The Influence of Additional Ni and Cu in Steel on the Galvanizability and Galvannealing Rate of Si-Mn Bearing Steels

Abstract

High strength steels have been developed in order to improve fuel economy as well as to increase safety. The conventional Si-Mn bearing high strength steels have the drawback of poor galvanisability due to the presence of complex Si-Mn oxides on their surface. In order to improve the galvanisability of Si-Mn steels, the effect of the addition of Ni and Cu on the wettability and galvannealing kinetics has been investigated.
It was show that the addition of Ni and Cu improved wettability and increased the galvannealing rate. This improvement was due to the change of the sub-micron oxide morphology under a deoxidized Fe layer just before the galvanizing treatment (oxidized and deoxidized). In the case of C-Si-Mn steel a film of Si-Mn oxide was formed under a deoxidized Fe layer. The addition of Ni and Cu made Si-Mn oxide intermittently and internal oxide formed remarkably.