JP2001065752A - Screw joint for oil well pipe and lublication film forming method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an anti-galling characteristic under a high temperature environment by forming a lubrication film of inorganic polymer compound having Ti-O obtained through dispersion mixing-in of molibdenum disulfide and/or graphite as a base on at least one of nonthreaded metal contact parts of a box and a pin. SOLUTION: A screw joint for oil well pipes to be used in taking crude oil under a high temperature embironment in the case of high depth, high temperature or steam injection type oil well or the like is constructed of a pin 2 and a box each of which has a threaded part and a nonthreaded metal contact part. On at least any one of nonthreaded metal contact parts of the pin 2 and the box, a lubrication film 6 made of inorganic polymer compound 7 having Ti-0 obtained through dispersion mixing-in of solid lubricant 8 as a base is formed. As the lubricant 8, only molibdenum disulfide or graphite is used, or both of them are used in a mixed condition. The surface roughness of a portion forming the film 6 is preferably 3-15 μm at Rmax.

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 having excellent seizure resistance, and more particularly, to repeated tightening and loosening in crude oil extraction in a high-temperature environment such as a high-depth, high-temperature oil well or a steam injection oil well. The present invention relates to a threaded joint for oil country tubular goods which can be used repeatedly without seizure and keeping airtightness even after performing the method, and a method of forming a lubricating film therefor.

[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.
In I (American Petroleum Institute), even if tubing is tightened 10 times (make-up) and casing is tightened 3 times (break-out), there is no seizure called galling and airtightness is maintained. Has been requested. When galling occurs, the airtightness becomes incomplete and 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. However, since high surface pressure acts on the metal seal portion and the threaded portion, galling is likely to occur particularly under high-temperature conditions. According to the API standard, 177 ° C. × 24H
After the heat resistance test of r is performed, it is required that airtightness be maintained even if retightening and retightening are performed.

In order to meet the above demand, various countermeasures have been proposed. 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-based chemical conversion coating film after forming an unevenness of 0 μm, and Japanese Unexamined Patent Publication (Kokai) No. 6-10154 specifies the maximum surface roughness of the metal seal portion and the thickness of the surface treatment coating layer. Japanese Patent Application Laid-Open No. 5-1494 / 1993
No. 85 discloses a threaded joint having a dispersed plating layer formed on the surface of a pin or a box, and Japanese Unexamined Patent Publication No. 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.

[0006]

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.

[0007] 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 high temperature and the lubricity decreases, so that a problem that predetermined airtightness cannot be obtained when retightening after retightening is problematic. is there. Accordingly, Japanese Patent Application Laid-Open No. HEI 5-117870, which is directed to compound grease application,
The techniques disclosed in JP-A-6-10154, JP-A-5-149485 and JP-A-2-885593 have a problem in securing airtightness at high temperatures.

Also, Japanese Patent Application Laid-Open Nos. 8-233164 and 9-29, wherein compound grease is not used.
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 maintained. It cannot be performed any more, resulting in poor fastening and seizure, and further deteriorates airtightness.

As described above, at present, a threaded joint having excellent galling resistance which 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 oil country tubular goods having excellent galling resistance. More specifically, in oil drilling in high-temperature environments such as high-depth, high-temperature oil wells, or steam-injected oil wells, it suppresses galling from repeated tightening and loosening, and has excellent airtight threaded joints for oil country tubular goods and its lubrication. An object of the present invention is to provide a method for forming a film.

[0011]

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 under a high temperature environment, and have studied a solid lubricant and a binder (lubricant) constituting the lubricating film. Fundamental studies were conducted on the heat resistance, lubricity and film processing properties of the binder), 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 good lubricity that does not change from 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 of more than 24 hours, and the function as a binder for coating the joint lubricant on the joint surface is increased. 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.

[0016]

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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. A lubricating coating of an inorganic polymer compound having a skeleton of Ti-O can be formed.

Based on the above basic study results, appropriate conditions for forming the lubricating coating on the threaded joint were examined, and the following findings were obtained.

(G) Seizure is suppressed by forming the lubricating coating on the threadless metal contact portion of at least one of the pin and the box.

