JPH0454744B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an improvement in a method for manufacturing a composite tube in which a metal layer and a ceramic layer are integrally coated on the inner surface of a main tube by a thermite reaction. The present invention relates to a manufacturing method for eliminating explosive reactions and allowing the reaction to proceed at a stable rate in the axial direction of the tube, thereby obtaining a stable and high-quality composite tube.

(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 utilizes, for example, an aluminum-iron oxide thermite reaction to integrally coat the inner surface of an iron or iron alloy cylindrical tube, such as a steel tube, with a ceramic layer of alumina (Al ₂ O ₃ ). As shown in Fig. 3, the inner surface of the metal frame 1, which can rotate at high speed, is equipped with a metal cylindrical tube that prevents seizure and reduces resistance when taking out the product, although not shown. A metal cylindrical tube having an outer diameter slightly smaller than the inner diameter of the metal frame 1, that is, a main tube 2, is inserted into the metal frame 1 in an internally-fitting manner, and both axial ends of the main tube 2 are coated with a mold release agent in advance. A band (holding lid) 3 fixed to the metal frame 1 side is attached, and a certain amount of powder or particles of aluminum (Al) and iron oxide (Fe ₂ O ₃ or Fe ₃ O ₄ ) is injected into the main tube 2. Thermite agent 4 consisting of a mixture of proportions,
Scatter and load through the center hole of the band, and load it into the metal frame 1.
The known thermite reaction is induced by ignition in the centrifugal force field caused by the high _- speed rotation _of The inner surface 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. Moreover, as 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.

When this thermite reaction is induced in a closed system such as inside a pipe, even if the ignition point is only one point, it will take some time (the size of the pipe, 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 the center of the reaction. In this case, the molten metal (molten product) scatters due to the boiling phenomenon, which becomes an ignition source and the reaction spreads 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. In this case, if the pipe length is long, especially if it is a small diameter pipe, the raw material powder or molten product in the main pipe will be blown out in large quantities from the same opening by the high-speed airflow, making it difficult to ensure the specified layer thickness. Otherwise, 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 the production of stable products, and has also been seen as a problem in terms of safety and health.

(Means for solving the problem) The present invention solves the above-mentioned conventional problems, eliminates explosive reactions, and allows the reaction to proceed at a stable rate in the tube axis direction, that is, solid-liquid propagation (melting In order to realize a form in which adjacent thermite agents react sequentially due to the heat of the object, the thermite agent is loaded into the mother tube and the thermite agent is ignited in a centrifugal force field to cause the thermite reaction to occur. In the method for manufacturing a composite tube in which the inner surface of the mother tube is integrally coated with a metal layer and a ceramic layer produced by a thermite reaction, the tube is formed in the front surface of the reaction part of the thermite reaction and in the axial direction of the tube substantially in synchronization with the progress speed of the reaction. This method employs a manufacturing method that uses a heat-resistant plug that moves to the unreacted area.

(Operation) The thermite agent at one end of the main tube is ignited at one point in the centrifugal force field, causing thermite reaction to start, and the combustion zone expands. To prevent this combustion zone from expanding rapidly, the combustion zone (reaction part)
When a heat-resistant stopper placed close to the tube was moved to the unreacted portion in the axial direction of the tube approximately in synchronization with the rate of progress of the reaction, the thermite reaction proceeded in a manner that substantially followed the movement.

(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 Reference numeral 4 indicates a thermite agent sprinkled on the inner surface of the main pipe 2, 5 indicates a product layer consisting of a metal layer and a ceramic layer, and 6 indicates a thermite reaction portion. Reference numeral 7 denotes a heat-resistant stopper located close to the reaction portion and in the unreacted portion, and this stopper 7 is provided with an operating rod 8 in the tube axis direction. The material of this plug 7 may be any material as long as it has a melting point of about 2000°C or higher, and ceramic materials such as oxides, nitrides, carbides, and borides are suitable, and its diameter is as shown in the figure. The diameter may be slightly smaller than the inner diameter of the agent layer.

In the above configuration, the stopper 7 is moved from outside the centrifugal field via the operating rod 8 in the non-reaction direction to the left in the figure, approximately in synchronization with the progress speed of the thermite reaction. At this time, the moving speed of the operating rod 8 is approximately 2 to 5 m/min, although the reaction progress speed in the case of solid-liquid propagation varies depending on the tube size, type and amount of thermite agent, as long as the conditions are determined. Since it is approximately constant, it can be determined relatively easily.

In this way, the stopper 7 reaches the left end, but if the movement of the stopper 7 is stopped just before that, the reaction will pass through the outer periphery of the stopper 7 (underneath the stopper 7) and proceed until it reaches the left end. become.

In addition, in practice, it is also possible to automatically control the stoppage of movement by providing a heat-sensitive sensor (thermocouple, etc.) on the front side of the stopper 7.

In addition, since it is easier to obtain a constant solid-liquid propagation velocity by avoiding air temperature rise between the ignition side end and the plug body, an exhaust device is provided at the ignition side end as shown in Fig. 2.
Preferably, this is carried out in conjunction with continuous evacuation of the hot air. In the figure, 9 indicates a suction hood, and 10 indicates a dust collector.

Furthermore, when carrying out the present invention, it is better to keep the stopper 7 quite close to the surface of the thermite agent (with a gap of about 10 mm or less), so depending on the method of construction, it may come into contact with the surface of the thermite agent. Since this may cause damage to the condition or swing of the operating rod, it is better to use a mechanism in which the joint between the stopper and the operating rod can freely rotate in the circumferential direction.

Next, more specific examples of the method of the present invention are as follows.

72 kg of thermite agent (50 kg of Fe ₂ O ₃ , 17 kg of Al,
The _centrifugal thermite method according to the present invention was carried out. A sintered alumina product with an outer diameter of 100 mm was used as the stopper, and it was set at a position 10 cm from the ignition end, and the thermite agent was ignited at a rotational speed of 100 G. Start moving the stopper 10 seconds after ignition, and
Anti-ignition end direction (unreacted part) at a constant speed of cm/sec.
It was evacuated to. The thermite reaction proceeded almost following the movement of the thermite, exhibiting a typical solid-liquid propagation pattern.

(Effects of the Invention) The present invention eliminates the explosive reaction in thermite reaction, allows the reaction to proceed at a stable rate in the tube axis direction, and makes it possible to produce stable and high-quality composite tubes.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the method of the present invention, FIG. 2 is an explanatory diagram showing another embodiment, and FIG.
The figure is an explanatory diagram of a conventional method. 1...Gold frame, 2...Main pipe, 3...Band, 4...
... thermite agent, 5 ... product layer, 6 ... thermite reaction part, 7 ... stopper, 8 ... operating rod, 9 ...
...Suction hood, 10...Dust collector.

Claims (1)

[Claims] 1. By loading a thermite agent into the main tube and igniting the thermite agent 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. In the method for manufacturing a composite pipe,
A method for manufacturing a composite tube, characterized in that the composite tube is obtained by using a heat-resistant stopper that moves in front of the reacting portion of the thermite reaction and toward the unreacted portion in the tube axis direction in approximately synchronization with the rate of progress of the reaction.