JP3056646B2 - Surface treatment method for steel pipe joints with excellent galling resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for forming a film having excellent seizure resistance and abrasion resistance on the surface of an oil country tubular good.

[0002]

2. Description of the Related Art Generally, steel pipes for oil wells are connected to each other via a coupling. A female screw formed on the inner surface of the coupling is fitted to a male screw formed at an end of the steel pipe, and these screws are connected to each other. By tightening the parts, a plurality of steel pipes are connected while maintaining airtightness and liquid adhesion. That is, a threaded portion formed at the tip of the oil country tubular good and a joint portion formed of a tapered portion formed at the base thereof, and a threaded portion to be screwed with the threaded portion and a coupling material formed with a tapered tapered portion at the tip. By rotating tightening,
A metal-to-metal seal portion is formed and connected while maintaining perfect sealing properties. However, since a high surface pressure acts on the metal-metal seal portion, when the joint is tightened (make-up) or tightened (break-out), the metal seal portion and the screw portion have scratches and galling defects, ie, seizure. Tends to occur. That is, when galling occurs, the sealing property is impaired, and the number of times the steel pipe can be used repeatedly decreases. In addition, if corrosion occurs in the joint, it becomes difficult to ensure sufficient sealing performance.

[0003] Therefore, various proposals have hitherto been made to obtain a steel pipe joint capable of reducing such galling. For example, a method of providing an electroplating layer of copper, zinc, or the like (Japanese Patent Publication No. 1-12995, etc.), the maximum surface roughness of a metal-metal seal portion and the thickness of a surface treatment film layer, particularly, the thickness of an electroplating layer of copper, zinc, or the like. (Japanese Patent Application Laid-Open No. Hei 6-10154), a method for forming a manganese phosphate-based chemical conversion coating layer (Japanese Patent Publication No. 5-40034, etc.), and a method for determining the maximum surface thickness of a metal-metal seal portion. A method of forming a synthetic resin film in which fluororesin powder is dispersed and mixed as specified (JP-A-61-124792) or a method of forming a synthetic resin film in which molybdenum disulfide powder is dispersed and mixed (Japanese Patent Application Laid-Open No. 61-13687) And the like have been proposed.

[0004]

However, each of these methods has the following problems. That is, (1) The method of providing a copper or galvanized layer by electroplating on a steel pipe joint is applied to a joint made of a high alloying and high strength material whose usage is increasing in recent years. In addition, there is a great risk that delayed fracture may occur due to H ₂ entering from the plating bath into the plating layer and the steel. Further, when a metal which is more noble than a steel material such as Cu plating is provided as a plating layer under a long-term exposure to a corrosive environment containing hydrogen sulfide or the like, drilling from a plating layer defective portion is performed. Corrosion and H in case of galvanized layer
There is a problem that there is a high possibility that the corrosion accompanied by the generation of ₂ proceeds and penetrates into the steel to cause delayed fracture.

[0005] (2) Regarding the method of providing a manganese phosphate-based chemical conversion coating layer, the formation of a uniform chemical conversion coating layer is hindered depending on the type of steel component used in the manufacture of a steel pipe joint, so that sufficient galling property is obtained. Is difficult to secure. Also,
An increase in the number of make-ups and break-outs causes abrasion and damage of the chemical conversion coating layer, thereby deteriorating the galling resistance due to a decrease in lubricating performance, so that the number of repeated use of the steel pipe joint is limited.

(3) Regarding a method of forming a so-called solid lubricating film layer on a steel pipe joint by dispersing and mixing a fluororesin powder or a molybdenum disulfide powder, the surface roughness of the metal-metal seal portion of the steel pipe joint is described. By setting the thickness of the solid lubricating film layer to be equal to or less than the maximum surface roughness, the lubricating performance is improved by a synergistic effect of these. However, when the steel pipe joints resulting from these treatments are exposed to a corrosive environment for a long period of time, the corrosive aqueous solution penetrates through the solid lubricating film layer or the defective portion, causing corrosion of the steel substrate under the film. Of the adhesive deteriorates. Therefore, the solid-state lubricating film layer has a great tendency to deteriorate with time in adhesion. In particular, this tendency is remarkably promoted when wear and damage of the solid lubricating film layer occurs due to repeated make-up and break-out. Also,
Since the solid lubricating film layer itself is worn and damaged, when used for a long period of time, the life that can ensure its lubricating function is limited by itself. Therefore, the steel pipe joint according to the method is
Since the galling resistance is deteriorated due to peeling of the solid lubricating film layer over time or abrasion and damage of the film layer due to repeated use, there is a problem that the number of times of repeated use is limited. As described above, conventional steel pipe joints have not been sufficiently satisfactory in terms of galling resistance, corrosion resistance, and the range of use of the material steel component as a base material. In particular, while steel pipe joints are repeatedly used for a long period of time, a joint having sufficiently excellent performance has not been obtained.

[0007]

SUMMARY OF THE INVENTION The present invention addresses the aforementioned problems of conventional oil country tubular good joints, and in particular, galling resistance due to wear, damage and corrosion of the joint coating layer for repeated use of steel tubular joints over a long period of time. An object of the present invention is to provide a steel pipe joint which has a long service life and is excellent in galling resistance and corrosion resistance. Therefore, the gist of the present invention is to provide a manganese phosphate-based chemical conversion coating having a thickness of 5 μm to 25 μm on at least one side of a pin or a coupling of a steel pipe joint, particularly on a screw portion and a metal seal portion of a coupling material. Layer or thickness 1 μm to 20 μm
A manganese phosphate-based chemical conversion coating layer having a thickness of 5 μm to 25 μm and further containing molybdenum disulfide powder and one selected from an epoxy resin, a furan resin and a polyamideimide resin as essential components; ≤ {content of (molybdenum disulfide powder)} / {content of (one selected from epoxy resin, furan resin, polyamideimide resin)} ≤ 3.0 (weight ratio) It is characterized in that a solid lubricant is applied and a heat treatment is applied to form a solid lubricant film layer having a thickness of 10 μm to 45 μm.

Further, the present invention provides a steel pipe having a thickness of 5 μm to 25 μm with respect to a thread portion and a metal seal portion of a joint portion.
Manganese phosphate-based chemical conversion coating layer or 1 μm thick
A manganese phosphate-based chemical conversion coating layer having a thickness of 5 to 25 μm and a molybdenum disulfide powder and one or more of Cu and Zn powders of 10 to 50% by weight based on the powder. Species and one selected from epoxy resin, furan resin and polyamide-imide resin as an essential component, 0.5 ≤ {content of molybdenum disulfide powder} /｝ (epoxy resin, furan resin, polyamide-imide resin Applying a solid lubricant composed of a composition ratio of 一種 ≦ 3.0 (weight ratio) selected from the above and applying a heat treatment to form a solid lubricant film layer with a thickness of 10 μm to 45 μm. It is characterized by.

Further, in the present invention, the particle diameter of the molybdenum disulfide powder is in the range of 0.45 μm to 10 μm as measured by the Fischer method,
One or two kinds of powder having a particle diameter of 0.5 μm to 10 μm, an epoxy resin having a molecular weight of 2,000 to 10,000, a furan resin having a molecular weight of 150 to 250, and a molecular weight of 10, A solid lubricant film layer is formed by using a solid lubricant characterized by being composed of one selected from polyamideimide resins in the range of 2,000 to 25,000.

As described above, the method of the present invention provides a solid lubricating film layer having excellent lubricating performance and hardly causing wear and damage to a steel pipe joint in order to cope with a use condition in which sliding is repeated under a high surface pressure. We took steps to make it happen. That is, the molybdenum disulfide powder having excellent lubricating performance and an organic resin binder effective for improving toughness and hardness are selected, and the appropriate composition of a solid lubricating coating agent containing the molybdenum disulfide powder as an essential component is checked to ensure the performance. A method for obtaining a possible solid lubricating film layer was found and applied to the present invention. Furthermore, in the present invention, by incorporating an appropriate amount of one or two of Cu powder and Zn powder into the solid lubricant, it is possible to further improve the wear resistance under a high surface pressure of the solid lubricating coating layer. Headings,
Countermeasures based on its application were also taken. Therefore, by forming a solid lubricating film layer using the solid lubricant according to the configuration of the present invention, lubricating properties and abrasion resistance, that is, an effect of improving the film strength can be obtained.

In addition, after the solid lubricating film layer is treated and when exposed to a corrosive environment for a long period of time, the so-called adhesion with time is improved, and further, the solid lubricating film is formed by repeated sliding under a high surface pressure. In order to further improve the lubrication life even when the layer is worn or damaged, a manganese phosphate-based chemical conversion coating layer or a base nitriding layer and a manganese phosphate-based chemical conversion coating layer beneath the solid lubricating film layer. A countermeasure was taken to generate In other words, the manganese phosphate-based chemical conversion coating layer has a high adhesion strength to the material, and many voids are generated between the generated crystal grains. ,
It is formed. Therefore, a solid lubricating film layer having excellent adhesion is formed, and an effect of improving the adhesion with time due to the effect of suppressing corrosion under the coating of the manganese phosphate-based chemical conversion coating layer can be obtained. Furthermore, even after the solid lubricating film layer is worn or damaged, a long-term connection effect of the lubricating function due to the synergistic effect of the manganese phosphate-based chemical conversion film layer and the solid lubricating film layer trapped in the film layer is possible.

In the present invention, a base nitriding layer formed by a diffusion treatment may be provided prior to the manganese phosphate-based chemical conversion coating layer in some cases. Due to the nitriding treatment, a porous film having a high adhesion to the material is generated, so that the effect of improving the adhesion of the manganese phosphate-based chemical conversion film layer by the anchoring effect and the uniform formation of the chemical conversion film layer are difficult. The effect of improving the chemical conversion treatment is obtained. Therefore, the effect of providing the manganese phosphate-based chemical conversion coating layer and the solid lubricating coating layer in combination is further promoted. That is, the method of the present invention provides a manganese phosphate-based chemical conversion coating layer or a base nitrided coating layer and a manganese phosphate-based chemical conversion coating layer on a steel pipe joint, and a solid lubricating coating layer excellent in toughness, hardness and lubrication performance. By forming a surface treatment film layer, the surface treatment film layer which is extremely excellent in adhesion, film strength and lubricating performance, and in particular, can secure a lubricating life for a long period of time is formed. Therefore, the steel pipe joint according to the method of the present invention is extremely excellent in long-term use of a steel pipe, that is, increase in the number of repetitions of makeup and breakout. That is, it is possible to obtain a steel pipe joint having extremely excellent galling resistance which can prevent the occurrence of seizure as compared with the conventional method when used repeatedly for a long period of time.

Hereinafter, a surface treatment method for manufacturing a steel pipe joint which achieves the object of the present invention will be described in detail. Thus, in the present invention, a manganese phosphate-based chemical conversion coating layer having a thickness of 5 μm or more and 25 μm or less, or a base nitriding treatment layer having a thickness of 1 μm or more and 20 μm or less with respect to the steel pipe joint. A manganese phosphate-based chemical conversion coating layer having a thickness of 5 μm or more and 25 μm or less is provided. In other words, if the thickness of the manganese phosphate-based chemical conversion coating layer is less than 5 μm, the uniform coverage of the chemical conversion coating layer is not sufficient, and a sufficient effect of improving the adhesion to the solid lubricating coating layer is obtained, in particular, a long exposure to a corrosive environment. The effect of improving the adhesion after soaking, that is, the so-called adhesion after aging, is not good, and the lubricating performance after the consumption of the solid lubricating film layer is not good. Is inadequate. on the other hand,
When the manganese phosphate-based chemical conversion coating layer is formed with a thickness of more than 25 μm, secondary crystals are more likely to be formed, thereby deteriorating the adhesion of the coating layer itself and the adhesion of the solid lubricating coating layer. It is not preferable because the property is deteriorated. Therefore, in the present invention, the thickness of the manganese phosphate-based chemical conversion coating layer is limited to the range of 5 μm to 25 μm, preferably 10 μm to 20 μm.

Further, in the present invention, if necessary, the manganese phosphate-based chemical conversion coating layer is further improved in adhesion strength, or the manganese phosphate-based chemical conversion coating is applied to a steel pipe joint of a steel component that inhibits uniform formation of the coating layer. For the purpose of promoting the uniform formation of the treated film layer and ensuring the lubrication effect after the consumption of the solid lubricating film layer for a long period of time, a nitriding layer by diffusion treatment is provided as a base treatment layer of the manganese phosphate-based chemical conversion film layer. . Thus, in order to obtain these effects, the thickness of the underlying nitrided layer is limited to the range of 1 μm to 20 μm. The thickness of the underlying nitrided layer is 1 μm.
If it is less than m, many defects are generated in the nitrided layer, so that the above effects are hardly obtained, which is not preferable. On the other hand, if the thickness of the under-nitrided layer exceeds 20 μm, the above-described effect is saturated, and the hardness of the nitrided layer is rather high. . Therefore, in the present invention, the thickness of the underlying nitrided layer is 1 μm or more to 20 μm or more.
The thickness is limited to a range of not more than μm, preferably not less than 5 μm and not more than 15 μm.

Thus, a manganese phosphate chemical conversion treatment is applied to the steel pipe joint.
Manufacture of a manganese phosphate with a coating layer or a base nitriding layer
The method of providing the pretreatment film layer is particularly limited.
Not something. In other words, manganese phosphate conversion treatment
Degrease, pickle, or degrease or short
Surface cleaning and activation treatment such as toblast
Later, to improve the galling resistance of such conventional steel pipe joints
A known manganese phosphate-based chemical conversion treatment method that has been performed is
Applied. For example, the surface cleaning and activation
Manganese phosphate system directly or after pretreatment
A chemical conversion treatment is performed. As the pretreatment bath, for example, the concentration
Is 0.1 to 3.0 g / l (titanium colloid-pyrroline
Acid soda) bath, (manganese colloid-so pyrophosphate)
D) A system bath is used, but it is not specified.
No. The subsequent manganese phosphate conversion treatment
However, in the present invention, it is not particularly specified.
For example, contains manganese phosphate as a main component
(Mn²⁺−Ni²⁺-PO_Four ^3--NO_Three ^-) Chemical conversion treatment
Bath or (Mn²⁺−Ni²⁺-Fe²⁺-PO_Four ^3--N
O _Three ^--F^-) A chemical conversion treatment bath is used, and the temperature is 75-
Coating at 98 ° C with processing time corresponding to target coating thickness
A layer is provided.

