JPH08118501A - Manufacture of composite tube - Google Patents

Abstract

PURPOSE: To weld with excellent workability and excellent quality by pushing a metal tie plate into a cylindrical mold and making the side edge end of the metal tie plate, which is passed through a guide, encounter a side edge end of a preceding metal tie plate so as to butt-join them. CONSTITUTION: On an inner face at the upstream side of a cylindrical mold 4, a guide 41 is provided for guiding a pushed metal tie plate so as to make it encounter and contact with a side edge end of a preceding metal tie plate. The length of the guide 41 is set to be long enough to guide the metal tie plate at an angle B (m-m represents a longitudinal direction of the guide and n-n represents a longitudinal direction of the cylindrical mold 4) of the guide 41 even when the angle of the metal tie plate which enters the guide changes more or less, and to be 1/4-1/2 of the inner peripheral length of the cylindrical mold. The guide has a T-shaped form and has grooves at both sides so as to transfer the metal tie plate in a state that the side edge end of the metal tie plate is housed in the grooves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite pipe, and more particularly, a method for producing a composite pipe having a resin layer on the inner surface of a metal pipe, which is used for drainage pipes, cold and hot water pipes for air conditioning, etc. It is about.

[0002]

2. Description of the Related Art In recent years, corrosion of metal pipes is remarkable due to deterioration of water quality (eg, dissolved chlorine, dissolved oxygen, PH acidification, etc.) flowing through drainage pipes, cold / hot water pipes for air conditioning, etc. For this, a metal-resin composite pipe in which a chemically stable resin layer is provided on the inner surface of the metal pipe has excellent reliability and is widely used.

Therefore, the composite pipe actually used for such an application has a polyvinyl chloride layer coated on the inner surface,
Examples thereof include those coated with a polyethylene layer and those coated with a polyphenylene sulfide layer.

Conventionally, in order to manufacture such a composite pipe, for example, first, a polyvinyl chloride pipe is manufactured in a separate step, an adhesive is applied to the surface of the pipe, and the pipe is inserted into a metal pipe. Or to shrink the diameter of the metal tube to bond the metal tube and the polyvinyl chloride tube to each other, after heating the metal tube to the resin melting temperature once, polyethylene powder resin on the inner surface A method of applying and then cooling the entire tube is used. However, these manufacturing methods are multistage and have many steps.

Therefore, the applicant of the present invention sequentially pushes the metal strips into the inside of the annularly arranged rolls so that the side edges of the metal strips are bent so that they are at least abutted against each other. The spiral pipe is made by continuously welding the mating parts while making a spiral shape and making a spiral pipe, and inside the spiral pipe, insert a mold that extrudes resin in a cylindrical shape from the tip. , Extruding the molten resin on the inner peripheral surface of the spiral pipe on the downstream side of the welding point, and extruding the resin extruded while rotating the tip of this mold in synchronization with the rotation of the spiral pipe at the time of pipe making. A method for producing a composite pipe, which is pressed against the surface, has been proposed (JP-A-4-4918).

According to this method of manufacturing a composite pipe, the number of steps can be reduced, the running cost can be reduced, etc., and in addition, the conventional continuous manufacturing method of a composite pipe (in a group of forming rolls arranged in tandem, a metal strip can be used). Compared with a method in which a plate is formed into a tubular shape having a straight butt portion through a U-shaped section, the joints are welded, and the inner surface of the welded pipe is covered with a resin layer with a mold inserted into the pipe), The line length can be shortened, which is advantageous in terms of line installation space.

[0007]

However, in the method of manufacturing a composite pipe disclosed in the above-mentioned Japanese Patent Laid-Open No. 4-4918, the pushing angle .theta. Of the metal strip into the annular array roll and the pitch of the spiral forming. The angle p is equal to the angle, and the pitch p of the spiral forming is given by p = T / sin θ where T is the width of the metal strip, and the change amount Δp of the pitch p with respect to the change Δθ of the pushing angle θ of the metal strip is It is given by Δp = −Tcos θ · Δθ / sin ² θ.

