THE INFLUENCE OF SOLIDIFICATION MORPHOLOGY ON THE HIGH-TEMPERATURE MECHANICAL-PROPERTIES OF AN 18-10CRNI STEEL

Cylindrical specimens of the grade X4CrNi18-10 (material no 1.4301) ha ving diameters of 10, 15 and 20 mm were examined on a hot tensile test ing unit after partial melting acid cooling al different rates. Experi ments were performed at temperatures between solidification and 1000 d egrees C. As a comparison non-melted specimens taken from a continuous ly cast slab were investigated. In the experiments in which specimens were partially melted the radially solidified area increases with enha ncing cooling rate. At cooling rates greater than or equal to 3 K/s it accounts for more than 80% of the specimen cross-section. The seconda ry dendrite arm spacings lambda(2) range between approx. 30 and 50 mu m at these cooling rates. As the radially solidified area increases, s trength at zero-toughness temperature decreases. At lower temperatures , on the other hand, the solidification morphology of these samples ha d no effect on the mechanical properties. Unlike the results achieved with partially melted specimens, with specimens taken from a continuou sly cast slab the solidification morphology was found to have a distin ct effect. Between 1350 and 1100 degrees C toughness is around 20% poi nts lower when tensile loading acts transversely to the direction of c rystal growth in comparison with axial loading. On the contrary streng th is slightly higher. These results show that when investigating the causes of fracture initiation and propagation during and after solidif ication, the solidification morphology is of prime concern.