JPS61283416A - Diameter reducing method for pipe - Google Patents

Abstract

PURPOSE:To reduce a pipe diameter and to form a self-tightening double-walled pipe at a low cost by simultaneously and parallellty subjecting the pipe to annular heating from the peripheral direction and cooling around the same to suppress the diameter expansion of the heated part then cooling the pipe to shrink. CONSTITUTION:The high-toughness outside pipe 1 consisting of a low-carbon steel, etc. and the high-wear-resistant inside pipe 2 consisting of a high-carbon steel, etc. are freely inserted to form a double-walled pipe stock 3. An annular high-frequency induction heater 4 is set onto the outside pipe 1 and coolers 5 for annular shower of cooling water are set before and behind the heater in the axial direction in proximity thereto. While the pipe stock 3 is moved in an arrow direction, the pipe stock is continuously subjected to the simultaneous and parallel heating and cooling with the heating and cooling devices 4, 5. The thermal expansion of the heated part is thereby restrained by the low- temp. parts from both sides to suppress the diametral expansion thereof. The heated part is thereafter shrunk by cooling to decrease the diameter of the outside pipe 1 from the initial diameter, by which both pipes are self-tightened and the double-walled pipe is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The disclosed technology belongs to the technical field of manufacturing pipes such as a wearable double pipe that connects an outer pipe and an inner pipe.

<Summary> In order to improve the wear resistance of piping used for slurry transportation, pneumatic transportation, etc., the invention of this application, for example, provides a double pipe in which an outer pipe and an inner pipe are layered relative to each other. Circumferential annular heating of the preceding stage by moving the base tube in the axial direction relative to the circumferential annular heating means and the cooling means of the subsequent stage, and
This invention relates to a method for reducing the diameter of a tube in which an outer tube and an inner tube are tightly connected by performing cooling in the latter stage.In particular, when performing ring-shaped front stage heating and latter stage cooling on a raw pipe, the latter stage cooling is performed in the former stage. A presser bending moment acts on the heated part in the axial direction toward the center of the pipe, restraining its expansion diameter, and continuously applies inward plastic deformation to the heated part after the cold part, creating a strong bond. This invention relates to a method for reducing the diameter of a tube that allows a fitting allowance of .

<Prior art> As is well known, piping is widely used for transporting fluids in various industrial fields. In slurry transport pipes or pneumatic transport pipes for transporting particulate matter such as dust and sand, there is a problem in that the inner surface of the pipe is extremely susceptible to cracking.

This type of piping usually uses inexpensive steel pipes such as gas pipes, and when the pipe wears out, it is replaced with a new pipe or welded a cover plate to the worn part.

(Problem to be solved by the invention) However, in applications where high wear resistance is required, pipes made of materials with excellent wear resistance such as high chromium #R iron may be used. be.

By the way, the wear resistance of steel materials generally has a good correlation with hardness, and materials with excellent wear resistance are uniformly extremely hard.

For example, 27Crvf, which is often used as a wear-resistant material.
Iron has a hardness of 81 or more on the Shore hardness scale.

However, on the other hand, as the hardness increases, the toughness of steel materials tends to decrease, and pipes made of wear-resistant materials such as high chromium cast iron mentioned above have the disadvantage that they are more likely to break when subjected to impact force. be.

In addition, Takasago 1Tate's wear-resistant material has extremely poor weldability and workability, so firstly, it is impossible to attach the flange to the main body by welding, and secondly, it is impossible to attach the flange to the main body by welding. Even when integrally formed, finishing and hole drilling are difficult, and thirdly, repair welding is difficult.

In addition, it also has the disadvantage of high manufacturing costs.

For this reason, so-called clad steel pipes, which are steel pipes lined with a wear-resistant material, have come into use.

This type of clad steel pipe is usually made by centrifugal casting or overlay welding, and the lining is metallurgically joined to the pipe body.

Since the inner surface of the clad steel pipe is covered with a wear-resistant material, the wear resistance of the clad steel pipe is far superior to that of a normal single-layer steel pipe made of a material that does not take wear resistance into consideration.

In addition, the pipe port (A) must be equipped with a wear-resistant material (31).
Therefore, a material with sufficient toughness and good weldability can be used.

Therefore, unlike a pipe made only of wear-resistant material, it has sufficient 1li4 impact performance, and it is also possible to form the flange separately and remove it by welding.

However, regardless of the manufacturing method used in clad steel pipes, tensile stress remains in the inner lining, resulting in the inconvenience of cracking.

