Research on Precision Die Forging Utilizing Divided Flow : Third report, Study on an optimum combination by 'two step method' proposed anew

A two step forging method is proposed anew here and an optimum combination of one step with the other is examined with intention of enlarging the possibility of applying the process utilizing a divided flow. In this method, a preliminary closed die forging step comes before the process which stands on the principie of the relief-axis or relief-hole. The working pressure required for the complete filling up of materials into die cavity decreases much more with an increase of the preliminary closed die forging pressure. But, the optimum combination is to be selected as the condition where the working pressure required for one step becomes equal to that for the other. The working pressure in this optimum combination is confirmed experimentally to become half of that in the conventional closed die forging in the case of utilizing the relief-axis principle and much lower in utilizing the relief-hole one. These results can be expected fairly well from the theoretical analysis.