Edited by Lawrence Kren
A $10 million walking beam coilhandling system and cooling pond are the latest additions to CSI's half-mile-long hot strip mill. The coil handler transports coils up to 72-in. wide to either the finishing facilities or to the cooling pond by high-speed coil cars, protecting the coil from damage. The cooling pond quenches hot coils in about 6 to 8 hr versus three days before they are further processed on the 62-in. continuous pickle line. The new coil-handling system replaces a manual system that was susceptible to handling damage. The new system also is safer. Conveyors, cars, and cranes stay on one path instead of haulers travelling the same roads as other traffic.
While Graphalloy bushings are usually spec'd to meet custom requirements, standard designs are available including cylindrical bushings with or without grooves, single, double-flanged, split, and metal backed bushings as well as pillow block and flange units. A constant, low coefficient of friction makes it ideal for low-speed operation, frequent starts and stops, and intermittent operation. FDA-accepted grades are available for food contact applications.
Graphite/alloy bushings let telescopic coil grabs from Avon Engineering Ltd., Waterdown, Ont., operate lube-free in a harsh environment. The coil grabs transport hot steel coils from the mill to a quenching pond at California Steel Industries, Fontana.
Avon engineers typically spec aluminum bronze or 660 bronze for wear components, both of which need lubricating grease to work. But the application's unusually high operating speeds and ambient temperatures quickly degrade such lubricants. Moreover, the system is fully automated, so a failed bushing may go unnoticed, perhaps damaging equipment. For these reasons Avon chose Graphalloy bushings from Graphite Metallizing Corp., Yonkers, N.Y., (www.graphalloy.com).
Graphalloy is graphite impregnated with metal alloy. The graphite acts like a deck of cards with individual layers that easily slide off one another.
This action makes the material self lubricating while the metal alloy adds durability. The bushings handle temperatures from cryogenic to 1,000°F in an oxidizing environment and can run without grease even when submerged in hostile liquids such as acids, alkalis, hydrocarbons, black liquor, and liquid gases. "The Graphalloy bushings have worked for 18 months at CSI with no noticeable wear," says Alan Robson, Avon Engineering project manager.
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