Microstructural Evolution of Two Automotive Steels Induced by Warm Forging and Subcritical Annealing

Hormaza W.; Oliveira C.A.S.; Castro Güiza G.M.; Méndez Moreno L.M. · Iron and Steel Technology (2020)

Resumen

In recent decades, environmental and safety regulations have encouraged the production of stronger and lighter steels. For this reason, this paper explores the associative action of grain refinement and carbide precipitation induced by warm forging and subcritical annealing in two automotive steels: C-Mn and high-strength, low-alloy (HSLA). To do so, several samples were warm forged at 550°C, quenched in water, and subcritically annealed between 1 and 10 minutes. Then, the microstructure and hardness of both steels were assessed in each processing stage through optical microscopy, scanning electron microscopy, transmission electron microscopy and Vickers hardness. These tests showed that the thermomechanical treatment significantly refined the grain size in both steels by means of controlled ferrite recrystallization. Furthermore, the recovery process in the HSLA was slowed by the precipitation of fine carbides in the grain boundaries. Finally, the thermomechanical treatment improved the hardness of both steels.

Instituciones: Universidad de Ingeniería y Tecnología