JPS61186466A - Plasma thermal spraying method of inner wall of tubular structural body - Google Patents

Abstract

PURPOSE:To line an inner wall of tubular structural body at a high adhesive strength, by providing a thermal spraying head in a tube, closing the tube ends, reducing pressure therein, then subjecting to plasma thermal spraying the tube body while revolving it, and moving the spraying head. CONSTITUTION:In a set composed of the thermal spraying head 2, a power supply source 6, a powder material supplying apparatus 5, a cooling water supplying apparatus 31, a controller 4, the head 2 part is provided in a tubular structural body 1. Both ends of the body 1 are closed with blind covers 7, and the pressure therein is reduced to <=150Torr. Plasma gas is supplied to the head 2, the tube 1 is revolved on a roller 26 to advance plasma thermal spraying in circumferential direction. If a sprayed film 32 is formed to a prescribed thickness on an inner wall 34, the head 2 is moved by a moving pitch of 10-100nm range.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides the inner wall of a tubular structure with properties such as corrosion resistance, abrasion resistance, heat resistance, etc. The present invention relates to a method of performing so-called lining using a plasma spraying method.

(Conventional techniques and their problems) Lining of tubular structures (hereinafter referred to as tubes) 11 is a technique commonly used in all industrial fields, and plasma spraying is known as one of these techniques, but in practice There are few examples of it being used, and the reason is t±.

The lining film made by plasma spraying, which is usually performed in the atmosphere, has pores of around 10z per volume ratio, which is rather convenient as a heat-resistant film, but as a corrosion-resistant and abrasion-resistant film, it completely isolates the substrate from the environment. 1. I was at the point where I couldn't cut N. Increasing the thickness of the film can prevent the cracking problem to some extent, but increasing the thickness also increases residual stress and impairs the adhesion strength to the substrate, so there are restrictions. Plasma spraying uses a high heat source temperature, and can be used to spray materials ranging from general metals to high melting point metals, oxides, nitrides, and carbides.

Although this method is extremely attractive as a lining method that can be applied to all kinds of materials, including ceramics such as borides, it is necessary to solve these problems in order to make it widely available.

In recent years, a method of thermal spraying in a reduced pressure environment has been proposed as a means of lowering the porosity and improving the adhesion strength of plasma sprayed coatings, and active research reports have begun to appear. When plasma spraying is carried out in the atmosphere, pores, oxides, and nitrides may be created in the film due to the interaction of the molten particles with oxygen and nitrogen, which are active gas components in the atmosphere, and the flight of the molten particles may be caused by the atmosphere. It was found that thermal spraying should be carried out in an environment that excludes the atmosphere as much as possible, since the deceleration may be reduced and the adhesion strength may be reduced. For this reason, in the field, a special chamber is constructed, the material to be melted and a thermal spray head are placed inside, and the thermal spraying is carried out by remote control while expelling the gas inside. Naturally, this method cannot be applied to items that cannot be accommodated in the chamber. The length of each tube to be lined is usually 10 m or more, and it has been thought that this technique cannot be applied to it.

(Means for Solving the Problems) The present invention was conceived in view of these circumstances, and aims to utilize the advantages of plasma spraying in a reduced pressure environment for lining the inner wall of a tubular structure.

Namely, the plasma spraying method of the present invention uses a spray head which is a main component of plasma spray equipment.

After housing the power source, powder material supply device, cooling water supply device, and the thermal spraying head part of the control device inside the tube and closing the tube end,
The pressure inside the tube is maintained at 150 Torr or less, and the tube body is rotated at a circumferential speed approximately equal to the thermal spraying speed in a fixed position. The opposing thermal spray head is 10 to 100 sl.
Plasma spraying is performed on the inner wall of the tubular structure multiple times while moving in the I-axis direction.

(Structure and operation of the invention) The present invention will be explained below based on the drawings.

FIG. 1a and FIG. 2 show an example of the configuration of the first invention, 1
is a horizontally placed tubular structure, 2 is a thermal spray head disposed inside the tubular structure 1, and a control device 4 is disposed outside via cables 3. Powder material supply device 5 and power supply 6
It is tied to Both ends of the tubular structure 1 are closed by blind lids 7, and the blind lids 7 on both sides are connected by an axis 8 passing through the center of the tube, a stopper 99 fixed to the axis 8, and bearings 11 on both sides. The tubular structure 1 is sandwiched therebetween. The contact portion between the blind lid 7 and the shaft 8 is an O-ring 12, and the end portions of the blind lid 7 and the tubular structure 1 are kept airtight by packings 13.

