. Elementary chemistry, for high school and academies . ith a layer of ferric oxicl. Theiron is melted and constantly stirred to expose the impurityto the air; for a time the mass appears to boil, owing tothe formation of carbon monoxid. As the impurities areoxidized, the mass becomes pasty, because of the highermelting point of wrought iron; and the pasty material iscollected on one side of the furnace and worked up into 160 CHEMISTRY large lumps or blooms which are passed through rolls toremove the liquid slag. The ferric oxid used for the liningor fettling assists materially in oxidizing th
. Elementary chemistry, for high school and academies . ith a layer of ferric oxicl. Theiron is melted and constantly stirred to expose the impurityto the air; for a time the mass appears to boil, owing tothe formation of carbon monoxid. As the impurities areoxidized, the mass becomes pasty, because of the highermelting point of wrought iron; and the pasty material iscollected on one side of the furnace and worked up into 160 CHEMISTRY large lumps or blooms which are passed through rolls toremove the liquid slag. The ferric oxid used for the liningor fettling assists materially in oxidizing the impurities,and the process above described is sometimes called pigboiling to distinguish it from the dry puddling pro-cess in which the cast iron requires preliminary interesting history of wrought iron see Roscoe andSchorlemmers Chemistry, Vol. II, pt. ii, p. 34. 246. Steel is malleable, has a fine crystalline structure,may receive a high polish, may be welded, is easily fusible,melting at about 1400° C. Its extensive use depends upon. the fact that it may be tempered. When heated to rednessand suddenly immersed in cold water, it is rendered veryhard and brittle ; if heated and slowly cooled, it is renderedsoft, and by regulating the temperature at which it is tem-X^ered, almost any desired degree of hardness, toughness, orelasticity may be obtained. Steel contains from ^ to 2 °/0of carbon. Preparation. — Steel may be made in three ways: (a) byadding carbon to wrought iron (the cementation process),(6) by burning out a part of the carbon of cast iron (theBessemer process), and (c) by melting together proper pro- IRON 161 portions of wrought and cast iron (the Siemens-Martinprocess). (a) TJie Cementation Process. — Bars of wrought iron arepacked in charcoal in fire-clay boxes which are kept at a redheat for a week or more; the carbon penetrates the iron,giving it a blistered appearance, hence its name blistersteel. It is not quite uniform in composition, bu
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