Analysis of heat treatment strategies for a modern manufacturing process using coupled thermo-mechanical processes

Abstract

The combination of mechanical and thermal treatments alters the characteristics of materials in thermo-mechanical processes. These procedures are frequently used to modify the material's characteristics in accordance with engineering specifications. This thesis served the purpose of presenting different heating strategies to accomplish a near net shape material while also displaying the possibility of having a gradation in mechanical properties. In this study, a dive into the hot forging of single flanges with contact cooling was conducted. Furthermore, the complexity of the geometry was increased to form a double flange. The cooling strategies applied were done over two stages while changing one variable which was the contact cooling time of the dies with the flanges. The contact cooling times ranged from 28 seconds to 14 seconds, to finally, 4 seconds. For 28 and 14 seconds, a full martensitic structure transformation was obtained for the surface and along the core. However, for 4 seconds, the austenite could not be transformed into martensite and the structure of the flanges returned to the original ferritic pearlitic structure of the material. Furthermore, a gradation of volume fraction of martensite and bainite was obtained under 28- and 14-seconds contact cooling. The martensitic percentages were higher at the surface of the flange and diminished gradually towards its core. This gradation of microstructure is the key for gradation in material mechanical properties.