The Great Industries of the United States; Being an Historical Summary of the Origin, Growth, and Perfection of the Chief Industrial Arts of This Country - Tapa blanda

This historic book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1873. Not illustrated. Excerpt: ... The process of cementation consists of heating iron bars, packed in charcoal, in a furnace, for a period of from six to ten days, according to the quality or characteristics of the product required. 1 'ie greater thd heat maintained the quicker is the process of conversion. Steel thus made is called blistered steel, from the fact of the bars being found covered with blisters. Steel of this kind has its interior texture very irregular; it is white like frosted silver, and its fracture shows crystalline angles and facettes, which are larger in proportion as the process has been further carried on, and the mixture with the carbon of the charcoal has been greater. The crystals of the centre are always smaller than those near the surface of the bar. Before using for tools, such steel needs to be subjected to the process of tilting, as it is called; that is, it is drawn out by hammering, by which the texture is made more uniform and dense. Cast steel is blistered steel, broken into fragments, and fused. The chief property, however, of steel, which gives it its value for so many purposes, is that of being hardened, or tempered. When exposed to a progressive heat, it takes in succession the following colors: 1, a faint yellow, which indicates the fit temper for lancets, which require the finest edge, with but little strength of metal; 2, a pale straw-color, indicating the temper for razors, and surgeons' amputating instruments; 3, a full yellow, indicating the temper for penknives, with increased toughness; 4, a brown yellow, indicating the temper for cold-chisels, and shears for cutting iron; 5, a brown with purple spots, indicating the temper for axes and plane irons; 6, a purple, indicating the temper for table-knives and shears for cloth; 7, bright blue, in...