JPH03180213A - Manufacture of welded steel pipe and its apparatus - Google Patents

Abstract

PURPOSE:To stabilize the forming of steel pipe and to improve the quality by sequentially arranging the edge bend roll, a 1st - a 4th center bend rolls, a 1st and 2nd fin pass rolls, the rotary seam guide roll, the high frequency welding machine and the squeeze roll. CONSTITUTION:The part from the edge part of the blank pipe till the boundary part with the side part is bent almost-similarly to the final forming arc with the edge bend roll EB. Next, the bottom part of the blank pipe is sequentially bent to the arc equal to or exceeding to the final forming arc with the 1st center bend roll 1CB, the 2nd, the 3rd, the 4th center bend rolls 2CB, 3CB 4CB, and the cage rolls CR of both sides. Next, by the 1st and the 2nd fin pass rolls 1F, 2F, work is bent to the arc nearly equal to final forming arc. After the edge part of blank pipe is subjected to bent back, by the rotary seam guide rolls RSG, the work is adjusted to the welding state, then the welding machine HFW executes welding the seam, and by the squeeze roll SQ the seam is joined by upsetting and the blank pipe is shaped to a circle.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a method and apparatus for manufacturing a welded steel pipe.

``Prior art and problems to be solved by the invention'' Welded steel pipes, in which steel strips are continuously roll-formed to form a blank pipe, and the butt joints are welded, are already well known. ERW steel pipes, whose seams are electrically welded (resistance welded), are the mainstream.

By the way, one of the roll forming methods in this case is an overall width bending process in which the entire raw tube is rolled up while progressively forming the band plate as a whole, and the forming equipment associated with this process is , those manufactured by Yoda Corporation (Japanese Patent Application Laid-Open No. 1983-29896) shown in Figures 8 and 9, and those shown in Figures 1O to 12.
The one shown in the figure is from Torrance Company in the United States (Utility Model Act 46-288
No. 97 Public I [i) and ga al. In the figure, +00 is a preforming roll, 102, 104.106108 is a breakdown roll, iii, 0-4, -inner roll, EF is an edge roll, CR is,
Cage roll, IF, 2F, and 3F are fin bath rolls, and SQ is squeeze roll.

However, these devices have ) The number of forming rolls is large.

1) The restraining force on the strip is weak and the strip is easy to roll.

iii) The range of roll rejection for changes in pipe manufacturing size is narrow.

iv) The molded shape of the raw tube tends to become a discontinuous polygon due to the influence of the rolls (see Figure 13).

(2) Since the bending process cannot be performed sufficiently in the rough and intermediate forming processes, the load in the final stage of fin pass forming is large, and in practice, at least three stages of fin pass rolls are required.

There are drawbacks such as.

Therefore, in order to improve these shortcomings, we first developed the
The molded W shown in FIG.
No. 11l) was developed. This device has upstream iii, i
ii, from the lower skin side, edge forming roll EF,
1st to 4th center bend roll IcB, 2CB, 3
CB, 4CB and a large number of cage rolls CR arranged only on the side of these rolls, multiple fin pass rolls IF, 2F
, 3F, squeeze rolls SQ are sequentially arranged, and the edge forming roll EF is used to bend the edge part of the blank tube of the strip. −
As shown in Fig. 15, c and d), the fourth center bend roll 4CB and cage roll Cr1- are used to bend the boundary between the side part of the raw pipe and the bottom part of the raw pipe. It is bent into a radius (Fig. 15 e) and formed into a 0-shaped cross section (Fig. 15 r), and this is made into a fin bath roll I.
Pressing is performed at F, 2F, and 3F to make the side part of the raw pipe protrude, and the edge part of the raw pipe, the boundary between the edge part of the raw pipe and the side part of the raw pipe, and the side part of the raw pipe and the bottom part of the raw pipe are The boundary part is bent and unbended, the joint is melted using an F6 welding machine, and the joint is upset and joined using a squeeze roll SQ.

However, even in this case, in practice, ■ the first to fourth center bend rolls lc [3°2C
B, 3CB, and 4CB are for bending only the boundary between the side part of the raw pipe and the bottom part of the raw pipe, or the bottom part of the raw pipe, and within a range of about 1/3 of the width at the center of the strip. (Fig. 15b-d), and since the first to third center bend rolls ICB, 2C8, and 3CB are twin-type split rolls, their contact area with the strip is small, and therefore, Even if all center bend rolls are driven, the feeding torque from the rolls to the strip is not sufficiently transmitted, and the strip does not move smoothly.

