JPS63137595A - Laser seal welding method - Google Patents

Abstract

PURPOSE:To stabilize the weld quality and to improve the productivity by welding the same position or the slightly deviated position for every pass with many times repeatedly and continuously in the laser seal welding of pipes to a pipe plate. CONSTITUTION:An NC gantry type robot 23 driven in X-Y-Z directions is arranged in the neighborhood of the pipes 21 and the pipe plate 22 of a feed water heater. Optical path systems 24 and 24', mirrors 25 and 25' and a TV monitoring device 27 are installed on the robot 23. Laser light 28 is converged via a convergent lens 17 and laser light 28 with high energy density is projected on the work surface 29 to perform the continuous multi-pass circumferential welding. The welding is simplified and the occurrence of an undercut and a dislocation defect is prevented, so a bead with excellent external appearance and quality is obtained by this method. Accordingly, the weld quality is stabilized and the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for laser sealing welding of tubes and tube sheets of heat exchangers and feed water heaters.

[Prior Art and Problems] A conventional method of laser seal welding between a tube and a tube sheet is as shown in FIG. In the figure, 1 is a tube, and 2 is a tube plate. A laser welding device processing head 4 is arranged above the groove portion 3 of the tube 1 and the tube plate 2, and this head 4 has a built-in lens 5. In addition, 6 in the figure shows a laser beam, and 7 shows a bead. However, in the case of laser seal welding of the tube 1 and tube sheet 2 as described above, in the case of a large structure heat exchanger application, the tube 1 and tube sheet 3 are
It is almost impossible to finish and temporarily fix the groove width with high accuracy, and the groove preparation situation as shown in Fig. 6 is likely to occur. Note that 8 in the figure indicates the groove width. In this state, when seal welding is performed by irradiating the laser beam 6 from the head 4 to the groove 3, the bead appearance as shown in FIG. 7 and the cross section as shown in FIGS. 8 to 11 are obtained. This can easily lead to macro situations.

In other words, in the arrow part 9 where the groove width 8 is large, undercuts 10 of the surface bead are likely to occur due to poor penetration (
(Illustrated in Figure 9). In addition, if the irradiation position of the laser beam 6 deviates from the center of the groove, a misaligned bead 12 may appear as shown by the arrow part 11.
This is likely to occur (as shown in Figure 8). Furthermore, when expanding the tube 1 to temporarily fix it to the tube plate 2, blowholes 14 are likely to occur due to the forced air blowing out, especially in the circumferential lap portion as shown by the arrow 13 (as shown in FIG. 11). .

Therefore, in order to prevent various defects caused by such groove variations, it is common to perform laser seal welding while adding filler wire 15 as shown in FIG. However, in this case, the laser beam 6 is very small and in order to sufficiently melt the filler wire 15, welding must be performed at low speed, resulting in poor welding efficiency. In addition, for temporary fixation, it was considered to prepare a groove that has undergone processing such as pipe expansion, and perform welding, but after welding one round, press-in air is blown out at the flange part as shown in arrow part 13 in Fig. 7. A blowhole 14 occurs due to
There is a construction problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser seal welding method that can always perform welding with stable quality, and can improve welding efficiency and productivity.

[Means and effects for solving the problems] The present invention provides a method for laser seal welding a tube and a tube sheet of a heat exchanger or feed water heater, in which the same position is continuously and repeatedly welded many times.
Alternatively, the gist is to weld at slightly shifted positions for each multiple pass.

[Example code] An embodiment of the present invention will be described below with reference to FIG.

Here, FIG. 1 shows a stage for laser seal welding of a tube and a tube plate of a heat exchanger high-pressure feed water heater.

Reference numeral 21 in the figure indicates a tube, which is laser-seal welded to the tube plate 22. These tubes 21. An NC gantry type robot 23 that is driven in the x-y-z directions is disposed near the tube plate 22. This robot 23 is provided with an optical path system 24.24, -5)-25, 25', a laser processing head 26, and a television monitoring device 27.

Next, the operation will be explained.

First, the laser beam 28 uses a laser oscillator (not shown) as a light source, passes through an optical path system 24, 24' from there, and passes through a mirror 25.
．． The direction is changed at 25' and guided to the laser processing head 26. Here, the laser beam 28 is focused by a focusing lens and irradiated onto the workpiece surface 29 as a high energy density laser beam 28. Note that the laser beam 28 is driven in the circumferential direction by the robot 23, making it possible to perform welding with high precision and high speed.

According to the laser seal welding method according to the present invention, compared to conventional laser seal welding that involves adding filler wire, etc., it is less complicated in terms of equipment and welding work, and there is no undercut or misalignment defect. It is possible to weld with stable quality. In addition, since it is continuous multi-pass circumferential welding, there is no backtracking process, making it possible to perform highly efficient welding and improve productivity.

In fact, when welding is performed as described above, the appearance of the bead for each pass is as shown in FIG. 2. As shown in FIG. 3, undercuts 31 and blowholes 32 were formed in the bead that had been welded only once, and welding defects were confirmed. On the other hand, in the case of the present invention, when continuous circumferential seal welding is performed two to three times in multiple passes, a good bead appearance 33 is obtained as shown in FIG. 4. From this, it can be confirmed that the present invention is superior to the conventional one.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to perform stable welding with constant quality without defects such as undercuts and misalignment, and also to provide a laser that can perform highly efficient welding and improve productivity. A seal welding method can be provided.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the laser seal welding method according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the appearance of the bead, and Fig. 3 is an explanatory diagram of welding defects in one-pass welding according to the conventional method. Fig. 4 is an explanatory diagram of a good bead appearance after multiple passes of continuous circumferential seal welding according to the method of the present invention. Fig. 5 is an explanatory diagram of the welding situation according to the conventional laser seal welding method. Fig. 6 is an explanatory diagram of the groove preparation situation. Figure 7 is an explanatory diagram of the external appearance after welding, and Figure 8 is an explanatory diagram of the appearance after welding.
9 is a sectional view taken along line A-A in the figure, FIG. 9 is a sectional view taken along line B-B in FIG. 7, FIG. 10 is a sectional view taken along line C-C in FIG. Cross-sectional view along line D-D in Figure 7, No. 12
The figure is an explanatory diagram of a conventional laser seal welding method using filler wire addition. 21... Tube, 22... Tube plate, 23... NC gantry type robot, 24.24'... Optical path system, 25° 25'... Mirror, 26... Laser processing head, 2
7... Television monitoring device, 28... Laser light, 29.
...Work surface, 31... Undercut, 32...
・Blowhole, 33...peed appearance. Applicant's sub-agent Patent attorney Takehiko Suzue Figure 1 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Prisoner Figure 11 Figure 12

Claims (1)

[Claims] A method of laser seal welding tubes and tube sheets of heat exchangers or feed water heaters, characterized by welding continuously and repeatedly many times at the same position or at slightly shifted positions for each pass. Laser seal welding method.