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Welding Glass To Metal Is Now Possible Using An Ultrafast Laser System, Researchers Report (phys.org)
An anonymous reader quotes a report from Phys.Org: Scientists from Heriot-Watt University have welded glass and metal together using an ultrafast laser system, in a breakthrough for the manufacturing industry. Various optical materials such as quartz, borosilicate glass and even sapphire were all successfully welded to metals like aluminum, titanium and stainless steel using the Heriot-Watt laser system, which provides very short, picosecond pulses of infrared light in tracks along the materials to fuse them together. The new process could transform the manufacturing sector and have direct applications in the aerospace, defense, optical technology and even healthcare fields. Professor Duncan Hand, director of the five-university EPSRC Center for Innovative Manufacturing in Laser-based Production Processes based at Heriot-Watt, said: "Traditionally it has been very difficult to weld together dissimilar materials like glass and metal due to their different thermal properties -- the high temperatures and highly different thermal expansions involved cause the glass to shatter. Being able to weld glass and metals together will be a huge step forward in manufacturing and design flexibility."
He added: "The parts to be welded are placed in close contact, and the laser is focused through the optical material to provide a very small and highly intense spot at the interface between the two materials -- we achieved megawatt peak power over an area just a few microns across. This creates a microplasma, like a tiny ball of lightning, inside the material, surrounded by a highly-confined melt region. We tested the welds at -50C to 90C and the welds remained intact, so we know they are robust enough to cope with extreme conditions."
He added: "The parts to be welded are placed in close contact, and the laser is focused through the optical material to provide a very small and highly intense spot at the interface between the two materials -- we achieved megawatt peak power over an area just a few microns across. This creates a microplasma, like a tiny ball of lightning, inside the material, surrounded by a highly-confined melt region. We tested the welds at -50C to 90C and the welds remained intact, so we know they are robust enough to cope with extreme conditions."
Welding typically creates a LOT of heat in the materials, and that creates the issue - at assembly time. Many welded products rarely are used at temperatures high enough to create thermal expansion issues - but the thermal expansion during welding is problematic.
Browsing at +1 - no ACs, I ignore their posts. So refreshing!
Yeah, the vacuum tube makers melted the glass and pressed it around metal rods, made from an alloy with the same thermal expansion as glass.
For the benefit of American readers, Heriot-Watt is in Edinborough. That's in Scotland.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
And that will change after welding because ... ?
Because the temperature range they seem to be interested in is -50C to 90C whereas welding requires much much higher temperatures; for instance around 1700C for glass.
That's not welding, but is more akin to soldering. It's very troublesome to get molten glass to wet a metal, keep the bond when cool, and avoid problems with thermal expansion differences between the metal and glass. This was first solved in the 1800s by using platinum as glass does wet it and its expansion is similar to glasses used in scientific equipment of the time and in early vacuum tubes and incandescent bulbs. After that things got fiddly. Being able to weld metal to glass means a lot of that and its complications can be avoided.
See this article on glass-to-metal sealing: https://en.wikipedia.org/wiki/...
The article itself.