Casting under pressure

[Jens Nordlunde]

I read in a newspaper, that The Danish Technical University (DTU) had developed a method to make brass/bronze (unfortunately I don’t remember whish it was) as hard as steel. They cast it under pressure, and the metal got harder and harder the more pressure they put on, but only to a certain point – they could not get it harder than steel. Is it at all possible that users of these metals could have know anything about this. I doubt it, but if yes, how did they make the pressure?

Jens

[Tim Simmons]

Yes. The mould is spun like in a sling shot. Today this can be done with a machine, centrifugal casting in some kind of spinner. This must of been a risky pass time. I do not know what size limits there must been. Hardness would also depend on the alloy.

[B.I]

hi jens,
tim is far more knowledgable about this than i, given his profession. but, i think modern bronze (ie the type bought in bulk from art suppliers) is made of an alloy that is much harder than 'old bronze'. i believe it is silica and i saw an artist try and file the bronze by hand and it was almost untouchable. i know i have filed down blade edges with much less effort. I have a feeling it could be even harder than steel.

[Tim Simmons]

Hand sling for casting. Some big chap might be able to swing quite large flasks.

[Tim Simmons]

Please forgive a little boasting. I will take them off latter but it is a subject dear to my heart.
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[Jens Nordlunde]

Hi Tim,

No wrong with a little boasting, is the figure made in the way you describe?

You don’t answer my question, is it possible that they a century or two ago could/would know this technique??

I always thought that bronze swords were interesting, but that they would break easily – but would they?

[Tim Simmons]

The techniques are ancient. I believe the figure was gravity cast, just poured in. Silver 1991, i can do better know, 9-10 inches tall. I really could not say if whole swords were spun in the casting. The weight may not have been a problem but the size of flask for the big chap to spin round would limit things. one thing for sure you would be able to cast some nice dense axe heads and spear blades.

[Rick]

I'm willing to bet that there was a mechanical way to swing a pretty large mold way back then; if they could figure out how to build a catapult; the technology could be adapted for casting .

[Battara]

The use of pressure in casting is essential for proper casting and as has been mentioned, very ancient. However, the amount of pressure equalling what we can do today is in serious doubt. Not only is the capability of technology at the time an issue, but in come cases one would not want to have steel solid bronze. Not only would it be ridiculously heavy, but the ability to expand when firing off a cannon shot could be compromised. Also, in brass and bronze mounts, one would want the softness to be such that one could easily chase or stamp designs into it.

[Jens Nordlunde]

Thank you for your explanations, The way I understood the article was, that the bigger pressure the smaller ‘grains’, and the smaller ‘grains’ made the metal harder. If you tried this on steel, would it work the same way?