JPS6024220A - Formation of electric welded steel pipe - Google Patents

Abstract

PURPOSE:To form a titled pipe stably and easily and to improve its dimensional accuracy by bending the central part of a strip into a U-shaped flower through rough and intermediate formings and forming its edge part into a prescribed curvature through a fin pass forming before providing a width bulging to it. CONSTITUTION:In rough and intermediate formings, only the central part of a strip is bent into a U-shaped flower by a supporting roll for continuously constraining the edge part of strip and plural bending rolls for constraining and forming the central part. In a fin pass forming, the edge part is formed into a prescribed curvature and each boundary part of edge, side, and bottom parts of a blank pipe is overbent by restraining the bend forming of the side part of blank pipe by a roll located at the upstream side, and the blank pipe is subjected to rolling reduction by succeeding rolls mainly in the decreasing direction of the longitudinal diameter to bulge it in the width direction in sequence, thereby bend forming the side part and return bending the overbent part. In this way, the forming of strip is performed stably and easily, and the dimensional accuracy of pipe shape and the quality of welding are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an electric resistance welded steel pipe, in which a strip is continuously roll-formed and the edges of the raw pipe are welded via fin pass rolls.

In general, in the manufacturing method of ERW steel pipes in which the seam line extends parallel to the pipe axis, a strip cut in advance to the developed size of the ERW steel pipe to be manufactured is rolled into various forming rolls during rough and intermediate forming processes. After forming into a specified shape, the seam edge is stably formed using fin pass rolls in the final forming process. After forming into a blank pipe of the specified shape and size, the seam edge is welded using squeeze rolls. It is carried out. In the VW of such ERW steel pipes, there are various factors such as the preforming of the raw pipe, the welding quality of the ERW steel pipes, the forming yield,
It affects productivity, mill operation rate, equipment cost, roll cost, etc., and therefore the selection of the molding method is extremely important.

The above method for forming electrically clamped steel pipes is achieved by selecting the coil cross-sectional forming shape, that is, the forming flower, in the forming process, which can be said to be a software technique, and the specific forming method using hardware forming equipment, and combining them. It is configured. Here, the J & shape flower is used when roll forming a strip. The process in which the strip is formed sequentially by each roll as the plate progresses,
It refers to a diagram expressed by the cross-sectional shape of the formed strip.

In the conventional ERW steel pipe forming method, the forming flower in the rough and intermediate forming processes is rejected during the subsequent fin pass forming process, and in order to reduce the forming load, the entire strip is bent during the phase and intermediate forming processes. For example, the circular bending method shown in FIG. 1(A), the combination molding method of circular bending and edge bending shown in FIG. 1(B), and the W bending and circular bending method shown in FIG. 1(C). A combination molding method of circular bend, edge bend, and center bend as shown in FIG. 1(D) is employed. However, these forming methods have problems such as an increase in the number of forming rolls in the intermediate forming process, an increase in the length of the forming line, an increase in roll adjustment and replacement time, and a narrowing of the range in which the rolls can be used together.

In addition, as a molded flower in the rough and intermediate molding process described in 1-
Although there is a center bend molding method, it is hardly adopted for the following reasons, and it is not technically established. In other words, the center bend forming method is a method in which bending is performed sequentially from the center of the strip toward the edge of the strip, and in the rough and intermediate forming processes, the center of the strip is bent. Bending during this forming process is easier than with other forming methods. However, since edge portions are not formed in the rough and intermediate forming processes, edge bending is required in the subsequent fin pass forming, which increases the fin pass forming C1 load and makes edge forming in the fin pass extremely difficult. In addition, this molding method
During the phase and intermediate forming processes, the spatial locus length of the strip edge is the longest compared to other forming methods, and edge stretch is large, and the buckling resistance is low because the edges are not bent. Therefore, there is a problem in that edge waves are likely to occur between roll stands.

