[en] Samples of 2.25Cr-1Mo cast steel (ASTM A387 grade 22) solidified by continuous casting were observed after preparation using various metallographic etchants (Nital, Murakami, Bechet-Beaujard and Groesbeck's reagent).
Influence of variations in local chemistry, due to varying cooling rates, on the structure of grade 22 steel was observed by optical microscopy and by SEM. Vickers microhardness measurements were also realized to determine the mechanism of formation of the hot tearing defects. Samples from the sub-surface area (chill zone) and from the center of the slab (equiaxial zone) were studied and difference in both chemistry and microstructure were observed.
Samples from two distinct casts, one considered defective, the other considered adequate were analyzed. The presence of chemical segregations and various defects such as cracks and microporosities were observed on samples from both casting conditions. However, the extent of those defects was lesser in the case of the accepted cast, and no defects were observable on the outer surface of the slab.
Presence of various phases in distinct areas of the slab was linked with cooling phenomena and variations of casting conditions.
Research center :
CRIM - Ingénierie des matériaux
Disciplines :
Materials science & engineering
Author, co-author :
Vitry, Véronique ; Université de Mons > Faculté Polytechnique > Métallurgie
