JP2001300743A - Joined body of metallic pipes for expanded pipe and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joined body of metallic pipes for an expanded pipe which has high corrosion resistance and is expandable at a high expansion ratio, and a method of manufacturing the joined body. SOLUTION: Two metallic pipes are butted at their end surface, diffusion- joined, and then cooled (joining process). The vicinity of the joined part is kept at a temperature not lower than (At transformation temperature -100 deg.C) and lower than At transformation temperature for at least 30 seconds so that the ratio of the maximum hardness of the vicinity of the joined part to the hardness of the metallic pipes before joined becomes 1.4 or smaller, and then cooled (tempering process). In a case where the tempering is performed with a heating means having a narrow band of a uniform temperature, it is preferable that the vicinity of the joined part is kept at a temperature not lower than the A1 transformation temperature and not higher than (A1 transformation temperature +100 deg.C) for at least 30 seconds before the tempering is performed, and then cooled (intermediate heat treatment process).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal pipe joint for pipe expansion and a method for producing the same, and more particularly, to a chemical industry,
Plant piping and line pipes used in the petrochemical industry, etc., or casing tubes used in oil wells,
TECHNICAL FIELD The present invention relates to a metal pipe joined body suitable for an oil country tubular good such as a production tube or a coiled tube, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, in the fields of chemical industry, petrochemical industry, etc., a target product is obtained by utilizing a chemical reaction under various environments, or a starting material, an intermediate product, and a target product of a chemical reaction are obtained. Long metal tubes are used to transport corrosive fluids, such as objects, over long distances.

[0003] A seamless steel pipe excellent in corrosion resistance is generally used for a metal pipe exposed to a corrosive environment. The length of a seamless steel pipe industrially mass-produced is 10 to 15 m.
The upper limit of the length that can be manufactured is about 100 m. Therefore, in such a case, a joined body in which a plurality of seamless steel pipes having a length of 10 to 15 m are joined (hereinafter, this is referred to as a "metal tube joined body") is used.

[0004] As a joining method of the metal pipe, a screw connection method (mechanical cup method), a welding method (orbital welding method), a friction welding method, a diffusion welding method and the like are known. Among these, the diffusion bonding method has a high airtightness, and a joint having a bonding strength equivalent to the base metal strength can be obtained.
There is an advantage that the working time is shorter than the welding method. Therefore, the liquid phase diffusion bonding method is expected to be applied as a bonding method for oil country tubular goods and line pipes.

[0005] Generally, a metal pipe joint is used as it is in a joined state. However, depending on the application, a process of enlarging the inner diameter of the metal pipe joint after joining (hereinafter, this is referred to as "expansion"). ). For example, in recent years, in the field of oil country tubular goods, in order to reduce the drilling cost of oil wells, a method has been proposed in which a metal pipe joined body is buried in the ground and then expanded.

For example, Japanese Unexamined Patent Publication No. 7-507610 discloses that a casing made of a malleable material is buried in a borehole excavated in the ground, and a hydraulic expansion tool is expanded in the casing to form a casing on the borehole wall. A method is disclosed for radially expanding with respect to.

[0007] International Publication No. W based on the Patent Cooperation Treaty
In O98 / 0062, a steel pipe made of a malleable steel type that causes strain hardening without necking or ductile fracture is inserted into a tunnel or a casing buried earlier, and has a tapered surface made of a nonmetallic material. A method of expanding a casing using a mandrel is disclosed.

[0008]

By the way, in order to expand the metal pipe joint, it is necessary that the joint has a high deformability. For example, in the case of oil country tubular goods, in order to reduce the drilling cost of oil wells, the expansion rate of the inner diameter before and after expansion (hereinafter, this is referred to as “expansion rate”) is at least five.
% Is necessary, and more preferably 20% or more.

On the other hand, as described above, the diffusion bonding method is a bonding method capable of producing a high quality metal pipe bonded body with high efficiency. Therefore, if the diffusion bonding method and the expansion are combined and applied to an oil country tubular good, a significant reduction in oil well drilling costs can be expected.

However, for a metal pipe exposed to a severe corrosive environment such as an oil country tubular good, a steel type excellent in corrosion resistance, that is, a steel type to which various alloying elements are added, is generally used. For this reason, when this is cooled after diffusion bonding, depending on the composition of the metal tube, the cooling rate after bonding, etc., the deformability of the bonded portion is greatly reduced, and a large pipe expansion rate may not be obtained.

