JPS643568B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a rectangular metal tube using concave rolls.

Conventionally, rectangular metal tubes are produced by forming and welding the tube into a normal circular cross section, and then reprocessing the tube into a rectangular cross section by applying pressure from the top, bottom, left and right sides using rolls having a square caliber.

However, in recent years, the demand for square metal pipes has increased in the fields of architecture and construction, and there is a desire to develop a highly efficient method for manufacturing square pipes that can easily meet various demands regarding size and shape.

In view of the actual situation, some of the applicants have previously filed Japanese Patent Application No. 55-032537 (Japanese Patent Application Laid-open No. 56-128618).
In "Method for Manufacturing Square Steel Pipe," a method for manufacturing a square steel pipe with a welded seam on one side by roll-forming a steel strip was proposed, but the present invention further improves this based on the process in the above proposal, and rolls a welding roll. This method uses a concave roll with a curvature on the roll surface to effectively prevent the occurrence of weld edge lapping.

There is a known method for manufacturing ERW tubes in which the edges of tube materials to be welded or pressure-welded are heated by electric resistance heating or electric induction heating, and then pressure is applied and joined using squeeze rolls. In manufacturing methods in which the weld seam is located in the weld, the lapping of the weld edge not only reduces the weld strength, but also significantly impairs the flatness of the welded surface of the finished product, and this is particularly dangerous for large-diameter rectangular metal pipes. .

The present invention is intended to solve the above-mentioned problems, and the gist thereof is to roll a rectangular tube material, which has been corner-bent by roll forming, into a desired circular arc on the roll surface. It is then introduced into a welding roll consisting of left and right rolls and a lower roll, and the welding edges on the upper side are butt welded under pressure by the upper and lower and left and right rolls, and then the four circumferences are flattened.

Hereinafter, in this specification, lapping means misalignment of the edge part on the welding surface, and squeeze roll is used to pressurize the pipe material whose edge part is heated in the manufacture of ERW pipes.
This is a roll for joining.

In addition, the metal pipes referred to in the present invention include steel pipes such as ordinary steel and stainless steel, nonferrous metal pipes such as copper, copper alloys, aluminum, and aluminum alloys,
This is a general term for items that can be manufactured by electric resistance welding.

The present invention will be explained in detail below with reference to the drawings.

Although the roll forming method of the square tube material according to the present invention is not particularly limited, one example thereof will be described below.

The strip material to be used may be a strip, a slit coil, or a plate material. In order to fully utilize the advantages of the continuous processing of roll forming in this method, a strip or a slit coil is suitable, but of course, even a regular length material may be difficult to process. It doesn't make any difference.

Coils such as strips of the required width according to the size of the rectangular metal tube to be manufactured are passed through an uncoiler, and in the case of regular length materials, they are fed one by one to pinch rolls using an appropriate feeding device. is as usual.

The strip material 1 is fed by one or two passes of the pinch rolls 2 while being prevented from meandering. For this reason, it is preferable to use a roll with a brim as the pinch roll, or to combine it with a vertical roll. The strip material 1 is first fed from the pinch rolls 2 to the upper corner bending rolls 3.

In this specification, an upper side corner refers to a corner where the upper side intersects the left and right sides in a cross section of a rectangular tube, and a lower side corner refers to a corner where the lower side intersects the left and right sides.

The upper corner bending rolls 3 are composed of upper and lower horizontal rolls, and have a profile that bends the strip material at positions 4, 4 which should be the left and right upper corners when it is made into a rectangular tube.

The strip material is placed at position 4, leaving widths l ₁ and l ₂ at both ends so that when the joint is welded, it will be the length of the top side of the square pipe.
Can be bent at 4. Bending positions 4 and 4 are roll center cc
It is preferable that the position be symmetrical with respect to the left and right sides.

In the upper side corner bending process, the bending angle a of the corner portion is determined by passing through the upper side bending roll for 3 to 5 passes.
Bend it to approximately 70° ± 10° to obtain material 5.

Next, the material 5 is sent to a lower corner bending roll 6 consisting of upper and lower rolls. The lower side bending roll 6 bends the material 5 at the positions of the lower side corners 7, 7 so that the intermediate portions of the upper left and right corners 4, 4 become the left and right sides and the lower side of the rectangular tube.

The upper roll 6a must pass between the openings on both side edges 8, 8 of the material 5, and the center part of the material's cross section must be sandwiched between the lower roll 6b and formed. The limit is to bend the corners 7 and 7 until the length of the bottom side is the same as the length of the lower side 7-7, so if you want to make the opening 8-8 even narrower, use a suspended upper roll, right and left rigid rolls, and a lower roll. A combination of forming rolls may be used.

