JPH08303656A - Screw joint excellent in seizure resistance property under non-lubrication - Google Patents

Abstract

PURPOSE: To improve seizure resistance property under non lubrication by arranging a phosphate chemical treatment film layer or a nitriding treatment layer and the phosphate chemical treatment film layer on the contacting surface of a box or a pin in the screw joint of a pipe which consists of the pin having a male screw and the box having a female screw. CONSTITUTION: About a box 1 as a coupler member and a pin (a steel pipe top end joint part) 2, a manganese phosphate chemical conversion treatment film layer or a base nitriding treatment layer and a manganese phosphate chemical treatment film layer and a resin film layer are applied to respective screw part 3 and a metal-metal contact part 4, on only the box 1 or on the contact interface of the box 1 and the pin 2. At this time, a resin film layer which is formed by separately mixing tungsten disulfide powder with resin is formed on a phosphate chemical treatment film layer, and the film thickness of the resin film is set to the surface rough or more of the phosphate chemical treatment film layer. The phosphate chemical treatment film layer is set to be 5 to 30μm, nitriding treatment layer is set to be 1 to 20μm, and the thickness of the phosphate chemical treatment film layer is set to be 5 to 30μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a threaded joint having excellent seizure resistance without lubrication, and more specifically, an oil country tubular goods threaded joint used for crude oil mining and a screw for a line pipe for transporting the mined crude oil. The joint does not seize even if it is tightened and loosened repeatedly without applying grease.
The present invention relates to a pipe threaded joint that can be repeatedly used.

[0002]

2. Description of the Related Art Threaded joints are generally used for tubing and casings used for oil well excavation. Since these screw joints are subjected to a combination of internal and external pressure, axial force, bending, etc. under the use environment, it is required that the joints do not leak and the joints do not break even under these combined loads. On the other hand, when the tubing or casing is lowered, the joints that have been tightened may be loosened once. Generally, it is possible to use the joints without seizing even after tightening and loosening 10 times for tubing and 3 times for casings.
It is also desired by (American Petroleum Institute). In order to satisfy the above-mentioned required performance, it has become common knowledge until now to apply the compound grease described in API BUL5A2 and tighten the joint. The role of the compound grease here is to secure seizure resistance and improve sealing performance.

After that, as an invention for further improving the sealing property, a special screw joint having a metal-to-metal contact portion, that is, a premium joint has been actively developed, and a premium joint having seal portions of various shapes (Japanese Patent Publication Sho 59). No. 44552 and Japanese Patent Publication No. 5-41876) have been invented. With such an invention, the gas sealability of the joint has been improved to a level equal to or higher than the yield strength of the tubular body. However, in order to obtain a better sealing property, it is necessary to apply a higher surface pressure to the metal contact part so as to exceed the yield point of the base material. It has become easier and the research to prevent the galling has been actively conducted.

As a measure to prevent this galling, the local surface pressure is reduced by developing a grease in which heavy metal powder such as zinc, lead, copper or the like, or an inorganic substance such as mica is appropriately contained in the compound grease and devising the shape of the seal portion. (JP-A-62-209291, JP-A-4-27739)
No. 2), one in which the properties of the sealing surface are controlled (Jpn. Pat. Appln. KOKAI No. 6-713), and one in which the goring property is improved by a surface treatment (JP-B-3-78517, JP-A-5-78517).
-117870, JP-A-62-258283, JP-A-60-26695, and JP-A-58-31.
097, JP-A-58-17285, JP-A-61-124792, JP-A-61-136087.
Issue gazette) etc. The techniques disclosed in the respective patent publications have their effects to some extent, and seizure resistance has been improved to a practically sufficient range by using an appropriate surface treatment and compound grease.

In particular, Japanese Patent Publication No. 3-78517 discloses that an oil well pipe threaded joint is provided with a resin coating in which molybdenum disulfide is dispersed and mixed. However, in this publication, the resin coating layer is formed so as to have a surface roughness less than that of the metal-to-metal contact portion. This is intended for compound grease application, aiming at the effect of grease being filled in the unevenness of the final surface, and selective for the tightening and loosening under grease-free lubrication by the surface roughness of the base. Stable seizure resistance cannot be obtained by contact. Further, there is no idea of a base treatment for minimizing deterioration with time, and there is a problem that stable seizure resistance cannot be obtained over a long period of time by mentioning only roughness.

Further, Japanese Laid-Open Patent Publication No. 6-10154 discloses that which defines the relationship between the maximum surface roughness before surface treatment and the film thickness of the surface treatment. However, this publication aims at improving the sealability by reducing the gap between the metal contact portions, and, while mentioning the effect of compound grease, the seizure resistance under non-lubrication is similar to the above. Not mentioned at all. Further, as described above, the metal-based surface treatment described as an example cannot be expected to have seizure resistance under grease-free lubrication.

[0007]

Under such circumstances, as a recent research, the grease applied has a high pressure during makeup (tightening) and deteriorates the use performance (Japanese Patent Laid-Open No. 63-210487). Japanese Patent Laid-Open No. 6-110
No. 78) and environmental problems caused by heavy metal components contained in compound grease, and problems related to compound grease such as commercialization of compound grease not containing heavy metal components have begun to occur. The AIP RP5C5 established in 1991 is also a program to evaluate the problems of grease amount and grease pressure that affect the joint performance. Moreover, the application of compound grease not only deteriorates the work environment but also reduces the work efficiency. Therefore, an epoch-making threaded joint which can eliminate the above-mentioned problems if the conventional performance, especially the galling property can be secured without using such compound grease at all. Nevertheless, the reason why compound grease has to be used is that the galling property is deteriorated by several steps in the conventional technique under completely grease-free lubrication.

