- THE MAGAZINE
The 39th Symposium on Refractories, sponsored by the St. Louis Section of the American Ceramic Society, was held April 9-10, 2003. The theme for this year’s annual spring refractories meeting was “Raw Materials and Monolithics.” The meeting attendance was 117, the highest in recent years, and attendees were provided with a copy of the 273-page proceedings of the meeting. Each year, this meeting provides a snapshot of U.S. refractories activities for topics of contemporary interest. Selected information from the presentations is highlighted below.
Monolithic RefractoriesD. Peters of Resco Products reviewed refractory practices in various industries, with emphasis on the use of monolithic refractories. He mentioned some considerations for needed developments, including a continuous lining concept where there is no tear-out or disposal of used refractory. According to Peters, the ideal concept would require no curing or controlled heat-up, and would use process heat for heat-up.
Considering monolithic refractory technology in Japan, K. Marakami of Krosaki-Harima indicated that 73 percent of the total 2001 refractory market was used in the iron and steel industry. He noted that the market share breakdown in Japan is Krosaki-Harima, 16.9 percent; Shinagawa, 12.6 percent; Youtai, 9.3 percent; Kawasaki, 4.7 percent; and Kyushu, 3.2 percent. The importance of monolithics continues to increase in Japan, as in other industrialized nations, at the expense of brick products.
V. Pandolfelli of the University of San Carlos, Brazil, reviewed mixing, pumping and installation issues for shotcrete (wet gunning) castables. Since its first use in 1993, many applications of refractory shotcrete have been successful, and a lot of pertinent research is in progress. Pandolfelli emphasized the need to better evaluate the technical details of shotcrete castables in order to establish science-based guidelines. Further improvements and new developments will no doubt result in increased usage of shotcrete castables. For example, a carbon-containing shotcrete castable is reportedly being used in hot metal (molten iron transport) cars in Japan.
C. Alt of Lafarge Aluminates discussed the importance of knowing and understanding the links between initial castable properties (as-installed), strength development and high-temperature properties, since the final installed properties govern the durability of a lining. Lafarge’s work documents the dependence of thermomechanical properties on the initial, as-installed properties of reduced-cement castables, based on the use of in-situ ultrasonic monitoring of Young’s modulus (E). A good correlation between hot strength at 1500 degrees C and E (by ultrasonic) was reported.
Refractory Fiber IssuesThe refractory fiber issue was reviewed from two perspectives—a user who decided to reduce the usage of refractory fiber to meet an expected new government guideline (0.2 fibers/cc of air), and the Refractory Ceramic Fibers Coalition (RCF), which works to preserve and build the market. Dofasco, a Canadian steel company, reported that by developing and using alternative materials for a variety of applications, it has reduced its usage of refractory fiber from 83 boxes per month in 1999 to 2.6 boxes per month in 2002. Dofasco’s view is that cost should not be a significant consideration for issues of safety and health.
RCF presented facts and historical information that raise questions about the validity of testing that has shown that fibers are hazardous to humans. In a statement, the organization said, “OSHA does not, at this time, consider refractory ceramic fiber to be a regulatory priority.” But respirable silica is a regulatory issue. (Refractory fibers, as-manufactured, do not contain crystalline phase silica. However, in use at elevated temperatures, crystalline phase silica can develop and cause a health concern.) The development of bio-soluble CaO-MgO-SiO2 fibers was noted as an alternative for alumino-silicate refractory fibers.
Benefits of Refractory TestingM. Rigaud of Ecole Polytechnique discussed the correlation of rheological and mechanical properties of low-cement, self-flow castables. He concluded that a rheometer is a good tool for designing mixes, including the prediction of pumpability.
L. Krietz of Plibrico reviewed the use of hot work of fracture data in developing advanced castables. He noted the need for balancing the resistance of crack initiation and crack growth in designing formulations, although most people still design refractories for strength, rather than for fracture characteristics.
This year’s St. Louis meeting clearly indicated that the advancement of refractories technology is continuing. Based on the comments of many attendees, the prospects look good for improved business in 2003.