Solid lubricant coating composition, threaded joint for pipes comprising solid lubricant coating formed using said composition, and production method for said threaded joint for pipes

Abstract

Provided are: a threaded joint for pipes that, even in an extremely low-temperature environment and without using a compound grease, suppresses the generation of rust, exhibits excellent seizure resistance and airtightness, and has a surface that is unlikely to be sticky; a production method therefor; and a composition for forming a solid lubricant coating on the threaded joint for pipes. A solid lubricant coating (24) formed from a composition containing a binding agent, a fluorine-based additive, a solid lubricant, and an anti-rust additive is coated, as an uppermost surface treatment coating, on the contact surface of at least either a pin or a box. The solid lubricant coating (24) is capable of maintaining adhesiveness even if exposed to extremely low-temperature environments, is capable of exhibiting a lubrication-applying function, is capable of suppressing thread joint seizure, and is capable of ensuring airtightness after fastening.

Description

The present invention relates to a solid lubricating film forming composition used for surface treatment of pipe thread fittings used for connecting steel pipes, particularly oil well pipes; a pipe thread fitting equipped with a solid lubricating film formed from the composition; and a method for manufacturing the pipe thread fitting. Oil wells for extracting crude oil and gas are drilled using oil well pipes, which include tubing through which crude oil or other fluids flow, and casings that enclose the tubing. Oil well pipes are generally connected (fastened) using pipe thread fittings. Traditionally, oil wells were 2,000 to 3,000 meters deep. However, in recent years, deep wells in offshore oil fields can reach depths of 8,000 to 10,000 meters. The length of individual oil well pipes is typically around 10 to 15 meters. Therefore, a vast number of oil well pipes, sometimes more than 1,000, are connected. Pipe thread fittings for oil well tubulars are subjected to various loads under operating conditions, including axial tensile forces resulting from the mass of the tubulars and fittings themselves, combined pressures such as internal and external pressures, and even heat from the ground. Therefore, pipe thread fittings are required to maintain airtightness without breaking even under such harsh conditions. A typical pipe threaded joint used for fastening oil well pipes is a pin-box structure, such as the one described in Patent Document 1, which consists of a part called a pin having a male thread and a part called a box having a female thread. Typically, the pins are formed at both ends of the oil well pipe, and the boxes are formed on the inner surfaces of both sides of a threaded joint component called a coupling. During the lowering of tubing and casing into an oil well, threaded joints that have already been tightened may need to be loosened due to various reasons such as malfunctions. These joints may then be temporarily removed from the well and re-tightened before lowering. According to API (American Petroleum Institute) standards, it is desirable that tubing joints can withstand 10 tightening (makeup) and loosening (breakout) cycles, and casing joints can withstand 3 cycles, without the occurrence of irreparable seizure known as goring, and that airtightness is maintained. When tightening the threaded joint of an oil well pipe, in order to improve seizure resistance and airtightness, a lubricant called "compound grease" is applied to the contact surface of the threaded joint (that is, the threaded part and the non-threaded metal contact part). Compound grease is a viscous liquid lubricant (grease lubricating oil) containing heavy metal powder. Examples of compound grease are described in API Specification BUL 5A2. Conventionally, in order to improve the retention and sliding properties of compound grease, it has been proposed to perform one or more layers of surface treatment on the contact surface of the threaded joint. Surface treatment includes, for example, nitriding treatment, various plating treatments including zinc-based plating and dispersion plating, or phosphate conversion treatment. Compound grease contains a large amount of heavy metal powder such as zinc, lead, and copper. Therefore, the influence on the use environment, for example, the influence on the marine environment and the working environment, has been pointed out. In recent years, strict regulations on the environment on a global scale have been progressing. The use of compound grease has already been restricted in some regions. Therefore, in the drilling operations of gas wells and oil wells, in order to avoid the influence on the environment and the human body, a threaded joint having excellent seizure resistance without using compound grease is required. As a threaded joint that can be used for fastening an oil well pipe without applying compound grease, the present applicants previously proposed a pipe threaded joint disclosed in Patent Document 2. The pipe threaded joint described in Patent Document 2 has at least one contact surface of the pin and the box coated with a two-layer coating composed of a viscous liquid or semi-solid lubricating film and a dry solid film formed thereon. The dry solid film is formed from a thermosetting resin film such as an acrylic resin or an ultraviolet curable resin film. The viscous liquid or semi-solid lubricating film is sticky and foreign matter is likely to adhere. By forming a dry solid film on the viscous liquid or semi-solid lubricating film, the stickiness is eliminated. Since the dry solid film is broken when the threaded joint is tightened, it does not interfere with the lubricity of the lubricating film below it. Furthermore, in Patent Document 3, the applicants proposed a screw joint in which a thin, non-sticky lubricating film is formed on the threaded portion (pin and box). The lubricating film described in Patent Document 3 is obtained by dispersing solid lubricant particles in a solid matrix that exhibits plastic or viscoplastic rheological behavior (flow properties). The melting point of the solid matrix is ​​preferably in the range of 80 to 320°C. This lubricating film is formed by spray application in a molten state (hot melt spray method), thermal spraying using powder, or spray application of an aqueous emulsion. The composition used in the hot melt spray method, for example, contains polyethylene as a thermoplastic polymer, wax (e.g., carnauba wax) and metal soap (e.g., zinc stearate) as lubricating components, and calcium sulfonate as a corrosion inhibitor. Furthermore, in Patent Document 4, the applicants proposed a pipe threaded joint in which a solid corrosion-preventive coating is formed on the contact surface of the pin and a solid lubricating coating is provided on the contact surface of the box. The solid corrosion-preventive coating mainly consists of an ultraviolet-curing resin and is preferably transparent. The solid lubricating coating is preferably formed by a hot-melt method from a composition containing a thermoplastic polymer, wax, metal soap, corrosion inhibitor, water-insoluble liquid resin, and solid lubricant, and has plastic or viscoplastic rheological behavior. Japanese Patent Publication No. 2006-526747, International Publication No. 2006 / 104251, International Publication No. 2007 / 042231, International Publication No. 2009 / 072486 The pipe thread fittings described in Patent Documents 2 to 4 above possess excellent adhesion and lubrication performance of the solid lubricating film in low-temperature and warm environments of approximately -10°C to +50°C, thus providing sufficient seizure resistance. However, when exposed to extremely low-temperature environments of -60°C to -20°C, the adhesion of the solid lubricating film deteriorates, making it prone to peeling and cracking due to film embrittlement, resulting in insufficient seizure resistance. Furthermore, tightening and loosening thread fittings in such extremely low-temperature environments requires extremely high torque. The object of the present invention is to provide a composition for forming a solid lubricating coating used for surface treatment of pipe thread fittings, which can suppress the occurrence of rust without using compound grease even when connecting steel pipes, especially oil well pipes, in an extremely low temperature environment, and which has excellent seizure resistance and airtightness and a surface that is not easily sticky; a pipe thread fitting equipped with a solid lubricating coating formed from the composition; and a method for manufacturing the pipe thread fitting. The composition according to this embodiment is a composition for forming a solid lubricating film on pipe thread fittings. The composition contains a binder, a fluorine-based additive, a solid lubricant, and a rust-preventive additive. The binder contains ethylene vinyl acetate resin, polyolefin resin, and a wax with a melting point of 110°C or lower. The ratio of the mass of ethylene vinyl acetate resin to the mass of polyolefin resin is 1.0 to 1.8. The ratio of the combined mass of polyolefin resin and ethylene vinyl acetate resin to the mass of wax is 0.7 to 1.6. The pipe thread fitting according to this embodiment comprises a pin and a box. Each of the pin and the box has a contact surface including portions that come into contact with each other. The solid lubricating film is formed on at least one of the contact surfaces of the pin and the box. The method for manufacturing a pipe threaded joint according to this embodiment includes the step of applying the above composition to the contact surface to form the solid lubricating film. A pipe thread fitting equipped with a solid lubricating film formed using the above composition suppresses rust formation even in extremely low temperature environments without the use of compound grease, exhibits excellent seizure resistance and airtightness, and has a surface that is less prone to stickiness. Figure 1 is a configuration diagram showing an example of a pipe threaded joint according to this embodiment. Figure 2 is a diagram showing an example of the tightening part of a pipe threaded joint, and is a cross-sectional view showing the threadless metal contact part (shoulder part and seal part) of a special threaded joint. Figure 3A is a cross-sectional view of the vicinity of the contact surface when the contact surface itself of the pipe threaded joint is roughened. Figure 3B is a cross-sectional view of the vicinity of the contact surface when a surface treatment film for roughening is formed on the contact surface of the pipe threaded joint. Figure 4 is a schematic diagram of a shear tensile test for measuring the adhesion strength of a solid lubricant film. Figure 5 is a flow chart showing the process of a low-temperature outdoor exposure test of a solid lubricant film. Figure 6 is a diagram showing the relationship between the rotational speed of the threaded joint and the torque. Figure 7 is a schematic diagram of a flat plate sliding test for measuring the coefficient of friction. Figure 8 is a diagram showing the relationship between the talc content in the solid lubricant film and the coefficient of friction. The inventors of this application have conducted research to develop a threaded joint that provides sufficient seizure resistance, rust prevention, and airtightness even when used in extremely cold regions where temperatures can reach -60°C to -20°C, as well as in low-temperature, warm, and tropical regions with temperatures ranging from -20°C to +50°C, and that does not require excessively high torque when fastening or loosening the threaded joint. As a result, they have obtained the following findings: In a solid lubricating film formed on a pipe threaded joint, and a composition for forming the solid lubricating film (solid lubricating film forming composition), by (1) blending ethylene vinyl acetate (EVA) resin, polyolefin resin, and wax with a melting point of 110°C or lower in specific proportions as a binder in the composition, (2) blending a fluorine-based additive in a specific proportion, and (3) further adding solid lubricating powder and rust-preventive additives, the solid lubricating film can maintain high adhesion even when exposed to extremely low temperatures. Therefore, the threaded joint has sufficient seizure resistance and airtightness, and can suppress the increase in torque required when fastening or loosening the threaded joint at low temperatures. Furthermore, (4) by blending talc of a specific particle size in a specific proportion, torque adjustment during fastening can be made easier. Based on the above findings, the composition of this embodiment is a composition for forming a solid lubricating film on pipe threaded fittings. The composition contains a binder, a fluorine-based additive, a solid lubricant, and a rust-preventive additive. The binder contains ethylene vinyl acetate resin, polyolefin resin, and a wax with a melting point of 110°C or lower. The ratio of the mass of ethylene vinyl acetate resin to the mass of polyolefin resin is 1.0 to 1.8. The ratio of the combined mass of polyolefin resin and ethylene vinyl acetate resin to the mass of wax is 0.7 to 1.6. According to the composition of this embodiment, a thermoplastic solid lubricant film with excellent seizure resistance can be formed on the contact surface of pipe thread fittings without using compound grease. This solid lubricant film shows almost no deterioration even in extremely low temperature environments such as -60°C to -20°C. Therefore, it exhibits the same excellent seizure resistance, airtightness, and rust prevention as when compound grease is used, and furthermore, it can suppress the increase in torque required when fastening and loosening thread fittings. Preferably, the composition contains 60 to 80% by mass of a binder, 8 to 18% by mass of a fluorine-based additive, 5 to 15% by mass of a solid lubricant, and 2 to 10% by mass of a rust-preventive additive. The above composition may further contain 2 to 15% by mass of talc. In this case, the difference between the yield torque and the shouldering torque can be increased, and as a result, torque adjustment during fastening can be made easier. The talc particles in the above composition have a diameter of, for example, 1 to 12 μm, and the specific surface area of ​​the talc is 4 to 12 m² / g. The pipe thread fitting according to this embodiment comprises a pin and a box. Each of the pin and the box has a contact surface including a portion that contacts each other. A solid lubricating film is formed on at least one of the contact surfaces of the pin and the box. The solid lubricating film contains a binder, a fluorine-based additive, a solid lubricant, and a rust-preventive additive. The binder contains ethylene vinyl acetate resin, polyolefin resin, and wax with a melting point of 110°C or lower. The ratio of the mass of ethylene vinyl acetate resin to the mass of polyolefin resin is 1.0 to 1.8. The ratio of the combined mass of polyolefin resin and ethylene vinyl acetate resin to the mass of wax is 0.7 to 1.6. Because the pipe thread fitting according to this embodiment includes the above-mentioned solid lubricating film, it can be used without applying compound grease and maintains high adhesion even when exposed to extremely low temperature environments. As a result, it exhibits excellent seizure resistance, airtightness, and corrosion prevention. Therefore, it is particularly useful for oil well drilling in extremely cold regions. In the above-mentioned pipe threaded fitting, for example, the solid lubricating film contains 60 to 80% by mass of a binder, 8 to 18% by mass of a fluorine-based additive, 5 to 15% by mass of a solid lubricant, and 2 to 10% by mass of a rust-preventive additive. In the above-mentioned pipe threaded fitting, the solid lubricating film may further contain 2 to 15% by mass of talc. If the solid lubricating film included in the pipe thread fitting according to this embodiment contains talc, the difference between the yield torque and the shouldering torque can be increased, and as a result, torque adjustment when fastening the thread fitting can be made easier. When a solid lubricating film contains talc, the particle size of the talc is, for example, 1 to 12 μm, and the specific surface area of ​​the talc is, for example, 4 to 12 m² / g. Preferably, the above-mentioned pipe thread fitting further includes a solid corrosion-resistant coating containing an ultraviolet-curing resin. The solid lubricating coating is formed on one contact surface of the pin and the box. The solid corrosion-resistant coating is formed on the other contact surface