JPH0152638B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Field of Application> The disclosed technology belongs to the technical field of equipping a coupling portion of a corrosion-resistant pipe such as an oil country tubular pipe with a corrosion-resistant function.

<Summary of the gist> The invention of this application provides that a pipe joint for interconnecting corrosive fluid transport pipes such as oil country tubular goods has a threaded part corresponding to a fastening threaded part at the end of the corrosion-resistant pipe. The present invention relates to a corrosion-resistant pipe joint structure having a coupling part and an underhang part at the base of the threaded part so as to be tightly sealed to the pipe end overhang part of the corrosion-resistant pipe. The hang part is formed of a corrosion-resistant material and integrated with the coupling part of the reinforcing material, and is formed at the underhang part after overlay welding of the corrosion-resistant material, or is further formed as a separately molded underhang part. This invention relates to a corrosion-resistant pipe joint structure that is integrally welded by electron beam welding or the like.

As is well known, piping for transporting corrosive fluids, such as oil country tubular goods and plant piping, is often used.Of course, these pipings must have corrosion resistance as well as pressure resistance, heat resistance, etc. To address this issue, various types of double-walled pipes have been developed and adopted, in which an outer pipe made of carbon steel or the like is lined with an inner pipe made of stainless steel or the like as a corrosion-resistant pipe. ing.

By the way, the type double pipe is made into a unit pipe of a predetermined length due to equipment conditions in the manufacturing process or restrictions such as transportation and on-site installation, and therefore, when used on-site as oil country tubular goods, it is necessary to flange connection, Pipe joints are connected to the designed length by means such as connecting pipes, but such joints as oil country tubular goods require quick tightening and are required to be connected releasably on the premise of repeated use. Coupling type threaded joints are widely used.

However, as mentioned above, although the general parts of double-pipe pipes have corrosion resistance and pressure resistance, if the joints lack corrosion resistance and pressure resistance, they will not function as piping. Become.

Therefore, as shown in Fig. 1, a male thread 4 is carved into the outer surface of the tube end of a double tube 3 consisting of an outer tube 2 made of carbon steel to which an inner tube 1 made of stainless steel is tightly connected. In order to provide corrosion resistance as a pipe joint 6 for a unit pipe with an overhang portion 5 formed therein, the corrosive fluid flow surface 7 between the tube ends should have corrosion resistance, and an underhang portion 9 may be provided at the base portion 8. to form;
A stainless steel coupling joint was used in which a female thread 10 as a tapered threaded part was carved into a male thread 4 as a tapered threaded part.

However, in this type of joint 6, the thickness of the stainless steel 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' of the applicant's earlier invention, as shown in FIG.
The outer side thereof is a fastening part 12, 12 of a screw coupling part made of carbon steel, and the corrosion-resistant ring 1 is
Electron beam welding 13,
13, it is possible to integrate the parts and reduce the weight and cost.

<Problems to be Solved by the Invention> Therefore, when a corrosive fluid (not shown) is allowed to flow through the seed joint 6', since the threaded portions 4 and 10 are fastening portions, the sealing action and labyrinth are lost. Due to its function, there is almost no leakage, but there is a risk of corrosive fluid entering from the underhang part 9 to the threaded part 10 in the vicinity, and therefore, this part, which does not have sufficient corrosion resistance, will corrode over time. In addition, the weld heat affected zone (so-called HAZ) on the carbon steel side of the coupling, which has been rapidly heated and rapidly cooled by electron beam welding, is hardened due to the formation of martensite, as shown in Figure 8. If we take the distance R from the flow surface 7 on the horizontal axis and the hardness F on the vertical axis, Inconel 625 (graph C ₁ ) and Incoloy 825 (graph
_C2 ) also had a problem with the above HAZ, where the hardness increased in a spike-like manner as shown in the figure, and there was a risk of delayed cracking due to hydrogen.

Moreover, since the penetration depth is limited by such means, there is also a problem that the length of the corrosion-resistant ring 11, that is, the length of the underhang portion is limited.

Therefore, as shown in FIG. 3, the corrosion-resistant annular member 1
A joint 6' has been devised in which the joint 1' is extended to the main body of the coupling ring, and there is a technique to compensate for the above-mentioned problems, but it also has the inconvenience of insufficient strength.

<Object of the invention> The object 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 improve the corrosion resistance of the underhang part.
The purpose is to provide an excellent corrosion-resistant pipe joint structure that maintains sufficient strength, has no hardened parts due to tempering of joints, and provides flexibility in length, thereby benefiting piping technology applications in various industries. be.

<Means/effects for solving the problem) In order to solve the above-mentioned object, the structure of the invention of this application, which is summarized in the above-mentioned claims, is to provide a coupling-type pipe joint that connects corrosion-resistant pipes to each other with high strength. An annular counterbore or an annular protrusion is formed in the center of the material, and a corrosion-resistant material is welded to the center of the material. By stacking these, the preceding welding beat is tempered and the heat-affected zone is heated. This prevents the formation of hardened parts such as martensite, thereby preventing delayed cracking caused by hydrogen, etc. due to the intrusion of flowing fluid into the product joint. Alternatively, a separate underhang part may be integrated into the machined part through a joining means such as radiation welding using an electron beam, or the underhang part may be re-machined to a shorter length by re-machining after the joint is disassembled. Technical measures have been taken to make it possible to use it.

