JP5055823B2 - High-efficiency manufacturing method for ERW pipes with good weld characteristics - Google Patents

Description

  The present invention relates to a flexible manufacturing method of a pipe that requires welded part toughness such as for oil well line pipes or a pipe that requires welded part strength such as casing pipe of oil well.

  Usually, pipes are roughly classified into welded pipes and seamless pipes. Welded pipes are manufactured by rolling a plate by roll forming or the like and welding by welding the end, as in the case of ERW steel pipes, and seamless pipes are made by drilling a lump of material at high temperature and using a mandrel mill, etc. Rolled and manufactured. In the case of a welded pipe, it is generally said that the properties of the welded part are inferior to that of the base metal, and in the application of the pipe, guarantees of toughness and strength of the welded part have always been discussed for each application.

  For example, in line pipes that transport crude oil, natural gas, etc., low temperature toughness is important because pipes are often laid in cold regions, and casing pipes that protect mining pipes are used in oil wells for crude oil mining. Needed, tube strength is valued.

  Normally, hot rolled sheets (strips) that are the base material of ERW pipes are subjected to component design and heat treatment in consideration of the base material characteristics after pipe manufacture, and the properties such as toughness and strength of the base metal are Secured.

  However, since the characteristics of the welded part are greatly influenced by the electric resistance welding method more than the component design and heat treatment of the base metal, the development of the welding technique has been important.

  The reason for the failure of ERW welding is that the oxide generated on the end face of the welded plate material called penetrator remains without being discharged from the end face together with the molten steel during ERW welding, and the toughness decreases due to this residual penetrator and the strength. There were many cases where there was a shortage.

Therefore, conventionally, in order to remove the penetrator, which is the main cause of poor ERW welding, from the welded portion, a technique for actively discharging molten steel from the plate end surface of the welded portion has been intensively studied. For example, Patent Literature 1 and Patent Literature 2 describe examples of examining the shape of the plate end face. In other words, the end surface of the hot-rolled sheet that is the base material is generally rectangular due to slits or end surface grinding, but this end surface is tapered before roll forming, and the end shape that has been tapered is electrically charged. The aim is to improve the discharge of molten steel during sewing welding.
JP 2001-17079A JP 2003-164909 A

  However, since Patent Document 1 and Patent Document 2 merely introduce a hole roll, a cutting tool, and a grinding roll as taper processing means, they are specifically applied to the ERW pipe manufacturing process. However, there are various problems and further detailed examination is required.

  For example, in the case of cutting, it is a problem to provide a predetermined taper shape with high accuracy, and it is not necessary to simply cut. In addition, when the taper shape is given by cutting, since the taper-shaped portion is not work-hardened, the applied taper shape is almost lost by fin pass molding in roll molding, and immediately before electro-welding welding. In many cases, the desired taper shape could not be obtained.

  On the other hand, if a tapered shape is imparted by rolling with a perforated roll, it is considered that the portion imparted with the tapered shape is work-hardened and the tapered shape is less likely to be damaged by fin pass molding. At that time, if a conventional general hole type roll is used, the upper end and the lower end of the plate (band material) are filled by filling the end of the plate with a hole having a shape as shown in FIG. Are tapered at the same time.

  However, with this method, there is no problem if the plate thickness is constant, but in the actual ERW tube manufacturing process, plates (bands) of various thicknesses are roll-formed into tubes, and if the plate thickness changes, It is necessary to replace the perforated roll each time, and the production efficiency is significantly reduced. Moreover, when the plate | board thickness fluctuation | variation is large in one steel strip (strip | belt material), the upper and lower parts of a perforated roll may be unable to endure reaction force, and may be damaged.

  The present invention has been made in view of the above circumstances, and when producing an electric resistance welded tube, by appropriately giving a tapered shape to the end of the plate (band material) before the electric resistance welding, An object of the present invention is to provide a high-efficiency manufacturing method for an electric resistance welded tube that can maintain good welding quality and can prevent a decrease in manufacturing efficiency, and is excellent in welded portion characteristics.

  As described above, if a conventional perforated roll is used alone and a tapered shape is simultaneously applied to the upper surface side end portion and the lower surface side end portion of the plate, problems such as roll breakage and efficiency reduction occur.

  In order to solve the problem, the present inventors have studied a method that can taper the end of the plate without reducing the production efficiency even if the thickness of the strip changes.

