JPH04178295A - Inside supporting device for manufacturing pipe - Google Patents

Abstract

PURPOSE:To accurately abut both ends in the cross direction on each other to perform welding and to manufacture a welded pipe having a fixed bead shape by holding the inside of a cylindrical body by an expandable inside supporting device. CONSTITUTION:A shape holding tool 30 is cut out from a hard copper-Al alloy block so that its outside diameter is slightly larger than the inside diameter of the welded pipe to be manufactured. The outside of the cylindrical body 50 to be welded is pressed down by squeeze rolls 60 and 61 and the cylindrical body is energized in the diameter expanding direction from the inside by the repulsive force of the shape holding tool 30. Further, the shape holding tool 30 abuts on a stepped part of an end 22 of a cylindrical block 20 and stops thrust when the cylindrical body 50 is continuously conveyed. Since the cylindrical body 50 is welded on a butt part 51 while the inside and outside diameters being surely guided, the desired cross-sectional shape is obtained without lapping the end and correction work in the succeeding stage is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the crosswise curling of a cylindrical body obtained by curling a metal strip in the widthwise direction using residual stress imparted by bending and unbending. The present invention relates to an inner surface support device that prevents both ends from wrapping and holds a cylindrical body to be welded in a predetermined cross-sectional shape when manufacturing a cylindrical body by butt welding both ends.

BACKGROUND OF THE INVENTION Conventional methods for producing tubes from metal strip use roll forming machines consisting of forming rolls, cage rolls, etc. with calibers arranged in a number of tandem mills. This forming machine sequentially bends the metal strip in the width direction and forms it into a tubular shape. Then, the tube body is continuously manufactured by butting and welding both ends of the formed metal strip in the width direction.

However, this method requires a molding machine with multi-stage molding stands, which places a heavy burden on the equipment.Also, as the equipment becomes more complex, maintenance and inspection work becomes troublesome. When trying to manufacture tubes with different diameters, changing the forming rolls becomes a time-consuming task.

Moreover, if a metal strip whose thickness is small compared to the width of the pipe is used as a material for pipe production, the influence of elastic deformation during the bending process will be significant. For example, a large springback occurs in the process from the former forming roll to the latter forming roll, and in particular, both ends in the width direction are sent to the latter forming roll without being sufficiently bent. Therefore,
The roundness of the manufactured tube deteriorates. Furthermore, since the edge stretch is large, green liquid is likely to be generated, making welding difficult.

The present inventors have developed a method for forming tubes that eliminates these problems by utilizing the elasticity of metal strips without using conventional forming rolls, and have published the patent application Publication No. 176611/1984, Japanese Patent Application Publication No. 1-4
It is introduced as Publication No. 8624, etc.

For example, in JP-A-62-176611, the fifth
The equipment configuration outlined in the figure is used. The metal strip S sent out from the uncoiler 1 is sent into the pre-deformation section 3 via the guide rolls 2. The pre-deformation section 3 includes a small-diameter bending roll 3a and a large-diameter support roll 3b, and an elastic lining 3c made of polyurethane or the like is provided on the surface of the support roll 3b.

Then, the inner surface of the obtained tube is a bending roll 3al! I
Bend the metal strip S so that it is in contact with the roll 3a
and the support roll 3b. Since the metal strip S is subjected to plastic bending by the bending rolls 3b, a uniform bending stress in the width direction remains in the metal strip S after passing through the pre-deformation section 3.

The metal strip S, which has been given residual stress due to bending and unbending, is passed through shape-retaining rolls 4. It is sent to the downstream side via side rolls 5 and feed rolls 6.

During this feeding process, the metal strip S is restrained from being deformed in the longitudinal direction, so it is elastically deformed into a tubular shape due to residual stress. Then, the metal strip S formed into a tubular shape is abutted against each other at both ends in the width direction, with the shape being restrained by the shape retaining rolls 4 and the side rolls 5. By welding this abutted portion with a welding torch 7, a tube body p is obtained.

