The effects of micro-alloying and microstructure on fatigue strength were investigated for 600 - 800 MPa tensile strength grade sheet steels for automotive use. The addition of titanium in amounts up to 0.1 % increases the endurance limit, which is defined as the ratio of fatigue strength to tensile strength, by hardening of the ferrite with fine titanium precipitates. However, titanium addition of more than 0.15 % coarsens the precipitates and therefore does not significantly improve the endurance limit. Moreover, strengthening by the martensitic second phase also increases the endurance limit. These results showed that the endurance limit is mainly improved by precipitation hardening of the ferrite phase, with an additional effect of transformation hardening using the second phase. A new 0.1 % titanium-bearing high tensile strength sheet steel with a 5 % martensitic second phase, which was developed on the basis of these results, showed an endurance limit of 0.65, which is greater than the 0.55 of conventional high strength sheet steel.
Effects of micro-alloying and microstructure on fatigue strength of hot-rolled high strength sheet steel
Einfluß der Mikrolegierung und der Mikrostruktur auf die Dauerfestigkeit von warmgewalztem, hochfestem Stahlblech
1997
7 Seiten, 7 Bilder, 5 Quellen
Conference paper
English
British Library Conference Proceedings | 1997
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