JPH091234A - Production of uo steel pipe - Google Patents

Abstract

PURPOSE: To provide UO steel pipe which can produce at a low cost only with the existing pressing tool and pipe expanding tool and has excellent shape and dimensional precision and mechanical property without using a special insert die for intermediate diameter or a stopper plate for preventing bucking in an O press, at the time of producing the UO steel pipe having a middle size of a stepped general size. CONSTITUTION: An open seam pipe POm having good dimensional precision without defective shape is obtd. by using the O press tool 2k for the general size below one size of the middle size Dm (Dk <Dm <Dk+1 ) in the O press 1 to form the pipe-shape. Successively, a first time pipe expansion is performed with a pipe expanding tool 11k for a general size below one size in an expander 10, in the following process a second time pipe expansion at is performed with a pipe expanding tool 11k+1 for the general size above one size to obtain a UO steel pipe Pm having the good shape dimensional precision and mechanical property by a large pipe expanding ratio, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a UO steel pipe by a so-called UOE forming system for producing a straight seam welded pipe having a relatively large diameter.

[0002]

2. Description of the Related Art In general, a UOE pipe manufacturing method is an end bending process for bending both ends of a plate whose end surface is ground by a press-a U pressing process for bending a plate into a U shape by a U press-a U-shaped plate. O press process of forming into O shape (open seam pipe) by O press-Welding process of temporarily welding the open seam pipe and then performing inner surface welding and outer surface welding on the seam-High dimensional accuracy and optimum mechanical properties In order to obtain the above, a pipe expanding process for slightly expanding the pipe diameter by an expander-a hydraulic pressure testing process for testing the pressure resistance of a steel pipe by applying hydraulic pressure-an inspection process for inspecting the dimensions and the like of the product. The expander includes a hydraulic expander and a mechanical expander, but recently, a mechanical expander with good pipe expansion efficiency and dimensional accuracy has been adopted.

Of these processes, the O press 1 is
In order to mold various sizes with one die set, as shown in FIGS. 5A and 5B, a master die composed of an upper die block 2A and a lower die block 2B has a predetermined thickness, for example, three layers. Insert die (insert liner)
The die inner diameter d is adjusted by combining and mounting 2C. Usually, insert die 2
The thickness of C is a constant thickness, for example, 2 inches. Therefore, the manufacturable outer diameter of the UO steel pipe is regulated by the die inner diameter d of the O press tool 2 as described above, and usually has a stepwise size of 2 inch pitch.

However, in practice, a size other than the stepwise general size, that is, an intermediate size may be ordered. When manufacturing such an intermediate size, it can be dealt with by purchasing an insert die with an inner diameter corresponding to the intermediate size, but the insert die is expensive, and an expensive die tool for producing a small amount of the intermediate size. Since purchasing the product increases the cost, there is a demand for a method of manufacturing the intermediate size at low cost.

Therefore, conventionally, there has been proposed a method of manufacturing an intermediate size using the current O press tool. This is the case when the intermediate size of the intermediate outer diameter _Dm ( _Dk < _Dm < _{Dk + 1} ) is ordered with respect to the general size of the final product outer diameters _Dk and _{Dk + 1} , as shown in FIG. ), The inner diameter d of the die corresponding to the general size D _k , which is one size smaller,
_{By using} an O press tool 2 _{k of k} (upper die block 2A / lower die block 2B or insert die 2C), by increasing the distance L between the upper die block 2A and the lower die block 2B when the press is at the lowest position ( L>
L ₀ : A space is opened even in the general size, and the minimum space is L ₀
In this case, the pipe longitudinal diameter after O-pressing, that is, the pipe circumference length is increased to obtain the pipe circumference length corresponding to the intermediate size open seam pipe outer diameter D _Om . In the expander in the subsequent step, the outer diameter D _m of the final product of the intermediate size can be obtained at the usual expansion ratio.

However, even with such a method, the distance between the upper die block 2A and the lower die block 2B becomes large, so that O is reduced especially in a thin steel pipe (thickness of 9.5 mm or less).
As shown in FIG. 5 (d), the open seam pipe P _Om buckles due to the drawing process in the press, and the bulging portion cannot be corrected even by the pipe expansion in the subsequent process. However, there was a risk of impairing the shape such as poor roundness.