Next, in the conventional method of forming electric resistance welded steel pipes,
Z J&, As for the fin pass molding flower in the shaping process, that is, the fin pass molding process, two molding methods shown in FIGS. 2(A) and 2(B) are known. One of them is shown in Fig. 2 (A), which is a forming method generally called Yoder or Matsukei molding flower, in which the entire raw pipe is gradually bent to the width, and the entire raw pipe is rolled up. This is an overall width bending method. The other one is the second
The molding method shown in Figure (B) is generally called Etna-type flower molding, in which the lower half of the raw tube is preformed to the final cylindrical curvature in the rough and intermediate forming areas. The upper half is formed to a curvature of about 50 to 70% of the final formed cylindrical curvature, and the upper half of the raw tube is bent to the width in the fin pass forming process, and the edge part is formed using a partial width bending method. be.

FIGS. 3(A) and 3(B) respectively show the above Yoder,
FIG. 3 is a diagram showing a change in projection locus in the fin pass forming process of the edge and side portion of the raw pipe based on the idea of the Matsukei type molded flower and the Etna type molded flower. According to FIG. 3, it can be seen that the projected locus in the width direction of the side portion of the blank tube is of a gradually decreasing type or constant type, and the projected locus of the edge of the blank tube in the height direction is of a gradually decreasing type. From this, it can be said that the conventional fin pass forming method is a reso-use type forming method that mainly involves bending the raw pipe toward its width.

In the above-mentioned Yoder and Matsukui molded flowers, since the entire raw tube must be bent and formed at each fin pass, the fin pass forming load is relatively large. However, since the width of the side part of the raw pipe is narrowed (l), roll defects are likely to occur, and the edge spacing of the raw pipe edges is successively pinched, resulting in a smaller edge spacing after the final fin pass. There is a problem that the V-shape angle becomes too small, causing type 3 welding phenomena, edge sparks in the shape, edge waves, etc.Furthermore, the fin angle in the -T flow fin path becomes too small. Since it is relatively large, there is also the problem that thickening of the edges tends to occur.

In addition, in the Etna molded flower described in -1-, Yoder,
Compared to Matsukei-type molded flowers, the reduction in the eaves of the befin pass forming load and the occurrence of roll defects are suppressed, but the bending of the entire strip during rough and intermediate forming processes, especially the finish bending of the lower half of the raw tube is required, making it difficult to perform molding in the rough and intermediate molding processes. Furthermore, problems such as narrowing of the weld area and shave angle due to the narrowing of the edge spacing after the final fin pass, as well as thickening of the edges due to an increase in the fin angle in the upstream fin pass, are the same problems as with Yoder and Matsukei molded flowers. In particular, there is a risk that Etsuji's increase in thickness will be larger than Yoder and Matsukei types.

That is, in the conventional practical method of forming ERW steel pipes, a circular bend forming method and a combination method of circular bend and other forming flowers are adopted as the forming flower in the rough and intermediate forming processes, Yoder, Matsukei, or Etna types are adopted as Finpass molded flowers, and these molded flowers are to be applied to specific molding methods such as step roll molding, vertical roll molding, and cage roll molding. FIG. 4 shows an example of the conventional molding method described above using a roll map. Figure 4 (A) shows the combined forming method of edge bend and circular bend and Yoder type fin pass forming method applied to the step roll forming method, and Figure 4 (B) shows the combined forming method of edge bend and circular bend. and the Etna type fin pass forming method is applied to the step roll forming method, and Figure 4 (C) shows the combined forming method of edge bend and circular bend, and the yoder and process 1.
・The intermediate fin pass forming method is applied to the step roll forming method, and Figure 4 (D) shows the combination forming method of edge bend and circular bend and the Yoder type fin pass forming method applied to the cage roll forming method. It is something. Here, the roll map is a diagram showing the progress of bending the strip in the width direction by each forming roll.

However, in the conventional forming method shown in Fig. 4, the number of forming roll stands increases due to the bending of the entire strip in the rough and intermediate forming processes, the narrowing of the range in which the rolls can be used together, the roll adjustment, and the replacement time are required. increase in the cross-sectional bending shape of the base pipe, increase in fin pass forming load, decrease in the weld V-shape angle due to narrowing of the final fin width, occurrence of thickening at the edge of the base pipe, and fin pass ligation due to changes in plate thickness and grade. There are many problems such as the need for adjustment and an increase in residual stress in the circumferential direction of the raw tube.

