JPH054436B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention has excellent seizure resistance and is used when connecting oil country tubular goods, which are dug deep underground to extract natural gas and crude oil produced underground, with pipe joints. This invention relates to lubricants for oil well pipe joints. (Background of the Invention) All oil country tubular goods that are inserted vertically into wells that produce crude oil are connected for a long time using pipe joints. Pipe fittings are subject to (1) axial tensile force due to the weight of the pipe or pipe fitting itself, (2) compressive force on the outer circumferential surface due to earth pressure, and (3) pressure on the inner circumferential surface due to internal fluid (crude oil). Various very large forces such as pressure act on it. Incidentally, the depth of oil wells has tended to become deeper in recent years. Therefore, the above-mentioned force applied to the pipe joint becomes more severe as the well deepens. In order for pipe fittings to be able to be used under such severe conditions, it is extremely important that they be able to withstand enormous tensile loads and maintain reliable air-tight sealing properties. (Conventional technology) Satisfactory results have been obtained with technology that can withstand strong tensile loads by improving the shape and pitch of the threaded part of the joint, and by developing high-strength, high-alloy materials. . In addition, a certain degree of airtight sealing is achieved by tightening the threaded part and the mechanical seal part through a lubricant made of a compound of grease and solid powder lubricant. . However, when high airtightness is required, the screws are strongly tightened, which causes problems with galling (seizure) when tightening the metal seal. In order to maintain a high level of airtightness, a high surface pressure of 100 to 150 kg/ ^mm2 is applied to the seals of oil country tubular goods and joints, which increases the generation of frictional heat during tightening and reduces the lubricant. It becomes impossible to hold the ball, and galling occurs. When galling occurs, it causes poor airtight sealing, which can lead to accidents such as leaks. In order to prevent this galling, methods of (1) improving the lubricant and (2) applying a lubricating base treatment to the joint seal portion have been carried out. (2) Lubricating base treatment includes (a) shot blasting or chemical conversion treatment (phosphate, oxalate) to increase lubricant retention, and (b) baking by electroplating, vapor deposition, etc. (c) a method of applying a lubricating organic film, etc. However, all of these treatments provide an auxiliary lubrication effect when lubricant is insufficient, and repeated tightening and untightening gradually wears out the lubricating base treatment layer and reduces its effectiveness. There are drawbacks to doing so. Considering this wear and tear, lubrication and surface treatment cannot be said to be a fundamental measure to prevent galling. The most important thing is to improve the performance of the lubricant itself. Regarding lubricants used for oil country tubular connections, the types of grease (particularly the thickeners included), the type and amount of solid powder, etc. are being studied, but oil country tubular goods that still have sufficient performance are still being studied. The reality is that there is no lubricant for joints. In the case of high-strength, high-alloy oil country tubular joints that have recently come into widespread use, since they are used in deep wells, the surface pressure at the sealing part is high, and the material has low thermal conductivity, so the friction surface Because the temperature rise is large and seizure is extremely easy, there is a desire for a lubricant that exhibits excellent lubricity and is suitable for oil country tubular joints. Usually, galling resistance is determined by the power tight test.
Although it is required to withstand tightening and untightening more than 10 times, in the case of high-alloy, high-strength pipe fittings, galling occurs after 5 to 8 times. Conventional lubricants for oil country joints include Ca, Li, and Al.
