The Metallography of Iron and Steel (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. 1912 Excerpt: ...carbon steel. Since steel containing very little carbon is essentially made up of ferrite, its occasional brittleness must be due to the occasional brittleness of ferrite, a constituent by nature soft and ductile. Stead has indicated two kinds of brittleness from which ferrite may, and occasionally does, suffer, namely, (1) "inter-granular" brittleness and (2) "inter-crystalline" or "cleavage" brittleness. By inter-granular brittleness is meant a lack of cohesion between the ferrite grains leading to ready fracture under shock, the line of fracture following the boundary Fig. 31.--Tensile stress, 38,000 lbs. per sq. in. Fig. 33.--Tensile stress, 42,000 lbs. per sq. in. Fig. 32.--Tensile stress, 40,000 lbs. per sq. in. Fig. 34.--Tensile stress, 44,000 lbs. per sq. in. Steel. Carbon 0.05 per cent. Magnified 6 diameters. Strained by tension and heated to 650 deg. C. for seven hours. Cross sections of strained bars. (J. O. Connolly in the author's laboratory.) lines of the grains. Such brittleness is usually due to the presence of impurities forming brittle and more or less continuous membranes surrounding the grains. The presence of much phosphorus, however, appears to produce inter-granular brittleness without producing surrounding membranes. Inter-crystalline or cleavage brittleness is caused by the ferrite grains assuming nearly the same crystalline orientation so that the plane of fracture follows the cleavage planes and passes from grain to grain almost in a straight line. The diagram shown in Figure 35 will make this clear. The cross lines represent the cleavage planes in each grain. In B the metal is made up of large ferrite grains but the crystalline orientation of these grains is so heterogeneous that a line of fracture c...