How to Forge Brass? Hot vs. Cold Forging


Brass is far less common among amateur blacksmiths than in industrial manufacturing. You may have worked with it before, or you may not have even heard about it. It could be widely used, or not at all, depending on where you live.

Forging brass requires precision, technique, and, more than anything else, a gentle hand to mold it into shape. We will explore this further in the article.

 

What Is Brass and What Is It Good For?

Brass is an alloy of copper (Cu) and zinc (Zn) in variable amounts to obtain different mechanical, electrical, and chemical characteristics.

Brass has long been a popular decorative material due to its brilliant, gold-like appearance; it is commonly used for drawer handles and doorknobs. Due to like low melting point, good workability (both with hand tools and contemporary turning and milling machines), durability, and electrical and thermal conductivity, it has also been frequently utilized to create cutlery.

Locks, hinges, gears, bearings, ammunition casings, zippers, plumbing, hose couplings, valves, and electrical plugs and sockets are all examples of applications where brass is still widely employed. It is widely used in musical instruments such as horns and bells. It is also utilized as a copper alternative in manufacturing costume jewelry, fashion jewelry, and other imitation jewelry.

 

Is Brass Good for Forging?

If brass is a good forging option is likely several millennia old question.

Brass is not the best forging option due to its difficulty to work with. However, it has properties that other metals in its price range lack.

Not all brass is equal too, which further complicates the question. Some brass types are made easier for blacksmiths to work with. For example, C37700 brass is widely known as “hot-forging brass” as it doesn’t break as easily in high temperatures.

Other types of brass often crack when hot forged.

 

Brass Forging Temperature

Brass that can be successfully hot forged, like C37700 or C360(C36000), is usually forged at around 800°C (1450-1500F).

I worked with both, and they are quite similar. C360 brass cracks on shorter lengths more often, making it slightly more difficult to work with. Although, great to practice on because of the smaller margin of error.

However, hot forging brass needs to be done with extra care because of zinc fumes toxicity. Always hot forge brass outside, never in a closed room.

You cannot heat brass to high temperatures without the zinc component volatilizing. From personal experience, you do not want to be exposed to zinc fumes. It seems like a combination of the flu and migraine; in rare cases, it can be lethal.

 

Can Brass Be Cold Forged?

Most brass is easier to cold forge. C34500, C35000, and C35300 brass are the most common cold-working brass. Brass is not soft enough to be shaped immediately, so it requires annealing. Annealing is the process of physically and chemically changing metal properties (in this case, only physical) by heat.

Forging brass is entirely dependent on the alloy. C260 cartridge brass is specially engineered to be extremely formable, so cold hammering will be simple with a few anneals in between to re-soften it. A solid bar is often made of C360 free machining brass, which becomes more crumbly when deformed cold.

More on the process of cold forging brass down below.

 

Can Brass Be Forge Welded?

Brass can be forge-welded to itself by a technique different than traditional hammer use. It requires clamping together and heating to high temperatures. I don’t have much experience with it, so I won’t go into details. However, it’s not difficult to figure out the temperature needed and other details on your own.

Forge welding brass to other metals is a completely different story.

The issue with many incompatible metal combinations is that their melting temperatures can differ, making it impossible to melt them simultaneously. If one melts and wets the other while the other does not, the result is a braze rather than a weld.

Welding some combinations may also result in brittle intermetallics or the induction of a more severe heat-affected zone and metallurgical damage on one side.

While the technology is not new, friction stir welding is becoming more popular and may be worth attempting on certain unusual metal junctions.

Another thing to remember when welding dissimilar materials is that it generates an electrochemical couple, which can accelerate corrosion if the exposed weld is submerged in an electrolyte (e.g., saltwater).

Welding brass or copper to steel is not recommended. However, you may braze them together with a silicon-bronze filler rod.

 

Can Brass Be Melted With a Propane Torch?

You can easily melt a small piece of brass with a propane torch.

Anything bigger will lose heat faster than the propane torch can heat it. Not at first, but the higher temperature you reach, the slower the heating process gets. Until it starts reversing, and you can’t heat it anymore.

You would need an oxygen-fed torch with a big flame. Even then, it isn’t easy to reach the melting point of brass unless the brass object is insulated.

Then there is the danger of zinc fumes I mentioned before. If you melt the brass in a closed forge/oven, you need to be extra careful when opening it.

 

Forged Brass vs. Cast Brass – Different Melting

Forged brass is much stronger because of the temperatures used. It’s not the same with any metal, but brass is comprised of copper and zinc, which melt at 600° different melting points.

Casting brass will weaken its structure by boiling zinc because not only will it melt before the copper, but the boiling point of liquid zinc is lower than the melting point of copper.

When cast into a new brass object, a copper component will harden while the zinc is still boiling, trapping tiny air bubbles and forming cracks within its structure.

If it was a smaller temperature difference, it could be prevented or at least minimized by heating faster.

 

Brass Forging Process

If you have never worked with brass before, you should know that brass conducts far more heat than iron or steel. You can’t handhold it like a long iron or steel bar, no matter how long it is. The heat will swiftly spread, even to areas outside of the fire. You will require tongs for everything.

Remember that, unlike steel, when you heat copper alloys to anneal them, you may immediately chill them in a pail of water to save time; you do not need to cool them slowly. Brass softens when quenched in water and hardens when cooled slowly, exactly the opposite of steel.

With all that in mind, the process is actually quite simple.

I begin by annealing the brass immediately, heating it to a glowing dark red, and quenching it in water. At this point, you can easily shape the metal into the overall shape you want. Don’t focus on details yet.

You want to get the rough shape as precise as possible because of the nature of brass and how it deforms when further working on details of the shape.

You can soften only the part you need later to prevent deforming when a hammer hits. Even though it conducts heat very well, the part which isn’t in the fire will lose heat quickly and won’t be annealed as much in the process.

Make sure the hammer hits become weaker and weaker as you move to thinner parts and details. Even the best cold-forging types of brass will crack way more easily than most other metals you are used to working on.

You can anneal the brass as often as you want, as long as you don’t overheat it, so the zinc doesn’t melt.

Some types of brass may require repeated annealing after only several hammer strikes. If you don’t anneal on time and keep hitting it with a hammer, the brass may form cracks, and you will have to repeat the whole process.

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