In this method, since the metal strip S is formed into a tubular shape using elastic deformation, the resulting tubular body p has excellent roundness. Furthermore, since no forming rolls are required for bending the metal strip S into a tubular shape, the equipment configuration is simplified, and this method is particularly suitable for manufacturing thin-walled tubes.

Further, in Japanese Patent Application Laid-Open No. 2-75418, a pre-deformation section having a schematic configuration shown in FIG. 6 was proposed.

In this pre-deformation section 3, a bending roll 3f is arranged between a pair of large diameter rolls 3d and 3e. metal strip S
After passing between the large diameter roll 3d and the bending roll 3f, the material goes around the bending roll 3f and is sent out from between the large diameter roll 3e and the bending roll 3f. During this traveling process, residual stress is applied to the metal strip S due to bending and unbending.

, This predeformation section 3 can omit a mechanism for backing up the small diameter bending roll 3f, and it becomes easy to apply a predetermined residual stress to the metal strip S.

[Problem to be Solved by the Invention J] This pipe-making method that utilizes elastic deformation eliminates the need for forming rolls, which were required in conventional pipe-making methods to plastically deform the metal strip into a predetermined shape. Become. Then, the metal strip curls in the width direction due to the applied residual stress and becomes a cylindrical body. At this time, when using a metal strip with a certain thickness as the material, by slightly tightening the squeeze roll, the metal strip can be pressed against the squeeze roll from the inside.
The butt shape can be held with high precision.

However, as the metal strip becomes thinner, if the squeeze roll is tightened a little, the edges may become misaligned at the abutting portions, making lapping more likely to occur.

And it becomes impossible to press the metal strip against the squeeze roll from the inside. As a result, the butt shape becomes unstable, making it difficult to weld under consistent conditions.

In order to prevent this lapping, it is conceivable to insert a plug inside the cylindrical body to suppress excessive curling. However, if the plug is simply inserted, there is a risk that the metal strip will be caught between the plug and the squeeze roll, resulting in surface flaws. Also, in extreme cases, the metal strip can get stuck between the plug and the squeeze roll.
It is also expected that materials will not be able to be transported.

Therefore, in order to solve this problem, the present invention prevents wrapping at both ends in the width direction by supporting the cylindrical body from the inner side with an inner surface support device equipped with an expandable shape retaining part. The object of this invention is to manufacture a welded pipe with a constant bead shape by molding a cylindrical body whose opposite end portions are accurately abutted, and by welding the abutted portions.

[Means for Solving the Problems] In order to achieve the object, the inner surface support device for pipe making of the present invention is a cylindrical body formed by curling a metal strip in the width direction to which residual stress is applied by bending and unbending. A device for supporting the inner surface of a cylindrical body when welding both ends of the cylindrical body against each other in the width direction, the apparatus comprising: a support shaft inserted into the cylindrical body; a cylindrical block attached to the support shaft; It is characterized by comprising an expandable shape retainer provided around the block.

Here, the shape retainer may be a cylindrical body made of an elastic material and provided with a gap in the longitudinal direction so as to be pressed against the inner surface of the cylindrical body by elastic force. Alternatively, it may be a shape retaining device in which an outer skin forming a pressurizing chamber is provided on the circumferential surface of a cylindrical block, and the outer skin is expanded by pressure fluid supplied to the pressurizing chamber and pressed against the inner surface of the cylindrical body. .

Further, the cylindrical block itself can have a shape-retaining function. This type of internal support device includes a hollow support shaft inserted into a cylindrical body, a cylindrical block attached to the hollow support shaft, and a gas outflow layer formed on the outer periphery of the cylindrical block. The pressurized gas is blown out from the hollow support shaft to the inner surface of the cylindrical body through a gas outflow layer.

[Function] A metal strip to which residual stress is applied by uniform bending and unbending in the width direction has a tendency to curl in the longitudinal direction in a free state without being constrained. When restraints are applied to this metal strip to prevent it from deforming in the longitudinal direction, it deforms in the width direction. When a metal strip is formed into a cylindrical shape by utilizing this property, particularly in the case of a thin metal strip, misalignment occurs at both ends in the width direction, which tends to result in mutual wrapping. As a result, butt welding becomes impossible.