On the other hand, with respect to a method of applying a base nitriding layer and a manganese phosphate-based chemical conversion coating layer, the nitriding layer is provided as follows. That is, after a steel pipe joint is subjected to degreasing, pickling or degreasing, surface cleaning such as shot blasting and activation treatment, and nitriding treatment, the treatment bath composition is as follows: (A) NaCN 25% KCN 10% NaCNO A molten salt bath containing a nitrogen compound such as 25% KCNO 10% Na ₂ CO ₃ 20% K ₂ CO ₃ 10% (B) NaCNO 10% KCNO 45% Na ₂ CO ₃ 10% K ₂ CO ₃ 35% The treatments used are selected in accordance with the applicable conditions such as the size of the steel pipe joint and the treatment temperature in order to obtain the desired thickness of the nitriding treatment layer at a bath temperature of 400 to 700 ° C. Processed in time.

Next, the steel pipe joint subjected to the nitriding treatment is subjected to a manganese phosphate-based chemical conversion treatment film layer in the same manner as described above, after degreasing and washing, or after surface cleaning and activation treatment such as pickling and washing with water. Is provided. Furthermore, in order to achieve the object of the present invention, the occurrence of seizure and scumming of a steel pipe joint having a manganese phosphate-based chemical conversion coating layer or a base nitriding layer and a manganese phosphate-based chemical conversion coating layer configured as described above. In order to further improve the function of preventing the problem, a solid lubricant film layer is provided. Thus, in order to achieve the object of the present invention, the solid lubricating film layer has excellent adhesion to the manganese phosphate-based chemical conversion coating layer, and has excellent lubricating performance and film strength under high surface pressure. It is necessary that a layer be formed.

Therefore, in the present invention, molybdenum disulfide powder for imparting a lubricating function to the film is contained as an essential component, and the molecular weight is 2,000 each for the purpose of improving the adhesion and the film strength of the film. Epoxy resin in the range of 10,000 to 15, 15
Furan resin in the range of 0 to 250 and 10,000 to 2
A solid lubricant composed of a binder selected from the group consisting of 5,000 polyamideimide resins is used. Further, with respect to the solid lubricant, for the purpose of further improving the wear resistance of the formed film,
If necessary, one or two of Cu powder and Zn powder are contained.

Therefore, in order to achieve the object of the present invention, the material to be treated is prepared by adding molybdenum disulfide powder having a particle size of 0.45 μm to 10 μm measured by the Fischer method and the above-mentioned organic resin to 0.5%. ≤ {content of molybdenum disulfide powder} / {content of (selected from epoxy resin, furan resin or polyamideimide resin)} ≤ 3.0 (weight ratio) solid lubrication composed of composition ratio Apply agent, 150 ℃ ~
It is necessary to form a solid lubricating film layer having a thickness of 10 μm or more and 45 μm or less by performing a heat baking treatment in a temperature range of 300 ° C. That is, when the particle diameter of the molybdenum disulfide powder added to the solid lubricant measured by the Fischer method is less than 0.45 μm, the effect of improving the lubrication function on the galling resistance of the molybdenum disulfide powder, which is the object of the present invention, is obtained. hard.

On the other hand, if the particle size exceeds 10 μm, the effect of improving the lubricity of the molybdenum disulfide powder contained in the film is saturated, and it is difficult to adjust the thickness of the target solid lubricating film layer. Therefore, it is not preferable. Therefore, the molybdenum disulfide powder used in the present invention has a particle diameter of 0.45 μm measured by the Fischer method.
m to 10 μm, preferably 2 μm to
It is restricted to a range of 5 μm or less. Further, the organic resin binder constituting the lubricant has an epoxy resin having a molecular weight of 2,000 to 10,000 and a furan resin having a molecular weight of 150 to 150, respectively.
~ 250, polyamide-imide resin is 10,000 ~ 2
Regulated to 5,000. That is, when the molecular weight of the epoxy resin is less than 2,000, the molecular weight of the furan resin is less than 150, and the molecular weight of the polyamide-imide resin is less than 10,000, the toughness and hardness aimed at by the present invention are imparted to the resulting film. When the molecular weight of the epoxy resin exceeds 10,000, the molecular weight of the furan resin exceeds 250, and the molecular weight of the polyamide-imide resin exceeds 25,000, the effect of improving the toughness and hardness of the formed film is reduced. In addition to being saturated, it is difficult to uniformly apply the treating agent to a predetermined thickness, and the adhesion between the formed film and the manganese phosphate-based chemical conversion film deteriorates.

Therefore, in the present invention, the organic resin binder used for the lubricant applied to the formation of the solid lubricating film layer has a molecular weight of 2,000 to 10,000 or less, preferably 3,000 to 5 Epoxy resin having a molecular weight of 150 to 250 or less, preferably 17 to 2,000.
Furan resin in the range of 0-220, molecular weight 10,000
~ 25,000 or less, preferably 15,000-20,
In addition to being restricted to polyamideimide resins in the range of 000, one kind selected from these resins is used.

In order to achieve the desired effects of the present invention, the composition ratio of the molybdenum disulfide powder and the organic resin binder is important for the solid lubricant for forming the solid lubricating film layer. In the present invention, the composition ratio is 0.5% by weight (content of molybdenum disulfide powder) / (content of one selected from epoxy resin, furan resin or polyamideimide resin) by weight. The amount is regulated within the range of ≤ 3.0 (weight ratio). When the composition ratio is less than 0.5, it is difficult to obtain the desired lubricating function of the solid lubricating film layer to be formed, and when the composition ratio exceeds 3.0, the solid lubricating film layer is formed. In addition, the adhesion of the solid lubricating film layer deteriorates, and in particular, the molybdenum disulfide powder is unpreferably peeled off from the film layer. Therefore,
The composition ratio of molybdenum disulfide powder, which is an essential component of the treatment agent used to form the solid lubricating film layer, and the organic resin binder is in the range of 0.5 to 3.0, preferably 0.8 to 3.0. It is regulated in the range of 2.0.

In the present invention, in order to further improve the wear resistance of the solid lubricating film layer formed, one or two of Cu powder and Zn powder are added to the treating agent as required. These powders have a particle size of 0.5 μm or more.
It is used in a range of 10 μm or less, and is added in a range of 10% to 50% (% by weight) to molybdenum disulfide powder contained in the treatment agent. That is, the particle size is 0.5
Even if Cu powder or Zn powder having a particle size of less than μm is contained in the solid lubricating coating layer, the effect of improving the strength of the coating layer is small, and when the particle size used exceeds 10 μm,
It is not preferable because it is difficult to adjust the thickness of the solid lubricating film layer to a predetermined thickness.

When the amount of these powders is less than 10% by weight with respect to the molybdenum disulfide powder, the intended effect of improving the abrasion resistance is small. It is not preferable because the lubricating performance of the solid lubricating coating layer and the adhesion to the manganese phosphate-based chemical conversion coating layer are deteriorated. Therefore, Cu is added to the solid lubricant.
When powder or Zn powder is added and used, the particle size is 0.5 μm or more and 10 μm or less, preferably 0.8 μm or less.
μm to 6.5 μm, and the amount of addition is limited to the range of 10% to 50% by weight, preferably 20% to 42.5% by weight based on the molybdenum disulfide powder. Is done.

