The Iron and steel magazine . erhaps by oxidation, an iron remains- which consistsonly of ferrite and pearlite, and so is malleable. This operation,which changes the white, brittle, non-malleable cast iron intoa soft metal, is called annealing; the final product, annealed ormalleable cast iron. This process of the division of the cementite into ferrite andtemper carbon has much bearing upon the theory. First of all, Iron ( cm bon . illoys 207 it musl be mentioned thai the materia] which served for theexperiments illustrated in 22 and 24 was almost free from Si, or at least did not contain more
The Iron and steel magazine . erhaps by oxidation, an iron remains- which consistsonly of ferrite and pearlite, and so is malleable. This operation,which changes the white, brittle, non-malleable cast iron intoa soft metal, is called annealing; the final product, annealed ormalleable cast iron. This process of the division of the cementite into ferrite andtemper carbon has much bearing upon the theory. First of all, Iron ( cm bon . illoys 207 it musl be mentioned thai the materia] which served for theexperiments illustrated in 22 and 24 was almost free from Si, or at least did not contain more than per cent of 11 ; tin-total carbon amounted to per cent, and it contained cent Mn, per cent P and per cent S. Pure cementite is then not a stable compound at 1000° C,but divides into the elements iron and carbon. A clear proofthat the dark areas within the ferrite areas are elementarycarbon or some carbide rich in carbon, which, when treated withHNO3, liberates carbon, would be hard to Fig. 24. Magnified 500 diameters When the division of the cementite has begun, it does notcease at the moment when all the superfluous cementite is de-composed, but possibly continues, till the formationof the systemferrite + temper carbon. The example given in 22 to 24shows,beside pearlite ( per cent carbon), much free ferrite ( percent carbon), or in the cross section about per cent carbon,the remainder — = ; that is, 89 percent of the totalcarbon is temper carbon. This fact speaks very much in favor ofHeyns * assumption, which considers the system ferrite + carbonas stable and the other systems as phenomena of rapid cooling. + Heyn: Article cited. 208 The Iron and Steel Magazine Moreover, it is not admissible to determine the dissolvingcapacity of the iron for carbon by melting pure carbide obtainedby treatment with acids and considering the carbon of the re-maining mass of iron as the saturation point. According to thedegree of t
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Keywords: ., bookcentury1800, bookdecade1890, bookidironsteel, booksubjectiron
