View Full Version : Steelmaking, semi-OT

02-09-2005, 11:58 AM
Maybe someone out there can put my mind to rest. Ever since I learned how steel is made, something has puzzled me.

The excess carbon is burned out either by blowing air or oxygen through molten iron. So here's the question: What keeps the iron from being burned up, too? After all, the oxy-acetylene cutting torch works by blasting oxygen at red-hot iron/steel.

I don't understand why carbon is selectively burned out instead of the iron during the steelmaking process.


So many projects. So little time.

02-09-2005, 12:11 PM
(I'm speculating here.)
It probably would if they continued to blow the O2 thru it, but they probably stop the air/O2 flow at the point the carbon is burned out.
I've read that when they do it, there's a big flare up, corresponding to the carbon burnout, which then dies down abruptly. I'd assume they shut off the air flow at that time.

It's a good question, and maybe someone who knows can give an authoritative answer.

02-09-2005, 12:18 PM
I think (although I am absolutely not an authority) that the answer is, more or less as lynnl says. Carbon is more reactive than iron (that is it has more of an affinity for oxygen) so the carbon "burns off" first. It's just a matter of knowing when to stop.

Again-that's more of a guess, but a semi-informed one, courtesy of the chemistry textbooks sitting in front of me.


02-09-2005, 12:27 PM
It's called a redox reaction. The oxygen reacts with the carbon to form 3CO and with the iron at the same time to form FE2O3. This combines via reduction and oxidation at the same time (hence redox). The FE2O3 reduces to FE2 while the 3CO oxidizes to 3CO2 which escapes as gas.