JPH11285729A - Manufacture of uoe steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture high strength thick UOE steel tube without a defective shape and without increasing the capacity of an existing O-press. SOLUTION: By arranging a U-shaped plate 15 so that butt-welding parts 15a and 15b are positioned in the uppermost part A of an upper die 11, a first O-press forming is performed. After the first O-press forming, by rotating the U-shaped plate 15 around a center axis, the parts 15a and 15b are arranged near the lowermost part B of the upper die 11, and a second O-press forming is performed. Further, after the second O-press forming, by rotating the U-shaped plate 15 around the center axis, and by arranging the parts 15a and 15b in a position which becomes symmetrical to the position of the parts 15a and 15b when the second O-press forming has been performed, a third O-press forming is performed with regard to the uppermost part A of the upper die 11, which is the position of the parts 15a and 15b when the first O-press forming is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a UOE steel pipe which can improve the dimensional accuracy of the UOE steel pipe when performing an O-press on a U-shaped steel sheet, and more particularly to a high strength thick UOE steel pipe. UOE can be manufactured with high dimensional accuracy without increasing the capacity of O-press machine
The present invention relates to a method for manufacturing a steel pipe.

[0002]

2. Description of the Related Art As is well known, UOE steel pipes are mainly used for oil and gas line pipes and have an outer diameter of 400 to 1650.
It is a large diameter welded steel pipe of mm. This UOE steel pipe is made from a thick steel plate with a thickness of 6 mm or more, and after being cold-formed into a U-shaped steel plate by a powerful U-press machine, O-pressed by an O-press machine and then welded, Manufactured.

FIGS. 6 (a) to 6 (e) are schematic views showing a state in which an O press is performed on a U-shaped steel plate 2 by an O press machine 1 with time. As shown in FIGS. 6 (a) to 6 (e), the U-shaped steel plate 2 is composed of an upper die 1a and a lower die 1b of an O-press machine 1.
Is manufactured by performing a submerged arc welding from the inner and outer surfaces by pressing both ends 2a and 2b against each other.

Conventionally, the wall thickness of this UOE steel pipe is almost 1
Inches (25.4 mm) or less, and the press capability of the O-press machine 1 was given only the capability corresponding thereto. However, in recent years, high-pressure operation of line pipes has been aimed at for the purpose of enhancing transportation capacity and efficiency. Therefore, UOE steel pipes having a thickness of up to 1.5 inches (38.1 mm) have been required. Also, the strength of UOE steel pipes tends to increase from the conventional X65 grade (yield strength YS: 450 MPa or more) to the X100 grade (yield strength YS: 700 MPa or more). As described above, when attempting to manufacture a thick UOE steel pipe having a high strength, a U-press machine or an O-press machine which has been conventionally used has insufficient press capability, and thus a shape defect occurs.

FIG. 7 shows the UOE after O-press and before welding.
It is sectional drawing of an example of the steel pipe 3. As shown in the figure, the shape defect of the UOE steel pipe 3 includes a seam gap g, which is an opening distance of the butted portions 3a and 3b, a butted portion 3a,
Peaking p which is a local shape defect of 3b, roundness calculated by (maximum outer diameter−minimum outer diameter) / nominal outer diameter, flatness generated at a position S corresponding to a shoulder of a UO pipe in an O press machine. Poor shape etc.

Here, with respect to the U-press machine, it is possible to cope with the shortage of the press-capability by introducing a U-press machine having a larger press-capability, but a significantly higher press-capability than the U-press machine is required. As for the O-press machines to be used, huge press machines of about 50,000 tons have already been introduced. For this reason, it is practically impossible to replace an existing O-press machine with an O-press machine having a greater press capability, in terms of cost and equipment.