An object of the present invention is to provide an expanded metal pipe assembly having high corrosion resistance and capable of expanding at a high expansion rate, and a method of manufacturing the same.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to an expanded metal pipe joint in which a plurality of metal pipes are diffusion-bonded. The ratio of the maximum hardness is 1.4 or less.

[0013] In addition, the method for manufacturing a joined metal pipe for pipe expansion according to the present invention is a joining step in which two metal pipes are joined at their end faces by diffusion joining and then cooling, and joining is performed on the hardness of the metal pipes before joining. The ratio of the maximum hardness in the vicinity of the part is 1.
4 as to become less, the vicinity of the joint portion (A ₁ transformation temperature -100 ° C.) or higher, and that and a tempering step of at least 30 seconds maintained at a temperature lower than the A ₁ transformation temperature, then cooled It is the gist.

[0014] In this case, before the tempering process, the vicinity of the joint portion _{A 1} transformation temperature or more, and, _{(A 1} transformation temperature +
An intermediate heat treatment step of holding at a temperature of 100 ° C. or lower for at least 30 seconds and then cooling may be further provided.

[0015] The vicinity of the joint for the hardness of the metal tube before joining
If the ratio of the maximum hardness of the metal pipe is 1.4 or less,
Regardless, the expandability of the metal pipe joint is improved,
Expansion can be performed. Such a metal pipe joint is
After joining, (A) ₁Transformation temperature -100 ℃)
Above and A₁At least 30 below the transformation temperature
After holding for 2 seconds, it is obtained by performing tempering to cool.
You.

Before the tempering, the vicinity of the joint is
After holding at a temperature of ₁ transformation temperature or more and (A ₁ transformation temperature + 100 ° C) or less for at least 30 seconds, and then performing an intermediate heat treatment for cooling, even if the heat treatment is performed using a heating means having a uniform and narrow tropical zone, The hardness in the vicinity of the joint can be reduced substantially uniformly.

[0017]

Embodiments of the present invention will be described below in detail. A metal pipe joint for pipe expansion according to the present invention is obtained by joining a plurality of metal pipes by a diffusion joining method, and a ratio of a maximum hardness in the vicinity of a joint to a hardness of the metal pipe before joining (hereinafter, this is referred to as "Hardness ratio") is 1.
4 or less.

If the hardness ratio exceeds 1.4, the deformability near the joint is greatly reduced, and cracks are generated near the joint when expanding the pipe, which is not preferable. In order to suppress the occurrence of defects due to expansion, the smaller the hardness ratio, the better.

Further, the material of the metal pipe to be joined, but are not particularly limited, specifically, the martensitic stainless steel tube, or, the carbon equivalent C _eq, defined by the formula for a number of 1 However, a preferable example is a carbon steel pipe or a low alloy steel pipe satisfying the relational expression represented by the equation (2).

[0020]

## EQU1 ## C _eq = C + (1/6) Mn + (1/15) Ni + (1/5) Cr + (1/4) Mo
+ (1/14) V + (1/13) Cu

[0021]

[Number 2] _{C eq ≧ (1.4xH base +200)} / 1200 ( _{where, H base,} the hardness before bonding of the metal tube)

The diffusion bonding method includes a solid-phase diffusion bonding method in which elements are diffused while maintaining a solid phase state, and an insert material interposed at a bonding interface, the insert material is melted, and components of the insert material are melted. Although there is a liquid phase diffusion bonding method in which a part is diffused to the metal pipe side, the metal pipe joined body according to the present invention may be bonded by any method.

Next, the operation of the expanded metal pipe assembly according to the present invention will be described. There is a certain relationship between the expandability near the joint and the hardness. The present invention is characterized by clarifying this relationship. That is, the ratio of the maximum hardness in the vicinity of the joint to the hardness of the metal tube before joining is 1.
When the number is 4 or less, the metal pipe joined body can be expanded at a high expansion rate without generating a defect near the joint.

This relationship holds regardless of the material of the metal tube. For example, when diffusion bonding is performed using a metal tube having a carbon equivalent C _eq that satisfies Equation 2, the hardness ratio usually exceeds 1.4. However, even with such a metal tube,
If the hardness ratio is set to 1.4 or less by a manufacturing method described later, it is possible to perform pipe expansion at a high pipe expansion rate.

Next, a method for manufacturing the joined metal pipe for pipe expansion according to the present invention will be described. FIG. 1 is a diagram showing a heating pattern used in the manufacturing method according to the first embodiment of the present invention. In FIG. 1, the manufacturing method according to the present embodiment includes a joining step and a tempering step.

