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

The present paper has attempted to briefly review the factors that inf luence the toughness properties of ferritic stainless steels. The stru cture and constitution of ferritic stainless steels were discussed tog ether with the effects of second phase particles on the toughness aspe cts. Generally the presence of second phases such as carbides, nitride s and oxides, as well as the chromium-rich ferrite, precipitates and s igma-phase, sigma, can cause a significant decrease in the toughness o f ferritic stainless steels. The influence of structural parameter or microstructural grain size on the toughness considerations, although w ell documented, are not always clearly understood. This is the result of other varying factors which can obscure the true effects of grain s ize. 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 precipitatio n of carbides, nitrides and sigma-phase. Finally, the detrimental effe cts of interstitial elements on the toughness of ferritic stainless st eels can be controlled by the addition of stabilising elements, e.g. t itanium and niobium.