RU2782310C1 - Threaded connection for pipes - Google Patents

Abstract

FIELD: engineering.

SUBSTANCE: invention relates to a threaded connection for pipes. Threaded connection for pipes comprises a nipple (3), a coupling (4), a metallised layer (5) of the thrust section and a metallised layer (6) of the non-thrust section. The metallised layer (5) of the thrust section has an extreme external layer formed by a metallised layer (50) with a high friction coefficient and is placed on the thrust section (33) on the side of the nipple and/or on the thrust section (43) on the side of the coupling. The metallised layer (6) of the non-thrust section has an extreme external layer formed by a metallised layer (60) with a low friction coefficient lower than the friction coefficient of the metallised layer (50) with a high friction coefficient, and the metallised layer (6) of the non-thrust section is placed on at least one of the threaded section (31) on the side of the nipple, the metal seal section (32) on the side of the nipple, the threaded section (41) on the side of the coupling, and the metal seal section (42) on the side of the coupling.

EFFECT: provided threaded connection for pipes with a high torque "delta" value, configured to be screwed both by the tightening torque equivalent to the tightening torque of a common threaded connection and by a tightening torque greater than that of a common threaded connection.

14 cl, 19 dwg, 2 tbl

Description

FIELD OF TECHNOLOGY

[0001]

The present invention relates to a threaded connection for pipes.

PRIOR ART

[0002]

Oilfield tubular products are used for production in oil or natural gas fields. Oil country tubular goods are formed by connecting several steel pipes according to the depth of the well. The steel pipes are connected by screwing together threaded pipe connections formed at the end portions of the steel pipes. Oil country tubular goods are pulled out of the well and screwed out for testing or the like. After the OCTG tubular products are inspected, the tubular products are re-twisted and used again.

[0003]

A threaded connection for pipes contains a nipple and a coupling. The nipple contains a section with an external thread and a metal contact section without a thread formed on the outer peripheral surface of the end section of the steel pipe. The coupling contains a section with an internal thread and a metal contact section without a thread formed on the inner peripheral surface of the end section of the steel pipe. Each non-threaded metal contact area contains a metal seal area and a thrust area. When the steel pipes are screwed together, the male thread portion and the female thread portion come into contact with each other, the metal seal portions come into contact with each other, and the abutment portions come into contact with each other.

[0004]

The threaded section and the metal contact section without the thread of the pin and box are repeatedly subjected to strong friction during the make-up and break-out of steel pipes. If these areas do not have sufficient abrasion resistance, repeated make-up and break-out causes galling (permanent galling). For this reason, a threaded connection for pipes must have sufficient resistance to friction, i.e. have excellent resistance to galling.

[0005]

Typically, a compound grease containing heavy metals is used to increase resistance to scuffing. Applying a compound grease to the surface of a pipe threaded joint can improve the galling resistance of a pipe threaded joint. However, heavy metals such as Pb contained in compound greases can adversely affect the environment. Accordingly, there is a need to develop threaded connections for pipes that do not use compound grease.

[0006]

International Application Publication No. WO2016/170031 (Patent Document 1) proposes a method for increasing the galling resistance of a threaded pipe joint by plating instead of using compound grease.

[0007]

The threaded pipe connection disclosed in Patent Document 1 comprises a threaded portion extending along an outer peripheral surface or an inner peripheral surface, a first sealing surface on the peripheral surface, and a second sealing surface configured to provide metal-to-metal contact with the first sealing surface. The threaded section and the first sealing surface of the aforementioned threaded pipe connection are coated with a metallic anti-corrosion and anti-seize layer in which zinc is the main element by weight.

[0008]

In addition to the above, Japanese Patent Application Publication No. 63-130986 (Patent Document 2) proposes a method for improving the gas-tightness of a pipe thread by providing a coating on the surface of a pipe thread.

[0009]

The threaded connection for pipes disclosed in Patent Document 2 is a conical thread and includes an external thread and an internal thread. The male thread and female thread of the threaded connection for pipes are made with partial surface treatment such as plating, sputtering or forming a phosphate film with a thickness of 30 to 200 µm to maintain the gas-tightness of the thread surface in increments of 1.0 to 2.0.

LIST OF CITED MATERIALS

PATENT LITERATURE

[0010]

Patent Document 1: International Application Publication No. WO2016/170031

Patent Document 2: Japanese Patent Application Publication No. 63-130986

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

[0011]

The torque of a threaded joint for pipes at which the make-up is completed (hereinafter referred to as "tightening torque") is predetermined. Threaded connections for pipes are screwed in such a way that a predetermined tightening torque can be obtained when the screwing is completed. In recent years, due to the increase in the depth of oil wells, make-up may in some cases require a higher tightening torque than a conventional threaded connection.

[0012]

The operation of making up threaded connections for pipes is performed on an offshore installation or on an oil rig. At the site of actual make-up of pipe threaded connections, it is preferred that the make-up operation be efficient. If the tightening torque changes significantly for each pipe screw connection, it is necessary to slightly adjust the tightening torque each time, which will reduce work efficiency. Accordingly, there is a need for a pipe threaded connection that can be screwed in with a tightening torque similar to conventional threaded connections, and which can also be screwed in with a tightening torque greater than that of a conventional threaded connection.

[0013]

Meanwhile, it is preferable that the tightening torque of the pipe threaded connection can be easily adjusted. In particular, when making up threaded connections for pipes, each of which has a thrust portion, the thrust portion of the pin and the thrust portion of the box come into contact with each other. The torque generated at this stage of the operation is called the stop torque. When making up pipe threaded connections, after the torque reaches the stop torque, the pipe threads are additionally tightened until the make-up is completed. With such operations, the gas tightness of the threaded connection for pipes is increased. When overtightened, the metal of at least one of the pin and box begins to experience plastic deformation. The torque at this stage of the operation is called the yield torque.

[0014]

When the torque "delta" value, which is defined as the difference between the yield torque and the stop torque, is large, the tightening torque can be easily adjusted. Accordingly, it is preferable that the pipe threaded connection has a large delta torque value.

[0015]

By using the method disclosed in Patent Document 1 or Patent Document 2, it is possible to increase the scoring resistance and gas tightness of a threaded joint for pipes. However, these documents do not disclose how to increase the "delta" torque value or achieve a tightening torque that is higher than that of a conventional pipe threaded connection when making up.

[0016]

The object of the present invention is to provide a threaded joint for pipes having a large torque delta and being both a tightening torque equivalent to that of a conventional threaded joint and a tightening torque higher than a conventional threaded connection.

THE SOLUTION OF THE PROBLEM

[0017]

The threaded connection for pipes according to the present invention comprises a nipple and a box. The nipple contains a threaded section on the nipple side, a metal seal section on the nipple side and a thrust section on the nipple side. The coupling contains a threaded portion on the coupling side, a metal seal portion on the coupling side, and a thrust portion on the coupling side. The threaded connection for pipes additionally comprises a metallized layer of the thrust section and a metallized layer of a non-thrust section. The metallized layer of the thrust section is placed on the thrust section on the side of the nipple and/or on the thrust section on the side of the coupling. The metallized layer of the thrust section includes one or more layers. The metallized layer of the thrust section has an outermost layer made of a metallized layer with a high coefficient of friction. The metallized layer of a non-thrust section is located on at least one of the following: a threaded section on the nipple side, a metal seal section on the nipple side, a threaded section on the box side, a section of the metal seal on the side of the box. The non-thrust plating layer includes one or more layers. The non-thrust portion metallized layer has an outermost layer made of a low friction metallized layer having a friction coefficient lower than the friction coefficient of the high friction metallized layer.

BENEFICIAL EFFECTS OF THE INVENTION

[0018]

The threaded pipe connection according to the present invention has a large torque delta value and is screwable both with a tightening torque equivalent to that of a conventional threaded connection and with a tightening torque greater than that of a conventional threaded connection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]

[Fig. 1] In FIG. 1 is a graph illustrating the relationship between the number of revolutions of a steel pipe and the torque during make-up of a threaded joint for pipes that have a thrust portion (torque chart).

[FIG. 2] In FIG. 2 is a diagram of tightening torques for the case where both the stop torque and the yield torque are high.

[FIG. 3] In FIG. 3 is a diagram of tightening torques for the case where both the stop torque and the yield torque are low.

[FIG. 4] In FIG. 4 is a diagram of tightening torques for the case where the stop torque is low and the yield torque is high.

[FIG. 5] In FIG. 5 is a graphical view illustrating the configuration of a socket-type pipe threaded connection according to the present embodiment.

[FIG. 6] In FIG. 6 shows a sectional view of a threaded connection for pipes at the initial stage of make-up.

[FIG. 7] In FIG. 7 shows a sectional view of a threaded connection for pipes after reaching the stop.

[FIG. 8] FIG. 8 is a graphical representation illustrating the configuration of an integral-type threaded joint for pipes according to the present embodiment.

[FIG. 9] FIG. 9 shows a sectional view of a threaded connection for pipes.

[FIG. 10] FIG. 10 is a sectional view of a pipe fitting according to the present embodiment.

[FIG. 11] In FIG. 11 is a sectional view of a pipe threaded joint according to another embodiment of the invention, the pipe threaded joint being different from that shown in FIG. ten.

[FIG. 12] FIG. 12 is a sectional view of a pipe threaded joint according to another embodiment of the invention, the pipe threaded joint being different from that shown in FIG. 10 and in FIG. eleven.

