The Al Allen Award, for the best published refractories paper in 2003-04, was given by the Refractory Ceramics Division to S. Ramachandran, K. Peaslee, Ph.D. and J. Smith, Ph.D. of the University of Missouri-Rolla for "Thermal Chemistry of Steel-Refractory Interactions in Continuous Casting Nozzles." The authors determined that gaseous species are the root cause of inclusions in molten steel, and the impurities in casting nozzles contribute to the buildup that restricts steel flow. A field trial will be run soon using a nozzle that was designed on the basis of this study.
Castables with reliable placement properties are a reality today, if the many variables related to the raw materials, CAC, fillers and additives are controlled. The dream of developing a robust cementitious system that is less affected by the many interdependent variables, and that can be easily placed consistently, still remains. Further progress in achieving this dream will require more study of the complex interactions in the binder phase.
In "Blowups Happen," L. Krietz of Plibrico Co. reviewed case histories of castable installation explosions, also known as thermally induced structural failures (TISFs). Although castables commonly receive the initial blame for spalling/explosion incidents, in most cases investigation reveals other contributing factors and causes.
I. Cobane of Hotwork-USA discussed experiences with more than 20,000 castable dryouts since 1965. The company has observed that (a) castable spalling is more common in warm weather than cold weather, (b) spalls commonly occur at about 800ºF, and (c) explosive spalls frequently occur when heating resumes after a hold period at a specified temperature. Although much work has been done and published on castable dryout, problems still continue.
C. Alt of Lafarge Aluminates discussed the development of improved flooring (castable) for the storage of 10-15 ton coils at an integrated steel plant. Such flooring must resist thermal shock and mechanical stress (point load and impact). This example illustrates how focused attention on a specific application can result in an improved product.
The St. Louis Symposium Proceedings can be obtained by contacting Patty Smith at the University of Missouri-Rolla, (573) 341-6256 or firstname.lastname@example.org.
Charles E. Semler, Ph.D., is an independent refractories consultant serving clients worldwide. He was a professor of ceramic engineering and director of the Refractories Research Center at The Ohio State University. He is a fellow of the ACerS, and also served as vice president-international and refractories division chairman. He is a distinguished life member of UNITECR and received the St. Louis Refractories Award in 1995. Semler can be contacted by phone (480) 895-9830 or fax (480) 895-9831.