Influência da rota de laminação a quente e a morno nas propriedades mecânicas, textura e conformabilidade após laminação a frio e recozimento de um aço IF-Ti

Abstract

Interstitial Free (IF) steels possess ideal mechanical properties for applications that require high formability, which are achieved through appropriate thermomechanical parameters that promote a high anisotropy coefficient. Traditionally, hot rolling of these steels is carried out at high temperatures to avoid variations caused by processing within the two-phase field. However, due to the high transformation temperatures, rolling in the ferritic phase, known as warm rolling, can also be applied to the production of IF steels. This study aimed to perform a comparative analysis of the microstructure, texture, mechanical properties, and formability of two industrially produced IF-Ti steel coils: one manufactured by conventional hot rolling and the other by warm rolling. The results showed that the warm-rolled coil exhibited greater microstructural variations after hot rolling and annealing. This instability was also observed in the texture, with larger variations through the thickness sheet for the warm-rolled coil. Therefore, a more heterogeneous gamma fiber was formed in this material, even after cold rolling and annealing. The more uniform texture obtained in the hot rolled coil was crucial for the better forming performance of the material. Both processing routes produced sheets with good formability; however, the sheet obtained from the hot-rolled coil showed a higher normal anisotropy coefficient, resulting from the more uniform texture, and superior performance in hole expansion tests and forming limit curves. On the other hand, the Limiting Drawing Ratio and Erichsen stretch tests did not show significant differences between the two conditions. Therefore, to achieve high levels of formability through warm rolling, it is necessary to review the processing temperatures and lubrication conditions in the hot rolling process to promote a more homogeneous texture in the warm-rolled coil.