[FIG. 13] FIG. 13 is a sectional view of a pipe threaded joint according to another embodiment of the invention, the pipe threaded joint being different from that shown in FIG. 10-12.

[FIG. 14] FIG. 14 is an enlarged view of the metallized layer of the thrust portion according to the present embodiment of the invention.

[FIG. 15] FIG. 15 is an enlarged view of the metallized layer of the anvil according to another embodiment of the invention, the metallized layer of the anvil being different from that shown in FIG. fourteen.

[FIG. 16] FIG. 16 is an enlarged view of the metallized layer of the anvil according to another embodiment of the invention, the metallized layer of the anvil being different from that shown in FIG. 14 and FIG. fifteen.

[FIG. 17] FIG. 17 is an enlarged view of the non-thrust plating layer according to the present embodiment.

[FIG. 18] FIG. 18 is an enlarged view of a non-thrust portion plating layer according to another embodiment of the invention, the non-thrust portion metallized layer being different from that shown in FIG. 17.

[FIG. 19] FIG. 19 is an enlarged view of a non-thrust portion plating layer according to another embodiment of the invention, the non-thrust portion metallized layer being different from that shown in FIG. 17 and FIG. eighteen.

DISCLOSURE OF EMBODIMENTS

[0020]

Hereinafter, the present embodiment of the invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding elements are identified in the same way, and the description of such elements is not repeated.

[0021]

The inventors of the present invention have made various studies on the relationship between the plating layer on the surface of a pipe threaded connection and the tightening torque and torque delta value. As a result of such various studies, the inventors of the present invention came to the following conclusions.

[0022]

When making up steel pipes, the optimal torque at which the make-up is completed (called the tightening torque) is predetermined. In FIG. 1 is a graph illustrating the relationship between the number of revolutions of a steel pipe and the torque during make-up of a threaded joint for pipes that have a thrust portion (torque chart). A graph illustrating the relationship between the number of revolutions of a steel pipe and torque is hereinafter referred to as a tightening torque diagram. As shown in FIG. 1, when pipe threads are screwed together, initially the torque increases in proportion to the number of revolutions. The rate of torque increase at this stage of the operation is slow. During further make-up of threaded connections for pipes, the thrust portions come into contact with each other. The torque generated at this stage of the operation is called the stop torque Ts. When the pipe threads are further screwed after reaching the stop torque Ts, the torque again increases in proportion to the number of revolutions. The rate of torque increase at this stage of the operation is high. The make-up is completed at the time when the torque reaches a predetermined numerical value (tightening torque To).

[0023]

When the torque during make-up reaches the tightening torque To, the metal seal portions interact with each other with a corresponding pressure between the surfaces. In this case, the gas-tightness of threaded pipe connections is increased. In addition, in an oil well, a threaded joint experiences high compressive stress and high bending stress. In order to prevent loosening of the pipe screw connection even under such loads, it is necessary that the pipe screw connections be screwed with a sufficiently high torque (corresponding to the tightening torque To).

[0024]

If pipe threads are further screwed after the torque reaches the tightening torque To, the torque becomes excessively high. When the torque becomes extremely high, the pin and box experience partial plastic deformation. The torque at this stage of the operation is called the yield torque Ty. When the torque delta value ΔT determined by the difference between the abutment torque Ts and the yield torque Ty is large, the tightening torque To can be easily controlled. Accordingly, a larger torque delta ΔT is preferred.

[0025]

To increase the torque delta value ΔT, it is useful to decrease the thrust torque Ts or to increase the yield strength torque Ty. The inventors of the present invention believe that the thrust torque Ts and the yield torque Ty can be controlled by changing the coefficients of friction of the pin and box surfaces. However, even if the pin and box surfaces are simply changed to increase or decrease the coefficients of friction, the thrust torque Ts and the yield strength torque Ty generally behave in a similar manner.

[0026]

In FIG. 2 is a diagram of tightening torques for the case where both the thrust torque Ts and the yield strength torque Ty are high. In FIG. 2, the tightening torque diagram for a conventional threaded connection is shown with a broken line. As shown in FIG. 2, as the coefficients of friction of the pin and box increase, although the yield torque Ty increases, the stop torque Ts also increases (which is referred to as "high stop"). As a result, even if the torque reaches the tightening torque To of a conventional threaded connection, there may be a case where the abutments do not come into contact with each other so that the make-up is not completed (this is called no abutment).

[0027]

In FIG. 3 is a diagram of tightening torques for the case where both the thrust torque Ts and the yield torque Ty are low. In FIG. 3, the tightening torque diagram for a conventional threaded connection is shown with a broken line. As shown in FIG. 3, when the coefficients of friction of the pin and box are reduced, although the thrust torque Ts is reduced, the yield torque Ty is also reduced. As a result, the torque reaches the yield torque Ty before reaching the predetermined tightening torque To, and consequently the abutment portions or the metal seal portions undergo plastic deformation. In this case, sufficient tightening torque To cannot be obtained.

[0028]

If the yield torque Ty can be increased while the thrust torque Ts can be kept low, not only can the torque delta ΔT be increased, but pipe threads can be screwed together with a torque To tightening torque equal to that of conventional threaded connections and, in addition, can be screwed with a tightening torque Toh greater than that of conventional threaded connections. In FIG. 4 is a diagram of tightening torques for the case where both the stop torque Ts and the yield strength torque Ty are high. In FIG. 4, the tightening torque diagram for a conventional threaded connection is shown with a broken line. As shown in Fig. 4, in the tightening torque diagram, where the thrust torque Ts is kept low and the yield torque Ty is increased, the delta value ΔT of the torque is larger than the delta value ΔT' of the conventional torque. threaded connection. In addition, even if the pipe threads are screwed with the tightening torque To of the conventional threaded connection, the torque reaches the abutment torque Ts or more, and therefore sufficient gas-tightness can be ensured. In addition, even if the pipe threaded connections are screwed with a tightening torque Toh greater than the tightening torque To of a conventional threaded connection, the torque is the yield torque Ty or less, and therefore the pipe threads can be screwed, without causing plastic deformation.

[0029]

As a result of intensive research carried out by the inventors of the present invention, it has been found that on the pin surface and the box surface, the region significantly affecting the generation of the thrust torque Ts is different from the region significantly affecting the generation of the yield torque Ty.

[0030]

In FIG. 5 is a graphical view illustrating the configuration of a socket-type pipe threaded connection according to the present embodiment. As shown in FIG. 5, a pipe threaded joint comprises a steel pipe 1 and a coupling 2. A nipple 3 having a male threaded portion on its outer surface is provided at both ends of the steel pipe 1. A coupling 4 having a female threaded portion on its inner surface is at both ends of the coupler 2. When the nipple 3 and the coupler 4 are screwed together, the coupler 2 is installed at the end of the steel pipe 1.

[0031]

In FIG. 6 shows a sectional view of a threaded connection for pipes at the initial stage of make-up. As shown in FIG. 6, the pin 3 comprises a pin-side stop portion 33, a pin-side metal seal portion 32, and a threaded pin-side portion 31. The sleeve 4 comprises a thrust section 43 on the sleeve side, a metal seal section 42 on the sleeve side, and a threaded section 41 on the sleeve side. At the initial stage of make-up, the threaded portion 31 on the pin side and the threaded portion 41 on the box side come into contact and slide against each other. Then, as the make-up is made, the pin-side metal seal portion 32 and the box-side metal seal portion 42 come into contact and slide relative to each other. Subsequently, the pin-side stop portion 33 and the box-side stop portion 43 come into contact with each other. The torque generated in this step of the operation is the stop torque Ts.

[0032]

Before the pin-side stop portion 33 and the box-side stop portion 43 come into contact with each other, the pin-side threaded portion 31 and the box-side threaded portion 41 come into contact and slide relative to each other, and the metal seal portion the sides of the pin 32 and the portion 42 of the metal seal on the side of the box come into contact and slide against each other. That is, it can be considered that the portions that significantly affect the thrust torque Ts are portions other than the pin-side thrust portion 33 and the box-side thrust portion 43. That is, the portions that significantly affect the stop torque Ts can be considered to be the pin-side threaded portion 31, the box-side threaded portion 41, the pin-side metal seal portion 32, and the box-side metal seal portion 42.

[0033]

In FIG. 7 shows a sectional view of a threaded connection for pipes after reaching the stop. As shown in FIG. 7, after the pin side abutment portion 33 and the box side abutment portion 43 come into contact with each other, the pin side abutment portion 33 and the box side abutment portion 43 slide with friction, absorbing a large force in the axial direction of the steel pipe 1. Accordingly, the pressure received by the abutment portion 33 on the pin side and the abutment portion 43 on the box side is expected to be greater than the pressure received by the threaded portion 31 on the pin side, the threaded portion 41 on the box side, the metal seal portion 32 on the side of the nipple and section 42 of the metal seal on the side of the coupling. That is, the portions that significantly affect the yield torque Ty can be considered to be the abutment portion 33 on the pin side and the abutment portion 43 on the box side.

