SOME CONSIDERATIONS ON THE TOUGHNESS PROPERTIES OF FERRITIC STAINLESS-STEELS - A BRIEF REVIEW

The present paper has attempted to briefly review the factors that influence the toughness properties of ferritic stainless steels. The structure and constitution of ferritic stainless steels were discussed together with the effects of second phase particles on the toughness aspects. Generally the presence of second phases such as carbides, nitrides and oxides, as well as the chromium-rich ferrite, precipitates and sigma-phase, sigma, can cause a significant decrease in the toughness of ferritic stainless steels. The influence of structural parameter or microstructural grain size on the toughness considerations, although well documented, are not always clearly understood. This is the result of other varying factors which can obscure the true effects of grain size. Thermomechanical processes, such as cold working, hot working and controlled rolling, can significantly influence toughness properties as a direct result of their effects on grain size and the precipitation of carbides, nitrides and sigma-phase. Finally, the detrimental effects of interstitial elements on the toughness of ferritic stainless steels can be controlled by the addition of stabilising elements, e.g. titanium and niobium.