Improvement in Mechanical Properties of Microalloyed Steel 30MSV6 by a Precipitation Hardening Process

The microstructural evolutions and mechanical properties of vanadium microalloyed steel (30MSV6) during precipitation hardening were studied. The effects of aging temperature and cooling rate on mechanical strength (yield strength and ultimate tensile strength) were similar. Increasing aging temperature or cooling rate firstly increased the mechanical strength of specimens up to their maximum values, which then decreased with further increase in aging temperature or cooling rate. Microstructural evolutions revealed that cooling rate had significant effects on the pearli-te interlamellar spacing and size of pre-eutectoid ferrite. Unlike the effect of austenitizing temperature, the pearlite interlamellar spacing and pre-eutectoid ferrite size were decreased by increasing the cooling rate from austenitizing temperature. According to the microstructural evolutions and mechanical properties, the optimal heat treatment process of microalloyed steel 30MSV6 was austenitizing at 950 °C for 1 h, air cooling (3. 8 °C/s) and aging at 600 °C for 1.5 h. This optimal heat treatment process resulted in a good combination of elongation and yield strength.