The joining step is a step in which two metal tubes are brought into contact with each other and pressurized, kept at the joining temperature for a certain period of time, and then cooled. Here, the joining is performed at a temperature lower than the melting point of the metal tube. In the case of the liquid layer diffusion bonding method, the bonding is performed at a temperature equal to or higher than the melting point of the insert material and lower than the melting point of the metal tube. As the pressure and the holding time, optimal values are used according to the material of the metal tube, the joining temperature, and the like so that the diffusion of the element on the joint surface is sufficiently performed.

The tempering process, after bonding, near the junction _{(A 1} transformation temperature -100 ° C.) or higher, and kept at a temperature lower than the _{A 1} transformation temperature, and then a step of cooling. The holding temperature at the tempering process _{(A 1} transformation temperature -100
C.) is not preferable because the hardness ratio cannot be reduced to 1.4 or less in a short time. Further, the holding temperature is A
_{If the} temperature is higher than _one transformation temperature, the hardness ratio cannot be reduced to 1.4 or less, which is not preferable. In the case of diffusion bonding the different metal pipes to each other in material, and "the A ₁ transformation temperature"
Of A ₁ transformation temperature of the metal tube, it means a lower one.

Further, in order to make the hardness ratio 1.4 or less, it is necessary to hold at the above-mentioned holding temperature for at least 30 seconds. The hardness ratio tends to decrease as the holding time becomes longer. However, if the holding time is made longer than necessary, there is no difference in the effect, and the working efficiency is rather lowered, which is not preferable. Although depending on the thickness of the metal tube, a sufficient effect can be obtained with a holding time of about 10 minutes.

Next, the operation of the manufacturing method according to the present embodiment will be described. After joining the metal tubes and cooling,
Depending on the material of the metal tube, the cooling rate, and the like, the vicinity of the joint may be hardened, and the expandability may be reduced. Tempering is known as a means for recovering this, but conventional tempering is generally performed over several tens of minutes to several hours.

[0030] In contrast, in order to obtain an excellent metallic tube assembly to pipe expansion capability, after bonding, near the junction (A ₁ transformation temperature -
100 ° C.) or higher, and, after maintaining at least 30 seconds at a temperature below the A ₁ transformation temperature, it is sufficient to cool. By such tempering in a short time, the maximum hardness in the vicinity of the joint with respect to the hardness before joining the metal pipe becomes 1.4 or less, and a high pipe expandability is imparted to the joined metal pipe.
This is the same even when a metal tube made of a material that is easily cured by air cooling is used.

Next, a description will be given of a method of manufacturing a joined metal pipe for pipe expansion according to a second embodiment of the present invention. FIG.
Shows a heating pattern used in the manufacturing method according to the present embodiment. In FIG. 2, the manufacturing method according to the present embodiment further includes an intermediate heat treatment step in addition to the above-described bonding step and tempering step.

The intermediate heat treatment step, before tempering, junction near the _{A 1} transformation temperature or more, and, _{(A 1} transformation temperature +
(100 ° C.) or less, and a step of holding for at least 30 seconds or more and then cooling.

[0033] When the holding temperature in the intermediate heat treatment step is less than the A ₁ transformation temperature, in particular, when the curing region over a wide range sandwiching the bonding surfaces has occurred, it is impossible to uniformly lower the hardness of the hardened zone Not preferred. Further, the holding temperature in the intermediate heat treatment step _{(A 1} transformation temperature +100
If the temperature exceeds (° C.), the hardened region is further expanded by performing the intermediate heat treatment, and the deformability near the joint is reduced, which is not preferable. In the case of diffusion bonding the different metal pipes to each other in material, and "the A ₁ transformation temperature", A ₁ of each metal tube
It means the lower one of the transformation temperatures.

Next, the operation of the manufacturing method according to this embodiment will be described. The manufacturing method according to the present embodiment is particularly effective when the heating means used for tempering has a narrow uniform area. That is, when a long metal tube is diffusion-bonded, a high-frequency induction heating method using a high-frequency induction coil is generally used to locally heat the vicinity of the bonding surface.

When a metal tube is heated using a high-frequency induction coil, only the soaking zone corresponding to the coil width is heated to the target temperature, and both sides of the soaking zone are heated to a temperature lower than the target temperature. Further, the heating temperature on both sides of the solitary tropic becomes lower as the distance from the solitary tropic becomes longer. Therefore, when tempering is performed using a coil having a small width after joining, only the tropic portion of the coil is softened, and both sides of the tropic remain hardened. Therefore, when such a metal pipe joint is expanded, a crack may be generated from the hardened region.

[0036] In contrast, prior to tempering, when the intermediate heat treatment using a narrow coil width, although the hardness of the soaking zone section does not decrease, the temperature of the region extending on either side of the soaking zone than the A ₁ transformation temperature Lower. Therefore, only the temperate sides are tempered. Next, when tempering is performed using a coil having the same coil width, the solitary zone is tempered. Therefore, even in the case where the heat treatment is performed using a heating means having a uniform and narrow tropical zone, the hardness in the vicinity of the joint can be reduced substantially uniformly.

[0037]

EXAMPLE 1 Liquid-phase diffusion bonding of a metal tube was performed using high-frequency induction heating. The metal pipe includes alloy steel pipe SCM420TK (JIS G 3445) for machine structure and martensitic stainless steel pipe SUS420J1TK.
A (JIS G 3446) was used. The insert material includes a Ni-based alloy foil BNi-2 (JIS Z32).
65) using a bonding temperature of 1250 ° C., a holding time of 60 s,
Bonding was performed under the conditions of a pressure of 4.0 MPa and a bonding atmosphere Ar. Next, tempering was performed using a high frequency induction heating method. About the obtained metal tube joined body, the micro Vickers hardness (load = 2.97 N) near the joint surface was measured,
The hardness ratio was determined. In addition, the obtained metal pipe joint was expanded under the conditions of a pipe expansion ratio of 20%. Table 1 shows the results.

[0038]

[Table 1]

Sample No. 1 was obtained by liquid-phase diffusion bonding of an alloy steel pipe. 1
Had a hardness ratio of 1.55 immediately after joining. In addition, since the pipe was expanded without tempering, a crack was generated near the joint surface during the pipe expansion. On the other hand, the sample N was subjected to liquid phase diffusion bonding of the alloy steel pipe and then tempered at 700 ° C. × 300 s.
o. In No. 2, the hardness ratio after tempering decreased to 1.07.
In addition, the tube could be expanded without generating defects. Sample No. having a holding time in tempering of 30 seconds. Sample No. 3 had a slightly higher hardness ratio after tempering of 1.25, but could be expanded without causing defects.

Similarly, sample No. 1 was prepared by liquid-phase diffusion bonding martensitic stainless steel pipe. In No. 4, the hardness ratio immediately after joining was 2.00. In addition, since the pipe was expanded without tempering, a crack was generated near the joint surface during the pipe expansion. On the other hand, after the martensitic stainless steel pipe was subjected to liquid phase diffusion bonding, it was tempered at 700 ° C. × 300 s. In No. 5, the hardness ratio after tempering decreased to 1.05. In addition, the tube could be expanded without generating defects. The holding time in the tempering process is 30
Sample No. No. 6 has a hardness ratio of 1.30 after tempering.
Although it was slightly higher, the tube could be expanded without generating defects.

Example 2 Under the same conditions as in Example 1,
The liquid phase diffusion bonding of the martensitic stainless steel pipe is performed, and the micro Vickers hardness near the bonding surface (load = 2.
97N) distribution was measured. Next, with respect to the obtained metal tube joined body, only the intermediate heat treatment was performed at 850 ° C. × 60 s by high-frequency induction heating using a narrow coil in a uniform zone, and the hardness distribution near the joint surface was measured. Similarly, a martensitic stainless steel pipe was subjected to liquid phase diffusion bonding under the same conditions as in Example 1, then tempered only at 750 ° C. × 60 s, and an intermediate heat treatment at 850 ° C. × 60 s. After that, the tempering was performed at 750 ° C. × 60 s, and the hardness distribution near the joint surface was measured. The results are shown in FIG.

Immediately after the bonding, a hardened region was formed within a range of the bonding surface ± 50 mm. On the other hand, when only tempering was performed, the hardness was reduced in the range of the bonding surface ± 20 mm, and the hardness did not decrease in a region 20 mm or more from the bonding surface. When only the intermediate heat treatment is performed,
The hardness remained high in the range of the bonding surface ± 20 mm, and decreased in the region 20 mm or more from the bonding surface. On the other hand, when tempering was performed after the intermediate heat treatment, the hardness near the joint surface was uniformly reduced to the hardness before the joint.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. It is.