Therefore, various inventions have been proposed for manufacturing a high-strength thick UOE steel pipe using an existing O-press machine.
For example, Japanese Patent Application Laid-Open No. 54-41260 discloses an invention in which an O-press machine is used to sequentially perform O-press for each of a plurality of portions in the longitudinal direction of a U-shaped steel sheet. The invention by setting the molding conditions of C molding optimally is described in 9-
No. 94611 discloses an invention in which the outer surface of a UO pipe is pressurized while being restrained by a flat deformation restraining jig before welding after O-pressing. Inventions in which the length is 3.5 times or more the plate thickness have been proposed.

[0008]

However, Japanese Patent Application Laid-Open No. 54-41
In the invention proposed in Japanese Patent Publication No. 260, since the shape of the butted portion of the U-shaped steel plate is hard to be constant in the longitudinal direction, the dimensional accuracy and welding quality of the UOE steel pipe deteriorate. In addition, since the O-press load is concentrated in a narrow part of the U-shaped steel plate in the longitudinal direction, it is necessary to control the press load in the longitudinal direction very strictly. If the press load cannot be accurately controlled, This may lead to a major accident such as damage to the pressurized part of the O-press machine.

Further, Japanese Patent Application Laid-Open Nos. 8-294727 and 9-23
The invention proposed by Japanese Patent No. 9447 does not drastically improve the forming ability in the O-press. Therefore, if the thickness of the UOE steel pipe increases, the O-press ability becomes insufficient.

Furthermore, the invention proposed in Japanese Patent Application Laid-Open No. 9-94611 is intended to suppress deformation during welding as much as possible, so that it is not possible to reinforce the pressing ability in the O-press.

As described above, according to any of the conventional techniques, it is possible to improve the dimensional accuracy of a UOE steel pipe without increasing the capacity of an O-press machine, and particularly to manufacture a high strength thick UOE steel pipe with a high dimensional accuracy. That was impossible.

Here, an object of the present invention is to provide a method of manufacturing a UOE steel pipe capable of improving dimensional accuracy by using an existing O-press machine, and more specifically, for example, a seam gap, An object of the present invention is to provide a method of manufacturing a high-strength thick-walled UOE steel pipe capable of improving peaking, roundness, poor shoulder shape, and the like.

[0013]

Means for Solving the Problems Normally, an O-press is used as shown in FIG.
As shown in FIGS. 6 (a) to 6 (e), in order to prevent the U-shaped steel plate 2 from coming off from the die of the die and leading to a serious situation such as equipment damage, the butted portion 2a of the U-shaped steel plate 2 is used. 2b top die
This is done at the top of 1a. Therefore, the present inventor has made the U-shaped steel plate 2 in this manner using an existing O-press machine.
The situation in which the O-press was performed was examined in detail.

As a result, the present inventor has determined that the compressive load acting on the vicinity of the butting portions 2a and 2b of the U-shaped steel plate 2 at the time of O pressing is the relative position of the butting portions 2a and 2b with respect to the upper die 1a and the lower die 1b. And the compressive load acting near the butting parts 2a and 2b
a and 2b are minimum when the upper die 1a is at the uppermost portion or at the lowermost portion of the lower die 1b, and when the butted portions 2a and 2b are at the lowermost portion of the upper die 1a or at the uppermost portion of the lower die 1b. It was found that

The present inventor has further studied and found that the position of the butting portions 2a and 2b is fixed to the uppermost portion of the upper die 1a at the time of O-press. The first O-press is performed so that the parts 2a and 2b are located at the uppermost part of the upper die 1a, and the U-shaped steel plate is rotated so that the butted parts 2a and 2b are located at the lowermost part of the upper die 1a. By performing the second O-press from the above, the compressive load acting on the butting portions 2a and 2b can be greatly increased without increasing the press capacity of the existing O-press machine at all. 2a, 2b
It has been found that the shape accuracy of can be remarkably improved.

Further, after performing the second O-press in this way, the present inventors reverse the U-shaped steel plate 2 by the same distance from the position of the butted portions 2a and 2b at the time of the first O-press. It has been found that the roundness of the obtained UOE steel pipe can be improved by performing the third O-press while rotating in the direction.

