Carbon steel vs Stainless steel at high temperatures - I'm confused...
Carbon steel vs Stainless steel at high temperatures - I'm confused...
(OP)
We make a nozzle that shoots oil into a furnace that is currently made of 1144 stressproof steel. The furnace that the nozzle assembly sits in is about 1500 degrees F. Carbon steel like this is not intended to be used at 1000+ degrees F (according to what I have read in the past)... normally I would think you would want to use stainless steel in these temps.
The carbon steel pieces seem to hold up though... some issues with threads siezing but other than that things seem to hold up...
I dont understand why the carbon steel holds up in those temps... is the recommendation on carbon steels being used in lower service temps more for structural purposes?
The only load on this part is the forces from the pressures of the fluid that is inside of about 50-60psi
can anyone help explain how this works? Thanks
The carbon steel pieces seem to hold up though... some issues with threads siezing but other than that things seem to hold up...
I dont understand why the carbon steel holds up in those temps... is the recommendation on carbon steels being used in lower service temps more for structural purposes?
The only load on this part is the forces from the pressures of the fluid that is inside of about 50-60psi
can anyone help explain how this works? Thanks





RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year
RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
We all believe that the temperature must be considerably lower than 1500 F because carbon steels will rapidly oxidize at that temperature. That is practically the austenitizing temperature for 1144.
RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
If it is the "air temp" of the furnace, then each further step outward away from the burner is cooler.
Temperature on a bare steel bar will drop 700 degrees in less than 4-6 inches in still air - how long is your injection tube, and where is it fastened to the furnace wall? Did you actually measure the whole tube with a IR thermometer?
More, you've got to realize that a "limit" of 1000 degrees for a class of steel doesn't mean that the steel is useless if it reached 1050, 1100, or even 1250 degrees. It will be less strong than rated, or may change crystal structure over time as the number of cycles add up, but it doesn't melt like a candy bar at 1001 degrees.
RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
RE: Carbon steel vs Stainless steel at high temperatures - I'm confused...
If this is in a place with little or no excess oxygen then heating to 1500F is no big deal.
Actually a lot of parts like this are made from various grades of 2.5%Cr, 5%Cr, 9%Cr, and 13%Cr alloys. These are not really stainless, but Cr is very powerful at helping resist high temp oxidation. So depending on conditions a little Cr may do everything that you need.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube