JPS58184385A - Corrosion-resisting pipe joint structure - 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 The disclosed technology belongs to the technical field of equipping a coupling part pipe joint of a corrosion-resistant pipe such as an oil country country pipe with a corrosion-resistant function.

Accordingly, the invention of this application provides a pipe joint for connecting corrosive fluid transport pipes such as oil country tubular goods, which has a threaded part in the coupling part that corresponds to the fastening threaded part at the end of the corrosion-resistant pipe. Furthermore, the invention relates to a structure in which the threaded part has an underhang part at the base thereof so as to be tightly sealed to the overhang part of the end of the corrosion-resistant pipe, and in particular, the underhang part is a coupling part made of a reinforcing material. It is formed of a corrosion-resistant material and integrated into the underhang after contacting the corrosion-resistant overlay bath, or it can be formed as a separate underhang by electron beam bath welding or the like. This invention relates to a joint structure for corrosion-resistant pipes that are in contact with an integral bath.

As is well known, there are many types of piping that transport corrosive fluids, such as oil country tubular goods and plant piping, and it is essential that they have corrosion resistance as well as pressure and heat resistance. To deal with this, various double pipes have been developed and adopted, in which an outer carbon steel pipe is lined with a stainless steel inner pipe as a corrosion-resistant pipe.

However, due to the manufacturing process conditions or restrictions on transportation, installation, etc., double-walled pipes are made into unit pipes of a specified length, and therefore, when used in the field as oil country tubular goods, they must be connected with flanges or pipe joints. However, coupling-type threaded joints are widely used as connection means that require quick tightening and repeated use, such as oil country tubular goods. There is.

If it lacks pressure resistance, it would be useless as piping.

Therefore, as shown in FIG.
In order to provide corrosion resistance as a pipe joint 6 for a pipe with an opart ring 5 formed at the end of the pipe, the surface 7 through which the corrosive fluid flows between the ends of the pipe is particularly resistant to corrosion. In order to achieve this, the base 8 was made of stainless steel with an underhang part 9 formed therein and a female thread 1O as a tapered threaded part screwed into the male thread 4 serving as the tapered threaded part.

However, in this type of joint 6, the wall thickness is increased in order to provide pressure resistance, so there are disadvantages of increased cost, increased weight, and difficulty in handling.

To deal with this, in the joint 6' in the applicant's earlier invention, as shown in FIG. A fastening part 12.12 of the coupling part is formed, and electron beam welding 13.13 is performed from both sides of the joint between the underhang part of the corrosion-resistant ring 11 and the fastening part 12. :.

It is embodied.

Therefore, when a corrosive fluid is passed through the seed joint 6', the threaded portion 4.10 is a fastened portion and there is no leakage, but from the underhang portion 9 to the threaded portion 10 in the vicinity, corrosive fluid leaks. There is a risk of fluid intrusion, and therefore, there is a disadvantage that there is a risk that the part that does not have sufficient corrosion resistance may corrode over time.
In addition, the weld heat shadow area (so-called HAZ) on the carbon steel side that has been rapidly heated and rapidly cooled by electron beam welding has hardened due to the formation of martensite, and as shown in Fig. Inconel 625C1 is obtained by taking the hardness down from the distance R on the vertical axis.
Even with 1 Incoloy 825 C2, the hardness increased in a spike-like manner at the above-mentioned HAZ, and there was a drawback that there was a risk of delayed cracking due to hydrogen.

In addition, since this method limits the penetration depth,
However, there was also a problem in that the length of the eclipse bulge, ie, the length of the underhang part, was limited.

As shown in FIG. 3, a joint 6' in which a corrosion-resistant annular member 11' is formed up to the main body has been devised to solve the above problem, but it also has the problem of insufficient strength.

The purpose of the invention of this application is to solve the problems of the coupling type pipe joint based on the above-mentioned prior art, and to solve the problem of the above-mentioned conventional coupling type pipe joint.
The purpose is to provide an excellent corrosion-resistant pipe joint structure that can benefit the corrosion-resistant pipe application field in the transportation industry by tempering the joint so that there is no hardened part and allowing flexibility in length. be.

The structure of the invention of this application, which is based on the above-mentioned purpose, is that a coupling type pipe joint that connects corrosion-resistant pipes to each other is made by applying a corrosion-resistant material to the center of the material of the reinforcing material, and by laminating the material, the preceding weld bead is removed. It is tempered to prevent the formation of hardened parts such as martensite in the heat-affected zone, thereby preventing delayed cracking due to hydrogen etc. due to fluid intrusion into the product joint, and to prevent the formation of a predetermined underhang part in the overlay weld. Alternatively, a separate underhang part is integrated with the machined part through a joining method such as radiation welding using an electron beam, or after the joint is disassembled, machining is performed again to create an underhang part. The gist of this is that technical measures have been taken to make it possible to reuse short sections.

Next, embodiments of the invention of this application will be described below based on FIGS. 4 to 7 and FIG. 9.

Note that the same parts as in FIGS. 1 to 3 and FIG. 8 will be described using the same reference numerals.

In the embodiment shown in Fig. 4.5.6, as shown in Fig. 4, an annular counterbore portion of set length and shallow depth is provided at the center of the carbon steel cable material 14, which is the strength material of the coupling type pipe joint. 15 is formed in advance by machining.