The block 14 supporting the thermal spraying head 2 is screwed onto a spindle 19 which is rotated via bevel gears 17 and 18 by a motor 16 attached to a base 15 fixed to the shaft 8, with the shaft 8 as a guide, and is horizontally rotated. It is supposed to move. As the thermal spraying head 2 moves, the cables 3 connected to the thermal spraying head 2 are connected to a trolley 21 suspended on a wire 20' stretched between brackets 20 fixed to a shaft 8 near both ends of the tubular structure 1. Move by hanging. Further, the shaft 8 is provided with suction ports 22 distributed in order to suck internal gas through an exhaust hose 23 by an exhaust device 24.

Further, a plurality of rollers 28 supporting the tubular structure 1 are arranged on the workbench 25, and the rollers 26 are rotated via a drive shaft 28 rotated by a motor reduction mechanism 27 on the workbench. When the rollers 26 rotate, the tubular structure 1 and the blind lid 7 supported by the group of rollers also rotate, but the shaft 8
Since a stopper 9 connected to the shaft 8 is tightened and fixed with a bolt 30 to a bracket 29 fixed on the workbench 25, the plasma jet 33 does not rotate together. Therefore, the plasma jet 33 always faces in a fixed direction. 34 is the inner wall of the tubular structure l, and 32 is a thermal spray coating that is in close contact with the inner wall.

31 is a cooling water supply device.

In the above configuration, the thermal spray head 2. Control device 4, powder material supply device 5. The cooling water supply device 31 and the power supply 6 are a set of ordinary plasma spraying equipment, and except for the spraying head 2, they are all placed outside the tubular structure 1, and are passed through the inside of the shaft 8 by the tube wall 34 and the blind M7. Electric current, plasma gas, powder spray material and cooling water are supplied to the spray head 2 via cables 3 communicating within the enclosed space. Before starting plasma spraying, the gas inside the tubular structure 1 is exhausted by an exhaust device 2.
Drive and eliminate 4. Through this operation, the internal pressure gradually decreases. The low pressure thermal spraying effect clearly appears 1
When the temperature drops below 50 Torr, plasma spraying begins. When thermal spraying begins, plasma gas is supplied to the spray head at a rate of 50 to 250 centimeters per minute.
Since gas expanded twice in volume is released, the exhaust capacity of the exhaust device 24 must exceed this amount of released gas in order to keep the internal pressure below 150 Torr during thermal spraying. The distance between the tip of the thermal spray head 2 and the inner wall 34 is 50 to 100 m.
Set to m. There are no particular restrictions on the direction of the thermal spraying head 2, but when there is only one thermal spraying head 2, the downward direction is selected.

Thermal spraying proceeds in the circumferential direction by rotating the tubular structure 1 on the roller 2B. This speed varies depending on the type of thermal spraying material and the diameter of the tubular structure 1, so it is determined in advance by experiment. Normally the circumferential speed is 500-1500
It is in the range of mm/min. The spray head 2 sprays a spray coating 3 to a predetermined thickness on the inner wall 34 at the starting point in the axial direction (usually at the tube end).
Once 5 is in close contact, move to the next location. This moving pitch is experimentally determined so that the thickness is uniform, and is usually within the range of 10 to 1100 a. In thermal spraying in a reduced pressure environment, the spraying pattern spreads out more widely than in the atmosphere, so the movement pitch may be coarser, and the work ends when the thermal spraying head 2 continues to move and reaches the other end.

FIG. 2 shows a configuration example of the second invention, in which 2', 2'' are thermal spraying heads newly added to the thermal spraying head 2 and arranged at equal intervals on the circumference, 33', 33'', and 32. '.

