JPH06262250A - Manufacture of thin walled welded pipe excellent in surface property - Google Patents

Abstract

PURPOSE:To obtain a high quality thin walled welded pipe having excellent surface conditions. CONSTITUTION:A preliminary shape changing part 3 provided with an uncoiler 1, a guide roll 2 and bending roll and a forming roll 4, a squeeze roll 5, a feeding roll 6, a welding torch 7, a regular size cutter 9, etc., are arranged in a clean room 10. After residual stress is applied by uniform bending and unbending on a metallic belt material S delivered from the uncoiler in the width direction by the bending roll, the material S is formed in a cylindrical shape and both end parts in the width direction are welded to be the welded pipe P. The shape of welded pipe P is corrected by a correcting roll 8 and the pipe P is cut in a regular size to be a mercantile welded pipe M and the pipe M is taken out from the clean room 10. The welded pipe P is corrected by the correcting roll 8 as required. Thus, a surface flaw on the mercantile welded pipe M caused by penetration of dust is not generated since the material is formed and welded in an atmosphere where no dust strays.

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 thin-walled welded pipe in which the surface quality is not deteriorated by dust in the atmosphere.

[0002]

2. Description of the Related Art Welded pipes of stainless steel, titanium, etc. are used for applications that make use of their surface properties. For example, a welded pipe made of stainless steel is used as a structural material, a decorative material, etc., but if there is a surface scratch or the like, the commercial value is significantly impaired. The occurrence of surface scratches becomes more remarkable as the welded pipe becomes thinner. In addition, in applications where heat exchange or chemical reaction is performed on the surface of the welded pipe, the scratched portion is likely to become a discontinuous point.
The surface scratches that occur on the welded pipe include those that originate in the band plate, which is the material, and those that originate in the welded pipe manufacturing stage. Surface scratches originating from the material can be prevented by managing the material. However, surface scratches that occur during the production of welded pipes are problematic in the welding line itself, so that the damage cannot be avoided. Surface scratches that occur during the production of welded pipes are often due to dust and the like in the atmosphere. For example, when welding is performed in an open atmosphere, dust floating in the atmosphere is trapped between the forming roll or the feed roll and the strip material and pressed against the surface of the strip material. As a result, indentation scratches occur on the surface of the strip material or the welded pipe.

[0003]

As a means for preventing dust from being caught between the roll and the strip, it is conceivable to house the entire welding device in a clean room.
It is expected that the adverse effect of dust can be suppressed to some extent by welding while maintaining a clean atmosphere in the clean room at all times. However, in the welding apparatus according to the conventional roll forming method incorporating the forming roll, a lubricating oil is required to lubricate the strip material and the roll surface. If such a welding device is housed in a clean room, maintenance and inspection in the clean room will be troublesome due to the lubricating oil.

Further, depending on the atmosphere in the clean room, the influence of the lubricating oil on the surface of the strip material is significant. For example, when welding is performed in a clean room while maintaining a vacuum atmosphere, the lubricating oil may actively evaporate from the surface of the strip, and smooth running of the strip may be hindered. The evaporated lubricant is
It easily adheres to internal equipment housed in a clean room.
As a result, running of the strip material or the welded pipe is hindered, welding conditions become unstable, and a sound welded part cannot be obtained. The present invention has been devised to solve such a problem, focusing on the advantages of the conventional rollless forming method that does not use a forming roll, and disposing the equipment of the rollless forming method in a clean room. Prevents surface damage caused by dust, and avoids the problem of lubricant evaporation that makes the running condition of the strip or welded pipe unstable, and provides a thin-walled welded pipe with good surface properties and sound welds. Intended to be manufactured.

[0005]

In order to achieve the object, the thin-walled welded pipe manufacturing apparatus of the present invention applies uniform bending and unbending in the width direction to a strip material sent from an uncoiler to reduce residual stress. After applying, it is a device for forming a cylindrical shape and welding both ends in the width direction, wherein the uncoiler and at least the welding device are arranged inside a clean room.

