HIP of feeder-less steel castings

Purpose and goal

In casting, feeders are used to compensate for solidification shrinkage and minimize pore formation. For steel castings this could make up to 90% extra weight. By eliminating feeders the yield and costs in the foundry could be reduced substantially, while defects increase markedly. Internal pores can be closed by a HIP treatment. The aim was to investigate whether the HIP can be used to seal the pores, obtained by casting without feeders, and if the additional cost for subsequent HIP can be offset by lower manufacturing costs.

Results and expected effects

The technical evaluation shows the formation of marked internal pores in feederless castings, but these can be sealed in a subsequent HIP treatment. For HIP to be effective, it is required that the inner pores are not in contact with the surface. This could not be avoided in these tests, but it could be solved by continued casting simulations and process optimization. Calculations gave comparable or lower cost for HIPped, feederless castings compared to conventionally produced. This provides opportunities for new market shares, provided that the technical difficulties are overcome.

Approach and implementation

Technical evaluation was done by casting simulation, design and casting of a stainless steel component without feeders and makes a HIP treatment of this. Characterization of defects and material properties was made before and after the HIP. Costs of materials and manufacturing with and without feeders were calculated as well as the cost for HIP. In parallel, an assessment of market potential and opportunities for expanding market for castings in competition with other manufacturing methods, such as forgings.