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    • 专利摘要:
    threaded pipe joint is a threaded pipe joint comprising a pin 1 and a housing 2 that each have a contact surface that includes a threaded portion 3, 7 and a non-threaded metallic contact portion. the non-threaded metal contact portion includes a sealing surface 5, 8 and a shoulder surface 9, 10, 11, 12. the shoulder surface of the pin is located over the end surface of the pin. a non-contact region 13 in which the pin and the box do not come into contact with each other is present between the sealing surfaces and the shoulder surfaces of the pin and the box. the threaded joint has one or more grooves formed on the shoulder surface of at least one between the pin and the box and which extend to the non-contact region and to the inner part of the threaded joint. at least the contact surface of at least one of the pins and the housing has a solid lubricant coating that exhibits plastic or viscoplastic rheological behavior formed on it. the total volume v (mm3) of the grooves and the coating weight w (g) of the solid lubricant coating satisfy the equation v / w (greater equal) 24 (mm3 / g).
    公开号:BR112014016961B1
    申请号:R112014016961-6
    申请日:2013-01-17
    公开日:2020-09-15
    发明作者:Masahiro Oshima；Shin Ugai；Takashi Okada；Masayoshi Sasaki；Suguru Yamaguchi；Masaaki Sugino
    申请人:Vallourec Oil And Gas France；Nippon Steel Corporation；
    IPC主号:
    专利说明:

    TECHNICAL FIELD
    [0001] This invention relates to a threaded pipe joint (also called a tubular threaded joint) suitable for connecting tubular products intended for the oil industry (oil country tubular goods - OCTG) and which have grooves on the shoulder surface of way to allow a high pressure fluid to escape. Specifically, this refers to a threaded pipe joint that prevents deterioration in the performance of the grooves by means of a solid lubricant coating. BACKGROUND TECHNIQUE
    [0002] In recent years, oil wells are deeper and developed in increasingly harsh environments. For that reason, there is a strong desire that tubular threaded joints that are used to connect oil field tubular goods (OCTG) include tubing and linings for oil or gas wells that increase the compressive strength under internal and external pressures and enhance properties sealing.
    [0003] Figure 1A is a cross-sectional view showing schematically the structure of a typical threaded joint for tubes, Figure 1B is an enlarged schematic cross-sectional view of portion A in Figure 1A and Figure 1C is a partial schematic cross-sectional view of the adjacency of the flange portion of a threaded pipe joint disclosed in Patent Document 1.
    [0004] As shown in Figures 1A to 1C, the tubular threaded joint 0 consists of a pin 1 formed on the outer surface of both ends of steel tubes and a box 2 formed on the inner surface of a coupling which is a separate member. Pin 1 has a threaded portion 3 that has male threads (outer threads) and a flange portion 4 that is a portion closest to the pin end. The flange portion 4 has a sealing surface 5 adjacent to the threaded portion 3 and a shoulder surface 9 on the front end surface of the pin 1. Correspondingly, the housing 2 has a threaded portion 7 which has female threads (threads internal surfaces), a sealing surface 8 and a shoulder surface 11. The threaded portions, sealing surfaces and shoulder surfaces of the pin and housing are contact surfaces of a threaded joint.
    [0005] A threaded joint is designed so that when the male threads and the female threads are tightened until the shoulder surfaces 9 and 11 of the pin and the housing come into contact with each other with a predetermined torque, the surfaces of seals 5 and 8 come in close contact with each other with a predetermined interference to form a metal-to-metal seal that ensures the desired gas tightness of a threaded joint. Before tightening, lubricating fats (typically compound grease) were applied conventionally to the contact surfaces of a threaded joint to prevent skinning of a threaded joint.
    [0006] In the pipe threaded joint shown in Figure 1C, the flange portion 4 of pin 1 extends in the axial direction to form a non-contact region 13 in which the pin and housing do not come into contact with each other and between surfaces seals 5, 8 and the shoulder surfaces 9, 11 of the pin and housing. By extending the flange portion in this manner, the pin has an increased resistance to deformation of the portion that is closer to the front end than the sealing surface. As a result, it is difficult for the sealing surface of the pin to be deformed even under a combined load of pressure and axial force and, through this, it becomes possible to improve the gas firmness of a threaded joint.
    [0007] The illustrated threaded joint has another non-contact region 14 between one or more male threads on pin 1 closest to the sealing surface 5 and the opposite surface of the housing 2. The non-contact region 14 is formed by providing a recess in the surface of the box and functions as a reservoir to collect lubricating fats expelled from the threaded portions that are tightened during the constitution of a threaded joint.
    [0008] In the threaded joint shown in Figure 1C, pin 1 has a second shoulder surface 10 between the shoulder surface 9 and the non-contact surface 13. The second shoulder surface 10 has a greater angle of inclination with respect to a plane perpendicular to the geometric axis of the tube and a smaller radial dimension compared to the shoulder surface 9. The larger and inner shoulder surface 9 is called the main shoulder surface and the smaller, outer shoulder surface 10 is called a surface below the shoulder. Correspondingly, the box 2 has a surface below the shoulder 12 in addition to the shoulder surface 11, which is a main shoulder surface. The main shoulder surfaces 9 and 11 of the pin and the box serve to withstand the compression stress applied during the constitution of a threaded joint and also limit the internal deformation radially of the edge of the flange 4, while the surfaces below the shoulder 10 and 12 they serve to limit the external deformation radially of the main shoulder surfaces when the main shoulder surfaces receive compression stress. As a result, the main shoulder surfaces of the pin and housing can be leveled out in a stable manner.
    [0009] When the sealing surfaces and the shoulder surfaces of the pin and the housing of a threaded joint come into deep contact with the opposite surfaces by constituting the threaded joint, the non-contact region 13, which is located between the sealing surfaces and the shoulder surfaces, it becomes a closed space. Lubricating fats and product fluid that are expelled from the sealing surfaces in close contact and from the shoulder surfaces flow into the closed space of the non-contact region 13 and are confined therein. If the pressure of the confined fluid in the non-contact region 13 becomes high due to an increased amount of the fluid, the non-contact region 13 tends to expand radially due to pressure and there is a possibility of a deterioration in the gas firmness of a threaded joint. which is achieved by intimate contact between the sealing surfaces of the pin and the housing.
    [0010] Then, the threaded joint disclosed in Patent Document 1 has at least one groove that has a depth of at least 0.1 mm on the shoulder surface of at least one between the pin and the box and which functions as a path flow rate for high pressure fluid confined to the non-contact region 13.
    [0011] Figures 2A to 2D are explanatory views showing grooves formed on a shoulder surface of a pin. As shown in this Figure, the groove portions 9a-1 and 9a-2 (which cooperatively form grooves 9a) are formed on the surface below the shoulder 10 and on the main shoulder surface 9, respectively, of a pin 1.
    [0012] Grooves 9a run both the main shoulder surface 9 and the surface below the shoulder 10 of pin 1. Grooves 9a can be formed on the shoulder surface of a box or the portion of grooves 9a can be formed on a surface of pin 1 with the residue that is formed on a shoulder surface of the box 2. Grooves 9a connect the non-contact region 13 with the inside of the tubular threaded joint 0. So even if the fluid confined in the non-contact region 13 produce a high pressure, the high pressure fluid can escape into the tubular threaded joint 0 through the grooves 9a and the state of contact between the sealing surfaces 5 and 8 does not change and thereby maintains the firmness of gas a threaded joint.
    [0013] When executing the constitution of a tubular threaded joint, a liquid lubricating fat that contains a large amount of heavy metals is applied in a conventional manner each time the constitution is carried out. From the point of view of environmental protection and work efficiency, tubular threaded joints that have a surface coated with a solid lubricant coating that does not release pollutants, such as heavy metals, to the surroundings have been developed.
