Either the puddle gets too large and sags, or flux needs to be removed between passes, or the work piece needs to be moved with a certain speed/force that doesn’t scale, or the heat can only be deposited on a single surface at a limited rate, which causes problematic distortion and limits penetration.
Welding a 6” thick piece of anything with stick/tig/mig may take dozens or even hundreds of passes depending on geometry, material, available welding positions, etc.
Welding the same thing with stir welding may take 100+ or even 1000+ tons of pressure in a moving weld fixture.
And because of that, will also cause major distortion to the part unless done very carefully.
Electron beam welding doesn’t have many of these issues because the electron beam doesn’t get absorbed in a point at the surface (and the beam can be very narrow), allowing very deep penetration compared to something like an electrical arc, also allowing a lot less total heat input to get the welded spots to fuse, and that also means weld joint shapes can be used that won’t need filler metal being added, or movement, it doesn’t have puddle size issues or flux removal problems (necessarily). Due to the lower total heat input, it also wouldn’t have as significant distortion effects.
The internal tension/distortion created from welding heat can be really mind blowing - we’re talking enough to twist automobile frames into pretzels if not done correctly, or rip apart armor plating and heavy machinery joints just from the act of cooling.
It also doesn’t have force scaling issues like stir welding (generally).
It would require completely, perfectly clean surfaces and a non-reactive environment, and clearance for the beam emission equipment though.
Pretty neat overall!
Thanks for that fascinating explanation!
The UK has lost it's capability to make tanks from scratch, maybe this approach could be used to substitute in some way?
No idea how they weld those things together!
There are some neat videos on youtube showing some pretty cool simulations of the how and why.