JP2001099364A - Rust-preventive oil composition and threaded joint for oil country tubular goods with its coating formed - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A threaded joint for oil country tubular goods having excellent seizure resistance and airtightness by suppressing rust generation and eliminating instability of tightening torque without using compound grease, and its oil well. Provided is a rust-preventive oil composition used for a pipe threaded joint. SOLUTION: A solid lubricating film is formed on one of a box and a pin constituting a threaded joint, and a rust preventive film is formed on the other. Alternatively, a solid lubricating coating is formed on both the box and the pin, and a rust-preventive coating is formed on at least one of the solid lubricating coating on the box and the pin. The solid lubricating film is a film of a resin or an inorganic polymer compound having M (metal) -O as a skeleton. The antirust coating contains an alkali metal salt of a carboxylic acid and / or an alkaline earth metal salt of a carboxylic acid and has a saponification value of 20 to 150 mg KOH.
/ G, the total base number is 15 to 100 mgKOH / g, and the content of alkali metal and alkaline earth metal is 2 to 20 in total.
A coating of a rust-preventive oil composition of mass%. The rust-preventive oil composition preferably contains 5 to 30% by mass of a lubricant comprising at least one of graphite, molybdenum disulfide and an organic Mo compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a threaded joint for oil country tubular goods in which a solid lubricating film is formed in place of a liquid lubricating film containing compound grease, which has been conventionally used, to improve seizure resistance and rust resistance. It relates to stabilization of tightening torque.

[0002]

2. Description of the Related Art A threaded joint is generally used in tubing and casing used for drilling an oil well. Normally, the depth of an oil well is 2,000 m to 3000 m, but in a deep oil well such as a recent marine oil field, it is 8,000 m to 10,000.
m.

[0003] The threaded joints connecting these oil country tubular goods are subjected to complex pressures and heats such as an axial tensile force and internal and external pressures caused by the weight of the oil country tubular goods and the joints themselves in a use environment. It is required to maintain hermeticity without being damaged even under a severe environment.

Further, when the tubing or casing is lowered, the joint once tightened may be loosened and then re-tightened. According to the API (American Petroleum Institute), 10 times for the tubing joint and 3 times for the casing joint. Even when tightening (make-up) and loosening-back (breakout) are performed, it is required that seizure called galling does not occur and airtightness is maintained.

[0005] By the way, as a threaded joint, usually, a threadless metal contact portion is formed at the tip of a male thread formed at an end of an oil country tubular good, and a threadless metal formed at the base of a female thread on the inner surface of the threaded joint member. A structure in which a metal seal portion is formed by fitting and tightening a metal contact portion and tightening the screwless metal contact portion. A threaded joint with a surface treatment applied to the screw portion or the screwless metal contact portion is used. . Also,
At the time of tightening, compound grease is applied to improve seizure resistance and airtightness.

However, since compound grease contains heavy metal powders such as Pb and Zn, there is a concern that if the applied grease is washed away, environmental pollution may occur. Further, the application of the compound grease deteriorates the working environment and lowers the working efficiency. Therefore, a threaded joint that does not use such compound grease is desired.

Japanese Patent Application Laid-Open Nos. 8-233164 and 9-7 disclose threaded joints that do not use compound grease.
No. 2,467 discloses a threaded joint having a resin solid lubricating film formed thereon.

[0008]

However, the threaded joint formed with a solid lubricating coating disclosed in the above publication has a problem that the tightening torque is more likely to fluctuate and the tightening becomes unstable as compared with the case of using compound grease. I have. Furthermore, threaded joints are less effective in preventing rusting of the joints from the time of shipment from the factory to the use of the joints than when compound grease is used. There is a problem that the fastening at the time of fastening becomes more unstable, seizure occurs, and airtightness is reduced.

FIG. 1 is a schematic view schematically showing an assembling structure of an oil country tubular goods and a threaded joint member at the time of shipping the oil country tubular goods. Reference numeral 1A indicates an oil country tubular good, 1B indicates a threaded joint member, 2 indicates a pin, 3 indicates a box, and 4 indicates a threaded portion.

As shown in FIG. 1, an oil country tubular good 1A is usually
One end of a pin 2 having a threaded portion 4 formed on the outer surface of both ends thereof is connected to a threaded portion 4 formed on the inner surface of the threaded joint member 1B.
Shipped with the box with

However, exposed pins and boxes are susceptible to rust. When compound grease is applied for the purpose of rust prevention from the time of shipment, little rust is generated.However, when compound grease is used only with a solid lubricating film, the rust resistance of the film is reduced. Rust is easy to generate because it is low.

Rust is poor in lubricity and has irregularities on the surface, which causes seizure during tightening.

An object of the present invention is to solve the above-mentioned conventional problems, to suppress the generation of rust without using compound grease, to eliminate the instability of the tightening torque, and to achieve excellent seizure resistance and airtightness. An object of the present invention is to provide a threaded joint for oil country tubular goods.

Still another object of the present invention is to provide a rust-preventive oil composition used for improving the rust-preventive property of the above threaded joint for oil country tubular goods.

[0015]

Means for Solving the Problems In order to solve the above problems, the present inventors have conceived the formation of a rust-preventive film together with the formation of a solid lubricating film. I got

(A) A coating containing a salt of a carboxylic acid and an alkali metal or a salt of an alkaline earth metal is semi-solid or solid at room temperature and is effective for long-term rust prevention. In addition,
Hereinafter, the above salt is also simply referred to as “metal salt of carboxylic acid”. (B) The higher the saponification value and the higher the total base number, the more effective the coating is for long-term rust prevention.

(C) The coating containing the above-mentioned salt and further containing a lubricant such as graphite, molybdenum disulfide and an organic Mo compound reduces the friction coefficient of the contact surface when the joint is tightened, and reduces the tightening torque of the joint. Can be stabilized at a low level.

