Hot ductility improvement in continuous casting by predeformation treatment

Predeformation treatment is known to be one of effective methods for preventing slab surface cracks in continuous casting. In order to clarify mechanism of improvement in hot ductility by predeformation, the influence of the amount of predeformation and the number of repeated predeformation operations on the hot ductility of carbon steel was investigated in laboratory-scale experiments. Small predeformation was given several times using a tensile machine, and reduction of area (RA) was evaluated. Metallographic observation was also carried out on these test pieces by optical microscopy and scanning electron microscopy (SEM). The metallographic examination revealed that the grain size of the test piece was refined from 195 micrometers to 160 micrometers, and RA improved from 45.6% to 76.1% by predeformation. One reason for improvement of hot ductility by predeformation is recrystallization of austenite grains by dislocation nucleation.