(H) The solid lubricant constituting the lubricating coating is:
Molybdenum disulfide or graphite powder, or a mixed powder of molybdenum disulfide and graphite, wherein the weight ratio (B / A) of the content A of the inorganic polymer compound to the content B of the solid lubricant is 0.3 to 9 Should be within the range.

(4) The surface roughness of the portion where the lubricating film is to be formed is 3 to 15 μm in Rmax, and the thickness of the lubricating film is 5 to 3 μm.
By setting it to 0 μm, seizure resistance is improved.

(Ii) After the titanium alkoxide and the solid lubricant are mixed and applied, co-hydrolysis is promoted by applying humidification and heating, so that the time for forming a lubricating film is reduced, and Volatilization and discharge of the decomposition product are promoted, the adhesion of the film becomes strong, and the seizure resistance is improved.

The present invention has been completed based on the above findings, and the gist thereof is as follows. (1) In a threaded joint composed of a pin and a box each having a threaded portion and a threadless metal contact portion, molybdenum disulfide and / or graphite are applied to at least one of the threadless metal contact portion of the box and the pin. A threaded joint for an oil country tubular good, wherein a lubricating coating of an inorganic polymer compound having a skeleton of Ti-O dispersed and mixed is formed.

(2) 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 as described in the above item (1), wherein

(3) The threaded joint for an oil country tubular good as described in the above item (1) or (2), wherein the surface roughness of the portion where the lubricating coating is formed is 3 to 15 μm in Rmax.

(4) The lubricating film has a thickness of 5 to 30 μm.
The threaded joint for an oil country tubular good according to any one of the above items (1) to (3), wherein

(5) Titanium alkoxide (Ti (OR) is applied to at least one of the unthreaded metal contact portions of the box and the pin of the threaded joint, which includes a pin and a box each having a threaded portion and a threadless metal contact portion. ₄ )
R: an alkyl group) and molybdenum disulfide and / or graphite are mixed and applied, humidified and co-hydrolyzed to form a lubricating film of an inorganic polymer compound having a Ti-O skeleton. A method for forming a lubricating film on a threaded joint for oil country tubular goods, characterized by the following.

(6) When forming the lubricating coating, a blasting process is performed in advance on a portion where the lubricating coating is to be formed, and the surface roughness of the portion is set to 3 to 15 μm in Rmax. The method for forming a lubricating coating of a threaded joint for oil country tubular goods according to the item (2).

[0029]

FIG. 1 is a schematic view schematically showing a configuration of a threaded joint for an oil country tubular good according to the present invention. Reference numeral 1 is a box, 2 is a pin, 3 is a screw portion, 4 is a metal contact portion without a screw,
5 indicates 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 film, 7 denotes an inorganic polymer compound, 8 denotes a solid lubricant, and the same elements as those in FIG. 1 are denoted by the same reference numerals.

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 is a box 1 comprising a threaded portion 3 formed on the inner surface of a threaded joint member and a threadless metal contact portion 4. And a pin 2 comprising a screw portion 3 and a screwless metal contact portion 4 formed on the outer surface of the end of the oil country tubular good. Further, in the threaded joint of the present invention, as shown in FIG. 2, the inorganic polymer compound 7 having a skeleton of Ti—O in which a solid lubricant 8 is dispersed and mixed on the surface of the threadless metal contact portion 4 of the pin 2 is used. A lubricating film 6 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 lubricating film is formed on the threadless metal contact portion 4 of the pin 2, it may be formed on at least the surface of either the pin or the box of the threadless metal contact portion.

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,
With threaded joints that have high material strength and high contact surface pressure also acts on the threaded portion, and threaded joints made of alloys with a large amount of alloying elements such as Cr and Ni, seizure is likely to occur. Further, it is desirable to form a lubricating film on the screw portion.

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 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 (R) of the formula (1) has an alkyl group such as methyl, ethyl, isopropyl, propyl, isobutyl, and butyl can be used.

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.

