Iron Micro Structure

Welcome to your Iron Micro structure walk through...



First Step: Identify the Iron. It all starts with this little "slug"
Lets say that we are in a Laboratory and we happen upon a little piece of iron that looks like this...
How to identify?
-Normal circumstances would tell you what kind of iron it was with some sort of sample ID
EX 03222023222202 would tell us the sample was today at 1020PM and it is a ductile iron of the 2202 grade...which basically tells us the hardness range we are looking for.
However that is hardly enough...we must uncover more about this little slug.


Second Step: Hardness

If you are lucky your lab will have a camera used specifically for checking hardness.
Check for calibration...there should be a block around labeled with the correct measurement.



Intermediate Step:
POLISH that surface until it appears like a mirror and then give it an etch.







Step 4: Examine under the microscope

After a proper polish under 100X the surface should appear something like this....

The nodularity of the second photo is much better. So a good polish is key to a good sample.

Better polish...worse picture.

poor polish however nodules still present

Gray Iron

Grey Iron has a few major differences than ductile

First the chemistry
gray iron has more of the following elements
-manganese
-Sulfur (bonded with pyrite)
-Silicon
-Chrome

Grey Iron

...hmmm
Less Carbon
....and
a dash of titanium

Polished up it looks like this



In a foundry gray iron gets poured much faster than the ductile iron because it can be melted faster and it needs less additions before it gets poured into a cast



As you can clearly see there are no nodules present. The addition of magnesium right before the iron gets poured forces the iron to form into nodules. This makes the iron much stronger in tensile and hardness aspects.
Gray iron is much better for absorbing and redistributing heat...so it still has plenty of uses.

Silicate Part 2 - Sorosilicates

After the Neso and Ortho silicates come the Sorosilicates.

These are less in number than the first type of silicon mineral and their crystal structure is a bit more complex. Their structure is more like isolated clusters of double tetrahedra  that attach at the points where they can share an oxygen molecule.

Tanzinite (Ca₂Al₃(SiO₄)(Si₂O₇)O(OH)) is an example of a Sorosilicate. Not exceedingly interesting but these double tetrehedra are the next step in the silicate family. From here on out the structure gets more complicated quickly.