Iron is not as easily founded as copper – iron melts at a temperature 900 degrees hotter than copper. I quote from Daniel R. Headrick, Technology, A World History:
“The simple furnaces used at the time – pits dug in a hillside and lined with stones or clay – could not get hot enough to melt iron. What came out was a spongy mixture of iron and slag (or dirt) known as a bloom. To drive out the slag, blacksmiths had to heat and hammer the bloom repeatedly, a tedious process that required a great deal of time and charcoal. The result – wrought iron – was softer than bronze, cracked easily, did not hold an edge as well, and rusted rapidly. Yet iron had one tremendous advantage: its ores are found in large quantities in almost every country, often close to the surface, where they are easy to dig up.
“Gradually, by trial and error, blacksmiths improved their product. To prevent cracking, they learned to cool hot iron by dipping it in cold water. To make it less brittle, they tempered it by reheating the quenched iron several times. By repeatedly placing an iron object in direct contact with burning charcoal, they turned its surface into steel. By the fourth century BCE, blacksmiths were making iron swords with a steel cutting edge that was hard enough to cut through bronze.”
Note that we can posit from the above that although iron was being used extensively at the beginning of the classical age, bronze had not gone out of fashion in the seventh and sixth centuries BCE. The fifth century Spartan hoplites were still using bronze weapons and shields, as were the Romans and Etruscans during the period of the Roman kings (prior to 509 BCE).
But cheaper, quality iron would eventually replace bronze weapons. Virtually all the weapons in Alexander the Great’s army would be iron, as would the weapons of India when the two armies met in the Battle of Hydaspes in 326 BCE. Iron had been introduced in India about 1000 BCE; long prior to that, and prior to its discovery by the Hittites, iron had been used by the Chinese. Thus, by the end of the Classical world and the rise of Rome, it was an iron world.
For those DMs out there who are working on Mesopotamian or even Assyrian campaigns, iron should exist either as a cheap alternative to bronze, both inexpensive and inferior. On the other hand, a specific race that has properly learned to forge iron as it was forged in the fourth century might have a decided advantage over others.
Apart from things I talked about yesterday, hard iron weapons might effectively destroy weapons as they strike. The same might be said for mithril vs. iron swords, or even magical weapons against non-magical. Where is the table that demands a saving throw to be made by inferior grade metals against superior alternatives? Shouldn’t there be a chance that my iron sword will split my opponent’s wooden spear?
I’ve never come up with a simple, workable arrangement that allows this ... but it seems like something that should happen – not just once in a blue moon, but with frightening regularity. Suppose that with every to hit roll that results in a ‘19’ (as opposed to a natural 20), the opponent’s weapon must make save. Would it be worth it?
I think it would have to be judged in terms of comparative materials. A quarterstaff against a quarterstaff would not incur a saving throw ... nor would the quarterstaff cause the magic weapon to have to save. This would be a one-way process – and so the saving throw would have to reflect the difference between the two weapons ... it couldn’t simply be a flat save vs. crushing blow.
If my combats weren’t already as complicated as they are, I might consider this. If I had someone who could keep track of these things, I would definitely be working on such a table. But I don’t think it very important just now. I leave it to you, gentle reader, to work on it as you will.