ZDP-189: not a 'steel'?

[briannife]

Ceramics can be amorphous or crystalline. Actually even metals can be amorphous = metallic glass.

The difference between cast iron and steel is microstructure & property based. The 2-3% carbon content is a general rule. However, depending on the alloying elements you can still get a cast iron structure below 2-3%. ZDP has a high carbon content but I would still consider it to be a steel due to it's structure. The high carbon content is attainable due to more modern powder metallurgy techniques...

If you look at the iron-carbon phase diagram the max solubility of carbon in iron is ~2% in the austenite phase. You can think of this like the max amount of salt you can dissolve in water. The amount of carbon and the cooling rate will determine the microstructure and properties of the alloy. The additions of other elements (even in small quanities) can change the microstructure / properties significantly.

 

[elkins45]

Ceramics can be amorphous or crystalline. Actually even metals can be amorphous = metallic glass.

The difference between cast iron and steel is microstructure & property based. The 2-3% carbon content is a general rule. However, depending on the alloying elements you can still get a cast iron structure below 2-3%. ZDP has a high carbon content but I would still consider it to be a steel due to it's structure. The high carbon content is attainable due to more modern powder metallurgy techniques...

If you look at the iron-carbon phase diagram the max solubility of carbon in iron is ~2% in the austenite phase. You can think of this like the max amount of salt you can dissolve in water. The amount of carbon and the cooling rate will determine the microstructure and properties of the alloy. The additions of other elements (even in small quanities) can change the microstructure / properties significantly.

Wow, that sounds way smarter than what I said! I wasn't sure if ceramics had to be amorphous.

I didn't know metals could be amorphous--I always assumed even rapidly cooled ones would have time to construct a crystal structure before they solidified, just one with very small grains. Where (how) do metallic glasses occur?

I did some reading about how particulate metal alloys are created. It's a very interesting process, but I wonder if there isn't at least a small possibility of lowering the overall tensile strength of the alloy due to partial fusion of all of those tiny particles. After all, if you get it hot enough to completely fuse then aren't you also getting it hot enough for the carbon to migrate out of solution? If not there are probably razor thin tolerances for heating/pressure when they squeeze it all together.

 

[antonio_luiz]

Steel is defined as having a range of carbon content. Both H1 and ZDP fall outside of that range. Obviously a more modern definition is needed.

sal

And I thought it was just cause no one reined in the marketing section - well that's the first thing I've learned today - maybe we should call them Glesser steels :thumbup:

Merry Xmas all

 

[yoda4561]

Wow, that sounds way smarter than what I said! I wasn't sure if ceramics had to be amorphous.

I didn't know metals could be amorphous--I always assumed even rapidly cooled ones would have time to construct a crystal structure before they solidified, just one with very small grains. Where (how) do metallic glasses occur?

I did some reading about how particulate metal alloys are created. It's a very interesting process, but I wonder if there isn't at least a small possibility of lowering the overall tensile strength of the alloy due to partial fusion of all of those tiny particles. After all, if you get it hot enough to completely fuse then aren't you also getting it hot enough for the carbon to migrate out of solution? If not there are probably razor thin tolerances for heating/pressure when they squeeze it all together.

I believe pure metallic iron is amorphous, lead as well?

 

[briannife]

If cooled fast enough any metal can be amorphous.Essentialy, if cooled fast enough, the atoms do not have enough time to assemble into a long range ordered crystal structure. For most metals, however, required cooling rate is soooooo fast it is only possible with very small amounts. Some combinations of metals can form into metalic glasses at slower cooling rates. The most famous one is a zirconium based metalic glass invented by some guy at cal tech. There are some different theores to explain why this happens with certain combinations of metals....