The Iron and steel magazine . edded, and it will also be apparent that the shape anddimensions of the graphite particles must also have their influ-ence. If the graphite could be made to occur in small, roundedparticles it would probably affect the ferrite to a much less extentthan when present, as is generally the case, in irregular and Metallography Applied to Foundry Work 123 curved plate. (See Fig. 3.) [ndeed, this is strikingly borne outby the strength and ductility of malleable cast-iron castings inwhich small, rounded particles of graphite are embedded in amass of ferrite, similar in ev
The Iron and steel magazine . edded, and it will also be apparent that the shape anddimensions of the graphite particles must also have their influ-ence. If the graphite could be made to occur in small, roundedparticles it would probably affect the ferrite to a much less extentthan when present, as is generally the case, in irregular and Metallography Applied to Foundry Work 123 curved plate. (See Fig. 3.) [ndeed, this is strikingly borne outby the strength and ductility of malleable cast-iron castings inwhich small, rounded particles of graphite are embedded in amass of ferrite, similar in every respect to the ferrite of gray castirons, as will be shown on another occasion. The foregoing considerations suggest three means of in-creasing strength of gray cast iron free from combined carbon:(1) By reducing the amount of graphitic carbon, (2) by decreas-ing the size of the graphite particles and (3) by regulating theshape of the graphite particles, causing them to occur as roundedgrains rather than as curved Fig. 4. Salamander. Magnified 30diameters (not etched). The amount of graphitic carbon (which here means theamount of total carbon) can be decreased by the use of steel orother low carbon metal in the cupola, or by oxidation in the air furnace. The sizes of the graphite particles are undoubtedly greatlyinfluenced by the rate of cooling of the castings during solidifica-tion and subsequent cooling, and this in turn is affected by thesize of the castings. It is probably true that the slower the cool-ing during solidification and subsequent cooling the larger thegraphite particles. In Fig. 4 is shown the structure of anothersalamander, formed in the crucible of a blast furnace magnified 124 The Iron and Steel Magazine only 30 diameters. The very large size of the graphite plates,caused undoubtedly by the extremely slow solidification andcooling of the iron, will be noted. In the references which have been made here to the rate ofcooling it has been supposed
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Keywords: ., bookcentury1800, bookdecade1890, bookidironsteel, booksubjectiron
