JPS5972391A - Steel pipe for oil well and production 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] The present invention relates to a steel pipe for oil wells and a method for manufacturing the same.

When drilling oil or gas wells, pumping out oil, etc.
It is well known that casing pipes are used to form walls like navigating pipes and oil wells. recently,
As oil fields are being developed to secure petroleum resources, the drilling environment is becoming increasingly corrosive, with large amounts of sulfide water and carbon dioxide present.

For this reason, the tubing pipes used,
For example, conventional gauging pipes and drill pipes A
At present, products made of PI 5A, 5AC, and 5AXK are unsatisfactory in terms of corrosion resistance.

The present invention was devised in view of the above circumstances, and aims to provide a steel pipe for LC oil wells that is excellent in tetraphagy with bamboo.
c. Another object of the present invention is to provide a method of manufacturing such a steel pipe while ensuring the strength of the joint.

Therefore, the steel pipe for oil wells of the present invention has austenitic two-phase early deposition or -meeting→→ system stainless steel pipe with an enlarged diameter on the -k 1, 1 side at the end of the pipe, and a stepped short single pipe. The basic feature is that the other end is joined through the other end, and the wall thickness of the pipe end at the joint part is υ larger than the wall thickness of the steel pipe main body. The end of an austenitic or 4-series stainless steel pipe is inserted, and pressure is applied to the split mold to tightly connect the pipe. Next, the end of the pipe inside the split mold is cold-rolled several times with a mandrel. By repeating the compression process, a swollen diameter portion is formed at the end of the tube, and the end portion of the swollen diameter portion has an swollen diameter on one end and a diameter that is approximately the same as the swollen diameter portion on the other end. Another basic feature is that it is manufactured by welding and joining a short single pipe with a step through the other end. 1. As another method, the above steel W'
During this H-rolling, the g end is air-core rolled without using a mandrel, so that the thickness of the pipe end is increased toward the inside diameter. form,
After rolling, a punch is inserted into the end of the tube to expand the diameter, and the increased thickness of the thick wall portion is transferred to the outer diameter side of the tube to form a swollen portion, and one end is added to the end of the swollen portion. Another basic feature is that a stepped short single tube having an expanded diameter on one side and approximately the same diameter as the expanded diameter portion at the other end is welded and joined via the other end.

Ru. The seed material has excellent side-food properties and has long-term durability even in corrosive environments where hydrogen sulfide and carbon dioxide exist.
Therefore, the present invention particularly uses a steel pipe made of the above material. Furthermore, oil country tubular goods (OCTGs) are used by being connected continuously using threaded joints, and the ends of the pipes are carved with threads, but these threads are prevented from becoming thin or damaged due to stress concentration. In order to achieve this, an enlarged diameter portion is formed at the end of the austenitic two-phase or No. 6+ stainless steel tube. FIG. 1 shows an example of a cross section of the formed swollen portion (8). In the present invention, the swollen portion (8)
is formed by joining (9) stepped short single pipes (7). It is also possible to form the expanded diameter part for forming the entire threaded joint by performing upset processing on the pipe end, but there is a limit to the size of the expanded diameter part that can be created by upset processing. In steel pipes for oil wells, which require a large wall thickness in the swollen diameter section, the swollen diameter section cannot be formed by an upset section.For this reason, in the present invention, a stepped short single pipe (7 ) is joined to the tube end to form the expanded diameter portion (8).

This step short single pipe (7) is joined to the end of the steel pipe by pressure welding or fusion welding, but the joint efficiency of 1 is not recognized for this joint (usually 0.9 to 0. ．．
7). In other words, the strength of the joint part cannot be considered to be the same as that of the parent part. Therefore, in the present invention, in order to compensate for the joint efficiency of the joint (9), the pipe end wall thickness t1 of the joint (9) is set to the wall thickness of the steel pipe main body, toj,! In the example of the mouth weight in which l) is also large, the inner thickness tl is secured by forming an expanded diameter part (101) at the end of the steel pipe by upsetting.

The specific composition and material of the austenitic or -→two-phase stainless steel pipe of the present invention are illustrated below.

(1) Austenitic Cr: 18-30 Ni: 8-55% TS; 50-100 Kg/+e+” Cr: 20-
35% Ni: 2~6% Ts: 100~130 to 9/mrlYs: 100~
120Kq/m2 Next, the method for manufacturing the above-mentioned oil country steel pipe will be explained based on FIGS. 2(a) to 2(c).

