JP2584667Y2 - T-head bolt for ductile cast iron pipe for water supply - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a T-head bolt for a ductile cast iron pipe for water supply, and more particularly to an improved structure of a T-head bolt used for connecting a ductile cast iron pipe for water supply having excellent corrosion resistance.

[0002]

2. Description of the Related Art Conventionally, most of water pipes for safely and reliably sending water, which is indispensable for living and industrial activities, to homes and places of various industrial activities are buried underground. Then, the total laying distance has reached an enormous length. And such water pipes are made of ductile cast iron pipes having various lengths, and a number of ductile cast iron bolts and nuts used in joints thereof for joining the ductile cast iron pipes. And is configured. For this reason, the water pipe having such a configuration has an advantage of being excellent in manufacturability and economical efficiency at the time of manufacturing, but it is inevitable that the pipe corrosion due to electrolytic corrosion occurs after the embedding.

[0003] Generally, in underground metal,
The current is more likely to flow out into the ground from a portion having unevenness and an uneven surface condition than a smooth portion. Therefore, pipe corrosion due to electrolytic corrosion as described above tends to concentrate on protrusions such as a joint between a pipe and a pipe rather than the pipe main body. Thread corrosion progresses significantly faster than others.
Therefore, in a water pipeline in which such corrosion of the pipeline is remarkable, the thread of the bolt is lost at the joint portion, and the screw engagement with the nut is canceled, and as a result, the fitting of the pipes to each other is performed. In some cases, the joint was loosened and water leaked from the joint. Moreover, depending on the burial environment, such leakage may even be triggered several years after the burial.

[0004] As described above, water pipes in which water leaks due to the progress of pipe corrosion cannot be used as they are anymore and repairs are unavoidable. , Resulting in significant economic losses. In addition, such pipe corrosion is affected not only by the buried environment but also by the type of soil, etc. Furthermore, since the water pipe is buried in the unreachable ground, the progress of pipe corrosion It is very difficult to accurately determine the extent of the problem. Therefore, it cannot be denied that such leakage due to pipeline corrosion leads to a great disaster.

[0005] By the way, the bolts used in the joints of such water pipes are made of T
Head bolts are used. As is well known, the T-head bolt has a substantially T-shape as a whole, and has a head portion having a detent function and a leg portion provided with a thread. Things. In use, as a countermeasure against corrosion, in order to avoid the problems caused by the pipe corrosion as described above, the entire surface of the T-head bolt is provided with an anticorrosion coating such as a paint or an oxide coating. Has become.

However, their anticorrosive coatings (coatings)
All have the drawback that not only are they easily damaged by mechanical shocks during transportation or the like, but they are also easily peeled off due to aging deterioration after embedding, soil stress, and the like.
Therefore, in the case where the T-head bolt provided with such anticorrosion coating is buried and used, the anticorrosion coating peels off with the passage of years, and a leakage current flows into the ground from the peeled portion. The effluent concentrates, and eventually, the corrosion of the T-head bolt progresses. As described above, the anticorrosion coating as described above is liable to cause a coating defect, and as a countermeasure against the corrosion of the T-head bolt for solving the above-mentioned problem, it cannot sufficiently meet the demand.

As another anticorrosion measure for T-head bolts,
It is conceivable that a T-head bolt itself is formed by a casting method or a forging method using a corrosion-resistant material having high strength, for example, a stainless steel material. However, casting of stainless steel material has poor yield and flow of molten metal, and is extremely inferior in both economic efficiency and manufacturability as compared with cast iron material. It is inevitable that the cost is high, and moreover, the stainless steel material itself is expensive. Therefore, irrespective of the casting method or the forging method, manufacturing a T-head bolt from a stainless steel material is not practical at all from an industrial viewpoint.

[0008]

Here, the present invention has been made in view of the above circumstances, and the problem to be solved is to suppress a rise in cost and a decrease in manufacturability as much as possible. An object of the present invention is to provide a T-head bolt for ductile cast iron pipe for water supply, in which corrosion resistance is advantageously improved.

[0009]

In order to solve the problem, the present invention is characterized in that a T-shaped T
The head portion of the head bolt is formed of a ductile cast iron material, while the leg portion having a thread engraved on the outer peripheral surface is formed of a stainless steel material, and the head portion and the leg portion are formed. And T-head bolts for ductile cast iron pipes for water supply, which are integrally joined by friction welding.