Furthermore, if all the center bend rolls are driven, the device will become larger and it will be difficult to secure a space for installing the cage rolls, leading to an increase in equipment costs.

■ 2nd and 3rd center bend roll 2C8゜3CB
is a twin-type split roll (see Figures 16 and 17. However, Figure 16 shows that when the pipe size is small,
FIG. 17 shows a case where the pipe size is large. ) In particular, in the case of a split roll of the lower roll, dents and roll flaws occur in the strip due to a part of the roll corner.

Ml to 4th center bend roll IcB.

Since 2CB, 3CB, and 4CB each have an independent stand structure, it takes a lot of effort and time to replace the rolls.

■ 2nd and 3rd center pen F' roll 2C83CB
Even though there are cage rolls on both sides of the bottom roll, the roll spacing must be changed every time the pipe size is changed, so it takes time and effort to adjust the rolls.

■ Since at least three stages of fin pass rolls IF, 2F, and 3F are required, it takes a lot of effort and time to change the rolls.

There are problems such as:

The present invention aims to solve these conventional drawbacks and problems, and includes stabilization of forming such as prevention of edge waves and strip rolling, expansion of the range of rolls that can be used for changing pipe sizes, prevention of roll flaws, The aim is to make the device more compact and to shorten roll exchange and adjustment time.

In order to achieve the above object, the invention of claim 1 provides a method for manufacturing a welded steel pipe by continuously roll-forming a strip to form a raw pipe, and welding a butted joint. In the method, a T edge bend roll is used to press down and restrain the band plate from the edge part of the raw pipe to the boundary part with the side part of the raw pipe, and bend the raw pipe junge part or the boundary part almost equal to the final forming arc. (2) The first center bend roll presses down and restrains the side part of the raw pipe of the strip plate, and bends the raw pipe side part slightly; (2) The second and third center bend rolls roll the strip plate. At the same time, the boundary between the side part of the raw pipe and the bottom part of the raw pipe is compressed and restrained, and at the same time, by multiple cage rolls arranged on both sides,
By applying lateral pressure to both sides of the raw pipe, the boundary part is bent more than the bending of the final formed arc, and at the same time, the bottom part of the raw pipe of the strip plate is pressed down and restrained by the fourth center bend roll, and at the same time A plurality of arranged cage rolls apply lateral pressure to both sides of the raw tube to bend the bottom part of the raw tube to an extent equal to or even more than the final forming arc. The side part of the raw pipe is stretched out in the direction of decreasing its II diameter, and the side part of the raw pipe is bent to almost the same shape as the final forming arc, and each boundary part and the raw material are Bend and unbend the pipe edges as appropriate; VI. Adjust the raw pipe to the specified welding position using a rotary nome guide roll; ■ Melt the joint using a welding machine; The method of manufacturing a welded steel pipe is characterized by upsetting and joining the joint and shaping the welded pipe into a circular shape.

The invention of claim 2 provides a welded steel pipe manufacturing apparatus that continuously roll-forms strips to form a blank pipe and welds the abutted joints. An edge bend roll that compresses and restrains the pipe edge part to the boundary part with the first part of the raw pipe size, and processes the raw pipe work, the edge part or the boundary part by db approximately equal to the final forming arc; a first center bend roll that compresses and restrains the side portion of the raw pipe and slightly bends the side portion of the raw pipe; , applying lateral pressure to both sides of the raw pipe,
The second and third center bend rolls bend the boundary part more than the bending of the final forming arc, and a plurality of cage rolls arranged on both sides of these rolls. At the same time, a fourth center bend roll that applies lateral pressure to both sides of the raw pipe to bend the bottom part of the raw pipe to an extent equal to or excessively the final forming arc; a plurality of cage rolls arranged on both sides of the roll; A pressure is applied to the pipe in the direction in which its longitudinal diameter is reduced to make the side part of the raw pipe protrude laterally, and the side part of the raw pipe is bent to a point where the final forming arc is almost the same, and each of the above boundary parts and First and second fimbus rolls for appropriately bending and unbending the edges of the raw pipe; ■ Rotary seam guide rolls for adjusting the raw pipe to a predetermined four-joint position; vi; Welding machine for melting the seam; Squeeze rolls are arranged in sequence for shaping the welded pipe into a circular shape while mooring and joining the joints, and driving means are provided for at least the above-mentioned enojihen roll, the first center bend roll, and the first and second fimbath rolls, and , each upper roll of the first to third center bend rolls and the lower roll of the first center bend roll are divided rolls whose width can be freely adjusted, and each of the lower rolls of the second to fourth center bend rolls is also used. It is characterized in that it is an integral roll with a caliber shape that fits the maximum pipe outer diameter of the common range obtained, and furthermore, all the centrally driven upper rolls of the second to fourth center bend rolls are set in one removable housing. / S-welded steel pipe manufacturing equipment.