Based on the results of the above basic studies, the rust resistance and lubricity of a threaded joint formed with a solid lubricating film and a rust-preventive film are determined by the salt spray test specified in JIS-Z2371. Further, the lubricating property was examined in more detail by a ring / block contact type friction test, and the following findings were obtained.

FIG. 2 is a graph showing the relationship between the rust generation area and the saponification value, the total base number, the alkali metal content, and the rust prevention coating film thickness in the salt spray test. (B) is a graph of rust generation area and total base number, (c) is a graph of rust generation area and alkali metal content, and (d) is a graph of rust generation area and rust prevention coating thickness.

FIG. 3 is a graph showing the relationship among the friction coefficient and the saponification value, the total base number, the alkali metal content, and the rust-preventing coating film thickness in the friction test. FIG. 3 (a) shows the friction coefficient and the saponification value. FIG. 2 (b) is a graph of friction coefficient and total base number, FIG. 2 (c) is a graph of friction coefficient and alkali metal content, and FIG. 2 (d) is a graph of friction coefficient and rust prevention coating thickness. In FIG. 2 and FIG. 3, the rust preventive coating is a solid coating containing an alkali metal salt of a carboxylic acid. The standard coating conditions are as follows: the content of the alkali metal salt is 10 mass%, and the saponification value is 50 mg KOH / g, total base number was 50 mgKOH / g, and coating thickness was 10 μm.

(D) FIGS. 2 (a) to 2 (c) and FIG.
As shown in (a) to (c), the rust preventive coating has a saponification value of 2
0 to 150 mgKOH / g, total base number is 15 to 100 m
gKOH / g, alkali metal content is 2-20 mass%
, Excellent in rust prevention and the friction coefficient is reduced to show good friction performance.

(E) When forming a rust-preventive film containing a metal salt of a carboxylic acid, the metal salt is diluted with an organic solvent, and a rust-preventive oil having a viscosity at 40 ° C. of 2 to 30 cSt after dilution is obtained. When used, the adhesion of the rust preventive oil is improved.

(F) When forming a rust preventive film on the solid lubricating film, as shown in FIGS. 2D and 3D, the thickness of the rust preventive film is set to 1 μm to 50 μm. Thereby, both the rust prevention property and the lubricity performance can be kept good.

(G) In the case where a solid lubricating film is formed on one of the box and the pin and a rust-preventive film is formed on the other, the thickness of the rust-preventive film should be 5 μm to 50 μm to improve the above performance. Can be maintained.

(H) When the rust-preventive coating contains a lubricant of graphite, molybdenum disulfide or an organic Mo compound, the friction coefficient is further reduced and stabilized, and the tightening torque can be further stabilized. Its content is 5-30 mass%.

Further, the present inventors have obtained the following findings regarding the lubricant and the binder (binder) constituting the solid lubricating film.

(I) Molybdenum disulfide, graphite or organic Mo
The compounds show excellent lubricity. (V) A resin can be used as a binder for the lubricant.

(L) Metal alkoxides such as titanium and silicon (M (OR) ₄ , M: metals such as silicon and titanium, R: alkyl group) have organic properties because of having an alkyl group, and exhibit properties of organic substances. Function. This substance is unstable in the air, absorbs water and causes co-hydrolysis, and the decomposed products bind to each other to form M
Changes to a thermally stable inorganic polymer compound having -O as a skeleton. The molecular structural formula of the inorganic polymer compound represented by the formula (1) is exemplified.

[0029]

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(E) Accordingly, the above-mentioned metal alkoxide is mixed and applied as a binder to a lubricant, and the mixture is subjected to a humidifying treatment, whereby a solid lubricant of an inorganic polymer compound containing a lubricant and having a skeleton of MO is provided. A coating can be formed.

The present invention has been completed based on the above findings, and the gist is as follows.

(1) It contains an alkali metal salt of a carboxylic acid and / or an alkaline earth metal salt of a carboxylic acid, and has a saponification value of 20 to 150 mgKOH / g and a total base value of 15 to 150 mgKOH / g.
A rust preventive oil composition comprising 100 mg KOH / g and a total content of alkali metal and alkaline earth metal of 2 to 20 mass%.

(2) The rust preventive oil composition according to the above (1), wherein the lubricant contains 5 to 30 mass% of a lubricant comprising at least one of graphite, molybdenum disulfide and an organic Mo compound. Antirust oil composition.

(3) In a screw joint composed of a box and a pin each having a threaded portion and a threadless metal contact portion, a solid lubricating film formed on one of the box and the pin and the other is formed on the other. The solid lubricating film is a film of a resin or an inorganic polymer compound having M (metal) -O as a skeleton, and the rustproof film is as defined in the above item (1) or (2). A threaded joint for oil country tubular goods, characterized in that it is a coating of the rust-preventive oil composition described in the above.

(4) The thickness of the antirust coating is 5 μm to 50 μm.
The threaded joint for oil country tubular goods as described in the above item (3), wherein the diameter is μm.

(5) In a screw joint composed of a box and a pin each having a threaded portion and a threadless metal contact portion, at least one of the solid lubricating coating formed on both the box and the pin and the box and the pin A rust prevention coating formed on one of the solid lubrication coatings, wherein the solid lubrication coating is a coating of a resin or an inorganic polymer compound having M (metal) -O as a skeleton; The above (1)
A threaded joint for oil country tubular goods, characterized in that the threaded joint is a film of the rust-preventive oil composition according to the above item or (2).