  As a result, the means for imparting a taper shape was changed for each of the upper surface side end portion and the lower surface side end portion of the plate, and the taper shape was given by a plurality of means. That is, a taper shape is given to the upper surface side end portion and the lower surface side end portion of the plate by a plurality of means, and after the taper shape is given to one surface side end portion, the other surface side end portion is tapered. If the shape is given, even if the plate thickness varies, it is possible to finely adjust the vertical position of the device that gives the taper shape, without reducing the manufacturing efficiency, and to the upper side end and the lower side end of the plate. This is because a tapered shape can be provided.

  At that time, as a means for imparting a tapered shape to any of the end portions on the surface side, it is preferable to perform rolling with a hole roll, taking advantage of the fact that the tapered portion is work-hardened. Since the perforated roll is relatively large, installation space is required, and it is difficult to install during or after roll forming, and the plate before roll forming is almost flat. The taper shape is preferably applied before roll forming.

  And as a means to give a taper shape to the edge part of the other surface side, it is good to utilize fin pass molding in the middle of roll forming. In the fin pass molding, the plate end is strongly pressed to fill the plate with the fin pass roll. Therefore, in the fin pass molding, the fin shape may be a two-step taper, and the fin shape may be transferred to the plate by utilizing the strong pressure at the end of the plate.

  Based on the above concept, the present invention has the above features.

[1] In a method for manufacturing an ERW pipe which is formed by band forming and end-to-end is welded to form a pipe, and before roll forming, a surface parallel to the end face of the band member and an inclined surface connected thereto are provided. In addition , a taper shape is given to the end on the upper surface side of the strip by rolling with a perforated roll that is movable in the vertical direction according to the thickness of the strip, and at the final stand of the roll forming fin pass molding Using a fin pass roll having fins with two-step taper , a taper shape is imparted to the end portion on the lower surface side of the band member, and the taper shape has an angle of 25 ° to the taper thickness direction. Absorption at −46 ° C. at the center of the weld thickness, characterized in that the length in the thickness direction of the taper is 20% to 40% of the plate thickness (excluding 20%). Energy is over 125J, brittle fracture surface A high-efficiency manufacturing method for ERW pipes for line pipes or casings with good weld properties, with a rate of 35% or less.

  INDUSTRIAL APPLICABILITY According to the present invention, an electric resistance welded tube having remarkably good toughness and welding strength can be produced with high efficiency.

  FIG. 1 shows an ERW pipe production line used in an embodiment of the present invention. In this electric sewing tube manufacturing line, the band material 20 is discharged from the uncoiler 1, straightened by the leveler 2, the band material 20 is gradually rounded by the roll forming machine 5, and both widths of the rounded band material 20 are measured. The end portion is electro-welded with an electric seam welding machine including an induction heating unit 6 and a squeeze roll (electro-sealed welding part) 7 to form a pipe 30, and the weld bead part of the pipe 30 is cut with a bead part cutting machine 8. The tube 30 after cutting is adjusted in outer diameter by the sizer 9 and then cut to a predetermined length by the tube cutting machine 10. The roll forming machine 5 includes a fin pass forming stand 4 having two stands at the last stage.

  And in this embodiment, in addition to said basic structure, the hole type roll 3 for providing a taper shape to the edge part of the strip | belt | material 20 between the leveler 2 and the roll molding machine 5 is provided.

  As shown in FIG. 2, the perforated roll 3 has a surface parallel to the substantially vertical plate end surface and a surface that is connected to the surface and is inclined to the substantially vertical plate end surface, and is movable in the vertical direction. It has become. As for the rotation method, as shown in FIG. 2 (a), for example, a surface parallel to the substantially vertical plate end surface is used as a rotary body, and a rotation axis parallel to the substantially vertical plate end surface is provided. Further, as shown in FIG. 2B, for example, a surface that is inclined to a substantially vertical plate end surface is a rotating body portion, and a rotation axis that is substantially parallel to the surface inclined to the plate end surface may be provided. Good.

  By rolling the strip 20 with such a perforated roll 3, as shown in FIG. 2, the end of the strip 20 on the upper surface side (the inner surface side of the tube 30) is tapered from the vertical end surface in the thickness direction of the taper. The taper shape in which the angle (angle with respect to the thickness direction of the taper) is γ and the length of the perpendicular from the taper start position to the end position on one side (length of the taper in the thickness direction) is δ can be given. it can.

