The effect of heat treatment on the mechanical properties of a low carbon steel (0.1%) for offshore structural application

In this study, a low carbon cast steel (0.1% C) alloy designed for offshore structures, and the mechanical properties of the alloy under different heat treatment cycles have been evaluated. The effect of austenitizing time on the austenite grain size was studied. Subsequently, the quenched samples with minimum austenite grain size subjected to tempering experiments at different tempering temperatures (450 C, 550 C, and 650 C) and cooling rates (0.23, 36, and 50 C/s) from the temperature. The results showed that by increasing the austenitizing time, the austenite grain size initially decreased and reached the minimum value with ASTM number of 6.35 and then followed by an increase. When the tempering temperature increased, yield and tensile strengths decreased, whereas the ductility properties improved. In addition, yield and tensile strengths were not affected by cooling rate from tempering temperature, whereas the ductility properties were slightly affected. The increase in tempering temperature significantly led to improvement in the toughness to fracture of the alloy. The effect of cooling rate on impact energy for the samples tempered at 450 C and 550 C was negligible. By the contrast, impact energy for the samples tempered at 650 C was markedly affected by cooling rate, in which the highest value was achieved for a cooling rate of 50 C/s. © IMechE 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav