JPS61147970A - Production of welded pipe - Google Patents

Abstract

PURPOSE:To prevent the generation of an undercut on the inside surface of a weld zone in the stage of bending a metallic plate or rod to a tubular shape and welding the butt part thereof by applying a backing strip consisting of the same material as said plate or rod to the inside surface of the butt part. CONSTITUTION:The metallic plate or rod 1 is bent to a tubular shape by roll forming, etc. and thereafter the backing strip 5 consisting of the same material as said plate or rod and having >=0.1mm thickness is applied on the inside surface of the butt part 2. The butt part 2 is welded by an electron beam, etc. and the inside surface of the weld zone 3 is polished to remove the strip 5. The strip 5 is integrally welded and the under cut 4 on the inside surface of the weld zone 3 is formed to the backing strip according to the above- mentioned method. The undercut is removed by polishing the inside surface by which the smooth inside surface is obtd. and the subsequent bending and bulging is made easy. A substantially high Q0 value is obtd. particularly with an Nb welded pipe when said pipe is worked to a cavity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a welded pipe, and particularly to a method for preventing the occurrence of undercuts on the inner surface of a welded portion.

[Conventional technology]

Generally, pipe materials are manufactured by welding, drawing, extrusion, etc., but welding is particularly used when a small thickness deviation is required or when the pipe diameter is large. As shown in FIG. 2(a), the welding method involves bending a metal plate or strip (1) into a tubular shape by roll forming or the like, and then welding the abutted portion (2) using an electron beam or the like.

[Problem that the invention seeks to solve]

However, as shown in Figure 2 (b), undercuts (4) tend to occur on the inner surface of the welded part (3), and if undercuts (4) occur, welding during subsequent processing, such as bending or bulge processing, is likely to occur. Part (3) is more prone to breakage and is a problem. In particular, Nb welded pipes that are bulged and used in superconducting cavities of particle accelerators are required to have excellent inner surface smoothness, and undercuts occur on the inner surface of the welded part. When this occurs, not only does bulge processing become difficult, but even if bulge processing is successful, a sufficiently high Qo value cannot be obtained, which poses a problem.

(Means for Solving the Problems) In view of this, the present invention has been developed as a result of various studies and has developed a method for manufacturing welded pipes that can prevent the occurrence of undercuts on the inner surface of welded parts. In the method of bending into a tubular shape and welding the butt portions, a back plate of the same material with a thickness of 0.1M or more is applied to the inner surface of the butt portion and welded, and then the inner surface of the welded portion is polished. It is characterized by:

That is, as shown in FIG. 1(a), the present invention involves bending a metal plate or strip (1) into a tubular shape by roll forming or the like, and then forming a layer with a thickness of 0.1 m or more on the inner surface of the abutting portion (2). A back plate (5) made of the same material is applied, and the abutting part (2) is welded using an electron beam or the like as shown in Fig. 1 (b), and then the welded part is welded as shown in Fig. 1 (c). The inner surface of (3) is polished to remove the back plate (5).

[Function]' By bending it into a tubular shape and applying a back plate of the same material to the inner surface of the abutting part and welding, the back plate (5) is welded together as shown in Figure 1 (B). , an undercut (4) on the inner surface of the welded part (3) will occur on the back plate. If this is removed by internal polishing, the undercut will be reliably removed and the inner surface will be smooth, making subsequent bending and bulge processing easier.Especially in Nb welded pipes, when processed into cavities, a sufficiently high Qo value can be achieved. can get. The size of the metal plate or strip to be used is determined based on the welded pipe C size, and the thickness of the back plate must be 0.1M or more.
．． If it is less than 11IIIm, an undercut may remain.

〔Example〕

Nb, Ti, Cu, Ai 5LJS-27
After forming a plate of size 0, 5 to 411 III into a tubular shape by roll forming, a back plate made of the same material with a thickness of 0.15 to 1.2 shoes is applied to the inner surface of the butt part, and the butt part is formed with an electron beam. After welding, the inner surface of the tube is polished and the first
Welded pipes of the sizes shown in the table were manufactured.

The depth of the undercut on the inner surface of the welded portion of these welded pipes was measured. These results are also listed in Table 1 in comparison with a pipe welded by the conventional method (welding without applying a back plate).

1''-5 As is clear from Table 1, between the conventional methods of welding without applying the back plate, in all cases 15 to 20, a depth of 0.15 to 0.15 mm was applied near the boundary between the welded part and the heat-affected zone on the inner surface of the tube. Whereas an undercut of 0.25 m occurs, the method of the present invention 1lk11~
It can be seen that no undercut remains in any case No. 10 after internal polishing.

On the other hand, in all comparative methods Nα11 to Nα14 in which the thickness of the back plate is less than 0.11 MR, an undercut with a depth of 0.05 to 0.15 m remains even if the back plate is removed by internal polishing.

Next, methods of the present invention (1 to 3) in Table 1. Comparative method Nα11-12
The central part of the Nb welded pipe manufactured by conventional methods 15 to 16 was expanded by bulge processing to create a cavity with the dimensions shown in Table 2, and the Qo values of these were measured, and the results are shown in Table 2. .

Table 2 As is clear from Table 2, Nb welded pipes made using the conventional method N015-16 have undercuts on the inner surface of the welded part, so they break during bulge processing and cannot be inflated to the specified inner diameter of the center part. Even if it could be inflated to a predetermined central inner diameter, the Qo value was so low that it could not be used in a particle accelerator. On the other hand, the present invention method N
The Nb welded pipes according to Nos. 1 to 3 have no undercut, can be bulged into a predetermined cavity, and can obtain a QO value on the order of 108 to 10''.

On the other hand, the Nb welded pipe according to the comparative method Nα11-12 is
As with conventional Nb welded pipes, undercuts occur on the inner surface of the welded part, which often breaks during bulge processing and cannot swell to the specified inner diameter at the center.
QoWi even if the inner diameter of the central part can be expanded
It can be seen that it cannot be used in particle accelerators because of its low value.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reliably prevent the occurrence of undercuts on the inner surface of the tube, and it is possible to manufacture welded tubes that are easy to bend and bulge, and in particular, when processed into cavities, the QO value is sufficiently high. This has the remarkable effect that it is possible to easily manufacture a Nb welded pipe that can obtain the following properties.

[Brief explanation of the drawing]

Figures 1 (a), (b), and (c) show an example of the manufacturing method of the present invention, in which (a) is a cross-sectional view in a bent state, (b) is a cross-sectional view in a welded state, and (c) is a cross-sectional view in a welded state. is the cross section in the polished state, Fig. 2 (
A) and (B) show examples of conventional manufacturing methods, and (A)
1 is a cross-sectional view in a bent state, and (b) is a cross-sectional view in a welded state. 1... Metal plate or strip, 2... Butt part, 3... Welded part. 4... Undercut, 5... Back plate Figure 1 (A) (B)
(A) Figure 2

Claims (1)

[Claims] In a method of bending a metal plate or strip into a tubular shape and welding the butt parts, a thickness of 0.1 mm is applied to the inner surface of the butt part.
A method for manufacturing a welded pipe, which comprises applying and welding a back plate made of the same material as described above, and then polishing the inner surface of the welded part.