JP2005066679A - Method and apparatus for manufacturing welded steel tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method and a manufacturing apparatus of a welded steel tube by which a small-diameter ultrathin ultrahigh strength welded steel tube is manufacturable by further improving a CBR forming method. <P>SOLUTION: This method comprises pressing both side parts near the bottom of a tube stock 2 in the thickness direction with press rollers 5 from the side of the inside until entrance to a first fin pass rolls 1F while both side parts are continuously restrained and supported with cage rolls CR after discharge from the final center bending roll 4CB. The apparatus therefor is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for manufacturing a welded steel pipe, and more specifically, an open tubular element pipe is formed by rounding the width of a strip by a CBR forming method (chance-free stretch roll forming method). In the method of manufacturing a welded steel pipe, in which a welded steel pipe is manufactured by welding a seam in a direction, the CBR forming method is applied to ultra-high strength (TS800 MPa class) welding with a small diameter (outer diameter of 100 mm or less), ultrathin wall (thickness of less than 2 mm). The present invention relates to a method for manufacturing a welded steel pipe adapted for manufacturing a steel pipe, and an apparatus suitable for carrying out the method.

In the ERW steel pipe manufacturing process, the CBR forming method (Chance-free roll forming) is known as a roll forming technique for forming a strip as a material into an open tubular element tube. (See, for example, Non-Patent Document 1, Patent Documents 1, 2, and 3). In Patent Documents 1 to 3, the name CBR molding method is not used, but a technique that is substantially included in the CBR molding method is disclosed. The CBR forming method involves upstream forming and bending of the strip width end and bending center of the strip width to form an oblong-shaped element tube, and downstream forming (fin pass forming) In addition to performing overhang forming, each stand performs shared forming in the circumferential direction of the pipe. In particular, in the first fin pass roll, four locations on the circumference of the pipe are formed to a radius smaller than the product radius. It has the feature of performing overbend molding. That is, as shown in FIG. 1 (b), a fin pass molding flower (flower is a figure drawn by an outline of a material cross section perpendicular to the tube forming pass line direction) in the CBR molding method is shown in FIG. 1 (a). 5) (R ₁ , R ₂ , R ₃ , R ₄ , R ₅ ) as opposed to 2 radians (R ₁ , R ₂ ) in the conventional circular bend-based molding method shown in FIG. In the CBR forming method, the first fin pass roll is used to suppress bending forming of the C portion corresponding to the raw pipe side portion, and overbend forming having a bending radius smaller than the product radius is added to the B and B ′ portions. Then, with the second fin pass roll (or further with the third fin pass roll), the portion C is stretched and bent, and the portions B and B ′ are bent back, and the whole is brought close to the product curvature. The A and D parts are molded to a predetermined curvature by upstream molding.

  According to this, several excellent characteristics such as expansion of the V-shape angle of the raw pipe joint, suppression of roll wrinkles, reduction of residual stress, and the like are brought about.

For the implementation of the CBR molding method, for example, a CBR molding mill having a line configuration as shown in a plan view in FIG. 2 is used. That is, the CBR forming mill includes, from the upstream side, an edge bend roll EB that bends the width end portion of the strip 1 and a center bend roll group (for example, center bend rolls 1CB, 2CB, 3CB, and the like) 4CB), a fin pass roll group (for example, first and second fin pass rolls 1F, 2F) that performs the horizontal bulge forming of the raw tube 2 bulging type and the divided forming in the circumferential direction of the raw tube at each stand Are arranged in this order, and the region extending from the edge of the strip 1 to the both sides of the raw tube 2 is continuous in the line area from the edge bend roll EB exit side to the first fin pass roll 1F entry side. A plurality of cage rolls CR that are restrained and supported are arranged. By using such a CBR forming mill, the center bend rolls 1CB, 2CB, 3CB, and 4CB for reducing the width of the strip 1 width, and both sides of the strip 1 from the width end of the strip 1 on both sides of these center bend rolls. The central portion of the strip 1 is bent by a plurality of cage rolls CR that continuously restrain and support the portion extending to the portion, and the oval-shaped element tube 2 is formed. The center bend rolls 1CB, 2CB, and 3CB all have a split twin roll structure. When the plate thickness and outer diameter size are changed, the roll is moved in the width direction and adjusted in the thickness direction. At the same time, the position of the cage roll CR is adjusted in accordance with the change of the size, and the roll is also used.
On the exit side of the CBR forming mill, a resistance welder RWD that heats the joint of the raw tube 2 to the welding temperature and a squeeze roll SQ that presses the heated joint are disposed. Instead of this resistance welder RWD, for example, as shown in a side view in FIG. 3, an induction welder IWD may be arranged on the squeeze roll SQ entry side. Further, as shown in this example, a rotary seam guide roll RSG for restraining the joint before welding may be disposed between the fin pass roll 2F and the induction welder IWD.
JP-A 61-135428 Japanese Patent Laid-Open No. 3-180212 JP 2000-343134 A Toyooka et al .: Kawasaki Steel Technical Report 22 (1990) 4, 236-244

