JPH0210867B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an improvement in the manufacturing method of a composite tube in which a metal layer and a ceramic layer are integrally coated on the inner surface of the main tube by a thermite reaction. This invention relates to a manufacturing method for obtaining a stable, high-quality composite tube by suppressing the air temperature within the tube within a range that does not cause explosive reactions.

(Prior art) Composite pipes made by coating the inner surface of the mother pipe with a ceramic layer are suitable for use as transport pipes for various fluids and for industrial use because the ceramic layer exhibits good properties such as heat resistance, abrasion resistance, and corrosion resistance. It has a wide range of applications as a piping member.

As a method for manufacturing this type of composite pipe, the so-called centrifugal thermite method, which utilizes centrifugal force and thermite reaction, has been proposed, for example, as disclosed in Japanese Patent Publication No. 57-40219, Japanese Patent Publication No. 59-27747, etc. There is.

This centrifugal thermite method uses, for example, an aluminum-iron oxide-based thermite reaction.
To give an overview of the equipment that integrally coats the inner surface of a cylindrical pipe made of iron or iron alloy, such as a steel pipe, with a ceramic layer of alumina (Al ₂ O ₃ ), as shown in Figure 3, it is possible to The inner surface of the frame 1 is coated with a release agent (not shown) in advance to prevent the metal cylindrical tube from seizing and to reduce the resistance when taking out the product. A metal cylindrical tube with an outer diameter, that is, a main tube 2, is inserted in a fit manner, and both ends of the main tube 2 in the axial direction are connected with bands (holding lids) 3 fixed to the metal frame 1 side, and the main tube is A thermite agent 4 consisting of a mixture of powders or particles of aluminum (Al) and iron oxide (Fe ₂ O ₃ or Fe ₃ O ₄ ) in a fixed ratio in 2 is sprayed and loaded through the center hole of the band. The known thermite reaction is induced by ignition in the centrifugal force field caused by the high speed rotation of the metal frame 1, and the molten metal (Fe) and molten ceramic (Al ₂ O ₃ ) produced by this exothermic reaction are separated by specific gravity, and the mother The inner surface of the tube 2 is integrally coated with a ceramic layer via a metal layer. This method is applicable not only to aluminum-iron oxide systems but also to thermite reaction systems consisting of various strong reducing elements and metal oxides, and by adjusting the loading amount of the thermite agent 4, it can be applied to various metal cylinders. It has the advantage that various ceramic layers can be easily formed on the inner surface of the tube to a desired thickness, and the coating layer can be bonded to the inner surface of the cylindrical tube in a highly adhesive state through the intermediary of the metal layer that is simultaneously produced. Furthermore, as is already clear, the device can suitably utilize a centrifugal force casting device and has good productivity.

(Problems to be Solved by the Invention) However, the conventional centrifugal thermite method has the following problems.

If this thermite reaction is induced in a closed system such as a pipe, even if the ignition point is only one point, it will take some time (the pipe size, the type of thermite agent,
After a few seconds (usually several seconds to several tens of seconds, depending on the amount), the reaction propagates explosively throughout the tube.

To explain this phenomenon in more detail, when ignition and reaction start at one point at the end, the combustion zone expands and the air temperature in the vicinity rises, eventually exceeding the ignition temperature of the thermite agent, and at the center of the reaction. The boiling phenomenon causes the molten metal (molten product) to scatter, which becomes an ignition source and spreads the reaction to the surrounding area. Once the reaction spreads, the reaction ring expands explosively (exponentially), and the propagation speed of the reaction at that time reaches from several meters/second to several tens of meters/second.