[0034]

As a result of the above studies, the authors of the present invention came to the following conclusions. A metallized layer having a low coefficient of friction is formed on at least one of the following: the threaded portion 31 on the side of the pin, the threaded portion 41 on the side of the box, the portion 32 of the metal seal on the side of the pin, the portion 42 of the metal seal on the box side, which significantly affect the abutment torque Ts, and a plating layer having a high coefficient of friction is formed on the pin-side thrust portion 33 and/or the box-side thrust portion 43, which greatly influence the yield torque Ty. With this configuration, the stop torque Ts can be kept low and the yield torque Ty can be increased. As a result, it is possible to obtain a pipe threaded connection having a large torque delta ΔT and being both a tightening torque To that is equivalent to the tightening torque of a conventional threaded connection and a tightening torque Toh greater than that of a conventional threaded connection.

[0035]

The threaded connection according to the present embodiment of the invention, implemented on the basis of the above conclusions, contains a pin and a box. The nipple contains a threaded section on the nipple side, a metal seal section on the nipple side and a thrust section on the nipple side. The coupling contains a threaded portion on the coupling side, a metal seal portion on the coupling side, and a thrust portion on the coupling side. The threaded connection for pipes additionally comprises a metallized layer of the thrust section and a metallized layer of a non-thrust section. The metallized layer of the thrust section is placed on the thrust section on the side of the nipple and/or on the thrust section on the side of the coupling. The metallized layer of the thrust section includes one or more layers. The metallized layer of the thrust section has an outermost layer formed by a metallized layer with a high coefficient of friction. The metallized layer of a non-thrust section is located on at least one of the following: a threaded section on the nipple side, a metal seal section on the nipple side, a threaded section on the box side, a section of the metal seal on the side of the box. The non-thrust plating layer includes one or more layers. The non-thrust portion metallized layer has an outermost layer formed by a low friction metallized layer having a friction coefficient lower than the friction coefficient of the high friction metallized layer.

[0036]

The threaded pipe connection according to the present embodiment has a large delta torque value and is screwable both with a tightening torque equivalent to that of a conventional threaded connection and with a tightening torque greater than that of a conventional threaded connection.

[0037]

The aforementioned plated layer of the thrust portion may be placed on the pin side thrust portion, and the aforementioned non-thrust portion plated layer may be placed on the threaded portion of the pin side and the metal seal portion of the pin side.

[0038]

The aforementioned plating layer of the thrust portion may be placed on the collar side thrust portion, and the aforementioned non-thrust portion metallized layer may be placed on the threaded portion of the coupling side and the metal seal portion of the coupling side.

[0039]

The thickness of the aforementioned metallized layer of the abutment portion may be 1 to 50 μm, and the thickness of the aforementioned metallized layer of the non-thrust portion may be 1 to 50 μm.

[0040]

When the thickness of each plated layer is within the above-mentioned range, it is possible to more stably obtain the beneficial effect of increasing the yield strength torque while keeping the abutment torque at a low level.

[0041]

The threaded pipe connection may further comprise a lubricating coating. The lubricating coating is placed as the outermost layer on at least one of the following: threaded section on the nipple side, section of the metal seal on the nipple side, thrust section on the nipple side, threaded section on the coupling side, section of the metal seal on the side coupling and thrust section on the coupling side.

[0042]

In the case where a pipe threaded joint contains a lubricity coating as an outermost layer, the lubricity of the pipe threaded joint is increased.

[0043]

The high friction plated layer may be selected from the group consisting of Ni-P alloy plated layer, Zn-Ni alloy plated layer, Cu plated layer, and Cr plated layer, and the low friction plated layer may be selected from the group , consisting of a metallized layer of Zn-Ni alloy, a metallized Cu layer, a metallized Cr layer, and a metallized Zn layer.

[0044]

In the case where the composition of each plating layer is the above composition, it is possible to more stably obtain the beneficial effect of increasing the yield torque while keeping the abutment torque at a low level.

[0045]

The high friction plating layer may be selected from the group consisting of a Ni-P alloy plating layer and a Zn-Ni alloy plating layer, and the low friction plating layer may be selected from the group consisting of a Cu plating layer, metallized Cr layer and metallized Zn layer.

[0046]

In the case where the composition of each plating layer is the above composition, it is possible to more stably obtain the beneficial effect of increasing the yield torque while keeping the abutment torque at a low level.

[0047]

Hereinafter, a threaded pipe connection according to the present embodiment will be described in detail.

[0048]

[Threaded pipe connection]

A threaded pipe connection according to the present embodiment of the invention comprises a nipple and a box. In FIG. 5 is a graphical view illustrating the configuration of a socket-type pipe threaded connection according to the present embodiment. As shown in FIG. 5, a socket-type pipe threaded connection comprises a steel pipe 1 and a coupling 2. A nipple 3 having a male thread portion on its outer surface is formed at both ends of the steel pipe 1. A sleeve 4 having a female thread portion on its inner surface , formed at both ends of the coupler 2. When the pin 3 and the coupler 4 are screwed together, the coupler 2 is installed on the end of the steel pipe 1. Although not shown in the drawing, to protect the threaded portion of the pin 3 and the threaded portion of the box 4 may be protectors are installed, respectively, on the nipple 3 of the steel pipe 1 and the sleeve 4 of the coupling 2, on which mating elements are not installed.

[0049]

Meanwhile, an integral type pipe threaded connection can be used where a coupling 2 is not used, and a nipple 3 is formed at one end of the steel pipe 1, and a coupling 4 is formed at the other end of the steel pipe 1. FIG. 8 is a graphical representation illustrating the configuration of an integral-type threaded joint for pipes according to the present embodiment. As shown in FIG. 8, an integral-type pipe threaded connection comprises a steel pipe 1. A nipple 3 having a male thread portion on its outer surface is formed on one end of the steel pipe 1. A sleeve 4 having a female thread portion on its inner surface is formed on the other end of the steel pipe 1. When the pin 3 and the box 4 are screwed together, the steel pipes 1 can be connected together. The threaded pipe connection according to the present embodiment can be used for both the socket-type pipe threaded connection and the integral-type pipe threaded connection.

[0050]

In FIG. 9 shows a sectional view of a threaded connection for pipes. As shown in FIG. 9, the pin 3 comprises a threaded portion 31 on the pin side, a metal seal portion 32 on the pin side, and a stop portion 33 on the pin side. The sleeve 4 comprises a threaded section 41 on the sleeve side, a metal seal section 42 on the sleeve side, and a thrust section 43 on the sleeve side.

[0051]

In the nipple 3 shown in FIG. 9, the pin-side thrust portion 33, the pin-side metal seal portion 32, and the pin-side threaded portion 31 are arranged in this order from the end of the steel pipe 1. In addition, in the box 4, the box-side threaded portion 41, the metal seal portion 42 on the coupling side and the thrust section 43 on the coupling side are located in this order from the end of the steel pipe 1 or coupling 2. However, the location of the threaded section 31 on the pin side and the threaded section 41 on the coupling side, the section 32 of the metal seal on the side of the pin and the box side metal seal portion 42 and the pin side thrust portion 33 and the box side thrust portion 43 are not limited to the arrangement shown in FIG. 9 and can be changed as needed. For example, as shown in FIG. 8, in the pin 3, the pin side metal seal portion, the threaded pin side portion, the pin side metal seal portion, the pin side thrust portion, the pin side metal seal portion, and the threaded pin side portion may be arranged in that order. from the end of the steel pipe 1. In the coupling 4, the metal seal section on the coupling side, the threaded section on the coupling side, the metal seal section on the coupling side, the thrust section on the coupling side, the metal seal section on the coupling side and the threaded section on the coupling side can be located in that order from the end of steel pipe 1 or coupling 2.

[0052]

In FIG. 10 is a sectional view of a pipe fitting according to the present embodiment. As shown in FIG. 10, the threaded pipe connection according to the present embodiment of the invention further comprises plated layers 5 of the thrust portion and plated layers 6 of the non-thrust portion.

[0053]

[Metallized layer of thrust area]

The metallized layer 5 of the stop section according to the present embodiment of the invention is placed on the stop section 33 on the pin side and/or on the stop section 43 on the box side. As shown in FIG. 10, the metallized layer 5 of the stop section can be placed both on the stop section 33 on the pin side and on the stop section 43 on the box side.

[0054]

The plated layer 5 of the thrust portion according to the present embodiment may also be placed on the thrust portion 33 on the pin side or on the thrust portion 43 on the box side. In FIG. 11 is a sectional view of a pipe threaded joint according to another embodiment of the invention, the pipe threaded joint being different from that shown in FIG. 10. In FIG. 12 is a sectional view of a pipe threaded connection according to another embodiment of the invention, said pipe threaded connection being different from those shown in FIGS. 10 and FIG. 11. In FIG. 13 is a sectional view of a pipe threaded connection according to another embodiment of the invention, said pipe threaded connection being different from those shown in FIGS. 10-12. As shown in FIG. 11 and FIG. 13, the metallized layer 5 of the stop section can only be placed on the stop section 33 on the pin side. As shown in FIG. 12, the metallized layer 5 of the stop section can only be placed on the stop section 43 on the sleeve side.

[0055]

The metallized layer 5 of the thrust portion according to the present embodiment of the invention includes one or more layers. In FIG. 14 is an enlarged view of the abutment portion metallized layer 5 according to the present embodiment. As shown in FIG. 14, the metallized abutment layer 5 may be formed in one layer. In this case, the metallized layer 5 of the thrust portion is a metallized layer 50 with a high coefficient of friction. In FIG. 15 is an enlarged view of a metallized abutment layer 5 according to another embodiment of the invention, said metallized abutment layer 5 differing from that shown in FIG. 14. As shown in FIG. 15, the metallized abutment layer 5 can be formed in several layers. In this case, the outermost layer of the metallized layer 5 of the thrust section is a metallized layer 50 with a high coefficient of friction. As shown in FIG. 15, the anvil plated layer 5 includes an optional plated layer 70 under the high friction plated layer 50. In addition, the optional metallized layer 70 may be a plurality of metallized layers deposited on top of each other.

