JPH0924433A - Expanding device of steel tube and manufacture of steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the circularity of a steel tube by providing grooves of prescribed number which are slightly wider than the width of the inner weld seam of the steel tube in the surface of one of a plurality of dies so that the interval of the grooves is prescribed times the width of the inner weld seam. SOLUTION: A plurality of dies 2 are arranged in a cylindrical manner, and the displacement is given in the direction orthogonal to the axis of the dies 2 to expand a steel tube 6 from the inner surface. Two or more grooves 4a, 4b are provided in the surface of one die 2b of a plurality of dies 2. The width of the grooves 4a, 4b is slightly wider than the width of the inner weld seam of the steel tube 6. The interval between the groove 4a and the groove 4b is >=1.5 times the width of the inner weld seam. The groove 4a agrees with the inner surface weld seam of the steel tube 6 to achieve the first expansion. A part 6b at which the inner surface of the steel tube 6 corresponds to the interval of the die 2 is straight. The groove 4b agrees with the inner weld line to achieve the second expansion. The part 6b is brought into contact with the surface of the die 2 and the straight part is curved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe expanding device for expanding the diameter of a steel pipe such as a UOE steel pipe from the inner surface using a die,
The present invention relates to a method for manufacturing a steel pipe using the same, particularly to a method for manufacturing a steel pipe for a steel pipe column, a steel pipe for a roll of a rotary press, etc., which requires roundness.

[0002]

2. Description of the Related Art A method of manufacturing a UOE steel pipe will be described as an example. UOE steel pipe is formed into a cylindrical shape by U and O pressing a steel plate so that the ends in the longitudinal direction of the steel plate face each other, and the facing ends are welded from the inner surface side and the outer surface side (called seam welding). Then, it refers to a steel pipe manufactured by applying plastic deformation from the inner surface side so that the diameter will be slightly increased by a pipe expanding device.

As shown in the principle diagram of the tube expanding device shown in FIG. 5, a plurality of dice 2 equally divided in the circumferential direction are arranged in a cylindrical shape on the outer surface of a cone 1 having a narrow tip. ,
When the pull rod 1 is pulled to the right by the pull rod 3, the cone 1 moves to the 1'position as shown by the broken line in the figure, and the die 2 moves in the direction perpendicular to the axis of the cone (radial direction of the steel pipe). The structure is such that it moves to the 2'position. In expanding the pipe, the cone in which the dies are arranged is inserted into the steel pipe, and the cone 1 is pulled in the axial direction to push the steel pipe from the inner surface through the die 2 to expand the pipe.

The surface of the die 2 has a curvature so that it becomes a cylindrical surface, but only one of the plurality of dies 2a has a groove 4 slightly wider than the width of the inner welding line on the surface as shown in FIG.
Is provided (called a bead die), and this groove 4
The pipe expanding operation is performed so as to match the inner surface welding line.

[0005]

However, when observing the cross-sectional shape of the steel pipe expanded according to the prior art in detail, the cross-sectional shape of the steel pipe is not a perfect circle but a polygonal shape having a portion near a straight line locally. There is. Therefore, there is a problem in applications where roundness is particularly required.

Particularly when a steel pipe is fitted into the opening of a diaphragm having an opening in the center to manufacture a steel pipe column with an outer diaphragm, it is desirable that the difference δ between the inner diameter of the diaphragm opening and the outer diameter of the steel pipe is as small as possible. If the degree is poor, δ will have to be set large, and this will hinder the subsequent welding of the steel pipe and diaphragm. On the other hand, if the steel pipe is fitted into the opening of the diaphragm with δ kept small, the fitting work becomes extremely difficult.

The present invention solves this problem and provides a pipe expanding device for producing a steel pipe having a particularly good roundness and a method for producing a steel pipe having a particularly good roundness using the pipe expanding device. Is.

[0008]

The above-mentioned problems can be solved by the following means.

That is, the invention according to claim 1 is a pipe expanding apparatus in which a plurality of dies are arranged in a substantially cylindrical shape, and the dies are displaced in a direction perpendicular to the axis of the cylinder to expand the diameter of the steel pipe from the inner surface. The surface of one of the plurality of dies has two or more grooves that are slightly wider than the width of the inner surface welding line of the steel pipe, and the interval between the first groove and the second groove is 1 of the width of the inner surface welding line. It is a pipe expanding device characterized by being more than 0.5 times.