(6) The thickness of the rust preventive coating is 1 μm to 50 μm.
The threaded joint for oil country tubular goods as described in the above item (5), wherein the diameter is μm.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a rust preventive oil composition and a threaded joint for oil country tubular goods (hereinafter also referred to as a threaded joint) of the present invention will be described in detail. First, each element constituting the rust-preventive oil composition of the present invention will be described.

[Metal Salt of Carboxylic Acid] The rust-preventive oil composition of the present invention contains one or more alkali metal salts of carboxylic acids and one or more alkaline earth metal salts of carboxylic acids. These metal salts have basicity and are excellent in rust prevention and lubricity.

The alkali metals include sodium, lithium and potassium, and the alkaline earth metals include calcium, magnesium and barium. As the carboxylic acid, a monocarboxylic acid having a carboxyl group of 1 or a dicarboxylic acid having a carboxyl group of 2 is preferable, and the carbon number of the hydrocarbon group is preferably 5 to 19 from the viewpoint of lubricity and rust prevention. Examples of the monocarboxylic acid include caproic acid, caprylic acid, capric acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, naphthenic acid, and benzoic acid. be able to. The dicarboxylic acids include suberic acid, azelaic acid and sebacic acid.

[Contents of Alkali Metal and Alkaline Earth Metal] The total content of the alkali metal and the alkaline earth metal is 2% by mass or more and 20% by mass or less. Content is 2 mass
% Or more than 20 mass%, the friction coefficient increases and lubricity decreases as shown in FIG. On the other hand, if it is less than 2 mass%, the rust resistance is low as shown in FIG. Therefore, when the content is 2 mass% or more,
By forming a rust-preventive coating of the rust-preventive oil composition of not more than mass% on the threaded joint, the rust-proof property of the threaded joint can be enhanced and the seizure resistance can be improved. In addition, the said content can be calculated | required by analyzing for every element by an atomic absorption spectrometry.

[Saponification value] When the saponification value is less than 20 mgKOH / g, the rust resistance is low as shown in FIG. 2 (a) and rust easily occurs, and the friction coefficient is reduced as shown in FIG. 3 (a). It becomes large and lubricity decreases. The saponification value is 150 mg
If it exceeds KOH / g, the rust-preventive coating is hardened and cracks easily occur. For this reason, the flakes are peeled off and the rust prevention is reduced. Therefore, the saponification value is 20 mgKOH /
By forming a rust-preventive coating of a rust-preventive oil composition of not less than 150 gKOH / g and not more than 150 mgKOH / g on a threaded joint, rust prevention can be enhanced and seizure resistance can be improved.

[Total base number] The total base number was 15 mgKOH /
If it is less than g, the rust resistance is low and rust easily occurs as shown in FIG. 2 (b), and the friction coefficient becomes large and the lubricity is reduced as shown in FIG. 3 (b). Further, when the total base number is 10
If it exceeds 0 mgKOH / g, as shown in FIG. 3 (b), the friction coefficient increases and lubricity decreases. Therefore,
Total base number is 15 mgKOH / g or more, 100 mgKOH
By forming a rust-preventive coating of a rust-preventive oil composition of not more than / g on a threaded joint, rust-preventive properties can be enhanced and seizure resistance can be improved.

[Lubricant] The rust preventive oil composition preferably contains 5 to 30% by mass of a lubricant containing one or more of graphite, molybdenum disulfide and an organic Mo compound. These lubricants have the effect of increasing the lubricity of the rust preventive oil composition and improving the seizure resistance. Examples of the organic Mo compound include Mo dialkyl thiophosphate and Mo dialkyl thiocarbamate each having a molecular structure represented by the following formulas (2) and (3).

[0045]

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[0046]

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If the content of the above-mentioned lubricant is less than 5 mass%, the effect of improving lubricity is small, and if it exceeds 30 mass%, the formation of a film of the rust-preventive oil is inhibited, and the film becomes porous and the rust-preventive property is reduced. In addition, graphite or molybdenum disulfide may be a powder having an average particle diameter of 0.4 μm or more and 3 μm or less. 0.
If it is less than 4 μm, the effect of improving the lubricity is small, and if it exceeds 3 μm, the rust-preventive property is reduced.

The rust-preventive oil composition of the present invention contains, in addition to the above-mentioned metal salts of carboxylic acids and lubricants, alkali metal salts of sulfonic acids, alkaline earth metal salts of sulfonic acids, paraffin wax, and wax oxidation. Ester, higher fatty acid monoester, natural wax and the like.

Alkali metal salts and alkaline earth metal salts of sulfonic acids are basic and have excellent rust prevention properties. For example, petroleum sulfonic acid obtained by sulfonating an aromatic component in a petroleum distillate component Alternatively, alkali metal salts, alkaline earth metal salts, and amine salts of synthetic sulfonic acids can be used. Examples of the synthetic sulfonic acid include dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and the like.

The paraffin wax has a molecular weight of 15
It is preferably from 0 to 500. Higher fatty acid monoesters include carboxylic acids such as myristic acid, palmitic acid, stearic acid, elaidic acid, arachinic acid, behenic acid, erucic acid, lignoceric acid, cerotic acid, montanic acid, and lanolinic acid, and octyl alcohol and caprylic alcohol. And synthetic monoesters with nonyl alcohol, decyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, decyl alcohol, ceryl alcohol, merisyl alcohol, and the like. .

Examples of the natural wax include carnauba wax, lanolin, dense wax, wood wax, and montan.

Further, a mineral oil or a synthetic mineral oil having a viscosity at 40 ° C. of 10 to 50 cSt may be added to the rust preventive oil composition of the present invention.

Next, each element constituting the threaded joint for oil country tubular goods of the present invention will be described. FIG. 4 is a schematic view schematically showing a tightening portion of the oil country tubular good threaded joint of the present invention. In the figure, reference numeral 5 denotes a screwless metal contact portion, 6 denotes a shoulder portion, and the same elements as those in FIG. 1 are denoted by the same reference numerals.

