WO2020021691A1

WO2020021691A1 - Screw joint for pipe and method for manufacturing screw joint for pipe

Info

Publication number: WO2020021691A1
Application number: PCT/JP2018/028165
Authority: WO
Inventors: 石井　一也; 後藤　邦夫; 雅也木本
Original assignee: 日本製鉄株式会社; バローレック・オイル・アンド・ガス・フランス
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2020-01-30

Abstract

The present invention provides a screw joint (1) which is for a pipe and has excellent seizure resistance. The screw joint (1) for a pipe according to the present embodiment includes a pin (4), a box (5), a Ni-W alloy plating layer (6), and a solid lubricating film (7). The pin (4) has a pin-side contact surface (40) that includes a pin-side screw portion (41). The box (5) has a box-side contact surface (50) that includes a box-side screw portion (51). The Ni-W alloy plating layer (6) is disposed on at least one among the pin-side contact surface (40) and the box-side contact surface (50). The Ni-W alloy plating layer (6) is composed of 35.0-45.0 mass% of W, and the remainder comprising Ni and impurities, and has a thickness of 1.0-20.0 μm. The solid lubricating film (7) is disposed on the Ni-W alloy plating layer (6) on at least one among the pin-side contact surface (40) and the box-side contact surface (50).

Description

Pipe threaded joint and method of manufacturing pipe threaded joint

The present invention relates to a threaded joint for pipes and a method for manufacturing a threaded joint for pipes, and more particularly, to a threaded joint for oil country tubular goods and a method for manufacturing a threaded joint for oil country tubular goods.

油 Oil well pipes are used for mining oil fields and natural gas fields. An oil country tubular good is formed by connecting a plurality of steel pipes according to the depth of the well. The connection of the steel pipes is performed by screwing together pipe threaded joints formed at the ends of the steel pipes. The steel pipe is pulled up for inspection or the like, unscrewed, inspected, screwed again, and used again.

ねじ Pipe threaded joints include pins and boxes. The pin includes a male screw portion formed on the outer peripheral surface of the tip of the steel pipe. The box includes a female screw portion formed on the inner peripheral surface of the distal end portion of the steel pipe. Pins and boxes may also have unthreaded metal contacts. The threaded portion of the pin and the box and the threadless metal contact portion repeatedly receive strong friction when screwing and unscrewing the steel pipe. If these parts do not have sufficient durability against friction, galling (irreparable seizure) occurs when the screwing and unscrewing are repeated. Therefore, threaded joints for pipes are required to have sufficient durability against friction, that is, excellent seizure resistance.

ねじ The threaded portion of the pin and the box and the metal contact portion without the screw repeatedly receive strong friction when screwing and unscrewing the steel pipe. If these parts do not have sufficient durability against friction, galling (irreparable seizure) occurs when repeated tightening and unscrewing. Therefore, threaded joints for pipes are required to have sufficient durability against friction, that is, excellent seizure resistance.

Conventionally, compound grease containing a heavy metal called a dope has been used to improve seizure resistance. However, heavy metals (Pb, Zn, Cu, etc.) contained in the compound grease may affect the environment. For this reason, development of a threaded joint for pipes in which use of compound grease is suppressed is desired.

WO2009 / 072486 (Patent Document 1) proposes a threaded pipe joint having excellent seizure resistance even without compound grease.

The pipe threaded joint described in Patent Document 1 includes a pin and a box each having a contact surface having a threaded portion and a threadless metal contact portion. The contact surface of the box has as its top layer a solid lubricating coating having a plastic or viscoplastic rheological behavior. The contact surface of the pin has, as the uppermost layer, a solid anticorrosive coating mainly composed of an ultraviolet curable resin. Thereby, without using compound grease, it is possible to obtain a threaded joint for pipes which suppresses rust generation, exhibits excellent seizure resistance and airtightness, has no sticky surface, and has excellent appearance and inspection properties. And Patent Document 1.

In order to suppress seizure of the threaded joint for pipes, it is effective to form a plating layer containing a metal having a high hardness and a high melting point. Therefore, conventionally, copper (Cu) plating or Cu alloy plating has been used. The hardness and melting point of Cu are high. Therefore, by including Cu in the plating layer, the hardness and the melting point of the entire plating layer increase. Therefore, the seizure resistance of the pipe threaded joint is enhanced.

Techniques for improving the seizure resistance of threaded joints for tubes by Cu alloy plating are described in JP-A-2003-074763 (Patent Document 2) and JP-A-2008-215473 (Patent Document 3).

管 The pipe threaded joint described in Patent Document 2 includes a pin portion and a coupling. The coupling is a steel pipe containing 9% by mass or more of Cr. At both ends of the coupling, a box portion having a female screw and a metal-metal seal portion is provided. A Cu—Sn alloy layer is disposed on the surface of the female screw and the metal-metal seal portion of the coupling. Patent Document 2 describes that the use of this threaded joint for pipes has a better sealing property and can significantly suppress galling even if a green dope (lubricant containing no Pb) is used. I have.

ねじ The pipe threaded joint described in Patent Document 3 includes a pin and a box. At least one contact surface of the pin and the box has a first plating layer made of a Cu—Zn alloy. Patent Literature 3 describes that the threaded joint for pipe shows sufficient leakage resistance and seizure resistance even when a green dope is applied or even when it is not doped.

International Publication No. 2009/072486 JP-A-2003-074763 JP 2008-215473 A

However, even when the techniques disclosed in Patent Documents 1 to 3 described above are used, the seizure resistance of the threaded pipe joint may not be sufficient.

目的 An object of the present invention is to provide a threaded pipe joint having excellent seizure resistance and a method for manufacturing the same.

ねじ The threaded joint for pipes of this embodiment includes a pin, a box, a Ni—W alloy plating layer, and a solid lubricating film. The pin has a pin-side contact surface that includes a pin-side thread. The box has a box side contact surface that includes a box side thread. The Ni—W alloy plating layer is disposed on at least one of the pin-side contact surface and the box-side contact surface. The Ni—W alloy plating layer is composed of 35.0 to 45.0 mass% of W, and the remainder is composed of Ni and impurities, and has a thickness of 1.0 to 20.0 μm. The solid lubricating coating is disposed on the Ni—W alloy plating layer on at least one of the pin-side contact surface and the box-side contact surface.

製造 The method of manufacturing a pipe threaded joint of the present embodiment is a method of forming a Ni—W alloy plating layer on a pipe threaded joint including a pin and a box. The pin has a pin-side contact surface that includes a pin-side thread. The box has a box side contact surface that includes a box side thread. The manufacturing method includes a Ni-W alloy plating layer forming step and a solid lubricating film forming step. In the Ni—W alloy plating layer forming step, at least one of the pin-side contact surface and the box-side contact surface is immersed in a plating solution. The plating solution contains nickel ions and tungsten ions. Next, at least one of the pin-side contact surface and the box-side contact surface immersed in the plating solution is energized. Thus, a Ni—W alloy plating layer is formed on at least one of the pin-side contact surface and the box-side contact surface. The Ni—W alloy plating layer is composed of 35.0 to 45.0 mass% of W, and the remainder is composed of Ni and impurities, and has a thickness of 1.0 to 20.0 μm. In the solid lubricant film forming step, a solid lubricant film is formed on the Ni—W alloy plating layer on at least one of the pin-side contact surface and the box-side contact surface.

ねじ The threaded joint for pipes of the present embodiment has excellent seizure resistance.

FIG. 1 is a view showing a configuration of a coupling type pipe threaded joint according to the present embodiment. FIG. 2 is a diagram showing a configuration of an integral type pipe threaded joint according to the present embodiment. FIG. 3 is a cross-sectional view of an example of a pipe threaded joint. FIG. 4 is a diagram showing a configuration of the pipe threaded joint according to the present embodiment in the case where the pipe has no metal seal portion and no shoulder portion. FIG. 5 is a sectional view of an example of the threaded pipe joint according to the present embodiment. FIG. 6 is a sectional view of an example of a pipe threaded joint according to another embodiment different from FIG. FIG. 7 is a cross-sectional view of an example of a pipe threaded joint according to another embodiment different from FIGS. 5 and 6. FIG. 8 is a sectional view of an example of a pipe threaded joint according to another embodiment different from FIGS. 5 to 7. FIG. 9 is a sectional view of an example of a pipe threaded joint according to another embodiment different from FIGS. 5 to 8.

Hereinafter, the present embodiment will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts have the same reference characters allotted, and description thereof will not be repeated.

者 The present inventors have conducted various studies on seizure resistance of threaded joints for pipes. As a result, the following findings were obtained.

In order to enhance the seizure resistance of the threaded pipe joint during screw tightening and unscrewing, it is effective to form a plating layer having high hardness and a high melting point on the contact surface having the screw portion, the metal seal portion, and the shoulder portion. is there. If the hardness of the plating layer is high, the plating layer is less likely to be damaged during screwing and unscrewing of the pipe threaded joint. Furthermore, if the melting point of the plating layer is high, a decrease in the hardness of the plating layer can be suppressed even when the plating layer is locally heated to a high temperature when screwing and unscrewing the threaded joint for pipes. As a result, seizure resistance of the pipe threaded joint is enhanced.

者 The present inventors have further studied a plating layer suitable for a threaded joint for pipes. As a result, the present inventors formed a Ni—W alloy plating layer containing 35.0 to 45.0 mass% of W and the balance of Ni and impurities on the contact surface of the pipe threaded joint, It has been found that the seizure resistance of the threaded joint for pipes during screwing and unscrewing can be improved. Hereinafter, this point will be described.