The present invention improves the formability in the rough and intermediate forming processes and the formability in the fin pass forming process, making it possible to manufacture ERW steel pipes with excellent material yield, pipe shape and welded part quality, and improving mill operation rate. The object of the present invention is to provide a method for forming an electric resistance welded steel pipe that can reduce mill equipment costs, reduce roll costs, and expand the range of possible production.

-1- In order to achieve the north exit target, the method for forming an electric resistance welded steel pipe according to the present invention includes (■) a support roll that continuously restrains and supports the strip edge portion, and a plurality of support rolls that restrain and mold the strip center portion. With the center bend roll, only the central part of the strip is bent and formed, and the remaining widthwise part of the strip is not bent, but roll-formed to obtain a U-shaped flower. ), ``The second fit side fin bath roll suppresses the bending process of the side part of the raw pipe, bends and forms the edge part of the raw pipe to a curvature of 80% or more of the curvature of the final formed pipe, and connects the side part of the raw pipe to the raw pipe. Overbend the pipe edge portion and each boundary between the side part and the bottom part of the raw pipe to a degree greater than the final formed pipe curvature (III), and mainly reduce the vertical diameter of the raw pipe by the subsequent fin pass roll. By adding the downstream direction, the side parts of the raw pipe whose bending was suppressed in the above (TI) are sequentially stretched in the width direction, and the horizontal bars of the raw pipe are formed in a direction that gradually increases. , bending of the side part of the raw pipe, and unbending of each boundary between the side part of the raw pipe and the edge part of the raw pipe, and the side part of the raw pipe and the bottom part of the raw pipe, which were overbended in -11 (II) It is designed to be processed.

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

FIG. 5 and FIG. 6 are model diagrams showing a molded flower according to the present invention. Figure 5 is a molded flower showing the center forming process of the center part of the strip in the rough and intermediate forming processes, and Figure 6 is a molded flower showing the forming process of the blank tube in the final forming process, that is, the fin pass forming process. .

Note that FIG. 6 shows a molded flower formed by the hole shape of each roll stand in the case of three-stand finpass molding.

First, the forming process in the rough and intermediate forming steps according to the present invention will be explained.

In the rough and intermediate forming processes, cage rolls are used as support rolls to continuously restrain and support the edge of the strip, and multiple center pend rolls are installed sequentially to restrain and form the center of the strip according to the progress stage of forming. Accordingly, only the bending process of the center part of the band plate is performed, in which the center part of the band plate is bent to 80% or more of the curvature of the final formed cylindrical tube, and the remaining part in the width direction of the band plate, that is, the edge part of the band plate, The plate 174 width part and the 374 width part are not intentionally bent and formed, but are center formed by cage roll forming to obtain a U-shaped formed flower on the entry side of the fin pass forming process, which corresponds to the finishing process 1. Perform processing.

Characteristics of the forming method in the rough and intermediate forming processes 1. The feature is that circular forming, which requires forming the side and edge portions of the raw tube, as in the conventional cage forming method, is not performed. be.

Further, in the present invention, the bending area at the center of the strip is in the range of 25% to 50% of the strip width.

In addition, as the process of the center forming process in the present invention, the forming area is sequentially increased in the width direction of the strip from the center of the strip, and the center portion of the strip is bent in the bending range of 41-, or vice versa. There is a method in which bending is performed sequentially from the farthest part from the center of the strip toward the center of the strip within the above bending range to perform bending at the center of the strip.

FIG. 5 shows a formed flower in the latter case, but the present invention is characterized by forming the central part of the strip in the cage forming area, and it is not possible to adopt any of the center forming processes described in . There may be.

Further, there are no particular limitations on the rolls and equipment for bending and forming the center portion of the strip, and rolls and equipment having any shape or structure may be used as long as they achieve the object 2 [1] of the present invention. It's okay. Also, in implementing the wood invention, if the pass line of the strip is made downhill, the occurrence of edge waves in thin materials can be further suppressed.

