JPH0576384B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The disclosed technology is a wear-resistant curved double pipe in which an outer pipe made of low carbon steel or the like and a wear-resistant inner pipe made of ceramic or the like are tightly connected. belongs to the field of manufacturing technology.

<Summary of the gist> The invention of this application, in order to improve the abrasion resistance of piping used for slurry transportation, etc., has a double-layer structure in which a curved outer pipe and a wear-resistant curved inner pipe are relatively layered. The pipe is made into a bent blank pipe, and the bent blank pipe is moved in the axial direction relative to a circumferential annular heating means such as a high-frequency induction heating device and cooling means such as a water shower device in the front and rear stages thereof to cool the former stage. This action is followed by a uniform annular heating action in the circumferential direction, followed by a cooling action at a later stage, and the bent outer pipe tightens the bent inner pipe to form a tight fit.It has wear resistance, etc. This invention relates to a method for manufacturing bent double pipes, and in particular,
A curved inner tube made of wear-resistant cast steel or the like is layered relative to a curved outer tube made of low-carbon steel, or a large number of short cylindrical pieces made of wear-resistant materials such as ceramics are placed adjacent to each other. When an annular heating action is performed on the bent outer pipe and a cooling action is performed on the front and rear stages, the annular cooling action portion of the front and rear stages becomes the heating action imparting portion of the middle stage. On the other hand, an annular heating action and a cooling action, which act toward the center of the tube in the axial direction and act to suppress the expansion diameter due to heating, and a cooling action cause inward plastic deformation to the heated portion after cooling. Continuously applying these annular heating and cooling effects in the axial direction over time, the passage of these annular heating and cooling effects to the bent tube causes the bent outer tube to tighten the bent inner tube, creating a strong fit. The present invention relates to a method for manufacturing a bent double pipe.

<Prior art> As is well known, piping is widely used for transporting fluids in various industrial fields. In pipes for transporting slurry mixed and dispersed in water, or pneumatic transport pipes for transporting particulate matter such as dust and silica sand, the inner surface of the pipe is likely to wear out over time during operation.

In particular, the bent pipe portions of the piping are subject to significant wear, which often poses a problem in terms of durability.

Up until now, this type of piping has often used inexpensive steel pipes such as gas pipes, and when they wear out, they can be replaced with new pipes or welded backing plates to the worn parts. This is being addressed.

<Problem to be solved by the invention> Therefore, in piping for applications where wear resistance is particularly required, pipes made of materials with excellent wear resistance such as high chromium cast iron are sometimes used. .

By the way, in general, the wear resistance of steel materials has a deep correlation with their hardness, and materials with excellent wear resistance are uniformly extremely hard. For example, 27Cr cast iron, which is often used as a wear resistant material, has a Schore hardness It has a hardness of 81 or higher.

However, as is well known to those skilled in the art, as the hardness of a steel material increases, its toughness tends to decrease, and pipes made of wear-resistant materials such as the high-chromium cast iron mentioned above may break when subjected to impact forces. It has the disadvantage of being easy.

By the way, flange joints are generally used to connect straight pipes and bent pipes for ease of removal, but bent pipes made of high-hardness cast steel require flat cutting of the flange portion or holes for bolts due to their high hardness. The disadvantage is that it is difficult to open and process.

That is, since high-hardness wear-resistant materials have extremely poor weldability and workability, the first drawback is that it is impossible to attach connecting flanges by welding to connect pipes. Second, even when the flange is integrally formed, it is difficult to finish the flange surface and drill holes for bolts, and third, repair welding is difficult.

In addition, there is also the disadvantage that manufacturing costs are high.

For this reason, so-called clad steel pipes, which are steel pipes used for wear-resistant piping 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 inner lining is metallurgically joined to the outer pipe body.

In curved pipes made of clad steel, the inner surface of the outer pipe body is covered with a lining made of wear-resistant material, so it is different from ordinary single-layer steel pipes made of materials that do not have wear resistance in mind. It has much better wear resistance than bent pipe.

Further, since the tube body outside the lining does not need to be provided with a wear-resistant material, a material having sufficient toughness and good weldability can be used.

Therefore, unlike a lining made only of wear-resistant material, the tube body has sufficient impact resistance, and
It is also possible to form a connecting flange separately and attach it by welding.

