Metallurgy, an Elementary Text-Book (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ...billet, after rolling down, is cut up, and piled, reheated, and again rolled. It then forms No. 3, or best iron, while, if this is again piled and reheated, best best iron results. The oxide of iron formed in the reheating combines with the sand of which the furnace-bed is made and forms a slag, which flows out of the flue towards which the bed inclines. It is known as flue cinder and mill-furnace slag. It consists of ferrous silicate, with a large excess of oxide of iron, and has a lustrous crystalline fracture. Light work is guided into the rolls by various devices, and is consequently known as guide iron. In rolling plates, plain rolls are employed. The billet is passed in one direction until the required width has been obtained, and then turned at right angles and rolled down to the desired thickness. The distance between the rolls is regulated by settingdown screws, which act on the top bearing of the upper roll; and in rolling plates, the distance between them is diminished at each pass, both ends being set down by the same amount. The weight of the upper roll is counterbalanced. The roughing rolls are of grain iron, but the finishing rolls are chilled on the surface. Heavy plate mills are either provided with reversing gear, or are driven by reversing engines, so as to obviate passing the work back over the top roll. Thin sheets are rolled by doubling and passing the compound sheet through the rolls. Sometimes as many as sixteen thicknesses are being rolled at one time (see Tin Plate). For light work, to save the time of passing it from the back to the front, and the consequent cooling down which takes place, three-high rolls are employed. The middle one is driven from the engine, and the others geared with it. The work having passed through the lowe...