It is desirable that the surface roughness (Rmax) of the portion (base) on which the lubricating film is formed be 3 μm or more and 15 μm or less. By providing an appropriate surface roughness as a base treatment when forming a lubricating film, the so-called anchor effect of physically capturing the lubricating film formed thereon is enhanced, and peeling of the lubricating film is prevented. Surface roughness is R
If max is less than 3 μm, the anchor effect is small and the lubricating coating tends to peel off. On the other hand, when the surface roughness exceeds 15 μm, the lubricating film formed on the convexity of the roughness at the time of tightening and retightening is broken, and seizure tends to occur. More preferable surface roughness is 4 μm or more and 10 μm or less. The surface roughness of the opposing surface on which the lubricating film is not formed is preferably smaller than the surface roughness of the portion on which the lubricating film is formed.

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, the method of the present invention will be described. The method of the present invention provides a method for preparing a titanium alkoxide (Ti (OR) ₄ , R:
(Alkyl group) and the molybdenum disulfide powder and / or graphite powder are mixed with a dispersing medium, and the mixture is applied to at least one of the metal contact portions of the pin and the box. Thus, a lubricating coating of an inorganic polymer compound having Ti-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 dispersants, xylene, methylene chloride, isopropyl alcohol, isobutyl alcohol,
Low boiling liquids such as 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.

In the present invention, when forming a lubricating film, it is desirable that blasting be performed in advance on the portion where the lubricating film is to be formed, and that the surface roughness of the portion be 3 to 15 μm in Rmax. By performing the blasting process, an active new surface appears on the surface, the adhesion of the lubricating film is strengthened, and the seizure resistance 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.

[0046]

EXAMPLES Screw joints made of carbon steel, 13Cr steel and high alloy having the composition shown in Table 1 (outer diameter: 7 inches, wall thickness:
Both the screw portion of the box and the pin and the metal contact portion were subjected to various surface treatments such as a base treatment and formation of a lubricating film. Tables 2 and 3 show the surface treatment conditions. In addition,
In the conventional examples shown in the table, a resin film was formed or compound grease was applied.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

Next, using the threaded joint having been subjected to the above-mentioned surface treatment, tightening and retightening operations were carried out up to 20 times in the manner shown in Table 4 to investigate the occurrence of seizure.

[0051]

[Table 4]

That is, as shown in Table 4, the first to tenth, the twelfth to fifteenth, and the seventeenth to twentieth are tightened and retightened at room temperature, while the eleventh and sixteenth are tightened and tightened at room temperature. Perform heat treatment at 400 ° C for 24 hours,
Thereafter, it was cooled and retightened at room temperature. Table 5 shows the conditions of the tightening speed and the tightening torque.

[0053]

[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.

[0055]

[Table 6]

(Example 1 of the Present Invention) The threaded joint made of carbon steel shown in Table 1 was subjected to the following surface treatment. The surface of the pin and the surface of the box were finished by mechanical grinding to have a surface roughness of 3 μm. A titanium alkoxide having an alkyl group of methyl, a powder of molybdenum disulfide having an average particle diameter of 1.5 μm and a powder of graphite having an average particle diameter of 3.5 μm were obtained by adding 0.77 of molybdenum disulfide and 0.1% of graphite to titanium alkoxide 1. The mixture was mixed at a weight ratio of 77, and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium to the box surface. Then, after standing for 6 hours in the air, the composition of the coating film was measured in a dry state. The content was 1 relative to the inorganic polymer compound having a skeleton of Ti-O as a relative value of weight, and the content was 1 molybdenum disulfide. , Graphite, and the coating thickness was 40 μm.

As shown in Table 6, up to the 16th fastening / unfastening operation in Table 3, there was no seizure, which was good. However, seizure occurred during the seventeenth tightening (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. Sand of # 80 was sprayed on the box surface to make the surface roughness 10 μm. A titanium alkoxide having an alkyl group of ethyl, a powder of molybdenum disulfide having an average particle size of 1.8 μm and a powder of graphite having an average particle size of 2.8 μm were prepared by mixing titanium alkoxide 1 with molybdenum disulfide 2 and graphite 1.33. The mixture was mixed at a weight ratio, and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium to the surface of the box. 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 was measured in a dry state, the content was Ti by weight.
Molybdenum disulfide 3 and graphite 2 were used for inorganic polymer compound 1 having —O as a skeleton, and the coating thickness was 40 μm.

