Effect of Heat Treatment on Anisotropy of Fatigue Strength of a Rolled Steel

Abstract

Rotating bending fatigue tests were carried out, using the plain and notched specimens cut out from a rolled steel in the rolling and thickness directions and heat-treated in order to obtain three kinds of hardness. The heat-treatment done before turning, did not change the shape and distribution of inclusions. The main results obtained are as follows: 1) The anisotropy of fatigue limit increases as the hardness of material increases. This phenomenon is explained from the fact that the notch radius at the branch point changes with the hardness of the material. 2) In a high-hardness material, the notch radius at the branch point is extremely small and hence the anisotropy of fatigue limit does not disappear unless the notch radius is made extremely small.