Modelling the quality of the steel products under challenging measurement conditions

Industry is increasingly moving towards data-driven business. With an abundance of data, the problem is no longer how to get access to data but how to extract the most value from it. The extracted knowledge helps to control industrial processes efficiently and automatically. The quality of products can be improved by finding root causes behind poor quality, hence improving the yield and competitiveness of the whole plant.

Thesis helps to understand the benefit of using statistical machine learning methods to improve manufacturing processes. With the methods presented, the future can be predicted based on historical data and data-driven decision support for the processes can be offered. The application area of this work is the steel industry. This work gives step-by-step advice for successfully implementing AI applications in the industry. In addition, methods for finding root causes behind poor quality are presented to improve the process and the quality of the products. Since data collected under challenging measurement conditions in the industry is never flawless, a quality model which can utilize incomplete data is also developed.

Machine learning methods are used in this work to process data and to develop data-driven quality models, which help to predict the desired quality characteristics and hence support the decision-making of the workers managing the process. Both supervised and semi-supervised machine learning methods are used. In addition, explainable machine learning is used to increase the transparency of the models. With the help of these methods, predictive quality models are developed for four different datasets consisting of measurements from steel manufacturing processes. The developed models have been implemented as a smart manufacturing tool, which enables real-time support for process workers during the manufacturing process. Using the tool, a worker can recognize the factors that can cause quality problems in the process in advance. Hence, the tool allows for fast reactions to improve the quality.

This work shows significant advantages the industry can obtain with a data-driven business model. By using the developed quality models, the yields of manufacturing processes were improved by better planning of material sufficiency, minimizing the amount of waste, improving the product quality, and reducing the risk of rejections. All of these methods are also entirely applicable to processes in other fields of industry such as food production, biomass drying, and health applications.