    [0014] Figure 3 is an explanatory view showing the coating structure formed on the surfaces of a tubular threaded joint disclosed in Patent Document 2, which is an example of a tubular threaded joint that has such a solid lubricant coating. In a tubular threaded joint 15 consisting of a pin 1 and a housing 2, the contact surface of the pin 1 has a preparatory surface treatment coating 18 which can be optionally supplied on a steel substrate 17 for the purpose of hardening surface and a solid anti-corrosion coating 19 based on a UV-curable resin. The contact surface of the box 2 has a preparatory surface treatment coating 21 which can optionally be provided on the steel substrate 20 for the purpose of surface hardening and on it a solid lubricant coating 22.
    [0015] The solid lubricant coating 22 is a coating that exhibits plastic or viscoplastic rheological behavior in which the fluidity of the coating varies markedly with pressure. A coating that has such properties may exhibit greater resistance to skinning compared to a solid lubricant coating that does not have the rheological behavior described above (such as a hard coating made of a thermostable resin that contains a lubricating powder). In addition, this type of coating can exhibit a self-repair function due to fluidity, which is increased under pressure. PREVIOUS TECHNICAL DOCUMENTS PATENT DOCUMENTS
    [0016] Patent Document 1 - WO 2009/060729 A
    [0017] Patent Document 2 - WO 2009/072486 A BRIEF DESCRIPTION OF THE INVENTION
    [0018] The tubular threaded joint 0 disclosed in Patent Document 1 is based on using a conventional liquid lubricating fat. In that case, even if the grooves 9a are filled with liquid lubricating fat, the grooves are not blocked due to the fluidity of the fat. In other words, if the pressure of the fluid confined in the non-contact region 13 is high, the fluid can escape into the tubular threaded joint through grooves 9a and the non-contact region 13 is maintained at the same pressure as the interior of a joint threaded.
    [0019] However, if a solid lubricant coating, as disclosed in Patent Document 2, which exhibits plastic or viscoplastic rheological behavior is applied to the tubular threaded joint 0 disclosed in Patent Document 1, at the time of forming a threaded joint, there is a possibility that a portion of the solid lubricant coating is extruded from the shoulder surface that flows into the grooves 9a and thereby causes the grooves 9a to be filled with the solid lubricant coating. If this occurs, due to the fact that the fluidity of the solid lubricant coating is much less than that of liquid lubricating fat, the grooves are blocked and cannot function as a flow path. As a result, the pressure in the non-contact region 13 is increased, which results in a deterioration of the gas firmness of a threaded joint that is achieved by the sealing surfaces.
    [0020] The purpose of the present invention is to provide a threaded gasket for tubes that has a solid lubricant coating that exhibits plastic or viscoplastic rheological behavior formed on the contact surface of at least one of a pin and a box that constitutes the threaded joint and that it has grooves formed on the shoulder surface where the grooves can be prevented from clogging and thereby prevent a decrease in the gas firmness of a threaded joint due to the groove obstruction.
    [0021] The present invention is a threaded joint for tubes comprising a pin and a housing that each has a contact surface that includes a threaded portion and an unthreaded metallic contact portion, wherein the metallic contact portion non-threaded includes a sealing surface and a shoulder surface, where the shoulder surface of the pin is located on the end surface of the pin, the non-contact region in which the pin and the box do not come into contact with each other is present between the sealing surfaces and shoulder surfaces of the pin and case, where the threaded joint has one or more grooves that are formed on the shoulder surface of at least one of the pin and case and extends to the non-contact region and inside a threaded joint, characterized by the fact that:
    [0022] at least the contact surface of at least one member of the pin and the housing has a solid lubricant coating that exhibits plastic or viscoplastic rheological behavior formed on it, and
    [0023] the total volume V (mm3) of the grooves and the coating weight W (g) of the solid lubricant coating satisfy the following equation (1): V / W> 24 (mm3 / g) (1).
    [0024] It is advantageous to form the solid lubricant coating over the entire surface of the pin and / or the housing in order to facilitate the formation of the coating. The surface of a pin or box means the surface facing the other member and which generally extends from the threaded portion to the shoulder surface.
    [0025] In a preferred embodiment of a threaded joint for tubes, the shoulder surfaces of the pin and the housing each have a main shoulder surface and a surface below the shoulder connected to the main shoulder surface. The main shoulder surface has a reverse angle of inclination and extends into a threaded joint and the surface below the shoulder is located between the main shoulder surface and the non-contact region and has an angle of inclination with respect to a plane perpendicular to the geometric axis of the tube that is larger than the main shoulder surface. The opening area (upper end) of the grooves in the shoulder surface or the main shoulder surface is preferably not greater than 40% of the surface area of the shoulder surface or the main shoulder surface.
    [0026] In a threaded joint for pipes, according to the present invention, which has a non-contact region between a sealing surface and a shoulder surface and a groove that functions as a flow path when the pressure of the confined fluid in the non-contact region becomes high, despite the presence of a solid lubricant coating that exhibits plastic or viscoplastic rheological behavior formed on the contact surface of at least one of a pin and a box, in which the groove is prevented from being filled with the lubrication lining, which can lead to groove malfunction as an outflow path. As a result, it is possible to reliably prevent deterioration of the sealing performance and therefore of the gas tightness of a threaded joint due to an excessively increased pressure of the confined fluid in the non-contact region. A threaded pipe joint according to the present invention has improved resistance to skinning and rust-preventing properties since the contact surface has a solid lubricant coating that has a plastic or viscoplastic rheological behavior. BRIEF EXPLANATION OF THE DRAWINGS
    [0027] Figure 1A is a cross-sectional view showing schematically the structure of a typical threaded joint for tubes, Figure 1B is an enlarged schematic cross-sectional view of portion A in Figure 1A and Figure 1C is a partial schematic cross-sectional view in the vicinity of the flange portion of a threaded pipe joint disclosed in Patent Document 1.
    [0028] Figures 2A to 2C are explanatory views showing grooves formed on the main shoulder surface and the surface below the shoulder of a pin and Figure 2D is an enlarged longitudinal cross-sectional view on the edge adjacency between the surface below the shoulder and the main shoulder surface.
    [0029] Figure 3 is an explanatory view showing the coating structure formed on the contact surfaces of a pin and a box.
    [0030] Figure 4 is a graph showing the relationship between the total groove volume and the coating weight of a solid lubricant obtained in a seal test.
    [0031] Figure 5 is a graph showing variations in the contact area of a main shoulder surface as a function of the groove width in a pipe threaded joint disclosed in Patent Document 1 that has two-level shoulder surfaces with grooves formed on it and which have an external diameter of 10-3 / 4 ”(27.3 cm) and a nominal weight of 90.4 kg / m (60.7 pounds / foot).
    [0032] Figure 6 is an explanatory view showing a method of measuring pressure within a non-contact region. WAYS TO CARRY OUT THE INVENTION
    [0033] The present invention will be explained while referring to the attached drawings. A pipe threaded joint has a structure similar to the conventional pipe threaded joint explained while referring to Figures 1A to 1C, Figures 2A to 2D and Figure 3, then, in the following explanation, reference will be made to these Figures.
    [0034] As shown by Figures 1A to 1C, a threaded gasket 30 for tubes, according to the present invention, consists of a pin 1, which is a gasket element that has male or external shanks and a box 2, which it is a joint element that has female or internal threads.
    [0035] As shown in Figure 1A, the typical threaded joints for tubes are of the type of coupling in which a pin 1 is formed on the outer surface of both ends of a steel tube and a box 2 is formed on the inner surface of a coupling, which is a separate member. There are also integral threaded joints that do not use a coupling and in which one end of a steel tube is made of a pin 1 and the other end is made of a box 2. A threaded joint 30 for tubes, according to the present invention , can be of any of these types. In the following explanation, the present invention will be explained in relation to a threaded joint 30 for tubes of the type of coupling shown in Figure 1A.
