1988 年 37 巻 417 号 p. 637-642
Fatigue strength and fatigue crack growth behaviors were studied for two types of dual phase steels with duplex ferrite and martensite structure: One was an ordinary dual phase steel processed to replace pearlite by martensite and another was a fine grained one obtained with the method developed by N. Matsumura and M. Tokizane. Major attention was paid to the fatigue properties of the fine grained dual phase steel.
The results of this study revealed the fatigue characteristics as follows:
(1) The fatigue strength of the dual phase steel, especially that of the fine grained one was excellent.
(2) The crack propagation life to failure from the initiation of small crack with the length of 0.1mm was longer for the fine grained dual phase steel than the ordinary one, indicating that the former material has a higher resistance against the crack growth of short cracks.
(3) The crack growth rate of long cracks for both materials was higher than those of the conventional structural carbon and alloy steels in the relatively low stress intensity region.