The invention according to claim 3 is characterized in that the non-driven full lower roll stands of the third and fourth center bend rolls are set on one removable common sub-base plate.
It is located in the manufacturing equipment of 8-joint pipes.

The invention set forth in claim 4 is based on the invention set forth in claim 2, in which drive means are also provided for each of the lower rolls and squeeze rolls of the second to fourth center bend rolls.

Further, the invention as claimed in claim 5 is based on the invention as claimed in claim 2, in which each cage roll is equipped to be able to move horizontally forward and backward, vertically move up and down, and adjust its angle.

Note that the edge bend roll may drive only the lower roll, and the squeeze roll may not be driven.

``Effect'' Since the structure is as above, the upper width fP +
Then, the strips are sequentially processed according to the above steps to become welded steel pipes.

"Example" 1 to 6 show an apparatus according to the invention.

As shown in FIG. 1, this device includes, from the upstream side to the downstream side, an edge bend roll EB, a first center bend roll CB, second to fourth center bend rolls 2CB,
3CB, 4CB and many cage rolls C arranged on both sides
R, first and second fin pass rolls IF and 2F, a rotary seam guide roll R3G, a high frequency welding machine HFW, and a squeeze roll SQ are arranged in this order.

Among these rolls, Edgebend roll EB, the first
The center bend roll ICB, the second to fourth center bend rolls 2CB, 3CB, 4CB, and the first and second fin bath rolls IF, 2F are composed of an upper roll and a lower roll, and a large number of cage rolls CR-, squeeze rolls, 1-le S
Q is a pair of left roll and right roll. And the first to fourth center bend rolls ICB, 2C8,
3CB and 4CB have a certain common range.

For example, if a steel pipe with an outer diameter of 22.22 am to 60.5 mm is to be made, as shown in FIG. O3m- ■ 31.03 s ~ 43.33 s 43.33
Three roll groups, ■, ■, and ■, are prepared with a common range of 0 to 60.51 degrees.

Also, among these rolls, edge bend roll EB
Driving means are provided for the lower roll, the upper and lower rolls of the first center bend roll 1CBO, and the soil and lower rolls of the first and second fin bath rolls IF and 2F. Specifically, the roll shaft is mechanically connected to the drive source via a universal joint. If necessary, it is also possible to drive the upper roll of the edge bend roll EB, the lower rolls of the second to fourth center bend rolls 2CB, 3CB, and 4CB, and the squeeze roll SQ.

As shown in Fig. 2 I, the edge bend roll EB has a split roll for both the upper and lower rolls, so that the width can be adjusted according to the pipe manufacturing size, and the edge bend roll EB is designed so that the width can be adjusted according to the pipe manufacturing size. At the same time, the strip is conveyed by pressing down and restraining the area up to the boundary between the parts and the raw pipe.

The edge portion or boundary portion is bent approximately equal to the final forming arc in anticipation of the spring bank (Fig. 3 EB).

The first center bend roll IcB, as shown in FIG.
and a relatively narrow intermediate member iii, and the upper roll is a split roll of two left and right members 14 and 15, so that the width of both can be adjusted according to the pipe manufacturing size. The side part of the raw pipe of the strip is restrained by pressing down, and the strip is fed and at the same time it is slightly bent (Fig. 3 ICB
M, bend ls here! The caliber radius at the midpoint in the range of pipe-making sizes (tube outside diameters) that can be used in this roll may be approximately 2.5 times the caliber radius of the squeeze roll SQ that is compatible with this roll.

2nd to 4th center bend rolls 2C8, 3C3, 4
As shown in Fig. 2 m-v and Fig. 5, in the CB, the lower roll is an integral roll 16, and these integral rolls are used for a certain range of pipe manufacturing sizes, but as mentioned above, the dual use is Range: 22°22mm ~ 31.03mm,
■31.03fl~43.33m-2■43.33 city~
If there are three rolls of 60.5 mm, prepare three integral rolls for ■ to ■, and for the integral roll for ■, 31 mm.
．． Caliber shape compatible with 03iii, iii, ■
The integral roll for 2000 is formed into a caliber shape suitable for 43.33 am, and the integral roll for 2 is formed into a 60.5 caliber shape. In other words, the caliber shape is formed to match the maximum pipe outer diameter in the common range that can be used for both purposes.

