Some of the research activities around the world by the refractories industry, on just three of the many important topics, are discussed in the column.
Throughout the decades, the refractories industry has continually developed new and improved products. Some of the research activities around the world, on just three of the many important topics, are mentioned below.
Refractory raw materials (natural and synthetic) are absolutely critical for developing new and improved products, for manufacturing consistent quality refractories, and for maintaining cost control and improving profit potential. Companies constantly scan the world for raw materials and conduct research to enhance their knowledge of raw materials (standard, new and novel) and expand their options.
For example, research is ongoing to discover and/or produce lower-cost raw materials, such as spinel from natural raw materials. Because spinel is a popular refractory raw material, reducing its cost can help manufacturers improve their profitability. Another important research topic is the development of graphite-containing castables, which are desired to replace MgO-C bricks for steel-making applications. Research is underway to develop graphite pellets for use in such castables.
The development and characterization of non-oxide materials is another interesting area of study. Many people consider this is potentially a big growth area for future refractory development and business.
As field experiences and successes with monolithic refractories continue to grow, the demand and expectation levels also increase. As a result, a great deal of research is ongoing to better understand and improve these products. One study, for example, aims to discover the correlation between rheology and mechanical properties for bauxite self-flow castables. The study of the effect of mix composition/characteristics on properties is important to guide future development and innovation.
The ability to measure the permeability of castables up to elevated temperatures is also being studied. This capability should eventually allow specification of a prescribed heatup schedule for any castable, which will be a major advancement. The repair of molten iron transfer (torpedo) car linings by castable shotcasting is also being investigated as a very practical and cost effective way to extend lining life.
Basic and Applied Science
The advancement of refractories technology has been, and continues to be, boosted by the generation and use of information from diverse sources, such as the creative application of new data, use of prior experience and state-of-the-art tools, cross-discipline interaction, and the development and use of intellectual property. For example, the fracture mechanics of castables, including R-Curve analysis, shows how the structure is actually affected by stresses. Understanding this relationship is critical for the ongoing development and improvement of refractories.
The role of additives on microstructural changes in nitride-bonded SiC refractories is also being studied. The ability to design and control refractory microstructures is an important method of improving properties and advancing the technology. Also underway are sessile drop experiments related to slag-wetting and attack of refractories. Slag attack is a major factor in refractory wear, so increasing the basic understanding of the mechanisms and control is important.
The Need for Research Never Stops
In the changed U.S. and world market, it is possible that more effort is being directed to applied research and field installation improvements to provide additional cost savings and other benefits for refractory manufacturers and users. Although there has possibly been some shift in focus, there is never a lack of refractory problems and needs—from sources inside and outside the refractories industry—that warrant research. Just a few examples of current refractories research needs are mentioned below:
• Develop more prescription spinels for application-specific uses. For example, refractories containing hercynite (FeAl2O4) are being successfully used in rotary cement kilns.
• Evaluate the properties of refractory compositions containing exotic aggregates (non-oxide, composite, cermet, etc.), and the associated benefits.
• As revealed in the investigation of the Columbia shuttle disaster, materials and procedures are needed for in-flight repair of the refractory materials that protect the shuttle’s metal skin and internal wing structure.
• Develop techniques for measuring refractory wall thickness in operating furnaces where equipment/procedures have not been developed.
• Develop cost-effective, chrome-free refractories for use in severe corrosion environments, e.g., chemical incinerators and slagging gasifiers.