Therefore, when the push-in angle θ is small, the change amount Δp of the pitch p with respect to the change Δθ of the push-in angle θ is large, and along with the change of the pitch, the metal positioned immediately below the welding torch of the welding machine The strip plate portion also changes, and even before the change of the pushing angle θ, even if the proper welding portion of the butt gap 0 is located just below the welding torch, even if the pushing angle θ is slightly changed, the proper welding portion thereof is changed. Is not directly under the welding torch, and it is difficult to guarantee proper welding.

Further, when the pushing angle decreases, the abutting portion tends to lap, and when the pushing angle increases, the abutting portion tends to separate from each other, so that defective welding is also caused in these cases. It

Further, as in the method of manufacturing a composite pipe disclosed in the above-mentioned Japanese Patent Laid-Open No. 4-4918, the mold is inserted into the spiral welded pipe and the inner surface of the pipe is covered with the resin layer. Welding must be performed on the outer peripheral surface side of the spiral-formed metal strip by using a welding machine provided outside. However, in the method for manufacturing a composite pipe disclosed in Japanese Patent Laid-Open No. 4-4918, the proper welding position is not always the pipe top position. Therefore, when welding is performed at the pipe top position, which is convenient for observing the welding state, the welding position becomes a position deviated from the position of the spiral butt gap 0, and welding failure occurs, or at the position of the gap 0. When welding is performed, the workability of welding while observing the welding state may be difficult.

Furthermore, in the method for manufacturing a composite pipe disclosed in the above-mentioned Japanese Patent Laid-Open No. 4-4918, the metal strip plate being formed into a spiral pipe and the spiral welded pipe are rolls of an annular array roll. It is supported at multiple points and, as a matter of course, the distribution of moments acting between adjacent fulcrum spans is not uniform, so that the spiral-formed metal strip and the spiral welded pipe are distorted unevenly, which causes There is also a fear of causing poor welding or damage to the welded portion.

An object of the present invention is to sequentially push metal strips into a spiral tube forming machine to form a spiral shape, weld a spiral joint portion of the formed body, and to form an inner surface of the spiral welded tube into a spiral shape. It is an object of the present invention to provide a method for producing a composite pipe, which is capable of performing welding with good workability and good quality when the composite pipe is continuously produced by coating with a resin extruded from a mold inserted in the pipe.

[0013]

According to the method of manufacturing a composite pipe of the present invention, metal strips are sequentially pushed into a cylindrical mold to form a spiral shape and sent forward, and the pushed metal strips are pushed forward. At the position where the side edge of the metal strip and the side edge of the preceding metal strip meet each other and continuously weld the butted portion to produce a spiral welded pipe, and the inner surface of the spiral welded pipe is A method of coating with resin extruded from a mold inserted in a pipe, wherein a guide is provided on the inner surface of the cylindrical mold, and the metal strip is pushed into the cylindrical mold along the guide, A structure characterized in that the side edge of the metal strip that has passed through the guide is brought into abutment with the side edge of the preceding metal strip, or the metal strip is pushed into the cylindrical metal mold. The structure is characterized by being performed on the top of the mold. .

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, and the composite pipe is manufactured in the line direction indicated by the arrow. (B) in FIG.
It is a sectional view taken along line (a) of FIG.

In FIG. 1A and FIG. 1B, 1 is a supply bobbin for the metal strip 2. 3 is a surface treatment device. Reference numeral 4 denotes a cylindrical mold for pushing the metal strip 2 in an oblique direction to form a spiral shape.
As shown in FIG. 2, a guide 41 is provided on the upstream inner surface of the guide for guiding the pushed metal strip and contacting the side edge of the preceding metal strip. The length of the guide 41 is such that, even if the angle of the metal strip entering the guide is changed to some extent, the angle of the metal strip is set to the angle β of the guide 41 (m-m in the longitudinal direction of the guide is n- n is a cylindrical mold 4
The length is set to be sufficiently long so that it can be guided by (1) to 1/4 to 1/2 of the inner peripheral length of the cylindrical mold.
It is preferable that It is preferable that this guide is T-shaped and has grooves on both sides, and that the metal strip is transferred with the side edge of the metal strip accommodated in the groove.

