Thermophysical properties of iron oxide scales

[fruglk]

Hi!

I am modelling heat transfer through the oxide scales on the surface of steel but I cannot find the accurate properties of oxide scales. I need thermal conductivity, density and specific heat capacity. They shloud be dependent on temperature. I have found only one book in which are some formulas but in my opinion they are wrong. Look at them:

http://postimg.org/image/4ykwyvadn/

Anyway, they hold only for short range of temperatures and I need the numbers for the whole spectrum (from room temperature to 1100 °C).

Does anybody know about a literature where I could get the exact numbers? Or do you know the formulas?

 

[Bystander]

the oxide scales on the surface of steel but

That's such a hopelessly non-uniform system, and so hopelessly irreproducible that you'll not find data.

 

[SteamKing]

Hi!

I am modelling heat transfer through the oxide scales on the surface of steel but I cannot find the accurate properties of oxide scales. I need thermal conductivity, density and specific heat capacity. They shloud be dependent on temperature. I have found only one book in which are some formulas but in my opinion they are wrong. Look at them:

http://postimg.org/image/4ykwyvadn/

Anyway, they hold only for short range of temperatures and I need the numbers for the whole spectrum (from room temperature to 1100 °C).

Does anybody know about a literature where I could get the exact numbers? Or do you know the formulas?

It's not clear why these formulas are unsatisfactory. The specific heat capacity and the thermal conductivity are dependent on temperature, and these formulas cover about half the temperature range in which you're interested (500 to 600 celsius degrees, which is rather a lot, IMO).

If 500 celsius degrees is a "short" temperature range, then I guess you'll have to get some rusty steel and do some experiments.

 

[Astronuc]

Hi!

I am modelling heat transfer through the oxide scales on the surface of steel but I cannot find the accurate properties of oxide scales. I need thermal conductivity, density and specific heat capacity. They shloud be dependent on temperature. I have found only one book in which are some formulas but in my opinion they are wrong. Look at them:

http://postimg.org/image/4ykwyvadn/

Anyway, they hold only for short range of temperatures and I need the numbers for the whole spectrum (from room temperature to 1100 °C).

Does anybody know about a literature where I could get the exact numbers? Or do you know the formulas?

What kind of steel? Those numbers may be representative of a particular range of composition, but steel oxides can vary according to the steel composition and the fluid in which the steel is operating. For example, stainless steels will have oxides of iron, chromium and nickel, and minor elements like Si, Mn. Then there is the water or gas chemistry, and scales could include sulfates, carbonates, silicates, . . . . .

What are the steel and environment cited in reference 24?

 

[fruglk]

The authors in that book consider mild steel which is commonly used in continual casting. I was not able to find the exact description of that material. There were only some formulas for its properties and again reference to another article.

 

[Astronuc]

Mild (or plain-carbon) steel is approximately 99% Fe, so iron oxide or rust is primarily Fe₂O₃, with some Fe₃O₄, but the composition depends on moisture and pH. Fe₂O₃ and it's hydrated version tend to be orange/brown, while magnetite (Fe₃O₄) tends to be dark brown to black. If enough moisture is present, then iron oxides may proceed to iron hydroxides.

http://www.corrosion-doctors.org/Experiments/rust-chemistry.htm
http://www.corrosion-doctors.org/Experiments/iron-products.htm

Carbon steel grades - http://www.eaglesteel.com/download/techdocs/Carbon_Steel_Grades.pdf

At high temperatures, the water would evaporate, and hydroxides can decompose to oxides.

http://www.mpmtechnologies.com/PDF/Miniature%20Specimen%20Technology/Thermal%20Expansion%20and%20Conductivity%20of%20Magnetite%20Flakes%20Taken%20From%20the%20Oconee-2%20Steam%20Generator.pdf

See page 78 for heat capacity of magnetite - http://preserve.lehigh.edu/cgi/viewcontent.cgi?article=1002&context=cas-lehighreview-vol-15

Maybe some data here - http://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3434&context=etdWhat is the service environment for the steel? Most mild steel is used at ambient temperature. Using at higher temperature would invite corrosion.

 

[fruglk]

Thank you for the tips! I really appreciate it.

The thing is that my work is mainly about the simulations. To be honest, I do not have time and knowledge for dealing with the material issues. In the beginning I thought that I can just take any "general" oxide scale on some ordinary used mild steel. Well it is obviously not so easy. So I restricted it only to the continuous casting.

One of the input variables of my latest model is thermal conductivity of the scale. It is constant (not dependent on the temperature) and it varies from 0.2 to 1.4 W/m*K. Specific heat is also constant, I take only one value 883 J/kg*K. And the density I consider is 5200 kg/m^3.

It is not such a big deal I am not interested in the exact values. I am mainly interested in the relative importance of the input parameters of the simulations. I just needed the numbers that won't be completely unreal. So I was just looking for some source (which I can cite) with approximate values of the properties of scales. It would be also very convenient if there was written that these numbers are highly changeable and very hard to determine exactly.

 

[Astronuc]

Is this for cooling of continual cast strand?

Then it may be possible to find properties for mill scale, or hematite and magnetite.

For hematite thermal conductivity - see http://www.netsu.org/JSCTANetsuSokutei/pdfs/05/05-1-11.pdf

For magnetite, see - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/03/020/3020579.pdf