On the potential of endless strip production routes for the processing of advanced high strength steels from lower quality obsolete scrap

The ongoing transformation of the steel industry towards environmentally friendly steel production represents a major challenge. New technologies aim to reduce energy consumption and direct CO₂ emissions by changing selected processes of conventional steel production routes. Thin Slab Casting and Rolling technologies, such as the Arvedi Endless Strip Production (Arvedi ESP), are proven technologies for reducing energy consumption in continuous casting and hot rolling significantly. Due to the increased use of electric arc furnaces and the rising need for using also low-grade scrap, a higher input of undesired tramp elements such as Cu and Sn is expected. Those tramp elements lead to a significant decrease of the product quality during casting and hot processing. Therefore, Thin Slab Casting and Rolling processes aim to suppress the negative influence of those tramp elements by increasing casting speed and accelerating slab cooling.

This PhD thesis deals with the investigation of intergranular crack formation during conventional continuous casting and Thin Slab Casting and Rolling with emphasis on the cooling strategy and the control of the negative effects of tramp elements through optimized casting parameters. Experiments are performed in the laboratory through the in-situ material characterization by bending test (IMC-B), simulating various continuous casting and the Arvedi ESP process. Boundary conditions, as for example cooling strategies and cooling atmospheres, can be controlled and simulated in the laboratory. Additionally, small-scale trials are performed using the Simultaneous Thermal Analysis (STA), investigating oxidation behavior of steels under controlled laboratory conditions.

The goal of this work is to determine Thin Slab Casting and Rolling conditions to prevent the formation of intergranular crack formation during the casting and rolling of Advanced High Strength steels for automotive applications, even at higher levels of undesired and harmful tramp elements. Therefore, deeper understanding of the mechanisms behind intergranular crack formation has to be gained during this PhD thesis.