JPS6188089A - High hermetic oil well pipe joint and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a highly airtight oil well pipe fitting, particularly a highly airtight oil well pipe joint having a soft metal spray layer on the metal seal portion and having excellent delayed fracture resistance. This invention relates to pipe fittings and their manufacturing methods.

(Prior Art) The oil well environment in which oil drilling is conducted today is becoming increasingly harsh, and under such environments oil country tubing typically has a hardness of 3.5 to 1.
4.0kg/+n! (5,000~20,000
Since high pressure (psi) is applied, oil country tubular joints are required to have a high degree of airtightness.

Generally, oil country tubular joints are composed of a threaded part and a metal seal part, and in order to exhibit sufficient airtightness to withstand the high pressure mentioned above, high surface pressure must be applied to the metal seal part and the threaded part. As a result, "seizing" and "peeling" of the metal seal and threaded parts cannot be avoided during fastening.

Therefore, the metal seal portion of oil country tubular joints is subjected to surface treatment to prevent seizure and improve airtightness. Generally, chemical conversion coatings such as zinc phosphate, manganese phosphate, iron oxalate, etc. are applied as such surface treatments, but they deteriorate in environments where the operating temperature exceeds 200°C, causing "leakage". occurrence has started to be seen.

As mentioned above, as oil well conditions become more severe,
Nowadays, oil country tubular joints are used in high-temperature environments (specifically 300 to 350°C), and plating with soft metals with high melting points is effective in dealing with the deterioration of such chemical conversion coatings. For example, Japanese Patent Application Laid-Open No. 58-31097 proposes providing an activation layer on a metal seal portion or threaded portion and then performing metal plating. On the other hand, plating on integral long pipes with male and female threads at both ends, such as oil country tubular joints, has many difficulties in terms of equipment and operation, and cannot be put into practical use immediately. This is the current situation, and in order to eliminate such drawbacks in terms of equipment and operation, the present applicant has proposed an automatic plating device that enables partial plating in Japanese Patent Application No. 58-116126 and No. 58-116127.
proposed as a number.

(Problem to be solved by the invention) The above-mentioned conventional methods have some effect in improving "burn-in" etc. However, even with these methods, there is a problem when using them. In some cases, destruction was observed, so-called delayed destruction. Needless to say, if such delayed failure occurs, it may lead to a serious accident at the oil well, so complete preventive measures must be taken in advance.

Regarding this point, since all conventional methods involve electroplating, absorption of hydrogen into the joint components cannot be avoided, and this has been found to cause delayed failure during use. In order to prevent delayed fracture, the hydrogen is diffused through a heat treatment known as ``heat treatment.'' However, there are disadvantages in that the processing takes a long time and it is not always possible to sufficiently prevent destruction after delay, and an improvement has been desired.

(Means for Solving the Problems) An object of the present invention is to simply attach a soft metal to the joints of long materials in place of conventional plating using a method similar to sandblasting to prevent seizing and to An object of the present invention is to provide a surface-treated oil country tubular joint with improved airtightness and a method for manufacturing the same. Since such oil country tubular joints do not absorb hydrogen compared to joints manufactured by conventional electroplating methods, delayed failure does not occur.

Here, the gist of the present invention is that a fine particle sprayed layer of steel with a thickness of 3 to 20 μm is formed on at least the surface of the metal seal portion, and is made of a soft metal or alloy whose melting point is higher than the operating environment temperature of the oil country pipe joint. This is a highly airtight oil well pipe fitting.

Further, the present invention provides a method for cutting and finishing a pipe having a melting point higher than the operating environment temperature of the oil well pipe joint, for example, a melting point of 400°C.
This is a method for producing a highly airtight oil country tubular joint, which comprises spraying particles of a soft metal or its alloy at a temperature of 0.degree.

Note that the soft metal includes Za, pH, and the like, and in the present invention, these are melted using the heat generated by the collision pressure of the particles against the cutting surface and adhered to the surface of the metal seal part. It is. Adhesion thickness is usually 3~
It is set to 20 μm. To get the desired effect, at least 3
Although a thickness of μ-μm is required, on the other hand, even if the thickness exceeds 5.20 μm, no further improvement in the effect is observed.

In preferred embodiments, the particle size is generally between 0.05 and 1.5.
The injection pressure is generally 2 to 6 kgf/cIi+. If the particle size is smaller than 0.05 mm, sufficient collision pressure, that is, heat generation, cannot be ensured even if the injection pressure is increased;
．． If it is larger than 5 mm, a uniform layer cannot be obtained by spraying. Also, injection pressures in the above range are necessary to ensure the required heat generation and mechanical bonding of the particles to the cutting surface.

As described above, according to the method of the present invention, the surface of the metal seal part can be coated with a soft metal by a simple method similar to sandblasting instead of the conventional wet electroplating, so handling is simple. Of course, since the process is carried out in a dry manner, there is almost no hydrogen absorption and no delayed destruction occurs.

Here, in the above-mentioned fine particle spraying, a layer is formed when fine particles of soft metal collide with the surface to be treated at high speed, a portion of which melts due to the heat generated, and this molten material adheres to the surface to be treated. It is a soft metal layer.

(effect) The invention will now be further described in connection with the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of an oil country tubular joint in the middle of connection, and even in the illustrated example, the tip of the oil country tubular l itself is interconnected with the tip of another oil country tubular goods 2, forming an oil country tubular joint 3. are doing. The oil country tubular goods l includes a threaded part 4 and a metal seal part 5 which is located at the tip of the threaded part, has a tapered shape when viewed from the pipe side, and is in contact with the outer surface of the oil country tubular product, and is generally made of metal. A convex surface portion (not shown in the figure) with a constant radius of curvature is provided on the joint side at the inlet portion of the seal portion in order to improve airtightness.

On the other hand, the end of the oil country tubular goods 2 constituting a part of the oil country country pipe joint is also provided with a metal seal portion 5' that prevents the threaded portion from tightening, as in the case of the oil country country pipe joint 1.

The oil country pipe joint formed in this way is usually finished by cutting as finishing forming, but the cutting surface of the threaded part and the metal seal part of the oil country pipe joint thus finished is processed according to the present invention. According to the method described below, a spraying device is used to spray a layer of soft metal.

FIG. 2 is a schematic cross-sectional view of the soft metal spraying apparatus 10 described above.

Conduit 11 is supplied with high pressure fluid, generally air, and side pipe 1
The metal particles 13 supplied from 2 are entrained and collide at high speed through the nozzle 14 against the cutting surface of the oil country tubular joint (not shown) including at least the metal seal portion. ij sudden moment (1
The sprayed particles partially melted by pressure form a sprayed layer on the treated surface. Unlike ordinary chemical conversion coatings or electroplated coatings, this spraying layer is partially embedded in the surface due to the impact pressure at the time of collision, forming a kind of mechanical bond with the treated surface. This shows extremely high bonding strength.

FIG. 3 is a schematic explanatory diagram of the sprayed layer obtained in this way, and the surface of the base material 20 is entirely provided with a layer 21 of molten fine particle sprayed particles, both of which are machined. They are firmly joined via the target joining region 22.

Next, the present invention will be described in detail with reference to examples, but these are merely illustrative of the present invention and do not limit the present invention in any way.

EXAMPLE A steel pipe was manufactured using an alloy steel material having the composition shown in Table 1, and was further threaded to obtain a steel pipe having an inner diameter of 126mm and having the shape shown in FIG.

Next, the threads and metal seals of the steel pipe thus obtained are subjected to finishing cutting, and then various soft metal particles are sprayed onto these threads and metal seals using a spraying device as shown in Figure 2. A layer with a thickness of 10 μm was formed on the surfaces of the threaded portion and the metal seal portion.

For comparison, we used a window with a conventional zinc phosphate chemical conversion coating and an electroplating coating on the threaded part and metal seal part, respectively.

The thus obtained pipe joints were actually fastened and their airtightness was examined under the conditions shown in Table 2 by increasing the internal pressure (water) until bursting or leakage of the pipe body occurred.

As shown in Tests 1ml and 2, leakage occurred already at a pressure of 950 kgf/cn+2 in the conventional chemical conversion coating treatment. On the other hand, in the conventional electroplating method, there are only 3 test holes.
As shown in Figures 4 and 4, no leakage occurred until the tube body ruptured, but the present invention also ensures sealing performance until the tube body ruptures, and is equivalent to that achieved by conventional electroplating methods. It was confirmed that it has the following performance.

The processing time according to the method of the present invention is approximately 20 minutes per piece, which is the same as the processing time of conventional electroplating.

Next, we conducted a delayed fracture test to examine the differences from conventional electroplating methods. Similar to Tests 3 and 5 shown in Table 2, Zn electroplating and spraying with a thickness of 10 μm were used to compare the effects of baking. Table 3 summarizes the delayed fracture test results.

Since hydrogen is absorbed during electroplating, delayed fracture due to hydrogen occurs in high-strength oil country tubing materials, causing a phenomenon in which the pipe portion of the joint breaks. In conventional electroplating, baking treatment (250°C x 24 hours) is required after plating.
Whereas delayed fracture can only be prevented by diffusing and removing occluded hydrogen by carrying out (retention), as shown in Tests 6 and 7, according to the present invention, delayed fracture can be prevented even without conventional baking treatment. No damage occurred; in fact, performance was significantly improved.

In addition, although Test No. 5 was obtained by adding baking treatment to the example of the present invention, there was almost no difference in terms of effectiveness.
It can be seen that the present invention does not require baking.

Therefore, as is clear from the above test results, according to the present invention, the processing time can be significantly shortened, and the oil well pipe fittings obtained in this way have excellent delayed fracture resistance. I understand what is shown.

Table 1 (wt%) CSi Mn P S
CrM.

O, 240, 291, 230, 020, 0070, 58
0,46 uLt practice parrot ekrohi\teγpuku) G2 table continuation) QD case (1) 2 particles 5 dragons, injection pressure 4 kg
f/cIlt case (2) 2 particles, 1 injection pressure 6
kgf/an! Rule section when planning to miss a night

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an oil country pipe joint; FIG. 2 is a schematic cross-sectional view of the spraying device used in the present invention; and FIG. 3 is a schematic illustration of the spraying layer obtained by the present invention. It is a diagram.

Claims (3)

[Claims] (1) A highly airtight oil country tubular joint having a fine particle sprayed layer of 3 to 20 μm thick, made of a soft metal or alloy whose melting point is higher than the operating environment temperature of the oil country tubular joint, on at least the surface of the metal seal portion. (2) Following cutting and finishing, particles of a soft metal or alloy whose melting point is higher than the operating environment temperature of the oil country tubular joint are sprayed at high speed onto at least the cut surface of the metal seal portion to form a fine particle spray layer. , a manufacturing method for highly airtight oil country tubular joints. (3) The average particle diameter of the particles is 0.05 to 1.5 mm, and the fine particle sprayed layer is provided by spraying the particles at an injection pressure of 2 to 6 kgf/cm^2. The method described in Section 2.