The Iron and steel magazine . ng proportions, and with correspondingly varyingphysical properties. Those cast irons which contain most of their carbon asgraphite are called gray cast irons because of the dull gray orblackish appearance of their fracture, while those in which thewhole of the carbon is combined are known as white cast ironsbecause of the bright metallic luster of their fracture. * The Foundry, January, 1906. I 20 The Iron and Steel Magazine The well-known causes to which the formation of these twodistinct kinds of carbon arc due will be alluded to on anotheroccasion, it being de
The Iron and steel magazine . ng proportions, and with correspondingly varyingphysical properties. Those cast irons which contain most of their carbon asgraphite are called gray cast irons because of the dull gray orblackish appearance of their fracture, while those in which thewhole of the carbon is combined are known as white cast ironsbecause of the bright metallic luster of their fracture. * The Foundry, January, 1906. I 20 The Iron and Steel Magazine The well-known causes to which the formation of these twodistinct kinds of carbon arc due will be alluded to on anotheroccasion, it being desired for the present merely to describe thestructure of these various grades of iron as revealed by themicroscope. The structure of a perfectly gray cast iron, that is, of an ironfree from combined carbon, is shown in Fig. 1 under a magni-fication of 50 diameters.* It will be found to consist of a numberof dark, irregular areas embedded in a light background, theformer representing the location of the graphite particles, the. Fig. i Gray Cast Iron from 50 diameters (etched). latter representing the metallic iron. It may at first sight seemsurprising that so large an area should be occupied by graphitein view of the fact that the iron did not probably contain muchover 4 per cent of graphite, £>ut this will be readily explained,if it be considered that this means percentage in weight, while the * As it was not possible to obtain a piece of gray cast iron absolutelyfree from combined carbon, we show here, for purpose of illustration, thestructure 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
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Keywords: ., bookcentury1800, bookdecade1890, bookidironsteel, booksubjectiron
