This category covers establishments primarily engaged in manufacturing clay firebrick and other heatresisting clay products. Establishments primarily engaged in manufacturing nonclay refractories and all graphite refractories, whether of carbon bond or ceramic bond, are classified under SIC 3297: Nonclay Refractories.
327124 (Clay Refractory Manufacturing)
Refractories are mineral- and chemical-based materials with very high heat-resisting properties, which make them ideal for use in the construction of walls, ceilings, and associated elements of iron and steel industry blast furnaces, glass manufacturing tanks, cement kilns, hot stoves, ceramic kilns, open hearth furnaces, nonferrous metallurgical furnaces, and steam boilers. Most clay refractory products are manufactured in the form of bricks, but refractory clay may also be formed into special shapes, such as the T-sections of refractory pipes or the small stands that support ceramic products during firing in a kiln. Refractories have been an essential element in heat engineering plants since the 1960s, where they were successfully used to improve performance and energy efficiency.
Total industry shipments declined steadily throughout the late 1990s, from $1.11 billion in 1997 to $1.08 billion in 1998 and to $903 million in 1999. In 2000, industry shipments fell to $888 million. The cost of materials that year increased to $427 million, while total industry employment decreased to 4,673 workers.
In 1995, the clay refractory industry consisted of four general product groups: refractory bricks and shapes, with 61 percent of the value of industry shipments; unshaped clay refractories, with 34 percent; other lump or ground refractory materials, with 2 percent; and unspecified refractories, with 2 percent. Included in the refractory bricks and shapes category were fireclay bricks and shapes, pouring pit refractories, clay kiln furniture, and radiant heater elements. As many as 38 U.S. firms made unshaped clay refractories in 1995, which included everything from refractory bonding mortars and plastic refractories to ramming mixes, castable refractories, and fire clay gunning mixes. Fifteen industry firms made lump or ground refractory materials in 1995. These were generally sold directly to customers in raw form or as an export.
The refractory brick and shapes industry was a highly specialized supplier to such heat manufacturing industries as the iron and steel industry, the ceramics industry, and the glass-making industry. Its terminology and the specific products it sold to end-user industries were as specialized as the products they helped to make. For example, one industry product, known as refractory tank blocks, consisted of blocks of refractory clay used in the lower portions of glass-tank furnaces; and refractory feeder parts were devices for supplying refractory raw materials to a preparation machine prior to firing in a ceramic or glass oven. Many industry products were specific to the iron and steel making industries. Refractory "nozzles," for example, were used in ladles for extracting molten steel; "runners" were refractory-lined channels in which molten iron flowed from a blast furnace when tapped; and ladle gate parts included refractory pouring spouts for molten iron or steel. Other specialized products manufactured by industry firms included clay refractory cement, refractory tile made out of fire clay, and various refractory elements used in glass manufacturing, such as glasshouse floaters, melting pots, rings, saggers, and stoppers.
One of the most common methods for manufacturing clay refractories was extrusion, in which moist refractory clay was forced by pressure through a die of specific dimensions, creating a rectangular shaft of clay that could then be cut at regular intervals to form bricks. The extruded bricks could then be sent through tunnel driers or dried on hot floors. Another common manufacturing process for noncomplex refractory shapes was power pressing, in which brick presses weighing as much 3,600 tons produced bricks of up to 28 inches in length. Unlike brick extruding machines, brick presses did not require large amounts of water, and thus simplified the drying and handling of the bricks.
Other methods of refractory manufacture included slip casting, hydrostatic pressing, fusion casting, and hand molding. After initial forming, clay refractory bricks and shapes were often fired in tunnel-shaped kilns to strengthen the brick or shape and stabilize it at a temperature equal to or higher than it would experience in actual use—often 1800 degrees Fahrenheit or more.