However, once a crack occurs in a curved pipe made of clad steel, the crack can easily propagate to the outer pipe body because the lining and the outer pipe body are metallurgically bonded as described above. There is also a negative point that it is prone to cracking through.

Therefore, we developed a curved double pipe in which the outer pipe body of a bent pipe with sufficient toughness for practical use and a lining with excellent wear resistance are layered, and the lining and outer pipe body are metallurgically bonded. It is desired to develop a self-tensioning double-pipe pipe in which the inner lining is in a state of compressive stress due to the contact with each other under a certain surface pressure.

This is because such a self-tightening bent double pipe has the same advantages as a bent steel pipe made of clad steel, and also eliminates the disadvantages of the bent pipe made of clad steel mentioned above.

<Object of the invention> The object of the invention of this application is to solve the problems of manufacturing bent double pipes based on the above-mentioned prior art, to provide high toughness to the bent outer pipe, and to provide the bent inner pipe with high toughness. With high hardness, both tubes are inserted relative to each other to generate a circumferential annular heating effect on the bent outer tube of the unbound bent tube, and an annular cooling effect around the front and rear of the bent outer tube simultaneously and continuously in the axial direction. For example, by applying a heating effect and a cooling effect while moving relative to each other in the axial direction, the diameter of the bent outer tube is reduced, and the bent inner tube is tightened by the bent outer tube to tighten it, and is used in various industries. It is an object of the present invention to provide a method for manufacturing an excellent wear-resistant bent double pipe that is useful in the piping technology application field.

<Means/effects for solving the problem> In order to solve the above-mentioned problem, the structure of the invention of this application, which is summarized in the above-mentioned claims, is based on a bent outer tube made of low carbon steel and a durable A curved inner tube for lining consisting of a curved inner tube made of abrasion-resistant cast steel and a large number of pieces made of wear-resistant ceramics in the form of segments, arches, etc. is relatively layered (inserting a curved inner tube into a curved outer tube, or Do the opposite, or do both at the same time)
When reducing the diameter of the bent outer tube of the bent outer tube, an annular heating action in the circumferential direction of the bent outer tube and an annular cooling action before and after the bent outer tube are simultaneously performed. The circumferential annular heating means, the circumferential annular cooling means, and the curved tube inside them are moved relative to each other in the axial direction over time, and by doing so, the annular heating is performed. By arranging the annular cooling means both in front and behind the means, the expansion diameter of the heating part is restrained by the cooling parts before and after it and yielded, and the diameter is reduced from the initial diameter by cooling contraction immediately after heating. In this way, the bent inner tube and each piece of the wear-resistant material of the bent inner tube are firmly brought into close contact with each other, and the bent outer tube is tightened with the bent inner tube. .

<Basic Background of the Invention> Generally, the diameter of a pipe is changed by subjecting the pipe to local heating or cooling in an annular manner.

This phenomenon is due to thermo-elasto-plastic behavior.

That is, when a local part of the tube in the circumferential direction is heated, the heated part tends to expand in diameter due to thermal expansion, but at this time, if the surroundings (front and rear) of the heated part are forcibly cooled, the expanded diameter is restrained by the cooling part. Since the yield stress is low at high temperatures, the heated part easily undergoes plastic deformation, and the amount of expansion becomes significantly smaller than that during free expansion.

Thereafter, when the heating section is cooled, the heating section thermally contracts relatively freely, so that the pipe diameter of the portion that has undergone this thermal history becomes smaller than the initial diameter.

By applying this heat treatment continuously in the longitudinal direction of the pipe, it is possible to reduce the pipe diameter uniformly over the entire lengthwise region, and by applying it partially, the pipe diameter can be reduced locally. It can also be reduced.

FIG. 7 is a graph simulating the basic phenomenon in which the diameter of a pipe changes by the annular thermal reduction method (a method of reducing the diameter by applying annular heating and cooling to the pipe) using thermoelastic-plastic analysis. In this case, the analysis model is a mild steel pipe (outer diameter 165.2 mmφ x wall thickness 5.5 mm), and the analysis conditions are as follows:
The tube is rapidly heated to 800°C and then cooled, giving it a continuous thermal history along its length.

In Fig. 7, the amount of plastic strain that occurs according to a given thermal history and the corresponding amount of transient change in pipe diameter (both values at the center of the plate thickness) are plotted on the vertical axis (left and right vertical axes).
, the longitudinal coordinates of the tube are shown on the horizontal axis.

