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 degrees C, 550 degrees C, and 650 degrees C) and cooling rates (0.23, 36, and 50 degrees 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 degrees C and 550 degrees C was negligible. By the contrast, impact energy for the samples tempered at 650 degrees C was markedly affected by cooling rate, in which the highest value was achieved for a cooling rate of 50 degrees C/s.