Impact properties of microalloyed steel

Impact properties of two grades of microalloyed steel (R-theta > 500 MPa), work hardened by static and dynamic uniaxial tension are presented. Properties are analysed by impact testing at very high impact loading rate (v=785 m s(-1)) and by fatigue testing at ultrasonic, very high frequency (20 kHz). Results showed that the tested mechanical properties of work hardened steel are not influenced by prime work hardening strain rate changes in the range from 10(-3) to 10(2) s(-1). At high-speed impact the steel showed good plastic properties and high resistance to perforation for the given strength. In fatigue the tested steel showed high resistance to fracture and was not significantly sensitive to the growth of loading frequency in the decreasing part of the Wohler Curve. The tested microalloyed steel is recommended for structures stressed by both static and dynamic loading.