of the pin and the box. The thickness of the above-mentioned solid corrosion-preventive coating is, for example, 5 to 50 μm. The thickness of the above-mentioned solid lubricating film is, for example, 10 to 200 μm. Preferably, the above-mentioned pipe thread fittings are used for oil well pipes. The method for manufacturing a pipe thread fitting according to this embodiment is a method for manufacturing a pipe thread fitting having a pin and a box. Each of the pin and the box has a contact surface including a portion that contacts each other. The method for manufacturing a pipe thread fitting according to this embodiment includes the step of applying the above composition to at least one of the contact surfaces of the pin and the box to form the above solid lubricating film. Preferably, the manufacturing method includes the step of forming the solid lubricating film on one contact surface of the pin and the box. The manufacturing method further includes the step of applying the composition for a solid corrosion-preventive coating, which includes the ultraviolet-curing resin, to the other contact surface of the pin and the box. The manufacturing method further includes the step of irradiating the composition for a solid corrosion-preventive coating with ultraviolet light to form the solid corrosion-preventive coating. The following describes a more specific embodiment of the pipe thread fitting according to this embodiment for illustrative purposes. Here, a pipe thread fitting for oil well pipes is described as a preferred embodiment. However, the present invention is not particularly limited to this embodiment and can also be applied to pipes used for purposes other than oil wells, for example. Figure 1 is a configuration diagram showing an example of a pipe thread fitting according to this embodiment. The pipe thread fitting comprises a steel pipe 2 and a coupling 8. Pins 6 having male threaded portions 4 on their outer surfaces are formed at both ends of the steel pipe 2. Boxes 12 having female threaded portions 10 on their inner surfaces are formed on both sides of the coupling 8. The coupling 8 is pre-attached to one end of the steel pipe 2 with screws. Although not shown, protectors (not shown) for protecting the threaded portions of the pins 6 of the steel pipe 2 (left side in the illustrated example) and the box 12 of the coupling 8 (right side in the illustrated example) are attached before shipment. In a typical pipe thread fitting, as shown in Figure 1, the pins 6 are formed on the outer surfaces of both ends of the steel pipe 2, and the box 12 is formed on the inner surface of the coupling 8. On the other hand, there is also an integral type pipe thread fitting that does not use a coupling, in which one end of the steel pipe is pin-shaped and the other end is box-shaped. The pipe thread fitting of this embodiment is applicable to both the coupling type and the integral type. Figure 2 is a cross-sectional view showing an example of the tightening portion of a pipe thread fitting. Seal portions 14 and 16 are formed on the outer circumferential surface near the end face of the pin 6 towards the tip of the male thread, and on the inner circumferential surface at the base of the female thread of the box 12, respectively. Shoulder portions (also called torque shoulders) 18 and 20 are formed on the end face of the tip of the pin 6 and on the innermost surface of the box 12 corresponding to the end face of the tip of the pin 6, respectively. The seal portions and shoulder portions constitute the threadless metal contact portion (so-called threadless metal contact portion) in the pipe thread fitting. The metal contact portion where the pin 6 and the box 12 contact each other and the threaded portion constitute the contact surface of the pipe thread fitting. When the pin 6 is inserted into the box 12 and the male and female threads are tightened, the shoulder portions 18 and 20 of the pin 6 and the box 12 come into contact with each other. The torque at this time is called the shouldering torque. Furthermore, when the male and female threads are tightened to the appropriate torque until they interfere with each other, the seal portions 14 and 16 of the pin 6 and the box 12 come into close contact, forming a metal-to-metal seal and ensuring the airtightness of the pipe thread fitting. The torque at this point is called the fastening torque. Further tightening of the male and female threads causes the metal constituting at least one of the pin 6 and the box 12 to begin plastic deformation. The torque at this point is called the yield torque. If the male and female threads are tightened with a torque greater than the yield torque, the airtightness of the pipe thread fitting may decrease. The fastening torque is set within a range greater than the shouldering torque and smaller than the yield torque. Therefore, a large difference between the yield torque and the shouldering torque makes it easier to adjust the fastening torque. As described above, in the pin 6 and the box 12, the threaded portion, the sealing portion, and the shoulder portion correspond to the contact surfaces of the threaded joint. These contact surfaces are required to have seizure resistance, airtightness, and corrosion resistance. Conventionally, compound grease containing heavy metal powder was applied to the contact surfaces. However, concerns arose regarding the effects of heavy metals on human health and the environment, leading to the consideration of threaded joints equipped with a solid lubricating coating that could be used for fastening oil well pipes without applying compound grease. The solid lubricating coating is typically a resin coating containing a solid lubricant. However, conventional solid lubricant coatings had a problem in that even a single exposure to extremely low temperatures of -60°C to -20°C would cause the coating itself to become brittle and crack. Furthermore, conventional solid lubricant coatings had a problem in that the difference in thermal expansion coefficients between them and the base material (steel) would reduce adhesion when the temperature returned to near room temperature, causing the coating to easily peel off. When pipe thread fittings are used in extremely low-temperature environments of -60°C to -20°C, the tightening (makeup) torque becomes high. As a result, the threads may not be properly tightened, and the metal contact points necessary to ensure airtightness may not make contact with the required surface pressure (this is called high shouldering). Even if tightening is achieved, seizing during tightening is more likely to occur, and the loosening (breakout) torque when loosening the threads becomes extremely high. Furthermore, if the capacity of the tongs used to tighten the pin and box is low, there is a possibility that tightening will not be possible due to insufficient torque. Figures 3A and 3B are cross-sectional views of the vicinity of the contact surface of the pipe threaded joint of the steel pipe in this embodiment. The contact surface of at least one of the members of the pin and the box is covered with a solid lubricating film 24 formed by a composition described later on the surface of the steel pipe 22 that constitutes that member. The solid lubricating film 24 can maintain its adhesion even when exposed to an extremely low temperature environment of -60°C to -20°C. The solid lubricating film 24 further provides lubrication to the threaded joint. Therefore, it is possible to prevent seizing of the threaded joint while preventing an increase in torque during fastening and loosening, and to ensure airtightness after fastening. The solid lubricating film 24 may be included in the coating on the surface of the steel pipe 22. For example, as shown in Figure 3A, it may be formed so as to be in direct contact with the surface of the steel pipe 22. As shown in Figure 3B, it may not be formed in direct contact with the surface of the steel pipe 22, but may be included in the coating formed on the surface of the steel pipe. It is desirable that the solid lubricating film 24 be placed on the uppermost surface of the coating on the surface of the steel pipe 22. However, the placement of the solid lubricating film 24 is not particularly limited, and for example, rust inhibitors or scratch-preventing coatings may be applied to the uppermost surface of the coating containing the solid lubricating film 24. The following description will explain the case in which the solid lubricating film 24 is formed directly on the contact surface of the steel pipe 22 as an example. Furthermore, it is preferable that the interface between the solid lubricating film 24 and the steel pipe 22 (i.e., the contact surface of the steel pipe 22) be roughened. This roughening can be achieved by directly roughening the surface of the steel pipe 22 by blasting or pickling, as shown in Figure 3A. As shown in Figure 3B, roughening can also be achieved by forming a roughened undercoat (for example, a phosphate coating, a porous zinc (alloy) plating coating) 26 on the surface of the steel pipe 22 before forming the lubricating film 24. The solid lubricating film 24 is formed, for example, by the following method: A composition for forming a thermoplastic solid lubricating film is prepared. The composition is melted at a predetermined temperature and applied to the contact surface by an appropriate method such as spraying, brushing, atomizing, and dipping. After application, the composition is solidified by a known cooling method such as air cooling or free cooling to form the solid lubricating film 24. The solid lubricating film may be formed on the contact surfaces of both the pin and the box. Alternatively, as shown in Figure 1, at the point where the pin and box are fastened together during shipment, the solid lubricating film may be formed on only one of the contact surfaces of the pin or the box. In this case, the coupling, which is shorter than the steel pipe, is easier to prepare for surface treatment and to apply the lubricating film than the steel pipe, which is longer. Therefore, it is generally preferable to form the lubricating film on the contact surface of the coupling, i.e., the contact surface of the box. In areas where the pin and box are not fastened together at the time of shipment, a solid lubricating coating may be formed on the contact surfaces of both the pin and the box to provide both lubrication and rust prevention. Alternatively, a solid lubricating coating may be formed on only the contact surface of one of the pins or the box (e.g., the box), and a solid corrosion-preventive coating may be formed on the contact surface of the other (e.g., the pin). In either case, the threaded joint can be provided with seizure resistance, airtightness, and rust prevention. The solid corrosion-preventive coating is preferably an ultraviolet-curing type coating. Furthermore, it is preferable that the solid corrosion-preventive coating is formed after surface treatment for roughening. Preferably, the solid lubricating film covers all of the contact surfaces of at least one of the pin and the box. However, the solid lubricating film may cover only a portion of the contact surface (for example, only the sealing portion). [Solid Lubricant Coating] As described above, in this embodiment, a solid lubricant coating is formed on at least one of the contact surfaces of the pin and the box constituting the pipe thread joint. This solid lubricant coating is required to maintain adhesion even when exposed to extremely low temperatures (-60°C to -20°C). Furthermore, the solid lubricant coating is required to prevent high fastening torque causing high shouldering or high loosening torque when fastening steel pipes together with the thread joint, not only in low, warm, and tropical regions (-20°C to +50°C) but also in extremely low temperature regions (-60°C to -20°C), thereby suppressing seizure. The solid lubricant coating is also required to prevent rusting during storage. If the adhesion strength (hardness) of the solid lubricant coating changes significantly between near room temperature and extremely low temperature environments, cracks may occur in the solid lubricant coating in the extremely low temperature environment, or peeling may occur in the solid lubricant coating when it returns to near room temperature. Therefore, solid lubricant coatings are also required to have a low adhesion strength (hardness) that does not change significantly between near-room temperature and extremely low-temperature environments. The composition for forming the solid lubricating film in this embodiment is the base material for the film. The composition contains a binder that exhibits high adhesion from room temperature to cryogenic temperatures, a fluorine-based additive for adhesion and reduced friction at cryogenic temperatures, a solid lubricant to prevent seizing, and a rust inhibitor for long-term rust prevention from application until use. [Binder] The binder in this embodiment consists of ethylene vinyl acetate resin (EVA), polyolefin resin (PO), and wax (W) with a melting point of 110°C or lower. In order to achieve high film adhesion from room temperature to cryogenic temperatures, the mass ratio of ethylene vinyl acetate resin, polyolefin resin, and wax is as follows: 1.0 ≤ (EVA / PO) ≤ 1.8 and 0.7 ≤ ((EVA + PO) / W) ≤ 1.6 The above mass ratio is a matter that has been experimentally determined for the first time in this invention. In the above formula, EVA, PO, and W represent the mass of ethylene vinyl acetate resin, polyolefin resin, and wax, respectively. If the mass ratio of ethylene vinyl acetate resin to polyolefin resin (EVA / PO) is less than 1.0, the adhesion strength of the solid lubricating film will be insufficient at temperatures above -20°C. On the other hand, if (EVA / PO) exceeds 1.8, the adhesion strength of the solid lubricating film will be insufficient at extremely low temperatures below -20°C. To maintain a good balance of adhesion throughout extremely low temperatures (-20 to -60°C), low temperatures (-20 to 0°C), and warm / tropical temperatures (-10 to 50°C), the lower limit of (EVA / PO) is 1.0 and the upper limit is 1.8. To make this effect more reliable, the preferred lower limit of (EVA / PO) is 1.05, more preferably 1.1, even more preferably 1.15, even more preferably 1.2, and even more preferably 1.35. The preferred upper limit of (EVA / PO) is 1.7, more preferably 1.65, and even more preferably 1.6. If the ratio of the combined mass of the two resins (ethylene vinyl acetate resin and polyolefin resin) to the mass of the wax ((EVA+PO) / W) is less than 0.7, the hardness of the solid lubricating film will be low, resulting in insufficient adhesion strength. On the other hand, if ((EVA+PO) / W) exceeds 1.6, the hardness of the solid lubricating film will be too high, and frictional resistance will be high, especially at extremely low temperatures. In this case, the torque during tightening and loosening of the screw joint will be too high. Therefore, from the viewpoint of adjusting hardness and friction suitable for a solid lubricating film for screw joints, the lower limit of ((EVA+PO) / W) is 0.7 and the upper limit is 1.6. To make this effect more reliable, the preferred lower limit of ((EVA+PO) / W) is 0.8, more preferably 0.85, and even more preferably 0.9. The preferred upper limit of ((EVA+PO) / W) is 1.5, more preferably 1.45, and even more preferably 1.4. Polyolefin resins (PO) are a general term for chain-like hydrocarbons that have a double bond at one location. Because polyolefin resins (PO) are composed of crystalline polymers, their physical properties change depending on the degree of crystallinity. Examples of resins in this category include polyethylene and polypropylene, and a specific example is HM712 (softening point 120°C) manufactured by Cemedyne Co., Ltd. Ethylene vinyl acetate resin (EVA) is a copolymer of ethylene and vinyl acetate. A specific example is HM224 (softening point 86°C) manufactured by Cemedyne Co., Ltd. Wax (W) suppresses seizing by reducing friction in the solid lubricating film. Furthermore, wax adjusts the hardness of the solid lubricating film, increasing its toughness. Any type of wax can be used, including animal, plant, mineral, and synthetic waxes. Usable waxes include, for example, beeswax, whale wax (both animal-based), wood wax, carnauba wax, candelilla wax, rice wax (all plant-based), paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokerite, ceresin (all mineral-based), oxide wax, polyethylene wax, Fischer-Tropsch wax, amide wax, and hydrogenated castor oil (castor wax) (all synthetic waxes). The wax should have a melting point of 110°C or lower. If the melting point of the wax is 110°C or lower, the difference between the adhesion strength (hardness) of the solid lubricating film