JP2008302379A - Method for manufacturing seam welded pipe having excellent welded property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making the shape of butted end portion just before a seam welding operation suitable for discharging penetrated oxide. <P>SOLUTION: Band steel 20 is formed by rolling by means of a rolling machine 4, and is formed into a pipe 30 by butting and seam-welding the end portions of the width. Tapered shapes are given to both of the inner surface side and the outer surface side of the end portions of the width so as to continue to the end surface perpendicular to the direction of the width by the same stand of the fin pass rolling 3 in the final step of the rolling operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an electric resistance welded tube excellent in welded portion characteristics, and in particular, manufactures a tube that requires welded portion toughness such as for oil well line pipes or a tube that requires welded portion strength such as a casing pipe for oil wells. Involved in how to do.

  Usually, pipes are roughly classified into welded pipes and seamless pipes. Welded pipes are manufactured by rolling strips (plates) by roll forming or the like and welding them with the end of the width, as in the case of ERW steel pipes. It is manufactured by rolling with a mandrel mill or the like. 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 are required to protect mining pipes in oil wells for crude oil mining. Therefore, the strength of the tube is regarded as important.
Usually, a hot-rolled sheet serving as 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 manufacture of the pipe, so that characteristics such as toughness and strength of the base material are ensured.

However, since the characteristics of the welded part are greatly influenced by the welding method more than the base material component design and heat treatment, especially in the case of ERW welding, the welded part has characteristics such as toughness and strength equivalent to the base metal. It was important to develop a weldable technique.
As a cause of failure in ERW welding, an oxide called penetrator is generated at the width end of the welded strip, and it remains without being discharged from the end surface together with the molten steel during ERW welding, and this residual penetrator causes toughness. 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 Document 1 and Patent Document 2 describe examples in which the shape of the width end portion of the band material is examined. Usually, the width end portion of the strip is made into a substantially rectangular end surface (end surface having the same shape as the end surface of the rectangular end portion) by slitting or end surface grinding. It aims at making molten steel discharge | emission favorable at the time of ERW welding with the processed width end part shape.
JP 57-31485 A Japanese Patent Laid-Open No. Sho 63-317212

However, in the above conventional method, it is difficult to make the taper shape at the end of the band width just before the ERW welding as intended, and the toughness of the welded portion of the ERW weld pipe has not been sufficiently improved. .
For example, in the case of Patent Document 1, a method is adopted in which the angle of the fin of the fin pass molding is set to one stage, and a taper is provided by partially contacting the material end portion (meaning the end portion of the band width). (See FIG. 3). However, when the present inventors examine this method, it is extremely difficult to change the upset amount of the fin pass molding from 0 to plus and try to bring only a part of the material edge into contact with the fin. There was found. This is because the material end portion is only slightly hardened, so the entire material end portion is easy to fully fill the fin (hole type), and the fin shape is almost completely transferred to the material end portion. It is. Alternatively, if the upset amount is negative, the material end portion does not completely fill the fin (hole type), and it is extremely difficult to contact only a part of the fin.

  For example, in the case of Patent Document 2, a smooth surface that is uniformly inclined over the entire thickness direction (inclined with respect to the thickness direction) is imparted to the end of the material by edger roll rolling during roll forming, and a part thereof A method is adopted in which only the material is made almost vertical (perpendicular to the width direction) by fin pass molding (see FIG. 4). However, when the present inventors examined, in order to give the smooth surface which inclined to the material edge part by the edger roll rolling in the middle of roll forming, as described in patent document 2, it corresponds to the inner surface side (pipe inner surface side). It is necessary to form with the edger roll 12 whose outer side is thicker than the outer side (the side corresponding to the outer side of the tube), but the end on the inner side of the material is scraped off by the roll and is called “beard” It is a problem because extra material may be generated. Furthermore, since a large reaction force that opens the pipe outwards acts in the cross-sectional direction of the material to be roll-formed (band material 20), the mutual pressure between the edger roll 12 and the material end is inevitably reduced. As a result, as in the case of Patent Document 1, even if the subsequent fin pass molding is performed while the material end is hard to be hardened under the edger roll pressure, the amount of upset in the fin pass molding is reduced. It has been found that it is difficult to give a shape as described in Patent Document 2 to the material end portion because the fin (hole type) is almost filled.

  As described above, in the conventional technique, there is a problem that it is difficult to make the shape of the butt end immediately before electro-sewing welding suitable for penetrator discharge.