In FIGS. 1A and 1B, 5 is a drive roll for pushing the metal strip 2 into the cylindrical mold 4. Reference numeral 61 is a welding machine, and 62 is a welding torch of the welding machine, which faces the inner surface of the cylindrical mold 4 from the outside of the cylindrical mold 4 through the cylindrical wall of the mold. 71 is a take-off device, 72
Is a standard length cutting device.

Reference numeral 8 is an extruder for coating the inner surface. Reference numeral 9 denotes the mold, which is inserted into the cylindrical mold 4 and the resin discharge port of the mold tip portion 90 is located downstream of the position where the welding torch 62 is arranged.

A heating device 10 is provided near the resin discharge port of the inner surface coating mold 9 or slightly upstream of the resin discharge port on the outer periphery of the cylindrical mold 4 as necessary. It is effective in strengthening the adhesion between the welded pipe and

In order to manufacture the composite pipe according to the present invention using the above-mentioned manufacturing apparatus, first, the metal strip 2 is pushed into the cylindrical mold 4 by the drive roll 5 and guided by the guide 41. And the guide 41 is passed through at an inclination angle β of the guide 41 (the metal strip is pressed against the guide so as to be pressed), and welding is not performed in the initial stage.
Only the spiral forming of is performed.

Considering the spiral bending state of the metal strip in the cylindrical die 4 in this initial stage, the spiral gap is completely opened at the downstream end of the cylindrical die due to the springback force of the metal strip. , The spiral gap becomes smaller toward the upstream side, and the gap becomes 0 at a certain position (If there is a metal strip plate on the upstream side beyond this position, a lap is formed at the spiral fitting portion of the metal strip plate portion. Will occur). The position where the gap becomes 0 is a position where the frictional resistance force and the spring back force received by the metal strip plate are equal, and the side edge of the metal strip plate that has been pushed into the cylindrical mold 4 i and passed through the guide 41. Is a position (hereinafter referred to as position a) where the metal strip plate comes into contact with and comes into contact with the side edge of the preceding (one pitch ahead) metal strip.

If the metal strip is spirally formed in the initial stage as described above, the welding torch 62 is placed on the position a.
Position the metal strip 2 by the drive roll 5.
From the bobbin 1, processed by the surface treatment device 3, pushed the metal strip 2 into the cylindrical mold 4, moved along the guide 41 at the guide angle β and passed through the guide 41, and spirally formed the metal strip. And position a (gap 0
The metal strip plate portion passing through the spiral butting portion) is continuously welded, and the spiral welding pipe is taken from the cylindrical die under spiral rotation from the take-up device 71 (synchronized with the rotation of the spiral welding pipe).
To pull out. At the same time, by driving the extruder 8 for coating the inner surface, the resin is discharged from the discharge port of the mold 9, and the discharged resin coats the inner surface of the welded pipe during the spiral rotation. In this case, as shown in (a) of FIG. 3, a strip-shaped resin having a width substantially equal to the above-mentioned one pitch is extruded from the inner surface coating die 9, and the strip-shaped resin is fused to the inner surface of the welded pipe during spiral rotation. You can let it go. In addition, as shown in FIG. 3B, a shaft 92 is attached to the core portion 91 of the mold 9.
Rotatably inserted through a ball bearing 93, and a ball bearing 96 is slidable between a land plate 94 at the tip of the shaft and a tip surface 95 of the mold, and the shaft 92 is driven to rotate so that the welded tube is spirally rotated. In tune with the land play
The resin from the discharge port 90 of the die 9 can be discharged into the non-shear 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 by rotating the mold 94.

The welded spiral tube coated with the resin layer on the inner surface is cut to a predetermined length by a cutting device, and the production of the composite tube is completed. In the above, at the welding position a, that is, at the position a where the side edge of the metal strip that has passed through the guide 41 meets / contacts the side edge of the preceding metal strip (gap 0).
Position) is located at the pipe top position or a position in the vicinity thereof, it is possible to perform welding while observing the welding state, which is advantageous in welding work. In this case, the metal strip is guided to the upper side of the cylindrical mold by the guide so that the side edge of the guide-passing metal strip meets and contacts the side edge of the preceding metal strip on the pipe top side, It is necessary to set the position of the guide to an appropriate position depending on the position where the metal strip is pushed into the cylindrical mold.

