Phosphorus-induced hot ductility enhancement of 1Cr–0.5Mo low alloy steel

The effect of phosphorus on the hot ductility of 1Cr–0.5Mo low alloy steel is investigated over a temperature range of 700–1050 °C using a Gleeble thermomechanical simulator. The steel samples undoped and doped with phosphorus are heated at 1300 °C for 3 min and then cooled at a rate of 5 K s−1 down to different test temperatures, followed by tensile deformation until fracture. The results show that the hot ductility of the steel, evaluated by the reduction in area, can be substantially enhanced by the addition of phosphorus, especially in the range 750–950 °C. Nanohardness measurements and microscopy indicate that, in the austenite–ferrite regions, the hot ductility improvement is mainly caused by the phosphorus-induced solid solution hardening of ferrite layers formed along austenite grain boundaries, and over 900 °C, by the phosphorus-promoted dynamic recrystallization of austenite.