at or near room temperature and the adhesion strength (hardness) of the solid lubricating film in an extremely low-temperature environment will be small. This suppresses cracking of the solid lubricant film in extremely low temperature environments. Furthermore, it suppresses peeling of the solid lubricant film when it returns to near room temperature. In other words, it is possible to maintain the adhesion strength (hardness) of the solid lubricant film within an appropriate range, and furthermore, the toughness of the solid lubricant film is increased. The melting point of the wax is preferably 100°C or lower, and paraffin wax with a melting point of 90°C or lower and a molecular weight of 150 to 500 is more preferable. The wax is further preferably solid at room temperature. The preferred lower limit of the melting point of the wax is 40°C. By using a wax that is solid at room temperature, the adhesion strength of the solid lubricant film at or near room temperature can be kept within an appropriate range. The binder content in the composition is preferably 60 to 80% by mass (hereinafter, unless otherwise specified, the content will be given in mass%). If the binder content is 60% or more, the adhesion of the solid lubricating film is further enhanced. If the binder content is 80% or less, the lubricity is maintained more effectively. It is preferable to use ethylene vinyl acetate resin or polyolefin resin as a binder, which has a melting temperature (or softening temperature, hereinafter the same) of 80 to 320°C. The molten base (binder) returns to a solid state when the temperature drops below the melting temperature. This melting temperature is more preferably in the range of 90 to 200°C. If the melting temperature of the ethylene vinyl acetate resin or polyolefin resin that forms the film base is too high, it becomes difficult to apply it in a molten state, such as with hot melt coating. On the other hand, if the melting temperature of the binder is too low, the solid lubricating film may soften when the temperature rises, potentially leading to a decrease in performance. The contact surface of the pipe thread fitting on which the lubricating film is formed may be pre-treated by chemical conversion treatment or plating, as described later. Considering the adhesion, film formation, and application properties of the solid lubricating film to the contact surface of the steel pipe, the viscosity of the solid lubricating film when melted, and the dispersibility of the solid lubricant, it is preferable that the ethylene vinyl acetate resin and polyolefin resin are a mixture of multiple types with different properties such as melting point, softening point, and glass transition point. The ethylene vinyl acetate resin used as a base (binder) is preferably a mixture of two or more ethylene vinyl acetate resins with different melting temperatures in order to suppress rapid softening due to rising temperatures. Similarly, the polyolefin resin used as a base (binder) is also preferably a mixture of two or more polyolefin resins with different melting temperatures. [Fluorine-based additive] The solid lubricating film of this embodiment uses a binder as a base and further contains a fluorine-based additive. The fluorine-based additive improves the lubricity during sliding. The fluorine-based additive further enhances the toughness of the solid lubricating film at extremely low temperatures. Examples of fluorine-based additives include liquid perfluoropolyethers (PFPE) and grease-like fluorinated polymers. PFPE and fluorinated polymers are preferred as fluorine-based additives due to their ease of addition to the binder. Perfluoropolyether modified products, such as fluorinated polyethers with a basic structure having a molecular weight of 500 to 10000, can also be used as fluorine-based additives. The preferred content of fluorine-based additives in the composition is 8 to 18%. A fluorine-based additive content of 8% or more enhances lubricity and adhesion at low temperatures. A fluorine-based additive content of 18% or less maintains better adhesion at room temperature. [Solid Lubricants] Solid lubricating films contain various solid lubricants to further enhance their lubricity. Here, a solid lubricant refers to a powder that possesses lubricating properties. Solid lubricants are broadly classified into the following four types: (1) Those that exhibit lubricity due to having a specific slippery crystal structure, such as a hexagonal layered crystal structure (e.g., graphite, zinc oxide, boron nitride); (2) Those that exhibit lubricity due to having reactive elements in addition to their crystal structure (e.g., molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfide, bismuth sulfide); (3) Those that exhibit lubricity due to chemical reactivity (e.g., certain thiosulfate-type compounds); and (4) Those that exhibit lubricity due to plastic or viscoplastic behavior under frictional stress (e.g., polytetrafluoroethylene (PTFE) and polyamides). In the present invention, any of the solid lubricants (1) to (4) above can be used. The preferred solid lubricant is (1). The solid lubricant (1) may be used alone, or it may be used in combination with at least one of the solid lubricants (2) and (4). From the viewpoint of adhesion and rust prevention, graphite is a preferred solid lubricant, and from the viewpoint of film formation, earthy graphite is more preferred. The content of the solid lubricant in the solid lubricating film (and in the composition for the solid lubricating film) is preferably in the range of 5 to 15% by mass. The composition for the solid lubricant coating may further contain inorganic powders for adjusting the sliding properties. Such inorganic powders are, for example, titanium dioxide and bismuth oxide. The inorganic powders may be included in the composition in an amount of up to 10% by mass in total. The solid lubricating film according to the present invention actively contains rust-preventive additives to ensure long-term rust prevention from application to actual use. Examples of rust-preventive additives include aluminum tripolyphosphate, aluminum phosphite, and calcium ion-exchange silica. Other commercially available reactive water-repellent agents can also be used. The preferred content of the rust inhibitor additive in the composition is 2 to 10% by mass. If the rust inhibitor additive is contained at 2% by mass or more, the rust-preventive properties of the solid lubricating film are further enhanced. If the rust inhibitor additive is contained at 10% by mass or less, the lubricity and adhesion of the solid lubricating film can be maintained more effectively. [Friction Modifier] The above composition for solid lubricating films may further contain talc as a friction modifier. Talc is a white or gray inorganic powder produced by crushing the ore called talc. The chemical name of talc is hydrated magnesium silicate, and it has the chemical composition Mg3Si4O10(OH)2. Talc contains about 60% by mass of SiO2, about 30% by mass of MgO, and about 4.8% by mass of crystal water. The true specific gravity of talc is 2.7 to 2.8, and its Mohs hardness is 1, which is the lowest among inorganic minerals. Furthermore, talc has excellent heat resistance and is a chemically stable substance. For this reason, talc can be used as a filler. Surface-modified talc, in which dispersibility is improved by chemically or physically bonding a treatment material to the surface of the talc, is also included in the talc of this embodiment. Talc has the effect of increasing the difference between yield torque (at high surface pressure) and shouldering torque (at low surface pressure) when fastening screw joints. A larger difference between yield torque and shouldering torque provides a margin in the range of fastening torque when fastening screw joints. As a result, it becomes easier to adjust the torque when fastening screw joints. This effect is obtained because talc maintains the coefficient of friction at an appropriate level when the surface pressure of the contact sliding surface of the screw joint is high. If the talc content in the composition is 2% by mass or more, this effect can be greatly increased, and if it is 15% by mass or less, there is little risk of impairing seizure resistance. Therefore, the talc content is preferably 2 to 15% by mass. From the viewpoint of seizure resistance and adhesion of the solid film, a more preferable lower limit for the talc content is 3% by mass, and even more preferably 5% by mass. A more preferable upper limit for the talc content is 10% by mass, and even more preferably 8% by mass. In this embodiment, the particle size of the talc is preferably 1 to 12 μm. If the particle size of the talc is 1 μm or larger, the effect of increasing the difference between the yield torque and the shouldering torque can be stably obtained. If the particle size of the talc is 12 μm or smaller, there is less risk of a decrease in dispersibility and adhesion in the solid lubricant film. A more preferable lower limit for the particle size of the talc is 3 μm, and even more preferably 4 μm. A more preferable upper limit for the particle size of the talc is 10 μm, and even more preferably 8 μm. In this specification, "particle size" refers to the median diameter (D50) determined from the particle size distribution. The particle size of talc can be determined, for example, by creating a cumulative particle size distribution using a laser diffraction particle size distribution analyzer, and then calculating the median diameter from the obtained particle size distribution. In this embodiment, the specific surface area of ​​the talc is preferably 4 to 12 m² / g. If the specific surface area of ​​the talc is 4 m² / g or more, the affinity between the talc and the binder in the solid lubricant film is increased. Therefore, the shedding of talc from the surface of the solid lubricant film during sliding can be suppressed. If the specific surface area of ​​the talc is 12 m² / g or less, the effect of increasing the difference between the yield torque and the shouldering torque can be stably obtained. A more preferable lower limit for the specific surface area of ​​the talc is 6 m² / g, and even more preferably 7 m² / g. A more preferable upper limit for the specific surface area of ​​the talc is 11 m² / g, and even more preferably 10 m² / g. The specific surface area of ​​talc can be determined, for example, by the BET method. Specifically, an automatic specific surface area measuring device is used to adsorb a gas (for example, nitrogen gas) whose adsorption area is already known onto the surface of the talc. The amount of single-molecule adsorbed is calculated using the BET formula from the relationship between the gas pressure and the amount of gas adsorbed. Furthermore, the specific surface area can be calculated by multiplying this by the adsorption area per unit gas molecule. [Other Components] In addition to the components mentioned above, the composition of this embodiment may also contain small amounts of additives selected from surfactants, colorants, antioxidants, etc., in a total amount of, for example, 5% by mass or less. The composition for solid lubricating films may also contain extreme pressure agents, liquid oils, etc., in very small amounts of 2% by mass or less. In this embodiment, a solid lubricating film-forming composition (hereinafter also referred to as a coating composition) for forming the above-mentioned solid lubricating film is provided. This coating composition may be a solvent-free composition consisting only of the aforementioned components, or a solvent-type composition in which the components are dissolved in a solvent. In the case of a solvent-type composition, the mass percentage of each component refers to the mass percentage when the total mass of all components other than the solvent contained in the composition is taken as 100%. Below, an example of a method for manufacturing a pipe threaded fitting using the coating composition will be described. Solvent-free coating compositions can be prepared, for example, by mixing a solid lubricant and rust inhibitor additives with a molten base and kneading the mixture. A powder mixture containing all components in powder form can also be used as a coating composition. Solvent-free compositions have the advantage of forming a lubricating film in a short time and eliminating the evaporation of organic solvents that affect the environment. Such solvent-free coating compositions can form a solid lubricating film, for example, using a hot-melt method. In this method, the coating composition (containing the above-mentioned base and various powders) is heated to melt the base, and the composition, now in a low-viscosity fluid state, is sprayed from a spray gun with a temperature-holding function to a constant temperature (usually around the same temperature as the molten composition). The heating temperature of the composition is preferably 10 to 50°C higher than the melting point (melting temperature or softening temperature) of the base (or mixture in the case of a mixture). It is preferable to preheat at least one of the contact surfaces of the pin and the box to which the composition is applied to a temperature higher than the melting point of the base material. This allows for good coating performance. The coating composition is heated and melted in a tank equipped with a suitable stirring device, and then supplied via a compressor and metering pump to the spray head of a spray gun (maintained at a predetermined temperature) for spraying. The temperature inside the tank and the temperature maintained in the spray head are adjusted according to the melting point of the base material in the composition. Subsequently, when the threaded joint is cooled by air cooling, free cooling, etc., the solid lubricating film-forming composition solidifies, and the solid lubricating film according to this embodiment is formed on the contact surface. The thickness of the solid lubricating film thus formed is preferably in the range of 10 to 200 μm, and more preferably in the range of 25 to 100 μm. If the thickness of the solid lubricating film is too small, the lubrication of the pipe threaded joint will be insufficient, and seizing will be more likely to occur during tightening or loosening. In addition, although this solid lubricating film has some corrosion resistance, if the thickness is too small, the corrosion resistance will also be insufficient, and the corrosion resistance of the contact surface will decrease. On the other hand, if the thickness of the solid lubricating coating is too large, it not only wastes the coating but can also have an impact on the environment. When forming both the solid lubricating coating and the solid anticorrosive coating (described later), which may be formed as needed, on a contact surface whose surface roughness has been increased by surface treatment, it is preferable to have a thickness greater than the Rmax of the substrate. Otherwise, it may not be possible to completely cover the substrate. When the substrate is a rough surface, the thickness is the average value of the total thickness of the coating, which can be calculated from the area, mass, and density of the coating. Furthermore, if the solid lubricating film is a thin film of 25 μm or less, a further thin-film rust-preventive coating of solid or liquid may be formed on or below the film. [Solid Corrosion Inhibitory Coating] When the above thermoplastic solid lubricating coating is formed only on the contact surface of one of the pins and boxes of a pipe thread fitting (for example, the box), the contact surface of the other (for example, the pin) may only undergo the surface treatment described later, but preferably a solid corrosion inhibitory coating is formed as the top surface treatment coating layer to provide rust prevention. As mentioned above with respect to Figure 1, in the case of pipe thread fittings, protectors are often attached to the pins and boxes that have not been tightened before actual use. The solid corrosion protection coating is required to be able to withstand at least the force applied when the protector is attached without damaging the coating, not dissolve when exposed to condensed water due to dew point during transportation and storage, and not easily soften even at high temperatures exceeding 40°C. As a coating that satisfies such properties, a solid anticorrosive coating is formed from a composition mainly composed of an ultraviolet-curable resin, which is known to be capable of forming a high-strength coating. As the ultraviolet-curable resin, a known resin composition composed of at least a monomer, an oligomer, and a photoinitiator can be used. There are no particular restrictions on the components and composition of the ultraviolet-curable