As shown in Table 6, there was no seizure during the 20 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 3 of the Present Invention) The following surface treatment was applied to a 13Cr 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 #
A No. 80 grid was sprayed to make the surface roughness 15 μm. A titanium alkoxide having an isopropyl alkyl group, 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 obtained by mixing titanium alkoxide 1 with molybdenum disulfide 2.77 and graphite 0.1. The mixture was mixed at a weight ratio of 83, and a mixture of methyl ethyl ketone, methylene chloride and butyl alcohol was applied as a dispersion medium to the box surface. Then, after leaving in the air for 3 hours, 15
Hot air of 0 ° C. was blown for 10 minutes. When the composition of the coating film was measured in a dry state, the content was 5 parts by weight of molybdenum disulfide and 1.5 parts of graphite with respect to 1 part of the inorganic polymer compound having a skeleton of Ti—O, and the coating thickness was 20 μm. Was.

As shown in Table 6, up to the nineteenth fastening / unfastening operation in Table 3, there was no occurrence of seizure, and the result was good. However, slight seizure occurred during the twentieth tightening. However, it was determined that it could be used further repeatedly due to care. The tightening amount and tightening torque at the time of tightening were appropriate.

(Invention Example 4) A threaded joint made of high alloy steel shown in Table 1 was subjected to the following surface treatment. No. 180 sand was sprayed on the pin surface and the box surface, and both had a surface roughness of 3 μm. A titanium alkoxide having an alkyl group of methyl and a powder of molybdenum disulfide having an average particle size of 1.2 μm were prepared by mixing titanium alkoxide 1 with molybdenum disulfide 2.
The mixture was mixed at a weight ratio of 31 and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium to both the pin surface and the box surface. 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 film was measured in a dry state, the content of both the pin and the box was molybdenum disulfide 3 with respect to the inorganic polymer compound 1 having a skeleton of Ti-O in weight ratio,
The coating thickness was 8 μm.

As shown in Table 6, there was no seizure in 20 times of tightening and retightening 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 5 of the Invention) The following surface treatment was applied to the carbon steel threaded joint shown in Table 1. The pin surface and the box surface were finished by mechanical grinding to have a surface roughness of 2 μm. A titanium alkoxide having an alkyl group of isobutyl, a powder of molybdenum disulfide having an average particle size of 3.1 μm, and an average particle size of 3.
5 μm of graphite powder was mixed with titanium alkoxide 1 at a weight ratio of 1.39 of molybdenum disulfide and 0.83 of graphite, and the mixture was applied to the surface of a box using a mixed solution of xylene, methylene chloride and isobutyl alcohol as a dispersion medium. Then, after leaving it in the air for 6 hours, the composition of the coating film was measured in a dry state. Assuming that the content of the inorganic polymer compound having a skeleton of Ti—O as 1 by weight, the content of molybdenum disulfide was 2.5%. , Graphite, and the coating thickness was 30 μm.

As shown in Table 6, up to the nineteenth tightening and re-tightening work in Table 3, there was no occurrence of seizure and the result was good. However, seizure occurred during the twentieth fastening. However, the tightening amount and the tightening torque at the time of tightening were appropriate.

(Example 6 of the Invention) A threaded joint made of 13Cr 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 titanium alkoxide having an alkyl group of ethyl and a powder of molybdenum disulfide having an average particle diameter of 1.0 μm are mixed at a weight ratio of 0.23 molybdenum disulfide to 1 titanium alkoxide, and a mixture of xylene, methylene chloride and butyl alcohol Was applied to both the pin surface and the box surface as a dispersion medium. Then, in the atmosphere 4
After standing for a while, hot air at 150 ° C. was blown for 15 minutes. When the composition of the coating film was measured in a dry state, the content of both the pin and the box was 0.3 wt% of molybdenum disulfide with respect to the inorganic polymer compound 1 having a skeleton of Ti—O.
5, and the coating thickness was 20 μm.

As shown in Table 6, up to the nineteenth tightening and retightening work in Table 3, there was no occurrence of seizure and the result was good. However, slight seizure was observed after the 20th tightening. However, it was determined that it could be used further repeatedly due to care. The tightening amount and tightening torque at the time of tightening were appropriate.

