METAL PIPE FOR OIL WELL

Abstract

The present invention provides a metal pipe for oil wells, the metal pipe being provided with a Zn-Ni alloy plating layer that has high hardness. A metal pipe for oil wells according to the present disclosure is provided with a pipe main body that comprises a pin and a box, and is additionally provided with a Zn-Ni alloy plating layer that is formed on a pin contact surface or a box contact surface. The Ni content in the Zn-Ni alloy plating layer is 14.8% by mass to 25.0% by mass, and the bulk density of the Zn-Ni alloy plating layer is 7.00 g / cm3 or more.

Description

1 / 40 METAL PIPE FOR OIL WELL TECHNICAL FIELD

[001] The present invention relates to a metal pipe, and more particularly to a metal pipe for oil wells. RELATED ART

[002] Metal pipes for oil wells are used for drilling in oil fields and gas wells (hereinafter, oil fields and gas wells are collectively referred to as oil wells). A metal pipe for an oil well has a threaded connection. Specifically, at an oil well drilling site, depending on the depth of the oil well, a plurality of metal pipes for oil wells are connected to form a connected body of tubular products for oil fields, which is typified by a casing pipe or a production pipe. A connected body of tubular products for oil fields is formed by fastening oil well pipes to each other. Inspections may in some cases be conducted on connected bodies of tubular products for oil fields. When conducting an inspection, the connected body of tubular products for oil fields is lifted and loosened.Next, the metal pipes for oil wells are detached from the connected body of oilfield tubular products by loosening and are inspected. After inspection, the metal pipes for oil wells are reattached to each other so that the metal pipes for oil wells can be reused as part of the connected body of oilfield tubular products.

[003] The metal oil well pipe includes a pin and a housing. The pin has a pin contact surface including an external thread portion on an outer peripheral surface of an end portion of the metal oil well pipe. The housing has a housing contact surface including an internal thread portion on a Petition 870250070618, dated 11 / 08 / 2025, pp. 92 / 139 2 / 40 inner peripheral surface of an end portion of the metal oil well pipe that is on the opposite side from the pin. When metal oil well pipes are fastened together, the contact surface of the pin comes into contact with the contact surface of the housing.

[004] The contact surface of the pin and the contact surface of the housing repeatedly experience strong friction during the tightening and loosening of the metal oil well pipe. For this reason, on the contact surface of the pin and the contact surface of the housing, scoring (irreparable scoring) is prone to occur when tightening and loosening are repeated. Consequently, the metal oil well pipe is required to have sufficient durability with respect to friction, i.e., to have excellent resistance to scoring.

[005] Until now, compound greases containing heavy metal powder, which are referred to as dopes, have been used to improve scuff resistance. Applying a compound grease to the pin contact surface and / or the housing contact surface can improve the scuff resistance of the oil well metal pipe. However, heavy metal powder contained in compound greases, such as Pb, Zn, and Cu, can affect the environment. For this reason, the development of oil well metal pipe that is excellent in scuff resistance even without the use of a compound grease is desired.

[006] In a metal oil well pipe disclosed in Patent Document 1 (International Application Publication No. WO2016 / 170031), a Zn-Ni alloy coating layer is formed on a pin contact surface or on a housing contact surface instead of using a compound grease. The Zn contained in the Zn-Ni alloy coating layer formed on a contact surface of the metal oil well pipe improves the corrosion resistance of the base metal of the metal oil well pipe by sacrificial protection. Furthermore, it is described in Patent Document 1 that the Zn-Ni alloy is also excellent in a characteristic of Petition 870250070618, dated 11 / 08 / 2025, pp. 93 / 139 3 / 40 wear resistance. LIST OF QUOTES PATENT DOCUMENT

[007] Patent Document 1: Publication of International Application No. WO2016 / 170031 SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[008] As described above, a Zn-Ni alloy coating layer improves the corrosion resistance of a metal oil well pipe through Zn. Furthermore, because the hardness of the Zn-Ni alloy coating layer itself is high, favorable scuff resistance is obtained. In general, the higher the hardness of a coating layer, the greater the wear resistance characteristic and the greater the scuff resistance. Therefore, with respect to a Zn-Ni alloy coating layer that is excellent in corrosion resistance, to further improve scuff resistance during the tightening and loosening of a metal oil well pipe, it is desirable to further increase the hardness. In particular, in a large-diameter metal oil well pipe, or in a metal oil well pipe composed of a high alloy, the susceptibility to scuffing is high.Therefore, in such types of metal pipe for oil wells, to obtain excellent resistance to scoring while also achieving corrosion resistance, it is desirable to further increase the hardness of a Zn-Ni alloy coating layer.

[009] One objective of the present invention is to provide a metallic oil well pipe that includes a Zn-Ni alloy coating layer that has high hardness. SOLUTION TO THE PROBLEM

[0010] A metal pipe for an oil well of the present invention includes: a main body of the tube including an initial portion of Petition 870250070618, dated 11 / 08 / 2025, pp. 94 / 139 4 / 40 end and a second end portion, wherein the main body of the tube includes: a pin formed in the first end portion, and a box formed in the second end portion; The pin includes: a pin contact surface including an externally threaded portion; and the box includes: a contact surface of the housing including an internally threaded part; The metal pipe for oil wells also includes: A Zn-Ni alloy coating layer is formed on the contact surface of the pin or on the contact surface of the housing, wherein the Zn-Ni alloy coating layer is composed of a Zn-Ni alloy, in which the Ni content in the Zn-Ni alloy coating layer is, by mass %, 14.8 to 25.0%, and the apparent density of the Zn-Ni alloy coating layer is 7.00 g / cm3 or more. ADVANTAGEOUS EFFECT OF THE INVENTION

[0011] A metal pipe for an oil well of the present embodiment includes a Zn-Ni alloy coating layer that has high hardness. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a graph illustrating the relationship between Ni content and Vickers hardness of a conventional Zn-Ni alloy coating layer. Figure 2 is a graph illustrating the relationship between Ni content and apparent density of a conventional Zn-Ni alloy coating layer. Figure 3 is a graph showing the relationship between Ni content and the Petition 870250070618, dated 11 / 08 / 2025, pp. 95 / 139 5 / 40 apparent density of a Zn-Ni alloy coating layer of the present embodiment is added to the graph illustrated in Figure 2. Figure 4 is a graph in which the relationship between the Ni content and the Vickers hardness of a Zn-Ni alloy coating layer of the present embodiment is added to the graph illustrated in Figure 1. Figure 5 is a side view of a metal pipe for an oil well of the present embodiment. Figure 6 is a partial cross-sectional view illustrating a cross-section (longitudinal cross-section) along one axis direction of a metal pipe coupling for an oil well illustrated in Figure 5. Figure 7 is a cross-sectional view parallel to the axis direction of the metal oil well pipe illustrated in Figure 5, which shows a portion near a pin of the metal oil well pipe. Figure 8 is a cross-sectional view parallel to the axis direction of the metal oil well pipe illustrated in Figure 5, which shows a portion near a metal oil well pipe casing. Figure 9 is a partial cross-sectional view including a longitudinal cross-section of the metal oil well pipe of the present embodiment having a different configuration from that in Figure 6. Figure 10 is a partial cross-sectional view including a longitudinal cross-section of an integral type metal oil well pipe according to the present embodiment. Figure 11 is an enlarged view of a pin contact surface illustrated in Figure 7. Figure 12 is an enlarged view of a contact surface of the box illustrated in Figure 8. Figure 13 is an enlarged view of a contact surface of Petition 870250070618, dated 11 / 08 / 2025, pp. 96 / 139 6 / 40 pin having a different structure from the pin contact surface illustrated in Figure 11. Figure 14 is an enlarged view of a contact surface of the box having a different structure from the contact surface of the box illustrated in Figure 12. DESCRIPTION OF THE MODALITIES

[0013] The present embodiment is described in detail below with reference to the accompanying drawings. The same reference symbols will be used throughout the drawings to refer to the same or similar parts, and their description will not be repeated. In the following description, % with respect to the elemental content in the Zn-Ni coating layer means percentage by mass.

[0014] The present inventors had the idea that if the Ni content in a Zn-Ni alloy coating layer is increased, the hardness of the Zn-Ni alloy coating layer will be further increased. Therefore, firstly, the present inventors investigated the relationship between the Ni content of a Zn-Ni alloy coating layer formed on a contact surface (pin contact surface or box contact surface) of a metal oil well pipe using the conventional method, and the hardness (Vickers hardness) of the Zn-Ni alloy coating layer, and obtained the results illustrated in Figure 1.