According to a second aspect of the present invention, there is provided a pipe expanding apparatus in which a plurality of dies are arranged in a substantially cylindrical shape, and the dies are displaced in a direction perpendicular to the axis of the cylinder to expand the diameter of the steel pipe from the inner surface. The first die of the plurality of dies has a first groove that is slightly wider than the width of the inner weld line of the steel pipe on the surface of the first die, and has a second groove that is slightly wider than the width of the inner weld line of the steel pipe on the surface of the second die. 2 has two grooves, the difference A-B between the distance A between the end of the first die and the first groove and the distance B between the end of the second die and the second groove is the inner surface welding line. Is 1.5 times or more the width of the tube expansion device.

According to a third aspect of the present invention, the inner surface welding line of the steel pipe is matched with the first groove of the pipe expanding device according to the first or second aspect, the first pipe expanding operation is performed, and then the steel pipe is expanded. Is a relative amount with respect to the die of the tube expanding device, the welding line is aligned with the second groove, and the second tube expanding operation is performed.

Here, the relative rotation means that the pipe expanding device may be fixed and the steel pipe may be rotated, or the steel pipe may be fixed and the die of the pipe expanding device may be rotated.

The operation of this means is as follows. As a result of detailed research, the steel pipe in the prior art is polygonal because the dies of the pipe expanding device are lined up on the cone without any gap before pipe expansion, but the dies are displaced in the radial direction of the pipe due to pipe expansion. It was found that when they did, they were in a state of having gaps between them.

FIG. 7 is a partially enlarged view of the expanded state of the steel pipe. The portion 6a of the steel pipe 6 where the inner surface contacts the surface of the die 2 has a curvature corresponding to the curvature of the die surface. The portion 6b corresponding to the gap has a linear shape, and due to the non-uniform curvature, it has a polygonal shape, and in particular, the portions (a) and (b) on the outer surface side of the steel pipe corresponding to the end where the die hits are angular. It was found that the roundness was adversely affected.

Further, in order to eliminate this angular state, after performing the first tube expansion, the tube is expanded again so that the portion 6b corresponding to the gap of the die contacts the surface of the die of the tube expanding device. I also found it good. The present invention is based on the above findings.

In the case of producing a steel pipe having a particularly good roundness by using this pipe expanding device, after the first pipe expanding, the steel pipe is rotated in the pipe circumferential direction at a predetermined angle relative to the pipe expanding device. Perform the second tube expansion. The reason for rotating is to match the inner surface welding line with the first groove of the die in the first tube expanding step, but to match the inner surface welding line with the second groove in the second tube expanding step. The amount corresponds to the distance between the first groove and the second groove of the die.

The reason why the distance between the first groove and the second groove is limited to 1.5 times the width of the inner surface welding line is as follows.

That is, in order to arrange the portion 6b corresponding to the gap of the die in the first pipe expanding step at the position corresponding to the die surface in the second pipe expanding step, the steel pipe is circumferentially arranged at least in the die. It is necessary to rotate by the gap.

The size of the die gap is generally designed to be about the width of the inner surface weld line when the steel pipe is expanded so as to have the final product diameter. The distance between the second groove and the second groove should theoretically be at least one time the width of the inner surface welding line.

Further, even if the position setting error at the time of operation is taken into consideration, if it is set to 1.5 times or more, the portion 6b corresponding to the die gap in the first pipe expanding step is diced in the second pipe expanding step. It can be reliably placed at a position corresponding to the surface, and as a result, the outer surface side parts (a) and (b) of the steel pipe corresponding to the die end also come into contact with the die surface in the second expansion step to accommodate the curvature of the die. Since the steel pipe is bent, the cross-sectional shape of the steel pipe does not become polygonal, and as a result, a steel pipe having good roundness can be obtained.

For the above reasons, the interval between the first groove and the second groove is limited to 1.5 times or more the width of the inner surface welding line.

[0022]

1 is a cross-sectional view of a grooved die according to a first aspect of the present invention, in which the surface of one die is provided with a first groove 4a and a second groove 4b. There is. The width of the groove is slightly larger than the width of the weld line on the inner surface, and is usually 50
Although it is about mm, this width may be appropriately determined according to the applied inner surface welding technique. Also, the first groove 4a and the second groove 4b
The distance W between and is 1.5 times or more the width of the inner surface welding line.

FIG. 2 shows an example in which the die according to the second aspect of the present invention is attached to a tube expanding device. In this example, it comprises a die 2c having a first groove 4c, a die 2d having a second groove 4d and a die having no remaining groove. Relative spacing of grooves Wb
-Wa is 1.5 times or more the width of the inner surface welding line.

In the example of FIG. 2, the die 2c and the die 2 are
One die having no groove is arranged between d, but this is not essential to the present invention. The die 2c and the die 2d may be adjacent to each other, and one or more die having no groove may be provided between the two. Even if it arranges, the effect of the present invention does not change.

[0025]

EXAMPLE Next, a concrete example of manufacturing a steel pipe having a particularly good roundness by using the pipe expanding apparatus of the present invention will be described.

Example 1 The steel pipe used has dimensions: outer diameter 750 mm × wall thickness 32 mm; inner surface welding: latent arc welding (width of inner surface welding line = 28 mm). The tube expanding device consists of 12 dies, and the distance between adjacent dies is 7.3 mm when the tube expanding dies are in the most contracted state and 24.6 mm when expanded to the final product diameter.

The tube expanding device is according to the invention of claim 1.
That is, the first groove and the second groove are installed in one die, and the distance W between them is 65 mm (W (65 mm) / width of inner surface welding line (28 mm) = 2.32).

As the pipe expanding method, first, the inner surface welding line is first
The pipe was then expanded by 0.4% and then the steel pipe was rotated so that the inner weld line was aligned with the second groove and expanded by 0.4%.

FIG. 3 shows a pipe expanding state according to the present invention. FIG. 3 (a) shows a first pipe expanding state, and FIG. 3 (b) shows a second pipe expanding state. At the time of the second pipe expansion, the steel pipe is rotated by a predetermined amount in the direction of the arrow so that the inner surface welding line is aligned with the first groove 4a and the second groove 4b. From FIG. 3, at the time of the first expansion, the parts (a) and (b) corresponding to the ends of the die were
At the time of the second pipe expansion, it was located on the die surface,
It can be seen that the bending corresponding to the curvature of the surface of the die is given by the expansion of the tube for the third time.

FIG. 4 shows the distribution of peaking near the portion (a) corresponding to the end of the die at the time of the first pipe expansion of the steel pipe after the second pipe expansion. This is a result of comparison with the case where the pipe was expanded by 0.8%. In the figure, the result of the present invention example is shown by x, and the result of the conventional example is shown by ◯.

The peaking was defined as peaking by using a dial gauge type instrument as shown in FIG. 8 and measuring the deviation p from the true circle at the center of the interval of width 25 mm in the circumferential direction.

From FIG. 4, according to the method of the present invention, the peaking of the steel pipe is 0.7 mm or less, but in the conventional example, the peaking is 1.2 mm or more at the position (a). It can be seen that the invention improves the polygonal shape.

Next, Table 1 shows the measurement results of the roundness of the steel pipe. The roundness is expressed as a percentage by dividing the difference between the maximum diameter and the minimum diameter of the steel pipe by the average value of the maximum diameter and the minimum diameter.

[0034]

[Table 1]

In Table 1, the tube expanding method 1 means the case where the tube is expanded by the tube expanding device in which the first groove and the second groove are provided in one die, and the tube expanding method 2 is the first groove and the second groove. This means a case in which the grooves are expanded by a tube expanding device provided in each die. Further, the numerical value of the groove interval indicates the value of W in FIG. 1 in the tube expanding method 1 and the value of Wb-Wa in FIG. 2 in the tube expanding method 2.

From Table 1, it can be seen that the steel pipe manufactured by the method of the present invention has a good roundness.

