JP2766551B2 - Inner surface support device for pipe making - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a width direction of a cylindrical body obtained by curling a metal strip in a width direction by using a residual stress given by bending and unbending. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner surface supporting device that prevents both ends from lapping and holds a cylindrical body to be welded in a predetermined sectional shape when a pipe is manufactured by butt welding both ends.

[Prior Art] In a conventional method of manufacturing a tubular body from a metal strip,
A roll forming machine including a forming roll, a cage roll, and the like having calipers arranged in a large number of tandem mills is used. With this forming machine, the metal strip is sequentially bent in the width direction and formed into a tubular shape. Then, the tubular body is continuously manufactured by abutting and welding both ends in the width direction of the formed metal strip.

However, this method requires a molding machine in which a multi-stage molding stand is arranged, so that the facility burden is increased. In addition, as the equipment becomes more complicated, operations such as maintenance and inspection become troublesome. And when it is going to manufacture pipes with different diameters, changing the forming rolls is an operation requiring a long time.

Moreover, when a metal strip having a smaller plate thickness than the plate width is used as a tube-forming material, the effect of elastic deformation during the bending process appears significantly. For example, a large spring pack is generated in the process from the former forming roll to the latter forming roll, and is particularly sent to the latter forming roll without being subjected to sufficient bending at both ends in the width direction. Therefore, the roundness of the manufactured tube deteriorates. In addition, since the edge stretch is large, edge waves are easily generated, and welding becomes difficult.

The present inventors have developed a method for forming a tube by using the elastic force of a metal strip without using a conventional forming roll as a tube manufacturing method that has solved such a problem. 62-176611 and JP-A-1-48624.

For example, Japanese Unexamined Patent Publication No. Sho 62-176611 uses the equipment configuration outlined in FIG. The metal strip s sent from the uncoiler 1 is sent to the pre-deformation section 3 via the guide roll 2. The pre-deformation unit 3 includes a small-diameter bending roll 3a and a large-diameter support roll 3b,
An elastic lining 3c of polyurethane or the like is provided on the surface of the support roll 3b.

Then, the metal strip s is fed between the bending roll 3a and the support roll 3b such that the inner surface side of the obtained tubular body contacts the bending roll 3a side. Since the metal strip s is plastically bent by the bending roll 3b, a uniform bending stress in the width direction remains on the metal strip s after passing through the pre-deformed portion 3.

The metal strip s to which the residual stress due to bending and unbending is applied is sent to the downstream side via the shape-retaining roll 4, the side roll 5, and the feed roll 6. During the feeding process, the metal strip s is elastically deformed into a tubular shape due to residual stress because the deformation in the longitudinal direction is restricted. Then, the metal strip s formed into a tubular shape is abutted at both ends in the width direction in a state in which the shape is constrained by the shape retaining roll 4 and the side roll 5. By welding the butted portion with a welding torch 7, a pipe body p is obtained.

In this method, since the metal strip s is formed into a tubular shape using elastic deformation, the roundness of the obtained tubular body p is excellent. Further, since a forming roll for bending the metal strip s into a tubular shape is not required, the equipment configuration is simplified, and this method is particularly suitable for manufacturing a thin-walled tube.

Further, Japanese Patent Application Laid-Open No. 2-75418 has proposed a pre-deformation section having a schematic configuration shown in FIG. In the pre-deformation section 3, a bending roll 3f is arranged between a pair of large-diameter rolls 3d and 3e. After passing between the large-diameter roll 3d and the bending roll 3f, the metal strip s 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 due to bending and unbending is applied to the metal strip s. The pre-deformation section 3 can omit a mechanism for backing up the small-diameter bending roll 3f, and can easily apply a predetermined residual stress to the metal strip s.

[Problem to be Solved by the Invention] The tube forming method utilizing such elastic deformation does not require a forming roll which is required in the conventional tube forming method to plastically deform a metal strip into a predetermined shape. Become. And
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 having a certain thickness as a material, the squeeze roll is slightly tightened, so that the metal strip can be pressed against the squeeze roll from the inside, and the butt shape can be accurately maintained. it can.