As a result of further studies based on these findings, the present inventor has performed a plurality of O-presses on the U-shaped steel sheet, and rotated the U-shaped steel sheet during the O-press, so that the U-shaped steel sheet was pressed against the die. By changing the position of the butted portion of the shaped steel plate, the seam gap after pressing is reduced, and the insufficient drawing of both shoulders due to insufficient load is eliminated.
The inventors have found that the shape accuracy of the OE steel pipe can be improved, and completed the present invention.

Here, the gist of the present invention is that U
When performing O-press on a shaped steel plate to produce UOE steel pipe,
The OOE is characterized in that the O-press is performed a plurality of times, and the position of the butted portion of the U-shaped steel plate with respect to the dies in each of the plurality of O-presses is changed.
This is a method for manufacturing a steel pipe.

In the above-described method for manufacturing a UOE steel pipe according to the present invention, the position of the butted portion is changed by rotating the U-shaped steel sheet around the central axis during a plurality of O-presses.

In the method of manufacturing a UOE steel pipe according to the present invention, the first O-press is performed by arranging the U-shaped steel sheet so that the butted portion is located at or near the uppermost part of the upper die. The U-shaped steel plate is arranged such that the butted portion is located at the lowermost portion of the upper die, the uppermost portion of the lower die, or in the vicinity thereof, and the second O-press is performed. Regarding the position of the butted portion when the O press is performed, the second O
An example is shown in which the U-shaped steel sheet is arranged so as to be symmetrical to the position of the butted portion when the press is performed, and the third O-press is performed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for manufacturing a UOE steel pipe according to the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1A to 1F are explanatory views schematically showing the manufacturing method of this embodiment with time. FIG. 2 is an explanatory diagram showing FIG. 1A in detail. As shown in FIG. 2, an upper insert liner 13 is incorporated into an upper die 11 and a lower insert liner 14 is incorporated into a lower die 12 in order to obtain a predetermined product outer diameter. And U-shaped steel plate 15
Is inserted between the upper insert liner 13 and the lower insert liner 14 and a load P is applied from above, thereby performing O-press to press-form the U-shaped steel plate 15 into O-shape. 1 (a) to 1 (f), the upper insert liner 13 and the lower insert liner 14 are omitted for convenience of description.

In this O-press molding, the load P
Are very unevenly distributed as a compressive load in the circumferential direction of the U-shaped steel plate 15. FIG. 3 is a graph showing an example of tensile loads distributed with respect to the circumferential positions A, B, C, and D of the U-shaped steel plate 15 in FIG. In the graph shown in FIG.
When the butting portions 15a and 15b of the upper die 11 are at the position A which is the uppermost part of the upper die 11, the position is 0 degree. The position at a certain position B or at the position D which is the uppermost part of the lower die 12 is shown as 90 degrees or 270 degrees.

As shown in the graph of FIG. 3, the compressive load distributed with respect to the circumferential position of the U-shaped steel plate 15 is 0 degree position A.
Or at position C at 180 degrees, the minimum
It changes continuously so that it becomes substantially maximum at the position B or D of the degree.

For this reason, when the U-shaped steel plate 15 is disposed and the O-press is performed as shown in FIG.
Since the compressive load applied to 15a and 15b is smaller than the compressive load applied to other portions, it is considered that peaking p shown in FIG. 7 occurs. In addition, U press
As shown in FIG. 6C, the deformation pattern of the shaped steel plate 15 is insufficiently drawn because the left and right shoulders are finally deformed into an arc shape. For this reason, a seam gap g, a decrease in roundness, and a defective shape of the shoulder portion S shown in FIG. 7 occur.

It is considered that these shape defects increase as the UOE steel pipe becomes higher in strength and thicker, because the upper limit of the O-pressing ability is exceeded.