According to the forming method in the rough and intermediate stages according to the above-mentioned wood invention, it is not necessary to install edge forming rolls and inside rolls for processing the side parts of the raw pipe as in the conventional cage forming method. The forming process, that is, the cage roll forming area, can be significantly shortened compared to the conventional method. In this case, the width of the strip edge will increase,
There is a risk that edge stretch will increase and edge waves will occur, but since the present invention uses a cage roll forming method that continuously constrains the edges of the strip, it is possible to , the generation of edge waves is prevented. According to the results of experiments and research by the wood inventor, the line length in the rough and intermediate forming processes is 15 to 2.
0×Dmax (Dmax: maximum outer diameter), which is 5 times smaller than the line length of the conventional cage molding method.
It becomes possible to reduce the length by 0 to 70%.

Next, the forming process in the first forming process, that is, the fin pass forming process according to the present invention will be explained.

In fin pass forming, when forming the U-shaped shaped flower blank tube formed in the rough and intermediate forming areas, the first fin pass roll (IF) intentionally performs the final bending process of the side part of the blank tube. The bending radius is suppressed to at least twice the radius of the formed cylindrical pipe, and the horizontal frame (width) of the side part of the raw pipe is
The size is equal to or larger than the horizontal frame of the U-shaped blank tube before the finpass roll, and through this suppression process, the edge part of the blank tube is bent to a curvature of 80% or more of the curvature of the final formed cylindrical tube. , the boundary between the side part of the raw pipe and the edge part of the raw pipe, and the boundary between the side part of the raw pipe and the bottom part of the raw pipe are overbended to the curvature of the final formed cylindrical tube.

By the forming process of the first fin pass roll (IF), the edge portion of the blank tube is easily bent and formed, fin pass reduction is reduced, and the fin pass forming load is reduced.

The reason for bending the raw pipe edge portion to a curvature of 80% or more of the final formed pipe curvature in the first fin pass roll (IF) is as follows.

In other words, according to numerous studies by the inventors, if the forming curvature of the raw pipe edge is less than 80% of the final formed pipe curvature, peaking of the edge occurs during welding, resulting in poor bead cutting and weld abutment. produce defects. In other words, if the edge bending curvature at IF is less than 80%, edge bending at 2F and 3F will not be performed sufficiently, resulting in insufficient edge bending.

FIG. 7 is a model diagram showing the state of forming the raw tube in the first fine pass roll and the force acting on the raw tube. Figure 7 (
A) shows the case according to the present invention, and (B) shows the case according to the conventional molding process.

For example, as shown in FIG. 7, when the same rolling blade F acts on the fin path in both the reshaping process, in the case of the present invention, the bending of the side portion C of the raw pipe is suppressed. The reaction force f3 from the roll is larger than that in the conventional forming method. Furthermore, in the present invention, the boundary part B between the side part C of the raw pipe and the edge part A of the raw pipe, which suppresses the north facing forming, is overbended to a bending curvature larger than the bending curvature of the edge part A of the raw pipe. For,
Compared to conventional forming methods, the edges can be tilted and the fin angle OF of the first fin pass roll can be made smaller. As a result, the circumferential component 1, which is a component of the fin bath compressing force F, decreases, and the radial component 2 increases. The thickening of the edge is reduced by reducing the circumferential component element +, and the bending of the raw pipe edge is reduced by the radial component element 2.
In addition, as the reaction force f3 from the roll increases, the bending moment acting on the edge portion increases, so that this can be easily achieved. As a result, the first aspect of the present invention
In the fin pass forming process, the increase in thickness of the base edge is reduced compared to the conventional forming process, and it is possible to reduce the number of fin pass reduction blades.

-h Note 26th fin pass roll (2F) following fin pass roll (IF) 3rd fin pass roll (3F)
), by applying rolling reduction mainly in the direction of reducing the vertical diameter of the raw pipe, the side portion C of the raw pipe whose bending was suppressed by the first fin pass roll (IF) is sequentially stretched out in the width direction, and the raw pipe is rolled out in the width direction. Shaping is performed in the direction in which the horizontal frame of the tube gradually increases. Through this stretch forming process, the side part of the raw pipe is bent, the raw pipe edge part, the raw pipe side part and the raw pipe bottom part are formed by overbending with the first fin pass roll (IF). This is a process in which the bending process of the boundary part B between the two parts is performed sequentially. FIG. 8 is a model diagram showing the forming process after the 2-fin pass roll.