For example, in the above-described embodiment, an example in which the present invention is applied to an alloy steel pipe and a martensitic stainless steel pipe has been described. However, the metal pipe to which the present invention is applied is not limited to this. The present invention can be applied to any type of steel in which the vicinity of the joint is easily hardened in the subsequent cooling process.

In the joining step or the second heat treatment step, cooling is performed after maintaining at a predetermined temperature.
It may be gradually cooled, or a temperature in the vicinity of the junction portion may be quenched upon reaching than the A ₁ transformation temperature. In particular, A
Rapid cooling when the temperature is equal to or lower than _one transformation temperature has an advantage that the cooling time can be shortened without hardening the vicinity of the joint, and the production efficiency is improved.

[0046]

According to the present invention, the ratio of the maximum hardness in the vicinity of the joint to the hardness before joining of the metal tubes is set to 1.4 or less in the expanded metal tube joint in which a plurality of metal tubes are diffusion-joined. In addition, there is an effect that the tube can be expanded at a high expansion ratio regardless of the material of the metal tube.

Further, the method for manufacturing a joined metal pipe for pipe expansion according to the present invention is a joining step of joining two metal pipes at their end faces by diffusion joining and then cooling, and joining the metal pipes to the hardness before joining. The ratio of the maximum hardness in the vicinity of the part is 1.
4 as to become less, the vicinity of the joint portion (A ₁ transformation temperature -100 ° C.) or higher, and at least 30 seconds maintained at a temperature lower than the A ₁ transformation temperature, then since a tempering step of cooling In addition, there is an effect that a metal pipe joined body having excellent pipe expandability can be efficiently obtained.

[0048] The prior to tempering process, the vicinity of the joint portion _{A 1} transformation temperature or more, and, _{(A 1} transformation temperature + 10
0 ° C.) or less, and further comprising an intermediate heat treatment step of holding for at least 30 seconds and then cooling.
Even in the case where the heat treatment is performed using a heating means with a narrow soaking zone, there is an effect that a metal pipe joined body having excellent pipe expandability can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a heating pattern used in a method for manufacturing a metal pipe joined body for pipe expansion according to a first embodiment of the present invention.

FIG. 2 is a view showing a heating pattern used in a method for manufacturing a metal-pipe joint for pipe expansion according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a hardness distribution near a bonding surface before and after heat treatment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 103: 04 B23K 103: 04 (72) Inventor Ryuzo Yamada 48-1, Ogusa Shikata, Chita City, Aichi Prefecture Rinkaiso A301 (72) Inventor Kazunari Kitoh 2-38, Konarumi, Midori-ku, Nagoya-shi, Aichi (72) Inventor Shigeyuki Inagaki 3-9-47, Tenpakucho, Minami-ku, Nagoya-shi, Aichi F-term (reference) 3H111 AA01 BA03 BA34 CB27 DA08 DA26 DB22 DB27 EA12 EA16 4E067 AA02 AA03 BA00 DD01 EA03 EB00 EC06 4K042 AA06 AA24 BA05 CA16 DA02 DA06 DC02 DC03

Claims (5)

[Claims] 1. A metal pipe joined body for expansion in which a plurality of metal pipes are diffusion-bonded, wherein a ratio of a maximum hardness in a vicinity of a joint to a hardness of the metal pipe before joining is 1.4 or less. Metal pipe joint for pipe expansion. Wherein said metal tube is carbon carbon equivalent _{C eq} is represented by the following formula _{C eq ≧ (1.4xH base +200)} / 1200 ( _{where, H base} is before bonding of the metal tube hardness) The joined metal pipe assembly for pipe expansion according to claim 1, which is a steel pipe or a low alloy steel pipe. 3. The joined metal pipe for expansion according to claim 1, wherein the metal pipe is a martensitic stainless steel pipe. 4. A joining step in which two metal pipes are joined by diffusion joining at the end faces thereof, and then cooled, and a ratio of a maximum hardness in the vicinity of a joining portion to a hardness before joining of the metal pipes is 1.4 or less. in the vicinity of the joint portion (a ₁ transformation temperature -100 ° C.) or higher, and at least 30 seconds maintained at a temperature lower than the a ₁ transformation temperature, then characterized by comprising a tempering step of cooling tube expansion Of manufacturing metal pipe joints for automobiles. 5. Prior to the tempering process, the vicinity of the joint portion _{A 1} transformation temperature or more, and, _{(A 1} transformation temperature +100
The method according to claim 4, further comprising an intermediate heat treatment step of holding at a temperature of not more than (° C) for at least 30 seconds and then cooling.