As a result of intensive studies, the inventors of the present invention should solve the above-mentioned problems. As a result, without using any liquid lubricant such as compound grease, which has been conventionally applied before the make-up of joints, the temperature of An object of the present invention is to provide a threaded joint for pipes that does not cause galling even when it is repeatedly tightened and loosened even if there is a history, and that can also satisfy the use performance such as sealing property. The gist of the invention is as follows: (1) In a threaded joint for a pipe composed of a pin consisting of a male screw and a metal contact part without a screw and a box consisting of a female screw and a metal contact part without a screw, the contact surface of the box or the pin A phosphoric acid-based chemical conversion coating layer or a nitriding layer and a phosphoric acid-based chemical conversion coating layer, and a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion coating layer. A threaded joint excellent in seizure resistance under no lubrication without grease and liquid lubricant when screwing a pin or a box in which the thickness of the resin coating is equal to or greater than the surface roughness of the phosphoric acid-based chemical conversion coating layer.

(2) In a threaded joint of a pipe composed of a pin consisting of a male screw and a metal contact portion without a screw and a box consisting of a female screw and a metal contact portion without a screw, the contact surface of the box or the pin is treated with phosphoric acid conversion treatment. A coating layer or a nitriding treatment layer and a phosphoric acid-based chemical conversion treatment coating layer are provided, and a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion treatment coating layer. Not less than the surface roughness of the phosphoric acid-based chemical conversion treatment coating layer, and the surface roughness of the opposite sliding surface is smaller than the thickness of the resin coating layer, and there is no lubrication without grease and liquid lubricant when screwing pins and boxes. Screw joint with excellent seizure resistance underneath.

(3) In a threaded joint of a pipe comprising a pin consisting of a male screw and a metal contact part without a screw and a box consisting of a female screw and a metal contact part without a screw, the contact surface of the box or the pin has a thickness of 5 to 5. 30 μm phosphoric acid-based chemical conversion treatment coating layer or 1-20 μm thick nitriding treatment layer and thickness 5
A phosphoric acid-based chemical conversion treatment coating layer having a thickness of up to 30 μm is provided, and tungsten disulfide powder is used as a resin. 0.2 ≦ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. A screw joint with excellent seizure resistance without lubrication without grease and liquid lubricant when screwing pins and boxes with surface roughness greater than that of the coating layer.

(4) In a threaded joint of a pipe composed of a pin consisting of a male screw and a metal contact part without a screw and a box consisting of a female screw and a metal contact part without a screw, on the contact surface of either the box or the pin, A phosphoric acid-based chemical conversion treatment coating layer having a thickness of 5 to 30 μm, or a nitriding treatment layer having a thickness of 1 to 20 μm and a phosphoric acid chemical conversion treatment coating layer having a thickness of 5 to 30 μm are provided, and tungsten disulfide powder is used as a resin. 2 ≦ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. The surface roughness of the coating layer should be equal to or greater than the surface roughness of the opposite sliding surface than the thickness of the resin coating layer, and seizure resistance without lubrication without grease and liquid lubricant when screwing pins and boxes Screw joint with excellent performance.

(5) In a threaded joint of a pipe composed of a pin consisting of a male screw and a metal contact part without a screw and a box consisting of a female screw and a metal contact part without a screw, the contact surface of the box or the pin is treated with phosphoric acid conversion treatment. A coating layer or a nitriding treatment layer and a phosphoric acid-based chemical conversion treatment coating layer are provided, and a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion treatment coating layer. A threaded joint excellent in seizure resistance without lubrication without grease and liquid lubricant when screwing a pin into a box and a box having a thickness greater than that of the phosphoric acid-based chemical conversion coating layer.

(6) In a threaded joint of a pipe composed of a pin consisting of a male screw and a metal contact portion without a screw and a box consisting of a female screw and a metal contact portion without a screw, the contact surface of the box or the pin is treated with phosphoric acid-based chemical conversion treatment. A coating layer or a nitriding treatment layer and a phosphoric acid-based chemical conversion treatment coating layer are provided, and a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion treatment coating layer. The thickness of the phosphoric acid-based chemical conversion treatment film layer is equal to or larger than that of the resin film layer, and the surface roughness of the opposing sliding surface is smaller than the thickness of the resin film layer. A screw joint with excellent seizure resistance.

(7) In a threaded joint of a pipe composed of a pin consisting of a male screw and a metal contact part without a screw and a box consisting of a female screw and a metal contact part without a screw, the contact surface of the box or the pin has a thickness of 5 to 5. 30 μm phosphoric acid-based chemical conversion treatment coating layer or 1-20 μm thick nitriding treatment layer and thickness 5
A phosphoric acid-based chemical conversion treatment coating layer having a thickness of up to 30 μm is provided, and tungsten disulfide powder is used as a resin. 0.2 ≦ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. Pins with a thickness greater than that of the coating layer,
Screw joint with excellent seizure resistance without grease and liquid lubricant when box is screwed.

