JP4720480B2 - Manufacturing method of electric resistance welded tube with good weld characteristics - Google Patents

Description

  The present invention relates to a method for manufacturing an electric resistance welded tube having good welded portion characteristics, and particularly, a welded portion strength such as a pipe required for welded portion toughness for oil well line pipes or a casing pipe for oil well is required. Related to the method of manufacturing the tube.

  Usually, pipes are roughly classified into welded pipes and seamless pipes. Welded pipes are manufactured by rounding plates by roll forming etc. and welding by welding the width ends, as in the case of ERW steel pipes. Seamless pipes are made by drilling a lump of material at a high temperature, etc. Rolled to produce. 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.

  Usually, a hot-rolled sheet that is a base material of a pipe is subjected to component design, heat treatment, and the like in consideration of the base material characteristics after the pipe is manufactured, and characteristics such as toughness and strength of the base material are secured.

  However, since the characteristics of the welded part are greatly influenced by the welding method more than the component design and heat treatment of the base metal, it is particularly important to develop a welding technique in the case of ERW welding.

  As a cause of the failure of ERW welding, the oxide generated at the width end of the welded strip called penetrator remains without being discharged from the end face together with the molten steel during ERW welding, and the toughness is caused by this remaining penetrator. There were many cases where the strength decreased and the strength was insufficient.

  Therefore, conventionally, in order to remove the penetrator from the welded portion, techniques for positively discharging molten steel from the width end face of the welded band material of the welded portion have been intensively studied. For example, Patent Literature 1 and Patent Literature 2 describe examples in which the shape of the width end face of the strip is examined. Normally, the width end face of the strip is almost rectangular due to slits and end grinding, but this width end face is processed before electro-welding, and the processed wide end shape improves the discharge of molten steel during welding. The purpose is that. The outline is as follows.

  That is, the basic ERW pipe production line is as shown in FIG. 1. This ERW pipe production line is a roll forming machine in which the band material 20 is discharged from the uncoiler 1 and straightened by the leveler 2. 4, the strip 20 is gradually rounded, and the left and right width end portions of the round strip 20 are electro-welded with an electric-welding machine including an induction heating unit 5 and a squeeze roll (electric-welding weld) 6. Then, the weld bead portion of the tube 30 is cut by the bead portion cutting machine 7, the outer diameter of the cut tube 30 is adjusted by the sizer 8, and then cut to a predetermined length by the tube cutting machine 9. It has the structure of. The roll forming machine 4 includes a predetermined number of fin pass forming stands 3 that constrain the end of the plate rounded to the last stage and have a shape close to a perfect circle. Here, the first stand 3a and the second stand are provided. It consists of 3b.

  In the technique described in Patent Document 1, as shown in FIG. 5A, a cross-sectional view, and in FIG. By bringing a part of the width end of the material 20 into contact with the fins of the fin pass hole roll, as shown in FIG. 5C, a tapered shape is given to the width end on the inner surface side of the tube, and FIG. As shown in the cross-sectional view in FIG. 5D and the partial detail view in FIG. 5E, in the fin-pass molding second stand 3b, the other part of the width end of the band member 20 is brought into contact with the fin, As shown in FIG. 5 (f), an X-shaped groove is formed by giving a taper shape to the width end portion on the outer surface side of the tube. In addition, the angle of the fin in the fin pass shaping | molding 1st stand 3a and the 2nd stand 3b is a normal one step angle.

Further, in the technique described in Patent Document 2, as shown in a cross-sectional view in FIG. 6A, the edger roll 11 is installed on the upstream side of the fin pass forming stand, and the edger roll 11 is used to form a tubular shape. By reducing the width end portion of the band member 20, as shown in FIG. 6B, a taper shape is given to the entire width end portion of the band member 20, and FIG. 6C shows a cross-sectional view. 5 (d), as shown in FIG. 5 (d), as shown in FIG. 5 (e), a part of the width end portion of the band member 20 is brought into contact with the fins of the fin pass hole type roll in the fin pass forming stand 3 as shown in FIG. In addition, the width end on the outer surface side of the tube is shaped into a vertical surface.
JP-A-57-031485 Japanese Patent Laid-Open No. Sho 63-317212

  However, when the present inventors examined the method described in Patent Document 1, even if the amount of upset in fin pass molding was changed significantly, only a part of the width end portion of the band member 20 was used as the fin of the fin pass hole type roll. It turned out to be extremely difficult to contact. This is because the width end portion of the band member 20 is only slightly hardened in the molding process so far, and the entire width end portion of the band member is easily deformed along the fins, so that the fin part is fully filled. This is because the shape of the fin is transferred to the width end of the strip. As a result, the width end portion of the strip 20 is not in a desired shape immediately before the electric resistance welding.

  Moreover, when the present inventors examined the method of patent document 2, the taper shape is provided to the whole width | variety edge part of the strip | belt material 20 using the edger roll 11 in the middle of roll shaping | molding (upstream side of a fin pass shaping | molding stand). Therefore, as described in Patent Document 2, since it is necessary to form using an edger roll whose diameter gradually increases from the pipe outer surface side to the pipe inner surface side, the width end portion on the pipe inner surface side is scraped off by the edger roll. Therefore, there is a problem that an extra material called “beard” is generated. Furthermore, since a large reaction force that opens the tubular strip 20 outwardly acts in the cross-sectional direction of the strip 20 to be roll-formed, the pressure between the edger roll 11 and the width end of the strip 20 is inevitably small. Become. As a result, similarly to the above-mentioned Patent Document 1, it becomes difficult to work harden under the pressure of the width end portion by the edger roll, and even if the amount of upset is reduced by subsequent fin pass molding, the band material is almost filled in the fin portion, It was confirmed that it was difficult to give the shape as described in Patent Document 2 to the width end portion of the band member 20.

  The present invention has been made in view of the above circumstances, and can make the shape of the width end portion immediately before ERW welding to be an appropriate shape, thereby sufficiently discharging molten steel during ERW welding. Thus, it is an object of the present invention to provide a method of manufacturing an electric resistance welded tube that can reliably remove the penetrator and obtain an electric resistance welded tube with good welded portion characteristics.

As described above, in the prior art described in Patent Documents 1 and 2, in order to give a taper shape to the width end surface of the band material, a part of the width end portion of the band material is pressed against the fin of the fin pass hole roll. However, according to the study by the present inventors, even if the fin pass hole-type roll is not filled with the entire circumference in the circumferential direction of the band material, the band material is mounted on the fin pass hole-type roll. When entering, it was grasped that the width end portion was strongly pressed by the fin and the width end portion was completely filled in the fin portion. That is, when the strip is inserted into the fin pass hole roll, the width end of the strip in contact with the fin and the width central portion (tubular bottom portion) of the strip located on the opposite side of about 180 degrees Is a beam bending state, and the reaction force of the band material that tries to bend the cross section into an arc shape acts greatly, even if the band material does not fill the fin pass hole roll, the width end of the band material As a result, it was understood that a large compressive force was applied in the circumferential direction, and as a result, the width end portion of the strip was strongly pressed by the fin, and the shape of the fin was transferred as it was to the width end of the strip.

  Therefore, the present inventors pay attention to the fact that the width end of the strip is strongly pressed by the fin in the fin pass molding, and by actively utilizing this phenomenon, the taper has a predetermined taper at the width end of the strip. Inspired by the method of giving shape. In other words, if the taper is provided with two or more stages of taper, even if the amount of upset in the fin pass molding is small, the desired taper shape can be given to the width end portion of the band material, so that the band material just before the ERW welding can be provided. It has been found that the shape of the width end portion can be an appropriate taper shape.

  The present invention is based on the above idea and has the following features.

[1] A method for manufacturing an electric resistance welded tube in which a strip is roll-formed and a width end portion is abutted to form an electric-welded pipe, and the fin has a two-stage angle in fin-pass forming during roll forming. In addition, by transferring the fin shape to the width end of the strip, a taper shape is given to both the strip width end on the side that becomes the outer surface of the tube and the width end of the strip on the side that becomes the inner surface of the tube. In addition, the taper shape is given to the band width end portion on the side that becomes the inner surface of the pipe in the previous stage of the fin pass molding, and the taper shape is given to the band width end portion on the side that becomes the outer surface of the pipe in the final stand of the fin pass molding , The shape is such that the angle of inclination from the width end surface of the strip to the surface serving as the tube outer surface and the surface serving as the tube inner surface is 25 ° to 50 °, and the taper starting position at the width end surface of the strip and the surface serving as the tube outer surface And the thickness of the strip with the surface that becomes the inner surface The absorbed energy at −46 ° C. at the center of the weld thickness is 125 J or more, and the brittle fracture surface ratio is less than the penetrator, characterized in that the direction distance is 20% to 40% of the strip thickness. A method for producing an electric resistance welded tube having a welded portion characteristic of 35% or less .

