JPS626906B2 - - Google Patents

Description

[Detailed description of the invention]

This invention uses TIG welding method, thickness: 1.5
The present invention relates to a method for increasing the welding speed when manufacturing thin-walled welded pipes by butt welding thin-walled materials of mm or less. Thin-walled Ti pipes and thin-walled stainless steel pipes have traditionally been used in various plants such as seawater desalination equipment and condensers in power plants, and their demand has continued to expand in recent years. Producing seamless pipes from such materials is difficult as they are extremely difficult to extrude or draw, so welded pipes are commonly used. Usually, this type of welded pipe is made of thin-walled materials such as Ti or stainless steel with a thickness of 1.5 mm or less.
Manufactured by butt welding using the TIG welding method. According to this TIG welding method, it is possible to form a very smooth and excellent weld bead on the front and back surfaces, but on the other hand, there are problems in that the welding speed is slow and productivity is low. Therefore, in order to increase the welding speed, a multi-electrode TIG welding method in which multiple electrodes are arranged in series was proposed, and it is true that with this method, the arc emitted from the leading electrode gives a preheating effect to the welding part. Therefore, the welding speed can be faster than in the case of a single electrode, but on the other hand, with this method, arc energy concentration is poor and local preheating is impossible, resulting in a wide weld bead. At the same time, the width of the weld heat affected zone becomes wider, which inevitably affects the strength and heat resistance of the weld.Furthermore, in this method, the arcs interfere with each other, causing so-called magnetic blowing. There are problems in that the arc is not stable and the weld bead that is formed as a result is also unstable. From the above-mentioned viewpoint, the present inventors conducted research to increase the welding speed without damaging the good weld bead obtained by the TIG welding method, and as a result, the present inventors developed a method using the TIG welding method. , Thickness: 1.5
When manufacturing thin-walled welded pipes by butt welding thin-walled materials of less than mm in diameter, the laser irradiation position must be set 5 to 60 degrees from the target position of the TIG welding electrode prior to welding.
mm forward, and the irradiation width is at least 1/3 of the weld bead width obtained by TIG welding, and when the welding area is locally preheated by laser beam irradiation, this laser beam will spread the irradiation width to the specified width. Since it can be adjusted, it is possible to preheat only the local areas that require preheating, and as a result, the thermal effect due to excessive heat input is reduced.Furthermore, since it does not interfere with the TIG welding arc, it is possible to preheat the arc by magnetic blowing. Since this phenomenon is eliminated, a stable weld bead can be obtained, and as a result, we have found that it is possible to form a very smooth weld bead on the front and back surfaces at high speed. This invention was made based on the above knowledge, but when carrying out the method of this invention, the thickness of the thin material should be 1.5 mm or less, and the laser beam irradiation position should be adjusted to the aim of the TIG welding electrode. 5 to 60mm in front of the position, and further increase the irradiation width.
The weld bead width obtained by TIG welding must be at least 1/3, which means that the thickness of the thin material is 1.5
If it exceeds 5 mm, it will not be possible to reliably provide a preheating effect in the thickness direction, and if the distance between the laser beam irradiation position and the target position of the TIG welding electrode is less than 5 mm, heat diffusion will be insufficient and the desired effect will not be achieved. On the other hand, even if the distance exceeds 60 mm, the heat will spread too much and it will not be possible to achieve the desired preheating effect. If it is less than 3, the spread of heat in the direction perpendicular to the welding line is insufficient, and not only will it be impossible to obtain the desired preheating effect, but the laser beam will be irradiated in a focused manner, resulting in a high energy density and This is because plasma is generated at the irradiated area, resulting in a perforation phenomenon, making it impossible to ensure a preheating effect. Next, the present invention will be specifically explained with reference to Examples. Example Thin-walled materials having the materials and wall thickness shown in Table 1 were prepared, and these thin-walled materials were welded under the welding conditions (welding current and welding speed) also shown in Table 1.
When manufacturing thin-walled welded pipes by butt welding using a high-frequency pulsed TIG welding machine that is often used for thin plate welding, laser beam irradiation is also used in the first step.
By setting the conditions shown in the table, the present invention method 1
-5 were carried out. Also, for comparison purposes, we also used laser beam irradiation.

【table】

[Table] Comparative methods 1 to 10 were carried out without preheating, and by setting the material and wall thickness of the thin wall material to be butt welded, and the TIG welding conditions to the same conditions shown in Table 1. Ta. Note that the markings marked * in Table 1 for Comparative Methods 1 to 10 indicate the welding conditions conventionally employed. Next, the width and surface roughness of the weld bead of the resulting thin-walled welded pipe were measured, and the measurement results are shown in Table 1. From the results shown in Table 1, it can be seen that the welding speed of the inventive method, especially as seen in inventive methods 1 and 4, is much higher than that of the conventional conditions of comparative methods 2, 4, 6, 8, and 10. However, if the weld zone is preheated by laser beam irradiation, a good weld bead can be obtained; however, if the welding speed is not preheated by laser beam irradiation and the welding speed is increased as in the methods 1 and 4 of the present invention, It is clear that Comparative Methods 1 and 7 cannot form a satisfactory weld bead. As mentioned above, according to the method of this invention, TIG
When manufacturing thin-walled welded pipes using a welding method, it is possible to form a good weld bead at a high welding speed, which greatly contributes to improving productivity.

Claims (1)

[Claims] 1 When manufacturing thin-walled welded pipes by butt-welding thin-walled materials with a thickness of 1.5 mm or less using the TIG welding method, the laser irradiation position must be adjusted prior to welding.
The welding area is locally preheated by laser beam irradiation, with the irradiation width set at 5 to 60 mm in front of the aiming position of the TIG welding electrode and at least 1/3 of the weld bead width obtained by TIG welding. A method for manufacturing thin-walled welded pipes using high-speed butt welding.