Improving the mechanical properties of 38MnVS6 microalloyed steel by thermomechanical processes

The present study focused on the replacement of commercial 41Cr4 (5140) tempered steel with a no heat-treatment demanding durable 38MnVS6 microalloyed steel for manufacturing tow hook used in automobiles. The forging processes of the hooks were performed in IZELTAS A.S. Company. The effect of forging temperature and cooling rate on metallurgical and mechanical porperties of 38MnVS6 microalloyed steel were investigated. However, the use of microalloyed steels are not common like conventional quenched and tempered steels because of being difficult to achive toughness. Thermomechanical processes such as warm forging followed by controlled cooling are the methods for improving toughness, while improving hardness and strength. The samples of 38MnVS6 were forged four different temperatures as 800°C – 850°C – 900°C – 1050°C followed by two different cooling rates as 0.75°C/s – 1.5°C/s. Forging and numerical simulations were carried out to verify the malleability and mechanical resistance of 38MnVS6 microalloyed steel. The γ→α transformation temperature was detected by DTA (differential thermal analysis). The microstructure was characterized by optical microscope, SEM (Scanning Electron Microscope) and EDS analysis. CCT (continuous cooling transformation) diagrams and the characterization of microstructure were calculated by JmatPro (Java-based Material Properties) computer simulations. The mechanical properties were obtained by Rockwell hardness measurement, tensile tests and charpy impact tests. The experimental and numerical studies showed that forging temperature and cooling rates had an significant effect on toughness.