32'' is the plasma jet and sprayed coating produced by thermal spray heads 2f and 2II, respectively. In this configuration, thermal spray heads 2, 2', and 2'' have the same thermal spraying capacity, so the working time can be calculated simply by the thermal spray head. This is 1/3 of the case with one unit. If n thermal spraying heads are arranged in one circumferential direction, the working time will be 1/n. In this example, the tubular structure 1
This is effective when the diameter of the

FIG. 3 shows a configuration example of the third invention, 2', 14',
33' and 32' are newly added thermal spray heads, blocks, plasma jets, and thermal spray coatings arranged in the axial direction of the tubular structure l. In this configuration, the spray heads 2.2' have the same spraying capacity.

By simple calculation, the working time is 172 hours for one thermal spray head. If n thermal spraying heads are arranged in the axial direction, the working time will be reduced to 1/n. This example is effective when the tubular structure l has a small diameter and is long in the axial direction.

In addition, in the present invention, the second. It should be added that it is also effective to combine the specific example of $3.

Next, examples will be shown.

(Example 1) φ tubular structure Drainage steel pipe diameter 400 mm φ x 24 m φ thermal spraying material Copper powder a Purpose ** ζ Each visit to top surface to prevent adhesion/decompression pressure 100 Tart ・Plasma spray head 1 & ・Plasma spraying conditions output 40 KW Plasma gas Argon + 10% helium 100fL/
Separating powder supply amount 150 g/dividing tube rotation 1 r-p, m (Example 2) - Tubular structure Oil well tubing vibe diameter 300
mmφ×12m ・Thermal spraying material Aluminum oxide powder ・Purpose
Corrosion prevention by carbon dioxide gas at high temperatures / Reduced pressure 100 Torr ・Plasma spray head 1 unit ・Plasma spray conditions Output 80 KW Plasma gas Argon + 10% hydrogen 100 g/min Powder supply amount 150 g/split tube rotation 1 r, p, m ( Example 3) ・Tubular structure Slurry steel pipe diameter 6001■φ ・Thermal spraying material Aluminum oxide powder φ Decompression pressure
100 Torr ・Plasma spraying head 2 units ・Plasma spraying condition output 100 KW Plasma gas Argon + IO% hydrogen 151/min Powder supply amount 200g/split tube rotation 1 r, p, m (Effects of the invention) Seen in the above examples As such, according to the present invention, it is possible to efficiently line the inner wall of a tubular structure with a material that is most suitable for the purpose and with high adhesion strength, which could not be done using conventional lining techniques.

[Brief explanation of drawings]

FIG. 1a is a block diagram of the present invention 1, FIG. 1 is a left side view of FIG. 1a, and FIGS. 2 and 3 are block diagrams showing other embodiments of the present invention. 1... Tubular structure, 2, 2', 2''... Thermal spray head, 3... Cables, 4... Control device, 5...
・Powder material supply device, 6...Power source, 7...Blind lid, 8
...shaft, 9...stopper, 10...bearing, 11...nut, 12...0 ring, 13...
Patsukin, 14...block, 15...base. 16...Motor, 17...Bevel gear, 18...
・Bevel gear, 19... spindle, 20... bracket, 20'... wire, 21... trolley,
2′! ...Suction port, 23...Exhaust hose, 24...
・Exhaust device, 25...Workbench, 2B...Roller,
27...Motor speed reduction mechanism, 28...Drive shaft, 28
Bracket, 30 Bolt, 31 Cooling water supply device, 32 Thermal spray coating, 33 Plasma jet, 34 Inner wall.

Claims (3)

[Claims] (1) In a method of applying plasma spraying to the inner wall of a tubular structure to impart properties not found in the tubular structure, the main components of plasma spraying equipment are a thermal spray head, a power source, a powder material supply device, and a cooling water supply device. After the spraying head part of the control device is accommodated in the tube and the tube end is closed, the pressure inside the tube is reduced to 15%.
Maintaining the pressure below 0 Torr, the tube body is rotated at a circumferential speed approximately equal to the thermal spraying speed in a fixed position, and at each appropriate rotation period, a thermal spraying head that is fixed at an appropriate position on the inner surface of the tube and faces the inner wall at a spraying distance is rotated. A method of plasma spraying the inner wall of a tubular structure while moving it in the axial direction by 10 to 100 mm. (2) The method according to claim 1, in which a plurality of thermal spray heads are provided on the same circumference. (3) The method according to claim 1 or 2, in which a plurality of thermal spraying head groups exist on the same tube axis.