JPH08117841A - Production of composite pipe - Google Patents

Abstract

PURPOSE: To produce a composite pipe having the excellent strength of adhesion of an outside surface resin layer with a simple outside surface coated die structure by forming a metallic strip to a spiral pipe, welding the joint parts of spirals and coating the outside surface of this welded pipe with a synthetic resin layer. CONSTITUTION: The metallic strip 2 is drawn out of a bobbin 1 by driving of a driving roll 5 and while this strip is pretreated by a pretreating device 3, the strip is successively pushed into the cylindrical die 4 from a direction diagonal with the cylindrical axis. A welding torch 62 is provided in a position where the pushed in metallic strip 2 comes into contact with the side marginal end of the forward spirally bent metallic strip by first one pitch. The joint parts of the butt spiral pipe are welded in this position. The resin is extruded under and at a prescribed pressure and resin flow rate from an extruder 81 for coating the outside surface and this resin is press fitted into a slit 7 of the cylindrical die 4. This press fitted resin is extruded from the opening of the resin flow passage groove of the inside surface of the cylindrical die through this groove, by which the outside surface of the welded pipe is successively coated with this resin.

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 having a synthetic resin layer on the outer surface or inner / outer surface of a metal tube.

[0002]

2. Description of the Related Art As a pipe material used for transporting a fluid, a composite pipe obtained by coating a metal pipe with a synthetic resin is used in order to have excellent mechanical strength of metal and excellent corrosion resistance of synthetic resin. Often.

As a continuous manufacturing method for such a composite pipe, metal strips are sequentially pushed into the inside of an annularly arranged roll to form a spiral shape and send it forward, and the spiral joint portion is continuously formed. There is known a method in which a welded tube is welded to a pipe to produce a welded tube, and at the same time, the inner surface and the outer surface of the welded tube are extruded and coated (see JP-A-4-4918).

In this composite pipe manufacturing method, in order to coat the outer surface of the welded pipe with the synthetic resin layer, the welded pipe coming out of the annular array roll is passed through a crosshead type mold,
The outer surface of the welded pipe is covered with the resin that is pressure-fed to the mold from the extruder. Further, in order to coat the synthetic resin layer on the inner surface of the welded pipe, an inner surface resin coating die is inserted into the annular array roll, and the resin discharge port of the die is positioned downstream from the welding point. Then, the resin from the inner surface coating extruder is discharged from the resin discharge port, and the discharged resin is coated on the inner surface of the welded pipe.

As is well known, when forming a metal strip into a spiral tube, p = πD / tan θ, where p is the pitch, D is the diameter of the spiral tube, and θ is the feeding angle of the metal strip to the molding machine. Have a relationship. Therefore, in the method for manufacturing the composite pipe described above, the length of the annular array roll needs to be at least one pitch, and from the formula, even if the pipe diameter D is large,
The pushing angle θ of the metal strip is 90 ° apart from 0.
P can be made sufficiently short by approaching
Since the length of the spiral tube forming machine can be sufficiently shortened, in the above-described method for producing a composite tube, even in the case of a large-diameter tube, the installation angle of the spiral tube forming machine can be set by appropriately setting the pushing angle of the metal strip. Can be made sufficiently small (when θ = 0,
This corresponds to the case of forming a metal strip into a tubular shape having a straight seam in the longitudinal direction through a U-shaped cross section. In this case, p becomes extremely large, and the length of the tubular forming machine becomes significantly long. ). Further, even if the width of the metal strip is narrow, it is possible to manufacture a large-diameter pipe. Therefore, from these points, the method for producing a composite pipe is advantageous for producing a large-diameter composite pipe.

[0006]

However, in the above-mentioned method for producing a composite pipe, the extrusion coating of the outer resin layer is
As mentioned above, a cross-head type mold that discharges resin from the entire circumference is used, and the peripheral length of the resin discharge port must be increased for large diameter pipes, and the external resin layer Coating is not easy.

Conventionally, as a method for coating an outer surface of a large-diameter pipe, a semi-molten resin strip which is continuously extruded from an extruder is spirally wound around the outer surface of the pipe which is transported in the axial direction of the pipe while being rotated. A method of coating is known.

However, in this extrusion / wrapping coating method, the strip-shaped resin discharged from the extruder is considerably cooled by the time it reaches the metal tube, and deterioration of the fusion property is unavoidable. It is difficult to sufficiently guarantee the adhesive strength between and the bonding strength of the band-shaped body joining portion.

For this reason, it has been proposed to provide a resin temperature control roll between the extruder and the metal tube to wind the strip-shaped resin while controlling the temperature (Japanese Patent Laid-Open No. 5-124103).

