INFLUENCE OF VANADIUM AND NIOBIUM MICROSTRUCTURE ON THE AUSTENITE GRAIN-GROWTH AND MECHANICAL-PROPERTIES OF 20K CARBON BOILER STEEL

The influence of vanadium and niobium microalloying (in the range less than or equal to 0.002-0.10% V, less than or equal to 0.01-0.04% Nb) on the grain growth and mechanical properties of 20K carbon boiler ste el at room temperature (sigma(b), sigma(0.2), delta, psi, KCV) and hig h temperature (sigma(b)(450), sigma(0.2)(450), delta(450), psi(450), s igma(10,000)(450)) is considered. On the basis of thermodynamic calcul ations, the content of the carbonitride phase MeCXNa(1-x) at austeniti zation temperatures of 850-1200 degrees C is estimated. The separate i nfluence of the carbonitride-forming element (vanadium and/or niobium) dissolved in austenite and the quantity of carbonitride on the austen ite grain growth of boiler steel is estimated.