A Simple Guide to Forging Aluminum
[last updated: 7/7/2024] I have spent many hours forging aluminum, with projects of various sizes under my belt. It’s one of those subjects where I feel like I have enough experience to give overall advice, but not enough to be an expert quite yet. Like in my other blogs, I will continue to update this guide as I gain knowledge. For now I will keep it short and sweet.
Alloys
There are two alloys that I have used: 6061 for solid aluminum, and 1100 for sheet aluminum. I was recommended 6061 for forging and it does seem to have the best properties for hammering on. The 1100 sheet I learned from taking a class with Evan Wilcox, who creates masterful hot rod and motorcycle parts out of 1100 aluminum. 6061 is used for architectural applications because of it’s high strength. 6063 can also be forged and is used for door frames and application where strength is not as important a factor.
Forging Temperatures
Annealed 1100 aluminum sheet metal can be forged cold, and often is. As you hammer sheet metal it will begin to work harden, thus increasing it’s strength and retaining it’s shape. Re-annealing will make it soft again. I’m sure you can hammer annealed 6061/63 sheet cold, but the annealing process is much more complicated.
Normally I hammer 6061 and 6063 at the very least a hot working condition of 500-700°F. Forging should take place at ideally 750°F to 900°F
When I texture my roses I make sure they are at least in the hot working temperatures range. Hot working temperatures are typically between 500-700° F. I am able to work them in the hot working range, as opposed to the forging range because they are merely textured with no appreciable change to the cross section of my material. For forged projects where you will be changing the cross section, 750 and 900° is my target.
How do I know when the aluminum is hot enough to forge?
Aluminum melts before you can see any luminescent colors so how do you tell when it’s hot enough to be forgeable? Any light the hot aluminum creates is drowned out by every other source of light around you. You need a stick to rub on it! In my experience any dry bit of tree will do. I’ve used 2x4s, paint stirrers (pine) and even the handle of my hammer (oak) to check the temperature of the aluminum. I use my gas forge, use low pressure on the gas, and block off some air on my venturi in an effort to have a cooler forge than steel forging. I absolutely BABYSIT my aluminum, marking with wood sticks as frequently as every 5 seconds for smaller pieces to catch it at the right temperature and to not melt my project. Aluminum melts devastatingly quick, before you know it, faster than the blink of an eye, etc. Forging aluminum on Venus is ideal, as an average surface temperature of 866°F slots nicely with many alloys.
Hot Working aluminum:
As soon as rubbing the wood on the hot aluminum leaves a distinct light brown residue, it has reached hot working temperature (500-700°F) and can be hot worked. Note this is not yet forging temperatures. This mild working heat is good for surface textures or light bending processes.
Forging aluminum
If the wood residue on the heated aluminum comes off as a dark brown residue, the aluminum has reached forging temperatures. You have a short amount of the time to forge your material (change it’s cross section) before it becomes too cold, and possibly hard and brittle. When the stick leaves a distinct black streak I can tell you from experience that you are seconds away from melting it. It’s very soft and bends like taffy at this stage which can be great for forging. It can be difficult to control drooping metal, but it will give you a decently long forging heat. I do not have an infrared thermometer but I suspect you may be able to use one in the right conditions.
“I have melted aluminum many times.”
Annealing Temperature
It is fairly simple to anneal 1100 aluminum. You must heat to 675 degrees and hold it at this temperature until the cross section of the material is heated through. Then you may air cool.
6061 is much harder to anneal. According to AZO Materials, “Annealing of Aluminium / Aluminum 6061 alloy can be performed at 775°F for 2 to 3hrs followed by controlled cooling at 10 to 260°C (50 to 500°F) per hour, and air cooling.” My advice would be to forge 6061 or 6063 aluminum hot.
Techniques for Forging
Now that you know how to determine the temperature of your aluminum, and ideally after a few practice heats, it’s time to start squishing that metal effectively. Aluminum is very soft and results in a beautiful and satisfying squish. I love how easily you can create texture on aluminum and how the hammer beautifully burnishes the surface. Here are some general concepts to keep in mind when working aluminum with a hammer:
To start, a repetition: You can’t see the heat. You need to be constantly pulling that aluminum out of the forge and using a wooden stick to check the temperature. This is your life now.
Aluminum is quite conductive: Aluminum is fantastically good at transferring heat right into your gloved hands. This will become immediately evident and you will be thinking of this fact upon discovery.
Babysit: I have melted aluminum many times. Most of the time it is the part sticking out of the forge that melts. I heat one section of the aluminum and then go to heat the next section. My previously heated section is sticking out of the forge, and enough heat transfers to that area to melt my metal. Pay attention to the overall heat, mark with wood even where the metal isn’t in the forge.
Aluminum can be brittle: Aluminum is sensitive to heat differentials. Cold aluminum is rather hard and brittle, hot aluminum is soft like taffy. When you have a piece of aluminum that is hot in one section and cold in the adjacent section, it will often fracture at the transition between hot and cold. So be careful when doing anything that will create a heat differential such as quenching a section in water or twisting in the vise.
Aluminum smears: Aluminum can be fun to forge, since it is so soft at temperature, but it is easy to accidently smear aluminum with a glancing blow. Deliberate, perpendicular blows should be sought. Aluminum residue will also cover every surface that you forge against. Yay!
FUN FACT:
Aluminum powder mixed with iron oxide can create thermite!
So sweep up your dust, clean up aluminum surfaces and never mix iron or steel abrasives with aluminum.
Never use aluminum on stone grinding wheels as it possible to create hot spots on the wheel causing it to break apart and come flying towards you.
Further Study on Working with aluminum
TIG Welding Aluminum with Welding Tips and Tricks
Aluminum Anodizing and Dyeing - I used Wiki How to experiment with anodizing aluminum. A few tips.
Lye is extremely corrosive to work with and difficult to rinse off. I have found that using a commercial aluminum cleaner for boats works better for preparing the surface.
It is worthwhile to buy Caswell brand dyes. It is possible to dye aluminum with fabric dyes but the results are typically of a lower quality and may fade over time.
Aluminum will interact with oxygen and become alumina, which is basically a ceramic. It is the white chalky surface you sometimes see. Even if you do not want to color your aluminum you should consider anodizing small parts
Clear Coating Aluminum with ProtectaClear or EverClear by Sculpt Nouveau
Anodized and dyed red aluminum rose
