The Iron and steel magazine . .0 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 mas
The Iron and steel magazine . .0 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 the decomposition of the carbide before melting, thesaturation point can amount to 90 per cent, as we have justseen, and a great part of the carbon will coat on the surface; howmuch of the latter will be taken up by the fluid metal dependsmainly on the time, though also on other not well-known circum-stances. To the latter belong, for example, the thickness of the. Fig. 25. Magnified 500 diameters carbon resting on the metal; these experiments have shown thatwith a light rust the carbonization of wrought iron to cast iron per cent took about 5 times as long as by means of heatedsugar charcoal in otherwise identical circumstances. Below 7000 C. the formation of carbon from cement it e inotherwise pure iron is not possible. Photograph 25 shows awhite iron (with traces of graphite) after 50 hours at 6500 C. Thecharacteristic laminated structure of the pearlite is completelygone, while the separate cementite laminations have rolled to-gether in small, irregular lumps. This form of the pearlite hasbeen well named granulated pearlite. Iron ( arbon . 1 Hoys 209 The laminations of which the pearlite is composed becomeplainer the slower the cooling from above 7100 C; if it coolsrapidly, it remains, as we have seen, martensite. According tothe rapidity of cooling there are more or less clearly marked transition forms, o
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