The purpose of this paper was testing suitability of the time-series analysis for quality control of the continuous steel casting process in

production conditions. The analysis was carried out on industrial data collected in one of Polish steel plants. The production data

concerned defective fractions of billets obtained in the process. The procedure of the industrial data preparation is presented. The

computations for the time-series analysis were carried out in two ways, both using the authors’ own software. The first one, applied to the

real numbers type of the data has a wide range of capabilities, including not only prediction of the future values but also detection of

important periodicity in data. In the second approach the data were assumed in a binary (categorical) form, i.e. the every heat(melt) was

labeled as ‘Good’ or ‘Defective’. The naïve Bayesian classifier was used for predicting the successive values. The most interesting results

of the analysis include good prediction accuracies obtained by both methodologies, the crucial influence of the last preceding point on the

predicted result for the real data time-series analysis as well as obtaining an information about the type of misclassification for binary data.

The possibility of prediction of the future values can be used by engineering or operational staff with an expert knowledge to decrease

fraction of defective products by taking appropriate action when the forthcoming period is identified as critical.