(Example 7 of the Present Invention) The joints made of carbon steel shown in Table 1 were subjected to the following surface treatment. The box surface was finished by mechanical grinding to have a surface roughness of 2 μm. A # 80 grid was sprayed on the pin surface to make the surface roughness 10 μm. A titanium alkoxide having an isopropyl alkyl group, molybdenum disulfide powder having an average particle diameter of 1.8 μm, and graphite powder having an average particle diameter of 2.5 μm were obtained by mixing molybdenum disulfide 3.05 and graphite 1. The mixture was mixed at a weight ratio of 94, and a mixture of methyl ethyl ketone, methylene chloride and isobutyl alcohol was applied to the pin surface as a dispersion medium. Next, hot air at 150 ° C. was blown for 15 minutes after standing in the air for 2 hours. When the composition of the coating film was measured in a dry state, the content was 5.5 parts by weight of molybdenum disulfide and 3.5 parts by weight of graphite relative to inorganic polymer compound 1 having Ti—O as a skeleton, and the coating thickness was 20 μm. Met.

As shown in Table 6, there was no occurrence of seizure in the tightening and retightening of 20 times in Table 3 and it was very good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 8 of the Invention) A joint made of 13Cr 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 4 μm. A titanium alkoxide having an alkyl group of propyl, 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 were obtained by adding 2.78 of molybdenum disulfide and graphite of 0.1 to titanium alkoxide.
The mixture was mixed at a weight ratio of 83 and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium to both the pin surface and the box surface. Next, after being left in the air for 3 hours, hot air at 140 ° C. was blown for 20 minutes. When the composition of the coating film was measured in a dry state, the content of both the pin and the box was determined by using molybdenum disulfide 5.0 and graphite 1.5 with respect to the weight of the inorganic polymer compound 1 having a skeleton of Ti—O. And the coating thickness was 5 μm.

As shown in Table 6, there was no seizure in 20 tightening / unfastening operations in Table 3 and the result was extremely good. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Example 9 of the Invention) The joints made of high alloy steel shown in Table 1 were subjected to the following surface treatment. The pin surface and the box surface were finished by mechanical grinding to have a surface roughness of 2 μm. A titanium alkoxide having an alkyl group of ethyl and an average particle diameter of 1.2;
μm molybdenum disulfide powder and average particle size 1.5 μm
Was mixed with 1.3 parts by weight of molybdenum disulfide and 1.0 part by weight of graphite with respect to 1 titanium alkoxide, and a mixture of xylene, methylene chloride and butyl alcohol was applied as a dispersion medium to the surface of the box. Then, after being left in the air for 6 hours, the composition of the film was measured in a dry state, and the content of both the pin side and the box side was 1 in the inorganic polymer compound having Ti-O as a skeleton by weight. ,
Molybdenum disulfide was 2.0, graphite was 1.5, and the coating thickness was 10 μm on the pin side and 30 μm on the box side.

As shown in Table 6, the seizure and retightening performed 20 times in Table 3 were extremely good with no occurrence of seizure. The tightening amount and the tightening torque at the time of tightening were also appropriate.

(Conventional Example 1) A joint made of 13Cr steel shown in Table 1 was subjected to the following surface treatment. # 80 sand is sprayed on the pin surface and the box surface, and both have a surface roughness of 1
It was set to 0 μm. An epoxy resin and molybdenum disulfide powder having an average particle diameter of 1.8 μm are mixed with epoxy resin 1 in a weight ratio of molybdenum disulfide 1 to a mixed solution of toluene, isopropyl alcohol, and the like as a dispersion medium, and both the pin surface and the box surface are mixed. Was applied. Then, after drying at 180 ° C., 3
A heat treatment for 0 minutes was performed. When the composition of the coating film after the heat treatment was measured, the content of both the pin and the box was 1 molybdenum disulfide to 1 epoxy resin in weight ratio, and the coating thickness was 20 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.