[0010]

[Operation / Effect] That is, in the T-head bolt for ductile cast iron pipe for water supply according to the present invention, a leg portion having a thread engraved on the outer peripheral surface is made of a stainless steel material having excellent corrosion resistance. From where it was formed
Compared with other parts, the corrosion resistance of threads with particularly fast corrosion progress can be dramatically improved, and unlike conventional ductile cast iron T-head bolts, during transportation, etc. Even if a mechanical shock or the like is received, furthermore, the corrosion resistance of the screw thread is not reduced due to the aging deterioration after the embedding or the soil stress.

Further, in such a T-head bolt for a ductile cast iron pipe for water supply, the head portion is formed of an inexpensive ductile cast iron material which is excellent in formability and is inexpensive similarly to the conventional product. Since a simple bar can be used as the stainless steel material constituting the leg portion, it can be manufactured with good manufacturability and at low cost as compared with a molded product made only of the stainless steel material.

Moreover, in such a T-head bolt, since the head portion and the leg portion are integrally joined by friction welding, the joining strength between the two portions is extremely high, and The detent function at the part is not inferior to conventional one-piece products made of a single material, and the joining operation can be performed relatively inexpensively and efficiently.

Therefore, in the T-head bolt for ductile cast iron pipe for water supply according to the present invention, the corrosion resistance is effectively improved without increasing the cost and without reducing the manufacturability. It can be achieved in the following.

[0014] By using such a T-head bolt with respect to the conventional water pipe, the service life of the water pipe can be remarkably prolonged, and a very advantageous economic effect is exhibited. Not only can it be obtained, but also a water leakage accident due to pipe corrosion at the joint of the water pipe, and a disaster resulting therefrom can be effectively prevented.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, representative embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 is a front view of a T-head bolt for a ductile cast iron pipe for water supply having a structure according to the present invention. As is clear from this figure, the T-head bolt 10 is composed of a head portion 12 and a leg portion 14, and the head portion 12 and the leg portion 14 are joined at a joining portion 16, and a conventional product is provided. Similarly, as a whole, it has a substantially T-shape.

In the T-head bolt 10, the head 12
Is formed by a casting method using a normal ductile cast iron (FCD450) material. The head 12
2 and 3 respectively showing a front view, a side view and a bottom view of FIG.
As is clear from FIG. 4 and FIG. 4, the head 12 has an engagement portion 18 having a substantially semi-cylindrical shape and a base portion 20 having a cylindrical shape.
The engaging portion 18 is integrally joined to the one end in the axial direction of the base portion 20 so that their respective axes are orthogonal to each other, and as a whole, the length of the foot is short. It has a T-shape. In the head 12, as in the conventional product, the vertical wall surfaces 22, 22 that constitute a part of the outer peripheral surface of the engaging portion 18 are positioned with respect to the outer wall surface of the joint portion of the ductile cast iron pipe (not shown). Thus, when engaged, the detent function can be effectively exerted.

On the other hand, the legs 14 are formed using an austenitic stainless steel (SUS304) material. 5 and 6, which show a front view and a bottom view of the leg 14, respectively.
Has a round bar shape of a predetermined length as a whole, and has a thread portion 24 formed by threading a male screw on the outer peripheral surface thereof over a predetermined length. In addition, such a leg 1
No. 4 is a stainless steel material formed by drawing into a round bar shape having a predetermined diameter, and further formed by cutting the stainless steel material into a predetermined length. The material that gives the leg 14
It goes without saying that any of the other products obtained by plastic deformation processing, casting, forging and the like can be adopted.

The head 12 and the leg 14 having such a structure are connected to the engaging portion 18 on the base 20 of the head 12.
And an end face opposite to the side on which the
4 and the end face opposite to the side where the screw portion 24 is engraved is integrally joined by friction welding. Thus, T having the overall shape as shown in FIG.
The head bolt 10 is realized.

As is well known, friction welding, which is a joining means between the head 12 and the leg 14 of the T-head bolt 10, brings the joining surfaces of members to be joined into contact with each other, as is well known. Further, one of the members is rotated under a constant pressing force, frictional heat is generated between the joining surfaces by the mechanical energy, and the two members are joined. In such a friction welding method, thin oxides, adsorbed substances, dirt, and the like on the joining surface are destroyed during the frictional heating, and are extruded as “burrs” from the joining portion. By being able to make contact between the surfaces, and by upsetting when the rotation is stopped, a strong metal bond is obtained, and further, due to the strong plastic flow at the bonding surface, the bonding temperature can be lowered, and the crystal Since coarsening and the formation of intermetallic compounds are effectively prevented, and high compressive residual stress is generated in the circumferential direction, it is possible to very strongly join dissimilar materials that are difficult to weld by fusion. It is. Moreover, such friction welding does not require skill in the work, so the work is easy and efficient, and unlike ordinary welding, consumable materials such as welding rods are not required. Therefore, it has many excellent features such as being economically efficient, being able to incorporate a friction welding machine in a processing line, and being easily automated as a line.

