COLD STAMPING WITH SELF-REGULATING COUNTERPRESSURE USING LIQUID AISI 52100 STEEL PUNCHES FOR COIN MINTING

Abstract

In the context of mass production of products using cold deep-drawing processes, the challenge is to improve the durability of punches and ejectors, which can be addressed by replacing machining with cold extrusion in the manufacture of such tools.This work employs FEM modeling using an elastic-plastic metal model to determine the parameters for cold extrusion with self-regulating counterpressure of AISI 52100 steel punches for coin minting, and experiments were conducted to produce the punches. For two geometric shapes of punches, the simulation established maximum fluid counterpressure values of 200 and 300 MPa, which ensured the extrusion of punches with deformation rates of 40.8% and 50.6%, respectively. The relationship between the extrusion force and the displacement of the forming tool, the force required to eject the formed blanks from the containers, and the distribution of specific forces on the surfaces of the blank in contact with the tool have been determined. The shape and dimensions of the punches after extrusion, as well as the distributions of temperature and the components of stresses and strains in the deformed metal, were identified. The work hardening of the metal structure due to cold plastic deformation was analyzed based on the distribution of strain intensity. The greatest work hardening occurs at the transition from the cylindrical deforming surface of the punches to the conical support surface, which is necessary to increase the stability of the punches during stamping. Experimental studies were conducted and confirmed the results of the calculations. The results of the modeling and experiments on extrusion with counterpressure for AISI 52100 steel are novel. Extrusion with self-regulating counterpressure can be used in the manufacture of forming tools from low-ductility die and tool steels for metal forming processes.