Volume 2, Issue 5 (September 1974)
The Influence of Interstitial Content on the Ductile-Brittle Transition Temperature of Fe-25Cr Ferritic Stainless Steels
The low temperature ductility of several vacuummelted, 25 percent chromium, ferritic stainless steels containing between 300 and 900 ppm total interstitials (C + N + O) has been investigated in the water-quenched condition using impact and tensile tests. In the low interstitial content alloys, the ductile-brittle transition temperature was markedly influenced by changes in interstitial content and grain size, whereas for the high interstitial contents such changes were not as significant. Tensile tests on the same alloys indicated that the yield stress was not sensitive to variations in either interstitial content or grain size.
It is shown that increasing the interstitial content in these high chromium ferritic steels effects an increase in the amount of second phase present, particularly at the grain boundaries. Such particles enhance cleavage fracture by reducing the surface energy. It is observed that the second phase content is a single valued function of the ductile-brittle transition temperature.