I appreciate the spirit of your suggestion, and I agree that metallurgy could use a bit of an overhaul in DF after material properties are sorted out. However, I disagree with you.
I wish I had more time today, or I would write a better researched and well-written post. But, basically, soft iron (IF you mean wrought iron)
should be the dominant metal for arms and armor if we are wanting to emulate 14th c. European metallurgy. Either that or bronze if resource distribution is different... but that's another matter entirely. Swords were a bit of an exception, but a vast majority of metal armor and arms (like spear heads, maces, and stuff) were made of wrought iron, and only some of it was case hardened. VERY rarely was actual temper-able steel ever made during this time period, and even then it was likely by accident. I get this information from among other sources the first few chapters of a book called "The Knight and the Blast Furnace" which I wish I owned but was only able to take a glimpse of through some online-library that wanted me to pay to see the rest.
Wrought iron can be work-hardened which played to an advantage in armor, and case hardening, though I don't know if it was common in the 14th c. and earlier, was known and practiced in arms and armor. As for weapons (and I really need to do more research on this cuz I don't know for 100% certain), I know that at least before the 14th century, there are many examples (and I can't say how many or if this was the most common or what) of sword blades made with a wrought iron core with steel (which was rare!) basically forge welded to the core to form the blade. This steel was able to be tempered. There are also examples of blades made from wrought iron that had enough carbon introduced into them through forging that the outer areas could be tempered and retain a durable edge. Keep in mind that the iron in armor did not have generally have the same properties of the iron (and steely-iron) in the blades of swords since likely (I think) it was not economical to work them in the same way to introduce the steely properties.
Bronze is better than wrought iron for weapons and the like due to its hardness, but I believe it was surpassed in use by iron mainly due to iron's relative abundance (I could be wrong though...).
What I would suggest doing to make metallurgy more realistic and reflect the 14th c. time-frame (and I believe in this case realism would make for a better game) in DF would be to emulate the following:
1. Realistic relative abundances of iron and other metals
2. Variance of quality of ore (I can deal with this being abstracted out, I guess, but I think it should be implemented) from one vein or region to another: not all iron ores, even of the same type, are created equal!
3. Better simulation of the bloomery and blast furnace (if we allow Chinese contemporary tech here, which I think we should) processes in how smelters work: i.e. have temp of furnace be affected by use of mechanisms to pump more air in, what kind of smelter it is, other engineering concerns maybe, etc...
4. Better simulation of the forging process, especially if knowledge spread of techniques (like case hardening, carburization, decarburization, etc.) and technologies is ever implemented.
There are other things, probably, but I am running out of time. I'm pretty sure the stuff I'm saying has been suggested before in the suggestions forum, but check out these two posts out from the modding forum that have similar concerns about metallurgy in the game:
http://www.bay12forums.com/smf/index.php?topic=33340.0http://www.bay12forums.com/smf/index.php?topic=47914.msg1182154#msg1182154Their suggestions rock!