The Iron and steel magazine . und mass is saturated withcementite. The amount of troostite will be the smaller thehigher the quenching temperature, because the crystals withincreasing temperature are more quickly saturated with cemen-tite, and also the longer the heating at a given temperature hascontinued, whereby time is given to the troostite to change intothe crystalline martensite. 204 The Iron and Steel Magazine On heating we have thus at 9000 C. the constituents cement-ite, martensite and troostite. If the condition could be keptcompletely unchanged through the cooling, only these three
The Iron and steel magazine . und mass is saturated withcementite. The amount of troostite will be the smaller thehigher the quenching temperature, because the crystals withincreasing temperature are more quickly saturated with cemen-tite, and also the longer the heating at a given temperature hascontinued, whereby time is given to the troostite to change intothe crystalline martensite. 204 The Iron and Steel Magazine On heating we have thus at 9000 C. the constituents cement-ite, martensite and troostite. If the condition could be keptcompletely unchanged through the cooling, only these threeconstituents would occur. But since even sudden coolingrequires a certain time, the martensite can partly the products of disintegration, whose character is stilluncertain, a specially striking one has been termed austenite*;this is the light ground mass in photograph 18 which is crossedby the darker needles of martensite. If the temperature isincreased still more, the amount of troostite plainly decreases,. Fig. 21. Magnified 500 diameters the disintegration of the crystals in martensite and austeniteincreases, since the time which the material needs to pass from15000 C. to 7000 C. is naturally greater than when it cools downfrom only 9000 C. Photograph 19 shows beside cementite andsome troostite the needles of martensite encased by the massof austenite. Very interesting is the observation that the austen-ite, which appears in high carbon steel only when quenched froma very high temperature, is found in cast iron at considerably * The author here evidently reverses the generally accepted mean-ings of austenite and martensite, by which the latter is considered as adisintegration product of the former. — Editor. Iron ( arbon . I lloys 205 Lower temperatures; and also the simultaneous appearandaustenite beside troostite. Quite similar conditions arc found in gray cast iron. [fwe examine the iron in photograph 14, we sec beside the pearliteonly a few narrow st
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Keywords: ., bookcentury1800, bookdecade1890, bookidironsteel, booksubjectiron