Thus, the viscosity of the solid lubricant constituted as described above is adjusted by using a solvent in accordance with a target film thickness, a coating method and the like, and the manganese phosphate-based chemical conversion is performed. It is applied to a steel pipe joint that has been subjected to a treatment or a base nitriding treatment and a manganese phosphate chemical conversion treatment. The viscosity adjusting method or the coating method of these solid lubricants is not particularly limited in the present invention, and the viscosity is adjusted by a conventionally used method, for example, using a ketone-based solvent as a solvent. The coating process is performed by a spray coating method or the like. Next, in the present invention in which the solid lubricating layer is formed by subjecting the steel pipe joint to which the solid lubricant has been applied to the heating and baking treatment to form the solid lubricating film layer intended for the present invention, the method or conditions for the heating and baking treatment is as follows. Not specifically defined, the heating temperature is arbitrarily set according to the properties of the organic resin binder used for the solid lubricant, and also regarding the heating method,
A conventionally known method is adopted. For example, hot air drying, gas or electric heating, an infrared method, etc. are used, and the heating temperature is 150 ° C to 300 ° C, preferably 180 ° C to 27 ° C.
Heat baking is performed in a temperature range of 0 ° C. The heat treatment time may be set arbitrarily in accordance with the size, shape, etc. of the steel pipe joint, and also shortens the heat treatment time and prevents sagging during the heat baking after the application of the solid lubricant. Therefore, measures such as performing a pre-heat treatment on the steel pipe joint before applying the solid lubricant may be taken.

According to these methods, the thickness of the solid lubricating film layer formed on the steel pipe joint is 10 μm or more to 45 μm.
It is regulated in the following range. When the coating thickness is less than 10 μm, the effect of improving the lubricating performance aimed at by the present invention is small, and in particular, problems such as a decrease in the number of repeated use of make-up and breakout of the steel pipe joint are caused. . On the other hand, if the thickness of the coating layer exceeds 45 μm, the effect of improving the lubricating function is saturated and it is economically disadvantageous. Rather, the tendency for the adhesion of the solid lubricating coating layer to degrade is increased, which is not preferable because it may cause stuffiness due to peeling of the coating layer. Therefore, in the method of the present invention, the solid lubricating film layer has a thickness of 1
0 μm or more to 45 μm or less, preferably 15 μm or more
It is restricted to a range of 30 μm or less.

By forming a solid lubricating film layer on the manganese phosphate-based chemical conversion coating film using the solid lubricant configured as described above, the solid lubricating film can be combined with the manganese phosphate-based chemical conversion coating film. The adhesiveness is extremely excellent due to the interaction of, and the toughness and hardness of the film, that is, the film strength and lubrication performance are extremely excellent. In particular, for the intended use of the present invention, of the above-described solid lubricants, a molybdenum disulfide powder-a polyamideimide resin and a solid lubricant obtained by adding a Cu powder or a Zn powder to each are used. The solid lubricating film layer is superior in toughness and hardness as compared with other resin systems, and the wear resistance is further improved by the effect of adding Cu powder and the like, so that a more excellent effect is obtained. In other words, the strength of the formed solid lubricating film layer is particularly excellent, so the make-up and breakout over a long period of time can be repeated due to the effect of improving the film life under the operating conditions of repeated sliding under high surface pressure. It is extremely effective for

As described above, in the present invention, the steel pipe joint is provided with a manganese phosphate-based chemical conversion coating layer or a base nitridation coating layer and a manganese phosphate-based chemical conversion coating layer, and through these coating layers, adhesion and film strength. Since a composite coating layer composed of a solid lubricating coating layer having extremely excellent lubricating performance is formed, a steel pipe joint having extremely excellent galling resistance can be obtained under a long-term use condition due to a synergistic effect of these respective coating layers. In addition, a steel pipe joint having a composite coating layer according to the method of the present invention is made up by applying compound grease to a thread portion or a metal seal portion,
Not only under normal working conditions where breakout is performed, but also under conditions where compound grease is not sufficiently applied, or under use conditions where compound grease is not applied intentionally, film seizure may occur. It hardly occurs and is extremely excellent in galling resistance.

Further, the treatment of the present invention relates to a joint portion used for connection of an oil country tubular good, that is, a pin formed of a threaded portion formed at the tip of the oil country tubular good and a tapered portion formed at the base thereof, and a screw portion formed between the threaded portion and the threaded portion. It may be applied to both the mating screw part and the coupling with a tapered part formed at the tip,
Also, it may be applied to only one of them, especially to the coupling. The present invention particularly refers to the coating structure of the oil country tubular good threaded joint, and does not specify the combination of the coating and the joint shape.

[0030]

According to the present invention, a manganese phosphate-based chemical conversion coating layer or a base nitriding coating layer and a manganese phosphate-based chemical conversion coating layer are provided on a steel pipe joint, and the adhesion is extremely improved through these coating layers. At the same time, a solid lubricating film layer having remarkably excellent toughness, hardness and lubricating performance is formed. As a result, the solid lubricating film layer having excellent film strength and lubricating performance under the use conditions of repeatedly subjecting to sliding under a high surface pressure by the method of the present invention, that is, under conditions where make-up and breakout are repeated, and phosphoric acid The synergistic effect of the manganese chemical conversion coating layer or the underlying nitriding coating layer and the manganese phosphate chemical conversion coating layer prevents the seizure of seals and threads due to contact between metals in the steel pipe joints, and prevents the occurrence of stuffiness, especially repeated use A steel pipe joint having remarkably excellent durability against an increase in the number of times can be obtained.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For a joint part of a steel pipe, that is, a coupling (joint member) 1 and a pin 2 (steel pipe end joint part) shown in FIG. 1, a screw part 3 and a metal-metal seal part 4 constituting each joint part. On the other hand, a steel pipe in which only the coupling 1 or the coupling 1 and the pin 2 are provided with a manganese phosphate-based chemical conversion coating layer, or a base nitriding treatment, a manganese phosphate-based chemical conversion coating layer, and a solid lubricating coating layer according to the method of the present invention. Joints were prepared and subjected to an evaluation test. That is, the coupling material 1 and the pin 2 were fitted to the evaluation material subjected to the treatment of the present invention as shown in FIG. Next, make-up is performed by a tightening machine at a predetermined torque value according to the test conditions, and a high surface pressure is applied to the screw portion 3 and the metal-metal seal portion 4 of the coupling 1 and the pin 2 in FIG. Slided. After that, the coupling 1 and the pin 2 were rotated in a direction opposite to the make-up by a tightening machine to break out. After the breakout, the coupling 1, the screw portion 3 of the pin 2, and the metal-metal seal portion 4 were observed, and the state of peeling of the surface treatment film and the state of occurrence of galling were investigated. As a result of the investigation, when peeling of the film and galling did not occur or when the degree was slight, the coupling 1 and the pin 2 were further fitted together, and make-up was performed under the same conditions using the above-described tightening machine. As described above, make-up and break-out were repeated for the evaluation material until peeling of the film and galling occurred, and the evaluation was performed up to 20 times for evaluation. At the time of make-up and break-out, an evaluation test was performed by rotating the pin with respect to the coupling at a speed of 1 to 3 rpm.

Example 1 Inner Diameter Made Using Steel Material Equivalent to API P110
5 inch coupling 1 and corresponding size
After degreasing the tip of the pin 2 using a water-based degreasing agent and washing with water,
Perform acid washing and water washing in a 2% HCl aqueous solution at room temperature for 20 seconds.
Immediately (9.5 g / l Mn²⁺-0.15g / l Ni²⁺−
1.0g / l Fe²⁺-36g / l PO_Four ^3--6.1 g / l NO
_Three ^--0.3g / l F^-Manganese phosphate based bath)
Phosphoric acid by treatment at 95 ° C for 10 minutes in a bath
A manganese chemical conversion coating layer was provided. Then average particles
Molybdenum disulfide powder having a diameter of 2.5 μm and an average molecular weight of 4,
Contains 200 epoxy resins as main component
｛(Molybdenum disulfide powder with an average particle size of 2.5 μm)
Content｝ / ｛(epoxy resin with average molecular weight of 4,200)
A solid lubricant having a composition ratio of｝ = 1.3 (weight ratio) is applied at 180 ° C.
Apply a 20-minute heat baking process to solid lubricant skin
A film layer was provided. That is, coupling by the treatment of the present invention.
For the threaded part 3 of the ring 1 and the pin 2 and the metal seal part 4
Each of the manganese phosphate-based chemical conversion coating layers 18 μm and
Evaluation of a two-layer coating layer consisting of 16.5 μm solid lubrication layer
It was formed into a material. Screw part 3 of coupling 1 and pin 2
API BU15A2 Se on the metal seal part 4
Apply compound grease equivalent to ct2 and seal
3,000 kg / cm for 4 ^Two While applying the surface pressure of
Make-up and breakout
Strike. The result of repeating this test 15 times is
There was no sticking or sticking of the seal,
Burn-in and stuffiness are quite raw in the 16th test
I did

Comparative Example 1 Inner Diameter Made of Steel Material Equivalent to API P110
The 5-inch coupling 1 and the tip of the pin 2 are degreased and washed with a water-based degreasing agent, and then pickled in a 12% HCl aqueous solution at room temperature for 20 seconds, washed with water, and then the solid lubricant of Example 1 is washed. A comparative example was provided in which only the solid lubricating film layer having a film thickness of 16.5 μm was provided on the screw portion 3 and the metal seal portion 4 of the coupling 1 and the pin 2. The comparative material was subjected to an evaluation test under the same conditions as in Example 1. As a result, the solid lubricating film layer was considerably peeled off at the seventh test, and seizure and stuffiness occurred remarkably at the eighth test.

Example 2 A 7-inch inner diameter steel plate made of steel equivalent to K-55
The coupling 1 is degreased and washed with a solvent-based degreasing agent,
(20% NaCN-15% KCN-17.5% NaCN
O-17.5% KCNO-10% Na_TwoCO_Three-20%
K_TwoCO_Three) At 450 ° C for 30 minutes
During the heating, nitriding treatment was performed, followed by cooling in an oil bath. The
Solvent degreasing of nitriding material, 5% H_TwoSO_FourIn aqueous solution
After pickling and water washing at room temperature for 5 seconds, 0.8 g / l (titanium
Lloyd-sodium pyrophosphate) at room temperature with a pretreatment bath
Minutes, and then (8.7 g / l Mn²⁺−
0.2g / l Ni²⁺-0.6 g / l Fe²⁺-32.3 g / l P
O_Four ^3--5.7 g / l NO_Three ^--0.6g / l F^-Or a system bath
Manganese phosphate-based chemical conversion bath at 90 ° C, 1
A manganese phosphate-based chemical conversion coating layer was formed by treating for 5 minutes.
I did. Next, molybdenum disulfide having an average particle size of 2.8 μm
Powder and furan resin with an average molecular weight of 185
｛(Molybdenum disulfide powder with an average particle size of 2.8 μm)
Content｝ / ｛(furan resin with average molecular weight of 185)
A solid lubricant having a composition ratio of the amount｝ = 1.8 (weight ratio) is applied, and at 200 ° C.
Heat baking for 30 minutes to give a solid lubricating film
Layers were provided. That is, the treatment of the present invention
To the thread 3 and metal-metal seal 4 of
6.4 μm of each nitrided layer, manganese phosphate chemical conversion treatment
From coating layer 14.5μm and solid lubricating coating layer 10μm
Was formed on the evaluation material. Same as Example 1
Apply compound grease to seal part 4
4,000kg / cm^Two While applying surface pressure to the joint
Make-up and break-out tests
Was done. Burn-in of the seal up to the 14th test
There was almost no swelling, but in the 15th test
There was considerable seizure and stuffiness.

Comparative Example 2 A coupling 1 having an inner diameter of 7 inches made of a steel material equivalent to K-55 was manufactured in the same manner as in Example 2.
A 6.4 μm-thick nitriding layer and a 14 μm-thick manganese phosphate chemical conversion coating layer were provided on the screw portion and the metal seal portion 4 of the coupling 1. Next, the average particle size is 2.8.
μm molybdenum disulfide powder and furan resin having an average molecular weight of 185 as main components, and the content of ｛(molybdenum disulfide powder having an average particle size of 2.8 μm)｝ / ｛(furan resin having an average molecular weight of 185) A solid lubricant composed of a composition ratio of content｝ = 0.3 (weight ratio) was applied, baked at 200 ° C. for 30 minutes, and a solid lubricant film layer having a thickness of 10 μm was provided. Example. An evaluation test was performed on the comparative material under the same conditions as in Example 2. As a result, the lubricating property was not sufficient, and seizure and stuffiness occurred remarkably at the seventh repetition test, and the evaluation test was interrupted.

Example 3 A 7-inch inner diameter tube made of a steel material equivalent to T-90.
After dewatering and washing the coupling 1 with water,
Shot (particle diameter♯100, pressure 5kgf / cm^Two ,
60%) followed by (25% NaCN-10% K
CN-25% NaCNO-10% KCNO-20% Na
_TwoCO_Three-10% K_TwoCO_Three) In a molten salt bath
Heat nitriding at ℃ for 20 minutes and cool in oil bath
Rejected. Degreasing the nitriding material with an aqueous degreasing agent, 10%
H_TwoSO_FourPickling, water washing for 10 seconds at room temperature in aqueous solution
Thereafter, 0.5 g / l of (manganese colloid-sodium pyrophosphate)
Pre-treatment for 20 seconds at room temperature using a system pre-treatment bath
(8g / l Mn²⁺−0.3g / l Ni²⁺−0.2
g / l Fe²⁺-29.5g / l PO_Four ^3--5.4 g / l NO _Three
^--0.8g / l F^-Manganese phosphate-based chemical bath
Using a treatment bath, the phosphoric acid polymer was treated at 85 ° C for 13 minutes.
A gun-based chemical conversion coating layer was provided. Then, the average particle size
3.0 μm molybdenum disulfide powder with an average molecular weight of 20,
000 polyamideimide resin as main component
｛(Molybdenum disulfide powder having an average particle size of 3.0 μm)
Content｝ / ｛(Polyamide with average molecular weight of 20,000)
A solid lubricant composed of a composition ratio of 固体 = 0.8 (weight ratio)
Heat baking for 30 minutes to give a solid lubricating film
Layers were provided. That is, the treatment of the present invention
To the screw 3 and metal seal 4 of
Passivation layer 10 μm, manganese phosphate-based passivation layer 12
μm and 18.5μm solid lubricant film layer
A film layer was formed on the evaluation material. As in the first embodiment,
Apply pound grease and apply 4,000k to seal part 4.
g / cm^Two Make the joint part
Up and breakout tests were performed repeatedly. The
Up to the 19th test, most of burn-in and stuffiness occurred
It did not occur, but burned in the 20th test
There was a lot of stuffiness.

