The Iron and steel magazine . erwise 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 co
The Iron and steel magazine . erwise 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, of which we have already noted one, has also been distinguished, which, magnified very greatly,gives, to be sure, an indication of laminated structure, but isstained by certain reagents, which does not occur with sorbite and troostite are really different componentsis not easy to determine, but the assumption is possible that they. Fig. 26. Magnified 500 diameters are the ends of a series of transitional forms of martensite andpearlite, or vice versa. Practically, as well as theoretically, it would be of thegreatest importance if these processes could be chemically investi-gated. The discovery that the carbon (cementite) of annealedsteel occurs in another state from the carbon in the quenched(martensite) steel led to the proof that in the slowly cooled steelsa carbide of the composition Fe3C is contained, which in dissolvingthe steel in dilute acids remains behind as a heavy powder and,as we have seen above, furnishes as cement ite a constituent ofthe structure. It is striking that the quantitative determina-tion of this carbide cannot be performed by dissolving the mate- 210 The Iron and Steel Magazine rial carefully in dilute acids. Photograph 26 shows us thestructure of a white iron which was slowly cooled, hence consistsonly of free cementite and pearlite. The total carbon is 2.
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Keywords: ., bookcentury1800, bookdecade1890, bookidironsteel, booksubjectiron
