Specification
Title of invention: Composition, and threaded joint for pipe provided with lubricating coating layer formed from the composition
Technical field
[0001]
　TECHNICAL FIELD The present invention relates to a composition, particularly a composition for forming a lubricating coating layer used in a threaded joint for oil country tubular goods, and a threaded joint for pipe provided with a lubricating coating layer formed from the composition.
Background technology
[0002]
　Oil well pipes are used for mining oil and natural gas fields. The oil well pipe is formed by connecting a plurality of steel pipes according to the depth of the well. The steel pipes are connected by screwing together threaded joints for pipes formed at the ends of the steel pipes. Oil well pipes are repeatedly pulled up, unscrewed, inspected for screw surfaces, etc. after troubles before the completion of the oil well or after the completion of the oil well, then screwed again, downcomed, and reused. It may be done.
[0003]
　The pipe threaded joint includes a pin and a box. The pin includes a male screw portion formed on the outer peripheral surface of the end portion of the steel pipe. The box includes an internally threaded portion formed on the inner peripheral surface of the end of the steel pipe. Pins and boxes may also include unthreaded metal contacts. The threaded portion of the pin and the box and the metal contact portion without the thread are repeatedly subjected to strong friction when the steel tube is screwed and unscrewed. If these parts do not have sufficient durability against friction, galling (irreparable seizure) occurs when screwing and unscrewing are repeated. Therefore, the pipe threaded joint is required to have sufficient durability against friction, that is, excellent seizure resistance.
[0004]
　Conventionally, in order to improve the seizure resistance, a compound grease containing a heavy metal called a dope has been used. By applying compound grease to the surface of the threaded joint for pipes, the seizure resistance of the threaded joint for pipes can be improved. However, heavy metals such as Pb, Zn and Cu contained in the compound grease may affect the environment. Therefore, development of a composition for forming a lubricating coating layer used in a threaded joint for pipes that does not use compound grease has been desired.
[0005]
　International Publication No. 2009/057754 (Patent Document 1) and International Publication No. 2014/024755 (Patent Document 2) are for forming a lubricating coating layer excellent in seizure resistance even without compound grease, and a lubricating coating layer. A composition is proposed.
[0006]
　The lubricating coating layer described in Patent Document 1 contains one or both of rosin and calcium fluoride, metal soap, wax, and basic aromatic organic acid metal salt. As a result, it is described in Patent Document 1 that it is excellent in seizure resistance, airtightness and rust prevention.
[0007]
　A composition for forming a lubricating coating layer on a tubular threaded joint described in Patent Document 2 includes melamine cyanurate, a basic aromatic organic acid metal salt, a pine resin material, a wax, a metal soap, and And at least one selected from lubricating powders. As a result, it is described in Patent Document 2 that it is excellent in seizure resistance, airtightness and rust prevention.
Prior art documents
Patent literature
[0008]
Patent Document 1: International Publication No. 2009/057754
Patent Document 2: International Publication No. 2014/024755
Summary of the invention
Problems to be Solved by the Invention
[0009]
　By the way, the threaded portion of the pin and the box and the non-threaded metal contact portion include a metal seal portion and a shoulder portion. When screwing a pipe threaded joint having a non-threaded metal contact portion, the shoulder portions of the pin and the box contact each other. The torque generated at this time is called shouldering torque. When tightening the threaded joint for pipes, after reaching the shouldering torque, further tightening is performed until the tightening is completed. This increases the airtightness of the threaded joint for pipes. When the screw is further tightened, the metal forming at least one of the pin and the box starts to undergo plastic deformation. The torque generated at this time is called yield torque.
[0010]
　The torque at the time of completion of fastening (hereinafter referred to as fastening torque) is set so that a sufficient sealing surface pressure can be obtained regardless of the magnitude of the screw interference amount. If the difference between the shouldering torque and the yield torque (hereinafter referred to as torque on-shoulder resistance ΔT′) is sufficient, the range of the fastening torque becomes wide. As a result, the tightening torque can be easily adjusted. Therefore, the pipe threaded joint is required to have both the above-mentioned seizure resistance and high torque on-shoulder resistance ΔT′, that is, overtorque performance. The same applies to a threaded joint for pipes that does not have a non-threaded metal contact portion (particularly a shoulder portion). Even when the pipe threaded joint does not have a shoulder portion, the fastening torque can be easily adjusted if a high torque is maintained at a high surface pressure.
[0011]
　An object of the present invention is to provide a composition for obtaining a pipe threaded joint having excellent seizure resistance and high overtorque performance, and a lubricating coating layer formed from the composition, which has excellent seizure resistance and It is intended to provide a pipe threaded joint having high overtorque performance.
Means for solving the problem
[0012]
　The composition according to the present embodiment is a composition for forming a lubricating coating layer on a threaded joint for pipes, containing Cr 2 O 3 , metal soap, wax, and a basic aromatic organic acid metal salt. To do.
[0013]
　The threaded joint for pipes according to the present embodiment is a threaded joint for pipes including a pin and a box. Each of the pin and box comprises a contact surface having a threaded portion and a non-threaded metal contact portion. The threaded joint for pipes has a lubricating coating layer made of the above composition as the outermost layer on the contact surface of at least one of the pin and the box.
Effect of the invention
[0014]
　The pipe threaded joint according to the present embodiment includes a lubricating coating layer. The composition for forming the lubricating coating layer contains Cr 2 O 3 . Therefore, the pipe threaded joint according to the present embodiment has excellent seizure resistance even when the fastening is repeated. Furthermore, the pipe threaded joint according to the present embodiment has high overtorque performance.
Brief description of the drawings
[0015]
FIG. 1 is a diagram showing a relationship between a rotation speed and a torque of a threaded joint for pipes having a shoulder portion.
FIG. 2 is a diagram showing the relationship between the Cr 2 O 3 content in the composition for forming the lubricating coating layer and the overtorque performance.
FIG. 3 is a diagram showing the relationship between the Cr 2 O 3 content in a composition for forming a lubricating coating layer and seizure resistance.
FIG. 4 is a diagram showing a configuration of a threaded joint for pipes of the present embodiment.
FIG. 5 is a cross-sectional view of the pipe threaded joint according to the present embodiment.
FIG. 6 is a cross-sectional view of a contact surface of the threaded joint for pipes according to the present embodiment.
FIG. 7 is a diagram for explaining the torque on-shoulder resistance ΔT′ in the example.
MODE FOR CARRYING OUT THE INVENTION
[0016]
　Hereinafter, the present embodiment will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and the description thereof will not be repeated.
[0017]
　The present inventor conducted various studies on the relationship between a composition for forming a lubricating coating layer for a threaded joint for pipes, a threaded joint for pipes, seizure resistance, and overtorque performance. As a result, the following findings were obtained.
[0018]
　[Overtorque Performance] When the
　steel pipes are screwed together, the optimum torque for finishing the screwing is predetermined. FIG. 1 is a diagram showing a relationship between a rotation speed and a torque of a pipe threaded joint when a pipe threaded joint having a shoulder portion is screwed. Referring to FIG. 1, when the pipe threaded joint is screwed, the torque initially increases in proportion to the number of revolutions. At this time, the rate of increase in torque is low. If the screws are further tightened, the shoulders will come into contact with each other. The torque at this time is called shouldering torque. If the screwing is further tightened after reaching the shouldering torque, the torque will increase again in proportion to the rotation speed. At this time, the rate of increase in torque is high. When the torque reaches a predetermined value (fastening torque), screw tightening is completed. If the torque when tightening the screw reaches the tightening torque, the metal seal portions interfere with each other with an appropriate surface pressure. In this case, the airtightness of the pipe threaded joint is increased.
[0019]
　If the screws are tightened further after the fastening torque is reached, the torque becomes too high. If the torque becomes too high, some of the pin and box will plastically deform. The torque at this time is called yield torque. If the torque on-shoulder resistance ΔT′, which is the difference between the shouldering torque and the yield torque, is large, there is a margin in the fastening torque range. As a result, the tightening torque can be easily adjusted. Therefore, it is preferable that the torque on-shoulder resistance ΔT′ is high. In this specification, high overtorque performance means that the torque on-shoulder resistance ΔT′ is high.