resin composition as long as it undergoes a photopolymerization reaction when irradiated with ultraviolet light to form a cured coating. Examples of the monomer include, in addition to polyvalent esters of polyhydric alcohols and (meth)acrylic acid (divalent or trivalent or higher), various (meth)acrylate compounds, N-vinylpyrrolidone, N-vinylcaprolactam, and styrene. Examples of the oligomer include, but are not limited to, epoxy (meth)acrylate, urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and silicone (meth)acrylate. A preferred photoinitiator is a compound having absorption at a wavelength of 260 to 450 nm. Examples of the photoinitiator include benzoin and its derivatives, benzophenone and its derivatives, acetophenone and its derivatives, Michler's ketone, benzyl and its derivatives, tetraalkylthiuram monosulfide, thioxanes, and the like. Particularly preferred photoinitiators are thioxanes. The solid anticorrosive coating formed from the ultraviolet-curable resin may contain additives selected from lubricants and rust preventives from the viewpoints of the coating strength and slipperiness. Examples of additives for improving the coating strength are fibrous fillers. The fibrous filler is, for example, needle-like calcium carbonate such as "Wiskal" manufactured by Maruo Calcium Co., Ltd. Examples of the lubricant are metal soaps such as calcium stearate or zinc stearate, and polytetrafluoroethylene (PTFE) resin. These one or more kinds of lubricants can be added in an amount of 0.05 to 0.35 in terms of mass ratio to 1 of the ultraviolet-curable resin. If it is 0.05 or less, the coating strength may be insufficient, while if it exceeds 0.35, the viscosity may increase, the coating workability may decrease, or conversely, the coating strength may decrease. The rust preventive agent is, for example, aluminum tripolyphosphate, aluminum phosphite, or the like. The rust preventive agent can be added up to about 0.10 at most in terms of mass ratio with respect to the ultraviolet curable resin 1. Many solid anticorrosive coatings formed from ultraviolet curable resins are transparent. From the viewpoint of facilitating quality inspection of the formed solid anticorrosive coating by visual inspection or image processing (inspection of the presence or absence of the coating, uniformity / non-uniformity of the coating thickness, etc.), the solid anticorrosive coating may contain a coloring agent. The coloring agent to be used can be selected from pigments, dyes, and fluorescent materials. Since the fluorescent material may not color the coating under visible light in some cases and at least colors the coating under ultraviolet light, it is included in the coloring agent in the present invention. These coloring agents may be commercially available products, and there is no particular limitation as long as quality inspection of the solid anticorrosive coating by visual inspection or image processing is possible. Either organic coloring agents or inorganic coloring agents can be used. When a pigment is added, the transparency of the solid anticorrosive coating decreases or is lost. When the solid anticorrosive coating becomes opaque, it becomes difficult to inspect the presence or absence of damage to the underlying pin screw part. Therefore, when using a pigment, a pigment of a color with high brightness such as yellow or white is preferable. From the viewpoint of corrosion prevention, the smaller the particle size of the pigment, the better, and it is preferable to use one with an average particle size of 5 μm or less. Since a dye does not significantly reduce the transparency of the solid anticorrosive coating, for example, a dye of a strong color such as red or blue does not cause any problems. The addition amount of the pigment and the dye is preferably up to 0.05 at most in terms of mass ratio with respect to the ultraviolet curable resin 1. If it exceeds 0.05, the corrosion prevention property may decrease. A more preferable addition amount in terms of mass ratio is 0.02 or less. The fluorescent material may be any of the phosphors used in fluorescent pigments, fluorescent dyes, and fluorescent paints. Fluorescent pigments are roughly classified into inorganic fluorescent pigments and daylight fluorescent pigments. Inorganic fluorescent pigments include, for example, zinc sulfide or zinc cadmium sulfide-based (containing a metal activator), calcium halophosphate-based, rare earth-activated strontium chloroapatite-based, etc., and often two or more of them are mixed and used. Inorganic fluorescent pigments are excellent in weather resistance and heat resistance. There are several types of daylight fluorescent pigments, but the mainstream is the synthetic resin solid solution type, in which fluorescent dyes are incorporated into a colorless synthetic resin to create the pigment. Fluorescent dyes themselves can also be used. In addition, various inorganic or organic fluorescent pigments, especially synthetic resin solid solution types, are used in fluorescent paints and fluorescent printing inks, and these fluorescent materials can be used as fluorescent pigments or fluorescent dyes. Solid corrosion-preventive coatings containing fluorescent pigments or dyes are colorless or colored and transparent under visible light, but they emit light and change color when irradiated with a black light or ultraviolet light, allowing for confirmation of the presence or absence of the coating and any unevenness in its thickness. Furthermore, because they are transparent under visible light, the substrate beneath the solid corrosion-preventive coating can be observed. Therefore, inspection of damage to the threaded portion of screw joints is not hindered by the solid corrosion-preventive coating. The amount of these fluorescent materials added is preferably up to approximately 0.05 by mass ratio per 1 part ultraviolet-curing resin. Exceeding 0.05 may reduce corrosion resistance. A more preferable mass ratio for the added amount is 0.02 or less. In addition, to enable quality control of the underlying threaded portion as well as the solid corrosion-preventive coating, it is preferable to use fluorescent materials, particularly fluorescent pigments, as colorants. A solid anticorrosion coating consisting of an ultraviolet-curing resin layer is formed by applying a composition mainly composed of an ultraviolet-curing resin (including a composition consisting solely of an ultraviolet-curing resin composition) to the contact surface of a screw fitting, and then curing the coating by irradiating it with ultraviolet light. By repeatedly applying the coating and irradiating it with ultraviolet light, a solid corrosion-preventive coating consisting of two or more ultraviolet-curable resin layers may be formed. This multi-layering of the solid corrosion-preventive coating further increases its strength, preventing it from being destroyed by the force applied during tightening of the screw joint, thus further improving the corrosion resistance of the screw joint. In this invention, since there is no lubricating coating beneath the solid corrosion-preventive coating, there is no need for the solid corrosion-preventive coating to be destroyed during tightening of the screw joint; in fact, the corrosion resistance of the screw joint is higher if the solid corrosion-preventive coating is not destroyed. Ultraviolet light can be emitted using a commercially available ultraviolet irradiation device with an output wavelength in the 200-450 nm range. Examples of ultraviolet light sources include high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, carbon arc lamps, metal halide lamps, and sunlight. The irradiation time and ultraviolet light intensity can be appropriately set by a person skilled in the art. The thickness of the solid corrosion protection coating (total thickness if it consists of two or more UV-curable resin layers) is preferably in the range of 5 to 50 μm, and more preferably in the range of 10 to 40 μm. It is also preferable that it be smaller than the thickness of the solid lubricating coating formed on the mating member. If the thickness of the solid corrosion protection coating is too thin, it may not function sufficiently as a corrosion protection coating, and the corrosion resistance of the pipe thread fitting may be insufficient. On the other hand, if the thickness of the solid corrosion protection coating is greater than 50 μm, when protective members such as airtight protectors are attached to the end of the oil well pipe, the solid corrosion protection coating may be destroyed by the force when attaching the protector, and the corrosion resistance of the pipe thread fitting will also be insufficient. In addition, wear particles will be discharged into the environment at that time, which will degrade the working environment. If the thickness of the solid corrosion protection coating is greater than the thickness of the solid lubricating coating on the mating member, it may impair the lubrication performance of the lubricating coating. Since the solid corrosion-preventive coating, which is mainly composed of ultraviolet-curing resin, is a transparent coating, the condition of the substrate can be observed without removing the coating, and the threaded portion can be inspected from above the coating before tightening. Therefore, by forming this solid corrosion-preventive coating on the contact surface of pins, where the threaded portion is formed on the outer surface and is more susceptible to damage, it becomes possible to easily inspect the threaded portion of pins, which are typically formed on the outer surface of steel pipe ends and are prone to damage, for damage while leaving the coating intact. [Surface Treatment] The threaded and sealing portions, which are the contact surfaces of pipe thread fittings, are formed by cutting processes including threading, and generally have a surface roughness of about 3 to 5 μm. Increasing the surface roughness of the contact surface can improve the adhesion of the coating formed thereon, and as a result, performance such as seizure resistance and corrosion resistance can be improved. For this reason, it is preferable to apply a surface treatment that increases the surface roughness to the contact surfaces of at least one of the components of the pin and the box, preferably both components, prior to coating formation. Examples of such surface treatments include blasting, which involves projecting blasting materials such as spherical shots or angular grids, or pickling, which involves immersing the material in a strong acid solution such as sulfuric acid, hydrochloric acid, nitric acid, or hydrofluoric acid to roughen the surface. These treatments can increase the surface roughness of the substrate itself. Other examples of surface treatments include chemical conversion treatments such as phosphate chlorination, oxalate conversion, and borate conversion, as well as metallic plating. These methods form a substrate coating on the surface of the base material that has a high surface roughness and high adhesion. Chemical conversion treatment forms a chemical conversion coating with a high surface roughness consisting of needle-shaped crystals. Metallic plating includes electroplating of copper, iron, and their alloys (the surface becomes slightly rougher because the raised parts are preferentially plated), impact plating of zinc or zinc alloys in which particles coated with zinc or zinc-iron alloy are projected onto an iron core using centrifugal force or air pressure to form a porous metallic coating in which zinc or zinc-iron alloy particles are deposited, and composite metallic plating which forms a coating in which solid fine particles are dispersed in a metal. Regardless of the method used for surface preparation of the contact surface, it is preferable to roughen the surface by the surface preparation so that the surface roughness Rmax is 5 to 40 μm. If Rmax is less than 5 μm, adhesion with the coating formed thereon may be insufficient. On the other hand, if Rmax exceeds 40 μm, friction will increase, and the coating may not be able to withstand the shear and compressive forces when subjected to high surface pressure, making it prone to breakage or peeling. Two or more types of surface preparation may be used in combination for roughening the surface. Also, different surface preparations may be applied to the pins and the box. From the viewpoint of adhesion of solid corrosion-preventive coatings or solid lubricating coatings, a surface treatment that can form a porous coating is preferred. In particular, phosphate treatment using manganese phosphate, zinc phosphate, iron-manganese phosphate, or zinc-calcium phosphate, and the formation of a zinc or zinc-iron alloy coating by impact plating are preferred as surface treatments. From the viewpoint of adhesion of the coating formed on top, a manganese phosphate coating is preferred, and from the viewpoint of corrosion resistance, a zinc or zinc-iron alloy coating that can be expected to have sacrificial corrosion protection ability due to zinc is preferred. Particularly preferred as a surface treatment for solid lubricating coatings is manganese phosphate conversion treatment, and particularly preferred as a surface treatment for solid anticorrosive coatings are zinc phosphate conversion treatment and zinc or zinc-iron alloy plating by impact plating. Both coatings formed by phosphate treatment and zinc or zinc-iron alloy coatings formed by impact plating are porous coatings. When a solid corrosion-preventive coating or a solid lubricating coating is formed on top of these, the adhesion of the coating is enhanced due to the so-called "anchor effect" of the porous coating. As a result, peeling of the solid lubricating coating becomes less likely even with repeated tightening and loosening, intermetallic contact is effectively prevented, and seizure resistance, airtightness, and corrosion resistance are further improved. Phosphate treatment can be carried out by immersion or spraying according to conventional methods. As the chemical treatment solution, an acidic phosphate treatment solution for general zinc plating materials can be used. For example, a zinc phosphate-based chemical treatment consisting of 1 to 150 g / L of phosphate ions, 3 to 70 g / L of zinc ions, 1 to 100 g / L of nitrate ions, and 0 to 30 g / L of nickel ions can be used. Manganese phosphate-based chemical treatment solutions, which are commonly used for threaded joints, can also be used. The solution temperature can be from room temperature to 100°C, and the treatment time can be up to 15 minutes depending on the desired film thickness. To promote film formation, a surface conditioning aqueous solution containing colloidal titanium can be supplied to the treatment surface before phosphate treatment. After phosphate treatment, it is preferable to wash with water or hot water and then dry. Impact plating can be performed by mechanical plating, in which particles and the object to be plated collide in a rotating barrel, or by projection plating, in which particles are impacted onto the object to be plated using a blasting device. In this invention, since it is only necessary to plate the contact surface, it is preferable to use projection plating, which allows for localized plating. For example, a projection material consisting of particles in which the surface of an iron-based core is coated with zinc or a zinc alloy (e.g., a zinc-iron alloy) can be projected onto the contact surface to be coated. The zinc or zinc alloy content in the particles is preferably in the range of 20 to 60% by mass, and the particle size is preferably in the range of 0.2 to 1.5 mm. By projection, only the zinc or zinc alloy, which is the coating layer of the particles, adheres to the contact surface, and a porous film made of zinc or zinc alloy is formed on the contact surface. This projection plating can form a plating film with good adhesion to the steel surface regardless of the steel material. The thickness of the zinc or zinc alloy layer formed by impact plating is preferably 5 to 40 μm, considering both corrosion resistance and adhesion. If it is less than 5 μm, sufficient corrosion resistance may not be ensured, while if it exceeds 40 μm, adhesion to the lubricating film may actually decrease. Similarly, the thickness of the phosphate film is also preferably in the range of 5 to 40 μm. As an alternative surface treatment, certain single-layer or multi-layer electroplating, although not having a roughening effect, is effective in improving seizure resistance, especially when used as a base for solid lubricant coatings. Examples of such plating include single-layer plating with Cu, Sn, or Ni metals, single-layer plating with Cu-Sn alloy as described in Japanese Patent Publication No. 2003-074763, two-layer