A Treatise on Steam Boilers Author:Robert Wilson Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III. PROPERTIES AND CHARACTER OF BOILER MATERIALS. CAST IRON. Cast Iron is the name given to a material, whose physical properties may vary through... more » a wide range of brittleness, hardness, and tenacity. It is sometimes found so brittle as to be almost incapable of being worked ; at other times it is found, or rather was once to be found, exhibiting such toughness as to render it capable of being chipped by a chisel or bent by pressure equally as well as many inferior specimens of material now sold as wrought iron. That cast-iron is unsuited for boiler mating no farther evidence is required than the fact of its almost total rejection for this purpose after having had a fair trial. Yet, despite the unanimous acceptance of its condemnation, it must be allowed that it possesses advantages which, considered in the abstract, appear to render it the most eligible of the scanty stock of materials from which the boiler-maker has to make his selection. Its low first cost, combined with facilities of working, place it in the first rank of constructive materials, and probably led to its being largely used for boiler making in the early days of steam engineering. In its power to resist wasting on exposure to the action of flame in a boiler furnace, or to the atmosphere when in contact with moisture, it is superior, if of suitable quality, to wrought iron, and also in its power of resisting the corrosive action of the feed water and of acids found in the products of combustion. Inferior strength alone can scarcely be regarded as a bar to its employment in vessels for resisting pressure, when we con- pider that the strength of a structure like a steam boiler depends as much on its size and form as on the actual strength of the material. The employment of cast iron to bear gr...« less