The Crystallization of Iron and Steel; An Introduction to the Study of Metallography (Paperback)

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. 1905 edition. Excerpt: ...and gradually bent, gives a well-defined fibrous fracture; while, if nicked on all four sides and suddenly broken, the fracture will be crystalline. But these are well-known "tricks of the trade." The fracture, when performed under definite conditions, furnishes a true indication of the coarseness of the crystallization. The degree of coarseness of the fracture, or the average size of the crystalline grains when a suitably prepared specimen is examined under the microscope, is called the grain size of the specimen. As a general rule, the smaller the grain size the better the steel, and we naturally ask: Is there any relation between the grain size and the highest temperature to which the steel has been heated in annealing? For practical purposes the physical properties of steel may be taken to depend upon--Fig. 39.--Iron with 13 per cent. Carbon. (F. Popplewoll.) fflt-jlfBW YORK POBLIC LIBRARY (1) Chemical composition, i.e., the relative amounts of other elements present; (2) Distribution of constituents, i.e., the relative proportions of ferrite, cementite, etc., present; (3) Size of grains. Here are a few tests, by Sauveur, on the relation between the size of the grain and the physical properties of the same piece of steel:1--The relation between the average area and the tenacity is--Tenacity = 75 5-0 004 A. An experienced man can generally give a surprisingly accurate guess of the temperature to which the steel has been heated, from the fracture, or from the microstructure of the metal. Tschernoff and Brinell have observed that the higher the temperature of annealing the larger the size of the grain. This will be evident on examination of Campbell's diagrams, Figs. 41 to 43, which represent the appearance of soft steel when...