plating of a Cu layer and a Sn layer, and even three-layer plating with Ni, Cu, and Sn layers. For steel pipes made of steel with a Cr content of 5% or more, Cu-Sn alloy plating, two-layer plating of Cu plating-Sn plating, and three-layer plating of Ni plating-Cu plating-Sn plating are preferred. More preferred are two-layer plating of Cu plating-Sn plating, three-layer plating of Ni strike plating-Cu plating-Sn plating, and Cu-Sn-Zn alloy plating. Such metal or metal alloy plating can be carried out according to a method described in Japanese Patent Publication No. 2003-074763. In the case of multilayer plating, the bottom layer of plating (usually Ni plating) is preferably an extremely thin plating layer with a thickness of less than 1 μm, called strike plating. The thickness of the plating (total thickness in the case of multilayer plating) is preferably in the range of 5 to 15 μm. The following describes embodiments of the present invention. However, the present invention is not limited by these embodiments. In the embodiments, the contact surface of a pin is referred to as the pin surface, and the contact surface of a box is referred to as the box surface. Also, unless otherwise specified, % and parts in the embodiments refer to mass % and parts by mass, respectively. [Example 1 of the present invention] The pin surface and box surface of a VAM21 (registered trademark) pipe thread fitting manufactured by Nippon Steel & Sumitomo Metal Corporation (outer diameter: 24.448 cm (9-5 / 8 inches), wall thickness: 1.199 cm (0.472 inches)), steel type: carbon steel (C: 0.21%, Si: 0.25%, Mn: 1.1%, P: 0.02%, S: 0.01%, Cu: 0.04%, Ni: 0.06%, Cr: 0.17%, Mo: 0.04%, remainder: iron and impurities) were subjected to the following surface treatment. The pin surface was machine-ground (surface roughness 3 μm), and then immersed in a zinc phosphate conversion treatment solution at 75-85°C for 10 minutes to form a 10 μm thick zinc phosphate coating (surface roughness 8 μm). On the other hand, the box surface was machine-ground (surface roughness 3 μm), and then immersed in a manganese phosphate conversion treatment solution at 80-95°C for 10 minutes to form a 12 μm thick manganese phosphate coating (surface roughness 10 μm). A solid lubricating film-forming composition having the composition described below was heated to 120°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the pin surface and box surface, which had been pre-treated as described above, were pre-heated to 130°C by induction heating. Then, using a spray gun with a spray head that had a heat retention function, the solid lubricating film-forming composition shown in Example 1 of the Invention in Table 1, in which the base resin had become molten, was applied to both the pin surface and the box surface. After cooling, a solid lubricating film with an average thickness of 30 μm was formed. Table 1 shows the component composition (mass%) of the lubricating film-forming composition, the mass ratio of ethylene vinyl acetate resin to polyolefin resin (EVA / PO), the ratio of the mass sum of the two resins to WAX ((EVA+PO) / W), and the sum of the mass percentages of the binder to the whole composition (mass%) for each of Example 1 of the Invention, Examples 2 to 8 described later, and Comparative Examples 1 to 6. The composition of the lubricating film-forming composition in Example 1 of the present invention is as follows. As mentioned above, the content (%) is expressed in mass % unless otherwise specified. (Binder) ・Ethylene vinyl acetate resin: 21.6% ・Polyolefin resin: 16% ・Wax (paraffin wax, melting point 69°C): 32.4% (Fluorine-based additive) ・PFPE (perfluoropolyether): 10% ・Fluorinated polymer: 4% (Solid lubricant) ・Clay-like graphite (average particle size 7 μm): 5% ・Fluorinated graphite (CFx): 4% (Rust-preventive additive) ・Ca ion-exchange silica: 5% ・Aluminum phosphite: 2% For Example 1 of the present invention, a tightening and loosening test (tightening speed 10 rpm, tightening torque 42.8 kN・m) of a pipe thread fitting was performed at a low temperature of approximately -40°C for up to 10 cycles. Specifically, the area around the thread fastening part was cooled to approximately -40°C with dry ice, and then the tightening and loosening test was performed. As a result, even when cooled to -40°C, the solid lubricating film did not peel off or crack. The seizure status of the contact surfaces of the pin and box after repeated tightening was investigated (the number of times tightening could be performed without seizure (maximum 10 times), in which case minor seizure that could be recovered was repaired and tightening continued). The results of the seizure occurrence status are shown in Table 2. For the second and subsequent tests, the tightening and loosening tests were performed after cooling to -40°C in the same manner as the first test, and as a result, no seizure occurred, and 10 tightening and loosening cycles could be performed. As shown in Table 2, a salt spray test was conducted in accordance with JIS Z2371:2000. As a result, no rust occurred in Example 1 of the present invention even after 1000 hours. Furthermore, based on previous experience, it has been shown that if there is no rust for 750 hours, the long-term rust prevention performance in actual pipes is sufficient. Furthermore, shear tensile tests were conducted to measure the adhesion strength of the solid lubricant coating at ambient temperatures of room temperature (approximately 25°C) and -40°C. The specific method of these shear tensile tests will be described below with reference to Figure 4. First, two metal plates (for example, carbon steel) 28 and 30, each 75 mm long, 25 mm wide, and 0.8 mm thick, were prepared. A solid lubricating film 32 with a thickness of 50 μm was formed in a 25 mm x 25 mm area between the two metal plates. Specifically, PTFE sheets 34 and 36 with a thickness of 50 μm were sandwiched between the metal plates 28 and 30 at predetermined positions as film thickness setting sheets. After applying a solid lubricating film composition heated to 120°C, the two metal plates were pressed together (up and down in Figure 4) and cooled to form the film 32. Next, the PTFE sheets 34 and 36 were removed, and one end of each of the metal plates 28 and 30 was grasped using appropriate chucks 38 and 40. The entire assembly was placed in the chamber 42 shown in the schematic diagram, and the chamber 42 was maintained at 25°C or -40°C. In this state, the chucks 38 and 40 were moved at a speed of 50 mm / min in a direction away from each other along the length of the metal plate (i.e., in the direction in which a shear force acts on the coating 32), and the load F (kPa) at which the coating 32 broke was measured. The results are shown in Table 2. It was confirmed that Example 1 of the present invention had significantly higher adhesion strength at both 25°C and -40°C compared to the conventional comparative examples 1 and 2 described later. The acceptable line for adhesion strength was set at 1500 kPa or higher at both 25°C and -40°C. Furthermore, for screw fittings (boxes) that had the same solid lubrication coating as those used in actual tightening and loosening tests, the degree of deterioration of the solid lubrication coating was investigated by exposing them to a low temperature for a predetermined time and then to an outdoor environment (low temperature-outdoor exposure test). Specifically, as schematically illustrated in the flowchart of Figure 5, first, it was confirmed that there was no peeling or cracking of the solid lubrication coating of the screw fitting in the initial state (step S1). Next, the screw fitting was exposed to a low temperature of -60°C for 24 hours with a protector attached (step S2), and then the condition of peeling and cracking was checked after removing the protector (step S3). Next, the screw fitting was fitted with a protector and exposed to a low temperature of -60°C again for 24 hours (step S4), and then the condition of peeling and cracking was checked after removing the protector (step S5). Finally, the screw fitting was left outdoors for one year while being periodically (once a day) showered with water (step S6) to investigate the low-temperature deterioration of the solid lubrication coating of the screw fitting, i.e., the condition of peeling and cracking due to the low temperature-atmosphere temperature cycle (step S7). Table 2 shows the results of the low-temperature-outdoor exposure test described above. In Example 1 of the present invention, no cracking, peeling, or blistering (lifting of the coating) of the solid lubricating film occurred even after exposure to a low temperature of -60°C for a total of 48 hours, or after further exposure to a temperature difference between the low temperature and ambient temperature, or after one year of outdoor exposure. Table 2 shows the results of the above seizure occurrence status, salt spray test, shear tensile test, and low-temperature-outdoor exposure test for Example 1 of the present invention, Examples 2 to 8 of the present invention described later, and Comparative Examples 1 to 6. [Example 2 of the present invention] The pin surface and box surface of the carbon steel pipe thread fitting used in Example 1 of the present invention were subjected to the following surface treatment. The pin surface was machine-ground (surface roughness 3 μm), then immersed in a zinc phosphate chemical treatment solution at 75-85°C for 10 minutes to form an 8 μm thick zinc phosphate coating (surface roughness 8 μm). Furthermore, a UV-curable resin coating composition was applied to the pin surface. This composition consisted of an acrylic resin-based UV-curable resin paint to which 0.05 parts of aluminum phosphite (a rust inhibitor) and 0.01 parts of polyethylene wax (a lubricant) were added by mass ratio to 1 part of the resin in the paint. The coating was then cured by irradiation with ultraviolet light under the following conditions to form a 25 μm thick UV-curable resin coating. The formed solid anticorrosion coating was colorless and transparent, and the male thread portion could be inspected with the naked eye or a magnifying glass from above the coating. UV lamp: Air-cooled mercury lamp; UV lamp output: 4kW; UV wavelength: 260nm The box surface was machine-ground (surface roughness 3 μm), and then electroplated first with Ni strike plating, followed by Cu-Sn-Zn alloy plating, to form a total plating film with a thickness of 8 μm. Subsequently, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the box surface, which had been pre-treated as described above, was preheated to 130°C by induction heating, and the molten solid lubricating film-forming composition was applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 50 μm was formed. The composition of the lubricating film-forming composition in Example 2 of the present invention is as follows: (Binder) Ethylene vinyl acetate resin: 17% Polyolefin resin: 12.2% Wax (paraffin wax, melting point 69°C): 36.8% (Fluorine-based additive) PFPE (perfluoropolyether): 10% Fluorinated polymer: 7% (Solid lubricant) Earthy graphite (average particle size 7 μm): 10% (Rust-preventive additive) Ca ion exchange silica: 5% Aluminum phosphite: 2% For Example 2 of the present invention, repeated tightening and loosening tests of pipe thread fittings were performed in the same manner as in Example 1. The results are shown in Table 2 for Example 2 of the present invention. Excellent effects similar to those in Example 1 of the present invention were confirmed. [Example 3 of the Invention] In the same screw type as in Example 1 of the Invention, the pin surface and box surface of a pipe thread fitting (outer diameter: 24.448 cm (9-5 / 8 inches), wall thickness: 1.105 cm (0.435 inches)) made of 13Cr steel (C: 0.19%, Si: 0.25%, Mn: 0.9%, P: 0.02%, S: 0.01%, Cu: 0.04%, Ni: 0.11%, Cr: 13%, Mo: 0.04%, remainder: iron and impurities), which is more prone to seizing than carbon steel, were subjected to the following surface treatment. The pin surface was machine-ground (surface roughness 3 μm), and then coated with a UV-curable resin coating composition. This composition consisted of an acrylic resin-based UV-curable resin paint to which, by mass ratio, 0.05 parts of aluminum tripolyphosphate (a rust inhibitor), 0.01 parts of polyethylene wax (a lubricant), and 0.003 parts of fluorescent pigment were added to 1 part of the resin in the paint. The coating was then cured by irradiation with ultraviolet light under the following conditions, forming a UV-curable resin coating with a thickness of 25 μm. The formed coating was colorless and transparent, and the male thread portion could be inspected with the naked eye or a magnifying glass from above the coating. UV lamp: Air-cooled mercury lamp; UV lamp output: 4kW; UV wavelength: 260nm The box surface was machine-ground (surface roughness 3 μm), and then electroplated first with Ni strike plating, followed by Cu-Sn-Zn alloy plating, to form a total plating film with a thickness of 8 μm. Subsequently, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to create a composition with a viscosity suitable for application and in a molten state. Meanwhile, the box surface, which had been pre-treated as described above, was preheated to 130°C by induction heating, and the molten solid lubricating film-forming composition was applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 25 μm was formed. The composition of the lubricating film-forming composition in Example 3 of the present invention is as follows: (Binder) Ethylene vinyl acetate resin: 22% Polyolefin resin: 21% Wax (paraffin wax, melting point 69°C): 31% (Fluorine-based additive) PFPE (perfluoropolyether): 10% Fluorinated polymer: 4% (Solid lubricant) PTFE: 10% (Rust inhibitor additive) Aluminum phosphite: 2% For Example 3 of the present invention, repeated tightening and loosening tests of pipe thread fittings were performed in the same manner as in Example 1. The results for Example 3 of the present invention are shown in Table 2. Excellent effects similar to those of Examples 1 and 2 were confirmed. [Example 4 of the Invention] Using the same pipe thread fittings and steel type as in Example 1 of the Invention, the surface treatment of Example 2 was applied to the pin and box. Then, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to create a composition with a viscosity suitable for application and in a molten state. Meanwhile, the surface of the box, which had been surface-treated as described above, was preheated to 130°C by induction heating. The molten solid lubricating film-forming composition was then applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 30 μm was formed. The composition of the lubricating film-forming composition in Example 4 of the present invention is as follows: (Binder) Ethylene vinyl acetate resin: 26% Polyolefin resin: 16% Wax (paraffin wax, melting point 69°C): 37% (Fluorine-based additive) PFPE (perfluoropolyether): 9% (Solid lubricant) Earthy graphite (average particle size 7 μm): 5% Fluorinated graphite (CFx): 4% (Rust inhibitor additive) Aluminum phosphite: 3% For Example 4 of the present invention, repeated tightening and loosening tests of pipe thread fittings were performed in the same manner as in Example 1. The results for Example 4 of the present invention are shown in Table 2. Excellent effects similar to those of Examples 1 to 3 were confirmed. [Example 5 of the Invention] Using the same pipe thread fittings and steel type as in Example 1 of the Invention, the surface treatment of Example 2 was applied to the pin and box. Then, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to create a composition with a viscosity suitable for application and in a molten state. Meanwhile, the surface of the box, which had been surface-treated as described above, was preheated to 130°C by induction heating. The molten solid lubricating film-forming composition was then applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 30 μm was formed. The composition of the lubricating film-forming composition in Example 5 of the present invention is as follows: (Binder) Ethylene vinyl acetate resin: 21.6% Polyolefin resin: 16% Wax (polyethylene wax, melting point 110°C): 32.4% (Fluorine-based additive) PFPE (perfluoropolyether): 10% Fluorinated polymer: 4% (Solid lubricant) Earthy graphite (average particle size 7 μm): 5% Fluorinated graphite (CFx): 4% (Rust-preventive additive) Ca ion exchange silica: 5% Aluminum phosphite: 2% For Example 5 of the present invention, repeated tightening and loosening tests of pipe thread fittings were performed in the same manner as in Example 1 of the present invention. The results for Example 5 of the present invention are shown in Table 2. Compared to Examples 3 and 4 of the present invention, the sum of the mass ratios of the binder was