    [0036] A threaded joint 30 for tubes, according to the present invention, is preferably applied to a steel tube that has a ratio (t / D) of the wall thickness t (mm) to the outside diameter D (mm) at least 0.03 and at most 0.17. An example will be given of the case in which the wall thickness is 9 to 16 mm and the outside diameter is 24.1 (9-1 / 2) to 34.3 (13-1 / 2) centimeters.
    [0037] The pin 1 and the box 2 each have contact surfaces that come into contact with each other when the threaded joint is constituted. The contact surface of pin 1 includes a threaded portion 3 that has male threads and an unthreaded metallic contact portion located closest to the front end of the pin. The portion of the pin that is closer to the front end than the threaded portion 3 is a shoulder portion 4. The non-threaded metal contact portion formed on the shoulder portion 4 of the pin 1 comprises a sealing surface 5 located adjacent to the threaded portion 3 and a shoulder surface (also called a torque shoulder surface) formed on the end surface of pin 1. Correspondingly, housing 2 has a threaded portion 7 which has female threads, a sealing surface 8 and a shoulder surface.
    [0038] With a common main joint, the compressive performance of approximately 40 to 60% of the pipe body yield resistance is required and, in some oil wells, the compressive performance that exceeds 80% is required. Certainly, a compressive load is supported not only by the shoulders, but also by the threaded portions and if threads that have a good ability to sustain a compressive load are used, the load on the shoulders can be reduced to that extent. However, the thickness of the flange portion 4 (the thickness of the pin wall in the middle of the sealing surface 5) is made up of at least 25% and preferably at least 50% of the thickness of the pipe body wall so that the rim portion will have the required compressive strength.
    [0039] The greater the thickness of the sealing surface of the pin, the greater the ability to seal it against external pressure. Then, a chamfer can be formed on the inner surface of the edge of the rim portion in order to prevent turbulence by increasing circularity.
    [0040] The shape of the sealing surfaces 5 and 8 of the pin 1 and the box 2 can be made of a straight line that is inclined in relation to the geometric axis of the joint or a curved line such as a circular arc (the former will be called frustoconical surface and then it will be called a curved rotation surface) or it can be a rotation surface formed by rotating a line segment that is a combination of both lines around the joint geometric axis (in other words, a combination of a frustoconical surface and a curved rotation surface). Preferably, the sealing surface of pin 1 and housing 2 is made of a frustoconical surface and the sealing surface of the other is a curved surface of rotation or a combination of a curved surface of rotation and a frustoconical surface. As a result, the sealing performance of the joint is increased and skinning is difficult to occur.
    [0041] If the angle of inclination of the sealing surfaces 5 and 8 in relation to the geometric axis of the pipe is very steep, it leads to a decrease in the sealing contact pressure over the time of a tension load, while if the inclination is very smooth, it becomes easier for skinning to occur due to an increase in sliding distance. The angle of inclination of the sealing surfaces is in the range of 5 ° to 25 ° and preferably in the range of 10 ° to 20 °. When tapered threads are used, the angle of inclination of the sealing surfaces is greater than the angle of inclination of threads 3, 7. For example, the angle of inclination of the threads is between 1 ° to 5 ° and preferably about 1.6 °.
    [0042] In the illustrated embodiment, as shown in Figure 1C, the shoulder surface of pin 1 has a two-level structure that has a main shoulder surface 9 on the inner side and a surface below the shoulder 10 on the outer side that it is continuous to the main shoulder surface. The main shoulder surface 9 is a reverse shoulder surface that has a reverse tilt angle (backward tilt toward the center of the tube in relation to the direction of pin insertion). Similarly, the shoulder surface of the box 2 also has a two-level structure that has a main shoulder surface 11 and a surface below the shoulder 12.
    [0043] The contact surfaces of the pin and the box, that is, the threaded portions, the sealing surfaces and the shoulder surfaces of the same are designed so that when the pin 1 is inserted into the box 2 and the threads are tightened until the shoulder surfaces come into contact with each other with a predetermined torque, the sealing surfaces intimately contact each other with a predetermined interference to form a metal-to-metal seal. When the shoulder surfaces have a two-tiered structure comprising internal main shoulder surfaces and other surfaces below the shoulder as shown in Figure 1C, thread tightening is performed until the main shoulder surfaces come into contact with each other with a predetermined torque.
    [0044] The angle of inclination θi of the main shoulder surfaces 9, 11 of the pin and the housing in relation to a plane perpendicular to the geometric axis of the tube is less than the angle of inclination θ2 of the surfaces below the shoulder 10, 12. The dimension radial (wall thickness) of the main shoulder surfaces 9, 11 is greater than that of the surfaces below the shoulder 10, 12. As a result, the main shoulder surfaces 9, 11 serve to withstand the compressive stress applied during the formation of a joint threaded and also limit the internal deformation radially of the edge of the rim 4, while the surfaces below the shoulder 10, 12 serve to limit the external deformation radially of the main shoulder surfaces when the main shoulders receive compressive stress.
    [0045] The inclination angle θi of the main shoulder surfaces 9, 11 with respect to a plane perpendicular to the geometric axis of the tube is preferably in the range of 5 ° to 25 ° and more preferably from 10 ° to 20 °. The main shoulder surfaces have a reverse tilt angle, that is, the backward tilt towards the center of the pipe in relation to the direction of pin insertion, while the surfaces below the shoulder tilt back towards the center of the pipe. in relation to the direction of pin insertion. Preferably, the angle of inclination θ2 of the surfaces below the shoulder in relation to a plane perpendicular to the geometric axis of the tube is 60 ° to 85 °, in other words, the inclination of the surfaces below the shoulder at an angle of 5 ° to 30 ° in relative to the pipe axis. The angle of inclination of the surfaces below the shoulder 10, 12 is preferably greater than that of the sealing surfaces 5, 8. The wall thickness of the main shoulder surface 9 of pin 1 is preferably greater than that of the surface below the shoulder 10 by a factor of at least 1.5, more preferably by a factor of at least 2.5 and at most 6 and even more preferably by a factor of at least 3 and at most 5.
    [0046] The junction between the main shoulder surface 9 and the surface below the shoulder 10 of pin 1 preferably forms a rounded apex with a radius of a maximum of 1.5 mm. As a result, the contact area of the main shoulder surface and the surface below the shoulder can be maximized and an increase in compressive strength and suppression of deformation in the radial direction of the shoulder surface is achieved.
    [0047] Details of the shape of a threaded pipe joint are described in Patent Document 1 identified above. As described therein, surfaces below the shoulder 10, 12 sometimes do not come into contact with each other when a threaded joint is formed, but are considered as contact surfaces in the present invention.
    [0048] More specifically, the geometric diametrical interference (difference in diameter measured in a reference plane before tightening the pin and the box) of the surfaces below the shoulder is made at most 1.1 times that of the sealing surfaces and preferably it is made substantially equal to the geometric diametrical interference of the sealing surfaces. The expression “substantially equal” allows a variation of up to 5%.
    [0049] When designing the surfaces below the shoulder 10, 12 of the pin and of the box in such a way that they have almost the same interference as between the sealing surfaces 5, 8 in a normal tightening state, the edge of the entire pin will curve inwardly (decrease in diameter) due to the effect of the interference of the sealing surfaces of the pin and the housing and the surface below the shoulder of the pin will curve inwardly by at least the same amount as the interference of the sealing surfaces, then the contact it will not occur between the surfaces below the pin and box shoulder.
    [0050] However, it is permissible for sub-members 10, 12 to come into contact with each other in a normal tightening state. In this case, the contact pressure of the sub-limbs is made at a maximum of 50% of the contact pressure of the sealing surfaces so that it does not have an adverse effect on the sealing properties.
