JPH0229739B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an inner-coated steel pipe, and its object is to form a thin metal or ceramic coating with small pores on the inner surface of the pipe. Seamless steel pipes or welded steel pipes are used for drilling and transporting crude oil and natural gas. In recent years, as crude oil and natural gas containing large amounts of corrosive substances such as CO ₂ , H ₂ S, and Cl ^- have been produced, the use of highly corrosion-resistant materials such as stainless steel, Ni-based alloys, Cu-based alloys, etc. has increased. It is considered. However, since these materials are expensive, they are used as cladding materials only on the inner surfaces of steel pipes where corrosion is a problem, and they are manufactured as lined steel pipes or metallically bonded clad steel pipes. In the former case, the liner and steel pipe are not joined metallically, so once a gas leak occurs in the liner, pressure is generated in the gap between the liner and the steel pipe, and the liner swells during rapid depressurization, a phenomenon known as implosion. However, many accidents have been reported in the past. Clad steel pipes can be manufactured as either seamless pipes or welded pipes, and various manufacturing methods have been established. However, in either method, the manufacturing process is complicated, and from a production standpoint, the laminate requires a certain thickness or more, and the current situation is that it is unavoidable to use a laminate that is thicker than necessary for corrosion resistance. Further, particularly in clad welded steel pipes, there is a problem in that longitudinal welding is difficult depending on the material, and at the same time, welding significantly reduces manufacturing efficiency. Furthermore, a problem has been raised that the corrosion resistance of the laminate is deteriorated due to the thermal influence of longitudinal seam welding with a relatively large heat input. On the other hand, plasma spraying has been known as a type of coating, and has the advantages of ease of processing, control of the sprayed layer thickness, and weldability.
However, in this plasma spraying method, the coating material, which is usually powder, is transported by a carrier gas and is sprayed onto the base material using a high-temperature, high-velocity plasma gas flow, so these gases and the surrounding air are drawn into the coating layer. , there is a problem that pores are generated. For this reason, in the past, when plasma spraying is applied to an object such as a steel plate, a method is known in which the material to be sprayed is placed in a vacuum chamber and the material is sprayed. However, when applying this method to medium- to large-diameter pipes (diameter: 100 to 1,400 mm, length: approximately 6 to 20 m), a large vacuum chamber is required, which requires a huge amount of cost when considering incidental equipment. becomes. The present invention has been proposed against the background of this current situation, and is characterized by coating the inner surface of the steel pipe with a thin metal or ceramic with few pores by applying plasma spraying to the inside of the steel pipe under reduced pressure. It is something to do. An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram for carrying out the method of the present invention, and 1 is a steel pipe to be thermally sprayed. For example, as shown in Figure 1-a, this steel pipe 1 is supported at multiple locations in the longitudinal direction by a pair of rotating rolls 2 and 3 arranged on the left and right, and by driving one of the rolls 2, , the entire steel pipe is designed to rotate. Such a steel pipe 1 has a sealing lid 4 at both end openings,
It is sealed by 5. FIG. 2 shows an example of an attachment mechanism for these sealing lids 4 and 5, in which a plurality of locking devices 6 are fixed to the outer periphery of the end of the steel pipe 1 with bands 7. This lock device 6 is composed of a hook 9 pivotally attached to a bracket 8, and a spring 10 that applies elastic force to the hook 9.
Connect the tip of the hook 9 to the outer edge protrusion 11 of the sealing lids 4 and 5.
The sealing lids 4 and 5 are pressed against the tube ends by engaging with the tube ends. In the figure, reference numeral 12 denotes a gasket interposed between the abutting portion of the tube end surface and the sealing lid. The sealing lids 4 and 5 in this embodiment are formed with outwardly projecting bulges 32 so that plasma spraying, which will be described later, can be completely applied to the inner surface of the tube end. In the center of one of the sealing lids 4 and 5, there is a support pipe 1 of the plasma spraying device 13.
4 is penetrated so that it can slide and rotate and maintain airtightness. Inside this support pipe 14, an input code for plasma generation necessary for the plasma spraying apparatus 13 and a supply route for thermal spraying materials are passed. FIG. 3 shows an example of a sealing mechanism for the penetrating portion. That is, a first oil seal 16, a second oil seal 17, and a stopper 20 are inserted into an annular notch 15 formed at the center of the sealing lid 4, and a spacer 18 is provided between the oil seals 16 and 17. A spring 19 is interposed between the second oil seal 17 and the stopper 20, respectively. Further, a presser flange 21 is fixed to the outside of the sealing lid 4 with bolts or the like, and the presser flange 21 presses down the stopper 20. Note that the first oil seal 16 has a cutout portion 1.
The second oil seal 1 is in close contact with the inner inner surface 22 of 5.
7 is in close contact with the outer surface of the support pipe 14. The stopper 20 also serves to center the support pipe 14. On the other hand, a vacuum device is connected to the sealing lid 5 on the opposite side of the sealing lid 4. That is, as shown in detail in FIG. 4, there is a connecting pipe 23 in the center of the sealing lid 5.
is fixed, and this connecting pipe 23 and an intake pipe 24 leading to a vacuum pump (not shown) are rotatably connected via a stuffing box 25. Inside the stuffing box 25, a sealing mechanism for the sealing lid 4 is disposed. That is, 26 is a first oil seal, 27 is a second oil seal, 28 is a spacer, 29 is a spring, 30 is a stopper, and 31 is a holding flange. The above configuration is merely an example for implementing the present invention, and it goes without saying that the configuration of each part can be changed as necessary according to the spirit of the invention. When carrying out the method of the present invention using the apparatus described above, the steel pipe 1 is first placed on the rotating rolls 2 and 3, and after the plasma spraying device 13 is inserted into the pipe, sealing lids 4 are placed in the openings at both ends. , 5 to connect the connecting pipe 23 of the sealing lid 5 and the intake pipe 24. Next, the vacuum pump is operated to suck the air inside the steel pipe 1 and reduce the pressure to a predetermined pressure or less. While rotating the steel pipe 1 in this reduced pressure state, the plasma spraying device 13 is moved from one end of the pipe to the other end to spray the entire inner surface of the pipe to a predetermined thickness. In this embodiment, the steel pipe 1 is rotated, but the plasma spraying device 13 itself may be rotatable in the inner circumferential direction of the pipe for thermal spraying. When carrying out the present invention, the atmospheric pressure inside the pipe is 10~
300 Torr is preferred. FIG. 5 shows the relationship between atmospheric pressure and porosity, and when the atmospheric pressure is set to 300 Torr or less, the porosity can be suppressed to 1% or less. That is, when the porosity is 1% or more, corrosive media such as water and air pass through the coating layer, resulting in a decrease in corrosion resistance. However, when the atmospheric pressure becomes less than 10 Torr, the plasma gas temperature decreases and a normal sprayed layer cannot be formed. Therefore, it is necessary to control the pressure inside the tube to be within the above range using a vacuum pump. Furthermore, in the present invention, when the outer periphery of the steel pipe 1 is cooled with cooling water or the like during plasma spraying, the sprayed layer can be quickly solidified, and the above-mentioned seal mechanisms can also be protected from plasma heat. The object to be thermally sprayed according to the present invention has a diameter of 100 to 1400 mm.
The main target is carbon steel pipes with lengths of 6 to 20 m. Further, as the thermal spraying material, metals such as various stainless steels, nickel, nickel alloys, copper alloys, aluminum, aluminum alloys, and titanium, and ceramics such as alumina and chromium oxide can be used.