(8) In a threaded joint of a pipe composed of a pin consisting of a male screw and a metal contact portion without a screw and a box consisting of a female screw and a metal contact portion without a screw, on the contact surface of either the box or the pin, A phosphoric acid-based chemical conversion treatment coating layer having a thickness of 5 to 30 μm, or a nitriding treatment layer having a thickness of 1 to 20 μm and a phosphoric acid chemical conversion treatment coating layer having a thickness of 5 to 30 μm are provided, and tungsten disulfide powder is used as a resin. 2 ≦ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. Seizure resistance under no lubrication without grease and liquid lubricant at the time of screwing pins and boxes by making the surface roughness of the coating layer greater than that of the resin coating layer Excellent screw joint. (9) A threaded joint excellent in seizure resistance under non-lubrication, characterized in that the resin according to (1) to (8) is dispersed and mixed with a corrosion inhibitor.

[0016]

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a schematic view of a joint constituent member to which the present invention is applied. As shown in FIG. 1, for a box 1 and a pin (steel pipe tip joint portion) 2 which are joint members, only the box 1 or the screw portion 3 and the metal-metal contact portion 4 constituting each joint member, or A manganese phosphate-based chemical conversion treatment coating layer or a base nitriding treatment and a manganese phosphate-based chemical conversion treatment coating layer and a resin coating layer are applied to the contact interface between the box 1 and the pin 2, and the base material facing the surface treatment layer during joint screwing. The surface slides.

FIG. 2 is a view showing the assembly structure of each joint component. As shown in FIG. 2, the box 1 and the pin 2 are fitted to each other, and the screw portion 3 and the metal-metal contact portion 4 are slid while applying high surface pressure. In such a structure, the seizure resistance generally becomes more severe as the joint diameter increases. So, for example, for tightening and loosening 10 times,
An evaluation test of seizure resistance was performed on a premium joint having a metal-to-metal contact portion having a maximum diameter of tubing of φ178 mm required not to cause galling.

FIG. 3 is a diagram showing the relationship between various surface treatments and the number of times of occurrence of goring. As shown in Fig. 3, each type when tightening and loosening is performed without applying lubricant to the galvanized, copper-plated, tin-plated, phosphate-treated, sandblasted box and as-machined pin. The number of occurrences of seizure is shown. Even with copper plating, which is said to have the best seizure property, galling occurs at the third time, and how difficult it is to ensure galling resistance without lubrication. It turns out to be technology. The reason for this is that, normally, a premium joint generates a high surface pressure in the metal-to-metal contact area that exceeds 600 MPa of the base metal itself in order to perform gas sealing, and during joint make-up and breakout. This is because the metals slide with each other under such a high surface pressure.

Therefore, the inventors focused their attention on tungsten disulfide, which has an excellent lubricating function under high surface pressure, and worked on a solid lubricating coating for an oil country tubular goods threaded joint. Generally, the lubrication effect of a lubricant depends on the conditions of use: surface pressure, sliding speed,
It is also known that there is a large difference depending on the type and presence of the lubricant, surface properties, temperature and the like. It is known that tungsten disulfide may exhibit extremely excellent seizure resistance or may be inferior to ordinary grease lubrication depending on the method of use. Particularly, it exhibits an excellent effect in a tightening and loosening test after heating at 350 ° C. for 24 hours or more. Further, in the case of tungsten disulfide, it is no exaggeration to say that the surface treatment and the binder (binder) determine the goodness of lubricity.

For the above reasons, it is most desirable to use a real joint for the evaluation of seizure resistance.
First, a pin-on-disk type seizure evaluation tester was developed from the viewpoint of relative comparison of film lubricity, and evaluation was performed using a small sample. Here, the original seizure evaluation tester was used instead of the existing seizure evaluation tester such as the Bowden friction tester because the seizure resistance improvement effect of the coating greatly differs depending on the use environment as described above. . This is because, in the case of the premium joint, the contact surface pressure is extremely large as described above, and therefore it is necessary to apply the high surface pressure even in the small test. FIG. 4 shows an outline of the test in the present invention. The samples and experimental conditions are shown below.

[0021]

The pins referred to herein are coated with a seizure-resistant coating, for example, assuming a box for an actual joint, and assuming a disk for an actual joint, for example, a surface roughness by lathe processing equivalent to that of the actual joint is given. did. Sliding distance per rotation is 1
Corresponding to a pipe with an outer diameter of 78 mm, a high surface pressure equivalent to that of the actual joint was applied at the maximum sliding speed allowed by the actual joint. What is more characteristic is that without using any lubricant such as grease,
It is in evaluating the seizure resistance. First, the inventors evaluated the so-called dispersion plating, which is a surface treatment in which tungsten disulfide is dispersed and mixed in an existing metal plating matrix. The result is shown in FIG. That is, FIG. 5 is a diagram showing the relationship between the type of surface coating by dispersion plating and the sliding distance until seizure. From this figure, the seizure resistance of dispersion plating is greatly influenced by the seizure resistance of the matrix metal,
The dispersion effect of tungsten disulfide hardly appears, rather,
It can be seen that the seizure resistance of the metal matrix alone is often superior. This is a phenomenon peculiar to high surface pressure, and the effect of tungsten disulfide appears as is generally said under a light load, and dispersion plating exhibits superior seizure resistance.

Next, FIG. 6 shows the evaluation results of the coating obtained by dispersing and mixing the tungsten disulfide powder in the binder of the resin such as polyamide-imide, epoxy and furan. That is, FIG. 6 is a diagram showing the relationship between the coating film obtained by dispersing and mixing tungsten disulfide powder in various resins and the sliding distance until seizure. Here, manganese phosphate chemical conversion treatment was performed as the base treatment. The seizure resistance of such a coating is 10 times or more that of copper plating, which was said to be the best in the past, and the maximum test sliding distance 8 which was temporarily set
No coating was performed even when it reached 0 m. A significant difference in seizure resistance depending on the type of binder clearly appears,
It was found that polyamideimide, epoxy, and furan were superior in that order. This is related to the tensile strength and impact value of the resin itself.

