JPH0471737A - Manufacture of large diameter pipe - Google Patents

Abstract

PURPOSE:To prevent a polygon from generation and to improve productive efficiency by setting the ratio of the outer diameter before the pipe expansion of a die used in the pipe expansion stage of the pipe stock for a large diameter pipe below a special thickness value to the finished inner diameter of the large diameter pipe after the pipe expansion at a specified value, and performing the pipe expansion. CONSTITUTION:A pipe stock for a UOE large diameter pipe below 12.7mm in thickness is manufactured into a large diameter pipe through a pipe expansion stage. The ratio D0/D1 of the outer diameter D0 before diameter expansion of the die used in the pipe expansion stage to the finished inner diameter D1 of the large diameter pipe after the pipe expansion is set to 0.98-1.00 to execute a pipe expansion stage. When the pipe expansion is performed, ideally, by the outer diameter D0 of the die equal to the finished inner diameter D1 of the product, no polygon generated. But since a bulky number of tools are required for that purpose, this method is not economical. The above method can prevent a polygon from generation in the large diameter pipe, requires no corrective work and can be applicable to a structural, working pipe stock severe in dimensional accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a method for manufacturing a UOE large-diameter pipe having a wall thickness of 12.7 mm or less into a large-diameter pipe through a pipe expansion process. For example, it relates to improvements in the tube expansion process.

(b) Prior Art Conventionally, large diameter pipes have been mainly used in pipelines for transporting oil, natural gas, and the like. Such large-diameter pipes are required to be mass-produced and at the same time have high dimensional accuracy (bending, roundness).

Various methods have been proposed to improve the dimensional accuracy of large diameter steel pipes obtained by the UOE pipe manufacturing method. For example, Japanese Patent Publication No. 61-50688 filed by the present applicant discloses a method of reducing zero press load to improve roundness. Also, in Japanese Patent Application Laid-Open No. 60-92015,
This patent discloses a method for improving the roundness of thick-walled, large-diameter pipes by significantly reducing the zero-breathing capacity.

However, these methods are limited to bending R and C in C press.
Only the working length of the press in the circumferential direction, the width of the U blank tube, and the bending radius of the U blank tube are regulated. Especially when the wall thickness is thin (1
2.7 m or less), die marks during the tube expansion process become noticeable, and in some cases polygonal shapes may occur (Figure 5).

In ordinary large-diameter pipes for pipelines, inner clamps are used when connecting the large-diameter pipes, so a slight decrease in accuracy is not a problem. However, with the expansion of the application of UOE steel pipes, which are low-cost straight seam pipes, problems arise in secondary processing. For example, when used in a gas chamber or the like, problems occur during bonding due to poor shape due to die marks.

Conventionally, the design standard for die segments of tube expansion tools has been to prevent abnormal stress from being applied to the tool during tube expansion (Japanese Patent Laid-Open No. 57-41836).

However, since this die segment does not take into account the shape after expansion, it becomes a polygonal shape in which the die shape is transferred in the radial direction from the circle center of the raw tube, and the above-mentioned die mark is generated during cutting.

Note that this die mark is measured by moving a portal gauge along the circumference of the tube.

(c) Problems to be Solved by the Invention The problem to be solved by the present invention is to reduce as much as possible the die marks of large-diameter blank tubes that occur during the tube expansion step in the UOE tube manufacturing method.

(d) Means for Solving the Problems The method for manufacturing a large diameter pipe of the present invention is a method for manufacturing a UOE large diameter pipe with a wall thickness of 12.7 m+ or less into a large diameter pipe through a pipe expansion process. Ratio p between the outer diameter D0 of the die used in the process before expansion and the finished inner diameter of the large diameter pipe after expansion,
The above problem is solved by setting (D, /D,) to 0.98 to 1.00 and performing the tube expansion process.

(E) Effect In the method of the present invention, the ratio PI (D0/D1) of the outer diameter D0 of the die used in the tube expansion process before expansion to the finished inner diameter of the large diameter tube after expansion is 0.98. Set to ~1.00.

Ideally, the die outer diameter D is equal to the finished product inner diameter D1.
If the tube is expanded at 0, the above-mentioned polygon will not occur. but,
This requires a huge number of tools and is not economical. Therefore, the relationship between P and the amount of pipe squaring was determined through experiments, and the results are summarized as shown in Figure 2.

Here, the pipe squaring amount refers to the difference between the maximum and minimum peaking values. The peaking value refers to the value determined using the portal gauge described above.

FIG. 3 shows experimental results showing the relationship between P and wall thickness for a finished pipe with an inner diameter of 24#.

As shown in Figures 2 and 3, the amount of squaring is 1m.
When it is n or less, P is preferably o, 98 or more. This allows it to be applied to pipes with a wall thickness of 0.5'' (12.7 mm) or less.

In the conventional method, the occurrence of angularity was initially thought to be due to buckling. However, no matter how many measures were taken to prevent the problem from breaking, it did not solve the problem. Therefore, the die dimensions of the present invention were adopted.

Further, normally, the tool dimensions of the tube expansion die are determined by dividing the manufacturing wall thickness range into three or two parts for the same outer diameter. Therefore, the pipe wall thickness (12
, 7m++ or less), one tool was assigned. In this wall thickness range, the die segment (
In Japanese Unexamined Patent Publication No. 57-41836), a pipe expansion force that would cause breakage cannot occur. Therefore, it is possible to simultaneously satisfy the requirements for equipment protection and pipe shape improvement necessary for the pipe expanding die.

(f) Example This will be explained with reference to FIG. 1 and Part 4. As mentioned above, the method of the present invention is applicable to UO with a wall thickness of 12.7 m++ or less.
E It is applied to the tube expansion process in the method of manufacturing large diameter tubes through the tube expansion process.

As shown in FIG. 1, the ratio PI (D0/D1) between the outer diameter D0 of the die 1 used in this tube expansion process before expansion and the finished inner diameter of the large diameter tube after expansion is set at 0.98 to 1.00
Set to .

In addition, in FIG. 1, the die 1a indicated by a broken line is a conventional die, and its outer diameter is designated as DN.

The results obtained using the die used in the method of the present invention and the die used in the conventional method are shown in Table 1 below. Further, a comparison of the peaking values of implementation No. 3 in Table 1 is shown in FIG. In FIG. 4, (A) shows the conventional method, and (B) shows the method of the present invention.

(g) Effects According to the present invention, it is possible to prevent the occurrence of polygons in large-diameter pipes, eliminate the need for correction work, improve production efficiency, and improve UOE size as raw pipes for structures and processing that require strict dimensional accuracy. Diameter plain pipes can now be applied.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the dimensional relationship of the tube expanding die used in the method of the present invention. Figure 2 is a graph showing the experimental results of the amount of squaring. FIG. 3 is a graph showing the experimental results of P+ and wall thickness, FIG. 4 is a graph showing the experimental results of peaking value, and FIG. 5 is a cross-sectional view of a large diameter pipe according to the conventional method. Patent applicant: Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] In the method of manufacturing a UOE large-diameter tube with a wall thickness of 12.7 mm or less into a large-diameter tube through a tube expansion process, the outer diameter D_0 of the die used in the tube expansion process before expansion and the large-diameter tube after expansion are The ratio P_I (D_0/D_1) to the finished inner diameter D_1 is 0.
．． 98 to 1.00, and performing a tube expansion step.