JPH0966373A - Formation of outer peripheral projecting part in tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the regulated detachment preventing force to a tube joint by firmly fitting a projecting part onto the tube even in the case of being the thin tube and to simply form this projecting part in a short time, at the time of forming the projecting part at the outer periphery of the tube. SOLUTION: A mold 13 having an annular space 14 in the inner periphery is fitted to the outer periphery of the iron-made tube 11. A thermit molten iron 17 obtd. by reacting the iron thermit agent 16, is poured into the annular space 14 of this mold 13 and integrated with a matrix on the outer surface of the tube 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an outer peripheral projection of a pipe.

[0002]

2. Description of the Related Art For cast iron pipes such as seismic resistant pipes, in order to prevent the fitting and the insertion opening of the pipe joint from coming out when the earthquake occurs, insert the insertion opening and the insertion opening so that they are engaged with each other. A protrusion is formed on the outer circumference of the mouth. The protrusion on the outer circumference of this insertion port is usually formed in advance at the pipe manufacturing plant, but if a cut pipe is made to adjust the pipe length at the site where the pipe is laid, it will be formed again at that site. Will be required.

FIG. 4 shows a conventional method of forming an outer peripheral projection of such a tube insertion opening. That is, when the insertion opening 2 of the pipe 1 is cut at the position A at the site where the pipe is laid as shown in FIG. 4A, a rectangular cross section is formed on the outer periphery of the pipe 1 near the cutting position A. The shaped groove 3 is cut. Cut tube position A
A taper surface 4 is formed on the outer circumference of the pipe end for convenience of joining the pipe joint. Then, the ring 5 is fitted into the groove 3 as shown in FIG. The ring 5 has a tapered surface 6 continuous with the tapered surface 4 of the tube 1.

As shown in FIG. 1 (c), the ring 5 is formed so as to be divided in the circumferential direction and is formed so as to be tightly fitted into the groove 3. The circumferential dividing portion 7 is formed thin, and the joining piece 8 is attached to the thin portion.
And the ring 5 is fixed to each other by spot welding or rivets.

[0005]

However, in such a conventional structure, the groove 3 cannot be formed too deep in a tube of a thin tube type, so that the groove 3 and the ring 5 are engaged with each other. Is not always sufficient,
There is a problem in that the prescribed stopping force for preventing departure cannot be secured in the event of an earthquake. Further, when the groove 3 is processed, there is a problem that a long time is required for the processing, for example, it takes about 40 minutes when the diameter is 150 mm.

In view of the above, the present invention solves such a problem so that even a thin-walled pipe can be provided with a protruding portion firmly to the pipe so as to ensure a prescribed separation preventing force. It is an object of the present invention to easily form a part in a short time.

[0007]

In order to achieve this object, the present invention is to mount a mold having an annular space in the inner periphery on the outer periphery of an iron pipe and allow the iron thermite agent to react in the annular space of the mold. The thermite molten iron obtained as a result is poured and integrated with the base on the outer surface of the pipe.

In this way, the projection formed by solidification of thermite molten iron is firmly joined to the outer peripheral surface of the tube by being integrated with the base on the outer surface of the tube. Therefore, the separation preventing force of the joined pipe joint becomes reliable. Further, since the protrusion is formed simply by pouring the molten thermite iron obtained by reacting the iron thermite agent into the annular space of the mold, compared with the case of processing the groove by cutting,
The protrusion can be formed easily and in a short time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2, reference numeral 11 denotes a ductile cast iron pipe, the insertion port 12 of which is cut at a position B at a site where a pipeline is laid. After cutting the tube, the paint on the outer surface of the insertion port 12 is peeled off with a grinder or the like. After that, a ring-shaped shell mold 13 divided into two at the upper and lower positions in the circumferential direction is attached to the outer periphery of the pipe 11 at that portion as shown in the figure. The shell mold 13 has an annular space 14 having a rectangular cross section on its inner circumference.