[0020]
　In order to increase the torque on-shoulder resistance ΔT′, it is effective to reduce the shouldering torque or increase the yield torque. Therefore, it is considered that when hard particles are contained in a composition for forming a lubricating coating layer (hereinafter, also simply referred to as a composition), the yield torque is increased at high surface pressure. As a result, the torque on-shoulder resistance ΔT′ is considered to increase.
[0021]
　However, as a result of investigating and examining by the present inventors, a high torque on-shoulder resistance ΔT′ could not be obtained even if the hard particles were simply contained in the composition. For example, CaF 2 is hard particles, but as shown in Examples described later, CaF 2 did not provide a high torque on-shoulder resistance ΔT′.
[0022]
　Then, the present inventors further conducted various studies and found that high torque-on-shoulder resistance ΔT′ can be obtained by including Cr 2 O 3 in the composition .
[0023]
　FIG. 2 is a diagram showing the relationship between the Cr 2 O 3 content in the composition and the overtorque performance. FIG. 2 was obtained by the example described below. Note that the overtorque performance is a relative value based on the numerical value of the torque on-shoulder resistance ΔT′ when the API standard dope is used instead of the lubricating coating layer in Test No. 8 in the example described later as a reference (100). I asked. 2 in FIG. 2 indicates the overtorque performance of the example in which the lubricating coating layer was formed. Δ in FIG. 2 indicates the overtorque performance when the API standard dope is used instead of the lubricating coating layer.
[0024]
　From FIG. 2, when Cr 2 O 3 is contained, the overtorque performance exceeds 100. That is, if Cr 2 O 3 is contained, high overtorque performance can be obtained.
[0025]
　[Seizure resistance] The
　present inventors have further found that when an appropriate amount of Cr 2 O 3 is contained in the composition , not only the overtorque performance is improved but also the seizure resistance is improved.
[0026]
　FIG. 3 is a diagram showing the relationship between the Cr 2 O 3 content in the composition and seizure resistance. FIG. 3 was obtained by the example described below. In FIG. 3, the vertical axis represents the number of times (times) the screw could be fastened without irreversible seizure at the screw portion and seizure at the metal seal portion.
[0027]
　From FIG. 3, if the composition contains an appropriate amount of Cr 2 O 3 , the number of times of fastening can exceed 10 times. That is, if the composition contains an appropriate amount of Cr 2 O 3 , high seizure resistance can be obtained.
[0028]
　The composition according to the present embodiment completed based on the above findings is a composition for forming a lubricating coating layer on a threaded joint for pipes, and comprises Cr 2 O 3 , metal soap, wax, and basic And an aromatic organic acid metal salt.
[0029]
　In the composition according to the present embodiment, the Cr 2 O 3 content is 1 to 20%, the metal soap content is 2 to 30%, and the wax content is 2 to 30% based on the total amount of the nonvolatile components. , And the basic aromatic content is preferably 20 to 70%.
[0030]
　In this case, the overtorque performance and the seizure resistance are further enhanced.
[0031]
　The composition according to the present embodiment may further contain a lubricating powder.
[0032]
　When the composition according to the present embodiment contains the lubricating powder, the content of the lubricating powder is preferably 0.5 to 20% by mass based on the total amount of the nonvolatile components.
[0033]
　The above-mentioned lubricating powder is preferably one or more selected from the group consisting of graphite and polytetrafluoroethylene.
[0034]
　The composition according to the present embodiment may further contain a volatile organic solvent.
[0035]
　The threaded joint for pipes according to the present embodiment is a threaded joint for pipes including a pin and a box. Each of the pin and box comprises a contact surface having a threaded portion and a non-threaded metal contact portion. The threaded joint for pipes has a lubricating coating layer made of the above composition as the outermost layer on the contact surface of at least one of the pin and the box.
[0036]
　The pipe threaded joint according to the present embodiment may include a metal plating layer between the lubricating coating layer and the contact surface of at least one of the pin and the box.
[0037]
　The threaded joint for pipes according to the present embodiment may include a chemical conversion coating having a surface in contact with the lubricating coating layer under the lubricating coating layer.
[0038]
　Further, in the threaded joint for pipes according to the present embodiment, the surface contacting the lubricating coating layer may be blasted. In the threaded joint for pipes according to the present embodiment, the surface that comes into contact with the lubricating coating layer may be pickled.
[0039]
　In the threaded joint for pipes according to the present embodiment, the contact surface may further have an unthreaded metal contact portion.
[0040]
　Hereinafter, the composition according to the present embodiment and the pipe threaded joint provided with the lubricating coating layer formed from the composition will be described in detail.
[0041]
　[Pipe Threaded Joint 1] The
　pipe threaded joint 1 includes a pin 5 and a box 8. FIG. 4 is a diagram showing the configuration of the pipe threaded joint of the present embodiment. The pipe threaded joint 1 includes a steel pipe 2 and a coupling 3. At both ends of the steel pipe 2, pins 5 having male threads 4 on the outer surface are formed. On both sides of the coupling 3, a box 8 having an internal thread portion 7 on its inner surface is formed. The coupling 3 is attached to the end of the steel pipe 2 by screwing the pin 5 and the box 8 together. Although not shown, a protector (not shown) may be attached to the pin 5 of the steel pipe 2 and the box 8 of the coupling 3 to which the mating members are not attached, in order to protect the respective screw portions. ..
[0042]
　As shown in FIG. 4, a typical pipe threaded joint 1 is a coupling system including a steel pipe 2 and a coupling 3. On the other hand, there is also an integral type threaded joint for pipes 1 in which one end of the steel pipe 2 has a pin shape and the other end has a box shape without using a coupling. The threaded joint for pipes 1 of the present embodiment can be applied to both the coupling system and the integral system.
[0043]
　The pin 5 and the box 8 have contact surfaces with threaded parts and unthreaded metal contact parts. FIG. 5 is a sectional view of the pipe threaded joint 1 according to the present embodiment. The pin 5 includes a male screw portion 4 and a screwless metal contact portion. The non-threaded metal contact portion of the pin 5 is formed at the tip of the pin 5 and includes a metal seal portion 10 and a shoulder portion 11. The box 8 comprises an internal thread part 7 and a non-threaded metal contact part. The unthreaded metal contact portion of the box 8 is formed at the tip of the box 8 and includes a metal seal portion 13 and a shoulder portion 12. The portion that comes into contact when the pin 5 and the box 8 are screwed together is called a contact surface. Specifically, when the pin 5 and the box 8 are screwed, the shoulder portions (shoulder portions 11 and 12), the metal seal portions (metal seal portions 10 and 13), and the screw portions (male screw portions 4 and The female screw portions 7) come into contact with each other. That is, the contact surface includes a shoulder portion, a metal seal portion, and a screw portion.
[0044]
　Although not shown, the contact surface of the pipe threaded joint 1 may not have a threadless metal contact. In this case, the contact surface of the pipe threaded joint 1 includes a threaded portion. Specifically, the pin 5 includes the male screw portion 4. The box 8 includes an internal thread portion 7.
[0045]
　[Lubrication Coating Layer 21] The
　threaded joint for pipes 1 is provided with the lubrication coating layer 21 on the contact surface of at least one of the pin 5 and the box 8. FIG. 6 is a sectional view of the contact surface of the threaded joint for pipes 1 according to the present embodiment. The lubricating coating layer 21 is formed by applying a composition for forming the lubricating coating layer 21 on the contact surface of at least one of the pin 5 and the box 8 and drying it, as in the manufacturing method described later.
