Effects of Cold‐Rolling Reduction on Microstructure, Thickness, Surface Roughness of AS20/20 and on Bending Toughness of AS20/20‐Coated Press‐Hardened Steel

Abstract

The tailor‐rolling blanks based on Al–Si‐coated press‐hardened steel (PHS) have attracted much attention along with the development of lightweight vehicles. The properties of Al–Si‐coated PHS with single surface weight of 20 g m−2 change after cold‐rolling and then austenitization, which are little studied. Herein, the effects of cold‐rolling reduction ratio on the microstructure, thickness, and roughness of AS20/20 coatings, and on the bending toughness of AS20/20‐coated PHS, are explored. The overall continuity of the coatings is unchanged as the reduction ratio increases. When the reduction ratio is 30% or above, rapid diffusion channels are formed at the cracks of Al‐filled intermetallic compound layer. Meanwhile, the thickness and surface roughness of the coatings are stable and do not decrease. After austenitization, the coatings are structurally consistent with the increase of the reduction ratio. When the reduction ratio is 30% and above, the thickness and surface roughness of the coatings are stable and do not decrease. The rapid diffusion channels lead to an increment in the proportion of FeAl phase to above 96% after austenitization, which makes the bending angle further increase. The bending angle is enlarged by 44% when the reduction ratio is 50%.