By: Takeji ARAI1, and Noritaka ASANO 1 (Chuo University)

The success or failure of the welding work is influenced by worker’s technological skill.

Actually, even the laser welding processing relies on worker’s sense and operations repeat a try and error. The purpose of this research is to catch the thermal deformation accurately by introducing the prediction technique by a scientific calculation into the welding operation work.

The thermal deformation of the metal is very important factor for the laser welding technology. For a highly accurate welding with sheet metal by the laser, it is necessary to understand the distortion caused by laser welding processing. In the first stage of this study, the welding model was assumed as a bead-on-plate, and calculated it in an ideal state of butt welding without gap. It is considered the standard to know the deformation of laser welding. However, there is a gap in the actual welding by all means. Therefore, it is necessary to consider this for a calculation.

The correct numeration way is not yet established now. To clarify these, influence of the gap in case of butt welding taken by real welding was examined. In the butt welding with a gap, the focal positions of lens and energy distributions to the materials are important. The deformation by the butt welding included thermal expansion of the melting zone became clear. As a result, various phenomena that had happened by the laser welding were calculated.

The research work of simulation shows that the deformation become smaller when the clamping time takes enough after laser welding ended.

Moreover, in butt welding, the narrow gaps bring the small deformations, but the molten metal pushed out in the welded welding section, and thermal deformation of sheet metal became big. On the other hand, wider gaps bring the small deformations, but the “under- fill” was caused in the welding section. The simulation result was compared with an actual experimental result. As a result, the validity of the calculation was shown. Fig.1, as the example, shows the simulation result of the butt welding, and the comparison between the numerical result and the photograph of cross section of metallurgical structure was shown in Fig.2.

This research is to propose the method of suppressing to the minimum the welding deformation inevitably caused by the laser welding and the method of counterbalancing thermal deformation of thermal processing in the future. In the present study, the case of the laser heat source was taken as an example. However, it is possible to apply it for other heat sources, TIG, MIG or the hybrid welding.

Fig.1 Moving picture simulation of butt welding

Fig.2 Comparison between simulation results and experimental cross section in butt welding

Experimental Conditions:

Material:SUS304, Size:100x100mm2, Thickness:1mm

Power:3.4kW, Spot size:0.6mm, Welding Speed:3m/min

The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here