JP2001065754A - Screw joint for oil well pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a threaded joint for an oil well pipe having the material of carbon steel or low alloy steel of Cr containing quantity of less than 10 wt.%, for suppressing the generation of galling to repititive fastening and unfasting, in mining crude oil under environments of deep depth, high- temperature oil well, or a high-temperature environment such as a steam injection oil well, and excellent in airtightness. SOLUTION: A phosphate chemically treated coat 9 is formed on the nonthreaded metal contacting part of at least any one side of a box and a pin 21, and moreover lubricating coat 6 of an inorganic macromolecular compound 7, dispersedly mixed with molybdenum disulfite and/or graphite, is formed on the coat 9. The weight ratio (B/A) between the containing quantity of the compound 7 (A) and that of the total of the molybdenum and the graphite (B) is 0.3-9.0, and the coat thickness of the coat 6 is preferably 5-30 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a threaded joint for oil country tubular goods made of carbon steel having excellent seizure resistance or a low alloy steel having a Cr content of less than 10% by weight.
No seizure due to repeated tightening and loosening in crude oil extraction in poor environments such as high temperature oil wells, and
The present invention relates to an oil country tubular goods joint that maintains airtightness and can be used repeatedly.

[0002]

2. Description of the Related Art Normally, the depth of an oil well is 2000 m to 300 m.
0 m, but 800 m in deep oil wells such as recent marine oil fields.
It reaches from 0m to 10000m. Generally, a threaded joint is used for connecting oil well pipes such as tubing and a casing that are laid vertically in such an oil well. That is, the male screw formed on the outer surface of the oil country tubular good and the female screw formed on the inner surface of the threaded joint are fitted and tightened to perform the connection.

[0003] Since complex pressure and heat such as axial tensile force and internal / external surface pressure act on the threaded joint in the use environment,
Even under such an environment, it is required that the airtightness of the threaded joint is maintained and that the threaded joint is not damaged. On the other hand, when lowering the tubing or casing, the joint once tightened may be loosened and re-tightened.
According to I (American Petroleum Institute), ten times of tubing and three times of make-up (break-out) of the casing are free of galling called galling and maintain airtightness. Is required. When galling occurs, the airtightness becomes incomplete,
The number of times of repeated use decreases.

[0004] By the way, as a threaded joint, a threadless metal contact portion is usually formed at the tip of a male thread formed at the end of an oil country tubular good, and a threadless metal contact formed at the base of a female thread on the inner surface of the threaded joint. A threaded joint having a structure in which a metal seal portion is formed by abutting the screwless metal contact portions by fitting and tightening the contact portions.

[0005] However, since high surface pressure acts on the metal seal portion and the threaded portion, galling tends to occur particularly under high-temperature conditions.
After the heat resistance test of 77 ℃ × 24Hr, tightening up
It is required that airtightness be maintained even after retightening.

Therefore, various countermeasures have been proposed to meet the above demands. For example, Japanese Patent Application Laid-Open No. 5-1
No. 17870 discloses an average roughness of 20 to 6 on the surface of a threaded joint.
A method of forming a phosphate chemical conversion coating film after forming an unevenness of 0 μm, and Japanese Unexamined Patent Publication No. 6-10154 discloses a method in which the maximum surface roughness of the metal seal portion and the thickness of the surface treatment coating layer are specified. The processing method is disclosed in Japanese Patent Application Laid-Open No. 5-149485.
Japanese Unexamined Patent Publication No. Heisei 2-885593 discloses a method of applying ceramic coating to a metal seal portion having a surface roughness of 20 to 50 μm. JP-A-233164 and JP-A-9-72467 each disclose a threaded joint in which a resin film in which molybdenum disulfide powder is dispersed and mixed is formed on a contact surface of a box or a pin.

[0007]

In recent years, for high-temperature oil wells used in an operating environment of 250 to 300 ° C.,
In order to increase the efficiency of crude oil recovery, a heat-resistant joint for a steam-injected oil well that injects high-temperature steam (350 ° C.) that reaches a critical temperature is required. Therefore, the threaded joint is required to have a performance of maintaining airtightness even after performing a heat-resisting test at a temperature exceeding 350 ° C. after the joint is fastened and then performing a tightening-refastening process.

[0008] However, it is difficult to secure the above performance with the conventional techniques disclosed in the above publications. That is, when fastening the threaded joint, API standard BUL5A
In the case of using compound grease as defined in 2, the grease component evaporates due to the high temperature and the lubricity decreases, so that a problem that a predetermined airtightness cannot be obtained at the time of retightening after retightening is problematic. is there. Therefore, Japanese Patent Application Laid-Open No. HEI 5-117870 in which application of compound grease is considered in mind.
Gazette, JP-A-6-10154, JP-A-5-1494
The technology disclosed in Japanese Patent Application Laid-Open No. 85-85, Japanese Unexamined Patent Application Publication No. 2-885593 and the like have a problem in securing airtightness at high temperatures.