Due to this explosive reaction, the air inside the tube expands rapidly and flows out as a high-speed airflow from the openings of bands 3, 3 fixed to both ends of the metal frame 1 in order to prevent thermite agent and molten product from leaking. At this time, if the pipe length is long, especially if it is a small diameter pipe, raw material powder and molten products in the main pipe may be blown out in large quantities from the opening by this high-speed airflow, making it impossible to secure the desired layer thickness. Alternatively, problems such as thinning of the layer near the center of the pipe length, which makes compression cracking more likely to occur, have occurred, which has hindered stable product manufacturing and has also been viewed as a health and safety issue.

(Means for Solving the Problems) The present invention solves the above-mentioned conventional problems, eliminates the explosive reaction, and allows the reaction to proceed at a stable speed in the tube axis direction, that is, solid-liquid propagation (solid-liquid propagation). In order to realize a form in which adjacent thermite agents react sequentially due to the heat of the melt, a thermite agent is loaded into the mother tube and the thermite agent layer is ignited in a centrifugal force field to cause thermite reaction to occur. In the method for manufacturing a composite tube in which the inner surface of the main tube is integrally coated with a metal layer and a ceramic layer produced by a thermite reaction, the main tube is heated in a state where a gas flow is created in the main tube from the anti-ignition side to the ignition side. This method employs a manufacturing method in which the thermite reaction proceeds from near one end of the tube.

(Operation) A thermite reaction is started by igniting near one end of the main tube 2 in a centrifugal force field, and the air whose temperature has increased due to the reaction is continuously sucked in and discharged by a dust collector as shown in FIG. As the reaction progresses toward the center, the high-temperature air is drawn in the direction where the reaction has already completed and does not diffuse toward the side where there is unreacted thermite agent. The reaction moves toward the other end at a substantially constant speed of 2 to 5 m/min, depending on the type of thermite agent, and exhibits an ideal solid-liquid propagation pattern.

(Example) FIG. 1 is an explanatory diagram showing one example of the method of the present invention. In the same figure, 1 is a metal frame, 2 is a metal cylindrical tube inserted into the metal frame 1 in a fit manner, that is, the main pipe, and 3, 3 is fixed to the metal frame 1 side at both axial ends of the main pipe 2. It is a band that has been 4 is a thermite agent sprinkled on the inner surface of the main tube 2.

Reference numeral 5 denotes a suction hood detachably provided at one end of the metal frame 1, that is, on the ignition side, and this hood 5 is fixed to the machine body side. 6 indicates an appropriate dust collector connected to the hood 5. In this case, remove the suction hood 5 from one end of the metal frame 1, ignite the thermite agent near one end, and then attach the suction hood 5 to one end of the metal frame 1 before the thermite reaction reaches explosive spread. A gas flow is created in the tube 2 from the anti-ignition side to the ignition side. In addition, for example, a gap may be provided between the suction hood 5 and one end of the metal frame 1, and after creating a gas flow, an ignition device may be inserted through the gap to ignite the metal frame. It is also possible to create a gas flow while attached to one end of the ignition device, and insert the ignition device from the anti-ignition side up to the ignition point to ignite. In practice, it is preferable to use a pattern in which combustion first proceeds in the circumferential direction at the ignition part, and then the combustion ring moves in the axial direction, but this is achieved by adding a high-speed combustion layer on the surface of the ignition part, such as a high-purity fine thermite agent, etc. An igniter layer containing magnesium or the like as a main ingredient may be provided.

In order to further ensure removal of high-temperature air, a means for blowing an inert gas, such as carbon dioxide gas or nitrogen gas, from the anti-ignition side can also be used. Even in the case of air, oxygen in the air participates in the oxidation of aluminum in the surface layer, but the amount is so small that almost no change is observed in the formed layer.

In the embodiment shown in Fig. 1 above, a unidirectional airflow is generated in the main pipe by suction from the ignition side, but the same effect can be obtained by simply blowing gas from the anti-ignition side. be able to. However, in this case, there are difficulties in adding equipment measures and controlling the reaction state.

Another method is to insert the boom from the anti-ignition side to the ignition point and move it to the anti-ignition side while blowing out gas from the tip. In this case, there is a slight problem in synchronizing the movement with the reaction rate.

