has a shoulder part, the relation between the number of tums of the oil-well métal pipe and the torque is as shown in FIG. 1.

Here, the terni wedge thread means a thread having the following structure. At an extemal thread part of a wedge thread, in the direction in which screwing of the pin advances, the width of a thread ridge of an extemal thread part gradually narrows along the thread hélix, the width of a thread groove of the extemal thread part gradually widens along the thread hélix. And further, at an internai thread part of a wedge thread, in the direction in which screwing of the box advances, the width of a thread groove of an internai thread part gradually narrows along the thread hélix, and the width of a thread ridge of the internai thread part gradually widens along the thread hélix. In the case of an oil-well métal pipe which has a wedge thread, as fastening progresses, the load flanks of the extemal thread part and the internai thread part corne in contact with each other and stabbing flanks of the extemal thread part and the internai thread part corne in contact with each other, and locking (interférence fitting) occurs. The torque at the time that locking occurs is also referred to as locking torque or locked flank torque.

In the présent description, unless specifically stated otherwise, no distinction is made between locking torque and shouldering torque, and the term shouldering torque Ts is used to refer thereto. In the case of an oil-well métal pipe having a wedge thread also, similarly to an oil-well métal pipe having a shoulder part, after reaching the shouldering torque Ts, if fastening is continued further, the torque will rapidly increase in proportion to the number of tums. That is, at the shouldering torque Ts, the interférence between the threaded connections increases rapidly. If fastening is continued further thereafter, the fastening torque To will be reached. After reaching the fastening torque To, if the oil-well métal pipes are further fastened excessively, the yield torque Ty will be reached and a portion of the pin and the box will yield.

As described above, a high fastening torque To is set for large-diameter oil-well métal pipes. However, in a case where the fastening torque To is set to a high value, in some cases, before the fastening torque To is reached, a portion of the pin and the box yields, and plastic deformation is caused. If the torque on shoulder résistance ΔΤ is large, fastening can be continued further after the shouldering torque Ts is reached. Therefore, if the torque on shoulder résistance AT is large, fastening with high torque can be performed even in the case of large-diameter oil-well métal pipes. In such a case, it is difficult for the oil-well métal pipes to become loose. In the présent description, the terni high torque performance is high means that the torque on shoulder résistance AT is large. In the présent description, the term largediameter oil-well métal pipe means an oil-well métal pipe having an extemal diameter of 254 mm (10 inches) or more.

To increase the torque on shoulder résistance AT, it is effective to decrease the shouldering torque Ts or to increase the yield torque Ty. However, it is known that, in general, the shouldering torque Ts and the yield torque Ty exhibit similar behavior. For example, in a case where the coefficient of friction of the surface of an oil-well métal pipe is lowered to decrease the shouldering torque Ts, the yield torque Ty also decreases, and not just the shouldering torque Ts. In this situation, in some cases a portion of the pin or the box yields before reaching the fastening torque To. Further, in a case where the coefficient of friction of the surface of an oil-well métal pipe is raised to increase the yield torque Ty, the shouldering torque Ts also increases, and not just the yield torque Ty. In this situation, in some cases shoulder parts may not corne in contact with each other even when the fastening torque To is reached.

In comparison with normal- to small-diameter oil-well métal pipes, in the case of largediameter oil-well métal pipes, there is also a demand to increase high torque performance. Therefore, the présent inventors investigated methods that can increase high torque performance even in the case of a large-diameter oil-well métal pipe. As a resuit, the présent inventors obtained the following findings.

FIG. 2A is a graph illustrating the relation between the content of copper phthalocyanine in a resin coating and high torque performance. The graph in FIG. 2A was obtained based on the results of Example 1 that is described later. In Example 1, a so-called large-diameter oilwell métal pipe (having an extemal diameter of 273.05 mm (10.75 inches) and a wall thickness of 12.570 mm (0.495 inches)) was used.

The abscissa in FIG. 2A represents the content (mass%) of copper phthalocyanine in a resin coating. The ordinate in FIG. 2A represents the torque on shoulder résistance ΔΤ. The torque on shoulder résistance ΔΤ was determined as a relative value in comparison to the torque on shoulder résistance ΔΤ in a case where a dope defined in API (American Petroleum Institute) standard BUL 5A2 (1998) was used and the value thereof was taken as 100. In FIG. 2A, the symbol of a white circle (O) dénotés that copper phthalocyanine was contained in the resin coating, and the symbol of a black circle (·) dénotés that copper phthalocyanine was not contained in the resin coating.

Referring to FIG. 2A, the torque on shoulder résistance ΔΤ increased when the resin coating contained copper phthalocyanine in comparison to a case where the resin coating did not contain copper phthalocyanine. That is, if the resin coating contains copper phthalocyanine, high torque performance increases. In this case, it is possible to perform fastening with high torque even when fastening large-diameter oil-well métal pipes.

FIG. 2B, is an enlarged view of a part of a graph illustrating the relation between the content of copper phthalocyanine in a resin coating and high torque performance. Referring to FIG. 2B, if the content of copper phthalocyanine in the resin coating is adjusted to be 0.2 mass% or more, the high torque performance of the oil-well métal pipe increases further.

The gist of the oil-well métal pipe and the method for producing the oil-well métal pipe of the présent embodiment that were completed based on the above fmdings is as follows.

[1]

An oil-well métal pipe, including:

a pin formed at the first end portion, and a box formed at the second end portion; the pin includes:

a pin contact surface including an extemal thread part; and the box includes:

a box contact surface including an internai thread part;

the oil-well métal pipe further including:

The oil-well métal pipe according to the présent embodiment includes a resin coating that contains copper phthalocyanine. Therefore, even when the oil-well métal pipe has a large diameter, it is possible to perform fastening with high torque. Note that, the oil-well métal pipe according to the présent embodiment is also applicable to a normal- to small-diameter oil-well métal pipe. Even in a case where the oil-well métal pipe according to the présent embodiment is applied to a normal- to small-diameter oil-well métal pipe, fastening at a necessary and sufficient torque is possible.

[2]

The oil-well métal pipe according to [1], wherein:

the resin coating contains 0.2 to 30.0 mass% of copper phthalocyanine.

In this case, the high torque performance of the oil-well métal pipe is further enhanced.

[3]

The oil-well métal pipe according to [2], wherein:

the resin coating contains:

0.2 to 30.0 mass% of copper phthalocyanine, to 90 mass% of the resin, and to 30 mass% of the solid lubricant powder.

[4]

The oil-well métal pipe according to [2] or [3], wherein:

the resin coating contains 0.2 to 9.0 mass% of copper phthalocyanine.

In this case, the galling résistance of the oil-well métal pipe increases, in addition to the high torque performance.

[5]

The oil-well métal pipe according to any one of [1] to [4], further including:

a plating layer between at least one of the pin contact surface and the box contact surface, and the resin coating.

[6]

The oil-well métal pipe according to any one of [1] to [4], further including:

a Chemical conversion treatment layer between at least one of the pin contact surface and the box contact surface, and the resin coating.

[7]

The oil-well métal pipe according to [5], further including:

a Chemical conversion treatment layer between the plating layer and the resin coating.

[8]

The oil-well métal pipe according to any one of [1] to [7], wherein: the resin coating further containing a rust préventive pigment.

[9]

The oil-well métal pipe according to any one of [1] to [8], wherein:

at least one of the pin contact surface and the box contact surface is a surface that is subjected to one or more types of treatment selected from the group consisting of a blasting treatment and pickling.

[10]

The oil-well métal pipe according to any one of [1] to [9], wherein:

the resin is one or more types selected from the group consisting of epoxy resin, phénol resin, acrylic resin, urethane resin, polyester resin, polyamide-imide resin, polyamide resin, polyimide resin and polyether ether ketone resin.

[H]

The oil-well métal pipe according to any one of [1] to [10], wherein:

the solid lubricant powder is one or more types selected from the group consisting of graphite, zinc oxide, boron nitride, talc, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfïde, bismuth sulfide, organic molybdenum, thiosulfate compounds, and polytetrafluoroethylene.

[12]

The oil-well métal pipe according to any one of [1] to [11], wherein:

the pin contact surface further includes a pin sealing surface and a pin shoulder surface, and the box contact surface further includes a box sealing surface and a box shoulder surface.

[13]

A method for producing the oil-well métal pipe according to [1], the method including the steps of:

Hereunder, the oil-well métal pipe according to the présent embodiment will be described in detail.

[Structure of oil-well métal pipe]

First, the structure of the oil-well métal pipe of the présent embodiment will be described. The oil-well métal pipe has a well-known structure. The available types of oil-well métal pipes are a T&C type oil-well métal pipe and an intégral type oil-well métal pipe. Hereunder, each type of oil-well métal pipe will be described in detail.

[Case where oil-well métal pipe 1 is T&C type]

FIG. 3 is a configuration diagram illustrating one example of an oil-well métal pipe 1 according to the présent embodiment. FIG. 3 is a configuration diagram illustrating the oil-well métal pipe 1 of a so-called T&C (threaded and coupled) type. Referring to FIG. 3, the oil-well métal pipe 1 includes a pipe main body 10.

The pipe main body 10 extends in the pipe axis direction. A cross section perpendicular to the pipe axis direction of the pipe main body 10 is a circular shape. The pipe main body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is an end portion on the opposite side to the second end portion 10B. In the T&C type oil-well métal pipe 1 illustrated in FIG. 3, the pipe main body 10 includes a pin tube body 11 and a coupling 12. The coupling 12 is attached to one end of the pin tube body 11. More specifically, the coupling 12 is fastened by threading to one end of the pin tube body 11.

FIG. 4 is a partial cross-sectional view illustrating a cross section (longitudinal cross section) that is parallel to the pipe axis direction of the coupling 12 of the oil-well métal pipe 1 illustrated in FIG. 3. Referring to FIG. 3 and FIG. 4, the pipe main body 10 includes a pin 40 and a box 50. The pin 40 is formed at the first end portion 10A of the pipe main body 10. When performing fastening, the pin 40 is inserted into the box 50 of another oil-well métal pipe 1 (not illustrated), and is fastened by threading to the box 50 of the other oil-well métal pipe 1.

The box 50 is formed at the second end portion 10B of the pipe main body 10. When performing fastening, the pin 40 of another oil-well métal pipe 1 is inserted into the box 50, and the box 50 is fastened by threading to the pin 40 of the other oil-well métal pipe 1.

[Regarding structure of pin 40]

FIG. 5 is a cross-sectional view of a portion in the vicinity of the pin 40 of the oil-well métal pipe 1 illustrated in FIG. 4, that is a cross-sectional view parallel to the pipe axis direction of the oil-well métal pipe 1. A dashed line portion in FIG. 5 represents the structure of the box 50 of another oil-well métal pipe in the case of fastening the oil-well métal pipe 1 to another oilwell métal pipe 1. Referring to FIG. 5, the pin 40 includes a pin contact surface 400 on the outer peripheral surface of the first end portion 10A of the pipe main body 10. When fastening to the other oil-well métal pipe 1, the pin contact surface 400 is screwed into the box 50 of the other oil-well métal pipe 1 and contacts a box contact surface 500 (described later) of the box 50.

The pin contact surface 400 includes at least an extemal thread part 41 formed in the outer peripheral surface of the first end portion 10A. The pin contact surface 400 may further include a pin sealing surface 42 and a pin shoulder surface 43. In FIG. 5, the pin shoulder surface 43 is disposed at the front end face of the first end portion 10A, and on the outer peripheral surface of the first end portion 10A, the pin sealing surface 42 is disposed further on the front end side of the first end portion 10A than the extemal thread part 41. In other words, the pin sealing surface 42 is disposed between the extemal thread part 41 and the pin shoulder surface 43. The pin sealing surface 42 is provided in a tapered shape. Specifically, the extemal diameter of the pin sealing surface 42 gradually decreases from the extemal thread part 41 toward the pin shoulder surface 43 in the longitudinal direction (pipe axis direction) of the first end portion 10A.