FIG. 5 is an enlarged sectional view showing an example of the state of formation of a solid lubricating film and a rust-preventive film according to the threaded joint for oily pipes of the present invention. FIG. (B) is the threadless metal contact of the pin. Reference numeral 7 denotes a solid lubricating coating, 8 denotes a binder, 9 denotes a lubricant, 10 denotes a rust-preventive coating, and the same elements as those in FIG. 4 are denoted by the same reference numerals.

FIG. 6 is an enlarged sectional view showing an example of the state of formation of a solid lubricating film and a rust-preventive film according to another threaded joint for oil country tubular goods of the present invention. FIG.
FIG. 4B shows a threadless metal contact portion of the pin. FIG.
The same elements as 5 are denoted by the same reference numerals.

As shown in FIG. 4, the threaded joint for an oil country tubular good according to the present invention comprises a box 3 comprising a threaded part 4 and a threadless metal contact part 5 formed on the inner surface of a threaded joint member, and an outer surface at the end of the oil country tubular good. And a pin 2 comprising a screwless metal contact portion 5.

Further, in the threaded joint of the present invention, FIG.
As shown in (a) and (b), a solid lubricating film 7 in which a lubricant 9 is dispersed and mixed in a binder 8 of a resin or an inorganic polymer compound is provided on both surfaces of the threaded portion of the pin 2 and the screwless metal contact portion. Then, a rust preventive coating 10 is formed on both surfaces of the screw portion and the screwless metal contact portion of the box 3. In the example shown,
Although the case where the solid lubricating film 7 is formed on the pin 2 and the rust-preventive film 10 is formed on the box 3 is shown, a rust-preventive film may be formed on the pin and a lubricating film may be formed on the box.

Another threaded joint of the present invention has the same structure as the above-described threaded joint of the present invention as shown in FIG. 4, and further has a pin 2 and a pin 2 as shown in FIGS. 6 (a) and 6 (b). A solid lubricating film 7 in which a lubricant 9 is dispersed and mixed in a binder 8 of a resin or an inorganic polymer compound is formed on both surfaces of both the screw portion and the screwless metal contact portion of the box 3. A rust preventive coating 10 is formed on 7. In the example shown,
Although the case where the rust-preventive film is formed on the pin is shown, a rust-preventive film may be formed on the box. Hereinafter, the solid lubricating film is also simply referred to as a lubricating film.

[Lubricant] As the lubricant, one type of molybdenum disulfide, graphite, and organic Mo compound is used, or two or more types are mixed and used. These lubricants are dispersed in a resin or an inorganic polymer compound having MO as a skeleton, adhere firmly to the threaded joint surface through them, and are thinly stretched by a tightening pressure at the time of a tightening operation. Therefore, the lubricating film has an effect of enhancing lubricity and improving seizure resistance. Therefore, repeated tightening of the threaded joint becomes possible without using compound grease. In addition, as the organic Mo compound, Mo dialkyl thiophosphate having a molecular structural formula represented by the above formula (2) or Mo dialkyl thiocarbamate represented by the above formula (3) can be used.

[Resin] As the resin, a material having a function as a binder for a lubricant such as molybdenum disulfide or graphite and having heat resistance, moderate hardness and wear resistance is used. Examples of such a material include a thermosetting resin such as an epoxy resin, a polyimide resin, a polyamide imide resin, polyether sulfone, and polyether ether ketone, a phenol resin, a polyethylene resin, and a silicone resin. Preferably, it is a thermosetting resin.

[Inorganic polymer compound having MO as a skeleton]
The inorganic polymer compound having a skeleton of MO (hereinafter, also simply referred to as an inorganic polymer compound) has a function as a binder for a lubricant such as molybdenum disulfide or graphite, and has heat resistance and appropriate hardness. Use a material having wear resistance. Such a material has a molecular structure exemplified in the above formula (1), and the alkyl group of the formula (1) is a Ti—O, Si— group having an alkyl group such as methyl, ethyl, isopropyl, propyl, and isobutyl. Inorganic polymer compounds having a skeleton of O, Zr-O, Mn-O, Ce-O, Ba-O, or the like can be given. Preferably, it is an inorganic polymer compound having a skeleton of Ti-O. More preferably, an inorganic polymer compound having an alkyl group having a skeleton of Ti-O of methyl, ethyl or isopropyl is used.

The weight ratio (B / A) of the content of the resin or the inorganic polymer compound (A) to the total content of molybdenum disulfide and graphite (B) is from 0.3 to 9.0. It is desirable to do. If the weight ratio is less than 0.3, the effect of improving the lubricity of the formed lubricating coating is small, and the improvement in seizure resistance is insufficient. If the weight ratio is more than 9.0, the adhesion of the solid lubricating coating is increased. In particular, the problem is that the lubricant is remarkably peeled off from the lubricating coating. More preferably, the weight ratio is 0.5 or more and 7.0 or less,
More preferably, it is 3.0 or more and 6.5 or less.

It is desirable that the thickness of the lubricating coating be 5 μm or more and 30 μm or less. When the thickness of the lubricating film is less than 5 μm, the effect of improving the lubricity is small. On the other hand, when the thickness is more than 30 μm, the processing cost of forming the lubricating film increases and the effect of improving the lubricity is saturated. However, there is a drawback that it is easy to peel off.
More preferably, the thickness of the lubricating coating is 5 μm or more and 15 μm or more.
m, more preferably 6 μm or more and 10 μm or less.