[0056]

[Metalized high friction layer]

The coefficient of friction of the high friction metallized layer 50 is greater than the coefficient of friction of the low friction metallized layer 60 described below. The pin-side thrust portion 33 and the box-side thrust portion 43 slide with friction while absorbing the high intersurface pressure in the final stage of make-up. Accordingly, when the outermost layer of the plated layer 5 of the pin side thrust portion 33 and/or the box side thrust portion 43 is a high friction plated layer 50, high torque can be obtained in the final make-up step. As a result, the yield torque Ty increases. The coefficient of friction of the high friction metallized layer 50 is not particularly limited, as long as the coefficient of friction of the high friction metallized layer 50 is greater than the coefficient of friction of the low friction metallized layer 60. The preferred lower friction coefficient limit of the high friction metallized layer 50 is 0.10, more preferably 0.11, even more preferably 0.12, and even more preferably 0.13. The preferred upper limit of the coefficient of friction of the high friction metallized layer 50 is 0.40, more preferably 0.30, and even more preferably 0.20. The coefficient of friction of the high friction metallized layer 50 can be controlled, for example, by changing the composition of the high friction metallized layer 50.

[0057]

In the present embodiment, the high friction plated layer 50 may be a single metal plated layer or may be an alloy plated layer. In addition, in the present embodiment, the chemical composition of the high friction metallized layer 50 is not specifically limited. The chemical composition of the high friction metallized layer 50 may be selected from widely known metallized layers. For example, the high friction plating layer 50 may be selected from the group consisting of Cu plating layer, Cr plating layer, Zn plating layer, Ni plating layer, Cu-Sn alloy plating layer, Zn-Co alloy plating layer, a Zn-Ni alloy layer, a Ni-P alloy metallized layer, and a Cu-Sn-Zn alloy metallized layer. The high friction plating layer 50 may be selected from the group consisting of a Ni-P alloy plating layer, a Zn-Ni alloy plating layer, a Cu plating layer, and a Cr plating layer. The high friction plating layer 50 may be selected from the group consisting of a Ni-P alloy plating layer and a Zn-Ni alloy plating layer.

[0058]

As described above, in the case where the anvil plating layer 5 includes multiple layers, the high friction metallized layer 50 is placed on the outermost layer of the anvil plating layer 5. However, the high friction metallized layer 50 may not be placed on the outermost layer of the pin side thrust portion 33 and/or the box side thrust portion 43. In FIG. 16 is an enlarged view of a metallized abutment layer 5 according to another embodiment of the invention, wherein the metallized abutment layer 5 differs from that shown in FIG. 14 and FIG. 15. As shown in FIG. 16, a lubricating coating 80 may be placed on the metallized layer 5 of the abutment area. The lubricating coating 80 will be described later.

[0059]

[Metallized layer of non-stubborn area]

The metallized layer 6 of the non-thrust portion according to the present embodiment of the invention is placed on at least one of the following: the threaded portion 31 on the pin side, the portion 32 of the metallic seal on the pin side, the threaded portion 41 on the side of the box, the portion 42 of the metal seal on the side of the box. As shown in FIG. 10, a plating layer 6 of a non-thrust portion is placed on all of: a threaded pin-side portion 31, a pin-side metal seal portion 32, a threaded box-side portion 41, and a box-side metal seal portion 42.

[0060]

The plating layer 6 of the non-thrust portion can be placed on a part of the threaded portion 31 on the pin side, the portion 32 of the metal seal on the side of the pin, the threaded portion 41 on the side of the box, and the portion 42 of the metal seal on the side of the box. As shown in FIG. 11, the metallized layer 6 of the non-thrust section can only be placed on the threaded section 31 on the pin side and on the metal seal section 32 on the side of the pin. As shown in FIG. 12 and FIG. 13, the metallized layer 6 of the non-thrust section can only be placed on the threaded section 41 on the box side and on the metal seal section 42 on the side of the box.

[0061]

In addition, the metallized layer 6 of the non-thrust section can only be placed on the threaded section 31 on the pin side and on the threaded section 41 on the box side. The metallized layer 6 of the non-stubborn section can only be placed on the section 32 of the metal seal on the side of the pin and on the section 42 of the metal seal on the side of the coupling. Thus, the plating layer 6 of the non-thrust portion can be placed on at least one of the following: threaded portion 31 on the pin side, portion 32 of the metallic seal on the pin side, threaded portion 41 on the side of the box, portion 42 of the metal seal on the side of the box.

[0062]

The plating layer 6 of the non-thrust portion according to the present embodiment of the invention includes one or more layers. In FIG. 17 is an enlarged view of the non-thrust plating layer 6 according to the present embodiment. As shown in FIG. 17, the metallized layer 6 of the non-thrust section may consist of a single layer. In this case, the metallized layer 6 of the non-thrust portion is a metallized layer 60 with a low coefficient of friction. In FIG. 18 is an enlarged view of a non-thrust metallized layer 6 according to another embodiment of the invention, said non-thrust metallized layer 6 differing from that shown in FIG. 17. As shown in FIG. 18, the metallized layer 6 of the non-thrust section may be composed of several layers. In this case, the outermost layer of the non-thrust metallized layer 6 is a low friction metallized layer 60. As shown in FIG. 18, the plated layer 6 of the non-thrust region includes an optional plated layer 70 under the low friction plated layer 60. In addition, the optional metallized layer 70 may be a plurality of metallized layers deposited on top of each other.

[0063]

[Metalized Low Friction Layer]

The coefficient of friction of the low friction metallized layer 60 according to the present embodiment is less than the coefficient of friction of the high friction metallized layer 50. The threaded section 31 on the pin side, the section 32 of the metal seal on the side of the pin, the threaded section 41 on the side of the box, and the section 42 of the metal seal on the side of the box slide with friction before reaching the stop when making up. Accordingly, if the outermost layer of the metallized layer 6 is not a thrust section, at least one of the following: threaded section 31 on the side of the pin, section 32 of the metal seal on the side of the pin, threaded section 41 on the side of the coupling, section 42 of the metal seal on the side coupling is a low friction metallized layer 60, low torque can be obtained at the initial stage of make-up. As a result, the stop torque Ts can be kept low. The coefficient of friction of the low friction metallized layer 60 is not particularly limited, as long as the coefficient of friction of the low friction metallized layer 60 is less than the coefficient of friction of the high friction metallized layer 50. The preferred lower friction coefficient limit of the low friction metallized layer 60 is 0.01, more preferably 0.05, even more preferably 0.08, and even more preferably 0.10. The preferred upper limit of the coefficient of friction of the low friction metallized layer 60 is less than 0.13, more preferably 0.12, and even more preferably 0.11. The coefficient of friction of the low friction metallized layer 60 can be controlled, for example, by changing the composition of the low friction metallized layer 60.

[0064]

The low friction plated layer 60 may be a single metal plated layer or may be an alloy plated layer. In addition, in the present embodiment, the chemical composition of the low friction metallized layer 60 is not specifically limited. The chemical composition of the low friction metallized layer 60 may be selected from the chemistries of widely known metallized layers. For example, the low friction plating layer 60 may be selected from the group consisting of Cu plating layer, Cr plating layer, Zn plating layer, Ni plating layer, Cu-Sn alloy plating layer, Zn-Co alloy plating layer, a Zn-Ni alloy layer, a Ni-P alloy metallized layer, and a Cu-Sn-Zn alloy metallized layer. The low friction plating layer 60 may be selected from the group consisting of a Zn-Ni alloy plating layer, a Cu plating layer, a Cr plating layer, and a Zn plating layer. The low friction metallized layer 60 may be selected from the group consisting of a Cu metallized layer, a Cr metallized layer, and a Zn metallized layer.

[0065]

As described above, in the case where the non-thrust portion plated layer 6 includes multiple layers, the low friction plated layer 60 is placed on the outermost layer of the non-thrust portion plated layer 6. However, the low friction metalized layer 60 may not be placed on the outermost layer of the pin side threaded portion 31, the pin side metal seal portion 32, the box side threaded portion 41, and the box side metal seal portion 42. In FIG. 19 is an enlarged view of a non-thrust metallized layer 6 according to another embodiment of the invention, the non-thrust metallized layer 6 being different from that shown in FIG. 17 and FIG. 18. As shown in FIG. 19, a lubricating coating 80 may be placed on the metallized layer 6 of the non-thrust area. The lubricating coating 80 will be described later.

[0066]

[Coefficient of Friction of High Friction Metallized Layer and Low Friction Metallized Layer]

In the present embodiment, the coefficient of friction of the high friction metallized layer 50 and the coefficient of friction of the low friction metallized layer 60 are measured in the following manner. Samples are prepared on which a high friction metallized layer 50 and a low friction metallized layer 60 are formed. The Bowden slip test is performed on the high friction metalized layer 50 and the low friction metalized layer 60. The Bowden sliding test is carried out under the following conditions: sliding indenter: steel ball 4.7625 mm (3/16'' in diameter) (Fe, steel grade SUJ2), pressure load: 3 kgf, sliding method: linear reciprocating sliding , sliding distance: 30 mm, number of sliding reciprocations: 5, sliding speed: 4 mm/s, test temperature: 25 °C, lubricant: SEAL-GUARD ECF (trade name) manufactured by JET-LUBE Inc., quantity applied lubricant: 40 g/m ² . For each metallized layer, the friction coefficient was determined as the arithmetic mean of the friction coefficients for five reciprocating sliding movements.

