A New Axial Upsetting Process for Large Ingots with Large Ratio of Height to Diameter

Abstract

To remove casting porosity and obtain smaller crystal grains, many large forgings need ingots to be upset axially with large ratio of height to diameter (H/D) greater than 3. But the ingots with large H/D are prone to buckling during upsetting process, and have non-uniform internal stress and strain distribution, cracks at barreling and other defects. A new axial upsetting process was proposed to handle these problems. Firstly, the research described deformation inhomogeneity and cracking tendency, and analyzed the causes of defects in the flat anvil upsetting process. Secondly, three two-stage upsetting processes were tried to improve the uneven deformation in the flat anvil upsetting, which applied symmetrical spherical convex die, conical convex die and multi-line sweeping concave die respectively in the first stage, and used flat anvils in the second stage. The effect of the die surfaces on constraining those defects was analyzed. Finally, three three-stage upsetting processes were suggested to take advantages of different die surfaces to stabilize the process. It was observed that the upsetting had better result from using conical convex die and multi-line sweeping concave die in the first stage, conical convex die and flat anvil in the second stage, two flat anvils in the third stage. The new axial upsetting process could improve the quality of the large forgings with more uniform deformation and less barreling.