According to FIG. 7, when heating, the amount of expansion is small;
A large compressive plastic strain occurs in the circumferential direction, and although tensile plastic strain occurs during cooling, the amount is smaller than during heating, and therefore, after cooling, compressive plastic strain remains in the pipe and the pipe diameter It can be seen that the amount decreases.

First, the principle aspect of the manufacturing method of the wear-resistant curved double pipe according to the invention of this application will be explained with reference to FIGS. The bent tube 3 inserted into the tube is set so as to be moved at a predetermined speed in the axial direction as shown by the arrow in FIG. 3, and further, as shown in FIG. As a heating means, for example, a high frequency induction heating device 4 (hereinafter abbreviated as a heating device) is set, and a ring-shaped heating device such as tap water is placed at a front and back position in the axial direction close to the heating device 4 at a predetermined distance. Shower-type cooling devices 5, 5 (hereinafter referred to as cooling devices) are set in fixed positions to form one unit, and by moving the bent tube 3 in the direction of the arrow, the heating device 4 and the cooling device are One unit of the devices 5, 5 is moved relative to the bent pipe 3.

Therefore, when the bent tube 3 is moved relative to the heating device 4 and the cooling devices 5, 5 as shown by the arrow at a predetermined speed, the bent outer tube is 1 is locally heated to give an expansion effect due to heating, but if the thermal expansion deformation of the heated part is not restrained during this process (until the desired fitting force is applied), the diameter will expand freely and the circumference will expand. However, as schematically shown in Fig. 4, the deformation of the heated part is actually restrained by the surrounding cooling part, so the deformation of the heated part is schematically shown in Fig. 5. As shown in FIG. 2, a radial pressing bending moment F is applied in the longitudinal direction toward the center to suppress the expansion diameter due to heating, and as a result, a curved plastically deformed portion is formed.

Then, as the bent tube 3 moves relative to the heating device 4 and the cooling devices 5, 5 in the direction of the arrow, the portion of the bent outer tube 1 that has been heated and plastically deformed by the heating device 4 passes through the heated portion. When the tube is cooled by the cooling devices 5, 5, the diameter is reduced from the initial diameter due to thermal contraction as shown in FIG. The hoop tightens and tightens the material.

Then, one of the heating device 4 and the cooling device 5, 5
Since the diameter reduction action by the unit acts on all the circumferential portions of the bent outer tube 1, the bent outer tube 3, 3'
By continuously moving relatively in the axial direction, all parts of the bent outer tube 1 are reduced in diameter, and the bent tube 3,
3', a fitted state is created over the entire length of the bent inner tube 2, and as a result, a bent double tube is formed.

Then, the above-mentioned tightening process
In other words, the bending is performed regardless of the wall thickness of each inner tube 2, and the bending is performed in all regions of the raw tube 3 regardless of the axial length. This process has almost no relation to the accuracy of the joint surface between 1 and the bent inner tube 2, and is extremely effective in manufacturing wear-resistant lined curved double tubes, which are used to extend the service life in abrasive environments. It is true.

<Example> Next, an example of the invention of this application will be described below with reference to the drawings in FIGS. 1 and 2.

The illustrated embodiment is a mode of manufacturing a curved double pipe with wear-resistant inner lining such as a slurry transport pipe. In the embodiment shown in FIG. For example, as the bent inner tube 2, use a bent tube of the same curvature made of wear-resistant high carbon steel of about 0.55% and hardened by quenching. As described above, the bent tube 3 is appropriately stacked inside the bent outer tube 1 so as to be inserted in a non-tight manner.

In the embodiment shown in FIG. 2, the bent inner tube 2' is a segment-shaped piece 2 made of ceramics (Al ₂ O ₃ ) having high wear resistance and high hardness and cut into a trapezoidal shape when viewed from the side. '', 2''... (In this case, it is generally difficult and expensive to form a curved inner tube as shown in Figure 1 using ceramics, so a straight pipe made of ceramics as shown in Figure 2) is used. Cut the pieces into trapezoidal shapes when viewed from the side and temporarily attach them to each other using adhesive, etc.). The tube 1 and the bent inner tube 2' are appropriately inserted relative to each other to form a bent blank tube 3'.

Then, an annular thermal diameter reduction effect is applied to these bent outer tubes 3 and 3' through relative movement in the axial direction by the heating device and the cooling device 5 shown in the above-mentioned principle mode, so that the bent outer tube 1 is Tighten the hoops on the bent inner pipe 2.