Also, the second and third center bend rolls 2013.3
CB is shown in Figure 2 III, . As shown in IV and FIG. 5, the upper rolls are divided rolls into left and right members 17 and 18, respectively, so that the width can be adjusted according to the pipe manufacturing size. teeth,
As shown in FIG. 2, the upper roll is an integral roll 27.

Therefore, as shown in Figure 2 - ■, the second and third 9-hen l' o-le 2 CB, 3 CB ha,
1; The boundary between the side part of the raw pipe of the F plate and the bottom part of the X pipe was restrained by rolling down, and the fourth center bend roll 4CB was arranged on both sides of these rolls, restraining the bottom part of the raw pipe by rolling down. Together with a plurality of cage rolls CR, the boundary part of the raw pipe is bent more than the bending of the final forming arc, and the bottom part of the raw pipe is bent to the same degree or more than the final forming arc (Fig. 3, 2C33C8, 4CB). .

The cage roll CR- is placed between both sides of the molding line: the trowel, and the fourth center bend roll from the -L flow position of the second center bend roll 2CB.
Up to the downstream position of center bend roll 4CI3, 12 each
1 [U arrangement, as shown in Figures 2 m-■ and Figure 6, apply appropriate lateral pressure to the raw pipe from both sides and wrestle with the 2nd and 4th center bend rolls. From the boundary between the side part of the pipe and the bottom part of the raw pipe to the bottom part of the raw pipe, one after another, as if improving (Fig. 3 2CB, 3C)
B, 4C13, CRI2) First and second fin pass rolls +r, 2Fri, equipped with an upper roll with fins and a lower roll without fins, and the first fin pass roll IF is a plain roll with an oval-shaped cross section. The pipe (CR12 in Fig. 3) is molded under the mold, and as shown in Fig. 4A, the boundary between the edge part of the stock pipe and the side part of the stock pipe, and the border between the bottom part of the stock pipe and the bottom part of the stock pipe are formed. The boundary part is further excessively bent and pressurized, and the blank part of the raw pipe is appropriately bent.Then, the second fin pass roll 2F continues to press-form the raw pipe, as shown in FIG. 4B. As shown in FIG. 2, the side portions of the raw pipe are extended outward and bent to form the final forming arc and the groove 1, and at the same time, the respective boundary ljv portions in -H are bent back to near the final forming arc.

The rotary seam guide roll R3G includes an upper roll with fins and a lower roll without fins, and the position, angle, etc. of the rolls can be adjusted, and the raw pipe is adjusted to the regular 78 joint position.

The high-frequency welding machine III and FW are a type of resistance/S welding machine, and they flow welding electrode into the joints of raw pipes to heat and melt the joints.

The squeeze roll SQ is equipped with a pair of left and right rolls, presses the raw tube from both sides, upsets and joins the 18-melted '41' eyes, and shapes the joined tube into a circular shape.

By the way, - the above-mentioned edge bend roll EB, first center bend roll ICB, first and second fin pass rolls IF, 2F, and rotary seam guide roll R3G are mounted on independent roll stands 19 for the upper and lower rolls.
- Equipped with roll exchangeable, squeeze roll SQ
The left and right rolls are equipped on a roll stand 20 so that the rolls can be exchanged.

In addition, the second to fourth center bend rolls 2cI3.3
CB and 4CB are equipped with only the lower rolls on independent roll stands 21-, and those roll stands 1
'21 is fixed to common sub-hairspray)・50,
The entire common sub-base plate can be replaced when replacing the roll. The upper roll is installed in one housing 22 common to all three, so that the rolls can be exchanged once. Therefore, to replace the lower roll, the housing and J
(Each can be replaced in three strokes at once by replacing the bushing plate that passes through it.

In the cage roll CR, each roll stand 23 is equipped with three cage rolls per zone, and as shown in FIG. and angle adjustment means 26.

Next, an experiment related to the above-mentioned apparatus will be explained.

(1) Outer diameter of the steel pipe to be prototyped (Fig. 7 Panel 1!!!)
2222~605 (2) Used iii,:I Thickness 0.8~3.0 - Material ■Ordinary steel 5S41 equivalent ■Stainless steel 5US304 +31 1st to 4th center bend roll ICB.

Compatible range for 2CB, 3CB, and 4CB (see Figure 7) ■ Steel pipe outer diameter 22.22 to 31.03 ms ■
31.03~4333 Axis ■ 4
3.33～6085 - 翳(Roll is 3 for ■～■
It's the size. ) In the Honjoken, I was able to meet my distant relatives without any hindrance to my intended purpose.

"Young Fruit of the Invention" According to the present invention, the edge part of the raw pipe is bent from the edge part to the boundary with the side part of the raw pipe approximately equal to the final forming arc, and the raw material is bent with the first center bend 1' roll. The side part of the pipe is slightly bent, and the boundary between the side part of the raw pipe and the bottom part of the raw pipe is bent more excessively than the bending of the final forming arc using the second and third center bend rolls and the cage rolls on both sides. Then, the fourth center bend roll and cage rolls on both sides bend the bottom part of the raw pipe to the same or excessive degree as the final forming arc, and the first and second fin pass rolls compress the raw pipe to bend the raw pipe side. At the same time, bend the parts to the side and bend them to almost the same shape as the final formed arc, and bend the above-mentioned boundary parts and the pipework 7-ji part to 3 mW.
Since the unbending process is performed, it can be formed accurately and efficiently without any problems caused by spring banks of the raw pipe or the risk of roll flaws, and only requires two stages of fin pass rolls, which previously required three or more stages. , the number of rolls can be reduced throughout, making the entire device more compact. Note that the slight bending of the side portion of the raw tube by the first center bend roll allows the side portion of the raw tube to be stretched out smoothly and accurately by the subsequent fin pass roll.

In addition, the edge bend roll is used to cover the edge part of the raw pipe to the boundary with the raw pipe side part, the first center bend roll is used to cover the raw pipe side part, and the second to fourth center bend rolls are used to cover the raw pipe side part and the raw pipe part. The boundary with the bottom part and the bottom part of the raw pipe are restrained by pressing down, and the cage rolls are used to restrain the raw pipe edge part and the raw pipe side part, so the sliding plate is sufficiently restrained over almost the entire width direction. As a result, not only misalignment and rolling of the strip but also edge waves do not occur, making it possible to stabilize molding and improve quality.

An edge bend roll that restrains the edge part of the raw pipe and the boundary part adjacent thereto, a first center bend roll that restrains the raw pipe site part, and a first center bend roll that restrains the upper and lower parts of the raw pipe.
Since the HA movement means is provided for the belt plate and the second fin pass roll, the belt plate receives torque transmission over a wide range in the width direction, and can be moved smoothly. Moreover, in the second to fourth center bend rolls, the upper roll is not driven, so that the apparatus can be made more compact, the cage roll installation space can be secured without any problem, and the equipment cost can be reduced.

Furthermore, since the lower rolls of the second to fourth center bend rolls are integrated into a caliber-shaped integral roll that fits the maximum pipe diameter in a common range, dents and roll flaws in the strip caused by part of the roll corners can be avoided. Furthermore, if the pipe production size is within a certain range, there is no need to adjust the roll interval when changing the pipe production size, and the roll adjustment does not take much time and effort.

Furthermore, since all the upper rolls of the second to fourth center bend rolls are set in one housing, and the lower rolls are set in a common sub-base plate, these upper and lower rolls can be replaced by replacing the housing and the common sub-base plate. It can be done all at once, greatly reducing the labor and time required to change rolls, and reducing line downtime.

Moreover, the range of dual use of rolls can be expanded, which is impossible to achieve by changing the pipe manufacturing size.

[Brief explanation of drawings]

1 to 7 show embodiments of the present invention, FIG. 1 is a side view of the configuration of the device, FIG. 2 is an explanatory view of the roll, and FIGS. 5 is a cutaway front view of the device at the second and third center bend roll portions, FIG. 6 is an enlarged front cutaway view of the main parts of the device at the cage roll portion, and FIG. 7 is a graph; 8 to 17 show conventional examples, FIG. 8 is a plan view of the configuration of the first conventional example, FIG. 9 is an enlarged front view of the main part of the same example, and FIG. A perspective view of the second conventional example, FIG. 1I is a sectional view taken along the line XI-XI in FIG.
[A sectional view taken along the + line, FIG. 13 is an explanatory diagram of the main parts of the first conventional example and the second conventional example, FIG. 14 is a plan view of the configuration of the third conventional example, and FIG. 15 a, b, f is the 14th
16 and 17 are enlarged front views of the main parts of the center bend roll of the same example. EB... Edge bend roll ICB... 1st center bend roll 2CB... 2nd center bend roll 3CB... 3rd center bend roll 4CB... 4th center bend roll 1F.
・・First fin pass roll 2F・・Second fin pass roll SQ・・Squeeze roll R2O・Raw crystal sim guide roll +1 F W ・・High frequency welding machine

