Residual stresses evolution and process route optimization of TC4 profiled rolled rings incorporating thermal bulging

The thermal processing of rolled rings inevitably generates and accumulates massive residual stresses, as quenching residual stresses produced by water cooling treatment. Non-uniformly distributed residual stresses would seriously affect the structural strength, dimensional stability and service life of the component. In the traditional rolling process of titanium alloy rings, the quenching residual compressive stresses introduced by solution treatment could reach – 400–600 MPa, for which effective control of the stresses is an urgent issue to be solved. In this research, the stress control efficiency of rolling rings under different process routes was explored according to the thermal bulge stress relief technique. The FEM model of the stress evolution in the whole process of the rolled ring was established. The residual stresses on the ring surface are characterized by the hole-drilling method, while the microstructures are characterized by electron backscatter diffraction. The results indicated that the optimized process incorporating the thermal bulging stress relief technique reduced the levels of stress values to within about ± 50 MP and the stress homogenization index by approximately 60–90%.