The Effect of Thermal History on the Hot Ductility of Microalloyed Steels

摘要

Transverse cracks in continuous cast steels can front if the hot ductility of the cast steel at the unbending stage is poor. To measure hot ductility, tensile specimens are usually reheated to a high temperature (preferably to the melting point), cooled to the test temperature and then isothermally fractured. In this work, high temperature tensile testing was used to determine the hot ductility of a Nb-Ti and a Ti-B microalloyed steel. However, instead of cooling directly to the test temperature after melting, the specimens were subjected to thermal histories typical of a continuously cast billet surface, and then, at the unbending temperature, subjected to a tensile test to fracture. In other words, physical simulations of the continuous casting procedure were performed. The results were compared with those generated by conventional isothermal tensile testing.