[0015] Referring to Figure 1, in the conventional Zn-Ni alloy coating layer, up to the Ni content of 14.8%, the Vickers hardness increased along with an increase in Ni content. However, when the Ni content was 14.8% or more, the Vickers hardness decreased as the Ni content increased.

[0016] Therefore, the present inventors investigated the reason why the hardness of the Zn-Ni alloy coating layer decreased when the Ni content was 14.8% or more. As a result, the present inventors clarified the following issues. When the Ni content in the Zn-Ni alloy coating layer was increased, many porosities were formed in the layer of Petition 870250070618, dated 11 / 08 / 2025, pp. 97 / 139 7 / 40 Zn-Ni alloy coating. Therefore, the present inventors investigated the apparent density, which serves as an index of the proportion of porosities, with respect to the Zn-Ni alloy coating layers plotted in Figure 1, and obtained the results illustrated in Figure 2.

[0017] Referring to Figure 2, as a result of the investigations, the present inventors discovered that in the conventional ZnNi alloy coating layer, the apparent density increased along with an increase in Ni content up to the Ni content of 14.8%. However, in a case where the Ni content was 14.8% or more, the apparent density decreased rapidly as the Ni content increased.

[0018] Based on the results of the investigations described above, the present inventors considered that the relationship between the Zn-Ni alloy coating layer, the Ni content, and the apparent density is as follows. An increase in the Ni content in the Zn-Ni alloy coating layer contributes to an increase in the hardness of the Zn-Ni alloy coating layer. However, when the Ni content becomes high, the apparent density decreases rapidly. In Figure 1 and Figure 2, when the Ni content is 14.8% or more, the margin of decrease in hardness that accompanied a decrease in apparent density is greater than the margin of increase in hardness that accompanied an increase in Ni content. Therefore, when the Ni content is 14.8% or more, the Vickers hardness of the Zn-Ni alloy coating layer decreases accompanying an increase in Ni content (Figure 1).

[0019] Based on the above findings, the present inventors had the idea that, in a Zn-Ni alloy coating layer, if a decrease in apparent density can be suppressed while increasing the Ni content, the Vickers hardness of the Zn-Ni alloy coating layer can be further increased by accompanying an increase in Ni content. Based on the idea mentioned above, the present inventors conducted tests which are described later, and obtained the results illustrated in Figure 3 and Figure 4. Petition 870250070618, dated 11 / 08 / 2025, pp. 98 / 139 8 / 40

[0020] Figure 3 is a graph in which the relationship between the Ni content and the apparent density of a Zn-Ni alloy coating layer of the present embodiment is added to the graph illustrated in Figure 2. Figure 4 is a graph in which the relationship between the Ni content and the Vickers hardness of a Zn-Ni alloy coating layer of the present embodiment is added to the graph illustrated in Figure 1. The O marks in Figure 3 and Figure 4 correspond to Inventive Examples among Examples that are described later. Referring to Figure 3, in the Zn-Ni alloy coating layer of the present embodiment, even when the Ni content is made 14.8% or more, the apparent density is 7.00 g / cm3 or more. In such a case, as illustrated in Figure 4, even when the Ni content is 14.8% or more, the Vickers hardness increases markedly accompanying an increase in the Ni content.

[0021] As described above, the present inventors have discovered that, in a Zn-Ni alloy coating layer, if the Ni content is 14.8% or more and, in addition, the apparent density is 7.00 g / cm3 or more, the hardness of the Zn-Ni alloy coating layer increases markedly.

[0022] The metallic oil well pipe of the present embodiment which was completed based on the above findings has the following structures.

[0023] [1] A metal pipe for an oil well, including: a main body of the tube including a first end portion and a second end portion, where the main body of the tube includes: A pin formed in the first end portion, and a box formed in the second end portion; the pin includes: a pin contact surface including an externally threaded portion; and the box includes: Petition 870250070618, dated 11 / 08 / 2025, pp. 99 / 139 9 / 40 a contact surface of the housing including an internally threaded part; The metal pipe for oil wells also includes: A Zn-Ni alloy coating layer is formed on the contact surface of the pin or on the contact surface of the housing, wherein the Zn-Ni alloy coating layer is composed of a Zn-Ni alloy, in which the Ni content in the Zn-Ni alloy coating layer is, by mass %, 14.8 to 25.0%, and the apparent density of the Zn-Ni alloy coating layer is 7.00 g / cm3 or more.

[0024] In the present embodiment of the metallic oil well pipe, the Ni content in the Zn-Ni alloy coating layer is, by mass %, 14.8 to 25.0%, and the apparent density of the Zn-Ni alloy coating layer is 7.00 g / cm3 or more. The hardness of a Zn-Ni alloy coating layer having this structure increases markedly. Therefore, the Zn-Ni alloy coating layer can suppress the occurrence of scoring during tightening and loosening. Furthermore, the Zn-Ni alloy coating layer contains Zn. Therefore, a corrosion resistance property can be increased by sacrificial protection.

[0025] [2] The metal pipe for oil wells [1] above, in which, in the Zn-Ni alloy coating layer: The Ni content is, as a mass percentage, 17.0% or more.

[0026] Hereafter, the metal pipe for oil wells according to the present embodiment is described in detail.

[0027] [Structure of metal pipe for oil well] First, the structure of the metal pipe for oil wells in this embodiment will be described. The metal pipe for oil wells has a well-known structure. The available types of metal pipe for wells Petition 870250070618, dated 11 / 08 / 2025, pp. 100 / 139 10 / 40 oil well pipes are T&C type metal pipes and integral type metal pipes. Each type of metal pipe for oil wells is described in detail below.

[0028] [Case in which the metal pipe for oil well 1 is of the T&C type] Figure 5 is a configuration diagram illustrating an example of a metal pipe for an oil well 1 of the present embodiment. Figure 5 is a configuration diagram illustrating the metal pipe for an oil well 1 of a so-called T&C (threaded and coupled) type. Referring to Figure 5, the metal pipe for an oil well 1 includes a main pipe body 10.

[0029] The main body of the pipe 10 extends in the direction of the pipe axis. A cross-section perpendicular to the direction of the pipe axis of the main body of the pipe 10 is a circular shape. The main body of the pipe 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is an end portion on the opposite side to the second end portion 10B. In the T&C type oil well metal pipe 1 illustrated in Figure 5, the main body of the pipe 10 includes a pin pipe body 11 and a coupling 12. The coupling 12 is attached to one end of the pin pipe body 11. More specifically, the coupling 12 is threaded onto one end of the pin pipe body 11.

[0030] Figure 6 is a partial cross-sectional view illustrating a cross-section (longitudinal cross-section) that is parallel to the axis direction of the coupling tube 12 of the metal oil well pipe 1 illustrated in Figure 5. Referring to Figure 5 and Figure 6, the main body of the pipe 10 includes a pin 40 and a housing 50. The pin 40 is formed in the first end portion 10A of the main body of the pipe 10. When fastening, the pin 40 is inserted into the housing 50 of another metal oil well pipe 1 (not illustrated), and is threaded onto the housing 50 of the other pipe. Petition 870250070618, dated 11 / 08 / 2025, pp. 101 / 139 1 1 / 40 metal for oil well 1.

[0031] The box 50 is formed in the second end portion 10B of the main body of the tube 10. When performing the fastening, the pin 40 of another metal oil well pipe 1 is inserted into the box 50, and the box 50 is fastened by threading to the pin 40 of the other metal oil well pipe 1.

[0032] [Regarding the structure of pin 40] Figure 7 is a cross-sectional view of a portion near pin 40 of the wellbore pipe 1 illustrated in Figure 5, which is a cross-sectional view parallel to the axis direction of the wellbore pipe 1. A dashed portion in Figure 7 represents the housing 50 structure of another wellbore pipe 1 in the case of attaching wellbore pipe 1 to another wellbore pipe 1. Referring to Figure 7, pin 40 includes a pin 400 contact surface on the outer peripheral surface of the first end portion 10A of the main body of pipe 10. At the time of attachment to another wellbore pipe 1, the pin 400 contact surface is threaded into the housing 50 of the other wellbore pipe 1 to contact the housing 500 contact surface (to be described later) of housing 50.

[0033] The contact surface of pin 400 includes at least one external thread portion 41 formed on the outer peripheral surface of the first end portion 10A. The contact surface of pin 400 may further include a pin sealing surface 42 and a pin shoulder surface 43. In Figure 7, the pin shoulder surface 43 is located on the front end face of the first end portion 10A, on the outer peripheral surface of the first end portion 10A, the pin sealing surface 42 is located more on the front end side of the first end portion 10A than the external thread portion 41. In other words, the pin sealing surface 42 is located between the external thread portion 41 and the pin shoulder surface 43. The sealing surface Petition 870250070618, dated 11 / 08 / 2025, pp. 102 / 139 12 / 40 of pin 42 is provided in a conical shape. Specifically, on the sealing surface of pin 42, the outer diameter of pin 40 gradually decreases from the external thread portion 41 towards the shoulder surface of pin 43 in the longitudinal direction (direction of the tube axis) of the first end portion 10A.