Therefore, in the present embodiment, uniform O-pressing is performed in the circumferential direction of the U-shaped steel sheet 15 by utilizing the distribution of the compressive load on the U-shaped steel sheet 15, which is exemplified using a graph in FIG. That is, as shown in FIGS. 1 (a) and 1 (b),
As in the conventional O-press, the first O-press is performed by arranging the U-shaped steel plate 15 so that the butted portions 15a and 15b are located at the uppermost portion A of the upper die 11, and FIG. 1 (c) and FIG. (d)
As shown in the figure, after the first O-press, the butted portions 15a and 15b are moved to the vicinity of the lowermost portion B of the upper die 11 by rotating the U-shaped steel plate 15 to the left around the central axis using, for example, a pipe rotating roller. After the second O-press was performed, the U-shaped steel sheet 15 was similarly moved to the center using a pipe rotating roller after the second O-press, as shown in FIGS. 1 (e) and 1 (f). By rotating the butt portions 15a and 15b around the axis in opposite directions, the second O-press is performed with respect to the uppermost portion A of the upper die 11 at the position of the butt portions 15a and 15b at the time of the first O-press. 3 is placed at a position that is symmetrical to the positions of the butting parts 15a and 15b when
Perform the second O-press.

Hereinafter, the first to third O-presses will be sequentially described. (First O-Press) The U-shaped steel sheet 15 is roughly formed by the first O-press shown in FIGS. 1 (a) and 1 (b), and is formed into a substantially circular shape. However, after the first O-press, as described above, the peaking, the seam gap g, the decrease in roundness, and the flat shape of the shoulder S are caused by insufficient compression load in the vicinity of the butting portions 15a and 15b. A defect or the like has occurred.

(Second O-Press) The second O-press greatly increases the compressive load near the butting portions 15a and 15b as compared with the first O-press, and causes the butting portions 15a and 15b to be compressed. Both peaking and poor shoulder shape are significantly improved. However, since the compressive load acting in the second O-press does not uniformly act on the butted portions 15a and 15b and is asymmetric, when the thickness and strength of the U-shaped steel plate 15 increase, the butted portions 15a and 15b Misalignment (offset) may occur.

Therefore, in the present embodiment, as shown in FIGS. 1 (e) and 1 (f), the butting portions 15a and 15b
The third O-press is performed by disposing them at positions symmetrical to the butting portions 15a and 15b in the third O-press. As a result, the butted portions 15a and 15b can be O-pressed symmetrically, and the roundness of the U-shaped steel sheet 15 after the O-press can be improved.

FIG. 4A is an explanatory view schematically showing the arrangement of the U-shaped steel plate 15 in the second O-press according to the present embodiment, and FIG. 4B is a diagram illustrating the U-shaped steel plate in the third O-press. It is explanatory drawing which shows arrangement | positioning of 15 typically.

As described above, in the present embodiment, the U-shaped steel plate 15
When an O-press is performed to manufacture a UOE steel pipe, the O-press is divided into three times, and the butt portion 15 of the U-shaped steel sheet 15 against the dies in each of the three O-presses is performed.
Changing the positions of a and 15b, specifically, as shown in FIG.
4 (b) and the angle θ in FIG.
Pressing, and then, as shown in FIG.
Is rotated by the angle θ, and the second O-press is performed.
Further, as shown in FIG. 4 (b), the U-shaped steel plate 15 is rotated by an angle 2θ in the reverse direction to perform the third O-press.

As a result, the butting portions 15a and 15b, which receive only the minimum compressive load in the first O-press, can apply a compressive load close to the maximum by the second and third O-presses. , 15b, the insufficient drawing (peaking) due to insufficient compressive load can be reduced, and the insufficient drawing at both shoulders can be eliminated, and a good dimensional shape can be obtained.

