Residual stress relaxation during heating of bearing rings produced in two different manufacturing chains

Bearing rings produced in two different manufacturing chains have been investigated in terms of residual stress relaxation behavior during heating. Cold rolled rings present almost constant compressive residual stresses at the external periphery and completely affected cross sections. Machined rings show high tensile residual stress with periodic variations along the outer periphery caused by clamping during machining. Residual stress states then are confined in a very thin layer. With increasing temperature residual stresses relax. Machined rings present a progressive loss of the residual stress periodicity with increasing temperature. The cold rolled rings show a different relaxation behavior between surface and core. Complementary investigations revealed that recrystallization occurs at a higher temperature in the core compared to the surface. The surface of cold rolled rings and machined rings present a similar behavior: recovery processes induce a decrease of residual stresses at temperatures up to 500 °C and recrystallization starts above 500 °C which causes a complete residual stress relaxation. In the core of cold rolled rings, recovery processes are still active until 600 °C where recrystallization begins. However, residual stresses in the core are already completely relaxed at 600 °C.