The lower end of the ceramic funnel 15 is placed on the upper end of the shell mold 13 so as to communicate with the annular space 14. Inside the funnel 15, the iron thermite agent 16, that is, ferric oxide powder and aluminum powder. Load the mixture with.

After that, the thermite agent 16 is caused to react by direct ignition using discharge sparks or gunpowder. The reaction formula is 3Fe ₃ O ₄ + 8Al → 9Fe + 4Al ₂ O ₃ . The thermite molten iron 17 is obtained by this chemical reaction, and this thermite molten iron 17 is introduced into the shell mold from the funnel 15.
It flows into the annular space 14 of 13 and solidifies together with the iron base on the outer peripheral surface of the pipe 11. Therefore, if the shell mold is removed after this solidification, a protrusion having a rectangular cross section corresponding to the annular space 14 is formed on the outer peripheral surface of the insertion opening 12 of the tube 11.

As described above, solidification of the thermite molten iron 17 forms a projection that is firmly integrated with the base of the outer peripheral surface of the pipe 11. Therefore, not only when the pipe 11 has a normal pipe thickness, but also when the pipe 11 is thin, ensure the disengagement-preventing force of the pipe joint configured by using this cutting pipe portion. You can Moreover, molten thermite obtained by the reaction of the iron thermite agent is used as a shell mold.
Since it only has to be poured into the annular space 14 of 13, the protrusion can be formed easily and in a short time, as compared with the case where the groove is formed by conventional cutting.

[0013]

EXAMPLE A shell mold having a cross-sectional shape as shown in FIG. 3 was mounted on the outer periphery of a ductile cast iron pipe having a diameter of 100 mm in the vicinity of the insertion end. The shell mold 13 had a cross-sectional dimension as shown, and was provided with an annular space 14 having a rectangular cross section of 3 mm × 30 mm. Then, 750 g of the iron thermite agent was loaded into a ceramic funnel similar to the above,
This was ignited by a discharge spark and reacted.

After that, the temperature near the insertion port of the cast iron pipe is 100
When the temperature fell below the temperature, the shell mold was removed, and it was confirmed that a projection having a rectangular cross section with a width of 30 mm and a height of 3 mm was formed on the outer peripheral surface of the tube insertion opening. The cross-sectional structure of the portion where the protrusion was formed was observed with a microscope having a magnification of 100 to confirm the fusion state. As a result, about 30% of pearlite was observed on the base material of the iron pipe over a width of 30 mm corresponding to the protrusion, but the molten iron produced by thermite and the base material of the iron pipe were completely integrated.

[0015]

As described above, according to the present invention, the protrusion formed by solidification of molten thermite iron can be firmly joined to the outer peripheral surface of the pipe by integrating with the base on the outer surface of the pipe. Not only when the pipe has a normal thickness, but also when the pipe has a thin wall, it is possible to ensure the separation preventing force of the pipe joint joined by using the pipe having the protrusion. In addition, since the protrusion can be formed simply by pouring molten thermite iron obtained by reacting the iron thermite agent into the annular space of the mold, the protrusion can be formed easily and in a short time compared with the case of machining a groove by cutting. Can be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement of respective members when forming an outer peripheral projection of a pipe according to the present invention.

FIG. 2 is a cross-sectional view of the portion shown in FIG.

FIG. 3 is a diagram showing a specific example of dimensions of a shell mold.

FIG. 4 is a diagram illustrating a conventional method for forming an outer peripheral projection of a pipe.

[Explanation of symbols]

 11 Tube 13 Shell Mold 14 Annular Space 16 Thermite Agent 17 Thermit Molten Iron

Claims (2)

[Claims] 1. A mold having an annular space on the inner circumference is attached to the outer circumference of an iron pipe, and molten thermite obtained by reacting an iron thermite agent is poured into the annular space of the mold to form a base on the outer surface of the pipe. A method for forming an outer peripheral projection of a pipe, characterized by being integrated. 2. A tubular structure, characterized in that a protrusion made of molten thermite obtained by a reaction of an iron thermite agent is formed on the outer periphery of an iron pipe.