When performing fastening with another oil-well métal pipe 1, the pin sealing surface 42 contacts a box sealing surface 52 (described later) of the box 50 of the other oil-well métal pipe 1. More specifically, during fastening, when the pin 40 is inserted into the box 50 of the other oil-well métal pipe 1, the pin sealing surface 42 contacts the box sealing surface 52. Subsequently, when the pin 40 is screwed further into the box 50 of the other oil-well métal pipe 1, the pin sealing surface 42 closely contacts the box sealing surface 52. By this means, during fastening, the pin sealing surface 42 closely contacts the box sealing surface 52 to thereby form a seal that is based on metal-to-metal contact. Therefore, the gastightness can be increased in each of the oil-well métal pipe 1 that are fastened to each other.

In FIG. 5, the pin shoulder surface 43 is disposed at the front end face of the first end portion 10A. In other words, in the pin 40 illustrated in FIG. 5, the extemal thread part 41, the pin sealing surface 42 and the pin shoulder surface 43 are disposed sequentially in that order from the center of the pipe main body 10 toward the first end portion 10A. During fastening to the other oil-well métal pipe 1, the pin shoulder surface 43 opposes and contacts a box shoulder surface 53 (described later) of the box 50 of the other oil-well métal pipe 1. More specifically, during fastening, the pin shoulder surface 43 contacts the box shoulder surface 53 as a resuit of the pin 40 being inserted into the box 50 of the other oil-well métal pipe 1. By this means, during fastening, a high torque can be obtained. Further, the positional relation between the pin 40 and the box 50 in the fastening state can be stabilized.

Note that, the pin contact surface 400 of the pin 40 includes at least the extemal thread part 41. In other words, the pin contact surface 400 includes the extemal thread part 41, and need not include the pin sealing surface 42 and the pin shoulder surface 43. The pin contact surface 400 may include the extemal thread part 41 and the pin shoulder surface 43, and need not include the pin sealing surface 42. The pin contact surface 400 may include the extemal thread part 41 and the pin sealing surface 42, and need not include the pin shoulder surface 43.

[Regarding structure of box 50]

FIG. 6 is a cross-sectional view of a portion in the vicinity of the box 50 of the oil-well métal pipe 1 illustrated in FIG. 4, that is a cross-sectional view parallel to the pipe axis direction of the oil-well métal pipe 1. A dashed line portion in FIG. 6 represents the structure of the pin 40 of another oil-well métal pipe 1 in the case of fastening the oil-well métal pipe 1 to another oil-well métal pipe 1. Referring to FIG. 6, the box 50 includes a box contact surface 500 on the inner peripheral surface of the second end portion 10B of the pipe main body 10. When performing fastening to another oil-well métal pipe 1, the box contact surface 500 contacts the pin contact surface 400 of the pin 40 of the other oil-well métal pipe 1 when the pin 40 is screwed into the box 50.

The box contact surface 500 includes at least an internai thread part 51 formed in the inner peripheral surface of the second end portion 10B. When performing fastening, the internai thread part 51 engages with the extemal thread part 41 of the pin 40 of the other oil-well métal pipe 1.

The box contact surface 500 may further include the box sealing surface 52 and the box shoulder surface 53. In FIG. 6, on the inner peripheral surface of the second end portion 10B, the box sealing surface 52 is disposed further on the pipe main body 10 side than the internai thread part 51. In other words, the box sealing surface 52 is disposed between the internai thread part 51 and the box shoulder surface 53. The box sealing surface 52 is provided in a tapered shape. Specifically, the internai diameter of the box sealing surface 52 gradually decreases from the internai thread part 51 toward the box shoulder surface 53 in the longitudinal direction (pipe axis direction) of the second end portion 10B.

When performing fastening to another oil-well métal pipe 1, the box sealing surface 52 contacts the pin sealing surface 42 of the pin 40 of the other oil-well métal pipe 1. More specifically, during fastening, when the pin 40 of the other oil-well métal pipe 1 is screwed into the box 50, the box sealing surface 52 contacts the pin sealing surface 42, and when the pin 40 is screwed in further, the box sealing surface 52 closely contacts the pin sealing surface 42. By this means, during fastening, the box sealing surface 52 closely contacts the pin sealing surface to thereby form a seal that is based on metal-to-metal contact. Therefore, the gastightness can be increased in each of the oil-well métal pipe 1 that are fastened to each other.

The box shoulder surface 53 is disposed further on the pipe main body 10 side than the box sealing surface 52. In other words, in the box 50, the box shoulder surface 53, the box sealing surface 52 and the internai thread part 51 are disposed sequentially in that order from the center of the pipe main body 10 toward the front end of the second end portion 10B. When performing fastening to another oil-well métal pipe 1, the box shoulder surface 53 opposes and contacts the pin shoulder surface 43 of the pin 40 of the other oil-well métal pipe 1. More specifically, during fastening, the box shoulder surface 53 contacts the pin shoulder surface 43 as a resuit of the pin 40 of the other oil-well métal pipe 1 being inserted into the box 50. By this means, during fastening, a high torque can be obtained. Further, the positional relation between the pin 40 and the box 50 in the fastening state can be stabilized.

The box contact surface 500 includes at least the internai thread part 51. When performing fastening, the internai thread part 51 of the box contact surface 500 of the box 50 contacts the extemal thread part 41 of the pin contact surface 400 of the pin 40 in a manner such that the internai thread part 51 corresponds to the extemal thread part 41. The box sealing surface 52 contacts the pin sealing surface 42 in a manner such that the box sealing surface 52 corresponds to the pin sealing surface 42. The box shoulder surface 53 contacts the pin shoulder surface 43 in a manner such that the box shoulder surface 53 corresponds to the pin shoulder surface 43.

In a case where the pin contact surface 400 includes the extemal thread part 41 and does not include the pin sealing surface 42 and the pin shoulder surface 43, the box contact surface 500 includes the internai thread part 51 and does not include the box sealing surface 52 and the box shoulder surface 53. In a case where the pin contact surface 400 includes the extemal thread part 41 and the pin shoulder surface 43 and does not include the pin sealing surface 42, the box contact surface 500 includes the internai thread part 51 and the box shoulder surface 53 and does not include the box sealing surface 52. In a case where the pin contact surface 400 includes the extemal thread part 41 and the pin sealing surface 42 and does not include the pin shoulder surface 43, the box contact surface 500 includes the internai thread part 51 and the box sealing surface 52 and does not include the box shoulder surface 53.

The pin contact surface 400 may include a plurality of the extemal thread parts 41, may include a plurality of the pin sealing surfaces 42, and may include a plurality of the pin shoulder surfaces 43. For example, the pin shoulder surface 43, the pin sealing surface 42, the extemal thread part 41, the pin sealing surface 42, the pin shoulder surface 43, the pin sealing surface 42 and the extemal thread part 41 may be disposed in that order on the pin contact surface 400 of the pin 40 in the direction from the front end of the first end portion 10A toward the center of the pipe main body 10. In such case, the internai thread part 51, the box sealing surface 52, the box shoulder surface 53, the box sealing surface 52, the internai thread part 51, the box sealing surface 52 and the box shoulder surface 53 are disposed in that order on the box contact surface 500 of the box 50 in the direction from the front end of the second end portion 10B toward the center of the pipe main body 10.

In FIG. 5 and FIG. 6 a so-called premium joint is illustrated in which the pin 40 includes the extemal thread part 41, the pin sealing surface 42 and the pin shoulder surface 43, and the box 50 includes the internai thread part 51, the box sealing surface 52 and the box shoulder surface 53. However, as described above, the pin 40 may include the extemal thread part 41 and need not include the pin sealing surface 42 and the pin shoulder surface 43. In this case, the box 50 includes the internai thread part 51 and does not include the box sealing surface 52 and the box shoulder surface 53. FIG. 7 is a view illustrating one example of the oil-well métal pipe 1 in which the pin 40 includes the extemal thread part 41 and does not include the pin sealing surface 42 and the pin shoulder surface 43, and the box 50 includes the internai thread part 51 and does not include the box sealing surface 52 and the box shoulder surface 53.

[Case where oil-well métal pipe 1 is intégral type]

The oil-well métal pipe 1 illustrated in FIG. 3, FIG. 4 and FIG. 7 is a so-called T&C type oil-well métal pipe 1, in which the pipe main body 10 includes the pin tube body 11 and the coupling 12. However, the oil-well métal pipe 1 according to the présent embodiment may be an intégral type instead of a T&C type.

FIG. 8 is a configuration diagram of an intégral type oil-well métal pipe 1 according to the présent embodiment. Referring to FIG. 8, the intégral type oil-well métal pipe 1 includes a pipe main body 10. The pipe main body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is disposed on the opposite side to the second end portion 10B. As described above, in the T&C type oil-well métal pipe 1, the pipe main body 10 includes the pin tube body 11 and the coupling 12. In other words, in the T&C type oil-well métal pipe 1, the pipe main body 10 is constituted by fastening two separate members (the pin tube body 11 and the coupling 12). In contrast, in the intégral type oil-well métal pipe 1, the pipe main body 10 is formed in an intégral manner.

The pin 40 is formed at the first end portion 10A of the pipe main body 10. When performing fastening, the pin 40 is inserted in and screwed into the box 50 of another intégral type oil-well métal pipe 1, and thereby fastened to the box 50 of the other intégral type oil-well métal pipe 1. The box 50 is formed at the second end portion 10B of the pipe main body 10. When performing fastening, the pin 40 of another intégral type oil-well métal pipe 1 is inserted in and screwed into the box 50, to thereby fasten the box 50 to the pin 40 of the other intégral type oil-well métal pipe 1.

The structure of the pin 40 of the intégral type oil-well métal pipe 1 is the same as the structure of the pin 40 of the T&C type oil-well métal pipe 1 illustrated in FIG. 5. Similarly, the structure of the box 50 of the intégral type oil-well métal pipe 1 is the same as the structure of the box 50 of the T&C type oil-well métal pipe 1 illustrated in FIG. 6. Note that, in FIG. 8, the pin shoulder surface 43, the pin sealing surface 42 and the extemal thread part 41 in the pin 40 are disposed in that order from the front end of the first end portion 10A toward the center of the pipe main body 10. Therefore, the internai thread part 51, the box sealing surface 52 and the box shoulder surface 53 in the box 50 are disposed in that order from the front end of the second end portion 10B toward the center of the pipe main body 10. However, similarly to the pin contact surface 400 of the pin 40 of the T&C type oil-well métal pipe 1, it suffîces that the pin contact surface 400 of the pin 40 of the intégral type oil-well métal pipe 1 includes at least the extemal thread part 41. Further, similarly to the box contact surface 500 of the box 50 of the T&C type oil-well métal pipe 1, it suffices that the box contact surface 500 of the box 50 of the intégral type oil-well métal pipe 1 includes at least the internai thread part 51.

In short, the oil-well métal pipe 1 of the présent embodiment may be a T&C type or may be an intégral type.

[Resin coating]

The oil-well métal pipe 1 according to the présent embodiment includes a resin coating 100 on or above at least one of the pin contact surface 400 and the box contact surface 500. FIG. 9 is an enlarged view of the pin contact surface 400 illustrated in FIG. 5. FIG. 10 is an enlarged view of the box contact surface 500 illustrated in FIG. 6. As illustrated in FIG. 9 and FIG. 10, the oil-well métal pipe 1 according to the présent embodiment may include the resin coating 100 on or above both the pin contact surface 400 and the box contact surface 500. However, a configuration may also be adopted in which the oil-well métal pipe 1 according to the présent embodiment includes the resin coating 100 on or above only one surface among the pin contact surface 400 and the box contact surface 500. For example, in a case where the resin coating 100 is provided on or above the pin contact surface 400 as illustrated in FIG. 9, the resin coating 100 need not be provided on or above the box contact surface 500. Further, in a case where the resin coating 100 is provided on or above the box contact surface 500 as illustrated in

FIG. 10, the resin coating need not be provided on the pin contact surface 400. In other words, the oil-well métal pipe 1 according to the présent embodiment includes the resin coating 100 on the pin contact surface 400 and/or on or above the box contact surface 500.