Moreover, the above-mentioned organic resin has a content of 0.2≤ {(content of tungsten disulfide powder)} /
It is necessary to form a resin coating layer dispersed and mixed in a ratio of {content of (resin)} ≦ 9 to a thickness of 10 to 45 μm on a phosphoric acid-based chemical conversion coating layer which is a base treatment. When the composition ratio of the tungsten disulfide powder and the organic resin binder is less than 0.2, it is difficult to obtain the desired effect of improving the lubricating function of the formed solid lubricating coating layer, and the composition ratio exceeds 9. In this case, the adhesion of the formed solid lubricating coating layer is deteriorated, and in particular, defects such as remarkable separation of the tungsten disulfide powder from the coating layer occur, which is not preferable. Therefore, the content composition ratio of the tungsten disulfide powder, which is an essential content component of the treatment agent used for forming the solid lubricating coating layer, and the organic resin binder is in the range of 0.2 to 9.

These resin coating layers are formed on the phosphoric acid-based chemical conversion coating layer which has been subjected to the base treatment to a thickness of 10 to 45 μm. When the coating thickness is less than 10 μm, the lubrication which is the object of the present invention. This is not preferable because it has a small effect of improving the performance and causes a problem that the number of times of repeated use of make-up and breakout of the steel pipe joint is reduced. on the other hand,
When the thickness of the coating layer exceeds 45 μm, the effect of improving the lubricating function is saturated and it is economically disadvantageous. Rather, it is not preferable because the tendency of the adhesion of the solid lubricating coating layer to deteriorate increases, which causes peeling of the coating layer to cause rusting. Therefore, the thickness of the resin coating layer is 10 to 10.
It was restricted to a range of 45 μm, preferably 15 to 40 μm.

Further, since the surface treatment of the coating is the most important factor to take advantage of the characteristics of tungsten disulfide,
FIG. 7 shows an evaluation of the effect of the base treatment on the seizure resistance. That is, FIG. 7 is a diagram showing the relationship between the surface coating in which the tungsten disulfide powder is dispersed and mixed in the resin and the sliding distance until seizure when various kinds of undercoating are performed. An evaluation test was conducted on treatment, nitriding treatment, sandblasting, and no treatment. As a result, seizure resistance is improved by manganese phosphate chemical conversion treatment,
It was found that nitriding treatment, sand blasting, and non-treatment were excellent in that order, and when there was no base treatment, there was only seizure resistance equivalent to copper plating. Further, the seizure resistance is most stable by performing the manganese phosphate treatment after nitriding. Another thing to notice is that when sandblasting is used for the surface treatment, the effect of tungsten disulfide varies greatly. This is because in a seizure test without a grease lubricant, the convex and concave parts due to sandblasting selectively contact the mating metal, the resin coating partly wears, and metal-metal adhesion occurs, which easily causes galling. It is supposed to be.

Focusing on this mechanism, the effect of the film thickness on the manganese phosphate-based chemical conversion treatment was examined, and it was found that it is optimal to provide a phosphoric acid-based chemical conversion coating layer having a thickness of 5 to 30 μm. That is, when the thickness of the phosphoric acid-based chemical conversion coating layer is less than 5 μm, the uniform coating property of the chemical conversion coating layer is not sufficient, and the sufficient adhesion improving effect on the solid lubricating coating layer, especially when exposed to a corrosive environment for a long time. It is difficult to obtain the effect of improving the adhesiveness, that is, the so-called adhesive property after aging, and the lubricating performance after the solid lubricating coating layer is worn is not good, so that the effect of improving the galling resistance of the steel pipe joint, which is the object of the present invention, is unsatisfactory. It is enough. On the other hand, the phosphoric acid-based chemical conversion coating layer has a thickness of 3
If it is formed to exceed 0 μm, secondary crystals tend to be formed remarkably, and the adhesiveness of the coating film itself is deteriorated, and also the adhesiveness of the resin coating layer is deteriorated, which is not preferable. Therefore, in the present invention, the phosphoric acid-based chemical conversion coating layer has a thickness in the range of 5 to 30 μm, preferably 10 to 25 μm.
The range is limited to m.

Further, in the present invention, a steel which, if necessary, further improves the adhesion strength of a phosphoric acid type chemical conversion coating layer, particularly a manganese phosphate type chemical conversion coating layer, or inhibits uniform formation of this coating layer. For the purpose of promoting uniform generation of manganese phosphate chemical conversion coating layer on steel pipe joints of various components and ensuring the lubrication effect after the resin coating layer is consumed for a long time, the nitriding layer by diffusion treatment is a manganese phosphate chemical conversion coating. It is provided as a base treatment layer for the layer. Therefore,
In order to obtain these actions and effects, the thickness of the underlying nitriding layer is limited to the range of 1 μm or more and 20 μm or less. If the thickness of the underlying nitriding layer is less than 1 μm, many defects are generated in the nitriding layer, so that the above effects are difficult to obtain, which is not preferable. On the other hand, when the thickness of the underlying nitriding layer exceeds 20 μm, the above-mentioned effects are saturated, and the hardness of the nitriding layer is rather high, which causes a change in the material of the steel pipe joint due to the increase in the thickness, which is not preferable. . Therefore, in the present invention, the thickness of the underlying nitriding layer is limited to the range of 1 to 20 μm, preferably 5 to 15 μm.