Therefore, by such friction welding,
In the T-head bolt 10 in which the head 12 and the leg 14 are integrally joined, both of these parts (12, 1)
4) The bonding strength of the head 12 is extremely high, and the detent function of the head 12 can be extremely advantageously exerted, similarly to the case where the head 12 is integrally formed of a conventional ductile iron material. The cost and labor burden associated with the addition of the joining operation between the part 12 and the leg 14 can be suppressed as much as possible.

As described above, in the T-head bolt 10 for a ductile cast iron pipe for water supply having the above-described structure, the leg portion 14 on which the screw portion 24 is screwed is made of a stainless steel material having high corrosion resistance. , The corrosion resistance of the screw portion 24 can be advantageously increased, and thereby the corrosion progress of the screw portion 24 due to electrolytic corrosion can be effectively prevented. Thus, a water leak accident at a joint of a water pipe, a disaster caused by the accident, and the like can be effectively prevented.

In the T-head bolt 10,
The head 12 has good formability, is formed of an inexpensive ductile cast iron material, and has a high work efficiency when joining the head 12 and the leg 14,
In addition, since the friction welding method having a low working cost is adopted, the productivity and economic efficiency in the manufacturing process are extremely effectively suppressed from being reduced as compared with the conventional product. It is.

Although one representative embodiment of the present invention has been described in detail, this is a literal example,
The present invention is not construed as being limited to such specific examples.

For example, in the above embodiment, the head 12 uses FCD450 as a ductile cast iron material, and the legs 14 use SUS304 as a stainless steel material.
Although each was formed, the material of the head and legs are not limited to them at all, any structure having any structure as long as it is a ductile cast iron material or a stainless steel material, Any type can be adopted.

In the above embodiment, the T-head bolt 10 was not provided with an anticorrosion coating such as an oxide film treatment. May be applied. And by doing so, a high quality product with more excellent corrosion resistance can be obtained.

Further, in the above-described embodiment, the leg portion 14 having the screw portion 24 provided in advance on the outer peripheral surface is integrally joined to the head portion 12 by friction welding. After the head and the head are joined by friction welding, a male screw can be formed by engraving a male screw on the outer peripheral surface of the leg.

In addition, according to the present invention, any of the conventionally known methods and apparatuses for friction welding used when joining the head part and the leg part can be adopted. Of course.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, various changes, modifications, improvements, and the like can be carried out, and any of such embodiments will not depart from the spirit of the present invention. It goes without saying that they are included in the range.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of a T-head bolt for a ductile cast iron pipe for water supply according to the present invention.

FIG. 2 is an explanatory front view showing a head portion of the T-head bolt for ductile cast iron pipe for water supply shown in FIG. 1;

3 is an explanatory side view showing a head portion of the T-head bolt for ductile cast iron pipe for water supply shown in FIG. 2;

FIG. 4 is an explanatory bottom view showing a head part of the T-head bolt for ductile cast iron pipe for water supply shown in FIG. 2;

FIG. 5 is an explanatory front view showing a leg portion of the T-head bolt for ductile cast iron pipe for water supply shown in FIG. 1;

FIG. 6 is an explanatory bottom view showing a leg portion of the T-head bolt for a ductile cast iron pipe for water supply shown in FIG. 5;

[Explanation of symbols]

 Reference Signs List 10 T-head bolt 12 Head 14 Leg 16 Joint 18 Engagement 20 Base 22 Vertical wall 24 Screw

Continuation of the front page (56) References JP-A-54-61044 (JP, A) JP-A-2-22985 (JP, A) JP-A-4-179791 (JP, A) JP-A-54-9353 (JP) JP-A-6-93387 (JP, A) JP-A-57-22581 (JP, U) JP-A-51-80562 (JP, U) JP-A-59-108809 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F16B 35/00 F16B 35/04

Claims (1)

(57) [Scope of request for utility model registration] 1. A head portion of a T-head bolt having a T-shape is formed of a ductile cast iron material, while a leg portion having a thread engraved on an outer peripheral surface is formed of a stainless steel material. And a T-head bolt for ductile cast iron pipe for water supply, wherein the head part and the leg part are integrally joined by friction welding.