Abstract
Ductility is the important indicator of transverse surface cracking susceptibility of slabs of microalloyed steels during continuous casting. Welding structure steel HG785 is selected to study the effect of different thermal schedule on ductility of microalloyed steel slabs during continuous casting in this paper. Surface Structure Control (SSC) cooling process parameters of HG785 microalloyed steel were confirmed by the aid of thermomechanical simulation experiment of Gleeble 3500. Results of tensile tests show that the ductilities of slabs under traditional thermal schedule and temperature fluctuation thermal schedule are very low in the III brittleness zone, and the reductions of area reach 29.7% and 26.0% at 800 °C, respectively. The ductility of slabs under SSC thermal schedule is obviously improved, since the pro-eutectoid ferrite film and aggregation of precipitates along the austenite grain boundary has not been discovered.
Highlights
Due to the solid solution strengthening effect of carbonitride precipitation, a good combination of strength, ductility, and welding performance of the microalloyed steels can be achieved [1,2,3,4,5]
The effects of different thermal schedules on the ductility of steel were analyzed through tensile experimentation, the effect of the Surface Structure Control (SSC) cooling process on the carbonitrides’ precipitation distribution, which provides the theoretical basis for surface quality control of microalloyed high strength steel
The R.A. of the SSC samples are higher than 50% at each test temperature, surface continuous cracking susceptibility of slabs with SSC cooling technology during continuous casting
Summary
Due to the solid solution strengthening effect of carbonitride precipitation, a good combination of strength, ductility, and welding performance of the microalloyed steels can be achieved [1,2,3,4,5]. A large number of studies have shown that the corner transverse cracks of microalloyed steel during continuous casting are related to the precipitates along austenite grain boundary and solid phase transition in straightening process [9,10,11]. Kato et al [14] believed that the size and position of the austenite grain boundary did not change before and after the intense cooling. The effects of different thermal schedules on the ductility of steel were analyzed through tensile experimentation, the effect of the SSC cooling process on the carbonitrides’ precipitation distribution, which provides the theoretical basis for surface quality control of microalloyed high strength steel
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