JPH0576396B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing laminated metal tubes used in corrosive environments.

[Prior art]

For example, in recent years there has been an increasing demand for pipes with high strength and excellent corrosion resistance, such as sour gas transport pipes where the inside is exposed to a corrosive environment, and line pipes laid on the seabed where the outside is exposed to a corrosive environment. be. Pipes made of high-alloy steel such as stainless steel pipes are examples of pipes with excellent corrosion resistance, but they are expensive because they contain large amounts of chromium, nickel, etc., and are not economically viable when used for long-distance line pipes. There is a problem. Therefore, a laminated metal tube in which a high-alloy steel tube is laminated on the inside or outside of a high-strength, inexpensive low-alloy steel tube has been put into practical use.

Various inventions have been made as methods for manufacturing such laminated metal tubes, for example, Japanese Patent Application Laid-Open No. 117515/1983.
Publication No. 117516, Japanese Patent Application Laid-open No. 117516, and Japanese Patent Application Publication No. 1987
In all of the methods disclosed in Publication No. 85684, an inner tube that is cooled and contracted is inserted into an outer tube that is heated and expanded, and then the inner tube is expanded and the two are crimped. , then heating the inner and outer tubes,
This is a method of joining the two by stopping cooling, contracting the outer tube, and expanding the inner tube.
In No. 55-117515 and No. 55-117516, the pressure of the cooling water sealed in the inner tube was increased to obtain tube expansion force, and in JP-A-57-85684, an explosion was caused inside the inner tube. Obtaining expansion power.

Also, JP-A-57-11717 and JP-A-57-11717
The method disclosed in Publication No. 11718 is to insert an inner tube whose outer circumferential surface is wrapped with metal foil into an outer tube, and then insert the inner tube into the outer tube.
This is a method in which this is cold-drawn to bring them into close contact with each other, then heated to a predetermined temperature to join the inner tube and outer tube, and then processed into a tube by a press method.

[Problem to be solved by the invention]

However, in the former method, a predetermined interference is given between the inner tube and the outer tube by the above-mentioned procedure, and the two are mechanically bonded, and a metallurgical bonding state cannot be obtained between the two. Because of this, there is a risk that the bond between the two may loosen due to external factors such as changes in ambient temperature, and the process of filling the inner tube with cooling water takes a lot of time, resulting in low tube manufacturing efficiency. It was hot.

On the other hand, in the latter method, the inner tube and the outer tube are metallurgically joined through the metal foil interposed between them by heating after cold drawing, but the wrapping process of the metal foil is automated. This is difficult and requires a large number of man-hours, as well as many other steps, resulting in a low pipe manufacturing efficiency.

Additionally, both methods have the disadvantage that it is difficult to manufacture long laminated metal tubes.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a laminated pipe that can continuously manufacture laminated pipes with good metallurgical bonding with high efficiency. .

[Means to solve the problem]

A method for manufacturing a laminated metal tube according to the present invention is a method for manufacturing a laminated metal tube in which an inner tube made of metal is covered with an outer tube made of a metal different from the inner tube. A metal strip plate to be a tube is fed in the same direction with one side facing each other, and a layer of amorphous metal is formed on one or both of the end face in the width direction and the opposing face, and then both are fed in the same direction. The laminated body is laminated in the thickness direction, and this laminate is formed into a cylindrical shape with a metal strip serving as the inner tube on the inside, and the end surfaces of the metal strip serving as the inner tube and the metal strip serving as the outer tube are The method is characterized in that a tube is formed by electric resistance welding, and then the tube is heated to a temperature above the melting point of the amorphous metal and below the melting points of both metals.

[Effect]

In the present invention, two strips of different metals are
A layer of amorphous metal is interposed between the two, and a layer of amorphous metal is formed on the end faces of both in the width direction, and the two are laminated, and the rear end faces of the cylindrical shape are electrically welded to form a double pipe. Subsequent heating causes the inner tube and outer tube to be metallurgically joined via the amorphous metal layer.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a schematic diagram showing the implementation state of the method for manufacturing a laminated metal tube according to the present invention (hereinafter referred to as the method of the present invention).

In the figure, 1 is a metal strip serving as an inner tube, and 2 is a metal strip serving as an outer tube. For example, the metal used for the inner tube is a high alloy steel with corrosion resistance suitable for the purpose of the laminated tube to be manufactured, such as austenitic stainless steel, austenitic-ferritic dual-phase stainless steel, and Inconel. The metal used is a low-alloy steel that has sufficient strength in the operating environment of the laminated tube to be manufactured.

