JPS58112612A - Manufacture of double pipe - Google Patents

Abstract

PURPOSE:To easily manufacture a double pipe having excellent adhesiveness without receiving any restriction in pipe dimensions, etc., by overlapping an outer pipe and an inner pipe having different coefficients of thermal expansion respectively, and expanding the inner pipe by a gas pressure while heating said inner pipe and then cooling it after expanding. CONSTITUTION:An inner pipe 2 consisting of a material having a thermal expansion coefficient smaller than that of a material of an outer pipe 1 is inserted to the inside of the pipe 1, and the whole length of overlapped pipes is housed in an electric furnace 5 to be heated. At the same time, both ends of the pipe 2 are hermetically sealed with seal caps 3 and 3, and compressed air is supplied to the pipe 2 from a air bomb 4 to pressurize and expand the pipe 2 in order to join it to the pipe 1. Next, the pipe 2 is squeezed strongly by the pipe 1 and bound with the pipe 1 tightly by means of the difference of thermal expansion coefficients of them by cooling the overlapped pipes. The binding between the overlapped pipes is made more firm by moving the heating zone through the whole length, or moreover, by loading a compressive force on the pipe 2 along the axial direction, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a double pipe, and in particular, the present invention relates to a method for manufacturing a double pipe, and in particular, the present invention relates to a method for manufacturing a double pipe, which comprises an inexpensive outer pipe and an inner pipe made of an expensive material that is resistant to corrosion or heat, for example. This is a method for connecting a double pipe, which is characterized by appropriately interpreting the coefficient of thermal expansion of each material of both pipes.

Since pipes are required to have various characteristics depending on their use, they are manufactured using materials that satisfy these characteristics. In recent years, due to the development of industry, especially the development of the chemical industry and related technologies, the characteristics required of pipes have become more diverse and severe. The current situation is that we have no choice but to use expensive materials.

In order to suppress the increase in pipe costs due to the use of the above-mentioned expensive materials, each has different characteristics! Methods for manufacturing multilayer pipes in which JI number of materials are bonded have been proposed one after another, and these methods can be broadly classified as follows.

1) When mechanically fitting pipes with slightly different diameters, the so-called shrink fitting method uses thermal expansion and contraction, or the fitting method uses a solid lubricant such as PB or Zn.

l) A method of wrapping the tube around the outside of the tube and welding the ends.

-) After inserting a small-diameter pipe into a large-diameter pipe to form a storm-bonded pipe, the pipes are joined by at least one of explosion bonding, hot rolling, and cold rolling, or the inner pipe is A method of joining using a brazing material as a bonding agent applied to the interface between the outer tube and the outer tube.

−) On the inside and or outside of the tube! s41! Either apply the overlay bath with a bath coat made of the material, or (see i above)
4. A method of hot or cold rolling a pipe overlaid with yuzu material to reduce its diameter and make it into a long pipe.

■) A method in which several steel strips are formed by stacking them on top of each other, or by welding them into a spiral shape.

However, all of the above-mentioned methods have the following drawbacks, and do not necessarily have satisfactory characteristics as a multilayer pipe or an industrial method for producing the same.

In other words, according to method I), dimensional accuracy during fitting is important, so it is difficult to implement for long items, and it is difficult to implement it for long items, and it is difficult to use at temperatures above the shrink fit temperature or repeatedly used at high and low temperatures. This method causes loosening of joints, and it is difficult to combine tubes with thin inner thickness when fitting with lubrication such as Pb or Zn, and it is also difficult to implement with large diameter tubes. According to the above, there are dimensional constraints on the tubes to be manufactured.

-) method, the inner and outer tubes are well bonded at the l@ contact area, but the other parts are not bonded. Therefore, heating under Ili & temperature, or w! under high temperature or low temperature.
Reheating may cause the joints to loosen or cracks may occur in some parts of the fabric. In addition, since it is subjected to bath welding, it is necessary to select materials that do not cause cracks from the viewpoint of bath weldability1.
! There is a restriction of 8 combination material selection + 67.

