JPS6171124A - Production of metallic pipe having differential thickness in pipe longitudinal direction - Google Patents

Abstract

PURPOSE:To obtain the metallic pipe having a differential thickness in longitudinal direction with good efficiency and at low cost by forming a metallic plate stock in cylindrical shape with heating the part which is formed thickly relatively by the part corresponding to the thicker thickness part of a pipe. CONSTITUTION:A high frequency conductive heating device 12 is installed on both side parts of a press bender device and a part of the thicker thickness part of a stock is heated prior to a formation. After the arrival to the prescribed working temp. the formation of both thicker and thinner thickness parts is performed and the formation of one part which is in width direction is completed. In succession the part A B is heated and a tubular body is made with repeating the formation in order and with welding a finished product is made.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a metal tube having wall thickness differences in the longitudinal direction of the tube.

(Conventional technology) In recent years, the development of offshore oil fields (including gas fields) has gradually become deeper in the ocean.Traditionally, one production of oil (including gas) from an offshore oil field requires fixing one submarine structure. Fixed production platforms were used in the past, but as water depth increased, flexible production platforms were devised, an example of which is the tension leg platform.

A tension leg platform is a structure in which a number of steel tubular members are screwed together, so-called tension legs (a floating production plant form is moored to a part of an anchor on the seabed).

This snow-like member is usually manufactured in unit lengths of about 12 m, and both i are provided with a male thread (pin part) and a female thread (box part), but the thread part (t) is designed to ensure the strength of the threaded part. The wall thickness of the tube is thicker at both ends (connector part).

During use, the production platform is subjected to ever-changing wind, wave, tidal current, and tidal forces, and the tubular members are required to have sufficient fatigue strength when submerged in seawater.

As a way to solve this problem, for example, in the manufacture of tension leg materials, part of the connector between the pin part and the box part is made of a forged product, and the straight pipe part in between is made of a forged product. The wall thickness is increased by a certain length, and there is a difference in wall thickness in the longitudinal direction of the pipe f! : One possible method is to make four pieces by molding and melting the straight pipe part, and then make circumferential contact with a part of the connector.

The present invention aims to provide a complete method for manufacturing the above-mentioned hollow metal tube having wall thickness differences in the longitudinal direction with high precision and at low cost. For this reason, the inventors
84688', but this proposal still has the following problem to be improved.

In the snap method, when the difference in thickness between the thick and thin parts is large, or when the thickness of the thick part is extremely large, it is difficult to obtain a bottom shape. In addition, it requires a single-sided thick plate as the material, and the process of obtaining it has the drawbacks of processing efficiency and cost problems.

The present invention solves the above-mentioned problems and provides a method for efficiently and inexpensively manufacturing snow metal snow having thickness differences in the longitudinal direction.

(Means 1 for Solving the Problems) The gist of the present invention for achieving the above object is to form a rectangular plane in which a portion corresponding to the inside thickness of the pipe is formed relatively one thicker. Using a metal plate material with The metal having a difference in wall thickness in the longitudinal direction of the pipe is characterized by heating the whole or a part of the part T.
It is in the manufacturing method of J2 tube.

This invention will be explained in detail below.

First of all, conventional! The pipe 1 to be manufactured will be explained from the A construction method and its problems.As shown in FIG. In order to manufacture the metal snow 1 (hereinafter referred to as differential thickness pipe) having a wall thickness difference of one inch in the longitudinal direction, first,
Prepare the 4-metal plate material shown in the figure. The length L of the plate material 4 is equal to the length of the differential thickness tube 1 to be manufactured, and the plate thickness B is the same as the circumferential length of the target neutral plane (circumferential direction (f: surface where expansion and contraction occurs)) of the thin wall portion 2. Accordingly, the width in the longitudinal direction is determined to be uniform, and the end face of the plate is beveled.In this way (the plate material 4 prepared in this manner is shown in FIG. 3), the plate 4 shown in FIG.
This is then formed and the joints are welded.