Moreover, if a -1q crack occurs, since the lining is metallurgically joined to the tube body, the crack will easily propagate to the tube body, resulting in a conduit crack.

Therefore, we developed a two-wheeled tube in which an outer tube with sufficient toughness for practical use and an inner tube with excellent abrasion resistance are layered, so that the two tubes are metallurgically joined and do not contact each other after a certain blood pressure. and
It is desired to develop a self-containing double pipe in which the inner pipe is under compressive stress.

This is because such a self-consolidated double pipe has the same advantages as the clad n4ff, but also eliminates the drawbacks of the above-mentioned four-pipe clad steel pipe.

By the way, conventional self-tightening double-pipe manufacturing techniques include firstly the shrink fitting method, secondly the tube expansion method, and thirdly the heat-expanding method, etc.However, the I! Each of these methods has disadvantages when it comes to construction methods.

First, the first method requires strict machining accuracy on the inner diameter of the outer tube and the outer diameter of the inner tube, but in the case of a biflat tube with internal wear resistance,
The inner tube is made of a wear-resistant material with poor machinability, so it is extremely difficult to perform the necessary machining.

In addition, this method generally makes it extremely difficult to fit long tubes.

In addition, in both the second and third methods, the inner tube is expanded plastically, but in this case, the inner tube has a very high strength (temperature breakdown point) and the strength of the inner tube is higher than that of a corrosion-resistant double tube. Since the pipe becomes somewhat thick, extremely high pressure for pipe expansion is required, which is not practical.

In particular, with the second method, in the case of this double-walled pipe, where the strength (M yield point) of the outer pipe is higher than the strength (yield point) of the inner pipe, even if the inner pipe is expanded plastically, the inner and outer pipes will not return due to elastic return. A gap is created between them.

As described above, although there is a strong need for wear-resistant dual-purpose pipes, conventional techniques have not been able to provide wear-resistant dual-Φ pipes that meet the requirements.

The purpose of the invention of this application is to solve the problems of manufacturing double pipes based on the above-mentioned prior art, and to provide circumferential ring-shaped heating for the outer pipe of a laminated pipe that is loosely inserted, and cooling around the outer pipe. The diameter of the outer tube is reduced by applying the action concurrently, for example, continuously while moving relatively in the axial direction,
It is an object of the present invention to provide an excellent method for reducing the diameter of a pipe, which is useful for piping applications in various industries, by tightening the inner pipe against the outer pipe.

Means/effect for solving the above-mentioned problems In accordance with the above-mentioned object, the structure of the invention of this application, which is summarized in the above-mentioned claims, provides a material pipe with high wear resistance in order to solve the above-mentioned problems. When reducing the diameter using a material, ring-shaped heating is applied to the tube, and the circumferential annular heating means and the raw tube are relatively moved in the axial direction. By installing cold JJI means at the front and rear, a radial presser bending moment acts toward the center at the rear, front, and rear of the heated portion, depending on the axial length. When the raw pipe tries to expand in diameter at the heating part, it is restrained by the cooling part on one or both sides and collapses, and when it is cooled immediately after heating, it becomes -b from its initial diameter. They took technical measures to reduce the diameter.

<Embodiment - Configuration> Next, one embodiment of the invention of this application will be described below based on the drawings.

The illustrated embodiment is a manufacturing method of a wear-resistant double pipe such as a slurry transport pipe, and the outer pipe 1 has a carbon content of, for example, 0.25%.
For the inner tube 2, use a material with high toughness such as low carbon steel with a carbon content of about 0.55%, and for the inner tube 2, use high carbon steel with a carbon content of about 0.55%. After the inner tube 2 is completely cooled, it is loosely inserted into the inner tube 2 to form a two-Φ tube blank 3.

Then, move the double tube tube 3 in the axial direction at a predetermined speed as shown by the arrow! Furthermore, as shown in FIG. 2, a high-frequency induction heating device 4, for example, is set as a heating means annularly around the outer circumference of the outer tube 1, and an axially adjacent high-frequency induction heating device 4 is set at a predetermined distance from the high-frequency induction heating device 4. Before and after, e.g.
By setting the cooling device 5 of the ring-shaped shower Vil for water flow, etc., and moving the double tube material tube 3 in the direction of the arrow, the heating device 4 and the cooling device 5 are set relative to the double tube material tube. be made to move.