    [0051] The normal tightening state means that the pin and housing of a threaded joint are tightened to achieve an appropriate tightening touch that is advised by the joint manufacturer according to the shape and material of the joint. In the normal tightening state, the shoulder surfaces (the main shoulder surfaces in the case of a threaded joint according to the present invention) of the pin and housing come into contact with each other with a certain amount of interference without extensive plastic deformation or total income.
    [0052] The present invention can be applied to a threaded joint for tubes in which each of the shoulder surfaces of the pin and the box have no surface below the shoulder and are constituted by a single main shoulder surface.
    [0053] A threaded joint for tube 30, according to the present invention, has a non-contact region 13 between the sealing surfaces 5, 8 and the shoulder surfaces (in the case of a two-level shoulder structure, the surfaces below the shoulder that are closest to the sealing surfaces) of the pin and the box and also have one or more grooves formed on the shoulder surface of at least one of the pin and the box and extending to the non-contact region 13 and to the inside of a threaded joint 30 (the inner end of the shoulder). When the shoulder surfaces of the pin and the box have a two-level structure, as shown in Figures 2A to 2C, for a shoulder surface of the pin, where the groove consists of a portion of groove 9a-1 formed on the outer surface below shoulder 10 (hereinafter called an outer groove portion 9a-1) and over a groove portion 9a-2 formed on the inner main shoulder surface 9 (hereinafter called an inner groove portion 9a-2) that are connected to each other. The groove made up of these two groove portions is called a 9a groove.
    [0054] The length of the non-contact region 13 in the axial direction is selected in order to make it possible to achieve the objective mentioned above that the resistance to deformation of the sealing surfaces is increased. In the case of a pipe size that is used for oilfield tubular goods (OCTG) (in the range of 50 to 550 mm in the outer diameter), the axial length (longitudinal length) of the non-contact region 13 is preferably in the fence range from 4 to 20 mm. When the shoulder surfaces have the structure mentioned above two levels, taking into account the fact that the surfaces below the shoulder may not come into contact with each other, it is preferable that the total axial length of the non-contact region 13 and of the surface below the shoulder 10, 12 is in the range of 4 to 20 mm. The dimension in the radial direction (perpendicular to the axial direction) of the non-contact region 13 is preferably 0.1 mm to 1 mm.
    [0055] In the illustrated modality, the non-contact region 13 consists of tapered surfaces of the pin and the box. In this case, the surface of that region of the box acts as a guide when the pin is inserted into the box, through which the sealing surfaces of the pin and the box can be brought into contact in a stable manner, which leads to an improvement in sealing performance and skin resistance. The angle of inclination of the tapered surfaces that forms the non-contact region in relation to the axial direction is preferably less than 10 ° and is less than the angle of inclination of the sealing surfaces. The surfaces of the pin and housing that form the non-contact region 13 can be cylindrical surfaces that are parallel to the axial direction of the tube. By employing this shape, the thickness of the pin shoulder wall can be increased within the limited wall thickness of the steel tube and thereby increases the compressive strength of a threaded joint.
    [0056] In the illustrated embodiment, groove 9a is formed on the shoulder surface of a pin. However, it can be formed on the shoulder surface of a box or a portion of the groove 9a (for example, a portion of groove 9a-1 on the surface below the shoulder) can be formed in a box and the residue (for example, a groove portion 9a-2 on the main shoulder surface) can be formed into a pin. Groove 9a provides communication between the non-contact region 13 and the interior of the tubular threaded joint 0. So, even if the fluid pressure in the non-contact region 13 becomes high, the high pressure fluid can escape into the threaded joint. tubular 0 through groove 9a. In the illustrated embodiment, the groove portions 9a-1 and 9a-2 run helically (diagonally) on the shoulder surface.
    [0057] In order to achieve the function described above, when the shoulder surface of the pin and housing each have a main shoulder surface and a surface below the shoulder, the outer groove portion 9a-1 formed on the surface below the shoulder and the internal groove portion 9a-2 formed on the main shoulder surface must communicate with each other. For this purpose, as shown in Figure 2D, a depression 9c can be provided to form a connecting channel in the circumferential direction of the last shoulder portion of box 2 that opposes apex 9b of the shoulder surfaces 9 and 10 of pin 1 ( the portion connects the main shoulder surface 9 and the surface below the shoulder 10 of the pin 1) at least from a point that opposes the inner end of the outer groove portion 9a-1 to a point that opposes the outer end of the portion internal groove 9a-2 (as shown by steep lines in Figure 2B). In this way, the groove portions 9a-1 and 9a-2 are connected through the depression 9c provided in the box next to the apex 9b of the pin. Alternatively, a connecting channel between the groove portions 9a-1 and 9a-2 can be reached by forming a chamfer or a depression near the apex 9b at least from the inner end of the outer groove portion 9a-1 to the outer end of the internal groove portion 9a-2. A connection channel can be formed around the entire circumference. In order to avoid obstruction, the connecting channel preferably has a cross-sectional area that is at least twice and more preferably at least three times the cross-sectional area of the groove portions 9a-1 and 9a-2.
    [0058] As shown in Figure 2C, the outer groove portion 9a-1 and the inner groove portion 9a-2 can be connected directly to the inner end of the outer groove portion 9a-1 adjacent to the outer end of the internal groove 9a-2. This arrangement makes it unnecessary to form a connection channel like the one described above, but as shown in Figure 2A, when providing the internal and external groove portions 9a-1 and 9a-2 in the same position in the circumferential direction, it takes the groove cut (formation grooves), in a way, easier. In both cases, cutting the groove portions 9a-1 and 9a-2 can be performed by using an NC lathe (numerical control) system, for example.
    [0059] In another embodiment of the invention, the outer groove portion 9a-1 and the inner groove portion 9a-2 do not extend diagonally as shown in Figures 2A to 2C, but extend in the radial direction and preferably both groove portions that extend in the radial direction are directly connected to each other. In this way, the length of each groove portion is minimized, the fluid can escape easily and the groove cut can be performed without using an NC atom. However, it is necessary to use a special groove cutter.
    [0060] In the mode shown in Figures 2B and 2C, in order to ensure communication between the non-contact region 13 and the interior of the tubular threaded joint, groove 9a is provided in three locations equally spaced in the circumferential direction. It is sufficient that groove 9a is provided in at least one location and there is no particular upper limit on the number of locations in groove 9a, but generally 8 or less locations are sufficient. Pin 1 preferably has 2 to 4 such grooves 9a.
    [0061] There is no particular limitation in the cross-sectional shape of groove 9a, but it must have an area in cross-section so that the fluid can pass through. The depth of each groove 9a is at least 0.1 mm and preferably at least 0.2 mm. In order to prevent a marked decrease in the performance of a compression threaded joint due to a decrease in the contact surface area of the main shoulder surface 9 caused by the formation of grooves 9a, the length in the circumferential direction of the internal groove portion 9a- 1 and the outer groove portion 9a-2 is preferably such that each of the groove portions 9a-1 and 9a-2 extends a maximum of 180 ° around the perimeter of the shoulder surface. For example, as shown in Figure 2B or 2C, in the case where 3 groove portions 9a-1 and 9a-2 are provided on the main shoulder surface 9 and on the surface below the shoulder 10, respectively, each portion of groove 9a- 1 and 9a-2 preferably have a length next to a circular arc that measures at most 180 ° and more preferably at most 120 °.
    [0062] As stated above, the threaded portions 3 and 7, the sealing surfaces 5 and 8 and the shoulder surfaces 9, 10 and 11, 12 of pin 1 and box 2, respectively, constitute the contact surfaces of a threaded joint 30 for tubes. The threaded joint is required to have properties such as skinning resistance, gas firmness and corrosion resistance. For this purpose, in the past, lubricating fats, such as compound grease, containing heavy metal powder have been applied to the contact surface of at least one of the pin and housing before each time a threaded joint is formed. fulfilled. However, this application had problems from the point of view of environmental protection and work efficiency.
