JPH11309587A - Butt joining method of metal tube and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a joined part wherein a groove shape of a butting part is controlled, both outside and inside diameters are not varied and moreover the strength of joining is excellent by optimizing a temperature distribution of a metal tube when the metal tubes such as steel tubes are mutually butt joined by liquid phase diffusion bonding or brazing. SOLUTION: A heating zone 2 of a metal tube is divided in the axial direction of the tube, an interval (d) between divided heating zones is set to 15-50 mm. The heating zone 2 is divided into a symmetrical position wherein a butting part 3 is put between the heating zones without or with including the butting part 3. Also, the heating zone 2 is divided by cooling the metal tube. A diameter of a coil in a work coil or winding density is varied by a position in the axial direction of the metal tube, or a cooling nozzle is also provided. Thus, grinding work or the like after being joined is unnecessitated in on-site construction of an oil well pipe or in joining work of a steel tube in a job site for civil and construction works, and a joined tube having excellent quality and high reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase diffusion bonding method in which an insert material is interposed between the end faces of metal pipes such as steel pipes, the butt portion is heated, and the insert material is melted and joined. The present invention relates to a butt joining method and apparatus by brazing.

[0002]

2. Description of the Related Art Liquid phase diffusion bonding has attracted attention as a means for joining metal pipes such as steel pipes in the longitudinal direction.
In this method, an insert material made of an amorphous metal foil is interposed between the end surfaces of the butted portions, and the insert material is melted to diffuse the amorphous phase forming metal element into the material to be joined. Since the amorphous phase forming metal element is easily diffused and can be joined by heating for a relatively short time and has excellent joining strength, liquid phase diffusion joining is used in oil well steel pipe on-site construction and various civil engineering construction sites. , Has begun to spread as a simple and excellent joining means replacing MIG welding and TIG welding. Further, depending on the type of the metal pipe and the field of use, brazing using a brazing material as an insert material is also performed.

As shown in FIG. 1 (a), the end faces of the metal pipes to be joined are not limited to the case where both metal pipes 12 and 13 are perpendicular to the pipe axis, or one end as shown in FIG. 1 (b). In some cases, the metal tube 12 has a concave taper 14 and the other metal tube 13 has a convex taper 15. In the former case, insert material 11
Is a flat ring, and in the latter case, it is a frustoconical ring shaped to match the taper angle θ.

As the heating means, for example, high-frequency induction heating is employed. At the time of heating, as shown in FIG. 2, a force P is applied in the tube axis direction to press the joint surface. At this time, as shown in FIG. 2, a phenomenon that the groove of the butting portion 3 opens outward may occur, and this phenomenon causes deterioration of the bonding strength.

Japanese Patent Application Laid-Open No. H8-300166 relates to the deformation of the joint during heating in the butt joining of metal tubes as described above.
In the publication, 1
By applying a compressive force of 0 to 50 MPa to plastically deform the groove, it is possible to suppress the increase in the inner diameter of the pipe at the butt portion, increase the outer diameter of the pipe, and increase the wall thickness to obtain a highly reliable joint. Proposed.

[0006]

The above-mentioned JP-A-8-300
According to the technology disclosed in Japanese Patent Publication No. 166, the butting portion 3 as shown in FIG.
The phenomenon that the groove of the opening opens outward is also improved. However, when the outer diameter of the pipe at the joint increases, for example, in the case of on-site construction when soil is reformed with a pipe roof, the steel pipe is pushed into the soil while being joined, so the enlarged diameter section becomes an obstacle. For this reason, it is necessary to grind the increased diameter portion after joining. Also, if the inner diameter of the pipe at the joint increases, even if it is very small, depending on the application,
There is also a concern that turbulence may occur in the fluid flowing in the pipe and erosion corrosion may occur.

Accordingly, the present invention relates to a liquid phase diffusion bonding or brazing in which an insert material is interposed between the end faces of metal pipes such as steel pipes, and the butted portion is heated, and the insert material is melted and joined. It is another object of the present invention to control the shape of the groove of the butt portion by optimizing the temperature distribution of the metal tube at the time of heating, and to obtain a joint portion having an invariable outer diameter and inner diameter and excellent joint strength.