  Further, in this embodiment, the final stand 4a of the fin pass forming stand 4 is shown in FIG. 3A as viewed in the direction of arrows AA in FIG. 1, and in FIG. The fin shape has a predetermined two-step taper (second-step taper inclination angle α, second-step inclined portion vertical length β). By transferring the fin shape to the width end portion of the band member 20, a predetermined taper shape can be given to the left and right end portions on the lower surface side (the outer surface side of the tube 30) of the band member 20.

  Thereby, when a taper shape is given to the end portions on the upper surface side and the lower surface side of the strip materials having different plate thicknesses, the end portion on the upper surface side (the inner peripheral side of the tube 30) of the strip material 20 Using the perforated roll 3, the position in the height direction is finely adjusted, the predetermined position in the plate thickness direction is rolled, and on the other hand, with respect to the end on the lower surface side (the outer peripheral side of the tube 30) of the band member 20 If a taper shape is transferred to a predetermined position in the plate thickness direction by fin pass molding, a predetermined taper shape is given to both ends of the upper and lower surfaces of the strip material according to the plate thickness without reducing the production efficiency. Can do.

  In this way, a combination of the perforated roll 3 having a surface parallel to the plate end surface and a surface inclined to the plate end surface and movable up and down and a fin path final stand 4a having a fin shape having a two-step taper is combined. Since the taper shape is applied to both the upper surface side end portion and the lower surface side end portion of the strip material, even when the taper shape is applied to the strip material having different thicknesses, the efficiency is not reduced. . Further, even when the plate thickness varies greatly with one strip, an excessive load is not applied to the perforated roll, and the perforated roll is not damaged.

  In addition, about the taper shape (namely, taper shape of the plate edge part just before ERW welding) provided with the perforated roll 3 and the fin pass final stand 4a, the angles α and γ from the vertical end face of the taper thickness direction are 25 °. As a range of ˜50 °, the lengths β and δ of perpendicular lines from the taper start position to the end position on one side may be 20% to 40% of the plate thickness.

  That is, if the taper angles α and γ are less than 25 °, the molten steel is not sufficiently discharged from the central portion of the plate thickness, the penetrator remains and becomes defective, and the toughness and strength after ERW welding are reduced. When α and γ exceed 50 °, the taper shape remains as a wrinkle of the tube of the product even after the electric resistance welding. Further, if the taper heights β and δ are less than 20% of the plate thickness, the molten steel discharge at the central portion of the plate thickness becomes insufficient and the penetrator tends to remain, and the taper heights β and δ exceed 40%. And the taper shape remains as a flaw of the pipe of the product even after the electric resistance welding.

  In this way, in this embodiment, since the taper shape can be appropriately imparted to the end portion of the band material before the ERW welding, the ERW pipe having remarkably good toughness and welding strength can be highly efficient. Can be manufactured.

  In this embodiment, a taper shape is applied to the end of the upper surface side (inner peripheral side of the tube 30) of the band member 20 before roll forming, and the lower surface side (outer surface side of the tube 30) of the band member 20 is obtained by fin pass forming. However, in some cases, a taper shape is given to the end on the lower surface side (the outer periphery side of the tube 30) of the band member 20 before roll forming, You may make it provide a taper shape to the edge part of the upper surface side (inner surface side of the pipe | tube 30) of the strip | belt material 20. FIG.

  In the above description, it is premised on a production line in which the upper surface side of the band member 20 is the inner peripheral side of the tube 30, but the present invention manufactures an electric resistance welded tube in which the upper surface side of the band member 20 is the outer peripheral side of the tube 30. Needless to say, the same applies to the line.

  Hereinafter, a description will be given based on examples.

  Here, an ERW pipe of φ600 is manufactured using a strip (steel strip) having a plate width of 1920 mm × 19.1 tmm, and subsequently, using a strip (steel strip) having a plate width of 1920 mm × 11.3 tmm. , Φ600 electric resistance welded tube was manufactured.