[0046]
　[Composition for Forming
　Lubrication Coating Layer 21 ] The composition for forming the lubrication coating layer 21 contains Cr 2 O 3 , metal soap, wax, and basic aromatic organic acid metal salt. To do. Therefore, the lubricating coating layer 21 also contains Cr 2 O 3 , metal soap, wax, and basic aromatic organic acid metal salt. The composition may be a solvent-free composition (that is, containing only the above-mentioned components) or a solvent-type composition dissolved in a solvent. In the case of a solvent type composition, the mass% of each component means the mass% when the total amount of nonvolatile components of the composition (the total mass of all components other than the solvent contained in the composition) is 100%. Say. That is, the content of each component in the composition is the same as the content of each component in the lubricating coating layer 21.
[0047]
　Hereinafter, each component in the composition will be described in detail. “%” for each component means mass% based on the total amount of nonvolatile components of the composition, unless otherwise specified. In the present embodiment, the non-volatile component means all components other than the solvent contained in the composition. The non-volatile components are, for example, Cr 2 O 3 , metal soap, wax, and basic aromatic organic acid metal salt. Each component can be selected independently and the selected combination does not produce a new effect.
[0048]
　[Cr 2 O 3 ]
　Cr 2 O 3 is also called chromium (III) oxide. Cr 2 O 3 is an inorganic compound. The formula weight of Cr 2 O 3 is 151.99. Cr 2 O 3 is obtained by thermal decomposition of ammonium dichromate (ammonium dichromate). Cr 2 O 3 becomes a dark green metallic luster crystal by sublimation purification. Cr 2 O 3 is extremely stable and harder than quartz. Cr 2 O 3 has no toxicity or danger.
[0049]
　As described above, the inclusion of Cr 2 O 3 enhances the overtorque performance. If Cr 2 O 3 is contained, seizure resistance is further enhanced.
[0050]
　The content of Cr 2 O 3 in the lubricating coating layer 21 is preferably 1 to 20% by mass% based on the total amount of nonvolatile components of the composition. When the Cr 2 O 3 content is 1% or more, sufficient overtorque performance can be obtained. When the Cr 2 O 3 content is 20% or less, the reduction in the strength of the coating film can be suppressed. When the Cr 2 O 3 content is 20% or less, further increase in friction can be suppressed and high seizure resistance can be maintained. The more preferable lower limit of the Cr 2 O 3 content is 5%, more preferably 7%, and further preferably 10%. A more preferable upper limit of the Cr 2 O 3 content is 18%, and further preferably 15%.
[0051]
　Cr 2 O 3 is, for example, dark green particles. The preferable particle size of Cr 2 O 3 is 45 μm or less. From the viewpoint of uniform dispersibility, it is more preferably 10 μm or less. The particle size is the arithmetic mean value of the effective size distribution obtained by the particle size distribution measurement (for example, SHIMADZU SALD series) by the laser diffraction/scattering method.
[0052]
　Cr 2 O 3 is, for example, chromium (III) oxide manufactured by Wako Pure Chemical Industries, Ltd.
[0053]
　[Metallic Soap]
　Metallic soap is a salt of a fatty acid with a metal other than an alkali metal. When the metallic soap is contained, the seizure resistance and rust prevention of the lubricating coating layer 21 are enhanced.
[0054]
　The fatty acid of the metal soap preferably has 12 to 30 carbon atoms from the viewpoint of lubricity and rust prevention. The fatty acid may be saturated or unsaturated. Fatty acids are mixed fatty acids or single compounds. The mixed fatty acids are derived from natural fats and oils such as beef tallow, lard, wool fat, palm oil, rapeseed oil and coconut oil. Fatty acids of a single compound include, for example, lauric acid, tridecyl acid, myristic acid, palmitic acid, lanopalmitic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, arachidic acid, behenic acid, erucic acid, lignoceric acid, lanoseric acid. , Sulfonic acids, salicylic acids and carboxylic acids.
[0055]
　The metals of the metallic soap are, for example, calcium, alkaline earth metals and zinc. The metal salt form is preferably a calcium salt. The salt may be either a neutral salt or a basic salt.
[0056]
　That is, metal soaps include, for example, beef tallow, lard, wool fat, palm oil, rapeseed oil, coconut oil, lauric acid, tridecylic acid, myristic acid, palmitic acid, lanopalmitic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, Group consisting of one or more fatty acids selected from the group consisting of arachidic acid, behenic acid, erucic acid, lignoceric acid, lanoseric acid, sulfonic acid, salicylic acid and carboxylic acid, and calcium, alkaline earth metal and zinc It is a salt with one or more metals selected from
[0057]
　The content of metal soap in the composition is preferably 2 to 30% by mass% based on the total amount of the nonvolatile components of the composition. When the content of the metal soap is 2% or more, the seizure resistance and rust prevention of the lubricating coating layer 21 can be sufficiently enhanced. When the content is 30% or less, the necessary adhesion and strength of the lubricating coating layer 21 can be sufficiently obtained. The more preferable lower limit of the content of metal soap is 4%, and more preferably 10%. The more preferable upper limit of the content of metal soap is 19%, and more preferably 17%.
[0058]
　[Wax]
　Wax is an organic substance that is solid at room temperature and becomes liquid when heated. The wax is one or more selected from the group consisting of animal, vegetable, mineral and synthetic waxes. Animal waxes are, for example, beeswax and spermaceti. Vegetable waxes are, for example, wood wax, carnauba wax, candelilla wax and rice wax. Mineral waxes are, for example, paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokerite and ceresin. Synthetic waxes are, for example, oxidized waxes, polyethylene waxes, Fischer-Tropsch waxes, amide waxes and hydrogenated castor oil (caster waxes). Preferably, the wax is a paraffin wax with a molecular weight of 150-500.
[0059]
　That is, the waxes include, for example, beeswax, spermaceti, carnauba wax, candelilla wax, rice wax, paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokerite, ceresin, oxidized wax, polyethylene wax, Fischer-Tropsch wax. , Amide wax and hydrogenated castor oil (caster wax).
[0060]
　Preferably, the wax is one or more selected from the group consisting of paraffin wax, microcrystalline wax and oxidized wax.
[0061]
　The wax reduces friction of the lubricating coating layer 21 and enhances seizure resistance. The wax further reduces the fluidity of the lubricating coating layer 21 and increases the strength of the lubricating coating layer 21.
[0062]
　The content of the wax in the composition is preferably 2 to 30% by mass% based on the total amount of the nonvolatile components of the composition. If the wax content is 2% or more, the above effects can be sufficiently obtained. When the content is 30% or less, the necessary adhesion and strength of the lubricating coating layer 21 can be sufficiently obtained. The more preferable lower limit of the wax content is 5%, and more preferably 10%. The more preferable upper limit of the content of wax is 20%, and further preferably 15%.
[0063]
　[Basic Aromatic Organic Acid Metal Salt] The
　basic aromatic organic acid metal salt is a salt composed of an aromatic organic acid and excess alkali (alkali metal or alkaline earth metal). The basic aromatic organic acid metal salt is, for example, a grease-like or semi-solid substance at room temperature. In the basic aromatic organic acid metal salt, an excess of alkali is dispersed in oil as a metal salt of colloidal fine particles.
[0064]
　When the basic aromatic organic acid metal salt is contained in the composition, the anticorrosive property is remarkably enhanced. If the basic aromatic organic acid metal salt is contained, the seizure resistance of the lubricating coating layer 21 is further enhanced. This effect is because the basic aromatic organic acid metal salt is present in the state of colloidal fine particles, so that the excess metal salt is physically adsorbed or chemically adsorbed by the organic acid group.
[0065]
　Aromatic organic acid metal salts are, for example, basic sulfonates, basic salicylates, basic phenates and basic carboxylates.
[0066]
　The alkali forming the cation portion of the basic aromatic organic acid metal salt is, for example, one or more selected from the group consisting of alkali metals and alkaline earth metals. The alkali is preferably an alkaline earth metal, and more preferably one or more selected from the group consisting of calcium, barium and magnesium.
