In a post-apocalyptic world, scavenging is the order of the day and you’ll likely be able to find plenty of scrap metal lying around (or still attached to something that nobody is using). That metal could be useful by itself, but it might be more useful if you could weld smaller pieces together to form one large structure. Plus, knowing how to weld is a skill you can trade on, unlike that Cisco certification you spent thousands of dollars on.
Fundamentally, welding is a simple process – heat two pieces of metal until they’re nearly liquid and force them together meshing one piece to the other. Most of the time, a filler material (commonly a more maleable, and thus easier to liquify metal than the one being welded) is used to aid in creating a cohesive bond, or joint, in the metal pieces. Over the years, industrial welding has evolved into a futuristic world of laser welders and using ultra sonic waves to fuse molecules together, but these types of welders are crippling expensive and rare, and thus you are unlikely to have access to them after The Event. For our purposes, there are three types of welding: forge, torch, and arc.
Forge welding is the most primitive form of welding. To forge weld, you heat the two pieces of metal until they are red hot, but not liquified. Place them on an anvil with one piece slightly overlapping the other and hammer them back down to the thickness of either piece of metal and thus forcing a mesh of the two pieces. Don’t expect this technique to work on steel, it will only work on more maleable metals that approach or cross the liquification point in forge temperatures (think bronze, copper, iron, etc).
The next step up is torch welding. To torch weld, you will need a torch – the most common torch used in welding is an acetylene torch, which is essentially a nozzle that mixes pure acetylene with pure oxygen, which you light as it comes out the end. An acetylene/oxygen flame burns at over 3000 degrees celsius which is the hottest flame you will get from readily available combustible gases. If you are making a makeshift torch, you can use any pure combustible gas and you can use compressed are instead of oxygen for your oxidizer, but you won’t achieve the same temperatures as your would with an acetylene/oxygen mix. Also, you need to make sure you are using some sort of non-return valve in order to ensure that you and your fuel cylinder don’t go up in flames while welding.
To perform a torch weld, place the two pieces of metal firmly together, turn on your acetylene just enough so that you hear gas escaping. Light the torch and adjust the acetylene until the flame is barely coming out of the nozzle. Turn on the oxidizer slowly until the flame turns blue. Point the flame at the joint and move the torch in a circular motion until the metal begins to melt. If you are using a filler rod, you can insert it slowly into the pool of molten metal to add more to the pool. Once you have a large enough pool, begin moving the torch slowly down the seam. If you go too fast, you will run out of molten metal. If you go too slow you will have too much. If you are using a filler rod, you will want to keep it in the hot zone of the torch (not close enough to melt it but not far enough that it cools off) to prevent a weaker “cold” weld. Turn the torch off in the reverse order you turned it on.
The final type of welding you should be familiar with is arc welding. Arc welding uses electricity to heat metal instead of flame and in this case, you NEED a filler rod. An arc welder is essentially a placeholder for your filler rod that is attached to a power source. As electricity passes in an arc from the end of the filler rod to the seam in the metal, it generates a great deal of heat, melting the rod and the metal equally. There are hundreds, if not thousands, of different types of filler rods available. Each one has a special purpose it was designed for, and sometimes you’ll need a certain type of rod to do any kind of welding on a certain kind of metal. We won’t get into that here, just be aware that this is a consideration if you have access to an arc welder post apocalypse.
To perform an arc weld, the first thing you need to do is attach a grounding clamp from your power source to your metal. This is important because if you don’t do this, the all-important arc will not be generated in order to heat the metal. To initiate the weld, or “strike the arc,” tap the end of the filler rod against the metal and then hold it at approximately 1/8 inch above the metal. You will see copious sparks shoot up from the metal – this means you got an arc. Angle the welder into the direction of movement at approximately 45 degrees and equidistant from each piece of metal (this is important if you aren’t welding two flat pieces of metal together), as if you were dragging the tip of the filler rod along the surface of the metal. Slowly move the rod across the seam until the joint is complete.
That covers the bare necessities of welding. These procedures and techniques will get you by in a situation where you need to weld. There are dozens of advanced techniques on how to weld in different situations, for different types of metal that I haven’t covered here. Just remember that practice makes perfect, and if you need to weld something intricate “measure twice, weld once.”