Physical modeling of the blocking process in open-die press forging

The purpose of blocking (reducing the ingot cross section) in open-die press forging is to maximize the internal deformation for better structural homogeneity and soundness of material in the core of the ingot. Forgings of high quality can be produced by specific control of the blocking parameters, e.g. die width, die configuration, die overlapping, die staggering, ingot shape, temperature gradient, draft design, pass design, etc. Physical modeling experiments, using plasticine as an easy-to-deform model material, have been conducted to study the effects of these blocking parameters on the deformation distribution in the forged ingots subjected to multiple-stroke blocking. To facilitate the multiple-stroke blocking study, new techniques had to be developed for better bonding between the layers of the plasticine specimens as well as for measuring the deformation strains in three dimensions from a single specimen. The evaluation of results shows substantial improvement in the internal-deformation distribution when the above-mentioned blocking parameters are optimized. This research work has resulted in providing better basic understanding of blocking parameters on centerline consolidation and product quality. Application of the laboratory modeling results to production forgings is reviewed also.