Propeller
An instrument placed at the back part of a steam-vessel for the purpose of propelling her through the water. See SCREW-PROPELLER. Puddled Steel, or Semi-steel, is produced by the decarburization of cast iron in the pudding-furnace. Krupp, of Germany, makes the bulk of his steel by this process, using irons rich in manganese and carbon, which are suited for conversion into steel. The puddling process for steel is very like that for malleable iron, except that the former is conducted at a lower temperature and needs more careful manipulation. There is no previous refinement of the iron to be operated upon when steel is produced by pudding. About 400 pounds are first melted, mixed with silicate of iron (slag), and kept stirred with a rabble. During this operation the carbon contained in the iron is oxidized by the oxygen present in the cinder, producing carbonic oxide, which as it escapes causes the appearance of boiling. When this boiling is general through the mass, the temperature is increased until the appearance of incipient solidification occurs; the temperature is then reduced, and the ordinary process of balling proceeded with. The work in this case demands more than ordinary skill. This steel, after being made into bars, is cut up and remelted in crucibles, in order to produce cast steel. See MALLEABLE IRON; CRUCIBLE STEEL.
Puddle-rolls are the pair of rolls on the left of the train, usually called the roughing-rolls. See MALLEABLE IRON; ROLLS; TRAIN.