In the present invention, the fin shape of the fin pass molding is a shape having a two-stage angle , and the fin shape is transferred to the width end of the band material. The shape can be an appropriate tapered shape. As a result, a sufficient amount of molten steel is discharged at the time of electric resistance welding, and the penetrator is surely removed, so that an electric resistance welded tube with good welded portion characteristics can be obtained.

  Embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The electric sewing tube manufacturing line used in the first embodiment which is a reference of the present invention is the one shown in FIG. That is, in this electric sewing tube manufacturing line, the band material 20 is discharged from the uncoiler 1 and straightened by the leveler 2, and the band material 20 is gradually rounded by the roll forming machine 4. Both width ends are electro-welded with an electric seam welding machine comprising an induction heating unit 5 and a squeeze roll (electro-sealed welding part) 6 to form a pipe 30, and a weld bead part of the pipe 30 is formed with a bead part cutting machine 7. After cutting, the cut tube 30 is adjusted to the outside diameter by the sizer 8 and then cut to a predetermined length by the tube cutting machine 9. The roll forming machine 4 includes a predetermined number of fin pass forming stands 3 that constrain the end of the plate rounded to the last stage and have a shape close to a perfect circle. Here, the first stand 3a and the second stand are provided. It consists of 3b.

  In the first embodiment, the fins of the fin-pass molding first stand 3a have a normal one-step taper shape. FIG. 2 (a) is a cross-sectional view, and FIG. As shown in the partial detail view, the fin of the second stand 3b has a two-step taper shape (second-step taper inclination angle α, second-step inclination portion vertical length β). As shown in FIG. 2 (c), by transferring to the left and right width end portions of the material 20, a predetermined taper shape (from the width end surface to the surface that becomes the tube outer surface) is formed on the left and right width end portions on the side that becomes the tube outer surface. And a plate thickness direction distance β) from the surface that becomes the outer surface of the tube at the start position at the width end face.

  And about the taper shape provided to both right and left width end parts of the band member 20, the inclination angle α from the width end surface of the band member 20 toward the surface which becomes the pipe outer surface is 25 ° to 50 °, The distance β between the taper start position and the surface serving as the outer surface of the pipe in the strip material thickness direction is set to 20% to 40% of the strip material plate thickness.

This is because if the inclination angle α is less than 25 °, the molten steel is not sufficiently discharged from the central portion of the strip thickness, the penetrator remains and becomes defective, and the toughness and strength after ERW welding are reduced. If the angle α exceeds 50 ° , the taper shape remains as a wrinkle of the pipe of the product even after the ERW welding, which is a problem. Further, if the taper start distance β is less than 20% with respect to the plate thickness, the molten steel discharge at the center portion of the plate thickness becomes insufficient and the penetrator tends to remain, and the taper start distance β is 40% of the plate thickness. If it exceeds 50%, the taper shape remains as a flaw of the pipe of the product even after ERW welding, which is a problem.

  As described above, in this embodiment, the fin shape of the fin pass molding final stand 3b has a shape having two-step angles, and the fin shape is transferred to the left and right width end portions of the band member 20. Therefore, the shape of the width end portion of the strip 20 immediately before the electric resistance welding can be set to an appropriate taper shape. As a result, a sufficient amount of molten steel is discharged at the time of electric resistance welding, and the penetrator is surely removed, so that an electric resistance welded tube with good welded portion characteristics can be obtained.

  In addition, in the above, a predetermined taper shape can also be given to the right-and-left both width | variety edge part used as a pipe inner surface side by changing a taper shape of two steps.

(Second Embodiment)
The electric sewing tube manufacturing line used in the second embodiment which is a reference of the present invention is also the one shown in FIG.