[0067]

[Optional Metallized Layer]

In the present embodiment, the optional metallized layer 70 may or may not be formed. In addition, the optional plating layer 70 includes one or more layers. In the present embodiment, the optional plated layer 70 may be a single metal plated layer or may be an alloy plated layer. In other words, in the present embodiment, the chemical composition of the optional metallized layer 70 is not specifically limited. The chemical composition of the optional plating layer 70 may be selected from commonly known metallized layer chemistries. For example, optional plating layer 70 may be selected from the group consisting of Cu plating layer, Cr plating layer, Zn plating layer, Ni plating layer, Cu-Sn alloy plating layer, Zn-Co alloy plating layer, Zn-Ni, Ni-P alloy plated layer, and Cu-Sn-Zn alloy plated layer.

[0068]

The optional metalized layer component 70 on the pin 3 side and the optional metalized layer component 70 on the sleeve 4 side may be equivalent to each other or may be different from each other. The optional plating layer 70 component below the high friction plating layer 50 and the optional plating layer 70 component below the low friction plating layer 60 may be equivalent to each other or may be different from each other. The chemical composition of the optional metalized layer 70 on the pin 3 side and the chemical composition of the optional metalized layer 70 on the sleeve 4 side may be equivalent to each other or may be different from each other. The chemical composition of the optional plating layer 70 under the high friction plating layer 50 and the chemistry of the optional plating layer 70 under the low friction plating layer 60 may be equivalent to each other or may be different from each other.

[0069]

[Position of plated layer of thrust portion and plated layer of non-thrust portion]

The placement of the metallized layer 5 of the thrust portion and the metallized layer 6 of the non-thrust portion are not limited to the arrangement shown in FIG. 10. For example, as shown in FIG. 11, a metallized layer 5 of the thrust portion may be placed on the thrust portion 33 on the pin side, and a plating layer 6 of the non-thrust portion may be placed on the threaded portion 31 on the pin side and the metallic seal portion 32 on the pin side. In this case, no coating may be placed on the box-side thrust portion 43, the box-side metal seal portion 42, and the box-side threaded portion 41, or a lubricating coating 80, described below, may be placed on or over the collar-side thrust portion 43. box side, the box side metal seal portion 42, and the box side threaded portion 41, or a layer obtained by chemical conversion such as a phosphated layer may be placed on the box side thrust portion 43, on the box side metal seal portion 42 and on the threaded section 41 on the coupling side.

[0070]

In addition, as shown in FIG. 12, a plated layer 5 of the thrust portion may be placed on the collar side thrust portion 43, and a non-thrust portion plating 6 may be placed on the threaded portion 41 on the box side and the metal seal portion 42 on the box side. In this case, no coating may be placed on the pin side thrust portion 33, the pin side metal seal portion 32, and the pin side threaded portion 31, or the lubricating coating 80 described below may be placed on or over the pin side thrust portion 33. pin side, the pin side metal seal portion 32 and the pin side threaded portion 31, or a layer obtained by chemical conversion such as a phosphated layer may be placed on the pin side thrust portion 33, on the pin side metal seal portion 32 and on the threaded section 31 on the nipple side. Moreover, as shown in FIG. 13, the plating layer 5 of the thrust portion may be placed on the thrust portion 33 on the pin side, and the plating layer 6 of the non-thrust portion may be placed on the threaded portion 41 on the box side and the metal seal portion 42 on the box side.

[0071]

[Metalized layer thickness]

The thickness of the metallized layer 5 of the thrust portion is not specifically limited. The preferred thickness of the metallized layer 5 of the thrust area is 1-50 µm. In this case, it is possible to obtain the beneficial effect of increasing the torque Ty at the yield point with greater stability. A more preferred lower limit for the thickness of the metallized layer 5 of the thrust portion is 3 µm, and even more preferably 5 µm. A more preferred upper limit for the thickness of the metallized layer 5 of the thrust portion is 40 µm, and even more preferably 25 µm.

[0072]

The thickness of the metallized layer 6 of the non-thrust portion is not specifically limited. The preferred thickness of the metallized layer 6 of the non-stubborn area is 1-50 µm. In this case, it is possible to obtain the beneficial effect of keeping the abutment torque Ts at a low level more stably. A more preferred lower limit for the thickness of the non-stubborn metallized layer 6 is 3 µm, and even more preferably 5 µm. A more preferred upper limit for the thickness of the non-stubborn metallized layer 6 is 40 µm, and even more preferably 25 µm.

[0073]

[Combination of high friction metalized layer and low friction metalized layer]

In the present embodiment, the combination of the high friction metallized layer 50 and the low friction metallized layer 60 is not particularly limited, as long as the coefficient of friction of the high friction metallized layer 50 is greater than the coefficient of friction of the low friction metallized layer 60 . The combination of the chemical composition of the high friction metalized layer 50 and the chemical composition of the low friction metalized layer 60 is, for example, as follows. In the case where the high friction plated layer 50 is a Ni-P alloy plated layer, the low friction plated layer 60 is selected from the group consisting of Cu plated layer, Cr plated layer, Zn plated layer, Ni plated layer, a Cu-Sn alloy plating layer, a Zn-Co alloy plating layer, a Zn-Ni alloy plating layer, and a Cu-Sn-Zn alloy plating layer. In the case where the high friction plating layer 50 is a Zn-Ni alloy plating layer, the low friction plating layer 60 is selected from the group consisting of Cu plating layer, Cr plating layer, Zn plating layer, Ni plating layer, a Cu-Sn alloy metallized layer, a Zn-Co alloy metallized layer, and a Cu-Sn-Zn alloy metallized layer. The chemical composition of the high friction metallized layer 50, the low friction metallized layer 60, and the optional metallized layer 70 may be appropriately selected from the chemistries of commonly known metallized layers.

[0074]

In the case where the low friction plated layer 60 is a Cu plated layer, the high friction plated layer 50 is selected from the group consisting of a Ni plated layer, a Cu-Sn alloy plated layer, a Zn-Co alloy plated layer, a Zn-Ni alloy plating layer, a Ni-P alloy plating layer, and a Cu-Sn-Zn alloy plating layer. In the case where the low friction plating layer 60 is a Cr plating layer, the high friction plating layer 50 is selected from the group consisting of Cu plating layer, Ni plating layer, Cu-Sn alloy plating layer, Zn-Co, Zn-Ni alloy plated layer, Ni-P alloy plated layer, and Cu-Sn-Zn alloy plated layer. In the case where the low friction plating layer 60 is a Zn plating layer, the high friction plating layer 50 is selected from the group consisting of a Cr plating layer, a Cu plating layer, a Ni plating layer, a Cu-Sn alloy plating layer, a Zn-Co alloy plating layer, a Zn-Ni alloy plating layer, a Ni-P alloy plating layer, and a Cu-Sn-Zn alloy plating layer.

[0075]

Preferably, the high friction plating layer 50 is selected from the group consisting of a Ni-P alloy plating layer, a Zn-Ni alloy plating layer, a Cu plating layer, a Cr plating layer, and a Cu-Sn-Zn alloy plating layer. Preferably, the low friction plating layer 60 is selected from the group consisting of a Zn-Ni alloy plating layer, a Cu plating layer, a Cr plating layer, a Cu-Sn-Zn alloy plating layer, and a Zn plating layer. Thus, preferably, the combination of the chemistry of the high friction metallized layer 50 and the chemistry of the low friction metallized layer 60 is as follows, from (1) to (5):

(1) In the case where the high friction plated layer 50 is a Ni-P alloy plated layer, the low friction plated layer 60 is selected from the group consisting of Zn-Ni alloy plated layer, Cu plated layer, a Cr layer, a Cu-Sn-Zn alloy metallized layer, and a Zn metallized layer;

(2) In the case where the high friction plating layer 50 is a Zn-Ni alloy plating layer, the low friction plating layer 60 is selected from the group consisting of Cu plating layer, Cr plating layer, Cu alloy plating layer -Sn-Zn and metallized Zn layer;

(3) In the case where the high friction plating layer 50 is a Cu plating layer, the low friction plating layer 60 is selected from the group consisting of a Cr plating layer, a Cu-Sn-Zn alloy plating layer, and a Zn plating layer. ;

(4) In the case where the high friction plated layer 50 is a Cr plated layer, the low friction plated layer 60 is selected from the group consisting of a Cu-Sn-Zn alloy plated layer and a Zn plated layer;

(5) In the case where the high friction plated layer 50 is a Cu-Sn-Zn alloy plated layer, the low friction plated layer 60 is a Zn plated layer.