    [0063] As shown in Figure 3, a threaded pipe joint according to the present invention has a solid lubricant coating 22 that exhibits plastic or viscoplastic rheological behavior on at least the contact surface of at least one of pin 1 and the housing 2. A coating that exhibits such rheological behavior does not flow under atmospheric pressure, but can flow under high pressure. In other words, the fluidity of the coating varies markedly depending on the pressure. As a result, it is possible to impart improved peeling resistance, gas firmness and corrosion resistance to the threaded joint and thereby make it possible to perform the joint construction without the application of lubricating greases and protect the surface of a threaded joint from rust.
    [0064] A solid lubricant coating means a coating that is solid at room temperature and specifically means that a coating is solid at 40 ° C or below. The term plastic as used in this document means the property of a material that produces a permanent deformation regardless of the time when it receives stress. The term viscoplastic means the property of a material that produces a permanent deformation that depends on the time when it receives a stress. A solid lubricant coating that exhibits plastic or viscoplastic rheological behavior exhibits behavior that the fluidity of the coating varies significantly depending on the pressure while in a solid state.
    [0065] In the embodiment shown in Figure 3, the surface of the pin 1 has a preparatory surface treatment coating 18 for surface hardening on the steel substrate 17 and a solid anticorrosive coating 19 and the surface of the box 2 has a coating of preparatory surface treatment 21 on the steel substrate 20 for surface hardening and a solid lubricant coating 22. In order to make the drawings easier to interpret, solid lubricant coating 22 and other coatings are omitted from Figures 1 and 2.
    [0066] The solid lubricant coating 22 can be formed on a surface of one of the pin and housing as shown in Figure 3. In that case, the coating that is formed on a surface of the other member is not limited to a solid anti-corrosion coating and it can be a solid lubricant coating that does not exhibit plastic or viscoplastic rheological behavior (for example, a coating that contains a solid lubricant dispersed in a thermostable resin, such as an epoxy resin). Alternatively, on a surface of the other member, no coating can be formed or only a preparatory surface treatment coating can be formed. Generally, a solid lubricating coating, a solid anticorrosive coating and a preparatory surface treatment coating are formed on the entire surface of the pin or housing, but such a coating can be omitted from the surface portion other than the contact surface (such as the portion of the non-contact region 13).
    [0067] Below, the various coatings shown in Figure 3 will be explained. PREPARATORY SURFACE TREATMENT
    [0068] The contact surfaces of pin 1 and housing 2 of a threaded joint 30 (the threaded portions, the sealing surfaces and the shoulder surfaces) are formed by cutting operations that include thread cutting and surface roughness. it is usually around 3 to 5 pm. If the surface roughness of the contact surfaces is made greater than this, the adhesion of the coating that is formed at the top can be increased and, as a result, properties such as skinning resistance and corrosion resistance can be improved. For this reason, the preparatory surface treatment that can increase the surface roughness is preferably carried out before the formation of a coating on the contact surfaces of at least one and preferably both of the pin 1 and the box 2.
    [0069] One type of such a preparatory surface treatment is the formation of a preparatory coating 18, 21 which has an increased surface roughness. This formation can be carried out by chemical conversion treatments such as phosphate treatment, oxalate treatment or borate treatment that form a coating of acicular crystals that increase surface roughness or by dynamized iron spheres coated with zinc or a zinc alloy to form a coating based on porous zinc.
    [0070] Other types of preparatory surface treatment include dynamized grain or dose treatment and pickling. These treatments can increase the surface roughness of the substrate by itself and no preparatory surface treatment coating is formed.
    [0071] Although it has no surface hardening effect, metal plating capable of increasing the adhesion of a solid lubricant coating or a solid anticorrosive coating can be used as a preparatory surface treatment. Metal plating can be multi-layered plating that forms two or more layers.
    [0072] The preparatory surface treatment generally forms a coating that has a uniform thickness on a threaded joint surface and the shape of the groove 9a is substantially maintained after the preparatory surface treatment. SOLID ANTICORROSIVE COATING
    [0073] A solid anti-corrosion coating has the requirements that are not easily destroyed under the applied force when a protector is installed to protect the contact surface of a pin or a box until the operation in place for the constitution of a threaded joint, that does not dissolve when exposed to condensed water during transport or storage and that does not soften easily even at high temperatures that exceed 40 ° C.
    [0074] A solid anticorrosive coating that has such properties can be formed from a thermostable resin, but is preferably a coating of a UV curable resin. Due to the fact that a UV curable resin coating is generally highly transparent, it is preferably formed on the contact surface of a pin. The pin that is typically formed on the outer surface of the ends of a steel tube is more susceptible to damage than the box during transport. Then, at the time of constitution, the surface of the pin and particularly the surface of the threaded portion of it is often controlled by visual inspection for the presence or absence of damage. A UV curable resin coating does not obstruct such visual inspection and makes it possible to inspect the top of the coating without removing it.
    [0075] The thickness of a solid anticorrosive coating is generally in the range of 5 to 50 pm and preferably in the range of 10 to 30 pm. The solid anti-corrosion coating is generally uniformly formed on a threaded joint surface that includes a groove and threaded portion and has strong adhesion in order to protect the surface of a threaded joint during transport and storage. Therefore, there is a small possibility of filling the previously mentioned grooves 9a on the shoulder surface and inhibiting the function of the grooves as a flow path.
    [0076] In addition, details of a UV curable resin coating are found in Patent Document 2 identified above. SOLID LUBRICATION COATING
    [0077] In the present invention, a solid lubricant coating that exhibits plastic or viscoplastic rheological behavior and is capable of supporting with improved peeling resistance, gas firmness and rust preventing properties to a threaded pipe joint is formed on the surface of contact of at least one between the pin and the box. When a UV curable resin coating is formed on the contact surface of the pin as a solid anti-corrosion coating as mentioned above, the solid lubricant coating is formed on the contact surface of the housing. Although the solid lubricant coating exhibiting plastic or viscoplastic rheological behavior is explained in detail in Patent Document 2, a brief explanation is given below.
    [0078] This type of solid lubricant coating is typically a coating that contains a small amount of a solid lubricant dispersed in a matrix that exhibits plastic or viscoplastic rheological behavior. A preferred solid lubricant coating comprises 70 to 95% by weight of a matrix and 5 to 30% by weight of a solid lubricant. Since the proportion of the solid lubricant is small, the coating as a whole exhibits the plastic or viscoplastic rheological behavior characteristic of the matrix.
    [0079] The die preferably has a casting time in the range of 80 to 320 ° C. As a result, it is possible to form a solid lubricant coating by spray coating a melted composition at a temperature of at least the casting time of the matrix. that uses a regular spray gun. The matrix preferably comprises a thermoplastic polymer, a wax and a metal soap and more preferably additionally contains a corrosion inhibitor and a water-insoluble liquid resin.
    [0080] The thermoplastic polymer that is used in the matrix is preferably polyethylene. Polyethylene has a relatively low melting time, so that the hot melt spray coating can be carried out at a temperature of 150 ° C or below and the coating that is formed has excellent lubricating properties.
    [0081] Metal soap is a soap with a higher fatty acid (a fatty acid that has at least 12 carbon atoms) and a metal, except an alkali metal. The metal soap provides the effect of capturing fragments that develop in the time of constitution or escape of a threaded joint and suppresses their release to the external environment. In addition, it has the effect of increasing the lubricity of the coating by decreasing the coefficient of friction and also has a corrosion inhibiting effect. The preferred metal soaps are zinc stearate and calcium stearate.
    [0082] The wax performs functions similar to those performed by a metal soap. Consequently, it is possible to contain only one of a metal soap and a wax in the solid lubricant coating, but it is preferred that the solid lubricant coating contains both a metal soap and a wax due to the fact that containing both improves the lubricating properties of the coating. A wax has a low melting time and therefore has the advantage of decreasing the melting time of the coating composition and, consequently, the temperature for spray coating. The wax can be any of animal, vegetable, mineral and synthetic waxes. One preferred wax in particular is carnauba wax.