[0067]
　That is, the basic aromatic organic acid metal salt is, for example, basic sodium sulfonate, basic potassium sulfonate, basic magnesium sulfonate, basic calcium sulfonate, basic barium sulfonate, basic sodium salicylate, basic potassium salicylate, basic Magnesium salicylate, basic calcium salicylate, basic barium salicylate, basic sodium phenate, basic potassium phenate, basic magnesium phenate, basic calcium phenate, basic barium phenate, basic sodium carboxylate, base One or more selected from the group consisting of basic potassium carboxylate, basic magnesium carboxylate, basic calcium carboxylate, and basic barium carboxylate.
[0068]
　The higher the base number of the basic aromatic organic acid metal salt, the higher the amount of the fine particle metal salt that functions as a solid lubricant. As a result, the seizure resistance of the lubricating coating layer 21 is enhanced. Further, when the base number is higher than a certain level, it has an action of neutralizing the acid component. As a result, the rust preventive power of the lubricating coating is also enhanced. Therefore, the basic aromatic organic acid metal salt preferably has a base value (JIS K2501) (when two or more kinds are used, a weighted average value of the base values ​​in consideration of the amount) of 50 to 500 mgKOH/g. .. When the base number is 50 mgKOH/g or more, the above effects can be sufficiently obtained. When the base number is 500 mgKOH/g or less, hydrophilicity can be reduced and sufficient rust prevention can be obtained. The more preferable lower limit of the base value of the basic aromatic organic acid metal salt is 100 mgKOH/g, more preferably 200 mgKOH/g, and further preferably 250 mgKOH/g. The more preferable upper limit of the base number of the basic aromatic organic acid metal salt is 450 mgKOH/g.
[0069]
　As described above, the basic aromatic organic acid metal salt is a grease-like or semi-solid substance and can also serve as a base of the lubricating coating layer 21. Therefore, it can be contained in a large amount up to 70% by mass% based on the total amount of nonvolatile components of the composition. The lower limit of the content of the basic aromatic organic acid metal salt is% by mass based on the total amount of the nonvolatile components of the composition, preferably 20%, more preferably 40%. The upper limit of the content of the basic aromatic organic acid metal salt is preferably 70%.
[0070]
　[Lubricating Powder] The
　composition may contain a lubricating powder in order to further enhance the lubricity of the lubricating coating layer 21. Lubricating powder is a general term for additives having lubricity. As the lubricating powder, known powders can be used.
[0071]
　Lubricating powders are roughly classified into the following five types. The lubricating powder contains at least one selected from the group consisting of the following (1) to (4).
　(1) A specific slippery crystal structure, for example, a hexagonal layered crystal structure that exhibits lubricity (eg, graphite, zinc oxide, boron nitride),
　(2) In addition to the crystal structure, a reactive element is added. Having lubricity by having (for example, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfide, bismuth sulfide),
　(3) Having lubricity by chemical reactivity (for example, thiosulfate compound) And
　(4) those exhibiting lubricity by plastic or viscoplastic behavior under friction stress (for example, polytetrafluoroethylene (PTFE) and polyamide).
[0072]
　Any of the above-mentioned lubricating powders (1) to (4) can be used. Thus, the lubricious powder comprises, for example, graphite, zinc oxide, boron nitride, molybdenum disulfide, tungsten disulfide, graphite fluoride, tin sulfide, bismuth sulfide, thiosulfate compounds, polytetrafluoroethylene (PTFE) and polyamide. It is one or more selected from the group.
[0073]
　As the lubricating powder, any one of the above (1) to (4) may be used alone. For example, the lubricating powder (1) may be used alone. The lubricating powder may be used in combination with a plurality of the above (1) to (4). For example, in addition to (1) above, (4) may be used in combination.
[0074]
　Preferably, the lubricating powder contains at least one selected from the group consisting of the above (1) and (4). As the lubricating powder (1), graphite is preferable from the viewpoint of adhesion and rust prevention of the lubricating coating layer 21, and earth graphite is preferable from the viewpoint of film forming property. Polytetrafluoroethylene (PTFE) is preferable as the lubricating additive (4).
[0075]
　More preferably, the lubricious powder is polytetrafluoroethylene (PTFE).
[0076]
　The content of the lubricating powder in the composition is preferably 0.5 to 20% by mass% based on the total amount of the nonvolatile components of the composition. If the content of the lubricating powder is 0.5% or more, the seizure resistance is further enhanced. For this reason, the number of times the screw can be tightened and unscrewed without causing seizure increases. On the other hand, when the content of the lubricating additive is 20% or less, the strength of the lubricating coating layer 21 is further increased. Therefore, wear of the lubricating coating layer 21 is suppressed. The more preferable upper limit of the content of the lubricating powder is 15%, more preferably 10%.
[0077]
　[Volatile Organic Solvent] The
　composition may contain a volatile organic solvent. When the coating is performed at room temperature, a volatile organic solvent is added to the mixture of the composition components of the lubricating coating layer 21 to prepare the composition. Unlike the base oil of the lubricating oil, the volatile organic solvent evaporates in the lubricating coating layer forming step. Therefore, the volatile organic solvent does not substantially remain in the lubricating coating. By "volatile" is meant that in film form it exhibits a tendency to evaporate at temperatures from room temperature to 150°C. However, since the lubricating coating layer 21 of the present embodiment may be a viscous liquid or a semisolid, some residual solvent is acceptable.
[0078]
　The type of volatile organic solvent is not particularly limited. The volatile organic solvent is, for example, a petroleum solvent. The petroleum solvent is, for example, one or more selected from the group consisting of solvent, mineral spirit, aromatic petroleum naphtha, xylene and cellosolve corresponding to industrial gasoline defined in JIS K2201.
[0079]
　Volatile organic solvents having a flash point of 30° C. or higher, an initial distillation temperature of 150° C. or higher, and an end point of 210° C. or lower are relatively easy to handle, evaporate quickly, and require a short drying time. It is preferable in terms.
[0080]
　The proportion of the volatile organic solvent may be adjusted to an appropriate viscosity according to the coating method. The content of the volatile organic solvent is, for example, 20 to 50 parts when the total amount of the nonvolatile components is 100 parts.
[0081]
　[Other Components] The
　composition may further contain known rust-preventive additives, preservatives, coloring pigments and the like.
[0082]
　[Rust-preventing additive] The
　lubricating coating layer 21 needs to have rust-preventing properties for a long period of time before being actually used. Therefore, the composition may contain an antirust additive. The antirust additive is a general term for additives having corrosion resistance. The rust preventive additive contains, for example, one or more selected from the group consisting of aluminum tripolyphosphate, aluminum phosphite and calcium ion exchange silica. Preferably, the antirust additive contains at least one selected from the group consisting of calcium ion exchange silica and aluminum phosphite. Other commercially available reaction water repellents can also be used as the rust preventive additive.
[0083]
　The content of the rust preventive additive in the composition is preferably 2 to 10% by mass% based on the total amount of the nonvolatile components of the composition. When the content of the rust preventive additive is 2% or more, the rust preventive property of the lubricating coating layer 21 is more stably enhanced. On the other hand, when the content of the rust preventive additive is 10% or less, the lubricity of the lubricating coating layer 21 is stably enhanced. If the content of the rust preventive additive exceeds 10%, the rust preventive effect is saturated.
[0084]
　[Preservative] The
　composition may further contain a preservative. Antiseptic is also a general term for additives having corrosion resistance.
[0085]
By mixing the 　above-mentioned Cr 2 O 3 , metal soap, wax, basic aromatic organic acid metal salt and other components, the threaded joint for pipe 1 of this embodiment having the lubricating coating layer 21 can be manufactured.
[0086]
　[Metal Plating Layer]
　The pipe threaded joint 1 of the present embodiment may further include a metal plating layer between the lubricating coating layer 21 and the contact surface of at least one of the pin 5 and the box 8. The metal plating layer is, for example, a single layer plating layer of Cu, Sn or Ni metal, a single layer plating layer of Cu—Sn alloy, a double layer plating layer of Cu layer and Sn layer, and a Ni layer, a Cu layer and Sn layer. It is a three-layer plating layer by layers.