The strip plate 1 and the strip plate 2 have approximately the same width, are supplied in a coiled state, and are aligned in the width direction by the rotation of separate pinch rolls 3 and 4, respectively. are pulled out at the same speed in the longitudinal direction, further sandwiched together between a pair of upper and lower lamination rolls 5, and stacked vertically with the strip 1 on top to form a laminate 6,
It is designed to be conveyed in the longitudinal direction by the rotation of the lamination roll 5. Between the positions of the pinch rolls 3 and 4 and the position of the laminated roll 5, a plurality of thermal spray nozzles 7 for spraying powder of amorphous metal are arranged in a row in the width direction, facing the upper surface of the strip plate 2. In addition, one piece is placed on each side of the strips 1 and 2 facing each other in the width direction. ,
A layer of amorphous metal is formed by powder spraying from each spray nozzle 7.

The laminate 6 is sandwiched from above and below or from the left and right by a forming roll group 8 consisting of multiple pairs of breakdown rolls 80 and side rolls 81 (only one pair of each is shown) arranged in parallel in the conveyance direction, and is then It is formed into a U-shaped cross section with the plate 1 on the inside, and is further formed into a cylindrical shape by a plurality of fin pass rolls 9, 9, etc. arranged on the downstream side in the conveyance direction of the laminate 6, and both ends in the width direction are formed into a cylindrical shape. They become open pipes facing each other with a slight gap between them.

Fin pass rolls 9, 9...In between, there is a laminate 6
The heating unit 10 is arranged in such a manner as to surround the periphery of the laminate 6, which is formed into an open pipe.
The heating unit 10 is configured to heat up to a predetermined temperature. FIG. 2 is a cross-sectional view of the laminate 6 before heating in the heating section 10, and FIG. 3 is a cross-sectional view of the laminate 6 after heating. When the widths of the strip plate 1 serving as the outer tube and the strip plate 2 serving as the inner tube are approximately equal,
The laminate 6 before heating has a cross-sectional shape as shown in FIG. becomes wider than The heating in the heating section 10 thermally expands the outer strip 1, and as shown in FIG. It is done so that it is matched simultaneously,
The heating temperature caused by this is determined in consideration of the thermal expansion coefficients of the strips 1 and 2.

A heating coil 11 is disposed downstream of the fine pass roll 9 with respect to the conveying direction of the laminate 6 in a manner wound around the laminate 6 having an open pipe shape. Further downstream of 11, there are a pair of left and right squeeze rolls 12 in the shape of a drum.
12 are arranged. The laminate 6 heated in the heating section 10 is heated by the end faces 1a, 1a, The vicinity of 1b, 2a, and 2b is further heated intensively, and then the end surfaces 1a, 2a and the end surfaces 1b, 2b are brought into abutment by a predetermined pressing force applied from the left and right by the squeeze rolls 12, 12, respectively. As shown in Fig. 4,
The tube body 13 is made up of an inner tube 13a made of the strip plate 1 and an outer tube 13b made of the strip plate 2, and then sent out. The heating temperature in the heating coil 11 is such that the amorphous metal layer formed on the end surfaces 1a, 1b, 2a, 2b of the strips 1 and 2 by the thermal spraying from the thermal spray nozzle 7 is mainly melted, or only the amorphous metal layer is melted. The strips 1 and 2 are melted.
The temperature is set to slightly exceed the melting point of the amorphous metal, which has a low melting point compared to Decided to give. FIG. 5 is an enlarged cross-sectional view of the vicinity of the joint exhibiting an undesirable joint condition. In the tube body 13 having such a large raised portion, when the inner and outer surfaces are finished in a later finishing process as shown by the broken line in the figure, the raised portion 13c on the inner surface side
Due to this removal, a part of the outer tube 13b made of the strip plate 2, which has inferior corrosion resistance compared to the inner tube 13a made of the strip plate 1, may be exposed to the inner surface. Therefore, the tube body 13 should be joined with a low upset. is necessary. The amorphous metal layer on the end surfaces 1a, 1b, 2a, 2b of the strips 1, 2 is formed to compensate for the lack of joint strength due to low upset welding, and at the joint of the tube body 13, the heating coil 1
Since a bonded state is obtained through the amorphous metal layer which is melted by heating in step 1, the bonded portion has sufficient bonding strength even by low upset welding.

The tubular body 13 thus formed is fed into the heating section 14 disposed upstream of the squeeze rolls 12, 12, and heated to a predetermined temperature while passing through the heating section 14. After being sent out from the heating section 14, it is cooled during further conveyance, and the inner tube 13
The outer surface of the tube a and the inner surface of the outer tube 13b become a laminated tube 15 that is metallurgically joined via a layer of amorphous metal interposed between the two. The heating temperature in the heating section 14 is set to be higher than the melting point of the amorphous metal in order to realize a strong metallurgical bonding state between the inner tube 13a and the outer tube 13b. In order to prevent deterioration of strength and toughness, the temperature is set so as not to exceed either the melting point of the strip 1 that will become the inner tube 13a and the melting point of the strip 2 that will become the outer tube 13b.

