JPH0452182B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an economical and high yield method for manufacturing seamless clad pipes.

Recently, chemical industry plant piping, oil country tubular goods, and gear ring line pipes have introduced CO2 and other substances into their environments.
They tend to contain large amounts of corrosive substances such as H ₂ S, and it is especially advantageous to use seamless black pipes under such harsh environmental conditions. In other words, the use of clad pipes, in which the inner surface of a base material made of carbon steel or low-alloy steel is lined with a corrosion-resistant material (composite material) such as high-alloy steel such as stainless steel, or nickel or nickel alloy, can be used as oil country tubular goods, for example. This is advantageous in terms of economically ensuring corrosion resistance.

Now, in the case of such OCTG applications, the clad pipe is required to have a complete metallurgical bond between the base material and the composite material, but it is difficult to manufacture such high-quality clad pipe on an industrial scale. Methods include the following. In other words, basically the first
The double tube A shown in Figure A is made up of an outer tube 1 made of base material or composite material and an inner tube 2 made of composite material or base material. A method in which seal welding is performed at both ends (symbol B in A in the same figure), and then heating to a predetermined temperature and hot elongation rolling (crimping rolling) as shown in A to C in the same figure (in this case, double tube rolling) is performed. (tentatively named the law). The above-mentioned double-ply tube A is one in which the outer tube 1 and the inner tube 2 are simply mechanically brought into close contact with each other (hereinafter referred to as a close-fitting pipe), or the two are crimped even if not completely. (hereinafter referred to as incompletely crimped pipe) is used. Regarding this tube,
During manufacture, a medium such as Ni may be interposed between the inner and outer tubes by plating or wrapping the outer surface of the inner tube in the form of a foil. This medium is
This method is effective in obtaining a high-quality clad tube with little mutual diffusion of components between the inner and outer tubes. This seal welding at both ends of the double-layered tube will be applied to the outer tube 1 and inner tube 2 during subsequent heating.
In addition to preventing the crimped surface from being oxidized due to the difference in thermal expansion between the two, it also prevents the base material and composite material from shifting in the axial direction during rolling, especially in the case of the above-mentioned tight-fitting pipe. It also has the meaning of prevention.
In the case of a close-fitting pipe, after this seal welding, the outer pipe 1
The air between the inner tube 2 and the inner tube 2 may be vented and replaced with inert gas. Needless to say, hot elongation rolling involves crimping the outer tube and the inner tube, and as shown in the figure, the process is first passed through an inclined roll rolling mill (for example, Mannesmann perforator 3), and then using a plug mill 4, an Atssel mill, a Pilger mill, etc. The rolling method is suitable.

According to such a method, it is possible to obtain a clad pipe in which the base material and the composite material are completely and firmly crimped together.

By the way, there are three main methods for obtaining the double element pipes used in this method, that is, tightly bonded pipes or incompletely crimped pipes, but they each have their own drawbacks. can be,
None of them are practically satisfactory. In other words, the explosion method, in which the inner tube is crimped or brought into close contact with the outer tube by explosive crimping or explosive tube expansion, has limitations on the length of the applicable tube, and it is difficult to obtain a duplex tube of the length practically required. is difficult. In addition, the method of heating the outer tube and press-fitting the inner tube into it has the problem of generating oxide scale due to heating, and if both the inner tube and the outer tube are not thick enough, there is a risk of buckling during press-fitting. This relationship has the disadvantage that the applicable pipe size is restricted. Compared to these two methods, the cold drawing method, in which loosely fitted inner and outer tubes are cold drawn and the outer tube is brought into close contact with the inner tube, has an absolute advantage in that it can manufacture double-layered tubes of any size. However, this also requires the introduction of a large drawing machine, and there are also problems in terms of work efficiency and work cost.Furthermore, after drawing, the front end (mouth part) and rear end of the double pipe are each approximately 200~ The yield is quite low because it is necessary to cut off about 300mm.

One method is to use the inner and outer tubes as a double tube with loose fitting, but in this case, even if the air is removed after welding the seals at both ends or the air is replaced with inert gas, Even if you go far enough,
It is difficult to obtain a completely crimped clad pipe.

The present invention provides that the raw pipe manufacturing method is significantly advantageous in terms of yield, efficiency, and cost compared to the cold drawing method described above, and that the pipe size to which it can be applied is not limited unlike the explosion method or the press-in method. The purpose is to provide a pipe manufacturing method.

The method of the present invention involves inserting an inner tube made of a composite material or base material into an outer tube made of a base material or composite material, and expanding the inner tube by hydraulic pressure to form a double layer in which the base material and composite material are in close contact with each other. In the method for manufacturing a seamless clad pipe in which a tube is obtained, a base material and a composite material are seal-welded at both ends of the double-layer tube, the tube is heated to a predetermined temperature, and then hot-stretched and rolled. For this, use a pipe with a length that allows both ends of the outer pipe to protrude outward from the outer pipe by at least three times the wall thickness of the inner pipe itself, seal both ends of the inner pipe, and apply water pressure. The sealing jig 5 includes an end cap 6 that comes into contact with the end surface of the protrusion of the inner tube, and a seal cup 8 that protrudes forward from the cap and that opens at the tip to be inserted into the inner tube and comes into close contact with the inner surface of the tube. It consists of an elastic liner 7 with a cylindrical shape and a flexible steel rib 9 provided so as to surround the outer surface of the elastic liner, and water pressure is applied through the through hole 10 of the end cap 6 of one sealing jig 5. It is characterized by the use of a structure in which the elastic liner 7 expands and the steel ribs 9 on its outer surface firmly grip the inner surface of the internal organ.