  And the test piece was cut out from the weld part of the manufactured ERW pipe, the Charpy test was done, and the performance was evaluated. Each Charpy test piece is taken from 10 points with different pipe longitudinal directions, the specimen length direction is parallel to the pipe circumferential direction, the notch length center is taken as the weld thickness center position, and 2 mmV of JIS5 An impact test at −46 ° C. was performed as a notch impact test piece, and the absorbed energy and the brittle fracture surface ratio were measured. In addition, the absorbed energy was 125 J or more and the brittle fracture surface ratio was 35% or less as the allowable performance range.

  (Example of the present invention) As an example of the present invention, the above-described electric sewing tube was manufactured based on the above-described embodiment. At that time, using the perforated roll 3 shown in FIG. 2, a substantially linear taper with a taper angle γ of 30 ° was given to the upper surface side end portion (the inner surface side end portion of the pipe) of the plate. In the fin pass molding, a substantially linear taper with a taper angle α of 30 ° was given to the upper surface side end portion (the outer surface side end portion of the pipe) of the plate. When the strip thickness was changed from 19.1 tmm to 11.3 tmm, the position of the perforated roll 3 was moved 7.8 mm downward for fine adjustment.

  (Comparative Example) As a comparative example, when manufacturing the above-mentioned electric resistance welded tube, after the leveler processing before roll forming, using the conventional perforated roll shown in FIG. A substantially linear taper with a taper angle of 30 ° was simultaneously applied to both side end plates. In addition, when the plate | board thickness of the strip | belt material changed from 19.1 tmm to 11.3 tmm, a production line was once stopped and the hole-type roll was replaced | exchanged for 19.1 mmt from 19.1 tmm.

  (Conventional example) As a conventional example, when manufacturing the above-mentioned electric resistance welded tube, after the leveler processing before roll forming, the edge of the plate is polished vertically and then the electric resistance welded tube is subjected to conventional roll forming. Manufactured. When the plate thickness was changed from 19.1 tmm to 11.3 tmm, the production line was temporarily stopped, but the operation was resumed immediately and the production was continued.

  Table 1 shows the results of measuring the Charpy impact value and the brittle fracture surface ratio at the welded portion of the electric resistance welded tube manufactured as described above. Moreover, the manufacturing efficiency of the comparative example was set to 1, and the ratio of the manufacturing efficiency of each example to that was shown in the same table.

  From Table 1, the ERW pipe according to the example of the present invention has high impact strength at the welded portion, low brittle fracture surface ratio, good toughness, and high product reliability. On the other hand, the electric resistance welded tube according to the conventional example has a low impact strength at the welded portion, a high brittle fracture surface ratio, a low toughness, and poor product reliability. Moreover, in the example of the present invention, the production efficiency is remarkably improved as compared with the comparative example.

  Therefore, it was confirmed that the ERW pipe having good welded portion characteristics can be manufactured with high efficiency by the present invention.

It is a figure which shows the ERW pipe manufacturing line in one Embodiment of this invention. It is a figure which shows the condition which provides a taper shape to the upper surface side edge part of a strip | belt material with a hole-type roll. It is a figure which shows the fin-shaped fin pass stand provided with the 2 step | paragraph taper. It is a figure which shows the conventional hole-type roll.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Uncoiler 2 Leveler 3 Hole type roll 4 Fin pass forming stand 5 Roll forming machine 6 Induction heating device 7 Squeeze roll (electricity welding part)
8 Bead cutting machine 9 Sizer 10 Pipe cutting machine 20 Band material 30 Pipe

Claims (1)

In the manufacturing method of the ERW pipe which forms the band material, butts the end portions, and welds it into an electric resistance welded pipe, before roll forming, the belt is provided with a surface parallel to the end surface of the band material and an inclined surface connected thereto, In the final stand of the roll forming fin pass forming, two stages are provided while the end on the upper surface side of the band material is tapered by rolling with a perforated roll that is movable in the vertical direction according to the thickness of the material. Using a fin pass roll provided with a tapered fin , a taper shape is given to an end portion on the lower surface side of the band material, and the taper shape has an angle with respect to the thickness direction of the taper of 25 ° to 50 °. The length of the taper in the plate thickness direction is 20% to 40% of the plate thickness (excluding 20%), and the absorbed energy at −46 ° C. at the center of the weld thickness is 125 J. As described above, the brittle fracture surface ratio is 3 A high-efficiency manufacturing method for electric pipes for line pipes or casings with good weld joint properties of 5% or less.

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