Monitoring the microstructural evolution in hot forging with closed matrix by physical and numerical simulation

• Grant number: 06/03346-1
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: November 01, 2006
• End date: October 31, 2009
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Transformation Metallurgy
• Principal Investigator: Sergio Tonini Button
• Grantee: Wiliam Regone
• Host Institution: Faculdade de Engenharia Mecânica (FEM). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Many automotive components are hot forged with microalloyed steels in closed dies. To improve the productivity of hot forging cross wedge rolling is used to form the initial blanks. Hot forging is influenced by many process variables like material chemical composition, geometry of the forged part, heat transfer between dies and workpiece, forging loads and pressures. The microstructural evolution of the forged material is defined by several metallurgical phenomena such as phase transition, precipitation, recovery, recrystallization and grain growth. The phase transition consists on transforming austenite to ferrite, perlite, bainite or martensite. When precipitation is observed an increase of the material strength is obtained. Static and dynamic recovery and recrystallization restore and control the microstruture during and between the forming steps, and as result, the mechanical properties are also controlled. Therefore an important improvement of the forging process can be achieved if the process variables are properly chosen to define an adequate microstructure. The main objective of this project is to define a sequence of steps to hot forge a V-Ti microalloyed steel with cross wedge rolled performs. These performs will be deformed in a hydraulic press to simulate hot forging with closed dies, and finally to analyze the microstructure with optical and electronic microscopy. The objective is to improve mechanical properties (hardness, tensile and fracture strength), as well as to control the microstrutural evolution in the austenitic region, in the transition phase region and in the products of the austenite decomposition after deformation. These results will be compared to maps of strain and temperature from the numerical analysis with the commercial software MSC.SuperForge. Thus, with microstrutural results and numerical maps it will be possible to define the metallurgical phenomena present in each region of the forgings.