Thermal Analisys Steady State, Thermal Diffusivity

how creo 7 works in thermal analisys in a steady state ? I mean as input for thermal load i've to consider Heat Flux (W/m^2). This means that load is time dependent. I use a load of 5000W/m^ 2 on a steel structure with 30mm thicknes and i get more than 170°c of temperature. Teoric calculation give me 21 °c after 20 seconds.

Does creo consider Fourier time to get Steady State: t= Thickness^2/(Thermal Diffusivity) ? and if it consider that how does it calculate that. Because in material specification ther is not thermal diffusivity value.

thanks for answering