JPS61238970A - Manufacture of composite pipe - Google Patents

Abstract

PURPOSE:To prevent the tensile cracking of a rotating mother pipe when a thermit reaction is caused in the pipe to form produced layers in the pipe, by previously forming a layer of a heat resistant material on the inside of the pipe. CONSTITUTION:A layer 5 of a heat resistant material is formed on the inside of a metallic mother pipe 1, and a thermit agent 2 consisting of a metallic oxide and a metallic reducing agent is put in the pipe 1 to form a layer of the thermit agent 2 on the layer 5. The thermit agent 2 is then ignited in the field of centrifugal force to cause a thermit reaction. A metallic layer and a ceramic layer produced by the thermit reaction are formed on the inside of the mother pipe 1.

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 ceramic layer (formed ceramic) is formed on the inner surface of a mother tube by utilizing a thermite reaction. The present invention relates to a method for manufacturing a composite pipe that reduces or suppresses the occurrence of cracks in produced ceramics.

(Prior art) Composite tubes made by coating the inner surface of the mother tube with a ceramic layer are suitable for use as transportation tubes 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 manufacturing method for this kind of composite pipe, for example,
So-called centrifugal thermite determination using centrifugal force and chillmint reaction has been proposed, such as inventions described in Japanese Patent Publication No. 40219 and Japanese Patent Publication No. 59-27747. That is,
In this method, as shown in FIG. 3, for example, A
A thermite agent consisting of a mixture of I, a metal reducing agent such as Fe2O3, and a metal oxide at a certain ratio is loaded to form a thermite agent layer 2, and this is ignited in a centrifugal force field due to high speed rotation, as shown in the following formula. A thermite reaction is carried out, and the molten metal and molten ceramic produced by this exothermic reaction are separated by specific gravity, and a desired ceramic layer is formed on the inner surface of the main tube 1 via the metal layer 3, as shown in FIG. 4 is coated.

(Problems to be Solved by the Invention) An example of the thermite reaction described above is as follows: Fe2O
3+2An →A1203+2Fe+199 Kcal
/A1203 moles In this case, the metal layer is iron and the ceramic layer is alumina.

Generally, the amount of heat generated by this type of thermite reaction is extremely large, and theoretically it is not uncommon for the maximum temperature reached by the reaction to exceed 3000°C. When such a reaction involving high temperatures is induced in a metal tube such as a steel pipe (hereinafter referred to as the mother tube), the latter, especially the produced ceramics, may crack during the cooling process due to the heterogeneity in the thermal expansion and contraction histories of the mother tube and the product. There was a problem in that it caused The form and density of these cracks vary depending on the thickness of the main pipe and the amount of thermite used, but tensile cracks have a particularly high crack incidence and crack distribution density. Compression cracking, which sometimes occurs, occurs when the shrinkage force of the main pipe exceeds the proof strength of the ceramics, but since the compressive strength of ceramics is generally extremely high, it is difficult to avoid it by striking a balance between the two. It's not difficult.

On the other hand, tensile cracking is strongly influenced by the interface between the main pipe and the product, and if the free shrinkage of the product is prevented here, tensile cracking will occur at an extremely high density. The reason for this will be outlined below.

When subjected to the heat of thermite reaction, the main tube expands, reaches its maximum temperature, and then begins to contract.

On the other hand, the product solidifies after being in a molten state for a while, but then continues to shrink as it is rapidly cooled.

While the temperature of the product is in a high range, the heat transfer to the main tube is relatively gentle, but the product is rapidly cooled, so the shrinkage rate is higher than that of the latter. ,
As a result, it is assumed that the fitted state between the two is extremely gentle. In such a state, even if the product shrinks first, no frictional force is generated at the interface with the main tube to prevent it from shrinking, so a free shrinkage state is obtained and no tensile cracks should occur.

However, in reality, the inner surface of the mother tube is roughened by the heat of the thermite reaction, and the outer surface of the product also becomes uneven. At this time, depending on the thickness of the main pipe and the amount of thermite used, the main pipe and the product may partially fuse into one.

It is clear that in the latter case the free shrinkage of the product is restricted. In the former case, although the interface between the mother tube and the product is separated, there are irregularities on each side, so
Even in a temperature range where the shrinkage rate of the product is high, the shrinkage is difficult to occur in a nearly non-resistance state such as when the interface is smooth. Ceramics lack tensile strength and toughness,
If such free shrinkage is bundled, tensile cracks will easily occur. Processes that involve unavoidable rapid cooling, such as the centrifugal thermite process, tend to produce impurities and defects at grain boundaries.
The fact that ceramics do not have the strength they should have also promotes the occurrence of cracks.

Therefore, as is clear from the causes of cracking mentioned earlier, it is important to keep the interface between the steel pipe and the product smooth in order to avoid this occurrence, and to achieve this purpose, thermite agent One possible method is to place heat-absorbing material underneath.

Specifically, there are a method in which a thin steel cylinder is fitted into a steel pipe that is a mother pipe, and a method in which steel particles or oxides are spread on the floor. These have the function of absorbing part of the heat of the thermite reaction that takes place thereon, and preventing that heat from reaching the inner surface of the main tube.
As a result, it is intended to have the effect of preventing the inner surface of the main tube from becoming rough due to heating.

However, with the above method, if the amount of bedding is too large or the construction accuracy is poor, the adhesion between the main tube and the product will be impaired, resulting in a lack of structural strength as a composite tube. It is conceivable that it may melt and change the ceramic composition or cause loss of homogeneity.