As a method of solving this, Japanese Patent Laid-Open No. 58-58
A method for molding an O pipe described in Japanese Patent Publication No. 41619- has been proposed. As shown in FIGS. 6A and 6B, this is because a buckling prevention stopper plate 50 is provided between the upper die block 2A and the lower die block 2B, and the buckling prevention stopper plate 50 is used. Prevents the steel sheet from bulging and buckling into the gap during pressing. The buckling prevention stopper plate 50 is fixed to one die block 2B by a key 51 and a key groove 52 or a bolt and a bolt hole.

[0008]

In the above-mentioned O-press 1, as shown in FIGS. 6 (C) and 6 (d), a length of about 3 m is provided so that a UO steel pipe having a length of, for example, 18 m can be manufactured. Die block 2A ・ 2B or insert die 2
When 6 pieces of C are used side by side and the buckling prevention stopper plate 50 is attached as in the prior art, the buckling prevention stopper plate 50 is, for example, 2 [sheets / die] × 6 [for the O press. Die] It will be attached, and workability will deteriorate when changing the size. In addition, the weight becomes heavy when the buckling prevention stopper plate 50 is placed, and in a small diameter size in which a large number of insert dies for adjusting the outer diameter are inserted and mounted in the die block, the crane capacity may be exceeded. It may become unusable. In this case, the buckling prevention stopper plates are removed one by one, resulting in poor workability.

Further, even when the buckling prevention stopper plate 50 can be formed without buckling, the upper and lower die block intervals L of the O press are large, so that the shape after pressing becomes a vertical ellipse (see FIG. 6 (b)). ), It is difficult to correct by expanding the pipe in the subsequent process, and there is also a problem that the steel pipe has poor roundness.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to use a conventional insert die for intermediate diameter and a buckling prevention stopper plate in an O press without using a conventional insert die. An object of the present invention is to provide a UO steel pipe manufacturing method capable of manufacturing an intermediate-sized UO steel pipe using only the current press tool and pipe expanding tool, and also capable of obtaining a UO steel pipe having good shape dimension accuracy and mechanical properties.

[0011]

According to the present invention, as shown in FIG. 1, a plate is bent into a U shape by a U press, and then formed into a tubular shape by an O press 1 equipped with a stepwise pressing tool,
After the joint has been seam welding and tube expansion by expander 10, by utilizing the method for producing a UO pipe to obtain a gradual UO steel pipe general size, the stepwise general size D _n of intermediate size D _m When manufacturing the UO steel pipe P _m ,
In the press 1, the intermediate size D _m (D _k <D _m <D
_{k + 1} ) is formed into a tubular shape by using an O press tool 2 _k for general size which is one size smaller than _{k + 1} ), and an expansion ratio larger than a normal expansion ratio is used by using the expansion tool 11 for general size in the expander 10 in the subsequent step. Expansion is performed at a rate of
characterized in that to obtain UO steel pipe P _m of _m.

When the intermediate size D _{m to} be produced has a size close to the general size D _k under one size, the final product is expanded only once by using the expansion tool 11 _k for the general size under one size. Although it is possible to obtain the final product with a normal intermediate size, it is not possible to obtain the final product with one expansion.
The pipe expansion is performed a plurality of times by a plurality of general-purpose pipe expansion tools 11. Furthermore, in an actual intermediate size, it only has to be performed twice.
Tube expansion tool for general size 1 size below the first tube expansion
1 _k , and the second finishing pipe expansion is performed with the general-purpose pipe expanding tool 11 _{k + 1,} which is one size larger.