[0008]

According to a first aspect of the present invention, there is provided a method according to the present invention for butt-joining metal pipes with an insert material interposed between end faces of the pipes, heating the butt-joint portion, In the method of melting and joining materials,
A butt joining method for a metal tube, characterized in that a heating zone of a metal tube is divided in a tube axis direction, and a distance d between the divided heating zones is 15 to 50 mm. The heating zone can be divided into symmetrical positions that do not include the butting portion and that sandwich the butting portion. Also, the heating zone can be divided into symmetrical positions that include the butting portion and that sandwich the butting portion. You can also. In the latter case, the distance d is set to 30 to 50 mm.

A second invention method is a method of joining by inserting an insert material between end faces of metal pipes, heating the butted portion, melting the insert material, and joining.
This is a butt-joining method for metal pipes, wherein a heating zone is divided in the pipe axis direction by cooling the metal pipe.

[0010] Next, a first invention device of the present invention for achieving the above object is a work coil for heating a butt portion by butt-inserting between end faces of metal pipes with an insert material interposed therebetween. A butt-joining apparatus for metal pipes, wherein a diameter is changed according to a position in a pipe axis direction of the metal pipe. The second invention apparatus is characterized in that the insert material is interposed between the end faces of the metal pipes to butt each other, and the winding density of the work coil for heating the butt portion is changed depending on the position of the metal pipe in the pipe axis direction. This is a butt joining device for metal tubes.

[0011] The device of the third invention is to butt the end portions of the metal tubes with an insert material interposed therebetween, and between the windings of the work coil for heating the butt portion, the cooling gas is directed toward the metal tubes. A metal pipe butt-joining device, characterized in that a nozzle for jetting is provided over at least one circumference in a pipe circumferential direction.

In a fourth aspect of the present invention, a work coil for heating an abutting portion is divided in the tube axis direction of the metal tube, and a work coil for heating the butted portion is divided between the end surfaces of the metal tubes. A butt-joining apparatus for a metal pipe, characterized in that a nozzle for injecting a cooling gas toward the metal pipe is provided at least one round in a circumferential direction between the coils.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventors of the present invention have concluded that the above-mentioned opening of the butted portion at the time of heating is mainly caused by a difference in thermal expansion due to a temperature gradient between both ends of the metal pipes at the butted portion 3. It has been clarified that the problem can sometimes be solved by properly adjusting the temperature distribution at the end of the tube. In liquid phase diffusion bonding and brazing, heating is performed to melt the insert material, usually,
Only the ends of both pipes including the butt 3 are heated by induction heating or the like. For this reason, the butting portion 3 has the highest temperature and a temperature gradient is generated in the tube axis direction, and the butting portion 3 also has the maximum thermal expansion of the metal tube.

The thermal expansion occurs in the radial direction and the axial direction, and the thermal expansion in the axial direction has a preferable effect because it is a force for pressing the metal tubes against each other. But the radial thermal expansion is
Due to the temperature gradient, the distance becomes smaller as the distance from the butting portion 3 increases, and the groove expands outward due to the difference in thermal expansion. In other words, a force to expand the pipe acts on the pipe end due to the thermal expansion in the radial direction. However, at a portion where the temperature rise is small away from the end of the pipe, the thermal expansion is small, so a restraining force acts on the expansion of the pipe. Opens outward.

The inventors of the present invention have made various studies to control the shape of the groove of the butt portion by optimizing the temperature distribution of the metal tube when heating the butt joint to prevent the groove from being opened. As a result, as shown in FIG. 3 and FIG.
The opening of the groove could be prevented by dividing the heating zone 2 of the metal tube in the tube axis direction.

According to a first aspect of the present invention, a heating zone of a metal tube is divided in a tube axis direction, and a distance d between the divided heating zones is set to 15 to 50 mm.
And FIG. 3 shows an example in which the heating zone 2 is divided into symmetrical positions sandwiching the butting portion 3 without including the butting portion 3, and FIG.
Is an example in which is divided. By dividing the heating zone 2 in this manner, the temperature distribution is as shown in the graphs illustrated in FIGS. 3 and 4, the opening of the groove can be prevented, the outer diameter and the inner diameter are unchanged, and the joining is performed. A joint having excellent strength was obtained.

In the temperature distributions of FIGS. 3 and 4, a solid line shows an example of distribution until the butting portion 3 reaches the melting temperature of the insert material, and a broken line shows an example of distribution after holding for a predetermined time after reaching the melting temperature. While maintaining for a predetermined time, the temperature becomes substantially uniform due to heat conduction. Here, when the heating zone 2 does not include the butt portion 3 as in the example of FIG. 3, the heating zone 2 is 600 mm until the butt portion 3 reaches 90% of the melting temperature of the insert material 11.
In the case where the butting portion 3 is included as in the example of FIG. 4, the region is set to be at least 600 ° C. before the butting portion 3 reaches the melting temperature of the insert material 11. The width W of the heating zone 2 and the distance d between the divided heating zones 2 are controlled by heating means.

As the heating means, induction heating or direct current heating can be employed. In the case of induction heating, for example, as shown in FIG. 7, the work coil 1 is divided and arranged in the tube axis direction. be able to. In the case of induction heating, the width W of the heating zone 2 of the metal tube is a region slightly longer than the length of the work coil 1.

When the heating zone 2 does not include the butt portion 3 as shown in FIG. 3, the distance d between the heating zones 2 is set to 15 mm to 50 mm depending on the size and material of the pipe. Heating zone 2 as shown in FIG.
Includes a butt 3, depending on the size and material of the pipe,
The width W of the heating zone 2 is set to 30 mm to 50 mm. In this case, the interval d between the heating zones 2 is preferably set to 30 to 100 mm.

By dividing the heating zone 3 in this way and adjusting the temperature distribution of the metal tube, when the butt 3 expands due to thermal expansion during heating, as shown in FIG.
Are expanded substantially in parallel. Therefore, the groove is not opened, and the outer and inner diameters are joined in an invariable state. After joining, the joined portion expanded by thermal expansion is cooled and returns to the original tube diameter, so that a joined tube in which both the outer diameter and the inner diameter are unchanged over the entire length is obtained.

In the second invention, the heating zone 3 is divided by cooling the metal tube during heating. Cooling can be performed by injecting a gas such as air, nitrogen gas, or an inert gas from a cooling nozzle arranged in the pipe circumferential direction. By cooling in this way, after the butting portion 3 reaches the melting temperature of the insert material, the heating zone 3
The temperature difference ΔT between the heating zone 3 and the heating zone 3 is maintained as shown in FIG. For this reason, the opening of the groove is more effectively prevented in combination with the action of the joining pressure. This ΔT is 100 to 300 ° C.
It is desirable that

In the case of brazing, since it is sufficient to heat until the insert material is melted, no holding time is required.
In both the invention method and the second invention method, a sufficient effect for preventing the opening of the groove can be obtained. However, in the case of the liquid phase diffusion bonding, after the insert material is melted, the holding for diffusing the contained elements into the metal pipe is performed. The second invention is superior in that time is required and ΔT can be maintained even during the holding time.

Next, the apparatus of the present invention will be described. First
As shown in FIG. 8, the apparatus according to the present invention changes the degree of induction heating by changing the coil diameter of the work coil 1 depending on the position of the metal tube in the tube axis direction, and divides the heating zone. In the example of FIG. 8, since the diameter of the work coil 1 is large at the butted portion 3 and its vicinity and small at both sides, the metal tube is heated by dividing the heating zone 2 as shown in FIG. .

As shown in FIG. 9, the second invention device changes the degree of induction heating by changing the winding density of the winding 4 of the work coil 1 in accordance with the position of the metal tube in the tube axis direction. Is to be divided. In the example of FIG. 9, the winding density of the winding 4 is rough at the butt portion 3 and the vicinity thereof, and dense on both sides thereof. You.

As shown in FIG. 10, the third invention device has a nozzle 5 provided between the windings 4 of the work coil 1,
The heating zone is divided by injecting a cooling gas toward the metal pipe from the heater. The nozzle 5 is provided over at least one circumference in the pipe circumferential direction as shown in FIG. 11 as viewed in the direction of arrows AA in FIG. 10, and by injecting a gas such as air, nitrogen, or an inert gas into the metal pipe, As shown in FIG. 3, the metal tube is heated by dividing the heating zone 2.

As shown in FIG. 12, the fourth invention device divides the work coil 1 in the axial direction of the metal tube, and provides a cooling ring 6 between the divided work coils 1. The heating zone is divided by injecting a cooling gas from the nozzle 5 formed on the inner surface toward the metal pipe. Cooling ring 6
By introducing a gas such as air, nitrogen, or an inert gas from a gas inlet 8 and injecting the gas from the nozzle 5 to the metal tube through the cavity 7 as shown in the example of FIG. The heating zone 2 is divided and heated as shown in FIG.
In the first invention device, the second invention device, the third invention device and the fourth invention device, when the heating zone 2 is divided into three parts as shown in FIG. The division can be performed in the same manner as in the case.