Grease is based on grease thickened with metal soaps such as graphite, MoS ₂ , Teflon (registered trademark: polytetrafluoroethylene), and metals such as Cu, Zn, and Pb. These are powders or solid powders such as oxides of these metals. However, the grease used in these products has low heat resistance, and when the temperature of the friction surface exceeds the dropping point, it loses its consistency and flows out from the friction surface, resulting in a decrease in lubricity. In addition, the solid powder is used not only for lubricating properties but also for providing airtight sealing properties, and if the particle size becomes too small, the sealing properties will deteriorate, so it contains particles that are quite large, 100 to 200 μm. If the particle size is large, the galling resistance deteriorates, so the lubrication performance is not sufficient. Grease with a dropping point of 100°C or higher and high heat resistance is well known as a mechanical lubricant. Also known are lubricants in which powders of graphite, MoS ₂ , graphite fluoride, Teflon, and the like are added to mineral oil or grease. (Problems to be Solved by the Invention) However, the conventional lubricants described above are not suitable for use under harsh conditions such as oil country pipe joints, especially oil country pipe joints made of high-alloy materials that are prone to seizure. , does not satisfy both lubricity and airtight sealing properties,
Therefore, while maintaining good airtight sealing properties,
Moreover, there has been a demand for a lubricant for oil country tubular connections that has excellent lubrication performance, especially galling resistance. (Means for Solving the Problems) As a result of various studies on the dropping point of the base grease, the type and particle size of the solid powder to be mixed therein, the inventors of the present invention found that by appropriately selecting these factors, It has been found that a lubricant for oil country pipe fittings that has both good lubrication performance and airtight sealing properties can be obtained. Here, the gist of the present invention is that the dropping point is
Grease with a temperature of 100℃ or higher, preferably 250℃ or higher,
fluorinated graphite powder and at least one kind of soft metal powder, the maximum particle diameters of the fluorinated graphite powder and metal powder are both 50 μm or less, and the fluorinated graphite powder is based on the total weight of the lubricant. 10~40
A lubricant for oil well pipe fittings, characterized in that the metal powder is contained in an amount of 30 to 60% by weight, and the total amount of graphite fluoride powder and metal powder is within a range of 50 to 75% by weight. be. Soft metals include Zn, Pb, Cu,
Sn and Al are preferred, and a combination of Zn, Pb, and Cu is particularly preferred. (Function) The present invention will be explained in detail below. The base grease of the lubricant according to the present invention is a grease having a dropping point of 100°C or higher, preferably 250°C or higher. The reason why the dropping point of the grease was limited to 100°C or higher is that if the dropping point is less than 100°C, the grease tends to flow out due to an increase in the temperature of the friction surface when fastening high-alloy OCTG joints, and it is difficult to lubricate the friction surface. This is because the amount of agent introduced is reduced and good lubricity cannot be obtained. Grease consists of a base oil such as mineral oil or synthetic oil and a thickener, but the grease with a dropping point of 100°C or higher used in the present invention has thickeners such as metal soaps such as Ca and Al, Al, Ca, and Li. Metal complexes such as (so-called complex soaps), alkyl diureas,
Examples include greases using diurea-based thickeners such as aryldiurea and alkylaryldiurea, or bentone. The amount of the thickener added may be within a normal range. Particularly suitable greases for use in the present invention are urea greases whose thickener is an organic compound with a molecular weight of 300 to 1000 (i.e., a diurea compound) having two [-NH-CO-NH-] bonds. be. Examples of such diurea thickeners include those represented by the general formula R ₁ -NHCONH-R ₂ NHCONH-R ₃ , where R ₂ is an isocyanate group, R ₁ and R ₃ are an alkyl group, It is a cycloalkyl group or an aryl group. _R1 and _R3
When both are an alkyl group, it is called an alkyldiurea, when both are an aryl group, it is called an aryldiurea, and when one is an alkyl group and the other is an aryl group, it is called an alkylaryldiurea. The number of carbon atoms in each alkyl group is preferably about 6 or more, and diurea compounds having a molecular weight of 300 to 1000 as a whole are effective as the grease thickener in the present invention. In the present invention, based on the weight of the lubricant, 10 to 40% by weight of fluorinated graphite powder, preferably 20 to 40% by weight, and 30 to 60% of soft metal powder are added to the grease having a dropping point of 100°C or higher. % by weight, preferably 35-55% by weight, in total 50-75% by weight,