  And in this 2nd Embodiment, although the fin of the fin pass shaping | molding 1st stand 3a has a normal 1 step | paragraph taper shape, FIG. 3 (a) is a cross-sectional view, FIG. As shown in the partial detail view, the fin of the second stand 3b has a three-step taper shape (vertical length δ of the first step inclined portion δ, taper inclination angle γ of the second step, taper inclination angle α of the third step, 3, and the shape of the inclined portion vertical length β) is transferred to the left and right end portions of the band member 20 to transfer the shape to the outer surface of the pipe as shown in FIG. A predetermined taper shape (inclination angle α from the width end surface toward the surface that becomes the tube outer surface, plate thickness direction distance β from the surface that becomes the tube outer surface at the start position of the width end surface) is given to the left and right width end portions. A predetermined taper shape at the left and right width ends on the side that becomes the tube inner surface (from the width end surface to the tube inner surface The inclination angle γ towards the surface, so as to impart a thickness direction distance [psi) from the surface of the inner surface of the starting position in the width end face. However, if one of the three fin angles is larger than the vertical direction of the fin pass roll, the width end of the band material is scraped off by the fin, resulting in a surplus material called “beard”. Since fins are formed at the time of forming the fin path and sparks of ERW welding are caused, the angle of the fin is preferably set to be equal to or less than the vertical direction.

  And about the taper shape provided to the both right and left width end portions of the band member 20, the inclination angle α from the width end surface of the band member 20 toward the surface that becomes the outer surface of the tube and the inclination angle toward the surface that becomes the inner surface of the tube γ is 25 ° to 50 °, and the distance β in the strip thickness direction between the taper start position on the width end face and the surface serving as the pipe outer surface and the distance ψ in the strip thickness direction between the surface serving as the pipe inner surface Each of them is set to 20% to 40% of the strip thickness.

The reason is that if the inclination angles α and γ are less than 25 °, the molten steel is not sufficiently discharged from the central portion of the strip thickness, the penetrator remains and becomes defective, and the toughness and strength after ERW welding decrease. When the inclination angles α and γ exceed 50 ° , the taper shape remains as a flaw of the pipe of the product even after the electric resistance welding. Further, if the taper starting distances β and ψ are less than 20% of the plate thickness, the molten steel discharge at the central portion of the plate thickness is insufficient and the penetrator tends to remain, and the taper starting distances β and ψ are the plate thickness. On the other hand, if it exceeds 40%, the taper shape remains as a wrinkle of the tube of the product even after the ERW welding, which is a problem.

  As described above, in this embodiment, the fin shape of the fin pass molding final stand 3b has a shape having three-step angles, and the fin shape is transferred to the left and right width end portions of the band member 20. Therefore, the shape of the width end portion of the strip 20 immediately before the electric resistance welding can be set to an appropriate taper shape. As a result, a sufficient amount of molten steel is discharged at the time of electric resistance welding, and the penetrator is surely removed, so that an electric resistance welded tube with good welded portion characteristics can be obtained.

(Third embodiment)
The electric sewing tube manufacturing line used in the third embodiment of the present invention is also the one shown in FIG.

  In the third embodiment, as shown in FIG. 4A, a cross-sectional view is shown, and FIG. 4B is a partial detailed view thereof, the fins of the first fin path molding first stand 3a have two stages. A taper shape (vertical length δ of the first-stage inclined portion, second taper inclination angle γ) is provided, and the shape is transferred to the left and right width end portions of the band member 20 to obtain the shape shown in FIG. ) As shown in the figure, the right and left width ends on the side that becomes the tube inner surface have a predetermined tapered shape (inclination angle γ from the width end surface toward the surface that becomes the tube inner surface, the surface that becomes the tube inner surface at the start position on the width end surface Plate thickness direction distance ψ), as shown in FIG. 4 (d), a cross-sectional view, and FIG. 4 (e), a partial detail view thereof. As shown in FIG. It has a taper shape (taper inclination angle α of the second stage, vertical length β of the inclined part of the second stage), 4 is transferred to the left and right width end portions of the band member 20, and as shown in FIG. 4 (f), a predetermined taper shape (from the width end surface to the pipe outer surface is formed on the left and right width end portions on the side that becomes the tube outer surface. An inclination angle α toward the surface, and a plate thickness direction distance β) from the surface that becomes the outer surface of the tube at the starting position at the width end surface.