As described above, the reason why the base treatment is specified as the phosphoric acid-based chemical conversion treatment layer is that the phosphoric acid-based chemical conversion treatment is less likely to deteriorate with time in terms of adhesion to the resin film, as compared with the base treatment such as sandblasting. , It is a problem in terms of workability.
Deterioration over time A similar resin coating was formed on the base treatment using manganese phosphate chemical conversion treatment and the one using sandblasting, and after immersion in water for 1 month, the adhesion state was observed. Although there was no change in the treated ones, in some of the sandblasted ones, floating of the resin film was observed, and it was found that there was a problem in storage and use especially in a humid environment. In terms of workability, when sandblasting is used as the base treatment, it is necessary to perform the coating treatment within 30 minutes after sandblasting, but it is often impossible due to the line structure at the manufacturing site. On the other hand, in the case of manganese phosphate-based chemical conversion treatment, it was confirmed that there is no problem in practical use even if the resin coating is applied after standing for 2 weeks after the treatment.

Another deterioration performance in the case where grease lubrication is not used is the gas sealing property of the metal sealing portion. In order to evaluate the gas sealability without lubrication, the joint was repeatedly tightened and loosened 10 times, and then the gas sealability was tried to be evaluated according to the load condition of API RP5C5. As a result, the joint did not leak even in the evaluation test within the processing tolerance range similar to the case where conventional grease lubrication was performed. This is because the resin film thickness that is more than the film thickness of the undercoating formed to secure seizure resistance makes the unevenness of the interface of the metal contact part that substantially seals extremely smooth, Since the resin is also sealed in the gap, the excellent sealing function can be achieved without using grease.

FIG. 8 is a diagram showing the relationship between the film thickness of the resin film and the surface roughness of the phosphoric acid-based chemical conversion treatment film layer according to the present invention.
The surface condition of the steel pipe joint that achieves the object of the present invention,
As shown in FIG. 8, the surface roughness R _M of the phosphoric acid-based chemical conversion treatment coating layer 5 or the nitriding treatment layer and the phosphoric acid-based chemical conversion treatment coating layer, and the tungsten disulfide powder formed on these base treatment layers are dispersed and mixed in the resin. If the film thickness δ _C of the resin coating layer 6 is
R _M <δ _C.
That is, it is necessary to increase the thickness [delta] _C of the resin coating layer from the surface roughness R _M of the phosphate-based chemical conversion coating layer or nitrided layer and phosphate-based chemical conversion treatment film layer. If it is smaller than this, not only the seizure resistance, which is the object of the present invention, cannot be maintained, but also the sealing property cannot be maintained. Also, the surface roughness R _{M of the} phosphoric acid-based chemical conversion treatment coating layer
Is in the range of 3 to 30 μm. If the thickness is less than 3 μm, the adhesion to the resin coating is poor, and if the surface roughness exceeds 30 μm, the phosphoric acid-based chemical conversion treatment coating layer becomes thick and secondary crystals tend to be generated remarkably, and the coating layer itself is brittle. Therefore, the adhesion will be deteriorated. Therefore, in the present invention, the surface roughness R _M of the phosphoric acid-based chemical conversion treatment coating layer is 3 to 3
The range was limited to 0 μm.

Next, in order to improve the seizure resistance of the metal contact portion of the joint, the contact interface is intentionally roughened by machining or sandblasted to obtain seizure resistance without using other surface treatment. The improvement has achieved a certain effect under the environment in which the compound grease is applied by a generally used means. However, there is no evaluation of the effect of the surface properties of this sliding mating material under grease-free lubrication, and the surface of the base material plated with copper under grease-free lubrication is sandblasted to R _max = 30 μm. Fig. 9 shows the result of repeated tightening and loosening of the pin treated in
Shown in That is, FIG. 9 is a diagram showing the relationship between various surface treatments when sanding is performed on the sliding mating material and the number of times of occurrence of galling. As shown in this figure, the surface of the sliding mating material is sandblasted. It can be seen that the seizure resistance is deteriorated by doing so. The reason for this is that the effect of roughening the surface is to create a gap at the contact interface by roughening the surface and to fill the gap with compound grease to improve the lubrication effect. This is because not only this effect is absent, but also the surface treatment having the sole function of anti-seizure is abraded by the unevenness of the sandblast.

FIG. 10 is a diagram showing the relationship between the film thickness of the resin coating according to the present invention, the surface roughness of the phosphoric acid-based chemical conversion treatment coating layer, and the surface roughness of the opposite sliding surface. It is a second invention for achieving the object of the present invention, and as shown in FIG. 10, the surface roughness R _{M of} the nitriding layer and the phosphoric acid-based chemical conversion coating layer which are the phosphoric acid-based chemical conversion coating layer 5 and There is a relationship of R _M <δ _C between the film thickness δ _C of the resin coating layer 6 obtained by dispersing and mixing the tungsten disulfide powder formed on these undercoating layers in the resin, and the sliding surfaces 7 facing each other. When the surface roughness R _max as the relationship R _max <[delta] _C holds is to determine R _max. That is, the surface roughness R _max of the opposing sliding surfaces
There in the thickness [delta] _C is greater than the present invention of the resin coating layer, causing a leakage since there is no grease or liquid lubricant, it is impossible to achieve the object of the present invention. The surface roughness R _max is in the range of 1 to 25 μm. 1 μm
Less than because it will affect the production efficiency of the joint,
If it exceeds 25 μm, there will be no lubricant and baking will occur.
It deteriorates the sealing property. Therefore, the surface roughness R _max of the opposing sliding surfaces is preferably in the range of 1 to 25 μm. The action and effect are shown in FIGS. 11 and 12.