By the way, in the overhang forming of the side portion of the raw pipe with the second fine pass roll, it is also possible to sequentially overhang and bend the entire portion where the bending has been suppressed with the first fine pass roll until it reaches a predetermined bending curvature. Similarly to the forming process using the first fin pass roll, it is also possible to suppress the bending of the side portion of the raw tube and to perform the bending of the overhang 17 while sequentially reducing the bending suppression area.

Although the following explanation has been given using three-stand fin pass roll forming as an example, the present invention is also applicable to fin pass roll forming with other numbers of stands. Furthermore, the present invention has a method of dividing the fin pass roll, that is, two
It is not limited to the 0-le type or the 40-le type.

FIG. 9 is a diagram showing the projected locus of the blank tube in the fin pass forming process according to the present invention. In the present invention, in the Yorfin pass roll process, in order to gradually increase the horizontal bar of the raw pipe,
It is possible to increase the edge spacing (W3F) in the final fin pass roll, and the V-shape angle (O
v) Can be made larger. This makes welding with the squeeze roll more stable and improves quality.

In addition, in the present invention, since the overbend-formed portion with the first finpass roll is unbent-formed after the second finpass roll, as shown in Fig. The direction of the bending moment is different from the case of the conventional formed raw pipe shown in FIG. 10(B), and the moment is in the direction of rolling the raw pipe. As a result, the shape and dimensions of the product pipe after welding are excellent.

In addition, in the explanation in 1.1-, it is assumed that the edge bending of the strip is not performed in the rough and intermediate forming processes, but the edge bending of the strip is performed in the composition region, and the edge bending and center bending are performed before fin pass forming. It is also possible to obtain a blank tube having a molded flower shape according to the method, and then perform finishing molding by the fin pass molding process according to the present invention.

According to this, particularly when forming thick-walled materials, it is possible to improve edge formability and at the same time reduce the load during fin pass forming. That is, in carrying out the present invention, an edge bend forming process may be added to the forming process in the rough and intermediate forming processes. In addition, the center forming process using cage roll forming in the rough and intermediate forming processes of the present invention is made possible by the fin pass forming process of the present invention, and is significantly different from the center bend forming method of the conventional example. It is something.

Further, the center forming process in the rough and intermediate forming processes according to the present invention is not performed only by the cage roll method described above, but any specific forming method can be used.

FIG. 11 is a scroll map showing an example of the molding process according to the present invention.

FIG. 12 is a diagram showing an example of the hole shape of a fin pass roll to enable the fin pass forming process according to the present invention. As fin pass roll forming progresses, each fin pass roll changes the roll hole shape dimensions Ri and θi (i=1 to 5), vertical diameter (H), horizontal frame (W), and fin width shown in FIG. (WF), fin angle (
θF) may be sequentially changed. For example, H, Wf, θ
FR3, 03 are sequentially decreased, W, R2, θ2, R4,
An example of a method is to create a hole shape in which θ4 is increased sequentially.

0 By the way, in the present invention, the squeeze roll hole shape is not necessarily a perfect circle, but the fin pass forming process of the present invention is extended to the squeeze roll, and the squeeze roll hole shape is polygonal as shown in FIG. It is also possible to have a shape. In this case, the degree of forming progress in the fin pass forming process of the present invention is reduced, and the bending suppressing part of the side part of the raw tube is maintained even in squeeze roll forming or a pull-out roll after squeeze roll forming, and the processing of this part is This will be done in the later process of sizer molding. As described above, by applying the present invention to the fin pass and squeeze roll forming regions, rotation of the raw pipe in the circumferential direction is suppressed, and circumferential twisting of the welded part of the raw pipe can be prevented. This makes it possible to stabilize bead cutting, stabilize seam annealing, and stabilize the welding state, making it possible to manufacture an electric resistance welded steel pipe with excellent welded part shape quality.

Note that the application of the forming process according to the present invention is not limited by the size of the raw pipe, but is applicable to the production of electric resistance welded steel pipes of any outer diameter size.