A strip material that is uniformly bent and unbent in the width direction tends to curl in the width direction when the length direction is constrained. The present inventors have developed a rollless forming method in which a strip material is formed into a cylindrical shape and welded by utilizing the residual stress caused by the bending and unbending.
It is introduced in Japanese Patent Laid-Open No. 2-176611, Japanese Patent Laid-Open No. 2-75418, and the like. This method is suitable for manufacturing a thin-walled welded pipe because of the mechanism of forming the strip into a cylindrical shape. The rollless forming method not only has a simple equipment configuration because it is not necessary to use a forming roll as in the related art, but is also freed from the problem of lubrication between the metal strip and the forming roll. Specifically, the equipment used in the rollless forming method has a simple structure,
Even if it is placed in a clean room, it will not cause any major trouble in maintenance and management. Further, since no lubricating oil is required, even if the inside of the clean room is maintained in a vacuum atmosphere, the problem caused by lubrication does not occur.

When the entire apparatus of the rollless forming method having such advantages is arranged in a clean room,
A welded pipe having no indentation damage due to dust on the surface can be obtained. In addition, since the welding conditions are also stabilized, a sound weld is formed. In the rollless forming method, as shown in FIG. 1, the metal strip S sent from the uncoiler 1 is used.
Is fed to the pre-deformation section 3 via the guide roll 2.
The pre-deformation part 3 includes a small-diameter bending roll 3a and a support roll 3b, and an elastic lining 3c of polyurethane or the like is applied to the surface of the support roll 3b. The bending roll 3a is a pair of large diameter rolls 3d as shown in FIG.
And 3e may be arranged.

The metal strip S is bent by a bending roll 3a so that the inner surface side of the obtained tube is in contact with the bending roll 3a.
And the support roll 3b. Since the metal strip S is uniformly bent and unbent in the width direction by the bending roll 3a, residual stress is applied to the metal strip S after passing through the pre-deformation portion 3. The metal strip S is then sent to the downstream side via the forming roll 4, the side roll 5 and the feed roll 6. During this conveyance process, the metal strip S is constrained from deforming in the longitudinal direction, so that it is elastically deformed into a cylindrical shape by residual stress. Both ends of the cylindrical metal strip S in the width direction are butted against each other in a state in which the shape is restricted by the forming roll 4 and the side rolls 5. The welded pipe P is obtained by welding the butt welded portion with the welding torch 7.

In this rollless forming method,
For example, as shown in FIG. 3, the uncoiler 1 to the sizing machine 9 are housed in the clean room 10, and the sizing machine 9 is installed.
The product welded pipe M cut into a predetermined product length by is taken out from the clean room 10. Reference numeral 11 indicates a lid provided at the outlet of the product-welded pipe M that has been cut to a certain size. Alternatively, a method may be adopted in which a discharge port is formed in the side wall 11a of the clean room 10 in the traveling direction of the welded pipe P and the welded pipe P taken out is cut to a predetermined size outside the clean room 10. The welded pipe P may be straightened using the straightening roll 8 in order to remove the distortion generated in the forming process and the welding process. In such a case, it is possible to arrange the straightening roll 8 on the upstream side of the sizing / cutting device 9 in the traveling direction of the welded pipe P sent out from the welded portion. However, it is necessary to supply the lubricant in consideration of the semi-finality between the straightening roll 8 and the surface of the welded pipe P. In this respect,
If the straightening roll 8 is not arranged in the clean room 10, the effect of the combination of the rollless forming method and the treatment in the clean room becomes more remarkable.

Also, the straightening process is separated from the pipe forming process,
It is also possible to arrange the uncoiler 1 to the welding torch 7 in the clean room 10 to form a dedicated pipe making line.
The advantages of the rollless forming method are more prominently exhibited in pipe-making lines. That is, in the rollless forming method, since the load on the forming roll is small and the number of forming rolls is also significantly small, the generation of dust is suppressed,
The contamination of the atmosphere by the lubricant is also suppressed. As a result, a welded pipe P having a good surface condition can be obtained. The clean room 10 includes an appropriate number of gas introduction pipes 12 and exhaust pipes 1.
3 is provided. Clean gas is introduced into the clean room 10 through the gas introduction pipe 12 and discharged through the exhaust pipe 13. As a result, the clean room 10 is always maintained in a clean atmosphere. In addition, foreign matter such as spatter generated during welding rides on the flow of gas and clean room 1
It is discharged from 0 to the outside of the system.