However, this temperature control is usually greatly influenced by the feed traveling speed of the belt-shaped resin under a constant heating roll temperature, and the feed speed must be made considerably low for the predetermined temperature control. Since it does not occur, it is difficult to increase the production speed by synchronizing the pipe-making speed of the spiral pipe and the feeding speed of the band-shaped resin.

Further, in the method for manufacturing a composite pipe disclosed in the above-mentioned Japanese Patent Laid-Open No. 4918/1992, the metal strip plate and the spiral pipe which are being formed into a spiral pipe are often formed by a roll of an annular array roll. It is supported by points, and naturally, the distribution of moments acting between adjacent fulcrum spans is not uniform,
There is also a fear that the spiral pipe or the welded pipe is distorted unevenly, resulting in poor welding or poor appearance of the resin coating.

An object of the present invention is to form a spiral tube by pushing metal strips into a spiral tube forming machine in an oblique direction in order.
When welding the spiral joint of this spiral pipe and coating the outer surface of this welded pipe with a synthetic resin layer to continuously manufacture a composite pipe, the resin coating has excellent adhesive strength and a simple mold structure. Another object of the present invention is to provide a method for manufacturing a composite pipe that can be coated with

[0013]

According to the method of manufacturing a composite pipe of the present invention, metal strips are sequentially pushed into a cylindrical mold from an oblique direction to form a spiral pipe, and the metal mold is applied from the outside of the mold. Welding the spiral mating portion of the spiral tube with a welding torch that faces the inner surface of the mold through the cylindrical wall, and sends this welded tube from the front end of the mold, and at the same time with the front end of the mold in the mold. Resin is press-fitted from the extruder for coating the outer surface into the slit provided between the welding point, and the press-fitted resin is delivered from the front end of the die and is coated on the outer surface of the welded pipe. When coating the resin layer, insert the inner resin coating mold into the cylindrical mold, position the resin discharge port of the mold downstream of the welding point, and remove the resin from the inner surface coating extruder. Is discharged from the resin discharge port, and the discharged resin is coated on the inner surface of the welded pipe. It is possible.

The structure of the present invention will be described below with reference to the drawings. FIG. 1A shows an example of a composite pipe manufacturing apparatus used in the present invention. 1B is a cross-sectional view taken along the line of FIG.

In FIGS. 1A and 1B, 1 is a supply bobbin for the metal strip plate 2, 3 is a surface treatment device, and 4 is a cylindrical mold. Reference numeral 5 is a drive roll for pushing the metal strip 2 into the cylindrical mold 4. 61 is a welding machine, and 62 is a welding torch of the welding machine.
Is exposed to the inside. Reference numeral 7 denotes a slit provided between the die front end of the cylindrical die 4 and the welding torch disposition point. The slit 7 is formed on the inner surface of the cylindrical die 4 as shown in FIG. A resin passage groove 71 is provided over the front end 40 of the cylindrical mold.

In FIGS. 1A and 1B, 81
Is an extruder for coating the outer surface, which has a strip extrusion die 81, for example, a T-shaped manifold die, and the resin discharge port of the die 81 communicates with the slit 7. Reference numeral 91 is a take-up device, and 92 is a standard length cutting device.

Reference numeral 11 is an extruder for coating the inner surface. Reference numeral 12 denotes the mold, which is inserted into the cylindrical mold 4 and the resin discharge port of the mold tip 121 is located downstream of the position where the welding torch 62 is disposed.

Reference numeral 13 denotes a heating device provided on the outer periphery of the cylindrical mold 4 near the resin discharge port of the inner surface coating mold 12 or slightly upstream of the discharge port, if necessary. It is effective for strengthening the adhesion between the welded pipe and the welded pipe.

According to the present invention, in order to manufacture a composite pipe by using the above-mentioned manufacturing apparatus, the metal strip 2 is pulled out from the bobbin 1 by driving the driving roll 5 and is pretreated by the pretreatment device 3. It is pushed into the cylindrical mold 4 from an oblique direction with respect to the cylindrical axis. In this pushed metal strip, if the pushing angle of the metal strip is θ and the inner diameter of the cylindrical mold 4 is D, the pushing force forcibly bends it into a butt spiral with a pitch p shown in the equation. It will be molded. The welding torch 62 is arranged at a position where the pushed metal strip comes into contact with the side edge of the forward spiral bent metal strip by the first pitch, and at this position, the butted spiral tubes are butted. The parts are welded. Therefore, the welded pipe a is fed in the pipe axial direction while being rotated in the spiral direction in the cylindrical mold 4.

