The earliest refractories for containing melts were quarried from natural deposits of limestone and dolomite. Today these two carbonate rocks serve important roles in the production of metal contact refractories. Early refractories for glass melting on the other hand were manufactured from clays and claystones. These materials are also still used extensively for the batch melting of glasses that are hand formed or blown into art and tableware. Glass contact refractories for the continuous (tank) melting of glass are often fired, cast into large shapes, and arranged in a soldier course which constitutes the sidewalls of the glass tank.

In this brief exposition of refractories technology and allied research, the articles by B. Brezny, T.F. Vazza and T.A. Leitzel, and by T.S. Busby cover materials development, selection, and properties of the systems which have evolved for the efficient melting of steels and glasses. As such they relate to extremes of technological flux in the processes for the manufacture of steel and glass, respectively.

The continuous melting of large volumes of commercial glasses has been carried out in tanks equipped with reverberators for at least 70 years. The basic design of the overall system and of many of the glass fabrication machines for pressing, rolling, and blowing the glass has been constant since World War I. Only the introduction of the float glass method, the famous Pilkington process, for the production of flat glass, has interrupted the slow quiet progress in the technology of continuous glass making.

The iron and steel industry is constantly undergoing technological changes in improving its processes to produce the highest quality world-class steels. As a consequence, the refractories industry has been challenged to keep in lock-step with the iron and steel industry to enhance, not detract from these processes.

Certain internal combinations have enabled these refractories changes. Three expositions can display the sophistication to which refractories have advanced, so this article will explore refractories for primary steelmaking, ladles, and slide-gate devices for continuous casting.

The start-up of the first top-blown oxygen vessel at the Linz Works in Austria 37 years ago was a historical milestone in the evolution of steelmaking. At that time the open-hearth process was the dominant steelmaking technology in the world. Ten to 12 hours were required to produce one batch of steel in the open-hearth furnace, but only one hour is needed to refine the same amount of steel in a basic oxygen furnace (BOF). In a top-blown BOF all oxygen required for refining is introduced into the vessel through the oxygen lance inserted through the top of the vessel.

Toward the end of the 1960s, bottom-blown processes, such as OBM and Q-BOP, became very important in oxygen steelmaking. In the bottom-blown process, oxygen and lime are blown into the steel batch through bottom tuyeres.

Glass melting has changed very little in general principles since the earliest times, still being produced in fireclay pots or crucibles—even up to the present day. In Europe, experiments to melt glasses in tank furnaces began about 1700 A.D., but this became an important form of glass manufacture after Siemens introduced the regenerative furnace in 1870. This design was the basis for the development of modern furnaces and there is still a considerable similarity to the original.

Until the late 1920s the glass contact refractories used in tank furnaces were based on fireclay or sandstone blocks. About this time important changes began when sillimanite and fusion-cast mullite refractories became available. However, because of the higher cost of fusion-cast refractories the introduction of these materials was delayed and they did not come into general use for lining the glass melting tank until the late 1940s.

The high performance of tank furnaces today is related to a number of factors such as improved furnace design and regeneration, but the most significant has been an improved melting rate brought about by the use of higher temperatures. This has only been achievable as a result of the improved quality of fusion-cast and other refractory materials, such as those used in the furnace superstructure and regenerators. Garstang showed that there has been a steady increase in melting temperatures in the container glass industry. In data going back to 1920, there has been an increase from about 1300°C to some 1590°C. Bondarev showed that the increase in production achieved by using higher temperatures reduces the specific consumption of fuel.

Over the past 10 to 20 years, cathodo-luminescence microscopy (CLM) has become an important, standard technique for studying many geological materials, but its application to ceramic material has not been fully realized. CLM has been found to be especially valuable in determining original porosity in carbonate rocks, a feature that was extremely important in determining the ability of petroleum and related fluids to migrate through the rocks and concentrate in the favorable structures where petroleum is found today. CLM constitutes one of the most significant techniques employed in the exploration for petroleum, but the results of those investigations remain largely unpublished in company files. A number of investigations have discussed the application of cathodoluminescence (CL) to studies of porosity in carbonates.

Other applications of CLM to geology involve metals exploration. Halos of red CL feldspar in the rocks around carbon-atite deposits, which may contain rare earths, copper, and other metals, contrast with feldspar crystals with blue or blue-green CL that are distal from the ore deposits. Dolomite associated with lead-zinc ores may exhibit growth zoning by CL that can be used to trace the path of the ore fluids for distances of 100 miles or more. The detection of host rock limestone alteration in the Tri-State zinc-lead district, potassic and argillic alteration at the Henderson molybdenite mine, and ore guides in other metallic deposits by CL was discussed by Hagni.

Burned periclase brick became a commonly used refractory material during the 1940s and early 1950s in the steel-making industry. Unfortunately, periclase brick easily reacts with water or water vapor and results in dimensional instability, i.e., a volume expansion. This may lead to the mechanical failure of any article made from it. Considerable research has been performed in the past 30 years to suppress the hydration susceptibility of magnesia refractory.

Boron has been found to be extremely effective in improving the hydration resistance of magnesia. It can be added to magnesite, brucite, light calcined magnesia or it can be deposited on post dead burned magnesia. However, the use of boron decreases the hot loading bearing properties of the magnesia and the dissolution of the boron into certain grades of steel may adversely affect their mechanical properties. Moreover, the addition of boron compounds requires a high-temperature calcination, normally higher than 1600°C, which has been proven uneconomical.

Other dopants, incorporated either on the surface or in the bulk, have been reported to have various effects on the hydration susceptibility. The ultimate goal of the work reported here is to determine if there is a correlation between the hydration susceptibility of MgO having various cation substitutions for Mg and the energies of the resulting lattices.

Lockheed's Research Laboratory was established in 1956 to support the recently founded Lockheed Missiles and Space Division. The earliest products of the division were a new generation of submarine-launched ballistic missile—Polaris and the Agena spacecraft. It was immediately recognized that both required advances in materials technology and the Materials Sciences Directorate was established in the research laboratory to address those needs. Today, materials researchers are conducting investigations in a wide range of topics in metallurgy, chemistry, structures, and nondestructive test/evaluation.

The laboratory has a particularly strong capability in performance analysis and problem identification/resolution for solid rocket propulsion systems. Current work on the Trident II continues the laboratory's contributions to the Polaris, Poseidon, and Trident I missiles. Efforts are also focused on materials for other aerospace applications, such as advanced aircraft, the NASA Space Station (Freedom), and the Strategie Defense Initiative.

Examples of materials sciences achievements include the development of the space shuttle's heat shield tiles, the first use of lithium as an anode in batteries, a real-time x-ray inspection system for large rocket motors, and coated and uncoated refractory metal hot gas manifolds for ballistic missile propulsion. The organization has a staff of about 170 professionals.