The resin coating 100 is a solid coating that contains a resin, a solid lubricant powder, and copper phthalocyanine. The resin and the solid lubricant powder can each be independently selected. Hereunder, the resin, the solid lubricant powder, and the copper phthalocyanine contained in the resin coating 100 according to the présent embodiment are described in detail.

[Resin]

The resin contained in the resin coating 100 according to the présent embodiment is not particularly limited. However, when fastening the oil-well métal pipe 1, the surface of the resin coating 100 is scratched and abrasion powder is generated. Therefore, to stably obtain the wear résistance (coating life) of the resin coating 100 and high torque performance, it is préférable to use a resin for which the adhesion to the substrate is high and which has a moderate hardness. A resin for which the adhesion to the substrate is high and which has a moderate hardness is, for example, one or more types selected from the group consisting of epoxy resin, phénol resin, acrylic resin, urethane resin, polyester resin, polyamide-imide resin, polyamide resin, polyimide resin, and polyether ether ketone resin.

Preferably the resin is one type or two types selected from the group consisting of epoxy resin and acrylic resin.

The content of the resin in the resin coating 100 is, for example, 60 to 90 mass%. In this case, the formability, galling résistance and high torque performance of the resin coating 100 can be more stably increased. The lower limit of the content of resin is preferably 62 mass%, more preferably is 63 mass%, and further preferably is 65 mass%. The upper limit of the content of resin is preferably 88 mass%, and more preferably is 86 mass%.

[Solid lubricant powder]

The solid lubricant powder contained in the resin coating 100 according to the présent embodiment is not particularly limited. The solid lubricant powder is, for example, one or more types selected from the group consisting of graphite, zinc oxide, boron nitride, talc, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfîde, bismuth sulfide, organic molybdenum, thiosulfate compounds, and polytetrafluoroethylene.

Preferably the solid lubricant powder is one or more types selected from the group consisting of graphite, polytetrafluoroethylene, and molybdenum disulfide. Further preferably, the solid lubricant powder is polytetrafluoroethylene.

The content of the solid lubricant powder in the resin coating 100 is, for example, 1 to 30 mass%. In this case, the formability and galling résistance of the resin coating 100 can be more stably enhanced. The lower limit of the content of the solid lubricant powder is preferably 2 mass%, and more preferably is 5 mass%. The upper limit of the content of the solid lubricant powder is preferably 25 mass%, and more preferably is 20 mass%.

[Copper phthalocyanine]

The resin coating 100 according to the présent embodiment contains copper phthalocyanine. In the oil-well métal pipe 1 according to the présent embodiment, copper phthalocyanine is the most important substance for exerting high torque performance. Copper phthalocyanine is one type of phthalocyanine complex in which phthalocyanine (C32H18N8) has coordinated with copper ions (Cu²⁺). The Chemical formula of copper phthalocyanine is shown below.

If copper phthalocyanine is contained in the resin coating 100, the high torque performance of the oil-well métal pipe 1 increases. The details regarding the reason the high torque performance increases hâve not been clarified. However, it has been verified by examples that are described later that, as a resuit of copper phthalocyanine being contained in the resin coating 100 according to the présent embodiment, the torque on shoulder résistance ΔΤ that is the différence between the yield torque Ty and the shouldering torque Ts increases. Therefore, even when the oil-well métal pipe 1 according to the présent embodiment has a large diameter, the oil-well métal pipe 1 can be fastened with high torque.

The content of copper phthalocyanine in the resin coating 100 according to the présent embodiment is not particularly limited. That is, even when a small amount of copper phthalocyanine is contained in the resin coating 100, an effect of enhancing the high torque performance of the oil-well métal pipe 1 is obtained to a certain extent. The lower limit of the content of copper phthalocyanine in the resin coating 100 may be 0.1 mass%. On the other hand, if the content of copper phthalocyanine in the resin coating 100 is 0.2 mass% or more, the high torque performance of the oil-well métal pipe 1 is further enhanced. Accordingly, in the présent embodiment, the lower limit of the content of copper phthalocyanine in the resin coating 100 is preferably 0.1 mass%, more preferably is 0.2 mass%, and further preferably is 0.4 mass%.

If the content of copper phthalocyanine in the resin coating 100 according to the présent embodiment is 30.0 mass% or less, the dispersibility of the copper phthalocyanine increases. Accordingly, a préférable upper limit of the content of copper phthalocyanine in the resin coating 100 is 30.0 mass%. In addition, if the content of copper phthalocyanine in the resin coating 100 according to the présent embodiment is 9.0 mass% or less, the galling résistance of the oil-well métal pipe 1 also increases, and not just the high torque performance. Therefore, the upper limit of the content of copper phthalocyanine in the resin coating 100 may be 9.0 mass%.

Thus, the upper limit of the content of copper phthalocyanine in the resin coating 100 according to the présent embodiment is preferably 30.0 mass%, more preferably is 14.0 mass%, further preferably is 12.0 mass%, further preferably is 10.0 mass%, further preferably is 9.0 mass%, and fùrther preferably is 6.0 mass%.

[Galling résistance]

In the oil-well métal pipe 1 according to the présent embodiment, if the upper limit of the content of copper phthalocyanine in the resin coating 100 is adjusted further, the galling résistance of the oil-well métal pipe 1 also increases, and not just the high torque performance. Hereunder, the content will be described more specifically with reference to a table.

Table 1 shows the contents of copper phthalocyanine in resin coatings 100 and results of the Bowden test as an index of galling résistance. Table 1 was obtained by extracting some of the results of Example 2 that is described later. In Example 2, a resin coating 100 containing the copper phthalocyanine content shown in Table 1 was formed on the surface of a Steel plate of each of the test numbers. The Bowden test was conducted using the steel plates of the respective test numbers on which a resin coating 100 was formed. In the Bowden test, a Steel bail was caused to slide on the surface of the resin coating 100 of the steel plate of each test number, and the coefficient of friction was determined. The content of copper phthalocyanine in the resin coating 100 and the number of sliding times until the coefficient of friction became more than 0.3 of each Test Numbers are shown in Table 1. Note that, a higher value for the number of sliding times until the coefficient of friction became more than 0.3 indicates a higher galling résistance.

[Table 1]

TABLE 1

Test Number	Copper Phthalocyanine Content	Number of Sliding Times until Coefficient of Friction Became More Than 0.3 (Times)
13	0.1 mass%	510
14	0.5 mass%	647
15	2.0 mass%	524
16	5.0 mass%	531
17	10.0 mass%	55
21	-	511

Referring to Table 1, if the content of copper phthalocyanine in the resin coating 100 is 0.2 to 9.0 mass%, the number of sliding times until the coefficient of friction becomes more than 0.3 increases in comparison to a case where the content of copper phthalocyanine in the resin coating 100 is 0.1 mass% or 10.0 mass%. That is, if the content of copper phthalocyanine in the resin coating 100 is 0.2 to 9.0 mass%, the galling résistance of the oil-well métal pipe 1 increases, and not only the high torque performance.

[Other Components]

The resin coating 100 according to the présent embodiment may also contain components other than the components described above. The other components are, for example, one or more types selected from the group consisting of a rust préventive agent, an antiseptie agent and an antioxidant agent. The rust préventive agent is, for example, one or more types selected from the group consisting of aluminum tripolyphosphate, aluminum phosphite and calcium ionexchanged silica. A commercially available water repellent agent may be employed as the rust préventive agent.

The resin coating 100 according to the présent embodiment may be formed of a single layer or may include multiple layers. The term include multiple layers refers to a state in which the resin coating 100 is deposited in two layers or more in the radial direction of the oilwell métal pipe 1. The resin coating 100 can be deposited and formed in two layers or more by repeating application and hardening of the composition for forming the resin coating 100. The resin coating 100 may be directly formed on at least one of the pin contact surface 400 and the box contact surface 500, or may be formed after subjecting the pin contact surface 400 and/or the box contact surface 500 to a preconditioning treatment described later. In a case where the resin coating 100 includes multiple layers, any one layer among the multiple layers of the resin coating 100 may contain the respective components within the aforementioned ranges, or ail of the multiple layers of the resin coating 100 may contain the respective components within the aforementioned ranges. Preferably, the resin coating 100 includes an anti-rust resin coating. In the présent embodiment, the anti-rust resin coating is an optional component. That is, in the oil-well métal pipe 1 according to the présent embodiment, the anti-rust resin coating may not be formed. Hereunder, the anti-rust resin coating will be described.

[Anti-rust resin coating]

The oil-well métal pipe 1 according to the présent embodiment may include an anti-rust resin coating in the resin coating 100 formed on or above at least one of the pin contact surface 400 and the box contact surface 500. The anti-rust resin coating contains a rust préventive pigment and an acrylic Silicon resin. The rust préventive pigment is, for example, one or more types selected from the group consisting of aluminum tripolyphosphate, aluminum phosphite, a zinc rich primer (JIS K5552 (2010)), and micaceous iron oxide. A commercially available acrylic Silicon resin can be employed as the acrylic Silicon resin. The commercially available acrylic Silicon resin is, for example, an acrylic Silicon resin with the trade name ACRYDIC manufactured by DIC Corporation. When the resin coating 100 of the oil-well métal pipe 1 includes the anti-rust resin coating 70, the corrosion résistance of the oil-well métal pipe 1 increases.

The content of the rust préventive pigment in the anti-rust resin coating is, for example, 5 to 30 mass%. The content of the acrylic Silicon resin in the anti-rust resin coating is, for example, 50 to 80 mass%. The anti-rust resin coating may contain other components in addition to the rust préventive pigment and the acrylic Silicon resin. Examples of the other components include one or more types selected the group consisting of a pigment, an antifoaming agent, a leveling agent, and a fïbrous filler. The content of the other components in the anti-rust resin coating is for example, 0 to 20 mass% in total.

As mentioned above, an anti-rust resin coating is included in the resin coating 100. Specifically, FIG. 11 is an enlarged view of the pin contact surface 400 according to the présent embodiment, that is different from FIG. 9. Referring to FIG. 11, the oil-well métal pipe 1 includes the anti-rust resin coating 70 and an upper layer 60 of the resin coating 100 in the resin coating 100 formed on or above the pin contact surface 400. In this case, the upper layer 60 of the resin coating 100 contains a resin, a solid lubricant powder, and copper phthalocyanine, and the anti-rust resin coating 70, as a lower layer of the resin coating 100, contains a rust préventive pigment and an acrylic Silicon resin.

In the oil-well métal pipe 1 according to the présent embodiment, the location at which the anti-rust resin coating 70 is provided is not limited to the location in the example illustrated in FIG. 11. Although not illustrated in the drawings, similar with illustrated in FIG. 11, the oilwell métal pipe 1 may include the anti-rust resin coating 70 in the resin coating 100 formed on or above the box contact surface 500. Also, the anti-rust resin coating 70 may be included only in the resin coating 100 formed on or above the pin contact surface 400, and may not be included in the resin coating 100 formed on or above the box contact surface 500. Further, the anti-rust resin coating 70 may not be included in the resin coating 100 formed on or above the pin contact surface 400, and may be included only in the resin coating 100 formed on or above the box contact surface 500. Furthermore, the anti-rust resin coating 70 may be included in both the resin coating 100 formed on or above the pin contact surface 400 and the resin coating 100 formed on or above the box contact surface 500.

In the présent embodiment, the anti-rust resin coating 70 may be included in the resin coating 100 formed on the plating layer that is described later, or may be included in the resin coating 100 formed on the Chemical conversion treatment layer that is described later. That is, in the présent embodiment, the anti-rust resin coating 70 may be formed on the pin contact surface 400, may be formed on the box contact surface 500, may be formed on the plating layer that is described later, or may be formed on the Chemical conversion treatment layer that is described later.

The resin coating 100 may be formed as the outermost layer on the pin contact surface 400 and/or the box contact surface 500. During fastening of the oil-well métal pipe 1, a liquid lubricant may further be applied onto the resin coating 100.