In the present invention, in order to prevent this lapping and to accurately abut both ends of the metal strip in the width direction to be welded, the cylindrical body is supported from the inner side with an expandable shape retainer or the like. A shape-retaining device constantly applies a force to the cylindrical body that tries to spread the inner surface.

At this time, since the outer diameter of the cylindrical body is restrained by a squeeze roll or the like, the cylindrical body is maintained in a predetermined shape, and both ends in the width direction are accurately butted together. Therefore, the welding conditions are stabilized, and a welded pipe in which a predetermined bead is formed can be obtained.

If an abnormally large force is applied from the outside of the cylindrical body by a squeeze roll or the like, the diameter of the shape retainer will be reduced. Therefore, the cylindrical body does not get stuck between the squeeze roll and the shape retainer, and smooth conveyance is performed.

[Examples] Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

Embodiment 1: As shown in FIG. 1, the inner surface support device of this embodiment includes a support shaft 10 inserted in the tube axis direction of a cylindrical body to be welded. As the support shaft 10, it is preferable to use a hollow tube with a closed tip 11 in order to provide this inner surface support device with an inner sealing effect.

A cylindrical block 20 with a diameter of 28.0 mm and a body length of 30 mm is inserted into the support shaft 10, and the support shaft 10 is fixed with a bolt 21.
concluded. The cylindrical block 20 has a flange 22 formed at least at one end in the axial direction. The other circumferential surface of the cylindrical block 20 is -B lower than the circumferential surface of the portion where the flange 22 is formed.

A shape retainer 30 was fitted onto the circumferential surface of the cylindrical block 20.

As the shape retainer 30, a cylindrical body with a wall thickness of 1.0 mm was used, which was cut out from a hard Cu-AP gold alloy block by a wire cutting method. Then, a slit with a width of 1°Omm was formed to form a gap 31.

In addition, the outer diameter of the shape retainer 40 is 28°5 mm under no load.
Met. In addition, it is preferable that the outer diameter of the shape retainer 30 in an unloaded state is slightly larger than the inner diameter of the welded pipe to be manufactured.

In the illustrated case, the shape retainer 30 was fitted into the cylindrical block 20 from the upstream side with respect to the transport direction of the cylindrical body 50, that is, from the side where the flange 22 is not formed. In addition,
Cylindrical block 20 with flanges formed at both ends in the axial direction
When using 1, the shape retainer 30 is opened against the elastic force and fitted onto the circumferential surface of the cylindrical block 200.

On both sides of the cylindrical block 20, sealants 40, 41 were fitted to the support shaft 10 in order to seal the inner surfaces of the cylinders to be welded. As the sealing material 40, 41, it is preferable to use heat-resistant fibers such as stainless steel fibers formed into a felt-like disk.

Furthermore, in order to inject an inert gas such as argon into the internal space surrounded by the inner surface of the cylindrical body to be welded with the sealing materials 40 and 41, the support shaft 10 between the sealing materials 40 and 41 and the cylindrical block 20 is A plurality of gas ejection holes 12 are bored in the support shaft 10, and the base end of the support shaft 10 is connected to an inert gas supply source (not shown).
connected to.

This inner surface support device was inserted into the interior of the cylindrical body 50 to be welded, as shown in FIG. Further, the outer surface of the cylindrical body 50 was restrained with squeeze rolls 60 and 61.

The cylindrical body 50 to be welded has a plate thickness of 0.1 mm and a plate width of 89 mm.
A 6 mm stainless steel plate was formed into a cylindrical shape with a diameter of 28° and 6 mm by applying a retaining stress by bending and unbending using the apparatus shown in FIG. 6 and curling it in the radial direction. Further, both ends in the width direction were butted against each other to form an abutment portion 51 with a set gap of Omm.

