Apprenticeship Session 7
Forge weldingwelding Welding is a process that joins metal by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal.. Today we tackle forge welding.
Okay, we dabbled in this once before, but now we’re getting down to brass tacks. We started the session in the “classroom” – meaning Doug’s dining room table – with a lecture on how forge welding works and the various fluxes that are used to clean the metal. Forge welding is considered a “solid state” weld as the metal does not liquefy. It is critical to have clean surfaces to allow the metal surfaces to forge together tightly.
While all fluxes help clean the surface they each have characteristics that make them unique. There are some fluxes that are magnetic, which in theory sounds good as it would stick to the metal, but it doesn’t really seem to provide as good an outcome as some of the others. The cheapest, most readily available is regular grocery store borax which can work just fine, but it is “hydrated” meaning it contains some water. You can watch that water bubble off when sprinkling it on your metal. There is also an “anhydrous” version, meaning without water, that seems to be the most straightforward flux and provides the most consistent results. Personal preference perhaps, but that’s going to be our go-to for the day.
We also talked about the different types of metals available and how well they work for forge welding. The old, and now hard to find, wrought iron worked really well forge welding. Some of the modern materials still work pretty good, but there are others that don’t work so well at all. Rule of thumb might be that the softer the steel, the easier it will forge weld.
So once we finished in the classroom, we moved out to the forge to practice. We set aside working on links and just focused on practicing the skill of taking two pieces of square stock steel and getting them to stick together. Building the fire like an oven (that’s what in one of those whiteboard drawings) so that the steel can be surrounded on all sides and heat evenly is important. A forge welding fire needs to run hotter that most.
So once it is in place, the next step was to shove the square stock in and heat it up. Then when it was good and yellow hot, we pulled it out and applied flux to clean it up. Then back into the fire to heat up again. And after a bit, you can touch the two pieces together and they should stick to each other. At that point you’re just looking for a bit of greenish-yellow smoke to come off and maybe just a few sparks. At that point you pull it quickly out of the fire, straight to the anvil, give it a solid smack on the top side, flip it over, give it a solid smack on the bottom side, and then back into the fire. That basically just sets the weld. Then once it’s heated up to yellow hot again, you pull it out of the fire and over to the anvil again and give it a couple of good whacks on the top and a couple more on the bottom to really meld the two pieces together. Back into the fire once again, back up to yellow hot, back over to the anvil, but this time you can take it a bit slower to seal up the weld and dress the sides. You’re kind of past the welding part at this point and back to the forging part to shape it the way you want.
Whew.
So enough practice. Rob had started a link during our previous session and we wanted to get it welded up.
So it was time to put what we learned to the test. We heated it up and followed the steps outlined above. It’s a little trickier to use tongs to grab the link than it was to use your hands to grab the square stock (tongs always makes things trickier), but the process of heating, fluxing, pounding, repeating was the same. After a few heats and some good solid smacks, it started coming together. Literally.
You don’t want to flatten or figure-8 the link too much as you’re pounding on it, so there’s a bit of finesse and being careful with hammer angles as you go. But if the weld is solid you can shape the link as needed to get it to the size and shape you intended.
So there’s one link done. Now to do dozens more so we can have an actual chain. I hear that you make separate links and then join two links by adding a third. That sounds easy enough, right? I guess I know what we’ll be doing next time.