JP5867071B2 - Manufacturing method for thick ERW steel pipe - Google Patents

Description

  The present invention relates to a method for manufacturing a thick ERW steel pipe. Here, the thick ERW steel pipe means an ERW steel pipe having a wall thickness of 19.1 mm or more.

  In a general ERW steel pipe production line, the fin pass equipment is a forming process that leads to a stable edge forming state while performing finish forming and angle management of both edge portions welded by a fin plate attached to a roll. . However, since the molding load may be increased depending on the molding method, a method for reducing the molding load has been studied (for example, see Patent Document 1). It is known that the forming with the fin pass roll greatly affects the butt shape at the time of ERW welding.

JP-A-8-215765

As shown in FIG. 3, when the plate end portion of the band plate 1 has a rectangular cross-sectional shape (FIG. 3 (a)), the opposite end face is formed in the tubular molded body 10 before welding which is rolled into a tubular shape with a reduced width. V-shaped butt shape (Fig. 3 (b)) with a gap open to the outer surface side of the pipe. When welding, the amount of pressure contact increases toward the inner surface side of the pipe, making it easier to weld first, thereby leaving inclusions on the weld surface. It is easy to cause a material difference in the thickness direction.
Therefore, for example, the I-type butt shape shown in FIG. 4 is considered preferable. This butted shape is formed in such a manner that the center portion in the thickness direction at the end of the plate is the vertical surface portion 2 with respect to the butting direction and they face each other. According to this, the amount of press contact is equalized in the thickness direction by the vertical surface portion 2, and inclusions hardly remain on the weld surface.

In order to obtain the I-type butted shape, the amount of processing on the tube inner surface side (upper surface side in the case of a strip) of the plate end must be made larger than that on the outer surface side (lower surface side in the case of a strip).
However, if the plate edge processing is performed only by the fin pass roll forming, the processing amount on the inner surface side of the tube is particularly large for the thick tube, so the forming load becomes excessive and the target is limited due to equipment constraints. It may be difficult to obtain a butt shape.

  That is, in the conventional ERW steel pipe manufacturing technology, there is a problem that it is difficult to give an I-type butt shape using existing equipment due to equipment restrictions and cost restrictions in the case of thick-walled pipes.

The inventor of the present invention solved the above-mentioned problem by adding a new idea to the plate end face cutting with the edge mirror and combining this with the plate end face forming with the fin pass roll. That is, the present invention is as follows.
(1) In a method for manufacturing an ERW steel pipe in which a strip is continuously discharged and roll-formed into a tubular shape, and then subjected to ERW welding by butting both ends in the plate width direction, from the discharge to the start of roll forming, A horizontal strip is temporarily elastically deformed from a flat plate shape to an upwardly bent shape in a cross section in the plate width direction, and both end portions in the plate width direction of the upwardly convex shape strip plate are perpendicular to the edge mirror rotation axis. The thickness is 19.1 mm or more, characterized in that the cutting surface is formed by cutting with an edge mirror, and the cutting surface is formed with a fin pass roll at the final stage of roll forming. A method for manufacturing ERW steel pipes.

  According to the present invention, the I-type butt shape can be easily realized in the thick-walled ERW steel pipe manufacturing technology using existing equipment.

It is the schematic which shows an example of embodiment of this invention. It is the schematic which shows one example of the ERW steel pipe manufacturing equipment used for the pipe making process to which this invention is applied. It is the schematic which shows V-shaped butt | matching shape. It is the schematic which shows I form butt | matching shape.

  The present invention is applied to a pipe making process using an ERW steel pipe manufacturing facility as illustrated in FIG. In this pipe making process, the strip 1 is continuously discharged by the uncoiler 11, the end of the plate is cut by the edge mirror 12, and then sequentially passed through the breakdown roll 13, the cage roll 14, and the fin pass roll 15 to form a roll. Then, the tubular molded body 10 is electrically heated by the power feeding means 16 to the melting point of the steel or higher by the power feeding means 16 and subjected to electro-welding welding in pressure contact with the squeeze roll 17 to form the tubular body 20. The body 20 is weld-bead-cut with a bead cutting machine (not shown), rolled with a constant diameter with a sizing roll (not shown), and cut into a predetermined length with a cutting machine (not shown).

In the present invention, as shown in FIG. 1 (a), the strip is in a horizontal position from the discharge (exit side of the uncoiler 11) to the start of roll forming (the entrance side of the first roll of the breakdown roll 13). 1 is temporarily elastically deformed from a flat plate shape to an upward convex bending shape in a cross section in the plate width direction, and both end portions in the plate width direction of the strip plate 1 of the upward convex bending shape are perpendicular to the edge mirror rotation shaft 12A. Cutting is performed by the edge mirror 12 to form a cutting surface 1A. A method for causing the strip 1 to elastically deform from a flat plate shape to an upwardly bent shape is that the strip 1 is supported by the lower roll 30 on the plate width center side and the upper width 31 on both sides of the plate width. This can be easily performed by three-point bending by pressing the part. Since it is elastically deformed, it is restored to a flat plate shape after end cutting (the exit side of the edge mirror 12). While the edge mirror rotating shaft 12A is held vertically as usual, as shown in the drawing, the end cutting amount (end processing amount) on the upper surface side of the tube, which is the inner surface side of the tube, is changed to the lower surface side of the plate, which is the outer surface side of the tube. It can be bigger than that.
It is not necessary to incline the edge mirror 12, and it is only necessary to provide a simple three-point bending mechanism, thereby eliminating the cost limitation.

And as shown in FIG.1 (b), although it shape | molds with the fin pass roll 15 which is the last stage of roll shaping | molding with respect to the obtained cutting surface 1A, it does not generate | occur | produce an excessive load, but welding Immediately before, an I-type butt shape as shown in FIG. 4 is obtained, and the equipment restrictions are eliminated.
Thus, when manufacturing a thick ERW steel pipe using existing equipment, it is possible to give an I-type butt shape.

  When forming a thick ERW steel pipe with an outer diameter of 609.6 mm and a wall thickness of 19.1 mm using the ERW steel pipe manufacturing equipment shown in Fig. 2, the I-type butt shape has been hitherto due to equipment constraints and cost constraints. It was difficult to get. On the other hand, when the present invention was applied to the embodiment shown in FIG. 1, an I-type butt shape could be easily realized.

1 Strip (tube material)
DESCRIPTION OF SYMBOLS 1A Cutting surface 2 Vertical surface part 10 Tubular molded object 11 Uncoiler 12 Edge mirror 12A Edge mirror rotating shaft 13 Breakdown roll 14 Cage roll 15 Fin pass roll 16 Power supply means 17 Squeeze roll 30 Lower roll 31 on the plate width center side Both plate width Upper side roll 20 tube

Claims (1)

In the method of manufacturing an ERW steel pipe in which the strip is continuously discharged and roll-formed into a tubular shape, and then both ends in the plate width direction are butted together and electro-welded, the horizontal posture is between the discharge and the start of roll forming. The edge of the band plate in the plate width direction is temporarily elastically deformed from a flat plate shape to an upward convex bending shape in the plate width direction cross section, and both edge portions in the plate width direction of the upward convex bending shape strip are perpendicular to the edge mirror rotation axis. A thick-walled electric-welded steel pipe having a wall thickness of 19.1 mm or more, characterized by forming a cut surface with a mirror to form a cut surface, and further forming the cut surface with a fin pass roll at the final stage of roll forming Manufacturing method.

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