By omitting the above guide, as shown in FIG.
By pushing the metal strip 2 into the cylindrical mold 4 from the top side, the position (the position of the gap 0) where the pushed metal strip meets and contacts the side edge of the preceding metal strip is located at the pipe top position or It can be provided in the vicinity thereof, and is effective for welding with the welding torch 62 while observing the welding state.

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 a particularly 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.

[0027]

When the guide is not provided, the pushing angle θ of the metal strip into the cylindrical mold coincides with the pitch angle of the spiral forming, and from the formula, the pitch p of the spiral forming is the width T of the metal strip. , As described above, given by p = T / sin θ, the change amount Δ of the pitch p with respect to the change Δθ of the pushing angle θ of the metal strip.
p is given by Δp = −Tcos θ · Δθ / sin ² θ.

Therefore, when the push-in angle θ is small, the change amount Δp of the pitch p with respect to the change Δθ of the push-in angle θ (mainly due to the deviation of the metal strip) is large, and the metal strip pushed in is large accordingly. Encounters the side edge of the preceding metal strip.
There is a fear that the position of contact changes, it cannot be guaranteed that the butt portion of the gab 0 passes under the welding torch, and welding failure occurs.

Further, when the pushing angle decreases, the abutting portion tends to lap, and when the pushing angle increases, the abutting portion tends to separate from each other, so that defective welding is also caused in these cases. There is a fear.

On the other hand, in the present invention, by pushing the metal strip into the cylindrical mold while pressing it against the guide, the pushed metal strip is always moved along the guide at a constant angle (guide angle β). The spiral state can be kept constant. Therefore, the abutting portion of the gap 0 can be always positioned immediately below the welding torch, and a certain high quality welding can be guaranteed (in the past, in order to maintain the welding quality due to the change of the pushing angle θ, the pushing angle θ Could be set only in the range of 20 ° to 40 °, but in the present invention, the welding quality could be sufficiently guaranteed even if the lower limit angle was lowered to 10 ° to 40 °).

Further, by adjusting the guide position or by pushing the metal strip into the cylindrical die at the top of the cylindrical die, the position where the pushed metal strip comes into contact with the preceding metal strip is contacted. Can be positioned above the pipe top, and welding can be performed while observing the welding state from above, and the welding quality can be guaranteed from this point as well.

Further, the contact between the metal strip 2 pushed into the cylindrical mold 4 and the spiral welded tube and the cylindrical mold 4 is the entire surface contact, and the conventional multi-row array roll is used. In contrast, it is possible to eliminate the non-uniform distribution of moments due to multi-point span support, which can well prevent the occurrence of non-uniform strain in the metal strip and the spiral welded pipe during spiral forming. Welding defects and damage below can be eliminated, and welding quality can be guaranteed from this point as well.

[0033]

【Example】

Example 1 A metal strip plate has a width of 131 mm and a thickness of 1.6.
A hot-rolled steel sheet of mm was used, and the pretreatment used was degreasing treatment with an alkaline solution and oxide film removal treatment with nitric acid. A tungsten inert gas arc welder was used as the welder. Silane-grafted polyethylene (1 part by weight of vinyltrimethoxysilane and 0.04 part by weight of di-t-butylperoxide was mixed with 100 parts by weight of polyethylene) was used as the resin, and the extrusion temperature was 190 ° C.
And the designed thickness of the inner surface resin coating layer was 2.3 mm.

A cylindrical die having an inner diameter of 214 mm is used, and a T-shaped guide having a height of 1.8 mm and a length of 2/5 of the inner circumference of the cylindrical die is used as the guide 30 on the inner surface of the die. Positioned at the top of the inner circumference of the cylindrical mold with an inclination of ° and at the position a (the position where the side edge of the metal strip that has passed through the guide meets and contacts the side edge of the preceding metal strip). As described above, the provided inner surface coating die is of a type in which the resin is extruded into a tubular shape while the land plate at the tip of the die is synchronously rotated with the spiral tube as shown in FIG. 3B. did.

The above-mentioned hot-rolled steel sheet is pressed into a cylindrical die while being pressed into a guide to be formed into a spiral shape and sent forward, and the heat which precedes the side edge of the hot-rolled steel sheet that has passed through the guide is preceded. The side edge of the cold-rolled steel plate is met at the apex position of the inner surface of the cylindrical mold and abutted, and the abutting portion is continuously welded by a welding torch positioned immediately above that position to produce a spiral welded pipe. The pipe was piped and the inner surface of the spiral welded pipe was coated with the resin discharged from the inner surface coating die to manufacture the composite pipe.

