Field of Expertise: Advanced Material Science
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Field of Expertise: Advanced Material Science | |
Assessing the surface cracking susceptibility during continuous casting of in-situ melted and solidified steels Apart from the chemical composition, the temperature cycles and the various stresses arising from the continuous casting process strongly influence the hot ductility behavior and thus the cracking susceptibility of steels. The hot ductility of as-cast constructional C-Mn steel has been studied in order to analyze the surface cracking mechanism by conducting hot tensile tests on a unique and modified thermo-mechanical testing machine developed at the Institute for Materials Science and Welding at Graz University of Technology. Tensile specimens were heated to the melting point, cooled to a temperature range between 650°C and 1100°C and were strained with 10-3 and 10-2 s-1 to rupture. Hot ductility curves of reduction of area vs. testing temperature and metallographic examinations have been used to depict the cracking sensitivity of the investigated steel. The preceding melting and the subsequent solidification process produce very coarse grains as well as shrinkage cavities, which strongly influence the materials cohesion and therefore significantly reduce the deformability. The ductility starts decreasing at 900°C in the single phase austenite-region, characterized by grain boundary sliding, reaches a minimum in the two-phase ferrite-austenite-region at 750°C and slightly increases with decreasing testing temperature. Distinct intergranular fracture and poor ductility was observed between 700°C and 800°C. |