At this time, if necessary, apply Ni to the outer peripheral surface of the inner tube.
As is the case with the prior art, the medium may be wrapped in plating or foil.

A specific example of this hydraulic pipe expansion method is shown below.

As shown in FIG. 2, an inner tube 2 which is six times longer than the outer tube in length and has a wall thickness of the inner tube itself is fitted onto the outer tube 1, and tube end sealing jigs 5 are set at both ends of the inner tube.
The tube end sealing jig 5 includes an end cap 6 with a base ring 6', and an elastic seal cup 8 that protrudes forward from the inner surface of the end cap and is an open-end seal cup 8 whose tip inserted into the tube is in close contact with the inner surface of the tube. It consists of a liner 7 and a flexible steel rib 9 fixed at both ends to the end cap 6 and sealing cup 8 and surrounding the elastic liner 7. In use, insert the seal cup 8 side into the inner tube up to the base ring 6' position, and open the through hole 1 of the end cap 6.
When water pressure is applied to the inside of the tube from zero, the elastic liner 7 expands and the steel ribs 9 firmly grip and fix the inner surface of the inner tube, thereby providing a seal at the end of the tube.

Now, after setting such sealing jigs 5 at both ends of the inner tube, water is injected into the inner tube 2 through the through hole 10 of one of the sealing jigs 5 to fill it (at this time, the inner tube 2 is filled with water). (The air inside the tube is removed from the through hole, and then the through hole is plugged.) Then, the inner tube 2 is expanded by applying a required water pressure to the inside of the tube. By this tube expansion, the inner tube 2 is brought into close contact with the inner surface of the outer tube 1 as shown by the chain line in the same figure, thereby obtaining a close-fitting pipe.

In this method, the inner tube 2 is made longer than the outer tube 1 because the tube end sealing jig 5 as described above leaves an incompletely expanded section at the end of the inner tube 1. The portion l′ that is longer than the outer tube is cut off after expansion, and the length of this cut off length l is the difference between the inner diameter of the outer tube and the outer diameter of the inner tube, that is, the inner tube expansion length. Although it depends on the size of the inner tube, it is sufficient that the length is three times the inner tube wall thickness or less. In other words, the sealing jig 5 described above has a structure in which the elastic liner 7 expands when subjected to water pressure and follows the expansion deformation of the inner tube. This is because the deformation of the end portion is not restricted, and the incompletely expanded portion can be made smaller accordingly.

Therefore, it is much more advantageous in terms of yield. In addition, from a cost perspective, the cost of the tube end sealing jig is incomparable to that of a large cold drawing machine, and the work itself can be done at a low cost, and of course it is much more efficient in terms of manufacturing efficiency. It is something.

According to this method, it is possible to obtain a pipe with sufficient tightness as a material to be used in the double tube rolling method, and through double tube rolling using a conventional method, it is possible to obtain a clad pipe in which the inner and outer tubes are completely metallurgically connected. It is possible to manufacture tubes.

Moreover, the hydraulic pipe expansion method described above can be applied to the production of double pipes of any size (length, thickness).

According to the inventor's experiments, it was found that 339.7φ×15.0t (outer pipe 13.0, inner pipe
2.0) x 10,000 (unit: mm), Materials: We aimed to manufacture a double tube with 5Cr steel for the outer tube and 316L steel for the inner tube (with 60 μNi foil interposed between the inner and outer tubes). In this case, in the conventional method, the cutting allowance after manufacturing the close-contact double layer tube is
450mm (300mm on the tip end and 150mm on the rear end), whereas with the method of the present invention, only 90mm was required at both ends.
It's mm. In addition, after heating the double tube obtained in this way to 1250℃ under exactly the same conditions,
When stretched and rolled using a Mannesmann plug mill, high-quality clad steel pipes with a crimp rate of 100% or higher were obtained in all cases.

As is clear from the above explanation, the method for manufacturing clad pipes of the present invention has no restrictions on applicable size or material, and can be expected to be advantageous in terms of yield, efficiency, and cost. It can be said that it has great utility value in mass production of high quality clad pipes for oil country tubing applications.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram of the double-pipe rolling method, and FIG. 2 is a longitudinal sectional side view showing a specific example of manufacturing a blank pipe by the hydraulic pipe expansion method according to the present invention. In the figure, 1: outer tube, 2: inner tube, 3 Mannesmann piercing mill, 4: plug mill, 5: tube end sealing jig, 6: end cap, 7: elastic liner, 8:
Seal cup, 9: steel rib, 10: through hole.

Claims (1)

[Claims] 1 Insert an inner pipe made of composite material or base material into an outer pipe made of base material or composite material, and expand the inner pipe by hydraulic pressure to obtain a double base pipe in which the base material and composite material are in close contact with each other. In the method of manufacturing seamless clad pipes, in which the base material and composite material are seal-welded at both ends of the double-layered pipe and then heated to a predetermined temperature and then hot-stretched and rolled, the inner pipe has a cutting allowance. The sealing jig 5 that seals both ends of the inner tube and applies water pressure is used with a length that allows both ends of the outer tube to protrude outward from the outer tube by at least three times the wall thickness of the inner tube itself. ,
an end cap 6 that abuts the end face of the protrusion of the inner tube;
and an elastic liner 7 formed in a front-opening type seal cup 8 which protrudes forward from the cap and whose distal end to be inserted into the inner tube comes into close contact with the inner surface of the tube, and an elastic liner 7 provided so as to surround the outer surface of the elastic liner 7. When water pressure is applied through the through hole 10 of the end cap 6 of one seal jig 5, the elastic liner 7 expands, and the steel rib 9 on the outer surface of the liner A method for manufacturing a seamless clad pipe, characterized by using a pipe with a structure that firmly grips the inner surface.