The invention relates to a high strength hot-dip galvanized and galvannealed steel sheets with excellent drawability for press forming and excellent plating adhesion that is useful as a member for automobiles, construction, electric devices and the like, and to a process for its manufacture. According to an embodiment of the invention, the steel sheet contains in terms of weight percent, C: 0.05-0.2%, Si: 0.2-2.0%, Mn: 0.2-2.5%, Al: 0.01-1.5%, Ni: 0.2-5.0%, P: <0.03% and S: <0.02%, the relationship between Si and Al being such that 0.4(%).ltoreq.Si+0.8 Al(%).ltoreq.2.0% and the remainder consisting of Fe and unavoidable impurities, the volume percentage of the retained austenite is 2-20% and the steel sheet surface wherein the relationship between the Ni and Si, Al in 0.5 .mu.m of the steel sheet surface layer is such that Ni(%).ltoreq.1/4 Si+1/3Al(%), has a Zn plating layer comprising Al: .ltoreq.1% with the remainder Zn and unavoidable impurities.

L'invention concerne un de haute résistance chaud-plongent galvanisé et galvannealed des tôles d'acier avec l'excellent drawability pour la formation de pression et l'excellente adhérence d'électrodéposition qui est utile en tant que membre pour les automobiles, la construction, les dispositifs électriques et les semblables, et à un processus pour sa fabrication. S'accordant à un mode de réalisation de l'invention, la tôle d'acier contient en termes des pour cent de poids, C : 0.05-0.2%, silicium : 0.2-2.0%, manganèse : 0.2-2.5%, Al : 0.01-1.5%, Ni : 0.2-5.0%, P :