Lorica Hinge Durability

[marsvigilia]

While working you will reach the point were the metal looses it's plasticity and will break, crack etc. when you try to deform it. I don't know the correct term for this state. Translated literally from the dutch term it would be 'metal-tirednes'.

In English the term is "metal fatigue", which is essentially the same.

@marsvigilia: The romans used many different kinds of brass. It is incorrect to say that aurichalcum was more like what we know as red brass/tomback. For rivets brass that consisted out of Copper (Cu) with only a slight ammount of Zinc (Zn) was used. This is just because it's easier, as this metal is softer than yellow brass (=brass with a higher Zn content). But more decorative things such as florettes on helmets and loricae were made out of brass with a high Zn content, to have a nice golden colour. The name 'aurichalcum' consists out of aurum (gold) and chalcum (copper). And can be translated as 'golden copper'.

Actually, ‘red brass’ (C230 85%Cu 15%Zn), is hardly red at all. ‘Red brass’ is very close in appearance to ‘yellow brass’ (C260 70%Cu 30%Zn & C270 65% Cu 35%Zn) but actually looks closer to gold. It is still used in American Indian jewelry as a relatively inexpensive alternative to gold. In this, the name "golden copper" makes sense. But it does NOT look like copper. ‘Gilding brass’ (C210) has just 5% zinc, and ‘commercial bronze’ has 10% zinc, note "bronze" is a bit of a misnomer as it has no tin in it. It is my understanding that the Romans did generally use brass at about 5% zinc for rivets, but 'red brass' has 15% zinc and really is closer to orichalcum. This makes perfect sense as ‘red brass’ is closer in appearance to gold and easier to work than ‘yellow brass’. The only disadvantage ‘red brass' has, is that it is harder to find in the modern context.

M.C. Bishop, "Lorica Segmentata Vol I", p77\\n[quote]Orichalchum, which is almost golden in appearance was a binary alloy of copper (80%-85%) and zinc (20%-15%) and was widely used in military equipment from the 1st to the 3rd centuries AD. As such it closely resembles the modern alloys of “low brassâ€

[QVINTVS ARTORIVS CORVINVS]

OK... so back to kickplates

I suppose the best thing would be to work them as they are without heat, correct?
That way they stay semi-hard and get work hardened as well. Don't want them flopping apart like el dante fettecine' now do I?? :lol:

[Marcus Mummius]

@Tony: Aha, I see what you mean. I agree with what you're saying. I always thought that when english speakers reffered to 'red brass' this was the same as 'tombac'. 'Tombac' most of the time has only 10% Zn and looks very much like copper. It's quite red in appearance.
Now that I know that 'red brass' isn't red I understand :lol:

When we cast brass at university last year to replicate some Roman objects and try out different techniques the Zn content was about 15%. This indeed resembles gold better than brass with a higher Zn content.

@Corvinus: Yes, IMO it'd be best not to anneal the hinges. The bending and forming of the hinge tube shouldn't present a problem with semi hard brass. Also the filing of the hinges would be a bit more difficult if you annealed the brass (it would get 'smeared' more).

Vale,

[marsvigilia]

@Tony: Aha, I see what you mean. I agree with what you're saying. I always thought that when english speakers reffered to 'red brass' this was the same as 'tombac'. 'Tombac' most of the time has only 10% Zn and looks very much like copper. It's quite red in appearance.
Now that I know that 'red brass' isn't red I understand :lol:

When we cast brass at university last year to replicate some Roman objects and try out different techniques the Zn content was about 15%. This indeed resembles gold better than brass with a higher Zn content.

Language can be such fun. But in point of fairness I need to say that 'red brass' can be made to look red. Once it has been heated to a nice orange glow, if you clean it up carefully, you can get down to a very thin red layer of higher copper content, where the zinc has been at least partially burned off. With further polishing you get down to regular gold colored 'red brass', but it is striking. It looks just like copper. I discovered this when I got lazy and threw some tie loops I had hammered out of RB rod into a tumble polisher rather than cleaning myself. When I took them out, they were a beautiful bright shiny copper. I was quite puzzled at first. :o

[Matt Lukes]

I can see a clear difference between red brass and normal yellow brass side-by-side, but had I not had the normal yellow brass to compare, I'd have thought the red was just tarnished or had been heated or something. Just running a torch over regular yellow brass to warm it a bit and cause just the tiniest bit of oxidation, it'll turn a beautiful golden color- I love the look myself- brass is fun :wink:

[Nerva]

The nearest thing you can get to red brass commercially is what we call guildingmetal. Not a bad approximation. Looks just like Copper when oxidised, looks like bright brass when polished, unfortunately it does not stay that way for long.