However, the following problems exist in such a manufacturing method: first, when the thickness of the thick part is too large, or when the thickness ratio relative to the thin part is When the thickness is large, even if Japanese Patent Application No. 145637 (1983) (longitudinal direction; tV = tV), the disadvantage that it is essentially difficult to form thick parts can be overcome. First, there is a limit in dimensional accuracy.21.Problems also occur in the production of differential thickness plates as such materials.

That is, when manufacturing a differentially thick plate by rolling, the shape of the plate after rolling is symmetrical about 1 and the neutral plane Nl, as shown in FIG. 4(b). To make this into a differential thick plate (single-sided differential thick plate) with the shape described above, after rolling, it is pressed to one side using a press, etc., and then machined into the shape shown in (C). This increases the overall manufacturing cost of the material.

In order to solve this problem, Japanese Patent Application No. 58-145639 proposes using double-sided plates with different thicknesses, and molding one side together at the same time when forming a tubular body. When using different thickness plates, it is sometimes difficult to form them.

To solve these problems, zeta molding can be easily formed by fully heating each part of the machine and performing hot working, and at the same time,
During press bending, from double-sided differential thickness plate to single-sided differential thickness tube (
It is even possible to make the bottom shape.

Figure 5 (showing the forming procedure) (a) (shown here) Both sides of the press bender machine 1111 The high-frequency induction heating device 12 is installed, and the material before forming. The end face and part of the thick wall are heated. At this time, if the capacity of the heating device is sufficient, the time required for heating is only a few minutes, which is within the industrial efficiency range. .

After the predetermined processing temperature (t) has been reached, forming is performed on both the thick and thin parts as shown in (b)l (nl), and a part of the widthwise part is completed.Subsequently, as shown in FIG. As shown, the next part is heated (A→B), and the molding is repeated in sequence.
The tubular body and f are bath-welded to form a finished product.

Although gas heating may be used as the force heating method, an induction heating method is preferable in terms of efficiency and heating accuracy. In addition, it is desirable for the heating temperature to be as low as possible for processing, but it is generally 700°~
There is one temperature within the range of 1200℃.

Furthermore, the present invention is not necessarily limited to the use of double-sided plates with different thicknesses, and may be applied only once when forming one-sided plates with different thicknesses for the purpose of ease of processing. Furthermore, the heating part may be the entire widthwise direction, or the heating part may be heated only in the longitudinal direction, where the plate thickness changes and where forming is most difficult, or in the floating part.

(Effects of the Invention) As described above, the present invention makes it possible to obtain a hollow metal tube with a difference in wall thickness in the longitudinal direction without pre-processing by using the difference in thickness on both sides as rolled. In addition, it has become possible to manufacture, for example, a dog-sized tube with a wall thickness of 127 ttm, which was previously impossible to form.

[Brief explanation of the drawing]

Fig. 1 is an 8-1 perspective view of the differential thickness plate manufactured by the method of the present invention, Fig. 2 is a perspective view of the plate before bending, and Fig. 3 is the punch 7 of the press bender used for bending. and a perspective view showing an example of the die 8, and FIGS. 4(a) to 4(C) are the shape of a plate immediately after the fc surface produced by rolling and the shape of a single-sided thick plate as a material, and FIGS. 5(a) to (C). Figure 6 shows an example of the heating forming procedure according to the present invention 1, and Figure 6 is a top view of the material; the position and order of heating are shown. ... Pipe thickness inside, 4-- Plate material, 5... Plate thin wall part, 6... Plate thickness inside,
7.9...Punch, 8.10...Dice, 11...
・Differential thick plate, 12...Heating device.

Claims (1)

[Claims] Using a metal plate material with a rectangular plane in which the portion corresponding to the thick wall portion of the tube is relatively thick, a tubular body having portions with different wall thicknesses in the axial direction is formed using a tool consisting of a punch and a die. A method for manufacturing a metal tube having a wall thickness difference in the longitudinal direction of the tube, which method comprises heating the entire or part of the relatively thick portion during forming.