Deep sea changing properties of steel/iron?

[feyn]

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.

 

[DrDu]

The metallurgy of iron is quite complex and I don't know too much about it. But I think the main effect of hammering was not to densen the iron but to reduce the carbon content of the iron which makes it less brittle. Increasing the pressure alone would only increase the density reversibly, i.e., when you bring the iron back to the surface, its volume would be as before.

 

[feyn]

So you could not get the iron to create a different crystal structure, which would stay this way when coming back ?

 

[ZapperZ]

You are ignoring the "heating" part of the process. It isn't just to hammer it down. The heating part allows for the iron to be more malleable and affects the structure of the iron. Simply by imparting pressure will not be the same.

Zz.

 

[Astronuc]

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.

One is describing the process of hot forging, which can change the microstructure depending on temperature, carbon content, and alloying elements. It does not change the density of Fe or steel at room temperature. Generally, hot or cold working/forging/extrusion/. . . processes are isochoric (i.e., constant volume/density).

Under hydrostatic compression, which is the case when a solid object is surrounded by a high pressure fluid it will undergo a slight decrease in volume (or increase in density), but it would not retain the higher density on return to atmospheric pressure. For non-spherical geometries, there would potentially be some deformation depending on geometry and conditions.

See some examples of steel used in deep submersible vehicles here - http://fas.org/man/dod-101/sys/ship/dsv.htm

On 27 January 1960 the Trieste took two men to a depth of 35,800 ft ft (10,910 meters) -- the deepest spot in the ocean -- in the Mariana Trench near Guam. It took 5 hours to fall 7 miles, and when the explorers reached the bottom they stayed 20 minutes. No one has been able to come near that depth since then. At this depth, the pressure is over 8 tons per square inch. (~16 ksi, or 110 MPa)

A pressure of 110 MPa is not significant. Pressure like 10s of GPa would be significant.

One might be interested in Phase Transitions in Solids Under High Pressure
https://www.crcpress.com/Phase-Transitions-in-Solids-Under-High-Pressure/Blank-Estrin/9781466594258

Chapter 5 addresses iron and steels: Phase transformations in iron and its alloys at high pressure