JPH05278143A - Production of composite pipe - Google Patents

Abstract

PURPOSE:To produce a composite pipe having a projecting part without releasing a resin by a method wherein a resin is applied to the inner surface of a metal pipe and the predetermined part of the pipe is subjected to plastic processing at temp. equal to or lower than the m.p. of the resin and the resin in the vicinity of the processed part is pressed at temp. equal to or higher than the m.p. of the resin. CONSTITUTION:A composite pipe 10 produced by lining the inner surface of a steel pipe 11 with a resin 12 is arranged in an outer mold 21 and a 60 deg. taper core 23 is inserted in one end of the composite pipe 10 at room temp. to conically expand the diameter of the end part of the composite pipe 10. Next, heaters 31 and cooling pipes 32 are respectively included in the outer mold 21 and a 180 deg. core 23 and, after the 180 deg. core 23 is inserted in the pipe under pressure, the surface temps. of the outer mold 21 and the 180 deg. core are heated to 125 AIACC in such a state that the pressure in the normal line direction of a flange forming resin surface due to the 180 deg. core is reduced to 20kg/cm<2> to be held for one min. Even when the end flange forming composite pipe thus obtained is incerted in an oven of 95 AIACC for a long time, no release is confirmed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a composite pipe in which at least the inner surface of a metal pipe is covered with a resin, and more specifically, it is provided with a diameter-expanded portion of the pipe end and a protruding portion of the pipe body. The present invention relates to a method for manufacturing a composite pipe.

[0002]

2. Description of the Related Art Conventionally, as a method for connecting pipes, in addition to a method of using a pipe joint member, a method of expanding a diameter of one end of the pipe to form a receiving portion and a collar bar portion For steel pipes and the like, a method of welding a flange is known.

As a pipe for transferring a fluid such as water supply / drainage or hot water supply, even in a composite pipe in which at least an inner surface of a metal pipe is coated with a resin in order to improve corrosion resistance and chemical resistance, the pipe is connected to another pipe. In addition, conventionally, mouthpiece molding by bulge molding and collar-back processing by punch molding have been adopted.

[0004]

By the way, in the mouth-forming and flange-reverse molding for the connection as described above, it is generally necessary to increase the diameter expansion rate to about 20 to 30%. In addition, since a large internal stress occurs in the coating resin and the adhesive strength between the metal and the resin also decreases, if the initial adhesive strength between the metal tube and the resin layer is not sufficient, the resin peels off. There was a problem that it would end up.

It is an object of the present invention to use a resin as a composite pipe having the above-described connecting pipe having a diameter-increased portion at the end of the pipe including a receiving portion and a flanged portion for connection, or a protruding portion at the pipe main body. It is to provide a method of manufacturing without peeling.

[0006]

A method for manufacturing a composite pipe according to the present invention is such that at least an inner surface of a metal pipe is coated with a resin, and then a predetermined portion of the pipe is plastically worked at a temperature equal to or lower than a melting point of the resin.
Thereafter, at least the resin in the vicinity of the processed portion is characterized by being pressed at a temperature equal to or higher than the melting point of the resin.

[0007]

When the plastic working is performed at a temperature lower than the melting point of the resin, the resin does not flow largely even when a large force is applied during the working, and the desired shape can be obtained. After such plastic working, if the resin in the vicinity of the processed part is pressed while being heated to a temperature higher than the melting point, the resin will be re-melted and the residual stress inside will be relieved. Since it will be pressure-bonded to the surface of the composite pipe, a composite pipe free from peeling at the processed portion can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of an example of main steps in the case of manufacturing a composite pipe having a pipe end flanged portion by applying the present invention.

First, after manufacturing a composite pipe 10 in which a silane-modified polyethylene resin 12 is run on the inner surface of a steel pipe 11, the composite pipe 10 is molded into an outer mold 2 as shown in FIG. 1 (A).
1, and the 60 ° taper core 22 was inserted into one end of the composite pipe 10 at room temperature to conically expand the pipe end.

Next, as shown in FIG.
The core 23 was press-fitted into the expanded diameter portion at room temperature to form a ribbed shape. In such a collar return process, the outer mold 21
The heater 31 and the cooling pipe 32 are respectively enclosed in the 180 ° core 23 and the 180 ° core 23 is press-fitted into the shape shown in FIG. The surface temperature of the outer mold 21 and the 180 ° core 23 was heated to 125 ° C. in a state where the linear pressure was depressurized to 20 kg / cm ² , and the temperature was maintained for 1 minute. It should be noted that the outer die 21 and the 180 ° core 23, in which the heater 31 and the cooling pipe 32 are disposed, are surrounded by a heat insulating material 33 in order to prevent heat transfer to other portions.

The tube-end flanged composite tube thus obtained was examined after being inserted into an oven at 95 ° C. for a long time, but no peeling was found at all. FIG. 2 is an explanatory view of an example of a main part process in the case where the present invention is applied to project the composite pipe.