According to the method (-), there is some shrinkage in terms of diameter, length, or efficiency in explosive bonding, but joining by hot rolling, cold rolling, or brazing is an excellent method. However, the drawback is that the process is complicated.

-) method can only be applied to large-diameter pipes, so there are dimensional restrictions, and the edges of the overlay may cause cracks or cracks in the base material. ,
In addition, because the workability of the overlay material is also poor, there are restrictions on the material combinations of the overlay material and the base material pipe.

According to Matt's method, it is difficult to install small diameter pipes, and joints other than welded parts require MJ use at humid temperatures or repeated heating.
This causes loosening. Furthermore, even in the case of large-diameter pipes, if the wall thickness is extremely black or the material is extremely thick, it will be difficult to contact the bath, and there will be restrictions on the materials and dimensions of the combination. An object of the present invention is to provide a method for manufacturing a double pipe that eliminates and improves the above-mentioned drawbacks of the conventional method for manufacturing a double pipe. can be achieved. That is, the present invention provides a method for manufacturing a double pipe in which an inner pipe is inserted inside an outer pipe and the outer pipe and the inner pipe are overlapped and joined. An inner tube is inserted into an outer tube manufactured to have a coefficient smaller than the coefficient of thermal expansion to form a stacked tube, and the stacked tube is heated at a temperature higher than the temperature at which the double tube is used, and at the same time the inner tube is heated with gas. III of the double tube characterized by compressing and expanding the tube, bringing it into close contact with the outer tube, and then cooling it to connect both the inner and outer tubes! It is related to the manufacturing method.

In the manufacturing method of the present invention, the heating may be performed simultaneously over the entire length of the east-aligned tube, or a partial heating zone may be moved along the entire length of the tube. When using zone heating as mentioned above, heat and pressurize with gas! In addition to pipe expansion, compressive force can be applied in the axial direction of the inner pipe to facilitate pipe expansion. The 11 double pipes made as described above are expanded or contracted by the usual method to obtain the desired dimensions wI4II! You can also t.

Next, the present invention will be explained with reference to the drawings.

In Fig. 7, the inner tube is inserted inside the outer tube L to form a stacked tube, and both ends of the inner tube are sealed with seal caps 3 and connected to an air or inert gas cylinder. A situation is shown in which the entire length of the tube is accommodated in the tubular electric furnace S. When the inner tube is pressurized and expanded with gas from a gas cylinder while heating the entire length of the storm-aligned tube together with this device, the inner tube qItλ is joined to the outer tube Vl. Next, when the superimposed tubes are cooled, the outer tube L shrinks more than the inner tube C due to the difference in thermal expansion coefficients taken into consideration when determining the inner@- and outer tubes III (jp+). l narrows the inner 1!r2, and both the inner and outer pipes are further connected to each other.

In Figure 1, a superimposition similar to that in Figure 1 is housed in the atmosphere dl [chamber 6, and Il! A part of the l-length is connected to the high frequency power supply wtt and the mobile device! This shows the situation in which the pipe is surrounded by a heating coil 7 capable of operating over the entire length of the pipe. If necessary, after reducing the pressure inside the atmosphere adjustment chamber 6 and the inner tube using the vacuum evacuation device 1O, an inert or reducing gas is introduced into the atmosphere adjustment chamber 6 from the atmosphere adjustment cylinder 1, and then the seal cap 3 Air or inert gas is pressurized into the sealed inner tube from a gas cylinder for pressurizing the inner tube, and the inside of the inner tube is pressurized. Frequency power supply equipment
While the heating coil 7 is moved by the heating coil moving device D, the inner tube 1 and the outer tube 1 are band-heated, and the inner tube 7 is heated at the heating section at each position during the movement of the heating coil 7. It is stretched and bonded to the outer tl by heating and pressurizing. After such heating is carried out over the entire length of the tube and the entire tube is cooled, the inner and outer tubes become a double tube strongly connected to one another. In addition, compression processing equipment /J and Tadashi measurement @ /,? during the first period pressurization and heating? By making it possible to apply opposing compressive forces along the longitudinal direction to both ends of the inner tube by means of a piston/da for compression processing, the inner! A compressive force can also be applied in the axial direction of - to help expand the tube and further promote the joining of the inner and outer tubes.Next, the present invention will be described with reference to embodiments.

