Salt solutions high-chromium cast irons

It consists of a hollow, cylindrical metal drum lying on its side trunnions that permit its rotation a sturdy, straight, adjustable knife and a shallow feed pan into which it dips. A large gear mounted on one trunnion is driven by a pinion actuated by motor or pulley. A cast-iron or welded steel frame furnishes the supports. The drum is cooled by water or brine introduced and wasted through the trunnions. A coating of liquid forms on the drum as it dips in the feed pan as the drum turns, the film at once begins to cool, so that after traveling about three-fourths of the rotation, it is hard and solid. It meets the knife, which scrapes it off, the coating breaking into flakes, chips, or other fragments characteristic of the material. The flakes drop into an apron from which they may be shoveled into shipping drums, or they may drop directly into a screw conveyor that moves them to a chute and packing boxes or barrels. The drum is usually made of a special grade of cast iron with a very smooth surface, which may be chromium-plated. The drum is also made of stainless steel, nickel, or bronze. The motion is generally a steady rotating one, but for certain products it has been found better to move the drum in a series of short jerks. Successful application of the flaker depends upon a low adhesion of the solidified material to the surface of the drum. Should the adhesion be too high, the knife will be unable to lift off the solid and will ride on the material instead of on the drum. The adhesion of some troublesome materials is lessened by a wetting roll, which leaves a film of moisture on the metal just before the coating is formed.  [c.158]

Because of its mechanical properties and the difficulties associated with its production, high-chromium iron is mostly used in environments which are particularly aggressive to other cast alloys. It is most useful for handling acid waters containing oxidising agents, for example mine waters and industrial effluents. Because many of these waters tend to contain solid matter in suspension, which can lead to abrasion of metals exposed to them, the very hard high-chromium iron is often the most suitable material for pumps handling these solutions. There is always a possibility that abrasive slurries  [c.614]

Corrosion, Volume 2 (2000) -- [ c.3 , c.133 ]