The hardness and melting point of a Ni—W alloy containing 35.0 to 45.0% by mass of W and the balance being Ni and impurities are determined by the hardness of a Cu plating layer conventionally used as a plating layer for threaded joints for pipes. And higher than the melting point. Therefore, the Ni—W alloy plating layer containing 35.0 to 45.0% by mass of W and the balance of Ni and impurities has high hardness (Hv 600 or more) and high melting point (1455 ° C. or more). As a result, the use of a Ni-W alloy plating layer containing 35.0 to 45.0% by mass of W and the balance of Ni and impurities increases the seizure resistance of the threaded joint for pipes.

The present inventors have further studied the thickness of the Ni—W alloy plating layer in detail. When screwing and unscrewing a pipe threaded joint, the pin and box slide frictionally while receiving significantly higher pressure. However, it has been found that when the thickness of the Ni—W alloy plating layer is 1.0 μm or more, seizure resistance is enhanced even under a high-pressure environment such as when screwing and unscrewing a threaded joint for pipes.

管 The threaded joint for pipes of the present embodiment completed based on the above findings includes a pin, a box, a Ni-W alloy plating layer, and a solid lubricating film. The pin has a pin-side contact surface that includes a pin-side thread. The box has a box side contact surface that includes a box side thread. The Ni—W alloy plating layer is disposed on at least one of the pin-side contact surface and the box-side contact surface. The Ni—W alloy plating layer is composed of 35.0 to 45.0 mass% of W, and the remainder is composed of Ni and impurities, and has a thickness of 1.0 to 20.0 μm. The solid lubricating coating is disposed on the Ni—W alloy plating layer on at least one of the pin-side contact surface and the box-side contact surface.

The threaded joint for pipes of the present embodiment contains a Ni-W alloy containing 35.0 to 45.0% by mass of W on at least one of the pin-side contact surface and the box-side contact surface, with the balance being Ni and impurities. It has a plating layer. The pipe threaded joint of the present embodiment further has a solid lubricating coating on the Ni—W alloy plating layer on at least one of the pin-side contact surface and the box-side contact surface. Therefore, it has excellent seizure resistance.

ピン The pin-side contact surface of the pipe threaded joint may further include a pin-side metal seal portion and a pin-side shoulder portion. The box side contact surface may further include a box side metal seal and a box side shoulder.

According to the manufacturing method of this embodiment, the Ni-W alloy plating layer is provided on at least one of the pin-side contact surface and the box-side contact surface, and the Ni-W alloy plating layer is provided on at least one of the pin-side contact surface and the box-side contact surface. A threaded joint for pipes having a solid lubricating coating on a W alloy plating layer can be manufactured. Therefore, the threaded pipe joint has excellent seizure resistance.

In the method for manufacturing a pipe threaded joint, the pin-side contact surface may further include a pin-side metal seal portion and a pin-side shoulder portion. The box side contact surface may further include a box side metal seal and a box side shoulder.

Hereinafter, the pipe threaded joint according to the present embodiment and the method for manufacturing the same will be described in detail.

[Pipe threaded joint 1]
The threaded pipe joint includes a pin and a box. FIG. 1 is a diagram showing a configuration of a pipe threaded joint 1 according to the present embodiment. Referring to FIG. 1, a pipe threaded joint 1 includes a steel pipe 2 and a coupling 3. Pins 4 each having an external thread portion on the outer surface are formed at both ends of the steel pipe 2. Boxes 5 each having a female screw portion on the inner surface are formed at both ends of the coupling 3. The coupling 3 is attached to the end of the steel pipe 2 by screwing the pin 4 and the box 5 together. Although not shown, a protector may be attached to the pin 4 of the steel pipe 2 and the box 5 of the coupling 3 to which the mating member is not attached in order to protect the respective screw portions.

On the other hand, an integral type pipe threaded joint 1 in which one end of the steel pipe 2 is a pin 4 and the other end is a box 5 without using the coupling 3 may be used. FIG. 2 is a diagram showing the configuration of the integral type pipe threaded joint 1 according to the present embodiment. With reference to FIG. 2, the threaded pipe joint 1 includes a steel pipe 2. At one end of the steel pipe 2, a pin 4 having an external thread portion on the outer surface is formed. At the other end of the steel pipe 2, a box 5 having a female screw portion on the inner surface is formed. The steel pipes 2 can be connected to each other by screwing the pins 4 and the box 5 together. The pipe threaded joint 1 of the present embodiment can be used for both coupling type and integral type pipe threaded joints 1.