[0076]

[Chemical composition of metallized layers]

The chemical composition of each of the metallized layers, for example, is as follows. The Cu plating layer is a metallized layer having a chemical composition containing Cu and random impurities. The Cr plating layer is a metallized layer having a chemical composition containing Cr and random impurities. The Zn plating layer is a metallized layer having a chemical composition containing Zn and random impurities. The Ni plating layer is a metallized layer having a chemical composition containing Ni and random impurities. Cu-Sn alloy plating layer is a plating layer having a chemical composition containing Sn: 10-75%, and the rest: Cu and random impurities. Zn-Co alloy plated layer is a plated layer having a chemical composition containing Co: 5-25%, and the rest: Zn and random impurities. Zn-Ni alloy plated layer is a plated layer having a chemical composition containing Ni: 5-25%, and the rest: Zn and random impurities. The Ni-P alloy plating layer is a plating layer having a chemical composition containing P: 0.1-20%, and the rest: Ni and random impurities. The Cu-Sn-Zn alloy plating layer is a plating layer having a chemical composition containing Sn: 20-60%, Zn: 3-30%, and the rest: Cu and random impurities.

[0077]

In the present embodiment, the chemical composition of the metallized layers can be determined by the following method. The chemical composition was determined using a portable X-ray fluorescence analyzer (DP2000 (trade name DELTA Premium) manufactured by JEOL Ltd.). In determining the chemical composition, the composition is analyzed at four points on the surface of the high friction plated layer 50, or the low friction plated layer 60, or the optional plated layer 70 (four points consisting of 0°, 90°, 180°, 270 ° in the pipe circumferential direction of the pipe fitting). The chemical composition is analyzed in Alloy Plus mode.

[0078]

[Lubricating Coating]

The threaded pipe connection may further comprise a lubricating coating 80. As shown in FIG. 16, a lubricating coating 80 may be placed on the metallized layer 5 of the abutment area. As shown in FIG. 19, a lubricating coating 80 may be placed on the metallized layer 6 of the non-thrust area. However, the placement of the lubricating coating 80 is not limited to the patterns shown in FIG. 16 and 19. It suffices that the lubricating coating 80 be placed as an outermost layer on or over at least one of the following: the threaded portion 31 on the pin side, the portion 32 of the metal seal on the side of the pin, the abutment portion 33 on the side of the pin, threaded section 41 on the side of the coupling, section 42 of the metal seal on the side of the coupling and thrust section 43 on the side of the coupling. In other words, in the case where the abutment portion metallized layer 5 is not formed, the lubricating coating 80 can be placed directly on the pin-side abutment portion 33 or the box-side abutment portion 43. In the case where the metallized layer 6 of the non-thrust portion is not formed, the lubricating coating 80 may be placed directly on at least one of the following: the threaded portion 31 on the pin side, the metal seal portion 32 on the pin side, the threaded portion 41 on the box side, section 42 of the metal seal on the side of the coupling. The lubricating coating 80 as an outermost layer can be placed on or over the entire threaded section 31 on the pin side, the section 32 of the metal seal on the side of the pin, and the abutment section 33 on the side of the pin. The lubricating coating 80 as an outermost layer may be located on or over the entire threaded portion 41 on the coupling side, the metal seal portion 42 on the coupling side, and the thrust portion 43 on the coupling side. In the case where the pipe threaded joint contains the lubricating coating 80 as the outermost layer, the lubricity of the pipe threaded joint is increased.

[0079]

The lubricating coating 80 is in liquid or semi-solid form. Liquid form means a state in which there is a certain volume, but no certain configuration. Semi-solid means a state in which fluidity is lost in a static state, but which can become fluid when an external force (pressure, heat, etc.) is applied. The liquid or semi-solid form includes a highly viscous substance such as a grease. As the lubricating coating 80, a well-known lubricant can be used. The lubricating coating 80 contains lubricating particles such as a metal salt of a basic aromatic organic acid, rosin, metallic soap, and wax. The lubricating coating 80 may contain a solvent and other components as needed.

[0080]

The lubricating particles are not particularly limited, as long as the lubricating particles are particles having lubricating properties. Lubricating particles are one or more types selected from the group consisting of, for example, graphite, MoS ₂ (molybdenum disulfide), WS ₂ (tungsten disulfide), BN (boron nitride), PTFE (polytetrafluoroethylene), CF _x (graphite fluoride ) and CaCO ₃ (calcium carbonate). Assuming that the total amount of all components of the lubricating coating 80, except for the solvent, is 100%, the content of lubricating particles is, for example, from 1 to 20%.

[0081]

A basic metal salt of an aromatic organic acid is a salt obtained from the reaction of an aromatic organic acid and an excess alkali metal (alkali metal or alkaline earth metal). Assuming that the total amount of all components of the lubricating coating 80, except for the solvent, is 100%, the content of the basic metal salt of the aromatic organic acid is, for example, from 40 to 90%.

[0082]

Rosin is a natural resin containing as the main component abietic acid, denoted C ₂₀ H ₃₀ O ₂ . Assuming that the total amount of all components of the lubricating coating 80, except for the solvent, is 100%, the rosin content is, for example, from 5 to 30%. Metallic soap is a metal salt of a fatty acid. Assuming that the total amount of all components of the lubricating coating 80, except for the solvent, is 100%, the content of metallic soap is, for example, from 2 to 30%. Wax means an organic substance that is in solid form at room temperature and turns into a liquid form when heated. Assuming that the total amount of all components of the lubricating coating 80, except for the solvent, is 100%, the wax content is, for example, from 2 to 30%.

[0083]

The lubricating coating 80 may contain a solvent such as water or an organic solvent. The lubricating coating 80 may contain a total of 10% or less of a known rust preventive agent, preservative, color pigment, and the like.

[0084]

A commercially available lubricant may be used as the lubricating coating 80. A commercially available lubricant may be, for example, SEAL-GUARD ECF (trade name) manufactured by JET-LUBE Inc. The chemical composition of the lubricating coating 80 formed on or over the side of the pin 3 and the chemical composition of the lubricating coating 80 formed on or over the side of the box 4 may be equivalent to each other or may be different from each other.

[0085]

The thickness of the lubricating coating 80 is not specifically limited. The thickness of the lubricating coating 80 is, for example, 10 to 300 µm. When the thickness of the lubricating coating 80 is 10 µm or more, the lubricity of the threaded pipe joint increases stably. Even if the thickness of the lubricating coating 80 becomes more than 300 μm, the excess of the lubricating coating 80 is removed during make-up, so that the above-mentioned beneficial effects are achieved by saturation.

[0086]

The thickness of the lubricating coating 80 can be measured in the following way. A nipple 3 or a box 4 containing the lubricating coating 80 is prepared. An arbitrary measuring area (area: 5 mm×20 mm) of the lubricating coating 80 is wiped with ethanol-impregnated absorbent cotton wool. The amount (g) of the lubricating coating 80 is calculated as the difference between the weight of the absorbent wadding before wiping and the weight of the absorbent wadding after wiping. The average thickness of the lubricating coating 80 is calculated from the amount (g) of the lubricating coating 80, the density (g/cm ³ ) of the lubricating coating 80, and the area of the measured areas, and the average thickness of the lubricating coating 80 is used as the thickness (µm) of the lubricating coating 80.

[0087]

[Base Metal of Pipe Threaded Connection]

The chemical composition of the base metal of the threaded pipe connection according to the present embodiment is not particularly limited. The base metal may be, for example, carbon steel, stainless steel, alloy steel, or the like. Among alloy steels, high alloy steel such as duplex stainless steel and Ni alloy containing alloying elements such as Cr, Ni and Mo have high corrosion resistance. Accordingly, when a high alloy steel is used as the base metal, the corrosion resistance of a pipe threaded joint can be improved.

[0088]

[Obtaining method]

A threaded pipe connection according to the present embodiment can be obtained, for example, by the following method. The production method includes the step of forming a metallized layer. In the step of forming the metallized layer, a high friction metallized layer 50 and a low friction metallized layer 60 are formed. The high friction metallized layer 50 and the low friction metallized layer 60 can be obtained, for example, by a masking process or a brushing process. Next, a method will be described as an example in which the Zn-Ni alloy plated layer is formed as the high friction plated layer 50 and the Cu plated layer is formed as the low friction plated layer 60.

[0089]

[Step of forming a metallized layer]

In the case where the pipe threaded joint according to the present embodiment is produced by the mask method, the pipe threaded joint can be made by the following process. Below, in order to specifically describe the step of forming the plating layer, the case where the Cu plating layer is formed on the pin-side threaded portion 31, the pin-side metal seal portion 32, the box-side threaded portion 41, and the box-side metal seal portion 42 will be described, and a Zn-Ni alloy plating layer is formed on the pin-side thrust portion 33 and the box-side thrust portion 43. First, two kinds of coating solutions are prepared. Two kinds of plating solutions are, for example, a solution for forming a Zn-Ni alloy plating layer and a solution for forming a Cu plating layer. The coating solution for forming the Zn-Ni alloy plating layer contains zinc ions and nickel ions. The metal ion concentrations are as follows, for example: zinc ions: 1 to 100 g/l, nickel ions: 1 to 150 g/l. For example, to form a metallized Cu layer, a commercially available plating bath can be used as a plating solution. The coating solution for making the Cu plating layer is, for example, DAIN COPPER LS-001 (trade name) manufactured by Daiwa Fine Chemicals Co. Ltd.

[0090]

The pin 3 and/or the box 4 are then dipped into the coating solution to form a Cu plating layer. Specifically, the pin 3 or the box 4 is energized to form a metallized Cu layer in the pin side thrust portion 33, the pin side metal seal portion 32 and the pin side threaded portion 31, and the box side thrust portion 43, the metal portion 42 seals on the coupling side and threaded section 41 on the coupling side. Appropriate conditions for electrodeposition can be set. Conditions for electrodeposition, for example, are as follows: pH of the coating solution: 1 to 10, temperature of the coating solution: 10 to 60 °C, current density: 1 to 100 A/dm ² , and treatment time: 0 ,1 to 250 minutes. In such an operation, a Cu plating layer, which corresponds to a low friction metallized layer 60, is formed on the entire surface of the pin 3 and/or the entire surface of the box 4.