  By the way, when the taper shape is given to the width end part which becomes the inner surface of the pipe by the fin pass molding first stand 3a, the portion is remarkably processed and hardened by strong pressure. Therefore, even if the taper shape is given by the fin pass molding second stand 3b, The taper shape provided by the first stand 3a is relatively difficult to collapse. Therefore, a predetermined taper shape can be imparted to the width end portion of the strip after completion of the fin pass molding on both the tube inner surface side and the tube outer surface side.

  And about the taper shape provided to the both right and left width end portions of the band member 20, the inclination angle α from the width end surface of the band member 20 toward the surface that becomes the outer surface of the tube and the inclination angle toward the surface that becomes the inner surface of the tube γ is 25 ° to 50 °, and the distance β in the strip thickness direction between the taper start position on the width end face and the surface serving as the pipe outer surface and the distance ψ in the strip thickness direction between the surface serving as the pipe inner surface Each of them is set to 20% to 40% of the strip thickness.

The reason is that if the inclination angles α and γ are less than 25 °, the molten steel is not sufficiently discharged from the central portion of the strip thickness, the penetrator remains and becomes defective, and the toughness and strength after ERW welding decrease. When the inclination angles α and γ exceed 50 ° , the taper shape remains as a flaw of the pipe of the product even after the electric resistance welding. Further, if the taper starting distances β and ψ are less than 20% of the plate thickness, the molten steel discharge at the central portion of the plate thickness is insufficient and the penetrator tends to remain, and the taper starting distances β and ψ are the plate thickness. On the other hand, if it exceeds 40%, the taper shape remains as a wrinkle of the tube of the product even after the ERW welding, which is a problem.

  As described above, in this embodiment, in the fin pass pressure, the fin shape of the first stand 3a at the front stage and the fin shape of the second stand 3b at the rear stage are each formed into a shape having two-stage angles, and those fin shapes Is transferred to both the left and right width end portions of the band member 20, the shape of the width end portion of the band member 20 immediately before ERW welding can be set to an appropriate taper shape. As a result, a sufficient amount of molten steel is discharged at the time of electric resistance welding, and the penetrator is surely removed, so that an electric resistance welded tube with good welded portion characteristics can be obtained.

  In the first to third embodiments described above, a taper shape is given to the tube outer surface side of the band material and / or the width end portion on the tube outer surface side of the fin-pass molding final stand (here, the second stand 3b). The reason for this is that electric resistance welding is performed immediately after that, so that electric resistance welding can be performed while maintaining a good taper shape. However, a taper shape may be given to the width end portion of the band material at the fin-pass molding start stand or the intermediate stand, and the taper shape may not be given to the fin-pass molding final stand. Once a taper shape is applied to the width end of the strip, the width end surface is significantly hardened by strong pressure, so that the taper shape is relatively difficult to collapse even after fin pass molding. The state to which the shape is imparted can be maintained.

  Hereinafter, a description will be given based on examples.

  Here, an electric resistance welded tube of φ600 was manufactured using a strip (steel strip) having a plate width of 1920 mm × 19.1 tmm. 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.

( Reference Example 1) As Reference Example 1, the above-described electric resistance welded tube was manufactured based on the first embodiment described above. That is, a taper shape was given to the band material width end portion on the side that becomes the outer surface of the pipe by a fin pass molding final stand in which the fin has a two-stage angle (the first stage angle of the fin is 85 °). The inclination angle α was 30 °.

( Reference Example 2) As Reference Example 2, the above-mentioned electric resistance welded tube was manufactured based on the second embodiment described above. That is, in the two-stand fin path molding, the first stand with the fins having three-stage angles (the second-stage angle of the fins is 40 °) and the band width end on the side that becomes the pipe outer surface and the pipe inner face A taper shape was given to the band material width end on the side to be formed. The inclination angle α on the tube outer surface side and the inclination angle ψ on the tube inner surface side were both 25 °.

  (Invention Example 3) As Invention Example 3, the above-mentioned electric resistance welded tube was manufactured based on the above-described third embodiment. That is, in the three-stand fin pass molding, a taper shape is formed at the end of the band material width on the side that becomes the inner surface of the pipe by a first stand having a two-step angle (the first step angle of the fin is 60 °). In addition, a taper shape was given to the band material width end portion on the side that becomes the outer surface of the tube by a third stand (an angle of the first step of the fin is 85 °) in which the fin has a two-step angle. The inclination angle α on the tube outer surface side was 30 °, and the inclination angle γ on the tube inner surface side was 40 °.