[Rust-Inhibiting Coating] The rust-preventing coating is a coating made of a rust-preventing oil composition formed by applying a rust-preventing oil obtained by diluting the above-mentioned rust-preventing oil composition of the present invention with a solvent. That is, the rust preventive coating contains at least one kind of alkali metal salt of carboxylic acid and alkaline earth metal salt of carboxylic acid, and the total content of alkali metal and alkaline earth metal is 2 to 20.
mass%, a saponification value of 20 to 150 mg KOH / g, and a total base number of 15 to 100 mg KOH / g, and preferably, a lubricant further comprising one or more of graphite, molybdenum disulfide and an organic Mo compound 5 to 30 mass%.

[Rust prevention coating thickness] If the thickness of the rust prevention coating is too small, the rust prevention effect is small, and if it is too large, the lubricating action of the lubricating coating is hindered, the friction coefficient increases, and seizure occurs. Therefore, as shown in FIG. 6, when forming a lubricating coating on both the pin and the box and forming a rust-preventive coating thereon,
The thickness of the rust preventive coating is 1 μm or more and 50 μm or less. Further, as shown in FIG. 5, when a lubricating film is formed on one of the pin and the box and a rust-preventive film is formed on the other, the thickness of the rust-preventive film is 5 μm or more and 50 μm or less. That is, when a rust-preventive film is formed on the lubricating film, the rust-preventing effect of the lubricating film acts, so that the lower limit of the rust-preventive film thickness can be reduced.

Next, a method for forming a lubricating film and a rust-preventive film according to the present invention will be described with reference to an example in which a lubricating film of an inorganic polymer compound is formed on both pins and a box, and a rust-preventive film is formed on the lubricating film. Will be described.

In forming a lubricating film, a dispersion medium is added to a metal alkoxide and a lubricant such as molybdenum disulfide or graphite, mixed, applied to both surfaces of the pin and the box, and further humidified. Co-hydrolyze to form a lubricating coating of an inorganic polymer compound. In addition, when forming a lubricating coating of a resin, for example, a dispersion medium is added to and mixed with an organic polymer material such as a thermosetting resin and the lubricant,
These may be applied in the same manner as described above. Next, a rust preventive oil obtained by diluting the rust preventive oil composition of the present invention with an organic solvent is applied on the lubricating film to form a rust preventive film.

As the metal alkoxide, a metal alkoxide such as titanium or silicon having an alkyl group such as methyl, ethyl, isopropyl, propyl, isobutyl and butyl can be used.

As the dispersant for the metal alkoxide, a low-boiling liquid such as xylene, methylene chloride, isopropyl, butyl alcohol and methyl ethyl ketone can be used alone or in combination of two or more.

As a dispersant for the resin material, a low-boiling liquid such as toluene or isopropyl alcohol can be used alone or as a mixture.

The humidification treatment can be carried out by leaving the humidification treatment in the atmosphere for a predetermined time, but it is desirable to carry out the humidification treatment in an atmosphere having a humidity of 70% or more. Further, it is desirable to perform a heat treatment after the humidification treatment. The co-hydrolysis is promoted by the heat treatment, and the discharge of the alkyl substance, which is a hydrolyzate, from the lubricating film can be promoted. The adhesion of the lubricating film becomes strong, and the seizure resistance is improved. The heating is preferably performed after the dispersion medium has evaporated. The heating temperature is preferably 100 to 200 ° C., which is close to the boiling point of the alkyl substance, and it is more effective to apply hot air.

The organic solvent for the rust-preventive oil composition is not particularly limited, and for example, various solvents, volatile oils, benzene, kerosene, hexane and the like can be used.

The rust preventive oil obtained by diluting the rust preventive oil composition with an organic solvent preferably has a viscosity at 40 ° C. of 2 cSt or more and 30 cSt or less. If the viscosity is less than 2 cSt, the thickness of the rust preventive coating is too thin, and sufficient rust preventive properties cannot be obtained. Also, 30 cS
If it exceeds t, the rust-preventive coating becomes too thick, the effect of improving lubricity by the formation of a lubricating coating is reduced, and seizure is likely to occur. In addition, the amount of the organic solvent is 30% by mass or more of the rust-preventive oil and 8%.
It is good to be 0 mass% or less.

[0074]

The present invention will be described in more detail with reference to the following examples. Various ground treatments, formation of lubricating coatings and formation of rust-preventive coatings on the threaded parts and metal contact parts of pins and boxes of screw joints (outer diameter: 7 inches, wall thickness: 0.408 inches) having the component compositions shown in Table 1. Surface treatment such as formation was performed.

Tables 2 and 3 show the composition and properties of the rust-preventive oil composition used for forming the rust-preventive film, and Table 4 shows the composition and properties of the rust-preventive oil.
Table 5 shows details of the surface treatment conditions.

[0076]

[Table 1]

[0077]

[Table 2]

[0078]

[Table 3]

[0079]

[Table 4]

[0080]

[Table 5]

Next, using the threaded joint having been subjected to the surface treatment described above, the JIS-JIS
The salt spray test specified in Z2371 was performed, and 33
The occurrence of rust after 6 hours was investigated.

Next, using the threaded joint subjected to the salt spray test, the tightening and re-tightening operations were repeated up to 20 times in the manner shown in Table 6 to determine the state of seizure and the tightening torque at the time of repeated tightening. The fluctuation situation was investigated.

[0083]

[Table 6]

That is, as shown in Table 6, the first to tenth, the 12 to 15th, and the 17 to 20th tightening and retightening are performed at room temperature, while the 11th and 16th rounds are performed after tightening at room temperature. , At 350 ° C. for 24 hours, and then cooled to perform retightening at room temperature. Table 7 shows the standard conditions of the tightening speed and the tightening torque.

