Liquid inclusions are important to avoid nozzle clogging during continuous casting of steel. To minimize clogging tendency at a Brazilian steelworks for a low‐sulphur Ca‐treated peritectic steel, deoxidation technique is changed from only Al addition as deoxidant to Fe–Si ferroalloy followed by Al addition, reducing the amount of Al by 20 wt%. Calcium treatment procedure is not changed. According to steelworks data, clogging occurrences are drastically reduced with this process change. In this context, quenched steel samples are collected from the tundish before and after the aforementioned process change. Nonmetallic inclusions characterization is manually performed using scanning electron microscope. For both conditions—before and after the industrial process changes—the inclusions are typically globular ones. However, before the changes, the inclusion modification is not complete because the core of the inclusions is composed by polygonal spinel. After the changes, the inclusions become homogeneous. Computational thermodynamics is applied to calculate the castability windows; they show that the amount of calcium dissolved in liquid steel is too low before the process changes, and this fact explains the blockage of the tundish nozzles, which is observed at steelworks, due to the deposition of high melting point spinel inclusions.

Sliver defects were detected in galvanized and uncoated cold-rolled strips, and their causes were investigated. Most of these strips were produced from transition ladle slabs, which were obtained in a sequence of twenty heats of an ultra-low carbon Al-killed steel. A significant reduction in the steel level in tundish occurred during these slabs' casting. The strip defects, and as a comparative, a mould flux inclusion found in a first slab of the sequence, were analysed with a scanning electron microscope (SEM). Also, each of the twenty heats was sampled in tundish, quenched in water, and manually analysed with SEM to characterize its dominant inclusions. Regarding the sliver defects, mainly silica together with alumina or Al-Ti-O systems particles were found in them. The primary sources for these particles are likely tundish flux and reoxidation products. Finally, a mechanism was proposed for the formation of these inclusions.

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After continuous annealing process (CAP) at 790°C, 85% of the coils of 50% cold-rolled low carbon microalloyed (LCM) steel did not exhibit yield-strength (YS) on the target range, while the 70% cold-reduced LCM coils did. In this context, the non-isothermal recrystallisation kinetics of ferrite for the above two full-hard LCM steel were investigated using differential scanning calorimetry and the Friedman differential isoconversional method. The recrystallisation kinetics of ferrite for the two deformed states showed different behaviour. Regarding a fixed degree of cold-rolling deformation, the soaking temperature was found as the manageable parameter to control YS during CAP. Consequently, a suitable YS of the 50% cold-rolled LCM steel was achieved by setting the soaking temperature at 773°C.

The present work is based on the characterization of nonmetallic inclusions in Ti stabilized ultra-low carbon steel, produced in a large steel mill. Due to a large incidence of submersed valve clogging in a continuous casting, the study is important in order to know the characteristics of the inclusions which are causing the problem. Total of 24 heats were sampled in the tundish and manually analyzed with a scanning electron microscope. The results revealed that 98.65% of the 3183 inclusions analyzed were solid in steelmaking temperature and 66.54% were alumina. The solid inclusions of alumina have low wettability for the iron bath, showing a high tendency of agglomeration in the submersed valves, affecting the castability. It has been concluded from the results and literature that some alternative measures such as the application of the treatment with calcium, precautions to avoid steel re-oxidation and the total or partial replacement of the pre-deoxidized element; would reduce the obstruction problem.

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