[0087]
　The hardness of the metal plating layer is preferably 300 or more in micro Vickers. When the hardness of the metal plating layer is 300 or more, the corrosion resistance of the threaded joint for pipes 1 is more stably enhanced.
[0088]
　The hardness of the metal plating layer can be measured as follows. In the metal plating layer of the obtained pipe threaded joint 1, five arbitrary regions are selected. In each selected region, Vickers hardness (HV) is measured according to JIS Z2244 (2009). The test conditions are, for example, a test temperature of room temperature (25° C.) and a test force of 2.94 N (300 gf). The average of the obtained values ​​(5 in total) is defined as the hardness of the Zn alloy plating layer.
[0089]
　In the case of the multi-layer plating treatment, it is preferable that the lowermost plating layer has a film thickness of less than 1 μm. The thickness of the plating layer (total thickness in the case of multi-layer plating) is preferably 5 to 15 μm.
[0090]
　The thickness of the metal plating layer is measured as follows. A probe of an overcurrent phase type film thickness meter conforming to ISO (International Organization for Standardization) 21968 (2005) is brought into contact with the contact surface on which the metal plating layer is formed. The phase difference between the high-frequency magnetic field on the input side of the probe and the overcurrent excited by the magnetic field is measured. This phase difference is converted into the thickness of the metal plating layer.
[0091]
　[Chemical conversion coating]
　The pipe threaded joint 1 of the present embodiment may further include a chemical conversion coating having a surface in contact with the lubricating coating layer 21 under the lubricating coating layer 21. The chemical conversion coating is, for example, an oxalate chemical conversion coating or a borate chemical conversion coating.
[0092]
　The chemical conversion coating is porous. Therefore, when the lubricating coating layer 21 is formed on the chemical conversion coating, the adhesion of the lubricating coating layer 21 is further enhanced by the so-called "anchor effect". The preferable thickness of the chemical conversion coating is 5 to 40 μm. When the thickness of the chemical conversion treatment film is 5 μm or more, sufficient corrosion resistance can be secured. When the thickness of the chemical conversion coating is 40 μm or less, the adhesiveness of the lubricating coating layer 21 is stably increased.
[0093]
　[Blasted or Pickled Surface] In
　the pipe threaded joint 1 of the present embodiment, the surface in contact with the lubricating coating layer 21 is a blasted or pickled surface. It may be.
[0094]
　The blasted surface or the pickled surface has a surface roughness. Regarding the surface roughness, it is preferable that the arithmetic average roughness Ra is 1 to 8 μm and the reference length is 2.5 mm. When the arithmetic average roughness Ra is 1 μm or more, the adhesion of the lubricating coating layer 21 is further enhanced. When the arithmetic average roughness Ra is 8 μm or less, friction is suppressed and damage and peeling of the lubricating coating layer 21 are suppressed.
[0095]
　The arithmetic mean roughness Ra referred to in this specification is measured based on JIS B0601 (2001). For example, it can be measured by using a scanning probe microscope SPI3800N manufactured by SII Nano Technology Inc. The measurement condition is, for example, a region of 2 μm×2 μm of the sample as a unit of the number of acquired data, and the number of acquired data is 1024×1024. The standard length is 2.5 mm. The larger the arithmetic mean roughness Ra, the larger the contact area with the lubricating coating layer 21. Therefore, the anchor effect enhances the adhesion to the lubricating coating layer. If the adhesion of the lubricating coating layer 21 is increased, the seizure resistance of the pipe threaded joint 1 is further increased.
[0096]
　[Base Material of
　Threaded Joint 1 for Pipe ] The composition of the base material of the threaded joint 1 for pipe is not particularly limited. The base material is, for example, carbon steel, stainless steel, alloy steel or the like. Among alloy steels, duplex alloy stainless steels containing alloy elements such as Cr, Ni and Mo and high alloy steels such as Ni alloys have high corrosion resistance. Therefore, when these high alloy steels are used as the base material, excellent corrosion resistance can be obtained in a corrosive environment containing hydrogen sulfide, carbon dioxide and the like.
[0097]
　[Manufacturing Method] The manufacturing method
　of the pipe threaded joint 1 according to the present embodiment will be described below.
[0098]
　The method for manufacturing the threaded joint for pipes 1 according to the present embodiment includes a lubricating film layer forming step of forming the lubricating film layer 21 using the composition of the present embodiment on the contact surface of at least one of the pin 5 and the box 8. Prepare
[0099]
　[Lubricating film layer forming step] In the
　lubricating film layer forming step, the mixture of the constituent components of the above-mentioned composition is liquefied by adding a solvent and/or heating, and applied on the contact surface of at least one of the pin 5 and the box 8. If necessary, the composition applied onto the contact surface is dried to form the lubricating coating layer 21. The property of the lubricating coating layer 21 does not matter. The property of the lubricating coating layer 21 is, for example, solid, viscous liquid, or semisolid.
[0100]
　First, the composition is manufactured. The solventless composition can be produced, for example, by heating a mixture of the constituent components of the above composition and kneading the mixture in a molten state. The composition may be a powder mixture obtained by mixing all the components in powder form.
[0101]
　The solvent type composition can be produced, for example, by dissolving or dispersing Cr 2 O 3 , metal soap, wax, and basic aromatic organic acid metal salt in a volatile organic solvent and mixing them.
[0102]
　In the case of a solventless composition, the composition can be applied using a hot melt method. In the hot-melt method, the composition is heated and melted to give a low-viscosity fluid state. It is carried out by spraying the composition in a fluid state from a spray gun having a temperature maintaining function. The composition is heated and melted in a tank equipped with a suitable stirring device, and is supplied to a spray head (maintained at a predetermined temperature) of a spray gun through a metering pump by a compressor to be sprayed. The heating temperature is, for example, 90 to 130°C. The holding temperature in the tank and in the spraying head are adjusted according to the melting point in the composition. The coating method may be brush coating, dipping or the like instead of spray coating. The heating temperature of the composition is preferably 10 to 50° C. higher than the melting point of the composition. When applying the composition, the contact surface of at least one of the pin 5 and the box 8 to which the composition is applied is preferably heated to a temperature higher than the melting point of the base material. As a result, good coverage can be obtained.
[0103]
　In the case of a solvent type composition, the composition in a solution state is applied onto the contact surface by spray coating or the like. In this case, the viscosity of the composition is adjusted so that it can be applied by spraying under the environment of normal temperature and normal pressure.
[0104]
　In the case of a solvent-free composition, the composition in a molten state is dried by cooling the composition applied to the contact surface to form the lubricating coating layer 21. A known cooling method can be used. The cooling method is, for example, air cooling or air cooling.
[0105]
　In the case of a solvent type composition, the lubricating coating layer 21 is formed by drying the composition applied to the contact surface. The drying method can be carried out by a known method. The drying method is, for example, natural drying, low temperature blast drying and vacuum drying.
[0106]
　The cooling may be performed by rapid cooling such as a nitrogen gas and carbon dioxide cooling system. When performing rapid cooling, cooling is performed indirectly from the surface opposite to the contact surface (the outer surface of the steel pipe 2 or the coupling 3 in the case of the box 8, the inner surface of the steel pipe 2 in the case of the pin 5). Thereby, deterioration of the lubricating coating layer 21 due to rapid cooling can be suppressed.
[0107]
　The lubricating coating layer 21 preferably covers all contact surfaces of at least one of the pin 5 and the box 8. The lubricating coating layer 21 may cover only a part of the contact surface (for example, only the metal seal portions 10 and 13).
[0108]
　The lubricating coating layer 21 may be a single layer or multiple layers. The multi-layer means a state in which two or more layers of the lubricating coating layer 21 are laminated from the contact surface side. By repeating the application and drying of the composition, two or more lubricating coating layers 21 can be formed. The lubricating coating layer 21 may be formed directly on the contact surface, or may be formed after the below-described base treatment.
