Yield Improvement in Steel Casting

Grant# 06-01
Principal Investigator: Christoph Beckermann
Organization: The University of Iowa
Technical Area: Energy Efficiency

Abstract
The steel casting industry in the U.S. consumes approximately 50 trillion BTU of energy per year. This project will develop new technologies for reducing that energy usage. The technologies are aimed at increasing casting yield (currently 50%) and reducing the occurrence and severity of casting defects. They are expected to increase overall casting yield by 3% (averaged over all castings; up to 35% on individual castings), and reduce rework and scrapping by at least 25%. The resulting yearly energy savings for the steel casting industry in the U.S. can be estimated to be at least 1.5 trillion BTU. Significant additional benefits for steel foundries arise from improved quality, reduced costs, and increased capacity.

The objective of the project is to develop novel computer simulation capabilities and unconventional casting techniques for use by steel foundries. Models will be implemented in widely used casting simulation software to predict reoxidation macro-inclusion and hot tearing defects. Such predictions allow for the design of improved casting processes that eliminate these defects and increase yield. The models will be validated by performing casting trials in the participating steel foundries and applied to production castings in the case studies. A riser pressurization method will be developed that increases yield by reducing the occurrence of porosity defects. The pressurization technique will be optimized and deployed for production parts in the foundries. Transfer of the project results to the steel foundry industry will be achieved by collaboration with the Steel Founders Society of America (SFSA) as well as with a casting simulation software company. This joint project between the University of Iowa and two Iowa steel foundries will result in direct implementation and demonstration of the technologies in a production setting.

Project Objectives:

The objectives for the entire three-year project are:

1. Develop a technique for computer simulation of reoxidation inclusion formation in steel casting, and develop new pouring methods to reduce or eliminate macro-inclusion defects and increase yield.

2. Develop a technique for computer simulation of hot tear formation in steel casting to reduce rework and eliminate scrapping of castings with hot tear defects.

3. Develop a riser pressurization technique for steel casting to increase casting yield and soundness.

The University of Iowa will work directly with two steel foundries in Iowa to implement the newly developed technologies in their plants. The new computer simulation capabilities will be made available to foundries as add-on models in the widely used MAGMASOFT casting simulation software, which ensures direct transfer of the results of the present project to a large portion of the steel casting industry. A wider audience will also be reached by collaborating with the SFSA and presenting all research results at meetings of the steel foundry industry in the U.S.

Work To Date: (Technical Report – March 2007)

Progress was made in all three areas of the grant. (1) Inclusions: implementation of the model for inclusion formation in steel casting is almost completed and. significant run- time savings were realized. (2) Hot Tears: stress analysis of the sand mold was added to the hot tear simulations and results were compared to experimental measurements.
Significant progress was made in implementing an advanced constitutive model for the mechanical behavior of steel during solidification. (3) Riser Pressurization: a pressurization system for the Keokuk valve casting was designed and simulations were performed to evaluate the effectiveness of the pressurization. Based on the results and additional discussions with Keokuk personnel, a different casting will be selected for the pressurization trials. A project review meeting with representatives from the Steel
Founders’ Society of America was held in January 2007.