Effect of rotary tube piercing process parameters on forming process of stainless bearing steel rings

Manufacturing high-performance 440 C stainless steel bearing rings is challenging due to coarse eutectic carbides arising from the alloy’s high carbon and chromium contents, which readily induce stress concentrations and cracking during rotary tube piercing (RTP). This study systematically investigates the RTP process for 440 C bearing rings through combined numerical simulation and experiments. Based on the necking behavior of 440 C stainless steel, and incorporating temperature- and strain-rate effects, a failure prediction model was established, achieving an average absolute relative error (AARE) of 3.0064%. Finite element simulation results indicate that increasing the distance between guide plates is beneficial for significantly improving the strain distribution uniformity of 440 C bearing rings. Increasing the plug advance effectively suppresses damage accumulation during the preparation stage; however, excessive plug advance (> 30 mm) intensifies strain localization during piercing. The failure level parameter exhibits a significant negative correlation with the distance between rolls, and helical cracks appear on the inner surface of the billet when the distance between rolls is less than 78 mm. Using a multi-objective optimization approach, the optimal process parameters were determined as follows: distance between rolls of 78 mm, distance between guide plates of 84 mm, and plug advance of 20 mm. Rolling tests confirm that these parameters produce 440 C bearing rings with a uniform microstructure and substantially mitigated carbide banding. Minor surface microcracks were observed only in the unsteady regions at the head and tail, which can be removed through subsequent processing. The proposed failure-modeling approach, based on conventional laboratory tests, shows promising engineering applicability. The optimized parameters provide critical theoretical guidance and technical support for the high-quality and high-efficiency manufacturing of 440 C stainless steel bearing rings.