In the present invention, a stepped short single pipe (7) is joined to the pipe end, and the inner thickness of the pipe end at this joint part is larger than the wall thickness of the steel pipe main body. First, an enlarged diameter portion is formed at the end of the steel pipe (1) to ensure the wall thickness t1. Therefore, the expanded diameter portion is formed by cold compression working multiple times using a split mold and a mandrel. Since this enlarged diameter part constitutes a part of the arm part or is located near the joint part, it requires a certain strength. For ordinary materials, it is possible to shape the expanded diameter portion by hot working and to improve the strength by heat treatment.

However, since there is no transformation point in the austy two-phase fast-wearing or Hibiki←H→system←−H-th→ stainless steel that is the object of the present invention, it is not possible to improve the strength by heat treatment as described above. Can not. Therefore, in the present invention, the expanded diameter portion is formed by cold working while improving the strength. However, if one cold working process is performed too large, it may cause buckling or cracking, so the entire molding process is completed by multiple cold working processes. That is, as shown in the second section, the split mold (2) has an austenitic or cloudy texture →
The end of the two-phase stainless steel pipe (1) is inserted and positioned within the mold (201), and in this state the split mold (2) is tightly joined. Then, in a cold state, a one-thread drill (3) is inserted into the tube end within the split mold (2), and compression processing is performed using this. This compression process is carried out several times,
Finally, an expanded diameter portion (101) as shown in FIG. 2(b) is formed. Through such processing, the processed portion is work hardened and a predetermined strength can be obtained.

As mentioned above, in cold working, if the amount of processing per time becomes large, there is a risk of buckling of the tube. Therefore, in the present invention, the amount of upset processing per time is set to 'a l l ε 4 5 εf1: Hot working strain amount εC: Cold working strain amount.

FIG. 3 and the table below show the change in the enlarged diameter portion size and the processing conditions when the tube end of a stainless steel tube with an outer diameter of 73 mm and a tube thickness of 7 tnm was machined into a 77' set in 5 machining steps. Note that (11 to (V) in FIG. 3 indicate the shape of the expanded diameter portion after each process treatment.

In carrying out the present invention, it is preferable to perform intermediate heat treatment multiple times during the compression process to remove residual stress, from the viewpoint of preventing cracks from occurring due to process distortion. In cases where the overall strength of the pipe body is insufficient, it is preferable to improve the strength by performing an aging treatment after processing.

Once the tube end has been processed as described above, the stepped short tube (7) is joined to the processed enlarged diameter portion (101) as shown in FIG. 2(C). This stepped short tube (7) has an expanded diameter at one end and an expanded diameter portion (101) at the other end.
), and the other end is welded to the enlarged diameter part (10-shaped end).This joining is done by pressure welding or fusion welding, but it is made of a uniform tubular material. In order to ensure good performance, it is preferable to join using a pressure welding method that does not use a filler rod.The pressure welding consists of a primary pressure welding process in which the pipes are rotated relative to each other, and a secondary pressure welding process in which the pipes are then stopped. However, the pressure welding is approximately twice that of the conventional pressure for both primary and secondary welding.

Needless to say, the short stepped small tube (7) is made of the same material as the steel pipe body, and the stepped portion is formed by forging or carving. However, in order to expect work hardening, cold IJ machining is performed once, even when forming by cutting out the above.
The best thing to do is to sand down the pipes that have been treated.

Next, a second manufacturing method of the present invention will be explained.

This method is similar to the method described above in finally joining the stepped short tube (7) to the tube end, but has a different configuration in the method of forming the bulge (101) at the tube end. have. That is, this method is based on the previously proposed patent application filed in 1973.
It is used in part of the tube rolling process using pilger rolling in No. 5-70-105. This rolling method is used in pilger rolling, in contrast to normal cored rolling in which the mandrel is inserted into the rolling joint r of the pipe, except when rolling a pipe section that is to be thickened. Air core rolling is performed in a state where the rolling part is set back from the rolling part so as not to interfere with the rolling part, and by this air core rolling, the thickness of the tube part of the rolling tube 75'' is increased on the inner diameter side of the tube. , the above mandrel is placed at 47
11, core rolling and air core rolling are carried out as appropriate, whereby the thick walled part, which has been increased to the pipe inner diameter t111, is separated from other thin walled parts at any point in the longitudinal direction of the C pipe. The structure is designed to prevent this from occurring. In the present invention, a thick-walled portion is formed at the end of the p-tube using such a method, and then a predetermined process is performed on the thick-walled portion to produce a tubular body in which an enlarged-diameter portion is formed at the end of the p-pipe.