lower at 70%, which may explain why the adhesion strength in the shear tensile test at 25°C was sufficient, but the adhesion strength in the shear tensile test at -40°C was somewhat lower. In Example 5 of the present invention, the difference between the adhesion strength at room temperature and the adhesion strength in the cryogenic environment was large. Furthermore, in the tightening and loosening test at -40°C, no seizing occurred until the 7th time, but slight seizing occurred in the threaded portion on the 8th time, and after maintenance, the test was completed up to the 10th time. In addition, in the low-temperature-outdoor exposure test, no cracking or peeling occurred even when exposed to low temperatures or subjected to temperature differences between low temperature and ambient temperature, but slight peeling of the solid lubricating film (lifting of the film) was observed after one year of outdoor exposure. However, this peeling was at a level that did not cause problems in practical use. [Example 6 of the Invention] Using the same pipe thread fittings and steel type as in Example 1 of the Invention, the surface treatment of Example 2 was applied to the pin and box. Then, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to create a composition with a viscosity suitable for application and in a molten state. Meanwhile, the surface of the box, which had been pre-treated as described above, was also preheated to 130°C by induction heating. The molten solid lubricating film-forming composition was then applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 30 μm was formed. The composition of the lubricating film-forming composition in Example 6 of the present invention is as follows: (Binder) ・Ethylene vinyl acetate resin: 20.5% ・Polyolefin resin: 19.5% ・Wax (polyethylene wax, melting point 78℃): 36% (Fluorine-based additive) ・PFPE (perfluoropolyether): 8% (Solid lubricant) ・Clay graphite (average particle size 7μm): 7% (Rust-preventive additive) ・Ca ion-exchange silica: 3% ・Aluminum phosphite: 4% (Friction modifier) ​​・Talc (particle size 4.5μm, specific surface area 9.5m2 / g): 2% The particle size of talc was determined as described above using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, SALD-2000J). The specific surface area of ​​talc was determined as described above. For Example 6 of the present invention, repeated tightening and loosening tests of pipe thread fittings were performed in the same manner as in Example 1. The results for Example 6 of the present invention are shown in Table 2. Excellent effects similar to those of Examples 1 to 4 were confirmed. For Example 6 of the present invention, the difference between yield torque and shouldering torque was further measured as follows. A threaded joint sample was prepared and fastened using a suitable torque wrench. After fastening, further torque was applied to tighten the joint, and a torque chart as shown in Figure 6 was created. On the torque chart, the shouldering torque, yield torque, and the difference between yield torque and shouldering torque were measured. Shouldering torque is the torque value when the shoulder portion makes contact and the torque change begins to move away from the first linear region (elastic deformation region). On the other hand, yield torque is the torque value when plastic deformation begins. Specifically, it is the torque value that occurs after reaching shouldering torque and begins to move away from the second linear region. The results for Example 6 of the present invention are shown in Table 2. When the difference between yield torque and shouldering torque in Example 3 of the present invention is set to 100, the difference between yield torque and shouldering torque in Example 6 of the present invention is 120, showing excellent over-torque performance. [Example 7 of the Invention] Using the same pipe thread fittings and steel type as in Example 1 of the Invention, the surface treatment of Example 2 was applied to the pin and box. Then, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to create a composition with a viscosity suitable for application and in a molten state. Meanwhile, the surface of the box, which had been surface-treated as described above, was preheated to 130°C by induction heating. The molten solid lubricating film-forming composition was then applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 30 μm was formed. The composition of the lubricating film-forming composition in Example 7 of the present invention is as follows: (Binder) Ethylene vinyl acetate resin: 20.5% Polyolefin resin: 19.5% Wax (polyethylene wax, melting point 78°C): 33% (Fluorine-based additive) PFPE (perfluoropolyether): 8% (Solid lubricant) Earthy graphite (average particle size 7 μm): 7% (Rust-preventive additive) Ca ion-exchange silica: 3% Aluminum phosphite: 4% (Friction modifier) ​​Talc (particle size 3.3 μm, specific surface area 12.0 m² / g): 5% The particle size and specific surface area of ​​talc were determined by the same method as in Example 6 of the present invention. For Example 7 of the present invention, repeated tightening and loosening tests of pipe thread fittings were performed in the same manner as in Example 1. The results for Example 7 of the present invention are shown in Table 2. Excellent effects similar to those of Examples 1 to 4 and Example 6 of the present invention were confirmed. For Example 7 of the present invention, the difference between yield torque and shouldering torque was further measured in the same manner as in Example 6 of the present invention. The results for Example 7 of the present invention are shown in Table 2. When the difference between yield torque and shouldering torque in Example 3 of the present invention is set to 100, the difference between yield torque and shouldering torque in Example 7 of the present invention was 145, demonstrating excellent over-torque performance. [Example 8 of the Invention] Using the same pipe thread fittings and steel type as in Example 1 of the Invention, the surface treatment of Example 2 was applied to the pin and box. Then, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to create a composition with a viscosity suitable for application and in a molten state. Meanwhile, the surface of the box, which had been surface-treated as described above, was preheated to 130°C by induction heating. The molten solid lubricating film-forming composition was then applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 30 μm was formed. The composition of the lubricating film-forming composition in Example 8 of the present invention is as follows: (Binder) Ethylene vinyl acetate resin: 20.5% Polyolefin resin: 19.5% Wax (polyethylene wax, melting point 78°C): 32% (Fluorine-based additive) PFPE (perfluoropolyether): 8% (Solid lubricant) Earthy graphite (average particle size 7 μm): 7% (Rust-preventive additive) Ca ion-exchange silica: 3% Aluminum phosphite: 4% (Friction modifier) ​​Talc (particle size 8.0 μm, specific surface area 7.0 m² / g): 6% The particle size and specific surface area of ​​the talc were measured in the same manner as in Example 6 of the present invention. For Example 8 of the present invention, repeated tightening and loosening tests of pipe thread fittings were performed in the same manner as in Example 1. The results for Example 8 of the present invention are shown in Table 2. Excellent effects similar to those of Examples 1 to 4 and Examples 6 to 7 of the present invention were confirmed. For Example 8 of the present invention, the difference between yield torque and shouldering torque was measured in the same manner as in Example 6 of the present invention. The results for Example 8 of the present invention are shown in Table 2. When the difference between yield torque and shouldering torque in Example 3 of the present invention is set to 100, the difference between yield torque and shouldering torque in Example 8 of the present invention was 180, demonstrating excellent over-torque performance. [Comparative Example 1] The pin surface and box surface of the same carbon steel pipe thread fitting used in Example 1 of the present invention were subjected to the following surface treatment. The pin surface was machine-ground (surface roughness 3 μm), and then immersed in a zinc phosphate conversion treatment solution at 75-85°C for 10 minutes to form a 10 μm thick zinc phosphate coating (surface roughness 8 μm). On the other hand, the box surface was machine-ground (surface roughness 3 μm), and then immersed in a manganese phosphate conversion treatment solution at 80-95°C for 10 minutes to form a 12 μm thick manganese phosphate coating (surface roughness 10 μm). A solid lubricating film-forming composition having the composition described below was heated to 130°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the pin surface and box surface, which had been pre-treated as described above, were also pre-heated to 140°C by induction heating. Then, using a spray gun with a spray head that had a heat retention function, the solid lubricating film-forming composition shown in Example 1 of the present invention in Table 1, in which the base resin was in a molten state, was applied to both the pin surface and the box surface. After cooling, a solid lubricating film with an average thickness of 50 μm was formed. The composition of the lubricating film-forming composition used in Comparative Example 1 was the same as the "Example" described on page 18 of Patent Document 3. For Comparative Example 1, repeated tightening and loosening tests of the pipe thread fitting were performed in the same manner as in Example 1 of the present invention. The results for Comparative Example 1 are shown in Table 2. No seizing occurred until the third time, but slight seizing occurred in the threaded portion on the fourth time. After cleaning, the test was continued up to the fifth time. However, seizing occurred on the sixth time that could not be cleaned, so the test was terminated. In the case of conventional solid lubricant coatings like those in Comparative Example 1, it is possible to perform five tightening and loosening tests at ambient temperatures (-10 to 30°C), but the performance deteriorates significantly at -40°C. Furthermore, although there are no practical problems in the salt spray test, slight rust occurs after 1000 hours. In other words, the present invention is a significant improvement over the conventional technology from the viewpoint of rust prevention. Moreover, the adhesion strength in the shear tensile test is significantly lower than that of the present invention example, and in particular, the adhesion strength at -40°C is extremely low, less than 1000 kPa. Furthermore, in Comparative Example 1, during the low-temperature outdoor exposure test, slight delamination of the coating occurred when the protector was removed at ambient temperature after being exposed to a low temperature of -60°C for 24 hours. When exposed again to -60°C for 24 hours, the delamination area increased, and after one year of outdoor exposure, it was observed that delamination (lifting of the coating) had occurred in 5-10% of the solid lubricating coating. [Comparative Example 2] The pin surface and box surface of the carbon steel pipe thread fitting used in Example 1 of the present invention were subjected to the same surface treatment as in Comparative Example 1, as described below. The pin surface was machine-ground (surface roughness 3 μm), and then immersed in a zinc phosphate conversion treatment solution at 75-85°C for 10 minutes to form a 10 μm thick zinc phosphate coating (surface roughness 8 μm). On the other hand, the box surface was machine-ground (surface roughness 3 μm), and then immersed in a manganese phosphate conversion treatment solution at 80-95°C for 10 minutes to form a 12 μm thick manganese phosphate coating (surface roughness 10 μm). A solid lubricating film-forming composition having the composition described below was heated to 130°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the pin surface and box surface, which had been pre-treated as described above, were also pre-heated to 140°C by induction heating. Then, using a spray gun with a spray head that had a heat retention function, the solid lubricating film-forming composition shown in Example 1 of the present invention in Table 1, in which the base resin was in a molten state, was applied to both the pin surface and the box surface. After cooling, a solid lubricating film with an average thickness of 50 μm was formed. The composition of the lubricating film-forming composition used in Comparative Example 2 corresponds to "Example 1 of the Invention" described on pages 20-21 of Patent Document 4. For Comparative Example 2, repeated tightening and loosening tests of the pipe thread fitting were performed in the same manner as in Example 1 of the present invention. The results for Comparative Example 2 are shown in Table 2. No seizing occurred until the fourth time, but slight seizing occurred in the threaded portion on the fifth time. After maintenance, the test was continued until the sixth time. However, seizing occurred on the seventh time to the point where maintenance was no longer possible, so the test was terminated. In the case of conventional solid lubricant coatings like those in Comparative Example 2, it can be seen that although 10 tightening and loosening tests are possible at ambient temperatures (-10 to 30°C), the performance deteriorates significantly at -40°C. Furthermore, although there are no practical problems in the salt spray test, slight rust occurs after 1000 hours. In other words, it can be seen that the present invention is a significant improvement over the conventional technology from the viewpoint of rust prevention. Moreover, it can be seen that the adhesion strength in the shear tensile test is significantly lower than that of the present invention example, and in particular, the adhesion strength at -40°C is extremely low, less than 1000 kPa. In Comparative Example 2, during the low-temperature outdoor exposure test, slight delamination of the coating occurred when the protector was removed at ambient temperature after being exposed to a low temperature of -60°C for 24 hours. Furthermore, when exposed again to -60°C for 24 hours, the delamination area increased, and after one year of outdoor exposure, it was observed that delamination (lifting of the coating) had occurred in 5-10% of the solid lubricating coating. [Comparative Example 3] The pin surface and box surface of the same carbon steel pipe thread fitting used in Example 1 of the present invention were subjected to the following surface treatment in the same manner as in Example 2 of the present invention. The pin surface was machine-ground (surface roughness 3 μm), then immersed in a zinc phosphate chemical treatment solution at 75-85°C for 10 minutes to form an 8 μm thick zinc phosphate coating (surface roughness 8 μm). Furthermore, a UV-curable resin coating composition was applied to the pin surface. This composition consisted of an acrylic resin-based UV-curable resin paint to which 0.05 parts of aluminum phosphite (a rust inhibitor) and 0.01 parts of polyethylene wax (a lubricant) were added by mass ratio to 1 part of the resin in the paint. The coating was then cured by irradiation with ultraviolet light under the following conditions to form a 25 μm thick UV-curable resin coating. The formed solid anticorrosion coating was colorless and transparent, and the male thread portion could be inspected with the naked eye or a magnifying glass from above the coating. UV lamp: Air-cooled mercury lamp; UV lamp output: 4kW; UV wavelength: 260nm The box surface was machine-ground (surface roughness 3 μm), and then electroplated first with Ni strike plating, followed by Cu-Sn-Zn alloy plating, to form a total plating film with a thickness of 8 μm. Subsequently, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the box surface, which had been pre-treated as described above, was preheated to 130°C by induction heating, and the molten solid lubricating film-forming composition was applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 35 μm was formed. The composition of the lubricating film-forming composition in Comparative Example 3 is as follows: (Binder) Ethylene vinyl acetate resin: 13.5% Polyolefin resin: 15% Wax (paraffin wax, melting point 69°C): 26.5% (Fluorine-based additive) PFPE (perfluoropolyether): 10% Fluorinated polymer: 4% (Solid lubricant) Earthy graphite (average particle size 7 μm): 5% Fluorinated graphite (CFx): 4% (Rust inhibitor additive) Calcium sulfonate derivative: 15% Ca ion exchange silica: 5% Aluminum phosphite: 2% For Comparative Example 3, repeated tightening and loosening tests of the pipe thread fitting were performed in the same manner as in Example 