Because of its low cost in comparison to other refractories, fire clay—a mixture of kaolinite clay and silica sand—was the preferred material for clay refractory brick, which was classified as "low," "intermediate," "high," and "superduty," according to the temperature at which softened when fired or baked. Typical specific uses of fire clay refractory bricks were boiler furnace linings, blast furnace linings, molten iron casting pit refractories, and other applications that did not entail extremely high temperatures.
Plastic fire clays were refractories that were moldable when mixed with water and were often used for furnace linings or as a binding agent in fire clay brick manufacture. Fire clay could be combined with other raw materials to increase its refractoriness and to reduce its shrinkage during firing. Because of improvements in the combustion properties of fuels used in industrial furnaces, performance requirements for refractory materials continued to be upgraded to extend operational life and conform to harsher furnace environments. This led to the development of "superrefractories" that consist of 50 to 80 percent alumina, a form of aluminum oxide found in minerals such as corundum and bauxite, used in the manufacture of aluminum.
In 1997, by value, more than 57 of the materials consumed in the manufacture of clay refractories consisted of clay, ceramic, and refractory minerals, such as kaolin and ball clay, extracted and processed by mining firms (see SIC 1455: Kaolin and Ball Clay, and SIC 1459: Clay, Ceramic, and Refractory Minerals, Not Elsewhere Classified ). More than 18 percent consisted of clay or nonclay refractories, while less than 2 percent came from industrial chemicals.
Between 1972 and 1987, the value of clay refractories shipments more than doubled from $336 million to more than $788 million. Shipments in 1997 reached $1.1 billion.
Since about 1990, the industrialized world has experienced a significant drop-off in the amount of refractories produced and consumed. A number of factors contributed to this downward trend: a decrease in the production of steel around the world during this period; the use of higher-grade refractory materials; the use of new non-refractory technologies in heat engineering industries; improvements in the durability of refractories already produced and sold; and the discontinuation of thermal pretreatment in the use of some raw materials.
Total industry shipments declined steadily throughout the late 1990s and into 2000, dropping from $1.11 billion in 1997 to $888 million in 2000. Over the same time period, the cost of materials declined from $552 million to $427 million, while total industry employment decreased from 5,781 workers to 4,673 workers.
Industry trends in the clay refractory industry in the late 1990s included the emergence of new seamless refractory furnace linings that reduced air leakage into and out of industrial furnaces. Improvements in furnace operation and refractory materials resulted in increases in the number of tons of steel (up to 1 million) that could be produced before refractory linings needed replacing. Partnerships were also formed between refractory suppliers and steelmakers to develop new refractory materials and techniques. The industry continued to seek ways to find purer grades of refractory minerals that would increase the temperature-resisting limits of refractory products.
The long-term trend toward increased automation of refractory manufacturing processes, such as automatic brick batching, also continued in the late 1990s. The development of robotic and remote control gunning machines enabled furnaces to be relined and refractory coatings applied without the expense of temporarily shutting down the furnace. The major issues facing refractories producers in the late 1990s were environmental antipollution standards, increases in cost for materials, and changing markets.
Major players in the clay refractory manufacturing industry included Indresco Inc. of Dallas, Texas; North American Refractories Co. of Cleveland, Ohio; Adience Inc. of Pittsburgh, Pennsylvania; A.P. Green Industries Inc. of Mexico, Missouri; and Harbison-Walker Refractories of Pittsburgh. Ohio, Missouri, Illinois, and Pennsylvania accounted for 66 percent of the industry's total shipments in 1997.
The industry grew from 86 firms to 111 firms between 1972 and 1987, while industry employment fell from 11,200 to 6,400 workers (production and nonproduction). By the late 1990s, the number of companies in the industry had inched back up to 115 firms. Employment, however, had fallen to 4,673 people, three-quarters of whom worked in production, by 2000.
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United States Census Bureau. 1997 Economic Census: Clay Refractory Manufacturing. Available from http://www.census.gov/prod/www/abs/97ecmani.html .
United States Census Bureau. "Statistics for Industries and Industry Groups: 2000." Annual Survey of Manufacturers. February 2002. Available from http://www.census.gov .