However, if the squeeze roll is slightly tightened as the thickness of the metal strip becomes thinner, the edges of the squeeze roll are shifted, and lapping is likely to occur. Then, the metal strip cannot be pressed against the squeeze roll from the inside. As a result, the butt shape becomes unstable, and it becomes difficult to perform welding under constant conditions.

In order to prevent this wrapping, it is conceivable to insert a plug inside the cylindrical body to suppress excessive curling. However, if the plug is simply inserted, the metal strip may be caught between the plug and the squeeze roll, and a surface flaw may be generated. In an extreme case, it is expected that the metal strip is clogged between the plug and the squeeze roll, and the material cannot be transported.

Therefore, the present invention solves such a problem,
By supporting the cylindrical body from the inner surface side with an inner surface support device with an expandable shape retaining part, wrapping is prevented at both ends in the width direction, and a cylindrical body that is accurately abutted at both ends in the width direction is formed. It is an object of the present invention to manufacture a welded pipe having a constant bead shape by welding the butt portion.

[Means for Solving the Problems] To achieve the object, a tube forming inner surface supporting device of the present invention is a cylindrical body formed by curling a metal strip to which a residual stress is given by bending and bending back in a width direction. An apparatus for supporting an inner surface of a cylindrical body when welding both ends in the width direction of the cylindrical body, wherein a supporting shaft inserted into the cylindrical body, a cylindrical block mounted on the supporting shaft, And an expandable shape retainer provided around the block.

Here, as the shape retainer, a cylindrical body made of an elastic material and provided with a gap in the longitudinal direction can be used so that the shape retainer is pressed against the inner surface of the cylinder by a resilient force. Alternatively, a shape retainer of a type in which an outer skin forming a pressurized chamber is provided on the peripheral surface of the cylindrical block, and the outer skin is expanded by the pressurized fluid supplied to the pressurized chamber and pressed against the inner surface of the cylindrical body may be used. .

Also, the cylindrical block itself may have a shape-retaining function. The inner surface support device of this type has a hollow support shaft inserted into a cylindrical body, a cylindrical block mounted on the hollow support shaft, and a gas outflow layer formed on an outer peripheral portion of the cylindrical block. A pressurized gas is blown from the hollow support shaft to the inner surface of the cylindrical body through a gas outflow layer.

[Operation] A metal strip to which a 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 where it is not restrained. When the metal strip is constrained to prevent deformation in the longitudinal direction, it deforms in the width direction. When the metal strip is formed into a cylindrical shape by utilizing this characteristic, particularly in the case of a thin metal strip, a discrepancy occurs at both ends in the width direction, and the metal strips tend to be wrapped with each other. Therefore, butt welding cannot be performed.

In the present invention, in order to prevent the lapping and to accurately abut the both ends in the width direction of the metal strip to be welded, the cylindrical body is supported from the inner surface side by an expandable shape retainer or the like. The shape retainer always applies a force to the cylinder to push the inner surface apart. 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. Therefore, the welding conditions are stabilized, and a welded tube 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 is reduced. Therefore, the cylinder is not clogged between the squeeze roll and the shape retainer, and smooth conveyance is performed.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings by way of examples.

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

A cylindrical block 20 having a diameter of 28.0 mm and a body length of 30 mm was fitted into the support shaft 10 and fastened to the support shaft 10 with bolts 21. The cylindrical block 20 has a flange 22 at least at one end in the axial direction.
Are formed. The other peripheral surface of the cylindrical block 20 is one step lower than the peripheral surface of the portion where the flange 22 is formed.

The shape retainer 30 was fitted on the peripheral surface of the cylindrical block 20. As the shape retainer 30, a 1.0 mm-thick cylindrical body cut out from a hard Cu-Al alloy block by a wire cutting method was used. Then, a slit having a width of 1.0 mm was formed to form a gap 31.
Further, the outer diameter of the shape retaining tool 30 was 28.5 mm in a no-load state. It is preferable that the outer diameter of the shape retainer 30 in the no-load state is slightly larger than the inner diameter of the welded pipe to be manufactured.

In the case shown in the figure, the shape retainer 30 is fitted to the cylindrical block 20 from the upstream side in the transport direction of the cylindrical body 50, that is, from the side where the flange 22 is not formed. When a cylindrical block 20 having flanges formed at both ends in the axial direction is used, the shape retainer 30 is opened against the resilience and fitted on the peripheral surface of the cylindrical block 20.

On both sides of the cylindrical block 20, sealing materials 40 and 41 were attached to the support shaft 10 to seal the inner surface of the cylindrical body to be welded. As the sealing materials 40 and 41, a material in which a heat-resistant fiber such as a stainless steel fiber is formed into a felt disk is preferable. Further, in order to blow an inert gas such as argon into an internal space surrounded by the inner surfaces of the cylindrical members to be welded to the seal members 40 and 41, the seal members 40 and 41 and the cylindrical block 2 are blown.
A plurality of gas ejection holes 12 were formed in the support shaft 10 between 0 and 0, and the base end of the support shaft 10 was connected to an inert gas supply source (not shown).

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

The cylindrical body 50 to be welded is given a residual stress by bending and unbending a stainless steel plate having a thickness of 0.1 mm and a width of 89.6 mm with the apparatus shown in FIG. 6 and curling in the width direction to have a diameter of 28.6 mm. Is formed into a cylindrical shape. In addition, both ends in the width direction were butted to form a butted portion 51 having a set gap of 0 mm.

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

On the other hand, the shape retainer 30 urges the cylindrical body 50 with a force in the radially expanding direction by a resilient force. Therefore, when welding the butt portion 51 while continuously transporting the cylindrical body 50, the cylindrical body 50 is welded.
Of the squeeze rolls 60 and 61 was constantly pressed against the roll peripheral surfaces of the squeeze rolls 60 and 61, and the butted portion 51 in which the both ends 52 and 53 in the width direction were in close contact with each other was maintained.

As the welding conditions, a method of performing microplasma welding with a welding current of 10 A while supplying Ar + 10% H ₂ gas as a shielding gas at a flow rate of 10 / min was adopted. The welding speed at this time was set to 3 m / min.

Observation of the shape of the bead formed at the butted portion 51 revealed that the bead width was within a range of ± 0.1 mm centered at 0.5 mm. The maximum bead height is 0.12 ± 0.01
mm range. That is, a welded tube having a bead having a substantially constant shape was obtained. Then, since a bead having excellent shape characteristics was formed, the work in the subsequent bead shaping step 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 supporting device of the present embodiment, it is understood that the welding conditions are extremely stable and a welded pipe having an excellent bead shape can be obtained. In addition, since welding is performed while the cylindrical body 50 is pressed against the roll peripheral surfaces of the squeeze rolls 60 and 61 by the shape retainer 30, the roundness of the obtained welded pipe is also improved. Therefore, the work load in the process of straightening the welded pipe has been reduced.

Embodiment 2 In this embodiment, an expandable member is 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 cover 70 made of a flexible material was attached around the cylindrical block 20. Outer skin
As 70, a stainless steel plate having a thickness of 0.1 mm was used.

The outer cover 70 was hermetically welded to the flanges 22 formed at both axial ends of the cylindrical block 20. Then, a cylindrical space having a gap of 1.0 mm was formed between the outer cover 70 and the peripheral surface of the cylindrical block 20 to form a pressure chamber 71.

On the other hand, a plurality of gas passages 23 radially extending from a through hole through which the support shaft 10 is inserted are formed in the cylindrical block 20. The gas passage 23 opens to 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 the support shaft. Therefore, this inert gas is partially branched and sent from the gas passage 23 to the pressurizing chamber 71. This allows
The pressure in the pressurizing chamber 71 increased, and the outer cover 70 expanded.

