JP4816015B2 - High-efficiency manufacturing method for ERW pipes with good weld characteristics - Google Patents

Description

  The present invention relates to a high-efficiency manufacturing method for electric resistance welded pipes with good welded part characteristics, and particularly welding for pipes that require toughness of welded parts such as for oil well line pipes or casing pipes for oil wells. The present invention relates to a manufacturing method capable of manufacturing a pipe that requires strength of a part with high efficiency in response to a change in product dimensions.

  Usually, the pipe is roughly classified into a welded pipe and a seamless pipe. The welded pipe is manufactured by rounding the width of the strip material and welding by welding both ends of the rounded width, as in the case of an ERW steel pipe, and the seamless pipe drills a lump of material at a high temperature, It is manufactured by rolling with a mandrel mill. 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 material, and in the application of the pipe, guarantee of the toughness and strength of the welded part has always been discussed for each application.

For example, in line pipes that transport crude oil, natural gas, etc., low temperature toughness is important because pipe laying sites often hit cold regions, and casings for protecting mining tubes in oil wells for crude oil mining Pipes are needed and the strength of the pipes is important.
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 ensured.

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, development of the welding technique was important.
As a cause of poor ERW welding, the oxide generated on the welded end face, called a penetrator, remains without being discharged from the end face together with the molten steel during ERW welding. There were many examples of insufficient strength.

Therefore, conventionally, in order to remove the penetrator, which is the main cause of poor ERW welding, from the welded portion, techniques for actively discharging molten steel from the welded end face have been intensively studied. For example, Patent Documents 1 and 2 describe examples in which the shape of the end face to be welded is examined. In other words, the welded end face is generally rectangular due to slits and end face grinding, but this is tapered before roll forming, and the processed end shape improves the discharge of molten steel during welding. It is aimed.
JP 2001-170779 JP 2003-164909

Since the conventional method described above merely introduced the taper processing means by using the taper processing means alone or giving the taper shape to the width end surface of the band material, it is specifically introduced between the electro-sewing processes. There are various problems in applying to the manufacturing process, and further detailed examination is necessary.
In the actual ERW manufacturing process, strips of various thicknesses are made into ERW welded pipes. For example, when the shape of the width end face of the strip is adjusted using a perforated roll alone, Since different perforated rolls must be prepared for each material thickness and replaced with the rolls, the production efficiency of the tube is low, which is a problem. Also in the case of cutting tools and grinding rolls, the positions of the cutting tools or grinding rolls on one end side and the other end side in the thickness direction of both ends of the width of the strip material are accurately determined according to the thickness of the strip material. In order to achieve a good taper shape for ERW welding, it is necessary to finely adjust the distance between these cutting tools or grinding rolls according to the thickness of the strip. The efficiency was significantly reduced.

  Therefore, the present invention flexibly corresponds to the change in the thickness of the strip material, and the shape of both ends of the rounded width of the strip material immediately before the ERW welding is surely formed into a desired tapered shape, so that the welding quality is improved. It is an object of the present invention to provide a highly efficient manufacturing method of an electric resistance welded tube that can be held and has good welded portion characteristics.

In order to achieve the above object, the inventors examined a means for providing a tapered shape at both ends of the width of the strip without reducing the production efficiency even if the thickness of the strip changes, and It came to an eggplant.
That is, the present invention relates to a method of manufacturing an electric resistance welded tube in which a strip is molded, end portions are butted together and welded to form a pipe, and the molding on either one of the upper and lower surfaces of the strip is performed before the molding. A taper shape is imparted by cutting or grinding the end portion, and a taper shape is imparted to the end portion on either one of the upper and lower surfaces facing the one surface side by fin pass rolling during the forming. This is a high-efficiency manufacturing method for ERW pipes with good weld-part characteristics.

  In the present invention, it is preferable that one surface side of the strip is an upper surface side, and the taper shape has an inclination angle from the width end surface of the strip to the inside of the strip starting from each of the upper and lower surfaces of the strip. It is preferable that the taper surface that is 25 degrees or more and 50 degrees or less has a shape in which the strip thickness direction distance from the start point to the end point is 20 to 40% of the strip thickness.

  According to the present invention, the shape of both ends of the rounded width of the band material immediately before the ERW welding is made into a desired taper shape in a flexible manner corresponding to the change in the thickness of the band material, and the welding quality is improved. Since it can hold | maintain, the ERW pipe which has remarkably favorable weld part toughness and weld strength can be manufactured with high efficiency.

In the present invention, the forming of the strip is to round the width of the strip in a stepwise manner so that the cross section of the strip is circular, and the forming process is performed at the ends on both sides in the width direction of the strip. A roll forming initial stage in which bending in the vicinity of the part is performed, and a fin pass rolling stage in which the strip is finally finished into a circular cross section.
In the present invention, a means for imparting a taper shape to an end portion on either one of the upper and lower surfaces of the belt member, and a taper shape to an end portion of any one of the upper and lower surfaces facing the one surface side are provided. The means are of different types, and a plurality of means are provided with a tapered shape at the end. As a result, if a taper shape is applied to the end portion on the one surface side and then a taper shape is applied to the end portion on the other surface side, the taper shape of the device that applies the taper shape can be obtained even if the band material thickness varies. Only by adjusting the position in the vertical direction, a taper shape can be imparted to the end portions on both the upper and lower surfaces of the band without lowering the production efficiency.

  Therefore, on the roll forming entrance side, since the strip is substantially flat, it is preferable to give a taper shape by grinding or cutting. These taper-shaped applying means require a relatively large installation space because the device is relatively large, and the width of the strip material being rounded during and after roll forming, and the mutual spacing between both ends of the rounded width It is difficult to install because it narrows. In addition, it is difficult for cutting and grinding devices to constrain the end of the strip material up and down by itself, so the installation position accuracy of the device is required in addition to the device that maintains the positional accuracy through which the strip material passes. Is done. Therefore, it is necessary to increase the rigidity of the gantry of the apparatus, and a wider installation space is required. Therefore, the cutting or grinding means is preferably before roll forming.

  Here, when the end of the strip is cut or ground on both the upper and lower sides, the end of the strip is strongly pressed in order to fill the strip with the fin pass roll in the fin pass rolling in the middle of roll forming. The shape may be crushed and a desired shape may not be obtained. Therefore, it is better to preliminarily give a taper shape larger than the desired taper shape in consideration of the crushing of the end of the strip in fin pass rolling. However, taper is given to both the upper and lower sides of the end of the strip. Then, since it is difficult to obtain a large taper shape due to the limitation of the thickness of the band material, it is preferable to cut or grind only one of the upper and lower surfaces.

  Next, for the other surface side portion of the end portion to which the taper shape has not yet been imparted, the taper shape is imparted by utilizing fin pass rolling. For the reasons described above, only one of the upper and lower surfaces is provided with a tapered shape. To provide a tapered shape on both the upper and lower surfaces, it is preferable to provide a tapered shape on the other surface side during or after roll forming. . Therefore, the inventors paid attention to the fact that the end portion of the strip material is easily crushed by the above-described fin pass rolling, and decided to utilize this. That is, if the fins of the fin pass rolling roll are tapered in two stages and the taper angle of the fin and the strip end contact position are optimized in accordance with the fin pass rolling drawing amount (upset), the taper shape is still A taper shape can also be imparted to the other surface side portion of the end portion that is not imparted. Since this taper processing is performed by fin pass rolling itself, it can be sufficiently processed even if both end portions whose widths are reduced by roll forming and whose interval is narrowed are very close to each other.

Thus, even if the thicknesses of the strips are different, both end portions of the rounded width of the strip just before welding are provided with a desired tapered shape corresponding to the thickness of the strip in a flexible manner.
In addition, it is good to perform taper shape provision by cutting or grinding with respect to the upper surface side part of a strip width end part so that a comparatively large apparatus may not interfere with the strip material conveyance table by the side of roll forming. In this case, the lower surface side portion of the band material width end portion is a portion to be tapered by fin pass rolling, but the band material is usually rounded so that both ends in the width direction are on the upper side, and the width end portion of the band material is Since the lower surface side is the pipe outer surface side and the fin pass rolling roll is installed on the same side, it is easy to give a tapered shape to the same side by changing the fin shape of the fin pass rolling roll.

  In addition, as a result of optimization of the taper shape, from the upper and lower surfaces of the band material to the inner side of the band material from the width end surface of the band material (end surface that is almost perpendicular to the width direction (90 ° ± 5 degrees)) The thickness direction distance (referred to as taper distance T) from the start point to the end point of each taper surface having an inclination angle (referred to as taper angle θ) of 25 degrees or more and 50 degrees or less is 20 to 40% of the thickness of the band material. I figured out that it would be good to have a shape to become.

  That is, if the taper angle θ is less than 25 degrees, the molten steel discharge from the central portion of the strip material thickness becomes insufficient, the penetrator remains and becomes defective, and the toughness and strength after ERW welding decrease, On the other hand, if it exceeds 50 degrees, the taper shape remains as a wrinkle of the tube of the product even after ERW welding, which is a problem. Also, if the taper distance T is less than 20% of the strip thickness, the molten steel is not sufficiently discharged from the central portion of the strip thickness, and the penetrator tends to remain, whereas 50% of the strip thickness. If it is super, the taper shape remains as a flaw in the tube of the product even after ERW welding, which is a problem.

Hereinafter, a description will be given based on examples.
(Invention Example 1) In Invention Example 1, the pipe making machine shown in FIG. 1 was used. As shown in FIG. 1 (a), this pipe making machine pays out the band material 20 from the uncoiler 1, straightens it with the leveler 2, and gradually rounds the width of the band material with the roll forming machine 5, Both ends of the rounded width are electro-welded with an electric seam welding machine (consisting of an induction heating unit 7 and a squeeze roll (electric seam welding part) 8) to form a pipe 30, and the weld bead part of the pipe 30 is a bead part. After cutting with the cutting machine 9, the outer shape of the cut pipe 30 is adjusted with the sizer 10, and then cut into a predetermined length with the pipe cutting machine 11. The roll forming machine 5 includes a first breakdown stand 3 on the front stage side and a fin pass rolling stand 6 on the last stage.

Furthermore, in addition to the above basic configuration, a cutting blade having a roll shape as cutting or grinding means 4 on the entry side of the roll forming machine 5 and on the exit side of the leveler 2 is shown in FIG. The roll-shaped cutting blade cuts the band material upper surface side part at both ends in the width direction of the band material 20 and is disposed so that a taper shape having a predetermined taper angle θ and a predetermined taper distance T can be given to the part. And the fin pass rolling roll of the fin pass rolling first stand 6A, as shown in FIG. 1 (c), the fins are provided with two stages of taper, and the strips at both ends of the strip 20 having a width being rounded The lower surface portion of the material is rolled so that a taper shape having a predetermined taper angle θ and a predetermined taper distance T can be given to the same portion.

A steel pipe (tube) with an outer diameter of 600 mm is manufactured from a steel strip (band A) with a width of 1920 mm × thickness 19.1 mm using the pipe making machine shown in FIG. 1, followed by a steel strip with a width of 1920 mm × thickness 11.3 mm ( A steel pipe (tube) having an outer diameter of 600 mm was manufactured from the strip material B). During pipe making, a taper shape was imparted to the upper surface side of the band width end portion by cutting or grinding means 4 and to the upper surface side of the band material width end portion by the fin pass rolling roll of the fin stand rolling first stand 6A. The taper shape for strip A is the taper angle θ = 30 degrees on both the upper and lower sides, and the taper distance T = 5 mm (26% of the strip thickness). = 30 degrees, taper distance T = 2.5 mm (22% of the strip thickness). When switching from the strip A (thickness 19.1 mm) to the strip B (thickness 11.3 mm), the cutting or grinding means 4 was moved 5.3 mm downward to finely adjust the cutting position.

  A test piece was cut out from the welded portion of the manufactured steel pipe and a Charpy test was performed to evaluate the performance. Each Charpy test piece is taken from 10 points with different positions in the longitudinal direction of the pipe, the length direction of the test piece is parallel to the circumferential direction of the pipe, the center of the notch length is taken as the center position of the weld thickness, and JIS 5 As a 2 mm V notch impact test piece of No. 1, an impact test was conducted at -46 ° C., and the absorbed energy and the brittle fracture surface ratio were measured. The acceptable performance range was an absorbed energy of 125 J or more and a brittle fracture surface ratio of 35% or less.

(Invention Example 2) In Invention Example 2, the taper angle θ was changed to 40 degrees in Invention Example 1, and a steel pipe was manufactured in the same manner as in Invention Example 1, and a Charpy test was performed. Evaluated.
(Comparative example) In the comparative example, the pipe making machine shown in FIG. 2 was used. As shown in the figure, this pipe making machine has the same basic configuration as FIG. Further, in addition to this basic configuration, a perforated rolling roll 12 is disposed on the entry side of the roll forming machine 5 and on the exit side of the leveler 2, and both ends of the strip 20 in the width direction are rolled to A taper shape having a predetermined taper angle θ and a predetermined taper distance T can be simultaneously imparted to the upper and lower surfaces of the belt material. Note that the fin pass rolling roll of the fin pass rolling roll stand 6 is different from the case of FIG. 1, as in the normal case, neither roll has a two-step taper on the fin.

