Hot dip galvanising and galvannealing of P and Mn strengthened TiNb IF steels

Phosphorus, Mn, or Si solid solution strengthened sheet steels stabilised with Ti and Nb are known to have poor galvanising and galvannealing properties. When these steels are continuously annealed in higher dewpoint atmospheres, selective oxidation processes can occur in the subsurface region of the sheet. A laboratory simulated continuous galvannealing process was therefore used to study this effect in P and P+Mn solid solution strengthened sheet steels stabilised with Ti and Nb, by making a detailed analysis of the fundamental surface and interface processes that control the wetting of the surface by the liquid Zn, the inhibition layer formation, and the Fe-Zn reaction.