This will be explained in detail based on Fig. 4 and Fig. 5 (a) to 5). Pilger rolling is the 4th
As shown in the figure, the tapered groove (5) is inserted into the tapered mantle (4) and extends around the top of the tube (1) semi-circumferentially.
(51)/ζ rolling roll (5) The (5) rolls back and forth to sequentially roll a predetermined amount of feed.

That is, the tapered groove (51) of the rolling roll (5) (5)
X51) has a caliber that narrows as the rolling roll (5) (5) rotates.
(5) moves forward in the direction of the arrow along the taper without rotating, and at this time the rolling roll (5 bar 5) and the mandrel (3
), and finally the tube (1) is rolled between rolling rolls (
5) The narrowest part of the caliber in (5) is finished into a pipe with an inner diameter corresponding to the diameter of the finished part (4) of the simandrel (4).

When the rotation of the rolling roll (5) (5) is completed, the rolling roll (5) (5) temporarily opens the pipe (1) due to its escape.
) is no longer in contact with υ, during which time the tube (1) rotates by a certain angle. Next, the rolling roll (5) (5) rotates in the opposite direction to the previous one to perform rolling while moving the taper in the opposite direction and returning to the original position, thereby completing the rolling process.

When the rolling of the rolling rolls (5) (5) is completed, the tube (1) is sent to the exit direction by a predetermined length, and the rolling by the rolling rolls (5) (5) described above is continued. °
I get turned around.

By such a rolling method, the p-tube is rolled from one end side. Fifth
In the figure, a is the starting point of rolling by the rolling rolls (5) (5);
O indicates the rolling completion point, and 8 indicates the roll stroke range. First, at the beginning of the rolling of the one end side, air core rolling is performed with the mandrel retracted as shown in FIG. 5(a). As a result, the pipe (1) is not interfered with by the mandrel (4), so it is not processed to have a thick wall, and the outer diameter of the rolling roll (5) (5) is reduced just like 1-JVc. As a result, the tube is processed to have a wall thickness of Jj, T that is equal to or greater than the original thickness of the tube (1), and the inside diameter of the tube is thicker than that obtained by cored rolling with a mandrel (4). It is possible to like the fattening part. When such air core rolling is performed for a predetermined length, that is, a length corresponding to the expanded diameter section to be formed at the tube end, the mandrel (4) is placed at a predetermined position and the slack rolling roll (5) (5) roll stroke range till
! Introducing the finishing blade part (41) of the mandrel (4) into S.
5 (Fig. 5).
As shown in (b) and (c), normal cored rolling is performed. As a result, the tube is processed to have a thin wall, and a part of the tube portion that was undergoing air core rolling forms a tapered introduction portion (lha) from the thick wall portion ('rta) to the thin wall portion (T3).

If rolling is performed at a predetermined length from the other end of the tube, that is, at a position corresponding to the expanded diameter section to be formed at the tube end,
As shown in Fig. 5), the mandrel (4) is retracted again and air core rolling is performed. Meat part (T+
b) is formed.

As a result of the above-described rolling, thick-walled portions are obtained in which both end portions of the tube are thickened on the inner side of the tube. Next, in the present invention, the above-mentioned thickened portion is moved to the outer diameter side of the tube, and the inner diameter of the tube end portion is formed to be the same diameter as the inner diameter of the other portion (non-thick walled portion). For this reason, the fifth
As shown in Figures) and (F), insert a punch (6) whose main body has an outer diameter approximately the same as the inner diameter of the non-thick walled part and has a small diameter portion (61) at the tip into each tube end. , expand the diameter of that part and move the outside of the increased thickness to the outer diameter side. By doing so, the expanded diameter part (101) of the tube end as shown in FIG.
) is formed.

Since the above-mentioned processing is also performed in the cold, the tube is work-hardened and can obtain a predetermined strength.

Then, a short stepped single pipe (7) is joined to the end of the enlarged diameter portion (101) obtained in this manner in the same manner as shown in FIG. 2(c), thereby manufacturing a steel pipe for oil wells.

