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) having diameters of 10, 15 and 20 mm were examined on a hot tensile testing unit after partial melting and cooling at different rates. Experiments were performed at temperatures between solidification and 1000°C. As a comparison non‐melted specimens taken from a continuously cast slab were investigated. In the experiments in which specimens were partially melted the radially solidified area increases with enhancing cooling rate. At cooling rates ≥ 3 K/s it accounts for more than 80 % of the specimen cross‐section. The secondary dendrite arm spacings λ 2 range between approx. 30 and 50 μm at these cooling rates. As the radially solidified area increases, strength at zero‐toughness temperature decreases. At lower temperatures, on the other hand, the solidification morphology of these samples had no effect on the mechanical properties. Unlike the results achieved with partially melted specimens, with specimens taken from a continuously cast slab the solidification morphology was found to have a distinct effect. Between 1350 and 1100°C toughness is around 20 % points lower when tensile loading acts transversely to the direction of crystal growth in comparison with axial loading. On the contrary strength is slightly higher. These results show that when investigating the causes of fracture initiation and propagation during and after solidification, the solidification morphology is of prime concern.