[0013]

With the above construction, the plate for the intermediate size D _m is formed into the open seam pipe P _Om by the O press through the end face grinding process, the end bending press process and the U press process. In this O-press, since the O-press tool 2 _k for general size, which is one size smaller than the intermediate size D _m, is used to form a tube, it is possible to sufficiently secure the expansion ratio in the subsequent expansion process. Unlike the conventional intermediate size manufacturing method in which the gap between the upper and lower dies is large, buckling does not occur, a vertical ellipse does not occur, and it is not necessary to provide a buckling prevention stopper plate. It is possible to manufacture an open seam pipe P _Om with good dimensional accuracy without a defective shape using a press tool. In addition, by using the O press tool 2 _k for the general size that is one size smaller, a good drawing ratio can be secured even when the plate width is narrowed to secure the pipe expansion ratio, and the shape near the abutting portion of the open seam pipe Can be eliminated, and the dimensional accuracy of the product can be sufficiently ensured.

In the pipe expanding process, the pipe expanding tool 11 for general size can be used to expand the pipe at a larger expansion ratio than the normal pipe expanding ratio. Only the current pipe expanding tool 11 can be used and the pipe expanding ratio is increased. And the processing rate is high,
The mechanical performance of the final product can be improved. Further, by expanding the pipe in multiple times, the result of the previous pipe expansion, for example, the direction of dimensional change (roundness / bending) can be grasped and reflected in the subsequent pipe expansion, improving the dimensional accuracy. Further, by shifting the die position of the pipe expanding tool in the pipe circumferential direction between the previous pipe expansion and the subsequent pipe expansion, it is possible to reduce the die marks and the defects due to the die marks.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; Manufacturing process of UO steel pipe used in the present invention, as shown in FIG. 1 (b), it is similar to the conventional general pipe producing process, the outer diameter D _O of O tubular open seam tube P _O in O pressing process The finished product is formed into a UO steel pipe P having an outer diameter D of the final product in the pipe expanding process. Expansion is performed by a mechanical expander, and the processing rate (expansion rate) is usually about 1%.

Most of UO steel pipes originally have API standard inch size products, and the sizes are gradually changed as shown in Table 1. However, recently, the demand for structural steel pipes has increased, and as consumers, mainly for domestic use,
As for the size, a 50 mm pitch is increasing in demand. For example, φ700mm (27.5inch), φ750m
m (29.5inch), φ800mm (31.5inch), ...
An intermediate size such as is required.

[0017]

[Table 1]

When manufacturing a UO steel pipe having an intermediate size as described above, for example, a final product outer diameter D _m of φ800 mm (31.5 inch), the closest general size is D _{k + 1} = 32 inch (one size higher). However, if the O press tool 2 _{k + 1} of this size is used, the outer diameter D _Om of the open seam pipe after the O press is already 8 mm for the final product.
It exceeds 00 mm (812.8 / 1.01≈80
5 mm), it becomes impossible to secure the processing rate in the pipe expansion in the subsequent process (see FIG. 1A).

Therefore, in the present invention, as shown in FIG. 1A, the final product outer diameter D _m = φ800 mm (31.5 inc.
General size D _k = 30inch (76)
2.0 mm O press tool 2 _k (upper die block 2A
-Use the lower die block 2B or insert die 2C). As a result, a sufficient expansion ratio can be secured, and the upper die block 2A and the lower die block 2B can be secured.
O with the interval between and is the same minimum L ₀ as the general size
Open seam pipe P of intermediate size that can be pressed and has good dimensional accuracy without buckling or oval shape defects
_Om is obtained.

The use of the O press tool 2 _k for 30 inch, which is one size smaller, has the following advantages. That is, in order to manufacture a steel pipe, a pipe expansion ratio of at least about 1.0% is required for pipe expansion after O-pressing.
In the case of φ800 mm, the perimeter after O-pressing is 800/1.
It is necessary to secure the tube expansion ratio by making it smaller than 01 = 792.0 mm. On the other hand, in order to make the shape after O-pressing into a perfect circle, an appropriate drawing ratio (about 0.3%) during O-pressing
It is necessary to prevent the opening of the butted part and the deterioration of the shape due to the springback of the steel pipe.