    [0083] The mass ratio of wax to metal soap is preferably in the range of 0.5 to 3 parts of wax in relation to one part of metal soap. This mass ratio is more preferably 0.5 to 2 and even more preferably approximately 1.
    [0084] Corrosion inhibitors of the type that have been added conventionally as corrosion inhibitors for lubricating oils are preferred due to the fact that they have excellent lubricating properties. Representative examples of this type of corrosion inhibitor include a calcium sulfonate derivative marketed by The Lubrizol Corporation under the trade name Alox ™ 606, a zinc phosphosilicate and strontium marketed by Halox under the trade name Halox ™ SZP-391 and NA-SUL ™ Ca / W1935 manufactured by King Industries, Inc. The presence of a corrosion inhibitor in the solid lubricant coating makes it possible to prevent corrosion of the contact surfaces to a certain extent only by the solid lubricant coating even if a solid anti-corrosion coating is not formed at the top. For this purpose, the solid lubricant coating preferably contains at least 5% by weight of a corrosion inhibitor.
    [0085] The water-insoluble liquid resin (a resin that is liquid at room temperature) increases the fluidity of the coating composition in a molten state and thereby reduces problems during the spray coating. If present in a small amount, the liquid resin does not adhere to the resulting solid lubricant coating. Preferred liquid resins are selected from a poly (methyl methacrylate), polybutene, polysobutene and a polyalkylasiloxane (liquid silicone resins, such as polydimethylsiloxane). Liquid polydialkylsiloxanes also function as a surfactant.
    [0086] In addition to the components described above, the matrix may contain small amounts of other additives selected from surfactants, dyes, antioxidants and the like. The matrix may also contain an extreme pressure agent, liquid lubricant or the like in an extremely small amount of a maximum of 2% by mass.
    [0087] An example of a preferred composition (% by mass) of the solid lubricant coating matrix is as follows:
    [0088] 5 to 40% of a thermoplastic polymer,
    [0089] 5 to 30% of a wax,
    [0090] 5 to 30% of a metal soap,
    [0091] 0 to 50% of a corrosion inhibitor,
    [0092] 0 to 17% of a water-insoluble liquid resin,
    [0093] 0 to 2% of each of a surfactant, a dye and an antioxidant, and
    [0094] 0 to 2% of each of an extreme pressure agent and a liquid lubricant.
    [0095] For each component, two or more materials can be used.
    [0096] An example of a more specific composition (% by mass) of the matrix of a preferred solid lubricant coating is as follows:
    [0097] 5 to 40% of a polyethylene homopolymer,
    [0098] 5 to 30% carnauba wax,
    [0099] 5 to 30% zinc stearate,
    [0100] 5 to 50% of a corrosion inhibitor,
    [0101] 0 to 15% of a poly (methyl methacrylate),
    [0102] 0 to 2% poly (dimethylsiloxane),
    [0103] 0 to 2% of a dye, and
    [0104] 0 to 1% of an antioxidant.
    [0105] A solid lubricant that is dispensed in the matrix means a powder that has lubricating properties. Preferably one or more solid lubricants selected from graphite, zinc oxide, boron nitrate, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfide, bismuth sulfide, polytetrafluoroethylene (PTFE) and polyamides can be used.
    [0106] In addition to a solid lubricant, the solid lubricant coating may contain an inorganic powder to adjust sliding properties. Examples of such an inorganic powder are tungsten disulfide and bismuth oxide. The inorganic powder can be contained in the solid lubricant coating in an amount of up to 20% by mass.
    [0107] The solid lubricant coating is preferably formed by the hot melt method. This method is accomplished by heating a coating composition (which contains the matrix described above and a powder of a solid lubricant) to melt the matrix and spray the composition in a molten state from a spray gun that has an ability to hold temperature. The heating temperature of the composition is preferably a temperature that is 10 to 50 ° C higher than the casting time of the matrix.
    [0108] The substrate that is coated (such as the contact surface of a box) is preferably preheated to a temperature higher than the casting time of the matrix. When preheating is performed, a good coating can be obtained. Alternatively, when the coating composition contains a small amount (such as a maximum of 2% by mass) of a surfactant such as polydimethylsiloxane, it is possible to form a good coating without preheating the substrate or by preheating to a temperature less than the casting time of the matrix.
    [0109] The coating composition is melted when heated in a tank equipped with a suitable stirring device and the melted composition is supplied by a spray head compressor (which is maintained at a predetermined temperature) from a spray gun through a metering pump and sprinkled on the substrate. The temperature which is kept inside the tank and the spray head is adjusted according to the casting time of the composition matrix.
    [0110] The coating thickness of the solid lubricant coating is preferably in the range of 10 to 150 pm and more preferably in the range of 25 to 80 pm. If the coating thickness of the solid lubricant coating is very small, the lubricating properties of a threaded pipe joint certainly become inadequate and skinning occurs easily in the time of constitution or leakage. In addition, although the solid lubricant coating has a degree of corrosion resistance, if the coating thickness is very small, the corrosion resistance becomes inadequate. Making the coating thickness of the solid lubricant coating too large not only wastes the lubricant, but goes against environmental pollution. In addition, the slip sometimes occurs at the time of constitution and constitution can become difficult. In the present invention, the coating thickness of the solid lubricant coating is limited to satisfy the equation described above (1).
    [0111] When both the solid lubricant coating and the anti-corrosion coating are formed on top of a contact surface that has an increased surface roughness as a result of a preparatory surface treatment, the coating thickness is preferably greater than the roughness Rz of the substrate. If this is not the case, the coating sometimes cannot completely cover the substrate. The coating thickness when the substrate is rough is the average value of the coating thickness of the entire coating, which can be calculated from the area, mass and density of the coating.
    [0112] A threaded pipe joint according to the present invention satisfies the relationship between the total volume V (mm3) of the grooves 9a and the coating weight W (g) of the solid lubricant coating 22 given by the following equation (1), preferably given by the following equation (T) and more preferably given by the following equation (1 ”): V / W ≥ 24 (mm3 / g)  (1) V / W ≥ 25 (mm3 / g)   (1 ') V / W ≥ 28 (mm3 / g)  (1 ”).
    [0113] The total volume V of the grooves is the total volume of the grooves 9a (groove portions 9a-1 and 9a-2 in the case of grooves having a two-level structure) formed on the shoulder surfaces of the pin and the box and when there are two or more grooves, it is the sum of the volumes of all the grooves. When there are plural grooves that have the same shape, the total volume of the grooves can be determined by the equation: (cross-sectional area of a groove) x (length of a groove) x (number of grooves).
    [0114] The coating weight W of the solid lubricant coating is the mass quantity of the solid lubricant coating deposited on the surfaces of a threaded joint, in other words, the opposite surfaces of the pin and its housing. When both the pin and the housing have a solid lubricating coating, the coating weight is the sum of the coating weight of the pin and housing. In other words, the coating weight of the solid lubricant coating is the amount per threaded joint. The coating weight of the solid lubricant coating per threaded joint can be determined by preparing a dummy sample of a threaded joint of the same size when using a lightweight material such as paper, for example, when applying the same coating composition to the sample dummy under the same conditions as used to form the solid lubricant coating on the actual threaded joint and calculate the weight difference of the dummy sample before and after application.
    [0115] In a threaded pipe joint according to the present invention, the solid lubricant coating formed on a contact surface of the same flows under the heavy stress applied at the time of constitution due to the viscoplastic or plastic nature and a considerable portion of the coating solid lubricant on the sealing surface and the shoulder surface is forced into the surroundings. Part of the dislodged solid lubricant coating enters the non-contact region 13. If the pressure of the fluid entering the non-contact region 13 becomes high, there is a possibility that the gas tightness of a threaded joint achieved by the sealing surfaces may be decreased. In order to eliminate this possibility, a groove 9a that communicates with the non-contact region 13 is formed on the shoulder surface and functions as a flow path.