The positions of the butting portions 15a and 15b in the second and third O-presses are as shown in the graph of FIG.
The closer the position is to 90 or 270 degrees, the more
, 15b because the compressive load acting near
It is desirable that the angle θ be as close as possible to 90 degrees. However, if the butted portions 15a and 15b are displaced from the upper die 11 to the outer diameter adjusting gap provided between the upper die 11 and the lower die 12, a serious problem such as equipment damage will occur, so that the angle θ Is desirably set to a value as large as possible without departing from the die. The angle θ may be appropriately set in consideration of the thickness, strength, and the like of the U-shaped steel sheet 15.

As described above, according to the present embodiment, the butting portions 15a, 15a are formed by the second and third O-presses.
By applying the maximum load evenly to b, it is possible to reduce insufficient drawing (peaking) due to insufficient compressive load and to eliminate insufficient drawing at both shoulders.
The dimensional accuracy of the E steel pipe can be extremely remarkably improved.

[0036]

EXAMPLES Further, a method of manufacturing a UOE steel pipe according to the present invention will be described more specifically with reference to examples.

The method of the present invention in which the O-press is divided into three times and
Outer diameter: 36 inches,
Samples No. 1 to No. 4 were obtained by performing an O-press on a high-strength thick UOE steel pipe having a wall thickness of 20 mm, a length of 12 m, a yield strength of 970 MPa and a tensile strength of 1040 MPa.

For these samples No. 1 to No. 4, peaking (deviation from a perfect circle in a diameter direction of 100 mm), shoulder curvature ratio R / R ₀ (R: measured radius, R ₀ : true) (Circular radius), outer diameter difference between vertical and horizontal, and seam gap
(Average value in the longitudinal direction) was measured. Table 1 summarizes the O-press conditions and test results.

[0039]

[Table 1]

Sample No. 1 is a conventional example in which the butted portion was arranged at the uppermost portion of the upper die and the O-press was performed once. This sample No. 1 has a large peaking, a shoulder curvature ratio, a difference in outer diameter, and a seam gap. When welding and expanding the sample No. 1 to produce a UOE steel pipe, a large residual stress is generated at the butt joint after welding due to a large seam gap. It was found that there was a risk of breaking in the direction. In addition, even if the dimensions and shape were corrected by expanding the pipe, local peaking etc. could not be completely corrected, and when performing on-site girth welding with the end faces abutting each other, it took a considerable amount of time to adjust the end faces. It was also found that the decline in sex was remarkable.

On the other hand, in each of Sample Nos. 2 to 4, the O-press was divided into three times, and the U-shaped steel sheet was rotated by an angle θ in the second and third O-presses. It is an invention example. FIG. 5 is a graph showing the influence of the angle θ at the time of the second O-press on the peaking and the seam gap for the samples No. 1 to No. 4.

From the graph shown in Table 1 and FIG.
Is larger, the seam gap (mm) and peaking (m
(m / 100mm span), the improvement effect of the shape improvement effect is large, but even if the angle θ is about 30 degrees, a remarkable improvement effect can be obtained compared to the case where the angle θ is 0 degree. Recognize.

From the graphs shown in Table 1 and FIG.
At the time of the second and third O-presses, the angle θ should be as small as 90
°, shoulder curvature ratio, outer diameter difference, and seam gap are improved. However, regarding peaking, the improvement effect is greater when the angle θ during the second and third O-presses is set to 60 °. I understand.

This is because if the angle θ is about 60 °, the shoulders of the U-shaped steel plate are almost right beside each other, so that a sufficient compressive load is applied to this part and the R part of the shoulder when the round part is a perfect circle It is considered that this is because the shape approaches the radius and the whole shape becomes good.

[0045]

[Modification] In the embodiments and examples, the O-press is set to 3
Although the example in which the process is performed in each time is taken as an example, the U
The method of manufacturing the OE steel pipe is not limited to such an embodiment, and the O-press may be divided into five or seven or more times. Thereby, the shape accuracy of the UOE steel pipe can be further improved.

