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Three heats of 0.40% carbon microalloyed steel, containing either 0.03 % or 0.10% sulfur, and with and without a 0.09% vanadium addition, were subjected to metallographic analysis and mechanical property testing. Bars were heated to austenitizing temperatures, between 1000°C and 1300°C. Significant amounts of intragranular ferrite, which has been associated with improved toughness, formed only in specimens containing vanadium and high sulfur which were austenitized above 1100°C. The balance of the microstructure consisted of ferrite which formed at prior austenite grain boundaries and large amounts of pearlite. High densities of manganese sulfide particles in the steels with high sulfur content effectively retarded austenite grain growth. The formation of significant amounts of intragranular ferrite decreased mean free ferrite spacing, effectively refined the pearlite structure, and lowered the Charpy V-notch impact transition temperature.

In recent years, microalloying has been advocated as a means for producing direct cooled forging steels. Microalloyed steels benefit from vanadium and niobium additions, but the carbonitrides formed by these elements are not stable at high temperatures. Micro-additions of titanium, which form a fine dispersion of carbonitrides that are stable at high temperature, have been promoted as an approach fox maintaining a fine austenite grain size at high forging temperatures. In this work two microalloyed steels were examined, 1522MoV and 1522MoV with 0.011 titanium addition. The effect of the titanium additions on the grain size and high temperature flow strength were studied. The titanium addition has a significant effect on maintaining a small austenite grain size at temperatures up to 1300°C. High temperature stress-strain data indicate that titanium causes an increased flow strength at 1100°C and 1200°C especially at higher strain rates.