The Iron and steel magazine . on a boring mill and in less than two daysplayed out, having been in use for only a very small part ofthis period. The bar from which the tool was made was the regulationsize, i\ inches by 1J inches in cross section, and was of cruciblesteel with the following composition: C , P , Mn ,Si , S At one place in the bar, within a space of 12 inches, werefound the fractures exhibited in Fig. 2. Fracture A is finegrained and silky, like a normal tool steel, while fracture B wouldbe called burnt by the average blacksmith. It is coarseand brilliant
The Iron and steel magazine . on a boring mill and in less than two daysplayed out, having been in use for only a very small part ofthis period. The bar from which the tool was made was the regulationsize, i\ inches by 1J inches in cross section, and was of cruciblesteel with the following composition: C , P , Mn ,Si , S At one place in the bar, within a space of 12 inches, werefound the fractures exhibited in Fig. 2. Fracture A is finegrained and silky, like a normal tool steel, while fracture B wouldbe called burnt by the average blacksmith. It is coarseand brilliant except at the center. Figs. 3 and 4 show the microstructure of the coarse-grainedfracture enlarged 60 diameters. In Fig. 3 we see pearlite andcementite, the latter being in distinct needle form, while thereis no network structure. In Fig. 4, there are areas of the cementite needles and thereis also a tendency to form a network, making a very heteroge-neous structure. * Received March 12, 1906. 20 2 The Iron and Steel Magazine. Fig. i . 1 Defective Bar o) Tool Steel 283 Fig; 5 shows the structure (x6o) of the fine grained frad In this we tii>tice a slighl ne1 work. Here, then, we find structures correspondingly as differenlas the two fractures. An attempl was made by treating thetwo pieces of steel represented in the two structures to sec itthey could not be duplicated. Fig. 6 shows the structure (x6o) of a piece of the fine-grained steel after being heated to 17000 F. and cooled in lime. Pig. 7 shows the structure (x6o) of the coarse grain treatedexactly the same. Com]tare these two structures with that
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Keywords: ., bookcentury1800, bookdecade1890, bookidironsteel, booksubjectiron
