Solution and precipitation of carbide phase in medium-carbon steels

Abstract

1. Carbide phase is almost completely dissolved in austenitic vanadium steel at 1200°. 2. Alloying of vanadium steel with nickel or chromium accelerates the solution of vanadium carbides at 1000–1150° but has almost no effect on the temperature at which the solution of the carbide particles is fairly complete. 3. With isothermal holding of supercooled austenite in the range of subcritical temperatures there are two possible mechanisms of transformation: precipitation of vanadium carbide directly from supercooled austenite and, with longer holding times, formation of a ferrite-carbide structure. 4. Under conditions where dispersed vanadium carbide is precipitated, chromium and, especially, nickel increase the stability of supercooled austenite and nickel also lowers the temperature at which the stability of austenite is minimal. 5. Precipitation of vanadium carbide from supercooled austenite in the process of isothermal holding is accompanied by an increase in hardness, and the formation of a ferrite-carbide structure by a reduction of the hardness. 6. When vanadium steel is alloyed with chromium or nickel there is a change in the morphology of the precipitating carbides from stringers (interphase precipitation) to fibers.