    [0116] However, if the coating weight of the solid lubricant coating is too large, the solid lubricant coating fills in the groove 9a formed on the shoulder surface. Since the heavy stress produced by the constitution is not applied to the interior of the groove 9a, the solid lubricating coating on the groove can hardly flow. Then, the groove becomes clogged with the solid lubricant coating and may no longer function as a flow path, which leads to the blockage of the non-contact region. As a result, a high pressure fluid is confined to the non-contact region 13, which leads to a deterioration in the gas firmness of a threaded joint.
    [0117] Figure 4 is a graph showing the relationship between the total volume of the grooves 9a and the coating weight of the solid lubricant on a threaded joint obtained in a seal test which is explained in the example. In this Figure, NG indicates that the non-contact region block occurs and OK indicates no such block occurrence.
    [0118] As shown in the graph in Figure 4, as the total groove volume increases, the maximum coating weight of the solid lubricant coating, in which the occurrence of blockage of the non-contact region is avoided, increases. It can be seen from this graph that blocking the non-contact region 13 due to the obstruction of the grooves 9a can be prevented if the total volume of the grooves 9a and the coating weight of the solid lubricant coating satisfy the above formula (1). Even if the solid lubricant coating not formed on the surface in the non-contact regions 13, 14, due to the proportion in the area of these regions that is very limited between the total surface area of a threaded joint, the satisfaction of the above formula (1) is enough to prevent a high pressure fluid from being confined to the non-contact region 13.
    [0119] The volume of a groove depends on the width of the opening at the upper end (groove width), the depth and the cross-sectional shape. In the case of a V-shaped groove, the width and depth of a groove depends on the tip angle of a cutting tool used in groove cutting. Then, when the requested coating weight provides a threaded joint with the desired peeling strength and rust preventing properties are known, the shape of a groove (the groove cut angle, the width, depth and length of a groove) and the number of grooves can be determined to satisfy the above equation (1).
    [0120] As the total volume of grooves 9a is increased, the contact area of the shoulder surfaces (the area of the shoulder surfaces that come into contact with each other) necessarily decreases due to the fact that the grooves do not come into contact with the opposite surface. Due to the fact that the shoulder surfaces (the main shoulder surfaces in the case of the two-level structure described above) provide torque performance (performs the function of supporting torque and compressive load), an excessive decrease in the area of contact of the shoulder surfaces results in a deterioration in torque performance.
    [0121] Figure 5 is a graph showing the relationship between the groove width (mm) and the area fraction of the contact area of a main shoulder surface in a threaded pipe joint revealed in Patent Document 1 that has two-level shoulder surfaces with three grooves 9a formed on it and having an outside diameter of 10-3 / 4 ”(27.3 cm) and a nominal weight of 90.4 kg / m (60.7 pounds / foot), which is an indicator of the wall thickness.
    [0122] It has been revealed that in order to guarantee the requested torque performance for the main shoulder surfaces, it is desirable that the area fraction of the contact area is at least 60%, in other words, that the fraction of the occupied area through the openings in the upper ends of the grooves 91 on the main shoulder surface in which the grooves are formed is less than 40%. As can be seen from Figure 5, in the case of a threaded pipe joint that has the shape mentioned above, if the width of the grooves 9a-1 is 3.6 mm or less, the fraction of the area of the contact area of the main shoulder surfaces is at least 60%. For a threaded pipe joint that has a different shape, the upper limit for the groove width can be determined in the same way. In the case of a threaded joint that does not have a two-level structure, the fraction of the area occupied by the groove or groove openings in the entire shoulder surface is preferably less than 40%.
    [0123] The following example is intended to illustrate the present invention without limiting it. EXAMPLE
    [0124] A sealing test (a test in which an internal pressure and an external pressure are applied to a threaded joint while a tension load and a compressive load are applied to it) was performed when using threaded joints for tubes that have the dimensions shown in Table 1. The threaded joints have the shape shown in Figures 1A to 1C and Figures 2A and 2B with grooves 9a formed on the shoulder surfaces that have the width and depth shown in Table 1.
    [0125] Pin 1 and box 2 of each of a threaded joint for tubes that were tested had contact surfaces made up of 3,7 threaded portions, sealing surfaces 5, 8 and shoulder surfaces and formed a non-contact region 13 between the sealing surfaces and the shoulder surfaces. The axial length of the sealing surfaces was 3 to 5 mm and that of the non-contact region was 5 to 15 mm. As shown in Figure 1C, the shoulder surfaces had main shoulder surfaces 9, 11 and surfaces below the shoulder 10, 12. The radial thickness (in the direction perpendicular to the geometric axis of the tube) of the main shoulders was 2 to 6 times that that of the sub-members. The angle of inclination θ2 of the surfaces below the shoulder was 65 to 75 ° and the angle of inclination θi of the main shoulder surfaces was 10 to 20 ° in relation to a plane perpendicular to the geometric axis of the tube. As shown in Figures 2A and 2B, each of the surfaces of the main shoulder surface 9 and the surface below the shoulder 11 of pin 1 has groove 9a or more specifically groove portions 9a-2 and 9a-1, respectively, in three locations. Each groove portion extends from 50 to 75 ° in the circumferential direction. As shown in Figure 2D, the groove portions 9a-1 and 9a-2 of each pair were connected by a connecting channel 9c formed on the shoulder surface portion of box 2 that opposes the apex 9b of the shoulder surface of the pin 1.
    [0126] On the surface of pin 1 that was finished by machine grinding (surface roughness of 3 pm), a zinc phosphate coating that has a surface roughness of 8 pm was formed with a thickness of 8 pm and on top a commercially available UV curable resin coating composition (ThreeBond 3113B manufactured by ThreeBond Co., Ltd., which is a solventless UV curable resin coating composition based on an epoxy resin) was applied by spraying and cured by irradiation with UV light to form a coating of UV-cured resin that has a thickness of 25 pm. This resin coating was transparent and the male threads of the pin can be inspected by observation with the naked eye or through a magnifying glass at the top of the coating.
    [0127] On the surface of box 2 which was finished by machine grinding (surface roughness of 3 pm), a manganese phosphate coating that has a surface roughness of 10 pm was formed with a thickness of 12 pm. A lubricating coating composition that has the composition shown below was heated to 150 ° C in a tank equipped with an agitator to form a melt that has a suitable viscosity for the application. The box surface treated in the manner described above was preheated to 130 ° C for inducing heat and the molten lubricating coating composition was applied to it using a spray gun that has a spray head capable of maintaining the temperature. The amount of the coating composition that is applied has been adjusted to the amount sufficient to form a coating that is 50 µm thick taking the surface area of the box into account. During application, the coupling that constituted the box was rotated at a constant circumferential speed. Upon cooling, a solid lubricating coating that exhibits rheological and viscoplastic behavior was formed. The coating weight of the solid lubricant coating was determined according to the difference in weight before and after application when the same coating composition was applied to a dummy box made of paper under the same conditions. The coating weight of the solid lubricant coating is shown in Table 1 along with the calculated value of the total groove volume 9a divided by the coating weight.
    [0128] The composition of the lubricating coating composition:
    [0129] - 9% polyethylene homopolymer (Licowax ™ PE 520 manufactured by Clariant);
    [0130] -15% carnauba wax;
    [0131] -15% zinc stearate;
    [0132] - 5% liquid polyalkyl methacrylate (Viscoplex ™ 6-950 manufactured by Rohmax);
    [0133] - 40% corrosion inhibitor (ALOX ™ 606 manufactured by Lubrizol);
    [0134] - 3.5% graphite fluoride;
    [0135] -1% zinc oxide;
    [0136] - 5% titanium dioxide;
    [0137] - 5% bismuth trioxide;
    [0138] -1% silicone (polydimethylsiloxane); and
    [0139] - antioxidant (manufactured by Ciba-Geigy) which consists of 0.3% Irganox ™ L150 and 0.2% Iragafos ™ 168.
