This book introduces the results that the authors have achieved on the study of functional principle of electroslag remelting for production of high-quality clean steel. The dependence of oxygen, sulfur, and non-metallic inclusions on the processing parameters of electroslag remelting is assessed. The fundamentals and technologies of clean steel production by electroslag remelting have been applied in the round to discuss oxygen, sulfur, and non-metallic inclusions evolution and control. A general concluding remark and a perspective for future work are present. The book is likely to be of interest to university teachers, researchers, R&D engineers, and graduate students in material processing and pyrometallurgy who wish to explore innovative technologies that lead to more energy-efficient and environmentally sustainable clean steel production.