Iron work is a foundational skill, literally shaping the bones of civilizations for well over a millennium today. As such, the earliest practitioners started out with nothing but ingenuity and raw natural materials. It is possible to do the same in a survival context, but the amount of labor necessary to smelt one’s own wrought iron from ore is prohibitive unless one has no other choice. Much more reasonable in a survival setting would be the repurposing of available metals. In history, this was extremely common. Viking societies would burn longships and sift the ashes to recover nails. We can use anything from the frame members of an old burnt-out trailer house to the steel leaf springs in a wrecked car as raw material for our forge. Everything made of steel is nearly infinitely recyclable.
The basic needs of a smith are simple, you need something to beat, something to beat it against, something to beat it with, and a fire to heat it up until it moves. We’ll tackle the basics in this order.
Something to beat
Salvaged steel is going to come in various grades, anything from the hard wearing d1 or d2 steel we find on the bucket of an earth moving machine to the millions of tons of mild structural steel we find distributed throughout our world. This material will have different properties depending on its alloy, but as a smith in a collapsed world you can determine how it behaves experimentally. Heat it up and beat on it, some steels will be harder to move, some will move easily at lower temperatures. Some will crumble when you heat them too hot, and others are very tolerant of overheating. You will need to experiment, but most any steel will make a functional knife, bracket, hook, tripod, fireplace poker, or myriad other useful tools. Note that I said functional. You’ll have to sharpen a mild steel knife far more often than a properly hardened and tempered blade, but it’ll still cut hide and meat.
Something to beat it on
This is the well-known anvil under the chestnut tree of Kipling fame. Luckily for humans, a proper anvil is completely unnecessary. The Kami’s in Nepal have been making beautiful Kukri knives using sledge hammer heads half buried in the earth as an anvil for generations now. The Vikings used a stone to make their small anvils. It’s quite easy to shape iron to a point on a rock and straighten it out on a cut block of wood.
What’s most important from an efficiency standpoint is the mass under the blow. Mass underneath your work is hard to move, its inertia reflects force back into the hot metal the worker is attempting to shape and potentially doubles the deforming effect of each blow.
One note on this: I’ve seen many hobby blacksmiths attempt to make an anvil out of railroad rail. These budding smiths seem more interested in making the rail look like a traditional London pattern anvil than they are in maximizing the efficiency of their work. If a chunk of rail were cut about 12 inches long and up-ended so that the work was being done on the cross-section, most of the mass would be directly under the work massively increasing working efficiency.
A hammer face is almost always going to be smaller than the cross-section of the working portion of the rail. Usually instead, the rail anvil is placed on its foot and the work is done on the face that the train rides on. While this may see some benefit from work hardening during the life of the rail in its original use, the only mass resisting the hammer to the ground is the web of the rail. That’s not as effective as placing the most mass possible, the body of the rail under the work.
Something to beat it with
This is most likely going to be a hammer. Any hammer. The back of a tomahawk. You can use a rock in your fist if you have nothing else, but I’d probably try to put some kind of a handle on it to keep my tender skin away from flying slag. That’s personal preference though. Seriously, I’ve used a claw hammer with a broken heel to forge. I’ve used drilling hammers, cut-down sledgehammers, wooden mallets, and even a crescent wrench to forge metal.
Flat faces are good because they reduce the marks you leave in your finished product, but they also contribute to maximum metal movement when the impact occurs. Ridges or grooves can grip the face of your work reducing the lateral slippage of the metal upon impact, so a smooth face is better for most forging operations.
Additionally, once the piece that you’re working is cut off for its final shaping, you’re going to have to hold onto it while you hit it. Pliers work well, but so does a set of primitive tongs. Take a stick about 1.5” in diameter and about a foot to a foot and a half long. Tightly bind about two inches of one end of it with twine or some other cordage. Split the stick to the bound portion. Shove a small wedge into the split and viola, you have a set of tongs like grill tongs. These will eventually burn up but work well enough to get started and take only seconds to make.
