Ash, you are good to be skeptical, however wrought iron is pretty soft unless you work harden it. Even low carbon steel is pretty soft. If you go by your local Lowes, you can find bars of steel used in a variety of things that you can bend fairly easily. We have a different conception of materials today because our industrial capabilities (machines and tools to regulate a variety of conditions) churn out fairly hard materials as the de facto norm.
As to the steel content of a Roman weapon during the 1st century BCE, I cannot link you directly to anything, but I do recall in discussion mention of their knowledge of tempering, which requires a certain concentration of carbon to work.
Steel is just an iron alloy. You can make technically correct steel by using things other than carbon (and we do), but the term usually means an iron carbon alloy with less than one percent carbon (though you can get it up to 3%). Basically the ratio is a range as opposed to a set amount. If you alloy it with oxygen, you get rust. This is how it generally occurs in nature.
I would look up the steel making process, which I will not waste your time with here. Particularly look into bloomeries, which is how our ancestors in the iron age and middle ages refined iron into something useful.
High quality bronze weapons are not on par with the average quality of medieval weapons. Bronze does not temper and cannot flex well (or at all for the most part). Bronze weapons would be expensive due to the materials and time required to prepare a casting mold.
Keep in mind I am not an expert in this matter. I have spoken to individuals who are experts (and practical experts) in the field, however, and I have done my homework. Bronze is a great metal, but it loses to iron for a grand range of reasons. By the time the high middle ages comes into play, bronze is only being used for hilt components for swords, and have not been weapons for a long, long time.
M.