February 8--Scientists from NPO Lavochkin, Russia, and colleagues from the All-Russia Research Institute of Experimental Physics (VNIIEF) in Sarov supported by Antonio Lapucci from the Institute of Applied Optics in Florence, Italy, and Ulrich Delthey, who is director of the Welding Institute in Aachen, Germany. Financial support for the project is from Russia's International Science and Technology Centre (ISTC).
The first experimental version of the lamp-laser combination, which is being tested by scientists from the ISTC, involves two energy sources: a Nd:YAG laser, which performs the spot weld, and a special light module with an adjustable spectrum. The system also features standard welding components and software, to enable automatic welding with a pre-set program.
The crux of the method lies in the use of the second light source. Its power and attributes are such that it quickly and effectively heats the weld area and surrounding space to at least 1000 degrees C. This ensures that defects that typically form under the welding of non-heated parts are significantly fewer, while the need for annealing ready products is eradicated altogether.
Welders have long known that the quality of a weld is essentially better if the parts to be welded are pre-heated. Cases have even been known when large metal parts are welded even before they have cooled after smelting.
A conventional welding problem has been how to pre-heat parts sufficiently quickly and effectively if one of them is made, for example, from invar, which hardly alters its dimensions when heated, and the other is made from a problematic material such as glass. How can this combination be heated to high temperatures without damage?
To resolve this problem, Valentin Sysoev and his colleages proposed the use of a powerful lamp to pre-heat the materials to the required temperature. In principle, such sources of energy would be the only types suitable for welding, but the excessively large diameter of these light beams (up to 2 to 3 mm) means that they cannot be used for spot welding.
Instead, Sysoev's team believes that using them not for welding directly but for heating surfaces, inside is not only possible, but also necessary. The weld laser beam is directed in to the center of the heating beam. With this approach, the drop in temperature between the point of the weld and the area around it is much smoother, and this feature is what defines the exceptionally high quality of the weld.
"If we take account of the fact that a combined approach of this kind can function on weaker lasers, than those that are traditionally applied, it transpires that the new method is not only more effective, but also more economical as the price of lasers is proportionate to their power," says Sysoev. "So it can be hoped that in the near future the process of laser welding of car chassis and other such items will become better and cheaper."