Why can't you cast swords? why does it have to be hammered?

why can't you cast swords? why does it have to be hammered?

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not that i don't want a bronze kopesh, though

To oversimplify some things a bit...

The properties of steel don't just depends on the composition. It will also depend on the crystalline structure of the metal (how exactly the atoms arrange themselves in the crystals, the size of the individual crystal grains, where any impurities/inclusions end up, etc). There's also the question of how well the alloying elements have been distributed throughout the metal, if there's any porosity, and so on.

As-cast, most metals will tend to have a rather poor internal structure (old smelting technology that never fully melts the material will also lead to this, often to a much worse degree). Large grains, large inclusions, uneven chemical composition, gas porosity, such things may occur. This has a harmful effect on the properties of the steel, and thus you get a pretty bad sword. Today we could almost certainly fiddle around with things until we could cast a decent enough sword blade, but there isn't enough money in swords to warrant the RnD investment.

Now the way to deal with most of these issues is to heat your metal and then, somewhat literally, to beat the crap out of it. This will help refine the grain size, close up porosity, crush inclusions to less harmful sizes and shapes if not completely beat it out of the metal, and help even out the composition. Obviously you get a bit of this automatically when forging, but historically there would be a varying degree of extra forging at various points from smelting furnace to finished product to further refine the material. Today most steel around you will have gone through this process in a hot strip mill (though it was probably better before than most historical stuff was when fully refined).

Now bronze sword were cast (though not ready to sue form the mould: bronze-age-swords.com/sword_finishing.htm ) so bronze would appear to behave much better when cats than most alloys, and iron/steel in particular.

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what makes bronze behave better than iron or steel? isn't bronze a metal like any other? aside from being an alloy

>bronze behave better t
it's worse. by a lot
but that's just how bronze works, you gotta cast it

Bronze isn't "better" than iron or steel, it's different. And this is rapidly turning into a subject which requires an awful lot of room to explain.

Generally speaking, you want to avoid cast parts because they tend to have a lot of defects like air bubbles inside, or inclusions. An inclusion is a bit of foreign material--could be dirt, slag, whatever--inside the casting. Both air pockets and inclusions are very difficult to avoid even with modern tech, and were impossible to avoid in prior centuries. These kinds of defects result in failures (broken sword).

The blows of the hammer in forging remove these defects. If you think of the classic blacksmith pounding on a red-hot iron bar with a hammer you might see sparks flying. Those sparks are slag being squeezed out of the metal via the blows of the hammer. What the blacksmith is doing with his hammer is not just shaping the metal into the part, but also forcing out the impurities. When the metal is clean there will be no sparks when hit with the hammer. This is just as true for modern forging, only that steam or hydraulic powdered hammers are used in place of hand-swung ones.

There's a NOVA special called "Secrets of the Viking Sword" which goes into a lot of detail about this. I'm sure it's up on youtube. Note the lack of sparks (impurities) when the smith goes to strike the special steel they made in the video.

hmm, but why are parts on tank armour cast if cast is bad?

Tanks are big

...to continue.

Also, different metals behave in very different ways when it comes to heat treating them. Steel is rather unique. It's mostly iron but has some carbon in it. It may have other elements present too. Depending on the carbon % and how it is heat treated, quenched, etc, the carbon will form very different patterns inside the steel. This can be seen under a microscope. Those different structures--pearlite, martensite, austentite, etc--have very different mechanical properties. So any sort of steel part is processed in some way--forging and/or quenching--to give it the properties it needs for its desired job. A blade needs to be hard so that it retains an edge, but not so hard that it is too brittle to parry a blow or chip on impact. The steel will be processed in a way to give it those properties. Other parts will be made in different ways: fence wire needs to be fairly soft so it can be twisted into place. A file needs to be incredibly hard--even to the point of brittleness--because of the job it needs to do. And so on.

That's steel, other metals are totally different. Aluminum alloys have a very different crystalline structure. Instead of being hardened via quenching to trap carbon in a specific state like a steel sword would be, aluminum alloys are hardened by heating them and keeping them at an elevated temperature for a long period of time. The goal is to get it very hot, but not so hot that it melts. Some of the alloying elements will slowly move together inside the aluminum and form little clumps. Those "clumps" are desirable--they disrupt the aluminum's crystal matrix so it cannot deform so easily, making the part stronger.