[Table] As is clear from the above examples, according to the present invention, when coating the inner surface of a steel pipe with metal or ceramics, it is possible to form an extremely thin coating layer with a low porosity, making it possible to coat the inner surface of a steel pipe with metal or ceramics. Internal corrosion resistance will improve. In addition, since plasma spray equipment moves along the axis of the tube in a reduced-pressure atmosphere, there is little air resistance to the flight of the spray particles, making it easy to set the required spray distance by simply adjusting the plasma output according to changes in the tube diameter. can do. Furthermore, compared to the method of constructing a vacuum chamber, various excellent effects can be obtained, such as lower cost, relatively easier design, and higher feasibility.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram for explaining the method of the present invention, Fig. 1-a is a side view of Fig. 1, Fig. 2 is a schematic diagram showing the mounting mechanism of the sealing lid, and Fig. 3 is a support for plasma spraying equipment. Schematic diagram showing the sealing mechanism of the pipe and the sealing lid,
FIG. 4 is a schematic diagram showing a sealing mechanism between a connecting pipe attached to a sealing lid and a suction pipe connected to a vacuum pump, and FIG. 5 is a graph showing the relationship between atmospheric pressure and porosity in plasma spraying. In the figure, 1 is a steel pipe, 4 and 5 are sealing lids, 13 is a plasma spraying device, and 24 is an intake pipe.

Claims (1)

[Scope of Claims] 1. When coating the inner surface of a steel pipe with metal or ceramics, the openings at both ends of the steel pipe are sealed with a sealing lid, and while the inside of the steel pipe is depressurized by a vacuum device connected to one sealing lid, the other end is depressurized. 1. A method for producing an inner-coated steel pipe, which comprises moving a plasma spraying device inserted through a sealed lid from one end of the steel pipe to the other to spray metal or ceramics onto the inner surface of the steel pipe. 2. When coating the inner surface of a steel pipe with metal or ceramics, the openings at both ends of the steel pipe are sealed with a hermetic lid, the inside of the steel pipe is depressurized by a vacuum device connected to one of the sealing lids, and the outer peripheral surface of the steel pipe is cooled. A method for manufacturing an inner-coated steel pipe, which comprises: moving a plasma spraying device inserted through the other sealing lid from one end of the steel pipe to the other to spray metal or ceramics onto the inner surface of the steel pipe.