Advanced feasible forming condition for reducing ring spreads in radial–axial ring rolling

• The plastic penetrating condition is determined by plane strain indentation theory.
• The mathematical model for the RARR process is developed based on the CGVC.
• An advanced feasible forming condition is exposited based on the plastic penetration, gripping conditions, CGVC and mathematical model.
• Considering the effective strain, temperature distribution, and geometry of the rolled ring, the proposed condition is recommended for the design of the RARR process.

In this study, we derive an advanced feasible forming condition for reducing ring spreads and maintaining process stability during radial–axial ring rolling (RARR) process. First, the plastic penetrating condition was determined using the mean thickness-to-length ratio of the plastic zone. This calculation was based on the plane strain indentation theory considering Coulomb friction at the ring blank–mandrel interface. Second, a mathematical model for the RARR process was developed assuming constant volume of ring blanks and constant growth velocity condition (CGVC) of the ring outer diameter. Finally, the advanced feasible forming condition was determined from the mathematical correlations among the main roll, mandrel and axial roll sets, and reasonable range of extreme growth velocities. To verify the proposed condition, we carried out FE-simulations by developing reliable three-dimensional finite element (3D-FE) models using Forge, a commercial finite-element software package. The simulation results show that the designed process results in relatively uniform deformation behavior and reduces ring spreads. Predicted rolled ring spreads were compared with the experimental results. The ring growth velocity, which is a median value of its reasonable range determined using the advanced feasible forming condition, is recommended for the forming process design considering the reduced ring spreads and uniform plastic deformation.