  The CBR forming method is a technique that can advantageously form a base pipe (open pipe) for electric resistance welding as described above. However, there is a demand for manufacturing a welded steel pipe having a strength TS1000 MPa class, a wall thickness of less than 1.4 mm, and an outer diameter of 89 mm, which has not been manufactured so far, and in order to meet this demand, a raw pipe is formed by a conventional CBR forming method, As a result of conducting an experiment in which a welded steel pipe was prototyped by welding the raw pipe, as shown in FIG. 4, the actual flower 10 at the entrance side of the first fin pass roll did not have the shape as the target designed flower 11, For this reason, it has been found that the problem that edge waves occur in the fin pass roll forming stage and the welding becomes unstable remains as an unsolved problem. The present invention solves this problem, and further improves the CBR forming method so that a super-high strength (TS800 MPa class) welded steel pipe with a small diameter (outer diameter of 100 mm or less), ultrathin wall (thickness of less than 2 mm) can be manufactured. An object of the present invention is to provide a method and an apparatus for manufacturing a welded steel pipe.

  The inventors have intensively studied to achieve the above object, and as a result, in the conventional CBR molding method, an oval flower shape is obtained by the reduction of the center portion of the strip and the restraining support of the both ends of the strip. However, between the final center bend roll exit side and the first fin pass roll entry side, the external force applied to the raw pipe is only the pushing force by the cage rolls from both sides. Below, if the strip is an ultra-thin and ultra-high-strength material, the rigidity is too strong and the bending stress concentrates on the bottom of the blank tube, causing the waist to break and it is difficult to achieve the target flower shape. It was. And it turned out that this difficulty can be overcome by pushing the both sides close to the bottom of the raw tube in the thickness direction from the inner surface side. The present invention has been made based on these findings.

  That is, according to the present invention, in the method of manufacturing a welded steel pipe using the CBR forming method, from the end of the final center bend roll until the first fin pass roll is entered while being continuously restrained and supported by the cage roll on both sides. It is a method for manufacturing a welded steel pipe, characterized in that both side portions close to the bottom of the blank pipe are pressed in the thickness direction by a pressing roller from the inner surface side.

  In the present invention, an edge bend roll, a center bend roll group, a fin pass roll group, or further a rotary seam guide roll is arranged in this order, and a line area from the exit side of the edge bend roll to the first fin pass roll entry side In addition, a CBR forming mill in which a cage roll that continuously restrains and supports a portion from the both width ends of the strip to both sides of the raw pipe is disposed, and the joint of the raw pipe that has exited the CBR forming mill is set to the welding temperature. In an apparatus for manufacturing a welded steel pipe having a welding machine for heating and a squeeze roll that presses the heated seam, both side portions close to the bottom of the raw pipe between the final center bend roll and the first fin pass roll It is an apparatus for manufacturing a welded steel pipe, characterized in that an inner roller that pushes in the thickness direction from the inner surface side is disposed.

  According to the present invention, in the method of manufacturing a welded steel pipe using the CBR forming method, the elements whose both side portions are pressed by the cage roll between the final center bend roll exit side and the first fin pass roll exit side are provided. Since both side portions close to the bottom of the tube are pushed in the thickness direction by a roll from the inner surface side, the concentration of bending stress on the bottom of the raw tube during that time can be alleviated. Therefore, even when an ultra-thin, ultra-high-strength strip is piped to a small diameter, the waist does not break, and a raw tube as designed can be obtained, and edge waves are generated at the fin pass roll forming stage. It does not occur and the welding is stable, so that an ultra-high strength welded steel pipe having a small diameter and an ultra-thin wall can be obtained.

In the present invention, in the CBR forming mill having the line configuration as shown in FIG. 2 or FIG. 3, the element between the final one in the center bend roll group (for example, the center bend roll 4CB) and the first fin pass roll 1F is used. On the inner surface side of the tube 2, for example, a presser roller (inner roller) 5 as shown in FIG. 5 supported by a holder 8 is arranged, and using this, both side portions close to the bottom of the raw tube 2, that is, the bottom portion and the cage roll A pressing force in the thickness direction is applied to a total of two portions (this portion is referred to as a pressing portion), one on each of the left and right sides, where the outer surface side is in an unconstrained state between the CR contact portion. In order to hold the tube 2 at the pass line position against the downward component force of this pushing force, the bottom of the tube 2 is supported by the support roller 6. Here, when the presser part is the above two places, if the presser part is included in the range including the bottom part, a relatively large peripheral speed difference is generated between the center and the end of the presser roll, which may cause internal scuffing. Because it becomes.