  A steel pipe (tube) with an outer diameter of 600 mm is manufactured from a steel strip (band A) with a width of 1920 mm x thickness of 19.1 mm using the pipe making machine shown in Fig. 2, followed by a steel strip with a width of 1920 mm x thickness of 11.3 mm ( A steel pipe (tube) having an outer diameter of 600 mm was manufactured from the strip material B). During pipe making, the upper and lower sides of the end portion of the strip material were rolled by a perforated rolling roll 12 to give a tapered shape to the same part. The taper shape was the same as Example 1 of the present invention. When switching from the strip A (thickness 19.1 mm) to the strip B (thickness 11.3 mm), the operation of the pipe making machine is temporarily stopped and the taper-applying hole roll 12 is changed to the thickness 19.1. It changed from the thing for mm to the thing for thickness 11.3mm.

About the manufactured steel pipe, the Charpy test was done like Example 1 of this invention, and performance was evaluated.
(Conventional example) In the comparative example, using the one obtained by removing the taper-applying hole-type roll 12 from the pipe making machine of FIG. 2, during pipe making, the band member 20 does not give a taper shape to both ends in the width direction, A steel pipe was manufactured in the same manner as in the comparative example except that the cross section was kept rectangular, and the performance was evaluated by performing a Charpy test.

  Table 1 shows the results of measuring the Charpy impact value and the brittle fracture surface ratio in the welded portion of the steel pipe manufactured according to these examples. The production efficiency in these examples is also shown in Table 1. This production efficiency is represented by a relative ratio of the reciprocal of the production time to the value of the conventional example (normalized to 1).

  From Table 1, the product steel pipe 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. Compared to the conventional example, the product steel pipe according to the comparative example has a high impact strength at the welded portion and a low brittle fracture surface ratio, good toughness, high product reliability, but a low production efficiency. On the other hand, it is clear that the steel pipe according to the example of the present invention has the toughness of the welded portion equal to or higher than that of the comparative example, and the manufacturing efficiency is as high as that of the conventional example.

  In the above-described embodiment, the taper shape in which the upper surface side and the lower surface side of the strip are symmetrical with respect to the thickness center plane is provided, but not limited to this, the upper surface side and the lower surface side of the strip are thick. A taper shape that is asymmetrical with respect to the center plane may be provided. In addition, when using a pipe making machine whose top and bottom are opposite to those in FIG. 1 (ie, the upper surface side of the strip is the outer surface of the tube), the cutting before forming is given a taper shape by grinding, and the strip at the end of the strip width. It is good to perform with respect to a material lower surface side part, and to give the taper shape by fin pass rolling to the band material upper surface side part of a band width end part.

(A) is the equipment arrangement | positioning figure which shows the pipe making machine used for this invention example 1, (b) is the AA arrow directional view of (a), (c) is the BB arrow directional view of (a). It is equipment arrangement | positioning figure which shows the pipe making machine used for the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Uncoiler 2 Leveler 3 Breakdown 1st stand 4 Cutting or grinding (cutting or grinding means)
5 Roll forming machine 6 Fin pass rolling (fin pass rolling stand)
6A Fin pass rolling 1st stand 7 Induction heating part 8 Squeeze roll
9 Bead cutting machine 10 Sizer 11 Pipe cutting machine 12 Perforated rolling roll 20 Steel strip (band)
30 Steel pipe (pipe)

Claims (3)

  In a method of manufacturing an electric resistance welded tube, which is formed by forming a strip and butting ends together and forming a pipe by electro-welding, cutting or grinding is performed on the end on one of the upper and lower surfaces of the strip before the forming. To give a tapered shape, and impart a tapered shape to the end portion on either one of the upper and lower surfaces facing the one surface side by fin pass rolling during the forming. A high-efficiency manufacturing method for good ERW pipes.   The method for manufacturing an electric resistance welded tube with good welded portion characteristics according to claim 1, wherein one surface side of the strip is defined as an upper surface side.   The taper shape is the thickness of the band material from the start point to the end point of each taper surface where the inclination angle from the width end surface of the band material to the inner side of the band material is 25 degrees or more and 50 degrees or less starting from the upper and lower surfaces of the band material. The method of manufacturing an electric resistance welded tube with good welded portion characteristics according to claim 1 or 2, wherein the distance in the length direction is 20 to 40% of the thickness of the strip.

Images