[0034] When fastening with another metal pipe for oil well 1, the sealing surface of pin 42 comes into contact with a sealing surface of housing 52 (described later) of housing 50 of the other metal pipe for oil well 1. More specifically, during fastening, when pin 40 is inserted into housing 50 of the other metal pipe for oil well 1, the sealing surface of pin 42 comes into contact with the sealing surface of housing 52. Subsequently, when pin 40 is further screwed into housing 50 of the other metal pipe for oil well 1, the sealing surface of pin 42 comes into close contact with the sealing surface of housing 52. By this means, during fastening, the sealing surface of pin 42 comes into close contact with the sealing surface of housing 52 to form a seal that is based on metal-to-metal contact.Therefore, gas tightness can be increased in each of the metal oil well pipes 1 that are fastened to each other.

[0035] In Figure 7, the shoulder surface of pin 43 is arranged on the face of the front end of the first end portion 10A. In other words, in the pin 40 illustrated in Figure 7, the external thread part 41, the sealing surface of the pin 42, and the shoulder surface of pin 43 are arranged sequentially in that order from the center of the main body of the pipe 10 towards the first end portion 10A. During fastening to another metal oil well pipe 1, the shoulder surface of pin 43 opposes and comes into contact with a shoulder surface of the housing 53 (described later) of the housing 50 of the other metal oil well pipe 1. More specifically, during fastening, the shoulder surface of pin 43 comes into contact with the shoulder surface of the housing 53 as a result of pin 40 being Petition 870250070618, dated 11 / 08 / 2025, pp. 103 / 139 13 / 40 inserted into the 50 housing of the other metal pipe for oil well 1. By this means, during fastening, a high torque can be obtained. In addition, the positional relationship between the 40 pin and the 50 housing in the fastened state can be stabilized.

[0036] Note that the contact surface of pin 400 of pin 40 includes at least the external thread part 41. In other words, the contact surface of pin 400 may include the external thread part 41, and need not include the sealing surface of pin 42 and the shoulder surface of pin 43. The contact surface of pin 400 may include the external thread part 41 and the shoulder surface of pin 43, and need not include the sealing surface of pin 42. The contact surface of pin 400 may include the external thread part 41 and the sealing surface of pin 42, and need not include the shoulder surface of pin 43.

[0037] [Regarding the structure of box 50] Figure 8 is a cross-sectional view of a portion near housing 50 of the wellbore pipe 1 illustrated in Figure 5, which is a cross-sectional view parallel to the axis direction of the wellbore pipe 1. A dashed portion in Figure 8 represents the structure of pin 40 of another wellbore pipe 1 in the case of fastening wellbore pipe 1 to another wellbore pipe 1. Referring to Figure 8, housing 50 includes a contact surface of housing 500 on the inner peripheral surface of the second end portion 10B of the main body of pipe 10. When fastening to another wellbore pipe 1, the contact surface of housing 500 comes into contact with the contact surface of pin 400 of the other wellbore pipe 1 when pin 40 is threaded into housing 50.

[0038] The contact surface of the housing 500 includes at least one internally threaded portion 51 formed on the inner peripheral surface of the second end portion 10B. When fastening, the internally threaded portion 51 is Petition 870250070618, dated 11 / 08 / 2025, pp. 104 / 139 14 / 40 engages with the external threaded part 41 of pin 40 of the other metal oil well pipe.

[0039] The contact surface of housing 500 may further include the sealing surface of housing 52 and the shoulder surface of housing 53. In Figure 8, on the inner peripheral surface of the second end portion 10B, the sealing surface of housing 52 is disposed more on the side of the main body of the tube 10 than the internal threaded part 51. In other words, the sealing surface of housing 52 is disposed between the internal threaded part 51 and the shoulder surface of housing 53. The sealing surface of housing 52 is provided in a conical shape. Specifically, on the sealing surface of housing 52, the inner diameter of housing 50 gradually decreases from the internal threaded part 51 towards the shoulder surface of housing 53 in the longitudinal direction (direction of the tube axis) of the second end portion 10B.

[0040] When fastening to another metal oil well pipe 1, the sealing surface of housing 52 comes into contact with the sealing surface of pin 42 of pin 40 of the other metal oil well pipe 1. More specifically, during fastening, when pin 40 of the other metal oil well pipe 1 is screwed into housing 50, the sealing surface of housing 52 comes into contact with the sealing surface of pin 42, and when pin 40 is screwed in further, the sealing surface of housing 52 comes into close contact with the sealing surface of pin 42. By this means, during fastening, the sealing surface of housing 52 comes into close contact with the sealing surface of pin 42 to form a seal that is based on metal-to-metal contact. Therefore, gas tightness can be increased in each of the metal oil well pipes 1 that are fastened to each other.

[0041] The shoulder surface of housing 53 is positioned further along the main body side of tube 10 than the sealing surface of housing 52. In other words, in housing 50, the shoulder surface of housing 53, the sealing surface of housing 52, and the internal threaded part 51 are positioned Petition 870250070618, dated 11 / 08 / 2025, pp. 105 / 139 15 / 40 sequentially in that order from the center of the main body of the tube 10 towards the front end of the second end portion 10B. When fastening to another metal oil well pipe 1, the shoulder surface of the housing 53 opposes and comes into contact with the shoulder surface of pin 43 of pin 40 of the other metal oil well pipe 1. More specifically, during fastening, the shoulder surface of the housing 53 comes into contact with the shoulder surface of pin 43 as a result of pin 40 of the other metal oil well pipe 1 being inserted into housing 50. By this means, during fastening, a high torque can be obtained. Furthermore, the positional relationship between pin 40 and housing 50 in the fastened state can be stabilized.

[0042] The contact surface of housing 500 includes at least the internal threaded part 51. When fastening, the internal threaded part 51 of the contact surface of housing 500 of housing 50 contacts the external threaded part 41 of the contact surface of pin 400 of pin 40 in such a way that the internal threaded part 51 corresponds with the external threaded part 41. The sealing surface of housing 52 contacts the sealing surface of pin 42 in such a way that the sealing surface of housing 52 corresponds with the sealing surface of pin 42. The shoulder surface of housing 53 contacts the shoulder surface of pin 43 in such a way that the shoulder surface of housing 53 corresponds with the shoulder surface of pin 43.

[0043] In a case where the contact surface of pin 400 includes the external thread part 41 and does not include the sealing surface of pin 42 and the shoulder surface of pin 43, the contact surface of housing 500 includes the internal thread part 51 and does not include the sealing surface of housing 52 and the shoulder surface of housing 53. In a case where the contact surface of pin 400 includes the external thread part 41 and the shoulder surface of pin 43 and does not include the sealing surface of pin 42, the contact surface of housing 500 includes the internal thread part 51 and the shoulder surface of housing 53 and does not Petition 870250070618, dated 11 / 08 / 2025, pp. 106 / 139 16 / 40 includes the housing sealing surface 52. In a case where the contact surface of pin 400 includes the external thread part 41 and the sealing surface of pin 42 and does not include the shoulder surface of pin 43, the contact surface of housing 500 includes the internal thread part 51 and the housing sealing surface 52 and does not include the shoulder surface of housing 53.

[0044] The contact surface of pin 400 may include a plurality of external thread parts 41, may include a plurality of pin sealing surfaces 42, and may include a plurality of pin shoulder surfaces 43. For example, the pin shoulder surface 43, the pin sealing surface 42, the external thread part 41, the pin sealing surface 42, the pin shoulder surface 43, the pin sealing surface 42, and the external thread part 41 may be arranged in that order on the contact surface of pin 400 from the front end of the first end portion 10A towards the center of the main body of the tube 10.In such a case, the internal thread part 51, the sealing surface of the housing 52, the shoulder surface of the housing 53, the sealing surface of the housing 52, the internal thread part 51, the sealing surface of the housing 52 and the shoulder surface of the housing 53 are arranged in that order on the contact surface of the housing 500 of the housing 50 from the front end of the second end portion 10B towards the center of the main body of the tube 10.

