What Is the Emissivity of Carbon Steel for IR Thermometer Use?

[soonsoon88]

May i know what is the emissivity for carbon steel ?
Is it suitable for me if i using IR thermometer(with emissivity 0.95fixed) to measure cutting temperature ?

 

[middlj]

Approximately 0.3

 

[soonsoon88]

Approximately 0.3

Omg...Just 0.3 ? Then if i use 0.95 to measure it...the accuracy is very slow right ?

 

[Mech_Engineer]

OMEGA has a large table of emissivity values for common materials. You can start there, and maybe use a scaling factor to correct for the incorrect emissivity assumption of the thermometer. Problem is, emissivity varies strongly as a function of tempertuare, surface finish, oxidation, etc. Based on the fact that Omega's table shows Steel can vary anywhere from 0.07-0.91, I think you're going to need to measure you specific sample's properties experimentally, or get a solid temperature-dependent published table of values for your specific material and surface finish.

http://www.omega.com/literature/transactions/volume1/emissivitya.html

 

[soonsoon88]

OMEGA has a large table of emissivity values for common materials. You can start there, and maybe use a scaling factor to correct for the incorrect emissivity assumption of the thermometer. Problem is, emissivity varies strongly as a function of tempertuare, surface finish, oxidation, etc. Based on the fact that Omega's table shows Steel can vary anywhere from 0.07-0.91, I think you're going to need to measure you specific sample's properties experimentally, or get a solid temperature-dependent published table of values for your specific material and surface finish.

http://www.omega.com/literature/transactions/volume1/emissivitya.html

Thanks for it...
but may i know Carbon steel roll is belong to which categories ? carbon unoxidized ?

 

[Mech_Engineer]

No, it would belong in the Steel category, probably under either "Cold Rolled," "Mild Steel, Smooth," or "Steel, Unoxidized." Problem is, Cold Rolled has an e of .75-.85, while Steel, Unoxidized has an e or .08.

Depending on your application, you may have to make an engineering decision based on what would be considered "worst case." If you need to minimize heat transfer, use the higher e so you at least have more heat flowing than might be "real." If you're hoping to maximize heat transfer, use the lower e. Doing any better than that will require you experimentally measure the emissivity to at least see which ballpark you should be in.