The present invention has been made to solve the above-described problems, and the gist thereof is as follows.
1. In a method for manufacturing an ERW pipe, which is formed by roll-forming a band material and welding the width end portions together to form a pipe by electro-welding, a pipe having a width end portion is transferred by fin-shaped transfer at the same stand of the fin pass forming that is the final stage of the roll forming. A method for producing an electric resistance welded tube excellent in welded portion characteristics, characterized in that both a portion on the outer surface side and a portion on the tube inner surface side are provided with a tapered shape connected to an end surface perpendicular to the width direction.

2. 2. The method of manufacturing an electric resistance welded tube excellent in welded portion characteristics according to item 1, wherein the tapered shape is imparted by a first stand of fin pass molding.
3. 2. The method of manufacturing an electric resistance welded tube excellent in welded portion characteristics according to the item 1, wherein the tapered shape is imparted at a final stand of fin pass molding.
4). The taper shape has an inclination angle from the end surface perpendicular to the width direction to the inner side in the width direction of 25 to 50 °, and the extending depth from the end of the strip thickness to the inner side in the thickness direction is the thickness of the strip The method for manufacturing an electric resistance welded tube excellent in welded portion characteristics according to any one of the preceding items 1 to 3, wherein the ratio is 20 to 45% of the thickness.

  According to the present invention, an electric resistance welded tube having remarkably good toughness and welding strength can be manufactured.

In order to utilize fin pass forming to give a taper to the material end in a conventional ERW pipe manufacturing method, a part of the material end is pressed against the fin without filling the roll hole mold with the taper. A method of imparting a shape has been studied.
However, according to the study by the present inventors, even when the roll hole mold is not filled with the entire circumference of the material in the circumferential direction, when the material is inserted into the fin pass forming stand, As a result, the end of the material completely fills the fin part of the roll hole type. That is, when the open tubular material in which both ends in the circumferential direction are not joined is inserted into a fin-pass molding stand, the present inventors are positioned on the opposite side of the material end in contact with the fin and approximately 180 °. Even if the material does not fill the roll hole shape, the reaction force of the material that tries to bend the cross section (cross section in the width direction) into an arc shape is greatly affected by the beam bent at the bottom of the open tube. It was understood that a large compressive force was exerted on the end portion in the circumferential direction, and as a result, the material end portion was strongly pressed by the fin and the shape of the fin was transferred as it was to the end portion of the material.

Accordingly, the present inventors have studied means for actively utilizing this phenomenon, paying attention to the fact that the material edge is strongly pressed by the fin as described above. In other words, if the fins are provided with two or more levels of taper, the taper shape can be sufficiently transferred to the material end portion if the upset amount in fin pass rolling is 0% or more, and the desired taper can be provided. That ’s it.
Furthermore, it has been found that in order to easily give a taper shape to the material end portion, it is preferable to apply it simultaneously to both the inner surface side and the outer surface side with one stand (meaning of a fin pass molding stand, hereinafter the same). That is, using a plurality of stands, for example, when taper is applied to the outer surface side with one stand first and the inner surface side with another stand later, at the end portion on the outer surface side that is tapered first, In some cases, the dogbone may be formed in another stand, and the target taper shape may not be sufficiently provided.

Therefore, if both ends of the material (both ends in the circumferential direction and corresponding to both ends in the width direction of the band material before roll forming) are tapered on the same stand on the same side (at the same time), There is no such problem, and the taper can be stably provided.
Further, in one stand used for giving a taper to the inner and outer surface sides of the material with the same stand, it is sufficient to have a fin shape having three-step angles on both side surfaces of the fin. However, if any of the three fin angles is larger than the vertical direction of the fin pass forming roll (90 ° angle), the end of the material is scraped off by the fins, and the surplus is called “beard” In some cases, a material may be generated, which may cause wrinkles at the time of fin pass molding or cause sparks of electric resistance welding, so the angle of the fin is preferably set to a vertical direction (angle 90 ° or less). The angle of the fin here refers to the tilt until the imaginary plane inside the fin side faces the fin rotation center axis when it is tilted inside the fin with the end on the fin rotation center axis side being fixed. Is an angle.

  In addition, when a taper shape is given to one or both of the inner surface side and the outer surface side of the strip material end portion in the first stand for fin pass molding, the strip material end portion is a horizontal portion of the fin pass top roll (fin roll) ( Since it comes into contact with the inside of the roll by approaching from the arc-shaped portions on both sides of the fin (approaching the fin side surface), the end of the strip material easily fills the fin taper portion in the roll hole mold and gives a stable taper shape It's easy to do. In addition, since the applied portion of the material end portion once tapered in this way is significantly hardened by strong pressure, the taper is relatively difficult to be crushed even after the subsequent fin pass molding. The tapered shape can be maintained as it is.

Further, when the taper is applied to the end portion of the material at the final stand of the fin path, the electric resistance welding is performed immediately thereafter, and therefore, the electric resistance welding can be performed while maintaining a good taper shape without being crushed.
Since only fin-pass molding is used in the present invention, an equipment such as an edger roll or a grinding roll is not required, and it is not necessary to replace those rolls or a grinding wheel, so that an ERW pipe with high efficiency and good welding quality can be manufactured.

Furthermore, as a result of optimizing the taper shape at the end of the strip immediately before pressure welding, the taper of each portion has an inclination angle from the end surface perpendicular to the width direction to the inside in the width direction of 25 to 50 °, and the thickness of the strip It was grasped that the taper shape in which the extending depth from the edge to the inner side in the thickness direction of the band material is 20 to 45% of the thickness of the band material.
That is, if the tilt angle is less than 25 °, the molten steel discharge from the central portion of the plate thickness is insufficient, the penetrator may remain, and the toughness and strength of the ERW weld may be reduced. When the inclination angle is more than 50 °, the taper shape tends to remain as a product tube fist after welding.
Further, if the extension depth is less than 20% of the plate thickness, the molten steel discharge from the center portion of the plate thickness is insufficient and the penetrator tends to remain, while the extension depth is less than the plate thickness. If it exceeds 45%, when the end part is pressed with an unwelded tubular strip sandwiched between squeeze rolls, the opposite left and right end parts are likely to be displaced up and down, and electro-sealing welding cannot be performed normally. In many cases, the pipe cannot be formed into a tube, and even when electro-welding is possible, the taper shape tends to remain as a flaw in the product pipe after welding.

  FIG. 1 is a schematic view showing an example of an ERW pipe production line used in the practice of the present invention. This line pays out the strip 20 from the uncoiler 1, straightens it with the leveler 2, gradually rolls the strip 20 with the roll forming machine 4, and heats the left and right width ends of the rolled strip 20. An electro-welding welder comprising an execution part (induction heating means) 5 and a pressure-welding execution part (squeeze roll) 6 is electro-welded to form a pipe 30, and the weld bead part of the pipe 30 is cut by a bead cutting machine 7 and cut. After the outer diameter of the subsequent tube 30 is adjusted by the sizer 8, the tube 30 is cut to a predetermined length by the tube cutting machine 9.

The roll forming machine 4 includes a predetermined number of fin pass forming 3 stands in a most downstream stage, constraining the rounded plate end portion to have a shape close to a perfect circle (cross sectional shape). In this example, the first stand 3a and 2nd stand 3b are comprised of all 2 stands, but may be all 1 stand or all 3 stands or more.
In carrying out the present invention, the same fin path forming stand, for example, the second stand 3b of FIG. 1, is used, and the inner surface side (side corresponding to the inner surface of the tube) and the outer surface side (corresponding to the outer surface of the tube). When a taper is applied to the side of the second stand 3b, the fin shape in the second stand 3b has three-step angles as shown in FIGS. 2 (a) and 2 (b). The fin shape may be designed to the shape of FIG. 2B that matches the target taper shape of FIG. As described above, the inclination angles α and γ on the outer surface side and the inner surface side are preferably in the range of 25 to 50 °. Further, the extension depths β and δ are both preferably in the range of 20 to 45% of the plate thickness, and more preferably in the range of 41 to 45%.

Hereinafter, a description will be given based on examples.
Here, an electric resistance welded tube having an outer diameter of 600 mm was manufactured using a steel strip having a plate width of 1920 mm and a plate thickness of 19.1 mm as a strip member (plate). A test piece was cut out from the welded part of the manufactured electric resistance welded tube and a Charpy test was performed to evaluate the performance. Charpy test pieces are taken from 10 points with different pipe longitudinal positions one by one, with the specimen length direction parallel to the pipe circumferential direction and the notch length center taken as the weld thickness center position. As a 2 mm V notch impact test piece, an impact test at −46 ° C. was performed, and the absorbed energy (impact strength) 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 1 of the present invention) In Example 1 of the present invention, the fins of the third (final) stand of the fin pass molding were used using the same ERW tube production line as in FIG. As shown in FIG. 2 (b), the shape is a three-step angle shape (a normal one-step angle shape for the first and second stands). The taper shape similar to that of) was applied. The target taper shape was as shown in Table 1.

  (Invention Example 2) In Invention Example 2, the same ERW pipe production line as in FIG. 1 (the total number of fin pass molding stands is two), and the fin shape of the first fin pass molding stand is shown in FIG. As shown in Fig. 2 (c), the same three-step angle shape (normal one-step angle shape for the second stand) is applied to the inner and outer surfaces of the plate end. It was. The target taper shape was as shown in Table 1.