In the embodiments and examples, the position of the butted portion in the second O-press and the position of the butted portion in the third O-press are symmetrical with respect to the position of the butted portion in the first O-press. Although the following example was taken as an example, the method for manufacturing a UOE steel pipe according to the present invention is not limited to such an aspect, and the UOE steel pipe may be positioned substantially symmetrically. Even in such a case, sufficient shape accuracy can be obtained depending on the thickness and strength of the U-shaped steel sheet.

In the description of the embodiments and examples,
The U-shaped steel plate was rotated by using a pipe rotating roller between each of the three O-presses to change the position of the butted portion with respect to the die.
The method for manufacturing the E-steel pipe is not limited to such an embodiment, and the U-shaped steel sheet may be rotated by a rotating means as appropriate.

In the description of the embodiments and examples,
Place the U-shaped steel plate so that the butted portion is located at the top of the upper die and perform the first O-press, and place the U-shaped steel plate so that the butted portion is located near the bottom of the upper die. The second O-press is performed, and U is adjusted so that the position of the butted portion at the time of the first O-press is symmetrical to the position of the butted portion at the time of the second O-press. Although the case where the shaped steel sheet is arranged and the third O-press is performed is taken as an example, the present invention is not limited to such a method of manufacturing a UOE steel pipe according to the present invention.

For example, in the first O-press, the butting portion is arranged at the uppermost part of the upper die, in the second O-press, it is arranged near the uppermost part of the lower die, and in the third O-press, the second part is the second one. In the case of symmetric arrangement, the first O-press is arranged near the uppermost part of the upper die, and the second O-press is arranged near the uppermost part of the upper die.
In the second O-press, various modifications can be exemplified, such as a mode in which the O-press is disposed at a position symmetrical to the second press.

That is, according to the present invention, in which the O-press is divided into a plurality of times and the position of the butted portion of the U-shaped steel plate with respect to the dies in each of the plurality of O-presses is changed, a sufficient compressive stress can be obtained by the first O-press. A sufficient compressive stress may be applied uniformly to the portion where the U-shaped steel sheet has not acted in the width direction of the U-shaped steel sheet by applying a sufficient compressive stress by the second and third O-presses.

[0051]

As described in detail above, according to the present invention, it is possible to improve the dimensional accuracy of a UOE steel pipe by using an existing O-press machine, and more specifically, to manufacture by using the existing O-press machine. Shape defects such as seam gap, peaking, roundness, and shoulder shape defects, which occur in the high-strength, thick-walled UOE steel pipe, can be remarkably improved. The breakage of the steel pipe can be eliminated and the workability of on-site girth welding can be significantly improved. The significance of the present invention having such an effect is extremely remarkable.

[Brief description of the drawings]

FIG. 1A to FIG. 1F are explanatory diagrams showing a manufacturing method of an embodiment over time and schematically.

FIG. 2 is an explanatory diagram showing FIG. 1 (a) in detail.

FIG. 3 is a graph showing an example of a compressive load distributed with respect to a circumferential position of a U-shaped steel sheet in FIG. 2;

FIG. 4A is an explanatory view schematically showing an arrangement of U-shaped steel sheets in a second O-press according to the present embodiment.
(b) is explanatory drawing which shows typically arrangement | positioning of the U-shaped steel plate in the 3rd O press.

FIG. 5 is a graph showing the influence of the angle θ at the time of the second O-press on the peaking and the seam gap for the sample Nos. 1 to 4 of the example.

FIGS. 6 (a) to 6 (e) are schematic views showing a state in which an O-press is performed on a U-shaped steel plate by an O-press machine over time.

FIG. 7 is a cross-sectional view of an example of a UOE steel pipe after O-press and before welding.

[Explanation of symbols]

 11 Upper die 12 Lower die 15 U-shaped steel plate 15a, 15b Butt joint

Claims (1)

[Claims] 1. When an O-press is performed on a U-shaped steel sheet to produce a UOE steel pipe, the O-press is performed in a plurality of times, and the U-shaped steel sheet is pressed against a die in each of the plurality of O-presses. A method of manufacturing a UOE steel pipe, wherein a position of a butt portion is changed.