From the outer surface coating extruder 81, resin is extruded at a predetermined pressure and a resin flow rate, the resin is press-fitted into the slit 7 of the cylindrical mold 4, and the press-fitted resin is flown on the inner surface of the cylindrical mold. After passing through the passage groove 71 (FIG. 2), it is extruded from the groove opening to cover the outer surface of the welded pipe. In this welded pipe, as described above, the welded pipe is fed from the front end of the cylindrical mold under the spiral rotation of the pitch p and the angle θ. Therefore, the angle of the resin flow path groove on the inner surface of the cylindrical mold [in FIG.
-N is the circumferential direction, and is indicated by β) is equal to the angle θ of the spiral rotation, and the width [indicated by w in FIG. 2] of the resin flow channel groove with respect to the tube axis direction is determined by the spiral rotation. And the outer surface of the welded pipe protruding from the front end of the cylindrical mold can be completely covered with the resin layer.

When the inner surface of the welded pipe is also coated with the resin, the resin is discharged from the discharge port of the die 12 by driving the inner surface coating extruder 11 in FIG. 1 (a). Is coated on the inner surface of the welded pipe during the spiral rotation. In this case, as shown in FIG. 3A, a strip-shaped resin having a width substantially equal to the above-mentioned one pitch is extruded from the inner surface coating die 12, and the strip-shaped resin is melted on the inner surface of the welded pipe a during spiral rotation. You can wear it. Further, as shown in FIG. 3B, the shaft 122 is attached to the core portion 121 of the mold 12.
Is rotatably inserted through the ball bearing 123,
Land plate 124 at the tip of the shaft and tip surface 12 of the mold
5 is made slidable with a ball bearing 126, and the land plate 124 is rotated in synchronization with the spiral rotation of the welded pipe a by the rotational driving of the shaft 122, and the resin from the discharge port 120 of the die 12 is rotated. Can be discharged into the non-shearing space b between the outer periphery of the land plate and the inner periphery of the welded spiral pipe to cover the inner surface of the welded pipe a.

In the above, the metal strip 2 is, for example,
Iron, steel, stainless steel, plated steel, copper, aluminum, etc. can be used. The surface treatment by the surface treatment device 3 is, for example, mechanical treatment such as sandblasting, degreasing treatment with alkali or the like, acid treatment with hydrochloric acid, sulfuric acid, nitric acid or the like,
Examples thereof include rust-preventing treatment with zinc phosphate, iron phosphate, oxalic acid, etc., priming treatment with silane coupling agent, titanium coupling agent, organic titanate and the like.

In the above, the welding machine 61 is, for example,
An inert gas arc (TIG or MIG) welder, an active gas arc (MAG) welder, a plasma welder, a laser welder, a high frequency resistance welder, etc. can be used.

In the above, it is preferable to use a resin having excellent adhesiveness to a metal, for example,
Silane-grafted polyethylene, carboxylic acid-modified polyethylene, polyvinyl acetate, polyvinyl acetal, polyvinyl alcohol, polyamide and the like are preferable.

[0025]

[Function] The resin pressed into the slit 7 of the cylindrical mold 4
After being pressure-fused to the welded pipe portion facing the resin flow path groove 71 on the inner surface of the cylindrical mold, the welded pipe is transferred along with the spiral rotation feed, so that the transfer amount and the press-fitting of the resin into the slit. By balancing the amount with the resin, it is possible to eliminate resin retention, resin breakage, etc., and smoothly coat the resin on the outer surface of the welded pipe.

In this case, the resin flow path groove 7 on the inner surface of the cylindrical mold 4
By lengthening the length of 1 to some extent and imparting an appropriate resin flow resistance to the resin flow channel groove to appropriately raise the resin press-fitting pressure, the resin temperature is within a range in which thermal decomposition of the resin can be eliminated. To increase the resin fusion property, the outer surface resin layer and the welded pipe can be sufficiently strongly bonded.

Further, the contact between the metal strip 2 pushed into the cylindrical mold 4 and the welded pipe a and the cylindrical mold 4 is the whole surface contact, and the conventional example using the annular multiple array roll is used. In contrast, the non-uniform distribution of moments due to multi-point span support can be eliminated, and accordingly, the occurrence of non-uniform strain in the metal strip and the spiral tube during spiral forming can be well prevented. It is possible to eliminate welding defects at the same time and resin coating defects under the same non-uniform strain, and from this aspect, the quality of the composite pipe can be guaranteed.

[0028]

Example: A metal strip has a width of 131 mm and a thickness of 1.6 m.
m hot-rolled steel sheet was used, and degreasing treatment with an alkaline solution and oxide film removal treatment with nitric acid were used for pretreatment. A tungsten inert gas arc welder was used as the welder. As the resin, silane-grafted polyethylene (1 part by weight of vinyltrimethoxysilane and 0.1 part by weight of di-t-butylperoxide per 100 parts by weight of polyethylene) was used.
04 parts by weight) was used, the extrusion temperature was 190 ° C., and the outer resin coating thickness and the inner resin coating thickness were 2.3.
mm.

