The Iron and steel magazine . tructure of a salamander, that is, one of those masses of iron and carbonwhich frequently form in the crucible of blast furnaces, under conditionsextremely favorable to the production of graphite and to the exclusion ofcombined carbon, namely, high silicon content and very slow cooling;such a metal may rightly be considered as an absolutely gray cast iron. Metallography Applied to Foundry Work microscope reveals the volume or bulk of the various constituents,and because of its relatively Low specific gravity the graphitewill necessarily occupy a relatively La
The Iron and steel magazine . tructure of a salamander, that is, one of those masses of iron and carbonwhich frequently form in the crucible of blast furnaces, under conditionsextremely favorable to the production of graphite and to the exclusion ofcombined carbon, namely, high silicon content and very slow cooling;such a metal may rightly be considered as an absolutely gray cast iron. Metallography Applied to Foundry Work microscope reveals the volume or bulk of the various constituents,and because of its relatively Low specific gravity the graphitewill necessarily occupy a relatively Large space. Iron considered as a microscopical constituent is called ferrite, and the structure of absolutely gray cast iron may thenbe described as consisting of a mass of ferrite in which are em-bedded numerous irregular particles of graphite. It will be noticed in Fig. i that the etching treatment hasresulted in resolving the ferrite into a number of irregular,polvhedric grains, giving to its structure a network Fig. 2. Carbonless Iron. Magnified 50 diameters. This network marks the junction lines between adjacent grains,the etching fluid having corroded the metal more deeply betweenthe grains than over their surface. Most of the grains are hex-agonal, which strongly suggests that iron, like most metals,crystallizes in the regular cubic system, these hexagonal grainsbeing probably due to interfering cubes and octahedra. If we now examine the structure of pure iron, or, at least, ofcarbonless iron as shown in Fig. 2, the striking similarity betweenthe structure of this metal and that of the metallic matrix ofgray cast iron free from combined carbon (Fig. 1) will be appar-ent. The ferrite which necessarily forms the totality of carbon-less iron exhibits the network structure seen also in the matrix ofthe gray cast iron. Both are made up of irregular, polyhedric 122 The Iron and Steel Magazine ferrite grains. There is much structural resemblance, therefore,between p
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Keywords: ., bookcentury1800, bookdecade1890, bookidironsteel, booksubjectiron
