Dimensional effects in the warm calibration of a stainless steel cylinder

To reduce the yield stress in austenitic stainless steels, the forming temperature can be increased to 200 °C. In order to assess the effect of this change on component accuracy, a benchmark process of closed-die calibration of a cylinder was simulated using finite element method (FEM). A fully coupled thermal-stress analysis was carried out for the whole process cycle, including closed-die compression, punch retraction, workpiece ejection and cooling to room temperature. The findings of this simulation confirmed the influence of die deflection, secondary yielding and component springback on accuracy. Thermal effects also played an important role. In particular, a modest increase of the initial temperature can compensate for oversizing and barreling errors caused by die deflection and springback. The speed of the process is another variable which influences component accuracy by changing the time scale of thermal phenomena.