The world of steel is amazingly diverse and so complex that it is not easy to keep track of in practice. In the form of portraits of selected steels and steel groups, this world of steel is to be brought closer to the reader; compact, understandable, informative, structured with examples from practice and suitable for reference. Hot work tool steels are a group of alloyed steels with high hot strength suitable for tools. These can withstand surface temperatures of more than 600 °C in use. For this purpose, they are optimally adapted to the most diverse requirements, especially for tools used in hot forming and die casting. Important are the chemical compositions, methods of production and processing as well as their properties or the material data of hot work tool steels, which are briefly and clearly presented in this book. · The history of hot work tool steels · Designations, chemical compositions, grades, microstructure and properties · Production (melting and powder metallurgy), heat and surface treatments Trainees in metal professions Students, practitioners, engineers in steel production, forming and production technology, in steel, metal and tool construction and in the steel trade