Volume 18, Issue 4 (July 1990)
Fatigue Behavior of a Cold-Rolled SAE Grade 945X HSLA Steel
A SAE Grade 945X HSLA steel was cold rolled to 30% and 61% thickness reductions. Monotonic tensile tests, smooth and notched specimen fatigue tests, and crack propagation tests were performed. The effect of loading direction was examined. As a general rule, cold rolling increased strength and decreased ductility. The strength was higher and the ductility was lower in the direction transverse to the rolling direction than in the longitudinal or rolling direction. The increase in smooth specimen fatigue strength was not as great as the increase in monotonic strength due to significant cyclic softening of the cold rolled metals. The notched fatigue strength was only slightly increased by cold rolling, since two opposing factors (the smooth specimen fatigue strength and notch sensitivity) were increased by cold rolling. The crack propagation rate and the threshold stress intensity were not significantly affected by cold rolling. All strength parameters of the SAE 945X HSLA steel, both hot rolled and cold rolled, were higher than those of a SAE 1010 plain carbon steel previously investigated.