In the embodiment shown in FIG. 2, the curved inner tube 2' made of ceramic has a large number of ring-shaped pieces 2'', 2'', . . . of segments in the axial direction arranged adjacent to each other. It is also possible to adopt a mode in which a large number of so-called Yatsuhashi-shaped pieces having an arch shape in the direction are set in the same shape as pieces 2'', 2'', etc., and are temporarily attached in the circumferential direction and the axial direction, and are adjacent to each other. It is also possible to construct a bent double pipe with a circular cross section in which the bent outer pipe 1 and the bent inner pipe 2 are mechanically restrained by the hoop tightening action of the bent inner pipe 2.

The above-mentioned process may be performed by passing the bent tube 3, 3' once in the axial direction, but by repeating the process two or more times, the amount of diameter reduction can be increased.

Next, an experimental example based on the above embodiment is as follows.

Figure 8 shows the amount of outside diameter change (cumulative) (on the left vertical axis) of the outer tube 1 for each passing ring thermal shrinking process in the production of double-walled pipes using the ring thermal shrinking method RHS (registered trademark) method. This shows the generation of fitting surface pressure (below the left vertical axis) between the inner and outer tubes 1 and 2 of the heavy tube stock tube 3,
The case where the bent raw pipe 3 of No. 2 is a steel pipe (material: STPG-38, shape: outer pipe 90A/Sch40, inner pipe 80A/Sch40) is shown.

In this case, the initial clearance (diameter difference) between the curved inner and outer tubes 1 and 2 is 1.5 mm, and this is brought into contact with each other through four ring heat reduction processes, and then the fifth ring heat reduction process. It can be seen that the curved inner and outer tubes 1 and 2 will fit together from then on.

Here, the initial clearance is the curved inner and outer tubes 1 and 2.
It is enough to relatively insert the , and in practice,
For example, it is about 1 to 5 mm.

Regarding the ring thermal diameter reduction treatment, the amount of diameter reduction per treatment can be arbitrarily determined depending on the conditions, but in reality, for example, it is about 0.5% of the diameter of the outer tube. Ta.

As can be seen from the data of the experimental example, as the number of treatments increases, the amount of diameter reduction of the bent outer tube 1 increases until the bent inner and outer tubes 1 and 2 come into contact with each other.
After 2 come into contact, a fitting surface pressure is generated.

Furthermore, since the fitting surface pressure increases as the number of processing repetitions increases, it is understood that the fitting surface pressure can be changed by controlling the number of processing repetitions.

In order to obtain the fitting allowance that matches the design,
A highly accurate bent double pipe can be obtained that is uniformly fitted not only in the circumferential direction but also in the longitudinal direction.

In the embodiment shown in FIG. 1, when one unit of the heating device 4 and the cooling devices 5, 5 is moved relative to the bent tube 3, as described above, the bent tube 3 In the case of a bent pipe with a normal curvature, experiments have shown that in one unit, if the diameter of the bent outer pipe 1 is 100φ and the wall thickness is 4t, the pipe diameter is reduced by about 0.5 mm in one diameter reduction treatment.

It goes without saying that the embodiments of the invention of this application are not limited to the above-mentioned embodiments, and various embodiments can be adopted, such as the possibility of using corrosion-resistant materials other than cast steel pipes and ceramic pipes for the bent inner pipe. It is possible.

Note that the invention of this application differs from the conventional mode in which the circumferential length is reduced by means of moving a linear heating and cooling means in the axial direction of the tube.
The expanded diameter of the heated annular portion of the outer tube is restrained by the adjacent cooling portion, and the heating portion contracts in diameter after cooling, so that the bent outer tube is tightly connected to the bent inner tube, The self-control mechanism is completely different.

<Effects of the Invention> As described above, according to the invention of this application, basically in a bent double pipe such as a slurry transport pipe, the bent inner pipe with the wear-resistant lining, which is tightened to the inner surface of the bent outer pipe, is made of bent cast steel. Formed by a number of tubes, short tubular segments, or arch-shaped pieces (either integral or divided) that are stacked relative to each other so that they are mechanically connected and abutted against each other. The excellent effect of forming a curved raw pipe regardless of the curvature is achieved by forming the bent raw pipe.