In this embodiment, the thermal spray nozzles 7, 7...
Although the amorphous metal layer is formed by spraying powder from..., the structure is not limited to this, and for example, the layer may be formed by depositing an amorphous metal foil.

Further, in this embodiment, an amorphous metal layer is formed on the upper surface of the strip plate 2, but if possible, a layer may be formed on the lower surface of the strip plate 1, or it may be formed on both. , Furthermore, in this embodiment, both end surfaces 1a, 1b, 2a, 2b in the width direction of the strips 1, 2
A layer of amorphous metal is formed on either one of the end surfaces 1a, 1b, and the end surfaces 2a, 2b.
The layer may be formed on either one of the two.

Furthermore, in this embodiment, a metal with excellent corrosion resistance is used for the strip plate 1 that becomes the inner tube 13a, and a metal that is both high strength and inexpensive is used for the strip plate 2 that becomes the outer tube 13b. It goes without saying that the method of the present invention is applicable even in such cases.

Finally, an example of manufacturing a laminated pipe by the method of the present invention will be described.

(Manufacturing example 1) As the strip plate 1 for the inner pipe, 0.02C−0.43Si−
It is made of high alloy steel (JIS SUS 316L) with a content of 0.98Mn−13.01Ni−17.30Cr−2.21Mo (all values are weight%), and the balance is essentially Fe, and has a thickness of 1 mm. 0.17C−0.26Si−1.27Mn−0.013P−
The upper surface of the strip plate 2 and the strip plate 1 are made of low-alloy steel with a content of 0.004S (value is % by weight) and the remainder is substantially Fe, and have a thickness of 3 mm. , 18.7Cr on the end surfaces 1a, 1b, 2a, 2b of 2.
Nickel-based amorphous metal (melting point: 1170
A layer of amorphous amorphous metal was formed by applying foil (thickness: 40 μm) made of aluminum foil (40 μm thick) made of aluminum foil (40 μm thick) made of 1200° C. and further increase the heating temperature in the heating section 14 to 1210
℃ and then cooled at an average cooling rate of 15° C./sec after heating to produce a laminated tube 15 with a nominal diameter of 38 mm.

As a result of conducting a close contact flattening test on this laminated pipe 15, it was found that cracks occurred at the joint and the inner pipe 13
No peeling was observed at the interface between a and the outer tube 13b, and it was confirmed that a good metallurgical bonding state was obtained.

In addition, a No. 11 test piece specified in JIS Z-2201 was prepared and a tensile test was performed on the test piece. As a result, it was confirmed that the test piece had a tensile strength of 58.3 Kg/ ^mm2 , and the fracture area is sufficiently narrowed down, and
It was observed that the fracture line did not develop at the joint, and that no peeling occurred at the interface between the inner tube 13a and the outer tube 13b.

Further, as a result of manufacturing the laminated tube 15 by setting the heating temperature in the heating coil 11 to 1100° C., which is lower than the melting point of the amorphous amorphous metal, and keeping the other conditions the same, the amorphous amorphous metal layer at the end surfaces 1a, 1b, 2a, and 2b was melted. It was confirmed that the bonding conditions were insufficient and a good bonding condition could not be obtained at the bonded portion.

Furthermore, the above-mentioned adhesion flattening test and tensile test were conducted on the laminated tubes 15 manufactured under the same conditions except that the heating temperature in the heating section 14 was 1100° C. and 1450° C. In the former case, the results of the close contact flat test,
The occurrence of peeling at the interface between the inner tube 13a and the outer tube 13b was observed, and it became clear that a sufficient bond was not obtained, and the tensile strength was 57.6 Kg/mm ² . In the latter case, the results of the close contact flat test,
Along with the occurrence of peeling at the interface, cracking was observed at the joint, and the tensile strength was 88.3Kg/
mm ² , and it became clear that excessive heating causes brittleness.

(Manufacturing example 2) As the strip plate 1 for the inner tube, 0.01C−0.40Si−
0.41Mn−0.012P−0.001S−1.70Cu−40.52Ni−
It is made of high alloy steel (Alloy 825) with a content of 20.06Cr-3.00Mo (all values are weight%) and the remainder is Fe, and a strip plate with a thickness of 3 mm is used. As plate 2, 0.08C−0.17Si
-1.54Mn-0.008P-0.002S (numbers are weight%), the remainder is made of low alloy steel consisting essentially of Fe, and the strip plate is 9 mm thick. 2 top surface and end surfaces 1a, 1b, 2 of strip plates 1, 2
For a and 2b, powder of nickel-based amorphous metal (melting point 890 to 920°C) having a content of 9P (values are % by weight) and the remainder being nickel was added to 75 μm.
A layer of amorphous metal is formed by thermal spraying to a thickness of
The squeeze rolls 12, 12 give an offset of approximately 0 mm, and the heating temperature in the heating section 14 is set to 950°C. After heating, the average cooling rate is 27°C/
sec to produce a laminated tube 15 with a nominal diameter of 16 inches.