FIG. 3 is a sectional view of an example of the threaded pipe joint 1. In FIG. 3, the pin 4 includes a pin-side screw part 41, a pin-side metal seal part 42, and a pin-side shoulder part 43. In FIG. 3, the box 5 includes a box-side screw portion 51, a box-side metal seal portion 52, and a box-side shoulder portion 53. The portions that come into contact when the pin 4 and the box 5 are screwed together are referred to as contact surfaces 40 and 50. Specifically, when the pin 4 and the box 5 are screwed together, the screw portions (the pin-side screw portion 41 and the box-side screw portion 51) and the metal seal portions (the pin-side metal seal portion 42 and the box-side metal seal portion) 52) and the shoulder portions (the pin-side shoulder portion 43 and the box-side shoulder portion 53) come into contact with each other. In FIG. 3, the pin-side contact surface 40 includes a pin-side screw portion 41, a pin-side metal seal portion 42, and a pin-side shoulder portion 43. In FIG. 3, the box-side contact surface 50 includes a box-side screw portion 51, a box-side metal seal portion 52, and a box-side shoulder portion 53.

In FIG. 3, the pins 4 are arranged in the order of the pin-side shoulder 43, the pin-side metal seal 42, and the pin-side screw 41 from the end of the steel pipe 2. In the box 5, from the end of the steel pipe 2 or the coupling 3, the box-side screw portion 51, the box-side metal seal portion 52, and the box-side shoulder portion 53 are arranged in this order. However, the arrangement of the pin side screw portion 41 and the box side screw portion 51, the pin side metal seal portion 42 and the box side metal seal portion 52, and the arrangement of the pin side shoulder portion 43 and the box side shoulder portion 53 are limited to the arrangement of FIG. However, it can be changed as appropriate. For example, as shown in FIG. 2, in the pin 4, a pin-side shoulder 43, a pin-side metal seal 42, a pin-side screw 41, a pin-side metal seal 42, and a pin-side shoulder from the end of the steel pipe 2. 43, the pin-side metal seal part 42 and the pin-side screw part 41 may be arranged in this order. In the box 5, from the end of the steel pipe 2 or the coupling 3, the box side screw portion 51, the box side metal seal portion 52, the box side shoulder portion 53, the box side metal seal portion 52, the box side screw portion 51, the box side metal portion The seal portion 52 and the box-side shoulder portion 53 may be arranged in this order.

FIGS. 1 and 2 illustrate a so-called premium joint including a metal seal portion (the pin-side metal seal portion 42 and the box-side metal seal portion 52) and a shoulder portion (the pin-side shoulder portion 43 and the box-side shoulder portion 53). . However, the metal seal portion (the pin-side metal seal portion 42 and the box-side metal seal portion 52) and the shoulder portion (the pin-side shoulder portion 43 and the box-side shoulder portion 53) may not be provided. FIG. 4 illustrates the pipe threaded joint 1 without the

metal seal portions

42 and 52 and the

shoulder portions

43 and 53. The pipe threaded joint 1 of the present embodiment can be suitably applied to the pipe threaded joint 1 without the

metal seal portions

42 and 52 and the

shoulder portions

43 and 53. Without the metal seals 42, 52 and the

shoulders

43, 53, the pin-side contact surface 40 includes a pin-side thread 41 and the box-side contact surface 50 includes a box-side thread 51.

5 is a sectional view of an example of the pipe threaded joint 1 according to the present embodiment. The threaded pipe joint 1 includes a Ni—W alloy plating layer 6 on at least one of the pin-side contact surface 40 and the box-side contact surface 50. In FIG. 5, the threaded pipe joint 1 includes a Ni—W alloy plating layer 6 on both the pin-side contact surface 40 and the box-side contact surface 50. The threaded pipe joint 1 further includes a solid lubricating coating 7 on the Ni—W alloy plating layer 6 on at least one of the pin-side contact surface 40 and the box-side contact surface 50. In FIG. 5, the threaded pipe joint 1 includes a solid lubricating coating 7 on both the Ni—W alloy plating layer 6 on the pin-side contact surface 40 and the Ni—W alloy plating layer 6 on the box-side contact surface 50. . If the solid lubricating film 7 is provided on the Ni—W alloy plating layer 6, the lubricating property is enhanced, and the seizure resistance of the threaded pipe joint 1 is further enhanced.

配置 The arrangement of the alloy plating layers of the present embodiment is not limited to FIG. As shown in FIG. 6, the Ni-W alloy plating layer 6 is provided on both the pin-side contact surface 40 and the box-side contact surface 50, and the Ni-W alloy plating layer 6 on the pin-side contact surface 40 is provided. The solid lubricant film 7 may be provided, and the solid lubricant film 7 may not be provided on the Ni—W alloy plating layer 6 on the box-side contact surface 50. As shown in FIG. 7, the Ni-W alloy plating layer 6 is provided on both the pin-side contact surface 40 and the box-side contact surface 50, and the Ni-W alloy plating layer 6 on the box-side contact surface 50 is provided. The solid lubricant film 7 may be provided, and the solid lubricant film 7 may not be provided on the Ni—W alloy plating layer 6 on the pin-side contact surface 40. As shown in FIG. 8, the Ni-W alloy plating layer 6 and the solid lubricant film 7 may be provided only on the pin-side contact surface 40. As shown in FIG. 9, the Ni—W alloy plating layer 6 and the solid lubricant film 7 may be provided only on the box-side contact surface 50. Although not shown, the Ni-W alloy plating layer 6 and the solid lubricant film 7 may be provided only on the pin-side contact surface 40, and only the solid lubricant film 7 may be provided on the box-side contact surface 50. The Ni-W alloy plating layer 6 and the solid lubricating film 7 may be provided only on the box-side contact surface 50, and only the solid lubricating film 7 may be provided on the pin-side contact surface 40. That is, nothing may be formed on the contact surface where the Ni—W alloy plating layer 6 is not formed, or the solid lubricating film 7 may be formed. Another coating (for example, a solid anticorrosion coating) may be formed on the contact surface where the Ni—W alloy plating layer 6 is not formed.

