This is probably a stupid question, but it came to me in a dream.
In the dream, I’m in a huge warehouse. There’s lots of big bins contains various bits of shaped iron. I’m apparently there to buy some of the these bits. I pick up one and examine it and I say to myself (since there’s no on else in the place), “Nope. This one’s been melted too many times.”
Uh, yeah.
The question:
Let’s say you take a lump of pure iron and form it into a shape, say, an I-beam. Then you melt it down and formed it again. You do this dozens or even hundreds of times. Will the last casting be as strong as the first one assuming you follow the exact same procedure?
:smack:
That title should read, “Effects of changing an element’s state of matter”.
[QUOTE=Let’s say you take a lump of pure iron and form it into a shape, say, an I-beam. Then you melt it down and formed it again. You do this dozens or even hundreds of times. Will the last casting be as strong as the first one assuming you follow the exact same procedure?[/QUOTE]
First off. You wouldn’t make an I-beam from pure iron. It would be structurally unsound.
Iron is alloyed with other ingrediatns to make steel for rolling into structural shapes such as angles, channels, I-beams, etc.
Scrap iron (mostly steel) is realloyed before reuse as structural steel.
Does that answer you question???
individual atoms don’t really ‘wear out’, neither do they really ‘remember’ much - so in theory, you could remelt and recast a pure metal any number of times with no worries. In practice, though, repeated remelting creates the possibility of introducing impurities, or, in the case of aloys, changing the proportions of the mix.
I wasn’t intending to use it in a structure. I used I-beam just as an example. It could be any shape.
That’s what I was trying to determine.
Unless conditions are rigorously controlled and reproduced exactly each time, melting and recasting can have huge effects on the character of metals, even impossibly pure metals. The size, shape, and distribution of the crystals directly affects the behavior of the metal, and crystal growth is determined by such things as working temperature, cooling rate, and even the size of the piece.
if you’re melting the metal completely, it’s quite true that there will be no “memory” of previous workings. If you merely heat and cool the metal, however, it can become impossible to work with after some number of cycles. So “melted too many times,” no. “Heated too many times,” yes.