The present book serves as a resource for students at RWTH Aachen for lectures, exercises, and practicals at the Institute of Iron and Steelmaking. It introduces the engineering approach to the development of steels and manufacturing processes, the targeted adjustment of properties, and the sensible application of materials in the field of steel materials science for study and practice. Examples from the content include: - Physical and chemical characteristics of the element iron and the materials based on it - Phase diagrams of important iron alloys - Segregation and segregation phenomena - Microstructure formation (ferritic-perlitic, martensitic transformation) - Hardening - Technical annealing treatments - ZTA/ZTU diagrams - Thermomechanical treatment.