[Ni-W alloy plating layer 6]
The Ni—W alloy plating layer 6 is disposed on at least one of the pin-side contact surface 40 and the box-side contact surface 50. The Ni—W alloy plating layer 6 is made of a Ni—W alloy. The Ni—W alloy contains Ni and W, with the balance being impurities. Here, the impurities are substances other than Ni and W, and are contained in the Ni—W alloy plating layer 6 during the production of the pipe threaded joint 1 and are contained in a content that does not affect the effects of the present invention. including. The impurities are, for example, Fe, S, O, C and the like. The hardness and melting point of the Ni—W alloy plating layer 6 are high. Therefore, the seizure resistance of the pipe threaded joint 1 is enhanced.

When the chemical composition of the Ni—W alloy plating layer 6 is 100% by mass, the Ni—W alloy plating layer 6 contains 35.0 to 45.0% by mass of W. In this case, the Ni—W alloy plating layer 6 has high seizure resistance. As a result, the threaded pipe joint 1 exhibits excellent seizure resistance.

If the W content is less than 35.0% by mass, the hardness of the Ni—W alloy plating layer 6 decreases, and the seizure resistance decreases. On the other hand, if the W content exceeds 45.0% by mass, the hardness of the Ni—W alloy plating layer 6 becomes too high, and the seizure resistance is rather lowered. Therefore, the W content in the Ni—W alloy plating layer 6 is 35.0 to 45.0% by mass. A preferable lower limit of the W content in the Ni—W alloy plating layer 6 is 38.0% by mass. The preferable upper limit of the W content in the Ni—W alloy plating layer 6 is 42.0% by mass.

ＷThe W content of the Ni—W alloy plating layer 6 is measured by the following method. The W content is measured using a handheld X-ray fluorescence spectrometer (DP2000 manufactured by Olympus (trade name: DELTA @ Premium)). The composition analysis is performed at any four locations (any 0 °, 90 °, 180 °, or 270 ° location in the circumferential direction of the tube) on the surface of the metal seal portion on which Ni—W has been applied. The measured contents of Ni and W are determined by the measurement mode of the alloy. The W content (% by mass) is obtained by dividing the measured W content by the total measured Ni and W content.

The thickness of the Ni—W alloy plating layer 6 is 1.0 to 20.0 μm. If the thickness of the Ni—W alloy plating layer 6 is less than 1.0 μm, the seizure resistance decreases. If the thickness of the Ni—W alloy plating layer 6 exceeds 20.0 μm, the adhesion of the plating decreases. The lower limit of the thickness of the Ni—W alloy plating layer 6 is preferably 5.0 μm, and more preferably 8.0 μm. The upper limit of the thickness of the Ni—W alloy plating layer 6 is preferably 15.0 μm, and more preferably 12.0 μm.

The thickness of the Ni—W alloy plating layer 6 is measured by the following method. The

contact surface

40 or 50 on which the Ni—W alloy plating layer 6 is formed is brought into contact with a probe of an overcurrent phase type film thickness measuring device conforming to ISO (International Organization for Standardization) 21968 (2005). The phase difference between the high frequency magnetic field on the input side of the probe and the overcurrent on the Ni—W alloy plating layer 6 excited by the high frequency magnetic field is measured. This phase difference is converted into a thickness of the Ni—W alloy plating layer 6. In the film thickness measurement at the threaded joint, four arbitrary points (any 0 °, 90 °, 180 °, 270 ° point in the circumferential direction of the tube) of the

contact surface

40 or 50 are measured.

[Solid lubricating coating 7]
5 to 9, the pipe threaded joint 1 further includes a solid lubricating coating 7 on the Ni—W alloy plating layer 6 on at least one of the pin-side contact surface 40 and the box-side contact surface 50. In this case, the lubricity of the pipe threaded joint 1 is further enhanced. As the solid lubricating film 7, a known material can be used. The solid lubricating coating 7 contains, for example, lubricating particles and a binder. The solid lubricating coating 7 may contain a solvent and other components as needed.

