JPH0730436B2 - Line explosive spraying method on the inner surface of a thin tube - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wire-explosion spraying method for the inner surface of a thin tube, and in particular, a thin tube capable of forming a dense and high-performance spray coating having excellent surface smoothness on the inner surface of the thin tube. It is related to the inner line explosive spraying method.

[Prior Art] The wire explosive spraying method is a method in which a wire material is exploded by passing a large shock current through a capacitor discharge into a wire-shaped spray material, and the wire material is made into high-temperature fine particles and sprayed at a high temperature. FIG. 2 is a diagram showing a discharge circuit of the line explosion spraying apparatus. In the figure, 1 is a charging device, 2 is a charging resistor, 3 is a capacitor, 4 is a charging switch, 5 is a spray wire, and 6 is a member to be sprayed. During thermal spraying, 40 to 45% of the wire material is gasified and 55 to 60% becomes molten particles, and these particles are scattered in the gas and sprayed onto the member to be sprayed.

The line explosion spraying method is not suitable for thick film spraying of 100 μm or more,
Although it has drawbacks such as not being able to spray non-conductive wire, it can be sprayed on the inner surface of small diameter pipes.

 Easy to spray high melting point metal.

 Since the sprayed particles collide at high speed, they have a large adhesive force.

The thermal spraying time is short, the thermal effect on the product is small, and the thermal spraying on the glass surface is possible.

 Little oxidation of spray particles and coating.

 It has a coating surface roughness of about 5 μm and is suitable for precision spraying.

It is a method with excellent features such as.

[Problems to be Solved by the Invention] The line explosive spraying method is usually performed under atmospheric pressure. However, in the conventional line explosive spraying under atmospheric pressure, the porosity of the obtained sprayed film is high and the surface roughness is also low. It had the drawback of being coarse.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a wire explosion spraying method for the inner surface of a thin tube, which is capable of forming a dense and high-performance sprayed coating having excellent surface smoothness.

[Means for Solving the Problems] The linear explosion spraying method for the inner surface of a thin tube of the present invention is a method for performing line explosion spraying on the inner surface of a thin tube under reduced pressure, in which gas is sucked while being introduced into the thin tube, and the introduction pressure and suction are applied. 50 to 400 Torr depending on the pressure difference
It is characterized in that the pressure is reduced.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view illustrating a wire explosion spraying method according to an embodiment of the present invention.

In the method of the present embodiment, perforated plugs 11 and 12 are attached to both ends of the thin pipe 10 for thermal spraying, and the gas introduction pipe 13 and the gas suction pipe 14 are respectively inserted into the thin pipe 10 through the holes of the perforated plugs 11 and 12. And introduce gas from the gas introduction pipe 13,
Gas is sucked from the gas suction pipe 14 by a suction pump (not shown), and the suction pressure is set to be higher than the introduction pressure at that time so that the inside of the thin tube 10 is depressurized.

The gas introduction pipe 13 and the gas suction pipe 14 also serve as electrodes for the line detonation, and the wire rod 15 for the line detonation is connected to the circuit 16 through the inside thereof, and the circuit 16 is closed to apply a voltage to the thin tube. Ten
A coating is formed on the inner surface by line explosion spraying.

In FIG. 1, 21 is a gas cock, 22 is a pressure gauge, 23 is a power supply, and 24 is a switch. In FIG. 1, the circuit 16 is
It is shown in a simplified manner, and actually has the circuit configuration shown in FIG.

In the present invention, the pressure in the thin tube during the line explosion spraying
Reduce the pressure to 50 to 400 Torr. The pressure in the thin tube is 50 Torr
If it is less than 400 Torr or more than 400 Torr, a sufficiently dense coating having high surface smoothness cannot be obtained. Therefore, the pressure in the thin tube is reduced to 50 to 400 Torr, preferably 100 to 200 Torr, more preferably about 150 Torr.

The method of the present invention can be carried out in the same manner as the conventional wire-blast thermal spraying method, except that the pressure is reduced in the thin tube to be sprayed by the pressure difference between the gas introduction pressure and the suction pressure.

In the present invention, a method has been shown in which the capillaries are attached to both ends of the thin tube to use the thin tube itself as a decompression container, but the method of the present invention is not limited to the method of FIG. 1 and the entire thin tube is inserted into the decompression container. Then, the pressure can be reduced.

In the present invention, suction while introducing gas into the thin tube,
A decompression state is set by the differential pressure. In this way, the explosive gas generated during the line explosion spraying is performed by introducing the gas by the appropriate gas introduction means and the suction means to suck and reduce the pressure. It is possible to remove dust and dust, prevent these from adhering to the inner surface of the thin tube, and form a beautiful spray coating with high purity. In this case, as the gas to be introduced, in addition to air, a non-oxidizing gas such as nitrogen can be used. In the present invention, the gas introduction and suction means are not limited to those shown in the figure, and other means may be used.

There is no particular limitation on the size or the like of the thin tube that can be sprayed by the wire explosion spraying method of the present invention.
It is possible to perform thermal spraying from an ultra-fine tube of about 20 mm to a relatively large diameter of about 100 mm. Also,
The length is usually about 100 to 300 mm, but it can be up to about 3 to 5 m by sliding the sprayed surface.

As the base material of the thin tube, Al, Ag, Au, Cu, Co, Cr, Fe, Mo, Ni, Ta,
Examples include metals such as Ti and W or alloys thereof such as SUS304. Furthermore, it is also possible to perform wire explosion spraying on materials other than these metals, such as ceramics and glass.