Example 1 The outer diameter of a coal bulk tube (STBAI) as the outer tube is go, g, wall thickness j, 0III11, and the inner tube is pure Ti (JIS
outer diameter J1. A TIG bath pipe with a thickness of OJu and θ was used.

The method for manufacturing the double tube was as follows. That is, as shown in Fig. 1, seal caps J are attached to both ends of the inner tube λ.
+Jl in a tubular electric furnace S that can accommodate the entire length of the straightened tube consisting of the outer tube / and the inner tube, which is in contact with the IG bath and inserted into the outer tube l.
It was hot. The heating temperature is ttoo'c. The pressurized gas in the inner tube was supplied from an argon gas cylinder at a pressure of 15%. After holding it in goo'c for S minutes, take it out from the furnace,
After cooling, the pressure was reduced. The tube created using the above method is
Inspection of the -1 plane perpendicular to the axial direction confirmed that the seeds were completely seeded.

Example 2 Outer diameter go, g of charcoal bulk tube (5TBA 2-) as outer tube
Shimaniku v#Q, r m, outer diameter of ^ pure ferritic stainless steel W4 (Fe -Jo%Or-1%MO>) as inner tube, 3t.

I am using a TIG bath contact pipe with a thick wall and a thin wall. The method for manufacturing the double tube was as follows.

That is, as shown in FIG. 1, seal caps 3 are welded to both ends of the inner tube, and the seal caps 3 are inserted into the outer tube L, and the overlapping tube consisting of the outer tube L and the inner tube is placed in the atmosphere adjustment chamber 6. After evacuating the inside of the channel (-6) using the vacuum evacuation device 10, argon gas was introduced from the atmosphere adjusting gas cylinder/l. After pressurizing to atmospheric pressure, the tube was heated by moving a zone heating coil over the entire length of the tube at 1M degrees at 00cm/min so that the heated part of the tube became lθso'c. The tube was confirmed to be completely fastened by inspection of a cross section at right angles to the axial direction.

Example 8: Outer diameter j of stainless steel pipe (8US 3t4) as outer pipe
;Q0gWm, wall thickness j, 0s1111 N1-based alloy (Inco*ru A1!r) as inner tube (D outer diameter 3g, Qflll
TIGi1 joint pipes with wall thicknesses of 11, 1, and s- were used. In addition to the same method as in Example 2, in the axial direction of the inner tube 8, the cart measuring device 18 and the compression processing piston
The heating temperature at 0 when a compressive force of about 100- is applied through 4' is t
The temperature inside the inner tube was 30 atm. It was confirmed by inspection of the cross section at right angles to the axial direction that the double pipe made by the above method was completely fastened.

Example 4 The double pipe produced in Example 3 was expanded to an outer diameter of 62.0 mm by a hydraulic expansion method. Further, the double-walled pipe produced in Example 1 was shrunk to 49.0 - by cold drawing. These expanded and contracted double tubes were inspected in cross section at right angles to the axial direction, and it was determined that they were completely connected together.

Jt11 Example 1 Outer diameter go, g of carbon-W (STB 22) as the outer tube
■, wall thickness g, Qfl1m, stainless steel-11 as inner tube
(SUS304I) outer diameter 3g, Qws, wall thickness 0. ! f
Using the TIG bath tube of III, heat 4&ttoo'c.
A double tube was prepared in exactly the same manner as in Example 1, except that the pressure applied to the inner tube was set to /j atm. For the double pipes as described above, the inner and outer pipes were confirmed to be fastened by inspection of the cross section at right angles to the axial direction.

From this table, it can be seen that the combination of materials for the inner tube and outer tube in the method of the present invention can be determined by making the coefficient of thermal expansion larger than that of the inner tube. It turns out that the selection is arbitrary. Heating temperature, pressing force, compression force, etc.
Since this is necessary for expanding the inner tube under static heat and deforming it so as to bring it into close contact with the inner surface of the outer tube, it can be determined by considering the strength, diameter, wall thickness, etc. of the inner tube.

Since the present invention utilizes the difference in thermal expansion coefficient between the materials of the inner and outer tubes to tighten the inner tube with the outer tube, it is naturally necessary that both materials be able to withstand the high temperatures of heating. However, in practice, the allowable temperature range is wider than conventional shrink fitting methods, and process management is easier. In addition, since internal pressure is applied to the inner tube to expand it and attach it to the outer tube, the dimensional density of the inner pole of the outer tube and the outer diameter of the inner tube is not as dense as in the shrink fit method. Not required and advantageous in implementation. This is even more effective for long double-wall construction. The above example is the diameter! gQwumI! ! However, the present invention can be applied to pipes of various diameters, except for special large-diameter and small-diameter pipes. Furthermore, by increasing the pressure/expansion t# temperature of the inner tube, the upper limit of the temperature at which the double tube can be used can be raised.

As described above, the double pipe manufacturing method of the present invention is optimal for lining an inexpensive outer pipe with an inner pipe made of an expensive material with high corrosion resistance or heat resistance, and is inexpensive overall. Since it is possible to provide highly corrosion-resistant or heat-resistant pipes, the present invention can greatly contribute to industry and technology by applying it to devices and pipes that conventionally required the use of pipes made of expensive materials.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view of a double-pipe manufacturing device that heats the entire length of the tube and expands it by pressurizing it with gas. Figure 2 shows the expansion of the tube by zone heating and expansion with gas, as well as by applying compressive force in the axial direction. FIG. L... Outer tube, C... Inner tube, 3... Seal cap, Ge... Gas cylinder for pressurizing the inner tube, S... Tubular electric furnace, 6... Atmosphere adjustment chamber, ? ... Heating coil, t... High frequency power supply device, t... Heating coil moving device, IO... Vacuum exhaust device, l/... Atmosphere adjustment gas cylinder, lko... Compressor processing device, /3...Load measuring device, /4t...Piston for compression processing.

Claims (1)

[Claims] 1. In a method for manufacturing a double pipe in which an inner pipe is inserted inside an outer pipe and the outer pipe and inner pipe are overlapped and joined, the coefficient of thermal expansion of the material of the inner pipe is lower than that of the outer pipe. The inner tube is inserted into the outer tube manufactured by selecting each material whose thermal coefficient is smaller than the heat l11m coefficient of the material, thereby forming a stacked tube.The stacked tube is heated, and at the same time, the inner tube is pressurized with gas. IM manufacturing method for a double-walled pipe, characterized in that the inner pipe and the outer pipe are joined together by expanding the pipe and then cooling it. 2. The l1ifk method for a double-pipe pipe according to claim 1, wherein the heating of the double-pipe pipe is performed by WI-cast heating, and the zone heating is carried out while moving over the entire length of the double-pipe pipe. 8. Patent Ii# in which compressive force is applied in the axial direction of the inner tube during band heating while pressurizing the inner tube of the stacked tubes with gas.
Claims 1 to 3 A method for producing a double pipe as described in claim 1 or 1. After forming a double pipe, the double pipe is expanded or contracted to have a predetermined size.Claims 1 to 3 The method for manufacturing a double pipe according to any one of the above.