Development of a toolbox for direct defect prediction and reduction through the characterisation of the meniscus-slag bed behaviour and initial shell solidification in CC (DIRECT DEFECT TOOLBOX-DDT) : final report

The aim of this project is to produce a set of novel numerical and experimental tools to predict explicitly the formation of defects. These tools imply the development of new measuring/modelling techniques and improved physics to understand the CC process. The output of the project will be a "toolbox" including measurement methods, experimental set-ups and numerical models. This project seeks to directly determine the transient occurrence of defects and process problems during slab casting of peritectic and Advanced High Strength Steels. Direct-defect prediction is possible through numerous plant trials and liquid-metal experiments to characterise the heat-transfer and dynamic behaviour of the slag-bed and meniscus (particularly, at the meniscus where initial solidification occurs). A series of different types of plant measurements have been performed at SSAB Luleå and Tata Steel, Ijmuiden. These measurements have generated input data for numerical models but it has also generated process knowledge for the plants. Extensive parametric campaigns have been performed in the liquid metal model (CCS1). And the findings in the metal level are in remarkable agreement with plant operational practices, which shows the applicability of the Simulator as well as opening the possibility of using CCS1 as a benchmark for testing process conditions and translate them directly into the casting practice. Microstructural evolution including the apparition of cracks has been observed through novel in-situ experiments. Steel properties have been addressed through high temperature measurements in a Gleeble 3800 equipment. Numerical models have been developed that predict metal-slag-argon flows, heat-transfer, mould-oscillation, solidification, stress-strain and microstructural evolution of the shell. The potential use of the "toolbox" developed in the project has already been proved at SSAB and TATA. Two process changes at SSAB Luleå have been implemented based on the results in the project, it has been validated and the result is improved yield. One change has been implemented at TATA with decreased defects.