Radiometric analysis of haze in bright-annealed AISI 430 ferritic stainless steel

The influence of both topography and optical constants on the optical reflection of bright-annealed AISI 430 ferritic stainless steel has been analyzed to correlate these characteristics with the occurrence of the unwanted haze effect in industrial products. This work reports the analysis of the total-integrated-scattering spectra of bright-annealed AISI 430 ferritic steel plates, on the basis of the microfacet model for the bidirectional reflectance function developed by He and Torrance [Siggraph '91, Proc. of the 18th Annual Conference on Computer Graphics and Interactive Techniques, (1991), p. 175]. Such an approach allows for modeling the optical reflection of these stainless-steel industrial products based on roughness parameters, root-mean square height, and autocorrelation length, derived from scale-limited topographic maps. The functional choice of the cutoff wavelength in the high-pass Gaussian filtering of the topographic map is proven critical. Additionally, optical constants n and k of the steels are estimated based on their total reflection spectra, measured in an 8°/di optical geometry. The results suggest that the haze effect could be due to a non-controlled increase in the thickness of the passive layer during the bright-annealing process.