Production and evaluation of cast-to-form forging dies in a special cast steel

Abstract

Cast-to-shape forging dies have been produced in a specially designed alloy employing a coarse dispersion of niobium carbide in a maraging steel matrix, the dispersion being developed in the melt. Effects ofcertain foundry conditions on the structure of the cast material are examined and the development of a technique for the casting ofa forging-die insert is described. The surface finish and quality of the castings were optimized by progressive refinement of the foundry technique, based on Shaw process investment moulding. The castings were assessed in respect of surface finish and the hardness and structural characteristics of the zone immediately beneath the critical surfaces. The surface region was shown to have an atypical microstructure offering no special advantage in terms of wear resistance. A pair of the cast inserts was fitted out and put into service for the manufacture of components in an industrial forge. The service life was found to be determined by eventual wear to an oversize condition after a long production run and not by premature failure. Characteristics of the cast dies are discussed in the overall economic and production context.