| Description |
ix, 68 leaves : illustrations, photographs ; 29 cm |
| Summary |
"Since metallographic studies of quenched and tempered cast iron have indicated that the carbon might precipitate directly as graphite rather than as carbides which are found in steels, this investigation used the Debye-Scherrer x-ray diffraction technique to examine electrolytically extracted residues from quenched and tempered ductile cast iron samples to determine if cementite was present. The precipitation of carbon in quenched samples of this ductile cast iron was found to be similar to the precipitation process in steels. Cementite was identified during the early stages of the tempering process when the tempering temperature was 800 degrees F, 900 degrees F, and 1000 degrees F. Cementite was not found in samples tempered at 600 degrees F and 700 degrees F. No attempt was made to identify carbides others than cementite, and it was not determined if transition carbides precipitated at the lower tempering temperatures. The cementite was found to be unstable in the cast iron and decomposed rather rapidly at the tempering temperatures at which it formed. No cementite was present after 30 minutes tempering at 800 degrees F, after 15 minutes at 900 degrees F or after 10 minutes at 1000 degrees F. The hardness was found to continue to drop after all the cementite had graphitized, presumably due to coarsening of the graphite precipitate and possibly also due to additional slow precipitation of carbon which could have graphitized as rapidly as it precipitated "--Abstract, leaves ii-iii. |
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