Embodiment 2 This embodiment is the case where the tube expanding device is the invention of claim 2, and the other conditions are the same as those of the first embodiment. The second grooved die was mounted at a position rotated 90 degrees in the circumferential direction from the first grooved die. Table 1 shows the detailed conditions and the obtained roundness.
Shown in

Example 3 The steel pipe used has dimensions: outer diameter 850 mm × wall thickness 38 mm; inner surface welding: latent arc welding (inner surface welding line width = 34 mm). The tube expanding device consists of 12 dies, and the distance between adjacent dies is 8.3 mm when the tube expanding dies are in the most contracted state, and 27.6 mm when expanded to the final product diameter.
The total expansion rate was 1.0%.

The pipe expanding operation was performed both when one die having two grooves was prepared and when two dice having one groove were prepared. The die groove width is 45 mm, and the die groove spacing is 90 mm (W (90 mm)
/ Width of inner surface welding line (34 mm) = 2.81). These results are also shown in Table 1.

As can be seen from Table 1, when the steel pipe is manufactured by the method of the present invention by the pipe expanding apparatus of the present invention, the roundness is 0.5.
It can be seen that it can be suppressed to less than or equal to%. Further, as a result of a test of fitting this steel pipe into the opening of the outer diaphragm having the opening, the roundness was better than that of the steel pipe according to the prior art, and the fitting work was extremely easy.

[0041]

According to the present invention, the pipe expanding apparatus for manufacturing a steel pipe is composed of a group of dies having a plurality of grooves, and the relative position between the inner surface welding line and the dies can be shifted to expand the pipe twice. Therefore, if the pipe expanding device is used, it is possible to manufacture a steel pipe having particularly good roundness.

Further, according to the method of the present invention, it is possible to manufacture a steel pipe having a particularly good roundness.

[Brief description of drawings]

1 is a cross-sectional view of a grooved die according to the invention of claim 1;

FIG. 2 is a view showing an example in which a die according to a second invention of claim 2 is attached to a tube expanding device.

FIG. 3 is a diagram showing a relative positional relationship between a die and a steel pipe when the first and second expansions are performed by the expansion device according to the first aspect of the present invention, and (a) is the first expansion pipe; (B) is the second
The state of the tube expansion

FIG. 4 is a diagram showing a distribution of deviation (peaking) from a perfect circle on the outer surface of a steel pipe expanded by the method of the present invention.

FIG. 5 is a diagram showing the principle of a steel pipe expanding device.

FIG. 6 is a view showing a die for expanding a portion including an inner surface welding line in a die of a pipe expanding device in a conventional technique.

FIG. 7 is a partially enlarged view of a state where a steel pipe is expanded by a conventional technique.

FIG. 8 is a diagram showing an instrument for measuring peaking.

[Explanation of symbols]

1 Tube expansion device cone. 2 dice. 3 pull rod. 4 A groove on the surface of the die that matches the inner welding line. 6 Steel pipe. 6a A portion of the steel pipe corresponding to the die surface in the first pipe expanding step. 6b A portion of the steel pipe corresponding to the die gap in the first pipe expanding step.

Claims (3)

[Claims] 1. A pipe expanding device in which a plurality of dies are arranged in a substantially cylindrical shape, and a displacement in a direction perpendicular to the axis of the cylinder is given to the dies to expand the diameter of the steel pipe from the inner surface. Has one or more grooves that are slightly wider than the width of the inner surface welding line of the steel pipe, and the interval between the first groove and the second groove is 1.5 times or more the width of the inner surface welding line. A tube expanding device characterized in that 2. A pipe expanding device in which a plurality of dies are arranged in a substantially cylindrical shape, and a displacement in a direction perpendicular to the axis of the cylinder is given to the dies to expand the diameter of the steel pipe from the inner surface. Has a first groove on the surface of the first die that is slightly wider than the width of the inner welding line of the steel pipe, and has a second groove that is slightly wider than the width of the inner welding line of the steel pipe on the second die surface. , The difference A−B between the distance A between the end of the first die and the first groove and the distance B between the end of the second die and the second groove is 1.5 of the width of the inner surface welding line. Tube expanding device characterized by being more than doubled. 3. The pipe of the first aspect of the pipe expanding device according to claim 1 or 2 is aligned with the inner surface welding line of the steel pipe, the first pipe expanding operation is performed, and then the steel pipe is attached to the die of the pipe expanding device. A method for manufacturing a steel pipe, characterized in that the welding line is made to coincide with the second groove by relatively rotating a predetermined amount and a second pipe expanding operation is performed.