Also, Japanese Patent Application Laid-Open Nos. 8-233164 and 9-29, which do not use compound grease.
According to the technology disclosed in Japanese Patent Application Laid-Open No. 72467/92, the resin deteriorates when exposed to a high temperature as high as 400 ° C. for a long time, so that the binder function of retaining a solid lubricant such as molybdenum disulfide is lost, and the lubricity is reduced. However, there is a problem that fastening failure or seizure occurs, and further, airtightness deteriorates.

As described above, at present, a threaded joint having excellent galling resistance that can be repeatedly used in a high temperature environment of as high as 400 ° C. has not been obtained.

An object of the present invention is to provide a threaded joint for an oil country tubular good having excellent galling resistance made of carbon steel or a low alloy having a Cr content of less than 10% by weight. More specifically, the present invention provides a threaded joint for oil country tubular goods which suppresses the occurrence of galling against repeated tightening and loosening in crude oil mining under high temperature environments such as high depth, high temperature oil wells, or steam injection oil wells, and has excellent airtightness. It is in.

[0012]

Means for Solving the Problems In order to solve the above problems, the present inventors have focused on the formation of a lubricating film having excellent galling resistance in a high-temperature environment, and have studied the heat resistance of a solid lubricant and a binder (binder). A basic study was conducted on the lubricity, lubricity, coating property, etc., and the following findings were obtained.

(A) Solid lubricants such as molybdenum disulfide and graphite do not deteriorate or decompose due to heat even at a temperature of about 400 ° C., and exhibit lubricity that is not different from that at ordinary temperature.

(B) When a resin is used as a binder for the solid lubricant, the resin deteriorates, decomposes or carbonizes under a long-time high-temperature environment exceeding 24 hours, and has a function as a binder for coating the solid lubricant on the joint surface. It is lost and lubricity is reduced.

(C) Inorganic compounds such as oxides, carbides and nitrides such as Si, Ti and Al are thermally stable.
There is no function as a binder for coating the solid lubricant. Therefore, since a film cannot be formed, lubricity is low even when a solid lubricant is mixed.

(D) Titanium alkoxide (Ti (OR)
₍₄ , R = alkyl group) has an alkyl group, and thus exhibits organic properties and functions as a binder. This substance is unstable in the air, absorbs moisture and causes co-hydrolysis, and the decomposed products are bonded to each other to form a thermally stable inorganic polymer compound with a skeleton of Ti-O having a network structure. Change. Formula (1) illustrates a molecular structural formula of a typical inorganic polymer compound.

[0017]

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(E) The above inorganic polymer compound is hard and has excellent wear resistance. (F) Therefore, by mixing and applying a titanium alkoxide as a binder to a solid lubricant such as molybdenum disulfide or graphite and performing a humidifying treatment, it contains molybdenum disulfide or graphite and has excellent lubricity and heat resistance. An inorganic lubricating coating having Ti-O as a skeleton can be formed.

Based on the results of the above basic studies, the appropriate conditions for forming the lubricating coating on a threaded joint made of carbon steel or a low alloy steel having a Cr content of less than 10% by weight were examined. I got

(G) A phosphate chemical conversion coating is formed on at least one of the threadless metal contact portions of the pin and the box, and a coating of the above inorganic polymer compound having a skeleton of Ti-O is further formed thereon. By doing so, burn-in is suppressed.

(H) The solid lubricant constituting the lubricating film is:
Molybdenum disulfide powder, graphite powder, or a mixed powder of molybdenum disulfide and graphite, wherein the weight ratio of the content A of the inorganic polymer compound to the content B of the solid lubricant (B /
A) may be in the range of 0.3 to 9.0.

(I) The surface roughness of the screw-free metal contact portion forming the phosphate conversion coating film is 3 to 15 μm in Rmax and the thickness of the lubricating coating is 5 to 30 μm to improve seizure resistance. .

The present invention has been completed based on the above findings, and the gist thereof is as follows. (1) In a screw joint made of carbon steel or a low alloy steel having a Cr content of less than 10% by weight, which is composed of a pin and a box each having a screw portion and a screwless metal contact portion,
A phosphate conversion coating is formed on a threadless metal contact portion of at least one of the box and the pin, and further, a skeleton of Ti-O in which molybdenum disulfide and / or graphite is dispersed and mixed is formed on the phosphate conversion coating. A threaded joint for oil country tubular goods characterized by forming a lubricating film of an inorganic polymer compound.

(2) The threaded joint for oil country tubular goods as described in the above item (1), wherein the phosphate conversion coating is a manganese phosphate conversion coating.

(3) The weight ratio (B / A) of the content (A) of the inorganic polymer compound to the total content (B) of molybdenum disulfide and graphite is 0.3 to 9.0. The threaded joint for oil country tubular goods according to the above item (1) or (2), wherein:

(4) The surface roughness of the screwless metal contact portion forming the above-mentioned phosphate conversion coating film is 3 to 15 μm in Rmax.
The threaded joint for an oil country tubular good according to any one of the above items (1) to (3), wherein

(5) The lubricating film has a thickness of 5 to 30 μm.
The threaded joint for oil country tubular goods according to any one of the above items (1) to (4), wherein

[0028]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a threaded joint made of high carbon steel or low alloy steel having a Cr content of less than 10% by weight.

