Abstract
Phosphatability and surface characteristics of silicon-manganese dual-phase steels have been investigated using bright annealed steel sheets of various contents of silicon and manganese. Silicon remarkably reduces the phosphatability because adsorption of titanium colloid, acting as a nucleating agent (chemical activator) for the phosphate crystal formation, is reduced with an increase in the silicon content. The reduction in the titanium adsorption is due to surface carbon enrichment, which is facilitated by the silicon in steel, during annealing. On the other hand, manganese increases the titanium adsorption because of prevention of the carbon enrichment, resulting in a good phosphatability. Therefore, the phosphatability of dual-phase steel is primarily controlled by a balance of silicon and manganese contents.
