It’s hard to imagine a world where the tri-faced king of processes didn’t reign supreme. But beyond MIG, TIG and Stick lies a fascinating realm of barely-known welding processes. Here are 2 you’ve probably never even heard of.
Not so much “cold” as “not hot,” Cold welding requires absolutely no heat. How’s that possible? Instead of using heat to bond 2 pieces together, this process tricks metal atoms into thinking they’re all part of the same piece. Here’s how it works:
Imagine metal pieces are made up of atoms that are obsessed with hugging. Specifically, atoms that love to hug other metal atoms. When you stick 2 pieces of metal together, their atoms desperately want to hug one another. But they can’t, because every piece of metal is covered on the outside by multiple layers of oxygen molecules and corrosion (plus dirt, grime, etc.). These layers act as barriers that prevent the metal atoms in one piece from hugging the atoms in another piece.
Now let’s say you’re in space. Since there’s no air, there are no oxygen molecules to act as a barrier. Only layers of corrosion keep the atoms in 2 pieces of metal from hugging one another. If you remove these layers (by cleaning or wear and tear) and push the 2 pieces together, there’s nothing left to separate the one from the other. Their atoms are now free to hug it out. In fact, the atoms from one piece will hug the atoms from the other so hard; it’ll create a solid-state weld between the two without any heat or filler material.
Originally, cold welding was more of a problem than a solution. Early satellites contained lots of metal parts. As these parts would interact with one another, their corrosive layers would rub off meaning there were no longer any barriers between their atoms. The pieces would accidentally be welded together in a permanent bond.
Today, cold welding is largely used for nanotechnology. Because nano-fabrication is so small, creating a micro-sized welding machine is incredibly difficult. By using a vacuum to suck out all the air molecules from a container, it’s possible to actually cold weld 2 micro-sized pieces together more effectively than any traditional welding process.
Imagine instead of a welding machine, you’ve got a napalm bomb. That’s similar to how Thermite welding works. Unlike cold welding, Thermite welding is all about cranking up the heat. Today, this process is mainly used to connect the ends of railroad tracks. As railroads are being built, a gap of about 1 inch is left where one rail ends and the next one starts. A rough mold in the shape of the track is placed around this gap. A large stack that looks like a Dutch oven is placed over the mold. This is called the “crucible.” The crucible is then filled with a Thermite mixture and metal alloys. Thermite is like black powder, in that it burns super hot for a very quick period of time.
Because the thermite weld is so hot, the ends of the rails must be preheated. Once everyone’s got their hot dogs and marshmallows out, the thermite in the crucible is ignited. The intense heat from the reaction causes the metal alloys in the crucible to melt into a molten liquid. Often times, this reaction can get as hot as 4500 degrees F. To put that in perspective, that’s twice as hot as the temperature of a lava flow.
Once the metal alloys have been melted down by the termite reaction, the bottom of the crucible is then breached. The molten metal flows down from the crucible and into the mold. Once the metal has cooled, it’s grinded down to a smooth surface. This allows the train to seamlessly glide from one rail to the next.
It’s mind-blowing to realize these are just a few of the most insane welding processes you’ve never heard of. If you thought that was entertaining, you should check out a few of our favorite posts below: