Unconventional Methods for Yield Improvement through Directional Solidification in Steel Castings
This project was designed to increase yield through the use of solidification software to simulate imposed thermal gradients and evaluating their effect on yield. A survey was conducted among American steel foundries to determine the current state of casting yield. The average casting yield was found to be only 53%. Through the survey, variables with the strongest statistical influence on average casting yield have been identified. Important factors having a positive impact on casting yield (where yield increases with their increase) are tons produced per pattern, amount of railroad and wear resistant end-use production, average section thickness, and use of risering rules developed in-house. A negative impact on yield was found to be related to pump and valve end-use production, and corrosion resistant steel production. Extensive computer simulations were conducted to re-examine the SFSA rules that have been used by industry for more than 30 years to determine riser sizes and locations. New rules were established and made available to industry through the SFSA (Steel Foundersí Society of America). Extensive casting trials were conducted at five steel foundries to verify the computer simulations and the new rules. (5) New and unconventional yield improvement techniques were analyzed by computer simulation. (6) Case studies were conducted to investigate the yield performance of complex production castings.
Follow-on research is investigating methods for improving yield in steel casting. Specific goals are:
1) Develop techniques to improve yield on current practices by 10% while maintaining the same quality level,
2) Develop novel techniques to improve yield by 25% on a fully optimized casting system, and
3) Document the developed techniques, procedures and findings in manuals and reports to allow all steel casting producers to benefit.
Important progress is being made in developing techniques to improve yield on current practices as well as developing unconventional techniques to improve yield.