I thought the specs for Corten were A242 and A588. It is basically a copper bearing plate for increased corrosion resistance. I seem to recall it has about 2 to 3 times the corrosion resistance of carbon steel plate like A36.
The thing about Corten is that it has to form an oxide on the surface to be effective. Which means it must go through a wet and dry cycle. If it is always wet it corrodes just like any other carbon steel.
Don't know anything about heat resistance. You need to define better your needs for thermal resistance.

The word "Corten" is a registered brand name of the U.S. Steel Corp. As R. Johnson says, its main purpose is to resist corrosion far better then straight carbon steel.
25 years ago, the piling for an elevated highway in downtown Rio de Janeiro was made nailing down Corten steel structural shapes directly into the earth, with no surface protection whatsoever. For those who know Rio, is the highway going from Praca XV to Benfica. Before doing that, they made a careful study and tests to estimate the degree of corrosion the steel was going to support. They concluded that, after eating up the first 3 millimeters of steel, corrosion was going to stop. 25 years have passed and the highway is still there and in use. If you still have any doubt on Corten steel, get in touch with U.S. Steel who knows it better than anybody.
Giovanni S. Crisi
Sao Paulo - Brazil