(Conventional Example 2) 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 2 μm thick molten oxynitride layer was formed on the box surface which had been subjected to mechanical grinding to a surface roughness of 2 μm, and a 15 μm thick manganese phosphate layer was formed thereon. Then, a polyamide imide resin and tungsten disulfide powder having an average particle diameter of 3.5 μm are mixed at a weight ratio of molybdenum disulfide 1 to the polyamide imide resin 1 with a mixed liquid of xylene, toluene and isopropyl alcohol 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 coating film after the heat treatment was measured, the content was 1 part of molybdenum disulfide with respect to 1 part of the polyamideimide resin by weight, 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.

(Conventional Example 3) Joints made of 13Cr steel shown in Table 1 were subjected to the following surface treatment. The box surface was finished by mechanical grinding to have a surface roughness of 2 μm. # 15 sand is sprayed onto the surface of the pin to make the surface roughness 10 μm.
A manganese phosphate layer having a thickness of μm is formed, and an epoxy resin and molybdenum disulfide powder having an average particle size of 1.8 μm are mixed thereon with a mixed solution of toluene, isopropyl alcohol and the like in a weight ratio of the molybdenum disulfide 1 to the epoxy resin 1. It was mixed and applied as a dispersion medium. Next, after drying, a heat treatment was performed at 180 ° C. for 30 minutes. When the composition of the coating film 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 observed in the twelfth tightening, and the tightening amount was insufficient, so that a predetermined surface pressure could not be applied to the shoulder.

(Conventional Example 4) A joint made of 13Cr 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. A 10 μm-thick Cu plating process was applied to the box surface that had been subjected to mechanical grinding to a surface roughness of 2 μm. 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 an insufficient tightening amount. Then, when the tightening torque was increased to tighten to the predetermined position, seizure occurred in the thirteenth tightening.

(Conventional 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. # 15 sand is sprayed onto the box surface with a surface roughness of 10 μm by spraying # 80 sand to a thickness of 15 μm
Manganese phosphate treatment. Then, about 20 g of compound grease corresponding to API-Bul5A2 was applied to both the pin surface and the box surface per unit area (1 dm ² ).
At a rate of

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.
Compared to conventional manganese phosphate coating, Cu plating, and coating using resin as binder,
It was found that the seizure resistance during the high temperature history was excellent.

[0083]

The threaded joint according to the present invention has remarkably improved seizure resistance when repeatedly tightening and loosening in crude oil mining under a high temperature environment of up to 400 ° C., such as a deep depth, a high temperature oil well, or a steam injection oil well. Can be done.

[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: screwless metal contact part, 5: shoulder part, 6: lubricating coating, 7: inorganic polymer compound, 8: solid lubricant.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H013 GA01 4K022 AA02 AA31 AA48 BA05 BA12 BA15 BA19 BA22 BA33 CA02 DA06 EA01

Claims (6)

[Claims] 1. A threaded joint comprising a pin and a box each having a threaded portion and a threadless metal contact portion, wherein at least one of the box and the pin has a threadless metal contact portion with molybdenum disulfide and / or molybdenum disulfide. A threaded joint for oil country tubular goods, wherein a lubricating coating of an inorganic polymer compound having a skeleton of Ti-O in which graphite is dispersed and mixed is formed. 2. Content (A) of the inorganic polymer compound
The threaded joint for oil country tubular goods according to claim 1, wherein the weight ratio (B / A) of the total content (B) of molybdenum disulfide and graphite is 0.3 to 9.0. 3. The threaded joint for an oil country tubular good according to claim 1, wherein the surface where the lubricating film is formed has a surface roughness of 3 to 15 μm in Rmax. 4. 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. 5. A titanium alkoxide (Ti (OR)) is applied to at least one of the threadless metal contact portion of the box and the pin of the threaded joint comprising a pin and a box each having a threaded portion and a threadless metal contact portion. ₄ , R:
(Alkyl group) and molybdenum disulfide and / or graphite are mixed, applied, humidified, and co-hydrolyzed to form a lubricating film of an inorganic polymer compound having a Ti-O skeleton. A method for forming a lubricating film on a threaded joint for oil country tubular goods. 6. The method according to claim 5, wherein when forming the lubricating film, a blasting process is performed in advance on a portion where the lubricating film is to be formed, and the surface roughness of the portion is 3 to 15 μm in Rmax. A method for forming a lubricating film for a threaded joint for oil country tubular goods as described in the above.