FIG. 11 is a diagram showing the relationship between the resin film thickness and the seizure resistance of the surface roughness according to the present invention. That is, it shows the initial resin film thickness and the resin film thickness after ten times of tightening and loosening when tungsten disulfide was dispersed and mixed in the polyamideimide resin with the manganese phosphate chemical conversion treatment as the base treatment. It can be seen that the rougher the surface roughness of the opposing sliding surfaces, the smaller the remaining film thickness and the lower the seizure resistance. FIG. 12 is a diagram showing the number of make breaks and the process of decreasing the thickness of the resin coating film at the opposite sliding surface roughness, and shows the process of decreasing the resin film thickness when tightening and loosening are repeated. From this figure, the wear tends to decrease when the total wear becomes equal to the roughness of the opposite sliding surfaces. Therefore, in order to obtain stable seizure resistance, it is necessary to design the film thickness of the resin film to be equal to or larger than the roughness of the sliding surfaces facing each other.

FIG. 13 is a diagram showing the relationship between the film thickness of the phosphoric acid treatment and the sliding distance until seizure. As shown in this figure, the manganese phosphate-based chemical conversion treatment thickness and the resin coating thickness have a specific tendency to exhibit better seizure resistance. Is.
As a reason why this combination is effective, it was found that even when the chemical conversion treatment was performed by the same mechanism as the above-mentioned sandblasting surface treatment, irregularities corresponding to the chemical conversion treatment film thickness appeared on the surface. Therefore, for the purpose of preventing selective contact, it is necessary to coat the resin film more than the chemical conversion treatment film thickness.

FIG. 14 shows the film thickness and phosphorus content of the resin coating according to the present invention.
It is a figure which shows the relationship with the film thickness of an acid type chemical conversion treatment coating layer. Book
It is a third invention for achieving the object of the invention, which comprises a steel pipe joint
As for the surface condition, as shown in FIG.
Physical coating layer 5 or nitriding layer and phosphoric acid-based chemical conversion coating layer
Film thickness δ_MAnd the disulfide sulphide formed on these base treatment layers.
A film of the resin coating layer 6 in which the Nungsten powder is dispersed and mixed in a resin
Thickness δ_CThen, δ_M<Δ_CFormed to be in a relationship
There is to let. That is, the film thickness δ of the resin coating layer_CPhosphorus
Acid-based chemical conversion coating layer or nitriding layer and phosphoric acid-based chemical conversion treatment
Film thickness δ_MNeed to be bigger. This
If it is smaller, the seizure resistance which is the object of the present invention is maintained.
In addition to being unable to hold the
I can't do it. In addition, this phosphoric acid-based chemical conversion treatment coating layer
Film thickness δ_MIs the above-mentioned 5 to 30 μm, the film thickness δ of the resin coating layer
_CIs 10 to 45 μm, so in both cases,
δ _M<Δ_CIt is necessary to form under the condition that

FIG. 15 shows the film thickness and phosphorus content of the resin coating according to the present invention.
Thickness of acid-based chemical conversion coating layer and surface roughness of opposite sliding surface
It is a figure which shows the relationship with. To achieve the object of the present invention
As shown in FIG. 15, a phosphoric acid-based
Chemical conversion treatment coating layer 5 and nitriding treatment layer and phosphoric acid chemical conversion treatment
Film thickness δ_MAnd disulfide formed on these undercoat layers
Resin coating layer 6 in which tungsten oxide powder is dispersed and mixed in resin
Film thickness δ_CBetween and_M<Δ_CHas a relationship of
Surface roughness R of opposing sliding surfaces 7_maxThen R _max<Δ
_CSo that the relationship of_maxIs to decide.
That is, the surface roughness R of the opposing sliding surfaces_maxIs a resin coating
Layer thickness δ_CIf it is larger, in the present invention, grease or
Is leaking due to the lack of liquid lubricant,
I cannot achieve my purpose. Also, this surface roughness R
_maxIs in the range of 1 to 25 μm. If it is less than 1 μm
This will affect the production efficiency of the
However, since there is no lubricant, it will cause baking, resulting in poor sealing performance.
Turn into Therefore, the surface roughness R of the opposing sliding surfaces_maxIs
The range of 1 to 25 μm is desirable.

Further, the use of a resin coating containing tungsten disulfide as the only dispersed particles was an essential condition without grease lubrication, but the adverse effect of using such dispersed particles is that S is in water. It is said that it combines with hydrogen to generate hydrogen sulfide, and particularly induces sulfide stress corrosion cracking when the base material has high strength. In order to deal with such a problem, 2-polymeric clinsade, 1-
Triethylenetriaminoimidazoline (2-polym
ericlinseed, 1-triethylene
By dispersing a corrosion inhibitor such as triaminoimidazoline, sulfide stress corrosion cracking can be prevented while maintaining seizure resistance.

[0039]

EXAMPLE For a box and a pin which are joint members shown in FIG. 1 which are joint portions of a steel pipe, the contact interface of the box is treated as a base treatment with respect to a screw portion and a metal-metal contact portion constituting each joint member. Manganese phosphate chemical conversion treatment coating layer or underlying nitriding treatment layer and manganese phosphate chemical conversion treatment coating layer or sandblast treatment is performed, and tungsten disulfide and polyamideimide resin, epoxy resin and furan resin are used as resin coatings at a predetermined composition ratio. The formed solid lubricant was applied and the film thickness of the resin film was changed and provided. Table 1 shows the number of times of occurrence of galling when there is no temperature history when the roughness of the opposing sliding surfaces is changed. As a result, as shown in Table 1, it is clearly shown that the effect of the present invention is high in the tightening and loosening test of the actual joint up to 20 times without grease lubrication when there is no temperature history.

Table 2 shows the number of occurrences of galling when there is a temperature history. According to this, for tightening / loosening at room temperature, as shown in Table 1, the film thickness of the undercoating (almost the same effect on the roughness), the resin film thickness, and the roughness of the opposite sliding surface are specified. Although excellent seizure resistance is exhibited by setting the relationship of, the seizure resistance decreases in the tightening and loosening test after heating at 350 ° C. for 24 hours or more. Table 3 shows that when tungsten disulfide is used as the solid lubricant, the film thickness of the surface treatment (the roughness is the same), the resin film thickness, and the roughness of the opposite sliding surface are obtained even if the temperature history of 350 ° C. is used. It can be seen that the predetermined target can be achieved even if the target is tightened and tightened 10 times if the specific condition is satisfied. In this way, since the filing effect of the sliding surface appears remarkably under no grease lubrication, when using a resin coating in which tungsten disulfide is dispersed and mixed in the resin, if the resin coating thickness is formed to be equal to or higher than the coating roughness of the base treatment. At the same time, it is necessary to form the surface roughness of the opposing sliding surfaces to be equal to or less than the resin coating film thickness as described above.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

As described above, in the threaded joint according to the present invention, a phosphoric acid type chemical conversion treatment coating layer or a nitriding treatment layer and a phosphoric acid type chemical conversion treatment coating layer are provided on the contact surface of the box or the pin, and the phosphoric acid type chemical conversion treatment layer is formed. A resin film layer is formed on the film layer, and the film thickness of this resin film is made equal to or greater than the surface roughness of the phosphoric acid-based chemical conversion film. The surface roughness is not less than that of the above, and in particular, by dispersing tungsten disulfide powder as a solid lubricant in the resin, there is no seizure against tightening and loosening even when subjected to temperature history, and in the past it was applied before making up the joint. Without using any liquid lubricant such as compound grease that has been used, it does not cause galling due to repeated tightening and loosening, and the performance such as sealing property can be satisfied. Can be obtained Umate excellent pipe threaded joint.

[Brief description of drawings]

FIG. 1 is a schematic view of a joint component member to which the present invention is applied,

FIG. 2 is a diagram showing an assembly configuration of each joint component member;

FIG. 3 is a diagram showing a relationship between various surface treatments and the number of times of occurrence of goring,

FIG. 4 is a diagram showing an outline of a test in the present invention,

FIG. 5 is a diagram showing the relationship between the type of surface coating by dispersion plating and the sliding distance until seizure,

FIG. 6 is a diagram showing a relationship between a coating obtained by dispersing and mixing tungsten disulfide powder in various resins and a sliding distance until seizure,

FIG. 7 is a diagram showing a relationship between a surface coating in which tungsten disulfide powder is dispersed and mixed in a resin and a sliding distance until seizure when various kinds of undercoating are performed,

FIG. 8 is a diagram showing the relationship between the film thickness of the resin film according to the present invention and the surface roughness of the phosphoric acid-based chemical conversion treatment film layer,

FIG. 9 is a diagram showing the relationship between various surface treatments and the number of times of occurrence of galling when the sliding mating material is sandblasted,

FIG. 10 is a diagram showing the relationship between the film thickness of the resin film according to the present invention, the surface roughness of the phosphoric acid-based chemical conversion treatment film layer, and the surface roughness of the opposing sliding surface,

FIG. 11 is a diagram showing the relationship between the resin coating thickness and the seizure resistance in the surface roughness according to the present invention,

FIG. 12 is a diagram showing a process of decreasing the number of make breaks and the thickness of the resin coating film at the opposite sliding surface roughness,

FIG. 13 is a diagram showing the relationship between the film thickness of a phosphoric acid-based chemical conversion treatment and the sliding distance until seizure;

FIG. 14 is a diagram showing the relationship between the film thickness of the resin film and the film thickness of the phosphoric acid-based chemical conversion treatment film layer according to the present invention.

FIG. 15 is a diagram showing the relationship between the film thickness of the resin film according to the present invention, the film thickness of the phosphoric acid-based chemical conversion treatment film layer, and the surface roughness of the opposing sliding surface.

[Explanation of symbols]

 1 box 2 pin 3 screw part 4 metal contact part 5 phosphoric acid type chemical conversion treatment coating layer 6 resin coating layer 7 opposing sliding surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toru Ono, Toru Ono 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Inside the Advanced Technology Research Laboratories, Nippon Steel Corporation (72) Seijun Higuchi, Satomi Sawami, Tobata-ku, Kitakyushu, Fukuoka Chome 7-5-208 (72) Inventor Ryusuke Inoue 2-28-12 Kumagaya, Kokurakita-ku, Kitakyushu, Fukuoka

Claims (9)

