JPS5924519A - Continuous manufacture of plurally-layered heat-insulating pipe - Google Patents

Abstract

PURPOSE:To obtain a plurally-layered heat-insulating pipe, which has a heat- insulating material hard to powder and, has high durability and is suitable for bending, by inserting an inner pipe covered with a heat insulating material into an outer pipe, and then, passing the pipe through rolls having projections and recesses and successively through sizing rolls. CONSTITUTION:A plurally-layered pipe formed by inserting an inner pipe 1 covered with a heat insulating material 2 into an outer pipe 3 is passed through a space between an upper roll 51, a lower roll 52 and side rolls 61, 62 having projections respectively in a group of radially contracting rolls. A part of the outer pipe 3 is rolled to have recesses as shown by 41 by the projections of respective rolls. Next, ordinary sizing rolls are arranged at the rear side of said rolls having projections, and the recesses 41 formed at the preceding stage are bent while radially contracting the pipe. The recesses are further bent as shown by 43 by the following sizing rolls 83, 84, 93, 94 arranged after said sizing rolls to have a strong spacing function.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides automatic 21? -Regarding a continuous manufacturing method for heat-insulating multilayer pipes used for exhaust pipes, etc.

1 piece for automobiles 1. Increasingly, the trachea is required to have unsophisticated characteristics. One of them is L heat insulation.

This is because the exhaust pipe, which is heated to a high temperature through engine exhaust gas with a temperature of 700 to 900 degrees Celsius while driving, becomes stationary relative to the ground when the car is stopped, and if there is dry grass underneath, there is a risk that it will ignite and cause a fire. Therefore, the outer peripheral surface of the exhaust pipe should be kept at a low temperature. As a countermeasure against this dry grass, a heat shield plate is installed, but since the heat shield plate vibrates during driving and becomes a source of noise, the exhaust pipe has insulation properties to prevent the outer peripheral surface temperature from rising. I hope not. The second is heat retention. As is well known, a catalyst is used to purify exhaust gas, and catalysts are more efficient at high temperatures, so exhaust gas is not cooled, so it is desirable to have heat retention properties.

In order to provide the exhaust pipe with heat insulation and heat retention properties, it is effective to form a double pipe as shown in FIG. 1 and insert a heat insulator 4') between the pipes as shown in FIG. In this figure, 1 is an inner tube, 2 is an intermediate insulation layer, and 3 is an outer tube.

By the way, the exhaust pipe is arranged in 4 parts, 1 out, 9::A dimensions, such as at the tail of the car body, bending it as appropriate for purposes such as avoiding obstacles from the engine, but when bending a multi-layer pipe, the The insulation material 2 receives a strong compressive force at the bent portion, and the thickness of the insulation material becomes smaller. Naturally, the thinner the insulation layer, the worse its insulation and heat retention properties. In addition, high-temperature exhaust gas flows through the exhaust pipe of a car, and the inner pipe of a multilayer pipe is in contact with the high-temperature exhaust gas, so the temperature is high, but the temperature is moderate, and the higher the urine temperature, the higher the temperature of the outer pipe. The temperature is low, and there is a large temperature difference between the inner and outer tubes. Therefore, the difference in expansion between the inner and outer tubes due to the humidity difference between the inner and outer tubes is large, so the outer tube is made of steel, the material is made of stainless steel, and the thickness of the insulation intermediate layer is 2.0 mm.
When an experiment was carried out by flowing exhaust gas at 700°C through a multi-layer pipe with a length of 1000 m, the inner pipe was about 8 times longer than the outer pipe, and the pipe 1Ii
It extended in the b direction. The temperature inside the exhaust pipe changes from low to high (up to about 900°C) depending on the driving conditions of the vehicle. For this reason, the amount of expansion and contraction of the inner tube of the multilayer tube is large, and the amount of expansion and contraction required is large.
1. The heat insulating intermediate layer material at the bent portion of the exhaust pipe is rubbed while being subjected to a particularly strong compressive force.

In addition, when the JUL trachea vibrates (chills due to failure of transmission of engine's 4-way motion, flow of J11 gas at pulsating pressure, etc.), the insulation intermediate layer wears out and becomes powder, reducing the thickness of the insulation material. or leak to the outside. The thickness of the first layer of insulation has become smaller, so if it leaks out, it will still have better insulation properties.
If the heat retention is poor, it will be difficult to meet the desired characteristics. Therefore, the trachea needs to have heat shielding properties, heat retention properties, bending workability, and powder resistance.

As a result of research conducted by the present inventors, it was found that a multilayer pipe having a cross-sectional shape as shown in Fig. 2.6 is effective for exhaust gas that satisfies these requirements. In the cross-sectional views of Figure 2, as shown in these figures, the multi-layer pipe has convex portions 4 on the inner pipe side at several places on the outer pipe, and the inner and outer pipes are held uniformly by 4. Even if the inner and outer tubes expand and contract during bending or due to thermal effects, the intermediate calendar month 2 will not be subjected to strong compressive force and will not be easily scratched.