1 of the present invention. The results for Comparative Example 3 are shown in Table 2. No seizing occurred until the fourth time, but slight seizing occurred in the threaded portion on the fifth time. After maintenance, the test was continued until the sixth time. However, seizing occurred on the seventh time to the point where maintenance was no longer possible, so the test was terminated. Furthermore, the adhesion strength in shear tensile tests was significantly lower than that of the present invention example, and in particular, the adhesion strength at -40°C was extremely low, less than 1000 kPa. In addition, in low-temperature outdoor exposure tests, it was observed that delamination (lifting of the coating) occurred in 5-10% of the solid lubricating film after one year of outdoor exposure. Thus, when the EVA / PO ratio is less than 1.0 and the sum of the mass percentages of the binder is 60% or less, the adhesion strength, especially at -40°C, becomes significantly lower. As a result, not only does the coating peel off during low-temperature outdoor exposure tests, but the resistance to seizing during fastening tests also decreases significantly. [Comparative Example 4] The pin surface and box surface of a pipe thread fitting made of carbon steel, the same as that used in Example 1 of the present invention, were subjected to the following surface treatment in the same manner as in Example 2 of the present invention. The pin surface was machine-ground (surface roughness 3 μm), then immersed in a zinc phosphate chemical treatment solution at 75-85°C for 10 minutes to form an 8 μm thick zinc phosphate coating (surface roughness 8 μm). Furthermore, a UV-curable resin coating composition was applied to the pin surface. This composition consisted of an acrylic resin-based UV-curable resin paint to which 0.05 parts of aluminum phosphite (a rust inhibitor) and 0.01 parts of polyethylene wax (a lubricant) were added by mass ratio to 1 part of the resin in the paint. The coating was then cured by irradiation with ultraviolet light under the following conditions to form a 25 μm thick UV-curable resin coating. The formed solid anticorrosion coating was colorless and transparent, and the male thread portion could be inspected with the naked eye or a magnifying glass from above the coating. UV lamp: Air-cooled mercury lamp; UV lamp output: 4kW; UV wavelength: 260nm The box surface was machine-ground (surface roughness 3 μm), and then electroplated first with Ni strike plating, followed by Cu-Sn-Zn alloy plating, to form a total plating film with a thickness of 8 μm. Subsequently, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the box surface, which had been pre-treated as described above, was preheated to 130°C by induction heating, and the molten solid lubricating film-forming composition was applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 35 μm was formed. The composition of the lubricating film-forming composition in Comparative Example 4 is as follows: (Binder) Ethylene vinyl acetate resin: 25.5% Polyolefin resin: 14% Wax (paraffin wax, melting point 69°C): 31.5% (Fluorine-based additive) PFPE (perfluoropolyether): 10% Fluorinated polymer: 4% (Solid lubricant) Earthy graphite (average particle size 7 μm): 5% Fluorinated graphite (CFx): 4% (Rust-preventive additive) Ca ion exchange silica: 5% Aluminum phosphite: 2% For Comparative Example 4, repeated tightening and loosening tests of the pipe thread fitting were performed in the same manner as in Example 1 of the present invention. The results for Comparative Example 4 are shown in Table 2. No seizing occurred during the first test, but slight seizing occurred in the threaded portion during the second test. After cleaning, the test was continued up to the third test. However, seizing occurred during the fourth test to the point where cleaning was no longer possible, so the test was terminated. Comparative Example 4 also showed significantly lower adhesion strength in shear tensile tests compared to the present invention example, with particularly poor adhesion at -40°C. However, because Comparative Example 4 had higher adhesion strength than Comparative Examples 1-3, in the low-temperature outdoor exposure test, less than 1% of the solid lubricating film peeled off (film lifting) after one year of outdoor exposure. However, it was found that when the EVA / PO ratio exceeded 1.8, the anti-seizure performance during fastening tests decreased. This is presumed to be because when the EVA / PO ratio exceeds 1.8, the film hardens, increasing the sliding resistance of the film and hindering lubrication. [Comparative Example 5] The pin surface and box surface of the same carbon steel pipe thread fitting used in Example 1 of the present invention were subjected to the following surface treatment in the same manner as in Example 2 of the present invention. The pin surface was machine-ground (surface roughness 3 μm), then immersed in a zinc phosphate chemical treatment solution at 75-85°C for 10 minutes to form an 8 μm thick zinc phosphate coating (surface roughness 8 μm). Furthermore, a UV-curable resin coating composition was applied to the pin surface. This composition consisted of an acrylic resin-based UV-curable resin paint to which 0.05 parts of aluminum phosphite (a rust inhibitor) and 0.01 parts of polyethylene wax (a lubricant) were added by mass ratio to 1 part of the resin in the paint. The coating was then cured by irradiation with ultraviolet light under the following conditions to form a 25 μm thick UV-curable resin coating. The formed solid anticorrosion coating was colorless and transparent, and the male thread portion could be inspected with the naked eye or a magnifying glass from above the coating. UV lamp: Air-cooled mercury lamp; UV lamp output: 4kW; UV wavelength: 260nm The box surface was machine-ground (surface roughness 3 μm), and then electroplated first with Ni strike plating, followed by Cu-Sn-Zn alloy plating, to form a total plating film with a thickness of 8 μm. Subsequently, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the box surface, which had been pre-treated as described above, was preheated to 130°C by induction heating, and the molten solid lubricating film-forming composition was applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 35 μm was formed. The composition of the lubricating film-forming composition in Comparative Example 5 is as follows: (Binder) Ethylene vinyl acetate resin: 13.5% Polyolefin resin: 10% Wax (paraffin wax, melting point 69°C): 46.5% (Fluorine-based additive) PFPE (perfluoropolyether): 10% Fluorinated polymer: 4% (Solid lubricant) Earthy graphite (average particle size 7 μm): 5% Fluorinated graphite (CFx): 4% (Rust-preventive additive) Ca ion exchange silica: 5% Aluminum phosphite: 2% For Comparative Example 5, repeated tightening and loosening tests of the pipe thread fitting were performed in the same manner as in Example 1 of the present invention. The results for Comparative Example 5 are shown in Table 2. No seizing occurred during the first test, but slight seizing occurred in the threaded portion during the second test, and the test was continued after maintenance. However, during the third test, seizing occurred to the extent that maintenance could not be performed, so the test was terminated. Comparative Example 5 also showed significantly lower adhesion strength in shear tensile tests compared to the present invention example, with particularly poor adhesion at -40°C. Furthermore, in the low-temperature outdoor exposure test, slight delamination of the coating occurred when the protector was removed at ambient temperature after exposure to a low temperature of -60°C for 24 hours. When exposed again to -60°C for 24 hours, the delamination area increased, and after one year of outdoor exposure, it was observed that more than 10% of the solid lubricating coating had delaminated (lifted) from the coating. As shown in Comparative Example 5, when (EVA + PO) / W is less than 0.7, the adhesion strength is generally low, and the decrease in adhesion strength at -40°C is particularly significant. As a result, significant delamination of the coating occurred during low-temperature outdoor exposure tests, and the anti-seize performance during fastening tests was also greatly reduced. The reason for this is presumed to be that when (EVA + PO) / W is less than 0.7, the coating becomes too soft, the adhesion strength decreases drastically, and lubricity cannot be maintained during repeated tightening and loosening tests. [Comparative Example 6] The pin surface and box surface of a carbon steel pipe thread fitting, the same as that used in Example 1 of the present invention, were subjected to the following surface treatment in the same manner as in Example 2 of the present invention. The pin surface was machine-ground (surface roughness 3 μm), then immersed in a zinc phosphate chemical treatment solution at 75-85°C for 10 minutes to form an 8 μm thick zinc phosphate coating (surface roughness 8 μm). Furthermore, a UV-curable resin coating composition was applied to the pin surface. This composition consisted of an acrylic resin-based UV-curable resin paint to which 0.05 parts of aluminum phosphite (a rust inhibitor) and 0.01 parts of polyethylene wax (a lubricant) were added by mass ratio to 1 part of the resin in the paint. The coating was then cured by irradiation with ultraviolet light under the following conditions to form a 25 μm thick UV-curable resin coating. The formed solid anticorrosion coating was colorless and transparent, and the male thread portion could be inspected with the naked eye or a magnifying glass from above the coating. UV lamp: Air-cooled mercury lamp; UV lamp output: 4kW; UV wavelength: 260nm The box surface was machine-ground (surface roughness 3 μm), and then electroplated first with Ni strike plating, followed by Cu-Sn-Zn alloy plating, to form a total plating film with a thickness of 8 μm. Subsequently, a lubricating film-forming composition having the following composition was heated to 120°C in a tank with a stirrer to a molten state with a viscosity suitable for application. Meanwhile, the box surface, which had been pre-treated as described above, was preheated to 130°C by induction heating, and the molten solid lubricating film-forming composition was applied using a spray gun with a spray head that had a heat retention function. After cooling, a solid lubricating film with an average thickness of 35 μm was formed. The composition of the lubricating film-forming composition in Comparative Example 6 is as follows: (Binder) Ethylene vinyl acetate resin: 27% Polyolefin resin: 20% Wax (paraffin wax, melting point 69°C): 23% (Fluorine-based additive) PFPE (perfluoropolyether): 10% Fluorinated polymer: 4% (Solid lubricant) Earthy graphite (average particle size 7 μm): 5% Fluorinated graphite (CFx): 4% (Rust-preventive additive) Ca ion exchange silica: 5% Aluminum phosphite: 2% For Comparative Example 6, repeated tightening and loosening tests of the pipe thread fitting were performed in the same manner as in Example 1 of the present invention. The results for Comparative Example 6 are shown in Table 2. No seizing occurred until the second time, but slight seizing occurred in the threaded portion on the third time. After maintenance, the test was continued until the fourth time. However, on the fifth time, seizing occurred to the extent that maintenance could not be performed, so the test was terminated. Furthermore, shear tensile tests revealed that the adhesion strength at -40°C was significantly lower than that of the present invention example. Moreover, there was a remarkably large difference between the adhesion strength at room temperature and the adhesion strength in an extremely low-temperature environment. In the low-temperature-outdoor exposure test, slight delamination of the coating occurred when the protector was removed at ambient temperature after being exposed to a low temperature of -60°C for 24 hours. Furthermore, when exposed again to -60°C for 24 hours, the delamination area increased, and after one year of outdoor exposure, it was observed that delamination (lifting of the coating) occurred in 5-10% of the solid lubricating coating. As shown in Comparative Example 6, when (EVA + PO) / W significantly exceeds 1.6, the adhesion strength at -40°C decreases, and as a result of film peeling at low temperatures during the low-temperature outdoor exposure test, the anti-seize performance during the fastening test also decreases significantly. The reason for this is thought to be that when (EVA + PO) / W exceeds 1.6, the film hardens, and while the adhesion strength increases at ambient temperatures, the improvement in adhesion strength at -40°C is small, the sliding resistance of the film increases, and lubrication is inhibited, resulting in low anti-seize performance during the fastening test. In the above embodiment, a pipe thread fitting with an outer diameter of 24.448 cm (9-5 / 8 inches) was described, but it has been verified that similar effects can be obtained with outer diameters from 2-3 / 8 inches to 14 inches, steel types from carbon steel to 13Cr steel, and even high-alloy steel (e.g., 25Cr steel), and various thread types (integral fittings such as VAM® Connection, VAM® TOP series, and VAM® SLIJII manufactured by Nippon Steel & Sumitomo Metal Corporation). [Flat Plate Sliding Test] A flat plate sliding test was conducted to investigate the relationship between the talc content in the solid lubricant film and the coefficient of friction when fastening screw joints. Specifically, the apparatus shown in Figure 7 was used. Figure 7 is a diagram showing an overview of the flat plate sliding test for measuring the coefficient of friction. Referring to Figure 7, the steel plate 51 was the same 13Cr steel as in Example 3 of the present invention, and was a steel plate with a width of 10 mm and a length of 25 mm. The steel plate 52 was also the same 13Cr steel as in Example 3 of the present invention. An ultraviolet curing resin film was formed on the surface of the steel plate 52, similar to the pin surface in Example 3 of the present invention. On the surface of the steel plate 51, a Cu-Sn-Zn alloy plating was applied, and then a solid lubricant film 53 was formed, similar to the box surface in Example 3 of the present invention. The composition of the solid lubricant film 53 was the same as in Example 6 of the present invention in terms of the content of all substances except talc, and only the talc content was varied between 1 and 20%. The steel plate 52 was mounted on the device so as to be sandwiched vertically between two steel plates 51, and one end of the steel plate 52 was gripped using a suitable chuck 54. With pressure P applied vertically to the flat surface of the steel plate, the steel plate 52 was slid horizontally. The vertical pressure P on the steel plates 51 and 52 was 17.5 kgf / mm2. The sliding distance of the steel plate 52 was 50 mm, and the sliding speed was 10 mm / s. The coefficient of friction became constant after approximately 10 seconds from the start of sliding. The coefficient of friction was measured after approximately 30 seconds from the start of sliding. The results are shown in Table 3. Figure 8 shows the relationship between the talc content in the solid lubricant film and the coefficient of friction. Referring to Table 3 and Figure 8, when the talc content in the solid lubricant film was 2 to 15 mass%, the coefficient of friction remained stable at around 0.30 to 0.35. When the talc content in the solid lubricant film is 2 to 15 mass%, it is considered that the coefficient of friction can be appropriately maintained even when the radial surface pressure of the screw joint is high. When the talc content exceeded 15 mass%, the coefficient of friction increased significantly. A coefficient of friction that is too high is undesirable because it can cause seizing. Therefore, a talc content of 15 mass% or less is appropriate. Although the present invention has been described above in relation to embodiments currently considered preferred, the present invention is not limited to the embodiments described above. Modifications are possible as long as they do not contradict the technical spirit of the invention as can be inferred from the claims and the specification as a whole, and screw fittings with such modifications should also be understood to be included within the technical scope of the present invention. The present invention is also applicable to pipe thread fittings used for pipes other than those used in oil well tubing, as described in the examples. 2 Steel pipe 4 Male threaded section 6 Pin 8 Coupling 10 Female threaded section 12 Box 14, 16 Seal section 18, 20 Shoulder section 22 Steel 24 Solid lubricant coating 26 Undercoat coating

