The Iron and steel magazine . cooling this iron would have become gray; so we havenow before us an incomplete reaction whose final product isgraphite and whose original constituent is either a solution ofcarbon in iron or cementite. This reaction which begins at themoment of solidification is not ended with the decrease of thetemperature of solidification. The cooling curves show, espe-cially for the gray iron, a delay in the fall of the temperature 196 The Iron and Steel Magazine which takes place not only at 11300 C. but also below this, asign that the reaction begun at the point of solidifi
The Iron and steel magazine . cooling this iron would have become gray; so we havenow before us an incomplete reaction whose final product isgraphite and whose original constituent is either a solution ofcarbon in iron or cementite. This reaction which begins at themoment of solidification is not ended with the decrease of thetemperature of solidification. The cooling curves show, espe-cially for the gray iron, a delay in the fall of the temperature 196 The Iron and Steel Magazine which takes place not only at 11300 C. but also below this, asign that the reaction begun at the point of solidification, 11300C, continues still further with the loss of heat, whereby a retarda-tion often of 10 to 150 C. is produced. In what way this retarda-tion is influenced by the separated graphite, especially as to thequantitative determination of the liberated heat, suggests veryinteresting determinations. Concerning the position and meaning of the point of solidi-fication at 11300 C. there is still to be noticed that it shows few. Fig. 13. Magnified 500 diameters variations in spite of the different percentages of carbon, asshown in the following table: 2 3 4 5 6 7 8 1135 1112 1138 1141 1149 1122 1130 3-29 3-76 3-79 3-94 19 6 14 18 17 11 16 Curve ...... 1 Degree C 113 2 Total carbon . 8 or at least it does not fall or rise perceptibly with increasingper cent of carbon. By other experiments it is sufficiently proved that themelting point of iron is lowered by the presence of carbon. Itis assumed that 1 per cent of carbon lowers it about ioo° C. Iron ( arbon . Uloys 197 This idea according to the above is no1 wholly correct. Assoon as the melting point of iron with a certain per cenl oi carbonnot yet more closely determined, has reached a certain minimum,apparently i 1300 C, further addition of carbon is withoutinfluence on the lowering of the melting point. Observing the cooling curves one is struck by their regularcourse between the two stopping pl
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