| Автор | K Girard |
| Автор | J M Jouvard |
| Автор | Ph Naudy |
| Дата выпуска | 2000-11-07 |
| dc.description | Significant problems in deep laser spot welding are the formation of welding defects, and particularly porosities in the case of tantalum joining. In this study, we investigate and model porosity formation and trapping. Two types of porosity are observed. (1) Small porosities are round shape bubbles of less than 250 µm diameter. These defects may come from gas bubbles generated following hydrogen rejection during solidification or they may come from bubbles induced by both an intense evaporation inside the keyhole and a turbulent flow in the molten pool. (2) Large porosities are voids generated in the bottom of the welded zone. They arise from a lack of matter inside the weld as if the molten metal had not had enough time to fill up the keyhole completely before it solidified. We elaborated a numerical model for the comprehension of small porosities trapping by comparing the calculated spot weld solidification time with the rise time of bubbles in the liquid phase. We also studied the melt flow back into the keyhole in order to explain the formation of the large voids observed. These two models are in good agreement with experimental observations, in particular with x-ray radiographs achieved during the solidification of tantalum spot welds. |
| Формат | application.pdf |
| Издатель | Institute of Physics Publishing |
| Название | Study of voluminal defects observed in laser spot welding of tantalum |
| Тип | paper |
| DOI | 10.1088/0022-3727/33/21/322 |
| Electronic ISSN | 1361-6463 |
| Print ISSN | 0022-3727 |
| Журнал | Journal of Physics D: Applied Physics |
| Том | 33 |
| Первая страница | 2815 |
| Последняя страница | 2824 |
| Выпуск | 21 |