Brasses and bronzes are a different beast entirely.

Bronze of course suffers from the same problems as steel with regards to casting and roughly the same improvement when hammered (as long as you are aware of how heat treatment affects bronze differently to steel). However the critical difference is in the melting point.

Bronze has a much lower melting point, to the point where it is practical and feasible to cast bronze. Steel has a high melting point. Nobody casts steel direct to the final shape, there just isn't a reason to. It's cheaper and easier to forge it, and it creates a stronger item. Now, you can cast a certain composition of "steel", but it has such different properties we call it by a different name: cast iron. Cast iron has a low enough melting point that it can be cast, but it's brittle. That is not to say you can't make blades of cast iron, it's just a terrible idea.

Casting has advantages too: it's cheap and fast to do. For wartime tank production that's a huge benefit.

Your question is kinda like asking why people eat fast food when 3-star fine dining exists. The answer is yeah, it's better and we know it, but we don't always have time or money for that!

I can't cast sword because my magic isn't high enough

Resistance to a projectile is a different mechanism to general strength.
The usual rule of thumb is that cast armor is 10% worse than RHA. However, casting means shapes that are not flat planes of metal can be used, which means greater geometrical efficiency in terms of space enclosed and promotion of deflection. In the end, neither method is noticeably superior over the other. Nowadays external armor is not cast, because every armor plating designed to defeat shaped charges need to be flat like ERA and NERA

You seem like you severely underestimate how complex metallurgy can be.

In high velocity impacts like you have with tank rounds, materials behave more like liquids instead of solids and material composition matters less.
The reason for this is that at low speeds, the chemical energy binding matter together is vastly greater than the kenetic forces so things act solid like.
However, at high velocities, the kenetic energy matches or is greater than the chemical energy binding the matter together and thus the types of bonds between the atoms matter less.

>Nobody casts steel direct to the final shape, there just isn't a reason to.
Ruger says hi.

Seriously, there's a lot of steel shit that gets investment cast near-net.

liquids? like hyperplasticity? i do not know how any of that works, but the copper in a heat projectile becomes hyperplasticied, and what hyperplasticity is i do not know, but apparently it works really well for punching through armour.

Dunno really, but for some possibilities...
It might have a greater natural tendency to go for a smaller grain size straight up due to various properties of it. (Surface tension between the phases involved, and how their free energies varies with the temperature. Looking at the phase diagram it also looks like the originally formed grains of alpha phase will tend to shrink as the temperature goes below ~450°C which could perhaps be one grain size control mechanism.) The normal culprits for gas porosity may have a lower solubility in the liquid metal and thus we simply get less of them in there. It may shrink less on solidification. Bronze is harder than copper to some degree because of small-scale variations in composition, so what unevenness we get from the casting process may not be an issue.

To some degree we can cast better today and thus avoid some of the issues. The effectiveness of armour also increases rapidly with thickness, so the tanks probably to some degree just "brute force" the issues with raw mass. At high impact velocities (HEAT or APFSDS) it's mostly just the density and thickness that matter anyway, while swords stay in the velocity range where hardness and strength are what matters. A lot of the issues with casting can also be removed by heat treatment, which appears to have been done to some tanks at last. And being able to make the tank quickly and easily can sometimes be more important than making the best possible tank.

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i thought it was because bronze work hardens thus making hammer forging either nieh impossible or at least extremely difficult to the point the gain in strength isn't worth the time and effort.

You can hammer forge bronze, you just have to anneal it every once in a while.

Work hardening is a thing whenever you cold work materials. It happens to iron and steel as well, which is why cold drawn wire (piano wire) will maul any cheap pliers tasked with cutting it. But you can get around that by simply heating the material up to a sufficient degree every now and then as that "resets" the crystalline structure and gets rid of the work hardening. (Part of the reason lead is so pliable is because it has a reset temperature below room temperature.) Or you can just hot forge, since that'll keep you over the critical temperature all the time.

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Based spadroonposter

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