A new hot forging method for the die temperature higher than the billet temperature

In the traditional hot forging, the temperature of the billet is heated to the forming range, and the die does not need to be heated or only slightly preheated. In isothermal forging, the temperature of the die needs to be heated to the same as that of the billet and kept constant during forging. This paper proposes a new method, which is to control the die temperature to a certain extent higher than that of the billets during the hot forming process. The method was verified by the upsetting process. The finite element analysis and upsetting experiment were carried out, and the method result was compared with the ordinary upsetting method and isothermal upsetting method. It has been found that this method can significantly improve the bulging phenomenon during upsetting. The KD value was introduced to characterize the bulging degree of the forging. Increasing the die temperature has a significant inhibiting effect on the instability of large-size billets during upsetting. By this method, when the billet is heated to 380 °C and the die temperature is stabilized at 405 °C, the upsetting of 2024 aluminum alloy with an aspect ratio of 3.7 can be realized. This method has not been reported to our knowledge.