  (Invention Example 3) In Invention Example 3, using the same ERW tube production line as in FIG. 1 (however, the fin-pass molding stands are all three stands), the fin shape of the second stand of the fin-pass molding is illustrated. 2 (b) is the same three-step angle shape (normal one-step angle shape for the first and third stands), and this stand is similar to FIG. 2 (c) on the inner surface side and outer surface side of the plate end. The provision of a tapered shape was attempted. The target taper shape was as shown in Table 1.

(Conventional example 1) In the conventional example 1, the same ERW pipe manufacturing line as in FIG. 1 (two fin-pass forming stands were used, and the fin shape of each stand was a normal one-step angle), and FIG. By the method shown (the method described in Patent Document 1), the first stand 3a was tapered on the inner surface side, and the second stand 3b was tapered on the outer surface side. The target taper shape was as shown in Table 1.
(Conventional example 2) In the conventional example 2, the same ERW tube production line as in FIG. 1 (two fin-pass forming stands are used, and the fin shape of each stand is a normal one-step angle) is used. After applying a flat taper over the entire plate thickness direction at the edge of the plate with the edger roll 12 provided on the upstream side of the fin pass molding (the method described in Patent Document 2), The portion on the outer surface side of the taper was pressed with the fins of the first stand 3a for fin pass molding so as to be perpendicular to the width direction. The target taper shape was as shown in Table 1.

(Conventional Example 3) In Conventional Example 3, in the prior art example 1, the end of the plate width is ground flat before roll forming to form a rectangular end face, and the fin end forming is not tapered and the rectangular end face is maintained. (Similar to normal fin pass molding).
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. Table 1 also shows the results of observing the cross-sectional shape by cutting out the taper shape observation sample from the end of the material immediately before the electric resistance welding.

  As shown in Table 1, in the inventive example, compared with the comparative example, 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. On the other hand, in the conventional example, the impact strength of the welded portion is extremely low, the brittle fracture surface ratio is large, the toughness is lowered, and the reliability of the product is poor. In addition, when comparing the shape of the material end portion immediately before ERW welding after the fin pass molding, the example of the present invention was able to give the desired tapered shape on both the inner and outer surfaces, whereas the conventional examples 1 and 2 were both tapered. Is insufficient, and it can be seen that the film has been smoothed in the thickness direction.

It is a side surface schematic diagram which shows an example of the ERW pipe manufacturing line used for implementation of this invention. It is a cross-sectional schematic diagram which shows an example of the taper provision method which concerns on this invention. It is a cross-sectional schematic diagram which shows one example (conventional example 1) of the conventional taper provision method. It is a cross-sectional schematic diagram which shows one example (conventional example 2) of the conventional taper provision method.

Explanation of symbols

1 Uncoiler 2 Leveler 3 Fin pass molding
3a The first stand for fin pass molding
3b 2nd stand of fin pass molding 4 Roll forming machine 5 Heating execution part (induction heating means)
6 Pressure welding section (squeeze roll)
7 Bead cutting machine 8 Sizer 9 Pipe cutting machine
11 End face perpendicular to the width direction of the strip
12 Edger roll
13 Fin part aligned with the end face perpendicular to the width direction of the strip
20 Band material (board)
30 tubes

Claims (4)

  In a method for manufacturing an ERW pipe, which is formed by roll-forming a band material and welding the width end portions together to form a pipe by electro-welding, a pipe having a width end portion is transferred by fin-shaped transfer at the same stand of the fin pass forming that is the final stage of the roll forming. A method for producing an electric resistance welded tube excellent in welded portion characteristics, characterized in that both a portion on the outer surface side and a portion on the tube inner surface side are provided with a tapered shape connected to an end surface perpendicular to the width direction.   The method of manufacturing an electric resistance welded tube excellent in welded portion characteristics according to claim 1, wherein the tapered shape is imparted by a first stand of fin pass molding.   The method of manufacturing an electric resistance welded tube excellent in welded portion characteristics according to claim 1, wherein the tapered shape is imparted at a final stand of fin pass molding.   The taper shape has an inclination angle from the end surface perpendicular to the width direction to the inner side in the width direction of 25 to 50 °, and the extending depth from the end of the strip thickness to the inner side in the thickness direction is the thickness of the strip The method for manufacturing an electric resistance welded tube excellent in welded portion characteristics according to any one of claims 1 to 3, wherein the ratio is 20 to 45%.

Images