Claims

1. A composition for forming a solid lubricating film on pipe thread fittings, comprising a binder, a fluorine-based additive, a solid lubricant, and a rust-preventive additive, wherein the binder comprises ethylene vinyl acetate resin, a polyolefin resin, and a wax having a melting point of 110°C or lower, the ratio of the mass of the ethylene vinyl acetate resin to the mass of the polyolefin resin being 1.0 to 1.8, and the ratio of the combined mass of the polyolefin resin and the ethylene vinyl acetate resin to the mass of the wax being 0.7 to 1.

6.

2. The composition according to claim 1, characterized in that it contains 60 to 80% by mass of the binder, 8 to 18% by mass of the fluorine-based additive, 5 to 15% by mass of the solid lubricant, and 2 to 10% by mass of the rust-preventive additive.

3. A composition according to claim 1 or claim 2, further characterized by containing 2 to 15% by mass of talc.

4. The composition according to claim 3, wherein the particle size of the talc is 1 to 12 μm and the specific surface area of ​​the talc is 4 to 12 m². 2 A composition characterized by being / g.

5. A pipe thread fitting comprising a pin and a box, wherein each of the pin and the box has a contact surface including a portion that contacts each other, and the pipe thread fitting has a solid lubricating film on at least one of the contact surfaces of the pin and the box, the solid lubricating film contains a binder, a fluorine-based additive, a solid lubricant, and a rust-preventive additive, the binder contains ethylene vinyl acetate resin, a polyolefin resin, and a wax having a melting point of 110°C or less, the ratio of the mass of the ethylene vinyl acetate resin to the mass of the polyolefin resin is 1.0 to 1.8, and the ratio of the combined mass of the polyolefin resin and the ethylene vinyl acetate resin to the mass of the wax is 0.7 to 1.

6.

6. A pipe thread fitting according to claim 5, wherein the solid lubricating film contains 60 to 80% by mass of the binder, 8 to 18% by mass of the fluorine-based additive, 5 to 15% by mass of the solid lubricant, and 2 to 10% by mass of the rust-preventive additive.

7. A pipe thread fitting according to claim 5 or claim 6, wherein the solid lubricating film further contains 2 to 15% by mass of talc.

8. A pipe threaded fitting according to claim 7, wherein the particle size of the talc is 1 to 12 μm, and the specific surface area of ​​the talc is 4 to 12 m². 2 A pipe thread fitting characterized by being / g.

9. A pipe thread fitting according to any one of claims 5 to 8, further comprising a solid anticorrosion coating containing an ultraviolet curing resin, wherein the solid lubricating coating is formed on the contact surface of one of the pin and the box, and the solid anticorrosion coating is formed on the other contact surface of the pin and the box.

10. A pipe thread fitting according to claim 9, characterized in that the thickness of the solid corrosion-resistant coating is 5 to 50 μm.

11. A pipe thread fitting according to any one of claims 5 to 10, characterized in that the thickness of the solid lubricating film is 10 to 200 μm.

12. A pipe thread fitting according to any one of claims 5 to 11, characterized in that it is used for oil well pipes.

13. A method for manufacturing a pipe thread fitting, comprising a pin and a box, wherein each of the pin and the box has a contact surface including a portion that contacts each other, and a solid lubricating film is provided on at least one of the contact surfaces of the pin and the box, the method comprising the step of applying the composition described in any one of claims 1 to 4 onto the contact surface to form the solid lubricating film.

14. A method for manufacturing a pipe thread fitting according to claim 13, wherein in the step of forming the solid lubricating film, the solid lubricating film is formed on the contact surface of one of the pin and the box, and the manufacturing method further comprises the steps of applying a composition for a solid corrosion-resistant film containing the ultraviolet curing resin to the other contact surface of the pin and the box, and irradiating the applied composition for a solid corrosion-resistant film with ultraviolet light to form the solid corrosion-resistant film.

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