Therefore, when the double tube blank tube 3 is moved at a predetermined speed, the heating device 4 applies an expansion effect due to heating to the cooling of the outer tube by the cooling device 5.5 before and after it. As shown in Fig. 2, if both ends of the heating part are free ends with respect to the cooling part, as shown in Fig. 2,
Although it freely expands in diameter and protrudes in the circumferential direction, in reality, both ends of the heating part are restrained by the cold part 81, so the heating part expands in the longitudinal direction as shown in Figure 4. On the other hand, a radial pressing bending moment F acts toward the center, and as a result, a ring-shaped curved plastically deformed portion is formed.

Then, as the double tube blank tube 3 moves relatively in the direction of the arrow, the part heated by the heating device 4 and plastically deformed passes through the heated part and is cooled by the cooling means, as shown in FIG. On the contrary, the diameter is greatly reduced, so that a large fitting margin is obtained, and the outer tube 1 is tightly connected to the inner tube 2.

Since this action acts on all the circumferential parts of the outer pipe, by continuously moving the double-walled wood pipe 3 in the axial direction, all parts of the outer pipe 1 are reduced in diameter, and the double-walled wood pipe 3 is reduced in diameter. pipe system pipe 3
At this point, a state of restraint is created, resulting in the formation of a large self-locking double tube.

And the above-mentioned tight connection? This is done regardless of the wall thickness of the inner tube 2, and regardless of the axial length of the full-double tube system tube 3.
Since it is formed at the same time, the process is performed almost independently of the accuracy of the joint surface between the outer tube 1 and the inner tube 2.
It is especially effective for manufacturing wear-resistant double-walled pipes where the inner pipe wall thickness is large and the pipe is long.

It should be noted that the embodiments of the invention of this application are of course not limited to the above-mentioned embodiments. Various aspects can be adopted, such as

Moreover, it is applicable not only to straight pipes but also to curved pipes such as bent pipes.

Note that the invention of this application is different from the circumferential diameter increasing/reducing means which uses a linear heating or cooling means in the moving direction. It is restrained by a cooling part, and the diameter is reduced by the diameter of the heating part being reduced after cooling, so that, for example, when manufacturing a double pipe, the outer pipe is tightened to the inner pipe, and its self-tightening mechanism are completely different.

<Effects of the Invention> As described above, according to the invention of this application, it is basically possible to reduce the diameter of the outer pipe when manufacturing a double pipe, etc., and as a result, the strength of the inner pipe is higher than that of the outer pipe, and the outer pipe has a higher strength than the outer pipe. There is no risk of clearance between the outer and inner tubes due to the expansion of the outer and inner tubes of double tubes with high wear resistance, and the excellent effect of obtaining extremely high precision self-containing double tubes is achieved. In addition, there is no need for the enormous pressure necessary for pipe expansion pressure, and the power cost for manufacturing is low, resulting in low-cost C manufacturing.

In addition, unlike conventional shrink fitting methods, the accuracy of the joint surface between the outer tube and the inner tube is not required to be very high, and therefore, it has the excellent effect of being able to freely manufacture long tubes, etc. .

Furthermore, even if the inner tube is wear resistant and the outer tube has high toughness, the diameter can be reduced without any restrictions on design freedom, and therefore the material selection for the outer tube and inner tube is free. This effect is achieved.

[Brief explanation of drawings]

The drawing is a schematic explanatory diagram of one embodiment of the invention of this application,
Figure 1 is a partial sectional side view of the outer tube and inner tube when they are stacked relative to each other, Figure 2 is a partial sectional view of the mechanism for applying presser bending moment due to heating, and Figure 3 is a diameter reduction through the presser bending moment due to cooling. A sectional view of the mechanism, and FIG. 4 is a schematic perspective view of the presser bending moment leaf application. 3...Pipe, 1...Outer tube, 4...Heating (means), 5...Cooling 7I] (means), F...Press bending moment...'+1).

Claims (2)

[Claims] (1) Annular heating in the circumferential direction and cooling of the surrounding area are simultaneously applied to the tube, the thermal expansion of the heated part is restrained by the low temperature parts on both sides to suppress the expansion diameter, and then the heated part is cooled A method for reducing the diameter of a tube, characterized by shrinking the tube so that the diameter of that portion becomes smaller than the initial diameter. (2) Annular heating in the circumferential direction and cooling of the surrounding area are simultaneously applied to the tube, the thermal expansion of the heated part is restrained by the low temperature parts on both sides to suppress the expansion diameter, and then the heated part is cooled The tube is contracted so that the diameter of that part is smaller than the initial diameter, and the tube and the heating/cooling means are moved relative to each other in the axial direction, so that the diameter of the tube after cooling is smaller than the initial diameter over the entire length of the heating section. A method for reducing the diameter of a tube, characterized in that: