CHAPTER 6

SPECIALIZED SAND CASTING

Thomas S. Piwonka

INTRODUCTION

Sand casting has historically been the most popular casting method, producing by far the greatest tonnage of castings used in any country. Today, however, with the widespread conversion of automotive components from ferrous metals to aluminum, sand casting's position as the dominant molding method is threatened. The process presently produces effluents that are considered to be toxic, it is sometimes difficult to control, and it lacks the dimensional accuracy that casting buyers often want. However, as it is usually the least expensive way of making a component, its inherent cost advantage over other methods continues to make it an attractive molding method. In fact, the innovations in sand casting over the last three decades (lost foam, V-process, and improved resin binders) indicate the resiliency of the process.

In the United States, the application of new sand casting processes has occurred at a steady rate. Comparatively new casting processes such as the V-process and the CLAS process are in production for a variety of products. In addition, the United States has a very strong research program in lost foam casting, sponsored by nearly 50 firms. Implementation of the findings from this project has been widespread in the industry, and lost foam foundries have been successful in applying the method to a variety of cast components. American foundries clearly lead Japanese and European foundries in lost foam technology and production.

American foundries have also actively implemented solidification modeling in designing gating and risering systems and in analyzing casting defects. This implementation includes many smaller foundries as well as large foundry organizations. The United States has active research programs, both privately and publicly funded, to extend the capabilities of models, including modeling of microstructure development, residual stress and casting distortion, interfacial heat transfer and gap formation, and surface reactions between cast metals and their molds. In addition, models of core injection and curing are actively being developed in the United States.

The U.S. foundry industry also actively supports university-based foundry research. Beginning with the Metalcasting Competitiveness Research Act of 1991 (PL101-425), foundries have matched Department of Energy federal dollars in a program specifically aimed at university/industry cooperative research efforts. These efforts on a variety of topics have been bolstered by funding from other agencies. Much of the funding requires establishment of consortia, an activity that often involves professional societies such as the American Foundrymen's Society, the Steel Founders Society of America, the Non-Ferrous Founders Society, and the North American Die Casting Association. Today these groups make up the Cast Metals Coalition, which coordinates industry research needs.

Many of the improvements in sand casting, such as the V-process, were originated in Japan or Europe, so it was of particular interest for this study to assess the current state of innovation in this field in Japan and Europe. In addition, the WTEC team wished to determine the status of solidification simulation and rapid prototyping in the Japanese and European foundry industries and to assess the role that university research plays in metalcasting innovation in Japan and Europe.


Published: March 1997; WTEC Hyper-Librarian