COMPARATIVE EXAMPLE 3 With respect to a coupling 1 having an inner diameter of 7 inches made of a steel material equivalent to T-90, a threaded portion 3 and a metal seal portion 4 were coated with a nitriding layer 10 μm and phosphoric acid in the same manner as in Example 3. A manganese chemical conversion coating layer 12 μm was provided. Next, while containing molybdenum disulfide powder having an average particle size of 3.0 μm and a polyamideimide resin having an average molecular weight of 20,000 as main components, the content of {(molybdenum disulfide powder having an average particle size of 3.0 μm) content} / A solid lubricant having a composition ratio of {(polyamideimide resin having an average molecular weight of 20,000)} = 4.0 (weight ratio) is applied, and heated and baked at 200 ° C. for 30 minutes. , Thickness 18.5
A solid lubricating film layer having a thickness of μm was formed to obtain a comparative example.
Compound grease was applied to the comparative material in the same manner as in Example 3, and a make-up and break-out test was repeatedly performed on the joint portion while applying a surface pressure of 4,000 kg / cm ² to the seal portion 4. Was. As a result, peeling of the solid lubricating film layer was remarkable, and the evaluation test was interrupted in the sixth test.

Example 4 Inner Diameter Made Using Steel Material Having 9% Cr-1% Mo
7-inch coupling 1 is water-based degreasing, glass beads
Shot (particle diameter: 、 100, pressure: 5kgf / cm ^Two , 90
Second), followed by (25% NaCN-10% KCN)
-20% NaCNO-15% KCNO-20% Na_TwoC
O_Three-10% K_TwoCO_Three) In a molten salt bath at 580 ° C.
Heat-nitrid for 15 minutes, cool in oil bath
Was. Degreasing the nitriding material with an aqueous degreasing agent, 10% H_Two
SO_FourAfter pickling and water washing for 5 seconds at room temperature in an aqueous solution, the solution was washed with water.
5 g / l (manganese colloid-sodium pyrophosphate) type
Have you performed the pre-treatment step in the pre-treatment bath at room temperature for 2 minutes?
Et al., (9 g / l Mn²⁺−0.2g / l Ni²⁺-0.6g / l F
e²⁺-33.5 g / l PO_Four ^3--5.7 g / l NO_Three ^-−
0.6g / l F^-) A manganese phosphate chemical conversion treatment consisting of a system bath
Manganese phosphate by treatment at 88 ° C for 10 minutes in a bath
A chemical conversion coating layer was provided. Then, coupling 1
After preheating at 175 ° C. for 15 minutes,
3.0 μm molybdenum disulfide powder with an average molecular weight of 20,
000 polyamideimide resin as main component
｛(Molybdenum disulfide powder having an average particle size of 3.0 μm)
Content｝ / ｛(Polyamide with average molecular weight of 20,000)
Solid resin consisting of a composition ratio of 比 = 1.0 (weight ratio) at 240 ° C.
Heat baking for 30 minutes to give a solid lubricating film
Layers were provided. That is, the treatment of the present invention
To the screw 3 and metal seal 4 of
Chemical conversion layer 11.5 μm, manganese phosphate chemical conversion coating layer
3 composed of 13.5 μm and a solid lubricating film layer of 20 μm
A layer coating layer was formed on the evaluation material. For the evaluation material,
Screw part 3 of coupling 1 and pin 2 and metal seal
Under conditions where no compound grease is applied to part 4,
3,500 kg / cm^Two Apply surface pressure
And make-up and break-out
A repeat test was performed. Repeat the test 12 times
As a result, the peeling of the coating layer was relatively small,
13th time
In the test, there was considerable seizure and stuffiness.

Comparative Example 4 A coupling 1 having an inner diameter of 7 inches made of a steel material having 9% Cr-1% Mo was subjected to water-based degreasing, and the inner surface of the coupling 1 was subjected to a pre-treatment by shot blast so that the inner surface of the coupling 1 had a maximum surface roughness. It was adjusted to 25 μm. Then at 175 ° C for 15
After preheating for 20 minutes, a solid lubricating film layer of 20 μm was formed under the same conditions as in Example 4 to obtain a comparative example. Repeated test of make-up and break-out on the joint part while applying a surface pressure of 3,500 kg / cm ² to the seal part 4 without applying compound grease to the comparative material as in Example 4. Was done. As a result, in the fourth test of the repetition test, burn-in and stuffiness were remarkable, and the evaluation test was interrupted.

Example 5 A coupling 1 having an inner diameter of 7 inches made of a steel material corresponding to L-80 was degreased and washed with a water-based degreasing agent, and was immersed in a 10% H ₂ SO ₄ aqueous solution at 50 ° C. After pickling for 10 seconds and washing with water, a pretreatment for 1 minute at room temperature was carried out with a 0.5 g / l (titanium colloid-sodium pyrophosphate) pretreatment bath to obtain (9.5 g / l Mn ²⁺ -0.1 g / l ⁾ . 15 g / l Ni2 ⁺ -0.
^{9g / l Fe 2+ -36g / l} PO 4 3- -6.1g / l NO 3 -
Using a manganese phosphate-based chemical conversion bath composed of a -0.5 g / l F ^- ) ^- based bath, a manganese phosphate-based chemical conversion coating layer was formed by treatment at 95 ° C for 10 minutes. Next, while containing, as main components, molybdenum disulfide powder having an average particle diameter of 4.0 μm and 1.0 μm and a polyamideimide resin having an average molecular weight of 16,000, [｛(molybdenum disulfide powder having an average particle diameter of 4.0 μm)
Of molybdenum disulfide powder composed of 75% by weight of the above and 25% by weight of (molybdenum disulfide powder having an average particle diameter of 1.0 μm) / {content of (polyamideimide resin having an average molecular weight of 16,000)} = 1.1 (weight ratio) A solid lubricant having a composition ratio of 1.1 was applied and heated and baked at 260 ° C for 25 minutes to form a solid lubricant film layer. That is, by the treatment of the present invention, a two-layer coating layer composed of a manganese phosphate-based chemical conversion coating layer 15 μm and a solid lubricating coating layer 15 μm was formed on the screw portion 3 and the metal seal portion 4 of the coupling 1 respectively. As in Example 1, the compound grease was applied, while applying a surface pressure of 4,000 kg / cmm ² the sealing portion 4, make-up, the repeated testing of breakout was performed on joint portions. No seizure and no wrinkles occurred up to the 18th test, but considerable seizures and wrinkles occurred in the 19th test.

COMPARATIVE EXAMPLE 5 For a coupling 1 having an inner diameter of 7 inches prepared using a steel material corresponding to L-80, a 15 μm thick phosphoric acid was applied to the screw portion 3 and the metal seal portion 4 in the same manner as in Example 5. A manganese chemical conversion coating layer was provided. Then, Example 5
A solid lubricant having the same composition as that described above was applied and subjected to a heat baking treatment at 260 ° C. for 25 minutes to form a solid lubricant film layer having a thickness of 5 μm, which was used as a comparative example. Compound grease was applied to the comparative material in the same manner as in Example 5, and a make-up and break-out test was repeatedly performed on the joint portion while applying a surface pressure of 4,000 kg / cm ² to the seal portion 4. Was. As a result, in the tenth repetition test, seizure and stuffiness were remarkable, and the evaluation test was interrupted.

Example 6 A coupling 1 having an inner diameter of 7 inches made of a steel material corresponding to API P110 was degreased using an aqueous degreasing agent.
After washing with water, pickling in a 15% H ₂ SO ₄ aqueous solution at room temperature for 18 seconds, and washing with water, immediately (9.5 g / l Mn ²⁺ −0.1
^{5g / l Ni 2+ -0.4g / l} Fe 2+ -36g / l PO 4 3- -
A manganese phosphate-based chemical conversion coating layer was formed by treatment at 90 ° C. for 20 minutes using a manganese phosphate-based chemical conversion bath composed of 6.1 g / l NO ₃ ⁻ -0.3 g / l F ⁻ ) -based bath. . Next, after pre-heating the coupling 1 at 180 ° C. for 15 minutes, molybdenum disulfide powder having an average particle diameter of 4.3 μm, Cu powder having an average particle diameter of 1.0 μm, and a polyamideimide resin having an average molecular weight of 20,000 were added. While containing as a main component, [｛(molybdenum disulfide powder with an average particle diameter of 4.3 μm)
Of {a mixture of 71% by weight of the above and 29% by weight of (Cu powder having an average particle diameter of 1.0 μm)} / {content of (a polyamideimide resin having an average molecular weight of 20,000)}
= 1.0 (weight ratio) (* Amount of Cu powder added to molybdenum disulfide powder;
A solid lubricant having a composition ratio of about 41% by weight) was applied, and a heat treatment was performed at 270 ° C. for 20 minutes to form a solid lubricant film layer. That is, by the treatment of the present invention, a two-layer coating layer composed of a manganese phosphate-based chemical conversion coating layer 16 μm and a solid lubricating coating layer 17 μm was formed on the screw portion 3 and the metal seal portion 4 of the coupling 1 respectively. Compound grease was applied in the same manner as in Example 1, and a repeated make-up and break-out test was performed on the joint while applying a surface pressure of 4,000 kg / cm ² to the seal 4. The test was repeated 20 times, and as a result, seizure of the seal portion and generation of stuffiness were extremely small and very good.

COMPARATIVE EXAMPLE 6 A coupling 1 having an inner diameter of 7 inches prepared using a steel material corresponding to API P110 was subjected to water-based degreasing and then subjected to a shot blast pretreatment to obtain a maximum surface roughness of the inner surface of the coupling 1 of 35 μm. The surface was adjusted. A manganese phosphate-based chemical conversion coating layer having a thickness of 16 μm was formed on the screw portion 3 and the metal seal portion 4 of the coupling 1 in the same manner as in Example 6 to obtain a comparative example. Compound grease was applied to the comparative material in the same manner as in Example 6, and the sealing portion 4
The joint was repeatedly subjected to make-up and break-out tests while applying a surface pressure of 4,000 kg / cm ² to the joint. As a result, in the ninth repetition test, burn-in and stuffiness were remarkable, and the evaluation test was interrupted.

Example 7 A coupling 1 having an inner diameter of 7 inches made of a steel material corresponding to L-80 was degreased and washed with a water-based degreasing agent, and then washed in a 12.5% H ₂ SO ₄ aqueous solution at room temperature. After pickling for 15 seconds, after washing with water, use a 0.3 g / l (manganese colloid-sodium pyrophosphate) -based pretreatment bath at room temperature for 30 seconds.
After pre-treatment for 8 seconds, (8 g / l Mn ²⁺ -0.15
g / l Ni ²⁺ -0.4 g / l Fe ²⁺ -29.5 g / l PO ₄ ^{3-
_{-6.1g / l NO 3 - -0.7g /}} l F -) using manganese phosphate chemical conversion treatment bath consisting based bath, 80 ° C., yielding manganese phosphate-based chemical conversion coating layer by the 10-minute treatment Was. Next, the coupling 1 was preheated at 180 ° C. for 15 minutes, and then molybdenum disulfide powder having an average particle diameter of 4.3 μm, Cu powder having an average particle diameter of 1.0 μm, and a polyamideimide resin having an average molecular weight of 19,000 were added. While containing as a main component, [｛(molybdenum disulfide powder with an average particle diameter of 4.3 μm)
Of 80% by weight and 20% by weight of (Cu powder having an average particle diameter of 1.0 μm) * {content of (a polyamideimide resin having an average molecular weight of 19,000)}
= 1.0 (weight ratio) (* Amount of Cu powder added to molybdenum disulfide powder;
A solid lubricant having a composition ratio of about 25% by weight was applied, and a heat treatment was performed at 270 ° C. for 20 minutes to form a solid lubricant film layer. That is, a two-layer coating layer composed of a manganese phosphate-based chemical conversion coating layer 10.5 μm and a solid lubricating coating layer 28.5 μm was formed on the screw part 3 and the metal seal part 4 of the coupling 1 by the treatment of the present invention, respectively. I was sorry. In the same manner as in the embodiment 4, under the condition that the compound grease is not applied to the screw portion 3 of the coupling 1 and the pin 2 and the metal seal portion 4, 4,000 is applied to the seal portion 4.
While applying a surface pressure of 0 kg / cm ² , a repeated make-up and break-out test was performed on the joint portion. The test was repeated 13 times. As a result, the seizure of the seal portion and the occurrence of stuffiness hardly occurred.
In the second test, seizure and stuffiness occurred considerably.

COMPARATIVE EXAMPLE 7 A coupling 1 having an inner diameter of 7 inches made of a steel material corresponding to L-80 and having a thickness of 10.5 μm was formed on the screw portion 3 and the metal seal portion 4 in the same manner as in Example 7. Was provided as a comparative example.
4,000 kg / cm ^{2 of the} comparative material was applied to the seal portion 4 without applying compound grease in the same manner as in Example 7.
Repeated make-up and break-out tests were performed on the joints while applying the surface pressure of. As a result, in the third test of the repetition test, burn-in and stuffiness were remarkable, and the evaluation test was interrupted.

Example 8 A nitrided layer and a manganese phosphate-based chemical conversion coating were applied to a coupling 1 having an inner diameter of 7 inches prepared using a steel material corresponding to T-90 by the same method and processing conditions as in Example 4. Layers were provided. Next, after the coupling 1 was preliminarily dried at 160 ° C. for 20 minutes, molybdenum disulfide powder having an average particle diameter of 3.5 μm, Cu powder having an average particle diameter of 0.8 μm, Zn powder having an average particle diameter of 5.0 μm, and It contains a polyamide-imide resin having an average molecular weight of 18,000 as a main component and [｛(molybdenum disulfide powder having an average particle diameter of 3.5 μm).
76% by weight, 12% by weight of (Cu powder having an average particle diameter of 0.8 μm) and 1% of (Zn powder having an average particle diameter of 5.0 μm)
2% by weight of mixture * {content} / {content of (polyamideimide resin having an average molecular weight of 18,000)} =
1.2 (weight ratio) (* Cu and Zn powders added to molybdenum disulfide powder; about 15.8% by weight of Cu powder, about 15.8% of Zn powder)
% By weight) of a solid lubricant having a composition ratio of 2% by weight.
Heat treatment was performed at 50 ° C. for 25 minutes to form a solid lubricating film layer. That is, the nitriding layer 11.5 μm and the manganese phosphate-based chemical conversion coating layer 1
A three-layer coating layer consisting of 3.5 μm and a solid lubricating coating layer of 18.5 μm was formed on the evaluation material. The same compound grease as in Example 1 was applied to the screw portion 3 of the pin 2 and the metal seal portion 4, and 4,000 kg / cm ² was applied to the seal portion 4.
Repeated make-up and break-out tests were performed on the joints while applying the surface pressure of. Test 2
As a result of repeating the process 0 times, the seizure of the seal portion and the occurrence of stuffiness were extremely small and very good.