[Thickness of resin coating]

The thickness of the resin coating 100 is not particularly limited. The thickness of the resin coating 100 is, for example, 1 to 100 pm. In this case, the high torque performance of the oil-well métal pipe 1 can be more stably increased. The lower limit of the thickness of the resin coating 100 is preferably 2 pm, more preferably is 5 pm, and further preferably is 10 pm. The upper limit of the thickness of the resin coating 100 is preferably 80 pm, more preferably is 70 pm, further preferably is 60 pm, and further preferably is 50 pm.

[Method for measuring resin coating]

The thickness of the resin coating 100 is measured by the following method. A probe of an electromagnetic induction type film thickness measuring instrument is brought into contact with the pin contact surface 400 or the box contact surface 500 on which the resin coating 100 is formed. The probe has an electromagnet, and when a magnetic body is brought close to it, electromagnetic induction occurs, and its voltage changes depending on the distance between the probe and the magnetic body. The thickness of the resin coating 100 is determined from the change in voltage amount. The measurement locations are twelve locations (twelve locations that are at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300° and 330°) in the tube circumferential direction of the oil-well métal pipe 1. The arithmetic mean of the measurement results of the twelve locations is taken to be the thickness of the resin coating 100.

The resin coating 100 may be formed on the pin contact surface 400 or the box contact surface 500, in direct contact with the pin contact surface 400 or the box contact surface 500. The oil-well métal pipe 1 may also include another coating between the pin contact surface 400 or the box contact surface 500, and the resin coating 100. The other coating is, for example, one or more types of coating selected from the group consisting of a plating layer and a Chemical conversion treatment layer.

[Optional Component]

[Plating layer]

The oil-well métal pipe 1 according to the présent embodiment may include a plating layer between at least one of the pin contact surface 400 and the box contact surface 500, and the resin coating 100. In the oil-well métal pipe 1 according to the présent embodiment, the plating layer is an optional component. Therefore, in the oil-well métal pipe 1 according to the présent embodiment, the plating layer may not be formed.

FIG. 12 is an enlarged view of the pin contact surface 400 according to the présent embodiment, that is different from FIG. 9 and FIG. 11. In FIG. 12, a plating layer 80 is provided between the pin contact surface 400 and the resin coating 100. Specifîcally, in FIG. 12, the plating layer 80 is formed on the pin contact surface 400, and the resin coating 100 is formed on the plating layer 80. However, a location at which the plating layer 80 is provided is not limited to the location illustrated in FIG. 12. Although not illustrated in the drawings, for example, the plating layer 80 may be provided between the box contact surface 500 and the resin coating 100. For example, the plating layer 80 may be provided between the pin contact surface 400 and the resin coating 100, and neither the resin coating 100 nor the plating layer 80 need be provided on the box contact surface 500. For example, the plating layer 80 may be provided between the pin contact surface 400 and the resin coating 100, and the plating layer 80 may also be provided between the box contact surface 500 and the resin coating 100.

In the présent embodiment, the anti-rust resin coating 70 is formed on the plating layer 80. FIG. 13 is an enlarged view of the pin contact surface 400 according to the présent embodiment, that is different from FIG. 9, FIG. 11 and FIG. 12. Referring to FIG. 13, a plating layer 80 may be provided between the pin contact surface 400 and the resin coating 100, and further, the anti-rust resin coating 70 and the upper layer 60 of the resin coating 100 may be included in the resin coating 100.

In the présent embodiment, the kind of the plating layer 80 is not particularly limited. The plating layer 80, for example, is selected from the group consisting of a Zn plating layer, an Ni plating layer, a Cu plating layer, a Zn-Ni alloy plating layer, a Zn-Co alloy plating layer, and a Ni-W alloy plating layer. In a case where the plating layer 80 is a Zn-Ni alloy plating layer, the Chemical composition of the Zn-Ni alloy plating layer consists of, for example, 10 to 20 mass% of Ni, with the balance being Zn and impurities. In a case where the plating layer 80 is a Cu plating layer, the Chemical composition of the Cu plating layer consists of, for example, Cu and impurities.

In a case where the oil-well métal pipe 1 according to the présent embodiment includes the plating layer 80 on the pin contact surface 400 and/or the box contact surface 500, the galling résistance of the oil-well métal pipe 1 is further enhanced.

FIG. 14 is a graph illustrating the relation between the plating layer 80, the content of copper phthalocyanine, and results of the Bowden test as an index of galling résistance. The graph in FIG. 14 was obtained based on Example 2 that is described later. The abscissa in FIG. 14 represents the content of copper phthalocyanine in the resin coating 100. The ordinate in FIG. 14 represents the number of sliding times until the coefficient of friction becomes more than 0.3. In Example 2, a Steel bail was caused to slide on the surface of a Steel plate on which the plating layer 80 and/or the resin coating 100 was formed, and the number of sliding times until the coefficient of friction became more than 0.3 was measured. A higher the value for the number of sliding times until the coefficient of friction became more than 0.3 indicates a higher galling résistance. In FIG. 14, the symbol of a white circle (O) dénotés that only the resin coating 100 was formed on the Steel plate surface, and the plating layer 80 was not formed thereon. In FIG. 14, the symbol of a square (□) dénotés that a Zn-Ni alloy plating layer was formed on the Steel plate surface, and the resin coating 100 was formed thereon. Referring to FIG. 14, for the oil-well métal pipe 1 that included the Zn-Ni alloy plating layer, the number of sliding fîmes until the coefficient of friction became more than 0.3 is large in comparison to the oil-well métal pipe 1 that did not include the plating layer 80. Thus, the galling résistance of the oil-well métal pipe 1 in which the plating layer 80 is formed on the pin contact surface 400 and/or the box contact surface 500 is further enhanced.

[Thickness of plating layer]

The thickness of the plating layer 80 is not particularly limited. The thickness of the plating layer 80 is, for example, 1 to 30 pm. In this case, the galling résistance of the oil-well métal pipe 1 can be more stably enhanced. The lower limit of the thickness of the plating layer 80 is preferably 2 pm, more preferably is 3 pm, and further preferably is 4 pm. The upper limit of the thickness of the plating layer 80 is preferably 20 pm, and more preferably is 10 pm.

[Method for measuring thickness of plating layer]

The thickness of the plating layer 80 is measured by the following method. A probe of an electromagnetic induction type film thickness measuring instrument is brought into contact with the pin contact surface 400 or the box contact surface 500 on which the plating layer 80 is formed. The probe is brought into contact with the pin contact surface 400 or the box contact surface 500 at a portion where the resin coating 100 is removed. The probe has an electromagnet, and when a magnetic body is brought close to it, electromagnetic induction occurs, and its voltage changes depending on the distance between the probe and the magnetic body. The thickness of the plating layer 80 is determined from the change in voltage amount. The measurement locations are twelve locations (twelve locations that are at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300° and 330°) in the tube circumferential direction of the oil-well métal pipe 1. The arithmetic mean of the measurement results of the twelve locations is taken to be the thickness of the plating layer 80.

[Chemical conversion treatment layer]

The oil-well métal pipe 1 according to the présent embodiment may further include a Chemical conversion treatment layer between at least one of the pin contact surface 400 and the box contact surface 500, and the resin coating 100. In the oil-well métal pipe 1 according to the présent embodiment, the Chemical conversion treatment layer is an optional component. That is, in the oil-well métal pipe 1 according to the présent embodiment, the Chemical conversion treatment layer may not be formed.

FIG. 15 is an enlarged view of the box contact surface 500 according to the présent embodiment, that is different from FIG. 10. In FIG. 15, a Chemical conversion treatment layer is provided between the box contact surface 500 and the resin coating 100. Specifically, in FIG. 15, the Chemical conversion treatment layer 90 is formed on the box contact surface 500, and the resin coating 100 is formed on the Chemical conversion treatment layer 90. However, a location at which the Chemical conversion treatment layer 90 is provided is not limited to the location illustrated in FIG. 15. Although not illustrated in the drawings, for example, the Chemical conversion treatment layer 90 may be provided between the pin contact surface 400 and the resin coating 100, and neither the resin coating 100 nor the Chemical conversion treatment layer 90 need be provided on the box contact surface 500. For example, the Chemical conversion treatment layer 90 may be provided between the pin contact surface 400 and the resin coating 100, and the Chemical conversion treatment layer 90 may also be provided between the box contact surface 500 and the resin coating 100.

Further, in the présent embodiment, the anti-rust resin coating 70 is provided on the Chemical conversion treatment layer 90. Specifically, FIG. 16 is an enlarged view of the pin contact surface 400 according to the présent embodiment, that is different from FIG. 9, FIG. 11, FIG. 12 and FIG. 13. Referring to FIG. 16, the Chemical conversion treatment layer 90 may be provided between the pin contact surface 400 and the resin coating 100, and further, the anti-rust resin coating 70 and the upper layer 60 of the resin coating 100 may be included in the resin coating 100.

Further, the pin contact surface 400 and the box contact surface 500 according to the présent embodiment may include both the plating layer 80 and the Chemical conversion treatment layer 90. FIG. 17 is an enlarged view of the pin contact surface 400 according to the présent embodiment, that is different from FIG. 9, FIG. 11, FIG. 12, FIG. 13 and FIG. 16. In FIG. 17, the plating layer 80 is provided on the pin contact surface 400, the Chemical conversion treatment layer 90 is provided on the plating layer 80, the resin coating 100 is provided on the Chemical conversion treatment layer 90. Therefore, in the case where the oil-well métal pipe 1 includes the plating layer 80, the oil-well métal pipe 1 includes the Chemical conversion treatment layer 90 between the plating layer 80 and the resin coating 100.

In the oil-well métal pipe 1 according to the présent embodiment, although the locations at which the plating layer 80 and the Chemical conversion treatment layer 90 are provided are not limited to the example illustrated in FIG. 17, in a case where the plating layer 80 and the Chemical conversion treatment layer 90 are provided between the pin contact surface 400 and the resin coating 100, the Chemical conversion treatment layer 90 may be provided on the plating layer 80, and the resin coating 100 may be provided on the Chemical conversion treatment layer 90. Further, in a case where the plating layer 80 is not provided between the pin contact surface

400 and the resin coating 100, the Chemical conversion treatment layer 90 may be provided on the pin contact surface 400, and the resin coating 100 may be provided on the Chemical conversion treatment layer 90. Similarly, in a case where the oil-well métal pipe 1 includes the plating layer 80 and the Chemical conversion treatment layer 90 between the box contact surface 500 and the resin coating 100, the Chemical conversion treatment layer 90 may be provided on the plating layer 80, and the resin coating 100 may be provided on the Chemical conversion treatment layer 90. Further, in a case where the oil-well métal pipe 1 does not include the plating layer 80 between the box contact surface 500 and the resin coating 100, the Chemical conversion treatment layer 90 may be provided on the box contact surface 500, and the resin coating 100 may be provided on the Chemical conversion treatment layer 90.

In the présent embodiment, in a case where the oil-well métal pipe 1 includes the plating layer 80 and the Chemical conversion treatment layer 90, the anti-rust resin coating 70 is provided on the Chemical conversion treatment layer 90. Specifically, FIG. 18 is an enlarged view of the pin contact surface 400 according to the présent embodiment, that is different from FIG. 9, FIG. 11, FIG. 12, FIG. 13, FIG. 16 and FIG. 17. Referring to FIG. 18, the plating layer 80 may be provided on the pin contact surface 400, the Chemical conversion treatment layer 90 may be provided on the plating layer 80, the resin coating 100 may be provided on the Chemical conversion treatment layer 90, and further, the anti-rust resin coating 70 and the upper layer 60 of the resin coating 100 may be included in the resin coating 100.