FIG. 1 is a schematic view schematically showing a configuration of a threaded joint for oil country tubular goods according to the present invention. Reference numeral 1 denotes a box, 2 denotes a pin, 3 denotes a screw portion, 4 denotes a screwless metal contact portion, and 5 denotes a shoulder portion.

FIG. 2 is an enlarged cross-sectional view of a threadless metal contact portion of a pin showing an example of a state of forming a lubricating film according to the present invention. Reference numeral 6 denotes a lubricating coating, 7 denotes an inorganic polymer compound, 8 denotes a solid lubricant, 9 denotes a phosphate chemical conversion coating, and the same elements as those in FIG.

As shown in FIG. 1, a threaded joint for an oil country tubular good (hereinafter also referred to as a threaded joint) according to the present invention comprises a box 1 comprising a threaded portion 3 formed on the inner surface of an oil country tubular good and a threadless metal contact portion 4. And a pin 2 comprising a threaded portion 3 formed on the outer surface of the threaded joint member and a metal contact portion 4 having no thread.
Further, as shown in FIG. 2, an inorganic polymer compound having a skeleton of Ti-O in which a phosphate chemical conversion coating is formed on the surface of the threadless metal portion of the pin, and a solid lubricant 8 is dispersed and mixed thereon. 7 is formed. As the solid lubricant, molybdenum disulfide or graphite is used alone or a mixture of molybdenum disulfide and graphite is used. Although FIG. 2 shows the case where the phosphoric acid-based chemical conversion treatment layer is formed on the threadless metal part of the pin, it may be formed on at least one of the threadless metal part of the pin and the box.

A screwless metal contact portion (hereinafter, also simply referred to as a metal contact portion) has a higher contact surface pressure than a screw portion and is in a severely lubricated state, and a screw joint fastens a pin and a box by screwing each other into each other. Therefore, by forming a lubricating coating on at least one of the metal contact portions of the pin and the box, seizure resistance can be improved. In addition,
In a threaded joint in which the material strength is high and a high contact surface pressure acts on the threaded portion, seizure easily occurs. Therefore, it is desirable to form a lubricating film on the threaded portion in addition to the metal contacted portion.

An inorganic high molecular compound having a skeleton of Ti—O (hereinafter also simply referred to as “inorganic high molecular compound”) has a molecular structure exemplified in the above formula (1), and is a solid such as molybdenum disulfide or graphite. It functions as a lubricant binder and forms a lubricating film. For example, as the inorganic polymer compound, a titanium compound in which the alkyl group of the formula (1) has an alkyl group such as methyl, ethyl, isopropyl, propyl, isobutyl, and butyl can be used.

Since both molybdenum disulfide and graphite are thinly stretched by the tightening pressure during the tightening operation,
It has the effect of improving the lubricity of the lubricating coating and improving the seizure resistance. Since molybdenum disulfide has higher lubricity than graphite, especially under a high surface pressure, it is desirable to use molybdenum disulfide alone for a threaded joint having high material strength.

The weight ratio (B / A) of the content (A) of the inorganic high molecular compound to the total content (B) of molybdenum disulfide and graphite should be 0.3 or more and 9.0 or less. Is desirable. 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 lubricating coating is improved. And, in particular, a problem such as remarkable separation of the solid lubricant from the lubricating coating occurs. More preferably, the weight ratio is 0.5 or more and 7.0 or less, and still more preferably 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.

As a base treatment for forming the lubricating coating, a phosphate chemical conversion coating is formed. The phosphate conversion coating is a reaction layer formed by a chemical reaction on the material surface of the joint, and the surface has a structure in which fine crystal grains are established. Therefore, the adhesiveness to the material below the layer is extremely high, and the so-called anchor effect for anchoring the lubricating film formed on the layer is enhanced, and the adhesiveness of the lubricating film is improved.

Examples of the phosphate chemical conversion coating include chemical conversion coatings such as manganese phosphate, zinc phosphate, calcium phosphate, and zinc calcium phosphate. The geometries of these crystals are different, with the manganese phosphate crystals being the finest and carpet-like. Therefore, it is desirable to use a manganese phosphate-based chemical conversion treatment layer from the viewpoint of improving the anchor effect.

The thickness of the phosphate conversion coating is not particularly limited. However, if the thickness is too small, the effect of suppressing the peeling of the lubricating coating is small, and if the thickness is too large, cracks occur in the chemical conversion coating and the coating falls off together with the lubricating coating. I do. Therefore, the film thickness is 3μ.
It is desirable that the thickness be not less than m and not more than 10 μm.