[0045] In Figure 7 and Figure 8, a so-called premium joint is illustrated in which pin 40 includes the external thread part 41, the sealing surface of pin 42, and the shoulder surface of pin 43, and housing 50 includes the internal thread part 51, the sealing surface of housing 52, and the shoulder surface of housing 53. However, as described above, pin 40 may include the external thread part 41 and need not include the sealing surface of pin 42 and the shoulder surface of pin 43. In this case, housing 50 includes the internal thread part 51 and does not include the sealing surface of housing 52 and the shoulder surface of housing 53. Figure 9 is a partial cross-sectional view illustrating a longitudinal cross-section of the metal well pipe. Petition 870250070618, dated 11 / 08 / 2025, pp. 107 / 139 17 / 40 oil well pipe of the present embodiment having a configuration different from that in Figure 6. In the metal oil well pipe 1 illustrated in Figure 9, pin 40 includes the external thread part 41 and does not include the sealing surface of pin 42 and the shoulder surface of pin 43. Furthermore, housing 50 includes the internal thread part 51 and does not include the sealing surface of housing 52 and the shoulder surface of housing 53. The metal oil well pipe 1 of the present embodiment may have the structure illustrated in Figure 9.

[0046] [Case in which the metal pipe for oil well 1 is of the integral type] The metal pipe for oil well 1 illustrated in Figure 5, Figure 6, and Figure 9 is a so-called T&C type metal pipe for oil well 1, in which the main body of the pipe 10 includes the pin pipe body 11 and the coupling 12. However, the metal pipe for oil well 1 according to the present embodiment may be an integral type instead of a T&C type.

[0047] Figure 10 is a partial cross-sectional view including a longitudinal cross-section of an integral type oil well metal pipe 1 according to the present embodiment. Referring to Figure 10, the integral type oil well metal pipe 1 includes a main pipe body 10. The main pipe body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is disposed on the opposite side to the second end portion 10B. As described above, in the T&C type oil well metal pipe 1, the main pipe body 10 includes the pin pipe body 11 and the coupling 12. In other words, in the T&C type oil well metal pipe 1, the main pipe body 10 consists of the attachment of two separate members (the pin pipe body 11 and the coupling 12).In contrast, in the integral type 1 metal oil well pipe, the main body of the pipe 10 is formed in an integral manner.

[0048] Pin 40 is formed in the first end portion 10A of the main body of tube 10. When fastening, pin 40 is inserted and Petition 870250070618, dated 11 / 08 / 2025, pages 108 / 139 18 / 40 threaded into the 50 housing of another integral type metal well pipe 1, and thus fixed to the 50 housing of the other integral type metal well pipe 1. The 50 housing is formed in the second end portion 10B of the main body of the pipe 10. When performing the fixing, the 40 pin of another integral type metal well pipe 1 is inserted and threaded into the 50 housing, thus fixing the 50 housing to the 40 pin of the other integral type metal well pipe 1.

[0049] The structure of pin 40 of the integral type oil well metal pipe 1 is the same as the structure of pin 40 of the T&C type oil well metal pipe 1 illustrated in Figure 7. Similarly, the structure of box 50 of the integral type oil well metal pipe 1 is the same as the structure of box 50 of the T&C type oil well metal pipe 1 illustrated in Figure 8. Note that, in Figure 7 and Figure 8, the shoulder surface of pin 43, the sealing surface of pin 42, and the external thread 41 on pin 40 are arranged in that order from the front end of the first end portion 10A towards the center of the main body of the pipe 10. Therefore, the internal thread 51, the sealing surface of box 52, and the shoulder surface of box 53 on box 50 are arranged in that order from the front end of the second end portion 10B towards the center of the main body of the tube 10.However, similarly to the contact surface of pin 400 of pin 40 of the T&C type metal pipe for oil well 1, it is sufficient that the contact surface of pin 400 of pin 40 of the integral type metal pipe for oil well 1 includes at least the external thread part 41. Furthermore, similarly to the contact surface of box 500 of box 50 of the T&C type metal pipe for oil well 1, it is sufficient that the contact surface of box 500 of box 50 of the integral type metal pipe for oil well 1 includes at least the internal thread part 51.

[0050] In summary, the metal pipe for oil well 1 of the present embodiment can be a T&C type or it can be an integral type.

[0051] [About the Zn-Ni alloy coating layer] Petition 870250070618, dated 11 / 08 / 2025, pp. 109 / 139 19 / 40 In the present embodiment of the metallic oil well pipe 1, a Zn-Ni alloy coating layer is formed on at least one contact surface between the contact surface of pin 400 and the contact surface of housing 500. In other words, the ZnNi alloy coating layer can be formed on the contact surface of pin 400, and does not need to be formed on the contact surface of housing 500. Alternatively, the Zn-Ni alloy coating layer can be formed on the contact surface of housing 500, and does not need to be formed on the contact surface of pin 400. Furthermore, the Zn-Ni alloy coating layer can be formed on both the contact surface of pin 400 and the contact surface of housing 500.

[0052] In the following description, the structure on the contact surface of pin 400 in a case where the Zn-Ni alloy coating layer is formed on the contact surface of pin 400, and the structure on the contact surface of housing 500 in a case where the ZnNi alloy coating layer is formed on the contact surface of housing 500 are described.

[0053] [Structure on the contact surface of pin 400 in the case where the Zn-Ni 100 alloy coating layer is formed on the contact surface of pin 400] Figure 11 is a cross-sectional view of the proximity of the contact surface of pin 400 in a case where a Zn-Ni 100 alloy coating layer is formed on the contact surface of pin 400. Referring to Figure 11, the metal pipe for oil well 1 further includes the Zn-Ni 100 alloy coating layer formed on the contact surface of pin 400 of pin 40.

[0054] The Zn-Ni 100 alloy coating layer can be formed on part of the contact surface of pin 400 or it can be formed on the entire contact surface of pin 400. The interfacial pressure increases, in particular, in the final stage of fastening on the sealing surface of the pin. Therefore, in a case where the Zn-Ni 100 alloy coating layer is partially formed on the contact surface of pin 400, the alloy coating layer Petition 870250070618, dated 11 / 08 / 2025, pp. 110 / 139 20 / 40 Zn-Ni 100 is preferably formed at least on the sealing surface of the pin. As mentioned above, the Zn-Ni 100 alloy coating layer can be formed on the entire contact surface of the 400 pin.

[0055] [Structure on the contact surface of the 500 housing in the case where the Zn-Ni 100 alloy coating layer is formed on the contact surface of the 500 housing] Figure 12 is a cross-sectional view of the proximity of the contact surface of the 500 housing in a case where the Zn-Ni 100 alloy coating layer is formed on the contact surface of the 500 housing. Referring to Figure 12, the Zn-Ni 100 alloy coating layer is formed on the contact surface of the 500 housing. The Zn-Ni 100 alloy coating layer may be formed on a portion of the contact surface of the 500 housing or it may be formed on the entire contact surface of the 500 housing. The interfacial pressure increases, in particular, in the final stage of bonding to the sealing surface of the housing. Therefore, in a case where the Zn-Ni 100 alloy coating layer is partially formed on the contact surface of the 500 housing, the Zn-Ni 100 alloy coating layer is preferably formed at least on the sealing surface of the housing.

[0056] [Regarding the Zn-Ni 100 alloy coating layer] As described above, the Zn-Ni 100 alloy coating layer is formed on at least one contact surface between the contact surface of pin 400 and the contact surface of housing 500. The Zn-Ni 100 alloy coating layer can be formed in contact with the contact surface(s) (contact surface of pin 400 and / or contact surface of housing 500). In other words, the Zn-Ni 100 alloy coating layer can be formed directly on the contact surface(s) (contact surface of pin 400 and / or contact surface of housing 500). Alternatively, another coating layer can be formed between the Zn-Ni 100 alloy coating layer and the contact surface(s) (contact surface of pin 400 and / or contact surface of housing 500). Petition 870250070618, dated 11 / 08 / 2025, pp. 111 / 139 21 / 40 another coating layer is, for example, a Ni coating layer.

[0057] The Zn-Ni 100 alloy coating layer is composed of a Zn-Ni alloy. The Zn-Ni alloy contains zinc (Zn) and nickel (Ni). Preferably, the Zn-Ni alloy consists of Zn and Ni, with the remainder being impurities. Here, the term Zn-Ni alloy impurities refers to substances other than Zn and Ni that are contained in the Zn-Ni 100 alloy coating layer during the production and similar processes of the metal pipe for oil wells, and whose contents are within a range that does not influence the effects of the present embodiment.

[0058] The Zn-Ni 100 alloy coating layer contains Zn. Zn is a base metal compared to Fe. Therefore, the Zn-Ni 100 alloy coating layer corrodes with priority over the steel material (sacrificial protection). By this means, the corrosion resistance property of the metal pipe for oil well 1 is improved.