    [0140] In the seal test, the pressure variation within the non-contact region 13 was measured. As shown in Figure 6, this measurement was performed by forming a drill cylinder 2a that passed only through box 2 to reach the non-contact region 13 and measure the pressure in that region.
    [0141] The sealing test was carried out under conditions in accordance with ISO 13679: 2002, Series A and Series B (room temperature and high temperature). ISO 13679: 2002 is an international standard for joint testing for tubular oilfield goods (OCTG) and comprises the following three types of seal tests that test the gas tightness of a joint under various loads and temperatures and the constitution-flight that tests how many times a joint can be submitted to constitution and flight.
    [0142] Series A: Internal and external pressures are applied in a state in which a tension / compression load is applied to a joint in a constituted state.
    [0143] Series B: An internal pressure is applied in a state in which a tension / compression / inclination load is applied to a joint in a constituted state.
    [0144] Series C: A heating cycle is applied to a joint in a state of constitution under tension and internal pressure.
    [0145] In this example, as a result of performing a Series A test followed by a Series B test on the same threaded joint, the occurrence or non-occurrence of confinement of a high pressure fluid in the non-contact region was determined based in the pressure variation within the region as described below.
    [0146] All threaded joints for tubes that are tested were made of P110 carbon steel. P110 carbon steel complies with API 5CT specification (ISO 11960: 2004) which is an international standard for tubular oilfield goods (OCTG). The specifications related to a threaded joint are a yield stress of 0.76 to 0.97 Mpa (110 to 140 psi) and a tensile strength of at least 0.86 MPa (125 psi).
    [0147] Grooves 9a were formed in a V shape with a depth of 0.4 mm, 0.6 mm, or 0.8 mm when using a cutting tool that has a 35 ° or 55 ° tip angle. The width at the opening of each of these grooves is shown in Table 1. The fraction of the main shoulder surface area of the pin occupied by grooves 9a (in the openings) was calculated from the width and length of each groove and the number of grooves. As shown in Table 1, for any of the threaded joints to be tested, the fraction of the area occupied by the groove openings was less than 40%, so the fraction of the contact surface area was at least 60%.
    [0148] In order to assess whether a high pressure fluid was confined to the non-contact region 13, the pressure in that region and the pressure within the pipe threaded joint were recorded. When a difference between the two pressures appeared so that the pressure within the non-contact region did not decrease even though the pressure within the threaded joint decreases, it was determined that the high pressure fluid was confined within the non-contact region. The test results are shown in Table 1. Table 1


    [0149] * V / W: the total groove weight / coating weight of the solid lubricant coating.
    [0150] ** The fraction of the pin's main shoulder surface area occupied by the grooves.
    [0151] As shown in Table 1, even when the outside diameter and nominal weight (wall thickness) of a threaded pipe joint varied (which leads to a variation in the shoulder area surface), it is possible to prevent the high pressure fluid is confined within the non-contact region 13 if the total volume of the grooves 9a and the coating weight of the solid lubricant coating satisfy the above equation (1).
    权利要求:
    Claims (6)
    [0001]
    1. Threaded joint (30) for tubes comprising a pin (1) and a housing (2), each of which has a contact surface that includes a threaded portion (3, 7) and a non-threaded metallic contact portion , the non-threaded metal contact portion including a sealing surface (5, 8) and a shoulder surface (9-12), the shoulder surface (9, 10) of the pin (1) is located on the surface of end of the pin, in which a non-contact region (13) in which the pin (1) and the housing (2) do not come into contact with each other is present between the sealing surfaces (5, 8) and the shoulder surfaces ( 9-12) of the pin (1) and the housing (2), and the threaded joint (30) has one or more grooves (9a- 1,9a-2) formed on the shoulder surface (9-12) of at least one between the pin and the box and extending to the non-contact region (13) and to the inner part of the threaded joint (30), FEATURED by the fact that at least the contact surface of at least one of the pin ( 1) and the box (2) has a solid lubricant coating (22) that exhibits plastic or viscoplastic rheological behavior formed on it, and the total volume V (mm3) of the grooves and the coating weight W (g) of the solid lubricant coating (22) satisfy the following equation (1 ): V / W> 24 (mm3 / g) ... (1), where the coating weight W (g) is the mass quantity of the solid lubricant coating deposited on opposite surfaces of the pin and housing.
    [0002]
    2. Threaded joint (30) for tubes, according to claim 1, CHARACTERIZED by the fact that the shoulder surfaces (9-12) of the pin (1) and the box (2) are each constituted by a main shoulder surface (9, 11) and a surface below the shoulder (10, 12) connected to the main shoulder surface (9, 11), the main shoulder surface (9, 11) having a reverse tilt angle and extends to the inside of the threaded joint (30), and the surface below the shoulder (10, 12) is located between the main shoulder surface (9,11) and the non-contact region (13) and has an angle of inclination in relation to a plane perpendicular to the geometric axis of the tube that is greater than that of the main shoulder surface (9, 11).
    [0003]
    3. Threaded joint (30) for tubes according to claim 1, CHARACTERIZED by the fact that an area of an upper end of the grooves (9a-1, 9a-2) on the shoulder surface (9-12) does not exceed 40% of a surface area of the shoulder surface (9-12).
    [0004]
    4. Threaded joint (30) for tubes according to claim 2, CHARACTERIZED by the fact that an area of an upper end of the grooves (9a-1, 9a-2) on the main shoulder surface (9, 11) does not exceeds 40% of a surface area of the main shoulder surface (9, 11).
    [0005]
    Threaded joint (30) for tubes according to any one of claims 1 to 4, CHARACTERIZED by the fact that the solid lubricant coating (22) is formed on the contact surface of the housing (2).
    [0006]
    6. Threaded joint (30) for tubes, according to claim 5, CHARACTERIZED by the fact that the surface of the pin (1) has a solid anticorrosive coating formed from a UV curable resin.
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    同族专利:
    公开号 | 公开日
    AR089748A1|2014-09-17|
    US9194515B2|2015-11-24|
    BR112014016961A2|2017-06-13|
    MY175905A|2020-07-15|
    CA2862833A1|2013-07-25|
    EP2805092A1|2014-11-26|
    EA025932B1|2017-02-28|
    CN104114926B|2015-09-16|
    EP2805092A4|2016-02-24|
    JP5690021B2|2015-03-25|
    MX350459B|2017-09-05|
    BR112014016961A8|2017-07-04|
    PL2805092T3|2017-09-29|
    AU2013210283A1|2014-07-31|
    EP2805092B1|2017-05-10|
    US20150001841A1|2015-01-01|
    IN2014DN06114A|2015-08-14|
    AU2013210283B2|2015-09-03|
    CN104114926A|2014-10-22|
    MX2014008661A|2015-02-24|
    JP2014535023A|2014-12-25|
    CA2862833C|2016-09-27|
    UA109617C2|2015-09-10|
    WO2013108931A1|2013-07-25|
    EA201491390A1|2014-10-30|
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    法律状态:
    2018-12-04| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2019-07-09| B06T| Formal requirements before examination [chapter 6.20 patent gazette]|
    2019-09-03| B25D| Requested change of name of applicant approved|Owner name: VALLOUREC OIL AND GAS FRANCE (FR) ; NIPPON STEEL C Owner name: VALLOUREC OIL AND GAS FRANCE (FR) ; NIPPON STEEL CORPORATION (JP) |
    2020-04-14| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2020-09-15| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 17/01/2013, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    JP2012008922|2012-01-19|
    JP2012-008922|2012-01-19|
    PCT/JP2013/051363|WO2013108931A1|2012-01-19|2013-01-17|Threaded joint for pipes|
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