Fire to heat it up until it moves
I’ve done plenty of metal shaping in a campfire. You build the fire, wait till it burns down to coals, and point an air pump at it. Our ancestors used a pair of goat skins piped together with clay pipes, alternating skins while opening the skins on the way up and closing them on the way down to push air into the fire. This was helped by threading sticks into the openings of the skins. The Chinese built a wooden box bellows, effectively a box with a moveable piston that compressed air through a hole at the bottom.
One native American smith in the 1800s, unable to afford a commercial blower, he built a rotary blower out of wood. Coal is nice for industrial-level work; it burns for a long time. Early American smiths in the Appalachian Mountains preferred charcoal because it’s much cleaner burning. You can even place green wood around your working fire to char as you work making the next layer of fuel. Fire management is supposedly the most difficult part of smithing. To be honest though, I’ve never found it that difficult. Place iron in fire, blow air at fire, when iron starts glowing, pull it out and hit it.
Forging
Forging consists of the following operations:
Drawing, upsetting, bending, shearing, and welding.
Drawing is to stretch metal making it longer and thinner, this is accomplished by forming dents in the face you want to move, then hitting the high spots to force the metal to flatten out. If you want a straight taper, you must work it on at least two sides.
Upsetting is to make the metal shorter and fatter, you hit it on the end, perpendicular to the direction you want it to move.
Bending can be accomplished around a form or freehand by hitting the metal. Twisting is a form of bending often used in decoration.
Shearing is either cutting off the metal or punching out a hole. This is accomplished by beating the metal against any sharp edge or using specialized punch and bolster plates. Be careful using a knife to cut hot metal as you will ruin the temper.
Metal moves best when it’s between a glowing red and a white-hot heat. It moves from red to orange, to yellow to white. The hotter it is, the easier it moves, unless it’s one of those metals that likes to crumble if you get it too hot. Once it’s white it starts to throw off sparks, which is an indication that you’re burning away your material. It rapidly loses carbon at this point though it gains some back from the fire. White hot and sparking is the indication that it’s ready to weld.
Welding is much like taking two ice cubes, wetting them, and sticking them together. You wind up with one larger ice cube. Technically steel likes to exchange electrons with steel, so a smoothly machined face can actually ‘forge weld’ at room temperature if it’s got enough surface contact. However, we’re talking about banging metal in a dirty forge, so it’s not usually as straightforward as that. The recommendation is to get it to sparking or nearly sparking prior to beating the two pieces together to get them to stick. This will take practice.
Heat Treating
Heat treating is not as esoteric as it can be made to sound. A steel with sufficient carbon content will harden when it’s heated to non-magnetic and rapidly cooled. This requires a cooling medium, water, air, or oil. Be careful cooling hot metal in oil because you may produce a small fireball. In almost all cases, red hot metal is not magnetic. If this process is followed and the steel doesn’t harden, it probably doesn’t have enough carbon in it to do so. Hardened steel is also brittle. Tempering is a controlled softening process. If a portion of the material is polished free of scale, it’s possible to see the ‘temper colors’ run. What this means, is that upon re-heating the hardened metal, colors like an oil slick will appear on the polished surface of the metal corresponding roughly to its hardness. The colors start from straw yellow, move to purple, then to blue, then to grey. Grey is dead soft, Purple to blue is decent for working knives and straw is for long lasting but hard edges such as razors.
Once the colors start to run they move quickly so have something to quench the material in when the portion you want correctly tempered reaches the color you want it to be. You can re-heat the piece over a fire, but a heated block is useful for controlling where the heat goes.
Obligatory safety comments
Fire is hot, metal conducts heat. Don’t touch metal unless you’ve felt for heat above it first. Wear safety glasses. Don’t breathe smoke from a smithing fire. Galvanized metal will deposit zinc in your body if you breathe in smoke from heating it. This heavy metal poisoning is cumulative over your lifetime and will eventually kill you, so don’t breathe smoke, and if you can avoid it, don’t heat galvanized metal.