Next, as shown in FIG.
IG) Insert a welding torch to the above-mentioned counterbore portion 15,
For example, inconel 625 corrosion-resistant material build-up bath welding 16.1
61, 162, 163, and 4 layers (3 layers or 5 layers may be possible depending on the anatomy) are sequentially formed.

In this case, the counterbore portion 15 is formed in order to leave the i, I contact material 16 on the corrosive fluid permeable surface after the subsequent machining. In some cases, the counterbore portion 15 may not be formed.

As for the first layer overlay 16, a spike-like part with large hardness is formed in the heat affected zone (HAZ) as shown in FIG. As the subsequent overlay welding is performed, one type of tempering will be performed by that bead. Therefore, multiple overlay welding will automatically perform tempering, and as shown in Figure 9, a type of tempering will occur, as shown in graph C3. <It can be seen that no spike-like high-strength hardened portions occur in the HAZ.

Furthermore, it can be seen that similar effects can be seen in graph C4 when the corrosion-resistant material is overlay welded with Incoloy 825.

Therefore, in the invention of this application, there is no need to use other means of tempering.

Then, as shown in Fig. 6, the set number of layers is applied to the corrosion-resistant overlay bath 1.
After carrying out steps 6 to 163'i, a processing device is carefully inserted through the openings at both ends, and the female screw portion 1O, the underhang portion 9, and the fluid flow passage 7 are cut to form a joint 6'.

In the joint 6" having the above structure, when the double-pipe corrosion-resistant pipes 3 are screwed and connected as shown in FIGS. Although it may enter from the underhang part 9, the joint 6'
Since the corrosion-resistant material 16 is in contact with the overlay bath up to the part where there is a risk of the intrusion, the reinforcing material 14 will not be corroded, and the heat affected zone (HAZ) is also tempered, so it is not hardened. Therefore, delayed cracking due to hydrogen does not occur.

When the joint is disassembled and the underhang part 9 is reworked, the underhang part 9 is made sufficiently long in advance, so that a short underhang part is formed.

Next, in the embodiment shown in FIG. 7, the reinforcing material 14 is
After contacting the corrosion-resistant material Incoloy 825 in a 16.161 overlay bath, the threaded portion 10 and cylindrical surface portion are formed by machining to form the inner side of the underhang, and the outer underhang of the ring of the corrosion-resistant material Incoloy 825 preformed on this is formed. 18'' may be welded together by electron beam bath welding 13.

This example is a corrosion-resistant overlay bath contact 16.161.162.
It is effective when there are multiple stages and helps reduce man-hours.

It goes without saying that the embodiments of the invention of this application are not limited to the above-mentioned embodiments; for example, counterbore processing of the strength material for overlay welding may be omitted, or alternatively, instead of electron beam welding, A wide variety of methods can be adopted, such as using industrial adhesives, and various types of piping such as oil country tubular goods, slurry pipes, and chemical plant piping can be used.

As mentioned above, according to the invention of this application, the underhang part of the coupling type pipe right is machined after welding the coupling part of the reinforcing material with a corrosion-resistant material. Firstly, the bath contact beads from the second layer automatically temper the preceding beads such as the first layer on the soil, which has the effect of ensuring sufficient strength, so that the hardness against the heat affected zone is kept low. As a result, delayed hydrogen cracking and the like are prevented, and therefore, there is an excellent effect of preventing corrosion and cracking even if corrosive fluid enters from the underhang portion and the tube end overhang portion.

Furthermore, since it is a build-up bath welding method, the length of the underhang part can be adjusted freely in terms of design, and when reusing it after disassembly, it is machined again and the short underhang part is υ1
It also has the advantage of being able to be used in a modified manner.
3. Also, by dividing the undercut into two parts, the outer part is welded overlay, and the inner part is integrated by electron beam bath welding or industrial adhesive. It has the excellent effect of forming a designed underhang part even when an underhang part cannot be formed by overlay welding alone due to the inner diameter etc.

[Brief explanation of drawings]

Fig. 1.2.3 is an explanatory sectional view of a pipe joint based on the prior art, Fig. 8 is an explanatory graph of hardness abnormality in the weld heat affected zone, and Fig. 4.5.6 is an explanatory sectional view of a pipe joint based on the prior art. 7 is an explanatory sectional view of the manufacturing process of the embodiment, FIG. 9 is a graph diagram illustrating the hardness of the bath heat-affected zone of the embodiment of the invention of this application corresponding to FIG. 8. It is. 3. Corrosion-resistant tube, 4. lO.. Threaded part, 9.16.1
B', 18"... underhang part, 5... overhang part,

Claims (2)

[Claims] (1) In a corrosion-resistant pipe joint structure that has a threaded part for the threaded end part of the corrosion-resistant pipe, and in which an underhang part formed at the base thereof is brought into close contact with the overhang part of the end part of the corrosion-resistant pipe, the threaded part A corrosion-resistant pipe joint structure characterized in that the underhang portion is integrally formed with a coupling portion having a corrosion-resistant material by processing and forming after overlay welding. (2) A corrosion-resistant pipe joint structure having a threaded part for the threaded end part of the corrosion-resistant pipe, and in which an underhang part formed at the base thereof is brought into close contact with the overhang part of the end part of the corrosion-resistant pipe, wherein the threaded part The underhang part is separately molded and integrally formed of a corrosion-resistant material with respect to the coupling part having a corrosion-resistant material, and the inner side of the underhang part is integrally formed with the coupling part after contacting with the overlay bath. A corrosion-resistant pipe joint structure characterized in that the outer side is integrated with the inner side via a joining means.