The lubricating particles reduce the coefficient of friction of the surface of the solid lubricating coating 7. The lubricating particles are not particularly limited as long as they have lubricating properties. The lubricating particles are, for example, graphite, MoS ₂ (molybdenum disulfide), WS ₂ (tungsten disulfide), BN (boron nitride), PTFE (polytetrafluoroethylene), CF _x (fluorinated graphite) and CaCO ₃ (carbonate Calcium) or one or more selected from the group consisting of: Preferably, graphite, fluorinated graphite, MoS ₂ and PTFE are used. Assuming that the solid lubricating coating 7 is 100% by mass, the preferable content of the lubricating particles is 5 to 40% by mass.

The binder binds the lubricating particles into the solid lubricating coating 7. The binder is, for example, one or two selected from the group consisting of an organic resin and an inorganic resin. When an organic resin is used, one selected from the group consisting of a thermosetting resin and a thermoplastic resin can be used. The thermosetting resin is, for example, one or two selected from the group consisting of an epoxy resin, a polyimide resin, a polycarbodiimide resin, a polyethersulfone, a polyetheretherketone resin, a phenol resin, a furan resin, a urea resin, and an acrylic resin. More than a species. The thermoplastic resin is, for example, one or more selected from the group consisting of a polyamideimide resin, a polyethylene resin, a polypropylene resin, a polystyrene resin, and an ethylene vinyl acetate resin. Assuming that the solid lubricating coating 7 is 100% by mass, the preferable content of the binder is 60 to 95% by mass.

ポリ When using an inorganic resin, polymetalloxane can be used. Polymetalloxane refers to a polymer compound in which a repeating metal-oxygen bond is a main chain skeleton. Preferably, polytitanoxane (Ti—O) and polysiloxane (Si—O) are used. These inorganic resins are obtained by hydrolyzing and condensing a metal alkoxide. The alkoxy group of the metal alkoxide is, for example, a lower alkoxy group such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an isobutoxy group, a butoxy group and a tert-butoxy group.

溶媒 If it is necessary to dissolve or disperse the lubricating particles and the binder, use a solvent. The solvent is not particularly limited as long as the components contained in the solid lubricating coating 7 can be dispersed or dissolved. As the solvent, one or two kinds selected from the group consisting of an organic solvent and water can be used. The organic solvent is, for example, one or two selected from the group consisting of toluene and isopropyl alcohol.

The solid lubricating coating 7 can contain other components as needed. Other components are, for example, rust inhibitors, corrosion inhibitors, surfactants, waxes, friction modifiers and pigments. The content of each of the lubricating particles, the binder, the solvent, and other components is appropriately set. When the amount of the solid lubricating coating 7 is 100% by mass, a preferable content of other components is, for example, 1 to 50% by mass, and preferably 5 to 30% by mass.

[Base material of pipe threaded joint 1]
The chemical composition of the base material of the threaded pipe joint 1 is not particularly limited. The base material is, for example, carbon steel, stainless steel, alloy steel, or the like. The alloy steel is, for example, a Ni alloy and a duplex stainless steel containing alloy elements such as Cr, Ni and Mo. The base material of the pipe threaded joint 1 is, for example, 13% Cr steel (C: 0.18%, Si: 0.23%, Mn: 0.8%, P: 0.02%), which is a kind of high alloy steel. , S: 0.01%, Cu: 0.04%, Ni: 0.1%, Cr: 13%, Mo: 0.04%, balance: Fe and impurities).

[Production method]
The method for manufacturing the threaded pipe joint 1 of the present embodiment is the method for manufacturing the above-described threaded pipe joint 1. The manufacturing method includes a Ni-W alloy plating layer forming step and a solid lubricating film forming step.

[Ni-W alloy plating layer forming step]
In the Ni—W alloy plating layer forming step, the Ni—W alloy plating layer 6 made of a Ni—W alloy is deposited on at least one of the pin-side contact surface 40 and the box-side contact surface 50 of the prepared pipe threaded joint 1. Form. The Ni—W alloy plating layer 6 is formed by electroplating. The electroplating is performed by immersing the pin-side contact surface 40 of the pin 4 or the box-side contact surface 50 of the box 5 as a material to be plated in a plating bath containing Ni ions and W ions, and supplying electricity. The plating bath preferably contains Ni ions: 0.13 to 0.3 mol / L and W ions: 0.3 to 0.42 mol / L. Electroplating conditions can be set as appropriate. The electroplating conditions are, for example, plating bath pH: 1 to 10, plating bath temperature: 10 to 60 ° C., current density: 1 to 100 A / dm ² , and treatment time: 0.1 to 30 minutes.

[Solid lubrication film forming process]
The solid lubricating coating 7 is formed on the Ni—W alloy plating layer 6 on at least one of the pin-side contact surface 40 and the box-side contact surface 50. In the solid lubricating film forming step, first, a composition for a solid lubricating film (hereinafter, also referred to as a composition) is prepared. The composition is formed by mixing the lubricating particles and the binder described above. The composition may further contain the above-mentioned solvents and other components.