The continuous manufacturing method for multilayer pipes shown in Fig. 1 was previously proposed by the applicant, and the method uses already made inner and outer pipes, and covers the inner pipe with a heat insulating material. This method involves inserting it into the outer tube, reducing the diameter of the outer tube, and integrating the inner IR1 intermediate insulation layer 1 and the outer tube.

Therefore, the present invention provides a method for continuously manufacturing a multi-layer tube having the structure shown in FIGS. Several parts of the tube are processed into inner and outer tube holders 4 to produce a multilayer tube having the cross section shown in FIGS. 2 and 3.

The amount of diameter reduction of 1 yen of outer ring in the diameter reduction process is usually 4 in outer diameter dimension.
~10. , about lll+. In the present invention, in the roll group in the diameter reduction process, there is a roll with a concave and convex shape that is machined so that several parts (at least 4 or more places) of the outer tube are formed with dents while the diameter is reduced, and behind the roll, the roll is By arranging shaping rolls that form the concave part of the pipe into a bent shape, we continuously create a multi-layered pipe with a structure in which the inner pipe, intermediate layer insulation, and part of the outer pipe are processed into inner and outer pipe holders. Manufacture.

This will be explained in detail using Figures 5 to 7.
As shown in FIG. 5, the composite tube constructed as described above is formed between the rolls having the convex portion 7 in the group of diameter-reducing rolls, i.e., the upper roll 51, the lower roll 52, and the side roll 61.62. pass. At the convex part of each roll, a part of the outer tube Otsu is 4
Make a recess as shown in 1. Next, as shown in FIG. 6, normal shaped rolls 81, 82.
91.92 are arranged, and the recess 41 formed by the front ball f- is bent as shown in 42 while the diameter is reduced h, and further in the rear regular roll part (83.84, 93.94 in Fig. 7). 43
It is bent like this and has a strong spacer function. That is, in this process, we first perform the eave-shape processing, and then apply the diameter reduction action in the diameter reduction process to form a sharper bent convex part. ? There is color.

In the present invention, is the inner tube and outer tube made? 1? After covering the inner tube with a heat insulating material and inserting it into the outer tube, the inner tube is coated with a heat insulating material, and then the unevenness is coated with a four-layer roll and a shaping roll. At the same time, the outer tube is brought into close contact with the inner tube and the outer tube is uneven, thereby producing a multilayer tube in which a gap holder between the inner tube and the outer tube is formed.

By the way, conventional insulated multi-layer pipes can be bent to cool i1. i1B test (1 μl of engine gas at 700°C in the exhaust pipe)
After running for 0 minutes to raise the temperature, the engine is stopped and the control pipe is cooled down.This operation is repeated several hundred to several thousand times (experiments). Although the heat insulating material at the bent portion was significantly powdered and the heat shielding and heat retaining properties were reduced, a thermal test of the heat insulating multilayer pipe of the present invention revealed that it was very effective. In other words, as shown in Table 1, when bent at 90 degrees and subjected to a thermal cycle test, conventional insulated multilayer pipes have a thermal insulation layer of 20 to 40 inches compared to the Jyutsuki ratio, and their heat shielding performance is superior. In contrast, the product of the present invention was powdered by only a few factors, and its heat shielding performance remained largely unchanged. This is because the compressive force during bending and the compression caused by vibrations and vibrations during expansion and contraction of the inner and outer tubes do not act directly on the heat insulating material, and a gap holder is formed by the inner tube or outer tube.

As explained above, the multi-layered pipe manufactured according to the present invention is extremely effective because the heat-insulating multi-layer pipe is difficult to powder, is suitable for bending, and has high durability.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional multi-layer pipe, FIG. 2 is a perspective view of a multi-layer pipe manufactured by the present invention, and FIG. 3 is a cross-sectional view of a multi-layer pipe manufactured by the present invention. The figure is a cross-sectional view showing the change in thickness of the intermediate material when a conventional multi-layer pipe is bent.
The figure shows the manufacturing process vI' of the present invention, FIG. 5 is a 4s, 7+ cross-sectional diagram of the roll and multilayer pipe of the diameter-reducing roll part with unevenness in the diameter-reducing roll group, and FIG. FIG. 5 is a cross-sectional structural diagram of a regular roll portion at the rear of the roll, and FIG. 7 is a cross-sectional structural diagram of a round-shaped roll portion further rearward from that of FIG. 6. 51 in the drawing. '52, 61.62 is a roll with a convex part, 81-84. 'J
: Outer tube, 4 is a gap holder. Applicant Nippon Steel Corporation

Claims (1)

[Claims] A roll having a convex portion and a shaping roll are placed behind the roll, and the outer tube, in which an inner tube coated with an intermediate layer material is inserted, is combined into a roll having a convex portion and a shaping roll. By passing the outer tube through, the outer tube is squeezed and brought into close contact with the inner tube coated with the intermediate layer material, and at the same time, the outer tube is recessed to form a gap holder between the inner tube and the outer tube, and the spacer and the gas are removed using the diameter reduction process. A continuous manufacturing method for a heat insulating composite pipe, characterized in that the gap retaining body is processed into a bent shape.