[Claims] 1. A threaded joint for a pipe, which comprises a pin consisting of a male screw and a metal contact without a screw and a box consisting of a female screw and a metal contact without a screw, wherein the contact surface of the box or the pin is a phosphoric acid type chemical conversion coating. A layer or a nitriding layer and a phosphoric acid-based chemical conversion coating layer, a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion coating layer, and the thickness of the resin coating is A threaded joint with excellent seizure resistance without lubrication without grease and liquid lubricant when screwing pins and boxes with a surface roughness not less than that of the phosphoric acid-based chemical conversion coating layer. 2. In a threaded joint of a pipe comprising a pin consisting of a male screw and a metal contact portion without a screw and a box consisting of a female screw and a metal contact portion without a screw, a phosphoric acid type chemical conversion coating on the contact surface of the box or the pin. A layer or a nitriding layer and a phosphoric acid-based chemical conversion coating layer, a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion coating layer, and the thickness of the resin coating is Not less than the surface roughness of the phosphoric acid-based chemical conversion coating layer, and the surface roughness of the opposing sliding surface is smaller than the thickness of the resin coating layer, without lubrication without grease and liquid lubricant when screwing pins and boxes. A screw joint with excellent seizure resistance. 3. A threaded joint for a pipe, which comprises a pin consisting of a male screw and a metal contact portion without a screw and a box consisting of a female screw and a metal contact portion without a screw, and a thickness of 5 to 30 μm on the contact surface of the box or the pin. Phosphoric acid-based chemical conversion coating layer or nitriding layer having a thickness of 1 to 20 μm and a thickness of 5 to 3
A phosphoric acid-based chemical conversion coating layer having a thickness of 0 μm is provided, and tungsten disulfide powder is used as a resin. 0.2 ≦ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. A screw joint with excellent seizure resistance without lubrication without grease and liquid lubricant when screwing pins and boxes with surface roughness greater than that of the coating layer. 4. A threaded joint for a pipe, which comprises a pin consisting of a male screw and a metal contact without a screw and a box consisting of a female screw and a metal contact without a screw, wherein the contact surface of either the box or the pin is thick. A phosphoric acid-based chemical conversion treatment coating layer having a thickness of 5 to 30 μm, or a nitriding treatment layer having a thickness of 1 to 20 μm and a phosphoric acid chemical conversion treatment coating layer having a thickness of 5 to 30 μm are provided, and tungsten disulfide powder is used as a resin. ≤ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. The surface roughness of the coating layer should be equal to or greater than the surface roughness of the opposite sliding surface than the thickness of the resin coating layer, and seizure resistance without lubrication without grease and liquid lubricant when screwing pins and boxes Screw joint with excellent performance. 5. A threaded joint for a pipe, which comprises a pin consisting of a male screw and a metal contact without a screw and a box consisting of a female screw and a metal contact without a screw, and a phosphoric acid-based chemical conversion coating on the contact surface of the box or the pin. A layer or a nitriding layer and a phosphoric acid-based chemical conversion coating layer, a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion coating layer, and the thickness of the resin coating is A threaded joint with excellent seizure resistance under no lubrication without grease and liquid lubricant when screwing pins and boxes that are thicker than the phosphoric acid-based chemical conversion coating layer. 6. A threaded joint for a pipe, which comprises a pin consisting of a male screw and a metal contact without a screw and a box consisting of a female screw and a metal contact without a screw, and a phosphoric acid chemical conversion coating film on the contact surface of the box or the pin. A layer or a nitriding layer and a phosphoric acid-based chemical conversion coating layer, a resin coating layer in which tungsten disulfide powder is dispersed and mixed in a resin is formed on the phosphoric acid-based chemical conversion coating layer, and the thickness of the resin coating is The thickness of the phosphoric acid-based chemical conversion coating layer is equal to or larger than that, and the surface roughness of the opposing sliding surface is smaller than the thickness of the resin coating layer,
A screw joint with excellent seizure resistance without grease and liquid lubricant when screwing pins and boxes together. 7. A threaded joint for a pipe, which comprises a pin consisting of a male screw and a metal contact without a screw and a box consisting of a female screw and a metal contact without a screw, wherein the contact surface of the box or the pin has a thickness of 5 to 30 μm. Phosphoric acid-based chemical conversion coating layer or nitriding layer having a thickness of 1 to 20 μm and a thickness of 5 to 3
A phosphoric acid-based chemical conversion coating layer having a thickness of 0 μm is provided, and tungsten disulfide powder is used as a resin. 0.2 ≦ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. Pins with a thickness greater than that of the coating layer,
Screw joint with excellent seizure resistance without grease and liquid lubricant when box is screwed. 8. A threaded joint for a pipe comprising a pin consisting of a male screw and a metal contact without a screw and a box consisting of a female screw and a metal contact without a screw, wherein the contact surface of either the box or the pin is thick. A phosphoric acid-based chemical conversion treatment coating layer having a thickness of 5 to 30 μm, or a nitriding treatment layer having a thickness of 1 to 20 μm and a phosphoric acid chemical conversion treatment coating layer having a thickness of 5 to 30 μm are provided, and tungsten disulfide powder is used as a resin. ≤ {(content of tungsten disulfide powder)} /
A resin coating layer dispersed and mixed in a proportion of {(resin) content ≦ 9 is formed to a thickness of 10 to 45 μm on the phosphoric acid-based chemical conversion treatment coating layer, and the thickness of the resin coating is adjusted to the phosphoric acid-based chemical conversion treatment. Seizure resistance under no lubrication without grease and liquid lubricant at the time of screwing pins and boxes by making the surface roughness of the coating layer greater than that of the resin coating layer Excellent screw joint. 9. A threaded joint having excellent seizure resistance in the absence of lubrication, which is obtained by dispersing and mixing a corrosion inhibitor in the resin according to claim 1.