The surface roughness of the screwless metal contact portion (base) forming the above-mentioned phosphate conversion coating is desirably not less than 3 μm and not more than 15 μm in Rmax. By providing appropriate surface roughness as a base treatment when forming the chemical conversion coating, the so-called anchor effect of physically capturing the phosphate chemical conversion coating formed thereon is enhanced, and the chemical conversion treatment layer is peeled off. Is blocked. Surface roughness 3μ at Rmax
When it is less than m, the anchor effect is small and the chemical conversion treatment layer is easily peeled. On the other hand, if the surface roughness exceeds 15 μm,
At the time of retightening, the lubricating coating on the chemical conversion coating formed on the convex portion of the roughness is easily broken and seizure is likely to occur. More preferable surface roughness is 4 μm or more and 10 μm or less. In addition,
When the treatment of the present invention is performed on only one surface, the surface roughness of the opposite surface on which the phosphate film is not formed is preferably smaller than the surface roughness of the base.

The threaded joint of the present invention can remarkably improve the galling resistance without using any lubricant such as compound grease applied before make-up.

In the threaded joint of the present invention, a rust-preventive additive or a corrosion inhibitor is added to the lubricating coating to prevent rust while maintaining seizure resistance. Known rust preventive additives and corrosion inhibitors can be used.

Next, a method for forming a film according to the present invention will be described. In the method of the present invention, the surface of the metal contact portion of at least one of the pin and the box is subjected to a chemical conversion treatment using a phosphate-based solution to form a phosphate film, and then a titanium alkoxide (Ti (OR) ₄ , R: an alkyl group) and a molybdenum disulfide powder and / or a graphite powder with a dispersing medium added and mixed, and these are applied on the above-mentioned phosphate film, subjected to humidification treatment and co-hydrolyzed to obtain Ti. A lubricating coating of an inorganic polymer compound having —O as a skeleton is formed.

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

A titanium alkoxide and molybdenum disulfide,
The mixing ratio of graphite is such that the weight ratio of the content of the inorganic polymer compound (A) to the total content of molybdenum disulfide and graphite (B) in the dried state after the formation of the lubricating coating is 0. 3
It is determined so as to be not less than 9.0 and not more than 9.0.

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

The humidification treatment can be performed by leaving the humidification treatment in the atmosphere for a predetermined time, but it is preferable to perform 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.

Further, according to the present invention, when forming a phosphate film, blasting processing is performed in advance as a base treatment,
It is desirable that the surface roughness of the underlayer be 3 to 15 μm in Rmax. By performing the blasting process, an active new surface appears on the surface, the adhesion of the phosphate film is strengthened, and the peeling resistance of the phosphate film is improved. The blasting process may be performed by a known sand blasting method, shot blasting method, grid blasting method, or the like, and can be performed by a method of spraying a hard material such as sand, shot, grid or cut wire at high speed.

[0049]

Examples: Carbon steel of the composition shown in Table 1, Cr-Mo
Various surface treatments such as undercoating and film formation are applied to both the threaded part and metal contact part of steel and 5Cr steel threaded joints (outer diameter: 7 inches, wall thickness: 0.408 inches) and pins. gave. Tables 2 and 3 show the surface treatment conditions. In addition,
Comparative examples shown in the table are those in which a resin film was formed or compound grease was applied.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

Next, using the threaded joint having been subjected to the above surface treatment, tightening and retightening operations were repeated up to 25 times in the manner shown in Table 4 to examine the occurrence of seizure.

[0054]

[Table 4]

That is, as shown in Table 4, the first to tenth, the 12 to 15th, the 17 to 20th, and the 22 to 25th are tightened and retightened at room temperature, while the 11th, 16th, and The 21st time is 40 after tightening at room temperature
A heat treatment was performed at 0 ° C. for 24 hours, followed by cooling and retightening at room temperature. Table 5 shows the conditions of the tightening speed and the tightening torque.

[0056]

[Table 5]

Table 6 shows the state of occurrence of seizure and the state of tightening. 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 an Rmax value.

[0058]

[Table 6]

(Example 1 of the Present Invention) The threaded joints made of carbon steel shown in Table 1 were subjected to the following surface treatment. The surface of the pin had a surface roughness of 3 μm while being mechanically finished. The box surface was machine-polished to a surface roughness of 3 μm, and a 5 μm-thick zinc phosphate coating was formed on the box surface by a chemical conversion treatment. Further, a titanium alkoxide having an alkyl group of methyl, a powder of molybdenum disulfide having an average particle size of 1.5 μm, and a powder of graphite having an average particle size of 3.5 μm were placed on the top surface of titanium alkoxide 0.77 with molybdenum disulfide 0.77. , Graphite at a weight ratio of 0.77, and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium. Then
After standing in the air for 6 hours, the composition of the coating formed on the top surface of the zinc phosphate coating in a dry state was measured. Then, molybdenum disulfide was 1 and graphite was 1, and the coating thickness was 40 μm.

