The non-return valve is an essential component of an injection molding machine. In combination with locking and pressure ring it prevents the back-flowing of the mold via custom-fit locking in the injection and holding-pressure phases, while it opens in the plasticizing phase. In these processes the forces within the different components are extremely high –pressures of even more than 2400 bar may occur in the injection phase. Thus non-return valves are subject to highest stress – especially at the so-called wings. Therefore both hardness and ductility at the wing tips have to be especially high in order to obtain a satisfactory lifetime of the non-return valve.