[0109]
　The thickness of the lubricating coating layer 21 is preferably 10-40 μm. When the thickness of the lubricating coating layer 21 is 10 μm or more, high lubricity can be stably obtained. On the other hand, when the thickness of the lubricating coating layer 21 is 40 μm or less, the adhesion of the lubricating coating layer 21 is stable. Further, when the thickness of the lubricating coating layer 21 is 40 μm or less, the screw tolerance (clearance) of the sliding surface is widened, so that the surface pressure during sliding becomes low. Therefore, it is possible to prevent the fastening torque from becoming excessively high. Therefore, the thickness of the lubricating coating layer 21 is preferably 10 to 40 μm.
[0110]
　The thickness of the lubricating coating layer 21 is measured by the following method. The lubricating coating layer 21 is applied to the flat plate under the same conditions as when the lubricating coating layer 21 is applied to the pipe threaded joint 1. Among the application conditions of the pipe threaded joint 1 and the flat plate, the conditions such as the distance between the application object and the nozzle tip, the injection pressure, the viscosity of the composition, and the rotation speed of the application object are matched. In order to make the viscosity of the composition the same, the temperatures of the tank, the pipe and the nozzle outlet are made to be the same in the pipe threaded joint 1 and the flat plate. The amount of the composition applied per unit time is calculated from the difference between the weight of the flat plate before applying the composition and the weight of the flat plate after applying the composition. The composition is dried on a flat plate to form the lubricating coating layer 21. The film thickness of the lubricating coating layer 21 is measured using a film thickness meter. The weight of the lubricating coating layer 21 is calculated from the difference between the weight of the flat sheet before applying the composition and the weight of the flat sheet after forming the lubricating coating layer 21. The density of the lubricating coating layer 21 is calculated from the thickness and weight of the lubricating coating layer 21. Next, the application target area of ​​the threaded joint for pipe 1 is calculated from the thread shape and size (inner diameter, wall thickness, etc.). The area to be applied corresponds to the area when the uneven screw forming surface is developed on a flat surface. The average film thickness of the lubricating coating layer 21 with respect to the pipe threaded joint 1 is calculated from the application time of the composition to the pipe threaded joint 1, the application target area, and the density of the lubricating coating layer 21.
[0111]
　[Metal plating layer forming step]
　The method for manufacturing the pipe threaded joint 1 according to the present embodiment may include a metal plating layer forming step before the lubricating coating layer forming step. The metal plating layer can be formed, for example, by electroplating or impact plating.
[0112]
　[Electroplating Treatment] The
　electroplating treatment is, for example, a treatment for forming a metal plating layer by electroplating. The metal plating layer is, for example, a Zn alloy plating layer. When forming the Zn alloy plating layer, the Zn alloy plating layer may be formed by the electroplating treatment on the contact surface of at least one of the pin 5 and the box 8 in the electroplating treatment.
[0113]
　Alternatively, in the electroplating process, a Zn alloy plating layer may be formed by electroplating on the surface roughness formed on the contact surface of at least one of the pin 5 and the box 8.
[0114]
　If the electroplating process is performed, seizure resistance and corrosion resistance of the pipe threaded joint 1 are enhanced. When forming a Zn alloy plating layer, the electroplating process includes, for example, a single layer plating process using Cu, Sn or Ni metal, a single layer plating process using a Cu—Sn alloy, and a double layer plating process including a Cu layer and a Sn layer. , And a three-layer plating process using a Ni layer, a Cu layer, and a Sn layer. For a steel pipe 2 made of steel having a Cr content of 5% or more, Cu-Sn alloy plating treatment, Cu plating-Sn plating two-layer plating treatment, and Ni plating-Cu plating-Sn plating three-layer plating Treatment is preferred. More preferable are Cu plating-Sn plating two-layer plating treatment, Zn-Co alloy plating treatment, Cu-Sn-Zn alloy plating treatment, and Zn-Ni alloy plating treatment.
[0115]
　The electroplating process can be performed by a known method. For example, a plating bath containing ions of metal elements contained in alloy plating is prepared. Next, at least one of the contact surfaces of the pin 5 and the box 8 is immersed in the plating bath. By energizing the contact surface, an alloy plating film is formed on the contact surface. Conditions such as the temperature of the plating bath and the plating time can be appropriately set.
[0116]
　More specifically, for example, when forming a Cu—Sn—Zn alloy plating layer, the plating bath contains copper ions, tin ions and zinc ions. The composition of the plating bath is preferably Cu: 1 to 50 g/L, Sn: 1 to 50 g/L and Zn: 1 to 50 g/L. The electroplating conditions are, for example, a plating bath pH: 1 to 10, a plating bath temperature: 60° C., a current density: 1 to 100 A/dm 2, and a treatment time: 0.1 to 30 minutes.
[0117]
　When forming a Zn—Ni alloy plating layer, the plating bath contains zinc ions and nickel ions. The composition of the plating bath is preferably Zn: 1 to 100 g/L and Ni: 1 to 50 g/L. The electroplating conditions are, for example, a plating bath pH: 1 to 10, a plating bath temperature: 60° C., a current density: 1 to 100 A/dm 2, and a treatment time: 0.1 to 30 minutes.
[0118]
　[Impact plating treatment] The
　impact plating treatment can be performed by mechanical plating in which the particles collide with the object to be plated in the rotary barrel, or projection plating in which the particles collide with the object to be plated using a blast device. is there.
[0119]
　In the method of manufacturing the threaded joint for pipes 1 according to the present embodiment, the surface in contact with the lubricating coating layer 21 may be blasted or pickled. Surface roughness can be formed by blasting or pickling.
[0120]
　[Blasting process] The
　blasting process is, for example, a process in which particles are collided with an object to be plated using a blasting device. The blasting process is, for example, a sandblasting process. The sandblast treatment is a treatment in which a blast material (abrasive) and compressed air are mixed and projected onto the contact surface. The blast material is, for example, a spherical shot material and a square grid material. The sandblast treatment can increase the surface roughness of the contact surface. The sandblast treatment can be performed by a known method. For example, the air is compressed by a compressor, and the compressed air and the blast material are mixed. The material of the blast material is, for example, stainless steel, aluminum, ceramic, alumina or the like. The conditions such as the projection speed of the sandblast process can be set appropriately.
[0121]
　[Pickling Treatment] The
　pickling treatment is a treatment for roughening the contact surface by immersing the contact surface in a strong acid solution such as sulfuric acid, hydrochloric acid, nitric acid or hydrofluoric acid. Thereby, the surface roughness of the contact surface can be increased. The pickling treatment is, for example, a chemical conversion treatment.
[0122]
　[Chemical conversion treatment step]
　The method for manufacturing the threaded joint for pipes 1 according to the present embodiment may include a chemical conversion treatment step before the lubricant film layer forming step. In the chemical conversion treatment step, chemical conversion treatment is performed to form a chemical conversion treatment film having a surface in contact with the lubricating coating layer 21 under the lubricating coating layer 21.
[0123]
　The chemical conversion treatment is a treatment for forming a porous chemical conversion film having a large surface roughness. The chemical conversion treatment is, for example, a phosphate chemical treatment, an oxalate chemical treatment, and a borate chemical treatment. From the viewpoint of the adhesiveness of the lubricating coating layer 21, the phosphate chemical conversion treatment is preferable. The phosphate chemical conversion treatment is, for example, a phosphate chemical conversion treatment using manganese phosphate, zinc phosphate, iron manganese phosphate or zinc calcium phosphate.
[0124]
　The phosphate chemical conversion treatment can be carried out by a known method. As the treatment liquid, a general acid phosphate chemical conversion treatment liquid for galvanized materials can be used. For example, there may be mentioned a zinc phosphate chemical conversion treatment containing 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. A manganese phosphate-based chemical conversion treatment liquid commonly used for the pipe threaded joint 1 can also be used. The liquid temperature is, for example, room temperature to 100°C. The treatment time can be appropriately set according to the desired film thickness, and is, for example, 15 minutes. In order to promote the formation of the chemical conversion film, the surface may be adjusted before the phosphate chemical conversion treatment. The surface conditioning is a treatment of immersing in a surface conditioning aqueous solution containing colloidal titanium. After the phosphate conversion treatment, it is preferable to wash with water or hot water and then dry.
