JPH029544B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Classification/Field> The disclosed technology belongs to the technical field of manufacturing corrosion-resistant double pipes such as oil country tubular goods from block-shaped fitting pipe materials by extrusion or the like.

<Explanation of the gist> Therefore, this invention mechanically fits thick and short base tube materials such as carbon steel and stainless steel, and seals the tube end at the fitting interface by seal welding or the like. This invention relates to a manufacturing method in which a fitting pipe body material is metallurgically bonded and then extruded in the axial direction and extended by drawing or the like to obtain a double pipe of a clad steel pipe with a predetermined wall thickness, In particular, after tightly fitting a core metal inside the base pipe material to form a fitting pipe material, the fitting pipe material is vacuumed and the entire boundary surface on the open end side is sealed and welded all around. Then, the boundary surfaces are kept in a vacuum state and diffusion welding is performed to provide metallurgical bonding to all the boundary surfaces to create a composite pipe material.Then, the above-mentioned core metal is cut into separate pieces to form a columnar body. This invention relates to a method for manufacturing a double clad steel pipe, in which a composite pipe block is formed by removing the composite pipe block, and then the composite pipe block is subjected to extension forming.

<Prior Art> As is well known, oil country tubular goods, plant piping, etc. are required to have not only pressure resistance and heat resistance against working fluids, but also corrosion resistance, abrasion resistance, and the like.

To deal with this, for example, corrosion-resistant double pipes consisting of a stainless steel inner pipe and a carbon steel outer pipe are used, but even in such corrosion-resistant double pipes, the inner pipe may undergo locus flexure fracture during operation. In addition, it is desirable that the inner and outer tubes be firmly connected to prevent slippage between the inner and outer tubes.

By the way, regarding the connection of the inner and outer tubes, for example,
It has been found that clad pipes formed by metallurgical bonding are preferable to multilayer pipes formed by mechanical fitting such as shrink fitting in terms of strength and the like.

Accordingly, as a manufacturing technology for clad steel pipes that corresponds to this, for example, as shown in Fig. 1, a stainless steel inner pipe 2 is layered relative to a carbon steel outer pipe 1 in a predetermined manner, and suitable methods such as hydraulic pipe expansion are used. After tightly fitting the tube ends by TIG welding, etc., the boundary surfaces are sealed all around the circumference (3) to fix them in the axial direction, and then high-temperature heating is applied as shown in Fig. 2. Rolling is carried out by extrusion or drawing through a die 4 and a mandrel 5, and in the process, a metallurgical bond between the inner and outer tubes 1 and 2 is formed on the entire boundary surface to obtain a clad steel double tube. I was doing it.

<Problems with the prior art> However, in manufacturing clad steel double-pipe pipes using the conventional technology, sufficient surface pressure is applied during the rolling process to achieve metallurgical bonding between dissimilar metals of the inner and outer pipes. Heating is required, particularly at temperatures much higher than the elongation temperature of conventional one-piece tubes.

For example, metallurgical joining of a carbon steel outer tube and a stainless steel inner tube requires a temperature of about 1200℃, which requires maintenance and inspection of the heat generating device and machinery, and maintenance of heat resistance.The device itself becomes expensive, and as a result, The disadvantage was that the cost was high.

In addition, the difference in ductility and deformation resistance at high temperatures during rolling between dissimilar metals has the disadvantage of causing tension and breakage.

Furthermore, there was a problem in that there were large limits to the combinations of materials for the double pipes.

In addition, there were disadvantages in that the bonding efficiency was poor and the product yield was low.

In addition, when operating conditions are severe, triple pipes,
Although quadruple tubes are sometimes required due to design, there is also the drawback that these double tubes cannot be rolled.

<Purpose of the Invention> The purpose of the present invention is to solve the problems of manufacturing double clad steel pipes based on the above-mentioned prior art, and to solve the problems in manufacturing double clad steel pipes based on the above-mentioned prior art. After that, metallurgical bonding of the joint surfaces is performed on the composite pipe material, which shortens the process of manufacturing double pipes, streamlines design and processing, and reduces manufacturing energy. It is an object of the present invention to provide an excellent method for manufacturing clad steel pipes that can be used in piping applications in various basic industries by making it possible to carry out the manufacturing process and also to ensure the accuracy of the joint surfaces.