For this reason, at the time of manufacturing φ800 mm, the plate width of the thick plate is narrowed in order to secure the pipe expansion ratio, and the size is increased by 32 inch.
When the O press tool 2 _{k + 1} for molding is used for forming, the draw ratio becomes insufficient, and the shape of the butted portion is significantly deteriorated as shown in Fig. 2 (b). However, it affects the quality of welding in the subsequent process, and it becomes difficult to secure the dimensional accuracy of the product, especially the roundness. On the other hand, one size below 30 mm
When the O press tool 2 _k for inch is used, a good drawing ratio can be secured even when the plate width is narrowed. As a result, as shown in FIG. It becomes good and the dimensional accuracy of the product can be sufficiently secured.

The mechanical expander 10 is shown in FIG.
As shown in (a), a tapered cone 13 is mounted through a jaw 12 in a cylindrical die 11 formed by arranging a large number of die segments 11A in the circumferential direction, and the cone 13 is pulled by a draw bar 14. This is a device for expanding the outer diameter of the die 11 to expand the pipe. The die 11 having a length of about 1 m is inserted from the pipe end, and the die 11
Alternatively, the welded pipe P is moved to expand the pipe over its entire length.

In such a mechanical expander, the effective length of the drawbar stroke is limited,
In the final product outer diameter D = φ30 inch (762 mm) size, the radius is about 18 mm. Moreover, this effective length cannot always be used sufficiently, and is usually about 50 to 80%. Therefore, in the present invention, in the case of the final product outer diameter D _m of the example given as D _m = φ800 mm (31.5 inch), as shown in FIG. 1 (a), 30 inch (762 mm)
For the first pipe expansion with a pipe expansion tool (die) 11 _k ,
Next, pipe expanding tool 11 for 32 inch (812.8 mm)
Finish with _{k + 1} .

In the first expansion, the outer diameter is about 780.
mm (30.7 inch) and the outer diameter is 80 at the second expansion.
It is set to 0 mm (31.5 inch). Also, open seam tube P _Om before pipe expansion is the same size as that of a 30inch general size, die inner diameter d _k of the O press tool 2 _k of 30inch (762.0mm) is 758.1Mm, The outer diameter D _Om of the formed open seam pipe is 75 from 1.002 (spring back ratio) × d _{k which} will be described in detail later.
It will be 9.6 mm. From the above, the first expansion rate is 2.7.
%, The pipe expansion ratio for the second time is 2.6%, and the pipe expansion ratio is larger than that for the normal general size (about 1%).

Since the pipe expansion ratio is higher than usual, the circumferential tensile working ratio in the pipe expansion process is increased and the mechanical performance (yield point) is improved. Also, by expanding the tube in two steps,
Although the replacement of the pipe expanding tool is troublesome, it has the following advantages as compared with the method of finishing to the product size by the usual one-time finishing in the pipe expanding process. That is, when the pipe is expanded in two steps, the direction of the dimensional change (roundness, bend) due to the expansion can be grasped to some extent by the first expansion.
It is possible to manufacture a steel pipe with better dimensional accuracy by reflecting the tendency of the first time by the second expansion. As shown in FIG. 3 (b), when there is a difference between the outer surface radius of curvature R _D of the die 11 and the radius of curvature R _P of the steel pipe, a die mark remains on the inner surface of the steel pipe, and the appearance of the steel pipe or fluid transfer in the pipe. Although there is a problem in terms of resistance, it is possible to reduce the problem caused by the die mark by shifting the die position in the second pipe expansion.

In this pipe expanding process, since the pipe is expanded twice, it is necessary to temporarily stock the steel pipes during the setup change of the pipe expanding tool. However, the production amount of such an intermediate size is not large. Since the number of pipes is about 20 or less, there is no problem in the place for stocking the steel pipes during the setup change of the pipe expanding tool.

Next, specific numerical examples will be described.
First, there is the following relational expression between the outer diameter D of the final product of the steel pipe, the peripheral length C of the open seam pipe after O-pressing, and the width W of the thick plate used as the material.

[0028]

(Equation 1)

Here, as an example, the intermediate size φ80.
When manufacturing a 0 mm steel pipe, E = 5.3% and R = 0.
3% and t = 16 mm. Further, there is the following relational expression between the die inner diameter d of the O press and the peripheral length C of the open seam tube after the O press.

[0030]

(Equation 2)

Therefore, when manufacturing a steel pipe of φ800 mm × t16 mm, C = π × 800 / (1 + 5.3 / 100) = 2386.
4 mm W = 2386.4 / (1-0.3 / 100) -π × 16
= 2343.3 mm Further, the inner diameter of the O press tool 2 _k for 30 inch is 75
Since it is 8.1 mm, from the formula, 2386.4 mm = {π
× 758.1 + (L-12.8) × 2} × 1.002⇒
L = 12.8 mm. Since the gap L between the upper and lower dies of this O-press is usually designed to be 12.8 mm (= L _o ), it is a perfect circle, and therefore, it is 3 smaller than the size of the present invention.
By using the 0-inch O press tool 2 _k , a sufficiently good shape could be obtained.

As for the pipe expanding, after the first pipe expanding is performed by the pipe expanding tool 11 _k for 30 inch, the pipe expanding tool 11 _{k + 1} for 32 inch is performed.
The second pipe expansion was performed by. Table 2 shows the expansion ratio.

[0033]

[Table 2]

FIG. 4A shows the result of measuring the roundness (maximum outer diameter-minimum outer diameter) of the final product. In the figure,
The present invention uses an O press tool for 30 inch, which is one size smaller than that of FIG. 2 (a), and expands the pipe twice with a pipe expanding tool for 30 inch and 32 inch.
This is a case where the O-press tool for 32 inch, which is one size larger than that in (b), is used, and the pipe is expanded once with the pipe expanding tool for 32 inch.

FIG. 4 (b) shows the results of measuring the roundness and bending due to pipe expansion. In the figure, the present invention is
When the pipe expansion is divided into two times and the first and second expansions are performed at a pipe expansion ratio of 0.6%, the comparative example shows that a pipe having the same diameter as the present invention is expanded once at a pipe expansion ratio of 1.2%. It is an example. As for the size, the intermediate size of φ800 mm like this time can not be completed with one tube expansion with the current tube expander, so the data this time is about the normal general size 32 inch (812.8 mm) The data are shown.

FIG. 4C shows the result of measuring the mechanical performance. In FIG. 4, the present invention and a comparative example are shown in FIG.
This is the same as the case (a). As for the intermediate size of 50 mm pitch, most of the structural steel pipes for domestic use are used, so STK490 (general structural carbon steel pipe) shown in Table 3 was referred to for the standard.

As shown in FIG. 4 (a), regarding the roundness, the average value is 8.7 → 1.8 due to the improved shape after O-pressing as in the manufacturing method of the present invention. It has become much better. Further, by increasing the expansion ratio, it has become possible to reduce the roundness variation, which has been a problem in the past, and to facilitate dimensional control within a lot.

As shown in FIG. 4 (b), regarding the mechanical performance, by increasing the pipe expansion ratio, the circumferential tensile working ratio in the pipe expansion before the tensile test was increased, resulting in a yield point of 100.
N / mm ² or more, rising. Since STK490 has no upper limit of yield point and no regulation of yield ratio (yield point / tensile strength), it was found that the manufacturing method of the present invention has no problem in mechanical performance.

As shown in FIG. 4 (C), the double expansion of the present invention has significantly improved both the roundness and the bend in comparison with the single expansion. Also, the variation is small.

[0040]

[Table 3]

[0041]

INDUSTRIAL APPLICABILITY The present invention, when manufacturing a UO steel pipe of an intermediate size of a general size, forms an open seam pipe by using an O press tool for a general size which is one size lower than the intermediate size in an O press, and In the pipe expanding process, the pipe is expanded at a pipe expanding ratio larger than the normal pipe expanding ratio by using the general-purpose pipe expanding tool to obtain the intermediate size UO steel pipe, and therefore the following effects are obtained.

(1) A medium-sized UO steel pipe can be manufactured by using the current O-press tool and expanding pipe tool in a general-sized UO steel pipe manufacturing facility, and a conventional special insert die for medium diameter can be used. No intermediate buckling prevention stopper plate is required, and an intermediate size for small-volume production can be manufactured at low cost.