(Means for Solving the Problems) The present invention solves the above-mentioned drawbacks, and in order to reduce and suppress the occurrence of cracks in the produced ceramics, the present invention provides a thermite agent consisting of a metal oxide and a metal reducing agent on the inner surface of the metal main tube. is charged to form a thermite agent layer, and the thermite agent layer is ignited in a centrifugal force field to cause a thermite reaction, thereby coating the inner surface of the metal mother tube with a metal layer and a ceramic layer generated by the thermite reaction. In this manufacturing method, a heat-resistant material film layer is formed in advance on the inner surface of a metal main tube, and a thermite agent layer is further formed on the inner surface to cause a thermite reaction.

(Function) When a heat-resistant material film layer is formed on the inner surface of the metal main tube, a thermite agent is further sprayed on the inner surface, and the thermite agent is ignited in a centrifugal force field to cause a thermite reaction, the heat-resistant material film layer prevents the reaction heat from directly reaching the inner surface of the main tube, prevents the inner surface of the main tube from becoming rough due to heat, and keeps the inner surface of the main tube smooth to minimize tensile cracks in the ceramic during the cooling process. .

(Example) An example of the present invention will be described with reference to FIGS. 1 and 2. In both figures, numeral 1 indicates a metal main pipe, and a steel pipe is used as the material. 5 is a heat-resistant material film layer sprayed on the inner surface of the main pipe. Normally, when spraying this thermal spray film, the inner surface of the main tube is roughened by blasting or the like in order to increase the degree of adhesion, but in the present invention, it is preferable to avoid such a state of adhesion. It is best to construct it directly. Thermal spraying may be performed using plasma or gas flame, but since it is better not to roughen the surface of the main tube too much, a large capacity is not required. Of course, it is not necessary to add an alloy layer to the base to increase the adhesion, which is generally done.

As thermal spray materials, most materials can be used as long as they have heat resistance and do not gasify even when subjected to the heat of reaction. Examples include alumina (Al2O2) and zirconia (Z).
rOz), etc. Other heat-resistant material film layers may be metal sprayed films. These are sprayed onto the inner surface of the main tube to a thickness of 30 to 300 microns prior to the centrifugal thermite method. In this case, if the thickness is less than 30 μm, there is no heat insulating effect, and if it is thinner than 300 μm, it is not necessary. After the heat-resistant material film layer is thus formed on the inner surface of the main tube, a thermite agent is further sprayed on the inner surface, and the thermite agent is ignited in a centrifugal force field to cause a thermite reaction. In this case, the type and amount of thermite agent to be used are appropriately determined by experience or calculation.

In addition, even if a small amount of the heat-resistant material film layer remains after the thermite reaction in the above example, since it and the main tube are in weak contact, it does not hinder the shrinkage of the product, and it is structurally integrated. It will not be enough to damage the country. As cooling progresses further, the shrinkage rate of the main tube exceeds that of ceramics, so in the final state, the product settles in a strongly compressed state in the main tube, so even if a thin layer of sprayed film remains below, In this state, the strength will not be adversely affected.

Further specific examples of the present invention are listed below.

Outer diameter 165.2in x thickness 7.11m x length 14301
A 100 μm thick alumina layer, which is a heat-resistant material film layer, is formed inside a steel pipe with a thickness of 100 μm by plasma spraying, and 21.5 kg of thermite agent (15 kg of iron oxide, 5 pupil of aluminum, 1.5 kg of densification aid) is applied inside the alumina layer. The mixture was sprayed and ignited under high speed rotation of 100G to perform a centrifugal thermite reaction. No visible tensile cracks were observed in the ceramic layer thus obtained.

(Effect of the invention) The heat-resistant material film layer previously formed on the inner surface of the main tube
Prevents reaction heat from directly reaching the inner surface of the main tube during the thermite reaction, and prevents the inner surface of the main tube from becoming rough due to heat. This state maintains the smooth state of the inner surface of the main tube and makes it difficult for tensile cracks to occur in the ceramic produced during the cooling process. Therefore, the present invention is industrially useful as a manufacturing method for reducing and suppressing the occurrence of cracks in produced ceramics.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a sectional view of the main pipe in the manufacturing process according to the present invention, and FIG.
The figure is a cross-sectional view of a composite pipe that is the object of manufacturing the present invention. FIGS. 3 and 4 show a cross-sectional view of a main tube, etc. and a cross-sectional view of a composite tube in the manufacturing process of the conventional centrifugal chill mint method. 1-.-mother pipe, 2-thermite agent layer, 3.-metal layer, 4
-.-Ceramics layer, 5-heat-resistant material film layer, 5'-heat-resistant material film layer remaining after thethermint reaction. Patent Applicant Tatsu Todoroki, Director General of the Agency of Industrial Science and Technology, Kubota Iron Works Co., Ltd. Representative Patent Attorney Yasu 1) Toshio Figure 7
Figure 3 Figure 2 Figure 4

Claims (1)

[Claims] 1. A thermite agent consisting of a metal oxide and a metal reducing agent is loaded onto the inner surface of the metal main tube to form a thermite agent layer,
In this method, the thermite agent layer is ignited in a centrifugal force field to cause a thermite reaction, and the inner surface of the metal mother tube is coated with a metal layer and a ceramic layer generated by the thermite reaction. A method for manufacturing a composite tube, comprising forming a material film layer and further forming a thermite agent layer on the inner surface of the material film layer to cause a thermite reaction.