JPS6186073A - Manufacture of dead thin weld pipe - Google Patents

Abstract

PURPOSE:To widen a width of a welding condition for executing an appropriate welding, and to obtain a weld zone of a high quality by giving a stretch of a specified quantity of a weld line direction, to a butt pat, when rounding a dead thin plate base material and executing a butt welding of each end part. CONSTITUTION:A dead thin plate stock 10 is rounded to a cylindrical shape by a suitable curving means, its each end part is butted, and thereafter, a stretch as indicated with an arrow is given to their butt part 12. Subsequently, welding is executed along the butt part 12 by a prescribed welding means 14 such as an arc welding, etc., under the condition that its stretch quantity (tensile strain) Q satisfies an expression [alpha: a coefficient of linear expansion (1/ deg.C) of the stock, T : a temperature ( deg.C) at which a deformation resistance of the stock scarcely comes to exist by heating executed immediately before welding]. In this way, a deformation caused by a free thermal expansion of the stock 10 is absorbed effectively by the stretch quantity : Q, a deformation of the butt part 12 caused by the free thermal expansion is softened, and the purpose can be attained.

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 portion, and particularly relates to This 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 Traditionally, when manufacturing welded pipes by rolling up extremely thin plate materials with a thickness of about 0.4 mm or less, butting the ends together, and performing fusion welding there, Welding was carried out while mechanically restraining the vicinity of the butt part, for example with an appropriate positioning jig, but the butt part itself along the welding line could not be restrained, and therefore the welding heat source, for example the There was a problem in that the heating of the welding arc (2) as shown in FIG. 2 expands the high temperature heating region (4) and deforms the butt portion (6).

In the circumferential direction, as is clear from Fig. 3, this appears as deformation in which the abutting 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 Figure 4, the free thermal expansion part (A) of the rolled plate material (8) along the tube-making direction produces tensile stress in the non-thermal shadow part 9 (B), and the free heat When the expanded part (A) receives compressive stress from the non-heat affected part (B), it mainly appears as waving deformation.

Due to such deformation caused by the heating of the welding heat source, the abutting portion may 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 has been made to solve these conventional problems, and is characterized by rolling up an extremely thin plate material and butt welding the ends to each other. When manufacturing ultra-thin welded pipes, stretch is applied to the butt part, and the amount of stretch in the weld line direction: Q is calculated using the following formula (1): % formula % (1) (However, α: coefficient of linear expansion of the material ( The reason is that welding is performed under conditions that satisfy 1/'C)).

That is, as shown in FIG. 1, the ultra-thin plate material ■0 is rolled into a cylindrical shape by an appropriate bending means (for example, a forming roll, etc.), and the ends are abutted against each other, and then the abutting portions 12 are formed. is given a stretch (tensile stress) as shown by the arrow, and the amount of stretch (tensile strain): Q is the above (1
) Welding is performed along the butt portion 12 using a predetermined welding means 14 such as arc welding under conditions that do not satisfy the following equation, thereby manufacturing the intended ultra-thin welded pipe.

Here, as the ultra-thin plate material 10, the plate thickness is usually 0.
Various fully bent plate materials with a bending strength of about 4 m+s or less are used, and as a means of giving stretch to the butt part 12, for example, the butt part is placed on the upstream side of the welded pipe, that is, in the part where welding has not been performed yet. A bending roll is placed on the opposite side from work 2 to curve the welded pipe, or the feeding speed of the straightening roll for straightening the welded pipe after welding is made faster than that of the forming roll on the upstream side. , various methods may be employed.

In addition, as the welding means 14, various welding methods such as not only ordinary arc welding but also plasma arc, bipulse arc (direct current arc superimposed with high frequency current), laser, etc. can be adopted, but If a heat source with a high energy density is used, the width of the heat affected zone becomes narrower, which is more convenient in preventing deformation due to heating.

Then, if the butt portion 12 is welded in this way,
Since the deformation due to the free thermal expansion of the ultra-thin plate material 1o due to heating is effectively absorbed by the stretch amount Q, the deformation of the butt portion 12 due to the free thermal expansion is alleviated, and appropriate welding can be performed. The range of conditions is widened, and high-quality welds without weld defects such as laps and waving can be obtained.

In addition, if the amount of stretch: Q is too small, the deformation due to free thermal expansion of the ultra-thin plate material 10 due to heating cannot be sufficiently absorbed, resulting in deformation of the protrusion-U portion I2. must be set so as to satisfy the above equation (1).

Next, one embodiment of the present invention will be shown, but it goes without saying that this is merely an example, and that the present invention should not be construed to be equally limited by the following description.

EXAMPLE An ultra-thin welded pipe was manufactured by butt welding using a titanium plate W 0.2 as an ultra-thin plate material under the welding conditions shown in Table 1. The coefficient of linear expansion of the titanium plate is about IXIO-5<1/'c), and the heating temperature at which the material is easily deformed by heating immediately before welding is about 700 to 800 ("C).

Table 1*: Arc welding using high-frequency current superimposed on a DC-TIG arc It was previously nearly impossible to obtain welded pipes from such ultra-thin titanium plates by butt welding.
As a result of the present invention, a welded pipe having a good welded portion with little distortion was obtained.

In addition, using a titanium plate with a plate thickness of 0.2 fins, welding method: high pulse arc welding, welding current: 25A.

When butt welding was performed under the welding conditions of a welding speed of 1.9 m/min and a stretch amount of 20, burn-through, poor fusion, and insufficient fusion occurred intermittently in the weld, making it difficult to obtain a good weld. I couldn't.

Effects of the Invention As detailed above, according to the pipe-making method of the present invention, deformation due to free thermal expansion caused by heating during welding is absorbed by the amount of stretch, so deformation of the butt portion is alleviated and improved. Butt welding was performed, 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 the drawing]

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. FIG. 3 and FIG. 4 are diagrams for explaining the generation mechanism of deformation that occurs in the abutting portion in the related art, respectively. 10: Ultra-thin plate material 12 Two butt parts 14: Welding means Applicant: Sumitomo Light Metal Industries, Ltd. Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] A method of 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 comprising: applying stretch to the abutting portion; The amount of stretch in the welding line direction: Q is expressed by the following formula: Q≧αT/10, where α: Linear expansion coefficient of the material (1/°C) T: Temperature at which the deformation resistance of the material is almost eliminated by heating immediately before welding (°C) A method for manufacturing an ultra-thin walled welded pipe, characterized by performing welding under conditions that satisfy the following.