(2) By using an O-press tool for general size which is one size smaller than the intermediate size, it is possible to eliminate the conventional buckling and vertical elliptical shape after O-press, and to obtain dimensional accuracy without shape defect. A good final product can be obtained, and workability becomes extremely good as compared with the case where a conventional buckling prevention stopper plate is used. Furthermore, by using an O press tool for general size that is one size smaller than the intermediate size, a good drawing ratio can be secured even when the plate width is narrowed to secure the pipe expansion ratio, and the vicinity of the abutting portion of the open seam pipe can be secured. The deterioration of the shape can be eliminated, and the dimensional accuracy of the product can be sufficiently ensured.

(3) In the pipe expanding process, it is possible to expand the pipe at a larger expansion ratio than the normal expansion ratio by using a general-purpose pipe expanding tool. The mechanical performance of can be improved. Further, by expanding the pipe in multiple times, the result of the previous pipe expansion, for example, the direction of dimensional change (roundness / bending) can be grasped and reflected in the subsequent pipe expansion, improving the dimensional accuracy. UO, which has excellent shape and dimensional accuracy in combination with the above-mentioned improvement in shape and dimensional accuracy in O-press.
A steel pipe can be obtained. In addition, by shifting the die position of the pipe expanding tool in the pipe circumferential direction between the previous pipe expansion and the subsequent pipe expansion, the die mark is reduced, and defects such as the appearance of the steel pipe due to the die mark and the fluid transfer resistance in the pipe are reduced. You can

[Brief description of the drawings]

FIG. 1 is an example of a method for manufacturing a UO steel pipe according to the present invention, in which (a) is a schematic sectional view of an O pressing step and a pipe expanding step, and (b) is a block diagram showing the entire UO steel tube manufacturing process.

2A and 2B are front views showing an O press tool, in which FIG. 2A shows the case of the O press tool of one size down of the present invention, and FIG. 2B shows the case of the O press tool of one size down.

FIG. 3 (a) is a perspective view showing a mechanical expander, and FIG. 3 (b) is a cross-sectional view showing a tube shape in which a tube is expanded twice.

FIG. 4 is a graph comparing the present invention with a comparative example,
(A) is the roundness, (b) is the roundness / bending due to pipe expansion,
(C) shows mechanical performance.

5A is a front view showing upper and lower die blocks of an O press tool, FIG. 5B is a front view showing an insert die of the O press tool, and FIG. 5C is a conventional O press tool at the time of manufacturing an intermediate size. The front view shown in FIG. 3D is a partial sectional view showing the bulging phenomenon occurring in the gap portion.

6A is a front view showing a relationship between a conventional buckling prevention stopper plate and an O press tool, FIG. 6B is a partial cross-sectional view showing a state at the time of manufacturing an intermediate size thereof, FIGS. 4A is a plan view and a side view showing an insert die of a general O press tool.

[Explanation of Codes] P _Om ... Medium-sized open seam pipe P _m ... Medium-sized UO steel pipe D _Om ... Medium-sized open seam pipe outer diameter D _m ... Medium-sized UO steel pipe product outer diameter d ... O Press tool Die inner diameter 1 ... O press 2 ... O breathing tool 2A ... Upper die block 2B ... Lower die block 2C ... Insert die 10 ... Mechanical expander 11 ... Die (expanding tool) 11A ... Die segment 12 ... Jaw 13 ... Cone 14 ... Drawbar

Claims (2)

[Claims] 1. A plate is bent into a U-shape by a U-press, then formed into a tube by an O-press equipped with a stepwise pressing tool, the joint is seam-welded, then expanded by an expander, and then stepwise When manufacturing a UO steel pipe of the intermediate size of the stepwise general size by using the UO steel pipe manufacturing method for obtaining the UO steel pipe of the size, in the O press, the O of the general size which is one size smaller than the intermediate size is used. Molded into a tubular shape using a press tool,
A UO steel pipe having an intermediate size is obtained by expanding the pipe at a larger expansion ratio than a normal expansion ratio using a general-purpose expansion tool in the expander in the subsequent step.
Steel pipe manufacturing method. 2. The method for producing a UO steel pipe according to claim 1, wherein the pipe is expanded a plurality of times.