It should be noted that the welding of the stepped shortening tube (7) as described above may reduce the strength of the welded heat-affected zone of the base metal, so this heat-affected zone is subjected to cold working, It is preferable to improve the strength. Figure 6 shows an example of this processing situation. For example, as shown in (a), the expanded diameter part (101) of a steel pipe (IJ) and the small diameter part of a stepped short single pipe of the same diameter are prepared in advance into the final product. The pipe is configured to have a larger diameter (thick wall) than the dimensions, and a mandrel 01 gold is inserted into the pipe and this part is subjected to cold compression processing to form the shape shown by the broken line in the figure.

As another method, as shown in FIG.
7) are provided with annular projections (12
a) (12b) and (13a) (13b) 'r-formed, insert a mandrel (l]) into the tube, and insert the annular projection (lza) Q2b) and (13a) (13b)
It is then cold compressed and finished into the shape shown by the broken line in the figure. The annular projection can also be formed only on either the inner surface or the outer surface of the tube.

It is preferable that the cold working after welding and joining as described above is performed on the area including the heat affected zone due to welding.

According to the present invention described above, it is possible to provide a steel pipe for oil country tubular goods that has excellent corrosion resistance and has a sufficient wall thickness at the joint part, and it is also possible to manufacture such a steel pipe with a single tm while ensuring the strength of the joint part. can do.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the t-end cross-sectional shape of the present invention. The 21st mark and (c) are explanatory diagrams showing the steps of the method of the present invention. FIG. 3 is an explanatory view showing the process of forming the enlarged diameter portion by several steps of compression processing. FIG. 4 is an explanatory diagram showing the rolling principle of the pilger rolling method used in the method of the present invention. FIG. 5 (a) to 5) are explanatory diagrams showing a part of the process of the present invention step by step. FIGS. 6(a) and 6(b) are explanatory diagrams showing the compression process of the welded hot-formed back part after joining the stepped short tubes, respectively. In the figure, (1) is a steel pipe, (2) is a split mold, (3) (
4) is a mandrel, (5) ij: rolling roll, (6
)ld punch, (7) is a short single tube with a step, (8) is a bulging part, (9) is a joint part, (101) is a bulging part, (T+a)
(T+b) indicates each thick portion. Takeho Ill IP, i' from Nippon Kokan Co., Ltd.
Akira Tsuki Osamu Rema
Yukihiko Ebihara
Akiyoshi Matsushita, 1st F1 Patent Attorney Sho Yoshihara 2'
□, (□ Same Takahashi Kiyoshi 1..., 1.1 Same Founder Hiroko Yoshihara,,","+"'F'j',, Pashi Figure 5 +l-□Sn ~--- S-,,--~

Claims (3)

[Claims] (1) A short stepped 143 pipe with an expanded diameter at one end is joined to the end of an austenitic or two-phase stainless steel pipe via the other end, and the wall thickness of the end of the joint is equal to that of the main body of the steel pipe. Steel pipes for oil wells are characterized by being larger than their thickness. (2) Insert the pipe end of the austenitic or two-phase stainless steel pipe into the split mold, apply pressure to the split mold to tightly connect the pipe, and then cold insert the pipe end inside the split mold with a mandrel. By repeating the compression process multiple times, an enlarged diameter part is formed at the end of the tube.
1. One end of the expanded diameter portion 9114 is expanded.
1 side is 1) 1n? 5 steps with the same diameter (=
A steel pipe for oil wells, characterized in that a J-shaped single pipe is welded and joined via the other end. manufacturing method. (3) Completely cold pilger rolling of austenitic or two-phase stainless steel pipe,
During this rolling, when rolling the tube end, air core rolling is performed with the mandrel retracted to a position where it does not interfere with the rolled portion of the tube. By forming a thickened part, and after rolling, inserting a punch with approximately the same diameter as the inner diameter of the non-thickened part into the end of the tube to transfer the increased thickness of the thickened part to the outer diameter side of the pipe, A swollen diameter portion is entirely formed at the end of the tube, and then a stepped short tube 1p, one end of which is swollen in diameter and the other end of which has approximately the same diameter as the swollen portion of the tube end, is placed at the end of the swollen portion. A method for manufacturing oil well steel pipes, characterized by joining by welding through the other end.