[0085]

[Table 7]

Table 8 shows the test results. Hereinafter, both surfaces of the screw portion and the metal contact portion of the pin are referred to as a pin surface, and both surfaces of the screw portion and the metal contact portion of the box are referred to as a box surface. The surface roughness is indicated by the value of Rmax.

[0087]

[Table 8]

(Example 1 of the Present Invention) The threaded joints made of carbon steel shown in Table 2 were subjected to the following surface treatment. The surface of the pin was made to have a surface roughness of 3 μm while being machine-finished, and a rust-preventive oil of the type X1 shown in Table 4 was applied to the pin surface to form a rust-preventive film having a thickness of 10 μm. The surface of the box is sprayed with # 80 sand to a surface roughness of 15 μm, and an epoxy resin having an average molecular weight of 15,000 and molybdenum disulfide powder having an average particle size of 1.5 μm are applied to the surface of the box. And a mixture of toluene and isopropyl alcohol was applied as a dispersion medium to form a lubricating film. When the lubricating coating thickness is measured in a dry state, it is 40
μm. Next, a rust preventive oil of type X1 shown in Table 4 was applied on the lubricating film to form a rust preventive film having a thickness of 10 μm.

As shown in Table 8, in the salt spray test, no rust was observed on both the pin and the box. In the tightening and unfastening test, seizure did not occur in the 20 tightening and unfastening operations shown in Table 6 and was extremely good. In addition, through 20 tightening / unfastening tests, the variation in tightening torque was stable and good at about ± 13%.

(Example 2 of the Invention) The following surface treatment was applied to the threaded joint made of carbon steel shown in Table 2. # 120 sand was sprayed on both the pin surface and the box surface, and the surface roughness of both was set to 5 μm. Next, a manganese phosphate film having a thickness of 10 μm was formed on both surfaces by a chemical conversion treatment. Further, on the box side, a polyamideimide resin having an average molecular weight of 15,000 and an average particle size of 1.000 were formed on the manganese phosphate coating.
A 0 μm powder of molybdenum disulfide was mixed with the polyamideimide resin 1 at a weight ratio of 2.5 of molybdenum disulfide, and a mixed solution of toluene and methyl ethyl ketone was applied as a dispersion medium to form a lubricating film. After drying, 20 at 180 ° C
After heating for 25 minutes, the lubricating coating thickness was measured to be 25 μm
Met. Next, the pin side is on the manganese phosphate coating,
On the box side, a rust preventive oil of type X2 shown in Table 4 was applied on the lubricating film to form a rust preventive film having a thickness of 15 μm.

As shown in Table 8, no rust was observed on both the pin and the box in the salt spray test.
In the tightening and unfastening test, seizure did not occur in the 20 tightening and unfastening operations shown in Table 6 and was extremely good. In addition, through 20 tightening / unfastening tests, the variation in tightening torque was stable and good at about ± 10%.

(Example 3 of the Present Invention) The following surface treatment was applied to a threaded joint made of Cr-Mo steel shown in Table 2. The surface of the pin was machine-finished to a surface roughness of 3 μm, and a 10 μm-thick zinc phosphate film was formed on the pin surface by a chemical conversion treatment. The surface of the box is sprayed with a # 80 shot to make the surface roughness 15 μm. The silicon alkoxide having an alkyl group of ethyl and molybdenum disulfide powder having an average particle diameter of 1.8 μm are applied to the silicon alkoxide 1 on the box surface. Molybdenum disulfide was mixed at a weight ratio of 2.3, and a mixed solution of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium to form a lubricating film. Next, hot air at 165 ° C. was blown for 30 minutes after standing in the air for 3 hours. When the composition of the lubricating film formed on the box surface in a dry state was measured, the content was expressed by weight ratio of molybdenum disulfide 3 to inorganic polymer compound 1 having a skeleton of Si—O.
And the coating thickness was 20 μm. Next, the pin side is on the zinc phosphate coating, the box side is on the lubricating coating,
A rust preventive oil of type X3 shown in Table 4 was applied to form a rust preventive film having a thickness of 40 μm.

As shown in Table 8, in the salt spray test, no rust was observed on both the pin and the box.
In the tightening / refastening test, the 19th tightening /
Until the end of the retightening, there is no seizure and it is good.
Mild seizure occurred at the time of the second tightening, but maintenance was possible. In addition, through 20 times of tightening and retightening,
The variation of the tightening torque was stable and good at about ± 10%.

(Example 4 of the Present Invention) The threaded joints made of carbon steel shown in Table 2 were subjected to the following surface treatment. A # 120 sand is sprayed on both the pin surface and the box surface to make the surface roughness 5 μm, and then the box surface is subjected to a chemical conversion treatment to a thickness of 8 μm.
A μm manganese phosphate coating was formed. Next, a titanium alkoxide having an alkyl group of ethyl and molybdenum disulfide powder having an average particle diameter of 1.0 μm were mixed on the pin surface and the manganese phosphate coating at a weight ratio of molybdenum disulfide to titanium alkoxide of 2.3. , A mixed solution of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium to form a lubricating film. Next, hot air of 150 ° C. humidified after being left in the air for 4 hours was blown for 20 minutes.
When the composition of the lubricating coating after drying was measured, the content was T
Molybdenum disulfide was 3.5 with respect to inorganic polymer compound 1 having i-O as a skeleton, and the coating thickness was 10 µm. Then, a rust preventive oil of type X4 shown in Table 4 was applied on both the lubricating films on the pin side and the box side to form a rust preventive film having a thickness of 15 μm.

As shown in Table 8, in the salt spray test, no rust was observed on both the pin and the box.
In the tightening and unfastening test, seizure did not occur in the 20 tightening and unfastening operations shown in Table 6 and was extremely good. In addition, through 20 fastening / unfastening tests, the variation in the fastening torque was stable and good with less than ± 10%.