[0125]
　Although only one type of treatment may be carried out before the formation of the lubricating coating layer, a plurality of treatments may be combined.
[0126]
　As the treatment before forming the lubricating coating layer, the same treatment may be performed on the pin 5 and the box 8, or different treatments may be performed on the pin 5 and the box 8.
Example
[0127]
　Examples of the present invention will be described below. However, the present invention is not limited to the examples. In the examples, the contact surface of the pin is called the pin surface and the contact surface of the box is called the box surface. Further,% in the examples means mass% unless otherwise specified.
[0128]
　In this example, VAM21 (registered trademark) manufactured by Nippon Steel & Sumitomo Metal Corporation was used. VAM21 (registered trademark) is a threaded joint for pipes having an outer diameter of 177.80 mm (7 inches) and a wall thickness of 11.506 mm (0.453 inches). The steel type was carbon steel. The composition of carbon steel is C: 0.24%, Si: 0.23%, Mn: 0.7%, P: 0.02%, S: 0.01%, Cu: 0.04%, Ni: 0.05%, Cr: 0.95%, Mo: 0.15%, balance: Fe and impurities.
[0129]
　As shown in Table 1, the surface treatment was performed on the pin surface and the box surface of each test number. The numbers in the "base treatment" column of Table 1 indicate the order in which the base treatment was performed. For example, in the case of “1. Grinding finish, 2. Zn phosphate”, Zn phosphate conversion treatment was performed after grinding finish. In the sandblasting process, abrasive grains Mesh100 were used to form the surface roughness. The arithmetic mean roughness Ra of each test number was as shown in Table 1. The arithmetic average roughness Ra was measured based on JIS B0601 (2013). A scanning probe microscope SPI3800N manufactured by SII Nano Technology Inc. was used to measure the arithmetic mean roughness Ra. The measurement conditions were such that the unit of the number of acquired data was a region of 2 μm×2 μm of the sample, and the number of acquired data was 1024×1024. The film thickness of the Zn—Ni alloy was measured by the above-mentioned measuring method.
[0130]
[table 1]

[0131]
　Then, a lubricating coating layer was formed using the composition having the composition shown in Table 2 to prepare the pins and boxes of the respective test numbers. In Table 2, the content in mass% based on the total amount of the nonvolatile components of the composition is shown in parentheses in the column of "Nonvolatile component composition of the composition". Cr 2 O 3 used was a product name Green F3 manufactured by Nippon Kagaku Kogyo Co., Ltd. As the metal soap, Ca-STEARATE manufactured by Dainippon Ink and Chemicals, Inc. was used. As the wax, paraffin wax manufactured by Nippon Seiro Co., Ltd. was used. As the basic aromatic organic acid metal salt, a product name Calcinate (registered trademark) C400CLR (base number 400 mgKOH/g) manufactured by CHEMTURA was used as the basic Ca sulfonate. As the lubricating powder, in the case of graphite, graphite powder manufactured by Nippon Graphite Industry Co., Ltd., product name Blue P (ash content: 3.79%, crystallinity: 96.9%, average particle size: 7 μm) was used. In the case of PTFE, Lubron (registered trademark) L-5F manufactured by Daikin Industries, Ltd. was used as the lubricating powder. The product name Exxol (registered trademark) D40 manufactured by Exxon was used as the volatile organic solvent. In Test No. 8, the compound grease specified in API standard BUL 5A2 was used instead of the composition for forming a lubricating coating layer. This compound grease contains a heavy metal such as lead and is harmful to the human body and the environment, but has good lubricity, so this was used as the standard for over torque performance evaluation described below.
[0132]
[Table 2]

[0133]
　[Test No. 1] In
　Test No. 1, mechanical grinding finish was performed on the pin surface and the box surface. Then, the composition for forming the lubricating coating layer was spray-coated at room temperature (about 20° C.) to form the lubricating coating layer. The film thickness is calculated from the predetermined spray pressure and the distance to the target surface, using the weight of the composition applied per unit area and unit time and its specific gravity to calculate the target average film thickness, and the value is 120- The range was set to 150 μm.
[0134]
　[Test No. 2 to Test No. 4] In
　Test No. 2 to Test No. 4, mechanical grinding finish was performed on the pin surface and the box surface. The pin surface was dipped in a chemical conversion treatment solution for zinc phosphate at 75 to 85° C. for 10 minutes to form a zinc phosphate coating having a thickness of 10 μm. The box surface was immersed in a chemical conversion treatment solution for manganese phosphate at 80 to 95° C. for 10 minutes to form a 12 μm thick manganese phosphate coating. A composition for forming a lubricating coating layer was sprayed thereon at room temperature (about 20° C.) to form a lubricating coating layer. The film thickness is calculated by calculating the target average film thickness from the predetermined spray pressure and the distance to the target surface, using the weight of the composition applied per unit area and unit time, and its specific gravity. The range was set to 150 μm.
[0135]
　[Test No. 5] In
　Test No. 5, mechanical polishing was performed on the pin surface. It was immersed in a chemical conversion treatment solution for zinc phosphate at 75 to 85° C. for 10 minutes to form a zinc phosphate coating having a thickness of 10 μm. Then, the composition for forming the lubricating coating layer was spray-coated at room temperature (about 20° C.) to form the lubricating coating layer. The film thickness was calculated by calculating the target average film thickness from the predetermined spray pressure and the distance to the target surface, using the weight of the composition applied per unit area and unit time and its specific gravity, and the value was 120- The range was set to 150 μm.
[0136]
　Mechanical grinding finish was performed on the box surface. Zn-Ni alloy plating was performed thereon by electroplating to form a Zn-Ni alloy plating layer. The Zn-Ni alloy plating bath used was Dainjin Alloy N-PL (trade name) manufactured by Daiwa Kasei Co., Ltd. The electroplating conditions were: plating bath pH: 6.5, plating bath temperature: 25° C., current density: 2 A/dm 2 , and treatment time: 18 minutes. The composition of the Zn—Ni alloy plating layer was Zn:85% and Ni:15%. A composition for forming a lubricating coating layer was applied thereon by heating (about 110° C.) by spray coating and then gradually cooled to form a lubricating coating layer. The film thickness was calculated by calculating the target average film thickness from the predetermined spray pressure and the distance to the target surface, using the weight of the composition applied per unit area and unit time and its specific gravity, and the value was 120- The range was set to 150 μm.
[0137]
　[Test No. 6 and Test No. 7] In
　Test No. 6 and Test No. 7, mechanical grinding finish was performed on the pin surface and the box surface. Then, the surface roughness was formed by blasting. Then, the composition for forming the lubricating coating layer was spray-coated at room temperature (about 20° C.) to form the lubricating coating layer. The film thickness is calculated from the predetermined spray pressure and the distance to the target surface, using the weight of the composition applied per unit area and unit time and its specific gravity to calculate the target average film thickness, and the value is 120- The range was set to 150 μm.
[0138]
　[Test No. 8] In
　Test No. 8, mechanical grinding finish was performed on the pin surface and the box surface. The pin surface was immersed in a chemical conversion treatment solution for zinc phosphate at 75 to 85° C. for 10 minutes to form a zinc phosphate coating having a thickness of 10 μm. The box surface was immersed in a chemical conversion treatment solution for manganese phosphate at 80 to 95° C. for 10 minutes to form a 12 μm thick manganese phosphate coating. Then, the API standard dope was applied with a brush. API standard dope is a compound grease for oil well pipe threads manufactured according to API Bul 5A2. The composition of the API standard dope is based on grease and is specified to contain graphite powder: 18±1.0%, lead powder: 30.5±0.6%, and copper flakes: 3.3±0.3%. ing. In this component range, it is understood that the compound grease for oil country tubular goods screws has equivalent performance.
