The effect of process treatment upon the fatigue strength of heavy carbon steel shafts

Abstract

1. The fatigue strength of type St 35 acid steel varies very little over the cross section of large shafts. 2. Virtually identical fatigue strengths were obtained on large St 35 shafts. surrounded by sleeves, after normalizing and annealing or after quench-hardening and annealing. 3. Increase in the diameter of the specimens from 12 to 160 mm reduced the endurance limit by 11% (from 12.9 to 11.5 kgf/mm2), regardless of the form of heat treatment of the St 35 steel. 4. Normalizing heavy forgings from St. 35, instead of thermal refining, is an effective process technique: the heat treatment cycle is shortened and there is no need for normally non-available, vertical, quench-hardening, ovens. 5. Surface work-hardening by cold plastic deformation is an effective method of increasing the fatigue strength of carbon steel shafts subjected to a press-fit, and is equally effective after normalizing or after thermal refining.