It is preferably added in an amount within the range of 55 to 75% by weight. Graphite fluoride is a solid having the molecular formula (CF)n, and its powder has been conventionally used as a solid lubricant in mechanical lubricants and the like. On the other hand, the metal powder used in the present invention is a soft metal such as Zn, Pb, Cu, Sn, or Al. Zn, Pb, and Cu are particularly preferred as the metal powder, and the use of a mixture of these three metals gives particularly good results. These solid powders, both graphite fluoride and metal powder, have a maximum particle size of 50 μm or less. If the particle size is larger than this, clusters will occur when introduced to the friction surface, resulting in a decrease in lubricity. As mentioned above, as the particle size of the solid powder becomes smaller, there is a tendency for the airtight sealing properties to generally deteriorate, and for this reason, conventional lubricants contain considerably large particles of 100 μm or more. However, the combination of graphite fluoride used as a solid powder in the present invention and a soft metal unexpectedly showed excellent airtight sealing properties even with small particle diameters when blended into grease with a dropping point of 100°C or higher. The effect of this can be obtained. The reason why the amount of graphite fluoride was limited to 10 to 40% by weight of the lubricant is that if it is less than 10% by weight, it will not improve the lubricity due to the synergistic effect with grease, and if it exceeds 40% by weight, it will cause damage to the metal. This is because the amount of powder added is limited and only a small amount can be added, making it impossible to obtain sufficient airtight sealing performance. At least 30% by weight of metal powder is required to obtain a good airtight sealing property, and if more than 60% by weight is added, the amount of graphite fluoride added will be limited and will decrease, so the lubricating performance of graphite fluoride will be reduced. No improvement can be obtained. The reason why the total amount of graphite fluoride and metal powder added was limited to 50 to 75% by weight based on the weight% of the lubricant is because if it is less than 50% by weight, the consistency of the lubricant will be low, and grease and This is because the amount of solid powder introduced is reduced, resulting in poor lubricity and airtight sealing properties. Furthermore, if the total amount exceeds 75% by weight, the consistency will not only become extremely high and workability will deteriorate;
This is because it becomes difficult for lubricant to be supplied to the fine irregularities of the threaded portion and the seal portion, making it impossible to obtain lubricity. Only one type of metal powder may be added, but preferably two or more types of Pb, Zn, and Cu are added, and particularly preferably these three types of metal powder are added based on the total weight of the lubricant. Pb: 15-35% by weight, Zn: 7
-15% by weight, Cu: added at a blending ratio within the range of 3-5%. In addition, known lubricating solid powders such as graphite, MoS ₂ , Teflon, etc., which are blended into lubricants, may be added in small amounts as long as the performance of the lubricant is not degraded. As mentioned above, the lubricant of the present invention is characterized by the addition of a specific combination and amount of solid powder to a specific grease. This is illustrated by
In the experiment, the number of reciprocating slidings until seizure occurred was determined using a Bowden friction tester under the following test conditions, and the galling resistance was evaluated based on this number of slidings. Test conditions for Bowden friction tester Pin and plate material: 25%Cr-6%Ni-3%Mo steel Pin tip shape: 3/16 inch diameter hemisphere Pin surface roughness: Hmax 0.5μm or less Pin pressing load: 3Kgf Plate shape: Thickness 3 x Width 15 x Length 100 (mm) Plate surface roughness: Hmax2μm Plate sliding width: 10mm Plate sliding speed: 4mm/sec Plate temperature (test temperature): 50, 100, 150,
200, 250℃ (Standard 250℃) Lubricant application amount: 30g/m ² Experimental example 1 In order to investigate the relationship between grease dropping point (thickener type) and galling resistance, the following Table 1 is shown. Using various greases with different dropping points, the above friction tests were conducted at various temperatures to determine the galling resistance (number of times of sliding). No solid powder was added to the grease in this experiment. The results are shown in the attached Figure 1 as the relationship between grease dropping point and galling resistance.

