JP3264153B2 - Method of manufacturing UOE steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a UOE steel pipe, and more particularly to a method of manufacturing a thick steel pipe having less peaking and excellent roundness by simple means.

[0002]

2. Description of the Related Art UOE steel pipes are formed by forming a steel sheet, which is an object to be molded, into C
Press, U-press, and O-press are formed and processed so that the cross-section becomes a circular tube, then the butted part is welded, and it is corrected to a predetermined size and shape while producing roundness by a pipe expander. Is done.

[0003] In recent years, steel pipes having high strength have been required for line pipes installed in the deep sea and the like. In order to manufacture such a steel pipe, it is necessary to increase the strength and thickness of the steel sheet as a steel pipe material. However, when manufacturing a high-strength, thick-walled steel sheet by the above-described general UOE steel pipe manufacturing method, However, the butted portion is not sufficiently deformed at the time of O-pressing, so that the butted portion is referred to as "peaking" or has poor roundness. The peaking and the roundness defect remain as they are even after welding, and are not sufficiently corrected by the subsequent pipe expansion correction, resulting in a defective shape.

To reduce peaking, Japanese Patent Publication No. 59-3
Japanese Patent Publication No. 8846 discloses a method in which a projection is provided on a part of an O-press die and a peaking generating portion is pushed in.
Japanese Patent No. 40934 proposes a method of optimizing C-press conditions and imparting a sufficient pre-bending shape to a plate edge.

[0005]

However, in the method described in Japanese Patent Publication No. 59-38846, the number of types of mold tools increases, so that the working efficiency is reduced, and the distribution of peaking and bending deformation in the pipe length direction are reduced. If something happens,
Correction becomes difficult. Further, in the method described in Japanese Patent Publication No. 60-40934, considering the press load, the possible increase in wall thickness is only 6% at most, and there is a restriction on the types of steel pipes that can be manufactured.

The present invention has been made in order to solve such a problem, and a UOE steel pipe having less peaking and excellent roundness can be obtained simply by using a material steel plate having various strengths and thicknesses. It is an object of the present invention to provide a method that can be manufactured.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method of manufacturing a UOE steel pipe, in which, after the O-press and before welding, only the butted portion of the workpiece is pressed in a direction perpendicular to the pipe axis. Is solved.
Pressing the butted part of the molded object from the direction perpendicular to the tube axis
When performing, from one end of the molded object to the other end
Pressurization may be performed sequentially. Furthermore, these manufacturing methods
, A flat deformation restraining jig for restraining a part of a molding object
May be used.

When the butt portion of the object is pressed from the direction perpendicular to the tube axis after the O-press and before welding, the object is pressed.
Min (and the flat deformation restraining jig)
Since it is not bent, the butted portion is flattened by this bending deformation, so that peaking can be significantly reduced.
In addition, although a bending deformation part remains in a part of the to- be-formed object after pressurization or a steel pipe after welding , it is corrected by the subsequent pipe expansion process. Therefore, it is possible to manufacture a UOE steel pipe with less peaking and excellent roundness.

[0009] In addition, by sequentially pressing the butted portion from one end to the other end of the molded object, the pressing device can be made compact, and the pressing can be performed by a simple method. Becomes Further, by controlling the degree of pressurization in accordance with the peaking amount generated in the tube length direction by the sequential pressurization, the flattening in the tube length direction can be made more uniform.

The method of the present invention can also be applied to steel sheets having various strengths and thicknesses by simply increasing the pressurizing capacity of the pressurizing device or adjusting the pressurizing length in the pipe length direction.

When a flat deformation restraining jig for preventing flat deformation of a molded object during pressurization is used, deterioration of roundness due to flat deformation can be prevented, and a steel pipe having better roundness can be manufactured. it can.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows an embodiment of a method for pressing a butt portion using a flat deformation restraining jig according to the present invention. In the figure, 1 is a molded object, 2 is a butt portion,
Reference numeral 3 denotes a pressing direction, and 4 denotes a flat deformation restraining jig.

When the butting portion 2 is pressed in the direction perpendicular to the tube axis, the flat deformation of the molding 1 can be prevented from outside the molding 1 by using the flat deformation restraining jig 4 as shown in the figure.

FIG. 2 schematically shows another embodiment of a method for pressing a butted portion using the flat deformation restraining jig of the present invention. The reference numerals in the figure represent the same as those in FIG.

As shown in the figure, even if the U-shaped flat deformation restraining jig 4 is inserted into the inside of the molded article 1, the flat deformation of the molded article 1 can be prevented.

[0016]

EXAMPLE Using a steel plate having a strength of 490 Mpa and a thickness of 45 mm, performing normal C-press, U-press, and O-press, and then restricting the flat deformation of the molded product as shown in FIG. Using a deformation restraining jig, pressure was applied to the butted portion from the direction perpendicular to the pipe axis, and welding and pipe expansion were corrected to produce a steel pipe having an outer diameter of 600 mm and a pipe length of 12000 mm.

The peaking distribution and roundness in the tube length direction were measured. For comparison, the same measurement was performed on a steel pipe manufactured without pressurizing the butted portion. Here, the peaking was measured after temporary welding.
The roundness was measured for the product, and evaluated by the difference between the diameter in the vicinity of the weld and the diameter orthogonal to the diameter.

FIG. 3 shows the results. The peaking distribution in the pipe length direction of the steel pipe manufactured by the method of the present invention was extremely uniform, and the value was as small as 2 mm at the maximum and 1.5 mm at the minimum. On the other hand, when manufactured by the conventional method, the peaking distribution in the tube length direction was non-uniform, and the value was as large as 7 mm at the maximum and 4 mm at the minimum.

The roundness of the steel pipe manufactured by the method of the present invention was ± 0.8 mm, which was much better than the roundness of the steel pipe of the conventional method ± 2 mm.

[0020]

As described above, the present invention is constructed as described above, so that even if a steel sheet of various strengths and thicknesses is used,
It is possible to provide a method capable of easily producing a UOE steel pipe with little peaking and excellent roundness.

[Brief description of the drawings]

FIG. 1 is a view schematically showing one embodiment of a method of pressing a butt portion using a flat deformation restraining jig of the present invention.

FIG. 2 is a view schematically showing another embodiment of a method of pressing a butted portion using the flat deformation restraining jig of the present invention.

FIG. 3 is a diagram showing a peaking distribution of a steel pipe in a pipe length direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded object 2 Butt part 3 Pressure direction 4 Flat deformation restraining jig

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-156619 (JP, A) JP-A-61-296925 (JP, A) JP-A-60-92015 (JP, A) JP-A 55-156 156618 (JP, A) JP-A-53-125954 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21C 37/08

Claims (3)

(57) [Claims] 1. A method of manufacturing a UOE steel pipe, comprising: pressing only a butt portion of an object to be formed from a direction perpendicular to a pipe axis after an O-press and before welding. 2. When pressurizing the butt portion of the molded product from the tube axis direction perpendicular claim, characterized in that applying sequential pressure the over one other end portion from the end portion of the molded product 1
A method for producing the UOE steel pipe according to the above . 3. A part of the object is restrained during the pressurization .
2. A flat deformation restraining jig that is used.
Or the method of manufacturing a UOE steel pipe according to claim 2.