  The pressing force of the presser roller 5 needs to be adjusted to an appropriate level without excess or deficiency according to the rigidity of the material or the like so that the actual flower of the raw tube 2 matches the designed flower. If the pressing force is too weak, the presser part moves to the inside of the designed flower and the effect of preventing hip breakage is poor. Conversely, if the pressing force is too strong, the presser part moves to the outside of the designed flower and the blank tube is deformed into a bulging shape. Tend to. In order to easily adjust the pressing force, the roller supporting arm 7 that supports the pressing roller 5 is provided with a pressing means that can adjust the pressing force, such as a manual jack, a spring with a variable spring constant, or a variable internal pressure. It is preferably supported by a fluid pressure cylinder or the like.

  FIG. 6 shows an example of a state in which the left and right coaxial type presser roller 5 shown in FIG. 5 is attached to the CBR forming mill. As shown in the figure, in this example, a support column 15 that collectively supports the center bend rolls 2CB, 3CB, and 4CB is erected between the last of the cage roll CR and the first fin pass roll 1F. The roller support arm 7 is supported by a manual jack 9 attached to the. In this example, the pass line length from the roll axis position of the edge bend roll EB to the roll axis position of the squeeze roll SQ is 10345 mm.

  The presser roller 5 is not limited to the left / right coaxial type as shown in FIG. 5, but, for example, as shown in FIG. 7, the left and right presser rollers 5 </ b> A and 5 </ b> B are arranged at different positions in the material direction. It is good. Since this staggered arrangement type can be configured to be smaller than the left and right coaxial type, there is a sufficient storage space, and it can be accommodated in an element pipe having a smaller diameter than the minimum diameter that can accommodate the left and right facing type. The cage roll CR and the support roller 6 illustrated in FIG. 7A are not illustrated in FIG. 7B.

  In the present invention, a shoe may be used instead of the presser roller. When a shoe is used instead of the presser roller, the bearing can be omitted and the holder can be further miniaturized, so it can be accommodated in a smaller diameter pipe, but it must be noted that internal flaws are likely to occur due to sliding. There is.

  This is a method in which a blank pipe is formed from a strip by means of the CBR forming method using the apparatus shown in FIG. 6 and the joint is welded. This is an ERW steel pipe (equivalent to JIS STKM) having a TS1000 MPa, a wall thickness of 1.4 mm, and an outer diameter of 88 mm. ) Was tried. The pressing force of the presser roll (inner roll) was set to a maximum of 9800 N with a manual jack. As a result, there was no edge wave at the fin pass molding stage, welding was stable and products with the desired quality were obtained. For comparison, an attempt was made to manufacture the ERW steel pipe using the same method as above except that the presser roll was removed from the apparatus shown in FIG. 6, but an edge wave was generated at the fin pass forming stage and welding was unstable. As a result, defects such as cold welding occurred frequently.

It is explanatory drawing of the comparison of the fin pass shaping | molding flower of the shaping | molding method (a) of a circular bend main body, and a CBR shaping | molding method (b). It is a top view which shows an example of the line structure of the conventional CBR shaping | molding mill. It is a side view which shows an example of the line structure of the conventional CBR shaping | molding mill. It is explanatory drawing which shows the problem of a prior art. It is sectional drawing (a) and the side view (b) of the left-right coaxial type presser roll which shows an example of embodiment of this invention. It is a side view of the whole apparatus which shows an example of the line structure of the CBR shaping | molding mill to which this invention is applied. It is sectional drawing (a) and side view (b) of the staggered arrangement type presser roll which shows an example of embodiment of this invention.

Explanation of symbols

1 Strip 2 Raw tube (open tube)
3 Welded steel pipe (ERW pipe)
5, 5A, 5B Presser roller (inner roller)
6 Lower support roller 7 Roller support arm 8 Holder 9 Manual jack
10 Actual flower on the first fin pass roll entry side ・ Designed flower on the first fin pass roll entry side
15 props
20 Direction of threading 1CB, 2CB, 3CB, 4CB Center bend roll 1F, 2F First and second fin pass roll CR Cage roll EB Edge bend roll IWD Welding machine (Induction welding machine)
RWD welding machine (resistance welding machine)
RSG rotary seam guide roll SQ squeeze roll

Claims (2)

  In the method of manufacturing a welded steel pipe using the CBR forming method, the bottom part of the raw pipe after the final center bend roll is entered and the both sides are continuously restrained and supported by the cage roll before entering the first fin pass roll. A method of manufacturing a welded steel pipe, characterized in that both side portions close to 1 are pressed in the thickness direction by a pressing roller from the inner surface side.   Edge bend roll, center bend roll group, fin pass roll group or further rotary seam guide roll are arranged in this order, and both widths of the strip in the line area from the exit side of the edge bend roll to the first fin pass roll entrance side A CBR forming mill in which a cage roll that continuously restrains and supports a portion from the end portion to both sides of the raw pipe is disposed, and a welding machine that heats the joint of the raw pipe that has exited the CBR forming mill to a welding temperature, In an apparatus for manufacturing a welded steel pipe having a squeeze roll that presses the heated seam, between the final center bend roll and the first fin pass roll, both side portions near the bottom of the base pipe are thickened from the inner surface side. An apparatus for manufacturing a welded steel pipe, wherein an inner roller that pushes in a direction is arranged.

Images