Also in this example, as in the previous example, the steel pipe 1
After manufacturing the composite pipe 10 in which the silane-modified polyethylene resin 12 is lined on the inner surface of 1, the composite pipe 10 is placed in the outer mold 41 as shown in FIG. An overhang was formed on the tube body of the tube 10. Here, 43 in the drawing is a seal ring, and 44
Is a pump, and the pressure of the oil 42 is 500 at room temperature.
A 20% overhang process was performed by applying a load of kg / cm ² .

After the overhanging is completed, the composite pipe 1
Oil of 125 ° C. was loaded under the pressure of 20 kg / cm ² and was held for 1 minute. The composite tube having the overhanging portion thus obtained was similarly inserted into an oven at 95 ° C. for a long time and investigated, but no peeling was found at all.

On the other hand, as a comparative example, the same equipment as that of the first embodiment of the present invention shown in FIG. 1 was used, and the same composite pipe 10 was subjected to conical diameter expansion by a 60 ° taper core 21 and then 18
Collar molding was performed by press-fitting the 0 ° core 23 at room temperature, and a tube-end collimated composite tube was manufactured without performing the subsequent heating / pressurizing treatment.

When the tube-end flange-return composite tube thus obtained was inserted into an oven at 95 ° C. in the same manner, peeling occurred in a portion corresponding to 30% of the total area of the flange portion after 24 hours. ..

Further, as a comparative example to the second embodiment of the present invention shown in FIG. 2, after the same hydraulic bulge forming is applied to the same composite pipe 10, the subsequent heating / pressurizing treatment with oil is performed. A composite pipe having overhangs was manufactured by omitting it.

When the composite tube thus obtained was similarly inserted into an oven at 95 ° C., after 24 hours, peeling occurred in 50% of the entire area of the projecting portion. In the present invention, as the plastic working method, other known plastic working methods such as the rubber pressure bulge forming method and the electromagnetic bulge forming method can be adopted in addition to the punch forming and the hydraulic bulge forming method as described above. . During this plastic working,
As described above, the temperature of the resin is set to the melting point or lower. The reason is that, in such processing, the composite pipe may have a wall thickness of, for example, 2.8 mm for a steel pipe, a resin wall thickness of 1.7 mm, and a pipe diameter of 10 mm.
This is because, in the case of 0 A, a force of about 30,000 kg is usually applied, and when the resin is plastically worked at a temperature higher than its melting point, the resin flow becomes large and it is difficult to obtain a desired shape.

Further, as the metal layer (tube) in the composite tube to which the present invention can be applied, a general steel tube (SGP and the like), an aluminum drawn tube, a copper tube, etc., having strength and elongation that can endure desired plastic working. As long as it is a metal tube having, the material of the resin layer, modified polyethylene, polyvinyl acetate,
Thermoplastic resins having excellent adhesiveness to metals such as polyvinyl acetal, polyvinyl alcohol, and polyamide can be applied. Further, a primer treatment such as a silane treatment or a titanate treatment may be applied to the interface between the resin layer and the metal tube.

The pressure applied when the temperature of the resin is raised above its melting point after the plastic working is 5 to 40 in terms of surface pressure.
kg / cm ² is suitable. If this pressure or the heating temperature of the resin is too low, the adhesive force of the resin will not be restored and the adhesive force to the metal tube will decrease, while if the pressure and temperature are too high, the molten resin will flow at the time of pressurization. Therefore, in consideration of such points, it is necessary to determine the optimum conditions according to the materials used and the processing conditions.

[0020]

As described above, according to the present invention,
After performing the desired plastic working at a temperature below the melting point of the resin used in the composite pipe, at least the resin near the processing part is heated to above the melting point and pressed, so processing compared to conventional The residual stress of the resin in the part is reduced,
The resin was remelted and adhered to the metal pipe, and it became possible to obtain a high-quality composite pipe with no peeling at the flange portion, the protruding portion, etc., at a high yield.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main process of an embodiment of the present invention.

FIG. 2 is an explanatory view of a main process of another embodiment of the present invention.

[Explanation of symbols]

 10 Composite Pipe 11 Steel Pipe 12 Silane-modified Polyethylene Resin 21 Outer Type 22 60 ° Tapered Core 23 180 ° Core 31 Heater 32 Cooling Pipe 33 Heat Insulating Material 41 Outer Type 42 Oil 43 Seal Ring 44 Pump

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B32B 1/08 A 7016-4F 15/08 103 7148-4F // B29K 23:00 B29L 9:00 4F 23: 22 4F

Claims (1)

[Claims] 1. After coating at least the inner surface of a metal pipe with a resin, a predetermined portion of the pipe is plastically worked at a temperature equal to or lower than the melting point of the resin, and then at least the resin in the vicinity of the worked portion is melted with the melting point of the resin. A method for producing a composite pipe, which comprises pressurizing at the above temperature.