[0059] [Regarding the Ni content and apparent density of the Zn-Ni 100 alloy coating layer] The Ni content in the Zn-Ni 100 alloy coating layer of the present embodiment is within the range of 14.8 to 25.0% by mass. Preferably, the chemical composition of the Zn-Ni 100 alloy coating layer contains Ni in an amount within the range of 14.8 to 25.0% by mass, with the remainder being Zn and impurities. Furthermore, the apparent density of the Zn-Ni 100 alloy coating layer in the present embodiment is 7.00 g / cm³ or more. In a conventional Zn-Ni alloy coating layer, in a case where the Ni content was increased to 14.8% or more, as illustrated in Figure 1, the hardness decreased. However, in the Zn-Ni 100 alloy coating layer of the present embodiment, the apparent density is made 7.00 g / cm³ or more while also making the Ni content a high amount of 14.8% or more. As a result, as illustrated in Figure 4, the hardness of the Zn-Ni 100 alloy coating layer is markedly greater than the hardness of the conventional Zn-Ni alloy coating layer. Petition 870250070618, dated 11 / 08 / 2025, pp. 112 / 139 22 / 40

[0060] If the Ni content in the Zn-Ni 100 alloy coating layer is too low, the hardness of the Zn-Ni 100 alloy coating layer will not be high enough. Conversely, if the Ni content in the Zn-Ni 100 alloy coating layer is too high, a large amount of hydrogen gas will be generated during the formation of the Zn-Ni 100 alloy coating layer. In this case, many porosities will be present in the formed Zn-Ni 100 alloy coating layer, and the apparent density will decrease excessively. As a result, the hardness of the Zn-Ni 100 alloy coating layer will not be sufficiently achieved. Therefore, the Ni content in the Zn-Ni 100 alloy coating layer is within the range of 14.8 to 25.0%.A preferred lower limit for the Ni content in the Zn-Ni 100 alloy coating layer is 15.2%, more preferably 15.5%, more preferably 15.7%, more preferably 16.0%, more preferably 16.2%, more preferably 16.5%, more preferably 17.0%, and even more preferably 17.5%. A preferred upper limit for the Ni content is 24.5%, more preferably 24.0%, and even more preferably 23.5%.

[0061] If the apparent density of the Zn-Ni 100 alloy coating layer is too low, many porosities will be present in the Zn-Ni 100 alloy coating layer. In this case, the hardness of the Zn-Ni 100 alloy coating layer will not be sufficiently obtained. If the apparent density of the Zn-Ni 100 alloy coating layer is 7.00 g / cm3 or more, on the premise that the Ni content is within the range of 14.8 to 25.0%, sufficient hardness will be obtained in the Zn-Ni 100 alloy coating layer. Therefore, the apparent density of the Zn-Ni 100 alloy coating layer is 7.00 g / cm3 or more. A preferred lower limit for the apparent density in the Zn-Ni 100 alloy coating layer is 7.30 g / cm3, more preferably 7.50 g / cm3, even more preferably 7.60 g / cm3, more preferably 7.70 g / cm3, even more preferably 7.80%, and most preferably 7.90 g / cm3. The upper limit for the apparent density is not particularly restricted.However, when the Ni content of the Zn-Ni alloy coating layer is within 100. Petition 870250070618, dated 11 / 08 / 2025, pp. 113 / 139 23 / 40 of the range from 14.8 to 25.0%, the upper limit of apparent density is, for example, 10.00 g / cm3.

[0062] [Method for measuring the chemical composition of the Zn-Ni 100 alloy coating layer] The chemical composition of the Zn-Ni 100 alloy coating layer is measured by the following method. A sample including the Zn-Ni 100 alloy coating layer (sample including the contact surface where the Zn-Ni 100 alloy coating layer is formed) is taken from the metal oil well pipe 1. The Zn-Ni 100 alloy coating layer from the obtained sample is dissolved in 10% hydrochloric acid to obtain a liquid solution. The liquid solution is subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry), and the chemical composition of the Zn-Ni 100 alloy coating layer is obtained. By the above methods, the Ni content (wt%) and Zn content (wt%) in the Zn-Ni 100 alloy coating layer are determined.

[0063] [Method for measuring the apparent density of the Zn-Ni 100 alloy coating layer] The apparent density of the Zn-Ni 100 alloy coating layer is measured by the following method. The Zn-Ni 100 alloy coating layer from the sample mentioned above is dissolved in a 10% hydrochloric acid solution from a predetermined volume to obtain a liquid solution. The liquid solution is subjected to elemental chemical composition analysis by ICP-AES, and the total mass (g) of Ni and Zn in the liquid solution is determined. The total mass of Ni and Zn in the liquid solution is divided by the surface area of ​​the sample (the surface area on which the Zn-Ni 100 alloy coating layer was formed) to determine the coating mass per unit area (g / cm²) of the Zn-Ni 100 alloy coating layer.

[0064] In addition, the thickness of the Zn-Ni 100 alloy coating layer is determined by the following method. Before measuring the chemical composition of the Zn-Ni 100 alloy coating layer of the sample Petition 870250070618, dated 11 / 08 / 2025, pp. 114 / 139 24 / 40 mentioned above, a specimen having a cross-section in the direction of the depth of the Zn-Ni 100 alloy coating layer determined as the observation surface is removed from the sample. The observation surface of the specimen is observed in a backscattered electron (BSE) image at a magnification of 3,000 times using a scanning electron microscope. In the observation in a backscattered electron (BSE) image using a scanning electron microscope (SEM), the base metal (tube) and the Zn-Ni 100 alloy coating layer are easily distinguishable by contrast. On the observation surface, the thickness of the ZnNi 100 alloy coating layer at five arbitrary locations is measured. The arithmetic mean value of the measured thicknesses is defined as the thickness (pm) of the Zn-Ni alloy.The apparent density (g / cm3) of the Zn-Ni 100 alloy coating layer is determined based on the coating mass per unit area (g / cm2) of the Zn-Ni 100 alloy coating layer and the thickness (pm) of the Zn-Ni 100 alloy coating layer.

[0065] [Thickness of Zn-Ni alloy coating layer 100] The thickness of the Zn-Ni 100 alloy coating layer is not particularly limited. For example, the thickness of the Zn-Ni 100 alloy coating layer is within the range of 1 to 20 µm. If the thickness of the Zn-Ni 100 alloy coating layer is 1 µm or more, the resistance to chipping can be further improved. Even if the thickness of the Zn-Ni 100 alloy coating layer is more than 20 µm, the effect mentioned above will be saturated. The lower limit of the thickness of the Zn-Ni 100 alloy coating layer is preferably 3 µm, and more preferably 5 µm. The upper limit of the thickness of the Zn-Ni 100 alloy coating layer is preferably 18 µm, and more preferably 15 µm.

[0066] As described above, in the metallic oil well pipe 1 of the present embodiment, the Ni content in the Zn-Ni 100 alloy coating layer is 14.8 to 25.0% and, furthermore, the apparent density of the layer Petition 870250070618, dated 11 / 08 / 2025, pp. 115 / 139 The hardness of a 25 / 40 Zn-Ni 100 alloy coating is 7.00 g / cm³ or more. Therefore, as illustrated in Figure 4, in the present embodiment, the Vickers hardness of the Zn-Ni 100 alloy coating layer can be increased. The hardness of the coating layer has a positive correlation with the resistance to scoring during tightening and loosening. In other words, the higher the hardness of the coating layer, the greater the resistance to scoring during tightening and loosening. Therefore, the oil well pipe 1 of the present embodiment has excellent resistance to scoring. Furthermore, the Zn-Ni 100 alloy coating layer suppresses corrosion of the steel material through sacrificial protection. Therefore, the oil well pipe 1 of the present embodiment is also excellent in corrosion resistance.

[0067] [Regarding other optional structures of the metal pipe for oil well 1 of the present embodiment] [Regarding chromate coating] The metallic oil well pipe 1 of the present embodiment may also include a chromate 110 coating on the Zn-Ni 100 alloy coating layer. Referring to Figure 13, in a case where the Zn-Ni 100 alloy coating layer is formed on the contact surface of pin 400, the chromate 110 coating may be formed on the Zn-Ni 100 alloy coating layer. Furthermore, referring to Figure 14, in a case where the Zn-Ni 100 alloy coating layer is formed on the contact surface of housing 500, the chromate 110 coating may be formed on the Zn-Ni 100 alloy coating layer.