[Table] **Bentone does not have a dropping point, so the dropping point is assumed to be >300°C for convenience.From the graph in Figure 1, it can be seen that at low temperatures, it exhibits approximately the same galling resistance regardless of the dropping point, but as the temperature rises, droplet resistance decreases. It can be seen that the more point grease is used, the lower the galling resistance becomes. Experimental Example 2 In order to investigate the relationship between the maximum particle size of solid powder added to grease and galling resistance,
A lubricant was prepared by adding a total of 65 parts by weight of a mixture of solid powders having various maximum particle sizes A to H shown in Table 2 below to 35 parts by weight of the grease with a dropping point of 198°C shown in No. 3 of the table. The galling resistance of each lubricant was measured by manufacturing and conducting the above friction tests at various temperatures. The 65 parts by weight of the solid powder mixture consists of graphite fluoride (or graphite,
MoS ₂ or fluorinated graphite/graphite mixture) 20 parts by weight, Pb powder 28 parts by weight, Zn powder 13 parts by weight, and
The Cu powder was 4 parts by weight. The experimental results are shown graphically in FIG. 2 as the relationship between test temperature and galling resistance at various maximum particle diameters. From FIG. 2, it can be seen that the smaller the maximum particle diameter, the higher the galling resistance. In particular, at temperatures of 200° C. or higher, solid powder mixtures with a maximum particle size of 50 μm or less exhibited galling resistance more than twice that of powder mixtures with a maximum particle size of 70 μm or more.

[Table] Experimental Example 3 In order to investigate the change in galling resistance due to the combination of the type of grease (dropping point) and the type of solid powder mixture, eight types of Nos. 1 to 8 shown in Table 1 above were used. For 35 parts by weight of grease, 65 parts by weight ( Composition: graphite fluoride,
20 parts by weight of graphite or MoS ₂ , 26 parts by weight of Pb powder, Zn
A lubricant containing 15 parts by weight of powder and 4 parts by weight of Cu powder was prepared, and the friction test described above was conducted at 250°C to measure the galling resistance of each lubricant. The results are shown graphically in FIG. 3 as a relationship between grease dropping point and galling resistance for each type of solid lubricant. When graphite or MoS ₂ is used as a solid lubricant component, the galling resistance is at most 230, regardless of the grease's dropping point, and remains below 150 in most cases.
When graphite fluoride is used, the dropping point of the grease is
The galling resistance was 250 or higher at temperatures above 100°C, showing excellent results. In particular, when graphite fluoride is used, if the dropping point of the grease is 250°C or higher,
As described above, extremely excellent galling resistance was demonstrated. In particular, it has been observed that the combination of graphite fluoride and grease with a dropping point of 100°C or higher exhibits remarkable galling resistance, which behaves completely differently than MoS ₂ or graphite. Also, from Figure 3, urea grease (dropping point 271℃)
It can be seen that the galling resistance of the lubricant based on this is particularly high. Experimental Example 4 In order to investigate the relationship between the amount of graphite fluoride added and galling resistance, 35 parts by weight of the four types of grease Nos. 1, 2, 5 and 7 shown in Table 1 were added with the amount shown in Table 2. Solid powder mixture with maximum particle size combinations shown in D
Lubricants were prepared by adding 65 parts by weight at various blending ratios shown in Table 3 below, and the galling resistance of each lubricant was measured by the friction test described above. The results are shown graphically in FIG. 4 as a relationship between galling resistance and the amount of graphite fluoride added (% by weight in the lubricant composition) for various greases. From the results shown in FIG. 4, in the case of A1 soap grease with a dropping point of 92° C., galling resistance improves as the amount of graphite fluoride increases, but the value is up to about 150.
On the other hand, Ca soap grease with a dropping point of 104℃,
In the case of A1 complex grease at 251°C and urea grease at 271°C, galling resistance improves rapidly when graphite fluoride is added in an amount of 10% by weight or more, and even Ca soap grease with the lowest dropping point has a resistance of 230 or higher. Urea grease exhibits galling property and has a high dropping point.
Extremely high galling resistance of around 350 was obtained.

[Table] Summarizing the results of Experimental Examples 1 to 4 above, it was found that a lubricant with excellent galling resistance had the following characteristics, leading to the present invention. The higher the dropping point of the grease serving as the base agent of the lubricant, the better the galling resistance (Experimental Example 1, Fig. 1). When the solid lubricant component in the solid powder mixture is graphite fluoride and the base agent is a grease with a dropping point of 100°C or higher, extremely good galling resistance is exhibited (Experimental Example 3, Figure 3). When the maximum particle size of the solid powder added to the grease is 50 μm or less, it exhibits good galling resistance (Experimental Example 2, Figure 2). When the amount of graphite fluoride added to a grease with a dropping point of 100°C or higher is 10% by weight or more of the lubricant, extremely good galling resistance is exhibited (Experimental Example 4, Figure 4). In particular, when using urea grease whose grease thickener is a urea derivative, it exhibits much better galling resistance than other greases (Experimental Example 3, Figure 3, and Experimental Example 4, Figure 4).
figure). Next, the effects of the lubricant of the present invention on galling resistance and airtight sealing properties will be specifically shown by Examples. (Example and Comparative Example) Among the greases shown in Table 1 above, No. 1,
2, 4, 6 and 7 greases with a molecular weight of 1050
-1200 and 700-1000 urea greases (dropping points of 280°C and 276°C, respectively), different from No. 7, with alkyl diureas as thickeners, and various types of largest particles. Lubricants were prepared by adding solid powder mixtures of various diameter combinations and blending ratios in various ratios, and their galling resistance was evaluated using a power tight test, and their airtight sealing performance was evaluated using an airtight test. Power tight test: outer diameter 139.7mm, wall thickness 7.72
mm oil country tubular pipe joint (material 25% Cr-6% Ni-3
%Mo steel) was repeatedly tightened and untightened at a tightening torque of 1000 m and a rotation speed of 4 rpm, and when the metal seal was tightened, the metal seal part was inspected to visually determine whether galling occurred. . The maximum number of tightening-untightening times without galling is evaluated as galling resistance. As mentioned above, the Power Tight test requires that the material be able to withstand tightening and untightening 10 times or more, that is, it must have galling resistance of 10 times or more. In addition, in the airtightness test, a tensile force of 80% of the yield strength of the pipe joint was applied to the pipe joint that had been tightened for the 10th time in the Power Tight test, and the inner surface of the pipe joint with this tensile force applied was This was done by applying an internal pressure of 70% of the yield strength to the steel, examining the change in internal pressure, and determining the presence or absence of leakage. The airtight sealability is evaluated in the following three stages, with 〇 being considered a pass. 〇: No leakage at all (no decrease in internal pressure), △: Slight leakage (internal pressure decrease within 50Kgf/cm ² ) ×: Significant leakage (internal pressure decrease of 100Kgf/cm ² or more) Based on the test results obtained, the type of grease used (Type of base oil, type and amount of thickener, dropping point) and amount, type, maximum particle size and amount of each component of the solid powder mixture, maximum particle size and amount of addition of the entire solid powder mixture, as well as the following: It is shown in Table 4.

【table】

[Table] (Note) *The amount of thickener is the amount relative to the base oil.
The following can be seen from the results in Table 4. Regarding the dropping point of grease: Comparative Example 1 has a dropping point of 92℃ using A1 soap as a thickener.
An example of using a lubricant in which a total of 65% by weight of solid powder, which is 20% by weight of graphite fluoride and 45% by weight of metal powder, is added to the grease as a solid powder mixture with the particle size combination shown in D in Table 2. However, the galling resistance did not reach the required level after 7 times, and the airtight sealing performance was also poor. On the other hand, in Examples 1 to 4, the solid powder mixture added was the same as in Comparative Example 1, but the dropping point of the base agent grease was within the range of the present invention.
℃ or above, specifically 104℃ in Example 1, 198℃ in Example 2, 265℃ in Example 3, and 265℃ in Example 4.