[0091]

Subsequently, a mask is formed in the pin-side metal seal portion 32 and the pin-side threaded portion 31 and/or the box-side metal seal portion 42 and the box-side threaded portion 41 on which the Cu plating layer corresponding to the low coefficient metallized layer 60 is formed. friction. The mask may be formed in a well known manner. Specifically, the pin side metal seal portion 32, the pin side threaded portion 31, the box side metal seal portion 42, and the box side threaded portion 41 may be sealed with an aluminum masking tape or may be coated with a sealing agent for masking.

[0092]

The pin 3 on which the mask is formed and/or the sleeve 4 on which the mask is formed are immersed in the coating solution to form a Zn-Ni alloy plating layer. Voltage is applied to pin 3 and/or sleeve 4 to form a metallized layer of Zn-Ni alloy. Specifically, the mask is formed in the pin-side metal seal portion 32, the pin-side threaded portion 31, the box-side metal seal portion 42, and the box-side threaded portion 41, and therefore the Zn-Ni alloy plating layer is formed only on the thrust a pin-side portion 33 and a sleeve-side abutment portion 43 on which no mask is formed. Appropriate conditions for electrodeposition can be set. Conditions for electrodeposition, for example, are as follows: pH of the coating solution: 1 to 10, temperature of the coating solution: 10 to 60 °C, current density: 1 to 100 A/dm ² , and treatment time: 0 ,1 to 250 minutes. By such operations, a Zn-Ni alloy plating layer corresponding to the high friction plating layer 50 is formed on the pin-side thrust portion 33 and the box-side thrust portion 43. When finished, the mask can be removed.

[0093]

In the case where the pipe screw joint according to the present embodiment is produced by the brush application method, the pipe screw joint is obtained by the following process. First, in the same manner as the above-mentioned mask method, two kinds of coating solutions are obtained. Two kinds of plating solutions are, for example, a solution for forming a plating layer of Cu and a solution for forming a plating layer of Zn-Ni alloy.

[0094]

Then, in the same manner as in the aforementioned mask method, a metallized Cu layer is formed on the pin side thrust portion 33, the pin side metal seal portion 32 and the pin side threaded portion 31, and/or the box side thrust portion 43, the portion 42 metal seal on the coupling side and threaded section 41 on the coupling side.

[0095]

The brush is then prepared, which is absorbent cotton wrapped around the electrode. The absorbent wool is immersed in a coating solution to form a Zn-Ni alloy plating layer to impregnate the absorbent wool with the solution. The absorbent wadding impregnated with the coating solution and the electrode come into contact with the abutment portion 33 on the pin side and/or the abutment portion 43 on the sleeve side and are energized. By such operations, a plating layer of Zn-Ni alloy can be formed on the pin-side thrust portion 33 and/or on the box-side thrust portion 43. Appropriate conditions for electrodeposition can be set. The conditions for electrodeposition are as follows: pH of the coating solution: 1 to 10, temperature of the coating solution: 10 to 60 °C, current density: 1 to 100 A/dm ² , and treatment time: 0.1 to 200 minutes. By such operations, a Zn-Ni alloy plated layer corresponding to the high friction plated layer 50 is formed on the pin side thrust portion 33 and/or the box side thrust portion 43.

[0096]

After the respective metallized layers have been formed, washing with water or drying can be carried out, if necessary. In the case of forming the optional plating layer 70, the pin 3 or the sleeve 4 is dipped into the plating solution to form the optional plating layer 70 before depositing the aforementioned Cu plating layer, thereby forming the optional plating layer 70. Appropriate conditions for forming the optional plating layer 70 can be set. .

[0097]

The threaded connection for pipes according to the present embodiment of the invention can be made by the above-mentioned steps. The above description describes a production method in which the Zn-Ni alloy plating layer is formed as a high friction plating layer 50 and the Cu plating layer is formed as a low friction plating layer 60. However, as the high friction metallized layer 50 and the low friction metallized layer 60, various metallized layers can be formed. In such a case, as in the above-mentioned production method, a plating bath containing metal ions to be contained in the formed plating layer can be used to form the plating layer.

[0098]

[Lubricating Coating Forming Step]

The step of forming a lubricating coating can be carried out after the aforementioned metallized layer has been formed. In the step of forming the lubricating coating, the lubricating coating 80 as an outermost layer is formed on or over one of the following: a pin-side thrust portion 33, a pin-side metal seal portion 32, a threaded pin-side portion 31, a pin-side thrust portion 43 side of the coupling, section 42 of the metal seal on the side of the coupling, threaded section 41 on the side of the coupling.

[0099]

The lubricating coating 80 can be formed by applying a composition containing the aforementioned components to at least one of the aforementioned: pin side thrust portion 33, pin side metal seal portion 32, pin side threaded portion 31, pin side thrust portion 43 side of the coupling, section 42 of the metal seal on the side of the coupling and threaded section 41 on the side of the coupling. The coating method is not particularly limited. The coating method may, for example, be spray coating, brush coating or dip coating. In the case where spray coating is adopted, the composition containing the above components can be heated and sprayed in a fluid state. The film forming step can be performed on either the pin 3 or the box 4 or either.

[0100]

[Pre-treatment step]

The aforementioned manufacturing method may include a pretreatment step before the metallized layer forming step, if necessary. The pre-treatment step may be, for example, pickling and alkaline degreasing. The pre-treatment step removes oil and the like adhering to the contact surface. The pretreatment step may further include grinding, such as sandblasting and machine fine grinding. One of these pre-treatments may be performed, or several pre-treatments may be performed in combination.

EXAMPLES

[0101]

Examples will be described below. In the example, "%" means % by weight.

[0102]

[Step of forming a metallized layer]

Various plating layers were formed on the surface of the carbon steel sheet, and their coefficients of friction were measured. Steel grade SPCC (JIS G3141(2017)) produced by Paltec Test Panels co., ltd. was used for the steel sheet. The composition of the steel sheet was as follows: C ≤ 0.15%, Mn ≤ 0.60%, P ≤ 0.100%, and S ≤ 0.050%. The plating layers were formed on the surface of the steel sheet under the following conditions.

[0103]

Metallized Ni-P alloy layer

A Ni-P alloy plating layer having a thickness of 10 µm was formed on the surface of the steel sheet using a coating solution (trade name) SEK797 manufactured by Japan Kanigen co., Ltd. Coating conditions were as follows: coating solution temperature: 90° C. and treatment time: 40 minutes (chemical reduction coating). The metallized Ni-P alloy layer has a chemical composition containing P: 5-15% by mass, and the rest: Ni and random impurities.

[0104]

Metallized Zn-Ni Alloy Layer

A Zn-Ni alloy plating layer having a thickness of 10 µm was formed on the surface of the steel sheet using a coating solution (trade name) DAIN Zinalloy N-PL manufactured by Daiwa Fine Chemicals Co., Ltd. Coating conditions were as follows: coating solution temperature: 35° C., current density: 4 A/dm ² , and treatment time: 15 minutes. The metallized layer of Zn-Ni alloy has a chemical composition containing Ni: 10-20% by mass, and the rest: Zn and random impurities.

[0105]

Metallized Cu layer

A Cu plating layer having a thickness of 10 µm was formed on the surface of the steel sheet using a coating solution obtained by preparing commercially available reagents. The coating solution contained 200 g/l copper sulfate pentahydrate and 50 g/l sulfuric acid. Coating conditions were as follows: coating solution temperature: 35° C., current density: 10 A/dm ² , and treatment time: 5 minutes. The metallized Cu layer has a chemical composition containing Cu: 99% by mass or more, and the rest: random impurities.

[0106]

Metallized Zn layer

A Zn plating layer having a thickness of 10 µm was formed on the surface of the steel sheet using a coating solution obtained by preparing commercially available reagents. The coating solution contained 350 g/l zinc sulfate heptahydrate and 75 g/l sodium sulfate and had a pH: 2. Coating conditions were as follows: temperature of the coating solution: 50 °C, current density: 10 A/dm ² , and processing time: 4 minutes. The metallized Zn layer has a chemical composition containing Zn: 99% by mass or more, and the rest: random impurities.

[0107]

Metallized Cu-Sn-Zn alloy layer

A Cu-Sn-Zn alloy plating layer having a thickness of 10 µm was formed on the surface of the steel sheet using a coating solution manufactured by NIHON KAGAKU SANGYO CO., LTD. Coating conditions were as follows: coating solution pH: 14, coating solution temperature: 45° C., current density: 2 A/dm ² , and treatment time: 40 minutes. The metallized Cu-Sn-Zn alloy layer has a chemical composition containing Sn: 40% by mass, Zn: 7%, and the rest: Cu and random impurities.

[0108]

Metallized Cr layer

A Cr plating layer having a thickness of 10 µm was formed on the surface of the steel sheet using a chromium-containing plating solution manufactured by SIFCO Industries, Inc. Coating conditions were as follows: coating solution temperature: 40° C., current density: 30 A/dm ² , and treatment time: 30 minutes. The Cr-plated layer has a chemical composition containing Cr: 95% by mass or more, and the rest: random impurities.