[0068] In some cases, the metal pipe for oil well 1 will be stored outdoors for a long period before it is actually used at the oil well drilling site. In a case where the metal pipe for oil well 1 is exposed to the atmosphere for a long period outdoors, a chromate coating 110 increases the corrosion resistance of the contact surface of pin 400, and can suppress the occurrence of rust (white rust) on the contact surface of pin 400. The coating of Petition 870250070618, dated 11 / 08 / 2025, pp. 116 / 139 26 / 40 chromate 110 is a coating containing trivalent chromium chromate. Preferably, the chromate 110 coating does not contain hexavalent chromium. The film thickness of the chromate 110 coating is not particularly limited. The film thickness of the chromate 110 coating is, for example, within the range of 10 to 200 nm. A preferred lower limit of the film thickness of the chromate 110 coating is 20 nm, more preferably 30 nm. A preferred upper limit of the film thickness of the chromate 110 coating is 100 nm, more preferably 90 nm.

[0069] [Lubricating coating] The metal pipe for oil wells 1 may also include a lubricating coating on the Zn-Ni alloy coating layer 100, on the chromate coating 110, or on a contact surface where the Zn-Ni alloy coating layer 100 is not formed (on the contact surface of the pin 400 or on the contact surface of the housing 500). The lubricating coating further increases the lubricity of the metal pipe for oil wells 1.

[0070] The lubricating coating may be solid, or it may be in a semi-solid or liquid state. A commercially available lubricant may be used as the lubricating coating. The lubricating coating contains, for example, lubricating particles and a binder. As required, the lubricating coating may contain a solvent and other components.

[0071] Lubricating particles are not particularly limited as long as they are particles having lubricity. Lubricating particles are, for example, one or more types selected from the group consisting of graphite particles, MoS2 (molybdenum disulfide), WS2 (tungsten disulfide), BN (boron nitride), PTFE (polytetrafluoroethylene), CFx (graphite fluoride), and CaCO3 (calcium carbonate).

[0072] The binder, for example, is one or two types selected from the group consisting of an organic binder and an inorganic binder. The organic binder is, for example, one or two types selected Petition 870250070618, dated 11 / 08 / 2025, pp. 117 / 139 27 / 40 of the group consisting of a thermosetting resin and a thermoplastic resin. The thermosetting resin, for example, is one or more types selected from the group consisting of polyethylene resin, polyimide resin, and polyamide-imide resin. The inorganic binder, for example, is one or two types selected from the group consisting of compounds containing alkoxysilane and siloxane linkages.

[0073] An example of a commercially available lubricant is Seal-Guard ECF (trade name) manufactured by Jet-Lube LLC. Other examples of lubricating coatings include a lubricating coating containing resin, metallic soap, wax, or a lubricating powder.

[0074] [Regarding the main body of the 10-piece metal pipe for oil well 1] The chemical composition of the main body of the pipe 10 of the metal pipe for oil well 1 according to the present embodiment is not particularly limited. The main body of the pipe 10 can be formed, for example, from any of carbon steel, stainless steel, an alloy, or similar materials. That is, the metal pipe for oil well 1 can be a steel pipe made of an Fe-based alloy or an alloy pipe represented by a Ni-based alloy pipe. The steel pipe is, for example, a low-alloy pipe, a martensitic stainless steel pipe, and a duplex stainless steel pipe, among others.

[0075] [Method for producing metal pipe for oil well 1] A method for producing the metallic oil well pipe 1 according to the present embodiment is described below. Note that, provided the metallic oil well pipe 1 of the present embodiment has the structure described above, a method for producing the metallic oil well pipe 1 is not limited to the following production method. However, the production method described below is a favorable example for producing the metallic oil well pipe 1 of the present embodiment.

[0076] The method for producing the metal pipe for wells Petition 870250070618, dated 11 / 08 / 2025, pp. 118 / 139 The 28 / 40 petroleum 1 includes a preparation process (S1) for preparing a hollow shell in which the 40 pin or 50 housing is formed, and a process for forming the Zn-Ni alloy coating layer (S2). In the present embodiment, in the process for forming the Zn-Ni alloy coating layer (S2), electrodeposition is carried out using a chloride bath containing nickel ions and a specific concentration of zinc ions as a coating bath. By this means, the Zn-Ni alloy coating layer 100, in which the Ni content is within the range of 14.8 to 25.0% by mass and the apparent density is 7.00 g / cm3 or more, can be formed on the contact surface of the 400 pin and / or on the contact surface of the 500 housing of the metallic oil well pipe 1. Each process of the method for producing the metallic oil well pipe of the present embodiment is described in detail below.

[0077] [Preparation process (S1)] First, a hollow shell in which the pin 40 or the box 50 is formed is prepared. In the present description, the phrase hollow shell in which the pin or box is formed means either the main body of the tube 10 and the body of the pin 11 in a T&C type metal oil well pipe 1 and the main body of the tube 10 in the integral type metal oil well pipe 1.

[0078] The hollow shell in which the 40 pin or 50 box is formed is produced, for example, by the following method. A starting material is produced using cast steel. Specifically, a casting (a block or billet) is produced by a continuous casting process using the cast steel. An ingot may also be produced by an ingot making process using the cast steel. As required, the block or ingot may be subjected to roughing rolling to produce a billet. The starting material (a block or billet) is produced by the process described above. The prepared starting material is subjected to hot working to produce a hollow shell. The hot working method may be punching rolling by means of the Mannesmann process, or it may be an extrusion process. Petition 870250070618, dated 11 / 08 / 2025, pp. 119 / 139 29 / 40 hot. The hollow shell after hot working is subjected to well-known quenching and tempering processes to adjust the strength of the hollow shell. A hollow shell is produced by the above process. Note that, in a case where the metal pipe for oil wells is of the T&C type, a hollow shell for coupling 12 is also prepared. The method for producing the hollow shell for coupling 12 is the same as the method for producing the hollow shell described above.

[0079] In a case where the metal pipe for oil well 1 is of the T&C type, the threading is performed with respect to the outer surface of both end portions of the hollow shell to the body of the pin 11 pipe, to form the pin 40 which includes the contact surface of the pin 400. By means of the above process, a hollow shell (the body of the pin 11 pipe) in which the pin 40 is formed is prepared in a case where the metal pipe for oil well 1 is of the T&C type. Note that, in a case where the metal pipe for oil well is of the T&C type, the coupling 12 can also be prepared. Specifically, the threading is performed with respect to the inner surface of both end portions of the hollow shell to the coupling 12, to form the housing 50 which includes the contact surface of the housing 500. The coupling 12 is produced by the above process.

[0080] In a case where the metal pipe for oil well 1 is of the integral type, threading is performed on the outer surface of the first end portion 10A of the hollow shell to form the pin 40 which includes the contact surface of the pin 400. Furthermore, threading is performed with respect to the inner surface of the second end portion 10B of the hollow shell to form the housing 50 which includes the contact surface of the housing 500. Through the above process, in a case where the metal pipe for oil well 1 is of the integral type, a hollow shell (main body of the pipe 10) in which the pin 40 and the housing 50 are formed is prepared.

[0081] The preparation process (S1) of this modality may also include at least one of a process of Petition 870250070618, dated 11 / 08 / 2025, pages 120 / 139 30 / 40 grinding and a Ni etching coating process.

[0082] In the case of performing a grinding process, a sandblasting treatment, and mechanical grinding finishing are carried out in the grinding process. The surface roughness of the contact surface can be increased by sandblasting treatment. Sandblasting treatment can be performed by a well-known method.

[0083] In the case of performing the Ni attack coating process, a Ni attack coating layer is formed on the surface of the hollow hull in the Ni attack coating process. The Ni attack coating layer is an extremely thin base coating layer, and it increases the adhesion of the ZnNi 100 alloy coating layer that is described later. Note that the coating bath to be used in the Ni attack coating process is not particularly limited, and a well-known bath can be used. Furthermore, the conditions for forming the Ni attack coating layer are not particularly limited, and can be appropriately adjusted and defined.

[0084] Note that, in a case where a Ni attack coating process is carried out, a Ni attack coating layer is formed between the main body of the pipe 10 and the Zn-Ni alloy coating layer 100. On the other hand, the thickness of the Ni attack coating layer formed is negligibly thin compared to the thickness of the Zn-Ni alloy coating layer 100. In other words, in the metallic oil well pipe 1 according to the present embodiment, a Ni attack coating layer can be included within the Zn-Ni alloy coating layer 100.

[0085] [Zn-Ni alloy coating layer formation process (S2)] In the process of forming the ZnNi (S2) alloy coating layer, the Zn-Ni 100 alloy coating layer is formed by Petition 870250070618, dated 11 / 08 / 2025, pp. 121 / 139 31 / 40 electrodeposition on the contact surface of pin 400 of the hollow shell in which pin 40 is formed, or on the contact surface of housing 500 of the hollow shell in which housing 50 is formed.

