Metallurgy, an Elementary Text-book

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 edition. Excerpt: ...heavy work are provided with rising and falling tables, which receive the work as it leaves the rolls, and raise or lower it as required. _ _ Rolls for rolling finished iron vary from 8 inches to 38 inches in diameter.. The rolling of malleable iron by welding together and elongating the particles of iron develops a fibrous structure, which is more pronounced the greater the number of' times it is piled and reheated. This treatment also renders the metal more uniform in character. (;.'.,_ r a. J Burnt Iron.--When iron is exposed at a very high temperature to an oxidizing atmosphere-, it loses its malleability and is known as burnt iron. Probably this is due to the formation of a suboxide of iron in the metal. Brands of Merchant Iron.--@ (Crown), common iron, or merchant bar (puddle bar, once piled and reheated). Best, twice piled and reheated. Best best, three times piled and re-heated. Treble best, four times piled and reheated., THE designation of steel was formerly confined to those varieties of iron which could be hardened by heating to redness and plunging in cold water. The introduction of the Bessemer process marked a new era. The metal produced by this process lacked the fibrous character associated with wrought iron, and partook more or less of the character of steel. Those varieties possessing more than 0'3 per cent. of carbon sensibly harden when treated in the same manner as steel, but with less carbon this is not the case. Other processes producing similar soft metal sprang up, and the term steel has come to include a great variety of material having widely different properties. Some are softer even than wrought iron, and cannot be hardened. Since the hardening property is dependent on the amount of carbon it contains,...