Hereinafter, specific implementation results of the present invention will be explained.

A conventional molding method using a cage roll molding method, for example, the molding flower one-type molding method shown in FIG.
, edge thickness increase rate in the raw pipe, fin past tar reduction, 1st when manufacturing electric resistance welded steel pipes of pipe standard API5LX-X60 and pipe standard API5LX-X56 with an outer diameter of 26 inches and a wall thickness of 6.35 mm. Table 1 was obtained by comparing the fine pass forming load and the number of occurrences of shape sparks during welding. This first
According to the table, compared to the conventional method, the forming method according to the present invention enables lighter downstream forming of fin pass rolls, reduces the fin pass total reduction by 50 to 70%, and reduces the fin pass forming load by 35 to 35%. A reduction of 50% is achieved. In addition, the edge thickness increase rate is 0% or less than the conventional rate, which stabilizes inward bead cutting and prevents wall thickness defects due to edge thickness increase in thick-walled materials. .

FIG. 13 is a diagram showing the thickening state of the edge portion of the blank tube after fin pass forming in the 24-inch material, in comparison with that by the conventional method. According to the present invention, it is recognized that the increase in thickness at the edge portion can be significantly reduced. Furthermore, according to the present invention, the oven length due to molding defects at the leading and trailing ends of the raw pipe was reduced by 50% compared to the conventional method, and the pass rate of welded parts in ultrasonic tests was improved by 5%. Furthermore, according to the present invention, since the direction of the residual bending moment in the circumferential direction of the raw pipe after fin pass roll forming is improved, the springback of the raw pipe is reduced, and a welded raw pipe with a predetermined shape and size is obtained. becomes possible.

By the way, in the present invention, t/D, which was difficult to manufacture in terms of moldability and equipment strength using conventional molding methods,
(Wall thickness/outer diameter) = 0.8% equivalent 26 inch XB, On
+ proverb (X60) and 20 equivalent to t/D=4.3z
Inch x 22 mm (x 52) 4 It is possible to manufacture stably, and therefore, it has the feature that the range of production is wide.

In addition, for six types of pipe forming diameters from 16 inches to 26 inches, the number of rough forming and intermediate forming rolls on hand is the second.
As shown in the table, compared to the 87 trees required in the conventional method, 4
Furthermore, as shown in Table 2, it is possible to omit the edge forming rolls and inside forming rolls required in conventional forming, and the line length for rough and intermediate forming processes can be reduced to 15 to 20Dmax. (Dmax
: maximum outer diameter), i.e. 50% to 70% of the conventional line length
It is possible to shorten the length to %. In addition, the time required for size changes due to changes in the diameter of the tube and the accompanying roll adjustment time was reduced by 40% compared to conventional molding methods.

Note that the present invention is applicable not only to the production of cylindrical tubes but also to square tubes.

As described above, the present invention provides an electric resistance welded steel pipe forming method in which a strip is continuously roll-formed and the edge of the raw pipe is welded through fin pass rolls. By supporting the support rolls and a plurality of center bend rolls that constrain and form the central part of the strip, only the central part of the strip is bent and formed, and the remaining part in the width direction of the strip is not bent and formed. (II) The upstream fin pass roll suppresses the bending process of the side part of the raw pipe, and the edge part of the raw pipe is made to have a curvature of 80% or more of the final formed pipe curvature. ”-, and overbend each boundary between the side part of the raw pipe and the edge part of the raw pipe, and the side part of the raw pipe and the bottom part of the raw pipe to a degree greater than the final formed pipe curvature, (m) , by applying rolling mainly in the direction of reducing the vertical diameter of the raw pipe using the subsequent fin pass rolls, the side parts of the raw pipe whose bending was suppressed in item 2 (n) are sequentially stretched out in the width direction,
Forming is performed in the direction in which the horizontal frame of the raw pipe gradually increases, and by this overhang forming process, the side parts of the raw pipe are bent, and the side parts and edge parts of the raw pipe that have been overbended in (II) above, Also, each boundary between the side part of the raw pipe and the bottom part of the raw pipe is bent back. Therefore, by making the forming of strips stable and easy in the rough and intermediate forming processes, shortening the line length by reducing the number of forming rolls, expanding the range of dual use of rolls, and shortening roll adjustment and replacement time, Furthermore, it is possible to bend the edge portion of the raw pipe in fin pass forming, and prevent thickening of the edge portion.

We aim to reduce the forming load by reducing the fin pass reduction, eliminate the need for reduction adjustment by changing the plate thickness grade, and also increase the fin width of the final fin pass roll to enlarge the welding part ■ sheave angle and reduce the circumference of the raw pipe. By making it possible to reduce directional residual stress,
To make it possible to manufacture ERW steel pipes with excellent material yield, pipe shape dimensions, and welded part quality, and to achieve improvements in mill operation rate, reduction in mill equipment costs, reduction in roll costs, expansion of the range of possible manufacturing, etc. becomes possible.

[Brief explanation of drawings]

Figures 1 (A) to (D) are model diagrams showing molded flowers in the conventional molding method, Figures 2 (A) and 7 and (B) are model diagrams showing conventional fin pass molded flowers, and Figure 3 ( A) and (B) are projected locus diagrams showing the tube forming process using the conventional fin pass forming method, Figure 4 is a roll map diagram showing the conventional forming method, and Figure 5 is the rough and intermediate forming process according to the present invention. FIG. 6 is a model diagram showing a molded flower in the center forming process of the present invention, FIG. A model diagram showing the state of raw tube forming in the first fine pass roll forming process according to the invention and the force acting on the raw tube, and FIG. 7(B) shows the state of raw tube forming with the first fine pass roll in the conventional forming method. FIG. 8 is a model diagram showing the forming process after the second fin pass roll according to the present invention, and FIG. 9 is a model diagram showing the forming process after the second fin pass forming process according to the present invention. Projected locus diagram showing the molding state, Figure 1θ (
A) is a model diagram showing the residual bending moment in the circumferential direction of a welded pipe formed by the present invention, 8 Figure 10 (B) is a model diagram showing the residual bending moment in the circumferential direction of a welded pipe formed by the conventional forming method. , 1st
Fig. 1 is a roll map diagram showing a forming process according to an example of the present invention, Fig. 12 is a line diagram showing an example of a fin pass roll hole shape that enables the fin pass forming process according to the present invention, and Fig. 13 is a diagram showing an example of a conventional method. FIG. 4 is a diagram comparing and showing the wall thickness distribution of the raw pipe edge portion after fin pass forming according to the present invention and the present invention. Agent Patent Attorney Osamu Shiokawa Figure 1 (A) (B) Figure 1 (C) (D) Figure 6 Figure 7 (A) (B) Figure 8 11 Figure 11 Figure 12

Claims (1)

[Claims] (1) In the forming method of electric resistance welded steel pipe in which a strip is continuously roll-formed and the end face of the raw pipe edge is welded through fin pass rolls, (I) a support roll and strip that continuously restrain and support the strip edge portion are used. By using a plurality of center pend rolls that constrain and form the central part of the strip, only the central part of the strip is bent and formed, and the remaining widthwise part of the strip is not bent.
Roll forming is performed to obtain a U-shaped flower, and (II), the J1 downstream fin pass roll is used to suppress bending of the side part of the raw pipe, and the edge part of the raw pipe is adjusted to 80% of the final molded pipe curvature. % or more, and overbend each boundary between the side part of the raw pipe and the edge part of the raw pipe, and the border between the side part of the raw pipe and the bottom part of the raw pipe to a curvature of 1- or less than the final formed pipe curvature. And (■). By adding downstream mainly in the direction of reducing the vertical diameter of the raw pipe by the subsequent fin pass roll,
The side parts of the raw pipe whose bending has been suppressed are sequentially stretched out in the width direction, and the horizontal frame of the raw pipe is formed in the direction in which it gradually increases.
Through this stretch forming process, the side parts of the raw pipe are bent, the edge parts of the raw pipe are formed by overbending in the above (TI), and the boundaries between the side parts of the raw pipe and the bottom part of the raw pipe are formed. A method for forming an electric resistance welded steel pipe, characterized by performing an unbending process.