In the présent embodiment, the kind of the Chemical conversion treatment layer 90 is not particularly limited. The Chemical conversion treatment layer 90 is, for example, selected from the group consisting of a phosphate Chemical conversion treatment layer, an oxalate Chemical conversion treatment layer, a borate Chemical conversion treatment layer and a chromate coating. From the viewpoint of the adhesiveness of the resin coating 100, a phosphate Chemical conversion treatment layer is préférable. In this case, the phosphate is, for example, one or more types selected from the group consisting of manganèse phosphate, zinc phosphate, manganèse iron phosphate, and calcium zinc phosphate. The Chemical conversion treatment layer 90 may be a chromate coating. The chromate coating may be formed by a well-known process. The chromate coating preferably does not contain hexavalent chromium.

In a case where the Chemical conversion treatment layer 90 is provided on the pin contact surface 400 and/or the box contact surface 500 of the oil-well métal pipe 1 according to the présent embodiment, the galling résistance of the oil-well métal pipe 1 increases further. The Chemical conversion treatment layer 90 increases the adhesiveness of the resin coating 100 provided thereon by an anchor effect. By this means, the galling résistance of the oil-well métal pipe 1 increases. Referring to Example 3 that is described later, the number of sliding times until the coefficient of friction becomes more than 0.3 is higher for the oil-well métal pipe 1 that includes the Chemical conversion treatment layer 90 than for the oil-well métal pipe 1 that does not include the Chemical conversion treatment layer 90. Thus, in the oil-well métal pipe 1 in which the Chemical conversion treatment layer 90 is provided on the pin contact surface 400 and/or the box contact surface 500, the galling résistance increases further.

It suffices that the oil-well métal pipe 1 of the présent embodiment includes the resin coating 100 on at least one of the pin contact surface 400 and the box contact surface 500. Regarding the arrangement of the plating layer 80, the Chemical conversion treatment layer 90 and the anti-rust resin coating 70, as described above, they may be arranged in the same manner on the pin contact surface 400 and the box contact surface 500, or may be arranged differently on the pin contact surface 400 and the box contact surface 500. The oil-well métal pipe 1 may, as necessary, also include other coatings.

[Preconditioning treatment]

In the oil-well métal pipe 1 according to the présent embodiment, at least one of the pin contact surface 400 and the box contact surface 500 may be a surface that is subjected to a preconditioning treatment. Therefore, in the présent embodiment, a preconditioning treatment is an optional process, and both of the pin contact surface 400 and the box contact surface 500 may not be a surface that is subjected to a preconditioning treatment. If the preconditioning treatment is performed, the preconditioning treatment is, for example, one or more types selected from the group consisting of a blasting treatment and pickling. If a preconditioning treatment is performed, the surface roughness of the pin contact surface 400 and/or the box contact surface 500 increases. Therefore, the adhesiveness of the resin coating 100, the plating layer 80 and/or the Chemical conversion treatment layer 90 formed thereon increases. As a resuit, the galling résistance of the oil-well métal pipe 1 increases.

[Chemical composition of pipe main body]

The pipe main body 10 of the oil-well métal pipe 1 according to the présent embodiment is not particularly limited. The feature of the oil-well métal pipe 1 according to the présent embodiment is the resin coating 100. Therefore, in the présent embodiment, the kind of Steel of the pipe main body 10 of the oil-well métal pipe 1 is not particularly limited.

The pipe main body 10 may be formed of, for example, carbon Steel, stainless Steel, alloy Steel or the like. Accordingly, the oil-well métal pipe may be a Steel pipe made of Fe-based alloy or an alloy pipe represented by a Ni-base alloy pipe. Here, the steel pipe is, for example, a low-alloy pipe, a martensitic stainless Steel pipe, and a duplex stainless Steel pipe. Meanwhile, among alloy steels, high alloy steels such as a Ni alloy and duplex stainless steels that contain alloying éléments such as Cr, Ni and Mo hâve high corrosion résistance. Therefore by using these high alloy steels as the pipe main body 10, excellent corrosion résistance is obtained in a corrosive environment that contains hydrogen sulfide or carbon dioxide or the like.

[Production method]

A method for producing the oil-well métal pipe 1 according to the présent embodiment will be described hereunder.

The method for producing the oil-well métal pipe 1 according to the présent embodiment includes a préparation process, an application process, and a hardening process. The hardening process is performed after the application process.

[Préparation process]

In the préparation process, the oil-well métal pipe 1 having the pipe main body 10 that includes the pin 40 including the pin contact surface 400 that includes the extemal thread part 41, and the box 50 including the box contact surface 500 that includes the internai thread part 51 is prepared. As described above, the oil-well métal pipe 1 according to the présent embodiment has a well-known structure. In other words, in the préparation process it suffices to préparé the oil-well métal pipe 1 that has a well-known structure.

[Application process]

In the application process, a composition containing a resin, a solid lubricant powder and copper phthalocyanine is applied onto at least one of the pin contact surface 400 and the box contact surface 500. The composition is a composition for forming the aforementioned resin coating 100. The composition contains a resin, a solid lubricant powder and copper phthalocyanine. The composition for forming the resin coating 100 is the same as the composition of the resin coating 100 described above, excluding a solvent.

The composition of a solventless type can be produced, for example, by heating the resin to a molten state, adding the solid lubricant powder and copper phthalocyanine thereto, and kneading them. The composition may be made of a powder mixture prepared by mixing ail the components in powder form.

The composition of a solvent type can be produced, for example, by melting or dispersing the resin, the solid lubricant powder and copper phthalocyanine in a solvent and mixing them. The solvent is, for example, water, alcohol or an organic solvent. The solvent may contain a small amount of a surfactant. The proportion of the solvent is not particularly limited. It suffîces to adjust the proportion of the solvent to an appropriate viscosity according to the application method. The proportion of the solvent is, for example, within a range of 40 to 60 mass% when taking the total of ail components other than the solvent as 100 mass%.

The method of applying the composition on the pin contact surface 400 and/or the box contact surface 500 is not particularly limited, and a well-known method may be used. In the case of the composition of a solventless type, for example, the composition can be applied on the pin contact surface 400 and/or the box contact surface 500 using a hot melt process. In the hot melt process, the composition is heated to melt the resin to place the composition in a fluid state with low viscosity. The composition in a fluid state can be sprayed from a spray gun having fonctions for température holding. Another application method, such as brushing or dipping may be employed as the method for applying the composition on the pin contact surface 400 and/or the box contact surface 500, instead of spray application. Note that, the température to which the composition is heated is preferably higher than the melting point of the resin by 10 to 50°C.

In the case of the solvent type composition, for example, the composition in solution form can be applied on the pin contact surface 400 and/or the box contact surface 500 by spray coating. In this case, the viscosity of the composition is to be adjusted so that it can be applied by spray coating in an environment at normal température and normal pressure. Another application method, such as brushing or dipping may be employed as the method for applying the composition on the pin contact surface 400 and/or the box contact surface 500, instead of spray application.

[Hardening process]

In the hardening process, the applied composition is hardened to form the resin coating 100. In the case of the solventless type composition, by cooling the composition that was applied onto at least one of the pin contact surface 400 and the box contact surface 500, the composition in a molten state hardens and the solid resin coating 100 is formed. In this case, the cooling method is not particularly limited, and a well-known method may be used. Examples of the cooling method include allowing to cool in the atmosphère and air cooling. In the case of the solvent type composition, by drying the composition that was applied onto at least one of the pin contact surface 400 and the box contact surface 500, the composition hardens and the solid resin coating 100 is formed. In this case, the drying method is not particularly limited, and a well-known method may be used. The drying method is, for example, naturel drying, low-temperature air drying or vacuum drying. Further, if the resin is a thermosetting resin, the solid resin coating 100 may be formed by causing the composition to harden by performing a thermal hardening process.

The oil-well métal pipe 1 according to the présent embodiment is produced by the above processes.

[Optional Process]

The method for producing the oil-well métal pipe 1 according to the présent embodiment may further include one or more processes of a plating layer formation process, a Chemical conversion treatment process, an anti-rust resin coating formation process, and a preconditioning treatment process. Ail of these processes are optional processes. Therefore, these processes may not be performed.

[Plating layer formation process]

The method for producing the oil-well métal pipe 1 according to the présent embodiment may further include a plating layer formation process prior to the application process. In a case where the plating layer formation process is performed, the plating layer 80 is formed on at least one of the pin contact surface 400 and the box contact surface 500.

A method for forming the plating layer 80 is not particularly limited, and a well-known method may be used. Formation of the plating layer 80 may be performed by electroplating or may be performed by electroless plating. For example, in the case of forming a Zn-Ni alloy plating layer by electroplating, the plating bath contains zinc ions and nickel ions. The composition of the plating bath preferably contains zinc ions: 1 to 100 g/L and nickel ions: 1 to 50 g/L. The electroplating conditions are, for example, as follows: plating bath pH: 1 to 10, plating bath température: 20 to 60°C, current density: 1 to 100 A/dm², and treatment time: 0.1 to 50 mins. For example, when forming a Cu plating layer by electroplating, the Cu plating layer can be formed by a well-known method.

[Chemical conversion treatment process]

The method for producing the oil-well métal pipe 1 according to the présent embodiment may further include a Chemical conversion treatment process prior to the application process.

In a case where the Chemical conversion treatment process is performed, the Chemical conversion treatment layer 90 is formed on at least one of the pin contact surface 400 and the box contact surface 500.

The method of Chemical conversion treatment is not particularly limited, and may be a well-known method. The Chemical conversion treatment is, for example, selected from the group consisting of a phosphate Chemical conversion treatment, an oxalate Chemical conversion treatment, a borate Chemical conversion treatment, and a chromate treatment. A common acidic solution for phosphate Chemical conversion treatment for zinc-plated products can be used as the treatment solution for the Chemical conversion treatment. As the treatment solution, for example, a solution for zinc phosphate Chemical conversion treatment 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. Solutions for manganèse phosphate Chemical conversion treatments which are conventionally used for the oil-well métal pipe 1 can also be used as the treatment solution. A commercially available chromate treatment solution can also be used as the treatment solution. The température of the treatment solution is normal température to 100°C, for example. The treatment time of the Chemical conversion treatment can be appropriately set depending on the desired thickness of the coating and, for example, is 0.5 to 15 minutes. To promote the formation of the Chemical conversion treatment layer 90, surface modification may be performed prior to the Chemical conversion treatment. The term surface modification refers to a treatment that includes immersion in a surface modification aqueous solution containing colloïdal titanium. In a case where the Chemical conversion treatment process is performed, after performing the Chemical conversion treatment it is préférable to perform rinsing with water or with warm water before drying.

Note that, as described above, in the oil-well métal pipe 1 according to the présent embodiment, the Chemical conversion treatment layer 90 is formed on either of the pin contact surface 400, the box contact surface 500, and the plating layer 80. That is, in the method for producing the oil-well métal pipe 1 according to the présent embodiment, in the case of performing both the plating layer formation process and the Chemical conversion treatment process, the Chemical conversion treatment process is performed after the plating layer formation process, and thereafter the application process is performed.

[Anti-rust resin coating formation process]

The method for producing the oil-well métal pipe 1 according to the présent embodiment may fiirther include an anti-rust resin coating formation process prior to the application process.

In a case where the anti-rust resin coating formation process is performed, the anti-rust resin coating 70 is formed on at least one of the pin contact surface 400, the box contact surface 500, the plating layer 80 and the Chemical conversion treatment layer 90.

A method for forming the anti-rust resin coating 70 is not particularly limited, and a wellknown method may be used. The anti-rust resin coating 70 can be formed, for example, by applying a composition containing a rust préventive pigment and acrylic Silicon resin onto at least one of the pin contact surface 400, the box contact surface 500, the plating layer 80 and the Chemical conversion treatment layer 90, and causing the composition to harden. The application method is not particularly limited, and may be spray application, brushing or dipping. The composition for forming the anti-rust resin coating 70 may include a solvent. The composition for forming the anti-rust resin coating 70 is the same as the composition of the antirust resin coating 70 described above, excluding a solvent. The hardening method is, for example, naturel drying, low-temperature air drying, or drying by heating.

