R. Hardin, Shouzu Ou, Kent Carlson, Liang Wang, and C. Beckermann
(sponsored through the Cast Metal Coalition, CMC, by DOE and numerous steel foundries within the Steel Founders' Society of America, SFSA)
The Steel Founders Society of America (SFSA) home page can be found here: SFSA
The University of Iowa, in collaboration with numerous foundries, is conducting a research project on yield improvement and defect reduction in steel casting. A survey among American steel foundries conducted in 1997 revealed that the present yield in the industry is only about 55%, implying that almost two tons of steel must be melted for every ton of casting produced. The additional metal is primarily present in so-called risers and used to prevent holes or voids from forming inside the casting due to shrinkage occuring when the liquid steel becomes solid. The survey indicated that a 10% increase in yield translates into an energy savings of 1.8 trillion BTUs per year for melting alone, which corresponds to a yearly cost savings of about $40 million. One emphasis in the project is to re-examine the engineering rules that have been used in the industry for more than 30 years to determine riser sizes and locations. Extensive three-dimensional computer casting simulations showed that the present rules are overly conservative and result in poor yields. New rules, which can increase yield by up to 20%, are currently being developed and made available to foundries. Another task in the project is to develop accurate methods that allow those foundries that are already using computer simulation to predict the exact casting soundness level and design risers without going through extensive casting trials in the foundry. Such simulations are especially important for complicated casting shapes where simple rules would not be applicable. More than five foundries are currently participating in casting experiments and case studies, which are needed to verify the new methods. Yet another project task is the development of novel yield improvement techniques promoting directional solidification through a variety of active heating/cooling schemes. It is envisioned that the techniques will allow certain castings to be produced with a yield that is at least 25% higher than the current level.
An image of a cast steel component analyzed in this project is here:
The new feeding and risering rules are described in the following report: Feeding and Risering Guidelines for Steel Castings, SFSA, 2001.