JPS63235025A - Manufacture of welded vent tube - Google Patents

Abstract

PURPOSE:To use a stock being partly thick for thickness reducing parts and partly thin for thickness increasing parts and to obtain bent tubes having an equal wall thickness by forming sheet stocks into a cylindrical shape and welding the butted parts, changing the thickness of the tube stock in the circular direction of the tube stock, and bending the stock with the thicker part being in the outside position. CONSTITUTION:A thick and a thin sheets are used as material of a tube stock 10; respective sheets are formed into semicylindrical bodies 12, 14 having an equal radius and both side edges are beveled to welded to form a cylindrical shape. In that time, the thickness of the thick sheet is selected to be a size found by considering a thickness reduction amount by bending work and is set to equal to the thickness of the semicylindrical body 14 of the thin sheet side after bending. A step is generated because different thicknesses of both the sheets and then the inner surface of the side edge part of the thick sheet side semicylindrical body 12 is sloped to smoothly change its inner diameter. At both ends of the tube stock 10, a cut slope 18 is formed on the inner surface of the body 12 so that a tube end thickness and the inner diameter are equal to those of the body 14, respectively. Thus, sheets having different thickness are formed into semicylindrical bodies and then are welded; the obtained tube stock 10 is bent.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of manufacturing a bent pipe by bending a joint pipe made by welding plate materials into a cylindrical shape.
The present invention relates to a method suitable for manufacturing a welded bend pipe having a diameter of 00φ or more.

[Prior Art] As shown in Figs. 8 and 9, the conventional method for manufacturing a welded bent pipe involves processing a metal plate of uniform thickness into a semi-cylindrical body,
The cylindrical tube material 3 is formed in advance by butt-welding the side edges of both sides (welded portion 2). Then, this cylindrical tube material 3 is bent using a bender to obtain a bent tube 4 as shown in FIG. 10.

[Problem that the invention seeks to solve]

However, in the conventional method, when the cylindrical tube material 3 is bent, elongation occurs on the outside of the bend across the neutral plane, and compression occurs on the inside of the bend. Therefore, when looking at the cross section of the bent pipe 4 after bending, as shown in Fig. 11, the wall thickness on the outside of the bend decreases by an amount corresponding to the amount of elongation along the neutral axis direction, and as a result, the bend The tube 4 had a problem of uneven thickness in cross section. Therefore, there was a drawback that a thick plate material had to be used so as to fall within the negative thickness tolerance of the bent pipe 4 after bending.

Here, as a technique for preventing uneven thickness of a bent pipe, there is a technique disclosed in Japanese Patent Application Laid-Open No. 10329/1983. This is done by cutting and machining the wall surface of the raw pipe when bending seamless pipes so that the outer side of the pipe is thicker than the inner side to prevent uneven thickness. However, in the case of large diameter pipes exceeding 300φ, the seam register vibe cannot be applied, and the pipe must rely on joint pipes. Moreover, if the pipe becomes large in diameter, JR or corrugation of the pipe wall becomes impossible. Therefore, the above-mentioned known example is problematic because it cannot be applied to welded bent pipes which are large diameter pipes.

The present invention has focused on the above-mentioned conventional problems, and aims to provide a method for manufacturing a welded bent pipe that reduces the occurrence of uneven thickness and reduces the weight of the material when manufacturing a large diameter bent pipe. .

[Means for solving problems]

In order to achieve the above object, the method for manufacturing a welded bent pipe according to the present invention uses a pipe material obtained by forming a plate material into a cylindrical shape and welding the butt part as a material, and forms a bent pipe by bending the pipe material. In the method for manufacturing a welded bent pipe, the thickness of the starting plate material is varied so that the thickness of the pipe material differs in the circumferential direction, and the pipe material is bent with the thick side facing outward. In this case, the pipe material is formed by forming two types of plate materials with different thicknesses into a semi-cylindrical shape and then welding, and bending the pipe material so that the weld line is located at the middle plane of the bend pipe, or The cylindrical body may be formed by welding the abutted portions of both side edges of a single plate having both ends thinly rolled, and then bent with the weld line on the inside.

[Effect]

According to the above configuration, the joint pipe is formed using plate materials with different thicknesses and is bent so that the thick side becomes the outer side of the bend. Therefore, the wall thickness of the outer side of the bend pipe with a high wall thinning rate is adjusted to the final thickness. The wall thickness of the bent pipe can be made uniform after bending. As a result, it is no longer necessary to use a thick plate material that matches the area of reduced thickness after bending, and it is possible to use a thicker material for the area of reduced thickness and a thinner material for the area of increased thickness, eliminating wasted material. It is possible to manufacture large welded bent pipes.

〔Example〕

EMBODIMENT OF THE INVENTION Below, the Example of the manufacturing method of the welded bend pipe based on this invention is described in detail with reference to drawings.

Figs. 1 and 2 show a pipe material 10 that is a raw material for a bent pipe. This tube material 10 uses thick plates and thin plates as starting materials, and each plate is formed into a semi-cylindrical body 12 having the same outer radius. .

14, and their both side edges are beveled and joined by welding into a cylindrical shape. In this case, the thickness of the thick plate material is determined to take into account the thickness reduction due to bending, and is set to be equal to the thickness of the semi-cylindrical body 14 on the thin plate side after bending. Further, the thickness of the thin plate material may be the same as the thickness of the straight pipe that is not bent.