<Structure of the Invention> In line with the above-mentioned object, the structure of the present invention, which is summarized in the above-mentioned claims, consists of a plurality of different materials having a predetermined thickness and length, in order to solve the above-mentioned problems. Columnar core metals serving as a base pipe material are relatively layered inside one base pipe material, and are mechanically bonded to form a fitting pipe material, and the fitting pipe material thus obtained. is brought into a vacuum state including the interface between the base tube materials, and in that state, the end boundary surface on the open end side of the base tube materials is sealed by seal welding or the like to maintain the degree of vacuum at the boundary surface, Next, well-known diffusion welding is performed to achieve metallurgical bonding of all interfaces of the mating tube material, and then a column of a predetermined diameter is cut out from the core bar to form a composite tube block. Then, the composite pipe block is extruded through a die, a mandrel, etc., and the composite pipe block is axially stretched by means such as drawing, thereby obtaining a composite clad steel pipe of a set length. be.

<Example> Next, an example of the present invention will be described below with reference to the drawings from FIG. 3 onwards.

Note that the same parts as in FIGS. 1 and 2 will be described using the same reference numerals.

In the embodiment shown in FIGS. 3 to 8, first, the third
As shown in the figure, a columnar stainless steel core 6 and
The stainless steel outer tubes 7 with both ends open are mutually overfitted at room temperature, at a predetermined low temperature, and at a high temperature, and when the temperature returns to room temperature, a fitting allowance is obtained for each to achieve a mechanically fastened state. 4. As shown in FIG. 4, a triple fastened fitting pipe material 8 having a set wall thickness and a short length is obtained.

Next, the fitting tube material 8 is set in a well-known electron beam welding device 9 as shown in FIG. At each of the three base tube materials 6,
Seal welding 3, 3 to a predetermined depth on the interface between the joining ends of 2, 7 is performed all around the entire circumference at both ends.

Therefore, in this embodiment, prior to the seal welding 3, 3 in the electron beam welding device 9, the entire interface 12,
Since the high vacuum state of 13 is revealed, seal welding 3,
After 3, the vacuum state is completely maintained.

Immediately or after a predetermined period of time after the seal welding 3, 3, the fitting tube material 8 whose open end is sealed is set in a well-known diffusion welding device 14 as shown in FIG. Diffusion welding is performed for a set time under a predetermined temperature H and pressure P in an argon gas atmosphere, and each base pipe material 6, 2,
Boundary surface 1 with the above degree of vacuum maintained between 7
A metallurgical joint 15, 16 is formed over the entire surface of the base pipes 2, 13, completing the integral metallurgical joint of the three base pipes 6, 2, 7.

Therefore, the metallurgically bonded fitting pipe material 8 is taken out from the diffusion welding device 14, and the concentric columnar body 17 is cut and hollowed out from the core bar 6 using a suitable hole-drilling device as shown in FIG. Then, the composite pipe block 18 is obtained, and then the eighth
As shown in the figure, a die 4 and a mandrel 5 of a well-known drawing device are set and drawing is performed in a predetermined manner to obtain a triple clad steel pipe 19 having a predetermined thin wall thickness.

In this process, as mentioned above, the composite pipe block 18 is pulled because the three interfaces 12 and 13 are strongly connected metallurgically before being pulled out.
There is no risk of damage etc.

After the long triple clad steel pipe 19 is obtained, it is only necessary to cut and separate it into each predetermined unit pipe, and each cut unit pipe has the boundary surfaces 12 and 1.
3 are metallurgically combined, allowing the original function to be fully achieved.

Of course, it is also possible to use it in the form of a long tube.

In addition, in the embodiment shown in FIGS. 9 and 10, the carbon steel medium tube 2 is attached to the stainless steel core 6 at the stage of the mating blank tube 8.
After fitting and welding the end seals in a vacuum state and metallurgically bonding the interface 12 by diffusion welding, the column 17 is cut out from the core metal 6 to obtain the desired composite pipe block 18. This is an embodiment in which a long double clad steel pipe is maintained.

It goes without saying that the embodiments of this invention are not limited to the above-mentioned embodiments; for example, it is possible to manufacture quadruple pipes in addition to triple pipes, TIG welding is also possible for end seal welding, and shaft Various aspects can be adopted for the directional stretching process, such as extrusion molding.

It goes without saying that the present invention is also applicable to cases where the outer base tube material has a bottomed shape at one end and an open shape at the other end.

<Effects of the Invention> According to the present invention, it is basically impossible to directly form a double pipe such as a normal corrosion-resistant pipe whose boundary joint surface is clad-jointed over its entire length. By using diffusion welding when manufacturing short thick-walled clad pipes in advance, it is possible to metallurgically join multiple boundary joint surfaces at once, and to achieve uniform precision throughout the entire surface without internal defects. , an excellent effect can be achieved in that design flexibility can be obtained in terms of material and shape.

By inserting and fitting the columnar mandrel inside the base tube material to form the fitting tube material, the fitting tube becomes block-shaped, making it easy to handle and preventing peeling during processing. , the effect that distortion or the like does not occur during work in each process is achieved.

Furthermore, since heat input is absorbed and dispersed in the core metal during welding and sealing, such as seal melting, on the edges of each boundary surface, there is an excellent effect that the influence of welding heat does not appear significantly on the boundary surfaces and edges.

Therefore, residual stress in the inner tube after the column is cut out from the composite tube block after diffusion welding is also reduced.

Further, it is possible to perform full-surface joining regardless of the length and thickness of the short base tube materials, and there is also the effect that a plurality of base tube fitting tube materials can be simultaneously diffusion welded.

Furthermore, during the diffusion welding, since the solid core metal is closely fitted inside, there is also the effect that maintaining the vacuum level is more reliably guaranteed.

Furthermore, since the composite pipe blocks are completely metallurgically connected by diffusion welding,
Like ordinary carbon steel pipes, extrusion molding equipment can be used as is, and there is no strain during elongation molding.
It does not cause product defects such as breakage, and it also has the advantage that it can be done at low temperatures, unlike cladding by rolling welding or the like.

In addition, unlike rolled cladding, it has the effect of providing a greater degree of freedom in selecting the material for the base pipe.

Furthermore, there is flexibility in that not only triple-layered pipes but also double-layered pipes such as quadruple-layered pipes can be manufactured.

In addition, the core metal has the advantage of being able to be used for the next production of small diameter pipes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a fitting tube of a double pipe based on the prior art, FIG. 2 is an explanatory sectional view of a pultrusion molding based on the prior art, and FIG. Figure 3 is a partially cutaway perspective view explaining the fitting of the base pipe material, Figure 4 is a cross-sectional view of the fitting pipe material, Figure 5 is a cross-sectional view of the end seal welding of the fitting pipe material, and Figure 6 is an explanation of diffusion welding. 7 is an explanatory sectional view of hollowing out a column from a core metal, FIG. 8 is an explanatory sectional view of tubular body extension molding, FIG. 9 is a sectional view corresponding to FIG. 5 of another embodiment, and FIG. 10 is a sectional view corresponding to FIG. 7. 6, 2, 7...Base pipe material, 12, 13...Boundary surface, 3...Seal welding, 8...Mating pipe material, 17
... Clad steel pipe, 6 ... Core metal, 11 ... Open end, 14 ... Diffusion welding (equipment), 17 ... Column,
18...Composite pipe block.

Claims (1)

[Claims] 1. In a manufacturing method in which a double clad steel pipe of a predetermined length is obtained by fitting base pipe materials, sealing the pipe ends at the interface between the base pipe materials by welding, and then extending and deforming the pipe in the axial direction. , A core metal is fitted inside the base pipe material to form a mating pipe material, and the interface between the mating pipe materials is brought into a vacuum state, and the open end of each boundary surface is circumferentially covered. The tube is sealed by welding, diffusion welding is performed while maintaining a vacuum state at the boundary surface, and the column is then cut and removed from the core bar to obtain a composite tube block. 1. A method for manufacturing a clad steel pipe, characterized in that a double clad steel pipe of a predetermined length is obtained by deformation.