[0139]
　[Test No. 9] In
　Test No. 9, mechanical grinding finish was performed on the pin surface and the box surface. The pin surface was dipped in a chemical conversion treatment solution for zinc phosphate at 75 to 85° C. for 10 minutes to form a zinc phosphate coating having a thickness of 10 μm. The box surface was immersed in a chemical conversion treatment solution for manganese phosphate at 80 to 95° C. for 10 minutes to form a 12 μm thick manganese phosphate coating. A composition for forming a lubricating coating layer was sprayed thereon at room temperature (about 20° C.) to form a lubricating coating layer. The film thickness was calculated by calculating the target average film thickness from the predetermined spray pressure and the distance to the target surface, using the weight of the composition applied per unit area and unit time and its specific gravity, and the value was 120- The range was set to 150 μm. In test number 9, no Cr 2 O 3 was contained in the composition .
[0140]
　[Test No. 10] In
　Test No. 10, mechanical grinding finish was performed on the pin surface and the box surface. The pin surface was dipped in a chemical conversion treatment solution for zinc phosphate at 75 to 85° C. for 10 minutes to form a zinc phosphate coating having a thickness of 10 μm. The box surface was immersed in a chemical conversion treatment solution for manganese phosphate at 80 to 95° C. for 10 minutes to form a 12 μm thick manganese phosphate coating. Then, the composition for forming the lubricating coating layer was spray-coated at room temperature (about 20° C.) to form the lubricating coating layer. The film thickness was calculated by calculating the target average film thickness from the predetermined spray pressure and the distance to the target surface, using the weight of the composition applied per unit area and unit time and its specific gravity, and the value was 120- The range was set to 150 μm. In Test No. 10, CaF 2 was contained as a component of the composition instead of Cr 2 O 3 .
[0141]
　[Seizure resistance evaluation test] The
　seizure resistance was evaluated by a repeated fastening test. Using the pins and boxes of Test No. 1 to Test No. 10, screw tightening and screw returning were repeated at room temperature (20° C.) to evaluate seizure resistance. The fastening torque was 24350 N·m. The pin surface and the box surface were visually observed each time the screw tightening and the screw returning were performed once. The state of occurrence of seizure on the screw part and the metal seal part was confirmed by visual observation. The test was completed because seizure occurred on the metal seal part. If the seizure of the screw part is slight and it can be recovered by cleaning with a file, etc., the seizure defect was repaired and the test was continued. The maximum number of repeated fastenings was set to 15 times. The evaluation index of seizure resistance was the maximum number of times of fastening in which neither seizure that cannot be recovered at the threaded part nor seizure at the metal seal part occurred. The results are shown in the column of "Seizure resistance (the number of times (fastening) which can be fastened without occurrence of seizure which cannot be recovered in the threaded portion and seizure in the metal seal portion)" in Table 3.
[0142]
[Table 3]

[0143]
　[Overtorque Performance Test] The
　torque-on-shoulder resistance ΔT′ was measured using the pins and boxes of test numbers 1 to 10. Specifically, the screw was tightened at a tightening speed of 10 rpm and a tightening torque of 42.8 kN·m. The torque was measured when tightening the screw, and a torque chart as shown in FIG. 7 was created. Ts in FIG. 7 represents the shouldering torque. MTV in FIG. 7 represents a torque value at which the line segment L and the torque chart intersect. The line segment L is a straight line having the same slope as that of the linear region in the torque chart after shouldering and having the rotational speed increased by 0.2% as compared with the linear region. Normally, Ty (yield torque) is used when measuring the torque on-shoulder resistance ΔT′. However, in this embodiment, the yield torque (the boundary between the linear range and the non-linear range in the torque chart after shouldering) was unclear. Therefore, the line segment L was used to define MTV. The difference between MTV and Ts was set as the torque on-shoulder resistance ΔT′ in this embodiment. The overtorque performance is the same as the torque-on-shoulder resistance ΔT′ of the present embodiment with reference to the numerical value of the torque-on-shoulder resistance ΔT′ when the API standard dope is used in place of the lubricating coating layer in Test No. 8 (100). Was calculated as the relative value of. The results are shown in Table 3.
[0144]
　[Evaluation Results]
　Referring to Tables 1 to 3, the compositions forming the lubricating coating layer of the threaded joints for pipes of Test Nos. 1 to 7 contained Cr 2 O 3 . Therefore, seizure did not occur even after 10 times of screw tightening and unscrewing, and excellent seizure resistance was exhibited. Further, the overtorque performance exceeded 100, and excellent overtorque performance was exhibited.
[0145]
　The threaded joints for pipes of Test Nos. 1 to 6 had a Cr 2 O 3 content of 1 to 20.0%. Therefore, the pipe threaded joints of Test Nos. 1 to 6 were able to be fastened more times without seizure than the pipe threaded joint of Test No. 7, and were even better in seizure resistance than the pipe threaded joint of Test No. 7. Showed sex.
[0146]
　On the other hand, the composition forming the lubricating coating layer of the threaded joint for pipes of Test No. 9 did not contain Cr 2 O 3 . Therefore, seizure resistance and overtorque performance were low.
[0147]
　The composition forming the lubricating coating layer of the threaded joint for pipe of Test No. 10 contained calcium fluoride CaF 2 instead of Cr 2 O 3 . Therefore, seizure resistance and overtorque performance were low.
[0148]
　The embodiments of the present invention have been described above. However, the embodiments described above are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments without departing from the spirit thereof.
Explanation of symbols
[0149]
　1 Pipe Threaded Joint
　4 Male Threaded Part
　5 Pin
　7 Female Threaded Part
　8 Box
　10, 13 Metal Sealing Part
　11, 12 Shoulder Part
　21 Lubricating Coating Layer
The scope of the claims
[Claim 1]
　A composition for forming a lubricating coating layer on a threaded joint for pipes, which comprises
　Cr 2 O 3 ,
　metal soap,
　wax, and a
　basic aromatic organic acid metal salt.
[Claim 2]
　The composition according to claim 1,
　wherein
　Cr 2 O 3 is 1 to 20%,
　metallic soap is 2 to 30%, and
　wax is 2 to , based on the total amount of the nonvolatile components of the composition. A
　composition containing 30% and a basic aromatic organic acid metal salt: 20 to 70%.
[Claim 3]
　A composition according to claim 1 or claim 2, further comprising a
　lubricating powder.
[Claim 4]

　4. The composition 　according to claim 3, wherein the composition contains the
　lubricating powder: 0.5 to 20% by mass% based on the total amount of non-volatile components of the composition.
[Claim 5]
　The composition according to claim 3 or 4,
　wherein the lubricating powder is one or more selected from the group consisting of graphite and polytetrafluoroethylene.
[Claim 6]
　The composition according to claim 1, further comprising a
　volatile organic solvent.
[Claim 7]
　A pipe threaded joint
　comprising a pin and a box, each of the pin and the box comprising a contact surface having a threaded portion, the
　pipe threaded joint on the contact surface of at least one of the pin and the box. A threaded joint for pipes, comprising a lubricating coating layer made of the composition according to any one of claims 1 to 6 as the outermost layer.
[Claim 8]
　The threaded joint for pipes according to claim 7, further
　comprising a metal plating layer between the lubricating coating layer and the contact surface of at least one of the pin and the box. Fittings.
[Claim 9]
　The threaded joint for pipes according to claim 7 or 8, further
　comprising a chemical conversion treatment film having a surface in contact with the lubricating film layer under the lubricating film layer.
[Claim 10]
　The pipe threaded joint according to claim 7 or 8,
　wherein the surface in contact with the lubricating coating layer is blasted or pickled.
[Claim 11]
　The pipe threaded joint according to any one of claims 7 to 10,
　wherein the contact surface further has a non-threaded metal contact portion.