Breaking New Ground

A silicon carbide furnace plant expansion will enable Washington Mills to increase capacity, control costs and improve quality.

Washington Mills has begun a construction project to expand its silicon carbide (SiC) furnace plant in Hennepin, Ill. The new expansion will boost the company's SiC crude manufacturing capacity by 10,000 tons per year, bringing the total to 70,000 tons. Completion is expected late this year.

Silicon carbide crude, which will be processed into silicon carbide microgrits and powders for a range of applications.

Some Background

When it was founded in 1868, Washington Mills was the first U.S.-based producer of abrasives. The company's initial products included aluminum oxide abrasives used in grinding wheels, sandpaper and other applications.

Acquisitions over the years have helped the company grow and diversify. "Washington Mills significantly expanded its product base and the markets it served through the acquisition of Carborundum Co.'s Electro Minerals Division in 1986," says Anne Williams, manager of Marketing. "It began producing boron carbide, silicon carbide, fused mullite, zirconia-mullite, white aluminum oxide, fused magnesium oxide, fused spinel and fused zirconia. These products are all sold today to diverse applications in the ceramic, refractory, and investment casting industries."

Washington Mills also expanded its SiC and microgrit capacity through its 2001 acquisition of The Exolon Co. "The purchase gave Washington Mills control of a silicon carbide crude manufacturing facility in Hennepin, Ill., as well as a crude and microgrit facility in Orkanger, Norway," says Williams.

The SiC requirements of ceramic manufacturers have evolved over the years. "We have more ceramic customers today with very specific chemistry or sizing requirements," she explains. "Our customers' needs have caused us to adapt our manufacturing process to cater to a much more technical product. At this level, silicon carbide for ceramic manufacturing has become less of a commodity product and more of a niche product for particular applications."

The expansion will boost the company's silicon carbide crude manufacturing capacity by 10,000 tons per year.

Expansion Details

It was the growing demand for the company's CARBOREX® silicon carbide microgrits and powders for applications in the advanced ceramic, semiconductor, and photovoltaic industries that led Washington Mills to decide to expand its SiC furnace facility in Hennepin. "The global supply of silicon carbide is tight and there has been an increase in demand for silicon carbide over the past several years," says Williams. "Our customers are requiring more of our silicon carbide products, so we've made the decision to expand with them."

According to Washington Mills, the best way to produce CARBOREX SiC powders to requested specifications is to control the manufacturing process from start to finish. Expanding its Hennepin SiC furnace plant will give the company control over the quality of the SiC crude used as feedstock to produce CARBOREX microgrits. "The grains and powders we make are only as good as the crude we use, so our furnace plant is an important part of our manufacturing process," explains Williams. "With the majority of silicon carbide coming from countries such as China, our domestic operation gives us a high-quality and reliable source of crude that we control."

The expansion is also aimed at continuing to supply a growing demand for a secure domestic source of metallurgical-grade SiC in North America. In addition to producing crystalline SiC for the applications noted previously, Washington Mills produces CARBOLON MA, a high-quality metallurgical-grade SiC that is used as a source of carbon and silicon in the production of iron castings. According to Washington Mills, CARBOLON MA is also a popular choice for the steel industry because its uniform deoxidizing properties can improve cost savings through effectively reducing slag and recovering valuable elements such as manganese and chromium.

Environmental Benefits

The Hennepin plant reportedly features one of the most advanced emission-control systems in the world. The SiC furnace expansion will feed into the company's patented SULFEROX environmental control system, which converts off-gases into a solid state through an environmentally friendly process. The system contains the off-gases and particulate matter, processes the particulates and treats the gases in order to remove sulphur from the process.

"We decided to expand in Hennepin because it is an excellent plant that is highly efficient," Williams explains. "Our 'big furnace' technology is more environmentally friendly because it is more energy efficient, and it collects and cleans the gases and particulate that would otherwise be released into the atmosphere."

Looking to the Future

Washington Mills believes that its SiC furnace operation makes the company a dependable and stable source of domestic SiC, putting it in an ideal position to respond to customers' needs. "There is a real advantage in today's market to being a high-volume supplier of high-quality integrated silicon carbide, because the market will continue to move toward higher quality, better performing silicon carbide," says Williams. "We will continue to seek ways to expand our silicon carbide business domestically as long as there is demand for silicon carbide."

For additional information, contact Washington Mills at 1801 Buffalo Ave., Niagara Falls, NY 14302; (716) 278-6600; fax (716) 278-6650; e-mail; or visit


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