<Examples> Next, examples of the invention of this application are shown in FIGS.
The following is an explanation based on 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 embodiments shown in FIGS. 4, 5, and 6, as shown in FIG. 15 is formed in advance by machining.

Next, as shown in FIG. 5, a TIG (or MIG) welding torch (not shown) is inserted into the material 14,
For the above-mentioned counterbore portion 15, for example, Inconel
625 corrosion-resistant material overlay weld layer 16, 161, 162,
Four layers (three or even five layers are possible depending on the design) of 163 are sequentially formed.

In this case, the counterbore 15 is formed to facilitate the formation of a corrosion-resistant material layer on the corrosive fluid permeable surface after subsequent machining, but as shown in FIG.
Since the weld portion 17 of the first layer is formed in the material, the counterbore portion 15 may not need to be formed in some cases.

As for the build-up of the first layer, a large spice-like hard part is formed in the heat affected zone (HAZ), as shown in FIG. As we overlay, a type of tempering is performed by the bead, so that multiple layers of overlay welding automatically undergo tempering.
As shown in graph _C3 shown in FIG. 9, it can be seen that no spike-like, high-strength hardened portions occur in the HAZ.

It can also be seen that the same effect can be seen in graph _C4 in FIG. 9 when the corrosion-resistant material is overlay-welded with Incoloy 825.

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

Then, as shown in FIG. 6, after forming a set number of overlay welding layers 16 to 163 of corrosion-resistant material, a processing device is inserted with the processing device facing from the openings at both ends, and the female screw 10 is inserted.
The underhang portion 9 and fluid flow surface 7 are cut to form a coupling type pipe fitting 6''.

When the above-described coupling type pipe fitting 6'' is used as an oil country pipe by connecting the double-pipe corrosion-resistant pipes with screws through the coupling type pipe fitting 6'', for example, the corrosive fluid crude oil is Crude oil may enter from the underhang part 9, but since there is a welded overlay of corrosion-resistant material to the part of the underhang type pipe fitting 6'' where there is a risk of crude oil entering, the strength material 14 is used.
is not corroded, and since the heat affected zone (HAZ) is also tempered, it is not hardened, and delayed cracking due to hydrogen does not occur.

When the coupling type pipe fitting 6'' is disassembled and the underhang part 9 is reworked, the underhang part 9 is made sufficiently long in advance.
A short underhang portion is formed.

Next, in the embodiment shown in FIG. 7, similar to the above-mentioned embodiment, after forming welding layers 16, 161, 162 of the corrosion-resistant material Incoloy 825 on the strength material 14, the female thread portion 10 and the cylindrical surface portion are formed by machining. The outer underhang part 18 of a ring made of Incoloy 825, which is a corrosion-resistant material formed in advance, may be integrally welded to the inner side of the underhang part 9 using an industrial adhesive 13.

This embodiment is effective when the overlay welding layer of the corrosion-resistant material is multi-stage, and is useful for reducing the number of 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, various embodiments can be adopted, such as omitting counterboring of the strength material for overlay welding. In addition to oil country tubular goods, various types of piping such as slurry pipes and chemical plant piping can be used.

<Effects of the Invention> As described above, according to the invention of this application, the underhang part of the coupling type pipe joint is machined after overlay welding with a corrosion-resistant material to the coupling part of the reinforcing material. Firstly, it has the effect of ensuring sufficient strength, and the weld bead from the second layer automatically tempers the preceding beads such as the first layer, so that the hardness against the heat affected zone is kept low. This prevents hydrogen-delayed cracking and the like.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 overlay welding, the length of the underhang part can be adjusted freely in terms of design, and when reusing it after disassembly, it can be machined again to create a short underhang part. The effect that can be achieved is also achieved.

Also, divide the underhang part into two parts, inside and outside.
By welding the outer part and integrating the inner part with an industrial adhesive, it is also designed for cases where underhangs cannot be created with only overlay welding due to the pipe inner diameter, etc. This has the excellent effect of forming an underhang part.

[Brief explanation of drawings]

Figures 1, 2, and 3 are cross-sectional views of a pipe joint based on the prior art, Figure 8 is a graph explaining the hardness abnormality of the weld heat affected zone, and Figures 4, 5, and 6 are one embodiment of the invention of this application. FIG. 7 is a sectional view explaining the manufacturing process of the example, FIG. 7 is a sectional view explaining another embodiment, and FIG. 9 is a graph showing the hardness of the weld heat affected zone of the embodiment of the invention of this application corresponding to FIG. . 3... Corrosion resistant pipe, 4, 10... Threaded part, 5... Overhang part, 6'', 6... Pipe joint, 9... Underhang part, 14... Coupling part, 16,161,
162,163...Overlay welding.

Claims (1)

[Scope of Claims] 1. A corrosion-resistant pipe joint structure having a threaded part for the threaded end part of a corrosion-resistant pipe, and in which an underhang part formed at the base thereof is brought into close contact with an overhang part of the end part of the corrosion-resistant pipe, A corrosion-resistant pipe joint structure, characterized in that the underhang portion is integrally formed with the coupling portion having the threaded portion by processing and forming after overlay welding of a corrosion-resistant material. 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 end overhang part of the corrosion-resistant pipe, which has the threaded part as described above. The underhang part is integrally formed with a corrosion-resistant material separately from the coupling part, and the inner side of the underhang part is integrally formed with the coupling part after overlay welding, while the outer part is integrally formed with the coupling part after overlay welding. A corrosion-resistant pipe joint structure, characterized in that it is integrated with the inner side via a joining means.