A laser welding based process for manufacturing safe glass containers for containing chemical waste

In response to the demand for safe storage of battery materials and industrial waste brought about by the popularization of electric vehicles, the Hanover Laser Center (LZH) has developed an innovative laser based processing technology in the "LasGlaReLa" project.

As the adoption of electric vehicles continues to grow, so does the need for the safe and permanent storage of battery materials and chemical industrial waste. Certain waste streams require disposal in what are known as Category IV landfills, which impose particularly stringent requirements on storage containers. These must simultaneously ensure environmental protection, safe handling, and long-term structural integrity.

Glass is a highly promising material for this application: it is exceptionally chemically inert — meaning it reacts with virtually no other substances — making thick-walled glass containers especially well-suited for the permanent containment of hazardous materials. Glass containers are also of particular interest in the context of potential new recycling methods in the future. The stored residual materials do not react with the containers and can be readily recovered from them. 

Until now, these glass containers have been manufactured primarily using thermal gas processes. However, these are limited by uncontrolled heat input, high residual stresses, and restricted automation potential. Laser welding, on the other hand, enables high processing speeds and shows excellent potential for automation. For this purpose, the researchers employed a CO2 laser as the primary laser source. Normally, this laser at a wavelength of 10.6 µm has a low optical penetration depth of just a few micrometers. Combined with the low thermal conductivity of silicate glass, this typically results in incomplete penetration welding. 

Continuous weld seam without micro-gaps

As the scientists were able to demonstrate, it is possible  to simultaneously heat both welding partners using a single CO2 laser source, and thus produce automated sealed glass containers. They achieved a continuous weld seam without micro-gaps or voids throughout the entire thickness of the 5 mm-thick flat glass. Furthermore, despite the heat input, mechanical strength is maintained. This was demonstrated through stress tests on samples after two weeks of storage.

The process is unique: the lid sinks during processing due to gravity. Complex handling systems or clamping fixtures become unnecessary, as the joining partners position themselves automatically through gravity. The scientists are now working on further optimization of the edge geometries of the flat glass components. They aim to further reduce friction during the welding process and minimize the formation of protrusions and notches at the joint location.

Source: optics.org