Claims (5)

[Claims] (1) In the manufacturing method of welded steel pipes, in which strips are continuously roll-formed to form a raw pipe, and the butted joints are welded, II. The edge part of the raw pipe or the boundary part is bent approximately equal to the final forming arc. II. The side part of the raw pipe of the strip is restrained by rolling down using the first center bend roll. Then, the side part of the raw pipe is slightly bent, and at the same time, the boundary between the side part of the raw pipe and the bottom part of the strip plate is pressed down and restrained by the second and third center bend rolls, and at the same time, the side part of the raw pipe is bent slightly. A plurality of cage rolls arranged in a row apply lateral pressure to both sides of the raw tube to bend the boundary part more than the bending of the final forming arc. At the same time, a plurality of cage rolls arranged on both sides apply lateral pressure to both sides of the raw pipe to bend the bottom part of the raw pipe to a degree equivalent to or even more than the final forming arc, thereby forming V, the first and The second fin pass roll applies pressure to the raw pipe in the direction of decreasing its vertical diameter, causing the side part of the raw pipe to bulge out laterally, and bending the side part of the raw pipe to almost the same shape as the final forming arc. At the same time, the above-mentioned boundaries and edges of the raw pipe are bent and unbended as appropriate. VI. The raw pipe is adjusted to the specified welding position using a rotary seam guide roll. VII. The seam is melted using a welding machine. A method for manufacturing a welded steel pipe, which comprises the steps of: joining the welded pipe by upsetting the joint using a squeeze roll; and shaping the welded pipe into a circular shape. (2) In a welded steel pipe production equipment that continuously roll-forms strips to form a raw pipe and welds the butted joints, from the upstream side to the downstream side, i. An edge bend roll that bends the raw pipe edge part or the boundary part approximately equal to the final forming arc by compressing and restraining up to the boundary with the pipe side part; ii. Rolling and restraining the raw pipe side part of the strip plate; , a first center bend roll for slightly bending the side part of the raw pipe, iii, compressing and restraining the boundary between the side part of the raw pipe and the bottom part of the raw pipe of the strip plate, and at the same time applying lateral pressure to both sides of the raw pipe; , second and third center bend rolls that bend the boundary part more than the bending of the final forming arc, and a plurality of cage rolls arranged on both sides of these rolls, iv. At the same time, a fourth center bend roll applies lateral pressure to both sides of the raw pipe to bend the bottom part of the raw pipe to an extent equivalent to or even more than the final forming arc; and a plurality of cage rolls arranged on both sides of the roll; Apply pressure to the raw pipe in a direction that reduces its vertical diameter to make the raw pipe side part protrude laterally, bend the raw pipe side part until the final forming arc is almost the same, and at the same time and first and second fin pass rolls that suitably bend and unbend the edge portion of the raw pipe, vi, a rotary seam guide roll that adjusts the raw pipe to a predetermined welding position, vii, a welding machine that melts the seam, Squeeze rolls for upsetting and joining the joint and shaping the welded pipe into a circular shape are sequentially arranged, and at least the edge bend roll,
A driving means is provided for the first center bend roll, the first and second fin pass rolls, and the width of each upper roll of the first to third center bend rolls and the lower roll of the first center bend roll is adjustable in width. into split rolls, and
The lower rolls of the second to fourth center bend rolls are integral rolls with a caliber shape that fits the maximum pipe outer diameter in the common range that can be used, and the non-driven upper rolls of the second to fourth center bend rolls are also made into integral rolls. A welded steel pipe manufacturing device, characterized in that the two are set in one removable housing. (3) A welded steel pipe manufacturing apparatus characterized in that the non-driven lower roll stands of the third and fourth center bend rolls are set on one removable common sub-base plate. (4) The welded steel pipe manufacturing apparatus according to claim 2, wherein each of the lower rolls of the second to fourth center bend rolls and the squeeze roll are also provided with driving means. (5) The welded steel pipe manufacturing apparatus according to claim 2, wherein each cage roll is equipped to move horizontally forward and backward, vertically up and down, and adjust its angle.