In the examples at 271°C, the galling resistance was 10 times or more in all cases, and the airtight sealability was also good. In particular, the lubricant of Example 4 using urea grease had extremely excellent galling resistance of 18 times. Regarding the type of solid powder lubricant: Comparative Examples 2 and 3 use the same grease and metal powder mixture as Example 2, but graphite and MoS ₂ were used instead of graphite fluoride as the solid lubricant, respectively. These are examples of added lubricants, and all have low galling resistance of 6 times, and also have poor airtight sealing properties. Regarding the maximum particle size of the solid powder: Comparative Example 4 has the same composition of grease and solid powder as Example 2, but the maximum particle size of the solid powder is 70 μm compared to 50 μm in Example 2, which is different from that of the present invention. This is an example of a lubricant that has grown beyond its upper limit. Compared to Example 2, in Comparative Example 4, although the composition was the same, the particle size was larger, so the galling resistance significantly decreased from 14 times in Example 2 to 8 times, and the airtight sealing performance also decreased. It is declining. On the other hand, the maximum particle size in the powder mixture may be smaller than 50 μm. Examples 22 and 23 have maximum particle sizes in the powder mixture of 30 and 10μ, respectively.
This is an example of the same lubricant as in Example 4 above except that m is smaller, but the galling resistance and airtight sealing properties are both at the same level as in Example 4. Regarding the amount of graphite fluoride added: Examples 5 and 6 and Comparative Examples 5 and 6 are the same as Example 4 in the type and amount of grease, the maximum particle size of the solid powder mixture, and the total amount added, but with the addition of graphite fluoride. Examples of lubricants with different amounts of graphite added are shown. Comparative Example 5 in which the amount of graphite fluoride was 5% by weight had a low galling resistance of 8 times, but this was within the scope of the present invention.
In Example 5, which is 17 times by weight, the galling resistance is significantly improved. On the other hand, Example 6 with a graphite fluoride content of 40% by weight has excellent galling resistance and airtight sealing properties, but Comparative Example 6 with 45% by weight, which exceeds the upper limit, has poor airtight sealing properties and does not meet the required standard. Not satisfied. Regarding the total amount of solid powder mixture added: Examples 7 and 8 and Comparative Examples 7 and 8 have the same combinations of grease type, graphite fluoride addition amount, and maximum particle size of the solid powder mixture as Example 4, but This is an example of a lubricant in which the amount of grease and the amount of metal powder added are different from those in Example 4. Comparative Example 7, in which the total amount of solid powder mixture added was 45% by weight, had good galling resistance but poor airtight sealing performance and did not meet the required level; Examples 7, 4 and 8 at 75% by weight show good galling resistance and hermetic sealing properties. On the other hand, in Comparative Example 8 in which the total amount of solid powder mixture added exceeded the upper limit of 80% by weight, the galling resistance (9
(times) and hermetic sealability both did not reach the required level. Regarding the molecular weight of diurea-based thickeners: Comparative Example 9 and Example 9 are examples of lubricants that are exactly the same as Example 4, except that alkyldiurea compounds with different molecular weights were used as diurea-based thickeners. . The molecular weight of the thickener for urea grease is 300.
In Examples 4 and 9, which are within the range of ~1000, very excellent galling resistance is obtained, and airtight sealing properties are also good. On the other hand, in Comparative Example 9 in which the molecular weight of the diurea compound exceeded 1000, both galling resistance (9 times) and airtight sealability did not reach the required levels. Regarding other changes in the grease: Examples 10 and 11 are examples of lubricants that are exactly the same as Examples 2 and 4, respectively, except that the content of thickener in the grease is different. 6%
It can be seen that even if the content is increased or decreased from 3% or 12%, there is no significant change in galling resistance and airtight sealing performance. Examples 12 and 13 are examples of lubricants that are the same as Example 4, except that the base oil of the grease was changed from mineral oil to α-olefin oil and pentaerythritol ester oil, respectively, and the galling resistance was improved. The airtight sealing property is good as in Example 4. These test results show that the amount of thickener in the grease and the type of base oil do not significantly change the performance of the lubricant. Regarding addition of other components: In Examples 14 and 15, in addition to graphite fluoride, graphite and MoS ₂ were used as solid powder lubricants, respectively.
This is an example of a lubricant using fluoride graphite and graphite or MoS ₂ , which has good galling resistance and
Good results are shown in terms of airtight sealing performance. Regarding the combination of metal powders: In the example explained above, the metal powders are Pb and Zn.
Examples 16 to 18 were mixtures of three types of Cu.