Note that, as described above, in the oil-well métal pipe 1 according to the présent embodiment, the anti-rust resin coating 70 is formed on either of the pin contact surface 400, the box contact surface 500, the plating layer 80, and the Chemical conversion treatment layer 90. That is, in the method for producing the oil-well métal pipe 1 according to the présent embodiment, in the case of performing each of the plating layer formation process, the Chemical conversion treatment process and the anti-rust resin coating formation process, the plating layer formation process, the Chemical conversion treatment process, and the anti-rust resin coating formation process are performed in that order, and thereafter the application process is performed.

[Preconditioning treatment process]

The method for producing the oil-well métal pipe 1 according to the présent embodiment may further include a preconditioning treatment process prior to the application process. In a case where a plating layer formation process is to be performed, the method for producing the oil-well métal pipe 1 may include a preconditioning treatment process prior to the plating layer formation process. In a case where a Chemical conversion treatment process is to be performed, the method for producing the oil-well métal pipe 1 may include a preconditioning treatment process prior to the Chemical conversion treatment process. In a case where an anti-rust resin coating formation process is to be performed, the method for producing the oil-well métal pipe 1 may include a preconditioning treatment process prior to the anti-rust resin coating formation process. In the preconditioning treatment process, for example, a pickling treatment and/or a blasting treatment or the like is performed. In addition, an alkaline degreasing treatment may be performed.

In the case of performing a pickling treatment, for example, the pin contact surface 400 and/or the box contact surface 500 is immersed in a strongly acidic solution such as sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid or a mixture of these acids, to thereby increase the surface roughness of the pin contact surface 400 and/or the box contact surface 500. In the case of performing a blasting treatment, for example, sand blasting is performed in which a blast material (an abrasive) is mixed with compressed air, and the mixture is propelled onto the pin contact surface 400 and/or the box contact surface 500. In this case, the surface roughness of the pin contact surface 400 and/or the box contact surface 500 increases.

Note that, with respect to the aforementioned plating layer formation process, Chemical conversion treatment process, and preconditioning treatment process, the pin contact surface 400 and the box contact surface 500 may be subjected to the same processes or may be subjected to different processes to each other. Further, these processes may be performed only on the pin contact surface 400, or may be performed only on the box contact surface 500.

The oil-well métal pipe 1 according to the présent embodiment is produced by the above processes. However, the production method described above is one example of a method for producing the oil-well métal pipe 1 according to the présent embodiment, and the présent embodiment is not limited to the production method described above. The oil-well métal pipe 1 according to the présent embodiment may also be produced by another method. [Example 1]

In Example 1, the resin coating 100 was formed on the pin contact surface 400 or the box contact surface 500 of the oil-well métal pipe 1, and high torque performance and galling résistance were evaluated. Specifically, in Example 1, an oil-well métal pipe with the trade name VAM21 (registered trademark) HT manufactured by NIPPON STEEL CORPORATION (extemal diameter: 273.05 mm (10.75 inches), wall thickness: 12.570 mm (0.495 inches)) was used. The Steel grade of the oil-well métal pipe was SM2535-M110 steel (C<0.03%, Si: <0.50%, Mn<1.0%, Cu<1.5%, Ni: 29.5 to 36.5%, Cr: 24.0 to 27.0%, balance: Fe and impurities).

For Test Numbers 1 to 12, a plating layer, an anti-rust resin coating was included in a resin coating were formed as appropriate on the box contact surface to préparé the oil-well métal pipes including a pin and a box of Test Numbers 1 to 12. The plating layers that were formed are shown in the Plating Layer column in Table 2. The symbol - in the Plating Layer column in Table 2 means that a plating layer was not formed. The thickness of each plating layer that was formed was 8 pm. The measurement of the thickness of the plating layer was performed by the method described above using an electromagnetic film thickness meter SDMpicoR manufactured by Sanko Electronic Laboratory Co., Ltd. Whether or not an anti-rust resin coating was formed is shown in the Anti-Rust Resin Coating column in Table 2. The term formation in the Anti-Rust Resin Coating column in Table 2 means that an anti-rust resin coating was formed. The Symbol in the Anti-Rust Resin Coating column in Table 2 means that an anti-rust resin coating was not formed. Note that, the anti-rust resin coating that was formed was the same as an anti-rust resin coating of Test Numbers 32 and 33 of Example 4 that is described later.

Whether or not a resin coating was formed is shown in the Resin Coating column in Table 2. The term formation in the Resin Coating column in Table 2 means that a resin coating was formed. The symbol in the Resin Coating column in Table 2 means that a resin coating was not formed. Note that, in each of Test Numbers 1 to 9 and 11 to 12, the thickness of each resin coating that was formed was 20 pm. In Test Number 10, the thickness of the resin coating was 20 pm except the thickness of an anti-rust resin coating. The measurement of the thickness of the resin coating was performed by the method described above using an electromagnetic film thickness meter SDM-picoR manufactured by Sanko Electronic Laboratory Co., Ltd. In each of Test Numbers 2 to 9 and 11 to 12, the resin coating was formed on the surface of the aforementioned plating layer.

In Test Number 1, a plating layer was not formed. Therefore, in Test Number 1, the resin coating was formed directly on the box contact surface. In Test Number 10, the resin coating was formed on the anti-rust resin coating. Therefore, in Test Number 10, the resin coating included multiple layers. The content of copper phthalocyanine in the respective resin coatings that were formed is shown in Table 2. Note that, the resin coatings that were formed also contained 1 to 30 mass% of polytetrafluoroethylene (PTFE) as a solid lubricant powder, and the balance consisted of epoxy resin as a resin. The symbol in the Copper Phthalocyanine Content column in Table 2 means that a resin coating was not formed, or that copper phthalocyanine was not contained in the resin coating that was formed. Note that, in Test Number 12, the formed resin coating did not contain copper phthalocyanine. In Test Number 12, the resin coating contained 8.6 mass% of CnCL instead of copper phthalocyanine. The resin coating of Test Number 12 also contained 1 to 30 mass% of polytetrafluoroethylene (PTFE) as a solid lubricant powder, and the balance consisted of epoxy resin as a resin.

[Table 2]

TABLE2

Test Number		Plating Layer	Anti-Rust Resin Coating	Resin Coating	Copper Phthalocyanine Content	High Torque Performance	M&B Count (Times)
1	Pin Contact Surface	-	-	-	-	120	-
Box Contact Surface	-	-	Formation	10.0 mass%
2	Pin Contact Surface	-	-	-	-	110	8
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	0.1 mass%
3	Pin Contact Surface	-	-	-	-	120	11
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	0.2 mass%
4	Pin Contact Surface	-	-	-	-	127	10
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	0.4 mass%
5	Pin Contact Surface	-	-	-	-	138	14
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	1.0 mass%
6	Pin Contact Surface	-	-	-	-	120	12
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	4.0 mass%
7	Pin Contact Surface	-	-	-	-	125	11
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	10.0 mass%
8	Pin Contact Surface	-	-	-	-	132	6
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	20.0 mass%
9	Pin Contact Surface	-	-	-	-	128	6
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	30.0 mass%
10	Pin Contact Surface	-	-	-	-	130	-
Box Contact Surface	-	Formation	Formation	10.0 mass%
11	Pin Contact Surface	-	-	-	-	65	8
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	-
12	Pin Contact Surface	-	-	-	-	90	10
Box Contact Surface	Zn-Ni Alloy Plating Layer	-	Formation	(Cr2O3: 8.6 mass%)

[Box contact surface]

[Plating layer formation process]

As shown in Table 2, a Zn-Ni alloy plating layer was formed by electroplating on the box contact surface of Test Numbers 2 to 9 and 11 to 12. The plating bath used was DAIN Zinalloy N-PL (trademark) manufactured by Daiwa Fine Chemicals Co., Ltd. The thickness of the ZnNi alloy plating layer was 8 pm. The measurement of the thickness of the plating layer was performed by the method described above using an electromagnetic film thickness meter SDMpicoR manufactured by Sanko Electronic Laboratory Co., Ltd. The electroplating conditions were as follows: plating bath pH: 6.5, plating bath température: 25°C, current density: 2 A/dm², and treatment time: 18 mins. The composition of the Zn-Ni alloy plating layer was Zn: 85% and Ni: 15%. In addition, a trivalent chromate coating was formed on the obtained Zn-Ni alloy plating layer. The treatment solution used for forming the trivalent chromate coating was DAIN Chromate TR-02 manufactured by Daiwa Fine Chemicals Co., Ltd. The conditions of the Chemical conversion treatment were as follows: bath température: 25°C, pH: 4.0, and treatment time: 50 secs.

[Application process and hardening process] .

As shown in Table 2, a resin coating was formed on the box contact surface of Test Numbers 1 to 12. In Test Numbers 2 to 9, 11 and 12, the resin coating was formed on the box contact surface on which a plating layer was formed. In Test Number 1, the resin coating was formed directly on the box contact surface. In Test Number 10, the upper layer of the resin coating was formed on the anti-rust resin coating. A composition for forming the resin coating was applied by spraying onto the box contact surface, the Zn-Ni alloy plating layer, or the antirust resin coating, and caused to harden. As described above, the components other than a solvent contained in the composition were polytetrafluoroethylene particles and copper phthalocyanine, with the balance being epoxy resin. The composition also contained a solvent. A mixed solution of water, alcohol and a surfactant was used as the solvent. After applying the composition onto the Zn-Ni alloy plating layer of the box surface by spraying, a thermal hardening process was performed for 20 mins at 210°C to form a resin coating. In Test Number 12, copper phthalocyanine was not used, and CnCh in an amount of 8.6 mass% was used instead.

[Pin contact surface]

The pin contact surface of each of Test Numbers 1 to 12 was subjected to fmishing by machine grinding. That is, as shown in Table 2, a plating layer and a resin coating were not formed on the pin contact surface of Test Numbers 1 to 12.

[High torque performance évaluation]

Torque on shoulder résistance ΔΤ was measured using the oil-well métal pipe having a pin contact surface and a box contact surface of each of Test Numbers 1 to 12. Specifically, at a fastening speed of 10 rpm, the fastening torque value was gradually increased, and the test was ended at a point when the material yielded. The torque at the time of fastening was measured, and a torque chart as illustrated in FIG. 19 was prepared. Reference characters Ts in FIG. 19 dénoté the shouldering torque. Reference characters MTV in FIG. 19 dénoté a torque value at which a line segment L and the torque chart intersect. The line segment L is a straight line that has the same slope as the slope of a linear région of the torque chart after shouldering, and for which the number of tums is 0.2% more in comparison to the aforementioned linear région. Normally, Ty (yield torque) is used when measuring the torque on shoulder résistance.

However, in the présent example, the yield torque Ty (boundary between a linear région and a non-linear région in the torque chart after shouldering) was indistinct. Therefore, MTV was defined using the line segment L. The différence between MTV and Ts was taken as the torque on shoulder résistance ΔΤ. The torque on shoulder résistance ΔΤ was determined as a relative value with respect to a torque on shoulder résistance ΔΤ in a case where a dope according to the API standards was used that was taken as a value of 100. The results are shown in the High Torque Performance column in Table 2.

[Repeated fastening test]

A repeated fastening test using a fastening torque of 53800 Nm was performed using the oil-well métal pipe having a pin contact surface and a box contact surface of Test Numbers 1 to 12. Fastening was performed until either unrepairable galling occurred at a thread part (extemal thread part and/or internai thread part) or galling occurred at a métal seal portion. The results are shown in the M&B Count (times) column in Table 2. The symbol in the M&B Count (times) column in Table 2 indicates that a repeated fastening test was not performed.

[Evaluation results]

Referring to Table 2, the oil-well métal pipes of each of Test Numbers 1 to 10 included a resin coating containing a resin, a solid lubricant powder and copper phthalocyanine on at least one of the pin contact surface and the box contact surface. Therefore, the torque on shoulder résistance ΔΤ for each of Test Numbers 1 to 10 was 100 or more, indicating excellent high torque performance.

In addition, in the oil-well métal pipes of Test Numbers 1 and 3 to 10, the content of copper phthalocyanine in the resin coating was 0.2 to 30.0 mass%. Therefore, the torque on shoulder résistance ΔΤ of the oil-well métal pipes of Test Numbers 1 and 3 to 10 was further increased in comparison to Test Number 2 in which the content of copper phthalocyanine was less than 0.2 mass%.