  (Conventional Example 1) As Conventional Example 1, the above-described electric resistance welded tube was manufactured based on the method described in Patent Document 1 described above. That is, in the fin-pass molding first stand where the fin has a one-step angle, the width end of the strip is brought into contact with the fin to approximately ½ of the plate thickness, thereby tapering the width end on the inner surface side of the pipe. In the second fin pass molding second stand having a shape and a fin having a one-step angle, the width of the band member is brought into contact with the fin for the other half of the plate thickness, It aimed to give a taper shape to the width end part. The inclination angle of the taper shape was 20 °.

  (Conventional Example 2) As Conventional Example 2, the above-described electric resistance welded tube was manufactured based on the method described in Patent Document 2 described above. That is, by installing an edger roll on the upstream side of the fin pass molding and using the edger roll to reduce the width end of the band, a taper shape is given to the entire width end of the band, and the fin has one stage. In the fin pass forming stand having an angle of, the width end portion on the outer surface side of the tube was shaped into a vertical surface by bringing the width end portion of the strip material into contact with the fin to approximately ½ of the plate thickness. . The inclination angle of the taper shape was 20 °.

  (Conventional Example 3) As Conventional Example 3, in the production line shown in FIG. 1, the width end portion of the band material is polished into a rectangle, and the fin path forming stand in which the fin has a one-step angle is used. The electric resistance tube was manufactured.

  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. Also. The result of observing the shape at the width end portion of the band end width just before ERW welding was cut out and collected.

From Table 1, in Reference Examples 1 and 2 and Invention Example 3, the impact strength of the welded portion is high, the brittle fracture surface ratio is small, the toughness is good, and the reliability of the product is high. Compared with this, in the conventional examples 1 to 3, the impact strength of the welded portion was low, the brittle fracture surface ratio was large, the toughness was lowered, and the reliability of the product was poor. Moreover, when comparing the band material width end shape immediately before ERW welding after the fin pass forming, in Reference Examples 1 and 2 and Invention Example 3, the width end on the tube inner surface side and the width on the tube outer surface side While the desired tapered shape was maintained at both ends, in the conventional examples 1 and 2, the width end was smoothed during fin pass molding, and the tapered shape was not maintained.

  Therefore, it was confirmed that an electric resistance welded tube with good welded portion characteristics can be manufactured by the present invention.

It is explanatory drawing of an electric sewing pipe manufacturing line. It is a figure for demonstrating 1st Embodiment used as a reference of this invention. It is a figure for demonstrating 2nd Embodiment used as a reference of this invention. It is a figure for demonstrating the 3rd Embodiment of this invention. It is a figure for demonstrating a prior art (technology of patent document 1). It is a figure for demonstrating a prior art (technology of patent document 2).

Explanation of symbols

1 Uncoiler 2 Leveler
3 Fin Pass Forming Stand 3a Fin Pass Forming First Stand 3b Fin Pass Forming Second Stand 4 Roll Forming Machine 5 Induction Heating Device 6 Squeeze Roll (Electro-Seam Welding Section)
7 Bead cutting tool 8 Sizer 9 Pipe cutting machine 20 Band material 30 Pipe

Claims (1)

A method for manufacturing an electric resistance welded tube, which is formed by roll forming a band material and butting the width end portion together to form an electric resistance welded tube, wherein the fin is formed into a shape having a two-stage angle in fin path forming during roll forming. by transferring the fin-shaped in the width end portion of, and applying a tapered shape in both strip width end portion of the tube outer surface and comprising a side strip width end and inner surface of the side fin pass forming The taper shape is given to the band width end portion on the side that becomes the tube inner surface in the preceding stage, the taper shape is given to the band width end portion on the side that becomes the tube outer surface in the fin pass molding final stand, and the taper shape is The angle of inclination from the width end surface of the strip to the surface serving as the tube outer surface and the surface serving as the tube inner surface is 25 ° to 50 °, and the taper starting position and the surface serving as the tube outer surface and the tube inner surface at the width end surface of the strip Distance in the thickness direction of the strip The absorbed energy at −46 ° C. at the center of the weld thickness is 125 J or more, and the brittle fracture surface ratio is 35%, where the penetrator characterized by the separation being 20% to 40% of the strip thickness is removed. A method for producing an electric resistance welded tube having good welded portion characteristics as follows .

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