Determination and Prediction of Austenite Grain Size in Relation to Product Quality of the Continuous Casting Process

摘要

Crack formation is a frequent problem in the continuous casting process. The formation of cracks is associated with an overcritical deformation of the strand shell in a low-ductility temperature range. Ductility troughs at elevated temperatures are attributed to the formation of precipitates, phases or segregates during cooling, particularly detrimental along grain boundaries. Besides the steel composition, process related factors, like deep oscillation marks on the strand surface associated with coarse austenite grain size, play an important role, too. The implementation of an austenite grain size prediction model into the quality assurance system of a continuous casting machine, has therefore been the objective of a joint research work of voestalpine Stahl and the Christian Doppler laboratory for "Metallurgical Fundamentals of Continuous Casting Processes". In a first step, slabs of different steel grades were investigated to determine the prior austenite grain size, followed by a feasibility study on the simulation of austenite grain growth under continuous casting conditions in a laboratory experiment. Following extensive experimental and metallographic work, the results served for the validation of an austenite grain size prediction model. The current work presents the applied experimental und metallographic methods, the results of the metallographic examinations as well as some results of the model.