(Example 5 of the Invention) A threaded joint made of Cr-Mo steel shown in Table 2 was subjected to the following surface treatment. The pin surface is machine-finished to a surface roughness of 3 μm, on which titanium alkoxide having an alkyl group of isopropyl, a powder of molybdenum disulfide having an average particle diameter of 2.6 μm, and an average particle diameter of 1.
3 μm graphite powder was mixed with titanium alkoxide 1 at a weight ratio of molybdenum disulfide 1.8 and graphite 0.9,
A mixed solution of methyl ethyl ketone, methylene chloride and butyl alcohol was applied as a dispersion medium to form a lubricating film. Then, after being left in the air for 3 hours, humidified at 150 ° C.
Was blown for 10 minutes. When the composition of the lubricating coating was measured in a dry state, the content was 3 parts by weight of molybdenum disulfide and 1.5 parts of graphite with respect to 1 part of the inorganic polymer having a skeleton of Ti—O, and the coating thickness was 15 μm. Was. On the other hand, the surface of the box was sprayed with # 80 sand to have a surface roughness of 10 μm, and a manganese phosphate film having a thickness of 15 μm was formed on the surface by a chemical conversion treatment. Then, a rust preventive oil of type X5 shown in Table 4 was applied on the lubricating film on the pin side and on the manganese phosphate film on the box side to form a rust preventive film having a thickness of 15 μm.

As shown in Table 8, in the salt spray test, no rust was observed on both the pin and the box.
In the tightening and unfastening test, seizure did not occur in the 20 tightening and unfastening operations shown in Table 6 and was extremely good. In addition, through 20 fastening / unfastening tests, the variation in the fastening torque was stable and good with less than ± 10%.

(Example 6 of the Present Invention) The following surface treatment was applied to a threaded joint made of carbon steel shown in Table 2. Spray # 80 sand on both the pin surface and box surface to reduce the surface roughness to 10μm
After that, a manganese phosphate film having a thickness of 8 μm was formed on both of them by a chemical conversion treatment. Next, an epoxy resin having an average molecular weight of 10,000 and molybdenum disulfide powder having an average particle size of 1.8 μm were mixed on the manganese phosphate coating at a weight ratio of molybdenum disulfide to epoxy resin 1 of 1.5. , Toluene and xylene were applied as a dispersion medium. Next, after drying, a heat treatment was performed at 180 ° C. for 20 minutes. When the composition of the lubricating film formed on the pin surface and the box surface after the heat treatment was measured, the content on both the pin side and the box side was molybdenum disulfide 3 with respect to the epoxy resin 1 in terms of weight ratio. The length was 10 μm. Next, a rust preventive oil of type X6 shown in Table 4 was applied on the lubricating film formed on the pin surface and the box surface to form a 2 μm thick rust preventive film.

As shown in Table 8, no rust was observed on both the pin and the box in the salt spray test.
In the tightening / unfastening test, there was no seizure until the 19th tightening / unfastening in Table 6 was completed, and the condition was good. In addition, through 20 times of tightening and retightening tests,
The variation of the tightening torque was stable and good at about ± 10%.

(Example 7 of the present invention) A surface treatment was carried out under the same conditions as in Example 2 of the present invention except that no rust preventive film was formed on the box side.

As shown in Table 8, in the salt spray test, no rust was observed on both the pin and the box.
In the tightening and unfastening test, seizure did not occur in the 20 tightening and unfastening operations shown in Table 6 and was extremely good. In addition, through 20 tightening / unfastening tests, the variation in tightening torque was stable and good at about ± 13%.

(Example 8 of the present invention) A surface treatment was carried out under the same conditions as in Example 6 of the present invention except that no rust preventive film was formed on the pin side.

As shown in Table 8, in the salt spray test, no rust was observed on both the pin and the box.
In the tightening and unfastening test, seizure did not occur in the 20 tightening and unfastening operations shown in Table 6 and was extremely good. In addition, through 20 tightening / unfastening tests, the variation in tightening torque was stable and good at about ± 15%.

(Comparative Example 1) A surface treatment was performed on the carbon steel threaded joint shown in Table 2 under the same conditions as in Example 6 of the present invention except that no rust-proof coating was formed. That is, a manganese phosphate coating having a thickness of 8 μm was formed on the pin surface and the box surface, and a 15 μm-thick lubricating coating made of an epoxy resin and molybdenum disulfide was formed on the manganese phosphate coating.

As shown in Table 8, rust appeared on almost all surfaces of the lubricating film in both the pin and the box, and peeling was observed in a part of the lubricating film. In the tightening / unfastening test,
Slight seizure was observed in the thirteenth tightening, and was completely seized in the fifteenth tightening, and the test was stopped. In addition, in the tightening / refastening test up to the 14th time, the variation in the tightening torque was as large as about ± 50% and was unstable.

Comparative Example 2 The carbon steel threaded joint shown in Table 2 was subjected to the following surface treatment. The surface of the pin was made to have a surface roughness of 3 μm with the machine grinding finish.
A rust-preventive oil of the type X7 shown in Table 2 was applied to form a rust-preventive film having a thickness of 15 μm. The surface of the box is sprayed with # 80 sand to have a surface roughness of 15 μm, and an epoxy resin having an average molecular weight of 15,000 and an average particle diameter of 1.000 are applied to the surface of the box.
5 μm of molybdenum disulfide powder was mixed with resin 1 at a weight ratio of 3 of molybdenum disulfide, and a mixed solution of toluene and isopropyl alcohol was applied as a dispersion medium to form a lubricating film. When the lubricating coating thickness is measured in a dry state, it is 40 μm
Met. Then, on the lubricating coating, type X7 shown in Table 4
Was applied to form a rust preventive film having a thickness of 15 μm.