Note that since the wall thicknesses of the plate materials are different, a stepped portion is formed on the inner wall of the pipe material 10 at the welded portion 16, but the inner diameter of the side edge of the thick semi-cylindrical body 12 is sloped at 173 to smoothly increase the inner diameter. Adjusted to change. Furthermore, at both ends of the pipe material IO,
As shown in FIGS. 3 and 4, after the tube material 10 is bent, the tube end wall thickness is uniform, and the inner diameter of the semi-cylindrical body 1 on the thin plate side is uniform.
A cutting device 8 is attached to the inner surface of the thick semi-cylindrical body 12 so as to have an inner diameter equal to the inner diameter of the thick-walled semi-cylindrical body 12. In this way, the tube material 10 obtained by forming two types of plate materials with different wall thicknesses into a semi-cylinder and then welding them is bent, but it is rumored that this is done by arranging the thick-walled semi-cylindrical body 12 so that it is on the outside of the bend. conduct. Then, the welded portion 16 may be positioned on the neutral plane of bending, and the bending process may be performed using a normal method. By locating the welded portion 16 on the neutral plane, the influence of deformation on the welded portion 16 during bending is minimized, and adverse effects on strength can be prevented.

According to this embodiment, the pipe material lO, which is the raw material of the cylinder, is joined by welding with a plate material whose wall thickness is equivalent to the amount of wall thinning on the outer surface due to the bending process and a plate material approximately equal to the wall thickness of the bent pipe. As a result, the wall thickness after bending is uniform as a whole, and unlike the conventional method in which both plates were made to have the same thickness in consideration of the amount of thinning, it is lighter and cheaper because thinner plates can be used. becomes. In particular, since welded bent pipes are applied to large pipes, they have a high weight reduction effect and also have a large contribution to cost reduction. In this embodiment, the welded portion 16 is placed on the neutral plane and bent, so that the influence of processing distortion on the welded portion 16 is small, and the occurrence of weak parts due to bending of the welded bend pipe is eliminated.

Next, a second embodiment is shown in FIGS. 5 to 7. In this embodiment, unlike the first embodiment, in which the pipe material lO was formed by welding two semi-cylindrical plates, the starting material was a single plate as shown in FIG. This uses two plate materials 20. This plate material 20 has different thicknesses in the width direction, with a thick part 22 at the center and thin parts 24 at both ends, and the thickness is varied in the width direction by rolling or the like.

A tube material is formed by processing such a plate material 20 from a U-shape to a O-shape, joining both side edges to each other, forming a groove and welding the material. In this case, the welded portion 26
The thick portion 22 is arranged so as to be on the inside of the bend, and the thick portion 22 is on the outside of the bend, and then bent to form the bent pipe 28 shown in FIG. 5. Even with this method, the thick part 2
2 is located on the outside of the bend where the rate of thickness reduction is large, so each section of the bent pipe 28 has a uniform wall thickness as shown in FIG.

In this embodiment, the thickness of the bent portion after bending can be made uniform, and the longitudinal welding line of the bent pipe can be placed at one location.

〔Effect of the invention〕

As explained above, according to the present invention, a tube material obtained by forming a plate material into a cylindrical shape as a starting material and welding the abutting portions thereof is prepared such that the thickness of the starting material differs in the circumferential direction. Since the pipe is bent with the thicker side facing outward, a bent pipe with uniform wall thickness can be obtained even if the compressed side during bending is made thinner. Therefore, the weight reduction effect is particularly high for large-sized welded bent pipes, and the cost reduction effect is also large.

[Brief explanation of drawings]

Fig. 1 is a side view of the pipe material used in the method of the embodiment, the second is an end view of the same, Fig. 3 is an enlarged sectional view of the same end, Fig. 4 is the end view of Fig. 3, and the fifth is the same end view. A side view of a welded bent pipe formed by the method according to the second embodiment, FIG. 6 is a sectional view taken along the line VT-VI in FIG. 5, FIG. 7 is a sectional view of the plate material used in the second embodiment, and FIG. A side view of the pipe material used in the conventional method, FIG. 9 is an end view of the same, and FIG. 1O is a side view of the bent pipe obtained by the conventional method.
FIG. 11 is a sectional view taken along the line XI-XI in FIG. 10. 10...Tube material, 12...Thick side semi-cylindrical body, 14...Thin plate side semi-cylindrical body, 16...
- Welded part, 20... Plate material, 22... Thick walled part, 24... Thin walled part, 26... Welded part. Patent applicant Hitachi Plant Construction Co., Ltd. Figure 7 Figure 8 Figure 9 Figure 10 Figure 11

Claims (3)

[Claims] (1) In a method for manufacturing a welded bent pipe, in which a pipe material is formed by forming a plate material into a cylindrical shape and welding the butt portions together, and a bent pipe is formed by bending the material, the wall thickness in the circumferential direction of the pipe material is A method for manufacturing a welded bent pipe, which comprises changing the thickness of a starting plate material such that the thickness of the pipe material is different, and bending the pipe material with the thick side facing outward. (2) The pipe material is formed by forming two types of plate materials with different thicknesses into a semi-cylindrical shape, and then welding the pipe material, and bending the pipe material so that the weld line is located at the middle plane of the bend pipe. A method for manufacturing a welded bent pipe according to scope 1. (3) The pipe material is formed by welding the abutted portions of both side edges into a cylindrical body using a single rolled plate that is thick in the center and thin at both ends, and is bent with the weld line on the inside. A method for manufacturing a welded bent pipe according to claim 1, characterized in that: