Boron added steels in quenched and tempered condition have been widely used in applications where good mechanical properties and low cost are required. In this study, impact resistance of DIN 39MnCrB6-2 steel grade was investigated due to its criticality in automotive components. Metastable phase diagrams were built to guide heat treatments. The influence heat treatment parameters and initial microstructure were evaluated. Impact toughness results showed low absorbed energy (<30J) for all tempering temperatures. CVN impact toughness was substantially increased in samples submitted to solution treatment. Microscopic observation showed coarse borocarbides in surface fracture of Q&T samples. It was concluded that the formation of borocarbides is inherent in boron steels and their coarse morphology should be avoided in order to reduce embrittlement.
Keywords:
boron steel; hardenability; borocarbide; Fe23 (B, C)6