When this composite pipe was disassembled and the welded portion was inspected, it was welded with a butt of 0 gap, and no defect was observed in the weld bead. [Embodiment 2] In contrast to Embodiment 1, a guide is omitted, and a hot rolled steel plate is pushed into a position directly above the inner surface of a cylindrical mold at an angle (θ) of 40 ° to meet and contact a metal strip (cylindrical metal). The position where the side edge of the metal strip pushed into the mold comes into contact with and comes in contact with the side edge of the preceding metal strip) is located at the top of the inner circumference of the cylindrical mold. The other conditions were the same as in Example 1.

Also in this example, welding could be performed while observing the welding state. Further, since the pushing angle is increased to 40 °, the change in the spiral pitch due to the pushing movement of the metal strip can be sufficiently reduced, and the displacement of the contact / contact position of the metal strip can be suppressed to a small extent. Therefore, the welding was performed sufficiently well.

[Comparative Example] Compared to Example 1, the guide was omitted and a hot rolled steel plate was placed at an angle of 30 at the lowermost position of the inner surface of the cylindrical mold.
Pushing in at °, welding was performed on the top of the cylindrical mold. The other conditions were the same as in Example 1.

Welding was at a butt portion with a gap, and there were variations in the welding site due to changes in the spiral pitch due to pushing displacement of the metal strips, and defects such as holes were observed in various places in the welding beads. .

[0040]

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. However, when a composite pipe is continuously manufactured by coating the inner surface of the spiral welded pipe with a synthetic resin, the spiral welded portion is welded at a position where the gap is small or 0 and the welding state is easily monitored. Further, even if the pushed metal strip is shaken, the welding can be performed with the displacement of the welding site well eliminated. Moreover, the metal strips pressed into the cylindrical mold used as the spiral tube forming machine and the contact between the spiral welded tube and the cylindrical mold are full-face contact, and the annular multi-row arrangement roll
Unlike the conventional example that uses a loop, it is possible to eliminate the non-uniform distribution of momentum due to multi-point span support.
Since it is possible to prevent the occurrence of non-uniform strain in the metal strip plate and the spiral welded pipe during the spiral forming, it is possible to enhance the reliability of the welded portion and the adhesive strength of the resin coating layer also from this aspect.

Therefore, according to the present invention, a high quality and highly reliable composite pipe having a resin layer on the inner surface of the spiral welded metal pipe can be continuously manufactured.

[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 a guide in 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.

FIG. 4 is an explanatory diagram showing the invention of claim 2;

[Explanation of symbols]

 2 Metal strip 4 Cylindrical mold 41 Guide 5 Drive roll 61 Welder 62 Welding torch 8 Extruder for inner surface coating 9 Inner surface coating mold

Claims (2)

[Claims] 1. A metal strip is sequentially pushed into a cylindrical mold to form a spiral shape and is sent forward, and a side edge of the pushed metal strip and a side edge of the preceding metal strip are formed. Is a method of coating the spiral welded pipe by welding the butted portions continuously at a position where they meet each other and coating the inner surface of the spiral welded pipe with a resin extruded from a mold inserted in the pipe. Then, a guide is provided on the inner surface of the cylindrical mold, the metal strip is pushed into the cylindrical mold along the guide, and the side edge of the metal strip that has passed through the guide precedes the metal. A method for producing a composite pipe, characterized in that the composite pipe is brought into contact with a side edge of a strip plate and abutted against each other. 2. A metal strip is sequentially pushed into a cylindrical mold to form a spiral shape and is sent forward, and a side edge of the pushed metal strip and a side edge of the preceding metal strip are formed. Is a method of coating the spiral welded pipe by welding the butted portions continuously at a position where they meet each other and coating the inner surface of the spiral welded pipe with a resin extruded from a mold inserted in the pipe. A method for manufacturing a composite pipe, wherein the pressing of the metal strip into the cylindrical mold is performed at the top of the cylindrical mold.