The expanded skin 70 pressed the cylindrical body 50 against the roll peripheral surfaces of the squeeze rolls 60 and 61 in the same manner as the shape retainer 30 of the first embodiment. The pressing force by the outer cover 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 accordance with the force. Therefore, the cylinder 50 could be smoothly transported without clogging of the cylindrical body 50 between the outer cover 70 and the squeeze rolls 60 and 61. In the steady state, the cylindrical body 50 is held in a shape along the concave crown of the squeeze rolls 60 and 61, so that the butt portion 1 is held with high accuracy, and a welded pipe having excellent shape characteristics as in the first embodiment. produced.

Embodiment 3 In this embodiment, as shown in FIG. 4, a cylindrical body made of porous ceramics or a sintered body of porous metal powder is fitted into the cylindrical block 20 to form an outer periphery of the cylindrical block 20. A gas outflow layer 80 was formed in the portion. Further, a gas dispersion chamber is provided between the gas outflow layer 80 and the peripheral surface of the cylindrical block 20.
81 were provided. Then, similarly to the second embodiment, the gas passage 23 radially bored in the cylindrical block 20 was opened to the gas dispersion chamber 81.

The inert gas introduced through the hollow support shaft 10 partially branches and flows into the gas passage 23. And the gas dispersion chamber
After uniform pressure distribution in the circumferential direction at 81, the gas outflow layer 80
Through the cylindrical block 20 in the radial direction. The cylindrical body 20 is squeezed by the pressure of
Of the roll. As a result, the cylindrical body 50
The squeeze rolls 60 and 61 were held in a shape along the concave crowns, the butted portions 51 were accurately maintained, and a welded pipe having excellent shape characteristics as in Example 1 was manufactured.

[Effects of the Invention] As described above, in the present invention, a shape retainer or the like is inserted into a cylindrical body formed by curling a metal strip in the width direction, and the metal strip is radially outwardly directed to the cylindrical body. The power of. Therefore, a butted portion having a constant gap is formed without lapping 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 after welding and the roundness of the welded pipe are also improved. Therefore, the work burden of shaping the bead, straightening the welded pipe, and the like in the subsequent process is reduced, and a welded pipe of excellent quality is manufactured.

[Brief description of the drawings]

FIG. 1 shows an inner surface supporting device according to a first embodiment of the present invention, FIG. 2 shows a state in which the inner surface supporting device is inserted into a cylindrical body to be welded, and FIGS. 7 shows an inner surface support device of Example 2 and Example 3. On the other hand, the fifth
FIG. 6 and FIG. 6 show the equipment configuration proposed by the present inventors previously. 10: support shaft, 20: cylindrical block, 23: gas passage, 30: shape retainer,
50: Cylindrical body, 51: Butt joint, 70: Outer skin, 80: Gas outflow layer

Claims (4)

(57) [Claims] The present invention is characterized in that when a metal strip to which a residual stress is applied by uniform bending and unbending in the width direction is curled in the width direction and both ends in the width direction of the cylindrical body are welded by butt welding. An apparatus for supporting an inner surface, comprising: a support shaft inserted into the cylindrical body; a cylindrical block mounted on the support shaft; and an expandable shape retainer provided around the cylindrical block. An inner surface support device for pipe making, comprising: 2. The shape retainer according to claim 1, wherein the shape retainer is made of an elastic material.
An inner surface support device for pipe making, which has a cylindrical shape with a gap provided in a longitudinal direction and is pressed against the inner surface of a cylinder by elasticity. 3. The holding tool according to claim 1, further comprising an outer skin forming a pressurizing chamber on a peripheral surface of the cylindrical block, wherein the outer skin expands by a pressurized fluid supplied to the pressurizing chamber, and the cylindrical body expands. An inner surface supporting device for pipe making, which is pressed against an inner surface of a body. 4. A cylindrical body formed by curling in the width direction a metal strip to which a residual stress has been applied by uniform bending and unbending in the width direction and welding both ends in the width direction of the cylindrical body. A device for supporting an inner surface, a hollow support shaft fed into the cylindrical body, a cylindrical block mounted on the hollow support shaft, and a gas outflow layer formed on an outer peripheral portion of the cylindrical block. And a pressurized gas is blown out from the hollow support shaft to the inner surface of the cylindrical body through the gas outflow layer.