A novel single-stage combined extrusion process for 22MnB5 HESH-T projectiles: Numerical assessment of efficiency and dynamic stability

The manufacturing of large-caliber projectile preforms in 22MnB5 steel imposes a critical trade-off between energy efficiency and dimensional precision. In this thermomechanical numerical study, a comparative analysis is conducted between two technological routes for the 105\,mm HESH-T (High Explosive Squash Head with Tracer) projectile shell body: an innovative single-stage combined extrusion process versus the conventional two-stage route (upsetting followed by backward extrusion). The constitutive modeling was based on a strain-compensated Arrhenius model, calibrated via plane strain compression tests between 800\,∘C and 1200\,∘C ( 100\,∘C intervals), under strain rates of 0.1, 1, and 10\,s⁻¹ , achieving a global accuracy of AARE = 4.91% in predicting plastic flow. In the dynamic stability analysis, it was revealed that, under ideal conditions, radial forces exhibit a stochastic nature and reduced magnitude. However, geometric perturbations induce severe directional polarization in the flow, resulting in critical lateral instability ( 1095\,kN ) in the single-stage route. In contrast, in the two-stage process, a “self-correction” mechanism was demonstrated, in which preliminary upsetting mitigates initial asymmetries and reduces radial forces by approximately three times ( 348\,kN ), restoring the stochastic regime in the extrusion stage. Quantitatively, the single-stage route proved to be energetically superior, with a 29% reduction in peak axial load ( 15.1\,MN vs. 21.2\,MN ), although both routes are sensitive to thermal gradients, which generate prohibitive lateral loads ( > 1.4\,MN ). It is concluded that the single-stage process is the ideal choice for regimes with rigorous raw material control and compact lines, while the segmented route is indispensable for ensuring tooling integrity and dimensional stability in scenarios of industrial variability.