In addition, since the bent inner tube is fastened by the hoop tightening of the bent outer tube, it is mechanically stable and there is an excellent effect that peeling does not occur during operation.

Furthermore, the bent inner tube receives compressive stress due to the hoop tightening with the bent outer tube, improving corrosion resistance, and in the case where the bent inner tube is made up of many pieces, it becomes easier to follow curved surfaces, which reduces durability. It has an excellent effect of improving.

Thus, the diameter of the bent outer tube can be reduced when manufacturing a bent double tube, etc., and the excellent effect of obtaining a self-tightening double tube with extremely high precision is achieved.

In addition, ceramic pipes with excellent wear resistance, high chromium cast iron pipes, high carbon steel pipes, stainless steel pipes and Inconel pipes with excellent corrosion resistance, etc. can be used for the bent inner pipe, and they have excellent wear resistance. For the bent outer tube, not only carbon steel tubes but also stainless steel etc. can be used to reduce the diameter without restricting the degree of design freedom. Therefore, material selection for the bent outer tube and bent inner tube is practical. , the effect of being free is produced.

Therefore, for the bent outer pipe of the bent raw pipe, the annular heating means (device) and the cooling means (device) before and after the same are integrated into one unit, and the bent raw pipe is subjected to annular plastic deformation and cooling contraction. By imparting a diameter reduction effect, the diameter is reduced as designed, and the bent outer tube is self-tightened by hoop tightening against the bent inner tube, making it possible to manufacture a bent double tube with sufficient fitting force. This is an excellent effect.

Therefore, the degree of freedom in design is increased without being restricted by the diameter and curvature of the bent double pipe, and the advantage is that the bent double pipe can be manufactured as desired.

[Brief explanation of the drawing]

The drawings are schematic explanatory diagrams of embodiments of the invention of this application, and FIG. 1 is a sectional view of one embodiment, FIG. 2 is a sectional view of another embodiment equivalent to FIG. 1, and FIG. 3 is a curved outer tube. Fig. 4 is a partial cross-sectional view of the mechanism for imparting presser bending moment by heating and cooling, and Fig. 5 is a schematic perspective view of the diameter reduction mechanism via presser bending moment due to cooling. ,
Figure 6 is a cross-sectional view of a bent double pipe that has been reduced in diameter and self-tightened.
FIG. 7 is a simulation graph of the basic phenomenon of ring thermal diameter reduction, and FIG. 8 is a graph of an example of ring thermal diameter reduction treatment. 1... Outer tube, 2, 2'... Inner tube, 3, 3'... Base tube, 4... Heating device, 5... Cooling device.

Claims (1)

[Claims] 1. A method for manufacturing a curved double pipe 3 by layering an inner tube 2 on an outer tube 1, in which a curved inner tube 2 made of wear-resistant material is relatively layered on the curved outer tube 1 and the curved As raw pipe 3,
An annular heating action in the circumferential direction and a cooling action around the circumferential direction are simultaneously applied to the bent outer tube 1, and the thermal expansion of the heating part is restrained by the surrounding low temperature part to suppress the expansion diameter, and then the heating part is cooled and contracted so that the diameter of that part becomes smaller than the initial diameter, and then the bent pipe 3 and the heating/cooling means 4, 5 are moved relative to each other in the axial direction to cool the entire length of the heated part. A method for manufacturing a bent double tube 3, characterized in that the diameter of the later bent outer tube 1 is smaller than the initial diameter to increase the degree of fitting between the inner and outer tubes 1 and 2. 2 The inner tube 2 is layered on the outer tube 1 to form a bent double tube 3.
In this method, a plurality of mutually engaged pieces 2'' of a large number of wear-resistant materials are placed in a bent outer tube 1 to form a bent inner tube 2', and are relatively layered to form a bent blank tube 3'. , annular heating in the circumferential direction and cooling of the surrounding area are simultaneously applied to the bent outer tube 1, the thermal expansion of the heating part is restrained by the surrounding low temperature part to suppress the expansion diameter, and then the heating part is The tube is cooled and contracted so that the diameter of that portion becomes smaller than the initial diameter, and the bent tube 3' and the heating and cooling means 4 and 5 are moved relative to each other in the axial direction to cool the entire length of the heating section. A method for manufacturing a bent double tube 3, characterized in that the diameter of the later bent outer tube 1 is smaller than the initial diameter to increase the degree of fitting between the inner and outer tubes 1 and 2.