A No. 14B test piece specified in JIS Z-2201 was prepared for this laminated pipe 15 so that the joint was located at the center of the test piece in the width direction, and a tensile test was performed on the test piece. Neither the propagation of the fracture line to the joint nor the occurrence of peeling at the interface between the inner tube 13a and the outer tube 13b was observed, and it was confirmed that the fracture occurred with sufficient constriction occurring at the fracture portion. The tensile strength was 63.7Kg/ ^mm2 .

In addition, as a result of bending tests in the front and back directions and width direction, and shear strength tests according to JIS G-0601,
In the former test, neither cracking at the joint nor peeling at the interface was observed, indicating that the joint had sufficient durability against bending. ² , a shear strength of 27 Kg/mm ² was measured at the interface, and it was confirmed that the material had sufficient shear strength.

(Production Example 3) Using the 3 mm thick alloy steel for the inner tube and the 9 mm thick low alloy steel for the outer tube shown in Production Example 1, 18.7Cr-
75μ powder of Ni-based amorphous metal (melting point 1170-1200℃) containing 9.75Si−0.1C
The upper surface of the strip plate 2 and the end surface 1 of the strip plates 1 and 2 to a thickness of m.
a, 1b, 2a, and 2b to form a layer of amorphous amorphous metal, heat it with a heating coil 11 until the end of the base material melts, and then press the squeeze roll 1.
2 and 12 to give an offset of 0.5 mm, normal electric resistance welding was performed, and the heating temperature in the heating section 14 was set to 1250°C, and the average cooling rate was 15 after heating.
It was cooled at °C/sec to produce a laminated tube with a nominal diameter of 16 inches.

For this laminated pipe, a No. 14B test piece specified in JIS-Z-2201 was prepared so that the butt part was at the center, and a tensile test was performed on the test piece. As a result, the inner pipe 13a and the outer pipe 13b were Although no delamination was observed at the interface between the two specimens, one out of 15 specimens had a fracture line extending to the joint.
However, their average tensile strength is 59.6Kgf/mm ²
It was confirmed that the material had sufficient strength.

In addition, as a result of bending tests in the front/back direction and width direction according to JIS-G-0601, and a shear strength test, in the former test, there was no occurrence of fracture at the joint or peeling at the interface, and the It has become clear that it has excellent durability,
Further, in the latter test, a shear strength of 33 Kgf/mm ² was measured at the interface, and it was confirmed that the material had sufficient shear strength.

〔effect〕

As described in detail above, according to the method of the present invention, strips made of different types of metal are laminated and formed together into a cylindrical shape, and the end surfaces of both are welded through the amorphous metal layer formed on the end surface. are heated and then metallurgically joined through a layer of amorphous metal interposed between them to produce a laminated metal tube. Therefore, it is possible to continuously manufacture laminated metal tubes with high efficiency. The present invention has excellent effects such as being able to easily obtain a long laminated metal tube.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the implementation state of the method of the present invention,
Figures 2 and 3 are cross-sectional views of the laminate in the middle of the forming process, Figure 4 is a cross-sectional view of the tube after electric resistance welding, and Figure 5 is a cross-sectional view of the tube near the joint showing an undesirable joint state. It is an enlarged cross-sectional view. DESCRIPTION OF SYMBOLS 1, 2... Band plate, 6... Laminate, 7... Thermal spray nozzle, 10... Heating part, 11... Heating coil, 1
3... tube body, 13a... inner tube, 13b... outer tube,
14... Heating section, 15... Laminated tube.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a laminated metal tube in which an inner tube made of metal is covered with an outer tube made of a different metal, comprising: a metal strip serving as the inner tube and a metal strip serving as the outer tube; The strip plates are fed in the same direction with one side facing each other, a layer of amorphous metal is formed on one or both of the end faces in the width direction and the opposing faces, and then both are laminated in the thickness direction. Then, this laminate is formed into a cylindrical shape with a metal strip serving as the inner tube on the inside, and the end faces of the metal strip serving as the inner tube and the metal strip serving as the outer tube are electrically welded. A method for manufacturing a laminated metal tube, which comprises forming a tube into a tube, and then heating the tube to a temperature above the melting point of the amorphous metal and below the melting points of both of the metals.