As shown in Table 6, up to the twentieth tightening and retightening work shown in Table 3, there was no occurrence of seizure and the result was good. However, seizure occurred at the time of retightening after the 21st heat treatment. (Example 2 of the present invention) The following surface treatment was applied to the carbon steel threaded joint shown in Table 1. The pin surface was finished by mechanical grinding to have a surface roughness of 2 μm. The surface of the box was sprayed with # 80 sand to have a surface roughness of 10 μm, and a 10 μm thick zinc phosphate film was formed on the surface of the box by a chemical conversion treatment.
Further, a titanium alkoxide having an ethyl alkyl group, a molybdenum disulfide powder having an average particle size of 1.8 μm, and a graphite powder having an average particle size of 2.8 μm were provided on the upper surface of the titanium alkoxide 1 with molybdenum disulfide 2 and graphite. The mixture was mixed at a weight ratio of 1.33, and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium. Next, hot air at 165 ° C. was blown for 30 minutes after standing in the air for 3 hours. When the composition of the coating formed on the top surface of the zinc phosphate coating in a dry state was measured, the content was molybdenum disulfide 3 and graphite 2 with respect to the inorganic polymer 1 having a Ti—O skeleton as a weight ratio. The thickness was 10 μm.

As shown in Table 6, up to the 22nd tightening and retightening work shown in Table 3, no seizure occurred and the result was good. However, seizure occurred during the 23rd tightening. The tightening amount and tightening torque at the time of tightening were appropriate.

(Example 3 of the Present Invention) A threaded joint made of 5% Cr steel shown in Table 1 was subjected to the following surface treatment. The box surface was finished by mechanical grinding to have a surface roughness of 2 μm. Pin surface is #
A No. 80 sand was sprayed to make the surface roughness 10 μm, and a 5 μm-thick calcium phosphate film was formed on the pin surface by a chemical conversion treatment. Furthermore, a titanium alkoxide having an isopropyl alkyl group, a molybdenum disulfide powder having an average particle diameter of 1.8 μm, and a graphite powder having an average particle diameter of 2.5 μm were added to the titanium alkoxide 3.00 with molybdenum disulfide 3.06 on the upper surface thereof. , Graphite at a weight ratio of 1.94, and a mixture of methyl ethyl ketone, methylene chloride and butyl alcohol was applied as a dispersion medium. Next, after being left in the air for 2 hours, humidified hot air at 150 ° C. was blown for 15 minutes, and further dried hot air at 150 ° C. was blown. When the composition of the film formed on the upper surface of the calcium phosphate film in a dry state was measured, the content was 5.5 parts by weight of molybdenum disulfide and 3.5 parts by weight of inorganic polymer 1 having Ti-O as a skeleton as a skeleton.
5, and the coating thickness was 20 μm.

As shown in Table 6, in 25 tightening and retightening operations in Table 3, there was no occurrence of seizure and the result was extremely good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 4 of the Invention) The following surface treatment was applied to the carbon steel threaded joint shown in Table 1. The box surface was finished by mechanical grinding to have a surface roughness of 2 μm. Pin surface is # 80
A No. shot was sprayed to make the surface roughness 15 μm, and a 10 μm-thick manganese phosphate film was formed on the pin surface by a chemical conversion treatment. Further, on the upper surface thereof, a titanium alkoxide having an alkyl group of propyl, a powder of molybdenum disulfide having an average particle diameter of 4.6 μm, and a powder of graphite having an average particle diameter of 1.3 μm were used.
8, and 0.83 graphite in a weight ratio, and a mixture of methyl ethyl ketone, methylene chloride and butyl alcohol was applied as a dispersion medium. Next, hot air of 150 ° C. humidified after being left in the air for 3 hours was blown for 10 minutes. When the composition of the film formed on the upper surface of the calcium phosphate film in a dry state was measured, the content was 5.0 parts by weight of molybdenum disulfide and 1.5 parts of graphite with respect to the inorganic polymer 1 having a skeleton of Ti—O. And the coating thickness was 20 μm.

As shown in Table 6, there was no occurrence of seizure in 25 tightening and retightening operations in Table 3, and the results were extremely good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 5 of the Present Invention) The following surface treatment was applied to a Cr-Mo steel threaded joint shown in Table 1. A # 180 sand was sprayed on the pin surface and the box surface, and both had a surface roughness of 3 μm. A manganese phosphate film having a thickness of 5 μm was formed on both surfaces by a chemical conversion treatment. Further, on both upper surfaces, the alkyl group is a titanium alkoxide of methyl,
Molybdenum disulfide powder having an average particle diameter of 1.2 μm was mixed at a weight ratio of molybdenum disulfide of 2.31 to titanium alkoxide 1 and applied as a dispersion medium of a mixed liquid of xylene, methylene chloride and butyl alcohol. Next, hot air of 165 ° C. humidified after being left in the air for 2 hours was blown for 30 minutes. When the composition of the coating formed on the upper surface of the manganese phosphate coating in a dry state was measured, the content was 3.0 by weight of molybdenum disulfide with respect to the inorganic polymer 1 having a skeleton of Ti—O. The length was 8 μm on both the pin side and the box side.