On the other hand, the wire-explosion sprayed wire is not particularly limited as long as it is conductive, and specific examples thereof include the metals mentioned above as the capillary base material and conductive ceramics such as WC. In the present invention, in addition to these, Ti, Nb, Ta and the like, which have been conventionally difficult to be wire-explosion sprayed due to their oxidizability, can be used as the wire-explosion sprayed wire. That is, easily oxidizable materials such as Ti, Nb, and Ta are easily oxidized at the time of line explosion, and an oxide film is easily formed.However, according to the low pressure line explosion spraying method of the present invention, these oxidations are prevented, It is possible to form a good film.

It is important that such a wire material and the thin tube base material are combined so that high adhesiveness can be obtained in consideration of the adhesiveness of both.

[Operation] In the conventional atmospheric ray explosion spraying method, the obtained sprayed coating has a bolus and high surface roughness, but according to the reduced pressure ray explosion spraying method of the present invention, it is dense and has high surface smoothness. A sprayed coating can be formed. Moreover, since the gas is introduced and sucked to reduce the pressure, the explosive gas and dust generated during the line explosion spraying are removed, the adhesion to the inner surface of these thin tubes is prevented, and a high-purity and beautiful spray coating is formed. Can be formed. For this reason, the characteristics of the wire explosion-sprayed wire were fully utilized,
It is possible to easily form a high-performance coating.

In particular, in the reduced pressure line-explosion spraying method of the present invention, even a readily oxidizable material such as Ti, Nb, or Ta can be prevented from being oxidized and a good line-explosion sprayed coating can be formed. Therefore, it is possible to easily form a dense and highly corrosion-resistant coating of Ti, Nb, Ta or the like on the inner surface of the corrosive fluid distribution thin tube or the like.

Also, by wire-blasting ceramics such as WC,
It is possible to easily form a fine wear-resistant coating.

The decompression line-explosion spraying method of the present invention is suitable for precision spraying because the amount of spraying per shot is constant for each line-explosion spraying condition.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Experimental Examples.

Example 1 200T was introduced into the inner surface of a steel pipe having an inner diameter of 30 mm and a length of 100 mm by introducing and sucking air according to the method shown in FIG.
Set to a reduced pressure of orr, and under the conditions shown in Table 1, diameter 1.0m
Wire explosion spraying was performed 6 times using a Ti wire rod having a length of 50 mm and a length of 50 mm. Table 1 shows the film thickness, surface roughness, pores, etc. of the obtained coating film.

Example 2 Wire-explosion spraying was performed under the conditions shown in Table 1 in the same manner as in Example 1 except that a piano wire having a diameter of 1.0 mm and a length of 50 mm was used as the wire material. The characteristics of the obtained coating film are shown in Table 1.

Comparative Examples 1 and 2 Line explosion spraying was performed under the conditions shown in Table 1 in the same manner as in Examples 1 and 2 except that the pressure was atmospheric pressure (760 Torr). The characteristics of the obtained coating film are shown in Table 1.

From Table 1, it is clear that the method of the present invention can provide a wire explosion-sprayed coating that is dense, has a small surface roughness, and is excellent in surface smoothness.

Experimental Example 1 400 mm x 20 mm (No.4, No.6, No.7) as a film forming member
Or, use a 40 mm x 40 mm (other) steel plate, and use a Ni wire rod having a diameter of 0.5 mm and a length of 60 mm as the wire explosion-sprayed wire rod,
A line explosion spraying test was conducted under the conditions shown in Table 2. The appearance of the obtained coating film was observed, and the results are shown in Table 2.

The relationship between pressure and discharge energy is shown in FIG.

It is clear from Table 2 that a dense line-explosive spray coating can be obtained by performing the line-explosive spray at 50 to 400 Torr according to the present invention.

It is also clear from FIG. 3 that the required energy amount increases as the degree of pressure reduction increases (pressure decreases).

[Effects of the Invention] As described in detail above, according to the wire-explosion spraying method for the inner surface of the thin tube of the present invention, a fine high-characteristic line-explosion sprayed coating that is dense and has excellent surface smoothness, and is highly pure is provided. It can be easily formed.

Further, according to the reduced pressure line explosion spraying method of the present invention, even a readily oxidizable material such as Ti, Nb or Ta can be prevented from being oxidized and a good line explosion sprayed coating can be formed.

Since the coating film formed by the method of the present invention is dense and highly pure, the characteristics of the coating material, for example, abrasion resistance, corrosion resistance, mechanical strength, etc. can be sufficiently exhibited, and It is extremely useful as a property improving film.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a method for carrying out the wire explosion spraying method on the inner surface of the thin tube of the present invention, FIG. 2 is a circuit diagram of the wire explosion spraying, and FIG. 3 is a graph showing the results of Experimental Example 1. 10 …… Narrow tube, 13 …… Gas introduction tube, 14 …… Gas suction tube, 15 …… Wire rod.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP 62-99452 (JP, A) JP 60-255965 (JP, A) JP 48-24936 (JP, B1)

Claims (1)

[Claims] 1. A method of line-explosion spraying on the inner surface of a thin tube under reduced pressure, in which gas is sucked while being introduced into the thin tube, and a reduced pressure state of 50 to 400 Torr is achieved by the differential pressure between the introduction pressure and the suction pressure. Characteristic is a line-explosive spraying method on the inner surface of a thin tube.