Examples 19 to 21 show examples in which only one type of metal powder was used, and two types of metal powders were used in Examples 19 to 21. The total amount of metal powder added and other conditions were the same as in Example 4. From these test results, it can be seen that even if the type of metal powder is reduced, neither the galling resistance nor the airtight sealing property changes significantly. As is clear from the above results, the lubricant composition of the present invention has the following characteristics. (1) Grease with a dropping point of 100°C or higher is used as a base agent for lubricants. In particular, grease with a dropping point of 250°C or higher is preferred, and a molecular weight of 300°C or higher is particularly preferable.
Urea greases with a thickening agent of ~1000 diurea compounds are preferred. (2) Grease contains fluorinated graphite powder, Zn,
A solid powder mixture consisting of powder of at least one soft metal such as Pb, Cu, Sn, Al, etc. is added to form a lubricant. (3) The maximum particle size of the solid powder mixture added to the grease is 50 μm or less. (4) The total amount of the solid powder mixture added to the grease is within the range of 50 to 75% by weight of the total lubricant. That is, the grease is 25-50% by weight. (5) Among solid powders, the amount of graphite fluoride added is 10 to 40% by weight of the entire lubricant, and the amount of metal powder is 30 to 60% by weight.
Weight%. (Effects of the Invention) The lubricant of the present invention has excellent galling resistance, which is difficult to achieve with conventional lubricants for oil country pipe fittings, by selecting a combination of high-drop point grease and a specific solid powder mixture. and exhibits excellent airtight sealing properties. That is, as detailed and exemplified above, the lubricant of the present invention is not novel in its components per se, but the lubricant of the present invention is unique in that it specifies the dropping point of the grease and the composition and amount of the solid powder mixture added thereto. Due to the synergistic effect of grease and solid powder, it exhibits excellent galling resistance and airtight sealing performance even when connecting oil well pipe joints under harsh conditions such as high-alloy steel pipe joints in deep wells. I can do it. In the above explanation, the grease base oil was mainly mineral oil, but other conventional base oils such as α-olefin oil, hindered ester oil such as trimethylolpropane ester and pentaerythritol ester, and silicone oil were also used. As shown in Examples 12 and 13, regardless of the grease used, the performance of the lubricant of the present invention remains essentially the same, with excellent galling resistance and airtight sealing properties similar to those of mineral oil. is obtained. Furthermore, it has been confirmed that the performance of the lubricant of the present invention does not deteriorate at all even when the lubricant of the present invention is used after a pipe joint is subjected to lubricating base treatment such as Cu plating or chemical conversion treatment.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the dropping point and galling resistance of grease in friction tests at various temperatures of grease without solid powder added.
Figure 3 is a graph showing the relationship between test temperature and galling resistance at various maximum particle sizes in a friction test conducted to investigate the influence of the maximum particle size of solid powder added to grease. Graph showing the relationship between grease dropping point and galling resistance of lubricants containing MoS ₂ , and the fourth
The figure is a graph showing the relationship between the graphite fluoride content and galling resistance of lubricants based on greases of various dropping points.

Claims (1)

[Claims] 1. Consisting of grease with a dropping point of 100°C or higher, fluorinated graphite powder, and at least one soft metal powder, wherein the maximum particle diameters of the fluorinated graphite powder and metal powder are both 50 μm. or less, and contains 10 to 40% by weight of the graphite fluoride powder and 30 to 60% by weight of the metal powder, based on the total weight of the lubricant, and the total amount of graphite fluoride powder and metal powder is 50 to 40% by weight. A lubricant for oil well pipe fittings, characterized in that the lubricant is within a range of 75% by weight. 2. The lubricant for oil country pipe fittings according to claim 1, wherein the grease has a dropping point of 250° C. or higher. 3 The grease has two [-NH-CO-NH
-] The lubricant for oil country pipe fittings according to claim 1 or 2, which is a urea grease containing an organic compound having a bond and a molecular weight of 300 to 1000 as a thickener. 4 The soft metal is Zn, Pb, Cu, Sn and Al.
The lubricant for oil country pipe fittings according to any one of claims 1 to 3, which is one or more of the above.