JPH0148113B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to a method of manufacturing an ultra-thin welded pipe by rolling an ultra-thin plate material, abutting the ends together, and performing fusion welding along the abutted parts.
In particular, the present invention relates to a method for obtaining a good ultra-thin-walled welded pipe by preventing deformation of the butt portion due to heating. Conventional technology and its problems Conventionally, when manufacturing a welded pipe by rolling up ultra-thin plate materials with a thickness of about 0.4 mm or less and butting the ends together, and performing fusion welding there, the butt part Welding was performed while mechanically restraining the vicinity, for example with an appropriate positioning jig, but the butt itself along the welding line could not be restrained, and therefore the welding heat source, for example, as shown in Figure 2, could not be restrained. There was a problem in that the heating of the welding arc 2 as shown in FIG. In the circumferential direction, as is clear from Fig. 3, this appears as deformation in which the butt ends mainly overlap due to free thermal expansion of the plate material 8 due to heating, and in the pipe forming direction, as shown in Fig. 4. As shown, the free thermal expansion area A along the tube manufacturing direction of the rolled plate material 8 generates tensile stress in the non-heat affected zone B, and the free thermal expansion area A generates compressive stress from the non-heat affected zone B. This will mainly appear as waving deformation. Due to such deformation caused by the heating of the welding heat source, the abutting portion cannot be stably restrained, resulting in poor welding and making it difficult to obtain a good welded pipe. In addition, since the abutted portion is easily deformed by heating, it is extremely difficult to set appropriate welding conditions, and conventionally, it has been difficult to manufacture welded pipes from extremely thin plate materials. Solution The present invention was made in order to solve such conventional problems, and its characteristics are that by rolling an ultra-thin plate material and butt welding the ends, When manufacturing ultra-thin welded pipes, the butt part is stretched, and the amount of stretch in the direction of the weld line: Q is calculated using the following formula (1): Q≧αT/10...(1) (where α: material The reason for this is that welding is performed under conditions that satisfy the linear expansion coefficient (1/°C) (T: temperature (°C) at which the material has almost no deformation resistance due to heating immediately before welding). That is, as shown in FIG. 1, an ultra-thin plate material 10 is rolled into a cylindrical shape using an appropriate bending means (for example, a forming roll, etc.), and after the ends are abutted against each other, the abutting portions 12 are marked with arrows. A predetermined welding method 14 such as arc welding is applied under the condition that the stretch (tensile stress) shown in FIG.
Welding is performed along the abutting portion 12 to produce the desired extremely thin-walled welded pipe. Here, as the ultra-thin plate material 10, various metal plate materials with a plate thickness of about 0.4 mm or less are usually used, and as a means for giving stretch to the butt part 12, for example, A bending roll is placed on the opposite side of the butt part 12 on the side, that is, the part where welding has not yet been performed, and the welded pipe is curved as a whole so that the butt part 12 is stretched, or Various methods may be adopted, such as increasing the feed speed of the straightening rolls for straightening the welded pipes than that of the upstream forming rolls. In addition, as the welding means 14, not only ordinary arc welding but also plasma arc, high pulse welding, etc.
Various welding methods can be used, such as arc (DC arc with high frequency current superimposed) and laser.
If you use a heat source with a highly focused energy density,
The width of the heat-affected zone is narrowed, which is more convenient for preventing deformation due to heating. If the butt portion 12 is welded in this manner, the deformation due to free thermal expansion of the ultra-thin plate material 10 due to heating is effectively absorbed by the stretch amount Q, so that the butt portion 12 due to the free thermal expansion is effectively absorbed by the stretch amount Q. The deformation of the portion 12 is alleviated, the range of welding conditions under which appropriate welding can be performed is widened, and a high-quality welded portion free from welding defects such as lapping and waving can be obtained. In addition, the above equation (1) is based on the ultra-thin plate material 1 by heating.
This is an experimental formula obtained as a result of various studies by the present inventors regarding the relationship between deformation due to free thermal expansion of 0 and the amount of stretch: Q. In such equation (1), the amount of stretch: Q If it is too small, it will not be able to sufficiently absorb the deformation due to free thermal expansion of the ultra-thin plate material 10 due to heating, and the abutting portion 12 will be deformed, resulting in burn-through, overlapping, and insufficient melting. This causes poor fusion and insufficient fusion due to
Stretch amount: Q must be set so as to satisfy the above equation (1). Next, one embodiment of the present invention will be shown, but this is merely an illustration, and it goes without saying that the present invention should not be interpreted in any way limited by the following description. Example Using a titanium plate with a thickness of 0.2 mm as an ultra-thin plate material, butt welding was performed under various stretching amounts under the welding conditions shown in Table 1 to produce ultra-thin welded pipes. The coefficient of linear expansion (α) of the titanium plate is 8.9×10 ^-6 (1/°C), and the heating temperature at which the material is easily deformed by heating immediately before welding is about 1000°C. The amount of stretch given to the welded pipe was measured using a strain gauge, and the welding results for various amounts of stretch are shown in Table 2 below.

[Table] Arc welding

[Table] As is clear from the above results, it was nearly impossible to obtain a welded pipe from the above-mentioned ultra-thin titanium plates by butt welding, but according to the present invention, αT As a result of applying a stretch amount Q larger than /10=8.9×10 ^-4 to the welded pipes (Nos. 1 to 3), welded pipes having good welded parts with little distortion were obtained. On the other hand, when similar butt welding is performed with a stretch amount smaller than αT/10 = 8.9×10 ^-4 (Nos. 4 to 6), the weld burns through,
Polymerization, poor fusion, insufficient fusion, etc. occurred intermittently, making it difficult to obtain a good welded joint and making welding difficult. Results of the Invention As detailed above, according to the pipe making method of the present invention, the deformation due to free thermal expansion caused by heating during welding is absorbed by the amount of stretch, so the deformation of the butt part is alleviated. Good butt welding was achieved, making it possible to manufacture extremely thin-walled welded pipes, which had been considered difficult in the past, and producing welded pipes with high-quality welded parts.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram conceptually showing a specific embodiment of the method of the present invention, and FIG. 2 is a diagram showing a conventional welding method during pipe manufacturing. FIGS. 3 and 4 are diagrams for explaining the mechanism of deformation occurring in the abutting portion in the conventional art. 10: Ultra-thin plate material, 12: Butt part, 14:
Welding means.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an ultra-thin welded pipe by rolling up an ultra-thin plate material, abutting the ends, and welding along the abutting portion, the method providing stretch to the abutting portion. , the amount of stretch in the direction of the welding line: Q is expressed by the following formula: Q≧αT/10 (where α: coefficient of linear expansion of the material (1/°C) T: heating immediately before welding almost eliminates the deformation resistance of the material A method for manufacturing an ultra-thin welded pipe, characterized by performing welding under conditions that satisfy the following temperature (°C).