[0086] In the process of forming the Zn-Ni (S2) alloy coating layer, it is preferable to use a coating bath containing chloride ions (hereinafter referred to as a chloride bath) than to use a coating bath containing sulfate (hereinafter referred to as a sulfate bath). As shown in examples described later, the Zn-Ni 100 alloy coating layer of the present embodiment can be formed by performing electrodeposition within a range satisfying conditions described later using a chloride bath.

[0087] Furthermore, in the coating bath, the Ni ion ratio is adjusted within the range of 50 to 70%. Here, the Ni ion ratio is defined by the following formula. Ni ion ratio = Ni concentration in the coating bath / (Ni concentration in the coating bath + Zn concentration in the coating bath) * 100 A Zn-Ni 100 alloy coating layer in which the Ni content is within the range of 14.8 to 25.0% and the apparent density is 7.00 g / cm3 or more can be formed by adjusting within the electrodeposition conditions described later using a coating bath containing chloride ions and in which the Ni ion ratio is adjusted within the range of 50 to 70%. The type and quantity of supporting electrolyte and various additive agents (brightening agent, etc.) can also affect the coating obtained and are selected appropriately.

[0088] The ratio of Ni ions in the coating bath mentioned above is lower than in a conventional Zn-Ni alloy coating bath. For example, in a commercially available coating bath with the trade name DAIN Zinalloy N-PL manufactured by Daiwa Fine Chemicals Co., Ltd, which is a Zn-Ni alloy coating bath. Petition 870250070618, dated 11 / 08 / 2025, pages 122 / 139 32 / 40 known, the Ni ion ratio is within the range of 75 to 90%, and thus the Ni ion ratio of the coating bath mentioned above is lower. In the present embodiment, as described above, the Zn-Ni 100 alloy coating layer having the structure mentioned above is formed using a coating bath that has a low Ni ion ratio and is a chloride bath. The chloride ion concentration of the coating bath is 215 to 230 g / L.

[0089] The Zn-Ni 100 alloy coating layer is formed by electrodeposition using the coating bath mentioned above. Taking the use of the aforementioned coating bath as a premise, the electrodeposition conditions can be appropriately adjusted according to well-known conditions. The electrodeposition conditions are, for example, a coating bath pH of more than 4.5 and less than 6.0, a coating solution temperature of 10 to 60°C, a current density of 1 to 15 A / dm2, and a treatment time of 0.1 to 30 minutes. If the coating bath pH is outside the above range, sufficient apparent density and sufficient Ni content cannot be obtained. Furthermore, if the current density is too high, sufficient apparent density cannot be obtained in the Zn-Ni alloy coating layer, nor can sufficient Ni content be obtained.It is adjusted that the coating solution and electrodeposition conditions are such that the coating mass and composition of the Zn-Ni 100 alloy coating layer are appropriately obtained within the range that satisfies the conditions mentioned above. In the case of forming the Zn-Ni 100 alloy coating layer on the contact surface of pin 400, the contact surface of pin 400 is immersed in the aforementioned coating bath and electrodeposition is performed. On the other hand, in the case of forming the Zn-Ni 100 alloy coating layer on the contact surface of housing 500, the contact surface of housing 500 is immersed in the aforementioned coating bath and electrodeposition is performed.

[0090] The metal pipe for oil well 1 of the present Petition 870250070618, dated 11 / 08 / 2025, pages 123 / 139 The 33 / 40 model, having the structure described above, is produced by the production processes described above.

[0091] [Other optional processes] In the present embodiment of the method for producing the metallic oil well pipe, at least one process among the following: chromating process, preconditioning treatment process, and film formation process may also be performed. These processes are optional processes. Consequently, these processes do not need to be performed.

[0092] [Chromating process] A chromating process can be carried out as needed. In other words, the chromating process is an optional process. In the case of forming a chromate 110 coating on the Zn-Ni 100 alloy coating layer, a well-known chromating process is carried out after subjecting the Zn-Ni 100 alloy coating layer to pickling following the Zn-Ni (S2) alloy coating layer formation process. In the chromating process, first, a chromating solution is prepared. The chromating solution, for example, contains trivalent chromium ions. The chromating solution can be made to contain trivalent chromium ions by, for example, dissolving chromium(III) chloride and chromium(III) sulfate in it. Preferably, the chromating solution does not contain hexavalent chromium. A commercially available chromating solution can be used for the chromating solution.The commercially available chromating solution is, for example, DAIN Chromate TR-02 (trade name) manufactured by Daiwa Fine Chemicals Co., Ltd. The contact surface (pin contact surface 400 and / or box contact surface 500) on which the Zn-Ni 100 alloy coating layer was formed is immersed in the chromating solution, and chromating is performed to form a chromate 110 coating on the Zn-Ni 100 alloy coating layer.

[0093] [Preconditioning treatment process] As needed, the production method of the present Petition 870250070618, dated 11 / 08 / 2025, pages 124 / 139 34 / 40 embodiment may include a preconditioning treatment process prior to the formation of the Zn-Ni alloy coating layer (S2). In other words, the preconditioning treatment process is an optional process. The preconditioning treatment process includes, for example, pickling and alkaline degreasing. In the preconditioning treatment process, oil or similar substances adhering to the contact surface are washed away. The preconditioning treatment process may also include a grinding process such as sandblasting and / or mechanical grinding finishing. Only one type of these preconditioning treatments may be performed, or a plurality of preconditioning treatments may be performed in combination.

[0094] [Filmmaking process] As needed, the production method of the present embodiment may include carrying out a film-forming process. In other words, the film-forming process is an optional process. In the film-forming process, a lubricating coating is formed on the Zn-Ni 100 alloy coating layer and / or on a contact surface (pin contact surface 400 or housing contact surface 500) where the Zn-Ni 100 alloy coating layer is not formed.

[0095] In the film-forming process, a lubricant or a composition containing the components of the aforementioned lubricating coating is applied. By this means a lubricating coating is formed. The application method is not particularly limited. Examples of application methods include spray coating, brushing, and immersion. When adopting spray coating as the application method, the composition or lubricant can be heated and then sprayed into a state in which the fluidity has been increased. The composition or lubricant is then dried to form a lubricating coating. EXAMPLES

[0096] The advantageous effects of metal pipe for wells Petition 870250070618, dated 11 / 08 / 2025, pages 125 / 139 35 / 40 of the present embodiment are described more specifically below by way of examples. The conditions adopted in the following examples are an example of conditions that are employed to confirm the viability and advantageous effects of the present embodiment of the metal oil well pipe. Consequently, the present embodiment of the metal oil well pipe is not limited to this example of conditions.

[0097] In the present examples, a commercially available cold-rolled steel sheet was used to simulate a metal pipe for an oil well. The dimensions of the cold-rolled steel sheet were a length of 150 mm χ width of 100 mm (the dimensions of the region where the Zn-Ni alloy coating layer was formed were a length of 100 mm χ width of 100 mm). The steel grade was ultra-low carbon steel. The chemical composition of the cold-rolled steel sheet was C: 0.19%, Si: 0.25%, Mn: 0.8%, P: 0.02%, S: 0.01%, Cu: 0.04%, Ni: 0.1%, Cr: 13% and Mo: 0.04%, the remainder being Fe and impurities.

[0098] [Zn-Ni alloy coating layer formation process] A Zn-Ni alloy coating layer was formed by electrodeposition on cold-rolled steel sheets of the respective test numbers. The details of the conditions for forming the Zn-Ni alloy coating layer of the respective test numbers are as follows. For Test Numbers 1 to 7 in Table 1, a sulfate bath was used as the coating bath. Specifically, the coating bath for Test Numbers 1 to 7 contained 0.5 mol / L sodium sulfate. In addition, an ammonium chloride is used as the supporting electrolyte of the coating bath, and a brightening agent and a pH buffer material (e.g., boric acid) are not added. Furthermore, the ratio of Ni ions in the coating bath was changed for each of Test Numbers 1 to 7.

[0099] [Table 1] TABLE 1 Petition 870250070618, dated 11 / 08 / 2025, pages 126 / 139 36 / 40 Test Number Coating Bath Ni Content (% by mass) Apparent Density (g / cm3) Vickers Hardness (Hv) 1 Sulfate Bath 0.0 6.77 109 2 Sulfate Bath 5.5 6.87 156 3 Sulfate Bath 7.9 7.36 277 4 Sulfate Bath 14.2 7.82 435 5 Sulfate Bath 16.6 6.63 392 6 Sulfate Bath 19.2 6.55 368 7 Sulfate Bath 63.3 6.28 114 8 Chloride Bath 10.7 7.59 271 9 Chloride Bath 11.3 8.06 308 10 Chloride Bath 11.4 7.75 305 11 Chloride 11.6 7.59 319 12 Chloride Bath 12.0 7.81 330 13 Chloride Bath 12.3 7.94 396 14 Chloride Bath 12.6 8.01 366 15 Chloride Bath 12.6 8.08 407 16 Chloride Bath 13.2 8.01 414 17 Chloride Bath 14.1 7.99 418 18 Chloride Bath 14.8 8.30 448 19 Chloride Bath 15.5 7.78 438 20 Chloride Bath 16.1 7.86 471 21 Chloride Bath 16.8 7.99 454 22 Chloride Bath 17.4 8.49 476 23 Chloride Bath 18.6 8.71 497 24 Chloride Bath 22.6 7.55 547

[00100] For Test Numbers 8 to 24 in Table 1, a chloride bath was used as the coating bath. Specifically, the coating bath for each of Test Numbers 8 to 24 contained a chloride ion concentration within the range of 215 to 230 g / L. The ratio of Ni ions in the coating bath was altered for each of Test Numbers 8 to 24. Note that for Test Numbers 18 to 24, the ratio of Ni ions in the coating bath was altered within the range of 50 to 70%. For Petition 870250070618, dated 11 / 08 / 2025, pp. 127 / 139 37 / 40 Test Numbers 8 to 17, the ratio of Ni ions in the coating bath was altered within a smaller range than for Test Numbers 18 to 24 (i.e., the ratio of Ni ions was less than 50%).

[00101] Note that it is adjusted so that the pH of the sulfate bath is 2.0 and the pH of the chloride bath is 5.5. The electrodeposition conditions, in addition to the coating bath, were adjusted appropriately within the following ranges: coating solution temperature: 10 to 60°C, current density: 1 to 15 A / dm2 and treatment time from 0.1 to 30 minutes.

[00102] Steel plates in which a Zn-Ni alloy coating layer was formed that simulated a metal pipe for an oil well were produced by the production method above.

[00103] [Assessment tests] [Test to measure the Ni content in the Zn-Ni alloy coating layer] The Ni content in the Zn-Ni alloy coating layer of each test number was measured using the following method. A sample including the Zn-Ni alloy coating layer (including a surface on which the Zn-Ni alloy coating layer 100 was formed) was taken from the steel plate of each test number. The Zn-Ni alloy coating layer from the obtained sample was dissolved in 10% hydrochloric acid, and a liquid solution was obtained. The liquid solution was subjected to ICP-AES, and elemental analysis of the chemical composition was performed to determine the Ni content (% by mass) in the Zn-Ni alloy coating layer. The determined Ni contents are shown in the Ni content (% by mass) column in Table 1.

[00104] [Method for measuring the apparent density of the Zn-Ni alloy coating layer] The apparent density of the Zn-Ni alloy coating layer of each test sample was measured using the following method. The Zn-Ni alloy coating layer of the aforementioned sample was dissolved in acid. Petition 870250070618, dated 11 / 08 / 2025, pp. 128 / 139 38 / 40 hydrochloric acid at a 10% concentration of a predetermined volume, and a liquid solution was obtained. The liquid solution was subjected to elemental chemical composition analysis by ICP-AES, and the total mass (g) of Ni and Zn in the liquid solution was determined. The total mass of Ni and Zn in the liquid solution was divided by the surface area of ​​the sample to determine the coating mass per unit area (g / cm2) of the Zn-Ni alloy coating layer. Furthermore, the thickness of the Zn-Ni alloy coating layer was determined by the following method. Before measuring the chemical composition of the Zn-Ni alloy coating layer of the aforementioned sample, a specimen having a cross-section in the direction of the depth of the Zn-Ni alloy coating layer, determined as the observation surface, was removed from the sample. The observation surface of the specimen was observed in a backscattered electron (BSE) image at a magnification of 3.000 times using a scanning electron microscope. On the observation surface, the thickness of the Zn-Ni alloy coating layer was measured at five arbitrary locations. The arithmetic mean of the measured thicknesses was defined as the thickness (pm) of the Zn-Ni alloy. The apparent density (g / cm3) of the Zn-Ni alloy coating layer was determined based on the coating mass per unit area (g / cm2) of the Zn-Ni alloy coating layer and the thickness (pm) of the Zn-Ni alloy coating layer. The determined apparent densities are shown in the Apparent Density (g / cm3) column in Table 1.

[00105] [Vickers hardness test of Zn-Ni alloy coating layer] The Vickers hardness (Hv) of the Zn-Ni alloy coating layer for each test number was determined by the following method. A sample having a cross-section of the Zn-Ni alloy coating layer was taken. Five arbitrary points (measurement points) on the cross-section of the Zn-Ni alloy coating layer were selected. The Vickers hardness at the selected measurement points was measured in accordance with JIS Z2244. Petition 870250070618, dated 11 / 08 / 2025, pages 129 / 139 39 / 40 (2009). A microhardness tester with the commercial name Fischerscope HM2000 manufactured by Fischer Instruments KK was used for the measurement. The test temperature was set to normal temperature (25°C), and the test force (F) was set to 0.01 N. Among the five measurement results obtained, the arithmetic mean of the measurement results obtained at three points, excluding the highest and lowest values, was defined as the Vickers hardness (Hv) of the Zn-Ni alloy coating layer. The Vickers hardness values ​​obtained are shown in the Vickers Hardness (Hv) column in Table 1.

[00106] [Test results] Referring to Table 1, in Test Numbers 18 to 24 the Ni content of the Zn-Ni alloy coating layer was, in mass %, 14.8% or more and, in addition, the apparent density of the Zn-Ni alloy coating layer was 7.00 g / cm3 or more. Therefore, the Vickers hardness of the respective Zn-Ni alloy coating layers of these test numbers was more than 435 Hv, and thus excellent hardness was obtained. Therefore, the steel sheets of these test numbers could be predicted as having excellent resistance to scoring during clamping and loosening.

[00107] On the other hand, for Test Numbers 1 to 7, a sulfate bath was used as the coating bath. Therefore, in the Zn-Ni alloy coating layers of Test Numbers 1 to 7, the Ni content was less than 14.8% or otherwise the apparent density was less than 7.00 g / cm3. As a result, the Vickers hardness of the Zn-Ni alloy coating layer of each of these test numbers was 435 Hv or less.

[00108] Furthermore, for Test Numbers 8 to 17, although a chloride bath was used as the coating bath, the Ni ion ratio was less than 50%. Therefore, in the Zn-Ni alloy coating layer of each of these test numbers, the Ni content was less than 14.8% and the Vickers hardness was 435 Hv or less.

[00109] One embodiment of the present invention has been described above. However, the previous embodiment is merely an example for Petition 870250070618, dated 11 / 08 / 2025, pp. 130 / 139 40 / 40 to implement the present invention. Consequently, the present invention is not limited to the above embodiment, and the above embodiment may be appropriately modified within a range that does not depart from the spirit of the present invention.

[00110] LIST OF REFERENCE SIGNS Metal Pipe for Oil Well Main Body of the Tube 10A First End Portion 10B Second End Portion Pin External Thread Part Box Internal Thread Part 100 Layer Zn-Ni Alloy Coating 400 Pin Contact Surface 500 Contact Surface of the Box Petition 870250070618, dated 11 / 08 / 2025, pages 131 / 139

Claims

1 / 1 CLAIMS 1. A metallic pipe for an oil well, CHARACTERIZED in that it comprises: a main body of the pipe including a first end portion and a second end portion, wherein the main body of the pipe includes: a pin formed in the first end portion, and a housing formed in the second end portion; the pin includes: a contact surface of the pin including an external thread portion; and the housing includes: a contact surface of the housing including an internal thread portion; the metallic pipe for an oil well further comprising: a Zn-Ni alloy coating layer formed on the contact surface of the pin or on the contact surface of the housing, the Zn-Ni alloy coating layer being composed of a Zn-Ni alloy, wherein the Ni content in the Zn-Ni alloy coating layer is, by mass %, 14.8 to 25.0%, and the apparent density of the Zn-Ni alloy coating layer is 7.00 g / cm3 or more.

2. Metallic pipe for oil well according to claim 1, CHARACTERIZED in that it comprises, in the Zn-Ni alloy coating layer: the Ni content is, by mass %, 17.0% or more. Petition 870250070618, dated 11 / 08 / 2025, pp. 132 / 139

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