On the other hand, in the oil-well métal pipe of Test Number 11, although a resin coating containing a resin and a solid lubricant powder was formed on the box contact surface, the resin coating did not contain copper phthalocyanine. As a resuit, the torque on shoulder résistance AT was 65, and thus the high torque performance was low.

In the oil-well métal pipe of Test Number 12, although a resin coating containing a resin and a solid lubricant powder was formed on the box contact surface, the resin coating did not contain copper phthalocyanine, and instead contained CnCL. As a resuit, the torque on shoulder résistance AT was 90, and thus the high torque performance was low. [Example 2]

In Example 2, a resin coating was formed on the surface of steel plates simulating an oilwell métal pipe, and the galling résistance was evaluated. Specifically, in Example 2, coldrolled steel plates (chemical composition: C < 0.15%, Mn < 0.60%, P < 0.100%, S < 0.050%, and the balance: Fe and impurities) were used.

Plating layers shown in Table 3 were formed as appropriate on the steel plate surfaces of Test Numbers 13 to 21. The plating layers that were formed are shown in the Plating Layer column in Table 3. The Symbol in the Plating Layer column in Table 3 means that a plating layer was not formed. The thickness of each plating layer that was formed was 8 pm. A resin coating was formed on the steel plate surfaces of Test Numbers 13 to 17 and 21. For Test Numbers 18 to 20, a resin coating was formed on the plating layer that was formed. The thickness of each resin coating that was formed was 20 pm. The measurement of the thickness of the resin coating was performed by the method described above using an electromagnetic film thickness meter SDM-picoR manufactured by Sanko Electronic Laboratory Co., Ltd., and the average value of the thicknesses at nine points on the same évaluation surface was taken as the thickness of the resin coating. In addition, the content of copper phthalocyanine in the resin coatings that were formed is shown in Table 3. Note that, the resin coatings that were formed also contained 1 to 30 mass% of polytetrafluoroethylene (PTFE) as a solid lubricant powder, and the balance consisted of epoxy resin as a resin. The symbol in the Copper Phthalocyanine Content column in Table 3 means that copper phthalocyanine was not contained in the resin coating that was formed.

[Table 3]

TABLE 3

Test Number	Plating Layer	Copper Phthalocyanine Content	Number of Sliding Times until Coefficient of Friction Became More Than 0.3 (Times)
13	-	0.1 mass%	510
14	-	0.5 mass%	647
15	-	2.0 mass%	524
16	-	5.0 mass%	531
17	-	10.0 mass%	55
18	Zn-Ni Alloy Plating Layer	0.5 mass%	743
19	Zn-Ni Alloy Plating Layer	2.0 mass%	660
20	Zn-Ni Alloy Plating Layer	5.0 mass%	609
21	-	-	511

[Plating layer formation process]

A Zn-Ni alloy plating layer was formed by electroplating on the surface of the Steel plate of each of Test Numbers 18 to 20. The plating bath used was DAIN Zinalloy N-PL (trademark) manufactured by Daiwa Fine Chemicals Co., Ltd. The thickness of the Zn-Ni alloy plating layer was 8 pm. The measurement of the thickness of the plating layer was performed by the method described above using an electromagnetic film thickness meter SDM-picoR manufactured by Sanko Electronic Laboratory Co., Ltd., and the average value of the thicknesses at nine points on the same évaluation surface was taken as the thickness of the plating layer. The electroplating conditions were as follows: plating bath pH: 6.5, plating bath température: 25°C, current density: 2 A/dm², and treatment time: 18 mins. The composition of the Zn-Ni alloy plating layer was Zn: 85% and Ni: 15%. In addition, a trivalent chromate coating was formed on the obtained Zn-Ni alloy plating layer. The treatment solution used for forming the trivalent chromate coating was DAIN Chromate TR-02 manufactured by Daiwa Fine Chemicals Co., Ltd. The conditions of the Chemical conversion treatment were as follows: bath température: 25°C, pH: 4.0, and treatment time: 50 seconds.

[Application process and hardening process]

A resin coating was formed on the surface of the Steel plate of each of Test Numbers 13 to 21. Specifically, a composition for forming a resin coating was applied onto the surface of the Steel plate of each of Test Numbers 13 to 21 using a bar coater, and caused to harden. The components other than a solvent contained in the composition were solid lubricant particles and copper phthalocyanine, with the balance being a resin. Epoxy resin was used as the resin in Test Numbers 13 to 21. Polytetrafluoroethylene parti clés were used as the solid lubricant particles in Test Numbers 13 to 21. The content of copper phthalocyanine was as shown in Table 3. The composition also contained a solvent. A mixed solution of water, alcohol and a surfactant was used as the solvent. In the case where there was a plating layer, the composition was applied with a bar coater onto the plating layer (or onto a Chemical conversion treatment layer formed thereon), and in the case where there was no plating layer the composition was applied with a bar coater onto the Steel plate surface, and thereafter a thermal hardening process was performed at 210°C for 20 mins to form a resin coating.

[Bowden test]

The Bowden test was carried out using the Steel plates of Test Numbers 13 to 21 on which a resin coating was formed, and the galling résistance was evaluated. Specifically, a steel bail was caused to slide on the surface of the resin coating of Test Numbers 13 to 21, and the coefficient of friction was determined. The steel bail had a diameter of 3/16 inch, and had a Chemical composition équivalent to SUJ2 defined in the JIS Standard. The load was set to 3 kgf (Hertz contact stress: average 1.56 GPa). The sliding width was set to 10 mm, and the sliding speed was set to 4 mm/sec. Sliding was performed without lubrication at room température. The coefficient of friction μ of the steel bail during sliding was measured, and the number of sliding times (number of round trips, that is, each time the steel bail slid back and forth once over a 10-mm area was counted as one time) until the coefficient of friction μ became more than 0.3 (équivalent to the coefficient of friction between the resin coating and the steel bail) was measured. A Bowden type stick-slip tester manufactured by Shinko Engineering Co., Ltd. was used for the test. The results are shown in the Number of Sliding Times until Coefficient of Friction Became More Than 0.3 column in Table 3.

[Evaluation Results]

Referring to Table 3, the steel plates of Test Numbers 13 to 20 included a resin coating containing a resin, a solid lubricant powder, and copper phthalocyanine on the surface. Referring further to Table 3, in the resin coating formed on the steel plate of each of Test Numbers 14 to 16 and 18 to 20, the content of copper phthalocyanine was within the range of 0.2 to 9.0 mass%. As a resuit, for the steel plates of Test Numbers 14 to 16 and 18 to 20, the number of sliding times until the coefficient of friction became more than 0.3 was high in comparison to the steel plate of Test Number 21 in which the resin coating did not contain copper phthalocyanine and the steel plates of Test Numbers 13 and 17 in which the content of copper phthalocyanine in the resin coating was outside the range of 0.2 to 9.0 mass%. That is, excellent galling résistance was exhibited.

[Example 3]

In Example 3, similarly to Example 2, a resin coating was formed on the surface of Steel plates simulating an oil-well métal pipe, and the galling résistance was evaluated. Specifically, in Example 3, cold-rolled steel plates (chemical composition: C < 0.15%, Mn < 0.60%, P < 0.100%, S < 0.050%, balance: Fe and impurities) were used.

Plating layers shown in Table 4 were formed as appropriate on the steel plate surfaces of Test Numbers 22 to 31. The plating layers that were formed are shown in the Plating Layer column in Table 4. The Symbol in the Plating Layer column in Table 4 means that a plating layer was not formed. The thickness of each plating layer that was formed was 8 pm. The measurement of the thickness of the plating layer was performed by the method described above using an electromagnetic film thickness meter SDM-picoR manufactured by Sanko Electronic Laboratory Co., Ltd., and the average value of the thicknesses at nine points on the same évaluation surface was taken as the thickness of the plating layer. A chemical conversion treatment layer was formed on the steel plate surface of Test Numbers 22 to 29 and 31. The chemical conversion treatment layer that was formed is shown in the Chemical Conversion Treatment Layer column in Table 4. The chemical conversion treatment solutions, treatment températures, and treatment times that were used for forming coatings A to D among the chemical conversion treatment layers in the Chemical Conversion Treatment Layer column are shown in Table 5. Note that, the term trivalent chromate in the Chemical Conversion Treatment Layer column in Table 4 means that a trivalent chromate coating was formed. The trivalent chromate coating is described later.

[Table 4]

TABLE 4

Test Number	Plating Layer	Chemical Conversion Treatment Layer	Copper Phthalocyanine Content	Sliding Distance until Coefficient of Friction Became More Than 0.6 (m)
22	-	Coating A	0.5 mass%	153.4
23	-	Coating A	2.0 mass%	155.8
24	-	Coating B	0.5 mass%	193.5
25	-	Coating B	2.0 mass%	201.0

26	-	Coating C	0.5 mass%	143.9
27	-	Coating C	2.0 mass%	151.2
28	-	Coating D	0.5 mass%	362.5
29	-	Coating D	2.0 mass%	375.8
30	Zn-Ni Alloy Plating Layer	-	2.0 mass%	108.8
31	Zn-Ni Alloy Plating Layer	Tri valent chromate	2.0 mass%	121.5

[Table 5]

TABLE 5

	Coating A	Coating B	Coating C	Coating D
Chemical Conversion Treatment Solution	System	Zinc Phosphate System	Zinc Phosphate System	Zinc Phosphate System	Manganèse Phosphate System
Free acidity	7.5pt/10mL	0.6pt/5mL	1,9pt/5mL	7.5pt/10mL
Total acidity	45.0pt/10mL	22.0pt/10mL	12.2pt/5mL	24.4pt/5mL
Treatment Température	80°C	40°C	60°C	90°C
Treatment Time	10 mins	2 mins	2 mins	5 mins

A resin coating was formed on the plating layer or on the Chemical conversion treatment layer of Test Numbers 22 to 31. The thickness of each of the formed resin coatings was 20 pm. The measurement of the thickness of the resin coating was performed by the method described above using an electromagnetic film thickness meter SDM-picoR manufactured by Sanko Electronic Laboratory Co., Ltd., and the average value of the thicknesses at nine points on the same évaluation surface was taken as the thickness of the resin coating. Note that, the resin coatings that were formed contained a copper phthalocyanine content shown in Table 4, and also contained 1 to 30 mass% of polytetrafluoroethylene (PTFE) as a solid lubricant powder, and the balance consisted of epoxy resin as a resin.

[Plating layer formation process]

A Zn-Ni alloy plating layer was formed by electroplating on the surface of the Steel plate of each of Test Numbers 30 and 31. The plating bath used was DAIN Zinalloy N-PL (trademark) manufactured by Daiwa Fine Chemicals Co., Ltd. The thickness of the Zn-Ni alloy plating layer was 8 pm. The measurement of the thickness of the plating layer was performed by the method described above using an electromagnetic film thickness meter SDM-picoR manufactured by Sanko Electronic Laboratory Co., Ltd., and the average value of the thicknesses at nine points on the same évaluation surface was taken as the thickness of the plating layer.

The electroplating conditions were as follows: plating bath pH: 6.5, plating bath température: 25°C, current density: 2 A/dm², and treatment time: 18 mins. The composition of the Zn-Ni alloy plating layer was Zn: 85% and Ni: 15%.

[Chemical conversion treatment layer formation process]

A Chemical conversion treatment layer was formed on the surface of the Steel plate or the plating layer of Test Numbers 22 to 29 and 31. Specifically, the Chemical conversion treatment solutions listed in Table 5 were used as the Chemical conversion treatment solutions for coatings A to D. The treatment solution used for forming a trivalent chromate coating was DAIN Chromate TR-02 manufactured by Daiwa Fine Chemicals Co., Ltd. The conditions of the Chemical conversion treatment for coatings A to D were as described in Table 5. The conditions of the Chemical conversion treatment for forming the trivalent chromate coating were: bath température: 25°C, pH: 4.0, and treatment time: 50 seconds.

[Application process and hardening process]

A resin coating was formed on the surface of the plating layer or the Chemical conversion treatment layer of Test Numbers 22 to 31. Specifically, a composition for forming a resin coating was applied onto the surface of the plating layer or the Chemical conversion treatment layer of Test Numbers 22 to 31 using a bar coater, and caused to harden. The components other than a solvent contained in the composition were solid lubricant particles and copper phthalocyanine, with the balance being a resin. Epoxy resin was used as the resin in Test Numbers 22 to 31. Polytetrafluoroethylene particles were used as the solid lubricant particles in Test Numbers 22 to 31. The content of copper phthalocyanine was as shown in Table 4. The composition also contained a solvent. A mixed solution of water, alcohol and a surfactant was used as the solvent. In the case where there was a Chemical conversion treatment layer, the composition was applied with a bar coater onto the Chemical conversion treatment layer, and in the case where there was no Chemical conversion treatment layer the composition was applied with a bar coater onto the plating layer, and thereafter a thermal hardening process was performed at 210°C for 20 mins to form a resin coating.

[Pin-on-disk test]

The galling résistance was evaluated by means of a pin-on-disk type sliding test machine using the steel plates of Test Nos. 22 to 31 on which a resin coating was formed. Specifically, the steel plate of each of Test Nos. 22 to 31 was affixed onto a rotary disk, and the rotary disk was rotated at 100 rpm while a Steel bail remained pressed against the rotary disk with a force of 60 N. The rotation direction of the rotary disk was set to one direction only. Note that, by rotating the rotary disk, sliding of the Steel bail with respect to the resin coating was performed without lubrication at room température. A coefficient of friction μ of the Steel bail during sliding was measured, and the sliding distance (m) until the coefficient of friction μ became more than 0.6 (équivalent to the coefficient of friction between the resin coating and the Steel bail) was measured. The results are shown in the Sliding Distance until Coefficient of Friction Became More Than 0.6 column in Table 4.

[Evaluation Results]

Referring to Table 4, the Steel plates of Test Numbers 22 to 31 included a resin coating containing a resin, a solid lubricant powder, and copper phthalocyanine on the surface. Referring further to Table 4, in the resin coating formed on the Steel plates of Test Numbers 22 to 31, the content of copper phthalocyanine was 0.2 to 9.0 mass%. As a resuit, the sliding distance until the coefficient of friction became more than 0.6 was long. That is, excellent galling résistance was exhibited.

The steel plates of Test Numbers 22 to 29 and 31 included a Chemical conversion treatment layer as an underlayer of the resin coating. As a resuit, in comparison to the steel plate of Test Number 30 that did not include a Chemical conversion treatment layer as an underlayer of the resin coating, the sliding distance until the coefficient of friction became more than 0.6 was even longer. That is, more excellent galling résistance was exhibited.

The steel plates of Test Numbers 22 to 29 included coatings A to D as a Chemical conversion treatment layer. As a resuit, in comparison to the steel plate of Test Number 31 that included a trivalent chromate coating as a Chemical conversion treatment layer, the sliding distance until the coefficient of friction became more than 0.6 was even longer. That is, more excellent galling résistance was exhibited.

[Example 4]

In Example 4, a resin coating was formed on the surface of steel plates simulating an oilwell métal pipe, and the galling résistance was evaluated. Specifically, in Example 4, coldrolled steel plates (chemical composition: C < 0.15%, Mn < 0.60%, P < 0.100%, S < 0.050%, balance: Fe and impurities) were used.

An anti-rust resin coating including a resin coating, or a resin coating as shown in Table 6 were formed on the steel plate surfaces of Test Numbers 32 to 34. The term formation in the

Anti-Rust Resin Coating column in Table 6 indicates that an anti-rust resin coating was formed on the Steel plate surface. The Symbol in the Anti-Rust Resin Coating column in Table 6 indicates that an anti-rust resin coating was not formed on the Steel plate surface.

[Table 6]

TABLE 6

Test Number	Anti-Rust Resin Coating	Copper Phthalocyanine Content	Rust Development Time Period (h)
32	Formation	0.5 mass%	1006<
33	Formation	2.0 mass%	1006<
34	-	2.0 mass%	768

[Anti-rust resin coating formation process]

An anti-rust resin coating was formed on the surface of the Steel plate of Test Numbers 32 and 33. The composition for forming the anti-rust resin coating contained rust préventive pigment in an amount of 8 mass%, and acrylic Silicon resin in an amount of 70 mass%. The composition for forming the anti-rust resin coating also contained a solvent. The composition for forming the anti-rust resin coating was applied to the surface of the steel plate of Test Numbers 32 and 33 by spraying, and was allowed to harden by natural drying. The thickness of the anti-rust resin coating of Test Number 32 was 13 pm. The thickness of the anti-rust resin coating of Test Number 33 was 11 μηι. The measurement of the thickness of the anti-rust resin coating was performed by the method described above using an electromagnetic film thickness meter SDM-picoR manufactured by Sanko Electronic Laboratory Co., Ltd., and the average value of the thicknesses at nine points on the same évaluation surface was taken as the thickness of the anti-rust resin coating.

[Application process and hardening process]

An upper layer of the resin coating was formed on the surface of the anti-rust resin coating of Test Numbers 32 and 33. A resin coating was formed on the surface of the Steel plate of Test Number 34. Specifically, a composition for forming a resin coating was applied onto the surface of the steel plate or onto the surface of the anti-rust resin coating of Test Numbers 32 to 34 using a bar coater, and caused to harden. The components other than a solvent contained in the composition were solid lubricant particles and copper phthalocyanine, with the balance being a resin. Epoxy resin was used as the resin. Polytetrafluoroethylene particles were used as the solid lubricant particles. The content of copper phthalocyanine was as shown in Table 6. The composition also contained a solvent. A mixed solution of water, alcohol and a surfactant was used as the solvent. In the case where there was an anti-rust resin coating, the composition was applied with a bar coater onto the anti-rust resin coating, and in the case where there was no anti-rust resin coating the composition was applied with a bar coater onto the surface of the steel plate, and thereafter a thermal hardening process was performed at 210°C for 20 mins to form a resin coating. The resin coatings that were formed also contained 1 to 30 mass% of polytetrafluoroethylene (PTFE) as a solid lubricant powder, and the balance consisted of epoxy resin as a resin.

The thickness of the resin coating of Test Number 32 was 35.5 pm, the thickness of the resin coating of Test Number 33 was 33.0 pm, and the thickness of the resin coating of Test Number 34 was 26.8 pm. Note that, the resin coating of Test Numbers 32 and 33 included the anti-rust resin coating. Therefore, the thickness of the upper layer of the resin coating of Test Numbers 32 was 22.5 pm and the thickness of the upper layer of the resin coating of Test Numbers 33 was 22.0 pm. The measurement of the thickness of the resin coating was performed by the method described above using an electromagnetic film thickness meter SDMpicoR manufactured by Sanko Electronic Laboratory Co., Ltd., and the average value of the thicknesses at nine points on the same évaluation surface was taken as the thickness of the resin coating.

[Sait spray test]

A sait spray test (SST) was carried out using the steel plates of Test Numbers 32 to 34 on which a resin coating was formed. A test instrument with the trade name Combined Cyclic Corrosion Test Instrument CY90 manufactured by Suga Test Instruments Co., Ltd. was used for the sait spray test. The sait spray test conformed to JIS Z 2371 (2015). The test conditions were as follows: NaCl concentration of spray: 5±0.5%, spray amount: 1.5±0.5mL/h/80cm², température: 35±2°C, pH during test: 6.5 to 7.2. In the présent example, the time period until blistering of the resin coating occurred was taken as a rust development time period. The rust development time periods are shown in Table 6.

[Evaluation results]

Referring to Table 6, the steel plates of Test Numbers 32 to 34 included a resin coating containing a resin, a solid lubricant powder, and copper phthalocyanine on the surface.

The steel plates of Test Numbers 32 and 33 included an anti-rust resin coating in the resin coating. As a resuit, the time period until rust developed was longer in comparison to the steel plate of Test Number 34 that did not include an anti-rust resin coating in the resin coating. That is, excellent corrosion résistance was exhibited.

An embodiment of the présent disclosure has been described above. However, the foregoing embodiment is merely an example for implementing the présent disclosure. Accordingly, the présent disclosure is not limited to the above embodiment, and the above embodiment can be appropriately modified within a range which does not deviate from the gist of the présent disclosure.

REFERENCE SIGNS LIST

Oil-well métal pipe

Pipe Main Body

OA First End Portion

10B Second End Portion

Pin Tube Body

Coupling

Extemal Thread Part

Pin Sealing Surface

Pin Shoulder Surface

Box

Internai Thread Part

Box Sealing Surface

Box Shoulder Surface

Anti-Rust Resin Coating

Plating Layer

Chemical Conversion Treatment Layer

100 Resin Coating

400 Pin Contact Surface

500 Box Contact Surface

Claims

49 CLAIMS

1. An oil-well métal pipe, comprising:

a pipe main body including a first end portion and a second end portion;

wherein:

the pipe main body includes:

a pin formed at the first end portion, and a box formed at the second end portion;

the pin includes:

a pin contact surface including an extemal thread part;

the box includes:

a box contact surface including an internai thread part;

the oil-well métal pipe further comprising:

a resin coating containing a resin, a solid lubricant powder and copper phthalocyanine on or above at least one of the pin contact surface and the box contact surface.
2. The oil-well métal pipe according to claim 1, wherein:

the resin coating contains 0.2 to 30.0 mass% of copper phthalocyanine.
3. The oil-well métal pipe according to claim 2, wherein:

the resin coating contains:

0.2 to 30.0 mass% of copper phthalocyanine,

60 to 90 mass% of the resin, and

1 to 30 mass% of the solid lubricant powder.
4. The oil-well métal pipe according to claim 2 or claim 3, wherein: the resin coating contains 0.2 to 9.0 mass% of copper phthalocyanine.
5. The oil-well métal pipe according to any one of daims 1 to 4, further comprising: a plating layer between at least one of the pin contact surface and the box contact surface, and the resin coating.
6. The oil-well métal pipe according to any one of daims 1 to 4, further comprising:

a Chemical conversion treatment layer between at least one of the pin contact surface and the box contact surface, and the resin coating.
7. The oil-well métal pipe according to claim 5, further comprising:

a Chemical conversion treatment layer between the plating layer and the resin coating.
8. The oil-well métal pipe according to any one of daims 1 to 7, wherein:

the resin coating further containing a rust préventive pigment.
9. The oil-well métal pipe according to any one of daims 1 to 8, wherein:

at least one of the pin contact surface and the box contact surface is a surface that is subjected to one or more types of treatment selected from the group consisting of a blasting treatment and pickling.
10. The oil-well métal pipe according to any one of daims 1 to 9, wherein:

the resin is one or more types selected from the group consisting of epoxy resin, phénol resin, acrylic resin, urethane resin, polyester resin, polyamide-imide resin, polyamide resin, polyimide resin and polyether ether ketone resin.
11. The oil-well métal pipe according to any one of daims 1 to 10, wherein:

the solid lubricant powder is one or more types selected from the group consisting of graphite, zinc oxide, boron nitride, talc, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfide, bismuth sulfide, organic molybdenum, thiosulfate compounds, and polytetrafluoroethylene.
12. The oil-well métal pipe according to any one of daims 1 to 11, wherein:

the pin contact surface further includes a pin sealing surface and a pin shoulder surface, and the box contact surface further includes a box sealing surface and a box shoulder surface.
13. A method for producing the oil-well métal pipe according to claim 1, the method comprising the steps of:

preparing an oil-well métal pipe comprising a pipe main body that includes a pin including a pin contact surface that includes an extemal thread part, and a box including a box contact surface that includes an internai thread part;

applying a composition containing a resin, a solid lubricant powder and copper

5 phthalocyanine onto at least one of the pin contact surface and the box contact surface; and hardening the composition that is applied to form a resin coating.