Experimental study of hot forming process by direct resistance heating

In order to increase heating efficiency and decrease heating time, a new hot-forging method by means of direct resistance heating was investigated in this paper. Based on the approach, the hot upsetting experiments with cylindrical billet of 42CrMo4 were performed. Moreover, the influence of the multi-layer aluminium foils inserted between the billet and the die as a forming condition on heating and forming was researched. The results of the experiments show that prior to forming the billet could be heated quickly to forming temperature in about 10 seconds. During the upsetting process the billet cooling rate was effectively decreased and the forming time was extended in relation to the resistance heating. The insertion of multi-layer aluminium foils not only improved the efficiency of the heating, but also avoided the plastic deformation of the die and the occurrence of cracks on the billet's surface.