Sorry, my question was simply too long and complex to fit into the title. Basically my question is this. In the middle ages Iron was treated by repeatedly hearting it up and hammering it on the anvil. As far as I understand this, this would create a more dense material. So I asked myself, could you achieve the same effect (or an even better effect) by lowering my piece of iron into the deep sea, say down into the Marianna Trench. The pressure down tere is definitely way more then anything I could achieve on the anvil.