Electrically-assisted manufacturing for reduction in forging forces of bearing steels

The aerospace industry regularly uses three high-strength steel alloys in the manufacture of their bearings: M50, M50 NiL, and Pyrowear P675. The high strength of these alloys causes increased force, friction, and temperature rise during forging operations, resulting in residual stresses and creating issues with distortion and springback in subsequent machining operations. Electrically-assisted manufacturing (EAM) has been studied for reduction or elimination of these issues in magnesium, aluminum, and titanium alloys as well as A2 tool steel and 304 stainless steel. This research determined the threshold current densities for EAM of Pyrowear P675, M50, and M50 NiL steels. Threshold current densities were determined for each material at 33, 48, and 37 A/mm² respectively. Once the test reached this threshold a significant reduction in yield stress occurred and the samples had an increase in hardness near the exterior, the authors assess the probability of a phase change due to resistive heating during this forming operation.