[0027]

EXAMPLES (1) SS400 ordinary steel pipes specified by JIS and SUS430 stainless steel pipes were butt-bonded by liquid phase diffusion bonding. The groove shape of the pipe end is θ = 90 ° as shown in FIG.
Used was an amorphous metal foil having a thickness of 20 μm and made of Fe-9 wt% Si-1.5 wt% B. Heating is performed by induction heating, and as shown in FIG.
Is divided into a total of two places, one on each side sandwiching the, the heating temperature of the butting portion is 1200 ° C, and the holding time at this temperature is 5 minutes,
After the holding, the work coil was turned off and allowed to cool. Also, a joining stress of 5 MPa was applied to the butt 3.

After joining by changing the material, outer diameter D, wall thickness t, and interval d of the heating zone of the steel pipe, the joining strength was measured, and the opening of the groove was measured by microscopic observation. Table 1 shows the results
Shown in For the joining strength, a tensile test was performed on each sample obtained by dividing the joined portion into eight parts in the pipe circumferential direction, and the average value of the tensile strength was shown as a ratio to the tensile strength of the steel pipe before joining. If the bonding strength ratio is 0.9 or more, it is good.

In the type of the work coil shown in FIG. 8, the inner diameter of the coil at the small diameter portion is +30 mm outside the tube and the inner diameter of the coil at the large diameter portion is +60 mm outside the tube. The interval between the windings was 1 mm in the dense portion and 20 to 60 mm in the rough portion. Each of the examples of the present invention has a bonding strength,
A good joint was obtained, and a joint was obtained in which both the outer diameter and the wall thickness did not change. In each of the comparative examples, the joining strength was insufficient, and the opening of the groove was recognized.

[0030]

[Table 1]

(2) For the same material as in (1) above, using the same groove and the same insert material, and by induction heating, as shown in FIG. And one each on both sides sandwiching the butting portion 3, a total of three locations. The heating temperature, the holding time, and the bonding stress are the same as in the above (1). After joining while changing the material and dimensions of the steel pipe and the interval d of the heating zone, the results of measuring the joining strength and the opening of the groove in the same manner as in (1) are shown in Table 2.

The work coil has a coil diameter changed as shown in FIG. 8, and the portion of the heating zone 2 shown in FIG.
The portion between them had a large diameter. The dimensions are the same as in (1) above. In each of the examples of the present invention, the joining strength and the opening of the groove were good, and the joining portion having the same outer diameter and thickness was obtained. In each of the comparative examples, the joining strength was insufficient, and the opening of the groove was recognized.

[0033]

[Table 2]

(3) As an example of the present invention, JIS standard STK400, outer diameter 264.4 mm, wall thickness 17.8 mm ordinary steel pipes are butt-joined to each other by liquid phase diffusion bonding using the apparatus shown in FIGS. 10 and 12. did. The groove shape, insert material, heating temperature, holding time, and joining stress are the same as in (1) above.

In the apparatus shown in FIG.
In FIG. 11, twelve nozzles 5 were arranged at equal intervals in the pipe circumferential direction. In the apparatus shown in FIG. 12, the length of the divided work coil 1 in the tube axis direction is set to 40.
A cooling ring 6 having a length of 20 mm in the tube axis direction was arranged at the divided portion, and slit-like nozzles 5 were arranged in the cooling ring 6 in a staggered manner as shown in FIG. The width of the slit is 2 mm and the length is 10 mm. In both cases, nitrogen gas was injected from the nozzle 5 as a cooling gas at a flow rate of 7 m / sec. ΔT when the butt 3 reached 1200 ° C. was 150 ° C., and this ΔT was maintained during the holding time of 5 minutes.

As a comparative example, a liquid phase diffusion bonding was carried out using a work coil 1 having a length of 80 mm in the tube axis direction without injecting a cooling gas under the same conditions as those of the present invention. In each of the examples of the present invention, the joint strength ratio was 0.95 or more, and the opening of the groove was 0.1 mm or less, which was a very good result, and a joint portion in which both the outer diameter and the wall thickness did not change was obtained. In the comparative example, the bonding strength ratio was less than 0.9, and the opening of the groove was 0.2 mm or more.

[0037]

According to the method of the present invention, an insert material is interposed between the end faces of metal pipes such as steel pipes, butted, the butted portions are heated, and the insert material is melted to perform liquid phase diffusion bonding or brazing. By doing so, the temperature distribution of the metal tube at the time of heating is optimized, the opening of the butt joint can be prevented, and the joint having excellent in both the outer diameter and the inner diameter and having excellent joint strength can be stably obtained. The device of the present invention has a simple structure and is easy to handle. Therefore, in the on-site construction of oil country tubular goods or the joining work of steel pipes at various civil engineering construction sites, a work such as grinding after joining is not required, and a high quality and highly reliable joined pipe can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are perspective views showing examples of butt joints to which the present invention is applied.

FIG. 2 is a cross-sectional view showing an example of the opening of a groove in a butt joint according to the present invention.

FIG. 3 is an example of a cross-sectional view including a butt portion of a metal tube in the method of the present invention and an example of a graph showing a temperature distribution thereof.

FIG. 4 is another example of a cross-sectional view including a butt portion of a metal tube in the method of the present invention, and another example of a graph showing a temperature distribution thereof.

FIG. 5 is another example of a graph showing a temperature distribution of a metal tube in the method of the present invention.

FIG. 6 is an example of a sectional view including a butted portion of a metal tube in the method of the present invention.

FIG. 7 is a cross-sectional view showing an example of a work coil that can be used in the method of the present invention.

FIG. 8 is a sectional view showing an example of the first invention device of the present invention.

FIG. 9 is a sectional view showing an example of the second invention apparatus of the present invention.

FIG. 10 is a sectional view showing an example of the third invention apparatus of the present invention.

11 shows an example of the device of the third invention of the present invention, and is a sectional view taken along the line AA of FIG.

FIG. 12 is a sectional view showing an example of the fourth invention apparatus of the present invention.

FIG. 13 is a partially cutaway perspective view showing an example of the fourth invention apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Work coil 2 ... Heating zone 3 ... Butt part 4 ... Winding 5 ... Nozzle 6 ... Cooling ring 7 ... Cavity 8 ... Gas inlet 11 ... Insert material 12, 13 ... Metal tube 14 ... Concave taper 15 ... Convex taper

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B23K 9/028 B23K 9/028 B

Claims (8)

[Claims] 1. A method for joining metal tubes by inserting an insert material between the end surfaces of the metal tubes, heating the butted portion, and melting and joining the insert material. A butt-joining method for metal pipes, wherein the distance d between the divided heating zones is 15 to 50 mm. 2. The heating zone, which does not include the butting portion,
2. The method as claimed in claim 1, wherein the butt portion is divided into symmetrical positions sandwiching the butt portion. 3. The heating zone is divided into symmetrical positions including the butting portion and sandwiching the butting portion, and the distance d is 30 to
2. The method as claimed in claim 1, wherein the diameter is 50 mm. 4. A method of joining a metal tube by inserting an insert material between end surfaces of the two metal tubes and heating the butted portion and melting and joining the insert material, wherein the metal tube is cooled to form a heating zone. Butt-joining method of a metal pipe, wherein the metal pipe is divided in a pipe axis direction. 5. The method according to claim 1, wherein an insert material is interposed between the end faces of the metal tubes to butt each other, and a coil diameter of a work coil for heating the butt portion is changed depending on a position of the metal tube in a tube axis direction. Butt joining device for metal pipes. 6. A butt is inserted between end faces of metal pipes with an insert material interposed therebetween, and a winding density of a work coil for heating the butt portion is changed depending on a position in a pipe axial direction of the metal pipe. Butt joining device for metal pipes. 7. A method for injecting a cooling gas toward a metal tube between windings of a work coil for heating an abutting portion with an insert material interposed between end surfaces of the metal tubes. A butt-joining apparatus for metal pipes, wherein the nozzle is provided over at least one circumference in the pipe circumferential direction. 8. A work coil for heating the butted portion is divided in the tube axis direction of the metal tube with an insert material interposed between the end faces of the metal tubes, and a work coil is divided between the divided work coils. And a nozzle for injecting a cooling gas toward the metal pipe over at least one circumference in the pipe circumferential direction.