As shown in Table 8, in the salt spray test, both the pin side and the box side had an area of about 30% and about 7%, respectively.
Rust was observed in the area of No. 1, and swelling of the coating was partially observed. In the test for tightening and retightening, 11
Slight seizure was observed at the time of the first tightening, and seizure was completely caused by the thirteenth tightening, making it impossible to continue the test. In addition, in the tightening and unfastening tests up to the twelfth time, the variation in the tightening torque was as large as about ± 35% and was unstable (Comparative Example 3). The following surface treatment was applied to the carbon steel threaded joint shown in Table 1. Was given. The pin surface was finished by mechanical grinding to have a surface roughness of 3 μm. The surface of the box with a surface roughness of 10 μm was sprayed with # 80 sand and subjected to a chemical conversion treatment to give a thickness of 1
A 5 μm manganese phosphate coating was formed. Next, API-Bul5 was applied to both the pin surface and the upper surface of the manganese phosphate coating.
Compound grease corresponding to A2 is applied to a unit area (1 dm
² ) About 20 g of the composition was applied per ² ).

As shown in Table 8, in the salt spray test, no rust was generated on both the pin side and the box side. Tightening
In the retightening test, slight seizure occurred after the eighth tightening, but the test was continued after performing the care. However, 1
Since the seizure occurred during the first retightening, the test could not be continued. In addition, in the tenth fastening / unfastening test, the variation in the fastening torque was stable at less than ± 10%.

As described above, the example of the present invention has the same excellent rust prevention as a threaded joint to which compound grease has been applied, has excellent seizure resistance and suppresses fluctuations in tightening torque as compared with the comparative example. It turned out that there was.

[0110]

The rust-preventive oil composition of the present invention has the same rust-preventive properties as compound grease, and can be used as a rust-preventive coating for threaded joints that do not use compound grease. The threaded joint for oil country tubular goods of the present invention has the same rust-prevention properties as conventional threaded joints coated with compound grease, and has remarkably better seizure resistance during repeated tightening and retightening than conventional threaded joints. improves. Therefore, the threaded joint for oil country tubular goods of the present invention can ensure rust prevention and improve seizure resistance without using any compound grease applied before shipment or before make-up.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing an assembling configuration of an oil country tubular goods and a threaded joint member at the time of shipping the oil country tubular goods.

FIG. 2 is a graph showing a relationship between a rust generation area and a saponification value, a total base number, an alkali metal content, and a rust prevention coating thickness by a salt spray test. FIG. 2 (b) is a graph of rust generation area and total base number, FIG. 2 (c) is a graph of rust generation area and alkali metal content, and FIG. 2 (d) is a graph of rust generation area and rust prevention coating thickness.

FIG. 3 shows a friction coefficient, a saponification value, a total base number,
FIG. 3A is a graph showing the relationship between the alkali metal content and the thickness of the rust preventive coating. FIG. 3A shows the friction coefficient and the saponification value, FIG. 3B shows the friction coefficient and the total base number, and FIG. And (d) are graphs of coefficient of friction and rust prevention coating thickness.

FIG. 4 is a schematic diagram schematically showing a tightening portion of the threaded joint for oil country tubular goods of the present invention.

FIG. 5 is an enlarged cross-sectional view showing an example of a state of formation of a solid lubricating film and a rust-preventive film according to the threaded joint for oily pipes of the present invention, wherein FIG. Is the unthreaded metal contact of the box.

FIG. 6 is an enlarged cross-sectional view showing a state of formation of a solid lubricating film and a rust-preventive film according to another threaded joint for oil country tubular goods of the present invention, wherein FIG. 6 (a) is a screwless metal contact portion of a pin, and FIG. ) Is the unthreaded metal contact of the box.

[Explanation of symbols]

1A: Oil country tubular goods, 1B: Threaded joint member, 2: Pin, 3: Box, 4: Threaded part, 5: Metal contact part without thread, 6: Shoulder part, 7: Solid lubricating coating, 8: Binder, 9: Solid Lubricant, 10: anti-rust coating.

Claims (6)

[Claims] An alkaline metal salt of a carboxylic acid and / or an alkaline earth metal salt of a carboxylic acid having a saponification value of 20 to 150 mgKOH / g and a total base value of 15 to 10
A rust preventive oil composition comprising 0 mgKOH / g and a total content of an alkali metal and an alkaline earth metal of 2 to 20 mass%. 2. The rust-preventive oil composition comprises a lubricant containing at least one of graphite, molybdenum disulfide and an organic Mo compound.
The rust-preventive oil composition according to claim 1, which contains 30 mass%. 3. A threaded joint comprising a box and a pin each having a threaded portion and a threadless metal contact portion, wherein a solid lubricating film formed on one of the box and the pin and a protection film formed on the other. A rust film, wherein the solid lubricating film is a film of a resin or an inorganic polymer compound having M (metal) -O as a skeleton, and the rust preventive film is a film.
A threaded joint for oil country tubular goods, which is a film of the rust-preventive oil composition according to claim 2. 4. The rust-preventive coating has a thickness of 5 μm to 50 μm.
The threaded joint for an oil country tubular good according to claim 3, wherein: 5. A threaded joint comprising a box and a pin each having a threaded portion and a threadless metal contact portion, wherein a solid lubricating film formed on both the box and the pin and at least one of the box and the pin Wherein the solid lubricating film is a film of a resin or an inorganic polymer compound having M (metal) -O as a skeleton. A threaded joint for an oil country tubular good, which is a coating of the rust-preventive oil composition according to claim 1 or 2. 6. The rust-preventive coating has a thickness of 1 μm to 50 μm.
The threaded joint for an oil country tubular good according to claim 5, wherein