In this case as well, 3
The material 5 is roughly formed into a pentagonal shape with open vertices by bending the corner bending angle b to approximately 70°±10° in 5 passes.

The material 5, whose upper and lower corners are bent to an intermediate angle, is then sent to a fin pass roll.

The fin pass roll 9 consists of an upper roll consisting of a fin roll 9a and a flange roll 9b, a vertical conical profile left and right roll 9c, and a cylindrical lower roll 9d. 8, flange roll 9b, left and right rolls 9c, lower roll 9d
The material 5 in the caliber consisting of is pushed from all four sides and the open ends 8, 8 are pressed against both sides of the flange roll 9a, and the thickness of the fin roll is made thinner with each pass to bring the shape of the material 5 closer to a square.
or bending angles a and b of each upper and lower corner in 3 passes
Bend it until it is approximately 85° ± 5°.

In this way, the corner bending is performed in the process up to the fine pass roll 9, and the raw material 5, which is formed into an open section with a roughly square cross section, is sent to the next welding roll 10.

The welding roll 10 of the present invention includes upper rolls 10a, 10b and left and right rolls 10 as shown in FIG.
c, 10d and the lower roll 10e are concave rolls each having a desired radius of curvature R.

The hole shape of the welding roll is preferably set slightly larger so as to give curvature to each side of the rectangular material to be formed. This is advantageous because it is possible to ensure uniform radius at the four corners by using the regular hole mold in the next step.

According to experiments, the radius of curvature is preferably 3 to 5 times the side length of the square material 5, but this is not particularly limited.

According to the present invention, reduction is applied in the circumferential direction by rolling down the welding roll, and this causes the material to conform to the upper, lower, left, and right rolls, creating surface pressure on each roll, and causing the welding edge to wrap or It can effectively prevent bending into the pipe.

In particular, according to experiments conducted by the present inventors, the present invention in which the welding rolls are provided with a curvature is extremely effective in manufacturing large-diameter square steel pipes.

Although an example in which the welding roll is a concave roll has been described above, it is also possible to provide a desired radius of curvature R to each roll of the fin pass roll 9 shown in FIG. 4 to make it a concave roll.

That is, by providing an arc in advance to each side of the material 5 in the fin pass roll, there is an advantage that the rigidity of the welded portion roll stand can be reduced.

Therefore, it is not particularly necessary that each side of the rectangular material be flat, but as long as the corners are sufficiently bent during the forming process up to the stage before the welding roll, each side can have an appropriate curvature. It goes without saying that the given square material may also be used.

In this way, the open ends of the upper sides are butted together and electrically welded to form a rectangular metal tube 12 with the weld seam 11 on the upper side.
become.

This metal tube 12 is then passed through a straightening Turks head roll 13 with a rectangular caliber to adjust its cross-sectional shape and longitudinal shape, and is further cut into a desired length by a suitable conventional cutting machine to become a product. .

Although the above explanation has been made based on drawings showing a method for manufacturing a rectangular tube with a substantially square cross section, the present invention is not limited thereto, and can also be applied to the manufacture of a rectangular tube with a rectangular cross section. It goes without saying that there is.

As explained above, the method of the present invention does not involve any pressing work, and is extremely efficient as it produces pipes only by roll forming. Since the amount of bending is extremely small, there is little change in the mechanical properties of the material, and especially when applied to the manufacture of large diameter rectangular steel pipes, products of excellent quality can be obtained.

[Brief explanation of drawings]

1 to 6 are sectional views of main parts for explaining the manufacturing process of a rectangular metal tube by the method of the present invention using rolls suitable for carrying out the method of the present invention, and FIG. 1 is a pinch roll, Figure 2 shows the upper corner bending roll, Figure 3 shows the lower corner bending roll, Figure 4 shows the fin pass roll, Figure 5 shows the welding roll, and Figure 6 shows the straightening roll, strip material, material, and metal pipe. It shows the relationship between 1... Band material, 2... Pinch roll, 3... Top corner bending roll, 4... Top corner bending position, 5... Material, 6... Bottom corner bending roll, 7... Bottom corner bending position, 8 ... Left and right ends, 9 ... Fin pass roll, 10 ... Welding roll, 11 ... Welding seam, 12 ... Metal tube, 1
3... Correction roll.

Claims (1)

[Claims] 1. A rectangular tube material whose corners have been bent by roll forming is introduced into a welding roll consisting of two upper rolls on the upper side, left and right rolls, and a lower roll that form the roll surface into a desired circular arc. A method for manufacturing a rectangular metal tube using concave rolls, characterized in that the weld edges on the upper side are butt-welded under pressure using upper and lower and left and right rolls, and then the four circumferences are flattened.