(4) The obtained composition is applied on the Ni—W alloy plating layer 6. The method of application is not particularly limited. For example, the composition is sprayed on the Ni—W alloy plating layer 6 using a spray gun. The pin 4 or the box 5 to which the composition has been applied is dried by heating. As a result, the composition is cured, and a solid lubricating film 7 is formed on the Ni—W alloy plating layer 6. The conditions for the heating and drying can be appropriately set in consideration of the boiling point and melting point of each component contained in the composition. For a composition that does not use a solvent, a hot melt method can be used. In the hot melt method, the composition is heated to a fluid state. The composition in a fluidized state is sprayed using, for example, a spray gun having a temperature maintaining function. The pin 4 or the box 5 to which the composition has been applied is cooled by air cooling or the like. As a result, the composition is cured, and a solid lubricating film 7 is formed on the Ni—W alloy plating layer 6.

[Substrate treatment step]
In the present manufacturing method, a base treatment step may be performed before the Ni—W alloy plating layer forming step, if necessary. The undercoating process is, for example, pickling and alkali degreasing. In the base treatment step, oil and the like attached to the contact surface forming the Ni—W alloy plating layer 6 are removed. The base treatment step may further include a grinding process such as sandblasting and mechanical grinding. Only one kind of these base treatments may be performed, or a plurality of base treatments may be performed in combination.

Hereinafter, examples will be described. In the embodiment, the contact surface of the pin is called the pin surface, and the contact surface of the box is called the box surface. Further,% in the examples means mass%.

The base material is a 13% Cr steel (C: 0.18%, Si: 0.23%, Mn: 0.8%, P: 0.02%, S: 0. 01%, Cu: 0.04%, Ni: 0.1%, Cr: 13%, Mo: 0.04%, balance: Fe and impurities). Using this 13% Cr steel, a seamless steel pipe and a coupling were manufactured. The size of the seamless steel pipe was 168.28 mm in outer diameter, 12.1 mm in wall thickness, and 1200 mm in length. Pins having a male thread portion and a threadless metal contact portion were formed on the outer surfaces of both ends of the seamless steel pipe by cutting. A box having a female thread portion and a threadless metal contact portion was formed on the inner surfaces of both ends of the coupling by cutting.

[Ni-W alloy plating layer forming step]
A Ni—W alloy plating layer was formed on the box surfaces of Test Nos. 1 to 7. The Ni—W alloy plating layer was formed by electroplating. Specifically, the coupling was immersed in the plating bath of each test number and energized to form a Ni—W alloy plating layer. The plating conditions were as follows: plating bath pH: 5, plating bath temperature: 60 ° C, current density: 20 A / dm ² (constant current electrolytic method). The composition of the plating bath for each test number was as shown in Table 1.

The plating bath was prepared by dissolving commercially available special grade nickel sulfate heptahydrate, disodium tungstate, and triammonium citrate: 0.6 mol / L in pure water. The total metal salt concentration was constant at 0.6 mol / L. Several types of plating baths were constructed by changing the ratio of the concentration of disodium tungstate to the concentration of all metal salts.

ＣｕA Cu—Sn—Zn alloy plating layer was formed on the box surface of Test No. 8. Specifically, a Cu—Sn—Zn alloy plating layer was formed on the box surface by electroplating using a cyan bath containing copper ions, tin ions, and zinc ions. The Cu—Sn—Zn alloy plating layer contained about 7% of Zn, about 40% of Sn, and about 53% of Cu.

[Solid lubrication film forming process]
A solid lubricating film was further formed on the box surfaces of Test Nos. 1 to 8. The composition for forming a solid lubricating film contained polyamideimide resin: 12% by mass, dimethyl sulfoxide: 45% by mass, PTFE particles: 5% by mass, and pure water: balance. After spray-coating this composition on the alloy plating layer, preliminary drying (85 ° C., 10 minutes) and main heating (280 ° C., 30 minutes) were performed to form a solid lubricating film having an average film thickness of 30 μm.

The pin surface was subjected to a mechanical grinding finish (surface roughness 3 μm), and then a solid anticorrosion film was formed. The composition for forming a solid anticorrosive film contained an acrylic resin-based UV-curable resin paint, aluminum phosphite, and polyethylene wax. The contents of aluminum phosphite and polyethylene wax were 0.05 and 0.01 with respect to the acrylic resin-based ultraviolet-curable resin 1, respectively. After applying this composition to the surface of a pin, the composition was cured by irradiating the composition with ultraviolet rays using a UV lamp (air-cooled mercury lamp, output 4 kW, ultraviolet wavelength: 260 nm). The thickness of the solid anticorrosion coating was 25 μm.

[Test for measuring W content in Ni-W alloy plating layer]
The W content in the Ni—W alloy plating layer of each test number was measured by the method described above. Table 1 shows the results.

[Thickness measurement test of Ni-W alloy plating layer]
The thickness of the Ni—W alloy plating layer of each test number was measured by the method described above. Table 1 shows the results.