COMPARATIVE EXAMPLE 8 For a coupling 1 having an inner diameter of 7 inches made of a steel material corresponding to T-90, the threaded portion 3 and the metal seal portion 4 were subjected to a base nitriding treatment in the same manner as in Example 4. A manganese phosphate-based chemical conversion treatment was performed to obtain a comparative example. That is, similar to the fourth and eighth embodiments, the thickness is 11.5 μm.
The coupling 1 provided with a m-nitriding layer and a 13.5 μm manganese phosphate-based chemical conversion coating layer was evaluated as a comparative material. Compound grease was applied to the comparative material in the same manner as in Example 8, and a make-up and break-out test was repeatedly performed on the joint portion while applying a surface pressure of 4,000 kg / cm ² to the seal portion 4. . As a result, in the tenth repetition test, seizure and stuffiness were remarkable, and the evaluation test was interrupted. As mentioned above,
The steel pipe joint composed of the composite coating layer of the manganese phosphate-based chemical conversion coating layer or the base nitriding layer and the manganese phosphate-based chemical conversion coating layer and the solid lubricating coating layer according to the present invention has excellent adhesion, coating strength, and lubricity of the coating. It can be seen that, as the number of repetitions of make-up and break-out increases, seizure of the film and generation of wrinkles hardly occur and the galling resistance is remarkably excellent.

[0048]

As described above, the steel pipe joint according to the present invention comprises a manganese phosphate-based chemical conversion coating layer or an undernitrided coating layer, a manganese phosphate-based chemical conversion coating layer, and molybdenum disulfide powder as an essential component or Cu A solid lubricating film layer having excellent toughness, hardness and lubricating performance, comprising one or two kinds of Zn powder and one kind of organic resin selected from epoxy resin, furan resin and polyamideimide resin. A coating layer is formed. By providing the multilayer coating layer, adhesion due to a synergistic effect of each coating layer,
A surface treatment film layer having extremely excellent film strength, lubrication performance and durability is formed on a steel pipe joint. Therefore, the steel pipe joint of the present invention, even if make-up and break-out in which sliding is repeatedly performed under high surface pressure is repeated for a long time,
The occurrence of image sticking and stuffiness is significantly suppressed. That is, according to the method of the present invention, it is possible to obtain a steel pipe joint having an excellent effect of preventing the occurrence of galling over a long period of time even if the number of repeated use of the steel pipe increases.

[Brief description of the drawings]

FIG. 1 is a diagram showing a joint constituting member to which the present invention is applied;

FIG. 2 is a view showing an assembly configuration of each joint constituent member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coupling 2 Pin 3 Screw part 4 Metal-metal seal part

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C23C 8/50 C23C 8/50 22/18 22/18 28/04 28/04 F16L 15/04 F16L 15/04 Z (72) Inventor Masaharu Oka 1-1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Haruyuki Nagayoshi 1-1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation (72) Inventor Akira Nakajima 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Nippon Steel Corporation Yawata Works (72) Inventor Seishin Higuchi Sawami, Tobata-ku, Kitakyushu-shi, Fukuoka Chome 7-5-208 (72) Inventor Ryusuke Inoue 2-28-12, Kumagaya, Kokurakita-ku, Kitakyushu-shi, Fukuoka (72) Inventor Toshio Akiyama 953 Nowagi Nogicho, Shimotsuga-gun, Tochigi Prefecture (72) Inventor Kazumi Sagara Ibaraki Nagai, Sakai-cho, Sarushima-gun 1686-25 (56) References JP-A-52-94519 (JP, A) JP-A-4-293798 (JP, A) JP-A-60-94466 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) B05D 1/00-7/26 B32B 15/08 C23C 8/50 C23C 22/18 C23C 28/04 F16L 15/04

Claims (4)

(57) [Claims] A manganese phosphate-based chemical conversion coating layer having a thickness of 5 μm to 25 μm or a nitriding layer having a thickness of 1 μm to 20 μm and a phosphoric acid having a thickness of 5 μm to 25 μm are provided on a thread portion and a metal seal portion of a joint portion of a steel pipe. In addition to providing a manganese-based chemical conversion coating layer, it further contains molybdenum disulfide powder and one selected from epoxy resin, furan resin and polyamideimide resin as essential components, and the content of 0.5 ≦ (molybdenum disulfide powder) ｝ / ｛(A type selected from epoxy resin, furan resin and polyamide imide resin)｝ ３ 3.0 (weight ratio) A solid lubricant composed of a composition ratio of (weight ratio) is applied and heat-treated. And forming a solid lubricating film layer having a thickness of 10 μm to 45 μm on the surface of the steel pipe joint having excellent galling resistance. 2. A manganese phosphate-based chemical conversion coating layer having a thickness of 5 μm to 25 μm or a nitriding layer having a thickness of 1 μm to 20 μm and a phosphoric acid having a thickness of 5 μm to 25 μm are formed on a thread portion and a metal seal portion of a joint portion of a steel pipe. A manganese chemical conversion coating layer is provided, and further, one or two types of molybdenum disulfide powder and 10% by weight to 50% by weight of Cu and Zn powders based on the powder and an epoxy resin, a furan resin,
One kind selected from polyamide imide resin is contained as an essential component, and 0.5 ≦ {(one or two kinds of molybdenum disulfide powder and Cu or Zn powder)} / エ ポ キ シ (epoxy resin, furan resin, polyamide imide) A solid lubricant composed of a composition selected from the following types of resins:｝ ≦ 3.0 (weight ratio) is applied and subjected to heat treatment to form a solid lubricant film layer having a thickness of 10 μm to 45 μm. A surface treatment method for a steel pipe joint having excellent galling resistance, characterized in that: 3. The particle size of molybdenum disulfide powder, which is an essential component of the solid lubricant for forming the solid lubricant film layer according to claim 1, is 0.4 as measured by a Fischer method.
5 μm to 10 μm range and molecular weight of 2,000 to 1
Epoxy resin in the range of 000, molecular weight 150-2
Furan resin in the range of 50, molecular weight 10,000-2
The surface treatment method for a steel pipe joint excellent in galling resistance according to the method according to claim 1, wherein the surface treatment is made of a kind selected from a polyamideimide resin in a range of 5,000. 4. The molybdenum disulfide powder, which is an essential component of the solid lubricant for forming the solid lubricant film layer according to claim 2, has a particle diameter of 0.4 as measured by a Fischer method.
One or two kinds in which the particle size of Cu or Zn powder ranges from 0.5 μm to 10 μm, an epoxy resin in which the molecular weight ranges from 2,000 to 10,000, the range in which the molecular weight ranges from 150 to 250 3. A steel pipe joint excellent in galling resistance according to the method according to claim 2, wherein the furan resin is a kind selected from polyamide imide resins having a molecular weight in the range of 10,000 to 25,000. Surface treatment method.