Comportamiento mecánico de aceros galvanizados por inmersión recocidos (Galvanneal), influencia del “skin–pass”.

I. VILCHEZ; L. VILLANUEVA; P.R. SERÉ; J.D. CULCASI

Valparaiso

Congreso; 12° CONGRESO BINACIONAL CONAMET/SAM 2012; 2012

Departamento de Ingeniería Metalúrgica y Materiales de la Universidad Técnica Federico Santa María

In the automotive industry, galvannealed steel sheets are gaining more and more markets, due to its low cost and excellent weldability conditions. The galvanneal process consists in applying an annealing heat treatment, after the process of hot-dip galvanized, during which Fe-Zn phases are formed by diffusion. The mechanical properties of the system steel/coating depend, besides the type of steel, of the heat treatment performed. The skin-pass, performed after the thermal treatment, aims to eliminate the discontinuous yielding of the steel and give it the desired surface roughness. In this work we studied the influence of heat treatment on the microstructure of the coatings and the mechanical behavior of the undeformed plate and with different degrees of skin-pass deformation. As reference was used a galvanized hot dip non-heat treated. Two different heat treatments were used (15 min at 450 °C and 30 min at 475 °C). The percentages of deformation applied in the skin pass ranged from 0.8 to 3.8%. The microstructures of the coatings obtained with both thermal treatments were  or 1 phase at the interface and  phase in the center and surface coating. The heat treatment produced a reduction of yield stress, tensile strength and Lankford coefficient, and increased the ductility and strain hardening coefficient. The results of tensile tests allow us to infer that the best formability properties for this steel are achieved by close to 1.5% deformation in skin-pass.