When forming, welding and straightening are performed in a clean atmosphere in this manner, dust and the like are prevented from being caught between the rolls 2 to 6 and the metal strip S or the welded pipe P.
It is possible to prevent the surface property of the product welded pipe M from being deteriorated due to the indentation damage caused by the dust. Further, when titanium or titanium alloy is used as the material of the metal strip S, for example, in order to prevent nitrogen in the air from being absorbed in the welded portion, an inert gas such as argon is used in the clean room 10.
It is also possible to circulate the air in the clean room 10 or control the atmosphere to reduce the thickness of the clean room 10. As a result, the obtained product welded pipe M has excellent surface properties and has a consistent and sound weld. Moreover, since the lubricating oil used in the normal roll forming method is unnecessary, the clean room 10 can be easily managed.

[0012]

Example A stainless steel plate SUS304 having a plate thickness of 0.15 mm and a plate width of 159.5 mm was used as the metal strip S. This stainless steel sheet has a 0.2% proof stress of 100 kg.
It was f / mm ² . Bending roll 3a with a diameter of 6.0 mm
Bending and unbending were performed by. A microplasma formed by forming a metal strip S having a uniform residual stress in the width direction into a cylindrical shape having a diameter of 50.8 mm, abutting both widthwise end portions with a squeeze roll 5, and using Ar + 7% H ₂ as a shield gas. Welded pipe P was manufactured by welding. Welded pipe P
Was cut to a length of 4 m and taken out as a product welded pipe M from the clean room 10.

At this time, the flow rate from the gas introduction pipe 12 is 0.1.
By introducing clean air at Nm ³ / min into the clean room 10 and taking out the same amount of air from the exhaust pipe 13,
The inside of the clean room 10 was maintained in an atmosphere of 1 atm. When the obtained product welded pipe M was observed, it had good surface properties and no surface scratches due to dust indentation were detected. Moreover, the welded part was also sound with a constant bead width and penetration depth. For comparison, assuming a normal atmosphere in the factory, air in which a large amount of dust is suspended is introduced into the clean room 10 from the gas introduction pipe 12,
Welding was performed under similar conditions. In the product welded pipe M obtained in this case, indentation scratches of 10 pieces / m were observed on average.

As is clear from this comparison, when the metal strip S from the uncoiler 1 to the welding torch 7 or the welded pipe P is placed in the clean room 10 in a protective atmosphere, a high quality product welded pipe having a clean surface condition. It turns out that M is obtained. In the example, the clean room 1
Clean air is introduced into 0. However, the metal strip S containing a metal element having a large affinity for oxygen and the like in the air
When welding is performed, the clean room 10 can be filled with an inert gas such as nitrogen or Ar. In addition, gas circulation can be omitted under conditions where there is little adverse effect due to sputtering or the like.

[0015]

As described above, in the present invention, the advantages of the rollless forming method are utilized for forming,
Welding etc. are performed in a clean room to prevent surface scratches caused by the intrusion of dust and the like. Since the obtained product welded pipe has an excellent surface condition, it is used as a high quality and highly reliable welded pipe in various fields. Further, since the lubricating oil used in the normal roll forming method is unnecessary, maintenance and management in the clean room becomes easy.

[Brief description of drawings]

FIG. 1 is a main part of a rollless forming method previously proposed by the present inventors.

FIG. 2 Bending rolls arranged between a pair of large-diameter rolls

FIG. 3 is an apparatus for manufacturing a thin-walled welded pipe in which an uncoiler and a constant-size cutting machine are arranged in a clean room according to the present invention.

[Explanation of symbols]

S: Metal strip P: Thin welded pipe M: Product welded pipe 1: Uncoiler 2: Guide roll 3: Pre-deformation part 4: Forming roll 5: Squeeze roll 6: Feed roll 7: Welding torch 8: Straightening roll 9: Fixed Slicing machine 10:
Clean room 11: Lid 12: Gas inlet pipe
13: Exhaust pipe

Claims (1)

[Claims] 1. A device for uniformly bending and unbending the strip material fed from an uncoiler in the width direction to give residual stress, and then forming it into a cylindrical shape to weld both widthwise end portions. An apparatus for manufacturing a thin-walled welded pipe having excellent surface properties, characterized in that the uncoiler and at least a welding device are arranged inside a clean room.