Modernization of roll calibration for the multipass radial shear rolling of cobalt-based alloy for medical applications

In the present work, we study the possibility of application of a special calibration of the working rolls containing calibration sections of limited length, in the process of radial shear rolling of alloys of the Co-Cr-Mo system and its influence on the parameters of the process and formation of the microstructure. The results of computer simulations demonstrate that the proposed calibration enables one to decrease the radial force applied to the roll by 12–25% and the drop of temperature in the deformation zone between the center and the surface by 5–7%. At the same time, we observe a decrease in the process cyclicity by 20% and the level of maximum compressive stresses increases by 10–15% as compared with the rolls of traditional configuration. The experimental testing of the proposed calibration revealed the stable process of rolling, and the bar obtained as a result did not have any external and internal defects. The analysis of microstructure revealed certain difference between the mean grain sizes at the front and rear ends of the bar, as well as in the central and subsurface areas caused by the different temperature and deformation conditions of rolling. The accumulated experimental data confirm the possibility of radial-shear rolling of high-strength alloys of the Co-Cr-Mo system with elongation ratio up to two even for a significant lowering of the surface temperature of the bar.