[Seizure resistance evaluation test]
Seizure resistance was evaluated for the pins and boxes of each test number. Specifically, using a seamless steel pipe having a pin and a box of each test number and a coupling, screwing and unscrewing were repeated at room temperature. Screw tightening and unscrewing were repeated up to 10 times. The tightening torque of the screw tightening was 49351.8 N · m (36400 ft · lbs). Each time the screw was tightened and unscrewed once, the pin surface was visually observed. The occurrence of seizure was confirmed by visual observation. The number of times the screw was tightened and unscrewed without seizure was measured. Table 1 shows the results. In Table 1, ">10" indicates that seizure did not occur even when screwing and unscrewing were repeated 10 times.

[Evaluation results]
Referring to Table 1, the threaded joints for pipes of Test Nos. 3 to 5 were provided with a Ni—W alloy plating layer on the box-side contact surface. Further, the W content in the Ni—W alloy plating layer was 35.0 to 45.0% by mass. The thickness of the Ni—W alloy plating layer was 1.0 to 20.0 μm. Therefore, it exhibited excellent seizure resistance. Specifically, in the pipe threaded joints of Test No. 3 to Test No. 5, seizure did not occur even if screwing and unscrewing were repeated nine times.

On the other hand, in the pipe threaded joint of Test No. 1, the W content of the Ni—W alloy plating layer was less than 35.0% by mass. Therefore, seizure occurred in the pipe threaded joint of Test No. 1 when screwing and unscrewing were repeated four times.

ねじ In the pipe threaded joint of Test No. 2, the W content of the Ni—W alloy plating layer was less than 35.0% by mass. Therefore, in the pipe threaded joint of Test No. 2, seizure occurred when the screw tightening and unscrewing were repeated three times.

ねじ In the pipe threaded joint of Test No. 6, the W content of the Ni—W alloy plating layer exceeded 45.0% by mass. Therefore, in the pipe threaded joint of Test No. 6, seizure occurred when the screw tightening and unscrewing were repeated five times.

ねじ In the pipe threaded joint of Test No. 7, the thickness of the Ni—W alloy plating layer was too thin, 0.5 μm. Therefore, in the pipe threaded joint of Test No. 7, seizure occurred when screwing and unscrewing were repeated twice.

管 The pipe threaded joint of Test No. 8 was provided with a conventional Cu-Sn-Zn alloy plating layer. Therefore, seizure occurred in the pipe threaded joint of Test No. 8 when the screw tightening and unscrewing were repeated seven times.

The embodiments of the present invention have been described above. However, the above-described embodiment is merely an example for embodying the present invention. Therefore, the present invention is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments without departing from the spirit thereof.

DESCRIPTION OF SYMBOLS 1 Screw joint for pipes 2 Steel pipe 3 Coupling 4 Pin 5 Box 6 Ni-W alloy plating layer 7 Solid lubricating film 40 Pin side contact surface 41 Pin side screw part 42 Pin side metal seal part 43 Pin side shoulder part 50 Box side contact surface 51 Box side screw part 52 Box side metal seal part 53 Box side shoulder part

Claims

A pipe threaded joint,
A pin having a pin-side contact surface including a pin-side thread;
A box having a box side contact surface including a box side thread;
On at least one of the pin-side contact surface and the box-side contact surface, 35.0 to 45.0% by mass of W, and the balance is made of Ni and impurities, and has a thickness of 1.0 to 20.0 μm. A Ni—W alloy plating layer,
A threaded joint for pipes, comprising: a solid lubricating coating on the Ni-W alloy plating layer on at least one of the pin-side contact surface and the box-side contact surface.
The pipe threaded joint according to claim 1,
The pin-side contact surface further includes a pin-side metal seal portion and a pin-side shoulder portion,
The threaded joint for pipe, wherein the box-side contact surface further includes a box-side metal seal portion and a box-side shoulder portion.
A method of manufacturing a threaded pipe joint,
At least one of the pin-side contact surface including the pin-side thread and the box-side contact surface including the box-side thread is immersed in a plating solution containing nickel ions and tungsten ions, and the pin-side contact immersed in the plating solution is immersed in the plating solution. By energizing at least one of the surface and the box-side contact surface, 35.0-45.0 mass% of W is placed on at least one of the pin-side contact surface and the box-side contact surface, and the balance is Ni. Forming a Ni—W alloy plating layer having a thickness of 1.0 to 20.0 μm, comprising:
Forming a solid lubricating coating on the Ni-W alloy plating layer on at least one of the pin-side contact surface and the box-side contact surface.
It is a manufacturing method of the pipe threaded joint of Claim 3, Comprising:
The pin-side contact surface further includes a pin-side metal seal portion and a pin-side shoulder portion,
The method for manufacturing a threaded pipe joint, wherein the box-side contact surface further includes a box-side metal seal portion and a box-side shoulder portion.