As the squeeze rolls 60 and 61, a pair of rolls having a concave crown with a radius of curvature of 14.3 mm corresponding to the diameter of the cylindrical body 50 was used.

The squeeze rolls 60 and 61 suppressed the force that would cause the cylindrical body 50 to expand in diameter.

On the other hand, the shape retaining tool 30 applies a force in the direction of diameter expansion to the cylindrical body 50 by elastic force. Therefore, when the butt portion 51 is welded while the cylindrical body 50 is continuously conveyed, the outer circumferential surface of the cylindrical body 50 is always pressed against the roll circumferential surfaces of the squeeze rolls 60, 61, and both widthwise ends 52, 53 The abutment s51 was maintained in close contact with each other without lapping with each other.

The welding conditions were Ar and 10% H as the shielding gas.
, gas flow rate 10p! , welding current 1 while supplying in 7 minutes
A method of microplasma welding at 0A was adopted. The welding speed at this time was set to 3 m 7 minutes.

When we observed the shape of the bead formed on the butt portion 51, we found that the bead width was ±0.1 mm with a center of 0.5 mm.
was contained within the range. Also, the maximum height of the bead is
It was in the range of 0.12±0.01 mm. That is, a welded tube with a bead of substantially constant shape was obtained.

Since a bead with excellent shape characteristics was formed, the work required in the subsequent bead shaping process was greatly reduced.

On the other hand, when welding was performed under the same conditions except that the shape retainer 30 was not attached to the cylindrical block 20, lapping occurred and stable welding could not be performed.

As is clear from this comparison, when the cylindrical body 50 is welded by inserting the inner surface support device of this example, the welding conditions are extremely stable and a welded pipe with an excellent bead shape can be obtained. Further, since welding is performed while the cylindrical body 50 is pressed against the circumferential surfaces of the squeeze rolls 60 and 61 with the shape retainer 30, the roundness of the obtained welded pipe is also improved. Therefore, the work load in the welded pipe straightening process was also reduced.

Example 2: In this example, an expandable member was provided around the cylindrical block 20 instead of the shape retainer made of an elastic material.

That is, as shown in FIG. 3, an outer skin 70 made of a flexible material was attached around the cylindrical block 20. As the outer skin 70, a stainless steel plate with a thickness of 0.1 nm was used.

The outer skin 70 was hermetically welded to flanges 22 formed at both ends of the cylindrical block 20 in the axial direction. And the outer skin 70
A cylindrical space with a gap of 1.0 mm was formed between the cylindrical block 20 and the circumferential surface of the cylindrical block 20 to form a pressurizing chamber 71.

On the other hand, the cylindrical block 20 is provided with a plurality of gas passages 23 extending radially from the through hole through which the support shaft 10 is inserted. The gas passage 23 opens into the pressurizing chamber 71 .

In order to provide the inner surface support device with the function of sealing the inner surface of the cylindrical body 50 to be welded, a hollow tube is used as the support shaft 10, and an inert gas such as argon is introduced through this support shaft. Therefore, part of this inert gas was branched off and sent into the pressurizing chamber 71 from the gas passage 23, thereby increasing the pressure in the pressurizing chamber 71 and causing the outer skin 70 to expand.

The expanded outer skin 70 is similar to the shape retaining device 30 of Example 1,
The cylindrical body 50 was pressed against the circumferential surfaces of squeeze rolls 60 and 61. The pressing force by the outer skin 70 uses gas pressure. Therefore, when an abnormally large force is applied to reduce the diameter of the cylindrical body 50 for some reason, the outer skin 70 contracts in response to the force. Therefore, the cylindrical body 50 is placed between the outer skin 70 and the squeeze rolls 60 and 61.
The cylindrical body 50 was conveyed smoothly without clogging (and was able to be conveyed smoothly).
In order to maintain the shape along the concave crown of 0.61, the abutting portion 51 was held with high precision, and a welded pipe with excellent shape characteristics as in Example 1 was manufactured.

Embodiment 3: In this embodiment, as shown in FIG. 4, a cylindrical body made of porous ceramics or porous metal powder sintered body is fitted into the cylindrical block 20, thereby forming the cylindrical block 20. A gas outflow layer 80 was formed on the outer periphery. Also,
A gas dispersion chamber 81 was provided between the gas outflow layer 80 and the circumferential surface of the cylindrical block 20. As in the second embodiment, the gas passages 23 are radially bored in the cylindrical block 20.
The gas dispersion chamber 81 was opened.

The inert gas introduced through the hollow support shaft 10 is partially branched and flows into the gas passage 23 . After a uniform pressure distribution is achieved in the circumferential direction in the gas distribution chamber 81, the gas flows out in the radial direction of the cylindrical block 20 through the gas outflow layer 80. The cylindrical body 20 is pressed against the circumferential surface of the squeeze rolls 60, 61 by the pressure of the inert gas that has flowed out. As a result, the cylindrical body 50 was held in a shape that conformed to the concave crowns of the squeeze rolls 60 and 61, and the butt portion 51 was maintained with high accuracy, producing a welded pipe with excellent shape characteristics as in Example 1. .

[Effects of the Invention] As explained above, in the present invention, a shape retainer or the like is inserted into the inside of a cylindrical body formed by curling a metal strip in the width direction, and the cylindrical body is oriented outward in the radial direction. It adds the power of Therefore, an abutting portion with a fixed gap is formed without wrapping at both ends in the width direction. Further, the desired cross-sectional shape of the cylindrical body itself is maintained. Therefore, the welding conditions are stabilized, and the bead shape and roundness of the welded pipe after welding are also improved. therefore,
Work burdens such as bead shaping and welded pipe straightening in subsequent processes are also reduced, and welded pipes of excellent quality are manufactured.

[Brief explanation of drawings]

FIG. 1 shows the inner surface support device in Example 1 of the present invention, FIG. 2 shows the state in which the inner surface support device is inserted into the cylindrical body to be welded, and FIGS. 3 and 4 show the inner surface support device according to the first embodiment of the present invention. Figure 2 shows the inner surface support devices of Example 2 and Example 3; On the other hand, FIGS. 5 and 6 show the equipment configuration previously proposed by the present inventors. 10: Support shaft, 20: Cylindrical block, 23: Gas passage, 30: Shape retainer, 50: Cylindrical body, 51: Butt part, 70
: Outer skin, 80 gas outflow layer Figure 5 Figure 3 Figure 4

Claims (4)

[Claims] (1) When welding both widthwise ends of a cylindrical body formed by curling a metal strip in the widthwise direction to which residual stress has been applied by uniformly bending and unbending in the widthwise direction, the inner surface of the cylindrical body is A supporting device, comprising a support shaft inserted into the cylindrical body, a cylindrical block attached to the support shaft, and an expandable shape retainer provided around the cylindrical block. An internal support device for pipe making, characterized by: (2) The shape retainer according to claim 1 is made of an elastic material, has a cylindrical shape with a gap in the longitudinal direction, and is used for pipe making, characterized in that it is pressed against the inner surface of the cylindrical body by elastic force. Internal support device. (3) The holder according to claim 1 is provided with an outer skin that forms a pressurizing chamber on the circumferential surface of the cylindrical block, and the outer skin is expanded by the pressure fluid supplied to the pressurizing chamber, and the cylindrical body is expanded. An inner surface support device for pipe making, characterized in that it is pressed against the inner surface. (4) When welding both widthwise ends of a cylindrical body formed by curling a metal strip to which residual stress has been applied by uniformly bending and unbending in the widthwise direction, the inner surface of the cylindrical body is A supporting device, comprising a hollow support shaft fed into the cylindrical body, a cylindrical block attached to the hollow support shaft, and a gas outflow layer formed on the outer periphery of the cylindrical block. An inner surface support device for pipe making, characterized in that pressurized gas is blown out from the hollow support shaft to the inner surface of the cylindrical body through the gas outflow layer.