An Investigation of the Effect of Post Forging Cooling Rate on the Microstructure and Properties of Microalloyed Steels

Medium carbon steels have been traditionally used for high strength forging applications. These steels contain several alloying elements like chromium, nickel and molybdenum which enable them to attain excellent hardenability and toughness upon heat treatment (quenching and tempering). Microalloyed (MA) medium carbon forging steels are gaining acceptance as a replacement for the traditional quenched and tempered grades as they do not require post forging heat treatment and hence represent substantial savings in manufacturing costs. Since the chief advantage of MA steels lies in the savings of heat treatment costs, the post-forging cooling rate is one of the primary parameters for controlling microstructure and toughness of the forged part.

This paper investigates the effect of different cooling rates on the microstructure and mechanical properties of MA steels. Experiments were conducted by cooling test billets in different media. The billets were then examined microstructurally and physical testing was also performed. Regression correlations (empirical relationships) analyzing the effect of cooling rate on the microstructure and mechanical properties have also been presented.