Next, another embodiment shown in FIG. 2 will be described.

This embodiment is different from the one shown in FIG. 1 in that the inner surface of the thermite agent layer 4 is coated with a combustible material 7 (hereinafter referred to as a combustible film) in a substantially adhering state. If this is done in combination with the above, explosive reactions can be minimized and a more stable and high quality composite pipe can be provided. At this time, the material of the combustion film 7 is highly combustible, but the combustion temperature is higher than that of the thermite agent 4.
It must not generate gas at or below the ignition temperature of the ceramic, and it must not have an adverse effect on the appearance or composition of the produced ceramic. Paper material is an example of the cheapest material that satisfies this requirement. When paper burns, it turns into ashes and floats into the air, but the hood 5 and dust collector 6
As the ash is discharged one after another by the action of the product, it does not enter the product or adhere to the surface.
There is no adverse effect on the ceramic layer. The combustion membrane 7 may be made of fiber cloth, resin, etc.
They are difficult to install, generate gas, and are less compatible than paper materials.

In addition, a suitable means for attaching the combustion membrane 7 will be explained. The fine powder of thermite agent 4 is compacted by the centrifugal force, and even after the centrifugal force is released, it retains its shape with its self-retention force. Therefore, the paper tube 7 which is a combustion film is partially polymerized and rolled into a cylindrical shape, and the metal frame 1 is
By reducing the diameter to a small diameter so as to pass through the opening of the band 3, and expanding the diameter by the elasticity of the paper tube 7 after passing through, the paper tube 7 is brought into close contact with the surface of the thermite agent layer 4. coated with. This coating state is as shown in Fig. 2, and it is preferable that the gap between the paper tube 7 and the surface of the thermite agent layer 4 be as small as possible;
There is no particular problem if the level is below. Further, it is preferable that the paper tube 7 is not one that easily burns and scatters, so it is suitable that the thickness is 1.5 mm to 0.3 mm, preferably about 0.5 mm.

In addition, in order to facilitate the start of the reaction, an ignition zone 8 not covered by the combustion film 7 is provided inside the band 3 at one end of the main pipe 2 to a depth of about 100 mm or less, and an exposed part of the thermite agent 4 is provided. . In this way, when the reaction is started by igniting the uncovered ignition zone 8 of the combustion film 7 at one end of the main pipe 2 in the centrifugal force field, the reaction first spreads in the circumferential direction in the ignition zone 8, and thereafter this combustion ring It exhibits a so-called solid-liquid propagation reaction pattern that moves in the direction of the tube axis, and exhibits a calm reaction state in which there is no scattering of the thermite agent 4, which is the raw material, and no wave motion of the molten metal.

(Effects of the Invention) The present invention is a method for inducing a thermite reaction in a main tube rotating at high speed and forming a generation layer in the main tube, in which a gas flow is created in the main tube from the anti-ignition side to the ignition side. Since the thermite reaction is allowed to proceed from near one end of the main tube, it does not impair workability.
Since the temperature of the air inside the tube could be kept within a range that would not cause an explosive reaction, a stable and good composite tube was obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the method of the present invention;
FIG. 2 is a sectional view showing another embodiment, and FIG. 3 is a sectional view showing a conventional example. 1...Gold frame, 2...Main pipe, 3...Band, 4...
...Thermite agent (thermite agent layer), 5... Hood, 6... Dust collector.

Claims (1)

[Claims] 1. By loading a thermite agent into the main tube and igniting the thermite agent layer in a centrifugal force field to cause a thermite reaction, the inner surface of the main tube is integrally coated with a metal layer and a ceramic layer generated by the thermite reaction. A method for manufacturing a composite tube thus formed, characterized in that the thermite reaction proceeds from near one end of the main tube while creating a gas flow in the main tube from the anti-ignition side to the ignition side.