A cylindrical mold having an inner diameter of 214 mm was used, the slit was provided 100 mm downstream of the welding point, and the width of the slit was 130 mm. The inner surface coating mold used was a system in which the land plate at the front end of the mold was rotated synchronously with the spiral tube to extrude the resin into a cylinder, as shown in FIG.

The above hot-rolled steel sheets were sequentially pushed into a cylindrical mold at an angle (θ) of 30 ° to form a spiral tube, and a spiral joining part of the spiral tube was formed by a tungsten inert gas arc welding torch. Welding this welded pipe from the front end of the cylindrical mold, press-fitting the resin from the T-die into the slit, and sending this press-fitted resin from the front end of the cylindrical mold to the outer surface of the welded pipe, and at the same time. The composite resin was manufactured by coating the inner surface of the welded pipe with the resin discharged from the inner surface coating mold.

The circumference of this composite pipe is divided into equal parts and the width is about 10 m.
A strip having a length of m and a length of about 100 mm was obtained, and the adhesive strength of the outer surface coating layer of this strip was measured according to JIS K6854 "Testing method for peeling adhesive strength of adhesive" The peel adhesive strength was measured to be 20 kgf / 10 mm, and the peel was due to cohesive failure of the resin layer.

In contrast to this embodiment, a strip-shaped body was extruded from an extruder, and the strip-shaped body was spirally wound around the outer surface of the welded pipe and the outer surface resin layer of the composite pipe coated with the outer surface resin layer was bonded to the same adhesive strength as the above. It was 8 kgf / 10 mm as measured by the method, and the peeling was due to peeling at the interface between the metal and the resin.

From the comparison between the adhesive strength and the adhesive strength of the above-mentioned products, it was confirmed that according to the present invention, the adhesive strength of the outer surface resin layer was remarkably increased.

[0034]

According to the method for manufacturing a composite pipe of the present invention, metal strips are sequentially pushed into the spiral pipe forming machine from an oblique direction to form a spiral pipe, and the spiral joint portion of the spiral pipe is welded. When a synthetic resin layer is coated on the outer surface of this welded pipe to continuously produce a composite pipe, a cylindrical metal mold is used as a spiral pipe molding machine, and a slit for resin press-fitting of the outer surface coating material is used in the cylindrical metal mold. The outer surface resin layer having excellent adhesive strength can be covered only by providing Moreover, the contact between the metal strip pressed into the cylindrical mold used as the spiral tube molding machine and the welded pipe and the cylindrical mold is full-face contact, and the conventional example using the annular multiple array roll is used. However, the multi-span support
The non-uniform distribution of the ment can be eliminated, and accordingly, the non-uniform strain in the metal strip plate and the spiral tube during the spiral forming can be well prevented, so that the quality of the composite tube can be assured from this aspect.

Therefore, according to the present invention, a composite pipe excellent in adhesive strength of the outer surface resin layer can be manufactured with a simple outer surface coating mold structure by a continuous manufacturing method using a spiral tube.

[Brief description of drawings]

1 (a) is an explanatory view showing an example of an apparatus for manufacturing a composite pipe used in the present invention, and FIG. 1 (b) is a sectional view taken along the line of (i) in FIG.

FIG. 2 is an explanatory view showing the back side of the slit of the cylindrical mold shown in FIG.

FIG. 3 is an explanatory view showing a different example of the inner surface coating mold used in the present invention.

[Explanation of symbols]

 2 Metal strip 4 Cylindrical mold 5 Drive roll 61 Welding machine 62 Welding torch 7 Slit 71 Resin flow channel groove 81 External coating extruder 11 Internal coating extruder 12 Internal coating mold

Claims (2)

[Claims] 1. A welding torch in which metal strips are sequentially pushed into a cylindrical mold from an oblique direction to form a spiral tube, and the inner surface of the mold is exposed from the outside of the mold through a mold cylinder wall. The welded portion of the spiral pipe is welded, and the welded pipe is fed from the front end of the mold, and the extruder for external surface coating is provided in the slit provided between the mold front end and the welding point in the mold. A method for producing a composite pipe, characterized in that a resin is press-fitted from the mold, and the press-fitted resin is delivered from the front end of the mold to cover the outer surface of the welded pipe. 2. A die for inner surface resin coating is inserted into a cylindrical die, the resin discharge port of the die is positioned downstream of a welding point, and the resin from the extruder for inner surface coating is set to the above resin. The method for producing a composite pipe according to claim 1, wherein the resin is discharged from a discharge port and the inner surface of the welded pipe is coated with the discharged resin.