As shown in Table 6, in 25 tightening and retightening operations in Table 3, there was no occurrence of seizure and the result was extremely good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 6 of the Present Invention) The following surface treatment was applied to a Cr-Mo steel threaded joint shown in Table 1. The pin surface was finished by mechanical grinding to have a surface roughness of 2 μm. The surface of the box was finished by mechanical grinding to have a surface roughness of 2 μm, and a manganese phosphate film having a thickness of 3 μm was formed on the surface of the box by a chemical conversion treatment. Further, a titanium alkoxide having an alkyl group of isobutyl, a powder of molybdenum disulfide having an average particle diameter of 3.1 μm, and a powder of graphite having an average particle diameter of 3.5 μm were added to titanium alkoxide 1.39 with molybdenum disulfide 1.39 on the upper surface. , Graphite at a weight ratio of 0.83, and a mixture of xylene, methylene chloride and isobutyl alcohol was applied as a dispersion medium. Subsequently, the composition was left to stand in the air for 6 hours, and the composition of the film formed on the upper surface of the manganese phosphate film in a dry state was measured. Molybdenum sulfide 2.5, graphite 1.5
And the coating thickness was 30 μm.

As shown in Table 6, up to the twenty-fourth tightening and retightening work shown in Table 3, there was no occurrence of seizure and the result was good. However, seizure occurred during the 25th tightening. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 7 of the Invention) A threaded joint made of 5% Cr steel shown in Table 1 was subjected to the following surface treatment. A # 120 sand was sprayed on the pin surface and the box surface, and both had a surface roughness of 5 μm. A manganese phosphate film having a thickness of 5 μm was formed on both surfaces by a chemical conversion treatment. Further, a titanium alkoxide having an alkyl group of ethyl and a powder of molybdenum disulfide having an average particle size of 1.0 μm were mixed on the upper surfaces of both at a weight ratio of molybdenum disulfide to titanium alkoxide of 0.23, and xylene and chloride were mixed. A mixture of methylene and butyl alcohol was applied as a dispersion medium. Next, hot air at 150 ° C. was blown for 15 minutes after standing in the air for 4 hours. When the composition of the film formed on the upper surface of the manganese phosphate film in a dry state was measured, the content was Ti-
Molybdenum disulfide is 0.35 with respect to the inorganic polymer 1 having O as a skeleton, and the coating thickness is 2 on both the pin side and the box side.
It was 0 μm.

As shown in Table 6, there was no occurrence of seizure in the 25 tightening and retightening operations in Table 3, and the results were extremely good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 8 of the Invention) The following surface treatment was applied to a Cr-Mo steel threaded joint shown in Table 1. A # 180 sand was sprayed on the pin surface and the box surface, and both had a surface roughness of 4 μm. A zinc phosphate coating with a thickness of 5 μm was formed on both surfaces by a chemical conversion treatment. Furthermore, a titanium alkoxide having an isopropyl alkyl group, a molybdenum disulfide powder having an average particle diameter of 1.2 μm, and a graphite powder having an average particle diameter of 1.5 μm are provided on both upper surfaces of the titanium alkoxide 1 and the molybdenum disulfide 2. And a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium. Then
After leaving in the air for 3 hours, humidified hot air at 140 ° C was applied for 20 hours.
Sprayed for minutes. When the composition of the film formed on the upper surface of the zinc phosphate film in a dry state was measured, the content was 5.0 parts by weight of molybdenum disulfide and 1.5 parts of graphite relative to the inorganic polymer 1 having a Ti—O skeleton as a skeleton. And the coating thickness is on the pin side,
It was 10 μm on both the box side.

As shown in Table 6, there was no occurrence of seizure in the 25 tightening and retightening operations in Table 3 and was extremely good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 9 of the Present Invention) The following surface treatment was applied to a threaded joint made of carbon steel shown in Table 1. The pin surface was finished by mechanical grinding to have a surface roughness of 2 μm. Box surface is # 18
No. 0 sand was sprayed to make the surface roughness 5 μm, and a manganese phosphate film having a thickness of 5 μm was formed on the box surface by a chemical conversion treatment. Further, a titanium alkoxide having an alkyl group of ethyl, a powder of molybdenum disulfide having an average particle diameter of 1.2 μm, and a powder of graphite having an average particle diameter of 1.5 μm are converted into titanium alkoxide 1 on the pin surface and the upper surface of the manganese phosphate coating. On the other hand, 1.33 molybdenum disulfide and 1.0 graphite were mixed in a weight ratio, and a mixed solution of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium. Then, in the atmosphere 6
After leaving for a period of time and measuring the composition of the coating formed on the surface of the pin and on the top surface of the zinc phosphate coating in the dry state, the content of both was by weight relative to the inorganic polymer 1 having a skeleton of Ti-O and disulfide. Molybdenum 2 and graphite 1.5, and the coating thickness was 5 μm.

As shown in Table 6, there was no occurrence of seizure in the 25 tightening and retightening operations shown in Table 3 and it was very good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 10 of the Invention) The following surface treatment was applied to a Cr-Mo steel threaded joint shown in Table 1. The surface of the pin had a surface roughness of 3 μm while being mechanically finished. The surface of the box was machine-finished to a surface roughness of 3 μm, and a 10 μm-thick zinc phosphate film was formed on the surface of the box by a chemical conversion treatment. Further, a titanium alkoxide having an alkyl group of ethyl, a powder of molybdenum disulfide having an average particle diameter of 3.5 μm, and a powder of graphite having an average particle diameter of 3.1 μm, and 4.0 of molybdenum disulfide with respect to titanium alkoxide 1 were provided on the upper surface. , Graphite 2.33, and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium. Then, after standing in the air for 6 hours, the composition of the film formed on the top surface of the zinc phosphate film in a dry state was measured, and the content was an inorganic polymer compound having Ti-O as a skeleton as a relative value of weight. Is 1, molybdenum disulfide is 6,
The graphite was 3.5 and the coating thickness was 20 μm.

As shown in Table 6, up to the fifteenth tightening and retightening work shown in Table 3, there was no seizure and the result was good. However, seizure occurred at the time of the 16th tightening. The tightening amount and tightening torque at the time of tightening were appropriate.

(Example 11 of the Present Invention) The following surface treatment was applied to the threaded joint made of carbon steel shown in Table 1. The box surface was finished by mechanical grinding to have a surface roughness of 2 μm. Pin surface is # 1
A No. 80 sand was sprayed to make the surface roughness 10 μm, and a 10 μm-thick calcium phosphate coating was formed on the pin surface by a chemical conversion treatment. Further, a titanium alkoxide having an alkyl group of propyl and molybdenum disulfide powder having an average particle diameter of 4.6 μm were mixed on the upper surface thereof in a weight ratio of 0.14 of molybdenum disulfide to titanium alkoxide 1, and methyl ethyl ketone, methylene chloride and A mixture of isobutyl alcohol was applied as a dispersion medium. Next, after being left in the air for 3 hours, humidified hot air at 150 ° C. was blown for 30 minutes. When the composition of the coating formed on the upper surface of the calcium phosphate coating in a dry state was measured, the content was Ti by weight.
Molybdenum disulfide was 0.25 with respect to inorganic polymer 1 having —O as a skeleton, and the coating thickness was 25 μm.

As shown in Table 6, up to the sixteenth tightening and retightening work in Table 3, there was no occurrence of seizure and the result was good. However, seizure occurred at the 17th tightening. The tightening amount and tightening torque at the time of tightening were appropriate.

Comparative Example 1 A 5% Cr steel threaded joint shown in Table 1 was subjected to the following surface treatment. # 80 sand was sprayed on the pin surface and the box surface, and both had a surface roughness of 10 μm. An epoxy resin and a powder having an average particle size of 1.8 μm were mixed and applied to both surfaces at a weight ratio of molybdenum disulfide (1) to epoxy resin (1) using a mixed solution of toluene, isopropyl alcohol, and the like as a dispersion medium.
Next, after drying, a heat treatment was performed at 180 ° C. for 30 minutes. When the composition of the coating after the heat treatment was measured, the content of the coating on both the pin side and the box side was 1 in molybdenum disulfide to 1 in epoxy resin and 2 in coating weight.
It was 0 μm.

As shown in Table 6, slight seizure was observed in the twelfth tightening, and a predetermined surface pressure could not be applied to the shoulder due to insufficient tightening. Then, when the tightening torque was increased to tighten to the predetermined position, seizure occurred in the thirteenth tightening.

(Comparative Example 2) The carbon steel threaded joint shown in Table 1 was subjected to the following surface treatment. The pin surface was finished by mechanical grinding to have a surface roughness of 2 μm. The surface of the box is machine-grinded to a surface roughness of 2 μm, a 2 μm thick molten salt nitride layer is formed on the box surface, and a 15 μm thick
m manganese phosphate layer was formed. Next, a polyamide imide resin and a tungsten disulfide powder having an average particle diameter of 3.5 μm are mixed at a weight ratio of tungsten disulfide 1 to the polyamide imide resin 1, and a mixed solution of xylene, toluene and isopropyl alcohol is mixed as a dispersant. Coated on top of manganese layer. Next, after drying, a heat treatment was performed at 180 ° C. for 30 minutes. When the composition of the film formed on the upper surface of the manganese phosphate layer after the heat treatment was measured,
The content was 1 part of tungsten disulfide relative to 1 part of the polyamideimide resin in weight ratio, and the coating thickness was 35 μm.

As shown in Table 6, no seizure was observed in the twelfth tightening, but the tightening amount was insufficient.
The prescribed surface pressure was not applied to the shoulder. Therefore,
After increasing the tightening torque to tighten to the specified position,
Seizure occurred in the 14th tightening.

Comparative Example 3 The carbon steel threaded joint shown in Table 1 was subjected to the following surface treatment. The box surface was finished by mechanical grinding to have a surface roughness of 2 μm. The surface of the pin is sprayed with # 80 sand to a surface roughness of 10 μm, a manganese phosphate layer having a thickness of 15 μm is formed on the surface of the pin, and an epoxy resin and molybdenum disulfide having an average particle size of 1.8 μm are formed thereon. The powder was mixed with epoxy resin 1 at a weight ratio of molybdenum disulfide 1 and mixed with toluene, isopropyl alcohol or the like as a dispersion medium and applied. Then, after drying 1
Heat treatment was performed at 80 ° C. for 30 minutes. When the composition of the coating formed on the upper surface of the manganese phosphate layer after the heat treatment was measured, the content was 1 molybdenum disulfide with respect to 1 epoxy resin in weight ratio, and the coating thickness was 30 μm.

As shown in Table 6, seizure was recognized in the twelfth tightening, and the tightening amount was insufficient, so that a predetermined surface pressure could not be applied to the shoulder portion.

Comparative Example 4 A threaded joint made of 5% Cr steel shown in Table 1 was subjected to the following surface treatment. The pin surface was finished by mechanical grinding to have a surface roughness of 2 μm. 10 μm thick C on the surface of a box which has been machine-finished to a surface roughness of 2 μm
u plating treatment was performed. Next, compound grease corresponding to API-Bul5A2 was applied to both the pin surface and the box surface at a rate of about 20 g per unit area (1 dm ² ).

As shown in Table 6, slight seizure was observed in the twelfth tightening, and a predetermined surface pressure could not be applied to the shoulder due to insufficient tightening. Then, when the tightening torque was increased to tighten to the predetermined position, seizure occurred in the thirteenth tightening.

Comparative Example 5 The joints made of carbon steel shown in Table 1 were subjected to the following surface treatment. The pin surface was finished by mechanical grinding to have a surface roughness of 2 μm. A # 80 sand was sprayed to form a 15-μm-thick manganese phosphate coating on the surface of the box having a surface roughness of 10 μm. The API is then applied to both the pin surface and the top surface of the manganese phosphate coating.
Compound grease corresponding to Bull5A2 was applied at a rate of about 20 g per unit area (1 dm ² ).

As shown in Table 6, slight seizure occurred from the eighth tightening, but care was carried out and the test was continued. However, seizure was recognized at the time of the eleventh tightening, and seizure became remarkable by the twelfth tightening.
As described above, the predetermined amount of surface pressure could not be applied to the shoulder due to insufficient tightening amount. As described above, the inorganic lubricating film having TO as a skeleton was formed on the phosphoric acid-based chemical conversion treatment film of the present invention. It was found that the formed threaded joint was superior in seizure resistance during a high-temperature history as compared with a conventional joint using a resin as a binder or a joint using compound grease.

[0090]

The threaded joint made of carbon steel or low-alloy steel according to the present invention can be repeatedly tightened and loosened in crude oil mining under a high temperature environment up to 400 ° C., such as a deep, high-temperature oil well or a steam injection oil well. In this case, the seizure resistance can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing a configuration of a threaded joint for oil country tubular goods of the present invention.

FIG. 2 is a schematic sectional view showing an example of a state of forming a lubricating film according to the present invention.

[Explanation of symbols]

1: Box, 2: Pin, 3: Screw part, 4: Metal contact part without screw, 5: Shoulder part, 6: Lubricant coating, 7: Inorganic polymer compound, 8: Solid lubricant 9: Phosphate conversion treatment Coating.

Continued on the front page F term (reference) 3H013 JA02 4K026 AA02 AA21 AA25 BA03 BA04 BA05 BA08 BA12 BB04 BB10 DA16 EA02 EB05 4K044 AA02 AB03 BA12 BA17 BA21 BB03 BC01 BC11 CA07 CA16 CA53 CA62

Claims (5)

[Claims] 1. A threaded joint made of carbon steel or low alloy steel having a Cr content of less than 10% by weight, comprising a pin and a box each having a threaded part and a threadless metal contact part. An inorganic polymer having a skeleton of Ti-O obtained by dispersing and mixing molybdenum disulfide and / or graphite on the phosphate conversion coating on one of the screwless metal contact portions. A threaded joint for oil country tubular goods characterized by forming a lubricating coating of a compound. 2. The threaded joint for oil country tubular goods according to claim 1, wherein the phosphate chemical conversion coating is a manganese phosphate chemical conversion coating. 3. The content of the inorganic polymer compound (A)
The weight ratio (B / A) of the total content (B) of molybdenum disulfide and graphite is 0.3 to 9.0, and the screw for oil country tubular goods according to claim 1 or 2, characterized in that: Fittings. 4. The screw for an oil country tubular good according to claim 1, wherein the surface roughness of the screw-free metal contact portion forming the phosphate conversion coating is 3 to 15 μm in Rmax. Fittings. 5. The threaded joint for an oil country tubular good according to claim 1, wherein the lubricating coating has a thickness of 5 to 30 μm.