[0109]

[Friction Coefficient Measurement Test]

The Bowden slip test was carried out on steel plates with metallized layers formed thereon to measure the coefficients of friction of the metallized layers. The Bowden sliding test was carried out under the following conditions: sliding indenter: steel ball 4.7625 mm (3/16" in diameter) (Fe, SUJ2 grade steel), pressure load: 3 kgf, sliding method: linear reciprocating sliding, sliding distance: 30 mm, number of sliding reciprocations: 5, sliding speed: 4 mm/s, test temperature: 25 °C, lubricant (trade name) SEAL-GUARD ECF manufactured by JET-LUBE Inc., amount of lubricant applied: 40 g / m ^2. For each metallized layer, the friction coefficient was determined as the arithmetic mean of the friction coefficients for five reciprocating sliding movements. The friction coefficients of the metallized layers are shown in table 1.

[0110]

[Table 1]

Coating type Friction coefficient Metallized Ni-P alloy layer 0.135 Metallized Zn-Ni Alloy Layer 0.134 Metallized Cu layer 0.121 Metallized Cr layer 0.116 Metallized Cu-Sn-Zn alloy layer 0.115 Metallized Zn layer 0.105

[0111]

[FEM Analysis]

Based on the results presented in Table 1, a FEM (finite element analysis) analysis of the stop torque, the yield torque, and the threaded joint torque “delta” value for pipes with each of the metallized layers formed On him. As a threaded pipe connection, VAM21HT (trade name), size: 9-5/8" 53.5#, manufactured by NIPPON STEEL CORPORATION was used. the surface on the box side was Fe) and were formed only on the pin side. Test number 7 was an example in which a Cu plating layer was formed on its entire surface, which is equivalent to the conventional example. The results of the analysis are shown in Table 2.

[0112]

[Table 2]

[0113]

In Table 2, the "Analytical Value" columns show the torque values (ft. lbs) obtained from the FEM analysis. In Table 2, the columns "Increase/Decrease Degree" show the degrees of fluctuation (%) with respect to the value in test number 7, a common example (Cu coating on the entire pin). In Table 2, Ts denotes the thrust torque, Ty denotes the yield torque, and ΔT denotes the delta value of the torque.

[0114]

[Evaluation results]

As shown in Table 1 and Table 2, with respect to test number 1 and test number 2, in which high friction plating layers were formed on the thrust portions and low friction plating layers were formed on the threaded portions and the metal seal portions, their torque values have been improved. In particular, with respect to test number 1 and test number 2, their yield strength torques were higher than in test number 7 (common example), while their stop torques corresponded to that of test number 7. In addition, their torque "delta" values were greater than in test number 7 (common example).

[0115]

On the contrary, with regard to test number 3 and test number 4, in which metallized layers having high coefficients of friction were formed not only in the thrust areas, but also in metal seal areas, their yield strength torques were higher than in test number 7 (common example), but their stop torques were also higher than in test number 7 (common example).

[0116]

With respect to test number 5 and test number 6, in which high friction plating layers were formed on the threaded portions and low friction metallized layers were formed on the metal seal portions and thrust portions, their thrust torques were lower than in test number 7 (common example), but their yield torques were also lower than in test number 7 (common example). In addition, the torque delta value in test number 5 and test number 6 were lower than in test number 7 (common example).

[0117]

With regard to Test No. 8 and Test No. 9, in which plating layers having friction coefficients greater than those of the conventional Cu plating were formed on threaded portions, metal seal portions, and thrust portions, their yield strength torques were higher. than in test number 7 (common example), but their stop torques were also higher than in test number 7 (common example).

[0118]

The embodiment of the present invention has been described above. However, the above embodiment of the invention only serves as an exemplary embodiment of the present invention. Accordingly, the present invention is not limited to the above embodiment, and the above embodiment can be implemented in a modified manner, if necessary, without departing from the gist of the present invention.

LIST OF REFERENCES

[0119]

1: steel pipe

2: coupler

3: nipple

31: threaded section on the nipple side

32: area of the metal seal on the side of the nipple

33: thrust area on the nipple side

4: coupler

41: threaded section on the coupling side

42: section of the metal seal on the coupling side

43: thrust section on the coupling side

5: metallized layer of thrust area

50: high friction metallized layer

6: metallized layer of non-stubborn area

60: low friction metallized layer

70: optional metallic layer

80: lubricity coating

Claims (29)

1. Threaded connection for pipes, containing: a nipple containing a threaded section on the side of the nipple, a section of a metal seal on the side of the nipple, and a thrust section on the side of the nipple; a coupling containing a threaded portion on the coupling side, a metal seal portion on the coupling side, and a thrust portion on the coupling side; a metallized thrust portion layer placed on the pin side thrust portion and/or on the box side thrust portion, and including one or more layers, wherein the outermost layer of the thrust portion metallized layer is a high friction metallized layer; and a metallized layer of a non-thrust section located on at least one of the following: a threaded section on the pin side, a metal seal section on the pin side, a threaded section on the box side, a section of the metal seal on the side of the box, and including one or more layers, wherein the outermost layer of the non-thrust metallized layer is a low friction metallized layer having a friction coefficient less than the friction coefficient of the high friction metallized layer. 2. A threaded connection for pipes according to claim 1, in which the metallized layer of the thrust section is placed on the thrust section on the pin side, and the metallized layer of the non-thrust section is located on the threaded section on the nipple side and on the metal seal section on the nipple side. 3. A threaded connection for pipes according to claim 1, in which the metallized layer of the thrust section is placed on the thrust section on the side of the coupling, and the metallized layer of the non-thrust section is located on the threaded section on the side of the coupling and on the section of the metal seal on the side of the coupling. 4. Threaded connection for pipes according to item 1, wherein the metallized layer of the thrust portion has a thickness of 1 to 50 μm, and the metallized layer of the non-thrust portion has a thickness of 1 to 50 μm. 5. Threaded connection for pipes according to item 2, wherein the metallized layer of the thrust portion has a thickness of 1 to 50 μm, and the metallized layer of the non-thrust portion has a thickness of 1 to 50 μm. 6. Threaded connection for pipes according to item 3, wherein the metallized layer of the thrust portion has a thickness of 1 to 50 μm, and the metallized layer of the non-thrust portion has a thickness of 1 to 50 μm. 7. Threaded pipe connection according to claim 1, further comprising a lubricating coating placed as an outermost layer on at least one of the following: a threaded section on the side of the pin, a section of the metal seal on the side of the pin, a thrust section on the side of the pin , a threaded section on the side of the coupling, a section of the metal seal on the side of the coupling, a thrust section on the side of the coupling, and the lubricating coating is in a liquid or semi-solid state. 8. A threaded pipe connection according to claim 2, further comprising a lubricating coating placed as an outermost layer on at least one of the following: a threaded section on the side of the pin, a section of the metal seal on the side of the pin, a thrust section on the side of the pin , a threaded section on the side of the coupling, a section of the metal seal on the side of the coupling, a thrust section on the side of the coupling, and the lubricating coating is in a liquid or semi-solid state. 9. A threaded pipe connection according to claim 3, further comprising a lubricating coating placed as an outermost layer on at least one of the following: a threaded section on the side of the pin, a section of the metal seal on the side of the pin, a thrust section on the side of the pin , a threaded section on the side of the coupling, a section of the metal seal on the side of the coupling, a thrust section on the side of the coupling, and the lubricating coating is in a liquid or semi-solid state. 10. A threaded pipe connection according to claim 4, further comprising a lubricating coating placed as an outermost layer on at least one of the following: a threaded section on the side of the pin, a section of the metal seal on the side of the pin, a thrust section on the side of the pin , a threaded section on the side of the coupling, a section of the metal seal on the side of the coupling, a thrust section on the side of the coupling, and the lubricating coating is in a liquid or semi-solid state. 11. A threaded pipe connection according to claim 5, further comprising a lubricating coating placed as an outermost layer on at least one of the following: a threaded section on the side of the nipple, a section of the metal seal on the side of the nipple, a thrust section on the side of the nipple , a threaded section on the side of the coupling, a section of the metal seal on the side of the coupling, a thrust section on the side of the coupling, and the lubricating coating is in a liquid or semi-solid state. 12. A threaded pipe connection according to claim 6, further comprising a lubricating coating placed as an outermost layer on at least one of the following: a threaded section on the side of the pin, a section of the metal seal on the side of the pin, a thrust section on the side of the pin , a threaded section on the side of the coupling, a section of the metal seal on the side of the coupling, a thrust section on the side of the coupling, and the lubricating coating is in a liquid or semi-solid state. 13. Threaded connection for pipes according to any one of paragraphs 1-12, in which the high friction plating layer is selected from the group consisting of a Ni-P alloy plating layer, a Zn-Ni alloy plating layer, a Cu plating layer, a Cr plating layer, and a Cu-Sn-Zn alloy plating layer, and the low friction metallized layer is selected from the group consisting of a Zn-Ni alloy metallized layer, a Cu metallized layer, a Cr metallized layer and a Cu-Sn-Zn alloy metallized layer, and a Zn metallized layer. 14. A threaded connection for pipes according to claim 13, in which the high friction plating layer is selected from the group consisting of a Ni-P alloy plating layer and a Zn-Ni alloy plating layer, and the low friction metallized layer is selected from the group consisting of a Cu metallized layer, a Cr metallized layer, a Cu-Sn-Zn alloy metallized layer, and a Zn metallized layer.

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